JPH03182391A - Thermal recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a heat-sensitive recording medium, and more specifically, the present invention relates to a heat-sensitive recording medium, and more specifically, it has high sensitivity, does not cause fading or whitening of the recorded image, and has a high background whiteness. It has excellent performance and can be used in all fields such as medicine, measurement, printers, image communication such as facsimile products, and labels such as POS (point of sale system). The present invention relates to a heat-sensitive recording material that can be advantageously used as various heat-sensitive recording papers or media.

[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 facsimiles, a thermal recording system using a thermal recording medium such as a 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 can develop color in the first step and obtain non-impact recording by second color development.

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, typified by O3, is experiencing particularly strong growth.

As a conventional example of such a heat-sensitive recording material, one using bisphenol A as a color developer is generally known. However, in this case, there is a drawback that thermal responsiveness is low and sufficient color density cannot be obtained during high-speed recording.

As a method to improve this drawback, methods using various color developers have been proposed, among which p-hydroxybenzoic acid ester (Japanese Unexamined Patent Publication No. 56-144193) and 4-hydroxyphthalic acid diester (Japanese Unexamined Patent Application Publication No. 1983-144193) have been proposed. Kaisho 58-15
It has been known that the most effective method is to use a color developer (Japanese Patent No. 3,692) as a color developer.

However, when these substances are used as color developers,
There are problems in that the recorded image easily fades and the image area tends to whiten (a phenomenon in which white powder forms on the surface).

[Problem to be solved by the invention]

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

The object of the present invention is to have excellent characteristics such as excellent color development sensitivity, remarkable resistance to fading and whitening of recorded images, and high whiteness of the background, and therefore suitability for high-speed recording, contrast and preservation of recorded images. The object of the present invention is to provide a thermosensitive recording material which is extremely advantageous in practice and which satisfies both stability and stability.

[Means to solve the problem]

As a result of intensive research to achieve the above object, the present inventors have found that by using bisphenols having a specific chemical structure as a color developer, an excellent heat-sensitive recording material that satisfies the above object can be obtained. 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 normally colorless or light-colored and a color developer that causes the color-forming substance to develop color when heated. , in the formula, X is a single bond, -0-3S-, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a carbon number 6
〜12 aryl group, ), -4CHJ''(P is
), 1 represents an integer from 2 to 10, R- and Hz each independently represent a halogen atom,
represents 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 O or an integer of 1 to 3. The present invention provides a thermosensitive recording material having the following characteristics.

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

In the above general 2N), R1, R1, R2 and R4 may be an alkyl group having 1 to 6 carbon atoms, and specific examples of the alkyl group include a methyl group, an ethyl group, a 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, cyclohexyl group etc. can be mentioned.

In the formula CI), R1, R1, R2 and R4
may be an aryl group having 6 to 12 carbon atoms, and specific examples of the aryl group include 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 isopropyl groups Phenyl group, various tetramethylphenyl groups,
Various methylpropylphenyl groups, various methylisopropylphenyl groups, various butylphenyl groups, various 5
Examples include ec-butylphenyl group, various tert-7' tylphenyl groups, various pentylphenyl groups, and various hexylphenyl groups.

In formula (1) above, R' and R1 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.

Note that any two or more of R1, R1, R3, and R4 may be the same, or all of them may be different.

In the above-mentioned formula (1), m and n are each independently,
O or an integer from 1 to 3, especially when m and n are both 0
or 1 is preferred, and m=n-0 is particularly preferred.

Specific examples of the bisphenols (1) include 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane and 3,3-bis(3-cyclohexyl-4-hydroxyphenyl). Pentane, 1-phenyl-1,1-bis(3-cyclohexyl-4-hydroxyphenyl)ethane, 1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane, bis(3
-cyclohexyl-4-hydroxyphenyl) sulfone, 3,3'-dicyclohexyl-4,4'-dihydroxybiphenyl, bis(3-cyclohexyl-4-hydroxyphenyl)methane, 1-phenyl-1, 1-bis(
3-cyclohexyl-4-hydroxyphenyl)methane, 1,1-bis(3-cyclohexyl-4-hydroxyphenyl)ethane, 1,2-bis(3-cyclohexyl-4-hydroxyphenyl)ethane, 1 .3-bis(3
-cyclohexyl-4-hydroxyphenyl)propane, 2.2-bis(3-cyclohexyl-4-hydroxyphenyl)butane, 1.4=bis(3-cyclohexyl-4-hydroxyphenyl)butane, 1. 1-bis(3
-cyclohexyl-4-hydroxyphenyl)-1-phenylbutane, 2,2-bis(3-cyclohexyl-4
-hydroxyphenyl)octane, 1,8-bis(3-
cyclohexyl-4-hydroxyphenyl)octane,
Bis(3-cyclohexyl-4-hydroxyphenyl) ether, bis(3-cyclohexyl-4-hydroxyphenyl) sulfide, 1.1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclopentane, 2.2
-bis(3-cyclohexyl-4-hydroxy-5-methylphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxy-5-chlorophenyl)propane, and the like. Among these, especially
2.2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 3.3-bis(3-cyclohexyl-4-hydroxyphenyl)pentane, 1-phenyl-
1,1 bis(3-cyclohexyl-4-hydroxyphenyl)ethane, 1. l-bis(3-cyclohexyl-4
-hydroxyphenyl)cyclohexane, 3,3'-dicyclohexyl-4,4'-dihydroxybiphenyl,
Bis(3-cyclohexyl-4-hydroxyphenyl)
Sulfone and the like are preferred.

In addition, the above-mentioned various bisphenols (1) 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 react with the color developer, that is, bisphenol 1(1), to form a color. 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, 2-anilino-3-methyl-6-
dinitylaminofluorane, crystal violet lactone, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-)luidino)
-6-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidine-6-methyl-7-anilinofluorane, 3
(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7
-(o-chloroanilino)fluoran, 3-diethylamino-7-(m-)lifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-chlorofluoran, 3-diethylamino-6-methylfluoran, 3
-cyclohexylamino-6-chlorofluorane, 3-
(N-isoamyl-N-ethylamino)-6-methyl-
Examples include 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 heat-sensitive recording material of the present invention needs to contain at least the bisphenol (I) and the color-forming substance.

The blending ratio of the bisphenols (1) component cannot be uniformly prescribed because it varies depending on the bisphenols CI) used and the type and combination of color-forming substances, but when using the leuco compound as the color-forming substance, It is appropriate that 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, a sufficient effect cannot 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 above-mentioned bisphenols N) and the above-mentioned color-forming substance, but these are usually dispersed in a binder according to a conventional method. Use in shape.

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, shellac, and the like.

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), 2,5-di-L-butylhydroquinone, 2,5-di-t-amylhydroquinone, bis(3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide, bis(3, 3'-bis(4'-hydroxy-3'-t-butylphenol)-butyric acid] glycol ester, 4,4'-methylene-bis(2,6-
di-t-7'-tylphenol), 2,6-bis(2'-
Hydroxy-3'L-phthyl-5-methylbenzyl)-
4-methylphenol, 2,2'-iso-butylidene-bis(4,6-sintylphenol), bis[2-(
2-hydroxy-5-methyl-3-t-butylbenzyl)-4-methyl-6-t-butylphenyl] terephthalate, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2-hydroxy-4-methoxy −2′−
Carboxybenzophenone, tris(3,5-di-t-
butyl-4-hydroxyphenyl) isocyanate, tris[β-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxyethyl] isocyanate,
1,3,5-trimethyl-2,4,6-tris(3,5
-di-t-butyl-4-hydroxybenzyl)benzene, N,N'-hexamethylene-bis(3,5-di-t-
Butyl-4-hydroxy-hydrocinnamide L 1,
1.3-) 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 according to a conventional method except for using the bisphenols [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 excellent properties such as excellent color development sensitivity, remarkable resistance to fading and whitening of the recorded image, and high background whiteness, and therefore has excellent high-speed recording suitability and recording properties. It is a high-performance heat-sensitive recording material that satisfies both image contrast and storage stability before and after use.

The heat-sensitive recording material of the present invention has various excellent features as described above. Among these, the feature of simultaneously satisfying high-speed recording performance and storage stability is a problem 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 (1).

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 a color developer, the greater the color development sensitivity to heating from a thermal head etc.0 The bisphenols (1) used in the present invention are used as a color developer. In addition to having these basic characteristics, it also has a relatively low melting point and high color development sensitivity.

For example, the melting point of 3,3-bis(3-cyclohexyl-4-hydroxyphenyl)pentane is 102°C, which is lower than that of bisphenol, which has been conventionally known as a color developer, and its color development sensitivity is significantly high.

Further, the heat-sensitive recording material of the present invention has features such as excellent running properties such as no deposit of residue on the thermal head during use and virtually no sticking phenomenon.

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 PO3.

〔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.

Example I Liquid A: 1 part by weight of 2-anilino-3-methyl-6-dinithylaminofluorane (ODB) 10% aqueous solution of polyvinyl alcohol 5 parts by weight Water 25 parts by weight Liquid B: 2
- Bis(3-cyclohexyl-4-hydroxyphenyl)propane 4 parts by weight Kaolin 4 parts by weight 10% polyvinyl alcohol aqueous solution 7 parts by weight Water 25 parts by weight Liquids A and B prepared to the above composition were each separately heated in a ball mill. 48
After time pulverization and dispersion, the mixture was 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 In place of 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane in Solution B in Example 1, 3
．． A thermosensitive recording material was obtained in the same manner as in Example 1, except that the same amount of 3-bis(3-cyclohexyl4-hydroxyphenyl)pentane was used.

Example 3 In place of 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane in solution B in Example 1, 1
．． A thermosensitive recording material was obtained in the same manner as in Example 1, except that the same amount of 1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane was used.

Comparative Example 1 In place of 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane in Solution B in Example 1, 2
, 2-bis(4-hydroxyphenyl)propane was used in the same amount as in Example 1 to obtain a thermosensitive recording material.

Comparative Example 2 In place of 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane in Solution B in Example 1, p
A thermosensitive recording material was obtained in the same manner as in Example 1, except that the same amount of benzyl hydroxybenzoate was used.

Each of the heat-sensitive recording materials obtained in the above Examples and Comparative Examples was actually printed using a facsimile, and the image density and background density at the time of printing were measured using a densitometer, and relative comparisons were made. .

The storage stability was evaluated under the conditions of 40℃ and 90% constant temperature.
After storage for a period of time, the concentration was measured again and the change in concentration was compared.

In addition, the quality of running performance, including the presence or absence of debris adhesion to the thermal head and sticking phenomenon, was examined and compared with each other.

These results are summarized in Table 1.

Table 1 with margins below: ◎...Good O...Good Δ...Slightly poor or better The results show that the thermal recording material of the present invention has superior color development sensitivity (thermal sensitivity) than conventional ones, and also records It has excellent properties such as being extremely resistant to image fading and whitening, and has a high degree of background whiteness, and is suitable for high-speed recording.
It is a high-performance thermal recording medium that satisfies both the contrast of the recorded image and the storage stability before and after use, and it has excellent runnability, such as no residue adhering to the thermal head during use and virtually no sticking phenomenon. It was found that it has features such as excellent performance.

〔Effect of the invention〕

The heat-sensitive recording material of the present invention uses bisphenols with a specific chemical structure as a color developer, so it has excellent color development sensitivity.
Moreover, the recorded images are extremely unlikely to fade or whiten.
Moreover, it has excellent properties such as high background whiteness, and is therefore a high-performance thermal recording medium that satisfies both high-speed recording suitability, recorded image contrast, and storage stability before and after use. Moreover, it has various excellent features as mentioned above.

Therefore, according to the present invention, it is possible to provide a heat-sensitive recording material that can be practically advantageously used in various fields of heat-sensitive recording materials.

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 ), ■CH_2■_p (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 1.
Indicates an integer between ~3. ] A heat-sensitive recording material characterized by using bisphenols represented by the following.