JPH01310358A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance electrophotographic characteristics and printing resistance by forming a surface protective layer made of organosilanol and polymethyl methacrylate on an organic photosensitive layer. CONSTITUTION:The electrophotographic sensitive body is obtained by successively laminating on a conductive substrate 1 the organic photosensitive layer 5 composed of an electric charge transfer layer 3 and a charge generating layer 2, and the surface protective layer 4 made of the organosilanol and the polymethyl methacrylate good in wettability with the binder resin to be used for the layers 2, 3, and it is high in electric resistance at low temperature and causes deterioration of sensitivity and background stains, but it can be lowered in the resistance to a desired value with the specified amount of organosilanol low in electric resistance, and this resin is small in water adsorptivity and can prevent image trailing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor using the Carlson process, and particularly relates to a surface protective layer of an electrophotographic photoreceptor.

[Conventional technology]

Photoreceptors used in electrophotographic devices using the Carlson process are broadly classified into those with a functionally separated multilayer structure and those with a single layer structure, depending on the structure of their photosensitive layers. In the former, a photosensitive layer is formed by a charge generation layer in which pairs of electrons and holes are generated by the incidence of light to form a latent image, and a charge transport layer that transports the generated charges; in the latter, a photosensitive layer is formed by charge generation and charge transport. A photosensitive layer is formed by a single layer that performs both functions.

Most conventional organic photoreceptors have a conductive substrate 1/charge generation layer 2.
It was originally a negatively charged type (Figure 2) with a functionally separated multilayer structure consisting of a charge transport layer 3, but a positively charged type (Figure 3) with a different layer structure is also being considered. In the layer structure, since the charge generation layer 3, which is extremely thin compared to the transport layer, is arranged on the front surface, damage and rigidity resistance of the photoreceptor become a problem, and due to the need for surface protection, the conductive substrate 1 is used in the positively charged type. /Charge transport layer 3/Charge generation layer 2/Surface protection layer 4 (FIG. 1) has been considered.As the surface protection layer, for example, a method using a crosslinked polymer or copolymer, a fluororesin, a silicone resin, Methods using polyester resins, aromatic polyamide resins, etc. are being considered.

[Problem to be solved by the invention]

However, when using the above-mentioned surface protective layer, the photosensitive layer may be damaged during the baking process to form a hardened film, the wettability of the surface of the photosensitive layer may be poor, and advanced techniques may be required for coating. There were problems such as decreased sensitivity of the photoreceptor due to the presence of the protective layer, occurrence of background fog, premature toner filming cycle, and occurrence of image deletion in high-temperature atmosphere.

The present invention has been made in view of the above points, and its object is to provide an electrophotographic photoreceptor having excellent electrophotographic properties and printing durability by using a surface protective film made of a new material.

[Means to solve the problem]

According to the present invention, the above object is to provide an electrophotographic photoreceptor in which an organic photosensitive layer 5 and a surface protective layer 4 are sequentially laminated on a conductive substrate 1. This is achieved by having the following.

The organic photosensitive layer 5 is composed of a charge transport layer 3 and a charge generation layer 2. The order in which the charge generation layer and charge transport layer are stacked does not matter.

The conductive substrate 1 serves as an electrical bridge for the photoreceptor and at the same time serves as a support for the other layers, and may be cylindrical, plate-shaped, or film-shaped, and may be made of aluminum, stainless steel, nickel, etc. It may be made of metal, glass, resin, or the like and subjected to conductive treatment.

The charge generation layer 2 is formed by coating a material in which a charge generation substance is dissolved and dispersed in a resin binder, for example, and generates charges by receiving light. In addition to the high charge generation efficiency, the ability to inject the generated charges into the charge transport layer or surface protective layer is also important, and it is desirable that the charge generation layer has little dependence on electric fields and can be easily injected even in low electric fields. It is also possible to use it by adding a charge transporting substance etc. to it. As the resin binder, polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, polymers and copolymers of methacrylic acid ester, etc. can be used in appropriate combinations.

The charge transport layer 3 is formed by applying, for example, a material in which a hydrazone derivative, a pyrazoline compound, a styryl compound, a triphenylamine compound, an oxazole compound, an oxadiazole compound, etc. are dissolved and dispersed as an organic charge transport substance in a resin binder. In the dark, it functions as an insulating layer to hold the charge on the photoreceptor, and when receiving light, it functions to transport the charge injected from the charge generation layer. As the resin binder, the same resin binder as that for the charge generation layer can be used.

The surface protective layer 4 receives and retains the charges of corona discharge in a dark place, and transmits the light to which the charge generation layer is sensitive.The charges generated in the charge generation layer are transferred to the surface of the surface protection layer. The surface protective layer mechanically and chemically protects the internal organic photosensitive layer and improves the rigidity of the photoreceptor.

Organosilanol is R, S when R is an alkyl group.
It is a substance represented by the chemical formula t (OH) a□ (n is an integer). Organosilanol is used in combination with polymethyl methacrylate.

[Effect]

Polymethyl methacrylate has good wettability with the resin binder used in the charge generation layer and charge transport layer. Polymethyl methacrylate has high electrical resistance at low temperatures, which can cause sensitivity loss and background fog, but it has low electrical resistance. By mixing a predetermined amount of organosilanol, the electrical resistance is lowered to a desired value. Furthermore, polymethyl methacrylate adsorbs less moisture and can prevent image deletion.

〔Example] Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a schematic cross-sectional view of an electrophotographic photoreceptor according to the present invention, in which 1 is an aluminum conductive substrate, 3 is a charge transport layer using a hydrazone derivative as a charge transporting substance, and 2 is a charge generating layer using a phthalocyanine compound. The charge generating layer 4 is a surface protective layer containing organosilanol and polymethyl methacrylate.

Such a photoreceptor can be manufactured by the following method. A charge transport layer coating solution was prepared by kneading 1 part by weight of a hydrazone derivative and 1 part by weight of an acrylic resin with 6 parts by weight of a solvent (tetrahydrofuran) using a mixer for 3 hours.
1 part by weight of a zero-order phthalocyanine compound and 2 parts by weight of a polyester resin, which are coated on a conductive substrate by a wire bar method and dried to form a charge transport layer 3 having a film thickness of 15 μ-〇, together with 50 parts by weight of THF. A coating solution for a charge generation layer is prepared by kneading the mixture using a mixer for 3 hours, and is applied onto the charge transport layer 3 by a wire bar method, followed by drying to form a charge generation layer 2 having a thickness of 1 μm.

Next, organociatool (liquid, OCD type 7, Tokyo Ohka Kogyo) and polymethyl methacrylate pellet were mixed in a predetermined ratio, and 1 portion of toluene was added to 1 portion of this mixture.
Add at a rate of 0 parts by weight. The surface protective layer coating solution obtained in this way was applied onto the charge generation layer 2 by a wire bar method, and dried at 50°C to 100°C for 1 to 2 hours to form a film with a thickness of 1.5 μm. A protective layer 4 is formed. Three types of &IIw1 were manufactured with a weight ratio of organocia tool to polymethyl methacrylate of 10:1.4:1.1:l.

(Comparative Example) A photoreceptor was manufactured in exactly the same manner as in the example except that the surface protection i1 layer 4 was not provided.

The electrophotographic properties of the photoreceptor produced as described above were measured using an electrostatic recording paper tester (SP-428, manufactured by Kawaguchi Denki ■). The surface potential Vs (volts) of the photoreceptor is +6. The initial surface potential when the photoreceptor surface is positively charged by corona discharge of OKV for 10 seconds,
The dark decay rate Vv is the rate at which the surface potential decays when stored in the dark with corona discharge stopped (7 volts), and the half-decay exposure IE'A (μJ/cd) is the rate at which the surface potential attenuates at a wavelength of 780 nm on the photoreceptor surface. The amount of exposure required to attenuate the surface potential to % by irradiating light with an intensity of 1μ-/d at -, residual potential Vr
(volt) is the surface potential after exposure of 5 μJ/c−. The results are summarized in Table 1.

As can be seen from Table 1, when the surface protective layer composition is 1O to 1, some moisture will be adsorbed at high temperatures such as 35°C and 85% relative humidity, resulting in slight image blurring. The upper surface works without any problems.The surface protective layer also firmly adheres to the base layer and has excellent rigidity. Other characteristics are almost the same as those without the surface protective film.

When the surface protective layer composition is 1:1, the resistance of the surface protective layer is high at low temperature and low humidity (e.g., 5°C, 20% relative humidity), and some ground fogging occurs, but this is hardly a problem in practical use. . However, in this case, when installed in a copying machine with a blade cleaning mechanism, etc., the surface protective layer wears out quickly in an electrophotographic process that applies relatively strong stress to the photoconductor, so make sure that the cleaning mechanism and photoconductor are compatible. It is necessary to understand.

When the composition of the protective layer is 4:1, there is no image blurring under high temperature and high humidity conditions, nor background fogging under low temperature and low humidity conditions, and other copying characteristics are also good. Further, it is possible to provide a photoreceptor that has a hard film quality, excellent printing durability, and is suitable for high-speed copying processes.

〔Effect of the invention〕

According to this invention, in an electrophotographic photoreceptor in which an organic photosensitive layer and a surface protective layer are successively laminated on a conductive substrate,
Since the surface protective layer is made of organosilanol and polymethyl methacrylate, the organic photosensitive layer will not be damaged during the formation of the surface protective layer due to the room temperature polymerization effect of the polymethyl methacrylate curing agent. It has good wettability with the resin binder of the photosensitive layer, and the surface protective layer firmly adheres to the organic photosensitive layer, improving rigidity. By mixing polymethyl methacrylate with organosilanol, the electrical resistance of the protective layer is adjusted to an optimal value, resulting in a photoreceptor with high sensitivity and no background fog. Furthermore, polymethyl methacrylate has low water adsorption properties and can provide a photoreceptor without image smearing.The surface protective layer of the present invention also lengthens the toner filming cycle. The protective layer provides an electrophotographic photoreceptor with excellent electrophotographic properties and rigidity resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an electrophotographic photoreceptor according to an embodiment of the present invention, and FIGS. 2 and 3 are schematic sectional views of a conventional electrophotographic photoreceptor. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Charge generation layer, 3... Charge transport layer, 4... Surface protective layer, 5... Organic photosensitive layer. Color 1 Figure ~ 2 ~ 1 Vines 2 Figure 1 2' Vocal name 31 yen 1 Charge transport layer charge is generated by the conductive substrate charge 茫伎屓 Poor charge 翰 transportation waste 1 蓼、Electricity? very tough

Claims (1)

[Claims] 1) An electrophotographic photoreceptor comprising an organic photosensitive layer and a surface protective layer sequentially laminated on a conductive substrate, the electrophotographic photoreceptor comprising a surface protective layer made of organosilanol and polymethyl methacrylate.