JPH10306228A - Purification of dye and recording by using the purified dye - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a dye useful as a dye for a new thermal recording method having an excellent thermal stability to be obtained by vaporizing and purifying a volatile dye. SOLUTION: A dye selected from methine-based, anthraquinone-based, azomethine-based, azo-based, quinophthalone-based, coumarin-based, perinone- based, xanthene-based, thioxanthene-based, azathioxanthene-based, oxazine-based and thiazine-based dyes is evaporated preferably under a reduced pressure (0.0001-500 Torr), in the presence of a thermal degradation inhibitor (an antioxidant, a light stabilizer, etc., e.g. a phenolic compound and a hindered amine compound) of the volatile dye, at a temperature higher than the evaporating temperature and lower than the degrading temperature, oridnary at 5-200 deg.C. The obtained dye is used as a dye for a new thermal recording method as it is, or by diluting so as to be several % to about 20%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a dye with high purity and a method for heat-recording a dye using a purified dye (sublimation or vaporization of a dye from a thermal recording head by selective heating according to image information). (An image recording method of flying and recording on an opposing photographic paper).

[0002]

2. Description of the Related Art In recent years, the demand for hard copy colorization has been rapidly increasing, and recording techniques such as electrophotography, ink jet, fusion type thermal transfer, and dye thermal transfer (sublimation type thermal transfer) have been studied. Among these recording technologies, the dye thermal transfer recording method accepts an ink ribbon or ink sheet, in which an ink layer in which a heat transferable dye is dispersed at a high concentration in a suitable binder resin, and a dye to be thermally transferred. The printing paper coated with the dye-dyeing resin is superimposed, and from the back surface of the ink sheet where the dye is applied, heat is applied by a thermal head according to the image information, and the transfer amount of the dye is determined according to the amount of heat. , And a gradation image can be recorded. By repeating the above operation for the image signals decomposed into the three primary colors of subtractive color mixing, that is, yellow, magenta, and cyan, a full-color image having continuous gradation can be obtained. This method is characterized in that high-quality images equivalent to silver halide color photographs can be obtained, and that the apparatus can be reduced in size and maintenance is easy. However, this method is a major drawback in that a large amount of waste is generated due to disposable use of the ink sheet and high running costs are hampered. The fusion type thermal transfer recording method also has the same drawbacks because it uses an ink ribbon or an ink sheet.

On the other hand, in the ink jet recording method, small droplets of a recording liquid are provided on a recording head by a method such as an electrostatic suction method, a vibration generation method (piezo method), or a thermal method (bubble jet method) in accordance with image information. The recording medium is made to fly from a given nozzle and adhere to photographic paper for recording.
Therefore, unlike the case where an ink sheet is used, there is almost no generation of waste, and the running cost is low. Therefore, the technology for easily outputting a color image has been widely used.
However, in the ink-jet system, the density gradation in the pixel is basically difficult, and it is difficult to reproduce a high-quality color image in a short time as obtained by the dye thermal transfer recording system. That is, in the conventional ink jet system, since one droplet of ink forms one pixel having a constant density, in-pixel gradation is difficult in principle. Attempts have been made to represent pseudo gradation by the dither method, but the image quality is inferior to that of the dye thermal transfer recording method, and the recording time is significantly reduced.

[0004] The electrophotographic method has a low running cost,
Although the recording speed is fast, it is difficult to reduce the size of the apparatus and the cost of the apparatus is high. As described above, there is no recording technology that satisfies all requirements such as image quality, running cost, apparatus cost, and recording speed. A new thermal recording method has been proposed which solves these problems (Japanese Patent Laid-Open No. 52-1982).
36033, JP-A-54-71636, JP-A-54-7
1637, JP-A-59-22759, JP-A-62-16
2593, JP-A-62-183392, JP-A-62-2
No. 20388). That is, these methods use a vaporizable (sublimable) dye or a recording liquid containing a vaporizable dye,
In this method, the dye is vaporized (sublimated) by direct heating, and the vaporized dye is caused to fly to a photographic paper for recording. In this thermal recording method, the amount of dye vaporization can be controlled according to the recording energy to the heating means, so that density gradation can be achieved, and high image quality similar to the conventional dye thermal transfer recording method using an ink sheet can be obtained. Color printing is possible, and since no ink sheet is used, low running costs similar to those of the ink jet system can be realized.

However, in these methods, the dye is directly heated and vaporized, so that the thermal stress on the dye is extremely large. With the conventional dye, thermal decomposition occurs during recording, and stable recording can be performed. It was difficult. Therefore, improvement of the heat resistance of the dye is an important issue.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for purifying a dye to obtain a highly purified dye having excellent thermal stability suitable as a dye for the above-mentioned new thermal recording system, and the dye. Another object of the present invention is to provide a new thermal recording method using the above method.

[0007]

That is, the gist of the first invention of the present application is a vaporizable dye, which is a methine dye, an anthraquinone dye, an azomethine dye, an azo dye, a quinophthalone dye, a coumarin dye. And a method for purifying a dye characterized by vaporizing and purifying a dye selected from the group consisting of perinone dyes, xanthene dyes, thioxanthene dyes, azathioxanthene dyes, oxazine dyes, and thiazine dyes. It is. Further, the gist of the second invention of the present application relates to a dye vaporization type thermal recording method using a vaporized purified dye.

[0008]

The dye purified by the vaporization purification method is free of impurities, and exhibits excellent thermal stability suitable as a dye for the above-mentioned new thermal recording method. In the present invention, vaporization purification means that a dye material containing impurities in a solid state is converted into a gas phase without or through a liquid phase, depending on the state of the raw material, and is returned to the solid state again. That is, it includes both pseudo-sublimation purification and sublimation purification. Hereinafter, these are collectively referred to as vaporization purification.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The vaporization purification is carried out under heating at a high temperature, but the heating temperature must be higher than the vaporization temperature of the dye and lower than the decomposition point. Usually 5 from decomposition point
To 200 ° C lower, preferably 20 to 200 ° C lower. Further, in order to prevent the decomposition of the dye and to lower the heating temperature and to accelerate the sublimation speed of the dye, it is effective to carry out the treatment under reduced pressure. Usually, the pressure condition is 0.000
1 to 500 torr, preferably 0.01 to 50 torr
r, particularly preferably 0.01 to 20 torr. As described later, it is effective to purify the dye in the presence of a thermal decomposition inhibitor. In addition, as the carrier gas, nitrogen, argon, helium, or the like, which has no reactivity with the dye, can be passed.

FIG. 1 is a cross-sectional view showing the main structure of an automatic heating apparatus having a gold furnace transparent electric furnace used as an example in the sublimation purification of the dye of the present invention. 1 is a gold furnace transparent electric furnace, 2 is alumina fiber, 3 is a test tube containing a raw material dye, 4 is a gooch funnel, 5 is a quartz tube, 6 is a raw material dye, 7 is a purified sublimation dye, 8
And 8 'represent thermocouple positions.

The dyes used in the present invention include methine dyes, azomethine dyes, azo dyes, quinophthalone dyes, coumarin dyes, anthraquinone dyes, and condensed polycyclic dyes. These dyes preferably have a nonionic structure in order to have good sublimability. The dye used for the dye vaporization type thermal recording usually has a vaporization temperature of 400 ° C. or lower at normal pressure, preferably 300 ° C. or lower, more preferably 100 to 300 ° C.
C. Examples of the methine dye include a dye represented by the following general structural formula (I).

[0012]

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Here, X ¹ and Y ¹ are X ¹ (Y ¹ ) CH
Represents the residue of an active methylene compound represented by _2, X ¹ and Y ^1, respectively, a cyano group, -COZ ² or -S
O ₂ Z ³ (As Z ² and Z ³ , respectively, -R ¹ ,
—OR ² , —NR ³ R ⁴ , or a 5- to 6-membered heterocyclic group, wherein R ^{1 to} R ⁴ are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group , A 5- or 6-membered heterocyclic group, or a 5- or 6-membered cycloalkyl group. ) Or X ¹ and Y
^{And 1} may be combined with each other to form a 5- to 6-membered carbocyclic or heterocyclic ring, and these rings may be condensed with another ring. Specific examples include those of the following general formulas (II) to (VII).

[0014]

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[0015]

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[0016]

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[0017]

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[0018]

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[0019]

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Where R^Five~ R^{twenty one}Are the hydrogen sources, respectively.
, Substituted or unsubstituted alkyl group, substituted or unsubstituted
Substituted aryl group, cyano group, -COZ^Four, -SO_TwoZ
^Five, -NR^{twenty two}R^{twenty three}, -OR^{twenty four}, -NR^{twenty five}COZ⁶, -N
R²⁶SO_TwoZ⁷, Nitro group or halogen atom
Then Z^Four~ Z⁷Is -R²⁷, -OR²⁸, -N
R ²⁹R³⁰Or a 5- to 6-membered heterocyclic group,^{twenty two}
~ R³⁰Is a hydrogen atom, a substituted or unsubstituted
Alkyl group, substituted or unsubstituted aryl group, 5 to 6
Membered heterocyclic group or 5- or 6-membered cycloalkyl
Represents a group. )

Z represents a hydrogen atom or a cyano group;
¹ is a benzene ring or a thiazole ring, a quinoline ring,
Represents a heterocyclic ring such as a pyridine ring, a thiophene ring or an imidazole ring, and these are represented by —NR ³¹ R ³² (R ³¹ and R ³² are
Each represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, -COZ ¹² or -SO ₂ Z ¹³ (Z ¹² and Z ¹³ are each -R ^42,, -
OR ⁴³ , —NR ⁴⁴ R ⁴⁵ or a 5- to 6-membered heterocyclic group (R ^{42 to} R ⁴⁵ are a hydrogen atom, a substituted or unsubstituted aryl group, a 5- to 6-membered heterocyclic group, or a 5- to 6-membered ring; Represents a cycloalkyl group of a ring). ). ), A substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or a halogen atom. Specific examples of methine dyes are shown in Tables 1a to 1j. Examples of the azomethine dye include a dye represented by the following general structural formula (VIII).

[0022]

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Here, X ² and Y ² are X ² (Y ² ) CH
A residue of an active methylene compound represented by ₂ are defined as for each of the X ¹ and Y ^1, A ² is the A
¹ and are similarly defined. Specific examples of the azomethine dyes are shown in Tables 2a to 2j. Examples of the azo dye include a dye represented by the following general structural formula (IX).

[0024]

Embedded image A ³ -N = NB (IX)

Here, A ³ represents a residue of a diazo component represented by A ³ —NH ₂ and is a benzene ring or a hetero ring which may have an arbitrary substituent. Examples of the heterocyclic ring represented by A ³ include thiazole, isothiazole, imidazole, pyrazole, triazole, 1,
Rings such as 2,4-thiadiazole, 1,3,4-thiadiazole, benzothiazole, benzoisothiazole and thiophene are exemplified. Examples of the substituent on the benzene ring or hetero ring represented by A ³ include a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a cyano group, a nitro group, a halogen atom, _{^{-COZ 8, -SO 2 Z 9,}} -NR
³³ R ³⁴ , —NR ³⁵ COZ ¹⁰ , —NR ³⁶ SO ₂ Z ¹¹ or —SR ⁴¹ ; and Z ^{8 to} Z ¹¹ each represent —R ³⁷ ,
—OR ³⁸ , —NR ³⁹ R ⁴⁰ or a 5- to 6-membered heterocyclic ring, wherein R ^{33 to} R ⁴¹ each represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, Represents a 6- to 6-membered heterocyclic group or a 5- to 6-membered cycloalkyl group.

B represents a residue of a coupling component represented by BH, and is a residue of a benzene ring, a hetero ring, or an active methylene compound which may have an arbitrary substituent. Examples of the hetero ring represented by B include rings such as thiazole, quinoline, pyridine, thiophene, and imidazole. Examples of the substituent of the benzene ring or heterocyclic ring represented by B, those similar to the substituent of the A ¹ and the like. Specific examples of the azo dyes are shown in Tables 3a to 3j. Quinophthalone dyes (4a to 4
b), coumarin dyes (5a-5b), anthraquinone dyes (6a-6k) and other condensed polycyclic dyes (7
Specific examples of a to 7j) are shown in Table 1.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

The dye thermal decomposition inhibitor used in the present invention is not limited as long as it does not affect the physical properties of the dye, and can be selected from antioxidants, light stabilizers, rubber aging inhibitors and the like. Particularly, the substances effective for suppressing the thermal decomposition of the dyes according to the present invention include, as antioxidants, phenolic compounds, phosphoric acid compounds and sulfur compounds shown in Tables 2, 3 and 4, respectively. And the like. Other antioxidants include natural antioxidants such as vitamin C and vitamin E, and dibutyloxytoluene, butyloxyanisole, and protocatechuic acid, which are synthetic antioxidants permitted to be added to foods under the Food Sanitation Law. Ethyl, isoamyl gallate, propyl gallate, guaiac, nordihydroguaiaretic acid and the like. Compounds known as light stabilizers include the hindered amine compounds shown in Table 5. Compounds known as rubber aging inhibitors include diphenylamine compounds shown in Table 6 and others.

[0033]

[Table 6]

[0034]

[Table 7]

[0035]

[Table 8]

[0036]

[Table 9]

[0037]

[Table 10]

[0038]

[Table 11]

[0039]

[Table 12]

[0040]

[Table 13]

[0041]

[Table 14]

[0042]

[Table 15]

[0043]

[Table 16]

In particular, hindered phenol compounds, hindered amine compounds, diphenylamine compounds and the like are preferable because they exhibit an excellent inhibitory effect. In terms of safety, dibutyloxytoluene, butyloxyanisole, and ethyl protocatechuate, which are natural antioxidants such as vitamin C and vitamin E, and synthetic antioxidants that are allowed to be added to foods under the Food Sanitation Law. And isoamyl gallate, propyl gallate, guaiac butter, nordihydroguaiaretic acid and the like.

The amount of the thermal decomposition inhibitor to be used with respect to the dye is selected from the range of 0.1 to 200% by weight, and particularly preferably 1 to 100% by weight. The thermal decomposition inhibitor is not limited to one type, and two or more types can be used in combination. The dye and the thermal decomposition inhibitor may be mixed before the start of the vaporization purification, but the thermal decomposition inhibitor may be dividedly supplied as needed during the vaporization purification. Alternatively, it can be prepared by dissolving both or both of the dye and the thermal decomposition inhibitor in a solvent having no reactivity with respect to both, followed by mixing and appropriately removing the solvent.

In an industrial vaporization purification process, a container containing a vaporizable dye to be purified is heated by a heater or the like to vaporize the dye. The vaporized dye gas is cooled by, for example, being guided to a cooling surface of a cooling drum or the like, and adheres as a purified dye (solid). Then, the purified dye is collected by scraping with a scraper or the like. The dye vaporized and purified as described above is used as it is, or in some cases, diluted with a high boiling point organic solvent to about several% to 20%, preferably about 5% to 15% to obtain a dye vaporized type. It is suitably used as a dye in the new thermal recording system for performing thermal recording. That is, the recording method is excellent in thermal stability, which is an extremely important physical property, and has a feature that good recording can be performed. Among these dyes, methine dyes and anthraquinone dyes are particularly suitable for the purpose of the present invention because they have excellent heat resistance and good sublimability.

[0047]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 20 g of N, N-di (n) butylaniline was charged into 50 ml of N, N-dimethylformamide, 11.5 g of tetracyanoethylene was added with stirring, and the mixture was stirred at room temperature for 3 hours. It reacted below. The precipitated crystals were filtered, washed with methanol and dried to obtain 25 g of a dye represented by the following structural formula (melting point: 129 ° C.).

[0049]

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1 g of the dye obtained by the above method was
The sample was placed in the bottom of a glass test tube having a length of 20 cm, and a thin film of alumina fiber was packed on the top of the sample. The test tube was placed in a quartz tube 5 of an automatic heating apparatus (manufactured by Thermo Riko Co., Ltd.) having a gold furnace transparent electric furnace 1 as shown in FIG. 6) was set. Connect the quartz tube to an oil rotary vacuum pump and an oil diffusion pump, evacuate, 7 × 10 ^-4 Torr
The pressure was reduced to r, and the mixture was heated at 170 ° C. for 3 hours to carry out vaporization purification. As a result, as shown in FIG. 1, the dye 7 purified by vaporization was deposited as red crystals on the vessel wall at the outlet of the test tube 3. The temperature near the outlet of the test tube 3 was 30 ° C.
A small amount of black non-sublimable residue remained at the bottom of the test tube. In addition, the mixture of the low-temperature sublimable component and the target dye thinly adhered to the wall of the gooch funnel 4 attached to the outlet of the test tube 3. The amount of the dye deposited at the outlet of the test tube was 0.
It was 95 g, and the purity was 99.9% or more as a result of analysis by high performance liquid chromatography. The residue remaining at the bottom of the test tube was 0.03 g, and no dye remained in this residue. The component attached to the gooch funnel was 0.02 g, and the component contained 85% of the dye.

When 1 g of the dye purified by the above method was re-vaporized and purified by the same method as above, no residue was left at the bottom of the test tube. 0.99 g of the dye was recovered from the outlet of the test tube and 0.01 g of the dye was recovered from the wall of the gooch funnel, and the purity of each was 99.9% or more. The dye having a purity of 99.9% or more and the unpurified dye (purity 98.6%) purified by
μg was sealed in an aluminum container (capacity: 40 μl) and heated at 200 ° C. for 2 hours with a differential scanning calorimeter Seiko DSC20 (manufactured by Seiko Instruments Inc.), and then the decomposition rate of the dye was examined. As a result, the purified dye was not decomposed at all, but 6% of the unpurified dye was decomposed. From the above test results, since the purified dye does not contain residues after heating, and because the decomposition of the dye during heating recording is suppressed due to improved thermal stability, when applied to the new thermal recording method, It has characteristics that enable good recording.

Example 2 3-Methyl-4-formyl-
24.7 g of N, N-di (i) butylaniline and 6.9 g of malononitrile were charged in 100 ml of methanol,
5 ml of a 1N aqueous sodium hydroxide solution was added, and the mixture was reacted with stirring at room temperature for 5 hours. The precipitated crystals were collected by filtration, washed with methanol and dried to give a dye represented by the following structural formula (melting point: 11
(7 ° C.).

[0053]

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1 g of the dye obtained by the above method was vaporized and purified in the same manner as in Example 1. However, the heating temperature is 150
° C. As a result, the purified dye was deposited as yellow crystals on the vessel wall at the outlet of the test tube. A small amount of black non-vaporizable residue remained at the bottom of the test tube. In addition, the mixture of the low-temperature vaporizable component and the target dye adhered thinly to the wall of the gooch funnel attached to the outlet of the test tube. The amount of the dye precipitated at the outlet of the test tube was 0.93 g, and the purity was 99.9% or more as a result of analysis by high performance liquid chromatography. The residue remaining at the bottom of the test tube was 0.02 g, and no dye remained in this residue.
The amount of the component attached to the gooch funnel was 0.05 g, and the component contained 90% of the dye.

When 1 g of the dye purified by the above method was revaporized and purified by the same method as above, no residue was left at the bottom of the test tube. 0.98 g of dye was recovered from the outlet of the test tube, and 0.02 g of dye was recovered from the wall of the gooch funnel, and the purity of each was 99.9% or more. The dye having a purity of 99.9% or more and the unpurified dye (purity 98.5%) purified by
μg was sealed in an aluminum container (capacity: 40 μl) and heated at 200 ° C. for 2 hours with a differential scanning calorimeter Seiko DSC20 (manufactured by Seiko Instruments Inc.), and then the decomposition rate of the dye was examined. As a result, the purified dye had no decomposition at all, but the unpurified dye had 5% of the dye decomposed. From the above test results, since the purified dye does not contain residues after heating, and because the decomposition of the dye during heating recording is suppressed due to improved thermal stability, when applied to the new thermal recording method, It has characteristics that enable good recording.

Example 3 1-isobutylamino-4-
155 g of bromoanthraquinone, 56 g of aniline, 3.3 g of sodium acetate and 0.1 g of copper sulfate were charged.
The reaction was carried out at 160 ° C. for 1 hour with stirring. After cooling to room temperature,
100 ml of methanol and 50 ml of concentrated hydrochloric acid were added, and 3
After stirring for 0 minutes, the precipitated crystals were filtered, washed with methanol and water, and dried to obtain a dye represented by the following structural formula (melting point: 1).
5.5 ° C.) (30 ° C., decomposition temperature 362 ° C.).

[0057]

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1 g of the dye obtained by the above method was purified in the same manner as in Example 1. However, the heating temperature was 180 ° C. As a result, the purified dye was deposited as blue crystals on the vessel wall at the outlet of the test tube. At the bottom of the test tube,
A small amount of black non-vaporizable residue remained. In addition, the mixture of the low-temperature vaporizable component and the target dye adhered thinly to the wall of the gooch funnel attached to the outlet of the test tube. The amount of the dye precipitated at the outlet of the test tube was 0.90 g, and the purity was 99.9% or more as a result of analysis by high performance liquid chromatography. The residue remaining at the bottom of the test tube was 0.09 g, and no dye remained in this residue. The component attached to the gooch funnel is 0.01 g,
This component contained 50% of the dye.

When 1 g of the dye purified by the above method was re-vaporized and purified by the same method as above, no residue was left at the bottom of the test tube. 0.99 g of the dye was recovered from the outlet of the test tube and 0.01 g of the dye was recovered from the wall of the gooch funnel, and the purity of each was 99.9% or more. The dye having a purity of 99.9% or more and the unpurified dye (purity 95.9%) purified by
μg was sealed in an aluminum container (capacity: 40 μl) and heated at 200 ° C. for 2 hours with a differential scanning calorimeter Seiko DSC20 (manufactured by Seiko Instruments Inc.), and then the decomposition rate of the dye was examined. As a result, the purified dye was not decomposed at all, but 10% of the unpurified dye was decomposed. From the above test results, since the purified dye does not contain residues after heating, and because the decomposition of the dye during heating recording is suppressed due to improved thermal stability, when applied to the new thermal recording method, It has characteristics that enable good recording.

Example 4 2.6 g of 2,6-di (t) butylphenol was charged in 50 ml of acetone, and 25 ml of aqueous ammonia (28%) and 25 ml of water were added thereto and cooled to 0 ° C. In this, 2-amino-5-
A solution of 2.6 g of (N, N diethylamino) toluene hydrochloride dissolved in 25 ml of water, and 4.6 parts of ammonium persulfate
g was dissolved in 25 ml of water, and the reaction temperature was kept at 0 to 5 ° C., and the solution was added dropwise at the same time. The reaction was carried out at the same temperature with stirring for 2 hours. The precipitated crystals were filtered, washed with methanol and dried to obtain 2 g of a dye represented by the following structural formula (melting point: 141 ° C., decomposition temperature: 296 ° C.).

[0061]

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1 g of the dye obtained by the above method was vaporized and purified in the same manner as in Example 1. However, the heating temperature is 150
° C. As a result, the purified dye was deposited as blue crystals on the vessel wall at the outlet of the test tube. A small amount of black non-vaporizable residue remained at the bottom of the test tube. In addition, the mixture of the low-temperature vaporizable component and the target dye adhered thinly to the wall of the gooch funnel attached to the outlet of the test tube. The amount of the dye precipitated at the outlet of the test tube was 0.94 g, and the purity was 99.9% or more as a result of analysis by high performance liquid chromatography. The residue remaining at the bottom of the test tube was 0.04 g, and no dye remained in this residue.
The component attached to the gooch funnel was 0.02 g, and the component contained 80% of the dye.

When 1 g of the dye purified by the above method was revaporized and purified in the same manner as described above, no residue was left at the bottom of the test tube. 0.99 g of the dye was recovered from the outlet of the test tube and 0.01 g of the dye was recovered from the wall of the gooch funnel, and the purity of each was 99.9% or more. Each of the dye having a purity of 99.9% or more and the unpurified dye (purity of 98.3%) purified by the above-described method was 1
μg was sealed in an aluminum container (capacity: 40 μl) and heated at 180 ° C. for 2 hours with a differential scanning calorimeter Seiko DSC20 (manufactured by Seiko Instruments Inc.), and then the decomposition rate of the dye was examined. As a result, the purified dye did not decompose at all, but 8% of the unpurified dye was decomposed. From the above test results, since the purified dye does not contain residues after heating, and because the decomposition of the dye during heating recording is suppressed due to improved thermal stability, when applied to the new thermal recording method, It has characteristics that enable good recording.

Example 5 m-Fluoroaniline 3.3
g, 70 ml of water and 6.8 ml of concentrated hydrochloric acid, and cooled to 0 ° C. A solution prepared by dissolving 2.4 g of sodium nitrite in 10 ml of water was added dropwise while controlling the reaction temperature at 0 to 5 ° C. The mixture was stirred at the same temperature for 2 hours to carry out a diazotization reaction.
On the other hand, 3-cyano-4-methyl-6-hydroxy-N-
(I) Butylpyridone-2 was charged and dissolved in an aqueous solution composed of 200 ml of water, 8 g of sodium acetate, and 3.6 g of caustic soda. About 5 ml of concentrated hydrochloric acid was added to the solution, the pH of the solution was adjusted to about 5.5, and the solution was cooled to 0 ° C. The diazo solution prepared previously was added dropwise to this solution at a temperature of 0 to 5 ° C. A 10% aqueous solution of caustic soda was added dropwise to the reaction solution, and the pH was readjusted to around 5.5. After the reaction, the precipitated crystals were filtered, washed with water and methanol, and dried, and the dye represented by the following structural formula (melting point: 1
82 ° C, decomposition temperature 297 ° C).

[0065]

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1 g of the dye obtained by the above method was purified by sublimation in the same manner as in Example 1. As a result, the dye purified by sublimation was deposited as yellow crystals on the vessel wall at the outlet of the test tube. A small amount of black non-sublimable residue remained at the bottom of the test tube. In addition, the mixture of the low-temperature sublimable component and the target dye thinly adhered to the wall of the gooch funnel attached to the outlet of the test tube. The amount of the dye precipitated at the outlet of the test tube was 0.91 g, and the purity was 99.9% or more as a result of analysis by high performance liquid chromatography. The residue remaining at the bottom of the test tube was 0.08 g, and no dye remained in this residue. The component attached to the gooch funnel was 0.01 g.
% Was included.

When 1 g of the dye sublimated and purified by the above method was resublimated and purified by the same method as above, no residue was left at the bottom of the test tube. 0.99 g of the dye was recovered from the outlet of the test tube and 0.01 g of the dye was recovered from the wall of the gooch funnel, and the purity of each was 99.9% or more. 1 μg of the dye having a purity of 99.9% or more and the unpurified dye (purity of 96.5%) purified by the above method were sealed in aluminum containers (capacity: 40 μl), respectively, and the differential scanning calorimeter Seiko DSC20 ( After heating at 180 ° C. for 2 hours with a Seiko Instruments Inc.), the decomposition rate of the dye was examined. As a result, the purified dye was not decomposed at all, but 6% of the unpurified dye was decomposed. From the above test results, since the dye purified by sublimation does not contain the residue after heating, and the decomposition of the dye during heating recording is suppressed due to the improvement in thermal stability, when applied to the above-mentioned new thermal recording method And has the property of enabling good recording.

[Example 6] 0.5 g of a 6k dye (melting point 89 ° C., decomposition temperature 329 ° C.) and 0.05 g of vitamin C were preliminarily mixed to prepare a dye mixture. Using this dye mixture, vaporization purification was performed in the same manner as in Example 1. However, the pressure was reduced to 0.8 Torr, the heating temperature was 200 ° C., and the heating time was 1 hour. As a result, the vaporized dye was deposited as blue crystals on the vessel wall at the outlet of the test tube. The purity of the dye was 99.1% as a result of analysis by high performance liquid chromatography, and the purity before purification was 99.1%.
The reduction in purity relative to 4% was 0.3%.

1 μg of the dye having a purity of 99.1% purified by the above-mentioned method, and an aluminum container (capacity: 40 μl)
After heating at 200 ° C. for 2 hours with a differential scanning calorimeter Seiko DSC20 (manufactured by Seiko Instruments Inc.), the decomposition rate of the dye was examined. As a result, the purified dye did not decompose at all. From the above test results, by performing vaporization purification in the presence of vitamin C, it is possible to suppress the thermal decomposition of the dye at the time of purification, and the purified dye is improved in thermal stability due to improved thermal stability. Since the decomposition of the dye is suppressed, when applied to the above-mentioned new thermal recording method, it has a characteristic of enabling good recording.

Comparative Example 2 Vitamin C used in Example 6
As a result of testing in the same manner as in Example 6 without using any of the above, the purity of the sublimed dye was 90.4% as a result of analysis by high-performance liquid chromatography, which was 99.4% of the purity before purification. The decrease was 9.0%. In addition, 1 μg of unpurified dye (purity 99.4%) was sealed in an aluminum container (capacity: 40 μl), and was charged with a differential scanning calorimeter Seiko DSC20 (manufactured by Seiko Instruments Inc.).
After heating at 200 ° C. for 2 hours, the decomposition rate of the dye was examined. As a result, 10% of the dye was decomposed.

[0071]

When the dye obtained by the vaporization purification of the present invention is applied to a recording method based on a dye vaporization type thermal recording system, good recording can be performed industrially advantageously.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main structure of an automatic heating apparatus having a gold furnace transparent electric furnace used in an example.

Continuation of the front page (72) Inventor Osamu Kawashima 1-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Mitsubishi Chemical Corporation Kurosaki Office

Claims (5)

[Claims] 1. A vaporizable dye, which is a methine dye, an anthraquinone dye, an azomethine dye, an azo dye,
It is characterized by vaporizing and purifying a dye selected from the group consisting of quinophthalone dyes, coumarin dyes, perinone dyes, xanthene dyes, thioxanthene dyes, azathioxanthene dyes, oxazine dyes, and thiazine dyes. Method for purifying a dye. 2. The purification method according to claim 1, wherein the purification is carried out under reduced pressure. 3. The purification method according to claim 1, wherein the dye is vaporized and refined in the presence of a thermal decomposition inhibitor of the vaporizable dye. 4. A dye vaporization type thermal recording method comprising using a dye purified by vaporization. 5. The dye is a methine dye, anthraquinone dye, azomethine dye, azo dye, quinophthalone dye, coumarin dye, perinone dye, xanthene dye, thioxanthene dye, azathioxanthene dye, 5. The recording method according to claim 4, wherein the recording method is a volatile dye selected from the group consisting of an oxazine dye and a thiazine dye.