JPS60260385A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having high sensitivity and less liable to fading or flushing of recorded images, by using an appropriate combination of two specified bisphenols as a color developer, in a thermal recording material using a leuco dye. CONSTITUTION:A compound of formula I, wherein n is 1 or 2, and a compound of formula II, wherein each of R1-R6 is hydrogen or 1-7C alkyl, are combined with each other in a weight ratio of 1:1-1:10, and the combination is used in an amount of 1-10pts.wt. per 1pt.wt. of a leuco dye to produce a thermal recording material. If required, a known phenolic acidic substance is added. The thermal recording material may have any of various constructions such as a construction wherein a leuco dye and a color developer are provided in the same coated layer or separate coated layers on a base and a construction wherein an intermediate layer is provided between a leuco dye layer and a color developer layer. A usual binder for forming the layers and additives are used, as required.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a heat-sensitive recording material, and more specifically, a leuco dye that is colorless or slightly pale at room temperature, and a color developer that develops color by reacting with the leuco dye when heated. This invention relates to an improvement in a heat-sensitive recording material in which a heat-sensitive coloring layer containing as a main 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 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 obtained recording material is similar to that of plain paper.
It is widely used in the fields of computer output, printers such as 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 manufactured by coating and drying a heat-sensitive coloring layer solution containing a coloring component that can cause a coloring reaction when heated, on a support such as ordinary paper, synthetic paper, or 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, Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-14039.
For example, such conventional heat-sensitive recording materials have low thermal responsiveness and cannot obtain sufficient color density during high-speed recording. As a method for improving such drawbacks, for example, Japanese Patent Laid-Open No. 49-38
No. 424, published by Acetamide, Stearoamide,
Nitrogen-containing compounds such as nitroaniline and dinitrile phthalate, acetoacetanilide in JP-A-52-106746, and N,N in JP-A-53-11036.
- diphenylamine derivatives, benzamide derivatives, and carbazole derivatives; JP-A-53-39139 discloses alkylated biphenyls and biphenylalkanes; JP-A-56-144193 discloses P-oxybenzoic acid ester derivatives, respectively. A method of increasing speed and sensitivity by including P-hydroxybenzoate as a color developer has been disclosed, and among these, the use of P-hydroxybenzoic acid ester as a color developer has been known as an effective method.

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〕

The present invention provides a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer, in which at least one compound of the following general formulas (I) and (II) is used as the color developer. This is a heat-sensitive recording material characterized by using.

(In the formula, n represents 1 or 2) (In the formula, R□ to R6 represent hydrogen or an alkyl group of 01 to C7) The main structure thereof is to use a compound represented by general formula (II) in appropriate combination as a color developer.

Examples of the compound represented by the general formula (I) include the following.

Specific examples of the compound represented by general formula (II) include:
Examples include those shown below.

2.2'-methylenebis-(4-methyl-6-t-butylphenol), 4.4'-isopropylidenediphenol, 4.4'
- Cyclohexylizonediphenol, 4.4' -
butylidene bis(6-L-butyl-m-cresol) and the like.

As described above, the bisphenol compound represented by the general formula (I) is used as one of the color developer components. It has higher thermal responsiveness than conventional color developers such as phenol and 4,4'-butylidene diphenol, and also has excellent uniformity of colored images. On the other hand, when the bisphenol compound represented by the general formula (n) used as the other color developer component is eutectic with the bisphenol compound of the general formula (1), it prevents recrystallization in the coloring part and causes the color to fade. This is thought to prevent image deterioration caused by development, such as whitening.

Additionally, in general, when two or more types of color developers are used in combination, the water solubility increases or the eutectic temperature becomes too low, resulting in increased fogging of the heat-sensitive coating liquid. Since the color developer 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 developer represented by general formulas (I) and (I[) is preferably 1:1 to 10:1, preferably 2:1 to 5:1. . Furthermore, a conventionally known phenolic acidic substance can be added as required.

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 a thermal transfer type thermal recording material, a receiving sheet is placed over the transfer sheet so that the receiving layer is in contact with the transfer layer of the transfer sheet,
A desired colored image can be formed on the receiving layer surface of the receiving sheet by thermally printing from the front or back side of the polymeric sheet.

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:
Any dye that has been applied to this type of heat-sensitive material may be used. For example, leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes are preferably used. Specific examples of such leuco dyes include those shown below. i 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-dibutylaminophenyl, 3.3- Bis(P-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethyl Fluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane.

3-diethylamino-7,8-benzfluorane, 3-
Diethylamino-6-methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ditylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilino Fluorane, 2-(N-(3'-trifluoromethylferlene)
amino)-6-ethylaminofluorane, 2-(3
, 6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-)-lichloromethylanilino)fluoran, 3-diethylamino-7- (0-Chloranilino)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) fluorane, Benzoylleucomethylene blue.

6'-Chloro-8'-methoxy-benzoindolino-pyrillospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrillospirane.

3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-'(2'-hydroxy-4'-dimethylaminophenyl)-3 -(2'-Methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-47-dimethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2 '-M-1-x-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)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3 -(N-ethyl-P-toluidino)-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-(O-methoxycarbonylphenylamino 3-diethylamino-5-methyl-7-(α-phenylethyl amino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-,
n-butylanilino)fluoran, 3-(N-benzyl-N-cyclohexylamino)-5
・6-penzo7-・-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, methoxycellulose, hydroxyl, etc. Ethyl cellulose.

Cellulose derivatives such as carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acryl amide/acrylic ester/methacrylic acid ternary copolymer, styrene /
In addition to water-soluble polymers such as maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, polyvinyl acetate, polyurethane, styrene/
Uses latex such as butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acid copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene l-acrylic copolymer, etc. be able to.

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, amide metals, etc. In addition to salts, 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 thermoplastics. Examples include those having a melting temperature of about 50 to 200°C, such as fusible organic compounds.

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〕

The heat-sensitive recording material of the present invention has general formula (1) and general formula (I
Since the combination with the compound represented by I) is used as a color developer, compared to conventional ones, there is extremely little fading or whitening of the recorded image, and it also has excellent thermal sensitivity, exhibits high color development, and improves image reliability. is high.

Example 1 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.

[Liquid A] 3-N-methyl-3-N-cyclohexylamino-6-
Methyl-7-anilinofluorane 300 parts 10% polyvinyl alcohol aqueous solution 300 parts Water 40
0 parts [Liquid B] 2.2'-methylenebis-(4-methyl-6-7-butylphenoful) 100 parts 10% polyvinyl alcohol aqueous solution 200 parts Water 50
0 parts of each of the mixtures having the above composition in a magnetic ball mill.
Liquids A and B were prepared by pulverization and dispersion for several days.

Next, a heat-sensitive coating liquid was prepared by mixing and stirring the A liquid and the B liquid so that the weight ratio was A:B=18, and the heat-sensitive coating liquid was prepared at 50 g/rrf (
It was coated with a wire bar on commercially available high-quality paper with a dry basis weight of 5 g/rrr. These coated papers were subjected to gear rendering to obtain a smoothness of 700 to 1200 seconds to prepare heat-sensitive recording sheets of the present invention. 1 Example 2 Same as Example 1 except that 4,4'-isopropylidendylphenol was used instead of 2,2'-methylenebis-(4-methyl-6-t-butylphenol) in cB solution]. A heat-sensitive recording sheet of the present invention was prepared.

Comparative Example 1 2,2′-methylenebis-(
A heat-sensitive recording sheet for comparison was prepared in the same manner as in Example 1 except that 4-methyl-6-butylphenol was used.

Comparative Example 2 Next, the mixture consisting of the formulations was pulverized and dispersed in a magnetic ball mill for one day to prepare a cC liquid.

[Liquid C]

Bisphenol A 150 parts Stearamide 75 parts Calcium carbonate 100 parts 10% polyvinyl alcohol aqueous solution 200 parts Water 47
5 parts Next, a heat-sensitive recording sheet of Comparative Example 2 was prepared in the same manner as in Example 1 using [Liquid C] 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: head power 0.451/cm using a thermal printing experimental device with a thin film head made of dropped electronic components.
Dots, 1 line recording time 20m5lj&, pulse width 1 under conditions of scanning line density 8 x 3.85 dots/mm
．． 0, 1.2, 1.4, 1.6° 1.8, 2. On+s
Printed with EC, and the print density was measured using Macbeth Densitometer RD-5.
14 (filter υ-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. was measured and designated as D), and the concentration reduction rate was calculated according to the following formula.

(3) Image whitening: The same test as in (2) was conducted, and the results were visually determined as shown below.

0: Almost no white powder is generated Δ: White powder is generated, but there is no practical problem The dynamic sensitivity is higher than that using bisphenol A/stearamide system (Comparative Example 2), and the general formula (1
) It was confirmed that the fading resistance and whitening of the image were improved compared to the one using only the bisphenol compound (Comparative Example 1).

Patent Applicant Ricoh Co., Ltd. - Attorney Toshiaki Ikeura Proceedings Amendment Document Date of February 1982 Patent Case 16 Indication of Patent Application No. 116917 No. 26 of 1982 Name of Invention Thermal Recording Material 3, Amendment Relationship with the case involving the patent applicant Address: 1-3-6 Nakamagome, Ota-ku, Tokyo Name (
674) Rico Co., Ltd. - Representative Hama 1) Hiro 4, Agent 〒151 Address 1-58-10-5 Yoyogi, Shibuya-ku, Tokyo Date of amendment order Voluntary 6 Number of inventions increased by amendment 0 7. Subject of correction.

Detailed description of the invention in the specification 8. Contents of amendment The following amendments have been made to the specification of this application.

(1) Table 1 on page 20 is corrected as follows.

Mouth Table-1

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 color developer may be of the following general formula (
A heat-sensitive recording material comprising at least one of the compounds represented by I) and (II). (In the formula, n represents 1 or 2) (In the formula, R1 to R6 represent hydrogen or an alkyl group having 1 to 7 carbon atoms)