JPH1035111A - Thermal recording material - Google Patents

Abstract

(57) [Summary] [Problem] To provide a heat-sensitive recording material excellent in storability [Solution] After emulsifying and dispersing a solution containing a polyvalent isocyanate compound as a solvent and a dye precursor as a solute in water in a thermosensitive coloring layer, It contains composite fine particles produced by accelerating the polymerization reaction of a polyvalent isocyanate compound, and contains a bis (hydroxyphenyl) ether compound, a bis (hydroxyphenyl) methane compound, 1,1′-
A heat-sensitive recording material containing at least one color-developing compound selected from bis (hydroxyphenyl) ethane-based compounds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording material containing dye precursor-containing composite fine particles and a specific substance as a color-developing compound, has excellent image stability after printing, and has little white paper fog.

[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 for obtaining a color image are widely known. Such heat-sensitive recording materials are relatively inexpensive, have compact recording devices, and are easy to maintain, so that they are widely used as recording media for facsimile machines, word processors, various computers, and other applications. ing.

[0003] With the expansion of such uses, the quality required for the heat-sensitive recording material has also been diversified. For example, high sensitivity, image stabilization, and the like have been demanded. However,
Conventional heat-sensitive recording materials have the drawback that the color image is erased by the influence of heat or humidity, oil, plasticizer, and 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 encapsulation of a solvent in a liquid state at normal temperature. An example in which a color-forming component is microencapsulated as a core substance is disclosed in JP-A-57-12.
No. 695 and JP-A-59-214691. However, when an oil-based liquid for dissolving the dye precursor is contained in the microcapsules, there is a problem that the capsules are destroyed due to pressure or frictional rubbing, and that color development easily occurs.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording material comprising a support and a thermosensitive coloring layer provided thereon.
An object of the present invention is to provide a thermosensitive recording material which has little white paper fogging and is excellent in image stability after printing.

[0006]

According to the present invention, there is provided a heat-sensitive recording material comprising a heat-sensitive coloring layer provided on a support, wherein the heat-sensitive coloring layer comprises a solution containing a polyvalent isocyanate compound as a solvent and a dye precursor as a solute. After emulsifying and dispersing in water, contains composite fine particles produced by accelerating the polymerization reaction of the polyvalent isocyanate compound, and further comprises a bis (hydroxyphenyl) ether compound, a bis (hydroxyphenyl) methane compound, A heat-sensitive recording material comprising at least one color-developing compound selected from 1,1'-bis (hydroxyphenyl) ethane-based compounds.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the heat-sensitive recording material of the present invention, a solution containing a polyvalent isocyanate compound as a solvent and a dye precursor as a solute is emulsified and dispersed in water to promote the polymerization reaction of the polyvalent isocyanate compound. Thus, the composite fine particles produced are contained in the thermosensitive coloring layer. The composite fine particles dissolve a dye precursor described in Japanese Patent Publication No. 4-4960 in a high-boiling solvent and, unlike microcapsules containing the solution, do not contain an organic solvent and thus are destroyed by pressure. Absent. Therefore, the thermal recording material of the present invention hardly generates pressure fog. In the production process, it is not necessary to use a low-boiling organic solvent as described in JP-A-4-247787 and JP-A-4-101885.

The composite fine particles used in the present invention are composed of polyurea or polyurethane-polyurea, and a dye precursor, and are a solid solution in which the dye precursor and a polymer substance are mixed at a molecular level. It is thought that there is. The appearance of the composite fine particles is almost spherical when observed with an electron microscope, or is in the shape of hemoglobin with a hollow center.

As described above, the thermal recording material using composite fine particles used in the present invention has less background fogging due to pressure than the thermal recording material using microcapsules containing an organic solvent and a dye precursor. The reason for this is that in microcapsules using organic solvents, the wall is easily broken by pressure, and the dye dissolved in the contained organic solvent is extruded out of the microcapsules and reacts with the color developing compound. On the other hand, it is considered that the composite fine particles used in the present invention do not contain a liquid organic solvent, but have a higher mechanical strength than microcapsules, and thus hardly generate pressure fog.

In the production of the composite fine particles used in the present invention, first, a solution is prepared by dissolving a dye precursor in a polyvalent isocyanate compound. The melting temperature at this time is 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 in the polyvalent isocyanate compound becomes insufficient, and uniform composite fine particles may not be produced. The dissolution can also be performed under pressure using a pressure vessel.

In the present invention, this 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. The temperature at the time of emulsification and dispersion is not particularly limited, but is desirably set to a temperature at which isocyanate and water do not rapidly react. Further, if necessary, after adding a reactive substance such as a water-soluble polyamine, the polymer-forming raw material is polymerized by raising the temperature of the emulsion as necessary, thereby forming composite fine particles comprising a dye precursor and polyurea or polyurethane-polyurea. .

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

As a dye precursor for giving a 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, among the dye precursors giving a black color, 3-di-n-amylamino-6-methyl-7-anilinofluoran and 3-diethylamino-6-methyl which are excellent in light resistance are used. -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 red, magenta and 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 which give 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 showing a color tone of red, magenta and orange colors, 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 tone correction, it is desirable to use a mixture of dyes having different color tones, for example, 3,3'-bis (1-n-butyl-2-methylindol-3-yl) phthalide or 3,3'-bis By blending a dye precursor that develops a red-purple color tone such as (1-ethyl-2-methylindol-3-yl) phthalide, a color tone with a stronger reddish tint can be obtained.

Dye precursors giving a blue color include:
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 which give yellowish color development include 3,6-dimethoxyfluoran and 1- (4-
n-dodecyloxy-3-methoxyphenyl) -2-
(2-quinolyl) ethylene and the like. The above dye precursor may be used alone, but may be used in combination with a dye precursor of another color for color tone correction.

The polyvalent isocyanate compound used in the present invention forms a urea bond by reacting with an amino compound in addition to water, and forms a urethane bond by reacting with a hydroxy compound to polymerize. The polymer formed is
Polyurea, or polyurethane-polyurea,
The polymer-forming material used may be only a polyvalent isocyanate compound, or a mixture of a polyvalent isocyanate compound and a polyol that reacts with the polyisocyanate compound, or a polyol adduct of a polyvalent isocyanate compound,
It may be a multimer such as a biuret form or an isocyanurate form. A dye precursor is dissolved in these polyvalent isocyanate compounds, and this solution is emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol or a surfactant, and further, if necessary, reacts with a polyamine or the like. After mixing the substances, the emulsified dispersion is heated to polymerize the polymer-forming material to polymerize. Thereby, composite fine particles composed of the dye precursor and the polymer substance can be formed.

Examples of the polyvalent isocyanate compound used as a polymer-forming raw material include 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
Diisocyanates such as diisocyanate and cyclohexylene-1,4-diisocyanate, 4,4 ', 4 "
-Triphenylmethane triisocyanate, toluene-
Triisocyanates such as 2,4,6-triisocyanate, 4,4'-dimethyldiphenylmethane-2,
And tetraisocyanates such as 2 ', 5,5'-tetraisocyanate. Examples of the adduct of a polyvalent isocyanate and a polyol include trimethylolpropane adduct of hexamethylene diisocyanate and 2,4
-Isocyanate prepolymers such as trimethylolpropane adduct of tolylene diisocyanate, trimethylolpropane adduct of xylylene diisocyanate, and hexanetriol adduct of tolylene diisocyanate can be used. In addition, these polyvalent isocyanate compounds, for example, a biuret of hexamethylene diisocyanate, an isocyanurate of hexamethylene diisocyanate, and the like can also be preferably used as the polymer-forming raw material of the present invention.

In the present invention, it is particularly desirable to use dicyclohexylmethane-4,4'-diisocyanate having a low viscosity and good workability. Of course, it can be used in combination with other polyvalent isocyanates.

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

Of course, the polyvalent isocyanate compound, the polyol compound and the like are not limited to the above compounds, and two or more kinds may be used in combination as needed.

The polyamine compound used in the polymer-forming raw material of the present invention includes, for example, ethylenediamine, trimethylenediamine, tetramethylenediamine,
Pentamethylenediamine, hexamethylenediamine, p
-Phenylenediamine, m-phenylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, epoxy Examples include amine adducts of compounds. Further, a tin compound, a polyamide compound, an epoxy compound and the like may be used in combination as long as the object of the present invention is not impaired. When a polyamine compound is used, it is more preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not reduced.

In the present invention, in addition to the dye precursor, a melting point of 40 is used as a solute at the time of preparing the composite fine particles in order to increase the color development sensitivity.
An organic compound having a boiling point of 150 ° C. or higher and a temperature of 150 ° C. or higher can be used in combination. As an organic compound having a melting point of 40 ° C. or more and 150 ° C. or less and a boiling point of 150 ° C. or more, an aromatic ketone compound, an aromatic ether compound, and an aromatic cyclic ester compound can be preferably used in the present invention. Specific examples are shown below. Benzophenone is used as the aromatic ketone compound, and 1,2-di (m-tolyloxy) ethane, 1,2-diphenoxyethane, 1- (4-
Methoxyphenoxy) -2- (2-methylphenoxy)
Examples of ethane and aromatic cyclic ester compounds include coumarin and phthalide. These organic compounds may be used alone or in combination of two or more.

The weight ratio of the dye precursor to the polyvalent isocyanate compound in the production of the composite fine particles is determined by the ratio of the dye precursor 10
0 parts by weight of the polyvalent isocyanate compound is 20 parts by weight.
The amount is preferably from 2000 to 2000 parts by weight, more preferably from 100 to 500 parts by weight. If the amount of the polyvalent isocyanate compound is less than 20 parts, the background fogging due to the pressure of the heat-sensitive recording material and the storage stability are unfavorable.
On the other hand, when the amount of the polyvalent isocyanate compound exceeds 2,000 parts, the coloring sensitivity of the heat-sensitive recording material is undesirably reduced.

In the present invention, examples of the emulsifier used for preparing the composite fine particles include modified polyvinyl alcohol such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and sulfonated polyvinyl alcohol, methylcellulose, carboxymethylcellulose, and the like.
In addition to a water-soluble synthetic polymer compound such as a styrene-maleic anhydride copolymer salt and a derivative thereof, 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 0.5 to 50% by weight based on the weight of the composite fine particles, and is preferably 3 to 50% by weight.
More preferably, it is about 30% by weight.

The average particle diameter of the 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-developed portion with respect to oil, plasticizer, etc. may be deteriorated. The average particle size is 2.
If it is larger than 0 μm, the color-forming sensitivity is lowered, so that it is necessary to excessively apply energy to the thermal head in order to obtain the color of the composite fine particles, which is not preferable.

When raw storage stability and image stability after printing are not so required in the present invention, solid fine particles comprising a dye precursor having the same color tone as the composite fine particles containing the dye precursor are contained in the thermosensitive coloring layer. You can also.

When the heat-sensitive recording material of the present invention is a heat-sensitive recording material capable of developing multiple colors, composite fine particles containing a first dye precursor having a black color tone and a second fine particle having a color tone different from black. Solid fine particles comprising a dye precursor are contained in the thermosensitive coloring layer. The low-temperature color tone is the color tone of the second dye precursor present in the solid fine particle state, and the high-temperature color tone is the color difference between the first dye precursor present in the composite fine particles and the second dye precursor present in the solid fine particle state. It becomes a mixed color tone. By making the second dye precursor black, even when color mixing occurs due to color development of the first dye precursor, the high-temperature color tone can be made black. In order to make the high-temperature color tone closer to a pure black color, the dye precursor having a color tone different from the low-temperature color tone, more preferably a dye precursor having a complementary color relationship, together with the black color-forming dye precursor is a composite fine particle. It is preferable to contain it. For example, when the low-temperature color tone is red, the high-temperature color tone can be made closer to pure black by including the dye precursor that emits blue or green in the composite fine particles.

The composite fine particles used in the present invention are known as heat-sensitive recording materials in addition to dye precursors, if necessary, as well as ultraviolet absorbers, antioxidants, oil-soluble fluorescent dyes and mold release agents. Such a sensitizer or the like may be added. Such an additive substance is preferably solid at room temperature, but may be liquid. Further, the dye precursor in the composite fine particles,
It may be a mixture of two or more. For example, red, blue,
By appropriately mixing the green and yellow dye precursors, it is possible to obtain black-colored composite fine particles.

The inclusion of an ultraviolet absorber in the composite fine particles is preferred from the viewpoint of light resistance, and particularly, a benzotriazole-based ultraviolet absorber such as 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole. Has an effect of improving not only the light fastness of a color image but also the effect of improving color sensitivity, and is preferably used.

When the dye precursor is used in the form of solid fine particles, the dye precursor is pulverized using water as a dispersion medium by various wet pulverizers such as a sand grinder, an attritor, a ball mill, and a cobo mill. In addition to 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, The dispersion may be dispersed in a dispersion medium together with a surfactant, an antifoaming agent, etc. in accordance with the above, to prepare a dispersion, which can be used for preparing a coating material for forming a thermosensitive coloring layer.

After dissolving the dye precursor in an organic solvent,
After emulsifying and dispersing this solution in water using the above-mentioned water-soluble polymer as a stabilizer, the organic solvent is evaporated from this emulsified solution to convert the dye precursor into solid fine particles. In each case, the average particle diameter of the dispersed particles of the dye precursor used in the state of solid fine particles is 0.2 to 0.2 to obtain an appropriate color sensitivity.
It is preferably 3.0 μm, more preferably 0.3 μm.
3 to 1.0 μm.

In the heat-sensitive recording material of the present invention, bis (hydroxyphenyl) ether compound, bis (hydroxyphenyl) methane compound, 1,1′-bis (hydroxyphenyl) are contained in the heat-sensitive recording layer together with the composite fine particles.
At least one of the ethane compounds is used as a color developing compound. Although the reason for these specific color developing compounds is not clear, not only the color developing sensitivity of the composite fine particles can be enhanced, but also the decoloration of the color formed image by a plasticizer or oil can be significantly suppressed.

The bis (hydroxyphenyl) ether compounds used in the present invention include 2,2'-dihydroxydiphenyl ether (melting point 121 ° C.), 3,3'-dihydroxydiphenyl ether (melting point 98 ° C.),
4'-dihydroxydiphenyl ether (melting point: 166
° C). Among them, especially 4,
4'-dihydroxydiphenyl ether is excellent in sensitivity and storage stability. Bis (hydroxyphenyl) methane-based compounds and 1,1′-bis (hydroxyphenyl) ethane-based compounds can also include some compounds depending on the difference in the position where the hydroxyl group is bonded. Structures in which a hydroxyl group is bonded at the para-position, such as' -dihydroxydiphenylmethane (melting point 120 ° C) and 1,1'-bis (p-hydroxyphenyl) ethane (melting point 123 ° C), have sensitivity and storage stability. Is more preferable in view of the above. In these compounds, dimers,
A multimer such as a trimer may be contained.

Other color developing compounds can be used in combination with the above specific color developing compounds. Representative color developing compounds include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol,
4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol,
1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (3-methyl-6-tert
-Butylphenol), phenols such as 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and bis (3-allyl-4-hydroxyphenyl) sulfone Compounds.

Further, in the present invention, compounds that can be used in combination with a specific color developing compound include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate,
Methyl hydroxybenzoate, propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, 4
Phenolic compounds such as -phenyl hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid Acid, salicylic acid,
Aromatic carboxylic acids such as 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and phenolic compounds thereof; Organic acid substances such as salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum and calcium are exemplified.

The color developing compound is usually a total of 1 dye precursor.
It is preferably used in an amount of 50 to 700 parts by weight, more preferably 100 to 400 parts by weight, based on 00 parts by weight. When two or more types of color developing compounds are used, a specific color developing compound which is a constituent element of the present invention,
That is, the ratio of bis (hydroxyphenyl) ether, bis (hydroxyphenyl) methane, 1,1′-bis (hydroxyphenyl) ethane and other color developing compounds is specified with respect to 100 parts by weight of the total of the color developing compounds. Is at least 25 parts by weight.

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

In the present invention, a sensitizer can be used to improve the heat-sensitive recording color development sensitivity. As the sensitizer, a compound conventionally known as a sensitizer for a thermosensitive recording material can be used. For example, parabenzyl biphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate can be used. ,
Di-o-chlorobenzyl adipate, 1,2-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-oxalate
Examples thereof include p-chlorobenzyl, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl, and benzophenone. Among these compounds, di-p-methylbenzyl oxalate and di-p-oxalate
When chlorobenzyl is used as a sensitizer, a sensitizing effect with less fogging can be obtained.

A color-developing compound used in the present invention;
Additives such as an image stabilizer and a sensitizer may be dispersed in water in the same manner as when the dye precursor is used in the form of solid fine particles, and may be mixed with the heat-sensitive coloring layer-forming paint when preparing the coating. . Further, these additives may be dissolved in a solvent, and the resulting solution may be emulsified in water using a water-soluble polymer compound as an emulsifier. Further, the image stabilizer and the sensitizer may be contained in the composite fine particles containing the dye precursor.

In the present invention, a fine pigment having a high whiteness and an average particle diameter of 10 μm or less can be contained in the heat-sensitive coloring layer in order to improve the whiteness of the heat-sensitive coloring layer and the uniformity of the image. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin and polystyrene resin can be used. Oil absorption is 50ml / 1 to prevent sticking to the thermal head and sticking.
It is preferred to use more than 00 g of pigment. The amount of the pigment is 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, an adhesive is used as another material constituting the heat-sensitive coloring layer.
Crosslinking agents, waxes, metal soaps, colored dyes, colored pigments,
And a fluorescent dye. Examples of the adhesive include polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, and acrylamide-acrylic acid ester. Coalescence, acrylamide-acrylate-methacrylate copolymer, styrene-maleic anhydride copolymer,
Isobutylene-maleic anhydride copolymer, casein, water-soluble polymer materials such as gelatin and derivatives thereof, and polyvinyl acetate, polyurethane, polyacrylic acid,
Emulsions such as polyacrylates, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, ethylene-vinyl acetate copolymers, and water-insoluble polymers such as styrene-butadiene copolymers and styrene-butadiene-acrylic copolymers Examples include coalesced latex.

Further, in order to improve the water resistance of the thermosensitive coloring layer, a crosslinking agent for three-dimensionally curing the adhesive can be contained in the thermosensitive coloring layer. For example, aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, and ammonium persulfate and ferric chloride, and chloride Magnesium, sodium tetraborate, potassium tetraborate or other inorganic compound or at least one crosslinkable compound selected from boric acid, boric acid triester, boron-based polymer, etc., 100 parts by weight of the total solid content of the thermosensitive coloring layer Is preferably used in the range of 1 to 10 parts by weight.

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

As the metal soap added to the thermosensitive coloring layer, higher fatty acid polyvalent metal salts such as zinc stearate,
Aluminum stearate, calcium stearate,
And zinc oleate. When a multi-color heat-sensitive recording material is used, the inclusion of a color dye and a color pigment having a color tone that is complementary to the low-temperature color tone in the heat-sensitive coloring layer adjusts the color tone of the blank portion of the recording material. It is preferable to Further, if necessary, various additives such as an oil repellent, an antifoaming agent, and a viscosity modifier can be added to the thermosensitive coloring layer as long as the effects of the present invention are not impaired. The thermosensitive coloring layer is coated on the support so that the coating amount after drying is ² to 20 g / m ² , more preferably 4 to 10 g / m ² .

In the present invention, a protective layer as used in conventionally 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 provided. The protective layer mainly composed of a resin cured by an electron beam or ultraviolet rays is more preferably provided on a protective layer containing a water-soluble polymer material and a pigment. The protective layer, the coating amount after drying 0.5 to 10 g / m ^2, more preferably 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 is no particular limitation on the type, shape, dimensions, and the like 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 In addition to coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, and the like, various transparent supports and the like can be appropriately selected and used.

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

The method for forming each of the above layers on the support includes known coating methods such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method. Either may be used. Further, 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.

[0056]

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
100 parts of hardwood bleached kraft pulp beaten ml, from 10 parts of talc, petroleum resin sizing agent 0.3 parts, form regulating the paper stock obtained by adding 0.5 parts of aluminum sulfate, the basis weight 64 g / m ² Paper was made. The base paper was coated with a 2% solution of polyvinyl alcohol by a size press. The coating amount was 0.8 g / m ² (dry). Oken type smoothness (J.TAPPI No.5) is 50 on machine calendar
A smoothing treatment was performed so that the time became seconds to obtain a support used in the present invention.

(2) Preparation of Materials Used for Undercoat Layer and Thermosensitive Coloring Layer <Preparation of Composite Fine Particle Dispersion Containing Black Coloring Dye Precursor> Black Fine Particle Dispersion Containing Black Coloring Dye Precursor: Black Coloring Dye Precursor 3-Di-n-amylamino-6-
5 parts of methyl-7-anilinofluoran are dissolved in 15 parts of dicyclohexylmethane-4,4'-diisocyanate heated to 120 ° C., and the solution is cooled to 35 ° C., and then the same temperature is applied to 20% sulfone-modified polyvinyl alcohol. (Manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Goselan L-3266) was gradually added to 100 parts of an aqueous solution, and a homogenizer was used.
After emulsifying and dispersing by stirring at a rotation speed of 12000 rpm, 150 parts of water was added to this emulsified dispersion to homogenize.
The temperature of the emulsified dispersion was raised to 90 ° C., and a polymerization reaction was carried out for 10 hours to prepare a composite fine particle dispersion containing a black color-forming dye precursor having an average particle diameter of 0.4 μm.

Composite fine particle dispersion containing a black color-forming dye precursor: 5 parts of 3-di-n-amylamino-6-methyl-7-anilinofluorane as a black color-forming dye precursor were added in an amount of 1 part.
Dicyclohexylmethane-4,4'- heated to 20 ° C
After dissolving in 15 parts of diisocyanate, the solution is cooled to 35 ° C., mixed with 6 parts of trimethylolpropane adduct of xylylene diisocyanate at the same temperature, and then emulsified in the same manner as the dispersion of composite fine particles containing a black color-forming dye precursor. According to the polymerization method, a composite fine particle dispersion containing a black color-forming dye precursor having an average particle diameter of 0.5 μm was prepared.

<Preparation of Dispersion of Dye Precursor and Developing Compound in Solid Fine Particle State> Black chromogenic dye precursor dispersion: 3-di-n-amylamino-6-methyl-7-anilinofluoran Active compound: 4,4'-dihydroxydiphenyl ether (hereinafter DH)
4,4'-dihydroxydiphenylmethane (hereinafter BPF)
1,1′-bis (p-hydroxyphenyl) ethane (hereinafter abbreviated as BPE) 4,4′-isopropylidene diphenol (hereinafter BPA)
Abbreviated)

The above-mentioned dye precursor and the color-developing compound are separately mixed with polyvinyl alcohol at the following compounding ratio,
The average particle diameter of each mixture was 1.2 μm using a vertical sand mill (manufactured by Imex Co., Ltd., sand grinder).
And crushed and dispersed.

Component Amount (parts by weight) Black color-forming dye precursor or color developing compound 40 Polyvinyl alcohol 10% solution 40 (polymerization degree 500, saponification degree 90%) Water 20

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

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

(3) Formation of Undercoat Layer The above-mentioned pigment silica dispersion and the above-mentioned adhesive liquid are mixed so that the solid content ratio is 85:15, and this paint is applied to one surface of the support using a Meyer bar. 7.0 g / m ² (dry)
Coating was performed to form an undercoat layer, which was used in each of Examples and Comparative Examples.

Example 1 A thermosensitive coloring layer paint prepared by mixing at the following compounding ratio (solid content) was applied on the previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, 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 40 DHPE 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 previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, 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 40 BPF 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 previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, 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 chromogenic dye precursor 40 BPE 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 previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, 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 40 DHPE dispersion 30 BPA dispersion 10 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 previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, 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 40 DHPE 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 applied on the previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, a heat-sensitive coloring layer was formed to obtain a heat-sensitive recording material. Component Amount (parts by weight) Black chromogenic dye precursor dispersion 10 DHPE dispersion 40 Pigment dispersion 30 Adhesive liquid 15 Lubricant dispersion 5

Comparative Example 2 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied onto the previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, a heat-sensitive coloring layer was formed to obtain a heat-sensitive recording material. Component Amount (parts by weight) Black color-forming dye precursor dispersion 10 BPF dispersion 40 Pigment dispersion 30 Adhesive liquid 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 previously formed undercoat layer 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) Black chromogenic dye precursor dispersion 10 BPE dispersion 40 Pigment dispersion 30 Adhesive liquid 15 Lubricant dispersion 5

Comparative Example 4 A thermosensitive coloring layer paint prepared by mixing at the following mixing ratio (solid content) was applied onto the previously formed undercoat layer at a coating amount of 5.0 g / m ² (dry). After drying, 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 chromogenic dye precursor 40 BPA dispersion 40 Pigment dispersion 15 Lubricant dispersion 5

The heat-sensitive recording material obtained by the above operation was subjected to a smoothing treatment using a super calender so that the surface of the heat-sensitive coloring layer had an Oken-type smoothness of 1000 seconds. This was a thermosensitive recording material corresponding to No. 4.

A test was performed on each of the above-mentioned heat-sensitive recording materials subjected to the smoothing treatment. Thermal recording was performed using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.) under the conditions of 1-line recording time: 4 msec, sub-scanning line density: 8 lines / mm, and applied energy per dot: 2.0 mJ.
Line solid printing was performed.

With respect to the color product thus obtained,
The recorded image density and blank paper density were measured. Recording image density,
The density of the blank portion was determined by measuring the recorded image portion and the blank portion of the recording sample with a Macbeth densitometer (manufactured by Macbeth, model number: RD-91).
It was determined by measuring in 4). Further, the easiness of occurrence of white paper fogging, the easiness of coloring by pressure, and the oil resistance were evaluated by the following methods. As for the fogging of blank paper, as an accelerated deterioration test, each sample was allowed to stand in an environment of 70 ° C. for 12 hours, and the degree of background color was evaluated by measuring a blank paper portion with a Macbeth densitometer. If the concentration after the test is 0.12 or less, it can be said that the concentration is at a practical level.

The degree of color development by pressure was evaluated by rubbing each sample with a nail and visually observing the degree of color development. ○ indicates that little color was formed, and X indicates that clear color was seen. The oil resistance was determined by immersing the above-mentioned recorded sample in salad oil at 20 ° C. for 12 hours, and then measuring the recorded image area with a Macbeth densitometer. 100).
If the preservation rate is 50% or more, it is a legible level,
No problem in practical use.

Table 1 shows the test results.

[0080]

[Table 1]

[0081]

As is evident from the results in Table 1, the heat-sensitive recording material of the present invention is a heat-sensitive recording material that hardly causes fogging of white paper and has excellent image stability after printing.

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a thermosensitive coloring layer provided on a support, wherein said thermosensitive coloring layer is obtained by emulsifying and dispersing a solution containing a polyvalent isocyanate compound as a solvent and a dye precursor as a solute in water. A composite fine particle produced by accelerating the polymerization reaction of a polyvalent isocyanate compound, and a bis (hydroxyphenyl) ether compound, a bis (hydroxyphenyl) methane compound,
A heat-sensitive recording material comprising at least one color-developing compound selected from 1,1'-bis (hydroxyphenyl) ethane-based compounds.