JPS6233674A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To make the high speed recording possible by sufficiently raising the density of coloration and the sensitivity of coloration and further to increase the degree of the ground whiteness, by jointly using specific aromatic disulfide compound as an anxiliary component with materials having leuco dye and its developer. CONSTITUTION:In the heat sensitive recording material utilizing the colorating reaction of leuco bye and developer, the aromatic disulfide compound expressed by formula (1) is used as an auxiliary component. In the formula (1), R<1> and R<2> represent alkylene group and ring A and ring B represent the aromatic nucleus which may have substituting group. This aromatic disulfide compound has high performance to dissolve developer and leuco bye when heated. If the fusing point of said compound is regulated, the heat sensitive recording material of an optional sensitivity can be obtained. The amounts of leuco dye, developer, and auxiliary component to be used should respectively be 5-40wt%, 20-60wt%, and 20-60wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent color development.

[Prior art]

General heat-sensitive recording materials are coated on a support such as paper or film, and contain a colorless or light-colored dye such as a leuco dye as a color former, and a phenolic compound (particularly bisphenol A) as a color developer to make the color develop when heated. For example, a heat-sensitive coloring layer is provided in which a coloring system made of an acidic substance such as an organic acid is further dispersed with a binder, a filler, a sensitivity improver, a lubricant, and other auxiliary agents.

Special Publication No. 43-4160, Special Publication No. 45-14039,
It was introduced in Japanese Patent Application Laid-Open No. 48-27736 and has been widely used in practice. This type of thermal recording sheet produces a colored image through an instantaneous chemical reaction between a coloring agent and a color developer during heating (a thermal printer or facsimile machine with a built-in thermal head is used for heating). Compared to other recording materials, records can be obtained in a short time using a relatively simple device without the need for complicated processing such as development and fixing, and there is less noise and environmental pollution, and the cost is low. Due to its low price, it is used not only for copying books and documents, but also as a recording material for various information and measuring instruments such as electronic computers, facsimiles, telex machines, and medical measuring instruments.

On the other hand, in recent years, along with the development of society, there has been an increasing demand for higher speed and higher density recording. For this reason, there is a strong desire not only to increase the speed of the recording apparatus itself, but also to develop recording materials that can be used for this purpose. The first method is to lower the melting point of the electron-accepting compound used as the color developer to a practically acceptable level (for example, 80 to 120°C), and lower the melting point with the leuco dye. The objective is to reduce the speed and speed up the process.

However, it is difficult to control the melting point of phenolic compounds, which are color developers that are currently widely used in the field of heat-sensitive recording materials, and the phenolic compounds themselves are expensive, making them impractical. As the second method, for example, JP-A-53-39139, JP-A-53-2
No. 6139, JP-A-53-5636, JP-A-53-1
As described in Japanese Patent No. 1036, heat-melting substances with low melting points such as various waxes, fatty acid amides, alkylated biphenyls, substituted biphenylalkanes, coumarins, and diphenylamines are added to the heat-sensitive coloring layer as a sensitizer ( Alternatively, there is a method of adding it as a melting point depressant). However, the heat-sensitive recording materials produced based on these methods are still not sufficient in terms of color density, color sensitivity, background whiteness, etc.

〔the purpose〕

The objects of the present invention are to have sufficient color density and color development sensitivity, to be suitable for high-speed recording, and to have high background whiteness.

It is an object of the present invention to provide a heat-sensitive recording material with extremely high practicality.

〔composition〕

The heat-sensitive recording material of the present invention is a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer, and uses an aromatic disulfide compound represented by the following general formula (1) as an auxiliary component.

In the above formula, R1 and RZ represent an alkylene group, and the radical and ring B represent an aromatic nucleus which may have a substituent.

In this case, the aromatic nucleus includes a benzene nucleus and a naphthalene nucleus, and its substituents include an alkyl group, an aralkyl group, and an aryl group.

Examples include an alkoxy group, an aryloxy group, an acyl group, an acyloxy group, and a halogen atom.

The aromatic disulfide compound represented by the general formula (1) used in combination as an auxiliary component in the present invention is a widely used color developer (electron-accepting compound) and leuco dye (electron-donating colorless dye). By adjusting the melting point of the aromatic disulfide compound of general formula (1) that has a high dissolving ability and is used in combination, a heat-sensitive recording material with arbitrary sensitivity can be obtained.

The aromatic disulfide compound of the general formula (1) used in the present invention preferably has a melting point of 40 to 150°C, particularly 50°C from the viewpoint of storage stability and sensitivity as a heat-sensitive recording material.
-120 degreeC is preferable. Specific examples of the compound of general formula (1) used in the present invention are shown below, but the present invention is not limited to these.

Compound No. Structural Formula The leuco dyes used in the present invention may be applied alone or in a mixture of two or more types, but such leuco dyes include:
Those applied to this type of heat-sensitive material can be arbitrarily applied. 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-diethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p-dimethyl aminophenyl)-6-diethylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide.

3.3-bis(p-dibutylaminophenyl)phthalide, 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-ditylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane.

2- (N-(3'-trifluoromethylphenyl)
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-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-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'- 3-(2'-hydroxy-4'-dimethylaminophenyl)-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)fluorane, 3-pyrrolidino-7-(di-ρ-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane, 3- (N-ethyl-P-)-luidino)-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)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

As the color developer used in the present invention, various electron-accepting compounds, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids and metal salts thereof, are preferably used, and the specific examples thereof are as follows. Give an example.

4.4'-isopropylidene bisphenol, 4.4
' -Isopropylidene bis(0-methylphenol) 4.4' -Secondary butylidene bisphenol 4.4' -Isopropylidene bis(2-tertiary-
butylphenol), 4.4'-cyclohexylidene diphenol, 4.4
′ -isopropylidene bis(2-chlorophenol)
, 2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4.4'-butylidenebis(6-tert-butyl- 2-methyl)phenol, 4,4'-thiobis(6-tert-butyl-2-
methyl) phenol, 4.4'-diphenolsulfone, 4.4'-diphenol sulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoates, benzyl protocatechuate, stearyl gallate, lauryl gallate, Octyl gallate, 1,7-bis(4-hydroxyphenylthio)-3,5
-Dioxahebutane, 1.5-bis(4-hydroxyphenylthio)-3-oxapentane, ■, 3-bis(4-hydroxyphenylthio)-propane, 1.3-bis(4-hydroxyphenylthio) -2-hydroxypropane N,N'-diphenylthiourea, N,N'-di(m-chlorophenyl)thiourea, salicylanilide, 5-chloro-salicylanilide.

salicyl-〇-chloroanilide, 2-hydroxy-3-naphthoic acid, 2-Hydroxy-1-naphthoic acid.

1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum, calcium, etc.

In the present invention, the leuco dye, color developer, and auxiliary components are bonded and supported on a support.

Various conventional binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolitone, and acrylic acid. Amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, In addition to water-soluble polymers such as sodium alginate, gelatin, and casein,
Polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic ester,
Latex such as vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. can be used.

In addition, in the present invention, in addition to the leuco dye, color developer, and auxiliary components, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material may be added.

For example, fillers, surfactants, thermofusible substances (or lubricants)
etc. can be used together. In this case, the filler is
For example, calcium carbonate, silica.

In addition to inorganic fine powders such as zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated calcium and silica, urea-polymarine resin, styrene/methacrylic acid copolymer, Examples include organic fine powder such as polystyrene resin.

The heat-sensitive recording material of the present invention is 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 the coated liquid. In this case, the amounts of leuco dye, color developer, and auxiliary components used are 5 to 40% by weight and 20 to 60% by weight, respectively.
% by weight, 20-60% by weight is suitable.

〔effect〕

The heat-sensitive recording material of the present invention has improved sensitivity, is suitable for high-speed recording, and has a high background whiteness, and is extremely practical.6 [Example] Next, the present invention will be described in an example. This will be explained in more detail below. Note that all parts and percentages shown below are based on weight.

Example 1 [Liquid A] 3-(N-methyl-N-cyclohequinolamino)-6-
Methyl-7-anirite fluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts Water
60 [Liquid B] Bisphenol A 20 parts 10% aqueous solution of hydroxyethylcellulose 20 Water
601! [Liquid C] 20 parts of dibenzyl disulfide (compound specific example No. 1, melting point 71-72°C) 5% aqueous solution of methylcellulose 20 parts water
60〃[D
Liquid] Calcium carbonate 20 parts Methyl cellulose 5% aqueous solution W 2011 water
6Q
u Next, add 10 parts of liquid A, 30 parts of liquid B, 30 parts of liquid C, and 20 parts of liquid D.
part and 20% of isobutylene-maleic anhydride copolymer
After mixing 10 parts of an alkaline aqueous solution to form a thermosensitive coloring layer forming solution, this was applied onto high-quality paper with a basis weight of 50 g/rrr so that the dry adhesion amount was 4 to 5 g/rd, and was dried to form a thermosensitive coloring layer. , the layer surface is further calendered to have a surface smoothness of 500 to 600 seconds to obtain a heat-sensitive recording material (a).
It was created.

Example 2 Heat-sensitive recording material (b) was prepared in the same manner as in Example 1 except that the following (El liquid) was used instead of the CBl liquid in Example 1.
It was created.

[E liquid]

P-hydroxybenzoic acid benzyl ester 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts Water
60II Example 3 Thermal recording material (C) was prepared in the same manner as in Example 1 except that the following liquid [F] was used instead of the CB) liquid in Example 1.
It was created.

[F liquid]

1,7-bis(4-hydroxyphenylthio)-3,5
-Dioxahebutane 20 parts 10% aqueous solution of hydroxyethylcellulose 20 parts water
60! ! Comparative Example 1 Example 1 except that water was used instead of liquid (C) in Example 1.
A thermosensitive recording material (d) was prepared in the same manner as above.

Comparative Example 2 A heat-sensitive recording material (e) was prepared in the same manner as in Example 1 except that water was used instead of liquid (C) in Example 2.

Comparative Example 3 A heat-sensitive recording material (f) was prepared in the same manner as in Example 3 except that water was used instead of liquid (C) in Example 3.

Comparative Example 4 A heat-sensitive recording material (g) was prepared in the same manner as in Example 1, except that the following liquid CG) was used instead of liquid [C] in Example 1.

[G liquid]

Stearic acid amide 20 parts Methyl cellulose 0.5% aqueous solution 201! water
6
0 Comparative Example 5 A heat-sensitive recording material (h) was prepared in the same manner as in Example 2, except that the liquid (G) was used instead of the liquid (C) in Example 2.

Comparative Example 6 A thermosensitive recording material (i) was obtained in the same manner as in Example 3, except that the liquid CG) was used instead of liquid [C] in Example 3.

The heat-sensitive recording materials (a) to (i) obtained as described above are
Using a thermal printing experimental device with a thin film head manufactured by Matsushita Electronic Components Co., Ltd., the head power was 0.45 W/dot, the recording time per line was 20 m5ec/Q, and the scanning line density was 8 x 3.85.
Tod/-1 condition with pulse width of 1.6.2.0.2.
4 (msec), and the print density was measured using a Macbeth densitometer RD-514 (filter W-106).

The results are shown in Table-1.

Table 1 Next, heat-sensitive recording materials (a) to (i) were subjected to a 24-hour storage test under dry conditions at 60° C., and changes in skin density were examined. The results are shown in Table-2.

Table-2 Procedures Amendment Written on July 77, 1985 Mr. Michibe Uga, Commissioner of the Patent Office ■, Indication of the case Patent Application No. 172640 of 1985 2, Name of the invention Thermal recording material 3, Person making the amendment Relationship to the incident Patent applicant address: 1-3-6 Nakamagome, Ota-ku, Tokyo Name
(674) Ricoh Co., Ltd. - Representative Hama 1) Hiro 4, Agent 〒151 Address 1-58-10-5 Yoyogi, Shibuya-ku, Tokyo
Date of amendment order: 6, Number of inventions increased by amendment: 07, Detailed explanation of the invention in the specification subject to amendment, column 8, Contents of amendment: The following amendments will be made in the specification of the application.

(1) General formula (I) on page 4, line 14 is corrected as follows.

Claims (1)

[Claims] (1) In a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and its color developer, the general formula (
I) ▲Mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R^1 and R^2 represent alkylene groups, and ring A and ring B are aromatic nuclei that may have substituents. A heat-sensitive recording material characterized in that an aromatic disulfide compound represented by the following formula is used in combination.