JPS60193692A - Heat-sensitive recording element - Google Patents

Abstract

PURPOSE:To increase the sensitivity of color formation and improve preservability by using a color-forming layer, a developer and a preservative stabilizer of respectively different specific component in a thermosensitive recording element mainly composed of basic achromatic dye and a developer which develops a color in reaction to the former. CONSTITUTION:Fluoran compound as a basic achromatic dye, a monophenol compound as a developer and thilendioxybisdibenzyl ester benzoate as shown in the formula as a preservative stabilizer are used. Thus it is possible to obtain a high sensitivity thermosensitive recording element suitable for high-speed recording, having high whiteness in texture and excellent preservability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a high-sensitivity heat-sensitive recording material in which the color development sensitivity of the heat-sensitive recording layer is improved and the storage stability is improved.

The present invention provides a heat-sensitive recording material mainly comprising a basic colorless dye and a color developer that reacts with the basic colorless dye to develop a color.
The coloring layer uses a fluoran compound as a basic colorless dye and a monophenol compound as a color developer,
It is characterized by containing 4,4' ethylenedioxybisbenzoic acid disantyl ester (1) represented by the following formula (1).

A heat-sensitive recording material containing a basic colorless dye and a color developer is already known, for example, from Japanese Patent Publication No. 14039/1983. This recording material is based on the principle that thermal energy is applied to the recording layer to soften or melt the basic colorless dye, color developer, and binder, and then bring the two coloring components into contact to cause a coloring reaction. Used in 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.

Conventionally, various phenolic substances such as bisphenol A, fatty acids, aromatic carboxylic acids, and the like are known as color developers, and bisphenol A in particular is a widely used substance. However, bisphenol A has a high melting point of 155° C., which limits the ability to increase sensitivity, and there is a strong need to develop a color developer suitable for high-speed facsimiles and high-speed printers.

From the above point of view, the present inventors actively developed color developers with low melting points, that is, various phenolic compounds with melting points in the range of 80 to 150°C, in order to increase the sensitivity of heat-sensitive recording materials. The findings of (1) and (2) were obtained.

(1) When a bis- or triphenol compound with a low melting point is used as a color developer, although the sensitivity improves, the whiteness of the background tends to decrease.

(2) When a monophenol compound with a low melting point is used as an organic color developer, the sensitivity is improved and the whiteness of the background is high, but the storage discoloration of the image and the erasure of fingerprints, which were not problems with bis- or triphenol compounds, were achieved. The problem of color arises.

In order to solve the problems described in (2) of fading of images of monophenol compounds and decoloring of fingerprint-attached areas, the present inventor conducted further intensive studies and as a result, arrived at the present invention.

That is, high-speed recording is possible by using a fluoran compound as a basic colorless dye, a monophenol compound as a color developer, and 4,4' ethylenedioxybisbenzoic acid dibenzyl ester as a storage stabilizer. We succeeded in obtaining a highly sensitive heat-sensitive recording material that is suitable for women's sex, has a high background whiteness, and has excellent storage stability.

The present invention will be explained in detail below.

The effective content of 4,4' ethylenedioxybisbenzoic acid dibenzyl ester used in the present invention is preferably 1 to 40 parts by weight in the heat-sensitive recording layer.

Also, it is not clear why storage stability is improved by using a water solution, but the basic rule is that the compatibility of the king with monophenolic compounds and fluoran compounds is extremely good, and the crystallization of the monophenolic compound in the coloring part is prevented. It is thought that he may be blocked. Note that when bisphenol A other than the one of the present invention is used as an organic color developer in combination with 4.4 ethylenedioxybisbenzoic acid dibenzyl ester, it is effective as a sensitivity improver, but it has no effect on improving storage stability. was not recognized.

In the present invention, the effective content of the monophenol compound used as an organic color developer in the heat-sensitive recording layer is preferably 1 to 40 parts by weight. The monophenol compounds that can be used in the present invention include ethyl 4-hydroxybenzoate,
Propyl 4-hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, inbutyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, methylbenzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, 4-
Hydroquinone 11A4 contains diimpropyl, dibenzyl 4-hydroxyphthalate, monobenzyl 4-hydroxyphthalate, dicyclohexyl 4-hydroxyphthalate, 4
- Diphenyl hydroxy heptatalate, diethyl 5-hydroxyisophthalate, hydroquinone monobenzyl ether, benzyl-4-hydroxyphenylacetate, resorcinol monobenzoate, 4-hydroxyacetophenone, 4-hydroxyacetophenone, p-cyclohexylphenol, 3-methyl- 4-isopropylphenol, 2,3.5)limethylphenol, 2-amino-4
Examples include -chlorophenol, 3-methyl-4-tertbutylphenol, etc. Among them, benzyl 4-hydroxybenzoate, 4-hydroxybenzoic acid benzyl, and Mention may be made of dimethyl hydroxyphthalate, dibenzyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, benzyl-4-hydroxyphenylacetate and resorcin monobenzoate.

As a two-way fluoran compound, 3-diethylamino-6
-Methyl-7-anilinofluorane (black), 3-(N
-ethyl-P-)luidino)-6-methyl-7-anilinofluorane (black), 3-diethylamine-6-methyl-7-(ortho, para-dimethylanilino)fluorane (black), 3-pyrrolidino 6-Methyl-7-anilinofluorane (black), 3-, piperidino 6-
Methyl-phoanilinofluorine 2nd (black), 3-(N
-cyclohexyl-N-methylamine)-6-methyl-
7-anilinofluoran (black), 3-diethylamino-7-(ortho-chloroanilino)fluoran (black)
, 3-diethylamino-7-(meta-trifluoromethylanilino)fluorane (black), 3-diethylamino-6-methyl-chlorofluorane (red), 3-diethylamino-6-methyl-fluorane (red), 3 -Cyclohexylamino-6-chlorofluorane (orange), 3
Examples include -(N-ynamyl-N-ethylamino)-6-methyl-7-anilinofluorane (black).

Next, other substances used in the present invention will be described.

(1) Color development accelerator In order to further improve the recording properties of the heat-sensitive recording medium of the present invention, conventionally known color development accelerators such as stearamide and other fatty acid amines can be used.゛ido, m-terphenyl,
p-benzylpiphenyl, dibenzyl terephthalate,
Benzylmandelic acid and the like can be used.

(2) Binder A water-soluble binder is used to isolate and fix the coloring agent dispersed in fine particles, such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid. , casein, gelatin, starch and their derivatives.

23) Storage Stabilizer The storage stability of the image on the thermal recording medium of the present invention is significantly improved by using 4°4-ethylenedioxybisbenzoic benzyl ester, but in order to further improve the storage stability. Various phenolic antioxidants and phenolic resins can be used together with 4,4'-ethylenedioxybisbenzoic acid benzyl ester. For example, 4,4-butylidene-bis(3-methyl-6-t-butylphenol) (melting point 208°C, L2,2'
-methylene-bis(4-methyl-6-t-butylphenol) (120℃), 2゜2'-methylene-bis(4-
ethyl-6-t-butylphenol) (119°C), 2
．． 5-di-t-butyl-hydroquinone (202°C), 2
．． 5-di-t-amyl-hydroquinone (172°C), bis(3-methyl-4-hydroxy-5-t-butyl-
benzyl) sulfide (115°C), 2,2'-methylene-bis(4-methyl-6-cyclohexyl-phenol) (118°C), bis-[3,3-bis-(4'-
hydroxy-3'-t-butylphenol)-butyric acid]
Glycol ester (165°C), 4,4'-methylene-bis(2,6-di-t-butylphenol) (154
°C), 4.4'-thiobis-(6-2-butyl-0-cresol), 2.6-bis(2'-hydroxy-3'
-phthyl-5-methylbenzyl)-4-methylphenol (171°C), 2,2'-iso-butylidene-bis-(4,6-di-methylphenol) (160°C),
4,4'-Thiobis-(2-methyl-6-t-butylphenol) (127°C), bis[2-(2-hydroxy-5-methyl-3-butyl-benzyl)-4-methyl-6- t-butylphenyl]terephthalate (24
0°C), 2-hydroxy-4-methoxy-4-chlorobenzophenone (112°C), 2-hydroxy-4-methoxy-2'-carboxybenzophenone (166°C),
Tris(3,5-di-t-butyl-4-hydroxy-phenyl) incyanate (221°C), Tris[β-(
3,5-di-t-butyl-4-hydroxy-phenyl)
Propionyl-oxyethyl]isocyanate (126
), 1.3.5-)dimethyl-2,4,6-)lis(3,5-di-tert-butyl-4-hydroxy-benzyl)benzene (244°C), N,N-hexamethylene-bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamide) (156°C), 1.1.3-)lis(2-
Methyl-4-hydroxy-5-t-butylphenyl)butane (185°C) 1.2.2-dihydroxy-3,3'
-di(α-methyl-cyclohexyl)-5,5-dimethyl-diphenylmethane (130°C) and the like.

(4) Other additives In addition to the components (1) to (3) above, calcium carbonate, kaolin, clay, talc, oxidized White pigments such as zinc and titanium oxide may be added, and fatty acid metal salts may also be added for the purpose of preventing head wear and sticking.

The substrate used in the present invention is generally paper such as wood-free paper, medium-quality paper, or coated paper, but other substrates such as glass fiber sheets, plastic sheets, and film-laminated papers can also be used. I can do it.

Next, typical examples and comparative examples of the present invention will be described in order to specifically explain the present invention.

Examples 1 to 6, Comparative Examples 1 to 9 Liquid A (dye dispersion) 10% polyvinyl alcohol water 4 parts Water 3 parts Liquid B (developer dispersion) Dimethyl 4-hydroxyphthalate 6 parts 10% polyvinyl Alcohol aqueous solution 15 parts Water 9 parts Liquid C (developer dispersion) Dibenzyl 4-hydroxyphthalate 6 parts 10% polyvinyl alcohol aqueous solution 15 parts Water 9 parts Liquid (developer dispersion) Benzyl 4-hydroxybenzoate 6 Parts 10% polyvinyl alcohol aqueous solution 15 parts Water 9 parts Solution H (developer dispersion) Hydroquinone monobenzyl ether 6 parts 10 parts Polyvinyl alcohol aqueous solution 15 parts Water 9 parts Solution H (developer dispersion) 10% polyvinyl alcohol aqueous solution 15 parts water 9 parts Solution C (developer dispersion) Resorcin monobenzoate 6 parts 10 parts Polyvinyl alcohol aqueous solution 15 parts Water 9 parts Solution H (Developer dispersion) Bisphenol A 6 parts 10 parts Polyvinyl alcohol aqueous solution 15 parts Water 9 parts Solution ■ (sensitizer and storage stabilizer dispersion) 10% polyvinyl alcohol aqueous solution 15 parts water 9 parts J solution (sensitizer dispersion) Stearamide 6 addition 1 10 Tivolivinyl alcohol aqueous solution 15 parts Water 9 parts Liquid (filler and lubricant dispersion) Calcium carbonate 10 parts Zinc stearate 3 parts 10% polyvinyl alcohol aqueous solution 10 parts Water 7 parts The canned liquid of the above composition is ground in a paint shaker (manufactured by Toyo Seiki) to a particle size of 2μ. .

Next, the dispersion liquid is mixed in the ratio shown in Table 1 to form a coating liquid.

Next, apply this coating liquid to the surface of high-quality paper of 50 hats using a Maya parr so that the amount of coating after drying is 7 f/rr? After coating and drying, a heat-sensitive recording material with a recording surface having a Bekk smoothness of 500 seconds was obtained by performing a supercalenter treatment. The obtained heat-sensitive recording bodies were evaluated by the following quality characteristic tests, and were designated as Examples 1 to 6 and Comparative Examples 1 to 9.

The results are shown in Table 2.

[Quality characteristic test]

FACOM FAX 621 indoors at 20℃ and 65% density
(manufactured by Fujitsu ■) with an applied pulse width of 0.45 m s
ec.

A third person's test was conducted by performing solid recording under the conditions of a period of 5 mBecs and a recording power of 0.96 watts/dot (0.8 watts/dot only in the case of (1) below). All concentration measurements were performed using Macbeth Densitometer RD514 (Visual Filter).

■Skin density The density of the unrecorded area was measured.

■ Recording density The density of the solid recorded area was measured. The higher the density, the better the high-speed recording performance.

■ After recording the storage stability of the colored part, store it indoors at 20℃ and 65%RH (500lux
, ), and then measure the density of the colored area after leaving it for 30 days. It is preferable that the concentration decreases less.

■ Decolorization due to fingerprint attachment. Fingerprints were attached to the colored area and 651 proteins (500 lu
x, ) After being left in the room for 10 days, the degree of discoloration was observed.

○...Does not erase the color △......or ＼Erases ×......Erases ■ Using the high-speed recording FACOM FAX 621, the recording power is set to 0. .8
Solid recording is performed in watts/dots, and the density of the colored area is measured immediately after recording. The higher the density, the better the high-speed recording performance.

According to the results in Table 2, the examples of the present invention have lower performance compared to the comparative examples.
0, which is excellent in all aspects: high-speed recording performance, whiteness of the background, and storage stability.

Claims (2)

[Claims] (1) In a thermosensitive recording material whose main components are a basic colorless dye and a color developer that develops a color by reacting with the basic colorless dye, the coloring layer uses a fluoran compound as the basic colorless dye, 4,4' ethylenedioxybisbenzoic acid dibenzyl ester using a monophenol compound as a color developer and represented by the following formula (1)... - A thermosensitive recording material characterized by containing (1). (2) The monophenol compound is selected from 2-benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, benzyl 4-hydroxyphenylacetate, or resoldino monobenzoate. 1. The heat-sensitive recording material according to item 1 of the patent claims.