JPH03236989A - Color forming compound for recording material - Google Patents

Abstract

PURPOSE:To obtain a developed color image having rapid color forming properties and light fastness by using a color forming compound for a recording material represented by a specific general formula as a blue color former. CONSTITUTION:A color forming compound for a recording material represented by formula I (wherein R<1> and R<2> are respectively a hydrogen atom, a lower alkyl group, a benzyl group or a phenyl group which may be substituted with an alkyl group and R<3> and R<4> are respectively a lower alkyl group, a benzyl group or a phenyl group which may be substituted with a halogen atom or a trifluoromethyl group) is used. This compound itself is an almost colorless or slightly monochromatically colored substance and rapidly shows a blue - bluish green developed hue by the contact with an electron acceptive substance, for example, an org. acid, acidic clay, a phenol/formalin resin, a metal salt of aromatic carboxylic acid or phenols and used in a color forming recording material, especially, a pressure-sensitive recording material, a thermal recording material or an electrothermorecording material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a color-forming compound for recording materials represented by the following general formula (1).

[In the formula, R1 and R2 each represent a hydrogen atom, a lower alkyl group, a benzyl group, or a phenyl group optionally substituted with a lower alkyl group, and R3 and R4 each represent a lower alkyl group, a benzyl group, or a halogen atom, Represents a phenyl group which may be substituted with a trifluoromethyl group. [In the formula, R1 and R2 each represent a hydrogen atom, a lower alkyl group, a benzyl group, or a phenyl group optionally substituted with a lower alkyl group, and R3 and R4 each represent a lower alkyl group, a benzyl group, or a halogen atom. , represents a phenyl group optionally substituted with a trifluoromethyl group. ] The compound represented by the general formula (1) is itself an almost colorless or slightly monochromatic substance, and contains electron-accepting substances such as organic acids, acid clay, phenol-formalin resins, and aromatic carboxylic acids. It rapidly develops a coloring hue from blue to blue-green upon contact with metal salts, phenols, etc., and is useful as a color-forming compound used in color-forming recording materials, especially pressure-sensitive recording materials, heat-sensitive recording materials, and electrically conductive heat-sensitive recording materials. It is something.

[Prior Art and Problems to be Solved by the Invention]-a) The following conditions are required for the color-forming compound used in the recording material.

(1) The compound quickly develops a deep color upon contact with an electron-accepting substance (2) It has good solubility in organic solvents (especially non-polar) (especially in the case of pressure-sensitive materials) (3) The compound During storage, there should be no decomposition, coloring, or other changes due to heat, light, moisture, etc. (4), and the colored image of the compound should be robust and stable against heat, light, moisture, etc. (5), sublimation. Crystal violet lactone with structure A, which is currently used in the largest quantity as a blue coloring agent, satisfies other conditions, but has low light fastness of colored images. The actual situation is that it is put to practical use in combination with N-benzoylleucomethylene blue of structure B described later, which has extremely poor color development and slow color development but good light resistance.

In addition, fluoran compounds represented by shell structure C (see below), which are widely used as color formers of various hues such as orange, red, black, and green, generally use acid clay-based color developers as electron-accepting substances. When a phenolic resin developer is used, the color density is high but the light resistance is poor, and when a phenolic resin developer is used, the light resistance is improved but the color density is low.

As described above, a color-forming compound having sufficient performance as required has not yet been obtained, and improvement in performance is desired.

In particular, with regard to blue dyes, CVL is currently used as the main dye, although it still has many problems, and there is a desire to develop a substitute.

Compounds having a benzofluorane skeleton, which is the basic skeleton of the compounds of the present invention, are disclosed in JP-A No. 48-6804 and JP-A No. 48-Sho.
24816, JP-A-48-27810, JP-A-48-2
9776, JP-A-48-55009, JP-A-48-57
707, JP-A-49-3715, JP-A-49-4722
, JP-A-49-7017, JP-A-49-83510, and JP-A-4985314.

In particular, JP-A-48-55009 discloses the compound of the present invention in the form of a general formula. but,
This publication not only does not specifically disclose the compound of the present invention, but also does not disclose any compound that develops a blue color.

=5- [Means and effects for solving the problems] An object of the present invention is to provide a color-forming compound that satisfies the above-mentioned conditions as a color-forming agent.

The inventors of the present invention conducted extensive research and discovered a new compound represented by the following general formula (1), and found that this new compound distantly achieves the intended purpose.

represents an optional phenyl group. ] The compound of the present invention can be synthesized, for example, as follows. Of course, the present invention is not limited to this.

[Scheme 1] [In the formula, R1 and R2 each represent a hydrogen atom, a lower alkyl group, a benzyl group, or a phenyl group optionally substituted with a lower alkyl group, and R3 and RA each represent a lower alkyl group, a benzyl group, or substituted with a halogen atom or a trifluoromethyl group [Scheme 2] [Scheme 3] + 10- In the formula, R1, R2, R3, and RJ represent the same meanings as in the above general formula, and X represents a halogen atom.

In [Scheme 1], the condensation of the amino-substituted benzophenone carboxylic acid and the corresponding aminonaphthol is carried out at 20°C to 100°C in an acidic condensing agent. Preferably,
The condensation can be carried out in 70% to 98% sulfuric acid at 25°C to 100°C to obtain the corresponding benzofluorane precursors in good yields.

The obtained benzofluorane precursor is treated with an alkyl halide, in a polar solvent such as methanol, ethanol, butanol, ethyl cellosolve, dimethylformamide, dimethyl sulfoxide, or without a solvent in the presence of an alkali agent such as potassium carbonate or sodium carbonate. The desired benzofluorane derivative can be produced by reacting halogenated aralkyl, halogenated phenyl, dialkylated sulfuric acid, etc. at 50°C to 200°C.

[Scheme 2] [In Scheme 3, the condensation reaction and amino group substitution reaction mean the same operations.

1- All of the compounds thus obtained are new compounds, and are themselves colorless or light-colored substances. Upon contact with an electron-accepting substance, the material rapidly developed a color, showing a blue to blue-green image, and this image was extremely stable against heat, light, moisture, and the like.

Below, the results of a light resistance comparison test conducted by the present inventors will be shown in comparison with known color-forming compounds.

Test Method> The following tests were conducted on color formers having the following structures, including the compounds of the present invention.

■ Hinoki - Coloring agent alkylated naphthalene (KM (-113 Kureha Chemical) 7% solution 1g, gum arabic 9g, gelatin 9g)
g, 25 g of a solution obtained by heating and dissolving 150 g of water, and 2 drops of the prepared antifoaming agent were mixed and emulsified using a homogenizer.

This emulsion is applied to base paper for pressure-sensitive paper using a wire bar to obtain dye-coated paper (top paper).

The obtained upper paper is overlapped with the lower paper coated with an acidic clay color developer and brought into contact with pressure to develop color.

This colored image was irradiated with sunlight for 4 hours, and the image survival rate was measured using a Macbeth colorimeter (RD-514, manufactured by Macbeth, USA).

3-14- <Results> As shown in the table, the compounds of the present invention show excellent results in both color density and image retention rate.

Pressure-sensitive copying paper may be produced by any known method using the compound according to the present invention. For example, U.S. Pat.
00458, 2806457, etc., or the interfacial polymerization method described in British Patent Nos. 867, 797, 950443, etc., using a color former-containing solvent. It can be obtained by microcapsulating (synthetic oils such as alkylated naphthalene, alkylated biphenyl, alkylated terphenyl, alkylated diphenylmethane, etc.) and coating it on a support such as paper or plastic sheet.

In addition, for the production of heat-sensitive recording paper, for example,
A known method described in Japanese Patent No. 039 may be employed. In principle, a binder is dissolved or dispersed in a solvent or dispersion medium, a coloring agent, an electron-accepting substance, and a thermofusible substance are pulverized and mixed sufficiently finely, and the mixture is applied to a support such as paper or a plastic sheet, and then dried. It is something.

When producing pressure-sensitive copying paper, heat-sensitive recording paper, etc. using the compounds of the present invention, these dyes may be used alone as color formers, but in order to improve the color hue, color density, and image stability. It is also possible to use known color formers that develop various hues within a range that does not impair the performance of the compound of the present invention.

For example, 3.3-bis(aminophenyl)-6-aminophthalide, 3.3-bis(indolyl>6-phthalide, 3-aminofluorane, aminobenzofluorane, 2,6-cyamitsufluorane, 2゜6 - Basics of diami2-3-methylfluorane, spiropyran, phenoxazine, phenothiazine, leukoolamine, carbazolylmethane, 3-indolyl-3-(aminophenyl) phthalide, 3-indolyl-3-(aminophenyl) azaphthalide, etc. It is used in combination with a derivative of a compound having a skeleton.

When manufacturing pressure-sensitive copying paper, alkylbenzene-based, alkylbiphenyl-based, alkylnaphthalene-based, diallylethane-based, hydrogenated terphenyl-based, and chlorinated paraffin-based solvents are used singly or in combination as solvents for dissolving coloring agents. For encapsulation, a coacervation method, an interfacial polymerization method, or an in-5itu method can be employed.

As a color developer, clays such as clay, bentonite, activated clay, acid clay, salicylic acid, salicylic acid ester,
Zinc salts such as salicylic acid derivatives and phenol derivatives, 2.
Hydroxy compounds such as 2-bis(p-hydroxyphenyl)propane (bisphenol A), p-hydroxyandara, and fragrant esters, p-phenylphenol formalin resin, p-octylphenol formalin resin, and their zinc salts are used. .

In addition, in manufacturing thermal recording paper, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic, gelatin, casein, starch, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, etc. are used as binders. I can do it.

In this case, the color developer is 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenyl ether, 4-hydroxybenzoic acid methyl ester, 4-hydroxybenzoic acid benzyl ester, 2.2-
Bis(hydroxyphenyl)propane, 4,4'-thiodiphenol, bis-(4-hydroxy-3-methylphenyl) sulfide, 4,4''-dihydroxydiphenyl 7-sulfone, 4-hydroxy-4'-methyldiphenyl Sulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4''-dihydroxy-3,3'-dimethyldiphenylsulfone, 4,4'-dihydroxy-
3,3”-diallyldiphenylsulfone, 1,5-di(
4-hydroxyphenylthio)-3-oxapentane,
1,7 di(4-hydroxyphenylthio)-3,5-dioxahebutane, 1,8-di(4-hydroxyphenylthio)-3,6-dioxaoctane, bis(4-hydroxy-3-methyl Hydroxy compounds such as phenyl) sulfide can be used alone or in combination.

Sensitivity improvers include acetanilide, paraffin wax, carnauba wax, higher fatty acids, higher fatty acid esters, higher fatty acid amides, phthalic esters, terephthalic esters, benzyl 4-benzyloxybenzoate, dibenzyl oxalate, naphthol benzyl ether, 1.4 -dialkoxynaphthalene, 1.5-dialkoxynaphthalene, m-te=19-ruphenyl, p-benzylbiphenyl, dibenzylbenzene, 1-hydroxy-2-naphthoic acid ester, 2-
Hydroxy-3-naphthoic acid ester, 1-phenoxy-2-naphthoxy(1)ethane, 1,2-di(3-methylphenoxy)ethane, 1-(2-isopropylphenoxy)-2-naphthoxy(2>ethane, Bis(P-methoxyphenoxyethyl) ether, 4,4'-dialkoxydiphenylsulfone, penzamide, diphenylamine, benzenesulfonamide, benzenesulfoneanilide, phenyl p-toluenesulfonate, hydroquinone dibenzyl ether, etc. alone or in combination. It can be used.

In addition, in order to improve the light resistance and storage stability of images, it is effective to add various antioxidants, deterioration inhibitors, ultraviolet absorbers, etc., or to overcoat with polymeric substances.

[Example] Hereinafter, the present invention will be explained in detail by giving an example of synthesis of the color-forming compound of the present invention, followed by a method for producing a color-forming recording material (parts indicate parts by weight).

Synthesis Example 1 375 g of 2-(4-p-)trueethylamino-2-hydroxybenzoyl)-benzoic acid and 15.9 g of 6-amino-1-naphthol were added to 150 g of 70% sulfuric acid, and
React at ℃ for 5 hours.

After that, the compound with the following structure [3-amino-10-(p-tolyl-ethylamino)-
32 g of a crude slurry of benzofluorane] was obtained.

Purification from tetrachloroethylene gave 25 g of crystalline crystals.

Sodium bicarbonate4. Add Og and react at 75°C for 7 hours. After completion of the reaction, the tar was discharged into water, extracted with toluene, and concentrated. The resulting tar was crystallized from isopropyl alcohol to obtain a compound with the following structure [3-(dibenzylamino)-10
-(p=nitrilethylamino)-benzofluorane]
Obtain 80g.

This lactone compound log is dimethylformamide 1-5
0cc, 8.2g of benzyl bromide, and a methanol solution of this compound are colored with acetic acid, λmax
600 nm, and the hue was blue.

Moreover, when the color was developed on silica gel, the color developed quickly and showed a bluish-green color.

Synthesis Example 2 = 21- 22- Benzofluorane precursor obtained in Synthesis Example 6 l, 3-
Amino-10-(p-trilyethylamino) 10 g of benzofluorane was added to 70 cc of nitrobenzene, and 18 g of iodobenzene, 4.2 g of potassium carbonate, and 1 Cu powder were added.
g and reacted at 200°C to 205°C for 13 hours.

After the reaction is completed, nitrobenzene and iodobenzene are distilled off by steam distillation, and the remaining tar is crystallized from a mixed solvent of 1 to luene and hexane to form a compound with the following structure [3-diphenylamino-10-(p-) 7.4 g of didylamino)benzofluorane are obtained.

Met.

In addition, color developed quickly on silica gel, showing a blue color.

Synthesis Example 3 313 g of 2-(4-diethylamino-2-hydroxybenzoyl)-benzoic acid and 23.5 g of 6-anisotu-1-naphthol were subjected to a condensation reaction and treatment in sulfuric acid in the same manner as in Synthesis Example 1. A compound with the following structure [3-anilino-1
127.5 g of 0-diethylaminohenschiff 7 leolane was obtained.

When a methanol solution of this compound is colored with acetic acid, λ
max 610 nm, and the hue is blue 23- 57 g of this lactone compound was mixed with 50 g of dimethylformamide
cc, 42 g of Hensyl bromide, 2.0 g of potassium carbonate.
g and reacted at 90'C for 5 hours. After the reaction is completed, the reaction mixture is poured into water, extracted with toluene and concentrated. The obtained tar is crystallized from a mixed solvent of toluene and hexane to obtain 2.7 g of a compound [3-phenyl-benzylamino-10-diethylamino-benzofluorane] having the following structure.

C, 2 g of sodium carbonate, 2.5 g of diethyl sulfate
g and reacted at 60°C for 5 hours. After the reaction was completed, it was drained into water, extracted with toluene, treated with carbon, added hexane and crystallized to obtain 35 g of crystals of the compound [3-ethyl-phenylamino-10-diethylamino-bazofluorane] with the following structure. obtain.

When a methanol solution of this compound is colored with #acid, λm
ax 605 nm, and the hue was blue.

Furthermore, on silica gel, the color developed quickly and showed a blue color.

Synthesis Example 4 Synthesis Example 37'' Obtained benzofluorane precursor [157 g of 3anilino-10-diethylamino-benzofluorane
is dimethylformamide 50c. When a methanol solution of this compound is colored with acetic acid, λm a x 603 n
m, and the hue was blue. Furthermore, on silica gel, the color developed quickly and showed a blue color.

Incidentally, all of the above-mentioned crystals showed mixed crystals according to DSC analysis, and did not show a clear melting point.

Below, the structural formulas of the compounds of Synthesis Examples 5 to 10 and silyl 25- Juichi Describe the hue of color developed on the catarrh.

(5) Blue (6) Blue 11 (9) Blue 21 (7) Blue-green 1*- Production example 1 - Production example of pressure-sensitive copying paper Synthesis example, compound of 1 5 parts KMC-
11,395 parts (alkylnaphthalene-based pressure-sensitive copying paper solvent manufactured by Kureha Chemical Industry ■) The above mixture was dissolved by heating, and in this solution, 24 parts of gelatin and 24 parts of gum arabic were dissolved in 100 parts of water, and the pH was adjusted to 7. was added and emulsified using a homogenizer. After adding 100 parts of warm water to this emulsion and stirring at 50°C for 30 minutes,
Add about 1 part of % caustic soda aqueous solution and boil at 50°C.
Stirred for 0 minutes.

Next, dilute acetic acid was gradually added to adjust the pH to 4.5.
After stirring at 0.degree. C. for about 1 hour, the mixture was cooled to 0 to 5.degree. C. and further stirred for 30 minutes. Next, 4% geltaraldehyde aqueous solution 35
After curing the capsules, the pH was adjusted to 6 with a dilute aqueous sodium hydroxide solution, and the mixture was stirred at room temperature for several hours to complete encapsulation. No coloring phenomenon occurred during this operation.

This capsule liquid was evenly applied to paper using a wire bar so that the coating weight after drying was 6 g/rn', and dried to obtain capsule coated paper (top paper).

When this paper was superimposed on paper (lower paper) coated with clay as a color developer and written with a ballpoint pen, dark blue-green letters appeared on the lower paper.

This image had extremely excellent light fastness and moisture fastness.

Furthermore, the capsule surface of the upper paper also showed excellent light resistance, and there was no coloration or decrease in coloring ability due to sunlight irradiation.

Further, even when the color was developed using a base paper coated with a phenol-formalin resin and a zinc salicylate color developer, a deep blue-green color was developed, and the colored image had excellent light fastness and moisture fastness.

Production Example 2 - Production Example of Thermosensitive Recording Paper 1) Preparation of color former dispersion liquid (A) Bottom example, compound of 2 5 parts Olin 1
5 parts 10% polyvinyl alcohol aqueous solution 100 parts water
85 parts The above mixture was pulverized using a paint shaker (■ Toyo Seiki Co., Ltd.) until the average particle size of the color former was 2 microns.

3l- 2) Color developer dispersion i'? ! (B) Preparation of liquid Bisphenol A 15 parts Zinc stearate
10 parts 10% polyvinyl alcohol aqueous solution 150 parts The above mixture was ground in a paint shaker until the average particle size was 3 microns.

3> Preparation and coating of heat-sensitive coating liquid 10 parts of liquid A and 6.5 parts of liquid B were mixed and stirred to obtain a heat-sensitive coating liquid. After drying this coating liquid on paper with a wire bar, the amount of coating is 8
g/rn' and dried to obtain heat-sensitive recording paper.

This thermal recording paper had no background fog and was almost colorless, and quickly developed a deep blue-green color when printed with a thermal head. This colored image had excellent light fastness and moisture fastness. or,
The coated surface also had excellent light resistance, and no coloration or decrease in coloring ability occurred due to sunlight irradiation.

[Effects of the Invention] The color-forming compound according to the present invention has excellent solubility, quickly develops color with a color developer, and the color-formed image 32- has excellent light resistance. Therefore, it is industrially suitable as a color-forming compound for recording materials. It has high utility value.

Claims (1)

[Scope of Claims] [1] A color-forming compound for recording materials represented by the following general formula (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) [In the formula, R^1 and R^2 each represent a hydrogen atom, a lower alkyl group, a benzyl group, or a phenyl group optionally substituted with a lower alkyl group. , R^3, R^4 are each lower alkyl group, benzyl group, or halogen atom,
Represents a phenyl group which may be substituted with a trifluoromethyl group. ]