JPH08104061A - Thermal recording body - Google Patents

Abstract

PURPOSE: To obtain a thermal recording body having an excellent recording shelf stability and a high recording sensitivity by a method wherein a color developer reacting with a dye precursor under heat to produce a color is prepared by incorporating an aromatic compound having specific sulfonyl(thio)urea groups, hydroxyl groups (-OH groups), and the like. CONSTITUTION: A thermal recording body effectively used for image recording paper, facsimile paper, and the like is formed by providing a thermally color- forming layer on at least one surface of a sheet substrate. The thermally color- forming layer is made of a material containing a colorless or light-colored dye precursor and a color developer reacting with the dye precursor under heat to produce a color. In this invention, the color developer is prepared by incorporating an aromatic compound having a sulfonyl(thio)urea group represented by a separate general formula (where X represents an oxygen atom or a sulfur atom), a hydroxyl group (-OH group), and the like in one molecule. In this manner, the obtained thermal recording body is superior in long-term shelf stability of a color image dependent on oil resistance, a resistance to plasticizer, and the like and is enhanced in recording sensitivity.

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 color image by heating, and in particular, there is no disappearance of an image once color-developed, the storage stability of the recording is excellent, and the heat-sensitive recording material has a high recording sensitivity. It concerns a recording body. More specifically, the present invention is excellent in long-term storage stability of recording, and at the same time is excellent in environmental resistance such as humidity resistance and heat resistance of recorded image, further excellent in oil resistance, plasticizer resistance, and recording sensitivity. With high whiteness, image recording paper, facsimile paper,
Cash dispenser paper, ticket, commuter pass, PO
The present invention relates to a thermal recording material useful for labels such as S-labels, cards such as prepaid cards, and pass tickets.

[0002]

2. Description of the Related Art A thermal recording material is generally composed of 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 a color-developing substance as described above as a main component is provided, and it is possible to obtain a recorded image by reacting them with thermal energy. Such a thermal recording material is disclosed in Japanese Examined Patent Publication No. 43-4160.
No. 4, JP-B-45-14039, and JP-A-48-27.
No. 736 and the like, and are widely used.

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

In the case of using a coloring system using a dye mainly composed of a colorless or light-colored lactone ring compound, a number of techniques have been developed in order to suppress this decoloring phenomenon.
For example, JP-A-60-78782 and JP-A-59-167.
No. 292, JP-A-59-114096, and JP-A-59-93387, in which a thermosensitive color-forming layer is blended with a phenolic antioxidant, and JP-A-SHO-5
No. 6,146,796 in which a hydrophobic polymer compound emulsion or the like is used for the protective layer, or
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 the hydrophobic polymer compound is used as a resin component on the intermediate layer. One provided with a surface layer of an oil-based paint, one containing an epoxy compound as shown in JP-A-62-164579, and a specific salicylic acid derivative as shown in JP-A-62-169681. Those using a metal salt as a color developer are known.

In the heat-sensitive color-forming layer containing the above-mentioned phenolic antioxidant, the environment resistance is slightly improved as compared with the image in the case where it is not added, but the oil resistance (for example, salad oil is brought into contact with the color-forming surface). For the storage ratio of the image density after a certain period of time), the plasticizer resistance (the storage ratio of the image density after a certain period of time when a wrap film containing a plasticizer, etc. is brought into contact with the coloring surface), etc. No improvement is recognized.

On the other hand, a thermal recording medium provided with a protective layer and a surface layer has a considerably improved environmental resistance, but decolorization is inevitable in a long-term test. Regarding oil resistance, the image storability immediately after contact with oil is improved, but the image disappears almost completely as the oil permeates, and it cannot be said to be an essential solution to the above problems. .

Further, in the case of containing an epoxy compound, a relatively long time is required from the heating color development operation to the stabilization of the color image, and for example, salad oil is applied to the color image immediately after color development. If it is exposed to light, or if it is brought into contact with a plasticizer, a considerable part of the color image is erased.

In the case of using a metal salt of a specific salicylic acid derivative as a developer, oil resistance and plasticizer resistance are improved, but a white paper color is observed in the heat resistance test, and an effective specific salicylic acid It has the drawback that the chemical structure is complicated and expensive.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above problems of the prior art, is excellent in long-term storage stability of a color image which depends on oil resistance, plasticizer resistance, moisture resistance, heat resistance and the like, and can be recorded. It is intended to provide a heat-sensitive recording material having high sensitivity.
INDUSTRIAL APPLICABILITY The present invention can be used, for example, as a heat-sensitive recording type ticket for an automatic ticket vending machine, and is also used for a ticket such as a coupon ticket or a commuter ticket that requires preservation, contact with a plasticizer and oils and fats. It is also suitable as a label for a POS barcode system that is attached to the packaging surface of foods wrapped in vinyl film. Also, as facsimile paper for long-term storage, word processor paper, image printer paper for CRT,
A useful thermosensitive recording medium can be provided.

[0010]

[Means for Solving the Problems] A compound having a specific chemical structure sulfonyl (thio) urea group has a strong color developing ability and is excellent in preservability for oils and plasticizers. Kaihei 5-32061, JP-A-5-147
No. 357 and JP-A-5-148220. The sulfonyl (thio) ureido compound is characterized by not having an acidic functional group such as a phenolic hydroxyl group or a carboxyl group. As a result of further diligent studies on the compound having a sulfonyl (thio) urea group, the present inventors have found that
A color image obtained by using a compound having at least one sulfonyl (thio) urea group and at least one hydroxyl group and one carboxyl group in one molecule as a developer is a storage medium for oils and plasticizers similar to the above compounds. It has been found that the thermosensitive color developing layer containing the compound as a developer has a high recording sensitivity, whereby a thermosensitive recording material having a high whiteness can be produced, and the present invention is completed. Came to.

The thermosensitive recording medium of the present invention is formed on a sheet-like substrate and at least one surface of the sheet-like substrate,
And, having a thermosensitive color developing layer containing a colorless or light-colored dye precursor, and a developer that reacts with this dye precursor under heating to develop a color, the developer is the following in one molecule: General formula (I):

Embedded image (Wherein X represents an oxygen atom or a sulfur atom), and at least one aromatic compound having at least one of a sulfonyl (thio) urea group, a hydroxyl group and a carboxyl group. It is a thing.

In the heat-sensitive recording material of the present invention, the developer aromatic compound is represented by the following general formula (II):

[Chemical 4] (In the above formula, A represents an unsubstituted aromatic ring group or an aromatic ring group substituted by at least one member of a lower alkyl group, a halogen atom and a lower alkoxy group, and B represents a hydroxyl group and a carboxyl group. A substituted aromatic ring group, or an aralkyl group substituted with a hydroxyl group and a carboxyl group, wherein the aromatic ring group and the aryl group of the aralkyl group are a lower alkyl group, an aryl group, a halogen atom, and a lower alkoxy group. It may be substituted by at least one member of the group). Expression (I
The compound I) exhibits particularly well-balanced performance as a color developer for thermal recording paper.

In the compound of formula (II), the unsubstituted and substituted aromatic ring groups represented by A can be preferably selected from the following groups.

Embedded image

In the compound of formula (II), the aromatic ring group and aralkyl group substituted by the hydroxyl group and the carboxyl group represented by B are preferably selected from the groups represented by the following formula.

[Chemical 6]

[0015]

The aromatic compound used in the present invention has at least one sulfonyl (thio) urea group, hydroxyl group and carboxyl group in one molecule and acts as a color developer. Specific examples of this aromatic compound are as follows.

N- (p-toluenesulfonyl) -N'-
(4-carboxy-3-hydroxyphenyl) urea,
N- (p-toluenesulfonyl) -N '-(4-carboxy-2-hydroxyphenyl) urea, N- (p-toluenesulfonyl) -N'-(3-carboxy-4-hydroxyphenyl) urea, N- (P-Toluenesulfonyl) -N '-(3-carboxy-5-hydroxyphenyl) urea, N- (p-toluenesulfonyl) -N'
-(2-Carboxy-4-hydroxyphenyl) urea, N- (p-toluenesulfonyl) -N '-(4-carboxy-5-hydroxy-3-methylphenyl) urea, N- (p-toluenesulfonyl)- N '-(4-carboxy-5-hydroxy-3-chlorophenyl) urea, N- (p-toluenesulfonyl) -N'-(4-carboxy-5-hydroxy-2-nitrophenyl) urea, N- (p -Toluenesulfonyl) -N '-(4-carboxy-5-hydroxy-1-naphthyl) urea, benzenesulfonyl-N'-(4-carboxy-3-hydroxyphenyl) urea, o-toluenesulfonyl-
N '-(4-carboxy-3-hydroxyphenyl) urea, p-chlorosulfonyl-N'-(4-carboxy-3-hydroxyphenyl) urea, p-methoxybenzenesulfonyl-N '-(4-carboxy-3 -Hydroxyphenyl) urea, N- (p-toluenesulfonyl) -N '-(4'-carboxy-3'-hydroxybenzyl) urea, and N- (p-toluenesulfonyl) -N'-(4'-carboxy -3'-hydroxyphenethyl) urea. These compounds may be used alone or as a mixture of two or more thereof.

In the heat-sensitive recording material of the present invention, the leuco dye used as a dye precursor can be selected from triphenylmethane type compounds, fluorane type compounds, diphenylmethane type compounds and the like. Examples of such dye precursors include 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-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-N-p-toluidino) -6-methyl-7-anilinofluorane, 3-
Pyrrolidino-6-methyl-7-anilinofluorane, 3
-Dibutylamino-6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7
-Chlorofluorane, 3-diethylamino-6-methylfluorane, 3-cyclohexylamino-6-chlorofluorane, 3- (N-ethyl-N-hexylamino)-
6-methyl-7- (p-chloroanilino) fluorane,
And one or more selected from 3-dibutylamino-7- (o-chloroanilino) fluorane and the like can be used.

Further, in the present invention, a conventionally known developer compound consisting of a phenol or an organic acid and a non-phenolic sulfonyl (thio) urea compound is used in the present invention as long as it does not inhibit the desired effect. It can be used in combination with an agent compound. Examples of these conventional developer compounds include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 1,1-bis (4-hydroxyphenyl) -1-phenylethane and 1,4- Screw (1-
Methyl-1- (4′-hydroxyphenyl) ethyl) benzene, 1,3-bis (1-methyl-1- (4′-hydroxyphenyl) ethyl) benzene, dihydroxydiphenyl ether (JP-A-1-180382), p -Benzyl 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, 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 '
-Benzylurea (above, JP-A-5-32061),
4,4'-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (o
-Toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane, 1,2-
Bis [4 ′-(p-toluenesulfonylaminocarbonylamino) phenyloxy] ethane, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether, and 3,3′-bis (p-toluenesulfonylaminocarbonyl) Amino) diphenyl sulfone (above, JP-A-5-147357) and the like can be used.

Further, in the present invention, it is preferable to use a heat-fusible substance (so-called sensitizer) together in the heat-sensitive color forming layer. As the sensitizer, a heat-fusible organic compound having a melting point of 50 to 150 ° C. is used.
91089), p-benzyl biphenyl (JP-A-60-
82382), benzyl naphthyl ether (Japanese Patent Application Laid-open No. Sho 5
8-87094), dibenzyl terephthalate (JP-A-58-98285), benzyl p-benzyloxybenzoate (JP-A-57-201691), diphenyl carbonate, ditolyl carbonate (JP-A-58-136489). ,
m-terphenyl (JP-A-57-89994), 1,
2-bis (m-tolyloxy) ethane (JP-A-60-5)
6588), 1,5-bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-181183).
No.), oxalic acid diesters (JP-A-64-1583).
No.), 1,4-bis (p-tolyloxy) benzene (JP-A-2-153787), di (4-methylbenzyl) oxalate (Japanese Patent Publication No. 5-62597), 1,2-di (3).
-Methylphenoxy) ethane (JP-A-60-56588)
No.) Diphenyl sulfone (Japanese Patent Publication No. 60-15667)
No.), benzenesulfoanilide (JP-A-58-2114)
No. 93), 2-chloroacetoacetanilide, 4-ethoxymethylsulfonylbenzene, 4-methoxyacetoacetanilide, o-methylacetanilide, 4-methoxybenzenesulphoanilide, 3,4-dimethylacetanilide, 2-methoxybenzenesulphoanilide and the like. You can choose from.

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention mainly contains a dye precursor, the novel developer compound of the present invention and a binder, and may contain a sensitizer as described above. preferable. Further, the heat-sensitive color developing layer may contain a conventionally known phenol-based developer, organic acid-based developer or non-phenolic sulfonyl (thio) urea-based developer, or wax, if necessary. Further, it preferably contains organic or inorganic pigments. The binder fixes 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. The content of the developer compound of the present invention is generally preferably 10 to 50% by weight.
If the content of the developer compound of the present invention is less than 10% by weight, the color developing ability may be insufficient, and even if it is used in an amount exceeding 50% by weight, the color developing ability is saturated and the result is exceptional. No improvement is seen and may be economically disadvantageous.

When a conventionally known phenol type developer, organic acid type developer or non-phenol type sulfonyl (thio) urea type developer is incorporated, the content thereof is 5 to 40% by weight. preferable. The content of the sensitizer 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 surface-treated calcium carbonate. Inorganic fine powder such as silica and silica, urea-formalin resin, styrene / methacrylic acid copolymer,
Alternatively, organic fine powder such as polystyrene resin can be used.

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

As for the binder, polyvinyl alcohol having 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, etc. Water-soluble polymer materials such as coalesce, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, and poly Vinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate Copolymers, and styrene /
Each latex such as butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the heat-sensitive recording material of the present invention is paper, coated paper having a surface coated with a pigment and / or latex, laminated paper, synthetic paper made of polyolefin resin, plastic film. You can choose from 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 form a thermosensitive coloring layer, thereby producing a thermosensitive recording medium. The coating amount of the heat-sensitive color developing layer is preferably 1 to 15 g / m ² in the dried state of the coating liquid layer, and 2 to 1
More preferably, it is 0 g / m ² .

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

[0028]

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

Synthesis Example 1 (N- (p-toluenesulfone
) -N '-(4-Carboxy-3-hydroxyphenyl)
3) Urea synthesis) Into a three-necked flask equipped with a dropping funnel, a thermometer, and a reflux condenser, 30.6 g of 4-amino-2-hydroxy-benzoic acid was added, 200 ml of acetonitrile was added, and the mixture was stirred. A portion of -amino-2-hydroxy-benzoic acid was dissolved in acetonitrile. While stirring this reaction solution with a magnetic stirrer, 39.4 g of toluenesulfonyl isocyanate was added dropwise thereto through a dropping funnel. When the stirring was continued, an exothermic reaction occurred and a large amount of white solid was precipitated. The reaction mixture was further heated at 90 ° C. for 1 hour, then cooled and filtered to give 69.5 g of white crystals.

The analytical values of this white crystal are as follows. Melting point: 198 ° C. Result of NMR measurement (in heavy acetone) (number is ppm): δ =
2.45 (s, 3H), 6.95 (d, 1H), 7.1
5 (s, 1H), 7.40 (d, 2H), 7.75
(D, 1H), 7.92 (d, 2H), others, NH
Alternatively, peaks which are considered to be caused by O-H appeared in the vicinity of δ = 8.6 and 9.7.

Results of IR measurement (KBr tablet method) (characteristic absorption
Yield only): 1660 cm ^-1 (derived from the carbonyl group of the urea group) 1700 cm ^-1 (derived from the carbonyl group of a carboxyl group) 1340cm ^-1, 1160cm ^-1 (derived from sulfonyl group)

Synthesis 2 (N- (p-toluenesulfonyl))
-N '-(3-carboxy-4-hydroxyphenyl)
Urea Synthesis) The same operation as in Synthesis Example 1 was performed. However, instead of 30.6 g of 4-amino-2-hydroxy-benzoic acid, 3
0.6 g of 5-amino-2-hydroxy-benzoic acid was used. 69.2 g of white crystals were obtained.

The analytical values of this white crystal are as follows. Melting point: 220 ° C. Result of NMR measurement (in heavy acetone) (number is ppm): δ =
2.45 (s, 3H), 6.90 (d, 1H), 7.2
0 (s, 1H), 7.45 (d, 2H), 7.70
(D, 1H), 7.90 (d, 2H), others, NH
Alternatively, peaks that are considered to be caused by O-H appeared at around δ = 8.6 and 9.2.

Results of IR measurement (KBr tablet method) (characteristic absorption
Yield only): 1670 cm ^-1 (derived from the carbonyl group of the urea group) 1690 cm ^-1 (derived from the carbonyl group of a carboxyl group) 1340cm ^-1, 1160cm ^-1 (derived from sulfonyl group)

Example 1 A thermosensitive recording paper was prepared by the following procedure . The sand grinder dispersion A prepared INGREDIENT AMOUNT (parts) 3- (N-isopentyl -N- ethylamino) -6-methyl-7-anilino fluoran 20 polyvinyl alcohol 10% solution 10 Water 70 The composition, average particle Diameter is 1
It was pulverized until it became less than μm.

[0036] Dispersion B prepared INGREDIENT AMOUNT (parts) N-(p-toluenesulfonyl) -N '- (4-carboxy-3-hydroxyphenyl) urea 10 diphenylsulfone 10 polyvinyl alcohol 10% solution 10 Water 70 The above composition The average particle size is 1 with a sand grinder
It was pulverized until it became less than μm.

Preparation of Pigmented Undercoat 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
A coating solution was prepared by mixing with 50 parts of a% oxidized starch aqueous solution. This coating liquid was applied onto one surface of a base paper having a basis weight of 48 g / m ² so that the coating amount after drying was 7.0 g / m ² , and dried to prepare a pigment-undercoated paper.

Formation of thermosensitive coloring layer In 50 parts of solution A and 200 parts of solution B, 33 parts of calcium carbonate pigment, 20 parts of 25% zinc stearate dispersion, 3
15 parts of 0% paraffin dispersion and 120 parts of 10% aqueous polyvinyl alcohol solution were mixed and stirred to prepare a coating solution. This coating liquid was applied and dried on the coated surface of the pigment-undercoated paper so that the coating amount after drying was 5.0 g / m ² , to form a thermosensitive color-developing layer to prepare a thermosensitive recording paper.

[0039] The heat-sensitive recording paper obtained in the manner of the calendar processing the processed by a super calender, the smoothness of the surface 800-120
It was set to 0 seconds.

Test The samples thus obtained were printed using a thermal color tester THPMD manufactured by Okura Electric Co., Ltd. under the conditions of a printing voltage of 21.7 v and a printing pulse of 1.0 ms. The print color density was measured with a Macbeth reflection densitometer RD-914. The test results are shown in Table 1. Next, a test piece was taken from this color-developed sample, salad oil or dioctyl terephthalate (representative plasticizer) was applied to the test piece, and left at room temperature for 3 hours, and then the remaining oil or plasticizer was wiped off, The residual image density was measured with a Macbeth reflection densitometer, and the measured value was used as a value representative of the image storability. The test results are shown in Table 1.

Example 2 A thermal recording paper was prepared in the same manner as in Example 1. However, in preparing the dispersion liquid B, N- (p-toluenesulfonyl) was used.
-N '-(4-carboxy-3-hydroxyphenyl)
Instead of urea, N- (p-toluenesulfonyl)-
N '-(3-carboxy-4-hydroxyphenyl) urea was used. The test results are shown in Table 1.

Example 3 A thermal recording paper was prepared in the same manner as in Example 1. However, in the preparation of the dispersion liquid B, N- (p-toluenesulfonyl) -N '-(4 instead of N- (p-toluenesulfonyl) -N'-(4-carboxy-3-hydroxyphenyl) urea was used. -Carboxy-5-hydroxy-3-
Chlorophenyl) urea was used, and oxalic acid diparamethylbenzyl ester was used instead of diphenyl sulfone. The test results are shown in Table 1.

Comparative Example 1 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, in preparing the dispersion liquid B, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A was used instead of N- (p-toluenesulfonyl) -N ′-(4-carboxy-3-hydroxyphenyl) urea. ) Was used. The test results are shown in Table 1.

Comparative Example 2 A thermal recording paper was prepared in the same manner as in Example 1. However,
In preparing Dispersion B, bis (4-hydroxyphenyl) sulfone (bisphenol S) was used instead of N- (p-toluenesulfonyl) -N ′-(4-carboxy-3-hydroxyphenyl) urea. The test results are shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1 above, the novel developer of the present invention is bisphenol A which is a representative of conventional developers.
Has a color-developing ability that exceeds that of the color-developing image, and the color-developed image obtained thereby exhibits good oil resistance and plasticizer resistance.
It surpasses bisphenol S, which is known as a developer with good print storability.

[0047]

The heat-sensitive recording material of the present invention exhibits a color developing performance superior to that using the conventional color developer due to the specific developer compound contained in the heat-sensitive color developing layer, and The resulting colored image shows good storage stability.

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 has the following general formula (I) in one molecule: (However, X represents an oxygen atom or a sulfur atom.) At least one type of compound having at least one of a sulfonyl (thio) urea group, a hydroxyl group (—OH group) and a carboxyl group (—COOH group) each represented by A heat-sensitive recording material comprising an aromatic compound. 2. The developer aromatic compound has the following general formula (II): (In the above formula, A represents an unsubstituted aromatic ring group or an aromatic ring group substituted by at least one member of a lower alkyl group, a halogen atom and a lower alkoxy group, and B represents
An aromatic ring group substituted by a hydroxyl group and a carboxyl group, or represents an aralkyl group substituted by a hydroxyl group and a carboxyl group, the aryl group portion of the aromatic ring group and the aralkyl group, further lower alkyl group, an aryl group, It may be substituted with at least one member of a halogen atom and a lower alkoxy group. ) The thermal recording material according to claim 1, represented by