JPH08295081A - Thermal recording - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the light resistance and the environment resistance of the color image and the blank area of the thermosensitive recording medium, thereby enhancing the long-term stability of the recorded image. [Structure] The color developer contained in the thermosensitive coloring layer of the thermosensitive recording medium together with the dye precursor is represented by the formula (I): (Wherein X represents an oxygen or sulfur atom) and at least one organic compound having at least one hydroxybenzoic acid ester structure in the molecule.

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 which forms a color image by heating, and more particularly to a heat-sensitive recording material having excellent light resistance and storage stability of recorded images. More specifically, the present invention has very little color fading (recording) image fading and erasing, and white paper part (non-recording part) discoloration and coloring when exposed to a fluorescent lamp or sunlight for a long time. The long-term storage of recorded images is excellent, the recorded images have excellent environmental resistance such as moisture resistance and heat resistance, and the whiteness is high. Therefore, image recording paper, facsimile paper, cash dispenser paper, boarding The present invention relates to a thermal recording material useful for tickets, commuter passes, labels such as POS labels, cards such as prepaid cards, and pass tickets.

[0002]

2. Description of the Related Art Generally, a thermosensitive recording medium comprises a support such as paper, synthetic paper, or a plastic film on which a color-forming component composed of an electron-donating leuco dye and an organic acidic substance such as an electron-accepting phenolic compound. A thermosensitive color-forming layer containing a color-developing component consisting of is provided, and a recorded image can be obtained by reacting these color-forming components with thermal energy. Such a thermal recording material is disclosed in Japanese Examined Patent Publication No. 43-416.
No. 0, JP-B-45-14039, and JP-A-48-2.
It is disclosed in Japanese Patent No. 7736 and is widely put into practical use.

The thermal recording medium as described above has a compact and inexpensive recording device and is easy to maintain. Therefore, the output of a computer, a facsimile, an automatic ticket vending machine, a printer of a scientific measuring instrument, or a CRT medical measuring instrument is used. Widely used for printers and the like.

However, in the conventional thermosensitive recording medium, fading and erasing of the colored image due to light from fluorescent lamps and sunlight, and discoloration and coloring of the white paper portion (non-recording portion) (these are collectively referred to as photodegradation). ) Is likely to occur and the recorded image becomes unclear, so that it was difficult to use in a field in which recording reliability is particularly required.

Various studies have been conducted so far to improve such drawbacks. For example, a method using a light-resistant leuco dye (JP-A-57-105155, JP-A-57-205449). Is proposed, but
In addition to low sensitivity, these dyes have bluish hues and low basic performance as dyes, and it is difficult to put them into practical use.

Further, the phenomenon of photodegradation of the thermosensitive recording material is said to be because the leuco dye is decomposed by ultraviolet rays.
A method of preventing such a phenomenon of photodegradation by using an ultraviolet absorber has also been proposed. However, the conventional method cannot obtain a sufficient photodeterioration preventive effect, and conversely causes a problem that the storability of a recorded image is deteriorated.
That is, as this method, a finely pulverized ultraviolet absorber is contained in the heat-sensitive recording layer (Japanese Patent Laid-Open No. 50-1046).
50, JP-A-54-18572, JP-A-57-19
No. 1089) and a method for providing a protective layer containing a finely pulverized ultraviolet absorber on the thermosensitive recording layer (JP-A-61-193).
883 and JP-A-62-48585), since the ultraviolet absorber is present in a discontinuous state, its light stabilizing effect is not sufficiently exerted, and its amount used in order to obtain a sufficient light stabilizing effect. Is not practical in terms of cost, and problems such as deterioration of environment resistance (heat resistance and humidity resistance) and chemical resistance (reduction of storage stability) and deterioration of printing runnability occur. .

Further, the method of incorporating an ultraviolet absorber in the recording layer causes a decrease in recording sensitivity and a background fog (unintentional color development of a blank portion). For example, when the benzotriazoles disclosed in JP-A-50-104650 and the salicylates disclosed in JP-A-57-191809 are used as UV absorbers, the color-forming sensitivity is significantly lowered, and high temperature It may cause severe fog in the high humidity environment.

On the other hand, when the protective layer contains a finely pulverized ultraviolet absorber, the ultraviolet absorber is eluted by contact with a plasticizer or oils and fats, impairing the function of the protective layer itself, and a recorded image is obtained. The storage stability of the above-mentioned is deteriorated, and new defects such as background fog occur. Therefore,
At present, it has not been possible to obtain a heat-sensitive recording material having sufficiently satisfactory light resistance.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above problems in the prior art and is excellent in light resistance (the colored image does not fade or disappear even when exposed to light for a long time,
Further, the present invention intends to provide a heat-sensitive recording material having high whiteness and excellent long-term storability of a color image under relatively high humidity and high temperature conditions in which the white paper portion is not discolored or colored.

INDUSTRIAL APPLICABILITY The present invention can be used not only as a heat-sensitive recording type ticket for an automatic ticket vending machine, but also as a label for a POS bar code system, such as a coupon ticket or a commuter ticket that requires preservation. Suitable for long-term storage, such as facsimile paper, word processor paper, CRT image printer paper, and gas, electricity, which are frequently used outdoors.
Another object of the present invention is to provide a highly reliable thermal recording material that can be used for handy terminal paper that can be used as a meter reading slip for water supply and the like.

[0011]

The fact that an organic compound having a sulfonyl (thio) urea group exhibits a strong color-developing ability has already been disclosed in JP-A-5-32061 and JP-A-5-147.
No. 357 and JP-A-5-148220. Such a sulfonyl (thio) ureido compound is characterized by exhibiting a strong color developing ability as described above, even though it does not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group. I am trying.

As a result of further diligent study on the compound having a sulfonyl (thio) urea group, the present inventors have found that an organic compound having at least one sulfonyl (thio) urea group and at least one hydroxybenzoic acid ester structure in the molecule. When used as a color developer, the resulting thermosensitive recording medium exhibits excellent light resistance, that is, fading and erasing of a colored (recorded) image when exposed to a fluorescent lamp or sunlight for a long time, and a white paper portion. It has been discovered that the non-recorded area has a characteristic that discoloration and coloring are extremely small, and that it is also excellent in environmental resistance (heat resistance and humidity resistance).

Further, the developer compound according to the present invention has a high color developing function, and therefore, the thermosensitive color developing layer containing this compound as a developer has a high recording sensitivity and the use thereof is required. It was found that a heat-sensitive recording material having high whiteness can be produced by the above-mentioned method, and the present invention has been completed.

The thermosensitive recording material of the present invention has the following general formula (I) as a developer in the thermosensitive coloring layer:

Embedded image (X represents an oxygen atom or a sulfur atom) and at least one organic compound having at least one hydroxybenzoic acid ester structure in the molecule, and are excellent. Light resistance,
It has a high color density and a high whiteness.

In the present invention, the hydroxybenzoic acid ester structure is represented by the following general formula.

[Chemical 4] In the hydroxybenzoic acid ester structure, the hydroxyl group is preferably in the ortho position with respect to the carboxyl group.

In the heat-sensitive recording material of the present invention, the above-mentioned developer compound is added to the following general formulas (II) and (III):

Embedded image (However, in the above formulas (II) and (III), R ¹ represents a member selected from a lower alkyl group, an aralkyl group, and an aryl group, and an aromatic ring constituting the aralkyl group and an aromatic group of the aryl group. The ring is a lower alkyl group, an alkoxy group,
R ² may be substituted with at least one member selected from an aryl group, a halogen atom, and an acetyl group.
Represents a member selected from an arylene group and an arylene alkyl group, and the arylene group and an arylene alkyl group are further substituted with at least one member selected from a lower alkyl group, an aryl group, a halogen atom, and a lower alkoxy group. R ³ and R
⁴ each independently represent a member selected from a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, and an aryl group, and R ³ and R ⁴ and ring A are connected to each other to form a naphthalene ring. ^May be formed, and R ⁵ represents a member selected from an alkyl group, an aralkyl group and an aryl group. By selecting from a hydroxybenzoic acid ester compound having a sulfonyl (thio) urea group represented by (4), a preferable thermosensitive recording paper can be obtained.

[0017]

In the above general formulas (II) and (III), R
¹ represents a member selected from a lower alkyl group, an aralkyl group, and an aryl group, an aromatic ring constituting the aralkyl group, and an aromatic ring of the aryl group further lower alkyl group, an alkoxy group, an aryl group, a halogen atom, R may be substituted by at least one member selected from a hydroxyl group, an acetyl group, and a carboxyl group, and R
¹ is preferably selected from, for example, a methyl group, an ethyl group, a benzyl group, a phenyl group, a p-tolyl group, an o-tolyl group, and a p-chlorophenyl group.

R ² represents a member of an arylene group or an arylene alkyl group, and the arylene group or arylene alkyl group is further substituted with at least one member selected from a lower alkyl group, an aryl group, a halogen atom and a lower alkoxy group. R ² is preferably selected from the group consisting of a phenylene group, a phenylenemethyl group, a phenyleneethyl group and the like.

R ⁵ represents an alkyl group, an aralkyl group or an aryl group, and the aromatic ring forming the aralkyl group and the aromatic ring of the aryl group further include a lower alkyl group, an alkoxy group, an aryl group, a halogen atom, a hydroxyl group,
It may be substituted with at least one member selected from an acetyl group and a carboxyl group, and preferably R
⁵ is selected from a methyl group, an ethyl group, a t-butyl group, a phenyl group, a benzyl group and the like.

R ³ and R ⁴ each represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group or an aryl group, preferably a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a benzyl group. , An ethoxy group, a phenoxy group and the like. R ³ and R ⁴ may be linked to the benzene ring A to form a naphthalene ring.

The following compounds can be mentioned as specific examples of the developer compound according to the present invention. 4- (p
-Toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenylmethyl
2-hydroxybenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxy-3-t-butylbenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 3,
5-di-t-butyl 2-hydroxybenzoate, 4
-(Benzenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-
Hydroxy-3-methylbenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2
-Hydroxy-5-phenylbenzoate, 4- (p-
Toluenesulfonylaminocarbonylamino) phenyl 2-hydroxy-4-ethoxybenzoate, 4-
(O-Toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, 4- (p-chlorobenzenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, phenyl 4- (p-
Toluenesulfonylaminocarbonylamino) -2-hydroxy-3-benzoate, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxynaphthoate, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -1-hydroxy −
2-naphthoate, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -3-hydroxy-2
-Naphthoate, methyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, ethyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, t-
Butyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, phenyl
4- (p-benzenesulfonylaminocarbonylamino) -2-hydroxybenzoate, phenyl 4-
(O-toluenesulfonylaminocarbonylamino)-
2-hydroxybenzoate, phenyl 4- (p-chlorobenzenesulfonylaminocarbonylamino) -2
-Hydroxybenzoate, phenyl 3- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate. These compounds may be used alone or as a mixture of two or more thereof.

Formula (II) used in the present invention and
The color-developing compound of (III) absorbs ultraviolet rays, firmly holds the dye that has once developed color in a colored state, suppresses the erasing reaction, suppresses photodecomposition of the dye precursor, and discolors the white paper part. Has the effect of preventing It is clear that the developer compounds represented by the formulas (II) and (III) have excellent light resistance because they have a salicylic acid ester structure having an ultraviolet absorbing ability in the molecule.

Further, the developer compound used in the present invention has one or more functional groups represented by the formula (I) in one molecule and acts as a developer. That is, an organic compound having at least one functional group represented by the formula (I) in one molecule does not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group, but has a strong manifestation against a basic leuco dye. It shows the color ability. It is considered that such strong development of color developing ability is due to strong interaction of the sulfonylurea group represented by the formula (I) with the dye.

The developer compounds of the formulas (II) and (III) as described above are novel compounds, and their synthesis can be carried out, for example, by the following reactions (1) and (2).

[Chemical 6] (However, in the above formula, R ¹ , R ² , R ³ , R ⁴ , and R ⁵
Is the same as above, and X represents an oxygen atom or a sulfur atom. )

The leuco dye used as the 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-).
Isopentylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-
(O, p-dimethylanilino) fluorane, 3- (N-
Ethyl-Np-toluidino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-
7-anilinofluorane, 3- (N-cyclohexyl-
N-methylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7-
(M-trifluoromethylanilino) fluorane, 3-
Diethylamino-6-methyl-7-chlorofluorane,
3-diethylamino-6-methylfluorane, 3-cyclohexylamino-6-chlorofluorane, 3- (N-
Ethyl-N-hexylamino) -6-methyl-7- (p
-Chloroanilino) fluorane, and 2-chloro-3
-Methyl-6-N, N-diethylaminoanilinofluorane, 3- (p-anilinoanilino) -6-methyl-7
-Anilinofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylaminophthalide), 3,3-bis (2- (p-dimethylaminophenyl)- It is possible to use one or more selected from 2- (p-methoxyphenyl) ethenyl) -4,5,6,7-tetrachlorophthalide, bis (p-dimethylaminostyryl) -p-toluenesulfonylmethane and the like. it can.

Further, in the present invention, a conventionally known developer which comprises a phenol or an organic acid can be used in combination with the developer compound of the present invention within a range that does not impair the desired effect. These conventional color developers include, for example, 2,
2-bis (4-hydroxyphenyl) propane (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
No.), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-13).
852), 1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane (JP-A-59-526).
94), 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone (JP-A-60-208286).
No.), N- (p-toluenesulfonyl) -N'-phenylurea (JP-A-5-116459), 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane (JP-A-5-147357). You can choose from

Further, in the present invention, it is preferable to use a heat-fusible substance (so-called sensitizer) in combination. As such a sensitizer, a heat-fusible organic compound having a melting point of 50 to 150 ° C. is used, for example, 1-hydroxy-2.
-Naphthoic acid phenyl ester (JP-A-57-1910)
89), p-benzylbiphenyl (JP-A-60-82).
382), benzylnaphthyl ether (JP-A-58-58).
No. 87094), dibenzyl terephthalate (Japanese Patent Laid-Open No. Sho 5)
8-98285), 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-60-56)
588), 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), diphenyl sulfone (melting point: 124 ° C.), p-toluenesulfonic acid phenyl ester (melting point: 96 ° C.), mesitylenesulfonic acid p-tolyl. Ester (melting point 100-102 ° C), 4,4'-diallyloxydiphenylsulfone (melting point 145 ° C), 4-ethoxyphenylmethylsulfone (melting point 91 ° C), 4,4'-
Diisopentyloxydiphenyl sulfone (melting point 100
C.), 4,4′-dimethoxydiphenyl sulfone (melting point 130 ° C.), 2,2-bis (4-benzenesulfonyloxyphenyl) propane (melting point 114 ° C.), 2,2-bis (4-methanesulfonyloxyphenyl) It can be selected from propane (melting point 101 ° C.), N-phenyl-4-methylphenylsulfonamide (melting point 102 ° C.), o-chloroacetoacetanilide (melting point 103 ° C.), N-benzyl-o-sulfophthalimide and the like.

Further, in the heat-sensitive color forming layer of the present invention, if necessary, an ultraviolet absorber such as a benzophenone compound, a triazole compound, a cyanoacrylate compound, a hindered phenol compound, a hindered amine (so-called HALS) compound. Compounds, phosphite-based compounds, organic sulfur-based compounds, antioxidants such as aromatic secondary amine-based compounds, various auxiliary agents such as fluorescent dyes and coloring dyes can also be added as appropriate, which further improves light resistance. The property is improved.

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention mainly contains a dye precursor, the developer compound of the present invention and a binder, and preferably contains a sensitizer. Further, the heat-sensitive color developing layer, if necessary, a conventionally known phenol-based developer, organic acid-based developer, or sulfonylurea-based developer,
Antioxidants, UV absorbers, or waxes may be included. Further, it preferably contains organic or inorganic pigments. The binder fixes these components to the support.

The content of the dye precursor in the thermosensitive color developing layer is generally preferably 5 to 20% by weight based on the dry weight of the thermosensitive color developing layer, and the content of the developer compound of the present invention is generally 10 to 10. It is preferably 50% by weight. When the content of the color developing agent compound of the present invention is less than 10% by weight, the color developing ability is insufficient, and when it exceeds 50% by weight, the color developing ability is saturated and no remarkable improvement is observed. May be disadvantageous.

When the thermosensitive coloring layer contains an antioxidant or an ultraviolet absorber, its content is preferably 1 to 10% by weight. When a conventionally known phenol-based or organic acid-based developer or known sulfonylurea-based developer is contained, its content is preferably 5 to 40% by weight, and a sensitizer is also contained. In that case, the content rate is 10
-40% by weight is preferred. When waxes and white pigments are contained in the thermosensitive coloring layer, their content is 5 to 20 respectively.
%, Preferably 10 to 50% 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 inorganic fine powder such as surface-treated calcium carbonate and silica, and urea-formalin resin, styrene / methacrylic acid copolymer ,
And organic fine powders such as polystyrene resin can be mentioned. However, if an alkaline earth metal salt such as calcium carbonate is frequently used, it may cause a decrease in sensitivity. It is preferably 20% by weight or less.

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

As the binder used in the present invention,
Polyvinyl alcohol of various molecular weights, starch and its derivatives, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic Acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate,
Water-soluble polymer materials such as gelatin and casein, as well as polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / Vinyl acetate copolymers, styrene / butadiene / acrylic copolymers, and the like can be used.

The sheet-like substrate used in the thermosensitive recording medium of the present invention is paper (including acidic paper and neutral paper), coated paper having a surface coated with pigment, latex, etc., laminated paper,
It can be selected from synthetic paper made from polyolefin resin, plastic film, etc.

On at least one surface of such a sheet-like substrate, a coating liquid containing a mixture of the above-mentioned required components is applied and dried to produce a heat-sensitive recording material. The coating amount is preferably 1 to 15 g / m ² when the coating liquid layer is dried, and ² to 10 g.
/ M ² is particularly preferred.

In the heat-sensitive recording material of the present invention, a coating surface layer such as a protective layer and a printing layer can be further formed on the heat-sensitive color forming layer. Further, various additives such as the above-mentioned antioxidant, ultraviolet absorber, fluorescent dye, and coloring dye can be appropriately added to this surface layer, which further improves the light resistance.

[0038]

The present invention will be further described with reference to the following examples.
Unless otherwise specified, "part" and "%" represent "part by weight" and "% by weight", respectively.

Synthesis Example 1 4- (p-toluenesulfonyl)
Aminocarbonylamino) phenyl 2-hydroxyben
Synthesis of zoate [1] An autoclave was charged with 10.4 g of 4-nitrophenyl 2-hydroxybenzoate, 0.35 g of platinum oxide and 400 ml of ethyl acetate, and the reaction mixture was heated under hydrogen pressure (3 atm). The reaction was carried out by stirring with a mechanical stirrer. After completion of the reaction, the solvent was distilled off to obtain 7.4 g of 4-aminophenyl 2-hydroxybenzoate white solid.

[2] In a three-necked flask equipped with a thermometer, a reflux condenser, and a dropping funnel, 4 prepared in the above step [1]
-Aminophenyl 2-hydroxybenzoate 7.4
g and 250 ml of acetonitrile were added, and while stirring this mixture with a magnetic stirrer, 6.3 g of p-toluenesulfonyl isocyanate was added dropwise from a dropping funnel at room temperature. An exothermic reaction occurred with the dropping. The reaction solution was refluxed for 1 hour with stirring, cooled, and then filtered to obtain 12.6 g of 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate as a white solid.

By NMR measurement, it was identified that the obtained compound was the desired product. Results of NMR measurement (in heavy DMSO) (number is ppm): δ
2.40 (s, 3H), 7.11 (m, 2H), 7.
20 (d, 2H), 7.42 (d, 4H), 7.60
(T, 1H), 7.82 (d, 2H), 7.98 (d,
1H), 8.28 (s, 1H), other OH and N
The peak that seems to be due to −H is δ = 3.37,8.
Appeared around 90 and 10.4.

Synthesis Example 2 Phenyl 4- (p-toluene)
Sulfonylaminocarbonylamino) -2-hydroxy
Synthesis of benzoate In a three-necked flask equipped with a thermometer, a reflux condenser and a dropping funnel, 9.2 g of phenyl 4-amino-2-hydroxybenzoate and 300 ml of acetonitrile were placed, and the mixture was stirred with a magnetic stirrer. At room temperature, 7.9 g of p-toluenesulfonyl isocyanate was added dropwise from the dropping funnel. An exothermic reaction occurred with the dropping. The reaction solution was refluxed for 1 hour with stirring, cooled, and then filtered to obtain 15.8 g of phenyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate as a white solid.

By NMR measurement, it was identified that the obtained compound was the desired product. Results of NMR measurement (in heavy DMSO) (number is ppm): δ
2.40 (s, 3H), 6.94 (d, 1H), 7.
18 (s, 1H), 7.34 (m, 3H), 7.42
(D, 4H), 7.89 (m, 3H), 8.28 (s,
1H), and other peaks that are thought to be caused by O—H and N—H appeared at δ = 3.39, 9.22 and around 10.38.

Example 1 A thermal recording paper was prepared by the following operation. (1) Preparation of Dispersion A Component (parts) 3-Diethylamino-7- (m-trifluoro-methylanilino) fluorane 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was used with a paint shaker to give an average particle diameter of 1
It was pulverized until it became less than μm.

(2) Preparation of Dispersion B Component Content (parts) 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate 10 diphenylsulfone 10 polyvinyl alcohol 10% liquid 10 water 70 The above composition was paint shaker With an average particle size of 1
It was pulverized until it became less than μm.

(3) Preparation of Pigmented Undercoat Paper 85 parts of calcined clay (trade name Ansilex) in 320 parts of water
To 40 parts of styrene-butadiene copolymer emulsion (solid content 50%) and 10%.
A coating liquid was prepared by mixing with 50 parts of an oxidized starch aqueous solution. The coating solution, on top of the base paper basis weight of 48 g / m ^2, the coating amount after drying was coated so as to 7.0 g / m ^2, to prepare a pigment undercoat paper.

(4) Formation of Coloring Layer In 50 parts of the above-mentioned solution A and 200 parts of solution B, 30 parts of HG clay pigment, 20 parts of 25% zinc stearate dispersion, 30%
15 parts of paraffin dispersion and 100 parts of 10% aqueous polyvinyl alcohol solution were mixed and stirred to prepare a coating solution. This coating solution was applied to one surface of the pigment-undercoated paper so as to have a coating amount after drying of 5.0 g / m ² and dried to form a thermosensitive color-developing layer to prepare a thermosensitive recording paper.

(5) Super calender treatment The thermal recording paper obtained as described above was treated with a super calender to obtain a surface smoothness of 1000-14.
It was set to 00 seconds.

(6) Light fastness test of recorded image As a sample of the thermal recording paper, a color development tester THP manufactured by Okura Electric Co., Ltd. was used.
Using MD, the printing color density at a printing voltage of 21.7 V was 1.1 to 1.2 as measured by Macbeth reflection densitometer RD-914.
Printing was performed so as to be D (original density). A test piece was prepared from this sample, left outdoors, and exposed to direct sunlight for a total of 40 hours. Then, the residual image density was measured with a Macbeth reflection densitometer and the light fastness of the image was calculated according to the following formula. (Preservation rate)
Was calculated. Image lightfastness (%) = [(remaining image density after sunlight irradiation) / (original density)] × 100 Test results (lightfastness of recorded image) are shown in Table 1.

Example 2 Thermal recording paper was manufactured and tested in the same manner as in Example 1. However, in preparing the dispersion liquid B, 4- (p-toluenesulfonylaminocarbonylamino) phenyl was used.
Phenyl 4 instead of 2-hydroxybenzoate
-(P-toluenesulfonylaminocarbonylamino)
2-hydroxybenzoate was used. The test results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed. However, in the preparation of the dispersion liquid B, 4-hydroxy-4′-isopropyloxydiphenyl sulfone (compound of JP-A-60-13852 was used instead of 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate. ), And instead of diphenyl sulfone,
1,2-bis (m-tolyloxy) ethane (JP-A-60
Compound of -56588) was used. Table 1 shows the test results
Shown in

Comparative Example 2 The same operation as in Example 1 was performed. However, in the preparation of the dispersion liquid B, 4-hydroxy-4′-isopropyloxydiphenyl sulfone (compound of JP-A-60-13852 was used instead of 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate. ), And instead of diphenyl sulfone,
Phenyl salicylate (compound of JP-A-57-191089) was used. The test results are shown in Table 1.

[0053]

[Table 1]

Example 3 Thermal recording paper was manufactured and tested in the same manner as in Example 1. However, in the preparation of Dispersion A, 3-dibutylamino-6-methyl- was used instead of 3-diethylamino-7- (m-trifluoromethylanilino) fluorane.
7-anilinofluoran was used.

(7) Light stability test of blank paper part (non-recording part) (test of discoloration and coloring by light) The sample obtained by the above-mentioned step was prepared from the test piece without print coloring, and this was prepared. After leaving it outdoors and exposing it to direct sunlight for a total of 40 hours, the density of the blank part was measured with a Macbeth reflection densitometer, and the density before exposure to direct sunlight (original density)
Compared with. The results of this test are shown in Table 2.

Example 4 The same operation as in Example 3 was performed. However, in preparing the dispersion liquid B, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate was used instead of 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate. The test results are shown in Table 2.

Comparative Example 3 The same operation as in Example 3 was performed. However, in the preparation of the dispersion liquid B, 4-hydroxy-4′-isopropyloxydiphenylsulfone was used instead of 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, and instead of diphenylsulfone, 1,2-bis (m-tolyloxy) ethane was used. The test results are shown in Table 2.

Comparative Example 4 The same operation as in Example 3 was performed. However, in the preparation of the dispersion liquid B, 4-hydroxy-4′-isopropyloxydiphenylsulfone was used in place of 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, and diphenylsulfone was used as the sensitizer. Instead, phenyl salicylate having an ultraviolet absorbing ability was used. The test results are shown in Table 2.

[0059]

[Table 2]

As is clear from Table 1, the color image formed using the novel developer compound of the present invention shows that when a general phenol-based developer (Comparative Examples 1 and 2) is used. Compared with this, it showed significantly superior light fastness. Further, as is clear from Tables 1 and 2, the heat-sensitive recording material obtained by using the novel developer compound of the present invention has an ultraviolet absorber having a chemical structure similar to that of the developer compound. In comparison with the heat-sensitive recording materials containing Comparative Examples (Comparative Examples 2 and 4), the white paper portion (non-recording portion) showed excellent light resistance stability, and the color recorded image had high light fastness.

[0061]

The heat-sensitive recording material of the present invention comprises a developer compound having a sulfonyl (thio) urea group and a hydroxybenzoic acid ester structure in the heat-sensitive color forming layer, preferably a compound of formula (II) or (III) Since it contains an organic compound represented by, it has excellent light resistance and the recorded image shows long-term stability even under severe environmental conditions.

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[Procedure amendment]

[Submission date] June 6, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

The following compounds can be mentioned as specific examples of the developer compound according to the present invention. 4- (p
-Toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenylmethyl
2-hydroxybenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-hydroxy-3-t-butylbenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 3,
5-di-t-butyl 2-hydroxybenzoate, 4
-(Benzenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2-
Hydroxy-3-methylbenzoate, 4- (p-toluenesulfonylaminocarbonylamino) phenyl 2
-Hydroxy-5-phenylbenzoate, 4- (p-
Toluenesulfonylaminocarbonylamino) phenyl 2-hydroxy-4-ethoxybenzoate, 4-
(O-Toluenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, 4- (p-chlorobenzenesulfonylaminocarbonylamino) phenyl 2-hydroxybenzoate, phenyl 4- (p-
Toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxynaphthoate, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -1-hydroxy-2- Naphthoate, phenyl 4- (p-toluenesulfonylaminocarbonylamino) -3-hydroxy-2-naphthoate, methyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate,
Ethyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, t-butyl 4- (p-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, phenyl 4-
(P-benzenesulfonylaminocarbonylamino)-
2-hydroxybenzoate, phenyl 4- (o-toluenesulfonylaminocarbonylamino) -2-hydroxybenzoate, phenyl 4- (p-chlorobenzenesulfonylaminocarbonylamino) -2-hydroxybenzoate, phenyl 3- (p-toluenesulfonylamino) Carbonylamino) -2-hydroxybenzoate. These compounds may be used alone,
Alternatively, two or more of them may be mixed and used.

Claims (2)

[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. And a thermosensitive color developing layer containing, wherein the developer is represented by the following general formula (I): (X represents an oxygen atom or a sulfur atom) and at least one organic compound having at least one hydroxybenzoic acid ester structure in the molecule. body. 2. The developer hydroxybenzoic acid ester compound is represented by the following general formulas (II) and (III): (However, in the above formulas (II) and (III), R ¹ represents a member selected from a lower alkyl group, an aralkyl group, and an aryl group, and an aromatic ring constituting the aralkyl group and an aromatic ring of the aryl group. May be substituted by at least one member selected from a lower alkyl group, an alkoxy group, an aryl group, a halogen atom and an acetyl group, R ² represents a member selected from an arylene group and an arylene alkyl group, The group and the arylenealkyl group may be further substituted with at least one member selected from a lower alkyl group, an aryl group, a halogen atom, and a lower alkoxy group, and R ³ and R ⁴ are each independently of each other, Represents a member selected from a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, and an aryl group, and represents R ³ and R ⁴ The ring A may combine with each other to form a naphthalene ring, and R ⁵ represents a member selected from an alkyl group, an aralkyl group and an aryl group.). Thermal recording material.