JPH0699661A - Heat-sensitive recording body - Google Patents

Abstract

PURPOSE:To provide heat-sensitive recording body, the keeping stability of the recorded image and recorded sensitivity by which are excellent in heat- sensitive recording layer containing colorless or light-colored basic dye and colorant is provided. CONSTITUTION:On base, heat-sensitive recording layer containing colorless or light-colored basic bye and colorant is provided. In the heat-sensitive recording body concerned, at least one of metal salt or ammonium salt of 2,2'-methylene bis(4,6-die-tert-butylphenyl) phosphate, 1,1,3-tris(2-methyl-4-hydroxy-5- cyclohexylphenyl)butane and 1,1,3-tris(2-metyl-4-hydroxy-5-tert-bytylphenyl)butane is added to the finely divided particles of the basic dye and/or the colorant as keeping quality improver.

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 excellent in storage stability of recorded images and recording sensitivity.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a reaction between a colorless or light-colored basic dye and a coloring agent is used to bring both color-forming substances into contact with each other by heat to obtain a recorded image.
Since such a thermosensitive recording medium is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields. Generally, the storage stability of the recorded image is not sufficient, and the recorded image is discolored over time. In particular, when the thermosensitive recording medium is stored under high humidity conditions or high temperature conditions, the recorded image disappears in a relatively short time, so that improvement is strongly demanded.

[0003]

In order to improve the storage stability of a recorded image, a thermosensitive recording layer containing a basic dye, a color developing agent, and a component in which the preservability improving agent is made into individual fine particles is contained in the thermosensitive recording layer. Although the body is well known, the present situation is that the result is not always satisfactory. An object of the present invention is to provide a thermosensitive recording medium which is excellent in storage stability of recorded images and recording sensitivity in a thermosensitive recording medium provided with a thermosensitive recording layer containing a colorless or pale color basic dye and a color former. Especially.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have proposed a storage stability improving agent in a heat-sensitive recording material in which a heat-sensitive recording layer containing a colorless or light-colored basic dye and a color former is provided on a support. 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate metal salt or ammonium salt, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3
-By including at least one of tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane in the fine particles of the basic dye and / or the color former, the above object can be achieved. Heading out, the present invention has been completed.

[0005]

According to the present invention, by containing the above specific storage stability improving agent in the fine particles of the basic dye or the color developing agent, the storage stability of the recorded image is remarkably improved as compared with the case where only the storage stability improving agent is made into fine particles. It is what is done. The reason why the storability of the recorded image is remarkably improved is that the specific storability improving agent is contained in the fine particles of the basic dye or the coloring agent,
It is considered that after the recording, the preservability improving agent enhances the crystallization suppressing effect of the basic dye or the color developing agent.

The following method can be used for incorporating the above-mentioned specific storage stability improving agent into the fine particles of the basic dye or color developing agent. 1. A method in which a storability improver and a basic dye or a coloring agent are mixed in a heat-melted state, and then cooled and individualized to form fine particles. 2. A method in which a storability improver and a basic dye or a coloring agent are mixed in a hot-melt state, and then emulsified by stirring and dispersing in an aqueous solution containing an emulsifier or the like to form fine particles. 3. A method in which a preservability improver and a basic dye or a color former are dissolved in a hydrophobic organic solvent, and then emulsified by stirring and dispersing in an aqueous solution containing an emulsifier and the like, and the organic solvent is removed to form fine particles.

In the present invention, when the fine particles are formed by the above method 2,
By including a heat-fusible substance having a melting point of 70 to 150 ° C. in the fine particles, the emulsification temperature can be lowered, and stable fine particles can be obtained. If the melting point of the heat-fusible substance is less than 70 ° C., background fog will occur on the heat-sensitive recording material, and if the melting point exceeds 150 ° C., the desired recording sensitivity cannot be obtained. If the average particle size of the fine particles exceeds 2.0 μm, the desired recording sensitivity cannot be obtained.

The amount of the above-mentioned specific storability improver used is not particularly limited, but 5 to 100% by weight based on the basic dye,
It is desirable to adjust it in the range of 10 to 50% by weight. The amount of the heat-fusible substance used is not particularly limited, but it is desirable to adjust it in the range of 50 to 500% by weight, preferably 100 to 300% by weight, based on the basic dye.

2,2'-methylenebis (4,6-di-te
Examples of the metal of the metal salt of rt-butylphenyl) phosphate include sodium, potassium, zinc, magnesium, barium, calcium, aluminum, tin, titanium, nickel, cobalt, manganese, iron and the like.

In the present invention, various known dyes can be used as the colorless or light-colored basic dye constituting the recording layer. The specific examples are as follows. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p
-Dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole -3-yl)
Phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-
Bis (1,2-dimethylindol-3-yl) -6-
Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide , 4-p-Dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide and other triallylmethane dyes, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether , N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and other diphenylmethane dyes, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and other thiazine dyes, 3-methyl-spiro- Dinaphthopyran, 3-ethyl-spiro-dinaphthopyran,
3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6 '
-Methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran and other spiro dyes, rhodamine-B
-Lactam dyes such as anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino -7-Methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3
-Diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N -Acetyl-
N-methylaminofluorane, 3-diethylamino-7
-N-methylaminofluorane, 3-diethylamino-
7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3
-Diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluorane ,
3- (N-ethyl-p-toluidino) -6-methyl-7
-(P-toluidino) fluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-di-n-butylamino-6- Methyl-7-phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 3- (N -Cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-
7- (o-chlorophenylamino) fluorane, 3-di-n-butylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7-p
-Butylphenylaminofluorane, 3- (N-methyl-Nn-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-amyl) amino-6- Methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamyl) amino-6-
Methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-)
Hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-β-ethylhexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N- Tetrahydrofurfuryl)
Amino-6-methyl-7-phenylaminofluorane,
3- (N-ethyl-N-cyclopentyl) amino-6-
Methyl-7-phenylaminofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthene) -2'- Fluoran dyes such as ilamino] phenyl} propane. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination.

Various compounds are known as colorants used in combination with the above basic dyes, and the following are exemplified. 4-tert-butylphenol, α-
Naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-
Butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxy-diphenylmethane, 4,4 '
-Isopropylidenediphenol, hydroquinone,
4,4'-cyclohexylidene diphenol, 4,4 '
-(1,3-dimethylbutylidene) bisphenol,
2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'- Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy -3 ', 4'-trimethylene diphenyl sulfone, 4-hydroxy-3', 4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) ) Sulfone, 1,3-di [2- (4-hydroxyphenyl) Phenyl) -2-propyl] benzene, hydroquinone monobenzyl ether, bis (4
-Hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 4-hydroxyphthalic acid Dimethyl, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, 4
-Propyl hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate,
Phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p. -Chlorobenzyl,
4-hydroxybenzoic acid-p-methoxybenzyl, novolac type phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-butylbenzoic acid,
Trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-
Hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-tert-
Butyl salicylic acid, 3-benzyl salicylic acid, 3- (α
-Methylbenzyl) salicylic acid, 3-chloro-5- (α
-Methylbenzyl) salicylic acid, 3-phenyl-5-
Aromatic carboxylic acids such as (α, α-dimethylbenzyl) salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, Organic acidic substances such as salts with polyvalent metals such as manganese, tin and nickel. As a matter of course, two or more kinds of the above-mentioned color developing agents can be used in combination.

The use ratio of the basic dye and the color developing agent should be appropriately selected according to the types of the basic dye and the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used.
About 100 to 700 parts by weight, preferably about 150 to 400 parts by weight, of the coloring agent is used with respect to 00 parts by weight.

In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfo group-modified polyvinyl alcohol, silicon modified polyvinyl alcohol are usually used as binders. ,
Acetoacetyl group-modified polyvinyl alcohol, graft copolymer of vinyl alcohol / vinyl acetate copolymer and acrylamide / allyl acetoacetate acrylate,
Styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion and the like are 2 to 40% by weight of the total solid content, preferably 5
About 25% by weight is blended.

Various auxiliaries can be further added to the coating liquid, for example, dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Examples thereof include dispersants such as lauryl alcohol sulfate / sodium salt and fatty acid metal salt, defoaming agents, fluorescent dyes, and coloring dyes. It is also possible to use the above compounds exemplified as the binder as a dispersion aid.

Further, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, in order to improve the adhesion of dust to the recording head,
Inorganic pigments such as activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as starch particles can also be added. Further, a dispersion liquid or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like may be added so that sticking does not occur due to contact with a recording device or recording head.

The melting point inherent in the fine particles of the present invention is 70 to
Specific examples of the heat-fusible substance at 150 ° C. include p-
Biphenyls such as benzyl biphenyl and p- (4-tolyloxy) biphenyl, 1,5-bis (4-methoxyphenoxy) -3-oxa-pentane, 1,2-bis (phenoxy) ethane, 1,2-bis ( Ethers such as 4-methylphenoxy) ethane, 1,2-bis (3-methylphenoxy) ethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, 2-naphtholbenzyl ether, diether Benzyl terephthalate, 1-
Examples thereof include esters such as hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, and oxalic acid di (4-chlorobenzyl) ester. Further, in the fine particles containing a specific storage stability improving agent in the basic dye,
(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole,
By using a UV absorber such as 2- (2'-hydroxy-4'-octyloxyphenyl) benzotriazole or 2-hydroxy-4-benzyloxybenzophenone together, a heat-sensitive material having excellent light resistance of a recorded image and a background part. A recording body is obtained.

As the support, paper, plastic film, synthetic paper or the like is used, but paper is preferably used in terms of cost and coating suitability. In the present invention, the method for forming the recording layer is not particularly limited, and it can be formed according to a conventionally well-known and conventional technique. For example, a coating solution for a heat-sensitive recording layer is formed on a support by an air knife coater or a blade. Examples of the method include coating and drying with a suitable coating device such as a coater, bar coater, gravure coater, curtain coater, and short dwell coater. Also, there are no particular limitation on the coating amount of the coating liquid, generally dry weight 2~12g / m ^2, it is adjusted preferably in the range of 2 to 8 g / m ^2. An overcoat layer may be provided on the recording layer for the purpose of protecting the recording layer, a protective layer may be provided on the back surface of the support, or an undercoat layer may be provided between the support and the thermosensitive recording layer. Needless to say, it is also possible to provide various known techniques in the field of manufacturing a thermosensitive recording medium, such as applying an adhesive treatment.

[0018]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1 Formation of Undercoat Layer Fired clay [trade name: Ansilex, manufactured by EMC] 1
00 parts, 15 parts of styrene-butadiene copolymer having a solid concentration of 50%, and a 10% aqueous solution of polyvinyl alcohol 30
Parts and 20 parts of water were mixed and stirred to prepare an undercoat layer and a liquid. The obtained coating liquid was applied to 50 g / m ² of high-quality paper so that the coating amount after drying was 10 g / m ^2, and dried to form an undercoat layer.

Liquid A Preparation 10 parts of 3-di-n-butylamino-6-methyl-7-phenylaminofluorane, 25 parts of 1,2-bis (3-methylphenoxy) ethane, and 2,2′-methylenebis A composition comprising 5 parts of sodium salt of (4,6-di-tert-butylphenyl) phosphate was melted by heating to 120 ° C., and then polyvinyl alcohol [trade name: PVA
217, Kuraray Co., Ltd.] aqueous solution (solution temperature 80 ° C.)
Emulsified and dispersed until the average particle diameter became 0.8 μm at 80 parts to obtain a liquid A.

Preparation of Solution B A composition comprising 20 parts of 4,4′-isopropylidenediphenol, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was pulverized with a sand mill until the average particle size became 1.5 μm. Liquid B was obtained.

Formation of Recording Layer 120 parts of solution A, 65 parts of solution B, light calcium carbonate 10
Parts, 100 parts of a 15% aqueous solution of polyvinyl alcohol, 15 parts of silicon oxide (oil absorption 180 ml / 100 g), and 15 parts of a 30% dispersion of zinc stearate.
The coating liquid for the recording layer was prepared by stirring.

The coating solution was applied onto the undercoat layer so that the coating amount after drying was 4 g / m ^2, and dried to obtain a thermal recording paper.

Example 2 In the preparation of solution A, 2,2'-methylenebis (4,6-
1,1,3-Tris (2-methyl-4-) instead of the sodium salt of di-tert-butylphenyl) phosphate
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that hydroxy-5-cyclohexylphenyl) butane was used.

Example 3 In the preparation of solution A, 2,2'-methylenebis (4,6-
2- (2'-hydroxy-3 ', instead of 5 parts of the sodium salt of di-tert-butylphenyl) phosphate,
Example 1 except that 5 parts of 5'-di-tert-butylphenyl) benzotriazole and 5 parts of 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane were used. Thermal recording paper was obtained in the same manner.

Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that p-benzylbiphenyl was used instead of 1,2-bis (3-methylphenoxy) ethane in the preparation of solution A.

Comparative Example 1 Preparation of Solution C Composition consisting of 10 parts of 3-di-n-butylamino-6-methyl-7-phenylaminofluorane and 25 parts of 1,2-bis (3-methylphenoxy) ethane. Twelve
After being heated and melted to 0 ° C., it is emulsified and dispersed in 70 parts of a 5% aqueous solution of polyvinyl alcohol (trade name: PVA217, manufactured by Kuraray Co., Ltd.) (solution temperature 80 ° C.) until the average particle diameter becomes 0.8 μm, and C liquid is obtained. Obtained.

Preparation of Solution D A composition consisting of 5 parts of a sodium salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, 5 parts of a 5% aqueous solution of methylcellulose, and 10 parts of water was sand-milled. And pulverized until the average particle diameter was 0.8 μm to obtain a liquid D.

Formation of Recording Layer 105 parts of C liquid, 65 parts of B liquid, 20 parts of D liquid, 10 parts of light calcium carbonate, 15% aqueous solution of polyvinyl alcohol 1
A coating solution for the recording layer was prepared by mixing and stirring a composition of 00 parts, 15 parts of silicon oxide (oil absorption 180 ml / 100 g), and 15 parts of a 30% dispersion of zinc stearate.

The above coating liquid for recording layer was applied onto the undercoat layer obtained in Example 1 so that the coating amount after drying was 4 g / m ^2.
It was dried to obtain a thermosensitive recording paper.

Comparative Example 2 In the preparation of solution A, 2,2'-methylenebis (4,6-
Thermosensitive recording as in Example 1 except that 5 parts of 2,2'-methylenebis (4-methyl-6-tert-butylphenol) were used instead of 5 parts of the sodium salt of di-tert-butylphenyl) phosphate. Got the paper.

The six kinds of thermal recording papers thus obtained were evaluated by the following methods, and the results are shown in [Table 1]. [Recording Density] A thermal recording paper was used with a thermal paper color tester (TH-PMD type, manufactured by Okura Electric Co., Ltd., applied voltage: 16 V, pulse cycle: 0.51 ms) and pulse width 0.30 m.
s, and the recorded density (D ₁ ) is recorded by a Macbeth densitometer (R
D-914 type, manufactured by Macbeth).

[Moisture Resistance of Recorded Image] The heat-sensitive recording paper after printing was left in an atmosphere of 40 ° C. and 90% RH for 72 hours, and then the recording density (D ₂ ) was measured again using a Macbeth densitometer.
In addition, the recording density residual rate (%) was determined by the following formula. Recording density residual rate = D ₂ / D ₁ × 100

[0034]

[Table 1]

[0035]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention was a recording medium excellent in storage stability of recorded images and recording sensitivity.

Claims (3)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent, which comprises 2,2'-methylenebis (4,6-di-tert-).
Butylphenyl) phosphate metal salt or ammonium salt, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,
3-tris (2-methyl-4-hydroxy-5-tert-
A heat-sensitive recording material comprising at least one of butylphenyl) butane in the fine particles of the basic dye and / or the color former. 2. The heat-sensitive recording material according to claim 1, wherein the fine particles contain a heat-fusible substance having a melting point of 70 to 150 ° C. 3. The heat-sensitive recording material according to claim 1, wherein the average particle diameter of the fine particles is 2.0 μm or less.