JPH0756368A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain a photoreceptor excellent in sensitivity and repetitive characteristics. CONSTITUTION:An electric charge transferring material represented by general formula I or II is used in a photosensitive layer. In the formula I, X is S or O, each of R1 and R2 is H, alkyl or optionally substd. aryl and each of Ar1 and Ar2 is optionally substd. aryl or a heterocyclic group. In the formula II, each of R3 and R4 is H, alkyl or optionally substd. aryl and Ar3 is optionally substd. aryl or a heterocyclic 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 inorganic photoconductive substance such as zinc oxide or cadmium sulfide is used as a resin. Those dispersed in a binder, organic photoconductive substances such as poly-N-vinylcarbazole or polyvinylanthracene, and organic photoconductive substances such as phthalocyanine compounds or bisazo compounds dispersed in a resin binder And those that are vacuum-deposited are used.

Further, the photoreceptor is required to have a function of retaining surface charges in a dark place, a function of receiving light to generate charges, and a function of receiving light to transport charges as well. Then, a so-called single-layer type photoconductor having these functions together, and a layer having a function separated mainly into a layer that contributes to charge generation and a layer that contributes to retention of surface charge in a dark place and charge transport during light reception. There is a so-called laminated type photoreceptor in which the layers are laminated. For example, the Carlson method is applied to the image formation by the electrophotographic method using these photoconductors. Image formation by this method is charging 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 surface of the photoconductor, electrostatic latent image formed The toner is used for development, and the developed toner image is fixed on a support such as paper. After the toner image is transferred, the photosensitive member is subjected to static elimination, residual toner removal, and the like, 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-
No. 2023, and as hydrazone compounds, JP-B-55-42380 and JP-A-57-101844.
Various charge-transporting materials are known from Japanese Patent Application Laid-Open No. 54-150128, and the like.

[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 by using a new organic material which has never been used as a charge transport material in a photosensitive layer, it is possible to obtain a copy having high sensitivity and excellent repeatability. An object is to provide an electrophotographic photoreceptor for machines and printers.

[0006]

According to the present invention, the above object has a photosensitive layer, and the photosensitive layer has at least one kind of benzodithiophene or benzodifuran compound represented by the following general formula (I). Inclusion as a substance,

[0007]

[Chemical 3]

[Wherein X represents a sulfur atom or an oxygen atom, R ₁ and R ₂ represent a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, and Ar ₁ and Ar ₂ each represent a substituted or unsubstituted group]. It represents an aryl group or a heterocyclic group. ] Further has a photosensitive layer, the photosensitive layer is represented by the following general formula
This can be achieved by including at least one of the benzodithiophene and benzodifuran compounds represented by (II) as a charge transport substance.

[0009]

[Chemical 4]

[Wherein R ₃ and R ₄ represent a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, and
r ₃ represents a substituted or unsubstituted aryl group or heterocyclic group. Furthermore, the photosensitive layer is formed by laminating a charge generation layer and a charge transport layer.

[0011]

There is no known example of using a benzodithiophene or benzodifuran compound represented by the general formula (I) or (II) in the photosensitive layer. These inventors have conducted a number of experiments on these compounds in the course of diligently examining various organic materials in order to achieve the above-mentioned object, and as a result, their technical elucidation has not yet been sufficiently conducted.
It has been found that the use of such a compound having a specific skeleton represented by the general formula (I) or (II) as a charge transport material is extremely effective for improving electrophotographic characteristics, and has high sensitivity and repetitive characteristics. That is, an excellent photoconductor has been obtained.

[0012]

EXAMPLES Synthesis of the compound represented by the general formula (I) or (II) used in the present invention can be easily obtained by carrying out a known reaction. For example, when exemplifying a specific example (I-1) or (II-7) of the compound described below, the compound (I-1) is a compound (a) and a compound (b) shown in [Chemical Formula 5], a compound (II-7). ) Can be obtained by synthesizing the compound (c) and the compound (d) shown in [Chemical Formula 6].

[0013]

[Chemical 5]

[0014]

[Chemical 6]

Specific examples of the compound represented by the general formula (I) are as follows.

[0016]

[Chemical 7]

[0017]

[Chemical 8]

Specific examples of the compound represented by the general formula (II) are as follows.

[0019]

[Chemical 9]

[0020]

[Chemical 10]

The photoreceptor of the present invention contains the above-mentioned benzodithiophene or benzodifuran compound in the photosensitive layer. It can be used as shown. 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 laminated type photoconductor according to the embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a positively charged layered type photosensitive member according to the first embodiment. 1 is a conductive substrate, 20, 21 and 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 transport layer, and 7 is a coating layer. In FIG. 1, a photosensitive layer 20 (a structure usually called a single-layer type photoreceptor) in which a charge generating substance 3 and a charge transporting substance 5 are dispersed in a resin binder (binder) is provided on a conductive substrate 1. Is. FIG. 2 shows a photosensitive layer 21 (usually a laminated type photosensitive layer) formed by stacking a charge generation layer 4 mainly composed of a charge generation substance 3 and a charge transport layer 6 containing a compound which is a charge transport substance 5 on a conductive substrate 1. The structure called the body) is provided. FIG. 3 is FIG.
It has the opposite layer structure. 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 coating a dispersion obtained by dispersing particles of the charge-generating substance in a solvent or a resin binder and drying the dispersion. It can be prepared by applying a solution in which a charge-transporting 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 on a conductive substrate and dried, and the charge generating substance is vacuum-deposited thereon, or particles of the charge generating substance are dissolved in a solvent or a resin. It can be prepared by coating a dispersion obtained by dispersing in a binder, drying and further forming a coating layer.

The conductive substrate 1 serves not only as an electrode of the photosensitive member but also as a support for other layers, and may be cylindrical, plate-shaped, or film-shaped, and is made of aluminum or stainless steel. A metal such as nickel, glass, resin, or the like that has been subjected to a conductive treatment may be used. The charge generation layer 4 is formed by applying a material in which particles of the charge generation substance 3 are dispersed in a resin binder as described above, or
Alternatively, it is formed by a method such as vacuum deposition and receives light to generate an electric charge. Further, it is important that the charge generation efficiency is high, and at the same time that the generated charge is injectable into the charge transport layer 6 and the coating layer 7 and that the electric field dependency is small and 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 dyes such as cyanine, squarylium, azurenium and pyrylium compounds, selenium or selenium compounds, etc. are used and used for image formation. A suitable substance can be selected according to the light wavelength region of the exposure light source used. 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 material and a charge transport material may be added to the charge generation layer. As the resin binder, it is possible to use polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, a polymer or copolymer of methacrylic acid ester in an appropriate combination.

The charge transport layer 6 is a coating film in which a compound represented by the above general formula (I) or (II) is dispersed as an organic charge transport substance in a resin binder. It retains an electric charge and exhibits a function of transporting an electric charge injected from the electric charge generation layer when receiving light. As the resin binder, polymers and copolymers such as polycarbonate and polyester 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. In addition, these organic materials and SiO
It is also possible to mix and use an inorganic material such as ₂ or a material such as a metal or a metal oxide that reduces electric resistance. The coating material is not limited to the organic insulating film forming material, but an inorganic material such as SiO ₂ or a metal,
It is also possible to form a metal oxide or the like by a method such as vapor deposition or sputtering. 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 mixed composition of the coating layer, but can be arbitrarily set within a range where there is no adverse effect such as increase in residual potential when repeatedly used continuously. [Example 1] x-type metal-free phthalocyanine (H ₂ Pc) 5
0 parts by weight and the compound _No. Represented by I-1 Compound 1
00 parts by weight of polyester resin (trade name: Byron 20
0: 100 parts by weight of Toyobo and tetrahydrofuran (T
HF) Kneading with a solvent for 3 hours with a mixer to prepare a coating solution, which is applied by a wire bar method onto an aluminum vapor-deposited polyester film (Al-PET) which is a conductive substrate, and the film thickness after drying is A photoconductor was prepared so as to have a thickness of 20 μm. _. EXAMPLE 2 The Compound No I-2 compound represented by 80 parts by weight of a polycarbonate resin (trade name: Panlite L-1225 of Teijin Chemicals Ltd.) coating solution to 100 parts by weight Deki was dissolved in methylene chloride A charge transport layer was formed on the aluminum vapor-deposited polyester film substrate by a wire bar method so that the film thickness after drying was 20 μm. On the charge transport layer thus obtained, titanyl phthalocyanine (T
50 parts by weight of iOPc), 50 parts by weight of polyester resin (trade name: Byron 200: manufactured by Toyobo), and a THF solvent are kneaded with a mixer for 3 hours to prepare a coating solution, which is applied by a wire bar method and dried. The charge generation layer was formed so that the film thickness was 1 μm. Furthermore, 10 parts by weight of a metal alkoxide (trade name CM-8000: manufactured by Toray), polyurethane resin (trade name: Nipporan: manufactured by Nippon Polyurethane Industry Co., Ltd.)
After stirring 10 parts by weight with 90 parts by weight of ethanol for 1 hour, polyisocyanate resin (trade name Takenate D16
5N90CX: Takeda Yakuhin Kogyo Co., Ltd.) After adding 2 parts by weight, the mixture is kneaded with a mixer for 30 minutes to prepare a coating solution for the coating layer, which is coated on the charge generation layer by the dip method and the film thickness after drying is 1 μ
A coating layer was formed to have a thickness of m. [Example 3] In Example 2, the TiOPc was replaced with a squarylium compound represented by the following structural formula (III), and the charge transporting material was replaced with the compound represented by the compound No. I-3 _. Similarly, a photoconductor was prepared.

[0028]

[Chemical 11]

[Example 4] In Example 2, TiOP
In place of c, for example, chlorodian blue which is a bisazo pigment as disclosed in JP-A-47-37543 is used, and the charge transporting material is replaced with the compound represented by the above compound No. II-1 _. Similarly, a photoconductor was prepared.

The electrophotographic characteristics of the photoconductor thus obtained were measured by the electrostatic recording paper testing apparatus "SP-428" manufactured by Kawaguchi Electric Co., Ltd.
Was measured using. The surface potential Vs (V) of the photoconductor is the initial surface potential when the surface of the photoconductor is positively charged by performing +6.0 kV corona discharge for 10 seconds in a dark place, and then in the state where the corona discharge is stopped. The surface potential Vd (V) when kept in the dark for 2 seconds is measured, and then the time (s) until Vd is halved by irradiating the surface of the photoconductor with white light having an illuminance of 2 lx is obtained and a half-attenuation exposure is performed. Quantity E _1/2 (lx ・ s)
And The surface potential when white light with an illuminance of 2 lx was applied for 10 seconds was defined as the residual potential Vr (V). Further, since high sensitivity to long-wavelength light can be expected in Examples 1 to 3, electrophotographic characteristics when monochromatic light having a wavelength of 780 nm was used were also measured. That is, the same measurement is performed up to Vd, and then 1 μW monochromatic light (780 n
m) was applied to determine the half-attenuated exposure dose (μJ / cm ² ), and the residual potential Vr (V) when the surface of the photoconductor was irradiated with this light for 10 seconds was measured. The measurement results are shown in Table 1.

[0031]

[Table 1] As can be seen in Table 1, Examples 1-4 have a half-attenuated exposure dose,
The residual potential is comparable to that of the residual potential, and the surface potential shows good characteristics. In addition, in Examples 1 to 3, the wavelength is 780n.
It can be seen that even with a long-wavelength light of m, it exhibits high sensitivity and can be sufficiently used for semiconductor laser printers. Example 5 Selenium was vacuum-deposited to a thickness of 1.5 μm on an aluminum plate having a thickness of 500 μm to form a charge generation layer,
Next, a coating solution prepared by dissolving 100 parts by weight of the compound represented by Compound No. I-1 and 100 parts by weight of a polycarbonate resin (trade name PCZ200: manufactured by Mitsubishi Gas Chemical Co., Ltd.) in methylene chloride is applied with a wire bar, The film thickness after drying is 20
The charge transport layer was formed to have a thickness of μm. When this photoreceptor was subjected to corona charging of -6.0 kV for 10 seconds, Vs = -650V, Vr = -20V, E1 _{/ 2} = under white light.
A good result of 1.1 lx · s was obtained. Example 6 As in Example 2, 50 parts by weight of x-type metal-free phthalocyanine, vinyl chloride copolymer (trade name MR-11)
0: manufactured by Zeon Corporation) was mixed with methylene chloride for 3 hours with a mixer to prepare a coating solution, which was coated on an aluminum support to a thickness of about 1 μm to form a charge generation layer.

Next, 100 parts by weight of the compound represented by Compound No. II-2, 100 parts by weight of a polycarbonate resin (trade name: Panlite L-1250: manufactured by Teijin Chemicals), and 0.1 part by weight of silicone oil are mixed with methylene chloride. Then, the charge transport layer was formed by coating the charge generation layer so as to have a thickness of about 20 μm. The thus obtained photoreceptor was subjected to corona charging at -6.0 kV for 10 seconds in the same manner as in Example 2. As a result, Vs = -645V, E1 _{/ 2} = 1.
A good result of 0 lx · s was obtained. [Example 7] In Example 6, a bisazo pigment represented by the following structural formula (IV) was used in place of the metal-free phthalocyanine, and the charge transport material was changed to the compound represented by the compound No. II-3. A photoconductor was prepared in the same manner as in No. 6. The photoreceptor thus obtained was subjected to corona charging at -6.0 kV for 10 seconds in the same manner as in Example 4. As a result, Vs = -660V and E1 _{/ 2} = 0.9lx under white light.
・ S and good results were obtained.

[0033]

[Chemical 12]

[0034]

According to the present invention, since the benzodithiophene or benzodifuran compound represented by the general formula (I) or (II) is used as the charge transporting material on the conductive substrate, positive charging and negative charging are performed. It is possible to obtain a photoreceptor having high sensitivity even in 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 in 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 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 laminated type photoreceptor 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.

[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 (3)

[Claims] 1. A conductive substrate having a photosensitive layer laminated thereon, wherein the photosensitive layer contains at least one benzodithiophene or benzodifuran compound represented by the following general formula (I) as a charge-transporting substance. A photoconductor for electrophotography. [Chemical 1] [Wherein X represents a sulfur atom or an oxygen atom, R ₁ and R ₂ represent a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, and Ar ₁ and Ar ₂ represent a substituted or unsubstituted aryl group or Represents a heterocyclic group. ] 2. A conductive layer having a photosensitive layer laminated thereon, wherein the photosensitive layer contains at least one benzodithiophene or benzodifuran compound represented by the following general formula (II) as a charge-transporting substance. A photoconductor for electrophotography. [Chemical 2] [In the formula, R ₃ and R ₄ represent a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, and Ar ₃ represents a substituted or unsubstituted aryl group or a heterocyclic group. ] 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is a laminate of a charge generation layer and a charge transport layer.