Heat-sensitive color-changing resin film

Abstract

To provide a thermosensitive color developing resin film which enables formation of a thermosensitive color developing ink layer between transparent resin films, and enables long-term storage.SOLUTION: A thermosensitive color developing resin film has a thermosensitive color developing ink layer between two resin films, in which the one transparent resin film is a thin transparent resin film having a thickness of 3-12 μm, the other is a thick resin film having a thickness of 25-120 μm, and the thermosensitive color developing ink layer is composed of two layers of a leuco dye layer formed from a leuco dye composition containing a leuco dye, a binder resin and a cyclic alkyl solvent that is substituted with an alkyl group having 1 to 3 carbon atoms and contains a cyclic alkyl solvent having 5 to 8 carbon atoms, and a developer layer formed from a developer composition containing a developer, a binder resin and a cyclic alkyl solvent that is substituted with an alkyl group having 1 to 3 carbon atoms and contains a cyclic alkyl solvent having 5 to 8 carbon atoms.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thermosensitive coloring resin film, and more particularly to a thermosensitive coloring resin film having a thermosensitive coloring ink layer between two transparent resin films. [Background technology]

[0002] Thermal color-developing paper is used at convenience stores and supermarkets' cash registers, and is obtained by applying and drying a leuco dye and a color developer, both of which are dispersed in water, onto a paper substrate, while making sure that the leuco dye and the color developer do not come into contact with each other. In this case, when heat is applied, the leuco dye and the color developer combine to develop color. However, thermal paper cannot be stored for long periods of time, as it develops color with even a slight impact or during storage.

[0003] It is possible to improve the performance of the film by using a resin film instead of paper, thereby extending the storage period. However, the paint normally used for the thermosensitive coloring layer is water-based and contains a leuco dye and a color developer. When this type of paint is applied to a resin film, the water does not soak in, so it takes a long time for the solvent (water) to dry. If the solvent is changed to one that is mainly organic, the leuco dye and the color developer will dissolve and come into contact, causing coloring, making it impossible to use the film as a thermosensitive coloring layer.

[0004] Japanese Patent Laid-Open Publication No. 8-039939 (Patent Document 1) proposes a thermosensitive color-developing film that uses a water-insoluble phenolic compound having a melting point range of 160° C. to 250° C. as a color developer. However, the usable compounds in this document are limited to specific phenolic compounds, which limits the degree of freedom in design and lacks versatility.

[0005] JP 2017-47634 A (Patent Document 2) describes a thermal paper having a structure in which a thermal coloring layer, an adhesive layer, a transparent resin film layer, and a heat-resistant layer are laminated in that order on one surface of a base paper. However, in this structure, the transparent resin film is only on one side, and the base paper is paper, rather than both sides being made of resin film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-039939 [Patent Document 2] JP 2017-47634 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the present invention, a thermosensitive coloring ink layer is formed between transparent resin films to provide a thermosensitive coloring resin film that can be stored for a long period of time. [Means for solving the problem]

[0008] That is, the present invention provides the following aspects: [1] A thermosensitive coloring resin film having a thermosensitive coloring ink layer between two transparent resin films, one of the transparent resin films is a thin transparent resin film having a thickness of 3 to 12 μm, and the other is a thick transparent resin film having a thickness of 25 to 120 μm; The thermosensitive coloring ink layer is composed of two layers, a leuco dye layer and a developer layer, which are in contact with each other, the leuco dye layer is formed from a leuco dye composition containing a leuco dye, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; the developer layer is formed from a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; Heat-sensitive color-changing resin film. [2] The thermosensitive color-developing resin film according to [1], wherein the transparent resin film is a PET (polyethylene terephthalate) film. [3] 3. The thermosensitive color-developing resin film according to claim 1, wherein the cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms is methylcyclohexane. [4] A thermosensitive color-developing resin film is laminated in the order of a developer layer, a leuco dye layer, and a thin transparent resin film from the thick transparent resin film side, The thermosensitive color-developing resin film according to any one of [1] to [3], wherein an adhesive layer is present between the thick transparent resin film and the color developer layer. [5] A heat-sensitive color-developing resin film is laminated in the order of a leuco dye layer, a developer layer, and a thin transparent resin film from the thick transparent resin film side, an adhesive layer is present between the thick transparent resin film and the leuco dye layer; a urethane resin layer is present between the color developer layer and the thin transparent resin film; A thermosensitive color-developing resin film according to any one of [1] to [3]. [6] the developer layer is composed of two layers, a first developer layer and a second developer layer, which are in contact with each other; the first developer layer is formed from a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; the second developer layer is formed from a developer composition containing a developer, a binder resin, and an organic solvent other than the cyclic alkyl solvent, the organic solvent other than the cyclic alkyl solvent being an organic solvent selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents, and mixtures thereof; the first developer layer is in contact with the leuco dye layer and the second developer layer is on the opposite side to the leuco dye layer; The thermosensitive color-developing resin film according to any one of [1] to [3] above, [9] The thermosensitive color-developing resin film according to any one of [1] to [6], wherein the binder resin is a rosin ester or a styrene-butadiene block copolymer. Effect of the Invention

[0009] In the present invention, a thermosensitive coloring ink is sandwiched between two transparent resin films. Therefore, when the thermosensitive coloring ink is transparent or a color close to that, a transparent, free-standing film is obtained, unlike paper, and when heat is applied to it, the heated part will develop color, and pictures or letters will appear in the transparent part. Compared to the uses of conventional thermal paper, there is a possibility that it can be used for various purposes, such as coloring a free-standing transparent resin film. In addition, if a colored substrate (e.g., colored paper) is placed behind this thermosensitive coloring resin film, pictures or letters can be formed on the colored substrate by heat, and if the color of the substrate and the coloring part are matched, it can also be used for impactful advertising, etc. It is therefore believed that the thermosensitive coloring resin film of the present invention can be used not only for cash register punching, for which thermosensitive paper has been used until now, but also for a wide range of other uses, and will open up a variety of uses.

[0010] In the thermosensitive coloring resin film of the present invention, the thermosensitive coloring ink layer is between the transparent resin films, and the thermosensitive coloring ink layer is not directly impacted, so that unwanted coloring such as coloring due to impact is unlikely to occur. In addition, the transparent resin film serves as a protective layer, so that the thermosensitive coloring ink layer is protected, and peeling or damage of the ink layer hardly occurs. Furthermore, one side of the transparent resin film is thinner than the other side, and when heat is irradiated from the thin side, it effectively develops color and forms an image.

[0011] The present invention is also characterized in that the thermosensitive coloring ink layer is composed of two layers, a leuco dye layer and a developer layer, which are in contact with each other, the leuco dye layer being formed from a leuco dye composition containing a leuco dye, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, and the developer layer being formed from a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms. By using a specific solvent, i.e., a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, in this way, both the leuco dye and the developer are less likely to dissolve, and unwanted color development (for example, so-called "fogging") can be prevented.

[0012] Furthermore, in the present invention, in order to ensure the transparency of the thermosensitive color-developing resin film, the color developer layer is made into two layers, a first color developer layer and a second color developer layer, which are in contact with each other, and the first color developer layer is formed from a color developer composition containing a color developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, and the second color developer layer is formed from a color developer composition containing a color developer, a binder resin, and an organic solvent other than the cyclic alkyl solvent, and the organic solvent other than the cyclic alkyl solvent is an organic solvent selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents, and mixtures thereof. When only a developer layer using a cyclic alkyl solvent (i.e., the first developer layer) is used, the developer tends to have a slight whitish color, which is thought to be due to the developer being dispersed within the layer.To prevent this, a second developer layer dissolved in a normal solvent is provided so as not to come into contact with the leuco dye layer, thereby maintaining the transparency of the thermosensitive color-developing resin film. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of one embodiment of a thermosensitive color-developing resin film of the present invention. [Diagram 2]FIG. 1 is a schematic cross-sectional view showing a first color developer layer, a second color developer layer, and a leuco dye layer in a case where the color developer layer of the thermosensitive color developing resin film of the present invention is two layers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] As described above, the thermosensitive coloring resin film of the present invention has a thermosensitive coloring ink layer between two transparent resin films, one of which is a thin transparent resin film having a thickness of 3 to 12 μm and the other is a thick transparent resin film having a thickness of 25 to 120 μm, the thermosensitive coloring ink layer consists of two phases, a leuco dye layer and a developer layer, which are in contact with each other, the leuco dye layer is formed from a leuco dye composition containing a leuco dye, a binder resin and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, and the developer layer is formed from a developer composition containing a developer, a binder resin and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms.

[0015] Furthermore, if necessary, particularly when the thermosensitive color-developing resin film needs to be transparent, the color developer layer may be formed into two layers, a first color developer layer and a second color developer layer, which are in contact with each other, and the compositions of each layer may be as follows: (a) first developer layer: containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; (b) Second developer layer: containing a developer, a binder resin and an organic solvent other than the cyclic alkyl solvent, wherein the organic solvent other than the cyclic alkyl solvent is selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents and mixtures thereof. The present invention is further characterized in that the first developer layer is in contact with the leuco dye layer, and the second developer layer is not in contact with the leuco dye layer. The present invention will be described in detail below.

[0016] FIG. 1 shows a schematic cross-sectional view of one embodiment of the thermosensitive coloring resin film of the present invention. In FIG. 1, 1 is a thick transparent resin film, and 2 is a thin transparent resin film. Between the thick transparent resin film 1 and the thin transparent resin film 2, there are an adhesive layer 3, a color developer layer 4, and a leuco dye layer 5, in this order from the thick transparent resin film 1 side, and the leuco dye layer 5 is in contact with the thin transparent resin film 2. On the outside of the thin transparent resin film 2 (the surface not in contact with the leuco dye layer 5), there is a heat-resistant layer 6. In the present invention, the transparent resin films 1 and 2, the color developer layer 4, and the leuco dye layer 5 are essential components, and the adhesive layer 3 and the heat-resistant layer 6 are layers that are formed as needed. In addition, the color developer layer 4 and the leuco dye layer 5 form a thermosensitive coloring ink layer A. In FIG. 1, the color developer layer 4 is on the thick transparent resin film 1 side, and the leuco dye layer 5 is on the thin transparent resin film 2 side, but there is no problem even if this order is reversed.

[0017] 2 is a schematic cross-sectional view showing the first color developer layer (4-1), the second color developer layer (4-2) and the leuco dye layer 5 in the case where the color developer layer 4 of the thermosensitive color developing resin film of the present invention is two layers that are in contact with each other. The first color developer layer (4-1) is a layer containing a color developer, a binder resin and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, and the second color developer layer (4-2) is a layer containing a color developer, a binder resin and an organic solvent other than the cyclic alkyl solvent, the organic solvent other than the cyclic alkyl solvent being selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents and mixtures thereof. In short, the solvents used in the first color developer layer (4-1) and the second color developer layer (4-2) are different. When the developer layer is thus made up of two layers, the first developer layer (the layer in which the solvent is a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms) is in contact with the leuco dye layer, and the second developer layer is located on the opposite side to the leuco dye layer. Each layer will be described below for each drawing.

[0018] <Description of each layer of the embodiment of FIG. 1> [Transparent resin film] In the present invention, the thermosensitive coloring ink layer A is disposed between two transparent resin films (thick transparent resin film 1 and thin transparent resin film 2). A transparent resin film can be used as the transparent resin film. In this specification, "transparent" means a state in which visible light is transmitted to an extent that does not interfere with the visibility of the image printed on the thermosensitive coloring ink layer, and also includes the concept of so-called translucency. Examples of transparent resin films include polyethylene films, polypropylene films, polycarbonate films, polyethylene terephthalate (PET) films, polyimide films, triacetate films, polyphenylene sulfide films, polyethylene naphthalate films, acrylic films, fluororesin films, and nylon films. In the present invention, a PET film is preferably used as the transparent resin film.

[0019] In the present invention, one of the transparent resin films is a thin transparent resin film 2 having a thickness of 3 to 12 μm, and the other is a thick transparent resin film 1 having a thickness of 25 to 120 μm. The reason for such a difference in thickness is that heat needs to be applied to make the thermosensitive coloring ink layer A color, but it is necessary to reach the thermosensitive coloring ink layer in a short time, so the transparent resin film on the side to which heat is applied is made thin, 3 to 12 μm, to form a thin transparent resin film. If the thin transparent resin film is thinner than 3 μm, it becomes difficult to handle as a film. It may be thicker than 12 μm, but if it is thicker, it becomes difficult to apply a sufficient amount of heat to make the thermosensitive coloring ink layer color. The thickness of the thin transparent resin film is preferably 4 to 11 μm, more preferably 4.5 to 10 μm. On the other hand, the thick transparent resin film needs to have a thickness of 25 to 120 μm, preferably 30 to 100 μm, more preferably 50 to 75 μm. If it is thinner than 25 μm, the resulting thermosensitive color-developing resin film will lose its strength and self-supporting ability, and conversely, if it is thicker than 120 μm, there will be no problem, but it will be wasteful due to the increased cost.

[0020] [Thermal coloring ink layer A] A thermosensitive coloring ink layer A is formed between the two transparent resin films (1 and 2), and the thermosensitive coloring ink layer A is composed of two layers, a leuco dye layer 5 and a developer layer 4, which are in contact with each other, the leuco dye layer 5 being formed from a leuco dye composition containing a leuco dye, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, and the developer layer 4 being formed from a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms. Either of the thermosensitive coloring ink layers may contain other components, etc., as necessary.

[0021] The leuco dye composition forming the leuco dye layer 5 contains a leuco dye, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms. Since the leuco dye layer is formed by applying the leuco dye composition and drying it, the cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms is hardly contained since it volatilizes during drying.

[0022] The leuco dye used in the leuco dye layer of the present invention can be any leuco dye commonly used in the field of thermal paper. Examples of the leuco dye include 3-diethylamino-7-methylfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-benzylaminofluoran, 3-diethylamino-7-anilinofluoran, 3-(N-methylanilino)-7-anilinofluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-7-afluoran, and the like. Examples of the leuco dye include nilinofluoran, 3-(N-methylcyclohexylamino)-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-(N-methyl-p-toluidino)-6-methyl-7-anilinofluoran, benzo-β-naphthospiropyran, crystal violet lactone, malachite green lactone, etc. These leuco dyes may be used alone or in combination of two or more kinds.

[0023] The amount of leuco dye contained in the leuco dye layer (amount after drying) can be appropriately selected depending on the type and hue of the leuco dye used. The amount of leuco dye is generally preferably 50 to 70% by mass, more preferably 60 to 65% by mass, based on the mass of the thermosensitive coloring ink layer. If it is less than 50% by mass, the coloring by the leuco dye becomes insufficient. On the other hand, if it is more than 70% by mass, there is no significant change in coloring and the coating film performance becomes poor.

[0024] The leuco dye layer contains a binder resin. The binder resin is used to hold the leuco dye in the leuco dye layer. The binder resin is also contained in the color developer layer. Examples of binder resins used in these layers include polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, rosin ester, terpene resin, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, and other water-soluble polymers, emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid ester, polymethacrylic acid ester, vinyl chloride / vinyl acetate copolymer, and ethylene / vinyl acetate copolymer, and latexes such as styrene / butadiene copolymer.

[0025] The amount of binder resin contained in the leuco dye layer (amount after drying) is generally preferably 10 to 50% by mass relative to the mass of the leuco dye layer. If it is less than 10% by mass, the leuco dye cannot be retained in the leuco dye layer. Conversely, if it is more than 50% by mass, the reaction between the leuco dye and the color developer due to heat becomes difficult to occur, and color development sensitivity decreases. The amount of binder resin is preferably 25 to 40% by mass, more preferably 25 to 35% by mass.

[0026] The cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, which is contained in the leuco dye composition used to form the leuco dye layer, is also contained in the color developer layer. In the present invention, this cyclic alkyl solvent does not dissolve either the leuco dye or the color developer, and the two layers do not mix or the leuco dye and the color developer do not react with each other. Therefore, by separating the leuco dye layer and the color developer layer and using a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, unnecessary color development (so-called fogging) does not occur.

[0027] The cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms is specifically cyclopentane, cyclohexane, cycloheptane, or cyclooctane substituted with an alkyl group having 1 to 3 carbon atoms (specifically, methane, ethane, or propane), and more specifically includes methylcyclopentane, methylcyclohexane, methylcycloheptane, methylcyclooctane, ethylcyclopentane, ethylcyclohexane, ethylcyclopentane, ethylcyclooctane, propylcyclopentane, propylcyclohexane, propylcyclopentane, and propylcyclooctane. A preferred cyclic alkyl solvent is methylcyclohexane. The cyclic alkyl solvent is contained in the leuco dye composition in an amount of 50 to 80% by mass, preferably 50 to 75% by mass, and more preferably 60 to 75% by mass. If it is less than 50% by mass, the solid content becomes too high and the viscosity becomes high. If it is more than 80% by mass, the viscosity becomes insufficient and coating becomes difficult.

[0028] The developer layer 4 contains a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms. As the developer, a developer that is commonly used in the field of thermal paper can be used. As the developer used in the developer layer, for example, an electron-accepting compound such as a phenolic compound, a thiophenolic compound, a thiourea derivative, an organic acid, or a metal salt thereof can be used. Specific examples of compounds that can be used as a color developer include 4,4'-isopropylidenebisphenol, 3,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis(o-methylphenol), 4,4'-sec-butylidenebisphenol, 4,4'-isopropylidenebis(ot-butylphenol), 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenebis(2-chlorophenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-butylidenebis(6-t-butylphenol-2-methyl)phenol, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,1 ,3-Tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis(6-t-butyl-2-methyl)phenol, 4,2'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis(4-hydroxyphenylthio)-3,5-dioxaheptane, 1,5-bis(4-hydroxyphenylthio)-3-oxapentane, 1,3-bis(4-hydroxyphenylthio)-propane, N,N'-diphenylthiourea, N,Examples of the color developers include N'-di(m-chlorophenyl)thiourea, salicylanilide, 5-chloro-salicylanilide, salicyl-o-chloroanilide, 2-hydroxy-3-naphthoic acid, antipyrine complex of zinc thiocyanate, zinc salt of 2-acetyloxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, zinc, aluminum, calcium and other metal salts of hydroxynaphthoic acid, bis(4-hydroxyphenyl)acetic acid methyl ester, bis(4-hydroxyphenyl)acetic acid benzyl ester, 4-{β-(P-methoxyphenoxy)ethoxy}salicylic acid, 1,3-bis(4-hydroxycumyl)benzene, 1,4-bis(4-hydroxycumyl)benzene, etc. These color developers may be used alone or in combination of two or more.

[0029] The amount of the developer contained in the developer layer is preferably 1 to 10 parts by mass, more preferably 1 to 6 parts by mass, per part by mass of the leuco dye contained in the leuco dye layer. If it is less than 1 part by mass, the color developing effect is insufficient, and if it is more than 10 parts by mass, the color developing effect does not increase in proportion to the increase in the amount. The amount of the developer in the developer layer (amount after drying) is 55 to 70% by mass, preferably 60 to 70% by mass, more preferably 60 to 65% by mass. The developer layer also contains the cyclic alkyl solvent having 5 to 8 carbon atoms substituted with the alkyl group having 1 to 3 carbon atoms described above. These are the same as those exemplified in the explanation of the leuco dye layer, and the amount used in the developer layer is the same as the amount used in the leuco dye layer.

[0030] The binder resin contained in the color developer layer is the same as that described for the leuco dye layer, and may be the same as or different from that used in the leuco dye layer.

[0031] The cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms is the same as that described for the leuco dye layer, and may be the same as or different from that used for the leuco dye layer. As described for the leuco dye layer, the cyclic alkyl solvent is hardly contained when the developer layer is dried.

[0032] Other components that may be optionally contained in the leuco dye layer or developer layer constituting the thermosensitive coloring ink layer include, for example, sensitizers. Specific examples of sensitizers include terephthalic acid esters, terephenyl, tribenzylamine, benzylmandic acid, parabenzylbiphenyl, di-o-chlorobenzyl adipate, dibenzyl oxalate, di-p-chlorobenzyl oxalate, 1-hydroxy-2-naphthoic acid phenyl, and 1,2-di-(3-methylphenoxy)ethane. When a sensitizer is used, it can be used in a range of amounts that are usually used. The sensitizer is blended in the leuco dye layer or developer layer in an amount of 10 to 50% by mass (amount after drying), preferably 20 to 40% by mass, and more preferably 20 to 30% by mass. If the amount of the sensitizer is less than 20% by mass, it cannot function as a sensitizer, and even if the amount is more than 50% by mass, no increase in effect is observed in proportion to the increase in the amount added, and instead the coating film performance is deteriorated.

[0033] Examples of other components other than the sensitizer include surfactants, waxes (e.g., stearamide, palmitamide, oleamide, lauric amide, ethylene bisstearamide, methylene bisstearamide, methylol stearate, etc.), dispersants (e.g., sodium dioctyl sulfosuccinate, etc.), defoamers (e.g., silicone-based, fluorine-based, and acrylic ester-based defoamers, etc.), and pigments (e.g., kaolin, calcined kaolin, talc, rosewood, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesia, titanium oxide, and barium carbonate, etc.). These components can be used as needed. These components are blended in the leuco dye layer or developer layer in an amount of 10 to 50% by mass (amount after drying), preferably 10 to 30% by mass, and more preferably 10 to 20% by mass. If the amount of these components is less than 10% by mass, they will not function as additives, whereas if the amount is more than 50% by mass, there will be no corresponding increase in effect, and instead the coating performance will deteriorate.

[0034] The thermosensitive coloring ink layer A is formed between two transparent resin films (1 and 2) by dispersing the above-mentioned components in a medium using a stirrer or the like. Usually, an adhesive layer 3 is formed on a thick transparent resin film 1. Next, a leuco dye layer 5 and a color developer layer 4 are formed in this order on a thin transparent resin film 2, and the thick transparent resin film 1 on which the adhesive layer 3 is formed is attached so that the color developer layer 4 and the adhesive layer 3 are in contact with each other to form the thermosensitive coloring resin film of the present invention. It is preferable to form a heat-resistant layer 6 on the thin transparent resin film 2 (the surface without the leuco dye layer) because the thermosensitive coloring ink layer develops color when heat is applied from the side of the thin transparent resin film. The heat-resistant layer 6 may be formed in advance on the surface of the thin transparent resin film 2 on which the thermosensitive coloring ink layer A is not formed. The order of the leuco dye layer 5 and the color developer layer 4 may be reversed from that shown in FIG. 1, with the leuco dye layer 5 being formed in contact with the adhesive layer 3 and the color developer layer 4 being formed thereon.

[0035] [Adhesive layer and heat-resistant layer] The adhesive layer 3 contains one or more resin components selected from the group consisting of ethylene-vinyl acetate copolymers and polyolefin resins. This adhesive layer can be formed by applying an adhesive layer-forming composition containing a resin component and an organic solvent onto the thick transparent resin film 1.

[0036] The ethylene-vinyl acetate copolymer that can be used as the resin component contained in the adhesive layer preferably has a number average molecular weight of 1,000 to 300,000. The number average molecular weight can be measured by GPC (gel permeation chromatography) and calculated based on a converted value using polystyrene as a standard.

[0037] The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content in the range of 10 to 50% by mass. The vinyl acetate content can be determined in accordance with JIS K7192 (1999).

[0038] The ethylene vinyl acetate copolymer may be a commercially available product. Examples of commercially available products include the Evaflex (trademark) series manufactured by DuPont-Mitsui Polychemicals Co., Ltd. (e.g., EV45X, EV45LX, EV40W, EV40LX, V5772ETR, V5773W, EV150, EV205WR, EV210, EV220, EV220ETR, EV250, EV260, EV310, EV360, V577, EV410, EV420, EV45 0, EV460, EV550, EV560, P1207, etc. The ethylene vinyl acetate copolymer preferably has a softening temperature of 40° C. or higher. A softening temperature of 40° C. or higher has the advantage that the resulting thermal paper has good storage stability.

[0039] Examples of polyolefin resins that can be used as the resin component contained in the adhesive layer include polypropylene resins and modified polyolefin resins. The polyolefin resins may be commercially available products. Examples of commercially available products include polypropylene resins manufactured by Clariant Japan, such as Ricosene (trademark) PP1302, PP1502, and PP1602, and modified polyolefin resins manufactured by Nippon Paper Industries Co., Ltd., such as the Auroren (trademark) series (e.g., 100S, 150S, 200S, 250S, 350S, 351S, 353S, and 359S).

[0040] The resin component preferably has a glass transition point of not more than 40° C. When the resin component has a glass transition point of not more than 40° C., the transparent resin film can be laminated well in the lamination step.

[0041] The adhesive layer forming composition used for forming the adhesive layer preferably contains an organic solvent in addition to the above resin components. The organic solvent contained in the adhesive layer forming composition may be, for example, one or more selected from the group consisting of methanol, ethanol, n-propyl alcohol, isopropyl alcohol, butanol, isobutyl alcohol, isopentyl alcohol, cyclohexanol, methylcyclohexanol, hexane, cyclohexane, methylcyclohexane, heptane, octane, ethyl ether, isobutyl acetate, isopropyl acetate, isopentyl acetate, methyl acetate, ethyl acetate, n-butyl acetate, n-propyl acetate, n-pentyl acetate, cyclohexanone, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylcyclohexanone, methyl-n-butyl ketone, toluene, and xylene.

[0042] The adhesive layer-forming composition may contain particulate matter such as organic particulate matter (e.g., resin fine particles) or inorganic pigments (e.g., silica, kaolin, calcined kaolin, talc, rosewood, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesia, titanium oxide, barium carbonate) as necessary. The inclusion of particulate matter can prevent defects such as wrinkles from occurring in the subsequent lamination step, and improve handleability. The adhesive layer-forming composition does not contain any component that causes color development or desensitization of the thermosensitive coloring ink layer upon contact with the thermosensitive coloring ink layer, or, even if it contains such a component, the amount is less than that causing defects.

[0043] The adhesive layer-forming composition can be applied to a transparent resin film by any method commonly used in the art. Specific examples of the application method include a method using a bar coater or a gravure coater. The adhesive layer-forming composition can be applied to a transparent resin film by, for example, applying the adhesive layer-forming composition to a transparent resin film with a dry mass of 1 to 5 g / m. 2 It is preferable to apply the coating amount so that the coating amount is 1g / m 2 If the coating amount is less than 5 g / m, the transparent resin film may not be laminated well. 2If it exceeds this value, the thickness of the adhesive layer will increase, which may result in a decrease in the sensitivity of the thermosensitive coloring ink layer.

[0044] After coating the adhesive layer-forming composition, it is preferable to dry it. By drying after coating, at least a part of the organic solvent can be removed. By removing the organic solvent, it is possible to prevent the organic solvent contained in the composition from acting on the thermosensitive coloring ink layer, causing color development before thermal processing. As drying conditions after coating, for example, drying at 80 to 120°C for 1 to 600 seconds can be mentioned.

[0045] In the present invention, the heat-resistant layer 6 that can be formed on the thin transparent resin film 2 (the surface without the leuco dye layer) preferably contains a silicone resin or a hydrolyzate having a -Si-O-Si- bond. Examples of silicone resins include silicone-modified acrylic resins and silicone-modified urethane resins. These resins can be those that are generally used in fields such as coating.

[0046] An example of a method for providing a heat-resistant layer containing a silicone resin is to coat a composition (heat-resistant layer-forming composition) containing a silicone resin such as a silicone-modified acrylic resin or a silicone-modified urethane resin, and optionally a curing agent, an organic solvent, etc., to provide a heat-resistant layer.

[0047] Examples of silicone-modified acrylic resins include copolymers of silicone monomers and / or silicone macromonomers and acrylic monomers. Commercially available silicone-modified acrylic resins may be used. Examples of commercially available products include the Cymac (trademark) series (e.g., US-120, US-270, US-350, US-352, US-380, US-450, US-480, GS-30, GS-101, GS-3000, etc.) manufactured by Toagosei Co., Ltd. Examples of silicone-modified urethane resins include copolymers of silicone monomers and / or silicone (macro)monomers and urethane monomers and / or urethane oligomers. Commercially available silicone-modified urethane resins may be used. Examples of commercially available products include the Dialomer (trademark) series (e.g., SP-2105, SP-3035, etc.) manufactured by Dainichiseika Chemicals Co., Ltd. When these silicone resins are used, the content thereof is preferably from 1 to 40 parts by mass, and more preferably from 5 to 30 parts by mass, per 100 parts by mass of the heat-resistant layer-forming composition.

[0048] Examples of the curing agent include polyisocyanates and polyamides. Examples of the polyisocyanate include diisocyanates such as tolylene diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, methyl-2,6-diisocyanate hexanoate, and norbornane diisocyanate, as well as isocyanurate-modified products of the above diisocyanates, adduct-modified products of the above diisocyanate monomers, biuret-modified products of the above diisocyanate monomers, and isocyanate prepolymers such as 2-isocyanate ethyl-2,6-diisocyanate caproate and triaminononane triisocyanate. Blocked products of these polyisocyanates can also be used. Examples of polyamides include melamine resins. These curing agents may be used alone or in combination of two or more. The content of the curing agent when used may be within a range that is usually used, for example, 1 to 40 parts by mass per 100 parts by mass of the silicone resin.

[0049] Examples of organic solvents include aromatic solvents such as toluene, xylene, and Solvesso; aliphatic solvents such as n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, and mineral spirits; ketone solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as diethyl ether, isopropyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, anisole, and phenetole; ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, and ethylene glycol diacetate; cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; and alcohol solvents such as methanol, ethanol, propanol, isopropyl alcohol, butanol, and 2-ethylhexanol. These solvents may be used alone or in combination. When an organic solvent is used, its content can be selected according to the coating conditions and the like without any particular limitation.

[0050] A thin film transparent resin film having a heat-resistant layer can be obtained by coating the above-mentioned composition on the surface of a thin film transparent resin film. The heat-resistant layer-forming composition can be coated by any method commonly used in the art. Specific examples of coating methods include coating methods using a gravure coater or a bar coater. In forming the heat-resistant layer, the heat-resistant layer-forming composition is applied to the surface of the thin film transparent resin film in an amount of, for example, 0.05 to 0.5 g / m2 on a dry basis. 2 It is recommended to apply the coating in an amount of 0.05 g / m 2 If the thickness is less than 0.5 g / m, problems such as sticking may occur when the thermal paper is fed through a thermal head printer. 2 If it exceeds this limit, it may adhere to the thermal head printer as head residue when the printer is in operation, which may cause poor printing.

[0051] [Lamination process] The adhesive layer of the thick transparent resin film obtained in the above adhesive layer forming step is brought into contact with the developer layer side of the thermosensitive coloring ink layer of the thin transparent resin film and laminated to obtain the thermosensitive coloring resin film of the present invention (lamination step). In this lamination step, it is preferable to bring the adhesive layer of the thick transparent resin film into contact with the developer layer side of the thermosensitive coloring ink layer of the thin transparent resin film and laminate them at, for example, 40 to 80°C, more preferably 40 to 70°C, and particularly preferably 40 to 65°C. The temperature in this lamination step must be within a range in which thermal coloring of the thermosensitive coloring ink layer does not occur.

[0052] This lamination step can be carried out using a commonly used laminating device, etc. In this manner, a thermosensitive color-developing resin film can be produced.

[0053] <Explanation of the embodiment of FIG. 2> In the present invention, the developer layer 4 can be made into two layers, a first developer layer 4-1 and a second developer layer 4-2. The developer layer 4 can be made into two layers when transparency of the thermosensitive color-developing resin film is required, and can be made into two layers to further increase transparency. In the present invention, the solvent of the developer layer 4 and the leuco dye layer 5 is a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms (hereinafter, sometimes referred to as a "cyclic alkyl solvent"), and the leuco dye and the developer are in a state close to dispersion, not in a dissolved state, to prevent unnecessary color development (for example, so-called "fogging"). However, depending on the materials used and the mixing state, transparency may be insufficient. In such a case (when greater transparency is required), the developer layer 4 can be made into the following two layers: (a) the first developer layer 4-1 is formed from a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms (i.e., a cyclic alkyl solvent); (b) The second developer layer 4-2 is formed from a developer composition containing a developer, a binder resin and an organic solvent other than the cyclic alkyl solvent, and the organic solvent other than the cyclic alkyl solvent is selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents and mixtures thereof. In this way, the first color developer layer 4-1 is in contact with the leuco dye layer 5, and the second color developer layer 4-2 is on the opposite side to the leuco dye layer 5, thereby ensuring the transparency of the obtained thermosensitive coloring resin film. This thermosensitive coloring resin film with enhanced transparency can also be one embodiment of the present invention. As described above, in FIG. 1, the order of the leuco dye layer 5 and the color developer layer 4 may be either the lower layer in FIG. 1, so even when the color developer layer 4 is the first color developer layer 4-1 and the second color developer layer 4-2, the layering order may be either the top or bottom as in FIG. 1, as long as the first color developer layer 4-1 is on the side in contact with the leuco dye layer 5.

[0054] The organic solvent other than the cyclic alkyl solvent used in the second developer layer 4-2 is selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents and mixtures thereof. Examples of such organic solvents include aromatic solvents such as toluene, xylene, and Solvesso; aliphatic solvents such as n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, and mineral spirits; ketone solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as diethyl ether, isopropyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, anisole, and phenetole; ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, and ethylene glycol diacetate; cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; and alcohol solvents such as methanol, ethanol, propanol, isopropyl alcohol, butanol, and 2-ethylhexanol. These solvents may be used alone or in combination. When an organic solvent is used, the content can be selected without any particular limitation according to the coating conditions, etc. The amount of the solvent used may be the same as that explained in the description of the color developer layer 4.

[0055] When the two developer layers 4-1 and 4-2 in Fig. 2 are applied to Fig. 1, and the layers are formed in the order of thick transparent resin film 1 ⇒ adhesive layer 3 ⇒ leuco dye layer 5 ⇒ first developer layer 4-1 ⇒ second developer layer 4-2 ⇒ thin transparent resin film 2 from the bottom in Fig. 1, the adhesion and compatibility can be improved by forming a urethane resin layer between the second developer layer 4-2 and the thin transparent resin film 2. Even in the case of the single-layer developer layer 4 in Fig. 1, when it comes into contact with the thin transparent resin film 2, a urethane resin layer may be formed.

[0056] The urethane resin layer is formed especially when improving the adhesion with a thin transparent resin film, and has a similar function to the above-mentioned adhesive layer, but uses a different resin. The urethane resin layer can be a commercially available product, such as Sanprene IB-465 and IB-2000 available from Sanyo Chemical Industries, Ltd., and Vylon UR-1350, UR-1400, and UR-8700 available from Toyobo Co., Ltd. The urethane resin layer is formed by coating these commercially available products, and the thickness is 0.1 to 1.0 μm, preferably 0.3 to 0.8 μm, and more preferably 0.4 to 0.6 μm. If the thickness is less than 0.1 μm, the adhesive strength is insufficient.

[0057] [Thermal color-changing resin film] The thermosensitive coloring resin film of the present invention is obtained by sandwiching a thermosensitive coloring ink layer between two transparent resin films. This thermosensitive coloring resin film exists in the form of a transparent or semitransparent resin film, and when heat is applied to the resin film, letters and pictures can be drawn on it. Moreover, since the displayed letters and pictures are sandwiched between the transparent resin films, the letters and pictures will not disappear or be damaged by simply rubbing the surface with a finger. Therefore, the thermosensitive coloring resin film of the present invention can be used not only as receipts received at the cash register of a supermarket or convenience store, but also as a resin sheet having letters and pictures that will not be damaged. If the color of the leuco dye layer is changed so that different colors are developed within the resin film, it is possible to enjoy a wide variety of colors.

[0058] As already mentioned, in the thermosensitive coloring resin film of the present invention, the thermosensitive coloring ink layer is between the transparent resin films, so the thermosensitive coloring ink layer is not directly subjected to impact, and unwanted coloring such as coloring due to impact is unlikely to occur. In addition, the transparent resin films act as a protective layer, so the thermosensitive coloring ink layer is protected, and peeling or damage to the ink layer hardly occurs.

[0059] The thermosensitive color-developing resin film of the present invention is quite transparent, but if the transparency is insufficient, the transparency can be increased by forming a two-layer developer layer, using a solvent for one of the developer layers that is not a cyclic alkyl solvent and that promotes dissolution of the developer, and forming the developer layer with promoted dissolution so that it is not in direct contact with the leuco dye layer. EXAMPLES

[0060] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0061] <Example of the first aspect> Production Example 1 (Preparation of Leuco Dye Composition 1) Leuco dye composition 1 was formed by dispersing the following ingredients for 2 hours on a paint shaker. TIFF0007607549000001.tif41145 ODB-2 is a black leuco dye, Pencel KK is blended as a binder resin, and Tufprene A is blended as a binder resin. MCH and toluene are solvents.

[0062] Production Example 2 (Preparation of Leuco Dye Composition 2) Leuco dye composition 2 was formed by dispersing the following components for 2 hours on a paint shaker. TIFF0007607549000002.tif36145 PA-100 was used as a binder resin.

[0063] Production Example 3 (Preparation of Leuco Dye Composition 3) Leuco dye composition 3 was formed by dispersing the following components for 2 hours on a paint shaker. TIFF0007607549000003.tif31145 Vylon 200 was used as a binder resin.

[0064] Production Example 4 (Preparation of Color Developer Composition 1) The following components were dispersed in a paint shaker for 2 hours to form developer composition 1. TIFF0007607549000004.tif36127 D-8 was used as a developer for thermal paper.

[0065] Production Example 5 (Preparation of Color Developer Composition 2) The following components were dispersed for 2 hours using a paint shaker to form developer composition 2. TIFF0007607549000005.tif36145

[0066] Production Example 6 (Preparation of Developer Composition 3) The following components were dispersed for 2 hours using a paint shaker to form developer composition 3. TIFF0007607549000006.tif31145

[0067] Production Example 7 (Preparation of Adhesive Composition) The following ingredients were mixed to form an adhesive layer composition: TIFF0007607549000007.tif41146

[0068] <Example of the first aspect> Example 1 The leuco dye composition 1 was applied to a 4.5 μm-thick PET (polyethylene terephthalate) film (corresponding to a thin transparent resin film) available from Toray Industries, Inc. under the trade name Lumirror, at a rate of 1.5 g / m using a bar coater. 2 and dried with hot air at 70°C. The coating amount was 1.5g / m 2 Next, the developer layer composition 1 was applied to the PET film on which the leuco dye layer was formed using a bar coater. The application amount was 2.5 g / m 2 It was.

[0069] The above adhesive composition was applied at a coating amount of 1.0 g / m to a 50 μm thick white PET film (corresponding to a thick transparent resin film) commercially available from Toyobo Co., Ltd. under the name Crisper K1212. 2 The coating was applied using a bar coater so that the coating weight was 100% (dry weight). The coating was attached to the PET film on which the leuco dye layer and developer layer had been formed, and heat-sealed using a commercially available laminator (Meiko Shokai: THS330) at 45 mm / sec and a temperature setting of 65°C to obtain a thermosensitive coloring resin film. The obtained thermosensitive coloring resin film was evaluated for background coloring (fog) immediately after coating and for fog after a storage stability test as described below. The results are shown in Table 1.

[0070] Evaluation of background color (fog) immediately after coating Immediately after applying the composition 1 for developer layer to the leuco dye layer, background color development (fog) was evaluated by visual observation and judged according to the following criteria. ◯: No fogging observed, white. △: Some fogging is observed. ×: Fog occurs.

[0071] Evaluation of fogging after storage test The above-mentioned thermosensitive color-developing resin film was printed with a thermal transfer printer (Zebra105SL, manufactured by Zebra Corporation) to obtain a print sample. The obtained print sample was stored in a thermo-hygrostat (LH-21, manufactured by Nagano Science Corporation) at a temperature of 40°C and a relative humidity of 80% for 48 hours. After storage, the color development state of the printed area and the background color development state (fog) were evaluated. ◯: Neither fogging nor deterioration in color development of the print is observed. △: Deterioration of print color is observed. ▲: Fog occurs. ×: Both print color deterioration and fogging occur.

[0072] Comparative Example 1 A coating composition was prepared in the same manner as in Example 1, except that the developer composition 1 in Example 1 was replaced with developer composition 2, and evaluation of fogging immediately after coating and after a storage test was performed in the same manner as in Example 1. The results are shown in Table 1.

[0073] Comparative Example 2 A coating composition was prepared in the same manner as in Example 1, except that developer composition 1 in Example 1 was replaced with developer composition 3, and evaluation of fogging immediately after coating and after a storage test was performed in the same manner as in Example 1. The results are shown in Table 1.

[0074] Comparative Example 3 A coating composition was prepared in the same manner as in Example 1, except that leuco dye composition 1 in Example 1 was replaced with leuco dye composition 2, and evaluation of fogging immediately after coating and after a storage test was performed in the same manner as in Example 1. The results are shown in Table 1.

[0075] Comparative Example 4 In Example 1, leuco dye composition 1 was changed to leuco dye composition 2, and developer composition 1 and developer composition 2 were changed to prepare a film similar to Example 1, and fogging was evaluated immediately after coating and after a storage test in the same manner as in Example 1. The results are shown in Table 1.

[0076] Comparative Example 5 In Example 1, leuco dye composition 1 was changed to leuco dye composition 2, and developer composition 1 and developer composition 3 were changed to prepare a film similar to Example 1, and evaluation of fogging immediately after coating and after a storage test was performed similarly to Example 1. The results are shown in Table 1. Comparative Example 6 A coating composition was prepared in the same manner as in Example 1, except that leuco dye composition 1 in Example 1 was replaced with leuco dye composition 3, and evaluation of fogging immediately after coating and after a storage test was performed in the same manner as in Example 1. The results are shown in Table 1.

[0077] Comparative Example 7 In Example 1, leuco dye composition 1 was changed to leuco dye composition 3, and developer composition 1 and developer composition 2 were changed to prepare a film similar to Example 1, and evaluation of fogging immediately after coating and after a storage test was performed similar to Example 1. The results are shown in Table 1.

[0078] Comparative Example 8 In Example 1, leuco dye composition 1 was changed to leuco dye composition 3, and developer composition 1 and developer composition 3 were changed to prepare a film similar to Example 1, and evaluation of fogging immediately after coating and after a storage test was performed similar to Example 1. The results are shown in Table 1.

[0079] [Table 1]

[0080] In Table 1 above, "not rated" in the evaluation of fogging after the storage test means that developer composition 3 was used, and fogging had already occurred immediately after coating, so evaluation of fogging after the storage test was not performed.

[0081] As is clear from Table 1 of the evaluation results, within the scope of claim 1 of the present invention, neither fog occurs immediately after coating nor after storage test. On the other hand, in the example where methylcyclohexane, a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms, is not used, fog occurs either immediately after coating or after storage test. This is because, when isopropyl alcohol (IPA) or methyl ethyl ketone (MEK) is used as a solvent instead of methylcyclohexane (MCH), as seen in Comparative Example 1, even if the leuco dye layer is a layer formed using MCH, if the developer layer uses IPA, a little fog is observed immediately after coating, and of course fog also occurs after storage. In Comparative Example 2, the developer layer uses MEK, and when the developer layer containing MEK is coated, MEK dissolves the leuco dye and color develops immediately. In Comparative Example 3, a developer layer using MCH is formed on a leuco dye layer using IPA, and when a leuco dye composition using IPA is applied and completely dried, and then a developer layer using MCH is applied, no color is developed immediately after application, but fogging occurs after storage for unknown reasons. Although details are not given for Comparative Examples 4 to 8, when IPA or MEK is used, the solubility functions and tends to cause a contact reaction between the developer and the leuco dye, which is thought to cause fogging.

[0082] <Example of the second aspect> Example 2 (dissolution ⇒ dispersion ⇒ leuco) The above-mentioned color developer composition 2 (Production Example 5) was applied at 1.5 g / m to a 4.5 μm-thick PET (polyethylene terephthalate) film (corresponding to a thin transparent resin film) available from Toray Industries, Inc. under the trade name Lumirror, using a bar coater. 2 and dried with hot air at 70°C (second developer layer). The coating amount was 1.5 g / m 2 Next, the developer composition 1 was applied to the PET film on which the developer layer composition 2 layer had been formed, using a bar coater (first developer layer). The application amount was 2.5 g / m 2 Furthermore, leuco dye composition 1 was applied onto the layer of developer composition 1 using a bar coater (leuco dye layer). The application amount was 2.0 g / m 2 It was.

[0083] The adhesive composition was applied at a coating rate of 1.0 g / m to a white PET film having a thickness of 50 μm and commercially available from Toyobo Co., Ltd. under the name Crisper K1212. 2 The coating was applied using a bar coater so that the coating weight was 100% (dry weight). The coating was attached to the PET film on which the above-mentioned leuco dye layer and developer layer were formed, and heat-sealed using a commercially available laminator (Meiko Shokai: THS330) at 45 mm / sec and a temperature setting of 65°C to obtain a thermosensitive coloring resin film. The obtained thermosensitive coloring resin film was evaluated for background coloring (fog) immediately after coating and for fog after a storage stability test in the same manner as in Example 1. The results are shown in Table 2.

[0084] Example 3 (dissolution ⇒ dispersion ⇒ leuco) In Example 2, the developer composition 2 was replaced with developer composition 3, and the coating of Example 2 was prepared, and evaluation of fogging immediately after coating and after a storage test was performed in the same manner as in Example 2. The results are shown in Table 2.

[0085] Comparative Example 9 (Dispersion → Dissolution → Leuco) A sample was prepared in the same manner as in Example 2 except that developer composition 2 was replaced with developer composition 1, and evaluation of fogging immediately after coating and after a storage test was performed in the same manner as in Example 1. The results are shown in Table 2.

[0086] Comparative Example 10 (Dispersion ⇒ Dissolution ⇒ Leuco) In Example 3, developer composition 3 was replaced with developer composition 1, and the same procedure as in Example 1 was repeated to prepare a coating composition, and the fogging was evaluated immediately after coating and after a storage test in the same manner as in Example 1. The results are shown in Table 2.

[0087] The transparency was also confirmed by the haze value. The haze value is a value expressed as (diffuse transmittance / total light transmittance)×100(%), and is measured in accordance with JIS K 7105. The measured values ​​are shown in Table 2.

[0088] [Table 2]

[0089] In the above-mentioned Examples 2 and 3, the developer layer is two-layered, but when the first developer layer (layer using developer composition 1) is in contact with the leuco dye layer and the second developer layer (layer using developer composition 2 or 3) is not in contact with the leuco dye layer, fogging does not occur. In addition, the haze value indicating transparency is also excellent at about 50%. In Comparative Examples 9 and 10, the order of the developer layers in Examples 2 and 3 is reversed, and the second developer layer (layer using developer composition 2 or 3) is in contact with the leuco dye layer. There is no fogging immediately after coating, but the fogging is bad after the storage test. The transparency (haze value) is not much worse than that before the order of the developer layers was reversed, but the fogging is bad after the storage test, making it difficult to use.

[0090] From the above examples, it is found that the occurrence of fog can be suppressed by using an organic solvent that hardly dissolves the leuco dye and the developer, that is, methylcyclohexane, which is a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms. The thermosensitive coloring resin film of the present invention has a thermosensitive coloring ink layer of a transparent resin film, so that it does not develop color even with a slight impact, and can be stored for a long time. In addition, since color is developed on the transparent film, it can be used for applications different from those of conventional thermal paper. In addition, when the layer containing the developer is made into two layers, a first developer layer and a second developer layer, and the layer in contact with the leuco dye layer is the first developer layer (an example using a cyclic alkyl solvent), it can be seen that both fog and transparency are excellent. [Explanation of symbols]

[0091] 1...Thick transparent resin film 2. Thin transparent resin film 3…Adhesive layer 4... Developer layer 4-1: First developer layer 4-2: Second developer layer 5...Leuco dye layer 6...Heat-resistant layer A…Thermal coloring ink layer

Claims

1. A thermosensitive coloring resin film having a thermosensitive coloring ink layer between two transparent resin films, one of the transparent resin films is a thin transparent resin film having a thickness of 3 to 12 μm, and the other is a thick transparent resin film having a thickness of 25 to 120 μm; The thermosensitive coloring ink layer is composed of two layers, a leuco dye layer and a developer layer, which are in contact with each other, the leuco dye layer comprises a leuco dye composition containing a leuco dye, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; the developer layer is made of a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; The cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms is methylcyclohexane; and The binder resin is a rosin ester or a styrene-butadiene block copolymer. Heat-sensitive color-changing resin film.

2. 2. The heat-sensitive color-developing resin film according to claim 1, wherein the transparent resin film is a PET (polyethylene terephthalate) film.

3. A thermosensitive color-developing resin film is laminated in the order of a developer layer, a leuco dye layer, and a thin transparent resin film from the thick transparent resin film side, an adhesive layer is present between the thick transparent resin film and the color developer layer; 3. The thermosensitive color-developing resin film according to claim 1 or 2.

4. A heat-sensitive color-developing resin film is laminated in the order of a leuco dye layer, a developer layer, and a thin transparent resin film from the thick transparent resin film side, an adhesive layer is present between the thick transparent resin film and the leuco dye layer; a urethane resin layer is present between the color developer layer and the thin transparent resin film; 3. The thermosensitive color-developing resin film according to claim 1 or 2.

5. the developer layer is composed of two layers, a first developer layer and a second developer layer, which are in contact with each other; the first developer layer is made of a developer composition containing a developer, a binder resin, and a cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms; the second developer layer is made of a developer composition containing a developer, a binder resin, and an organic solvent other than the cyclic alkyl solvent; The cyclic alkyl solvent having 5 to 8 carbon atoms substituted with an alkyl group having 1 to 3 carbon atoms is methylcyclohexane; and the binder resin is a rosin ester or a styrene-butadiene block copolymer; the organic solvent other than the cyclic alkyl is an organic solvent selected from the group consisting of aromatic solvents, aliphatic solvents, ketone solvents, ether solvents, ester solvents, cellosolve solvents, alcohol solvents, and mixtures thereof; the first developer layer is in contact with the leuco dye layer and the second developer layer is on the opposite side to the leuco dye layer; 5. The heat-sensitive color-developing resin film according to claim 1,

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