JP2006175852A - Heat-sensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sensitive recording medium which has a high coloring sensitivity, and is excellent in the preservation stability of recorded images. <P>SOLUTION: In this heat-sensitive recording medium, in an organic color developer for the heat-sensitive coloring layer, a compound which is represented by general formula (1) or general formula (2), and Bisphenol C are contained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a colorless or light-colored basic dye and an organic developer.

  In general, a thermosensitive recording medium having a thermosensitive coloring layer composed mainly of a colorless or light-colored basic dye (or precursor) and an organic developer that reacts with the dye (or precursor) when heated to develop a color. Widely put into practical use (for example, Patent Document 1). Recording of an image (information) on such a heat-sensitive recording medium is usually performed by heating a portion to be an image of the heat-sensitive color developing layer with a thermal head. Such a thermal recording method (method) has no noise during recording (less), no need for development and fixing, and is maintenance-free compared to other known recording methods (methods). It is widely used for information (image) recording in the fields of facsimiles, computers, and various measuring instruments because it is inexpensive and compact, and the recorded image is relatively clear. And the thermal recording medium that is the recording material is not only used as a recording medium for information (image) only for visually recognizing information (image) in a facsimile, a computer, various measuring devices, etc. By attaching to various articles, it is increasingly used for labels for adding various designs and information in addition to desired identification and display relating to the articles. However, with the recent diversification and higher performance of thermal recording apparatuses, the required quality for thermal recording media that are recording materials has become higher. For example, with regard to color development sensitivity, as recording apparatuses are miniaturized and speeded up, the ability to obtain a clear color image with a high density even with minute heat energy is required.

Conventionally, various compounds having a phenolic hydroxyl group have been proposed as a developer to be contained in the thermosensitive coloring layer of the thermosensitive recording material (Patent Documents 1 to 5, etc.). Of these, bisphenol compounds typified by 2,2′-bis (4-hydroxyphenyl) propane (bisphenol A) are generally used, and 4,4′- is particularly desirable for high storage stability and high whiteness. Diphenylsulfone compounds derived from diphenylsulfone (Patent Documents 6 to 9 and the like) are put into practical use alone or in combination of several kinds (Patent Document 10). However, the heat-sensitive recording material produced using such a conventionally proposed developer has, for example, low thermal responsiveness, a sufficient color density cannot be obtained during high-speed recording, and color unevenness occurs. The density of the color image changes over time after recording, discoloration occurs during storage, heat resistant background deteriorates, surface precipitation of white powder called so-called dusting occurs, and reprintability decreases Have problems. In addition, a method of increasing color sensitivity by using an appropriate sensitizer together with a dye and a developer (Patent Documents 11 and 12) and a method of improving storage stability by using an appropriate image stabilizer (Patent Document) 13 and 14) have also been proposed. However, even if these methods are used, a heat-sensitive recording material having satisfactory image stability while satisfying recent high sensitivity requirements has not been obtained.
Japanese Examined Patent Publication No. 45-14039 Japanese Patent Publication No. 40-9309 Japanese Patent Publication No.43-4160 Japanese Patent Publication No.51-29830 JP 56-144193 A Japanese Patent Publication No.7-12751 Japanese Patent Laid-Open No. 10-100500 Japanese Patent Laid-Open No. 10-278431 Japanese Patent Laid-Open No. 11-60976 Japanese Patent Laid-Open No. 1-232095 JP 58-132591 A Japanese Patent Publication No. 7-45266 JP 58-136493 A Japanese Examined Patent Publication No. 7-41744

In view of the above circumstances, the problem to be solved by the present invention is that it has a high color development sensitivity, does not develop the background color, does not easily cause a decrease in density or disappearance of the color image with respect to heat or humidity, and It is an object to provide a heat-sensitive recording material that hardly causes unnecessary color development.
In addition, it has a high color development sensitivity, does not develop the background color, is less likely to cause a decrease in density or disappearance of the color image even when contacted with heat, humidity, and plasticizer, and it is also difficult to cause unnecessary color development on the background. It is to provide a thermal recording material.

  As a result of diligent research to solve the above problems, the present inventors have found that as an organic developer used with a basic dye, bisphenol sulfone or a derivative thereof, or a specific diphenyl sulfone cross-linked compound, bisphenol C and In combination with an organic sensitizer to form a thermosensitive color-developing layer, not only high color sensitivity can be obtained, but also the heat and humidity resistance of the recorded image after color development is improved, resulting in high heat and high humidity. The present inventors have found that the recorded image is hardly deteriorated even when placed in the above environment, and that the recorded image is hardly deteriorated even when contacted with the plasticizer, and the present invention has been completed.

That is, the present invention is (1) a thermosensitive recording medium provided with a thermosensitive coloring layer containing a colorless or pale basic dye, an organic developer and an organic sensitizer as main components on a support, The thermosensitive coloring layer as an organic developer is represented by the general formula (1):

[Wherein, R ₁ represents a hydrogen atom, a lower alkyl group (excluding an isopropyl group) or an aryl group. R ₂ represents a hydrogen atom, a lower alkyl group or an alkenyl group, and m R _{2 s} may be the same or different from each other, and m represents an integer of 0 to 4. And a bisphenol C, a heat-sensitive recording material,
(2) The heat-sensitive recording material as described in (1) above, wherein R ₁ in the general formula (1) is an n-propyl group,
(3) A thermosensitive recording medium comprising a thermosensitive color-developing layer containing a colorless or light basic dye, an organic developer and an organic sensitizer as main components on a support, wherein the thermosensitive color-developing layer comprises: As an organic developer, general formula (2):

 [Wherein, X and Y may be the same as or different from each other, and each represents a linear or branched saturated or unsaturated divalent hydrocarbon group having 1 to 12 carbon atoms which may have an ether bond. Or the formula:

(Wherein R ₄ represents a methylene group or an ethylene group, and T represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). R ₃ represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, p R _{3 s} may be the same as or different from each other, and p represents an integer of 0 to 4. n shows the integer of 0-2. And a bisphenol C, and (4) a colorless or pale basic dye and an organic developer on the support. A heat-sensitive recording material provided with a heat-sensitive color developing layer containing an organic sensitizer as a main component, wherein the heat-sensitive color developing layer is used as an organic developer.

[Wherein, R ₁ represents a hydrogen atom, a lower alkyl group (excluding an isopropyl group) or an aryl group. R ₂ represents a hydrogen atom, a lower alkyl group or an alkenyl group, and m R _{2 s} may be the same or different from each other, and m represents an integer of 0 to 4. And a compound represented by the general formula (2):

[Wherein, X and Y may be the same as or different from each other, and each represents a linear or branched saturated or unsaturated divalent hydrocarbon group having 1 to 12 carbon atoms which may have an ether bond. Or the formula:

(Wherein R ₄ represents a methylene group or an ethylene group, and T represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). R ₃ represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, p R _{3 s} may be the same as or different from each other, and p represents an integer of 0 to 4. n shows the integer of 0-2. And a bisphenol C, and a heat-sensitive recording material characterized by comprising:

  According to the heat-sensitive recording material of the present invention, a high color development sensitivity is exhibited without causing a problem that the ground color develops, and the obtained clear and high density color image is a high heat (high temperature) or high humidity. Even when placed in an environment, it maintains a high-density image without coloring the background. Moreover, even if it contacts with a plasticizer, the fall of a color development image can be suppressed at a high level. Therefore, when the heat-sensitive recording material of the present invention is used, a clear and high-density recorded image can be obtained, and further, deterioration due to the influence of the external environment such as heat and humidity of the recorded image is suppressed. You can get things.

Hereinafter, the present invention will be described in more detail.
The heat-sensitive recording material of the present invention is a heat-sensitive recording material provided with a heat-sensitive color-developing layer containing a colorless to light-colored basic dye, an organic developer, and an organic sensitizer as main components on a support. As the agent, a compound represented by the general formula (1) (hereinafter also referred to as “compound of the formula (1)”) or a diphenylsulfone cross-linked compound represented by the general formula (2) (hereinafter, It is characterized by containing “the compound represented by the general formula (2)” or “the compound of the formula (2)” together with bisphenol C.

The compound of the formula (1) used in the present invention is bisphenol sulfone or a derivative thereof. In the formula, when R ₁ and R ₂ are hydrogen atoms, 4,4′-bisphenol sulfone, 2,4′-bisphenol Indicates sulfone.
In R ₁ , the lower alkyl group preferably has 1 to 5 (more preferably 1 to 4) carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, t-butyl, t-amyl group, and the like. It is done. Examples of the aryl group include phenyl, tolyl, and naphthyl groups. Among these, R ₁ is preferably a hydrogen atom or a lower alkyl group (excluding an isopropyl group), particularly preferably a hydrogen atom or an n-propyl group. When a compound of the formula (1) in which R ₁ is a hydrogen atom or n-propyl can be used, heat resistant background color development can be suppressed at an extremely high level.

In R ₂ , the lower alkyl group preferably has 1 to 5 (more preferably 1 to 4) carbon atoms, and examples thereof include methyl, ethyl, n-propyl, n-butyl, t-butyl, and t-amyl. Groups and the like. The alkenyl group preferably has 2 to 5 carbon atoms (more preferably 2 to 4), and examples thereof include vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, and 3-butenyl. Among these, R ₂ is preferably a hydrogen atom or an alkenyl group, particularly preferably a hydrogen atom or an allyl group. Further, m R _{2 s} may be the same or different but are preferably the same. When m is 1 to 4, it is preferable that R ₂ is bonded to the o-position of the hydroxyl group of the phenol group.

  Preferable specific examples of the compound of the formula (1) include, for example, 4,4′-bisphenolsulfone, 2,4′-bisphenolsulfone, 4-hydroxy-4′-n-propoxydiphenylsulfone, 4-hydroxy-4 ′. -Butyloxydiphenyl sulfone, 3,3′-diallyl-4,4′-dihydroxydiphenyl sulfone, etc.

  In the diphenylsulfone bridged compound of the formula (2) used in the present invention, X and Y each have a linear or branched saturated or unsaturated carbon number of 1 which may have an ether bond. The divalent hydrocarbon group of -12 is shown, Preferably it is C2-C4. Specific examples of the saturated hydrocarbon group include, for example, methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, undecamethylene, dodecamethylene, methylmethylene, dimethylmethylene, and methylethylene. 1,2-dimethylethylene, 1-methyltrimethylene, 1-methyltetramethylene, 1,3-dimethyltrimethylene, 1-ethyl-4-methyl-tetramethylene group, etc., and unsaturated hydrocarbons Specific examples of the group include vinylene, propenylene, 2-butenylene, ethynylene, 2-butynylene, 1-vinylethylene group and the like. Examples of the hydrocarbon group that may have an ether bond include ethyleneoxyethylene, tetramethyleneoxytetramethylene, ethyleneoxyethyleneoxyethylene, ethyleneoxymethyleneoxyethylene, 1,3-dioxane-5,5. -Bismethylene etc. are mentioned. Also the formula:

In the divalent group represented by the above, the alkyl group having 1 to 4 carbon atoms represented by T may be linear or branched, and examples thereof include methyl, ethyl, n-propyl, n-butyl, and t-butyl groups. . Specific examples of the divalent group include, for example, 1,2-xylyl, 1,3-xylyl, 1,4-xylyl, 2-hydroxytrimethylene, 2-hydroxy-2-methyltrimethylene, 2-hydroxy- Examples include 2-ethyltrimethylene, 2-hydroxy-2-propyltrimethylene, 2-hydroxy-2-isopropyltrimethylene, 2-hydroxy-2-butyltrimethylene group and the like.

Moreover, in R < ₃ > in Formula (2), when it is a C1-C6 alkyl group, it may be linear or branched, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, s- Examples include butyl, t-butyl, n-pentyl, isopentyl, neopentyl, t-pentyl, n-hexyl, isohexyl, 1-methylpentyl and 2-methylpentyl groups. The number of carbon atoms is preferably 2 to 4, and examples thereof include vinyl, allyl, isopropenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl, 2-methyl-2-propenyl group and the like. Examples of the halogen atom include chlorine, bromine, fluorine, iodine and the like.

Moreover, in Formula (2), n shows the integer of 0-2 and p shows the integer of 0-4. When p is 2 to 4, p R ₃ may be the same or different, but the same is preferable.
As the substituent of the diphenyl sulfone of formula (2), R ₃ is a hydrogen atom, or all of R ₃ the same, that is in the same position preferred.

  A preferred example of the diphenylsulfone cross-linking compound represented by the general formula (2) is, for example, a developer composition containing 2,2′-bis [4- (4-hydroxyphenylsulfone) phenoxy] diphenyl ether. (Nippon Soda Co., Ltd. product: D-90). In addition, when D-90 is used alone as the developer, sensitivity may be insufficient. However, in the present invention in which D-90 and bisphenol C are used in combination as the developer, in the plasticizer resistance test. A high color sensitivity can be obtained while suppressing a decrease in image density at a very high level.

  In the present invention, the bisphenol C used as a developer together with the compound represented by the general formula (1) or the compound represented by the general formula (2) is the compound represented by the general formula (1) or the general formula (2). It is preferably used at a ratio of 0.01 to 10.0 parts by weight per 1 part by weight of the compound represented by the formula (1), more preferably 0.1 to 5.0 parts by weight. It is particularly preferable to use it in a proportion of 0.0 part by weight. That is, when the amount of bisphenol C is less than 0.01 part by weight with respect to 1 part by weight of the compound represented by the general formula (1) or the compound represented by the general formula (2), it is difficult to obtain high color development sensitivity. If the amount exceeds 10.0 parts by weight, the resistance to heat and humidity of the recorded image after color development and contact with the plasticizer tends to decrease.

  In the present invention, bisphenol C is used as the organic developer together with the compound represented by the general formula (1) or (2). However, the sensitivity, image stability, and the like are compared with the combined system using the bisphenol C. However, in consideration of cost, inexpensive bisphenol A may be used instead of bisphenol C. Moreover, you may use together 3 types of the compound represented by General formula (1), the compound represented by General formula (2), and bisphenol C as an organic color developer. In addition, when using both the compound represented by General formula (1) and the compound represented by General formula (2) as an organic color developer, components other than these compounds which comprise a thermosensitive coloring layer are both of these. It is determined on the basis of the total amount. For example, the blending amount of the above bisphenol C is used within the above numerical range per 1 part by weight of the total amount of the compound represented by the general formula (1) and the compound represented by the general formula (2).

  As the colorless to light-colored basic dye used in the present invention, known basic dyes that are conventionally known as colorless to light-colored basic dyes in the field of heat-sensitive recording materials and pressure-sensitive recording materials can be used without limitation. However, a leuco coloring type is preferable, and among them, a triphenylmethane compound, a fluoran compound, a fluorene compound, a divinyl compound, and the like are particularly preferable, and a fluoran compound is particularly preferable. In the present invention, the basic dye may be used alone or in combination of two or more. Specific examples of typical basic dyes are shown below.

<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-diethylamino-6-methyl -7-chlorofluorane 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane 3-diethylamino-6-methyl-7- (o-chloroanilino) fluorane 3-diethylamino-6-methyl- 7- (p-chloroanilino) fluorane 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluorane 3-diethylamino-6-methyl-7- (m-methylanilino) fluorane 3-diethylamino-6-methyl- 7-n-octylanilinofluorane 3-diethylamino- 6-methyl-7-n-octylaminofluorane 3-diethylamino-6-methyl-7-benzylanilinofluorane 3-diethylamino-6-methyl-7-dibenzylanilinofluorane 3-diethylamino-6-chloro -7-methylfluorane 3-diethylamino-6-chloro-7-anilinofluorane 3-diethylamino-6-chloro-7-p-methylanilinofluorane 3-diethylamino-6-ethoxyethyl-7-anilino Fluorane 3-diethylamino-7-methylfluorane 3-diethylamino-7-chlorofluorane 3-diethylamino-7- (m-trifluoromethylanilino) fluorane 3-diethylamino-7- (o-chloroanilino) fluorane 3- Diethylamino-7- (p-chloroanilino) fluor 3-diethylamino-7- (o-fluoroanilino) fluorane 3-diethylamino-benzo [a] fluorane 3-diethylamino-benzo [c] fluorane 3-dibutylamino-6-methyl-fluorane 3-dibutylamino-6 Methyl-7-anilinofluorane 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluorane 3-dibutylamino-6-methyl-7- (o-chloroanilino) fluorane 3-dibutylamino -6-methyl-7- (p-chloroanilino) fluorane 3-dibutylamino-6-methyl-7- (o-fluoroanilino) fluorane 3-dibutylamino-6-methyl-7- (m-trifluoromethylani Lino) fluorane 3-dibutylamino-6-methyl-7-chlorofluorane 3-di Butylamino-6-ethoxyethyl-7-anilinofluorane 3-dibutylamino-6-chloro-7-anilinofluorane 3-dibutylamino-6-methyl-7-p-methylanilinofluorane 3-dibutyl Amino-7- (o-chloroanilino) fluorane 3-dibutylamino-7- (o-fluoroanilino) fluorane 3-di-n-pentylamino-6-methyl-7-anilinofluorane 3-di-n- Pentylamino-6-methyl-7- (p-chloroanilino) fluorane 3-di-n-pentylamino-7- (m-trifluoromethylanilino) fluorane 3-di-n-pentylamino-6-chloro-7 -Anilinofluorane 3-di-n-pentylamino-7- (p-chloroanilino) fluorane 3-pyrrolidino-6-methyl-7- Anilinofluorane 3-Piperidino-6-methyl-7-anilinofluorane 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane 3- (N-methyl-N- Cyclohexylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-xylamino) -6 -Methyl-7- (p-chloroanilino) fluorane 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-isoamylamino) -6-methyl- 7-anilinofluorane 3- (N-ethyl-N-isoamylamino) -6-chloro-7-anilinofluorane 3- (N-ethyl-N-tetrahydrofurfurylami) ) -6-Methyl-7-anilinofluorane 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-ethoxypropylamino) -6 -Methyl-7-anilinofluorane 3-cyclohexylamino-6-chlorofluorane 2- (4-oxahexyl) -3-dimethylamino-6-methyl-7-anilinofluorane 2- (4-oxahexyl) ) -3-Diethylamino-6-methyl-7-anilinofluorane 2- (4-oxahexyl) -3-dipropylamino-6-methyl-7-anilinofluorane 2-methyl-6-p- ( p-dimethylaminophenyl) aminoanilinofluoran 2-methoxy-6-p- (p-dimethylaminophenyl) aminoanilinofluoran 2-chloro-3-me 6-p- (p-phenylaminophenyl) aminoanilinofluoran 2-chloro-6-p- (p-dimethylaminophenyl) aminoanilinofluoran 2-nitro-6-p- (p-diethylamino) Phenyl) aminoanilinofluorane 2-amino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 2-phenyl-6 -Methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2-benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane 2-hydroxy-6-p- (p- Phenylaminophenyl) aminoanilinofluorane 3-methyl-6-p- (p-dimethylaminophenyl) Aminoanilinofluorane 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane 2,4-dimethyl- 6-[(4-Dimethylamino) anilino] -fluorane

<Fluorene leuco dye>
3,6,6′-tris (dimethylamino) spiro [fluorene-9,3′-phthalide]
3,6,6′-tris (diethylamino) spiro [fluorene-9,3′-phthalide]

<Divinyl leuco dye>
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-dimethylaminophenyl) -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, the colorless to light-colored basic dye is 0.1 to 5 weights per 1 part by weight of the total amount of the compound represented by the general formula (1) and / or the compound represented by the general formula (2) and bisphenol C. It is preferable to use it in the ratio of parts, and it is more preferable to use it in the ratio of 0.5 to 2 parts by weight. The amount of the colorless to light-colored basic dye is less than 0.1 parts by weight per part by weight of the total amount of the compound represented by the general formula (1) and / or the compound represented by the general formula (2) and bisphenol C. The color density tends to be insufficient, and if it exceeds 5 parts by weight, the background tends to deteriorate and tailing of the printed part tends to appear.

  In the heat-sensitive recording material of the present invention, the compound represented by the general formula (1), the compound represented by the general formula (2), bisphenol C, a basic dye, an organic sensitizer and the like are each dispersed together with a binder. Prepare dispersions and mix each of these dispersions together with a dispersion of other additives such as fillers as necessary to make a coating solution. Manufactured by forming layers. The binder is suitably used in an amount of 5 to 25% by weight based on the total solid content of the thermosensitive coloring layer.

  Examples of the binder include fully saponified polyvinyl alcohol having a polymerization degree of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and other modified polyvinyl alcohols. Polyvinyl alcohols such as alcohol; cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, acetyl cellulose, etc. are preferable, but polystyrene, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, Polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polyamide resin, silicone Fat, can be petroleum resins, terpene resins, ketone resins, also be used coumarone resin. The binder may be one type or two or more types.

  Examples of the solvent used in the dispersion include water, alcohols, ketones, esters, and hydrocarbons, with water being preferred. In addition, a binder may be used in the state dissolved in this solvent, or may be used in the state disperse | distributed to emulsification or paste form. Alternatively, a dispersion liquid in which a binder is dissolved in a solvent and a dispersion liquid in which a binder is emulsified or pasty dispersed in a solvent may be prepared, and a coating liquid obtained by mixing them may be used.

  Examples of the organic sensitizer used in the present invention include the following examples.

  Fatty acid monoamide (preferably saturated fatty acid monoamide such as stearic acid amide), ethylenebisamide, montanic acid wax, polyethylene wax, 1,2-di (3-methylphenoxy) ethane, p-benzylbiphenyl, 4-biphenyl-p-tolyl Ether, m-terphenyl, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, diphenylsulfone, 1,2-di (3-methylphenoxy ) Ethylene, 1,2-diphenoxyethylene, bis [2- (4-methoxy-phenoxy) ethyl] ether, methyl p-nitrobenzoate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl- α-Naphthyl carbonate, benzyloxy naphth And lene, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, 4- (m-methylphenoxymethyl) biphenyl, etc., and any one of these may be used alone. Or you may use 2 or more types together. Among these, saturated fatty acid monoamide, diphenyl sulfone, benzyloxynaphthalene and the like are preferable. The organic sensitizer is used at a ratio of 0.01 to 10 parts by weight per part by weight of the total amount of the compound represented by the general formula (1) and / or the compound represented by the general formula (2) and bisphenol C. It is preferable to use it at a ratio of 0.1 to 5 parts by weight.

  In addition, when using the compound (especially D-90) of a formula (2) as an organic developer, by using benzyloxynaphthalene as a sensitizer (that is, the compound (especially, D-90)), bisphenol C, and benzyloxynaphthalene)), high color development sensitivity is obtained, and not only heat resistance and moisture resistance but also extremely low image density reduction due to contact with a plasticizer Can be suppressed by level.

  In addition to the compound represented by the general formula (1) or / and the compound represented by the general formula (2), bisphenol C, basic dye and sensitizer, An image stabilizer may be blended. Such image stabilizers include, for example, a copolymer of glycidyl methacrylate and a vinyl monomer (average molecular weight 9000 to 11000, epoxy equivalent 300 to 600, melting point 110 ° C. or lower), 4-benzyloxy-4 ′-(2,3- Epoxy-2-methylpropoxy) diphenylsulfone, 4,4'-butylidene (6-tert-butyl-3-methylphenol), 2,2'-di-tert-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-tert-butyl) Phenyl) butane and the like, and any one of them may be used alone, or two or more thereof may be mixed and used. Among these, a copolymer of glycidyl methacrylate and a vinyl monomer (average molecular weight 9000 to 11000, epoxy equivalent 300 to 600, melting point 110 ° C. or lower), 4-benzyloxy-4 ′-(2,3-epoxy-2- Methylpropoxy) diphenyl sulfone is preferred. At least one selected from these is blended in the thermosensitive coloring layer together with the compound represented by the general formula (1) or / and the compound represented by the general formula (2), bisphenol C, basic dye and sensitizer. As a result, the storability of the image is further improved.

  If the amount of the image stabilizer used is too small relative to the total amount of the compound represented by the general formula (1) and / or the compound represented by the general formula (2) and bisphenol C, the image stabilizing effect (oil resistance Effect of improving the plasticity and the effect of improving the plasticizer resistance) are difficult to appear, and if it is too much, the color development sensitivity, heat resistance and the like tend to decrease. Therefore, the compound represented by the general formula (1) or / and the compound represented by the general formula (2) and the total amount of bisphenol C are used in a ratio of 0.01 to 0.9 parts by weight. It is more preferable to use it at a ratio of 0.1 to 0.5 parts by weight.

  In the thermosensitive recording material of the present invention, a filler is usually added to the thermosensitive coloring layer. Examples of the filler include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, aluminum hydroxide, and the filler is usually a compound represented by the general formula (1) or It is preferable to add about 0.5 to 4 parts by weight per part by weight of the total amount of the compound represented by the general formula (2) and bisphenol C. In addition, lubricants such as waxes, benzophenone or triazole ultraviolet absorbers, water resistance agents such as glyoxal, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like may be added as necessary.

  In the thermosensitive recording material of the present invention, examples of the support on which the thermosensitive coloring layer is provided include paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, nonwoven fabric, and the like, and are selected from these. You may use the composite sheet which combined 2 or more types as a support body.

  In addition, an overcoat layer made of a polymer material or the like is further provided on the heat-sensitive color developing layer for the purpose of improving the storage stability of the heat-sensitive recording material, or an undercoat layer made of a polymer material containing a filler for the purpose of improving the color developing sensitivity. Can also be provided under the thermosensitive coloring layer.

  In the production of the heat-sensitive recording material of the present invention, as described above, the compound represented by the general formula (1) or / and the compound represented by the general formula (2), bisphenol C, basic dye, and sensitization. Each dispersion liquid of an agent and a dispersion liquid of additives to be added as needed are prepared, and these dispersion liquids are mixed to form a coating liquid to be applied to a support. It is preferable to prepare by performing wet grinding so that the particle size of the dispersed particles becomes a particle size of several microns or less with a pulverizer such as a sand grinder or a suitable emulsifying device. The means for applying the coating liquid to the support is not particularly limited, and any conventionally known coating machine can be used without limitation. For example, various coaters such as an air knife coater, a rod blade coater, a bill blade coater, and a roll coater can be used. The provided off-machine coating machine, on-machine coating machine, etc. are used.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, “parts” means “parts by weight”. “%” Is “% by weight”.

[Example 1]
For each material of the dye and developer, a dispersion having the following composition was prepared in advance, and wet grinding was performed with a sand grinder until the average particle size became 0.5 microns.

<Developer dispersion-1>
4-hydroxy-4'-n-propoxydiphenylsulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts water 11.2 parts <Developer dispersion-2>
Bisphenol C 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts

<Dye dispersion>
3-Di-n-butylamino-6-methyl-7-anilinofluorane
3.0 parts 10% aqueous polyvinyl alcohol solution 6.9 parts water 3.9 parts

<Sensitizer dispersion-1>
Diphenylsulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts

Using the above developer dispersion, dye dispersion and sensitizer dispersion, a 50% kaolin clay dispersion and a 30% zinc stearate dispersion are mixed in the following formulation to form a thermosensitive coloring layer coating liquid. Obtained. Then, this coating solution is applied to one side of a base paper (high quality paper) having a basis weight of 50 g / m ² so that the coating amount after drying is 6.0 g / m ^2, and dried, and the Beck smoothness is measured with a super calendar. Processing was performed for 200 to 600 seconds to obtain a heat-sensitive recording material.

Developer dispersion-1 32.7 parts Developer dispersion-2 3.3 parts Dye dispersion 13.8 parts Sensitizer dispersion-1 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 2]
Using the developer dispersions 1 and -2, the dye dispersion and the sensitizer dispersion 1 used in Example 1, a thermosensitive coloring layer coating solution having the following formulation was prepared. And a thermal recording material was obtained in the same manner as in Example 1.
Developer dispersion-1 16.0 parts Developer dispersion-2 20.0 parts Dye dispersion 13.8 parts Sensitizer dispersion-1 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 3]
Using the developer dispersions 1 and -2, the dye dispersion and the sensitizer dispersion 1 used in Example 1, a thermosensitive coloring layer coating solution having the following formulation was prepared. And a thermal recording material was obtained in the same manner as in Example 1.
Developer dispersion-1 7.2 parts Developer dispersion-2 28.8 parts Dye dispersion 13.8 parts Sensitizer dispersion-1 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 4]
The 4-hydroxy-4′-n-propoxydiphenyl sulfone in the developer dispersion-1 used in Example 1 was changed to 4,4′-bisphenolsulfone (developer dispersion-3) and increased. Diphenylsulfone in Sensitizer Dispersion-1 was changed to stearamide (Sensitizer Dispersion-2), and a thermosensitive coloring layer coating solution having the following formulation was prepared. Using this coating solution, Example 1 and A heat-sensitive recording material was obtained in the same manner.
Developer dispersion-3 18.0 parts Developer dispersion-2 18.0 parts Dye dispersion 13.8 parts
Sensitizer dispersion-2 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 5]
Using the developer dispersions-3 and -2, dye dispersion and sensitizer dispersion-2 used in Example 4, a thermosensitive coloring layer coating solution having the following formulation was prepared, and the coating solution was And a thermal recording material was obtained in the same manner as in Example 4.
Developer dispersion-3 3.3 parts Developer dispersion-2 32.7 parts Dye dispersion 13.8 parts Sensitizer dispersion-2 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 6]
The 4-hydroxy-4′-n-propoxydiphenylsulfone in the developer dispersion-1 used in Example 3 was changed to 2,4′-bisphenolsulfone (developer dispersion-4) and increased. A thermosensitive recording material was obtained in the same manner as in Example 3 except that the diphenylsulfone of -1 in the sensitizer dispersion was changed to benzyloxynaphthalene (sensitizer dispersion-3).

[Example 7]
Using the developer dispersions 4 and -2, the dye dispersion and the sensitizer dispersion 3 used in Example 6, a thermosensitive coloring layer coating solution having the following formulation was prepared, and the coating solution was used. In the same manner as in Example 6, a heat-sensitive recording material was obtained.
Developer dispersion-4 25.7 parts Developer dispersion-2 10.3 parts Dye dispersion 13.8 parts Sensitizer dispersion-3 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 8]
4-hydroxy-4′-n-propoxydiphenyl sulfone in the developer dispersion-1 used in Example 1 was changed to 3-3′-allyl-4,4′-dihydroxydiphenyl sulfone (TGSA manufactured by Nippon Kayaku Co., Ltd.). (Hereinafter abbreviated as “TGSA”)) (developer dispersion-5), and the others were the same as in Example 1 to obtain a heat-sensitive recording material.

[Example 9]
Using the developer dispersions-5 and -2, the dye dispersion liquid and the sensitizer dispersion liquid-1 used in Example 8, a thermosensitive coloring layer coating liquid having the following formulation was prepared, and the coating liquid was used. In the same manner as in Example 8, a heat-sensitive recording material was obtained.
Developer dispersion-5-7.2 parts Developer dispersion-2-28.8 parts Dye dispersion-13.8 parts Sensitizer dispersion-1-36.0 parts Kaolin clay 50% dispersion-26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 10]
A developer composition containing 2,2′-bis [4 (4-hydroxyphenylsulfone) phenoxy] diphenyl ether in place of 4,4′-diphenylsulfone in developer dispersion-3 used in Example 4 ( Nippon Soda Co., Ltd .: D-90 (hereinafter abbreviated as “D-90”)) (developer dispersion-6), a thermosensitive coloring layer coating liquid having the following formulation was prepared, and the coating liquid was And a thermal recording material was obtained in the same manner as in Example 4.
Developer dispersion-6 21.2 parts Developer dispersion-2 14.8 parts Dye dispersion 13.8 parts Sensitizer dispersion-2 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 11]
Using the developer dispersions-6 and -2, dye dispersion and sensitizer dispersion-2 used in Example 10, a thermosensitive coloring layer coating solution having the following formulation was prepared, and the coating solution was used. In the same manner as in Example 10, a heat-sensitive recording material was obtained.
Developer dispersion-6 10.3 parts Developer dispersion-2 25.7 parts Dye dispersion 13.8 parts Sensitizer dispersion-2 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 12]
Using the developer dispersions 6 and -2 and the dye dispersion liquid used in Example 10, the sensitizer dispersion liquid-2 was changed to the sensitizer dispersion liquid-3, and the thermosensitive coloring layer having the following formulation was used. A coating solution was prepared, and a thermal recording material was obtained using the coating solution in the same manner as in Example 10.
Developer dispersion-6-32.7 parts Developer dispersion-2 3.3 parts Dye dispersion 13.8 parts Sensitizer dispersion-3 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 13]
Using the developer dispersions-6 and -2, dye dispersion and sensitizer dispersion-3 used in Example 12, a thermosensitive color-developing layer coating solution having the following formulation was prepared, and the coating solution was used. In the same manner as in Example 12, a heat-sensitive recording material was obtained.
Developer dispersion-6 18.0 parts Developer dispersion-2 18.0 parts Dye dispersion 13.8 parts Sensitizer dispersion-3 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Example 14]
The same as in Example 11 except that the developer dispersions-6 and -2 and the dye dispersion liquid used in Example 11 were used, and the sensitizer dispersion liquid-2 was changed to the sensitizer dispersion liquid-3. A heat-sensitive recording material was obtained.

[Example 15]
Using the developer dispersions-6 and -2, dye dispersion and sensitizer dispersion-3 used in Example 12, a thermosensitive color-developing layer coating solution having the following formulation was prepared, and the coating solution was used. In the same manner as in Example 12, a heat-sensitive recording material was obtained.
Developer dispersion-6 3.6 parts Developer dispersion-2 32.4 parts Dye dispersion 13.8 parts Sensitizer dispersion-3 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Comparative Example 1]
From 4-hydroxy-4′-n-propoxydiphenyl sulfone in developer dispersion-1 used in Example 1 to 4-hydroxy-4′-isopropoxydiphenyl sulfone (manufactured by Nippon Soda Co., Ltd .: D-8 (below) And abbreviated as “D-8”) (developer dispersion-7), and otherwise, a heat-sensitive recording material was obtained in the same manner as in Example 1.

[Comparative Example 2]
Using the developer dispersions -7 and -2, the dye dispersion and the sensitizer dispersion-1 used in Comparative Example 1, a thermosensitive coloring layer coating solution having the following formulation was prepared, and the coating solution was used. In the same manner as in Comparative Example 1, a heat-sensitive recording material was obtained.
Developer dispersion-7 3.3 parts Developer dispersion-2 32.7 parts Dye dispersion 13.8 parts Sensitizer dispersion-1 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Comparative Example 3]
Using the developer dispersions -7 and -2, the dye dispersion and the sensitizer dispersion-1 used in Comparative Example 1, a thermosensitive coloring layer coating solution having the following formulation was prepared, and the coating solution was used. In the same manner as in Comparative Example 1, a heat-sensitive recording material was obtained.
Developer dispersion-7 18.0 parts Developer dispersion-2 18.0 parts Dye dispersion 13.8 parts Sensitizer dispersion-1 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Comparative Example 4]
In Example 1, only the developer dispersion-2 is used as the developer dispersion (only bisphenol C is used), and the sensitizer dispersion-1 is changed to the sensitizer dispersion-3. A thermosensitive color-developing layer coating solution having the above formulation was prepared, and a thermosensitive recording material was obtained in the same manner as in Example 1 using the coating solution.
Developer dispersion-2 36.0 parts Dye dispersion 13.8 parts Sensitizer dispersion-3 36.0 parts Kaolin clay 50% dispersion 26.0 parts Zinc stearate 30% dispersion 6.7 parts

[Comparative Example 5]
A heat-sensitive recording material was obtained in the same manner as in Comparative Example 4 except that the developer dispersion-2 was changed to the developer dispersion-1.

[Comparative Example 6]
The developer dispersion-2 was changed to the developer dispersion-3, the sensitizer dispersion-3 was changed to the sensitizer dispersion-2, and heat sensitivity was the same as in Comparative Example 4 except for these. A record was obtained.

[Comparative Example 7]
The developer dispersion-2 was changed to the developer dispersion-4, the sensitizer dispersion-3 was changed to the sensitizer dispersion-1, and heat sensitive in the same manner as in Comparative Example 4 except these. A record was obtained.

[Comparative Example 8]
A heat-sensitive recording material was obtained in the same manner as in Comparative Example 7 except that the developer dispersion-4 was changed to the developer dispersion-5.

[Comparative Example 9]
A heat-sensitive recording material was obtained in the same manner as in Comparative Example 6 except that the developer dispersion-3 used in Comparative Example 6 was changed to the developer dispersion-6.

[Comparative Example 10]
A heat-sensitive recording material was obtained in the same manner as in Comparative Example 9, except that the sensitizer dispersion-2 used in Comparative Example 9 was changed to the sensitizer dispersion-3.

[Thermal recording aptitude evaluation]
The performance of the thermosensitive recording materials obtained in the above Examples and Comparative Examples was evaluated by the following methods.

(Thermal recording test (color sensitivity test))
Using TH-PMD manufactured by Okura Electric Co., Ltd., printing was performed on the thermosensitive coloring layer of the thermosensitive recording medium with an applied energy of 0.34 mJ / dot. The image density after printing was measured with a Macbeth densitometer (using an amber filter).

(Heat resistance test)
The thermal recording material on which an image was recorded in the thermal recording test was left in a dry environment at a temperature of 60 ° C. for 24 hours, and then the image density of the recording area and the density of the background area were measured with a Macbeth densitometer.

(Moisture resistance test)
The thermal recording material on which an image was recorded in the thermal recording test was left in an environment of a temperature of 40 ° C. and a humidity of 90% RH for 24 hours, and then the image density of the recording area and the density of the background area were measured with a Macbeth densitometer.

(Plasticizer resistance test)
Wrapping vinyl chloride wrap (high wrap KMA made by Mitsui Toatsu) on a paper tube, and sticking a thermal recording material on which an image was recorded in the thermal recording test, and further wrapping the vinyl wrap in triplicate. After being left in an environment at a temperature of 20 ° C. for 2 hours, the image density of the recording portion and the density of the background portion were measured with a Macbeth densitometer.

  In the aptitude evaluation described above, the higher the numerical value is, the better the recording portion of color development sensitivity, heat resistance, moisture resistance, and plasticizer resistance, and the lower the numerical value, the better the background portion.

  Table 1 below shows the composition of the heat-sensitive color developing layer of the heat-sensitive recording material of each Example and Comparative Example, and Table 2 below shows the color developing sensitivity (printed image density) and heat resistance of the heat-sensitive recording material of each Example and Comparative Example. Image density after test, moisture resistance test and plasticizer resistance test.

As is apparent from Table 2, in Comparative Examples 1 to 3, the background color development in the heat resistance test is remarkably high, and the bisphenol C of Comparative Example 4 alone has very low storage stability (heat resistance and moisture resistance). On the other hand, in Examples 1 to 3, a recorded image with a high color density was obtained, and the background color development in the heat resistance test and the background color development in the moisture resistance test were low, and the storage stability (heat resistance and moisture resistance) was excellent. I understood that. Further, comparing Comparative Example 5 with Examples 1 to 3, Examples 1 to 3 have low background color development of 0.2 or less in the heat resistance test, and both sensitivity and storage stability (heat resistance and moisture resistance) are low. In comparison with Comparative Example 6 and Examples 4 and 5, Comparative Example 7 and Examples 6 and 7, Comparative Example 8 and Examples 8 and 9, Comparative Example 9 and Examples 10 and 11, In all of Examples 4 to 11, it was found that the background color development in the heat resistance test was extremely low, and both the sensitivity and the storage stability were improved. Furthermore, comparing bisphenol C alone of Comparative Example 4 with Examples 14 and 15, it was found that the plasticizer resistance was greatly improved in addition to the above effects. Further, comparing Comparative Example 10 with Examples 12 and 13, the image stability against the plasticizer is extremely high, the background color development in the heat resistance test is extremely low, and both the sensitivity and the storage stability are improved. I understood. From the above results, when bisphenol sulfone or a derivative thereof, or a diphenylsulfone crosslinked compound coexists with bisphenol C (Examples 1 to 15), bisphenolsulfone or a derivative thereof or a diphenylsulfone crosslinked compound is used alone. Compared to the cases (Comparative Examples 5 to 10), the color development sensitivity is high, the decrease in the image density of the image area by the heat resistance test and the moisture resistance test is small, and the background color development is also small, and the storage stability of the recorded image is excellent. I understand that. Further, it can be seen that when bisphenol C and the compound represented by the general formula (2), particularly D-90, coexist, an effect excellent in plasticizer resistance of a recorded image is exhibited in addition to the above effects. In particular, when the developer coexisting with bisphenol C is a compound represented by the general formula (1), when a compound in which R ₁ is an n-propyl group is used, compared to a compound in which R ₁ is an isopropyl group. It can be seen that a particularly excellent effect is obtained in terms of suppressing the color development of the background under a high temperature environment.

Claims (4)

A thermosensitive recording medium comprising a thermosensitive color-developing layer containing a colorless or light-colored basic dye, an organic developer and an organic sensitizer as main components on a support, wherein the thermosensitive color-developing layer is an organic developer. As an agent, general formula (1):

[Wherein, R ₁ represents a hydrogen atom, a lower alkyl group (excluding an isopropyl group) or an aryl group. R ₂ represents a hydrogen atom, a lower alkyl group or an alkenyl group, and m R _{2 s} may be the same or different from each other, and m represents an integer of 0 to 4. And a bisphenol C. A heat-sensitive recording material comprising: 2. The heat-sensitive recording material according to claim ₁ , wherein R ₁ in the general formula (1) is an n-propyl group. A thermosensitive recording medium comprising a thermosensitive color-developing layer containing a colorless or light-colored basic dye, an organic developer and an organic sensitizer as main components on a support, wherein the thermosensitive color-developing layer is an organic developer. As an agent, general formula (2):

[Wherein, X and Y may be the same as or different from each other, and each represents a linear or branched saturated or unsaturated divalent hydrocarbon group having 1 to 12 carbon atoms which may have an ether bond. Or the formula:

(Wherein R ₄ represents a methylene group or an ethylene group, and T represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). R ₃ represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, p R _{3 s} may be the same as or different from each other, and p represents an integer of 0 to 4. n shows the integer of 0-2. A heat-sensitive recording material comprising a diphenylsulfone cross-linking compound represented by formula (II) and bisphenol C: A thermosensitive recording medium comprising a thermosensitive color-developing layer containing a colorless or light-colored basic dye, an organic developer and an organic sensitizer as main components on a support, wherein the thermosensitive color-developing layer is an organic developer. As an agent, general formula (1):

[Wherein, R ₁ represents a hydrogen atom, a lower alkyl group (excluding an isopropyl group) or an aryl group. R ₂ represents a hydrogen atom, a lower alkyl group or an alkenyl group, and m R _{2 s} may be the same or different from each other, and m represents an integer of 0 to 4. And a compound represented by the general formula (2):

[Wherein, X and Y may be the same as or different from each other, and each represents a linear or branched saturated or unsaturated divalent hydrocarbon group having 1 to 12 carbon atoms which may have an ether bond. Or the formula:

(Wherein R ₄ represents a methylene group or an ethylene group, and T represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). R ₃ represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, p R _{3 s} may be the same as or different from each other, and p represents an integer of 0 to 4. n shows the integer of 0-2. A heat-sensitive recording material comprising a diphenylsulfone cross-linking compound represented by formula (II) and bisphenol C: