JPH1086526A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording body excellent in recording sensitivity and the preservation of a recorded image by a method wherein 4,4'- dihydroxydiphenylsulfone and 2,4-dihydroxy-2'-methoxybenzanilde are used in combination as a coloring agent in a recording layer, which is formed on a support and consists of a leuco dye and the coloring agent. SOLUTION: In a recording layer, which is formed on a support and contains a leucodye and a coloring agent, as the coloring agent, 4,4'- dihydroxydiphenylsulfone and 2,4-dihydrox-2'-methoxybenzanilide are used. The use ratio of both is not especially limited. However, a preferable ratio is about 100-400 pts.wt. of 4,4'-dihydroxydiphenylsulfone to 100 pts.wt. of 2,4- dihydroxy-2'-methoxybenzanilide. As a result, a recording body excellent in recording sensitivity and the preversation of a recorded image is obtained.

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 color-forming reaction between a leuco dye and a color former, and more particularly to a heat-sensitive recording material excellent in recording sensitivity and preservation of a recorded image.

[0002]

2. Description of the Related Art Conventionally, heat-sensitive recording media in which a colorless or light-colored leuco dye is colored with a colorant using thermal energy of a heat-sensitive head or the like are well known. Such a thermosensitive recording medium is relatively inexpensive, and the recording equipment is compact and relatively easy to maintain, so that it is used not only as a recording medium for facsimile and various computers but also in a wide range of fields such as a thermosensitive label. I have.

[0003] In recent years, there has been a remarkable expansion in the use of ATMs for banks, meter reading of electricity and gas, and the like, and characteristics that have not been a problem in the past have been demanded, and improvements have been demanded. In other words, demands for performance such as fading of images, such as weather resistance and chemical resistance, have become strict.

However, since a phenolic colorant such as bisphenol A is used in a usual thermosensitive recording medium, background fogging is caused by a solvent or the like, and a recorded image is discolored by oils and fats or chemicals. Has the disadvantage that Therefore, for example, when touching stationery and office supplies such as water-based pens, oil-based pens, fluorescent pens, vermilion, adhesives, glues, diazo developers, etc., white parts will develop color and the density of the recorded image will be significantly reduced. Or discolored, significantly impairing the commercial value.

For the purpose of improving such disadvantages, there has been proposed a method of providing a protective layer on a recording layer. For example,
JP-A-56-146794 discloses forming a protective layer using a hydrophobic polymer emulsion or the like. In JP-A-58-99189, a water-soluble polymer compound or a hydrophobic polymer emulsion is provided as an intermediate layer on a recording layer, and the recording layer is protected with an oil-based paint containing a hydrophobic polymer compound as a resin component. A thermosensitive recording medium provided with a layer is described. Although the effect of improvement was recognized by these means, it was not a sufficient means for long-term storage.

A heat-sensitive recording material using 2,4-dihydroxy-2'-methoxybenzanilide as a colorant excellent in storage stability of a recording portion is disclosed in JP-A-7-3294.
Although described in Japanese Patent Publication No. 18, there is a problem in storage stability against chemicals such as plasticizers and oils.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording medium having excellent recording sensitivity and preservability of a recorded image.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a thermosensitive recording medium having a recording layer containing a leuco dye and a coloring agent provided on a support, as one means for solving the above-mentioned problems. In the invention, 4,4'-dihydroxydiphenylsulfone and 2,4-dihydroxy-2'-methoxybenzanilide are used in combination as a color developer. Furthermore, 2,4-
By using 100 to 400 parts by weight of 4,4'-dihydroxydiphenylsulfone per 100 parts by weight of dihydroxy-2'-methoxybenzanilide, a heat-sensitive recording medium having particularly excellent recording sensitivity and preservability of a recorded image can be obtained. Was done.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a heat-sensitive recording material having a recording layer containing a leuco dye and a colorant on a support, wherein 4,4'-dihydroxydiphenylsulfone and 2,4'-dihydroxydiphenylsulfone are used as colorants. Characterized in that 4-dihydroxy-2'-methoxybenzanilide is used, wherein 4,4'-dihydroxydiphenylsulfone and 2,4-dihydroxy-
The ratio of use with 2'-methoxybenzanilide is not particularly limited, but about 100 to 400 parts by weight of 4,4'-dihydroxydiphenylsulfone per 100 parts by weight of 2,4-dihydroxy-2'-methoxybenzanilide. preferable. When the amount of 4,4′-dihydroxydiphenyl sulfone is less than 100 parts by weight, the storage stability of the recorded image is reduced,
If it exceeds 400 parts by weight, the recording sensitivity may decrease.

The amount of 2,4-dihydroxy-2'-methoxybenzanilide used is 5 to 4 based on the total solids of the recording layer.
0% by weight, preferably about 10 to 30% by weight.

As the leuco dye contained in the recording layer, various known colorless or pale leuco dyes can be used. For example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3
-(N-ethyl-N-p-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-cyclohexyl Amino-6
Chlorofluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (m-tri Fluoromethylanilino)
Fluoran, 3- (N-methyl-N-cyclohexyl)
Amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran,
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-chloroanilino) fluoran, 3-
Di (n-butyl) amino-7- (o-fluoroanilino) fluoran, 3- (N-ethyl-p-toluidino)
-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7
-Anilinofluoran, 3- (N-methyl-NN-propylamino) -6-methyl-7-anilinofluoran, 3,3-bis [1- (4-methoxyphenyl) -1
-(4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,
6, -bis (dimethylamino) fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide, 3- (N
-Ethyl-N-2-tetrahydrofurfurylamino)-
6-methyl-7-anilinofluoran, 3- (4-dimethylamino) anilino-5,7-dimethylfluoran and the like. Of course, the present invention is not limited to these, and two or more of them can be used in combination as needed. The amount of the leuco dye used is not particularly limited, but is preferably about 3 to 35% by weight based on the recording layer.

The present invention relates to a coloring agent for carp dyes,
Although 4'-dihydroxydiphenyl sulfone and 1,1-bis (4-hydroxyphenyl) -1-phenylethane are used in combination, other known coloration is not impaired as long as the desired effect of the present invention is not impaired. Agents can be used in combination. Specific examples of such a coloring agent include, for example, hydroquinone monobenzyl ether, 4,4′-isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′-dihydroxydiphenylmethane, 2,2 -Bis (4-hydroxyphenyl)-
4-methylpentane, bis (4-hydroxyphenylthioethoxy) methane, 1,4-bis [α-methyl-α-
(4'-hydroxyphenyl) ethyl] benzene, 1,
3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenyl sulfide, di (4-hydroxy-3-methylphenyl) sulfine, 2,4′-dihydroxydiphenyl Sulfone, 4-hydroxy-4′-methyldiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxyphenyl-4′-benzyloxyphenylsulfone, 4-hydroxy-3 ′,
4'-tetramethylenebiphenylsulfone, 3,4-dihydroxyphenyl-p-tolylsulfone, benzyl 4-hydroxybenzoate, 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.

If necessary, the recording layer may contain a sensitizer for increasing the recording sensitivity, or may contain a storability improving agent for further improving the storability of the recorded image. Specific examples of such a sensitizer include, for example, stearic acid amide, methylolamide stearic acid, ethylenebisstearic acid amide, dibenzyl oxalate,
Di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, dimethyl terephthalate, dibenzyl terephthalate, phenyl 1-hydroxynaphthoate, 1,2-di (3-
Methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2-naphthoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, 1-
(4-methylphenoxy) -2-naphthoxyethane,
1,3-naphthoxypropane, 1,4-naphthoxybutane, p-benzylbiphenyl, m-terphenyl, benzyl-2-naphthyl ether, 1,2-bis (3,4-
Dimethylphenyl) ethane, 1,4-bis (p-tolyloxy) benzene, diphenylsulfone, diphenyl carbonate, 2- (2′-hydroxy-5′-methylphenyl)
Benzotriazole and the like.

Specific examples of the preservability improver include, for example, 2,2'-methylenebis (4-methyl-6-tert-butylphenol) and 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-butylphenol) (Hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4)
-Hydroxy-5-tert-butylphenyl) butane;
N, N'-di-2-naphthyl-p-phenylenediamine, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, 4,4'-bis (ethyleneiminecarbonylamino) Examples include diphenylmethane, 4-benzyloxy-4 ′-(2-methyl-2,3-epoxypropyloxy) diphenylsulfone, and novolak-type resins. The use amount of these sensitizers and storage stability improvers is preferably about 5 to 400 parts by weight with respect to 100 parts 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, using a pulverizer, a leuco dye, a color former, and if necessary, a sensitizer,
A recording layer coating prepared by finely dispersing a preservability improver together or separately with a dispersant so that the volume average particle diameter is about 0.3 to 3 μm, and then adding an adhesive while mixing and stirring. It is formed by applying and drying a liquid on a support.

The adhesive used for the recording layer can be any of a water-soluble resin and a water-dispersible resin. Specific examples of such an adhesive include completely (partially) saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, starch, oxidized starch, gum arabic,
Gelatin, casein, chitosan, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, styrene-acrylic acid copolymer salt, styrene-maleic anhydride copolymer salt, methyl vinyl ether-maleic anhydride copolymer salt, isopropylene-anhydride Water-soluble resins such as maleic acid copolymer salts, vinyl acetate latex, acrylate copolymer latex, methacrylate copolymer latex, vinyl acetate- (meth) acrylate copolymer latex, polyurethane Latex, polyvinyl chloride latex, polyvinylidene chloride latex, styrene
Water-dispersible resins such as butadiene-based latex are exemplified. The amount of the adhesive used is 5 to 30 with respect to the recording layer.
% By weight is preferred.

Further, the recording layer includes a dialdehyde compound such as glyoxal and dialdehyde starch, a polyamine compound such as polyethyleneimine, an epoxy compound, a polyamide resin, a melamine resin, and a diglycidyl compound such as glycerin diglycidyl ether. Dimethylol urea compound, aziridine compound, blocked isocyanate compound, ammonium persulfate, boric acid, borax, ferric chloride and magnesium chloride and other water-resistant agents, calcium carbonate, magnesium carbonate, magnesium oxide, kaolin, clay, talc, calcined clay, Amorphous silica,
Diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, pigments such as urea-formalmarine resin filler, surfactants such as acetylene glycol, sodium dialkyl sulfosuccinate, sodium alkylbenzene sulfonate, stearic acid Lubricants such as zinc and calcium stearate, waxes such as polyethylene wax, carnauba wax, paraffin wax and ester wax, and coloring dyes and fluorescent dyes can also be added.

The recording layer is formed on at least one surface of a support such as high-quality paper (acid paper, neutral paper), synthetic paper, film, or coated paper, using an air knife system or a Meyer bar system conventionally used by those skilled in the art. The coating amount after drying the coating liquid for the recording layer by a coating method such as a pure blade method, a rod blade method, a reverse roll method and a slit die method is 1 to 10 g / m ² , preferably ² to 7 g / m ² . It is formed by coating and drying so that

In the thermosensitive recording medium of the present invention, by providing a protective layer containing a film-forming adhesive on the recording layer, the preservability of the recorded image can be further improved.
Specific examples of such an adhesive include, for example, the adhesive used for the recording layer as described above. Among them, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferably used because of their excellent effect as a protective layer.

Further, in order to further improve the water resistance of the protective layer, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea,
Ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin,
A curing agent such as a ketone-aldehyde resin, borax, boric acid, ammonium zirconium carbonate, or an epoxy compound can also be used in combination.

Further, in the protective layer, in order to further improve printability and sticking, for example, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, aluminum hydroxide, barium sulfate, talc, kaolin, Pigments such as clay, calcined kaolin, nylon filler, and urea-formalin resin filler can also be included. The amount of the pigment used is desirably adjusted to about 5 to 500 parts by weight based on 100 parts by weight of the adhesive.

The protective layer is generally coated with a protective layer coating solution prepared by mixing and stirring water, as a dispersion medium, a film-forming adhesive, and, if necessary, a pigment and a water-proofing agent. It is formed by drying. In addition, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax,
Lubricants such as ester wax, surfactants such as dioctyl sodium sulfosuccinate, and various auxiliaries such as antifoaming agents can be added as appropriate.

The coating solution for the protective layer thus prepared is applied onto the recording layer. However, if the applied amount is less than 10 g / m ² in terms of dry weight, the recording sensitivity of the thermosensitive recording medium may be reduced. Is about 0.5 to 10 g / m ² , preferably 1
It is desirable to adjust the amount to about 7 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storability. In addition, various known techniques in the field of heat-sensitive recording material may be added as necessary, such as providing an undercoat layer between the support and the recording layer, or applying an adhesive treatment to the back surface of the recording material and processing it into an adhesive label. Can be done.

[0025]

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 to such specific Examples. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Formation of undercoat layer Fired clay [trade name: Ansilex, manufactured by EMC] 1
00 parts, styrene-butadiene-based latex (solid content:
(50%) 15 parts of a 10% aqueous solution of polyvinyl alcohol, 30 parts of a composition comprising 30 parts of water and 200 parts of water were mixed and stirred, and the undercoat layer coating liquid obtained was dried on a high-quality paper of 70 g / m ² after drying. After coating and drying so that the coating amount was 7 g / m ² , a super calender treatment was performed to form an undercoat layer having a Beck smoothness of 200 seconds.

Preparation of Solution A 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 15 parts of di-p-methylbenzyl oxalate, 5% aqueous solution of methylcellulose 20
Parts and 55 parts of water were pulverized by a sand mill until the average particle diameter became 0.8 μm.

Liquid B Preparation A composition comprising 25 parts of 2,4-dihydroxy-2′-methoxybenzanilide, 10 parts of a 5% aqueous solution of methylcellulose, and 65 parts of water is subjected to sand milling until the average particle diameter becomes 1.2 μm. Crushed.

Preparation of Solution C 25 parts of 4,4′-dihydroxydiphenyl sulfone, 10% aqueous solution of sulfone-modified polyvinyl alcohol 10
Parts and 65 parts of water were pulverized with a sand mill until the average particle size became 1.5 μm.

Formation of Recording Layer 100 parts of solution A, 40 parts of solution B, 40 parts of solution C, 100 parts of a 10% aqueous solution of polyvinyl alcohol, calcium carbonate 10
, 20 parts of amorphous silica, 30 parts of a 30% dispersion of zinc stearate, and 100 parts of water were mixed and stirred to obtain a coating solution for a heat-sensitive recording layer. The obtained coating liquid is applied on the above-mentioned undercoat layer so as to have a dry weight of 6 g / m ² and dried to form a recording layer, and then subjected to a super calender treatment to be subjected to thermal recording with a Beck smoothness of 500 seconds. I got a body.

Example 2 In the formation of the recording layer of Example 1, 40 parts of solution B and C
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 20 parts of solution B and 60 parts of solution C were used instead of 40 parts of solution.

Example 3 In forming the recording layer of Example 1, 40 parts of solution B and C
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 50 parts of the liquid B and 30 parts of the liquid C were used instead of 40 parts of the liquid.

Example 4 In the formation of the recording layer of Example 1, 40 parts of solution B and C
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 15 parts of the liquid B and 65 parts of the liquid C were used instead of 40 parts of the liquid.

Comparative Example 1 In the formation of the recording layer of Example 1, 40 parts of solution B and C
Example 1 except that 80 parts of liquid B was used instead of 40 parts of liquid
In the same manner as in the above, a thermosensitive recording medium was obtained.

Comparative Example 2 In the formation of the recording layer of Example 1, 40 parts of solution B and C
Example 1 except that 80 parts of liquid C was used instead of 40 parts of liquid
In the same manner as in the above, a thermosensitive recording medium was obtained.

Comparative Example 3 Thermal recording was carried out in the same manner as in Example 1 except that 4,4'-dihydroxydiphenylsulfone was used in place of 4,4'-dihydroxydiphenylsulfone. I got a body.

The following evaluation tests were performed on the thus obtained heat-sensitive recording medium, and the results are shown in Table 1.

[Recording sensitivity] Thermal recording material evaluation machine [Product name:
TH-PMD, manufactured by Okura Electric Co., Ltd.]
V, the pulse density was 2 ms, and the color density and the unrecorded portion of the recording portion where each thermosensitive recording material was colored were measured in a visual mode using a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth).

[Plasticizer resistance] Polypropylene pipe (4
A plastic wrapped vinyl chloride wrap film is wound three times on a 0 mm Φ tube, and each of the above colored heat-sensitive recording materials is sandwiched on the vinyl chloride wrap film so that the recording portion surface is outside. Wrap the vinyl chloride wrap film three times from
The recorded portion and the unrecorded portion after being left at 20 ° C. for 6 hours were measured by the Macbeth densitometer (visual mode).

[0040]

[Table 1]

[0041]

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

Claims (2)

[Claims] 1. A thermosensitive recording medium having a recording layer containing a leuco dye and a colorant on a support, wherein the colorant is 4,4.
4'-dihydroxydiphenyl sulfone and 2,4-
A heat-sensitive recording material, which is dihydroxy-2'-methoxybenzanilide. 2. The heat-sensitive recording material according to claim 1, wherein 4,4'-dihydroxydiphenyl sulfone is used in an amount of 100 to 400 parts by weight per 100 parts by weight of 2,4-dihydroxy-2'-methoxybenzanilide.