JPH0361083A - Thermal recording medium - Google Patents

Abstract

PURPOSE:To produce a recorded image which can be stored in satisfactory condition for a long time using a thermal recording medium best suited to high-speed recording process by using more than one kind of specific compound as a coloring agent. CONSTITUTION:A thermal recording layer containing leuco compound and a coloring agent which forms a color in reaction with the leuco compound is provided on a support. In formula, R1 is hydrogen or CnR2n+1; R2, R3 are CnH2n+1; n is 1 to 5. High-quality paper, intermediate-quality paper and coated paper are normally used as the support. In addition, glass fiber sheet, plastic sheet, filmlaminated paper and unwoven cloth are used. A system containing a coloring material and a system containing a coloring agent are subjected to crushing process in their respective water media containing binder. Then these two different materials are blended into a thermally sensitive paint. The paint thus obtained is applied to or used for impregnation of the support, and the paint applied or used for impregnation is dried to prepare a thermal recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording medium, and particularly to a heat-sensitive recording medium that has excellent suitability for high-speed recording and excellent storage stability.

(Prior Art) A thermosensitive recording paper containing a normally colorless or light-colored color-forming substance (hereinafter referred to as a leuco compound) and a color developer is, for example,
This is already known from Japanese Patent Publication No. 45-14039. This recording paper is based on the principle that heat energy is applied to the recording layer to soften or melt the leuco compound and color developer, and the two color components are brought into contact to cause a color reaction. used in The recording characteristics of the recording paper differ depending on the application, but for example, in order to increase the recording speed, it is necessary to improve the recording device and promote the color development of the recording paper itself, and in recent years there has been a demand for the development of thermal paper in this direction. ing.

Conventionally, bisphenol A has been commonly used as a color developer, but bisphenol A has a melting point of 157°C.
However, although it has been proposed to add various sensitizers to increase the suitability for high-speed recording, none has yet been found to be sufficiently effective.

In addition, in order to improve suitability for high-speed recording, many proposals have been made for color developers with lower melting points, and a practical one is P-hydroxybenzoic acid ester (JP-A-56-14
4193) and 4-hydroxyphthalic acid diester (Japanese Unexamined Patent Publication No. 153692/1989), etc. However, thermal recording materials using these substances have (1) extremely low image density immediately after recording; The concentration increases over time.

(2) The density of the recorded image fades significantly during storage.

(3) Powder builds up in the dark recorded image area (whitening development).

There is a serious drawback.

[Problems to be Solved by the Invention] Therefore, the present inventors conducted intensive research with the aim of obtaining a heat-sensitive recording medium that has excellent high-speed recording performance and excellent storage stability of recorded images, and as a result, the present inventors have discovered the present invention. He came up with an invention.

[Means for Solving the Problems 1] That is, the present invention provides a heat-sensitive recording material in which a heat-sensitive recording layer is provided on a support and includes at least a leuco compound and a color developer that develops color by reacting with the leuco compound. This is a heat-sensitive recording material characterized by using one or more compounds represented by the following general formula as a coloring agent.

3 <In the formula, R is hydrogen or C1. +1, R2, R3 are C
One bite. +1, and n is 1-5. ) By using the color developer of the present invention, the storage stability of recorded images is better than that of P-hydroxybenzoic acid ester, 4-hydroxyphthalic acid diester, etc. that have been proposed as color developers so far. , and a heat-sensitive recording medium excellent in high-speed recording suitability can be obtained. It is still not clear why the heat-sensitive recording material using the color developer of the present invention has the above-mentioned effects.

Examples of the color developer of the present invention contained in the compound represented by the above general formula are as follows.

Diethylstilbestrol 020.

020, m, p, 171°C Diethylstilbestrol monomethyl ether 02m.

C20.

m, p, 116 to 117.5° C. In the present invention, the object can be achieved by incorporating the color developer of the present invention in an amount of 1 to 40% by weight in the total solid content of the heat-sensitive recording layer. It is also possible to use the color developer of the present invention in combination with other known color developers.

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

(1) Leuco compounds are colorless or light-colored substances that develop color by reacting with color developers, such as triphenylmethane, triphenylmethanephthalide, fluoran, leucoolamine, diphenylmethane, phenodeazine, and phenoxazine. Various derivatives such as spiropyran derivatives, indoline derivatives, and indigo derivatives may be mentioned, and the following may be exemplified, although they are not particularly limited.

Crystal violet lactone (blue), 3-diethylamino-6-methyl-7-anilinofluorane (black), 3-(N-ethyl-P-toluidino)-6-methyl-7-anilinofluorane (black) , 3-diethylamino-6-methyl-7-(ortho, para-dimethylanilino)fluoran (black), 3-pyrrolidino-6methyl~
7-anilinofluorane (black), 3-piperidino-6
-Mejiru 7-anilinofluorane (black), 3-(N
-cyclohexyl N-methylamino)-6-methyl-7
-Alinofluorane (black), 3-diethylamino 7-
(Alutochloroanilino)fluorane (black), 3-
Diethylamine-7-(metatrifluoromethylanilino) fluorane (black), 3-diethylamino-6-methyl-9-fluorane (red), 3-diethylamino 6-methyl-fluorane (red), 3-cyclohexylamino-6 -ri "] Rofluorane (orange), 3-(N-
isoamyl-N-ethylamino)-6-methyl-7-7-nylinofluorane (black) 3-dibutylamino-6-methyl-77-nylinofluorane (black).

(2) Color development accelerator In order to improve the recording properties of the heat-sensitive recording medium of the present invention, conventionally known color development accelerators such as fatty acid amide such as stearamide, prephthalic acid ester, cuphenyl, 1-ribenzyl amine, etc. , benzylmandelic acid, parabenzylbiphenyl, and the like.

(3) Binders Examples of the binders used in the present invention include polyvinyl alcohol, casein, starch powder, and modified starch.
Carboxymethylcellulose, hydroxyethylcellulose, polyvinylpyrrolidone, styrene-maleic anhydride copolymer and its alkaline solution, polyacrylamide, latexes such as styrene-butadiene copolymer, polyvinyl acetate, polyacrylic ester, gelatin, Examples include, but are not limited to, sheratsk.

(4) Storage Stabilizer By adding a storage stabilizer to the recording medium of the present invention, it is possible to further improve storage stability.

The storage stabilizer used in the present invention is 4゜4'-butylidene-bis(3-methyl-6-t-butylphenol).
(melting point 208°C, the same applies below), 2.2'-methylenebis(4-methyl6-t-butylphenol) (120
°C), 2°2'-methylene-bis(4-ethyl-6-t
butylphenol) (119°C), 2,5-di-butyl-hydroquinone (202°C), 2,5-di-t-amyl-hydroquinone (172°C), bis(3-methyl-4
-Hydroxy-5-t-butyl-benzyl) sulfide (215°C), bis[3,3'-bis-(4'-hydroxy-3't-butylphenol)-butyric acid] glycol ester (165°C), 4 .4'-methylenebis(
2,6-di-t-butylphenol) (154°C), 2
．． 6-bis(2'-hydroxy-3'-t-butyl-5
-Methylbenzyl〉-4 methylphenol (171℃)
, 2,2'-isobutylidene-bis-(4,6-di-
methylphenol) (160℃), bis[2-(2-
and droxy-5-methyl-3-t-butyl-benzyl)
4-Methyl-6-t-butylphenyl]terephthalate (240°C), 2-hydroxy 4-methoxy-4'-
Ruboxybenzophenone (166°C), Tris (3,5
-di-t-butyl-4-hydroxyphenyl)isocyanate (221°C), tris[β-(3,5-di-t
-Butyl-4-hydroxy-phenyl>propionyl-
oxyethyl]isocyanate (126°C), 1,3.
5-t-dimethyl-2,4,6=tris(3,5-di-butyl-4-hydroxy-benzyl)benzene(24
4℃), 1.1.3-tris(2-methyl4-hydroxy-5-cyclohexylphenyl)butane (220℃)
, N,N'-hexamethylene bis(3,5-di-
t-butyl-4-hydroxy-hydrocinnamide) (
156℃), 1,1゜3-]helis(2-methyl-4-
Hydroxy-5t-butylphenyl)butane (185℃
), 2°2'-dihydroxy-3,3'-di(α-methyl-cyclohexyl)-5,5'-dimethyldiphenylmethane (130°C), and various phenolic resins.

(5) Other additives 0 The heat-sensitive recording material of the present invention may contain other additives such as clay, calcium carbonate, aluminum hydroxide, synthetic silica, talc, titanium oxide, lead oxide, etc. in the heat-sensitive layer as necessary. It is possible to add inorganic pigments and organic pigments, waxes, various fatty acid metal salts to prevent stickiness, water-resisting agents to improve water resistance, surfactants, etc.

(6) Support The support used in the present invention is usually paper such as high quality paper, medium quality paper, coated paper, etc., but also glass I&LI fiber sheets, plastic sheets, film laminated paper, Nonwoven fabrics and the like can also be used as supports.

The heat-sensitive recording material of the present invention is produced as follows. A system containing a color-forming substance and a system containing a color developer of the present invention are each separately pulverized in an aqueous medium containing a binder, and then the two are mixed to obtain a heat-sensitive paint. The heat-sensitive recording material of the present invention is obtained by coating or impregnating a support with the paint thus prepared and drying it.

1 (Example) The effects of the present invention will be explained in more detail below with reference to Examples.

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

Solution A: 3-(N-isoamyl-N-ethyl)amino-6
-Methyl near-anilifluorane 5g Aluminum hydroxide 28! ? Zinc stearate 5g polyvinyl alcohol 12% solution 35g water
52g B solution: Diedyl stilbeth [-rol 53 parabenzyl phenyl 109 kaolin
2o! ? Zinc stearate 3g
Polyvinyl alcohol 12% liquid 3592 water
527 Next, liquid A 1259. Add 125 g of liquid B, 50 g of 12% polyvinyl alcohol liquid, and 409 g of water, mix, stir, and adjust to make a coating liquid.
A heat-sensitive recording material was obtained by applying and drying the coating onto the surface of high-quality paper using a Meyer bar so that the coating amount after drying was 8 g/TIt.

Example 2 Solution C: Diethylstilbestrol seven methyl ether 10g1.1.3
-Tris(2-methyl4-hydroxy-5-cyclohexylphenyl>butane 5g kaolin
209 Zinc stearate
3g polyvinyl alcohol 12% liquid
359 water
52g A heat-sensitive recording material was obtained in the same manner as in Example 1 except that in J3 of Example 1, the B liquid was replaced with the above C liquid.

Comparative Example 1 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that bisphenol 8 was used instead of diethylstilbestrol in the formulation of liquid B used in Example 1.

Comparative Example 2.3 In the formulation of Solution D used in Example 3, 4-hydroxyphthalic acid dimethyl ester (Comparative Example 2), P-hydroxybenzoic acid benzyl ester ( A thermosensitive recording material was obtained in the same manner as in Example 3 except that Comparative Example 3 was used.

The heat-sensitive recording bodies obtained in the above examples and comparative examples were surface-treated with a test super calender so that the recording surface had a Bekk smoothness of 500 seconds.

Next, regarding the surface-treated heat-sensitive recording material, commercially available G.
I[[Facsimile device FACOM FAX621C
(manufactured by Fujitsu ■) with a recording power of 0.85 W/dat.

Energizing time 0.45m5ec, periodic 5m5 (IC/,
Printing was performed under conditions of 0, and the image density and background density upon printing were measured using Macbeth density ff1RD-514.

Storage stability was measured by storing the image for 48 hours in a constant temperature private room maintained at 40° C., 90% R and 60° C., 15% R, and then measuring the image'a degree and the background'a degree.

Further, the recorded images were stored for one week at 20° C. in an atmosphere of 60% R1=1, and dusting in the image area was visually determined.

Powdering criteria ○: Good ×: Powder adheres when touched with hands The results obtained for Examples and Comparative Examples are shown in the table.

From the results shown in the table, Examples 1 to 3 using the color developer of the present invention showed superior color development immediately after recording compared to Comparative Examples 1 to 3 using a conventional color developer. It has a good shelf life and does not leave a crust.

Also, there is no problem with dusting during storage.

[Effects of the Invention] The heat-sensitive recording material of the present invention is a heat-sensitive recording material that has excellent high-speed recording properties and excellent storage stability of recorded images.

Claims (1)

[Scope of Claims] 1. In a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a leuco compound and a color developer that develops color by reacting with the leuco compound on a support, the color developer is formed by the following general formula: A heat-sensitive recording material characterized by using one or more kinds of compounds represented by the following. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1 is hydrogen or C_nH_2_n_+_1,
R_2 and R_3 represent C_nH_2_n_+_1,
n is 1-5. )