JPS6087331A - Composite electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention provides a composite electrophotographic photoreceptor having high sensitivity in the long wavelength region, which is formed by forming a charge generation layer and a charge transport layer on a conductive support. In particular, the present invention relates to an electrophotographic photoreceptor that has high sensitivity and is suitable for improving the stability of long-term repeatability.

[Background of the invention]

Conventionally, as a charge generating material for a composite type electrophotographic photoreceptor, organic No.
Monoazo dyes, disazo dyes and squaric acid derivative dyes soluble in amines, quinocyanine pigments shown in JP-A-53-42830 and JP-A-53-41230, /l? A large number of organic substances have been proposed, such as the copper phthalocyanine pigment shown in Japanese Patent Publication No. 11763/1983. In addition, the tellurium-arsenic-glassy selenium series disclosed in Japanese Patent Publication No. 15137-1982, Japanese Patent Publication No. 49-1427
Polymers having imide bonds as shown in Publication No. 2 and inorganic substances such as amorphous selenium have also been proposed.

On the other hand, as a charge transport material, Japanese Patent Application Laid-Open No. 52-77730
Poly-N-vinylcarbazole series shown in JP-A-52-753929, etc., JP-A-49-105
Pyrazoline derivatives shown in JP-A No. 537, JP-A-11
Trinitrofluorenone shown in Japanese Patent Publication No. 346-4484, various nitro- and cyano-substituted compounds shown in Japanese Patent Publication No. 53-301, etc. are proposed. Electrophotographic photoreceptors using these materials all have good electrophotographic properties, but their sensitivity wavelength range is from 400 to 7QQ.
It shows high sensitivity to visible light of nm, and has high sensitivity to near infrared light (750r1m
It was said that it had no sensitivity at all to the above), and even if it had sensitivity, the sensitivity was low and it could not be used as a photoreceptor for electrophotography using near-infrared light as a light source (e.g., a semiconductor laser). It had drawbacks.

In recent years, as a type of high-speed printer, a method of printing using an electrophotographic method using a laser as a light source has been devised. In particular, when a semiconductor laser is used as a light source, the light source section can be made very small, making it possible to miniaturize printers, significantly reduce power consumption, and increase functionality, which is attracting a lot of attention. has been done. Since the oscillation wavelength of a semiconductor laser is a long wavelength of 770 nm or more, conventional charge transport materials as described above cannot be used in electrophotographic photoreceptors. Therefore, it is desired to develop an electrophotographic photoreceptor that has high sensitivity to specific wavelengths.

On the other hand, some methods have been put into practical use, although the sensitivity is still not sufficient. However, the lifespan is still insufficient, and there is a strong desire for an even longer lifespan.

The inventors of the present invention have made intensive studies to provide an electrophotographic photoreceptor that has excellent various electrophotographic properties and has sufficient properties for practical use. Charge transport layers are formed above and below, and the charge transport substance concentration in the charge transport layer formed on the intermediate layer is
It has been found that this problem can be solved by making the charge transport layer formed below the intermediate layer smaller υ.

[Purpose of the invention]

An object of the present invention is to overcome the drawbacks of conventional composite type electrophotographic photoreceptors and to provide a composite type electrophotographic photoreceptor with extremely excellent durability.

[Summary of the invention]

In general, factors that determine the lifespan of composite electrophotographic photoreceptors include the occurrence of scratches due to friction with external paper (transfer paper) and developer, in addition to deterioration due to corona discharge and light of the charge transport material. etc.

In particular, in the case of a composite type electrophotographic photoreceptor, the structure of the charge transport material layer on the surface may be mainly charge transport material/binder resin = 3/1 (weight ratio). Compared to the selenium photoreceptor, it is significantly softer, and the material of the charge transport layer has a problem of poor corona resistance. As a result of various studies based on this fact, the present inventors found that in a composite electrophotographic photoreceptor consisting of a layer containing a charge generating substance and a layer containing a charge transporting substance, the charge transporting layer does not carry charges. The charge transport material concentration in the layer formed on the intermediate layer is higher than that in the charge transport layer formed below the intermediate layer. It has been discovered that the above-mentioned problems can be overcome by reducing the concentration of the charge transporting substance, leading to the present invention.

Generally, the wavelength range to which a photoreceptor is sensitive depends on the absorption wavelength range of the charge-generating material, as long as the charge-transporting layer used does not interfere with the light absorbed by the charge-generating material. Many studies have been conducted on long-wavelength absorbing charge-generating materials, such as S
For e, Cds, etc., a method has been found to increase the sensitivity in the long wavelength range by adding a sensitizer, but among the various organic photoconductive materials mentioned above, various phthalocyanine compounds have a relatively high sensitivity in the long wavelength range. The sensitivity is good. Generally, a charge generating substance generates charges due to light passing through the charge transport layer, and the generated charges must be efficiently transferred into the charge transport layer by an electric field. Therefore, it is necessary to disperse the charge generating substance on the conductive support in such a form that the generated charges are efficiently transferred to the charge transport layer. This dispersion form is a major controlling factor for various electrophotographic properties of an electrophotographic photoreceptor, and particularly has a great influence on sensitivity, sharpness, and gradation. Therefore, it is important for electrophotographic photoreceptors to properly control the dispersion form of the charge generating substance on the conductive support.

The charge transport layer in the composite electrophotographic photoreceptor of the present invention has the following structure. That is, the charge transport layer formed on the charge generation layer supported on the conductive support is formed above and below the intermediate layer that can transfer charges, and is formed below the intermediate layer. The concentration of the charge transport substance in the charge transport layer (I) is 15% or more, preferably 30 to 80%. The charge transporting substance concentration in the charge transporting layer (II) formed on the intermediate layer is 50 to 5
The length is preferably 35 to 5. The intermediate layer may contain a resin alone or have a charge transport substance concentration of 50 or less, preferably 20 or less. Furthermore, the thickness of the intermediate layer is preferably 10 μm or less, preferably 5 μm or less. The thicknesses of the charge transport layer (I) and the charge transport layer (n) can be changed as desired and are not particularly limited. In addition, film-forming aids may be used to improve film-forming properties during the formation of the charge-generating layer, and adhesion-directing agents or sensitizing aids may be added to improve the adhesion between the charge-generating substance and the conductive support or charge transport layer. There are no restrictions on the addition of various auxiliary agents that are effective in improving the properties of electrophotographic photoreceptors. Furthermore, conventionally known techniques can be used to form a protective film or the like on the charge transport layer (n).

In the present invention, the charge transport layer is divided into (1) and (I[) via an intermediate layer, and the concentration of the charge transport substance in each layer is limited, based on the following reasons. It is. The thickness of the intermediate layer is preferably 10 μm or less, and 5 μm or less.
If it exceeds μm, the residual potential becomes large and desired electrophotographic characteristics cannot be obtained. In addition, the concentration of the charge transport substance is preferably 50% or less, but if it exceeds 50%, the coating solvent may not be used when coating the charge transport layer (II) formed on the intermediate layer. Since the elution amount of the charge transport substance in the intermediate layer increases, it becomes impossible to control the viscosity of the coating liquid, and it becomes impossible to control the concentration of the charge transport substance in the intermediate layer and the charge transport layer (II), as well as the film thickness. , a photoreceptor with stable characteristics cannot be obtained, and mass productivity becomes poor. On the other hand, the concentration of the charge transport substance in the charge transport layer (1) is preferably 15 or more, but if it is less than that, the charges generated in the charge generation layer cannot be efficiently transported, resulting in an increase in residual potential and sensitivity. As a result, desired electrophotographic properties cannot be obtained. In addition, if the concentration of the charge transport substance exceeds 8 (l), the charge transport layer (I)
The strength of the film is significantly reduced, making it unusable. On the other hand, the concentration of the charge transport substance in the charge transport layer (II) is preferably 50% or less, but if the concentration is higher than that, the strength of the film will be low and corona deterioration will be significant.

Therefore, if the charge generation layer, charge transport layer (I), (old and intermediate layer) are made as described above, the type of charge generation substance, the type of charge transport substance, the type of material of the intermediate layer, and the formation of these layers. It has sufficient electrophotographic properties and long-term durability as a photoreceptor for electrophotography, without being restricted in any way by law, etc.
It has characteristics that can withstand repeated use.

Next, a method for forming the charge generation layer and charge transport layer on the conductive support will be described. First, the charge generation layer is prepared by thoroughly mixing and stirring an organic solvent such as tetrahydrofuran, ethyl acetate, acetone, methyl ethyl ketone, halogenated hydrocarbon, etc. that can disperse the charge generation substance well or dissolve the resin and additives used as necessary. Adjust the coating liquid of the charge generating material. A conductive support is immersed in this liquid, or this liquid is dropped onto a conductive support and coated using a bar coater, a coater, an applicator, or a casting method, and then three-dimensionally cured or heated. to remove the solvent and form a film. As the resin, a known three-dimensional curing resin or thermoplastic resin can be used. The charge transport layer and intermediate layer are prepared by mixing and stirring the charge transport substance and resin or resin alone in a solvent such as total tetrahydrofuran, halogenated hydrocarbon, benzene, dioxane, dimethylformamide, and alcohol to form a coating liquid of the charge transport material. adjust.

Using this solution, perform the same method as for forming the charge generation layer described above.
A charge transport layer (■), an intermediate layer, and a charge transport layer (n) are sequentially formed on the charge generation layer.

The charge generating substance used in the present invention is, for example, known pigments such as 7-thalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, anthraquinone pigments, indigoid pigments, quinacrypan pigments, perylene pigments, polyquinone pigments, and methine squaric acid pigments. These pigments can be used alone or in combination of two or more.

Examples of the charge transport substance used in the present invention include oxadiazole, triazole, imidasilone, oxazole, pyrazoline, imidazole, imidazolidine, benzothiazole, benzoxazole, triphenylamine, and derivatives of these substances. These charge transport substances can be used alone or in combination of two or more.

Examples of the binder resin and intermediate layer resin used in the present invention include silicone resin, phenol resin, area resin, melamine resin, furan resin, EBOKI 7 resin, silicone resin, vinyl chloride-vinyl acetate copolymer, Examples include xylene resin, toluene resin, urethane resin, vinyl acetate-methacrylic copolymer, acrylic resin, phenoxy resin, polycarbonate resin, polyester resin, polyarylate resin, etc., and these resins may be used alone or in combination.
Can be used in combination with more than one species.

Examples of the conductive support for the composite electrophotographic photoreceptor of the present invention include metals such as aluminum, aluminum-other metal alloys, steel, iron, and copper, as well as conductive plastics, paper, and glass. These supports may have a cylindrical shape, a sheet, etc., and are not limited to any shape.

[Embodiments of the invention]

Next, the present invention will be explained in more detail using examples. The present invention is not limited to these in any way.

Examples 1 to 4 ε-type copper fucrocyanine pigment (manufactured by Toyo Ink Co., Ltd., Lionol Blue BS) was mixed with O22,5,0g1 silicone resin (
0.2゜5.0g of K-5240) manufactured by Shin-Etsu Chemical Co., Ltd.
Methylphenyl siloxane compound (manufactured by Shin-Etsu Chemical Co., Ltd., K
l) Weighed 0.005 g of -323), placed it in a glass container together with 80.8 g of tetrahydrofushiy (solid content = 0.5 to 5%), and stirred and dispersed using an ultrasonic vibrator for 15 hours. Then, adjust the coating liquid for the charge generation layer. This coating liquid was dropped onto an aluminum plate with a thickness of 100 μm, and a film was formed using an automatic applicator.
It was placed in a hot air dryer and dried at 90C for 30 minutes to form.

Next, 1.0 to 8.0 g of an oxazole compound represented by the following structural formula, 2.0 to 6.6 g of polycarbonate resin (Lexan 141, manufactured by GE), and 0.0077 g of silicone resin (KP-323, manufactured by Shin-Etsu Chemical). ~0.1 g 65 g of methylene chloride was placed in a glass container and stirred by vibration using an ultrasonic vibrator until the contents were completely dissolved to prepare a coating liquid for the charge transport layer (1).

In addition, 1 g of an oxazole compound represented by the above structural formula
1 Put 7 g of the above polycarbonate resin, 0.086 g of the above silicone resin, and 47 g of methylene chloride into a glass container, and carry out the same method as in the above coating liquid dissolution method for charge transport layer (I).
A charge transport layer (previously used coating solution) was prepared: 3 g of acrylate resin (Shin Nakamura Chemical Co., Ltd., A-TMM3), 97 g of ethyl alcohol, 0.003 g of the above silicone resin.
was placed in a glass container and stirred for 1 hour using an ultrasonic vibrator to prepare a coating liquid for the intermediate layer.

First, a charge transport layer coating liquid (
1) was added dropwise to form a film using an automatic applicator, air-dried, and then dried at 110C for 1 hour to form a charge transport layer (I). The charge transport layer (1) was immersed in the intermediate layer coating solution, pulled up, air-dried, and then heated and cured at 160 C for 30 minutes to form an intermediate layer. Next, the charge transport layer (n) coating liquid was dropped onto the intermediate layer, and the film was formed and air-dried in the same manner as the charge transport layer (I) to form the charge transport layer (If).

After drying, electrophotographic properties were measured. The electrophotographic properties were measured using an electrostatic recording paper tester (manufactured by Kawaguchi Denki, 5P-428). In this case, charge by performing corona discharge of -5 kV for 10 seconds (the surface potential o (v) immediately after charging for 10 seconds is the initial potential), and leave it in a dark place for 30 seconds (at this time, change the potential to V2O ( ■) Expressed by V3G/
VO) The attenuation of the surface potential and the time at this time were recorded, and V3
The sensitivity (half-reduction exposure amount, Eso(t,,s)) was expressed as the product of the time t (seconds) required for O to become 1/2 and the illuminance.

The results are shown in Figure 1 (-〇-).

Comparative Examples 1 to 2 1 g of the charge transport substance used in Example 1, 9 to 19 g of polycarbonate resin, 0.01 g of silicone resin, and 67 to 135 g of methylene chloride were placed in a glass container, and a charge transport layer was prepared in the same manner as in Example 1. (1) was formed. and,
An intermediate layer and a charge transport layer (II) were formed on the charge transport layer (I) using the intermediate layer coating liquid and the charge transport layer (II) coating liquid used in Example 1 in the same manner as in Example 1. The results are shown in Figure 1 (-/-).

Examples 5-9 100 parts by weight of metal-free phthalocyanine, epoxy resin [(
100 parts by weight of Resin M (manufactured by Maruzen Oil Co., Ltd.), 2.0 parts by weight of 2-ethyl-4-methylimidazole (manufactured by Shikoku Kasei Co., Ltd.) 1 part, 3 parts by weight of a methylphenyl siloxane compound (manufactured by Shin-Etsu Chemical Co., Ltd., KP-323), and 2700 parts of tetrahydrofuran were placed in a glass container and stirred under vibration for 24 hours in an ultrasonic vibrator to obtain a charge generation layer coating liquid. adjusted. The coating solution was applied to a 120 go+φ conductive drum using a dip coating method, and dried for 2 hours in a 1 oot:' hot air dryer to heat and cure to form a charge transport layer.

Next, a coating liquid having the same composition as the charge transporting layer (I) with a charge transporting substance concentration of 67 cm used in Example 1 was prepared and coated onto the charge generating layer by a dipping method, and then placed in a hot air dryer. The mixture was dried for 2 hours to form a charge transport layer (I).

A coating liquid having the same composition as that of the intermediate layer used in Example 1 was prepared thereon, and a film was formed by dipping, followed by heating and curing at 160 C for 1 hour to form an intermediate layer. Furthermore, 100 parts by weight of the oxazole compound used in Example 1, polycarbonate resin (
In a coating liquid prepared by mixing 100 to 900 parts by weight of Lexan 141) and 1300 to 6700 g of silicone resin (KP-323) and 0.2 to 1°Og's methylene chloride and stirring until the contents are completely dissolved. The drum formed up to the intermediate layer is immersed in the process, and the charge transport layer (II) is coated and formed.
After air drying, it was dried at 1.20 t:' for 2 hours to form a charge transport layer (II).

The drum was attached to a semiconductor laser beam copying machine (manufactured by Hitachi, Ltd., 5L-1000), and the electrophotographic characteristics were measured. The corona applied voltage is -5.2 kV. 30
The results when 00 sheets were printed continuously are shown in Figure 2-3.

〔Effect of the invention〕

The above results show that the electrophotographic photoreceptor of the present invention has excellent electrophotographic properties that are practically sufficient.

[Brief explanation of drawings]

1 to 3 are graphs showing the concentration characteristics of a charge transporting substance in a composite electrophotographic photoreceptor according to an embodiment of the present invention. 1I2] 1 Akebono ``Mottea 4-51/ftrrt Noriref I (abbreviation)
6 Is mackerel ff 1 degree (Z) 1 ■? Self-sent Rinto, / Hibiki (X
) ≠ 4JM pressure 1 to 9 Rut /%JyI3 Figure and load (IH's 1AJ TeI to it Naguga' thick waste t%) Continuation of page 1 @ Inventor Narahara Convenient Day 5 Place F

Claims (1)

[Scope of Claims] 1. In a composite electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge transport layer is formed through an intermediate layer that allows charge to move. A composite electrophotographic photoreceptor characterized by being divided into upper and lower layers. 2. The concentration of the charge transport substance in the charge transport layer is lower in the charge transport layer formed on the intermediate layer and closer to the surface of the photoreceptor than in the charge transport layer formed on the charge generation layer. A composite electrophotographic photoreceptor according to claim 1, characterized in that: 3. The concentration of the charge transport substance is 15% or more in the charge transport layer formed on the charge generation layer, 50% or less in the intermediate layer, and 5% in the charge transport layer formed on the intermediate layer.
3. The composite electrophotographic photoreceptor according to claim 1 or 2, wherein the photoreceptor has a particle size of 50 to 50 cm.