JPS634989A - Sensitizer for thermal recording material - Google Patents

Abstract

PURPOSE:To provide a sensitizer ensuring color forming with high sensitivity to produce developed color image with excellent fastness, when using a color developer having a high melting point, particularly, a bisphenol S derivative, by using a specified ether derivative of sulfonyldiphenol as a main constituent. CONSTITUTION:An ether derivative of sulfonyldiphenol of general formula, wherein each of R1 and R2, which may be the same or different, is a 1-4C alkyl or alkenyl, benzyl, chlorobenzyl or a group of the formula-CH2COOR3, is used as a sensitizer for enhancing the sensitivity of a thermal recording material in which a thermal color forming layer comprising a colorless or light-colored leuco dye as a color forming substance and a phenol compound as a color developing substance is provided on a base. When the thermal recording material is produced by using this sensitizer, color formation takes place at a lower temperature even when a color developer having a high melting point is used, and it is possible to sufficiently cope with a high-speed printing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sensitizer for heat-sensitive recording materials, and more particularly to a sensitizer for heat-sensitive recording materials comprising an ether derivative of sulfophenyl diphenol.

[Conventional technology]

Thermal recording materials, in which a thermosensitive coloring layer that develops color when heated, is placed on a support such as paper, synthetic paper, or plastic film, can be used in facsimile machines, calculators, thermal printers such as microcomputers, thermopen recorders such as electrocardiograms and analytical instruments, train tickets, etc. Used for supermarket Teno PO3 labels, etc.

Heat-sensitive recording materials are usually produced by separately pulverizing a colorless or light-colored lactone, lactam, or spiropyran-based leuco dye as a color-forming substance, and a color-developing substance that reacts with the color-forming substance under heat to develop a color using a ball mill or sand mill. After dispersing in a solvent, a binder is added and mixed, wax, sensitizer, surfactant, antifoaming agent, inorganic pigment, etc. are added as necessary, and the mixture is spread on a support such as paper. Manufactured by coating and drying. Conventionally, various phenol compounds have been used as color developers. Bisphenol A (isopropylidene diphenol) is particularly frequently used. However, this alone is insufficient for high-speed facsimile applications that require high sensitivity, and a sensitizer is added to the color developer to lower the color development temperature. Sensitizers currently used for this purpose include, for example, paraffin wax, fatty acid amides, amides such as dimethyl terephthalate,
There are ether, ester compounds, etc.

[Problem that the invention seeks to solve]

However, these sensitizers are not sufficiently effective, especially when 4,4'-dihydroxydiphenylsulfone, which is a color developer with a high melting point, is used. The inventors of the present invention have arrived at the present invention as a result of extensive studies regarding a sensitizer with good performance that can solve the above-mentioned problems. That is, the present invention
The object of the present invention is to provide a sensitizer that can develop color with high sensitivity and provide a color-forming layer and image with excellent fastness when a high-melting-point color developer, particularly a bisphenol S derivative, is used.

[Means for solving problems]

Specifically, the present invention aims to improve the sensitivity of a heat-sensitive recording material comprising a heat-sensitive coloring layer provided on a support, each containing a colorless or light-colored leuco dye as a color-forming substance and a phenol compound as a color-developing substance. The purpose of the present invention is to provide a sensitizer to be used, and this sensitizer has the following general formula (1
) contains at least one ether derivative of sulfonyl diphenol as a main component.

In the above formula, R+ and R2 may be the same or different, and each represents an alkyl group or alkenyl group having 1 to 4 carbon atoms, a benzyl group, a chlorobenzyl group, or a formula -CL
COOR3 (in the formula, R3 represents an alkyl group or an alkenyl group having 1 to 3 carbon atoms).

Colorless or light-colored coloring substances useful in the heat-sensitive recording material of the present invention include crystal violet lactone, malachite green lactone, 3,3-bis(P-dimethylaminophenyl)-6-aminophthalide, 3,3-bis(P-dimethylaminophenyl)-6-aminophthalide,
-dimethylaminophenyl)-6-, (P-)luenesulfonamido)phthalide, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-phenylfluorane, 3-cyclohexylamino-6-chlorofluoran Oran, 3-N-methyl-N-cyclohexylamino-
6-Methyl-,7-anirite fluorane, 1.3.3-
) trimethyl-6'-chloro-8'methoxyindolinobenzospiropyran and the like. These coloring materials and qualities may be used independently, or 1. May be used in combination. Further, the usage ratio may be changed as appropriate depending on the color developer used.

Color developers useful in the present invention include P-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters,
Examples include bisphenol Aii, bisphenol S derivatives, and the like. In particular, bisphenol S derivatives, such as 4,4'-dihydroxydiphenylsulfone, 2.
4'-dihydroxydiphenylsulfone, 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone are used.

The sensitizer of the present invention may be used in combination with other sensitizers. Sensitizers used in combination include higher fatty acids or their esters, amides, and metal salts, as well as various waxes, condensates of aromatic carboxylic acids and amines, higher linear glycols, higher ketones, and bisphenol S derivatives. etc. In particular, combination use with bisphenol S derivatives is preferable since it has excellent robustness.

Techniques for applying color forming substances and color developing substances onto a support such as paper include methods in which they are dispersed in a binder together with various additives and applied according to commonly used methods. Examples of the binder include hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, starch, polyacrylic acid, polyacrylamide, and styrene-maleic acid copolymer.

〔Effect of the invention〕

By manufacturing a heat-sensitive recording material using the sensitizer of the present invention, it becomes possible to develop color at a low temperature even if a high-melting point developer is used, and it becomes fully compatible with high-speed printing. .

Table 1 shows the melting points of several examples of the compounds represented by the general formula (1) of the present invention.

R, -R2 melting point ('C) -C1,123~124 Cal (s 128~129n
-C3H? 118-119C
HzCJs 139-140-C
■2CII = CHg102~103- C112C
00C■3 105~106-
CII2COOC2) 15 7
7-7B [Example] In order to explain the present invention more specifically, examples are shown below. Note that parts and % in the examples represent parts by weight and % by weight, respectively.

Example 1 The following liquids A, B, and C were separately prepared as thermosensitive color forming layer format liquids, and were dispersed by finely pulverizing them using a sand mill for 3 hours.

Liquid A (color-forming substance dispersion) Water 2.
0 parts B Solution (color developer dispersion) Water 5.
2 parts Solution C (sensitizer dispersion) 2.4'-'; J F"r>';7"'2.8□Rusulfone 10% polyvinyl alcohol aqueous solution 12.0 parts water
5.2 parts Next, liquid B and liquid C were mixed to prepare liquid D.

D liquid B liquid 3.0 parts C liquid
3.0 parts kaolin
0.61 parts Next, 0.78 parts of liquid A and 10 parts of liquid D were mixed to prepare a coating liquid for a heat-sensitive coloring layer.
Dry coating amount is approximately 7 g/nf on high-quality paper with a basis weight of 65 g/nf.
It was coated to give rr+ and air-dried to obtain thermal recording paper.

Examples 2 to 4 Instead of the sensitizer 2,4'-dimethoxydiphenylsulfone in Solution C in Example 1, 2,4'-di-n-propoxydiphenylsulfone, 2°4'-diallyloxydiphenylsulfone and A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 2°4'-jethoxycarbonylmethoxydiphenyl sulfone was used. These are referred to as Examples 2.3 and 4, respectively.

Comparative example 1 Solution B in Example 1 was prepared as Solution E.

E liquid B liquid 3.0 parts water
1.2S kaolin 0.61 part then,
A comparative thermal recording paper was obtained in the same manner as in Example 1, except that 0.78 parts of liquid A and 10 parts of liquid E were mixed.

Comparative Example 2 A comparative thermosensitive recording paper was obtained in the same manner as in Example 1 except that the sensitizer 2,4'-dimethoxydiphenylsulfone in Solution C in Example 1 was replaced with stearic acid amide.

Example 5 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that the color developer 4,4'-dihydroxydiphenylsulfone in Solution B in Example 1 was replaced with 2,4'-dihydroxydiphenylsulfone.

Examples 6 to 8 The sensitizer 2,4'-dimethoxydiphenylsulfone in Solution C in Example 5 was replaced with 2,4'-di-n-propoxydiphenylsulfone, 2,4'-diallyloxydiphenylsulfone and 2.4 A thermosensitive recording paper was obtained in the same manner as in Example 5 except that '-jethoxycarbonylmethoxydiphenyl sulfone was used. These are referred to as Examples 6.7 and 8, respectively.

Comparative Example 3 A comparative thermosensitive recording paper was obtained in the same manner as in Example 5, except that liquid B in Example 5 was prepared in the same manner as in Comparative Example 1.

Comparative Example 4 A comparative thermal recording paper was obtained in the same manner as in Example 5 except that the sensitizer 2,4'-dimethoxydiphenylsulfone in Solution C in Example 5 was replaced with stearic acid amide.

Example 9 The color developer 4,4'-dihydroxydiphenylsulfone of Solution B in Example 1 was replaced with 3,3'-diallyl-4,4'-
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that dihydroxydiphenyl sulfone was used instead.

Examples 10 to 12 The sensitizer 2.4'-dimethoxydiphenylsulfone in Solution C in Example 9 was replaced with 2,4'-di-n-propoxydiphenylsulfone, 2,4'-diallyloxydiphenylsulfone and 2,4'-dimethoxydiphenylsulfone. A thermosensitive recording paper was obtained in the same manner as in Example 9 except that '-jethoxycarbonylmethoxydiphenylsulfone was used. Example 10 and
11 and 12.

Comparative Example 5 A comparative thermal paper was obtained in the same manner as in Example 9, except that liquid B in Example 9 was prepared in the same manner as in Comparative Example 1.

Comparative Example 6 A comparative thermal paper was obtained in the same manner as in Example 9, except that the sensitizer 2,4'-dimethoxydiphenylsulfone in Solution C in Example 9 was replaced with stearic acid amide.

Performance Test Examples Performance comparison tests of the thermal recording papers obtained in Examples and Comparative Examples were conducted as follows.

(1) Sample pressurization 2 using a chromogenic thermal gradient tester (Toyo Seiki Seisakusho)
Color was developed with kg/cJ heating time of 5 seconds. The coloring temperature was set in 5°C increments. Next, the color density C" was measured using a color computer (Suga Test Instruments). The color density of the thermal recording paper before color development was defined as Co" (background fog), and the color density after color development was defined as C-.

a) Skin fog The smaller the background fog, the better.

b) Plot the color development temperature and the color density C9 at that time on a graph, draw a tangent line, and from the intersection point, calculate the rise density, color density C", and the end temperature and color density C". The smaller the difference between the rising temperature and the ending temperature, the better.

(2) Using a heat gradient tester for PVC resistance, heat-sensitive recording paper that had been heated and colored was brought into close contact with a PVC sheet, and after being held at 60°C for 6 hours, the color density c'' of the background and colored areas was measured. The residual rate of the colored part is: residual rate - (color density after adhesion/color density after adhesion) x 100
Expressed in (%). The higher the survival rate, the better.

The results of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 2, the results of Examples 5 to 8 and Comparative Examples 3 and 4 are shown in Table 3, and the results of Examples 9 to 12 and Comparative Examples 5 and 6 are shown. are shown in Table 4.

Table λ actual f! I: 4.4'-Dihydroxydiphenylsulfone Table J Color developer IJ: 2,4'-dihydroxydiphenylsulfone Topsoil Color developer: 3,3'-diallyl-4,4
'Dihydroxydiphenylsulfone From Tables 2.3 and 4 above, 4'4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone and 3,3'-diallyl-4,4'-dihydroxy are used as color developers. Compared to using each diphenyl sulfone alone,
If the sensitizer of the present invention is used in combination, the rise temperature can be lowered,
At the same time, it can be seen that the temperature at the end of the process is lowered. Furthermore, it can be seen that the temperature difference is much smaller than that of stearic acid amide.

Regarding PVC plasticizer resistance, good results were obtained when 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, and 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone were used alone. Therefore, it can be confirmed that even if the sensitizer of the present invention is used in combination with these color developers, their properties do not deteriorate.

Claims (1)

[Scope of Claims] 1. Improving the sensitivity of a heat-sensitive recording material comprising a heat-sensitive coloring layer provided on a support, each containing a colorless or light-colored leuco dye as a color-forming substance and a phenol compound as a color-developing substance. A sensitizer for heat-sensitive recording materials, which is a sensitizer used for heat-sensitive recording materials, the main component being at least one ether derivative of sulfonyl diphenol represented by the following general formula (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) In the above formula, R_1 and R_2 may be the same or different, and each represents an alkyl group or alkenyl group having 1 to 4 carbon atoms, a benzyl group, Chlorbenzyl group or formula -
CH_2COOR_3 (in the formula, R_3 represents an alkyl group or alkenyl group having 1 to 3 carbon atoms).