JP2001113832A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a heat-sensitive recording material which is almost free from texture fogging and shows superb color development and retention properties. SOLUTION: This heat-sensitive recording material has a heat-sensitive color developing layer containing a normally colorless or pale-colored developing compound and a color developing compound which develops the color of the colorless or pale-colored developing compound during heating, formed on a support. In addition, this heat-sensitive recording material is characterized in that it contains a 4,4'-dihydroxydiphenylsulfone or a 2,4'- dihydroxydiphenylsulfone, a p-acetotoluidide and an o-acetotoluidido.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-sensitive recording material. More specifically, it has high sensitivity and low background fog,
The present invention relates to a heat-sensitive recording material having excellent image storability.

[0002]

2. Description of the Related Art Generally, a thermosensitive recording material is prepared by separately dispersing a developer such as a leuco dye and a phenolic substance into fine particles, and then mixing the two with a binder, a sensitizer, a filler and a lubricant. A coating liquid is prepared by adding additives such as, etc., and applied to paper, film, synthetic paper, etc., and the color record is formed by the chemical reaction that occurs when one or both of the leuco dye and the developer melts and contacts by heating. What you get. For color development of the heat-sensitive recording sheet, a thermal printer or the like having a built-in thermal head is used. Compared with other recording methods, this thermal recording method is (1) no noise during recording, (2) there is no need for development and fixing, (3) maintenance-free, (4) machine is relatively inexpensive. With features such as
Facsimile field, computer output, printer field such as calculator, medical measurement recorder field,
It is widely used in the field of automatic ticket vending machines, the field of heat-sensitive recording labels, and the like.

[0003] In recent years, the use of POS systems in retail stores and supermarkets, and automated transportation systems has increased the use of labels, tickets, coupons, and the like. In these applications, it is desired that the heat-sensitive recording material is further improved in storage stability. The demand for high-speed recording has further increased, and there has been a strong demand for the development of heat-sensitive recording materials that can sufficiently cope with high-speed recording. However, the drawback that background fogging generally occurs when the sensitivity of heat-sensitive recording materials is increased to improve thermal response. Is easy to appear. Conventionally, various methods have been proposed to improve the heat responsiveness and further improve the storage stability, but none of them are satisfactory.

[0004]

The object of the present invention is as described above.
It is to solve the disadvantages of the prior art. That is, it is an object of the present invention to provide a heat-sensitive recording material having high sensitivity, little background fog, and excellent image storability.

[0005]

The present inventor has made various studies to achieve the above object, and as a result, completed the present invention. That is, the present invention provides: (1) a heat-sensitive color-forming layer comprising, as main components, a colorless or light-colored color-forming compound, a color-developing compound capable of forming the color-forming compound when heated, and a sensitizer on a support. A heat-sensitive recording material comprising: 4,4'-dihydroxydiphenylsulfone or 2,4'-dihydroxydiphenylsulfone as a color developing compound; and p-acetotoluidide and o-acetotoluidide as sensitizers. Material,

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a colorless compound which is usually colorless or pale, and 4,4'-
Dihydroxydiphenylsulfone or 2,4′-dihydroxydiphenylsulfone and p-acetotoluide and o-acetotoluide as sensitizers as main components, a binder as shown below and other fillers and other additives as necessary Thus, a thermosensitive coloring layer is prepared.
4,4′-dihydroxydiphenyl sulfone or 2,
The amount of 4'-dihydroxydiphenylsulfone, p-acetotoluidide and o-acetotoluide used is 0.5 to 20 parts by weight, preferably 1 to 5 parts by weight, per 1 part by weight of the coloring compound. Further, in the heat-sensitive recording material of the present invention, a known color developing compound or a sensitizer other than the main component of the present invention may be used in combination.

In forming the thermosensitive coloring layer in the present invention, the coloring compound is usually 1 to 50% by weight, preferably 5 to 30% by weight, 4,4'-dihydroxydiphenylsulfone or 2,4'-dihydroxydiphenylsulfone. Is usually 1 to 80% by weight, preferably 5 to 40% by weight, p
-Acetotoluide and o-acetotoluide are each usually 0.5 to 80% by weight, preferably 5 to 40% by weight, the binder is usually 1 to 90% by weight, the filler is usually 0 to 80% by weight, other lubricants, The activator, antifoaming agent, ultraviolet absorber and the like are each used in an arbitrary ratio, for example, usually 0 to 30% by weight, respectively (% by weight is the weight ratio of each component in the thermosensitive coloring layer).

Examples of the color-forming compound that can be used are not particularly limited as long as they are those generally used for pressure-sensitive recording paper or heat-sensitive recording paper. Specific examples include, for example, fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, and the like.

The fluoran compounds include, for example, 3-
Diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilino Fluoran, 3- (N
-Ethyl-N-isopentylamino) -6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluoran,
3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-N-hexylamino) -6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-propylamino) -6 -Methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (p-chloroanilino)
Fluoran, 3-diethylamino-6-methyl-7-
(P-fluoroanilino) fluoran, 3- [N-ethyl-N- (p-tolyl) amino] -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-
7- (p-toluidino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran,
3-diethylamino-7- (o-fluoroanilino) fluoran, 3-dibutylamino-7- (o-fluoroanilino) fluoran, 3-diethylamino-7- (m-
(Trifluoromethylanilino) fluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7- Ethoxyethylaminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-
7-chlorofluorane, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-octylfluoran, 3- [N-ethyl-N- (p-tolyl) amino] -6-methyl-7-phenethyl Fluoran and the like.

As the triarylmethane compound, for example, 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide (alias: crystal violet lactone or CVL), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylaminoindole- 3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3-
(2-phenylindol-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-ethylcarbazole-3)
-Yl) -5-dimethylaminophthalide, 3,3- (2
-Phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
(1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

Examples of spiro compounds include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran,
Benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro (indoline-2,2'- Benzopyran) and the like, as diphenylmethane compounds, for example, N-halophenyl-leuco auramine,
4-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-trichlorophenylleucouramine and the like; thiazine compounds such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue; Examples of the fluorene-based compound include rhodamine B anilinolactam and rhodamine B-p-chloroanilinolactam, and examples of the fluorene-based compound include 3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6. '-Dimethylaminophthalide, 3,6-bis (dimethylamino) fluorenespiro (9,3')-6'-pyrrolidinophthalide,
3-dimethylamino-6-diethylaminofluorenespiro (9,3 ')-6'-pyrrolidinophthalide and the like. These coloring compounds are used alone or in combination.

Examples of the color-developing compound that can be used in the present invention are not particularly limited as long as they are generally used for pressure-sensitive recording paper or thermosensitive recording paper. For example, α-
Naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, pt-butylphenol, p-phenylphenol, 1,1-bis (p-
Hydroxyphenyl) propane, 2,2-bis- (p-
Hydroxyphenyl) propane (alias: bisphenol A or BPA), 2,2-bis- (p-hydroxyphenyl) butane, 1,1-bis- (p-hydroxyphenyl) cyclohexane, 4,4′-thiobisphenol,
4,4′-cyclo-hexylidenediphenol, 2,
2'-bis- (2,5-dibromo-4-hydroxyphenyl) propane, 4,4'-isopropylidenebis (2
-T-butylphenol), 2,2'-methylenebis (4-chlorophenol), bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-
Phenolic compounds such as isopropocodiphenyl sulfone, methyl bis (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate, and benzyl bis (4-hydroxyphenyl) acetate; benzyl p-hydroxybenzoate; Ethyl hydroxybenzoate, 4-
Dibenzyl hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,
Aromatic carboxylic acid derivatives such as 5-di-t-butylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids and polyvalent metal salts thereof are generally used for pressure-sensitive recording paper and thermosensitive recording paper. Some are used,
You are not limited to these.

The sensitizers (thermofusible compounds) which can be used in combination in the present invention include, for example, waxes such as animal and vegetable waxes, synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, naphthalene derivatives, aromatics Use ether, aromatic carboxylic acid derivative, aromatic sulfonic acid ester derivative, carbonic acid or oxalic acid diester derivative, biphenyl derivative, terphenyl derivative, sulfone derivative, etc., which are solid at room temperature and have a melting point of about 70 ° C. or more. be able to.

Examples of waxes that can be used in combination include wood wax, carnauba wax, shellac, paraffin, montan wax, paraffin oxide, polyethylene wax, polyethylene oxide and the like, and higher fatty acids such as stearic acid and behenic acid. As higher fatty acid amides,
For example, stearic acid amide, oleic acid amide, N-methylstearic acid amide, erucic acid amide, methylolbehenic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide and the like, as higher fatty acid anilide, for example, stearic acid anilide, Linoleic acid anilide and the like, as naphthalene derivatives, for example, 1-
Benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester and the like, and aromatic ethers such as 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis (3 -Methylphenoxy) ethane, 1,2-bis (4
-Methoxyphenoxy) ethane, 1,2-bis (3,4
-Dimethylphenyl) ethane, 1-phenoxy-2-
(4-chlorophenoxy) ethane, 1-phenoxy-2
Examples of aromatic carboxylic acid derivatives include-(4-methoxyphenoxy) ethane and the like. Examples of aromatic carboxylic acid derivatives include p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester and the like. Derivatives include, for example, p-toluenesulfonic acid phenyl ester, phenylmesitylenesulfonate, 4-methylphenylmesitylenesulfonate, and the like. Carbonic acid or oxalic acid diester derivatives include, for example, diphenyl carbonate, dibenzyl oxalate, dioxalate. (4-chlorobenzyl) ester, oxalic acid di (4-methylbenzyl) ester and the like include biphenyl derivatives such as p-benzylbiphenyl and p-benzylbiphenyl.
Examples of allyloxybiphenyl and the like are terphenyl derivatives such as m-terphenyl, and examples of the sulfone derivative are diphenyl sulfone and the like.

The amounts of the color-developing compound and the sensitizer which can be used in combination as described above are within a range not to impair the effects of the present invention, for example, 4,4'-dihydroxydiphenyl sulfone or 2,2.
It is preferable that the proportions of the 4'-dihydroxydiphenyl sulfone, p-acetotoluidide and o-acetotoluidide do not exceed the respective amounts used.

Examples of the binder which can be used include, for example, methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol,
Polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer, iso (or diiso) butylene /
Water-soluble ones such as alkali salts of maleic anhydride copolymer or polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polystyrene, polyacrylate, polyurethane, styrene / butadiene (SB) copolymer, carboxylation Examples include hydrophobic polymer emulsions such as styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, and composite particles of colloidal silica and acrylic resin.

Examples of fillers that can be used include, for example, calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina,
Examples include magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, and urea-formalin resin.

Other additives that can be used include, for example, metal salts of higher fatty acids such as zinc stearate and calcium stearate for the purpose of preventing thermal head abrasion and sticking, and phenol derivatives having an antioxidant or antiaging effect. UV absorbers such as benzophenone-based and benzotriazole-based surfactants, various surfactants, antifoaming agents and the like are added as required.

The heat-sensitive recording material of the present invention is prepared using the above-mentioned materials by, for example, the following method. That is, first, a color-forming compound, 4,4'-dihydroxydiphenylsulfone or 2,4'-dihydroxydiphenylsulfone, p-acetotoluidide, and m-acetotoluide are separately prepared by a conventional method (p-acetotoluidide and o-acetotoluide are previously mixed. After grinding and dispersing with a dispersing machine such as a ball mill, attritor, or sand mill together with a binder or other additives as necessary (when the grinding and dispersion are performed by a wet method, usually water is used as a medium). To prepare a coating solution for the thermosensitive coloring layer, and apply it to a support such as paper, plastic sheet, synthetic paper or the like by a bar coater, a blade coater or the like so that the dry weight is usually 1-20 g / m ² ( The ratio of the color-forming compound to the color-developing compound is usually 1: 1 to 1:10 by dry weight ratio). A light thermosensitive recording material is obtained. If necessary, an intermediate layer may be provided between the thermosensitive coloring layer and the support, or an overcoat layer (protective layer) may be provided on the thermosensitive coloring layer. The intermediate layer and the overcoat layer (protective layer) are pulverized and dispersed in the same manner as in the preparation of the thermosensitive coloring layer coating solution together with a binder or other additives as necessary, and then the intermediate layer coating solution or the overcoat layer (protection layer). Layer) After the coating solution is formed, the coating solution is applied so that the dry weight is usually about 0.1 to 10 g / m ² .

A colorless or pale-colored coloring compound,
4'-dihydroxydiphenyl sulfone or 2,4'-
The heat-sensitive recording material of the present invention containing dihydroxydiphenylsulfone, p-acetotoluidide and o-acetotoluidide has higher sensitivity, less background fog, and excellent image storability than conventionally known ones.

[0021]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" indicates parts by weight.

Example 1 A mixture having the following composition was pulverized and dispersed using a sand grinder so as to have an average particle size of 1 μm or less, and the solutions [A], [B], [C] and [D] were respectively obtained. Prepare liquid. [A] solution: 3-dibutylamino-6-methyl-7-anilinofluoran 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] solution: 4,4′-dihydroxydiphenylsulfone 5 parts 25% PVA aqueous solution 20 parts water 55 parts [C] liquid: p-acetotoluidide 25 parts 25% PVA aqueous solution 20 parts water 55 parts [D] liquid: o-acetotoluidide 25 parts 25% PVA aqueous solution 20 parts water 55 parts

Next, a thermosensitive coloring layer coating solution was prepared by mixing at the following ratios, coated on a high quality paper having a basis weight of 50 g / m ² so as to have a weight of 8 g / m ² when dried, and dried to obtain a thermosensitive coloring layer. A coloring layer is obtained. [A] Liquid 8 parts [B] Liquid 16 parts [C] Liquid 18 parts [D] Liquid 6 parts 50% calcium carbonate dispersion 12 parts 50% carboxylated styrene / butadiene copolymer latex 7 parts (Formation of protective layer) Further, a protective layer coating solution having the following ratio is applied onto the thermosensitive coloring layer so as to have a dry weight of 2 g / m ² and dried to obtain a thermosensitive recording material of the present invention. 40% styrene / acrylate copolymer emulsion 20 parts 5% bentonite aqueous dispersion 40 parts 30% zinc stearate dispersion 3 parts

Example 2 The procedure of Example 1 was repeated, except that the 25% 3-dibutylamino-7- (o-chloroanilino) fluoran dispersion obtained by pulverization and dispersion was used in place of the solution [A] in Example 1. In the same manner as in Example 1, a heat-sensitive recording material of the present invention is obtained.

Example 3 25% 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilino obtained by pulverizing and dispersing in the same manner as in Example 1 except that the solution [A] was used. A heat-sensitive recording material of the present invention is obtained in the same manner as in Example 1 using a fluoran dispersion.

Example 4 A heat-sensitive recording material of the present invention is obtained in the same manner as in Example 1 except that 2,4'-dihydroxydiphenylsulfone is used instead of 4,4'-dihydroxydiphenylsulfone.

Example 5 A heat-sensitive recording material of the present invention is obtained in the same manner as in Example 1 except that the following heat-sensitive color-forming layer coating solution is used instead of the heat-sensitive color-forming layer coating solution of Example 1. [A] liquid 8 parts [B] liquid 16 parts [C] liquid 12 parts [D] liquid 12 parts 50% calcium carbonate dispersion 12 parts 50% carboxylated styrene / butadiene copolymer latex 7 parts

Comparative Example 1 A heat-sensitive recording material for comparison was obtained in the same manner as in Example 1 except that bisphenol A was used in place of 4,4'-dihydroxydiphenylsulfone of Example 1.

Comparative Example 2 A comparative thermosensitive recording material was obtained in the same manner as in Example 1 except that N-methylol stearamide was used in place of p-acetotoluizide and o-acetotoluizide in Example 1. Tables 1 and 2 show quality performance tables of the present invention and the comparative thermosensitive recording material obtained as described above.

Table 1 Quality Performance Test Background 1) Color density 2) Color density 3) Color density 4) Example 1 0.05 1.51 1.61 1.63 Example 2 0.04 1.49 1.60 1.61 Example 3 0.05 1.55 1.62 1.65 Example 4 0.04 1.55 1.62 1.64 Example 5 0.05 1.56 1.62 1.63 Comparative Example 1 0.09 1.45 1.47 1.50 Comparative Example 2 0.05 1.42 1.56 1.58

Table 2 Quality Performance Test Heat Resistance 5) Water Resistance 6) Plasticizer Resistance 7) Example 1 1.64 1.47 1.64 Example 2 1.61 1.45 1.60 Example 3 1 .65 1.49 1.65 Example 4 1.64 1.47 1.60 Example 5 1.64 1.47 1.63 Comparative Example 1 0.30 0.86 0.75 Comparative Example 2 1.42 1.01 0.95

1) Background: A value obtained by measuring an uncolored portion of the sample with a Macbeth reflection densitometer RD-914 (Macbeth reflection density). 2) Coloring density: Macbeth reflection density value of an image portion printed at a voltage of 23 V using a thermal printer (D-805P) manufactured by Ishida Koki Co., Ltd. 3) Coloring density: Macbeth reflection density value of an image portion printed with a voltage of 25 V using a thermal printer (D-805P) manufactured by Ishida Koki Co., Ltd. 4) Color density: Macbeth reflection density value of an image portion printed at a voltage of 27 V using a thermal printer (D-805P) manufactured by Ishida Hoki Co., Ltd. 5) Heat resistance: Macbeth reflection density of an image portion after a sample colored at a voltage of 27 V of the above printer was left in a thermostat at 100 ° C. for 24 hours. 6) Water resistance: Macbeth reflection density of an image portion after immersing a sample colored at a voltage of 27 V of the printer in tap water at room temperature for 24 hours. 7) Plasticizer resistance: A PVC wrap film was added to both sides of a sample colored at a voltage of 27 V of the above-mentioned printer so as to have a resistance of 0.1%.
Macbeth of the image portion after leaving for 24 hours at room temperature under a load of 0294 MPa (0.3 kg / cm2)
Reflection density.

As is clear from the table, the heat-sensitive recording material of the present invention is excellent in the whiteness of the background and color density, and in the color image, is excellent in heat resistance, water resistance, plasticizer resistance and the like.

[0034]

As described above, a heat-sensitive recording material having high sensitivity, little background fog, and excellent image storability was obtained.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive color-forming layer mainly comprising a colorless or light-colored color-forming compound, a color-developing compound capable of forming the color-forming compound when heated, and a sensitizer as main components. 3. The heat-sensitive recording material according to claim 1, further comprising 4,4'-dihydroxydiphenylsulfone or 2,4'-dihydroxydiphenylsulfone as a color-developing compound, and p-acetotoluizide and o-acetotoluizide as sensitizers.