JP6024509B2 - Thermal recording material - Google Patents

Description

  The present invention utilizes a coloring reaction between a colorless or light-colored electron-donating leuco dye (hereinafter also referred to as “leuco dye”) and an electron-accepting developer (hereinafter also referred to as “developer”). It is a heat-sensitive recording material and has good suitability for an optical character reader having a reading wavelength in the near infrared region, color development performance (printing density), image area water resistance, plasticizer resistance, light resistance, and blank paper The present invention relates to a heat-sensitive recording material having excellent heat resistance.

In general, a thermal recording material is usually a colorless or light leuco dye and a developer such as a phenolic compound, each of which is ground and dispersed into fine particles, and then mixed together to form a binder, a filler, a sensitivity improver, A coating solution obtained by adding a lubricant and other auxiliary agents is applied to a support such as paper, synthetic paper, film, plastic, etc., such as thermal head, hot stamp, thermal pen, laser beam, etc. Color is generated by an instantaneous chemical reaction by heating, and a recorded image is obtained. Thermosensitive recording media are widely used as recording media for facsimiles, computer terminal printers, automatic ticket vending machines, recorders for measurement, receipts for supermarkets and convenience stores, and the like.
In recent years, for ticket applications such as admission tickets and boarding passes, systems have become widespread that can be entered by simply printing QR CODE at the time of ticketing and holding it over a barcode reader when entering. In general, the wavelength of a reading light source used in a bar code reader is from the visible region to the near red region, but a small and inexpensive semiconductor laser is often used as a light source in a small scanner for reading a bar code. Therefore, the thermal recording material used for the ticket use is required to have barcode readability with a small scanner, that is, readability with a light source having a wavelength in the near infrared region (near 700 to 1000 nm).

However, the recorded image obtained by the leuco dye used in the conventional thermal recording medium has readability for a visible light source, but the absorbance of the recorded image is large for a near-infrared light source. As a result, the readability could not be obtained. In addition, because it is often used outdoors for ticket applications, it is not difficult to interpret the image area due to moisture such as sunlight or rain, and it is often stored in a wallet or the like. With regard to the storage stability such as light resistance, water resistance, plasticizer resistance, etc., which has not been a problem with conventional thermal recording materials, such as that it is difficult to read the image area with the plasticizer contained in the synthetic leather. Excellent performance is required.
In order to improve the readability to a visible light source, a heat-sensitive recording material (Patent Document 1) is disclosed in which a heat-sensitive recording layer contains a dye precursor exhibiting strong absorption with respect to a near-infrared light source. However, the light resistance, plasticizer resistance and color developability after light irradiation (so-called light recurrence resistance) of the image area are insufficient. In addition, by using a dye precursor that exhibits strong absorption against a near-infrared light source and 2,2 ′, 4,4′-tetrahydroxybenzophenone, a salicylic acid derivative, or a metal salt of a salicylic acid derivative as a developer. Although a heat-sensitive recording material (Patent Document 2) having improved light resistance and light recurrence color resistance of an image portion is disclosed, 2,2 ′, 4,4′-tetrahydroxybenzophenone, salicylic acid derivatives, salicylic acid derivatives Since the metal salt is highly water-soluble, its water resistance is inadequate, and because it is highly reactive and the heat resistance of the white paper portion is poor, the white paper portion will develop color when the thermal recording medium is stored in a high temperature environment. There is a drawback that the bar code reading ability is lowered.

JP 2004-160805 A JP2007-050579

  Therefore, the present invention has good suitability for an optical character reader having a reading wavelength in the near infrared region, color development performance (printing density), water resistance of the image portion, plasticizer resistance, light resistance, and blank paper portion. An object of the present invention is to provide a heat-sensitive recording material having excellent heat resistance.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by incorporating a specific developer and a leuco dye in the heat-sensitive recording layer, and have completed the present invention.
That is, the present invention provides a heat-sensitive recording material comprising a support on which a heat-sensitive recording layer containing an electron-accepting developer and a colorless to light-colored electron-donating leuco dye is provided. A diphenylsulfone crosslinkable compound represented by the general formula (Chemical Formula 1) and 2,4′-dihydroxydiphenylsulfone as the developer and a divinyl compound represented by the General Formula (Chemical Formula 4) as the electron-donating leuco dye are used. These are heat-sensitive recording materials characterized by containing each of them.

（式中、Ｒ^１は、それぞれ同じであっても異なってもよく、水素原子、ハロゲン原子、炭素数が１〜６のアルキル基又はアルケニル基を表し、ｍは、それぞれ同じであっても異なってもよく、０〜４の整数を表し、ｎは１〜１１の整数を表し、Ｒ^２は、それぞれ同じであっても異なってもよく、エーテル結合を有してもよい炭素数１〜１２の飽和若しくは不飽和の直鎖若しくは分枝の炭化水素基、下記一般式

(In the formula, R ¹ may be the same or different, and represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, and m is the same or different. Each represents an integer of 0 to 4, n represents an integer of 1 to 11, and R ² may be the same or different, and may have an ether bond. A saturated or unsaturated linear or branched hydrocarbon group of the following general formula

（式中、Ｒ^３はメチレン基又はエチレン基を表す。）で表される置換フェニレン基、又は下記一般式

(Wherein R ³ represents a methylene group or an ethylene group), or a substituted phenylene group represented by the following general formula:

（式中、Ｒ^４は水素原子又は炭素数が１〜４のアルキル基を表す。）で表される２価基を
表す。）で表されるジフェニルスルホン架橋型化合物。

(Wherein R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). Diphenylsulfone cross-linking compound represented by

（式中、Ｒ_５、Ｒ_６は炭素数８以下のアルキル基を示し、Ｘ_１は水素原子、ハロゲン原子、炭素数８以下のアルキル基を示し、Ｘ_２は炭素数８以下のアルコキシ基を示す。）

(Wherein R ₅ and R ₆ represent an alkyl group having 8 or less carbon atoms, X ₁ represents a hydrogen atom, a halogen atom or an alkyl group having 8 or less carbon atoms, and X ₂ represents an alkoxy group having 8 or less carbon atoms. Show.)

  According to the present invention, the suitability for an optical character reader having a reading wavelength in the near infrared region is good, the color development performance (printing density), the water resistance of the image portion, the plasticizer resistance, the light resistance, and the blank paper portion. It is possible to provide a heat-sensitive recording material excellent in heat resistance.

  Embodiments of the present invention will be described below.

The heat-sensitive recording material of the present invention is a heat-sensitive recording material comprising a support on which a heat-sensitive recording layer containing an electron-accepting developer and a colorless to light-colored electron-donating leuco dye is provided. A diphenylsulfone cross-linked compound represented by the general formula (Chemical Formula 1) and 2,4′-dihydroxydiphenylsulfone as the accepting developer are represented by the general formula (Chemical Formula 4) as an electron-donating leuco dye. A heat-sensitive recording material comprising a compound, respectively.

（式中、Ｒ^１は、それぞれ同じであっても異なってもよく、水素原子、ハロゲン原子、炭素数が１〜６のアルキル基又はアルケニル基を表し、ｍは、それぞれ同じであっても異なってもよく、０〜４の整数を表し、ｎは１〜１１の整数を表し、Ｒ^２は、それぞれ同じであっても異なってもよく、エーテル結合を有してもよい炭素数１〜１２の飽和若しくは不飽和の直鎖若しくは分枝の炭化水素基、下記一般式

(In the formula, R ¹ may be the same or different, and represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, and m is the same or different. Each represents an integer of 0 to 4, n represents an integer of 1 to 11, and R ² may be the same or different, and may have an ether bond. A saturated or unsaturated linear or branched hydrocarbon group of the following general formula

（式中、Ｒ^３はメチレン基又はエチレン基を表す。）で表される置換フェニレン基、又は下記一般式

(Wherein R ³ represents a methylene group or an ethylene group), or a substituted phenylene group represented by the following general formula:

（式中、Ｒ^４は水素原子又は炭素数が１〜４のアルキル基を表す。）で表される２価基を
表す。）で表されるジフェニルスルホン架橋型化合物。

(Wherein R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). Diphenylsulfone cross-linking compound represented by

（式中、Ｒ_５、Ｒ_６は炭素数８以下のアルキル基を示し、Ｘ_１は水素原子、ハロゲン原子、炭素数８以下のアルキル基を示し、Ｘ_２は炭素数８以下のアルコキシ基を示す。）

(Wherein R ₅ and R ₆ represent an alkyl group having 8 or less carbon atoms, X ₁ represents a hydrogen atom, a halogen atom or an alkyl group having 8 or less carbon atoms, and X ₂ represents an alkoxy group having 8 or less carbon atoms. Show.)

  The divinyl compound represented by the general formula (Formula 4) used as the leuco dye of the present invention exhibits near infrared absorption performance when the lactone ring is cleaved. However, when bisphenol A or the like, which is generally used for heat-sensitive recording materials, is used as a developer, the reaction product with these developers is low in stability and is easily exposed to light irradiation or contact with a plasticizer. Decomposes and deactivates near infrared absorption performance. On the other hand, when the diphenylsulfone crosslinkable compound represented by the general formula (Chemical Formula 1) is used as a developer, the decrease in infrared absorption performance due to light irradiation or contact with a plasticizer is small, that is, the light resistance of the image area. And good plasticizer resistance. The reason for this is not clear, but the reaction product of the divinyl compound represented by the general formula (Formula 4) and the diphenylsulfone bridged compound represented by the general formula (Formula 1) is chemically stable. It is guessed.

  Next, various materials used in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention are exemplified, but the binder, the cross-linking agent, the pigment, etc. are within a range that does not impair the desired effect on the above problems, such as a protective layer and an undercoat layer, It can also be used for each coating layer provided as necessary.

  In the present invention, a diphenylsulfone cross-linked compound represented by the following general formula (Formula 1) is used as a developer.

ここで、Ｒ^１は、それぞれ同じであっても異なってもよいが、好ましくは同一であり、水素原子、ハロゲン原子、炭素数が１〜６のアルキル基又はアルケニル基、好ましくは水素原子を表す。
このアルキル基又はアルケニル基は、炭素数が１〜６のアルキル基又はアルケニル基であり、例えば、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基、ｎ−ペンチル基、イソペンチル基、ネオペンチル基、ｔｅｒｔ−ペンチル基、ｎ−ヘキシル基、イソへキシル基、１−メチルペンチル基、２−メチルペンチル基、ビニル基、アリル基、イソプロペニル基、１−プロペニル基、２−ブテニル基、３−ブテニル基、１，３−ブタンジエニル基、２−メチル−２−プロペニル基等が挙げられる。
また、ハロゲン原子としては塩素、臭素、フッ素又はヨウ素、好ましくは塩素又は臭素を表す。
ｍは、それぞれ同じであっても異なってもよく、好ましくは同一であり、０〜４、好ましくは０を表す。
ＯＨ基及び−ＯＲ^２Ｏ−基は、ＳＯ_２基に対して、パラ位にあることが好ましい。
ｎは１〜１１である。この化合物はｎが１〜１１の混合物であることが好ましい。

Here, R ¹ may be the same or different from each other, but is preferably the same and represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, preferably a hydrogen atom. .
This alkyl group or alkenyl group is an alkyl group or alkenyl group having 1 to 6 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert group. -Butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, n-hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl group, vinyl group, allyl group, isopropenyl Group, 1-propenyl group, 2-butenyl group, 3-butenyl group, 1,3-butanedienyl group, 2-methyl-2-propenyl group and the like.
The halogen atom represents chlorine, bromine, fluorine or iodine, preferably chlorine or bromine.
m may be the same or different, and is preferably the same and represents 0 to 4, preferably 0.
The OH group and —OR ² O— group are preferably in the para position with respect to the SO ₂ group.
n is 1-11. This compound is preferably a mixture of n of 1 to 11.

R ² may be the same or different, but is preferably the same.
R ² is a saturated or unsaturated, preferably saturated, straight chain or branched, preferably straight chain hydrocarbon having 1 to 12, preferably 3 to 7 carbon atoms that may have an ether bond It may be a group. Such hydrocarbon is preferably a polyalkylene oxide chain or an alkylene group, preferably a polyalkylene oxide chain. When R ² is a polyalkylene oxide chain, as the _{^{-OR 2 O-, -O- (C o}} H 2o O) 1~3- ( wherein, o = 2 to 4, preferably 2 to 3, more preferably 2). The alkylene group, _{-C p} H2 p - (wherein, p = 1 to 12, preferably 3 to 7) can be mentioned.

As R ² , the following general formula

（式中、Ｒ^３はメチレン基又はエチレン基を表す。Ｒ^３は互いにパラ位にあることが好ましい。）で表される置換フェニレン基であってもよい。
更に、Ｒ^２としては、下記一般式

(In the formula, R ³ represents a methylene group or an ethylene group. R ³ are preferably para to each other).
Further, as R ² , the following general formula

（式中、Ｒ^４は水素原子又は炭素数が１〜４のアルキル基、好ましくは水素原子を表す。）で表される２価基を表す。）であってもよい。
Ｒ^２としては、これらの中で、上記のエーテル結合を有してもよい炭素数１〜１２の飽和若しくは不飽和の直鎖若しくは分枝の炭化水素基が好ましい。

(Wherein R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, preferably a hydrogen atom). ).
Among these, R ² is preferably a saturated or unsaturated linear or branched hydrocarbon group having 1 to 12 carbon atoms which may have the ether bond.

Specific examples of the group represented by R ² in the diphenylsulfone cross-linked compound represented by the general formula (Formula 1) include the following. Methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, methylmethylene group, dimethylmethylene Group, methylethylene group, methyleneethylene group, ethylethylene group, 1,2-dimethylethylene group, 1-methyltrimethylene group, 1-methyltetramethylene group, 1,3-dimethyltrimethylene group, 1-ethyl-4 -Methyl-tetramethylene group, vinylene group, propenylene group, 2-butenylene group, ethynylene group, 2-butynylene group, 1-vinylethylene group, ethyleneoxyethylene group, tetramethyleneoxytetramethylene group, ethyleneoxyethyleneoxyethylene group , Ethylene oxide Methyleneoxyethylene group, 1,3-dioxane-5,5-bismethylene group, 1,2-xylyl group, 1,3-xylyl group, 1,4-xylyl group, 2-hydroxytrimethylene group, 2-hydroxy- 2-methyltrimethylene group, 2-hydroxy-2-ethyltrimethylene group, 2-hydroxy-2-propyltrimethylene group, 2-hydroxy-2-isopropyltrimethylene group, 2-hydroxy-2-butyltrimethylene group Etc.

The diphenylsulfone bridged compound represented by the general formula (Chemical Formula 1) may be used by mixing several kinds of substituents (R ¹ ) and / or n having different numbers, and the content ratio is arbitrary. is there. The mixing method is not particularly limited, such as mixing in powder, mixing in the state of a dispersion dispersed in water or the like, and a method of simultaneously producing and containing a plurality of types of diphenylsulfone cross-linking compounds depending on production conditions.

  Specific examples of the diphenylsulfone bridged compound represented by the general formula (Formula 1) include, for example, 4,4′-bis [4- [4- (4-hydroxyphenylsulfonyl) phenoxy] -2-trans-butenyloxy. Diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-4-butyloxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-3-propyl Oxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyloxy] diphenylsulfone; 4- [4- (4-hydroxyphenylsulfonyl) phenoxy-4-butyloxy] -4 '-[4- (4-Hydroxyphenylsulfonyl) pheno 4- (4- (4-hydroxyphenylsulfonyl) phenoxy-4-butyloxy] -4 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyloxy] diphenylsulfone; 4- [4- (4-hydroxyphenylsulfonyl) phenoxy-3-propyloxy] -4 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyloxy] diphenylsulfone; 4,4′-bis [ 4- (4-hydroxyphenylsulfonyl) phenoxy-5-pentyloxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-6-hexyloxy] diphenylsulfone; 4- [4- [4- (4-hydroxyphenyl Sulfonyl) phenoxy] -2-trans-butenyloxy] -4 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy-4-butyloxy] diphenylsulfone; 4- [4- (4-hydroxyphenylsulfonyl) phenoxy-2- Trans-butenyloxy] -4 '-[4- (4-hydroxyphenylsulfonyl) phenoxy-3-propyloxy] diphenylsulfone; 4- [4- [4- (4-hydroxyphenylsulfonyl) phenoxy] -2-trans- Butenyloxy] -4 '-[4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyloxy] diphenylsulfone; 1,4-bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenoxy-2- Trans-Butenyloxy] phenylsulfo Nyl] phenoxy] -cis-2-butene; 1,4-bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenoxy-2-trans-butenyloxy] phenylsulfonyl] phenoxy] -trans-2- 4,4′-bis [4- [4- (2-hydroxyphenylsulfonyl) phenoxy] butyloxy] diphenylsulfone; 4,4′-bis [4- [2- (4-hydroxyphenylsulfonyl) phenoxy] butyloxy Diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyleneoxyethoxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenyl-1 , 4-phenylenebismethyleneoxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenyl-1,3-phenylenebismethyleneoxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenyl-1,2, -Phenylenebismethyleneoxy] diphenylsulfone; 2,2'-bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyleneoxyethoxy] phenylsulfonyl] phenoxy] diethyl ether; α, α '-Bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenyl-1,4-phenylenebismethyleneoxy] phenylsulfonyl] phenoxy] -p-xylene; α, α'-bis [4- [ 4- [4- (4-Hydroxyphenylsulfonyl) phenyl-1,3-phenyle Bismethyleneoxy] phenylsulfonyl] phenoxy] -m-xylene; α, α′-bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenyl-1,2-phenylenebismethyleneoxy] phenylsulfonyl] 2,4′-bis [2- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyleneoxyethoxy] diphenylsulfone; 2,4′-bis [4- (2-hydroxyphenylsulfonyl) Phenoxy-2-ethyleneoxyethoxy] diphenylsulfone; 4,4′-bis [3,5-dimethyl-4- (3,5-dimethyl-4-hydroxyphenylsulfonyl) phenoxy-2-ethyleneoxyethoxy] diphenylsulfone; 4,4′-bis [3-allyl-4- (3-allyl -4-hydroxyphenylsulfonyl) phenoxy-2-ethyleneoxyethoxy] diphenylsulfone; 4,4'-bis [3,5-dimethyl-4- (3,5-dimethyl-4-hydroxyphenylsulfonyl) phenyl-1, 4-Phenylenebismethyleneoxy] diphenyl sulfone; 4,4′-bis [3,5-dimethyl-4- (3,5-dimethyl-4-hydroxyphenylsulfonyl) phenyl-1,3-phenylenebismethyleneoxy] diphenyl 4,4'-bis [3,5-dimethyl-4- (3,5-dimethyl-4-hydroxyphenylsulfonyl) phenyl-1,2-phenylenebismethyleneoxy] diphenylsulfone; 4,4'-bis [3-allyl-4- (3-allyl-4-hydroxyphenylsulfonyl) 1, -Phenylenebismethyleneoxy] diphenylsulfone; 4,4'-bis [3-allyl-4- (3-allyl-4-hydroxyphenylsulfonyl) 1,3-phenylenebismethyleneoxy] diphenylsulfone; Bis [3-allyl-4- (3-allyl-4-hydroxyphenylsulfonyl) 1,2-phenylenebismethyleneoxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-2 -Hydroxypropyloxy] diphenylsulfone; 1,3-bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenoxy-2-hydroxypropyloxy] phenylsulfonyl] phenoxy] -2-hydroxypropane .

In addition, when a mixture of several types of diphenylsulfone cross-linking compounds represented by the general formula (Chemical Formula 1) is used, a particularly preferable composition contains two or more types in which R ¹ is the same and only the value of n is different. To do. If it is such a compound, a manufacturing method is also simple and the compound from which the value of n differs can be synthesize | combined at arbitrary content ratios by changing the reaction ratio of a raw material. Among these, especially as a compound represented by n = 1, for example, 1,3-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] -2-hydroxypropane; 1,1-bis [4- ( 4-hydroxyphenylsulfonyl) phenoxy] methane; 1,2-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] ethane; 1,3-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] propane; 1,5-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] butane; 1,5-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] pentane; 1,6-bis [4- (4-hydroxyphenylsulfonyl) ) Phenoxy] hexane; α, α′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy ] -P-xylene; [alpha], [alpha] '-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] -m-xylene; [alpha], [alpha]'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] -o- 2,2′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] dibutyl ether; 1,2-bis [ 4- (4-hydroxyphenylsulfonyl) phenoxy] ethylene; 1,4-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] -2-butene (for example, JP-A-7-149713, International Publication WO93) / 06074, WO95 / 33714 etc.).
Such a compound is available, for example, as Nippon Soda Co., Ltd. D-90 (the following formula).

  Examples of the developer other than the diphenylsulfone cross-linked compound represented by the general formula (Formula 1) used in the present invention include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate, and 4,4 ′. -Isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 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- Loxyphenyl) sulfone, 4-hydroxy-4′-methyldiphenylsulfone, 4-hydroxyphenyl-4′-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4′-methylphenylsulfone, 1- [4- (4 -Hydroxyphenylsulfonyl) phenoxy] -4- [4- (4-isopropoxyphenylsulfonyl) phenoxy] butane, a phenol condensation composition described in JP-A-2003-154760, and 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, 1,1-bis ( -Hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxy) Phenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2′-thiobis (4-tert-octylphenol), WO02 / 081229 Or compounds described in JP-A No. 2002-301873, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, bis [4- (n-octyloxy) Carbonylamino) zinc salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid 4- [3- (p-Tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid carboxylic acids, and zinc and magnesium of these aromatic carboxylic acids And salts with polyvalent metal salts such as aluminum, calcium, titanium, manganese, tin, and nickel, as well as antipyrine complexes of zinc thiocyanate, complex zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids, etc. . These developers can be used alone or in combination of two or more. 1- [4- (4-Hydroxyphenylsulfonyl) phenoxy] -4- [4- (4-isopropoxyphenylsulfonyl) phenoxy] butane is available, for example, under the trade name JKY-214 manufactured by API Corporation. Yes, the phenol condensation composition described in JP-A No. 2003-154760 is available, for example, as trade name JKY-224 manufactured by API Corporation. Moreover, the compound as described in WO02 / 081229 etc. is available as Nippon Soda Co., Ltd. brand name NKK-395 and D-100. 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.

  When the heat-sensitive recording layer of the present invention contains a developer other than the diphenylsulfone crosslinkable compound represented by the general formula (Formula 1), the inclusion of the diphenylsulfone crosslinkable compound represented by the general formula (Formula 1) The amount is preferably 70% by weight or more, more preferably 90% by weight or more of the total developer (including the diphenylsulfone crosslinking compound represented by the general formula (Chemical Formula 1)) contained in the heat-sensitive recording layer. is there.

In the present invention, a divinyl compound represented by the general formula (Formula 4) is used as the leuco dye.
Examples of the divinyl compound represented by the general formula (Chemical Formula 4) include 3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6, 7-tetrachlorophthalide, 3,3-bis- [2- (p-diethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3 -Bis- [2- (p-dipropylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p -Methylethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p-dibutylaminophenyl) -2- (P-methoxyphenyl) etheni ] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-ethoxyphenyl) ethenyl] -4,5,6,7 -Tetrachlorophthalide, 3,3-bis- [2- (p-diethylaminophenyl) -2- (p-ethoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3- Bis- [2- (p-dipropylaminophenyl) -2- (p-ethoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p- Methylethylaminophenyl) -2- (p-ethoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p-dibutylaminophenyl) -2- ( p-ethoxyphenyl) ethenyl] -4, , 6,7-tetrachlorophthalide, 3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-isopropoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalyl 3,3-bis- [2- (p-diethylaminophenyl) -2- (p-isopropoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [ 2- (p-dipropylaminophenyl) -2- (p-isopropoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p-methylethyl) Aminophenyl) -2- (p-isopropoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (p-dibutylaminophenyl) -2- (p -Isopropoxyphenyl ) Ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [2- (o-methyl-p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4 , 5,6,7-tetrachlorophthalide, 3,3-bis- [2- (o-methyl-p-diethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7 -Tetrachlorophthalide, 3,3-bis- [2- (o-methyl-p-dipropylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthali 3,3-bis- [2- (o-methyl-p-methylethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3, 3-bis- [2- (o-methyl-p-di Tylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide and the like can be exemplified, particularly 3,3-bis- [2- (p-dimethylamino) Phenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide is preferred. 3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide is, for example, NIRBLACK78 manufactured by Fukui Yamada Co., Ltd. It is available. Moreover, you may use the divinyl compound represented by these general formula (Formula 4) individually or in mixture of 2 or more types.

  As the leuco dye other than the divinyl compound represented by the general formula (Formula 4) used in the present invention, all known leuco dyes in the conventional pressure-sensitive or thermal recording paper field can be used, and are not particularly limited. However, triphenylmethane compounds, fluorane compounds, fluorene compounds, divinyl compounds and the like are preferable. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These leuco 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-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-di Tilamino-6-methyl-7-n-octylaminofluorane, 3-diethylamino-6-methyl-7-benzylaminofluorane, 3-diethylamino-6-methyl-7-dibenzylaminofluorane, 3-diethylamino- 6-chloro-7-methylfluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-chloro-7-p-methylanilinofluorane, 3-diethylamino-6-ethoxy Ethyl-7-anilinofluorane, 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) fluorane, 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-trifluoromethylanilino) fluorane, 3-dibutylamino- 6-methyl-7-chlorofluorane, 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane, 3-dibutylamino-6-chloro-7-anilinofluorane, 3-dibutylamino-6- Methyl-7-p-methylanilinofluorane, 3-dibutylamino-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-trifluoro Methylanilino) fluorane, 3-di-n-pentylamino-6-chloro-7-anilinofluorane, 3-di-n-pentylamino-7- (p-chloro) Nilino) 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-toludino) -6-methyl-7-ani Linofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-chloro-7-a Linofluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofur Oran, 3- (N-ethyl-N-ethoxypropylamino) -6-methyl-7-anilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2- (4-oxahexyl) -3-dimethyl Amino-6-methyl-7-anilinofluorane, 2- (4-oxahexyl) -3-diethylamino-6-methyl-7-anilinofluorane, 2- (4-oxahexyl) -3-dipropyl Amino-6-methyl-7-anilinofluorane, 2-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-methoxy-6-p -(P-dimethylaminophenyl) aminoanilinofluorane, 2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-chloro-6-p- (p- Dimethylaminophenyl) aminoanilinofluorane, 2-nitro-6-p- (p-diethylaminophenyl) 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-phenylamino) Nophenyl) 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- [1, 1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide

<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) Enyl) -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

  When the heat-sensitive recording layer of the present invention contains a leuco dye other than the divinyl compound represented by the general formula (Formula 4), the content of the divinyl compound represented by the general formula (Formula 4) It is preferably 5% by weight or more, more preferably 10% by weight or more of the total leuco dye (including the divinyl compound represented by the general formula (Formula 4)) contained therein.

  A conventionally well-known sensitizer can be used as a sensitizer used by this invention. Examples of the sensitizer include fatty acid amides such as stearamide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-bis- (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-me Tilphenoxymethyl) 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, phenyl p-toluenesulfonate, o-toluenesulfonamide, p-toluenesulfonamide and the like can be exemplified. These sensitizers may be used alone or in combination of two or more.

  Examples of the pigment used in the present invention include kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, and silica, depending on the required quality. It can also be used together.

  The binder used in the present invention includes 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, and olefin-modified. Polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, silicone modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and Cellulose like ethyl cellulose, acetyl cellulose Derivatives, casein, gum arabic, 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, coumarone resin, and the like. 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 lubricant used in the present invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

  In the present invention, when the heat-sensitive recording layer further contains a benzotriazole compound represented by the general formula (Formula 5) as an ultraviolet absorber, the reaction product of the leuco dye and the developer is decomposed by light irradiation, Inactivation of near infrared absorption performance can be suppressed. This is preferable because the light resistance of the image area is improved.

（式中Ｒ_７は炭素数４〜３０の直鎖又は分岐したアルキル基を示す。）
本発明で紫外線吸収剤として使用する一般式（化５）で表されるベンゾトリアゾール系化合物としては、例えば２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４ｔ−ブチルフェノール）、２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４ｎ−ブチルフェノール）、２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４（１，１，３，３−テトラメチルブチル）フェノール）、２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４（１，１，３，３，５，５−ヘキサメチルヘキシル）フェノール）、２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４（１，１，３，３，５，５，７，７，−オクタメチルオクチル）フェノール）などが例示可能であり、特に下記化学式（化６）で示される、２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４（１，１，３，３−テトラメチルブチル）フェノール）が好ましい。２，２’メチレンビス（６−（２Ｈ−ベンゾトリアゾール−２−イル）−４（１，１，３，３−テトラメチルブチル）フェノール）は、例えば、ＡＤＥＫＡ社製アデカアークルズＬＡ３１やケミプロ化成社製ＫＥＭＩＳＯＲＢ２７９として入手可能である。

(In the formula, R ₇ represents a linear or branched alkyl group having 4 to 30 carbon atoms.)
As the benzotriazole-based compound represented by the general formula (Formula 5) used as an ultraviolet absorber in the present invention, for example, 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4t-butylphenol) 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4n-butylphenol), 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4 (1,1, 3,3-tetramethylbutyl) phenol), 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4 (1,1,3,3,5,5-hexamethylhexyl) phenol) 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4 (1,1,3,3,5,5,7,7, -octamethyloctyl) phenol) And 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4 (1,1,3,3-tetramethylbutyl) represented by the following chemical formula (Formula 6) ) Phenol) is preferred. 2,2′methylenebis (6- (2H-benzotriazol-2-yl) -4 (1,1,3,3-tetramethylbutyl) phenol) is, for example, ADEKA ARKLES LA31 or Chemipro Kasei Co., Ltd. manufactured by ADEKA. It is available as KEMISORB 279 manufactured by the manufacturer.

  In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol), 2 as a stabilizer for improving the oil resistance and the like of the image area as long as the desired effect on the above problems is not impaired. 2,2'-di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane and the like can also be added. In addition, a dispersant, an antifoaming agent, an antioxidant, a fluorescent dye, and the like can be used.

  Types of leuco dyes, developers, sensitizers, pigments, ultraviolet absorbers (benzotriazole compounds represented by the above general formula (Chemical Formula 5)) and other various components used in the heat-sensitive recording layer of the present invention And the amount are determined according to the required performance and recording suitability, and are not particularly limited. Usually, the developer is 0.5 to 10 parts by weight with respect to 1 part by weight of the leuco dye, and the sensitizer 0. 1 to 10 parts by weight, 0.5 to 20 parts by weight of pigment, 0.01 to 2 parts by weight of ultraviolet absorber (benzotriazole compound represented by the above general formula (chemical formula 5)), 0.01 to other components Use about 10 parts by weight. The binder is suitably about 5 to 25% by weight based on the solid content of the heat-sensitive recording layer.

  In the present invention, the leuco dye, the developer, and the material 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, or a sand glider, or an appropriate emulsifying device, and a binder. Depending on the purpose, various additive materials are added to obtain a coating solution. As a solvent used for this coating liquid, water or alcohol can be used, and its solid content is about 20 to 40% by weight.

In the heat-sensitive recording material of the present invention, a protective layer can be further provided on the heat-sensitive recording layer.
The protective layer is mainly composed of a pigment and a resin, and binders, pigments, crosslinking agents and the like exemplified as materials that can be used for the heat-sensitive recording layer can be used.

  In the present invention, the content of the pigment and the binder in the protective layer is about 30 to 300 parts by weight in solid content of the binder with respect to 100 parts by weight of the pigment.

  The heat-sensitive recording material of the present invention has a heat-sensitive recording layer on the support, but an undercoat layer can also be provided between the support and the heat-sensitive recording layer.

This undercoat layer mainly comprises a binder and a pigment.
As the binder used for the undercoat layer, a commonly used water-soluble polymer or hydrophobic polymer emulsion or the like can be appropriately used. Specific examples include cellulose derivatives such as polyvinyl alcohol, polyvinyl acetal, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, polyacrylic acid soda, polyvinyl pyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid Water-soluble polymers such as amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, Polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / acetic acid Cycloalkenyl copolymer, can be used styrene / butadiene / emulsion of a hydrophobic polymer such as an acrylic copolymer. These binders may be used alone or in combination of two or more.

As the pigment used in the undercoat layer, known pigments generally used conventionally, specific examples include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcined kaolin, clay, talc, etc. Inorganic pigments, organic hollow plastic pigments, solid plastic pigments, and the like can be used. These pigments may be used alone or in combination of two or more.
The pigment in the undercoat layer is usually 50 to 95 parts by weight, preferably 70 to 90 parts by weight with respect to 100 parts by weight of the total solid content.
Various auxiliary agents such as a dispersant, a pH adjuster, an antifoaming agent, a water retention agent, a preservative, a coloring dye, and an ultraviolet ray preventing agent may be appropriately blended in the coating liquid for the undercoat layer as necessary.

In the present invention, the means for applying the heat-sensitive recording layer and the coating layer other than the heat-sensitive recording layer is not particularly limited, and can be applied according to a well-known conventional technique. For example, an off-machine coating machine or an on-machine coating machine equipped with various coaters such as an air knife coater, a rod blade coater, a vent blade coater, a bevel blade coater, a roll coater, and a curtain coater is appropriately selected and used.
The coating amount of the heat-sensitive recording layer and the coating layer other than the heat-sensitive recording layer is determined according to the required performance and recording suitability, and is not particularly limited, but the general dry coating amount of the heat-sensitive recording layer is It is about ² to 12 g / m ² .
Further, various known techniques in the heat-sensitive recording material field can be added as appropriate, such as applying a smoothing process such as supercalendering after coating each layer.

  The following examples illustrate the invention but are not intended to limit the invention. In Examples and Comparative Examples, “parts” represents “parts by weight” and “%” represents “% by weight” unless otherwise specified. Various dispersions or coating solutions were prepared as follows.

[ Reference Example 1 ]
A composition comprising the following composition was stirred and dispersed to prepare an undercoat layer coating solution.
<Undercoat layer coating solution>
Baked kaolin (trade name: Ansilex 93, manufactured by BASF) 100.0 parts Styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.,
Product name: ST5526, solid content 48%) 10.0 parts water 50.0 parts

Next, after coating the undercoat layer coating liquid on one side of the support (high-quality paper having a basis weight of 47 g / m ² ) with a vent blade coater so that the coating amount is 10.0 g / m ² in solid content, Drying was performed to obtain an undercoat layer-coated paper.

  Leuco dye dispersions 1 to 2 (A1 to A2 liquids), developer dispersions 1 to 2 (B1 to B2 liquids), sensitizer dispersion liquid (C liquid), and ultraviolet absorber dispersion liquid (D liquid) ) Were separately ground by a sand grinder until the average particle size became 0.5 microns.

Leuco dye dispersion 1 (A1)
Divinyl compound (trade name: NIRBLACK78 manufactured by Fukui Yamada Co., Ltd.) ^* 6.0 parts anion-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.,
(Product name: L3266, solid content 10%) 5.0 parts Water 1.5 parts * NIRBLACK 78 is represented by the following formula.

Leuco dye dispersion 2 (A2)
3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd.,
Product name: ODB-2) 6.0 parts Anion-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.)
Product name: L3266, solid content 10%) 5.0 parts water 1.5 parts

Developer dispersion 1 (B1 solution)
Diphenylsulfone cross-linking compound (Nippon Soda Co., Ltd., D-90) ^* 6.0 parts Anion-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.,
(Product name: L3266, solid content 10%) 5.0 parts water 1.5 parts * D-90 is represented by the following formula:

Developer dispersion 2 (B2 liquid)
2,4′-dihydroxydiphenyl sulfone (manufactured by Nikka Chemical Co., Ltd.,
Product name: BPS-24C) 6.0 parts Anion-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.,
Product name: L3266, solid content 10%) 5.0 parts water 1.5 parts

Sensitizer dispersion (liquid C)
1,2-bis- (3-methylphenoxy) ethane (manufactured by Sanko Co., Ltd.,
Product name: KS232) 6.0 parts Anion-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.,
Product name: L3266, solid content 10%) 5.0 parts water 1.5 parts

Ultraviolet absorber dispersion (liquid D)
Benzotriazole compounds (manufactured by ADEKA,
Product name: Adeka Arcles LA31) ^* 6.0 parts Anion-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.)
(Product name: L3266, solid content 10%) 5.0 parts Water 1.5 parts * Adeka Arcles LA31 is represented by the following formula.

Next, each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 1.
<Thermosensitive recording layer coating solution 1>
Leuco dye dispersion 1 (A1 liquid) 18.0 parts Developer dispersion 1 (B1 liquid) 36.0 parts Sensitizer dispersion (liquid C) 36.0 parts Silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., product) Name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermosensitive recording layer coating solution 1 was applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount was 6.0 g / m ^{2 in} terms of solid content, followed by drying. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[ Reference Example 2 ]
Heat-sensitive recording layer coating solution 2 was prepared by mixing the dispersions at the following ratio.
<Thermosensitive recording layer coating solution 2>
Leuco dye dispersion liquid 1 (liquid A1) 18.0 parts Developer dispersion liquid 1 (liquid B1) 36.0 parts Sensitizer dispersion liquid (liquid C) 36.0 parts Ultraviolet absorber dispersion liquid (liquid D) 9 0.0 part silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermosensitive recording layer coating solution 2 was applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount was 6.0 g / m ² in solid content, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[ Reference Example 3 ]
Each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 3.
<Thermosensitive recording layer coating solution 3>
Leuco dye dispersion 1 (A1 liquid) 9.0 parts Leuco dye dispersion 2 (A2 liquid) 9.0 parts Developer dispersion 1 (B1 liquid) 36.0 parts Sensitizer dispersion (liquid C) 36 0.0 part UV absorber dispersion (D liquid) 9.0 parts silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 3 was applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount was 6.0 g / m ² in solid content, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[ Reference Example 4 ]
Each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 3.
<Thermosensitive recording layer coating solution 4>
Leuco dye dispersion 1 (Liquid A1) 2.0 parts Leuco dye dispersion 2 (Liquid A2) 16.0 parts Developer dispersion 1 (Liquid B1) 36.0 parts Sensitizer dispersion (Liquid C) 36 0.0 part UV absorber dispersion (D liquid) 9.0 parts silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 4 is applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount is 6.0 g / m ² in solids, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[ Reference Example 5 ]
<Thermosensitive recording layer coating solution 5>
Leuco dye dispersion 1 (Liquid A1) 1.0 part Leuco dye dispersion 2 (Liquid A2) 17.0 parts Developer dispersion 1 (Liquid B1) 36.0 parts Sensitizer dispersion (Liquid C) 36 0.0 part UV absorber dispersion (D liquid) 9.0 parts silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 5 is applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount is 6.0 g / m ^{2 in} terms of solid content, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[Example 6]
Each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 6.
<Thermosensitive recording layer coating solution 6>
Leuco dye dispersion 1 (A1 liquid) 18.0 parts Developer dispersion 1 (B1 liquid) 33.0 parts Developer dispersion 2 (B2 liquid) 3.0 parts Sensitizer dispersion (C liquid) 36.0 parts Ultraviolet absorber dispersion (liquid D) 9.0 parts Silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 6 is applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the solid content is 6.0 g / m ^2, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[Example 7]
Each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 7.
<Thermosensitive recording layer coating solution 7>
Leuco dye dispersion 1 (A1 liquid) 18.0 parts Developer dispersion 1 (B1 liquid) 26.0 parts Developer dispersion 2 (B2 liquid) 10.0 parts Sensitizer dispersion (liquid C) 36.0 parts Ultraviolet absorber dispersion (liquid D) 9.0 parts Silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 7 is applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount is 6.0 g / m ² in solids, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[Comparative Example 1]
Each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 8.
<Thermosensitive recording layer coating solution 8>
Leuco Dye Dispersion 2 (A2) 18.0 parts Developer Dispersion 1 (B1) 36.0 parts Sensitizer Dispersion (C) 36.0 parts UV Absorber Dispersion (D) 9 0.0 part silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 8 was applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount was 6.0 g / m ² in solid content, and then dried. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[Comparative Example 2]
Each dispersion was mixed at the following ratio to prepare a thermal recording layer coating solution 9.
<Thermosensitive recording layer coating solution 9>
Leuco dye dispersion liquid 1 (A1 liquid) 18.0 parts Developer dispersion liquid 2 (B2 liquid) 36.0 parts Sensitizer dispersion liquid (C liquid) 36.0 parts Ultraviolet absorber dispersion liquid (D liquid) 9 0.0 part silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, the thermal recording layer coating solution 9 is applied onto the undercoat layer of the undercoat layer-coated paper with a rod blade coater so that the coating amount is 6.0 g / m ^{2 in} terms of solid content, followed by drying. Then, a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[Comparative Example 3]
A heat-sensitive recording material was used in the same manner as in Example 1 described in Japanese Patent Application Laid-Open No. 2007-0505579 except that a high-quality paper having a basis weight of 47 g / m ² was used instead of the high-quality paper having a basis weight of 60 g / m ^2. Was made.

  The following evaluation was performed about the produced thermosensitive recording material.

<Coloring performance (print density)>
The produced thermal recording medium was checked using a checkerboard pattern with an applied energy of 0.35 mJ / dot and a printing speed of 50 mm / sec using a TH-PMD (equipped with thermal recording paper printing tester, Kyocera thermal head) manufactured by Okura Electric Co., Ltd. Is printed. The printing density of the printing part was measured with a Macbeth densitometer (RD-914, using an amber filter) to evaluate the color development performance.

<Optical character readability by near infrared light>
A bar code (code 39) was printed at a printing level of +10 and a printing speed of 6 inches / sec using a thermal label printer 140XiIII manufactured by Zebra Co., Ltd. The quality of the printed barcode was evaluated with a barcode verification machine (manufactured by Honeywell, QC800, light source 940 nm). Evaluation was performed according to ANSI standards (CEN method, average of 10 measurements).
(Excellent) A>B>C>D> F (Inferior)

<Water resistance of image part>
A bar code (code 39) was printed at a printing level of +10 and a printing speed of 6 inches / sec using a thermal label printer 140XiIII manufactured by Zebra Co., Ltd.
After being immersed in water at 23 ° C. and 50% Rh for 24 hours and air-dried, the quality of the barcode was evaluated with a barcode verification machine (QC 800, light source 940 nm, manufactured by Honeywell). Evaluation was performed according to ANSI standards (CEN method, average of 10 measurements).
(Excellent) A>B>C>D> F (Inferior)

<Plasticizer resistance of image area>
A bar code (code 39) was printed at a printing level of +10 and a printing speed of 6 inches / sec using a thermal label printer 140XiIII manufactured by Zebra Co., Ltd.
A vinyl chloride wrap (manufactured by Mitsui Toatsu Co., Ltd., High Wrap KMA) is wrapped around a paper tube in a single layer, and the thermal recording material is placed on the paper so that the barcode image printed on it is the outer surface. The wrap was fixed in three wraps. After processing for 24 hours in an environment of 23 ° C. and 50% RH, the quality of the barcode was evaluated with a barcode verification machine (QC 800, light source 940 nm, manufactured by Honeywell). Evaluation was performed according to ANSI standards (CEN method, average of 10 measurements).
(Excellent) A>B>C>D> F (Inferior)

<Light resistance of image area>
A bar code (code 39) was printed at a printing level of +10 and a printing speed of 6 inches / sec using a thermal label printer 140XiIII manufactured by Zebra Co., Ltd.
After processing for 2 hours at an output of 67 w / m ² using a xenon fade meter (Toyo Seiki Co., Ltd., Atlas Weather Ometer Ci3000F), the quality of the barcode is changed to a barcode verification machine (Honeywell, QC800, light source 940 nm). And evaluated. Evaluation was performed according to ANSI standards (CEN method, average of 10 measurements).
(Excellent) A>B>C>D> F (Inferior)

<Heat resistance of blank paper part>
The produced thermal recording material was treated in an environment of 40 ° C. and 90% RH for 24 hours, and then left to stand in an environment of 23 ° C. and 50% RH for 3 hours, and the density of the non-printing area (blank area) was set to the Macbeth density. It measured with the meter (RD-914, amber filter use), and the heat resistance of the non-printing part (white paper part) was evaluated on the following reference | standard by the difference of the value before and behind a process.
A: Difference in value before and after treatment is less than 0.01 B: Difference in value before and after treatment is 0.01 or more and less than 0.05 Δ: Difference in value before and after treatment is 0.05 or more and less than 0.10 ×: Treatment Difference between before and after values is 0.10 or more

  The evaluation results are shown in Table 1.

表１から、感熱記録層に顕色剤として一般式（化１）で表されるジフェニルスルホン架橋型化合物及び２，４’−ジヒドロキシジフェニルスルホンを、ロイコ染料として一般式（化４）で表されるジビニル化合物を、それぞれ含有させた場合には、近赤外領域に読み取り波長を有する光学文字読取装置に対する適性が良好であり、発色性能（印字濃度）、画像部の耐水性、耐可塑剤性、耐光性、及び白紙部の耐熱性が優れていることがわかる。
さらに、感熱記録層に更に紫外線吸収剤として一般式（化５）で表されるベンゾトリアゾール系化合物を含有させることにより、特に画像部の耐光性が優れることがわかる。

From Table 1, the diphenylsulfone cross-linked compound represented by the general formula (Chemical Formula 1) and 2,4′-dihydroxydiphenylsulfone represented by the general formula (Chemical Formula 1) as the developer in the heat-sensitive recording layer are represented by the general formula (Chemical Formula 4) as the leuco dye. When the divinyl compound to be contained is contained, the suitability for an optical character reader having a reading wavelength in the near-infrared region is good, the color development performance (print density), the water resistance of the image area, and the plasticizer It can be seen that the heat resistance, the light resistance, and the heat resistance of the white paper portion are excellent.
Furthermore, it can be seen that the light resistance of the image area is particularly excellent when the heat-sensitive recording layer further contains a benzotriazole compound represented by the general formula (Formula 5) as an ultraviolet absorber.

（式中、Ｒ^１は、それぞれ同じであっても異なってもよく、水素原子、ハロゲン原子、炭素数が１〜６のアルキル基又はアルケニル基を表し、ｍは、それぞれ同じであっても異なってもよく、０〜４の整数を表し、ｎは１〜１１の整数を表し、Ｒ^２は、それぞれ同じであっても異なってもよく、エーテル結合を有してもよい炭素数１〜１２の飽和若しくは不飽和の直鎖若しくは分枝の炭化水素基、下記一般式

(In the formula, R ¹ may be the same or different, and represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, and m is the same or different. Each represents an integer of 0 to 4, n represents an integer of 1 to 11, and R ² may be the same or different, and may have an ether bond. A saturated or unsaturated linear or branched hydrocarbon group of the following general formula

（式中、Ｒ^３はメチレン基又はエチレン基を表す。）で表される置換フェニレン基、又は下記一般式

(Wherein R ³ represents a methylene group or an ethylene group), or a substituted phenylene group represented by the following general formula:

（式中、Ｒ^４は水素原子又は炭素数が１〜４のアルキル基を表す。）で表される２価基を
表す。）で表されるジフェニルスルホン架橋型化合物。

(Wherein R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). Diphenylsulfone cross-linking compound represented by

（式中、Ｒ_５、Ｒ_６は炭素数８以下のアルキル基を示し、Ｘ_１は水素原子、ハロゲン原子、炭素数８以下のアルキル基を示し、Ｘ_２は炭素数８以下のアルコキシ基を示す。）

(Wherein R ₅ and R ₆ represent an alkyl group having 8 or less carbon atoms, X ₁ represents a hydrogen atom, a halogen atom or an alkyl group having 8 or less carbon atoms, and X ₂ represents an alkoxy group having 8 or less carbon atoms. Show.)

（式中Ｒ_７は炭素数４〜３０の直鎖又は分岐したアルキル基を示す。）

(In the formula, R ₇ represents a linear or branched alkyl group having 4 to 30 carbon atoms.)

Claims (4)

In a heat-sensitive recording material provided with a heat-sensitive recording layer containing an electron-accepting developer and a colorless or light-colored electron-donating leuco dye on a support, the heat-sensitive recording layer has the general formula as an electron-accepting developer. The diphenylsulfone crosslinkable compound represented by (Chemical Formula 1) and 2,4′-dihydroxydiphenylsulfone are used as electron donating leuco dyes, respectively, and the divinyl compound represented by the general formula (Chemical Formula 4) is contained. A characteristic thermal recording material.

(In the formula, R ¹ may be the same or different, and represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, and m is the same or different. Each represents an integer of 0 to 4, n represents an integer of 1 to 11, and R ² may be the same or different, and may have an ether bond. A saturated or unsaturated linear or branched hydrocarbon group of the following general formula

(Wherein R ³ represents a methylene group or an ethylene group), or a substituted phenylene group represented by the following general formula:

(Wherein R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). Diphenylsulfone cross-linking compound represented by

(Wherein R ₅ and R ₆ represent an alkyl group having 8 or less carbon atoms, X ₁ represents a hydrogen atom, a halogen atom or an alkyl group having 8 or less carbon atoms, and X ₂ represents an alkoxy group having 8 or less carbon atoms. Show.) 2. The heat-sensitive recording material according to claim 1, wherein the content of the diphenylsulfone cross-linking compound represented by the general formula (Chemical Formula 1) is 70% by weight or more of the total developer contained in the heat-sensitive recording layer. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer further contains a benzotriazole compound represented by the general formula (Formula 5) as an ultraviolet absorber.

(In the formula, R ₇ represents a linear or branched alkyl group having 4 to 30 carbon atoms.) The heat-sensitive recording material according to claim 3, wherein the benzotriazole-based compound is a compound represented by a chemical formula (Formula 6).