JPS59190890A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance color forming property and preservability, by a method wherein a specified 4-hydroxyphthalic acid ester as a color developer, and benzyl terephthalate is used as an adjuvant, in a thermal recording material using a basic colorless dye. CONSTITUTION:A 4-hydroxyphthalic acid ester of formula (wherein each of R<1> and R<2> is hydrogen, an alkyl group, a benzyl group or a phenyl group) is used as a color developer for a basic colorless dye based on triphenylmethane, fluoran, leucoauramine or the like, and benzyl terephthalate is uses as a stabilizer for color development and preservation. The color development is used in a quantity of 1-40wt% of the total solid content of the thermal recording layer, while benzyl terephthalate is used in a quantity of 1-40wt% of the total solid content, and they are applied to a base such as a paper or a plastic sheet together with a color development accelerator, a water-soluble binder, a phenolic antioxidant or the like to provide a thermal recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording medium, and more specifically, the present invention relates to a heat-sensitive recording medium, and more specifically, in order to improve the color development of a heat-sensitive recording layer and improve its storage stability, a color developer and a monomer are used.
4-hydroxyphthalic acid ester represented by the general formula - (R1 and R2 represent hydrogen, alkyl group, benzyl group, phenyl group) and terephthalic acid dibenzyl ester as a color development and storage stabilization aid. Regarding the body.

A heat-sensitive recording layer containing a basic colorless dye and an organic acid is already known in Japanese Patent Publication No. 14039/1973.3 This recording paper applies heat energy to the recording layer to absorb a leuco compound, an organic acid and It is based on the principle of softening or melting a binder and bringing both coloring components into contact to cause a coloring reaction, and has recently been used in various fields such as printers and facsimile machines. The recording characteristics of the recording paper vary depending on the use, but for example, in order to increase the recording speed,
It can be said that it is necessary to improve the color development of the recording paper itself as well as improving the recording apparatus.

As a method for improving color development, (1) Use a more reactive color developer as a color developer.

(2) Contain low acid 11-point compound Pr in the 6-mineral layer.

(3) A method of smoothing the surface of the recording layer [-1 by increasing the contact with the recording element] is generally known.

The present invention relates to (1) and (2). Conventional color developer and [
- each fΦphenolic property fatty acids, aromatic carboxylic acids, salicylic acid derivatives and p-oxybenzoic acid derivatives z2
However, bisphenol A is generally used because it is known and has a relatively good storage stability. Since 6, which is a contingency, is not satisfactory, methods (2) and (3) are generally used in combination.

The present inventors have investigated the drawbacks of these conventional disinfectants and investigated gI? After conducting research, we found that 4-hydroxyphthalic acid ester was used as the color developer and 17, and 1. It has been found that by using terephthalic acid dibenzyl ester, a heat-sensitive δα recording medium with excellent recording properties and excellent storage stability f1 can be produced.

At the time of the invention, the %i coloring agent 4-hydroxyphthalate ester of the present invention had a slow rise in density after recording (the density was low immediately after recording, and the density +11' became dull over time), and it could not be used indoors. Although it was recognized that the major drawback was that the image density decreased when left for a long time, the present inventors investigated further in order to improve the drawbacks of Kone 1 etc., and as a result, terephthalic acid was used as an aid for color development and storage stability. It has been found that the above problem can be completely solved by using dibenzyl ester.

It has been previously proposed to use various phenolic antioxidants to prevent a decrease in image density, but while the addition of these substances is certainly effective, Another drawback of slow startup could not be improved.

In addition to phenolic antioxidants, various P'nT-
Considering the chemical substances in the phthalic acid 3-ster σ), it was found that the dibenzyl ester in the phthalic acid 3-ster σ) was particularly combined with the 1/C droplet, but those in the ortho or meta position had a low melting point. It has been found that terephthalic acid dibenzyl ester at the para position has an outstanding effect of 1-1, which overcomes the problem of low skin density.

When 61fJ ff=agent 4-hydroxyphthalate of the present invention and terephthalic acid dibenzyl ester as an aid for color development and storage stability are contained in 1 m of the dye (i
J] Although it is not clear whether the recording properties and storage stability are improved, it is unlikely that the 4-hydroxyphthalate ester crystallizes after recording due to the extremely good compatibility with both of them and the basic colorless dye. It is thought that it is lf.

In addition, the present invention! It goes without saying that the storage stability is further improved by adding a conventionally known phenolic antioxidant to the tp and P layers.

Examples of the 4-hydroxyphthalate color developer used in the present invention include the following 5 ic compounds.

-4 = dimethyl 4-hydroxyphthalate 103°C diisopropyl 102 dibenzyl 90 monobenzyl 152 The content of 4-hydroxyphthalate is 1 to 40 times the total solid content of the heat-sensitive recording layer; The content of is 1 to 40% of the total solid content of the heat-sensitive recording layer.
Be able to achieve the purpose of the weight defense.

Various derivatives such as triphenylmethane type, triphenylmethanephthalide type, fluoran type, leucoauramine type, diphenylmethane type, phenothiazine type, phenoxazine type, spiropyran type, indoline thread, indigo type, etc. are mentioned in the compound IJgJ. . Among basic colorless dyes, fluoran dyes have excellent storage stability, and examples of such substances include 3-diethylamino-6-methyl-7-anilinofluoran (black), 3-I N-
--Ethyl-P-toluideino)-6-methyl-7-anilinofluorane (black f'') 3-diethylami/6-methyl-7-(ortho, para-dimethylanilino)fluoran (hot-stretched), 3 -pyrrolidino fj-methyl-7-
Ryo = 1.1 / Fluorane (hot speech), 3-bipe 11 dino 6-methyl-7-anilinofluorane (black),
3-(N-cyclohexyl-N-methylamine)-6-
Methyl-7-ani1) nofluorane (black), 3-diethylamine-7(ortho-chloroanilino)fluorane (black t'h), 3-diethylamine-7-(meta-trifluoromethylanilino)fluorane (hot valve), 3-
Diethylamine-6-methyl-chlorofluorane (red?
), 3-diethylamine-6-methyl-fluorane (red), 3-cyclohexylamino-6-chlorofluorane (orange'), 3-(N-1-amy-N-ethyl-ami, /')-fi-methyl- 7-7 Nilinofluorane (black).

(2) Color development accelerator In order to further improve the recording properties of the heat-sensitive recording material of the present invention, conventionally known color development accelerators such as fatty acid amides such as stearamide can be used.

(3) Binder A water-soluble binder is mainly used to separate color formers dispersed in fine particles and solidify them. Polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid , casein, gelatin, starch and their derivatives.

(4) Storage stabilizer In order to improve the storage stability of the image of the heat-sensitive recording material of the present invention, various phenolic antioxidants can be used.

For example, 4,4-ptylidene bis(3-
Methyl-6-t-butylphenol) (@ point 208℃,
(same below), 2,2'-methylene-bis(4-methyl-
6-t-buty7-ruphenol') (120°C), 2,2'-methyleneno-
Bis(4-ethyl-6-t-butylphenol) (11
9°C), 2,5-di-1-butyl-hydroquinone (20°C), 2,5-di-1-butyl-hydroquinone (20
2°C), 2,5-di-t-amyl-hydroquinone (17
2°C), bis(3-methyl-4-hydroxy-5-t
-butyl-benzyl) sulfide (115°C), 2,2
-methylene-bis(4-)f-6-cyclohexyl-phenol) (118°C), bis-[:3.3'-bis-(4'-hydroxy-3-t-butylphenol)-butyric acid] glycol ester (165℃), 4,4'
-methylene-bis(2,6-di-t-butylpheno-A
Heat (]554℃, 4,4'-thiobis-(6-1-butyl-0-cresol), 2,6-bis(2-hydroxy-3'-1-butyl-5-methylbenzyl)-4- Methylphenol (]7]℃), 2,2'-iso-butylene 1
1 Denbis-(4,6-di-methylphenol) (]
f'i0℃), 4,4'-thiobis-(2-methyl-6
-t-butylphenol) (127°C), bis[2-(
2-Hydro 8-xy-5-methyl-3-t-butyl-benzyl)-4-
Methyl-6-t7'f-ruphenyl]terephthalate (
240°C), 2-hydroxy-4jtoxy-4-chlorobenzophenone (112°C), 2-hydroxy-4-methoxy-2'-carboxybenzophenone (]fi6°C
), Tris(3,5-di-t-butyl-4-hydroxy-phenyl)isocyanate (221°C), Tris[β
-(3,5-di-t-butyl-4-hydroxy-phenyl)flopionyl-oxyethyl] incyane) (
126°C), L3.5-)dimethyl-2,4,6-)
Lis(3,5-di-t-butyl-4-hydroxy-benzyl)benzene (244°C), N,N'-hexamethylene-bis(3,5-di-t-butyl-4-hydroxy-
hydrocinnamide) (156°C),],]L3-tris2-methy,TI/-4-hy)”roxy5-t-butylphenyl)butane (185°C), 2,2-dihydroxy-3,3'- cy(α-methyl-cyclohexyl) −
Examples include 5,5-dimethyl-diphenylmethane (130°C).

(5) Other additives In addition to the components (1) to (4) above, calcium carbonate, kaolin, clay, talc, oxidized +11j Adding white pigments such as lead and titanium oxide,
A fatty acid metal salt or the like can also be added deeply for the purpose of preventing head wear and sticking.

The substrate used in the present invention is generally paper such as high-quality paper, medium-quality paper, and coated paper, but other materials such as glass fiber sheets, plastic sheets, and film laminates can also be used as substrates. You can do it.

Next, examples of the present invention will be shown.

Example 1 a) Production of heat-sensitive recording material Liquids A and B having the following compositions were separately dispersed in a paint shaker (manufactured by Toyo Seiki) for 10 hours.

Solution A: 3-(N-isomeryl-N-ethylamino)-6-methyl-7-anilite fluorane 52 Light calcium carbonate 282 Zinc stearate 5 Polyvinyl alcohol 12%
Liquid 35y water
52fB liquid: 4-hydroxyphthalic acid dimethyl ester 15
y-prephthalic acid dibenzyl ester
52 aluminum hydroxide 189 polyvinyl alcohol 12% liquid 35f water
522 next A
Add liquid 12FM', B liquid 1252, polyvinyl alcohol 12 liquid 50, and water 402, mix and stir, and adjust 1~
Next, apply this coating liquid to the surface of 507 Takano Tetsu paper using a Meyer bar, and after drying, the coating surface will be 8 f! /d
The coating was coated and dried, and then subjected to calender treatment to obtain a heat-sensitive recording material whose recording layer had a Bekk smoothness of 500 seconds.

-]J- The following quality evaluation tests were performed on the obtained heat-sensitive recording material. The results are shown in the table.

b) Characteristic test 28℃, 05 section J (l;'ACOM F
'AX 62] (Fujitsu ■ high-speed thermal fax) was used to perform solid recording under the conditions of an applied pulse width of 0.45 m sec, a cycle of 5 m sec, and a recording power of 0.96 w/dat, the following characteristics were obtained. I conducted a test.

0) After recording, the density is measured at the peak of the recording peak of all color depth IV and when it is left in a room at 20° C. and 65 RH for 5 minutes, 60 minutes, and 1 day. As for the recording layer, it is desirable that the density at the ridges is high and that the saturation density is reached as quickly as possible.

■ Image storage stability Measure the image density after storing the solid Ht-recorded image in an open room at 20°C and 5% RH (illuminance 500 IuX) for 10 days.The one with the least decrease in image density. is desirable.

, ■ High-speed recording performance -] 2- Perform solid recording with the recording power set to 0.8 Q w/d (lt), and measure the image density immediately after the second recording.

It can be said that the higher the image density, the better the high-speed recording performance.

Example 2 The basic colorless dye in Solution A in Example 1 was replaced with 3-(N-methyl-N-ethylamino)-6-methyl-7-anilite fluorane and 3-(N-cyclohexyl- N
-Methylamine)-6-Methyl-7-anilite fluorane The test was carried out in the same manner as in Example 1 except for using 1-.

The results are shown in the table.

Example 3 A test was conducted in exactly the same manner as in Example 1, except that dibenzyl 4-hydroxyphthalate was used in place of dimethyl 4-hydroxyphthalate in Solution B in Example. The results are shown in the table.

Example 4 A -C test was conducted in the same manner as in Example 1 except that diisopropyl 4-hydroxyphthalate was used instead of dimethyl 4-hydroxyphthalate in Solution B in Example 1.・Example In Example 1, 42 of the 18y of aluminum hydroxide in the filter B solution was replaced with 4,4-butylizonobis(3-methyl-6-
1-Butylphenol) Vcl or I- was tested in exactly the same manner as in Example 1 with the exception of Example 1. The results are shown below.

Comparative Example 1 In Example J, the terephthalic acid dibenzyl ester in solution B was added to water at 1-1'', except for J (+ll)
The test was conducted with total < li:1-like K t. The results are shown in the table-1-.

Comparative Example 2 Example 1 except that in Example 1, 4,4-butylphenol was used instead of liquid terephthalic acid dibenzyl ester.
A test was conducted in exactly the same manner as above, and the results are shown in the table.

Comparative Example 3 A test was conducted in exactly the same manner as in Example 1, except that bisphenol A was used instead of dimethyl 4-hydroxyphthalate in Solution B in Example.

The results are shown in the table.

According to the results in the table, the examples of the present invention are more effective than the comparative examples.
It is excellent in all recording characteristics, including rise in overall density after recording, image storage stability, and high-speed recording.

table Patent applicant: Honshu Paper Co., Ltd. -4ノ

Claims (1)

[Claims] In a pA-sensitive recording material containing a basic colorless dye and a color developer that reacts with the homogeneous non-combining dye and develops a color, 5fE is used.
4-hydroxyphthalic acid ester represented by the general formula (R1 and R2 represent hydrogen, an alkyl group, a benzyl group, or a phenyl group) as a 4 f'' agent,
A thermosensitive recording material characterized in that it is completely cured of terephthalic acid dibenzyl ester as a coloring and storage stabilizing aid.