JPH07140684A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain a photoreceptor excellent in sensitivity and repetitive characteristics. CONSTITUTION:At least one kind of azulene deriv. represented by the formula is used as an electric charge transferring material in a photosensitive layer. In the formula, each of R1 and R2 is H, alkyl, aryl or a heterocyclic group, each of R3 and R4 is H, alkyl or alkoxy and each of Ar1 and Ar2 is 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 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 object has a photosensitive layer, which is represented by the general formula (I)
It is achieved by including an azulene-based dielectric material represented by the formula (1) as a charge transport material.

[0007]

[Chemical 2]

[In the formula (I), R ₁ and R ₂ are each a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, and R ₃ and R 2
₄ represents a hydrogen atom, an alkyl group or an alkoxy group, and Ar ₁ and Ar ₂ each represent an aryl group or a heterocyclic group. Specific examples of the azulene-based dielectric material represented by the general formula (I) are represented by the chemical formulas (I-1) to (I-10) of the chemical formulas 3 and 4.

[0009]

[Chemical 3]

[0010]

[Chemical 4]

[0011]

There is no known example in which the azulene-based dielectric represented by the general formula (I) is used in the photosensitive layer. We have
As a result of conducting a number of experiments on these azulene-based dielectrics while earnestly examining various organic materials in order to achieve the above-mentioned object, the technical elucidation has not yet been sufficiently conducted. It was found that the use of an azulene-based dielectric material having a specific structure as shown in Fig. 1 as a charge transport material is extremely effective in improving electrophotographic characteristics, leading to a photoreceptor having high sensitivity and excellent repeating characteristics. It was.

[0012]

EXAMPLES Synthetic examples of the compounds used in the present invention are shown below. For example, the azulene-based dielectric represented by the chemical formula (I-6) can be synthesized by the Wittig-Hornor reaction shown in Chemical formula 5.

[0013]

[Chemical 5]

The photoconductor of the present invention contains the above-mentioned azulene-based dielectric in the photoconductive layer. Depending on the application of these azulene-based dielectrics, it may be possible to use any one of FIG. 1, FIG. 2 or FIG. Can be used as shown in. Figure 1
FIG. 4 is a cross-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 (referred to as a single-layer type photosensitive body) in which a charge generating substance 3 and an azulene type dielectric substance which is a charge transporting substance 5 are dispersed in a resin binder (binder) on a conductive substrate 1. ) Is provided.

In FIG. 2, the charge generating substance 3 is formed on the conductive substrate 1.
A photosensitive layer 21 (referred to as a laminated type photoreceptor) is provided, which is composed of a charge generation layer 4 mainly composed of and a charge transport layer 6 containing an azulene-based dielectric which is a charge transport substance 5. 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 positive charging system is used in the layer structure of FIG. 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.

In the photoreceptor of FIG. 2, a charge generating substance is vacuum-deposited on a conductive substrate, or a dispersion liquid obtained by dispersing particles of the charge generating substance in a solvent or a resin binder is applied and dried. 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 photosensitive member but also as a support for 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 azulene-based dielectrics represented by the general formula (I) is dispersed in a resin binder as an organic charge transport material, and in a dark place, it is an insulating layer. Holds the charge of the photoconductor and transports the charge injected from the charge generation layer at the time of receiving light. As the resin binder, polymers, copolymers of polycarbonate, polyester, polystyrene, methacrylic acid ester and the like 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 that does not cause adverse effects such as increase in residual potential when repeatedly and continuously used. Example 1 50 parts by weight of x-type metal-free phthalocyanine (H ₂ Pc) and 100 parts by weight of the azulene-based dielectric material represented by the chemical formula I-1 were added to 100 parts by weight of a polyester resin (trade name: Byron 200: Toyobo) and tetrahydrofuran ( (THF) Kneading with a solvent for 3 hours with a mixer to prepare a coating liquid,
Aluminum vapor-deposited polyester film (A
1-PET) was coated by the wire bar method to prepare a photoconductor so that the film thickness after drying was 20 μm. Example 2 80 parts by weight of the azulene-based dielectric material represented by the chemical formula I-1 and a polycarbonate resin (trade name: Panlite L-12)
25: Teijin Chemicals Co., Ltd.) A coating solution prepared by dissolving 100 parts by weight of methylene chloride in a methylene chloride was applied onto a substrate of aluminum vapor-deposited polyester film with a wire bar, and the film thickness after drying was 20 μm.
Was formed on the charge transport layer.

On the charge transport layer thus obtained,
T: 50 parts by weight of titanyl phthalocyanine (TiOPc) crushed by a ball mill for 150 hours and 50 parts by weight of a polyester resin (trade name: Byron 200: Toyobo)
Knead with a HF solvent for 3 hours with a mixer to prepare a coating solution, apply with a wire bar, and dry to a film thickness of 1μ.
The charge generation layer was formed so as to have a thickness of m.

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), 10 parts by weight of polyurethane resin (trade name Nippon Polyurethane Industry Co., Ltd.) Was dried with 90 parts by weight of ethanol for 1 hour and then polyisocyanate resin (trade name Takenate D1
65N90CX: Takeda Pharmaceutical Co., Ltd.) 2 parts by weight are added and mixed for 30 minutes to prepare a coating solution for the coating layer, and the coating layer is formed on the charge generation layer by the dip method so that the dry film thickness is 1 μm. did. Example 3 In Example 2, the squarylium compound represented by Chemical formula 6 was used in place of TiOPc, and the charge transporting material was changed to the azulene-based dielectric material represented by the chemical formula I-2.
A photoconductor was prepared in the same manner as in.

[0025]

[Chemical 6]

Example 4 In Example 2, instead of TiOPc, for example, Japanese Patent Laid-Open No.
Example 2 using the chlorodiamble, which is the bisazo pigment disclosed in JP-A 7-37543, and replacing the charge transport material with the azulene-based dielectric represented by the chemical formula I-3.
A photoconductor was prepared in the same manner as in.

Electrophotography of the photoconductor thus obtained
Characteristics of Kawaguchi Denki's electrostatic recording paper testing device "SP-428"
Was measured using. Surface potential V of photoreceptor_S(V) is a dark place
Positively charges the surface of the photoconductor by +6.0 kV corona discharge
This is the initial surface potential of the photoconductor, and then the surface of the photoconductor.
The surface potential is halved by irradiating the surface with white light with an illuminance of 2 lx.
Half-attenuated exposure E_1/2(Lx
・ S). In addition, white light with an illuminance of 2 lx for 10 seconds
The surface potential when irradiated is the residual potential V_r(V).
Further, in Examples 1 to 3, high sensitivity with long-wavelength light is expected.
When you use monochromatic light with a wavelength of 780 nm, you can wait
The electrophotographic characteristics were also measured at the same time. That is, up to Vd
Measure in the same way, and then use 1 μW monochromatic light instead of white light.
(780 nm) to irradiate, and the half-attenuation exposure amount (μJ / c
m²) And irradiate this light on the surface of the photoconductor for 10 seconds.
Residual potential V when _r(V) was measured. The measurement result is
It is shown in Table 1.

[0028]

[Table 1]

As can be seen in Table 1, Examples 1, 2,
In Nos. 3 and 4, the half-attenuated exposure dose and the residual potential are not inferior to each other, and the surface potential shows good characteristics. In addition, Example 1
In Nos. 3 to 3, high sensitivity is exhibited even with long-wavelength light having a wavelength of 780 nm, and it can be seen that it 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 an azulene-based dielectric and a polycarbonate resin (PCZ200: Mitsubishi Gas Chemical) 10
A coating solution prepared by dissolving 0 part by weight in methylene chloride was applied by a wire bar method to form a charge transport layer so that the film thickness after drying was 20 μm. -6.
When a corona discharge of 0 kV was performed for 10 seconds, Vs = -740 V.V. under white light. Vr = -20V, E _1/2 is 1.1
Good results with lx ・ s were obtained. 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 together with methylene chloride in a mixer for 3 hours to prepare a coating solution. The charge generation layer was formed by coating on a support so as to have a thickness of about 1 μm.

Next, 100 parts by weight of the azulene-based dielectric represented by the chemical formula I-2, 100 parts by weight of a polycarbonate resin (Panlite L-1250), and silicon oil 0.1.
Part by weight is mixed with methylene chloride and about 2 parts above the charge generation layer.
It was applied so as to have a thickness of 0 μm to form a charge transport layer. When a corona discharge of -6.0 kV was applied to the thus obtained photoreceptor for 10 seconds, Vs = -745 V, E
_A good result of _1/2 = 0.9 lx · s was obtained. Example 7 In Example 6, instead of metal-free phthalocyanine,
A photoconductor was prepared in the same manner as in Example 6, except that the bisazo pigment shown in 1 was used and the charge transport material was replaced with the azulene-based dielectric represented by the chemical formula I-3.

[0031]

[Chemical 7]

With respect to the photoreceptor thus obtained,
When 6.0 kV corona discharge was performed for 10 seconds, Vs =
Good results were obtained at −760 V, E _1/2 = 1.2 lx · s. Example 8 The azulene-based dielectric in Example 4 was converted to the chemical formula (I-4).
Or a photoconductor was prepared in place of the azulene-based dielectric represented by the chemical formula (I-10) and measured using an electrostatic recording paper testing device “SP-428” manufactured by Kawaguchi Denki.

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

[0034]

[Table 2]

Chemical formulas (I-4) to (I-1)
The half-attenuated exposure dose E _1/2 was also good for the photoconductor using the azulene-based dielectric shown in 0).

[0036]

According to the present invention, a photosensitive layer is provided, and the photosensitive layer contains at least one of the azulene-based dielectrics represented by the following general formula (I) as a charge-transporting substance. It is possible to obtain a photoreceptor having high sensitivity and excellent repeatability in charging and negative charging. 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 (5)

[Claims] 1. A photoconductor for electrophotography, comprising a photosensitive layer, wherein the photosensitive layer contains an azulene-based dielectric represented by the general formula (I) shown in Chemical formula 1 as a charge transporting substance. [Chemical 1] [In the formula (I), R ₁ and R ₂ are each a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, R ₃ and R ₄ are each a hydrogen atom, an alkyl group or an alkoxy group, Ar ₁ and A
Each r ₂ represents an aryl group or a heterocyclic 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 photosensitive member according to claim ₁ , wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms, and Ar ₁ and Ar ₂ are 4- (N-, respectively). A photoconductor for electrophotography, which is a phenyl-N-paratolyl) amino-1-phenyl group. 4. The electrophotographic photosensitive member according to claim 1, wherein the azulene-based dielectric is R ₁ , R ₂ , R ₃ and R ₄ each is a hydrogen atom, and Ar ₁ and Ar ₂ are each 4- (N, N
-Diparatolyl) amino-1-phenyl group. 5. The electrophotographic photosensitive member according to claim ₁ , wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms and Ar ₁ and Ar ₂ are 4- (N-, respectively). A photoconductor for electrophotography, which is a phenyl-N-metatolyl) amino-2-methyl-1-phenyl group.