FLUORAN COMPOUNDS AND COLOR-FORMING RECORDING MATERIALS CONTAINING SAME

Abstract: Fluoran compounds represented by general formula (I) (wherein R represents an alkyl group containing 9 to 12 carbons atoms) and a color-forming recording material containing same as the color-forming component are disclosed. Benzoic acid derivatives represented by general formula (II) (wherein R represents an alkyl group containing 9 to 12 carbon atoms) are also disclosed.

Description: [Technological Fields] This invention relates to fluoran compounds and coloring recording materials with the said compound as coloring component, and to intermediates useful for the syntheses of fluoran compounds. [Background Technology ] Coloring recording materials based on a coloring system consisting of a coloring dye which gives rise to a color by an action of developer though itself is colorless or has almost no color (hereinafter referred to "coloring dye") and a developer coloring the dye are used for, for instance, pressure sensitive copying paper, thermographic recording paper, prepaid cards or POS (point of sales) labels. Their applications are expanding. A large number of proposals have been offered with regard to fluoran compounds as coloring dyes used for these coloring recording materials, and the fluoran compounds are used in a large amount in the market as well. Out of the fluoran compounds, those having an anilino group at the 2 position and a methyl group at the 3 position as substituents and a substituted amino group at the 6 position are important as black coloring dyes, are a mainstream of the current market, and have a large number of proposals. That is, compounds having all alkyl groups for all the substituents of the said substituted amino group were proposed in U.S. patent No. 3681390, etc. Compounds having a cyclohexyl group and lower alkyl group as the substituents of the said substituted amino group are proposed in U.S. patent No. 4410708, etc. Compounds having a cyclohexyl group and an alkyl group having 5 to 8 carbon atoms are proposed in Japanese open patent No. Sho 60-35053. EP-A-180643 discloses fluoran compounds of the above type wherein the 6-amino group bears a cyclohexylalkyl group and a C₁-C₈ alkyl group. US-A-4,580,153 teaches the use of such a compound containing an N-methyl-N-cyclohexylamino group at position 6 among a large group of largely undefined dialkylamino substituted compounds, as colouring agent. EP-A-81228 likewise discloses such compounds in general including the 6-diethylamino and the 6-(N-methyl-N-cyclohexylamino) groups in particular as colouring agents. EP-A-220515 discloses 6-cyclohexyl-6-alkylamino fluorans of the present type as colouring intermediates, wherein alkyl may have 1-9 carbon atoms, illustrated by C₁₋₆ and C₈ alkyl and exemplified with methyl and ethyl. JP-A-62-273264 describes a method of preparing the same compounds as those of EP-A-220515. EP-A-112710 broadly describes similar N-cycloalkyl-N-alkylamino compounds wherein unsubstituted cyclohexyl is excluded. JP-A-59-157153 relates to the production of fluoran compounds having an N-cycloalkyl-N-alkenylamino group (wherein alkenyl is lower alkenyl or lower alkynyl) at position 6. EP-A-276980 (JP-A-63-192777) broadly discloses fluoran compounds which may have an N-cycloalkyl-N-alkylamino group at position 6, but not an unsubstituted anilino group at position 2. JP-A-49-109120 (JP-B-51-23204) discloses the use of a broad group of fluoran compounds for copying. CH-A-654839 (JP-A-60-105680) teaches the production of fluorans, which do not include 3-methyl compounds. However, the coloring performance of these known fluoran coloring dyes is not satisfactory yet. Particularly the improvement of the storability of the dyes is very desired. The object of this invention is to provide coloring dyes with excellent coloring performance and storability, or coloring dyes with excellent solubility required when used for pressure sensitive copying paper. [Disclosure of the Invention ] This invention is a fluoran compound represented by the general formula (I) (where R is an alkyl group having 10 to 12 carbon atoms) and a coloring recording material containing the said fluoran compound as a coloring dye. In the fluoran compound represented by the general formula (I), R is a decyl, undecyl or dodecyl group. The fluoran compound represented by the general formula (I) is prepared in a way that a benzoic acid derivative represented by the general formula (II) (where R is as defined above) is reacted with a derivative represented by the following formula of which phenol or phenolic hydroxide group is converted to a lower alkoxy group such as methoxy or ethoxy group, at a molar ratio of about 1:1 in sulfuric acid. The concentration of sulfuric acid used is preferably 80% or more, and the intended product can be obtained by reaction at 0 to 50 °C for several to several 10 hours. Concrete examples of fluoran compounds thus obtained and represented by the general formula (I) are listed in Table 1. Compound R Melting point (°C) Color No. 1 n-C₉H₁₉ 159 - 161 a little reddish black No. 2 n-C₁₀H₂₁ 135 - 138 a little reddish black No. 3 n-C₁₂H₂₃ 114 - 117 a little reddish black The compounds of this invention have superior coloring sensitivity and superior property of less staining on the background, when compared with known analog compounds. The compounds represented by the general formula (I) in which R has 10 or 12 carbon atoms have extremely high coloring sensitivity and extremely high solubility in organic solvents. The fluoran compounds of this invention can of course be used singly to manufacture recording materials coloring black. In addition, two or more of the compounds can be used by mixing or the compound can be used by mixing with other coloring dyes: for instance, the fluoran compound is used by mixing with a coloring dye coloring black, red, blue, green, etc so that the black tone can be varied. Coloring dyes applicable by mixing with the fluoran compound of this invention include compounds of fluoran, triphenylmethane-phthalide, phenothiazine spiropyran and rhodamine lactam, and in addition coloring dyes with absorption in the near infrared region, which are attracting attention in recent years, including such compounds as triphenylmethane-phthalide, thiofluoran, fluoren and fluoran. The coloring recording materials manufactured by using the fluoran compounds of this invention or a mixture of the fluoran compound with other coloring dyes are applicable to heat sensitive recording paper, which is the main application of the material, as well as pressure sensitive copying paper in addition to, for example, recording paper by thermographic transfer, electro-thermo sensitive recording paper, electronic photographs using toner containing an acidic compound as a developer, ultrasonic recording paper, photosensitive printing materials, electron beam recording paper, materials for stamping, stamp ink, and typewriter ribbon. Methods for the preparation of heat sensitive recording paper using the fluoran compounds of this invention are similar to those for existing coloring dyes: for example, fine particle of a fluoran compound of this invention or a mixture of it with other coloring dyes and fine particle of developer are dispersed in an aqueous solution of water-soluble binder, the resulting suspension is applied on paper to dry so as to give heat sensitive recording paper with excellent coloring property. An addition of sensitizer into the said suspension gives in heat sensitive recording paper with extremely high sensitivity. The suspension may additionally contain a filler, dispersant, colored image stabilizer, antioxidant, desensitizing agent, adhesion preventive agent, defoaming agent, light stabilizer, and optical whitening agent. When doing so, developers used include bisphenol compounds such as bisphenol A, 4,4'-secondary-butylidene-bisphenol, 4,4'-cyclohexylidene-bisphenol, 2,2'-dihydroxy-diphenyl and pentamethylene-bis(4-hydroxybenzoate); bisphenol compounds containing sulfur such as 1,7-di(4-hydroxyphenylthio)-3-dioxaheptane; 4-hydroxybenzoates such as benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, isobutyl 4-hydroxybenzoate, chlorobenzyl 4-hydroxybenzoate, methylbenzyl 4-hydroxybenzoate and diphenylmethyl 4-hydroxybenzoate; metal benzoates such as zinc benzoate and zinc 4-nitrobenzoate; hydroxy-sulfones such as 4-hydroxy-4'-methyl-diphenyl sulfone, 4-hydroxy-4'-isopropoxy-diphenyl sulfone and 4-hydroxy-4'-butoxy-diphenyl sulfone; 4-hydroxy-phthalic acid diesters such as dimethyl 4-hydroxyphthalate, dicyclohexyl 4-hydroxyphthalate and diphenyl 4-hydroxyphthalate ; esters of hydroxynaphthoic acid such as 2-hydroxy-6-carboxynaphthalene; hydroxyacetophenone, p-phenylphenol, benzyl 4-hydroxyphenylacetate , p-benzylphenol, hydroquinone-monobenzyl ether; and tribromomethylsulfones such as tribromomethylphenyl sulfone. Sensitizers used include higher fatty acid amides, benzamide, stearic acid anilide, acetoacetanilide, thioacetoanilide, dimethyl phthalate, dibenzyl terephthalate, dibenzyl isophthalate, bis-(tert-butylphenol)s, bisphenol S diethers such as 4.4'-dimethoxy-diphenyl sulfone, 4-iso-propoxy-4'-n-butoxydiphenyl sulfone, 4.4'-dibutoxydiphenyl sulfone and 4,4'-di-n-(or iso) pentyloxydiphenyl sulfone; diphenyl amine, carbazol, 2,3-di-m-tolylbutane, 4-benzyl-biphenyl, 4,4'-dimethylbiphenyl and di-β-naphthylphenylene diamine. Fillers used include clay, talc, kaolin, satin white, titanium oxide, calcium carbonate, magnesium carbonate, barium sulfate, magnesium silicate and aluminum silicate. In addition, dispersants used include sulfosuccinates such as sodium dioctylsulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate sodium salt and fatty acid salts. Colored image stabilizers used include salicylic acid derivatives, metal salts (particularly zinc salts) of oxynaphthoic acid derivatives, and other water-insoluble zinc compounds. Antioxidants used include 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 4,4'-propylmethylene-bis-(3-methyl-6-tert-butylphenol) and 4,4'-thiobis-(2-tert-butyl-5-methylphenol). Desensitizing agents used include aliphatic higher alcohols, polyethylene glycol and guanidine derivatives. Adhesion preventive agents used include stearic acid, zinc stearate, calcium stearate, carnauba wax, paraffin wax and ester wax. The fluoran compound of this invention is of course used for pressure sensitive copying paper, for which known methods can be applied similar to those for known fluoran compounds: for example, a microcapsuled compound of this invention is dispersed with a proper dispersant and applied on paper to give a sheet with color former and separately a dispersion of developer is applied on paper to prepare a developer sheet. The two sheets thus prepared are combined to give pressure sensitive copying paper. Developers used at the time are known agents, including inorganic acidic substances such as acid clay, activated clay, attapulgite, bentnite, colloidal silica, aluminum silicate, magnesium silicate, zinc silicate, tin silicate, calcined kaolin and talc; aliphatic carboxylic acids such as oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid and stearic acid; aromatic carboxylic acids such as benzoic acid, p-tert-butyl-benzoic acid, phthalic acid, gallic acid, salicylic acid, 3-isopropyl-salicylic acid, 3-phenyl-salicylic acid, 3-cyclohexyl-salicylic acid, 3,5-di-tert-butyl-salicylic acid, 3-methyl-5-benzyl-salicylic acid, 3-phenyl-5-(2,2-dimethylbenzyl)-salicylic acid, 3,5-di-(2-methylbenzyl) salicylic acid and 2-hydroxy-1-benzyl-3-naphtoic acid; metal salts with these aromatic carboxylic acids such as zinc, magnesium, aluminum and titanium; phenol resin developers such as p-phenylphenol-formalin resin and p-butylphenol-acetylene resin; arid mixtures of these phenol resin developers and the said metal salts of aromatic carboxylic acids. The benzoic acid derivative represented by the general formula (II), which is used for synthesis of fluoran compound represented by the general formula (I), is a new compound and easily synthesized by usual reaction such as shown by the following reaction formula: (where R is as defined above). The reaction represented by the above reaction formula is attained by heating in an inactive organic solvent such as toluene, xylene, perchloroethylene or trichloroethylene, at a temperature between 80°C and the boiling point of the solvent used, for 2 to 8 hours. Various methods are applicable to separate the intended product after the reaction is completed: for example, a NaOH solution is added to the reaction solution, deposited Na salt is filtrated to separate to neutralize with aqueous sulfuric-acid solution, and then the product is extracted with solvent. Aminophenol derivatives which are materials to prepare benzoic acid derivatives represented by the general formula (II) can be prepared according to known methods. [Brief Description of Drawings ] Figure 1 is an IR absorption spectrum of 2-(4-N-cyclohexyl-n-decylamino-2-hydroxybenzoyl) benzoic acid obtained in Example 5. Figure 2 is an NMR spectrum (¹H-NMR, 60MHz, CDCl₃ ) of 2-(4-N-cyclohexyl-n-dodecylamino-2-hydroxybenzoyl) benzoic acid obtained in Example 6. The absorption intensity is at the ordinate and the intensity of magnetic field (PPM) at the abscissa. [Best Form to Execute the Invention] This invention is further described in detail by reference to the following examples. Reference Example (Example of fluoran compound synthesis) To 81.3g of concentrated sulfuric acid were added 17.0g of 2-(4-N-cyclohexyl-n-nonylamino-2-hydroxybenzoyl) -benzoic acid and 8.3 g of 2-methyl-4-methoxydiphenylamine. The resulting mixture was reacted with stirring at 15 to 25°C for 24 hours. Then the reaction mixture was poured into 300ml of ice water and deposited reaction product was filtrated to collect. The filtrated deposit was heated under reflux for an hour while stirring with 200ml of water, 20g of aqueous solution of sodium hydroxide and 160ml of toluene for extraction. The toluene layer was washed with water several times, filtrated and concentrated. The deposited crystal was filtrated. The obtained light yellow crystal was refluxed in n-hexane, cooled, filtrated and dried to give 16.0g of 2-anilino-3-methyl-6-N-cyclohexyl-n-nonylaminofluoran (Compound No. 1) as white crystal with melting point of 159.2 to 160.5°C. This compound forms an addition product with toluene if deposited from toluene solvent, and heating the addition product in n-hexane under reflux gives the said crystal free from toluene. Example 1 (Example of fluoran compound synthesis) The Reference Example was repeated nearly similarly except that 21.0 g of 2-(4-N-cyclohexyl-n-decylamino-2-hydroxybenzoyl)-benzoic acid was used instead of 2-(4-N-cyclohexyl-n-nonylamino-2-hydroxybenzoyl)-benzoic acid. The compound does not form an addition product with toluene. Therefore the toluene solution was concentrated to deposit crystal to filtrate to dry to give 11.7 g of 2-anilino-3-methyl-6-N-cyclohexyl-n-decylaminofluoran (Compound No. 2) as white crystals with melting point of 135.2 to 138.4°C. Example 2 (Example of fluoran compound synthesis) The Reference Example was repeated nearly similarly except that 20.0 g of 2-(4-N-cyclohexyl-n-dodecylamino-2-hydroxybenzoyl)-benzoic acid was used instead of 2-(4-N-cyclohexyl-n-nonylamino-2-hydroxybenzoyl)-benzoic acid. The compound does not form an addition product with toluene. Therefore the toluene solution was concentrated to deposit crystal to filtrate to dry to give 19.6 g of 2-anilino-3-methyl-6-N-cyclohexyl-n-decylaminofluoran (Compound No. 3) as white crystals with melting point of 114.5 to 117.4°C. Example 3 (Heat sensitive recording paper) (Adjustment of suspension and preparation of heat sensitive recording paper) * Dye suspension : 3.5g of fluoran compound, 15.0g of clay, 41.5g of 15% polyvinyl alcohol aqueous solution, 40.0g of water * Developer suspension : 10.5g of developer, 8.0g of clay, 41.5g of 15% polyvinyl alcohol aqueous solution, 40.0g of water Each of the suspensions with the said composition was placed in a polyethylene bottle together with 150g of glass beads (diameter:1-1.5mm). The bottles were hermetically stoppered and each suspension was ground by paint conditioner of Red Devil Co for several hours for the preparation of dye and developer suspensions respectively. The dye and developer suspensions were mixed at a ratio of 1:1 to give an application solution. This application solution was applied on white paper by using wire rod No. 12, and the paper was dried to give heat sensitive paper. According to the above procedure, heat sensitive recording papers I, II and III with the following fluoran compound and developer were prepared. Heat sensitive recording paper Fluoran compound Developer I No. 1 Bisphenol A II No. 2 Bisphenol A III No. 3 Bisphenol A These heat sensitive recording papers were each heated the two sides at 150°C by using a Dry Heating Tester (produced by Kishino Science Machinery Co., ltd.) in order to color a part of the paper. The part colored black clearly. The heat sensitive recording papers with colored and non-colored portions were examined by storability tests consisting of humidity/heat resistance tests (50 C, relative humidity: 90%, 24 hours) and light resistance test (sunlight, 20 hour exposure). Both of the background and colored portion of the heat sensitive recording paper showed almost no difference between before and after the test. Furthermore, the background of these papers before and after the test was measured by using Macbeth reflection densitometer Model RD-514. The results are summarized in Table 2 with those for Comparative Example 1. Comparative Example 1 Example 3 was repeated to prepare heat sensitive recording paper IV except that 2-anilino-3-methyl-6-N-cyclohexyl-n-octylaminofluoran was used instead of the compound of this invention in Example 3. In addition, according to the procedure of Example 4, a part of the paper was heated the two sides to color, tested for the storability similar to Example 4, and measured the background by Macbeth reflection densitometer. The results are shwon in Table 2 together with those of Example 4. Heat sensitive recording paper No. Background Before test Humid/heat resistance Light resistance I 0.07 0.11 0.19 II 0.06 0.10 0.17 III 0.06 0.11 0.17 IV 0.07 0.27 0.38 When the measured values of the papers before and after the tests by Macbeth reflection densitometer are compared in the above table, heat sensitive recording paper has better storability with smaller difference in the measured values: The above results indicate that the fluoran compounds of this invention whose alkyl group represented by R has 10 to 12 carbon atoms has clearly less fluctuation and is thus a coloring dye with excellent storability, when compared with known fluoran compound with alkyl group having 8 carbon atoms. Example 4 (Pressure sensitive copying paper) 2.0g of Compound No. 2 synthesized in Example 1 was mixed with 25.0g of alkyldiphenylmethane (Nippon Petroleum Chemical Co., Ltd. "Hisol SAS296") and 18.0 g of diisopropylnaphthalene (Kureha Chemical Industry "KMC-113"), and heated to dissolve (Solution A). Meanwhile, 15.0g of 10% aqueous solution of sulfonate modified polyvinyl alcohol (the Nippon Synthetic Chemicals Industry Co., Ltd. "Gosenol CSK-50"), 34g of pure water, 7.5g of 10% aqueous solution of ethylene-maleic anhydride copolymer (Monsanto "EMA-31"), 2.5g of urea and 0.25g of resorcinol were mixed and the pH was adjusted to 3.4 by using 20% sodium hydroxide (Solution B). Solution A was added to Solution B to make an emulsion by using a homomixer, to which 7.0g of 35% aqueous formalin solution was added to keep stirring for an hour at temperatureof 60 to 65 °C. After cooled to 40°C, 28% aqueous ammonia was added to adjust the pH to 7.5 to give a microcapsule dispersion. 27.0g of this dispersion, 3.5g of wheat starch, 8.5g of 8% aqueous wheat starch solution and 34.0ml of water were mixed to prepare an application solution. The obtained application solution was applied on white paper by using wire bar No. 12, and the paper was dried to prepare top paper of pressure sensitive copying paper. The solution-applied side of the obtained top paper was each placed on the solution-applied side of each of bottom paper prepared by applying phenol-formalin resin to dry and clay bottom paper (Fuji Photo Film). Each obtained paper was typed by typewriter to color. As the result, clear black printed characters appeared on the two bottom papers. Example 5 (Example of synthesis of benzoic acid derivative) 34.7g of m-(N-cyclohexyl-n-decylamino) phenol and 15.5g of phthalic anhydride were added to 60ml of toluene to stir for 6 hours under refluxing. 20g of 4% aqueous NaOH solution was added and heated under reflux. The resulting mixture was left still to separate layers. The toluene layer was washed with 20ml of water, to which 5.1 g of flaked sodium hydroxide and 36ml of water were added to stir. After cooled to room temperature, the deposited crystals (Na Salt) were filtrated. These crystals were washed with acetone, then neutralized with 50% sulfuric acid in 60ml of water and 60ml of toluene, and adjusted to pH 4. After heated to reflux, the solution was separated to layers, the toluene layer was washed with 20ml of warm water, and then dried under reduced pressure to give 25g of glutenous substance. This substance was proved to be a single substance by thin layer chromatography (developing solvents: chloroform 9, toluene 3, methanol 1.5). It has absorptions of OH (3400 cm⁻¹), CH₂ (2925, 2850 cm⁻¹) and C=O (1700 cm⁻¹) on the IR absorption spectrum. Thus the substance was proved to be the intended product of 2-(4-N-cyclohexyl-n-decylamino-2-hydroxybenzoyl)-benzoic acid. Example 6 (Example of synthesis of benzoic acid derivative) Example 5 was repeated except using m-(N-cyclohexyl-n-dodecylamino) phenol instead of m-(N-cyclohexyl-n-decylamino) phenol. Glutenous 2-(4-N-cyclohexyl-n-dodecylamino-2-hydroxybenzoyl) benzoic acid was obtained. [Possibility of Industrial Applications ] The new fluoran compounds of this invention have melting points as low as in a range of 115 to 160°C, thereby being very superior coloring dyes for heat sensitive recording paper in which the melting point affects the coloring sensitivity. In addition, the compounds are excellent instorability in a way that the background is less stained when compared with conventional fluoran compounds. They are also advantageous to apply to pressure sensitive copying paper because of excellent solubility in organic solvents. The benzoic acid derivatives of this invention, when used as material compounds, give various fluoran compounds extremely good as coloring dyes, being useful as synthetic intermediates.

Claims: A fluoran compound represented by the general formula (I) (where R is an alkyl group having 10 to 12 carbon atoms). A coloring recording material which contains one or more fluoran compounds represented by the general formula (I) (where R is an alkyl group having 10 to 12 carbon atoms), as coloring dyes. A benzoic acid derivative represented by the general formula (II) (where R is an alkyl group having 10 to 12 carbon atoms).

Inventors: IGAKI TETUO TOKYO PLANT NIPPON, KANEKO AKIO TOKYO PLANT NIPPON, KINOSITA KIMIAKI, MANAKA SUMIO TOKYO PLANT NIPPO, IGAKI, TETUO TOKYO PLANT, NIPPON SODA CO., LTD., KANEKO, AKIO TOKYO PLANT, NIPPON SODA CO., LTD., KINOSITA, KIMIAKI, MANAKA, SUMIO TOKYO PLANT, NIPPON SODA CO., LTD.
Applicants: NIPPON SODA CO, NIPPON SODA CO., LTD.
Application year: 1989
Main classification: C07D493
IPC codes: C07D493, B41M5, C07C229