JP6255889B2 - 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”). The present invention relates to a heat-sensitive recording material, which is excellent in color development performance, water resistance, plasticizer resistance in an image area, and heat resistance in a blank paper area.

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, the media used has been miniaturized, such as for handy terminals, and for recording and labeling and ticketing applications, color sensitivity and image quality, especially barcode readability, are required. It has been. In addition, for example, it is often used outdoors for labels and used for food, etc., so that it is not difficult to read the image part due to moisture and moisture such as rain, etc. Since it is often stored, the plasticizer contained in the synthetic leather used in these materials does not make it difficult to read the image area. With respect to storage stability such as plasticizer properties, excellent performance has begun to be required.
As a method for improving the storage stability of the image area, it is generally known to provide a protective layer on the thermosensitive recording layer. However, when a protective layer is provided on the thermal recording medium, the protective layer absorbs the thermal energy given from the thermal head, so the color development performance, that is, the color development sensitivity and image quality, particularly the barcode reading ability is inferior. There is.
In addition, a thermal recording material (Patent Documents 1 and 2) in which the storage stability of the image area is improved by using a specific developer and stabilizer in combination, or a specific sensitizer and stabilizer are used in combination. Has disclosed a heat-sensitive recording material (Patent Document 3) that has improved the storage stability of the image area. However, when used in harsh environments such as labels and tickets described above, water resistance In addition, storage stability such as plasticizer resistance is insufficient.
Furthermore, a heat-sensitive recording material (Patent Document 4) is disclosed in which the color development performance and the storage stability of the image part are improved by using a combination of two specific developers, but the heat resistance of the blank paper part is disclosed. For this reason, when the thermal recording material is stored in a high temperature environment, the white paper portion is colored, and the barcode readability is insufficient.

JP2003-154760 JP 2001-347757 A WO2004 / 002748 JP 2006-264255 A

  Therefore, the present invention has an object to provide a heat-sensitive recording material that has good color development performance even in a harsh environment, and is excellent in water resistance, plasticizer resistance in an image area, and heat resistance in a white paper area. To do.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by including two specific types of color developer in a specific ratio in the heat-sensitive recording layer and further including a specific binder and a crosslinking agent . The present invention has been completed.
That is, the present invention relates to a heat-sensitive recording material in which a heat-sensitive recording layer containing a colorless or light leuco dye and a developer is provided on a support, and the heat-sensitive recording layer is represented by the following chemical formula ) And a diphenylsulfone crosslinkable compound represented by the following general formula (Chemical Formula 2) , and the diphenylsulfone crosslinkable compound is 0.1 to 1 part by weight of the urea compound. The thermosensitive recording material is characterized in that the thermosensitive recording layer further comprises a carboxyl group-containing resin, an epichlorohydrin resin, and a polyamine / polyamide resin .

（式中、Ｒ^３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のアルキル基またはアルケニル基を表し、ｏ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、ｐは１〜１１の整数を表し、Ｒ^４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 ³ may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, and o is the same or different. May represent an integer of 0 to 4, p represents an integer of 1 to 11, and R ⁴ 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^５はメチレン基またはエチレン基を表す。）で表される置換フェニレン基、または下記一般式

(Wherein R ⁵ represents a methylene group or an ethylene group), or a substituted phenylene group represented by the following general formula:

（式中、Ｒ^６は水素原子または炭素数が１〜４のアルキル基を表す。）で表される２価基を表す。）

(Wherein R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms ). )

According to the present invention, there is provided a heat-sensitive recording material that has good color development performance, particularly barcode readability, and is excellent in water resistance, plasticizer resistance in an image area, and heat resistance in a blank area even under severe conditions. It is possible to provide.
Furthermore, by providing a protective layer on the heat-sensitive recording material, it is possible to provide a heat-sensitive recording material that is particularly excellent in water resistance, plasticizer resistance in the image area, heat resistance in the blank paper area, and good color development performance. is there. Further, by incorporating a specific binder and a crosslinking agent in the heat-sensitive recording layer, it is possible to provide a heat-sensitive recording material having particularly good water 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 in which a heat-sensitive recording layer containing a colorless or light-colored leuco dye and a developer is provided on a support. Containing a urea compound represented by Chemical Formula 1) and a diphenylsulfone cross-linking compound represented by the above general formula (Chemical Formula 2), and the diphenyl sulfone cross-linking compound is added to 0.1 part by weight of the urea compound. 1 to 5.0 parts by weight, and the heat-sensitive recording layer further contains a carboxyl group-containing resin, an epichlorohydrin resin, and a polyamine / polyamide resin .

When the heat-sensitive recording layer of the present invention contains a urea compound represented by the chemical formula (Chemical Formula 1) and a diphenylsulfone cross-linked compound represented by the General Formula (Chemical Formula 2) as a developer, the heat-sensitive recording layer contains The coexistence of two types of phenylsulfone compounds increases the reaction efficiency with leuco dyes than when only one of them is contained, so that an electron transfer complex is easily formed and the reverse reaction hardly occurs. Therefore, it is presumed that the resulting thermal recording material is excellent in color development performance, water resistance, image area plasticizer resistance, and white paper area heat resistance.
Further, when a protective layer is provided on the thermal recording material, that is, when the protective layer absorbs part of the thermal energy given from the thermal head or the like and the thermal energy is low, the developer and leuco Since the stability of the electron transfer complex, which is a reaction product with the dye, is sufficiently high, it is presumed that the resulting thermal recording material has good color development performance.

  Next, various materials used in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention are exemplified, but a binder, a crosslinking agent, a pigment, and the like are provided as necessary as long as the desired effects on the above-described problems are not inhibited. It can also be used for each coating layer.

  In the present invention, a urea compound represented by the following chemical formula (Chemical Formula 1) and a diphenylsulfone cross-linked compound represented by the following General Formula (Chemical Formula 2) are used as the developer.

ここで、Ｒ^３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のアルキル基またはアルケニル基、好ましくは
水素原子を表す。
このアルキル基またはアルケニル基は、炭素数が１〜６のアルキル基また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、フッ素またはヨウ素、好ましくは塩素または臭素を表す。
ｏは、それぞれ同じであっても異なってもよく、０〜４、好ましくは０を表す。
ＯＨ基及び−ＯＲ^４Ｏ−基は、ＳＯ_２基に対して、パラ位にあることが好ましい。
ｐは１〜１１である。この化合物はｐが１〜１１の混合物であることが好ましい。

Here, each R ³ may be the same or different, 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. For example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, 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.
o may be the same or different and represents 0 to 4, preferably 0.
The OH group and the —OR ⁴ O— group are preferably in the para position with respect to the SO ₂ group.
p is 1-11. This compound is preferably a mixture having p of 1 to 11.

R ⁴ may be the same or different, but is preferably the same.
R ⁴ is a saturated or unsaturated, preferably saturated, linear or branched, preferably linear hydrocarbon having 1 to 12, preferably 3 to 7 carbon atoms, which 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. Examples of the polyalkylene oxide chain (—OR ⁴ O—) include —O— (C _n H _2n O) _1-3 — (n = 2 to 4, preferably 2 to 3, more preferably 2). The alkylene _group, -C _{m H 2m} - and the like.

In addition, as R ⁴ , the following general formula

（式中、Ｒ^５はメチレン基またはエチレン基を表す。Ｒ^５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。

(In the formula, R ⁵ represents a methylene group or an ethylene group. R ⁵ is preferably in the para position with respect to each other).

Further, as R ⁴ , the following general formula

（式中、Ｒ^６は水素原子または炭素数が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価基であってもよい。
Ｒ^４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 ⁶ is a hydrogen atom or an alkyl group having a carbon number 1 to 4, preferably it represents. A hydrogen atom) may be a divalent group represented by.
Among these, R ⁴ 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 ⁴ in the diphenylsulfone bridged compound of the general formula (Formula 2) 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 2) may be used by mixing several kinds of substituents (R ³ ) and / or p 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.

  Examples of the compound represented by the general formula (Formula 2) include 4,4′-bis [4- [4- (4-hydroxyphenylsulfonyl) phenoxy] -2-trans-butenyloxy] diphenylsulfone; '-Bis [4- (4-hydroxyphenylsulfonyl) phenoxy-4-butyloxy] diphenylsulfone; 4,4'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-3-propyloxy] diphenylsulfone; 4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyloxy] diphenylsulfone; 4- [4- (4-hydroxyphenylsulfonyl) phenoxy-4-butyloxy] -4 ′-[4- (4 -Hydroxyphenylsulfonyl) phenoxy-3-propyloxy] diphe 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-to -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] phenylsulfonyl] Phenoxy] -cis-2-bu 1,4-bis [4- [4- [4- [4- (4-hydroxyphenylsulfonyl) phenoxy-2-trans-butenyloxy] phenylsulfonyl] phenoxy] -trans-2-butene; 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] diphenyl Sulfone; 4,4′-bis [4- (4-hydro 2,4′-bis [4- (4-hydroxyphenylsulfonyl) phenyl-1,2-phenylenebismethyleneoxy] diphenylsulfone; 2,4'-bis [4- (4-hydroxyphenylsulfonyl) phenyl-1,2-phenylenebismethyleneoxy] diphenylsulfone; 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-phenylenebismethyleneoxy] phenyls Phonyl] phenoxy] -m-xylene; α, α′-bis [4- [4- [4- (4-hydroxyphenylsulfonyl) phenyl-1,2-phenylenebismethyleneoxy] phenylsulfonyl] phenoxy] -o— 2,4′-bis [2- (4-hydroxyphenylsulfonyl) phenoxy-2-ethyleneoxyethoxy] diphenyl sulfone; 2,4′-bis [4- (2-hydroxyphenylsulfonyl) phenoxy-2-ethylene 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-hydroxyphenylsulfonate) L) phenoxy-2-ethyleneoxyethoxy] diphenylsulfone; 4,4′-bis [3,5-dimethyl-4- (3,5-dimethyl-4-hydroxyphenylsulfonyl) phenyl-1,4-phenylenebismethylene 4,4′-bis [3,5-dimethyl-4- (3,5-dimethyl-4-hydroxyphenylsulfonyl) phenyl-1,3-phenylenebismethyleneoxy] diphenyl sulfone; '-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) 1,4-phenylenebismethyleneoxy 4,4′-bis [3-allyl-4- (3-allyl-4-hydroxyphenylsulfonyl) 1,3-phenylenebismethyleneoxy] diphenylsulfone; 4,4′-bis [3-allyl- 4- (3-allyl-4-hydroxyphenylsulfonyl) 1,2-phenylenebismethyleneoxy] diphenylsulfone; 4,4′-bis [4- (4-hydroxyphenylsulfonyl) phenoxy-2-hydroxypropyloxy] diphenyl Sulfone; 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 2) is used, a particularly preferable composition contains two or more types in which R ³ is the same and only the value of p is different. To do. If it is such a compound, a manufacturing method is also simple and the compound from which the value of p differs by changing the reaction ratio of a raw material can be synthesize | combined at arbitrary content ratios at once. Among these, as the compound represented by p = 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; 1,4 -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; α, α'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] -m-xylene; α, α'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] -o-xylene 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 D90 (the following formula) manufactured by Nippon Soda Co., Ltd.

  In the present invention, the ratio of 0.1 to 5.0 parts by weight of the diphenylsulfone cross-linked compound represented by the general formula (Chemical Formula 2) with respect to 1 part by weight of the urea compound represented by the chemical formula (Chemical Formula 1). It is preferably used at a ratio of 0.5 to 3.0 parts by weight. When the diphenylsulfone cross-linking compound represented by the general formula (Chemical Formula 2) is less than 0.1 part by weight with respect to 1 part by weight of the urea compound represented by the chemical formula (Chemical Formula 1), the color of the resulting heat-sensitive recording material is developed. There is a tendency for performance to decline. On the other hand, if it exceeds 5.0 parts by weight, the water resistance, the plasticizer resistance of the image part, and the heat resistance of the blank paper part may not be sufficient.

  Examples of the developer other than the urea compound represented by the chemical formula (Chemical Formula 1) and the diphenylsulfone cross-linked compound represented by the General Formula (Chemical Formula 2) used in the present invention include, for example, activated clay, attapulgite, Inorganic acidic substances such as colloidal silica and aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane 4,4′-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenyl Sulfone, 4-hydroxy-4'-n-pro Xidiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) 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, phenol condensation composition described in JP-A-2003-154760 Aminobenzenesulfonamide derivatives, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p-hydroxy) described in JP-A-8-59603 Phenyl) butyl acetate, bis ( -Hydroxyphenyl) methyl acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3 -Bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2 '-Thiobis (4-tert-octylphenol), compounds described in WO02 / 081229 or JP2002-301873, and thiourea compounds such as N, N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid , Stearyl gallate, zinc bis [4- (n-octyloxycarbonylamino) salicylate] dihydrate, 4- [2- p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic aromatic carboxylic acid, and these Of aromatic carboxylic acids with zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel and other polyvalent metal salts, as well as antipyrine complexes of zinc thiocyanate, terephthalaldehyde acid and other aromatic carboxylic acids And a composite zinc salt. 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 urea compound represented by the chemical formula (Chemical Formula 1) and the diphenylsulfone cross-linked compound represented by the General Formula (Chemical Formula 2), the chemical formula The total content of the urea compound represented by (Chemical Formula 1) and the diphenylsulfone cross-linking compound represented by the above General Formula (Chemical Formula 2) is the total developer (the above chemical formula It is preferably 50% by weight or more, more preferably 90% by weight or more of the urea compound represented by (Chemical Formula 1) and the diphenylsulfone crosslinking type compound represented by the general formula (Chemical Formula 2).

  As the leuco dye used in the present invention, any known leuco dyes in the field of conventional pressure-sensitive or thermal recording paper can be used, and are not particularly limited, but include triphenylmethane compounds, fluoran compounds, fluorenes. Of these, divinyl compounds and divinyl compounds are preferred. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These dye precursors 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- [2- (P-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ) Ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3,3-bis- [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2- Yl] -4,5,6,7-tetrachlorophthalide

<Others>
3- (4-Diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- ( 1-octyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 4-azaphthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,6-bis (diethylamino) fluorane-γ- (3′-nitro) anilinolactam, 3,6 -Bis (diethylamino) fluorane-γ- (4′-nitro) anilinolactam, 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylamino) 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

  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. 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.

  Moreover, in this invention, a crosslinking agent can also be used together. Examples of the crosslinking agent include epichlorohydrin resins such as polyamine epichlorohydrin resins and polyamide epichlorohydrin resins, polyamide urea resins, polyalkylene polyamine resins, polyalkylene polyamide resins, polyamine polyurea resins, and modified polyamines. Polyamine / polyamide resins such as resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, or polyalkylene polyamine polyamide polyurea resins, glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, potassium persulfate, ammonium persulfate, persulfate Examples thereof include sodium sulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride.

In the present invention, it is preferable to add a carboxyl group-containing resin as a binder and an epichlorohydrin-based resin and a polyamine / polyamide-based resin as a crosslinking agent to the heat-sensitive recording layer, respectively, because the water resistance becomes particularly good.
In the present invention, when the heat-sensitive recording layer contains a carboxyl group-containing resin as a binder and an epichlorohydrin resin and a polyamine / polyamide resin as a cross-linking agent, respectively, the reason why water resistance is particularly good is as follows. So guessed.

  A crosslinking reaction (first water resistance) occurs between the carboxyl group of the carboxyl group-containing resin and the amine part or amide part of the epichlorohydrin-based resin as a crosslinking agent. Next, since the hydrophilic cross-linking site formed by the carboxyl group-containing resin and the epichlorohydrin resin attracts the hydrophilic site of the polyamine / polyamide resin, this cross-linking site is a hydrophobic group of the polyamine / polyamide resin. In a state where the cross-linked portion having hydrophilicity is protected from water by a hydrophobic group (second water resistance). Therefore, it is estimated that extremely high hydrophobicity is imparted to the reaction site between the carboxyl group-containing resin and the crosslinking agent, and the water resistance is particularly good.

The carboxyl group-containing resin used in the heat-sensitive recording layer of the present invention may be any resin as long as it mainly has a carboxyl group, such as methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylamino methacrylate. Examples include acrylic resins containing monofunctional acrylic monomers having a carboxyl group such as ethyl, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, oxidized starch, carboxymethyl cellulose, carboxy-modified polyvinyl alcohol having a carboxyl group introduced into polyvinyl alcohol, and the like. It is possible.
In particular, when the carboxyl group-containing resin is carboxy-modified polyvinyl alcohol, the plasticizer resistance of the image area and the heat resistance of the blank paper area are further improved, which is preferable. This is presumably because, in addition to the above-described crosslinking reaction, the cationic site of the polyamine / polyamide resin further undergoes a crosslinking reaction with the carboxyl group of the carboxy-modified polyvinyl alcohol.

  The carboxy-modified polyvinyl alcohol used in the heat-sensitive recording layer of the present invention is a reaction product of polyvinyl alcohol and a polyvalent carboxylic acid such as fumaric acid, phthalic anhydride, mellitic anhydride, itaconic anhydride, or an ester of these reactants. And a saponified product of a copolymer of vinyl acetate and an ethylenically unsaturated dicarboxylic acid such as maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid or methacrylic acid. Specific examples include the production method exemplified in Example 1 or 4 of JP-A-53-91995. The saponification degree of the carboxy-modified polyvinyl alcohol is preferably 72 to 100 mol%, the polymerization degree is preferably 500 to 2400, and more preferably 1000 to 2000.

The epichlorohydrin-based resin used in the heat-sensitive recording layer of the present invention is a resin characterized by containing an epoxy group in the molecule, and the above-mentioned polyamide epichlorohydrin resin, polyamine epichlorohydrin Examples thereof include resins.
As the amine present in the main chain of the epichlorohydrin resin, those from primary to quaternary can be used, and there is no particular limitation. Further, the degree of cationization and the molecular weight are preferably water resistance, so that the degree of cationization is preferably 5 meq / g · Solid or less (measured value at pH 7), and the molecular weight is preferably 500,000 or more. These epichlorohydrin resins can be used alone or in combination of two or more.
Specific examples of the epichlorohydrin-based resin used in the heat-sensitive recording layer of the present invention include Sumire Resin 650 (30), Sumire Resin 675A, Sumire Resin 6615 (above, manufactured by Sumitomo Chemical Co., Ltd.), WS4002, WS4020. , WS4024, WS4030, WS4046, WS4010, CP8970 (manufactured by Starlight PMC) and the like.

The polyamine / polyamide resin used in the heat-sensitive recording layer of the present invention is a resin characterized by having no epoxy group in the molecule, and the above-mentioned polyamide urea resin, polyalkylene polyamine resin, polyalkylene polyamide resin And polyamine polyurea resin, modified polyamine resin, modified polyamide resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea resin, and the like.
Among these polyamine / polyamide resins, polyamine resins (polyalkylene polyamine resins, polyamine polyurea resins, modified polyamine resins, polyalkylene polyamine urea formalin resins, polyalkylene polyamine polyamide polyureas are particularly good because of their good water resistance. It is preferable to use a tree. These polyamine / polyamide resins can be used alone or in combination of two or more.
Specific examples of the polyamine / polyamide resin used in the heat-sensitive recording layer of the present invention include Sumire Resin 302 (manufactured by Sumitomo Chemical Co., Ltd .: polyamine polyurea resin), Sumire Resin 712 (manufactured by Sumitomo Chemical Co., Ltd .: polyamine polyurea resin). ), Sumire Resin 703 (Sumitomo Chemical Co., Ltd .: polyamine polyurea resin), Sumire Resin 636 (Sumitomo Chemical Co., Ltd .: polyamine polyurea resin), Sumire Resin SPI-100 (Sumitomo Chemical Co., Ltd .: modified polyamine resin) , Sumire Resin SPI-102A (Sumitomo Chemical Co., Ltd .: modified polyamine resin), Sumire Resin SPI-106N (Sumitomo Chemical Co., Ltd .: modified polyamide resin), Sumire Resin SPI-203 (50) (Sumitomo Chemical Co., Ltd.) , Sumirez resin SPI-198 (manufactured by Sumitomo Chemical Co., Ltd.), printable A-700 ( (Made by Kasei Co., Ltd.), Principal A-600 (made by Asahi Kasei Co., Ltd.), PA6500, PA6504, PA6664, PA6638, PA6640, PA6664, PA6646, PA6654, PA6702, PA6704 ) 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, 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, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

  The types and amounts of the leuco dye, developer, sensitizer, and other various components used in the heat-sensitive recording layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, 0.5 to 10 parts by weight of developer, 0.1 to 10 parts by weight of sensitizer, 0.5 to 20 parts by weight of pigment, and 0.01 to 10 parts by weight of stabilizer for 1 part by weight of leuco dye. Parts and other components of about 0.01 to 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. As a protective layer in this invention, the structure of the protective layers 1 thru | or 3 shown below is preferable.

[Protective layer 1]
The protective layer contains a carboxyl group-containing resin, particularly carboxy-modified polyvinyl alcohol, and an epichlorohydrin resin and a polyamine / polyamide resin.
When the protective layer of the present invention has a constitution of the protective layer 1, that is, a constitution containing an epichlorohydrin resin and a polyamine / polyamide resin together with a carboxyl group-containing resin, the water resistance and the plasticizer resistance of the image area It is preferable because the heat resistance of the white paper portion is good.
When only one of epichlorohydrin resin and polyamine / polyamide resin is used together with the carboxyl group-containing resin, or any of epichlorohydrin resin and polyamine / polyamide resin with the carboxyl group-containing resin When only one of them is used, and when another general crosslinking agent is used in combination, for example, the above effect is exhibited even when epichlorohydrin resin and glyoxal are used in combination, but the configuration of the protective layer 1 Since the said effect expresses notably, it is preferable. The reason is estimated as follows.

  A crosslinking reaction (first water resistance) occurs between the carboxyl group of the carboxyl group-containing resin and the amine part or amide part of the epichlorohydrin-based resin as a crosslinking agent. Next, since the hydrophilic cross-linking site formed by the carboxyl group-containing resin and the epichlorohydrin resin attracts the hydrophilic site of the polyamine / polyamide resin, this cross-linking site is a hydrophobic group of the polyamine / polyamide resin. In a state where the cross-linked portion having hydrophilicity is protected from water by a hydrophobic group (second water resistance). Therefore, it is estimated that extremely high hydrophobicity is imparted to the reaction site between the carboxyl group-containing resin and the crosslinking agent, and the water resistance is particularly good.

  In particular, when the carboxyl group-containing resin is carboxy-modified polyvinyl alcohol, in addition to the crosslinking reaction described above, the cationic site of the polyamine / polyamide resin further undergoes a crosslinking reaction with the carboxyl group of the carboxy-modified polyvinyl alcohol. It is presumed that the plasticizer resistance and the heat resistance of the white paper portion are further improved.

  The carboxyl group-containing resin used in the configuration of the protective layer 1 may be any resin as long as it mainly has a carboxyl group, and can be appropriately selected from the carboxyl group-containing resins used in the heat-sensitive recording layer.

  The epichlorohydrin resin used in the structure of the protective layer 1 is a resin characterized by containing an epoxy group in the molecule. From the epichlorohydrin resin used in the heat-sensitive recording layer, It can be appropriately selected and used.

  The polyamine / polyamide resin used in the constitution of the protective layer 1 is a resin characterized by having no epoxy group in the molecule, and is appropriately selected from the polyamine / polyamide resins used in the above-mentioned thermal recording layer Can be used. From the viewpoint of color development sensitivity, it is preferable to use polyamine resins (polyalkylene polyamine resin, polyamine polyurea resin, modified polyamine resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea resin, etc.).

[Protective layer 2]
An acrylic resin is contained in the protective layer.
It is preferable that the protective layer of the present invention has the structure of the protective layer 2, that is, the structure containing an acrylic resin, because the water resistance, the plasticizer resistance of the image area, and the heat resistance of the blank area are good.

  The acrylic resin used in the configuration of the protective layer 2 includes (meth) acrylic acid and a monomer component copolymerizable with (meth) acrylic acid, and (meth) acrylic acid is contained in 100 parts by weight of the acrylic resin. It is preferable that it is 1-10 weight part. (Meth) acrylic acid is alkali-soluble and has the property of making an acrylic resin a water-soluble resin by the addition of a neutralizing agent. By changing the acrylic resin to a water-soluble resin, particularly when a pigment is contained in the protective layer, the binding property to the pigment is remarkably improved, and a protective layer having excellent strength even when containing a large amount of pigment is formed. be able to. Examples of components copolymerizable with (meth) acrylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, By alkyl acrylate resins such as pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and epoxy resins, silicone resins, styrene or derivatives thereof Modified alkyl acrylate resins such as the above-mentioned alkyl acrylate resins, (meth) acrylonitrile, acrylate esters, and hydroxyalkyl acrylate esters can be exemplified, but in particular, (meth) acrylonitrile and / or methyl methacrylate is blended. Is preferred. (Meth) acrylonitrile is preferably blended in an amount of 15 to 70 parts per 100 parts of the acrylic resin. Moreover, it is preferable that methyl methacrylate contains 20-80 parts in 100 parts of acrylic resins. When (meth) acrylonitrile and methyl methacrylate are included, it is preferable to blend 15 to 18 parts of (meth) acrylonitrile in 100 parts of acrylic resin and 20 to 80 parts of methyl methacrylate in 100 parts of acrylic resin.

  The acrylic resin used in the configuration of the protective layer 2 preferably has a glass transition point (Tg) higher than 30 ° C, more preferably higher than 30 ° C and lower than or equal to 130 ° C, and Tg higher than 50 ° C and 95 ° C. More preferably, it is as follows. When Tg is 30 ° C. or lower, water resistance is sufficient, but heat resistance may not be sufficient. On the other hand, when Tg is high, printing runnability (stick resistance) and scratch resistance tend to be improved, but when Tg is higher than 130 ° C., the protective layer becomes brittle, water resistance, plasticizer resistance and solvent resistance. In some cases, the desired effect cannot be obtained, such as not being sufficient. The Tg of acrylic resin is measured by differential scanning calorimetry (DSC).

The acrylic resin used in the configuration of the protective layer 2 is preferably a non-core shell type. In general, the core-shell type acrylic resin is frequently used because it has better heat resistance than the non-core-shell type acrylic resin, and has excellent stick resistance when used in a coating layer. However, since the shell portion of the core-shell type acrylic resin usually has a low thermal conductivity, it also has the disadvantage of poor color development sensitivity. On the other hand, the normal non-core shell type acrylic resin has low heat resistance and has the disadvantage that sticks and head debris are easily generated. However, the non-core shell type has a Tg of 30 ° C. or higher and 130 ° C. or lower. Acrylic resins are excellent in heat resistance, and thus have good color development sensitivity and good print running properties (head debris resistance, sticking resistance).
The Tg of acrylic resin is measured by differential scanning calorimetry (DSC).

[Protective layer 3]
The protective layer contains acetoacetyl-modified polyvinyl alcohol.
It is preferable that the protective layer of the present invention has the structure of the protective layer 3, that is, the structure containing acetoacetyl-modified polyvinyl alcohol, because the water resistance, the plasticizer resistance of the image area, and the heat resistance of the blank paper area are good.

  When the protective layer of the present invention has the structure of the protective layer 2 or the structure of the protective layer 3, the protective layer includes various crosslinking agents used for the heat-sensitive recording layer as necessary within a range that does not inhibit the desired effect. May be used in combination.

The protective layer of the present invention preferably further contains a pigment. By including a pigment in the protective layer, particularly good printing runnability (head debris resistance, sticking resistance) can be obtained.
Examples of the pigment used in the protective layer of the present invention include inorganic or organic fillers such as kaolin, calcined kaolin, aluminum hydroxide, silica, calcium carbonate, diatomaceous earth, talc, and titanium oxide. In consideration of the wear properties of the thermal head, kaolin, calcined kaolin and aluminum hydroxide are preferred.

  In particular, when the protective layer of the present invention is the constitution of the protective layer 1 and the carboxyl group-containing resin is carboxy-modified polyvinyl alcohol, that is, epichlorohydrin resin and polyamine / polyamide resin together with carboxy-modified polyvinyl alcohol. In the case of a structure containing, the protective layer has a three-dimensional structure due to a crosslinking reaction between the carboxy-modified polyvinyl alcohol and the epichlorohydrin resin. If an anionic pigment such as kaolin, aluminum hydroxide, magnesium hydroxide or the like is further added, the cationic polyamine / polyamide resin exhibits a dispersion effect on the anionic pigment. It is thought that it will be in a particularly porous state. Therefore, the melt of the material with low heat resistance in the heat-sensitive recording layer is adsorbed in the voids in the protective layer and does not elute to the surface of the heat-sensitive recording material, and extremely excellent print running properties (head debris resistance, sticking resistance) ) Is expressed.

The pigment used in the protective layer of the present invention preferably has an aspect ratio of 30 or more. In particular, kaolin having an aspect ratio of 30 or more is preferable because a heat-sensitive recording material of better quality can be obtained.
In the present invention, the aspect ratio of the pigment is a value obtained by calculating an average of 100 particles obtained by photographing a powder with an electron microscope and randomly extracted, using a calculation formula (aspect ratio = diameter / thickness). The greater the aspect ratio value, the greater the flatness of the pigment.

  The kaolin having an aspect ratio of 30 or more used in the protective layer of the present invention is very flat compared to a pigment generally used as a papermaking material, and compared with a case where a pigment having a smaller aspect ratio is used. The amount of kaolin used to cover the same area is reduced. That is, since the protective layer can be made thin, it is considered that the decrease in the thermal conductivity to the heat-sensitive recording layer can be suppressed, and excellent color development performance and image quality can be obtained. Kaolin having an aspect ratio of 30 or more can be obtained by classifying delaminated kaolin by special grinding.

  In the present invention, the preferred aspect ratio of kaolin used in the protective layer is 30 to 100, more preferably 30 to 75. When the aspect ratio is larger than 100, the water retention of the coating solution is lowered, the coating suitability is remarkably lowered, and the protective layer is locally dense, which may cause problems such as uneven coloring sensitivity. The kaolin desirably has an average diameter of 4 μm or less. When the average diameter of kaolin having an aspect ratio of 30 or more is larger than 4 μm, the surface smoothness of the protective layer is lowered, which may cause problems such as deterioration in print image quality.

The kaolin having an aspect ratio of 30 or more used in the protective layer of the present invention usually has an oil absorption of 50 to 80 ml / 100 g and a BET specific surface area of 10 to 30 m ² / g. On the other hand, mica (mica) having an aspect ratio of 100 or more has a low ability to absorb water and solvent, with an oil absorption of about 10 to 30 ml / 100 g and a BET specific surface area of about ² to 10 m ² / g. When kaolin having an aspect ratio of 30 or more is used in the protective layer of the present invention, the water resistance, solvent resistance, and print running property (head residue resistance, sticking resistance) of the thermal recording material are higher than when mica is used. Excellent.

In the present invention, the content of the binder, pigment, crosslinking agent and the like in the protective layer is determined according to the required performance and recording suitability, and is not particularly limited. Usually, the binder is used with respect to 100 parts by weight of the pigment. It is preferable to use about 1 to 100 parts by weight of the solid content of the crosslinking agent with respect to about 30 to 300 parts by weight of the solid content and 100 parts by weight of the solid content of the binder.
Moreover, when the protective layer of this invention is the structure of the protective layer 1, content (solid content) of the carboxyl group-containing resin, epichlorohydrin resin, and polyamine / polyamide resin used in the structure of the protective layer 1 is Although not particularly limited, each of the protective layers (solid content) is preferably 1 part by weight or more in 100 parts by weight. If any of them is less than 1 part by weight, a sufficient film for protecting the heat-sensitive recording layer located in the lower layer cannot be formed, and water resistance, plasticizer resistance of the image area, and heat resistance of the blank paper area are sufficiently obtained. There may not be.
In addition, the content of the epichlorohydrin resin and the polyamine / amide resin is preferably 1 to 100 parts by weight in terms of solid content with respect to 100 parts by weight of the solid content of the carboxyl group-containing resin. More preferred are parts by weight. When the content is 1 part by weight or more, more preferably 5 parts by weight or more, respectively, the image quality and the color development performance are particularly good. Further, when the content is 100 parts by weight or less, more preferably 50 parts by weight or less, respectively, increase in viscosity of the coating liquid and gelation hardly occur, and the operability is good. In addition, since the epichlorohydrin resin undergoes a crosslinking reaction at a pH of 6.0 or higher, it is preferable to adjust the pH of the protective layer coating solution to 6.0 or higher.

  The heat-sensitive recording material of the present invention has a heat-sensitive recording layer on a support, but an undercoat layer can 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 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 additives such as a dispersant, a plasticizer, a pH adjuster, an antifoaming agent, a water retention agent, an antiseptic, a coloring dye, and an ultraviolet ray inhibitor may be appropriately blended in the undercoat layer coating liquid as necessary. Good.

In the present invention, the means for coating the heat-sensitive recording layer and the coating layer other than the heat-sensitive recording layer, that is, the protective layer, the undercoat layer and the like are not particularly limited, and can be applied according to well-known conventional techniques. 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 coating layer other than the heat-sensitive recording layer and the heat-sensitive recording layer is determined according to the required performance and recording suitability, and is not particularly limited, but the general coating amount of the heat-sensitive recording layer is solid. a 2~12g / ^{m 2} approximately in minutes, the coating amount of the protective layer is 0.5 to 5.0 g / ^{m 2} is preferred solids.
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 coating 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>
Firing kaolin (BASF, trade name: Ansilex 90) 90.0 parts Styrene-butadiene copolymer latex (Nippon Zeon,
Product name: ST5526, solid content 48%) 10.0 parts water 50.0 parts

Next, after coating the undercoat layer coating solution on one side of a support (high-quality paper having a basis weight of 47 g / m ² ) by the vent blade method so that the coating amount is 10.0 g / m ^{2 in} solid content. Then, drying was performed to obtain an undercoat layer-coated paper.

  First developer dispersions 1 to 3 (A1 to A3), second developer dispersion (B), leuco dye dispersion (C) and sensitizer dispersion (D) ) Were separately ground with a sand grinder until the average particle size became 0.5 μm.

First developer dispersion (A1 solution)
Urea compounds represented by the chemical formula (Chemical Formula 1) (Nippon Soda Co., Ltd.,
Product name NKK1304) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (trade name: PVA117, manufactured by Kuraray Co., Ltd.)
(Solid content 10%) 5.0 parts Water 1.5 parts First developer dispersion 2 (A2 liquid)
2,4′-dihydroxydiphenyl sulfone (manufactured by Nikka Chemical Co., Ltd.,
Product name: BPS-24C) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (trade name: PVA117, manufactured by Kuraray Co., Ltd.)
(Solid content 10%) 5.0 parts Water 1.5 parts First developer dispersion 3 (A3 liquid)
4-hydroxy-4′-isopropoxydiphenylsulfone (manufactured by API Corporation, trade name: NY-DS) 6.0 parts complete saponified polyvinyl alcohol aqueous solution (trade name: PVA117, manufactured by Kuraray Co., Ltd.)
(Solid content 10%) 5.0 parts Water 1.5 parts

Second developer dispersion (liquid B)
Diphenylsulfone cross-linking compound represented by the general formula (Chemical Formula 2) (Nippon Soda Co., Ltd., trade name: D90) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117)
(Solid content 10%) 5.0 parts Water 1.5 parts

Leuco dye dispersion (liquid C)
3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd.,
Product name: ODB-2) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name: PVA117)
(Solid content 10%) 5.0 parts Water 1.5 parts

Sensitizer dispersion (liquid D)
Oxalic acid-bisparamethylbenzyl (Dainippon Ink Chemical Co., Ltd.,
Product name: HS3520) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., product name: PVA117,
(Solid content 10%) 5.0 parts Water 1.5 parts

Subsequently, each dispersion liquid was mixed in the following ratio to prepare a thermosensitive recording layer coating liquid.
<Thermosensitive recording layer coating solution 1>
1st developer dispersion (liquid A1) 18.0 parts 2nd developer dispersion (liquid B) 18.0 parts Leuco dye dispersion (liquid C) 18.0 parts Sensitizer dispersion (liquid D) ) 36.0 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, on the undercoat layer of the undercoat layer-coated paper, the thermosensitive recording layer coating solution 1 is applied by a rod blade method so that the coating amount is 6.0 g / m ^{2 in} solid content, and then dried. And a heat-sensitive recording material was obtained by processing with a super calendar so that the smoothness was 500 to 1000 seconds.

[ Reference Example 2 ]
Reference Example , except that 9.0 parts of the first developer dispersion 1 (A1 liquid) and 27.0 parts of the second developer dispersion (B liquid) in the thermal recording layer coating liquid 1 were used. A heat-sensitive recording material was produced in the same manner as in Example 1 .
[ Reference Example 3 ]
Reference Example , except that 27.0 parts of the first developer dispersion 1 (A1 liquid) and 9.0 parts of the second developer dispersion (B liquid) in the thermal recording layer coating liquid 1 were used. A heat-sensitive recording material was produced in the same manner as in Example 1 .

[Example 4]
Each dispersion was mixed at the following ratio to prepare a heat-sensitive recording layer coating solution.
<Thermosensitive recording layer coating solution 2>
1st developer dispersion (liquid A1) 18.0 parts 2nd developer dispersion (liquid B) 18.0 parts Leuco dye dispersion (liquid C) 18.0 parts Sensitizer dispersion (liquid D) ) 36.0 parts silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
17.5 parts carboxy-modified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: KL318,
Degree of polymerization: about 1700, degree of saponification: 95-99 mol%, solid content 10%) 21.0 parts Polyamide epichlorohydrin resin (manufactured by Seiko PMC, trade name: WS4030)
Cation degree: 2.7, molecular weight: 2.2 million, quaternary amine,
0.8 part modified polyamine resin (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumires resin SPI-102A,
0.5% solids) 0.5 parts

Next, on the undercoat layer of the undercoat layer-coated paper, the thermosensitive recording layer coating solution 2 is applied by a rod blade method so that the coating amount is 6.0 g / m ^{2 in} solid content, and then dried. And a heat-sensitive recording material was obtained 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 heat-sensitive recording layer coating solution.
<Thermosensitive recording layer coating solution 3>
1st developer dispersion (liquid A1) 18.0 parts 2nd developer dispersion (liquid B) 18.0 parts Leuco dye dispersion (liquid C) 18.0 parts Sensitizer dispersion (liquid D) ) 36.0 parts silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizukasil P-537, solid content 25%)
7.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

Next, on the undercoat layer of the undercoat layer-coated paper, the thermosensitive recording layer coating solution 3 is applied by a rod blade method so that the coating amount is 6.0 g / m ^{2 in} solid content, and then dried. And processed with a super calendar so that the smoothness was 500 to 1000 seconds to obtain a heat-sensitive recording layer coated paper.

Subsequently, the mixture which consists of the following ratio was mixed and the protective layer coating liquid was prepared.
<Protective layer coating solution 1>
Aluminum hydroxide dispersion (manufactured by Martinsberg,
Product name: Martyfin OL, solid content 50%) 9.0 parts Carboxy-modified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., product name: KL318)
Degree of polymerization: about 1700, degree of saponification: 95-99 mol%, solid content 10%) 30.0 parts Polyamide epichlorohydrin resin (manufactured by Seiko PMC, trade name: WS4030,
4.0 parts modified polyamine resin (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumires resin SPI-102A, solid content 25%)
Solid content 45%) 2.2 parts Zinc stearate (manufactured by Chukyo Yushi Co., Ltd., trade name: Hydrin Z-7-30,
(Solid content 30%) 2.0 parts water 22.8 parts

Next, on the heat-sensitive recording layer of the heat-sensitive recording layer-coated paper, after coating the protective layer coating liquid 1 by a rod blade method so that the coating amount is 3.0 g / m ^{2 in} solid content, Drying was performed, and a heat-sensitive recording material was produced by processing with a super calendar so that the smoothness was 1500 to 2000 seconds.

[ Reference Example 5 ]
A thermosensitive recording material was produced in the same manner as in Reference Example 4 except that instead of the protective layer coating solution 1, a protective layer coating solution 2 in which a composition having the following ratio was mixed was used.
<Protective layer coating solution 2>
Aluminum hydroxide dispersion (manufactured by Martinsberg,
Product name: Martyfin OL, solid content 50%) 4.0 parts Non-core shell type acrylic resin (Mitsui Chemicals, product name: ASN1004K,
Tg 55 ° C., solid content 18%) 30.0 parts water 15.0 parts

[ Reference Example 6 ]
A heat-sensitive recording material was produced in the same manner as in Reference Example 4 except that instead of the protective layer coating solution 1, a protective layer coating solution 3 in which a composition having the following ratio was mixed was used.
<Protective layer coating solution 3>
Aluminum hydroxide dispersion (manufactured by Martinsberg,
Product name: Martyfin OL, solid content 50%) 9.0 parts Acetoacetyl-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Gosei Co., Ltd.,
Product name: Gohsenx Z-300, degree of polymerization: 300,
Degree of saponification: 99 mol%, solid content 10%) 30.0 parts Zinc stearate (manufactured by Chukyo Yushi Co., Ltd., trade name: Hydrin Z-7-30,
(Solid content 30%) 2.0 parts water 13.0 parts

[Comparative Example 1]
Reference Example 1 except that 36.0 parts of the first developer dispersion 1 (A1 liquid) and 0 parts of the second developer dispersion (B liquid) in the thermal recording layer coating liquid 1 were used. A heat-sensitive recording material was produced in the same manner.
[Comparative Example 2]
Reference Example 1 except that 1 part of the first developer dispersion 1 (A1 liquid) and 36.0 parts of the second developer dispersion (B liquid) in the thermal recording layer coating liquid 1 were used. A heat-sensitive recording material was produced in the same manner.

[Comparative Example 3]
A heat-sensitive recording material was prepared in the same manner as in Reference Example 1 except that the heat-sensitive recording layer coating solution 1 was replaced with the following heat-sensitive recording layer coating solution.
<Thermosensitive recording layer coating solution 4>
First developer dispersion 2 (A2 liquid) 36.0 parts Leuco dye dispersion (liquid C) 18.0 parts Sensitizer dispersion (liquid D) 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

[Comparative Example 4]
A heat-sensitive recording material was prepared in the same manner as in Reference Example 1 except that the heat-sensitive recording layer coating solution 1 was replaced with the following heat-sensitive recording layer coating solution.
<Thermosensitive recording layer coating solution 5>
First developer dispersion 3 (A3 liquid) 36.0 parts Leuco dye dispersion (liquid C) 18.0 parts Sensitizer dispersion (liquid D) 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

[Comparative Example 5]
A heat-sensitive recording material was prepared in the same manner as in Reference Example 4 except that the heat-sensitive recording layer coating solution 2 was replaced with the following heat-sensitive recording layer coating solution.
<Thermosensitive recording layer coating solution 6>
First developer dispersion 3 (A3 liquid) 36.0 parts Leuco dye dispersion (liquid C) 18.0 parts Sensitizer dispersion (liquid D) 36.0 parts Silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., (Product name: Mizukasil P-537, solid content 25%)
7.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA117,
(Solid content 10%) 25.0 parts

  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.

<Water resistance (blocking property)>
About the produced thermal recording body, 10 ml of tap water was dripped at the thermal recording layer surface of one thermal recording body, and the thermal recording layer surface of another thermal recording body was piled up on it. After applying a load of 10 g / cm ² and treating for 24 hours in an environment of 23 ° C. and 50% RH, the two thermal recording bodies were peeled off, and the thermal recording layer was peeled off at the part where water was dropped. The water resistance was evaluated.
○: The thermal recording layer does not peel at all. Δ: The surface of the thermal recording layer peels slightly, but there is no practical problem. ×: The entire thermal recording layer is peeled off, and there is a practical problem.

<Water resistance (image storability)>
The produced thermal recording medium was solid-printed with an applied energy of 0.41 mJ / dot using a TH-PMD (equipped with thermal recording paper printing tester, Kyocera thermal head) manufactured by Okura Electric. After being immersed in water at 23 ° C. for 24 hours, it was air-dried. The printing density of the printing part was measured with a Macbeth densitometer (RD-914, using an amber filter), the residual ratio was calculated from the values before and after the treatment, and the water resistance was evaluated.
Residual rate (%) = (printing density of the printed part after processing / printing density of the printed part before processing) × 100
◎: Residual rate is 90% or more ○: Residual rate is 75% or more and less than 90% Δ: Residual rate is 50% or more and less than 75% ×: Residual rate is less than 50%

<Plasticizer resistance (image area)>
About the produced thermal recording medium, the Okura Electric company TH-PMD (Thermal recording paper printing test machine,
A checkerboard pattern was printed at an applied energy of 0.35 mJ / dot and a printing speed of 50 mm / sec.
A polyvinyl 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 tube so that the printed part is on the outer surface. It was wound around and fixed. After processing for 24 hours in an environment of 23 ° C. and 50% RH, the print density of the printed part is measured with a Macbeth densitometer (RD-914, using an amber filter), and the residual rate is calculated from the values before and after the process. Evaluation based on the criteria.
Residual rate (%) = (printing density of the printed part after processing / printing density of the printed part before processing) × 100
◎: Residual rate is 90% or more ○: Residual rate is 75% or more and less than 90% Δ: Residual rate is 50% or more and less than 75% ×: Residual rate is less than 50%

<Heat resistance (white paper part)>
The produced thermal recording material was treated in an environment of 80 ° C. for 24 hours, and then allowed to stand in an environment of 23 ° C. and 50% RH for 3 hours, and the density of the non-printed portion (blank paper portion) was measured using a Macbeth densitometer (RD- 914, using an amber filter), the background color development value was calculated from the difference between the values before and after the treatment, and the heat resistance of the non-printed portion (blank portion) was evaluated according to the following criteria.
Ground color development value = (density of non-printed part after processing)-(density of non-printed part before processing)
A: Ground color development value is less than 0.1 B: Ground color development value is from 0.1 to less than 0.3 Δ: Ground color development value is from 0.3 to less than 0.5 x: Ground color development value is 0.00. 5 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化学式（化１）で表されるウレア系化合物及び一般式（化２）で表されるジフェニルスルホン架橋型化合物を特定の割合で含有させた場合には、発色性能、耐水性、画像部の耐可塑剤性、白紙部の耐熱性に優れていることがわかる。
さらに、感熱記録層にカルボキシル基含有樹脂とエピクロロヒドリン系樹脂とポリアミン／ポリアミド系樹脂とを含有する、あるいは感熱記録層上に保護層を設けることにより、耐水性、画像部の耐可塑剤性、白紙部の耐熱性が特に優れると共に、発色性能が良好である。

From Table 1, when the heat-sensitive recording layer contains a urea compound represented by the chemical formula (Chemical Formula 1) and a diphenylsulfone cross-linked compound represented by the General Formula (Chemical Formula 2) as a developer in a specific ratio. Is excellent in color development performance, water resistance, plasticizer resistance in the image area, and heat resistance in the blank area.
Further, the heat-sensitive recording layer contains a carboxyl group-containing resin, an epichlorohydrin resin, and a polyamine / polyamide resin, or a protective layer is provided on the heat-sensitive recording layer, thereby providing water resistance and a plasticizer for image areas. And the heat resistance of the white paper portion are particularly excellent, and the coloring performance is good.

Claims (3)

A heat-sensitive recording material provided with a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer on a support, wherein the heat-sensitive recording layer is used as an electron-accepting developer. It contains a urea compound represented by the following chemical formula (Chemical Formula 1) and a diphenylsulfone cross-linked compound represented by the following General Formula (Chemical Formula 2), and the diphenyl sulfone cross-linked compound is added to 1 part by weight of the urea compound. Is a ratio of 0.1 to 5.0 parts by weight, and the thermal recording layer further contains a carboxyl group-containing resin, an epichlorohydrin resin, and a polyamine / polyamide resin. .

(In the formula, R ³ may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 6 carbon atoms, and o is the same or different. May represent an integer of 0 to 4, p represents an integer of 1 to 11, and R ⁴ 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 ⁵ represents a methylene group or an ethylene group), or a substituted phenylene group represented by the following general formula:

(Wherein R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and represents a divalent group represented by:   The heat-sensitive recording material according to claim 1, further comprising a protective layer provided on the heat-sensitive recording layer. The heat-sensitive recording layer according to claim 1 or 2, wherein the heat-sensitive recording layer further contains oxalic acid-bisparamethylbenzyl .