JPH0784385A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To provide a photoreceptor excellent in sensitivity and a repetition characteristic. CONSTITUTION:In a photosensitive layer, at least one kind of a benzothiophene derivative expressed by a formula I or II is used as charge transport material. In the formula I, R1 represents a hydrogen atom or an alkyl group, R2 represents a hydrogen atom, an alkyl group or an aryl group, and Ar1 represents an aryl group. In the formula II, R3, R4 represent an hydrogen atom, an alkyl group or an aryl group, and Ar2, Ar3 represent an aryl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive layer of an electrophotographic photoreceptor, and more particularly to a charge transport material used in the photosensitive layer.

[0002]

2. Description of the Related Art Conventionally, as a photosensitive material for an electrophotographic photoreceptor (hereinafter also referred to as a photoreceptor), an inorganic photoconductive substance such as selenium or a selenium alloy, or an organic photoconductive substance such as a phthalocyanine compound or a bisazo compound is used as a resin. Those dispersed in a binder or the like and those vacuum-deposited are used.

The photoconductor is required to have a function of holding a surface charge in a dark place, a function of receiving light to generate a charge, and a function of receiving light to transport a charge, but with one layer. A so-called single-layer type photoreceptor having these functions together,
There is a so-called laminated type photoreceptor in which functionally separated layers are laminated mainly on a layer that contributes to charge generation and a layer that contributes to holding surface charges in a dark place and transporting charges when receiving light. For example, the Carlson method is applied to the image formation by the electrophotographic method using these photoconductors. Image formation by this method is performed by corona discharge to a photoconductor in a dark place, formation of an electrostatic latent image such as characters and pictures of an original on the charged photoconductor surface,
The formed electrostatic latent image is developed with toner, and the developed toner image is fixed on a support such as paper, and the photoconductor after the toner image transfer is neutralized, residual toner is removed, and optical neutralization is performed. And then reused.

In recent years, many applications of photoconductive organic compounds having excellent charge transporting ability to photoconductors have been proposed due to advantages such as flexibility, thermal stability, and film forming property. For example, as an oxadiazole compound, US Pat.
No. 7, as a pyrazoline compound, Japanese Patent Publication No. 59-2
No. 023, and as a hydrazone compound, Japanese Patent Publication No.
Various charge transport materials are known from JP-A 5-42380, JP-A-57-101844 and JP-A-54-150128.

[0005]

As described above, the organic material has many advantages that the inorganic material does not have, but at the same time, an organic material sufficiently satisfying all the characteristics required for the electrophotographic photoreceptor can be obtained. However, there is a problem with the sensitivity and the characteristics during repeated continuous use. The present invention has been made in view of the above points, and its object is to use a new organic material which has never been used as a charge transporting material in a photosensitive layer, and thus has high sensitivity and excellent repeating characteristics. An object is to provide an electrophotographic photoreceptor for a copying machine and a printer.

[0006]

According to the present invention, the above-mentioned object has a photosensitive layer, and the photosensitive layer contains at least one of benzothiophene derivatives represented by the following general formula (I) or (II). It is achieved by including as a charge transport material.

[0007]

[Chemical 3]

[In the formula (I), R ₁ is a hydrogen atom or an alkyl group, R ₂ is a hydrogen atom, an alkyl group or an aryl group,
Ar ₁ represents an aryl group. ]

[0009]

[Chemical 4]

[In the formula (II), R ₃ and R ₄ represent a hydrogen atom, an alkyl group or an aryl group, and Ar ₂ and Ar ₃ represent an aryl group. Specific examples of the benzothiophene derivative represented by the general formula (I) include chemical formulas (I-1) to (I-1).
0). Specific examples of the benzothiophene derivative represented by the general formula (II) are represented by the chemical formulas (II-1) to (II-10).

[0011]

[Chemical 5]

[0012]

[Chemical 6]

[0013]

[Chemical 7]

[0014]

[Chemical 8]

[0015]

There is no known example in which the benzothiophene derivative represented by the general formula (I) or (II) is used in the photosensitive layer. The present inventors have conducted various experiments on these benzothiophene derivatives while earnestly examining various organic materials in order to achieve the above-mentioned object, and as a result, the technical elucidation thereof has not been sufficiently conducted. It has been found that the use of a benzothiophene derivative having a specific structure represented by the general formula (I) or (II) as a charge transport material is extremely effective in improving electrophotographic properties, and has high sensitivity and repetitive properties. It came to obtain an excellent photoconductor.

[0016]

EXAMPLES Synthetic examples of the compounds used in the present invention are shown below. For example, the benzothiophene derivative represented by the chemical formula (I-1) is synthesized by the Wittig reaction represented by the reaction formula A, and the benzothiophene derivative represented by the chemical formula (II-1) is synthesized by the Wittig reaction represented by the reaction formula B. You can

[0017]

[Chemical 9]

[0018]

[Chemical 10]

The photoconductor of the present invention contains the above-mentioned benzothiophene derivative in the photoconductive layer. Depending on how the benzothiophene derivative is applied, it is shown in FIG. 1, FIG. 2 or FIG. It can be used as an egg. FIG. 1 is a sectional view showing a single-layer type photoconductor according to an embodiment of the present invention. FIG. 2 is a sectional view showing a negatively-charged laminated type photoreceptor according to the embodiment of the present invention.

FIG. 3 is a sectional view showing a positively charged layered type photoreceptor according to an embodiment of the present invention. 1 is a conductive substrate, 2
Reference numerals 0, 21, 22 are photosensitive layers, 3 is a charge generating substance, 4 is a charge generating layer, 5 is a charge transporting substance, 6 is a charge transporting layer, and 7 is a coating layer. FIG. 1 shows a photosensitive layer 20 in which a charge generating substance 3 and a benzothiophene derivative which is a charge transporting substance 5 are dispersed in a resin binder (binder) on a conductive substrate 1 (a structure usually called a single layer type photoreceptor). ) Is provided.

In FIG. 2, the charge generating substance 3 is formed on the conductive substrate 1.
And a charge generation layer 4 mainly composed of a charge transport layer 5 and a charge transport layer 6 containing a benzothiophene derivative which is a charge transport substance 5, and a photosensitive layer 21 (usually referred to as a laminated photoreceptor). Is. FIG. 3 shows a layer structure opposite to that of FIG. In this case, it is general to further provide a coating layer 7 to protect the charge generation layer 4.

The reason why the two types of layer structures shown in FIGS. 2 and 3 are used is that even if the layer structure shown in FIG. 2 which is usually used as a negative charging system is used in the positive charging system, a charge transport material suitable for this is used. This is because the layer structure shown in FIG. 3 is required at the present stage as a positive charging type photosensitive member. The photoreceptor of FIG. 1 can be prepared by dispersing a charge generating substance in a solution in which a charge transporting substance and a resin binder are dissolved, and applying this dispersion liquid onto a conductive substrate.

The photosensitive member of FIG. 2 is obtained by vacuum-depositing a charge-generating substance on a conductive substrate, or by applying a dispersion obtained by dispersing particles of the charge-generating substance in a solvent or a resin binder, and drying. It can be prepared by applying a solution in which a charge transport substance and a resin binder are dissolved thereon and drying it. In the photoreceptor of FIG. 3, a solution in which a charge transporting substance and a resin binder are dissolved is applied onto a conductive substrate and dried, and then the charge generating substance is vacuum-deposited thereon, or particles of the charge generating substance and the resin are dissolved in a solvent. It can be prepared by coating a dispersion liquid obtained by dispersing the dispersion liquid inside, drying it, and further forming a coating layer.

The conductive substrate 1 serves not only as an electrode of the photoconductor but also as a support for each of the other layers, and may be cylindrical, plate-shaped or film-shaped, and made of aluminum, stainless steel, A metal such as nickel, glass, resin, or the like that has been subjected to a conductive treatment can be used. The charge generation layer 4 is formed by coating a material in which particles of the charge generation substance 3 are dispersed in a resin binder as described above, or by a method such as vacuum deposition, and receives light to generate charges. . In addition, it is important that the charge generation efficiency is high, and at the same time, the generated charge is injectable into the charge transport layer 6 and the coating layer 7, and the electric field dependence is small and it is desirable that the injection is good even in a low electric field. As the charge generating substance, phthalocyanine compounds such as metal-free phthalocyanine and titanyl phthalocyanine, various azo, quinone, indigo pigment or cyanine, squarylium,
A dye such as an azurenium or pyrylium compound or selenium or a selenium compound is used, and a suitable substance can be selected according to the light wavelength region of the exposure light source used for image formation. Since the charge generating layer has only to have a charge generating function, its thickness is determined by the light absorption coefficient of the charge generating substance and is generally 5 μm or less, preferably 1 μm or less. The charge generation layer may be mainly composed of a charge generation substance and a charge transporting substance or the like may be added thereto.
As the resin binder, polycarbonate, polyester, polyamide, polyurethane, vinyl chloride, phenoxy resin, polyvinyl butyral, diallyl phthalate resin, methacrylic acid ester polymers and copolymers, and the like can be appropriately combined and used.

The charge transport layer 6 is a coating film in which at least one of the benzothiophene derivatives represented by the general formula (I) or (II) is dispersed as an organic charge transport material in a resin binder, and in a dark place. As an insulating layer, it holds the charge of the photoconductor and exhibits the function of transporting the charge injected from the charge generation layer when receiving light. Resin binders include polycarbonate, polyester, polystyrene,
Polymers and copolymers of methacrylic acid ester can be used.

The coating layer 7 has a function of receiving and holding a charge of corona discharge in a dark place, and also has a property of transmitting a light to which the charge generation layer is sensitive, and transmits a light at the time of exposure,
It is necessary to reach the charge generation layer and receive the injection of the generated charges to neutralize and eliminate the surface charges. As the coating material, an organic insulating film forming material such as polyester or polyamide can be applied. Further, these organic materials may be mixed and used with a glass resin, an inorganic material such as SiO _2, or a material such as a metal or a metal oxide that reduces electric resistance. As described above, it is desirable that the coating material be as transparent as possible in the wavelength region of the maximum light absorption of the charge generating substance.

The film thickness of the coating layer itself depends on the compounding composition of the coating layer, but can be arbitrarily set within a range such that the residual potential does not increase when repeatedly used continuously. Example 1 50 parts by weight of x-type metal-free phthalocyanine (H ₂ Pc) and the benzothiophene derivative 10 represented by the above chemical formula I-1.
0 parts by weight of polyester resin (trade name: Byron 200:
100 parts by weight of Toyobo and tetrahydrofuran (TH
F) Kneading with a solvent for 3 hours with a mixer to prepare a coating solution, which is applied onto an aluminum vapor-deposited polyester film (Al-PET) which is a conductive substrate by a wire-bar method, and a film thickness after drying. Was prepared to have a thickness of 20 μm. Example 2 Benzothiophene derivative 8 represented by the chemical formula I-2
0 parts by weight and polycarbonate resin (trade name: Panlite L
-1225: Teijin Chemicals Co., Ltd.) A coating solution prepared by dissolving 100 parts by weight of methylene chloride in a methylene chloride is applied onto a substrate of aluminum vapor-deposited polyester film with a wire bar, and the film thickness after drying is 2
The charge transport layer was formed to have a thickness of 0 μm. On the charge transport layer thus obtained, 150 by a ball mill.
h Grinded titanyl phthalocyanine (TiOPc)
50 parts by weight, polyester resin (trade name Byron 20
(0: manufactured by Toyobo Co., Ltd.) 50 parts by weight was kneaded with a THF solvent by a mixer for 3 h to prepare a coating solution, which was coated with a wire bar and formed into a charge generation layer so that the film thickness after drying was 1 μm.

Further, 200 parts by weight of metal alkoxide (trade name Atron NSi-310: Nippon Soda), 10 parts by weight of modified polyamide (trade name CM-8000: Toray), and 10 parts by weight of polyurethane resin (trade name Nipporan: Nippon Polyurethane Industry). Was dried with 90 parts by weight of ethanol for 1 h and then polyisocyanate resin (trade name Takenate D16
5N90CX: Takeda Pharmaceutical Co., Ltd.) 2 parts by weight are added and kneaded for 30 minutes by mixing to prepare a coating solution for the coating layer, and the coating layer is formed on the charge generation layer by a dip method so that the dry film thickness is 1 μm. did. Example 3 In Example 2, the following structural formula (II
A photoreceptor was prepared in the same manner as in Example 2 except that the squarylium compound represented by I) was used and the charge transport material was replaced by the benzothiophene derivative represented by the chemical formula I-3.

[0029]

[Chemical 11]

Example 4 In Example 2, the same as Example 2 except that TiOPc was replaced with, for example, a bisazo pigment, chlorodiamble, and the charge transporting material was replaced with the benzothiophene derivative represented by the chemical formula II-1. A photoconductor was prepared. The electrophotographic characteristics of the photoconductor thus obtained were measured by using an electrostatic recording paper test device “SP-428” manufactured by Kawaguchi Electric.

Surface potential V of photoconductor_S(V) is in the dark +
The surface of the photoconductor is positively charged by a corona discharge of 6.0 kV.
It is the initial surface potential when
Irradiate white light with an illuminance of 2 lx until the surface potential becomes half.
Time (s) at_1/2(Lx ・ s)
did. Also, white light with an illuminance of 2 lx was irradiated for 10 s.
The surface potential at this time is the residual potential V_r(V). Also implemented
For Examples 1 to 3, high sensitivity in long-wavelength light can be expected.
Therefore, electrophotography using monochromatic light with a wavelength of 780 nm
The characteristics were also measured at the same time. That is, the same measurement is performed up to Vd.
Then, instead of white light, 1 μW monochromatic light (780 n
m) to irradiate half-attenuated exposure (μJ / cm ²),
In addition, when the surface of the photoconductor is irradiated with this light for 10 s, the residual
Potential V_r(V) was measured. The measurement results are shown in Table 1.

[0032]

[Table 1] As can be seen from Table 1, Examples 1, 2, 3, and 4 show comparable characteristics with respect to the half-attenuation exposure amount and the residual potential, and the surface potential shows good characteristics. In addition, in Examples 1 to 3, high sensitivity is exhibited even with long-wavelength light having a wavelength of 780 nm, and it can be seen that the present invention can be sufficiently used for semiconductor laser printers. Example 5 1.5 parts of selenium was placed on an aluminum plate having a thickness of 500 μm.
Vacuum deposition is performed to a thickness of μm to form a charge generation layer.
-1) 100 parts by weight of a benzothiophene derivative and 100 parts by weight of a polycarbonate resin (PCZ200: Mitsubishi Gas Chemical Co., Ltd.) are dissolved in methylene chloride to apply a coating solution by a wire bar method, and a film thickness after drying is obtained. 20 μm
Was formed on the charge transport layer. When the corona discharge of −6.0 kV was performed on this photosensitive member for 10 s, Vs = −750 V.V. Vr = -20V, E _1/2
Was 1.2 lx.s, which was a good result. Example 6 50 parts by weight of x-type metal-free phthalocyanine and 50 parts by weight of vinyl chloride copolymer (trade name MR-110: manufactured by Nippon Zeon Co., Ltd.) were kneaded with methylene chloride in a mixer for 3 hours to prepare a coating solution, which was supported on aluminum. The charge generation layer was formed by applying the solution on the body to a thickness of about 1 μm. Next, the chemical formula II-
100 parts by weight of a benzothiophene derivative represented by 2 and 100 of a polycarbonate resin (Panlite L-1250)
By weight, 0.1 part by weight of silicone oil was mixed with methylene chloride and coated on the charge generation layer so as to have a thickness of about 20 μm to form a charge transport layer.

With respect to the photoreceptor thus obtained,
When corona discharge of 6.0 kV was performed for 10 s, Vs =
Good results of −745 V and E _1/2 = 0.9 lx · s were obtained. Example 7 In Example 6, the metal-free phthalocyanine was replaced with a bisazo pigment represented by the following structural formula (IV), and the charge transport material was replaced with the benzothiophene derivative represented by the chemical formula II-3. Similarly, a photoconductor was prepared.

With respect to the photoconductor thus obtained,
When corona discharge of 6.0 kV was performed for 10 s, Vs =
Good results were obtained at −760 V, E _1/2 = 1.2 lx · s.

[0035]

[Chemical 12]

Example 8 The benzothiophene derivative of Example 4 was prepared according to the chemical formula (I
-4) to the benzothiophene derivative represented by the chemical formula (I-10) or the benzothiophene derivative represented by the chemical formula (II-4) to the chemical formula (II-10) to prepare a photoconductor and produce an electrostatic product manufactured by Kawaguchi Electric Co., Ltd. Recording paper testing device "SP
-428 ".

A +6.0 kV corona discharge is performed for 10 s to positively charge the surface of the photoconductor, and then an illuminance of 2 is applied to the surface of the photoconductor.
The time (s) until the surface potential was halved by irradiating lx white light was obtained and defined as the half-attenuation exposure amount E _1/2 (lx · s). The results are shown in Table 2.

[0038]

[Table 2] As shown in Table 2, the benzothiophene derivative represented by the chemical formula (I-4) to the chemical formula (I-10) or the benzothiophene derivative represented by the chemical formula (II-4) to the chemical formula (II-10) was used. The half-attenuated exposure amount E _1/2 was also good for the photoconductor.

[0039]

According to the present invention, a photosensitive layer is provided, and the photosensitive layer contains at least one of the benzothiophene derivatives represented by the following general formula (I) or (II) as a charge transporting substance. Therefore, it is possible to obtain a photoconductor having high sensitivity even in positive charging and negative charging and excellent in repeating characteristics.
Further, as the charge generating substance, a suitable substance can be selected according to the type of the exposure light source. For example, a phthalocyanine compound, a squarylium compound and a certain bisazo compound can be used as a photoconductor which can be used as a semiconductor laser printer. Can be obtained. Further, if necessary, a coating layer may be provided on the surface to improve durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a single-layer type photoconductor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a negatively charged layered photoconductor according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a positively charged laminated type photoreceptor according to an embodiment of the present invention.

[Simple explanation of symbols]

 1 Conductive Substrate 3 Charge Generating Material 4 Charge Generating Layer 5 Charge Transporting Material 6 Charge Transporting Layer 7 Covering Layer 20 Photosensitive Layer 21 Photosensitive Layer 22 Photosensitive Layer

Claims (4)

[Claims] 1. A photosensitive layer, which has the following general formula (I):
Alternatively, an electrophotographic photoreceptor containing at least one of the benzothiophene derivatives represented by (II) as a charge transport material. [Chemical 1] [In the formula (I), R ₁ represents a hydrogen atom or an alkyl group, R ₂ represents a hydrogen atom, an alkyl group or an aryl group, and Ar ₁ represents an aryl group. ] [Chemical 2] [In the formula (II), R ₃ and R ₄ represent a hydrogen atom, an alkyl group or an aryl group, and Ar ₂ and Ar ₃ represent an aryl group. ] 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is a laminate of a charge generation layer and a charge transport layer. 3. The electrophotographic photoreceptor according to claim 1, wherein the benzothiophene derivative has hydrogen atoms as R ₁ and R ₂ .
Ar ₁ is a 4- (N-phenyl-N-paratolyl) amino-1-phenyl group, which is a photoreceptor for electrophotography. 4. The electrophotographic photoreceptor according to claim 1, wherein R ₃ and R ₄ are hydrogen atoms in the benzothiophene derivative,
A photoreceptor for electrophotography, wherein Ar ₂ and Ar ₃ are 4- (N-phenyl-N-paratolyl) amino-1-phenyl group.