JP2018094796A - Thermosensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording body excellent in color developing performance under severe environment, especially bar code readability and heat resistance of a blank paper part.SOLUTION: In a thermosensitive recording body having an undercoat layer on a supporter and a thermosensitive recording layer containing a colorless or pale color electron donating leuco dye and an electron acceptable developer arranged on the undercoat layer, the thermosensitive recording layer contains a specific sulfone compound and a specific urea urethane compound as the electron acceptable developer at a specific ratio. The protective layer contains preferably carboxy modified polyvinyl alcohol or non-core shell type acrylic resin having glass transition point (Tg) of 50°C or higher as a binder.SELECTED DRAWING: None

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 has good color development performance in a harsh environment, in particular, good bar code readability and heat resistance of a white paper portion.

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 use of thermal recording media has been expanded to various tickets, receipts, labels, bank ATMs, gas and electric meter readings, and vouchers such as car betting tickets. There is a need to preserve the image area and the blank paper area under such conditions as, for example, an environment such as a high temperature in a car in midsummer.
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 particular, if the color development sensitivity decreases and the difference in contrast between the print area and the white paper area becomes small, when the barcode is printed, it cannot be read by a reader even if it can be visually observed. There was a problem that aptitude was insufficient.
On the other hand, 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. Discloses a heat-sensitive recording material (Patent Document 3) that improves the storage stability of the image area.
Furthermore, a thermal recording material (Patent Document 4), a urea compound or a urea urethane compound, and a BPS developer that have improved color development performance and storability of the image area by using two specific types of developers in combination. Thermal recording materials (Patent Documents 5 to 8) are disclosed which have improved storage stability by using a combination of two kinds of color developers.

JP2003-154760 JP 2001-347757 A International Publication WO2004 / 002748 JP 2006-264255 A JP 2002-178646 A JP 2002-178645 A JP2000-143611 International Publication WO00 / 014058

When the heat-sensitive recording material is used for a use in a severe environment such as the above-described label use or ticket use whose use has been expanding in recent years, the storability of the image portion and the white paper portion is insufficient.
Furthermore, the heat-sensitive recording material (Patent Document 4) or the like using a combination of the above two specific types of color developer is used for applications used in harsh environments because the heat resistance of the white paper portion is inferior. The white paper portion is colored, and the barcode reading ability is insufficient.
In addition, in a heat-sensitive recording material (Patent Documents 5 to 8) using a combination of two types of developer such as a urea compound or urea urethane compound and a BPS developer, depending on the compound and developer used for the combination. The performance is very different.
SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having good color development performance in a harsh environment, in particular, barcode reading ability and heat resistance of a white paper portion. In the present invention, the harsh environment refers to, for example, a high temperature and / or high humidity condition, the high temperature refers to, for example, 70 ° C. or higher, and the high humidity refers to, for example, 80% RH or higher.

（式中、Ｒ^１は水素原子又は水酸基、Ｒ^２及びＲ^３は，それぞれ独立して、水素原子、炭素数１〜６のアルキル基又はアルコキシ基、ｍは１〜３の整数を表す。）

As a result of intensive studies, the present inventors have provided an undercoat layer on a support, and the heat-sensitive recording layer provided on the undercoat layer contains two specific types of color developer in a specific ratio, thereby causing a severe environment. It has been found that the bar code reading ability and the heat resistance of the white paper portion are improved.
Furthermore, the present inventors have also found that the heat resistance of the blank paper portion in a harsh environment can be further improved by containing a specific amount of plastic hollow particles in the undercoat layer.
That is, the present invention is a thermosensitive recording medium in which an undercoat layer is provided on a support, and a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer is provided on the undercoat layer. The heat-sensitive recording layer contains a sulfone compound represented by the following general formula (Chemical Formula 1) and a urea urethane compound represented by the following General Formula (Chemical Formula 2) as an electron-accepting developer. The heat-sensitive recording material contains 0.01 to 12.0 parts by weight of a urea urethane compound represented by the general formula (Chemical Formula 2) with respect to 1 part by weight of the sulfone compound represented by (Chemical Formula 1).

(In the formula, R ¹ represents a hydrogen atom or a hydroxyl group, R ² and R ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group, and m represents an integer of 1 to 3).

  According to the present invention, it is possible to provide a heat-sensitive recording material that is well-balanced in color development performance, particularly barcode readability and heat resistance of the white paper portion even under harsh environments. Furthermore, the heat resistance of the white paper portion in a harsh environment can be further improved by containing a specific amount of plastic hollow particles in the undercoat layer.

  The heat-sensitive recording material of the present invention is provided with an undercoat layer on a support, and a heat-sensitive recording layer containing a colorless or light leuco dye and a developer is provided on the undercoat layer. It contains a specific sulfone compound and a specific urea urethane compound as a colorant in a specific ratio.

この式中、Ｒ^１は水素原子又は水酸基、好ましくは水酸基である。
またＲ^２及びＲ^３は、それぞれ独立して、水素原子、炭素数１〜６、好ましくは炭素数１〜３のアルキル基又はアルコキシ基である。より好ましくは、Ｒ^２及びＲ^３の少なくとも一方が水素原子であり、さらに好ましくはＲ^２及びＲ^３が共に水素原子である。
ｍは１〜３の整数、好ましくは１又は２、より好ましくは１である。 The sulfone compound used in the present invention is represented by the following general formula (Formula 1).

In this formula, R ¹ is a hydrogen atom or a hydroxyl group, preferably a hydroxyl group.
R ² and R ³ are each independently a hydrogen atom, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. More preferably, at least one of R ² and R ³ is a hydrogen atom, and more preferably R ² and R ³ are both hydrogen atoms.
m is an integer of 1 to 3, preferably 1 or 2, and more preferably 1.

Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 1- Methylbutyl group, 2-methylbutyl group, 1,2-dimethylpropyl group, hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 1,1-dimethylbutyl group, 1, 2-dimethylbutyl group, 2,2-dimethylbutyl group, 1.3-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, 1, 1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethyl-1-methylpropyl group, 1-ethyl Examples include linear or branched alkyl groups having 1 to 6 carbon atoms such as ru-2-methylpropyl group, preferably alkyl groups having 1 to 3 carbon atoms, that is, methyl group, ethyl group, propyl group, isopropyl group. It is a group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy (amyloxy) group, an isopentyloxy group, and a tert- Examples thereof include linear or branched alkoxy groups having 1 to 6 carbon atoms such as pentyloxy group, neopentyloxy group, 2-methylbutoxy group, 1,2-dimethylpropoxy group, 1-ethylpropoxy group, hexyloxy group. And preferably a methoxy group, an ethoxy group, a propoxy group, or an isopropoxy group.

この式中、Ｒ^２、Ｒ^３及びｍは上記と同様に定義される。
本発明で用いられる更に好ましいスルホン化合物として、４−ヒドロキシ−４'−ベンジルオキシジフェニルスルホン、４−ヒドロキシ−４'−フェネチルオキシジフェニルスルホン、４−ヒドロキシ−４'−（３−フェニルプロポキシ）ジフェニルスルホンが挙げられ、最も好ましくは４−ヒドロキシ−４'−ベンジルオキシジフェニルスルホン（下式）である。

A preferred sulfone compound used in the present invention is represented by the following general formula (Formula 3).

In this formula, R ² , R ³ and m are defined as described above.
More preferred sulfone compounds used in the present invention include 4-hydroxy-4′-benzyloxydiphenylsulfone, 4-hydroxy-4′-phenethyloxydiphenylsulfone, 4-hydroxy-4 ′-(3-phenylpropoxy) diphenylsulfone. 4-hydroxy-4′-benzyloxydiphenyl sulfone (the following formula) is most preferable.

The urea urethane compound used in the present invention is represented by the following general formula (Formula 2).

When the heat-sensitive recording layer of the present invention contains a sulfone compound represented by the general formula (Chemical Formula 1) and a urea urethane compound represented by the general formula (Chemical Formula 2) as a developer, the thermal formula is represented by the general formula (Chemical Formula 1). Since the oxygen atom of the aralkyloxy group of the sulfone compound takes in π electrons from the aralkyl group and has high electronegativity, it exhibits basicity when heated and melted.
In a basic environment, the urea urethane compound is likely to be an enol type, and in particular, the reaction efficiency between the urea urethane compound and the leuco dye is increased, and an electron transfer complex is easily generated and the reverse reaction is less likely to occur. As a result, it is presumed that the resulting heat-sensitive recording material has good color development performance, particularly barcode readability, and is excellent in heat resistance of the blank paper portion.

  The urea urethane compounds used as the developer in the present invention are specifically three types represented by the following formulas (Chemical Formula 5) to (Chemical Formula 7), and these are used alone or in combination of two or more. May

In the heat-sensitive recording layer of the present invention, the urea urethane compound represented by the general formula (Chemical Formula 2) is used as a developer in an amount of 0.01 to 12% with respect to 1 part by weight of the sulfone compound represented by the General Formula (Chemical Formula 1). Contains 0 parts by weight. Further, the heat-sensitive recording layer contains a urea urethane compound, preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, with respect to 1 part by weight of the sulfone compound. In addition, the thermosensitive recording layer contains a urea urethane compound, preferably 10.0 parts by weight or less, more preferably 3.0 parts by weight or less, still more preferably 1.1 parts by weight or less, relative to 1 part by weight of the sulfone compound. It is particularly preferably 0.5 parts by weight or less, most preferably less than 0.5 parts by weight.
When the content ratio of the urea urethane compound represented by the general formula (Chemical formula 2) to the sulfone compound represented by the general formula (Chemical formula 1) is within this range, the color development performance of the thermosensitive recording medium in a harsh environment, In particular, the bar code readability is the best (see the examples described later). If the urea urethane compound represented by the general formula (Chemical Formula 2) is less than 0.01 part by weight with respect to 1 part by weight of the sulfone compound represented by the general formula (Chemical Formula 1), the barcode readability is sufficient. It may not be. In addition, when the urea urethane compound exceeds 1.1 parts by weight with respect to 1 part by weight of the sulfone compound, the whiteness of the white paper part tends to decrease.

  The heat-sensitive recording layer of the present invention may contain a developer other than the sulfone compound represented by the general formula (Formula 1) and the urea urethane compound represented by the general formula (Formula 2) as a developer. . However, the total content of the sulfone compound represented by the general formula (Chemical Formula 1) and the urea urethane compound represented by the general formula (Chemical Formula 2) is the total developer (general) contained in the thermosensitive recording layer. The sulfone compound represented by the formula (Formula 1) and the urea urethane compound represented by the general formula (Formula 2) are preferably 50% by weight or more, more preferably 70% by weight or more. It is preferably 90% by weight or more, and particularly preferably 100% by weight, that is, the total developer contained in the heat-sensitive recording layer is a sulfone compound represented by the general formula (Formula 1) and the general formula (Formula 2). It is a urea urethane compound represented.

  Examples of the developer other than the sulfone compound represented by the general formula (chemical formula 1) and the urea urethane compound represented by the general formula (chemical formula 2) used in the present invention include activated clay, attapulgite, colloidal silica, Inorganic acidic substances such as aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4, 4′-dihydroxydiphenylsulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4 -Hydroxy-4'-n-propoxydiphenylsulfone 4-hydroxy-4′-allyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-methyldiphenylsulfone, 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, JP-A-8- 59603 aminobenzenesulfonamide derivative, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, Methyl bis (p-hydroxyphenyl) acetate, , 1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α -(4'-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2'-thiobis (3-tert-octylphenol), 2,2'-thiobis (4-tert- Octylphenol), phenolic compounds such as diphenylsulfone cross-linking compounds described in WO 97/16420, compounds described in WO 02/081229 or JP 2002-301873, N, N′-di-m-chlorophenylthiourea, etc. Thiourea compound, p-chlorobenzoic acid, stearyl gallate, bis [4- (n-octyloxycarbonylamino) B) Zinc salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p -Methoxyphenoxyethoxy) cumyl] aromatic carboxylic acids of salicylic acid and salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and thiocyan Examples thereof include an antipyrine complex of zinc acid, and a complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid. 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, under the trade name JKY-224 manufactured by API Corporation, and is a diphenylsulfone cross-linking compound described in International Publication No. WO 97/16420 Is available under the trade name D-90 manufactured by Nippon Soda Co., Ltd. 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.

  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 coating layers other than the heat-sensitive recording layer, that is, protective layers and undercoat layers.

  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 alcohols such as polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, and other modified polyvinyl alcohols, (meth) acrylic acid, and monomer components copolymerizable with (meth) acrylic acid Acrylic resin (excluding olefins), hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carbo Cellulose derivatives such as methylcellulose, ethylcellulose, acetylcellulose, starches such as oxidized starch, etherified starch, esterified starch, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, casein, arabic rubber, polyvinyl chloride, Examples thereof include polyvinyl acetate, polyacrylamide, polyacrylic ester, polyvinyl butyral, polystyrose and copolymers thereof, 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.
The binder content (solid content) in the heat-sensitive recording layer is preferably about 5 to 25% by weight.

  Examples of the crosslinking agent used in the present invention include zirconium chloride, zirconium sulfate, zirconium nitrate, zirconium acetate, zirconium carbonate, zirconium stearate, zirconium octoate, zirconium silicate, zirconium oxynitrate, zirconium carbonate potassium salt, zirconium carbonate ammonium salt and the like. Zirconium compounds, glyoxal, glutaraldehyde, polyvalent aldehyde compounds such as aldehyde starch, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, Examples include sodium persulfate, ferric chloride, 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, 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.

  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, an undercoat layer is 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, binders usable for the above-mentioned heat-sensitive recording layer can be appropriately used. These binders may be used alone or in combination of two or more.

As the pigment used for the undercoat layer, known pigments generally used conventionally, specific examples include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, kaolin, calcined kaolin, clay, Inorganic pigments such as talc and organic pigments such as plastic hollow particles can be used. These pigments may be used alone or in combination of two or more.
The hollow plastic particles of the present invention are fine hollow particles that are already in a foamed state and contain a thermoplastic resin as a shell and contain air or other gas inside. Examples of the thermoplastic resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. In particular, styrene resins such as polystyrene, acrylic resins such as polyacrylic acid esters and polyacrylonitrile, copolymers thereof, or copolymer resins mainly composed of polyvinylidene chloride and polyacrylonitrile are preferable. Such organic hollow particles are available as SX8782 manufactured by JSR, MH5055, MH8108A manufactured by Nippon Zeon, Ropaque HP-91 manufactured by Rohm & Haas Japan, Microsphere manufactured by Matsumoto Yushi.
The volume hollow ratio of the plastic hollow particles of the present invention is preferably about 40 to 95%. By setting the volumetric hollow ratio to 40% or more, it is possible to improve heat insulation and further improve the color development performance. On the other hand, by setting it to 95% or less, it becomes easy to increase the shell strength of the hollow particles to effectively maintain the hollow state and to obtain an undercoat layer having a good surface strength. Here, the volume hollowness is a value obtained by (d3 / D3) × 100. In the formula, d represents the inner diameter of the organic hollow particles, and D represents the outer diameter of the organic hollow particles.

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.
In the present invention, the undercoat layer preferably contains plastic hollow particles as a pigment. When the undercoat layer contains plastic hollow particles as a pigment, the undercoat layer preferably contains 45% by weight or more of plastic hollow particles based on the total amount (solid content) of the pigment.
As the pigment other than the plastic hollow particles contained in the undercoat layer, the above inorganic pigments can be used, but calcined kaolin is preferably used.
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.

The heat-sensitive recording material of the present invention may further have a protective layer on the heat-sensitive recording layer.
This protective layer mainly comprises a binder and a pigment, and a crosslinking agent may be further added thereto.
As the binder, binders that can be used in the above-mentioned heat-sensitive recording layer can be used as appropriate, and carboxy-modified polyvinyl alcohol and non-core-shell type acrylic resins having a glass transition point (Tg) higher than 50 ° C. are preferable. These binders may be used alone or in combination of two or more.
Moreover, as a crosslinking agent, although the crosslinking agent which can be used for the above-mentioned thermosensitive recording layer can be used suitably, epichlorohydrin type resin and polyamine / polyamide type resin (what is contained in epichlorohydrin type resin is used. Is preferred).
More preferably, the protective layer contains an epichlorohydrin resin and a polyamine / polyamide resin together with carboxy-modified polyvinyl alcohol, thereby further improving the color development performance.

  This carboxy-modified polyvinyl alcohol is, for example, a reaction product of polyvinyl alcohol and a polycarboxylic acid such as fumaric acid, phthalic anhydride, melittic anhydride, itaconic anhydride, or an esterified product of these reactants, and vinyl acetate. It is obtained as a saponified product of a copolymer with an ethylenically unsaturated dicarboxylic acid such as maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid or methacrylic acid. Specific examples of the production method include the method exemplified in JP-A-53-91995. Moreover, it is preferable that the saponification degree of carboxy modified polyvinyl alcohol is 72-100 mol%, and a polymerization degree is 500-2400, More preferably, it is 1000-2000.

The glass transition point (Tg) of this non-core-shell type acrylic resin is higher than 50 ° C., preferably 95 ° C. or lower. This Tg is measured by differential scanning calorimetry (DSC).
This non-core-shell type acrylic resin contains (meth) acrylic acid and a monomer component copolymerizable with (meth) acrylic acid, and (meth) acrylic acid is 1 in 100 parts by weight of the non-core-shell type acrylic resin. It is preferable that it is -10 weight part. (Meth) acrylic acid is alkali-soluble and has the property of making a non-core shell acrylic resin a water-soluble resin by the addition of a neutralizing agent. By changing the non-core-shell type acrylic resin to a water-soluble resin, especially when the protective layer contains a pigment, the binding property to the pigment is remarkably improved, and the protective layer has excellent strength even when containing a large amount of pigment. Can be formed. 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 non-core shell acrylic resin. Moreover, it is preferable that methyl methacrylate contains 20-80 parts in 100 parts of non-core-shell type acrylic resins. When (meth) acrylonitrile and methyl methacrylate are included, (meth) acrylonitrile is blended in 15 to 18 parts in 100 parts of non-core-shell acrylic resin, and methyl methacrylate is blended in 20 to 80 parts in 100 parts of non-core-shell acrylic resin. It is preferable.

  This epichlorohydrin resin is a resin characterized by containing an epoxy group in the molecule, and examples thereof include polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, These can be used alone or in combination. Moreover, as an amine which exists in the principal chain of an epichlorohydrin-type resin, the thing from a primary to a quaternary can be used, and there is no restriction | limiting in particular. Furthermore, since the water resistance is good, the degree of cationization and the molecular weight are preferably a cationization degree of 5 meq / g · Solid (measured value at pH 7) and a molecular weight of 500,000 or more. Specific examples of the epichlorohydrin resin include Sumire Resin 650 (30), Sumire Resin 675A, Sumire Resin 6615 (manufactured by Sumitomo Chemical Co., Ltd.), WS4002, WS4020, WS4024, WS4030, WS4046, WS4010, CP8970 (manufactured by Starlight PMC) and the like.

  This polyamine / polyamide resin does not have an epoxy group in the molecule. For example, it is a polyamide urea resin, polyalkylene polyamine resin, polyalkylene polyamide resin, polyamine polyurea resin, modified polyamine resin, modified polyamide resin, polyalkylene polyamine. Examples include urea formalin resin, polyalkylene polyamine polyamide polyurea resin, and the like, and these can be used alone or in combination. Specific examples of the polyamine / polyamide resin include Sumire Resin 302 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin 712 (manufactured by Sumitomo Chemical: polyamine polyurea resin), and Sumire Resin 703 (Sumitomo Chemical). Manufactured by: Polyamine Polyurea Resin), Sumire Resin 636 (Sumitomo Chemical Co .: Polyamine Polyurea Resin), Sumire Resin SPI-100 (Sumitomo Chemical: Modified Polyamine Resin), Sumire Resin SPI-102A (Sumitomo) Chemical Company: Modified Polyamine Resin), Sumire Resin SPI-106N (Sumitomo Chemical: Modified Polyamide Resin), Sumire Resin SPI-203 (50) (Sumitomo Chemical), Sumire Resin SPI-198 (Sumitomo) Chemical Co., Ltd.), Printive A-700, Printive A-600 (or more Asahi Kasei Co., Ltd.), PA6500, PA6504, PA6634, PA6638, PA6640, PA6664, PA6646, PA6654, PA6702, PA6704 (above, manufactured by Seiko PMC: polyalkylene polyamine polyamide polyurea resin), CP8994 (produced by Seiko PMC: polyethyleneimine) Resin). Although there is no particular limitation, a polyamine resin (polyalkylene polyamine resin, polyamine polyurea resin, modified polyamine resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea resin) is used because the printing density is good. It is preferable.

  The content in the case of using epichlorohydrin resin and polyamine / polyamide resin together with carboxy-modified polyvinyl alcohol in the protective layer is preferably 1 to 100 parts by weight with respect to 100 parts by weight of carboxy-modified polyvinyl alcohol. 5 to 50 parts by weight, more preferably 10 to 40 parts by weight.

As the pigment used in the protective layer, pigments usable in the above-mentioned heat-sensitive recording layer can be used as appropriate, but kaolin, calcined kaolin, aluminum hydroxide, and silica are preferable. These pigments may be used alone or in combination of two or more.
The content (solid content) of the binder in the protective layer is preferably 20% by weight or more, and more preferably about 20 to 80% by weight. When the protective layer contains a pigment, the content of the pigment and the binder is 100 parts by weight of the pigment. On the other hand, the binder preferably has a solid content of about 30 to 300 parts by weight.
As necessary, the coating liquid for the protective layer includes a crosslinking agent, a lubricant, a stabilizer, an ultraviolet absorber, a dispersant, an antifoaming agent, an antioxidant, a fluorescent dye, and the like that can be used in the above-mentioned heat-sensitive recording layer. You may mix | blend various adjuvants suitably.

In the present invention, the means for coating 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 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. It is about ² to 12 g / m ² per minute. Moreover, typical coating amount of the undercoat layer is 1 to 15 g / m ² approximately in solids, general coating amount of the protective layer is 1 to 5 g / m ² approximately in solids. In this invention, it is preferable that the coating amount of a protective layer shall be 1-3 g / m < ² > by solid content.
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 and coating solutions were prepared as follows.

[Preparation of each coating solution]
Undercoating liquids 1-2 were prepared by stirring and dispersing a composition comprising the following composition.
<Coating liquid 1 for undercoat layer>
Baked kaolin (trade name: Ansilex 90, 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 <Coating liquid 2 for undercoat layer>
Firing kaolin (made by BASF, trade name: Ancilex 90) 50.0 parts Plastic hollow particles (made by Nippon Zeon, trade name: Nipol MH8108A,
185.0 parts Styrene / butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.)
(Product name: ST5526, solid content 48%) 10.0 parts

  Developer liquid dispersion (A1 liquid to A8 liquid), leuco dye dispersion liquid (B liquid) and sensitizer dispersion liquid (C liquid) of the following composition were each separately separated to a mean particle size of 0.5 microns with a sand grinder. Wet grinding was performed until

Developer dispersion 1 (A1 solution)
4-hydroxy-4′-benzyloxydiphenyl sulfone (manufactured by Nikka Chemical Co., Ltd.,
Product name: BPS-MA3) 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 Developer dispersion 2 (A2 liquid)
Urea urethane compound represented by the chemical formula (Chemical Formula 2) (Chemipro Kasei Co., Ltd.,
Product name: UU) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., PVA117) 5.0 parts Water 1.5 parts Developer dispersion 3 (A3 liquid)
4,4′-dihydroxydiphenyl sulfone (manufactured by Nikka Chemical Co., Ltd.,
Product name: BPS-P (T)) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., PVA117) 5.0 parts Water 1.5 parts Developer dispersion 4 (A4 liquid)
4-hydroxy-4′-n-propoxydiphenyl sulfone (Mitsubishi Chemical Corporation,
Product name: TOMILAC KN) 6.0 parts 5.0 parts of a completely saponified polyvinyl alcohol aqueous solution (Pura117, manufactured by Kuraray Co., Ltd.)
Water 1.5 parts Developer dispersion 5 (A5 liquid)
Diphenylsulfone cross-linking compound (Nippon Soda Co., Ltd., trade name: D90) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., PVA117) 5.0 parts Water 1.5 parts

Developer dispersion 6 (A6 liquid)
Urea compounds represented by the chemical formula (Chemical Formula 8) (manufactured by API Corporation,
Product name: SU727) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., PVA117) 5.0 parts Water 1.5 parts

Developer dispersion 7 (A7 liquid)
4-Hydroxyphenyl-4′-phenoxyphenyl sulfone (chemical formula (Chemical Formula 9))
6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., PVA117) 5.0 parts Water 1.5 parts

Developer dispersion 8 (A8 liquid)
2,4′-dihydroxydiphenyl sulfone (manufactured by Nikka Chemical Co., Ltd.,
Product name: BPS-24C) 6.0 parts Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., PVA117) 5.0 parts Water 1.5 parts

Leuco dye dispersion (liquid B)
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., PVA117) 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 Completely saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., PVA117) 5.0 parts Water 1.5 parts

Subsequently, each dispersion liquid was mixed in the following ratio to prepare thermal recording layer coating liquids 1 to 9.
<Thermosensitive recording layer coating solution 1>
Developer Dispersion (Liquid A1) 18.0 parts Developer Dispersion (Liquid A2) 18.0 parts Leuco Dye Dispersion (Liquid B) 18.0 parts Sensitizer Dispersion (Liquid C) 9.0 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 (Pura117, manufactured by Kuraray Co., Ltd.)
25.0 parts

<Thermosensitive recording layer coating solution 2>
Developer Dispersion (Liquid A1) 36.0 parts Leuco Dye Dispersion (Liquid B) 18.0 parts Sensitizer Dispersion (Liquid C) 9.0 parts Silica Dispersion (Mizusawa Chemical Co., Mizukasil P-) 537) 17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 3>
Developer Dispersion (Liquid A2) 36.0 parts Leuco Dye Dispersion (Liquid B) 18.0 parts Sensitizer Dispersion (Liquid C) 9.0 parts Silica Dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-) 537) 17.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 4>
Developer dispersion (liquid A3) 18.0 parts Developer dispersion (liquid A2) 18.0 parts Leuco dye dispersion (liquid B) 18.0 parts Sensitizer dispersion (liquid C) 9.0 Part Silica dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-537) 17.5 parts Complete saponification type polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 5>
Developer dispersion (liquid A4) 18.0 parts Developer dispersion (liquid A2) 18.0 parts Leuco dye dispersion (liquid B) 18.0 parts Sensitizer dispersion (liquid C) 9.0 Part Silica dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-537) 17.5 parts Complete saponification type polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 6>
Developer dispersion (liquid A5) 18.0 parts Developer dispersion (liquid A2) 18.0 parts Leuco dye dispersion (liquid B) 18.0 parts Sensitizer dispersion (liquid C) 9.0 Part Silica dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-537) 17.5 parts Complete saponification type polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 7>
Developer dispersion (liquid A1) 18.0 parts Developer dispersion (liquid A6) 18.0 parts Leuco dye dispersion (liquid B) 18.0 parts Sensitizer dispersion (liquid C) 9.0 Part Silica dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-537) 17.5 parts Complete saponification type polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 8>
Developer Dispersion (Liquid A1) 18.0 parts Developer Dispersion (Liquid A2) 18.0 parts Leuco Dye Dispersion (Liquid B) 18.0 parts Sensitizer Dispersion (Liquid C) 9.0 Part Silica dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-537) 7.5 parts Completely saponified polyvinyl alcohol aqueous solution (Kuraray Co., PVA117)
25.0 parts

<Thermosensitive recording layer coating solution 9>
Developer dispersion (liquid A7) 18.0 parts Developer dispersion (liquid A2) 18.0 parts Leuco dye dispersion (liquid B) 18.0 parts Sensitizer dispersion (liquid C) 9.0 Part Silica dispersion (Mizusawa Chemical Co., Ltd., Mizukasil P-537) 17.5 parts Complete saponification type polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., PVA117)
25.0 parts

Subsequently, the mixture which consists of the following ratio was mixed and the protective layer coating liquid was prepared.
<Protective layer coating solution>
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 1800, degree of saponification: 85 to 90 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 Taoka Chemical Co., Ltd., trade name: Sumirez 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

[Example 1]
After coating undercoat layer coating liquid 1 on one side of a support (basis weight 47 g / m ² high-quality paper) with a 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.
On the undercoat layer of this undercoat layer-coated paper, the thermal recording layer coating solution 1 is applied by a rod blade method so that the coating amount is 6.0 g / m ^{2 in} terms of solid content, and then dried. A heat-sensitive recording material was produced by processing with a calendar so that the smoothness was 500 to 1000 seconds.

[Example 2]
Implementation was performed except that the blending amount of the developer dispersion liquid (A1 liquid) in the thermal recording layer coating liquid 1 was 31.5 parts and the blending amount of the developer dispersion liquid (A2 liquid) was 4.5 parts. A thermosensitive recording material was produced in the same manner as in Example 1.
[Example 3]
Except that the blending amount of the developer dispersion (A1 liquid) in the thermosensitive recording layer coating liquid 1 was 25.5 parts and the blending amount of the developer dispersion (A2 liquid) was 10.5 parts. A thermosensitive recording material was produced in the same manner as in Example 1.
[Example 4]
Implementation was performed except that the blending amount of the developer dispersion (A1 liquid) in the thermosensitive recording layer coating liquid 1 was 4.5 parts and the blending amount of the developer dispersion (A2 liquid) was 31.5 parts. A thermosensitive recording material was produced in the same manner as in Example 1.

[Example 5]
Instead of the undercoat layer coating liquid 1, the amount of calcined kaolin in the undercoat layer coating liquid 2 is changed to 80.0 parts, the amount of plastic hollow particles is changed to 74.0 parts, and water is 81.0 parts. A heat-sensitive recording material was produced in the same manner as in Example 1 except that the coating liquid instead of was used.
[Example 6]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the undercoat layer coating solution 2 was used instead of the undercoat layer coating solution 1.
[Example 7]
Except for using the coating liquid in which the blending amount of the calcined kaolin in the coating liquid 2 for the undercoat layer was changed to 0 part and the blending amount of the plastic hollow particles was replaced with 370.0 parts in place of the coating liquid 1 for the undercoat layer A thermosensitive recording material was produced in the same manner as in Example 1.

[Example 8]
After coating undercoat layer coating liquid 1 on one side of a support (basis weight 47 g / m ² high-quality paper) with a 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.
On the undercoat layer of this undercoat layer-coated paper, the thermal recording layer coating solution 8 is applied by a rod blade method so that the coating amount is 6.0 g / m ^{2 in} terms of solid content, and then dried. A heat-sensitive recording layer-coated paper was produced by processing with a calendar so that the smoothness was 500 to 1000 seconds.
Next, on the heat-sensitive recording layer of the heat-sensitive recording layer-coated paper, a protective layer coating solution is applied by a rod blade method so that the coating amount is 2.0 g / m ² in solids, and then dried. To produce a heat-sensitive recording material.
[Example 9]
Except that the blending amount of the developer dispersion liquid (A1 liquid) in the thermal recording layer coating liquid 8 was 31.5 parts and the blending amount of the developer dispersion liquid (A2 liquid) was 4.5 parts. A thermosensitive recording material was produced in the same manner as in Example 8.

[Comparative Example 1]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 2 was used instead of the thermosensitive recording layer coating solution 1.
[Comparative Example 2]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 3 was used instead of the thermosensitive recording layer coating solution 1.
[Comparative Example 3]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 4 was used instead of the thermosensitive recording layer coating solution 1.
[Comparative Example 4]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 5 was used instead of the thermosensitive recording layer coating solution 1.

[Comparative Example 5]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the heat-sensitive recording layer coating solution 6 was used instead of the heat-sensitive recording layer coating solution 1.
[Comparative Example 6]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 7 was used instead of the thermosensitive recording layer coating solution 1.
[Comparative Example 7]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 9 was used instead of the thermosensitive recording layer coating solution 1.

[Comparative Example 8]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the developer dispersion (A2 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A3 liquid). did.
[Comparative Example 9]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the developer dispersion (A2 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A8 liquid). did.
[Comparative Example 10]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the developer dispersion (A2 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A4 liquid). did.

[Comparative Example 11]
A heat-sensitive recording material was prepared in the same manner as in Example 6 except that the developer dispersion (A1 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A3 liquid). did.
[Comparative Example 12]
A heat-sensitive recording material was prepared in the same manner as in Example 6 except that the developer dispersion (A1 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A4 liquid). did.
[Comparative Example 13]
A heat-sensitive recording material was produced in the same manner as in Example 6 except that the developer dispersion (A2 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A3 liquid). did.
[Comparative Example 14]
A heat-sensitive recording material was produced in the same manner as in Example 6 except that the developer dispersion (A2 liquid) in the heat-sensitive recording layer coating liquid 1 was replaced with a developer dispersion (A4 liquid). did.

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), and the color development performance (printing density) was evaluated.

<Heat resistance of blank paper part>
The produced thermal recording material was treated for 24 hours under an environmental condition of 80 ° C. or 90 ° C. and then allowed to stand for 3 hours under an environmental condition of 23 ° C. × 50% RH.
The density of the non-printed area (blank area) is measured with a Macbeth densitometer (RD-914, using an amber filter), and the ground color development value is calculated from the difference between the values before and after processing. Part) was evaluated for heat resistance.
Ground color development value = (density of non-printed part after processing)-(density of non-printed part before processing)
Excellent: Ground color development value is less than 0.1 Good: Ground color development value is 0.1 or more and less than 0.3 Possible: Ground color development value is 0.3 or more and less than 0.5 Impossibility: Ground color development value is 0.00. 5 or more

<Bar code reading aptitude>
The prepared thermal recording medium was placed under the environmental conditions of (1) to (3) below, and then using a label printer 140XiIII manufactured by Zebra Corporation at a printing level of +10 and a printing speed of 15.2 cm / second (6 inches / second). A bar code (CODE 39) was printed.
(1) The mixture was allowed to stand for 3 hours under 23 ° C. × 50% RH environmental conditions.
(2) After being placed under 80 ° C. environmental conditions for 24 hours, it was allowed to stand under 23 ° C. × 50% RH environmental conditions for 3 hours.
(3) After being placed under 50 ° C. × 90% RH environmental condition for 24 hours, it was allowed to stand under 23 ° C. × 50% RH environmental condition for 3 hours.

Next, a reading test was performed on the printed barcode with a barcode verification machine (manufactured by Honeywell, QCPC600, light source 640 nm) to evaluate barcode readability. The evaluation results are shown in ANSI standard symbol grades.
Symbol grade: Bar code is divided into 10 in the vertical direction with the bar, and a reading test is performed once for each location. The average value is (excellent) A, B, C, D, F (poor) Represented by

The evaluation results are shown in Table 1.

From Table 1, an undercoat layer is provided on the support, and the heat-sensitive recording layer provided on the undercoat layer is represented by the sulfone compound represented by the general formula (Chemical Formula 1) and the general formula (Chemical Formula 2) as a developer. When the urea urethane compound is contained in a specific ratio, it can be seen that the color development performance under severe conditions, in particular, the barcode readability and the heat resistance of the white paper portion are improved in a well-balanced manner (Example 1 to Example 1). 4, 8, 9).
Furthermore, when a specific amount of plastic hollow particles is contained in the undercoat layer, it can be seen that the heat resistance of the white paper portion (particularly, the heat resistance of the white paper portion at 90 ° C.) in a harsh environment is further improved. (Examples 6 and 7).

Claims (8)

A thermosensitive recording medium comprising an undercoat layer on a support, and a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer on the undercoat layer, The recording layer contains, as an electron-accepting developer, a sulfone compound represented by the following general formula (Formula 1) and a urea urethane compound represented by the following general formula (Formula 2). A heat-sensitive recording material containing 0.01 to 12.0 parts by weight of a urea urethane compound represented by the general formula (Formula 2) with respect to 1 part by weight of the sulfone compound represented by formula (1).

(In the formula, R ¹ represents a hydrogen atom or a hydroxyl group, R ² and R ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group, and m represents an integer of 1 to 3).

The heat-sensitive recording material according to claim 1, wherein the undercoat layer contains plastic hollow particles as a pigment. The heat-sensitive recording material according to claim 2, wherein the undercoat layer contains 45% by weight or more of plastic hollow particles with respect to the total amount (solid content) of the pigment. The urea urethane compound represented by the general formula (Chemical Formula 2) is contained in a proportion of 0.01 to 1.1 parts by weight with respect to 1 part by weight of the sulfone compound represented by the General Formula (Chemical Formula 1). The thermal recording body as described in any one of 1-3. The heat-sensitive recording material according to any one of claims 1 to 4, wherein the sulfone compound is represented by the following general formula (Formula 3).

(Wherein R ² and R ³ are defined in the same manner as described above, and m is 1 or 2). The heat-sensitive recording material according to claim 1, wherein at least one of R ² and R ³ is a hydrogen atom. The heat-sensitive recording material according to any one of claims 1 to 6, wherein m is 1. The heat-sensitive recording material according to claim 1, wherein the sulfone compound is 4-hydroxy-4′-benzyloxydiphenyl sulfone.