JPH0924672A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise whiteness degree by improving developing sensitivity by a method wherein 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane is contained as an electron acceptive developing compound in a heat sensitive coloring layer. SOLUTION: Though the content of 1,1-bis(4-hydroxyphenyl)-3,3,5- trimethylcyclohexane is not especially limited, it is contained within a range of generally 30-600 pts.wt., preferably 150-300 pts.wt. to 100 pts.wt. of dye precursor. When the content is less than 30 pts.wt., an effect for improvement of sensitivity is not sufficient. When it is more than 600 pts.wt., a problem on tailing and sticking is apt to be generated. It can be independently used, or used jointly with another electron acceptive developing compound. Well-known urea compound or organic acid material of multi-valent metal salt or the like is exemplified therefor. As an electron donative developing dye precursor constituting a heat sensitive coloring layer, it can be selected in well-known material such as triaryl series or the like.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material. More specifically, the present invention relates to a thermosensitive recording material having excellent color development sensitivity.

[0002]

2. Description of the Related Art A heat-sensitive recording material for forming a color image by utilizing a color development reaction of a colorless or light-colored electron-donating color forming dye and a phenol or an organic acid is disclosed in, for example, JP-B-43-4160. It is disclosed in JP-B-45-14039 and JP-B-48-27736. In recent years, such a heat-sensitive recording material has various advantages such that a color image can be formed by simply heating it, and the recording apparatus can be made relatively compact. Is widely used as.

In particular, thermal facsimiles, thermal printers and the like have been improved in their apparatus, and high-speed printing and high-speed image formation, which have been difficult in the past, have become possible. It has come to be used in the field. On the other hand, with the speeding up of printing as described above, it is desired that the color sensitivity of the thermosensitive recording material be greatly improved.

As the application of the heat-sensitive recording material for which the sensitivity is particularly required to be improved, for example, a heat-sensitive recording type ticket or ticket for an automatic ticket vending machine, a label thermal paper used in a POS bar code system, a facsimile paper, or the like. Word processor paper, C
There are image printer papers for RT and printer papers for slips.

On the other hand, many proposals have been made so far in order to satisfy the demand for improving the color developing sensitivity. Among them, 4,4'-isopropylidenediphenol (hereinafter referred to as BPA) which has been used conventionally as a color-developing compound that develops an electron-donating dye under heating is positively performed.
It is the development of a new material that replaces Although BPA is cheap, it does not always meet the market demand for sensitivity.

Therefore, many color-developing compounds have been proposed so far as alternatives to BPA. These are described in the Paper and Pulp Technology Times magazine, May 1987 issue to February 1988 issue.
It can be seen that hundreds of compounds have already been proposed. However, many of these compounds are not practical solutions because the effect of improving the sensitivity is not sufficient or the whiteness is significantly reduced.

[0007]

DISCLOSURE OF THE INVENTION The present invention is intended to solve these problems and provide a heat-sensitive recording material having excellent color development sensitivity and high whiteness.

[0008]

In the present invention, an electron-donating color-forming dye precursor is provided on a support, and an electron-accepting color-developing compound that is brought into contact with the color-forming dye precursor to develop a color when heated. In a thermosensitive recording material provided with a thermosensitive coloring layer containing,
1,1 as an electron-accepting color-developing compound in the thermosensitive coloring layer
-Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane is contained in the heat-sensitive recording material.

The present inventors have investigated various electron-accepting color developing compounds in order to improve color developing sensitivity, and found that 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane The inventors have found that the coloring sensitivity is significantly improved without adversely affecting the whiteness and the like, and have completed the present invention.

The content of 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane in the heat-sensitive color developing layer is not particularly limited, but is generally based on 100 parts by weight of the dye precursor. 30 to 600 parts by weight,
More preferably, it is contained in the range of 150 to 300 parts by weight. If it is less than 30 parts by weight, the effect of improving the sensitivity is not sufficient, and if it is more than 600 parts by weight, problems such as dust and sticking tend to occur.

In the present invention, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane can be used alone or in combination with other electron-accepting color developing compounds. Other electron-accepting color-developing compounds can be selected from conventionally known compounds.
For example, 4-t-butylphenol, 4-acetylphenol, 4-t-octylphenol, 4,4'-se
c-butylidene diphenol, 4-phenylphenol, 4,4′-dihydroxydiphenylmethane, 4,
4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (3-methyl-6-t-butylphenol), 4,4'- Dihydroxydiphenyl sulfone, 4-hydroxy-4′-isopropoxydiphenyl sulfone, bis (3-allyl-4)
-Hydroxyphenyl) sulfone, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, -sec-butyl 4-hydroxybenzoate, 4-
Phenolic compounds such as phenyl hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate and 4,4′-dihydroxydiphenyl ether, 4,
Examples of the urea compound include 4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane and N- (p-toluenesulfonyl) -N'-phenylurea.

Further, benzoic acid, pt-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid,
Aromatic carboxylic acids such as 3-t-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid and 3,5-di-t-butylsalicylic acid and these aromatic carboxylic acids ,
Examples thereof include organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, calcium and aluminum.

In the present invention, the electron-donating color-forming dye precursor constituting the thermosensitive coloring layer is selected from conventionally known ones such as triaryl dyes, diphenylmethane dyes, thiazine dyes, spiro dyes and lactam dyes. It is possible. For example, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3
-Piperidino-6-methyl-7-anilinofluoran,
3-Diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-Np-toluidino) -6-
Methyl-7-anilinofluorane, 3-pyrrolidino-6
-Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-
Cyclohexyl-N-methylamino) -6-methyl-7
-Anilinofluorane, 3- (N-methyl-N-isobutylamino) -6-methyl-7-anilinofluorane,
3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-Np -Tolylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isopentylamino) -7- (2-chloro) anilinofluorane, 3
-Diethylamino-7- (2-trifluoro) anilinofluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3- (N
-Ethyl-N-n-hexylamino) -6-methyl-7
Color-forming dyes such as-(2-chloro) anilinofluorane can be mentioned.

Further, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-dibutylamino-6-methyl-7-
Bromofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-7,8-benzofluorane, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3 , 3-bis (1-n
-Butyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-n-octyl-2-methylindol-3-yl) phthalide, 3-diethylamino-6
-Diethylamino-N-phenylrhodamine B lactam, 3-diethylamino-6-diethylamino- (N-
2-chlorophenyl) rhodamine B lactam, 3,6-
Bis (diethylamino) fluorane-γ-anilinolactam, 3,6-bis (diethylamino) fluorane-γ
-(4'-nitro) anilinolactam, 3-hexylamino-6-chlorofluorane, 3-diethylamino-7
-Methylfluorane, 3- (N-ethyl-N-tolylamino) -7-methylfluorane, 3-diethyl-5-methyl-8-t-butylfluorane, 3- (N-ethyl-
Color forming dyes such as N-isopentylamino) -7,8-benzofluorane can be mentioned.

Further, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide, 3- (1-ethyl-2-methylindol-3-yl) -3 -(2-Methyl-4-diethylaminophenyl) -4-azaphthalide, 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-dimethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (1-ethyl) -2-Methylindol-3-yl) -3- (4-diethylamino-2)
-N-hexyloxyphenyl) -4-azaphthalide,
3- (N-ethyl-Nn-hexylamino) -7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl)- 4-azaphthalide, 3-
(N-ethyl-N-p-tolylamino) -7- (N-phenyl-N-methylamino) fluorane, 3,6-dimethoxyfluorane, 1- (4-n-dodecyloxy-3
-Methoxyphenyl) -2- (2-quinolyl) ethylene, 3- [p- (p-anilinoanilino) anilino]-
6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'
One or more selected from color forming dyes such as -dimethylamino) phthalide can be used.

The thermosensitive coloring layer of the present invention comprises, in addition to the compounds constituting the coloring system, a heat-fusible substance (so-called sensitizer).
Or a storage stabilizer. Further, it is necessary to contain an adhesive for binding these and bonding the thermosensitive coloring layer to the sheet-shaped support. Further, it is preferable to contain a pigment mainly for preventing sticking to the thermal head, and if necessary, waxes, metal soaps, ultraviolet absorbers, fluorescent dyes and the like can be contained.

Examples of the heat-fusible substance (sensitizer) that can be used in the present invention include heat-fusible organic compounds having a melting point of 50 to 150 ° C. For example, 1-hydroxy-2-naphthoic acid phenyl ester, p-benzylbiphenyl, benzylnaphthyl ether, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate, m-terphenyl, 1,2-bis. (M-tolyloxy) ethane, 1,5
-Bis (p-methoxyphenoxy) -3-oxapentane, diphenyl oxalate, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, dibenzyl oxalate, 1,4-bis (trioxymethoxymethyl) ) Benzene, 1,2-di (3-methylphenoxy) ethane,
1,2-diphenoxyethane, 1,2-bis (3,4-
Examples include dimethylphenoxy) ethane and the like.

In the present invention, the thermosensitive color developing layer may contain a compound for improving the storage stability after printing, that is, a so-called storage stabilizer. Examples of storage stabilizers include
1,1,3-tris (2-methyl-4-hydroxy-5)
-Cyclohexylphenyl) butane, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 4-benzyloxyphenyl-4 '-(2-methyl-2,2 3-epoxypropyloxy) phenyl sulfone, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane , 1,1-bis (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4,4′-
[1,4-phenylenebis (1-methylethylidene)]
Phenolic compounds such as bisphenol, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol, and 4- (1,2-epoxyethyl-)
Examples thereof include epoxy compounds such as 2-methyl) diphenyl sulfone and 4- (1,2-epoxyethyl-2-ethyl) diphenyl sulfone, but the present invention is not limited thereto. Further, two or more kinds of these storage stabilizers may be contained.

The color-forming dye precursor, the color-developing compound, the heat-fusible substance and the storage stabilizer are generally polyacrylamide, using water as a dispersion medium by a wet grinder such as a sand grinder, a ball mill, an attritor or a sand mill. In addition to water-soluble polymer compounds such as polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer salts and their derivatives, etc., they are dispersed and dispersed together with a surfactant such as sodium dialkylsulfosuccinate. After being made into a liquid, it can be used for preparing a thermosensitive coloring layer coating material.

As the adhesive used in the present invention, polyvinyl alcohol having various molecular weights, starch and its derivatives, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone and acrylic acid amide. / Acrylic ester copolymer,
Acrylic amide / acrylic ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, water-soluble polymer materials such as casein, and polyvinyl acetate , Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer Etc. of each latex can be used.

As the pigment used in the thermosensitive coloring layer, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate,
Kaolin, clay, calcined clay, talc, and inorganic pigments such as surface-treated calcium carbonate and silica, and organic pigments such as urea-formalin resin, styrene / methacrylic acid copolymer, acrylic resin, and polystyrene resin Can be mentioned.

Further, the thermosensitive color developing layer of the present invention may contain various waxes, if necessary. Examples of the waxes include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, polyolefin wax, higher fatty acid ester, higher fatty acid amide such as stearic acid amide,
Examples thereof include ethylenebisstearic acid amide. Examples of the metal soap include higher fatty acid metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like. In addition, various additives such as an oil repellent, an antifoaming agent, a wetting agent, and a viscosity adjusting agent may be added as long as the effects of the present invention are not impaired.

The support used in the heat-sensitive recording material of the present invention is not particularly limited, and includes, for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, plain paper, coated paper, medium-coated paper, Lightly coated paper, art paper, cast coated paper, clear coated paper, glassine paper, semi-glassine paper, resin laminated paper,
In addition to synthetic fiber paper, synthetic resin film paper, metal foil, and the like, various transparent supports and semitransparent supports can be appropriately used, and composite sheets obtained by combining these can also be optionally used. On at least one surface of such a sheet-like support,
A coating solution containing a mixture of the above-mentioned required components is applied and dried to produce a heat-sensitive recording material. The coating amount is preferably 1 to 15 g / m ² in the dried state of the coating liquid layer, and particularly preferably ² to 10 g / m ² .

In the present invention, a protective layer may be provided on the heat-sensitive color forming layer and an undercoat layer may be provided below the heat-sensitive color forming layer. These layers are protective layers used in conventionally known heat-sensitive recording materials. , An undercoat layer can be applied. Both the protective layer and the undercoat layer are mainly composed of pigments and adhesives, and the coating amount is not particularly limited, but generally 1
It is provided in the range of up to ²⁰ g / m ² . In particular, in the protective layer, in order to prevent sticking to the thermal head, in addition to a lubricant such as calcium stearate, zinc stearate, polyolefin wax, polyethylene wax, paraffin wax, an auxiliary agent such as a dispersant or an antifoaming agent is added. be able to. Further, a curing agent such as glyoxal, an epoxy compound, boric acid, dialdehyde starch, and a methylol group-containing compound can be added for the purpose of improving water resistance. Further, the back surface of the heat-sensitive recording material may be provided with a back layer for preventing blocking at the time of contact between the front surface and the back surface, suppressing permeation of water or oil from the back surface, and controlling curl.

As a method for forming each layer, any known coating method such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method may be used. .

In the present invention, the heat-sensitive recording material can be further processed in order to increase the added value of the heat-sensitive recording material to give a heat-sensitive recording material having higher functions. For example, heat-sensitive recording that can be magnetically recorded on the back side by applying pressure sensitive adhesive, rewetting adhesive, or delayed tack type adhesive to make adhesive paper, rewetting adhesive paper, delayed tack paper, or magnetic processing It can be a material. Further, the back side can be used to have a function as a thermal transfer paper, an inkjet paper, a carbonless paper, an electrostatic recording paper, or a xerographic paper so that the recording paper can be recorded on both sides. Of course, a double-sided heat-sensitive recording material can also be used.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples. Unless otherwise specified, "part" and "%" are
Represents "parts by weight" and "% by weight", respectively. A thermal recording material was prepared by the following operation. (1) Preparation of Dispersion A Component (parts) 3-dibutylamino-6-methyl-40 7-anilinofluorane Sulfon group-modified polyvinyl alcohol 10% liquid 40 (Nippon Gosei Chemical Co., Ltd., Gocelan L- 3266) Water 20 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm. (2) Dispersion B Preparation Component Amount (parts) 3-Diethylamino-6methyl-40 7-chlorofluorane Sulfon group-modified polyvinyl alcohol 10% liquid 40 (Nippon Gosei Kagaku Kogyo, Gocelan L-3266) Water 20 The above composition was subjected to a sand grinder and the average particle size was 1
It was pulverized to a size of μm.

(3) Dispersion C Preparation Component (parts) 1,1-bis (4-hydroxyphenyl) -40 3,3,5-trimethylcyclohexane Sulfon group-modified polyvinyl alcohol 10% liquid 40 (Japan Synthetic Chemical Industry, Gocelan L-3266) Water 20 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm. (4) Dispersion D Preparation Component (parts) 4,4′-isopropylidenediphenol 40 Sulfon group-modified polyvinyl alcohol 10% liquid 40 (Nippon Gosei Chemical Co., Ltd., Goselan L-3266) Water 20 The above composition The material is subjected to a sand grinder and the average particle size is 1
It was pulverized to a size of μm.

(5) Preparation of Dispersion E Component amount (part) 4-hydroxy-4′-isopropoxy 40 diphenylsulfone sulfone group-modified polyvinyl alcohol 10% liquid 40 (manufactured by Nippon Synthetic Chemical Industry, Gocelan L-3266 ) Water 20 The composition was subjected to a sand grinder and the average particle size was 1
It was pulverized to a size of μm. (6) Dispersion F Preparation Component Content (parts) Bis (p-methylbenzyl) oxalate 40 Sulfon group-modified polyvinyl alcohol 10% liquid 40 (Nippon Gosei Chemical Co., Ltd., Gocelan L-3266) Water 20 The above composition The material is subjected to a sand grinder and the average particle size is 1
It was pulverized to a size of μm.

(7) Preparation of Dispersion G Component amount (part) 1,2-di (3-methylphenoxy) ethane 40 Sulfon group-modified polyvinyl alcohol 10% liquid 40 (Nippon Gosei Chemical Co., Ltd., Gocelan L- 3266) Water 20 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm. (8) Preparation of Dispersion H Component (parts) 1,3,5-Tris (2,6-dimethyl-40 3-hydroxy-4-t-butyl) isocyanuric acid Sulfon group-modified polyvinyl alcohol 10% Liquid 40 (Nippon Gosei Kagaku Kogyo, Gocelan L-3266) Water 20 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm. (9) Preparation of Dispersion I Component Content (parts) Calcium carbonate 60 Sodium polyacrylate 0.7% solution 40 The above composition was dispersed with a Cowles disperser. Furthermore, 10% polyvinyl alcohol (NM11Q,
40% polyolefin wax was prepared as a lubricant dispersion K liquid (manufactured by Nippon Synthetic Chemical Industry).

Preparation of thermosensitive coloring layer These dispersions and an adhesive were mixed so that the weight ratio after drying was as shown in Table 1 to obtain a thermosensitive coloring layer coating solution. The coating solution for the thermosensitive color developing layer thus obtained was coated on 50 g / m ² of high quality paper (acidic paper) so that the coating amount after drying was 6.0 g / m ^2, and dried to obtain a thermosensitive recording material.

Using a commercially available heat-sensitive facsimile HIFAX-45 obtained by modifying this heat-sensitive recording material for testing, 1 line recording time is 10 msec, scanning line density is 8 lines / mm, and applied energy is 0.30 mJ per dot. It printed. The color density of the thus obtained printed matter was measured by a Macbeth densitometer (RD914 type, manufactured by Macbeth). In addition, the whiteness (using a blue filter) specified by JIS P8123 was measured using a Hunter whiteness meter (manufactured by Toyo Seiki). The results thus obtained are summarized in Table 1. When the color density is 1.2 or more and the whiteness is 72 or more, there is no problem in practical use.

[0033]

[Table 1]

[0034]

As is apparent from Table 1, the present invention makes it possible to provide a heat-sensitive recording material having high whiteness and excellent color development sensitivity.

Claims (1)

[Claims] 1. A thermosensitive coloring layer containing, on a support, an electron-donating color-forming dye precursor and an electron-accepting color-developing compound which is brought into contact with the color-developing dye precursor to develop a color when heated. In the heat-sensitive recording material, the heat-sensitive color forming layer contains 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane as an electron-accepting color-developing compound. Recording material.