JP2869196B2 - Tetraphenylfuran derivative and electrophotographic photoreceptor containing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel tetraphenylfuran derivative and an electrophotographic photoreceptor containing the same. More specifically, the present invention relates to an electrophotographic photoconductor in which a photosensitive layer on a conductive support contains a novel tetraphenylfuran derivative as a charge transporting substance.

[0002]

2. Description of the Related Art Conventionally, inorganic photosensitive materials such as selenium, cadmium sulfide, and zinc oxide have been widely used as photosensitive materials for electrophotographic photosensitive members. However, photoreceptors using these photosensitive materials have not sufficiently satisfied the required performance as an electrophotographic photoreceptor, such as sensitivity, light stability, moisture resistance, and durability. For example, a photoreceptor using a selenium-based material has excellent sensitivity, but is easily crystallized due to heat or adhesion of dirt, and the characteristics of the photoreceptor are easily deteriorated. In addition, it has many drawbacks, such as high cost because it is manufactured by vacuum evaporation, and difficulty in processing it into a belt shape due to lack of flexibility. A photoreceptor using a cadmium sulfide-based material has a problem in moisture resistance and durability, and a photoreceptor using zinc oxide has a problem in durability.

In order to overcome the disadvantages of the photoreceptor using the inorganic photosensitive material, various photoreceptors using the organic photosensitive material have been studied.

[0004] In recent years, among photoconductors developed to improve the above-mentioned drawbacks, a function-separated type photoconductor in which a charge generation function and a charge transport function are shared by different substances has attracted attention. In this function-separated type photoreceptor, substances having each function can be selected from a wide range and combined, so that a photoreceptor with high sensitivity and high durability can be manufactured.

The characteristics required of the charge transporting substance contained in the electrophotographic photoreceptor include: (1) a sufficient ability to accept the charge generated by the charge generating substance; and (2) a rapid transfer of the received charge. And (3) sufficient charge transport even in a low electric field so that no charge remains.

Further, as a photoreceptor, light received in a repeated process of charging, exposing, developing and transferring during copying,
Durability is required to be stable against heat and the like and to obtain a reproduced image with good reproducibility faithful to the original image.

Various compounds have been proposed as charge transport materials. For example, poly-N-vinyl carbazole has long been known as a photoconductive substance, and a photoreceptor using this as a charge transporting substance has been put to practical use, but has poor flexibility in itself, and is fragile and cracked. The durability was inferior to repeated use because it easily occurred. Also,
When the flexibility is improved in combination with the binder, there is a disadvantage that the electrophotographic properties are inferior.

[0008] On the other hand, a low-molecular compound generally has no film properties, and is usually mixed with a binder with an arbitrary composition to form a photosensitive layer. Many charge transport materials composed of low molecular weight compounds have been proposed. For example, a thiophene compound has been studied as a charge transporting substance, and is disclosed in JP-A-63-158560 and JP-A-1-9434.
No. 9 and the like. However, the sensitivity has not yet reached a sufficiently good value.

Although many other charge transport materials have been proposed, at present there is no such material which sufficiently satisfies the required performance as an electrophotographic photoreceptor, and the development of a more excellent photoreceptor is desired. I was

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel compound useful as a charge transport material. Another object of the present invention is to provide an electrophotographic photoreceptor having sufficient sensitivity and excellent durability.

[0011]

Means for Solving the Problems The present inventors have intensively studied to solve the above-mentioned problems, and the tetraphenylfuran derivative represented by a specific structural formula is useful as a charge transport compound, and has high sensitivity and high sensitivity. The present inventors have found that an electrophotographic photoconductor having excellent properties such as durability is provided, and have completed the tetraphenylfuran derivative and the electrophotographic photoconductor of the present invention. That is,

The tetraphenylfuran derivative of the present invention comprises
It is represented by the general formula (I) (Formula 1).
Further, the electrophotographic photoreceptor of the present invention is characterized in that the photosensitive layer on the conductive support contains a tetraphenylfuran derivative represented by the following general formula (I).

In the general formula (I), R ₁ and R ₂
Examples include alkyl groups such as methyl group, ethyl group, isopropyl group, butyl group, isobutyl group, pentyl group, hexyl group, heptyl group, octyl group, aralkyl groups such as benzyl group, phenethyl group, phenyl group, naphthyl group, etc. And the like.

These groups may have a substituent. When R ₁ or R ₂ is an aryl group, the substituent may be a halogen atom, a methyl group, an ethyl group, a butyl group,
Alkyl group such as octyl group, methoxy group, ethoxy group,
Alkoxy groups such as butoxy group, carbomethoxy group, carboxylate group such as carboethoxy group, benzyl group,
Examples include, but are not limited to, aralkyl groups such as a phenethyl group and the like, and aryl groups such as a phenyl group and a naphthyl group. Examples of the group in which R ₁ and R ₂ are bonded to form a ring together with a nitrogen atom include a pyrrolidino group and a piperidino group. These exemplified R ₁ and R ₂
Among them, R ₁ and R ₂ are preferably an aryl group from the viewpoints of high sensitivity, solubility in an organic solvent, and the like.

The tetraphenylfuran derivative represented by the general formula (I) of the present invention can be synthesized by the following method. For example, (1) General formula (II)

Embedded image (Where k, p, m, and n satisfy 4 ≧ k + p + m + n ≧ 1 and are each an integer of 0 or 1), and p-toluenesulfonic acid alkyl ester, dialkyl sulfate, alcohol , Alkyl halide, aryl halide and the like.

(2) General formula (III)

Embedded image (Where k, p, m, and n satisfy 4 ≧ k + p + m + n ≧ 1, each is an integer of 0 or 1, and x is a halogen atom).

Embedded image (Here, R ₁ and R ₂ are the same as those in the general formula (I)). It is easily synthesized by such a method. The halogen atom represented by x in the compound represented by the general formula (III) is more preferably an iodine atom.

[0017] The tetraphenylfuran derivatives of the present invention are more specifically shown in Tables 1, 2 and 3, but are not limited thereto.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

The electrophotographic photoreceptor of the present invention has the general formula (I)
A photosensitive layer containing a tetraphenylfuran derivative represented by formula (1) and a conductive support. This photosensitive layer comprises a charge transport compound and a charge generating substance, and the tetraphenylfuran derivative acts as a charge transport compound. When the photosensitive layer is a mixed system of a charge generating substance and a charge transport compound,
The photosensitive layer may be composed of a charge transport layer and a charge generation layer. The photosensitive layer is formed by depositing or coating a charge transport compound and a charge generation substance on a conductive support.

The charge transport layer of the photoreceptor of the present invention may contain various additives. For example,
Plasticizers such as diphenyl, m-terphenyl and dibutyl phthalate, silicone oils, graft-type silicone polymers, surface lubricants such as various fluorocarbons,
Dicyanovinyl compounds, potential stabilizers such as carbazole derivatives, beta-carotene, N _i complexes, and the like 1,4-diazabicyclo [2,2,2] Antioxidants such as octane.

The charge generating layer in the photoreceptor of the present invention comprises an inorganic charge generating substance such as selenium, selenium-tellurium, amorphous silicone, a pyrylium dye, a thiapyrylium dye, an azulenium dye, a thiacyanine dye,
Cationic dyes such as quinocyanine dyes, squarylium salt dyes, phthalocyanine pigments, anthantrone pigments, dibenzopyrene quinone pigments, polycyclic quinone pigments such as pyranthrone pigments, indigo pigments, quinacridone pigments, azo pigments, etc. These materials may be used alone or in combination, and used as an evaporation layer or a coating layer.

Among the above-mentioned charge generating substances, azo pigments are particularly diversified. Representative examples of azo pigments having particularly high effects are described below. The central skeleton as follows as a general formula of the azo pigments show A, a coupler moiety as C _p, where n is 1 or 2, Specific examples.

As a specific example of A─ (─N = N−C _p ) n A,

Embedded image

Embedded image

Embedded image

As a specific example of C _p ,

Embedded image

Embedded image And so on. These central skeleton A and coupler C
_p forms a pigment serving as a charge generating substance by an appropriate combination.

The charge generation layer can be formed by dispersing the above-described charge generation material in an appropriate binder and coating the dispersion on a support, or forming a vapor deposition film by a vacuum vapor deposition device. Can be formed by The binder can be selected from a wide range of insulating resins, and can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (polycondensate of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide,
Polyvinyl pyridine, cellulosic resin, urethane resin, epoxy resin, casein, polyvinyl alcohol,
And polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably at most 80% by weight, preferably at most 40% by weight.

Examples of the organic solvent used for coating include alcohols such as methanol, ethanol and isopropanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; N, N-dimethylformamide;
Amides such as N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride, dichloroethylene, An aliphatic halogenated hydrocarbon such as carbon tetrachloride or trichloroethylene, or an aromatic compound such as benzene, toluene, xylene, monochlorobenzene, or dichlorobenzene can be used.

The coating can be performed by a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a curtain coating method and the like. . Drying is preferably performed by touch drying at room temperature and then heating and drying. Heat drying is generally 30 to
It is preferable to perform the reaction at a temperature of 200 ° C. for 5 minutes to 2 hours in a stationary or blown state.

The charge generation layer contains as much of the organic photoconductive polymer as possible in order to obtain sufficient absorbance, and injects carriers into the charge transport layer within the life of the generated charge carriers. It is desirable that the thin film layer has a thickness of, for example, 5 μm or less, preferably 0.01 to 1 μm.

The photosensitive layer having such a laminated structure of the charge generation layer and the charge transport layer is provided on a support having a conductive layer. As the support having a conductive layer, a support having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, panadium, molybdenum, chromium, titanium, nickel, indium, tin oxide, indium oxide-oxide Plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.) having a layer in which a tin alloy or the like is formed by a vacuum deposition method, conductive particles (for example, aluminum powder,
Titanium oxide, tin oxide, zinc oxide, carbon black,
Silver or other suitable binder and a support coated with a plastic or the conductive support on the conductive support, a support in which the conductive particles are immersed in plastic or paper, or a plastic having a conductive polymer. .

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The undercoat layer is formed of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. it can. The thickness of the undercoat layer is suitably from 0.1 to 5 μm, preferably from 0.5 to 3 μm.

In the case of using a photoconductor in which a conductive support, a charge generation layer, and a charge transport layer are laminated in this order, the charge transport compound of the present invention, that is, the tetraphenylfuran derivative represented by the general formula (I) is used for hole transport. Therefore, it is necessary to charge the surface of the charge transport layer negatively, and when exposed after charging, in the exposed area, holes generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the negative charge. And the surface potential is attenuated, and an electrostatic contrast is generated between the unexposed portions. At the time of development, it is necessary to use a positively charged toner.

In another specific example of the photoreceptor of the present invention, the azo pigment described above or US Pat. Nos. 3,554,745, 3,567,438, and 3,586,
Increasing photoconductive pigments and dyes such as pyrylium dyes, thiapyrylium dyes, selenapyrylium dyes, benzopyrylium dyes, benzothiapyrylium dyes, naphthopyrylium dyes, and naphthiapyrylium dyes disclosed in 500 specification It can also be used as a sensitizer.

In another embodiment, US Pat.
A eutectic complex of a pyrylium dye and an electric insulating polymer having an alkylidene diarylene moiety disclosed in JP-A-84,502 or the like can also be used as a sensitizer. This eutectic complex is, for example, 4- [4-bis (2-chloroethyl)
[Aminophenyl] -2,6-diphenylthiapyrylium perchlorate and poly (4,4'-isopropylidenediphenylene carbonate) are halogenated hydrocarbon solvents such as dichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane. , 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene,
After dissolving in bromobenzene, 1,2-dichlorobenzene, etc., add a non-polar solvent, such as hexane, octane, decane, 2,2,4-trimethylbenzene, ligroin, etc. to form a particulate eutectic complex. can get.

The electrophotographic photoreceptor in this specific example includes styrene-butadiene copolymer, silicone resin, vinyl resin, vinylidene chloride-acrylonitrile copolymer, styrene-acrylonitrile copolymer, vinyl acetate-vinyl chloride copolymer, polyvinyl butyral, and polymethyl methacrylate. , Poly-N-butyl methacrylate, polyesters, cellulose esters and the like can be contained as a binder.

The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, and electrophotographic plate making systems.

[0038]

Hereinafter, the present invention will be described specifically with reference to the production examples of the tetraphenylfuran derivative represented by the general formula (I) and the examples of the electrophotographic photoreceptor, whereby the embodiments of the present invention will be described. It is not limited.

(Preparation Example 1) (Synthesis of Exemplified Compound No. 10) 2,5-bis (4-iodophenyl) -3,4-diphenylfuran 12 g, N-phenyl-2-naphthylamine 10 g, anhydrous potassium carbonate 10 g And electrolytic copper 8g
Was dispersed in 50 ml of sulfolane and stirred at 190 ° C. for 40 hours. After allowing to cool, the mixture was discharged into 100 ml of water, and the resulting precipitate was separated by filtration, washed with water and methanol in that order, and dried. The obtained crude product was extracted with toluene, and the extract was purified by silica gel column chromatography using a mixed solvent of toluene: hexane (1: 1) as a developing solvent. Recrystallized with a mixed solvent of toluene-acetonitrile to give pale yellow crystals.
g was obtained. Based on the following elemental analysis values, Exemplified Compound No. 1
It was confirmed to be 0. Elemental analysis _{(%) C 52 H 38 N} 2 O C H N Theoretical values 88.35 5.42 3.96 Analytical values 88.25 5.37 4.04

(Production Example 2) (Synthesis of Exemplified Compound No. 1)
4.1 g of 2- (4-aminophenyl) -3,4,5-triphenylfuran is dissolved in 200 ml of o-dichlorobenzene (hereinafter abbreviated as ODCB), and iodobenzene 5.0 is dissolved.
g, 11 g of anhydrous potassium carbonate, 2.6 g of electrolytic copper, and 0.6 g of 18-crown-6-ether, and the mixture is heated to reflux under a nitrogen atmosphere with vigorous stirring for 48 hours.
After the solids are removed by filtration, the
ODCB was distilled off. The obtained residue was purified by silica gel column chromatography using toluene as a developing solvent, and recrystallized with a mixed solvent of toluene and hexane (1: 1) to obtain 2.5 g of pale yellow crystals. Based on the following elemental analysis values, it was confirmed that the compound was Exemplified Compound No.-1. Elemental analysis _{(%) C 40 H 29 NO} C H N Theoretical values 89.02 5.42 2.60 Analytical values 89.13 5.37 2.70

(Production Example 3) (Synthesis of Exemplified Compound No. 6)
From 4.1 g of 2- (4-aminophenyl) -3,4,5-triphenylfuran and 8.2 g of p-iodoanisole, 3 g of yellow crystals were obtained in the same manner as in Production Example 2. Based on the following elemental analysis values, it was confirmed that this was Exemplified Compound No. 6. Elemental analysis (%) C ₄₂ H ₃₃ NO ₃ CH N Theoretical 84.11 5.55 2.34 Analytical 84.00 5.57 2.42

Example 1 5 g of a disazo pigment represented by the following structural formula and a butyral resin (butyralization degree: 63 mol%)
2 g was dispersed in a sand mill for 24 hours together with a solution of 100 g of cyclohexanone to prepare a coating solution.

Embedded image The coating liquid was applied on an aluminum sheet with a wire bar so that the dry film thickness was 0.2 μm, to form a charge generation layer.

Next, as the charge transport compound, one of the tetraphenylfuran derivatives of the present invention (compound No. 10 in Table 1) was used.
0 g and 10 g of polycarbonate (average molecular weight: 20,000) were dissolved in 70 g of chloroform, and this solution was applied on the previous charge generation layer with a wire bar to form a charge transport layer having a dry film thickness of 20 μm. A photoreceptor was prepared. The electrophotographic photoreceptor thus prepared was corona-charged at −6 KV in a static manner using an electrostatic copying paper tester Model-EPA-8100 manufactured by Kawaguchi Electric Co., Ltd.
After holding for 2 seconds, exposure was performed at an illuminance of 5 lux, and charging characteristics were examined.

The charging characteristics include surface potential (V _o ) and 1
The amount of exposure (E _1/2 ) required to attenuate the potential (V ₁ ) after dark decay for half a second to _half was measured. Further, in order to measure the fluctuation of the dark portion potential and the bright portion potential when repeatedly used, the electrophotographic photosensitive member prepared in the present embodiment was mounted on a photosensitive drum cylinder of a PPC copier NP-3525 manufactured by Canon Inc. 5,000 copies are made by the same machine, and the dark area potential (V _D ) at the initial stage and after copying 5,000 copies
And the fluctuation of the light part potential (V _L ) was measured. The initial V _D and V _L were set to be -700 V and -200 V, respectively.

Comparative Example 1 A compound having the following structure was used instead of the charge transporting compound used in Example 1 (JP-A-63-1585).
60 exemplified compound No. 14)

Embedded image To prepare an electrophotographic photoreceptor similar to that of Example 1,
Similarly, the electrophotographic characteristics were measured. Table 4 shows the results.

Example 2 A tetraphenylfuran derivative which is the charge transport compound used in Example 1 (No. 1 in Table 1)
, And electrophotographic photoreceptors were measured in the same manner as in Example 1, except that the No. 10 compound in Table 2 was used in place of Compound No. 10). Table 4 shows the results.

(Comparative Example 2) A compound having the following structure (Example compound No. 9 of JP-A-1-94349) was used instead of the charge transporting compound of Example 2.

Embedded image To prepare an electrophotographic photoreceptor in the same manner as in Example 1,
The electrophotographic properties were measured for each. Table 4 shows the results.

[0048]

[Table 4] As is evident from the results in Table 4 above, when the tetraphenylfuran derivative of the present invention was used as the charge transport compound, it had good sensitivity and little fluctuation in potential during durability.

(Examples 3 to 16) In each of the examples, the compound of No. 1 in Table 1 used in Example 1 was replaced with
(3), (4), shown in Tables 1, 2 and 3;
(5), (6), (7), (8), (9), (10),
Example 11 (11), (12), (22), (23), (28) and (29) were used, and a pigment having the following structural formula was used as a charge generating material. In the same manner as in the above, an electrophotographic photoreceptor was produced.

Embedded image The electrophotographic characteristics of each photoconductor were measured by the same method as in Example 1. Table 5 shows the results.

[0050]

[Table 5]

Example 17 An aqueous ammonia solution of casein (11.2 g of casein,
1 g of 28% aqueous ammonia and 222 ml of water) were applied by a blade coating method to form an undercoat layer having a dry film thickness of 1 μm. Next, 10 g of a charge generating substance represented by the following structural formula,

Embedded image 5 g of butyral resin (butyralization degree: 63 mol%) and 200 g of cyclohexanone were dispersed by a ball mill disperser for 48 hours. This dispersion was applied onto the previously formed undercoat layer by a blade coating method to form a charge generation layer having a dry film thickness of 0.15 μm.

Next, 10 g of the compound of No. 2 in Table 1 and 10 g of polymethyl methacrylate (average molecular weight: 50,000) were dissolved in 70 g of chlorobenzene, and coated on the previously formed charge generating layer by a blade coating method. Thus, a charge transport layer having a dry film thickness of 19 μm was formed. The electrophotographic photosensitive member thus produced was subjected to a corona discharge of -5 KV.
The surface potential at this time was measured (initial potential V _o ). Further, the surface potential of this photoconductor after leaving it in a dark place for 1 second was measured. The sensitivity was evaluated by measuring the exposure amount (E _1/2 , μJ / cm ² ) required to attenuate the potential V ₁ after dark decay to _half . At this time, a gallium / aluminum / arsenic ternary semiconductor laser (output: 5 m) was used as the light source.
w, oscillation wavelength 780 nm). The results are shown.

Example 18 3 g of 4- (4-dimethylaminophenyl) -2,6-diphenylthiapyrylium perchlorate and 5 g of the compound No. 18 in Table 2 were mixed with a polyester (Polyester Adhesive 49000, Dupont). Co., Ltd.) toluene (50 parts by weight) -dioxane (50
Parts by weight) and dispersed in a ball mill for 6 hours. This dispersion was applied on an aluminum sheet with a wire bar so that the film thickness after drying was 15 μm.

The electrophotographic characteristics of the electrophotographic photosensitive member thus manufactured were measured in the same manner as in Example 1. The results are shown below.

Example 19 A 5% methanol solution of soluble nylon (6-66-610-12 quaternary nylon copolymer) was applied on an aluminum plate to form a subbing layer having a dry film thickness of 0.5 μm. Formed. Next, 5 g of a pigment having the following structural formula was dispersed in 95 ml of tetrahydrofuran using a sand mill for 20 hours.

Embedded image Next, 5 g of the compound of No. 2 in Table 1 and bisphenol Z
A solution prepared by dissolving 10 g of a type polycarbonate (viscosity average molecular weight: 30,000) in 30 ml of chlorobenzene was added to the dispersion prepared above, and the mixture was further dispersed by a sand mill for 2 hours. The dispersion was applied to a previously formed undercoat layer with a wire bar so that the film thickness after drying was 20 μm, and dried. The electrophotographic characteristics of the electrophotographic photoreceptor thus manufactured were measured in the same manner as in Example 1. The results are shown below.

[0056]

The electrophotographic photoreceptor of the present invention is characterized in that it contains a tetraphenylfuran derivative represented by the general formula (I) as a charge transporting compound. During continuous image formation by exposure, the change in the light-area potential and the dark-area potential is small, and it has excellent durability and high sensitivity so that performance is not deteriorated by repeated use.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C07D 307/38 G03G 5/06 316

Claims (2)

(57) [Claims] 1. A compound of the general formula (I) (Wherein R ₁ and R ₂ are an alkyl group, an aralkyl group or an aryl group which may be substituted, and R ₁ and R ₂
May combine to form a ring together with the nitrogen atom. k,
p, m, and n satisfy 4 ≧ k + p + m + n ≧ 1, and are integers of 0 or 1, respectively. ). 2. An electrophotographic photoconductor comprising a tetraphenylfuran derivative represented by the general formula (I) according to claim 1.