JP4400396B2 - Multicolor thermal recording medium - Google Patents

Description

The present invention relates to a multicolor thermosensitive recording medium that develops colors different from each other due to differences in heating application conditions from a thermal head. More specifically, the present invention provides a clear color tone with almost no color mixing of the high temperature color tone in the low temperature color tone, that is, excellent in color separation and high sensitivity, and further required for a thermal recording material. The present invention relates to a multicolor heat-sensitive recording material having excellent chemical resistance, light resistance and little background fogging.

Conventionally, a thermal recording medium that utilizes a color development reaction between a dye precursor and a color developer that is brought into contact with color by heating and melts and contacts both color developing materials by heating to obtain a color image. Widely known. Such a thermal recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, so a facsimile, a word processor, various computers, etc.
In addition, it is used in a wide range of recording media for other purposes. In particular, two-color separability in high-speed printing has been demanded recently.

The quality required for thermal recording media has been diversified along with the expansion of its applications, and there can be mentioned demands such as higher sensitivity, image stabilization, and multicolor recording. In particular, the multi-color recording means has an advantage that characters and figures to be emphasized can be displayed clearly and clearly with a color tone different from other parts, and there is an increasing demand for practical use.

Attempts have been made to utilize the difference in heating temperature or the difference in heat energy as a multicolor recording system, and various multicolor thermal recording materials have been proposed. In general, a multicolor thermosensitive recording material is formed by sequentially laminating a high-temperature color-developing layer and a low-temperature color-developing layer that develop colors in different colors on a support. 2 and 3) and additive type (Patent Document 4,
5, 6, and 7) and methods using microcapsules (Patent Documents 8, 9, and 10)
, 11, 12). Furthermore, a method using composite particles composed of an organic polymer and a dye precursor (see Patent Documents 13, 14, 15, and 16) is also disclosed. Furthermore, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) is used as a developer and composite particles composed of at least one polymer selected from polyurea and polyurethane, and a dye precursor. A method using phenylurea is also disclosed (Patent Document 1).
6).

Japanese Patent Laid-Open No. 50-17865 JP-A-57-14320 Japanese Patent Laid-Open No. 2-80287 Japanese Patent Publication No.49-27708 Japanese Patent Publication No.51-19989 Japanese Patent Laid-Open No. 51-146239 JP-A-56-99697 JP 57-12695 A Japanese Patent Publication No.49-70 JP 59-214691 A Japanese Patent Publication No. 4-4960 Japanese Patent Laid-Open No. 4-101885 JP-A-9-263057 Japanese Patent Laid-Open No. 10-226175 Japanese Patent Laid-Open No. 10-95173 JP 2001-341432 A

In order to obtain a sufficient decoloring effect for the low temperature coloring layer, a large amount of decoloring agent needs to be added to the decoloring type multicolor thermosensitive recording material. The recorded color image fades during long-term storage due to the action of the decolorant added in large amounts, and an extra amount of heat is required to melt the decolorant, which places an excessive burden on the thermal head. There are problems, such as image recording reliability and recording sensitivity,
It was not always satisfactory.

The additive color multicolor thermosensitive recording medium is a method of obtaining two distinct colors by laminating two color developing layers that develop different colors and applying different amounts of heat. The upper color-developing layer develops color at low temperature, and the upper and lower color-development layers develop color at high temperature, and an image having a mixed tone of both colors can be obtained. Since no color eraser is used in the additive recording medium, it has the advantage of being excellent in long-term storage of recorded images and being relatively inexpensive to manufacture, and requires extra heat to melt the color eraser. Therefore, there is an advantage that the high-temperature coloring layer can be colored with low energy as compared with the decoloring type. However, the additive type two-color thermosensitive recording material has a problem in that if the amount of heat is excessively applied during low-temperature color development, a part of the color of the high-temperature color development layer is mixed, resulting in color mixing, and the low-temperature color-development image is difficult to be clear. In addition, a method of mixing two or more kinds of dye precursors having different color tone and different average particle diameters in the same layer has been described, but there is also a problem that color mixing is unavoidable at low temperature color development. .

In addition, it has been known for a long time that microcapsules are applied to heat-sensitive recording materials. Encapsulating a solvent in a liquid state at room temperature or microencapsulating a coloring component as a core material, the coloring components that develop colors in different colors. Is dissolved in a solvent, and each of them is contained in two or more kinds of microcapsules having different glass transition temperatures, or at least one kind of color forming component is contained in the microcapsules to be multicolored. However, if two or more types of dye precursors that develop colors in different colors are separately microencapsulated, the color sensitivity of each of the dye precursors will be reduced, making it difficult to classify the sensitivity, which makes it easy to mix colors. There was a problem. Further, when the oil-based liquid solution of the dye precursor is encapsulated in the microcapsule, there is a problem that ground coloring easily occurs due to breakage of the capsule due to pressure or friction rubbing.

Furthermore, the method using composite particles composed of an organic polymer and a dye precursor has good chemical resistance but is difficult to obtain sensitivity, and the dye precursor exists in an amorphous state. There were problems such as the discoloration of the recording part and the background fogging being larger in the light resistance test than the disperse dye precursor.

An object of the present invention is to provide a multicolor thermosensitive recording medium provided with a thermosensitive coloring layer containing two or more kinds of dye precursors that develop colors in different tones and a color developing compound that develops the dye precursors on a support. Provided is a multicolor thermosensitive recording material that has a clear color tone with almost no color mixing of the high-temperature color tone and the low-temperature color tone, has excellent chemical resistance in the recording area, has high sensitivity and light resistance, and has little background fog. There is.

In order to solve the above problems, the multicolor thermosensitive recording material according to the present invention is provided with a first thermosensitive coloring layer containing a dye precursor that develops black and a developer on the support, and further includes a first thermosensitive coloring layer. A second thermosensitive coloring layer comprising composite particles comprising an organic polymer and a dye precursor that develops black color on the thermosensitive coloring layer, solid dispersed fine particles comprising a dye precursor that develops a color tone different from the composite particles, and a developer. A multicolor thermosensitive recording material, wherein the black color developing dye precursor in the first thermosensitive coloring layer is 3- (N-ethyl-p-toluidino) -6-methyl-7-anis Linofluorane, a dye precursor that develops a color tone different from that of the composite particles in the second thermosensitive coloring layer, is 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide And the developer in the first thermosensitive coloring layer and the second thermosensitive coloring layer is N- It is p-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea.

  By adding spherical plastic resin particles or hollow plastic resin particles in the first thermosensitive coloring layer, the contrast between the black coloring of the second thermosensitive coloring layer and the color that develops in a color tone different from black is improved. Furthermore, it has been found that the storage stability of a color that develops a color tone different from that of black contained in the second thermosensitive coloring layer, particularly the chemical resistance of plasticizers and oils, is greatly improved, and this is a more preferable method.

  Further, among organic polymers, at least one selected from polyurea and polyurea-polyurethane is preferable because the storage stability of the recording area is particularly good.

  Further, the developer in the second thermosensitive coloring layer is Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenyl because it has good heat resistance (background fogging) during high-temperature storage. Urea is preferred.

  Further, the developer of the first thermosensitive coloring layer is also Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea because it improves the heat resistance (background fogging) during high-temperature storage. It is preferable that

  The dye precursor that develops a color tone different from that of the composite particles contained in the second thermosensitive coloring layer is 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide. In addition, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea as a developer is used in the first heat-sensitive layer and the second heat-sensitive layer so that the heat resistance during storage at high temperature (background) This is preferable because there is little fogging and chemical resistance such as plasticizer and oil is excellent.

  In addition, the dye precursor that develops black color in the first thermosensitive coloring layer preferably has a melting point of 200 ° C. or higher from the viewpoint of color separation.

Further, in order to improve the readability with a barcode reader, a further 3, 3 ′ is added to the composite particles.
It is preferable to contain -bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, and the addition amount is about 1 to 50 parts by mass with respect to the total solid content of the composite particles.

According to the present invention, a clear color tone having almost no mixed color of a high-temperature color tone and a low-temperature color tone can be obtained, the chemical resistance of the recording part is excellent, and the multi-color heat-sensitive recording medium has high sensitivity and light resistance and less background fog. It became possible to provide.

In the multicolor thermosensitive recording material of the present invention, the thermosensitive coloring layer comprises a first thermochromic layer containing a black color developing dye precursor and a developer, and an organic high color layer provided on the first thermosensitive coloring layer. It is composed of composite particles composed of molecules and a dye precursor that develops black color, solid dispersed fine particles composed of a dye precursor that develops a color tone different from that of the composite particles, and a second thermosensitive coloring layer containing a developer. In the present invention, the low temperature coloring color tone is the coloring color tone of the dye precursor present in the solid dispersed fine particle state in the second thermosensitive coloring layer.

The composite particles can be produced by the methods described in Patent Documents 13, 14, 15, and 16. As described above, among organic polymers, at least one of polyurea and polyurea-polyurethane is preferably used because of particularly good storage stability of the recording area.

  Here, a method for producing composite particles in which the organic polymer is at least one of polyurea and polyurea-polyurethane will be described. The composite particles are prepared by dissolving a dye precursor and a polymer-forming raw material that forms at least one of polyurea and polyurea-polyurethane by polymerization in a water-insoluble organic solvent having a boiling point of 100 ° C. or less. The solvent solution is emulsified and dispersed in a hydrophilic protective colloid solution such as polyvinyl alcohol so that the average particle size is about 0.5 to 3 μm, and further, if necessary, a reactive substance such as polyamine is mixed, and then this emulsified dispersion is added. The organic solvent is removed by volatilization by heating, and then the polymer precursor is prepared by polymerizing the polymer former or the dye precursor is dissolved in the polymer former. This is prepared by polymerizing the polymer-forming raw material after emulsification and dispersion by the above method.

The polymer-forming raw material forming at least one selected from the polyurea and the polyurea-polyurethane may be only a polyvalent isocyanate compound, or a polyvalent isocyanate compound and a polyol, polyamine that reacts with the polyvalent isocyanate compound Or a mixture with
It may be a multimer such as an adduct of a polyvalent isocyanate compound and a polyol, a biuret body or an isocyanurate body.

A polyisocyanate compound and water react to form an amine compound, and the amine compound and polyvalent socyanate compound react to form polyurea. Such a reaction further reacts with an organic compound having a hydroxyl group and a polyvalent isocyanate compound to form a polyurea-polyurethane.

  Examples of the polyvalent isocyanate compound used as the polymer-forming raw material include p-phenylene diisocyanate, 1,3-bis (1-isocyanato-1-methylethyl) benzene, 2,6-tolylene diisocyanate, 2,4 -Tolylene diisocyanate, naphthalene-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, Xylylene-1,4-diisocyanate, 4,4′-diphenylpropane diisocyanate, hexamethylene diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-dii Cyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, trimethylolpropane adduct of hexamethylene diisocyanate, trimethylolpropane adduct of 2,4-tolylene diisocyanate And a trimethylolpropane adduct of xylylene diisocyanate.

Examples of the polyol compound used for the polymer-forming raw material include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,7-heptanediol, 1,8-octanediol, propylene glycol, 1,3-dihydroxybutane,
2,2-dimethyl-1,3-propanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, phenylethylene glycol, pentaerythritol 1,4-di (2-hydroxyethoxy) benzene, 1,3-di (2-hydroxyethoxy) benzene, p-xylylene glycol, m-xylylene glycol, 4,4′-isopropylidenediphenol, 4 , 4′-dihydroxydiphenylsulfone, 2-hydroxyacrylate and the like.

Of course, the polyisocyanate compound, the adduct of polyisocyanate and polyol, the polyol compound, and the like are not limited to the above-mentioned compounds.
More than one species may be used in combination. In addition, it is especially preferable to use what has 3 or more isocyanate groups in a molecule | numerator among the polyvalent isocyanate compounds used in this invention, or the addition product of a polyvalent isocyanate compound and a polyol compound.

Examples of the polyamine compound used in the polymer-forming raw material of the present invention include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine, 2,5-dimethylpiperazine, and triethylene. Examples include triamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, and pentaethylenehexamine.

In the present invention, a surfactant, an antifoaming agent and the like may be used in addition to the hydrophilic protective colloid agent in the emulsification dispersion during the preparation of the composite particles. The amount of the hydrophilic protective colloid agent used in preparing the composite particles is not particularly limited, but in general, it is preferably 1 to 50% by mass, and about 3 to 30% by mass with respect to the total solid content of the composite particles. More preferably.

  In addition, the content of the dye precursor that develops black color in the composite particles of the present invention is preferably about 5 to 80% by mass, and more preferably about 20 to 50% by mass with respect to the total solid content of the composite particles.

The average particle size of the composite particles used in the present invention is 0.1 to
It is preferable that it is 15 micrometers, and it is more preferable to adjust so that it may become the range of 1.0-6.0 micrometers.

  Examples of the dye precursor of the first thermosensitive coloring layer and the composite precursor contained in the second thermosensitive coloring layer used in the present invention include 3-diethylamino-6-methyl-7-anilinofluorane, 3 -Di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N- Isoamylamino) -6-methyl-7-arininofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-piperidino-6-methyl-7- Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3- (N-cyclohexyl-N-methylamino) -6 Methyl -7-anilinofluorane), 3- (4-dimethylamino) alinino-5,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- (N-isoamyl-N-ethylamino) -7- (o- Chloroanilino) fluorane, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- ( Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-ethylamino] -6-methyl-7 Anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-di At least one kind such as (n-butylamino) -7- (2-chloroanilino) fluorane can be used.

In particular, the dye precursor contained in the first thermosensitive coloring layer is preferably a dye precursor having a melting point of 200 ° C. or more from the viewpoint of color separation, for example, 3- (N-ethyl-p-toluidino) -6-methyl-anilino. Fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl -7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3- (N-cyclohexyl-N-methylamino) -6 -Methyl-7-anilinofluorane), 3- (4-dimethylamino) alinino-5,7-dimethylfluorane and the like, but high sensitivity and light resistance are excellent. For this reason, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane is more preferred.

Examples of the dye precursor of the composite particles contained in the second thermosensitive coloring layer include 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane and 3-di (n-butylamino). -7
-(2-Chloroanilino) fluorane, 3-di (n-butyl) amino-6-methyl-7-
Anilinofluorane is more preferable in that it hardly causes background fogging.

In the composite particles used in the present invention, in addition to a dye precursor that develops a black color, 3,3′-bis (4-diethylamino-2-) is further added to improve the readability with a barcode reader.
A dye such as ethoxyphenyl) -4-azaphthalide, an aromatic organic compound (sensitizer) having a melting point of about 40 to 150 ° C. to enhance recording sensitivity, if necessary, an ultraviolet absorber for enhancing light resistance, an oxidation An inhibitor, an oil-soluble fluorescent dye, a release agent, or the like may be added. Such an additive substance is preferably solid at room temperature, but may be liquid. The dye precursor that produces black color may be a mixture of two or more dye precursors. When making the composite particles contain a dye precursor with a color tone that becomes a black color tone by mixing with the color tone formed by low-temperature color development, that is, a color tone that is complementary to the color tone, thereby making the high-temperature color tone black It is possible to obtain a high-temperature coloring color tone with a stronger blackness. In this case, a black color-forming dye precursor and a dye precursor that develops a color tone complementary to the low-temperature color tone can be used in combination as a dye precursor in the composite particles. Only a dye precursor that develops a color tone that is complementary to the color tone may be contained in the composite particles as a single dye precursor.

By using the composite particles of the present invention, it is possible to suppress background coloring due to pressing force and background fogging when stored for a long time in a blank paper state, and also suppress decolorization due to plasticizers and oil in the recording area can do.

Since the dye precursor in the composite particles used in the multicolor thermosensitive recording material of the present invention is covered with a polymer substance, the color development sensitivity is reduced as compared with the solid fine particle state existing alone. In addition, there is a drawback that the stability of the recording part in the light resistance test is inferior.

In order to solve the above-mentioned drawbacks, by providing a first thermosensitive coloring layer containing a dye precursor and a developer that newly develops a black color on the support, the black coloring sensitivity can be improved or a light resistance test can be performed. This is intended to improve the stability of the recording part.

In addition, by including spherical plastic resin particles or hollow plastic resin particles in the first thermosensitive coloring layer, the contrast between black coloring and a color that develops in a color tone different from black is improved, and a color tone different from black. It has become possible to greatly improve the storage stability of the color that develops, especially the chemical resistance of plasticizers and oils.
Such plastic resin particles are resin particles mainly composed of polystyrene, and the main monomer is styrene, aromatic vinyl compounds such as α-methylstyrene and vinyltoluene, methyl acrylate, ethyl acrylate, acrylic acid. Resin particles using acrylic acid esters such as butyl, vinyl esters such as vinyl acetate and vinyl propionate, vinylcyan compounds such as acrylonitrile, and vinyl halide compounds such as vinyl chloride and vinylidene chloride. The particle size is preferably about 0.2 to 3.0 μm in terms of sensitivity and image quality.
The content of the plastic particles used in the present invention is 5 to 30% by mass, preferably 10 to 20% by mass, and preferably less than 5% by mass of the total solid content of the first thermosensitive coloring layer. If it exceeds 30% by mass, the coloring ability is lowered, which is not preferable.

  As the dye precursor that develops a color tone different from that of the composite particles contained in the second heat-sensitive layer, a dye precursor that develops a color tone different from black, for example, red, magenta, orange, blue, green, etc. The body is raised.

For example, as dye precursors that give red, magenta, or orange colors, 3, 6
-Bis (diethylamino) fluorane-γ-anilinolactam, 3,6-bis (diethylamino) fluorane-γ- (p-nitro) anilinolactam, 3,6-bis (diethylamino) fluorane-γ- (o-chloro) ) Anilinolactam, 3-dimethylamino-7-bromofluorane, 3-diethylaminofluorane, 3-diethylamino-6-methylfluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluor Oran, 3-diethylamino-7-bromofluorane, 3-diethylamino-7,8
-Benzofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-tert-butylfluorane, 3- (N-ethyl- N-tolylamino) -7-methylfluorane, 3- (
N-ethyl-N-tolylamino) -7-ethylfluorane, 3- (N-methyl-N-isoamylamino) -7-phenoxyfluorane, 3- (N-ethyl-N-isobutylamino) -6-methyl Examples thereof include -7-chlorofluorane and 3- (N-ethyl-N-isoamylamino) -7,8-benzofluorane.

Examples of dye precursors that give red, magenta, and orange color shades include 3-cyclohexylamino-6-chlorofluorane and 3-di-n-butylamino-6-methyl-7.
-Bromofluorane, 3-di-n-butylamino-7,8-benzofluorane, 3-tolylamino-7-methylfluorane, 3-tolylamino-7-ethylfluorane, 2- (N
-Acetylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N-
Propionylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N
-Benzoylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N
-Carbobutoxyanilino) -3-methyl-6-di-n-butylaminofluorane, 2-
(N-formylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (
N-benzylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N
-Allylanilino) -3-methyl-6-di-n-butylaminofluorane, and 2- (N
-Methylanilino) -3-methyl-6-di-n-butylaminofluorane.

  Further, 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,3′-bis as dye precursors exhibiting red, magenta, and orange color tone (1-Ethyl-2-methylindol-3-yl) phthalide, 3,3′-bis (1-n-octyl-2-methylindol-3-yl) phthalide, 7- (N-ethyl-N-isoamyl) Amino) -3-methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3′-phthalide], 7- (N-ethyl-N-isoamylamino) -3-methyl-1-p-methylphenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3′-phthalide], and 7- (N-ethyl-Nn) -Hexylamino) -3-methyl-1- Enirusupiro [(1,4-dihydro-chromate Bruno [2,3-c] pyrazole) 4,3' phthalide] and the like.

Among the above-mentioned compounds, 3-diethylamino-7-chlorofluorane and 3-diethylamino-6-methyl-7- are examples of dye precursors that give red color development because they have high color development sensitivity and little background fogging. Chlorofluorane, 3- (N-methyl-N-isoamylamino) -7-phenoxyfluorane is preferred, and as the dye precursor that gives orange color, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino -6,8
-Dimethylfluorane, and 7- (N-ethyl-N-isoamylamino) -3-methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3 ' -Phthalide] is preferred, and 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide is preferred as a dye precursor that gives a reddish purple color. Note that 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide is excellent in oil resistance of the recording portion. In particular, when 3-diethylamino-7-chlorofluorane or 3-diethylamino-6-methyl-7-chlorofluorane is used as a red coloring dye precursor, dyes having different color tones are used for color correction. It is rather desirable to use a mixture, such as 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide or 3,3′-bis (1-ethyl-2-methylindole-3). -Il) By blending a small amount of a dye precursor that develops a reddish purple color tone such as phthalide, it is possible to develop a color tone that feels more reddish.

As a dye precursor that gives blue color, 3,3-bis (p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3
-(4-Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (1-ethyl-
2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide, 3
-(1-Ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindole-3-
Yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3-
(1-Ethyl-2-methylindol-3-yl) -3- (2-n-hexyloxy-4)
-Diethylaminophenyl) -4-azaphthalide, 3-diphenylamino-6-diphenylaminofluorane, and the like. In particular, among these blue color-forming dye precursors, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide is said to have less background fog. It is preferable from the point.

As a dye precursor that gives a green color, 3- (N-ethyl-Nn-hexylamino)
-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3
, 3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3- (
N-ethyl-Np-tolylamino) -7- (N-phenyl-N-methylamino) fluorane, 3- [p- (p-anilinoanilino) anilino] -6-methyl-7-chlorofluorane, and 3 , 6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide. Among these, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide is
It is preferable from the point that there is little background fog.

As dye precursors that give yellowish color development, 3,6-dimethoxyfluorane, and 1-
(4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) ethylene and the like. The above dye precursor may be used alone, but it is also effective to use it together with other color developing dyes for color tone correction.

In the present invention, when the dye precursor is used as a dye precursor in a solid fine particle state,
The dye precursor is pulverized by various wet pulverizers such as a sand grinder, attritor, ball mill, and cobo mill using water as a dispersion medium. Polyvinyl alcohol, methylcellulose, carboxymethylcellulose, styrene
In addition to water-soluble synthetic polymer compounds such as maleic anhydride copolymer salts and their derivatives, as well as surfactants and antifoaming agents as necessary, they are dispersed in a dispersion medium to form a dispersion, and this dispersion is heat-sensitive. It can be used to prepare a coating material for forming a color developing layer. Alternatively, after the dye precursor is dissolved in a solvent, the solution is emulsified and dispersed in water using the above water-soluble polymer as a stabilizer, and then the solvent is evaporated from the emulsion to make the dye precursor into solid fine particles. it can. In any case, the average particle diameter of the dispersed particles of the dye precursor used in the solid fine particle state is preferably 0.2 to 3.0 μm, more preferably 0.3 to 3.0 in order to obtain appropriate color development sensitivity. 1.0 μm.

In the second thermosensitive coloring layer, about 50 to 300 parts by mass of a dye precursor that develops a color tone different from 100 parts by mass of the dye precursor in the composite particles is included.

As the developer used in the present invention, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidenediphenol, 4-phenylphenol, 4,4′-dihydroxy Diphenylmethane, 4,
4′-isopropylidene diphenol, 4,4′-cyclohexylidene diphenol, 1
, 1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4′-dihydroxydiphenyl sulfide, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-dihydroxydiphenyl Sulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, and bis (
Phenolic compounds such as 3-allyl-4-hydroxyphenyl) sulfone, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, 4- Methyl hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl, 4
-Phenolic compounds such as phenyl-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl ether, or benzoic acid, p-tert-butylbenzoate Acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid,
Aromatic carboxylic acids such as 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and zinc, for example , Magnesium, aluminum,
Organic acidic substances such as salts with polyvalent metals such as calcium, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, N- (p-toluenesulfonyl) -N ′-( and urea compounds such as p-butoxycarboyl) urea and Np-tolylsulfonyl-N′-phenylurea.

  Among these developers, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) is used for the thermosensitive coloring layer from the viewpoints of storage stability, sensitivity, and heat resistance during high temperature storage (background fogging). It is preferable to use phenylurea, and it is more preferable to use the same developer for the first and second thermosensitive coloring layers from the viewpoint of background fogging during high-temperature storage. Furthermore, 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide is used as the dye precursor that develops a color tone different from that of the composite particles contained in the second thermosensitive coloring layer. When Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea is used as a color developer for the first and second thermosensitive coloring layers, the heat resistance (background fogging) during high-temperature storage is also obtained. It is more preferable because of its excellent chemical resistance such as plasticizer and oil.

The developer is usually preferably used in an amount of 100 to 700 parts by mass, more preferably 150 to 400 parts by mass, with respect to 100 parts by mass in total of the dye precursor. Of course, if necessary, two or more colorants can be used in combination.

In the present invention, an image stabilizer may be used mainly for improving the storage stability of the color-recorded image. As such an image stabilizer, for example, 1,1,3-tris (2-methyl-4-
Hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-
4-hydroxy-5-tert-butylphenyl) butane, 1,1-bis (2-methyl-
4-hydroxy-5-tert-butylphenyl) butane, 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisphenol, and 4,4 ′-[1,3-phenylenebis (1- Methylethylidene)]] phenolic compounds such as bisphenol, 4-benzyloxyphenyl-4 ′-(2-methyl-2,3-epoxypropyloxy) phenylsulfone, 4- (2-methyl-1,2-epoxyethyl) ) Epoxy compounds such as diphenylsulfone and 4- (2-ethyl-1,2-epoxyethyl) diphenylsulfone, and 1,3,5-tris (2,6-dimethylbenzyl-3-hydroxy-4-tert-) What contains 1 or more types chosen from isocyanuric acid compounds, such as a butyl) isocyanuric acid, can be used. Of course, the image stabilizer is not limited to these, and two or more kinds of compounds may be used in combination as required.

In order to adjust the color development sensitivity of the thermosensitive coloring layer of the thermosensitive recording material, a thermofusible substance can be contained in the thermosensitive coloring layer as a sensitizer. As the sensitizer, compounds conventionally known as sensitizers for thermal recording materials can be used. For example, parabenzylbiphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate Di-o-chlorobenzyl adipate, 1,2-di (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, 1,2-bis (3,4 −
Examples thereof include dimethylphenyl) ethane and 1,3-bis (2-naphthoxy) propane. In particular, when di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate are used as sensitizers, a sensitizing effect with less fog is obtained.

Additives such as developers, image stabilizers, and sensitizers used in the present invention are dispersed in water in the same manner as when the dye precursor is used in the form of solid fine particles, so What is necessary is just to mix with this in the case of preparation. Moreover, these additives can be dissolved in a solvent and emulsified in water using a water-soluble polymer compound as an emulsifier. Furthermore, composite fine particles containing these compounds may be prepared by the same method as the composite fine particle preparation method described above, and this may be contained in the thermosensitive coloring layer. Further, the image stabilizer and the sensitizer may be contained in the composite fine particles containing the dye precursor. In particular, the color sensitivity can be adjusted to a desired value by incorporating a sensitizer into the composite fine particles together with the dye precursor.

In the present invention, in order to improve the whiteness of the thermosensitive coloring layer and improve the uniformity of the image, a fine pigment having a high whiteness and an average particle size of 10 μm or less can be contained in the thermosensitive coloring layer. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface treated calcium carbonate and silica, etc. Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, and polystyrene resin can be used. In order to prevent residue adhesion and sticking to the thermal head, it is preferable to use a pigment having an oil absorption of 50 ml / 100 g or more. The amount of the pigment blended is preferably an amount that does not lower the color density, that is, 50% by mass or less based on the total solid content weight of the thermosensitive color developing layer.

In the present invention, an adhesive is used as another component material constituting the thermosensitive coloring layer, and a cross-linking agent, waxes, metal soaps, colored dyes, colored pigments, and fluorescent dyes can be used as necessary. . Examples of the adhesive include polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose.
Polyacrylic acid soda, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein Water-soluble polymer materials such as gelatin and derivatives thereof, and polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer Examples thereof include emulsions such as blends and latexes of water-insoluble polymers such as styrene-butadiene copolymers and styrene-butadiene-acrylic copolymers.

Moreover, in order to improve the water resistance of the thermosensitive coloring layer, a crosslinking agent for three-dimensionally curing the adhesive can be contained in the thermosensitive coloring layer. For example, aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, and ammonium persulfate, ferric chloride, and chloride Inorganic compound such as magnesium, sodium tetraborate, potassium tetraborate or at least one crosslinkable compound selected from boric acid, boric acid triester, boron-based polymer, etc. with respect to the total solid content weight of the thermosensitive coloring layer It is preferably used in the range of 1 to 10% by weight.

Examples of the wax added to the thermosensitive coloring layer include waxes such as paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax, and polyethylene wax, and higher fatty acid amides such as stearamide, ethylenebisstearic amide, and higher. Examples thereof include fatty acid esters and derivatives thereof. In particular, when methylolated fatty acid amide is added to the thermosensitive coloring layer, a sensitizing effect can be obtained without deteriorating the background fog resistance.

Examples of the metal soap added to the heat-sensitive color developing layer include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. Further, the inclusion of a colored dye and / or a colored pigment having a color tone complementary to the low temperature color tone in the heat-sensitive color developing layer is preferably used for adjusting the color tone of the recording material before printing. If necessary, various additives such as an oil repellent, an antifoaming agent, and a viscosity modifier can be further added to the thermosensitive coloring layer within a range not impairing the effects of the present invention.

There are no particular limitations on the type, shape, dimensions, and the like of the support material used in the present invention. In addition to glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film, and the like, various transparent supports can be appropriately selected and used.

  In the present invention, in order to increase the added value of the multicolor thermal recording material, it can be further processed to provide a thermal recording material having a higher function. For example, adhesive paper, rewet adhesive paper, delayed tack paper can be used by applying coating with adhesive, rewet adhesive, delayed tack type adhesive, etc. on the back side, or magnetic processing is applied Thus, a thermosensitive recording material having a magnetically recordable layer on the back surface can be obtained. In particular, those subjected to adhesive processing and magnetic processing are useful for applications such as two-color heat-sensitive labels and two-color heat-sensitive magnetic tickets. Further, by using the back surface, a function as a thermal transfer paper, an ink jet paper, a carbonless paper, an electrostatic recording paper, and a xerographic paper can be added to the recording paper which can be recorded on both sides. Of course, a double-sided thermal recording material can also be used. As the multicolor thermal recording material of the present invention, when two or more types of two-color thermal recording materials having different low-temperature color tone are used, various colors such as file color coding, delivery destination color coding, receipt and journal color coding, etc. It becomes possible to perform recognition with different colors depending on the application.

In the present invention, a protective layer can be provided on the thermosensitive coloring layer, and an undercoat layer can be provided below the thermosensitive coloring layer. As these additional layers, a protective layer and an undercoat layer that have been used in conventionally known heat-sensitive recording materials can be used. Both the protective layer and the undercoat layer are mainly composed of a pigment and an adhesive. In particular, for the purpose of preventing sticking to the thermal head, it is preferable to add a lubricant such as polyolefin wax and zinc stearate to the protective layer, and it can also contain an ultraviolet absorber, and it is composed of two or more layers. You can also In addition, the added value of the product can be increased by providing a glossy protective layer.

By using a pigment having a high porosity such as silica or calcined kaolin for the undercoat layer, the color development sensitivity of the thermosensitive color developing layer thereon can be increased. In addition, the inclusion of plastic pigments, hollow particles, foams and the like in the undercoat layer is also effective in improving the color development sensitivity of the thermosensitive color development layer formed thereon.

A protective layer containing a UV curable resin or an EB curable resin can be provided on the thermosensitive coloring layer of the present invention, and printing can be performed with UV ink, flexographic ink or the like thereon. By using a release agent such as silicon for the protective layer, the heat-sensitive recording material of the present invention can also be used as a linerless adhesive label. In this case, a release agent may be applied after printing.

As a method for forming each layer on the support, any of known coating methods such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method is used. May be. It is also possible to partially print the heat-sensitive color developing layer paint of the present invention using a printing machine or the like. The heat-sensitive coloring layer coating is applied to one surface of the support so that the weight after drying is 1 to 10 g / m 2 in both the first and second heat-sensitive coloring layers, thereby forming the heat-sensitive coloring layer. The Further, a back layer can be provided for suppressing permeation of oil and plasticizer from the back surface of the recording material, or for curling control.
Further, smoothing the thermosensitive coloring layer using a known smoothing method such as a super calender or a soft calender is effective in increasing the coloring sensitivity. The surface of the heat-sensitive color developing layer may be applied to either a calendar metal roll or an elastic roll.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Unless otherwise specified, “parts” and “%” represent “parts by mass” and “mass%”, respectively.

Example 1
・ Preparation of paint for undercoat layer: 88 parts of calcined kaolin having an oil absorption amount of 110 ml, 20 parts of styrene-butadiene latex (solid content concentration: 50%), carboxymethylcellulose (trade name: Cellogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 20 parts of 5% aqueous solution, 5 parts of 20% aqueous solution of sodium polyacrylate and water 1
90 parts of the mixture were uniformly mixed to obtain an undercoat layer coating solution.

Preparation of dye precursor-containing composite particle dispersion (liquid A) 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane (6 parts) and 2-hydroxy-4-as UV absorber 3 parts of octyloxybenzophenone was dissolved in 9 parts of dicyclohexylmethane-4,4′-diisocyanate heated to 100 ° C., this solution was cooled to 35 ° C., and then 8% polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry, (Trademark: Gohsenol GM-14L) The resulting solution was gradually added to 100 parts of an aqueous solution and emulsified and dispersed by stirring at a rotational speed of 8000 rpm using a homogenizer, and then 60 parts of water was added to the emulsified dispersion and homogenized. The emulsion dispersion was heated to 90 ° C. and allowed to undergo a curing reaction for 10 hours, and then water was added so that the solid content concentration was 20%, and a composite particle dispersion having an average particle diameter of 0.8 μm was obtained. Obtained.

-Preparation of Dye Precursor Dispersion (Liquid B) 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 20 parts, sulfone-modified polyvinyl (Goceran L-3266: Nihon Gosei) 20% of chemical industry)
10 parts of liquid, 20 parts of water, vertical sand mill (made by Imex Co., Ltd., sand grinder)
Was used to grind and disperse so that the average particle size was 0.8 μm.

Preparation of dye precursor dispersion (liquid C) 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide 20 parts, sulfone-modified polyvinyl (trade name: Goceran L- 3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10 parts of 20% liquid and 20 parts of water were pulverized and dispersed using a vertical sand mill (made by IMEX Co., Ltd., sand grinder) so that the average particle size became 0.7 μm. did.

-Preparation of developer dispersion (liquid D) Np-toluenesulfonyl-N'-3- (p-toluenesulfonyloxy) phenylurea 20 parts, sulfone-modified polyvinyl (trade name: Gocelan L-3266, 10 parts of 20% liquid (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 30 parts of water were pulverized and dispersed using a vertical sand mill (made by IMEX Co., Ltd., sand grinder) so that the average particle diameter was 1.2 μm.

Preparation of sensitizer dispersion (solution E) 1: 1 mixture of di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate
(Product name: HS7150, manufactured by Dainippon Ink Chemical Co., Ltd.) 20 parts, sulfone-modified polyvinyl (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10 parts 20% liquid, 30 parts water (Imex Co., Ltd. product, sand grinder) was used, and it grind | pulverized and disperse | distributed so that an average particle diameter might be set to 1.0 micrometer.

-Preparation of coating solution for first thermosensitive coloring layer B part 30 parts, D part 60 parts, E part 60 parts, aluminum hydroxide 10 parts, polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.) 10 parts aqueous solution 100 parts And 70 parts of water were mixed and stirred uniformly to obtain a first thermosensitive coloring layer coating solution.

・ Preparation of coating liquid for second thermosensitive coloring layer A liquid 265 parts, C liquid 30 parts, D liquid 30 parts, E liquid 30 parts, aluminum hydroxide 10 parts, polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.) 100 parts of a 10% aqueous solution and 70 parts of water were uniformly mixed and stirred to obtain a second thermosensitive coloring layer coating solution.

・ Preparation of coating solution for protective layer Acetacetyl-modified polyvinyl alcohol (trade name: Goosefimmer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10% liquid 100 parts, kaolin 200 parts, zinc stearate 30% dispersion (product) Name: Hydrin Z-7, manufactured by Chukyo Yushi Co., Ltd.) and 100 parts of water were uniformly mixed to obtain a protective layer coating solution.

-Preparation of multi-color thermal recording material On one side of a high-quality paper (paper surface pH 5.9) having a basis weight of 81.4 g / m ² , an undercoat layer coating solution, a first thermal coloring layer coating solution, and a second thermal coloring layer The coating amount after drying the coating solution for the protective layer and the coating solution for the protective layer is 8 g.
Multicolor having an undercoat layer, a first thermosensitive color developing layer, a second thermosensitive color developing layer, and a protective layer in order by coating / drying so as to be / m ² , 4 g / m ² , 3 g / m ² , and 2 g / m ² After obtaining the heat-sensitive recording material, smoothing treatment was performed with a super calendar so that the Beck smoothness (JIS-P8119) of the heat-sensitive recording surface was 3500 seconds to produce a multicolor heat-sensitive recording material.

Reference example 1
In preparing the liquid C of Example 1, 3- (N-methyl) was used instead of 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide as a red-purple chromogenic dye precursor. A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that -N-isoamylamino) -7-phenoxyfluorane was used.

Reference example 2
In preparing the liquid C of Example 1, 3-diethylamino-7- in place of the 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide of the reddish purple coloring dye precursor A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that chlorofluorane was used.

Reference example 3
In the preparation of the liquid C used in the coating solution for the second thermosensitive coloring layer of Example 1, the reddish purple coloring dye precursor 3,3′-bis (1-n-butyl-2-methylindol-3-yl) ) When 3-diethylamino-7-chlorofluorane was used instead of phthalide, and N-p-toluenesulfonyl-N′- was used as a developer in the preparation of solution D, which was also used for the coating solution for the second thermosensitive coloring layer. A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used instead of 3- (p-toluenesulfonyloxy) phenylurea.

Reference example 4
In the preparation of the liquid D used for the first thermosensitive color-developing layer coating liquid of Example 1, instead of the developer Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, 4 was used. A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that -hydroxy-4'-isopropoxydiphenyl sulfone was used.

Reference Example 5
In the preparation of the liquid D used for the first thermosensitive coloring layer coating liquid of Example 1, bis instead of the developer Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea was used. A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that (p-hydroxyphenyl) butyl acetate was used.

Example 2
A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that the sensitizer dispersion liquid (E liquid) was not used in the preparation of the first thermosensitive coloring layer coating liquid of Example 1.

Reference Example 6
In the preparation of the liquid B used for the first thermosensitive coloring layer coating liquid of Example 1, instead of the dye precursor 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane was used.

Example 3
In the preparation of solution A in Example 1, 3-di (n-pentyl) amino was used instead of 6 parts of 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane as a black color developing dye precursor. Example 1 was repeated except that 4 parts of -6-methyl-7-anilinofluorane and 2 parts of 3,3′-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide were used. A multicolor thermal recording material was prepared.

Example 4
Example 1 is the same as Example 1 except that 12 parts of spherical plastic particles (trade name: Grosdale 130S, manufactured by Mitsui Chemicals) were used in place of 10 parts of aluminum hydroxide in the preparation of the first thermosensitive coloring layer coating solution of Example 1. Similarly, a multicolor thermal recording material was produced.

Example 5
In the preparation of the first thermosensitive coloring layer coating solution of Example 1, the same procedure as in Example 1 was carried out except that 10 parts of hollow plastic resin particles (trade name: AE851, manufactured by JSR) were used instead of 10 parts of aluminum hydroxide. Thus, a multicolor thermal recording material was produced.

Comparative Example 1
A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that the first thermosensitive coloring layer was not provided in Example 1.

Comparative Example 2
A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that the liquid A was not used in Example 1.

Comparative Example 3
In the preparation of the coating solution for the second thermosensitive coloring layer of Example 1, solution A was not used, but instead of solution B, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane. 3-di (n-
A multicolor thermosensitive recording material was produced in the same manner as in Example 1 except that 60 parts of a dispersion using pentyl) amino-6-methyl-7-anilinofluorane was used.

  The obtained multicolor thermal recording material was subjected to the following evaluation tests, and the results are shown in Table 1.

・ Printing test Using a printer (model name: Barrabe 300, manufactured by Sato Co., Ltd.), applied energy:
Low temperature color development was performed at 0.10 mJ / dot, and high temperature color development was further performed at 0.27 mJ / dot.
The print pattern was a bar code.

The recorded portion thus obtained was visually evaluated for color tone according to the following evaluation criteria.

・ Sensitivity ○: Black color with high density is obtained.
Δ: Although the black color density is slightly low, there is no practical problem.
X: The black color density is low and there is a problem in practical use.

-Two-color separation property (circle): The clear low-temperature color development (red) was clear and was excellent in two-color separation property.
(Triangle | delta): Although the low temperature color development part is muddy color development with which the high temperature color development color tone was mixed a little, the separability of two colors is a level which is satisfactory practically.
X: The low temperature color development part was turbid color development mixed with the high temperature color development hue, and the two colors could not be separated.

・ Oil resistance Soak edible oil with a cotton swab, reciprocate 10 times on the high temperature recording part, wipe off after 1 hour and observe the recording part after 1 week.
A: Not disappeared at all.
○: Almost no disappearance.
Δ: Partial erasing tendency is observed, but it is a level that is not problematic in practical use.
X: The recording part has almost disappeared.

-Light resistance After exposing the high-temperature coloring part of the barcode in an environment of 10,000 Lux for 100 hours, the PCS value at 660 nm was measured using a barcode verifier (Macbeth, PCM-II).

・ Heat resistance Leave in a high-temperature bath at 70 ° C for 24 hours. After testing, the density of the background is measured by Macbeth densitometer (RD-91
(4 type, manufactured by Macbeth Co., Ltd.) using a magenta filter, and heat resistance was evaluated.

A composite particle comprising a first thermosensitive coloring layer containing a black color developing dye precursor and a developer on a support, and further comprising an organic polymer and a black coloring dye precursor on the first thermosensitive coloring layer. By having the second thermosensitive coloring layer containing the solid dispersed fine particles composed of a dye precursor that develops a color tone different from that of the composite particles and the developer, the low-temperature coloring color tone has almost no color mixing of the high-temperature coloring color tone. Applicable to multicolor thermal recording media that can produce color tone, that is, excellent in color separation and high sensitivity, and excellent in chemical resistance of the recording part required for thermal recording media, and also has good light resistance and little background fog. it can.

Claims (5)

A composite particle comprising a first thermosensitive coloring layer containing a black color developing dye precursor and a developer on a support, and further comprising an organic polymer and a black coloring dye precursor on the first thermosensitive coloring layer. A multicolor thermosensitive recording medium comprising a second thermosensitive coloring layer containing solid dispersed fine particles composed of a dye precursor that develops a color tone different from that of the composite particles and a developer , wherein the first thermosensitive coloring The dye precursor that develops black color in the layer is 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, and has a color tone different from that of the composite particles in the second thermosensitive coloring layer. The dye precursor that develops color is 3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide, and the developer in the first and second thermosensitive coloring layers is: Np-toluenesulfonyl-N′-3- (p-toluenesulfonyl) Carboxymethyl) multicolor heat-sensitive recording material is phenyl urea.   The multicolor thermosensitive recording material according to claim 1, wherein spherical plastic resin particles or hollow plastic resin particles are contained in the first thermosensitive coloring layer. The multicolor thermosensitive recording material according to claim 1, wherein the organic polymer is at least one selected from polyurea and polyurea-polyurethane. The dye precursor used for the composite particles contained in the second thermosensitive coloring layer is 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6. 2. The multicolor thermosensitive recording material according to claim 1, which is at least one selected from -methyl-7-anilinofluorane and 3-di (n-butylamino) -7- (2-chloroanilino) fluorane. 3,3'-bis (4-diethylamino-2) is further added to the composite particles contained in the second thermosensitive coloring layer.
The multicolor thermal recording material according to claim 1 or 4, which contains -ethoxyphenyl) -4-azaphthalide.