JP2008194912A - Thermosensitive recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording body, which is superior in bar-code readability, the water resistance and resistance to plasticizer of an image part even under severe environments and, at the same time, which gives a little influence to environments. <P>SOLUTION: In the thermosensitive recording body, the support of which is overlaid with a thermosensitive color developing layer including a colorless or light-colored electron donative leuco dye and an electron acceptive developer, the thermosensitive color developing layer includes a condensation composition expressed by general formula 1 as a first electron acceptive developer and an urea-urethane base compound expressed by general formula 2 as a second electron acceptive developer and a protective layer includes carboxyl group containing resin, epichlorohydrin base resin and modified polyamine/amide base resin in order to manifest excellent effects. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a basic colorless dye and a developer, and more particularly to a heat-sensitive recording material excellent in water resistance and plasticizer resistance of an image area.

In general, a thermosensitive color development mainly composed of a colorless or light-colored electron-donating leuco dye (hereinafter referred to as a dye) and an electron-accepting color developer (hereinafter referred to as a developer) that reacts with the dye when heated. Thermal recording materials having layers have been widely put into practical use. In order to perform recording on this thermal recording medium, a thermal printer or the like with a built-in thermal head is used. Compared with other recording systems that have been put to practical use, this thermal recording system has no noise during recording, does not require development and fixing, is maintenance-free, is relatively inexpensive, and is compact. The developed color is very clear, and it is widely used in facsimiles, computer terminal printers, automatic ticket vending machines, measuring recorders, handy terminals used outdoors, and the like. In addition to the output sheets of various devices described above, the thermal recording medium is used in fields such as voucher sheets that require high storage stability.
When heat-sensitive recording materials are used for various tickets, receipts, labels, bank ATMs, gas and electricity meter readings, car betting tickets, etc., moisture and humidity due to rain, sunlight, high temperature In the midsummer car environment, there is a demand for storage stability such as heat resistance, water resistance, and heat and humidity resistance in the image area that does not cause problems in barcode readability.
As a method for improving the storage stability of the image area, it is generally well known to provide a protective layer on the thermosensitive coloring layer, but in addition to this, a specific developer or a specific stabilizer is used ( Patent Documents 1 and 2) disclose a technique for improving the storage stability of an image portion by using a specific sensitizer and a specific stabilizer in combination (Patent Document 3).

JP2003-154760 JP 2001-347757 A WO2004-002748

However, as thermal recording media are often used in applications that are used in harsh environments such as gold voucher applications, image storability and barcode suitability that are higher than conventional ones are required. In the current situation, sufficient quality is not obtained with the conventional technology as described above. In addition, when a protective layer is provided on the heat-sensitive recording material, there is a problem that the color reading sensitivity and the image quality are lowered, so that the barcode readability is lowered. In addition, the present inventors have disclosed an invention for obtaining high barcode readability by including a phenol novolac developer and a diphenylsulfone crosslinkable compound. However, the diphenylsulfone crosslinkable compound used here is disclosed. Commercially available products contain about 5% of 44 'hydroxydiphenyl sulfone, which is designated as the Chemical Substances Control Law Class 2 Monitoring Chemical Substance, and may affect the environment.
Therefore, the present invention provides a heat-sensitive recording material that is excellent in water resistance and plasticizer resistance of an image area and has little influence on the environment, which does not cause a problem in bar code readability even in a severe environment. For the purpose.

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 electron-accepting color developers in the thermosensitive coloring layer, and have completed the present invention.
That is, the present invention is a heat-sensitive recording material provided with a heat-sensitive coloring layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer on a support, and the heat-sensitive coloring layer comprises The following general formula (chemical formula 1)

（式中、Ｒ^１は、それぞれ同じであっても異なってもよく、水素原子、ハロゲン原子、水酸基、低級アルキル基、アルコキシル基、シアノ基、ニトロ基、アリール基又はアラルキル基を表し、Ｒ^２は、それぞれ同じであっても異なってもよく、水素原子、アルキル基又はアリール基を表し、ｍは０〜３の整数を表し、ｎは０〜３の整数を表す。）で表される縮合組成物、及び第二電子受容性顕色剤として下記一般式（化２）

(In the formula, R ¹ each may be the same or different, represent a hydrogen atom, a halogen atom, a hydroxyl group, a lower alkyl group, an alkoxyl group, a cyano group, a nitro group, an aryl group or an aralkyl group, R ² , Which may be the same or different, each represents a hydrogen atom, an alkyl group or an aryl group, m represents an integer of 0 to 3, and n represents an integer of 0 to 3). As a composition and a second electron-accepting developer, the following general formula (Formula 2)

で表されるウレアウレタン系化合物を含有し、かつ前記保護層が、カルボキシル基含有樹脂、エピクロロヒドリン系樹脂及び変性ポリアミン／アミド系樹脂を含有することを特徴とする感熱記録体である。

And a protective layer containing a carboxyl group-containing resin, an epichlorohydrin resin, and a modified polyamine / amide resin.

  In addition, the present inventors further provide a specific protective layer on such a thermosensitive coloring layer, thereby improving image storage stability and barcode suitability without deteriorating coloring sensitivity and image quality. I found it. That is, by containing kaolin having an aspect ratio of 20 or more in the protective layer, better barcode readability can be obtained, and the protective layer contains a carboxyl group-containing resin, epichlorohydrin resin, and modified polyamine / amide. By containing a resin, better heat resistance, water resistance, and moist heat resistance can be obtained.

In the heat-sensitive recording material of the present invention, the reason why the heat resistance, water resistance, and heat-and-moisture resistance of the image area are excellent has not been clearly clarified, but the condensation composition represented by the general formula (Formula 1) and Presumably, the coexistence of the urea urethane compound represented by the formula (Chemical Formula 2) increases the stability of the electron transfer complex which is a reaction product of the developer and the basic dye.
Furthermore, when a protective layer containing kaolin is provided, the smoothness of the protective layer is very excellent, so that the adhesion with the thermal head is increased and heat is more easily conducted to the thermal layer. It is considered that the barcode readability is improved because the generation rate is increased and a high color density is obtained.

Hereinafter, the present invention will be described in more detail.
The heat-sensitive recording material of the present invention comprises a heat-sensitive coloring layer provided on a support, and this heat-sensitive coloring layer contains an electron donating leuco dye and two kinds of electron accepting developers.

  The first electron-accepting developer used in the present invention is represented by the following formula.

ここで、Ｒ^１は、同じであっても異なってもよいが、好ましくは同じであって、水素原子、ハロゲン原子、水酸基、低級アルキル基、アルコキシル基、シアノ基、ニトロ基、アリール基又はアラルキル基を表すが、この中で低級アルキル基、アリール基又はアラルキル基が好ましく、低級アルキル基が特に好ましい。
低級アルキル基の炭素数は好ましく１〜５、より好ましくは１〜４であり、低級アルキル基としては、例えば、メチル、エチル、ｎ−プロピル、イソプロピル、ｎ−ブチル、ｔ−ブチル、ｔ−アミル等が挙げられる。また、アルコキシル基の炭素数は好ましくは１〜５であり、アルコキシル基として、例えば、メトキシ、エトキシ、プロポキシ、イソプロポキシ、ブトキシ、ｔ−ブトキシ等が挙げられる。また、アリール基としては、例えば、フェニル、トリル、ナフチル等、好ましくはフェニル基が挙げられ、アラルキル基としては、α−メチルベンジル、クミル等が挙げられる。

Here, R ¹ may be the same or different, but is preferably the same, and is a hydrogen atom, halogen atom, hydroxyl group, lower alkyl group, alkoxyl group, cyano group, nitro group, aryl group or aralkyl. Of these, a lower alkyl group, an aryl group or an aralkyl group is preferred, and a lower alkyl group is particularly preferred.
The lower alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms. Examples of the lower alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, and t-amyl. Etc. The alkoxyl group preferably has 1 to 5 carbon atoms. Examples of the alkoxyl group include methoxy, ethoxy, propoxy, isopropoxy, butoxy, and t-butoxy. Examples of the aryl group include phenyl, tolyl, naphthyl, and the like, preferably a phenyl group. Examples of the aralkyl group include α-methylbenzyl, cumyl, and the like.

R ² may be the same or different, but is preferably the same and represents a hydrogen atom, an alkyl group or an aryl group, and at least one of ^two R ² bonded to the same carbon is It is preferably a hydrogen atom, and more preferably both are hydrogen atoms. The alkyl group preferably has 1 to 5 carbon atoms, particularly preferably 1 to 4 carbon atoms. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl and the like. Is mentioned. Examples of the aryl group include phenyl, tolyl, naphthyl, and the like, and a phenyl group is preferable.

n represents an integer of 0 to 3. The condensation composition represented by the above general formula (Formula 1) is a mixture containing each condensate when n is 0, 1, 2, or 3, and at least two of the four kinds of condensates. including.
m represents 0 to 3, preferably 1 to 3, and more preferably 1. When m is 1 to 3, R ¹ is preferably bonded to the m-position or p-position of the hydroxyl group of the phenol group, and R ¹ is bonded to the p-position of the hydroxyl group of the phenol group. More preferred.

  As a specific example of a binuclear condensate (that is, a condensate having two phenol skeletons of n = 0) among the condensates represented by the general formula (Chemical Formula 1), for example, 2,2′-methylenebisphenol 2,2′-methylenebis (4-chlorophenol), 2,2′-methylenebis (5-chlorophenol), 2,2′-methylenebis (4-hydroxyphenol), 2,2′-methylenebis (5-hydroxy) Phenol), 2,2'-methylenebis (4-methylphenol), 2,2'-methylenebis (5-methylphenol), 2,2'-methylenebis (4-ethylphenol), 2,2'-methylenebis (5 -Ethylphenol), 2,2'-methylenebis (4-n-propylphenol), 2,2'-methylenebis (4-isopropylphenol), 2,2 ' Methylene bis (5-n-propylphenol), 2,2′-methylene bis (5-isopropylphenol), 2,2′-methylene bis (4-n-butylphenol), 2,2′-methylene bis (4-t-butylphenol) 2,2'-methylenebis (5-n-butylphenol), 2,2'-methylenebis (5-t-butylphenol), 2,2'-methylenebis (4-t-amylphenol), 2,2'-methylenebis (4-methoxyphenol), 2,2'-methylenebis (5-methoxyphenol), 2,2'-methylenebis (4-cyanophenol), 2,2'-methylenebis (5-cyanophenol), 2,2 ' -Methylenebis (4-nitrophenol), 2,2'-methylenebis (5-nitrophenol), 2,2'-methyl Bis (4-phenylphenol), 2,2′-methylenebis (5-phenylphenol), 2,2′-methylenebis (4-cumylphenol), 2,2′-methylenebis (5-cumylphenol), 2 2,2'-ethylidenebisphenol, 2,2'-ethylidenebis (4-chlorophenol), 2,2'-ethylidenebis (5-chlorophenol), 2,2'-ethylidenebis (4-hydroxyphenol), 2 , 2′-ethylidenebis (5-hydroxyphenol), 2,2′-ethylidenebis (4-methylphenol), 2,2′-ethylidenebis (5-methylphenol), 2,2′-ethylidenebis (4 -Ethylphenol), 2,2'-ethylidenebis (5-ethylphenol), 2,2'-ethylidenebis (4-n-propyl) Phenol), 2,2'-ethylidenebis (4-isopropylphenol), 2,2'-ethylidenebis (5-isopropylphenol), 2,2'-ethylidenebis (4-n-butylphenol), 2,2 ' -Ethylidenebis (4-t-butylphenol), 2,2'-ethylidenebis (5-n-butylphenol), 2,2'-ethylidenebis (5-t-butylphenol), 2,2'-ethylidenebis (4 -T-amylphenol), 2,2'-ethylidenebis (4-methoxyphenol), 2,2'-ethylidenebis (5-methoxyphenol), 2,2'-ethylidenebis (4-cyanophenol), 2 , 2'-ethylidenebis (5-cyanophenol), 2,2'-ethylidenebis (4-nitrophenol), 2,2'-ethylidene Bis (5-nitrophenol), 2,2'-ethylidenebis (4-phenylphenol), 2,2'-ethylidenebis (5-phenylphenol), 2,2'-ethylidenebis (4-cumylphenol) 2,2′-ethylidenebis (5-cumylphenol), 2,2 ′-(phenylmethylene) bisphenol, 2,2 ′-(phenylmethylene) bis (4-chlorophenol), 2,2 ′-( Phenylmethylene) bis (5-chlorophenol), 2,2 ′-(phenylmethylene) bis (4-hydroxyphenol), 2,2 ′-(phenylmethylene) bis (5-hydroxyphenol), 2,2′- (Phenylmethylene) bis (4-methylphenol), 2,2 ′-(phenylmethylene) bis (5-methylphenol), 2,2 ′-(phenyl) Nilmethylene) bis (4-ethylphenol), 2,2 ′-(phenylmethylene) bis (5-ethylphenol), 2,2 ′-(phenylmethylene) bis (4-propylphenol), 2,2 ′-( Phenylmethylene) bis (4-isopropylphenol), 2,2 ′-(phenylmethylene) bis (5-isopropylphenol), 2,2 ′-(phenylmethylene) bis (4-tert-butylphenol), 2,2 ′ -(Phenylmethylene) bis (5-t-butylphenol), 2,2 '-(phenylmethylene) bis (4-t-amylphenol), 2,2'-(phenylmethylene) bis (4-methoxyphenol), 2,2 ′-(phenylmethylene) bis (5-methoxyphenol), 2,2 ′-(phenylmethylene) bis (4-cyanopheno) 2,2 ′-(phenylmethylene) bis (5-cyanophenol), 2,2 ′-(phenylmethylene) bis (4-nitrophenol), 2,2 ′-(phenylmethylene) bis (5) -Nitrophenol), 2,2 '-(phenylmethylene) bis (4-phenylphenol), 2,2'-(phenylmethylene) bis (5-phenylphenol) and the like.

In addition, specific examples of the 3-5 nuclear condensate (that is, the condensate having 3 to 5 phenol skeletons where n = 1 to 3 in the formula) are listed as specific examples of the above binuclear condensate, respectively. Mention may be made of compounds and corresponding compounds.
The condensation composition represented by the general formula (Chemical Formula 1) is a binuclear condensate, or a condensation composition mainly composed of a binuclear condensate and further including at least one of 3 to 5 nuclear condensates. In particular, the condensation composition is mainly composed of a binuclear condensate and further contains at least one of 3 to 5 nuclear condensates. Here, “at least one of 3 to 5 nuclear condensates” means only 3 nuclear condensates, 2 types of 3 nuclear condensates and 4 nuclear condensates, or 3 nuclear condensates and 4 nuclei. This means any of the three types of condensate and pentanuclear condensate, and “mainly binuclear condensate” means that the ratio of dinuclear condensate is the largest among the condensates constituting the condensation composition. Means. In the present invention, the condensation composition represented by the general formula (Chemical Formula 1) is a condensate in which n in the general formula (Chemical Formula 1) as an impurity is 4 or more as long as the object of the present invention is not impaired. It may be used in the state where (condensate of 6 nuclei or more) coexists.

  Preferred condensates (binuclear condensates) are 2,2′-methylenebis (4-methylphenol), 2,2′-methylenebis (4-ethylphenol), 2,2′-methylenebis (4-isopropylphenol). 2,2'-methylenebis (4-t-butylphenol), 2,2'-methylenebis (4-n-propylphenol), 2,2'-methylenebis (4-n-butylphenol), 2,2'-methylenebis (4-t-amylphenol), 2,2′-methylenebis (4-cumylphenol), 2,2′-ethylidenebis (4-methylphenol), 2,2′-ethylidenebis (4-ethylphenol) 2,2′-ethylidenebis (4-isopropylphenol), 2,2′-ethylidenebis (4-t-butylphenol), 2,2′- Tylidenebis (4-n-butylphenol), 2,2′-ethylidenebis (4-t-amylphenol), 2,2′-ethylidenebis (4-cumylphenol), 2,2′-butylidenebis (4-methyl) Phenol), 2,2′-butylidenebis (4-t-butylphenol), etc., of which 2,2′-methylenebis (4-methylphenol), 2,2′-methylenebis (4-isopropylphenol), 2 , 2′-methylenebis (4-t-butylphenol), 2,2′-methylenebis (4-n-butylphenol), 2,2′-methylenebis (4-n-propylphenol), 2,2′-methylenebis (4 -T-amylphenol), 2,2'-methylenebis (4-cumylphenol), 2,2'-ethylidenebis (4-t Butylphenol), 2,2'-butylidene bis (4-t-butylphenol) are particularly preferred.

Specific examples of preferable condensation compositions (condensation compositions mainly composed of binuclear condensates and further containing at least one of 3 to 5 nuclear condensates) include specific examples of the above preferred binuclear condensates. And a condensate composition further comprising a 3-5 nuclear condensate corresponding to the above compound (binuclear condensate).
In such a condensation composition, the content of the binuclear condensate is preferably 40 to 99%, more preferably 45 to 98%, and particularly preferably 50 to 80%. Here, “%” means “area%” in the results of high performance liquid chromatography analysis.
The condensation composition represented by the above general formula (Formula 1) used in the present invention includes, for example, a substituted phenol and a ketone compound or an aldehyde compound in the presence of an acid catalyst (for example, hydrochloric acid, p-toluenesulfonic acid, etc.). It can be easily obtained by a known synthesis method such as reaction. The reaction can dissolve the raw materials and reaction products and can be an appropriate organic solvent inert to the reaction (for example, water, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, acetonitrile, toluene, chloroform, diethyl ether, N, N-dimethylacetamide, benzene, chlorobenzene, dichlorobenzene, diethyl ketone, ethyl methyl ketone, acetone, tetrahydrofuran, etc.) at a reaction temperature of 0 to 150 ° C. for several hours to several tens of hours. After the reaction, the unreacted substituted phenols can be obtained with high yield by removing them by distillation.

Specific examples of substituted phenols include phenol, p-chlorophenol, m-chlorophenol, o-chlorophenol, catechol, resorcinol, hydroquinone, p-cresol, m-cresol, o-cresol, p-ethylphenol. M-ethylphenol, o-ethylphenol, p-propylphenol, o-propylphenol, p-isopropylphenol, m-isopropylphenol, o-isopropylphenol, pt-butylphenol, mt-butylphenol, o- t-butylphenol, p-t-amylphenol, p-methoxyphenol, m-methoxyphenol, o-methoxyphenol, p-cyanophenol, m-cyanophenol, o-cyanophenol, p-nitrophenol m-nitrophenol, o-nitrophenol, p-phenylphenol, m-phenylphenol, o-phenylphenol, p-cumylphenol, m-cumylphenol, o-cumylphenol, p- (α-methylbenzyl) ) Phenol and the like.
Specific examples of the ketone compound and aldehyde compound include, but are not limited to, dimethyl ketone, diethyl ketone, ethyl methyl ketone, methyl isobutyl ketone, formaldehyde, benzaldehyde and the like.

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

Specifically, there are three types represented by the following formula.

  The urea urethane compound is preferably used at a ratio of 0.01 to 10.0 parts by weight per 1 part by weight of the condensation composition represented by the general formula (Chemical Formula 1). More preferably, it is used in a proportion by weight. When the amount of the urea urethane compound is less than 0.01 parts by weight per 1 part by weight of the condensate or the condensation composition represented by the general formula (Chemical Formula 1), it is difficult to obtain sufficient plasticizer resistance. On the other hand, if it exceeds 10.0 parts by weight, the sensitivity and image quality of the heat-sensitive recording material (heat-sensitive color forming layer) tend to be lowered.

  In the present invention, in addition to the condensation composition represented by the general formula (Chemical Formula 1) and the general formula (Chemical Formula 2) as long as the desired effect is not hindered, a conventionally known developer as a developer. May be used in combination. Examples of such a developer include 4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-hydroxy-4′-propoxydiphenyl sulfone, benzyl paraoxybenzoate, and bis- (3-allyl-4-hydroxyphenyl). ) Sulfone, 2,4-bisphenol sulfone, 4,4-bisphenol sulfone, 4,4′-isopropylidene-di-o-cresol and the like. The amount of the developer used is about 0.1 to 10 parts by weight with respect to 1 part by weight of the condensation composition represented by the general formula (Formula 1).

  Furthermore, various materials used for the thermosensitive coloring layer of the present invention are exemplified, but the developer and the stabilizer can be used in combination as long as the desired effects on the above-mentioned problems are not impaired, and a binder, a crosslinking agent, and a pigment. Can be used in the protective layer as long as the desired effect on the above-mentioned problems is not impaired, and it can be used not only in the protective layer but also in each coating layer provided as necessary, including a thermosensitive coloring layer. Can do.

As the electron-donating leuco dye used in the present invention, those known in the conventional pressure-sensitive or heat-sensitive recording paper field can be used, and are not particularly limited, but include triphenylmethane compounds, fluorane compounds. Compounds, fluorene compounds, divinyl compounds and the like are preferable. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These 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; Diethylamino-6-methyl-7- (p-chloroanilino) fluorane; 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluorane; 3-diethylamino-6-methyl-7- (m-methylanilino) fluorane 3-diethylamino-6-methyl-7-n-octylanilinofluorane; 3-diethylamino-6-methyl-7-n-octylaminofluorane; 3-diethylamino-6-methyl-7-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-ethoxyethyl-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-dibutylamino-6-methyl-7- (o); 3-dibutylamino-6-methyl-7- (o; 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-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- 3-di-n-pentylamino-6-methyl-7-anilinofluorane; 3-di-n-pentylamino-6-methyl-7- (p-chloroanilino) fluorane; Di-n-pentylamino-7- (m-trifluoromethylanilino) fluorane; 3-di-n-pentylamino-6-chloro-7-anilinofluorane; 3-di-n-pentylamino-7 -(P-chloroanilino) fluorane; 3-pyrrolidino-6-methyl-7-anilinofluorane; 3-piperidino-6-methyl-7-anilinofluorane 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane; 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane; -(N-ethyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-xylamino) -6-methyl-7- (p-chloroanilino) fluorane; (N-ethyl-p-toludino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane; 3- (N- Ethyl (N-isoamylamino) -6-chloro-7-anilinofluoran; 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane; Til-N-isobutylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-ethoxypropylamino) -6-methyl-7-anilinofluorane; 3-cyclohexylamino-6 -Chlorofluorane; 2- (4-oxahexyl) -3-dimethylamino-6-methyl-7-anilinofluorane; 2- (4-oxahexyl) -3-diethylamino-6-methyl-7-ani Linofluorane; 2- (4-oxahexyl) -3-dipropylamino-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); 2-chloro-6-p- (p-dimethylaminophenyl) aminoanilinofluorane; 2-nitro-6-p- (p-diethylaminophenyl) aminoanilinofluorane; -Amino-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 2-phenyl-6-methyl-6-p -(P-phenylaminophenyl) aminoanilinofluorane; 2-benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane; 2-hydroxy-6-p- (p-phenylaminophenyl) Aminoanilinofluorane; 3-methyl-6-p- (p-dimethylaminophenyl) aminoanilinov Oran; 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; -Bis (diethylamino) fluorane-γ- (4'-nitro) anilinolactam; 1,1-bis- [2 ', 2', 2 ", 2" -tetrakis- (p-dimethyla Nophenyl) -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

  As the electron-accepting developer that can be used in combination with the present invention, any of those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and is not particularly limited. Inorganic acidic substances such as clay, attapulgite, colloidal silica, 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, 4-hydroxybenzoic acid benzyl, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4 ' -Isopropoxydiphenyl sulfone, 4-hydroxy-4 ' n-propoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl- 4'-methylphenylsulfone, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane , Butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bi [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 International Publication WO02 / 081229 or JP-A-2002-301873, 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] sa Aromatic carboxylic acids of tyric acid, and salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and further antipyrine complexes of zinc thiocyanate, Examples include composite zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids. These developers can be used alone or in combination of two or more. A metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A No. 10-258577 can also be contained.

  A conventionally well-known sensitizer can be used as a sensitizer used by this invention. Examples of such sensitizers include fatty acid amides such as stearamide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-di- (3-methylphenoxy) ethane, p-benzylbiphenyl, β- Benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, di (p-methylbenzyl) oxalate, Dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis -(Phenyl ether), 4- (m-methyl) Ruphenoxymethyl) biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3-methylphenoxy) ethylene, bis [2- (4-methoxy- Examples thereof include, but are not limited to, phenoxy) ethyl] ether, methyl p-nitrobenzoate and phenyl p-toluenesulfonate. These sensitizers may be used alone or in combination of two or more.

  In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol), 2 as a stabilizer exhibiting the oil resistance effect of the recorded image and the like within a range not impairing the desired effect on the above problems. 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.

  In the heat-sensitive recording material of the present invention, a fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl having a polymerization degree of 200 to 1900 as a binder. Alcohol, butyral modified polyvinyl alcohol, 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 Polymer, styrene-butadiene copolymer and ethyl cellulose, Cellulose derivatives such as chilled cellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrose and the like Examples of such a copolymer include polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and coumaro resin. These polymer substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, hydrocarbons, etc., and are used in the state of being emulsified or pasted in water or other media to achieve the required quality. It can also be used in combination.

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

The type and amount of the dye, developer, and other various components used in the heat-sensitive color developing layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. On the other hand, 0.5 to 10 parts of developer, 0.5 to 10 parts of sensitizer, 0.01 to 10 parts by weight of stabilizer, and 0.01 to 10 parts by weight of other components are used.
Dye, developer, and materials to be added as necessary are finely pulverized to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, a sand glider, or an appropriate emulsifier, and depending on the binder and purpose. Various additive materials are added to form a coating solution. As a solvent used in the coating liquid, water or alcohol can be used, and the solid content is about 20 to 40% by weight.

In the thermosensitive recording material of the present invention, it is preferable to further provide a protective layer on the thermosensitive coloring layer. The electron-donating leuco dye and the electron-accepting developer contained in the heat-sensitive recording layer are easily dissolved in various solvents, so that the white paper part develops color, and when a chemical such as a plasticizer touches the recorded image, the color fades. There is a problem, and it is preferable to provide a protective layer. The protective layer also improves storage stability such as water resistance.
The protective layer is often mainly composed of a pigment and a resin. For example, a water-soluble polymer such as polyvinyl alcohol or starch is used as the main component. When these water-soluble polymers are used, it is general to further use a crosslinking agent such as glyoxal or melamine formalin resin in order to impart water resistance.

The protective layer of the present invention contains a kaolin having a flat aspect ratio of 20 or more, such as silica or aluminum hydroxide, which is usually used, and thus good color sensitivity and high image quality can be obtained. Further, since the storage stability of the image part and the blank paper part is improved, an image with clear contrast can be obtained. The reason is presumed as follows.
For example, when the same area is coated, when the pigment A having an aspect ratio of 20 and the pigment B having an aspect ratio of 40 are compared, the minimum required amount of the pigment B is theoretically half of the minimum required amount of the pigment A. That is, a coating layer with high coverage can be formed with a small coating amount. In addition, since the thickness of the pigment with a large aspect ratio is thin, the unevenness of the surface of the thermal recording medium is reduced, and excellent surface smoothness is exhibited. In this case, since the flat surface tends to be oriented upward, it is considered that the penetration of the protective layer paint into the heat-sensitive coloring layer is suppressed, and the covering property and the surface smoothness are improved. As described above, since a good surface smoothness is expressed by including a pigment having a large aspect ratio in the heat-sensitive recording material, it is possible to minimize the processing pressure such as a super calender treatment that gives the target smoothness. Thus, a heat-sensitive recording material having a porous and excellent surface smoothness, that is, a heat-sensitive recording material having a high heat insulating effect and uniformly contacting the thermal head can be obtained. As a result, it is possible to obtain color development sensitivity and high image quality with good barcode readability, and an image with clear contrast can be obtained due to the effect of improving the storage stability of the image portion and the white paper portion by providing the protective layer. .

In the present invention, the particle diameter of kaolin having an aspect ratio of 20 or more contained in the protective layer is desirably 4 μm or less. When the average diameter of kaolin having an aspect ratio of 20 or more is larger than 4 μm, the pigment is exposed on the surface of the coating layer, so that the surface smoothness is lowered, the recording image quality is lowered, the friction with the thermal head is increased (head wear), etc. A problem occurs. Further, the oil absorption amount of kaolin having an aspect ratio of 20 or more is preferably 30 to 100 ml / 100 g from the viewpoints of ink inking properties and gloss of printed parts in general printing. If the oil absorption amount is 30 ml / or less, the ink for general printing is difficult to be absorbed, which causes a problem in ink inking property. If the oil absorption amount is 100 ml / 100 g or more, the ink for general printing is excessively absorbed. Therefore, a heat-sensitive recording material having a high print area gloss cannot be obtained.
Furthermore, when the aspect ratio of kaolin contained in the protective layer is 100 or more, the protective layer becomes dense, which causes problems such as a decrease in ink setting property and ink drying property and a decrease in color development sensitivity in general printing. The aspect ratio of kaolin contained in the protective layer of the present invention is desirably 20 to 100, more preferably 30 to 75.

In the present invention, kaolin having an aspect ratio of 20 or more is preferably used alone, but is less than 50 parts by weight, more preferably 80 parts by weight with respect to 100 parts by weight of the total amount of kaolin having an aspect ratio of 30 or more. Less than 30 kaolin, (calcined) kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, diatomaceous earth, talc, etc. It is possible.
The kaolin having an aspect ratio of 20 or more of the present invention can be obtained by classifying the delaminated kaolin by special grinding. In the present invention, the content of the pigment and the binder in the protective layer is about 30 to 300 parts by weight in solid content of the binder with respect to 100 parts by weight of the pigment.

In the present invention, it is desirable that the protective layer contains a carboxyl group-containing resin, particularly a carboxy-modified polyvinyl alcohol, an epichlorohydrin resin, and a modified polyamine / amide resin from the viewpoint of heat resistance, water resistance, and heat and humidity resistance. 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 or amide portion of the epichlorohydrin resin as the crosslinking agent. Next, since the hydrophilic cross-linking site formed of the carboxyl group-containing resin and epichlorohydrin resin attracts the hydrophilic site of the modified polyamine / amide resin, this cross-linking site is the same as that of the modified polyamine / amide resin. It is in a state of being wrapped with the hydrophobic group on the outside, that is, in a state where the hydrophilic crosslinking site is protected from water by the hydrophobic group (second water resistance). Thus, it is presumed that good water resistance and moisture resistance can be obtained by imparting higher hydrophobicity to the reaction site between the resin used in the protective layer and the crosslinking agent.

In particular, when the carboxyl group-containing resin is carboxy-modified polyvinyl alcohol, the hydrophilic part of the modified polyamine / polyamide resin and the carboxy-modified polyvinyl alcohol are attracted, and the carboxy-modified polyvinyl alcohol has the hydrophobic group of the modified polyamine / amide resin outside. When the cationic site of the modified polyamine / amide resin is cross-linked with the carboxyl group of the carboxy-modified polyvinyl alcohol, high water resistance is exhibited and heat resistance is also improved. it is conceivable that.
Also, a modified polyamine / amide resin that has a three-dimensional structure by a crosslinking reaction between carboxy-modified polyvinyl alcohol and epichlorohydrin resin, and is cationic when a pigment is contained in the protective layer. Is considered to be a porous layer compared to the prior art because it exhibits a dispersion effect on anionic pigments. For this reason, since the melt of the material with low heat resistance in the coating layer is adsorbed in the voids in the protective layer, excellent print running properties (head debris resistance, sticking resistance) can be exhibited.

In the protective layer of the present invention, it is desirable to use an epichlorohydrin resin and a modified polyamine / amide resin in combination. When each of them is used alone, sufficient water resistance cannot be obtained, and adverse effects such as blocking occur. In addition, sufficient water resistance cannot be obtained even when other general crosslinking agents such as glyoxal and epichlorohydrin resin or modified polyamine / amide resin are used in combination.
In the present invention, the carboxyl group-containing resin used as the binder of the protective layer may be any resin having mainly a carboxyl group, such as methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate. , A resin containing a monofunctional acrylic monomer having a carboxyl group, such as dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, oxidized starch, carboxymethylcellulose, Examples include carboxy-modified polyvinyl alcohol in which a carboxyl group is introduced into polyvinyl alcohol. Particularly, carboxy-modified polyvinyl alcohol having excellent heat resistance and solvent resistance. It is preferable to use.

The carboxy-modified polyvinyl alcohol used in the present invention is a product in which a carboxyl group is introduced for the purpose of enhancing the reactivity to a water-soluble polymer, such as polyvinyl alcohol and fumaric acid, phthalic anhydride, melittic anhydride, itaconic anhydride, etc. A reaction product of a polycarboxylic acid, or an esterified product of these reaction products, and an ethylenically unsaturated dicarboxylic acid such as vinyl acetate and maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid or methacrylic acid As a saponified product of Specific examples include the production methods exemplified in JP-A-53-91995.
Furthermore, the carboxy-modified polyvinyl alcohol used in the present invention has a low Hercules viscosity, that is, a high fluidity in a state where a rotational force (share) is applied, and is easily immobilized at a low share. For this reason, it is considered that the coating liquid extends smoothly during coating and solidifies immediately after coating to form a coating layer that is homogeneous and has no unevenness, thereby improving the image quality and sensitivity of the printed image. In addition, since carboxy-modified polyvinyl alcohol has high water retention, the penetration of the binder into the support can be suppressed, and this effect also improves the image quality and sensitivity because a coating layer without unevenness is formed. It is guessed.
The degree of polymerization and the degree of saponification of the carboxy-modified polyvinyl alcohol used in the present invention can be appropriately selected and used from the viewpoint of the water retention of the paint and the surface strength of the coating layer.

  Specific examples of the epichlorohydrin-based resin used in the present invention include polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and the like, and they can be used alone or in combination. Moreover, as an amine which exists in the principal chain of an epichlorohydrin-type resin, the thing from a primary to a quaternary can be used, and there is no restriction | limiting in particular. Further, the degree of cationization and molecular weight are preferably water cation resistance, so that the degree of cationization is 5 meq / g · Solid (measured value at pH 7) and the molecular weight is 500,000 or more. Specific examples include Sumire's Resin 650 (30) (manufactured by Sumitomo Chemical), Sumire's Resin 675A (manufactured by Sumitomo Chemical), Sumire's Resin 6615 (manufactured by Sumitomo Chemical), WS4002 (manufactured by Seiko PMC), WS4020. (Made by Starlight PMC), WS4024 (made by Starlight PMC), WS4046 (made by Starlight PMC), WS4010 (made by Starlight PMC), CP8970 (made by Starlight PMC), and the like.

  In the present invention, the modified polyamine / amide resin is a polyamide urea resin, polyethylene imine resin, polyalkylene polyamine resin, polyalkylene polyamide resin, polyamine polyurea resin, modified polyamine resin, modified polyamide resin, polyalkylene polyamine urea formalin. Resin, polyalkylene polyamine polyamide polyurea resin, and the like are listed. Specific examples include Sumire Resin 302 (manufactured by Sumitomo Chemical Co., Ltd .: polyamine polyurea resin) and Sumire Resin 712 (manufactured by Sumitomo Chemical Co., Ltd .: polyamine polyurea resin). ), Sumire Resin 703 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin 636 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin SPI-100 (manufactured by Sumitomo Chemical: modified polyamine) Tree ), Sumire Resin SPI-102A (Sumitomo Chemical Co .: modified polyamine resin), Sumire Resin SPI-106N (Sumitomo Chemical Co .: modified polyamide resin), Sumire Resin SPI-203 (50) (Sumitomo Chemical Co., Ltd.) : Polyamide resin), Sumirez resin SPI-198 (manufactured by Sumitomo Chemical Co., Ltd .: polyamide resin), printable A-700 (manufactured by Asahi Kasei), printable A-600 (manufactured by Asahi Kasei), PA6500 (manufactured by Seiko PMC): Polyalkylene polyamine urea formalin resin), PA6504 (manufactured by Starlight PMC: polyalkylene polyamine urea formalin resin), PA6664, PA6638, PA6640, PA6664, PA6664, PA6654, PA6702, PA6704 (above, manufactured by Starlight PMC: polyalkylenepolyamide) Polyamide polyurea resin), CP8994 (manufactured by Seiko PMC: polyethyleneimine resin), and the like. Although not particularly limited, polyamine resins (polyalkylene polyamine resins, polyamine polyurea resins) are considered in terms of color development sensitivity. It is desirable to use a modified polyamine resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea resin).

  The content of the epichlorohydrin resin and the modified polyamine / amide resin used in the present invention is preferably 1 to 100 parts by weight, more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the carboxy-modified polyvinyl alcohol. 50 parts by weight. If the content is too small, the crosslinking reaction becomes insufficient and good water resistance cannot be obtained. If the content is too large, there arises a problem in operability due to an increase in viscosity of the coating liquid or gelation. Moreover, since epichlorohydrin resin cross-links at pH 6.0 or higher, it is desirable to adjust the pH of the protective layer coating to 6.0 or higher.

The types and amounts of various components used in the protective layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, polyvinyl alcohol is 10 to 500 parts per 100 parts by weight of the pigment. It is preferable to use 1 to 100 parts by weight of the crosslinking agent component with respect to 100 parts by weight of polyvinyl alcohol.
These materials are pulverized to a particle size of several microns or less by a pulverizer such as a ball mill, attritor or sand glider or an appropriate emulsifying device, and various additives are added according to the binder and purpose to form 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.

The following examples illustrate the invention but are not intended to limit the invention.
In the following examples and comparative examples, an under layer, a thermosensitive coloring layer (recording layer) and a protective layer were formed on one side of the support, and a back layer was formed on the other side.
The coating liquid used for each coating layer of the heat-sensitive recording material was prepared as follows.
In the description, parts and% indicate parts by weight and% by weight, respectively.

Under layer coating liquid -calcined kaolin (Ansilex 90 manufactured by Engelhard) 90.0 parts-Styrene-butadiene copolymer latex (solid content 50%) 10.0 parts-Water 50.0 parts A mixture comprising the above composition The under layer coating solution was prepared by mixing and stirring.

Thermosensitive coloring layer coating solution The following solutions A to D were separately wet-ground with a sand grinder until the average particle size became 0.5 μm.
Liquid A (first developer dispersion)
-Condensation composition containing 60% of 2,2'-methylenebis (4-t-butylphenol) (trade name: JKY224, manufactured by API Corporation) 6.0 parts-1% aqueous solution of polyvinyl alcohol 10%-water 11.2 parts

Liquid B (second developer dispersion)
-Urea urethane developer composition (trade name: UU, manufactured by Chemipro Kasei Co., Ltd.) 6.0 parts -Polyvinyl alcohol 10% aqueous solution 18.8 parts -Water 11.2 parts C liquid (basic colorless dye dispersion)
-3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd., trade name: ODB-2) 3.0 parts-polyvinyl alcohol 10% aqueous solution 6.9 parts-water 3.9 parts D Liquid (sensitizer dispersion)
-1,2-bis (phenoxymethyl) benzene (manufactured by Nikka Chemical Co., Ltd., trade name: PMB-2)
6.0 parts-polyvinyl alcohol 10% aqueous solution 18.8 parts-water 11.2 parts

Next, the dispersions were mixed at the following ratio to obtain a thermosensitive coloring layer coating solution.
Liquid A (first developer dispersion) 36.0 parts Liquid B (second developer dispersion) 36.0 parts Liquid C (basic colorless dye dispersion) 18.0 parts Liquid D (sensitizer) Dispersion) 36.0 parts Aluminum hydroxide (50% dispersion) 3.2 parts Polyvinyl alcohol (10% solution) 25.0 parts

Protective layer coating liquid -Kaolin 50% dispersion (trade name: Konza 1500, manufactured by Imeris Co., Ltd., aspect ratio: 60, average particle size: 2.5 μm, oil absorption: 45 ml / 100 g) 9.0 parts-Carboxy-modified polyvinyl alcohol (Kuraray brand name: KL118 <degree of polymerization: about 1700, degree of saponification: 95-99 mol%, sodium acetate: 3% or less>) 10% aqueous solution
30.0 parts-Polyamide epichlorohydrin resin (trade name: WS4020 manufactured by Seiko PMC Co., Ltd., solid content 25% <degree of cationization: 2.7, molecular weight: 2.2 million, quaternary amine>) 4.0 parts-modification Polyamine resin (trade name, Sumirez Resin SPI-102A, manufactured by Sumitomo Chemical Co., Ltd., 45% solid content) 2.2 parts-Zinc stearate (trade name, manufactured by Chukyo Yushi Co., Ltd .: Hydrin Z-7-30, 30% solid content) )
2.0 parts

[Example 1]
Apply and dry the under layer coating solution on one side of high-quality paper (47 g / m ² base paper) with a Meyer bar to 10.0 g / m ² (fan dryer, 60 ° C., 2 minutes) Coated paper was obtained. The thermosensitive coloring layer coating solution is applied onto the underlayer of this undercoated paper and dried (fan drying at 60 ° C. for 2 minutes) so that the coating amount is 6.0 g / m ^2. After applying the protective layer coating solution on the color forming layer so that the coating amount is 3.0 g / m ² , drying is performed, and the sheet is processed with a super calendar so that the smoothness becomes 1500 to 3000 seconds. A heat-sensitive recording material was obtained.

[Example 2]
A thermosensitive recording material was produced in the same manner as in Example 1 except that the sensitizer was changed to a stearic acid amide / paltimic acid amide mixture (mixing ratio: 7/3, Nippon Kasei Co., Ltd., trade name: AP-1). .
[Example 3]
A thermal recording medium was prepared in the same manner as in Example 2 except that the dye was changed to 3-N-di-n-pentylamino-6-methyl-7-anilinofluorane (trade name: BLACK305, manufactured by Yamada Chemical Co., Ltd.). Produced.

[Example 4]
The kaolin 50% dispersion was replaced with aluminum hydroxide 50% dispersion (manufactured by Martinsberg, aspect ratio: 5, average particle size: 3.5 μm, oil absorption: 50 ml / 100 g) to prepare a protective layer coating solution. A heat-sensitive recording material was produced in the same manner as in Example 1 except that it was used.
[Example 5]
A thermosensitive recording material was prepared in the same manner as in Example 4 except that the sensitizer was changed to stearic acid amide / paltimic acid amide mixture [= 7/3] (product name: AP-1 manufactured by Nippon Kasei Co., Ltd.).
[Example 6]
A thermal recording medium was prepared in the same manner as in Example 5 except that the dye was changed to 3-N-di-n-pentylamino-6-methyl-7-anilinofluorane (trade name: BLACK305, manufactured by Yamada Chemical Co., Ltd.). Produced.

[Comparative Example 1]
A thermal recording material was produced in the same manner as in Example 1 except that the first developer was changed to 2,4′-dihydroxydiphenylsulfone (manufactured by Nikka Chemical Co., Ltd., trade name: 2,4′BPS). .
[Comparative Example 2]
A heat-sensitive recording material was produced in the same manner as in Comparative Example 1 except that the developer was changed to 4-hydroxy-4′-isopropoxydiphenyl sulfone (trade name: NY-DS, manufactured by API Corporation).
[Comparative Example 3]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the second developer was not blended.

[Comparative Example 4]
The kaolin 50% dispersion was replaced with aluminum hydroxide 50% dispersion (manufactured by Martinsberg, aspect ratio: 5, average particle size: 3.5 μm, oil absorption: 50 ml / 100 g) to prepare a protective layer coating solution. A heat-sensitive recording material was prepared in the same manner as in Comparative Example 1, except that the sensitizer was changed to 1,2-bis (3-methylphenoxy) ethane (manufactured by Sanko Co., Ltd., trade name: KS232).
[Comparative Example 5]
A heat-sensitive recording material was produced in the same manner as in Comparative Example 4 except that the developer was changed to 4-hydroxy-4′-isopropoxydiphenylsulfone (manufactured by API Corporation, trade name: NY-DS).
[Comparative Example 6]
Thermosensitive recording medium in the same manner as in Comparative Example 5 except that the dye was changed to 3-N-di-n-pentylamino-6-methyl-7-anilinofluorane (trade name: BLACK305, manufactured by Yamada Chemical Co., Ltd.) Was made.

The following evaluations were performed on the heat-sensitive recording materials obtained in the above Examples and Comparative Examples, and the results are shown in Table 1.
The average particle diameter of the pigment is measured with the electron microscope, and the length of each of 100 particles in the X-axis direction, the Y-axis direction, and the Z-axis direction is measured. The axis was averaged to calculate the diameter of each particle, and the average value was obtained. The aspect ratio of the pigment is an average value obtained by photographing the pigment with an electron microscope and using a calculation formula (aspect ratio = diameter / thickness) from the diameter and the length (thickness) of the shortest axis for 100 particles. Asked.
The oil absorption was measured according to JIS K-5101.

Printing density A checkerboard pattern was printed with a thermal printer TH-PMD (pattern No. 8) manufactured by Okura Co., Ltd., and the colored portion was measured with a Macbeth densitometer.
Water Resistance The heat-sensitive recording material printed as described above was immersed in tap water at 23 ° C. for 24 hours, dried and then evaluated for barcode reading.
Plasticizer Resistance A dial wrap (manufactured by Mitsui Chemicals) was brought into contact with the front and back of the heat-sensitive recording material printed as described above, and allowed to stand in an environment of 40 ° C. and 80% for 24 hours.

Barcode readability The barcode printing part (CODE39) was evaluated with a barcode reader (Nihon Systex, Quick Check PC600). Evaluation is performed by ANSI grade (CEN method, number of measurements 10 times), and evaluation is as follows. If the rating is C or higher, the bar code reading aptitude is at a level that is not practically problematic. On the other hand, if the rating is equal to or lower than D, the bar code reading aptitude is practically problematic.
(Excellent) A>B>C>D> F (poor)

  The results are shown in the table below.

From Table 1, the heat-sensitive color-developing layer is represented by the general formula (Chemical Formula 2) as the condensation composition represented by the general formula (Chemical Formula 1) as the first electron-accepting color developer. When the urea urethane compound is contained, the heat-sensitive recording material has good water resistance and plasticizer resistance, and is excellent in image storability and barcode suitability. Furthermore, it can be seen that when the protective layer containing the kaolin of the present invention is provided on the thermosensitive coloring layer, these properties are further improved.

Claims (3)

A heat-sensitive recording material provided with a heat-sensitive coloring layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer on a support, the heat-sensitive coloring layer having a first electron-accepting color development The following general formula (chemical formula 1)

(In the formula, R ¹ each may be the same or different, represent a hydrogen atom, a halogen atom, a hydroxyl group, a lower alkyl group, an alkoxyl group, a cyano group, a nitro group, an aryl group or an aralkyl group, R ² , Which may be the same or different, each represents a hydrogen atom, an alkyl group or an aryl group, m represents an integer of 0 to 3, and n represents an integer of 0 to 3). As a composition and a second electron-accepting developer, the following general formula (Formula 2)

And a protective layer containing a carboxyl group-containing resin, an epichlorohydrin resin, and a modified polyamine / amide resin. The heat-sensitive recording material according to claim 1, further comprising a protective layer on the heat-sensitive color developing layer, wherein the protective layer contains kaolin having an aspect ratio of 20 or more. The heat-sensitive recording material according to claim 1, wherein the modified polyamine / amide resin is a polyamine resin.