JPH0376346B2 - - 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 an alkoxyalkyl group at the 3-position and useful as a dye precursor for use in heat-sensitive recording paper, electrically conductive heat-sensitive recording sheets, and photosensitive color recording sheets. be. 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 thermal recording paper, electrically conductive thermal recording paper, thermal 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 aimed at improving the above-mentioned drawbacks, the present inventors found that a new fluoran compound represented by the general formula (I) described below is a colorless or light-colored solid that is stable in the atmosphere, and that it comes into contact with acidic substances. It has been found that by using these compounds, a deep black color is developed, and by using these compounds, the performance as a heat-sensitive recording paper is significantly improved. That is, the present invention provides general formula (I), (In the formula, R ₁ and R ₂ are each hydrogen atom, carbon number 1
-8 linear or branched alkyl group, cyclohexyl group, phenyl group or benzyl group,
_R3 is a hydrogen atom, a chlorine atom, a fluorine atom, a lower fluoroalkyl group, an acetyl group, and has 1 to 8 carbon atoms.
represents an alkoxy group, an alkoxyalkyl group having a total of 2 to 8 carbon atoms, or a linear or branched alkyl group having 1 to 8 carbon atoms, and R ₄ is an alkoxy group having 1 to 8 carbon atoms;
8 straight chain or branched alkyl group, cyclohexyl group, phenyl group or benzyl group, n
represents an integer from 1 to 8. ) It relates to a fluoran compound characterized by having an alkoxyalkyl group at the 3-position. The novel fluoran compound represented by general formula (I) of the present invention is produced by the following method. general formula (In the formula, R ₃ , R ₄ and n are the same as defined above, and R ₅ represents a hydrogen atom, an acetyl group or a lower alkyl group.) A diphenylamine derivative represented by the general formula (wherein R ₁ and R ₂ are the same as defined above) is reacted with a benzophenone derivative represented by the formula (wherein R 1 and R 2 are 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. Add toluene and 5-10% aqueous sodium hydroxide solution to the cake, and stir under reflux for 1-3 minutes.
Stir for a while, separate the toluene layer, wash with water, concentrate, and collect the precipitated crystals by filtration. General formula that is slightly colored by drying the crystals
A novel fluoran compound represented by (I) can be obtained with high purity and high yield. Toluene, if necessary
Recrystallize from volatile organic solvents like acetone, butyl acetate, hexane, etc. Condensing agents used in the present invention include concentrated sulfuric acid, acetic anhydride, phosphoric acid, polyphosphoric acid, phosphorus oxychloride, and zinc chloride. A preferred method for production is to use 80 to 100% sulfuric acid, which is both a solvent and a condensing agent for the benzophenone compound represented by the above general formula (). 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 heat-sensitive recording paper containing the fluoran compound of the present invention obtained as a color former has excellent coloring sensitivity, moisture decoloring resistance, and oil resistance, and has a low background density (background fogging). It had the following characteristics: Next, the present invention will be explained by examples. Example 1 2-anilino-3-ethoxyethyl-6-diethylaminofluoran [Compound No. 1]. 2-(2-hydroxy-4-
diethylamino)phenylcarbonylbenzoic acid 15
After completely dissolving the mixture while maintaining the temperature at approximately 8 to 14°C, 10 g of 2-ethoxyethyl-4-methoxydiphenylamine was added and the reaction was carried out at 20 to 25°C for 10 hours. In addition, an aqueous sodium hydroxide solution was added to adjust the pH to 10 or higher. The precipitate was collected by filtration. toluene in cake
After adding 450 ml and 340 g of 10% aqueous sodium hydroxide solution and stirring under reflux for 2 hours, the toluene phase 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 the cake with 150 ml of methanol, the crystals were collected again by filtration. The crystals were dried to obtain 11 g of slightly pink 2-anilino-3-ethoxyethyl-6-diethylaminofluorane. The melting point of this fluoran compound was 150.5-152.5°C.
In addition, the λmax and molecular extinction coefficient of this compound in 95% acetic acid solution are 449nm (19.4×10 ⁴ ), 595n
m (1.73×10 ⁴ ). A solution obtained by dissolving this product in toluene was colorless, but it quickly developed color due to the silica gel, giving it a reddish-black color. Example 2 2-anilino-3-ethoxyethyl-6-di-
n-Butylaminofluorane [Compound No. 2] 2-(2-hydroxy-4-
Add 15g of di-n-butylamino)phenylcarbonylbenzoic acid and dissolve completely while keeping at about 8-14℃, then add 10g of 2-ethoxyethyl-4-methoxydiphenylamine and heat at 20-25℃. Reacted for 10 hours. A slightly pink 2-anilino-
10 g of 3-ethoxyethyl-6-di-n-butylaminofluorane was obtained. The melting point of this thing is 126
The temperature was ~128°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 reddish-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 solvent (dispersion medium) that can be used is most preferably water, and 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-dipromophenol), bis(4-hydroxyphenyl) sulfone, benzyl p-hydroxybenzoate, p- Hydroxybenzoic 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, the thermal recording paper using the fluoran compound of the present invention will be described with reference to usage examples. The performance of the thermal recording paper was determined by the following test method. In other words, the color density in terms of the background density, the decoloring density of the coloring agent in humidity after color development by heating at each temperature (moisture decoloring resistance), the decoloring density when it comes into contact with castor oil (oil resistance), etc. , Macbeth RD
Measurements were made using a -514 reflection densitometer. Thermal coloring was performed using a low-day aceta type thermotest tester (manufactured by the French National Textile Research Institute) at a heating temperature of 60 to 170°C.
The heating time was 3 seconds and the load was 100 g/cm ² . Further, decoloring of the coloring agent after coloring by heating was carried out using a constant temperature and humidity tester. Usage example 1 Apply a paint conditioner (trade name: Red Devil) to each mixture with the following composition separately.
The mixture was ground for 3 hours to prepare liquid, liquid, and liquid C. Liquid composition 2-anilino-3-ethoxyethyl-6-diethylaminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (San Nobuco 1407, San Nobuco product) 2 parts by weight Bisphenol A 6 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts 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 in a ratio of 3:9:5:3 by weight A paint for heat-sensitive recording paper was obtained by mixing at the same ratio. 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 paper was prepared in exactly the same manner except that liquid or liquid was used instead of the liquid in Use Example 1.
I got (nu)~(ru). Liquid composition 2-anilino-3-methyl-6-diethylaminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (Sannobuco 1407) 2 parts by weight Liquid composition 2-anilino-3-methyl-6- N-methyl-
N-cyclohexyl-aminofluorane
4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (San Nobuco 1407) 2 parts by weight Color properties, oil resistance, and background fog were tested. The results are shown in Table 1. Usage example 2 2-phenylamino-3-ethoxyethyl- instead of 2-anilino-3-ethoxyethyl-6-diethylaminofluorane used in usage example 1
6-dibutylaminofluorane, 2-phenylamino-3-ethoxyethyl-6-N-cyclohexyl-N-methylaminofluorane, 2-phenylamino-3-ethoxymethyl-6-diethylaminofluorane, 2-phenylamino-3- Ethoxymethyl-6-dibutylaminofluorane, 2
-phenylamino-3-isopropoxymethyl-
6-N-cyclohexyl-N-methylaminofluorane, 2-phenylamino-3-octoxyethyl-6-N-benzyl-N-methylaminofluorane, 2-(2-chlorophenylamino)-3-
Butoxypropyl-6-N-phenyl-N-isopropylaminofluorane or 2-(2-fluorophenylamino)-3-cyclohexylolaxybutyl-6-cyclohexylaminofluorane was used in the same manner as in Example 1. Thermal recording paper
I got (b)～(li). 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 has color development sensitivity,
It has excellent moisture fade resistance and oil resistance.
It also had characteristics such as a small background fog. In particular, compared to comparative thermal recording paper, it is superior in color development sensitivity, moisture decoloring resistance, and oil resistance, and is used in various recording fields, especially for high-speed recording, POS
It had sufficient practical value as a thermosensitive recording paper.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ and R ₂ are each hydrogen atom, carbon number 1
-8 linear or branched alkyl group, cyclohexyl group, phenyl group or benzyl group,
R ₃ is a hydrogen atom, a chlorine atom, a fluorine atom, a lower fluoroalkyl group, an acetyl group, an alkoxy group having 1 to 8 carbon atoms, an alkoxyalkyl group having a total number of 2 to 8 carbon atoms, or a straight alkoxy group having 1 to 8 carbon atoms. Represents a chain or branched alkyl group, R ₄ has 1 to 8 carbon atoms
represents a straight chain or branched alkyl group, cyclohexyl group, phenyl group or benzyl group, and n represents an integer of 1 to 8. ) A fluoran compound having an alkoxyalkyl group at the 3-position represented by: