JPH10175374A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material having excellent pressure fog and preservability and a multicolor thermal recording material having satisfactory color separability. SOLUTION: This recording material comprises a thermal color developing layer containing a dye precursor, developable compound for reacting with the precursor by heating to color develop it. In this case, composite fine particles obtained by expediting polymerization reaction of a polyvalent isocyanate after a solution in which the polyvalent isocyanate is used as a solvent, and the dye precursor is used as a solute is emulsion dispersed in water are contained in the color developing layer, and as the polyvalent isocyanate, a bivalent isocyanate and a trivalent or higher isocyanate of one or more types are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material which is less fogged by pressure and has excellent preservability of a colored portion. Further, the present invention includes a heat-sensitive recording material capable of forming a plurality of colors having different color tones depending on a condition of applying heat from a thermal head. Such a heat-sensitive recording material is capable of obtaining a clear multicolored color tone with little color mixture of a low-temperature color tone and a high-temperature color tone.

[0002]

2. Description of the Related Art Conventionally, a dye precursor, and a color developing reaction between the dye precursor and a color developing agent which is brought into contact with the color of the dye under heating to form a color therewith, are used to fuse both color forming substances by heating.
Thermal recording materials for obtaining a color image are widely known. Such heat-sensitive recording materials are relatively inexpensive,
Because the recording equipment is compact and easy to maintain, facsimile, word processor, various computers,
And as a recording medium for other uses. However, such a conventional heat-sensitive recording material has a disadvantage that when a protective layer is not provided on the heat-sensitive coloring layer, color formation due to fogging or rubbing due to pressure tends to occur, and the coloring part is erased by a plasticizer or oil. Have.

With respect to the heat-sensitive recording material, the required quality has been diversified with the expansion of uses thereof. For example, there have been demands for high sensitivity, image stabilization, multicolor recording, and the like. In particular, the multicolor recording means has the advantage that characters or graphics to be emphasized can be displayed clearly and clearly with a different color tone from other parts. Among them, a two-color heat-sensitive recording material capable of recording in two colors of red and black is excellent in general versatility, and therefore there is a high demand for practical use.

As a multicolor heat-sensitive recording system, attempts have been made to utilize a difference in heating temperature or a difference in heat energy, and various multicolor heat-sensitive recording materials have been proposed. In general, a multicolor heat-sensitive recording material is formed by sequentially laminating a high-temperature coloring layer and a low-temperature coloring layer that form different colors on a support, and these are roughly classified into a decoloring type and an additive type. 2
Divided into types.

Examples of the decolorizable multicolor heat-sensitive recording material include, for example, JP-A-50-17865 and JP-A-57-14.
As disclosed in JP-A-320-320 and JP-A-2-80287, only a low-temperature coloring layer develops color by a low-temperature coloring operation, and when heating at a high temperature, the coloring system of the low-temperature coloring layer is erased. This is a method in which a decoloring agent having a color effect acts to obtain color development only in the high-temperature coloring layer. This method has the advantage that the color tone can be freely selected, but it is necessary to add a large amount of a decoloring agent in order to obtain a sufficient decoloring effect on the low-temperature coloring layer. Then, the action of the decoloring agent added in a large amount causes the recorded color-developed image to fade during long-term storage, or requires an extra amount of heat to melt the decoloring agent, so that an excessive load is imposed on the thermal head. However, it is not always satisfactory in terms of the reliability of the recorded image and the recording sensitivity.

On the other hand, a color-added multicolor heat-sensitive recording material is
JP-B-49-27708, JP-B-51-1998
No. 9, JP-A-51-146239, etc., a method of laminating two color-forming layers that develop different colors and applying two different amounts of heat to obtain two distinguishable colors. It is. In this method, the upper color-forming layer develops color at low temperature to obtain the upper color-forming tone, and at high temperature, the upper and lower color-forming layers develop color to obtain an image of a mixed color tone of both colors. Suitable when used as a system. Since no color erasing agent is used in an additive color recording material, there is an advantage that compared with a color erasure type recording material, the recorded image has excellent long-term storage properties and can be manufactured relatively inexpensively. Also, since no extra heat is required for melting the decoloring agent, there is an advantage that the high-temperature coloring layer can be colored with lower energy as compared with the decoloring type. However, the color-added multicolor heat-sensitive recording material having such a configuration has a problem in that when heat is applied too much at the time of low-temperature coloring, the coloring of the high-temperature coloring layer is partially mixed, resulting in color mixing, which makes it difficult to sharpen the low-temperature coloring image. was there. JP-A-56-99697 describes a method of mixing two or more dye precursors having different color tones and different average particle diameters in the same layer. There is a problem that color mixing becomes more intense.

[0007] The application of microcapsules to heat-sensitive recording materials has been known for a long time.
No. 0 describes that a solvent in a liquid state at normal temperature is encapsulated. An example of microencapsulation of a coloring component as a core substance is disclosed in JP-A-57-12695.
And JP-A-59-214691. Further, Japanese Patent Publication No. 4-4960 and Japanese Patent Application Laid-Open No. 4-101885 disclose a color-forming component that develops a color tone different from each other in a solvent and contain each of the components in two or more types of microcapsules having different glass transition temperatures. It is described that the color is multiplied by performing the above. However, separately encapsulating two or more types of dye precursors that develop different color tones reduces the color development sensitivity of each of the two dye precursors, making it difficult to classify the sensitivity, and as a result, mixing of the color tones is likely to occur. There was a problem. In addition, when an oil-based liquid for dissolving the dye precursor is contained in the microcapsules, there is a problem that the capsules are broken due to pressure or frictional rubbing, and that color development easily occurs.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive coloring layer containing a dye precursor and a color developing compound which reacts with the dye precursor under heating to develop the color on a support. It is an object of the present invention to provide a heat-sensitive recording material provided with less fogging due to pressure and excellent storage stability of a color-developed portion. Furthermore, the present invention provides a thermosensitive coloring layer containing two or more dye precursors that develop different colors depending on the difference in the heating application conditions from the thermal head and a color developing compound that develops the dye precursor. In a multicolor heat-sensitive recording material, it is an object to provide a multicolor heat-sensitive recording material excellent in whiteness with low mixing of the color tone at the time of high-temperature coloring in low-temperature coloring tone at low-temperature printing, and low background fog. .

[0009]

According to the present invention, there is provided a heat-sensitive coloring layer containing a dye precursor and a color-developing compound which reacts with the dye precursor under heating to develop the color on a support. In the heat-sensitive recording material comprising, after emulsifying and dispersing a solution containing a polyvalent isocyanate as a solvent and a dye precursor as a solute in water,
Containing composite fine particles obtained by accelerating the polymerization reaction of polyvalent isocyanate in the thermosensitive coloring layer,
Divalent isocyanate and 3
And at least one isocyanate having a valency or higher.

The present invention also resides in a heat-sensitive recording material wherein the divalent isocyanate is dicyclohexylmethane-4,4'-diisocyanate.

Further, the present invention resides in a heat-sensitive recording material in which the isocyanate having a valence of 3 or more is a trimethylolpropane adduct of hexamethylene diisocyanate.

Further, the present invention resides in a heat-sensitive recording material wherein the weight ratio of the polyvalent isocyanate is 10 to 1000 parts by weight of the trivalent or higher isocyanate with respect to 100 parts by weight of the divalent isocyanate.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the heat-sensitive recording material of the present invention, a solution containing a polyvalent isocyanate as a solvent and a dye precursor as a solute is emulsified and dispersed in water, and then the polymerization reaction of the polyvalent isocyanate is promoted. The obtained composite fine particles are contained in a thermosensitive coloring layer.

The composite fine particles used in the present invention are composed of a base material composed of at least two kinds of polymer substances (resins) selected from polyurea or polyurethane-polyurea, and a dye precursor contained therein. Thing,
It is considered that the dye precursor and the polymer substance exist in a solid solution state. It is preferable from the viewpoint of pressure fogging that the composite fine particles do not contain a liquid such as an oily solvent.

Further, the present invention is characterized in that a divalent isocyanate and a trivalent or higher isocyanate are used in combination. The divalent isocyanate easily dissolves the dye precursor, and even after dissolution, the precipitation of the dye precursor is small, so that composite fine particles are easily obtained in a stable manner. On the other hand, when a trivalent or higher isocyanate is used, the three-dimensional cross-linking of the composite fine particles easily proceeds, the physical strength and the barrier property of the obtained composite fine particles are improved, pressure fog is hardly generated, and the color forming body is formed. Storage stability, especially resistance to oils and plasticizers.
By using divalent and trivalent or higher isocyanates in combination, composite fine particles can be obtained stably, and a heat-sensitive recording material using the obtained composite fine particles has little pressure fog and is excellent in storage stability of a color-developed portion.

The appearance of the composite fine particles used in the present invention is substantially spherical when observed with an electron microscope, or is in the form of a hemoglobin with a somewhat concave center. In cross-sectional observation with an electron microscope, the shape is an internal body, a porous body, or a hollow body. The average particle diameter is preferably from 0.2 to 5.0 μm. When applied to a multicolor heat-sensitive recording material, the average particle size is 0.8μ.
m to 5.0 μm. When the average particle diameter is smaller than 0.8 μm, it is difficult to classify the coloring sensitivity with the dye precursor in the form of solid fine particles to be mixed, and color mixing occurs at low temperature, which is not preferable. If the average particle size is larger than 5.0 μm, the color development sensitivity is reduced, so that it is necessary to excessively apply energy to the thermal head, which is not preferable. When applied to a monochrome thermal recording material,
The average particle size is 0.2 μm in order to obtain appropriate color sensitivity.
It is preferable that the thickness be 1.5 μm. When the particle size is small, the storage stability of the colored portion with respect to oil, plasticizer and the like may be deteriorated, and it is not desirable to make the average particle size smaller than 0.2 μm.

As the dye precursor that can be contained in the composite fine particles used in the present invention, a leuco compound such as a triaryl compound, a diphenylmethane compound, a thiazine compound, a spiro compound, a lactam compound or a fluoran compound can be preferably used. These dye precursors each give a unique color tone upon contact with a color developer, and the color tone is black,
It ranges from red, magenta, orange, blue, green, and yellow.

In order to obtain a heat-sensitive recording material capable of forming multiple colors in the present invention, for example, a composite fine particle containing a first dye precursor having a black color tone and a second dye which develops a color tone different from black are used. Solid fine particles comprising a precursor are contained in the thermosensitive coloring layer. The low-temperature color tone is a color tone of the second dye precursor present in the state of solid fine particles, and the high-temperature color tone is a mixed color tone of the first dye precursor and the second dye precursor present in the composite fine particles. By making the second dye precursor black, even when color mixing occurs due to color development of the first dye precursor, the high-temperature color tone can be made black. The color-forming dye precursor contained in the composite fine particles may be a single compound and may be black-color-forming, or may be a mixture of two or three or more different color-forming dye precursors to form a black color. It is good.

In order to make the high-temperature color tone close to pure black, a dye precursor having a color tone different from the low-temperature color tone, more preferably a dye precursor having a complementary color relationship, is replaced with a black color dye precursor. It is desirable that the fine particles be contained together with the composite fine particles. When the low-temperature color tone is red, a dye precursor that develops a blue or green color is contained in the composite fine particles together with a black color-forming dye precursor.

The dye precursor that can be used in the present invention includes 3-pyrrolidino-6-methyl-7-anilinofluoran,
Diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-isoamyl-N-ethylamino) -7- (o-chloroanilino) fluoran, 3-
(N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran, 3 -Diethylamino-6-chloro-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-amylamino-6-methyl-7-anilino Fluoran, 3- (N
-Isoamyl-N-ethylamino) -6-methyl-7-
Anilinofluoran, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluoran,
3- [N- (3-ethoxypropyl) -N-ethylamino) -6-methyl-7-anilinofluoran, 3- [N
-(3-ethoxypropyl) -N-methylamino) -6
-Methyl-7-anilinofluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-di-
n-butylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-
(2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluoran, 2,4-dimethyl-6- (4-dimethylaminoanilino) fluoran, And 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluoran.

In the present invention, among the dye precursors giving a black color, 3-di-n-amylamino-6-methyl-7-anilinofluoran, which is particularly excellent in light resistance,
-Diethylamino-6-methyl-7- (2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluoran,
It is preferably at least one selected from 2,4-dimethyl-6- (4-dimethylaminoanilino) fluorane.

The dye precursors which can be used in the present invention to develop a red color include 3,6-bis (diethylamino) fluoran-γ-anilinolactam and 3,6-bis (diethylamino) fluoran-γ- (p- Nitro) anilinolactam, 3,6-bis (diethylamino) fluoran-γ- (o-chloro) anilinolactam, 3-dimethylamino-7-bromofluorane, 3-diethylaminofluoran, 3-diethylamino-6- Methylfluoran, 3-diethylamino-7-methylfluoran,
3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluoran, 3-diethylamino-7,8-benzofluoran, 3-diethylamino-
6,8-dimethylfluoran, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-diethylamino-7-tert-butylfluoran, 3- (N-ethyl-N-tolylamino) -7-methylfluoran, 3-
(N-ethyl-N-tolylamino) -7-ethylfluoran, 3- (N-ethyl-N-isobutylamino) -6
-Methyl-7-chlorofluorane, and 3- (N-ethyl-N-isoamylamino) -7,8-benzofluoran.

Further, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 3-di-n -Butylamino-7,8-benzofluoran, 3-tolylamino-7-methylfluoran, 3-tolylamino-7-ethylfluoran, 2-
(N-acetylanilino) -3-methyl-6-di-n-
Butylaminofluoran, 2- (N-propionylanilino) -3-methyl-6-di-n-butylaminofluoran, 2- (N-benzoylanilino) -3-methyl-
6-di-n-butylaminofluoran, 2- (N-carbobutoxyanilino) -3-methyl-6-di-n-butylaminofluoran, 2- (N-formylanilino)-
3-methyl-6-di-n-butylaminofluoran, 2
-(N-benzylanilino) -3-methyl-6-di-n
-Butylaminofluoran, 2- (N-allylanilino) -3-methyl-6-di-n-butylaminofluoran, and 2- (N-methylanilino) -3-methyl-
6-di-n-butylaminofluoran, 3-diethylamino-7-phenoxyfluoran, 3- (N-ethyl-
(N-isoamylamino) -7-phenoxyfluoran.

Further, 3,3'-bis (1-n-butyl-2-methylindol-3-yl) phthalide,
3'-bis (1-ethyl-2-methylindole-3-
Yl) phthalide, 3,3'-bis (1-n-octyl-
2-methylindol-3-yl) phthalide, 7- (N
-Ethyl-N-isoamylamino) -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-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3 ′
-Phthalide] can be mentioned as a red dye precursor.

The dye precursor giving a blue color includes:
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-methylindol-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-diphenylaminofluoran, and the like.

As the dye precursor giving green color, 3
-(N-ethyl-NN-hexylamino) -7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4 -Azaphthalide, 3-
(N-ethyl-Np-tolylamino) -7- (N-phenyl-N-methylamino) fluoran, 3- [p-
(P-anilinoanilino) anilino] -6-methyl-7
-Chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, and the like.

Dye precursors that give yellowish color development include 3,6-dimethoxyfluoran and 1- (4-
n-dodecyloxy-3-methoxyphenyl) -2-
(2-quinolyl) ethylene and the like.

In the production of the composite fine particles used in the present invention, first, a solution is prepared by dissolving a dye precursor in a polyvalent isocyanate. The dissolution temperature at this time is preferably 60 ° C. or higher. If the dissolution temperature is lower than 60 ° C., the dissolution of the dye precursor in the polyvalent isocyanate becomes insufficient, so that uniform composite fine particles may not be produced. In some cases, the dye precursor is difficult to dissolve in the trivalent or higher isocyanate. In this case, the trivalent isocyanate is added after dissolving the dye precursor in the divalent isocyanate.

In the present invention, this solution is cooled if necessary, and then emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol. The temperature at the time of emulsification and dispersion is not particularly limited, but is desirably set to a temperature at which isocyanate and water do not rapidly react. Further, if necessary, after adding a reactive substance such as a water-soluble polyamine, the polymer-forming raw material is polymerized to form composite fine particles comprising a dye precursor and polyurea or polyurethane-polyurea.

The isocyanate reacts with water to form a urea bond to polymerize. In the present invention, together with the polyvalent isocyanate, a polyol compound which reacts with the isocyanate to form a urethane bond can also be used.

Examples of the divalent isocyanate that can be used in the present invention include m-phenylene diisocyanate and p-isocyanate.
Phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, dicyclohexylmethane
4,4'-diisocyanate, 5-isocyanate-1
-(Isocyanatomethyl) -1,3,3-trimethylcyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-
Diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate,
Examples thereof include diisocyanates such as cyclohexylene-1,2-diisocyanate and cyclohexylene-1,4-diisocyanate. Among them, it is particularly preferable to use dicyclohexylmethane-4,4'-diisocyanate.

Examples of the trivalent or higher isocyanate include triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate, and 4,4'-dimethyldiphenylmethane. There are tetraisocyanates such as 2,2 ', 5,5'-tetraisocyanate, etc. Examples of the adduct of a polyvalent isocyanate and a polyol include trimethylolpropane adduct of hexamethylene diisocyanate and 2,4-triene. Isocyanate prepolymers such as trimethylolpropane adduct of diisocyanate, trimethylolpropane adduct of xylylene diisocyanate, and hexanetriol adduct of tolylene diisocyanate can be used. For example biuret of hexamethylene diisocyanate, isocyanurate of hexamethylene diisocyanate, or the like can be used. It is more particularly preferable to use trimethylolpropane adduct of xylylene diisocyanate in this.

As the polyol compound used for the polymer-forming raw material, for example, ethylene glycol, 1,3-
Propanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,7
-Heptanediol, 1,8-octanediol, propylene glycol, 2,3-dihydroxybutane, 1,
2-dihydroxybutane, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propanediol,
2,4-pentanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-
Cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,
Aliphatic polyols such as 1-trimethylolpropane, hexanetriol, pentaerythritol and glycerin, 1,4-di (2-hydroxyethoxy) benzene,
Condensation product of an aromatic polyhydric alcohol such as 1,3-bis (2-hydroxyethoxy) benzene and an alkylene oxide, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropyl Benzene, 4,4'-dihydroxydiphenylmethane, 2- (p, p'-dihydroxydiphenylmethyl)
Benzyl alcohol, 4,4'-isopropylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide,
Examples thereof include ethylene oxide adducts of 4,4'-isopropylidene diphenol, propylene oxide adducts of 4,4'-isopropylidene diphenol, and acrylates having a hydroxyl group in the molecule such as 2-hydroxyacrylate.

Needless to say, the polyvalent isocyanate compound, the polyol compound and the like are not limited to the above compounds, and several kinds of compounds may be used in combination as needed.

In the present invention, other polyamine compounds that can be used as a polymer-forming raw material include:
For example, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine, m-phenylenediamine, piperazine, 2-methylpiperazine,
Examples thereof include 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, and amine adducts of epoxy compounds. Further, other polymer substances can be contained within a range not to impair the object of the present invention.

In the present invention, in addition to the dye precursor, a melting point of 40 is used as a solute at the time of preparing the composite fine particles for the purpose of increasing color development sensitivity.
An organic compound having a boiling point of 150 ° C. or higher and a temperature of 150 ° C. or higher can be used in combination. As the organic compound having a melting point of 40 ° C. or higher and 150 ° C. or lower and a boiling point of 150 ° C. or higher, an aromatic ketone compound, an aromatic ether compound, an aromatic cyclic ester compound, and a phenol compound are preferably used. it can. Specific examples are shown below.

The aromatic ketone compound is benzophenone, and the aromatic ether compound is 1,2-di (m
Examples of -tolyloxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, and aromatic cyclic ester compounds include coumarin and phthalide. Examples of the phenol compound include p-benzyloxyphenol. These organic compounds may be used alone or in combination of two or more.

The weight ratio of the dye precursor to the polyvalent isocyanate in the production of the composite fine particles is preferably from 100 parts by weight of the polyvalent isocyanate to 100 parts by weight of the dye precursor from the viewpoints of color sensitivity and ease of production. It is preferably 2000 parts by weight, more preferably 250 to 600 parts by weight. Polyvalent isocyanate is a low-viscosity liquid at room temperature and has high solubility in dye precursors.

The weight ratio of the divalent isocyanate to the trivalent or higher isocyanate in the production of the composite fine particles is preferably in the range of 10 to 1,000 parts by weight of the trivalent or higher isocyanate to 100 parts by weight of the divalent isocyanate.
More preferably, it is 50 to 200 parts by weight. If the amount is less than 10 parts by weight, the storage stability of the obtained recorded image is low, and if it is more than 1000 parts by weight, the stability of the production of the composite fine particles such as precipitation of the dye precursor and poor emulsification is reduced.

In the present invention, the emulsifier (protective colloid agent) used in the preparation of the composite fine particles includes modified polyvinyl alcohol such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and sulfone group-modified polyvinyl alcohol; methyl cellulose; carboxymethyl cellulose; Water-soluble synthetic high molecular compounds such as maleic anhydride copolymer salts and derivatives thereof can be used. If necessary, a surfactant, an antifoaming agent and the like may be used at the same time. The amount of the emulsifier used in preparing the composite fine particles is not particularly limited, but is generally preferably 0.5 to 200% by weight, and more preferably about 3 to 100% by weight based on the weight of the composite fine particles. preferable.

The composite fine particles used in the present invention are known as heat-sensitive recording materials in addition to dye precursors, if necessary, as well as ultraviolet absorbers, antioxidants, oil-soluble fluorescent dyes, mold release agents. Such a sensitizer or the like may be added. Such an additive substance is preferably solid at room temperature, but may be liquid. In particular, an ultraviolet absorber or a hindered phenol-based antioxidant can improve light resistance and can be preferably used. In particular, benzotriazole-based ultraviolet absorbers such as 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole,
It can be used preferably.

When producing the composite fine particles used in the present invention, an organic solvent acting as a solvent for the dye precursor is mixed with the polyvalent isocyanate compound and used as long as the object of the present invention is not impaired. Can also. The amount used is 100% by weight or less, more preferably 50% by weight or less, based on the weight of the composite fine particles. 100% by weight
If the amount is larger, fogging cannot be prevented by the pressure, which is the object of the present invention, and an undesirable result may be obtained. The solvent is not particularly limited, and a solvent that acts as a solvent for the dye precursor and is hydrophobic can be used.
Specifically, for example, tricresyl phosphate, phosphates such as octyl diphenyl phosphate, dibutyl phthalate, phthalates such as dioctyl phthalate, carboxylic esters such as butyl oleate, various fatty acid amides, Alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene, diisopropyl naphthalene, 1-methyl-1-phenyl-
Alkylated benzenes such as 1-tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropylbiphenyl, and xenoxyalkanes such as o-phenylphenol glycidyl ether , Acrylates such as trimethylolpropane triacrylate,
In addition to esters of polyhydric alcohols and unsaturated carboxylic acids, chlorinated paraffins, kerosene and the like, ethyl acetate, butyl acetate, methylene chloride and the like can be mentioned. Needless to say, two or more of these can be used in combination.

In addition, tin compounds, polyamide compounds,
An epoxy compound, a polyamine compound or the like may be used in combination. When a polyamine compound is used, it is preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not reduced.

In the present invention, when a multicolor heat-sensitive recording material is used, a dye precursor that develops a color tone different from that of the dye precursor contained in the composite fine particles can be used in the form of solid fine particles. In this case, the dye precursor is pulverized by various wet pulverizers such as a sand grinder, an attritor, a ball mill, and a cobo mill using water as a dispersion medium,
Polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as sulfone group-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer salts and other water-soluble polymer compounds such as derivatives thereof, If necessary, the dispersion may be dispersed in a dispersion medium together with a surfactant, an antifoaming agent, and the like to prepare a dispersion, and this dispersion can be used for preparing a coating material for forming a thermosensitive coloring layer. After dissolving the dye precursor in an organic solvent, this solution is emulsified and dispersed in water using the water-soluble polymer as a stabilizer, and the organic solvent is evaporated from the emulsion to form the dye precursor into solid fine particles. You can also. In each case, the average particle size of the dispersed particles of the dye precursor used in the state of solid fine particles,
The thickness is preferably from 0.2 to 3.0 μm, more preferably from 0.3 to 1.0 μm, in order to obtain appropriate color sensitivity. Of course, a dye precursor having the same color tone can be used in the form of solid fine particles together with the composite fine particles to obtain a single-color heat-sensitive recording material.

The color-developing compound used in the present invention is not particularly limited, but generally has a property of liquefying or dissolving with an increase in temperature and a property of contacting with the dye precursor to form a color. It is selected from those having. Representative color developing compounds include 4-tert-butylphenol, 4-acetylphenol, and 4-tert-phenol.
-Octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenol, 1,1 -Bis (4-hydroxyphenyl)-
1-phenylethane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (3-methyl-6
-Tert-butylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and bis (3-allyl-4-
Phenolic compounds such as (hydroxyphenyl) sulfone can be mentioned.

Further, in the present invention, compounds that can be used as a color developing compound include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate,
Phenolic compounds such as 4-sec-butyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, and 4,4'-dihydroxydiphenyl ether Or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, Aromatic carboxylic acids such as 3,5-di-tert-butylsalicylic acid, and phenolic compounds, and organic acidic substances such as salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum and calcium. But That.

In the present invention, it is particularly preferable to use a diphenylsulfone derivative containing a hydroxyl group in the molecule as the color developing compound. Such compounds include, for example, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-
Hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone and the like can be mentioned. Such a color-developing compound has excellent properties in preserving a color image. This is presumed to be due to the strong electron-withdrawing property of the sulfone group of the color-developing compound. In order to form a color-developed image that is less likely to be decolored even when it comes in contact with oil or a plasticizer, it is necessary to use 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane or N It is preferred to use-(p-toluenesulfonyl) -N'-phenylurea.

The color-developing compound is preferably used in an amount of 30 to 300 parts by weight, more preferably 50 to 200 parts by weight, based on 100 parts by weight of the composite fine particles. Of course, if necessary, two or more types of color developing compounds can be used in combination.

In the present invention, an image stabilizer may be used mainly for improving the storability of the color recording image. Examples of such an image stabilizer include 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane and 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,
Phenolic compounds such as 4-phenylenebis (1-methylethylidene)] bisphenol and 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol; 4-benzyloxyphenyl-4'
-(2-methyl-2,3-epoxypropyloxy) phenylsulfone, 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone, and 4- (2-ethyl-1,2-epoxyethyl) diphenyl Epoxy compounds such as sulfones, and those containing at least one selected from isocyanuric acid compounds such as 1,3,5-tris (2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl) isocyanuric acid Can be used. Of course, the image stabilizer is not limited to these, and two or more compounds can be used in combination as needed.

In the present invention, as the sensitizer which can be used for improving the color sensitivity of heat-sensitive recording, a compound conventionally known as a sensitizer for heat-sensitive recording materials is used. For example, parabenzyl biphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate, 1,2-diphenoxyethane, 1,2-bis ( 3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-p oxalate
-Chlorobenzyl, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl, benzophenone and the like. Among these compounds,
When di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate are used as sensitizers, a sensitizing effect with less fogging can be obtained.

Additives such as a color-developing compound, an image stabilizer and a sensitizer used in the present invention are dispersed in water in the same manner as when a dye precursor is used in the form of solid fine particles. What is necessary is just to mix with this at the time of preparation of a forming paint. Further, these additives may be dissolved in a solvent, and the resulting solution may be emulsified in water using a water-soluble polymer compound as an emulsifier. Further, the image stabilizer and the sensitizer may be contained in the composite fine particles containing the dye precursor.

In the present invention, a fine pigment having a high whiteness and an average particle diameter of 10 μm or less can be contained in the thermosensitive coloring layer in order to improve the whiteness of the thermosensitive coloring layer and the uniformity of the image. 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 Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin and polystyrene resin can be used. Oil absorption is 50ml / 1 to prevent sticking to the thermal head and sticking.
It is preferred to use more than 00 g of pigment. The amount of the pigment is such that the color density is not reduced, that is,
The content is preferably 50% by weight or less based on the total solid content of the thermosensitive coloring layer.

In the present invention, an adhesive is used as another component material constituting the heat-sensitive coloring layer.
Crosslinking agents, waxes, metal soaps, colored dyes, colored pigments,
And a fluorescent dye. Examples of the adhesive include polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, and acrylamide-acrylic acid ester. Coalescence, acrylamide-acrylate-methacrylate 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,
Emulsions such as polyacrylates, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, ethylene-vinyl acetate copolymers, and water-insoluble polymers such as styrene-butadiene copolymers and styrene-butadiene-acrylic copolymers Examples include coalesced latex.

Further, 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 and ferric chloride, and chloride Magnesium, sodium tetraborate, potassium tetraborate or other inorganic compound or at least one crosslinkable compound selected from boric acid, boric acid triester, boron-based polymer, etc., 100 parts by weight of the total solid content of the thermosensitive coloring layer Is preferably used in the range of 1 to 10 parts by weight.

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

As the metal soap added to the thermosensitive coloring layer, higher fatty acid polyvalent metal salts such as zinc stearate,
Aluminum stearate, calcium stearate,
And zinc oleate. When the heat-sensitive recording material of the present invention is a two-color heat-sensitive recording material, it is possible to include a colored dye and / or a colored pigment having a color tone complementary to the low-temperature color tone in the thermosensitive coloring layer by printing. It is preferably used for adjusting the color tone of the previous recording material. If necessary, within a range that does not impair the effects of the present invention, in the thermosensitive coloring layer, further an oil repellent, an antifoaming agent,
Various additives such as a viscosity modifier can be added. The heat-sensitive coloring layer has a coating amount after drying on the support of 2 to 20 g /
m ² , more preferably 4 to 10 g / m ² .

In the present invention, a magnetic recording layer may be provided on the surface of the support on which the thermosensitive coloring layer is not provided, or between the support and the thermosensitive coloring layer. As the magnetic recording layer, a magnetic recording layer conventionally used for a magnetic ticket, a prepaid card, a magnetic commuter pass, or the like can be used.
When the magnetic recording layer is provided between the support and the thermosensitive coloring layer, even when provided on the surface of the support where the thermosensitive coloring layer is not provided, the magnetic recording layer is coated before the thermosensitive coloring layer is applied. This is desirable to keep the whiteness of the thermosensitive coloring layer high.

In the present invention, a resin cured by an electron beam or ultraviolet rays can be provided as a protective layer on the thermosensitive coloring layer.
An example of a resin cured by an electron beam is disclosed in JP-A-58-17.
No. 7,392, JP-A-58-177392 and the like. In such a resin, a non-electron beam curable resin, a pigment, and additives such as an antifoaming agent, a leveling agent, a lubricant, a surfactant, and a plasticizer can be appropriately added.
In particular, it is preferable to add a pigment such as calcium carbonate or aluminum hydroxide, or a lubricant such as waxes or silicon, because it helps prevent sticking to the thermal head. The resin layer cured by electron beam or ultraviolet light
Coating is performed on the support such that the coating amount after drying is 0.5 to 10 g / m ² . More preferably, it is applied so as to be 1 to 5 g / m ² .

In the present invention, a protective layer containing a water-soluble polymer material and a pigment as used in a conventionally known heat-sensitive recording material may be provided on the heat-sensitive coloring layer. A resin layer cured by an electron beam or ultraviolet light can be provided thereon. As the water-soluble polymer material and the pigment, the materials exemplified for the thermosensitive coloring layer can be used. At this time, it is more desirable to add a crosslinking agent to impart water resistance to the protective layer. Such a protective layer is coated on a support such that the coating amount after drying is 0.5 to 10 g / m ² . More preferably, it is applied so as to be 1 to 5 g / m ² .

In the present invention, printing can be performed with UV ink, flexo ink, or the like. In this case, printing may be performed on any layer such as a thermosensitive layer, a protective layer, an electron beam curable resin layer, or an ultraviolet curable resin layer.

The type, shape, dimensions, etc. of the support material used in the present invention are not particularly limited. For example, high quality paper (acid paper, neutral paper), medium paper, coated paper, art paper, cast paper In addition to coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, and the like, various transparent supports and the like can be appropriately selected and used. When the present invention is used for magnetic ticket use, it is preferable to use paper. However, when the present invention is used for magnetic commuter pass use, a plastic base made of polyethylene terephthalate having a thickness of 100 μm or more is used. It is desirable to use a material, especially a foamed substrate. Of course, a laminate substrate with paper or the like can also be used.

In the present invention, an undercoat layer used in a conventionally known heat-sensitive recording material can also be used. In particular, when paper is used as the support, it is desirable to provide an undercoat layer. By using a pigment having a high porosity, such as silica or calcined kaolin, for the undercoat layer, the coloring sensitivity of the thermosensitive coloring layer thereon can be increased. Including a plastic pigment, hollow particles, foam, or the like in the undercoat layer is also effective in improving the color sensitivity of the thermosensitive coloring layer formed thereon.

In the present invention, in order to increase the added value of the heat-sensitive recording material, the heat-sensitive recording material can be further processed to obtain a heat-sensitive recording material having higher functions. For example, an adhesive paper, a rewet adhesive paper, or a delayed tack paper can be obtained by applying a coating process using an adhesive, a rewet adhesive, a delayed tack type adhesive, or the like on the back surface. In particular, those obtained by subjecting the heat-sensitive recording material of the present invention to an adhesive treatment are useful as heat-sensitive labels because of their good storage stability. In addition, a recording paper capable of performing double-sided recording can be provided by using the back surface thereof and imparting the functions of thermal transfer paper, ink-jet paper, carbonless paper, electrostatic recording paper, and xerography paper. Of course, a double-sided heat-sensitive recording material can also be used.

The method for forming each of the above-mentioned layers on the support includes known coating methods such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dipping method, a bar method, and an extrusion method. Either may be used. Further, a back layer can be provided for suppressing penetration of oil or plasticizer from the back surface of the recording material, or for controlling curl. Smoothing the heat-sensitive coloring layer using a known smoothing method such as a super calendar or a soft calendar is effective in increasing the coloring sensitivity. The surface of the thermosensitive coloring layer may be treated by applying it to either a metal roll or an elastic roll of a calender.

[0065]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
Unless otherwise specified, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

(1) Preparation of Materials Used for Undercoat Layer and Thermosensitive Coloring Layer <Preparation of Composite Fine Particle Dispersion Containing Black Coloring Dye Precursor> Composite Fine Particle Dispersion Containing Black Coloring Dye Precursor Black Coloring Dye 5 parts of 3-di-n-amylamino-6-methyl-7-anilinofluoran as a precursor at 100 ° C.
The solution was dissolved in 13 parts of dicyclohexylmethane-4,4'-diisocyanate as a divalent isocyanate heated in Example 1 and 8 parts of a trimethylolpropane adduct of xylylene diisocyanate as a trivalent or higher isocyanate was added. After the solution was cooled to 25 ° C., it was gradually added to 100 parts of an aqueous solution of 20% sulfone group-modified polyvinyl alcohol (trade name: L-3266, manufactured by Nippon Synthetic Chemical Industry) at the same temperature, and stirred at 10,000 rpm using a homogenizer. After emulsification and dispersion, the emulsified dispersion was added to water 10
0 parts were added for homogenization. The temperature of the emulsified dispersion was raised to 90 ° C., and a curing reaction was carried out for 10 hours.
A dispersion liquid of 4 μm black composite particles containing a color-forming dye precursor was prepared.

Composite Fine Particle Dispersion Containing Black Chromogenic Dye Precursor The same formulation as the composite fine particle dispersion containing the black chromogenic dye precursor, except that norbornene diisocyanate was used as the divalent isocyanate, According to the emulsification method and the polymerization method, a dispersion liquid of the composite particles containing the black color-forming dye precursor having an average particle diameter of 0.4 μm was prepared.

Composite fine particle dispersion containing black color-forming dye precursor Except that 4,4 ′, 4 ″ -triphenylmethane triisocyanate was used as a trivalent or higher isocyanate, The same formulation as the composite fine particle dispersion containing the precursor, emulsification method, by polymerization method,
A dispersion liquid of composite fine particles containing a black color-forming dye precursor having an average particle diameter of 0.4 μm was prepared.

Composite Fine Particle Dispersion Containing Black Color-forming Dye Precursor The same formulation as the composite fine particle dispersion containing the black color-forming dye precursor except that trivalent or higher isocyanate was not added, Depending on the emulsification method and polymerization method,
A dispersion liquid of composite fine particles containing a black color-forming dye precursor having an average particle diameter of 0.4 μm was prepared.

Composite Fine Particle Dispersion Containing Black Chromogenic Dye Precursor An attempt was made to dissolve the black chromogenic dye precursor in trivalent or higher valent isocyanate without using divalent isocyanate. No composite fine particles containing a black color-forming dye precursor could be prepared.

<Preparation of Dye Precursor, Developing Compound, and Sensitizer Dispersion in Solid Fine Particle State> Black color-forming dye precursor: 3-di-n-amylamino-6
-Methyl-7-anilinofluoran Red color-developing dye precursor: 3-diethylamino-7-chlorofluorane Color-developing compound: bis (3-allyl-4-hydroxyphenyl) sulfone Sensitizer: di-oxalate p-methylbenzyl

The above-mentioned dye precursor, color-developing compound, and sensitizer are separately mixed with polyvinyl alcohol at the following compounding ratio, and each mixture is mixed using a vertical sand mill (manufactured by IMEX Co., Ltd., sand grinder). , Pulverized and dispersed so that the average particle diameter became 1.2 μm.

Component Amount (parts by weight) Each compound 40 Polyvinyl alcohol 10% solution 40 (polymerization degree 500, saponification degree 90%) Water 20

<Preparation of Pigment Dispersion> Pigment: silica (Mizukasil P527, oil absorption 190 ml / 100 g, manufactured by Mizusawa Chemical Industry Co., Ltd.) was mixed with sodium polyacrylate in the following mixing ratio, and the mixture was treated with Cowles. Dispersed with a disperser. Component Amount (parts by weight) Silica 30 0.7% sodium polyacrylate solution 70

Separately, an aqueous solution of polyvinyl alcohol (NM11Q, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) having a solid content of 10% was used as an adhesive solution, and an aqueous dispersion of zinc stearate having a solid content of 21% (Z- 7, Chukyo Yushi Co., Ltd.).

(2) Formation of Undercoat Layer The above-mentioned pigment dispersion and adhesive liquid were mixed at a solid content of 80:
20 and 9.0 g of this paint was coated on a high-quality paper (neutral paper) with a basis weight of 60 g / m ² using a Meyer bar.
/ M ² (dry) to form an undercoat layer.

(3) Formation of heat-sensitive coloring layer Example 1 A coating of a heat-sensitive coloring layer mixed and prepared at the following mixing ratio (solid content) on the undercoat layer of the support at 5.0 g / m ² . Apply in the amount (dry), dry to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor-containing composite fine particle dispersion 40 parts Developing component dispersion 40 parts Pigment dispersion 10 parts Lubricant dispersion 10 parts

Example 2 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor-containing composite fine particle dispersion 40 parts Developing component dispersion 40 parts Pigment dispersion 10 parts Lubricant dispersion 10 parts

Example 3 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor-containing composite fine particle dispersion 40 parts Developing component dispersion 40 parts Pigment dispersion 10 parts Lubricant dispersion 10 parts

Comparative Example 1 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor-containing composite fine particle dispersion 40 parts Developing component dispersion 40 parts Pigment dispersion 10 parts Lubricant dispersion 10 parts

Comparative Example 2 A thermosensitive coloring layer paint prepared by mixing and preparing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor-containing composite fine particle dispersion 40 parts Developing component dispersion 40 parts Pigment dispersion 10 parts Lubricant dispersion 10 parts

Comparative Example 3 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor dispersion 10 parts Color developing component dispersion 40 parts Pigment dispersion 40 parts Lubricant dispersion 10 parts

Example 4 A thermosensitive coloring layer paint prepared by mixing at the following compounding ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor-containing composite fine particles 30 parts Red coloring dye precursor dispersion 10 parts Color developing component dispersion 40 parts Pigment dispersion 10 parts Lubricant dispersion 10 parts

Comparative Example 4 A thermosensitive coloring layer paint prepared by mixing at the following compounding ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Drying to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Black coloring dye precursor dispersion 10 parts Red coloring dye precursor dispersion 10 parts Color developing component dispersion 40 parts Pigment dispersion 30 parts Lubricant dispersion 10 parts

In each of Examples 1 to 4 and Comparative Examples 1 to 4, the heat-sensitive recording materials obtained by the above operations
Was subjected to a smoothing treatment using a super calender, and the Oken-type Beck smoothness of the heat-sensitive coloring surface was controlled to 1000 seconds.

Each of the above-mentioned heat-sensitive recording materials subjected to the smoothing treatment was subjected to the following tests. <Single-color heat-sensitive recording material, Examples 1 to 3, Comparative Examples 1 to 3
Evaluation> In the thermal recording test, the thermal printing tester TH
-Recording time per line using PMD (Okura Electric):
Solid printing of 256 lines was performed under the conditions of 4 msec, sub-scanning line density: 8 lines / mm, and applied energy per dot: 2.0 mJ.

The color product thus obtained was
The recorded image density was measured. The recorded image density was determined by measuring the coloring density of the recorded image portion and the blank portion of the above recorded sample with a Macbeth densitometer (manufactured by Macbeth, model number: RD-914). Further, the easiness of coloring by pressure and the oil resistance were evaluated by the following methods. In the test of the ease of color development by pressure, each sample was rubbed with a nail and the degree of color development was visually evaluated. ○ indicates that little color was formed, and x indicates that a clear color was formed. In the oil resistance test, the recorded sample was placed in salad oil at 20 ° C. for 1 hour.
After immersion for 2 hours, the color density of the recorded image area was measured with a Macbeth densitometer, and storage stability (%) = [(density after immersion) / (density before immersion)] × 100 was evaluated. If the storage ratio is 50% or more, the image is at a readable level, and there is no practical problem. Table 1 shows the test results.

[0088]

[Table 1]

<Evaluation of Two-Colored Thermosensitive Recording Material, Example 4 and Comparative Example 4> Thermal recording was performed using a thermal printing tester TH-P.
Using MD (manufactured by Okura Electric), 1 line recording time: 5m
The solid printing of 256 lines was performed under the conditions of sec, a sub-scanning line density of 8 lines / mm, and an applied energy per dot of 0.5 mJ, and low-temperature red coloring in low-temperature printing was performed. Separately, solid printing of 256 lines was performed under the conditions of 1-line recording time: 5 msec, sub-scanning line density: 8 lines / mm, and applied energy per dot: 2.0 mJ, and high-temperature black coloring was performed in high-temperature printing.

The color product thus obtained was
The color tone was evaluated visually. In Example 4, the color separation between red and black was good, and a clear red color was formed in the low-temperature color-developing portion, and a black color was obtained in the high-temperature color. However, in Comparative Example 4, black color was already formed in the low-temperature color forming portion, and color separation could not be performed.

[0091]

According to the present invention, it has become possible to produce a heat-sensitive recording material having less fogging due to pressure and having excellent preservability of the colored portion. Further, it has become possible to produce a multicolor heat-sensitive recording material in which a low-temperature color tone and a high-temperature color tone are not mixed.

Claims (4)

[Claims] 1. A heat-sensitive recording material comprising a dye precursor and a heat-sensitive coloring layer containing a color developing compound which reacts with the dye precursor under heating and develops a color on the support, comprises After emulsifying and dispersing a solution containing a dye precursor as a solute with a polyvalent isocyanate as a solvent in water, the composite fine particles obtained by accelerating the polymerization reaction of the polyvalent isocyanate are contained in the thermosensitive coloring layer. A heat-sensitive recording material characterized in that one or more divalent isocyanates and one or more trivalent isocyanates are used as the monovalent isocyanate. 2. The heat-sensitive recording material according to claim 1, wherein the divalent isocyanate is dicyclohexylmethane-4,4′-diisocyanate. 3. The heat-sensitive recording material according to claim 1, wherein the trivalent or higher isocyanate is a trimethylolpropane adduct of hexamethylene diisocyanate. 4. The heat-sensitive recording material according to claim 1, wherein the weight ratio of the polyvalent isocyanate is 10 to 1000 parts by weight of the trivalent or higher isocyanate with respect to 100 parts by weight of the divalent isocyanate.