JP2003165276A - Heat-sensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material which has excellent transparency, and excellent recording sensitivity and fogging resistance and in which the color tone of a recorded part is a black without color expression even under a different light source such as a solar light, a fluorescent light, an incandescent light or the like. <P>SOLUTION: The heat-sensitive recording material comprises a heat-sensitive layer containing composite fine particles made of at least a leuco dye and a resin, a developer and an adhesive, and a protective layer sequentially provided on a transparent support in such a manner that, as one means, a L*a*b* value (based on JIS Z 8729-1987) of the recorded part recorded by a thermal head satisfies (1) when the L* value according to a CIF standard light source A is 10.0 to 15.0, an a* value is -2.0 to 6.0, a b* value is -7.0 to 2.0, and when the L* value is 50.0 to 55.0, the a* value is -6.0 to 3.0, the b* value is -7.5 to 5.0, (2) when the L* value according to a CIF standard light source D is 10.0 to 15.0, the a* value is -2.0 to 7.0, the b* value is -9.5 to 2.0, and when the L* value is 50.0 to 55.0, the a* value is -5.5 to 5.0, and the b* value is -7.5 to 3.5. <P>COPYRIGHT: (C)2003,JPO

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 which utilizes a color reaction between a leuco dye and a color developer.

[0002]

2. Description of the Related Art A heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color-developing agent which reacts with this leuco dye under heating to develop a color is relatively inexpensive, and a recording device is compact. Moreover, since it is easy to maintain, it is used in a wide range of fields as a recording medium for various purposes such as a facsimile, a word processor, an overhead projector (OHP), a recording medium in the medical device field, and various calculators in accordance with diversification of applications. .

Depending on the application, there is a demand for a black thermosensitive recording material having no tint in the recording portion from the low density portion to the high density portion. A heat-sensitive recording material containing composite fine particles composed of a leuco dye having a plurality of spectral characteristics and a resin in the heat-sensitive recording layer in order to make the recording part have a black color without a tint is disclosed in JP-A No. 2-212058.
Although it is described in Japanese Patent Application Laid-Open No. 000-232940, a tint may occur in a recording portion due to a difference in light source.

[0004]

An object of the present invention is that it is excellent in transparency, and the color tone of the recording portion is black with no tint even under different light sources such as sunlight, fluorescent lamps and incandescent lamps. It is intended to provide a heat-sensitive recording material having excellent recording sensitivity and resistance to background fog.

[0005]

[Means for Solving the Problems] On a transparent support,
Composite fine particles consisting of at least leuco dye and resin, developer
And a thermosensitive recording layer containing adhesive and a protective layer
In order to solve the above-mentioned problems in a heat-sensitive recording material having
As a means to
L of the recording unit^*a^*b^*Value (JIS Z 8729-1987
Based on the following), the conditions of (a) and (b) below are met.
It is something. (A) L by CIF standard light source A^*Value is 10.0 to 1
When 5.0, a^*Value is -2.0 to 6.0, b^*value
-7.0 to 2.0, and L^*Value is 50.0-5
When 5.0, a^*Value is -6.0 to 3.0, b^*value
It is -7.5 to 5.0. (B) CIF standard light source D₆₅By L^*Value 10.0
When ~ 15.0, a ^*Value is -2.0 to 7.0, b^*
Value is -9.5 to 2.0 and L^*Value is from 50.0
When 55.0, a^*Value is -5.5 to 5.0, b^*value
Is -7.5 to 3.5.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Means for satisfying the above conditions (a) and (b) by using an L ^* a ^* b ^* value (based on JIS Z 8729-1987) of a recording portion recorded by a thermal head. For example, the light wavelength of the recording unit is 400 to 7
The minimum optical density value B at 00 nm is the maximum optical density value A
It is obtained by using a plurality of leuco dyes having different color tones in the composite fine particles so that the value (B / A) divided by is 0.7 or more. Optical density is the value of transmission density.

The fine composite particles preferably contain substantially no organic solvent and are formed from at least a resin such as an acrylic resin, a styrene resin or a urea resin and a leuco dye. As the resin, a urea resin is preferable, and the composite fine particles composed of a urea resin and a leuco dye are, for example, about 20 to 60% by mass, preferably about 20 to 60% by mass of the leuco dye in a solvent composed of a polyisocyanate compound. A polyvalent isocyanate compound is obtained by emulsifying and dispersing a solution of about 40 to 55% by mass in water so that the average particle diameter is about 0.1 to 2.0 μm, and then heating to 50 to 95 ° C. Are polymerized to form composite fine particles. The average particle size of the obtained composite fine particles is about 0.1 to 2.0 μm.

By including an ultraviolet absorber in the composite fine particles, a black color having no color difference in the color tone of the recording portion can be obtained even if the light source is different. The amount of the ultraviolet absorber used is about 5 to 60% by mass, more preferably about 10 to 40% by mass, based on the composite fine particles.
When the content of the leuco dye exceeds 60% by mass, the leuco dye used as a solute is insufficiently dissolved in the polyvalent isocyanate compound, so that the composite fine particles having a sufficient isolation property are stably produced. You may not be able to.

Examples of ultraviolet absorbers include benzophenone type ultraviolet absorbers and benzotriazole type ultraviolet absorbers, and benzophenone type ultraviolet absorbers are preferable because of their excellent solubility with leuco dyes.

Specific examples of such an ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroquinone-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, and 2- (2'-hydroxy-5 '. -Methylphenyl) benzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4",
5 ", 6" -tetrahydrophthalimidomethyl) -5 '
-Methylphenyl] benzotriazole, 2- (2'-
Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2 '
-Hydroxy-5'-tert-octylphenyl) benzotriazole, 2- (2'-hydroxy-3 ',
5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-te
rt-amylphenyl) benzotriazole, 2,4-
Di-tert-butylphenyl-3,5-di-tert
-Butyl-4-hydroxybenzoate, 2- (2'-
Hydroxy-5'-tert-butylphenyl) benzotriazole, 2- [2'-hydroxy-3 ', 5'-
Bis (α, α-dimethylbenzyl) phenyl-2H-benzotriazole, 2- (2′-hydroxy-3 ′,
5'-di-tert-butylphenyl) -5-chlorobenzotriazole, bis [2-hydroxy-3- (2 '
-H-henzotriazol-2'-yl) -5-octylphenyl] methane and the like.

The ultraviolet absorber is not limited to the above compounds, and if necessary, two or more kinds may be used in combination.

The composite fine particles containing no liquid such as an oily solvent used in the present invention are solid solids without voids (internal substance).
Or may be a porous solid having a large number of pores or a hollow solid having a hollow portion having a diameter less than ½ of the particle diameter. Among them, a porous solid having a large number of pores is preferable because it has excellent recording sensitivity.

The leuco dye that can be contained in the composite fine particles used in the present invention is a triarylmethane type,
Leuco compounds such as diarylmethanes, thiazines, spiros, lactams, and fluorans can be preferably used. Such leuco dyes, when brought into contact with a color developer, each give a unique color tone, and the color tone ranges from black, red, magenta, orange, blue, green, and yellow. The combination of dyes gives a dull black.

It is desirable in the present invention to arbitrarily adjust the color tone by allowing three or more kinds of leuco dyes having different color tones to be present in the composite fine particles.

Examples of leuco dyes that give a black coloration include 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- (N -Isoamyl-N
-Ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-).
2-Tetrahydrofurfurylamino) -6-methyl-7
-Anilinofluorane, 3-di-n-butylamino-6
-Methyl-7-anilinofluorane, 3-di-n-amylamino-6-methyl-7-anilinofluorane, 3-
(N-isoamyl-N-ethylamino) -6-methyl-
7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino) -6-methyl-7-anilinofluorane, 3-di-n-butylamino-7- (2
-Chloroanilino) fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane and the like can be used.

Examples of leuco dyes that give red, magenta, or orange color development include 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-dimethylamino-7-bromofluorane, and 3-diethylamino. Fluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane 3-diethylamino-7,8-benzofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino- 6-methyl-7-chlorofluorane, 3- (N
-Ethyl-N-isoamylamino) -7,8-benzofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-7,8-benzofluorane, 3-tolylamino-7 -Methylfluorane,
2- (N-benzoylanilino) -3-methyl-6-di-n-butylaminofluorane, 2- (N-benzylanilino) -3-methyl-6-di-n-butylaminofluorane and 2- (N-methylanilino) -3-methyl-6-di-n-butylaminofluorane, 3,3'-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 7- ( N-ethyl-N-isoamyl)-
3-methyl-1-phenylspiro [chromeno (2,3-
c) pyrazole) -4- (1H), 3′-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 leuco dyes that give blue color,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide, 3 -(1-ethyl-2
-Methylindol-3-yl) -3- (2-methyl-
4-diethylaminophenyl) -4-azaphthalide, 3
-(1-Ethyl-2-methylindol-3-yl)-
3- (2-ethoxy-4-diethylaminophenyl)-
4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-n-hexyloxy-
4-diethylaminophenyl) -4-azaphthalide, 3-diphenylamino-6-diphenylaminofluorane and the like can be mentioned.

As the leuco dye which gives a green color, 3
-(N-ethyl-N-n-hexylamino) -7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,3'-bis (4-diethylamino-2-ethoxyphenyl)- 4-azaphthalide, 3-
(N-ethyl-Np-tolylamino) -7- (N-phenyl-N-methylamino) fluorane, 3- [p-
(P-anilinoanilino) anilino] -6-methyl-7
Examples include -chlorofluorane and 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide.

Leuco dyes that give a yellowish color are 3,6-dimethoxyfluorane and 1- (4-
n-dodecyloxy-3-methoxyphenyl) -2-
(2-quinolyl) ethylene and the like.

In the present invention, the polyvalent isocyanate compound used for forming the fine composite particles forms a urea bond by reacting with water and an amino compound and a urethane bond by reacting with a hydroxy compound such as a polyol. And polymerize. That is, the polymer formed is polyurea or a polyurethane-polyurea resin. The polyvalent isocyanate compound may contain only a polyvalent isocyanate compound, or may be a mixture of a polyvalent isocyanate compound and a polyol that reacts with the polyvalent isocyanate compound, or a polyol of a polyvalent isocyanate compound. Addendum, biuret body,
Alternatively, it may be a multimer such as isocyanurate.

Examples of the polyvalent isocyanate compound include dicyclohexylmethane-4,4'-diisocyanate, m-tetramethylxylylene diisocyanate and p.
-Phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-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, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,
2-diisocyanate, cyclohexylene-1,4-diisocyanate, 1,3-bis (1-isocyanato-1)
-Methylethyl) benzene and other diisocyanates,
Triisocyanates such as 4,4 ′, 4 ″ -triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate And other tetraisocyanates.

The color developer used in the heat-sensitive recording material of the present invention is not particularly limited, but generally has the property of liquefying or dissolving when the temperature rises, and develops it by contacting with the above leuco dye. It is selected from those having the property of causing. Typical developer is, for example, 4,4 '
-Isopropylidenediphenol, 1,1-bis (4-
Hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane,
4,4'-dihydroxydiphenyl sulfone, 2,4 '
-Dihydroxydiphenyl sulfone, 4-hydroxy-
4'-isopropoxydiphenyl sulfone, bis (3-
Allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4′-benzyloxyphenyl sulfone, 3,4-dihydroxyphenyl-4′-methylphenyl sulfone, 1,1-bis (4-hydroxyphenyl) -1- Phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, etc. Phenolic compounds; Np-tolylsulfonyl-N'-p-butoxycarbonylphenylurea, 4,4'-bis (Np-tolylsulfonylaminocarbonylamino) diphenylsulfone, 4,4'-bis [(4 -Methyl-3-phenoxycarbonylaminophenylurea)] diphenylsulfone urea compound; 4- [2- (p-me Kishifenokishi) ethyloxy] zinc salicylate, 4- [3- (p-
Tolylsulfonyl) propyloxy] zinc salicylate,
Examples thereof include zinc, which is an aromatic carboxylic acid such as 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid.

The color developer is preferably used in a proportion of 30 to 300 parts by mass, more preferably 50 to 200 parts by mass, relative to 100 parts by mass of the composite fine particles. Of course, two or more kinds of color developers can be used in combination, if necessary.

In the present invention, an image stabilizer may be contained in the heat-sensitive recording layer, mainly for improving the storability of the recording portion. Examples of such an image stabilizer include 1,
3,5-tris (4-tert-butyl-3-hydroxy-
2,6-dimethylbenzyl) isocyanuric acid, 1,1,
3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-
Methyl-4-hydroxy-5-tert-butylphenyl)
Butane, 2,2'-methylenebis (4-methyl-6-te
rt-butylphenol), 2,2'-methylenebis (4
-Ethyl-6-tert-butylphenol), 2,2'-
Methylenebis [4,6-di (tert-butyl) phenol], 2,2'-ethylidenebis (4,6-di-tert-)
Butylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 2,2-bis (4-
Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, 4-benzyloxy-
Epoxy compounds such as 4 ′-(2-methylglycidyloxy) diphenyl sulfone, diglycidyl terephthalate, phenol novolac type epoxy resin, and bisphenol A type epoxy resin can be used. Of course, the image stabilizer is not limited to these, and if necessary, two or more kinds of compounds can be used in combination.

In the present invention, a sensitizer may be contained in the heat-sensitive recording layer in order to improve the heat-sensitive recording sensitivity. As the sensitizer, compounds conventionally known as sensitizers for heat-sensitive recording materials can be used, and examples thereof include parabenzyl biphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate and dibenzyl oxalate. , Di-o-chlorobenzyl adipate,
1,2-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, 1,2-bis (3,4-dimethyl) Examples thereof include phenyl) ethane, 1,3-bis (2-naphthoxy) propane, metaterphenyl, diphenyl and benzophenone. Among these compounds, when di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate are used as sensitizers, a sensitizing effect with less fog can be obtained.

In the heat-sensitive recording layer, pigments such as kaolin, calcium carbonate, amorphous silica, titanium oxide, aluminum hydroxide, calcined kaolin and zinc oxide, paraffin wax, polyethylene wax and zinc stearate may be used as auxiliary agents, if necessary. , Lubricants such as calcium stearate, aldehyde compounds such as glyoxal, melamine resins, dimethylol urea compounds, aziridine compounds, boric acid, borax, ammonium zirconium carbonate,
Oxazoline group-containing resin, carbodiimide group-containing resin,
Water resistant agents such as adipic acid dihydrazide and polyamidoamine / epichlorohydrin resin, and fluorescent dyes, coloring dyes, ultraviolet absorbers, surfactants and the like can also be added.

The heat-sensitive recording layer contains, for example, water as a medium, the above-mentioned composite fine particles, a color developer crushed to an average particle size of about 0.1 to 2 μm, an image stabilizer and a sensitizer, and an adhesive. And, if necessary, the coating liquid for heat-sensitive recording layer prepared by mixing and stirring an auxiliary agent on one surface of a transparent support has a coating amount after drying of about 2-35 g / m ² , preferably 4-28 g / m ^{2. 2}
It is formed by applying and drying so as to have a certain degree.

Additives such as a color developer, an image stabilizer and a sensitizer are dissolved in an organic solvent, and then the solution is emulsified and dispersed in water using the water-soluble polymer as a stabilizer. It is also possible to evaporate the organic solvent from the emulsion and make additives such as an image stabilizer and a sensitizer into solid fine particles for use.

As the adhesive contained in the coating liquid for the heat-sensitive recording layer, for example, starches such as oxidized starch, esterified starch and etherified starch, cellulosic resins such as methyl cellulose, carboxymethyl cellulose, methoxy cellulose and hydroxyethyl cellulose, Completely (or incompletely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, polyvinyl alcohol such as silicon-modified polyvinyl alcohol, styrene / maleic anhydride copolymer and its alkali salt, isobutylene / maleic anhydride Copolymers and their alkali salts, casein,
Examples thereof include gelatin, vinyl acetate resin-based latex, urethane resin-based latex, styrene / butadiene copolymer-based latex, and acrylic resin-based latex.

These adhesives can be used alone or in combination of two or more kinds. The total amount of the adhesive used is 10 with respect to the total solid amount of the heat-sensitive recording layer.
It is preferably about 50 parts by mass.

The heat-sensitive recording layer is colored blue or the like.
After drying the heat-sensitive recording layer coating solution on a transparent substrate
Coating amount is 2-35g / m^Two, More preferably 4 to 30 g
/ M ^TwoIt is formed by applying and drying so as to have a certain degree.

As the transparent support, for example, a thickness of 30 to
A film of a cellulose derivative such as a cellulose triacetate film having a thickness of about 200 μm, polyethylene terephthalate,
Polybutylene terephthalate, polyester film such as polyethylene naphthalate, polyolefin film such as polyethylene, polypropylene, polystyrene, polyvinyl chloride film, polycarbonate film, polyamide film, polysulfone film, polyethersulfone film, poly Examples thereof include ether ether ketone-based films, polyetherimide-based films, polyphenylene sulfide-based films, polyester ether-based films, fluororesin-based films, polyurethane-based films, acrylic-based films, polyvinyl butyral-based films, and the like.

In the present invention, a protective layer as conventionally used in heat-sensitive recording materials can be provided on the heat-sensitive recording layer by a known method. Providing a protective layer is also preferable in order to improve storage stability and suitability for a thermal head.

The protective layer contains a water-based adhesive having a film-forming property as a main component, and as the water-based adhesive, for example, the adhesive contained in the heat-sensitive recording layer is used. Further, the protective layer may contain various auxiliaries contained in the heat-sensitive recording layer.

The protective layer uses water as a medium, an adhesive, and
A protective layer coating prepared by mixing and stirring an auxiliary agent if necessary
The amount of the liquid applied onto the thermosensitive recording layer is 0.5 to 10 g after drying.
/ M ^Two, More preferably 1 to 5 g / m^TwoTo be about
Formed by coating and drying

A transparent support is used as the support of the heat-sensitive recording material of the present invention. By using this transparent support, not only the recorded matter after thermal recording can be used as an OHP sheet, but also it can be seen as a transparent image on a Schaukasten.
The total light transmittance defined by 7361 is preferably 50% or more.

The heat-sensitive recording material of the present invention may have a heat-sensitive recording layer formed on at least one surface of a transparent support,
In addition to providing one heat-sensitive recording layer on one surface of the transparent support, providing multiple heat-sensitive recording layers that develop different hues on both surfaces of the transparent support also facilitates multicoloring.

The transparent support may be colored, and a blue-colored transparent support is particularly preferable when viewed as a transparent image on the Schaukasten. The degree of coloring in this case is preferably 0.3 or less, and more preferably 0.2 or less, if expressed by a transmission density (measured with Macbeth transmission densitometer manufactured by Macbeth Co., trade name: TR-927 type). is there.

The transparent support is preferably activated on both sides of the support by a known method. As a method of activation treatment, etching treatment with acid, flame treatment with a gas burner, corona discharge treatment, glow discharge treatment or the like is used.

In the present invention, an undercoat layer may be provided between the transparent support and the thermosensitive recording layer in order to enhance the adhesion between the two layers. The undercoat layer contains an adhesive as a main component.
As the adhesive, a water-resistant resin is preferable, and examples thereof include acrylic resin, styrene resin, urethane resin, vinyl acetate resin and the like which are three-dimensionally polymerized. At this time, it is preferable to further add a crosslinking agent to give the undercoat layer stronger water resistance. Further, as the other material constituting the undercoat layer, pigments, waxes, metal soaps, fluorescent dyes, ultraviolet absorbers and the like can be used. Further, if necessary, in the range not impairing the effects of the present invention, in the undercoat layer, an antistatic agent, a surfactant,
Various additives such as an oil repellent, a defoaming agent, and a viscosity modifier can be added.

In the present invention, a backside layer for preventing curling and antistatic may be provided on the other surface of the transparent support provided with the heat-sensitive recording layer. Examples include adhesives, antistatic agents, pigments, waxes, metal soaps, fluorescent dyes, and ultraviolet absorbers.
Further, if necessary, various additives such as a surfactant, an oil repellent, a defoaming agent, and a viscosity modifier can be added to the back surface layer within a range that does not impair the effects of the present invention.

The method for forming each of the above layers on the support is not particularly limited, and air knife coating, varibar blade coating, pure blade coating, rod blade coating, curtain coating, die coating, gravure coating, slide bead coating, Any known coating method such as gravure coating, offset gravure coating, and five roll coating may be used.

After forming each layer, a smoothing treatment may be carried out, if necessary, by using a known smoothing method such as a super calendar or a soft calendar.

[0044]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention. Unless otherwise specified, "part" and "%" indicate "part by mass" and "% by mass", respectively.

Example 1 Preparation of Composite Fine Particle Dispersion Leuco Dye A (Black Coloring): 3-di-n-butylamino-6-methyl-7-anilinofluorane, Leuco Dye B (red coloring) : 3-diethylamino-7-chlorofluorane, leuco dye C (green color forming): 3- [1,1
-Bis (1-ethyl-2-methylindol-3-yl)]-3-p-diethylaminophenylphthalide, leuco dye D (green color forming): 3,3'-bis (4-diethylamino-2-ethoxy) Phenyl) -4-azaphthalide, leuco dye E (orange coloring): 7- (N-ethyl-N-isoamyl) -3-methyl-1-phenylspiro [chromeno (2,3-c) pyrazole) -4 -(1
H), 3'-phthalide], ultraviolet absorber: 2-hydroxy-4-octyloxybenzophenone, polyvalent isocyanate A: dicyclohexylmethane-4,4'-diisocyanate, polyvalent isocyanate B: m-tetramethylxylylene diisocyanate And the leuco dye or the leuco dye and the ultraviolet absorber at 1 in the compounding ratio shown in Table 1.
It was dissolved in polyvalent isocyanate heated to 50 ° C., and the solution in Table 1 was polyvinyl alcohol (trade name: PVA-
217EE, manufactured by Kuraray Co., Ltd.) and, as a surfactant, an ethylene oxide adduct of acetylene glycol (trade name: Olfine E1010, manufactured by Nisshin Chemical Co., Ltd.).
It was gradually added to 100 parts of an aqueous solution containing 5 parts, and emulsified and dispersed by stirring with a homogenizer at a rotation speed of 12000 rpm. To this emulsion dispersion, an aqueous solution prepared by dissolving 30 parts of water and 2.5 parts of a polyvalent amine compound (trade name: Epicure T, manufactured by Yuka Shell Epoxy Co., Ltd.) in 22.5 parts of water was added and homogenized. The temperature of this emulsified dispersion is raised to 75 ° C.,
The polymerization reaction was carried out for a period of time to prepare a composite fine particle dispersion liquid having an average particle diameter of 0.8 μm.

[0046]

[Table 1]

Preparation of color developer dispersion A 3,4 parts of 4,4′-dihydroxydiphenyl sulfone as a color developer and polyvinyl alcohol (trade name: PVA-203, manufactured by Kuraray Co., Ltd.) 25 as a dispersant %
A composition consisting of 31.4 parts of an aqueous solution, 9.8 parts of a 2% emulsion of a natural oil and fat type antifoaming agent, 15.6 parts of a 5% aqueous solution of sodium salt of dioctylsulfosuccinic acid and 24 parts of water was applied to a horizontal sand mill (Ultraviscomyl). (UVX
2), manufactured by IMEX Co., Ltd., has an average particle diameter of 0.3μ.
A developer dispersion liquid A was prepared by pulverizing to m.

Preparation of Developer Dispersion Liquid B 3,4 parts of 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenylurea)] diphenylsulfone as a developer and a dispersant, Polyvinyl alcohol (trade name: PVA-203, manufactured by Kuraray Co., Ltd.)
Of a 25% aqueous solution of 25% aqueous solution of 2%, a 2% emulsion of a natural oil-and-fat defoaming agent, 15.6 parts of a 5% aqueous solution of dioctylsulfosuccinic acid sodium salt, and 24 parts of water were added to a horizontal sand mill ( The average particle size is 0.3 with an Ultra Visco Mill (UVX2) manufactured by IMEX.
The developer dispersion liquid B was prepared by pulverizing to a particle size of μm.

Preparation of coating liquid for heat-sensitive recording layer 93 parts of composite fine particle dispersion A, 87 parts of developer dispersion A, 15 parts of developer dispersion B, polyvinyl alcohol (trade name:
19 parts of a 7% aqueous solution of PVA235, manufactured by Kuraray Co., Ltd., styrene-butadiene latex (trade name: SMARTEX 752A, solid content 48%, manufactured by A & L Japan)
59 parts, UV absorber polymer (trade name: NK polymer PUVA-400, solid content 40%, Shin Nakamura Chemical Co., Ltd.) 7
Part, adipic acid dihydrazide 5% aqueous solution 15 parts, water 1
A composition comprising 05 parts was mixed and stirred to prepare a coating liquid for the heat-sensitive recording layer.

Preparation of coating liquid for protective layer 628 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group (trade name: Gocefimer Z320, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), colloidal silica (trade name: Snowtex OL , Solid content 20%, Nissan Chemical Co., Ltd. 29 parts, kaolin (trade name: UW-90, Engelhart Co., Ltd.) 40% water dispersion 50 parts, zinc stearate water dispersion (trade name: L- 111, solid content 20%, Chukyo Yushi Co., Ltd.) 34 parts, 10% aqueous dispersion of potassium stearyl phosphate 5 parts, 10% aqueous solution of dioctyl sulfosuccinate sodium salt 10 parts, natural oil and fat defoamer 6 parts of 5% emulsion, 5% aqueous solution of potassium alum 1
A composition consisting of 1 part, 76 parts of a 3% aqueous solution of boric acid and 151 parts of water was mixed and stirred to prepare a coating liquid for protective layer.

Preparation of heat-sensitive recording material On one side of a 175 μm transparent polyethylene terephthalate film (trade name: HPE, manufactured by Teijin Ltd.), the coating amount after drying the heat-sensitive recording layer coating liquid and the protective layer coating liquid respectively. Is 2
A thermal recording layer and a protective layer were provided by sequentially coating and drying so that the thermal recording material was 4 g / m ² , 4 g / m ^2, and a thermal recording material was obtained.

Example 2 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion B93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Example 3 In the preparation of the coating liquid for heat-sensitive recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion C93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Example 4 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion D93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Example 5 In the preparation of the coating liquid for the thermal recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion E93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Example 6 In the preparation of the coating liquid for the thermal recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion F93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Comparative Example 1 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, a composite fine particle dispersion G93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Comparative Example 2 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion H93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Comparative Example 3 In the preparation of the coating liquid for the thermal recording layer of Example 1, instead of 93 parts of the composite fine particle dispersion A93, the composite fine particle dispersion I93 was prepared.
A thermosensitive recording material was prepared in the same manner as in Example 1 except that parts were used.

Comparative Example 4 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, the following leuco dye dispersion 3 was used instead of 93 parts of the composite fine particle dispersion A.
7 parts, polyvinyl alcohol (trade name: PVA23
5, polyvinyl alcohol (trade name: PVA20) instead of 19 parts of a 7% aqueous solution of Kuraray Co., Ltd. and 105 parts of water
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 50 parts of a 25% aqueous solution of Kuraray Co., Ltd.) and 130 parts of water were used.

Preparation of leuco dye dispersion 19.7 parts of leuco dye A, 7.1 parts of leuco dye B,
2.2 parts of leuco dye C, 4.4 parts of leuco dye D, 5.8 parts of leuco dye E, and 2 parts of polyvinyl alcohol (trade name: PVA-203, manufactured by Kuraray Co., Ltd.) as a dispersant.
A composition consisting of 31.4 parts of a 5% aqueous solution, 9.8 parts of a 2% emulsion of a natural oil-and-fat defoaming agent, 15.6 parts of a 5% aqueous solution of sodium salt of dioctylsulfosuccinate and 24 parts of water was applied to a horizontal sand mill (Ultra Viscomil (UVX
2), manufactured by IMEX Co., Ltd., the average particle diameter is 0.3 μm.
The leuco dye dispersion liquid was prepared by pulverizing to m.

Evaluation of heat-sensitive recording materials The heat-sensitive recording materials thus obtained were subjected to the following evaluation tests, and the results are shown in Tables 2 to 4.

Total Light Transmittance The total light transmittance of the thermosensitive recording material was measured. A thermosensitive recording material having a total light transmittance of less than 50% was marked as "-" without performing the following evaluation test items because it was unusable.

Color-sensitive thermosensitive recording material, thermal printer (trade name: NP
1760, manufactured by CODONICS) was used to record 17 gradation patterns, and the maximum density of the recording portion was measured in a visual mode of a Macbeth transmission densitometer (TR-927 type, manufactured by Macbeth).

A value obtained by dividing the minimum optical density value B at the light wavelength of 400 to 700 nm by the maximum optical density value A (B / A). With a spectrophotometer, the transmission density after recording is 0.8 to 1.2.
The spectral density at the light wavelength of 400 to 700 nm of the recording portion of was measured, and the value (B / A) obtained by dividing the minimum optical density value B by the maximum optical density value A was obtained.

After processing a heat-sensitive recording material having a background fog resistance to fog under the environmental conditions of 40 ° C. and 90% RH for 7 days, the transmission density of an unrecorded portion was measured by a Macbeth transmission densitometer (TR-927 type, manufactured by Macbeth Co.). Measured in visual mode.

Color tone of recording section under each light source Thermal printer for thermal recording material (trade name: NP166
No. 0, manufactured by CODONICS) was used to record 17 gradation patterns, and the color tone of the recording portion under each light source of sunlight, fluorescent lamp, and incandescent lamp was visually evaluated.

[0068] · ^{L * a} * ^b * value of the recording section of the ^L * ^a * ^{b *} value recording section, was measured by using an instantaneous multi-photometric system MCPD-3000 made by Otsuka Electronics Co., Ltd..

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

As is clear from the results shown in Tables 2 to 4, the heat-sensitive recording material of the present invention has excellent transparency and shows excellent recording performance even under different light sources such as sunlight, fluorescent lamps and incandescent lamps. It is a heat-sensitive recording material capable of forming a color image with almost no change in color tone, having high color density, and having little background color development (color fog).

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toru Murai             Prince, 3-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture             Amagasaki Research Center, Paper Manufacturing Co., Ltd. (72) Inventor Toshiro Hata             Prince, 3-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture             Amagasaki Research Center, Paper Manufacturing Co., Ltd. F term (reference) 2H026 AA07 BB02 EE05 FF01 FF11                       GG10

Claims (3)

[Claims] 1. At least a leuco dye on a transparent support.
Composite fine particles consisting of dye and resin, developer and adhesive
Thermal recording layer having the same, and thermal recording having a protective layer in sequence
Recording part recorded by thermal head in material
L^*a^*b^*Value (based on JIS Z 8729-1987
Meet the conditions of (a) and (b) below.
A heat-sensitive recording material characterized by: (A) L by CIF standard light source A^*Value is 10.0 to 1
When 5.0, a^*Value is -2.0 to 6.0, b^*value
-7.0 to 2.0, and L^*Value is 50.0-5
When 5.0, a^*Value is -6.0 to 3.0, b^*value
It is -7.5 to 5.0. (B) CIF standard light source D₆₅By L^*Value 10.0
When ~ 15.0, a ^*Value is -2.0 to 7.0, b^*
Value is -9.5 to 2.0 and L^*Value is from 50.0
When 55.0, a^*Value is -5.5 to 5.0, b^*value
Is -7.5 to 3.5. 2. The heat-sensitive recording material according to claim 1, wherein a value (B / A) obtained by dividing the minimum optical density value B at the light wavelength of 400 to 700 nm of the recording portion by the maximum optical density value A is 0.7 or more. 3. The heat-sensitive recording material according to claim 1, which has a total light transmittance of 50% or more defined by JIS K 7361 of the heat-sensitive recording material.