JP3277822B2 - Multicolor thermal recording material - Google Patents

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 recording material which develops a plurality of different colors depending on different heating conditions. More specifically, the present invention relates to a multicolor heat-sensitive recording material which has a low-temperature color tone and a clear red color, and has good storage stability 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.

[0003] The quality required of heat-sensitive recording materials has also been diversified with the expansion of their uses. 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 the low-temperature color-forming layer develops color by the low-temperature color-forming operation. 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 two or more dye precursors which form different colors on a support and a color developing compound which forms the dye precursor. In the multicolor heat-sensitive recording material provided with, low-temperature coloring is a clear red coloring with excellent storability, and there is little mixing of colors at high-temperature coloring at low-temperature printing, and furthermore, high-temperature coloring Another object of the present invention is to provide an excellent multicolor heat-sensitive recording material.

[0009]

SUMMARY OF THE INVENTION The present invention provides a support, two or more kinds of dye precursors formed on the support and emitting colors different from each other, and reacting with the dye precursor under heating. In a multicolor heat-sensitive recording material having a heat-sensitive color-developing layer containing a color-developing compound for developing the color ,
The thermochromic layer is composed of (1) a polyvalent isocyanate compound as a solvent.
And emulsifying and dispersing a solution containing the first dye precursor as a solute in water.
After that, accelerate the polymerization reaction of polyvalent isocyanate compound
And (2) the first fine particles obtained by
A dye precursor is a second dye precursor that develops a different color tone
As a 3-diethylamino-7-phenoxy sihr Oran, 3- (N-ethyl--N- isoamyl) -7-
A multicolor heat-sensitive recording material characterized by containing solid fine particles formed from at least one red color- forming dye precursor selected from phenoxyfluorane.

Further, the present invention provides a support, two or more kinds of dye precursors formed on the support and developing colors different from each other, and a developer which reacts with the dye precursor under heating to form a color. In a multicolor heat-sensitive recording material having a heat-sensitive coloring layer containing a coloring compound, the heat-sensitive coloring layer comprises: (1) a solution containing a polyvalent isocyanate compound as a solvent and a first dye precursor as a solute in water; After the emulsification and dispersion, the composite fine particles obtained by accelerating the polymerization reaction of the polyvalent isocyanate compound, and (2) the first dye precursor, as the second dye precursor that develops a different color,
-Diethylamino-7-phenoxyfluoran, 3-
A multicolor heat-sensitive recording material characterized by containing solid fine particles comprising at least one kind of red color-forming dye precursor selected from (N-ethyl-N-isoamylamino) -7-phenoxyfluoran.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the multicolor heat-sensitive recording material of the present invention, 3-diethylamino-7-phenoxyfluoran and 3- (N-ethyl-N-isoamylamino) -7-phenoxyfluor are used as dye precursors. The heat-sensitive layer contains at least one red color-forming dye precursor selected from silane and a color-developing compound. These red coloring dye precursors are desirably used as solid fine particles, and not only develop a vivid red color upon contact reaction with a developing compound under heating, but also from the viewpoint of preservation of the recorded image. It is remarkably superior to conventionally known red coloring dye precursors. In the present invention, it is preferable that the low-temperature color tone be a red color by using at least one of these two types of red-coloring dye precursors, and the high-temperature color tone be a black color.

In the present invention, the first dye precursor for obtaining a high-temperature color tone is prepared by emulsifying and dispersing a solution containing a polyvalent isocyanate compound as a solvent and the dye precursor as a solute in water. It can be contained in the thermosensitive coloring layer as composite fine particles obtained by accelerating the molecular reaction. By containing the composite fine particles in the same heat-sensitive coloring layer as the red dye-forming second dye precursor of the solid fine particles, a thermosensitive recording material capable of developing two colors of low-temperature red coloring and high-temperature black coloring can be obtained. The first dye precursor to be 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.

The composite fine particles used in the present invention are disclosed in
Unlike microcapsules in which a dye precursor described in, for example, JP-A-4960 is dissolved in a high-boiling-point solvent and contains the solution, it does not contain an organic solvent and thus does not break down due to pressure. Therefore, the thermal recording material of the present invention hardly generates pressure fog. In the manufacturing process, Japanese Patent Application Laid-Open Nos. Hei 4-247787 and Hei 4-101885
No organic solvent having a low boiling point as used in the publication is used, so that the manufacturing process can be simplified and there is no safety problem associated with the organic solvent having a low boiling point.

In the present invention, as described above, the composite fine particles containing the red dye-forming second dye precursor in the form of solid fine particles and the first dye precursor that develops a color tone different from that of the second dye precursor are heat-sensitive. It can be contained in a layer. further,
In the present invention, 3-diethylamino-7-phenoxyfluoran, 3- (N-
At least one dye precursor selected from ethyl-N-isoamylamino) -7-phenoxyfluorane is contained in the upper heat-sensitive coloring layer, and a heat-sensitive coloring layer containing a dye precursor that develops a different color is provided. A two-color development can be made possible by adopting a laminated structure as a lower layer. In this case, the chromogenic dye precursor may of course be contained in the composite fine particles. Providing an intermediate layer between the upper and lower thermosensitive coloring layers is useful for improving the color separation in such a configuration.

Heretofore, as a dye precursor used for a heat-sensitive recording material, a leuco compound such as a triallyl compound, a diphenylmethane compound, a thiazine compound, a spiro compound, a lactam compound or a fluoran compound has been widely used. Dye precursors that develop a red color include 3,6-bis (diethylamino) fluoran-γ-anilinolactam, 3,6-bis (diethylamino) fluoran-γ- (p-nitro) anilinolactam, 6-bis (diethylamino) fluoran-γ
-(O-chloro) anilinolactam, 3-dimethylamino-7-bromofluoran, 3-diethylaminofluoran, 3-diethylamino-6-methylfluoran, 3
-Diethylamino-7-methylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-bromofluoran, 3-diethylamino-7,8
-Benzofluoran, 3-diethylamino-6,8-dimethylfluoran, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-te
rt-butyl fluoran, 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 and the like are known.

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 can be mentioned.

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.

3-diethylamino-7-phenoxyfluoran, a red-color-forming dye precursor used in the present invention,
At least one kind of dye precursor selected from 3- (N-ethyl-N-isoamylamino) -7-phenoxyfluoran has a color tone higher than that of a conventionally known red color precursor. Has a vivid reddish color and has excellent storage stability after coloring. In the present invention, of course, these dye precursors and other dye precursors may be mixed and used.

The composite fine particles used in the present invention are composed of at least one polymer selected from polyurea or polyurethane-polyurea, and a dye precursor. Are mixed at a molecular level and are considered to exist in a solid solution state. The appearance of the composite fine particles is almost spherical when observed with an electron microscope, or is in the shape of hemoglobin with a somewhat concave center.

As described above, the heat-sensitive recording material using composite fine particles used in the present invention has less background fogging due to pressure than the heat-sensitive recording material using microcapsules containing an organic solvent and a dye precursor. For this reason,
The microcapsules using an organic solvent break the wall easily due to pressure, and the dye dissolved in the contained organic solvent is extruded out of the microcapsules and reacts with the color developing compound to form a color. It is. Since the composite fine particles used in the present invention do not contain a liquid organic solvent, they are considered to have higher mechanical strength than microcapsules.

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 compound. The melting temperature at this time is 60
C. or higher is preferred. If the dissolution temperature is lower than 60 ° C., the dissolution of the dye precursor in the polyvalent isocyanate compound becomes insufficient, and uniform composite fine particles may not be produced.

In the present invention, the 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 dye precursor that can be contained in the composite fine particles used in the present invention includes, as dye precursors that give black coloring, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-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-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-anilino Fluoran, 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-
Examples thereof include 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.

In the present invention, a black coloring dye precursor and a dye precursor of another color can be used in combination in order to make the black coloring of the high-temperature coloring tone closer to pure black. In this case, it is more preferable to use a dye precursor having a color tone that is complementary to the low-temperature color tone red. Alternatively, for example, only a blue-coloring dye precursor may be used without using a black-coloring dye precursor, and the high-temperature color tone may be purple.

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.

The polyvalent isocyanate compound used in the present invention reacts with water to form a urea bond,
Polymerize. The polymer to be formed is polyurea or polyurethane-polyurea, and the polymer-forming material used may be a polyvalent isocyanate compound alone or a polyvalent isocyanate compound and a polyol that reacts with the polyvalent isocyanate compound. Or a polymer such as a polyol adduct of a polyvalent isocyanate compound, a biuret compound, an isocyanurate compound, or the like. 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, if necessary, mixed with a reactive substance such as polyamine. By heating the emulsified dispersion, the polymer-forming material is polymerized to polymerize. Thereby, composite fine particles composed of the dye precursor and the polymer substance can be formed.

Examples of the polyvalent isocyanate compound used as a polymer-forming raw material include norbornene diisocyanate, m-phenylene diisocyanate, p-
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,
Diisocyanates such as cyclohexylene-1,2-diisocyanate and cyclohexylene-1,4-diisocyanate; triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate And tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate.

Examples of the adduct of a polyvalent isocyanate and a polyol include a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of 2,4-tolylenediisocyanate, a trimethylolpropane adduct of xylylenediisocyanate, An isocyanate prepolymer such as a hexanetriol adduct of tolylene diisocyanate can be used. In addition, these polyvalent isocyanate compounds, for example, a biuret of hexamethylene diisocyanate, an isocyanurate of hexamethylene diisocyanate, and the like can also be preferably used as the polymer-forming raw material of the present invention.

In the present invention, it is particularly preferable to use dicyclohexylmethane-4,4'-diisocyanate. Dicyclohexylmethane-4,4'-diisocyanate has good workability due to its low viscosity, and has high solubility in a color-forming dye precursor. Further, it is also desirable to improve the distinction between the color-forming sensitivity of the color-forming dye precursor in the composite fine particles and the low-temperature color-forming sensitivity. Of course, it can be used in combination with other polyvalent isocyanates.

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 and the polyol compound are not limited to the above compounds, and two or more kinds may be used in combination 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.

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 an organic compound having a melting point of 40 ° C. or more and 150 ° C. or less and a boiling point of 150 ° C. or more, an aromatic ketone compound, an aromatic ether compound, and an aromatic cyclic ester compound can be preferably used in the present invention. Specific examples are shown below. 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. 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 compound in the production of the composite fine particles is from 20 parts by weight to 2,000 parts by weight of the polyvalent isocyanate compound with respect to 100 parts by weight of the dye precursor from the viewpoint of color development sensitivity. Preferably, it is 100 to 500 parts by weight.

In the present invention, as an emulsifier (protective colloid agent) used for preparing the composite fine particles, 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 1 to 50% by weight, more preferably about 3 to 30% by weight, based on the weight of the composite fine particles.

The average particle diameter of the composite fine particles containing the first dye precursor used in the present invention is preferably 0.6 to 5.0 μm. More preferably, 1.2-3.0μ
m. When the average particle size is smaller than 0.6 μm, the sensitivity is increased, and the red chromogenic property of the solid fine particles to be mixed is increased.
It is difficult to classify the color development sensitivity with the dye precursor, and color mixing occurs at low temperature, which is not preferable. In addition, the storage stability of the colored portion with respect to oil and plasticizer may be deteriorated when the particle size is small. If the average particle diameter is larger than 5.0 μm, the coloring sensitivity is lowered, and it is necessary to apply excessive energy to the thermal head to obtain the coloring of the composite fine particles, which is not preferable.

The composite fine particles used in the present invention are known as a heat-sensitive recording material in addition to a dye precursor, if necessary, as well as an ultraviolet absorber, an antioxidant, an oil-soluble fluorescent dye, and a release agent. Such a sensitizer or the like may be added. 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 kinds as described above. For example, by appropriately mixing red, blue, green, and yellow dye precursors, composite fine particles having a black color can be obtained.

The inclusion of an ultraviolet absorber in the composite fine particles is preferred from the viewpoint of light resistance, and particularly, a benzotriazole-based ultraviolet absorber such as 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole. Can be preferably used.

In addition, when a polymer is prepared in the preparation of the composite fine particles, a tin compound, a polyamide compound,
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 the dye precursor is used in the form of solid fine particles, the dye precursor is pulverized using water as a dispersion medium by various wet pulverizers such as a sand grinder, an attritor, a ball mill, and a cobo mill. This is modified with a water-soluble synthetic polymer such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as a sulfone group-modified polyvinyl alcohol, methylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer salt and derivatives thereof. If necessary, the dispersion may be dispersed in a dispersion medium together with a surfactant, an antifoaming agent, and the like to form a dispersion, and the 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 any case, the average particle diameter of the dispersed particles of the dye precursor used in the state of solid fine particles is preferably 0.2 to 3.0 μm, more preferably 0.3 to 3.0 μm, in order to obtain appropriate color sensitivity. 1.0μ
m.

In the multicolor heat-sensitive recording material of the present invention, the dye precursor contained in the composite fine particles and the red-coloring 3-diethylamino-7-phenoxyfluoran, 3- (N-ethyl) which is present in the form of solid fine particles. -N-isoamylamino) -7-phenoxyfluorane is not particularly limited in ratio with at least one dye precursor selected from the group consisting of solids and solids with respect to 100 parts by weight of the dye precursor contained in the composite fine particles. When the amount of the dye precursor to be present in the form of fine particles is 20
The amount is preferably set to about 600 parts by weight, more preferably 50 to 300 parts by weight.

In the present invention, by using the composite fine particles, it is possible to suppress the background color development due to the pressing force and the occurrence of the background fog when the white paper is stored for a long period of time. Decoloring by a plasticizer or oil can also be significantly suppressed.

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 above-mentioned dye precursor to form a color. Is selected. 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 which 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.

In the present invention, it is particularly preferable to use a diphenylsulfone derivative containing a hydroxyl group in the molecule as a color developer. Such compounds include, for example, 4,4'-dihydroxydiphenyl sulfone,
Examples include 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and bis (3-allyl-4-hydroxyphenyl) sulfone. 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 which is hardly decolored even when it comes in contact with oil or a plasticizer, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane or N-
It is preferred to use (p-toluenesulfonyl) -N'-phenylurea.

The color developing compound is usually composed of a total of 1 dye precursor.
It is preferably used in an amount of 100 to 700 parts by weight, more preferably 150 to 400 parts by weight, based on 00 parts by weight. 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, a sensitizer can be used to improve the heat-sensitive recording color development sensitivity. 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. ,
Di-o-chlorobenzyl adipate, 1,2-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-oxalate
Examples thereof include p-chlorobenzyl, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl, and benzophenone. Among these compounds, di-p-methylbenzyl oxalate and di-p-oxalate
When chlorobenzyl is used as a sensitizer, 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 thermosensitive 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. The inclusion of 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 color tone of the recording material before printing. 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 may 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 can 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, and the like of the support material used in the present invention are not particularly limited, and include, for example, high quality paper (acid paper, neutral paper), medium paper, coated paper, art paper, and 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 multicolor heat-sensitive recording material, the multicolor heat-sensitive recording material can be further processed to obtain a heat-sensitive recording material having a higher function.
For example, adhesive paper, re-wet adhesive, delayed-tack-type adhesive, etc. are applied to the back surface to make adhesive paper, re-wet adhesive paper, delayed-tack paper, or magnetic processing A heat-sensitive recording material having a recordable layer can be obtained. In particular, two-color heat-sensitive labels and two-color heat-sensitive labels
It is useful for applications such as color thermal magnetic tickets. Also, using the back side, thermal transfer paper, inkjet paper,
A recording paper capable of performing double-sided recording may be provided by imparting functions as carbonless paper, electrostatic recording paper, and xerographic paper. Of course, a double-sided heat-sensitive recording material can also be used.

The method for forming each of the above 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 dip 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.

[0066]

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, thermosensitive coloring layer and protective layer <Preparation of composite fine particle dispersion containing black coloring dye precursor>
3-di-n-amylamino-6- as a black color-forming dye
6 parts of methyl-7-anilinofluoran are dissolved in 24 parts of dicyclohexylmethane-4,4'-diisocyanate heated to 120 ° C., and the solution is cooled to 25 ° C., and then 8% polyvinyl alcohol (Nihon Gosei) at the same temperature (Trade name: Gohsenol GM-14L, manufactured by Kagaku Kogyo Co., Ltd.), gradually added to 250 parts of an aqueous solution, and rotated at 700 rpm using a homogenizer.
After emulsifying and dispersing by stirring at 0 rpm, 100 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 carried out for 10 hours to prepare a dispersion of the black chromogenic dye precursor-containing composite fine particles having an average particle diameter of 1.6 μm.

<Preparation of Dye Precursor, Developing Compound, and Sensitizer Dispersion in Solid Fine Particle State> Red chromogenic dye precursor: 3-diethylamino-7-phenoxyfluoran 3- (N-ethyl-N- Isoamylamino) -7-phenoxyfluoran 3-diethylamino-7-chlorofluorane Color-developing compound: bis (3-allyl-4-hydroxyphenyl) sulfone Sensitizer: di-p-methylbenzyl oxalate

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 subjected to 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.) and sodium polyacrylate at the following mixing ratio, and this mixture was dispersed by a Cowles dispersing machine. 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 pigment dispersion and adhesive liquid were mixed at a solid content of 80:
20 and 7.0 g of this paint 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 thermosensitive coloring layer The solid content was 30 parts of the composite fine particles containing the black coloring dye precursor, and the red coloring dye precursor 3-diethylamino-
7-phenoxyfluoran 7 parts, a color-developing compound 25 parts,
The respective dispersions and dissolved materials were mixed so that 15 parts of a sensitizer, 10 parts of a pigment, 8 parts of an adhesive, and 5 parts of a lubricant were mixed to prepare a thermosensitive coloring layer paint. On top of the undercoat layer formed earlier with this paint,
The coating was applied at a coating amount (drying) of 5.0 g / m ² and dried to form a thermosensitive coloring layer.

(4) Formation of Protective Layer The mixing ratio of the solid content was 40 parts of the pigment dispersion, and 55 parts of the adhesive liquid.
Parts and 5 parts of a lubricant dispersion, to prepare a protective layer paint. This coating solution was applied on the previously formed thermosensitive coloring layer at a coating amount (drying) of 2.0 g / m ² and dried to form a protective layer. The multicolor heat-sensitive recording material thus obtained was subjected to a smoothing treatment with a super calender so that the Bekk smoothness of the surface of the protective layer became 500 seconds, to obtain a multicolor heat-sensitive recording material of Example 1.

Example 2 Instead of 7 parts of the red chromogenic dye precursor, 3-diethylamino-7-phenoxyfluoran used in Example 1,
Except for using 7 parts of a red-color-forming dye precursor, 3- (N-ethyl-N-isoamylamino) -7-phenoxyfluoran, the multicolor heat-sensitive material of Example 2 was prepared in the same manner as in Example 1. A recording material was obtained.

Comparative Example 1 Instead of 7 parts of the red chromogenic dye precursor, 3-diethylamino-7-phenoxyfluoran used in Example 1,
A multicolor heat-sensitive recording material of Comparative Example 1 was obtained in the same manner as in Example 1 except that 7 parts of a red coloring dye precursor and 3-diethylamino-7-chlorofluorane were used.

A test was performed on each of the heat-sensitive recording materials obtained by the above operation. Thermal recording was performed using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.) under the conditions of one line recording time: 5 msec, sub-scanning line density: 8 lines / mm, and applied energy per dot: 0.5 mJ. , And low-temperature red coloring in low-temperature printing was performed. Separately, recording time per line: 5 msec, sub-scanning line density: 8 lines / mm, applied energy per dot:
Solid printing of 256 lines was performed under the condition of 2.0 mJ, and high-temperature black coloring was performed in high-temperature printing.

With respect to the color product thus obtained,
The color tone was evaluated visually.

Further, in order to examine the resistance to the plasticizer, a vinyl chloride wrap film (KMA manufactured by Mitsui Toatsu) was superimposed on the heat-sensitive recording material after coloring under a pressure of 20 g / cm ² , and the temperature was changed to 40 ° C. and 90% RH. After standing for 24 hours under the condition, the degree of the decoloration was examined. ○ indicates that there was no decoloration, and X indicates that decolorization was observed. Table 1 shows the test results.

[0081]

[Table 1]

[0082]

As is evident from the results in Table 1, the present invention makes it possible to produce a multicolor heat-sensitive recording material having a low-temperature color tone and a clear red color and excellent storage stability. .

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-309272 (JP, A) JP-A-9-142025 (JP, A) JP-A-2-93459 (JP, A) JP-A 8- 224962 (JP, A) JP-A-6-8620 (JP, A) JP-A-9-263057 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5 / 28-5 / 34 CAPLUS (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A support, two or more kinds of dye precursors formed thereon and developing colors different from each other, and a color developing compound which reacts with the dye precursor under heating to form a color. in multicolor heat-sensitive recording material comprising a thermosensitive coloring layer containing the heat-sensitive coloring layer, (1) a polyvalent iso
Using a cyanate compound as a solvent and a first dye precursor as a solute
After emulsifying and dispersing the solution in water, the polyvalent isocyanate compound
Composite microparticles obtained by accelerating the polymerization reaction of
The particles and (2) the first dye precursor have different color tones.
3-diethylamino- as the second dye precursor for coloring
Formed from at least one red color- forming dye precursor selected from 7-phenoxyfluoran and 3- (N-ethyl-N-isoamylamino) -7-phenoxyfluoran
A multicolor heat-sensitive recording material characterized by containing solid fine particles .