GB2059984A

GB2059984A - Chromogenic compounds and their use as color formers in copying or recording materials

Info

Publication number: GB2059984A
Application number: GB7929611A
Authority: GB
Original assignee: Yamada Chemical Co Ltd
Current assignee: Yamada Chemical Co Ltd
Priority date: 1979-08-24
Filing date: 1979-08-24
Publication date: 1981-04-29

Abstract

Chromogenic phthalide compounds are represented by the general formula: <IMAGE> wherein R1, R2, R3, R4, R5 and R6 each independently represent a hydrogen atom or an alkyl radical containing from 1 to 5 carbon atoms, with the proviso that at least one of <IMAGE> These compounds may be used in pressure-sensitive or heat-sensitive copying sheets.

Description

SPECIFICATION Chromogenic compounds and their use as color formers in copying or recording materials This invention relates to the novel chromogenic phthalide compounds represented by the general formula:

wherein R1, R2, R3, R4, R5 and R6 represent each a hydrogen atom or a lower alkyl radical containing from 1 to 5 carbon atoms, provided that at least one of the combinations of R1 with R2, B3 with B4, and Rg with B6 is joined to form the group -CH2-CH2-CH2-CH2- or -CH2-CH2-CH2-CH2-CH2-, and a chromogenic recording material containing such compounds.

The phthalide compounds represented by the above-shown general formula (I) are per se an almost colorless material. They can be used for pressure-sensitive copying sheets, thermo-sensitive paper and the like as a chromogen which quickly develops a bluish purple color upon intimate contact with certain material such as organic acids, acid clay, activated clay, phenol-formaldehyde resin, metallic salts of aromatic carboxylic acids, or electron acceptors such as bisphenol A.

Among the chromogenic phthalide compounds known in the art is the following for example: (A) 3,3-bis(paradimethylaminophenyl)-6-dimethylamino-phthalide

The inventors found that the phthalide compounds represented by the general formula (I), as compared with the above-shown prior art compound, have the following advantages: (1) Higher solubility in organic solvents.

(2) Capable of providing higher color density when contacted with an electron acceptor such as organic acid.

(3) Small in degree of color development after dissolved in a dilute acid solution.

(4) Capable of developing color at low temperature when used for thermo-sensitive paper.

It was thus learned that these compounds are of value as a color reactive colorless substance for chromogenic recording material used for pressure-sensitive copying sheets, thermo-sensitive recording paper and the like, and this invention was reached on the basis of these findings.

For instance, a comparative test conducted on the above-shown compound (A) and one of the phthalide compounds of this invention represented by the general formula (I), that is, (B) 3,3-bis(paradimethylaminophenyl)-6-pyrrolidino-phthalide

(C) 3,3-bis(paradimethylaminophenyl)-6-pipendino-phthalide

gave the following results.

(1) Solubility in organic solvents: Product name (A) (B) (C) Hi-sol SAS 1.3% 10.0% 12.0% K.M.C. 4.6% 20.0% 20.0% D.B.P. 6.0% 12.5% 15.5% Notes: Figures in the above table show solubility at 250C. "Hi-sol SAS" is a product by Nippon Sekiyu Co., Ltd., "K.M.C." is a product by Kureha Chemicals, and "D.B.P." is a product by Daihachi Chemicals.

As viewed above, the phthalide compounds (B) and (C) of this invention have better solubility in organic solvents than the known phthalide compound (A). This points to the advantages of the phthalide compounds of this invention in that there is no possibility of crystal separation in the micro-capsules in the course of preparation of pressure-sensitive copying sheets and that it is possible to lessen the amount of costly aromatic solvent required for encapsulization while allowing increase of relatively inexpensive petroleum solvent to provide an economical benefit.

62J Color development in acetic acid: 20.0 mg of each said phthalide compound was dissolved in 100 ml of methyl alcohol, and 5 ml of this solution was added with a predetermined amount of acetic acid and further added with methyl alcohol so that the total amount of the solution became 100 ml, and then coloration of this acetic acid solution was measured by Shimazu's spectrophotometer UV 200.

Compound (A) Acetic acid conc.(%) 10 50 80 Max. absorption wavelength (mu) 601 603 604 Absorvance 0.454 0.776 0.846 Compound (B) Acetic acid conc.(%) 10 50 80 Max. absorption wavelength (mew) 600 602 603 Absorbance 0.657 1.048 1.094 As seen from the above tables, the phthalide compound (B) of this invention develops color with extremely high density in acetic acid as compared with the known phthalide compound (A). This is indicative of high-density color development by the phthalide compounds of this invention when forming color upon contact with other material such as an electron acceptor, activated clay, phenol-formaldehyde resin, etc.

(3) Degree of color development after dissolved in dilute acid solution: 15 ml of a 3% toluene solution of each said phthalide compound was added with 10.5 ml of a 15% acetic acid solution, shaken vehemently for one minute and then allowed to stand still, and thereafter, resultant coloration of the acetic acid solution was measured in the same way as in (2) above.

Compound (A) (B) (C) Max. absorption wavelength (may) 600 606 601 Absorbance 0.502 0.158 0.150 It will be seen that the phthalide compounds (B) and (C) of this invention is colored to a smaller degree in a dilute acid solution than the known compound (A). This implies that coloration of the phthalide compounds of this invention is very limited in the step of coagulation of the gelatin solution with a dilute acid during manufacture of microcapsules used for pressure-sensitive copying sheets.

(4) Degree of color development at low temperatures when used for thermo-sensitive paper: Each said phthalide compound was finely pulverized with a polyvinyl alcohol solution according to the method described in Japanese Patent Publication No. 14039/70 and then mixed with bisphenol A (or the like) to prepare a thermo-sensitive paper coating, and the latter was coated on a base paper to form a thermo-sensitive paper and its color developing property was measured by Macbeth reflection densitometer (using WRATTEN &num;25 for filter).

Compound 120"C 140 C 1600C (A) 0.53 1.10 1.15 (B) 1.00 1.24 1.25 (C) 0.98 1.20 1.21 It will be noted that the phthalide compounds (B) and (C) of this invention are high in developed color density at low temperatures in comparison with the known phthalide compound (A), and this denotes very excellent color-developing property of the phthalide compounds of this invention when used for thermo-sensitive paper.

15) Degree of color development after contact with electron-accepting substance such as organic acid, etc.: 1.5% HB40 solution of each said phthalide composition was applied on the commercially available clay paper and resin paper at the rate of 1 mg/cm2 and the resultant density of color development was measured by Macbeth reflection densitometer (using WRATTEN &num;25 for filter).

Compound Clay paper Resin paper (A) 0.85 0.70 (B) 0.93 0.92 (C) 0.93 0.91 It will be noted that the phthalide compounds (B) and (C) of this invention show a higher value of color development especially on the resin base paper in comparison with the known phthalide compound (A) and this denotes very excellent color-developing property of the phthalide compounds of this invention.

Utilization of the phthalide compounds of the general formula (I) for pressure-sensitive copying sheets may be accomplished according to the methods described in the U.S. Patent Nos. 2,800,458; 2,806,457; etc., and for application of said compounds to preparation of thermosensitive recording material, there may be employed, for example, a method shown in Japanese Patent Publication No. 14039/70.

The phthalide compounds represented by the general formula (I) according to this invention can be obtained by reacting substantially equimolar quantities of m-pyrrolidinobenzoic acid (II) and tetraalkyldiamino-diphenyl-hydrole (III) in sulfuric acid, hydrochloric acid, or the like and then oxidizing the reaction product with an oxidant such as potassium chromate, lead peroxide, potassium permanganate, hydrogen peroxide or the like. The m-pyrrolidinobenzoic acid used in this reaction may be synthesized by heating 1 mole of m-aminobenzoic acid and 1 to 2 moles of I ,4-dibromobutane at 70 to 800C, or by further adding sodium bicarbonate and heating at 70 to 80"C.

(wherein R1, R2, R3, R4, R5 and B5 are as defined above).

As described above, the color reactant colorless substance contained in the chromogenic recording material according to this invention has many advantages such as (1) good solubility in organic solvents, (2) high density of color formed upon contact with an electron acceptor material such as organic acid, (3) small degree of color development when dissolved in a dilute acid solution, and (4) good color development at low temperatures, so that the material of this invention not only proves very advantageous in use for manufacture of pressure-sensitive copying sheets, thermo-sensitive copying sheets, etc., but can also provide a final product with excellent functional properties.

The invention is now described in further detail by way of synthesis and process examples, but the scope of this invention is not limited to these examples.

Tone of developed color Absorption in R1 R2 R3 R4 R5 R6 with silica 95% acetic gel acid (m ) H- CH3- CH3- CH3 -CH2-CH2-CH2-CH2- Bluish-purple 589 CH3- CH3- CH3- CH3- " " 601 C2H5- C2H5- C2H5- C2H5- " " 607 -CH2-CH2-CH2-CH2- CH3- CH3 CH3- CH3- " 608 -CH2-CH2-CH2-CH2- -CH2-CH2-CH2-CH2- CH3- CH3- " 610 CH3- CH3- CH3- CH3- -CH2-CH2-CH2-CH2-CH2- " 602 Synthesis Example 1:

19.1 gr of m-pyrrolidinobenzoic acid was dissolved in 49 gr of water and 5.4 gr of 98% sulfuric acid.

Separately from this, 27.0 gr of tetramethyl-diaminodiphenylhydrole was dissolved in 132 gr of water and 14.6 gr of 98% sulfuric acid, and this solution was added to the first-said sulfuric acid solution at 85 C for 3 hours, and the mixed solution was further reacted for 2 hours and the reaction solution was neutralized with ammonia water, with the resultant precipitate being filtered and washed with water. The obtained precipitate was added into 500 gr of water, 27.0 gr of sodium carbonate and 21 gr of isopropyl alcohol and the mixture was then added with 24 gr of a 35% hydrogen peroxide solution at 92 C for the period of 1.5 hours.The reaction solution was cooled and filtered, and the precipitate was recrystallized with n-butyl alcohol to obtain 10.0 gr of 3,3-bis(paradimethylaminophenyl)-6-pyrrolidino-phthalide in the form of light yellow crystal with melting point of 170.0 - 171.5"C.

Synthesis Example 2:

19.1 gr of m-pyrrolidionobenzoic acid was dissolved in 49 gr of water and 5.4 gr of 98% sulfuric acid, and another solution separately prepared by dissolving 32.6 gr of tetraethyldiaminodiphenylhydrole in 132 gr of water and 14.6 gr of 98% sulfuric acid was added to the first-said solution, and the mixed solution was reacted and treated in the same way as Synthesis Example 1, obtaining 5.0 gr of 3,3-bis(paradiethylaminophenyl)-6-pyrrolidinophthalide in the form of white crystal with melting point of 174.5 - 176.5"C.

Synthesis Example 3:

20.5 gr of m-piperidinobenzoic acid was dissolved in 49 gr of water and 5.4 gr of 98% sulfuric acid, and another solution separately prepared by dissolving 27.0 gr of tetramethyldiaminobenzhydrol in 132 gr of water and 14.6 gr of 98% sulfuric acid was added to the first-said solution, and the mixed solution was reacted and treated in the same way as Synthesis Example 1 to obtain 5.0 gr of 3,3-bis(paradimethylaminophenyl)-6-piperidinophthalide in the form of white crystal with melting point of 174 - 177"C.

Example 1: 3 parts of 3-3-(bisparadiethylaminophenyl)-6-pyrrolidinophthalide obtained in Synthesis Example 2 was dissolved in 100 parts of monopropylbiphenyl, and this solution was added with a solution consisting of 20 parts of gum arrabic and 160 parts of water to effectuate emulsification and this emulsion was further added with a solution of 20 parts of acid-treated gelatin and 160 parts of water and then added with acetic acid under agitation to adjust pH 5. Then the solution was added with 500 parts of water to perform corcervation, and after forming a concentrated gelatin-gum arrabic liquid film around the oil droplets of the solvent in which the color former was dissolved, pH was lowered to 4.4 and 3.8 parts of a 37% formalin solution was added.The hardened liquid film was cooled to 10"C, added with a sodium hydroxide solution to increase pH to 9 and then allowed to stand as it was for 5 to 6 hours to effectuate perfect encapsulization. This encapsulized liquid was coated on a paper and dried, and this paper was tightly attached to a paper coated with acid clay as acid electron acceptive adsorbent. When a pressure by a writing operation with a ball-point pen or impact by typewriting was applied to the paper, there promptly manifested itself a thick bluish purple image on the acid clay surface.

Example 2: 3,3-bis(paradimethylamynophenyl)-6-piperidino-phthalide obtained in Synthesis Example 3 is used as the chromogenic component in the pressure-sensitive recording material of the type of Example 1, and gives the same results therewith.

Example 3: 30 parts of 3-3-(bisdimethylaminophenyl)-6-pyrrolidinophthalide obtained in Synthesis Example 1 was mixed and pulverized with 150 parts of a 10% polyvinyl alcohol solution and 65 parts of waterfor one hour to prepare "component A". The pulverized phthalide particle diameter was 1 to 3 microns. Separately from this, 35 parts of bisphenol A was mixed and pulverized with 150 parts of a 10% polyvinyl alcohol solution and 65 parts of water for one hour to prepare "component B". The pulverized bisphenol A particles had diameter of 1 to 3 microns. Then, 3 parts af component A and 67 parts of component B were mixed and the mixture was coated on a paper at the rate of approximately 5 g/m2 and then dried. The obtained thermo-sensitive paper, when heated by a thermal pen, promptly developed a bluish purple color and the color image showed strong light resistance.

Claims

1. Chromogenic phthalide compounds represented by the formula (I)

in which R1, R2, B3, R4, R5 and B6 each independently represent a hydrogen atom or an alkyl radical containing from 1 to 5 carbon atoms, with the proviso that at least one of represent

2. A chromogenic compound according to claim 1 in which only

represents

3. A chromogenic compound according to claim 1 in which

represents

and B3, R4, R5 and B6 each independently represent a hydrogen atom or an alkyl radical containing from 1 to 5 carbon atoms.

4. A chromogenic compound according to claim 1 in which

represents

and R1, R2, R3 and R4 each independently represent a hydrogen atom or an alkyl radical containing from 1 to 5 carbon atoms.

5. 3,3-Bis(paradimethylaminophenyl )-6-pyrrolidino-phthalide.

6. 3,3-Bis(paradiethylaminophenyl)-6-pyrrolidino-phthalide.

7. 3,3-Bis(paradimethylaminophenyl)-6-piperidino-phthalide.

8. 3-(Paramethylaminophenyl)-3-(paradimethylamino-phenyl)-6-pyrrolidino-phthalide.

9. 3-(Paradimethylaminophenyl)-3-(parapyrrolidino-phenyl)-6-dimethylamino-phthalide.

10. 3,3-Bis(parapyrrolidinophenyl)-6-dimethylamino-phthalide.

11. A process for the production of a compound of formula (I) as claimed in any one of the preceding claims, which process comprises reacting a compound of formula (ill):

with a compound of formula (III):

wherein R1, R2, R3, R4, R5 and Be are as defined in claim 1, under acidic conditions and oxidising the resultant compound.

12. A process according to claim 11 substantially as hereinbefore described with reference to any one of the Synthesis Examples.

13. A compound of formula (I) which has been produced by a process as claimed in claim 11 or 12.

14. A color developing composition suitable for use in pressure- or heat-sensitive copying sheets, comprising at least one chromogenic compound as claimed in any one of claims 1 to 10 or 13 as a color reactant colorless substance.

15. A pressure-sensitive copying sheet comprising a sheet support having a face thereof coated with microcapsules containing at least one chromogenic compound as claimed in any one of claims 1 to 10 or 13 dissolved in a solventtherefor.

16. A sheet according to claim 15 substantially as hereinbefore described with reference to Example 1 or Example 2.

17. A heat-sensitive copying sheet comprising a sheet support having a face thereof coated with particles containing at least one chromogenic compound as claimed in any one of claims 1 to 10 or 13..

18. A sheet according to claim 17 substantially as hereinbefore described with reference to Example 3.