JPH02239978A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain the excellent storage stability of a recording image by containing a coupler forming a color through the contact of a specific basic dye and 4,4'-thiobis(3-methyl-6-tertiary butylphenol). CONSTITUTION:4,4'-thiobis(3-methyl-6-tertiary butylphenol) is used along with 3-dibutylamino-6-methyl-7-phenylaminofluorane being a basic dye and a coupler and the use ratio thereof is adjusted pref. within a range of 2-100 pts.wt. and more pref. within a range of 5-50 pts.wt. per 100 pts.wt. of the sum total of the basic dye and the coupler. The compounding ratio of the coupler to the basic dye is pref. 100-700 pts.wt. per 100 pts.wt. of the basic dye. Further, the coating amount of the coating solution forming a thermal recording layer to a support is controlled within a range of 2-12g/m<2> on a dry wt. basis.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heat-sensitive recording medium, and particularly to a heat-sensitive recording medium that has excellent whiteness of the recording medium and storage stability of recorded images.

(Prior Art) Conventionally, heat-sensitive recording materials utilize a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent, and obtain a recorded image by bringing both color-forming substances into contact with heat. well known.

However, such heat-sensitive recording materials generally have a problem in that the recorded images do not have sufficient storage stability and discolor over time. In particular, heat-sensitive recording materials containing 3-dibutylamino-6-methyl-7-phenylaminofluorane as a basic dye have the advantage of providing high whiteness;
If stored under high humidity, the recorded image would disappear within a relatively short period of time.

In order to improve the storage stability of such recorded images, heat-sensitive recording materials to which various storage improvers are added have been proposed, but the improvements come with new drawbacks such as a decrease in whiteness. No satisfactory results have been obtained.

(Problems to be Solved by the Invention) In view of the current situation, the present inventors have developed 3-dibutylamino-
4,4°-thiobis(3-methyl-6-
The present inventors have discovered that the inclusion of tert-butylphenol (tert-butylphenol) can provide excellent storage stability for recorded images, and have completed the present invention.

(Means for Solving the Problems) The present invention contains at least 3-dibutylamino-6-methyl 7-phenylaminofluorane as a colorless or light-colored basic dye, and which develops color upon contact with the basic dye. This is a heat-sensitive recording material containing a coloring agent that can be used as a coloring agent, and 4,4'-thiobis(3-methyl-6-tert-butylphenol).

(Function) The present invention is directed to the basic dye 3-dibutylamino-6-
A major feature is that 4.4''-thiobis (3-methyl-6-tert-butylphenol) is used in combination with methyl-7-phenylaminofluorane and a coloring agent, and thermal recording generally contains each of the above components. Preferably, the layer is formed on a support.

4,4'-thiobis(3-methyl-6-tert-butylphenol) also has the ability to color basic dyes. Generally, when two or more coloring agents are used in combination, recording sensitivity improves, but background fogging tends to occur.
When 4,4゛-thiobis(3-methyl-6-tertiarybutylphenol) is used in combination with dibutylamino-6-methyl-7-phenylaminofluorane and a coloring agent that can react with it, the skin's strength is improved. This makes it possible to obtain a recording medium with high whiteness. Moreover, it has been found that by incorporating 4,4'thiobis(3-methyl-6-tert-butylphenol), excellent storage stability of recorded images can be obtained even under high temperature and high humidity conditions.

4.4°-thiobis(3) for basic dyes and color formers
-Methyl-6-tert-butylphenol) is preferably used in a ratio of 2 to 100 parts by weight, more preferably 5 to 5 parts by weight, per 100 parts by weight of the basic dye and coloring agent.
It is adjusted within a range of about 0 parts by weight.

In the present invention, 3-dibutylamino-6methyl-7
In addition to -phenylaminofluorane, various colorless or light-colored basic dyes may be used in combination as long as the effects of the present invention are not impaired. Although the ratio of combined use is not necessarily limited, it is preferably about 20 parts by weight or less per 100 parts by weight of 3-dibutylamino-6-methyl-7-phenylaminofluoran.

Examples of such basic dyes include the following.

3.3-bis(p-dimethylaminophenyl) 6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl) phthalide, 3-(p-dimethylaminophenyl) -3- (1.2-dimethyl indol-3-yl)fucrido, 3-(p-dimethylaminophenyl)-
3-(2-methylindol-3-yl)phthalide,
3.3-bis(1.2-dimethylindol-3-yl)5-dimethylaminophthalide, 3.3-bis(l2-
dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylruhazol-3)
-yl)-6-dimethylaminophthalide, 3.3-bis(2-1phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-
Triallylmethane dyes such as 3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'
Bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl leukoolamine N-2.4.5
-Diphenylmethane dyes such as 4-lichlorophenyl leuco auramine, penzoyl leucomethylene blue, p-
Thiazine dyes such as nitrobenzoyl leucomethylene blue, 3-me, thirose bilodinaphthopyran, 3-ethyloose bilodinaphthopyran, 3-phenylose spirodinaphthopyran, 3-pendylose spirodinaphthopyran, 3- Spiro dyes such as methylnaphtho (6'-methoxybenzo) spiropyran, 3-probyl-spiro dibenzopyran, rhodamine B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (O
-lactam dyes such as chloroanilino)lactam, 3-
Dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7
-Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6.7
-dimethylfluorane, 3- (N-ethyl-p-toluidino)-7methylfluorane, 3-diethylamino-
7-N acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-
Diethylamino-7-(N-methyl-N-pendylamino)fluoran, 3-diethylamino-7-(N-chloroethyl-N-methylamino)fluoran, 3-diethylamino? -N-diethylaminofluorane, 3-(N
Ethyl-p-}luidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-toluidino)
-6-methyl-7-(p-toluidino)fluoran,
3-diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carpomethoxyphenylamino)fluorane, 3-(N-ethyl-Nisoamyl)amino-6-methyl-7-phenylaminofluoran Orane, 3-(N-cyclohexyl N-methylamino)-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl 7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenyl Aminofluorane, 3-diethylamino-6-methyl-
7-xylidinofluorane, 3-diethylamino-7-
(0-chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluoran, 3
-(N-methyl-N-nprobyl)amino-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6
-Methyl 7-p-butylphenylaminofluorane, 3
(N-ethyl-Nn-probyl)amino-6methyl-
7-phenylaminofluorane, 3-(N-ethyl-N
-isobutyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-methyl-N-n-hexylamino-6-methyl 7-phenylaminofluorane, 3-(
N-ethyl-N-n-hexyl)amino-6-methyl-
Fluoran dyes such as 7-phenylaminofluorane, 3-(N-ethylN-cyclopentyl)a)mino-6-methyl 7-phenylaminofluorane, and the like. Of course, the dyes are not limited to these dyes.

Moreover, various compounds can be used as a coloring agent, for example, the following are exemplified.

Inorganic acidic substances such as activated clay, acid clay, acpulgite, bentonite, colloidal silicate, aluminum silicate, 2,2-bis(4-hydroxyphenyl)-4-
Methylbentane, 4-tert-butylphenol, 4
-Hydroxyphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-ter
t-octyltecol, 2,2゛-dihydroxydiphenol, 2,2゛-methylenebis(4-methyl-6
-tert-isobutylphenol), 4.4' -
Isopropylidene bis(2-tert-butylphenol), 4.4'-sec-butylidene diphenol, 4
-Phenylphenol, 4.4'-isopropylidenediphenol, 2,2'-methylenebis(4-chlorophenol), hydroquinone, 4.4'-cyclohexylidenediphenol, Henzil 4-hydroxybenzoate, 4-hydroxy Dimethyl phthalate, hydroxymonohendyl ether, 4-hydroxy-4゛-isoprobyloxydiphenyl sulfone, 3゜, 4゜-
Tetramethylene-4-hydroxydiphenylsulfone, 4.4"-(1.3-dimethylbutylidene)bisphenol, 4.4'-(1-phenylethylidene)bisphenol, 4.4'-(p-phenylenediisopropylidene) ) diphenol, 4.4'-
Phenolic compounds such as (m-phenylene diisopropylidene) diphenol, novolac type phenolic resin, phenol polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3
-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isoprobylsalicylic acid, 3-tertbutylsalicylic acid,
3-pendylsalicylic acid, 3-(α-methylbenzyl)
Salicylic acid, 3-chloro-5-(α-methylbenzylsalicylic acid, 3.5-di-tert-butylsalicylic acid,
Aromatic carboxylic acids such as 3-phenyl-5-(α,α-dimethylpenzyl)salicylic acid and 3,5-diα-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, Salts with polyvalent metals such as aluminum, calcium, titanium, manganese, tin, and dichloride, as well as zinc, magnesium, aluminum, calcium, titanium, manganese,
Antipyrine, salts of polyvalent metals such as tin, nitrous, etc.
Examples include organic acidic substances such as complexes with organic compounds such as pyridine and dimethylaminoantipyrine;
Particularly preferred is hydroxy-4'-isoproboxydiphenyl sulfone.

The proportion of the basic dye and coloring agent used in combination is not necessarily limited, but is preferably 100 to 700 parts by weight, more preferably 150 to 400 parts by weight per 100 parts by weight of the basic dye. agent is added.

Preparation of coating liquids containing these generally uses water as a dispersion medium,
Basic dyes are produced by stirring and grinding machines such as ball mills, attritors, and sand mills. It is prepared by dispersing a coloring agent, 4,4'-thiobis(3-methyl-6-tert-butylphenol), etc. together or separately.

Such coating liquids usually contain starches,
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. have a total solid content. It is blended in an amount of about 10 to 40% by weight, preferably about 15 to 30% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid.
For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, ultraviolet absorbers such as triazoles, and other antifoaming agents,
Examples include fluorescent dyes and colored dyes. In addition, dispersions of stearic acid, polyethylene wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. are used to prevent the thermal recording material from causing stenosis due to contact with recording equipment or recording heads. Emulsions and the like can also be added.

Further, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, 2,2'-methylene bis(4
-methyl-6-tertbutylphenol), 1,1
．． 3-}Lis(2methyl-4-hydroxy-5-te
Hindered phenols such as rt-butylphenyl)butane, 1,2-bis(phenoxy)ethane, 1.2-bis(4-methylphenoxy)ethane, 1.2-bis(3
Various known thermofusible substances such as ethers such as -methylphenoxy)ethane, 2-naphthol benzyl ether, and benzy-4-methylthiophenyl ether, and esters such as -hydroxy 2-naphthoic acid phenyl ester and dibenzyl terephthalate. It is also possible to obtain even better recording sensitivity by using them together.

In addition, inorganic pigments such as kaolin, clay, talc, calcined calcium carbonate clay, titanium oxide, diatomaceous earth, particulate anhydride, silicic acid, and activated clay can be added to improve the adhesion of residue to the recording head.

As the support, paper, plastic film, synthetic paper, etc. can be used, but paper is most preferably used in terms of cost, coatability, etc. Further, the amount of the coating liquid for forming the heat-sensitive recording layer to be applied to the support is not particularly limited, and is usually 2 to 1 on dry weight.
It is adjusted within a range of about 2 g/m, preferably about 3 to 10 g/rd.

Note that it is also possible to provide an overcoat layer on the heat-sensitive recording layer for the purpose of protecting the heat-sensitive recording layer, and of course it is also possible to provide a protective layer on the back side of the support or provide an undercoat layer on the support. This is possible, and various known techniques in the field of heat-sensitive recording material production, such as not applying adhesive processing to the back surface of the support, can be added.

In the heat-sensitive recording material of the present invention, the method of forming the coating layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques.

For example, it may be applied by a suitable coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater, and the like, and then dried.

"Example" The present invention will be described in more detail with reference to Examples below, but the present invention is of course not limited to these.

Further, unless otherwise specified, parts and percentages in the examples indicate parts by weight and percentages by weight, respectively.

Example 1 ■ Formation of undercoat layer 100 parts of ultrafine anhydrous silica (trade name: Mizuka Seal P527, manufactured by Mizusawa Chemical Co., Ltd., oil absorption: 190 m7!/100 g), hydroxyethylated starch (trade name: Aheresox 25)
30, 250 parts of a 12% aqueous solution of Abebe Co., Ltd.), styrene-butadiene copolymer emulsion (trade name: DOW-
1571 (manufactured by Asahi Dow Co., Ltd., 48% solids) and coated with an air knife coater on a 48 g/rd base paper to give a coated amount of 10 g/m after drying. A base paper with an undercoat layer was obtained by applying the coating as described above and supercalendering it.

■ Preparation of solution A 3-dibutylamino-6-methyl-7-phenylaminofluorane 10 parts 1.2-di(3-
Methylphenoxy) monoethane 30 parts Methyl cellulose 5% water soluble Wft. 20 parts Water 80 parts This composition was ground to a particle size of 1 μm using a sand grinder.

■ Preparation of Solution B 4.4”-Isopropylidenediphenol 20 parts Methylcellulose 5% aqueous solution 20 parts Water
30 parts of this composition was ground to a particle size of 2 μm using a sand grinder.

■ Preparation of liquid C 4.4”-thiobis(3-methyl-6-tert-butylphenol) 7 parts methylcellulose 5% aqueous solution 3 parts water
15 parts of this composition was ground to a particle size of 2 μm using a sand grinder.

■ Formation of heat-sensitive recording layer 140 parts of liquid A, 70 parts of liquid B, 25 parts of liquid C, 15 parts of silicon oxide pigment, modified polyvinyl alcohol (solid content concentration 15 parts)
%), 5 parts of calcium carbonate, 27 parts of zinc stearate emulsion (solid content concentration 30%), and 60 parts of water were mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer. This coating liquid was coated onto the undercoat layer so that the coating amount after drying was 6 g/n{, and dried to form a heat-sensitive recording layer, followed by supercalendering to obtain a heat-sensitive recording material.

Example 2 In the preparation of Solution B in Example 1, 4-hydroxy-4 was used instead of 20 parts of 4.4''-isopropylidene diphenol.
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 20 parts of -isopropoxydiphenylsulfone was used.

Example 3 A thermosensitive recording material was prepared in the same manner as in Example 2 except that 1,2-di(3methylphenoxy)monoethane was replaced with henzyl-4-methylthiophenyl ether in the preparation of liquid A. I got it.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that Liquid C was not used.

Comparative Example 2 A thermosensitive recording material was obtained in the same manner as in Example 2 except that Liquid C was not used.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 3 except that Liquid C was not used.

Comparative example 4 3-dibutylamino-6methyl- in the preparation of solution A in Example 2
A thermosensitive recording material was obtained in the same manner as in Example 2 except that 3-(N-ethyl-N-isoamyl)amino 6-methyl-phenylaminofluorane was used instead of 7-phenylaminofluorane.

Comparative Example 5 3-dibutylamino-6methyl-
3-(N-methyl-N-cyclohexyl)amino-6-methyl-7- instead of 7-phenylaminofluorane
A thermosensitive recording material was obtained in the same manner as in Example 2 except that phenylaminofluorane was used instead.

Eight types of thermal recording paper thus obtained (Hitachi HIFA
Record the recorded density (D,) using a Macbeth densitometer (RD-100 type, amber filter).
The results are shown in Table 1.

The whiteness of the thermal recording paper was measured using a Hunter whiteness meter. The results are shown in Table 2.

(2) The thermosensitive recording paper after the On-Goku printing was left in an atmosphere of 40° C. and 90% RH for 24 hours, and then the recording density (D2) was measured again using a Maches densitometer. Table 1 also shows the recording density residual rate (%) according to the following formula.

Recording density residual rate (%) -Dz / D+ ×1 0
0 Randomness Next, the thermal recording paper after printing was left in an atmosphere of 60'C and 10% Rl+ for 24 hours, and then the recording density (D3) was measured again using a Macbeth densitometer.

Table 1 also shows the recording density residual rate (%) according to the following formula.

Recording density residual rate (%) = D3 / DIX L O
O-Tomo 1 Junshin, heat sensitive recording paper at 40°C. In an atmosphere of 90% RH or 6
After being left in an atmosphere of 06C and 10% Rl1 for 24 hours, the fog color density of the white paper portion was measured using a Macbeth densitometer. The results are also shown in Table 2.

Table 1 Table 2 (Effects) The thermal recording material of the present invention had excellent recording storage stability, and was an excellent thermal recording material with almost no occurrence of fogging or coloring due to the improved recording storage stability. .

Display of incidents May 9, 1999 1999 Patent Application No. 62568

Claims (2)

[Claims] (1) a coloring agent containing at least 3-dibutylamino-6-methyl-7-phenylaminofluoran as a colorless or light-colored basic dye and capable of forming a color upon contact with the basic dye; and 4. 4'-thiobis(3-methyl-
6-tertiarybutylphenol). (2) The heat-sensitive recording material according to claim (1), wherein the coloring agent contains 4-hydroxy-4'-isopropoxydiphenylsulfone.