JPS59165684A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material free from discoloration of recorded images or blushing, excellent in heat sensitivity and high in color forming property and reliability of images, wherein a combination of a specified p-hydroxybenzoic acid ester and a specified bisphenol derivative is used as a color developer. CONSTITUTION:In a thermal recording material utilizing a color forming reaction between a leuco dye, e.g., 3-N-methyl-3-N-cycloalkylamino-6-methyl-7-anilinofluoran, and a color developer, a combination of a p-hydroxybenzoic acid ester of formula I , wherein R1 is H or 1-3C alkyl, e.g., benzyl p-hydroxybenzoate, and a bisphenyl derivative of formula II, wherein X is halogen, Y is -SO2- or -C(CH3)2-, and m is 1 or 2, X's in the left and right benzene rings being located at positions symmetrical with respect to Y, e.g., 2,2',6,6'-tetrabromo-4,4'-sulfonyldiphenol, in a ratio of preferably 2-5:1 is used as the color developer.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a heat-sensitive recording material, and more specifically, it comprises a leuco dye that is colorless or slightly pale at room temperature, and an acidic substance that reacts with the leuco dye when heated to develop a color. The present invention relates to an improvement in a heat-sensitive recording material in which a heat-sensitive color-forming layer containing a color-forming component is provided on a support.

[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 simple device, and the resulting recording material can be handled. (3) Paper is often used as a support, and in this case, not only is the support cost low, but the feel of the resulting recording material is also similar to that of plain paper. Because of its advantages such as being close to the computer output, it is widely used in the field of printers such as computer outputs, calculators, recorders for medical measurement, 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. 49-348
No. 42 discloses acetamide, stearamide (',
Nitrogen-containing compounds such as m-nitroaniline and dinylphthalate are used, acetoacetanilide is used in JP-A-52-106746, and N,N-diphenylamine is used in JP-A-53-11036. derivatives, benzamide derivatives, carbazole derivatives, alkylated piphenyl, biphenylalkane in JP-A-53-39139,
JP-A-56-144193 discloses a method for increasing speed and sensitivity by incorporating p-oxybenzoic acid ester derivatives. It was known that the most effective method was to use it as a coloring agent.

However, these various color developers still have drawbacks such as fading of recorded images and whitening of image areas (white powder is produced on the surface).

〔the purpose〕

An object of the present invention is to provide a high-sensitivity thermal recording material that improves the above-mentioned conventional drawbacks, that is, to provide a thermal recording material that is highly sensitive and in which recorded images are less prone to fading or whitening. There is a particular thing.

〔composition〕

According to the present invention, in a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer, the color developer includes p-hydroxybenzoic acid ester represented by the following general formula (1) and the following general formula (1). A heat-sensitive recording material characterized by using a combination with a bisphenol derivative represented by formula (II) is provided.

(In the formula, R1 represents hydrogen or an alkyl group having 1 to 3 carbon atoms) mXm (In the formula,
H3) 2-m is represented by 1 or 2, and X of the left and right Bunsen rings is placed at a symmetrical position with respect to Y) As described above, the present invention is based on the general formula (1) The main structure is to use the compound represented by the formula (5) and the compound represented by the general formula (■) in appropriate combination as a color developer.

Examples of the p-oxybenzoic acid ester represented by the general formula (I) include the following.

Examples of compounds represented by the general formula (■) include the formula Examples of the compounds shown are:

The compound represented by the general formula (I) used in the present invention has a melting point of 100 to 150°C and a high color developing ability, so 4,4'-isozolobylidene diphenol,
Compared to conventional color developers such as 4,4'-butylidenephenol, it has better thermal response and superior uniformity of colored images. The compound represented by general formula (II) has a much higher melting point than the color developing substance of formula (1) above, but when the two types are mixed together, they become eutectic, and the color developing substance of formula (I) has a eutectic effect. It is thought that the phenomenon of fading and whitening is prevented by preventing recrystallization.

Additionally, in general, when two or more color-developing substances are used in combination, the water solubility increases, the eutectic temperature becomes too low, and the fog of the heat-sensitive coating liquid increases, and the fog on the skin increases during storage. However, since the color developing substance represented by the above fID formula has low water solubility, such a problem does not occur.

In the present invention, the color developer consisting of the above combination is generally used in an amount of 1 to 10 parts by weight, preferably 2 to 6 parts by weight, per 1 part by weight of the leuco dye. Further, the weight ratio of the color developing substance represented by the general formula (■) and the color developing substance represented by the general formula (II) is 1:1 to 10:1.
The ratio is preferably 2:1 to 5:1. Furthermore, a conventionally known phenolic acidic substance may be added if necessary.

The heat-sensitive recording material of the present invention can have various structures, including all conventionally known structures that utilize a color-forming reaction between a leuco dye and a color developer. For example, the heat-sensitive recording material of the present invention includes a heat-sensitive recording material having a structure in which a leuco dye and a color developer are supported on a support as the same coating layer or separate coating layers, or a leuco dye layer and a color developer. In addition to heat-sensitive recording materials with a structure in which an intermediate layer is interposed between the two layers, heat-sensitive recording materials with a structure in which a protective layer is provided on the front or back side of the heat-sensitive coloring layer, there are also heat-sensitive recording materials with a structure in which a protective layer is provided on the front or back side of the heat-sensitive coloring layer, as well as heat-sensitive recording materials with a structure in which a protective layer is provided on the front or back side of the heat-sensitive coloring layer. It can be used as a thermal transfer type heat-sensitive recording material consisting of the formed transfer sheet and a receptor sheet supported on a support using a color developer as a receptor layer. In the case of thermal transfer type heat-sensitive recording materials, the receiving sheet is stacked on the transfer sheet so that its receiving layer is in contact with the transfer layer of the transfer sheet, and the receiving sheet is printed by thermal printing from the front or back side of the polymerized sheet. A desired colored image can be formed on the surface of the receptor layer. - The leuco dyes used in the present invention can be applied singly or in a mixture of two or more types, but such leuco dyes include:
Any dye that has been applied to this type of heat-sensitive material can be used, and for example, leuco compounds of triphenylmethane-based, fluoran-based, phenothiacune-based, auramine-based, and spiropyran-based dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3~bis(p-dimethylaminophenyl)-phthalyl, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthali 1? (also known as crystal violet lactone), 3.3-bis(p-)methylaminophenyl)-6-
Dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorphthalide, 3.3-bis(p-dibutylaminophenyl)phthalide
3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-, diethylamine-7-methylfluoran, 10 -3-,)ethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-(N-P-tolyl-N-ethylamino)-16-methyl-7 -anilinofluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 2-(N-(3'-toIJfluoromethylphenyl)amine)-6-diethylaminofluorane, 2-(
3,6-bis(diethylamino)-9-(0-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamine-
? -(o-chloroanilino)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-diethylamine-6
-Methyl-7-anilinofluorane, 3-(N,N-diethylamino)-5-methyl-7-(
N, N-J benzylamino)fluoran) pensoylleucomethylene blue, 6'-chloro-87-medoxybenzoindolino-pyrylospirane, 6'-zolomo3'-methoxy-benzoindolino-pyrylosvirane, 3-(2 '-Hiroxy4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)
Phthalide, 3-(2'-Hyproxy-47-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthali r1 a (2/-hydroxy-47-ethylaminophenyl )-3-(2'-methoxy-57-methylphenyl)7talide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-
methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluoran, 3 e o IJ , -) 7-7-dolifluoromethylanilinofluoran, 3-diethylamino-5-chloro- 7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylmethylamino ) fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 13-3-diethylamino-7-(o-methoxycarzenylphenylamino)fluoran, 3-diethylamino-5 -Methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluorane 1 2-chloro-3-(N-methyltoluidino)-7-(p
-n-butylanilino)fluoran, 3-(N-benzyl-cyclohexylamino)-5,6-penzo7-
α-Naphthylamino-47-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
7, 5/-benzofluorane, etc. These may be used alone or in combination of two or more.

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, methoxycellulose, hydroxyl, etc. Ethyl cellulose, cardixymethyl cellulose, methyl cellulose, -14 = cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide/
Acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, inzotylene/
In addition to water-soluble polymers such as maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymers, polyacrylic acid, polyacrylic acid esters, and chloride Vinyl/vinyl acetate copolymer, polydityl methacrylate, ethylene/vinyl acetate copolymer,
A latex such as styrene/citadiene/acrylic copolymer can be 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 carbonate and silica. In addition, organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned, and 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,
Examples include other thermofusible organic compounds having a melting point of about 50 to 200°C.

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

〔effect〕

Since the heat-sensitive recording material of the present invention uses a mixture of compounds represented by general formulas (1) and (II) as a color developer, fading and whitening of recorded images are extremely less compared to conventional ones. , and has excellent thermal sensitivity, high color development, and high image 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.

Example 1 [Liquid A] Hung 10% polyvinyl alcohol aqueous solution 300 parts Water 40
0 parts [Liquid B] Benzyl p-hydroxybenzoate 150 parts 17- Calcium carbonate 100 parts 10% polyvinyl alcohol aqueous solution 20 parts water
500 parts of the mixtures having the above compositions were each pulverized and dispersed in a magnetic ball mill for one day to prepare liquids A and B.

Next, liquid A and liquid B were mixed and stirred so that the weight ratio was A:B=1:8 to prepare a heat-sensitive coating liquid. 7m2 (
After drying, the coating amount is 5? /m2 using a wire parser. These coated papers were calendered to a smoothness of 700 to 1200 seconds to prepare heat-sensitive recording sheets of the present invention.

Example 2 In Example 1, 2,2-bis(3,5-dibromo-4- A heat-sensitive recording sheet of the present invention was prepared in exactly the same manner except that hydroxyphenyl)propane was used.

Comparative Example 1 Liquid [B] 2, 2', 6, 6 in Example 1
'-tetrazo18-como-4,4'-sulfonyldiphenol,! A comparative heat-sensitive recording sheet was prepared in the same manner as in Example 1 except that benol p-hydroxybenzoate was used.

Comparative Example 2 A mixture consisting of the following formulation was pulverized and dispersed in a magnetic ball mill for one day to prepare liquid [C].

[Liquid C]

Bisphenol Al 50 parts Amino stearate P 75 // Calcium carbonate 10011 10% polyvinyl alcohol aqueous solution 200 // Water
475〃
Next, a heat-sensitive recording sheet of Comparative Example 2 was prepared in the same manner as in Example 1 except that Liquid [C] was used in place of Liquid [B] of Example 1.

The above heat-sensitive recording sheets were tested for fading and whitening of dynamic color sensitivity images. The results are shown in Table 1. The test method was performed as follows.

(1) Dynamic coloring sensitivity: Using a thermal printing experimental device equipped with a thin film spatula P manufactured by Kishita Electronics Co., Ltd., the spatula P power was 0.45.
W/)” dot, 1 line recording time 20m5/11 scanning line density 8X 3.85 dots/key, pulse width 1
．． 0, 1.2, 1.4, 1.6, 1.8.

Printing was performed at 2.0 m5ec, and 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), those with a print density of 1.0 to 1.2 (this is Do) the density after being left at room temperature for 15 days. (to be measured and designated as D), and the concentration reduction rate was determined according to the following formula.

J).

(3Wml1mhi...) The same test as in (2) was conducted, and the judgment was made visually as shown below.

21- As can be seen from Table 1, the thermal recording sheet of the present invention has higher dynamic sensitivity than the conventional one using bisphenol A/stearamide system (Comparative Example 2), and also has p-hydroxybenzoic acid. It was confirmed that the fading resistance and whitening of the image were improved compared to the one in which only one was used (Comparative Example 1).

Patent applicant Ricoh Co., Ltd. Agent Patent Attorney Toshiaki Ikeura 22-

Claims (1)

[Claims] (1) In a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer, the developer is a p-hydroxybenzoic acid ester represented by the following general formula (T) and a p-hydroxybenzoic acid ester represented by the following general formula (II). ) A heat-sensitive recording material characterized by using a combination with a bisphenol derivative represented by: (In the formula, R1 represents hydrogen or an alkyl group having 1 to 3 carbon atoms) mXm (In the formula, X is a halogen, Y is -8O2- or 0 (OH
3) 2-1m is represented by 1 or 2, and X of the left and right benzene rings is substituted in a symmetrical position with respect to Y)