METHOD OF DRYING COATING FILM AND PROCESS FOR PRODUCING LITHOGRAPHIC PRINTING PLATE PRECURSOR

Abstract

 A method for drying a coating film according to the present invention aims to suppress development of abnormal appearance and performance failures produced on a product surface when a solvent of a coating liquid is dried while vapor of a solvent having a boiling point lower than that of the solvent of the coating liquid is sprayed to the coating film with a vapor spray nozzle within a drying box. For this, the method for drying a coating film according to the present invention, includes: drying a coating film to a drying point, the coating film which is formed by applying a coating liquid containing a high boiling point solvent onto a support to be conveyed; and subsequently, drying the high boiling point solvent while spraying vapor of a solvent having a boiling point lower than that of the high boiling point solvent to the coating film with a vapor spray nozzle within a drying box, wherein the support is heated so as to have a predetermined temperature T within the drying box, and conveyed.

Description

Technical Field

[0001] The present invention relates to a method for drying a coating film and a process for producing a lithographic printing plate precursor, and particularly to a method for drying a coating film, comprising the steps of drying a coating film to a drying point, the coating film comprising a coating liquid containing a high boiling point solvent applied onto a support to be conveyed; and subsequently, drying the high boiling point solvent while giving vapor of a solvent having a boiling point lower than that of the high boiling point solvent to the coating film with a vapor spray nozzle within a drying box; and to a process for producing a lithographic printing plate precursor.

Background Art

[0002] In recent years, digitization techniques to electronically process image information using a computer have been spread, and new platemaking techniques to support such digitization techniques are put into practical use. Specifically, high directive light such as a laser beam is modulated according to digitized image information, and an original plate for a lithographic printing plate is scanned and exposed with this laser beam. Thereby, computer to plate (CTP) techniques for directly producing a printing plate, not through a lith film, are put into practical use. As a result, a demand for the so-called digital direct lithographic plates adapted for such CTP techniques is increasing.

[0003] An example of such digital direct lithographic plates includes a positive type lithographic printing plate precursor for an infrared laser. The positive type lithographic printing plate precursor for an infrared laser is usually produced by applying a coating liquid serving as a photosensitive layer onto a support such as a aluminum plate, and subsequently drying the coating liquid by heating the coating liquid using a heater or spraying hot air onto the coating liquid. Here, from the viewpoint of quality of a lithographic printing plate precursor, preferably, a solvent included in the photosensitive layer is dried and removed as much as possible. As a drying method, a method for using hot air is generally used and not limited to the case of the lithographic printing plate precursor. In recent years, a drying method using hot air containing vapor of a solvent has been proposed. For example, Patent Document 1 has disclosed a drying method in which an object to be dried including moisture is continuously dried using superheated vapor. Patent Document 2 has disclosed a printing method in which by applying superheated vapor at a high temperature to a printing ink on a sheet, the printing ink is heated and dried so that a moisture content of the sheet is adjusted. Patent Document 3 has disclosed a method for drying a food product using superheated vapor.

Patent Document 1: Japanese National Publication of International Patent Application No. 1997-502252

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-19310

Patent Document 3: Japanese Patent Application Laid-Open No. 2002-333275

Disclosure of Invention

Technical Problem

[0004] However, there has been a problem in the methods of Patent Documents 1 to 3 that appearance and performance failures are produced in peripheral devices or on a product surface when a coating film is formed by applying a coating liquid including a high boiling point solvent onto a support to be conveyed, the coating film is dried to a drying point, and subsequently the high boiling point solvent is dried while vapor of a solvent having a boiling point lower than that of the high boiling point solvent are given to the coating film with a vapor spray nozzle within a drying box.

[0005] The present invention has been made in consideration of such circumstances.
An object of the present invention is to provide a method for drying a coating film and a process for producing a lithographic printing plate precursor that can suppress abnormal appearance and performance failures produced on a product surface even when a solvent of a coating liquid is dried while vapor of a solvent having a boiling point lower than that of the solvent of the coating liquid are given to the coating film with a vapor spray nozzle within a drying box.

Technical Solution

[0006] In order to achieve the object, a method for drying a coating film according to a first aspect of the present invention is a method for drying a coating film, comprising the steps of: drying a coating film to a drying point, the coating film which is formed by applying a coating liquid containing a high boiling point solvent onto a support to be conveyed; and subsequently, drying, in a drying box, the high boiling point solvent while spraying vapor of a solvent having a boiling point lower than that of the high boiling point solvent to the coating film with a vapor spray nozzle, wherein the support is heated so as to have a predetermined temperature T within the drying box, and conveyed.

[0007] The present inventor obtained the following knowledge in a case where a high boiling point solvent is dried while vapor of a solvent having a boiling point lower than that of the high boiling point solvent is sprayed to a coating film with a vapor spray nozzle within a drying box. That is, in the case where the solvent in the coating film is quickly removed in an atmosphere of superheated water vapor, the superheated vapor has a higher ability to remove the solvent as the superheated water vapor has a higher concentration. On the other hand, a risk of condensation of the superheated water vapor on a surface of the film is increased as the concentration of the superheated water vapor is higher. When condensation occurs, the surface of the coating film becomes rough and abnormal appearance and performance failures are produced on a product surface. Similarly, in an atmosphere of an organic solvent within the drying box, the vapor of the low boiling point solvent has a higher ability to remove the solvent as the vapor has a higher concentration. However, an excessively high concentration of the vapor adversely causes absorption of the low boiling point solvent by the film and reduction in a drying speed.

[0008] Accordingly, it is necessary to maximize a drying ability while preventing condensation in the case where the solvent in the coating liquid is dried while the vapor of the solvent having a boiling point lower than that of the solvent in the coating liquid are sprayed to the coating film with the vapor spray nozzle within the drying box.

[0009] So, a temperature of the support before the support entered the drying box is measured, and the temperature of the support is adjusted so as to avoid condensation. Subsequently, the support is conveyed to the drying box. As a method for adjusting the temperature, a method for heating using a heating roller at an inlet of the drying box, a method for spraying hot air, a method for heating by radiant heat using infrared radiation, a heating plate, or the like can be considered.

[0010] According to the first aspect, the support is heated so as to have the predetermined temperature T within the drying box, and is conveyed so that abnormal appearance and performance failures on a product surface caused by condensation on the coating film can be suppressed.

[0011] According to a second aspect of the present invention, in the first aspect, an inner wall of the drying box is heated.

[0012] In the second aspect, the heated inner wall of the drying box can prevent droplets produced by condensation of the vapor of the solvent from adhering onto the inner wall or the vapor spray nozzle. Accordingly, it is possible to suppress abnormal appearance on the product surface and performance failures caused by falling and adhering of condensed droplets onto the coating film, and apparatus failures caused by the droplets adhering to peripheral devices.

[0013] In the method for heating the inner wall, while the inner wall is heated by hot air for drying, it is preferred that adhesion of water droplets onto the inner wall of the drying box is prevented by using a heat insulating structure to prevent heat dissipation by a heat insulator, a vacuum insulating structure having a vacuum between an inner wall and an outer wall, a double wall structure to pass warm water or vapor between an inner wall and an outer wall of a drying zone, a structure to actively heat an inner wall by a heating wire, and the like.

[0014] According to a third aspect of the present invention, in the first or the second aspect, the support and the drying box are heated to have a temperature of (the predetermined temperature T - 5 (°C)) or more.

[0015] In the third aspect, since the support and the drying box are heated to have the temperature of (the predetermined temperature T - 5 (°C)) or more, it is possible to suppress condensation on the coating film, abnormal appearance and performance failures on the product surface caused by falling and adhesion of the droplets condensed within the drying box onto the coating film, and apparatus failures caused by adhesion of the droplets onto peripheral devices.

[0016] Here, the predetermined temperature T (°C) is preferably T = 16 x X^0.286 where an amount of the vapor supplied within the drying box is X (g/m³). This equation is a modification of the Wagner-Pruss equation to calculate a saturated vapor pressure.

[0017] According to a fourth aspect of the present invention, an inlet and an outlet for the support in the drying box are sealed, in any one of the first to the third aspects.

[0018] In the fourth aspect, it is possible to prevent the vapor from leaking out of the drying box, and the vapor of the solvent from condensing due to cold air flown from an open air. As a method for preventing leakage of the vapor and inflow of the open air, a method for air sealing the inlet and the outlet for the support in the drying box by hot air, or a method for prevent leakage of the vapor by a roll or a windshield board is preferably used. In the case of air sealing, preferably, a drying air has a dew point of 5 to 15°C, and an air velocity is not less than 5 m/s.

[0019] According to a fifth aspect of the present invention, the vapor spray nozzle is insulated, in any one of the first to the fourth aspects.

[0020] In the fifth aspect, since the vapor spray nozzle is insulated, the droplets are prevented from adhering onto the vapor spray nozzle. Accordingly, it is possible to suppress abnormal appearance and performance failures on the product surface caused by adhesion of the droplets onto the coating film, and apparatus failures caused by adhesion of the droplets onto peripheral devices.

[0021] According to a sixth aspect of the present invention, the superheated vapor sprayed to the coating film is subsequently discharged to an exhaust system provided in the drying box, in any one of the first to the fifth aspects.

[0022] In the sixth aspect, the superheated water vapor is preferably discharged to the exhaust system so as not to be discharged to an outside of the drying box together with the support. This is because the superheated water vapor become water droplets to cause abnormal appearance and performance failures on the product surface when the superheated water vapor is discharged to an outside of the drying box together with the support.

[0023] According to a seventh aspect of the present invention, a heating roller contacting the support is provided within the drying box to heat the support, in any one of the first to the sixth aspects.

[0024] In the seventh aspect, because the support conveyed to the drying box is heated within the drying box, a temperature of the support can be raised to prevent condensation on the support.

[0025] According to an eighth aspect of the present invention, the drying box is provided so that a surface of the coating film on the support passes through the drying box vertically or with facing downward, and the vapor spray nozzle is provided in a position where the vapor of the solvent is sprayed to the coating film from under the coating film, in any one of the first to the seventh aspects.

[0026] In the eighth aspect, even if the droplets adhere onto the vapor spray nozzle, adhesion of the water droplets onto the support can be avoided so that abnormal appearance on the product surface, and the like can be prevented.

[0027] According to a ninth aspect of the present invention, on an internal ceiling surface of the drying box, grooves or gutters are provided parallel to a traveling direction of the support at approximately an equal interval, in any one of the first to the eighth aspects.

[0028] In the ninth aspect, even if the droplets adhere to an internal surface of the drying box, the grooves or gutters provided on a top surface of the drying box at approximately an equal interval can prevent adhesion of the droplets onto the support.

[0029] According to a tenth aspect of the present invention, the vapor of the solvent is superheated water vapor from which contained droplets and foreign substances are removed by a separator filter, in any one of the first to the ninth aspects.

[0030] In the tenth aspect, the vapor of the solvent converted into the superheated water vapor from which the contained droplets and foreign substances are removed by the separator filter are used as the vapor of the solvent. Thus, because drying is performed using the superheated water vapor from which the contained droplets and foreign substance have been removed by the separator filter, the high boiling point solvent of the coating film can be effectively removed. Additionally, it is possible to suppress performance failures caused by foreign substances on the product surface and abnormal appearance and performance failures caused by adhesion of the droplets.

[0031] Here, the "drying point" means a state where the coating liquid does not adhere to a cloth even if the cloth contacts with the coating liquid, or a state where a solid concentration is not less than 60% and preferably 70 to 80%. Here, the contained droplets mean droplets in a form of a mist and having a mist particle size of not less than 200 nm.

[0032] According to an eleventh aspect of the present invention, the superheated vapor is mixed with hot air, and sprayed to the coating film, in any one of the first to the tenth aspects.

[0033] Also preferably, superheated water vapor is mixed with hot air and sprayed to the coating film in the eleventh aspect.

[0034] A twelfth aspect of the present invention is a process for producing a lithographic printing plate precursor using the method for drying coating film according to any one of the first to the eleventh aspects.

[0035] By using the method for drying a coating film according to the twelfth aspect for manufacturing of a lithographic printing plate precursor, a lithographic printing plate precursor can be suitably produced.

Advantageous Effects

[0036] In a method for drying coating film and a process for producing a lithographic printing plate precursor according to the present invention, abnormal appearance and performance failures produced on a product surface can be suppressed in a case where a solvent of a coating liquid is dried while vapor of a solvent having a boiling point lower than that of the solvent of the coating liquid are sprayed to a coating film with a vapor spray nozzle within a drying box.

Brief Description of Drawings

[0037] 

Figure 1 is a diagram illustrating a basic configuration of a production line for a lithographic printing plate precursor in the present embodiment;

Figure 2 is a diagram illustrating an example of a configuration of a dryer according to the present invention;

Figure 3 is a diagram illustrating an example of a configuration according to a superheated water vapor drying unit;

Figure 4 is a diagram illustrating a basic configuration of a superheated water vapor drying unit according to the present invention;

Figure 5A is a diagram illustrating an example of a method for sealing an inlet and outlet of a superheated water vapor drying unit according to the present invention;

Figure 5B is a diagram illustrating other example of the method for sealing the inlet and outlet of the superheated vapor drying unit according to the present invention;

Figure 5C is a diagram illustrating further other example of the method for sealing the inlet and outlet of the superheated water vapor drying unit according to the present invention;

Figure 6 is a diagram illustrating a method for controlling a temperature of a support in the superheated water vapor drying unit according to the present invention;

Figure 7 is a diagram illustrating a preferable configuration of a superheated vapor drying unit according to the present invention;

Figure 8A is a diagram illustrating other aspect of the superheated water vapor drying unit according to the present invention; and

Figure 8B is a diagram illustrating an example of a preferable vapor spray nozzle in the aspect of Figure 8A.

Explanation of Reference

[0038] 10 ... apparatus for producing lithographic printing plate precursor, 14 ... surface treatment unit, 16 ... coating liquid preparation and feed unit, 18 ... coating unit (image recording layer), 20 ... drying unit (dryer), 22 ... coating unit (overcoat layer), 24 ... drying unit (dryer), 28 ... hot air drying unit, 29 ... superheated water vapor drying unit, 34, 34' ... nozzle, 36 ... exhaust port, 38 ... hot air, 40 ... windshield board, 42 ... roll, 44 ... groove or gutter, 46 ... heating roller, 60 ... hot air feeder, 62 ... water softener, 64 ... boiler, 66 ... separator filter, 68 ... superheated water vapor generator, 70 ... pressure reducing valve, 72 ... vapor flow meter, 80 ... superheated water vapor feeder

Best Mode for Carrying Out the Invention

[0039] Hereinafter, according to the accompanying drawings, preferable embodiments of a method for drying a coating film and a process for producing a lithographic printing plate precursor according to the present invention will be described. Figure 1 shows an example of a production line 10 of an original plate for a lithographic printing plate according to the present invention, and the example of this production line 10 will be described below. In the present embodiment, a dryer for vaporizing and drying a less volatile solvent contained in an image forming layer coating film in a production line for a lithographic printing plate precursor is described as an example. However, the present invention will not be limited to this technical field, and can be applied to methods of drying a coating film in various technical fields.

[0040] First, a basic configuration of the producing apparatus 10 for a lithographic printing plate precursor according to the present invention will be described.

[0041] Figure 1 is a diagram showing a basic configuration of the producing apparatus 10 for a lithographic printing plate in the present embodiment. In Figure 1, an arrow A shows a conveying direction of a support 16.

[0042] The production line 10 for a lithographic printing plate precursor of Figure 1 mainly includes a feeder 12 that feeds the support 16, a surface treatment unit 14 that treats with an applied surface of the support 16, an coating unit 18 that applies a coating liquid for an image forming layer (image forming layer coating liquid) onto the support 16, a drying unit 20 that dries an applied image recording layer, an coating unit 22 that applies a overcoat layer onto the image forming layer, a drying unit 24 that dries the overcoat layer, and a take-up unit 26 that takes up the support 16. The production line 10 for a lithographic printing plate precursor shown in Figure 1 is an example, and an coating unit that applies a coating liquid for an undercoat (an undercoat coating liquid) may be provided before applying the image forming layer coating liquid, for example. Alternatively, after the drying unit 24 for the overcoat layer, a moisture controller that controls moisture of the overcoat layer may be provided.

[0043] The support 16 fed from the feeder 12 is guided by guide rollers 27, 27..., and the like, and is conveyed to each step.

[0044] First, in the surface treatment unit 14, pretreatment necessary for the support 16 is performed: The pretreatment includes: degreasing treatment in order to provide good adhesion of the image forming layer to the support 16 and to give water retentivity to a non-image area; surface roughening treatment for roughening the surface of the support 16 (graining treatment or the like); anodizing treatment for forming an oxidized coating on the surface in order to improve wear resistance, chemical resistance, and water retentivity of the support 16; and silicate treatment for improving coating strength of the anodized coating, hydrophilicity, and adhesion to the image forming layer, for example.

[0045] The coating unit 18 is an apparatus that applies the image forming layer coating liquid onto the surface of the support 16. As an application method, a slide bead coating method, a curtain coating method, a bar coating method, a spin coating method, a spray coating method, a dip coating method, an air knife coating method, a blade coating method, a roll coating method, and the like are used, for example. Although the application method is not limited in particular, the slide bead coating method, the curtain coating method, the bar coating method, and the like are preferably used among these. Figure 1 shows a case of bar coating.

[0046] The drying unit 20 is an apparatus that dries the image forming layer formed on the support 16. The drying unit 20 includes a superheated water vapor drying unit 29 according to the present invention, a hot air drying unit 28 at a front stage of the superheated water vapor drying unit 29, and a cooling unit 30 at a rear stage thereof. Here, the applied image forming layer coating film contains a high boiling point solvent having less volatility as a first solvent. Effective vaporization and drying of this first solvent (hereinafter, written as a high boiling point solvent) is important to quality of the lithographic printing plate precursor. A detailed configuration of this drying unit 20 (hereinafter, written as a dryer 20) is described later.

[0047] The coating unit 22 is an apparatus that forms a water soluble overcoat layer on the image forming layer in order to shut off oxygen from the image forming layer and prevent contamination of the surface of the image forming layer by oleophilic substances. The water soluble overcoat layer can be removed easily at the time of printing, and contains a resin selected from water soluble organic polymer compounds. As a method for applying the water soluble overcoat layer, the same methods as those mentioned in the coating unit 18 above can be used. The support 16 to which the water soluble overcoat layer is applied is dried by the drying unit 24. Subsequently, the water soluble overcoat layer is eventually taken up by the take-up unit 26.

[0048] Next, an example of a configuration of the dryer 20 according to the present invention will be described.

[0049] Figure 2 is a diagram illustrating the configuration of the dryer 20 according to the present invention. As shown in Figure 2, the dryer 20 mainly includes the superheated water vapor drying unit 29 that dries the support 16 in an atmosphere of vapor of a solvent, a hot air drying unit 28 that applies hot air to the support 16 to dry the support 16 at the front stage of the superheated water vapor drying unit 29, and the cooling unit 30 that cools the support 16 by cold air at the rear stage of the superheated water vapor drying unit 29. Openings through which the support 16 goes in and comes out are formed in the hot air drying unit 28, the superheated water vapor drying unit 29, and the cooling unit 30. Each of the opening has a box shape in a conveying direction of the support 16.

[0050] A nozzle (not shown) that sprays hot air or cold air to the support 16 is provided in the hot air drying unit 28 and the cooling unit 30. Thereby, the hot air drying unit 28 is configured to apply the hot air to the support 16 to dry the support 16 before the support is conveyed to the superheated vapor drying unit 29, and the cooling unit 30 is configured to apply the cool air to the support 16 to cool the support 16 after the support is dried by the superheated water vapor drying unit 29. The number of the nozzles and an installation location of the nozzles are not limited.

[0051] The hot air drying unit 28 dries the support 16 by hot air or the like to the drying point (a state where the coating liquid does not adhere to a cloth even if the cloth contacts with the coating liquid, a state where surface glossiness does not change, or a state where a solid concentration is not less than 60% and preferably 70 to 80%).

[0052] Then, in the present invention, the support 16 is heated so as to have a predetermined temperature T within a drying box 32 of the superheated water vapor drying unit 29, and conveyed.

[0053] This is because it is necessary to ensure the maximum drying ability while preventing condensation in the case where the solvent of the coating liquid is dried while vapor of a solvent having a boiling point lower than that of the solvent of the coating liquid are given to the coating film with the vapor spray nozzle within the drying box 32. Then, a temperature of the support before entering the drying box 32 is measured, and adjusted so as to avoid condensation, and the support is conveyed to the drying box 32. Here, as a method for adjusting the temperature, although not shown, at an inlet of the drying box, a method for heating by a heating roller, a method for spraying hot air, a method for heating by radiant heat using infrared radiation, a heating plate, or the like can be conceivable.

[0054] The superheated water vapor drying unit 29 can vaporize and dry the high boiling point solvent included in the image forming layer coating film by giving the vapor of the solvents to the coating film surface in the vicinity of the image forming layer coating film applied to the support 16. Here, in the present embodiment, superheated water vapor is used as the vapor of the solvent.

[0055] Figure 3 is a schematic diagram showing an example of a superheated water vapor feeder 80 that feeds the vapor of the water solvent to the superheated water vapor drying unit 29. First, water that passes through a water softener 62 is fed to a boiler 64, and the fed water is changed into water vapor by the boiler 64. Foreign substances are removed from the water vapor by a separator filter 66, and then, the water vapor is changed into superheated water vapor by a superheated water vapor generator 68 through a pressure reducing valve 70. The water vapor is adjusted at a desired flow rate by a vapor flow meter 72, and is fed to the superheated water vapor drying unit 29. Here, for example, as the boiler 64, a simplified once-through steam boiler ME-40 made by Miura Co., Ltd. can be suitably used. As the separator filter 66, a separate filter SF-1 made by TLV Co., Ltd. can be suitably used. As the superheated water vapor generator 68, a superheated water vapor generator Super-Hi 70W made by Dai-Ichi High Frequency Co., Ltd. can be suitably used. Preferably, the superheated water vapor thus produced is fed to the superheated water vapor drying unit 29.

[0056] Then, preferably, the superheated water vapor thus produced is mixed with hot air of a hot air feeder 60, and fed to the superheated water vapor drying unit 29, as shown in Figure 2.

[0057] As shown in Figure 4, the superheated water vapor drying unit 29 is formed of a drying box 32 that accommodates the support 16. A vapor spray nozzle 34 is provided within the drying box 32. In addition, preferably, an exhaust port 36 for discharging the water vapor within the drying box 32 to an outside of the drying box 32 is provided. A configuration in order to discharge the water vapor to the outside of the drying box 32 is not limited to that shown in Figure 4, and exhaust means may be provided in an inlet 32a and outlet 32b for the support 16. An inner wall of the drying box 32 is preferably heated. As a method for heating the inner wall of the drying box 32, a structure in which a heat insulator is used and an inner wall is insulated by drying hot air, a vacuum insulation structure having an vacuum between an inner wall and an outer wall, a double wall structure in which warm water or vapor pass between an inner wall and an outer wall, or a method for actively heating an inner wall by heating wire may be used in order to prevent heat dissipation. At this time, the inner wall has a temperature not less than the dew point in the drying box 32. As a material for the drying box 32, SUS (304, 306, 316, and the like) and iron (SECC and the like), for example, are preferable. Glass wool, rock wool, and ALK24, and the like are preferable as a material for the heat insulator. As an insulating method, ceramic spraying, paint by a coating containing ceramic, and the like are preferable. An amount of the superheated water vapor is not less than 50 g/m³ and not more than 600 g/m³, and preferably not less than 100 g/m³ and not more than 400 g/m³. A temperature of the superheated water vapor is (hot air drying temperature) ± 20°C, and preferably the drying temperature ± 5°C. A dryness of the vapor is not less than 95%, and preferably not less than 98%.

[0058] A heating temperature to heat the support 16 and the drying box 32 is preferably not less than a temperature of (predetermined temperature T - 5(°C)). Because the support and the drying box are heated to be (predetermined temperature T - 5(°C)) ore more, it is possible to suppress condensation on the coating film, abnormal appearance and performance failures on the product surface caused by falling and adhesion of the condensed droplets onto the coating film within the drying box, and apparatus failures caused by adhesion of the droplets onto peripheral devices.

[0059] Here, the predetermined temperature T (°C) is preferably T = 16 × X^0.286 when a fed vapor amount within the drying box is X (g/m³). When 100% of humidity is expressed as a vapor amount of saturation absolute humidity, the fed vapor amount X is approximately 590 g/m³ at 100°C, approximately 2475 g/m³ at 150°C, and approximately 7330 g/m³ at 200°C, for example. Accordingly, when a certain amount of vapor (the fed vapor amount X) is fed, it is necessary to adjust the temperature T of the support so that the humidity may not be 100%. For example, when 590 g/m³ of vapor is fed, the temperature T of the support is preferably not less than 100°C.

[0060] As shown in Figures 5A to 5C, the inlet 32a and the outlet 32b of the drying box 32 are preferably sealed in order to prevent leakage of the superheated water vapor and inflow of an open air. As a method for preventing leakage of the superheated water vapor and inflow of an external air, a method for air sealing the inlet and outlet for the support in the drying box by hot air, or a method of preventing leakage of the vapor by a roll or a windshield board are preferably used. In the case of air sealing, it is preferred that drying air has a dew point of 5 to 15°C and an air velocity of not less than 5 m/s.

[0061] Figure 5A shows a case of sealing by hot air 38. Flow of the hot air 38 can prevent the vapor from diffusing and passing in sealing. Figure 5B shows a case of sealing by the hot air 38 and a windshield board 40. This can physically narrow an opening from which the vapor leaks to an outside. Figure 5C shows a case of sealing by the hot air 38 and a roll 42. These sealing methods can also be used in combination thereby to seal the heated vapor at a constant temperature within the apparatus more effectively.

[0062] Further, the vapor spray nozzle 34 is preferably insulated. In that case, a structure in which the vapor spray nozzle 34 is insulated by a heat insulator or a dual structure (a heating medium is flown) is used. The vapor spray nozzle 34 also has a structure enabling to uniformly spray the vapor in a width direction of the vapor spray nozzle. A blow-off exit of the vapor spray nozzle 34 has any shape such as a slit, in-series holes, random holes (punching metal structure), and the like. In order to prevent condensation and adhesion of water droplets, the vapor spray nozzle 34 preferably has a double tube structure or a heat insulated structure. Moreover, a structure having a uniform nozzle internal pressure and no blows-off distribution in the width direction is used. A blow-off angle to the support 16 to be used can be vertical or parallel to the support 16. When the support is conveyed at a high speed (not less than 30 m/min), the vapor is preferably blown vertical to the support at a high air velocity (not less than 5 m/sec).

[0063] The temperature of the support 16 may be actively adjusted by radiation, radiation, thermal conduction, and the like. Figure 6 shows an example of a method for controlling the temperature of the support 16 to be the dew point or more within the drying box 32. Jacket type heating rollers 46, 46... are provided so as to contact the support 16 within the drying box 32. Thus, since the temperature of the support when conveyed to the drying box is controlled to be the dew point or more within the drying box, water droplets on the coating film caused by the superheated water vapor can be prevented.

[0064] As shown in Figure 7, grooves or gutters 44 are preferably provided on an internal ceiling surface of the drying box 32 at approximately an equal interval and parallel to the traveling direction of the support. In addition, the ceiling surface is preferably inclined so that the water droplets may easily flow through the grooves or gutters 44. The humidity and the dew point within the drying box 32 may change due to various factors such as insufficient heating of each place at the time of start of the line, stopping of the line accompanied by stopping of heating of each place, and switching of drying conditions or a drying solvent to a different one, and the like. Therefore, even if the water droplets adhere onto the inner surface of the drying box, the grooves or gutters provided on the internal ceiling surface of the drying box at approximately an equal interval can prevent the water droplets from adhering onto the support. The ceiling surface is preferably inclined so that the water droplets may easily flow through the grooves or gutters 44.

[0065] Moreover, although not shown, preferably, in the drying box 32, the support 16 is provided so that the coating film surface of the support 16 may be vertical or face downward, and the vapor spray nozzle is provided in a position where the superheated water vapor is given to the coating film from under the coating film. Even if the water droplets adhere onto the vapor spray nozzle, adhesion of the water droplets onto the support can be avoided, therefore preventing abnormal appearance on the product surface and the like.

[0066] The heated water vapor is discharged to an outside of the drying box 32 from the exhaust port 36 with the high boiling point solvent contained in the coating film. The superheated water vapor is preferably recovered and aggregated by a heat exchange mechanism to separate water from the high boiling point solvent for recovery and reuse.

[0067] As mentioned above, according to the method for drying a coating film and the process for producing a lithographic printing plate precursor according to the present invention, it is possible to suppress performance failures caused by foreign substances on the product surface or abnormal appearance and performance failures caused by adhesion of the droplets in the case where the solvent of the coating liquid is dried while the vapor of the solvent having a boiling point lower than that of the solvent of the coating liquid is given to the coating film with the vapor spray nozzle within the drying box.

[0068] Preferably, when conveyance of the support 16 is started, the drying box 32 is heated at a temperature not less than 100°C by hot air, and then, the superheated water vapor is supplied; when conveyance of the support 16 is ended, supply of the superheated water vapor to the drying box 32 is stopped, and then, the drying box 32 is cooled. When conveyance of the support 16 is started, the drying box 32 is heated at a temperature not less than 100°C by hot air, and then, the superheated water vapor is supplied; when conveyance of the support 16 is ended, supply of the superheated water vapor to the drying box 32 is stopped, and then, the drying box 32 is cooled. Thereby, the water droplets are harder to adhere, so that it is possible to suppress abnormal appearance and performance failures produced in peripheral devices or on the product surface.

[0069] Here, instead of the vapor spray nozzle as shown in Figures 4 to 7, a plurality of vapor spray nozzles 34' each of which is a nozzle standalone type may be provided as shown in Figure 8A, for example. The vapor spray nozzle 34' in this case preferably has a heat insulation structure such as a double pipe as shown in Figure 8B. The vapor spray nozzle may be a two-fluid nozzle. Here, the two-fluid nozzle is a spray nozzle that grinds and atomizes a liquid of a low boiling point solvent (water in the present invention) by a high-speed air flow such as compressed air, and sprays a fine mist at a low pressure. Known two-fluid nozzles can be used as such a two-fluid nozzle.

[0070] In the present embodiment, an example in which the hot air drying unit 28, the superheated water vapor drying unit 29, and the cooling unit 30 are sequentially disposed in the conveying direction of the support 16 has been shown. However, the present invention will not be limited to this.

[0071] Moreover, in the present embodiment, the case where the superheated vapor is superheated water vapor has been described. As long as a solvent has a boiling point lower than that of the high boiling point solvent of the coating liquid, however, the same description is true to a case of superheated vapor obtained by overheating the solvent.

[0072] Next, various materials used for the present embodiment will be described.

[A support]

[0073] In the present invention, the support is not limited to a band-like material. Metals, resins, papers, cloths and the like having a shape other than band-like, are included.

[0074] An aluminum plate used for a lithographic printing plate precursor according to the present embodiment is made of a metal mainly including aluminum having dimensional stability, and is made of aluminum or an aluminium alloy. Other than a pure aluminum plate, an alloy plate mainly including aluminum and including a small amount of a different element, and a plastic film or paper on which aluminum or an aluminium alloy is laminated or vapor-deposited can also be used. A composite sheet obtained by bonding an aluminium sheet onto a polyethylene terephthalate film can also be used.

[0075] A composition of the aluminum plate used for the present embodiment is not limited in particular, and a pure aluminum plate is suitably used. It is difficult to produce a fully pure aluminum from the viewpoint of refining techniques. Accordingly, an aluminum plate slightly containing a different element may be used. For example, known materials described in Aruminiumu Handobukku (Aluminum Handbook), fourth edition (Japan Light Metal Association (1990)), specifically, aluminum alloy plates such as JIS A1050, JIS A1100, JIS A3003, JIS A3004, JIS A3005, and international registration alloy 3103A can be used where relevant, for example. An aluminium alloy that contains 99.4 to 95% by mass of aluminum and includes not less than three kinds selected from the group consisting of Fe, Si, Cu, Mg, Mn, Zn, Cr, and Ti, and an aluminum plate in which an aluminum scrap material or secondary ingot is used can also be used.

[0076] An aluminum content of the aluminum alloy plate is not limited in particular, and the aluminum content may be 95 to 99.4% by mass. Further, preferably, this aluminum plate contains not less than three kinds of different elements selected from the group consisting of Fe, Si, Cu, Mg, Mn, Zn, Cr, and Ti in the following ranges. This enables to obtain aluminum with fine crystal grains. Fe: 0.20 to 1.0% by mass, Si: 0.10 to 1.0% by mass, Cu: 0.03 to 1.0% by mass, Mg: 0.1 to 1.5% by mass, Mn: 0.1 to 1.5% by mass, Zn: 0.03 to 0.5% by mass, Cr: 0.005 to 0.1% by mass, and Ti: 0.01 to 0.5% by mass.

[0077] The aluminum plate may also contain an element such as Bi and Ni as well as inevitable impurities.

[0078] A method for producing an aluminum plate may be either of a continuous casting method and a DC casting method. An aluminum plate produced by the DC casting method in which intermediate annealing and soaking treatment are omitted can also be used. An aluminum plate having depressions and projections given by sandwich rolling, transfer, and the like in finish rolling can also be used. The aluminum plate used for the present embodiment may be an aluminum support that is a continuous band-like sheet material or plate material, or may be sheet-like sheet cut into a size corresponding to a lithographic printing plate precursor to be shipped as a product.

[0079] The aluminum plate used for the present embodiment usually has a thickness of approximately 0.05 mm to 1 mm, and preferably a thickness of 0.1 mm to 0.5 mm. This thickness can be changed where relevant according to a size of a printing machine, a size of a printing plate, and a request by a user.

[0080] In the process for producing a support for a lithographic printing plate in the present embodiment, the support for a lithographic printing plate is obtained by performing surface treatment including at least surface roughening treatment, anodizing treatment, and particular sealing treatment on the above-mentioned aluminum plate. This surface treatment may further include various kinds of treatments. At various steps of the present embodiment, alloy components of the aluminum plate to be used are eluted in a treatment solution used for the step. Accordingly, the treatment solution may contain the alloy components of the aluminum plate. Particularly, the treatment solution is preferably used by adding those alloy components to the treatment solution into a steady state before treatment.

[0081] As the above-mentioned surface treatment, alkali etching treatment or desmut treatment is preferably performed before electrolysis surface roughening treatment. It is also preferable that the alkali etching treatment and the desmut treatment are performed in this order. The alkali etching treatment or desmut treatment is preferably performed after the electrolysis surface roughening treatment. It is also preferable that the alkali etching treatment and the desmut treatment are performed in this order. The alkali etching treatment after the electrolysis surface roughening treatment may be omitted. It is also preferable that mechanical surface roughening treatment is performed before these treatments. The electrolysis surface roughening treatment may be performed not less than twice. It is also preferable that subsequently, anodizing treatment, sealing treatment, hydrophilization treatment, and the like are performed.

[A low boiling point solvent]

[0082] A low boiling point solvent used for the present embodiment preferably has a boiling point of not less than 30°C and not more than 130DC. Examples of such a low boiling point solvent include the followings, but the present invention is not limited to these. The boiling point is shown within parentheses.

[0083] Alcohols such as methanol (64.5°C to 64.65DC), ethanol (78.32°C), n-propanol (97.15°C), isopropanol (82.3°C), n-butanol (117.7°C), and isobutanol (107.9 °C); ethers such as ethyl ether (34.6°C) and isopropyl ether (68.27°C); ketones such as acetone (56.2°C), methyl ethyl ketone (79.59°C), methyl-n-propyl ketone (103.3°C), methyl isobutyl ketone (115.9°C), and dimethyl ketone (102.2°C); esters such as methyl acetate (57.8°C), ethyl acetate (77.1°C), acetic acid-n-propyl (101.6°C), and acetic acid-n-butyl (1265°C); hydrocarbons such as n-hexane (68742°C) and cyclohexane (80.738°C); and water.

[A high boiling point solvent]

[0084] A high boiling point solvent used for the present embodiment preferably has a boiling point of not less than 150°C. Examples of such a high boiling point solvent include the followings, but the present invention is not limited to these. The boiling point is shown within parentheses.

[0085] γ-butyl lactone (204°C), acetamide (222°C), 1,3-dimethyl-2-imidazolidinone (225.5°C), N,N-dimethylformamide (153°C), tetramethyl uric acid (175°C to 177°C), nitrobenzene (211.3°C), formamide (210.5°C), N-methyl pyrrolidone (202°C), N,N-dimethylacetamide (166°C), and dimethyl sulfoxide (189°C).

<An image forming layer>

[0086] In the present invention, a lithographic printing plate precursor can be obtained by providing an image forming layer on the treated layer formed as mentioned above.

[0087] The image forming layer provided here may be any known image forming layer in the present invention, and is preferably an image forming layer allowing recording in a heat mode or a photon mode. From the viewpoint of an effect, the image forming layer is preferably an image forming layer allowing image formation by heat mode exposure using an infrared laser and the like.

[0088] The image forming layer may have a single layer structure, or may have a laminated layer structure formed of a plurality of layers.

[0089] Hereinafter, various kinds of lithographic printing plate precursors having a different kind of the image forming layer will be described.

(An infrared laser recording type lithographic printing plate precursor)

[0090] A lithographic printing plate precursor that allows image formation by an infrared laser and is suitable for the present invention will be described. For the lithographic printing plate precursor allowing image formation by an infrared laser, a known image recording method is selected arbitrarily, such as a method for using an image forming layer of a negative type or a positive type for which a material whose solubility to an alkaline aqueous solution changes by infrared laser exposure is used, and a method for using an image forming layer that contains a hydrophobized precursor that can form an ink receptiveness region so that a hydrophobized region is formed in a portion exposed by an infrared laser.

[0091] First, an image forming layer of a positive type or a negative type will be described. In such an image forming layer, an image is exposed by an infrared laser, and developed by an alkaline aqueous solution. The image forming layer is classified into two: a negative type in which alkaline development properties deteriorate by irradiation with active light so that the irradiated (exposed) part serves as an image area, and a positive type in which development properties improve conversely so that the irradiated (exposed) part serves as a non-image area.

[0092] Examples of the positive type image forming layer include interaction releasing system (heat-sensitive positive) image forming layers, known acid catalyst decomposition system image forming layers, and o-quinone diazide compound containing system image forming layers. These become soluble to water or alkaline water by such action that a bond of a high molecular compound that forms the layer is dissociated by production of acids or heat energy themselves by irradiation with light or heating. As a result, these image forming layers are removed by development to form a non-image area.

[0093] Examples of the negative type image forming layers include known acid catalyized crosslinking system (also including cationic polymerization) image forming layers and polymerization curing system image forming layers. Among these, some are cured to form an image area by a crosslinking reaction of a compound that forms an image forming layer where acids produced by irradiation with light or heating serves as a catalyst, and some are cured to form an image area by progression of a polymerization reaction of a polymerizable compound by radicals produced by irradiation with light or heating.

[0094] Although the particular intermediate layer in the present invention shows a high effect even when any of the above-mentioned image forming layers is formed, the particular intermediate layer is suitably used for the positive type image forming layer.

[0095] Hereinafter, each image forming layer will be described in detail.

1. The positive type image forming layer

[0096] A preferable aspect of the present invention includes a lithographic original plate having a positive type image forming layer in which an alkali soluble resin and a sulfonium compound or an ammonium compound are contained, not less than 50% by mass of the alkali soluble resin is a novolac resin, and an image forming layer allowing recording by an infrared laser is provided. As a more preferable aspect, this positive type image forming layer contains (A) an infrared absorber described later in order to increase sensitivity. The positive type image forming layer may have a single layer, or may have a laminated layer structure formed of a plurality of image forming layers.

[A novolac type phenol resin]

[0097] First, a novolac type phenol resin will be described. The novolac resin means a resin obtained by polycondensing at least one kind of phenol with at least one kind of aldehydes or ketones under an acid catalyst.

[0098] Here, examples of phenols include phenol, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol, o-ethylphenol, m-ethylphenol, p-ethylphenol, propylphenol, n-butylphenol, tert-butylphenol, 1-naphthol, 2-naphthol, pyrocatechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol, phloroglucinol, 4,4'-biphenyldiol, 2,2-bis(4'-hydroxyphenyl)propane. Examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and furfural. Examples of ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0099] Preferably, a polycondensate of phenols selected from phenol, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol, and resorcinol with aldehydes selected from formaldehyde, acetaldehyde, and propionaldehyde or ketones is preferable. Particularly, a polycondensate of mixed phenols of 40 to 100:0 to 50:0 to 20:0 to 20:0 to 20 in a mole ratio in a mixing ratio of m-cresol:p-cresol:2,5-xylenol:3,5-xylenol:resorcinol with formaldehyde, or a polycondensed body of (mixed) phenols of 0 to 100:0 to 70:0 to 60 in a mole ratio in a mixing ratio of phenol:m-cresol:p-cresol with formaldehyde is preferable.

[0100] As these novolac resins, novolac resins having 500 to 20,000 of a polystyrene-converted weight average molecular weight by gel permeation chromatography measurement (hereinafter, referred to as only "weight average molecular weight") are preferably used. Novolac resins having 1,000 to 15,000 of a weight average molecular weight are more preferably used, and novolac resins having 3,000 to 12,000 of a weight average molecular weight is particularly preferably used. The weight average molecular weight within this range is preferable for sufficient film-forming properties and excellent alkaline development properties of an exposed portion.

[0101] When the novolac resin is used as a binder resin for the image forming layer, only one kind may be used or not less than two kinds may be used in combination. All of the binder resins may be the novolac resin, or other resin can also be used in combination. Further, when other resin is used in combination, the novolac resin is preferably a main binder. A ratio of the novolac resin in the binder resin (alkali soluble resin) that forms the image forming layer is preferably not less than 50% by mass, and more preferably within the range of 65 to 99.9% by mass.

[0102] As the binder resin that can be used in combination, alkali soluble resins that are usually used, insoluble to water and soluble to alkalis, and have acidic groups at least in one of a principal chain and a side chain in a polymer can be used. Phenol resins other than novolac resins, for example, resole resins, polyvinyl phenol resins, acrylic resins having phenolic hydroxyl groups, and the like are preferably used. Specific examples of the resins that can be used in combination can include polymers described in Japanese Patent Application Laid-Open No. 11-44956, and Japanese Patent Application Laid-Open No. 2003-167343, for example.

[A light-and-heat conversion agent]

[0103] The image forming layer in the present invention preferably contains light-to-heat conversion agent. The light-to-heat conversion agent used here has no limitation on an absorption wavelength region in particular, and any substance can be used as the light-to-heat conversion agent as long as it is a substance that absorbs light energy irradiation to generate heat. From the viewpoint of conformity to an easily available high output laser, preferable examples of the light-to-heat conversion agent include an infrared absorbing dye or pigment having an absorption maximum at a wavelength of 760 nm to 1200 nm.

[0104] As the dye, known dyes such as commercially available dyes and ones described in documents such as "Senryo Binran (Dye Handbook)" (edited by Society of Synthetic Organic Chemistry, Japan, published in Showa 45 (1970)) can be used. Specifically, examples of the dye include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinonimine dyes, methine dyes, cyanine dyes, squarylium pigments, pyrylium salts, metal thiolate complexes, oxonol dyes, diimonium dyes, aminium dyes, and croconium dyes.

[0105] Examples of preferable dyes include cyanine dyes described in Japanese Patent Applicatian Laid-Open Nos. 58-125246, 59-84356, 59-202829, 60-78787; methine dyes described in Patent Application Laid-Open Nos. 58-173696, 58-181690, 58-194595; naphthoquinone dyes described in Patent Application Laid-Open Nos. 58-112793, 58-224793, 59-48187, 59-73996, 60-52940, 60-63744; squarylium pigments described in Patent Application Laid-Open No. 58-112792: and cyanine dyes described in UK Patent No. 434,875.

[0106] A near-infrared absorption sensitizer described in U.S. Patent No. 5,156,938 is also suitably used. A substituted arylbenzo(thio)pyrylium salt described in U.S. Patent No. 3,881,924, a trimethine thiapyrylium salt described in Japanese Patent Application Laid-Open No. 57-142645 (U.S. Patent No. 4,327,169), pyrylium compounds described in Japanese Patent Application Laid-Open Nos. 58-181051, 58-220143, 59-41363, 59-84248, 59-84249, 59-146063, and 59-146061, a cyanine dye described in Japanese Patent Application Laid-Open No. 59-216146, a pentamethine thiopyrylium salt described in U.S. Patent No. 4,283,475, and pyrylium compounds disclosed in Japanese Examined Application Publication Nos. 05-13514 and 05-19702 are also preferably used.

[0107] Another preferable examples of the dye can include a near infrared absorption dye described as the formula (I) and the formula (II) in U.S. Patent No. 4,756,993.

[0108] Among these dyes, examples of particularly preferable dyes include cyanine dyes, phthalocyanine dyes, oxonol dyes, squarylium pigments, pyrylium salts, thiopyrylium dyes, and nickel thiolate complexes. Further, compounds described on pages 26 to 38 in Japanese Patent Application Laid-Open No. 2005-99685 are preferable for high light-to-heat conversion efficiency. Particularly, a cyanine dye represented by the general formula (a) in Japanese Patent Application Laid-Open No. 2005-99685 is most preferable because the cyanine dye provides high interaction with an alkali soluble resin and excels in stability and economy when the cyanine dye is used as a photosensitive composition of the present invention.

[A decomposable dissolution suppressing agent]

[0109] A decomposable dissolution suppressing agent can be further added to the positive type image forming layer in the present invention. Particularly, a substance (decomposable dissolution suppressing agent) such as an onium salt, an o-quinone diazide compound, and alkyl ester sulfonate, which is thermally decomposable and substantially reduces the solubility of an alkali soluble resin when the substance is not decomposed, is preferably used in combination from the viewpoint of improvement in a dissolution suppressing ability of an image area in a developer. As the decomposable dissolution suppressing agent, onium salts such as sulfonium salts, ammonium salts, diazonium salts, and iodonium salts, and o-quinone diazide compounds are preferable. Sulfonium salts, ammonium salts, and diazonium salts are more preferable.

[0110] Suitable examples of onium salts used in the present invention include: ammonium salts described in U.S. Patent Nos. 4,069,055, 4,069,056, and Japanese Patent Application Laid-Open Nos. 03-140140, 2006-293162, and 2004-117546; and sulfonium salts described in J. V. Crivello et al., Polymer J. 17, 73 (1985), J. V. Crivello et al., J. Org. Chem., 43, 3055 (1978), W.R. Watt et al., J. Polymer Sci., Polymer Chem. Ed., 22, 1789 (1984), J. V. Crivello et al., Polymer Bull., 14, 279 (1985), J. V. Crivello et al., Macromorecules, 14(5), 1141 (1981), J. V. Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 2877 (1979), European Patent Application Nos. 370,693, 233,567, 297,443, and 297,442, U.S. Patent Nos. 4,933,377, 3,902,114, 5,041,358, 4,491,628, 4,760,013, 4,734,444, and 2,833,827, DE Patents Nos. 2,904,626, 3,604,580, and 3,604,581, and Japanese Patent Application Laid-Open Nos. 2006-293162 and 2006-258979.

[0111] Other suitable onium salts include diazonium salts shown in S. I. Schlesinger, Photogr. Sci. Eng., 18, 387 (1974), T. S. Bal et al., Polymer, 21, 423 (1980), Japanese Patent Application Laid-Open No. 05-158230, the general formula (1) described in Japanese Patent Application Laid-Open No. 05-158230, the general formula (1) described in Japanese Patent Application Laid-Open No. 11-143064, and the general formula (1) described in Japanese Patent Application Laid-Open No. 11-143064.

[0112] Other examples of preferable onium salts include phosphonium salts described in D. C. Necker et al., Macromolecules 17, 2468 (1984), C. S. Wen et al., Teh, Proc. Conf. Rad. Curing ASIA, p. 478, Tokyo, Oct. (1988), U.S. Patent Nos. 4,069,055 and 4,069,056; iodonium salts described in J. V. Crivello et al., Macomorecules, 10(6), 1307 (1977), Chem. & Eng. News, Nov. 28, p. 31 (1988), European Patent No. 104,143, U.S. Patent Nos. 5,041,358, and 4,491,628, and Japanese Patent Application Laid-Open Nos. 02-150848 and 02-296514; selenonium salts described in J. V. Crivello et al., Macromorecules, 10(6), 1307 (1977), J. V. Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 1047 (1979); and arsonium salts described in C. S. Wen et al., Teh, Proc. Conf. Rad. Curing ASIA, p. 478, Tokyo, Oct. (1988).

[0113] Examples of counter ions for the onium salts include tetrafluoroboric acid, hexafluorophosphoric acid, triisopropyl naphthalenesulfonic acid, 5-nitro-o-toluenesulfonic acid, 5-sulfosalieylic acid, 2,5-dimethylbenzencsulfonic acid, 2,4,6-trimethyl benzenesulfonic acid, 2-nitrobenzenesulfonic acid, 3-chlorobenzenesulfonic acid, 3-bromobenzenesulfonic acid, 2-fluorocaprylnaphthalenesulfonic acid, dodecylbenzenesulfonic acid, 1-naphthol-5-sulfonic acid, 2-methoxy-4-hydroxy-5-benzoyl-benzenesulfonic acid and p-toluenesulfonic acid. Among these, alkyl aromatic sulfonic acids such as hexafluorophosphoric acid, triisopropylnaphthalenesulfonic acid, and 2,5-dimethylbenzenesulfonic acid are particularly suitable.

[0114] These onium salts may be used alone, or may be used as a compound of two or more of these onium salts. When the image forming layer has a laminated layer structure, the onium salts may be added only to a single layer, or may be added to a plurality of layers. Alternatively, a compound made of two or more kinds of the onium salts may be added to individual layers.

[0115] Suitable examples of quinone diazides can include o-quinonediazide compounds. The o-quinone diazide compounds used for the present invention are a compound having at least one o-quinone diazide group, and have alkali solubility that increases by thermal decomposition. The compounds having various structures can be used. In other words, o-quinone diazide helps dissolution of a photosensitive material system by an effect that o-quinone diazide is thermally decomposed to deprive a dissolution suppressing ability of the binder and by an effect that o-quinone diazide itself changes to an alkali soluble substance. The o-quinone diazide compound used for the present invention can be a compound described on pages 339 to 352 in "Light-Sensitive Systems" authored by J. Cohser (John & Wiley & Sons. Inc.), for example. Particularly, sulfonate or sulfonamide of o-quinone diazide obtained by reacting with various aromatic polyhydroxy compounds or aromatic amino compound is suitable. Moreover, an ester of benzoquinone(1,2)-diazidosulfonic acid chloride or naphthoquinone-(1,2)-diazido-5-sulfonic acid chloride and a pyrogallol-acetone resin as described in Japanese Examined Application Publication No. 43-28403, and an ester of benzoqainone-(1,2)-diazidosulfonic acid chloride or naphthoquinone-(1,2)-diazido-5-sulfonic acid chloride and a phenol-formaldehyde resin as described in U.S. Patent Nos. 3,046,120 and 3,188,210 are also suitably used.

[0116] Further, an ester of naphthoquinone-(1,2)-diazido-4-sulfonic acid chloride and a phenol formaldehyde resin or a cresol-formaldehyde resin, and an ester of naphthoquinone-(1,2)-diazido-4-sulfonic acid chloride and a pyrogallol acetone resin are also suitably used. Other useful o-quinone diazide compounds are reported in a large number of patents, and are known. Examples of such o-quinone diazide compounds include those described in examined or unexamined patent documents such as Japanese Patent Application Laid-Open Nos. 47-5303, 48-63802, 48-63803, 48-96575, 49-38701, and 48-13354, and Japanese Examined Application Publication Nos. 41-11222, 45-9610, and 49-17481, and descriptions such as U.S. Patent Nos. 2,797,213, 3,454,400, 3,544,323, 3,573,917, 3,674,495, and 3,785,825, U.K. Patent Nos. 1,227,602, 1,251,345, 1,267,005, 1,329,888, and 1,330,932, and DE Patent No. 854,890.

[0117] An amount of an onium salt and/or an o-quinone diazide compound to be added as a decomposable dissolution suppressing agent is preferably 0.1 to 10% by mass based on the total solid content of the image forming layer according to the present invention, more preferably 0.1 to 5% by mass, and particularly preferably a range of 0.2 to 2% by mass. These compounds can be used alone, or may be used in combination of several kinds.

[0118] An amount of an additive to be added other than the o-quinone diazide compound is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and particularly preferably 0.1 to 1.5% by mass. The additive and the binder used for the present invention are preferably contained in the same layer.

[0119] A non-decomposable dissolution suppressing agent may also be used in combination. Preferable examples of such a dissolution suppressing agent can include sulfonic esters, phosphate esters, aromatic carboxylic acid esters, aromatic disulfones, carboxylic acid anhydrides, aromatic ketones, aromatic aldehydes, aromatic amines, aromatic ethers described in detail in Japanese Patent Application Laid-Open No. 10-268512; an acid coloring dye having a lactone skeleton, an N,N-diaryl amide skeleton, and a diaryl methylimino skeleton and serving as a colorant, which is described in detail in Japanese Patent Application Laid-Open No. 11-190903, and a nonionic surfactants described in detail in Japanese Patent Application Laid-Open No. 2000-105454.

[Other additives]

[0120] In the image forming layer according to the present invention, a polymer having a (meth)acrylate monomer having 2 or 3 perfluoroalkyl groups having a carbon number of 3 to 20 in a molecule as a polymerization component can be used in combination as described in Japanese Patent Application Laid-Open No. 2000-187318 in order to enhance reinforcement of discrimination (distinctiveness of hydrophobacity/hydrophilicity) and resistance against surface scratches of an image An amount of such a compound to be added is preferably 0.1 to 10% by mass based on the total solid content of the image forming layer according to the present invention, and more preferably 0.5 to 5% by mass.

[0121] In order to give resistance against scratches, a compound that reduces a surface static friction coefficient can also be added into the image forming layer according to the present invention. Specific examples of such a compound can include esters containing a long chain alkyl carboxylic acid used in U.S. Patent No. 6,117,913. An amount of such a compound to be added is preferably 0.1 to 10% by mass based on the total solid content of the image forming layer according to the present invention, and more preferably 0.5 to 5% by mass.

[0122] The image forming layer according to the present invention may include a compound having an acidic group with a low molecular weight when necessary. Examples of the acidic group can include a sulfonic group, a carboxylic acid group, and a phosphate group. Among these, a compound having a sulfonic group is preferable. Specific examples of such a compound can include aromatic sulfonic acids and aliphatic sulfonic acids such as p-toluenesulfonic acid and naphthalene sulfonic acid.

[0123] In addition, in order to improve sensitivity, cyclic anhydrides, phenols, and organic acids can also be used in combination. As the cyclic anhydrides, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 3,6-endoxy-Δ4-tetrahydrophthalic anhydride, tetrachlorphthalic anhydride, maleic anhydride, chlormaleic anhydride, α-phenylmaleic anhydride, succinic anhydride, a pyromellitic dianhydride can be used as described in U.S. Patent No. 4,115,128. Examples of phenols include bisphenol A, p-nitrophenol, p-ethoxy phenol, 2,4,4'-trihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 4-hydxoxybenzophenone, 4,4',4"-trihydroxytriphenylmethane, and 4,4',3",4"-tetrahydroxy-3,5,3',5'-tetramethyl triphenylmethane. Further, examples of organic acids include sulfonic acids, sulfinic acids, alkyl sulfuric acids, phosphonic acids, phosphate esters, and carboxylic acids described in Japanese Patent Application Laid-Open Nos. 60-88942, 02-96755, and the like. Specific examples include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, p-toluene sulfinic acid, ethyl sulfuric acid, phenyl phosphonic acid, phenyl phosphinic acid, phenyl phosphate, diphenyl phosphate, benzoic acid, isophthalic acid, adipic acid, p-toluylic acid, 3,4-dimethoxybenzoic acid, phthalic acid, terephthalic acid, 4-cyclohexene-1,2-dicarboxylic acid, erucic acid, lauric acid, n-undecane acid, and ascorbic acid.

[0124] When the above-mentioned cyclic anhydride, phenols, and organic acids are added into the image forming layer, a ratio of these in the image forming layer is preferably 0.05 to 20% by mass, more preferably 0.1 to 15% by mass, and particularly preferably 0.1 to 10% by mass.

[0125] When a coating liquid for the image forming layer according to the present invention is prepared, a nonionic surfactant described in Japanese Patent Application Laid-Open Nos. 62-251740 and 03-208514, an amphoteric surfactant described in Japanese Patent Application Laid-Open Nos. 59-121044 and 04-13149, a siloxane based compound described in EP No. 950517, and a monomer copolymer containing fluorine described in Japanese Patent Application Laid-Open No. 11-288093 can be added in order to enhance treatment stability to development conditions.

[0126] Specific examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, and polyoxyethylene nonylphenyl ether. Specific examples of the amphoteric surfactant include alkyl di(aminoethyl)glycine, alkyl polyamino ethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethyl imidazolinium betaine, and an N-tetradecyl-N,N-betaine type (for example, trade name: AMOGEN K, made by Dai-Ichi Kogyo Seiyaku Co., Ltd.).

[0127] As the siloxane based compound, a block copolymer of dimethylsiloxane and polyalkylene oxide is preferable. Specific examples can include polyalkylene oxide denatured silicone such as DBE-224, DBE-621, DBE-712, DBP-732, DBP-534, made by Chisso Corp., and Tego Glide 100 made by Tego Co. in Germany.

[0128] A ratio of the above-mentioned nonionic surfactant and amphoteric surfactant in the image forming layer is preferably 0.05 to 15% by mass, and more preferably 0.1 to 5% by mass.

[0129] A printing-out agent for obtaining a visible image immediately after heating by exposure and a dye and a pigment as an image coloring agent can be added into the image forming layer of the lithographic printing plate precursor according to the present invention.

[0130] Typical examples of the printing-out agent can include a combination of a compound (optically acid-releasing agent) that releases an acid by heating by exposure and an organic dye that can form a salt. Specific examples include a combination of o-naphthoquinonediazide-4-sulfonic acid halogenide and a salt-formable organic dye described in Japanese Patent Application Laid-Open Nos. 50-36209 and 53-8128; and a combination of a trihalomethyl compound and a salt-formable organic dye described in Japanese Patent Application Laid-Open Nos. 53-36223, 54-74728, 60-3626, 61-143748, 61-151644, and 63-58440. Examples of the trihalomethyl compound include oxazol based compounds and triazine based compounds, and both have high stability over time and provide clear printing-out images.

[0131] As the image coloring agent, other dyes can be used than the above-mentioned salt-formable organic dye. Suitable examples of the dyes including the salt-formable organic dye can include oil soluble dyes and basic dyes. Specific examples include Oil Yellow #101, Oil Yellow #103, Oil Pink #312, Oil Green BG, Oil Blue BOS, Oil Blue #603, Oil Black BY, Oil Black BS, Oil Black T-505 (these are made by Orient Chemical Industries, Co., Ltd.), Victoria Pure Blue, Crystal Violet (CI 42555), Methyl Violet (CI 42535), Ethyl Violet, Rhodamine B (CI 145170B), Malachite Green (CI 42000), and Methylene Blue (CI 52015). Particularly, a dye described in Japanese Patent Application Laid-Open No. 62-293247 is preferable. These dyes can be added in a ratio of 0.01 to 10% by mass and preferably in a ratio of 0.1 to 3% by mass based on the total solid content of the image forming layer. In order to give flexibility to a coating, and the like, a plasticizer is further added into the image forming layer coating liquid according to the present invention, when necessary. For example, butyl phthalyl, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phtalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate, oligomeric and polymeric acrylic acid or methacrylic acid, and the like are used.

[0132] Moreover, other than these, epoxy compounds, vinyl ethers, phenol compounds having a hydroxymethyl group described in Japanese Patent Application Laid-Open No. 08-276558, phenol compounds having an alkoxy methyl group, and crosslinkable compounds having an alkali dissolution suppressing action described in Japanese Patent Application Laid-Open No. 11-160860 can be added properly depending on a purpose.

[0133] The image forming layer in the image recording material according to the present invention thus obtained is excellent in film formability and film strength, and shows high alkali solubility in an exposed portion exposed by infrared rays.

2. The negative type image forming layer

2-1. A polymerization curing layer

[0134] One example of the negative type image forming layer includes a polymerization curing layer. This polymerization curing layer contains (A) an infrared absorber, (B) a radical generator (radical polymerization initiator), and (C) a radical polymerizable compound polymerized by the generated radicals to cure, and preferably contains (D) a binder polymer. The infrared absorber converts absorbed infrared radiation into heat. The heat generated at this time decomposes the radical polymerization initiator such as onium salts to generate radicals. The radical polymerizable compound is selected from compounds having at least one ethylenically unsaturated double bond, and having at least one and preferably not less than two of terminal ethylenically unsaturated bonds. A polymerization reaction occurs as a result of the generated radicals so that the radical polymerizable compound is cured.

2-2. An acid crosslinking layer

[0135] Other aspect of the image forming layer includes an acid crosslinking layer. The acid crosslinking layer contains (E) a compound that generates acids by light or heat (hereinafter, referred to as an acid generator), and (F) a compound that is crosslinked by the generated acids (hereinafter, referred to as a crosslinking agent). The acid crosslinking layer further contains (G) an alkali soluble polymer for forming a layer containing these and that can react with the crosslinking agent in the presence of acids. In this acid crosslinking layer, the acids generated by decomposition of the acid generator caused by irradiation with light or heating accelerates an action of the crosslnking agent to form a firm crosslinked structure between the cross linking agents or the cross linking agent and the binder polymer. Thereby, alkali solubility deteriorates, resulting in insolubility to a developer. At this time, in order to efficiently use energy of an infrared laser, (A) the infrared absorber is blended in the image forming layer.

[(A) An infrared absorber]

[0136] An image forming layer allowing formation of an image by an infrared laser contains the infrared absorber. The infrared absorber has no limitation in particular on the absorption wavelength region, and any substance can be used for the infrared absorber as long as it is a substance that absorbs light energy irradiation used for recording to generate heat. From the viewpoint of conformity to an easily available high output laser, however, preferable examples of the infrared absorber include infrared absorbing dyes and pigments having an absorption maximum at a wavelength of 800 nm to 1200 nm.

[0137] As the dye, known dyes such as commercially available dyes and ones described in documents such as "Senryo Binran (Dye Handbook)" (edited by Society of Synthetic Organic Chemistry, Japan, published in Showa 45 (1970)) can be used. Specifically, examples of the dye include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinonimine dyes, methine dyes, cyanine dyes, squarylium pigments, pyrylium salts, and metal thiolate complexes.

[0138] Examples of preferable dyes include cyanine dyes described in Japanese Patent Application Laid-Open Nos. 58-125246, 59-84356, 59-202829, and 60-78787; methine dyes described in Patent Application Laid-Open Nos. 58-173696, 58-181690, and 58-194595; naphthoquinone dyes described in Patent Application Laid-Open Nos. 58-112793, 58-224793, 59-48187, 59-73996, 60-52940, and 60-63744; squarylium pigments described in Patent Application Laid-Open No. 58-112792; and cyanine dyes described in UK Patent No. 434,875.

[0139] A near-infrared absorption sensitizer described in U.S. Patent No. 5,156,938 is also suitably used. A substituted arylbenzo(thio)pyrylium salt described in U.S. Patent No. 3,881,924, a trimethine thiapyrylium salt described in Japanese Patent Application Laid-Open No. 57-142645 (U.S. Patent No. 4,327,169), pyrylium based compounds described in Japanese Patent Application Laid-Open Nos. 58-181051, 58-220143, 59-41363, 59-84248, 59-84249, 59-146063, and 59-146061, a cyanine dye described in Japanese Patent Application Laid-Open No. 59-216146, a pentamethine thiopyrylium salt described in U.S. Patent No. 4,283,475, and pyrylium compounds disclosed in Japanese Examined Application Publication Nos. 05-13514 and 05-19702 are also preferably used. Another preferable examples of the dye can include a near infrared absorption dye described as the formula (I) and the formula (II) in U.S. Patent No. 4,756,993.

[0140] Preferable other examples of the infrared absorption pigment according to the present invention include a particular indolenine cyanine dye described in Japanese Patent Application-No. 2001-6326 and Japanese Patent Application-No. 2001-237840, which is exemplified below:

[0141] Among of these dyes, particularly preferable examples of the dye include cyanine dyes, squarylium pigments, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Cyanine dyes and indolenine cyanine dyes are more preferable. A particularly preferable example includes the cyanine dye represented by the following general formula (A).

[0142] In the general formula (A), X¹ designates a hydrogen atom, halogen atoms, - NPh₂, and X²-L¹ or a group shown below. Here, X² designates an oxygen atom, a nitrogen atom, or a sulfur atom, L¹ designates a hydrocarbon group having a carbon number of 1 to 12, an aromatic ring having a hetero atom, and a hydrocarbon group having a carbon number of 1 to 12 and including a hetero atom. The hetero atom designates N, S, O, halogen atoms, and Se here. Xa is defined similarly to Za described later, and Ra designates a substituent group selected from a hydrogen atom, an alkyl group, an aryl group, a substituted or non-substituted amino group, and halogen atoms.

[0143] R¹ and R² each individually designate a hydrocarbon group having a carbon number of 1 to 12. For preservation stability of the coating liquid of the image forming layer, R¹ and R² are preferably a hydrocarbon group having a carbon number of 2 or more. In addition, R¹ and R² are particularly preferably bonded to each other to form a five-membered ring or a six-membered ring.

[0144] Ar¹ and Ar² may be the same or different from each other, and designate an aromatic hydrocarbon group that may have a substituent. Preferable examples of the aromatic hydrocarbon group include the benzene ring and the naphthalene ring. Preferable examples of the substituent include a hydrocarbon group having a carbon number of 12 or less, halogen atoms, and an alkoxy group having a carbon number of 12 or less. Y¹ and Y² may be the same or different from each other, and designate a sulfur atom or a dialkyl methylene group having a carbon number of 12 or less. R³ and R⁴ may be the same or different from each other, and designate a hydrocarbon group having a carbon number of 20 or less and that may have a substituent. Preferable examples of the substituent include an alkoxy group, a carboxyl group, and a sulfo group having a carbon number of 12 or less. R⁵, R⁶, R⁷, and R⁸ may be the same or different from each other, and designate a hydrogen atom or a hydrocarbon group having a carbon number of 12 or less. For availability of a raw material, a hydrogen atom is preferable. Za^- designates a counter anion. However, Za^- is unnecessary when the cyanine dye represented by the general formula (A) has an anionic substituent within the structure and neutralization of charges is unnecessary. For preservation stability of the image forming layer coating liquid, preferable examples of Za^- include halogen ions, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ion. Particularly preferable examples include a perchlorate ion, a hexafluorophosphate ion, and an aryl sulfonate ion.

[0145] In the present invention, specific examples of the cyanine dyes that are represented by the general formula (A) and can be suitably used can include cyanine dyes described in paragraph numbers [0017] to [0019] of Japanese Patent Application Laid-Open No. 2001-133969.

[0146] Particularly preferable examples of other cyanine dyes further include particular indolenine cyanine dyes described in Japanese Patent Application Nos. 2001-6326 and 2001-237840 mentioned above.

[0147] The pigment used in the present invention includes commercially available pigments and pigments described in "Karah Indekkusu Binran (C. I.) (Handbook of Color Index)"; "Saishin Ganryo Binran (Latest Pigment Handbook)" (Japan Association of Pigment Technologies), 1977; "Saishin Ganryo Oyo Gijutsu (Latest Pigment Application Technologies)," CMC Publishing Co., Ltd., 1986; and "Insatsu Inki Gijutsu (Printing Ink Technologies)," CMC Publishing Co. Ltd., 1984.

[0148] Examples of kinds of the pigments include black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and other polymer bound pigments. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone based pigments, perylene and perinone based pigments, thioindigo based pigments, quinacridone based pigments, dioxazine based pigments, isoindolinone based pigments, quinophthalone based pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like can be used. Among these pigments, carbon black is preferable.

[0149] These pigments may be used without surface treatment, or may be subjected to surface treatment to be used. Examples of a surface treatment method include a method for coating a surface with a resin or wax, a method for attaching a surfactant, or a method for bonding an active substance (for example, a silane coupling agent, an epoxy compound, polyisocyanate, and the like) to a pigment surface. The above-mentioned surface treatment methods are described in "Kinzoku Sekken no Seishitu to Oyo (Properties and Applications of Metal Soaps)," Saiwai Shobo Co., Ltd.; "Insatsu Inki Gijutsu (Printing Ink Technologies)," CMC Publishing Co., Ltd., 1984; and "Saishin Ganryo Oyo Gijutsu (Latest Pigment Application Technologies)," CMC Publishing Co., Ltd., 1986.

[0150] From the viewpoint of stability of dispersed objects in the image forming layer coating liquid and uniformity of the image forming layer, the particle size of the pigment is preferably in the range of 0.01 µm to 10 µm, more preferably in the range of 0.05 µm to 1 µm, and particularly preferably in the range of 0.1 µm to 1 µm.

[0151] As a method for dispersing the pigment, known dispersion techniques used for ink production, toner production, and the like can be used. Examples of dispersion machines include ultrasonic dispersion machines, sand mills, attritors, pearl mills, super mills, ball mills, impellers, dispersers, KD mills, colloid mills, dynatrons, 3 roll mills, and pressurized kneaders. Details are described in "Saishin Ganryo Oyo Gijutu (Latest Pigment Application Technologies)," CMC Publishing Co. Ltd., 1986.

[0152] A content of the infrared absorber in the image forming layer is preferably 0.01 to 50% by mass based on the total solid mass of the image forming layer, more preferably 0.1 to 10% by mass, and most preferably 0.5 to 10% by mass. The content in this range allows highly sensitive recording, and formation of a high-quality image without occurrence of stain in a non-image area.

[(B) A compound that generates radicals]

[0153] The radical generator means a compound that generates radicals by energy of light, heat, or both, and starts and accelerates polymerization of a compound having polymerizable unsaturated groups. The radical generator that can be used in the present invention can be selected from known thermal polymerization initiators and compounds having a bond with small bond dissociation energy, and used. Examples of the radical generator include onium salts, organic halogenated compounds such as s-triazine compounds having a trihalomethyl group and oxazol compounds, peroxides, azo based polymerization initiators, aryl azide compounds, carbonyl compounds such as benzophenones, acetophenones, and thioxanthones, metallocene compounds, hexaaryl biimidazole compounds, organic boron salt compounds, and disulfone compounds.

[0154] In the present invention, particularly suitable examples of the radical generator include onium salts. Especially, the onium salts represented by the following general formulas (B-1) to (B-3) are preferably used.

[0155] In the formula (B-1), Ar¹¹ and Ar¹² each individually designate an aryl group having a carbon number of 20 or less and that may have a substituent. Preferable examples of the substituent when this aryl group has a substituent include halogen atoms, a nitro group, an alkyl group having a carbon number of 12 or less, an alkoxy group having a carbon number of 12 or less, and an aryloxy group having a carbon number of 12 or less. Z^11- designates an inorganic anion or an organic anion.

[0156] In the type (B-2), Ar²¹ designates an aryl group having a carbon number of 20 or less and that may have a substituent. Preferable examples of the substituent include halogen atoms, a nitro group, and an alkyl group having a carbon number of 12 or less, an alkoxy group having a carbon number of 12 or less, an aryloxy group having a carbon number of 12 or less, an alkylamino group having a carbon number of 12 or less, a dialkylamino group having a carbon number of 12 or less, an arylamino group having a carbon number of 12 or less, and a diaryl amino group having a carbon number of 12 or less. Z^21- designates the same counter ion as Z^11-.

[0157] In the formula (B-3), R³¹, R³², and R³³ may be the same or different from each other, and each designate a hydrocarbon group having a carbon number of 20 or less and that may have a substituent. Preferable examples of the substituent include halogen atoms, a nitro group, an alkyl group having a carbon number of 12 or less, an alkoxy group having a carbon number of 12 or less, and an aryloxy group having a carbon number of 12 or less. Z^31- designates the same counter ion as Z^11-.

[0158] Z^11-, Z^21-, and Z^31- in the general formulas (B-1) to (B-3) designate an inorganic anion or an organic anion. Examples of the inorganic anion include halogen ions (F^-, Cl^-, Br^-, I^-), a perchlorate ion (ClO₄^-), a perbromate ion (BrO₄^-), a tetrafluoroborate ion (BF₄^-), SbF₆^-, and PF₆^-. Examples of the organic anion include an organic borate anion, a sulfonate ion, a phosphonic acid ion, a carboxylate ion, R⁴⁰-SO₃H^-, R⁴⁰-SO₂^-, R⁴⁰-SO₂S^-, and R⁴⁰-SO₂N^--Y-R⁴⁰ ions (here, R⁴⁰ designates an alkyl group having a carbon number of 1 to 20 or an aryl group having a carbon number of 6 to 20, and Y designates a single bond, -CO-, or -SO₂-).

[0159] In the present invention, specific examples of the onium salts that can be suitably used can include those described in paragraph numbers [0030] to [0033] of Japanese Patent Application Laid-Open No. 2001-133696.

[0160] The onium salts used in the present invention preferably has an absorption maximum at a wavelength of not more than 400 nm, and more preferably at a wavelength of not more than 360 nm. Thus, the absorption wavelength in an ultraviolet region enables handling of the lithographic printing plate precursor under white light.

[0161] These onium salts may be used alone, or may be used in combination with not less than two kinds.

[0162] These onium salts can be added in a ratio of 0.1 to 50% by mass based on the total solid content of the image forming layer coating liquid, preferably in a ratio of 0.5 to 30% by mass, and particularly preferably in a ratio of 1 to 20% by mass. At the amount of addition in the above-mentioned range, highly sensitive recording is achieved, and stain produced in a non-image area at the time of printing is suppressed.

[0163] These onium salts do not always need to be added into the image forming layer, and may be added to other layer provided adjacent to the image forming layer.

[(C) A radical polymerizable compound]

[0164] The radical polymerizable compound used for the image forming layer in the present aspect is a radical polymerizable compound having at least one ethylenically unsaturated double bond, and is selected from compounds having at least one terminal ethylenically unsaturated bond and preferably not less than two terminal ethylenically unsaturated bonds. Such compounds are widely known in the field of industry, and these can be used in the present invention without any particular limitation. These have chemical forms such as monomers, prepolymers, namely, dimers, trimers and oligomers, a mixture thereof, and copolymers thereof, for example. Examples of the monomers and copolymer thereof include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like), and esters and amides thereof. Preferably, esters of an unsaturated carboxylic acid and an aliphatic polyhydric alcohol compound and amides of an unsaturated carboxylic acid and an aliphatic polyfunctional amine compound are used. Moreover, addition reaction products of unsaturated carboxylic acid esters or amides having a nucleophilic substituent such as a hydroxyl group, an amino group, a mercapto group with monofunctional or polyfunctional isocyanates or epoxies, and dehydrating condensation reaction products with monofunctional or polyfucntional carboxylic acids are suitably used. Addition reaction products of unsaturated carboxylic acid esters or amides having an electrophilic substituent such as an isocyanate group and an epoxy group with monofunctional or polyfunctional alcohols, amines or thiols are suitable. Further, substitution reaction products of unsaturated carboxylic acid esters or amides having a leaving substituent such as halogen groups and an osyloxy group with monofunctional or polyfunctional alcohols, amines or thiols are also suitable. As another example, it is also possible to use compounds having an unsaturated phosphonic acid, styrene, and the like instead of the above-mentioned unsaturated carboxylic acids.

[0165] Specific examples of acrylic acid ester, methacrylic acid ester, itaconic acid ester, crotonic acid ester, isocrotonic acid ester, and maleic acid ester, which are a radical polymerizable compound, i.e., ester of an aliphatic polyfunctinal alcohol compound and an unsaturated carboxylic acid, are described in paragraph numbers [0037] to [0042] of Japanese Patent Application Laid-Open No. 2001-133696. These can also be applied to the present invention.

[0166] As examples of other esters, aliphatic alcohol based esters described in Japanese Examined Application Publication No. 46-27926, Japanese Examined Application Publication No. 51-47334, and Japanese Patent Application Laid-Open No. 57-196231, esters having an aromatic based skeleton described in Japanese Patent Application Laid-Open Nos. 59-5240, 59-5241, and 02-226149, and esters containing an amino group described in Patent Application Laid-Open No. 01-165613 are suitably used.

[0167] Specific examples of amide monomers of an aliphatic polyfunctional amine compound and an unsaturated carboxylic acid include methylenebis-acrylamide, methylenebis-methacrylamide, 1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide, diethylenetriaminetrisacrylamide, xylylenebisacrylamide, and xylylenebismethacrylamide.

[0168] Examples of other preferable amide system monomers can include those having a cyclo hexylene structure described in Japanese Examined Application Publication No. 54-21726.

[0169] Urethane system addition polymerized compounds produced using an addition reaction of isocyanate with a hydroxyl group are also suitable. Specific examples of such compounds include a vinyl urethane compound containing not less than two polymerizable vinyl groups in one molecule and obtained by adding a vinyl monomer containing a hydroxyl group represented by the following formula (VI) to a polyisocyanate compound having not less than two isocyanate groups in one molecule, which is described in Japanese Examined Application Publication No.48-41708.

[0170] 

        General formula (VI)     CH₂=C(R⁴¹)COOCH₂CH(R⁴²)OH

(wherein R⁴¹ and R⁴² designate H or CH₃.)

[0171] Urethane acrylates described in Japanese Patent Application Laid-Open No. 51-37193, Japanese Examined Application Publication Nos. 02-32293, and 02-16765 and urethane compounds having an ethylene oxide based skeleton described in Japanese Examined Application Publication Nos. 58-49860, 56-17654, 62-39417, and 62-39418 are also suitable.

[0172] Further, radical polymerizable compounds described in Japanese Patent Application Laid-Open Nos. 63-277653, 63-260909, and 01-105238 and having an amino structure or a sulfide structure in a molecular may be used.

[0173] Other examples can include polyfunctional acrylates and methacrylates of polyester acrylates and epoxy acrylates obtained by reacting an epoxy resin with a (meth)acrylic acid, which are described in Japanese Patent Application Laid-Open No. 48-64183, and Japanese Examined Application Publication Nos. 49-43191 and 52-30490. Further other examples can include particular unsaturated compounds described in Japanese Examined Application Publication Nos. 46-43946, 01-40337, and 01-40336, and a vinyl phosphone acid system compound described in Japanese Patent Application Laid-Open No. 02-25493. In some case, a structure containing a perfluoroalkyl group described in Japanese Patent Application Laid-Open No. 61-22048 is suitably used. Further, compounds introduced as a light curable monomer and an oligomer on pages 300 to 308 in Nippon Secchaku Kyokaishi (Journal of Japan Adhesion Society), vol. 20, No. 7 (1984) can also be used.

[0174] About these radical polymerizable compounds, details of usage such as a structure used, using alone or in combination, and an amount of addition can be set arbitrarily in accordance with performance design of a final recording material. For example, selection is performed from the following viewpoints. From the viewpoint of sensitivity, a structure having a large content of unsaturated groups per molecule is preferable, and in many cases, a structure having not less than two functional groups is preferable. In order to increase strength of an image area, namely, a cured film, a structure having not less than three functional groups is preferable. In addition, a method of adjusting both photosensitivity and strength by using these radical polymerizable compounds in combination with a compound having the different number of functional groups and a different polymerizable group (for example, an acrylic acid ester based compound, a methacrylic acid ester based compound, a styrene based compound) is also effective. Compounds having a large molecular weight and highly hydrophobic compounds are excellent in sensitivity or film strength. On the other hand, such compounds may not be preferable in terms of a development speed or deposition in a developer. Moreover, selection and usage of the radical polymerization compound are important factors with respect to compatibility with other components (for example, a binder polymer, an initiator, a coloring agent) in the image forming layer and dispersibility. For example, compatibility may be improved by use of a low purity compound or use in combination with not less than two kinds of compounds. A particular structure may be selected in order to improve adhesion between the support and the overcoat layer. A larger blending ratio of the radical polymerizable compound in the image forming layer is advantageous in sensitivity. However, an excessive amount of the radical polymerizable compound may produce phase separation not preferable, or may produce problems on a production process caused by adhesiveness of the image forming layer (for example, production failures derived from transfer or adhesion of an image forming layer component) and problems such as deposition from a developer.

[0175] From these viewpoints, a preferable blending ratio of the radical polymerizable compound is 5 to 80% by mass based on all the composition components in many cases, and preferably 20 to 75% by mass. These may be used alone, or may be used in combination with not less than two kinds. In addition, in usage of the radical polymerizable compound, an appropriate structure, blending, and the amount of addition can be arbitrarily selected from viewpoints of a degree of polymerization inhibition to oxygen, resolution, fogging, change n refractive index, surface adhesiveness, and the like. Depending on a case, a layered structure such as an undercoat and an overcoat and a coating method therefore may also be performed.

[(D) A binder polymer]

[0176] In such an image forming layer, a binder polymer is preferably used from the viewpoint of improvement in film properties of the image forming layer. A linear organic polymer is preferably used as a binder. Any linear organic polymer may be used as the "linear organic polymer." Preferably, in order to allow water development or weak alkaline water development, a linear organic polymer soluble or swellable to water or weak alkaline water is selected. The linear organic polymer is selected and used according to application not only as a coating formation agent for forming the image forming layer, but also as a water, weak alkaline water, or organic solvent developer.

[0177] For example, use of a water soluble organic polymer enables water development. Examples of such a linear organic polymer include radical polymers having a carboxylic acid group in a side chain, such as those described in Japanese Patent Application Laid-Open No. 59-44615, Japanese Examined Application Publication Nos. 54-34327, 58-12577, and 54-25957, Japanese Patent Application Laid-Open Nos. 54-92723, 59-53836, and 59-71048, namely, methacrylic acid copolymers, acrylic acid copolymers, itaconic acid copolymers, crotonic acid copolymers, maleic acid copolymers, and partial esterified maleic acid copolymers. Similarly, examples of the linear organic polymer include acid cellulose derivatives having a carboxylic acid group in a side chain. Besides these, polymers obtained by adding a cyclic anhydride to a polymer having a hydroxyl group are useful.

[0178] Among these, particularly, (meth)acrylic resins having a benzyl group or an allyl group and a carboxyl group in a side chain are excellent in a balance among film strength, sensitivity, and development properties, and suitable.

[0179] Moreover, urethane system binder polymers containing acid radicals described in Japanese Examined Application Publication Nos. 07-12004, 07-120041, 07-120042, and 08-12424, Japanese Patent Application Laid-Open No. 63-287944, 63-287947, 01-271741, and 11-352691 largely excel in strength and are advantageous in terms of print durability and low exposure suitability.

[0180] In addition to these, polyvinyl pyrrolidone, polyethylene oxide, and the like are useful as a water soluble linear organic polymer. In order to increase strength of a cured film, alcohol-soluble nylon, polyethers of 2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin, and the like are useful.

[0181] The polymer used by the present invention preferably has a weight average molecular weight of not less than 5000 and more preferably that from 10,000 to 300,000, and has a number average molecular weight of not less than 1000 and more preferably that from 2000 to 250,000. Polydispersity (weight average molecular weight/number average molecular weight) is preferably not less than 1, and more preferably from 1.1 to 10.

[0182] These polymers may be any of random polymers, block polymers, and graft polymers, and are preferably random polymers.

[0183] The binder polymers used in the present invention may be used alone, or may be used as a mixture of the binder polymers. These polymers are added into the image forming layer in a ratio of 20 to 95% by mass based on the total solid content of the image forming layer coating liquid, and preferably in a ratio of 30 to 90% by mass. When the amount of addition is less than 20% by mass, an image area has insufficient strength upon formation of an image. No image is formed when the amount of addition exceeds 95% by mass. A mass ratio of a radically polymerizable compound having an ethylenically unsaturated double bond to the linear organic polymer is preferably 1/9 to 7/3.

[0184] Next, components of an acid crosslinking layer will be described. The same infrared absorber as that in the polymerization curing type image forming layer can be used for an infrared absorber used here.

[0185] A preferable content is preferably 0.01 to 50% by mass based on the total solid mass of the image forming layer, more preferably 0.1 to 10% by mass, and most preferably 0.5 to 10% by mass.

[0186] In the above-mentioned range of the content, highly sensitive recording can be achieved, and stain produced in a non-image area for lithography obtained is further suppressed.

[(E) An acid generator]

[0187] In the present embodiment, an acid generator that decomposes by heat to generate acids refers to a compound that generates acids by irradiating the compound with light in a wavelength region of 200 to 500 nm or heating the compound at a temperature of not less than 100°C.

[0188] Examples of the acid generator include known compounds and a mixture thereof that can decompose by heat to generate acids such as photoinitiators for photo cationic polymerization, photoinitiators for photo radical polymerization, photodecolorizers for pigment, photodiscolorizers therefor, and known acid generators used for micro resist or the like.

[0189] Among the above-mentioned acid generators, the compounds represented by the following general formulas (E-1) to (E-5) are preferable.







        General formula (E-4)     Ar¹-SO₂-SO₂-Ar²

[0190] In the general formulas (E-1) to (E-5), R¹, R², R⁴, and R⁵ may be the same or may be different from each other, and designate a hydrocarbon group having a carbon number of 20 or less that may have a substituent. R³ designates halogen atoms, a hydrocarbon group having a carbon number of 10 or less and that may have a substituent, or an alkoxy group having a carbon number of 10 or less. Ar¹ and Ar² may be the same or may be different from each other, and designate an aryl group having a carbon number of 20 or less and that may have a substituent. R⁶ designates a divalent hydrocarbon group having a carbon number of 20 or less and that may have a substituent. n designates an integer of 0 to 4.

[0191] In the formulas, R¹, R², R⁴, and R⁵ are preferably a hydrocarbon group having a carbon number of 1 to 14.

[0192] A preferable aspect of the acid generators represented by the general formulas (E-1) to (E-5) is described in detail as the compounds represented by the general formulas (1) to (V) in paragraph numbers [0197] to [0222] of Japanese Patent Application Laid-Open No. 2001-142230. These compounds can be synthesized by the methods described in Japanese Patent Application Laid-Open No. 02-100054 and Japanese Patent Application Laid-Open No. 02-100055, for example.

[0193] Examples of (E) the acid generator can also include onium salts having halogenides, sulfonate, and the like as counter ions. Among these, suitable examples thereof can include onium salts having a structural formula of iodonium salts, sulfonium salts, or diazonium salts represented by the following general formulas (E-6) to (E-8).

[0194] 

        General formula (E-6)     Ar³-I⁺-Ar⁴ X^-





        General fomula (E-8)     Ar³-N₂⁺ X^-

[0195] In the general formulas (E-6) to (E-8), X^- designates halide ions, ClO₄^-, PF₆^-, SbF₆^-, BF₄^-, or R⁷SO₃^-, and R⁷ designates a hydrocarbon group having a carbon number of 20 or less and that may have a substituent here. Ar³ and Ar⁴ each individually designate an aryl group having a carbon number of 20 or less and that may have a substituent. R⁸, R⁹, and R¹⁰ designate a hydrocarbon group having a carbon number of 18 or less that may have a substituent.

[0196] Such onium salts are described as the compounds represented by the general formulas (I) to (III) in paragraph numbers [0010] to [0035] of Japanese Patent Application Laid-Open No. 10-39509.

[0197] The amount of the acid generator to be added is preferably 0.01 to 50% by mass based on the total solid mass of the image forming layer, more preferably 0.1 to 25% by mass, and most preferably 0.5 to 20% by mass.

[0198] When the amount of addition is less than 0.01 % by mass, an image may not be obtained. When the amount of addition exceeds 50% by mass, a non-image area may have stain generated during printing as the original plate for lithography.

[0199] The above-mentioned acid generator may be used alone, or may be used in combination with not less than two kinds.

[(F) A crosslinking agent]

[0200] Next, a crosslinking agent will be described. Examples of the cross linking agent include as follows.

(i) Aromatic compounds substituted by a hydroxymethyl group or an alkoxymethyl group

(ii) Compounds having an N-hydroxymethyl group, an N-alkoxymethyl group, or an N-acyloxymethyl group

(iii) Epoxy compounds

[0201] Hereinafter, the compounds (i) to (iii) will be described in full detail.

[0202] Examples of the aromatic compounds (i) substituted by a hydroxymethyl group or an alkoxymethyl group include aromatic compounds or heterocyclic compounds polysubstituted by a hydroxymethyl group, an acetoxymethyl group, or an alkoxymethyl group. Note that resin-like compounds obtained by condensation polymerization of phenols known as a resole resin with aldehydes under a basic condition are also included.

[0203] Among the aromatic compounds or heterocyclic compounds polysubstituted by a hydroxymethyl group or an alkoxymethyl group, compounds having a hydroxymethyl group or an alkoxymethyl group at a position adjacent to a hydroxy group are particularly preferable.

[0204] Among the aromatic compounds or heterocyclic compounds polysubstituted by an alkoxymethyl group, compounds having an alkoxymethyl group having a carbon number of 18 or less are preferable, and compounds represented by the following general formulas (F-1) to (F-4) are more preferable.

[0205] In the general formulas (F-1) to (F-4), L¹ to L⁸ each individually designate a hydroxyethyl group or an alkoxymethyl group substituted by an alkoxy group having a carbon number of 18 or less, such as methoxymethyl and ethoxy methyl.

[0206] These crosslinking agents are preferable for high crosslinking efficiency and improved print durability.

[0207] Examples of (ii) the compounds having an N-hydroxymethyl group, an N-alkoxymethyl group, or an N-acyloxymethyl group include monomeric and oligomeric melamine-formaldehyde condensates, and urea-formaldehyde condensates described in European Patent Laid-Open (hereinafter, expressed as "EP-A".) No. 0.133,216, West German Patent Nos. 3,634,671, and 3,711,264; and alkoxy substituted compounds descried in EP-A No. 0,212,482.

[0208] Among these, for example, melamineformaldehyde derivatives having at least two free N-hydroxymethyl groups, N-alkoxy methyl groups, or N-acyloxy methyl groups are preferable, and N-alkoxymethyl derivatives are most preferable.

[0209] Examples of (iii) the epoxy compound include monomeric, dimeric, oligomeric and polymeric epoxy compounds having not less than one epoxy group, and include reaction products of bisphenol A with epichlorohydrin and reaction products of low molecular weight phenol-formaldehyde resins with epichlorohydrin.

[0210] Other examples can include epoxy resins described in U.S. Patent No. 4,026,705 and United Kingdom Patent No. 1,539,192, and used.

[0211] An amount of addition in a case of using the compounds (i) to (iii) as the crosslinking agent is preferably 5 to 80% by mass based on the total solid mass of the image forming layer, more preferably 10 to 75% by mass, and most preferably 20 to 70% by mass.

[0212] When the amount of addition is less than 5% by mass, durability of the image forming layer of the image recording material obtained may deteriorate. When the amount of addition exceeds 80% by mass, stability during preservation may deteriorate.

[0213] In the present invention, (iv) phenol derivatives represented by the following general formula (F-5) can also be suitably used as the crosslinking agent.

[0214] In the general formula (F-5), Ar¹ designates an aromatic hydrocarbon ring that may have a substituent, and R¹, R², and R³ designate a hydrogen atom or a hydrocarbon group having a carbon number of 12 or less. m designates an integer of 2 to 4 and n designates an integer of 1 to 3.

[0215] In terms of availability of a raw material, the benzene ring, the naphthalene ring, and the anthracene ring are preferable as the aromatic hydrocarbon ring. The substituent is preferably halogen atoms, a hydrocarbon group having a carbon number of 12 or less, an alkoxy group having a carbon number of 12 or less, an alkylthio group having a carbon number of 12 or less, a cyano group, a nitro group, a trifluoromethyl group, and the like.

[0216] Among the above-mentioned groups, for increase in sensitivity, Ar¹ is more preferably the benzene ring and naphthalene ring that do not have a substituent, or the benzene ring and naphthalene ring that have halogen atoms, a hydrocarbon group having a carbon number of 6 or less, an alkoxy group having a carbon number of 6 or less, an alkylthio group having a carbon number of 6 or less, an alkyl carbamoyl group having a carbon number of 12 or less, or a nitro group as a substituent.

[0217] The hydrocarbon group represented by R¹ and R² above is preferably a methyl group for easiness of synthesis. The hydrocarbon group represented by R³ is preferably hydrocarbon groups having a carbon number of 7 or less, such as a methyl group and a benzyl group, for high sensitivity. For easy synthesis, m is preferably 2 or 3, sand n is preferably 1 or 2.

[(G) An alkaline-water soluble high molecular compound]

[0218] Examples of alkaline-water soluble high molecular compounds that can be used in a crosslinked layer applicable to the present invention include novolac resins and polymers having a hydroxy aryl group in a side chain. Examples of the novolac resins include resins obtained by condensing phenols and aldehydes under an acidic condition.

[0219] Among them, preferable examples include a novolac resin obtained from phenol and formaldehyde, a novolac resin obtained from m-cresol and formaldehyde, a novolac resin obtained from p-cresol and formaldehyde, a novolac resin obtained from o-cresol and formaldehyde, a novolac resin obtained from octylphenol and formaldehyde, a novolac resin obtained from m-/p-mixed cresol and formaldehyde, a novolac resin obtained from a mixture of phenol/cresol. (any of m-, p-, o-, m-/p-, m-/o-, and o-/p-mixed) and formaldehyde, and a high ortho bonding, high molecular weight novolac resin obtained by reacting phenol with paraformaldehyde as raw materials under high pressure in a closed condition without a catalyst.

[0220] According to a purpose, a suitable novolac resin may be selected and used as the novolac resin among the novolac resins having a weight average molecular weight of 800 to 300,000 and a number average molecular weight of 400 to 60,000.

[0221] Polymers having a hydroxy aryl group in the side chain are also preferable, and examples of the hydroxy aryl group in the polymer include an aryl group to which not less than one OH radical is bonded.

[0222] Examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group. Among these, the phenyl group and the naphthyl group are preferable from the viewpoint of availability and physical properties.

[0223] Examples of the polymers having a hydroxy aryl group in the side chain that can be used in the present embodiment can include polymers including any one kind of constitutional units represented by the following general formulas (G-1) to (G-4). However, in the present invention, the polymers are not limited to these.

[0224] In the general formulas (G-1) to (G-4), R¹¹ designates a hydrogen atom or a methyl group. R¹² and R¹³ may be the same or may be different from each other, and designate a hydrogen atom, halogen atoms, a hydrocarbon group having a carbon number of 10 or less, an alkoxy group having a carbon number of 10 or less, or a aryloxy group having a carbon number of 10 or less. R¹² and R¹³ may be bonded or fused to each other to form a benzene ring or a cyclohexane ring. R¹⁴ designates a single bond or a divalent hydrocarbon group having a carbon number of 20 or less. R¹⁵ designates a single bond or a divalent hydrocarbon group having a carbon number of 20 or less. R¹⁶ designates a single bond or a divalent hydrocarbon group having a carbon number of 10 or less. X¹ designates a single bond, an ether bond, a thioether bond, an ester bond, or an amide bond. p designates an integer of 1 to 4. q and r designate an integer of 0 to 3, respectively.

[0225] These alkali soluble polymers are described in detail in paragraph numbers [0130] to [0163] of Japanese Patent Application Laid-Open No. 2001-142230.

[0226] The alkaline-water soluble high molecular compounds that can be used in the present embodiment may be used alone, or may be used in combination with not less than two kinds.

[0227] An amount of the alkaline water soluble high molecular compound to be added is preferably 5 to 95% by mass based on the total solid content of the image forming layer, more preferably 10 to 95% by mass, and most preferably 20 to 90% by mass.

[0228] When the amount of the alkaline water soluble resin to be added is less than 5% by mass, durability of the image forming layer may deteriorate. When the amount of the alkaline water soluble resin to be added exceeds 95% by mass, no image may be formed.

[0229] Examples of known recording materials that can be applied to the image forming layer according to the present invention include a negative type image recording material containing a phenol derivative described in Japanese Patent Application Laid-Open No. 08-276558, a negative type recording material containing a diazonium compound described in Japanese Patent Application Laid-Open No. 07-306528, and a negative type image forming material described in Japanese Patent Application Laid-Open No. 10-203037 and obtained by using a crosslinking reaction by an acid catalyst in which a polymer having a heterocycle group having an unsaturated bond in the ring is used. The image forming layers described in these documents can be used as the acid crosslinking layer for the negative type image forming layer in the present invention.

[Other components]

[0230] Besides these, various compounds may be further added to such a negative type image forming layer, when necessary. For example, a dye having a large absorption in a visible light region can be used as a coloring agent for an image. Pigments such as phthalocyanine pigments, azo pigments, carbon black, and titanium oxide can also be suitably used.

[0231] In the present invention, when the image forming layer is a polymerization curing layer, desirably, a small amount of a thermal polymerization inhibitor is added in order to prevent unnecessary thermal polymerization of a compound having an ethylenically unsaturated double bond and allowing radical polymerization during preparation or preservation of the coating liquid. Examples of appropriate thermal polymerization inhibitors include hydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butyl catechol, benzoquinone, 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), and N-nitroso-N-phenylhydroxylamine aluminum salt. An amount of the thermal polymerization inhibitor to be added is preferably approximately 0.01% by mass to approximately 5% by mass based to the mass of all the compositions. When necessary, in order to prevent polymerization inhibition by oxygen, higher fatty acid derivatives as behenic acid and behenic acid amide may be added to be unevenly distributed on the surface of the image forming layer in a drying process after coating. An amount of the higher fatty acid derivative to be added is preferably approximately 0.1% by mass to approximately 10% by mass based on all the compositions.

[0232] In order to increase stability of treatment to development conditions, nonionic surfactants as described in Japanese Patent Application Laid-Open Nos. 62-251740 and 03-208514 and amphoteric surfactants as described in Japanese Patent Application Laid-Open Nos. 59-121044 and 04-13149 can be added into the image forming layer coating liquid in the present invention.

[0233] Specific examples of the nonionic surfactants include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, and polyoxyethylene nonylphenyl ether.

[0234] Specific examples of the amphoteric surfactants include allyl di(aminoethyl)glycine, alkylpolyamino ethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine, and an N-tetradecyl-N,N-betaine type (for example, Amogen K made by Daiichi Kogyo Seiyaku Co., Ltd.).

[0235] A ratio of the above-mentioned nonionic surfactant and amphoteric surfactant in the image forming layer coating liquid is preferably 0.05 to 15% by mass, and more preferably 0.1 to 5% by mass.

[0236] A plasticizer is added into the image forming layer coating liquid in the present invention, when necessary, in order to give flexibility to the coating. For example, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phtalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate, and the like are used.

3. A hydrophobized precursor containing image forming layer

[0237] Further other examples of the image forming layer that can be used as the support for a lithographic printing plate according to the present invention include a heat-sensitive image forming layer containing a compound that can form a hydrophobic region by heating or irradiation of radiant rays (hereinafter, referred to as a hydrophobized precursor where relevant). Such an image forming layer contains a compound such as (a) a particulate polymer having a thermally reactive functional group and (b) a microcapsule that encapsulates a compound having a thermally reactive functional group, the compound forming an image area, namely, a hydrophobic area (inkphilic area) by fusion by heating, or a chemical reaction of the encapsulated object caused by heat in the case of the microcapsule, for example. These are preferably dispersed in a hydrophilic binder. Accordingly, after formation (exposure) of an image, the lithographic printing plate precursor is mounted on a cylinder of a printing machine, and fed with a dampening water and/or an ink so that on-press development can be carried out without any particular development treatment.

[0238] Such an image forming layer contains (a) a particulate polymer having a thermally reactive functional group or (b) a microcapsule that encapsulates a compound having a thermally reactive functional group.

[0239] Examples of the thermally reactive functional group common to (a) and (b) above include ethylenically unsaturated groups that undergo a polymerization reaction (for example, an acrylyl group, a methacryloyl group, a vinyl group, an allyl group); an isocyanate group and blocked groups thereof that undergo an addition reaction; functional groups having active hydrogen atoms as a reaction counterpart of the isocyanate groups and blocked groups thereof (for example, an amino group, a hydroxyl group, a carboxyl group); an epoxy group that undergoes an addition reaction; an amino group as a reaction counterpart of the epoxy group; a carboxyl group or a hydroxyl group; a carboxyl group that undergoes a condensation reaction and a hydroxyl group or an amino group; and acid anhydrides that undergo a ring opening addition reaction and an amino group or a hydroxyl group. The thermally reactive functional groups used for the present invention are not limited to these, and any functional group that undergoes any reaction may be used as long as the functional group forms a chemical bond.

[(a) A particulate polymer having a thermally reactive functional group]

[0240] Examples of functional groups suitable for (a) the thermally reactive particulate polymer include an acrylyl group, a methacryloyl group, a vinyl group, an allyl group, an epoxy group, an amino group, a hydroxyl group, a carboxyl group, an isocyanate group, an acid anhydride group, and protected groups thereof. The thermally reactive functional group may be introduced into the polymer particulates at the time of polymerization of the polymer, or may be introduced after polymerization using a polymer reaction.

[0241] When the thermally reactive functional group is introduced at the time of polymerization of the polymer, emulsion polymerization or suspension polymerization is preferably performed using a monomer having the thermally reactive functional group.

[0242] Specific examples of such a monomer having the thermally reactive functional group include allyl methacrylate, allyl acrylate, vinyl methacrylate, vinyl acrylate, glycidyl methacrylate, glycidyl acrylate, 2-isocyanateethyl methacrylate, blocked isocyanates thereof with alcohol and the like, 2-isocyanateethyl acrylate, blocked isocyanates thereof with alcohol and the like, 2-aminoethyl methacrylate, 2-aminoethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid, maleic anhydride, bifunctional acrylate, and bifunctional methacrylate. The monomer having the thermally reactive functional group used for the present invention is not limited to these.

[0243] Examples of monomers that can be copolymerized with these monomers and have no thermally reactive functional group include styrene, alkyl acrylate, allyl methacrylate, acrylonitrile, and vinyl acetate. The monomer having no thermally reactive functional group used for the present invention is not limited to these.

[0244] Examples of the polymer reaction used when the thermally reactive functional group is introduced after polymerization of the polymer include a polymer reaction described in International Publication WO 96/34316.

[0245] Among the above-mentioned (a) particulate polymers having a thermally reactive functional group, particulate polymers whose particulates are easily fused by heat and bonded to each other are preferable from the viewpoint of image formability. In addition, particulate polymers that have hydrophilicity on the surface thereof and are dispersed in water are particularly preferable from the viewpoint of on-press development properties. Preferably, a contact angle (water droplets in air) of the coating produced by applying only the particulate polymer and drying the particulate polymer at a temperature lower than a solidifying temperature is lower than that of the coating produced by drying the particulate polymer at a temperature higher than the solidifying temperature.

[0246] The surface of the particulate polymer may adsorb a hydrophilic polymer or oligomer such as polyvinyl alcohol and polyethylene glycol, or a hydrophilic low molecular compound to make hydrophilicity on the surface of the particulate polymer into such a preferable state. However, a method for hydrophilicizing the surface of the particulates is not limited to these, and known various surface hydrophilization methods can be applied.

[0247] A thermal fusing temperature of (a) the particulate polymer having a thermally reactive functional group is preferably not less than 70°C, and more preferably not less than 80°C in consideration of stability over time. However, an excessively high thermal fusing temperature is not preferable from the viewpoint of sensitivity. Accordingly, the range of 80 to 250°C is preferable, and the range of 100 to 150°C is more preferable.

[0248] An average particle size of (a) the particulate polymer is preferably 0.01 to 20 µm, particularly preferably 0.05 to 2.0 µm, and preferably 0.1 to 1.0 µm. Good resolution and stability over time can be obtained at the average particle size within this range.

[0249] An amount of (a) the particulate polymer to be added is preferably 50 to 98% by mass based on the solid content of the image forming layer, and more preferably 60 to 95% by mass.

[(b) A microcapsule that encapsulates a compound having a thermally reactive functional group]

[0250] Examples of thermally reactive functional groups suitable for (b) the microcapsule include the functional groups previously mentioned as those common to (a) and (b), a polymerizable unsaturated group, a hydroxyl group, a carboxyl group, a carboxylate group, an acid anhydride group, an amino group, an epoxy group, an isocyanate group, a blocked isocyanate group.

[0251] The compound having the polymerizable unsaturated group is preferably compounds having at least one and preferably not less than two of ethylenically unsaturated bonds, for example, an acrylyl group, a methacryloyl group, a vinyl group, and an allyl group. Such compounds are widely known in the field of industry concerned, and can be used in the present invention without particular limitation to these. These chemical forms are monomers, prepolymers, namely, dimers, turner, oligomers, a mixture thereof, and copolymers thereof.

[0252] Specific examples include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid), esters thereof, and unsaturated carboxylic acid amide. Among them, ester of unsaturated carboxylic acid and aliphatic polyhydric alcohol and amide of unsaturated carboxylic acid and aliphatic polyfunctional amine are preferable.

[0253] Addition reaction products of unsaturated carboxylic acid ester or unsaturated carboxylic acid amide having nucleophilic substituents such as a hydroxyl group, an amino group, and a mercapto group with monofunctional or polyfunctional isocyanate or epoxide, and dehydrating condensation reaction products thereof with monofunctional or polyfunctional carboxylic acid are suitably used.

[0254] Addition reaction products of unsaturated carboxylic acid ester or amide having electrophilic substituent, such as an isocyanate group and an epoxy group with monofunctional or polyfunctional alcohol, amine or thiol, and substitution reaction products of unsaturated carboxylic acid ester or amide having leaving substituents such as a halogen group and a tosyloxy group with monofunctional or polyfunctional alcohol, amine or thiol are also suitable.

[0255] Other suitable examples include compounds having unsaturated phosphonic acid or chloro methylstyrene instead of the above-mentioned unsaturated carboxylic acid.

[0256] These specific compounds are described in paragraph numbers [0014] to [0035] of Japanese Patent Application Laid-Open No. 2001-27742 previously proposed by the applicant. A detailed process for producing the microcapsule that encapsulates these compounds is described in paragraph numbers [0036] to [0039] of Japanese Patent Application Laid-Open No. 2001-27742, and these descriptions can be applied also to the present invention.

[0257] A microcapsule wall suitably used for (b) the microcapsule has three-dimensional crosslinking, and is swellable by a solvent. From such a viewpoint, a wall material for the microcapsule is preferably polyurea, polyurethane, polyester, polycarbonate, polyamides, and a mixture thereof. Particularly, polyurea and polyurethane are preferable. A compound having a thermally reactive functional group may be introduced into the microcapsule wall.

[0258] An average particle size of (b) the microcapsule is preferably 0.01 to 20 µm, more preferably 0.05 to 2.0 µm, and particularly preferably 0.10 to 1.0 µm. Good resolution and stability over time can be obtained at the average particle size within the above-mentioned range.

[0259] In an image forming mechanism using (b) the microcapsule having a thermally reactive functional group, a microcapsule material, a compound encapsulated therein, and further, other optional components existing in the image forming layer in which the microcapsules are dispersed may react with each other to form an image area, namely, a hydrophobic area (inkphilic area). Examples of the mechanism include a type in which the microcapsules are fused to each other by heat as described above; a type in which a compound in the microcapsule encapsulated products that seeps out to the capsule surface or an outside of the microcapsule during coating, or a compound that seeps into the microcapsule wall from the outside causes a chemical reaction by heat; a type in which the microcapsule material and the encapsulated compounds react with an added hydrophilic resin or an added low molecular compound; and a type in which the microcapsules are reacted with each other by using not less than two kinds of microcapsule wall materials or the encapsulated products thereof having different functional groups that thermally react with each other.

[0260] Accordingly, fusing and bonding of the microcapsules by heat is preferable on image formation but not essential.

[0261] An amount of (b) the microcapsule to be added to the image forming layer is preferably 10 to 60% by mass at a solid content conversion, and more preferably 15 to 40% by mass. The amount in the above-mentioned range can provide good on-press development properties as well as good sensitivity and print durability at the same time.

[0262] When (b) the microcapsule is added into the image forming layer, a solvent that dissolves the encapsulated products and swells the wall material can be added into the microcapsule dispersion medium. Such a solvent accelerates diffusion of the compound having an encapsulated thermally reactive functional group to the outside of the microcapsule.

[0263] Such a solvent can be easily selected from many solvents commercially available depending on the microcapsule dispersion medium, the material of the microcapsule wall, a wall thickness, and the encapsulated products. For example, in the case of a water-dispersible microcapsule formed of a crosslinked polyurea or polyurethane wall, alcohols, ethers, acetals, esters, ketones, polyhydric alcohols, amides, amines, and fatty acids are preferable.

[0264] A solvent that is not soluble in the microcapsule dispersion liquid and becomes soluble by mixing the above-mentioned solvent can also be used. An amount of addition of the solvent is determined depending on a combination of the materials. The amount of addition thereof smaller than a proper value causes insufficient image formation. The amount of addition thereof larger than the proper value deteriorates stability of the dispersion liquid. Usually, the amount of addition is preferably 5 to 95% by mass of the coating liquid, more preferably 10 to 90% by mass, and particularly preferably 15 to 85% by mass.

[Other components]

[0265] In the heat-sensitive image forming layer in the present aspect, various additives can be used in combination according to a purpose, in addition to (a) the particulate polymer having a thermally reactive functional group, and (b) the microcapsule that encapsulates the compound having a thermally reactive functional group, which have the image formability.

(A reactional initiator, a reaction accelerator)

[0266] In the heat-sensitive image forming layer, a compound that starts or accelerates these reactions may be added when necessary. Examples of the compound that starts or accelerates the reactions include a compound that generates radicals or cations by heat. Specific examples thereof include lophine dimers, trihalomethyl compounds, peroxides, azo compounds, onium salts containing diazonium salts or diphenyliodonium salts, acyl phosphine, and imide sulfonate.

[0267] These compounds are preferably added in the range of 1 to 20% by mass based on the solid content of the image forming layer, and more preferably in the range of 3 to 10% by mass. The amount of addition within the above-mentioned range provides a good reaction start effect or reaction accelerating effect without impairing on-press development properties.

(A hydrophilic resin)

[0268] A hydrophilic resin may be added in such a heat-sensitive image forming layer in the present invention. The added hydrophilic resin improves on-press development properties, and additionally improves coating strength of the heat-sensitive image forming layer itself.

[0269] The hydrophilic resin preferably has hydrophilic groups such as hydroxyl, carboxyl, hydroxyethyl, hydroxypropyl, amino, aminoethyl, aminopropyl, and carboxymethyl.

[0270] Specific examples of the hydrophilic resin can include gum arabic, casein, gelatin, starch derivatives, carboxymethyl cellulose and sodium salt thereof, cellulose acetate, sodium arginine, vinyl acetate-maleic acid copolymers, styrene-maleic acid copolymers, polyacrylic acids and salts thereof, polymethacrylic acids and salts thereof, homopolymers and copolymers of hydroxyethyl methacrylate, homopolymers and copolymers of hydroxyethyl acrylate, homopolymers and copolymers of hydroxypropyl methacrylate, homopolymers and copolymers of hydroxypropyl acrylate, homopolymers and copolymers of hydroxybutyl methacrylate, homopolymers and copolymers of hydroxybutyl acrylate, polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, hydrolyzed polyvinyl acetate having a hydrolysis degree of at least 60% by mass and preferably at least 80% by mass, polyvinyl formal, polyvinyl butyral, polyvinyl pyrrolidone, homopolymers and copolymers of acrylamide, homopolymers and polymers of methacrylamide, and homopolymers and copolymers of N-methylolacrylamide.

[0271] The amount of the hydrophilic resin to be added to the heat-sensitive image forming layer is preferably 5 to 40% by mass based on the solid content of the image forming layer, and more preferably 10 to 30% by mass. The amount of addition within this range provides good on-press development properties and coating strength.

[0272] In order to form an image in such a heat responsive image forming layer (heat-sensitive image forming layer) by scanning and exposure with infrared laser light or the like, the image forming layer contains (A) the infrared absorber. A preferable amount of addition is preferably 1 to 30% by mass based on the total solid content of the image forming layer coating liquid, more preferably 5 to 25% by mass. The content within the above-mentioned range provides an image forming layer excellent in sensitivity and image formability.

[0273] In the image forming layer containing the hydrophobizing precursor, each necessary component mentioned above is dissolved or dispersed in the solvent to prepare the coating liquid, and the coating liquid is applied onto a hydrophilic surface of the support. A solid concentration of the coating liquid is preferably 1 to 50% by mass.

(Other lithographic printing plate precursors)

[0274] The present invention can be preferably used also for lithographic printing plate precursors using a method other than infrared laser exposure. Hereinafter, examples of lithographic printing plate precursors using a method other than infrared laser exposure and the image forming layer therefor will be described in detail.

[0275] Preferable examples of a positive type image forming layer can include conventionally known positive type image forming layers [(a) and (b)] shown below.

(a) A conventional positive type image forming layer used in the past and containing naphthoquinonediazide and a novolac resin.

(b) A chemical amplification type positive type image forming layer containing a combination of an alkali soluble compound protected by an acid-decomposable group and an acid generator.

[0276] The above (a) and (b) are well known in the art, and more suitably are used in combination with positive type image forming layers ((c) to (f)) shown below.

(c) A laser sensitive positive type image forming layer containing a sulfonic ester polymer and an infrared absorber that can produce a lithographic printing plate without development treatment, described in Japanese Patent Application Laid-Open No. 10-282672.

(d) A laser sensitive positive type image forming layer containing a carboxylate ester polymer and an acid generator or an infrared absorber that can produce a lithographic printing plate without development treatment, described in EP No. 652483 and Japanese Patent Application Laid-Open No. 6-502260.

(e) A laser sensitive positive type image forming layer containing an alkali soluble compound and a substance that is thermally decomposable and substantially reduces solubility of the alkali soluble compound in the state where the substance is not decomposed, described in Japanese Patent Application Laid-Open No. 11-095421.

(f) An alkaline developing elution positive type image forming layer that contains an infrared absorber, a novolac resin, and a dissolution suppressing agent and can produce an alkaline developing elution type positive lithographic printing plate.

[0277] On the support for a lithographic printing plate according to the present invention, the image forming layer is formed by dissolving components of a coating liquid for a desired layer such as an image recording coating liquid to a solvent and applying the coating liquid. Thus, a lithographic printing plate precursor can be produced. In addition to the image forming layer, according to a purpose, a protective layer, a resin intermediate layer, an undercoat, a backcoat layer, and the like can be similarly formed in the lithographic printing plate precursor.

[0278] Examples of the solvent used here can include, but not limited to, ethylene dichloride, cyclohexanone, methylethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate, ethyl lactate, N,N-dimethylacetamide, N,N-dimethylformamide, tetramethyl urea, N-methyl pyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene, and aqueous solvents such as water and alcohols when a water soluble image forming layer is used. In accordance with physical properties of the image forming layer, the solvent may be selected where relevant. These solvents are used alone or in combination.

[0279] A concentration of the above-mentioned components (total solid content including the additive) in the solvent is preferably 1 to 50% by mass.

[0280] An amount of coating (solid content) on the support obtained after coating and drying varies with applications, and is generally preferably 0.5 to 5.0 g/m² with respect to the photosensitive printing plate. As the amount of coating is smaller, apparent sensitivity is larger while the coating properties of the film more deteriorate.

[0281] Various methods can be used as a method for applying, and example thereof can include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.

[0282] The lithographic printing plate precursor according to the present invention has excellent adhesion between the support and the image forming layer. Additionally, the hydrophilic surface of the support is quickly exposed by development. As a result, printing anti-stain properties of a non-image area are improved, and a large number of printed matters with high quality are obtained even under severe printing conditions.

[0283] A lithographic printing plate can be obtained by applying a known platemaking method according to the image forming layer to the lithographic printing plate precursor according to the present invention.

[0284] Subsequently, the obtained lithographic printing plate is mounted on a printing machine, and is used to print a large number of sheets.

[A backcoat layer]

[0285] In the lithographic printing plate precursor thus obtained, a covering layer made of an organic polymer compound (hereinafter, also referred to as a "backcoat layer") may be provided on the rear surface thereof (the surface in which the image forming layer is not provided), when necessary, so as to prevent the image forming layer from being damaged even if the lithographic printing plate precursors are piled up. As principal components of the backcoat layer, at least one kind of resins selected from the group consisting of saturated copolymerized polyester resins, phenoxy resins, polyvinyl acetal resins, and vinylidenechloride copolymerized resins having a glass transition point of not less than 20°C is preferably used.

[0286] The saturated copolymerized polyester resin is composed of dicarboxylic acid units and diol units. Examples of the dicarboxylic acid units include aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, tetrabrominephthalic acid, and tetrachlorphthalic acid; and saturated aliphatic dicarboxylic acids such as adipic acid, azelaic acid, succinic acid, oxalic acid, suberic acid, sebacic acid, malonic acid, and 1,4-cyclohexanedicarboxylic acid.

[0287] Further, the backcoat layer further can contain a dye and pigment for coloring, a silane coupling agent for improving adhesion to the support, a diazo resin composed of diazonium salt, organic phosphonic acid, organic phosphorus acid, cationic polymer, a wax usually used as a sliding agent, higher fatty acids, higher fatty acid amides, a silicone compound composed of dimethylsiloxane, denatured dimethylsiloxane, polyethylene powder, where relevant.

[0288] Basically, the backcoat layer may have a thickness so that without a slip sheet, the image forming layer may be hard to be damaged, and preferably has a thickness of 0.01 µm to 8 µm. When the thickness is less than 0.01 µm, it is difficult to prevent the image forming layer from being scratched when the lithographic printing plate precursors are dealt with in piles. On the other hand, when the thickness exceeds 8 µm, the backcoat layer may be swelled by a chemical used around the lithographic printing plate during printing so that the thickness is changed. As a result, printing pressure is changed so that printing properties deteriorate.

[0289] Various methods can be used as a method for providing the backcoat layer on the rear surface of the lithographic printing plate precursor. Examples thereof include a method in which a solution is prepared by dissolving the above-mentioned components for the backcoat layer in an appropriate solvent, applied, and dried, or an emulsification dispersion solution is prepared, applied, and dried; a method in which a film-like layer molded in advance is applied onto the lithographic printing plate precursor by an adhesive or heat; and a method in which a molten coating is formed by a melting extruder and is applied onto the lithographic printing plate precursor. In order to ensure a suitable thickness, a most preferable method is the method in which a solution is prepared by dissolving the components for the backcoat layer in an appropriate solvent, applied, and dried.

[0290] In production of the lithographic printing plate precursor, either of the backcoat layer on the rear surface and the image forming layer on the front surface may be first provided on the support, or both may be provided simultaneously.

[0291] The thus-obtained lithographic printing plate precursor is cut into an appropriate size according to necessity, exposed, and developed to make a printing plate. Thus, the lithographic printing plate is obtained. In the case of a lithographic printing plate precursor provided with a visible light exposure type platemaking layer (photosensitive platemaking layer), while a transparent film having a formed printing image is layered on the lithographic printing plate precursor, the lithographic printing plate precursor is irradiated with usual visible light to be exposed, and then, developed to make a printing plate. In the case of a lithographic printing plate precursor provided with a laser exposure type platemaking layer, the lithographic printing plate precursor is exposed by writing a printing image directly into the lithographic printing plate precursor by irradiation with various laser beams, and then, developed to make a printing plate.

[0292] As mentioned above, use of the method for drying a coating film according to the present invention can suppress abnormal appearance and performance failures produced on the product surface.

[0293] As mentioned above, the drying method of the lithographic printing plate precursor has been described as an example of the method for drying a coating film according to the present invention, but the present invention will not be limited to the above-mentioned embodiment. For example, the present invention can be applied to other drying process in the process for producing the lithographic printing plate precursor. The present invention will not be limited to the field of production of the lithographic printing plate precursor, and can be applied the present invention to various technical fields, for example, processes for producing electrode materials, functional films, and optical films.

Examples

[0294] Next, the present invention will be described further in detail according to Examples; however, the present invention will not be limited to Examples below. Hereinafter, a drying test on an image forming layer coating film was performed in the dryer 20 of Figure 1.

[0295] As an aluminum (Al) plate, the aluminum support 16 (material JIS A1050) (JIS: Japanese Industrial Standards) having a width of 300 mm and a thickness of 0.3 mm was used. In the coating unit 18, the coating liquid was applied so as to have a wet thickness of 20 cc/m² using a bar coater. The coating liquid was photosensitive material A/organic solvent B. A boiling point of A was 80°C, a boiling point of B was 200°C, a viscosity of the coating liquid was 1.05 mPa·s, a specific gravity thereof was 0.9, and a surface tension thereof was 22 mN/m. A temperature and humidity of the coating unit 18 were 25°C and 30% RH. The image forming layer coating film was formed at a line velocity of 80 m/min and a tension of the support of 1000 N.

[0296] The superheated water vapor produced by the superheated water vapor feeder 80 shown in Figure 3 was fed to the superheated water vapor drying unit 29. The boiler 64 used was an simplified once-through steam boiler ME-40 made by Miura Co. The separator filter 66 used was a separate filter SF-1 made by TLV Co., Ltd. The superheated water vapor generator 68 used was a superheated water vapor generator Super-Hi 70W made by Dai-Ichi High Frequency Co., Ltd.

[0297] In Levels below, a nozzle having two slits, and a pitch of 60 mm and a slit clearance of 2.0 mm was used as the nozzle 34 that sprays the heated water vapor of the superheated water vapor drying unit 29. A distance between the slit and the support 16 was 30 mm, and an air velocity of the superheated water vapor at the slit outlet was 10 m/s. A temperature of the Al plate at the outlet 32b of the drying box 32 was 80°C, and a dew point of the hot air was 8°C. A temperature and humidity of the outlet 32b of the drying box were 25°C and 40% RH. An air velocity of the sealing air at the inlet 32a and the outlet 32b was 10 m/s.

[Level 1 (reference data)]

[0298] In the hot air drying unit 28, drying by hot air was performed. Using the hot air having a temperature f 150°C and an amount of air of 10 m/s, drying was performed for 18 seconds.

[Level 2 (reference data)]

[0299] In the hot air drying unit 28, drying by hot air was performed. Using the hot air having a temperature of 150°C and an amount of air of 10 m/s, drying was performed for 40 seconds.

[Level 3]

[0300] Drying by hot air was performed under the conditions of Level 1. Additionally, drying by superheated water vapor was performed in the superheated water vapor drying unit 29. The superheated water vapor was sprayed for 1 second at a temperature of the superheated water vapor of 120°C and an amount of vapor of 300 g/m³. The inlet and the outlet were sealed.

[Level 4]

[0301] Drying by hot air was performed under the conditions of Level 1. Additionally, drying by superheated water vapor was performed under the conditions of Level 3. The drying box was insulated by sealing the inlet and the outlet and by superheating the inner wall of the drying box.

[Level 5]

[0302] Drying by hot air was performed under the conditions of Level 1. Additionally, drying by superheated water vapor was performed under the conditions of Level 3. The drying box was insulated by sealing the inlet and the outlet and by superheating the inner wall of the drying box. The nozzle was also insulated.

[Level 6]

[0303] Drying by hot air was performed under the conditions of Level 1. Additionally, drying by superheated water vapor was performed under the conditions of Level 3. The inner wall of the drying box and the nozzle were not insulated, and the inlet and the outlet were not sealed (without condensation prevention measure).

[A method for measuring an amount of a residual high boiling point solvent]

[0304] An aluminum plate to which a coating film sample had been applied was cut into 30 mm × 10 mm, and was put into a vial bottle, and was closed. This vial bottle was placed into a separate apparatus, and heated for 5 minutes at 180°C. Subsequently, part of gas in the vial bottle was extracted by a syringe equipped within the apparatus, and analyzed by gas chromatography. On the basis of a peak area of the obtained chromatogram and a calibration curve prepared in advance, a concentration of a solvent (solvent) that remained in the coating film was calculated. Table 1 shows this result. Here, a "sheet outlet" in Table 1 designates the inlet and the outlet of the dryer that gives the superheated vapor, and presence of condensation on the sheet is evaluated. The "inside of the drying box" designates the inside of the dryer that gives the superheated vapor, and presence of condensation in the inner wall and the nozzle is evaluated.

[Table 1]

Level No	Hot air drying conditions			Superheated vapor spray conditions			Presence of condensation (visually observed)		Residual solvent amount B
	Temperature	Air amount	Time	Temperature	Vapor amount	Time	Sheet outlet	Inside of drying box
	°C	m/sec	Second	°C	g/m3	Second			mg/m2
1	150	10	18	-	-	-	None	None	100
2	150	10	40	-	-	-	None	None	32
3	150	10	18	120	300	1	None	Condensed	30
4	150	10	18	120	300	1	None	None	32
5	150	10	18	120	300	1	None	None	31
6	150	10	18	120	300	1	Condensed	Condensed	30

[0305] As shown in Table 1, comparison of Level 1 to Level 2 shows that the amount of the residual solvent in the coating film can be significantly reduced by performing hot air drying for a long time. On the other hand, Level 6 shows that the amount of the residual solvent in the coating film can be reduced similarly by giving the heated water vapor, without hot air drying for a long time. However, Level 6 also shows that condensation is observed in the outlet of the drying box and the inside of the drying box, and abnormal appearance and performance failures may be produced on the product surface. In Levels 3 to 5, the inlet and outlet of the drying box are sealed unlike Level 6. In Levels 4 and 5, the drying box was further insulated. It turns out that by sealing the inlet and outlet of the drying box, there was no condensation in the outlet, and by further insulating the drying box, there was no condensation within the drying box, either.

[0306] Additional experiments were performed in the following Levels 7 to 9.

[Level 7]

[0307] Drying by hot air was performed in the hot air drying unit 28. Drying was performed for 12 seconds using the hot air having a temperature of 150°C and the amount of air of 10 m/s. Then, drying by superheated water vapor was performed under the conditions of level 3. The drying box was insulated by sealing the inlet and the outlet and by superheating the inner wall of the drying box. The nozzle was also insulated. The Al plate was heated at a low temperature so that the temperature of the A1 plate in the inlet of the drying box might be 60°C.

[Level 8]

[0308] Drying by hot air was performed in the hot air drying unit 28. Drying was performed for 18 seconds using the hot air having a temperature of 150°C and the amount of air of 10 m/s. Then, drying by superheated water vapor was performed under the conditions of level 3. The drying box was insulated by sealing the inlet and the outlet and by superheating the inner wall of the drying box. The nozzle was also insulated. The Al plate was heated at a high temperature so that the temperature of the Al plate in the inlet of the drying box might be 80°C.

[Level 9]

[0309] Drying by hot air was performed in the hot air drying unit 28. Drying was performed for 12 seconds using the hot air having a temperature of 150°C and the amount of air of 10 m/s. Then, drying by superheated water vapor was performed under the conditions of Level 3. The drying box was insulated by sealing the inlet and the outlet and by superheating the inner wall of the drying box. The nozzle was also insulated. Additionally, the heating roller 46 shown in Figure 6 was provided. The heating roller used had a diameter of 100 mm and a surface length of 400 mm. At a temperature of the heating roller of 100°C, the Al plate was heated so that the temperature of the Al plate in the inlet of the drying box might be 75°C.

[Table 2]

Level No	Hot air drying conditions			Superheated vapor spray conditions			Presence of condensation (visually observed)		Residual solvent amount B
	Temperature	Air amount	Time	Temperature	Vapor amount	Time	Sheet outlet	Inside of drying box
	°C	m/sec	Second	°C	g/m3	Second			mg/m2
7	150	10	12	120	300	1	None	Condensed	30
8	150	10	18	120	300	1	None	None	31
9	150	10	12	120	300	1	None	None	29

* Temperature and humidity within vapor drying box 100°C and 25% RH

[0310] As shown in Table 2, in Levels 8 and 9 in which the temperature of the support conveyed to the drying box is controlled at a temperature of not less than the dew point within the drying box, the inside of the drying box had no condensation. Thus, it is possible to prevent abnormal appearance and performance failures produced on the product surface caused by adhesion of water droplets onto the coating film.

Claims

1. A method for drying a coating film, comprising the steps of:

drying a coating film to a drying point, the coating film which is formed by applying a coating liquid containing a high boiling point solvent onto a support to be conveyed;and

subsequently, drying, in a drying box, the high boiling point solvent while spraying vapor of a solvent having a boiling point lower than that of the high boiling point solvent to the coating film with a vapor spray nozzle, wherein

the support is heated so as to have a predetermined temperature T within the drying box, and conveyed.

2. The method for drying a coating film according to claim 1, wherein an inner wall of the drying box is heated.

3. The method for drying a coating film according to claim 1 or 2, wherein the support and the drying box are heated to have a temperature of (the predetermined temperature T - 5 (°C)) or more.

4. The method for drying a coating film according to any one of claims 1 to 3, wherein an inlet and outlet for the support in the drying box are sealed.

5. The method for drying a coating film according to any one of claims 1 to 4, wherein the vapor spray nozzle is insulated.

6. The method for drying a coating film according to any one of claims 1 to 5, wherein the superheated vapor sprayed to the coating film is subsequently discharged to an exhaust system provided in the drying box.

7. The method for drying a coating film according to any one of claims 1 to 6, wherein a heating roller contacting the support is provided within the drying box to heat the support.

8. The method for drying a coating film according to any one of claims 1 to 7, wherein the drying box is provided so that a surface of the coating film on the support passes through the drying box vertically or with facing downward, and the vapor spray nozzle is provided in a position where the vapor of the solvent is sprayed to the coating film from under the coating film.

9. The method for drying a coating film according to any one of claims 1 to 8, wherein on an internal ceiling surface of the drying box, grooves or gutters are provided parallel to a traveling direction of the support at approximately an equal interval.

10. The method for drying a coating film according to any one of claims 1 to 9, wherein the vapor of the solvent is superheated vapor from which contained droplets and foreign substances are removed by a separator filter.

11. The method for drying a coating film according to any one of claims 1 to 10, wherein the superheated vapor is mixed with hot air, and sprayed to the coating film.

12. A process for producing a lithographic printing plate precursor using the method for drying a coating film according to any one of claims 1 to 11.

Drawing