JP2008149623A - Heat-sensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sensitive recording medium with excellent recording sensitivity, resistance to heat, water, alcohol and oil. <P>SOLUTION: This heat-sensitive recording medium keeps the support overlaid with an undercoat layer and a heat-sensitive recording layer which is formed on the former, containing a colorless or pale-color leuco dye and a coloring agent. In addition, a special compound is added as the coloring agent and the undercoat layer is multistructured, comprising at least, a first layer and a second layer formed on the former. The heat-sensitive recording layer contains at least, one chemical compound selected from the group consisting of a 1,5-(3-oxapentamethylene)bis(3-(3-(p-toluenesulfonyl)ureide)benzoate), a 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureide]diphenylsulfone and a 4,4'-[oxybis(ethyleneoxybis-p-phenylenesulfone)]diphenol. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material utilizing a coloring reaction between a colorless or light-colored basic dye and a color former.

  A heat-sensitive recording material is known that utilizes a color reaction between a colorless or light-colored leuco dye and an organic or inorganic colorant so that a recording image is obtained by bringing both coloring materials into contact with each other by heat. Such heat-sensitive recording materials are relatively inexpensive, and the recording equipment is compact and easy to maintain, so that they are used not only as recording media for facsimiles and various computers but also in a wide range of fields.

  The fields of use include, for example, cash register paper and ticket paper for POS (point of sales) systems, but with the expansion of the system, the usage environment and usage methods are diversified, increasing use under severe conditions. Have been doing. In addition, the printing speed of printers increases year by year, and it is desired that printing can be performed even with lower printing energy. Furthermore, since it is used as a receipt, the recording section needs to be stored in water, vinegar, alcohol such as liquor and disinfectant, oil, plasticizer, office supplies, hand cream and the like.

  It is known that a heat-sensitive recording material provided with a heat-sensitive coloring layer mainly composed of a leuco dye and a colorant on a support has a reversible coloring reaction, so that the color-developing image is decolored with time. . This decolorization is accelerated under light exposure, high temperature and high humidity atmosphere, and further proceeds rapidly by contact and impregnation with water, vinegar, alcohol such as liquor, oil, wrap, plasticizer contained in film, etc. However, the recorded image is erased until it cannot be read, or the non-printing part of the thermal recording medium is colored, and the contrast between the printing part and the non-printing part is lost. . On the other hand, in order to improve the storage stability of recording, a method of providing a protective layer on the thermosensitive coloring layer and a method of adding an epoxy compound to the thermosensitive coloring layer have been proposed. However, a sufficient effect is not obtained. Further, when the protective layer is provided, there is a problem of a decrease in sensitivity. Further, in recent years, development of colorants having high storage stability has progressed and the above problems are being solved, but there is a disadvantage that the color development sensitivity is low.

  In addition, there is an attempt to use a phenol trinuclear as a colorant as a colorant or a part of the colorant (see Patent Document 1), but the compatibility between color development sensitivity and storage stability is insufficient. is there. In addition, there is an attempt to improve the sensitivity by reducing the eutectic point to 150 to 200 ° C. by mixing two or more of such phenol trinuclear bodies (see Patent Document 2). A composition containing a phenol trinuclear product obtained by condensing all phenols at the ortho position of the OH group does not provide sufficient sensitivity and storage stability of the recording portion, similar to the colorant disclosed in Patent Document 1. In addition, a novel trinuclear structure in which p-substituted phenol is condensed with other alkylphenols at the para position of the OH group via a methylene group at both ortho positions of the hydroxyl group has been proposed (Patent Document). 3), sufficient sensitivity and storage stability of the recording part are still not obtained. In addition, although it has been proposed to use a specific phenol trinuclear body (see Patent Document 4), a heat-sensitive recording material excellent in storage stability of the recording portion, particularly oil resistance and alcohol resistance has not been obtained. is the current situation.

On the other hand, in order to improve the recording sensitivity and image quality of the heat-sensitive recording material, an undercoat layer containing a pigment and a binder is provided between the support and the heat-sensitive recording layer, and a void is formed to make it porous or bulky. It is known to provide thermal insulation. For example, in order to obtain a uniform and stable undercoat layer structure, it is described that an undercoat layer coating solution having a specific viscosity is applied by blades (Patent Document 5). Further, it is described that the variation of the thickness of the undercoat layer is within a certain range in order to improve the image quality of the thermal paper (Patent Document 6). Furthermore, it is described that two or more undercoat layers are formed by blade coating in order to reduce the static friction coefficient of the surface (Patent Document 7).
However, in recent years, printing speed has been increasing and the demand for high sensitivity and high image quality of thermal recording media has been increasing. It is sufficient to use highly smooth base paper or simply to provide an undercoat layer. It is no longer possible to obtain good quality.
As a method of providing an undercoat layer, the undercoat layer usually exhibits a heat insulating effect and improves the recording sensitivity as the coating amount increases, but the higher the coating amount, the more difficult it is to obtain a uniform coating layer, and the heat sensitivity to be formed thereafter. Since it is difficult to make the recording layer and the protective layer uniform, as a result, the recording sensitivity and the image quality are lowered, and the protective layer barrier performance is lowered.
In addition, in the thermal recording medium market, which is shifting to a mature market, manufacturing costs have become an important issue, and low-productivity coating systems and coating systems that are prone to coating defects are expensive. Even when a quality product is obtained, it is difficult to actually manufacture the product.

Japanese Patent Laid-Open No. 06-115255 JP 2001-96926 A JP 09-278695 A WO2005 / 000597 Publication Japanese Patent Laid-Open No. 04-290789 JP 2004-122483 A JP 2005-103864 A

  An object of the present invention is to provide a heat-sensitive recording material excellent in recording sensitivity, heat resistance, water resistance, alcohol resistance and oil resistance.

  As a result of intensive studies to solve the above problems, the inventor of the present invention uses a specific phenol trinuclear compound and a specific compound in the heat-sensitive recording layer, thereby recording sensitivity, water resistance, oil resistance and alcohol resistance. In addition, the present inventors have found that the above-mentioned object can be achieved by forming the undercoat layer into a multilayer structure of two layers and forming a specific heat-sensitive recording layer on the undercoat layer, thereby completing the present invention. It was.

  That is, the present invention provides the following thermal recording material.

  Item 1: In a heat-sensitive recording medium in which an undercoat layer is provided on a support and a heat-sensitive recording layer containing a colorless or light leuco dye or a colorant is provided on the undercoat layer, the colorant is represented by the following general formula: Containing a compound represented by (1),

（式中、Ｒはｎ−ブチル基、ｉｓｏ−ブチル基、ｓｅｃ−ブチル基またはｔｅｒｔ−ブチル基を表す。）
前記下塗り層が、少なくとも第一層及び該第一層上に形成された第二層からなる多層構造を有し、感熱記録層中に、さらに１，５−（３−オキサペンタメチレン）ビス（３−（３−（ｐ−トルエンスルホニル）ウレイド）ベンゾエート）、４，４’−ビス［（４−メチル−３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホン、４，４’−[オキシビス（エチレンオキシビス−ｐ−フェニレンスルホン）]ジフェノールから選ばれる少なくとも１つの化合物が含有されていることを特徴とする感熱記録体。
項２：前記第一下塗り層と第二下塗り層とが同一の下塗り層用塗液からなり、前記第一下塗り層と第二下塗り層との乾燥後の塗工量の割合が２：８〜８：２である、請求項１に記載の感熱記録体。
項３：前記第一下塗り層及び第二下塗り層の乾燥後の合計塗工量が５〜３０ｇ／ｍ^２である、請求項１または２に記載の感熱記録体。
項４：第一下塗り層がブレード塗工方式で塗布及び乾燥することにより形成され、更に、第二下塗り層がロッド塗工方式で塗布及び乾燥することにより形成されてなる、請求項１〜３のいずれか一項に記載の感熱記録体。
項５：前記４，４’−ビス［（４−メチル−３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホンが、４，４’‐ビス［（４−メチル‐３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホンと無機化合物を同時分散した分散液組成物（Ａ）あるいは前記４，４’‐ビス［（４−メチル‐３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホンの分散液組成物と無機化合物の分散液組成物を混合して調製した分散液組成物（Ｂ）を、４０℃以上で加熱して得られた化合物の形態である、請求項１に記載の感熱記録体。
項６：前記４，４’‐ビス［（４−メチル‐３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホン１００質量部に対して、前記無機化合物が０.５〜１０質量部である、請求項５に記載の感熱記録体。
項７：前記無機化合物が、珪酸マグネシウム、珪酸カルシウム、炭酸マグネシウム、炭酸カルシウム、硫酸カルシウム、リン酸マグネシウム、酸化マグネシウム、酸化アルミニウム、酸化チタン、水酸化マグネシウムから選ばれる少なくとも一種である、請求項５または６に記載の感熱記録体。
項８：前記上記一般式（１）で表される化合物１００質量部に対して、１，５−（３−オキサペンタメチレン）ビス（３−（３−（ｐ−トルエンスルホニル）ウレイド）ベンゾエート）、４，４’−ビス［（４−メチル−３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホン、４，４’−[オキシビス（エチレンオキシビス−ｐ−フェニレンスルホン）]ジフェノールから選ばれる化合物の総量が３〜１００質量部である、請求項１〜７のいずれか一項に記載の感熱記録体。
項９：前記ロイコ染料の融点が２００℃以上である、請求項１〜８のいずれか一項に記載の感熱記録体。
項１０：前記ロイコ染料が、３−（N−エチル−ｐ−トルイジノ）−６−メチル−７−アリニノフルオラン、３−（N−エチル−ｐ−トルイジノ）−６−メチル−７−（ｐ−トルイジノ）フルオラン、３−ジエチルアミノ−７−（ｏ−クロロアニリノ）フルオランから選ばれる少なくとも１つである、請求項９に記載の感熱記録体。

(In the formula, R represents an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)
The undercoat layer has a multilayer structure composed of at least a first layer and a second layer formed on the first layer. In the thermosensitive recording layer, 1,5- (3-oxapentamethylene) bis ( 3- (3- (p-toluenesulfonyl) ureido) benzoate), 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4 ′-[oxybis (ethyleneoxy) (Bis-p-phenylenesulfone)] diphenol. A thermosensitive recording material comprising at least one compound selected from diphenols.
Item 2: The first undercoat layer and the second undercoat layer are composed of the same undercoat layer coating solution, and the ratio of the coating amount after drying of the first undercoat layer and the second undercoat layer is 2: The heat-sensitive recording material according to claim 1, which is 8 to 8: 2.
Claim 3: The total coating amount after drying of the first subbing layer and second subbing layer is 5 to 30 g / m ^2, the heat-sensitive recording material according to claim 1 or 2.
Item 4: The first undercoat layer is formed by applying and drying by a blade coating method, and further, the second undercoat layer is formed by applying and drying by a rod coating method. 4. The thermal recording material according to any one of 3 above.
Item 5: The 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone is converted to 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido]. The dispersion composition (A) in which diphenylsulfone and an inorganic compound are simultaneously dispersed, or the dispersion composition of the 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone and the inorganic compound The heat-sensitive recording material according to claim 1, which is in the form of a compound obtained by heating the dispersion composition (B) prepared by mixing the dispersion composition at 40 ° C or higher.
Item 6: The inorganic compound is 0.5 to 10 parts by mass with respect to 100 parts by mass of the 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone. 5. The heat-sensitive recording material according to 5.
Item 7: The inorganic compound is at least one selected from magnesium silicate, calcium silicate, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium phosphate, magnesium oxide, aluminum oxide, titanium oxide, and magnesium hydroxide. Or a heat-sensitive recording material according to 6.
Item 8: 1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate) with respect to 100 parts by mass of the compound represented by the general formula (1) 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4 ′-[oxybis (ethyleneoxybis-p-phenylenesulfone)] diphenol The heat-sensitive recording material according to claim 1, wherein the total amount is 3 to 100 parts by mass.
Item 9: The heat-sensitive recording material according to any one of claims 1 to 8, wherein the leuco dye has a melting point of 200 ° C or higher.
Item 10: The leuco dye is 3- (N-ethyl-p-toluidino) -6-methyl-7-arininofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- ( The thermosensitive recording material according to claim 9, which is at least one selected from p-toluidino) fluorane and 3-diethylamino-7- (o-chloroanilino) fluorane.

  The heat-sensitive recording material of the present invention has an effect excellent in recording sensitivity, heat resistance, water resistance, oil resistance and alcohol resistance.

  Hereinafter, the present invention will be described in more detail.

  As a colorant in the heat-sensitive recording layer,

（式中、Ｒはｎ−ブチル基、ｉｓｏ−ブチル基、ｓｅｃ−ブチル基またはｔｅｒｔ−ブチル基を表す。）
を使用することで、記録感度および耐水性に優れた感熱記録体は得られるが、一方で、記録部の耐アルコール性、耐油性が劣っていた。

(In the formula, R represents an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)
Can be used to obtain a heat-sensitive recording material excellent in recording sensitivity and water resistance, but on the other hand, the recording portion has poor alcohol resistance and oil resistance.

  In the present invention, 1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate), 4,4′-bis [(4- A colorant containing at least one compound selected from methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone and 4,4 ′-[oxybis (ethyleneoxybis-p-phenylenesulfone)] diphenol It has been found that alcohol resistance and oil resistance are improved without impairing the original recording sensitivity and water resistance of the ink.

The color former represented by the general formula (1) can be obtained by the synthesis method described in WO 2005/000597.
For example, it is preferable to condense a p-substituted phenol derivative represented by the following general formula (2) and at least one of the phenolic compounds represented by the following general formula (3).

The p-substituted phenol derivative represented by the general formula (2) is a dihydroxymethylated corresponding p-substituted phenol, in which R _d is an n-butyl group, an iso-butyl group, a sec-butyl group. , Tert-butyl group, preferably sec-butyl group, tert-butyl group. R _e is a group selected from the group consisting of hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a halogen atom, and R _e may be the same as or different from each other. Of these, hydrogen or a methyl group is preferable.

  Examples of such compounds include 2,6-dihydroxymethyl-4-butylphenol, 2,6-dihydroxymethyl-4-isobutylphenol, 2,6-dihydroxymethyl-4-tert-butylphenol, and 2,6-dihydroxymethyl. -4-sec-butylphenol and the like.

  Dihydroxymethylation of these p-substituted phenols can be carried out by a conventional method. For example, p-substituted phenol and formaldehyde are reacted in the presence of water and a basic catalyst, and the reactive organism is reacted with an acid. It can be obtained by neutralization or acidification.

On the other hand, the phenolic compound to be condensed with the p-substituted phenol derivative is represented by the general formula (3), and an unsubstituted phenol in which R _f is a hydrogen atom is preferable.

  Using the p-substituted phenol derivative and the phenolic compound, a colorant used in the present invention can be prepared according to a conventionally known method. For example, when a predetermined amount of the above p-substituted phenol derivative and a phenolic compound are heated and reacted in the presence of an appropriate acid catalyst, condensation of both occurs, and a phenol trinuclear compound represented by the general formula (1) is obtained. It is done. This is because, in this condensation reaction, the phenolic compound generally has a high reaction activity at the para-position and the ortho-position with respect to the OH group represented by the formula (3).

  The condensation product thus obtained can be used as a colorant as it is, but in particular, when the purity of the colorant is required, a general purification method, if necessary, For example, the condensation product is once dissolved in a good solvent, then added to a poor solvent and reprecipitated. Alternatively, the product may be washed with a solvent in which other condensate is dissolved, and further purified by heating and dissolving the product in a solvent, followed by cooling and recrystallization, and then used as a colorant.

  Examples of the colorant represented by the general formula (1) used in the present invention include 2,6-bis [(4-hydroxyphenyl) methyl] -4- (sec-butyl) phenol, 2,6. -Bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol, 2,6-bis [(4-hydroxyphenyl) methyl] -4- (n-butyl) phenol, 2,6-bis [(4-Hydroxyphenyl) methyl] -4- (iso-butyl) phenol, 2,-[(4-hydroxyphenyl) methyl] -6- (2-hydroxyphenyl) methyl] -4- (sec-butyl) Phenol, 2,-[(4-hydroxyphenyl) methyl] -6- (2-hydroxyphenyl) methyl] -4- (tert-butyl) phenol, 2,-[(4-hydroxyphenyl) methyl] -6 (2-hydroxy Phenyl) methyl] -4- (n-butyl) phenol and 2,-[(4-hydroxyphenyl) methyl] -6- (2-hydroxyphenyl) methyl] -4- (iso-butyl) phenol.

  The ratio of the compound represented by the general formula (1) used in the present invention in the heat-sensitive recording layer is appropriately selected according to the basic dye to be used, and is not particularly limited. In general, the amount is about 50 to 500 parts by mass, preferably about 100 to 400 parts by mass with respect to 100 parts by mass of the basic dye. If it is in the range of 50 to 500 parts by mass, both the water resistance of the recording part and the recording sensitivity can be achieved.

  Moreover, about the average particle diameter of the compound represented by the said General formula (1), Preferably it is about 0.7-2.0 micrometers, More preferably, it is about 0.8-1.8 micrometers. When the thickness is in the range of 0.7 to 2.0 μm, a more excellent thermal recording material in heat resistance and recording sensitivity can be obtained. In addition, an average particle diameter is a 50% average particle diameter in a Shimadzu laser diffraction type particle size distribution measuring apparatus (trade name: SALD2000).

  Furthermore, 1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate), 4,4′-bis [(4-methyl-3) contained in the heat-sensitive recording layer -Phenoxycarbonylaminophenyl) ureido] diphenylsulfone and 4,4 ′-[oxybis (ethyleneoxybis-p-phenylenesulfone)] diphenol are used in the above-mentioned general formula (1). The amount is about 3 to 100 parts by mass, more preferably about 5 to 60 parts by mass with respect to 100 parts by mass of the compound. When the content is in the range of 3 to 100 parts by mass, a thermal recording material with less deterioration in recording sensitivity and excellent oil resistance and alcohol resistance can be obtained.

  1,5- (3-Oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate) is synthesized, for example, by the method described in the Examples of Japanese Patent Application No. 2004-242569. be able to.

(1) Synthesis of raw material 1,5- (3-oxapentamethylene) bis (3-aminobenzoate) In a three-necked flask equipped with a thermometer, a reflux tube and a dropping funnel, 9.84 g of 3-aminobenzoic acid and 120 ml Of N, N-dimethylformamide (dehydrated) and 9.96 g of potassium carbonate (anhydrous) are added to the solution. While stirring this mixture with a magnetic stirrer, 5.16 g of bis (2-chloroethyl) ether was added at room temperature. The reaction suspension was stirred at room temperature, heated to reflux at 130 ° C. for 4 hours, cooled to room temperature, added to 300 ml of water, and vigorously stirred to precipitate a white solid. By filtering the aqueous suspension, 10.5 g of 1,5- (3-oxapentamethylene) bis (3-aminobenzoate) white solid was obtained.
The obtained white solid was confirmed to be the target product by various instrumental analyses.

(2) Synthesis of 1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate) In a three-necked flask equipped with a dropping funnel, a thermometer and a reflux condenser, 5 g of 1,5- (3-oxapentamethylene) bis (3-aminobenzoate) was added, and 200 ml of acetonitrile was added thereto and stirred to dissolve. While stirring this mixed solution with a magnetic stirrer, 13.8 g of p-toluenesulfonyl isocyanate was added dropwise at room temperature from a dropping funnel. As the reaction mixture continued to stir, a large amount of white solid precipitated. The reaction mixture was heated at 80 ° C. for 4 hours, cooled and filtered to give 19.5 g of white crystals.

The analysis value of this white crystal is as follows.
Melting point (from DSC): 139.8 ° C
Results of NMR measurement (in DMSO) (numbers are in ppm)
δ = 2.36 (s, 6H), 3.77 (t, 4H), 4.36 (t, 4H), 7.32 (t, 2H), 7.41 (d, 4H), 7.52 -7.54 (m, 4H), 7.83 (d, 4H), 7.98 (t, 2H)
In addition, a peak that may be attributed to NH appeared near δ = 9.07, 10.85.

  The 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone contained in the heat-sensitive recording layer is excellent in heat resistance when used in the form treated by the following method. A record is obtained. That is, the 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone is converted into 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl. Dispersion composition (A) in which sulfone and inorganic compound are simultaneously dispersed, or dispersion composition of inorganic compound with 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone It is the form of the compound obtained by heating the dispersion composition (B) prepared by mixing a liquid composition at 40 degreeC or more. The temperature is preferably 40 to 90 ° C. for 3 hours or more. More preferably, heat treatment is performed at 50 ° C. to 80 ° C. for 3 hours or more. When the temperature is in the range of 40 to 90 ° C. and the heat treatment time is 3 hours or more, the heat resistance effect is more easily exhibited, and 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl. There is no practical problem with respect to the stability of the sulfone, and there is no practical problem with respect to workability.

  The inorganic compound is preferably 0.5 to 10 parts by mass, and 1 to 5 parts by mass with respect to 100 parts by mass of 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone. Is more preferable. When the content is in the range of 0.5 to 10 parts by mass, a heat-sensitive recording material excellent in heat resistance can be obtained.

  The inorganic compound is preferably at least one selected from magnesium silicate, calcium silicate, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium phosphate, magnesium oxide, aluminum oxide, titanium oxide, and magnesium hydroxide. Sexual effects are difficult to develop.

  A dispersion composition in which 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone and an inorganic compound are co-dispersed or the 4,4′-bis [(4-methyl-3- Phenoxycarbonylaminophenyl) ureido] diphenylsulfone dispersion composition and an inorganic compound dispersion composition prepared by mixing the dispersion composition further heated at 40 ° C. or higher, the average particle size of the compound obtained Is preferably 0.7 to 2.0 μm, more preferably about 0.9 to 1.5 μm. When the thickness is in the range of 0.7 to 2.0 μm, a heat-sensitive recording material superior in heat resistance can be obtained.

As the colorless or light-colored basic dye used for the heat-sensitive recording layer, various known dyes can be used. Specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide Blue coloring dyes such as 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide and fluorane, 3- (N-ethyl-Np- Tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, etc., green coloring dye, 3,6-bis (diethylamino) ) Fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluora Red coloring dyes such as 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N- (Cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6 Methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N-ethyl-N-tetrahydrofluorine) Ruamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6 -Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3' Black coloring dyes such as methyl spiro [phthalide-3,9′-xanthen-2′-ylamino] phenyl] propane, 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane, 3,3- Bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- 4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-dimethylaminoanilino) anilino-6 -Methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6 Dye etc. having an absorption wavelength in the near infrared region such as' -dimethylamino) phthalide. Of course, it is not limited to these, Moreover, 2 or more types can also be used together as needed.
In particular, a compound having a melting point of 200 ° C. or more is preferable from the viewpoint of heat resistance, and in particular, 3- (N-ethyl-p-toluidino) -6-methyl-7-arininofluorane, 3- (N-ethyl-p-toluidino). ) -6-methyl-7- (p-toluidino) fluorane and 3-diethylamino-7- (o-chloroanilino) fluorane are preferred.

The colorant used in combination with the leuco dye as described above is a specific colorant of the present invention, but various known materials such as activated clay, attapulgite, colloidal silica, silicic acid, as long as there is no hindrance. Inorganic acidic substances such as aluminum, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,4 '-Dihydroxydiphenylsulfone, 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, Np-toluenesulfonyl-N'-3- (p-toluenesulfonyloxy) phenyl Urea, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4 -Benzyl hydroxybenzoate, 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone Phenolic compounds such as 4-hydroxyphenyl-4′-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4′-methylphenylsulfone, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, N- (p-toluenesulfonyl) carbamoyl acid p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N- (o-toluoyl) -p-toluenesulfoamide, N- (P-Toluenesulfonyl) -N ′-( p-Tolyl) Urea and other molecules having —SO ₂ NH— bond, p-chlorobenzoic acid, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolyl) Sulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid and the like, and zinc, magnesium, aluminum, calcium, titanium, manganese of these aromatic carboxylic acids, A salt with a polyvalent metal such as tin or nickel, an organic acid substance such as an antipyrine complex of zinc thiocyanate, or a complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid can be used in combination.

  A sensitizer may be added to the heat-sensitive recording layer of the present invention, such as stearamide, methoxycarbonyl-N-stearic acid benzamyl, N-benzoyl stearamide, N-eicosanoic acid amide, ethylenebisstearic acid. Amides, behenic acid amides, methylenebis stearic acid amides, N-methylol stearic acid amides, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2 -Naphtylbenzyl ether, m-terphenyl, p-benzylbiphenyl, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ) Ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide , P-acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, etc. In particular, from the viewpoint of sensitivity and heat resistance, 1,2-di (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate It is preferable to use at least one selected from esters, oxalic acid di-p-chlorobenzyl ester, 2-naphthylbenzyl ether, 1,2-phenoxymethylbenzene, and diphenylsulfone.

  In the heat-sensitive recording layer of the present invention, the content of the leuco dye in the heat-sensitive recording layer is generally 5 to 20% by mass, and the content of the developer is generally 5 to 40% by mass. When a sensitizer is included, the content of the sensitizer is preferably 10 to 40% by mass.

  In the heat-sensitive recording layer of the present invention, a storability improving agent may be added, for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-). 6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4′-hydroxyphenyl) ethyl] Benzene, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-te) t-butylphenyl) butane, 4,4′-thiobis (3-methylphenol), 4,4′-dihydroxy-3,3 ′, 5,5′-tetrabromodiphenylsulfone, 4,4′-dihydroxy-3 , 3 ′, 5,5′-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane Hindered phenol compounds such as 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenylsulfone, 4-benzyloxy -4 '-(2-methylglycidyloxy) diphenylsulfone, diglycidyl terephthalate, cresol novolac type epoxy Epoxy resin such as styrene resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebis (4,6-di-tert- Butylphenyl) phosphate sodium or polyvalent metal salt, bis (4-ethyleneiminocarbonylaminophenyl) methane, and the like.

  The coating solution for the heat-sensitive recording layer containing these substances generally uses water as a dispersion medium, and dyes, colorants, specific compounds used in the present invention, and sensitizers by agitating and pulverizing machines such as a ball mill, an attritor, and a sand mill. Etc. are prepared by blending materials obtained by dispersing them together or separately.

  In the coating solution for heat sensitive recording layer, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol , Diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin At least one of melamine resin, amide resin, polyurethane resin and the like is blended in the range of about 5 to 50% by mass with respect to the total solid content of the heat-sensitive recording layer.

  In addition, various auxiliary agents can be added to the heat-sensitive recording layer coating liquid as necessary. For example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt, etc. Agents, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, antifoaming agents, coloring dyes, pigments and the like are appropriately added. Examples of the pigment include inorganic pigments such as kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, aluminum hydroxide, diatomaceous earth, particulate anhydrous silica, activated clay, styrene microballs, nylon powder, polyethylene powder, urea. -Organic pigments such as formalin resin filler and raw starch particles. It is preferable that the lubricants and the pigment are contained at a content of 1 to 20% by mass and 10 to 50% by mass, respectively.

  In the present invention, an effect of improving heat resistance can be obtained in the heat-sensitive recording material by forming the undercoat layer into a multilayer structure of two or more layers. By providing two or more undercoat layers, the sensitivity and image quality can be improved, but there is an effect of suppressing the penetration of the paint during the application of the heat-sensitive paint, thereby further improving the strength of the heat-sensitive recording material.

  The undercoat layer is composed of at least two layers. The number of undercoat layers is not particularly limited as long as it is 2 or more, but the upper limit may be about 4 layers. A particularly preferred number of layers is two.

  By making the undercoat layer have a multilayer structure of two or more layers, uneven penetration of the thermal recording layer coating liquid can be greatly reduced. As a result, the coloring component contained in the heat-sensitive recording layer can effectively utilize the printing energy received from the surface layer during printing, so that high sensitivity can be achieved.

  In the present invention, of the plurality of layers constituting the undercoat layer, at least two of the first undercoat layer and the second undercoat layer may be composed of the same undercoat layer coating solution, or different undercoat layer coatings. Although it may consist of a liquid, in the present invention, it is preferable to consist of the same undercoat layer coating liquid. By using the same coating solution for the undercoat layer, it is possible to integrate the preparation of paints, improve the paint yield, and suppress the manufacturing cost.

  The undercoat layer is usually at least one selected from the group consisting of i) an oil-absorbing pigment having an oil absorption of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g, ii) organic hollow particles, and iii) thermally expandable particles. In addition, an undercoat layer coating solution containing an adhesive as a main component can be formed by coating and drying on a support.

  By using at least one pigment selected from the group consisting of the oil-absorbing pigment, organic hollow particles, and thermally expandable particles, the gap in the undercoat layer is increased, and heat energy is provided when a thermal recording layer or the like is provided thereon. Therefore, it is possible to obtain a high color density because it is possible to prevent the diffusion of the ink in the direction of the base paper and to effectively use the printing energy.

Here, the oil absorption is a value determined according to the method of JIS K5101-1991.
Various oil-absorbing pigments can be used, and specific examples include inorganic pigments such as calcined kaolin, silica, and light calcium carbonate.
The average particle diameter of the oil-absorbing pigment is preferably about 0.01 to 5 μm, particularly preferably about 0.02 to 3 μm. Here, the average particle diameter is a 50% value measured by a laser diffraction particle size distribution measuring device (trade name: SALD2000, manufactured by Shimadzu Corporation).
The amount of the oil-absorbing pigment used can be selected from a wide range, but generally it is preferably about 50 to 95% by mass, particularly preferably about 60 to 90% by mass in the pigment component in the undercoat layer.

Moreover, as an organic hollow particle, a conventionally well-known thing, for example, the particle | grains whose hollow rate which a film | membrane material consists of acrylic resin, a styrene resin, vinylidene chloride resin etc. are about 50 to 99% can be illustrated. Here, the hollow ratio is a value obtained by (d / D) × 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 average particle diameter of the organic hollow particles is preferably about 0.5 to 10 μm, particularly preferably about 0.7 to 2 μm. In addition, this average particle diameter is measured by the same measuring method as the average particle diameter of the oil-absorbing pigment.
The amount of the organic hollow particles to be used can be selected from a wide range, but generally it is preferably about 20 to 90% by mass, particularly about 25 to 70% by mass in the pigment component in the undercoat layer.

Various types of thermally expandable particles can be used. Specific examples include thermally expandable fine particles obtained by microencapsulating low-boiling hydrocarbons with a copolymer such as vinylidene chloride and acrylonitrile by an in situ polymerization method. Can be given. Examples of the low boiling point hydrocarbon include ethane and propane.
The use amount of the heat-expandable particles can be selected from a wide range, but is generally about 1 to 80% by mass, and particularly preferably about 10 to 70% by mass in the pigment component of the undercoat layer.

  When two or more kinds selected from oil-absorbing inorganic pigments, organic hollow particles and thermally expandable particles are used in combination, the total amount is 40 to 90% by mass, particularly 50 to 80% by mass, based on the total solid content of the undercoat layer. It is preferable that it is about.

  As the pigment used in the undercoat layer, in addition to the oil-absorbing inorganic pigment, the organic hollow particles, and the heat-expandable particles, various known coating pigments may be used as long as the effects of the present invention are not impaired. Examples thereof include kaolin, heavy calcium carbonate, titanium oxide, magnesium carbonate, aluminum hydroxide, and synthetic mica. These may be used alone or in combination of two or more pigments.

  Examples of the adhesive used in the coating solution for the undercoat layer include polyvinyl alcohols having various molecular weights, modified polyvinyl alcohols, starches and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate , Polyvinylpyrrolidone, acrylic acid amide-acrylic acid ester copolymer, acrylic acid amide-acrylic acid ester-methacrylic acid terpolymer, styrene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, And water-soluble polymer materials such as casein, polyvinyl acetate, polyurethane, styrene-butadiene copolymer, polyacrylic acid, polyacrylate ester, vinyl chloride-vinyl acetate copolymer, poly Latex of hydrophobic polymer such as til methacrylate, ethylene-vinyl acetate copolymer, styrene-butadiene-acrylic copolymer, silylated urethane, acrylic-silicon composite, acrylic-silicon-urethane composite emulsion, etc. It is also possible to use one kind or two or more kinds in combination.

  The content of the adhesive in the undercoat layer is preferably 3 to 35% by mass, more preferably 5 to 30% by mass with respect to the total solid content of the undercoat layer. By setting it as 3 mass% or more, the intensity | strength of a coating layer can be improved. On the other hand, when the content is 35% by mass or less, the target void of the undercoat layer can be increased, and the recording sensitivity can be improved.

  As the auxiliary agent, for example, surfactants such as sodium alkylbenzene sulfonate, sodium dioctyl sulfosuccinate, sulfone-modified polyvinyl alcohol, sodium polyacrylate, glyoxal, boric acid, dialdehyde starch, methylol urea, epoxy compound, epichlorohydrin resin, Waterproofing agents (crosslinking agents) such as hydrazine compounds such as adipic acid dihydrazide, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, ultraviolet absorbers, fluorescent dyes, colored dyes, release agents Examples include molds and antioxidants. The usage-amount of auxiliary agent can be suitably set from a wide range.

  The method for preparing the coating solution for the undercoat layer is not particularly limited, and the concentration of the coating solution is not particularly limited, but is usually 20 to 50% by mass, preferably 35 to 45% by mass. By setting the content to 20% by mass or more, the viscosity of the coating liquid can be increased, the occurrence of uneven penetration and hence unevenness of the undercoat layer can be suppressed, and the image quality can be improved. At the same time, the coating speed can be increased to improve productivity. Moreover, by setting it as 50 mass% or less, the viscosity of a coating material can be made moderate and a process can be made easy.

  The viscosity of the undercoat layer coating solution may be adjusted as appropriate by selecting the type and blending amount of pigments, adhesives, auxiliaries, etc. used in the preparation of the undercoat layer coating solution.

The coating amount of the undercoat layer is not particularly limited, and the thickness of the undercoat layer is 3 to 12 μm (preferably 5 to 10 μm), and the total thickness of the undercoat layer is 6 to 30 μm (preferably 10 to 25 μm). ) May be adjusted as appropriate. The coating amount after drying per layer is about 1 to 15 g / m ² (preferably 2.5 to 10 g / m ² , and the total coating amount of the undercoat layer is about ² to 35 g / m ² . There, more preferably 5 to 30 g / ^{m 2.}

In particular, the ratio of the coating amount after drying of the first undercoat layer and the second undercoat layer is preferably 2: 8 to 8: 2, more preferably 4: 6 to 6: 4.
By setting it within this range, the undercoat layer can exhibit a function as a sufficient heat insulating layer and can enhance the effect of suppressing excessive penetration during coating of the thermal recording layer. Can be formed.

  Further, the smoothness of the undercoat layer after the undercoat layer coating is preferably 200 to 1200 seconds, more preferably 300 to 1000 seconds. The smoothness is measured with a Oken type smoothness meter (J.TAPPI No. 5).

  The undercoat layer of the present invention is produced by forming the first undercoat layer by a blade coating method and further forming the second and subsequent undercoat layers by a rod coating method.

  In general, the coating method of the undercoat layer includes a Mayer bar coating method, an air knife coating method, a blade coating method, a rod coating method, and the like. In the present invention, the Mayer bar coating method is a method in which a paint is applied to paper by a roll method, and then a stick (bar) in which a thin wire is wound around a metal cylinder is pressed to scrape the paint. In this method, the coating amount is controlled. The air knife coating method is to control the coating amount by scraping the coating material applied to the paper in general by roll method with air pressure using high-pressure air applied from a thin slit. It is a method. Since these are not suitable for high-speed coating, there is a drawback that productivity is lowered.

  With blade coating, paint is applied to paper by the roll or fountain method, and then a thin steel plate with a thickness of several millimeters typified by the bevel type and vent type is pressed to scrape the paint. This is a control method. The blade coating method can form a uniform coated surface with high surface smoothness, but has a drawback that coating defects such as streaks and scratches are likely to occur.

  On the other hand, the rod coating method is a method of controlling the coating amount by scraping off the applied paint by pressing while rotating a metal cylinder instead of a thin steel plate. Although there are relatively few coating defects, there is a drawback that it is difficult to obtain a uniform coated surface especially when coated on a coated surface with low smoothness such as a base paper. In the present invention, the rod coating method and the Mayer bar coating method are clearly distinguished, and the Mayer bar coating method is not included in the rod coating method of the present invention.

  On the other hand, in the heat-sensitive recording material of the present invention, a uniform and highly smooth coated surface is formed by forming the first undercoat layer by a blade coating method, and further an undercoat layer is formed thereon by a rod coating method. This makes it possible to form a uniform and highly smooth undercoat layer with few coating defects. Overcoming the above-mentioned drawbacks and achieving high sensitivity and high image quality through the interaction of these coating methods. it can.

When forming the undercoat layer, for example, in the case of forming two undercoat layers, the first layer is applied to the base paper fed from the unwinder, dried, and then the second layer is applied without going through the winding process. A method of winding after drying is preferable. That is, it is preferable to wind up after forming the second undercoat layer continuously without winding up the first undercoat layer-formed paper support obtained by forming the first undercoat layer. After coating the first layer, before coating the second undercoat layer, once the winding process is performed, the back surface of the base paper comes into contact with each other. Therefore, a highly smooth coated surface formed by the blade coating method (first coating) There is a risk of adversely affecting the surface of the undercoat layer. On the other hand, since the second undercoat layer can be formed in a state in which the coating surface formed by blade coating is highly smooth by not performing the winding step during the formation of the undercoat layer, A highly smooth coated surface is formed in the coating layer.
Furthermore, in the present invention, for example, after the second and subsequent undercoat layers are formed by a rod coating method or the like, a smoothing process such as a super calendar may be performed according to the required quality.

  In the heat-sensitive recording material of the present invention, a protective layer may be provided on the recording layer for the purpose of improving the storability of the recorded image with respect to chemicals such as plasticizers and oils, or recording suitability. The preparation method is not particularly limited. Generally, water is used as a dispersion medium, and starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol It is prepared by mixing and stirring a binder such as silicon-modified polyvinyl alcohol and a pigment such as kaolin, light calcium carbonate, and fine particle silica.

  Furthermore, in the protective layer coating solution, a surfactant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, or a surfactant such as sodium dioctylsulfosuccinate (dispersant, wetting) Agent), an antifoaming agent, and various auxiliary agents such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate can be appropriately added. In order to further improve the water resistance, a known crosslinking agent can be used in combination, such as glyoxal, boric acid, dialdehyde starch, epoxy compound, epichlorohydrin resin, hydrazide compounds such as adipic acid dihydrazide, and the like. .

The coating amount of the protective layer coating composition is about 0.5 to 6.0 g / ^{m 2} by dry weight, preferably about 0.8~3.5g / ^{m 2,} low in order to improve the recording sensitivity There is a need for a coating amount that is easy to read even when printed with low energy.

  In particular, microcapsules encapsulating a UV absorber that is liquid at room temperature, such as 2- (2′-hydroxy-3′-dodecyl-5′-methylphenyl) benzotriazole, in the protective layer are adjusted to the total solid content of the protective layer. On the other hand, when the ultraviolet absorber is added so as to be 10 to 40% by mass, yellowing of the background portion and fading of the recorded image are remarkably improved with respect to light exposure.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, for example, by an appropriate application method such as air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. After the undercoat layer coating solution is applied and dried on the support, the heat sensitive recording layer coating solution and further the protective layer coating solution are applied and dried on the undercoat layer. In addition, as a support body, it selects suitably from paper, a plastic film, a synthetic paper, a nonwoven fabric, a metal vapor deposition, etc., and is used. The coating amount of the heat-sensitive recording layer coating composition is 2~12g / ^{m 2} in dry weight, preferably 3 to 10 g / ^{m 2} approximately, the coating amount of the protective layer coating liquid for a dry weight 0.5 to 15 g / m ² , preferably adjusted in the range of about 1.0 to 8 g / m ² .

  If necessary, a protective layer can also be provided on the back side of the heat-sensitive recording material to further improve the storage stability or give it a high gloss. Applying a smoothing process such as supercalendering after smearing each layer, or applying adhesive treatment to the back of the recording material to process an adhesive label, providing a magnetic recording layer, a coating layer for printing, and a thermal transfer recording layer, etc. Various known techniques in the heat-sensitive recording material manufacturing field can be added as necessary.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.

Example 1
(Preparation of coating solution for undercoat layer)
To a dispersion (average particle size: 0.6 μm) obtained by dispersing 85 parts of calcined kaolin (trade name: Ansilex, Engelhard, Inc., oil absorption 90 ml / 100 g) in 100 parts of water, 40 parts of a polymer emulsion (solid content 50%), 50 parts of a 10% aqueous solution of oxidized starch, and 1 part of carboxymethylcellulose (trade name: Serogen AG Gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are mixed and stirred to form a coating for an undercoat layer A liquid was obtained.

-Solution A preparation 3- (N-ethyl-p-toluidino) -6-methyl-7-arininofluorane 10 parts, 5 parts of a 5% aqueous solution of methylcellulose, and a composition comprising 40 parts of water with a sand mill average particle size The solution A was prepared by dispersing until 0.5 μm.

-Preparation of solution B 2,6-bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol, 25 parts, polyvinyl alcohol (trade name: Go-Selan L-3266, Nippon Synthetic Chemical Co., Ltd.) A B composition was prepared by dispersing a composition comprising 20 parts of a 10% aqueous solution and 10 parts of water in a vertical sand mill (manufactured by Imex) until the average particle size was 1 μm.

-Preparation of liquid C 10 parts of 1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate), polyvinyl alcohol (trade name: Go-Selan L-3266, A composition consisting of 10 parts of 10% aqueous solution (manufactured by Nippon Synthetic Chemical Co., Ltd.) and 15 parts of water was dispersed with a vertical sand mill (manufactured by Imex Co., Ltd.) until the average particle size became 1 μm to prepare solution C.

Preparation of solution D 20 parts of 1,2-di (3-methylphenoxy) ethane, 20 parts of 10% aqueous solution of polyvinyl alcohol (trade name: Go-Selan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) and 10 parts of water A composition D was dispersed with a vertical sand mill (manufactured by Imex Co., Ltd.) until the average particle size became 1 μm to prepare solution D.

(Preparation of thermal recording layer coating solution)
50 parts of A liquid, 75 parts of B liquid, 35 parts of C liquid, 50 parts of D liquid, 170 parts of 10% aqueous solution of polyvinyl alcohol, 36% dispersion of zinc stearate (trade name: Hydrin Z-8, manufactured by Chukyo Yushi Co., Ltd.) ) 12 parts and 50 parts of a 60% dispersion of calcium carbonate (trade name: Brilliant 15, manufactured by Shiroishi Kogyo Co., Ltd.).

・ Preparation of thermal recording material A coating solution for an undercoat layer was applied and dried on one side of a 58 g / m ² base paper by a blade coating method so that the coating amount after drying was 7.0 g / m ^2. The first undercoat layer is formed, and the undercoat layer coating solution is applied on the first undercoat layer by the rod coating method so that the coating amount after drying is 8.0 g / m ² without further winding. The coating was dried to form a second undercoat layer. After drying on the resulting two-layered undercoat layer, the thermosensitive recording layer coating solution was applied and dried on the undercoat layer so that the coating amount after drying was 5.0 g / m ^2, and then the super calender. Processing was performed to obtain a heat-sensitive recording material.

Example 2
In the preparation of the liquid B of Example 1, 2,6-bis [(4-hydroxyphenyl) methyl] instead of 2,6-bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -4- (sec-butyl) phenol was used.

Example 3
In the preparation of solution B of Example 1, 2,-[(4-hydroxyphenyl) methyl] -6 was used instead of 2,6-bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that-(2-hydroxyphenyl) methyl] -4- (tert-butyl) phenol was used.

Example 4
In the preparation of solution B of Example 1, 2,-[(4-hydroxyphenyl) methyl] -6 was used instead of 2,6-bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that-(2-hydroxyphenyl) methyl] -4- (sec-butyl) phenol was used.

Example 5
In preparation of the liquid C of Example 1, 4,4 ′-[oxybis (ethyleneoxy) instead of 1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that (bis-p-phenylenesulfone)] diphenol was used.

Preparation of solution E: 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone 10 parts, magnesium silicate 0.2 parts, polyvinyl alcohol (trade name: Go-Selan L- 3266 (manufactured by Nippon Synthetic Chemical Co., Ltd.), a composition comprising 10 parts of a 10% aqueous solution and 15 parts of water was dispersed with a vertical sand mill (manufactured by Imex) until the average particle size became 1 μm, and heat treated at 70 ° C. for 4 hours Then, solution E was prepared.

Example 6
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 35 parts of E liquid was used instead of 35 parts of C liquid in the preparation of the thermal recording layer coating liquid of Example 1.

Example 7
In the preparation of solution A in Example 1, 3- (N-ethyl-p-toluidino) -6-methyl-7 instead of 3- (N-ethyl-p-toluidino) -6-methyl-7-arininofluorane A thermosensitive recording material was obtained in the same manner as in Example 1 except that-(p-toluidino) fluorane was used.

Example 8
In the preparation of solution A of Example 1, except that 3-diethylamino-7- (o-chloroanilino) fluorane was used instead of 3- (N-ethyl-p-toluidino) -6-methyl-7-arininofluorane Obtained a heat-sensitive recording material in the same manner as in Example 1.

Example 9
In Example 1, a heat-sensitive recording material was obtained in the same manner as in Example 1 except that the coating amounts of the first undercoat layer and the second undercoat layer were respectively 10 g / m ² and 10 g / m ² .

Example 10
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 35 parts of liquid C was changed to 70 parts in the preparation of the thermosensitive recording layer coating liquid of Example 1.

Example 11
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 35 parts of the liquid C was changed to 8.75 parts in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Example 12
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 35 parts of the liquid C was changed to 2.5 parts in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Example 13
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 35 parts of the liquid C was 131 parts in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Example 14
In Example 1, to obtain a thermal recording material except that coating amount of each ^{2g / m 2, 2g / m} 2 coated the first subbing layer sequence the second subbing layer in the same manner as in Example 1.

Example 15
In Example 1, to obtain a thermal recording material except that coating amount of each ^{1g / m 2, 8g / m} 2 coated the first subbing layer sequence the second subbing layer in the same manner as in Example 1.

Comparative Example 1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the second undercoat layer was omitted and the coating amount of the first undercoat layer was 15 g / m ² .

Comparative Example 2
In Example 1, a heat-sensitive recording material was obtained in the same manner as in Example 1 except that the liquid C was not used.

Comparative Example 3
In the preparation of the liquid B of Example 1, 4-hydroxy-4′-isopropoxydiphenyl sulfone was used instead of 2,6-bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol. Except for the above, a heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 4
In the preparation of the liquid B of Example 1, 2,2-bis (4-hydroxyphenol) propane was used instead of 2,6-bis [(4-hydroxyphenyl) methyl] -4- (tert-butyl) phenol. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that.

  The following evaluation tests were conducted on the 19 types of thermal recording materials thus obtained, and the results are shown in Table 1.

[Color development]
Using the thermal evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), the resulting thermal recording material was developed with an applied energy of 0.34 mJ / dot, and the color density of the resulting recording portion was the Macbeth density. Measurement was performed in the visual mode of a total (RD-914 type, manufactured by Macbeth Co.).

〔Heat-resistant〕
In the above [color development] evaluation test, color was applied at an applied energy of 0.42 mJ / dot, and the resulting thermal recording material after recording was allowed to stand at 90 ° C. for 24 hours. The measurement was performed in the visual mode of a densitometer (RD-914 type, manufactured by Macbeth).

〔water resistant〕
The recording density after recording the heat-sensitive recording material after recording obtained in the above [color development] evaluation test in a tap water at 20 ° C. for 24 hours was measured with a Macbeth densitometer (RD-914 type, manufactured by Macbeth). Measured in visual mode.

[Alcohol resistance]
Ethyl alcohol was dipped in a cotton swab and applied to the recording part, and after standing for 24 hours at 20 ° C., the recording part concentration was measured with a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.) in a visual mode.

〔Oil resistance〕
Edible oil was applied to the recording part with a cotton swab and wiped immediately after standing, and after standing at 20 ° C. for 24 hours, the recording part concentration was measured in a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.) in the visual mode.

Claims (10)

In a heat-sensitive recording medium in which an undercoat layer is provided on a support and a heat-sensitive recording layer containing a colorless or light-colored leuco dye or a colorant is provided on the undercoat layer, the colorant is represented by the following general formula (1). Containing a compound represented by

(In the formula, R represents an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)
The undercoat layer has a multilayer structure composed of at least a first layer and a second layer formed on the first layer. In the thermosensitive recording layer, 1,5- (3-oxapentamethylene) bis ( 3- (3- (p-toluenesulfonyl) ureido) benzoate), 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4 ′-[oxybis (ethyleneoxy) (Bis-p-phenylenesulfone)] diphenol. A thermosensitive recording material comprising at least one compound selected from diphenols.   The first undercoat layer and the second undercoat layer comprise the same undercoat layer coating solution, and the ratio of the coating amount after drying of the first undercoat layer and the second undercoat layer is from 2: 8 to 8-8. The heat-sensitive recording material according to claim 1, wherein The heat-sensitive recording material according to claim 1, wherein the total coating amount after drying of the first undercoat layer and the second undercoat layer is 5 to 30 g / m ² .   The first undercoat layer is formed by applying and drying by a blade coating method, and further, the second undercoat layer is formed by applying and drying by a rod coating method. A heat-sensitive recording material according to claim 1.   The 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone is converted to 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, Dispersion composition (A) in which inorganic compounds are simultaneously dispersed, or dispersion composition of 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone and dispersion composition of inorganic compounds The heat-sensitive recording material according to claim 1, which is in the form of a compound obtained by heating the dispersion composition (B) prepared by mixing the product at 40 ° C. or higher.   6. The inorganic compound is 0.5 to 10 parts by mass with respect to 100 parts by mass of the 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone. Thermal recording material.   The inorganic compound is at least one selected from magnesium silicate, calcium silicate, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium phosphate, magnesium oxide, aluminum oxide, titanium oxide, and magnesium hydroxide. The heat-sensitive recording material described.   1,5- (3-oxapentamethylene) bis (3- (3- (p-toluenesulfonyl) ureido) benzoate), 4, based on 100 parts by mass of the compound represented by the above general formula (1) The total amount of compounds selected from 4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone and 4,4 ′-[oxybis (ethyleneoxybis-p-phenylenesulfone)] diphenol is 3 The thermosensitive recording material according to any one of claims 1 to 7, which is -100 mass parts.   The heat-sensitive recording material according to claim 1, wherein the leuco dye has a melting point of 200 ° C. or higher.   The leuco dye is 3- (N-ethyl-p-toluidino) -6-methyl-7-arininofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) The thermosensitive recording material according to claim 9, which is at least one selected from: fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran.