Recording material

Abstract

 A recording material contains both a microcapsule containing an electron-donating color former dissolved in a solvent and an electron-accepting developer. The solvent comprises a glyceride and the electron-donating color former comprises a fluoran compound of the formula :


in which R¹ represents an alkyl group of 1 to 4 carbon atoms, R² represents a branched alkyl group of 4 to 12 carbon atoms or a tetrahydrofurfuryl group, and each of R³ and R⁴ represents independently a hydrogen atom, a halogen atom or a methyl group, provided that R¹ differs from R².

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a recording material which is employable for a pressure sensitive material and a heat sensitive material.

BACKGROUND OF THE INVENTION

[0002] Recording materials that contain both a micro capsule containing an electron-donating color former (hereinafter may be referred to as "color former") dissolved in a solvent and an electron-accepting developer (hereinafter may be referred to as "developer"), are widely used. In the recording material, the color former reacts with the developer to form a colored image.

[0003] Such recording material is roughly divided into a pressure sensitive material and a heat sensitive material. The pressure sensitive material utilizes the mechanisms that the micro capsule containing the color former is ruptured by application of pressure to form a color image through the reaction of the color former with the developer. The pressure sensitive recording material includes a no-carbon-paper-type recording material that a color former layer comprising a micro capsule containing a color former (hereinafter may be referred to as "color former layer") and a developer layer containing an electron-accepting developer (hereinafter may be referred to as "developer layer") are respectively formed on surfaces of separate supports or separate surfaces of one support and are in contact with each other to be used; and a self-coloring-type pressure sensitive recording material (e.g., pressing-type paper or self-contained paper) comprising a self-coloring layer having both the color former and the developer provided on one side surface of a support.

[0004] The no-carbon-paper-type recording material consists of a upper paper having a color former layer provided on one side surface of a support (which usually is paper sheet), an intermediate paper having a color former layer provided on one side surface of a support and a developer layer on another side surface of the support, and a lower paper having a developer layer provided on one side surface of a support. The intermediate paper is usually used in the form of two or more sheets. Such no-carbon-paper-type recording material is employed by bringing the color former into contact with the developer to form a colored image.

[0005] In the self-coloring-type pressure sensitive recording material, when pressure is applied to a surface having a self-coloring layer, a microcapsule in the layer is ruptured to form a color image on the self-coloring layer through the reaction of the color former with the developer. Therefore, the material is usually employed for writing or drawing an image such as a letter on a paper placed on the self-coloring layer with writing instruments or a typewriter, for directly printing a colored image on the self-coloring layer with a printer or a typewriter, or for printing a letter for OCR (optical character reader) on the self-coloring layer.

[0006] In preparation of plural copies, a self-coloring-type pressure sensitive recording material using a upper paper having a self-coloring layer provided on one side surface of a support and a color former layer on another side surface of the support, in combination with an intermediate paper having a color former layer and developer layer and a lower paper having a developer layer is occasionally employed. Types of the self-coloring layer of the self-coloring-type pressure sensitive recording material includes a two layers-type layer consisting of a color former layer containing a microcapsule containing a color former and a developer layer containing a developer which are superposed upon each other, and a one layer-type layer consisting of one layer containing a color former and a developer.

[0007] The heat sensitive recording materials containing a microcapsule, for example, are those having a heat sensitive layer which contains a microcapsule containing a color former and a developer, as described in Japanese Patent Provisional Publications No. 63(1988)-265682 and No. 1(1989)-105782. Such recording material has the advantages that can be designed for OHP (over head projector) or multicolor type.

[0008] The microcapsule, which is contained in the above recording materials, contains a color former dissolved in a solvent. It is necessary that such solvent is capable of dissolving the color former. Examples of the solvents generally include kerosine, paraffin, naphthene oil, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated naphthalene, diaryl alkane and phthalic acid ester. However, such solvents generally give off ill smell. Some of them are harmful to living things so that they have the danger that bring out environmental pollution (e.g., poor working condition). In more detail, when the recording material is prepared using such solvents or the recording material containing the solvents is used, the above problem occur.

[0009] Japanese Patent Provisional Publication No. 50(1975)-90409 describes a process for preparation of a pressure sensitive recording paper comprising the steps of dissolving a color former in an animal or vegetable oil heated at 105 to 260°C to prepare a color former solution, and forming a microcapsule layer containing the color former solution on support.

[0010] The animal or vegetable oils used in the process are natural edible materials mainly composed of triglyceride. Such oils have no ill smell and assured safety from the viewpoint of ecology, and further are available at low prices. Therefore, the oils are suitable for a solvent for the color former solution contained in the microcapsule.

[0011] However, the animal or vegetable oils generally do not have a sufficient dissolving power required for dissolving a color former and therefore it is difficult to increase a concentration of the color former in its solution. In the process described in the Japanese Patent Provisional Publication No. 50(1975)-90409, a color former is dissolved in an animal or vegetable oil by heating the oil at a high temperature of 105 to 260°C. However, such heating brings about deterioration of quality of the oil due to oxidation, and the heated oil occasionally gives off ill smell. Further, the oil itself inhibits occasionally coloring of the color former (i.e., desensitizes the color former).

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a recording material which has no ill smell and assured safety, and shows coloring of high density.

[0013] It is another object of the invention to provide a pressure sensitive recording material which has no ill smell and assured safety, and shows coloring of high density.

[0014] It is a further object of the invention to provide a heat sensitive recording material which has no ill smell and assured safety, and shows coloring of high density.

[0015] The present inventor has studied to find a color former that easily dissolves in glycerides such as vegetable or animal oils in high concentration at relatively low temperature. In more detail, finding of such color former enables the glycerides to use as a solvent for the color former solution contained in the microcapsule.

[0016] As a result, he has found the specific fluoran compound of the following formula (I) as such color former. Thus, he has been complete the invention.

[0017] The invention resides in a recording material which contains both a microcapsule containing an electron-donating color former dissolved in a solvent and an electron-accepting developer;
wherein the solvent comprises a glyceride and the electron-donating color former comprises a fluoran compound of the formula (I):


in which R¹ represents an alkyl group of 1 to 4 carbon atoms, R² represents a branched alkyl group of 4 to 12 carbon atoms or a tetrahydrofurfuryl group, and each of R³ and R⁴ represents independently a hydrogen atom, a halogen atom or a methyl group, provided that R¹ differs from R².

[0018] Preferred embodiments of the recording material are as follows:

(1) The recording material wherein R¹ represents methyl, ethyl, n-propyl or isopropyl, R² represents isobutyl, sec-butyl, isopentyl, isohexyl, 2-methylhexyl, 2-ethylhexyl, 2-ethyldecyl and tetrahydrofurfuryl, and each of R³ and R⁴ represents independently hydrogen, chlorine or methyl, there being no case that R¹ and R² represent the same group.

(2) The recording material wherein the solvent is vegetable oil.

(3) The recording material described above (2) wherein the vegetable oil.is at least one selected from the group consisting of soybean oil, sesame oil, corn oil, rapeseed oil, cotton seed oil, olive oil, peanut oil, castor oil, palm oil, coconut oil, sunflower oil, camellia oil, palm kernel oil, hardened oil and epoxidated oil.

(4) The recording material wherein the solvent consists essentially of triglyceride.

(5) The recording material wherein the microcapsule is prepared by dissolving the electron-donating color former in the glyceride at a temperature of 80 to 100°C and encapsulating the obtained solution.

(6) The recording material wherein the developer comprises clay materials.

[0019] Further, the invention resides in a pressure sensitive recording material which contains both a pressure rupturable color former layer comprising a microcapsule which contains an electron-donating color former dissolved in a solvent and a developer layer comprising an electron-accepting developer; wherein the solvent comprises a glyceride and the electron-donating color former comprises a fluoran compound of the above formula (I).

[0020] Furthermore, the invention resides in a pressure sensitive recording material which comprises a upper paper comprising a paper sheet and a pressure rupturable color former layer provided on the paper sheet, and a lower paper comprising a paper sheet and a developer layer provided on the paper sheet, said color former layer comprising a microcapsule which contains an electron-donating color former dissolved in a solvent and said developer layer comprising an electron-accepting developer;

[0021] wherein the solvent comprises a glyceride and the electron-donating color former comprises a fluoran compound of the formula (I).

[0022] Preferred embodiment of the above pressure sensitive recording material are as follows:

(1) The pressure sensitive recording material which further has at least one intermediate paper which has a paper sheet, a color former layer provided on one side surface of the paper sheet and a developer layer on another side surface of the paper sheet between the upper paper and the lower paper.

[0023] The recording material of the invention employs glycerides as a solvent for dissolving the color former. The glycerides generally give off no ill smell and are not harmful to living things. Therefore, they do not bring out poor working condition, and naturally do not environmental pollution. Further, the recording material shows coloring of high density due to use of the specific fluoran compound (color former) in combination with the glycerides because the fluoran compound is not desensitized by the glycerides. Hence, the recording material of the invention is one that has assured safety and shows coloring of high density. Particularly, it is useful for a pressure sensitive recording material.

BRIEF DESCRIPTION OF DRAWINGS

[0024] 

Fig. 1 is a schematic sectional view of a typical structure of the no-carbon-paper-type pressure sensitive recording material according to the invention.

Fig. 2 is a schematic sectional view of a typical structure of the self-coloring-type pressure sensitive recording material according to the invention.

Fig. 3 is a schematic sectional view of another structure of the self-coloring-type pressure sensitive recording material according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The recording material of the invention contains both a microcapsule containing an electron-donating color former dissolved in a solvent and an electron-accepting developer. The recording material is not restricted in its form so long as it contains a microcapsule containing a color former dissolved in a solvent.

[0026] The typical structures of the recording materials of the invention are described below.

Fig. 1 shows a typical structure of the no-carbon-paper-type pressure sensitive recording material. A upper paper 1 has a color former layer 3 provided on one side surface of a support 2. An intermediate paper 4 has a developer layer 5 provided on one side surface of a support 6 and a color former layer 7 on another side surface of the support 6. A lower paper 8 has a developer layer 9 provided on one side surface of a support 10. The three paper are superposed in the order as shown in Fig. 1. Although the intermediate paper4 is usually used in the form of a pile of two or more sheets, it may be not used. Recording (formation of image) is generally performed by applying pressure to the opposite surface of the color former layer 3 of the support 2 to bring the color former into contact with the developer.

Fig. 2 shows a typical structure of the self-coloring-type pressure sensitive recording material. Both a color former layer 11 and a developer layer 12 are provided on one side surface of a support 13.

Fig. 3 shows another structure of the self-coloring-type pressure sensitive recording material. A self-coloring layer 14 containing both a color former and a developer is provided on one side surface of a support 13.

[0027] The heat sensitive recording material has the same structure as that shown in Fig. 3. The self-coloring layer 14 corresponds to a heat sensitive layer.

[0028] The recording material of the invention is characterized by the use of the specific compound as the color former contained in the microcapsule and glyceride as the solvent for dissolving the color former. As for an example of the no-carbon-paper-type pressure sensitive material, a detail explanation is given below. It will be easily understand that the similar effect is obtained in recording materials having other forms.

[0029] Glyceride employed in the invention is used for dissolving the color former. Any natural glycerides and synthesis glycerides are employable in the invention. Further, any of triglycerides, diglycerides, monoglycerides and a mixture thereof are employable in the invention. It is preferred that the glyceride is mainly composed of triglyceride. The glyceride preferably is a ester of glycerin and saturated fatty acid.

[0030] Examples of the glycerides include 1-monocaprin, 1-monoundecanoin, 1-monolaurin, 1-monotridecanoin, 1-monomyristin, 1-monopentadecanoin, 1-monopalmitin, 1-monostearin, 1-monoolein, 1-monoelaidin, 1- monolinolenin, 1-monoarachin, 1-monobutyrin, 2-monocaprin, 2-monolaurin, 2-monomyristin, 2-monopaimi- tin, 2-monostearin,

[0031] 1,3-dicaprin, 1,3-diundecanoin, 1,3-dilaurin, 1,3-ditridecanoin, 1,3-myristin, 1,3-pentadecanoin, 1,3-dipalmitin, 1,3-distearin, 1,3-diarachin, 1,2-dilaurin, 1,2-dimyristin, 1,2-dipalmitin, 1,2-distearin,

[0032] triacetin, tributyrin, 1-aceto-2,3-dipalmitin, 1-aceto-2,3-distearin, tricaproin, 1-caproyl-2,3-distearin, 1- caproyl-2,3-diolein, tricaprylin, 1-elaido-2,3-dicaprylin, 1-linoleo-2,3-dicaprylin, 1-caprylyl-2,3-distearin, 1- caprylyl-2,3-diolein, trinonanoin, tricaprin, 1-lauro-2,3-dicaprin, 1-myristo-2,3-dicaprin, 1-palmito-2,3-dicaprin, 1-stearo-2,3-dicaprin, 1-oleo-2,3-dicaprin, 1-elaido-2,3-dicaprin, 1-linoleo-2,3-dicaprin, 2-lauro-1,3-dicaprin, 1-capryl-2,3-dilaurin, 1-capryl-2-lauro-3-myristin, 2-myristo-1,3-dicaprin, 1-capryl-2,3-dimylistin, 2-paimito-1,3-dicaprin, 1-capryl-2,3-dipalmitin, 2-stearo-1,3-dicaprin, 1-capryl-2,3-distearin, 2-oleo-1,3-dicaprin, 1-cap- ryl-2,3-diolein, 1-capryl-2,3-dielaidin, 1-capryl-2,3-dilaurin, trilaurin, 1-myristo-2,3-dilaurin, 1-palmito-2,3-dilaurin, 1-stearo-2,3-dilaurin, 1-oleo-2,3-dilaurin, 1-elaidino-2,3-dilaurin, 1-linoleo-2,3-dilaurin, 2-myristo-1,3- dilaurin, 1-lauro-2,3-dimyristin, 1-lauro-2-myristo-3-palmitin, 2-palmito-1,3-dilaurin, 1-lauro-2,3-dipalmitin, 2- stearo-1,3-dilaurin, 1-lauro-2,3-distearin, 2-oleo-1,3-dilaurin, 1-lauro-2,3-diolein, 1-lauro-2,3-dielaidin, 1-lauro-2,3-dilinolein, 2-capryl-1,3-dimyristin, 1-myristo-2-capryl-3-stearin, trimyristin, 1-palmito-2,3-dimyristin, 1-stearo-2,3-dimyristin, 1-oleo-2,3-dimyristin, 1-elaidino-2,3-dimyristin, 1-linoleo-2,3-dimyristin, 2-paimito-1,3-dimyrstin, 1-myristo-2,3-dipalmitin, 1-myristo-2-palmito-3-stearin, 2-stearo-1,3-dimyristin, 1-myristo-2,3- distearin, 2-oleo-1,3-dimyristin, 1-myristo-2,3-diolein, 1-myristo-2,3-dielaidin, 1-mylisto-2,3-dilinolein, 2-cap- ryl-1,3-dipalmitin, 1-palmito-2-capryl-3-stearin, 2-lauro-1,3-dipalmitin, 1-palmito-2-lauro-3-stearin, 2-myristo-1,3-dipalmitin, tripalmitin, 1-stearo-2,3-dipalmitin, 1-₀Ieo-2,3-dipalmitin, 1-linoleo-2,3-dipalmitin, 2-stearo-1,3-dipalmitin, 1-paImito-2,3-distearin, 2-oleo-1,3-dipalmitin, 1-palmito-2,3-diolein, 1-palmito-2,3-dilinolein, 2-cap- ryl-1,3-stearin, 2-lauro-1,3-distearin, 2-myristo-1,3-distearin, 2-palmito-1,3-distearin, tristearin, 1-oleo-2,3- distearin, 1-linoleo-2,3-distearin, 2-oleo-1,3-distearin, 1-stearo-2,3-diolein, 1-stearo-2,3-dilinolein, 2-stearo-1,3-diolein and a mixture thereof.

[0033] Although these glycerides may be synthesis glycerides or natural oil, it is convenience to use the natural oil. Preferred examples of the natural oil include vegetable oils such as soybean oil, sesame oil, corn oil, rapeseed oil, cotton seed oil, olive oil, peanut oil, castor oil, palm oil, coconut oil, sunflower oil, camellia oil and palm kernel oil. These oils are employable singly or in combination. Further, hardened oil prepared by hydrogenation of unsaturated glyceride and epoxidated oil prepared by epoxidation of unsaturated bond of unsaturated glyceride are also employable as glyceride of the invention.

[0034] In the invention, a conventional solvent mentioned previously is employable in the amount that the resultant recording material does not give off ill smell (not more than 30 weight % per glyceride), in combination of glyceride.

[0035] The color former employed in the invention is a fluoran compound of the formula (I) mentioned previously. Examples of the alkyl group of 1 to 4 carbon atoms represented by R¹ include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl. Preferred are methyl, ethyl, n-propyl and isopropyl. Particularly, ethyl is preferred.

[0036] Examples of the branched alkyl group of 4 to 12 carbon atoms represented by R² include isobutyl, sec-butyl, tert-butyl, isopentyl, sec-pentyl, tert-pentyl, isohexyl, 2-methylhexyl, 2-ethylhexyl and 2-ethyldecyl. Preferred examples of the group represented by R² include isobutyl, sec-butyl, isopentyl, isohexyl, 2-methylhexyl, 2-ethylhexyl, 2-ethyldecyl and tetrahydrofurfuryl. Particularly, isobutyl and tetrahydrofurfuryl are preferred.

[0037] Preferred examples of the group represented by R³ include hydrogen, chlorine and methyl. Particularly, methyl is preferred.

[0038] Preferred examples of the group represented by R⁴ include hydrogen, chlorine and methyl. Particularly, hydrogen is preferred.

[0039] Preferred examples of the fluoran compound of the formula (I) include 2-anilino-3-methyl-6-N-ethyl-N-iso- butylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isopentylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-isobutylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-isopentylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isohexylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-(2-ethylhexyl)aminofluoran, 2-toluidino-3-methyl-6-N-ethyl-N-isobutylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-(2-ethyldecyl)aminofluoran, 2-anilino-3-methyl-6-N-n-propyl-N-isobutylaminofluoran, 2-anilino-3-methyl-6-N-isopropyl-N-isobutylaminofluoran, 2-(o-chloroanilino)-6-N-ethyl-N-isobutylaminofluoran, 2-anilino-3-chloro-6-N-ethyl-N-(sec-butyl)aminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-tetrahydrofurfurylamonofluoran and 2-anilino-3-methyl-6-N-methyl-N-tetrahy- drofurfurylaminofluoran.

[0040] In the invention, the known color formers can be employed together with the fluoran compound for purpose of controlling tone. Examples of the known color formers include triphenylmethanphthalide compounds, fluoran compounds other than the fluoran compounds of the invention, phenothiazine compounds, indolylphthalide compounds, leucoauramine compounds, rhodaminelactam compounds, triphenylmethan compounds, tria- zene compounds and spiropyran compounds. The fluoran compound of the invention is preferably used in the amount of not less than 70 weight % based on the total amount of the used color formers to give an image of high coloring density.

[0041] The microcapsule containing the color former of the fluoran compound having the formula (I) is prepared by dissolving the color former in the solvent of the glyceride. The fluoran compound is preferably dissolved in a solvent of the glyceride at a temperature of 80 to 100°C. In the case of a temperature lower than 80°C, the fluoran compound is not easily dissolved in the glyceride. In the case of a temperature higher than 100°C, the glyceride is occasionally deteriorated. The fluoran compound of the formula (I) is contained in the solution of the color former in the amount of 3 to 8 % by weight based on the amount of the glyceride. Color formers other than the fluoran compound of the formula (I) are dissolved in the glyceride at the temperature within the above range so long as in the amount of lower than 1 weight %. For dissolving these colorformers in the above amount (3 to 8 weight %), it is required to heat a mixture containing them to approx. 150°C.

[0042] The microcapsule of the invention containing the color former dissolved in the solvent is prepared according to the known method such as an interfacial polymerization method, an internal polymerization method, a phase separation method, an external polymerization method or a coaservation method.

[0043] As the shell material of the microcapsule, water-insoluble or oil-insoluble polymers which is used in the conventional pressure sensitive material are employable. The shell material is preferred to be polyurethane/polyurea resin having high resistance to heat-fogging. The microcapsule dispersion forforming the shell of polyurethane/polyurea resin to incorporate the color former, is prepared by, for example, the steps of dissolving a multi-functional isocyanate compound and a multi-functional hydroxyl compound (further UV absorbent if desired) in the solution prepared by dissolving the color former in glyceride as above, dispersing the resultant solution to a hydrophilic liquid, adding a multi-functional amine to the resultant dispersing solution, and coating the polyurethane/polyurea resin around a drop of the glyceride solution. The multi-functional hydroxyl compound and the multi-functional amine may be used in combination as above, or either of them may be used.

[0044] The dispersing solution of the microcapsule prepared above is directly employed as a coating solution for forming the color former layer. Otherwise, the coating solution is prepared by adding further a binder and/or an agent for protecting a capsule to the dispersing solution. The resultant coating solution is coated on the support according to a known coating method and the coated layer is dried. Thus, the color former layer for the no-carbon-paper-type pressure sensitive recording material is formed. Examples of the binder include a water-soluble binder and a latex binder and examples of the agent for protecting a capsule include powders of cellulose, powders of starch and talc.

[0045] As materials of the support, materials employed for the support of the conventional pressure sensitive recording material and the conventional heat sensitive recording material. Examples of the materials of the support include a paper made of pulp, a surface treated paper, a synthetic paper made of plastic and a plastic film.

[0046] The coated amount of the color former layer formed on the support after drying generally is in the range of 0.05 to 0.30 g/m², and preferably is in the range of 0.08 to 0.20 g/m².

[0047] Examples of the developer contained in the developer layer of the no-carbon-paper-type pressure sensitive recording material include clay materials such as acid clay, activated clay, attapulgite, zeolite, bentonite and kaolin, metal salts of aromatic carboxylic acids (e.g., salicylic acid derivatives), and a phenol formaldehyde resin. The developer preferably is clay materials from the viewpoint of ecology.

[0048] A coating solution for forming the above developer layer is prepared according a known method. For example, the coating solution may further contain a binder. Examples of the binder include natural or synthetic polymers such as styrene/butadiene copolymer latex, polyvinyl acetate latex, polyacrylate latex, polyvinyl alcohol, polyacrylic acid, maleic anhydride/styrene copolymer, starch, casein, carboxymethyl cellulose and methyl cellulose. The developer layer is formed on the support utilizing a known coating method.

[0049] The coated amount of the developer layer formed on the support after drying generally is in the range of 0.1 to 4.0 g/m², and preferably is in the range of 0.2 to 3.0 g/m².

[0050] The no-carbon-paper-type pressure sensitive recording material according to the invention has a composition similar to a conventional one except for employing the fluoran compound of the formula (I) as colorformer and the glyceride as the solvent for dissolving the color former. Therefore, the no-carbon-paper-type pressure sensitive material of the invention can be prepared utilizing the known process.

[0051] As for other recording materials such as the self-coloring-type pressure sensitive recording material and the heat sensitive recording material described previously, they have a composition similar to conventional one except for employing the above specific compounds as color former and as the solvent for dissolving the color former which are contained in the microcapsule. Therefore, the recording materials can be prepared utilizing the known processes.

[0052] The present invention is further described by the following examples.

EXAMPLE 1

[0053] (Preparation of coating solution for forming color former layer)

[0054] In 120 g of cotton seed oil, 5.0 g of 2-anilino-3-methyl-6-N-ethyl-N-isobutylaminofluoran as a colorformer was dissolved by heating at 90°C for 1 hour. In the resultant oily solution, 10 g of a carbodiimide-modified di- phenylmethandiisocyanate (Milionate MTL, available from Nippon Polyurethane Co., Ltd.) and 5 g of a biuret body of hexamethylenediisocyanate (Sumijule N-3200; available from Sumitomo Bayer Urethane Co., Ltd.) as a multi-functional isocyanate compound, and 3.0 g of butylene oxide adduct of ethylenediamine (adduct molar number of butylene oxide to ethylenediamine: 16.8 moles; Molecularweight: 1,267) as an alkylene oxide adduct of amine were dissolved to prepare a primary solution.

[0055] Subsequently, 10 g of polyvinyl alcohol and 5 g of carboxymethylcellulose were dissolved in 140 g of water to prepare a secondary solution. The primary solution was poured into the secondary solution while the secondary solution was vigorously stirred. Thus oil-in-water emulsion was formed. When a size of the oil droplet of the emulsion became 5.0 f..lm, the stirring power was weakened and then 100 g of water of 20°C was added to the emulsion. Subsequently, the temperature of the emulsion was gradually raised to 70°C and this temperature was kept for 90 minutes. Thus a capsule solution was obtained.

[0056] To the obtained capsule solution, 80 g of a polyvinyl alcohol 15 weight % solution, 30 g (solid content) of carboxyl-modified SBR (styrene butadiene rubber) latex and 60 g of starch particles (mean particle size: 15 f..lm) were added, and further the solution was adjusted to 20 weight % by the addition of water to prepare a coating solution for forming a color former layer which contains a microcapsule containing a color former. (Preparation of color former sheet)

[0057] On the one side of a paper of 50 g/m², the above coating solution for forming a color former layer was so coated as to have 4.0 g/m² in terms of solid content using an air-knife coater, and dried to prepare the color former sheet. This color former sheet scarcely gave off smell.

[0058] (Preparation of coating solution "A" for forming developer layer)

[0059] A mixture of 200 g of activated clay, 20 g of sodium carbonate, 8 g of magnesium oxide, 1 g of sodium hexametaphosphate, 20 g of 20 weight % sodium hydroxide and 500 g of water was dispersed by means of a cady mill. To the resultant dispersing solution, 40 g (solid content) of a carboxyl-modified SBR (styrene butylene rubber) latex and 60 g of a starch aqueous solution (10 weight %) were added to prepare the coating solution "A" for forming a developer layer.

[0060] (Preparation of developer sheet "A")

[0061] On the one side of a paper of 50 g/m², the above coating solution "A" for forming a developer layer was so coated as to have 6.0 g/m² in terms of solid content using an air-knife coater, and dried to prepare the developer sheet "A".

[0062] (Evaluation of developed color density)

[0063] The resultant color former sheet was placed on the resultant developer sheet "A" in such a manner that the color former layer and the developer layer came into contact each other. Load of 300 kg/cm² was applied to the resultant composite to form a developed image on the developer layer. After the image of the developer layer was allowed to stand at room temperature for 24 hours, its density (D) was measured using Machbeth reflective densitometer. The result is set forth in Table 1.

EXAMPLE 2

[0064] (Preparation of color former sheet)

[0065] Procedures of Example 1 was repeated except for using the same amount of soybean oil instead of cotton seed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet scarcely gave off smell.

[0066] (Evaluation of developed color density)

[0067] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

EXAMPLE 3

(Preparation of color former sheet)

[0068] Procedures of Example 1 was repeated except for using the same amount of corn oil instead of cotton seed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet scarcely gave off smell.

(Evaluation of developed color density)

[0069] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

EXAMPLE 4

(Preparation of color former sheet)

[0070] Procedures of Example 1 was repeated except for using the same amount of epoxidated soybean oil instead of cotton seed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet scarcely gave off smell.

(Evaluation of developed color density)

[0071] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

EXAMPLE 5

(Preparation of color former sheet)

[0072] Procedures of Example 1 was repeated except for using the same amount of 1,2-dilaurin instead of cotton seed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet scarcely gave off smell.

(Evaluation of developed color density)

[0073] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

COMPARISON EXAMPLE 1

(Preparation of color former sheet)

[0074] Procedures of Example 1 was repeated except for using the same amount of 1-phenyl-1-xylylethane instead of cotton seed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet gave off a stimulative smell.

(Evaluation of developed color density)

[0075] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

COMPARISON EXAMPLE 2

(Preparation of color former sheet)

[0076] 5.0 g of 2-anilino-3-methyl-6-N,N-diethylaminofluoran as a color former was dissolved in 120 g of cotton seed oil by heating at 90°C for 1 hour. However, most of the color former was not dissolved in the oil and therefore the insoluble color former formed the deposit in the solution of the oil and the color former.

[0077] Procedures of Example 1 was repeated except for using the oily solution prepared above instead of one of Example 1, to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet.

(Evaluation of developed color density)

[0078] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

COMPARISON EXAMPLE 3

(Preparation of color former sheet)

[0079] 5.0 g of 2-anilino-3-methyl-6-N-ethyl-N-cyclohexylaminofluoran as a color former was dissolved in 120 g of cotton seed oil by heating at 90°C for 1 hour. However, most of the color former was not dissolved in the oil and therefore the insoluble color former formed the deposit in the solution of the oil and the color former.

[0080] Procedures of Example 1 was repeated except for using the oily solution prepared above instead of one of Example 1, to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet.

(Evaluation of developed color density)

[0081] Using the resultant color former sheet and the developer sheet "A" prepared in the same manner as Example 1, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

EXAMPLE 6

(Preparation of coating solution for forming color former layer)

[0082] In 100 g of rapeseed oil, 2.5 g of 2-anilino-3-methyl-6-N-ethyl-N-terahydrofrufurylaminofluoran and 2.5 g of 2-anilino-3-methyl-6-N-ethyl-N-isopenthylaminofluoran as a color former was dissolved by heating at 95°C for 30 minutes. To the resultant oily solution, 20 g of paraffin solvent (IP solvent 1620, available from Idemitsu protochemical Co., Ltd.) was added to prepare a color former oily solution.

[0083] 12 g of acid-treated gelatin having an isoelectric point of 8.2 and 10 g of gum Arabic were dissolved in 80 g of water (40°C). To the solution, 0.2 g of Turkey red oil was added as an emulsifier to prepare a colloidal solution. The above color former oily solution was added to the colloidal solution with vigorously stirring to emulsify, and thus an oil in water emulsion was obtained. With stirring, 370 g of warm water (40°C) was added to the emulsion and 20% hydrochloric acid was dropwise added to the emulsion to adjust its pH to 4.4. A vessel having the emulsion therein was cooled from the outside with stirring the emulsion to set a colloid wall deposited on the oil drop to gel. When the temperature of the emulsion became 10°C with continuously stirring, 3.0 g of formaldehyde 37 % solution was added to the emulsion and further 40 g of 7 weight % aqueous solution of sodium salt of carboxymethyl-cellulose (etherification degree: 0.75) was added. Then, sodium hydroxide 10 weight % aqueous solution was dropwise added to the emulsion till the pH became 10, and the vessel having the emulsion therein was heated from the outside to raise its temperature to 40°C. The emulsion was kept at this temperature for 1 hour to prepare a capsule solution containing the color former.

[0084] To the resultant capsule solution, 120 g of oxidized starch 15 % aqueous solution and 40 g of starch particle having mean particle size of 12 f..lm were added. Further, water was added to the capsule solution to adjust its solid content (concentration) to 20 weight %. Thus, the coating solution for forming a color former layer which contains the microcapsule containing the color former was prepared.

(Preparation of color former sheet)

[0085] On the one side of a paper of 50 g/m², the above coating solution for forming the color former layer was so coated as to have 4.5 g/m² in terms of solid content using an air-knife coater, and was dried to prepare the color former sheet. This color former sheet scarcely gave off smell.

(Preparation of coating solution "B" for forming developer layer)

[0086] A mixture of 120 g of calcium carbonate, 20 g of zinc oxide, 5 g of zinc 3,5-bis(a-methylbenzyl)salicylate, 1 g of sodium hexametaphosphate and 200 g of water was subjected to atomization treatment using a sand mill to prepare a dispersing solution. To 300 g of the dispersing solution, 200 g of 9 % aqueous solution of polyvinyl alcohol (PVA-117, available from Kuraray Co., Ltd.) and 4 g (solid content) of a carboxyl-modified SBR (styrene butylene rubber) latex (SN307, available from Sumitomo Norgatack Co., Ltd.) were added and adjusted the solid content to 20 weight % by addition of water to prepare the coating solution "B" for forming a developer layer.

(Preparation of developer sheet "B")

[0087] On the one side of a paper of 50 g/m², the above coating solution "B" for forming a developer layer was so coated as to have 4.5 g/m² in terms of solid content using an air-knife coater, and dried to prepare the developer sheet "B".

(Evaluation of developed color density)

[0088] The obtained color former sheet was placed on the resultant developer sheet "B" in such a manner that the color former layer and the developer layer came into contact. Using the resultant composite, the evaluation of the developed color density was performed in the same manner as that of Example 1. The result is set forth in Table 1.

EXAMPLE 7

(Preparation of color former sheet)

[0089] Procedures of Example 6 was repeated except for using the same amount of triacetin instead of rapeseed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet gave off a stimulative smell.

(Evaluation of developed color density)

[0090] Using the resultant color former sheet and the developer sheet "B" prepared in the same manner as Example 6, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

COMPARISON EXAMPLE 4

(Preparation of color former sheet)

[0091] Procedures of Example 6 was repeated except for using the same amount of monoisopropylbiphenyl instead of rape-seed oil to prepare the coating solution for forming a color former layer and then to prepare the color forming sheet. The resultant color former sheet gave off a stimulative smell.

(Evaluation of developed color density)

[0092] Using the resultant color former sheet and the developer sheet "B" prepared in the same manner as Example 6, the evaluation of the developed color density was performed in the same manner as Example 1. The result is set forth in Table 1.

COMPARISON EXAMPLE 5

(Preparation of color former sheet)

[0093] In 120 g of cotton seed oil, 2.5 g of 2-anilino-3-methyl-6-N,N-dibutylaminofluoran and 2.5 g of 2-anilino-3-methyl-6-N,N-diethylaminofluoran as a color former was dissolved by heating at 90°C for 1 hour. However, most of the color formers were not dissolved in the oil and therefore the insoluble color former formed the deposit in the solution of the oil and the color former.

[0094] Although a capsule was tried to form using the oily solution of the oil and the color former prepared above in the same manner as procedures of Example 6, aggregation of the oily drops was generated with violence in the course of formation of the capsule. Therefore, the capsule was not formed and thus the color forming sheet which contains capsule containing the color former was not prepared.

[0095] Any recording materials prepared in the Examples scarcely gave off smell. Further, these materials showed the color images of high color densities with combination of the developer sheets. In contrast, the recording materials of Comparison Examples 1 and 4 which used materials other than glyceride as a solvent, gave off a stimulative smell to give unpleasant feeling to users, although they showed the color images of high color densities similar to those of Examples. Further, in the recording materials of Comparison Examples 2, 3 and 5 which used glyceride as a solvent and the color formers outside of the scope of the invention, the color formers were little dissolved or were insoluble in the triglyceride and therefore the use of them did not result in formation of capsule, or merely resulted in formation of capsule which gave the color image of an extremely low density on the developer sheet.

[0096] The color formers used in Comparison Examples 2 and 3 have structure similar to the color former of the invention, but it was unexpected that the color formers showed an extreme low color density compared with those of the invention.

Claims

1. A recording material which contains both a microcapsule containing an electron-donating colorformerdis- solved in a solvent and an electron-accepting developer;

wherein the solvent comprises a glyceride and the electron-donating color former comprises a fluoran compound of the formula (I):

in which R¹ represents an alkyl group of 1 to 4 carbon atoms, R² represents a branched alkyl group of 4 to 12 carbon atoms or a tetrahydrofurfuryl group, and each of R³ and R⁴ represents independently a hydrogen atom, a halogen atom or a methyl group, provided that R¹ differs from R².

2. The recording material as defined in claim 1, wherein R¹ represents methyl, ethyl, n-propyl or isopropyl, R² represents isobutyl, sec-butyl, isopentyl, isohexyl, 2-methylhexyl, 2-ethylhexyl, 2-ethyldecyl and tetrahydrofurfuryl, and each of R³ and R⁴ represents independently hydrogen, chlorine or methyl.

3. The recording material as defined in claim 1, wherein the solvent is a vegetable oil.

4. The recording material as defined in claim 3, wherein the vegetable oil is at least one selected from the group consisting of soybean oil, sesame oil, corn oil, rapeseed oil, cotton seed oil, olive oil, peanut oil, castor oil, palm oil, coconut oil, sunflower oil, camellia oil, palm kernel oil, hardened oil and epoxidated oil.

5. The recording material as defined in claim 1, wherein the solvent consists essentially of a triglyceride.

6. The recording material as defined in claim 1, wherein the microcapsule is prepared by dissolving the electron-donating color former in the glyceride at a temperature of 80 to 100°C and encapsulating the obtained solution.

7. The recording material as defined in claim 1, wherein the developer comprises clay materials.

8. A pressure sensitive recording material which has both a color former layer comprising a pressure rupturable microcapsule which contains an electron-donating color former dissolved in a solvent and a developer layer comprising an electron-accepting developer;
wherein the solvent comprises glyceride and the electron-donating color former comprises a fluoran compound of the formula (I):


in which R¹ represents an alkyl group of 1 to 4 carbon atoms, R² represents a branched alkyl group of 4 to 12 carbon atoms or a tetrahydrofurfuryl group, and each of R³ and R⁴ represents independently a hydrogen atom, a halogen atom or a methyl group, provided that R¹ differs from R².

9. The pressure sensitive recording material as defined in claim 8, wherein R¹ represents methyl, ethyl, n-propyl or isopropyl, R² represents isobutyl, sec-butyl, isopentyl, isohexyl, 2-methylhexyl, 2-ethylhexyl, 2-ethyldecyl and tetrahydrofurfuryl, and each of R³ and R⁴ represents independently hydrogen, chlorine or methyl.

10. The pressure sensitive recording material as defined in claim 8, wherein the solvent is a vegetable oil.

11. The pressure sensitive recording material as defined in claim 10, wherein the vegetable oil is at least one selected from the group consisting of soybean oil, sesame oil, corn oil, rapeseed oil, cotton seed oil, olive oil, peanut oil, castor oil, palm oil, coconut oil, sunflower oil, camellia oil, palm kernel oil, hardened oil and epoxidated oil.

12. The pressure sensitive recording material as defined in claim 8, wherein the solvent consists essentially of a triglyceride.

13. The pressure sensitive recording material as defined in claim 8, the microcapsule is prepared by dissolving the electron-donating color former in the glyceride at a temperature of 80 to 100°C and encapsulating the obtained solution.

14. The pressure sensitive recording material as defined in claim 8, wherein the developer comprises clay materials.

15. A pressure sensitive recording material which comprises a upper paper comprising a paper sheet and a color former layer provided on the paper sheet, and a lower paper comprising a paper sheet and a developer layer provided on the paper sheet, said color former layer comprising a pressure rupturable microcapsule which contains an electron-donating color former dissolved in a solvent and said developer layer comprising an electron-accepting developer;
wherein the solvent comprises a glyceride and the electron-donating color former comprises a fluoran compound of the formula (I):


in which R¹ represents an alkyl group of 1 to 4 carbon atoms, R² represents a branched alkyl group of 4 to 12 carbon atoms or a tetrahydrofurfuryl group, and each of R³ and R⁴ represents independently a hydrogen atom, a halogen atom or a methyl group, provided that R¹ differs from R².

16. The recording material as defined in claim 15, which further has at least one intermediate paper which has a paper sheet, a color former layer provided on one side surface of the paper sheet and a developer layer on another side surface of the paper sheet between the upper paper and the lower paper.

Drawing