JPS639996B2 - - 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 types of information and measuring equipment such as electronic computers, facsimiles, and telex. In recent years, there has been an increasing demand for higher speed and higher density of image information, and along with this, there has been a demand for heat-sensitive recording materials that can accommodate higher speed and higher density. The heat-sensitive coloring layer of conventional heat-sensitive recording materials contains a colorless or light-colored leuco dye having a lactone ring, lactam ring, or spiropyran ring, and an acidic substance or phenolic compound that reacts with the leuco dye to develop color when heated. It has been widely used because it has a clear color tone and little fogging (color development around the heated part). However, when a heat-sensitive recording material using a heat-sensitive 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 heat-sensitive coloring layer are thermally separated. Ingredients stick to the thermal head or pen, causing so-called scum adhesion and staking phenomena. In addition, such heat-sensitive recording materials are sensitive to scratches and friction, so
This has the disadvantage that it is accompanied by a pressure coloring phenomenon. For this reason, the density of the obtained colored image is low, the image lacks sharpness, and furthermore, when recording for a long time, the running performance of the thermal head is hindered, which is a drawback. 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 present invention provides a heat-sensitive recording material comprising a heat-sensitive coloring layer on a support, which contains 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. It is characterized in that the coloring layer contains zinc stearate and a compound represented by the following general formula. (In the formula, R ₁ is an alkyl group having 1 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, and specific examples include the following compounds. 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 A lactone compound represented by the following general formula. (In the formula, R ₁ and R ₂ represent hydrogen, a lower alkyl group, a substituted or unsubstituted aralkyl group, a phenyl group, a cyanoethyl group, or a β-halogenated ethyl group, or R ₁ and R ₂ are a bond) (-CH ₂ )- ₄ , (-CH ₂ )- ₅ or (-CH ₂ )-O
(-
CH ₂ ) _—2 , R ₃ and R ₄ represent hydrogen, a lower alkyl group, an amino group or a phenyl group,
Either one of R ₃ and R ₄ is hydrogen, and X ₁ , X ₂ and X ₃ are hydrogen, lower alkyl group, lower alkoxyl group, halogen, halogenated methyl group, nitro group, amino group or substituted amino represents the group,
X ₄ represents hydrogen, halogen, a lower alkyl group or a 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-chlorophenyl)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'- Methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide The acidic substance or phenolic compound used in the present invention reacts with the leuco dye during heating. Specifically, the following compounds can be mentioned. 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-hydroxyphenyl)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 Phloroglycin carboxylic acid In the present invention, stearic acid is added to the heat-sensitive coloring layer in order to prevent scum adhesion, staining, pressure coloring, etc. Zinc and the following general formula ()
Add the compound shown. (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms.) Among the compounds represented by the general formula (), those in which R ₁ has 14 to 22 carbon atoms are particularly preferred. In the present invention, the amount of zinc stearate added to the heat-sensitive coloring layer is 0.1 of the total weight of the leuco dye and the acidic substance or phenolic compound.
The amount is preferably 10 to 10 times the amount (parts by weight). The amount of the compound represented by the general formula () to be added is preferably 0.1 to 5 times (by weight) the total weight of the leuco dye and the acidic substance or phenolic compound. It is preferable to use a binder when disposing each component to be contained in the heat-sensitive coloring layer on a support such as paper. Specific examples of the binder include the following compounds. 1 Polyvinyl alcohol 2 Methoxycellulose 3 Hydroxyethylcellulose 4 Carboxyethylcellulose 5 Polyvinylpyrrolidone 6 Polyacrylamide 7 Polyacrylic acid 8 Starch 9 Gelatin 10 Polystyrene 11 Vinyl chloride-vinyl acetate copolymer 12 Polybutyl methacrylate In the thermosensitive color forming layer of the present invention By further adding fine powders such as calcium carbonate, silica, magnesia, talc, barium sulfate, and aluminum stearate, the clarity of the colored image can be improved. The present invention will be further explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 Mixtures having the following compositions were pulverized and dispersed for 24 hours using a Pall mill to prepare liquids [A] and [B].

[Table] Next, liquid [A] and liquid [B] were mixed to prepare a thermosensitive coloring layer forming liquid. This thermosensitive color forming layer forming liquid was applied onto a commercially available high-quality paper having a standard basis weight of 50 g/m ² so that the dry coating amount was 6 g/m ² , and then dried. The heat-sensitive coloring layer thus formed was then calendered to give a surface smoothness of 300 to 400 sec in terms of Beck smoothness to produce a heat-sensitive recording material. Comparative Example 1 In Example 1 above, CH ₃ in the [B] solution
( _CH2 ) ₁₇

A heat-sensitive recording material was produced in the same manner as in Example 1 except that a conventionally known stearic acid amide was used in place of [Formula]. Colored images were formed on the heat-sensitive recording material of the present invention and the comparative heat-sensitive recording material produced in this way by printing at high speed using a facsimile machine [OKIFAX-7100 manufactured by Oki Electric Industry Co., Ltd.]. The presence or absence of dust adhesion, states king phenomenon, and image density were investigated. The results are shown in Table 1.

【table】

[Table] As shown in Table 1, it can be seen that the heat-sensitive recording material according to the present invention has no scum adhesion or statesking phenomenon, and also has good image density compared to the conventional heat-sensitive recording material. .

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. A heat-sensitive recording material, characterized in that the heat-sensitive coloring layer contains zinc stearate and a compound represented by the following general formula, (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms).