JPS639998B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to heat-sensitive recording materials. A heat-sensitive recording material is a recording material in which a heat-sensitive coloring layer that can form a colored image by heating is provided on a support such as paper, and the heating is performed using a thermal printer equipped with a thermal head. Widely used. These heat-sensitive recording materials can easily produce colored images simply by heating, so their uses have rapidly expanded with the development of the information industry, and today they are used only for copying books, documents, etc. It is also widely used for recording the output of various information and measuring instruments such as electronic calculators, facsimiles, and telex. In recent years, there has been an increasing demand for higher speed and higher density image information, and there is a need for heat-sensitive recording materials that can meet these demands. The heat-sensitive coloring layer of conventional heat-sensitive recording materials contains a colorless or light-colored leuco dye having a lactone ring, a lactam ring, or a spiropyran ring, and an acidic substance or phenolic compound that reacts with the leuco dye to develop color when heated. What you do is
It has been widely used because its color tone is clear and there is little fogging (color development around the heated part). However, when a thermosensitive recording material equipped with a thermosensitive coloring layer having the above composition is brought into contact with a thermal element such as a thermal head or a thermal pen to obtain a colored image, the components in the thermosensitive coloring layer melt. It sticks to the thermal head or hot pen, causing so-called scum adhesion and staking phenomena. In addition, such heat-sensitive recording materials are sensitive to rubbing friction, and therefore have the disadvantage of being accompanied by a pressure coloring phenomenon in which coloring occurs due to rubbing friction. For this reason, the density of the obtained colored image becomes low, and the image lacks clarity.
Moreover, when recording for a long time, it had the disadvantage that it hindered the running performance of thermal heads and the like. The present invention aims to solve the above-mentioned drawbacks, and is capable of increasing the speed and density of image information without causing deposits on thermal elements such as thermal heads and the staking phenomenon. It is an object of the present invention to provide a heat-sensitive recording material that has excellent heat-sensitive properties capable of coping with the above problems and is less likely to be accompanied by pressure coloring phenomena. The heat-sensitive recording material according to the present invention is a heat-sensitive recording material in which a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and an acidic substance or a phenolic compound that reacts with the leuco dye to develop color when heated is provided on a support. In the material, in the thermosensitive coloring layer,
It is characterized by containing compounds represented by the following general formulas () and (). (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms.) (In the formula, R ₂ and R ₃ are alkyl groups having 10 to 30 carbon atoms.) As the leuco dye used in the heat-sensitive coloring layer in the present invention, conventionally known colorless or light-colored leuco dyes are used. Specifically, the following compounds may be mentioned. a Triphenylmethane-based leuco dye represented by the following general formula (In the formula, R ₁ , R ₂ and R ₃ are hydrogen, hydroxyl group,
halogen, alkyl group, nitro group, amino group,
dialkylamino group, monoalkylamino group or allyl group). The following compounds are listed as representative examples of such leuco dyes. 1 3,3-bis(p-dimethylaminophenyl)-phthalide 2 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (commonly known as crystal violet lactone) 3 3,3-bis (p-dimethylaminophenyl)-6-diethylaminophthalide 4 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide 5 3,3-bis(p-dimethylaminophenyl)-phthalide b Below Fluorane leuco dye represented by the general formula (wherein R ₁ , R ₂ and R ₃ are as defined above). The following are listed as typical compounds of such leuco dyes. 1 3-cyclohexylamino-6-chlorofluorane 2 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane 3 3-dimethylamino-5,7-dimethylfluorane Oran 4 3-diethylamino-7-methylfluorane 5 3-diethylamino-7,8-dibenzfluorane 6 3-diethylamino-6-methyl-7-chlorofluorane 7 3-pyrrolidino-6-methyl-7-ani Linofluorane c Lactone compound represented by the following general formula (In the formula, R ₁ and R ₂ are hydrogen, a lower alkyl group, a substituted or unsubstituted aralkyl group, a phenyl group, a cyanoethyl group, or a β-
represents a halogenated ethyl group or R ₁ and
R ₂ combines with -(CH ₂ )- ₄ , -(CH ₂ )- ₅ or -(
CH ₂ )—O—(CH ₂ )— ₂ , R ₃ and R ₄
represents hydrogen, a lower alkyl group, an amino group or a phenyl group, one of R ₃ and R ₄ is hydrogen, and X ₁ , X ₂ and X ₃ are hydrogen, a lower alkyl group, a lower alkoxyl group ,halogen,
represents a halogenated methyl group, nitro group, amino group or substituted amino group, X ₄ represents hydrogen, halogen, lower alkyl group or lower alkoxyl group, and n is an integer of 0 to 4). The following are listed as representative lactone compounds. 1 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5-chlororphenyl) phthalide 2 3-(2'-hydroxy-4'-dimethylaminophenyl) -3-(2'-methoxy-5'-nitrophenyl)phthalide 3 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2-methoxy-5'-methylphenyl)phthalide 4 3-(2 '-Methoxy4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide The acidic substance or phenolic compound used in the present invention is capable of reacting with the leuco dye during heating. It is a compound that develops color by reaction, and specifically includes the following compounds. 1 Boric acid 2 Oxalic acid 3 Maleic acid 4 Tartaric acid 5 Citric acid, 6 Succinic acid 7 Benzoic acid 8 Stearic acid 9 Gallic acid 10 Salicylic acid 11 1-Hydroxy-2-naphthoic acid 12 O-Hydroxybenzoic acid 13 m-Hydroxybenzoic acid 14 2-hydroxy-p-toluic acid 15 3,5-xylenol 16 Thymol 17 p-tert-butylphenol 18 4-hydroxyphenoxide 19 Methyl-4-hydroxybenzoate 20 4-hydroxyacetophenone 21 α-naphthol 22 β-naphthol23 Catechol24 Resorcinol25 Hydroquinone26 4-tert-octylcatechol27 4,4'-sec-butylidenephenol28 2,2'-dihydroxydiphenyl29 2,2'-methylenebis(4-methyl-6-
tert-butylphenol) 30 2,2-bis(4-hydroxyphenol)
Propane (commonly known as bisphenol A) 31 4,4'-isopropylidene-bis(2-tert
-butylphenol) 32 4,4'-sec-butylidene diphenol 33 Pyrogallol 34 Phloroglucin 35 Phloroglucin carboxylic acid In the present invention, in order to prevent scum adhesion, statesking phenomenon and pressure coloring in the heat-sensitive coloring layer, , compounds represented by the following general formulas () and () are added. (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms) (In the formula, _R2 and _R3 are alkyl groups having 10 to 30 carbon atoms). Among the compounds represented by the general formula (), those in which R ₁ has 1 to 10 carbon atoms are particularly preferred. Also, among the compounds represented by the general formula (),
It is particularly preferable that R ₂ and R ₃ have 14 to 22 carbon atoms. The amount of the compound represented by the general formula () added to the heat-sensitive coloring layer is preferably 1 to 10 times (by weight) the weight of the leuco dye, and the amount of the compound represented by the general formula ()
The amount of the compound represented by is preferably 1 to 20 times (by weight) the weight of the leuco dye. In the present invention, paper, synthetic paper, synthetic resin film, metal laminated paper, etc. can be widely used as the support on which the thermosensitive coloring layer is applied. It is preferable to use a binder when each component to be contained in the thermosensitive coloring layer is provided on a support such as paper. As a binder,
Although widely known compounds can be used, specific examples include the following compounds. 1 Polyvinyl alcohol 2 Methoxycellulose 3 Hydroxycellulose 4 Carboxymethylcellulose 5 Carboxyethylcellulose 6 Polyvinylpyrrolidone 7 Polyacrylamide 8 Polyacrylic acid 9 Starch 10 Gelatin 11 Vinyl chloride-vinyl acetate copolymer 12 Polybutyl methacrylate Carbonic acid is added in the heat-sensitive coloring layer. By adding fine powders such as calcium, silica, alumina, magnesia, talc, barium sulfate, and aluminum stearate, the clarity of colored images can be improved. In addition, when coating and providing a thermosensitive coloring layer on a support, an antifoaming agent,
Wetting agents or gases can be added to improve coatability and thermal response. EXAMPLES The present invention will be further explained in detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example A mixture consisting of the following components was pulverized and dispersed for 24 hours using a ball mill to prepare liquids [A] and [B]. [A] Liquid composition Crystal violet lactone 60 parts by weight 5% polyvinyl alcohol solution 60 parts by weight Water 180 parts by weight [B] Liquid composition Bisphenol A 60 parts by weight 5% polyvinyl alcohol solution 60 parts by weight Water 180 parts by weight Next, the following ingredients The mixture consisting of was pulverized and dispersed in an attritor for 6 hours to form liquid [C] and liquid [D].
A liquid was prepared.

【table】

[Table] Next, [A] 1 part by weight of liquid, [B] 4 parts by weight of liquid,
2 parts by weight of solution [C], 2 parts by weight of solution [D], and 2 parts by weight of a 20% polyvinyl alcohol aqueous solution were thoroughly mixed to prepare a thermosensitive coloring layer forming solution. This thermosensitive coloring layer forming liquid was coated on a commercially available high quality paper with a standard basis weight of 60 g/m ² so that the dry coating amount was 7 to 8 g/m ² to produce a thermosensitive recording material. Comparative Example 1 A comparative heat-sensitive recording material was produced in the same manner as in the above example except that the heat-sensitive coloring layer forming liquid was prepared without using liquid [C]. Comparative Example 2 A heat-sensitive recording material was produced in the same manner as in the above example except that the heat-sensitive color forming layer forming liquid was prepared without using liquid [D]. Printing was performed at high speed on the heat-sensitive recording material according to the present invention and the heat-sensitive recording material for comparison produced as described above using a facsimile machine [OKI FAX-7100 manufactured by Oki Electric Industry Co., Ltd.]. In the heat-sensitive recording material according to the present invention, adhesion of residue to the thermal head, staking phenomenon, and pressure coloring are hardly observed, and high-speed running of the thermal head is not hindered.
A clear blue image with high density was obtained. On the other hand, the heat-sensitive recording material produced in Comparative Example 1 was similar in color development to that of the example, but the runnability of the thermal head was hindered, and there was
Significant statesking phenomenon was observed, and some pressure coloring was also observed. Furthermore, the heat-sensitive recording material produced in Comparative Example 2 was similar to that of the example in terms of thermal head runnability and pressure color development.
The coloring property was poor, and the density of the colored image obtained was not sufficient. As described above, in the present invention, excellent effects can be obtained by incorporating both the compounds represented by the general formulas () and () into the heat-sensitive coloring layer.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material provided on a support with a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and an acidic substance or phenolic compound that reacts with the leuco dye to develop color when heated. , the following general formulas () and () are present in the heat-sensitive coloring layer.
A heat-sensitive recording material characterized by containing a compound represented by (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms), (In the formula, _R2 and _R3 are alkyl groups having 10 to 30 carbon atoms).