JP2002059665A - Thermal recording composition and thermal recording material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording composition bringing about high coloring density, having excellent coloring sensitivity and being excellent in the shelf stability of an image part and further in heat resistance and chemical resistance, and a thermal recording material using the same. SOLUTION: The thermal recording composition is constituted mainly of leuco dye, a developer and a sensitizer. The developer is a condensation product of a (poly) 4-hydroxybenzoic acid and a multivalent alcohol of trivalence or above expressed by the following general formula (1), and the sensitizer is 4-acetylbiphenyl. (In the formula, m denotes an integer of 0-2).

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 composition and a heat-sensitive recording material using the same. More specifically, the present invention has a high color density, a good color sensitivity, a storage stability of an image area, a heat resistance, The present invention relates to a heat-sensitive recording composition having excellent chemical resistance and a heat-sensitive recording material using the same.

[0002]

2. Description of the Related Art A heat-sensitive recording material is mainly composed of a color-forming substance and a color developing agent.
A recording material having a structure formed on a support such as paper, synthetic paper, or a resin film. A thermal printer or the like having a built-in thermal head is used for recording, that is, heating for coloring. .

[0003] Compared with other methods, this recording method does not require processing such as development and fixing, allows recording in a short time using a relatively simple apparatus, and has the advantages of low cost and the like. There are POS for fresh foods, lunch boxes and prepared dishes
It is used in various fields such as fields, copying fields such as books and documents, communication fields such as facsimile, ticket vending machines, receipts, and receipts.

Among the fields of application of these heat-sensitive recording materials, P
It is rapidly being used in the OS field, especially in fields where importance is placed on image reliability, such as lunch boxes and prepared dishes, and is used for plasticizers and fats and oils contained in organic polymer materials used for packaging and the like. Used for applications requiring high storage stability,
It is also used for applications requiring storage stability for several years, such as receipts and receipts, and the quality required for thermal recording materials is increasing year by year.

For this purpose, auxiliaries such as a color-forming substance, a color developer, and a storage stabilizer have been developed. However, those which can sufficiently satisfy the color development sensitivity and the storage stability of an image have been found. Not.

[0006] Among these, as a developer exhibiting high storage stability especially to plasticizers and fats and oils, International Publication No. WO /
99/51444 has a carboxylic acid component containing (poly) 4-hydroxybenzoic acid represented by the following general formula (1) as an essential component and optionally containing other monovalent carboxylic acid and / or divalent carboxylic acid. And a condensation reaction product of a polyhydric alcohol component containing a trihydric or higher polyhydric alcohol as an essential component and a dihydric low molecular alcohol as an optional component (hereinafter, this condensation product is simply referred to as (poly) 4-hydroxy (Abbreviated as benzoate derivative)).

[0007]

Embedded image (In the formula, m represents an integer of 0 to 2.)

However, in a thermosensitive recording material comprising only a combination of the (poly) 4-hydroxybenzoic acid ester derivative and a color-forming substance, the color-forming sensitivity at a practical level is insufficient. There is a demand for the development of a heat-sensitive recording material having excellent sensitivity and storage stability.

However, the international publication number WO99 /
In 51444, sensitizers used in combination for the purpose of improving color sensitivity include bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate, acetoacetic acid-o-chloroanilide, diphenyl Sulfone, stearic acid amide, and the like are exemplified. However, in heat-sensitive recording materials using these, the color density is low, the practical color sensitivity is insufficient, and further improvement has been desired.

On the other hand, Japanese Patent Application Laid-Open No. 61-246088 discloses that 4-acetylbiphenyl is useful as a sensitizer for heat-sensitive recording materials. However, this 4-
It was not known that a combination of acetylbiphenyl and a (poly) 4-hydroxybenzoic acid ester derivative specifically exhibited a sensitizing effect.

The present inventors have made intensive studies and found that (poly) 4
-Hydroxybenzoic acid ester derivatives (product name K-5,
1 part by weight of fine powder of Asahi Denka Co., Ltd.
Mix 1 part by weight of acetylbiphenyl fine powder
A detailed observation of the melting state when the temperature was raised at a rate of 2 ° C. per minute from 0 ° C. showed that the mixture melted at 107 ° C., which is lower than the melting point of 4-acetylbiphenyl, 120 ° C. At first, it was found that the transparent and molten state was quickly and uniformly obtained at 109 ° C.

On the other hand, international publication number WO99 / 5
Bis (4-methylbenzyl) oxalate (melting point: 101 ° C.) exemplified as a sensitizer used in combination with 1444 to improve color sensitivity was observed in the same manner as 4-acetylbiphenyl. 101 ° C., the melting point of bis (4-methylbenzyl) oxalate
After a short time, it was found that the mixture began to partially melt and became a uniformly transparent molten state at 120 ° C.

From these observations, it can be seen that 4-acetylbiphenyl has a very high compatibility with (poly) 4-hydroxybenzoic acid ester derivatives. It is thought that it may dissolve into the benzoate derivative instantaneously.

That is, it is shown that the color development sensitivity is remarkably improved by using the (poly) 4-hydroxybenzoic acid ester derivative and 4-acetylbiphenyl in combination.

However, the (poly) 4-
Conditions such as the mixing ratio of the hydroxybenzoic acid ester derivative and 4-acetylbiphenyl and the method of raising the temperature are merely examples, and do not limit the present invention, but describe the qualitative quality thereof.

[0016] International Publication No. WO 99/51444
Diphenylsulfone (melting point 128) exemplified as a sensitizer used in combination for the purpose of improving color sensitivity.
C), the same observations as for 4-acetylbiphenyl were carried out.
At 114 ° C., less than 8 ° C., the mixture began to melt and was found to quickly become a uniformly transparent molten state at 117 ° C.

From these observations, it was found that diphenylsulfone also showed a similar effect to (acetyl) 4-hydroxybenzoic acid ester derivatives as did 4-acetylbiphenyl.
It was found that the compatibility was high. However, diphenylsulfone is slightly higher than the melting temperature of 4-acetylbiphenyl, has a low color density when used as a heat-sensitive recording material, and has insufficient color-forming sensitivity at a practical level.

Many ideas have been proposed for the coloring mechanism and coloring sensitivity of the thermosensitive recording material. However, the fact that the coloring properties greatly differ due to a slight difference in melting temperature and a difference in compatibility is considered in the thermal recording industry. It is widely known that obtaining a practical thermosensitive recording material requires a great deal of execution and error, and the same is true in the present invention.

[0019]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by providing a high color density, good color sensitivity, and excellent storage stability of the image area, as well as excellent heat resistance and chemical resistance. An object of the present invention is to provide a heat-sensitive recording composition and a heat-sensitive recording material using the same.

[0020]

Means for Solving the Problems As a result of repeated investigations based on the above-mentioned observation results, the present inventors have found that the use of a (poly) 4-hydroxybenzoic acid ester derivative and 4-acetylbiphenyl results in color development. The inventors have found that the density is high and the coloring sensitivity is dramatically improved, leading to the present invention.

According to the present invention, first, in a heat-sensitive recording composition containing a leuco dye and a developer as main components, at least (poly) 4 represented by the following general formula (1) is used as the developer. -Containing a condensation reaction product of hydroxybenzoic acid and a trihydric or higher polyhydric alcohol, and
A heat-sensitive recording composition comprising acetyl biphenyl is provided.

Embedded image (In the formula, m represents an integer of 0 to 2.)

Second, in a heat-sensitive recording composition containing a leuco dye and a developer as main components, at least (poly) 4-hydroxybenzoic acid represented by the following general formula (1) is used as the developer. It further contains a condensation reaction product of a carboxylic acid component containing a monohydric carboxylic acid and / or a dihydric carboxylic acid and a polyhydric alcohol component containing a trihydric or higher polyhydric alcohol and a dihydric low molecular alcohol, and A heat-sensitive recording composition comprising 4-acetylbiphenyl as a sensitizer is provided.

Embedded image (In the formula, m represents an integer of 0 to 2.)

Third, there is provided a heat-sensitive recording composition wherein the trihydric or higher alcohol is a compound represented by the following general formula (2).

Embedded image (In the formula, n represents an integer of 0 to 9, R ₁ and n R ₂ each independently represent hydroxymethyl or an alkyl group having 1 to 8 carbon atoms.)

Fourth, in the composition, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (2 4,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate Is provided.

Fifthly, there is provided a heat-sensitive recording material characterized in that at least a heat-sensitive recording layer comprising the heat-sensitive recording composition according to any one of the above-mentioned first to fourth aspects is provided on a support.

Sixth, an undercoat layer containing hollow particles is provided on a support, and a heat-sensitive recording layer comprising the heat-sensitive recording composition according to any one of the above-mentioned first to fourth is provided on the undercoat layer. A thermosensitive recording material is provided.

Seventh, the hollow particles contained in the undercoat layer are made of a thermoplastic resin as a shell and have a hollow ratio of 30% or more and a volume average particle diameter of 0.4 to 10 μm. The thermal recording material according to the sixth aspect is provided.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the heat-sensitive recording composition of the present invention, (poly) 4
High sensitivity is achieved by the combined use of the -hydroxybenzoic acid ester derivative and 4-acetylbiphenyl.
In particular, when the compound represented by the general formula (2) is used as a trihydric or higher alcohol when the (poly) 4-hydroxybenzoic acid ester derivative is produced, higher sensitivity is achieved.

The content of the (poly) 4-hydroxybenzoic acid ester derivative and 4-acetylbiphenyl is 1 to 5 parts by weight of the (poly) 4-hydroxybenzoic acid ester derivative to 1 part by weight of the leuco dye (preferably). Is 2-3.5 parts by weight), 4-acetylbiphenyl 0.1-
5 parts by weight (preferably 0.5 to 3 parts by weight) is suitable.

When the amount of the (poly) 4-hydroxybenzoic acid ester derivative is less than 1 part by weight, the color development is of course insufficient. The increase causes a decrease in concentration, which is not preferable. In addition, 4-acetylbiphenyl is contained in 0.1.
When the amount is 1 part by weight or less, the effect of improving the color sensitivity is insufficient, and when the amount is 5 parts by weight or more, (poly) 4-
As in the case of the hydroxybenzoate derivative, a decrease in the concentration occurs due to an increase in the amount not involved in color development.

Further, the heat-sensitive recording composition of the present invention comprises tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate as a storage stabilizer. Or tetrakis (2,2,
6,6-tetramethyl-4-piperidyl) -1,2,2
By containing 3,4-butanetetracarboxylate, a heat-sensitive recording composition free from background fog can be obtained.

With respect to 1 part by weight of a developer containing a (poly) 4-hydroxybenzoic acid ester derivative as an essential component,
Tetrakis (1,2,2,6,6-pentamethyl-4-
Piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate is 0 0.01 to 1 part by weight (preferably 0.05 to 0.3 part by weight) is appropriate. Incidentally, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate and tetrakis (2,2,6,6-tetramethyl-4-piperidyl) Even when used together with (piperidyl) -1,2,3,4-butanetetracarboxylate, the total amount is suitably from 0.01 to 1 part by weight per 1 part by weight of the developer.

Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (2,2,2
6,6-tetramethyl-4-piperidyl) -1,2,2
When the amount of 3,4-butanetetracarboxylate or a combination thereof is less than 0.01 part by weight, the effect of suppressing background fog is of course small. An increase in substances not involved causes an undesired decrease in concentration.

The above-described heat-sensitive recording composition is applied as a heat-sensitive recording layer on a support such as paper, film, or synthetic paper to provide a heat-sensitive recording material.

In the present invention, the leuco dye (color-forming substance) used in the heat-sensitive recording composition or the heat-sensitive recording material may be used alone or in combination of two or more. What is applied to the material is applied arbitrarily.

Representative examples thereof include triphenylmethane, fluoran, phenothiazine, auramine,
Leuco compounds of dyes such as spiropyrans and indolinophthalides are preferably used, but most preferably 3-leuko compounds are used.
Dibutylamino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-
Anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-N-isoamylamino) -6-methyl-7-
Anilinofluoran or 3-diethylamino-6-methyl-7- (3-methylanilino) fluoran.

Specific examples of other leuco dyes include, for example, those shown below. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3
-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl)-
6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-
Bis (p-dibutylaminophenyl) phthalide,

3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran, 3- (N-methyl-N-isobutylamino)-
6-methyl-7-anilinofluoran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7
-Methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7
-Chlorofluorane, 3-pyrrolidino-6-methyl-7
-Anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran,

2- {3,6-bis (diethylamino)-
Lactam 9- (o-chloroanilino) xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino -7- (o-chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-
7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6 Methyl-7-
(2 ', 4'-dimethylanilino) fluoran, 3-
(N, N-diethylamino) -5-methyl-7- (N,
N-dibenzylamino) fluoran,

Benzoylleucomethylene blue, 6'-
Chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2 ' -Methoxy-5 '
-Chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl) phthalide, 3- (2'-
Hydroxy-4'-diethylaminophenyl) -3-
(2'-methoxy-5'-methylphenyl) phthalide,
3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-
Methylphenyl) phthalide,

3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-
Diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (Α-
Phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α
-Phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3-
(N-methyltoluidino) -7- (pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran,

3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino)
-5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-chloro-7
-Anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl- 7-anilinofluoran, 3-
Diethylamino-6-methyl-7-mesitidino-4 ',
5'-benzofluoran,

3- (p-dimethylaminophenyl) -3
-{1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2 -Yl} -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3-
(1-p-dimethylaminophenyl-1-phenylethylene-2-yl) phthalide,

3- (p-dimethylaminophenyl) -3
-(1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4'-dimethylamino-2'-methoxy) -3- (1 "- p-dimethylaminophenyl-1 "-
p-chlorophenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide, 3- (4'-dimethylamino-
2'-benzyloxy) -3- (1 "-p-dimethylaminophenyl-1" -phenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide, 3-dimethylamino-
6-dimethylaminofluorene-9-spiro-3'-
(6′-dimethylamino) phthalide,

3,3-bis {2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl}
-4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bis (4-pyrrolidinophenyl) ethylene-
2-yl} -5,6-dichloro-4,7-dibromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl) -1-p-tolylsulfonylmethane etc.

The (poly) 4-hydroxybenzoic acid ester derivative used in the heat-sensitive recording composition or heat-sensitive recording material of the present invention itself has an effect as a color developer, but if necessary, other color developer may be used. Can be used. As an auxiliary additive, various hindered phenol compounds which are electron-accepting but have relatively low coloring ability can be used in combination. Specific examples include the following, but are not limited thereto.

2,2'-methylenebis (4-ethyl-6
-Tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,
1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4′-thiobis (6-tert-butyl-3-methylphenol),
Tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis (2-methylphenol), 4,4'-thiobis (2-chlorophenol)
etc.

In order to produce the heat-sensitive recording composition or the heat-sensitive recording material of the present invention, when a leuco dye, a (poly) 4-hydroxybenzoic acid ester derivative, 4-acetylbiphenyl or the like is bound and supported on a support, a conventional method is used. Various binders can be used as appropriate, and specific examples thereof include:
For example, the following are mentioned.

Polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylic acid Water-soluble polymers such as ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer, polyacrylamide, sodium alginate, gelatin, casein, etc. Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer Emulsion and styrene / butadiene copolymers such as the body, styrene / butadiene / latex such as acrylic copolymer.

In the present invention, 4-acetylbiphenyl has the most sensitizing effect, but a heat-fusible substance used in a heat-sensitive recording composition or a heat-sensitive recording material can be used in combination, if necessary. . Specific examples thereof include the following.

Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, zinc stearate, aluminum stearate;
Fatty acid metal salts such as calcium stearate, zinc palmitate, zinc behenate, p-benzylbiphenyl, m
-Terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate , Glayacol carbonate, dibensil terephthalate, dimethyl terephthalate,
1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2
-Diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxy-2-butene, 1,
2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4-diphenylthiobutane, 1,4
-Diphenylthio-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-vinyloxyethoxy) biphenyl, p-aryl Oxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyldisulfide, 1,1-diphenylethanol, 1,1
-Diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis (4-methoxyphenoxy) propane , 1,5-bis (4-methoxyphenoxy) -3-oxapentane, 1,2-bis (3,4-dimethylphenyl) ethane, dibenzyl oxalate, bis (4-oxalate)
Methylbenzyl) ester, oxalic acid bis (4-chlorobenzyl) ester, 4-acetotoluidide, diphenylsulfone and the like.

In the present invention, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording composition or heat-sensitive recording material, such as fillers, surfactants, lubricants, and pressure-coloring inhibitors, may be used in combination. Can be.

In this case, examples of the filler include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay kaolin,
In addition to inorganic fine powders such as talc and surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin can be given.

As a lubricant, higher fatty acids and metal salts thereof,
Examples include higher fatty acid amides, higher fatty acid esters, various animal, vegetable, mineral or petroleum waxes.

In the present invention, in order to increase the sensitivity of the heat-sensitive recording layer of the heat-sensitive recording composition or the heat-sensitive recording material, an undercoat layer containing hollow particles as a main component is provided between the support and the heat-sensitive recording layer. preferable.

The hollow particles contain air or other gas inside, and are minute hollow particles already in a foamed state. The hollow particles useful in the present invention have a hollow ratio of 30% or more (preferably 50 to 99%) using a thermoplastic resin as a shell.
%) And a volume average particle diameter of 0.4 to 10 μm can be used.

The hollow ratio here is a ratio of the outer diameter to the inner diameter of the hollow particles, and is (inner diameter of hollow particles / outer diameter of hollow particles) ×
Expressed as 100%.

The average particle diameter (particle outer diameter) is 0.4 μm
Smaller ones have production problems such as difficulty in achieving an arbitrary hollow ratio. Conversely, ones larger than 10 μm decrease the smoothness of the surface after coating and drying. And the effect of improving sensitivity is reduced.

Therefore, it is preferable that the particle distribution is such that the particle diameter is in the above-mentioned range and the distribution peak with little variation is uniform.

The hollow particles used in the present invention have a shell made of a thermoplastic resin as described above. Examples of the resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and polyacryl. Acid esters,
Examples thereof include polyacrylonitrile, polybutadiene, and a copolymer resin thereof.

Usually, the hollow particles are used as an undercoat layer between the heat-sensitive color-forming layer and the support to improve the heat insulation and the adhesion to the head, thereby improving the color-forming sensitivity. The same is true for

The undercoat layer is composed of the above hollow particles dispersed in a binder resin. The binder resin used here may be a conventionally known water-soluble polymer and / or aqueous polymer. It is preferable to appropriately select from emulsions. Specific examples thereof include, as water-soluble polymers, for example, polyvinyl alcohol, starch and derivatives thereof,
Cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic ester copolymer, acrylamide / acrylic ester / methacrylic terpolymer, styrene / Examples include maleic anhydride copolymer alkali salts, isobutylene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, casein and the like. Examples of the aqueous polymer emulsion include latexes such as styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, vinyl acetate resin, vinyl acetate /
Emulsions of acrylic acid copolymers, styrene / acrylic ester copolymers, acrylic ester resins, polyurethane resins, and the like can be given.

The undercoat layer has an adhesion amount of 2 to
10 g / m ^2, preferably can be provided in a range of 2.5~7g / m ^2.

Further, in the heat-sensitive recording material of the present invention, a pigment, a binder, a crosslinking agent, a lubricant, etc. may be added on the heat-sensitive coloring layer, if necessary, for the purpose of improving head matching and writing on the recording material. Can be provided as a protective layer.

The heat-sensitive recording composition or the heat-sensitive recording material of the present invention is prepared or prepared by using the above-mentioned materials, for example, by the following method. That is, first leuco dye by a conventional method,
After crushing and dispersing the color developer, sensitizer, etc. separately with a binder or other additives as necessary, using a dispersing machine such as a ball mill, an attritor, a sand mill, etc. Is usually used as a medium) and mixed to prepare a coating solution for the heat-sensitive recording layer. Separately, a coating solution for the undercoat layer and a coating solution for the overcoat layer are prepared using a binder or other additives as necessary. When an undercoat layer is provided on a support such as paper, plastic sheet, synthetic paper, etc., each coating solution is repeatedly applied and dried in the order of forming the undercoat layer, the heat-sensitive recording layer, and the overcoat layer as necessary. The heat-sensitive recording material of the present invention is obtained.

[0066]

Next, the present invention will be described in more detail with reference to examples. In addition, the following parts and% (however,% of hollow ratio
) Are based on weight.

<Example-1>

The following compositions [Solution A] to [Solution E] were prepared using a sand grinder so that the average particle diameter was about 1.0 μm.

[Solution A] 3-Dibutylamino-6-methyl-7-anilinofluoran 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts

[Solution B] (Poly) 4-hydroxybenzoic acid ester derivative 20 parts

Embedded image m = 3-4, n = 10-12 (manufactured by Asahi Denka Co., Ltd., K-5: number average molecular weight 1900, weight average molecular weight 2600, softening point 115 ° C.) 10% aqueous solution of polyvinyl alcohol 20 parts Amorphous silica 10 parts 50 parts of water

[Solution C] 4-acetylbiphenyl 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts

[Solution D] Aluminum hydroxide 30 parts 10% aqueous solution of polyvinyl alcohol 30 parts Water 40 parts

[Solution E] Montanic ester wax 20 parts (manufactured by Hoechst: WAX-E) 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts

Next, 10 parts of [solution A], 30 parts of [solution B]
[Liquid C] was mixed at a ratio of 10 parts to prepare a coating solution for the thermosensitive recording layer.

Next, an overcoat liquid having the following composition was prepared. (Overcoat solution) [Solution D] 15 parts 10% aqueous solution of polyvinyl alcohol 40 parts 25% aqueous solution of polyepichlorohydrin 7 parts [Solution E] 3 parts Water 35 parts

A heat-sensitive recording layer was formed by coating and drying on a commercially available high-quality paper (basis weight: 45 g / m ² ) so that the adhesion amount of the leuco dye after drying was 0.5 g / m ² . The overcoat solution was applied and dried on the heat-sensitive recording layer so that the adhesion amount after drying was 3.0 g / m ² to form an overcoat layer. Further, the surface smoothness is 800 to 15
The heat-sensitive recording material of the present invention was calendered so as to be 00 seconds.

Example 2 An undercoat liquid having the following composition was prepared. (Undercoat liquid) Styrene acrylic hollow particles 40 parts (Rohm & Haas HP-91, solid content 27.5%, hollow ratio 80%) Styrene butadiene latex (solid content 50%) 10 parts Water 50 parts

The above-mentioned undercoat liquid was applied to a commercially available high-quality paper (basis weight: 45 g / m ² ) after drying to obtain an adhesion amount of 4.0.
g / m ² and dried by application to form an undercoat layer. A heat-sensitive recording material of the present invention was obtained in the same manner except that the heat-sensitive recording layer and the overcoat layer described in Example 1 were laminated thereon.

<Embodiment 3> In Embodiment 2, [A
Liquid] 10 parts, [Liquid B] 30 parts and [Liquid C] 20 parts were mixed in the same manner to prepare a thermosensitive recording layer coating solution, thereby obtaining a thermosensitive recording material of the present invention.

<Example-4> [Solution F] having the following composition was prepared using a sand grinder in the same manner as in Example-1 so that the average particle size was about 1.0 µm.

[Solution F] Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 Part The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 3, except that 3 parts of [Solution F] was added as a coating solution for the heat-sensitive recording layer.

<Example 5> A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 4, except that the overcoat solution was not applied.

<Example-6> In Example-4, [A
Liquid], except that 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran was used in place of 3-dibutylamino-6-methyl-7-anilinofluoran A heat-sensitive recording material of the present invention was obtained.

<Embodiment-7> In the embodiment-4, [A
Liquid], except that 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran was used in place of 3-dibutylamino-6-methyl-7-anilinofluoran Similarly, a heat-sensitive recording material of the present invention was obtained.

<Embodiment-8> In Embodiment-4, [A
Liquid] of the present invention except that 3- (N-ethyl-p-toluidino) -7-anilinofluorane was used in place of 3-dibutylamino-6-methyl-7-anilinofluoran Was obtained.

<Embodiment-9> In the embodiment-4, [A
Liquid] of the present invention, except that 3-diethylamino-6-ethyl-7- (3-methylanilino) fluoran was used instead of 3-dibutylamino-6-methyl-7-anilinofluoran A recording material was obtained.

<Example-10> In Example-4,
Instead of 3-dibutylamino-6-methyl-7-anilinofluoran in [Solution A], 3- (N-methyl-N-cyclohexylamino) -diethylamino-6-ethyl-
A heat-sensitive recording material of the present invention was obtained in the same manner except that 7-anilinofluoran was used.

<Example-11> [Solution G] having the following composition was prepared in the same manner as in Example-1 using a sand grinder so that the average particle diameter was about 1.0 µm.

[G Solution] Tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts Further, in Example 3, [G
Liquid] was prepared in the same manner as above except that 3 parts were added to obtain a heat-sensitive recording material of the present invention.

<Comparative Example-1> In Example-3, [C
Liquid], except that 4-acetylbiphenyl was removed to obtain a heat-sensitive recording material of the present invention.

<Comparative Example-2> In Example-3, [C
Liquid], a heat-sensitive recording material of the present invention was obtained in the same manner except that bis (p-methylbenzyl) oxalate was used in place of 4-acetylbiphenyl.

<Comparative Example-3> In Example-3, [C
Liquid] of the present invention was obtained in the same manner except that diphenylsulfone was used in place of 4-acetylbiphenyl.

The following test was carried out on the heat-sensitive recording material prepared as described above.

(Coloring characteristics) A printing energy of 0.45 m was measured by a printing simulator of a thermosensitive recording material manufactured by Okura Electric Co., Ltd.
J / dot, pulse time 0.60 ms, 0.80 m
s, 1.00 ms, and 1.20 ms under four different printing conditions, and each color density was measured using a Macbeth densitometer RD-914.
Was measured. At the same time, the density of the unprinted area was taken as the background density. A heat block (150 ° C., 2 kgf / cm ² ,
1 second), the color density of the portion printed by the Macbeth densitometer RD
The measurement was performed at -914.

(Heat Resistance) The density of the image portion and the background after printing for 24 hours under the environmental conditions of 80 ° C. was measured with the Macbeth densitometer RD-914. A measurement was taken.

(Plasticizer resistance) An image portion and a background portion printed by using the above-described heat block are placed on three sheets of Shin-Etsu Polymer PVC (Polymer Wrap 300), and placed on a 10 ×
5kg load per 10cm2, ^{2 in} a 40 ° C environment
The density of the image portion and the background portion after storage for 4 hours was measured with a Macbeth densitometer RD-914.

The above results are shown in Table 1 and FIG.

[0098]

[Table 1]

[0099]

As is clear from Table 1, the heat-sensitive recording material of the present invention has a high color density and a high color sensitivity by using a (poly) 4-hydroxybenzoic acid ester derivative and 4-acetylbiphenyl in combination. It is good, has little coloration of the background due to heat resistance, and has little decoloration of the image due to plasticizer resistance, and is extremely practical.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between printing conditions and image density.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Kajikawa 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H026 AA07 BB33 BB35 DD02 DD43 DD45 DD46 DD48 DD53 DD57 FF15

Claims (7)

[Claims] 1. A thermosensitive recording composition containing a leuco dye and a color developer as main components, at least a compound represented by the following general formula (1):
A polycondensation reaction product of a (poly) 4-hydroxybenzoic acid represented by
-A thermosensitive recording composition containing acetyl biphenyl. Embedded image (In the formula, m represents an integer of 0 to 2.) 2. A thermosensitive recording composition comprising a leuco dye and a developer as main components, wherein at least the following general formula (1):
A carboxylic acid component containing a (poly) 4-hydroxybenzoic acid and a monohydric carboxylic acid and / or a dihydric carboxylic acid, and a polyhydric alcohol containing a trihydric or higher polyhydric alcohol and a dihydric low molecular alcohol A heat-sensitive recording composition comprising a condensation reaction product with a component and further containing 4-acetylbiphenyl. Embedded image (In the formula, m represents an integer of 0 to 2.) 3. The heat-sensitive recording composition according to claim 1, wherein the trihydric or higher alcohol is a compound represented by the following general formula (2). Embedded image (In the formula, n represents an integer of 0 to 9, R ₁ and n R ₂ each independently represent hydroxymethyl or an alkyl group having 1 to 8 carbon atoms.) 4. The composition according to claim 1, wherein said composition comprises tetrakis (1,2,2).
2,6,6-pentamethyl-4-piperidyl) -1,
2,3,4-butanetetracarboxylate, or
The heat sensitivity according to any one of claims 1 to 3, further comprising tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate. Recording composition. 5. A heat-sensitive recording material comprising a support and at least a heat-sensitive recording layer comprising the heat-sensitive recording composition according to claim 1. 6. An undercoat layer containing hollow particles is provided on a support, and a heat-sensitive recording layer comprising the heat-sensitive recording composition according to claim 1 is provided on the undercoat layer. Characteristic thermal recording material. 7. The hollow particles contained in the undercoat layer are made of a thermoplastic resin as a shell, and have a hollow ratio of 30% or more and a volume average particle diameter of 0.4 to 10 μm. 6. The heat-sensitive recording material according to item 6.