JP3085077B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, photoreceptors for organic electrophotography (hereinafter referred to as photoreceptors) have been used for laser beam printers and copiers.
Is widely used, and research on organic photoconductive substances has been widely promoted as a photosensitive material. Photosensitive materials using organic photoconductive materials are more flexible, thermally stable, film-forming, transparent, and more expensive than those that use inorganic photoconductive materials such as selenium, which are mainly used in the past. Although it has many advantages, it has a disadvantage that it is inferior in dark resistance and light sensitivity. Taking advantage of the ease of film formation, the photosensitive layer of the photoreceptor is functionally separated into a layer that mainly contributes to charge generation, and a layer that contributes to charge retention and surface charge in dark places and charge transport during photoreception. A stacked structure has been devised, and a configuration that improves the electrophotographic characteristics as a whole by selecting a material suitable for the function of each layer is now mainstream.

[0003] This type of laminated photoreceptor usually employs a structure in which a charge generation layer containing an organic charge generation material and a charge transport layer containing an organic charge transport material are formed on a conductive substrate. The charge generation layer is a phthalocyanine compound having an absorption peak in an infrared light region for a laser beam printer, and an azo compound having an absorption peak in a visible light region for a copying machine.
It is formed by coating with a coating liquid dispersed in a binder resin binder such as acryl. On the other hand, the charge transport layer is formed by applying a coating solution in which a low molecular compound such as hydrazone or pyrazoline is mixed as a charge transport material with a binder resin binder such as polycarbonate. In actual image formation using the laminated photoconductor, the Carlson method is applied. Specifically, charging of the photoreceptor by corona discharge in a dark place, formation of an electrostatic latent image such as characters and pictures of a document by exposing the charged photoreceptor surface, and development by the formed electrostatic latent image The developed toner image is transferred and fixed to a support such as paper, and is subjected to charge removal after transfer of the toner image, removal of residual toner, light charge removal, and the like, and then reused. Such a stacked photoreceptor has become mainstream at present because it has a charge-separating portion and a charge-transporting portion that are functionally separated, and can be designed optimally.

[0004]

As described above, the laminated photoreceptor has many advantages. However, the charging characteristics, dark decay characteristics,
At the present time, none at the same time and sufficiently satisfies all of the optical attenuation characteristics, the repetition characteristics, the optical fatigue characteristics, the spectral characteristics, the response characteristics, the image characteristics, and the like. Some charge transport materials have good dark decay characteristics but poor sensitivity characteristics, while others have good sensitivity characteristics but poor dark decay characteristics. In addition, since the solubility is low, the ratio with respect to the binder cannot be increased, and some of them do not have practical characteristics. Attempts have been made to mix charge transport materials to improve these properties. However, it is known that charge traps are newly formed by the materials to be mixed, and the mobility in the mixing may be lower than the mobility of the charge transporting substance as an individual component.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the solubility by mixing a specific charge transporting substance, and in particular, to improve the electron sensitivity and the dark decay characteristics. An object of the present invention is to provide an electrophotographic photosensitive member having good photographic characteristics.

[0006]

According to the present invention, it is an object of the present invention to provide a photoreceptor having a photosensitive layer made of an organic material on a conductive substrate, wherein the photosensitive layer comprises at least a charge generation layer and a charge transport layer. Provided on the conductive substrate in this order, and the following general formulas (I) to (I)
The distyryl derivative represented by II) is contained as at least two kinds of charge transport substances. Further, the charge generation layer contains at least one of bisazo compounds represented by the following general formulas (IV) and (V) as a charge generation substance;
Alternatively, it is achieved by including at least one of x-type metal-free phthalocyanine and titanyl phthalocyanine as the charge generating substance in the charge generating layer.

It is effective that A (coupler residue) represented by the above general formulas (IV) and (V) is one represented by the following general formulas (VI) to (XI).

[0008]

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[In the general formulas (I) to (III), R ₁ to R ₂₁ represent a hydrogen atom, an alkyl group or an alkoxy group.
N represents the number of substituents. ]

[0010]

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[In the general formulas (IV) and (V), A represents a coupler residue. ]

[0012]

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[Notes on general formulas are omitted. ]

[0014]

In the organic photoreceptor, the charge transport layer contains at least two kinds of the distyryl derivatives represented by formulas (I) to (III) as a charge transport material, and the charge generation layer further contains the general formula (IV) And at least one of the bisazo compounds represented by (V) as a charge-generating substance, or at least one of x-type non-metallic phthalocyanine or titanyl phthalocyanine as a charge-generating substance in the charge-generating layer. A photoreceptor characteristic having both advantages is obtained.

For example, a general formula having a good sensitivity characteristic of a photoreceptor
General formula (II) having good solubility with the distyryl derivative of (I)
Alternatively, by using a mixture of the distyryl derivative represented by (III), a photoconductor having good sensitivity characteristics and solubility can be obtained. In addition, since a solubility is low and an optimal coating solution cannot be prepared, even a compound which cannot be used alone as a charge transporting substance can substantially increase a dilution ratio by mixing, so that a coating solution can be easily prepared. be able to.

[0016]

Examples Specific examples of the distyryl derivatives represented by the above general formulas (I) to (III) used in the present invention are as follows.

[0017]

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[0018]

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[0019]

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The photoreceptor of the present invention contains the above-mentioned compound in a photosensitive layer. Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a single-layer photosensitive member according to an embodiment of the present invention, FIG. 2 is a sectional view showing a negatively charged laminated photosensitive member according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. 1 is a cross-sectional view illustrating a positively-charged laminated photoconductor according to the first embodiment. 1 is a conductive substrate, 20, 2
Reference numerals 1 and 22 are photosensitive layers, 3 is a charge generating material, 4 is a charge generating layer, 5 is a charge transporting material, 6 is a charge transporting layer, and 7 is a coating layer.

FIG. 1 shows that a charge generating substance 3 is placed on a conductive substrate 1.
And a photosensitive layer 20 (usually referred to as a single-layer type photosensitive member) in which a charge transport material 5 is dispersed in a resin binder (binder). FIG. 2 shows a charge generation layer 4 mainly composed of a charge generation substance 3 on a conductive substrate 1 and a charge transport substance 5.
And a photosensitive layer 21 (usually referred to as a laminate type photoreceptor) formed of a laminate with the charge transport layer 6 containing the compound of formula (1). FIG. 3 shows the reverse layer configuration 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 kinds of layer constitutions shown in FIGS. 2 and 3 are employed is that even if the layer constitution shown in FIG. Has not been found yet, and it is therefore necessary at this stage to form the layer structure shown in FIG. 1 can be manufactured by dispersing the charge generating substance 3 in a solution in which the charge transporting substance 5 and the resin binder are dissolved, and applying this dispersion on the conductive substrate 1.

In the photoreceptor shown in FIG. 2, the charge generating substance 3 is vacuum-deposited on the conductive substrate 1, or a dispersion obtained by dispersing the particles of the charge generating substance 3 in a solvent or a resin binder is applied. It can be prepared by drying, applying a solution in which the charge transport material 5 and the resin binder are dissolved, and drying. The photosensitive member in FIG. 3 is obtained by applying a solution in which the charge transporting substance 5 and the resin binder are dissolved on the conductive substrate 1 and drying it, and then vacuum-depositing the charge generating substance 3 thereon, Is dispersed in a solvent or a resin binder, and a dispersion obtained by coating and drying is further formed to form a coating layer 7.

The conductive substrate 1 serves as an electrode of the photoreceptor and serves as a support for the other layers, and may be cylindrical, plate-like or film-like. , A metal such as nickel, or a material obtained by conducting a conductive treatment on glass, resin, or the like. 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,
Alternatively, it is formed by a method such as vacuum evaporation, and receives light to generate charges. In addition, the charge generation efficiency is high, and at the same time, it is important to inject the generated charges into the charge transport layer 6 and the coating layer 7, and it is desirable that the electric field is less dependent on the electric field and the injection is good even at a low electric field. As the charge generating substance 3, a bisazo compound represented by the above general formula (IV) or (V), a phthalocyanine compound such as x-type non-metallic phthalocyanine, titanyl phthalocyanine, or the like is used. A suitable substance can be selected according to the region. Since the charge generation layer 4 only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance 3 and is generally 5 μm or less, preferably 1 μm or less. The charge generation layer 4 may be mainly composed of the charge generation substance 3 and added with the charge transport substance 5 and the like. As the resin binder, polycarbonate, polyester, epoxy, silicone resin, methacrylic acid ester polymers and copolymers, and the like can be used in appropriate combination.

The charge transport layer 6 is a coating film in which a mixture of the distyryl derivative represented by the general formulas (I) to (III) as the charge transport material 5 is dispersed in a resin binder.
In a dark place, it has the function of holding the charge of the photoreceptor as an insulator layer and transporting the charge injected from the charge generation layer 4 when receiving light. As the resin binder, polycarbonate,
Polymers and copolymers such as polyester can be used.

The coating layer 7 has a function of receiving and holding the charge of corona discharge in a dark place, and has a performance of transmitting light which the charge generating layer 4 is sensitive to. It is necessary to reach the charge generation layer 4 and neutralize the surface charge by receiving the generated charge. As the coating material, an organic insulating film forming material such as polyester and polyamide can be applied. In addition, these organic materials can be used as a mixture of an inorganic material such as a glass resin and SiO _2, and a material such as a metal or a metal oxide that reduces electric resistance. The coating material is not limited to an organic insulating film-forming material, and may be used in combination with an inorganic material such as SiO _2, or a material that reduces electric resistance such as a metal or a metal oxide. As described above, the coating material is desirably as transparent as possible in the wavelength region where the light absorption of the charge generating substance 3 is maximum.

The thickness of the coating layer 7 itself depends on the mixed composition of the coating layer 7, but can be arbitrarily set within a range in which repeated use of the coating layer 7 does not adversely affect the residual potential. Hereinafter, a case where the present invention is applied to a negatively-charged laminated photoconductor will be described. However, this embodiment does not limit the scope of the present invention. [Example 1] A charge was obtained by using a coating liquid in which 60 parts by weight of a bisazo compound represented by the following structural formula (XII) and 40 parts by weight of a vinyl chloride resin were dispersed in a methyl ethyl ketone solvent as a charge generating substance 3 on a conductive substrate 1. The generation layer 4 was formed. On top of this, compound No. 5 was used as charge transport material 5. The distyryl derivative of (I-1) and the compound No. 50 parts by weight of a 2: 8 mixture of the distyryl derivative of (II-1) and 50 parts by weight of a bisphenol A type-biphenyl copolymer polycarbonate (trade name: BP-PC: manufactured by Idemitsu Kosan Co., Ltd.) were added to dichloromethane 400 The charge transport layer 6 was formed with a coating solution dissolved in parts by weight so that the film thickness after drying was 20 μm, thereby producing a laminated photoreceptor.

[0028]

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Example 2 In the charge transport layer 6, Compound No. 5 was used as the charge transport material 5. The distyryl derivative of (I-2) and the compound No. A laminated photoconductor was prepared in the same manner as in Example 1, except that a mixture of the distyryl derivative of (III-3) in a ratio of 5: 5 was used. Example 3 In the charge transporting layer 6, Compound No. 1 was used as the charge transporting substance 5. The distyryl derivative of (II-3) and the compound No. A laminated photoconductor was prepared in the same manner as in Example 1, except that a mixture of the distyryl derivative of (III-1) at 8: 2 was used. [Comparative Example 1] In the charge transport layer 6, Compound No. A laminated photoconductor was prepared in the same manner as in Example 1, except that the distyryl derivative of (I-2) was used. Comparative Example 2 A laminated photoconductor was prepared in the same manner as in Example 1, except that a distyryl derivative represented by the following structural formula (XIII) was used as the charge transport material 5 in the charge transport layer 6.

[0030]

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The electrophotographic characteristics of the photoreceptor thus obtained were evaluated by using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.
It measured using. The surface of photoreceptor is -6 by corona discharge
After charging to 00 V, the charge retention in the dark after 5 seconds was defined as V _K5 (%). It is charged to -600V and the illuminance 2
The time required for the surface potential to become -300 V by irradiating (lx) white light was determined and defined as a half-attenuated exposure amount E _1/2 (lx · s).

[0032]

[Table 1] As can be seen from Table 1, the charge retention ratio V _K5 (%) does not differ greatly, but the example is superior to the comparative example in the half-attenuation exposure amount E _1/2 (lx · s). The effect of the invention is remarkably exhibited. Example 4 x as a charge generating substance 3 on a conductive substrate 1
The charge generation layer 4 was formed using a coating solution in which 50 parts by weight of a moldless metal phthalocyanine and 50 parts by weight of a polyester resin were dispersed in dichloromethane. Charge transport material 5
As compound No. The distyryl derivative of (I-4) and the compound No. The film thickness after drying the charge transport tank 6 with a coating solution obtained by dissolving 50 parts by weight of a mixture of the distyryl derivative of (III-1) in a ratio of 5: 5 and 50 parts by weight of polycarbonate in 400 parts by weight of dichloromethane is obtained. It was formed so as to have a thickness of 20 μm to prepare a laminated photoreceptor. Comparative Example 3 In the charge transport layer 6, Compound No. A laminated photoconductor was prepared in the same manner as in Example 4 except that the distyryl derivative of (II-2) was used. [Comparative Example 4] A coating solution in which 50 parts by weight of a squarylium compound represented by the following structural formula (XIV) and 50 parts by weight of a vinyl chloride resin were dispersed in an ethyl acetate solvent as the charge generating substance 3 on the conductive substrate 1 was used. The charge generation layer 4 was formed. On top of this, compound No. 5 was used as charge transport material 5. (II-1) distyryl derivative and Compound No. The film thickness after drying the charge transport tank 6 with a coating solution obtained by dissolving 50 parts by weight of a mixture of the distyryl derivative of (III-3) in a ratio of 5: 5 and 50 parts by weight of polycarbonate in 400 parts by weight of dichloromethane is obtained. It was formed so as to have a thickness of 20 μm to prepare a laminated photoreceptor.

[0033]

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The electrophotographic characteristics of the photoreceptor thus obtained were evaluated by using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.
It measured using. The surface of photoreceptor is -6 by corona discharge
After charging to 00 V, the charge retention in the dark after 5 seconds was defined as V _K5 (%). Also charged to -600V and illuminance 1μ
Irradiation with W monochromatic light (wavelength 780 nm) to reduce the surface potential to -3
The time until the voltage reaches 00 V is determined, and the half-attenuated exposure amount E _1/2 (μ
J / cm ² ). Table 2 shows the measurement results.

[0035]

[Table 2] As can be seen from Table 2, the charge retention ratio V _K5 (%) does not differ greatly, but the example is superior to the comparative example in the half-attenuation exposure amount E _1/2 (lx · s). The effect of the invention is remarkably exhibited.

[0036]

According to the present invention, in a laminated type photoreceptor, by using a mixture of a specific distyryl derivative for a charge transport layer and a bisazo compound or a specific phthalocyanine compound for a charge generation layer, a photoreceptor having both advantages is provided. Characteristics are obtained. Also, by using a mixture of a distyryl derivative of the general formula (I) having good sensitivity characteristics of the photoreceptor and a distyryl derivative of the general formula (II) or (III) having good solubility, sensitivity characteristics and solubility are improved. But a good photoreceptor can be obtained. In addition, since it is difficult to prepare an optimal coating solution having low solubility, even a compound which cannot be used alone as a charge transporting substance can substantially increase a dilution ratio by mixing, so that a coating solution can be easily prepared. Thus, a photosensitive member having high sensitivity and excellent dark decay characteristics can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a negatively-charged laminated photoconductor according to the embodiment of the present invention;

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 3 charge generating material 4 charge generating layer 5 charge transporting material 6 charge transporting layer 7 coating layer 20 photosensitive layer 21 photosensitive layer 22 photosensitive layer

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI G03G 5/06 371 G03G 5/06 371 (56) References JP-A-56-29245 (JP, A) JP-A-57-205746 (JP, A) JP-A-3-287170 (JP, A) JP-A-63-189872 (JP, A) JP-A-63-198068 (JP, A) JP-A-57-125941 (JP, A) 57-125942 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 5/06

Claims (4)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer made of an organic material provided on a conductive substrate, wherein the photosensitive layer comprises at least a charge generation layer and a charge transport layer, and is laminated on the conductive substrate in this order. In the charge transport layer, the following general formula
An electrophotographic photoreceptor comprising the distyryl derivative represented by any one of (I) to (III) as at least two kinds of charge transporting substances. Embedded image [In the general formulas (I) to (III), R ₁ to R ₂₁ represent a hydrogen atom, an alkyl group or an alkoxy group. N represents the number of substituents. ] 2. The photoreceptor according to claim 1, wherein the charge generation layer contains at least one of bisazo compounds represented by the following general formulas (IV) and (V) as a charge generation material. Photoconductor for electrophotography. Embedded image [In general formulas (IV) and (V), A represents a coupler residue. ] 3. The photoreceptor according to claim 2, wherein A (coupler residue) represented by the general formulas (IV) and (V).
Is a photoreceptor for electrophotography, which is represented by the following general formulas (VI) to (XI). Embedded image [In the general formulas (VI) to (XI), Z represents a residue condensed with a benzene ring to form an aromatic ring or an aromatic heterocyclic ring;
₁ is a hydrogen atom or COOR ¹ , CONR ² , R
³ (R ¹ , R ² and R ³ each represent a hydrogen atom, an optionally substituted alkyl group, an aryl group, or a heterocyclic group), X ₂ and X ₅ each represent an optionally substituted alkyl group or aryl X ₃ and X ₆ represent a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group or an acyl group, X ₄ and X ₁₁ represent a hydrogen atom, an optionally substituted alkyl group , A cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group or a heterocyclic group; X ₇ and X ₈ each represent a hydrogen atom, a halogen group, a nitro group, an alkyl group or an alkoxy group which may be substituted, ₉ represents an optionally substituted alkyl group, aryl group, carboxyl group, ester group, X ₁₀ represents an optionally substituted aryl group or heterocyclic group, and Y represents an aromatic group. Represents a residue forming a group heterocycle. ] 4. The photoconductor according to claim 1, wherein the charge generation layer contains at least one of x-type non-metallic phthalocyanine and titanyl phthalocyanine as a charge generation substance.