JPS6334190A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance not only humidity resistance and plasticizer resistance but also the storability of a developed color image, by integrating specific 1,1-bis(4-hydroxyphenyl)cyclohexane in a thermal recording layer consisting of a color former being a specific divinyl phthalide compound and a coupler. CONSTITUTION:In a thermal recording material containing a divinyl phthalide compound represented by formula (1), 1,1-bis(4-hydroxyphenyl)cyclohexane represented by general formula (2) is contained in a thermal recording layer consisting of a color former and a coupler. By integrating 1,1-bis(4- hydroxyphenyl)cyclohexane represented by the formula (2) in the thermal recording layer consisting of the color former and the coupler of the thermal recording material containing the divinyl phthalide compound represented by the formula (1) as the color former, humidity resistance and plasticizer resistance are markedly enhanced and not only the visible color in a developed color image is not faded but also the near infrared adsorption capacity of said developed color image is not deteriorated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the improvement of a heat-sensitive recording material containing a divinylphthalide compound represented by the following formula (1) as a coloring agent. The present invention relates to a heat-sensitive recording material with good storage stability.

(In the formula, R1 and R'' are an alkyl group having 6 or less carbon atoms, which may have an alkoxy group as a substituent, or a cycloalkyl group having 5 to 7 carbon atoms, and XI, XZ are hydrogen atoms, alkyl groups having 8 or less carbon atoms. group, an alkoxy group having 8 or less carbon atoms,
A fluorine atom or a chlorine atom is represented, X3 represents a chlorine atom or a bromine atom, and )il and R2 can also form a linked heterocycle. ) [Prior art and problems to be solved by the invention] The heat-sensitive recording material containing the compound represented by the aforementioned general formula (1) as a coloring agent was developed by the present inventor and has already been filed. When heated, it quickly develops a blackish color, and in addition to the visible part,
As it has absorption in the near-infrared region, it is expected to be used as a recording material for OCR (optical character reader), which has been in increasing demand in recent years.

While investigating the storage stability of colored images (particularly moisture resistance and plasticizer resistance) for promising recording materials containing the above-mentioned compound (1) as a coloring agent, the present inventor discovered that there were some difficulties with these. I learned.

Therefore, the present inventors have proposed stabilizers 1.1 for improving the storage stability of colored images in recording materials containing fluoran compounds that do not absorb in the near-infrared region.
．． 3-) Lis(2-methyl-4-hydroxy-5te
As we continued to study the incorporation of rt-butylphenyl)butane into color formers (Japanese Unexamined Patent Publication No. 160191/1983), we found that compounds other than the above-mentioned stabilizers were used in combination with the compound (1) of the present invention. In the above, we found that the storage stability of colored images can be improved, and as a result of further studies, we arrived at the present invention.

[Means for solving problems]

That is, the present invention provides a heat-sensitive recording material containing the divinylphthalide compound represented by the above formula (1) as a color former, in which the following (2
The present invention provides a heat-sensitive recording material characterized by containing 1,1-bis(4-hydroxyphenyl)cyclohexane represented by the formula:

Here, specific examples of the divinylphthalide compound represented by the formula (1) are as follows.

The compound of the general formula (1) of the present invention is prepared by combining 2 moles of the ethylene derivative of the following formula (5) and 1 mole of the phthalic acid derivative of the following formula (6) in the presence of a dehydrating agent such as acetic anhydride or sulfuric acid. Obtained by subcondensation.

Incidentally, the ethylene derivative of the above formula (5) can be synthesized by any of the following Grignard reactions a, b, and c (in the formula, X is a halogen atom).

).

In producing heat-sensitive recording materials, for example,
5-14039 and JP-A-59-33186 may be employed.

Further, in addition to the compound of general formula (1) described above, a normal fluoran compound that does not have near-infrared absorption may be added as a coloring agent, and when preparing a mixture of coloring agents, each compound must be dissolved in advance. Alternatively, the mixture may be mixed by melting, or the crystals may be mixed before or after the crystals are pulverized.

In the production of heat-sensitive recording materials, 2.2-
Bis(p-hydroxyphenyl)propane (bisphenol A), methyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 4,4''-thiodiphenol,
Bis-(4-hydroxy-3-methylphenyl) sulfide, 4,4°-dihydroxydiphenylsulfone, 4-hydroxy-4°-methyl-diphenylsulfone, 4-hydroxy-4°-propoxydiphenylsulfone, 4.4° -dihydroxy-3,3°-diallyldiphenylsulfone, 1,5-di(4-hydroxyphenylthio)-3-oxapentane, 1,7-di(4
-hydroxyphenylthio')-3,5-dioxahebutane, 1,8-di(4-hydroxyphenylthio)-3
, 6-thioxaoctane, dimethyl hydroxyphthalate, 2,4-dihydroxybenzophenone, etc. can be used, and as the binder, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic, gelatin can be used. , casein, starch, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, and the like can be used. Also,
In addition, various sensitivity improvers, ultraviolet absorbers, etc. can be used in combination.

[For production]

In a heat-sensitive recording material containing a divinylphthalide compound represented by the above formula (1) as a color former, 1 represented by the above formula (2) is contained in a heat-sensitive recording layer consisting of a color former and a color developer.
When 1-bis(4-hydroxyphenyl)cyclohexane is contained, the moisture resistance and plasticizer resistance are significantly improved compared to when it is not contained, and visible colors in colored images are easily changed. Not only does the color not fade, but the near-infrared absorption ability of the same colored image is not easily inferior.

[Examples, etc.]

Next, the present invention will be specifically explained with reference to Examples.

Example 1 1) Preparation of color former dispersion (liquid A) Kaolin 15 parts lO% polyvinyl alcohol aqueous solution 100 parts water
85 parts The above mixture was ground in a paint shaker until the average particle size of the color former was 2 microns.

2) Preparation of color developer dispersion (solution B) Bisphenol A 15 parts 1
．． 1-bis(4-hydroxyphenyl)cyclohexane 8 parts zinc stearate
10 parts 10% polyvinyl alcohol 15 (1) The above mixture was ground in a paint shaker until the average particle size was 3 microns.

3) Preparation and coating of heat-sensitive coating liquid 10 parts of liquid A and 6.5 parts of liquid B were mixed and stirred to obtain a heat-sensitive coating liquid. After drying this coating liquid on paper with a wire bar, the weight is 6
g/n? A heat-sensitive recording paper was obtained by uniformly coating and drying. This thermal recording paper has no background fog and is colorless.
It quickly developed a deep black color when heated with a thermal pen or the like. This colored image has excellent light resistance and moisture resistance, and has a rating of 700 to 11
Since it had strong absorption at 000n, it was possible to read it by OCR. In addition, the coated surface has excellent light resistance,
No coloration due to sunlight exposure.

Comparative Example 1 In the composition of Solution B of Example 1, 1.1.3 was used instead of 1.1-bis(4-hydroxyphenyl)cyclohexane.
- ) Lis(2-methyl-4-hydroxy-5tert
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that -butylphenyl)butane was used.

Comparative Example 2 In the composition of Solution B of Example 1, 4,4'-
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that thiobis(5-tert-butyl-3-methylphenol) was used.

Comparative Example 3 In the composition of Solution B of Example 1, 2.2'-
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that methylenebis(6tert-butyl-4-methylphenol) was used.

Comparative Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1 except for 1,1-bis(4-hydroxyphenyl)cyclohexane in the composition of Solution B of Example 1.

Example 2 Among the compositions of solution A of Example 1, 3,3-bis[2-(p-
3,3-bis[2-(p-pyrrolidinophenyl)-2- (p-methoxyphenyl)ethynyl)
4+ 5+ 6+ 7 7 ) 7 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that chlorophthalide (previous compound No. 6) was used.

Example 3 Among the compositions of solution A of Example 1, 3,3-bis[2-(p-
dimethylaminophenyl)-2-(p-methoxyphenyl)ethynyl)-4,5,6,7--r toy instead of chlorophthalide, 3,3-bis[2-(p-dimethylaminophenyl)-2 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that -(p-methylphenyl)ethynyl]-4,5,6,7-titrachlorophthalide (from compound 2) was used.

Comparative Example 5 The composition of Solution B of Example 2 was the same as Example 2 except for 1,1-bis(4-hydroxyphenyl)cyclohexane.
A thermosensitive recording paper was obtained in the same manner as above.

Comparative Example 6 The composition of Solution B of Example 3 was the same as Example 3 except for 1.1-bis(4-hydroxyphenyl)cyclohexane.
A thermosensitive recording paper was obtained in the same manner as above.

[Comparative test]

The moisture resistance and plasticizer resistance of the heat-sensitive recording bodies obtained in the above Examples and Comparative Examples were tested by the following method. Table 1 shows the results.
It was shown to.

(1) Moisture Resistance Test Each heat-sensitive recording paper was colored using a heat-sensitive coloring tester (manufactured by Matsushita Electronic Parts) at an applied voltage of 19 V and a pulse duration of 2.5 milliseconds. This colored image was heated at 40℃ and relative humidity was 90℃.
% atmosphere for 4 days, the absorbance at 900 nm was measured using a spectrophotometer (FI Shimadzu UV-365 model). Calculate the image survival rate using the following formula,
Made moisture resistant.

(2) Plasticizer resistance test Cover the image area that has been colored under the same conditions as (1) with a soft PVC sheet (Koriyo 64), apply a load of 4 g/cd, and place it in a constant temperature bath at 60°C. I left it inside for 3 hours. 900n
The absorbance at m was measured in the same manner as in (1), and the image survival rate was determined using the following formula, which was defined as the plasticizer resistance.

Table 1 The above tests confirmed that the thermal recording paper of the present invention has excellent moisture resistance and plasticizer resistance.

〔Effect of the invention〕

The heat-sensitive recording material of the present invention not only can achieve the much-desired black colored image and has absorption in the near-infrared region, but also has excellent moisture resistance, plasticizer resistance, and other properties. It exhibits high performance and has high industrial utility value as a heat-sensitive thermal recording material for OCR.

Claims (1)

[Scope of Claims] [1] In a heat-sensitive recording material containing a divinylphthalide compound represented by the following formula (1) as a color former, the following ( 2) A heat-sensitive recording material containing 1,1-bis(4-hydroxyphenyl)cyclohexane represented by the formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) (In the formula, R^1 and R^2 are alkyl groups with 6 or less carbon atoms, which may have an alkoxy group as a substituent, and 5 to 5 carbon atoms.
7 is a cycloalkyl group, X^1 and X^2 are hydrogen atoms,
An alkyl group having 8 or less carbon atoms, an alkoxy group having 8 or less carbon atoms, a fluorine atom, a chlorine atom, X^3 represents a chlorine atom or a bromine atom, and R^1 and R^2 are connected to form a heterocycle. You can also. ) ▲ Contains mathematical formulas, chemical formulas, tables, etc. ▼ (2)