JPH0377229B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel fluoran compounds. More specifically, the present invention relates to a novel fluoran compound characterized by having a tetrahydrofurfurylamino group at the 6-position, which is useful as a dye precursor for use in heat-sensitive recording paper, electrically conductive heat-sensitive recording sheets, and photosensitive color recording sheets. It is something. Known fluoran compounds related to the present invention include Japanese Patent Publication No. 51-23204, Japanese Patent Publication No. 51-29180,
This can be seen in Japanese Patent Publication No. 56-52759 and Japanese Patent Application Laid-Open No. 56-162690. The fluoran compounds disclosed in these publications are used as color formers (dye precursors) for heat-sensitive recording paper, electrically conductive heat-sensitive recording paper, pressure-sensitive copying paper, and the like. However, thermal recording paper using these fluoran compounds as color formers requires a high temperature to obtain a color density of 1.0, that is, a large amount of energy is consumed to reach a practical color density. Furthermore, it had drawbacks in humidity and decoloring resistance, oil resistance, resistance to surface fogging, etc. As a result of intensive studies to improve the above-mentioned drawbacks, the present inventors found that a new fluoran compound represented by the following general formula () is a colorless or light-colored solid that is stable in the atmosphere, and that it does not come into contact with acidic substances. It has been found that the performance of thermal recording paper is significantly improved by using these compounds. That is, the present invention provides the following general formula (), (In the formula, R ₁ is hydrogen, an alkyl group having 1 to 8 carbon atoms,
It represents a tetrahydrofurfuryl group, a phenyl group or a cyclohexyl group which may be substituted with an alkyl group, and R ₂ is hydrogen, chlorine, fluorine, a lower alkyl group, a lower alkoxy group, a lower alkoxyalkyl group, a phenyl group or a benzyl group. and R ₃ represents hydrogen, chlorine, fluorine, a lower alkyl group or an acetyl group. ) is a fluoran compound characterized by having a tetrahydrofurfurylamino group at the 6-position. The novel fluoran compound represented by the general formula () of the present invention is produced by the following method. general formula (In the formula, R ₂ and R ₃ are the same as defined above, and R ₄
represents a hydrogen atom, an acetyl group, or a lower alkyl group. ) and a diphenylamine derivative represented by the general formula (wherein R ₁ is the same as defined above) is reacted with a benzophenone derivative represented by the formula (R 1 is the same as defined above) at a temperature of 0 to 80° C. for several hours in the presence of 80 to 100% sulfuric acid. After the reaction, the reaction mixture is added to water, sodium hydroxide is added to adjust the pH to 8-10, and the precipitate is collected by filtration. Cake with toluene and 5-10%
Add an aqueous solution of sodium hydroxide, and under reflux,
Stir for 3 hours, separate the toluene layer, wash with water,
Concentrate and collect the precipitated crystals by filtration. By drying the crystals, a novel slightly colored fluoran compound represented by the general formula () can be obtained with high purity and high yield. If necessary, recrystallize from bright organic solvents such as toluene, acetone, butyl acetate, hexane, etc. Condensing agents used in the present invention include concentrated sulfuric acid, acetic anhydride, phosphoric acid, boriphosphoric acid, phosphorus oxychloride, and zinc chloride. For production purposes, preferably 80 to 100, which is both a solvent and a condensing agent, such as a benzophenone compound represented by the above general formula ().
% of sulfuric acid is used. Next, representative examples of the fluoran compound represented by the general formula () of the present invention will be described. The hue indicates the hue when the color is developed on a thin layer of silica gel.

【table】

[Table] The thus obtained thermosensitive recording paper containing the fluoran compound of the present invention as a color former was particularly excellent in coloring sensitivity, moisture decoloring resistance, and oil resistance. Next, the present invention will be explained by examples. Example 1 2-anilino-3-methyl-6-N-ethyl-
N-tetrahydrofurfurylaminofluorane [Compound No. 1]. 2-(4-N-ethyl-N-
Add 16.6 g of tetrahydrofurfurylamino-2-hydroxy-benzoyl)-benzoic acid and heat at approximately 5°C.
After completely dissolving the 2-methyl-
Add 11.5g of 4-methoxydiphenylamine and 5~
React at 10℃ for 10 hours and then at 20-25℃ for 6 hours.
The reaction mixture was added to ice water 1, and then an aqueous sodium hydroxide solution was added to adjust the pH to 10 or higher. The precipitate was collected by filtration. 450ml of toluene for the cake
After adding 340 g of 10% aqueous sodium hydroxide solution 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 ml of methanol to the cake, the crystals were collected again by filtration. The crystals are dried to give a white 2-anilino-3
-Methyl-6-N-ethyl-N-tetrahydrofurfurylaminofluorane, 17.8 g was obtained. The melting point of this fluoran compound was 165-167°C. In addition, the λmax and molecular extinction coefficient of this compound in 95% acetic acid solution are 452 nm (1.944×
10 ⁴ ) and 594 nm (1.949×10 ⁴ ). A solution obtained by dissolving this product in toluene was colorless and quickly developed color due to the silica gel, giving it a black color. Example 2 2-anilino-3-methyl-6-N-methyl-
N-tetrahydrofurfurylaminofluorane [Compound No. 2] 2-(4-N-methyl-N-
Add 16.0 g of tetrahydrofurfurylamino-2-hydroxy-benzoyl)-benzoic acid and heat at approximately 5°C.
After completely dissolving the 2-methyl-4
- Add 11.5g of methoxydiphenylamine for 5 to 10 minutes.
The reaction was carried out at ℃ for 10 hours. By treating in the same manner as in Example 1 and recrystallizing from ethanol, 17.0 g of white 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylamino-fluorane was obtained. The melting point of this product was 155 to 159°C, and the solution obtained by dissolving this product in toluene was colorless, but quickly developed color due to the silica gel, giving it a black color. Example 3 2-anilino-3-methyl-6-N,N-di-
Tetrahydrofurfurylaminofluorane [Compound No. 3] 2-(4-N,N-di-tetrahydrofurfurylamino-2-hydroxy-
2-methyl-4-
Add 11.5g of methoxydiphenylamine and 10-20℃
It reacted for 10 hours. The mixture was treated in the same manner as in Example 1 and recrystallized from ethanol to obtain 15.9 g of white 2-anilino-3-methyl-6-N,N-di-tetrahydrofurfurylaminofluorane. The melting point of this product was 174 to 176°C, and the solution obtained by dissolving this product in toluene was colorless, but quickly developed color due to the silica gel, giving it a black color. Example 4 2-(2-chlorophenyl)-amino-6-N-
Methyl-N-tetrahydrofurfurylamino-
Fluorane [Compound No. 4] In place of 16.6 g of 2-(4-N-ethyl-N-tetrahydrofurfurylamino-2-hydroxy-benzoyl)-benzoic acid in Example 1,
-ethyl-N-tetrahydrofurfurylamino-
2-Hydroxy-benzoyl)-benzoic acid 16.0g
, and using 12.6 g of 2'-chloro-4-methoxydiphenylamine instead of 11.5 g of 2-methyl-4-methoxydiphenylamine, react in the same manner as in Example 1, and recrystallize from toluene. 2-(2-chlorophenyl)-amino-6
17.7 g of -N-methyl-N-tetrahydrofurfurylaminofluorane was obtained. The melting point of this substance is
The temperature was 169 to 173°C, and a solution obtained by dissolving this product in toluene was colorless, but the color quickly developed due to the silica gel, giving it a black color. Example 5 2-anilino-3-chloro-6-N-methyl-
N-tetrahydrofurfurylamino-fluorane [Compound No. 5] In place of 16.6 g of 2-(4-N-ethyl-N-tetrahydrofurfurylamino-2-hydroxy-benzoyl)-benzoic acid in Example 1, 2- (4-N
-Methyl-N-tetrahydrofurfurylamino-
2-Hydroxy-benzoyl)-benzoic acid 16.0g
, and by using 12.6 g of 2-chloro-4-methoxydiphenylamine instead of 11.5 g of 2-methyl-4-methoxydiphenylamine, reacting in the same manner as in Example 1, and recrystallizing from ethanol. 14.5 g of white 2-anilino-3-chloro-6-N-methyl-N-tetrahydrofurfurylamino-fluorane were obtained. The melting point of this substance is 146~
The temperature was 151°C, and the solution obtained by dissolving this product in toluene was colorless, but quickly developed color due to the silica gel, giving it a green-black color. Example 6 2-(2-chlorophenyl)-amino-6.N,N
-di-tetrahydrofurfurylaminoralolane [Compound No. 6] 2-(4-N-ethyl-N-tetrahydrofurfurylamino-2-hydroxy-benzoyl)-benzoic acid in place of 16.6 g of Example 1 -(4-
N,N-di-tetrahydrofurfurylamino-2
-hydroxy-benzoyl)-benzoic acid 19.1 g,
In addition, 12.6 g of 2'-chloro-4-methoxydiphenylamine was used instead of 11.5 g of 2-methyl-4-methoxy-diphenylamine, and the reaction was carried out in the same manner as in Example 1. By recrystallizing from ethanol, a white product was obtained. 2-(2-chlorophenyl)-amino-6-
16.4 g of N,N-di-tetrahydrofurfurylamino-fluorane were obtained. The melting point of this thing is 164
The temperature was ~166°C, and the solution obtained by dissolving this product in toluene was colorless, but quickly developed color due to the silica gel, giving it a black color. Next, a general method for producing thermal recording paper using the fluoran compound of the present invention will be described. A fluoran compound, an acidic substance, and a thermofusible substance (used when the fluoran compound or acidic substance does not melt at the desired temperature) are sufficiently finely ground and mixed into a liquid in which the binder is dissolved or dispersed in a solvent or dispersion medium. , by coating and drying on a support such as paper, plastic sheet, or resin-coated paper. When preparing a mixed solution, all the components may be mixed and pulverized at the same time from the beginning, or they may be combined in an appropriate combination and separately pulverized and dispersed, and then mixed. The amounts of each component constituting the thermal recording paper are: 1 part by weight of a fluoran compound, 2 to 10 parts by weight of an acidic substance, 0 to 10 parts by weight of a thermofusible substance, 2 to 10 parts by weight of a binder, and 50 parts by weight of a solvent (dispersion medium). ~150 parts by weight. The solvent (dispersion medium) is preferably one that hardly dissolves either the fluoran compound or the acidic substance, and the most preferable solvent (dispersion medium) that can be used is water, and other examples include hydrocarbons such as hexane and ligroin. Next, examples of the binder used in the present invention include polyvinyl alcohol, hydroxyethyl cellulose, polyvinylpyrrolidone, and a styrene-maleic anhydride copolymer. Thermofusible substances include stearamide,
Oleic acid amide, ethylene bisstearamide, benzenesulfoanilide, benzyloxyacetanilide, etc. can be used. Next, the acidic substance that can be used in the present invention has the property of developing color when it comes into contact with the fluoran compound, and specifically, 4-t-butylphenol, 4-phenylphenol, methyl-4
-Hydroxybenzoate, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene (2,6-dibromophenol), bis(4-hydroxyphenyl) sulfone, benzyl p-hydroxybenzoate, p-hydroxy Benzoic acid -sec-
Examples include conventionally known compounds such as butyl and 3-(α-methylbenzyl)salicylic acid. Note that two or more of these acidic substances can also be used in combination. Furthermore, various auxiliary agents can be added to the coating liquid. Examples include dispersants such as sodium dioctylsulfosuccinate and sodium dodecylbenzenesulfonate, ultraviolet absorbers such as benzophenone and triazole, antifoaming agents, fluorescent dyes, and coloring dyes. Supports include paper, plastic film,
Synthetic paper, woven fabric sheets, etc. are used, and paper is preferably used. The amount of coating on the support is not particularly limited, but is in the range of 2 to 15 g/m ² , preferably 3 to 10 g/m ² . Hereinafter, a usage example of a thermal recording paper using the fluoran compound of the present invention will be shown. The performance of the thermal recording paper was determined by the following test method. In other words, the decoloring density of the coloring agent in humidity after coloring by heating at each temperature (humidity decoloring resistance),
The color density, such as the decolorization density (oil resistance) upon contact with castor oil, was measured using a Macbeth RD-514 reflection densitometer. Thermal coloring was carried out using a Rhoday Aceta type thermotest tester (manufactured by the French National Textile Research Institute) under conditions of a heating temperature of 60 to 170°C, a heating time of 3 seconds, and a load of 100 g/m ² . Further, decoloring of the coloring agent after coloring by heating was carried out using a constant temperature and humidity tester. Usage example 1 Mixtures consisting of the following compositions were applied separately to a paint conditioner (trade name: Red Devil).
The mixture was ground for 3 hours to prepare liquid, liquid, and liquid. 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 Nopco 1407, San Nopco product) 2 parts by weight Liquid composition Bisphenol A 6 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Part water 14 parts by weight Liquid composition Aluminum hydroxide 10 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Water 10 parts by weight Liquid, liquid, liquid and water were mixed in a weight ratio of 3:9:5:3, and heat-sensitive recording paper was prepared. I got paint for it. This paint is applied to the surface of high-quality paper using a wire bar so that the solid content after drying is 5 g/m ² , and the paint is placed in a blower dryer and dried at room temperature to produce the thermal recording paper (A) according to the present invention. Obtained. Comparative Example 1 Comparative thermal recording papers (T) to (S) were obtained in exactly the same manner except that a liquid or liquid or liquid was used instead of the liquid in Use Example 1. Liquid composition 2-(2-chlorophenyl)amino-6-N,
N-dibutylaminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 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 Liquid composition 2-anilino-3-methyl-6-N-ethyl-
N-isoamylamino-fluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% Antifoaming agent (San Nopco 1407) 2 parts by weight Thermal recording paper according to the present invention and comparative thermal recording paper obtained as above The coloring sensitivity, moisture decoloring resistance, and oil resistance were tested. Table 1 shows the results.
Shown below. Usage example 2 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylaminofluorane used in usage example 1 was replaced with 2-anilino-3-
Methyl-6-N-ethyl-N-tetrahydrofurfurylaminofluorane, 2-anilino-3-methyl-6-N,N-di-tetrahydrofurfurylamino-fluorane, 2-(2-chlorophenyl)
-amino-6-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3
-chloro-6-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-(2-chlorophenyl)-amino-6-N,N-di-tetrahydrofurfurylamino-fluorane, 2-anilino-3-methyl -6-N-isoamyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-methyl-6-N-butyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-methyl-6-N -(p-tolyl)-N
-tetrahydrofurfurylamino-fluorane,
2-anilino-3-methyl-6-N-cyclohexyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-ethoxyethyl-6
-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-phenyl-
6-N-Methyl-N-tetrahydrofurfurylamino-fluorane, 2-anilino-3-benzyl-6-N-methyl-N-tetrahydrofurfurylamino-fluorane, 2-(4-benzoylphenyl)-amino- 3-ethyl-6-N-methyl-
N-tetrahydrofurfurylamino-fluorane, 2-(2-fluorophenyl)-amino-6-
Thermal recording papers (B) to (Y) were obtained in the same manner as in Use Example 1 using N-methyl-N-tetrahydrofurfurylaminofluorane. Performance tests on the thermal recording paper according to the present invention were carried out in the same manner as in Use Example 1. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, the thermal recording paper using the fluoran compound of the present invention was extremely excellent in color development sensitivity, moisture decoloring resistance, and oil resistance. In particular, the fluoran compound of the present invention is superior in color development sensitivity and oil resistance compared to comparative thermal recording paper, and is useful in various recording fields, especially for high-speed recording.
It had sufficient practical value as thermal recording paper for POS.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ is hydrogen, an alkyl group having 1 to 8 carbon atoms,
It represents a tetrahydrofurfuryl group, a phenyl group or a cyclohexyl group which may be substituted with an alkyl group, and R ₂ is hydrogen, chlorine, fluorine, a lower alkyl group, a lower alkoxy group, a lower alkoxyalkyl group, a phenyl group or a benzyl group. and R ₃ represents hydrogen, chlorine, fluorine, a lower alkyl group or an acetyl group. ) A fluoran compound characterized by having a tetrahydrofurfurylamino group at the 6-position represented by: