JPS60184878A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To obtain a thermal recording paper having excellent color forming sensitivity, moisture decolorizing resistance and oil resistance, by using a specified fluoran compound as a color former (electron-donative color former). CONSTITUTION:At least one fluoran compound of general formula ( I ), wherein R1 is hydrogen, 1-8C alkyl, tetrahydrofurfuryl, subst. or unsubst. phenyl or cycloalkyl, R2 is hydrogen, chlorine, fluorine, lower alkyl, lower alkoxy, lower alkoxyalkyl, phenyl or benzyl, and R3 is hydrogen, chlorine, fluorine, lower alkyl or acyl, is incorporated in a thermal color forming layer. The fluoran compound of formula ( I ), e.g., 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylaminofluoran or 2-anilino-3-methyl-6-N-ethyl-N-tetrahydrofurfurylaminofluoran, is substantially colorless per se, but when being brought into contact with an electron- acceptive substance, it rapidly forms a color. Namely, the fluoran compound forms a blackish color on making contact with a phenol derivative such as bisphenol A or a p-hydroxybenzoic acid derivative such as benzyl p-hydroxybenzoate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording paper characterized in that it contains at least one type of novel fluoran compound as a color former (electron-donating coloring agent).

Thermosensitive recording paper is a recording paper with a structure in which a so-called thermosensitive coloring layer that develops color when heated is formed on a support such as paper. It is used. Compared to other types of recording paper, recording paper with a structure that has a heat-sensitive coloring layer has the advantages of being inexpensive, making less noise, and being able to record in a short time. It's being used. The most important thing about thermal recording paper is that it has poor color development sensitivity, but recently it has also begun to be used for display labels for POS (point of sale) etc.
It has become an essential condition that colored images have good storage stability.

The minimum properties that a coloring layer of thermal recording paper should possess are excellent self-coloring resistance (resistance to surface fogging), pressure coloring resistance, coloring sensitivity, moisture decoloring resistance, heat decoloring resistance, oil resistance, and light resistance. However, we have not yet obtained anything that completely combines these aspects.

In the heat-sensitive coloring layer, a color former that produces a bright black color is often used in the summer, but fluoran compounds as color formers are used in Japanese Patent Publication No. 51-25204, Japanese Patent Publication No. 51-29180, and Japanese Patent Publication No. 56. -52759, JP-A-57-5g562, JP-A-58-7455, and U8F-5681590. Regarding heat-sensitive recording paper using a color former, Japanese Patent Publications No. 45-4160, Japanese Patent Publication No. 3680-1973, and Japanese Patent Publication No. 17748-1974 are known.

The present inventors manufactured thermal recording paper using known fluoran compounds as color formers according to conventionally known methods or the methods described in the above-mentioned patent publications. When tested under pressure, each of these thermal recording papers showed high color development sensitivity, moisture resistance,
It had shortcomings in oil resistance, resistance to surface fogging, etc.

The inventors of the present invention have conducted extensive studies on thermal recording paper that has improved these drawbacks, and have discovered that the performance of the thermal recording paper can be pleasantly improved by using a specific fluoran compound.

That is, the present invention has the following general formula (1), general formula (wherein s R1 is hydrogen, an alkyl group having 1 to 8 carbon atoms, a nato2hydrofurfuryl group, a substituted or unsubstituted phenyl group, a cyclic alkyl group) where R2 represents hydrogen, -) chlorine, fluorine, a lower alkyl group, lower alkoxy group, lower alkoxyalkyl group, phenyl group, or benzyl group, and R3 represents hydrogen, chlorine, fluorine, a lower alkyl group, or an acyl group. . ) This is a heat-sensitive recording paper characterized by containing at least one type of novel fluoran compound represented by the following as a color former.

The fluoran compound represented by general 2〇) is almost colorless in itself, but has the property of rapidly developing color when it comes into contact with an electron-accepting substance. That is, it develops a blackish color due to phenol derivatives such as bisphenol A and p-hydroxybenzoic acid rust conductors such as p-hydroxybenzoic acid benzyl ester.

An example of the novel fluoran compound represented by general formula (1) used in the color former of the present invention is 2-anilino-3-methyl-6-N-methyl-N.
-tetrahydrofurfurylamino-fluorane, 2-anilino-3-methyl-6-N-ethyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-5-
Chloro-6-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-(2-chloroanilino)-6
-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-(2-chloroanilino)-6-N,N-
Di-tetrahydrofurfurylamino-fluorane, 2-
Anilino-3-methyl-6-N, N-di-tetrahydrofurfurylamino-fluorane, 2-anilino-3-methyl-6-N-ynamyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-6- Methyl-6
-N-butyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-ethoxyethyl-6-N
-Methyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-methyl-6-N-p-)Clue N-tetrahydrofurfurylamino-fluorane,
2-anilino-3-methyl-6-N-cyclohexyl-
N-tetrahydrofurfurylamino-fluorane, 2-
Anilino-3-methyl-N-tetrahydrofurfurylamino-fluorane, -2-anilino-6-phenyl-6
-N-methyl-tetrahydrofurfurylamino-fluorane, 2-anilino-3-phenyl-6-N-ethyl-N-tetrahydrofurfurylamino-fluorane,
2-anilino-3-benzyl-6-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-5-methoxy-6-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-p- Toluidino
3-Methyl-6-N-methyl-N-tetrahydrofurfurylamino-fluoran, 2-(p-penzoylphenyl ε))-3-ethyl-6-N-methyl-N-tetrahydrofurfurylamino-fluoran, 2 -(2-fluoroanilino)-3-methyl-6-N-methyl-N-tetrahydrofurfurylamino-pluorane, 2-anilino-3=benzyl-6-N,N-ditetrahydrofurfurylamino-fluorane etc.

In order to synthesize the fluoran compound represented by the general formula (1) according to the present invention, the following formula is used: ) and a benzophenone derivative represented by the general formula (in which R is the same as the bait definition) in a condensing agent such as sulfuric acid, phosphoric acid, or polyphosphoric acid, It can be obtained by treatment in alkaline water. For example, 2-anilino-3-methyl-6
-N-Ethyl-N-tetrahydrofurfurylamino-fluorane is synthesized as follows.

(4-N-ethyl-N-tetrahydrofurfurylamino-2- and droxybenzoyl) in 98% sulfuric acid 1501
After adding 13.5 F of benzoic acid and completely dissolving it while maintaining the temperature at about 5°C, process 6.4 F of 2-methyl-4-methoxy-diphenylamine at 20 to 25°C for 1 hour and then for 2 hours.
The reaction was carried out at 0°C for 18 hours. Pour the reaction mixture into 1# of ice water as follows.
Then, an aqueous solution of IJ was added to give a concentration of 91410 or higher. The precipitate was collected by filtration.

After adding 450 g of toluene and 340 f of 10% aqueous sodium hydroxide solution to the cake and stirring under reflux for 2 hours, the toluene layer was separated and washed with water, and the toluene was distilled off by steam distillation. The precipitated crystals were collected by filtration, and after washing by adding 50 methanol to the cake, the crystals were collected again by filtration. The crystals are dried to give white 2-anilino-3-
Methyl-6-N-ethyl-N-tetrahytomifurfurylaminofluorane 9,61 was obtained. The melting point of this fluoran compound was 165°C to 167°C. The λmax and molecular extinction coefficient of this compound in a 95% acetic acid solution were 452 nm (1,944X10') and 594 nm (1,949XID'). A solution obtained by dissolving this product in toluene was colorless, and the color developed more quickly than bisphenol AK, giving it a black color.

In addition, color developers used in combination with fluoran compounds include 4-t-butylphenol, 4-phenylphenol, methyl-4-hydroxybenzoate a,
al-isopropylidene diphenol, 4,4'-isopropylidene bis(2,6-dibromophenol),
Bis(4-hydroxyphenyl)sulfone, hensyl p-hydroxybenzoate, p-hi)"Q *5ec-butylcybenzoate, 3-<d.

-Methylbenzyl) salicylic acid and other conventionally known color developers.

Various water-soluble or water-insoluble binders are used in the heat-sensitive coloring layer of the present invention for binding onto the support. Typical examples include polyvinyl alcohol, methylcellulose, hydroxyethylcellulose,
Carboxymethyl cellulose, gum arabic, starch,
There are gelatin, casein, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, etc., but the binder that can be particularly preferably used in the present invention is a water-soluble binder, a typical example of which is polyvinyl alcohol. Teal.

In addition, in the heat-sensitive coloring layer, if necessary, auxiliary additives such as fillers such as aluminum hydroxide, calcium carbonate, magnesia, barium sulfate, and calcium stearate, dimethyl terephthalate, dibenzyl terephthalate, and β-naphtholbenzyl are added. By adding conventionally known sensitivity improvers such as ether, amyl stearate), benzyl p--Z-benzyloxybenzoate, etc., the clarity of the colored image or the color density can be improved.

The thermal recording paper of the present invention is produced by applying and drying a coating liquid for forming a thermosensitive coloring layer containing each of the above-mentioned components onto a support such as paper.
It was particularly excellent in moisture fade resistance and oil resistance.

The performance of the thermal recording paper was determined by the following test method. In other words, the color density of K, such as the decolorization density of the coloring agent in humidity after color development by heating at each temperature (moisture decolorization resistance), and the color decolorization density when it comes into contact with castor oil (oil resistance), is determined by Macbeth. Measurements were made using an RD-514 reflection densitometer. The heating color development was carried out using a Rhodiaceta type thermotest tester (manufactured by France National Textile Research Institute) under the false conditions of a heating temperature of 60 to 170° C., a heating time of 3 seconds, and a load of 1 o o. Further, decoloring of the coloring agent after coloring by heating was carried out using a constant temperature and humidity tester.

Next, the present invention will be explained in detail with reference to Examples.

Example 1 A mixture having the following composition was separately ground for 3 hours using a paint conditioner (trade name: Red Debika) to prepare liquids (1), (2), and (2).

■Liquid composition 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylamino-fluorane 4 parts by weight 10
% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (San Noguco 1407. San Nobuco product) 2 parts by weight Metzenol 6 parts by weight 10% polyvinyl alcohol aqueous solution 2 Oifi parts water
14 parts by weight ■Liquid composition Aluminum hydroxide 10! Parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Water 1
Parts by weight of O: Liquid (2), liquid (2), liquid O, and water were mixed in a weight ratio of 3:9:5:3 to obtain a paint for heat-sensitive recording paper. This paint was applied to the surface of high-quality paper using a wire bar until the solid weight after drying was 5 f.
/rrl, placed in a blow drying mold, and dried at room temperature to obtain thermal recording paper 0) of the present invention.

Comparative Example 1 Comparative thermal recording paper (B) to 0 was produced in the same manner as in Example 1, except that the O solution, [F] solution, or [F] solution obtained in the same manner was used instead of the liquid (①) of Example 1. I got it.

0 Liquid composition 2-(2-ri-aloanilino)-6-dibutyl aminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 54 parts by weight M 5% Antifoaming agent (San Nopco 1407) 2 parts by weight ■Liquid composition 2-anilino- 3-Methyl-6-N-methyl-N-cyclohexyl-amino-fluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (San Nopco 1407) 2 parts by weight [F] Liquid composition 2-anilino-3- Methyl-6-N-ethyl-N-isoamyl 1 Mino-fluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution The coloring sensitivity, moisture decoloring resistance, and oil resistance of the thermal recording paper were tested for =4=li14-≠-4=4. The results are shown in Table 1.

Example 2 2-anilino-6-methyl-6-N used in Example 1
-Methyl-N-tetrahydrofurfurylamino-Fluorane shown in Table IK was used in place of fluorane, and in the same manner as in Example 1, thermal recording paper intermediates) to (→ were obtained. A performance test was conducted in the same manner as in Example 1. The results are shown in Table 1.

The thermal recording paper of the present invention has excellent color development sensitivity, moisture decolorization resistance, and oil resistance, and compared to comparative thermal recording paper,
In particular, it has excellent color development sensitivity and oil resistance, and has sufficient practical value as a heat-sensitive recording paper for various recording fields, especially for high-speed recording and POS.

Example 3

Claims (1)

[Claims] General formula (where RI represents hydrogen, an alkyl group having 1 to 8 carbon atoms, a tetrahydrofurfuryl group, a substituted or unsubstituted phenyl group, or a cyclic alkyl group, and R2 represents hydrogen, chlorine, or fluorine) , a lower alkyl group, a lower alkoxy group, a lower alkoxyalkyl group, a phenyl group, a benzyl group, and R3 represents hydrogen, chlorine, fluorine, a lower alkyl group, or an acyl group. 1. A heat-sensitive recording paper containing as a color former.