JPH11235875A - Thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording material having a high preservation stability, further excellent sensitivity and image uniformity by smoothing by high calendering treatment and to obtain a multicolor thermosensitive recording material having similar properties and small mixture of a color tone. SOLUTION: In the thermosensitive recording material having a thermosensitive color developing layer on a support; (1) the developing layer contains composite fine particles made of at least one type of a polymer substance selected from a polyurea and a polyurethane and a dye precursor and a developer for color developing the precursor by reacting with the precursor by heating, and (2) a thermosensitive recording surface has a smoothness of 500 to 10,000 sec of a Bekk smoothness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monochromatic or multicolor heat-sensitive recording material used as a recording medium for facsimile, word processor, various computers, and other uses.

[0002]

2. Description of the Related Art Conventionally, a dye precursor, and a color developing reaction between the dye precursor and a color developing agent which is brought into contact with the color of the dye under heating to form a color therewith, are used to fuse both color forming substances by heating.
Thermal recording materials for obtaining a color image are widely known. Such heat-sensitive recording materials are relatively inexpensive,
Because the recording equipment is compact and easy to maintain, facsimile, word processor, various computers,
And as a recording medium for other uses.

With respect to the heat-sensitive recording material, the required quality has been diversified with the expansion of uses thereof. For example, there have been demands for high sensitivity, image stabilization, multicolor recording, and the like.

[0004] The conventional heat-sensitive recording material has a drawback that the colored portion after printing is erased by oil or a plasticizer and storage stability is poor. Various proposals have been made so far for the purpose of improving storage stability. For example, a method of microencapsulating a color-forming component as a core substance is disclosed in
No. 695 and JP-A-59-214691. However, since the color-forming dye precursor is encapsulated in the microcapsules, there is a problem that the color-forming sensitivity is lower than that of the color-forming dye precursor existing in the form of solid fine particles. Further, there is a disadvantage that capsules are broken by pressure or frictional rubbing, and color development is likely to occur, and there has been a problem that high-level calendering cannot be performed.

[0005] The surface smoothness of the heat-sensitive recording surface is important for increasing the sensitivity of the heat-sensitive recording material and improving the image uniformity of the colored portion. This is because the loss of heat applied from the thermal head is small, it is uniformly transmitted to the thermosensitive coloring layer to contribute to color development, and in order to obtain high print pixel reproducibility, the adhesion between the recording surface and the thermal head is improved. It is because it is effective to improve.

For this reason, Japanese Patent Application Laid-Open Nos. 57-208296, 58-65694, and 59-41
295 and JP-A-59-155094,
It describes that a heat-sensitive recording surface is subjected to a smoothing process using a known smoothing method such as a super calender or a soft calender to increase the color sensitivity. However, there is a problem that background fogging occurs when performing advanced calendar processing.

On the other hand, the multicolor recording means has the advantage that characters and graphics to be emphasized can be displayed clearly and clearly with a different color tone from other parts. Among them, a two-color heat-sensitive recording material capable of recording in two colors of red and black is excellent in general versatility, and therefore there is a high demand for practical use.

As a multicolor heat-sensitive recording system, attempts have been made to utilize a difference in heating temperature or a difference in heat energy, and various multicolor heat-sensitive recording materials have been proposed. In general, a multicolor heat-sensitive recording material is formed by sequentially laminating a high-temperature coloring layer and a low-temperature coloring layer that form different colors on a support, and these are roughly classified into a decoloring type and an additive type. 2
Divided into types.

As a decolorizable multicolor heat-sensitive recording material, for example, disclosed in Japanese Patent Application Laid-Open No. 2-80287, etc., the recorded color-developed image fades during long-term storage, Since an extra amount of heat is required to melt the colorant, there is a problem that an excessive load is imposed on the thermal head, and it is not always satisfactory with respect to the reliability and recording sensitivity of a recorded image. Did not.

On the other hand, a color-added multicolor heat-sensitive recording material is
JP-B-49-27708, JP-B-51-1998
No. 9, JP-A-51-146239, etc., a method of laminating two color-forming layers that develop different colors and applying two different amounts of heat to obtain two distinguishable colors. It is. Compared to the decoloring type, there is an advantage that the recorded image is excellent in long-term preservability and can be manufactured relatively inexpensively. Also, since no extra heat is required for melting the decoloring agent, there is an advantage that the high-temperature coloring layer can be colored with lower energy as compared with the decoloring type. However, the multicolor heat-sensitive recording material having such a structure is
If too much heat is applied at the time of low-temperature coloring, the coloring of the high-temperature coloring layer is also partially mixed, causing color mixing, and there is a disadvantage that the low-temperature coloring image is difficult to be sharp.

[0011] Both the decolorizable type and the additive color type have a drawback that a multilayer coating is required. Also, JP-A-56-996
No. 97 discloses a method in which two or more dye precursors having different color tone and different average particle diameters are mixed in the same layer.
In addition, there is a drawback that background fogging occurs when performing advanced calendar processing.

Japanese Patent Publication No. 4-4960 and Japanese Patent Application Laid-Open No. 4-101885 disclose a color-forming component which develops a color tone different from each other in a solvent, and respectively dissolve two or more types of microcapsules having different glass transition temperatures. It is described that the color is multiplied by containing the compound. However, separately microencapsulating two or more types of dye precursors that develop different colors will reduce the color development sensitivity of both dye precursors, making it difficult to classify the sensitivity,
For this reason, there is a drawback that mixing of the color tone is likely to occur. Further, similarly to the case of a single color, there is a problem that the capsule is destroyed when performing advanced calendar processing.

[0013]

As described above, in either case of single color or multi-color, there is a drawback that background fog is caused when advanced calendar processing is performed in order to enhance color development sensitivity and image uniformity. Further, the use of microcapsules for storage stability and multicoloring has the same disadvantage. Therefore, an object of the present invention is to propose a heat-sensitive recording material having high storage stability, and further excellent in sensitivity and image uniformity by performing high-level calendering and smoothing. It is another object of the present invention to obtain a multicolor heat-sensitive recording material having the same high performance as described above and having less color tone even when multicolored.

[0014]

The present invention employs the following configuration in order to solve the above-mentioned problems. That is, the first invention of the present invention relates to a thermosensitive recording material having a thermosensitive coloring layer provided on a support, wherein (1) the thermosensitive coloring layer comprises at least one polymer substance selected from polyurea and polyurethane. (2) a thermosensitive recording surface having a Bekk smoothness of 500 to 100, which comprises composite fine particles comprising a dye precursor and a color developer which reacts with the dye precursor under heating to form a color.
A heat-sensitive recording material having a smoothness of 00 seconds ".

According to a second aspect of the present invention, in the first aspect, the heat-sensitive coloring layer has a color tone different from that of the dye precursor contained in the composite fine particles. A thermosensitive recording material characterized by containing a body.

[0016]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a dye precursor and a polyurea or a polyurethane, or a polyurethane-
By using the composite fine particles made of polyurea, it is possible to make the preservability of the color-developing portion extremely excellent with respect to oils, plasticizers, and the like. Alternatively, the coloring sensitivity is slightly lowered as compared with solid fine particles in which the dye precursor exists in a crystalline state.

The present inventors have continued their research to solve this problem, and as a result, the smoothness of the heat-sensitive recording surface was 5% in Beck's smoothness.
By setting the time in the range of 00 to 10000 seconds, it was found that the coloring sensitivity was improved and the uniformity of the image was excellent, and the present invention was completed. In the present invention, since the composite fine particles are used, no background fogging occurs even when a high-level calendering treatment is performed, so that a surface with high smoothness can be obtained without any problem.

As a method of smoothing, any method which has been widely known to those skilled in the art may be used. Generally, the heat-sensitive recording surface is smoothed using a super calender or a soft calender. To process. The smoothing process is
It may be performed directly on the heat-sensitive coloring layer, or after forming a protective layer as described later.

If the Beck's smoothness is 500 seconds or less, the quality of the recorded image is poor, such as low color development sensitivity, more white spots in the printed portion, and low sharpness. In particular, in a multi-color heat-sensitive recording material that develops a different color depending on the difference in the heating application condition from the thermal head, the color tone of the high-temperature color becomes more mixed with the color tone of the low-temperature printing, and the color classification becomes unclear. . On the other hand, even if the Bekk smoothness is 10,000 seconds or more, the image quality is not improved beyond a certain level, and on the other hand, the adhesion to the thermal head is increased, which tends to cause printing trouble due to poor running such as sticking, which is not preferable. .

The composite fine particles used in the present invention include a base material composed of at least one polymer substance (resin) selected from polyurea or polyurethane-polyurea, and a dye precursor contained therein. It is considered that the dye precursor and the polymer substance exist in a solid solution state. It is desirable that the composite fine particles do not contain a liquid such as an oily solvent from the viewpoint of pressure fogging.

In a general microcapsule, a solution of a dye precursor serves as a core material as a liquid portion, which is protected by a capsule wall material, and the core and the shell are clearly separated. Therefore, the state and shape of the dye precursor are significantly different from those of the composite fine particles containing the dye precursor which is considered to exist in a solid solution state with the polymer.

The color precursor of the dye precursor contained in the composite fine particles has extremely good storage stability, especially excellent resistance to oils and plasticizers, as compared with the color former colored in the form of solid fine particles. . Although the reason is not always clear, it seems that the color former and the polymer substance (base material) have some interaction and are stabilized.

The external appearance of the composite fine particles used in the present invention is almost spherical when observed with an electron microscope, or is at least somewhat depressed erythrocyte. In cross-sectional observation with an electron microscope, the shape is an internal body, a porous body, or a hollow body. When applied to a single-color heat-sensitive recording material, the average particle size is desirably 0.2 μm to 1.5 μm in order to obtain appropriate color sensitivity. When the particle size is small, the storage stability of the colored portion with respect to oil, plasticizer and the like may be deteriorated, and it is not desirable to make the average particle size smaller than 0.2 μm. When applied to a multicolor heat-sensitive recording material, the average particle size is 0.8 μm to 5.0.
μm is desirable. If the average particle size is smaller than 0.8 μm, it becomes difficult to distinguish the color developing sensitivity from the dye precursor in the form of solid fine particles having different color developing tones to be mixed, and color mixing may occur at low temperature. If the average particle size is larger than 5.0 μm, the color development sensitivity is reduced, so that it is necessary to excessively apply energy to the thermal head, which is not preferable.

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.

The color-forming dye precursor contained in the composite fine particles may be a single compound, but a desired color-forming tone can be obtained by mixing two or three or more different color-forming dye precursors. You can also get

In the present invention, in order to obtain a heat-sensitive recording material capable of forming multiple colors, in addition to the composite fine particles containing the first dye precursor, the second dye which develops a color tone different from that of the first dye precursor is used. It is necessary to use a precursor. In this case, the second dye precursor may be used as solid fine particles, or may be used as composite fine particles with polyurea or polyurethane. As an example, for the case where composite fine particles containing a first dye precursor having a black color tone and black and solid fine particles consisting of a second dye precursor that develops a color tone different from black are contained in the same thermosensitive coloring layer. explain. In this case, the low-temperature color tone is a color tone of the second dye precursor present in the form of solid fine particles, and the high-temperature color tone is a black color which is a color mixture with the color of the first dye precursor present in the composite fine particles. Becomes In the case of a multicolor heat-sensitive recording material, a dye precursor having a color tone different from the low-temperature color tone, more preferably a dye precursor having a complementary color relationship, is preferably black in order to make the high-temperature color tone closer to pure black. It is contained in the composite fine particles together with the coloring dye precursor. When the low-temperature color tone is a reddish color, a dye precursor that develops a blue or green color is contained in the composite fine particles together with a black color-forming dye precursor. Of course, as the first dye precursor, black-based colors and blue to
In addition to the green dye precursor, a dye precursor having various color tones can be contained to correct the color tone.

[0027] Furthermore, by incorporating a chromogenic dye having a strong absorption in the near-infrared region into the chromogenic dye precursor contained in the composite fine particles, readability with an optical character reader or a bar code reader is improved. It is also possible to obtain a heat-sensitive recording material having excellent heat resistance.

As a dye precursor giving a black color, 3-
Pyrrolidino-6-methyl-7-anilinofluoran, 3
-Diethylamino-7- (m-trifluoromethylanilino) fluoran, 3-diethylamino-6-methyl-
7- (m-methylanilino) fluoran, 3- (N-isoamyl-N-ethylamino) -7- (o-chloroanilino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-ani Linofluoran, 3- (N
-Ethyl-N-2-tetrahydrofurfurylamino)-
6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-di-
n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-amylamino-6-methyl-7-anilinofluoran, 3- (N-isoamyl-N-ethylamino) -6 Methyl-7-anilinofluoran, 3-
(Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3- [N- (3-ethoxypropyl) -N-ethylamino) -6-methyl-7-anilino Fluoran, 3- [N- (3-ethoxypropyl) -N-methylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-di-n -Butylamino-7-
(2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl -7
-(2,4-dimethylanilino) fluoran, 2,4-
Examples thereof include dimethyl-6- (4-dimethylaminoanilino) fluoran and 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluoran.

Among the dye precursors giving a black color, 3-di-n-amylamino-6-methyl-7-anilinofluoran and 3-diethylamino-6-methyl-7, which are relatively excellent in light resistance. -(2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl-7
-(2,4-dimethylanilino) fluoran, 2,4-
It is preferably at least one selected from dimethyl-6- (4-dimethylaminoanilino) fluoran.

The dye precursor giving a blue color includes:
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) ) -4-Azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, 3- (1-ethyl-2-methyl) Indole-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-methylindole-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 having absorption in the near infrared region include 3,3'-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,3-bis [1,1-bis ( 4-pyrrolidinophenyl) ethylene-
2-yl] -4,5,6,7-tetrabromophthalide,
3,3-bis [1- (4-methoxyphenyl) -1-
(4-dimethylaminophenyl) ethylene-2-yl]
-4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6 , 7
-Tetrachlorophthalide, 3- [p- (p-anilinoanilino) anilino] -6-methyl-7-chlorofluoran, 3- [p- (p-dimethylaminoanilino) anilino] -6-methyl-7 -Chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3'-
(6'-dimethylamino) phthalide, bis (p-dimethylaminostyryl) -p-tolylsulfonylmethane, 3
-[P- (p-dimethylaminoanilino) anilino]-
6-methylfluorane, 3-di (n-pentyl) amino-6,8,8-trimethyl-8,9-dihydro- (3,
2, e) pyridofluoran, 3-di (n-butyl) amino-6,8,8-trimethyl-8,9-dihydro-
(3,2, e) pyridfluoran, 3- [1,1-bis (p-diethylaminophenyl) ethylene-2-yl]
-6-dimethylaminophthalide, 3- (pn-butylaminoanilino) -6-methyl-7-chlorofluorane, 2-mesidino-8-diethylamino-benz [C]
Fluoran and the like can be mentioned.

Dye precursors that develop a red color that can be used in the present invention 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-chlorofluorane, 3-diethylamino-7-bromofluoran, 3-diethylamino-7,8-benzofluoran, 3-diethylamino-
6,8-dimethylfluoran, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-diethylamino-7-tert-butylfluoran, 3- (N-ethyl-N-tolylamino) -7-methylfluoran, 3-
(N-ethyl-N-tolylamino) -7-ethylfluoran, 3- (N-ethyl-N-isobutylamino) -6
-Methyl-7-chlorofluorane, and 3- (N-ethyl-N-isoamylamino) -7,8-benzofluoran.

Further, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 3-di-n -Butylamino-7,8-benzofluoran, 3-tolylamino-7-methylfluoran, 3-tolylamino-7-ethylfluoran, 2-
(N-acetylanilino) -3-methyl-6-di-n-
Butylaminofluoran, 2- (N-propionylanilino) -3-methyl-6-di-n-butylaminofluoran, 2- (N-benzoylanilino) -3-methyl-
6-di-n-butylaminofluoran, 2- (N-carbobutoxyanilino) -3-methyl-6-di-n-butylaminofluoran, 2- (N-formylanilino)-
3-methyl-6-di-n-butylaminofluoran, 2
-(N-benzylanilino) -3-methyl-6-di-n
-Butylaminofluoran, 2- (N-allylanilino) -3-methyl-6-di-n-butylaminofluoran, and 2- (N-methylanilino) -3-methyl-
6-di-n-butylaminofluoran, 3-diethylamino-7-phenoxyfluoran, 3- (N-ethyl-
(N-isoamylamino) -7-phenoxyfluoran.

Further, 3,3'-bis (1-n-butyl-2-methylindol-3-yl) phthalide,
3'-bis (1-ethyl-2-methylindole-3-
Yl) phthalide, 3,3'-bis (1-n-octyl-
2-methylindol-3-yl) phthalide, 7- (N
-Ethyl-N-isoamylamino) -3-methyl-1-
Phenylspiro [(1,4-dihydrochromeno [2,3
-C] pyrazole) -4,3'-phthalide], 7- (N
-Ethyl-N-isoamylamino) -3-methyl-1-
p-methylphenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3′-phthalide], and 7- (N-ethyl-Nn-hexylamino) -3- Methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3 ′
-Phthalide] can be mentioned as a red dye precursor.

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.

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 which is a polymer-forming raw material. The dissolution temperature at this time is preferably 60 ° C. or higher. If the dissolution temperature is lower than 60 ° C., the dissolution of the dye precursor in the polyvalent isocyanate compound becomes insufficient, and uniform composite fine particles may not be produced. In the present invention, as necessary, not only a polyvalent isocyanate compound but also a polyol compound and a polyamine compound can be added as a polymer-forming raw material.

In the present invention, this solution is cooled if necessary, and then emulsified and dispersed in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved and contained. 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. The equipment used for emulsification and dispersion may be a high-speed rotary stirrer such as a stirrer (mixer), homomixer, or disper, or a homogenizer (homogenizer) using ultrasonic waves, vibration, high pressure, an electrostatic field, or a forced interval type. A colloid mill, a roll mill, a roller mill, a sand mill which is a medium stirring type disperser, a sand grinder, an attritor, a ball mill and the like can be mentioned. Further, an emulsified dispersion can be obtained by using any of the methods used for ordinary emulsification of fine particles, including a film emulsification method using porous glass and the like.

After the emulsification and dispersion, if necessary, a reactive substance such as a water-soluble polyamine is added to polymerize the polymer-forming raw material to form composite fine particles comprising a dye precursor and polyurea or polyurethane-polyurea. The isocyanate forms a urea bond by reacting with water to polymerize. Further, the polyol compound reacts with the isocyanate to form a urethane bond. The polyvalent isocyanate compound that can be used in the present invention may be a multivalent isocyanate compound such as a polyol adduct, a biuret compound, an isocyanurate compound, or the like.

Examples of the polyvalent isocyanate compound include norbornene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate,
2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, 4,4'-diphenylmethane diisocyanate,
Polymeric diphenylmethane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 5
-Isocyanate-1- (isocyanatomethyl)-
1,3,3-trimethylcyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4 '
-Diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate,
Propylene-1,2-diisocyanate, butylene-
1,2-diisocyanate, cyclohexylene-1,2
And diisocyanates such as diisocyanate and cyclohexylene-1,4-diisocyanate.

Further, triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate;
Tetraisocyanates such as -dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate; Examples of the adduct of a polyvalent isocyanate and a polyol include a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of 2,4-tolylene diisocyanate, a trimethylolpropane adduct of xylylene diisocyanate, and tolylene diisocyanate. An isocyanate prepolymer such as hexanetriol adduct of the above 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 used.

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

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

In the present invention, other polyamine compounds which can be used as a polymer-forming raw material include:
For example, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine, m-phenylenediamine, piperazine, 2-methylpiperazine,
Examples thereof include 2,5-dimethylpiperazine, 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, and amine adducts of epoxy compounds. Further, other polymer substances can be contained within a range not to impair the object of the present invention.

In the present invention, in addition to the dye precursor, a melting point of 40 is used as a solute at the time of preparing the composite fine particles for the purpose of increasing color development sensitivity.
An organic compound having a boiling point of 150 ° C. or higher and a temperature of 150 ° C. or higher can be used in combination. As the organic compound having a melting point of 40 ° C. or higher and 150 ° C. or lower and a boiling point of 150 ° C. or higher, an aromatic ketone compound, an aromatic ether compound, an aromatic cyclic ester compound, and a phenol compound are preferably used. it can. Specific examples are shown below.

Benzophenone is used as the aromatic ketone compound, and 1,2-di (m
Examples of -tolyloxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, and aromatic cyclic ester compounds include coumarin and phthalide. Examples of the phenol compound include p-benzyloxyphenol. 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 based on 100 parts by weight of the dye precursor from the viewpoints of color sensitivity and ease of production.
The polyvalent isocyanate compound is preferably 50 parts by weight to 2000 parts by weight, more preferably 250 to 6 parts by weight.
00 parts by weight. It is desirable to select a polyvalent isocyanate compound that is a low-viscosity liquid at room temperature and has high solubility in the dye precursor. Particularly, dicyclohexylmethane-4,4'-diisocyanate, norbornene diisocyanate, hexamethylene diisocyanate, isocyanurate of hexamethylene diisocyanate and the like can be preferably used because of their low viscosity.

In the present invention, examples of the emulsifier (protective colloid agent) used for preparing the composite fine particles include modified polyvinyl alcohol such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and sulfonated polyvinyl alcohol, methylcellulose, carboxymethylcellulose, and styrene. Water-soluble synthetic high molecular compounds such as maleic anhydride copolymer salts and derivatives thereof can be used. If necessary, a surfactant, an antifoaming agent and the like may be used at the same time. The amount of the emulsifier used in preparing the composite fine particles is not particularly limited, but is generally preferably 1 to 50% by weight, more preferably about 3 to 30% by weight, based on the weight of the composite fine particles.

The 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. In particular, an ultraviolet absorber or a hindered phenol-based antioxidant can improve light resistance and can be preferably used. In particular, benzotriazole-based ultraviolet absorbers such as 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole,
It can be used preferably.

When producing the composite fine particles used in the present invention, an organic solvent which acts as a solvent for the dye precursor is mixed with the polyvalent isocyanate compound within a range not to impair the object of the present invention. Can also. The use amount is 50% by weight or less, more preferably 20% by weight or less based on the weight of the composite fine particles. If the amount is more than 50% by weight, fogging cannot be prevented due to pressure, which is the object of the present invention, and an undesirable result may be obtained. The solvent is not particularly limited, and a solvent that acts as a solvent for the dye precursor and is hydrophobic can be used. Specifically, for example, tricresyl phosphate, phosphates such as octyl diphenyl phosphate, dibutyl phthalate, phthalates such as dioctyl phthalate, carboxylic esters such as butyl oleate, various fatty acid amides, Alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene, diisopropyl naphthalene, 1-methyl-1-phenyl-1-
Alkylated benzenes such as tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropylbiphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether; In addition to acrylates such as trimethylolpropane triacrylate, esters of polyhydric alcohol and unsaturated carboxylic acid, chlorinated paraffin, kerosene, etc., ethyl acetate, butyl acetate, methylene chloride and the like can be mentioned. Needless to say, two or more of these can be used in combination.

In addition, when a polymer is prepared in the preparation of the composite fine particles, a tin compound, a polyamide compound,
An epoxy compound, a polyamine compound or the like may be used in combination. When a polyamine compound is used, it is preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not reduced.

In the multicolor heat-sensitive recording material of the present invention, the second dye precursor which develops a color tone different from that of the first dye precursor contained in the composite fine particles is used in the form of solid fine particles. In this case, the second dye precursor is pulverized by various wet pulverizers such as a sand grinder, an attritor, a ball mill, and a cobo mill using water as a dispersion medium, and this is modified with polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and a sulfone group. In addition to water-soluble polymer compounds such as modified polyvinyl alcohol such as polyvinyl alcohol, methylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer salt and derivatives thereof, if necessary, dispersed together with a surfactant and an antifoaming agent It is dispersed in a medium to form a dispersion, and this dispersion can be used for preparing a coating material for forming a thermosensitive coloring layer. After dissolving the dye precursor in an organic solvent, this solution is emulsified and dispersed in water using the water-soluble polymer as a stabilizer, and the organic solvent is evaporated from the emulsion to form the dye precursor into solid fine particles. You can also. In each case, the average particle size of the dispersed particles of the dye precursor used in the state of solid fine particles,
The thickness 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. Of course, a dye precursor having the same color tone can be used in the form of solid fine particles together with the composite fine particles to obtain a single-color heat-sensitive recording material.

The color-developing compound used in the present invention is not particularly limited, but generally has a property of liquefying or dissolving with an increase in temperature and a property of contacting with the dye precursor to form a color. It is selected from those having. Representative color developing compounds include 4-tert-butylphenol, 4-acetylphenol, and 4-tert-phenol.
-Octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenylether, 4,4'- Cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) -ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4'-dihydroxydiphenyl sulfide, 4,4'- Thiobis (3-methyl-6-te
rt-butylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and bis (3-allyl-4-hydroxyphenyl) sulfone Phenolic compounds can be mentioned.

Further, in the present invention, compounds that can be used as a color developing compound include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, and 4-hydroxybenzoic acid. Phenolic compounds such as -sec-butyl, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl ether, or
Benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-
Butylsalicylic acid, 3-isopropylsalicylic acid, 3-
Aromatic carboxylic acids such as benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, etc. And organic acidic substances such as salts with polyvalent metals.

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. Such a color-developing compound has excellent properties in preserving a color image. This is presumed to be due to the strong electron-withdrawing property of the sulfone group of the color-developing compound. 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 300 parts by weight, more preferably 50 to 200 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 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, as a sensitizer which can be used for improving the color sensitivity of heat-sensitive recording, a compound conventionally known as a sensitizer for heat-sensitive recording materials is used. For example, parabenzyl biphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate, 1,2-diphenoxyethane, 1,2-bis ( 3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-p oxalate
-Chlorobenzyl, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl, benzophenone and the like. 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.

The additives such as the color-developing compound, the image stabilizer and the sensitizer used in the present invention are dispersed in water in the same manner as when the dye precursor is used in the form of solid fine particles. What is necessary is just to mix with this at the time of preparation of a forming paint. Further, these additives may be dissolved in a solvent, and the resulting solution may be emulsified in water using a water-soluble polymer compound as an emulsifier. Further, the image stabilizer and the sensitizer may be contained in the composite fine particles containing the dye precursor.

In the present invention, a fine pigment having a high whiteness and an average particle diameter of 10 μm or less can be contained in the thermosensitive coloring layer in order to improve the whiteness of the thermosensitive coloring layer and the uniformity of the image. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin and polystyrene resin can be used. Oil absorption is 50ml / 1 to prevent sticking to the thermal head and sticking.
It is preferred to use more than 00 g of pigment. The amount of the pigment is such that the color density is not reduced, that is,
The content is preferably 50% by weight or less based on the total solid content of the thermosensitive coloring layer.

In the present invention, an adhesive is used as another component material constituting the thermosensitive coloring layer.
Crosslinking agents, waxes, metal soaps, colored dyes, colored pigments,
And a fluorescent dye. As the adhesive, those similar to those used in the undercoat layer, for example, polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose derivatives such as ethyl cellulose, sodium polyacrylate , Polyvinylpyrrolidone, acrylamide-acrylate copolymer, acrylamide-
Water-soluble polymer materials such as acrylate-methacrylate copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, and polyvinyl acetate Emulsions such as polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, and styrene-butadiene-acrylic copolymer. A latex of a water-insoluble polymer such as a polymer can be used.

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, it can be preferably used because 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 the heat-sensitive recording material of the present invention is a two-color heat-sensitive recording material, it is possible to include a colored dye and / or a colored pigment having a color tone complementary to the low-temperature color tone in the thermosensitive coloring layer by printing. It is preferably used for adjusting the color tone of the previous recording material. If necessary, within a range that does not impair the effects of the present invention, in the thermosensitive coloring layer, further an oil repellent, an antifoaming agent,
Various additives such as a viscosity modifier can be added. The heat-sensitive coloring layer has a coating amount of 2 to 20 g after drying on the undercoat layer.
/ M ² , more preferably 4 to 10 g / m ² .

In the present invention, the light resistance is greatly improved by including microcapsules containing an ultraviolet absorber or solid fine particles of the ultraviolet absorber in the heat-sensitive coloring layer or the protective layer provided thereon. Can also. Specific examples of the ultraviolet absorber include the following. Phenyl salicylate, p-tert-butylphenyl salicylate, salicylic acid-based ultraviolet absorbers such as p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-
Examples include benzophenone-based ultraviolet absorbers such as dimethoxybenzophenone and 2-hydroxy-4-methoxy-5sulfobenzophenone.

Further, 2- (2′-hydroxy-5 ′)
-Methylphenyl) benzotriazole, 2- (2'-
Hydroxy-5'-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-
Di-tert-butylphenyl) benzotriazole,
2- (2'-hydroxy-3'-tert-butyl-
5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-ter
t-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-ter
(t-amylphenyl) benzotriazole, 2- [2 ′
-Hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimido-methyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-
5′-tert-octylphenyl) benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α,
α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-3′-dodecyl-
5′-methylphenyl) benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylhexyl)
Oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300) and methyl-3- [3-te
rt-butyl-5- (2H-benzotriazole-2-
Benzotriazole-based ultraviolet absorbers such as condensates with yl) -4-hydroxyphenyl] propionate, 2 ′
And cyanoacrylate-based ultraviolet absorbers such as -ethylhexyl-2-cyano-3,3-diphenylacrylate and ethyl-2-cyano-3,3-diphenylacrylate. Of course, the present invention is not limited to these, and two or more kinds can be used in combination as needed.

Among these ultraviolet absorbers, benzotriazole-based ultraviolet absorbers are preferred, and particularly, 2- (2'-
(Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-dodecyl) -5'-
Methylphenyl) benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethylhexyl) oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300) and methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl)-
A condensate with [4-hydroxyphenyl] propionate is more preferable because it exhibits a particularly remarkable effect of improving light resistance.

The addition amount of the microcapsules containing the ultraviolet absorbent or the solid fine particles of the ultraviolet absorbent is not particularly limited, but may be contained in the thermosensitive coloring layer or in the protective layer provided on the thermosensitive coloring layer. In any case, the content is preferably about 5 to 70% by weight based on the total solid content of each layer. Particularly preferably, 1
Adjust to a range of 5 to 50% by weight. If the amount is less than 5% by weight, the effect of improving light resistance is poor. If the amount is more than 70% by weight, not only the effect of improving light resistance is poor, but also the sensitivity of the thermosensitive coloring layer may be reduced. The microcapsules containing the ultraviolet absorber or the solid fine particles of the ultraviolet absorber can be more effectively improved in light resistance when contained in the protective layer than in the thermosensitive coloring layer.

The microcapsules of the ultraviolet absorbent used in the present invention can be prepared by various known methods. In general, the solid or liquid ultraviolet absorbent at room temperature is dissolved in an organic solvent as required. The obtained core substance (oil-based liquid) is emulsified and dispersed in an aqueous medium, and is prepared by a method of forming a wall film made of a polymer substance around oil-based droplets. As a specific example of the polymer substance which becomes the wall film of the microcapsule,
For example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin,
Styrene-methacrylate copolymer resin, styrene-acrylate resin, gelatin, polyvinyl alcohol, and the like. Among them, particularly, a microcapsule having a wall film made of a polyurethane-polyurea resin or an aminoaldehyde resin is excellent in heat resistance, and therefore, in order to prevent sticking to a thermal head, a heat-sensitive coloring layer or a protective layer is used. It has an excellent accompanying effect of also performing the function of an inorganic pigment to be added, and has a lower refractive index than microcapsules made of other wall films and ordinary pigments, and has a spherical shape, Even if a large amount is added to the protective layer, it is preferably used because there is no possibility of causing a decrease in density due to irregular reflection of light.

The microcapsules containing the ultraviolet absorbent used in the present invention are those in which the ultraviolet absorbent is a core substance as a liquid part, which is protected by the capsule wall material, and the dye precursor is high. Composite particles containing a molecule and a dye precursor which is considered to exist in a solid solution state are completely different in the state of existence, shape, and desired function.

In the present invention, the addition of a fluorescent whitening agent to the thermosensitive coloring layer and the protective layer also has an effect of improving light resistance and can be preferably used. Fluorescent whitening agents are widely used as whitening agents because they have the effect of absorbing light in the ultraviolet region and emitting light in the visible region with longer wavelengths. The dye precursor contained in the composite fine particles used in the present invention has a property of being easily decomposed and yellowed by light in a high-energy ultraviolet region, but has a longer wavelength region in which ultraviolet light is more harmless by a fluorescent whitening agent. By changing to light, not only yellowing can be prevented but also an effect on whiteness can be obtained. Also, decoloring of the printed portion by light can be improved by including a fluorescent whitening agent.

The fluorescent whitening agents usable in the present invention include:
For example, derivatives of pyrene, coumarin, oxazole, imidazole, imidazolone, pyrazole, benzidine, diaminocarbazole, naphthalic acid and diaminostilbene disulfonic acid can be mentioned. More specifically, 1,2-bis (5-methyloxazol-2-yl) ethylene, β, 4-bis (5-methyloxazol-2-yl) -styrene, 3-ethyloxycarbonyl-7,8 -Benzocoumarin, N-methyl-4-methoxynaphthalene-1,8-dicarboxylic imide, 4- [3-
(4-chlorophenyl) -5-phenyl-1-pyrazolin-1-yl] -sodium benzenesulfonate, 1,2-
Bis [4- (phenylaminocarbonylamino) -2-
Sodium oxysulfonylphenyl] ethylene, 1,2
-Bis {4- [2- (p-sodiumoxysulfonylanilino) -4-bis (2-hydroxyethyl) amino-
1,3,5-triazin-6-yl] amino-2-sodiumoxysulfonylphenyl} ethylene and the like. Among these compounds, diaminostilbene disulfonic acid derivative 1,2-bis {4- [2- (p
-Sodiumoxysulfonylanilino) -4-bis (2
-Hydroxyethyl) amino-1,3,5-triazin-6-yl] amino-2-sodiumoxysulfonylphenyl {ethylene is also preferred from the viewpoint of easy handling during preparation of a coating solution.

The amount of the fluorescent whitening agent is not particularly limited, but may be 0.5 to the total solid content of the thermosensitive coloring layer.
About 15% by weight is preferable. Particularly preferably, 1-1
Adjust so as to be in the range of 0% by weight. If the amount is less than 0.5% by weight, a sufficient effect cannot be obtained. If the amount is more than 10% by weight, the background is colored by the color of the fluorescent whitening agent itself, resulting in a heat-sensitive recording material having a poor natural paper feeling.

In the present invention, a magnetic recording layer may be provided on the surface of the support on which the thermosensitive coloring layer is not provided, or between the support and the thermosensitive coloring layer. The magnetic recording layer
A magnetic recording layer conventionally used for a magnetic ticket, a prepaid card, a magnetic commuter pass, or the like can be used. When the magnetic recording layer is provided between the support and the thermosensitive coloring layer, even when provided on the surface of the support where the thermosensitive coloring layer is not provided, the magnetic recording layer is coated before the thermosensitive coloring layer is applied. This is desirable to keep the whiteness of the thermosensitive coloring layer high.

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

In the present invention, it is desirable to provide a protective layer containing a water-soluble polymer material and a pigment as used in conventionally known thermosensitive recording materials on the thermosensitive coloring layer. As the water-soluble polymer material and the pigment, the materials exemplified for the thermosensitive coloring layer can be used. At this time, it is more desirable to add a crosslinking agent to impart water resistance to the protective layer. Such a protective layer is coated on the thermosensitive coloring layer so that the coating amount after drying is 0.5 to 10 g / m ² . More preferably, it is applied so as to be 1 to 5 g / m ² .

In the present invention, a resin layer cured by an electron beam or ultraviolet rays may be provided on the thermosensitive coloring layer or on the protective layer. Japanese Patent Application Laid-Open No.
These are described in JP-A-8-177392 and JP-A-58-177392. In such a resin, a non-electron beam curable resin, a pigment, an antifoaming agent, a leveling agent, a lubricant,
Additives such as surfactants and plasticizers can be added as appropriate. In particular, it is preferable to add a pigment such as calcium carbonate or aluminum hydroxide, or a lubricant such as waxes or silicon, because it helps prevent sticking to the thermal head. The resin layer cured by an electron beam or ultraviolet rays is applied so that the coating amount after drying is 0.5 to 10 g / m ² . More preferably, it is applied so as to be 1 to 5 g / m ² .

In the present invention, printing can be performed with UV ink, flexo ink, or the like. In this case, printing may be performed on any layer such as a thermosensitive layer, a protective layer, an electron beam curable resin layer, or an ultraviolet curable resin layer.

There are no particular restrictions on the type, shape, dimensions, etc. of the support material used in the present invention, and examples thereof include high quality paper (acid paper, neutral paper), medium paper, coated paper, art paper, and cast paper. In addition to coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, and the like, various transparent supports and the like can be appropriately selected and used. When the present invention is used for magnetic ticket use, it is preferable to use paper. However, when the present invention is used for magnetic commuter pass use, a plastic base made of polyethylene terephthalate having a thickness of 100 μm or more is used. It is desirable to use a material, particularly a foamed base material, from the viewpoint of heat-sensitive coloring sensitivity. Of course, a laminated substrate of a foamed polyethylene terephthalate film and a non-foamed polyethylene terephthalate film can be used.

In the present invention, in order to increase the added value of the heat-sensitive recording material, the heat-sensitive recording material can be further processed to obtain a heat-sensitive recording material having higher functions. For example, an adhesive paper, a rewet adhesive paper, or a delayed tack paper can be obtained by applying a coating process using an adhesive, a rewet adhesive, a delayed tack type adhesive, or the like on the back surface. In particular, those obtained by subjecting the heat-sensitive recording material of the present invention to an adhesive treatment are useful as heat-sensitive labels because of their good storage stability. In addition, a recording paper capable of performing double-sided recording can be provided by using the back surface thereof and imparting the functions of thermal transfer paper, ink-jet paper, carbonless paper, electrostatic recording paper, and xerography paper. Of course, a double-sided heat-sensitive recording material can also be used.

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, a back layer can be provided for suppressing penetration of oil or plasticizer from the back surface of the recording material, or for controlling curl. Smoothing the heat-sensitive recording surface using a known smoothing method such as a super calender or a soft calender is effective in increasing the color sensitivity. The heat-sensitive recording surface may be applied to either a metal roll or an elastic roll of a calender.

[0082]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
Unless otherwise specified, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

(1) Preparation of Materials Used for Undercoat Layer, Thermosensitive Coloring Layer, and Protective Layer <Preparation of Composite Fine Particle Dispersion Containing Coloring Dye Precursor> 3-Di (n-pentyl) amino as a coloring dye precursor -6
10 parts of -methyl-7-anilinofluorane was dissolved in 24 parts of dicyclohexylmethane-4,4'-diisocyanate heated to 100 ° C, and the solution was cooled to 25 ° C.
250% aqueous solution of 8% polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry, trade name: Gohsenol GM-14L) at the same temperature
TK homomixer (Model HV-
M, manufactured by Tokushu Kika Kogyo Co., Ltd.)
After emulsifying and dispersing by stirring, water is added to this emulsified dispersion.
00 parts were added to homogenize. The temperature of the emulsified dispersion was raised to 80 ° C., and a curing reaction was performed for 10 hours to prepare a dispersion of composite fine particles containing a color-forming dye precursor having an average particle diameter of 1.2 μm.

<Preparation of Dye Precursor, Developing Compound, and Sensitizer Dispersion in Solid Fine Particle State> Black color dye precursor: 3-di (n-pentyl) amino-6-methyl-7-anilino Fluorane Red color dye precursor: 3-Diethylamino-7-chlorofluorane Color-developing compound: Bis (3-allyl-4-hydroxyphenyl) sulfone Sensitizer: Di-p-methylbenzyl oxalate

The above-mentioned dye precursor, color-developing compound, and sensitizer are separately mixed with polyvinyl alcohol at the following mixing ratio, and each mixture is used with a vertical sand mill (manufactured by IMEX Co., Ltd., sand grinder). Then, the mixture was pulverized and dispersed so that the average particle diameter became 1.2 μm, thereby obtaining a dispersion of each compound in the form of solid fine particles.

Component amount (parts by weight) Each compound 40 Polyvinyl alcohol 10% liquid 40 (Polymerization degree 500, saponification degree 90%) Water 20

<Preparation of Inorganic Pigment Dispersion> Silica was mixed with sodium polyacrylate in the following mixing ratio, and this mixture was dispersed using a Cowles disperser. Component amount (parts by weight) Silica 50 1.0% sodium polyacrylate solution 50

Separately, an aqueous solution of polyvinyl alcohol (NM11Q, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) having a solid content of 10% was used as an adhesive solution, and an aqueous dispersion of zinc stearate having a solid content of 21% (Z- 7, Chukyo Yushi Co., Ltd.).

(2) Formation of Undercoat Layer The above pigment dispersion and adhesive liquid were mixed at a solid content of 8
0:20, and this paint was applied on a high-quality paper (neutral paper) with a basis weight of 60 g / m ² using a Meyer bar.
2.0 g / m ² (dry) was applied to form an undercoat layer.

(3) Formation of heat-sensitive color-forming layer The solids content ratio of each of Examples 1 to 10 in Tables 1 and 2 was
A thermosensitive coloring layer coating solution formulated to correspond to Comparative Examples 1 to 6 was applied to the previously formed undercoat layer using a Meyer bar so that the coating amount (dry) was 8.0 g / m ^2. Coating,
A heat-sensitive coloring layer was formed.

(4) Formation of Protective Layer First, a protective layer coating liquid was prepared by mixing the pigment dispersion, the adhesive liquid, and the lubricant such that the solid content ratio was 40: 55: 5. Using a Meyer bar, a coating amount (dry) of 3.0 g / m ² was applied on the heat-sensitive coloring layer thus obtained to obtain each heat-sensitive recording material before the smoothing treatment.

The heat-sensitive recording material thus obtained was adjusted by using a super calender under pressure conditions so that the Beck smoothness (JIS-P8119) of the heat-sensitive recording surface was 300 to 120.
A smoothing process was performed so as to be 00 seconds.
-Thermal recording materials corresponding to Examples 1 to 10 and Comparative Examples 1 to 6 in Table 4 were obtained.

<Evaluation of Single-Colored Thermosensitive Recording Material> The single-colored thermosensitive recording materials shown in Tables 1 and 2 were printed using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.) in one-line recording time: 5 msec, sub-scanning. Solid printing of 256 lines was performed under the conditions of a line density of 8 lines / mm and an applied energy per dot of 2.0 mJ, to obtain a black color printed matter. The density of the printed portion is measured using a Macbeth densitometer RD914, and is at a practically acceptable level if the color density is 1.20 or more. Further, the image uniformity of the color-developed portion was evaluated by the degree of white spots. ○ indicates that almost no white spots were observed and the image uniformity was high, and x indicates that there were many white spots and the uniformity was poor. The obtained heat-sensitive recording material after color development was immersed in salad oil at 20 ° C. for 24 hours to examine the degree of color erasure thereof as an oil resistance storage test. ○ indicates that almost no decoloration was observed, and X indicates that the color was erased and the print density was significantly reduced.

<Evaluation of Two-Colored Thermosensitive Recording Material> The two-colored thermosensitive recording materials shown in Tables 3 and 4 were recorded using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.) for one line recording time of 5 msec. Solid printing of 256 lines was performed under the conditions of a sub-scanning line density of 8 lines / mm and an applied energy per dot of 0.5 mJ, and red coloring was recorded in low-temperature printing. Separately, recording time per line: 5 msec, sub-scanning line density: 8 lines / mm, applied energy per dot:
Solid printing of 256 lines was performed under the condition of 2.0 mJ, and black color recording in high-temperature printing was performed.

The color product obtained in this manner is:
The color separation was evaluated visually. O indicates that a clear red color was obtained at low-temperature coloring and a black color was obtained at high-temperature coloring. X indicates that red was mixed with black of a low-temperature color tone and the color was reddish to black, indicating that color separation was not possible. Further, an oil storage stability test was performed on the two-color heat-sensitive recording material in the evaluation of the single-color heat-sensitive recording material, and the results are shown in Tables 3 and 4.

<Evaluation of Runnability> The runnability of the printer in printing a single-color and two-color heat-sensitive recording material was evaluated. × indicates that running failure such as sticking occurred and printing could not be performed normally. ○ indicates that printing was normally performed.

[0097]

[Table 1]

[0098]

[Table 2]

[0099]

[Table 3]

[0100]

[Table 4]

[0101]

According to the present invention, a heat-sensitive recording material having a high storage stability and a high degree of sensitivity and uniformity of image can be obtained by smoothing by performing a high-level calendering process. In addition, even in the case of multicoloring, a multicolor heat-sensitive recording material having the same high performance as described above and little mixing of color tones can be obtained.

Claims (2)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive coloring layer provided on a support, wherein (1) the heat-sensitive coloring layer comprises at least one polymer selected from polyurea and polyurethane and a dye precursor. And (2) a heat-sensitive recording surface having a Beck's smoothness of 500 to 100 which contains fine particles and a color developer which reacts with the dye precursor under heating to develop the color.
A heat-sensitive recording material having a smoothness of 00 seconds. 2. The thermosensitive coloring layer according to claim 1, further comprising a second dye precursor that develops a color tone different from that of the dye precursor contained in the composite fine particles.
2. The heat-sensitive recording material according to item 1.