JPH07117355A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having a substantially transparent recording layer excellent in the stability of heat sensitivity to environment. CONSTITUTION:In a thermal recording material wherein a substantially transparent thermal recording layer containing at least a microcapsule containing an electron donating dye precursor and an emulsion of an electron acceptive compd. is provided on a support, the thermal recording layer contains a phenolic compd. in a solid dispersion state.

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 having a substantially transparent heat-sensitive recording layer which is excellent in stability of heat sensitivity regardless of environmental changes.

[0002]

2. Description of the Related Art In a thermal recording method, (1) development is unnecessary, (2) when the support is paper, the paper quality is close to that of ordinary paper,
(3) high color density, (5) recording device is simple and inexpensive, and (6) there is no noise during recording.
In the field of facsimiles and printers, it has spread rapidly in recent years,
Applications for thermal recording are also expanding.

Against this background, in recent years, electronic recording is possible directly with a thermal head in order to adapt to multiple colors or to be used in an overhead projector (abbreviated as OHP). A heat-sensitive recording material having a substantially transparent heat-sensitive recording layer containing a donor dye precursor and an electron-accepting compound (referred to as a leuco type heat-sensitive recording layer) has also been developed (for example, JP-A-63-2).
65682).

[0004]

However, the thermal sensitivity of such a substantially transparent heat-sensitive recording layer depends on the amount of water contained in the heat-sensitive recording layer at the time of heat recording, so that the heat sensitivity before recording is not increased. It was found that the thermal sensitivity changes depending on the storage environment and the environment in which it is used, resulting in poor stability. That is,
The above-mentioned substantially transparent heat-sensitive recording layer has a high heat sensitivity because it absorbs moisture in the air when the humidity of the surrounding environment where the recording material is placed is high, thereby increasing the moisture content. On the other hand, when the humidity becomes higher, the thermal sensitivity lowers as the water content decreases.

Therefore, as a result of intensive investigations by the present inventors to reduce the dependence of the thermal sensitivity of the heat-sensitive recording material on the humidity environment, when the leuco-type heat-sensitive recording layer contains a phenolic compound in a solid dispersion state, Have found that the dependence of thermal sensitivity on the humidity environment is remarkably improved and arrived at the present invention. Therefore, an object of the present invention is to provide a heat-sensitive recording material having a substantially transparent leuco-type heat-sensitive recording layer, which has excellent stability of heat sensitivity to the environment.

[0006]

The above objects of the present invention are as follows.
A heat-sensitive recording material having, on a support, at least a microcapsule containing an electron-donating dye precursor and a substantially transparent heat-sensitive recording layer containing an emulsion of an electron-accepting compound. Was achieved by a heat-sensitive recording material characterized by containing a phenolic compound in a solid dispersion state. Next, materials used in the heat-sensitive recording material of the present invention will be described.

The electron-donating dye precursor (color former) and the electron-accepting compound (developing agent) used in the present invention are color-forming components which cause a color-forming reaction upon contact of substances by heating. Examples of the electron-donating dye precursor include triarylmethane-based compounds, diphenylmethane-based compounds, thiazine-based compounds, xanthene-based compounds, spiropyran-based compounds, and the like, but particularly triarylmethane-based compounds and xanthene-based compounds have a coloring density. Is useful because it is expensive.

Specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet lactone),
3,3-bis (p-dimethylamino) phthalide, 3-
(P-Dimethylaminophenyl) -3- (1,3-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-
3-yl) phthalide, 3- (o-methyl-p-dimethylaminophenyl) -3- (2-methylindole-3-
Il) phthalide;

4,4'-bis (dimethylamino) benzhydrin benzyl ether; N-halophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine; rhodamine-B-anilinolactam, rhodamine (P-nitroanilino) lactam, rhodamine-
B- (p-chloroanilino) lactam, 2-benzylamino-6-diethylaminofluorane, 2-anilino-
6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-
3-methyl-6-cyclohexylmethylaminofluorane, 2-anilino-3-methyl-6-isoamylethylaminofluorane, 2- (o-chloroanilino) -6-
Diethylaminofluorane, 2-octylamino-6-
Diethylaminofluorane, 2-ethoxyethylamino-3-chloro-2-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane;

Benzoyl leuco methylene blue, p-nitrobenzyl leuco methylene blue; 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran,
Examples include 3-benzyl-spiro-dinaphthopyran and 3-propyl-spiro-dibenzopyran. Examples of the electron-accepting compound used in the present invention include phenol derivatives, salicylic acid derivatives, hydroxybenzoic acid esters and the like. Among these, bisphenols and hydroxybenzoic acid esters are particularly preferable.

Some examples of these are 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A) and 2,2-bis (p-hydroxyphenyl).
Pentane, 2,2-bis (p-hydroxyphenyl) ethane, 2,2-bis (p-hydroxyphenyl) butane, 2,2-bis (4'-hydroxy-3 ', 5'-dichlorophenyl) propane, 1 , 1- (p-hydroxyphenyl) cyclohexane, 1,1- (p-hydroxyphenyl) propane, 1,1- (p-hydroxyphenyl) pentane, 1,1- (p-hydroxyphenyl)-
2-ethylhexane, 3,5-di (α-methylbenzyl) salicylic acid and its polyvalent metal salt, 3,5-di (te
rt-Butyl) salicylic acid and its polyvalent metal salts, 3-
α, α-dimethylbenzyl salicylic acid and its polyvalent metal salts, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p-cumylphenol, etc. Can be mentioned.

The electron-donating dye precursor used in the present invention is a raw storage of a heat-sensitive recording layer which prevents contact between the electron-donating dye precursor (color former) and the electron-accepting compound (developing agent) at room temperature. From the viewpoint of the property (prevention of fogging) and the viewpoint of controlling the color development sensitivity of causing color development with a desired heat energy, it is preferable to encapsulate the electron donating dye precursor before use.

Any of an interfacial polymerization method, an internal polymerization method and an external polymerization method can be adopted for producing the microcapsules used in the present invention. In particular, the color former is dissolved or dispersed in a non-aqueous solvent. It is preferable to employ an interfacial polymerization method in which the impregnated core substance is emulsified in an aqueous solution in which a water-soluble polymer is dissolved, and then a wall of the polymer substance is formed around the oil droplets. The reactant forming the polymer substance is added inside the oil droplet and / or outside the oil droplet.

Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer,
Examples thereof include styrene-acrylate copolymer. Preferred polymeric substances are polyurethanes, polyureas, polyamides, polyesters and polycarbonates, particularly preferably polyurethanes and polyureas. Two or more polymer substances can be used in combination.

Specific examples of the water-soluble polymer include gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like. For example, when using polyurea as a capsule wall material, diisocyanate, triisocyanate, tetraisocyanate, polyisocyanate such as polyisocyanate prepolymer, and polyamine such as diamine, triamine, tetraamine, and two amino groups The microcapsule wall can be easily formed by reacting the prepolymer, piperazine or a derivative thereof, a polyol or the like containing the above with an interfacial polymerization method in an aqueous solvent.

For example, the composite wall made of polyurea and polyamide or the composite wall made of polyurethane and polyamide is added, for example, by using polyisocyanate and acid chloride or polyamine and polyol after adjusting the pH of the emulsifying medium as the reaction liquid. It can be prepared by warming. For details of the method for producing a composite wall composed of these polyurea and polyamide, see JP-A-58-6.
6948.

Further, a sensitizer may be added to swell the microcapsule wall during heating. As the sensitizer, those which are solid at room temperature and have a melting point of 50 ° C. or higher, preferably 120 ° C. or lower, can be selected and used from among the plasticizers of polymers used for the microcapsule wall. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamic acid ester compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound and the like are preferably used.

The substantially transparent thermosensitive recording layer in the present invention does not have an electron-accepting compound dispersed in a solid state,
After being dissolved in a water-insoluble or insoluble organic solvent, it is mixed with an aqueous phase having a surfactant and / or a water-soluble polymer as a protective colloid and used in the form of an emulsion-dispersed dispersion. can get.

In the present invention, "substantially transparent" means haze (%) (integrating sphere method HTR manufactured by Nippon Seimitsu Kogyo Co., Ltd.).
It means that it must be 60% or less if expressed by a meter). It is preferably 30% or less, more preferably 20% or less. However, since the actual transparency of the heat-sensitive recording layer test sample is greatly affected by light scattering due to fine irregularities on the surface of the heat-sensitive recording layer, the substantial transparency of the heat-sensitive recording layer which is a problem in the present invention is simple. As a method, a transparent adhesive tape is attached on the heat-sensitive recording layer, and the value measured by removing the surface scattering is evaluated.

From the viewpoint of facilitating the emulsification and dispersion, it is preferable to use a surfactant. The organic solvent used in this case can be appropriately selected, for example, from the high boiling point oils described in JP-A-2-141279. Among these, it is preferable to use the esters from the viewpoint of the emulsion stability of the emulsified dispersion, and above all, when tricresyl phosphate is used alone or as a mixture, the emulsion dispersion stability of the color developer is particularly good. Yes preferred. The above oils can be used together or with other oils.

In the present invention, an auxiliary solvent can be added to the above organic solvent as a dissolution aid having a low boiling point. As such an auxiliary solvent, for example, ethyl acetate, isopropyl acetate, butyl acetate, methylene chloride and the like can be mentioned as particularly preferable ones. In some cases, it is possible to use only the low boiling auxiliary solvent without the high boiling oil.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase mixed with the oil phase containing these components is appropriately selected from known anionic polymers, nonionic polymers and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable.

As the surface active agent to be contained in the aqueous phase, an anionic or nonionic surface active agent which does not cause precipitation or aggregation by acting on the protective colloid may be appropriately selected and used. it can. Preferred surfactants include sodium alkylbenzene sulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.

The emulsified dispersion according to the present invention comprises means used for ordinary fine particle emulsification such as high speed stirring and ultrasonic dispersion of an oil phase containing the above components and an aqueous phase containing a protective colloid and a surfactant. It can be easily mixed and dispersed by using. Further, the ratio of the oil phase to the water phase (oil phase weight / water phase weight) is preferably 0.02 to 0.6, and particularly preferably 0.1 to 0.4. If it is 0.02 or less, the amount of the water phase is too large to be diluted, and sufficient color development cannot be obtained.
On the other hand, when it is 0.6 or more, the viscosity of the liquid becomes high, which causes inconvenience in handling and a decrease in coating liquid stability.

In the present invention, from the viewpoint of improving the stability of the heat sensitivity of the heat-sensitive recording material to the humidity environment, the phenolic compound is contained in a solid dispersion state in the heat-sensitive recording layer containing the electron-donating dye precursor. . Phenolic compounds used in the present invention include paper pulp technology Times (May 1987, page 33, June, page 56, July, page 40, September, page 48, October issue, page 50, November issue, page 53, December issue, page 8; January 1988 page 58 and February issue, page 1). be able to.

Among these phenolic compounds, diphenol compounds represented by the following chemical formulas 1 to 7 and chemical compounds 8 to 1
Monophenol compounds represented by 0 and chemical formulas 11 to 13
It is preferable to use a polyphenol compound represented by

[Chemical 1]

[Chemical 2]

[Chemical 3]

[Chemical 4]

[0027]

[Chemical 5]

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

[Chemical 10]

[Chemical 11]

[Chemical 12]

[Chemical 13]

The solid dispersion is prepared by adding a phenolic compound and, if necessary, a surfactant such as sodium dodecylbenzenesulfonate to an aqueous solution containing polyvinyl alcohol, phthalated gelatin, a water-soluble polymer such as gelatin as a protective colloid. It can be easily carried out by finely pulverizing with a stirring and dispersing machine such as a ball mill, an attritor or a sand grinder. The particle size of the phenolic compound, from the viewpoint of ensuring the transparency of the heat-sensitive recording layer,
0.1 μm to 0.8 μm is preferable, and
The amount used is preferably 5% to 60% by weight of the thermosensitive recording layer.

In the present invention, it is preferable that the heat-sensitive recording layer contains a binder for fixing various materials such as color-developing materials on the support. Examples of the binder include gelatin such as alkali-treated gelatin or acid-treated gelatin, modified gelatin obtained by modifying some functional groups of gelatin (eg, phthalated gelatin), polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic gum. ,
Examples thereof include polyvinylpyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic ester, various emulsions of ethylene-vinyl acetate copolymer and the like.

The amount of binder used is preferably 0.5 to 5 g / m ² in terms of solid content. When a developer or the like is used as a solid dispersion by a sand mill or the like, a substantially transparent thermosensitive recording material in the present invention cannot be obtained. In the present invention, a single-color heat-sensitive recording material having only one heat-sensitive recording layer can be used, but a multi-color heat-sensitive recording material in which two or more heat-sensitive recording layers that develop different hues are laminated can also be used. it can.

In this case, a diazo-type heat-sensitive recording layer containing a combination of a diazo compound and a coupler as a color-forming component capable of photo-fixing may be laminated on the leuco-type heat-sensitive recording layer (on the recording layer side). . The phenolic compound may be contained in the diazo type heat-sensitive recording layer in a solid dispersion state. The diazo compound and the coupler include
For example, those described in JP-A-5-169803 can be mentioned.

On one surface of the support, a cyan-colored leuco-type heat-sensitive recording layer, magenta capable of being optically fixed,
When yellow-colored diazim type thermosensitive recording layers are sequentially provided, a full-color multicolor thermosensitive recording material can also be used. When a multicolor thermosensitive recording material is used, it is preferable to provide an intermediate layer between the thermosensitive recording layers from the viewpoint of preventing color mixture between the thermosensitive recording layers and obtaining a good recorded image.

The intermediate layer is preferably an intermediate layer containing gelatin and / or modified gelatin, from the viewpoint of improving raw storage stability and production suitability. The above gelatin and modified gelatin are the same as the gelatin used as the binder in the thermosensitive recording layer. In addition to the above binders, other binders may be used in combination in the intermediate layer. Specific examples of these binders are described in, for example, Japanese Patent Application Laid-Open No.
It is described in detail in Japanese Patent Publication No. 169803.

In the present invention, it is preferable to provide a protective layer on the heat-sensitive recording layer. When the protective layer is provided on the uppermost layer of the thermosensitive recording layer, the mechanical strength of the surface of the thermosensitive recording layer can be improved. A pigment, a metal soap, a wax, a cross-linking agent and the like are added to the protective layer for the purpose of improving matching property with a thermal head during thermal recording and improving water resistance of the protective layer. These pigments, metal soaps, waxes,
For details of the cross-linking agent, etc., see, for example, JP-A-2-141.
No. 279.

Further, a surfactant is added to the coating solution for forming the protective layer in order to uniformly form the protective layer on the heat-sensitive recording layer. Surfactants include sulfosuccinic acid-based alkali metal salts, fluorine-containing surfactants, and the like. Specifically, di- (2-ethylhexyl) sulfosuccinic acid, di- (n-
Hexyl) sodium salts such as sulfosuccinic acid or ammonium salts. Further, in the protective layer, a surfactant, a polymer electrolyte or the like for preventing the heat-sensitive recording material from being charged may be added. The solid coating amount of the protective layer is usually 0.2 to 5
g / m ² is preferable, and more preferably 1 g to 3 g / m ^2.
Is.

The support used in the present invention may be transparent or opaque. Examples of the opaque support include paper, a paper laminated with a polymer film (support for photographic printing paper), synthetic paper, an aluminum vapor-deposited base, and a transparent support described later coated with a white pigment. You can The paper used for the support is neutral paper having a heat extraction pH of 6 to 9 and sized with a neutral sizing agent such as alkyl ketene dimer (for example, JP-A-55).
No. 14281) is advantageous in terms of storage stability over time.

On the other hand, examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polystyrene films, polypropylene films, polyolefin films such as polyethylene films, polyimide films, and the like. Examples thereof include polyvinyl chloride film, polyvinylidene chloride film, polyacrylic acid copolymer film, and polycarbonate film. These can be used alone or by laminating them, but especially polyester film is subjected to heat treatment and antistatic treatment. Those obtained are preferred. The thickness of the transparent support is 20 to 200 μm,
Particularly, those having a thickness of 50 to 100 μm are preferable.

In the present invention, when a polymer film support is used, an undercoat layer is preferably provided between the support and the heat-sensitive recording layer in order to enhance the adhesiveness between them. As a material for the undercoat layer, gelatin, synthetic polymer latex, nitrocellulose or the like is used. The coating amount of the undercoat layer is preferably in the range of ^{0.1g / m 2 ~2.0g / m 2} , preferably in the range particularly ^{0.2g / m 2 ~1.0g / m 2} .

A hardener is used for the undercoat layer, because when the heat-sensitive recording layer is coated thereon, it may swell with water contained in the heat-sensitive recording layer to deteriorate the image quality of the heat-sensitive recording layer. It is desirable to cure. Examples of the hardener include those described in JP-A-2-141279.

The amount of these hardeners added is in the range of 0.20% by weight to 3.0% by weight based on the weight of the undercoat material, and the amount added is appropriate depending on the coating method and the desired degree of curing. You can choose. Depending on the hardener used, if necessary, caustic soda may be further added to bring the pH of the solution to the alkaline side, or the pH of the solution may be brought to the acidic side with citric acid or the like. Also, in order to eliminate the bubbles generated during application,
It is possible to add an antifoaming agent, or to add a surfactant in order to improve the leveling of the liquid and prevent the generation of coating streaks.

Further, it is desirable to activate the surface of the support by a known method before applying the undercoat layer.
As a method of activation treatment, etching treatment with acid,
Flame treatment with a gas burner, corona treatment, glow discharge treatment, or the like is used, but from the viewpoint of cost or simplicity, US Pat. Nos. 2,715,075 and 2
The corona discharge treatment described in No. 846,727, No. 3,549,406, No. 3,590,107 and the like is most preferably used.

The heat-sensitive recording material of the present invention comprises microcapsules containing an electron-donating dye precursor, a dispersion in which at least a color developer is emulsified and dispersed, a binder, a dispersion in which a phenolic compound is solid-dispersed, and other additives. To prepare a coating solution containing paper, bar coating, blade coating, air knife coating, gravure coating, roll coating coating, spray coating, dip coating, etc. on a support such as paper, photographic printing paper support or the above-mentioned film. It is produced by coating and drying by a method to provide a heat-sensitive recording layer having a solid content of 2.5 to 25 g / m ² .

The coating amount of the color-forming component is preferably 0.5 to 15 g / m ² as the color-forming component (the sum of the electron-donating dye precursor and the developer) in the heat-sensitive recording layer, and particularly preferably 0.
It is preferably 8 to 10 g / m ² . If necessary, US Pat. Nos. 2,761,791 and 3,50
No. 8,947, No. 2,941,898, and No. 3,526,528, Yuji Harasaki, “Coating Engineering”, page 253 (published by Asakura Shoten in 1973). It is also possible to divide the coating into two or more layers and simultaneously coat them, and an appropriate method can be selected according to the coating amount, coating speed and the like.

If necessary, a pigment dispersant, a thickener, a flow modifier, an antifoaming agent, a foam suppressor, a release agent, a colorant and the like may be appropriately added to the coating liquid used in the present invention. There is no problem as long as it does not damage. The heat-sensitive recording material of the present invention can be used as a heat-sensitive recording material for a printer of a facsimile or an electronic computer, or a heat-sensitive recording material for OHP, which requires high-speed recording.

[0045]

As described above in detail, the heat-sensitive recording material of the present invention is excellent in stability of heat sensitivity in a humidity environment, and thus not only has good storage stability, but is also safe under different environments. Can be used in mind.

[0046]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.
In addition, "part" indicating the addition amount indicates "part by weight".

Example 1. (1) Preparation of coating liquid for heat-sensitive recording layer (preparation of capsule liquid containing electron-donating dye precursor)
14 g of crystal violet lactone, 60% of xylyl resin isocyanate / addition product of trimethylolpropane (Takenate D-110N: trade name of capsule wall agent manufactured by Takeda Pharmaceutical Co., Ltd.), and Sumithorpe 20
0 g (Sumitomo Chemical Co., Ltd. UV absorber) of 2 g was added to a mixed solvent of 20 g of 1-phenyl-1-xylylethane and 55 g of methylene chloride and dissolved.

The resulting solution was treated with polyvinyl alcohol 8
A 100% by weight aqueous solution, 40 g of water, and 1.4 g of a 2% by weight aqueous solution of a sodium salt of dioctyl sulfosuccinate were added to the mixed aqueous solution and uniformly mixed to obtain a solution of an electron-donating dye precursor. The obtained solution was emulsified with an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.) at 10,000 rpm for 5 minutes, then 150 g of water was added and the mixture was heated to 40 ° C. with stirring to obtain an average capsule size. Particle size is 0.
The encapsulation reaction was performed for 3 hours to obtain a capsule solution of 7 μm.

(Preparation of Emulsion Dispersion of Electron-Accepting Compound) 8 g of the compound represented by the following chemical formula 14, 4 g of the compound represented by the following chemical formula 15 and 30 g of the compound represented by the following chemical formula 16,
1.0 g of 1-phenyl-1-xylylethane, 2.0 g of dibutyl phthalate and 30 g of ethyl acetate were dissolved in a mixed solution. The obtained solution is polyvinyl alcohol 8
After 100 g of a wt% aqueous solution and 0.5 g of sodium dodecyl sulfonate were mixed into the aqueous solution, the mixture was emulsified with an ace homogenizer at 10,000 rpm for 5 minutes so that the particle size was 0.5 μm. An emulsified dispersion was obtained.

[0050]

[Chemical 14]

[Chemical 15]

[Chemical 16]

(Preparation of Phenolic Compound Dispersion) A solution prepared by mixing 30 g of the phenolic compound represented by Chemical Formula 1 with 30 g of an aqueous solution of 8% by weight of polyvinyl alcohol, 60 g of water and 2 g of an aqueous solution of 2% by weight of sodium dodecylbenzenesulfonate. And a phenolic compound having a particle size of 0.4 μm was dispersed using Dynomill to obtain a phenolic compound dispersion. (Preparation of coating liquid for thermosensitive recording layer) 5 g of a capsule liquid containing an electron-donating dye precursor, an electron-accepting compound emulsion dispersion 1
0 g, 5 g of water and 2 g of the phenolic compound dispersion liquid were mixed to obtain a coating liquid.

(2) Preparation of coating liquid for protective layer 20% aqueous solution of polyvinyl alcohol 10% by weight, water 30
g, dioctyl sulfosuccinate sodium salt 2% by weight
Aqueous solution 0.3 g, polyvinyl alcohol 3 g, water 100
g and 35 g of kaolin were dispersed using a ball mill, 3 g of kaolin dispersion, and 40% by weight zinc stearate dispersion (Hydrin Z: trade name of Chukyo Yushi Co., Ltd.).
The protective layer liquid was obtained by stirring and mixing 0.5 g.

(3) Preparation of Thermosensitive Recording Material A thermosensitive recording layer coating solution and a protective layer solution were sequentially coated on one surface of a 70 μm thick polyethylene terephthalate support and dried to obtain a thermosensitive recording material. In this case, each coating solution was applied such that the thermal recording layer had a solid content of 6 g / m ² and the protective layer had a solid content of 2.0 g / m ^{2 in} terms of solid content after drying. The haze of the obtained recording material was 15%.

(4) Thermal recording The obtained recording material was heated at 25 ° C. and a relative humidity of 10 using a thermal head KST type (trade name of Kyocera Corporation).
% (Referred to as low humidity) and 80% (referred to as high humidity) at the same temperature under different environmental conditions, the recording energy is adjusted by changing the applied power and the pulse width, and the blue image is made to have the same density. Was recorded, and the difference between the recording energy at low humidity and the recording energy at high humidity was measured.

Example 2. The amount of the phenolic compound dispersion liquid was changed to 4 g and the coating amount of the thermosensitive recording layer was 9 g /
A recording material was prepared in the same manner as in Example 1 except that m ² was changed, and the difference in recording energy was measured in the same manner. The haze of the recording material was 20%.

Example 3. Change the amount of phenolic compound dispersion used to 8g and apply 15g of heat-sensitive recording layer.
The recording material was prepared in the same manner as in Example 1 except that / m ² was used, and the difference in recording energy was measured in the same manner. The haze of the recording material was 50%.

Example 4. Instead of the compound represented by the chemical formula 1 used in the phenolic compound dispersion of Example 2,
A recording material was prepared in exactly the same manner as in Example 2 except that the bisphenol A represented by Chemical Formula 3 was used, and the difference in recording energy was measured in exactly the same manner. The haze of the recording material was 20%.

Example 5. Instead of the compound represented by the chemical formula 1 used in the phenolic compound dispersion of Example 2,
A recording material was prepared in exactly the same manner as in Example 2 except that the compound represented by Chemical formula 5 was used, and the difference in recording energy was measured in exactly the same manner. The haze of the recording material is 2
It was 0%.

Comparative Example 1. A recording material was prepared in the same manner as in Example 1 except that the following phenolic emulsion dispersion was used instead of the phenolic compound dispersion used in Example 1, and the difference in recording energy was measured in exactly the same manner. did.
The haze of the recording material was 10%.

(Preparation of Emulsion Dispersion of Phenolic Compound)
42 g of the compound represented by the above Chemical Formula 1 was converted into 1-phenyl-1
-Xylylethane 1.0 g, dibutyl phthalate 2.0 g
And 30 g of ethyl acetate were dissolved in the mixed solution. The obtained solution was used as a 10% aqueous solution of polyvinyl alcohol 10%.
0 g and 0.5 g of sodium dodecyl sulfonate were mixed into an aqueous solution, which was then emulsified for 5 minutes at 10,000 revolutions / minute using an ace homogenizer so that the particle diameter was 0.5 μm. Got

Comparative Example 2. The phenolic compound dispersion liquid used in Example 1 was not used, and the electron-accepting compound emulsion dispersion liquid used in Example 1 was further supplemented with 9 g of the compound represented by the above Chemical Formula 1 except that. A recording material was prepared in exactly the same manner as in Example 1, and the difference in recording energy was measured in exactly the same manner. The haze of the recording material was 10%.

The above results are summarized in Table 1.

[Table 1]

Claims (1)

[Claims] 1. A heat-sensitive recording material having, on a support, at least a microcapsule containing an electron-donating dye precursor and a substantially transparent heat-sensitive recording layer containing an emulsion of an electron-accepting compound. The heat-sensitive recording material, wherein the heat-sensitive recording layer contains a phenolic compound in a solid dispersion state.