JP3071883B2 - Crystal of fluoran compound, method for producing the crystal, and recording material containing the crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluoran compound useful as a color-forming compound used in recording materials such as pressure-sensitive recording materials and heat-sensitive recording materials, and more particularly, to a crystal of a fluoran compound and a method for producing the crystal. And a recording material containing the crystal.

[0002]

2. Description of the Related Art Conventionally, a colorless or pale-colored electron-donating compound (color-forming compound) and an organic or inorganic electron-accepting substance (a color developing agent) are used to develop a color, such as pressure, heat or electricity. As a method of recording information transmitted through the mediation of external energy, there are pressure-sensitive recording, thermal recording, energized thermal recording, and the like. In these recording systems, a fluoran compound is widely used as a coloring compound.

Heretofore, for example, compounds of formulas (A) and (B) are known as fluoran compounds.

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Embedded image However, when the compounds of the formulas (A) and (B) are used as a color-forming compound for a heat-sensitive recording material, the resulting heat-sensitive recording paper has a drawback that the light-fastness of the uncolored portion (background) is poor.

JP-A-60-47067 suggests compounds of formulas (C) and (D). However, when these compounds are used as color-forming compounds to prepare a heat-sensitive recording paper, there is a drawback that the light resistance of uncolored portions (background) of the paper is poor.

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Embedded image Further, JP-A-60-47068 discloses a compound of the formula (E). However, a thermosensitive recording paper prepared by using this compound as a color-forming compound also has an uncolored paper. The light resistance of the part (background) was poor.

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[0005]

DISCLOSURE OF THE INVENTION The present inventors have searched various compounds to solve the above-mentioned problems, and as a result,
The present invention has been reached. That is, the present invention relates to general formula (1)

Embedded image (Wherein R ₁ represents a methyl group or an ethyl group), a method for producing a crystal of the fluoran compound, and a recording material containing the crystal. is there.

In the present invention, the fluoran compound represented by the general formula (1) is specifically a compound represented by the formulas (1-a) and (1-b).

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The fluoran compound represented by the general formula (1) of the present invention is represented by the general formula (2)

Embedded image (Wherein, R ₂ represents a methyl group or an ethyl group), more specifically, a compound represented by the formula (2-a) or (2-b):

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Embedded image General formula (3)

Embedded image (Wherein, R ₃ represents a lower alkyl group having 1 to 4 carbon atoms)
The diphenylamine derivative represented by, for example, concentrated sulfuric acid, concentrated sulfuric acid to which fuming sulfuric acid is added, polyphosphoric acid, phosphorus pentoxide, in the presence of a dehydrating condensing agent such as anhydrous aluminum chloride, particularly preferably, in concentrated sulfuric acid After that, it is manufactured by making it alkaline. The dehydration condensation reaction is usually
The reaction is carried out at a reaction temperature of 0 to 100 ° C for several hours to 100 hours. The reaction temperature is between 0 and 0, especially when the reaction is carried out in concentrated sulfuric acid.
Temperatures of 5050 ° C. are particularly preferred. Since the reaction time depends on the reaction temperature, the reaction is carried out for a sufficient time. After the dehydration condensation, the alkali treatment usually carried out is to adjust the pH to 9 to 12 with aqueous potassium hydroxide, aqueous sodium hydroxide or the like.
It is preferably carried out in a temperature range of 0 to 100 ° C. At this time, the alkali treatment may be performed in the presence of an organic solvent other than water, such as benzene or toluene.

[0008] The crystals of the fluoran compound of the present invention are obtained by subjecting the product obtained by the above reaction to an aromatic hydrocarbon solvent such as benzene, toluene or xylene, or an alcohol solvent such as methanol, ethanol, isopropanol or n-butanol. Or a polar solvent such as acetonitrile, dimethylformamide, or the like, or a mixture of these, and then can be isolated as stable crystals. In particular, among the above solvents, an alcohol solvent or a polar solvent may be used as a mixed solvent with water. In this case, the water content is preferably 50% by weight or less, more preferably 30% by weight or less, and still more preferably 10% by weight or less. If the water content exceeds 50% by weight, an amorphous (amorphous) precipitates, making it difficult to isolate stable crystals.

As a method for depositing crystals, a method is often used in which a fluoran compound is once completely dissolved in a solvent and then precipitated by cooling. At this time, if necessary, the fluoran compound may be completely dissolved by heating at room temperature or higher in the range of the boiling point of the solvent.
After complete dissolution, crystals are precipitated with stirring or standing. Isolation of the precipitated crystals can be suitably performed by a known method, for example, a filtration method, without any special method. After the isolation, if necessary, an operation of washing or re-dissolving with an organic solvent having a water content of 50% by weight or less (for example, the above-mentioned organic solvent) and then precipitating as crystals may be performed. After the isolation, the crystals are dried by a usual method to obtain crystals of the fluoran compound.

In producing the compound of the general formula (1), the compound of the general formula (2) and the compound of the general formula (3) are subjected to a dehydration condensation reaction in the presence of a dehydration condensing agent (for example, concentrated sulfuric acid). After that, when an alkali treatment with alkaline water is performed in the presence of a substantially water-insoluble organic solvent such as benzene or toluene, the generated fluoran compound of the general formula (1) is dissolved in the organic solvent. Therefore, when such an alkali treatment is performed, the crystals of the fluoran compound represented by the general formula (1) of the present invention are obtained by separating the organic solvent solution from the aqueous layer,
It can also be suitably isolated by precipitating it as crystals from an organic solvent solution containing the fluoran compound.

The crystal of the fluoran compound represented by the general formula (1) of the present invention, which is suitably produced by the above method, will be described in detail. In the general formula (1), the crystal of the compound (1-a) in which R ₁ is a methyl group has a strong peak at a diffraction angle (2θ) of 9.0 ° in X-ray diffraction by Cu-Kα ray, 14.8 °, 16.0 °. , 18.7 °, 19.7 °, 20.1 °, 2
It is a crystal characterized by an X-ray diffraction pattern showing relatively strong peaks at 1.0 °, 21.3 ° and 22.7 °. The powder X-ray diffraction pattern is shown in FIG.

In the general formula (1), the crystal of the compound (1-b) in which R ₁ is an ethyl group is formed by X-rays with Cu-Kα ray.
This is a crystal characterized by an X-ray diffraction pattern showing a strong peak at a diffraction angle (2θ) of 8.9 ° in a line diffraction method. The powder X-ray diffraction pattern is shown in FIG.

The crystals of the fluoran compound represented by the general formula (1) of the present invention produced as described above can be used as a coloring compound in various recording materials. The recording material of the present invention is a pressure-sensitive recording material or a heat-sensitive recording material. The crystal of the fluoran compound represented by the general formula (1) of the present invention can be suitably used particularly as a color-forming compound for a heat-sensitive recording material. In this case, it may be used alone, or further, for example, in order to adjust the color hue or the like, other color-forming compounds such as triphenylmethanelactones, fluorans, and spiropyrans are desired. Can be used in combination. When the fluoran compound crystal represented by the general formula (1) is used, for example, as a pressure-sensitive recording material, it is converted into a solvent commonly used in this field, for example, an alkylbenzene (n-
Dotesylbenzene, etc.), alkylbiphenyls (triethylbiphenyl, diisopropyldiphenyl, etc.), hydrogenated terphenyls, alkylnaphthalenes (diisopropylnaphthalene, etc.), diarylethanes (phenylxylylethane, styrenated ethylbenzene, etc.), or chlorine Dissolved in a single or mixed solvent of various paraffinic solvents, and the solution is subjected to a coacervation method, an interfacial polymerization method, or the like, and gelatin, melamine-aldehyde or urea-aldehyde resin, polyurethane, polyurea, polyamide, etc. Encapsulated in a microcapsule having a partition wall of
An aqueous dispersion of the obtained capsules may be mixed with a suitable binder (for example,
It can be used as a pressure-sensitive recording sheet by coating it on a suitable support (eg, paper, plastic sheet, resin-coated paper, etc.) together with starch paste, latex, etc.).

Of course, the above-mentioned capsule dispersion liquid is applied to one surface of the support, and a developer coating solution mainly containing a color developer is applied to the other surface. Coating the capsule and the developer together on the same surface by applying a coating solution in which the capsule and the developer are mixed, or by applying a developer coating solution after applying a capsule dispersion. It can also be used for so-called single copy sheets.

In this case, as a developer, a copolymer of salicylic acid, phenols and aldehydes (for example, formaldehyde), substituted salicylic acid (alkyl-substituted,
Very many of the aryl-substituted or aralkyl-substituted forms are known, for example 3,5-di-α-methylbenzylsalicylic acid), co-condensation resins of substituted salicylic acids with styrene,
Alkylphenols (eg, octylphenol), phenol-aldehyde resins (eg, novolak resin of p-phenylphenol) or metal salts thereof (eg, metal salts of zinc, magnesium, aluminum, calcium, tin, nickel, etc.), and further Activated clays.

When a heat-sensitive recording material is used, a fluoran compound crystal represented by the general formula (1) and a developer (for example, bisphenol A or a halide or alkylated product thereof, dihydroxydiphenyl sulfone or a halide thereof) are used. Or organic color developing agents such as alkylated products, hydroxybenzoic acid esters, phenols such as hydroquinone monoethers, salicylic acid derivatives, salicylic acid amide derivatives, urea derivatives, thiourea derivatives, or acid clay, attapulgite, activated clay Binder (eg, polyvinyl alcohol or a modified product thereof, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gum arabic, styrene) And maleic anhydride copolymers or isobutylene-acrylic acid-maleic anhydride copolymers), pigments (talc, kaolin, calcium carbonate, etc.), and, if necessary, sensitizers (higher fatty acids). Amides, aromatic carboxylic acids, or sulfonic acid esters, aromatic or aromatic group-substituted aliphatic ethers, or aromatic or aromatic group-substituted aliphatic hydrocarbons, and other commonly known sensitizers for thermosensitive recording materials. ), Other additives (for example,
An ultraviolet absorber, an antifoaming agent, etc.) is added to form a fine dispersion, which is applied to a suitable support (eg, paper, plastic sheet, resin-coated paper, etc.) and can be used as a heat-sensitive recording material. . Of course, it can be used without problem in a system using a solvent instead of an aqueous dispersion system. It can also be used for applications using other color-forming compounds (for example, temperature indicating materials).

[0017]

When the fluoran compound crystal represented by the general formula (1) of the present invention is used as a color-forming compound, the uncolored portion (background) of the paper is smaller than when a conventionally known fluoran compound is used. A heat-sensitive recording paper having good light fastness and excellent storage stability can be obtained. That is, the formula (1-
Using the crystals of the fluoran compound represented by a) and (1-b) as a color-forming compound, bisphenol A was used as a color developer to prepare a thermosensitive recording paper. On the other hand, as a comparison, a fluoran compound of formulas (A), (B), (C), (D) and (E) was used as a color-forming compound, and bisphenol A was used as a color developer. Created.

Table 1 shows the results of a light fastness test of the background of the uncolored portions of these heat-sensitive recording papers.

[Table 1] In the light fastness test, the yellowing degree of the uncolored portion (background) of each heat-sensitive recording paper after exposing it to sunlight for 10 hours was examined. The judgment of the result was made visually. In the table, ○ indicates a thermosensitive recording paper having a high degree of whiteness with almost no yellowing, and x indicates a thermosensitive recording paper which is significantly yellowed or yellow-brown.

As is evident from Table 1, when the fluoran compound crystal represented by the general formula (1) of the present invention is used for a heat-sensitive recording material, it is compared with a conventionally known fluoran compound using a fluoran compound. Thus, the light resistance of the uncolored portion (background) of the paper is very excellent. The fluoran compound represented by the general formula (1) according to the present invention has the above-mentioned formula (A), (B),
The fluoran compounds of (C), (D) and (E)
Although the fluoran structure has a structure in which only the substituent on the 3-position amino group is different, as described above, it has a very excellent characteristic as, for example, a color-forming compound for a heat-sensitive recording material.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 [Preparation of crystal of compound (1-a) in which R ₁ is a methyl group in general formula (1)] 2- (4′-N-2 ″ -ethoxyethyl-N-methylamino-2 ′ -Hydroxybenzoyl) benzoic acid [compound of formula (2-a)]
After dissolving 200 g in 500 ml of concentrated sulfuric acid at 10 ° C, 4-methoxy-2
-Methyldiphenylamine [in the general formula (3), R
Compound in which ₃ is a methyl group) 125 g is added at the same temperature, and 10 to
Stirred at 15 ° C. for 24 hours. The reaction mixture was discharged into 5000 ml of ice water, and the precipitated solid was collected, washed with water, and then washed with 20% Na
After adding 1000 ml of toluene and 1000 ml of toluene,
Stirred at 60-70 ° C for 2 hours. The toluene layer was separated, washed with warm water until neutral, and the toluene layer was separated and taken out. The toluene was concentrated under reduced pressure at 40 ° C., and the precipitated crystals were filtered. After washing with a small amount of toluene, further washing with methanol, drying at 60 ° C. for 24 hours, 3-N-2′-ethoxyethyl-N-methylamino-6-methyl-7-anilinofluoran [formula 186 g of (compound of (1-a)) were obtained as almost colorless crystals. Melting point: 165 to 168 ° C. A toluene solution of crystals of this compound was colorless and transparent, and quickly developed black on silica gel. The powder X-ray diffraction pattern is shown in FIG.

Example 2 [Preparation of crystal of compound (1-b) wherein R ₁ is an ethyl group in general formula (1)] In Example 1, 2- (4'-N-2 "-ethoxyethyl Instead of -N-methylamino-2'-hydroxybenzoyl) benzoic acid, 2- (4'-N-2 "-ethoxyethyl-N-ethylamino-
According to the method described in Example 1, except that 2'-hydroxybenzoyl) benzoic acid [compound of the formula (2-b), melting point 130-132 ° C] was used, 3-N-2'-ethoxyethyl-N- Ethylamino-6-methyl-7-anilinofluoran [formula (1-
Compound b) was obtained as almost colorless crystals. Melting point 185-186 ° C. A toluene solution of crystals of this compound was colorless and transparent, and quickly developed black on silica gel. The powder X-ray diffraction pattern is shown in FIG.

Example 3 [Preparation of Thermal Recording Paper Using Crystal of Fluoran Compound of Formula (1-a) of the Present Invention] 10 g of the crystal obtained in Example 1 was added to 5 g of a 10% aqueous polyvinyl alcohol solution and water. 37.5 g of the mixture was pulverized with a sand mill to a particle size of 3 μm. On the other hand, bisphenol A was similarly dispersed to obtain a 38% developer dispersion. 65.8 g of this developer dispersion was mixed with 50 g of an aqueous dispersion of the above crystals, 18.3 g of an aqueous dispersion of 60% light calcium carbonate, 88 g of a 10% aqueous polyvinyl alcohol solution, and 51.9 g of water. This mixture was applied to white base paper using a wire rod No. 10 and then air-dried at room temperature to obtain a very white thermosensitive recording paper free from background contamination. The heat-sensitive recording paper developed a very reddish black color very quickly upon heating. Apply this thermal recording paper to sunlight
Even after the exposure for 10 hours, the uncolored portion (background) of the paper remained high in whiteness with almost no yellowing. (Table 1)

Example 4 [Preparation of Thermosensitive Recording Paper Using Crystal of Fluoran Compound of Formula (1-b) of the Present Invention] In Example 3, instead of using the crystal of fluoran compound of formula (1-a), According to the method described in Example 3, except that a crystal of the fluoran compound of the formula (1-b) was used,
Thermal recording paper was made. This thermosensitive recording paper is heated,
It developed very quickly to a slightly reddish black. Further, even after the thermal recording paper was exposed to sunlight for 10 hours, the uncolored portion (background) of the paper remained high in whiteness with almost no yellowing. (Table 1)

Comparative Example In Example 3, instead of using crystals of the fluoran compound of the formula (1-a), 3-N, N-di-n-propylamino-6 was used.
-Methyl-7-anilinofluoran [compound of formula (A)], 3-Nn-butyl-N-isopropylamino-6-methyl-
7-anilinofluoran [compound of formula (B)], 3-N-2'-
Methoxyethyl-N-methylamino-6-methyl-7-anilinofluoran [compound of formula (C)], 3-N-ethyl-N-
2'-methoxyethylamino-6-methyl-7-anilinofluoran [compound of formula (D)], and 3-N-isopropyl
Using -N-2'-methoxyethylamino-6-methyl-7-anilinofluoran [compound of formula (E)], a thermal recording paper was prepared according to the method described in Example 3. After exposing these heat-sensitive recording papers to sunlight for 10 hours, the yellowing degree of uncolored portions (background) of the papers was visually examined. The results are shown in Table 1. In these thermal recording papers, remarkable yellowing due to sunlight was observed.

Example 5 [Preparation of Pressure-Sensitive Recording Paper Using Crystal of Fluoran Compound of Formula (1-a) of the Present Invention] Preparation of ordinary (CB) paper and lower (CF) paper is as follows. Manufactured. That is, 100 g of a 10% aqueous solution of ethylene-maleic anhydride copolymer and 240 g of water were mixed, and 10%
After adjusting the pH to 4.0 with an aqueous sodium hydroxide solution, 200 g of phenylxylylethane (SAS-296 made by Nippon Petrochemical) in which 5% by weight of the crystals obtained in Example 1 were dissolved, and emulsifying with a homomixer, the solid was solidified. Then, 60 g of a 50% aqueous solution of methylolmelamine (Euramine T-30 manufactured by Mitsui Toatsu Chemicals, Inc.) was added, and the mixture was kept at 55 ° C. for 3 hours with stirring to obtain a microcapsule dispersion having an average particle size of 5.0 μm. This microcapsule dispersion 10
0 g, wheat flour starch 4.0 g, 20% oxidized starch paste 20 g and water 1
16 g was added and dispersed, and the mixture was applied to a paper weighing 40 g / m ^{2 so} that the application amount was 5 g / m ^{2 in} solid content, to obtain CB paper. On the other hand, C
F-paper uses a zinc salt of a co-condensation resin of substituted salicylic acid and styrene as a color developer, and is pulverized in a sand grinding mill in water in the presence of a small amount of a polymeric anionic surfactant to obtain a solid content of 40% by weight. Was obtained. Using this aqueous dispersion, an aqueous paint (solid content 30%) having the following composition was prepared.
It was applied to a high-quality paper weighing 40 g / m ^{2 so} as to have a dry coating amount of 5.5 g / m ² , thereby producing CF paper. When the microcapsule-coated surface of the CB paper and the developer-coated surface of the CF paper were overlapped so as to face each other, and writing and pressing were performed, a red-black color image was obtained on the developer-coated surface. Light fastness of the color images, moisture resistance and NO _X resistance practically no problem.

Example 6 [Preparation of pressure-sensitive recording paper using crystals of the fluoran compound of formula (1-b) of the present invention] In Example 5, the formula (1-a) obtained in Example 1 was obtained. CB paper and CF paper were prepared by the method described in Example 5, except that the fluoran compound crystal of the formula (1-b) produced in Example 2 was used instead of the fluoran compound crystal. A red-black color image was obtained. The light resistance of the color image, moisture resistance and NO _X resistance was not practically problematic.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of a crystal of a fluoran compound represented by the formula (1-a) produced in Example 1.

FIG. 2 is an X-ray diffraction diagram of a crystal of a fluoran compound represented by the formula (1-b) produced in Example 2.

Continued on the front page (72) Inventor Kazuyoshi Yoshikawa 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Akihiro Yamaguchi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Mitsui Toatsu Chemical Co. (56) References JP-A-60-47067 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09B 11/28 B41M 5/12 105

Claims (3)

(57) [Claims] [Claim 1] The general formula (1) (Wherein R ₁ represents a methyl group or an ethyl group) . When R ₁ is a methyl group, X represented by Cu-Kα ray
In the line diffraction method, a strong peak at a diffraction angle (2θ) of 9.0 ° was obtained.
H, 14.8 °, 16.0 °, 18.7 °, 19.7
°, 20.1 °, 21.0 °, 21.3 ° and 22.
Shows a relatively strong peak at 7 °, and R ₁ is an ethyl group
In the X-ray diffraction method using Cu-Kα ray, the diffraction angle
(2θ) X-ray diffraction pattern showing a strong peak at 8.9 °
Characterized fluoran compound crystals. 2. A method according to claim 1 formula according (1) ## STR2 ## (Wherein, R ₁ represents a methyl group or an ethyl group)
Water content containing fluoran compound is less than 50% by weight
The compound was precipitated as crystals from the organic solvent solution below
2. The fluora according to claim 1, which is isolated afterwards.
A method for producing a crystal of a compound. 3. A crystal of the fluoran compound according to claim 1,
Recording material to be included.