JPH10291367A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent water resistance and recording running properties by incorporating casein or acetoacetyl-modified polyvinyl as adhesive in a recording layer or protective layer, and incorporating ketone resin as crosslinking agent of the adhesive. SOLUTION: Casein or acetoacetyl-modified polyvinyl alcohol is contained as adhesive in a recording layer or protective layer, and ketone resin is contained as crosslinking agent of adhesive. A using amount of the adhesive is about 5 to 40 wt.% to overall solid amount of the recording layer in the recording layer, and about 20 to 99 wt.% to overall solid content amount of the protective layer in the protective layer. A using amount of the ketone resin is preferably about 2 to 30 wt.% to the adhesive. As the polyvinyl alcohol, polyvinyl alcohol having polymerization degree of about 200 to 3000 containing about 0.01 to 10 mol % of acetoacetyl group in a molecule of the alcohol is used. As the ketone resin, condensate of acetone and formaldehyde or the like is used.

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 utilizing a leuco dye, a color former and a color-forming reaction, and more particularly to a heat-sensitive recording material excellent in water resistance and recording running property.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known which utilizes a color reaction between a colorless or light-colored leuco dye and a color former to contact both color developing substances by heat to obtain a recorded image. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and easy to maintain, so that it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

For example, as another field of use, there is a recording medium of a hand-held terminal machine used for meter reading and the like. Such handy terminal machines are increasingly used in various places and conditions, including outdoors. When used outdoors, the recording layer surface may naturally become wet with water in rainy weather. Therefore, there is a demand for a heat-resistant recording material having excellent water resistance, which does not peel off or melt out even when wet.

JP-B-58-33117 and JP-B-59-30555 describe methods using sodium tetraborate and an aldehyde compound as crosslinking agents for polyvinyl alcohol in a recording layer, respectively. The coating liquid for forming the recording layer may gel. Also, JP-A-59-16995 discloses that
A method using an aldehyde compound as a cross-linking agent for acetoacetyl-modified polyvinyl alcohol in the protective layer is described, and JP-A-60-154095 describes a method using methylol urea as a cross-linking agent for casein in the protective layer. However, in the case of aldehyde compounds or methylol urea, it is necessary to heat to about 100 ° C. in order to achieve sufficient water resistance, which poses a practical problem.

Further, Japanese Patent Application Laid-Open No. 61-64991 discloses a method in which a ketone resin is used as a crosslinking agent for silicon-modified polyvinyl alcohol in a recording layer or a protective layer. Is required.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording medium having excellent water resistance and recording running property.

[0007]

Means for Solving the Problems In a heat-sensitive recording medium in which a recording layer containing a leuco dye and a colorant on a support or a protective layer is provided on the recording layer, the above-mentioned object is achieved. In the present invention, the recording layer or the protective layer contains casein or acetoacetyl-modified polyvinyl alcohol as an adhesive and a ketone resin as a crosslinking agent for the adhesive.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a thermosensitive recording medium comprising a recording layer containing a leuco dye and a color former on a support or a protective layer provided on the recording layer. A casein or acetoacetyl-modified polyvinyl alcohol as an adhesive, and a ketone resin as a cross-linking agent for the adhesive. About 5 to 40% by weight with respect to the total solids of the protective layer, and about 20 to 99% by weight with respect to the total solids of the protective layer in the protective layer.
The amount of the ketone resin used is 1 to 5 for a specific resin.
100, preferably about 2 to 30% by weight.

As acetoacetyl-modified polyvinyl alcohol, an acetoacetyl group in a molecule of polyvinyl alcohol having a degree of polymerization of about 200 to 3000 is 0.01 to 10%.
What contains about mol% is used.

Examples of the ketone resin include a condensate of acetone and formaldehyde, and a condensate of a cyclic ketone such as acetophenone and cyclohexanone with formaldehyde.

The heat-sensitive recording layer contains various known leuco dyes and coloring agents. Such leuco dyes include, for example, 3,3-bis (p-dimethylaminophenyl) -6-
Dimethylaminophthalide, 3- (4-diethylamino-
2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-anilinofluoran, 3-diethylamino-
7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-
Isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-ani Linofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-
7-anilinofluoran, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluoran, 3
-(N-ethyl-N-isobutyl) amino-7- (p-
Trifluoromethylanilino) fluoran, 3- (N-
Ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3,3-bis [1- (4-methoxyphenyl) -1- (4-Dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-anilinoanilino) anilino-6
-Methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-
Dimethylamino) phthalide, 3- (N-ethyl-N-isobutyl) amino-7- (p-trifluoromethylanilino) fluoran, 3- (N-ethyl-N-isobutyl) amino-7- (o-tri Fluoromethylanilino)
Fluoran, 3- (N-ethyl-N-isoamyl) amino-7- (p-trifluoromethylanilino) fluoran, 3-di (n-butyl) amino-7- (m-trifluoromethylanilino) fluoran And the like. Two or more of these leuco dyes may be used in combination. The amount of the leuco dye used is 5 to the total solid content of the recording layer.
About 35% by weight is preferable.

Examples of the coloring agent include hydroquinone monobenzyl ether, 4,4'-isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, and 4,4'-dihydroxydiphenyl-2,4.
2-butane, 4,4'-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (hydroxyphenyl) heptane, bis (4-hydroxyphenylthioethoxy)
Methane, 1,5-di (4-hydroxyphenylthio)-
3-oxapentane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [ α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenylsulfide, di (4-hydroxy-3-methylphenyl) sulfine, 4,4′-dihydroxydiphenylsulfone, 2, 4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxydiphenylsulfone, 4-hydroxy-3 ',
4'-tetramethylenebiphenylsulfone, 3,4-dihydroxyphenyl-p-tolylsulfone, benzyl 4-hydroxy-benzoate, N, N-di-m-chlorophenylthiourea, 4- [2- (p-methoxyphenoxy) )
Ethyloxy] zinc salicylate, 4- [3- (p-tolylsulfonyl) propyloxy] zinc salicylate, 5-
[P- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate, 4,4'-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane, N
-P-tolylsulfonyl-N'-phenylurea and the like.

The proportion of the leuco dye to the color former is not particularly limited, but is 1 to 8 parts by weight, preferably about 2 to 5 parts by weight, per 1 part by weight of the leuco dye.

Further, the recording layer may contain a sensitizer for increasing the recording sensitivity and a storability improving agent for improving the aging stability of the recording portion. Specific examples of such a sensitizer include, for example, stearic acid amide, ethylene bisamide stearate, 2-naphthylbenzyl ether, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, Dibenzyl terephthalate, dibenzible terephthalate, phenyl 1-hydroxynaphthoate, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2
-(4-methylphenoxy) ethane, p-acetotoluidide, p-acetophenethidide, N-acetoacetyl-
p-Toluidine, p-benzylbiphenyl and the like.

Further, specific examples of the preservability improver include, for example, 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 2,2′-ethylenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol),
2,2'-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-tert-butylphenol), 1,1,3-tris (2-methyl- 4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, N, N'-di-2-naphthyl-p-phenylene Diamine, 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate, 4-benzyloxy-
4 '-(2-methyl-2,3-epoxypropyloxy) diphenyl sulfone, novolak resin and the like. These sensitizers and storability improvers are usually used in an amount of about 0.1 to 4 parts by weight based on 1 part by weight of the leuco dye.

The recording layer is generally formed by using water as a dispersion medium, stirring with a ball mill, an attritor, a sand mill or the like, and using a pulverizer, a leuco dye, a color former, and if necessary, a sensitizer,
After finely dispersing the preservability improver together or separately with a dispersant so that the average particle diameter becomes about 0.3 to 3 μm, a specific adhesive and a ketone resin are added, and the mixture is stirred and prepared. The coating liquid for a recording layer thus formed is applied on a support and dried to form a coating.

The protective layer is formed by applying a protective layer coating solution containing a specific adhesive dissolved in water to the recording layer and drying it.

As long as the desired effect of the present invention is not impaired, the recording layer or the protective layer may contain, in addition to the specific adhesive,
Other adhesives may be included. Other adhesives include, for example, completely (partially) saponified polyvinyl alcohol, silicon-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, starch, oxidized starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, arabic gum, diisobutylene. Water-soluble adhesives such as maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, and styrene / butadiene-based latex, Water-dispersible adhesives such as acrylic latex and urethane latex are exemplified. Among them, the combined use with an acrylic latex having an average molecular weight of 5,000,000 or more is preferable because of excellent recording runnability.

In the coating liquid for the recording layer or the coating liquid for the protective layer,
Various auxiliaries can be added. Such auxiliaries include, for example, kaolin, clay, talc, calcium carbonate, calcined clay, aluminum hydroxide, amorphous silica,
Pigments such as urea / formalin resin filler, surfactants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, sodium stearate, calcium stearate,
Lubricants such as zinc stearate, paraffin wax, and polyethylene wax; benzophenone-based and triazole-based ultraviolet absorbers; other defoamers; fluorescent dyes;

In the present invention, the method of forming the recording layer and the protective layer is not particularly limited, and can be formed according to a conventionally well-known and commonly used technique. For example, air knife coating, variver blade coating, pure blade coating, rod The coating liquid for the recording layer is applied to one side of the support by a coating method such as blade coating, short dwell coating, curtain coating, and die coating to form a recording layer, and then the coating liquid for the protective layer is applied and dried. Thus, a protective layer is formed. The support is appropriately selected from paper, plastic film, synthetic paper, nonwoven fabric, metal deposit, and the like. Further, 2~12g / m ² coating amount of the recording layer coating liquid for a dry weight, preferably 3 to 10 g / m ² approximately, the coating amount of the protective layer coating composition is 0.5 dry weight
10 g / m ^2, preferably from 1 to 6 g / m ² approximately.

It is also possible to provide a protective layer on the back side of the support, if necessary. Furthermore, an undercoat layer may be provided between the support and the recording layer to enhance recording sensitivity and recording image quality, or a smoothing process such as super calendering may be performed after coating each layer, or an adhesive treatment may be applied to the back surface of the recording material. And various known techniques in the heat-sensitive recording material manufacturing field can be added as necessary.

[0022]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. Unless otherwise specified, “parts” and “%” in the examples indicate “parts by weight” and “% by weight”, respectively.

Example 1 Preparation of Coating Liquid for Undercoat Layer 100 parts of calcined kaolin having an oil absorption of 110 ml, 2 parts of a 40% aqueous solution of sodium polyacrylate, 100 parts of water, polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.) )) And a composition comprising 10 parts of a styrene / butadiene latex having a solid concentration of 48% were mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of Solution A A composition comprising 40 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 20 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol, and 40 parts of water was subjected to sand milling. Was pulverized until the average particle diameter became 1.5 μm or less to obtain a liquid A.

Solution B Preparation of 40 parts of di-p-methylbenzyl oxalate, 20 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol,
And a composition comprising water and 40 parts of water were pulverized with a sand mill until the average particle diameter became 2 μm or less to obtain a liquid B.

Preparation of Solution C 40 parts of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 20 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol, and 40 parts of water
Part C of the composition was pulverized by a sand mill until the average particle diameter became 2 μm or less to obtain a liquid C.

Preparation of Coating Solution for Recording Layer 25 parts of solution A, 40 parts of solution B, 40 parts of solution C, solid concentration of 50
%, 10 parts of an acrylic latex having an average molecular weight of 10,000,000 or more (trade name: AM2250, manufactured by Showa Polymer Co., Ltd.) and acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 100 parts of a 10% aqueous solution, 30 parts of aluminum hydroxide, 15 parts of a 30% dispersion of zinc stearate, 10 parts of a 30% dispersion of paraffin wax, a ketone resin aqueous solution as a crosslinking agent (trade name: SI-668, non-volatile content) 6 parts (50%, manufactured by PMC Japan) were mixed and stirred to obtain a coating liquid for a recording layer.

Preparation of heat-sensitive recording medium On one surface of neutral paper of 60 g / m ² , the coating amounts of the undercoat layer coating solution and the recording layer coating solution after drying were 8 g / m ² and 6 g / m ² .
^Then, the undercoat layer and the recording layer were formed in this order by coating and drying to obtain a thermosensitive recording medium. After forming each layer, a super calender treatment was performed.

Example 2 In the preparation of solution C of Example 1, 4 parts of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane was replaced by 40 parts.
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 40 parts of -hydroxy-4'-isopropoxydiphenylsulfone was used.

Example 3 In the preparation of the coating solution for the recording layer of Example 1, 100 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used. Was used in the same manner as in Example 1 except that 100 parts by weight of a 10% aqueous solution of casein dissolved in aqueous ammonia was used in place of the above.

Example 4 In the preparation of the coating liquid for a recording layer of Example 1, an acrylic latex having an average molecular weight of 10,000,000 or more (trade name: AM2250, manufactured by Showa Polymer Co., Ltd.)
Instead of 0 parts, 1 of casein dissolved in aqueous ammonia
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 100 parts by weight of a 0% aqueous solution was used.

Example 5 In the preparation of the coating solution for the recording layer of Example 1, a ketone resin aqueous solution (trade name: SI-66) was used.
8, non-volatile content 50%, manufactured by Japan PMC Co.) On the recording layer formed in the same manner as in Example 1 using 6 parts of water instead of 6 parts, the coating amount of the following protective layer coating liquid after drying was applied. Is 3 g / m ²
After coating and drying to form a protective layer, a super calender treatment was performed to obtain a thermosensitive recording medium.

Preparation of Coating Solution for Protective Layer 100 parts of a 60% aqueous dispersion of aluminum hydroxide (average particle size: 1 μm), acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) ), 30 parts of a 30% dispersion of zinc stearate, 20 parts of a ketone resin aqueous solution (trade name: SI-668, nonvolatile content: 50%, manufactured by Nippon PMC) as a crosslinking agent were mixed and stirred. Thus, a coating solution for a protective layer was obtained.

Example 6 In the preparation of the coating liquid for a protective layer in Example 5, 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10 parts of an acrylic latex having an average molecular weight of 10,000,000 or more (trade name: AM2250, manufactured by Showa Polymer Co., Ltd.), acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10% of
A thermosensitive recording medium was obtained in the same manner as in Example 5, except that 200 parts of the aqueous solution was used.

Example 7 In the preparation of the coating solution for the protective layer in Example 5, aluminum hydroxide (average particle diameter 1 μm) was used.
100 parts of a 60% aqueous dispersion of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z)
-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Instead of 0 parts, 100 parts of a 60% aqueous dispersion of kaolin (average particle diameter 0.8 μm) and 300 parts of a 10% aqueous solution of casein dissolved in aqueous ammonia were used,
A thermosensitive recording medium was obtained in the same manner as in Example 5.

Comparative Example 1 In the preparation of the coating solution for the recording layer of Example 1, an aqueous ketone resin solution (trade name: SI-66)
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 6 parts of water was used instead of 6 parts (8, nonvolatile content: 50%, manufactured by PMC Japan).

[Comparative Example 2] In the preparation of the coating liquid for the recording layer in Example 1, an aqueous ketone resin solution (trade name: SI-66)
8, 7 parts of a 40% aqueous solution of glyoxal were used instead of 6 parts of a non-volatile content (manufactured by PMC Japan), and the coating liquid for the recording layer gelled after 1 hour, and the recording layer could not be formed. .

Comparative Example 3 In the preparation of the coating solution for the recording layer of Example 1, 100 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used. Instead of partially saponified polyvinyl alcohol (trade name: PVA217,
Except that 100 parts of a 10% aqueous solution of Kuraray Co., Ltd.) was used.
A thermosensitive recording medium was obtained in the same manner as in Example 1.

Comparative Example 4 In the preparation of the coating solution for the protective layer of Example 5, a ketone resin aqueous solution (trade name: SI-66) was used.
8, non-volatile content 50%, manufactured by Nippon PMC Co., Ltd.) 6 parts were used instead of 7 parts of a 40% aqueous solution of glyoxal, and the coating liquid for the protective layer gelled after 1 hour, and the protective layer could not be formed. .

Comparative Example 5 In the preparation of the coating solution for the protective layer of Example 5, 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) Instead of fully saponified polyvinyl alcohol (trade name: PVA117,
Except that 100 parts of a 10% aqueous solution of Kuraray Co., Ltd.) was used.
A thermosensitive recording medium was obtained in the same manner as in Example 5.

The thermal recording medium thus obtained was subjected to the following quality evaluation tests, and the results are shown in Table 1.

[Coloring property] Thermal recording evaluation device (TH-PMD)
Mold, Okura Electric Co., applied energy 0.4mJ / dot)
Was used to record the thermosensitive recording medium, and the recorded portion and the unrecorded portion were measured in a visual mode using a Macbeth densitometer (trade name: RD-914R, manufactured by Macbeth).

[Water Resistance] The state of the recording layer when 1 ml of tap water was dropped on the heat-sensitive recording surface and rubbed 10 times with a finger was visually judged as follows. <Evaluation Criteria> A: The recording layer is not peeled off at all. ：: The recording layer is slightly peeled off. ×: The recording layer peels off.

[Recording runnability] Thermal recording evaluation machine (TH-P
MD type, manufactured by Okura Electric Co., Ltd., applied energy 0.45mJ /
dot), the thermosensitive recording medium was recorded, and the sticking state appearing in the recording portion was visually determined as follows. <Evaluation Criteria> A: No trace of sticking is observed in the recorded image. Good: Slight sticking marks are seen in the recorded image. X: Many sticking marks are seen in the recorded image.

[0045]

[Table 1]

[0046]

As is clear from the results shown in Table 1, the heat-sensitive recording material of the present invention was a heat-sensitive recording material having excellent effects on water resistance and recording running property.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09J 189/00 C09J 189/00 B41M 5/18 E

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a recording layer containing a leuco dye and a coloring agent on a support or a protective layer on the recording layer, wherein casein or glue is used as an adhesive in the recording layer or the protective layer. A heat-sensitive recording material comprising acetoacetyl-modified polyvinyl alcohol and a ketone resin as a crosslinking agent for the adhesive.