JP2000052659A - Thermal recording material - Google Patents

Abstract

(57) [Summary] [Problem] A heat-sensitive recording material capable of recording two or more colors. The color at low-temperature coloring is sharp, with little color mixing due to high-temperature coloring, and has excellent contrast with high-temperature coloring. An object of the present invention is to provide a heat-sensitive recording material. SOLUTION: The support has a support and a thermosensitive coloring layer formed thereon, and the thermosensitive coloring layer develops a chromatic color with at least one polymer substance selected from (1) polyurea and polyurethane. (2) a second dye precursor (solid fine particles or composite fine particles) that is not contained in the composite fine particles and develops a chromatic color, and (3) the composite fine particles composed of the first dye precursor and the first fine particles. A color developer containing the first and second dye precursors and a color developer which reacts with heating to develop the color, and the color tone of the first dye precursor and the color tone of the second dye precursor are complementary. A heat-sensitive recording material characterized by the following relationship:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor heat-sensitive material which develops different colors depending on the conditions of application of heat from a thermal head. More specifically, the present invention relates to a heat-sensitive recording material which is vivid at low temperature and has a clear color with little color mixing due to high-temperature color tone, and has excellent contrast with high-temperature color tone.

[0002]

2. Description of the Related Art Conventionally, a color development reaction between a dye precursor and a color developer which comes into contact with the dye precursor under heating to form a color is utilized, and the two color forming substances are melted and contacted by heating to form a color. Thermal recording materials for obtaining images are widely known. Such a heat-sensitive recording material is relatively inexpensive, has a compact recording device, and is easy to maintain. Therefore, it is widely used as a recording medium for facsimile machines, word processors, various computers, and other applications. Have been.

[0003] With respect to the heat-sensitive recording material, the required quality is diversified with the expansion of its use. For example, there are demands for high sensitivity, image stabilization, multicolor recording, and the like. In particular, the multicolor recording means has the advantage that characters or figures to be emphasized can be displayed clearly and clearly with a different color tone from other parts, and the demand for practical use thereof has been increasing.

Attempts have been made to utilize the difference in heating temperature or the difference in heat energy as a multicolor recording system.
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. Are divided into two types.

The decolorable multicolor heat-sensitive recording material has not always been satisfactory with respect to image recording reliability and recording sensitivity.

On the other hand, the color-added heat-sensitive recording material is a multicolor heat-sensitive recording material as disclosed in JP-B-49-27708, JP-B-51-19989 and JP-A-51-19899.
Japanese Patent Application Laid-Open No. 146239/1999 describes a method in which two color-forming layers that emit different colors are stacked, and two colors that can be identified are obtained by applying different amounts of heat. This method
At a low temperature, the upper color-forming layer forms a color, and at a high temperature, the upper and lower color-forming layers form a color, and an image having a mixed color tone of both colors can be obtained.
However, if a sufficient amount of heat is applied to produce low-temperature coloring, a part of the coloring of the high-temperature coloring layer is also mixed, resulting in color mixing, which makes it difficult to make low-temperature coloring images clear. Japanese Patent Application Laid-Open No. 56-99697 describes a method in which two or more dye precursors having different color tones and different average particle diameters are mixed in the same layer, but still in a sufficiently low temperature. If heat is applied to generate color, there is a problem that some color mixture of high-temperature color cannot be avoided.

In order to improve these disadvantages, the present inventors disclosed in Japanese Patent Application Laid-Open No. 9-290565 an emulsion of an oily solution containing a polyvalent isocyanate compound as a solvent and a dye precursor as a solute in a hydrophilic protective colloid solution. We proposed a multicolor thermosensitive recording material using composite fine particles produced by accelerating the polymerization reaction of a polyvalent isocyanate compound after dispersion, but it was not always satisfactory in terms of low-temperature color tone and high-temperature color tone contrast. It was not obtained.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material which is vivid at low temperature and hardly mixes color due to high-temperature color tone and has excellent contrast with high-temperature color tone. It is in.

[0009]

In order to solve the above problems, the present invention employs the following constitution. That is, the present invention
"A first layer which has a support and a heat-sensitive color-forming layer formed thereon, wherein the heat-sensitive color-forming layer forms a chromatic color with at least one polymer substance selected from (1) polyurea and polyurethane. Composite fine particles composed of a dye precursor,
(2) a second dye precursor solid fine particle which is not contained in the composite fine particles and which forms a chromatic color; and (3) reacts with the first and second dye precursors under heating to form a color. A heat-sensitive recording material comprising a coloring agent, and wherein the color tone of the first dye precursor and the color tone of the second dye precursor have a complementary color relationship. Further, in the above invention, an embodiment is also included in which the second dye precursor is contained in the second composite fine particles.

In the present invention, the first dye precursor and the second dye precursor
The combination of the color tone of the dye precursor needs to be in a complementary color relationship. That is, it is a pair of combinations selected from magenta, cyan, and yellow having a complementary color relationship.

The red-purple (magenta) dye precursor used in the present invention is 3-diethylamino-7,8-benzofluoran, 3,3'-bis (1-n-butyl-2-methylindole-3). -Yl) phthalide, 3,3'-bis (1-
At least one of ethyl-2-methylindol-3-yl) phthalide, wherein the green dye precursor is 3- (N-ethyl-Np-tolylamino) -7- (N-phenyl-N-
Methylamino) fluoran, 3- (N-ethyl-Nn
-Hexylamino) -7-anilinofluoran and at least one of 3-diethylamino-7-dibenzylaminofluoran.

The blue-green (cyan) dye precursor used in the present invention is 3,3'-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,6-bis (dimethylamino) fluorene- 9-spiro-3 '-(6'
-Dimethylamino) phthalide, 3- (1-ethyl-2-
Methylindol-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, wherein the red dye precursor is 3-diethylamino-
7-chlorofluorane, 3- (N-ethyl-p-toluidino) -7-methylfluoran, 3-diethylamino-
It is desirably at least one of 6-methyl-7-chlorofluorane and 3- (N-ethyl-N-isoamyl) amino-7-phenoxyfluorane.

The yellow (yellow) dye precursor used in the present invention is 3,6-dimethoxyfluoran, 1- (4-n
-Dodecyloxy-3-methoxyphenyl) -2- (2
-Quinolyl) ethylene, at least one of 1,3,3-trimethylindoline-2,2'-spiro-6'-nitro-8'-methoxybenzopyran and a blue dye precursor of 3,3-bis ( p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) ) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-
Ethyl-2-methylindol-3-yl) phthalide,
3-diphenylamino-6-diphenylaminofluoran, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylamino-2-n-hexyloxyphenyl) -4-azaphthalide, -(2-Methyl-1-n-octylindol-3-yl) -3- (4
-Diethylamino-2-ethoxyphenyl) -4-azaphthalide is desirable.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a dye precursor used in the present invention, a leuco compound such as a triaryl compound, a diphenylmethane compound, a thiazine compound, a spiropyran compound, a lactam compound or a fluoran compound can be preferably used. In the case of forming a multicolor heat-sensitive recording material in the present invention, a dye precursor in the form of solid fine particles that combines two or more kinds of composite fine particles having different coloring temperatures and different color tones with a color developing compound or develops a color tone different from the composite fine particles. When the body and the color developing compound are combined, it is possible to obtain a multicolor heat-sensitive recording material in which low-temperature coloring and high-temperature coloring are less mixed.

It is necessary that the combination of the dye precursors is in a complementary color relationship. Among them, a red-purple (magenta) dye precursor and a green dye precursor, and a blue-green (cyan) dye precursor and a red dye A precursor, a combination of a yellow dye precursor and a blue dye precursor is preferred. Either of the dye precursors may be used for low-temperature coloring and high-temperature coloring.

Examples of the magenta dye precursor include 3-diethylamino-7,8-benzofluoran and 3,3'-bis (1-n-butyl-2-methylindol-3-yl).
Phthalide, 3,3′-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,6-bis (diethylamino) fluoran-γ-anilinolactam, 3,6
-Bis (diethylamino) fluoran-γ- (p-nitro) anilinolactam, 3,6-bis (diethylamino) fluoran-γ- (o-chloro) anilinolactam, 3- (N-ethyl-N-isoamylamino ) -7,
8-benzofluoran, 3-di-n-butylamino-
7,8-benzofluoran, 3,3'-bis (1-n-
At least one of octyl-2-methylindol-3-yl) phthalide and the like can be used, and among them, 3-diethylamino-7,8-benzofluoran,
3,3′-bis (1-n-butyl-2-methylindol-3-yl) phthalide and 3,3′-bis (1-ethyl-2-methylindol-3-yl) phthalide are preferred.

As the green dye precursor, 3- (N-ethyl-Np-tolylamino) -7- (N-phenyl-N-
Methylamino) fluoran, 3- (N-ethyl-Nn
-Hexylamino) -7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-
[P- (p-anilinoanilino) anilino] -6-methyl-7-chlorofluoran, 3-diethylamino-7-
At least one of (o-chloroanilino) fluoran and the like can be used, and among them, 3- (N-ethyl-Np-tolylamino) -7- (N-phenyl-N-
Methylamino) fluoran, 3- (N-ethyl-Nn
-Hexylamino) -7-anilinofluoran and 3-diethylamino-7-dibenzylaminofluoran are preferred.

As the blue-green dye precursor, 3,3'-bis (4-diethylamino-2-ethoxyphenyl) -4-
Azaphthalide, 3,6-bis (dimethylamino) fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide, 3- (1-ethyl-2-methylindole-3
-Yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide and the like.

Examples of the red dye precursor include 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane, and 3-diethylamino-6-methyl-7-chlorofluorane. Oran, 3- (N-ethyl-N-isoamyl) amino-7-phenoxyfluoran, 3-dimethylamino-7-bromofluoran, 3
-Diethylaminofluoran, 3-diethylamino-6
-Methylfluorane, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-bromofluoran, 3-diethylamino-6,8-dimethylfluoran, 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, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 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-butylaminofluorane and the like can be used, and among them, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane is particularly preferable. , 3-diethylamino-6-methyl-7-chlorofluoran, and 3- (N-ethyl-N-isoamyl) amino-7-phenoxyfluoran are preferred.

As the yellow dye precursor, 3,6-dimethoxyfluoran, 1- (4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) ethylene,
At least one of 1,3,3-trimethylindoline-2,2'-spiro-6'-nitro-8'-methoxybenzopyran and the like can be used.

As a blue dye precursor, 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino- 2-
Ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-
Diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-diphenylamino-6-diphenylaminofluoran, 3- (1-
Ethyl-2-methylindol-3-yl) -3- (4
-Diethylamino-2-n-hexyloxyphenyl)
At least one of -4-azaphthalide and 3- (2-methyl-1-n-octylindol-3-yl) -3- (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide can be used. .

Further, as a dye precursor that can be contained in the composite fine particles or used in the form of solid fine particles, an oxidative color-forming dye can be used in addition to the above-described electron-donating color-forming dye. Further, a reaction between a diazonium salt and a coupler can also be used.

Further, when a black color dye precursor is added, the lightness of the color tone is lowered, and the contrast between the low temperature color tone and the high temperature color tone is lowered. Therefore, the black color dye precursor is used in the present invention. do not use.

Unused black color dye precursors include 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, and 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-anilinofluoran, 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-butylamino7- (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-
Dye precursors such as 7-anilinofluoran are exemplified.

In the present invention, when the second dye precursor having a complementary color with the first dye precursor contained in the composite fine particles is used in the form of solid fine particles, the second dye precursor is Using water as a dispersion medium, pulverized by various wet pulverizers such as a sand grinder, an attritor, a ball mill, a cobo mill, and the like, and denatured polyvinyl alcohol, methyl cellulose, Methyl cellulose,
In addition to a water-soluble synthetic polymer compound such as a styrene-maleic anhydride copolymer salt and a derivative thereof, if necessary, a surfactant, an antifoaming agent, and the like are dispersed in a dispersion medium to form a dispersion. Can be used for preparing a coating material for forming a thermosensitive coloring layer.

After dissolving the dye precursor in a solvent, the solution is emulsified and dispersed in water using the above water-soluble polymer as a stabilizer, and the 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 is 0.2 to 3.0 μm in order to obtain appropriate color sensitivity.
m, more preferably 0.3-1.m.
5 μm.

In the present invention, at least one polymer selected from polyurea and polyurethane is used as the polymer material forming the composite fine particles. In the present invention, the at least one polymer substance selected from polyurea and polyurethane is a polymer obtained by polymerizing a polymerizable component containing a polyvalent isocyanate compound, and includes polyurea, polyurethane, and polyurethane. It may be either polyurea or a mixture of two or more of these.

The composite fine particles are produced by emulsifying and dispersing an oily solution in which a polyvalent isocyanate compound and a dye precursor are dissolved in a hydrophilic protective colloid solution, and then promoting the polymerization reaction of the polyvalent isocyanate compound. so,
Under heating, it reacts with a color developing compound to form a color. In this case, the color development temperature is appropriately adjusted mainly by selecting the type of the polyvalent isocyanate and the polyol described below, the polyvalent amine, and the mixing ratio of the dye precursor and the polymer substance, and further, the particle size of the composite fine particles. Can be changed freely.
The dye precursor in the composite fine particles has a high degree of isolation from the outside, has little background fogging due to heat or humidity, and has little decoloration of a color image, and has excellent storage stability.

The composite fine particles that can be used in the present invention are prepared by emulsifying and dispersing a solution containing a polyvalent isocyanate compound as a solvent and a dye precursor as a solute in a hydrophilic protective colloid solution. The compound is characterized by accelerating the polymerization reaction of the polyvalent isocyanate compound. Since the composite fine particles do not substantially contain an organic solvent, their physical strength is high. Therefore, a multicolor heat-sensitive recording material using composite fine particles is excellent in pressure resistance and friction resistance. In addition, since a low-boiling organic solvent or the like is not used at the time of forming the polymer compound, there is no adverse effect due to evaporation of the solvent and the like, and high separability is exhibited, and background fogging due to heat and humidity and decoloration of a color image are small. The composite fine particles are composed of at least one polymer selected from polyurea and polyurethane formed by a polymerization reaction of polyvalent isocyanate, and a dye precursor, and the dye precursor and the polymer Are mixed at the molecular level and exist in a solid solution state. The appearance of the composite fine particles is almost spherical when observed with an electron microscope, or is a red blood cell with a hollow center.

In the production of the composite fine particles used in the present invention, first, a solution in which a dye precursor is dissolved in a polyvalent isocyanate compound is prepared. The melting temperature at this time is 70
C. or higher is preferable, and at temperatures lower than this, the solubility of the solute dye precursor in the polyvalent isocyanate compound is low, and it may not be possible to produce composite fine particles having sufficient separability. This solution is emulsified and dispersed in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved and, if necessary, a reactive substance such as a water-soluble polyamine is added. To form composite fine particles comprising a dye precursor and polyurea or polyurethane-polyurea.

The polyvalent isocyanate compound used in the present invention is a compound which reacts with water to form polyurea or polyurethane-polyurea. It may be a polyisocyanate compound alone, or may be a mixture of a polyvalent isocyanate compound and a polyol that reacts with the polyisocyanate compound, or a multimer such as an adduct of a polyvalent isocyanate compound and a polyol, a biuret form, or an isocyanurate form. You may. After dissolving the dye precursor in these polyvalent isocyanate compounds, this solution is emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol, and further mixed with a reactive substance such as polyamine if necessary. By heating the emulsified dispersion, the polymer-forming raw material is polymerized to polymerize, thereby forming composite fine particles comprising a dye precursor and a polymer substance.

Examples of the polyvalent isocyanate compound used as the polymer-forming raw material include m-phenylene diisocyanate, p-phenylene diisocyanate,
2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 5-isocyanato-1- ( Isocyanatomethyl)
-1,3,3-trimethylcyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylenediisocyanate, 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, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4- Diisocyanates such as diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, toluene-2,4,6-
Triisocyanates such as triisocyanate, 4,
4'-dimethyldiphenylmethane-2,2 ', 5,5'
-Tetraisocyanates such as tetraisocyanate,
and so on. As an adduct of a polyvalent isocyanate compound and a polyol, for example, a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of 2,4-tolylene diisocyanate,
Isocyanate prepolymers such as trimethylolpropane adduct of xylylene diisocyanate and hexanetriol adduct of tolylene diisocyanate can be used. In addition, a polyvalent isocyanate compound, for example, a polymer such as a biuret or isocyanurate of hexamethylene diisocyanate can also be used as the polymer-forming raw material of the present invention.

As the polyol compound used for the polymer-forming raw material, for example, ethylene glycol, 1,1,
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,
Aliphatic polyols such as 1,1-trimethylolpropane, hexanetriol, pentaerythritol, and glycerin; aromatics such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-di (2-hydroxyethoxy) benzene Condensation product of polyhydric alcohol and alkylene oxide, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropylbenzene, 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 hydroxy group in the molecule such as 2-hydroxyacrylate.

Of course, the polyvalent isocyanate compound, the adduct of the polyvalent isocyanate and the polyol, and the polyol compound are not limited to the above compounds.
Moreover, you may use 2 or more types together as needed.

Examples of the polyamine compound used for the polymer-forming raw material of the present invention include ethylenediamine, trimethylenediamine, tetramethylenediamine, and the like.
Pentamethylenediamine, hexamethylenediamine, p
-Phenylenediamine, m-phenylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, epoxy Examples include amine adducts of compounds. Also, within a range that does not impair the purpose of the present invention,
Other polymer substances may be included.

The weight ratio of the dye precursor to the polyvalent isocyanate compound in the production of the composite fine particles may be such that the weight of the dye precursor is from 5 to 100% by weight based on the weight of the polyvalent isocyanate from the viewpoint of color development sensitivity. Preferably 20-7
More preferably, it is 0% by weight. In the production of the composite fine particles, the total amount of the polyvalent isocyanate compound and the dye precursor is desirably 90% by weight or more based on the total weight of the oily solution, since a thermosensitive recording material with less white paper fog can be obtained.

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 such an organic compound, an aromatic ketone compound, an aromatic ether compound, and an aromatic cyclic ester compound can be preferably used.
Benzophenone is used as the aromatic ketone compound, and 1,2-di (m-tolyloxy) ethane, 1,2-diphenoxyethane, 1- (4-
Methoxyphenoxy) -2- (2-methylphenoxy)
Examples of ethane and aromatic cyclic ester compounds include coumarin and phthalide. The above organic compounds may be used alone or in combination of two or more. In the present invention, when the second dye precursor is also contained in another composite fine particle, the composite fine particle containing the second dye precursor can be produced by the same method as the composite fine particle containing the first dye precursor. However, the color may be formed at a temperature lower than that of the composite fine particles containing the first dye by applying the above-described method for improving color-forming sensitivity or changing the monomer composition.

In the present invention, as the emulsifier (protective colloid agent) used in the preparation of the composite fine particles, the same water-soluble polymer used when dispersing the dye precursor in the form of solid fine particles is used. Can be. At the same time, a surfactant, an antifoaming agent and the like may be used. The amount of the emulsifier used during the preparation of the composite fine particles is not particularly limited, but is generally preferably 1 to 50% by weight, more preferably about 3 to 30% by weight, based on the weight of the composite fine particles.

In the composite fine particles used in the present invention, an ultraviolet absorber, an antioxidant, an oil-soluble fluorescent dye, a release agent, and the like may be added, if necessary, in addition to the dye precursor. . Such an additive substance is preferably solid at room temperature, but may be liquid. The dye precursor may be a mixture of two or more. The average particle size of the composite fine particles of the present invention is preferably from 0.1 to 15 μm, more preferably from 0.2 to 4.0 μm, in consideration of the coloring sensitivity.

By using the composite fine particles of the present invention, it is possible to suppress background color development due to pressing force and background fogging due to heat and humidity, and remarkably suppress decoloration of a color image due to heat and humidity. . In the present invention, a microcapsule containing a high boiling point solvent in which a dye precursor is dissolved can also be used. However, microcapsules have a disadvantage that pressure fogging is likely to occur.

In the present invention, the ratio of the high-temperature coloring dye precursor to the low-temperature coloring dye precursor in forming the two-color heat-sensitive recording material is not limited, but generally, the high-temperature coloring dye precursor 1 is used.
The amount of the low-temperature coloring dye precursor is 20 to 6 parts by weight, and
00 parts by weight, more preferably 40 parts by weight.
３００300 parts by weight.

These heat-sensitive recording materials may have a structure of a multi-layered color-forming layer in which a plurality of dye precursors are respectively arranged in different layers, or a single-layered color-forming layer in which a plurality of dye precursors are contained in the same layer. It may be a configuration. However, from the viewpoint of haze, a single color developing layer having a plurality of dye precursors contained in the same layer is preferable.

The color-developing compound used in the present invention is not particularly limited, but generally has a property of liquefying or dissolving by an increase in temperature and a property of contacting with a dye precursor to form a color. Selected from things. Representative color developing compounds include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 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-te
rt-butylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and bis (3-allyl-4-hydroxyphenyl) sulfone Phenolic compounds can be mentioned.

Further, in the present invention, compounds that can be used as the 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.

The color-developing compound used in the present invention is more preferably a diphenylsulfone derivative containing a hydroxyl group in the molecule, for example, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy -4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone and the like can be exemplified. 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. Further, in order to form a color-developed image that is less likely to be decolored even when it comes in contact with oil, a plasticizer, or the like, 4,4′-bis (p
-Toluenesulfonylaminocarbonylamino) diphenylmethane, or N- (p-toluenesulfonyl)-
It is preferable to use N'-phenylurea alone or in combination.

The color-developing compound is preferably used in a proportion of 100 to 700% by weight, more preferably in a proportion of 150 to 400% by weight, based on the total weight of the dye precursor. 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 order to adjust the color sensitivity of the heat-sensitive coloring layer of the heat-sensitive recording material, a heat-fusible substance can be contained in the heat-sensitive coloring layer as a sensitizer. As the sensitizer, a compound conventionally known as a sensitizer for a thermosensitive recording material can be used. For example, parabenzyl biphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate can be used. , Adipic acid di-o-
Chlorbenzyl, 1,2-di (3-methylphenoxy)
Ethane, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy)
Propane can be given. Especially oxalic acid di-
When p-methylbenzyl and di-p-chlorobenzyl oxalate are used as sensitizers, a sensitizing effect with less fogging can be obtained.

The color developing compound used in the present invention,
Additives such as an image stabilizer and a sensitizer may be dispersed in water in the same manner as when the dye precursor is used in the form of solid fine particles, and may be mixed with the heat-sensitive coloring layer-forming paint when preparing the coating. . In addition, 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 in the same manner as the above-described composite fine particle preparation method, and 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.

To improve the whiteness of the thermosensitive coloring layer and the image uniformity, 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.
For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide,
Inorganic pigments such as aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica, and urea
Formalin resin, styrene-methacrylic acid copolymer resin,
Organic pigments such as polystyrene resin can be used. The amount of the pigment is preferably such that the transparency and the color density are not reduced, that is, 40% by weight or less based on the total solid weight of the thermosensitive coloring layer.

In the present invention, an adhesive is used as another component material constituting the thermosensitive coloring layer, and a crosslinking agent, a wax, a metal soap, a colored dye, a colored pigment, a fluorescent dye, and the like are used if necessary. Can be. 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. Water-soluble polymer materials such as coalesced, acrylamide-acrylate-methacrylate copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and derivatives thereof, and , Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-
Examples include emulsions such as vinyl acetate copolymers, and latexes of water-insoluble polymers such as styrene-butadiene copolymers and styrene-butadiene-acrylic copolymers.

Further, in order to improve the water resistance of the thermosensitive coloring layer, a crosslinking agent for three-dimensionally curing the adhesive may 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, inorganic compounds such as potassium tetraborate or boric acid, boric acid triesters, at least one crosslinkable compound selected from boron-based polymers and the like with respect to the total solid weight of the thermosensitive coloring layer It is preferable to use it in the range of 1 to 10% by weight.

The waxes added to the thermosensitive coloring layer include 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.

Examples of the metal soap added to the thermosensitive coloring layer include higher fatty acid polyvalent metal salts such as zinc stearate,
Aluminum stearate, calcium stearate,
And zinc oleate. Including a colored dye and / or a colored pigment having a color tone that is complementary to the low-temperature color tone in the thermosensitive coloring layer is preferably used to adjust the 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 added to the thermosensitive coloring layer as long as the effects of the present invention are not impaired.

There is no particular limitation on the type, shape, dimensions, etc. of the support material used in the present invention, for example, high-quality paper (acid paper, neutral paper), medium paper, coated paper, art paper, cast-coated paper. In addition to glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven 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 heat-sensitive recording material, the heat-sensitive recording material can be further processed to provide a heat-sensitive recording material having a higher function. For example, adhesive paper, re-wet adhesive paper, delayed tack paper by applying a coating process with adhesive, re-wet adhesive, delayed tack type adhesive on the whole surface or a part of the back surface, or magnetic processing on the back surface Is applied to the entire surface or a part thereof to obtain a thermosensitive recording material having a magnetically recordable layer. In addition, a recording paper capable of performing double-sided recording can be provided by using the back surface thereof and imparting functions as thermal transfer paper, ink-jet paper, carbonless paper, electrostatic recording paper, and xerographic paper. Of course, a double-sided heat-sensitive recording material can also be used.

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, known protective layers and undercoat layers used for heat-sensitive recording materials can be used. It is desirable that both the protective layer and the undercoat layer be composed mainly of a pigment and an adhesive. In particular, a lubricant such as polyolefin wax or zinc stearate is preferably added to the protective layer for the purpose of preventing sticking to the thermal head, and the protective layer may be composed of two or more layers. By providing a glossy protective layer, the added value of the product can be increased.
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.

A protective layer containing a UV-curable resin or an electron beam-curable resin may be provided on the thermosensitive coloring layer of the present invention or on the protective layer as an intermediate layer. Printing with ink or the like is also possible.

The method for forming each of the above layers on the support may be 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. May be used. Further, the thermosensitive coloring layer coating composition of the present invention can be partially printed and used by using a printing machine or the like. The coating material for the heat-sensitive coloring layer is usually applied to the support at 1 to 20 g / m ² (dry) to form a heat-sensitive coloring layer. Further, a back layer can be provided on the back surface of the recording material for curl control.

Smoothing the heat-sensitive recording material using a known smoothing method such as a super calender or a soft calender is effective in increasing the color development sensitivity. The heat-sensitive coloring layer side may be applied to either a metal roll or an elastic roll of a calender.

[0061]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

Examples 1 to 19 (1) Preparation of Solid Dispersion of Developing Compound / Sensitizer The developing compound bis (3-allyl-4-hydroxyphenyl) sulfone and the sensitizer dioxalate -P-Methylbenzyl ester was mixed with polyvinyl alcohol at the following mixing ratio, and pulverized and dispersed using a vertical sand mill (manufactured by Imex Co., Ltd., sand grinder) so that the average particle diameter became 1.0 μm. . Component amount (parts by weight) Color-developing compound 40 Sensitizer 10 Polyvinyl alcohol 10% solution (polymerization degree 500, saponification degree 90%) 40 Water 20

(2) Preparation of Solid Dispersion of Dye Precursor [for Low-Temperature Color Development] The dye precursors shown in Tables 1 and 2 were prepared in the same manner as in the case of the color developing compound and the sensitizer, and the average particle diameter was adjusted. The mixture was pulverized and dispersed to have a thickness of 0.6 μm to obtain a solid dispersion of a dye precursor. (3) Preparation of Dispersion of Dye Precursor-Containing Composite Fine Particles [for High-Temperature Color Development] 11 parts of the dye precursors described in Tables 1 and 2 were added to 24 parts of dicyclohexylmethane-4,4′-diisocyanate heated to 100 ° C. After dissolving and cooling this solution to 35 ° C., 8% polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry,
(Trademark: Gohsenol GM-14L) was gradually added to 100 parts of an aqueous solution, and the number of revolutions was 8,000 rp using a homogenizer.
After emulsifying and dispersing by stirring with a pressure of m 2, 40 parts of water was added to the emulsified dispersion to homogenize. The temperature of the emulsified dispersion was raised to 90 ° C., and a curing reaction was performed for 10 hours to prepare a dispersion of the dye precursor-containing composite fine particles having an average particle diameter of 0.9 μm.

Separately, a styrene / butadiene latex having a solid content of 48% (Polylac 750K,
An aqueous solution in which a 10% aqueous solution of polyvinyl alcohol (NM11Q, manufactured by Nippon Synthetic Chemical Industry) is blended with a 10% aqueous solution of polyvinyl alcohol (manufactured by Mitsui Chemicals, Inc.) so that the solid content ratio is 2: 1;
A stearic acid amide emulsion having a solid concentration of 22% was prepared as a wax liquid.

(4) Formation of Undercoat Layer Silica (Mizukasil P527, manufactured by Mizusawa Chemical Industry Co., Ltd.)
A mixture of 30 parts and 70 parts of 0.7% sodium polyacrylate was dispersed with a Cowles disperser, and a 10% aqueous solution of polyvinyl alcohol (NM11Q, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was mixed with a solid content ratio of 85:15. This coating liquid was coated on a high-quality paper (neutral paper) having a basis weight of 60 g / m ² using a Meyer bar at a coating amount of 7.0 g / m ² (dry).
To form an undercoat layer.

(5) Formation of thermosensitive coloring layer The solid dispersion of the above dye precursor, the dispersion of the composite fine particles containing the dye precursor, the color developing compound / sensitizer dispersion, the wax liquid, and the adhesive liquid are solidified. 5: 20: 40: 5:
10 to prepare a thermosensitive coloring layer coating solution. This coating solution was applied on the undercoat layer using a Mayer bar at a coating amount (drying) of 5.0 g / m ² and dried to prepare a thermosensitive recording material. Then, using a super calendar, the Bekk smoothness of the heat-sensitive recording surface (JIS-P-811)
9) was subjected to a smoothing treatment to 500 seconds to prepare a two-color heat-sensitive recording material.

<Example 20> A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the dispersion of solid fine particles of the dye precursor [for low-temperature color development] was changed to the following (2a) in (2) of Example 1. Created. (2a) Preparation of Dispersion of Dye Precursor-Containing Composite Fine Particles [for Low-Temperature Color Development] Dicyclohexylmethane-4,4′-diisocyanate 1 obtained by heating 11 parts of dye precursor shown in Table 2 to 100 ° C.
8 parts, dissolved in 6 parts of n-hexane-1,6-diisocyanate, the solution was cooled to 35 ° C., and then an aqueous solution of 8% polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry, trade name: Gohsenol GM-14L) at the same temperature 100 Slowly add
The mixture was emulsified and dispersed by stirring at a rotation speed of 8000 rpm using a homogenizer, and 40 parts of water was added to the emulsified dispersion to homogenize. This emulsified dispersion was heated to 90 ° C.
Time curing reaction, average particle diameter 0.9μm,
A dispersion of the dye precursor-containing composite fine particles was prepared.

<Comparative Examples 1 to 5> Using the dye precursors shown in Table 3, heat-sensitive recording materials were produced in the same manner as in Example 1.

<Comparative Example 6> In Example 1, the dye precursor 3-di- (n-pentyl) amino-6-methyl- with a black color was used in place of the dispersion of the dye precursor-containing composite fine particles.
Example 1 was repeated except that a dispersion obtained by pulverizing and dispersing 7-anilinofluoran in the same manner as in the color developing compound / sensitizer of Example 1 so that the average particle diameter became 5.0 μm was used. A heat-sensitive recording material was produced in the same manner as in Example 1. Component amount (parts by weight) Dye precursor 40 Polyvinyl alcohol 10% liquid (polymerization degree 500, saponification degree 90%) 40 Water 20

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

[Table 3]

A test was performed on each of the heat-sensitive recording materials obtained by the above operation. The thermal recording was performed using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.) using a sub-scanning line density of 8 lines / mm and an applied energy per dot of 0.
Two thin lines were printed under the condition of 3 mJ, and low-temperature coloring in low-temperature printing was performed. Also, separately with this printing,
Two thin lines were printed under the conditions of sub-scanning line density: 8 lines / mm and applied energy per dot: 1.0 mJ, and high-temperature coloring was performed in high-temperature printing. In addition, solid color development of 160 lines was performed under the conditions of low-temperature printing and high-temperature printing.

The quality of the thus obtained thermosensitive recording material was evaluated by the following method. <Segmentation of Coloring Portion> The segmentation of the two thin lines was visually evaluated according to the following evaluation criteria. ：: Very clearly distinguishable Δ: Slightly indistinct ×: Cannot be distinguished <Contrast> The contrast of solid color was visually evaluated according to the following evaluation criteria. ：: Difference in color tone is clear and easy to distinguish △: Difference in color tone is small and difficult to distinguish ×: Almost indistinguishable

Table 4 shows the test results.

[Table 4]

[0076]

As is evident from the results in Table 4, the present invention provides a heat-sensitive recording material which has a sharp coloration at low temperature color development with little color mixing due to high temperature color tone and excellent contrast with high temperature color tone. It has become possible to manufacture.

Claims (2)

[Claims] 1. A support having a heat-sensitive color-forming layer formed thereon, wherein said heat-sensitive color-forming layer forms a chromatic color with at least one polymer substance selected from (1) polyurea and polyurethane. (2) solid second fine particles of a dye precursor, which are not contained in the composite fine particles and which develop a chromatic color, and (3) the first and second fine particles. And a developer that reacts under heating to develop a color by heating, and the color tone of the first dye precursor and the color tone of the second dye precursor are in a complementary color relationship. A heat-sensitive recording material characterized in that: 2. A support having a heat-sensitive coloring layer formed thereon, wherein said heat-sensitive coloring layer forms a chromatic color with at least one polymer substance selected from (1) polyurea and polyurethane. And (2) at least one polymer substance selected from polyurea and polyurethane and a second dye precursor that develops a chromatic color. Composite fine particles,
(3) a color developer which contains the first and second dye precursors and a color developer which reacts with heating to form a color, and the color tone of the first dye precursor and the second dye precursor A heat-sensitive recording material, characterized in that the color tone is complementary.