JPH01214473A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain excellent color forming sensitivity and prevent ununiformity of color, fading or discoloration during preservation from being generated, by providing a color forming layer comprising a colorless or light-colored color forming substance and a specified color developer for developing the substance into a color when being heated. CONSTITUTION:A color forming layer is provided which comprises a normally colorless or light-colored color forming substance and a color developer constituted of a 2-substd. cyclohexyl sulfonate compound of formula (I), wherein R is an alkyl, aryl, cycloalkyl, aralkyl or alkylaryl, and each of X and Y is independently hydrogen, an alkyl, cycloalkyl or aralkyl, with the proviso that X and Y are not simultaneously hydrogen. The compound of formula (I) and the color forming colorless dye are generally pulverized by a mill, e.g., a ball mill or a sand grinder, or an emulsifier, and a binder (e.g., methyl cellulose), a filler (e.g., kaolin) and other additives are added thereto to prepare a coating liquid. The coating liquid is applied to a paper or 8 film to obtain a thermal recording material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-sensitive recording material, and more specifically, the present invention relates to a heat-sensitive recording material.
- A thermosensitive recording material containing a substituted cyclohexyl ester derivative.

[Prior art and problems to be solved by the invention] Heat-sensitive recording materials are made by separating a color-forming substance, which is normally colorless or light-colored, and a color developer, which causes the color-forming substance to develop color when exposed to heat, in a separated state. It is produced by coating the surface of a support such as paper, synthetic paper, plastic film or sheet together with a sensitizer, binder and other additives.

Then, in the recording device, when a heat generating element such as a thermal head or a hot pen comes into contact with this recording medium, the dye and the color developer react to develop a color such as black, and the recording is performed.

Compared to other recording materials, such recording materials do not require complicated processing such as development and fixing, can produce records in a short time using relatively simple equipment, and generate less noise. Due to its advantages such as small size, low environmental pollution, and low cost, it is used for copying books, documents, etc.
It is widely used as a recording material for various measurement recording papers, computers, facsimile machines, telex machines, ticket vending machines, prepaid cards, labels, etc.

Conventionally, color developers that thermally develop color from color-forming substances include:
Various acidic substances have been proposed, especially phenolic compounds such as bisphenol A, p-hydroxybenzoic acid benzyl ester, 4゜4゛-cyclohexylidene diphenol, LL3-)lis(3゛-tertiary). Butyl-
4'-Hydroxy-6'-methylphenyl)butane and the like are used alone or in combination. However, when these phenols are used,
The color development sensitivity was not yet sufficient, and there were drawbacks such as color unevenness, color reversion, and discoloration during storage.

Therefore, attempts have been made to achieve higher sensitivity by using a sensitizer, which is a third substance, as a color-forming substance or developer. For example, 4-benzyloxybiphenyl, dimethyl phthalate, stearamide, phenyl benzoate, etc. have been used in combination, but these have not been sufficient.

Therefore, it was proposed to use, for example, sulfonic acid ester derivatives as sensitizers (JP-A-59-73990
(see publication). Although this improves the color development sensitivity to some extent, it is still not sufficient, causing color unevenness and color deterioration, and problems with storage stability remain. moreover,
It has been proposed to use sulfonic acid ester derivatives as color developers (see JP-A-59-109388), but since using them alone is insufficient for printing speed and color development sensitivity, they are used as color development aids. An amine compound is also used. However, although the color development sensitivity is improved by using a color development aid in combination, a problem arises in storage stability, and further improvement has been desired.

[Means to solve the problem]

In view of the above-mentioned current situation, the present inventors have conducted intensive studies to obtain a color developer that not only has excellent color development sensitivity but also has no color unevenness or color change, and does not change color or change color during storage. As a result of stacking, by using a sulfonic acid-2-substituted cyclohexyl ester compound represented by the following general formula (r), without using a sensitizer or a coloring aid,
The present invention has been achieved by discovering that not only is the printing speed excellent, and the coloring sensitivity is significantly improved (but also the solvent resistance and storage stability are significantly improved).

That is, the present invention generally comprises a color-forming substance that is colorless or light-colored;
Provided is a heat-sensitive recording material provided with a color-forming layer containing a color developer that causes the color-forming substance to develop color when heated, which contains a compound represented by the following general formula (1) as the color developer. It is something.

(In the formula, R represents an alkyl group, an aryl group, a cycloalkyl group, an arylalkyl group, or an alkylaryl group, and X and Y each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, or an arylalkyl group. ,
X and Y cannot become hydrogen atoms at the same time. ) The heat-sensitive recording material of the present invention will be explained in detail below.

In the compound represented by the above general formula (1) used in the present invention, the alkyl groups represented by X and Y include methyl, ethyl, propyl, isopropyl, n-butyl,
Examples include isobutyl, nibutyl, tert-butyl, hexyl, and trifluoromethyl groups.

Therefore, the compounds represented by the above general formula (1) used in the present invention include, for example, the compounds shown in Table 1.

The sulfonic acid-2-substituted cyclohexyl ester compound can be easily synthesized by applying a well-known synthesis method such as reacting benzenesulfonic acid chloride and a 2-substituted cyclohexanol compound in the presence of a hydrochloric acid scavenger. can be manufactured.

Next, a specific synthesis example of the 2-substituted sulfonic acid cyclohexyl ester compound used in the present invention will be shown.

Synthesis Example 1 In a flask equipped with a stirrer, thermometer, and reflux condenser, 12.47 g of β-naphthalenesulfonic acid chloride and 2-
9.16 g of cyclohexylcyclohexanol was dissolved in 40% of pyridine and stirred at room temperature for 5 hours. Next, the generated pyridine hydrochloride was removed by filtration, and the filtrate was desolvented to obtain a crude product. The obtained crude product was recrystallized from ethanol to obtain 18.0 g of white crystals.

Melting point: 71-72°C (decomposition) As a result of infrared spectroscopic analysis, the following characteristic absorption was observed, confirming that it was the desired compound.

C-H2920cm-', C-O1350 cm-', 1190 cm-', 67
Synthesis Example 2 - Naphthalenesulfone-2,6-dimethylcyclohexyl esul (No. 3 8) Example 1 2-
Instead of cyclohexylcyclohexanol, 2.6-
A crude product was obtained in the same manner as in Example 1, except that 7.05 g of dimethylcyclohexanol was used. Recrystallization from isopropyl alcohol gave white crystals.

Melting point: 111°C As a result of infrared spectroscopy, the following characteristic absorption was observed, confirming that it was the desired compound.

C-H2950cm-', 2890cm-'v
s-01360cm-', 1350cm-', 1
180 cm-', 660 cm-' As mentioned above, these sulfonic acid-2=substituted cyclohexyl ester compounds not only have excellent effects as color developers themselves, but also have the effect of improving storage stability. Color developers that are conventionally used depending on the purpose and required performance: p-octylphenol,
p-tert-butylphenol, p-phenylphenol,
Bisphenol A, Ll-bis(p-hydroxyphenylbutane), 2,2-bis(4-hydroxy-3,5-
dichlorophenyl)propane, bis(2-(4-hydroxyphenylthio)ethoxycomethane, 4-isopropoxybenzenesulfonyl)phenol, 4-hydroxyphthalic acid dimethyl ester, bis(4-hydroxyphenyl)acetic acid butyl ester, sulfobis (3,4-
dihydroxyhensen), benzyl p-hydroxybenzoate, zinc salt of salicylic acid dodecyl ester, 3,5-di-tert-butylsalicylic acid, 4,4゛-cyclohexylidene diphenol, p-hydroxydiphenoxide, α-naphthol, β- Naphthol, p-hydroxyacetophenone, p-tertiary octylphenol, 2,2'-dihydroxybiphenyl, 2,2-bis-(3-methyl-4-
hydroxyphenyl)propane, 2,2-bis(3,5
-dimethyl-4-hydroxyphenyl)propane, LL
, 3-1-lis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, LL, 3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)
It can also be used in combination with phenols such as butane, organic acids, or metal salts thereof.

Various dyes are well known as the usually colorless or light-colored color-forming substance used in the present invention, and there are no particular limitations as long as they are used in general pressure-sensitive recording paper or heat-sensitive recording paper.

Specific examples of these dyes (coloring substances) are (1
) Triarylmethane compounds; for example, 3゜3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3-
(p-dimethylaminophenyl)-3-(1,2-dimethyl-3-indolyl)phthalide, 3- (p-dimethylaminophenyl)-3-(2-phenyl-3-indolyl)phthalide, 3.3- Bis(9-ethyl-3-carbazolyl)-5-dimethylaminophthalide, 3,3-bis(2-phenyl-3-indolyl)-5-dimethylaminophthalide, etc. (2) diphenylmethane compounds; for example, 4.4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleucoolamine,
N-2,4,5-trichlorophenylleucoauramine, etc., (3) xanthine compounds; for example, rhodamine-
β-anilinolactam, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-(2
-chloroanilino)fluoran, 3-diethylamino-
6-Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-(β-ethoxyedylamino)
Fluoran, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexylmethylanilino-6-methyl-7-ani Linofluorane, 3-
Diethylamino-6-chloro-7-T-chloropropylaminofluorane, etc., (4) Thiazine compounds; Examples include Eva, benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc., (5) Spiro compounds;
Examples include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho(3-methoxyhenzo)spiropyran, and several types of these dyes may be mixed. It can also be used as

The compound of the general formula (I) and the color-forming colorless dye used in the present invention are usually atomized using a grinder such as a ball mill, an atlyzer, or a sand grinder, or a suitable emulsifying device, and various additives are added depending on the purpose. Add to make a coating liquid.

This coating liquid usually contains polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, polyacrylamide polymer, starch, styrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, styrene-butadiene copolymer, etc. binder, kaolin, silica,
Fillers such as diatomaceous earth, talc, titanium dioxide, calcium carbonate, magnesium carbonate, and aluminum hydroxide are blended, but in addition to these, 4-benzyloxybiphenyl, 4-benzylbiphenyl, 1.2-bis(3-methylphenoxy) Exacerbating agents such as ethane, methyl bisbenzoate, benzyl 1-hydroxy-2-naphthyl ester, amines such as triethylenetetramine, N,N-bis(3-aminopropyl)ethylenediamine, and amide compounds such as stearic acid amide. , metal soaps such as zinc stearate, waxes, light stabilizers, waterproofing agents, dispersants, antifoaming agents, etc. can be used.

By applying this coating liquid to paper and various films, the desired heat-sensitive recording material can be obtained.

The amount of the sulfonic acid 2-substituted cyclohexyl ester compound represented by the general formula (r) used in the present invention varies depending on the required performance and recording suitability, and the type and amount of other additives used in combination. Therefore, it is usually used in an amount of 0.1 to 10 parts per part of the color-forming dye, although it is not particularly limited.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example-1 20g of 2-anilino-3-methyl-6-dinithylaminofluorane in 10% polyvinyl alcohol aqueous solution
Grind in a ball mill with g to obtain a dye dispersion (liquid A).
I got it.

Similarly, 20 g of bisphenol A was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a color developer dispersion. (Liquid B) Furthermore, 20 g of the sample compound shown in Table 1 was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a dispersion.

(Liquid C) Liquids A, B, and C were mixed at a weight ratio of 3:20:5, and 50 g of calcium carbonate was added to 200 g of the mixed liquid and dispersed to obtain a coating liquid.

This coating liquid was applied to a base paper of 50 g/m'J with a solid content of 6 g/m
A heat-sensitive recording material was prepared by applying a coating amount of 3 and drying with warm air.

Using the obtained thermal paper, a commercially available thermal facsimile machine (
The color density of the recorded image printed using NEFAX-3000 (Nippon Denki type) was measured using a Macbeth densitometer (Macbeth RI).
-933 type).

In addition, this heating element was stored at a temperature of 50° C. and a humidity of 90%, and dioctyl phthalate was stamped at 50° C. for 48 hours in a dry double-striped state, and the density of the background after storage and the density after printing were the same. The remaining rate of the density of the printed area after storage was determined using the following formula, and the results are shown in Table 2.

Example-2 20 g of 3-dibutylamino-7-(o-chlorophenyl)aminofluorane was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a dye dispersion (liquid A).

Similarly, 10 g of Hensyl p-hydroxybenzoate was added to
% polyvinyl alcohol aqueous solution in a ball mill to obtain a color developer dispersion. (Liquid B) Furthermore, 20 g of the sample compound shown in Table 1 was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a dispersion.

(Liquid C) Liquids A, B, and C were mixed at a weight ratio of 3:20:5, and 50 g of calcium carbonate was added to 200 g of the mixed liquid and dispersed to obtain a coating liquid.

A heat-sensitive recording material was prepared using this coating liquid in the same manner as in Example 1, and tests were conducted on color density and storage stability, and the results are shown in Table 3.

From the results in Tables 2 and 3, it is understood that the heat-sensitive recording material of the present invention not only has excellent color development sensitivity but also extremely excellent storage stability.

Claims (1)

[Claims] A color-forming substance that is normally colorless or light-colored, and the following general formula (I
) A heat-sensitive recording material characterized by containing a compound represented by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, R represents an alkyl group, an aryl group, a cycloalkyl group, an arylalkyl group, or an alkylaryl group, and X and Y each independently represent a hydrogen atom, Indicates an alkyl group, cycloalkyl group or arylalkyl group,
X and Y cannot become hydrogen atoms at the same time. )