JPH021379A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance color forming sensitivity of a thermal recording material at low temperature by providing a thermal recording layer comprising a color forming substance, a phenolic compound having a melting point of 80-130 deg.C and bis(4-benzyloxyphenyl) sulfide on a support. CONSTITUTION:A colorless or light-colored color forming substance, a phenolic compound having a melting point of 80-130 deg.C as a color developer, and bis(4- benzyloxyphenyl) sulfide of formula I as both a color developer and a sensitizer for controlling thermal sensitivity are sufficiently mixed and ground together with a binder in water or an organic solvent to prepare a dispersed coating liquid. The coating liquid is applied to a support, and is dried to provide a thermal recording layer, thereby obtaining a thermal recording material. The thermal recording material obtained has a lowered eutectic point, so that it is capable of forming a deep color at a low temperature and in a narrow temperature range, is free of spontaneous color formation or ground color development, and is capable of providing a jet-black image.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material. More specifically, a phenolic compound with a melting point of 80 to 130°C is used as a color developer that melts by heating and acts on a color-forming substance to develop color, and a sensitizer that controls the thermal coloring temperature is used as a bis(4). - A thermosensitive recording material using benzyloxyphenyl) sulfide.

(Prior art) Recording materials that utilize the coloring phenomenon caused by contact between an electron-donating color-forming substance and an electron-accepting biological coloring agent include, for example, pressure-sensitive recording paper, thermal recording paper, and thermal copying. Paper, etc., has come into widespread use in recent years as the streamlining of office work has progressed.

In conventionally known, so-called dye-coloring thermosensitive recording papers that use triphenylmethane dyes or leuco bases of fluoran dyes as color-forming substances, bisphenol △ is a typical color developer that has been widely used in the past. (2,2
'-Bis(4-hydroxyphenyl)propane, melting point,
156°C] (Japanese Patent Publication No. 44-3680) is well known, or is rarely used alone.

Generally, dyes have relatively high melting points, so when a color developer with a high melting point, such as bisphenol A, is used, it is usually used in combination with a sensitizer that lowers the thermal coloring temperature.

As the sensitizer, higher fatty acid amides, such as stearic acid amide (melting point 108.5 to 109°C), have conventionally been used. (Japanese Unexamined Patent Publication No. 58-183287) However, for applications such as high-speed facsimile paper and POS labels, which have rapidly expanded in demand in recent years, the color development sensitivity at low temperatures and the light fastness of the color image are 1. Since the storage stability of color images is still insufficient, many patents have been filed for combinations with other color developers, sensitizers, storage improvers, etc.

For example, compared to stearinamide, 1-hydroxy-2
-Phenyl naphthoate (melting point 94°C) (JP-A-57-
191089) and p-benzylbiphenyl (melting point: 86°C) (Japanese Patent Application Laid-Open No. 60-82382).

(Problem to be solved by the invention) The color development sensitivity of thermal recording paper is usually correlated with the eutectic point of the color developer and sensitizer contained in the recording paper, so the eutectic point suitable for the desired thermal paper is determined. It is necessary to select a combination of color developer and sensitizer that has the following properties. In this case, if the eutectic point is too low, there is a risk of spontaneous coloring during the production or storage of the recording paper, and if the eutectic point is too high, the thermal energy given to the recording paper will be insufficient, resulting in low color development). , cannot be used practically.

For this reason, color developers with a high melting point such as bisphenol A must be used in combination with expensive sensitizers such as phenyl 1-hydroxy-2-naphthoate and p-benzylbiphenyl, which have a low melting point. is often insufficient.

The above-mentioned color development sensitivity refers to the temperature at which a practically sufficient color density is developed, but even if this color development sensitivity is high, if the temperature range from the start of color development to the maximum density is not narrow, the color image of thermal paper will not work. This causes the inconvenience that the image becomes unclear. For this reason, especially in recent years, the recording monthly rate of thermal recording paper for high-speed printers with short heating pulse widths develops color at low temperatures, reaches sufficient color development within a narrow range of 8 degrees from the coloring start temperature, and instantly develops color when heated. The combination of developer and sensitizer
has been requested to leave.

In addition, thermal recording paper prepared by combining bisphenol A and various sensitizers has the drawback that the water resistance of the colored image is poor and the image tends to disappear and become difficult to see.

Thermal paper generally has to be colored black, but black with a red tint, such as bisphenol A, tends to be avoided because it looks dirty, and jet black with a green tint is generally preferred. ing.

The purpose of the present invention is to improve the color development sensitivity at low temperatures by using a suitable combination of a color developer and a sensitizer, and to provide a heat sensitive image with high storage stability, with less background fog and less thermal fog during storage. The purpose is to provide recording vJ fees.

(Means for Solving the Problem) As a result of investigating various compounds effective as a color developer and a sensitizer, the present inventors used sulfite of formula (I) as a sensitizer, and found that a relatively The inventors have discovered that by using a phenolic compound with a low melting point, it is possible to obtain a heat-sensitive recording material that is free from the above-mentioned drawbacks and has excellent performance, and has thus arrived at the present invention.

Specifically, the low melting point phenolic compound mentioned above is:
It refers to a substance with a melting point of 80 to 130°C, especially the formula (n
) 4-benzyloxyphenyl 4'ditroxyphenyl sulfide (melting point 116°C) of the formula (I (I
) benzyl 4-hydroxyphenyl sulfide (melting point 94°C), bis(
4 pencyloxyphenyl) (IV) 7-5-his(4-hydroxyphenylthio)-3-oxapentane (melting point 109°C) represented by CH2CH2-8+OH, 4-isopropyloxyphenyl 4 represented by formula (V) '-Hydroxyphenylsulfone (melting point 130°C), formula (■
) Bis(4-hydroxy-3-methylphenyl)sulfite (melting point 124°C), benzyl 4-hydroxybenzoate (melting point 1), represented by the formula <vi> H3 H3
10°C), represented by formula (VI): 2-(3,4-dihydroxyphenyl)
2,/1.4-trimedelpentane (melting point 109°C)
, when used as a color developer, an excellent heat-sensitive recording material can be obtained.

For example, the thermal recording paper using the sensitizer, color developer, and color-forming substance of the present invention has lower Color develops to sufficient density at heating temperature.

■ Color develops instantly when heated within a narrow temperature range from the temperature at which color development begins.

■ There is almost no color development on the background, and 'f? , the water resistance of the color image is good.

■ The color is jet black with a green tint.

A superior thermal recording paper is obtained, and has sufficient performance for use in high-speed facsimiles and high-speed printers. Furthermore, when used for thermal copying paper, a practically sufficient coloring performance can be obtained.

As the color-forming substance used with the recording material of the present invention, various electron-donating dyes that develop color by melting reaction with a color developer may be used. -chloroanilino)fluoran, 3-
Ethyl ISO ~ amyl-6-medy-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-methyl cyclohexylamino-
〇-Methyl-7-anilitofluorane, 3-diethylamine-7(o-chloroanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluoran Oran, 3-
Ethyl-p-tolylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-medy-7-(p
-ter↑-butylanilino)fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-
Cyclohexylamino-7-chlorofluorane, 3-diedylamino-7-methylfluorane, 3.3'-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl (Crystal Violet Rough 1-N), 3.
3-bis(4-dimethylaminophenyl)phthalide [
Malachite green rough 1hen), 1.3゜3-
Trimethylindolino-6-chloro8-methoxypenzospiropyran, 3-(4-diethylamine-
2-ethoxyphenyl)-3(1-ethyl-2-methylindol-3-yl)4-azaphthalide, tris-4
-dimethylaminophenylmethane, etc.

The heat-sensitive recording material of the present invention (within the film) is manufactured by the following method.

First, the sensitizer and color developer of the present invention and the usually colorless or light-colored color former are thoroughly mixed together with a binder in a medium that does not dissolve them separately (for example, water and organic solvent such as petroleum). Pulverize to make a dispersion.

In this case, it is desirable that the dispersed particles be ground into as small particles as possible, specifically, to a particle size of 1 micron or less, using a grinding machine such as a caulking ball mill.

Binders used to prepare these dispersions include synthetic polymers such as polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, styrene maleic copolymer, polyacrylic acid, polyacrylamide, and styrene-butadiene rubber latex. , natural or modified natural polymers. The resulting dispersion is coated onto a support such as paper and dried to produce a heat-sensitive recording sheet. Generally, both dispersions are mixed and applied to the support, but both dispersions may be applied separately in two parts. The amount of color developer, sensitizer, and binder to be used for the color-forming substance differs depending on the combination thereof, so it cannot be determined unconditionally, but it is usually preferable to use the color developer, sensitizer, and binder for 1 part by weight of the color-forming substance. 0.3 to 15 parts by weight, 0.01 to 8 parts by weight of sensitizer.

1 to 3 parts by weight of binder, particularly preferably 1 to 3 parts by weight of color developer
It is preferable to use 5 parts by weight of the sensitizer, 1 to 5 parts by weight of the sensitizer, and 1 to 3 parts by weight of the binder.

When producing the heat-sensitive recording sheet of the present invention, if necessary, talc, kaolin, titanium oxide, calcium carbonate, zinc oxide, diatomaceous earth, urea-formaldehyde resin, etc., may be added to the coating liquid. , a water-soluble binder with convexity or a crosslinking accelerator, a protein adhesive and a water resistance agent such as gel tar aldehyde, beeswax,
Animal waxes such as shellac wax, colored waxes (such as carnauba wax), synthetic waxes such as petroleum waxes, paraffin waxes, microcrystalline waxes, polyethylene waxes, calcium stearate,
Lubricants such as metal soaps (highly handled fatty acid metal salts) such as zinc stearate, pressure coloring inhibitors, various surfactants,
Coating suitability and durability of the recording sheet can also be improved by using an antifoaming agent or the like.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.
The present invention is not limited to these examples.

The method for producing the heat-sensitive recording sheets 1 to 1 used in the examples and the measurement methods for various coloring characteristics, water resistance, etc. were carried out by the methods described below.

(1) Method for producing a heat-sensitive recording sheet.

(A) Liquid (parts are shown by weight) Color forming substance 1.0 parts Sensitizer 2.0 parts 10% by weight Polyvinyl alcohol 6.0 parts Water 9.8 parts CB) Liquid 1.0 parts 1. 0 parts 0.1 parts Color developer Calcium carbonate Zinc stearate 10 @ suspension% Polyvinyl alcohol 4.0 parts Water 6.5 parts (A) Color forming substance in solution, CB) Various color developers in solution Then, liquids (A) and (B) were blended and each was dispersed using a paint shaker to prepare a dispersion liquid.

1 part by weight of liquid (A) and 3 parts of liquid (B) obtained as described above were mixed again in a paint shaker, and this was coated on high-quality paper in a dry coating amount of 4.5±0.5 g/ A heat-sensitive recording sheet was prepared by coating and drying to give Td.

(II) Method for measuring coloring properties and water resistance of heat-sensitive recording sheets.

Using a YSS type heat sealer (manufactured by Tester Sangyo), the a0 color development characteristic recording sheet was placed on a metal block with a temperature gradient of 60 to 130°C (pressure 14, manufactured by Macbeth) to determine the color density and color development. The relationship between temperature was determined.

b. Maximum color density Heating the metal block mentioned above to 200℃, pressure 0.6
K! j/cti for 3 minutes to develop color.

After color development, the density was measured using the method described above.

After soaking the C0 water-resistant thermosensitive recording sheet in water for 24 hours, the density was measured by the method described above.

Example 1. (A) to (G) Using bis(4-benzyloxyphenyl) sulfide as a sensitizer and 4-benzyloxyphenyl 4'-hydroxyphenyl sulfide (formula 2) as a color developer, various colors shown in Table 1 were developed. A heat-sensitive recording sheet was created by combining the materials. The manufacturing method is as described above. Table 3 shows the evaluation results of the obtained heat-sensitive recording sheets.

Examples 2-7 Bis(4-benzyloxyphenyl) sulfide 2.0
1 part as a sensitizer, 1.0 part of various phenolic compounds having a melting point of 80 to 130°C shown in Table 2 as a color developer,
A heat-sensitive recording sheet was prepared by combining it with various color-forming substances.

Table 3 shows the evaluation results of the obtained heat-sensitive recording sheets.

Comparative Example 1 2.0 parts of stearic acid amide as a sensitizer, 91.0 parts of bisphenol AC2,2-bis(4-hydroxyphenyl)propane as a color developer, and 3-
A thermosensitive recording sheet was prepared using dibutylamino-6-methyl-7-anilinofluorane.

Comparative Example 2 A heat-sensitive recording sheet was produced under the same conditions as in Example 1 (F) except that no sensitizer was used.

Comparative Example 3 A thermosensitive recording sheet was produced under the same conditions as in Example 2 except that no sensitizer was used.

The measurement results of the evaluation of the heat-sensitive recording sheets evaluated in Comparative Examples 1 to 3 are also shown in Table 3.

(Effect of Enmei) As shown in Table 3, the heat-sensitive recording material using a combination of a sensitizer and a color developer of the present invention has a lower eutectic point;
It produces tonal colors at low temperatures and within a narrow temperature range, has no natural coloration or background coloration, and has excellent performance in producing jet-black images.

This is also clear from a comparison of the conventionally widely used combination of Suphenol A and stearic amide (Comparative Example 1). Furthermore, from Comparative Examples 2 and 3, it is clear that the sensitizer of the present invention has a remarkable low-temperature coloring effect.

Applicant: Steel Chemical Industry Co., Ltd. representative increase Field Yutaka Medicine

Claims (8)

[Claims] (1) A colorless or light-colored color-forming substance provided on a support;
In the heat-sensitive layer consisting of a color developer that causes the color-forming substance to develop color when heated and a sensitizer that controls the heat sensitivity, a phenolic compound having a melting point of 80 to 130°C is used as the color developer, and a phenolic compound having a melting point of 80 to 130°C is used as the sensitizer, and the formula ( I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) A heat-sensitive recording material characterized by using bis(4-benzyloxyphenyl) sulfide. (2) The thermosensitive compound according to claim (1), wherein the phenolic compound is 4-benzyloxyphenyl 4'-hydroxyphenyl sulfide represented by formula (II) ▲Mathematical formula, chemical formula, table, etc.▼(II) Recording materials. (3) The heat-sensitive recording material according to claim (1), wherein the phenolic compound is benzyl 4-hydroxyphenyl sulfide represented by the formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (III). (4) Phenolic compounds are 1,5-bis(4-hydroxyphenylthio)- represented by the formula (IV) Claim (1) which is 3-oxapentane
The heat-sensitive recording material described. (5) The phenolic compound is bis(4-hydroxy-3-methylphenyl) sulfide represented by formula (V) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (V) Heat-sensitive recording material. (6) The heat-sensitive recording material according to claim (1), wherein the phenolic compound is benzyl 4-hydroxybenzoate represented by the formula (VI) ▲Mathematical formula, chemical formula, table, etc.▼(VI). (7) Claim (1) in which the phenolic compound is 4-isopropyloxyphenyl 4'-hydroxyphenyl sulfone represented by formula (VII) ▲Mathical formula, chemical formula, table, etc.▼(VII)
The heat-sensitive recording material described. (8) The phenolic compound is 2-(3,4-dihydroxycyphenyl)- represented by the formula (VIII) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(VIII)
The heat-sensitive recording material according to claim (1), which is 2,4,4-trimethylpentane.