JPS5945193A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To form a color forming image which forms color of a high density at a low temperature but won't face by using a mixture of phenol based color developing substance and paracumylphenol in a thermographic material to be usd widely in thermal printers of computers, thermopen recorder as medical measuring instrument or the like, thermal facsimile or the like. CONSTITUTION:As color developing substance, paracumylphenol and at least one kine of phenol compound selected from a group comprising bisphenol type compounds and thiobisphenol type compounds are combined. The mixture is dispersed into a binder together with a color forming substance and additives such as surfactant, defoaming agent and inorganic pigment and applied on a support. Black unicolor forming images by thermal recording using the heat sensitive recording paper thus formed are excellent in the temperature sensitivity and the fadability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in heat-sensitive recording materials. The heat-sensitive recording material of the present invention develops color with high density and uniformity at low temperatures, and is highly resistant to fading.

A heat-sensitive recording material is a heat-sensitive recording material in which a heat-sensitive coloring layer that develops color when heated is provided on a support such as paper, synthetic paper, or plastic film.
It is widely used in calculators, computer terminal thermal terminals, 7" IJ printers, thermopen recorders for medical measuring equipment, as recording material for thermal facsimiles, and even in ticket vending machines.

To make a heat-sensitive recording material, first, a colorless or light-colored lactone, lactam, or spiropyran-based leuco dye is first used as a color-forming substance, and a phenol compound is used as a color-developing substance that develops color when the color-forming substance is heated, respectively. After pulverizing and dispersing with a ball mill or sand mill, a binder is added and mixed, and wax, surfactant, antifoaming agent, inorganic pigment, etc. are added as necessary to prepare a thermosensitive coloring layer forming liquid. The mixture is mixed in an appropriate proportion, applied to a support such as paper, synthetic paper, plastic film, etc., and dried. The heat-sensitive recording material thus obtained is heated with a thermal head or thermopen made of a heating resistor or nichrome wire to form a colored image.

Conventionally, phenolic color developing substances include bisphenol A, bisphenol-type compounds such as 4,4'-cyclohexylidene bisphenol, and 4,4'-thiobisphenol (commonly known as "bisphenol SJ"), 4,4'
Thiobisphenol type compounds such as -thiobis-3-methyl-6-tert-butylphenol (commonly known as "thiobis3M6B") have been used. However, these known phenolic color developing substances generally have a high color development temperature and have the disadvantage that they cannot meet recent demands for high-speed printing.

The present inventors investigated para-cumylphenol as a color developer that has excellent color development properties at low temperatures and is suitable for high-speed printing, but it has become clear that the color fading property is significant and that it is not suitable for practical use.

As a result of further research, we found that by using a mixture of the above-mentioned known phenolic color developing substances, i.e., bisphenol-type compounds or thiobisphenol-type compounds, and para-cumylphenol, the drawbacks of each were compensated for. The inventors have discovered the surprising fact that high-density color development occurs at a much lower temperature than the color development temperature of various known phenolic color-developing substances, and no fading is observed, leading to the present invention.

Therefore, the heat-sensitive recording material of the present invention is a heat-sensitive recording material in which a heat-sensitive coloring layer containing 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 support. As a color substance, (a) Hala-cumylphenol, Zrahi (bt) is characterized in that at least one phenol compound selected from the group consisting of bisphenol-type compounds and thiobisphenol-type compounds is used in combination.

Examples of bisphenol-type compounds and thiobisphenol-type compounds belonging to the group (b) above include the above-mentioned bisphenol A, i.e., 4,4'-isopropylidene bisphenol, 4,4'-cyclohexylidene bisphenol, 4'+ 4'-butylidene bisphenol, 4.4'-isopropylidene-bis(2-
methylphenol), 4,4'-isopropylidene-bis(2-tert-butylphenol), the above-mentioned bisphenol S, i.e., 4,4'-thiobisphenol, and thiobis3M6B, i.e., 4,4'-thiobis(3 -methyl-6-tert-butylphenol).

4,4'-ethylidene bisphenol, 4,4'-benzyritine bisphenol and 2,2'-bisphenol-4- were discovered by the present inventors to be useful as phenolic color developing substances and were proposed separately. Methylpentane can be used similarly. These are examples, and the present invention is not limited thereto.

The mixing ratio of para-cumylphenol (a) and the phenol compound of group (b) is 1:9 to 9:1, preferably 1:3 to 3:1 by weight.
The total amount of the color developing substance used is the amount necessary to sufficiently develop the color developing substance. It will be effective at the same level as known color developing substances.

Examples of colorless or light-colored coloring substances used in the heat-sensitive recording material of the present invention include crystal violet lactone, malachite green lactone, 3,3-bis(p-dimethylaminophenyl)-6-7minophthalide, 3,3-bis (
p-dimethylaminophenyl) 6-1)-) luenesulfonamide, 2-(2'-chloroanilino)-6-dinithylaminofluorane, 3-diethylamine-6-methyl-7-N-phenylaminofluorane, 3-diethylamine-7-cybenzylaminofluorane, 3-cyptylamino-6-methyl-7-chlorofluorane, 3-diethylamine-6-methyl-7-chlorofluorane, 3
-diethylamino-7-phenylfluorane, 3-dimethylamine-6-medoxyfluorane, 3-dimethylamine-7-(N-methyl-p-toluidino)fluorane, 6'-chloro-8'-methoxybenzoindoly Nopyrillospiran, 3-morpholino-5,6-dibenzofluoran, 3;'Chiluzy β-naphthospiropyran 0
, benzo-β-naphthospiropyran A.

The heat-sensitive recording material of the present invention uses the above-mentioned color-forming substance and color-developing substance as a binder together with desired additives such as a surfactant, an antifoaming agent, and an inorganic pigment according to a technique commonly used for forming a heat-sensitive color-forming layer. It is manufactured by dispersing the material in a liquid and coating it on a support such as paper, synthetic paper or plastic film.

The binder may be appropriately selected from conventionally known binders such as starch, hydroxyethylcellulose, methyl-oxycellulose, carboxyethylcellulose, polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, and the like.

EXAMPLES In order to explain the present invention more specifically, Examples will be shown below.

Example 1 The following liquids A and B were separately prepared as thermosensitive color forming layer forming liquids, and were pulverized using a ball mill to a particle size of 2 μm to ensure complete dispersion.

1 (color-forming substance dispersion) 2-(2'-chloroanilino)-6-dinitylaminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 2o Water
20 〃B
i (color developer dispersion) 4.4'-ethylidene bisphenol 7 TE
Part H paracumylphenol 21 〃10
% polyvinyl alcohol aqueous solution 4o water
1o 〃
The 4,4'-ethylidene bisphenol used for Bi is
It is one of the phenolic color developing substances that the present inventors used for the first time.

Next, liquids A and B were mixed and applied to general paper with a basis weight of 5o2/- so that the dry coating amount was about 2 g/m', and the mixture was air-dried to obtain thermal recording paper.

Using this thermosensitive recording paper, thermal recording was carried out for 5 seconds using a Rhodiaceta type thermal tester, and at the same time, black solid colored images were obtained on sheets (temperature difference in 5°C increments).

Table 1 shows the evaluation results of temperature sensitivity and fading property.

"Thermosensitivity" refers to the temperature at which the heated fabric portion of a heat-sensitive recording material reaches a practical density.

The lowest temperature is indicated by ◎, the considerably higher temperature is indicated by XX, and the intermediate stages are marked by ○, △, and ×.
Practical density means that the density measured by Macbeth MS-2020 type colorimeter is 0.7 or more.

"Fadeability" refers to the change in density after developing a color to a practical tonicity and leaving it indoors under natural light for 30 days. The case where the discoloration was significant was rated as ×, the case where there was no practical problem was rated as ○, and the case where it was hardly observed was rated as ◎.

Examples 2 to 7 In place of 4,4'-ethylidene bisphenol in Solution B in Example 1, various phenolic color developing substances listed in the component (b) column of Table 1 were used.

Table 1 shows the results of measuring the characteristics of the obtained thermal recording paper.

In place of the combination of 4,4'-ethylidene bisphenol and para-cumylphenol in the B solution of Ichirei "Niji V Go" Work Example 1,
Various phenolic color developers listed in Table 1 were used alone.

The test results of the thermal recording paper are also shown in Table 1.0 Examples 8 to 12 In Example 2, para-cumylphenol 4 of liquid B
．． Example 2 was repeated by varying the ratio of 4'-1 sobropylidene bisphenol, ie, bisphenol A, as shown in Table 2.

The results are shown in Table 2.

Examples 13 to 17 In Example 7, para-cumylphenol of liquid B and 4
, 4'-thiobis(3-methyl-6-tert-butylphenol) or thiobis3M6B was repeated as shown in Table 2.

The results are shown in Table 2.

Table 2 Patent applicant: Mitsui Petrochemical Industries, Ltd. Osaka Godo Co., Ltd.

Claims (2)

[Claims] (1) Colorless or light-colored leuco dye as a coloring substance,
In a heat-sensitive recording material comprising a heat-sensitive color forming layer provided on a support, each containing a phenol compound as a color developer, the color developer includes (a) para-cumylphenol, and (b) a hisphenol type compound and a thiophenol compound. A heat-sensitive recording material characterized in that it contains at least one phenol compound selected from a group consisting of bisphenol type compounds. (2) As a color developer, para-cumylphenol (a) and phenol compound (b) are used in a weight ratio of 1:9 to
The heat-sensitive recording material according to claim 1, used in combination in a ratio of 9:1, preferably 1:3 to 3:1.