JPH0872410A - Thermal recording material - Google Patents

Abstract

PURPOSE: To provide a thermal recording material excellent in recording sensitivity and forming a recording image excellent in preservability. CONSTITUTION: In a thermal recording material wherein a thermal recording layer containing a colorless or light-colored basic dye and a coupler is provided on a support, 1-(4-methoxyphenoxy)-2-(2-methylphenoxy) ethane and zinc 4-(3-p- tolylsulfonylpropyloxy) salicylate are added to the thermal recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between a colorless or light-colored basic dye and a color-developing agent, and particularly to a recording material excellent in recording sensitivity and storability of recorded images. It is about.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording material which utilizes a coloring reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to bring a recording image by contacting both coloring substances with heat well known. Recently, with the remarkable progress of the thermal recording system, a thermal fax or the like is capable of high-speed printing, and a standard document of A4 size can be recorded in 10 seconds or less. With the increase in speed in the field of hardware, a recording material having excellent high-speed recording suitability is required as a thermal recording material to be used.

As a conventional means for improving the color developing sensitivity of a thermosensitive recording medium, a thermofusible substance having a melting point lower than that of a basic dye or a color developing agent is added to the thermosensitive recording layer, and the thermofusible substance which is previously melted is melted. A method (described in JP-A-49-34842, JP-A-53-39139, etc.) in which a dye and a color developing agent are dissolved by a volatile substance to lower the color development start temperature is widely known. However, it is generally difficult to give one type of heat-fusible substance a property of dissolving both a basic dye and a color developing agent, and a heat-fusible substance having such a property is However, the eutectic phenomenon of the ternary system of dye / coloring agent / heat-fusible substance causes the melting point to drop, so that the color formation start temperature is excessively lowered, and the whiteness of the heat-sensitive recording layer is significantly lowered.

Therefore, the applicants have proposed a diaryloxyalkane derivative (JP-A-60-56588, JP-A-61-16) as a heat-fusible substance which does not have the above-mentioned drawbacks.
1988). However, in recent years
In hardware fields such as heat-sensitive fax machines, miniaturization of the device itself is rapidly progressing along with speeding up, and with it, even a smaller amount of heat (amount of heat energy) can develop a high density recorded image with high sensitivity. Recording materials are strongly demanded.

In addition to the recent remarkable progress of the thermal recording system, the fields of application and forms thereof have been diversified, and not only as recording media for thermal facsimiles and thermal printers but also POS (Point of Sales) labels and the like. There is also a rapid increase in the use of the new materials. These heat-sensitive recording materials are strongly required to have performances such as excellent storability of recorded images under external environment such as heat, humidity, light and chemicals, in addition to sufficient recording density and recording sensitivity. ing. However, at present, there is no product that completely satisfies these requirements, and there is a strong demand for improvement thereof.

[0006]

The object of the present invention is to develop a high density of color even with a small amount of heat energy, and to obtain heat, humidity,
Another object of the present invention is to provide a heat-sensitive recording material having excellent storability of a recorded image under an external environment such as light and chemicals.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have proposed a thermosensitive recording material in which a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent and a coloring agent is provided on a support. In the layer, 1- (4-methoxyphenoxy) -2- (2
It was found that the above problem can be solved by containing -methylphenoxy) ethane and zinc 4- (3-P-tolylsulfonylpropyloxy) salicylate,
The present invention has been completed.

[0008]

In the present invention, 1- (4
-Methoxyphenoxy) -2- (2-methylphenoxy) ethane and the use of zinc 4- (3-p-tolylsulfonylpropyloxy) salicylate as a colorant are excellent in color developability, especially in the low energy region, And fever,
The reason why a heat-sensitive recording material having excellent storage stability of a recorded image in an external environment such as humidity, light, and chemicals is obtained is not necessarily clear, but the heat-meltable substance has a heat of fusion and a melt viscosity of diaryloxy. It is particularly small among alkane derivatives, and in combination with the high storage performance of the colorant zinc 4- (3-P-tolylsulfonylpropyloxy) salicylate to be used in combination, the desired high sensitivity and high storage stability are achieved. It is speculated that it will work.

In the heat-sensitive recording material of the present invention, 1- (4-
Methoxyphenoxy) -2- (2-methylphenoxy)
The amount of ethane used is not necessarily limited, but it is desirable to adjust it in the range of 10 to 700 parts by weight, preferably 50 to 500 parts by weight, relative to 100 parts by weight of the basic dye. Further, the amount of the colorant 4- (3-p-tolylsulfonylpropyloxy) salicylate zinc used in combination is not particularly limited, but it is generally the basic dye 1
100 to 700 parts by weight, preferably 150 to 600 parts by weight, of the coloring agent is used with respect to 00 parts by weight. In the present invention, various types of basic dyes which are colorless or light-colored and constitute the heat-sensitive recording layer of the heat-sensitive recording material are known, and examples thereof include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3
-Bis (p-dimethylaminophenyl) phthalide, 3,
3-bis (1,2-dimethylindol-3-yl)-
6-Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) Triarylmethane dyes such as -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-
Diphenylmethane dyes such as 2,4,5-trichlorophenyl leuco auramine, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4, 5,6,7-Tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2
-Yl] -divinylphthalide dye such as 4,5,6,7-tetrachlorophthalide, thiazine dye such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue, 3-methyl-spiro-dinaphthopyran, 3- Benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3
Spiro dyes such as propyl-spiro-dibenzopyran, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam,

3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3
-Diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-dibenzylaminofluorane, 4-benzylamino-8-diethylamino-benzo [a] fluorane, 3- (N-ethyl-p-toluidino) ) -6-Methyl-7-phenylaminofluorane, 3
-(N-ethyl-p-toluidino) -6-methyl-7-
(P-Toluidino) fluorane, 3-diethylamino-
6-methyl-7-phenylaminofluorane, 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 3-di (n-pentyl) amino-6-methyl-7-phenylamino Fluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N-
Methylamino) -6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-7- (o-chlorophenylamino) fluorane, 3- (N- Ethyl-N
-Tetrahydrofurfurylamino) -6-methyl-7-
Fluoran dyes such as phenylaminofluorane and 3- (N-ethyl-N-cyclopentylamino) -6-methyl-7-phenylaminofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 ′-(6 ′
-Dimethylamino) phthalide, 3-diethylamino-6
-(N-allyl-N-methylamino) fluorene-9-
Spiro-3 '-(6'-dimethylamino) phthalide,
3,6-bis (diethylamino) -3'-methyl-spiro [fluorene-9,6'-6'H-chromeno (4,3
-B) indole] and the like. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination.

Among the above basic dyes,
Especially 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane or 3-di (n-pentyl)
The use of amino-6-methyl-7-phenylaminofluorane is more preferable because a thermosensitive recording medium having extremely little decrease in whiteness even when stored under high temperature conditions can be obtained.

In the present invention, a specific color developing agent is used, but various known color developing agents can be used in combination within a range that does not impair the effects of the present invention. Specific examples include the following. it can. Activated clay, activated clay, colloidal silica,
Inorganic colorants such as aluminum silicate, magnesium silicate, zinc silicate, 4-chlorobenzoic acid, p-nitrobenzoic acid,
4-methyl-3-nitrobenzoic acid, 2-chloro-4-nitrobenzoic acid, p-tert-butylbenzoic acid, 3,5-di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3- Phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di- (α-methylbenzyl) salicylic acid, 4- [2- (p-methoxyphenoxy) ethoxy] salicylic acid, 2-hydroxy-1-benzyl -3-aromatic carboxylic acid such as naphthoic acid,

4,4'-isopropylidenediphenol, 4,4'-isopropylidenebis (2-chlorophenol), 4,4'-isopropylidenebis (2,6-)
Dimethylphenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-sec-
Butylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4 '-(1-
Phenylethylidene) diphenol, 4,4'-cyclohexylidene diphenol, 4,4'-cyclohexylidene bis (2-methylphenol), benzyl-4-hydroxybenzoate, 4-hydroxyphthalic acid dimethyl ester, 2,2 ′ -Thiobis (4,6-dichlorophenol), 2,2′-methylenebis (4-methyl-6)
-Tert-butylphenol), 2,2'-dihydroxybiphenyl, methylbis (4-hydroxyphenyl) acetate, ethylbis (4-hydroxyphenyl) acetate, 4,4'-dihydroxydiphenylsulfone,
2,4'-dihydroxydiphenyl sulfone, 4-hydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 3,3'-diallyl-4,
Phenolic compounds such as 4'-dihydroxydiphenylsulfone, 4-hydroxy-3 ', 4'-tetramethylenediphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, p-phenylphenol-formalin resin, p-butylphenol -Organic colorants such as acetylene resin and other phenolic resins, and salts of these organic colorants with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, 1,3 -Thiourea compounds such as diphenyl-2-thiourea and 1,3-bis (m-chlorophenyl) -2-thiourea, metal complexes such as antipyrine complex of zinc thiocyanate and the like. Of course, these colorants can also be used in combination of two or more, if necessary.

As described above, the present invention has an important feature in using a specific heat-fusible substance together with a specific color-developing agent, but various types are available within the range that does not impair the effects of the present invention. It is also possible to use a known heat-fusible substance together. Examples of such a heat-fusible substance include fatty acid amides such as stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide, 1,2-diphenoxyethane, 1,2-
Bis (4-methylphenoxy) ethane, 1,2-bis (3-methylphenoxy) ethane, 1,3-bis (4-
Methoxyphenoxy) propane, 1,4-bis (phenylthio) butane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, 2-benzyloxynaphthalene, 1,4-bis [2- (vinyloxy) ethoxy ]
Ethers such as benzene, dibenzyl terephthalate,
1-hydroxy-2-naphthoic acid phenyl ester,
1,2-bis (4-benzyloxycarbonylphenoxy) ethane, oxalic acid dibenzyl ester, oxalic acid di- (p-methylbenzyl) ester, oxalic acid di-
Examples thereof include esters such as (p-chlorobenzyl) ester and p-benzyloxybenzoic acid benzyl ester, and aromatic compounds such as m-terphenyl and p-benzylbiphenyl.

The coating liquid containing these is generally prepared by using water as a dispersion medium and a dye, a color developing agent and a specific heat-fusible substance together or separately by a ball mill, attritor or sand mill stirring / grinding machine. It is prepared by dispersing in.
In such a coating liquid, starch is usually used as a binder,
Hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc. The amount is 10 to 40% by weight, preferably 15 to 30% by weight.

Various auxiliaries can be added to the coating solution, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzene sulfonate, dispersant for sodium lauryl alcohol sulfate / sodium salt, fatty acid metal salt, triazole, etc. Examples thereof include ultraviolet absorbers such as a system, defoaming agents, fluorescent dyes, antioxidants, and coloring dyes.
In addition, a dispersion liquid or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. is added so that the thermal recording medium does not cause sticking due to contact with a recording device or recording head. You can also

In addition, kaolin, clay, talc, calcium carbonate,
It is also possible to add an inorganic pigment such as calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay.

As the support, paper, plastic film, synthetic paper and the like are used, but paper is most preferably used in terms of cost, coating suitability and the like. The coating amount of the coating liquid for forming the heat-sensitive recording layer on the support is not particularly limited, and is usually ² to 12 g / m ² , preferably 3 to 10 g / m ² in terms of dry weight.
It is adjusted in the range of about ² . The heat-sensitive recording material of the present invention thus obtained, since a specific heat-fusible substance is selectively used together with a specific color developing agent, excellent in color developability, especially in a low energy region, and recording. It has excellent storability and exhibits excellent characteristics with little background fog.

An overcoat layer may be provided on the heat-sensitive recording layer for the purpose of protecting the heat-sensitive recording layer, and the like.
It is of course possible to provide a protective layer on the back surface of the support, or to provide an undercoat layer on the support, and to add various known techniques in the field of thermal recording medium production, such as applying a pressure sensitive adhesive to the back surface of the support. I will get it.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in examples are parts by weight and% by weight, respectively.

Example 1 Preparation of Liquid A 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane 10 parts, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ) 20 parts of ethane,
15 parts of a 5% aqueous solution of methyl cellulose and 120 parts of water
The composition consisting of 1 part was pulverized with a sand mill until the average particle size became 1 μm to obtain a liquid A.

Preparation of Solution B 30 parts of zinc 4- (3-p-tolylsulfonylpropyloxy) salicylate, 5% aqueous solution of methylcellulose 30
Part and 70 parts of water were pulverized with a sand mill until the average particle size became 3 μm to obtain a liquid B.

Preparation of Coating Liquid for Intermediate Layer Baking clay (trade name: Ansilex, apparent specific gravity:
0.22 g / cm ³ manufactured by Engelhard Co., Ltd. 100 parts, styrene / butadiene copolymer latex (solid content: 5)
0%), 15 parts, 30 parts of a 10% aqueous solution of polyvinyl alcohol, and 30 parts of water were mixed to obtain a coating liquid for the intermediate layer.

Preparation of thermosensitive recording medium 50 g / m²Coating amount after drying on high quality paper is 10g / m²
The coating liquid for the intermediate layer is applied and dried to form the intermediate layer.
165 parts of liquid A, 130 parts of liquid B, and a silicon oxide face
(Oil absorption 180ml / 100g) 30 parts, 20% oxidized starch water
Heat sensitivity obtained by mixing and stirring 150 parts of solution and 55 parts of water
Drying weight of coating liquid for recording layer is 5.0g / m ²So that
After coating and drying to provide a heat-sensitive recording layer, super calen
To obtain a thermosensitive recording medium.

Example 2 In the preparation of solution A, 3-di (n-pentyl) 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 Example 1 except that 7-phenylaminofluorane was used.

[Comparative Example 1] In the preparation of solution B, 4- (3
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 4,4'-isopropylidenediphenol was used instead of zinc -P-tolylsulfonylpropyloxy) salicylate.

Comparative Example 2 In the preparation of solution A, 1- (4
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 1,2-bis (3-methylphenoxy) ethane was used instead of -methoxyphenoxy) -2- (2-methylphenoxy) ethane.

The four types of thermal recording materials thus obtained were evaluated as follows, and the results obtained are shown in Table 1. [Color density] Thermosensitive evaluation machine (TH-PMD manufactured by Okura Electric Co., Ltd.
Applied energy of 0.17, and 0.29
Recording was performed at each thermal energy of mJ / dot, and the color density was measured with a Macbeth densitometer (RD-100R type, using an amber filter).

[Moisture resistance and heat resistance] 0.29 mJ / do
After recording the t, heat-sensitive recording paper under high temperature drying condition of 60 ° C.
Leave for 0 hours and under high humidity conditions of 40 ° C and 90% RH 2
After being left for 0 hour, the color density of each recorded image was measured again with a Macbeth densitometer to evaluate the heat resistance and moisture resistance of the recorded image.

[Chemical resistance] To evaluate the chemical resistance,
When a vinyl chloride film was placed on the coloring surface of the thermosensitive recording paper after recording and left at room temperature for 20 hours (plasticizer resistance), and when ethanol was applied to the coloring surface (alcohol resistance), the white paper part The degree of fog and fading of the recorded image were evaluated.

[0031]

[Table 1]

Evaluation Criteria for Chemical Resistance ⊚: Excellent. ◯: Excellent. ×: inferior

[0033]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention is extremely excellent in color developability in a low energy region, and has a good preservability of recorded images, especially, fading of the color-developed portion due to chemicals and less background fog. It was an excellent thermosensitive recording medium.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support and a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent, wherein 1- (4-methoxyphenoxy)-is contained in the thermosensitive recording layer. 2- (2-methylphenoxy) ethane and 4-
A thermosensitive recording medium comprising (3-p-tolylsulfonylpropyloxy) salicylate zinc. 2. A colorless or light-colored basic dye is 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane or 3-di (n-pentyl) amino-6.
The thermosensitive recording medium according to claim 1, which is -methyl-7-phenylaminofluorane.