JPH03164294A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material not generating the fog of a blank part and the deterioration of recording density even when exposed to temp. environment by using a specific basic dye and a specific coupler in a specific ratio. CONSTITUTION:In a thermal recording medium utilizing the color forming reaction of a colorless-light-colored basic dye and a coupler capable of forming a color upon the contact with the dye, as the basic dye, 3-di(n-butyl)amino-6- methyl-7-phenylaminofluorane is used and, as the coupler, at least one of 4,4' isopropylidenephenol, 4-hydroxy-4'-isopropoxydiphenylsulfone and 2, 2-bis(4- hydroxyphenyl)-4-methylpentane is used. 150-250 pts.wt. of the coupler is used per 100 pts.wt. of the basic dye. When the coupler is less than 150 pts.wt., developed color density is markedly lowered and, when the coupler is more than 250 pts.wt., the fading preventing effect of a printed part under high temp. environment is lowered. This thermal recording medium is reduced in the fog of a blank part at high temp. even when a heat-meltable substance is together used as a sensitizer.

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 exhibits little fogging in blank areas and extremely little decrease in recording density even when stored in a high-temperature environment. It is.

``Prior Art'' Heat-sensitive recording materials are well known that utilize a color reaction between a colorless or light-colored basic dye and a coloring agent, and obtain a recorded image by bringing both coloring substances into contact with each other using heat. .

Such a heat-sensitive recording medium is relatively inexpensive, and the Ltc
JR. Because the device is compact and maintenance-free, it is used in a wide range of fields, but as the field of use has expanded, it has come to be used in high-temperature environments that were previously unforeseen.

However, when a thermosensitive recording material, particularly a highly sensitive thermosensitive recording material, is stored in a high-temperature environment, a coloring reaction (fogging in the blank area) occurs in some parts and the recording material becomes unusable.

In such a high temperature environment, fogging of blank areas is caused by 3-di(n-butyl)amino 6-methyl-7- as a basic dye.
Significant improvements can be made by using phenylaminofluorane.

However, heat-sensitive recording materials using this dye have the disadvantage that the storage stability of recorded images is extremely poor, especially in high-temperature environments, and there is currently a strong demand for improvement.

``Problems to be Solved by the Invention'' An object of the present invention is to obtain a heat-sensitive recording material that does not cause fogging in blank areas or deterioration of recording density even when exposed to a high-temperature environment.

"Means for Solving the Problems" The present inventors have developed a thermosensitive recording material that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color upon contact with the dye. 3-di(n-butyl)amino-6-methyl 7-phenylaminofluorane was used as the basic dye, and 4,4'-isobropylidene diphenol and 4-hydroxy-4'-isopropylene were used as the coloring agents. At least one of boxydiphenylsulfone and 2,2-bis(4-hydroxyphenyl)-4-methylpentane is used, and 150 parts by weight of the coloring agent is added to 100 parts by weight of the basic dye. The present inventors have found that such drawbacks can be solved extremely efficiently by using the particles in the range from 250 double star parts to 250 double star parts, and have completed the present invention.

"Function" The present invention has an important feature in that a specific basic dye and a specific coloring agent are used in combination in a specific ratio.

As mentioned above, 3-di(n-butyl)amino-6-methyl-7-phenylaminofluoran is used as a specific basic dye, but the capri of the blank area of this dye is extremely low in high-temperature environments. Although it is small, it has a serious drawback that the storage stability of recorded images is extremely poor, and the coloring agent used in combination is 4,4'-isopropylidene diphenol, 4-hydroxy-4'-isopropoxydiphenyl sulfone, or 2, By selectively using 2-bis(4-hydroxyphenyl)-4-methylbentane,
These drawbacks can be addressed to some extent. However, simply combining the above-mentioned basic dye and coloring agent does not provide sufficient storage stability of the recorded image.
It is used in a range of 250 parts by weight, preferably 180 to 230 parts by weight.

Incidentally, it has been found that if the amount of the coloring agent is less than 150 parts by weight, the color density will be significantly reduced, and if it is more than 250 parts by weight, the effect of preventing fading of the printed area in a high temperature environment will be significantly reduced. It is not clear why the anti-fading effect of the printed area is significantly reduced when the amount exceeds 250 parts by weight, but it is thought to be due to the compatibility with the dye.

In addition, as a basic dye, for example, commonly used 3-
(N-ethyl-N-isoamyl)amino-6-methyl-
7-phenyla-5nofluorane, 3-(N-methyl-N
-cyclohexyl)amino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, etc.
When stored in a high-temperature environment, there is significant fogging on the blank areas.
Further, even if the amount of the coloring agent is more than 250 parts by weight, the printed portion will not fade. Furthermore, when hengelu p-hydroxybenzoate, which is commonly used as a coloring agent, is combined with the basic dye of the present invention, the storage stability of recorded images is extremely poor even if the usage range is limited to 150 to 250 parts by weight.

Since the heat-sensitive recording medium of the present invention uses a specific basic dye and coloring agent, it is said that capri in the blank area is extremely small at high temperatures even if a thermofusible substance is used as a sensitizer. It has excellent characteristics. Therefore, the present invention is preferably applied to a highly sensitive heat-sensitive recording material using a thermofusible substance as a sensitizer, since its effects can be fully exhibited.

Various known compounds can be used as such thermofusible substances, such as fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, stearic acid ethylene bisamide, oleic acid amide, balmitic acid amide, coconut fatty acid amide, etc. '-Methylenebis(4-methyl-6-tert-butylphenol), 4.4'
-butylidene bis(6-tert-butyl-3-methylphenol), 1,1.3-4lis(2-methyl-4-
hydroxy-5-tert-butylphenyl)butane,
Engineering. 1.3-Hindered phenols such as tris(5-cyclohexyl-4-hydroxy-6-methylphenyl)butane, 2-bis(phenoxy)ethane, 1.2-
Bis(4-methylphenoxy)ethane, 1,2-bis(
3-methylphenoxy)ethane, 1-phenoxy2-
(4-methylphenoxy)ethane, 2-naphtholbenzyl ether, 1.4-dimethoxynaphthalene, 1.4
- Ethers such as diethoxynaphthalene, esters such as dibutyl terephthalate, dibenzyl terephthalate, l-hydroxy-2-naphthoic acid phenyl ester, 3,4,5-trimethoxybenzoic acid methyl ester, 2
-(2'-hydroxy-5'methylphenyl)penzotriazole, 2-hydroxy-4-penzyloxybenzophenone, P-benzylbiphenyl and the like.

Among these thermofusible substances, 1. 2bis(phenoxy)ethane, 1,2-bis(3methylphenoxy)ethane, l-hydroxy 2-naphthoic acid phenyl ester, p-pendylbiphenyl, especially 1,2-
Bis(phenoxy)ethane and 1,2-bis(3-methylphenoxy)ethane have high compatibility with the specific basic dyes and coloring agents of the present invention, and have low melt viscosity, so they have excellent properties. It is particularly preferably used because a high-quality, highly sensitive thermosensitive recording material can be obtained.

The amount of the thermofusible substance to be used is not necessarily limited, but it is preferably used in a range of 0.7 to 1.5 times the total amount of the basic dye and coloring agent. By the way, 0. If it is less than 7 times, the sensitizing effect will be poor;
．． If the amount is more than 5 times, there will be a drawback that the adhesion of residue to the thermal hend will be poor.

As mentioned above, in the present invention, specific basic dyes and coloring agents are used in specific ranges, but other basic dyes may also be used in combination as long as the desired effects of the present invention are not inhibited. It is possible.

Examples of such basic dyes include the following.

3.3-bis(p-dimethylagonophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylagonophenyl)
nophenyl) phthalide, 3-(p-dimethylagonophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
- (2-methylindol-3-yl)phthalide, 3
．． 3-bis(1,2-dimethylindol-3-yl)
-5-dimethylaminophthalide, 3,3-bis(12-
dimethylindol-3-yl)-6-dimethylaminophthalide, 3 3-bis(9-ethylcarbazole-3
-yl)-6-dimethylanophthalide, 3.3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-P-dimethylanophenyl-3
- Triallylmethane dyes such as (1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4.4'
-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl leucoaura ξn-2.4.
5-1-Diphenylmethane dyes such as lycrophenyl leucooragon, penduyl leucomethylene blue,
Thiazine dyes such as p-bitropene soil leucomethylene blue, 3-me, tylus spirodinaphthopyran, 3
-Subiro dyes such as ethyl-spirodinaphthopyran, 3-phenyl-spirodinaphthopyran, 3-pendyl-spirodinaphthopyran, 3-methylnaphtho(6'-methoxybenzo)spiropyran, 3-propyl-spirodibenzopyran, rhoda Lactam dyes such as 2-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (O-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-
Diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-dimethylfluorane) Ethyl-p-}luidino)-7=methylfluorane, 3-diethylamino-7-N acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluoran oran, 3-diethylamino-7-(N-methyl-N-
henzylamino) fluorane, 3-diethylamino-7
-(N-chloroethyl-N-methylamino)fluorane, 3-diethylamino-7-N-diethylaminofluorane, 3=(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N (1-ethyl-P-toluidino)-6-methyl-7-(p-toluidino)fluoran, 3-diethylamino-6-methyl-7
-phenyla fluorane, 3-diethyla ξno-7
-(2-Carpomethoxyphenylamino)fluoran, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-cyclohexyl-N-methylamino)-6 -methyl-7-
-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-quiziridinofluorane , 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-(N-ethyl-N
-tetrahydrofurfuryl)amino-6-methyl-7-
Phenyluanofluorane, 3-(N-methyl-N-n
provyl) amino-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl 7-P-butylphenylaminofluorane, 3-(N-ethyl-N-
n-propyl)amino-6-methyl-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
Fluoran dyes such as -n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-cyclobentyl)a)mino-6-methyl7-phenylaminofluorane, and the like. Of course, the dyes are not limited to these dyes.

In addition, when using other basic dyes such as those mentioned above,
It is desirable to adjust the proportion of other dyes to the total basic dyes to be 20% by weight or less.

Preparation of coating liquids containing these generally uses water as a dispersion medium,
It is prepared by dispersing the dye, the coloring agent, and a thermofusible substance added as necessary together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl group modification
Total solid content includes various modified polyvinyl alcohols such as sulfonic group modification, acetoacetyl group modification, and silicon modification, styrene/maleic anhydride copolymer salts, styrene/acrylic acid copolymer salts, styrene/butadiene copolymer emulsions, etc. It is blended in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight. Of course, two or more of these binders can also be used in combination.

Furthermore, various auxiliary agents can be added to the coating liquid.
Examples include dioctyl sulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt, sodium lauryl alcohol sulfate ester, fatty acid metal salt, and other fitting agents, antifoaming agents, fluorescent dyes, coloring dyes, and the like.

In addition, inorganic pigments such as kaolin, clay, talc, calcium carbonate, yakukai clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, activated clay, styrene microballs, nylon powder, etc. are used to improve the adhesion of debris to the recording head. Organic pigments such as polyethylene powder, urea/formalin resin filler, and raw starch can also be added.

In addition, to prevent sticking from contact with recording equipment or recording heads, we use stearate ester wax, Microcrystawanwanx, polyethylene wax, carnauba wax, paraffin wax, carboxy-modified paraffin wax, zinc stearate,
A dispersion or emulsion of calcium stearate or the like may also be added.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, a coating liquid for a heat-sensitive recording layer is applied onto a support using a suitable coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater, etc., and dried to form a recording layer.

Further, the amount of the coating liquid to be applied is not particularly limited, and is generally adjusted within the range of 1.5 to 12 g/ni, preferably 2.5 to 10 g/rd in terms of dry weight.

Paper, plastic film, synthetic paper, etc. can be used as the support, but paper is most preferably used in terms of cost and coatability.

The heat-sensitive recording material of the present invention thus obtained uses a specific basic dye and a coloring agent within a specific usage range, so even when exposed to a high-temperature environment, there is no fogging in blank areas or deterioration of recording density. It is extremely small in amount and can exhibit excellent effects especially as a highly sensitive thermosensitive recording material.

Note that it is of course possible to provide a protective layer on the front and/or back surface of the heat-sensitive recording material, to provide an undercoat layer between the support and the heat-sensitive recording layer, or to apply adhesive processing, etc., if necessary. Various known techniques in the field of heat-sensitive recording material manufacturing can be added.

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

Note that parts and % in the examples indicate parts by weight and % by weight, respectively, unless otherwise specified.

Example 1 ■ Form of undercoat layer Calcined clay (trade name: Ansilex, manufactured by EMC) 100 parts styrene-putadiene copolymer latex (solid content: 50%)
15 parts lO% polyvinyl alcohol aqueous solution
30 parts water
A coating solution for an undercoat layer was prepared by mixing and stirring 200 parts of the above composition. The obtained coating liquid was applied to a high-quality paper of 50 g/rrc so that the coating amount after drying was 1 O g/rrf, and dried to form an undercoat layer.

■ Preparation of solution A 3-di(n-butyl)amino-6-methyl-7-phenylaminofluorane 10 parts 1.2-bis(3-
methylphenoxy)ethane
2 5 parts 5%
Methylcellulose aqueous solution 30 parts water
20 parts of this U material was ground in a sand mill until the average particle size was 1.0 μm.

■ Preparation of Solution B 15 parts of 4,4'-isopropylidenediphenol 5% methylcellulose aqueous solution 15 parts of water
1 5 parts This composite material was ground in a sand mill until the average particle size was 1.5 μm.

■ Form of heat-sensitive recording layer: 85 parts of liquid A, 45 parts of liquid B, 20 parts of silicon oxide pigment, 10 parts of calcium carbonate pigment, 140 parts of 10% polyvinyl alcohol aqueous solution, 80 parts of 20% oxidized starch aqueous solution, 30% zinc stearate. 30 parts of the dispersion liquid and 60 parts of water were mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer. The obtained coating liquid was applied onto the undercoat layer in a coating amount of Uf4 so that the basic dye amount was 0.4 g/r+{, and after drying, a heat-sensitive recording paper was obtained.

Examples 2 to 3 Same as Example 1 except that in the preparation of Solution B, 22 parts (Example 2) and 24 parts (Example 3) were used instead of 5 parts of 4,4'-isopropylidenediphenol. A thermosensitive recording paper was obtained in the same manner.

Example 4 In A night preparation, 1,2-bis(phenoxy) was used instead of 1,2-bis(3-methylphenoxy)ethane.
The procedure was carried out in the same manner as in Example 1 except that ethane was used and 18 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone was used instead of 15 parts of 4.4'-isopropylidenediphenol in the preparation of Solution B. A thermosensitive recording paper was obtained.

Example 5 In preparing liquid A, 1. P-penzylbiphenyl was used instead of 2-bis(3-methylphenoxy)ethane, and 2,2-bis(4-hydroxy 18 parts of phenyl)-4-methylpentane and 1,1
．． 3-Tris(3-cyclohexyl-4-hydroxy-
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 5 parts of 6-methylphenyl)butane was used.

Comparative Examples 1 to 2 In preparing Solution B, instead of 15 parts of 4,4'-isopropylidenediphenol, 13 parts (Comparative Example 1),
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 25.5 parts (Comparative Example 2) of each was used.

Comparative Examples 3 to 4 In the preparation of Solution A of Comparative Example 2, 3-(N-ethyl-N-isoatanyl)amino-6 was used instead of 3-di(n-butyl)amino-6-methyl-7-phenylaminofluorane. -Methyl-7-phenylaminofluorane (Comparative Example 3)
) and 3-diethylamino-6-methyl-7-phenylaminofluorane (Comparative Example 4) were used to obtain thermal recording paper in the same manner as in Comparative Example 2.

Comparative Example 5 In the preparation of Solution B of Example 4, 13 parts of 4-hydroxy 4'-isopropoxydiphenyl sulfone was used instead of 18 parts.
A thermosensitive recording paper was obtained in the same manner as in Example 4, except that 100% of the heat-sensitive recording paper was used.

Comparative Example 6 In preparing liquid B of Example 4, 4-hydroxy-4'-
2 parts instead of 18 parts of isopropoxy diphenyl sulfone
A thermosensitive recording paper was obtained in the same manner as in Example 4 except that 5.5 parts were used.

Comparative Example 7 Heat-sensitive was prepared in the same manner as in Example 5, except that 25.5 parts of 2.2-bis(4-hydroxyphenyl)-4-methylpentane was used in place of 18 parts of 2.2-bis(4-hydroxyphenyl)-4-methylpentane in the preparation of Solution B in Example 5. I got the recording paper.

Comparative Example 8 A thermosensitive recording paper was prepared in the same manner as in Example 5, except that 13 parts of 2,2-bis(4-hydroxyphenyl)-4-methylpentane was used instead of 18 parts in the preparation of Example 50B solution. Obtained.

Comparative Example 9 In the preparation of Solution A of Comparative Example 7, 3-(N-methyl-N-cyclohexyl)amino-6-methyl- was used instead of 3-di(n-butyl)amino-6-methyl-7-phenylaminofluorane. A thermosensitive recording paper was obtained in the same manner as in Comparative Example 7 except that 7-phenylaminofluorane was used.

Comparative Example 10 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that 22 parts of benzyl-p-hydroxybenzoate was used instead of 15 parts of 4,4'-isopropylidene diphenol in the preparation of Liquid B.

The 15 types of thermal recording paper thus obtained were recorded using a high-speed thermal facsimile (Panafax UF-60, manufactured by Matsushita Electric Transmission Co., Ltd.). The color density of the obtained recorded image and the density of the blank area (non-print area) were measured using a Macbeth reflection densitometer (RD-
Type 914. (manufactured by Macbeth), and the results were
Shown in the table.

After recording, the thermal recording paper was left in a dry condition of 60"C.12% for 12 hours, and the density of the recorded area and blank area was measured again using a Macbeth reflection densitometer. The results are shown in Table 1. Furthermore, the storage stability under high temperature environment was evaluated as follows, and the results are also shown in Table 1.

Printed area density after processing Printed area remaining rate = ×100 (%)
Printed Area Density Before Processing Table 1 "Effects" As is clear from the results in Table 1, the thermal recording materials obtained in each example of the present invention have no blank area even when stored under high temperature conditions. It was an excellent heat-sensitive recording medium with very little deterioration in capri and recording density.

Claims (1)

[Claims] 3-di(n-butyl)amino-6 is used as the basic dye in a thermosensitive recording material that utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent that can change color when it comes into contact with the dye. - Using methyl-7-phenylaminofluorane,
In addition, at least one of 4,4'-isopropylidenediphenol, 4-hydroxy-4'-isopropoxydiphenylsulfone, and 2,2-bis(4-hydroxyphenyl)-4-methylpentane is used as a coloring agent. In addition, 15 parts of the coloring agent was added to 100 parts by weight of the basic dye.
A heat-sensitive recording material characterized in that it is used in a range of 0 to 250 parts by weight.