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(11) | EP 0 826 509 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Porous ink acceptor sheet for thermal dye transfer printing |
| (57) Hot-melt type thermal ink transfer printing medium has an ink acceptance layer in
which pores and microgrooves are contained, used for transferring hot-melt ink to
the ink acceptance layer of the printing medium by using a thermal head. The printing
medium satisfies at least one condition from a group of tow conditions that a 100
% stress of the ink acceptance layer in conformity with a measuring method of JIS-K-7127
is not less than 3,000 kN/m2 and a Young's modulus of the ink acceptance layer in
conformity with a measuring method of JIS-K-7127 is not less than 8,000 kN/m2. |
BACKGROUND OF THE INVENTION
Field of the Invention:
[0001] The present invention relates to improvements of a hot-melt type thermal ink transfer printing medium for printing an image in multiple gradation, and, in particular, relates to a hot-melt type thermal ink transfer printing medium having excellent surface smoothness and capable of printing a high grade picture and easily being loaded and unloaded to and from a printing apparatus.
Description of the Related Art:
[0002] As well known, in order to realize a multiple gradation print by using a hot-melt ink, there have been applied a dither method using plural pixels (matrix), or a heat concentration method using a special thermal head provided with small heat generating elements, for instance, as shown in "Imaging Part 1", pages 103 to 108, published by the Photographic Industry Publishing Company.
[0003] Generally, in the dither method using the plural pixels, there is a problem that a resolution of the image is prominently degraded, resulting in a degradation of quality of the image. Further, in the heat concentration method using the special thermal head, there is a problem of cost rise.
[0004] Recently, as a method capable of controlling the gradation of an image at every pixel, there has been proposed a hot-melt thermal printing method employing a hot melt thermal transfer printing paper (referred to as printing paper hereinafter) provided with an ink acceptance layer made of a porous-surface layer on a surface of the printing paper as shown in ITE Technical Report, Vol. 17, No. 27 (May 1993), pages 19 to 24.
[0005] In this method, upon thermally transferring melted ink from a thermal transfer printing ink ribbon onto the porous-surface layer of the printing paper, the melted ink readily penetrates into pores of the porous-surface layer. Thus, it is possible to thermally transfer even a slight amount of the melted ink onto the printing paper due to an anchor effect of the pores of the porous-surface layer. This fact allows to thermally transfer the melted ink from the ink ribbon onto the printing paper at every pixel in accordance with an amount of heat given to the thermal head. Further, it has been confirmed that an ink acceptance layer made of such a microgroove-surface layer containing plentiful microgrooves as proposed in the Japanese Patent Laid-open publication 7-246785/1995 has the same effect as that of the porous-surface layer.
[0006] As mentioned above, the printing paper having the ink acceptance layer such as the porous-surface layer or the microgroove-surface layer certainly renders an excellent multiple gradation print. However, a printing paper is also required to have other characteristics in printing, for instance, a high printing density (excellent adhesion and fixing of the melted ink), a high surface brightness, curling-free after and before printing, and an excellent paper loading and unloading characteristic.
[0007] As a method for forming the porous-surface layer or the microgroove-surface layer, there is, for instance, a wet solidification method, which has been used to produce synthetic leather. In this method, a substrate coated with a dimethylformamide (DMF) solution containing a resin is processed in water. Thereby, the water is substituted for the DMF. Thus, when the resin is dried to be solidified, the resin becomes porous. As the resin, urethane resin is usually used because of its texture, easiness for forming process and high degree of freedom in design as polymer.
[0008] However, when the urethane resin is used as the ink acceptance layer, it does not satisfy all the requirements mentioned above, resulting in a difficulty in practical use.
[0009] This results mainly from a principle of the hot-melt thermal ink transfer printing. As well known, when the melted or softened ink is transferred from the ink ribbon onto the ink acceptance layer made of the porous-surface or microgroove-surface layer, the melted or softened ink penetrates into the pores or microgrooves of the porous-surface or microgroove-surface layer being depressed by the thermal head, and adheres thereon being cooled down to be solidified.
[0010] First problem occurring at that time is that since the porous-surface or microgroove-surface layer has a resilient (elastic) property, a pressure applied from the thermal head is apt to be relatively weakened, so that the melted or softened ink can not penetrate into the pores or the microgrooves, resulting in a printed image having an insufficient density and gradation. In addition, there is a problem that the paper loading and unloading characteristic is degraded.
[0011] Second problem is that since the surface of the porous-surface or microgroove-surface layer is not smooth, the thermal head unequally contacts the surface thereof. As a result, an uneven thermal conduction occurs on the surface of the printing paper, which causes uneven adherence of the melted ink thereon.
[0012] In this case, pin holes are developed because of falling off of ink dots on positions where the ink dots have to be adhered, resulting in a printed image having graininess.
[0013] Further, the printing paper having such a porous-surface layer or a microgroove-surface layer is used not only for printing an image thereon but also for being attached on goods after printed. This type of printing paper is so called a seal paper. The seal paper has a adhesive layer on a back of the recording paper, i.e., an opposite surface of the printing surface, and is laminated to a released sheet to protect the adhesive layer. Before the seal paper is attached on goods, the released sheet is removed from the adhesive layer.
[0014] Such printing paper with the adhesive layer is composed of a printing paper member with a adhesive layer and a released sheet member having a anti-stick treated surface, and is generally produced by laminating both the printing paper member and released sheet member in such a manner that the anti-stick treated surface of the released sheet member faces to the adhesive layer of the printing paper member.
[0015] However, in this method, pores of the porous-surface or microgrooves of the microgroove-surface layer formed as the ink acceptance layer are crushed by a pressure due to the lamination of both the members. The crush of the pores or the microgrooves prevents the melted ink from penetrating into the ink acceptance layer sufficiently to disable such a function as the ink acceptance layer.
[0016] It is possible to compromise a condition that the porous-surface or microgroove-surface layer is not crushed. However, in that case, the air is apt to be contained between the printing paper member and the released sheet member, and the pressure for lamination is apt to become insufficient, which causes a difficulty in a practical use.
SUMMARY OF THE INVENTION
[0017] Accordingly, a general object of the present invention is to provide a hot-melt thermal ink transfer printing medium, in which the above disadvantages have been eliminated.
[0018] A specific object of the present invention is to provide a hot-melt type thermal ink transfer printing medium having an ink acceptance layer in which pores or microgrooves are contained, used for transferring hot-melt ink to the ink acceptance layer of the printing medium by using a thermal head, characterized in that the printing medium satisfies at least one condition from a group of two conditions that a 100 % stress of the ink acceptance layer in conformity with a measuring method of JIS-K-7127 is not less than 3,000 kN/m2 and a Young's modulus of the ink acceptance layer in conformity with a measuring method of JIS-K-7127 is not less than 8,000 kN/m2.
[0019] A more specific object of the present invention is to provide a hot-melt type thermal ink transfer printing medium having an ink acceptance layer in which pores or microgrooves are contained, used for transferring hot-melt ink to the ink acceptance layer of the printing medium by using a thermal head, characterized in that the ink acceptance layer is composed of a mixture of urethane resin and vinyl chloride resin and/or vinyl acetate, and a mixing ratio of the urethane resin to the vinyl chloride and/or vinyl acetate resin is from 95 : 5 to 30 to 70.
[0020] Another and more specific object of the present invention is to provide a hot-melt type thermal ink transfer printing medium having an ink acceptance layer in which pores or microgrooves are contained, on one surface of the printing medium used for transferring hot-melt ink to the ink acceptance layer of the printing medium by using a thermal head, the printing medium further comprising a released sheet on another surface of the printing medium through an adhesive layer interposed therebetween, characterized in that the released sheet has a resilient property.
[0021] Other objects and further features of the present invention will be apparent from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022]
Fig. 1 is a partially enlarged schematic view for explaining a thermal ink transfer printing method applied to a printing paper of the present invention;
Fig. 2 (A) is a partially enlarged schematic view of a printing paper having a porous-surface layer of a first embodiment in the present invention;
Fig. 2 (B) is a partially enlarged schematic view of a printing paper having a microgroove-surface layer of the first embodiment in the present invention;
Fig. 3 (A) is a partially enlarged schematic view of a printing paper having an adhesive layer and a released sheet in addition to a porous-surface layer in a second embodiment of the present invention;
Fig. 3 (B) is a partially enlarged schematic view of another printing paper having a film layer between a released sheet substrate and an anti-stick agent layer in the second embodiment of the present invention, and
Fig. 4 is a schematic view for explaining a laminating process of the printing paper with an adhesive layer in the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[First embodiment]
[0023] First, description is given of a thermal transfer printing method for applying a hot-melt thermal ink transfer printing medium (referred to as "printing paper" hereinafter) of the present invention referring to Fig. 1.
[0024] Fig. 1 is a partially enlarged schematic view for explaining a thermal ink transfer printing method applied to a printing paper of the present invention.
[0025] Referring to Fig. 1, an ink ribbon 1 and a printing paper 2 placed on the ink ribbon 1 is transported together by being interposed between a thermal head 3 and a platen roller 4. Ink layer 1a containing color materials is transferred to a porous-surface layer 2a of the printing paper 2 from the ink ribbon 1 being pressed against the platen roller 4 by the thermal head 3 and being heated by heating heat generating elements (not shown) of the thermal head 3. Thus, an image is printed on the printing paper 2.
[0026] Each of the heat generating elements of the thermal head 3 is generally formed in a rectangular shape. And each of the heat generating elements has such a gradient of temperature distribution that the temperature is highest at a center part thereof and it gradually decreases toward a periphery thereof.A part of the ink ribbon 1 heated at a temperature more than a melting point of the ink of the ink ribbon 1 is melted correspondingly with an area of thus heated heat generating elements.
[0027] Thus, it is possible to control the area of ink to be melted by making use of the temperature gradient.
[0028] Further, as ink of the ink ribbon 1, when such ink that its viscosity is decreased responsive to a rise in the temperature, is employed, the viscosity of the ink at the central part of the area is the smallest, and at the periphery the highest Thus, an amount of ink penetrating into the porous-surface layer or the microgroove-surface layer of the printing paper 2 is the largest at the central part, and less at a part away from the central part.
[0029] Accordingly, it is possible to control the penetrating amount of ink and the penetrating area of ink at the same time by controlling the amount of the current flowing through the element, resulting in a multigradation print.
[0031] Fig. 2 (A) is a partially enlarged schematic view of a printing paper having a porous-surface layer of a first embodiment in the present invention; and
[0032] Fig. 2 (B) is a partially enlarged schematic view of a printing paper having a microgroove-surface layer of the first embodiment in the present invention.
[0033] As shown in Figs. 2 (A) and 2 (B), a porous-surface layer 2a or a microgroove-surface layer 2a' is formed on a printing paper substrate (referred to as paper substrate hereinafter) 2b.
[0034] Here, as the paper substrate 2b, there are employed transparent or opaque plastics such as polyethylene terephtharate film, polyimid film, polyethylene naphtharate film, polypropylene film, polyamid film and alamid film, non-coated paper such as fine quality paper and PPC paper (for plain paper copy machine), coated paper such as art paper, synthetic paper (for instance, "YUPO" OJI-YUKA SYNTHETIC PAPER CO, LTD.) by a non-woven paper fabrication, wherein a film is produced by mixing filler and additives to a plastic resin, and extruding the kneaded mixture from a die-slit, synthetic paper by a surface coating method, wherein a white pigment layer is formed on a surface of a plastic film, and a laminated substrate of these films mentioned above.
[0035] Among the above substrates, the synthetic paper by the non-woven paper fabrication is preferable as the paper substrate 2a because of its superior resistance to moisture, solvent and heat, and its excellent surface smoothness, high whiteness and high strength.
[0036] Further, a thickness of the paper substrate 2b is preferably 25 to 500 µm and more preferably 50 to 300 µm, taking account of mechanical strength, moderate stiffness as the printing paper, easiness of handling, and cost.
[0037] Next, as methods for forming the porous-surface layer 2a on the surface of the paper substrate 2b, it is possible to employ various kinds of well known methods.
[0038] Specifically, there are "a wet solidification method", wherein the paper substrate 2b coated with a dimethylformamide (DMF) solution containing a resin is processed in water so as to replace the DMF with the water and the resin is dried to be solidified, resulting in the porous-surface layer, "a mechanical stirring method", wherein foams are mechanically generated in a water soluble resin solution by adding a foaming agent and a foaming control agent thereto and stirring them, and the solution containing the foams is coated on the paper substrate 2b to form the porous-surface layer, "a pigment addition method", wherein a porous-surface layer is formed by using porous pigment (inorganic or organic fine particles), "a solvent solution method", wherein a polymer solution is prepared by adding a good solvent and a poor solvent having a boiling point higher than that of the good solvent to a certain polymer, and this polymer solution is coated and dried on the paper substrate 2b, and first, the good solvent having a lower boiling point is evaporated so that the poor solvent remains in the coated layer, and polymer having a lower solubility to the solution is gelatinized, and subsequently the poor solvent having the higher boiling point is evaporated, resulting in a porous-surface layer, "a foaming agent method", wherein a porous-surface layer is obtained by using a foaming agent of an organic or inorganic material which generates nitrogen gas by being heated, and "soluble particles dissolution removal method", wherein inorganic powder such as salt or organic powder such as starch are added in a resin to be coated, and after coated on the printing base, these powder are removed being dissolved.
[0039] For the structure of the porous-surface layer 2a, the pores are desirable to be communicated to each other. In other words, when the melted ink penetrates into the porous-surface layer 2a, it is desirable to have air escape passages in the porous-surface layer 2a. An average depth of pores formed in the porous-surface layer 2a is preferably not less than 8 µm when an ink ribbon having four kinds of ink layers such as yellow, magenta, cyan and black, each having a thickness of 2 µm, is employed. An average diameter of pores is preferably 1 to 30 µm and more preferably 1-10 µm. When the average depth and diameter of the pores are larger than those ranges mentioned above, there may be a case where the ink returns to the ink ribbon without adherence of the ink on the porous-surface layer 2a. On the other hand, when the average depth and diameter thereof are smaller than those ranges, there may be a case where the ink is impossible to penetrates into the porous-surface layer 2a. A thickness of the porous-surface layer 2a is preferably 2 to 100 µm or more preferably 5 to 50 µm, taking account of a number of colors and a thickness of the ink layer, a pour rate of the porous-surface layer 2a, a mechanical strength of the ink coated layer.
[0040] Further, as forming methods of the microgroove-surface layer 2a', there can be employed many well known minute machining techniques. For instance, a flat or roller master having a pattern of microgrooves is made by a well known method. Then, a replica of microgrooves can be transferred on a surface of a polymer layer on which the microgrooves are to be formed, by hot-pressing the master onto the polymer layer. For making such a master, a laser machining method or a chemical or dry etching method using a photo-lithography is applicable. The microgrooves are mostly formed in parallel or intersecting to each other at right angles. A width of the microgroove is preferably 1 to 30 µm. When the width of the microgroove is less than 1 µm, it may be difficult for the ink to seep into the microgrooves, and when the width of the microgrooves is larger than 30 µm, it may also be difficult for the ink to seep into the microgrooves by capillarity.
[0041] One of the requirements of the present invention is that the material for forming the porous-surface layer 2a or the microgroove-surface layer 2a' is to allow a use of the methods mentioned above to be applied, and that the mechanical strength of the porous-surface layer 2a or the microgroove-surface layer 2a' have to satisfy at least one of conditions that a 100 % stress in conformity with a measuring method of JIS-K-7127 is not less than 3,000 kN/m2 and a Young's modulus in conformity with a measuring method of JIS-K-7127 is not less than 8,000 kN/m2.
[0042] When values of both the 100 % stress and the Young's modulus are smaller than the abovementioned values, it is impossible to cause the ink to adhere on the porous-surface layer 2a or the microgroove-surface layer 2a', resulting in a difficulty to obtain a sufficient gradation due to the adherence of the ink. This brings a problem of a low quality of an image having graininess. Further, this causes a degradation of the paper loading and unloading characteristic in a printing machine.
[0043] When the porous-surface 2a and microgroove-surface layers 2a' are made of resin, the 100 % stress and Young's modulus mentioned above can be realized by selecting a suitable kind or structure of an available resin, or by a resin crosslinking method using such as a crosslinking agent or a radiation, or by an organic or inorganic pigment addition method.
[0044] Specifically, there are a selection of molecular structure by establishing an amount of a hard segment such as polyurethane and polyester, a thermal crosslinking of polyurethane or polyester by using isocyanate, an ultraviolet ray crosslinking of photopolymerization oligomers which have radical double bond by photopolymerization initiators such as photopolymerization acryl oligomer, polyestel oligomer and urethane oligomer, or addition of organic; particles such as acrylic resin and olefin resin, or addition of inorganic particles such as silica, titan oxide calcium carbonate.
[0045] In addition to the strength of the porous-surface layer 2a or the microgroove-surface layer 2a', it is necessary to select a resin, taking account of an affinity with the hot melt ink, heat-resisting property, conformity to the process, and porous property.
[0046] Specifically, ethylene type resin such as ethylene-vinyl acetate copolymer, vinyl chloride type resin such as vinyl chloride-vinyl acetate copolymer, vinyl acetate type resin, cellulose type resin, polyamid type resin, polyester type resin, polyurethane type resin, polyolefin type resin, epoxy type resin, styrene type resin, acryl type resin, and emulsion type such as a petroleum type resin, water soluble type, and solvent type are available. Other than these resins, it is possible to use such materials as metal type materials and ceramic type materials as the material of the porous-surface layer 2a or the microgroove-surface layers 2a'.
[0047] Another feature of the present invention is that the material used for the porous-surface layer 2a is made of mixed components of urethane resin, vinyl chloride type resin and/or vinyl acetate type resin.
[0048] The vinyl chloride type resin and vinyl acetate type resin are preferably selected from a group composed of vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, ethylene-vinyl chloride copolymer resin, ethylene-vinyl-acetate-vinyl chloride copolymer resin and chlorinated vinyl chloride-vinyl acetate type copolymer, More preferably, from a group of vinyl chloride-vinyl acetate type copolymer resin.
[0049] When the porous-surface layer 2a is made of only urethane resin, the surface roughness thereof is very low. As a result, a brightness of the surface is degraded, resulting in a printed image having graininess as mentioned in the foregoing.
[0050] The surface roughness is improved by adding other resins mentioned above to the urethane resin.
[0051] A weight ratio of urethane resin to other resin in the resin composition is selected within a range of 95 : 5 to 30 : 70. When the weight ratio-of other resin in the resin composition is less than 5, a sufficient effect is not obtained. When the weight ratio of other resin is more than 70 %, the average diameter of pores and a density of pores in the porous-surface layer 2a is decreased. The more preferable weight ratio of urethane resin to other resin in the resin composition is 95 : 5 to 50 : 50.
[0052] Incidentally, in the present invention, it is possible to add an anti static agent for preventing electrostatic problems, a lubricant for improving the paper loading characteristic in printing, a fluorescent brightening agent/whitening pigment for improving whiteness of a printing paper and an ultraviolet ray absorption agent for improving light resistance, to the porous-surface and microgroove-surface layers 2a, 2a', if necessary.
[Examples 1- 6]
[0053] Description is now given of a hot melt type thermal ink transfer printing medium (referred to as printing paper) of examples 1 to 6 of the first embodiment and comparatives 1 to 3.
[0054] Each kind of polyurethane shown in Table 1 along with vinyl chloride-vinyl acetate resin and other additives was dissolved in DMF, and each porous-surface layer forming material having a component shown below was obtained.
-porous-surface layer forming composition:-
(solution)
[0055]
| 1) urethane resin: (corresponding to (1) to (9) in Table 1) | 10.79 (weight parts) |
| 2) vinyl chloride-vinyl acetate resin: (NIPPON ZEON CO., LTD) | 2.70 |
| 3) pigment: (SiO2 fine particles) | 1.35 |
| 4) antistatic agent: (NIPPON OIL & FATS CO., LTD, ELEGAN 264) | 0.13 |
| 5) fluorescent brightening agent: (CIBA-GEIGY LTD. UVITEX-OB) | 0.03 |
| 6) DMF: | 85.00 |
[0056] Each solution to be evaluated was coated on a synthetic; paper (made by OJI-YUKA SYNTHETIC PAPER CO., LTD, FPG-150, a thickness of 150 µm) by using a doctor blade. After wet-solidified in a water for 60 seconds, printing papers shown as printing paper No. (1) to (9) were obtained by drying with the air. Thickness of the porous-surface layer 2a of each paper was 20 µm. Coated layer Young's modulus and a 100 % stress of each porous-surface layer 2a were measured in conformity with a measuring method of JIS-K-7127 by using a tension test apparatus (made by ORIENTIC, TENSILON). The results are shown in Table 1.
Table 1
| printing paper No. | resin (maker) | Young's modulus (kN/m2) | 100 % stress (kN/m2) |
| (1) | NIPPON POLY URETHANE | 125,000 | 16,800 |
| (2) | same as above | 47,600 | 8,500 |
| (3) | same as above | 11,200 | 4,300 |
| (4) | SANYO CHEMICAL | 9,500 | 3,300 |
| (5) | NIPPON POLY URETHANE | 7,000 | 4,000 |
| (6) | same as above | 112,000 | 2,800 |
| (7) | same as above | 7,100 | 2,800 |
| (8) | same as above | 5,900 | 1,500 |
| (9) | SANYO CHEMICAL | 6,400 | 1,600 |
[0057] Next, an evaluation test was conducted for the examples 1 to 6 corresponding to the printing papers No. (1) to (6) and the comparatives (1) to (3) corresponding to the printing paper No. (7) to (9) by printing actual images thereon by using a color printer with a thermal head having a resolution of 300 dots/inch (JVC, Trueprint 2200).
[0059] The hot-melt type thermal transfer printing ink ribbon used for the evaluation test is such that a thermal resistance layer mainly made of thermosetting acryl resin having a thickness of 0.2 µm is provided on one surface of polyethylene telephthalate film having a thickness of 4.5 µm, and on an opposite surface of the thermal resistance layer, an ink layer having following ink components is coated. Items of the evaluation test are shown below.
-the ink layer composition-
[0060]
| 1) color material pigment: (Sumipurasuto red FG) | 15 (weight parts) |
| 2) paraffin wax: | 60 |
| 3) carnauba wax: | 5 |
| 4) kyanderira wax: | 5 |
| 5) rosin ester: | 5 |
| 6) ethylene-vinyl acetate copolymer: | 10 |
-items of evaluation test-
1) Paper loading and unloading characteristics of the printing paper:
[0061] Mark X denotes presence of defects of paper loading characteristic of the printing paper in the printer, and a mark ○ no defect.
2) Printing density:
[0062] Each value shows a density of an image printed by a printer having the ink ribbon. The density is measured by using Macbeth density meter (Macbeth, RD-918).
3) Graininess:
[0063] Graininess is evaluated by observing the printed image, and the result is expressed in 5 steps, wherein a rank 5 denotes a highest image quality and ranks 1 and 2 denote an unsatisfactory printed image in a practical use.
4) Brightness:
[0064] Each value shows a brightness at 60 ° on a surface of the porous-surface layer 2a. The brightness is measured in conformity with the measuring method of JIS-Z-8741 by using an apparatus (Suga Sikenki).
5) Gradation:
[0065] Gradation is evaluated by observing a reproduction of a highlight portion, and the results are expressed in 5 steps, wherein a rank 5 denotes an printed image having an excellent reproduction of the highlight portion, and ranks 1 and 2 denote an unsatisfactory printed image in a practical use.
6) Overall evaluation:
[0066] The evaluation with respect to items 1) to 5) are summarized into a relative evaluation, wherein the mark X denotes a printing paper unsatisfactory in practical use and a mark ○ denotes a printing paper which is acceptable in a practical use.
Table 2
| prt. pap. No. | *P. L. | dnsty | graininess | bright. ( % ) | grad. | overall eval. | ||
| ex. | 1 | (1) | ○ | 1.56 | 5 | 65 | 5 | ○ |
| 2 | (2) | ○ | 1.45 | 4 | 57 | 5 | ○ | |
| 3 | (3) | ○ | 1.40 | 4 | 52 | 4 | ○ | |
| 4 | (4) | ○ | 1.35 | 3 | 50 | 4 | ○ | |
| 5 | (5) | ○ | 1.36 | 4 | 51 | 4 | ○ | |
| 6 | (6) | ○ | 1.47 | 4 | 59 | 5 | ○ | |
| com. | 1 | (7) | X | 1.10 | 2 | 15 | 2 | X |
| 2 | (8) | X | 0.86 | 2 | 8 | 2 | X | |
| 3 | (9) | X | 0.74 | 1 | 6 | 1 | X | |
| * paper loading and unloading characteristic of the printing paper |
[0067] As seen from the results shown in Table 2, the printing papers of the examples 1 to 6 which satisfy at least one condition, either the conditions of 100 % stress or the Young's modulus mentioned in the foregoing, respectively show an excellent paper loading characteristic, a high density, an excellent gradation and a high quality of image. On the other hand, the comparatives 1 to 3 which satisfy neither the 100 % stress condition nor the Young's modulus condition, show poor results compared with those of the examples 1 to 6 of the present invention.
[Examples 7 to 20]
[0068] Next, the description is given of examples 7 to 20 in the first embodiment and comparatives 4 to 7.
[0069] In the porous-surface layer forming composition (solution) in the first embodiment, weight parts of 13.49 corresponding to a sum of weight parts of 1) urethane resin and 2) vinyl chloride-vinyl acetate resin were replaced with the same weight parts of a specified resin composition. The combined weight parts of the specified resin composition were varied as shown in Table 3, however, other components of 3) to 6) in the material components (the solution) remained as they were. As a result, each printing paper having the porous-surface layer 2a was obtained as shown with the printing papers No.(10) to (27) in Table 3 in the same manner as mentioned in the first embodiment.
Table 3
| printing paper No. | resin component urethane resin/other rein | ratio of comp. (weight ratio) |
| (10) | A/C | 95 : 5 |
| (11) | A/C | 80 : 20 |
| (12) | A/C | 70 : 30 |
| (13) | A/C | 60 : 40 |
| (14) | A/C | 50 : 50 |
| (15) | B/C | 95 : 5 |
| (16) | B/C | 80 : 20 |
| (17) | B/C | 70 : 30 |
| (18) | B/C | 60 : 40 |
| (19) | B/C | 50 : 50 |
| (20) | A/C | 40 : 60 |
| (21) | A/C | 30 : 70 |
| (22) | B/C | 40 : 60 |
| (23) | B/C | 30 : 70 |
| (24) | A/C | 100 : 0 |
| (25) | A/C | 20 : 80 |
| (26) | B/C | 100 : 0 |
| (27) | B/C | 20 : 80 |
[0070] In Table 3, a character A denotes urethane resin from TOYO-MORTON, LTD, a character B urethane resin from NIPPON POLYURETHANE INDUSTRY CO., LTD, and a character C vinyl chloride-vinyl acetate copolymer resin from NIPPON ZEON CO., LTD.
[0071] Next, the evaluation tests with respect to the printing papers of the examples 7 to 20 corresponding to printing paper No. (10) to (23) and the comparatives 4-7 corresponding to printing paper No. (24) to (27) were conducted in the same manner as mentioned in the first embodiment, however, the test of the paper loading and unloading characteristic of the printing paper was omitted.
[0072] The results are shown in Table 4.
Table 4
| prt. pap. No. | density | graininess | bright. ( % ) | grad. | overall eval. | ||
| ex. | 7 | (10) | 1.31 | 4 | 17 | 5 | ○ |
| 8 | (11) | 1.35 | 4 | 25 | 5 | ○ | |
| 9 | (12) | 1.45 | 5 | 29 | 5 | ○ | |
| 10 | (13) | 1.32 | 4 | 33 | 4 | ○ | |
| 11 | (14) | 1.28 | 4 | 56 | 3 | ○ | |
| 12 | (15) | 1.37 | 4 | 21 | 5 | ○ | |
| 13 | (16) | 1.42 | 4 | 34 | 5 | ○ | |
| 14 | (17) | 1.45 | 5 | 39 | 5 | ○ | |
| 15 | (18) | 1.40 | 4 | 45 | 4 | ○ | |
| 16 | (19) | 1.30 | 4 | 60 | 3 | ○ | |
| 17 | (20) | 1.25 | 4 | 60 | 3 | ○ | |
| 18 | (21) | 1.21 | 4 | 60 | 3 | ○ | |
| 19 | (22) | 1.27 | 4 | 64 | 3 | ○ | |
| 20 | (23) | 1.22 | 4 | 69 | 3 | ○ | |
| com. | 4 | (24) | 0.84 | 2 | 6 | 2 | X |
| 5 | (25) | 1.05 | 2 | 72 | 1 | X | |
| 6 | (26) | 0.98 | 2 | 9 | 2 | X | |
| 7 | (27) | 1.11 | 1 | 75 | 1 | X | |
[0073] As seen from Table 4, the printing papers of examples 7 to 20 each having the porous-surface layer 2a formed by the resin composition of urethane resin and vinyl chloride-vinyl acetate with a mixing ratio of urethane resin to other resin such as vinyl chloride-vinyl acetate within a range of 95 : 5 to 30 : 70 enable to print a high quality image having a high density and an excellent gradation without graininess.
[0074] On the other hand, the printing papers of comparatives 4 to com. 7 each having the porous-surface layer 2a formed by a sole component resin of only urethane resin or a resin composition of urethane resin and vinyl chloride-vinyl acetate with a mixing ratio of urethane to vinyl chloridevinyl acetate more than 30 : 70 is impossible to print a high quality image on the porous-surface layer 2a because of graininess and low gradation.
[Second embodiment]
[0075] Next, the description is given of a printing paper having a porous-surface or microgroove-surface layer of a second embodiment in the present invention, wherein the printing paper further comprises at least an adhesive layer and a released sheet.
[0076] Fig. 3 (A) is a partially enlarged schematic view of a printing paper having an adhesive layer and a released sheet in addition to a porous-surface layer in a second embodiment of the present invention; and
[0077] Fig. 3 (B) is a partially enlarged schematic view of another printing paper having a film layer between a released sheet substrate and an anti-stick agent layer in the second embodiment of the present invention.
[0078] The hot-melt type thermal ink transfer printing method applied to the printing paper of the second embodiment is the same as that of the first embodiment. Thus, the description thereof is omitted here. The description is given of a structure of the printing paper of the second embodiment, referring to Figs. 3(A) and 3(B), wherein like parts are shown by corresponding reference characters used in the first embodiment.
[0079] As shown in Fig. 3(A), a printing paper 102 of the second embodiment generally comprises a paper substrate 2b and a released sheet substrate 2e. The paper substrate 2b has a porous-surface layer 2a or a microgroove-surface layer 2a' (not shown) formed on one surface thereof and an adhesive layer 2c formed on another surface thereof. The released sheet substrate 2e has an anti-stick agent layer (referred to as anti-stick layer) 2d on a surface thereof for allowing a removal of the released sheet substrate 2e from the adhesive layer 2c. Both the paper substrate 2b and the released sheet substrate 2e are laminated such that the adhesive layer 2c of the paper substrate 2b faces to the anti-stick layer 2d of the released sheet substrate 2e.
[0080] The features of the paper substrate 2b and the porous-surface layer 2a (or microgroove-surface layer 2a') formed on the paper substrate 2b in the second embodiment are the same as those of the first embodiment. Thus, the description is omitted here.
[0081] As the adhesive used for forming the adhesive layer 2c, ordinary adhesives such as a rubber type adhesive and an acrylic adhesive are available.
[0082] As the released sheet substrate 2e, it is necessary to employ such a substrate capable of preventing deformation of the pores of the porous-surface layer 2a or the microgrooves of the microgroove-surface layer 2a' by the pressure due to laminating, for instance, an elastic substrate.
[0083] Specifically, polypropylene resin, a synthetic paper ("YUPO" by OJI YUKA SYNTHETIC PAPER CO., LTD.) made by a non-woven paper fabrication, wherein a film is mainly composed of polypropylene resin and inorganic filler and contains numerous micro-voids formed by biaxially oriented film forming method, polyethylene type and polypropylene type porous-surface sheet (TOKUYAMA), and blowing polyester film ("CRISPER" by TOYOBO CO., LTD.) containing voids therein generated due to void generating mechanism at a stretching process are available.
[0084] Another materials, polyorephine such as polyethylene and polypropylene, plastic foaming sheets and films such as polyurethane, polyester, polystylene and polyamid, and sheets and films having rubber-like elasticity such as urethane, acryl, stylene-butagene rubber are also available.
[0085] A thickness of the released sheet substrate 2e is desirable to be selected taking account of the function as the released sheet and convenience to use.
[0086] Specifically, the thickness of the released sheet substrate 2e is preferably 25 µm to 1000 µm and more preferably 30 µm to 200 µm.
[0087] The anti-stick layer 2d is formed on another surface of the released sheet substrate 2e. As the anti-stick layer 2d, ordinary anti-stick materials such as silicon, fluoride, silicon acryl and wax coating type anti-stick agent are available. The anti-stick layer 2d can be formed on the surface of the released sheet substrate 2e by using ordinary coating methods such as a multiple roll method, an off-set gravure method, a direct gravure method and a blade method.
[0088] Further, as shown in Fig. 3(B), in the printing paper of the second embodiment in the present invention, a film layer 2f can be provided interposed between the released sheet substrate 2e and the anti-stick layer 2d to increase the smoothness of the release sheet to improve the an image quality. The film layer 2f preliminarily formed with the anti-stick layer 2d can be directly laminated to the released sheet substrate 2e.
[0089] The printing papers 102, 103 with the adhesive layer 2c can be produced by using an ordinary laminating process.
[0090] Fig. 4 is a schematic view for explaining a laminating process of the printing paper with an adhesive layer in the present invention.
[0091] A printing paper base sheet 5 formed with the porous-surface or microgroove-surface layer (not shown) on one surface thereof is put in a coating process, where an adhesive is coated on a back surface of the base sheet 5 to form the adhesive layer 2c. Then, the base sheet 5 is dried by a dryer 9.
[0092] On the other hand, a released sheet substrate base sheet 6 formed with the anti-stick layer 2d (not shown) is supplied to a pair of pressure rolls 10, the base sheet 6 is laminated on the printing paper base sheet 5 in such a manner that the anti-stick layer 2d thereof faces to the adhesive layer 2c of the printing paper base sheet 5. Then, the laminated base sheets 5, 6 are taken up by a take-up drum 7, resulting in the printing paper base sheet 5 laminated with the released sheet substrate base sheet 6. By slitting it to a desired size, the printing paper 102 with adhesive layer is obtained.
[0093] According to the printing paper having the adhesive layer and the released sheet for protecting the adhesive layer in the present invention, it is possible to prevent the deformation of the pores of the porous-surface or the microgrooves of the microgroove-surface layer even when an excessive pressure is given to the pores or the microgrooves at the lamination process because the released sheet substrate is made of an elastic material which lessens the direct pressure given to the pores or microgrooves.
[Examples 21 to 23]
[0094] The printing paper with the adhesive layer of the second embodiment is now explained of examples 21 to 23 and comparatives 8 to 11.
〈Production of the printing paper with adhesive layer〉
[0095] The printing paper: As the printing paper, a sheet substrate having the porous-surface layer (a synthetic paper having a thickness of 150 µm formed with a porous-surface layer from NISSHIN BOUSEKI CO., LTD,) was used.
[0096] On a back surface of the sheet substrate, the adhesive layer was formed by using an adhesive ("ACRYL EMULARSION AE-230" by JAPAN SYNTHETIC RUBBER CO., LTD.). Thickness of the adhesive layer after dried was made to be about 15 µm.
The released sheets:
[0097] As the released sheet, released sheet materials shown in Table 5 were prepared, and the printing papers of examples 21 to 23 and comparatives 9 to 11 were respectively prepared by giving a conditions of lamination (impression cylinder pressure by the pressure roll 10 shown in Fig. 4) to each of the released sheet materials.
[0098] Further, on a surface of each of the released sheets, an anti-stick agent ("Ultraviolet ray silicon anti-stick agent, KS5500 by SHINETSU KAGAKU) was coated to a thickness of 0.2 µm after dried.
Table 5
| released sheet | cylinder line pressure | ||
| ex. | 21 | * synthetic paper (S. P.) 1 | 9,800 N/m |
| 22 | ** synthetic paper (S. P.) 2 | 9,800 N/m | |
| 23 | *** OPP | 9,800 N/m | |
| com. | 8 | coated paper (80 g/m2) | 9,800 N/m |
| 9 | same as above | 4,900 N/m | |
| 10 | same as above | 490 N/m | |
| 11 | ****PET (thickness of 100 µm) | 9,800 N/m | |
| * OJI-YUKA SYNTHETIC PAPER CO., LTD, YUPO FPG-80 | |||
| ** TOYOBO CO., LTD, CRISPER, thickness of 75 µm | |||
| *** oriented polypropylene film | |||
| ****polyethylene telephthalate film |
〈Evaluation〉
[0099] The printing papers of the examples 21 to 23 and the comparatives 8 to 11 were evaluated by actually printing an image thereon using a color printer with a thermal head having a resolution of 300 dots/inch ("Trueprint 2200" by Victor Company of Japan, ). The results are shown in Table 6. Ink ribbon used in the evaluation is made of a polyethylene telephthalate film having a thickness of 4.5 µm. On a surface thereof, there is provided a heat resistance smooth surface mainly made of thermosetting acryl resin having a thickness of 0.2 µm, and on another surface thereof there is provided an ink layer containing ink components as follows.
-Ink layer composition-
[0100]
| (weight parts) | |
| 1) color pigment: (Sumiburasuto red FG) | 15 |
| 2) paraffin wax: | 60 |
| 3) canauba wax: | 5 |
| 4) kyandeira wax: | 5 |
| 5) rosin ester: | 5 |
| 6) ethylene-vinyl acetate copolymer | 10 |
-evaluation test-
1) Lamination quality:
[0102] Uneveness of the printing paper laminated with the adhesive layer caused by the lamination process was evaluated visually by sighting.
2) Deformation of pores of the porous-surface layer:
[0103] Deformation of pores of the porous-surface layer caused in the lamination process is observed by using a microscope and compared with the ones before being laminated, wherein a mark X denotes the porous-surface layer having unacceptable deformation of pores of the porous-surface layer, and a mark ○ one having no deformation of pores, and a mark △ one having a degree of deformation between the mark ○ and the mark X .
3) Quality of printed image
[0104] The mark ○ denotes a distinct printed image, and the mark X an indistinct printed image.
Table 6
| released sheet | lamination quality | deformation of pores | quality of printed image | ||
| ex. | 21 | S. P. 1 | ○ | ○ | ○ |
| 22 | S. P. 2 | ○ | ○ | ○ | |
| 23 | OPP | ○ | △ | ○ | |
| com. | 8 | coat pa. | ○ | X | * X |
| 9 | coat pa. | X | △ | ** X | |
| 10 | coat pa. | X | ○ | *** X | |
| 11 | PET | ○ | X | **** X | |
| * lower ink density because of deformation of pores of the porous-surface layer. | |||||
| ** uneveness because of air contained in the adhesive layer. | |||||
| *** impossible to obtain an even lamination. | |||||
| **** lower ink density because of deformation of pores of the porous-surface layer. |
[0105] As seen from the results shown in Table 6, each of the examples 21 to 23 which employs an elastic material as the released sheet, shows an excellent lamination quality without deformation of pores of the porous-surface layer even when a sufficient pressure is applied to improve the adherence between the adhesive layer and the released sheet, resulting in a distinct printed image.
[0106] On the other hand, each of the comparatives 8 and 11 which employs a coated paper or PET without an elastic property shows an excellent lamination quality when an excessive cylinder line pressure is applied, however, the deformation of pores of the porous-surface layer is observed, resulting in an indistinct printed image. Further, when the impression cylinder pressure is low enough to keep the pores of the porous-surface layer, each of the comparatives 9 and 10 which employs a coated paper or PET without an elastic property, shows a degradation of the lamination quality, resulting in an indistinct printed image.
1. Hot-melt type thermal ink transfer printing medium having an ink acceptance layer
in which pores or microgrooves are contained, used for transferring hot-melt ink to
the ink acceptance layer of the printing medium by using a thermal head, characterized
in that the printing medium satisfies at least one condition from a group of two conditions
that a 100 % stress of the ink acceptance layer in conformity with a measuring method
of JIS-K-7127 is not less than 3,000 kN/m2 and a Young's modulus of the ink acceptance layer in conformity with a measuring
method of JIS-K-7127 is not less than 8,000 kN/m2.
2. Hot-melt type thermal ink transfer printing medium having an ink acceptance layer
in which pores or microgrooves are contained, used for transferring hot-melt ink to
the ink acceptance layer of the printing medium by using a thermal head, characterized
in that the ink acceptance layer is composed of a mixture of urethane resin and vinyl
chloride resin and/or vinyl acetate resin, and a mixing ratio of the urethane resin
to the vinyl chloride and/or vinyl acetate resin is from 95 : 5 to 30 to 70.
3. Hot-melt type thermal ink transfer printing medium having an ink acceptance layer
in which pores or microgrooves are contained, on one surface of the printing medium
used for transferring hot-melt ink to the ink acceptance layer of the printing medium
by using a thermal head, the printing medium further comprising a released sheet on
another surface of the printing medium through an adhesive layer interposed therebetween,
characterized in that the released sheet has an elastic property.
4. Hot-melt type thermal transfer printing medium as claimed in claim 3, characterized
in that a thickness of the released sheet having the elastic property is made to be
25 to 1000 µm.