JPH08282122A - Thermal recording sheet - Google Patents

Abstract

PURPOSE: To obtain a thermal recording sheet having high sensitivity and excellent in heat resistance, plasticizer resistance or the like by adding a specific aminobenzenesulfonamide derivative to a thermal color forming layer as an org. coupler and adding a specific diphenylsulfone derivative thereto as a stabilizer. CONSTITUTION: In a thermal recording sheet having a thermal color forming layer formed by coating a support with a coating soln. obtained by respectively grinding a colorless or light-colored basic colorless dye and an org. coupler such as a phenolic substnace into fine particles to disperse them and mixing both of them, an aminobenzenesulfonamide derivative represented by formula I (wherein X is a 1-4C lower alkyl group, a 1-3C alkoxy group, a hydrogen atom, a nitro group, a cyano group or a halogen atom and m is an integer of 1-3) is added to the thermal color forming layer as the org. coupler and, as a stabilizer, 4-benzyloxy-4'-(2,3-epoxy-2-methylpropoxy)diphenylsulfone represented by formula II is added.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording sheet having excellent heat resistance, water resistance and plasticizer resistance.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording sheet is usually prepared by grinding and dispersing a colorless or light-colored basic colorless dye and an organic developer such as a phenolic substance into fine particles, and then mixing them together to prepare a binder and a filler. A coating solution obtained by adding agents, sensitivity enhancers, lubricants and other auxiliaries to a support such as paper, synthetic paper, film, plastic, etc., such as a hot pen, thermal head, hot stamp, laser light. Color recording is obtained by an instant chemical reaction by heating such as.

These thermal recording sheets are used for measuring recorders, computer terminal printers, facsimiles,
It has been applied to a wide range of fields such as automatic ticket vending machines and bar code labels, but recently, with the diversification and high performance of these recording devices, the quality requirements for thermal recording sheets have become higher. . For example, as recording speed increases, it is required to obtain a clear color image with high density even with a small amount of heat energy, and light resistance on the other hand,
There is a demand for a heat-sensitive recording sheet having excellent storage stability such as weather resistance and oil resistance.

As a conventional example of a heat-sensitive recording sheet, for example, Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-1403.
The heat-sensitive recording material disclosed in Japanese Patent No. 9 is mentioned, but such a conventional heat-sensitive recording material has a low thermal response, for example, and sufficient color density cannot be obtained during high-speed recording.

As a method of improving such a defect, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane is used as a leuco dye (JP-A-49-109120), 3- Dibutylamino-
Development of high-sensitivity dyes such as using 6-methyl-7-anilinofluorane (JP-A-59-190891) has been made, and a substance having a good coloring property as a developer 1,7-
Bis (4-hydroxyphenylthio) -3,5-dioxaheptane (JP-A-59-106456), 1,
By using 5-bis (4-hydroxyphenylthio) -3-oxaheptane (JP-A-59-116262) and 4-hydroxy-4'-isopropoxydiphenyl sulfone (JP-B-63-46067). Techniques for achieving high speed and high sensitivity have been disclosed.

[0006]

However, although these heat-sensitive recording sheets have high sensitivity, they generally have a problem in heat resistance such that when they are stored at a high temperature, color development of the background portion (background fog) occurs. . Further, the storage stability of the recorded image is remarkably poor, so that water or sebum components adhere to the color image or contact with a plasticizer (DOP, DOA, etc.) contained in a wrap film such as a vinyl chloride film causes image density. However, there are still some drawbacks such as a significant decrease in color and decolorization.

An object of the present invention is to provide a heat-sensitive recording sheet having high sensitivity, heat resistance, water resistance and plasticizer resistance.

[0008]

According to the present invention, a thermosensitive color-developing layer contains an aminobenzenesulfonamide derivative represented by the following general formula (I) as an organic developer and a stabilizer represented by the following formula (II): 4-benzyloxy-4 '-(2,3-epoxy-2-methylpropoxy) represented by
By containing diphenyl sulfone, the above problems are solved all at once.

[0009]

Embedded image (In the formula, X is a lower alkyl group having 1 to 4 carbon atoms and 1 carbon atom.
~ 3 alkoxy group, hydrogen atom, nitro group, cyano group,
Represents a halogen atom. m represents an integer of 1 to 3. )

[Chemical 4]

In the present invention, the compound number and structural formula of the aminobenzenesulfonamide derivative used as the organic developer are exemplified, but the invention is not limited thereto. Further, the following aminobenzenesulfonamide derivatives can be used alone or in combination of two or more as required.

[0011]

Embedded image

[Chemical 6]

[0012]

[Chemical 7]

Embedded image

The basic colorless dye used in the present invention is not particularly limited, but triphenylmethane type, fluorane type, fluorene type, divinyl type and the like are preferable, and specific examples thereof are shown below. These dyes can be used alone or in combination of two or more.

<Triphenylmethane Leuco Dye> 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide [also known as crystal violet lactone] <Fluoran leuco dye (I)> 3-diethylamino -6-Methyl-7-anilinofluorane 3- (N-ethyl-p-toluidino) -6-methyl-
7-anilinofluoran 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluoran 3 -Pyrrolidino-6-methyl-7-anilinofluorane 3-piperidino-6-methyl-7-anilinofluorane 3- (N-cyclohexyl-N-methylamino) -6-
Methyl-7-anilinofluorane 3-diethylamino-7- (m-trifluoromethylanilino) fluorane 3-Nn-dibutylamino-6-methyl-7-anilinofluorane 3-Nn-dibutyl Amino-7- (o-chloroanilino) fluorane 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane 3-dibutylamino-6-methyl-7- (o, p -Dimethylanilino) fluorane 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane 3-diethylamino-6-chloro-7-anilinofluorane 3-dibutylamino-7- (O-Chloranilino) fluorane 3-diethylamino-7- (o-chloranilino) fluorane 3-diethylamino-6-methyl-ku Lorfluorane 3-diethylamino-6-methyl-fluorane 3-cyclohexylamino-6-chlorofluorane 3-diethylamino-benzo [a] -fluorane 3-n-dipentylamino-6-methyl-7-anilinofluorane 2- ( 4-oxo-hexyl) -3-dimethylamino-
6-Methyl-7-anilinofluorane 2- (4-oxo-hexyl) -3-diethylamino-
6-Methyl-7-anilinofluorane 2- (4-oxo-hexyl) -3-dipropylamino-6-methyl-7-anilinofluorane 3-diethylamino-6-methyl-7- (m-methylanilino ) Fluoran 3-dibutylamino-6-methyl-7- (m-methylanilino) fluorane <fluorene-based leuco dye> 3,6,6′-tris (dimethylamino) spiro [fluorene-9,3′-phthalide] 3, 6,6'-Tris (diethylamino) spiro [fluorene-9,3'-phthalide] <Fluoran-based leuco dye (II)> 2-methyl-6-p- (p-dimethylaminophenyl)
Aminoanilinofluorane 2-Methoxy-6-p- (p-dimethylaminophenyl) aminoanilinofluorane 2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2 -Chloro-6-p- (p-dimethylaminophenyl)
Aminoanilinofluoran 2-nitro-6-p- (p-diethylaminophenyl)
Aminoanilinofluorane 2-amino-6-p- (p-diethylaminophenyl)
Aminoanilinofluorane 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 2-phenyl-6-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2- Benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2-hydroxy-6-p- (p-phenylaminophenyl) aminoanilinofluorane 3-methyl-6-p- (p-dimethyl Aminophenyl)
Aminoanilinofluorane 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane <Divinyl-based leuco dye> 3,3-bis- [2- (p-dimethylaminophenyl)
-2- (p-Methoxyphenyl) ethenyl] -4,5,
6,7-Tetrabromophthalide 3,3-bis- [2- (p-dimethylaminophenyl)
-2- (p-Methoxyphenyl) ethenyl] -4,5,
6,7-Tetrachlorophthalide 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide 3,3- Bis- [1- (4-methoxyphenyl) -1-
(4-pyrrolidinophenyl) ethylene-2-yl]-
4,5,6,7-Tetrachlorophthalide <Others> 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2 ，
2-Dinitrileethane 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2-
β-naphthoylethane 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,
2-Diacetylethane bis- [2,2,2 ', 2'-tetrakis- (p-dimethylaminophenyl) -ethenyl] -methylmalonic acid dimethyl ester

Similar to the dye, an organic developer may be added with another developer as long as the effect of the present invention is not impaired.

Further, as sensitizers, fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide, montan wax, polyethylene wax, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate. , P-benzylbiphenyl, phenyl α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-
2-naphthoic acid phenyl ester, 1,2-di- (3-
Methylphenoxy) ethane, di (p-methylbenzyl) oxalate, β-benzyloxynaphthalene, 4-biphenyl p-tolyl ether, O-xylerin-bis- (phenyl ether), 4- (m-methylphenoxymethyl) biphenyl Etc. can also be added.

As the binder used in the present invention, completely saponified polyvinyl alcohol having a degree of polymerization of 200 to 1900, partially saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl. Alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and ethyl cellulose, cellulose derivatives such as acetyl cellulose, polyvinyl chloride, polyvinyl acetate,
Examples thereof include polyacrylamide, polyacrylic acid ester, polyvinyl butyral polystyrol and copolymers thereof, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin and coumarone resin. These polymeric substances are water, alcohols, ketones,
In addition to using it by dissolving it in a solvent such as ester or hydrocarbon,
It may be used in a state of being emulsified in water or another medium or dispersed in a paste form and used together depending on the required quality.

In the present invention, a known stabilizer p-nitrobenzoic acid metal salt (Ca, Zn) or phthalic acid monobenzyl ester metal salt (Ca, Zn) is used within a range that does not impair the effects of the present invention. It is also possible to add.

The filler used in the present invention is silica,
Examples include inorganic or organic fillers such as calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, tanks, titanium oxide, and aluminum hydroxide.

In addition to these, a release agent such as a fatty acid metal salt, a lubricant such as waxes, a benzophenone-based or triazole-based UV absorber, a water-proofing agent such as glyoxal, a dispersant, an antifoaming agent, etc. should be used. You can

The amount of the organic developer and the stabilizer used in the present invention and the type and amount of other various components are determined according to the required performance and recording suitability, and are not particularly limited, but usually, With respect to 1 part of the basic colorless dye, 1 to 8 parts of an organic developer and 1 to 20 parts of a filler are used, and 10 to 25% of the total solid content of the binder is suitable.

The desired heat-sensitive recording sheet can be obtained by applying a coating solution having the above composition to any support such as paper, synthetic paper, film, plastic and the like.

Further, an overcoat layer of a polymeric substance containing a filler may be provided on the thermosensitive color developing layer for the purpose of improving the storage stability. Further, an undercoat layer containing an organic filler or an inorganic filler may be provided under the thermosensitive color developing layer for the purpose of enhancing the storage stability and the sensitivity.

The above-mentioned organic color developer, basic colorless dye and materials to be added as necessary are finely divided by a pulverizer such as a ball mill, attritor, or sand grinder or an appropriate emulsifying device until the particle diameter becomes several microns or less. Then, the binder and various additives according to the purpose are added to obtain a coating liquid.

[0025]

The reason why the effect of the present invention can be obtained when the specific organic developer and the specific stabilizer are combined in the present invention is considered as follows. First, the excellent dynamic color development ability is due to the large melt-dissolution diffusion rate and saturation solubility of the dye with respect to the color developer of the present invention, and instantaneous recording is achieved by momentary contact of a high-heat thermal head. An image can be formed.

The reason why the recorded image is extremely stable in terms of water resistance and plasticizer resistance is explained as follows. Generally, a thermal recording paper is composed of a basic colorless dye as an electron donor and an organic acidic substance such as a phenol compound, an aromatic carboxylic acid or an organic sulfonic acid as an electron acceptor. The heat-melting reaction between the basic colorless dye and the color developer is an acid-base reaction based on electron donation / acceptance, whereby a metastable "charge transfer complex" is formed and a color image is obtained. .

When the specific aminobenzenesulfonamide derivative which is the organic developer of the present invention and the specific diphenylsulfone derivative which is the stabilizer are used in combination, the aminobenzenesulfonamide derivative and the basic colorless dye in the coloring process are used. The chemical bond between and becomes extremely strong. on the other hand,
When a stabilizer is not used and a developer other than the present invention (for example, benzyl 4-hydroxybenzoate, 4-hydroxy-
4'-isopropoxydiphenyl sulfone, 4,4'-
When isopropylidenediphenol) and the stabilizer of the present invention are used in combination, the chemical bond strength is weak. Therefore, a thermal recording sheet composed of a combination of a specific aminobenzenesulfonamide derivative, a specific diphenylsulfone derivative and a basic colorless dye is exposed to environmental conditions affected by water, plasticizer, etc. for a long time. It is considered that the chemical bond is not broken and the stability of the color image is maintained.

Further, in the case of thermal recording, the thermal head instantaneously reaches a high temperature of 200 to 300 ° C. or higher, so that it is the developer of the present invention contained in the recording layer of the thermal recording medium which is in contact with the thermal head. It is considered that the urea skeleton contained in the aminobenzenesulfonamide derivative undergoes tautomerism to become an enol type and develops a color developing function, and the lactone ring of the dye precursor is cleaved to develop color.

However, when heat energy is slowly applied, the urea skeleton does not change to an enol type structure, so that the color developing function is not expressed and the reaction with the dye precursor does not occur, so that the ground coloration does not occur. Absent. This is considered to be the reason for the high heat resistance.

[0030]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. In the description, parts indicate parts by weight. [Example 1 (Test Nos. 1 to 40)] Liquid A (dye dispersion liquid) 3-n-dibutylamino-6-methyl-7-anilinofluorane 2.0 parts 10% polyvinyl alcohol aqueous solution 4.6 parts Water 2.5 parts Liquid B (developing agent dispersion) Aminobenzenesulfonamide derivative 6.0 parts (see Tables 1 and 3) 10% polyvinyl alcohol aqueous solution 18.8 parts Water 11.2 parts Liquid C (stabilizer Dispersion) 4-benzyloxy-4 '-(2,3-epoxy-2-methylpropoxy) diphenylsulfone 2.0 parts 10% polyvinyl alcohol aqueous solution 4.6 parts water 2.5 parts Each liquid of the above composition Was ground to a particle size of 1 micron with a sand grinder. Then, the dispersion liquids are mixed in the following proportions to prepare a coating liquid. Liquid A (dye dispersion) 9.1 parts Liquid B (developer dispersion liquid) 36.0 parts Liquid C (stabilizer dispersion liquid) 9.1 parts Kaolin clay (50% dispersion liquid) 12.0 parts Each of the above Apply the coating solution to one side of 50g / m ² base paper with a coating amount of 5.0
The sheet was coated and dried so as to be g / m ² , and this sheet was treated with a super calendar so that the smoothness was 500 to 600 seconds to obtain a black color thermosensitive recording paper.

[Comparative Example 1 (Test Nos. 41 to 45)]
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the stabilizer of the liquid C was not used.

Comparative Example 2 (Test No. 46 to 50) Liquid A (dye dispersion liquid) 3-n-dibutylamino-6-methyl-7-anilinofluorane 2.0 parts 10% polyvinyl alcohol aqueous solution 4 .6 parts Water 2.5 parts D liquid (developing agent dispersion) Developer (see Table 5) 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts C liquid (stabilizer dispersion) ) 4-benzyloxy-4 '-(2,3-epoxy-2-methylpropoxy) diphenylsulfone 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts water 2.5 parts Sandwiching each liquid of the above composition The particles were ground with a grinder to a particle size of 1 micron. Then, the dispersion liquids are mixed in the following proportions to prepare a coating liquid. Liquid A (dye dispersion) 9.1 parts Liquid D (developing agent dispersion) 36.0 parts Liquid C (stabilizer dispersion) 9.1 parts Kaolin clay (50% dispersion) 12.0 parts above Apply the coating solution to one side of 50g / m ² base paper with a coating amount of 5.0
The coated sheet was dried so as to be g / m ² , and this sheet was treated with a super calender so as to have a smoothness of 500 to 600 seconds to obtain a thermal recording paper.

The thermal recording papers obtained in the above Examples and Comparative Examples were subjected to the following quality performance tests, and the results are shown in Table 2.
The results are shown in Tables 4 and 6. However, the stabilizer A in Table 1, Table 3 and Table 5 is the following compound. A; 4-benzyloxy-4 '-(2,3-epoxy-
2-Methylpropoxy) diphenyl sulfone

Note (1) Dynamic color density; manufactured by Tokyo Shibaura Denki-
Thermal facsimile KB-4800 is used and the applied voltage is 1
The image density recorded at 8.03 V and a pulse width of 3.2 milliseconds was measured with a Macbeth densitometer (RD-914, using an amber filter. The same applies hereinafter). Note (2) Heat resistance: The uncolored thermal paper sample was allowed to stand under high temperature drying conditions of 80 ° C for 24 hours, and the density of the background was measured with a Macbeth densitometer. Note (3) Water resistance: The thermal paper sample dynamically recorded by the method of Note (1) was immersed in water at 20 ° C for 24 hours, dried, and the recorded portion was measured with a Macbeth densitometer. The residual rate is calculated from the following formula.

[Equation 1] Note (4) Plasticizer property: The image density of the sample dynamically recorded by the method of Note (1) was measured with a Macbeth densitometer and defined as an untreated density. Then, a vinyl chloride film (Hilap KMA manufactured by Mitsui Toatsu Co., Ltd.) was superposed on the front surface and the back surface of this recording sample, and the image density after standing for 24 hours in a thermostatic tester at 40 ° C. was measured with a Macbeth densitometer. The residual rate is calculated from the following formula.

[Equation 2]

[0035]

[Table 1]

[Table 2]

[0036]

[Table 3]

[Table 4]

[0037]

[Table 5]

[Table 6]

[0038]

【The invention's effect】

(1) Because of its excellent thermal response, a clear high-density image can be obtained even at high speed and high density recording. (High sensitivity) (2) Almost no discoloration occurs in the image area even when it comes into contact with a plasticizer, salad oil, vinegar, etc. (Chemical resistance) (3) Almost no discoloration occurs in the image area even when contacted with water. (Water resistance) (4) The ground color is stable even under high temperature conditions. (Heat-resistant)

Claims (1)

[Claims] 1. A thermosensitive recording sheet comprising a support and a thermosensitive coloring layer containing a colorless or light-colored basic colorless dye and an organic developer as main components, wherein the thermosensitive coloring layer is an organic developer. A heat-sensitive recording sheet containing an aminobenzenesulfonamide derivative represented by the following general formula (I) and a diphenylsulfone derivative represented by the following formula (II) as a stabilizer. Embedded image (In the formula, X is a lower alkyl group having 1 to 4 carbon atoms and 1 carbon atom.
~ 3 alkoxy group, hydrogen atom, nitro group, cyano group,
Represents a halogen atom. m represents an integer of 1 to 3. )