JPS59209192A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve natural decolorizing property and bleeding property of a developed color image part, by a method wherein a p-hydroxybenzoic acid ester is used as a color developer, and an undercoat layer comprising a specified compound is provided, in a leuco based thermal recording material. CONSTITUTION:The undercoat layer comprising a compound of the formula, wherein R is 2-5C straight chain or branched chain alkylene group, is provided on the lower side of a thermal color forming layer consisting of an ordinary leuco dye, a p-hydroxybenzoic acid ester as a color developer, an ordinary binder and auxiliary additive components. To contrive to obtain favorable image stability, it is preferable to use a water-soluble polymer such as polyvinyl alcohol as a binder for the undercoat layer, to which an ordinary water-proofing agent can be added. The p-hydroxybenzoic acid ester may be either an alkyl ester or an aromatic ester.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material that utilizes a heat-sensitive coloring reaction between a leuco dye and a color developer.

[Prior art]

Leuco-based heat-sensitive recording materials are widely known in which a heat-sensitive color-forming layer containing as main components a leuco dye and a color developer that causes the leuco dye to develop color when heated is provided on a support. The colored image obtained by thermally coloring this heat-sensitive recording material is very clear, and has the excellent advantage of showing a white background and a large contrast layer. Color developers are extremely poor in terms of background whiteness and thermal color development. However, these 11
-Those using hydroxybenzoic acid ester as a color developer:
It has disadvantages in that the colored image area naturally fades and white powder is generated in the colored image area (bleeding).

〔the purpose〕

The present invention overcomes the drawbacks of heat-sensitive recording materials that use p-hydroxybenzoic acid ester as a color developer, and provides a heat-sensitive recording material with excellent background whiteness and improved natural decolorization and bleeding properties in colored image areas. The purpose is to provide recording materials.

〔composition〕

According to the present invention, in a heat-sensitive border material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, P-hydroxybenzoic acid ester is used as the color developer, and 1 There is provided a heat-sensitive recording monthly charge, characterized in that an undercoat layer containing a compound represented by the following general formula is provided on the lower surface of the heat-sensitive coloring layer.

``°\ C○○H In the above formula, R represents an alkylene having 2 to 5 carbon atoms, and includes both a linear type and a branched type.

The present invention is characterized in that ρ-hydroxybenzoic acid ester is used as a color developer, and a compound represented by the general formula 1 is contained in Undercoat 1-WJ as an auxiliary component thereof. By using this auxiliary ingredient, P
- The problems of decoloring and bleeding in the colored image area, which were observed when using only hydroxybenzoic acid ester as a color developer, can be overcome. In addition, when the auxiliary component represented by the above general formula is contained in the heat-sensitive coloring layer, the disadvantages of decolorization and bleedability of the colored image area are improved, but the coloring of the background during coating and storage is poor. , it is not possible to obtain a thermal recording rate that is practically satisfactory11). In the present invention, the content of the compound represented by the above general formula used as an auxiliary component in the undercoat layer is determined by taking into account the thermal properties of the layer, etc. It is preferable to use the same amount or more as the leuco dye contained therein.

The color developer used in the present invention is p-hyaloxybenzoic acid ester, and either an alkyl ester or an aromatic 7iff ester of p-hyphenzoic acid may be used. Specific examples thereof include ))-hydroxybenzoic acid methyl ester, ethyl ester, isopropyl ester, n-propyl ester, butyl ester, benzyl ester, [)-chlorobenzyl ester, 0-chlorobenzyl ester, P -Methyl pencil ester and the like.

The leuco dye used in the present invention may be used alone or in combination.
The leuco dyes used in this type of heat-sensitive dye can be arbitrarily applied, such as 1-heliphenylmethane type, fluoran type, etc.
Leuco compounds of furanothiazine, auramine, and spiropyran dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3,:3-His(P-dimethylaminophenyl)-phthalide, 3.3-bis(P-dimethylaminophenyl)-6-dimethylaminophthalide (also known as Crystal Violet Rough 1-N), 3.3- Bis(p-dimethylaminophenyl)-6-dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-lyrolphthalide, 3.3-bis(P-dibutylaminophenyl)phthalide, 3- Cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluoran. Oran,
3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3 (N -11-1~Riru N-ethylamino)-6-
Methyl-7-anilite fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-1-lifluoromethylphenyl)amino)-6-ethylaminofluorane, 2-(:
! , 6-bis(diethylamino)-9-(o-chloroanilino)xanthylbenzene, "Frozen acid ucta IS), :)-diethylamino-6-methyl-7-(ml-lichloromethylanilino)fluoran" , :)-diethylamino-7-(o-chloroanilino)fluoran-based fluoran, 3' N-methyl-N-amylamino-6-methyl-
7-Anilitofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N -diethylamino)-5-methyl-7-(
N.

N-dibenzylamino) fluorane, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylosvirane, 6'-bromo-3'-me-1-xybenzoindolino-pyrylospirane, 3-( 2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthari 1~. 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3 -(2'-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane.

3-Diethylamino-5-gullo-7-(N-benzyl-1hes=fluoromethylanilino)fluoran, 3-
Pyrrolisino 7-(di-P-chlorphenyl)methylaminofluorane, :)-diethylamino-5-chloro-7-(α-)methylethylamino)fluoran, 3-(N-ethyl-P-toluidino)-7- (α-phenylethylamino)fluoran, : 3-diethylamino-7-(o-me1-xycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3- Diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p--
TI-butylanilino)fluoran, 3-(N-benzyl-N-cyclohexylamino)-5,6-penzo 7
-α-naphthylamino-4'-bromofur 4rane.

3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, cellulose, hydroxyethylcellulose, carboxymethylcellulose,
Cellulose derivatives such as methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone,
Amino acrylic acid 1-/acrylic ester copolymer, ami acrylic acid 1-/acrylic acid ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer In addition to water-soluble polymers such as combined alkali salts, polyacrylamide I, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, and vinyl chloride. Latexes such as /vinyl acetate copolymer, polybutyl methacrylate-1-, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer can be used. .

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, this type of heat-sensitive i! L! Auxiliary additive components commonly used in K materials, such as fillers, surfactants, thermofusible substances (or lubricants), etc. can be used in combination. In this case, the filler may be, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, Nosuri sulfate 11, clay, talc, surface-treated calcium or inorganic fine powder such as warp. In addition, organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned, and examples of thermofusible substances include higher fatty acids or their esters, ~ or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4
-Epoxy-dialkyl hexahydrophthalate, higher ketones, other thermofusible organic compounds, etc. at 50-200℃
Examples include those having a melting point of about .

The compound represented by the above general formula is contained in the under two layers provided on the lower surface of the heat-sensitive coloring layer constructed as described in Section 2 below. As a binder for supporting the compound represented by the above general formula on a support, a binder used for a heat-sensitive coloring layer can be used. Note that, in order to improve the stability of recorded images, it is preferable to use a water-soluble polymer as the binder for Undercoat 1-[. In this case, water-soluble polymers include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, casein,
Examples include sodium alginate, polyvinylpyrrolidone, polyacrylamine 1-, styrene-maleic acid copolymer, and the like. This water-soluble polymer can be used together with a conventional water-resistant agent that can make it water-resistant. Examples of the water-resistant agent include formalin, glyoxazole, chromium melamine, melamine-formalin, polyamide resin, polyamide Examples include chlorhythrin resin.

〔effect〕

The product of the present invention uses P-H1 as a color developer in the heat-sensitive coloring layer.
~ By using roxybenzoic acid ester and containing the compound represented by the above general formula as an auxiliary component in the undercoat layer, it has an excellent background white color, and
The problems of decolorization and bleaching properties of the colored image area have been overcome.

rExample] Next, the present invention will be explained in more detail with reference to Examples. Note that both "parts" and "%" shown below are based on weight.

[Liquid A]

3-(N-methyl-N-cyclohexylamino)-6-
Methyl-7-anirite fluorane 1 part Calcium carbonate l n20% starch oxide aqueous solution 2n water
1 n [Liquid B] 1 part benzyl p-hydroxybenzoate 20% oxidized starch aqueous solution 3 n water
ν.

[Liquid C]

4.7 I-bis(ρ-hydroxyphenyl)pentanoic acid (a compound in which R is ethylene in the above general formula) 1 part polyvinyl alcohol (10% aqueous solution) 2n calcium carbonate 2 water
1011 attached liquid C was applied to a high-quality paper with a basis weight of 57 g and 7 m2 so that the weight after drying was 3 u/
Apply so that it becomes m 2! ! Under two 1
Form a single layer, and then add a heat-sensitive coloring layer forming liquid obtained by mixing liquid A and liquid B in a ratio of 1=4 on the surface, and after drying, the weight is 5 g.
The heat-sensitive recording material of the present invention was obtained by coating and drying the coating to a thickness of /m2.

Example 2 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the following liquid was used instead of liquid C.

[Liquid D]

7.7-bis(P-hydroxyphenyl)octanoic acid (
Compounds in which R is pentamethylene in the above general formula)
1 part polyvinyl alcohol (10%
aqueous solution) 271 calcium carbonate
2〃Water
10... Comparative Example 1 A mixture of Shiki Δ solution and F solution in a ratio of 1 = 4 was directly applied and dried on high-quality paper with a basis weight of 7 g/a- at a dry adhesion amount of 5. dry/m2. A comparative product without an undercoat layer was obtained.

Next, send the product obtained as described above by fax: IJ
(Gru, Y Eve, RIFAX 3300, Lee-IH Co., Ltd.) was used for thermal printing, and the density of the image area immediately after printing was set to dl at Macbeth density δ1. After leaving it for one month in an environment of 60% humidity at °C, the image area density and background density were measured using Macbeth density, 11 and Fo1-Volt density RI, respectively, and the bleeding property of the image area was determined by white powder adhesion. The results were evaluated as yes or no.The results are shown in the table below.

As is clear from the results shown in Table 1 above, the product of the present invention has excellent color development and background whiteness, and does not cause problems in natural decolorization and bleachability in the image area. is understood.

Patent applicant Ricoh Co., Ltd. -Representative patent attorney
Toshiaki Ikeura

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, P-hydroxybenzoic acid ester is used as the color developer, and the heat-sensitive color forming layer 1. A heat-sensitive recording material, characterized in that a single layer of under-two 1 containing a compound represented by the following general formula is provided on the lower surface of the material. K\0OH (in the formula, R represents alkylene having 2 to 5 carbon atoms)