JPH03169883A - Fluorane compound, its production and heat-sensitive recording material containing the compound - Google Patents

Abstract

NEW MATERIAL:3-N-cyclohexyl-N-n-propylamino-6-methyl-7-anilinofluorane. USE:A color-developing compound for heat-sensitive recording material. PREPARATION:2-(4'-N-cyclohexyl-N-n-propylamino-2'-hydroxybenzoyl)benzoic acid of formula II is made to react with a diphenylamine derivative of formula III (R is lower alkyl) (e.g. 4-methoxy-2-methyldiphenylamine) e.g. in the presence of a dehydrative condensation agent such as concentrated sulfuric acid at 0-50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fluoran compound useful as a color-forming compound used in a heat-sensitive recording material, a method for producing the same, and a heat-sensitive recording material containing the compound.

[Conventional technology]

2. Description of the Related Art Conventionally, thermosensitive recording using a color reaction between a colorless or light-colored electron-donating compound (color-forming compound) and an organic or inorganic electron-accepting substance (color developer) has been widely used.

In this recording method, fluoran compounds are widely used as color-forming compounds.

Conventionally, as a fluoran compound, for example, formula (A) formula (B) and Eq. (C) (Special Publication No. 48-43296) (Special Publication No. 51-23204) (Unexamined Japanese Patent Publication No. 60-35053) compounds are known.

However, when the compound of formula (A) is used in a heat-sensitive recording material, the mixture with a color developer such as bisphenol A produces a gray or black-gray color by itself, and when applied to paper, it produces a gray or black-gray color. Colored black and gray (
The disadvantage was that only paper with smudges could be obtained.

Further, although the compound of formula (B) or formula (C) can provide paper with a relatively high degree of whiteness immediately after being applied, it has the disadvantage that it discolors from gray to brown due to humidity, light, or heat.

Recently, heat-sensitive recording materials have come to be used not only indoors, such as in facsimile machines, but also outdoors, and under harsher conditions, such as in prepaid cards, such as telephone cards. Ta. Therefore, heat-sensitive recording materials are required to have even higher storage stability.

[Problem to be solved by the invention]

An object of the present invention is to provide a novel fluoran compound with excellent storage stability as a color forming compound for heat-sensitive recording materials, and also to provide a method for producing this compound and a heat-sensitive recording material containing this compound. It is to provide.

[Means to solve the problem]

The present inventors have searched for various compounds to solve the above-mentioned problems and have arrived at the present invention.

That is, the present invention is a fluoran compound represented by formula (I), which is combined with a benzoic acid derivative represented by formula (II) and general formula (III) (wherein R represents a lower alkyl group). A heat-sensitive recording material characterized by containing the fluoran compound.

The benzoic acid derivative of formula (II) used to produce the fluoran compound of formula (I) of the present invention is typically:
3-N-cyclohexy-N-n-propylaminophenol and phthalic anhydride are mixed without solvent or in benzene,
It can be produced by reaction in a solvent such as toluene, xylene or tetrachloroethylene. Further, during this reaction, a Lewis acid such as zinc chloride may be added.

Further, in the diphenylamine derivative represented by the general formula (III), in the general formula (III), R represents a lower alkyl group, and preferred examples of the lower alkyl group include a methyl group or an ethyl group. can.

In particular, methyl group is preferred.

The fluoran compound of formula (I) can be prepared by combining the benzoic acid derivative of formula (II) and the diphenylamine derivative of general formula (II It can be suitably produced as an alkaline product after reaction in the presence of a dehydration condensation agent such as aluminum chloride, more preferably in concentrated sulfuric acid. -The reaction of dehydration condensation is o-
Reaction temperatures of 100°C are preferred, particularly when the reaction is carried out in concentrated sulfuric acid, temperatures of 0 to 50°C are particularly preferred. Although the reaction time largely depends on the reaction temperature, it is usually preferable to carry out the reaction for several hours to 100 hours. After dehydration and condensation, an alkaline treatment is usually performed, but when an alkali treatment is performed, it is preferable to adjust the pH to 9 to 12 with potassium hydroxide, sodium hydroxide, etc., and carry out at a temperature range of 0 to 100°C. . At this time, the alkali treatment may be performed in the presence of a solvent such as benzene or toluene as a solvent other than water.

In order to use the fluoran compound of the present invention in a heat-sensitive recording material, the fluoran compound of formula (I) and a color developer (for example, bisphenol A or its halides, alkylated products,
Dihydroxydiphenyl sulfone or its halides, alkylated hydroxybenzoic acid esters, phenols such as hydroquinone monoethers, organic color developers such as salicylic acid derivatives, salicylic acid amide derivatives, urea derivatives, thiourea derivatives, acid clay , attapulgite, activated clay, aluminum chloride, zinc bromide) into a fine aqueous dispersion of a binder (e.g., polyvinyl alcohol or its modified products, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gum arabic, salts of styrene-maleic anhydride copolymers, isobutylene-acrylic acid monomaleic anhydride copolymers, etc.), pigments (talc, kaolin, calcium carbonate, etc.), and, if necessary, sensitizers (higher fatty acid amides). , esters of aromatic carboxylic acids or sulfonic acids, aromatic or aromatic group-substituted aliphatic ethers, aromatic or aromatic group-substituted aliphatic hydrocarbons (generally known sensitizers for heat-sensitive recording materials), and other Additives (e.g., ultraviolet absorbers, antifoaming agents, etc.) are added to make a fine dispersion, and the mixture is coated on a suitable support (e.g., paper, plastic sheet, resin-coated paper, etc.), and thermal recording is performed. Can be used as a material. Of course, it can also be used in a system using a solvent instead of an aqueous dispersion system without any problem.

The compound of formula (I) can be used alone as a color-forming compound, and furthermore, for example, in order to adjust the color, other color-forming compounds such as triphenylmethane lactones, fluorans, subiropyran can be used. It is also possible to mix and use these as desired.

The melting point of the fluoran compound of formula (I) of the present invention is from 257 to
258°C, and the melting point of the known compound of formula (A) is 19
5-198° C1 The melting point of the compound of formula (B) is 195-1
97°C, and the melting point of the compound of formula (C) is 124 to 126
It is very high compared to ℃.

Furthermore, the compounds of the present invention have extremely low solubility in various organic solvents (eg, hydrocarbon solvents such as benzene and toluene, esters such as ethyl acetate, and ketones such as acetone). For example, the results of comparing the solubility in toluene with the compounds of formulas (A), (B) and (C) are shown in Table 1.

Solubility was expressed as weight % in toluene at 25°C.

Table 1: When the compound of the present invention having the above-mentioned properties is used in a heat-sensitive recording material, a thermal paper with high whiteness without background staining can be obtained, and the storage stability of the paper (e.g., heat and humidity resistance, solvent resistance) can be obtained.
is very good. For example, a thermal paper using bisphael A as a color developer and a compound of formula (I) of the present invention as a color-forming compound and a compound of formula (A), formula (B), or formula (C
Table 2 shows the results of a comparison of the heat-moisture resistance and oil resistance of the background (uncolored area) of heat-sensitive recording paper using the compound (2).

In the heat-and-moisture resistance test, thermal paper prepared using each compound was held at 60° C. and 90% relative humidity for 24 hours, and stains on the paper were visually observed.

In addition, in the oil resistance test, thermal paper was brought into contact with dioctyl phthalate, left for one week, and then soiling of the paper was visually observed.

In the table; O represents paper with high whiteness without background stains, Δ represents paper with slightly gray background stains, and × represents paper with gray background stains.

The fluoran compound of formula (I) of the present invention has a structure that differs from the fluoran compounds of formula (A), formula (B), and formula (C) only in the substituent on the amino group at the 3-position in the fluoran structure, In particular, the only structural difference from the fluoran compound of formula (B) is that one methyl group on the amino group is converted to an n-probyl group. ) has a much higher melting point than fluoran compounds, and also has very low solubility in organic solvents. When the metal fluoranide of the formula (1) of the present invention having such properties is used in a thermal recording material, the storage stability of the thermal paper is greatly improved.

In particular, with regard to solubility in organic solvents, converting a methyl group to a longer chain alkyl group, such as converting a methyl group to an n-probyl group, usually results in lower solubility in organic solvents, especially hydrocarbon solvents. It is believed that the price will increase. However, the fluoran compound of formula (I) of the present invention and the formula (
When comparing the solubility of the fluoran compound of formula (A) in toluene, it is surprising that the fluoran compound of formula (I) has a much lower solubility than the fluoran compound of formula (A).

In particular, regarding solubility in organic solvents, when a longer chain alkyl group is introduced, for example, in the compound of formula (D) in which the methyl group on the amino group of the compound of formula (B) is changed to an isoamyl group, organic solvents become more soluble. It is known that the solubility is particularly high in hydrocarbon solvents (eg, toluene) (eg, JP-A-54-34909).

However, the fluoran compound of formula (I) of the present invention having an n-probyl group on the amino group has a previously undiscovered characteristic that it has a very low solubility in toluene compared to the fluoran compound of formula (B). By using this as a color-forming compound, it is possible to provide a thermosensitive recording paper with excellent storage stability.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example I [Preparation of compound of formula (I)] 2-(4'-N-cyclohexyl-N-n-propylamino-2'-hydroxybenzoyl)benzoic acid [formula (I)
After dissolving 20 g of compound t) in 100-m concentrated sulfuric acid at 10°C, 4-methoxy-2-methyldiphenylamine [compound in which R is a methyl group in general formula (III)] Ilg
1. Invite the same person to my 11-9. ? -- Discharge the Gashin 3 mixture into 600 ml of ice water, collect the precipitated solid, wash with water, and add 10% NaOH to the solid.
The mixture was added to water (500 d) and stirred at 60-70°C for 2 hours. After filtering the solid and washing with water, add isopropanol 100-
Washed with.

Furthermore, the desired 3-N-cyclohexy-N-n-propylamino-6-methyl-
20 g (yield 69%) of 7-anilinofluorane was obtained as almost colorless crystals.

Melting point 257-258°C. The infrared absorption spectrum of this compound (KBr tablet) is shown in FIG. Further, a powder X-ray diffraction pattern is shown in FIG.

Example 2 [Preparation of thermal recording paper using the compound of formula (I)] lOg of linofluorane, 5g of 10% polyvinyl alcohol aqueous solution and 37. Sand mill 5g of the mixture to particle size 3.
Atomized to μ. On the other hand, bisphenol A was similarly dispersed to obtain a 38% developer dispersion. This color developer dispersion 65
．． 8 g, 50 g of the aqueous dispersion of the above 3-N-cyclohexyl-N101 probylamino-6-methyl-7-anilinofluorane, 18.3 g of a 60% light calcium carbide aqueous dispersion, 100% poly 88 g of vinyl alcohol aqueous solution and 51.9 g of water were mixed.

This mixed solution was coated on white base paper using wire rond NIllO, and then air-dried at room temperature to obtain a very white thermosensitive recording paper with no background stains. This thermosensitive recording paper very quickly developed a slightly reddish black color upon heating.

The storage stability (heat resistance, moist heat resistance, light resistance, etc.) of this colored image was good.

In addition, this thermal recording paper was heated at 60°C and 90% relative humidity.
When stored for 24 days, the paper maintained its whiteness immediately after application,
No dirt was observed at all. Further, when the surface of the paper was brought into contact with dioctyl phthalate and then stored for one week, no scumming was observed on the paper (Table 2).

Comparative Example In Example 2, 3-N-cyclohexylN-n-
3-N-ethyl-N-ethylamino-6-methyl-7-anilinofluorane [compound of formula (A)] or 3-N-cyclohexyl-N-methylaminofluorane in place of brobylamino-6-methyl-7-anilinofluorane 6-
Methyl-7-anilinofuran [compound of formula (B)]
and 3-N-cyclohexyl-N-n-cutylamino-6-methyl-7-anilinofluorane [formula (C)
Compounds] were used to prepare thermosensitive recording paper according to the method described in Example 2, and a heat-and-moisture resistance test and a liquor test were conducted. The results are shown in Table 2.

The surface of the heat-sensitive recording paper coated with the compound of formula (A) was already slightly gray and stained immediately after coating.

[Brief explanation of the drawing]

FIG. 1 shows an infrared absorption spectrum (KBr tablet) of the fluoran compound of formula CI). The vertical axis represents transmittance, and the horizontal axis represents wave number (am-'). FIG. 2 shows a powder X-ray diffraction pattern of the fluoran compound of formula (I). The vertical axis represents the diffraction intensity, and the horizontal axis represents the diffraction angle (2θ).

Claims (3)

[Claims] (1) Formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) A fluoran compound represented by (2) Formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) Benzoic acid derivatives represented by and general formula (III) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III) (In the formula, A method for producing a fluoran compound represented by formula (I) according to claim (1), characterized in that the fluoran compound is reacted with a diphenylamine derivative represented by (R represents a lower alkyl group). (3) A heat-sensitive recording material containing a fluoran compound represented by formula (I) according to claim (1).