JPH08290673A - Thermal recording body - Google Patents

Abstract

PURPOSE: To enhance a shelf stability of a color image by a method wherein a color developer contains a compound having a specific sulfonylurea group, and a thermal color-forming layer contains an organic compound having a specific chemical structure. CONSTITUTION: In a thermal recording body formed by providing a thermal color-forming layer containing a dye precursor and a color developer on one surface of a sheet substrate, at least one of compounds represented by a formula I (in the formula, R<1> represents an unsubstituted or substituted aromatic group, A represents an organic or inorganic group having two or more valences, and (n) represents an integer of 2 or more) is incorporated as the color developer, and at least one selected among aromatic compounds represented by formulas II, III (in the formulas, R<2> represents a lower alkyl group, R<3> represents an unsubstituted or substituted phenyl group or a naphthyl group, X represents an oxygen atom, a sulfur atom, a sulfonyl group, or a carbonyloxy group, (m) is an integer of 2 or more, R<4> represents a lower alkyl group, and R<5> represents an aralkyl, a lower alkoxy group, or a phenyl group substituted by an aryloxy group) is incorporated in the thermal color-forming layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material for forming a colored image by heating. More specifically, the present invention is directed to the storage stability of a recorded image without the disappearance of the once colored image. The present invention relates to a heat-sensitive recording material having excellent recording sensitivity and excellent recording sensitivity. The thermal recording material of the present invention has good long-term storage stability of recording, and at the same time has excellent water resistance, oil resistance and plasticizer resistance of recorded images, image recording paper, cash dispenser paper, ticket, commuter pass, POS
It is useful for labels such as 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 recording image can be obtained by causing a coloring reaction of these coloring components by thermal energy. Such a thermal recording material is disclosed in Japanese Examined Patent Publication No. 43-4.
No. 160, Japanese Patent Publication No. 45-14039, and Japanese Patent Publication No. 48
No. 27736, etc., and is widely put into practical use.

The thermosensitive recording medium having the above structure has a compact recording apparatus, is inexpensive, and is easy to maintain. Therefore, the output of a computer, a facsimile, an automatic ticket vending machine, a printer for scientific measuring instruments, or It is used in a wide range of applications such as printers for CRT medical measurement. However, in a dye-type thermosensitive recording medium constituted by coating a conventional thermosensitive coloring layer containing a color-developing dye substance, a color-developing substance and a binder as an active ingredient on a support, the coloring reaction Is reversible, it is known that the color image disappears over time. This decolorization is accelerated by exposure to light, high humidity, and high temperature atmosphere, and then left in water for a long time,
Contact with oils, such as salad oil, or plasticizers significantly progresses and eventually the image is erased to unreadable levels.

A number of techniques have been disclosed in order to suppress this decoloring phenomenon in a color-forming system which usually uses a dye mainly composed of a colorless to light-colored lactone ring compound. For example, JP-A-60-78782 and JP-A-59-1672.
92, JP-A-59-114096 and JP-A-59.
No. 93387, a phenolic antioxidant is blended in the thermosensitive color developing layer, and JP-A-56-56
As disclosed in JP-A-146796, there are those in which a hydrophobic polymer compound emulsion or the like is used for a protective layer.

As disclosed in JP-A-58-199189, a water-soluble polymer compound on the thermosensitive coloring layer, or
Providing a hydrophobic polymer compound emulsion as an intermediate layer,
A surface layer provided with an oily coating containing a hydrophobic polymer compound as a resin component is further provided thereon, JP-A-62-164579.
JP-A-62-169681, in which a phenol-based developer is used in combination with an epoxy compound,
As disclosed in Japanese Patent Publication No. 2004-242242, there is known one using a metal salt of a specific salicylic acid derivative as a developer.

The color-developed image obtained in the heat-sensitive color-developing layer containing the above-mentioned phenolic antioxidant is more oil-resistant (for example, when the salad oil is brought into contact with the color-developing surface for a certain period of time) than the image without the color-developing agent. No improvement is recognized in respect of the storage ratio of the image density after that) and the plasticizer resistance (the storage ratio of the image density after a certain time when a wrap film containing a plasticizer is brought into contact with the color developing surface).

Further, in the thermosensitive recording medium provided with the protective layer and the surface layer, the decoloration of the image is suppressed by the contact with the oil and the plasticizer for a short time, but the decolorization by the contact for a long time is suppressed. It is unavoidable and cannot be said to be an essential solution to the above problems.
Further, in the case where a phenol compound and an epoxy compound are used in combination, 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.

Further, in the case of using a specific metal salt of salicylic acid, the image storability is improved, but color development is observed in the white paper part in the heat resistance test, and the effective chemical structure of the specific salicylic acid is complicated and expensive. It has the drawback of being. Further, in general, a heat-sensitive recording material having a high storage stability has no choice but to add an additive or to use a slightly special coloring material.
They often have the drawback of being relatively insensitive.

[0009]

The present invention solves the above problems in the prior art and is capable of forming a color image which is excellent in oil resistance, plasticizer resistance and the like, and is therefore excellent in long-term storage stability, and It is intended to provide a heat-sensitive recording material having high sensitivity.

INDUSTRIAL APPLICABILITY The present invention can be used not only as a heat-sensitive recording type ticket for an automatic ticket vending machine, but is also suitable for use as a coupon ticket or a commuter ticket requiring long-term storage, and a plasticizer,
Facsimile paper or word processor for long-term storage, which is suitable as a label for POS bar code system and is attached to the packaging surface of food wrapped with polyvinyl chloride film that cannot avoid contact with oils and fats. Paper,
Another object of the present invention is to provide a thermal recording material that can be used as a CRT image printer paper.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied to develop a thermosensitive recording paper which has a high storage stability of a color image and a high sensitivity, and as a result, has a specific chemical structure as the developer. It has been discovered that the above-mentioned problems can be achieved by using an organic compound having a specific chemical structure and an organic compound having a specific chemical structure in the heat-sensitive color developing layer, and has completed the present invention. .

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):

Embedded image (In the formula (I), R ¹ represents an unsubstituted aromatic group, and a member selected from an aromatic group substituted with at least one member selected from a lower alkyl group and a halogen atom, and A is A Represents a divalent or higher valent organic group or inorganic group,
N represents an integer of 2 or more. ) And at least one of the compounds represented by the following general formulas (II) and (III):

[Chemical 4] (However, in the formula (II), R ² represents a lower alkyl group,
R ³ represents a member selected from an unsubstituted phenyl group, a naphthyl group, and a phenyl group substituted with at least one member selected from a halogen atom, a lower alkyl group, an alkoxy group, an aryloxy group, and an aryl group. , X represents an oxygen atom, a sulfur atom, and a member selected from a sulfonyl group and a carbonyloxy group, m represents an integer of 2 or more, and in the formula (III), R ⁴ represents a lower alkyl group, R ⁵ represents a member selected from an aralkyl group and a phenyl group substituted by at least one member selected from a lower alkoxy group and an aryloxy group. And at least one aromatic compound selected from the above.

[0013]

In the formula (I) representing the developer compound contained in the thermosensitive coloring layer of the thermosensitive recording material of the present invention, n represents an integer of 2 or more, preferably 2, and A has a valence equal to n. Represents an organic group or an inorganic group. There is no limitation on the kind of the organic or inorganic group represented by A, but it is generally preferable to be selected from the following groups.

(A) carbonyl group, thiocarbonyl group,
And functional groups such as sulfonyl groups (b) Divalent or higher valent organic groups derived from aliphatic hydrocarbons (c) Divalent or higher valent derived from aliphatic hydrocarbons containing one or more heteroatoms in the main chain (D) one or more carbonyl group, thiocarbonyl group, imide group, imino group, sulfonyl group, divalent or more organic group derived from aliphatic hydrocarbon containing ester bond in main chain

(E) Divalent or higher-valent organic group derived from an aliphatic hydrocarbon containing one or more substituted or unsubstituted aromatic hydrocarbons in the main chain (f) Substituted or unsubstituted in the main chain A divalent or higher valent organic group derived from an aliphatic hydrocarbon containing one or more heteroaromatic rings (g) a divalent or higher valent organic group derived from an unsubstituted aromatic hydrocarbon (h) a substitution or 2 derived from unsubstituted heteroaromatic ring
Valent or higher valent organic group (i) an aromatic hydrocarbon and a divalent or higher valent organic group derived from a compound in which two or more of the heteroaromatic rings are bound by the polyvalent groups of (a) to (d) above .

In the formula (I), R ¹ is an unsubstituted aromatic group such as a phenyl group and a naphthyl group, and a lower alkyl group, preferably a methyl, ethyl and propyl group,
And a halogen atom, preferably an aromatic group substituted by at least one member selected from chlorine and fluorine atoms, for example, a member selected from a phenyl group, a naphthyl group, etc., preferably a phenyl group, p-tolyl Group, o-tolyl group, p-chlorophenyl group.

In the formula (II), R ² represents a lower alkyl group, preferably an alkyl group having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, a propyl group. R ³ is an unsubstituted phenyl group or naphthyl group and a halogen atom, preferably chlorin, fluorin atom, etc., a lower alkyl group, preferably methyl, ethyl, propyl group, etc., an alkoxy group, preferably methoxy, ethoxy, propyloxy group, etc., aryl group. It preferably represents a member selected from phenyl groups substituted with at least one member selected from phenyl groups and the like, and preferred R ³ groups are phenyl group, naphthyl group, p-tolyl group, o-
Examples thereof include a tolyl group, p-chlorophenyl group, p-methoxyphenyl group, o-methoxyphenyl group, p-phenoxyphenyl group, and p-biphenyl group.

In the formula (III), R ⁴ represents a lower alkyl group and is preferably selected from an alkyl group having 1 to 3 carbon atoms (eg, methyl group, ethyl group, propyl group, etc.). R ⁵ is an aralkyl group (preferably an aralkyl group having an alkylene group having 1 or 2 carbon atoms), a lower alkoxy group (preferably methoxy, ethoxy, and propyloxy groups), and an aryloxy group (preferably Represents one member selected from a phenyl group substituted by at least one member selected from a phenoxy group). R ⁵ is preferably selected from a benzyl group, a p-methylbenzyl group, a p-methoxyphenyl group, a p-ethoxyphenyl group, a p-phenoxyphenyl group and the like.

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 exhibits a strong color developing ability for a leuco basic dye.
This strong color developing ability is understood to be due to the urea group in the compound of formula (I) being activated by the sulfonyl group adjacent thereto.

Illustrative compounds of 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-toluenesulfonylaminocarbonylamino) ) -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) diphenylsulfone, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone. These compounds may be used alone or as a mixture of two or more thereof.

In the present invention, the organic compounds represented by the formulas (II) and (III) used in combination with the developer compound of the formula (I) are so-called sensitizers and improve the color developing sensitivity of the thermosensitive color developing layer. Contribute to. The reason why the sensitivity of the resulting thermosensitive recording medium is particularly improved when the sensitizer compound of the formulas (II) and (III) is combined with the developer compound of the formula (I) is as follows.
In the first place, it is not clear because the physical properties of the sensitizer govern the color developing sensitivity of the thermosensitive recording medium have not been clarified. However, considering that the main functional group of the developer compound of the formula (I) is a sulfonylurea group having a strong electron-withdrawing property, most of the compounds represented by the formulas (II) and (III) donate electrons. Since it has an aromatic ring substituted with a group alkoxy group, the electron-deficient developer compound of the formula (I) interacts with the electron-excessive sensitizer compound and mutually interacts well. It is considered that melting is one of the causes. The sensitizer compounds of the formula (III) include those having no alkoxy group but exhibiting a high sensitizing property, which are due to the sulfonylurea group and the structure of the developer compound of the formula (I). It is considered that the compound has a sulfonyl group having similar similarity, is substituted with a relatively small substituent, and has a small molecular volume, and thus has a large ability to dissolve the developer compound of the formula (I). be able to.

Examples of the sensitizer compounds of formulas (II) and (III) are as follows. 1- (4-methoxyphenoxy) -2-phenoxyethane (melting point 104 ° C.),
1,3-bis (4-methoxyphenoxy) propane (melting point 87 ° C.), 1- (4-methoxyphenoxy) -3-phenylsulfonylpropane (melting point 88 ° C.), methyl (4
-Phenoxyphenyl) sulfone (melting point 86 ° C), methyl (4-ethoxyphenyl) sulfone (melting point 93 ° C),
Ethylbenzyl sulfone (mp 87 ° C).

In the present invention, the leuco dye used as the dye precursor can be selected from conventionally known ones such as triphenylmethane type compounds, fluorane type compounds 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-alininofluorane, 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-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7-
(M-trifluoromethylanilino) fluorane, 3-
Diethylamino-6-methyl-7-chlorofluorane,
3-diethylamino-6-methylfluorane, and 3
-Cyclohexylamino-6-chlorofluorane, 3-
(N-ethyl-N-hexylamino) -6-methyl-7
One or more selected from-(p-chloroanilino) fluorane 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 having one sulfonylurea group in one molecule, as long as the desired effect is not impaired. The compounds can be used in combination with a developer compound of formula (I) according to the invention. Examples of these conventional color developers include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) and 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)
2), 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 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, and N- (p-chlorobenzenesulfonyl) -N'-phenylurea.

Further, in the heat-sensitive color forming layer of the present invention, a conventionally known heat-fusible substance (sensitizer) may be used in combination within a range that does not impair the desired effect. Typical examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-191089), p-benzylbiphenyl (JP-A-60-82382), and benzylnaphthyl ether (JP-A-60-82382). 58-87094), dibenzyl terephthalate (JP-A-58-98285), p-
Benzyl benzyloxybenzoate (JP-A-57-201
691), diphenyl carbonate, ditolyl carbonate (Japanese Patent Application Laid-Open No. Sho 5
8-136489), m-terphenyl (JP-A-57 / 1982).
-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-2-153787).

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention mainly comprises a leuco dye, a developer compound of the above formula (I) and a sensitizer compound of the above formula (II) or (III). The heat-sensitive color developing layer may further contain a conventionally known phenol-based or organic acid-based developer or wax, if desired, and preferably contains organic or inorganic pigments. The heat-sensitive color forming layer further contains a binder for fixing these components to the support.

The content of the dye precursor in the heat-sensitive color developing layer is generally preferably 5 to 20% by weight based on the dry weight of the heat-sensitive color developing layer, and the content of the developer compound of the formula (I) of the present invention. Is generally preferably 5 to 50% by weight based on the weight of the thermosensitive coloring layer. If the content is less than 5% by weight, the color developing ability may be insufficient, and even if the content exceeds 50% by weight, the color developing ability is saturated and no particular improvement is seen, which is economically disadvantageous. May be. The content of the sensitizer compound represented by the formula (II) or (III) is preferably 5 to 50% by weight based on the weight of the thermosensitive color developing layer. If it is added in an amount of less than 5%, the sensitizing effect may be insufficient, and if it is added in an amount of more than 50%, the sensitizing effect may be saturated, and further increase in sensitivity may not be expected.

When the heat-sensitive color developing layer contains a conventionally known phenol type or organic acid type color developer, its content is 5%.
It is preferably ˜40 wt%, and when a conventional sensitizer is included, its content is preferably 10-40 wt%. When waxes and white pigments are contained in the thermosensitive coloring layer, the contents thereof are 2 to 20% by weight and 2 to 50%, respectively.
It is preferably in% by weight, and the content of binder 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. Inorganic fine powder such as silica and silica, urea-formalin resin, styrene / methacrylic acid copolymer,
And organic fine powder such as polystyrene resin. Examples of waxes include paraffin, amide wax, bisimide wax,
Known ones such as metal salts of higher fatty acids can be used.

Regarding 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 acid amide / acrylic acid ester Polymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and water-soluble polymer material such as 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 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. 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 1 to 15 g / when the coating liquid layer is dried.
m ² is preferable, and ² to 10 g / m ² is more preferable.

In the heat-sensitive recording material of the present invention, a coating layer such as a protective layer or a printing layer can be further formed on the heat-sensitive color forming layer.

[0033]

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.

Example 1 A thermosensitive recording paper was prepared by the following procedure . (1) Preparation of pigment-coated base paper 85 parts of calcined clay (trade name Ansilex) in 320 parts of water
40 parts of styrene-butadiene copolymer emulsion (solid content 50%) and 10 parts of
% Oxidized starch aqueous solution were mixed with 50 parts of a coating solution is prepared, coating the coating liquid on a base paper basis weight 48 g / m ^2, as the coating amount after drying becomes 7.0 g / m ² Then, a pigment-coated paper was prepared.

[0035] (2) Preparation Ingredients Amount of Dispersion A (parts) 3- (N, N-dibutylamino) -6-methyl-7-anilinofluoran 20 polyvinyl alcohol 10% solution 10 Water 70 The composition Using a sand grinder, the average particle size is 1
It was pulverized until it became less than μm.

[0036] (3) Preparation Ingredients Amount of Dispersion B (parts) of 4,4'-bis (p- toluenesulfonyl-amino - carbonylamino) - sand grinder diphenylmethane 20 polyvinyl alcohol 10% solution 10 Water 70 The composition With an average particle size of 1
It was pulverized until it became less than μm.

[0037] (4) Preparation Ingredients Amount of Dispersion C (parts) 1- (4-methoxyphenoxy) -2-phenoxyethane 20 polyvinyl alcohol 10% solution 10 Water 70 The composition using a sand grinder to an average particle Diameter is 1
It was pulverized until it became less than μm.

(5) Formation of thermosensitive coloring layer HG Clay (trademark, kaolinite pigment manufactured by Huber) is added to 60 parts of the above-mentioned liquid A, 120 parts of liquid B and 120 parts of liquid C.
23 parts, 25% zinc stearate dispersion 20 parts, 30%
15 parts of paraffin dispersion liquid and 120 parts of 10% polyvinyl alcohol aqueous solution were mixed and stirred to obtain a coating liquid.
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.

(6) Test of thermosensitive recording paper The thermosensitive recording paper sample obtained as described above was applied with an applied pulse width of 0.5 ms and 0 using a dynamic thermosensitive coloring simulator THPMD (printing voltage 21.7 V) manufactured by Okura Electric. .7 ms
The sample was colored in a checkered pattern under the printing conditions. The color density was measured with a Macbeth reflection densitometer RD-914, and this measured value was used as a value representative of the recording sensitivity. Further, dioctyl terephthalate (representative plasticizer) was applied to the sample developed with the applied pulse width of 0.7 ms within 30 minutes after the development of the color, and allowed to stand 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 retention rate was calculated according to the following formula. Image preservation ratio (%) = (color density after plasticizer immersion) / (color density before plasticizer immersion) × 100 The test results are shown in Table 1.

Example 2 A thermal recording paper was prepared and tested in the same manner as in Example 1. However, in the preparation of Dispersion C, instead of 1- (4-methoxyphenoxy) -2-phenoxyethane,
1- (4-Methoxyphenoxy) -3-phenylsulfonylpropane was used. The test results are shown in Table 1.

Example 3 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in the preparation of Dispersion C, methyl (4-phenoxyphenyl) sulfone was used instead of 1- (4-methoxyphenoxy) -2-phenoxyethane. The test results are shown in Table 1.

Example 4 Thermal recording paper was prepared and tested in the same manner as in Example 1. However, in the preparation of Dispersion C, methyl (4-ethoxyphenyl) sulfone was used instead of 1- (4-methoxyphenoxy) -2-phenoxyethane. The test results are shown in Table 1.

Example 5 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in the preparation of Dispersion C, ethylbenzyl sulfone was used instead of 1- (4-methoxyphenoxy) -2-phenoxyethane. The test results are shown in Table 1.

Comparative Example 1 A thermal recording paper was prepared and tested in the same manner as in Example 1. However, in the preparation of Dispersion C, p-benzylbiphenyl (melting point 87 ° C.) was used instead of 1- (4-methoxyphenoxy) -2-phenoxyethane.
The test results are shown in Table 1.

Comparative Example 2 A thermal recording paper was prepared and tested in the same manner as in Example 1. However, in the preparation of Dispersion C, diphenyl sulfone (melting point 126 ° C.) was used instead of 1- (4-methoxyphenoxy) -2-phenoxyethane. The test results are shown in Table 1.

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

[0047]

[Table 1]

As is clear from Table 1, it was confirmed that the thermosensitive recording medium of the present invention has high image storability and high sensitivity.

[0049]

INDUSTRIAL APPLICABILITY The heat-sensitive recording material of the present invention has, in its heat-sensitive color-developing layer, a compound represented by the formula (I) as a developer and having 2 in one molecule.
Since it contains a compound having one or more sulfonylurea groups and further contains at least one organic compound represented by the formula (II) or (III) as a sensitizer, it has high image storability and high It has recording sensitivity and is highly practical.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiyuki Takahashi 1-10-6 Shinonome, Koto-ku, Tokyo Shin-Oji Paper Co., Ltd. Central Research Laboratory (72) Torasuke Saito 1-10-24, Itsukaichi, Ibaraki-shi, Osaka No. Sanko Institute of Development Science Co., Ltd. (72) Inventor Takashi Ishibashi 1-10-24 Itokaichi, Ibaraki-shi, Osaka Prefecture Sanko Research Institute of Science and Development (72) Inventor Tomoyuki Tanemura 1-10-24, Itsukaichi, Ibaraki-shi, Osaka Sanko Institute of Development Science, Inc.

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. And a thermosensitive color developing layer containing, wherein the developer is represented by the following general formula (I): (In the formula (I), R ¹ represents an unsubstituted aromatic group, and a member selected from an aromatic group substituted with at least one member selected from a lower alkyl group and a halogen atom, and A is A Represents a divalent or higher valent organic group or inorganic group,
N represents an integer of 2 or more. ) And at least one of the compounds represented by the following general formulas (II) and (III): (However, in the formula (II), R ² represents a lower alkyl group,
R ³ represents a member selected from an unsubstituted phenyl group, a naphthyl group, and a phenyl group substituted with at least one member selected from a halogen atom, a lower alkyl group, an alkoxy group, an aryloxy group, and an aryl group. , X represents an oxygen atom, a sulfur atom, and a member selected from a sulfonyl group and a carbonyloxy group, m represents an integer of 2 or more, and in the formula (III), R ⁴ represents a lower alkyl group, R ⁵ represents a member selected from an aralkyl group and a phenyl group substituted by at least one member selected from a lower alkoxy group and an aryloxy group. ) A thermosensitive recording medium containing at least one aromatic compound selected from the following.