JPH0376679B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal recording paper using a novel fluoran compound. More specifically, the present invention provides a dye precursor having 1 to 1 carbon atoms at the 10th and/or 11th position, which is useful as a dye precursor for use in heat-sensitive recording paper, electrically conductive heat-sensitive recording paper sheets, and photosensitive color recording sheets.
The present invention relates to a thermal recording paper using a novel fluoran compound characterized by having 4 lower alkyl groups. 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 general formula ( It has been found that the performance as a heat-sensitive recording paper is significantly improved by using these compounds, which develop a blackish color. That is, the present invention is based on the general formula () (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclohexyl group, a tetrahydrofuryl group, or a cyclohexylmethyl group, and R ₃ is a hydrogen atom. , represents a halogen atom, a methyl group, a benzyl group, or an alkoxyalkyl group having a total number of carbon atoms of 2 to 8,
X represents a hydrogen atom or a halogen atom, and R ₄ and R ₅ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. However, at least one of R ₄ and R ₅ is an alkyl group. ) is a heat-sensitive recording paper containing a fluoran compound having a lower alkyl group at the 10th and/or 11th positions as a coloring agent. The novel fluoran compound represented by the general formula () used in the present invention is produced by the following method. general formula (In the formula, R ₃ and X have the same meanings as defined above,
R ₆ represents a hydrogen atom, an acetyl group, or a lower alkyl group. ) and a diphenylamine derivative represented by the general formula (In the formula, R ₁ , R ₂ , R ₄ and R ₅ have the same meanings as defined above.) in the presence of 80 to 100% sulfuric acid at a temperature of 0 to 80°C. Allow time to react. After the reaction, add the reaction mixture to water, add sodium hydroxide, and adjust the pH to 8-8.
10 and collect the precipitate by filtration. Add toluene and a 5-10% aqueous sodium hydroxide solution to the cake, stir under reflux for 1-3 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.
Toluene, acetone, butyl acetate, if necessary.
Recrystallize from volatile organic solvents such as hexane. 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 () used in the present invention will be described. The hue is
Shows the hue when developed on a thin layer of silica gel.

[Table] The thermosensitive recording paper containing at least one of the novel fluoran compounds obtained as a color former was excellent in coloring sensitivity, moisture decoloring resistance, and oil resistance. Next, the present invention will be explained in more detail with reference to production examples and examples. Production Example 1 2-(2-chlorophenylamino)-6-diethylamino-10-methylfluorane (Compound No.
1) and 2-(2-chlorophenylamino)-
6-diethylamino-11-methylfluorane (compound No. 2) 2-(2'-hydroxy-4'-
Add 15 g of a mixture of 2-(2'-hydroxy-4'-diethylaminophenylcarbonyl)-5-methylbenzoic acid and 2-(2'-hydroxy-4'-diethylaminophenylcarbonyl)-4-methylbenzoic acid, and heat completely while keeping at about 0 to 10°C. After dissolving, 13 g of 2-chloro-4'-methoxydiphenylamine was added and reacted at 20-25°C for 10 hours. The reaction mixture was added to 1 cup of ice water, and then an aqueous sodium hydroxide solution was added to adjust the pH to 10 or higher. . The precipitate was collected by filtration. 450 ml of toluene and 340 g of 10% aqueous sodium hydroxide solution were added to the cake, and after 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 200 ml of methanol to the cake, the crystals were collected again by filtration, and further fractionated by column chromatography. The crystals were dried and turned into a slightly pink 2-
(2-Chlorphenylamino)-6-diethylamino-10-methylfluoran (Compound No. 1) 8 g and 2-(2-chlorophenylamino)-6-diethylamino-11-methylfluoran (Compound No. 2)
6g was obtained. The melting points of these fluoran compounds were all 193°C to 195°C. In addition, the λ _nax and molecular extinction coefficient of these compounds in 95% acetic acid solution are both 438 nm (1.90 × 10 ⁴ ) and 580 nm.
(1.68×10 ⁴ ). A solution prepared by dissolving these substances in toluene was colorless and quickly developed color due to the silica gel, giving it a reddish-black color. Production Example 2 2-(2-chlorophenylamino)-6-diethylamino-10-methylfluoran (Compound No.
3) and 2-(2-chlorophenylamino)-
6-dibutylamino-11-methylfluorane (compound No. 4) 2-(2'-hydroxy-4'-
Add 15 g of a mixture of dibutylaminophenylcarbonyl)-5-methylbenzoic acid and 2-(2'-hydroxy-4'-dibutylaminophenylcarbonyl)-4-methylbenzoic acid, and while maintaining the temperature at about 0 to 10°C. After complete dissolution, 13 g of 2-chloro-4'-methoxydiphenylamine was added and reacted at 20-25°C for 10 hours. After being treated in the same manner as in Production Example 1 and recrystallized from methanol, it was fractionated by column chromatography to obtain pale pink 2-(2-chlorophenylamino)-6-dibutylamino-10-methylfluorane ( Compound No. 3) 7g and 2-(2
5 g of -chlorophenylamino)-6-dibutylamino-11-methylfluorane (Compound No. 4) was obtained. The melting point of these things is 178℃~180℃ (No.
3) and 176 to 179°C (No. 4), and the solution obtained by dissolving these in toluene was colorless, but quickly developed color due to the silica gel, and took on a reddish-black color. Production Example 3 2-anilino-3-methyl-6-N-cyclohexyl-N-methylamino-10-methylfluorane (compound No. 5) and 2-anilino-3-methyl-6-N-cyclohexyl-N- Methylamino-11-methylfluorane (compound No. 6) 2-(2'-hydroxy-
4'-N-cyclohexyl-N-methylaminophenylcarbonyl)-4-methylbenzoic acid and 2-
(2'-hydroxy-4'-N-cyclohexyl-N
-Methylaminophenylcarbonyl)-5-methylbenzoic acid (15g) was added, and after completely dissolving it while keeping the temperature at about 0~10℃, 13g of 2-methyl-4-methoxydiphenylamine was added and the mixture was heated to 20~25℃. at °C
Reacted for 10 hours. After being treated in the same manner as in Production Example 1 and recrystallized from methanol, a pale pink 2-anilino-3 was obtained by fractionating it by column chromatography.
-Methyl-6-N-cyclohexyl-N-methylamino-10-methylfluorane (Compound No. 5) 4
g and 2.5 g of 2-anilino-3-methyl-6-N-cyclohexyl-N-methylamino-11-methylfluorane (Compound No. 6) were obtained. The melting points of these are 124-126℃ (No. 5) and 121.5
~124°C (No. 6), and the solution obtained by dissolving these substances 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, pulverized and dispersed separately, 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. For example, dispersants such as sodium dioctyl sulfosuccinate and sodium dodecylbenzenesulfonate, ultraviolet absorbers such as benzophenone and triazole, and other antifoaming agents,
Examples include fluorescent dyes and colored 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, thermal recording paper using a fluoran compound will be shown as an example. 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),
Color densities such as decolorization densities (oil resistance) upon contact with castor oil were measured using a Macbeth RD-514 reflection densitometer. Thermal color development 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/cm ² . Further, decoloring of the coloring agent after coloring by heating was carried out using a constant temperature and humidity tester. Example 1 A mixture consisting of the following composition was separately applied with a paint conditioner (trade name Red Devil).
The mixture was ground for 3 hours to prepare liquids (A), (B), and (C). (A) Liquid composition 2-(2-chlorophenylamino)-6-diethylamino-10-methylfluorane 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 (B) Liquid composition Bisphenol A 6 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Water 14 parts by weight (C) Liquid composition Aluminum hydroxide 10 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Water 10 parts by weight (A A paint for heat-sensitive recording paper was obtained by mixing liquids (), (B), (C) and water in a weight ratio of 3:9:5:3. This paint was applied to the surface of high-quality paper using a wire bar so that the solid content weight after drying was 5 g/m ² , and the paint was placed in a blow dryer and dried at room temperature to obtain the thermal recording paper (A) of the present invention. Ta. Comparative Example 1 Comparative thermal recording paper (G) was prepared in the same manner as in Example 1 except that liquid (D) or liquid (E) was used instead of liquid (A)
I got (ch). (D) Liquid composition 2-(2-chlorophenylamino)-6-dibutylaminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (San Nopco 1407) 2 parts by weight (E) 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 Coloring sensitivity, moisture decolorization resistance, and oil resistance of the thermal recording paper of the present invention and for comparison obtained as described above was tested. The results are shown in Table 1. Example 2 Instead of 2-(2-chlorophenylamino)-6-diethylamino-10-methylfluorane used in Example 1, 2-(2-chlorophenylamino)-6-diethylamino-11- Methylfluorane, 2-(2-chlorophenylamino)-6-dibutylamino-10-methylfluorane, 2-(2
-chlorophenylamino)-6-dibutylamino-11-methylfluorane, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylamino-10-methylfluorane and 2-anilino-
Thermal recording papers (b) to (f) were obtained in the same manner as in Example 1 using 3-methyl-6-N-cyclohexyl-N-methylamino-11-methylfluoran. A performance test of these thermal recording papers of the present invention was carried out in Example 1.
I did the same thing. The results are shown in Table 1.

[Table] As is clear from the results in Table 1, the heat-sensitive recording paper of the present invention was extremely excellent in color development sensitivity, moisture fade resistance, and oil resistance. In the above general formula,
Due to the effect of introducing an alkyl group into at least one of R ₄ and R ₅ , compared to the comparative thermal recording paper (g) to (h), it is particularly excellent in color development sensitivity, moisture decoloring resistance, and oil resistance, respectively. It has sufficient practical value as a thermal paper for various recording fields, especially high-speed recording and POS. Example 3 Instead of 2-(2-chlorophenylamino)-6-diethylamino-10-methylfluoran used in Example 1, 2-anilino-3-methyl-
6-N-cyclohexyl-N-methylamino-10
- 2 parts by weight of methylfluorane and 2-anilino-3-methyl-6-N-cyclohexyl-N-
A thermosensitive recording paper (2) was obtained in the same manner as in Example 1 using a mixture of 2 parts by weight of methylamino-11-methylfluorane. A performance test of the thermal recording paper of the present invention was conducted in the same manner as in Example 1. As a result, the color development sensitivity is 116, the moisture decolorization resistance is 96.1, and the oil resistance is 50.
Compared to thermal recording paper (G) to (H) of Comparative Example 1 in Table 1,
It was excellent in color development sensitivity, moisture decoloring resistance, and oil resistance.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclohexyl group, a tetrahydrofurfuryl group, or a cyclohexylmethyl group, and R ₃ is hydrogen atom,
represents a halogen atom, a methyl group, a benzyl group, or an alkoxyalkyl group having a total number of carbon atoms of 2 to 8, X represents a hydrogen atom or a halogen atom, R ₄ ,
R ₅ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. However, at least one of R ₄ and R ₅ is an alkyl group. ) A thermal recording paper characterized by containing a fluoran compound represented by the following as a coloring agent.