JPH0664320A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance color forming properties and a shelf stability by a method wherein when a color developer, a sensitizer, and N-methylol fatty acid amide each of which is specifically determined are used in combination and ground in the same mixing system, a specific styrene maleic anhydride copolymer ammonium salt is used as a dispersing agent. CONSTITUTION:In a thermal recording material, a thermal recording layer is provided on a substrate. The thermal recording layer contains a colorless or light-colored basic dye and a color developer reacting with the dye to develop a color. In this invention, at least one kind of color developer selected out of 4,4'-isopropyridene diphenol and the like, at least one kind of sensitizer selected out of 2-benzyloxynaphthalene and the like, and N-methylol fatty acid amide are used in combination and ground in the same mixing system. As a dispersing agent at the time of grinding, a styrene maleic anhydride copolymer ammonium salt having a 50 or more esterification degree and a 10000-60000 average molecular weight is used. In this manner, the materials are finely ground and, thus, color forming properties and a shelf stability are enhanced.

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, more specifically, a heat-sensitive color-forming material containing a colorless or slightly light-colored color-forming material and a color-developing material capable of coloring the color-forming material when heated. The present invention relates to a thermosensitive recording material having a layer provided on a support.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally comprises a support such as paper, synthetic paper, plastic film, etc., on which a heat-sensitive color-forming layer containing a thermo-color-forming composition as a main component is provided. A colored image can be obtained by heating with a flash lamp or the like. Compared with other recording materials, this type of recording material can perform recording in a short time with a relatively simple device without performing complicated processing such as development and a fixing agent.
It is widely used as a recording material for various fields such as electronic calculators, facsimiles, ticket vending machines, label recorders, etc. because it is used for copying books and documents due to its advantages such as noise generation, low environmental pollution, and low cost. It's being used.

The heat-sensitive color-forming layer which develops a color by heating to record an image contains a combination of a color-forming substance and a color-developing substance which reacts with the color-forming substance to produce a color when heated. In this case, as the color-forming substance, for example, lactone,
A colorless or light-colored leuco dye having a lactam or spiropyran ring is used, and various acidic substances such as 4,4′-isopropylidenediphenol (general name bisphenol A) are used as the color-developing substance. The combination of such a color-developing substance and a color-developing substance has been applied to more heat-sensitive recording materials than before because of its clear color tone.

As a conventional means for improving the color developing sensitivity of a heat-sensitive recording material, a heat-fusible substance having a lower melting point than a basic dye or a color developer is added as a sensitizer to a recording layer and melted first. A method in which a dye and a color developing agent are dissolved by a heat-fusible substance to lower the color development start temperature is widely known (JP-A-49-34842, JP-A-53-39139, and JP-A-61-16888). Etc.).

Usually, such a heat-fusible substance is dispersed in water together with a basic dye or a developer, if necessary, and wet-milled by a mill such as a sand grinder, a ball mill or an attritor. Used after miniaturization. As such a heat-fusible substance, use of 2-benzyloxynaphthalene, p-benzylbiphenyl and di (p-methylbenzyl oxalate) has been proposed, and it is possible to reduce the melting point or generate acid by hydrolysis. Therefore, an excellent sensitizing effect is expected, and the effect is dramatically improved by the combined use of N-methylol fatty acid amide.

However, while a specific action is expected,
In the usual wet pulverization method, the stability of the dispersion liquid is poor, such as agglomeration occurring during the treatment, which is not easily made into fine particles, and the particles are re-aggregated after being made fine, and the expected sensitizing effect is sufficient. It is the current situation that it is not demonstrated.

[0007]

In view of the present situation, the present inventor aims to obtain a thermosensitive recording material which develops a high density even with a small amount of heat energy, does not cause a decrease in whiteness, and has excellent storage characteristics. Widely examined. As a result, especially 4,4'-isopropylidenediphenol in the heat-sensitive recording layer, 4,
4'-dihydroxydiphenyl sulfone, bis- (3-
From at least one developer selected from allyl-4-hydroxyphenyl) sulfone and bis (4-hydroxyphenyl) sulfone, and 2-benzyloxynaphthalene, p-benzylbiphenyl and di (p-methylbenzyl) oxalate. When at least one selected sensitizer and N-methylol fatty acid amide are combined and pulverized in the same mixing system, a degree of esterification of 5 is used as a dispersant.
The inventors have found that the fine pulverization can be carried out extremely efficiently and is stable when the ammonium salt of a styrene-maleic anhydride copolymer having an average molecular weight of 0% or more and 10,000 to 60,000 is selectively used, and the present invention has been completed.

[0008]

In the present invention, 4,4'-isopropylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, bis- (3-allyl-4-hydroxyphenyl) sulfone and bis (4-hydroxyphenyl) sulfone And at least one selected from 2-benzyloxynaphthalene, p-benzylbiphenyl, and di (p-methylbenzyl oxalate).
When sensitizers of various kinds and N-methylol fatty acid amides are combined and pulverized in the same mixing system, the degree of esterification is 50% or more and the average molecular weight is 10,000 to 6 as a dispersant.
The use of styrene ammonium salt of styrene-maleic anhydride copolymer of 0000 makes it possible to form fine particles extremely efficiently.

From these finely divided 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenyl sulfone, bis- (3-allyl-4-hydroxyphenyl) sulfone and bis (4-hydroxyphenyl) sulfone At least one color developer selected, and
When at least one sensitizer selected from benzyloxynaphthalene, p-benzylbiphenyl and di (p-methylbenzyl oxalate) and N-methylol fatty acid amide are used in combination in the heat-sensitive recording layer, color developability, especially It is possible to obtain a heat-sensitive recording material which has excellent color development in a low energy region and excellent storage characteristics.

These color developers 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenyl sulfone, bis- (3-allyl-4-hydroxyphenyl)
The amounts of sulfone and bis (4-hydroxyphenyl) sulfone used are not particularly limited, but basic dye 1
It is preferable to adjust the amount in the range of 10 to 700 parts by weight, preferably 50 to 500 parts by weight, relative to 00 parts by weight.

The amount of N-methylol fatty acid amide used is not particularly limited, but 2-benzyloxynaphthalene or oxalic acid dibenzyl ester derivative 10 is used.
2 to 50 parts by weight, preferably 15 to 0 parts by weight
It is preferable to adjust in the range of 35 parts by weight.

In the present invention, 4,4'-isopropylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, bis- (3-allyl-4-hydroxyphenyl) sulfone and bis (4-hydroxyphenyl) sulfone. And at least one type of sensitizer selected from 2-benzyloxynaphthalene, p-benzylbiphenyl and di (p-methylbenzyl oxalate), and N-methylol fatty acid amide. A styrene-maleic anhydride copolymer salt is contained as a combination and a dispersant. The styrene-maleic anhydride copolymer salt has an average molecular weight of 10
The sodium salt, potassium salt, ammonium salt and the like of the copolymer of about 000 to 60,000 are preferably used, and the ammonium salt is particularly preferably used. The amount of the styrene-maleic anhydride copolymer salt to be used is not particularly limited, but it is 1 per 100 parts by weight of the color developer.
It is preferably adjusted in the range of 0 to 80 parts by weight.

In the thermosensitive recording medium of the present invention, examples of N-methylol fatty acid amides include N-methylol stearic acid amide and N-methylol behenic acid amide. Furthermore, it is of course possible to appropriately add an antifoaming agent and other various auxiliaries to the above dispersion liquid.

In the present invention, the basic dyes which are used in the recording layer of the thermosensitive recording medium and which are used in a colorless or light color may be used alone or in admixture of two or more, if necessary. What has been applied to the heat-sensitive material of any kind is arbitrarily applied, for example, trianylmethane-based, fluoran-based, thiazine-based, spiropyran-based, lactam-based dye leuco compounds are preferably used, particularly fluoran-based leuco Dyes are widely and commonly used, and specific examples thereof include the following.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p
-Dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole -3-yl)
-5-Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl)- Triallylmethane dyes such as 6-dimethylaminophthalide, 6 '-[ethyl (3-methylbutyl) amino] -3'-methyl-2'-(phenylamino) -spiro [isobenzylfuran-1-9 ' −
Xanthene] -3-one, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N
-Propylamino) -6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino)
-6-Methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7-chlorofluorane, 3-dimethylamino-7-methyl-7-chlorofluorane, 3-
Dimethylamino-6-methyl-7-anilinofluorane, 3,3-bis (4-dimethylaminophenyl) 6-
Diethylaminophthalide, 3-diethylamino-7 (2
-Chloroanilino) fluorane, 3-dibutylamino-
7 (2-chloroanilino) fluoran and other fluoran dyes, benzoyl leuco methylene blue, p-nitribenzoyl leuconetylene blue and other thiazine dyes, 3
-Methyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran and other spiropyrans Examples thereof include lactam dyes such as dyes, rhodamine (p-nitroanilino) lactam, and rhodamine (o-chloroanilino) lactam.

Further, in the present invention, as the binder for binding and supporting the heat-sensitive color forming layer on the support, various ones as shown below are applied.

Derivatives of polyvinyl alcohol, starch and its derivatives, methyl cellulose, hydroxymethyl cellulose, carboxymethyl cellulose, ethyl cellulose, polyvinyl pyrrolidone, polyacrylamide, sodium polyacrylate, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / Methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, sodium alginate, gelatin, casein, gum arabic and other water-soluble polymers,
Aqueous emulsion binders such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, and polybutylmethacrylate Can be used as

In the heat-sensitive recording material of the present invention, the above-mentioned leuco dye and color developer may be incorporated in the heat-sensitive color forming layer, if necessary.
Auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, surfactants, lubricants and the like can be used in combination.
In this case, as the filler, for example, calcium carbonate,
Inorganic fine powder such as silica, alumina, magnesium, talc, barium sulfate, zinc oxide, titanium oxide, surface-treated calcium and silica, as well as urea / formalin resin, styrene / methacrylic acid copolymer, polystyrene and other organic materials Mention may be made of fine powders of the system. Examples of the lubricant include higher fatty acids or esters thereof, amides or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoates, higher linear glycols and other heat-fusible organic compounds. Compounds. Add fine powder such as aluminum stearate to improve the sharpness of the color image, and add thermal lubricant by adding lubricant such as linseed oil, tung oil, wax, paraffin, polyethylene wax, chlorinated paraffin, and higher fatty acid metal salt. The running property of the head can be further improved.

An overcoat layer may be provided on the recording layer for the purpose of protecting the recording layer, and a protective layer may be provided on the back surface of the support or an under layer may be provided on the support. Needless to say, various known techniques in the field of heat-sensitive recording material production, such as applying an adhesive treatment to the back surface of the support, can be added.

Paper is generally used as the support, but a resin film, synthetic paper, woven cloth or the like can also be used. It is also possible to provide an under layer between these supports and the heat sensitive layer. A coater head such as a blade coater, an air knife coater, a roll coater, a rod coater or a curtain coater can be used as an apparatus used for coating the under layer and the heat-sensitive recording layer.

Further, in order to improve the surface smoothness of the coated product, a machine calender, a super calender, a gloss calender, a brushing machine or the like can be used. The coating amount when the under layer is provided is not particularly limited, but 3 to 20 g / m ^{2 is} preferable, and 5 to 10 g / m ² is suitable. The coating amount of the thermosensitive recording layer on the support is not limited, but is usually 3 to 15 g.
/ M ^{2 It is} preferably in the range of 4 to 10 g / m ² .

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The parts and% shown below are based on weight.

Example 1 (Preparation of coating liquid for under layer)

An underlayer coating liquid comprising the following components was applied to a base paper having a standard basis weight of 40 g / m ^{2 by} a blade coater so that the dry weight was 6 g / m ^2, and dried to obtain an underlayer. Ansilex (manufactured by Engelhart, calcined kaolin) 100 parts by weight 10% sodium hexametaphosphate 4 parts by weight 20% phosphate esterified starch 30 parts by weight 48% styrene-butadiene copolymer latex 40 parts by weight water 50 parts by weight

Preparation of Coloring Layer (1) Preparation of Solution A Liquids A and B having the following component compositions were obtained by dispersing for 10 hours. 10% Polyvinyl alcohol solution 100 parts by weight 3-Dibutylamino-6-methyl-7-anilinofluorane 100 parts by weight Water 150 parts by weight A solution using Dynomill (manufactured by Shinmaru Enterprises Co., Ltd.) volume average, 0.8 μm Crushed into (2) Preparation of solution B 15% styrene maleic anhydride copolymer ammonium salt (average molecular weight 40,000 to 60,000) 35 parts by weight 4,4'-isopropylidenediphenol 55 parts by weight 2-benzyloxy-naphthalene 40 parts by weight N -Methylol stearic acid amide 10 parts by weight Water 200 parts by weight Solution B was pulverized to a volume average of 0.8 μm using Dynomill (manufactured by Shinmaru Enterprises).

Next, using the prepared [solution A] and [solution B],
A thermosensitive color developing layer coating solution comprising the following components was prepared and air-dried on the underlayer so that the dry weight was 5 g / m ^2.
It was dried and coated with a knife coater. After that, the coated paper is calendered and the Beck smoothness is 400 to 600.
The heat-sensitive recording paper of the present invention was obtained after finishing to the second. Polyvinyl alcohol solution (10% aqueous solution) 50 parts by weight Calcium carbonate 10 parts by weight Solution A 10 parts by weight Solution B 35 parts by weight 40% zinc stearate dispersion 4 parts by weight Water 25 parts by weight

Example 2 Thermal recording was carried out in the same manner as in Example 1 except that 4-hydroxy-4'-isopropoxydiphenyl sulfone was used in place of 4,4'-isopropylidenediphenol in the liquid B of Example 1. Got the paper.

Example 3 All were carried out in the same manner as in Example 1 except that bis- (3-allyl-4hydroxyphenyl) -sulfone was used in place of 4,4'-isopropylidenediphenol in the liquid B of Example 1. A thermosensitive recording paper was obtained.

Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that bis (4-hydroxyphenyl) sulfone was used instead of 4,4'-isopropylidenediphenol in the liquid B of Example 1. It was

Example 5 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that p-benzylbiphenyl was used in place of 2-benzyl-oxynaphthalene in the liquid B of Comparative Example 1.

Example 6 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that di- (p-methylbenzyl) oxalate was used instead of 2-benzyl-oxynaphthalene in the liquid B of Comparative Example 1.

Examples 7 to 12 Liquid B of Examples 1 to 6 has an average molecular weight of 40,000 to 6,000.
In place of the 0% 15% styrene-maleic anhydride copolymer ammonium salt, a 20% styrene-maleic anhydride copolymer ammonium salt having an average molecular weight of 10,000 to 20,000 was used, and the heat sensitivity was the same as in Examples 1 to 6. I got the recording paper.

Comparative Examples 1 to 6 Heat sensitive materials were prepared in the same manner as in Examples 1 to 6 except that sulfonated polyvinyl alcohol was used in place of the styrene-maleic anhydride copolymer ammonium salt in the liquid B of Examples 1 to 6. I got the recording paper.

Comparative Example 7 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the B liquid of Example 1 was excluded from N-methylolstearic acid amide.

Regarding the above-mentioned 6 kinds of heat-sensitive recording materials, a test machine manufactured by Okura Electric Co., Ltd. using a head having a head resistance of 1335Ω (a head manufactured by Kyocera) was used for 10 ms / Line.
Printing was performed with an energy of 25 mj / dot, the print density of the background portion and the image portion at that time was measured, and the storage stability was evaluated under all environmental conditions. As a result, Examples are shown in Tables 1 and 2 and Comparative Examples are shown in Table 3. The print density was measured using Macbeth RD918.

The conditions for evaluating the stability of the dispersion and evaluating the storage stability are as follows. [Evaluation of Stability of Dispersion] ○ ... Evenly dispersed and no aggregation is observed. △ ・ ・ Partially aggregated, but can be redispersed by stirring. × ·· Aggregation and precipitation are remarkable, and redispersion is impossible with stirring. [Evaluation of storability] (1) Water resistance test: Put 300 g of water in a 500 cc glass beaker, immerse the printed sample in it, and measure the concentration after storage for 24 hours at 20 ° C. To do. (2) Heat resistance test: The printed sample is stored at 60 ° C. for 24 hours, and the density is measured. (3) Moisture and heat resistance test: Printed sample at 40 ° C
The concentration after storage for 24 hours under the condition of 90% RH is measured.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

Results From the results of Tables 1, 2, and 3, in the present invention, a thermosensitive recording layer containing a colorless or pale basic dye on the support and a color developer capable of developing a color by reacting with the dye. In the thermosensitive recording medium provided with 4,4'-isopropylidenediphenol,
4,4'-dihydroxydiphenyl sulfone, bis-
At least one developer selected from (3-allyl-4-hydroxyphenyl) sulfone and bis (4-hydroxyphenyl) sulfone, 2-benzyloxynaphthalene, p-benzylbiphenyl and di (p-oxalate).
Methylbenzyl) and at least one sensitizer selected from N-methylol fatty acid amide are combined and pulverized in the same mixing system, and styrene having a degree of esterification of 50% or more and an average molecular weight of 10,000 to 60,000 is used as a dispersant. When the ammonium salt of maleic anhydride copolymer was used, the thermosensitive recording medium was remarkably efficiently miniaturized and had good stability, excellent color development in a low energy region, and good storage characteristics.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a developer capable of developing a color by reacting with the dye, which comprises 4,4'-isopropylamine. 2-benzyl, at least one developer selected from lidenediphenol, 4,4'-dihydroxydiphenyl sulfone, bis- (3-allyl-4-hydroxyphenyl) sulfone and bis (4-hydroxyphenyl) sulfone A combination of at least one sensitizer selected from oxynaphthalene, p-benzylbiphenyl and di (p-methylbenzyl oxalate) with N-methylol fatty acid amide, and a degree of esterification of 50% as a dispersant.
And in the presence of a styrene maleic anhydride copolymer ammonium salt having an average molecular weight of 10,000 to 60,000,
A heat-sensitive recording material characterized by being finely pulverized and contained in the same mixing system. 2. A heat-sensitive recording material according to claim 1, wherein the N-methylol fatty acid amide is methylol stearic acid amide or methylol behenic acid amide.