JPH07304259A - Production of thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the long-term preservability of a developed color image, in a thermal recording material having a thermal color forming layer containing a dye precursor and a coupler composed of a specific aromatic compd. reacting with the precursor under heating to develop a color, by preparing a dispersion contained in the color forming layer using a specific methyl cellulose compd. CONSTITUTION:A thermal color forming layer containing an electron donating dye precursor and an aromatic compd. represented by formula I (wherein X is an oxygen atom or a sulfur atom, R is one member selected from a non- substituted aromatic group, a lower alkyl group, a lower alkoxy group, a halogen atom and the like, Z is a divalent or more group and n is an integer of 2 or more) being a coupler reacting with the dye precursor to develop a color is provided on a support to produce a thermal recording material. At the time of production, the dispersion of at least one substance among the components contained in the color forming layer is prepared by using a methyl cellulose compd. composed of a repeated unit represented by formula II [wherein R1-R6 are H, CH3, CH2CH(OH)CH3 or the like] as a dispersant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material on which a color-developed image is formed by heating, and more particularly to a heat-sensitive recording material which is free from loss of a once-color-developed image and has excellent storage stability. More specifically, the long-term storage stability of the record is good, and at the same time, the recorded image has excellent moisture resistance, environment resistance such as heat resistance, oil resistance, plasticizer resistance, and high whiteness.
In addition, a heat-sensitive recording material and a method for producing the same, in which the white paper portion (non-printed portion) has extremely little color development (ground color development) in a high temperature and high humidity atmosphere or when contacted with a polyvinyl chloride film containing a plasticizer. Regarding Further, the present invention is, for example,
Not only can it be used as a thermal recording type ticket for an automatic ticket vending machine, but it can also be used for foods wrapped in polyvinyl chloride film that cannot be kept in contact with coupons, commuter passes, water, plasticizers, oils and fats that require preservation. The present invention relates to a thermal recording material that can be used as a label for a POS bar code system to be stuck on a packaging surface, facsimile paper or word processing paper for long-term storage, and image printer paper for CRT, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A thermal recording material is generally composed of a color-forming substance such as an electron-donating leuco dye and an organic acid substance such as an electron-accepting phenolic compound on a support such as paper, synthetic paper and plastic film. A thermosensitive color-developing layer containing such a color-developing substance as a main component is provided, and they can be reacted with thermal energy to obtain a recorded image. Such thermal recording materials are disclosed in Japanese Examined Patent Publication Nos. 43-4160 and 45-14.
It is disclosed in Japanese Patent Application Laid-Open No. 039, JP-A-48-27736 and the like, and is widely put into practical use.

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

A large number of techniques have been disclosed for suppressing this decoloring phenomenon while using a coloring system which usually uses a dye mainly composed of a colorless or light-colored lactone ring compound. For example, JP-A-60-78782 and JP-A-59-1672.
92, JP-A-59-114096, and JP-A-59-9.
JP-A-56-14, wherein the thermosensitive color-developing layer contains a phenolic antioxidant as disclosed in JP-A-3387.
No. 6796 using a hydrophobic polymer compound emulsion or the like in the protective layer, or a water-soluble polymer compound on the thermosensitive coloring layer as disclosed in JP-A-58-199189, or An emulsion in which a hydrophobic polymer compound emulsion is provided as an intermediate layer, and a surface layer made of an oil-based paint containing a hydrophobic polymer compound as a resin component is provided thereon, and an epoxy as disclosed in JP-A-62-164579. Compounds containing a compound, and those using a metal salt of a specific salicylic acid derivative found in JP-A-62-169681 as a developer are known.

In the heat-sensitive color-developing layer containing the above-mentioned phenolic antioxidant, compared with the image without it,
Although the environmental resistance is somewhat improved, oil resistance (for example, storage ratio of image density after a certain time when salad oil is brought into contact with the color development surface), plasticizer resistance (wrap film containing plasticizer, etc.) No improvement is observed in the storage ratio of the image density after a certain period of time when it is brought into contact with the coloring surface). On the other hand, a thermal recording medium provided with a protective layer and a surface layer has a slightly improved environmental resistance, but erasing 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, it takes a relatively long time from the heating color development operation until the color image is stabilized. 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. Further, the one using a specific salicylic acid metal salt has improved oil resistance and plasticizer resistance, but color development of the white paper part is observed in the heat resistance test, and the effective chemical structure of a specific salicylic acid is complicated and expensive. It has the drawback of being.

The present inventors have developed a new technique for solving these problems and have already filed a patent application (Japanese Patent Laid-Open No. Hei 5-
147357). The invention is a technique of using an aromatic compound represented by the general formula (I), which is different from a conventional phenolic compound, as a color developer for developing the dye precursor described above. The body fulfilled all the above conditions. However, the heat-sensitive recording material using this color developer also has a problem that has not been completely solved as in the case of using the conventional phenolic color developer. This is a phenomenon in which the heat-sensitive recording paper using the above-mentioned color developer is left in a high temperature and high humidity atmosphere or is brought into contact with a polyvinyl chloride film containing a plasticizer to cause grounding of the white paper portion.

[0008]

DISCLOSURE OF THE INVENTION The present invention suppresses the background color of a white paper portion of a heat-sensitive recording material under a high temperature and high humidity atmosphere and suppresses the background coloration of a white paper portion by a polyvinyl chloride film containing a plasticizer, Moreover, it is intended to provide a thermal recording material having high whiteness and excellent long-term storage stability of a color image such as oil resistance, plasticizer resistance, moisture resistance, and heat resistance. The present invention is
For example, it can be used not only as a thermal recording type ticket for automatic ticket vending machines, but also for use on coupons and commuter tickets that require preservation, and avoids contact with plasticizers and oils and fats. A thermal recording material that can be used as a label for POS bar code system, long-term storage facsimile paper or word processor paper, or CRT image printer paper, which can be attached to the packaging surface of food that is not packaged with polyvinyl chloride film. It is the one we are trying to provide.

[0009]

SUMMARY OF THE INVENTION The inventors of the present invention suppress the background color formation of a blank paper portion of a thermal recording material under a high temperature and high humidity atmosphere or with a polyvinyl chloride film containing a plasticizer to obtain a high whiteness. In order to obtain a heat-sensitive recording material having excellent storage stability, a dispersion of at least one substance selected from the dye precursor and each component of the color developer contained in the heat-sensitive color-developing layer is used as a specific methylcellulose compound. The present invention has been completed by discovering that it is effective to prepare a thermosensitive color forming layer using a thermosensitive color developing layer coating solution containing the dispersion liquid.

That is, the present invention provides a colorless or light-colored electron-donating dye precursor on a support and a developer which reacts with the dye precursor to develop a color, represented by the following general formula (I);

[Chemical 3] (However, X represents an oxygen atom or a sulfur atom, R represents an unsubstituted aromatic group, or an aromatic group selected from a lower alkyl group, a lower alkoxy group and a halogen atom and substituted by at least one member. Represents the selected member, Z
Represents a divalent or higher valent group. Also, n is 2
Represents the above integers. In the production of a thermosensitive recording material provided with a thermosensitive coloring layer containing an aromatic compound represented by the formula (1), a dispersion liquid of at least one substance selected from the components contained in the coloring layer is represented by the following general formula (II);

[Chemical 4](However, R₁~ R₆Is H, CH₃, CH₂CH (O
H) CH₃, CH₂CH ₂A member of members selected from OH
And at least one is CH₃Is. )
Methylcellulose compound used as a repeating unit as a dispersant
It is characterized by being prepared and used by using
It

In the above general formula (I), Z is not particularly limited as long as it has a divalent or higher valent group, but preferable examples include the following groups. a. Divalent and higher valent radicals derived from aliphatic hydrocarbons. b. Divalent and higher valent radicals derived from aliphatic hydrocarbons containing one or more heteroatoms in the main chain. c. 1 or more substituted or unsubstituted aromatic hydrocarbons in the main chain
A divalent or higher valent group derived from an aliphatic hydrocarbon containing one or more. d. A divalent or higher divalent group derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted heteroaromatic ring in the main chain. e. A divalent or higher valent group derived from a substituted or unsubstituted aromatic hydrocarbon. f. 2 derived from a substituted or unsubstituted heteroaromatic ring
Valence and higher radicals. g. A divalent group derived from a compound in which two or more aromatic hydrocarbons or heteroaromatic rings are bonded to the organic groups a to e and functional groups such as a carbonyl group, a thiocarbonyl group and a sulfonyl group described above. More than that.

Representative examples of the methylcelluloses used in the present invention include hydroxypropylmethylcellulose and hydroxyethylmethylcellulose in addition to methylcellulose in a narrow sense. These dispersants may be used alone or as a mixture of two or more thereof. The above-mentioned addition amount of each dispersant is preferably 0.1% to 20%, and more preferably 1% to 10%, in terms of weight, with respect to each of the materials to be dispersed. If the addition amount is less than 0.1% by weight, the effect of suppressing the background color development of the white paper part in a high temperature and high humidity atmosphere is not sufficient, and even if it is added in an amount of 20% by weight or more in a high temperature and high humidity atmosphere. There is no further suppression of the background coloration of the white paper portion and the background coloration of the white paper portion due to the vinyl chloride wrap, and conversely, there is a drawback that the sensitivity of the obtained thermal recording material is lowered.

The thermosensitive coloring layer of the thermosensitive recording medium produced by the production method of the present invention mainly contains a leuco dye and an aromatic compound represented by the above general formula (I). The thermosensitive coloring layer has various inorganic or organic pigments and, if necessary, a melting point of 50 to 150 ° C. known as a sensitizer.
The heat-fusible aromatic compound, a conventionally known phenolic or non-phenolic color developer, an antioxidant, an ultraviolet absorber, or a wax can be included. Further, it contains a binder for fixing these components.

Specific examples of the aromatic compound represented by the above general formula (I) which can be used in the present invention are as follows. 1,2-bis (p-chlorobenzenesulfonylaminocarbonylamino) -ethane,
1,3-bis (p-toluenesulfonylaminocarbonylamino) -benzene, 1,4-bis (p-toluenesulfonylaminocarbonylamino) -benzene, 1,2
-Bis (o-toluenesulfonylaminocarbonylamino) -benzene, 4,4'-bis (p-chlorobenzenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (p-methoxybenzenesulfonylaminocarbonylamino) -diphenylmethane , 4, 4
-Bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (o-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (3,4-dichlorobenzenesulfonylaminocarbonylamino) -Diphenyl sulfide, 4,4'-bis (3,4-dichlorobenzenesulfonylaminocarbonylamino) -biphenyl, 4,4 '
-Bis (p-methoxybenzenesulfonylaminocarbonylamino) -diphenyl ether, 3,3'-bis (m-chlorobenzenesulfonylaminocarbonylamino) -diphenylsulfone, 3,3'-bis (p-methoxybenzenesulfonylaminocarbonylamino) -Diphenyl sulfone, 2,5-bis (p-methoxybenzenesulfonylaminocarbonylamino) -furan, 1,
5-bis (m-chlorobenzenesulfonylaminocarbonylamino) -naphthalene, 4,4'-bis (3,4-
Dichlorobenzenesulfonylaminothiocarbonylamino) -diphenyl sulfide, 4,4'-bis (p-toluenesulfonylaminothiocarbonylamino) -diphenylmethane, 4,4'-bis (o-toluenesulfonylaminothiocarbonylamino) -diphenylmethane,
4,4'-Bis (benzenesulfonylaminothiocarbonylamino) -diphenyl sulfide. These compounds may be used alone or as a mixture of two or more thereof.

The leuco dye used as the dye precursor in the present invention includes triphenylmethane type, fluorane type, diphenylmethane type compounds and the like, which can be selected from conventionally known ones. For example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N-ethyl-N-).
Isopentylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-
(O, p-dimethylanilino) fluorane, 3- (N-
Ethyl-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-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-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
1 selected from-(p-chloroanilino) fluorane, etc.
More than one species can be used.

In the thermosensitive recording medium produced by the production method of the present invention, phenols which have been conventionally used together with the aromatic compound represented by the general formula (I) are used within a range that does not impair the desired effect. Alternatively, a color developer composed of an organic acid can be used in combination.

These conventional color developers are, for example, 2,2-
Bis (4-hydroxyphenyl) propane (bisphenol A), 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis (1-methyl-1-
(4'-hydroxyphenyl) ethyl) benzene, 1,
3-bis (1-methyl-1- (4'-hydroxyphenyl) ethyl) benzene, dihydroxydiphenyl ether (JP-A-1-180382), benzyl p-hydroxybenzoate (JP-A-52-140483), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-1
No. 3852), 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-60-20
8286).

Further, in the heat-sensitive recording material produced by the production method of the present invention, the non-phenolic developer is added to the aromatic compound represented by the above general formula (I) within a range that does not impair the desired effect. It can be used together with the compound. Examples of these non-phenolic color developing agents include thiourea type color developing agents (JP-A-58-93190).
JP-A-58-222887, JP-A-59-133
No. 096), a sulfonylurea-based color developing agent (Japanese Patent Laid-Open No. Hei 5)
-32061), and specific compounds include N, N'-bis (3-chlorophenyl) thiourea, N, N'-bis (3-trifluoromethylphenyl) thiourea, N- ( p-toluenesulfonyl) -N '
-Phenylurea, N- (p-toluenesulfonyl)-
Examples thereof include N '-(m-tolyl) urea and N- (p-toluenesulfonyl) -N'-benzylurea.

Further, in the present invention, it is preferable to use a heat-fusible substance (so-called sensitizer) in combination. As the sensitizer, a heat-fusible organic compound having a melting point of 50-150 C is used,
Examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-191089), p.
-Benzyl biphenyl (JP-A-60-82382), benzylnaphthyl ether (JP-A-58-870)
94), dibenzyl terephthalate (JP-A-58)
-98285), benzyl p-benzyloxybenzoate (JP-A-57-201691), diphenyl carbonate, ditolyl carbonate (JP-A-58-136489), and m-terphenyl (JP-A-57-281). 89994), 1,2-bis (m-tolyloxy) ethane (JP-A-60-56588), 1,5-bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-1).
181183), oxalic acid diesters (JP-A-64-1583), 1,4-bis (p-tolyloxy) benzene (JP-A-2-153787), and diphenylsulfone (JP-B-59-25673). ),
p-Toluenesulfonic acid phenyl ester (JP-A-59)
-73990), mesitylenesulfonic acid p-tolyl ester (JP-A-2-80285), 4,4 '.
-Diallyloxydiphenyl sulfone, 4,4'-diisopentyloxydiphenyl sulfone, 4,4'-dimethoxydiphenyl sulfone (Japanese Patent Publication No. 2-9951), and 4,4'-di-n-pentyloxydiphenyl sulfone (JP-A-60-47070).

The thermosensitive color-developing layer produced by the production method of the present invention contains, as pigments, silica, clay, calcined clay, barium sulfate, light calcium carbonate, heavy calcium carbonate, ultrafine calcium carbonate, aluminum hydroxide,
Magnesium hydroxide, calcium hydroxide, magnesium carbonate, aluminum silicate, talc, alkali-modified clay, surface-treated calcium carbonate, inorganic pigments such as silica, and urea-formalin resin, styrene /
Examples thereof include methacrylic acid copolymers and organic fine powders such as polystyrene resins.

The heat-sensitive layer of the present invention may further contain a hindered phenol compound or an ultraviolet absorber.
They are disclosed in, for example, JP-A-57-151394 and JP-A-SHO-5.
8-160191, JP-A-58-69096, JP-A-59-2884, JP-A-59-95190, JP-A-60-22288, JP-A-60-255485,
JP-A-61-44686 and JP-A-62-169683
JP-A-63-17081 and JP-A-1-24938.
The compounds described in each publication of No. 5, Japanese Patent Application No. 2-266645, and the like. The content of the leuco dye in the thermosensitive coloring layer in the thermosensitive coloring layer is generally preferably 5 to 20% by weight based on the dry weight of the thermosensitive coloring layer, and the content of the aromatic compound represented by the general formula (I) is Generally, the content is preferably 5 to 50% by weight.

When the thermosensitive coloring layer contains an antioxidant or an ultraviolet absorber, its content is preferably 1 to 10% by weight. When a conventionally known phenol type or non-phenol type color developer is contained, its content is 5 to 4
It is preferably 0% by weight, and the content of the sensitizer is preferably 10 to 40% by weight. When waxes and white pigments are contained in the thermosensitive coloring layer, their content ratios are 5 to 5%, respectively.
20% by weight, preferably 10 to 50% by weight,
The binder content is generally 5 to 20% by weight.

As the waxes, known waxes such as paraffin, amide wax, bisimide wax, and metal salt of higher fatty acid can be used.
Regarding the binder, polyvinyl alcohol having various molecular weights, starch and its derivatives, methoxycellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, Acrylic amide /
Acrylic ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, water-soluble polymer materials such as casein, and polyvinyl acetate, polyurethane, styrene / Butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene /
Each latex such as vinyl acetate copolymer and styrene / butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the thermosensitive recording medium produced by the production method of the present invention is a rosin sizing agent,
So-called acidic paper made with sulphate sulfate, paper made with an inorganic salt of an alkaline earth metal such as calcium carbonate as an internal additive pigment, coated paper with a surface coated with pigment, latex, etc. , Laminated paper, 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 preferably 1 to 15 g / m ² when the coating liquid layer is dried, and 2
Particularly preferred is 10 g / m ² . In the thermosensitive recording medium produced by the production method 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.

[0025]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless stated otherwise, "part" and "%" are
Represents "parts by weight" and "% by weight", respectively.

Example 1 A thermosensitive recording paper was prepared by the following operation. Dispersion A prepared INGREDIENT AMOUNT (parts) 3- (N-isopentyl -N- ethylamino) -6-methyl-7-anilino fluoran 20 Polyvinyl alcohol - le 10% solution 10 (Nippon Synthetic; GOHSERAN L3266) water 70 above The composition was pulverized using a sand grinder until the average particle size became 1 μm or less.

[0027] Dispersion B prepared INGREDIENT AMOUNT (parts) 4,4 '-bis (p over toluenesulfonyl aminocarbonylamino) - Jifenimetan 20 cellulose 10% solution 10 (Shin-Etsu Chemical; SM-15) water 70 The above composition Using a sand grinder, it was pulverized until the average particle diameter became 1 μm or less.

[0028] Dispersion C prepared INGREDIENT AMOUNT (parts) diphenyl sulfone 20 polyvinyl alcohol 10% solution 10 (Nippon Synthetic; GOHSERAN L3266) using a sand grinder of water 70 the composition, milled to a mean particle size becomes 1μm or less did.

Formation of Coloring Layer 60 parts of solution A, 120 parts of solution B, 120 parts of solution C, 26 parts of clay pigment for papermaking, 25% zinc stearate dispersion 12
And 80 parts of a 10% polyvinyl alcohol aqueous solution were stirred to obtain a thermosensitive coloring layer coating solution. Using this thermosensitive coloring layer coating liquid, one side of a base paper having a basis weight of 50 g / m ² was coated and dried so that the coating amount after drying was 6.5 g / m ^2, and the thermosensitive coloring layer was applied. Was formed.

Super calender treatment The thermal recording paper obtained as described above was treated with a super calender to obtain a surface smoothness of 800 to 100.
It was set to 0 seconds.

Various tests (a) Whiteness The whiteness of the above thermal recording paper sample was measured using a Hunter whiteness meter (manufactured by Toyo Seiki Seisaku-sho, Ltd.).

(B) Color development test The thermal recording material thus obtained was printed using a thermal color development test 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 color density of the printed portion was measured with a Macbeth reflection densitometer RD-914. This color density value is called a color development sensitivity value.

(C) White paper portion wetland color development test The above heat-sensitive recording paper sample was placed in a thermo-hygrostat controlled at 40 ° C. and 90% for 24 hours, and the density of the white paper portion was the same as in (b) above. Measured. The results are shown in Table 1. (D) Polyvinyl chloride film test As the polyvinyl chloride film, MAT-W manufactured by Mitsui Toatsu Chemicals Inc. was used, a thermal paper sandwiched with the polyvinyl chloride film was sandwiched between glass plates, and left standing in an environment of 60 ° C. for 24 hours. The density of the white paper portion was measured in the same manner as in (b) above. The results are shown in Table 1.

Example 2 The same operation as in Example 1 was performed. However, instead of 10 parts of a 10% methylcellulose solution of dispersion B of Example 1,
10 parts of a 10% hydroxypropylmethylcellulose solution (Metroze 60SH03 manufactured by Shin-Etsu Chemical Co., Ltd.) was used.
The results are shown in Table 1.

Example 3 The same operation as in Example 1 was performed. However, instead of 10 parts of a 10% solution of polyvinyl alcohol in Dispersion C of Example 1, a 10% solution of methylcellulose (Metroze SM-1
5) 10 parts were used. The results are shown in Table 1.

Example 4 The same operation as in Example 1 was performed. However, 10 parts of a 10% solution of polyvinyl alcohol in the dispersion C of Example 1 was used instead of 10 parts of a 10% solution of polyvinyl alcohol (Metroze 60SH03). The results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed. However, instead of 10 parts of a 10% methylcellulose solution of dispersion B of Example 1,
10 parts of a 10% solution of polyvinyl alcohol was used. The results are shown in Table 1.

[0038]

[Table 1] As is clear from Table 1 above, in the present example in which methylcellulose or hydroxypropylmethylcellulose was used in the dispersion liquid, the background color of the white paper portion under high temperature and high humidity atmosphere and the background of the white paper portion formed by the polyvinyl chloride film containing a plasticizer were used. Coloring is suppressed.

[0039]

The heat-sensitive recording material of the present invention has the aromatic compound represented by the above-mentioned general formula (I) in the heat-sensitive color forming layer, and the developer is represented by the general formula (II). By using the dispersion liquid in which the methyl celluloses are dispersed as the coating liquid, the background color of the white paper portion under the high temperature and high humidity atmosphere and the background color of the white paper portion due to the plasticizer-containing polyvinyl chloride film are suppressed. In addition, the whiteness is high, and the obtained recorded image has high storage stability and is extremely valuable in practical use.

Claims (1)

[Claims] 1. A sheet-like substrate, a colorless or light-colored dye precursor which is formed on at least one surface of the sheet-like substrate, and the following general formula which reacts with the dye precursor under heating to develop a color: (I); (However, X represents an oxygen or sulfur atom, and R is selected from an unsubstituted aromatic group or an aromatic group substituted by at least one member selected from a lower alkyl group, a lower alkoxy group and a halogen atom. Member, Z represents a divalent or higher valent group, and n represents an integer of 2 or more.) In the method for producing a thermosensitive recording material having a layer, a dispersion liquid of at least one substance among the components contained in the color forming layer is represented by the following general formula (II); (However, R _{1 to} R ₆ are H, CH ₃ , CH ₂ CH (O
H) Any one member selected from CH ₃ and CH ₂ CH ₂ OH, at least one of which is CH ₃ . A method for producing a heat-sensitive recording material, which comprises preparing and using a methylcellulose compound having a repeating unit of 1) as a dispersant.