JPH03120088A - Thermal recording material - Google Patents

Abstract

PURPOSE:To achieve improvement of suitability for high speed recording and stability for preservation by a method wherein specified bisphenols are used as a developer. CONSTITUTION:Bisphenols as represented by the formula I are used as a developer. In the formula I, X represents single bond, -O-, -S-, -SO-, -SO2-, etc., R<1> and R<2> respectively independently represent halogen atom, 1-6C alkyl group or 6-12C aryl group, and m and n respectively independently represent 0 or 1-3 integer. Thereby, a thermal recording material which is excellent in suitability for high speed recording and excellent in stability for preservation can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a heat-sensitive recording medium, and more specifically, it has excellent high-speed recording performance and storage stability, and is used, for example, in medicine, measurement, etc. field, printer field, image communication field represented by facsimiles, point of sale system (PO
The present invention relates to a heat-sensitive recording material that can be advantageously used as various heat-sensitive recording papers or media in all fields such as the label field represented by 3).

[Conventional technology]

In recent years, with the progress of the information society, the demand for information recording paper used for equipment in all fields that involves recording, including office automation equipment, has been rapidly expanding. printer,
Among various recording systems such as facsimile machines, a thermal recording system using leuco dye-based thermal recording paper is attracting particular attention.

This leuco dye-based thermal recording paper was developed in the US in 1968 by
Developed by Company R, it utilizes a color-forming reaction between a colorless leuco dye (color-forming substance) and a certain phenolic compound (color-developing agent) by heating, and all you have to do is heat it with a thermal head, etc. This is a recording paper that develops color with primary color development and provides non-impact recording.

The main applications are medical, measurement, printer,
These include the image communication field and the label field.

Among these, the field of image communication represented by facsimile,
The label field, represented by OS, is experiencing particularly large growth.

The recording characteristics required of thermal recording paper vary depending on the use, but generally speaking, whether or not it is suitable for high-speed recording is important. In other words, in order to increase the recording speed, it is necessary to improve the recording device and improve the color development of the recording paper itself.
In order to improve this color development, the selection of the color developer is particularly important.
In recent years, there has been a demand for the development of thermal recording paper in this direction.

Bisphenol A has been commonly used as a color developer since ancient times. However, bisphenol A has a melting point of 57 months.
°C, and its color development sensitivity to heat is low, making it unsuitable for high-speed recording as it is.

Therefore, in order to improve this problem, methods of adding various sensitizers to bisphenol A have been proposed.

However, this method has the disadvantage that the configuration is complicated, and a method that is sufficiently effective has not yet appeared.

Furthermore, in order to improve suitability for high-speed recording, many methods have been proposed in which a color developer with a lower melting point is used.

Among these, p-hydroxybenzoic acid ester (Japanese Patent Application Laid-Open No. 56144, 193
4-hydroxyphthalic acid diester (Japanese Unexamined Patent Publication No. 153692/1982). However, when these substances are used as color developers, serious problems arise in that the resulting images are significantly discolored and have poor storage stability.

Therefore, attempts have been made to add antioxidants and the like to suppress this discoloration. However, the effect is insufficient, and no product with satisfactory storage stability has been obtained.

Furthermore, relatively recently, a method using 2-(4-hydroxyphenyl)-2-(3'-hydroxyphenyl)propane as a color developer has been proposed (Japanese Unexamined Patent Publication No. 63-27290). However, although this conventional heat-sensitive recording material is said to be excellent in suitability for high-speed recording, it cannot be said that it fully satisfies suitability for high-speed recording because the melting point of the color developer compound is rather high.

In addition, some use halogen-substituted bisphenol alkanes as color developers, but these have problems such as still low color development sensitivity and insufficient suitability for high-speed recording.

As described above, none of the conventional heat-sensitive recording materials satisfies both the color development sensitivity, that is, the suitability for high-speed recording, and the storage stability of the obtained images.

[Problem to be solved by the invention]

The present invention has been made in view of the above circumstances.

An object of the present invention is to provide a heat-sensitive recording material which has excellent characteristics such as excellent color development sensitivity and extremely little fading of images, and is therefore extremely advantageous in practice, satisfying both high-speed recording performance and storage stability. It's about doing.

[Means to solve the problem]

As a result of extensive research to achieve the above object, the present inventors have found that by using bisphenols having a specific chemical structure as a color developer, the above object can be satisfied, and the resulting images can be made more robust. In addition to the extremely high whiteness of the recording body itself, it is possible to increase the contrast with the image, and furthermore, it is possible to obtain a thermal recording body that has excellent features and effects such as less adhesion of residue to the thermal head. The present invention was completed based on this finding.

That is, the present invention provides a heat-sensitive recording material having a heat-sensitive recording layer containing a color-forming substance that is usually colorless or light-colored and a color developer that causes the color-forming substance to develop color when heated. , in the formula, χ is a single bond, -O--S-3 warm 5O-1-SO2--C- (R3 and R4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or Carbon number 6
~12 aryl groups are shown. ), JCtl z”fr
(P represents an integer of 2 to 10.), (q represents 4 to I
Indicates an integer of O. ), R' and R2 each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 96 to 12 carbon atoms, and m and n each independently represent 0 or Indicates an integer from 1 to 3. ] The present invention provides a heat-sensitive recording material characterized by using bisphenols represented by the following.

In the present invention, bisphenols having a specific chemical structure represented by the above-mentioned maximum (T) are used as color developers (hereinafter, these may be referred to as bisphenols [■]).
One or more of these are used.

In the above-maximum [1], R1, R2, R3 and R4
may be an alkyl group having 1 to 6 carbon atoms, and specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, 5ec
-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, isohexyl group, neohexyl group, cyclopentyl group, methylcyclopentyl group, cyclopentylmethyl group,
Examples include cyclohexyl group.

In the above-maximum [1], R1, RZ, R3 and R4
may be an aryl group having 6 to 12 carbon atoms, and specific examples of the aryl group include, for example, phenyl group,
2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, various xylyl groups, various ethylphenyl groups, various trimethylphenyl groups, various ethylmethylphenyl groups, various propylphenyl groups, various Isopropylphenyl group, various tetramethylphenyl groups, various methylpropylphenyl groups, various methylisopropylphenyl groups, various butylphenyl groups, various 5ec-butylphenyl groups, various terL-butylphenyl groups, various pentyl groups Examples include phenyl group and various hexylphenyl groups.

In (-maximum CI) above, R1 and R2 may be halogen atoms, and specific examples of the halogen atoms include fluorine atom, chlorine atom, bromine atom, and iodine atom. Among these various halogen atoms, chlorine atoms are particularly preferred.

In the above-maximum [I], m and n are each independently,
It is 0 or an integer from 1 to 3, and preferably m and n are both O or 1, particularly preferably m=n=Q.

Specific examples of the bisphenol [1) include, for example,
2.2-bis(3-phenyl-4-hydroxyphenyl)propane, 1-phenyl-1゜1-bis(3-phenyl-4-hydroxyphenyl)ethane, 1,1-bis(
3-phenyl-4-hydroxyphenyl)cyclohexane, 3,3-bis(3-phenyl-4-hydroxyphenyl)pentane, bis(3-phenyl-4-hydroxyphenyl)sulfone, 3,3'-diphenyl-4° 4′
-dihydroxybiphenyl, bis(3-phenyl-4-
hydroxyphenyl)methane, 1-fuynyru-1,1-
Bis(3-phenyl-4-hydroxyphenyl)methane, 1.1-bis(3-phenyl-4-hydroxyphenyl)ethane, 12-bis(3-phenyl-4-hydroxyphenyl)ethane, 1.3-bis (3-phenyl-4
hydroxyphenyl)propane, 2,2-bis(3-phenyl-4-hydroxyphenyl)butane, 1,4-bis(3-phenyl-4-hydroxyphenyl)butane,
1,1-bis(3-phenyl-4-hydroxyphenyl)-1-phenylbutane, 2,2-bis(3-phenyl-4-hydroxyphenyl)octane, 1,8-bis(
3-phenyl-4-hydroxyphenyl) octane, bis(3-phenyl-4-hydroxyphenyl) ether, bis(3-phenyl-4-hydroxyphenyl) sulfide, 1.1-bis(3-phenyl-4-hydroxy) phenyl)cyclopenkune, 2,2-bis(3-phenyl-4-hydroxy-5-methylphenyl)propane,
Examples include 22-bis(3-phenyl-4-hydroxy-5-chlorophenyl)propane. Among these, 2,2-bis(3-phenyl-4-
hydroxyphenyl)propane, 1-phenyl-1,I
-bis(3-phenyl-4-hydroxyphenyl)ethane, 1.1-bis(3-phenyl-4-hydroxyphenyl)cyclohexane, 3.3-bis(3-phenyl-
Preferred are 4-hydroxyphenyl)pentane, bis(3-phenyl-4-hydroxyphenyl)sulfone, and the like.

In addition, the above-mentioned various bisphenols I(I) may be used alone, or two or more types may be used in combination as a mixture or the like.

As the color-forming substance used in the present invention, any substance can be used as long as it is usually colorless or light-colored and can develop color by reacting with the color developer, that is, bisphenols (I). Although it is also possible to use leuco dye compounds (hereinafter sometimes referred to as leuco compounds).

) is preferably used.

The leuco compounds include triphenylmethane type, triphenylmethanephthalide type, fluoran type, leuco auramine type, diphenylmethane type, phenothiazine type,
There are various derivatives such as phenoxazine derivatives, spiropyran derivatives, indoline derivatives, and indigo derivatives, but they are not particularly limited and any of them can be used.

Specifically, for example, crystal violet lactone, 3-diethylamino-6-methyl-7anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3- diethylamino-
6-Methyl-7-anilinofluorane, 3-piperidino6-methyl-7-anilitofluorane, 3-(N
-cyclohexyl-N-methylamino)-6-methyl7
-anilinofluorane, 3-diethylamine-7-(o
-chloroanilino)fluoran, 3-diethylamino-
7-(m-)lifluoromethylanilino)fluorane,
3-diethylamino-6-methyl-chlorofluorane,
3-diethylamino-6-methylfluorane, 3-cyclohexylamino-6-chlorofluorane, 3-(N-
Examples include isoamyl-N-ethylamino)-6-methyl-7-anilinofluorane.

The above-mentioned various coloring substances may be used alone or in combination of two or more as a mixture.

The heat-sensitive recording layer of the swear record of the present invention includes at least the above-mentioned bisphenol! It is necessary to contain (I) and the color-forming substance.

The blending ratio of the bisphenol [component (1)] cannot be uniformly prescribed because it varies depending on the bisphenols [■] used and the type and combination of color-forming substances, but when using the above-mentioned leuco compound as a color-forming substance. For this purpose, the amount is usually 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, per 1 part by weight of the leuco compound component used.

If this ratio is too small, sufficient high-speed recording suitability will not be obtained, while if it is too large, the color development sensitivity will decrease.

In addition, in this invention, the said bisphenol (1) and other color developers can also be used together as a color developer.

The heat-sensitive recording layer of the heat-sensitive recording material of the present invention can be obtained by blending at least the bisphenols (1) and the color-forming substance, but these are usually dispersed in a binder according to a conventional method. Use it in a different way.

Various types of binders can be used as the binder, but
Normally, it is sufficient to select and apply the appropriate one from among conventionally known ones depending on the purpose and the like.

Specific examples of the binder include polyvinyl alcohol, casein, starch, modified starch, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, styrene-maleic anhydride copolymer and its alkaline solution, polyacrylamide, and styrene. −
Examples include butadiene copolymers, polyvinyl acetate, latexes of polyacrylic esters, gelatin, and Sierran.

In addition, the above-mentioned various binders may be used alone or in combination of two or more as a mixture or the like.

In order to improve recording characteristics, the heat-sensitive recording layer of the heat-sensitive recording material of the present invention contains an appropriate color accelerator in addition to the color-forming substance such as the leuco compound and the bisphenols (1) used as a color developer. It is preferable to use

Various types of color accelerators can be used, but usually one may be appropriately selected from conventionally known ones.

Examples of the color development accelerator include fatty acid amides such as stearamide, terephthalic acid esters, terephenyl, tribenzylamine, penzylmandonic acid, and parabenzylbiphenyl.

The various color development accelerators mentioned above may be used alone or in combination of two or more as a mixture.

By adding a storage stabilizer to the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, storage stability can be further improved.

Various types of storage stabilizers can be used, but usually one can be appropriately selected from conventionally known ones.

Specific examples of storage stabilizers that can be suitably used in the present invention include 4.4'butylidene-bis(3-methyl-6-t-butylphenol), 2.2'
-methylene-bis(4-methyl-6-t-butylphenol), 2,2'-methylene-bis(4-ethyl-6-t
-butylphenol L2,5-di-butylhydroquinone, 2,5-di-t-amylhydroquinone, bis(3
-methyl-4-hydroxy-5-t-butylbenzyl)
Sulfide, bis(3,3'-bis(4'-hydroxy-3'-L-butylphenol)-butyric acid) glycol ester, 4,4'-methylene-2,6-di-t-butylphenol, 2゜6-bis (2'-hydroxy-3'
-t-butyl-5-methylbenzyl)-4-methylphenol, 22'-iso-butylidene-bis(4,6-dimethylphenol), bis(2-(2-hydroxy-5
-methyl-3-t-butylbenzyl)-4methyl-6-
t-butylphenyl) terephthalate, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2-hydroxy-4-methoxy-21-carboxybenzophenone, tris(3,5-di-butyl-4-hydroxyphenyl) isocyanate , tris[β-(3,5-
di-L-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanate, 1. 35-trimethyl2.4.6-tris(3,5-di-t-butyl-4
-hydroxybenzyl)benzene, N,N'-hexamethylene-bis(3,5 di-t-butyl-4-hydroxy-hydrocinnamide), i, 1,3-1-lis(2-methyl-4-hydroxy-5 -t-butylphenyl)butane, 2,2'-dihydroxy-3,3'-di(α-methylcyclohexyl)-5,5'-dimethyl-diphenylmethane, and various phenolic resins.

The various storage stabilizers mentioned above may be used alone or in combination of two or more as a mixture.

In the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, if necessary,
Other additives, such as clay, calcium carbonate, aluminum hydroxide, talc, pigments such as titanium oxide, zinc oxide, waxes, various fatty acid metal salts to prevent stickiness, waterproofing agents to improve water resistance, It is possible to add surfactants and the like.

The heat-sensitive recording material of the present invention has the heat-sensitive recording layer provided on a substrate.

Various types of substrates can be used for the heat-sensitive recording material of the present invention, and the substrate can be selected as appropriate depending on the purpose, but generally, for example, wood-free paper, medium-quality paper, coated paper, etc. Various types of paper are used, including glass fiber sheets, plastic sheets, film laminated paper, non-woven fabrics, etc., can also be used as the substrate.

The method for producing the heat-sensitive recording material of the present invention is not particularly limited, and can be produced by any conventional method except for using the bisphenol M(1) as a color developer.

For example, the system containing the color-forming substance and the system containing the color developer are separately pulverized in an aqueous medium containing the binder, and then mixed to form a heat-sensitive composition paint, which is then applied to the substrate. The heat-sensitive recording material of the present invention can be obtained by coating or impregnating the material on the resin and drying it.

The heat-sensitive recording material of the present invention has sufficient suitability for high-speed recording, and has excellent storage stability after use, such as resistant to discoloration of the obtained image. It also has excellent stability.

In addition to the above, the heat-sensitive recording material of the present invention has high fastness of the obtained image, high whiteness of the recording material itself, and therefore can increase the contrast with the image, and furthermore, during use, It has excellent features such as less adhesion of debris to thermal heads, etc.

As described above, the thermal recording medium of the present invention is a thermal recording medium that is extremely excellent in practical use.
It can be advantageously used as various heat-sensitive recording papers or media in all fields such as the label field represented by PC)S.

[Function] The heat-sensitive recording material of the present invention has various excellent features as described above. Among these, the feature of satisfying high-speed recording suitability and storage stability at the same time is something that could not be fully achieved with conventional heat-sensitive recording materials. This could only be achieved by using bisphenols having a specific chemical structure, that is, bisphenols (i).

It is not clear at present why the above-mentioned superior features can be obtained by using this particular color developer, but among these, the reason for its superior suitability for high-speed recording is that
The inventor of the present invention thinks as follows.

That is, the color-forming substance in the heat-sensitive recording layer provided on the substrate by coating or the like is heated by a thermal head or the like during use, and at a temperature higher than the melting point of the coexisting color developer,
Since color is developed by reaction with a color developer, the lower the melting point of the compound used as the color developer, the greater the color development sensitivity to heating by a thermal head or the like. Bisphenol [(1) used in the present invention has basic characteristics as a color developer, has a relatively low melting point, and has high color development sensitivity.

For example, the melting point of 2,2-bis(3-phenyl-4-hydroxyphenyl)propane is 115°C, which is lower than that of bisphenol, which has been conventionally known as a color developer, and its color development sensitivity is extremely high.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following description, parts represent parts by weight.

Example I Solution A: 2-anilino-3-methyl-6-dinithylaminofluorane (ODB) 1 part polyvinyl alcohol 10% aqueous solution W 5 parts water
25 parts B liquid: 2,2-bis(3-
Phenyl-4-hydroxyphenyl)propane
4 parts kaolin 4 parts polyvinyl alcohol 10% aqueous solution 7 parts water
25 parts Liquids A and B prepared to have the above composition were each separately ground and dispersed in a ball mill for 48 hours, and then mixed to obtain a coating liquid for heat-sensitive recording. This coating liquid was applied to the surface of high-quality paper so that the dry coating amount was 5 g/n, and then dried to obtain a heat-sensitive recording material.

Example 2 2,2-bis(3-phenyl-
A thermosensitive recording material was prepared in the same manner as in Example 1, except that the same amount of 1-phenyl-1,1-bis(3-phenyl-4-hydroxyphenyl)ethane was used in place of 4-hydroxyphenyl)propane. Obtained.

Example 3 2,2-bis(3-phenyl-
Instead of 4-hydroxyphenyl)propane, 1.1-
A thermosensitive recording material was obtained in the same manner as in Example 1, except that the same amount of bis(3-phenyl-4-hydroxyphenyl)cyclohexane was used.

Example 4 2.2-bis(3-phenyl-
4-hydroxyphenyl)brovani, bis(3
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the same amount of -phenyl-4-hydroxyphenyl) sulfone was used.

Comparative Example 1 2.2-bis(3-phenyl-
2.2- instead of 4-hydroxyphenyl) propane
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the same amount of bis(4-hydroxyphenyl)propane was used.

Drivability was also compared.

These results are shown in Table 1.

Comparative Example 2 Thermal recording material was prepared in the same manner as in Example 1, except that the same amount of benzyl P-hydroxybenzoate was used in place of 2,2-bis(3-phenyl4-hydroxyphenyl)propane in Example t. I got it.

Printing was actually performed using a facsimile on the thermal recording materials obtained in the Examples and Comparative Examples above, and the image density and background density at the time of printing were measured using a densitometer and relative comparisons were made.

As for storage stability, the concentration was measured again after storing for 48 hours at a constant temperature of 40°C and 190%.

No adhesion of residue or sticking phenomenon, etc. Table 1 ◎...Good ○...Good △...Slightly poor [Effects of the Invention] The heat-sensitive recording material of the present invention has a specific chemical structure as a color developer. Since it uses bisphenols, it has excellent suitability for high-speed recording and storage stability, and also has various excellent features as described above.

Therefore, according to the present invention, it is possible to provide a heat-sensitive recording material that can be used extremely advantageously in practice.

Claims (1)

[Claims] 1. In a heat-sensitive recording material having a heat-sensitive recording layer containing a normally colorless or light-colored color-forming substance and a color developer that causes the color-forming substance to develop color when heated, the following general color developer may be used as the color developer. Formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [I] [However, X in the formula is a single bond, -O-, -S-, -S
O-, -SO_2-, ▲ Numerical formulas, chemical formulas, tables, etc.▼ (R^3 and R^4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms ), ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (p represents an integer from 2 to 10) or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (q represents an integer from 4 to 10) ), R^1 and R^2 each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and m
and n each independently represent 0 or an integer of 1 to 3. ] A heat-sensitive recording material characterized by using bisphenols represented by the following.