JPH1148617A - Thermosensible recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise preservation stability and sensitivity by adding an organic compound having a specific chemical constitution in the thermal coloring layer. SOLUTION: The developer of a thermosensible recording layer in the thermosensible recording material contains a compound expressed by formula I. The thermosensible coloring layer further contains a compound expressed by formula II. Herein, R<1> represents a member selected from aromatic group substituted by at least a member selected from unsubstituted aromatic groups, lower alkyl group, and halogen atoms. R<2> represents a member selected from methyl group, ethyl group, methoxy group, ethoxy group, phenyl group, benzil, group, phenoxy group, benziloxy group, acetyl group, and acetyloxy group. R<3> represents member selected from alkyl group of 1-4C, phenyl group, benzil group, tolyl group and methoxyphenyl group. However, at least one of R<2> and R<3> contains a benzen cycle. The symbol A represents a divalent or more organic or inorganic group.

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 medium which forms a color image by heating. The present invention relates to a thermosensitive recording medium having excellent recording sensitivity and high recording sensitivity. The present invention has good long-term storage characteristics of a record, and at the same time, has excellent water resistance, oil resistance, and plasticizer resistance of a recorded image, and can be used for image recording paper, cash dispenser paper, a ticket, a commuter pass, a POS label, and the like. The present invention relates to a heat-sensitive recording material useful for cards such as labels and prepaid cards, and pass tickets.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording material is formed on a support such as paper, synthetic paper, plastic film or the like by using a color-forming substance such as an electron-donating leuco dye and an organic acidic substance such as an electron-accepting phenolic compound. It is provided with a thermosensitive coloring layer mainly composed of a color-developing substance, and a color-forming reaction of these coloring components by thermal energy can obtain a recorded image. Such a thermal recording medium is disclosed in JP-B-43-416.
No. 0, JP-B-45-14039, and JP-B-48-2
No. 7736, etc., and are widely used.

[0003] The thermal recording medium having the above configuration has a compact recording device, is inexpensive, and is easy to maintain. Therefore, the output of an electronic computer, a facsimile, an automatic ticket vending machine, a printer of a scientific measuring instrument, or a printer of a scientific measuring instrument. It is used for a wide range of applications such as printers for CRT medical measurement. However, in a conventional dye-type thermosensitive recording medium formed by applying a thermosensitive coloring layer containing a color-forming dye substance, a color-developing substance and a binder as active ingredients on a support, the color-forming reaction is not performed. It is known that a color image loses its color over time because it is reversible. This decolorization is accelerated by exposure to light, high humidity, and high temperature atmospheres, and is further promoted by prolonged standing in water, contact with oils such as salad oil, and plasticizers. It will be erased up to.

[0004] In a color-forming system using a dye mainly containing a colorless or light-colored lactone ring compound, various techniques have been disclosed for suppressing this decoloring phenomenon. For example, JP-A-60-78782, JP-A-59-167292
JP-A-59-114096, JP-A-59-933
No. 87, a phenolic antioxidant compounded in a thermosensitive coloring layer, and JP-A-56-146.
As described in JP-A-796-796, there is one using a hydrophobic polymer compound emulsion or the like for the protective layer.

[0005] As disclosed in JP-A-58-199189, a water-soluble polymer compound or a hydrophobic polymer compound emulsion is provided as an intermediate layer on a thermosensitive coloring layer, and a hydrophobic polymer compound is formed on the heat-sensitive coloring layer. As shown in JP-A-62-164579, a composition in which an epoxy compound is used in combination with a phenolic developer, and in JP-A-62-169681. As described above, those using a metal salt of a specific salicylic acid derivative as a color developer are known.

The color image obtained in the heat-sensitive coloring layer containing the above-mentioned phenolic antioxidant has a higher oil resistance (for example, a constant value when the salad oil is brought into contact with the coloring surface) than the color image obtained without the coloring compound. No improvement in the image density storage rate after a period of time) and the plasticizer resistance (preservation rate of the image density after a certain period of time when a wrap film or the like containing a plasticizer is brought into contact with a coloring surface) are not observed. .

[0007] Further, in a thermosensitive recording medium provided with a protective layer and a surface layer, decoloration of an image is suppressed in a short-time contact with an oil or a plasticizer, but decoloration in a long-time contact is prevented. Is inevitable,
It is not an essential solution to the above problem. In the case of using a phenolic compound and an epoxy compound in combination, a relatively long time is required from the time when the heating and coloring operation is performed to the time when the coloring image is stabilized, for example, by applying salad oil to the coloring image immediately after coloring. When a colored image is brought into contact with a plasticizer or a plasticizer, a considerable portion of the color image is erased.

Further, those using a specific metal salt of salicylic acid have improved image storability, but the coloration of a white paper portion is observed in a heat resistance test, and the chemical structure of an effective specific salicylic acid is complicated and expensive. There is a disadvantage that there is. Furthermore, in general, heat-sensitive recording materials having high preservability have to add additives or use a somewhat special coloring material,
It often has the disadvantage of relatively low sensitivity.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and can form a color image excellent in oil resistance, plasticizer resistance and the like, and therefore excellent in long-term storage. An object of the present invention is to provide a thermosensitive recording medium having high sensitivity. The present invention can be used, for example, as a heat-sensitive recording type ticket for an automatic ticket vending machine, and is suitable for use in a coupon or a commuter pass requiring long-term storage, such as a plasticizer.
It is suitable as a label for POS barcode systems to be attached to the packaging surface of food packed with a polyvinyl chloride film that cannot avoid contact with oils and fats, and high-sensitivity long-term storage facsimile paper and word processing paper And a thermal recording medium that can be used as an image printer paper for CRT.

[0010]

Means for Solving the Problems The present inventors have studied to develop a thermosensitive recording paper having high storage stability of color images and high sensitivity, and as a result, a specific chemical structure as the color developer It has been found that the above problem can be solved by using an organic compound having a specific chemical structure together with the specific color developer compound in the heat-sensitive color-forming layer together with the specific color developer compound, thereby completing the present invention. .

The heat-sensitive recording material of the present invention comprises a sheet-like substrate, a colorless or pale-colored dye precursor formed on at least one surface of the sheet-like substrate, A heat-sensitive recording layer containing a color developing agent, wherein the color developing agent has the following general formula (I):

Embedded image (Wherein, in the formula (I), R ¹ is an unsubstituted aromatic group, and
Represents a member selected from a lower alkyl group and an aromatic group substituted by at least one member selected from a halogen atom, A represents a divalent or higher valent organic group or an inorganic group, and n represents an integer of 2 or more. Represent. And at least one compound represented by the formula (1), and the thermosensitive coloring layer is
Further, the following structural formula (II):

Embedded image (However, in the formula (II), R ² represents a member selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a phenyl group, a benzyl group, a phenoxy group, a benzyloxy group, an acetyl group, and an acetyloxy group. , R ³ represents a member selected from C ^{1 to} C ⁴ alkyl, phenyl, benzyl, tolyl, and methoxyphenyl, provided that R ² and R ³
At least one contains a benzene ring. ) Is included.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the formula (I) representing the developer compound contained in the thermosensitive coloring layer of the thermosensitive recording medium of the present invention, n is an integer of 2 or more, preferably 2, and A is equal to n. Represents an organic or inorganic group having a valence. The type of the organic or inorganic group represented by A is not limited, but is generally preferably selected from the following groups (a) to (i).

(A) carbonyl group, thiocarbonyl group,
Functional groups such as sulfonyl groups (b) divalent or higher organic groups derived from aliphatic hydrocarbons (c) divalent or higher organic groups derived from aliphatic hydrocarbons containing one or more hetero atoms in the main chain (D) at least one carbonyl group, thiocarbonyl group, imide group, imino group, sulfonyl group, divalent or higher organic group derived from an aliphatic hydrocarbon containing an ester bond in the main chain

(E) 2 derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted aromatic hydrocarbon in the main chain.
(G) divalent or higher organic group derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted heteroaromatic ring in the main chain (g) substituted or unsubstituted aromatic carbon Divalent or more organic group derived from hydrogen (h) 2 derived from a substituted or unsubstituted heteroaromatic ring
Organic group having a valency of 2 or more (i) a divalent or higher valent organic group derived from a compound in which two or more of an aromatic hydrocarbon and a heteroaromatic ring are bonded by the above polyvalent groups (a) to (d) .

In the formula (I), R ¹ is an unsubstituted aromatic group,
For example, a phenyl group and a naphthyl group, and a lower alkyl group, preferably a methyl, ethyl, and propyl group, and an aromatic group substituted by at least one member selected from a halogen atom, preferably a chlorin, and a fluorin atom, specifically Is a p-tolyl group, an o-tolyl group, p
-Selected from chlorophenyl groups.

The compound of the formula (I) used in the present invention acts as a color developer. That is, the compound of the formula (I) does not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group, but exhibits a strong color developing ability with respect to a leuco basic dye.
This strong color-developing ability is understood because the urea group in the compound of the formula (I) is activated by the sulfonyl group adjacent thereto.

Examples of the compound of the formula (I) are as follows. Bis (p-toluenesulfonylaminocarbonylamino) ketone, 1,2-bis (p-toluenesulfonylaminocarbonylamino) ethane, 1,1,6,6
-Tetra (p-toluenesulfonylaminocarbonylamino) heptane, 1,5-bis (p-toluenesulfonylaminocarbonylamino) -3-oxapentane,
1,3-bis (p-toluenesulfonylaminocarbonylaminomethyl) -benzene, 1,4-bis (p-toluenesulfonylaminocarbonylaminomethyl) -benzene, 4,4'-bis (p-toluenesulfonylaminocarbonylaminomethylamino) ) -Diphenylmethane, 4,4′-bis (o-toluenesulfonylaminocarbonylamino)
-Diphenylmethane, 4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane,
4,4′-bis (1-naphthalenesulfonylaminocarbonylamino) -diphenylmethane, 2,2-bis (4 ′, 4 ″-(p-toluenesulfonylaminocarbonylamino) phenyl) propane, 1,2-bis ( 4 ′-(p-toluenesulfonylaminocarbonylamino) phenyloxy) ethane, 1,3-bis (p-toluenesulfonylaminocarbonylamino) benzene,
1,4-bis (p-toluenesulfonylaminocarbonylamino) benzene, 1,5-bis (p-toluenesulfonylaminocarbonylamino) naphthalene, 1,8-
Bis (p-toluenesulfonylaminocarbonylamino) naphthalene, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether,
3,3′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl sulfone, 4,4′-bis (p
-Toluenesulfonylaminocarbonylamino) diphenylsulfone. These compounds may be used alone or as a mixture of two or more.

In the present invention, the compound represented by the general formula of the formula (II) used in combination with the developer compound represented by the general formula of the formula (I) is used as a so-called sensitizer, so that the color sensitivity of the thermosensitive coloring layer is improved. It contributes to the improvement of. One of the reasons that the compound represented by the general formula of the formula (II) contributes to the improvement of the color development sensitivity of the thermosensitive coloring layer using the developer compound represented by the general formula of the formula (I) is that its melting point is sensitized. The fact that the compound represented by the general formula of the formula (II) has a specifically high sensitizing effect as compared with other heat-fusible organic compounds is explained by the fact that it is suitable for the action. Can not. Although the other reasons have not been elucidated yet, the solubility of the compound represented by the general formula (II), which dissolves the compound represented by the formula (I) appropriately when heated and melted, has a large effect. Is estimated to have been given. Specific examples of the compound represented by the general formula of the formula (II) are as follows. Phenyl benzoate, benzoic acid-p-methylphenyl ester, benzoic acid-p-ethylphenyl ester, benzoic acid-p-methoxyphenyl ester (melting point 87.4 ° C), benzoic acid-p-ethoxyphenyl ester, p-methyl Phenyl benzoate, p-methylbenzoic acid-p-methylphenyl ester (melting point 8
9.7 ° C), p-methylbenzoic acid-p-ethylphenyl ester, p-methylbenzoic acid-p-methoxyphenyl ester (melting point 94.6 ° C), p-methylbenzoic acid-p
-Ethoxyphenyl ester, benzyl p-methylbenzoate, phenyl p-ethylbenzoate, p-methylbenzoic acid-p-methylphenyl ester, p-ethylbenzoic acid-p-ethylphenyl ester, benzyl p-ethylbenzoate, p-ethylbenzoic acid-p-methoxyphenyl ester, p-ethylbenzoic acid-p-ethoxyphenyl ester, p-methoxybenzoic acid phenyl, p-methoxybenzoic acid-p-methylphenyl ester, p-methoxybenzoic acid-p -Ethylphenyl ester, p-methoxybenzoic acid-p-methoxyphenyl ester (melting point 12
4.0 ° C.), p-methoxybenzoic acid-p-ethoxyphenyl ester, benzyl p-methoxybenzoate, phenyl p-ethoxybenzoate, p-ethoxybenzoic acid-p-
Methylphenyl ester, p-ethoxybenzoic acid-p-
Ethylphenyl ester, p-ethoxybenzoic acid-p-
Methoxyphenyl ester, p-ethoxybenzoic acid-p
-Ethoxyphenyl ester, p-benzyl benzoate, phenyl p-acetylbenzoate, p-acetylbenzoic acid-p-methylphenyl ester, p-acetylbenzoic acid-p-ethylphenyl ester, p-acetylbenzoic acid-p -Methoxyphenyl ester, p-acetylbenzoic acid-p-ethoxyphenyl ester, benzyl acetylbenzoate, phenyl p-acetoxybenzoate (melting point 79.9 ° C), p-acetoxybenzoic acid-p-methylphenyl ester, p- Acetoxybenzoic acid-p-
Ethylphenyl ester, p-acetoxybenzoic acid-p
-Methoxyphenyl ester, p-acetoxybenzoic acid-p-ethoxyphenyl ester, benzyl acetoxybenzoate, methyl p-phenylbenzoate, ethyl p-phenylbenzoate, methyl p-benzylbenzoate, p-
Ethyl benzyl benzoate, methyl p-phenoxybenzoate, ethyl p-phenoxybenzoate, methyl p-benzyloxybenzoate (melting point 98.6 ° C), ethyl p-benzyloxybenzoate. These compounds may be used alone or as a mixture of two or more.

In the present invention, the leuco dye used as the dye precursor can be selected from conventionally known dyes such as triphenylmethane, fluoran and diphenylmethane 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-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-
(O, p-dimethylanilino) fluoran, 3- (N-
Ethyl-Np-toluidino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-
7-anilinofluoran, 3- (N-cyclohexyl-
N-methylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7-
(M-trifluoromethylanilino) fluoran, 3-
Diethylamino-6-methyl-7-chlorofluoran,
3-diethylamino-6-methylfluoran, and 3
-Cyclohexylamino-6-chlorofluoran, 3-
(N-ethyl-N-hexylamino) -6-methyl-7
One or more selected from-(p-chloroanilino) fluoran and the like can be used.

Further, in the present invention, a conventionally known color developer comprising a phenol or an organic acid or a color developer compound having one sulfonylurea group in one molecule as long as the desired effect is not impaired. Can be used in combination with the developer compound of the formula (I) of the present invention. These conventional 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-1-18038)
No. 2) Benzyl p-hydroxybenzoate (Japanese Unexamined Patent Publication No.
140483), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenylsulfone (JP-A-60-13852), 1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxy Phenylthio) -3,5-dioxaheptane (JP-A-59-52694), 3,3′-diallyl-4,
4'-dihydroxydiphenyl sulfone (JP-A-60-
208286) and N- (p-toluenesulfonyl) -N'- disclosed in JP-A-5-32061.
Phenylurea, N- (p-toluenesulfonyl) -N '
-(P-methoxyphenyl) urea, N- (p-toluenesulfonyl) -N '-(o-tolyl) urea, N- (p-
Toluenesulfonyl) -N '-(m-tolyl) urea, N
-(P-toluenesulfonyl) -N '-(p-tolyl)
Urea, N- (p-toluenesulfonyl) -N '-(o-
Chlorophenyl) urea, N- (benzenesulfonyl)-
N'-phenylurea, N- (p-chlorobenzenesulfonyl) -N'-phenylurea and the like can be mentioned.

Further, in the heat-sensitive coloring layer of the present invention, a conventionally known heat-fusible substance (sensitizer) may be used in combination within a range not to impair the desired effect. Representative examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-19089), p-benzylbiphenyl (JP-A-60-82382), and benzylnaphthyl ether (JP-A-60-82382). 58-87094), dibenzyl terephthalate (JP-A-58-98285), p-
Benzyl benzyl benzoate (JP-A-57-201)
No. 691), diphenyl carbonate, ditolyl carbonate (JP-A-5
8-136489), m-terphenyl (JP-A-57 / 1979)
-89994), 1,2-bis (m-tolyloxy)
Ethane (JP-A-60-56588), 1,5-bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-181183), oxalic acid diesters (JP-A-64-1583), 1,4-bis (p-tolyloxy) benzene (JP-A-2-153783) and the like.

The thermosensitive coloring layer of the thermosensitive recording medium of the present invention is mainly composed of a leuco dye, a compound of the above formula (I) and a compound of the above formula (I).
It contains the compound of I). The heat-sensitive coloring layer may further contain a conventionally known phenol-based or organic acid-based developer or wax, if necessary.
It preferably contains organic or inorganic pigments. The thermosensitive coloring layer further contains a binder for fixing these components to the support.

The content of the above dye precursor in the thermosensitive coloring layer is generally preferably from 5 to 20% by weight of the dry weight of the thermosensitive coloring layer, and the content of the developer compound of the formula (I) of the present invention is preferred. Is preferably 5 to 50% by weight of the thermosensitive coloring layer. If the content is less than 5% by weight, the color developing ability may be insufficient. If the content is more than 50% by weight, the color developing ability is saturated and no particular improvement is observed, which is economically disadvantageous. It may be. The compound of the formula (II) is preferably 5 to 50% by weight based on the weight of the thermosensitive coloring layer. If the addition is less than 5% by weight, the sensitizing effect may be insufficient, and if the addition exceeds 50% by weight, the sensitizing effect may be saturated, and a further increase in sensitivity may not be expected.

When a conventionally known phenolic or organic acid developer is contained in the thermosensitive coloring layer, its content is 5%.
Preferably, the content is 10 to 40% by weight, and when a conventional sensitizer is contained, its content is preferably 10 to 40% by weight. When waxes and white pigments are contained in the thermosensitive coloring layer, their contents are respectively 2 to 20% by weight and 2 to 50% by weight.
% By weight, and the binder content is generally 5 to 20% by weight.

Examples of the above 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. And inorganic fine powders such as silica and urea-formalin resin, styrene / methacrylic acid copolymer,
And organic fine powders such as polystyrene resin. Examples of the waxes include, for example, paraffin, amide wax, bisimide wax,
Known materials such as metal salts of higher fatty acids can be used.

As the binder, polyvinyl alcohol having various molecular weights, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide / acrylic ester can be used. Water-soluble polymer materials such as polymers, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein;
Polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate,
Latexes 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 thermal recording medium of the present invention includes paper (including acidic paper and neutral paper), coated paper coated with pigment, latex, etc. on its surface, laminated paper,
It can be selected from synthetic paper, plastic film, etc. made from polyolefin resin. A coating solution containing a mixture of the above-mentioned required components is applied on at least one surface of such a sheet-like substrate, and dried to produce a thermosensitive recording medium. The amount of coating is from 1 to 15 g /
m ² is preferred, and ² to 10 g / m ² is more preferred.

In the thermosensitive recording medium of the present invention, a coating layer such as a protective layer or a printing layer may be further formed on the thermosensitive coloring layer. Also, an undercoat layer containing a pigment (preferably an oil-absorbing pigment) and an adhesive can be provided on the support.

In the present invention, the thermosensitive recording medium can be further processed in order to increase the added value of the thermosensitive recording medium, and a thermosensitive recording medium having a higher function can be obtained. For example, adhesive paper, re-wet adhesive paper, delayed tack paper can be processed by applying adhesive, rewet adhesive, delayed tack type adhesive to the back surface, or heat-sensitive recording that can be magnetically recorded on the back surface by magnetic processing It can be a material. In addition, thermal transfer paper, inkjet paper, carbonless paper,
Adds functions as electrostatic recording paper and xerographic paper,
It is also possible to use recording paper capable of recording on both sides. Of course, a double-sided thermosensitive recording medium can also be used.

[0030]

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

Example 1 A heat-sensitive recording paper was prepared by the following operation. (1) Preparation of pigment-coated paper 85 parts of calcined clay (trade name: Ansilex) were mixed with 320 parts of water.
In a dispersion obtained by dispersing styrene / butadiene copolymer emulsion (solid content: 50%), 40 parts, 10%
Adjust the coating liquid by mixing with 50 parts of oxidized starch aqueous solution,
The coating liquid onto the base paper basis weight 48 g / m ^2, the coating amount after drying was coated so as to 7.0 g / m ^2, was prepared pigment undercoat paper.

[0032] (2) Preparation Ingredients Amount of Dispersion A (parts) 3- (N, N-dibutylamino) -6-methyl-7-anilinofluoran 20 polyvinyl alcohol - le 10% solution 10 Water 70 The above Using a sand grinder, the composition has an average particle size of 1
It was pulverized until it became not more than μm.

Le 10% solution 10 Water 70 The composition - [0033] (3) Preparation Ingredients Amount of Dispersion B (parts) of 4,4'-bis (p- toluenesulfonyl-amino - carbonylamino) - diphenylmethane 20 Polyvinyl alcohol Using a sand grinder, pulverization was performed until the average particle size became 1 μm or less.

[0034] (4) Preparation Ingredients Amount of Dispersion C (parts) p-benzyloxybenzoate 20 Polyvinyl alcohol - using a sand grinder Le 10% solution 10 Water 70 The composition, average particle size of 1μm or less And crushed.

(5) Formation of heat-sensitive coloring layer 60 parts of the above-mentioned liquid A, 120 parts of liquid B, 120 parts of liquid C, 23 parts of HG clay (Kaolinite pigment manufactured by Huber), 20 parts of a 25% zinc stearate dispersion liquid, 15 parts of 30% paraffin dispersion and 12% aqueous solution of polyvinyl alcohol 12
0 parts were mixed and stirred to obtain a coating solution. This coating solution was applied on one side of a pigment-coated paper at a coating amount of 5.0 g / m ² after drying.
To form a heat-sensitive coloring layer, and a heat-sensitive recording paper was prepared.

(6) Test of Thermal Paper The sample obtained as described above was subjected to a dynamic thermal coloring simulator THPMD (printing voltage: 21.7 V) manufactured by Okura Electric.
The sample was colored in a checkered pattern under the printing conditions of an applied pulse width of 0.5 ms and 0.7 ms. The color density was measured with a Macbeth reflection densitometer RD-914 black filter, and this measured value was used as a value representative of the recording sensitivity. Further, dioctyl terephthalate (a typical plasticizer) was applied to the sample that had been colored with the applied pulse width of 0.7 ms within 30 minutes after the color development, left at room temperature for 3 hours, and then the oil or plasticizer on the surface was wiped off. The residual image density was measured with a Macbeth reflection densitometer, and the image storage rate was calculated according to the following equation. Image preservation ratio (%) = (color density after immersion of plasticizer) / (color density before immersion of plasticizer) × 100 The test results are shown in Table 1.

<Example 2> A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing dispersion C, phenyl p-acetoxybenzoate was used in place of methyl p-benzyloxybenzoate. Table 1 shows the test results.

Example 3 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing the dispersion C, p-methoxybenzoic acid-p-methoxyphenyl ester was used in place of methyl p-benzyloxybenzoate. Table 1 shows the test results.

Example 4 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing the dispersion A, crystal violet lactone was used instead of 3- (N, N-dibutylamino) -6-methyl-7-anilinofluoran, and a Macbeth reflection densitometer RD-9 was used.
Measured with a 14 blue filter. Table 1 shows the test results.

Example 5 A thermosensitive recording paper was produced in the same manner as in Example 1. However, 5 parts of a kaolinite clay dispersion (solid content: 60%), 35 parts of a 10% modified polyvinyl alcohol aqueous solution, 22 parts of a 10% aqueous solution of casein, and 25%
1 part of a zinc stearate dispersion, 2 parts of a dimethylol urea crosslinking agent and 35 parts of water were mixed and adjusted by stirring, and the amount of the coating solution after drying on the thermosensitive coloring layer was 1.5%.
g / m ² was applied and dried to form an overcoat layer, and a test was conducted. Table 1 shows the test results.

<Comparative Example 1> A thermosensitive recording paper was produced and tested in the same manner as in Example 1. However, in preparing Dispersion C, p-benzylbiphenyl (melting point 87 ° C.) was used instead of methyl p-benzyloxybenzoate.
Table 1 shows the test results.

<Comparative Example 2> A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion C, dibenzyl terephthalate (melting point 94 ° C.) was used instead of methyl p-benzyloxybenzoate. Table 1 shows the test results.

Comparative Example 3 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing dispersion B, 4,4'-dihydroxydiphenyl sulfone (bisphenol S) was used instead of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane. Table 1 shows the test results.

[0044]

[Table 1] As is evident from Table 1, the thermosensitive recording medium of the present invention has:
It was confirmed that it had high sensitivity together with high image storability.

[0045]

The heat-sensitive recording material of the present invention contains, as a color developer, a compound having two or more sulfonylurea groups in one molecule represented by the formula (I) in the heat-sensitive coloring layer.
Further, since it contains an organic compound represented by the general formula (II) as a sensitizer, it has high image storability, high recording sensitivity, and excellent practicability.

Claims (2)

[Claims] 1. A sheet-like substrate, a colorless or light-colored dye precursor 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. Wherein the color developer has the following general formula (I): (Wherein, in the formula (I), R ¹ is an unsubstituted aromatic group, and
Represents a member selected from a lower alkyl group and an aromatic group substituted by at least one member selected from a halogen atom, A represents a divalent or higher valent organic group or an inorganic group, and n represents an integer of 2 or more. Represent. ), And the thermosensitive coloring layer further comprises the following general formula (II): (However, in the formula (II), R ² represents a member selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a phenyl group, a benzyl group, a phenoxy group, a benzyloxy group, an acetyl group, and an acetyloxy group. , R ³ represents a member selected from C ^{1 to} C ⁴ alkyl, phenyl, benzyl, tolyl, and methoxyphenyl, provided that R ² and R ³
At least one contains a benzene ring. A) a heat-sensitive recording material comprising at least one compound represented by 2. The developer represented by the general formula (I) is an organic compound represented by the following chemical formula (III).
The thermosensitive recording medium as described. Embedded image