JP4531429B2 - Method for refining electronic product materials - Google Patents

Description

The present invention relates to a material for an electrophotographic photoreceptor used in an electrophotographic copying machine, a printer, or the like, a charge transport material used as a material for an organic electroluminescent element, and a method for producing an intermediate thereof with high purity. About.

Conventionally, stilbene derivatives are known as useful compounds as charge transport materials and intermediates used in electrophotographic photoreceptors and organic electroluminescent devices. These compounds are usually produced by the Wittig reaction, which is the final stage, or the Ullmann reaction, in the intermediate stage.

As a reaction for synthesizing a stilbene derivative, a dialkyl aromatic phosphonate represented by the general formula (2),

(In the formula, Ar1 represents a substituted or unsubstituted phenyl group , Ar2 represents a substituted or unsubstituted phenyl group or a hydrogen atom, and R3 represents an aliphatic hydrocarbon group.)
An aromatic aldehyde compound represented by the general formula (3),

(In the formula, Ar3 represents a substituted or unsubstituted phenylene group , R1 and R2 each represents a substituted or unsubstituted phenyl group, and R1 and R2 may be the same or different.)

The method of condensing in the presence of a base in a solvent is mentioned (for example, refer patent document 1 and patent document 2).

Japanese Patent Publication No. 63-19867 Japanese Patent Publication No. 2-24864

  Alternatively, in the stilbene derivative represented by the general formula (1), as a synthesis reaction in the case where Ar2 is a hydrogen atom and n = 1, an aromatic phosphonate dialkyl represented by the general formula (4),

(In the formula, Ar1 represents a substituted or unsubstituted phenyl group, and R3 represents an aliphatic hydrocarbon group.)
Examples include a method of condensing the aromatic aldehyde compound represented by the general formula (3) in a solvent in the presence of a base (see, for example, Patent Document 2 and Patent Document 3).

Japanese Patent Publication No. 5-47533

As described above, in the reaction for obtaining the stilbene derivative, the aromatic aldehyde compound represented by the general formula (3) is frequently used as a reaction raw material, but the aromatic aldehyde compound represented by the general formula (3) is Since it is a tertiary amine, in the production process of the previous stage until it reaches general formula (3), it often passes the Ullmann reaction on the way.

  The synthesis reaction as described above is accompanied by side reactions due to severe reaction conditions, and by-products are generated that inhibit the performance of charge transport agents required for electrophotographic photoreceptors and organic electroluminescent devices. Since the purification method used to remove these by-products was initially only recrystallization (see, for example, Patent Document 1 and Patent Document 2), for electrophotographic photoreceptors and organic electroluminescent devices. In order to satisfy the electrical properties required for the charge transport material used, sufficient purity could not be obtained. As a purification method for obtaining sufficient purity to satisfy such electrical characteristics, an adsorption purification method using activated clay or activated carbon has been disclosed, and is currently generalized with other adsorbents in the technical field. (For example, refer to Patent Document 4). However, since the adsorption purification method using an adsorbent cannot achieve satisfactory purity if only one stage is implemented, the adsorption purification process must be combined several times, resulting in problems such as a decrease in yield, an increase in cost, and an increase in the amount of waste. Have.

JP-A-7-56365

  There is distillation as a method other than the purification method described above, but a purification method in which a diaminodiphenyl compound is distilled under reduced pressure in the presence of an alkali base is disclosed (for example, see Patent Document 5). However, this purification method is applied because the diaminodiphenyl compound is a compound that is difficult to purify, and in order to obtain a high-purity product, distillation is performed in two stages of rough distillation and precision distillation. Precision distillation requires a distillation apparatus having 10 to 50 theoretical plates.

JP-A-1-272558

  The present invention does not require a material to be used for the refining process, the amount of waste generated by the refining process is particularly small, a short refining process is sufficient, and an electronic product with excellent electrical characteristics that does not require a large-scale distillation apparatus The object is to provide a purification method for obtaining the material.

In the technical field targeted by the present invention, a high-purity product excellent in electrical characteristics is required, and an adsorption purification method is generalized as a purification method suitable therefor. Although vacuum distillation is intended for compounds that are difficult to purify and has no other means of purification, and is considered disadvantageous in terms of cost, the present inventors have performed vacuum distillation on crude products of stilbene derivatives. As a result, it was found that a high-purity product can be obtained by only one stage of distillation, and the present invention has been completed.

That is, the present invention provides a stilbene derivative represented by the general formula (1).

(In the formula, Ar1 represents a substituted or unsubstituted phenyl group , Ar2 represents a substituted or unsubstituted phenyl group or a hydrogen atom, Ar3 represents a substituted or unsubstituted phenylene group , and R1 and R2 are substituted or unsubstituted, respectively. Represents an unsubstituted phenyl group , R1 and R2 may be the same or different, and n represents 0 or 1.)

In order to improve electrical characteristics, the present invention is a method for purifying an electronic product material, characterized by performing vacuum distillation under a high vacuum condition of 10 Pa or less.

Since the vacuum distillation of the present invention can be carried out by simple distillation, a particularly large-scale distillation apparatus is not required. In addition, since it is not necessary to combine other purification steps in addition to the distillation step, a high-purity product having excellent electrical characteristics can be obtained very simply. Further, various materials such as a solvent and an adsorbent necessary for the purification process are not required, and generation of waste accompanying the purification process need not be considered. In general, incorporating vacuum distillation into the purification process is considered costly disadvantageous, but there is a demand for high-purity products with excellent electrical characteristics as in the technical field of the present invention. In particular, the purification method of the present invention, which can achieve the object by one-step purification, is particularly suitable.

Formula (1) represented by stilbene derivative of the groups of the present invention, Ar1, Ar2, R1, Oite in R2, may also be also be substituted with these groups unsubstituted, Ar @ 1 and Ar2 is either the same or different R1 and R2 may be the same or different.

Ar3 of the stilbene derivative represented by the general formula (1) may be unsubstituted or substituted.

Examples of the substituent that can be taken by the group of the aforementioned stilbene derivative, Ar1, Ar2, Ar3, R1, and R2 include an alkyl group and an alkoxy group .

The stilbene derivative represented by the general formula (1) targeted by the purification method of the present invention is a charge transport material used as a material for an electrophotographic photoreceptor or a material for an organic electroluminescence device. The purification method of the present invention is also intended for the case of purifying at the intermediate stage of the stilbene derivative represented by the general formula (1) for the purpose of improving electrical characteristics.

  According to the purification method using the vacuum distillation apparatus of the present invention, there is no need for materials to be used for the purification process, almost no waste is generated by the purification process, a short purification process is sufficient, and a large-scale distillation apparatus is required. It has the advantage that it is not necessary. Further, since it does not contain impurities that hinder the performance of the charge transport agent, it is possible to provide an electronic product material with excellent electrical characteristics.

Examples of the compound to which the purification method of the present invention is applied include the following compounds as stilbene derivatives. In the case where isomers having different substitution positions exist in the exemplified compounds, they may be a single compound or a mixture.
4-diphenylamino stilbene, 4- (4-methyl diphenylamino) stilbene, 4- (4,4'-dimethyl-diphenylamino) stilbene, 4- (4-methoxy diphenylamino) -4' Mechirusuchiru Ben, 4- ( 4-methoxydiphenylamino) -4′-methoxystilbene, 4- (3,4-dimethyldiphenylamino) stilbene, 4- (2-methyl-4-methoxydiphenylamino) -4′-methylstilbene, α-phenyl- 4′-diphenylaminostilbene, α-phenyl-4 ′-[bis (4-methylphenyl) amino] stilbene, α-phenyl-4 ′-(4-methoxydiphenylamino) stilbene, α- (4-methylphenyl) 4-methyl-4 '- (4-methyl diphenylamino) stilbene, alpha-phenyl-4' - (3,4 Dimethyldiphenylamino) stilbene, α-phenyl-4 ′-(2,4-dimethyl-4′-methoxydiphenylamino) stilbene, α-phenyl-4 ′-(2-methyl-4-methoxydiphenylamino) stilbene, α -(4-Ethoxyphenyl) -4-ethoxy-4'-diphenylaminostilbene.

1-phenyl-4- (4-diphenylaminophenyl) -1,3-butadiene, 1- (4-methylphenyl) -4- (4-diphenylaminophenyl) -1,3-butadiene, 1-phenyl-4 -[4-Bis (4-methylphenyl) aminophenyl] -1,3-butadiene, 1,1-diphenyl-4- (4-diphenylaminophenyl) -1,3-butadiene, 1,1-diphenyl-4 - [4- bis (4-methylphenyl) aminophenyl] -1,3-butadiene, 1,1-bis (4-methoxyphenyl) -4- (4-diphenylamino-phenyl) -1,3-butadiene.

The vacuum distillation apparatus of the present invention does not require particularly large equipment, and even the simple distillation apparatus can sufficiently achieve its purpose. The high vacuum condition during vacuum distillation is 10 Pa or less, preferably 0.1 to 1 Pa.

Since the vacuum distillation of the present invention can achieve its purpose by one-step purification, it is not necessary to use other purification methods starting from the crude product stage, and is necessary for other purification steps. This material is characterized in that it does not require the above-mentioned materials and that there is no need to worry about the generation of waste associated with other purification processes.

Hereinafter, the present invention will be described specifically by way of examples. The part in an Example represents a mass part and a density | concentration represents the mass%.

[Synthesis Example 1]
4- [N, N-bis (4-methoxyphenyl) amino] benzaldehyde 66.67 g (0.20 mol), diethyl phenylmethylphosphonate 50.20 g (0.22 mol), and 230 ml of tetrahydrofuran as a solvent were added and dissolved. At room temperature, 29.17 g (0.26 mol) of potassium tertiary butoxide was added over 30 minutes. After the addition, the mixture was further stirred at 40 to 45 ° C. for 2 hours. After confirming disappearance of the formyl compound, the reaction was terminated. After cooling to 30 ° C., 690 ml of methanol was added dropwise, and the mixture was stirred at 0 to 5 ° C. for 30 minutes. The crystals obtained by filtration were dried under reduced pressure at 60 ° C. and 4- [N, N-bis (4-methoxyphenyl). ) Amino] stilbene 73.3 g (yield 89.9%) was obtained.

In a simple distillation apparatus, 500 g of 4- [N, N-bis (4-methoxyphenyl) amino] stilbene obtained in Synthesis Example 1 was charged under the conditions of a tower top pressure of 0.35 Pa and a tower bottom temperature of 230 to 255 ° C. Distillation was performed. As a main fraction, 420 g of 4- [N, N-bis (4-methoxyphenyl) amino] stilbene was obtained. The purity analysis result by LC analysis was 99.9%. The LC analysis conditions were as described in [HPLC condition 1].
[HPLC condition 1]
Model: TOSO UV-8000
Column: Inertsil, ODS-2, 4.6φ × 250 mm
Column temperature: 40 ° C
Mobile phase: THF / methanol = 1/10
Flow rate: 0.9 ml / min
Measurement wavelength: 254 nm

[Comparative Example 1]
After dissolving 50 g of 4- [N, N-bis (4-methoxyphenyl) amino] stilbene obtained in Synthesis Example 1 in 250 ml of toluene at 40 ° C., adding 250 ml of cyclohexane and stirring, and then adding 10 g of activated carbon. After stirring at 40 ° C. for 30 minutes, the activated carbon was removed by filtration. After adding 25 g of activated clay to the filtrate and stirring at 40 ° C. for 30 minutes, the activated clay was removed by filtration. Thereafter, the same combination of adsorption purification using activated clay and adsorption purification using activated carbon was repeated twice, and the obtained filtrate was concentrated. To the yellow oily substance obtained by concentration, 200 ml of normal propanol was added, and after heating and dissolving at 80 ° C., the mixture was allowed to cool to 30 ° C. to precipitate crystals. Further, 200 ml of methanol was added, and the crystals obtained by filtration were dried under reduced pressure at 50 ° C. and purified 41.5 g of 4- [N, N-bis (4-methoxyphenyl) amino] stilbene (yield 83%). ) The LC analysis result by [HPLC condition 1] was a purity of 99.9%.

[Photoreceptor Example 1]
After dissolving 10 parts of alcohol-soluble polyamide in 190 parts of methanol, it was coated and dried on the aluminum surface of the aluminum-deposited PET film using a wire bar to form an undercoat layer having a thickness of 1 μm.

  Next, titanyl phthalocyanine (charge generating agent No. 1) having a strong peak at 9.6, 24.1, 27.2 in the diffraction angle 2θ ± 0.2 ° in the X-ray diffraction spectrum of Cu—Kα.

1.5 parts was added to 50 parts of a 3% cyclohexanone solution of polyvinyl butyral resin and dispersed with an ultrasonic disperser for 1 hour. The obtained dispersion was applied onto the undercoat layer using a wire bar, and then dried at 110 ° C. for 1 hour under normal pressure to form a charge generation layer having a thickness of 0.6 μm.

On the other hand, 100 parts of the purified product obtained in Example 1 as a charge transport agent was added to 962 parts of a 13.0% tetrahydrofuran solution of polycarbonate resin and completely dissolved by applying ultrasonic waves. This solution was applied onto the charge generation layer with a wire bar and dried at 110 ° C. for 30 minutes under normal pressure to form a charge transport layer having a thickness of 20 μm to produce a photoreceptor.

[Photoreceptor Comparative Example 1]
In place of the purified product of Example 1 used in Example 3, the purified product of Comparative Example 1 was used, and a photoconductor for comparison was produced in the same manner as in Example 3.

The photoconductors produced in Photoreceptor Example 1 and Photoreceptor Comparative Example 1 were evaluated for electrophotographic characteristics using an electrostatic copying paper test apparatus (trade name “EPA-8100A”). First, a corona discharge of −6.5 kV was performed on the photosensitive member in a dark place, and the charging potential V0 (−V) at this time was measured. Subsequently, the film was exposed to 1.0 μW / cm 2 of 780 nm monochromatic light, and a half-exposure amount E1 / 2 (μJ / cm 2) and a residual potential Vr (−V) after exposure for 5 seconds were obtained. The evaluation results are shown in [Table 1].

From the results of [Table 1], in the case of 4- [N, N-bis (4-methoxyphenyl) amino] stilbene, in order to obtain a compound having performance equivalent to that of a high-vacuum distilled product, 6 adsorption purifications were performed. Is necessary.

[Synthesis Example 2]
In a 5-liter flask, 602.7 g (2.0 mol) of 4- [N, N-bis (4-methylphenyl) amino] benzaldehyde, 532.9 g (2.2 mol) of diethyl 4-methylbenzylphosphonate, tetrahydrofuran 1 as a solvent. 4 liters was added and dissolved. While maintaining the temperature at 45 ° C. or lower, 291.7 g (2.6 mol) of potassium tertiary butoxide was added, and the mixture was stirred at 40 to 45 ° C. for 1 hour. The mixture was cooled to 30 ° C., methanol was added dropwise, and the mixture was stirred at 0-5 ° C. for 30 minutes. The crystals obtained by filtration were dried under reduced pressure at 60 ° C. -Methylphenyl) amino] stilbene (759.3 g, yield 97.5%) was obtained.

  500 g of 4-methyl-4 ′-[N, N-bis (4-methylphenyl) amino] stilbene obtained in Synthesis Example 2 was charged into a simple distillation apparatus, the tower top pressure was 0.37 Pa, and the tower bottom temperature was 240 to 240. Distillation was performed at 260 ° C. As a main fraction, 450 g (90% yield) of 4-methyl-4 '-[N, N-bis (4-methylphenyl) amino] stilbene was obtained. The purity analysis result by LC analysis was 99.9%. The LC analysis conditions were as described in [HPLC condition 1].

[Comparative Example 2]
50 g of 4-methyl-4 ′-[N, N-bis (4-methylphenyl) amino] stilbene obtained in Synthesis Example 2 was dissolved in 250 ml of toluene at 40 ° C., and 25 g of activated clay was added. After stirring at 40 ° C. for 30 minutes, the activated clay was removed by filtration. After adding 10 g of activated carbon to the filtrate and similarly stirring at 40 ° C. for 30 minutes, the activated carbon was removed by filtration. Thereafter, the same adsorption purification using activated clay and adsorption purification using activated carbon were repeated once, the whole amount was concentrated to 100 ml, and then 300 ml of methanol was added to precipitate crystals. The crystals obtained by filtration were dried at 60 ° C. under reduced pressure to obtain 44.0 g (yield 88%) of 4-methyl-4 ′-[N, N-bis (4-methylphenyl) amino] stilbene. The LC analysis result by [HPLC condition 1] was a purity of 99.9%.

[Photoreceptor Example 2]
The following bisazo pigment (charge generator No. 2) as a charge generator

1.0 part and 8.6 parts of a 5% cyclohexanone solution of polyvinyl butyral resin were added to 83 parts of cyclohexanone, and pulverized and dispersed in a ball mill for 48 hours. The obtained dispersion was applied to the aluminum surface of an aluminum vapor-deposited PET film, which is a conductive support, using a wire bar and dried at 110 ° C. for 1 hour under normal pressure to form a charge generation layer having a thickness of 0.8 μm. Formed.

On the other hand, 100 parts of the purified product obtained in Example 5 as a charge transport agent was added to 962 parts of a 13.0% tetrahydrofuran solution of polycarbonate resin and completely dissolved by applying ultrasonic waves. This solution was applied onto the charge generation layer with a wire bar and dried at 110 ° C. for 30 minutes under normal pressure to form a charge transport layer having a thickness of 20 μm to produce a photoreceptor.

[Photoreceptor Comparative Example 2]
In place of the purified product of Example 5 used in Example 6, the purified product of Comparative Example 2 was used, and a photoconductor for comparison was produced in the same manner as in Example 6.

The photoconductors produced in Example 6 and Photoconductor Comparative Example 2 were evaluated for electrophotographic characteristics using an electrostatic copying paper test apparatus (trade name “EPA-8100A”). First, the photoconductor was subjected to corona discharge of -6.0 kV in the dark, and the charging potential V0 (-V) at this time was measured. Next, exposure was performed with 1.0 Lux white light, and a half-exposure amount E1 / 2 (Lux · sec) and a residual potential Vr (−V) after exposure for 5 seconds were obtained. The evaluation results are shown in [Table 2].

  From the results of [Table 2], in the case of 4-methyl-4 ′-[N, N-bis (4-methylphenyl) amino] stilbene, in order to obtain a compound having performance equivalent to that of a high-vacuum distilled product It can be seen that four adsorption purifications are necessary.

Electronic product materials with high purity and excellent electrical properties that do not contain substances that impede the performance of charge transport agents.

Claims (5)

Of the stilbene derivative represented by the general formula (1)

(In the formula, Ar1 represents a substituted or unsubstituted phenyl group , Ar2 represents a substituted or unsubstituted phenyl group or a hydrogen atom, Ar3 represents a substituted or unsubstituted phenylene group , and R1 and R2 are substituted or unsubstituted, respectively. Represents an unsubstituted phenyl group, and R1 and R2 may be the same or different, and n represents 0 or 1.) In order to improve electrical characteristics, vacuum distillation is performed under a high vacuum condition of 10 Pa or less. A method for refining electronic product materials.   The method for purifying an electronic product material according to claim 1, wherein the high vacuum condition is 0.1 to 1 Pa.   3. The method for purifying an electronic product material according to claim 1, wherein the distillation apparatus for vacuum distillation performed under the high vacuum condition is a single distillation apparatus.   The stilbene derivative represented by the general formula (1) is purified in one step of vacuum distillation without using another purification method from the crude product step. A method for purifying an electronic product material according to any one of the items. The purification method of the electronic product material in any one of Claims 1-4 whose stilbene derivative represented by General formula (1) is an electronic product material or its intermediate body.