JPH11208119A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material having high recording sensitivity and excellent recording running properties, causing little tailings of head and being excellent in the oil-resisting shelf life of a color developing part and in resistance to washing, in regard to a thermal recording material having a thermal recording layer provided on a synthetic resin film support or a multicolor thermal recording material for which two kinds or more of dye precursors of which the colors are developed in different color tones according to differences in conditions of heating impression, and a developer are used. SOLUTION: In a thermal recording material having an undercoat layer and a thermal color development layer provided sequentially on a synthetic resin film support, the thermal color development layer contains composite fine particles constituted of at least one kind of macromolecular substance selected from polyurea and polyurethane and of a dye precursor and a developer which develops the color of this dye precursor in reaction therewith in heating, and the undercoat layer contains a hydrophobic macromolecular substance as a main constituent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material suitable for a prepaid card, a commuter pass and the like, which has excellent oil-resistant storage stability and high washing resistance.

[0002]

2. Description of the Related Art Conventionally, a dye precursor and a color-developing compound which makes contact with the dye precursor under heating to develop a color are used, and the two color-forming substances are brought into melting contact by heating. Thermal recording materials capable of obtaining color images are widely known. Such a heat-sensitive recording material is relatively inexpensive, has a compact recording device, and is easy to maintain. Therefore, it is widely used as a recording medium for facsimile machines, word processors, various computers, and other applications. Have been.

[0003] With the expanded use of the heat-sensitive recording material, the required quality is also diversified. For example, there are demands for high sensitivity, image stabilization, multicolor recording, and the like. In particular, in recent years, thermal facsimile and printer devices have been improved, and high-speed recording, which has been difficult in the past, has become possible, and the thermal recording materials used therein are required to further improve the recording sensitivity. In addition, fields such as prepaid cards, commuter passes, boarding passes, and other cash vouchers that require washing resistance and print storage stability are also expanding.

[0004] Prepaid cards, commuter passes, various types of coupons and the like must be able to withstand many uses depending on the use conditions, and may be washed by mistake. A synthetic resin film having excellent physical strength such as stiffness, tensile strength, tear strength and bending strength, or excellent water resistance is selected from paper. In general, a synthetic resin film substrate has a higher heat sensitivity than a paper substrate and thus has a higher recording sensitivity. However, when using a synthetic resin film for the base material,
There is a disadvantage that the adhesive strength between the base material and the thermosensitive coloring layer cannot be obtained sufficiently, and there is a problem such as peeling of the thermosensitive layer during washing. In general, this problem is particularly serious in a case where a water-soluble or water-dispersible resin is used as a binder for the thermosensitive coloring layer.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material having a heat-sensitive recording layer provided on a synthetic resin film support, which has high recording sensitivity, excellent recording running property, low head scum, and a color-developing portion. An object of the present invention is to provide a heat-sensitive recording material that is excellent in oil-resistant storage stability and washing resistance. Furthermore, the present invention provides a thermosensitive coloring layer containing two or more dye precursors that develop different colors depending on the difference in the heating application conditions from the thermal head and a color developing compound that develops the dye precursor. In multi-color heat-sensitive recording materials, the color tone of low-temperature printing is less mixed with the color tone of high-temperature color development, recording runability is excellent, head scum is less, oil-storing resistance of the colored part is excellent, and washing resistance is excellent. It is to provide an excellent heat-sensitive recording material.

[0006]

In order to solve the above problems, the present invention employs the following constitution. That is, the first invention of the present invention relates to "a heat-sensitive recording material in which an undercoat layer and a heat-sensitive coloring layer are sequentially provided on a synthetic resin film support, wherein (1) the heat-sensitive coloring layer is selected from polyurea and polyurethane. And (2) an undercoat layer having a high hydrophobicity, comprising composite fine particles comprising at least one polymer substance and a dye precursor, and a color developer which reacts with the dye precursor under heating to develop a color. A heat-sensitive recording material characterized by containing a molecular substance as a main component ”.

A second invention of the present invention is the "thermosensitive recording material according to the first invention, wherein the hydrophobic polymer substance is a styrene-butadiene copolymer".

The third invention of the present invention is "The heat-sensitive recording material according to the first or second invention, wherein the undercoat layer contains a pigment."

The fourth invention of the present invention is directed to the "first to third embodiments"
Wherein the heat-sensitive coloring layer comprises a second dye precursor which develops a color tone different from that of the dye precursor contained in the composite fine particles, in addition to the dye precursor contained in the composite fine particles. .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a synthetic resin film is used as a support because of its excellent rigidity, tensile strength, tear strength and water resistance. Synthetic resins include polyolefin, polystyrene, polyvinyl chloride, polyester,
Polyamide, polycarbonate and the like can be used. Further, the synthetic resin referred to in the present invention includes a semi-synthetic resin such as cellulose acetate. Further, a composite film of the above film may be used.

As the polyolefin, polypropylene,
As polyester, polyethylene terephthalate (P
ET) is preferred. The synthetic resin film used in the present invention may have fine voids inside like a foamed PET. Further, the film surface may be subjected to a surface treatment such as an antistatic treatment and an easy adhesion treatment.

The undercoat layer of the present invention is indispensable for securing the bonding strength between the thermosensitive recording layer containing the composite fine particles and the support film. The undercoat layer needs to contain a hydrophobic polymer as a main component from the viewpoint of washing resistance. It is necessary that the amount of the hydrophobic polymer is 50% by weight or more based on the total weight of the undercoat layer.

Examples of the hydrophobic polymer include styrene-butadiene polymer, acrylic polymer, vinyl acetate polymer, ionomer polymer, polyvinyl chloride, polyvinylidene chloride, and polyurethane. Examples of the styrene-butadiene-based polymer include a styrene-butadiene copolymer and a styrene-butadiene-acrylonitrile copolymer. Among them, the styrene-butadiene copolymer has excellent washing resistance. As the acrylic polymer, acrylic acid, acrylic acid ester, methacrylic acid, polymer of acrylic monomer selected from methacrylic acid ester, or a copolymer of two or more of these,
Alternatively, a copolymer of these and another vinyl monomer may be used. Specifically, polyacrylates, polymethacrylates, and copolymers of (acrylic acid and / or methacrylic acid) and (acrylic acid ester and / or methacrylic acid ester) can be used. Further, as other monomers copolymerized with the acrylic monomer,
Examples include ethylene, vinyl acetate, and styrene. Examples of copolymers of acrylic monomers and other monomers include, for example, ethylene-acrylate copolymer, styrene-acrylate copolymer, acrylate-vinyl acetate copolymer, and the like. . Examples of the vinyl acetate polymer include polyvinyl acetate, vinyl acetate-
Acrylic copolymer, ethylene-vinyl acetate copolymer,
And vinyl chloride-vinyl acetate copolymers.

[0014] The hydrophobic polymer of the present invention increases the opacity of the heat-sensitive recording material and prevents the phenomenon (blocking) that the coated surface sticks to the back of the base paper when the undercoat layer is coated and wound up. Therefore, it is also possible to mix and use an inorganic pigment or an organic pigment. Specific examples of such pigments include inorganic pigments such as calcium carbonate, magnesium carbonate, kaolin, calcined kaolin, talc, aluminum hydroxide, amorphous silica, titanium oxide, polystyrene, polymethyl acrylate, polyvinyl chloride, and polyvinylidene chloride. And an organic pigment having a filled structure or a hollow structure composed of urea-formaldehyde resin.

[0015] Such undercoat layer on the support, the coating amount after drying 0.5 to 20 g / m ^2, preferably formed by coating and drying so as to 1 to 5 g / m ² approximately You.

The hydrophobic polymer substance used for the undercoat layer may be used in the form of an emulsion dispersed in an aqueous system, or may be used by dissolving it in an organic solvent.
Further, it may be used in the form of melt extrusion. Further, a water-soluble polymer can be used in combination with the undercoat layer of the present invention as long as the effects of the present invention are not impaired. Examples of these water-soluble adhesives include polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acryl. Examples include acid ester copolymers, acrylamide-acrylic acid ester-methacrylic acid ester copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, casein, gelatin, and derivatives thereof.
When the heat-sensitive layer containing the composite fine particles is directly provided on the synthetic resin film, the adhesion between the heat-sensitive layer and the base material cannot be said to be high, but an undercoat layer mainly composed of a hydrophobic polymer is provided therebetween. As a result, the adhesiveness of the heat-sensitive layer to the base material is dramatically increased, the amount of head scum resulting from the peeling of the heat-sensitive layer is small, and the running property of the head is also improved. Also, peeling of the heat-sensitive layer during washing is not easy. The reason for this is not necessarily clear, but the hydrophobic polymer has a high affinity with both the polymer such as polyurea and polyurethane, which form the composite fine particles, and also with the synthetic resin film as the base material. We believe that it strengthens the bonding of the heat-sensitive layer.

In the undercoat layer coating liquid, if necessary, various auxiliaries such as a dispersant, an antifoaming agent, a coloring dye, a fluorescent dye, and a curing agent can be appropriately added.

As a method for forming a coating liquid for an undercoat layer on a support, an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dipping method,
Any of known coating methods such as a bar method and an extrusion method may be used.

A thermosensitive coloring layer is provided on the undercoat layer thus formed. The thermosensitive coloring layer used in the present invention includes a base material composed of at least one polymer substance (resin) selected from polyurea or polyurethane and composite fine particles composed of a dye precursor contained therein. contains. It is considered that the dye precursor and the polymer substance exist in a solid solution state in the composite fine particles.
It is desirable that the composite fine particles do not contain a liquid such as an oily solvent from the viewpoint of pressure fogging.

The color precursor of the dye precursor contained in the composite fine particles has extremely excellent storage stability, particularly excellent resistance to oils and plasticizers, as compared with color formers formed 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 concave 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.

In order to obtain a heat-sensitive recording material capable of forming multiple colors in the present invention, 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 which is solid fine particles, and the high-temperature color tone is a mixed color tone of the first dye precursor and the second dye precursor present in the composite fine particles. By making the second dye precursor black, the first
Even when color mixture occurs due to color development of the dye precursor, the high-temperature color tone can be made black. The first dye precursor to be contained in the composite fine particles may be a single compound and may have a black coloring property, or may be a mixture of two or three or more different coloring tone dye precursors to form a black coloring property. It is good.

In order to make the high-temperature color tone closer to pure black, 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 used as a black color dye. It is desirable to include it in the composite fine particles together with the precursor. When the low-temperature color tone is red, the composite fine particles contain a blue or green coloring dye precursor together with the black coloring dye precursor.

The dye precursor that can be used in the present invention includes 3-pyrrolidino-6-methyl-7-anilinofluoran,
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-anilino Fluoran, 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-anilinofluoran.

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-bromofluoran, 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] and the like as a red dye precursor.

As a dye precursor giving a blue color,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide, 3 -(1-ethyl-2
-Methylindol-3-yl) -3- (2-methyl-
4-diethylaminophenyl) -4-azaphthalide, 3
-(1-ethyl-2-methylindol-3-yl)-
3- (2-ethoxy-4-diethylaminophenyl)-
4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-n-hexyloxy-
4-diethylaminophenyl) -4-azaphthalide and 3,6-bis (diphenylamino) fluoran.

As the dye precursor giving green color, 3
-(N-ethyl-NN-hexylamino) -7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4 -Azaphthalide, 3-
(N-ethyl-Np-tolylamino) -7- (N-phenyl-N-methylamino) fluoran, 3- [p-
(P-anilinoanilino) anilino] -6-methyl-7
-Chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, and the like.

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

As a method for preparing composite fine particles comprising a dye precursor and at least one polymer selected from polyurea and polyurethane used in the present invention, for example, a method in which a dye precursor has a low boiling point of 100 ° C. or less is used. It is dissolved in a boiling water-insoluble organic solvent, and a polymer-forming raw material such as a polyvalent isocyanate compound alone or a mixture of a polyvalent isocyanate and a polyol reacting with the same, or an adduct of a polyvalent isocyanate and a polyol, A multimer such as a biuret or isocyanurate of a polyvalent isocyanate is added, and this mixture is emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol. After mixing the active substance, the organic solvent is volatilized and removed by heating the emulsified dispersion, The polymerized by the polymerization of a polymer-forming material after, whereby there is a method of forming a composite fine particles comprising a dye precursor and polymer substance. In this method, in order to sufficiently volatilize and remove the organic solvent, the conditions may be set experimentally in consideration of the type of the solvent, the emulsification and dispersion conditions, the mixing ratio of the dye precursor and the solvent, and the like. . Generally, when a solvent having a boiling point of 50 ° C. or less is used, an open container is used, and the dispersion after emulsification and dispersion is heated at a temperature 5 to 10 ° C. lower than the boiling point of the solvent for 2 hours or more, more preferably 5 hours. By holding as described above, the organic solvent can be volatilized and removed. After removing the organic solvent, the dispersion is heated to 80 ° C. to polymerize the polymerized raw material.
The composite fine particles can be produced by heating to about 95 ° C. and maintaining the temperature at this temperature for 1 hour or more, more preferably 2 hours or more.

The organic solvent used for preparing the composite fine particles may have a boiling point of 100 ° C. or less, more preferably 80 ° C.
It is preferable that the content be the following or hydrophobic. For example, such low-boiling hydrophobic (water-insoluble) organic solvents include butyl chloride (boiling point 78 ° C.), ethylidene chloride (57 ° C.), propyl chloride (46 ° C.), and methylene chloride (42 ° C.). ,
It can be selected from ethyl acetate (77 ° C) and methyl acetate (57 ° C). Acetone (56 ° C.) and methanol (65 ° C.) are not preferable because they are compatible with water and the resulting emulsion may become unstable. Another method for preparing composite fine particles comprising a dye precursor and at least one polymer substance selected from polyurea and polyurethane used in the present invention is as follows. Only an isocyanate compound or a mixture of a polyvalent isocyanate and a polyol reacting with the polyisocyanate, or an adduct of a polyvalent isocyanate and a polyol, a biuret of a polyvalent isocyanate, dissolved in a multimer such as an isocyanurate,
This solution is emulsified and dispersed in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved and, if necessary, a reactive substance such as polyamine is mixed. It can be produced by a method of polymerizing a forming raw material to form a polymer, thereby forming composite fine particles comprising a dye precursor and a polymer substance. Since this method does not use a low-boiling-point solvent, it has the advantage of not requiring an evaporation step, and is also capable of obtaining composite fine particles having excellent separability.

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
-Isocyanato-1- (isocyanatomethyl) -1,
3,3-trimethylcyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1 , 2-diisocyanate, butylene-1,2-
Examples thereof include diisocyanates such as diisocyanate, cyclohexylene-1,2-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-butanediol, 1,2-
Butanediol, 1,3-butanediol, 2,2-dimethyl-1,3-propanediol, 2,4-pentanediol, 2,5-hexanediol, 3-methyl-
1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, Aliphatic polyols such as glycerin, 1,4-di (2
-Hydroxyethoxy) benzene, 1,3-bis (2-
Condensation products of aromatic polyhydric alcohols such as hydroxyethoxy) benzene and alkylene oxide, p-xylylene glycol, m-xylylene glycol, α, α '
-Dihydroxy-p-diisopropylbenzene, 4,
4'-dihydroxydiphenylmethane, 2- (p, p '
-Dihydroxydiphenylmethyl) benzyl alcohol, 4,4'-isopropylidenediphenol, 4,
4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, ethylene oxide adduct of 4,4'-isopropylidenediphenol,
Examples thereof include 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 development 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. As the polyvalent isocyanate compound, it is preferable to select a polyisocyanate 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 acting as a solvent for the dye precursor is mixed with the polyvalent isocyanate compound and used as long as the object of the present invention is not impaired. 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 may give undesired results. 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,
Alkylated benzenes such as 1-methyl-1-phenyl-1-tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropylbiphenyl, o-
Examples include xenoxyalkanes such as phenylphenol glycidyl ether, acrylic esters such as trimethylolpropane triacrylate, esters of polyhydric alcohol and unsaturated carboxylic acid, chlorinated paraffin, and kerosene. Needless to say, two or more of these can be used in combination.

In addition, tin compounds, polyamide compounds,
An epoxy compound, a polyamine compound or the like may be used in combination. When a polyamine compound is used, it is preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not reduced.

In the present invention, when a multicolor heat-sensitive recording material is used, a 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,
Polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohol such as sulfone group-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer salts and other water-soluble polymer compounds such as derivatives thereof, If necessary, the dispersion may be dispersed in a dispersion medium together with a surfactant, an antifoaming agent, and the like to prepare 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 by increasing the temperature and a property of contacting with the above-mentioned 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 which can be used as the color developing compound include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate,
Phenolic compounds such as 4-sec-butyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, and 4,4'-dihydroxydiphenyl ether Or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, Aromatic carboxylic acids such as 3,5-di-tert-butylsalicylic acid, and phenolic compounds, and organic acidic substances such as salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum and calcium. But That.

In the present invention, it is particularly preferable to use a diphenylsulfone derivative containing a hydroxyl group in the molecule as 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 500 parts by weight, more preferably 50 to 300 parts by weight, based on 100 parts by weight of the composite fine particles. Of course, if necessary, two or more types of color developing compounds can be used in combination.

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

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

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

In the present invention, a fine pigment having a high whiteness and an average particle diameter of 10 μm or less can be contained in the thermosensitive coloring layer in order to improve the whiteness of the thermosensitive coloring layer and the uniformity of the image. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin and polystyrene resin can be used. To prevent head residue and sticking to the thermal head, the oil absorption amount should be 50 ml / 1.
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, examples of the adhesive used for the heat-sensitive coloring layer include those exemplified for the undercoat layer. If necessary, a crosslinking agent, waxes, metal soap, colored dye, colored pigment, fluorescent dye, and the like can be used.

Examples of the crosslinking agent added for improving the water resistance of the thermosensitive coloring layer include 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 inorganic compounds such as magnesium chloride, sodium tetraborate, and potassium tetraborate, or boric acid, boric acid triesters, boron-based polymers, and the like. It is preferable to use the selected at least one crosslinkable compound in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total solid content of the thermosensitive coloring layer.

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, various additives such as a fluorescent dye, an ultraviolet absorber, 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 has a coating amount after drying on the support of ² to 20 g / m ² , more preferably 4 to 1 g / m ² .
Coating is performed so as to be 0 g / m ² .

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

In the present invention, a protective layer containing a water-soluble polymer material and a pigment as used in conventionally known thermosensitive recording materials can be provided 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.
It is described in JP-A-8-177392. In such a resin, a non-electron beam curable resin, a pigment, and additives such as an antifoaming agent, a leveling agent, a lubricant, a surfactant, and a plasticizer can be appropriately added. In particular, it is preferable to add a pigment such as calcium carbonate or aluminum hydroxide, or a lubricant such as waxes or silicon, because it helps prevent sticking to the thermal head. The resin layer cured by an electron beam or ultraviolet light has a coating amount of 0.5 to 10 after drying.
g / m ² . More preferably 1 to
Coating is performed so as to be 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 heat-sensitive layer, a protective layer, an electron beam curable resin layer, or an ultraviolet curable resin layer.

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 a higher function. 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.

The method for forming each of the above layers on the support includes known coating methods such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method. Either may be used. Further, a back layer can be provided for suppressing penetration of oil or plasticizer from the back surface of the recording material, or for controlling curl. Smoothing the heat-sensitive 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.

[0066]

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

Example 1 (1) Preparation of Coating Solution for Undercoat Layer A styrene-butadiene-based latex having a solid concentration of 48% (trade name: L-1571, manufactured by Asahi Kasei Corporation) was used for the undercoat layer. It was a coating liquid.

(2) Preparation of coating solution for thermosensitive coloring layer and protective layer <Preparation of composite fine particle dispersion containing black coloring dye precursor>
13 parts of 3-di-n-amylamino-6-methyl-7-anilinofluoran as a black color-forming dye precursor is dissolved in 50 parts of methylene chloride, and the isocyanurate of hexamethylene diisocyanate (trade name) is added to this solution. : 70 parts of Takenate D-170HN (concentration: 100%, manufactured by Takeda Pharmaceutical Co., Ltd.) was added and uniformly mixed and dissolved. While gradually adding this mixed solution to 400 parts of an aqueous solution of 10% polyvinyl alcohol (trade name: Gooselan L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), a TK homomixer (Model HV-M, Tokushu Kika Kogyo Co., Ltd.) (Manufactured by Co., Ltd.), and emulsified and dispersed by stirring at a rotation speed of 6000 rpm. Then, 100 parts of water was added to the emulsified dispersion to homogenize. The temperature of the emulsified dispersion was raised to 45 ° C., and stirring was continued for 5 hours to remove methylene chloride in the emulsified particles by evaporation. Thereafter, the obtained dispersion was heated to 85 ° C. over 30 minutes, and then subjected to a polymerization curing reaction at this temperature for 3 hours to obtain a black color-forming dye precursor-containing composite fine particle having an average particle diameter of 1.4 μm. A dispersion was prepared.

<Preparation of Developing Compound and Sensitizer Dispersion> Developing compound: bis (3-allyl-4-hydroxyphenyl) sulfone Sensitizer: di-p-methylbenzyl oxalate

The color-developing compound and the sensitizer were separately mixed with polyvinyl alcohol at the following compounding ratio, and each mixture was mixed with a vertical sand mill (manufactured by IMEX Co., Ltd., sand grinder) to obtain an average particle size. The particles were pulverized and dispersed to have a diameter of 1.2 μm to obtain a dispersion of each compound in the form of solid fine particles.

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

<Preparation of Pigment Dispersion> Pigment: silica (trade name: Mizukasil P527, oil absorption 1)
90 ml / 100 g (manufactured by Mizusawa Chemical Industry Co., Ltd.) was mixed with sodium polyacrylate in the following mixing ratio, and this mixture was dispersed with a Cowles disperser. Component amount (parts by weight) Silica 50 1.0% sodium polyacrylate solution 50

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

(3) Formation of Undercoat Layer The above-mentioned undercoat layer coating solution was applied to 2.0 g / m ² (dry) on 188 μm foamed PET (East Rell Miller E62) using a Mayer bar, and the undercoat was applied. A coat layer was formed.

(4) Formation of Thermosensitive Color-Developing Layer and Protective Layer The above-described composite fine particle dispersion containing a black color-forming dye precursor, a color developing compound dispersion, a sensitizer dispersion, a pigment dispersion, and an adhesive were solidified. The blending ratio was 30: 25: 15: 15: 10 to prepare a thermosensitive coloring layer coating solution. Further, the above-mentioned pigment dispersion, adhesive liquid and lubricant dispersion were blended so as to have a solid content of 40: 55: 5 to prepare a coating solution for a protective layer. Using a Mayer bar, apply this coating solution to the previously formed undercoat layer by applying 7.0 g / m ² of the thermosensitive coloring layer and 3.0 g / m ² (drying) of the protective layer,
A thermosensitive coloring layer and a protective layer were formed to obtain a thermosensitive recording material.

Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the undercoat layer was formed in the same manner as in Example 1 except that the undercoat layer coating liquid prepared as described below was used. (1) Preparation of Coating Solution for Undercoat Layer 200 parts of a 20% dispersion of a fine particle aggregated organic pigment (trade name: Grosdale 110M, manufactured by Mitsui Toatsu Chemicals, Inc.),
Carboxy-modified styrene-butadiene latex having a solid concentration of 48% (trade name: SN307K, Sumika A & L)
100 parts) were mixed and stirred to obtain a coating liquid for an undercoat layer.

Example 3 The same procedure as in Example 1 was carried out except that in the preparation of the coating material for the thermosensitive coloring layer of Example 1, a dispersion prepared by the following method was used as the composite fine particle dispersion containing a black coloring dye precursor. Thus, a heat-sensitive recording material was prepared. <Preparation of Black Fine Particle Precursor-Containing Composite Fine Particle Dispersion>
6 parts of 3-di-n-amylamino-6-methyl-7-anilinofluoran as a black color-forming dye precursor at 100 ° C.
The solution was dissolved in 24 parts of dicyclohexylmethane-4,4'-diisocyanate heated to 25 ° C., and the solution was cooled to 25 ° C., and then 8% polyvinyl alcohol at the same temperature (trade name: Gohsenol GM-14L, Nippon Synthetic Chemical Industry Co., Ltd.) Made)
The solution was gradually added to 250 parts of the aqueous solution, and emulsified and dispersed by stirring using a TK homomixer (Model HV-M, manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rotation speed of 6000 rpm. In addition, it was homogenized. The temperature of the emulsified dispersion was raised to 80 ° C., and a curing reaction was carried out for 10 hours to prepare a dispersion of black chromogenic dye precursor-containing composite fine particles having an average particle diameter of 1.4 μm.

Example 4 In preparing the undercoat layer coating liquid of Example 3, colloidal silica-containing acrylic emulsion (LX825-D2, manufactured by Hoechst Gosei Co., Ltd.) was used instead of the carboxy-modified styrene-butadiene latex. A heat-sensitive recording material was obtained in the same manner as in Example 3 except for using.

Example 5 In preparing the undercoat layer coating liquid of Example 3, an acrylic ester copolymer emulsion (A-106 manufactured by Toagosei Co., Ltd.) was used instead of the carboxy-modified styrene-butadiene latex. A heat-sensitive recording material was produced in the same manner as in Example 3 except that (3) was used.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the undercoat layer of Example 1 was not provided.

The following tests were carried out on the six types of single-color heat-sensitive recording materials obtained by the above-mentioned operations, and the evaluation results are shown in Table 1. <Evaluation of monochromatic heat-sensitive recording material> [Recording sensitivity] Using a thermal printing tester TH-PMD (manufactured by Okura Electric Co., Ltd.), one-line printing time: 5 msec, sub-scanning line density: 8 lines / mm, applied energy per dot : 2.
Solid printing of 256 lines was performed under the condition of 0 mJ, and the density of the black color developing portion was measured with a Macbeth densitometer RD-914. There is no practical problem if the recording sensitivity is 1.15 or more.

[Head Debris] Under the same conditions as in the evaluation of the recording sensitivity described above, ten sheets of the obtained thermosensitive recording material were printed in A4 size, and the state of the debris adhering to the head was visually evaluated.は indicates that little scum was observed, and x indicates that considerable scum adhered and printing trouble was observed.

[Oil Storage Resistance] The color-developed heat-sensitive recording material obtained in the same manner as in the above-described evaluation of the recording sensitivity was added to salad oil for 2 hours.
It was immersed at 0 ° C. for 24 hours, and the degree of decoloration was examined. ○ indicates that almost no decoloration was observed, and X indicates that the color was erased and the print density was significantly reduced.

[Washing Resistance] The color-developed heat-sensitive recording material obtained in the same manner as in the above evaluation of the recording sensitivity was immersed in a 0.2% aqueous neutral detergent solution for 12 hours, and then washed for 30 minutes with a washing machine (Sanyo Electric Co., Ltd.). The degree of peeling of the heat-sensitive layer when turning Copa 25SW-S6) was examined. ◎ indicates that little peeling of the heat-sensitive layer was observed, ○ indicates that slight peeling of the heat-sensitive layer was observed, and x indicates that the heat-sensitive layer was largely peeled.

[0085]

[Table 1]

Example 6 In the preparation of the coating solution for the thermosensitive coloring layer of Example 3, a red coloring dye precursor solid dispersion prepared by the following method, and a black coloring dye precursor similar to that of Example 3 The compound fine particle dispersion, the color developing compound dispersion, the sensitizer dispersion, the pigment dispersion, the adhesive liquid, and the lubricant dispersion had a solid content ratio of 7: 30: 25: 10: 15: 8: 5. Thus, a multicolor heat-sensitive recording material was prepared in the same manner as in Example 3 except that a thermosensitive coloring layer coating solution was prepared.

<Preparation of Solid Dispersion of Red Chromogenic Dye Precursor> A red chromogenic dye precursor and polyvinyl alcohol were mixed at the following mixing ratio, and the mixture was prepared using a vertical sand mill (manufactured by IMEX Co., Ltd., sand grinder). Then, the dispersion was pulverized and dispersed so that the average particle diameter became 0.8 μm to obtain a dispersion of a red coloring dye precursor in the form of solid fine particles. Component amount (parts by weight) 3-diethylamino-7-chlorofluoran 40 Polyvinyl alcohol 10% liquid 40 (polymerization degree 500, saponification degree 90%) Water 20

<Evaluation of Two-Colored Thermosensitive Recording Material> [Color Separation] Using the above thermal printing test apparatus, one-line recording time: 5 msec, sub-scanning line density: 8 lines / mm, applied energy per dot: 0 Solid printing of 256 lines was performed under the condition 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:
When solid printing of 256 lines was performed under the condition of 2.0 mJ and black coloring was recorded at high temperature printing, clear red coloring was obtained at low temperature coloring, and black coloring without reddish color was obtained at high temperature coloring. The color separation was good.

[Head residue] Under the same conditions as in the evaluation of the recording sensitivity and the color separation, the applied energy per dot was as follows:
Solid printing of 0.5 mJ of 256 lines of red color recording and solid printing of 256 lines of applied color per dot: 2.0 mJ of 256 lines of black color recording are repeatedly printed for 10 sheets in A4 size and attached to the head. When the state of the dregs was visually evaluated, adhesion of dregs was hardly observed.

[Oil resistance storage stability] Using the above thermal printing test apparatus, 256 lines were solid under the conditions of one line recording time: 5 msec, sub-scanning line density: 8 lines / mm, and applied energy per dot: 2.0 mJ. The heat-sensitive recording material, which has been printed and subjected to black color recording at high temperature printing, is added to salad oil for 20 minutes.
Almost no discoloration was observed even after immersion at 24 ° C. for 24 hours.

[Washing Resistance] The color-developed heat-sensitive recording material obtained in the same manner as in the above evaluation of the recording sensitivity was immersed in a 0.2% neutral detergent aqueous solution for 12 hours, and then washed for 30 minutes with a washing machine (Sanyo Electric Co., Ltd.). Even when Copa 25SW-S6) was turned, little peeling of the heat-sensitive layer was observed.

[0092]

According to the present invention, it is possible to produce a heat-sensitive recording material having high recording sensitivity, excellent recording running properties, low head scum, high washing resistance, and excellent oil storage preservation of the colored portion. Was. Furthermore, to color tone of low-temperature printing,
It has become possible to produce a multicolor heat-sensitive recording material which has less mixing of color tone at the time of high-temperature coloring, has excellent recording running properties, has less head residue, has high washing resistance, and has excellent oil-storing preservation resistance at the color-developing portions.

Claims (4)

[Claims] 1. A thermosensitive recording material in which an undercoat layer and a thermosensitive coloring layer are sequentially provided on a synthetic resin film support, wherein (1) the thermosensitive coloring layer is at least one polymer selected from polyurea and polyurethane. (2) The undercoat layer contains a hydrophobic polymer as a main component, comprising composite fine particles composed of a substance and a dye precursor, and a developer that reacts with the dye precursor under heating to develop the color thereof. A thermosensitive recording material characterized by containing. 2. The heat-sensitive recording material according to claim 1, wherein the hydrophobic polymer is a styrene-butadiene copolymer. 3. The heat-sensitive recording material according to claim 1, wherein the undercoat layer contains a pigment. 4. The thermosensitive coloring layer according to claim 1, further comprising a second dye precursor which develops a color tone different from that of the dye precursor contained in the composite fine particles.
The heat-sensitive recording material according to claim 3.