JPH0747773A - Thermal recording medium - Google Patents

Abstract

PURPOSE:To enhance sensitivity of a thermal recording medium, to improve oil resistance, plasticizer resistance of a color developed image and to hence enhance long-term stability of the image by forming developer contained together with dye precursor in a thermal color developed layer of the medium of compound having a specific structure. CONSTITUTION:The thermal recording medium comprises a sheetlike base, and a thermal color developed layer formed at least on one surface of the base and containing colorless or light-color dye precursor and developer for color developing the precursor in reaction by heating. The developer contains at least one type of compound represented by a formula (wherein X is O, S, R is at least aromatic group substituted with at least one member selected from non-substituted aromatic group, lower alkyl group, lower alkoxy group and halogen atom, A is bivalent or higher group, and n is integer of 2 or more). As a result, the medium in which the image having excellent oil resistance, plasticizer resistance, moisture resistance, heat resistance, etc., i.e., excellent long-term preservability can be formed can be obtained.

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 on which a color-developed image is formed by heating, and more particularly to a heat-sensitive recording material which is free from loss of a once-color-developed image and has excellent storage stability. More specifically, the present invention has good long-term storage stability for recording, and at the same time, is excellent in environmental resistance such as humidity resistance and heat resistance of recorded images, oil resistance, and plasticizer resistance. The present invention relates to a thermosensitive recording medium useful for facsimile sheets, cash dispenser sheets, boarding tickets, commuter passes, labels such as POS labels, cards such as prepaid cards, and pass tickets.

[0002]

2. Description of the Related Art A thermal recording material generally comprises a support such as paper, synthetic paper, or plastic film on which a color-forming substance such as an electron-donating leuco dye and an organic acid substance such as an electron-accepting phenolic compound. A thermosensitive coloring layer containing such a color-developing substance as a main component is provided, and a recorded image can be obtained by reacting these components with thermal energy. Such a thermosensitive recording medium is disclosed in Japanese Examined Patent Publication No. 43-4160.
No. 4, JP-B-45-14039, and JP-A-48-27.
It is disclosed in Japanese Patent No. 736, etc., and will be widely put into practical use.

Since the recording device of the thermal recording medium is compact, inexpensive and easy to maintain, the output of an electronic computer, a facsimile, an automatic ticket vending machine, a printer for scientific measuring instruments, a printer for CRT medical measurement, etc. Widely used in. However, in a conventional so-called dye-type thermosensitive recording medium in which a thermosensitive coloring layer containing a color-developing dye substance, a color-developing substance and a binder as an active ingredient is coated on a support, the coloring reaction is reversible. For this reason, it is known that a colored image disappears over time. This decoloring is accelerated under exposure to light, high humidity and high temperature, and further progresses rapidly due to contact with a plasticizer and oil, and the image is decolorized to an unreadable level.

A number of techniques have been disclosed for suppressing the above-mentioned decoloring development in the conventional color forming system using a dye mainly composed of a colorless or light-colored lactone ring compound. For example, (1) JP-A-60-78782 and JP-A-59-1
No. 67292, JP-A-59-114096, and JP-A-59-93387, wherein a thermosensitive color developing layer contains a phenolic antioxidant, (2) JP-A-56-146796. What uses a hydrophobic polymer compound emulsion as seen in the protective layer, (3) Water-soluble polymer compound or hydrophobic polymer on the thermosensitive coloring layer as seen in JP-A-58-199189 A compound emulsion is provided as an intermediate layer, and a surface layer made of an oily coating containing a hydrophobic polymer compound as a resin component is provided thereon, and (4) contains an epoxy compound as disclosed in JP-A-62-164579. And (5) those using a metal salt of a specific salicylic acid derivative found in JP-A-62-169681 as a developer.

In the color-developed image of the thermosensitive color-developing layer containing the above-mentioned phenolic antioxidant, the environment resistance is slightly improved as compared with the image without the color-developing agent, but the oil resistance (for example, coloring of salad oil) is improved. Of image density after a certain period of time when brought into contact with the surface), plasticizer resistance (preservation rate of image density after a certain period of time when a wrap film containing a plasticizer is brought into contact with the color surface) No improvement is allowed for the above. On the other hand, the color-developed image of the thermosensitive recording medium provided with the above-mentioned protective layer and surface layer has a slightly improved environmental resistance, but decolorization is inevitable in a long-term test. Also regarding the oil resistance, the image storability immediately after being brought into contact with oil is improved, but the image disappears almost completely as the oil permeates, which is an essential solution to the above problems. Absent. Further, in a thermosensitive recording medium containing an epoxy compound, a relatively long time is required from the heating color development operation until the color image is stabilized, and for example, salad oil is applied to the color image immediately after color development. Or, if a color image is brought into contact with a plasticizer, a considerable part of the color image is erased. Furthermore, in a heat-sensitive recording material using a specific salicylic acid metal salt, although the oil resistance and plasticizer resistance of the color-developed image are improved, in the heat resistance test, coloration of a blank sheet is observed,
It also has the drawback that the chemical structure of the specific effective salicylic acid is complex and expensive.

[0006]

The present invention solves the above problems in the prior art and can form a colored image excellent in oil resistance, plasticizer resistance, moisture resistance, heat resistance, etc., that is, long-term storage stability. It is intended to provide a thermosensitive recording medium.
The heat-sensitive recording material of the present invention can be used not only as a heat-sensitive recording type ticket for an automatic ticket vending machine, but can also be used for a number of tickets and a commuter pass that require storage, contact with a plasticizer, oil and fat. Not only suitable as a label for POS bar code system to be stuck on the packaging surface of foods that are inevitable polyvinyl chloride film, but also as facsimile paper or word processor paper for long-term storage, or image printer paper for CRT. It is available.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have developed a thermosensitive color development in which a storage stability improving effect such as oil resistance and plasticizer resistance of a color image is developed within a short time after color image formation. A layer improvement method was examined, and as a result, an arylamino (thio) carbonylaminosulfonyl group represented by the following formula (II):

[Chemical 2] (However, X represents an oxygen or sulfur atom, and R represents an unsubstituted aromatic group or an aromatic group substituted by at least one member selected from a lower alkyl group, a lower alkoxy group and a halogen atom.) It was discovered that a compound having two or more molecules per molecule has excellent color developing ability and high oil and plasticizer resistance, and thus can form a color image having an excellent long-term storage stabilizing effect. The invention was completed.

The heat-sensitive recording material of the present invention is formed on a sheet-like substrate and at least one surface of the sheet-like substrate, and a colorless or light-colored dye precursor reacts with the dye precursor under heating to form a dye. And a heat-sensitive color developing layer containing a color developing agent that develops a colorant, wherein the color developing agent has the following general formula (I):

[Chemical 3] (However, X represents an oxygen or sulfur atom, R represents an unsubstituted aromatic group, or an aromatic group substituted by at least one member selected from a lower alkyl group, a lower alkoxy group and a halogen atom, A represents a divalent or higher valent group, and n represents an integer of 2 or more.).

[0009]

The compound of formula (I) used in the present invention acts as a developer. That is, the compound of formula (I) does not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group, but has a strong color developing ability for a basic leuco dye. It is understood that this is because the (thio) urea group in the compound of formula (I) is activated by the sulfonyl group adjacent to it. In addition, the image formed by the compound of formula (I) and the leuco dye has a high storability under various environments.
Arylamino (thio) containing two or more in the molecule
It is understood to be due to the synergistic effect of the carbonylaminosulfonyl group (formula II).

In the formula (I), the group represented by A is not particularly limited as long as it has a divalent or higher valency, but preferable ones can be selected from the following groups. . a: divalent and higher groups derived from aliphatic hydrocarbon b: divalent and higher groups derived from aliphatic hydrocarbon containing one or more heteroatoms in the main chain c: main chain A divalent or higher-valent group derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted aromatic hydrocarbon d: containing at least one substituted or unsubstituted heteroaromatic ring in the main chain Divalent and higher groups derived from aliphatic hydrocarbon e: Divalent and higher groups derived from substituted or unsubstituted aromatic hydrocarbon f: From substituted or unsubstituted heteroaromatic ring Induced 2
A group having a valency or more g: two or more aromatic hydrocarbons, a compound in which a heteroaromatic ring is bound to the organic groups a to e and a functional group such as a carbonyl group, a thiocarbonyl group or a sulfonyl group More derived divalent and higher valent groups

Specific examples of the compound of formula (I) are as follows. 1,2-bis (p-chlorobenzeneaminocarbonylaminosulfonyl) -ethane, 1,3-
Bis (p-methoxybenzeneaminocarbonylaminosulfonyl) -benzene, 4,4'-bis (p-tolueneaminocarbonylaminosulfonyl) -benzene, 1,
2-bis (o-tolueneaminocarbonylaminosulfonyl) -benzene, 4,4'-bis (p-chlorobenzeneaminocarbonylaminosulfonyl) -diphenylmethane, 4,4'-bis (p-methoxybenzeneaminocarbonylaminosulfonyl)- Diphenylmethane, 4,
4'-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenyl sulfone, 4,4'-bis (3,4
4-dichlorobenzeneaminocarbonylaminosulfonyl) -diphenyl sulfide, 4,4'-bis (3,4
-Dichlorobenzeneaminocarbonylaminosulfonyl) -biphenyl, 4,4'-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenyl sulfide, 4,4'-bis (p-tolueneaminocarbonylaminosulfonyl) -biphenyl, 3, 3'-bis (m-
Chlorobenzene aminocarbonylaminosulfonyl)-
Diphenyl sulfone, 3,3'-bis (p-methoxybenzeneaminocarbonylaminosulfonyl) -diphenyl sulfone, 4,4'-bis (benzeneaminocarbonylaminosulfonyl) -diphenyl sulfide, 4,
4'-bis (benzeneaminocarbonylaminosulfonyl) -biphenyl, 4,4'-bis (p-methoxybenzeneaminocarbonylaminosulfonyl) -diphenyl sulfide, 4,4'-bis (p-methoxybenzeneaminocarbonylaminosulfonyl) -Diphenyl ether, 4,4'-bis (p-chlorobenzeneaminocarbonylaminosulfonyl) -diphenyl sulfone, 2,5
-Bis (p-methoxybenzeneaminocarbonylaminosulfonyl) -furan, 4,4'-bis (p-chlorobenzeneaminocarbonylaminosulfonyl) -biphenyl, 1,5-bis (m-chlorobenzeneaminocarbonylaminosulfonyl) -naphthalene, 4,4'-bis (m-chlorobenzeneaminocarbonylaminosulfonyl) -biphenyl, 1,6-bis (m-trifluoromethylbenzeneaminocarbonylaminosulfonyl) -naphthalene, 2,6-bis (m-trifluoromethylbenzene) Aminocarbonylaminosulfonyl) -naphthalene, 4,4'-bis (3,4-dichlorobenzeneaminothiocarbonylaminosulfonyl) -diphenyl sulfide, 4,4'-bis (3,4-dichlorobenzeneaminothiocarbonylamido Sulfonyl) - biphenyl,
4,4'-bis (p-tolueneaminothiocarbonylaminosulfonyl) -diphenyl sulfide, 4,4'-
Bis (p-tolueneaminothiocarbonylaminosulfonyl) -biphenyl, 4,4'-bis (benzeneaminothiocarbonylaminosulfonyl) -diphenyl sulfide.

These compounds may be used alone or in a mixture of two or more thereof. Many of the above-mentioned compounds of formula (I) are novel compounds that have not been previously reported, and can be synthesized, for example, by the following reactions (1) to (3).

[Chemical 4]

The leuco dye used as a dye precursor in the present invention can be selected from conventionally known ones such as triphenylmethane type, fluorane type and diphenylmethane type compounds. For example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N-ethyl-N-iso). Pentylamino) -6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (o, p
-Dimethylanilino) fluorane, 3- (N-ethyl-)
N-p-toluidino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3 -(N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3
-Diethylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylamino-
6-methylfluorane, 3-cyclohexylamino-6
One or more selected from -chlorofluorane, 3- (N-ethyl-N-hexylamino) -6-methyl-7- (p-chloroanilino) fluorane and the like can be used.

Further, in the present invention, a conventionally known developer containing a phenol or an organic acid may be used in combination with the compound of the formula (I) of the present invention within a range that does not impair the desired effect. . These conventional color developers are, for example, 2,2
-Bis (4-hydroxyphenylpropane (bisphenol A), 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis (1-methyl-1-)
(4'-hydroxyphenyl) ethyl) benzene, 1,
3-bis (1-methyl-1- (4'-hydroxyphenyl) ethyl) benzene, dihydroxydiphenyl ether (JP-A-1-180382), benzyl p-hydroxybenzoate (JP-A-52-140483), bisphenol S , 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-13852),
1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxyphenylthio) -3,
5-dioxaheptane (JP-A-59-52694),
3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone (JP-A-60-208286) and the like.

Further, in the present invention, it is preferable to use a heat-fusible substance (so-called sensitizer) together with the heat-sensitive color forming layer. As the sensitizer, a heat-fusible organic compound having a melting point of 50 to 150 ° C. is used, and examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-19).
1089), p-benzylbiphenyl (JP-A-60-
82382), benzyl naphthyl ether (Japanese Patent Application Laid-open No. Sho 5)
8-87094), dibenzyl terephthalate (JP-A-58-98285), benzyl p-benzyloxybenzoate (JP-A-57-201691), diphenyl carbonate, ditolyl carbonate (JP-A-58-136489). ,
m-terphenyl (JP-A-57-89994), 1,
2-bis (m-tolyloxy) ethane (JP-A-60-5)
6588), 1,5-bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-181183).
No.), oxalic acid diesters (JP-A-64-1583).
No.), 1,4-bis (p-tolyloxy) benzene (JP-A-2-153787).

The thermosensitive coloring layer of the present invention may further contain a hindered phenol compound or an ultraviolet absorber. They are, for example, JP-A-57-151394, JP-A-58-160191, JP-A-58-69096,
JP-A-59-2884, JP-A-59-95190,
JP-A-60-22288, JP-A-60-255485
JP-A-61-44686 and JP-A-62-1696.
83, JP-A-63-17081, and JP-A-1-
249385 and the like, specifically, for example, 1,1,3-tris (3′-cyclohexyl-4′-hydroxyphenyl) butane, 1,1,3
-Tris (2-methyl-4-hydroxy-5-tert)
-Butylphenyl) butane, 4,4'-thiobis (3-
Methyl-6-tert-butylphenol), 1,3
5-trimethyl-2,4,6-tris (3,5-di-t
ert-butyl-4-hydroxybenzyl) benzene,
2,2'-dihydroxy-4,4'-dimethoxybenzophenone, p-octylphenyl salicylate, 2-
(2'-hydroxy-5'-methylphenyl) benzotriazole, ethyl-2-cyano-3,3'-diphenyl acrylate, tetra (2,2,6,6, -tetramethyl-4-piperidyl) 1,2 , 3,4-butane tetracarboate and the like.

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention mainly contains a leuco dye, the compound of the above formula (I) of the present invention, and a sensitizer. Further, the heat-sensitive color forming layer may contain a conventionally known phenol type or organic acid type color developer, antioxidant, ultraviolet absorber, or waxes, if necessary, and an organic or inorganic pigment. It is preferable to include. Further, the thermosensitive coloring layer contains a binder for fixing these components to the support.

The content of the above-mentioned leuco dye in the thermosensitive coloring layer is generally 5% of the dry weight of the thermosensitive coloring layer.
-20% by weight, preferably of formula (I) according to the invention.
In general, the content of the developer compound is preferably 10 to 50% by weight. When the content of the compound of the formula (I) is less than 10% by weight, the color developing ability is insufficient, and even when it is added in excess of 50% by weight, the color developing ability is saturated and no remarkable improvement is observed, which is economical. May be disadvantageous.

When the thermosensitive coloring layer contains an antioxidant or an ultraviolet absorber, its content is preferably 1 to 10% by weight. A conventionally known phenol-based or organic acid-based color developer, the content thereof is preferably 5 to 40% by weight, and the content of the sensitizer is preferably 10 to 40% by weight. When waxes and white pigments are contained in the thermosensitive coloring layer, the contents thereof are 5 to 20% by weight and 10 to 5%, respectively.
It is preferably 0% by weight and the binder content is generally 5 to 20% by weight.

Examples of the above-mentioned organic or inorganic pigments include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, calcined clay, talc, and surface-treated calcium carbonate. Examples thereof include inorganic fine powder such as silica and silica, and organic fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

As the waxes, known waxes such as paraffin, amide wax, bisimide wax, and metal salt of higher fatty acid can be used.

Regarding the binder, polyvinyl alcohol having various molecular weights, starch and derivatives thereof, methoxycellulose, carboxymethylcellulose, cellulose derivatives such as methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester. Water-soluble polymer materials such as copolymers, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymers, styrene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, and ,
Polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic ester,
Each latex such as vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the heat-sensitive recording material of the present invention is selected from paper, coated paper having a surface coated with a pigment, latex, etc., laminated paper, synthetic paper made from polyolefin resin, plastic film and the like. be able to. At least one surface of such a sheet-like substrate is coated with a coating solution containing a mixture of the above-mentioned required components and dried to produce a thermosensitive recording medium. The coating amount is preferably ¹ to 15 g / m ² when the coating liquid amount is dry,
² to 10 g / m ² is more preferable.

In the thermosensitive recording medium of the present invention, a coating layer such as a protective layer or a printing layer can be further formed on the thermosensitive coloring layer.

[0025]

EXAMPLES The present invention will be specifically described with reference to the following examples. In the examples, "parts" and "%" represent "parts by weight" and "% by weight", respectively, unless otherwise specified.

Synthesis Example 1 [ Synthesis of 4,4'-bis (benzeneaminocarbonylaminosulfonyl) -diphenylsulfide] In a three-necked flask equipped with a dropping funnel and a thermometer,
10 g of diphenyl sulfide-4,4'-disulfonamide was added and this was dissolved in 5% NaOH aqueous solution.
Acetone was added to this solution to make a uniform solution, and 7.1 g of phenyl isocyanate was added dropwise from a dropping funnel while vigorously stirring with a magnetic stirrer. About 10 minutes after the completion of dropping, the reaction solution became cloudy. The white turbid liquid was further stirred at room temperature for 2 hours and then filtered to remove a white solid. When this filtrate was weakly acidified with a 5% aqueous hydrochloric acid solution, a white solid was deposited. This mixed solution was filtered to obtain 10.6 g of white crystals. Its melting point was 184-192 ° C.

The results of NMR measurement (in heavy DMSO) are as follows. δ (ppm) = 7.08 (t, 2H), 7.38 (m, 4)
H), 7.65 (d, 2H), 8.04 (d, 2H) and other peaks which are considered to be attributed to N-H are δ = 9.
It appeared around 0, 10.8 ppm. As a result, it was confirmed that the product was the target compound.

Synthesis Example 2 [ Synthesis of 4,4'-bis (benzeneaminocarbonylaminosulfonyl) -biphenyl] The same operation as in Synthesis Example 1 was performed. However, 7.8 g of 4,4'-biphenyldisulfonamide was used instead of 10 g of diphenylsulfide-4,4'-disulfonamide, and the amount of phenyl isocyanate used was 6.6 g. As a result, 12.8 g of white crystals were obtained. The melting point of this compound was 183 to 186 ° C., and it was identified by NMR measurement that the obtained compound was the target product.

The results of NMR measurement (in heavy DMSO) are as follows. δ (ppm) = 6.98 (t, 2H), 7.23 (t, 4)
H), 7.38 (d, 4H), 7.95 (d, 4H),
8.10 (d, 4H) Other peaks that are thought to be due to NH are δ = 9.
2, appeared at 10.8 ppm.

Synthesis Example 3 [ Synthesis of 4,4'-bis (p-tolueneaminocarbonylaminosulfonyl) diphenyl sulfide] The same operation as in Synthesis Example 1 was performed. However, the amount of diphenyl sulfide-4,4'-disulfonamide used was 8.6.
In addition, 6.7 g of p-toluene isocyanate was used in place of 7.1 g of phenyl isocyanate. As a result, 11.6 g of white crystals were obtained. The melting point of this compound was 190 to 200 ° C., and it was identified by NMR measurement that the obtained compound was the target product.

The results of NMR measurement (in heavy DMSO) are as follows. δ (ppm) = 2.28 (s, 6H), 7.11 (d, 4)
H), 7.25 (d, 4H), 7.65 (d, 4H),
8.02 (d, 4H) Other peaks that are thought to be due to NH are δ = 8.
It appeared around 8 and 10.5 ppm.

Synthesis Example 4 [ Synthesis of 4,4'-bis (p-tolueneaminocarbonylaminosulfonyl) biphenyl] The same operation as in Synthesis Example 1 was performed. However, 7.8 g of 4,4'-biphenyldisulfonamide was used in place of 10 g of diphenylsulfide-4,4'-disulfonamide, and 6.7 in place of phenylisocyanate.
g of p-toluene isocyanate was used. as a result,
11.2 g of white crystals were obtained. The melting point of this compound is 3
It was at least 00 ° C.

The results of NMR measurement (in heavy DMSO) are as follows. δ (ppm) = 2.25 (s, 6H), 7.05 (d, 4)
H), 7.28 (d, 4H), 8.00 (d, 4H),
8.13 (d, 4H) In addition, the peak that seems to be due to NH is δ = 8.
Appeared around 8ppm. This identified the product as the target compound.

Synthesis Example 5 [ Synthesis of 4,4'-bis (3,4-dichlorobenzeneaminocarbonylaminosulfonyl) diphenyl sulfide] The same operation as in Synthesis Example 1 was performed. However, the amount of diphenyl sulfide-4,4'-disulfonamide used was 8.6.
g, and instead of 7.1 g of phenyl isocyanate, 9.4 g of 3,4-dichlorophenyl isocyanate was used. As a result, 8.2 g of white crystals were obtained.
The melting point of this compound was 152 to 160 ° C.

The results of NMR measurement (in heavy DMSO) are as follows. δ (ppm) = 7.30 (d, 2H), 7.55 (m, 6)
H), 7.75 (d, 2H), 7.98 (d, 4H) and other peaks that are thought to be due to N-H are δ =
Appeared near 9.2 ppm. This identified the product as the target compound.

Example 1 A thermosensitive recording paper was prepared by the following procedure . (1) Preparation of Dispersion A Component Weight (part) ──────────────────────────────── 3- (N- Isopentyl-N-ethylamino) -6-methyl-7-anilinofluorane 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was pulverized using a sand grinder until the average particle size became 1 μm or less.

(2) Preparation of Dispersion B Component Weight (parts) ──────────────────────────────── 4, 4′-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenylsulfide 10 oxalic acid di-p-methylbenzyl ester 10 polyvinyl alcohol 10% liquid 10 water 70 The above composition was used with a sand grinder to have an average particle size of 1 μm or less. Crushed until

(3) Preparation of Pigmented Undercoat Paper 85 parts of calcined clay (trademark: Ansilex) was added to 320 parts of water.
40 parts of styrene-butadiene copolymer emulsion (solid content 50%) and 50 parts of 10% oxidized starch aqueous solution were mixed with the resulting dispersion to prepare a coating solution. A base paper having a basis weight of 48 g / m ² was coated on one side so that the coating amount after drying was 7.0 g / m ² to prepare a pigment-undercoated paper.

(4) Formation of Thermosensitive Coloring Layer 30 parts of calcium carbonate pigment, 20 parts of 25% zinc stearate dispersion liquid were added to 50 parts of solution A and 200 parts of solution B.
A coating liquid was prepared by mixing 15 parts of a 30% paraffin dispersion liquid and 100 parts of a 10% polyvinyl alcohol aqueous solution and stirring them. This coating solution was applied onto the pigment-coated surface of the above-mentioned pigment-undercoated paper so that the coating amount after drying would be 5.0 g / m ^2, and dried to form a thermosensitive color-developing layer to prepare a thermosensitive recording paper. .

The thermal recording paper obtained as described above was surface-treated with a super calender, and the Beck smoothness of the surface was adjusted to 800 to 1000 seconds.

The thus-obtained sample was color-developed with an applied energy of 0.49 mj / dot using a dynamic color-developing tester obtained by modifying a commercial thermal facsimile machine manufactured by Hitachi, Ltd. Color density is Macbeth reflection densitometer RD-9
It was measured at 14 (this is called the original concentration). Then, a predetermined test piece is prepared from this color-developed sample, and within 30 minutes after color development, salad oil or dioctyl terephthalate (representative plasticizer) is applied to the test piece and allowed to stand at room temperature for 3 hours. The plasticizer was removed, the residual image density was measured with a Macbeth reflection densitometer, and the image retention rate was calculated according to the following formula.

[0042]

[Equation 1]

The results of the above tests are shown in Table 1.

Example 2 A thermal recording paper was prepared in the same manner as in Example 1. However, in the preparation of the dispersion liquid B, 4,4′-bis (benzeneaminocarbonylaminosulfonyl) -biphenyl was used instead of 4,4′-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenylsulfide. The test results are shown in Table 1.

Example 3 A thermal recording paper was prepared in the same manner as in Example 1. However, in the preparation of the dispersion liquid B, 4,4′-bis (benzeneaminocarbonylaminosulfonyl) -diphenylsulfide was used instead of 4,4′-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenylsulfide. . The test results are shown in Table 1.

Example 4 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, in the preparation of the dispersion liquid B, 4,4′-bis (3,4-dichlorobenzeneaminocarbonylaminosulfonyl) -instead of 4,4′-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenylsulfide was prepared. Biphenyl was used. The test results are shown in Table 1.

Example 5 A thermal recording paper was prepared in the same manner as in Example 1. However, in the preparation of the dispersion liquid B, 4,4′-bis (3,4-dichlorobenzeneaminocarbonylaminosulfonyl) -instead of 4,4′-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenylsulfide was prepared. Diphenyl sulfide was used. The test results are shown in Table 1.

Comparative Example 1 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, in the preparation of the dispersion liquid B, 2,2′-bis (4-hydroxyphenyl) propane (that is, bisphenol A) was used instead of 4,4′-bis (p-tolueneaminocarbonylaminosulfonyl) -diphenylsulfide. Using. The test results are shown in Table 1.

[0049]

[Table 1]

As is clear from Table 1, the color-developed image obtained by using the novel developer of the present invention is remarkably excellent as compared with the case where bisphenol A which is a typical developer is used. It also exhibits oil resistance and plasticizer resistance.

[0051]

The heat-sensitive recording material of the present invention contains a compound having two or more arylamino (thio) carbonylaminosulfonyl groups in one molecule as a developer in the heat-sensitive color forming layer. The color-developed image obtained by this thermosensitive color-developing layer exhibits excellent oil resistance and plasticizer resistance immediately after color development.

Claims (1)

[Claims] 1. A sheet-like substrate and a colorless or light-colored dye precursor which is formed on at least one surface of the sheet-like substrate, and a developer which reacts with the dye precursor under heating to develop a color. Which has a thermosensitive color-developing layer, wherein the developer has the following general formula (I): (However, X represents an oxygen or sulfur atom, R represents an unsubstituted aromatic group, or an aromatic group substituted by at least one member selected from a lower alkyl group, a lower alkoxy group and a halogen atom, A represents a divalent or higher valent group, and n represents an integer of 2 or more.) A thermosensitive recording medium comprising at least one compound represented by the formula: