JP3402116B2 - 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 different colors depending on the heating conditions. More specifically, the present invention relates to a multicolor heat-sensitive recording material which has a vivid red color at low temperature and has good storability in low temperature color and high temperature color.

[0002]

2. Description of the Related Art Conventionally, by utilizing a color forming reaction between a dye precursor, a dye precursor and a color developing agent which is brought into a color by being heated, both color forming substances are melt-contacted by heating,
A heat-sensitive recording material for obtaining a color image is widely known. Such a thermal recording material is relatively inexpensive,
Since the recording device is compact and easy to maintain, it can be used for facsimiles, word processors, various computers,
It is used in a wide range of fields as a recording medium for other purposes.

With respect to the heat-sensitive recording materials, the required quality has been diversified with the expansion of their applications. For example, there are demands for higher sensitivity, image stabilization and multicolor recording. In particular, the multicolor recording means has an advantage that a character or figure to be emphasized can be markedly and clearly displayed in a color tone different from that of other portions. Among them, a two-color heat-sensitive recording material capable of two-color recording of red and black is excellent in versatility and thus highly demanded for practical use.

As a multicolor thermosensitive recording system, attempts have been made so far to utilize a difference in heating temperature or a difference in thermal energy, and various multicolor thermosensitive recording materials have been proposed. Generally, a multicolor thermosensitive recording material is composed of a high-temperature coloring layer and a low-temperature coloring layer, which are colored in different colors on a support, and are sequentially laminated. Of 2
It is divided into types.

Examples of the erasable multicolor heat-sensitive recording material include, for example, Japanese Patent Publication No. 50-17865 and Japanese Patent Publication No. 57-14.
As disclosed in JP-A-320-80 and JP-A-2-80287, only the low-temperature color-developing layer develops color by a low-temperature color-developing operation, and upon high-temperature color-heating, the color-developing system of the low-temperature color-developing layer is erased. This is a method in which a decoloring agent having a color action acts to obtain color only in the high temperature color developing layer. This method has an advantage that the coloring 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 for the low temperature coloring layer. Then, due to the action of the decoloring agent added in a large amount, the recorded color image is discolored during long-term storage, or an additional amount of heat is required to melt the decoloring agent, which causes an excessive load on the thermal head. However, there have been problems such as the reliability of the recorded image and the recording sensitivity.

On the other hand, the additive type multicolor heat-sensitive recording material is
JP-B-49-27708, JP-B-51-1998
As described in JP-A No. 9 and JP-A No. 51-146239, a method of obtaining two distinguishable colors by laminating two color-developing layers that develop different colors and applying different amounts of heat. Is. In this method, the upper color-developing layer is colored at a low temperature to obtain the upper color-developing color tone, and at the high temperature, both upper and lower color-developing layers are colored to obtain an image of a mixed color tone of both colors, so that the lower color-developing layer is colored black. Suitable when used as a system. Since the decolorizing agent is not used in the color-addition type recording material, it is advantageous in that the recorded image is excellent in long-term storability and can be manufactured at a relatively low cost, as compared with the decoloring type. Further, since there is no need for extra heat for melting the decoloring agent, there is an advantage that the high temperature coloring layer can be colored with low energy as compared with the decoloring type. However, the color-added multicolor heat-sensitive recording material having such a structure has a problem in that if too much heat is applied during low-temperature color development, color mixture in the high-temperature color development layer also partially mixes, making it difficult to obtain a clear low-temperature color development image. was there. Further, JP-A-56-99697 describes a method in which two or more kinds of dye precursors having different color tones and different average particle sizes are mixed in the same layer. There was a problem that color mixing became more intense.

The application of microcapsules to heat-sensitive recording materials has long been known, for example, Japanese Patent Publication No. 49-7.
No. 0 publication describes encapsulating a solvent in a liquid state at room temperature. As an example of microencapsulating a color-forming component as a core substance, JP-A-57-12695 is known.
JP-A No. 59-214691, and the like. Further, in JP-B-4-4960 and JP-A-4-101885, color-forming components that develop different color tones are dissolved in a solvent and contained in two or more types of microcapsules having different glass transition temperatures. It is described that multicoloring is achieved by making the color change. However, if two or more dye precursors that develop different colors are separately encapsulated in microcapsules, the color development sensitivities of both dye precursors decrease, and sensitivity classification becomes difficult. Therefore, mixing of color development colors is likely to occur. There was a problem. In addition, when an oily liquid for dissolving the dye precursor is included in the microcapsules, there is a problem that the capsules are broken due to pressure or frictional rubbing, and the base color is likely to occur.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive coloring layer containing two or more kinds of dye precursors which develop different color tones on a support, and a color-developing compound which develops the dye precursors. In a multicolor thermosensitive recording material provided with, the low-temperature color is a vivid red color with excellent storage stability, and there is little mixing of the color tone during high-temperature color development during low-temperature printing. Another object is to provide an excellent multicolor thermosensitive recording material.

[0009]

The present invention comprises a support, two or more kinds of dye precursors formed on the support, and coloring in different color tones, and reacting with the dye precursor under heating. In a multicolor thermosensitive recording material having a thermosensitive coloring layer containing a color-developing compound that develops the color, the thermosensitive coloring layer comprises (1) a polyvalent isocyanate compound as a solvent.
Then emulsify and disperse a solution containing the solute as the first dye precursor in water
After that, the polymerization reaction of the polyvalent isocyanate compound was accelerated.
And (2) the first composite fine particles obtained by
The dye precursor is a second dye precursor that develops a different color tone.
As 3- (N-isoamyl-N-ethylamino)-
7-methylfluorane, 3- (Nn-hexyl-N-
Solid fine particles composed of at least one low-temperature color-developing red color-forming dye precursor selected from ethylamino) -7-methylfluorane and 3- (N-isobutyl-N-ethylamino) -7-methylfluorane. It exists in a multicolor heat-sensitive recording material characterized by containing.

[0010]

In the heat-sensitive recording material of the invention, a support
And a different color tone is formed on it.
Two or more dye precursors, and
Contains a color-developing compound that reacts under heat to develop color
In a multicolor thermosensitive recording material having a thermosensitive coloring layer,
The thermosensitive coloring layer contains (1) a polyvalent isocyanate compound.
Polymerization component containing and hydrophobic having a boiling point of 20 to 100 ° C
Solvent using a soluble organic solvent as the solvent and the solute as the first dye precursor
The liquid is emulsified and dispersed in water.
Organic solvent is removed by volatilization at a temperature of 20-55 ° C
By polymerizing the polymerizing component in the emulsified dispersed particles
The obtained composite fine particles, and (2) the first dye precursor
As a second dye precursor that develops different color tones, 3-
(N-isoamyl-N-ethylamino) -7-methylphenyl
Luoran, 3- (N-n-hexyl-N-ethylami)
No) -7-methylfluorane, 3- (N-isobutyl-)
Selected from N-ethylamino) -7-methylfluorane
At least one low-temperature color-forming red color-forming dye precursor
Multicolored appearance characterized by containing solid fine particles consisting of
It may be a thermal recording material .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the multicolor heat-sensitive recording material of the present invention, 3- (N-isoamyl-N-) is used as a dye precursor.
Ethylamino) -7-methylfluorane, 3- (Nn)
-Hexyl-N-ethylamino) -7-methylfluorane, 3- (N-isobutyl-N-ethylamino) -7-
The heat-sensitive layer contains at least one low-temperature color-developing red color-forming dye precursor selected from methylfluorane and a color-developing compound. These red color-forming dye precursors are preferably used as solid fine particles, and not only develop a clear red color by contact reaction with a color-developing compound under heating,
In terms of the storability of the recorded image, it is significantly superior to the conventionally known red color-forming dye precursors. In the present invention, it is desirable that the low-temperature color tone is red color by using at least one of these three types of red color-forming dye precursors, and the high temperature color tone is black color.

In the present invention, the first dye precursor for obtaining a high-temperature color tone is obtained by emulsifying and dispersing a solution containing a polyvalent isocyanate compound as a solvent in the solute and then increasing the amount of the polyvalent isocyanate compound. The composite fine particles obtained by promoting the molecular reaction can be contained in the thermosensitive color developing layer. By containing the composite fine particles in the same thermosensitive coloring layer as the solid fine particles of the red coloring second dye precursor, it is possible to obtain a thermosensitive recording material capable of forming two colors of low temperature red coloring and high temperature black coloring. The first dye precursor contained in the composite fine particles may be a single compound and may have a black color-forming property, or by mixing two or more kinds of color-forming dye precursors having different color tones, a black color-forming property may be obtained. Also good.

The composite fine particles used in the present invention are described in
Unlike microcapsules in which the dye precursor described in Japanese Patent Publication No. 4960 or the like is dissolved in a high boiling point solvent and the solution is encapsulated therein, it does not contain an organic solvent and therefore is not destroyed by pressure. Therefore, the thermal recording material of the present invention hardly causes pressure fog. Further, in the manufacturing process thereof, JP-A-4-247987 and JP-A-4-101885.
Since a low boiling point organic solvent as used in Japanese Patent Laid-Open Publication No. 2003-242242 is not used, the manufacturing process can be simplified and there is no safety problem associated with the low boiling point organic solvent.

In the present invention, as described above, the composite fine particles containing the red color-forming second dye precursor in the form of solid fine particles and the first dye precursor which develops a color tone different from that of the second dye precursor are subjected to the same heat treatment. It can be contained in a layer. further,
In the present invention, it is used as a low-temperature red color developer 3-
(N-isoamyl-N-ethylamino) -7-methylfluorane, 3- (Nn-hexyl-N-ethylamino) -7-methylfluorane, 3- (N-isobutyl-)
At least one dye precursor selected from N-ethylamino) -7-methylfluorane is contained in the thermosensitive color developing layer of the upper layer, and the thermosensitive color developing layer containing the dye precursor that develops a different color tone is used as the lower layer. It is also possible to develop two colors by adopting a laminated structure of In this case, the color forming 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 color separation in such a structure.

Conventionally, leuco compounds such as triallyl, diphenylmethane, thiazine, spiro, lactam, and fluorane are often used as dye precursors used in heat-sensitive recording materials. Examples of dye precursors that develop a red color include 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3,6-bis (diethylamino) fluorane-γ- (p-nitro) anilinolactam, 3, 6-bis (diethylamino) fluorane-γ
-(O-chloro) anilinolactam, 3-dimethylamino-7-bromofluorane, 3-diethylaminofluorane, 3-diethylamino-6-methylfluorane, 3
-Diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorane, 3-diethylamino-7,8
-Benzofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-te
rt-Butylfluorane, 3- (N-ethyl-N-tolylamino) -7-methylfluorane, 3- (N-ethyl-N-tolylamino) -7-ethylfluorane, 3-
(N-ethyl-N-isobutylamino) -6-methyl-
7-chlorofluorane, and 3- (N-ethyl-N-
Isoamylamino) -7,8-benzofluorane and the like are known.

Further, as a dye precursor which gives a reddish color, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 3-di-n. -Butylamino-7,8-benzofluorane, 3-tolylamino-7-methylfluorane, 3-tolylamino-7-ethylfluorane, 2-
(N-Acetylanilino) -3-methyl-6-di-n-
Butylaminofluorane, 2- (N-propionylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N-benzoylanilino) -3-methyl-
6-di-n-butylaminofluorane, 2- (N-carbobutoxyanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N-formylanilino)-
3-methyl-6-di-n-butylaminofluorane, 2
-(N-benzylanilino) -3-methyl-6-di-n
-Butylaminofluorane, 2- (N-allylanilino) -3-methyl-6-di-n-butylaminofluorane, and 2- (N-methylanilino) -3-methyl-
Mention may be made of 6-di-n-butylaminofluorane.

Further, 3,3'-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 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- (N-isoamyl-N-ethylamino) -7-methylfluorane, 3- (Nn-hexyl-N-), which is a precursor of a red color-forming dye having a low temperature color development used in the present invention. Ethylamino) -7-methylfluorane, 3-
At least one dye precursor selected from (N-isobutyl-N-ethylamino) -7-methylfluorane is
Compared with conventionally known dye precursors that develop a reddish color, the color tone of the color is clear red, and the storage stability after color development is excellent. In the present invention, of course, these dye precursors and other dye precursors may be mixed and used.

The dye precursor used in the present invention as a high-temperature black color tone includes 3-pyrrolidino-6-methyl-7-anilinofluorane and 3-diethylamino-7- (dye precursors that give a black color. m-trifluoromethylanilino) fluorane, 3- (N-isoamyl-N
-Ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-).
2-Tetrahydrofurfurylamino) -6-methyl-7
-Anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n
-Amylamino-6-methyl-7-anilinofluorane, 3- (N-isoamyl-N-ethylamino) -6-
Methyl-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N
-Ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino) -6-methyl-7-anilinofluorane, 3-
Diethylamino-7- (2-chloroanilino) fluorane, 3-di-n-butylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane,
3-Diethylamino-6-methyl-7- (2,4-dimethylanilino) fluorane, 2,4-dimethyl-6-
(4-dimethylaminoanilino) fluorane, and 3
Examples thereof include-(N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane.

In the present invention, among the dye precursors which give the above-mentioned black color development, 3-di-n-amylamino-6-methyl-7-anilinofluorane, which is particularly excellent in light fastness, 3
-Diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluorane,
It is preferably at least one selected from 2,4-dimethyl-6- (4-dimethylaminoanilino) fluorane.

In the present invention, in order to make the black color of the high temperature color tone closer to that of pure black, the black color forming dye precursor may be used in combination with the dye precursor of another color tone. 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 color. Further, it is also possible to use, for example, only the blue-coloring dye precursor without using the black-coloring dye precursor, and to make the high-temperature coloring color tone purple.

As the dye precursor which gives a blue color,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide, 3 -(1-ethyl-2
-Methylindol-3-yl) -3- (2-methyl-
4-diethylaminophenyl) -4-azaphthalide, 3
-(1-Ethyl-2-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-diphenylaminofluorane and the like can be mentioned.

The dye precursor that gives a green color is 3
-(N-ethyl-Nn-hexylamino) -7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4 -Azaphthalide, 3-
(N-ethyl-Np-tolylamino) -7- (N-phenyl-N-methylamino) fluorane, 3- [p-
(P-anilinoanilino) anilino] -6-methyl-7
-Chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like can be mentioned.

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

The dye precursor used for these high-temperature color-developing tones can be contained in the thermosensitive color-forming layer in the form of being contained in solid fine particles or composite fine particles. Therefore, it is desirable to include the dye precursor in the composite fine particles.

The composite fine particles used in the present invention are composed of at least one polymer substance selected from polyurea or polyurethane-polyurea and a dye precursor, and the dye precursor and the polymer substance. Are considered to exist as a solid solution by mixing at the molecular level. The appearance of the composite fine particles is almost spherical when observed with an electron microscope, or is red blood cell-like with a slightly depressed center.

As described above, the thermal recording material using the composite fine particles used in the present invention has less background fog due to pressure than the thermal recording material using the microcapsules containing the organic solvent and the dye precursor. For this reason,
The microcapsules using an organic solvent are easily destroyed by pressure, and the dye dissolved in the encapsulating organic solvent is extruded outside the microcapsules and reacts with a color-developing compound to develop color. Is. Since the composite fine particles used in the present invention do not contain a liquid organic solvent, the mechanical strength is considered to be stronger than that of the microcapsules.

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 60
C. or higher is preferable. If the melting temperature is lower than 60 ° C, the dye precursor may not be sufficiently dissolved in the polyvalent isocyanate compound, and uniform composite fine particles may not be produced.

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

In another example of the method for producing composite fine particles of the present invention, the first dye precursor and the polyvalent isocyanate compound-containing polymerization component are mixed and dissolved in a hydrophobic organic solvent having a boiling point of 20 to 100 ° C. , The obtained solution is emulsified and dispersed in water, and if necessary, a reactive substance such as polyamine is mixed with the emulsified dispersion, and the organic solvent is volatilized and removed by heating the emulsified dispersion, and then the above-mentioned. The polymerization component in the emulsion-dispersed particles is polymerized, thereby forming the composite fine particles containing the first dye precursor in a solid solution state in the matrix composed of the polyurea resin or the polyurethane-polyurea resin.

In this method, in order to sufficiently volatilize and remove the organic solvent from the emulsified dispersion, the conditions are experimentally determined in consideration of the type of solvent, the emulsification / dispersion conditions, the mixing ratio of the dye precursor and the solvent, and the like. Should be set. In general,
When a solvent having a boiling point of 50 ° C. or lower is used, the organic solvent can be volatilized and removed by using an open container and maintaining the emulsion dispersion at a desired concentration, preferably for 5 hours or more. After removing the organic solvent, in order to polymerize the polymerization components in the emulsified dispersed particles, the dispersion is heated to 60 to 95 ° C,
By holding at this temperature for 3 hours or longer, more preferably 5 hours or longer, the composite fine particles can be produced.

The organic solvent used for preparing the composite fine particles has a boiling point of 20 to 100 ° C., more preferably a boiling point of 20.
What is -80 degreeC and is hydrophobic is used. For example, such low-boiling point hydrophobic organic solvents include butyl chloride (boiling point 78 ° C.), ethylidene chloride (57 ° C. same), propyl chloride (46 ° C. same), methylene chloride (42 ° C. same),
It can be selected from ethyl acetate (77 ° C) and methyl acetate (57 ° C). Acetone (at 56 ° C. at the same temperature), methanol (at 65 ° C. at the same temperature), etc. are not preferable because the emulsified state of the obtained emulsion becomes unstable because they are compatible with water.

The polyvalent isocyanate compound used in the present invention forms a urea bond by reacting with water,
Polymerize. The polymer to be formed is polyurea or polyurethane-polyurea, and the polymer-forming material to be used may be a polyvalent isocyanate compound alone, or a polyvalent isocyanate compound and a polyol reactive therewith. Or a polyol adduct of a polyvalent isocyanate compound, a biuret body, a multimer such as an isocyanurate body. The dye precursor is dissolved in these polyisocyanate compounds, this solution is emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol, and further, if necessary, a reactive substance such as polyamine is mixed. By heating this emulsion dispersion, the polymer-forming material is polymerized to be polymerized. Thereby, composite fine particles composed of the dye precursor and the polymer substance can be formed.

Examples of the polyvalent isocyanate compound used as the 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-isocyanato-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, cyclohexylene Diisocyanates such as -1,2-diisocyanate and cyclohexylene-1,4-diisocyanate, triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate, There are tetraisocyanates such as 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate, and the like.

Examples of adducts of polyisocyanates and polyols include trimethylolpropane adduct of hexamethylene diisocyanate, trimethylolpropane adduct of 2,4-tolylene diisocyanate, trimethylolpropane adduct of xylylene diisocyanate, Isocyanate prepolymers such as hexanetriol adducts of tolylene diisocyanate can be used. In addition, these polyvalent isocyanate compounds, such as biuret form of hexamethylene diisocyanate and isocyanurate form of hexamethylene diisocyanate, can 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 a low viscosity and thus has good workability, and has a high solubility in a color forming dye precursor. Further, it is desirable in order to make a good 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 also be used in combination with other polyvalent isocyanate.

Examples of the polyol compound used as the polymer-forming raw material include ethylene glycol and 1,3-
Propanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,7
-Heptanediol, 1,8-octanediol, propylene glycol, 2,3-butanediol, 1,2-
Butanediol, 1,3-butanediol, 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, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, Aliphatic polyols such as glycerin, 1,4-di (2
-Hydroxyethoxy) benzene, 1,3-bis (2-
Condensation products of aromatic polyhydric alcohols such as (hydroxyethoxy) benzene and alkylene oxides, p-xylylene glycol, m-xylylene glycol, α, α ′
-Dihydroxy-p-diisopropylbenzene, 4,
4'-dihydroxydiphenylmethane, 2- (p, p '
-Dihydroxydiphenylmethyl) benzyl alcohol, 4,4'-isopropylidenediphenol, 4,
4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, ethylene oxide adduct of 4,4'-isopropylidene diphenol,
Examples thereof include a propylene oxide adduct of 4,4′-isopropylidenediphenol and an acrylate having a hydroxyl group in the molecule such as 2-hydroxyacrylate.

Of course, the polyisocyanate compound, the polyol compound and the like are not limited to the above compounds, and if necessary, two or more kinds may be used in combination.

Examples of the polyamine compound used as the polymer-forming raw material of the present invention include ethylenediamine, trimethylenediamine, tetramethylenediamine,
Pentamethylenediamine, hexamethylenediamine, p
-Phenylenediamine, m-phenylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, epoxy Examples thereof include amine adducts of compounds. Further, within the range that does not impair the object of the present invention,
Other polymeric substances can also be included.

In the present invention, the solute used in the production of the composite fine particles has a melting point of 40 in addition to the dye precursor for the purpose of increasing the color development sensitivity.
An organic compound having a boiling point of 150 ° C or higher and a boiling point of 150 ° C or higher can be used together. As the organic compound having a melting point of 40 ° C. or higher and 150 ° C. or lower and a boiling point of 150 ° C. or higher that can be used in the present invention, aromatic ketone compounds, aromatic ether compounds, and aromatic cyclic ester compounds can be preferably used. A specific example is shown below. The aromatic ketone compound is benzophenone, and the aromatic ether compound is 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 and the polyvalent isocyanate compound in the production of the composite fine particles is 20 to 2000 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. It is preferably present, and more preferably 100 to 500 parts by weight.

In the present invention, as the emulsifier (protective colloid agent) used for preparing the composite fine particles, polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as sulfo group-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene- Water-soluble synthetic polymer compounds such as maleic anhydride copolymer salts and their derivatives can be used. If necessary, a surfactant and a defoaming agent may be used at the same time. The amount of the emulsifier used in the preparation of the composite fine particles is not particularly limited, but generally it is preferably 1 to 300% by weight, and more preferably 3 to 100% by weight, based on the weight of the composite fine particles.

The average particle size of the fine composite particles containing the first dye precursor used in the present invention is preferably 0.6 to 5.0 μm. More preferably 1.2 to 3.0 μ
m. If the average particle size is smaller than 0.6 μm, the sensitivity becomes faster, and the red color developability in the state of mixed solid fine particles.
It is not preferable because it is difficult to distinguish the color development sensitivity from that of the dye precursor, and color mixing occurs at low temperature color development. In addition, the storage stability of the colored portion with respect to oil, plasticizer, etc. may deteriorate when the particle size is small. If the average particle diameter is larger than 5.0 μm, the color developing sensitivity is lowered, and it is not preferable because it is necessary to excessively apply energy to the thermal head in order to obtain the color of the composite fine particles.

The fine composite particles used in the present invention are known in addition to dye precursors, if necessary, UV absorbers, antioxidants, oil-soluble fluorescent dyes, release agents, and heat-sensitive recording materials. Such a sensitizer 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, red, blue, green, and yellow dye precursors may be appropriately mixed to form black color-forming composite fine particles.

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

Further, at the time of polymerizing in preparing the composite fine particles, a tin compound, a polyamide compound, as a reaction accelerator,
You may use together an epoxy compound, a polyamine compound, etc. In addition, when using a polyamine compound, it is preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not deteriorated.

In the present invention, when the dye precursor is used in the form of solid fine particles, the dye precursor is pulverized by various wet pulverizers such as a sand grinder, an attritor, a ball mill and a cobo mill using water as a dispersion medium. In addition to water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as sulfo group-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer salts and their derivatives. If necessary, it may be dispersed in a dispersion medium together with a surfactant, a defoaming agent, etc. to prepare a dispersion liquid, and this dispersion liquid may be used for the preparation of the coating material for forming the thermosensitive color developing layer.
Further, after the dye precursor is dissolved in an organic solvent, this solution is emulsified and dispersed in water by using the water-soluble polymer as a stabilizer, and then the organic solvent is evaporated from the emulsion to be used as solid fine particles of the dye precursor. You can also In any case, the average particle size of the dispersed particles of the dye precursor used in the solid fine particle state is preferably 0.2 to 3.0 μm, and more preferably 0.3 to 3.0 μm, in order to obtain appropriate color development sensitivity. 1.0μ
m.

In the multicolor thermosensitive recording material of the present invention, the red color forming 3- (N-isoamyl-N-ethylamino) -7-methyl which is present in the form of solid fine particles with the dye precursor contained in the composite fine particles. Fluorane, 3- (Nn-hexyl-N-ethylamino) -7-methylfluorane, 3
The ratio with at least one dye precursor selected from-(N-isobutyl-N-ethylamino) -7-methylfluorane is not limited, but is generally 100 weight% of the dye precursor contained in the composite fine particles. The amount of the dye precursor to be present in the form of solid fine particles is preferably 20 to 600 parts by weight, more preferably 50 to 300 parts by weight, based on parts.

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 generation of the background fog when the white paper is stored for a long period of time. Decolorization due to 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 by an increase in temperature and a property of contacting the dye precursor to develop a color thereof. Selected from those having. Typical developing compounds include 4-tert-butylphenol, 4-acetylphenol, 4-tert.
-Octylphenol, 4,4'-sec-butylidene diphenol, 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-).
Mention may be made of phenolic compounds such as hydroxyphenyl) sulfone.

Further, in the present invention, as compounds which can be used as the color-developing compound, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate,
Phenolic compounds such as 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 organic acidic substances such as salts of these phenolic compounds and aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum and calcium Are listed That.

In the present invention, it is particularly preferable to use a diphenylsulfone derivative containing a hydroxyl group in the molecule as a developer. Examples of such compounds include 4,4′-dihydroxydiphenyl sulfone,
2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone and the like can be mentioned. Such a color-developing compound has a property of excellent storage stability of a color image. It is speculated that this is due to the strong electron-withdrawing property of the sulfone group of the color-developing compound. Further, in order to form a color image which is hard to be erased even when contacted with oil or a plasticizer, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane or N- is used as a color-developing compound.
Preference is given to using (p-toluenesulfonyl) -N′-phenylurea.

The color-developing compound is usually 1 in total of the 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 kinds 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 recorded image. Examples of such an image stabilizer include 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-).
4-hydroxy-5-tert-butylphenyl) butane, 1,1-bis (2-methyl-4-hydroxy-5-
tert-butylphenyl) butane, 4,4 ′-[1,
4-Phenylenebis (1-methylethylidene)] bisphenol, and phenolic compounds such as 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol, 4-benzyloxyphenyl-4 ′
-(2-Methyl-2,3-epoxypropyloxy) phenyl sulfone, 4- (2-methyl-1,2-epoxyethyl) diphenyl sulfone, and 4- (2-ethyl-1,2-epoxyethyl) diphenyl Epoxy compounds such as sulfone, and those containing one or more 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 if necessary, two or more kinds of compounds can be used in combination.

In the present invention, a compound conventionally known as a sensitizer for heat-sensitive recording materials is used as the sensitizer which can be used for improving the color-developing sensitivity of heat-sensitive recording. For example, parabenzyl biphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate, 1,2-diphenoxyethane, 1,2-bis ( 3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-p oxalate
-Chlorobenzyl, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl, benzophenone and the like can be mentioned. Among these compounds,
When di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate are used as sensitizers, a sensitizing effect with less fog 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 the dye precursor is used in the form of solid fine particles to prepare a thermosensitive coloring layer. It may be mixed with this when the forming paint is prepared. It is also possible to dissolve these additives in a solvent and emulsify this in water using a water-soluble polymer compound as an emulsifier for use. Further, the image stabilizer and the sensitizer may be contained in the composite fine particles containing the dye precursor.

In the present invention, in order to improve the whiteness of the thermosensitive coloring layer and the uniformity of the image, a fine-particle 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, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica, etc. Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, polystyrene resin, etc. can be used. In order to prevent sticking and sticking on the thermal head, the oil absorption should be 50 ml / 1.
It is preferred to use more than 00 g of pigment. The amount of pigment blended is such that the color density is not reduced, that is,
It 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 the other component material constituting the thermosensitive coloring layer, and if necessary,
Cross-linking agents, waxes, metal soaps, colored dyes, colored pigments,
And fluorescent dyes can be used. 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 copolymer. Coalesce, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer,
Water-soluble polymer materials such as isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, and polyvinyl acetate, polyurethane, polyacrylic acid,
Emulsion of polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, etc., and water-insoluble polymer such as styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer, etc. 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, dimethylolurea compounds, aziridine compounds, blocked isocyanate compounds, and ammonium persulfate and ferric chloride, and chloride. Inorganic compounds such as magnesium, sodium tetraborate, and potassium tetraborate, or at least one crosslinkable compound selected from boric acid, boric acid triesters, boron-based polymers, etc., is used as the total solid content of the thermosensitive coloring layer 100 parts by weight. On the other hand, it is preferably used in the range of 1 to 10 parts by weight.

As the wax added to the thermosensitive coloring layer, 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, the sensitizing effect can be obtained without deteriorating the background fog.

The metal soap added to the thermosensitive coloring layer includes 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 complementary to the low temperature color tone in the thermosensitive color developing layer is preferably used for controlling the color tone of the recording material before printing. If necessary, an oil repellent, a defoaming agent, or an oil repellent may be further added to the heat-sensitive color-developing layer within a range that does not impair the effects of the present invention.
Various additives such as a viscosity modifier can be added. The thermosensitive coloring layer has a coating amount of 2 to 20 g / after drying on the support.
m ^2, more preferably is applied so as to 4~10g / 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, of course, even when it is provided on the surface of the support on which the thermosensitive coloring layer is not provided, it is applied before the thermosensitive coloring layer is applied. Is desirable for keeping the whiteness of the thermosensitive coloring layer high.

In the present invention, a resin cured by an electron beam or an ultraviolet ray may be provided as a protective layer on the thermosensitive coloring layer.
As an example of a resin cured with an electron beam, Japanese Patent Application Laid-Open No. 58-17 is available.
7392 and JP-A-58-177392. Into such a resin, a non-electron beam curable resin, a pigment, and additives such as a defoaming agent, a leveling agent, a lubricant, a surfactant, a plasticizer and the like can be appropriately added.
In particular, it is preferable to add pigments such as calcium carbonate and aluminum hydroxide, and lubricants such as waxes and silicon because they help prevent sticking to the thermal head. The resin layer cured by electron beams and ultraviolet rays,
It is coated on a support so that the coating amount after drying is 0.5 to 10 g / m ² . The coating amount is more preferably 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 conventionally known heat-sensitive recording materials may be provided on the heat-sensitive color developing layer. It is also possible to provide a resin layer cured with an electron beam or ultraviolet rays 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 the support so that the coating amount after drying is 0.5 to 10 g / m ² . The coating amount is more preferably 1 to 5 g / m ² .

In the present invention, it is possible to print with UV ink, flexo ink or the like. In this case, the printing may be performed on any layer such as the heat sensitive layer, the protective layer, the electron beam curable resin layer, or the ultraviolet curable resin layer.

The type, shape, size, etc. of the support material used in the present invention are not particularly limited, and include, for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast In addition to coated paper, glassine paper, resin laminated paper, polyolefin synthetic paper, synthetic fiber paper, non-woven 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 applications, it is desirable to use paper, but when the present invention is used for prepaid cards or magnetic commuter pass applications, a plastic substrate made of polyethylene terephthalate having a thickness of 100 μm or more is used. It is desirable to use materials, especially foamed substrates. Of course, a laminated base material such as paper can be used.

In the present invention, an undercoat layer which has been conventionally used in known heat-sensitive recording materials can also be used. Particularly when paper is used as a 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, it is possible to increase the color development sensitivity of the heat-sensitive color development layer thereon. Further, the inclusion of plastic pigments, hollow particles, foams, etc. in the undercoat layer is also effective in improving the color development sensitivity of the thermosensitive color development layer formed thereon.

In the present invention, in order to increase the added value of the multicolor thermosensitive recording material, it can be further processed to obtain a thermosensitive recording material having higher functions.
For example, adhesive paper, re-wet adhesive paper, delayed tack paper can be made by applying processing to the back surface with an adhesive, rewetting adhesive, delayed tack type adhesive, or magnetic processing can be applied to the back surface by applying magnetic processing. It can be a heat-sensitive recording material having a recordable layer. In particular, those that have been subjected to adhesive processing and magnetic processing are two-color heat-sensitive labels and
It is useful for applications such as color-sensitive magnetic tickets. Also, using the back side, thermal transfer paper, inkjet paper,
It is also possible to provide a double-sided recording paper by adding a function as carbonless paper, electrostatic recording paper, or xerographic paper. Of course, a double-sided heat-sensitive recording material can also be used.

As the method for forming each of the above layers on the support, 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 are used. Either may be used. Further, a back layer may be provided to suppress the penetration of oil or plasticizer from the back surface of the recording material or to control curl. The smoothing treatment of the thermosensitive 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.

[0071]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention.
Unless otherwise specified, “part” and “%” indicate “part 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 color forming dye precursor>
3-di-n-amylamino-6-as a black color-forming dye
6 parts of methyl-7-anilinofluorane was dissolved in 24 parts of dicyclohexylmethane-4,4′-diisocyanate heated to 120 ° C., and this solution was cooled to 25 ° C. Chemical industry, trade name: Gohsenol GM-14L) was gradually added to 250 parts of an aqueous solution, and a rotating speed was 700 using a homogenizer.
After emulsification and dispersion by stirring at 0 rpm, 100 parts of water was added to this emulsification dispersion to homogenize. The emulsified dispersion was heated to 90 ° C. and cured for 10 hours to prepare a dispersion of composite particles containing a black color forming dye precursor having an average particle diameter of 1.6 μm.

<Preparation of Dye Precursor in Solid Fine Particle State, Color-Developing Compound, Sensitizer Dispersion Liquid> Red color-forming dye precursor: 3- (N-isoamyl-N-ethylamyl) -7-methylfluorane 3 -(N-n-hexyl-N-ethylamyl) -7-methylfluorane 3- (N-isobutyl-N-ethylamyl) -7-methylfluorane 3-diethylamino-7-chlorofluorane Color developing compound: bis (3-allyl-4-hydroxyphenyl) sulfone sensitizer: di-p-methylbenzyl oxalate

The above dye precursor, the color-developing compound, and the sensitizer were separately mixed with polyvinyl alcohol at the following compounding ratios, and each mixture was subjected to vertical sand mill (Sand grinder manufactured by AIMEX Co., Ltd.). The powder was pulverized and dispersed so that the average particle diameter was 1.2 μm.

[0075]                 Amount of ingredients (parts by weight)   Each compound 40   Polyvinyl alcohol 10% liquid 40   (Polymerization degree 500, Saponification degree 90%)   Water 20

<Preparation of Pigment Dispersion> Pigment: Silica (Mizukasil P527, oil absorption 190 ml /
100 g of the product (manufactured by Mizusawa Chemical Industry Co., Ltd.) was mixed with sodium polyacrylate in the following blending ratio, and the mixture was dispersed with a Cowles disperser. Ingredient Amount (parts by weight) Silica 30 Sodium polyacrylate 0.7% 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 liquid, and an aqueous zinc stearate dispersion having a solid content of 21% (Z- was used as a lubricant dispersion). 7. Chukyo Yushi Co., Ltd. was prepared.

(2) Formation of Undercoat Layer The pigment dispersion and the adhesive liquid are mixed in a solid content ratio of 80:
20g, and this paint was applied to a high-quality paper (neutral paper) having a basis weight of 60g / m ² using a Mayer bar to give 7.0g.
/ M ² (dry) to form an undercoat layer.

(3) Formation of thermosensitive coloring layer The solid content is 30 parts by weight of the composite fine particles containing the black coloring dye precursor and the red coloring dye precursor 3- (N-isoamyl-N-ethylamyl) -7-methyl. 7 parts of fluoran, 25 parts of color-developing compound, 15 parts of sensitizer, 10 parts of pigment, 8 parts of adhesive, 5 parts of lubricant are mixed with each dispersion and melt to prepare a thermosensitive coloring layer coating material. did. This coating material was applied on the undercoat layer previously formed at a coating amount (dry) of 5.0 g / m ² and dried to form a thermosensitive coloring layer.

(4) Formation of protective layer The solid content ratio is 40 parts of pigment dispersion liquid, 55 of adhesive liquid.
Parts and 5 parts of the lubricant dispersion liquid were mixed to prepare a protective layer coating material. This coating solution was applied on the thermosensitive color forming layer previously formed at a coating amount (dry) 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 calendar so that the Bekk smoothness of the protective layer surface was 500 seconds, to obtain a multicolor heat-sensitive recording material of Example 1.

Example 2 Red color-forming dye precursor used in Example 1, 3- (N-
Instead of 7 parts of isoamyl-N-ethylamyl) -7-methylfluorane, a red-colorable dye precursor, 3- (N-
A multicolor thermosensitive recording material of Example 2 was obtained by the same method as in Example 1 except that 7 parts of n-hexyl-N-ethylamyl) -7-methylfluorane was used.

Example 3 Red color forming dye precursor used in Example 1, 3- (N-
Instead of 7 parts of isoamyl-N-ethylamyl) -7-methylfluorane, a red-colorable dye precursor, 3- (N-
A multicolor thermosensitive recording material of Example 3 was obtained by the same method as in Example 1 except that 7 parts of isobutyl-N-ethylamyl) -7-methylfluorane was used.

Comparative Example 1 Red color forming dye precursor used in Example 1, 3- (N-
Prepared in the same manner as in Example 1 except that 7 parts of a red color forming dye precursor, 3-diethylamino-7-chlorofluorane, was used in place of 7 parts of isoamyl-N-ethylamyl) -7-methylfluorane. Then, a multicolor heat-sensitive recording material of Comparative Example 1 was obtained.

A test was conducted on each of the heat-sensitive recording materials obtained by the above operation. For thermal recording, using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.), 256 lines under the conditions of 1 line recording time: 5 msec, sub-scanning line density: 8 lines / mm, applied energy per dot: 0.5 mJ. Solid printing was performed, and low temperature red color development was performed in low temperature printing. Separately, solid printing of 256 lines was performed under the conditions of 1 line recording time: 5 msec, sub-scanning line density: 8 lines / mm, applied energy per dot: 2.0 mJ, and high temperature black color development was performed in high temperature printing. .

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

Further, in order to examine the resistance to the plasticizer, a vinyl chloride wrap film (KMA manufactured by Mitsui Toatsu Co., Ltd.) was superposed on the heat-sensitive recording material after color development under a pressure of 20 g / cm ² , and the environment was kept at 40 ° C. and 90% RH. After being left under the condition for 24 hours, the degree of decolorization was examined. ○ means that there was no decoloring, and × means that decoloring was observed. The test results are shown in Table 1.

[0087]

[Table 1]

[0088]

As is clear from the results of Table 1, the present invention makes it possible to produce a multicolor thermosensitive recording material which has a clear red color at low temperature and has excellent storage stability. .

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41M 5/28-5/34 CAPLUS (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A support, two or more kinds of dye precursors formed on the support and different in color tone from each other, and a color-developing compound which reacts with the dye precursor under heating to develop a color. In a multicolor heat-sensitive recording material having a heat-sensitive color-forming layer containing, the heat-sensitive color-forming layer is (1) after emulsifying and dispersing in water a solution of a polyisocyanate compound as a solvent and a first dye precursor as a solute. The composite fine particles obtained by accelerating the polymerization reaction of the polyvalent isocyanate compound and (2) the first dye precursor are the second dye precursor that develops a different color tone, and the 3- (N -Isoamyl-N-ethylamino) -7-methylfluorane, 3-
At least 1 selected from (Nn-hexyl-N-ethylamino) -7-methylfluorane and 3- (N-isobutyl-N-ethylamino) -7-methylfluorane.
A multicolor heat-sensitive recording material, characterized in that it contains solid fine particles composed of one kind of low-temperature color-forming red-colorable dye precursor. 2. A support and a support formed on it and to each other.
Two or more kinds of dye precursors that develop different colors, and
A dye that reacts with this dye precursor under heating to develop a color.
Multicolor heat sensitive having a thermosensitive coloring layer containing a color compound
In the recording material, the thermosensitive coloring layer comprises (1) polyvalent
Polymerization component containing cyanate compound and 20-100 ° C
Using a hydrophobic organic solvent having a boiling point of
Emulsify and disperse a solution containing the solute as a solute in water.
The hydrophobic organic solvent is dispersed from the dispersed particles at a temperature of 20 to 55 ° C.
Volatilized to remove the polymerization component in the residual emulsified dispersion particles.
Composite fine particles obtained by combining
The first dye precursor is the second dye precursor that develops a different color tone.
As a precursor, 3- (N-isoamyl-N-ethylamido)
No) -7-methylfluorane, 3- (Nn-hexyl)
-N-ethylamino) -7-methylfluorane, 3-
(N-isobutyl-N-ethylamino) -7-methylphenyl
At least one low-temperature color-producing red selected from Luoran
Contain solid fine particles consisting of color-developing dye precursor
A multicolor thermosensitive recording material characterized by.