JPH10166729A - Thermosensible recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form thermosensible recording material for forming highly stable coloring images undergoing no yellowing due to light. SOLUTION: The thermosensible recording material having composite minute particles containing a dye precursor-benzophenone compound is manufactured in its thermosensible coloring layer such that a solute containing a dyeprecursor and a benzophenone compound is dissolved in solvent consisting of a polymerized component containing a multivalent isocyanate compound, and the solution is emulsion dispersed in water, and then a polymeric component in the emulsion dispersed particles is polymerized, or in the foregoing process, a water insoluble organic solvent having a melting point of 100 deg.C or lower is still contained in the solvent, and the emulsion dispersed liquid obtained is heated to volatilization remove the organic solvent before conducting polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material having excellent image stability after printing and little yellowing of a white paper portion due to light.

[0002]

2. Description of the Related Art Conventionally, a dye precursor and a color-developing compound which is brought into contact with the dye precursor under heating to form a color by utilizing the color-forming reaction are used. Thermal recording materials that form color images are widely known. Such thermosensitive recording materials are relatively inexpensive, the recording equipment is compact, and the maintenance thereof is easy, so that facsimile, word processor, various computers,
And as a recording medium for other uses.

[0003] With the expansion of such uses, the quality required for heat-sensitive recording materials has also been diversified. For example, high sensitivity and stable images have been demanded. However, the conventional heat-sensitive recording material has a drawback that the color image is erased by the influence of heat or moisture or by contact with oil, plasticizer, or the like.

On the other hand, the application of microcapsules to a heat-sensitive recording material has been known for a long time.
No. 9-70 describes encapsulating a solvent for a dye precursor in a liquid state at normal temperature. Examples of microencapsulation of a coloring component as a core substance are described in JP-A-57-12695 and JP-A-59-214.
No. 691, for example. However, 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. Further, since the dye precursor is dissolved in the solvent, there is a problem that photodecomposition is apt to occur and yellowing of a white paper portion is apt to occur.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a heat-sensitive recording material having a heat-sensitive coloring layer provided on a support. An object of the present invention is to provide a heat-sensitive recording material having excellent stability of a later image.

[0006]

The heat-sensitive recording material of the present invention comprises a support and a heat-sensitive coloring layer formed on one surface of the support and containing a dye precursor, a developer and a binder. Having the dye precursor, the solute containing the dye precursor is dissolved in a solvent composed of a polymerization component containing a polyvalent isocyanate compound, the solution is emulsified and dispersed in water, and the polymerization in the emulsified dispersion particles is performed. It is contained in the composite fine particles formed by polymerizing the components, and the solute further includes a benzophenone-based compound, whereby the benzophenone-based compound is contained in the composite fine particles. is there. In the heat-sensitive recording material of the present invention, the benzophenone-based compound is represented by the following formula (I):

Embedded image [Wherein, in the formula (I), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom, a hydroxyl group, or an alkyl group]. In the heat-sensitive recording material of the present invention, the benzophenone-based compound is more preferably 2-hydroxy-4-octoxybenzophenone. Further, the heat-sensitive recording material of the present invention has a support and a heat-sensitive coloring layer formed on one surface of the support, and the heat-sensitive coloring layer contains a dye precursor, a benzophenone-based compound, and a polyvalent isocyanate compound. The polymerization component is dissolved and mixed in a water-insoluble organic solvent having a boiling point of 100 ° C. or less, the resulting solution is emulsified and dispersed in water, and the emulsified dispersion is heated to volatilize and remove the organic solvent. Composite fine particles formed by polymerizing the polymerization component in the dispersed particles and containing the dye precursor and the benzophenone-based compound, and a developer,
And a binder.
In the heat-sensitive recording material of the present invention, the benzophenone-based compound is represented by the following formula (I):

Embedded image [However, in the formula (I), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom, a hydroxyl group, or an alkyl group]. In the heat-sensitive recording material of the present invention, it is more preferable that the benzophenone-based compound is 2-hydroxy-4-octoxybenzophenone.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the heat-sensitive recording material of the present invention,
The heat-sensitive coloring layer contains composite fine particles containing a dye precursor and a benzophenone-based compound, and the composite fine particles contain a dye precursor and a benzophenone-based compound in a solvent composed of a polymerization component containing a polyvalent isocyanate compound. It is produced by dissolving a solute, emulsifying and dispersing this solution in water, and polymerizing the polyvalent isocyanate compound-containing polymer component in the emulsified and dispersed particles. The composite fine particles are formed by using conventional microcapsules, for example,
Unlike microcapsules prepared by dissolving a dye precursor in a high-boiling solvent and enclosing the solution as described in JP-A-960 No. Has high resistance to breaking. Therefore, the heat-sensitive recording material of the present invention hardly generates pressure fog. Further, the composite fine particles of the present invention do not use a low-boiling organic solvent as described in JP-A-4-247987 and JP-A-4-101885 in the production process. .

The composite fine particles produced by the above method are
A polyurea resin or a polyurethane-polyurea resin and a dye precursor and a benzophenone-based compound, wherein the dye precursor and the benzophenone-based compound are mixed at a molecular level in a matrix made of the resin to form a solid solution. It is thought that it is doing. According to observation with an electron microscope, the appearance of the composite fine particles is substantially spherical, or a hemoglobin-like shape in which a part of the spherical surface forms a concave curved surface and is dented.

As described above, the heat-sensitive recording material containing the composite fine particles used in the present invention has a higher pressure than the heat-sensitive recording material in which microcapsules containing an organic solvent and a dye precursor are used. The characteristic that the occurrence of background fogging due to the above is small. The reason for this is that the shell wall of the microcapsule containing the organic solvent is easily broken by pressure, and the dye dissolved in the organic solvent contained therein is pushed out of the shell wall of the microcapsule. However, while this reacts with the color developing compound to form a color, the composite fine particles used in the present invention do not contain a liquid organic solvent, so their mechanical strength is stronger than that of microcapsules,
This is presumably because pressure fogging is unlikely to occur.

In the production of the composite fine particles used in the present invention, first, a solution is prepared by dissolving a dye precursor and a benzophenone compound in a polyvalent isocyanate compound. The dissolution temperature at this time is preferably 50 ° C. or higher, more preferably 90 ° C. or higher. If the dissolution temperature is lower than 50 ° C., the dissolution of the dye precursor and the benzophenone-based compound in the polyvalent isocyanate compound-containing polymerization component becomes insufficient, and uniform composite fine particles may not be obtained. The dissolution can also be performed under pressure using a pressure vessel.

In the preparation of the composite fine particles used in the present invention, the solution is cooled, if necessary, and then emulsified and dispersed in an aqueous medium containing a protective colloid such as polyvinyl alcohol and a surfactant. I do. The temperature at the time of emulsification and dispersion is not particularly limited, but is preferably set to a temperature at which a polymerization component, particularly a polyvalent isocyanate, and water do not rapidly react. Further, if necessary, a reactive substance such as a water-soluble polyamine is added to the emulsified dispersion system, and if necessary, the temperature of the emulsified dispersion system is increased, thereby polymerizing the polymerization component in the emulsified dispersion particles, and produced by polymerization. A composite fine particle comprising a matrix made of a polyurea resin or a polyurethane-polyurea resin, and a dye precursor and a benzophenone-based compound solidly dissolved in a molecular state therein is formed.

The composite fine particles of the present invention are obtained by dissolving and mixing a dye precursor, a benzophenone compound and a polyvalent isocyanate compound-containing polymerization component in a water-insoluble organic solvent having a boiling point of 100 ° C. or lower. After emulsifying and dispersing in water, and further mixing a reactive substance such as polyamine as necessary, the organic solvent is volatilized and removed by heating the emulsified dispersion, and then the polymerization component is polymerized to form a polyurethane-polyurea resin. Composite fine particles containing a dye precursor and the benzophenone compound in a base material made of

In this method, in order to sufficiently volatilize and remove the organic solvent, the conditions are set experimentally in consideration of the type of the solvent, the emulsification and dispersion conditions, the mixing ratio of the dye precursor and the solvent, and the like. It is good. Generally, 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, more preferably by holding the solvent for 5 hours or more. After the removal of the organic solvent, the dispersion is heated to 60 ° C. to 95 ° C. in order to polymerize the polymerization component, and the temperature is kept at this temperature for 3 hours or more, more preferably 5 hours or more, to produce composite fine particles. it can.

The organic solvent used for preparing the composite fine particles by the above method preferably has a boiling point of 100 ° C. or lower, more preferably 80 ° C. or lower, and is hydrophobic. For example, such low boiling hydrophobic (water-insoluble) organic solvents include butyl chloride (boiling point 78 ° C.), ethylidene chloride (57 ° C.), propyl chloride (46 ° C.), methylene chloride (42 ° C.), It can be selected from ethyl acetate (77 ° C) and methyl acetate (57 ° C). Acetone (56 ° C.) and methanol (65 ° C.) are not preferable because they are compatible with water and the resulting emulsion becomes unstable.

The dye precursor that can be contained in the composite fine particles used in the present invention is selected from leuco dye precursors such as triaryl, diphenylmethane, thiazine, spiro, lactam, and fluoran. Is preferred. Such a dye precursor, upon contact with a developer under heating, develops a color tone unique to each, and the color tone is not limited, and is black, red, magenta, or orange. , Blue, green, yellow and the like.

As the dye precursor giving black color, 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-anilinofluoran, 3-
[N- (3-ethoxypropyl) -N-methylamino)
-6-methyl-7-anilinofluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-
Di-n-butylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7
-(2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluoran, 2,4-dimethyl-6- (4-dimethylaminoanilino) fluoran , And 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-
Anilino fluoran or the like can be used.

In the present invention, the dye precursor giving black color is 3-di-n-amylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-yl, which has relatively good light fastness. Methyl-7- (2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluoran, 2,
It is preferably selected from 4-dimethyl-6- (4-dimethylaminoanilino) fluoran.

Dye precursors giving a red, magenta, or orange color development include 3,6-bis (diethylamino) fluoran-γ-anilinolactam and 3,6-bis (diethylamino) fluoran-γ- ( p-nitro)
Anilinolactam, 3,6-bis (diethylamino) fluoran-γ- (o-chloro) anilinolactam, 3-
Dimethylamino-7-bromofluorane, 3-diethylaminofluoran, 3-diethylamino-6-methylfluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-chlorofluoran, 3-
Diethylamino-7-bromofluorane, 3-diethylamino-7,8-benzofluoran, 3-diethylamino-6,8-dimethylfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino- 7-tert-butylfluoran, 3- (N-ethyl-N-tolylamino) -7-methylfluoran, 3
-(N-ethyl-N-tolylamino) -7-ethylfluoran, 3- (N-ethyl-N-isobutylamino)-
6-methyl-7-chlorofluoran, and 3- (N-
Ethyl-N-isoamylamino) -7,8-benzofluoran.

Dye precursors that provide red, magenta and orange color tones are further exemplified by 3-cyclohexylamino-6-chlorofluoran and 3-di-n-butylamino-6-methyl-7-bromo. Fluoran, 3-di-
n-butylamino-7,8-benzofluoran, 3-tolylamino-7-methylfluorane, 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.

As a dye precursor exhibiting red, magenta and orange color tone, 3,3'-bis (1-n-butyl-2-methylindol-3-yl)
Phthalide, 3,3'-bis (1-ethyl-2-methylindol-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].

When 3-diethylamino-7-chlorofluorane or 3-diethylamino-6-methyl-7-chlorofluorane is used as a red dye precursor,
For color correction of these dye precursors, it is desirable to use a mixture of dye precursors having different color tones, for example, 3,
3'-bis (1-n-butyl-2-methylindole-
By blending a dye precursor that develops a red-purple color tone, such as 3-yl) phthalide or 3,3′-bis (1-ethyl-2-methylindol-3-yl) phthalide, The color recording image can be made to have a color tone that makes the reddish color more intense.

As the dye precursor giving 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-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 above-mentioned dye precursor may be used alone, or two or more kinds thereof may be used as a mixture, and may be used in combination with a dye precursor which develops another color for color tone correction. Good.

The polyvalent isocyanate compound used in the present invention reacts with water and an amino compound,
A urea bond is formed to polymerize, and by reacting with a hydroxy compound, a urethane bond is formed to polymerize. The polymer substance formed from the polymerization component containing a polyvalent isocyanate is a polyurea resin or a polyurethane-
Polyurea resin. The polymerization component for forming the composite fine particles,
It may be composed solely of a polyvalent isocyanate compound, or may be a mixture of a polyvalent isocyanate compound and a polyol reacting therewith, or a multimer such as a polyol adduct of a polyvalent isocyanate compound, a biuret compound, an isocyanurate compound, or the like. It may be. In a solvent composed of these polyvalent isocyanate compound-containing polymerization components, a solute containing a dye precursor and a benzophenone compound is dissolved, and this solution is dissolved and contained a protective colloid substance such as polyvinyl alcohol or a surfactant as necessary. Emulsifying and dispersing in an aqueous medium, and further mixing a reactive substance (a part of a polymerization component) such as a polyamine, if necessary, into the emulsified dispersion system. To polymerize the polymerization component. As a result, it is possible to form composite fine particles in which the dye precursor and the benzophenone compound are dissolved in a matrix made of a polymer substance.

In the present invention, the polyvalent isocyanate compound used as a main component in the polymerization component for forming composite fine particles is, for example, 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, cyclohexylene-1,2-diisocyanate, and cyclohexylene-1 Diisocyanates such as 2,4-diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, and toluene-2,4,6
Triisocyanates such as triisocyanate, and 4,4'-dimethyldiphenylmethane-2,2 ',
And tetraisocyanates such as 5,5'-tetraisocyanate. Further, an adduct of a polyvalent isocyanate and a polyol used as a polymerization component, that is, an isocyanate prepolymer is, for example, a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of 2,4-tolylene diisocyanate, It can be selected from xylylene diisocyanate trimethylolpropane adduct, tolylene diisocyanate hexanetriol adduct, and the like.
Further, the polyvalent isocyanate compound used as the polymerization component, in addition to the above compounds, biuret and isocyanurate of the polyvalent isocyanate compound, for example, biuret of hexamethylene diisocyanate, and isocyanurate, etc. It can be preferably used as a polymerization component for forming composite fine particles.

In the present invention, it is particularly preferable to use dicyclohexylmethane-4,4'-diisocyanate having low viscosity and good workability as a polyvalent isocyanate compound as a polymerization component for forming composite fine particles. Of course, this can be used in combination with another polyvalent isocyanate compound.

In the polymerization component for forming composite fine particles, examples of the polyol compound used together with the polyvalent isocyanate compound include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 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, 1,1,1-trimethylolpropane, hexanetriol, penta Erythritol, and aliphatic polyols such as glycerin,
Aromatic polyhydric alcohol-alkylene oxide condensation products such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-bis (2-hydroxyethoxy) benzene, 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'-dihydroxydiphenylsulfone,
4,4'-dihydroxydiphenyl sulfide, 4,
Examples include 4'-isopropylidene diphenol-ethylene oxide adduct, 4,4'-isopropylidene diphenol-propylene oxide adduct, and acrylates having a hydroxyl group in the molecule such as 2-hydroxyacrylate. .

Of course, the polyvalent isocyanate compound, the polyol compound and the like are not limited to the above compounds, and they may be used alone or as a mixture of two or more. Is also good.

The polyamine compound used together with the polyvalent isocyanate compound in the polymerization component for forming composite fine particles of the present invention includes, for example, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine. , M-phenylenediamine, piperazine,
2-methylpiperazine, 2,5-dimethylpiperazine,
Examples thereof include 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, and amine adducts of epoxy compounds. Furthermore, a tin compound, a polyamide compound, and / or an epoxy compound may be mixed and used with the polymerization component as long as the object of the present invention is not impaired. In addition, when using a polyamine compound, it is more preferable to use an aliphatic polyamine compound which has an advantage that light resistance is not reduced.

The benzophenone compound used in the present invention suppresses the dye precursor from being decomposed by ultraviolet rays and yellowing white paper. A hindered amine compound generally widely used as an ultraviolet absorber easily reacts with a polymerization component, particularly a polyvalent isocyanate compound, and causes a problem of inhibiting the formation of composite fine particles. Further, when an ultraviolet absorber composed of a benzotriazole-based compound or a cyanoacrylate-based compound is used, the effect of suppressing the decomposition of the dye precursor by ultraviolet rays is insufficient, so that it is impossible to prevent yellowing of the white portion.

In the present invention, among the benzophenone compounds, the following formula (I):

Embedded image It is more preferable to use the compound represented by In the formula (I), R ¹ = hydrogen or an alkyl group, R ² =
Hydrogen, hydroxyl, or alkyl. The benzophenone-based compound used in the present invention includes 2,4-dihydroxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2'-di-hydroxy-4-.
It is preferable to be selected from methoxybenzophenone and the like. Particularly, when 2-hydroxy-4-octoxybenzophenone is used, the effect of improving yellowing is large, and the coloring sensitivity is also improved. Benzophenone compounds are dye precursor 1
It is preferable to use 0.1 to 10 parts by weight based on parts by weight. If the amount of the benzophenone-based compound is less than 0.1 part by weight, a sufficient yellowing improvement effect cannot be obtained,
If the amount exceeds 10 parts, the stability of the color image after printing will be reduced.

In the present invention, in order to improve the coloring sensitivity of the thermosensitive coloring layer, the solute at the time of preparing the composite fine particles has a melting point of 4 in addition to the dye precursor and the benzophenone compound.
A fusible organic compound having a temperature of 0 ° C. or more and 150 ° C. or less and a boiling point of 150 ° C. or more can be contained. Such a fusible organic compound is a sensitizer and includes 1,2-di (m-tolyloxy) ethane, 1,2-diphenoxyethane, and 1- (4-methoxyphenoxy) -2- (2- It is preferred to be selected from methylphenoxy) ethane and aromatic cyclic ester compounds such as 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 used in the production of the composite fine particles is such that the polyvalent isocyanate compound is 20 to 2,000 parts by weight based on 100 parts by weight of the dye precursor. Preferably, it is more preferably 100 to 500 parts by weight. If the amount of the polyvalent isocyanate compound used is less than 20 parts by weight, the background fog and the storage stability may be poor due to the pressure of the heat-sensitive recording material. On the other hand, if the amount of the polyvalent isocyanate compound exceeds 2,000 parts by weight, the color sensitivity of the resulting heat-sensitive recording material may be insufficient.

In the present invention, emulsifiers used for preparing the composite fine particles include polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and modified polyvinyl alcohol, such as sulfonate-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, and styrene-maleic anhydride. Water-soluble synthetic polymer compounds such as polymer salts and derivatives thereof, and various surfactants can be used. If necessary,
An antifoaming agent or the like may be used. The amount of the emulsifier used in the preparation of the composite fine particles is not particularly limited, but is generally preferably from 0.5 to 200% by weight, more preferably from 3 to 100% by weight, based on the weight of the composite fine particles. .

The average particle diameter of the dye precursor-containing composite fine particles used in the present invention is preferably from 0.05 to 2.0 μm, more preferably from 0.1 to 1.0 μm. If the average particle size is smaller than 0.05 μm, the storage stability of the color image to oil, plasticizer, and the like may be insufficient. On the other hand, if the average particle size is larger than 2.0 μm, the coloring sensitivity of the obtained composite fine particles is reduced, so that it is necessary to apply excessive energy to the thermal head in order to form the composite fine particles. Sometimes.

When the demand for storage stability and image stability after printing of the heat-sensitive recording material obtained in the present invention is not so high, the dye precursor having the same color tone as the dye precursor containing the dye precursor together with the composite fine particles containing the dye precursor is used. Solid fine particles can be contained in the thermosensitive coloring layer.

The heat-sensitive recording material of the present invention includes, as one embodiment, a heat-sensitive recording material capable of developing multiple colors. Such a multicolor image recording material comprises a heat-sensitive coloring layer comprising a composite fine particle containing a first dye precursor which develops black and solid fine particles (powder) of a second dye precursor which develops a color tone different from black. It is desirable that it be contained in. Such a multicolor image recording material can record two-color images having different tones by a low-temperature coloring operation and a high-temperature coloring operation, and the low-temperature coloring tone is a solid fine particle of the second dye precursor. The high-temperature color tone is a mixed color tone of the color tone of the first dye precursor present in the composite fine particles and the color tone of the second dye precursor. By using a black color-forming dye precursor as the first dye precursor, it is possible to make the high-temperature color tone black even if color mixing occurs due to color development of the second dye precursor. In order to make the high-temperature color tone closer to pure black, the third dye precursor having a color tone different from the low-temperature color tone of the second dye precursor together with the black dye-forming first dye precursor in the composite fine particles. It is more preferable to include a dye precursor that develops a third color tone that is complementary to the low-temperature color tone. For example, when the low-temperature color tone of the second dye precursor is red, the high-temperature color tone is made closer to pure black by incorporating the third dye precursor that develops blue or green into the composite fine particles. be able to.

The dye precursor contained in the composite fine particles is 2
It may be a mixture of more than one kind. For example, red, blue,
By appropriately blending green and yellow dye precursors, composite fine particles having black coloring properties can be obtained.

When the dye precursor is used in the form of solid fine particles (powder), 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. Water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as sulfone group-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer salts and derivatives thereof, Further, if necessary, the dispersion may be dispersed in a dispersion medium together with a surfactant, an antifoaming agent, and the like to obtain a dispersion, and this dispersion can be used for preparing a coating material for forming a thermosensitive coloring layer.

When preparing the fine particles of the dye precursor (fine powder), the dye precursor is dissolved in an organic solvent, and this solution is emulsified and dispersed in water using the water-soluble polymer as a stabilizer. The dye precursor may be turned into solid fine particles by evaporating the organic solvent from the liquid. In any case, the average particle diameter of the dispersed particles of the dye precursor is preferably from 0.2 to 3.0 μm, more preferably from 0.3 to 1.0 μm, in order to obtain appropriate color sensitivity. is there.

In the heat-sensitive recording material of the present invention, the type of the color-developing compound contained in the heat-sensitive coloring layer is not particularly limited.
Alternatively, it is selected from those having a dissolving property and a property of contacting with the dye precursor to form a color. Representative color developing phenol compounds useful in the present invention include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol,
4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,
4'-cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
4,4'-dihydroxydiphenyl sulfide, 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-
Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxybenzophenone, 4,4'-dihydroxydiphenyl ether, and bis (3-allyl-
Phenolic compounds such as 4-hydroxyphenyl) sulfone can be mentioned.

The organic carboxylic acid compounds usable as the color developing compound in the present invention further include dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate and 4-hydroxybenzoic acid-sec. -Butyl, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 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, and 3,5-di-ter
Aromatic carboxylic acids such as t-butylsalicylic acid and the like can be used. In addition, the phenolic compound and the carboxylic acid compound may form a salt with a polyvalent metal such as zinc, magnesium, aluminum, and calcium.

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

The color-developing compound is usually preferably used in an amount of 30 to 500 parts by weight, more preferably 50 to 300 parts by weight, based on 100 parts by weight of the composite fine particles. Of course, if necessary, two or more types of color developing compounds can be used in combination.

In the present invention, an image stabilizer may be used mainly for improving the storage stability of a color-recorded 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 these may be used alone or in combination of two or more.

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-p-chlorobenzyl oxalate, , 2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl, benzophenone and the like. Among these compounds, when di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate are used as sensitizers, a sensitizing effect with less fogging can be obtained.

In the present invention, in order to add additives such as a color-developing compound, an image stabilizer and a sensitizer to the heat-sensitive coloring layer, they are finely pulverized and dispersed in water. What is necessary is just to mix a dispersion liquid at the time of preparation of a thermosensitive coloring layer forming coating material. Further, those obtained by dissolving these additives in a solvent and emulsifying the same in water using a water-soluble polymer compound as an emulsifier can also be used. Further, the image stabilizer and the sensitizer may be contained in the resin matrix 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 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 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 preferably such that the coloring density is not reduced, that is, 50% by weight or less based on the total solid weight of the thermosensitive coloring layer.

In the present invention, the thermosensitive coloring layer contains a binder, and may further contain a crosslinking agent, a wax, a metal soap, a colored dye, a colored pigment, a fluorescent dye, and the like, if necessary. As the binder, for example, polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylate copolymer Water-soluble polymer materials such as acrylamide-acrylate-methacrylate copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and derivatives thereof, polyacetic acid Vinyl, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate Emulsion coalescence and the like, as well styrene - butadiene copolymer, and styrene - butadiene - such as latex of water-insoluble polymers such as acrylic copolymers can be used. Generally, the content of the binder is preferably 1 to 30% by weight based on the total weight of the thermosensitive coloring layer.

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 An inorganic compound such as magnesium, sodium tetraborate, potassium tetraborate, or at least one crosslinkable compound selected from boric acid, boric acid triesters, boron-based polymers, and the like, and a total solid content of 100% by weight of the thermosensitive coloring layer It is preferably used in an amount of 1 to 10 parts by weight based on parts.

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. Further, in the case of a multicolor heat-sensitive recording material, a color dye or a color pigment having a color tone having a complementary color to the low-temperature color tone is contained in the heat-sensitive color layer in order to adjust the color tone of the white paper part. Is preferred. Further, if necessary, within a range that does not impair the effects of the present invention, an oil repellent in the thermosensitive coloring layer,
Various additives such as an antifoaming agent and a viscosity modifier can be added. The heat-sensitive coloring layer has a coating amount of 2 to 2 after drying on the support.
20 g / m ^2, and more preferably is applied so as to 4~10g / m ^2.

In the present invention, a protective layer as used in known thermosensitive recording materials can be provided on the thermosensitive coloring layer. Such a protective layer usually contains a water-soluble polymer material and a pigment. As the water-soluble polymer material and the pigment, the materials exemplified as the components of the thermosensitive coloring layer can be used. At this time, it is more preferable to add a crosslinking agent to impart water resistance to the protective layer. Further, a resin layer cured by an electron beam or a resin layer cured by an ultraviolet ray can be used as the protective layer. It is more preferable that the protective layer containing a resin cured by an electron beam or ultraviolet rays as a main component is provided on the protective layer containing a water-soluble polymer material and a pigment. The coating amount of the protective layer after drying is 0.5 to
10 g / m ^2, more preferably is coated on a support so as 1 to 5 g / m ^2.

The heat-sensitive recording material of the present invention can be printed with UV ink, flexo ink or the like. in this case,
The 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.

There are no particular restrictions on the type, shape, dimensions, etc. of the support material used in the present invention. For example, high quality paper (acid paper, neutral paper), medium paper, coated paper, art paper, cast paper, etc. It can be appropriately selected from coated paper, glassine paper, resin laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film and the like, as well as various transparent supports.

In the present invention, an undercoat layer used in a conventional heat-sensitive recording material can be used. In particular, when paper is used as a support, it is preferable to provide an undercoat layer between the support and the thermosensitive coloring layer. The undercoat layer is
By using a pigment having a high porosity such as silica or calcined kaolin, 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.

Examples of the method for forming each of the above layers on the support include 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, it is also possible to suppress the penetration of oil or plasticizer from the back surface of the recording material, or to provide a back layer for curl control on the back surface of the support. 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.

[0059]

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 Support Canadian Standard Freeness (CSF) 480
to 100 parts of bleached hardwood bleached kraft pulp
Talc 10 parts, petroleum resin sizing agent 0.3 parts, sulphate ban
To prepare a papermaking raw material by adding 0.5 parts
Basis weight 64g / m ^TwoPaper was made. Size paper on this base paper
And apply a 2% solution of polyvinyl alcohol
Was. 0.8 g / m^Two(Dry). this
Oken-type smoothness (JT
Smoothing processing so that APPI No. 5) becomes 50 seconds
To form a support.

(2) Preparation of Materials Used for Undercoat Layer and Thermosensitive Coloring Layer <Preparation of Composite Fine Particle Dispersion Containing Black Coloring Dye Precursor > Containing Black Coloring Dye Precursor and Benzophenone Compound
And 3-di -n- Amiruamino 6-methyl-7-anilinofluoran 5 parts as a composite particle dispersion black coloring dye precursor, a 2-hydroxy-4-octoxybenzophenone 1 part benzophenone compounds Was dissolved in 15 parts of dicyclohexylmethane-4,4'-diisocyanate heated to 120 ° C., and the solution was cooled to 35 ° C., and then cooled to 20% of the same temperature.
The solution was gradually added to 100 parts of an aqueous solution of a sulfone group-modified polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Goselan L-3266), and the number of revolutions was 120 using a homogenizer.
The mixture was emulsified and dispersed by stirring at 00 rpm. 150 parts of water was added to the emulsified dispersion to homogenize it, and the emulsified dispersion was
C. and heated for 10 hours. A composite fine particle dispersion containing a black color-forming dye precursor having an average particle diameter of 0.4 μm and a benzophenone-based compound was obtained.

Black chromogenic dye precursor and benzophenone
Compound Fine Particle Dispersion Containing Compound Except for using 2,4-dihydroxybenzophenone as the benzophenone-based compound, the same formulation and emulsification as for the composite fine particle dispersion containing the black chromogenic dye precursor and the benzophenone-based compound are used, except that According to the method and the polymerization method, a composite fine particle dispersion containing a black chromogenic dye precursor having an average particle diameter of 0.5 μm and a benzophenone-based compound was prepared.

Black color-forming dye precursor and benzophenone-based
Compound Fine Particle Dispersion Containing Compound Except that 2-hydroxy-4-methoxybenzophenone was used as the benzophenone-based compound, the same formulation as the composite fine particle dispersion containing the black color-forming dye precursor and the benzophenone-based compound was used. According to the emulsification method and the polymerization method, a composite fine particle dispersion containing a black chromogenic dye precursor having an average particle diameter of 0.5 μm and a benzophenone-based compound was prepared.

Black color-forming dye precursor and benzophenone-based
Compound Fine Particle Dispersion Containing Compound Except for using 2,2 ', 4,4'-tetrahydroxybenzophenone as the benzophenone-based compound, the other is the composite fine particle containing the black color-forming dye precursor and the benzophenone-based compound. Same formulation as dispersion, emulsification method,
According to the polymerization method, a composite fine particle dispersion containing a black chromogenic dye precursor having an average particle diameter of 0.5 μm and a benzophenone-based compound was prepared.

Black color-forming dye precursor and benzophenone-based
Compound Fine Particle Dispersion Containing Compound 5 parts of 3-di-n-amylamino-6-methyl-7-anilinofluoran and 1 part of 2-hydroxy-4-octoxybenzophenone as black color-forming dye precursors Dissolve in 30 parts of methylene chloride, and then add 12 parts of a 1: 3 adduct of trimethylolpropane and xylene diisocyanate (manufactured by Takeda Pharmaceutical Co., Ltd., trademark: Takenate D-110N, diluting solvent: ethyl acetate, concentration 75%). This mixture was gradually added to 100 parts of a 20% aqueous solution of a sulfone group-modified polyvinyl alcohol in water, and emulsified and dispersed using a homogenizer with stirring at a rotation speed of 12,000 rpm. Next, the temperature of the emulsified dispersion was raised to 45 ° C., and the mixture was stirred for 10 hours to evaporate methylene chloride and ethyl acetate. Then 80 ° C
And a curing reaction is performed for 3 hours.
m, a composite fine particle dispersion containing a black color-forming dye precursor and a benzophenone-based compound was prepared.

Composite fine particle dispersion containing black color-forming dye precursor
Except that the liquid benzophenone-based compound is not added, the same formulation, emulsification method, and polymerization method as for the composite fine particle dispersion containing the black chromophoric dye precursor and the benzophenone compound, the black chromophore having an average particle diameter of 0.5 μm is used. A dye precursor-containing composite fine particle dispersion was prepared.

Including a black color-forming dye precursor and an ultraviolet absorber
Except for using 2- (2-hydroxy-3-t-butyl-5-methylphenyl) -5-chlorobenzotriazole instead of the benzophenone-based compound dispersion, By the same formulation, emulsification method, and polymerization method as the composite fine particle dispersion containing the benzophenone-based compound and the polymer, a composite fine particle dispersion containing a black chromogenic dye precursor having an average particle diameter of 0.5 μm and an ultraviolet absorber was prepared. .

<Dye precursor in the form of solid fine particles (powder),
Preparation of Developing Compound and Additive Dispersion> Black Color Dye Precursor: 3-bis-n-amylamino-6
-Methyl-7-anilinofluoran Color-developing compound: bis (3-allyl-4-hydroxyphenyl) sulfone benzophenone-based compound: 2-hydroxy-4-octoxybenzophenone

Each of the above-mentioned dye precursor, color-developing compound and benzophenone-based compound is separately mixed with polyvinyl alcohol at the following mixing ratio, and each mixture is mixed with a vertical sand mill (manufactured by Imex Co., Ltd., sand grinder). )
Pulverized so that the average particle diameter becomes 1.2 μm,
Dispersed.

Component amount (parts by weight) Dye precursor, color developing compound or additive 40 Polyvinyl alcohol 10% liquid 40 (Polymerization degree 500, saponification degree 90%) Water 20

<Preparation of Pigment Dispersion> Pigment: silica (trade name: Mizukasil P527, oil absorption 19)
0 ml / 100 g, manufactured by Mizusawa Chemical Industry Co., Ltd.) and sodium polyacrylate were mixed at the following mixing ratio, and this mixture was dispersed with a Cowles disperser. Component amount (parts by weight) Silica 30 0.7% sodium polyacrylate solution 70

Separately, as a binder solution, a solid content concentration of 1
A 0% aqueous solution of polyvinyl alcohol (NM11Q, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and an aqueous dispersion of zinc stearate having a solid content of 21% (Z-7,
Chukyo Yushi Co., Ltd.) was prepared.

(3) Formation of Undercoat Layer The above-mentioned pigment silica dispersion and the above-mentioned adhesive liquid are blended so that the blending ratio of solids is 85:15, and this paint is coated on one side of a support using a Mayer bar. The coating amount is 7.0 g / m
² (dry) to form an undercoat layer.

Example 1 A thermosensitive coloring layer coating prepared by mixing at the following mixing ratio (solid content) was coated on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. Then, the resultant was dried to form a thermosensitive coloring layer, and a thermosensitive recording material was obtained. Component amount (parts by weight) Composite fine particle dispersion containing a black color-forming dye precursor and a benzophenone-based compound 40 Color developing component dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

Example 2 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount of 5.0 g / m ² (dry). After drying, a thermosensitive coloring layer was formed to obtain a thermosensitive recording material. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor and benzophenone-based compound 40 Color developing compound dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

Example 3 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. After drying, a thermosensitive coloring layer was formed to obtain a thermosensitive recording material. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor and benzophenone-based compound 40 Color developing compound dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

Example 4 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount of 5.0 g / m ² (dry). After drying, a thermosensitive coloring layer was formed to obtain a thermosensitive recording material. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor and benzophenone-based compound 40 Color developing compound dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

Example 5 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied on the undercoat layer of the support at a coating amount of 5.0 g / m ² (dry). And dried to form a thermosensitive coloring layer,
A heat-sensitive coloring layer was formed to obtain a heat-sensitive recording material. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor and benzophenone-based compound 40 Color developing compound dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

COMPARATIVE EXAMPLE 1 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was coated on the undercoat layer of the support at a coating amount of 5.0 g / m ² (dry). And dried to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Component amount (parts by weight) Black color-forming dye precursor dispersion 40 Color-developing compound dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

COMPARATIVE EXAMPLE 2 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was coated on the undercoat layer of the support at a coating amount of 5.0 g / m ² (dry). And dried to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor 40 Color developing compound dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

COMPARATIVE EXAMPLE 3 A thermosensitive coloring layer paint prepared by mixing at the following compounding ratio (solid content) was applied on the undercoat layer of the support at a coating amount (dry) of 5.0 g / m ^2. And dried to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor and ultraviolet absorber 40 Color developing compound dispersion 40 Pigment dispersion 30 Lubricant dispersion 5

COMPARATIVE EXAMPLE 4 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was coated on the undercoat layer of the support at a coating amount of 5.0 g / m ² (dry). And dried to form a thermosensitive coloring layer,
A heat-sensitive recording material was obtained. Component amount (parts by weight) Composite fine particle dispersion containing black color-forming dye precursor 40 Developer compound dispersion 40 Ultraviolet absorber dispersion 10 Pigment dispersion 5 Lubricant dispersion 5

In each of Examples 1 to 5 and Comparative Examples 1 to 4, the heat-sensitive recording materials obtained by the above operations
Was subjected to a smoothing treatment using a super calender, and the Oken-type Beck smoothness of the surface of the heat-sensitive coloring layer was controlled at 1000 seconds.

Each of the above heat-sensitive recording materials subjected to the smoothing treatment was subjected to the following tests. In the thermal recording test, using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.), one-line recording time: 4 msec, sub-scanning line density: 8 lines / mm,
Applied energy per dot: 25 under the condition of 2.0 mJ
Solid printing of 6 lines was performed.

The color product thus obtained was
The recorded image density was measured. The recorded image density was determined by measuring the coloring density of the recorded image portion and the blank portion of the above recorded sample with a Macbeth densitometer (manufactured by Macbeth, model number: RD-914). Further, the easiness of occurrence of yellowing of the white paper portion by light, the easiness of color development by pressure, and oil resistance were evaluated by the following methods. In the white paper yellowing test, the test sample was irradiated with a 5,000 Lux fluorescent lamp for 100 hours, and the white paper after irradiation was measured with a color difference meter (SM Color Computer, manufactured by Suga Test Instruments Co., Ltd.) to determine the degree of yellowing. evaluated. If the b value of the test white portion is 5.0 or less, it can be said that it is at a practical level.

In the test of the ease of color development by pressure, each sample was rubbed with a nail and the degree of color development was visually evaluated. ○ indicates that little color was formed, and X indicates that clear color was seen. In the oil resistance test, the above recorded sample was placed in salad oil at 20 ° C. for 12 hours.
After soaking for a period of time, the color density of the recorded image area was measured with a Macbeth densitometer, and the preservation ratio (%) = [(density after soaking) /
(Concentration before immersion)] × 100 was evaluated. Save rate is 50
% Or more, the image is at a readable level, and there is no practical problem.

Table 1 shows the test results.

[0088]

[Table 1]

[0089]

As is clear from the results shown in Table 1, the heat-sensitive recording material of the present invention is hardly discolored by light, has excellent image stability after printing, and has high practicality. is there.

Claims (6)

[Claims] 1. A support comprising: a support; and a thermosensitive coloring layer formed on one surface of the support, wherein the thermosensitive coloring layer comprises a polyvalent isocyanate compound containing a solute containing the dye precursor and a benzophenone-based compound. Is dissolved in a solvent composed of a polymerization component containing, and this solution is emulsified and dispersed in water, and the polymerization component in the emulsified and dispersed particles is formed by polymerization, and a composite containing the dye precursor and the benzophenone-based compound is formed. A heat-sensitive recording material comprising fine particles, a color developer, and a binder. 2. The benzophenone-based compound is represented by the following formula (I): [Wherein, in the formula (I), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom, a hydroxyl group or an alkyl group]. Thermal recording material. 3. The heat-sensitive recording material according to claim 1, wherein the benzophenone-based compound is 2-hydroxy-4-octoxybenzophenone. 4. A support having a support and a thermosensitive coloring layer formed on one surface of the support, wherein the thermosensitive coloring layer is a polymer containing a dye precursor, a benzophenone compound and a polyvalent isocyanate compound. The components are dissolved and mixed in a water-insoluble organic solvent having a boiling point of 100 ° C. or less, the resulting solution is emulsified and dispersed in water, and the emulsified dispersion is heated to volatilize and remove the organic solvent. A heat-sensitive recording material characterized by comprising composite fine particles formed by polymerizing the polymerization component in particles and containing the dye precursor and the benzophenone-based compound, a developer, and a binder. 5. The benzophenone compound according to the following formula (I): The method according to claim 4, wherein R ¹ represents a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom, a hydroxyl group, or an alkyl group in the formula (I). Thermal recording material. 6. The benzophenone-based compound is 2-hydroxy-4-octoxybenzophenone.
Or the heat-sensitive recording material according to 5.