JPS6394881A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having high sensitibility and causing no fading or whitening of recorded image, by employing 4- hydroxyphthalic acid dimethyl ester and a bisphenol series compound shown by formula (I) as a developer in combination. CONSTITUTION:A thermal coloring layer composed mainly of a leuco dye and a developer is provided on a supporting material, and 4-hydroxyphthalic acid dimethyl ester and a bisphenol compound shown by formula (I) are employed in combination as the developer. Preferably, the compound shown by formula (I) includes bis(4-hydroxyphenyl) acid phenyl, bis(4-hydroxy phenyl) acid benzyl, bis(3-methyl-4-hydroxyphenyl) acid phenyl, etc. and the leuco dye includes triphenyl methane series, fluoran series, phenothiazine series, oramine series, spiropyrane series, indolinophthalid series, etc.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a heat-sensitive recording material, and more specifically, a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye, which is colorless or slightly pale at room temperature, and a color developer for the leuco dye. Regarding improvement of materials.

[Prior art]

Recently, various recording materials have been researched and developed and put into practical use in the information recording field, in response to social demands such as diversification and increase in information, resource conservation, and pollution-free technology.Among them, thermal recording materials are (1) A colored image is recorded simply by heating, eliminating the need for a complicated development process. (2) It can be produced using a relatively simple and compact device, and the resulting recording material is easy to handle. (3) paper is often used as the support;
In this case, not only the cost of the support is low, but also the feel of the resulting recorded material is similar to that of plain paper. It is widely used in the field of low and high speed facsimiles, automatic ticket vending machines, thermal copying, etc.

The above-mentioned heat-sensitive recording material is produced by applying and drying a heat-sensitive coloring layer liquid containing a coloring component capable of causing a coloring reaction when heated on a support such as ordinary paper, synthetic paper, or a synthetic resin film. A colored image is recorded on the heat-sensitive recording material thus obtained by heating it with a thermal pen or a thermal head.

Conventional examples of such heat-sensitive recording materials include, for example, the heat-sensitive recording materials disclosed in Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-14039; Responsiveness was low, and sufficient color density could not be obtained during high-speed recording.

As a method for improving such drawbacks, for example, Japanese Patent Application Laid-Open No. 49-3
No. 4842 discloses acetamide, stearamide, m
-Nitrogen-containing compounds such as nitroaniline and dinitrile phthalate; JP-A-52-106746 describes acetoacetanilide; JP-A-53-11036 describes N,
N-diphenylamine derivatives, benzamide derivatives, carbazole derivatives, and in JP-A-53-39139, alkylated biphenyls, biphenylalkanes,
Furthermore, in JP-A-56-144193, p-oxybenzoic acid ester derivatives are incorporated in JP-A-59-52,694 and JP-A-59-68,295 by incorporating a highly sensitive bisphenol compound. A method for increasing the color density and sensitivity has been disclosed, and it is also known as an effective method to use 4-hydroxyphthalic acid dimethyl ester as a color developer.

However, these various color developers still have the disadvantage that the recorded image may fade, the image area may become white (white powder forms on the surface), or the color may be erased by oils and fats such as fingerprints. There is.

〔the purpose〕

An object of the present invention is to provide a highly sensitive thermal recording material that has improved the above-mentioned conventional drawbacks, that is, to provide a highly sensitive thermal recording material with high whiteness and high sensitivity, and which does not cause the recorded image to fade or whiten or to be free from oils and fats such as fingerprints. An object of the present invention is to provide a heat-sensitive recording material that is less likely to be discolored by heat.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer as main components is provided on a support,
There is provided a heat-sensitive recording material characterized in that 4-hydroxyphthalic acid dimethyl ester and a bisphenol compound represented by the following general formula (1) are used in combination as the color developer.

(In the formula, R1 is an aryl group or an aralkyl group, R2
represents hydrogen or an alkyl group. ) 4-Hydroxyphthalic acid dimethyl ester used in the present invention has a low melting point and high color developing ability, so it has high thermal responsiveness and excellent density uniformity of colored images. Furthermore, when used alone, the bisphenol compound represented by the general formula (1) has a relatively strong color developing ability, although it is slightly inferior in thermal response and the density and uniformity of a colored image compared to 4-hydroxyphthalic acid dimethyl ester. The present inventors have discovered that when a bisphenol compound represented by the general formula (1) and 4-hydroxyphthalic acid dimethyl ester are used together as a color developer, these compounds undergo eutectic melting, resulting in image crystallization in the color developing area. The inventors have discovered that image deterioration due to phenomena such as fading and whitening can be prevented, and the present invention has been completed based on this knowledge.

Specific examples of the compound represented by the general formula (1) used in the present invention include the following.

Bis(4-hydroxyphenyl)phenyl acetate, bis(
4-hydroxyphenyl)benzyl acetate, bis(4-hydroxyphenyl)phenethyl acetate, bis(3-methyl-4-hydroxyphenyl)phenyl acetate, bis(3-methyl-4-hydroxyphenyl)benzyl acetate, bis(3-hydroxyphenyl)benzyl acetate -methyl-4-hydroxyphenyl) phenethyl acetate, etc.

In the present invention, the color developer consisting of the above combination is generally 1 to 10 parts by weight, preferably 2 parts by weight, per 1 part by weight of the leuco dye.
It is used in a range of 6 parts by weight. Furthermore, a conventionally known color developer can be added if necessary.

The leuco dyes used in the present invention can be applied singly or in combination of two or more types, but such leuco dyes include:
Those applied to this type of heat-sensitive material can be arbitrarily applied, and for example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes are preferably used. . Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p- dimethylaminophenyl)-6-diethylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(p-dibutylaminophenyl) Watari 3
-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-)-lifluoromethylphenyl)amino)-6-dinithylaminofluorane, 2-(
3,6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o -chloranilino) = 7
- Fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N- diethylamino)-5-methyl-7-(
N,N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2 '-Hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'- Methoxy-5'-nitrophenyl) phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl) phthalide, 3-(2'-methoxy- 4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-( N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-P-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(0-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-( α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluoran, 3-(N-benzyl-
N-cyclohexylamino)-5,6-penzo 7-α
-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxy cellulose, Cellulose derivatives such as hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic acid ternary copolymer, styrene /maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt,
In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic ester, vinyl chloride/vinyl acetate copolymer, and Latex such as butyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. are used.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, thermofusible substances ( or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin, styrene/methacrylic acid copolymer, polystyrene resin, and other organic fine powders. Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts. In addition, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, and other thermofusible organics. Examples include compounds having a melting point of about 50 to 200°C.

The heat-sensitive recording material of the present invention is produced, for example, by applying a coating liquid for forming a heat-sensitive coloring layer containing each of the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying it. It is applied to various recording fields.

〔effect〕

The heat-sensitive recording material of the present invention has the above-mentioned structure, has high whiteness, excellent heat sensitivity, and high color development, and has extremely low fading, whitening, and discoloration due to fingerprints, etc. of the recorded image. The image has high reliability.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Examples 1 to 3 [Liquid A] 3-N-methyl-3-N-cyclohexylamino-20
0 parts 6-methyl-7-anilite fluorane water
600# total
100011 [Liquid B] 300 parts of 4-hydroxyphthalic acid dimethyl ester -
Color developer A shown in 1 10011 Calcium carbonate 20011 Water
2
00++ total
100011 Each of the mixtures with the above composition was dispersed in a ball mill for 100 hours, and 20 parts of Part A and 40 parts of Part B were mixed and stirred, and the resulting solution was placed on high-quality paper with a basis weight of 50 g/m so that the weight after drying was 4.0 g/m. The heat-sensitive recording material of the present invention was obtained by coating and drying so as to obtain the following.

Comparative Example 1 A heat-sensitive recording material of a comparative example was obtained in the same manner as in Example 1 except that the color developer A of Example 1 was omitted.

Comparative Example 2.3 Example 2 except that benzyl p-hydroxybenzoate or bisphenol A was used instead of the color developer 4-hydroxyphthalic acid dimethyl ester.
A heat-sensitive recording material of a comparative example was obtained in the same manner as above.

The following heat-sensitive recording materials were tested for dynamic color development sensitivity, image fading resistance, whiteness, and image oil resistance. The results are shown in Table-1. The test method was performed as follows.

(1) Dynamic color development sensitivity: head power 0.6 using a thermal printing experimental device with a thin film head manufactured by Matsushita Electronic Components Co., Ltd.
Printing was performed with a pulse width of 0.2.0.3.0.4.0.5 m5ec under the conditions of 0 W/dot, 1 line recording time of 5.0 ms/Q, and scanning line density of 8 x 3.85 dots/mm.
The print density was measured using a Macbeth densitometer RD-514 (filter-W-106).

(2) Image fading property...For the samples whose dynamic color development sensitivity was measured in (1), the print density was 1.0 to 1.2 (this is Do) and the density after being left at room temperature for 15 days. For measurement purposes, this is referred to as D), and the concentration decrease is determined according to the following formula,
This was defined as the fading property of the image.

D.

(3) Image whitening... Perform the same test as (2),
Judgment was made by visual inspection as follows.

○... Almost no white powder generated △... White powder generated, but no practical problem ×... Too much white powder generated, impractical (4) Oil resistance... Castor oil 0.5 g / in the image area
The same test as in (2) was conducted except that g was attached, and the results were determined as follows.

○・・・Concentration reduction rate within 30%

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, 4-hydroxyphthalic acid dimethyl ester and the following general formula (I) are used as the color developer. 1. A heat-sensitive recording material characterized by using the bisphenol compounds shown below. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 is an aryl group or an aralkyl group, R
_2 represents hydrogen or an alkyl group. )