JP2009126024A - Thermal recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording body, which is superior in color developing sensitivity and image quality and, at the same time, in imprinting properties, scratching properties, resistance to plasticizer and resistance to moist heat of an image part and heat resistance of a white paper part. <P>SOLUTION: In the thermal recording body, in which a thermal recording layer including at least colorless or light-colored basic leuco dye and electron acceptive developer is provided as a coating layer on a substrate, at least the uppermost layer among the thermal recording layer and other arbitrarily provided coating layers includes powdered cellulose produced by being dry-ground at normal temperature and, in addition, as the developer, 4-hydroxy-4'-allyloxydiphenyl sulfone is included. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material that obtains a recorded image by utilizing a color development reaction between a basic leuco dye and an electron-accepting developer.

  The heat-sensitive recording material contains a colorless or light-colored basic leuco dye (hereinafter referred to as “dye”) and an electron-accepting developer (hereinafter referred to as “developer”) such as a phenolic compound. After grinding and dispersing into fine particles, the two are mixed, and a coating solution obtained by adding a binder, a filler, a sensitivity improver, a lubricant and other auxiliary agents is used for paper, synthetic paper, film, plastic, etc. The coated image is applied to a support, and a recorded image can be obtained by developing a color by an instantaneous chemical reaction by heating such as a thermal head, hot stamp, thermal pen, laser beam or the like. This thermal recording medium is widely used in facsimiles, computer terminal printers, automatic ticket vending machines, measuring recorders, etc., and for various tickets, receipts, labels, bank ATMs, It is also used for gas and electricity meter readings and for cash vouchers such as car betting tickets.

However, since the dye and the developer contained in the heat-sensitive recording layer are easily dissolved in various solvents, when the plasticizer contained in the ink (aqueous, oily), adhesive, etc. touches the heat-sensitive recording material, Problems related to storage stability such as color development and color density decrease occur. Further, in addition to storability, sealability is required for delivery slip sheets, bills, receipts, and the like.
As a method for improving the storage stability of the image area, it is generally well known to provide a protective layer on the thermosensitive coloring layer, but in addition to this, a specific developer or a specific stabilizer may be used. (Patent Documents 1 and 2) and a technique for improving the storage stability of an image portion by using a specific sensitizer and a specific stabilizer in combination (Patent Document 3) are disclosed.
On the other hand, the powdered cellulose used in the present invention is a product obtained by hydrolyzing cellulose fibers such as pulp and then dry-pulverized at room temperature and atomized, and has an absorptivity such as organic solvent. 4) etc.

JP2003-154760 JP 2001-347757 A International Publication WO2004 / 002748 Japanese Patent No. 3790648

  It is an object of the present invention to provide a heat-sensitive recording material which has excellent color development sensitivity and image quality, and is excellent in imprintability, scratch resistance, image area plasticizer resistance, moist heat resistance, and white paper area heat resistance.

  The above-mentioned problem is a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a colorless or light-colored basic leuco dye and an electron-accepting developer as a coating layer on a support, At least the outermost layer of the other optionally provided coating layers is made of wood pulp or non-wood pulp, and is produced by dry pulverization at room temperature, and contains powdered cellulose having an average particle size of 5 μm to 30 μm. And the heat-sensitive recording layer as an electron-accepting developer is represented by the following general formula (Formula 1)

（式中、Ｒ^３は、炭素数が１〜１２の直鎖又は分岐の飽和又は不飽和炭化水素を表し、Ｒ^４〜Ｒ^９は、それぞれ独立して、ハロゲン原子、炭素数が１〜１２のアルキル基若しくはアルケニル基を表し、ｐ、ｑ、ｒ、ｓ、ｔ及びｕはそれぞれ０〜４の整数を表し、ｏは０〜５の整数を表し、Ａは、それぞれ独立して、エーテル結合を有してもよい炭素数が１〜１２の直鎖若しくは分枝の飽和若しくは不飽和の炭化水素基を表す。）で表されるジフェニルスルホン誘導体を含有することにより解決された。

(In the formula, R ³ represents a linear or branched saturated or unsaturated hydrocarbon having 1 to 12 carbon atoms, and R ^{4 to} R ⁹ are each independently a halogen atom and 1 to 12 carbon atoms. Wherein p, q, r, s, t and u each represents an integer of 0 to 4, o represents an integer of 0 to 5, and A independently represents an ether bond. And a diphenylsulfone derivative represented by a straight-chain or branched saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms.

  According to the present invention, it is possible to obtain a heat-sensitive recording material excellent in sufficient color development sensitivity and image quality, and excellent in imprintability, scratch resistance, plasticizer resistance of image areas, heat and moisture resistance, and heat resistance of blank areas.

Embodiments of the present invention will be described below.
The heat-sensitive recording material is usually formed by laminating an under layer, a heat-sensitive recording layer, and a protective layer in this order as a coating layer on a support. Of these, coating layers other than the heat-sensitive recording layer may be omitted, and an intermediate layer may be provided between the heat-sensitive recording layer and the protective layer. Providing a protective layer in the heat-sensitive recording material of the present invention is desirable from the viewpoint of the storage stability of the image area and the white paper area.
In the heat-sensitive recording material of the present invention, at least the outermost layer of these coating layers, particularly the protective layer, is produced by dry pulverization at room temperature using wood pulp or non-wood pulp as an average particle size. Contains powdered cellulose of 5 μm to 30 μm, and heat-sensitive recording layer contains 4-hydroxy-4′-isopropoxydiphenylsulfone or 4-hydroxy-4′-n-propoxydiphenylsulfone as an electron-accepting developer It is characterized by doing. Furthermore, in addition to the outermost layer, a coating layer containing this powdered cellulose may be provided separately. As such a heat-sensitive recording material, for example, 1) a heat-sensitive recording material provided with a heat-sensitive recording layer containing powdered cellulose (without a protective layer), 2) a heat-sensitive recording layer / a protective layer containing powdered cellulose 3) Thermal recording layer / coating layer containing powdered cellulose / thermal recording body provided with protective layer sequentially 4) Thermal recording layer / protective layer / coating layer containing powder cell roll Examples of the heat-sensitive recording material may be provided, but the invention is not limited thereto.
It is also possible to provide an undercoat layer between the support and the heat-sensitive recording layer, and it is possible to contain powdered cellulose in all of the undercoat layer, the heat-sensitive recording layer and the coating layer provided on the heat-sensitive recording layer. It is.

  The powdered cellulose used in the present invention is produced through the steps of acid hydrolysis of wood pulp and non-wood pulp, followed by filtration / washing, dehydration / drying, pulverization / sieving, and drying. It is characterized by being pulverized (so-called dry pulverization). Wood pulp refers to pulp derived from wood fibers made from coniferous or broad-leaved trees, and non-wood pulp refers to straw, sardine, ganpi, flax, cannabis, kenaf, manila hemp, abaca, sisal hemp, straw (rice , Wheat) refers to pulp derived from fibers other than wood fibers made from sugarcane bagasse, bamboo, esparto, cotton, linter and the like. In the present invention, dry pulverization refers to a process in which dried pulp is treated under high pressure, and is not heated or cooled, so that the pulps collide with each other in the air using a jet mill, and the frictional force generated at the time of the collision. Is a method of pulverizing pulp. The pulverization by this jet mill hardly causes an increase in temperature. This frictional force is generally smaller than the collision force generated between the pulp and the beads when the beads and the pulp are processed (that is, wet pulverized) in water. For this reason, it is considered that the powdered cellulose obtained by the dry pulverization is one in which the pulp is pulverized and the pulp surface becomes fluffy in the state where the internal voids of the conduit-derived pulp are present.

For this reason, the powdered cellulose absorbs and fixes the ink in the voids of the powdered cellulose itself as well as the inorganic pigment, and absorbs the ink by the capillary phenomenon between the cellulose fibers constituting the powdered cellulose. Accordingly, it is considered that the heat-sensitive recording material containing the powdered cellulose in the outermost layer, particularly the protective layer, has a high ink absorption rate and exhibits excellent stamping properties.
In addition, this powdered cellulose has finer fibers extending from the center fiber of the cellulose and fluffing on the surface thereof due to the above-mentioned production characteristics. Since sufficient coating layer strength is obtained and the frictional resistance is reduced, good scratching properties can be obtained.

  Therefore, when this powdered cellulose is contained in the outermost layer of the coating layer of the heat-sensitive recording material, particularly the protective layer, the stamping properties and the scratching properties that are superior to those when other powdered cellulose is used are developed. For example, when cellulose is freeze-dried and pulverized (Japanese Patent Laid-Open No. Sho 54-128349, etc.), it is pulverized by a mechanical pulverizer with the elasticity of the cellulose being made as small as possible. It does not have a shape that is dry pulverized at room temperature, and therefore the heat-sensitive recording material has poor absorbency of organic solvent and the like, and has poor stamping and scratching properties. In addition, porous cellulose obtained by foaming viscose or the like with carbon dioxide (JP-A-5-139033, JP-A-2001-323095, etc.) is in the form of a foam containing bubbles and is shaped like a dry pulverization at room temperature. In other words, the heat-sensitive recording material is inferior in sealability and scratching properties.

Compared with inorganic pigments such as silica and calcium carbonate, the powdered cellulose produced by this dry pulverization has a smaller difference in refractive index from the binder added to the same layer, and is less likely to cause internal scattering (internal haze). Therefore, when it is contained in the heat-sensitive recording layer or a layer provided on the heat-sensitive recording layer, good color development sensitivity and image quality can be obtained.
In addition, this powdery cellulose has a heat insulating property (oil absorbing property) equal to or higher than that of inorganic pigments such as silica with a high oil absorption amount, and heat from the thermal head is efficiently used. When it is contained, good color development sensitivity and image quality can be obtained.

  As the powdered cellulose produced by dry pulverization at room temperature as described above, a powdered cellulose product (manufactured by Nippon Paper Chemical Co., Ltd.) crowned with NP fiber, specifically NP fiber W-10MG2 (above, Nippon Paper Chemicals Co., Ltd. Manufactured). KC floc W-50, KC floc W-100G, KC floc W-200G, KC floc W- manufactured by acid hydrolysis of wood pulp and non-wood pulp, followed by filtration, washing with water, dehydration and drying Powdered cellulose obtained by dry pulverizing a powdered cellulose product (manufactured by Nippon Paper Chemical Co., Ltd.) bearing KC floc such as 300G and KC floc W-400G can be used. Furthermore, you may use the equivalent product of the powdered cellulose manufactured by the same dry-type grinding | pulverization as these.

Such powdered cellulose that can be used in the present invention has the following physical properties.
The average particle diameter is 5 μm to 30 μm, preferably 5.5 μm to 15 μm. The average particle diameter is measured by a laser diffraction / scattering method. When this average particle size is increased, the sealability is improved, but there is a tendency that the color development sensitivity and image quality when printed by a thermal printer tend to be low, and when the average particle size is small, there is a gap between the cellulose fibers constituting the powdered cellulose. Since it is crushed, a sufficient sealability cannot be obtained. Moreover, when processing the dried pulp like this invention under high pressure, it is technically difficult to make the average particle diameter less than 5 micrometers.
The oil absorption is 100 to 300 ml / 100 g. This oil absorption is measured according to JIS K-5101.
The density is 0.3 to 0.6 g / cm ³ . This density means what was measured according to JIS K-5101.
The saturated water absorption is 1.5 to 4.0 cm ³ / g. The saturated water absorption is measured according to JIS L-1907.
The whiteness is 75% or more. The whiteness is measured according to JIS P8148.

  In the present invention, this powdered cellulose can be used alone or in combination with various pigments in the coating layer provided on the support. In addition, when using this powdered cellulose together with a pigment, it is desirable to contain 20 parts or more of powdered cellulose by solid content with respect to 100 parts by weight of the total amount of powdered cellulose and pigment.

  In the present invention, the layer containing powdered cellulose provided on the support has a water-soluble polymer such as starch, polyvinyl alcohol, methylcellulose, and carboxymethylcellulose as a binder, a styrene / butadiene copolymer, and an acrylic acid copolymer. It is necessary to contain a synthetic resin emulsion such as coalescence, and when it is contained in the protective layer, the content of powdered cellulose (or further added pigment) and binder is powdered cellulose (or further added pigment) The binder is about 30 to 300 parts by weight with respect to 100 parts by weight, and the content of the powdered cellulose is 10 to 80 parts by weight, preferably 20 to 100 parts by weight with respect to the total solid content of the protective layer. 50 parts by weight, more preferably about 30 to 45 parts by weight, when contained in the heat-sensitive recording layer The content of powdered cellulose is about 1 to 20 parts by weight with respect to 100 parts by weight of the total solid content of the heat-sensitive recording layer, and when contained in the undercoat layer, the content of powdered cellulose with respect to the total solid content of the undercoat layer Is preferably about 1 to 90 parts by weight.

  For example, various water-soluble polymers (various polyvinyl alcohols, various starches), various water-soluble polymers and various cross-linking agents, synthetic resins such as acrylic and SBR, and the like are formed on the outermost layer of the heat-sensitive recording material of the present invention, particularly the protective layer. Inclusion of a resin and various cross-linking agents is desirable from the viewpoint of storage stability and water resistance of the image area and blank paper area, and in particular, carboxyl-modified polyvinyl alcohol, epichlorohydrin resin, and polyamine / amide resin are included. This is desirable from the viewpoint of water resistance and printing runnability.

  The carboxyl-modified polyvinyl alcohol is a reaction product of polyvinyl alcohol and a polycarboxylic acid such as fumaric acid, phthalic anhydride, melittic anhydride, itaconic anhydride, or an esterified product of these reactants, and further vinyl acetate and maleic acid. And saponified products of copolymers with ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, crotonic acid, acrylic acid and methacrylic acid. Specifically, for example, the production method exemplified in Example 1 or 4 of JP-A-53-91995 can be mentioned. Moreover, it is preferable that the saponification degree of carboxyl modified polyvinyl alcohol is 72-100 mol%, and a polymerization degree is 500-2400, More preferably, it is 1000-2000.

Specific examples of the epichlorohydrin-based resin include polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and the like, which can be used alone or in combination. Moreover, as an amine which exists in the principal chain of an epichlorohydrin-type resin, the thing from a primary to a quaternary can be used, and there is no restriction | limiting in particular. Further, the degree of cationization and the molecular weight preferably have a cationization degree of 5 meq / g · Solid (measured value at pH 7) and a molecular weight of 500,000 or more because of good water resistance. Specific examples are Sumire Resin 650 (30), Sumire Resin 675A, Sumire Resin 6615 (manufactured by Sumitomo Chemical Co., Ltd.), WS4002, WS4020, WS4024, WS4030, WS4046, WS4010, CP8970 (above, Starlight PMC) Manufactured).
Polyamine / amide resins include polyamide urea resins, polyalkylene polyamine resins, polyalkylene polyamide resins, polyamine polyurea resins, modified polyamine resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, polyalkylene polyamine polyamide polys. Specific examples include urea resin, Sumire Resin 302 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin 712 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin 703 (Sumitomo Chemical). Company: Polyamine polyurea resin), Sumire Resin 636 (Sumitomo Chemical: polyamine polyurea resin), Sumire Resin SPI-100 (Sumitomo Chemical: modified polyamine resin), Sumire Resin SPI-102A Sumitomo Chemical Co., Ltd .: modified polyamine resin), Sumire Resin SPI-106N (Sumitomo Chemical Co., Ltd .: modified polyamide resin), Sumire Resin SPI-203 (50) (Sumitomo Chemical Co., Ltd.), Sumire Resin SPI-198 ( Sumitomo Chemical Co., Ltd.), Principal A-700 (manufactured by Asahi Kasei Co., Ltd.), Principal A-600 (manufactured by Asahi Kasei Co., Ltd.), PA6500, PA6504, PA6634, PA6638, PA6640, PA6664, PA6664, PA6654, PA6702, PA6704 (above, Starlight PMC: Polyalkylene polyamine polyamide polyurea resin), CP8994 (Starlight PMC: polyethyleneimine resin) and the like are not particularly limited, and these may be used alone or in combination of two or more. Is it a point of color development sensitivity? Polyamine resin (polyalkylene polyamine resins, polyamine polyurea type resins, modified polyamine resins, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea tree) be used preferably.

The content of the epichlorohydrin resin and the modified polyamine / amide resin used in the present invention is preferably 1 to 100 parts by weight, more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the carboxyl-modified polyvinyl alcohol. 50 parts by weight. If the content is too small, the crosslinking reaction becomes insufficient and good water resistance cannot be obtained. If the content is too large, there arises a problem in operability due to an increase in viscosity of the coating liquid or gelation.
When a protective layer containing carboxyl-modified polyvinyl alcohol, epichlorohydrin resin and polyamine / amide resin is provided, epichlorohydrin resin and / or carboxyl-modified polyvinyl alcohol is added to the heat-sensitive recording layer in contact with the protective layer. It is desirable to contain. By including the component contained in the protective layer, the adhesiveness between the heat-sensitive recording layer and the protective layer is improved, and the immersion water resistance is improved. The epichlorohydrin resin is preferably added in an amount of 0.2 to 5.0 parts by weight (dry weight) in the heat-sensitive recording layer. When the amount of the epichlorohydrin resin added increases, the stability of the paint decreases.

The heat-sensitive recording layer of the present invention contains a dye and a developer, and may optionally contain a sensitizer, a binder, a cross-linking agent, a stabilizer, a pigment, a lubricant, and the like as necessary in addition to the above powdered cellulose. .
As the dye, all known dyes in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used and are not particularly limited, but include triphenylmethane compounds, fluoran compounds, fluorene compounds, divinyl compounds, and the like. Is preferred. Specific examples of typical colorless or light-colored basic colorless dyes are shown below. These basic colorless dyes may be used alone or in combination of two or more.
<Triphenylmethane leuco dye>
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide (also known as malachite green lactone)
<Fluoran leuco dye>
3-diethylamino-6-methylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3-dibutylamino -6-methyl-fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3-dibutylamino- 7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3-n-dipentylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl- N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-chloro-7- Nirinofuruoran, 3-cyclohexylamino-6-chloro-fluoran <divinyl leuco dyes>
3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide, 3,3-bis- [2- (P-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ) Ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3,3-bis- [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2- Yl] -4,5,6,7-tetrachlorophthalide

<Others>
3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- ( 1-octyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 4-azaphthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,6-bis (diethylamino) fluorane-γ- (3′-nitro) anilinolactam, 3,6 -Bis (diethylamino) fluorane-γ- (4′-nitro) anilinolactam, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylamino) Phenyl) -ethenyl] -2,2-dinitrileethane, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2- β-naphthoylethane, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-diacetylethane, bis- [2, 2,2 ′, 2′-Tetrakis- (p-dimethylaminophenyl) -ethenyl] -methylmalonic acid dimethyl ester

  In the present invention, by including the diphenylsulfone derivative represented by the following formula (Formula 1) used as a developer in the heat-sensitive recording layer, excellent image portion plasticizer resistance, moisture heat resistance, and white paper portion heat resistance. Can be obtained.

（式中、Ｒ^３は、炭素数が１〜１２の直鎖又は分岐の飽和又は不飽和炭化水素を表し、Ｒ^４〜Ｒ^９は、それぞれ独立して、ハロゲン原子、炭素数が１〜１２のアルキル基若しくはアルケニル基を表し、ｐ、ｑ、ｒ、ｓ、ｔ及びｕはそれぞれ０〜４の整数を表し、ｏは０〜５の整数を表し、Ａは、それぞれ独立して、エーテル結合を有してもよい炭素数が１〜１２の直鎖若しくは分枝の飽和若しくは不飽和の炭化水素基を表す。）

(In the formula, R ³ represents a linear or branched saturated or unsaturated hydrocarbon having 1 to 12 carbon atoms, and R ^{4 to} R ⁹ are each independently a halogen atom and 1 to 12 carbon atoms. Wherein p, q, r, s, t and u each represents an integer of 0 to 4, o represents an integer of 0 to 5, and A independently represents an ether bond. Represents a straight-chain or branched saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms, which may have

Here, R ³ represents a linear or branched saturated or unsaturated hydrocarbon having 1 to 12, preferably 1 to 5, and more preferably 1 to 4 carbon atoms. As the saturated hydrocarbon group, for example, Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isoamyl and the like. The unsaturated hydrocarbon group preferably has 2 to 5 carbon atoms, and examples of the unsaturated hydrocarbon group include ethylene, 1-n-propylene, 2-n-propylene, isopropylene, and 1-n-butylene. , 2-n-butylene, 3-n-butylene and the like.

R ^{4 to} R ⁹ each independently represent a halogen atom, an alkyl group or an alkenyl group having 1 to 12 carbon atoms, and examples of the halogen atom include chlorine, bromine, fluorine, and iodine. Bromine is preferred.
The alkyl group of R ^{4 to} R ⁹ represents a linear or branched saturated hydrocarbon having 1 to 12 carbon atoms, and the saturated hydrocarbon group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms. is there. For example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, n-pentyl group, isopentyl group, neopentyl group, t-pentyl group, n-hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl group, etc. are mentioned.
The alkenyl group of R ^{4 to} R ⁹ represents a linear or branched unsaturated hydrocarbon having 2 to 12 carbon atoms. Of these, vinyl groups and allyl groups are preferred. For example, vinyl group, allyl group, isopropenyl group, 1-propenyl group, 2-butenyl group, 3-butenyl group, 1,3-butanedienyl group, 2-methyl-2-propenyl group, etc. are mentioned, among them vinyl group An allyl group is preferred.

p, q, r, s, t and u each represent an integer of 0 to 4, preferably 0 to 2, and more preferably 0. However, when p, q, r, s, t, and u are 2 to ⁴ , R ^{4 to} R ⁹ may be the same or different, and the same is preferable.

A each independently represents a straight chain or branched saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms which may have an ether bond, but has a straight chain ether bond. Saturated hydrocarbons that may be present are preferred, and saturated hydrocarbons having no linear ether bond are more preferred.
As a saturated hydrocarbon group of A, a C1-C12 linear or branched saturated hydrocarbon is mentioned, A C2-C6 hydrocarbon group is preferable and C3-C4 is still more preferable.
Specific examples of saturated hydrocarbon groups include methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, undecamethylene, Dodecamethylene group, methylmethylene group, dimethylmethylene group, methylethylene group, methyleneethylene group, ethylethylene group, 1,2-dimethylethylene group, 1-methyltrimethylene group, 1-methyltetramethylene group, 1,3- Examples thereof include dimethyltrimethylene group and 1-ethyl-4-methyl-tetramethylene group. Among them, saturated hydrocarbons having 2 to 6 carbon atoms such as ethylene group, trimethylene group, tetramethylene group, pentamethylene group and hexamethylene group. Groups are preferred.
Examples of the unsaturated hydrocarbon group for A include linear or branched unsaturated hydrocarbons having 1 to 12 carbon atoms, preferably 2 to 6 hydrocarbon groups, and more preferably 2 to 4 carbon atoms. . Specific examples of the unsaturated hydrocarbon group include a vinylene group, an ethynylene group, a propenylene group, a 2-butenylene group, a 2-butynylene group, and a 1-vinylethylene group. Among them, a propenylene group, a 2-butenylene group, etc. Aromatic hydrocarbon groups are preferred.
Examples of the hydrocarbon group having an ether bond include an ethyleneoxyethylene group, a tetramethyleneoxytetramethylene group, an ethyleneoxyethyleneoxyethylene group, an ethyleneoxymethyleneoxyethylene group, and a 1,3-dioxane-5,5-bismethylene group. Among them, ethyleneoxyethylene group and ethyleneoxyethyleneoxyethylene group are preferable.

Although o represents the integer of 0-5, Preferably it is 0-2, More preferably, it is 0.
The diphenylsulfone derivative may be a compound having a specific o in the general formula (Chemical Formula 1), or may be a mixture of any ratio of compounds having different o in the general formula (Chemical Formula 1).

Examples of the diphenylsulfone derivative of the general formula (Formula 1) include, but are not limited to, the following compounds.
1- [4- (4-hydroxyphenylsulfonyl) phenoxy] -2- [4- (4-isopropoxyphenylsulfonyl) phenoxy] ethane, 1- [4- (4-hydroxyphenylsulfonyl) phenoxy] -3- [ 4- (4-Isopropoxyphenylsulfonyl) phenoxy] propane, 1- [4- (4-hydroxyphenylsulfonyl) phenoxy] -4- [4- (4-isopropoxyphenylsulfonyl) phenoxy] butane, 1- [4 -(4-Hydroxyphenylsulfonyl) phenoxy] -5- [4- (4-isopropoxyphenylsulfonyl) phenoxy] pentane, 1- [4- (4-hydroxyphenylsulfonyl) phenoxy] -6- [4- (4 -Isopropoxyphenylsulfonyl) phenoxy] hexane, 1- [4- 4-hydroxyphenylsulfonyl) phenoxy] -7- [4- (4-isopropoxyphenylsulfonyl) phenoxy] heptane, 1- [4- (4-hydroxyphenylsulfonyl) phenoxy] -8- [4- (4-iso Propoxyphenylsulfonyl) phenoxy] octane, 4- (4- [4- (4-hydroxyphenylsulfonyl) phenoxy] butoxy) -4 ′-(4- [4- (4-methoxyphenylsulfonyl) phenoxy] butoxy) diphenylsulfone 4- (4- (2- (4- (4- (2- (4- (4- (2- (4- (4-methoxyphenylsulfonyl) phenoxy) butoxy) phenylsulfonyl) phenoxy) butoxy) phenylsulfonyl) ) Phenoxy) butoxy) phenylsulfonyl) phenol and the like. Among these, 1- (4- (4-hydroxyphenylsulfonyl) phenoxy) -4- (4- (4-isopropoxyphenylsulfonyl) phenoxy) butane is preferable from the viewpoint of the balance between color development sensitivity and storage stability.

  In the present invention, it is desirable from the viewpoint of color development sensitivity that the heat-sensitive color developing layer is used in combination with the above-mentioned diphenylsulfone derivative represented by the general formula (Formula 1) and another developer as a color developer. As the developer that can be used in combination with the diphenylsulfone derivative represented by the formula 1), those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used. For example, activated clay, attapulgite Inorganic acidic substances such as colloidal silica and aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methyl Pentane, 4,4′-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4 ′ Dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4′-n-propoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone 4-hydroxy-4′-methyldiphenylsulfone, 4-hydroxyphenyl-4′-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4′-methylphenylsulfone, aminobenzene described in JP-A-8-59603 Sulfonamide derivatives, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, bis (p-hydroxyphenyl) Methyl acetate, , 1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α -(4'-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2'-thiobis (3-tert-octylphenol), 2,2'-thiobis (4-tert- Octylphenol), phenolic compounds such as diphenylsulfone cross-linking compounds described in International Publication WO 97/16420, phenolic compounds described in International Publication WO 02/081229 or JP-A No. 2002-301873, international publication WO 02/098774 or WO 03 / Phenol novolak-type condensation composition described in No. 029017, International Publication WO00 / 4058 or JP-A 2000-143611, urea urethane compounds, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, bis [4- (n- Octyloxycarbonylamino) zinc salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- ( 2-p-methoxyphenoxyethoxy) cumyl] aromatic carboxylic acids of salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, In addition, antipyrine complexes of zinc thiocyanate, terephthalaldehyde acid and other aromatics. Composite zinc salt of family carboxylic acid. These developers can be used alone or in combination of two or more. In addition, a metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A-10-258577 can also be contained. These developers may be used alone or in combination of two or more.

  In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol), 2,2 is used as a stabilizer exhibiting the oil resistance effect of the recorded image and the like within a range not impairing the effects of the present invention. '-Di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1 , 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane can be used. These stabilizers may be used alone or in combination of two or more.

  A conventionally well-known sensitizer can be used as a sensitizer used by this invention. Examples of such sensitizers include fatty acid amides such as stearamide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-di- (3-methylphenoxy) ethane, p-benzylbiphenyl, β- Benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, di (p-methylbenzyl) oxalate, Dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis -(Phenyl ether), 4- (m-methyl) Ruphenoxymethyl) biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3-methylphenoxy) ethylene, bis [2- (4-methoxy- Phenoxy) ethyl] ether, methyl p-nitrobenzoate, and phenyl p-toluenesulfonate are not particularly limited, and may be used alone or in combination of two or more. . In the present invention, among these sensitizers, it is desirable to use a sensitizer having a melting point of 100 to 120 ° C., specifically oxalic acid (bis-p-methylbenzyl).

  In the thermosensitive recording material of the present invention, as a binder, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, Olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer Coalescers and cells such as ethyl cellulose and acetyl cellulose. Loin derivatives, casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrose and copolymers thereof, Examples thereof include polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and coumaro resin. These polymer substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, hydrocarbons, etc., and are used in the state of being emulsified or pasted in water or other media to achieve the required quality. It can also be used in combination.

Examples of the crosslinking agent used in the present invention include glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, sodium persulfate, chloride chloride Examples include ferric iron, magnesium chloride, borax, boric acid, alum, ammonium chloride and the like.
Examples of the pigment used in the present invention include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide.
Examples of the lubricant used in the present invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.
In addition, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

Binders, cross-linking agents, pigments, etc. were provided as needed, including not only layers containing powdered cellulose but also protective layers, heat-sensitive recording layers, undercoat layers, etc., as long as the effects of the present invention were not impaired. It can also be used for each coating layer.
The type and amount of the dye, developer, and other various components used in the heat-sensitive recording layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. 0.5 to 10 parts developer, 0.5 to 20 parts pigment (including powdered cellulose), 0.5 to 10 parts sensitizer, and 0.01 to 10 parts by weight stabilizer. About 0.01 to 10 parts by weight of other components are used.

  Dye, developer, and materials to be added as necessary are finely pulverized to a particle size of several microns or less by a pulverizer such as a ball mill, attritor or sand glider or an appropriate emulsifying device. Various additive materials are added to form a coating solution. As a solvent used in the coating liquid, water or alcohol can be used, and the solid content is about 20 to 40% by weight.

By applying the coating liquid having the above composition to any support such as paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, non-woven fabric, etc., the desired thermal recording material can be obtained. Moreover, you may use the composite sheet which combined these as a support body.
Dye, developer, and materials to be added as necessary are finely divided to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, a sand glider, or an appropriate emulsifier, and depending on the binder and purpose. Various additive materials are added to form a coating solution. Water or alcohol can be used as the solvent used in the paint, and its solid content is about 20 to 40%. Further, the means for applying is not particularly limited, and can be applied according to well-known conventional techniques. For example, various coaters such as an air knife coater, rod blade coater, vent blade coater, bevel blade coater, roll coater, curtain coater, etc. The provided off-machine coating machine or on-machine coating machine is appropriately selected and used. The coating amount of the heat-sensitive recording layer is not particularly limited and is usually in the range of ² to 12 g / m ^{2 by} dry weight. Further, the coating amount of the protective layer provided on the thermosensitive recording layer is not particularly limited, and is usually in the range of 1 to 5 g / m ² .

  The heat-sensitive recording material of the present invention can further be provided with an under layer comprising a filler and a binder between the support and the heat-sensitive recording material for the purpose of increasing the color development sensitivity. It is also possible to correct the curl by providing a backcoat layer on the opposite side of the support from the thermosensitive recording layer. Further, various known techniques in the heat-sensitive recording material field, such as applying a smoothing process such as supercalendering after coating each layer, can be added as necessary.

  The following examples illustrate the invention but are not intended to limit the invention. In the description, parts and% indicate parts by weight and% by weight, respectively. The average particle size was measured by a laser diffraction / scattering method (Malvern, apparatus name: Mastersizer S). The oil absorption and the apparent specific volume were JIS K-5101, the saturated water absorption was JIS L-1907, the whiteness. Was measured according to JIS P8148.

Production Example 1
In this production example, powdered cellulose was produced by dry grinding.
10 g of wood pulp (conifer kraft pulp) was mixed with 500 ml of 1N sulfuric acid and hydrolyzed by heating in a water bath at 100 ° C. for 60 minutes. The pulp slurry was filtered with a 300 mesh filter cloth, and the residue was washed with 500 ml of 0.1N ammonia water and then sufficiently washed with tap water. The obtained acid-hydrolyzed cellulose was dried for 12 hours by an air dryer kept at 120 ° C. This was pulverized with a dry pulverizer (manufactured by Aisin Nanotechnology Co., Ltd., NanoJet Mizer NJ-300) at normal temperature, and the following pulverized cellulose was obtained by changing the pulverization time.
[Powdered cellulose 1] Average particle diameter: 5.5 μm, oil absorption: 170 ml / 100 g, apparent specific volume 0.50 g / cm ³ , whiteness 85%, saturated water absorption 1.9 cm ³ / g
[Powdered cellulose 2] Average particle diameter: 11 μm, oil absorption: 190 ml / 100 g, apparent specific volume 0.50 g / cm ³ , whiteness 84%, saturated water supply 2.2 cm ³ / g
[Powdered cellulose 3] Average particle diameter: 20 μm, oil absorption: 220 ml / 100 g, apparent specific volume 0.50 g / cm ³ , whiteness 84%, saturated water supply 2.5 cm ³ / g

Production Example 2
In this production example, powdered cellulose was produced by wet grinding.
Powdered cellulose (Nippon Paper Chemical Co., Ltd., KC Flock W100, average particle size: 50 μm) was dispersed in water to make a 10% slurry. 200 cc of this slurry was pulverized at room temperature for 2 hours using a 500 mL sand grinder (manufactured by Ashizawa Finetech Co., Ltd., 0.5 gm glass bead filling rate of 50%). Then, it dried for 12 hours with the 120 degreeC ventilation drying machine. As a result, fine cellulose (average particle size 6 μm, oil absorption: 90 ml / 100 g, apparent specific volume 0.20 g / cm ³ , whiteness 80%, saturated water absorption 1.3 cm ³ / g) was obtained.

  Each layer coating solution was prepared by stirring and dispersing various solutions, dispersions, or coating solutions of the following composition.

[Under layer paint adjustment]
Underlayer coating liquid Baked kaolin (Ansilex 90, manufactured by BASF) 90.0 parts Styrene-butadiene copolymer latex (solid content 50%) 10.0 parts Water 50.0 parts A mixture of the above composition is mixed and stirred. To prepare an under layer coating solution.

[Adjustment of heat-sensitive coloring layer paint]
The developer dispersion, the basic colorless dye dispersion, the sensitizer dispersion, and the stabilizer dispersion having the following composition were separately wet-ground with a sand grinder until the average particle size became 1 micron.

<A liquid (developer dispersion 1)>
1- (4- (4-hydroxyphenylsulfonyl) phenoxy) -4- (4- (4-isopropoxyphenylsulfonyl) phenoxy) butane (synthesized by the method described in JP-A-2003-212841: the following formula (Chemical Formula 2)) 6.0 parts

１８．８部
水 １１．２部
＜Ｂ液（顕色剤分散液２）＞
４−ヒドロキシ−４'−イソプロポキシジフェニルスルホン（エーピーアイコーポレーション社製、商品名：ＮＹＤＳ） ６．０部
カルボキシ変性ポリビニルアルコール（ＰＶＡ−ＫＬ３１８） １８．８部
水 １１．２部
＜Ｃ液（塩基性無色染料分散液）＞
３−ジブチルアミノ−６−メチル−７−アニリノフルオラン（山本化成社製、ＯＤＢ−２）
２．０部
カルボキシ変性ポリビニルアルコール（ＰＶＡ−ＫＬ３１８） ４．６部
水 ２．６部
＜Ｄ液（増感剤分散液）＞
シュウ酸ビスパラメチルベンジル（大日本インキ社製、ＨＳ３５２０） ６．０部
カルボキシ変性ポリビニルアルコール（ＰＶＡ−ＫＬ３１８） ２０．０部
水 １１．０部

18.8 parts water 11.2 parts <Liquid B (developer dispersion 2)>
4-hydroxy-4'-isopropoxydiphenyl sulfone (manufactured by API Corporation, trade name: NYDS) 6.0 parts carboxy-modified polyvinyl alcohol (PVA-KL318) 18.8 parts water 11.2 parts <C solution (base) Colorless dye dispersion)>
3-dibutylamino-6-methyl-7-anilinofluorane (Yamamoto Kasei Co., Ltd., ODB-2)
2.0 parts carboxy-modified polyvinyl alcohol (PVA-KL318) 4.6 parts water 2.6 parts <Liquid D (sensitizer dispersion)>
Bisparamethylbenzyl oxalate (Dainippon Ink Co., Ltd., HS3520) 6.0 parts Carboxy-modified polyvinyl alcohol (PVA-KL318) 20.0 parts Water 11.0 parts

Subsequently, the dispersion liquid was mixed at the following ratio to obtain a recording layer coating liquid.
<Recording layer coating solution 1>
Liquid A (22% developer dispersion 1) 25 parts Liquid B (22% developer dispersion 2) 25 parts Liquid C (30% basic colorless dye dispersion) 25 parts Liquid D (16% sensitizer) Dispersion) 50 parts Silica (Mizusawa Chemical Co., Ltd. Mizukasil P604, average particle size: 1.7 μm) 25% dispersion
4 parts Carboxy-modified polyvinyl alcohol (PVA-KL318) 40 parts <Recording layer coating solution 2>
Liquid A (22% developer dispersion 1) 25 parts Liquid B (22% developer dispersion 2) 25 parts Liquid C (30% basic colorless dye dispersion) 25 parts Liquid D (16% sensitizer) Dispersion) 50 parts Powdered cellulose 1 (prepared by the method of Production Example 1) 15% dispersion 7 parts Carboxy-modified polyvinyl alcohol (PVA-KL318) 40 parts

[Adjustment of protective coating]
The protective layer coating amount 1 to 6 was adjusted by mixing at the following ratio.
<Protective layer paint 1>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 100 parts Polyamide epichlorohydrin resin (manufactured by Seiko PMC, WS4020, solid content 25%, cationization degree: 2.7, molecular weight: 2.2 million, quaternary amine) 10 parts Modification Polyamide resin (Sumitomo Chemical Co., Ltd., Sumirez resin SPI-106N, solid content 45%)
3 parts Powdered cellulose 1 (prepared by the method of Production Example 1) 15% dispersion 200 parts Zinc stearate (manufactured by Chukyo Yushi Co., Ltd., Hydrin E-366, solid content 40%) 5 parts <Protective layer paint 2>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 10% solution 100 parts Polyamide epichlorohydrin resin (WS4020) 10 parts Modified polyamide resin (Smileds resin SPI-106N) 3 parts Powdered cellulose 3 (produced by the method of Production Example 1) 15% dispersion 200 parts zinc stearate (hydrin E-366) 5 parts <protective layer coating liquid 3>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 10% solution 100 parts Polyamide epichlorohydrin resin (WS4020) 10 parts Modified polyamide resin (Smireds resin SPI-106N) 3 parts Cellulose (Asahi Kasei Chemicals, Theolas cream FP-03 , Average particle size: 3 μm) 10% dispersion 300 parts zinc stearate (hydrin E-366) 5 parts

<Protective layer coating solution 4>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 10% solution 100 parts Polyamide epichlorohydrin resin (WS4020) 10 parts Modified polyamide resin (Smiledes resin SPI-106N) 3 parts Powdered cellulose (Nippon Paper Chemicals, KC Flock W100) , Average particle size: 50 μm, oil absorption: 200 ml / 100 g, apparent specific volume 0.25 g / cm 3, whiteness 84%, saturated water supply 2.8 cm 3 / g) 15% dispersion 200 parts zinc stearate (hydrin E- 366) 5 parts <Protective layer coating solution 5>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 10% solution 100 parts Polyamide epichlorohydrin resin (WS4020) 10 parts Modified polyamide resin (Smileds resin SPI-106N) 3 parts Dispersion of wet-pulverized cellulose obtained in Production Example 2 10% Liquid 300 parts Zinc stearate (Hydrin E-366) 5 parts <Protective layer coating liquid 6>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 10% solution 100 parts Polyamide epichlorohydrin resin (WS4020) 10 parts Modified polyamide resin (Smireds resin SPI-106N) 3 parts Silica (Mizusawa Chemical Co., Ltd., Mizukasil P603, average particle) Diameter: 2.2 μm) 25% dispersion
120 parts Zinc stearate (Hydrin E-366) 5 parts <Protective layer paint 7>
Carboxy-modified polyvinyl alcohol (PVA-KL318) 10% solution 100 parts Polyamide epichlorohydrin resin (WS4020) 10 parts Modified polyamide resin (Smileds resin SPI-106N) 3 parts Powdered cellulose 2 (prepared by the method of Production Example 1) 200 parts of 15% dispersion

[Back layer coating solution adjustment]
Aluminum hydroxide 50 parts Polyvinyl alcohol (manufactured by Kuraray Co., Ltd .: PVA117) 10% aqueous solution 500 parts Water 70 parts

[Example 1]
The under layer coating solution was coated on high-quality paper (basis weight: 47 g / m 2) with a Meyer bar so that the coating amount after drying was 7 g / m 2, and dried with a blow dryer (120 ° C., 1 minute). On this under paper, the recording layer coating solution 1 was coated with a Mayer bar so that the coating amount after drying was 4.5 g / m 2, and dried with a blow dryer (60 ° C., 2 minutes). On this coated paper, the protective layer coating solution 1 was coated with a Mayer bar so that the coating amount after drying was 2.5 g / m 2. Furthermore, on the back surface, the back layer coating material was applied with a Mayer bar so that the coating amount after drying was 1.5 g / m 2, and after drying with a blow dryer (60 ° C., 2 minutes), the smoothness was 200- A super calendar process was performed so as to be 500 seconds to obtain a heat-sensitive recording material.
[Example 2]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the protective layer coating solution 2 was used instead of the protective layer coating solution 1.
[Example 3]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the protective layer coating solution 7 was used instead of the protective layer coating solution 1.
[Example 4]
The same as in Example 1 except that the recording layer coating liquid B (second developer dispersion) was changed to 4-hydroxy-4′-n-propoxydiphenyl sulfone (trade name JKY146, manufactured by API Corporation). Thus, a heat-sensitive recording material was produced.
[Example 5]
Thermosensitive recording medium in the same manner as in Example 1 except that the recording layer coating liquid B (second developer dispersion) was changed to 2,4′dihydroxydiphenylsulfone (manufactured by Nikka Chemical Co., Ltd., trade name: 24 BPS). Was made.
[Example 6]
The under layer coating solution was coated on high-quality paper (basis weight: 47 g / m 2) with a Meyer bar so that the coating amount after drying was 7 g / m 2, and dried with a blow dryer (120 ° C., 1 minute). On this under paper, the recording layer coating liquid 2 was coated with a Mayer bar so that the coating amount after drying was 4.5 g / m 2, and dried with a blow dryer (60 ° C., 2 minutes). On the back side of this coated paper, the back layer coating was applied with a Mayer bar so that the coating amount after drying was 1.5 g / m 2, dried with a blow dryer (60 ° C., 2 minutes), and then smoothness Was subjected to supercalender treatment so that the time became 200 to 500 seconds to obtain a heat-sensitive recording material.

[Comparative Example 1]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the protective layer coating liquid 3 was used instead of the protective layer coating 1.
[Comparative Example 2]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the protective layer coating solution 4 was used instead of the protective layer coating 1.
[Comparative Example 3]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the protective layer coating solution 5 was used instead of the protective layer coating 1.
[Comparative Example 4]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the protective layer coating liquid 6 was used instead of the protective layer coating 1.
[Comparative Example 5]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the liquid A of Example 1 was not blended and the blending ratio of the liquid B was 50 parts.
[Comparative Example 6]
A thermosensitive recording material was produced in the same manner as in Example 4 except that the powdered cellulose of Example 6 was changed to silica (Mizusawa Chemical Co., Ltd., Mizukasil P603, average particle size: 2.2 μm).

The following evaluation was performed on the heat-sensitive recording material obtained above.
<Recording sensitivity>
About the produced thermal recording body, it printed by the applied energy 0.27mJ / dot using the thermal recording paper printing test machine (The Okura Electric TH-PMD, the Kyocera thermal head was mounted | worn). The recording density of the recording part was measured and evaluated with a Macbeth densitometer (RD-914).
<Image quality>
The solid print portion was visually evaluated.
A: There are almost no white spots or white blurs in the printed part. ○: There are slight white spots or white blurs in the printed part. X: There are white spots or white blurs in the printed part.
The coated surface was visually evaluated for rubbing color development with steel wool to which a load of 1000 g / cm 2 was applied.
◎: Little color developed ○: Slight color developed ×: Dark color developed <Sealability>
The produced heat-sensitive recording medium was printed with a killer whale stamp, wiped with tissue paper after 5 seconds, and visually evaluated.
○: Slightly fading but characters remain clearly ×: Fading is not possible

<Preservability>
A checkerboard pattern was printed at an applied energy of 0.35 mJ / dot using the above-mentioned thermal recording paper printing tester, and the following storability was evaluated for the colored portion.
(Residual rate of plasticizer resistance)
A sample of vinyl chloride wrap (Mitsui Toatsu High Wrap KMA) wrapped around a paper tube and pasted on the sample, and then wrapped in three layers of vinyl wrap on top of that before and after standing at 23 ° C for 4 hours The partial density was measured, and the residual ratio (= color density after test / color density before test × 100 (%)) was calculated. The higher the residual ratio, the better the plasticizer resistance.
◎: Residual rate is 90% or more ○: Residual rate is 85% or more and less than 90% △: Residual rate is 75% or more and less than 85% ×: Residual rate is less than 75% (moisture and heat resistance residual rate)
The density of the colored portion before and after being left for 24 hours in an environment of 50 ° C. and 90% was measured, and the residual ratio was calculated. The higher the residual rate, the better the heat and moisture resistance.
○: Residual rate is 90% or more Δ: Residual rate is 75% or more and less than 90% ×: Residual rate is less than 75% (heat resistance)
After being left in a 90 ° C. environment for 24 hours, the color density of the white paper portion was measured. The smaller the value, the better the heat resistance.
◎: Less than 0.20 residual rate is 90% or more ○: Less than 0.3 △: Less than 0.8 ×: 0.8 or more

  The evaluation results are shown in the table below.

As shown in the table, a diphenylsulfone derivative containing powdered cellulose having an average particle size of 5 to 30 μm produced by dry pulverization on the surface layer and represented by the general formula (Chemical Formula 1) as an electron-accepting developer The heat-sensitive recording materials of Examples 1 to 6 produced using the above are excellent in sensitivity, image quality, scratchability, imprintability and storage properties, but Comparative Example 1 in which the average particle size of the powdered cellulose is fine is rubbing and imprintability. However, Comparative Example 2 having a large average particle size was inferior in sensitivity and image quality. Further, Comparative Example 3 having a different method for producing powdered cellulose could not obtain the printing suitability, and Comparative Example 4 using silica instead of powdered cellulose was inferior in sensitivity and scratching. In Comparative Example 5 in which the developer of the general formula (Chemical Formula 1) was not used, the storage stability was inferior.

Claims (2)

A heat-sensitive recording layer provided with a heat-sensitive recording layer containing at least a colorless or light-colored basic leuco dye and an electron-accepting developer as a coating layer on a support, the heat-sensitive recording layer and other optional At least the outermost layer of the coating layer provided is made from wood pulp or non-wood pulp, and is produced by dry pulverization at room temperature, containing powdered cellulose having an average particle size of 5 μm to 30 μm, and the heat sensitive The recording layer has the following general formula as an electron-accepting developer.

(In the formula, R ³ represents a linear or branched saturated or unsaturated hydrocarbon having 1 to 12 carbon atoms, and R ^{4 to} R ⁹ are each independently a halogen atom and 1 to 12 carbon atoms. Wherein p, q, r, s, t and u each represents an integer of 0 to 4, o represents an integer of 0 to 5, and A independently represents an ether bond. A linear or branched saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms which may have a diphenylsulfone derivative represented by formula (1).
The thermosensitive recording material according to claim 1, further comprising a protective layer on the thermosensitive recording layer, wherein the outermost layer is the protective layer.