JP2996175B2 - High definition image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for exposing an electrophotographic photosensitive member to digitally processed image signals.

[0002]

2. Description of the Related Art In recent years, electrophotographic technology has advantages such as high speed and high printing quality.
It plays a central role in the fields of printers and facsimile machines. 2. Description of the Related Art As an electrophotographic photoreceptor used in the electrophotographic technology, a photoconductor using an inorganic photoconductive material such as selenium, a selenium-tellurium alloy, or a selenium-arsenic alloy has been widely known. On the other hand, research on electrophotographic photoreceptors using an organic photoconductive material, which has advantages in terms of cost, manufacturability and disposability compared to these inorganic photoreceptors, has become active. Photoconductors have surpassed inorganic photoconductors. In particular, the development of photoreceptors consisting of photosensitive layers with a function-separated layer structure in which photovoltaic generation and charge transport, which are the elementary processes of photoconductivity, are assigned to separate layers, has increased the freedom of material selection. With the increase, it has become possible to achieve a remarkable improvement in performance. At present, this function-separated and laminated organic photoreceptor has become the mainstream of the electrophotographic photoreceptor.

The charge generation layer for such a function-separated laminated organic photoreceptor includes quinone pigments, perylene pigments,
Azo pigments, phthalocyanine pigments and pigments having a charge generating ability such as selenium, etc., which are directly formed into a film by vapor deposition,
Alternatively, those in which these are dispersed at a high concentration in a binder resin have been put to practical use. On the other hand, as the charge transport layer, a layer in which a low-molecular compound having a charge transport ability such as a hydrazone compound, a benzidine compound, an amine compound, or a stilbene compound is molecularly dispersed in an insulating resin is used.

Conventionally, as a photosensitive member used in an analog type electrophotographic copying machine in which a document is optically imaged on a photosensitive member and exposed, the reproducibility of halftones based on density gradation is improved. Therefore, as shown in FIG. 1, a photoreceptor having photo-induced potential decay characteristics, that is, a photoreceptor which causes a potential decay in proportion to an exposure amount (hereinafter, a “J-shaped photoreceptor”)
That. ) Is required. The above-mentioned inorganic photoconductors and function-separated stacked organic photoconductors all exhibit photoinduced potential decay characteristics falling within this category.

However, with the recent demand for higher image quality, higher added value, networking, and the like, digital electrophotographic apparatuses, which are being actively researched and developed, generally require an area ratio of dots or the like. As shown in FIG. 2, the potential is not attenuated until a certain amount of exposure is reached, and a sharp potential decay occurs when the amount of exposure is exceeded. It is desirable to use a photoreceptor having the photo-induced potential decay characteristic (hereinafter, referred to as an “S-shaped photoreceptor”) because it has advantages such as enhancement of pixel sharpness.

As another measure for increasing the sharpness of a pixel, a spot diameter of a light beam of an exposure light source for scanning an electrophotographic photosensitive member is reduced in accordance with an image signal digitally processed based on image data. There are things. In order to reduce the spot diameter, there are two measures of improving the design accuracy of the optical system and narrowing the beam diameter, and shortening the emission wavelength of the light source. In the former case, there is a concern that the price of the product will increase due to the need to further improve the accuracy and redesign, but the latter will be proportional to the same optical system by shortening the wavelength. Since it is possible to reduce the size, the method has many practical advantages, and is a more desirable method.

The photo-induced potential decay characteristic of the S-shaped photoreceptor is
This is a known phenomenon in a single-layer photoreceptor in which an inorganic pigment such as nO or an organic pigment such as phthalocyanine is dispersed in a resin. M. Schaffert: "El
electrophotography ", Focal P
ress, p. 344 (1975); W. Weig
l. Mammino, G .; L. Whitake
r, R. W. Radler, J .; F. Byrne: "C
current Problems in Electr
ophotography ", Walter de G
ruyter, p. 287 (1972)]. In particular, a large number of single-layer photoreceptors for laser exposure in which a phthalocyanine-based pigment having photosensitivity in the near infrared, which is the emission wavelength of semiconductor lasers and LEDs, which are widely used at present, are dispersed in a resin have been proposed [for example, Nguyen -Chan K, Aizawa: Journal of the Chemical Society of Japan, p. 393 (1986), JP-A-1-169
454, 2-207258, 3-31
No. 847, No. 5-313873].

[0008] However, in the single-layer type photoreceptor, although a single material needs to fulfill both functions of charge generation and charge transport, materials having excellent performance in both functions are rare and can withstand practical use. Materials have not yet been obtained. In particular, since pigment particles generally have many trap levels, they have disadvantages such as low charge transport ability and residual charges, and are unsuitable for carrying charge transport. The only exceptional practical example is a ZnO resin-dispersed single-layer type photoreceptor, and a master plate for offset printing in which a plate is formed by an area gradation method based on the presence or absence of a hydrophobic toner utilizing the hydrophilicity of ZnO. [Edited by the Society of Electrophotography, published by Corona Co., Ltd., “Basics and Application of Electrophotographic Technology” p. 424 (1988)] is only a successful example used in the special field of a master plate having a low demand for high speed and printing durability. The photoconductor used is not at a level that can withstand practical use. From these viewpoints, in the case of the S-shaped photoreceptor, it is desired to introduce a photosensitive layer having a function-separated type layer structure in order to increase the degree of freedom in material selection and, consequently, to improve overall photoreceptor characteristics. ing.

To address this problem, D.S. M. Pai et al. Disclose that in a laminated photoreceptor having a charge generation layer and a charge transport layer, the charge transport layer includes at least two charge transport regions and one electrically inactive region, and the charge transport regions are in contact with each other. It has been reported that an S-shaped photo-induced potential decay characteristic can be realized by using a heterogeneous charge transport layer forming a convoluted charge transport path and combining it with an arbitrary charge generation layer. JP-A-6-83077, U.S. Pat. No. 5,306,586). However, in the present invention, the function of the charge transport layer has a function of making the photo-induced potential decay characteristic into an S-shape (hereinafter, referred to as “S-shape”) and a charge transport function. That the S-shaped function is added compared to the charge transport layer of a stacked photoreceptor having photo-induced potential decay characteristics, which limits the degree of freedom in the design of the charge transport layer. Was.

As a means for greatly expanding the degree of freedom in designing a charge transport layer, a charge transport layer of an electrophotographic photosensitive member having a charge generation layer and a charge transport layer on a conductive substrate is provided in an electrically inert matrix. It has been proposed to comprise a heterogeneous charge transport layer in which charge transport domains are dispersed and a uniform charge transport layer comprising a charge transport matrix.

In the electrophotographic photoreceptor having the above structure, the charge generation is performed by the charge generation layer, and the S-shaped photoinduced potential decay curve is obtained by dispersing the charge transporting domains in the electrically inert matrix. The function of the uniform charge transport layer is mainly separated from that of the charge transport layer, and the main charge transport performance is achieved by the function of the uniform charge transport layer composed of the charge transporting matrix. As an example of the configuration of this type of electrophotographic photoreceptor, as shown in FIGS. 3 and 4, a charge generation layer, a non-uniform charge transport layer, and a uniform charge transport layer are sequentially laminated on a conductive substrate. There is an electrophotographic photosensitive member.

The above electrophotographic photoreceptor has many excellent characteristics. When the photoreceptor is set in a laser printer and the image quality of the obtained image is evaluated, ghost may be generated in some cases. confirmed. As shown in FIG. 5, the occurrence of ghost is usually caused by applying a charge removing layer to an electrophotographic photosensitive member having a charge generation layer and a charge transport layer sequentially laminated on a conductive substrate called a laminated photosensitive member. Problems often arise when using a printer that does not have one. This occurs because the charge generation layer enters the charging / exposure step in the next cycle while the charge generation layer cannot eliminate the exposure history in the previous cycle, and the exposure history is visualized in the steps from latent image formation to developed image formation. It is thought that it happens by doing.

[0013]

However, as shown in FIGS. 3 and 4, an electrophotographic photosensitive member in which a charge generation layer, a non-uniform charge transport layer, and a uniform charge transport layer are sequentially laminated on a conductive substrate. In the body, even if the exposure history of the charge generation layer can be eliminated by providing the charge removal light irradiation step, since the non-uniform charge transport layer has a function of controlling the charge transportability, The exposure history in the cycle may be recorded, which is considered to be the cause of the ghost as described above. The residual charge that causes this ghost affects the stability of the surface potential within the cycle, and, like the occurrence of the ghost,
This is considered to be a cause of image quality instability.

On the other hand, regarding the mechanism of the light-induced potential decay characteristic in the S-shaped photoreceptor, a trap theory [Kitamura, Komon; Journal of the Institute of Electrophotography, Vol. 20, p. 60 (198
2) etc.] and D.I. M. Several proposals have been made, such as the convolutional conduction theory described in Pai et al. In the above-mentioned patent, but no theory has been established yet. However, the above-described pigment resin-dispersed single-layered photoreceptors and D.I. M. In a laminated photoreceptor using a heterogeneous charge transport layer such as Pai, the charge transport path shows a non-uniform structure in which charge transport domains are dispersed in an electrically inactive matrix. One can see in common that the non-uniform structure of the transport path is throughout the layers involved in charge transport.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and provides a novel electrophotographic apparatus capable of overcoming the above-mentioned problems. That is, the object of the present invention is to use a photoreceptor for electrophotography having a specific charge transport layer, to achieve high definition,
It is an object of the present invention to provide an image forming apparatus which has high performance, has no ghost, and has stable image quality and is suitable for a digital system.

[0016]

The present inventors have conducted intensive studies on the S-shaped photoreceptor, and as a result, although the detailed mechanism is not always clear, the conventional J-shaped function-separated stacked photoreceptor has been proposed. The discovery that a two-layer photoconductor in which a pigment resin dispersion layer known as an S-shaped photoconductor is laminated on the charge transporting layer used in the present invention exhibits S-shaped photoinduced potential decay characteristics. The key to the emergence of the S-shaped photoinduced potential decay characteristic is the existence of a charge transport path having a non-uniform structure in the initial stage of charge transport, which is not necessarily the charge common to conventional S-shaped photoconductors. Based on the idea that a non-uniform structure over the entire transport route is unnecessary, the above D.C. M. The present inventors have found that it is possible to further design the S-shaped photoreceptor with further separation of functions by further developing the work of Pai et al., And have completed the present invention.

That is, the image forming apparatus of the present invention comprises a charge transport layer having a charge generating capability for light in a wavelength range of 400 to 900 nm in a charge generating layer and an electrically inactive matrix on a conductive substrate. Photoreceptor provided in this order with a heterogeneous charge transport layer formed by dispersing anionic domains and a uniform charge transport layer formed by a charge transporting matrix, and exposure corresponding to an image signal digitally processed based on image data. An exposure light source that scans the electrophotographic photoreceptor that is a light and selects a wavelength region in which the transmittance of exposure light that passes through the non-uniform charge transport layer is 70% or more; The charge generation layer has a charge elimination light source that emits charge elimination light having a wavelength at which charge is generated.

The electrophotographic photosensitive member used in the image forming apparatus of the present invention has an exposure amount required for a 50% potential decay of 10%.
It is preferable that the exposure amount is less than three times the exposure amount required for% potential decay. The non-uniform charge transport layer of the electrophotographic photoreceptor includes a binder resin having an electrical resistivity of 10 ¹³ Ωcm or more, and an average particle diameter of 0.5 μm or less dispersed in the binder resin at a volume ratio of 20 to 50%. It is preferable to contain the charge transporting domain fine particles of the above. Further, the charge generation layer has a thickness of 400 to
It is preferable to include a charge generation material having a charge generation ability for light in a wavelength range of 900 nm. The transmittance at which the above-mentioned static elimination light passes through the non-uniform charge transport layer is 5 to 95%.
It is preferred that As the static elimination light source used in the image forming apparatus of the present invention, a first static elimination light source in which the transmittance of static elimination light passing through the non-uniform charge transport layer is 50% or less, and transmission through the non-uniform charge transport layer. It is preferable to include a second charge removing light source having a transmittance of the charge removing light of 50% or more and having an emission wavelength in an absorption wavelength range of the charge generation layer.

[0019]

Embodiments of the present invention will be described below. The electrophotographic photoreceptor used in the present invention has a charge generation layer and a charge transport layer provided sequentially on a conductive substrate, and the charge transport layer has a charge transport layer in an electrically inert matrix. It has a heterogeneous charge transport layer in which domains are dispersed and a uniform charge transport layer comprising a charge transporting matrix. Here, “electrically inactive” means that the transport energy level is
It is far from the transport energy level of the main transport charge, meaning that at normal electric field strength, the transport charge is substantially not injected and is in a practically electrically insulating state for the main charge.

The S-shaped decay curve of the photo-induced potential of the electrophotographic photoreceptor is, for example, an exposure amount E _50% required to attenuate the charged potential by 50% and attenuated by 10%. E expressed as a ratio to the exposure amount E required for _10%
A value of _50% / E _10% can be used. In the case of an ideal J-shaped photoreceptor and the potential decay is proportional to the exposure, the value of E _50% / E _10% is 5. However, in a general J-shaped photoreceptor, as the electric field intensity decreases, the charge generation efficiency and / or the charge transport ability decrease, and E _50% / E
_10% indicates a value exceeding 5. On the other hand, a step-like photo-induced potential decay curve, which is an S-shaped ultimate, does not attenuate the potential at all up to a certain exposure amount, but abruptly attenuates to the residual potential level at that exposure amount, has E50 _% / E10 _% The value is 1. Therefore, the S-shaped photoreceptor, although E _50% / E _10% value is defined as being within the scope of 1-5, to exhibit preferred digital properties, E _50% / E _10% Preferably, the value is less than 3, more preferably less than 2.

Although the reason why the electrophotographic photoreceptor exhibits the S-shaped photo-induced potential decay characteristic is not necessarily clear,
The key to the S-shaped potential decay is thought to be due to the non-uniform structure related to charge transport existing during charge transport, particularly at the beginning of charge transport. D. M. According to the patent of Pai et al., It is estimated that the process in which the S-shaped photoinduced potential decay occurs is as follows. First, in the heterogeneous charge transport layer, it is considered that the charge transport domains dispersed in the electrically inert matrix are in contact with each other to form a spiral charge transport path.

That is, when the electrophotographic photosensitive member is charged and a high electric field is applied to the photosensitive layer, charges generated in the charge generation layer by exposure are injected from the charge generation layer into the charge transport layer along the electric field by Coulomb force. Moving in the charge transporting domain in a direction perpendicular to the surface, but encounters a barrier of an electrically inert matrix, where charge transfer is halted.
If the moving distance of the electric charge during this period is sufficiently smaller than the total thickness of the photosensitive layer, the decay of the electric potential during that time will be negligible. After a charge equivalent to almost all surface charges has been injected, the local electric field perpendicular to the surface near the charge becomes negligibly small, and the suspended charge escapes the binding of the electric field. It is possible to move in a direction other than the direction perpendicular to the surface, and to follow a spirally-connected connection path to reach a deeper position than the place where the charge was first stopped. At this depth, as before, the charge is again exposed to a sufficiently high electric field and encounters the barrier of the electrically inert matrix and stops moving. However, because the electric field strength has decreased due to the movement of the previous charge,
More charge passes through the convoluted charge transport path to the next insulating barrier. Thus, the transfer of charge occurs in a cascade resulting in an S-shaped photoinduced potential decay,
M. Pai et al. However, once the barriers in the electrically inert matrix stop most of the charge and once the cascade of charges has begun, there is no need for a subsequent barrier, but rather a uniform charge transport path. It is considered that it is advantageous to move the electric charges smoothly.

According to the present invention, based on the above concept, the light-induced potential decay curve is converted into an S-shape by a non-uniform charge transport layer in which charge transport domains are dispersed in an electrically inert matrix. The main charge-transporting function is carried out by a uniform charge-transporting layer composed of a charge-transporting matrix. By promoting the function separation, the degree of freedom in photoreceptor design can be greatly improved, and the heterogeneous charge-transporting layer can be formed in a thickness of 400 to 900.
It has a region that absorbs light in the wavelength region of nm and a region that transmits light, and generates charges in the region where the light is absorbed, thereby eliminating ghosts and preventing defects in image quality. Hereinafter, the heterogeneous charge transport layer in which the charge transport domains are dispersed in an electrically inert matrix is abbreviated simply as `` heterogeneous charge transport layer, '' and the uniform charge transport layer composed of the charge transport matrix is referred to as Simply referred to as “uniform charge transport layer”.

The electrophotographic photoreceptor used in the present invention has a structure in which a non-uniform charge transport layer for forming an S-shape is added to a J-shaped function-separated laminated photoreceptor, for which many researches and developments have been conducted. Therefore, for the charge generation layer and the uniform charge transport layer, arbitrarily select a material, a composition and a method for forming the charge generation layer and the charge transport layer of the conventionally known J-shaped function-separated laminated photoreceptor, Can be used. This is a very advantageous point from the viewpoint of improving the development efficiency and performance of the S-shaped photoreceptor, and is one of the excellent advantages of the present invention. Further, in an electrophotographic photoreceptor in which the non-uniform structure of the charge transport path, which has been conventionally reported as an S-shaped photoreceptor, extends over all layers, the charge transport path over all layers is non-uniform. It is feared that the transport capacity is difficult to obtain. In contrast, in the present invention, the non-uniform structure of the charge transport path is only a part of the charge transport path, and a wide range of materials can be selected, so that a high transport ability can be obtained more easily. It is.

Hereinafter, each layer constituting the electrophotographic photosensitive member used in the present invention will be described in detail. 3 and 4
FIG. 1 is a schematic cross-sectional view showing a laminated structure of an electrophotographic photoconductor of the present invention. In FIG. 3, on the conductive support 3,
A charge generation layer 1 for generating photocharges is provided, and S
The photoreceptor is provided with a non-uniform charge transport layer 5 for forming a character, and further provided thereon with a uniform charge transport layer 6 for smooth charge transport. The charge transport layer 2 is formed by the uniform charge transport layer 6. In FIG. 4, the undercoat layer 4 is further provided between the conductive support 3 and the charge generation layer 1 on the photoreceptor shown in FIG. These electrophotographic photoreceptors can further include a protective layer and / or a diffuse reflection layer, if desired.

As described above, the distance traveled until the charge generated in the charge generation layer encounters the barrier of the electrically inactive matrix of the non-uniform charge transport layer and first stops temporarily is the entire film thickness of the photosensitive layer. If it is sufficiently smaller than the thickness, the potential decay during that time is negligible, and a more ideal S-shaped photoconductor is obtained. That is, it is considered that a material in which the charge generation layer and the non-uniform charge transport layer for forming the S-shape are close to each other provides excellent S-shape like the electrophotographic photoreceptor used in the present invention.

As in the present invention, the electrophotographic photosensitive member having the structure shown in FIGS. 3 and 4 in which the charge generation layer is on the conductive support side is more effective because the uniform charge transport layer is on the surface side. It is. Generally, the layer on the surface side of the electrophotographic photosensitive member is
Besides photoelectric functions, the charge retention time of charging, ozone generated from the charging member and the like, resistance to discharge products such as NO _x, and paper, functions of resistance such as to wear by the cleaning member or the like is required at the same time . That is, in the single-layer type photoreceptor, in addition to the functions of charge generation, charge transport and S-shape, the above-mentioned other functions are required for the single photosensitive layer itself. D. M. In the case of a stacked type including only a charge generation layer such as Pai and a charge transport layer having a non-uniform structure, the non-uniform charge transport layer is required to have the above-mentioned functions in addition to the functions of charge transport and S-shape. However, it is extremely difficult for these conventional photoconductors to satisfy all of the above functions at the same time. On the other hand, in the electrophotographic photoreceptor of the present invention having the structure shown in FIGS. 3 and 4, charge generation is performed by the charge generation layer, and S-shape is performed by the S-shaped charge transport layer inside the photosensitive layer. Since the above-described functions required for the surface layer can be designed separately from the charge generation and the S-shape, there is an advantage that the degree of design freedom is further increased.

The material used for the electroconductive support of the electrophotographic photosensitive member may be opaque or substantially transparent. Metals such as aluminum, nickel, chromium and stainless steel, and aluminum ,Titanium,
Plastic films, glass, etc. provided with a thin film of nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, ITO, etc .; paper, plastic films, glass, etc. coated or impregnated with a conductivity imparting agent. Can be These conductive supports are used in an appropriate shape such as a drum shape, a sheet shape, and a plate shape, but are not limited thereto. The surface of the conductive support may be further subjected to various treatments, if necessary, within a range that does not affect the image quality. For example,
Oxidation treatment, chemical treatment, coloring treatment, or the like, or irregular reflection treatment such as graining can be performed on the surface.

One or more subbing layers may be provided between the conductive support and the photoconductive layer used in the present invention.
The undercoat layer acts as an adhesive layer that prevents the injection of charges from the conductive support into the photosensitive layer when the photosensitive layer is charged, and that integrally holds the photosensitive layer on the conductive support. Or, in some cases, an antireflection effect of light from the conductive support. As the undercoat layer, known materials can be used, for example, polyethylene resin, acrylic resin, methacrylic resin, polyamide resin,
Vinyl chloride resin, vinyl acetate resin, phenol resin, polycarbonate resin, polyurethane resin, polyimide resin, vinylidene chloride resin, polyvinyl acetal resin,
Vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol resin, water-soluble polyester resin, alcohol-soluble nylon resin, nitrocellulose, casein, gelatin,
Polyglutamic acid, starch, starch acetate, amino starch, polyacrylic acid, resins such as polyacrylamide and their copolymers, or zirconium alkoxide compounds, titanium alkoxide compounds, curable metal organic compounds such as silane coupling agents, They can be used alone or in combination of two or more. Further, a material capable of transporting only charges having the same polarity as the charged polarity can be used.
The thickness of the undercoat layer is suitably from 0.01 to 10 μm, and preferably from 0.05 to 5 μm. As a coating method, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method can be used.

In the charge generation layer used in the present invention, as the charge generation material, known materials used in the charge generation layer of the conventional J-shaped laminated photoreceptor can be used. For example, amorphous selenium, selenium-tellurium alloy, selenium-arsenic alloy, other selenium compounds and selenium alloys,
Inorganic photoconductive materials such as zinc oxide, titanium oxide, a-Si, a-SiC, phthalocyanine, squarium,
Organic pigments and dyes such as anthrone-based, perylene-based, azo-based, anthraquinone-based, pyrene-based, pyrylium salts, and thiapyrylium salts can be used, but are not limited thereto. These organic pigments and dyes can be used alone or in combination of two or more.

Among the above-mentioned charge generating materials, phthalocyanine-based compounds have excellent photosensitivity in the wavelength range of 600 to 850 nm, which is the emission wavelength of LEDs and laser diodes currently used as light sources in digital electrophotographic devices. Is particularly preferable as the charge generation material of the present invention. Specifically, they are metal-free phthalocyanine and metal phthalocyanine, and the central metal of the metal phthalocyanine is Cu, Ni, Zn, Co, Fe, V, S
i, Al, Sn, Ge, Ti, In, Ga, Mg, Pb
And oxides, hydroxides, halides, alkylated compounds, alkoxylated compounds and the like of these central metals. Specifically, metal-free phthalocyanine, titanyl phthalocyanine, chlorogallium phthalocyanine,
Examples include hydroxygallium phthalocyanine, vanadyl phthalocyanine, chloroindium phthalocyanine, dichlorotin phthalocyanine, and the like. Further, those having an arbitrary substituent in these phthalocyanine rings can also be used. Furthermore, those in which an arbitrary carbon atom in these phthalocyanine rings is substituted with a nitrogen atom are also effective. As the form of these phthalocyanine-based compounds, amorphous forms or all crystalline polymorph forms can be used.

Among the above phthalocyanine compounds, titanyl phthalocyanine, chlorogallium phthalocyanine,
Since hydroxygallium phthalocyanine and dichlorotin phthalocyanine have particularly excellent photosensitivity, they are particularly preferably used as charge generation materials. Most of the phthalocyanine compounds have the property of a p-type semiconductor with holes as the main transport charge, while dichlorotin phthalocyanine has the properties of an n-type semiconductor with electrons as the main transport charge. have.
Therefore, the S-shaped photoreceptor containing dichlorotin phthalocyanine as a charge generation material, and formed by sequentially laminating a charge generation layer and a charge transport layer on a conductive substrate,
When it is used with negative charge, it has high sensitivity, suppresses the injection of positive charge from the conductive substrate, and exhibits good electrophotographic characteristics with low dark decay and high chargeability.

The charge generation layer can be formed by the above-mentioned charge generation material by a vacuum evaporation method or by dispersing or dissolving the charge generation material in a binder resin.
Examples of the binder resin used for the charge generation layer include polyvinyl butyral resin, polyvinyl formal resin, partially modified polyvinyl acetal resin, polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinyl acetate resin, and vinyl chloride-acetic acid. Examples include, but are not limited to, vinyl copolymers, silicone resins, phenolic resins, poly-N-vinylcarbazole resins, and the like. These binder resins can be block copolymers, random copolymers or alternating copolymers, and can be used alone or in combination of two or more.

The mixing ratio (volume ratio) of the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10. More preferably, it is set in the range of 3: 1 to 1: 1. When the compounding ratio of the charge generating material to the binder resin is larger than the above range, dark decay is increased and mechanical properties are deteriorated. When the compounding ratio is smaller than the above range, problems such as a decrease in photosensitivity and an increase in residual potential are caused. Happens. The thickness of the charge generation layer used in the present invention is generally in the range of 0.05 to 5 μm, preferably in the range of 0.1 to 2.0 μm. As a coating method, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method can be used.

In the electrophotographic photoreceptor used in the present invention, the heterogeneous charge transport layer has a heterogeneous structure in which charge transport domains are dispersed in an electrically inert matrix.
The charge-transporting domain is a layer that forms a charge-transporting path having a charge-generating ability for light in a wavelength range of 400 to 900 nm. Can be. For example, fine particles of a charge transporting material (hereinafter, referred to as “charge transporting fine particles”) are dispersed in a solution in which an insulating binder resin is dissolved in an appropriate solvent,
After being applied by a dip coating method or the like, it can be obtained by drying. Further, the charge transporting fine particles previously insolubilized by coating with an insulating material such as a thermosetting resin or a silane coupling agent are dispersed in a solution obtained by dissolving the insulating binder resin in an appropriate solvent to obtain a dispersion. It can also be obtained by applying the obtained solution by a dip coating method or the like and then drying it.

In these methods for forming the non-uniform charge transport layer, the formation of the convoluted charge transport path depends on the probability that the charge transport domains contact each other. If the probability of the contact is too large, the charge transport path will not be formed in a spiral shape,
If the probability of the contact is too small, a charge transport path cannot be formed. The charge transport domains need not necessarily be in direct contact. Providing a very thin insulating layer between the charge transporting domains allows the presence of the insulating layer if charges can jump over the gap and negligible trapping there. Here, the convoluted charge transport path is a charge transport path that is formed so that the movement of charges reverses at least once in the film thickness direction.

The heterogeneous charge transporting layer can be formed, more specifically, from a dispersion in which charge transporting fine particles are dispersed in an appropriate binder resin. Materials used as the charge transporting fine particles include hexagonal selenium, cadmium selenide, other selenium compounds and selenium alloys,
Cadmium sulfide, zinc oxide, titanium oxide, a-Si, a
-Inorganic materials such as SiC, phthalocyanine, squarium, anthantrone, perylene, azo,
Organic pigments such as anthraquinone-based compounds, pyrene-based compounds, pyrylium-based compounds, and thiapyrylium-based compounds; and hole-transporting low-molecular compounds such as benzidine-based compounds, amine-based compounds, hydrazone-based compounds, stilbene-based compounds, and carbazole-based compounds, or fluorenone-based compounds. Examples include, but are not limited to, compounds, electron transporting low molecular weight compounds such as malononitrile compounds and diphenoxyquinone compounds. In addition, these charge transport materials alone,
Alternatively, two or more kinds can be used in combination. Among them, hexagonal selenium fine particles substantially transmit light of 700 nm or more, which is the transmission wavelength of a laser diode currently used as a light source in a digital electrophotographic apparatus,
It is particularly preferable as charge transporting fine particles for a non-uniform charge transport layer because it has the ability to absorb light of less than 700 nm, generate charges, and has excellent charge transport ability .

The phthalocyanine-based compound is the emission wavelength of a laser diode in the visible region, which is considered to be a promising light source for future digital electrophotographic devices.
Substantially transmitting light in the range of 50 to 550 nm;
It is particularly preferable as charge transporting fine particles for a non-uniform charge transport layer because it absorbs light having a wavelength of at least nm and has a charge generating ability and an excellent charge transporting ability.

Among the phthalocyanine compounds, metal-free phthalocyanine, titanyl phthalocyanine, chlorogallium phthalocyanine and hydroxygallium phthalocyanine have been used as charge generating materials because they have particularly excellent photosensitivity. Further, it has the property of a p-type semiconductor having holes as a main transport charge, and is used as a transportable fine particle capable of transporting holes to form the material for forming the heterogeneous charge transport layer of the present invention. It is also suitable.

The binder resin used as the electrically inert matrix includes polyvinyl butyral resin, polyvinyl formal resin, partially modified polyvinyl acetal resin, polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, and polyvinyl acetate resin. , A vinyl chloride-vinyl acetate copolymer, a silicone resin, a phenol resin, and the like, but are not limited thereto. These binder resins can be block copolymers, random copolymers or alternating copolymers, and can be used alone or as a mixture of two or more. In addition, the volume resistivity of the binder resin serving as the electrically inert matrix is as follows:
It is preferably 10 ¹³ Ω · cm or more, more preferably 10 ¹⁴ Ω · cm or more. If the volume resistivity is lower than this value, the electrical insulation of the electrically inactive matrix is impaired, and the S-character tends to be lost.

The volume ratio between the charge transporting domain and the electrically inert matrix is arbitrarily set in the range of 3/1 to 1/20, preferably in the range of 7/3 to 1/10. If the charge transporting domain has not been subjected to insulation coating treatment,
The volume ratio of the charge transporting domain to the electrically inert matrix is more preferably in the range of 5/5 to 2/8. If the volume ratio of the charge transporting domain is larger than the above range, the charge transporting domains come into close contact to form a charge transporting path having a substantially uniform structure, and the S-shaped photoinduced potential decay characteristic described above. The inhomogeneous structure of the charge transport path, which is indispensable for the expression of, tends to disappear, and the S-shape tends to be lost. Furthermore, it tends to cause obstacles such as an increase in dark attenuation and a decrease in mechanical strength. On the other hand, if the volume ratio of the charge-transporting domain is less than the above range, sufficient charge-transporting ability cannot be obtained, which tends to cause problems such as an increase in residual potential, a decrease in photosensitivity, and a decrease in response speed.

Also, the volume ratio of the charge-transporting domain to the electrically-inactive matrix is 7/3 by, for example, incompletely coating the particles forming the charge-transporting domain with an electrically inactive substance in advance. It can be improved so that it can be preferably used in the range of ２ to ８. This is because the insulating coating can reduce the probability of electrical contact between the charge transporting domains and can form a convoluted charge transport path due to incomplete portions of the insulating coating.

When the heterogeneous charge transporting layer is formed by dispersing and coating charge transporting fine particles in an insulating binder resin, it is preferable to use a solvent that does not dissolve the charge transporting fine particles in the coating. When a solvent that dissolves the charge-transporting fine particles is used, the substances constituting the charge-transporting fine particles are mixed in a molecularly dispersed state into the insulating binder resin, thereby impairing the insulating property of the electrically inactive matrix. This is because the sex tends to deteriorate. Another method of forming a heterogeneous charge transport layer is by crystallizing a charge transporting dye or molecule in a solid solution with an insulating binder resin to precipitate as microcrystals, and to phase separate. .

The thickness of the heterogeneous charge transporting layer used in the present invention is suitably from 0.1 to 50 μm, preferably from 0.2 to 50 μm.
To 15 μm, more preferably 0.5 to 5 μm. If the thickness is smaller than the above range, the S-character tends to be lost. The upper limit of the film thickness is limited by the charge transporting ability of the S-shaped charge transporting layer to be used, and the response speed, the residual potential, and the like are set within allowable ranges.

The average particle size of the charge transporting domain is preferably from 0.001 to 1 μm, more preferably from 0.005 to 0.5 μm, particularly preferably from 0.05 to 0.5 μm.
It is in the range of 1 to 0.2 μm. When the average particle diameter of the charge transporting domain is larger than the above range, the formation of a non-uniform structure of the charge transporting path necessary for forming the S-shape is stochastically reduced within the preferable thickness range, and the S-shape is lost. Will be. On the other hand,
When the average particle size of the charge transporting domain is smaller than the above range, the charge transporting path approaches a uniform structure, and the S-shaped property is lost. When the charge-transporting domain in the S-shaped charge transport is composed of an aggregate of charge-transporting fine particles,
The particle size of the charge transporting domain refers to the aggregate secondary particle size. However, when the charge transporting fine particles are insulated and coated, the particle diameter of the charge transporting domain is the same as that of the charge transporting fine particles themselves, even if the insulative coated charge transporting fine particles form an aggregate. Refers to particle size.

Further, by adding a compound capable of transporting only a charge having a polarity opposite to that of the main transport charge to the heterogeneous charge transport layer, effects such as a decrease in residual potential and an improvement in repetition stability can be obtained. it can. The coating methods include blade coating, wire bar coating,
Conventional methods such as spray coating, dip coating, bead coating, air knife coating, and curtain coating can be used.

As the uniform charge transporting layer used in the present invention, that is, the layer comprising the charge transporting matrix, a conventional J
A known material used as a charge transport layer in a letter-shaped laminated photoreceptor can be used. For example, a hole transporting low molecular weight compound such as a benzidine-based compound, an amine-based compound, a hydrazone-based compound, a stilbene-based compound, a carbazole-based compound, or a low electron-transporting property such as a fluorenone-based compound, a malononitrile-based compound, or a diphenoxyquinone-based compound. A molecular compound, alone or as a mixture of two or more kinds, is used as a solid solution film in which molecules are uniformly dispersed in an insulating resin such as polycarbonate, polyarylate, polyester, polysulfone, and polymethyl methacrylate, or the charge transport ability itself. Having a high molecular compound can be used. Further, an inorganic substance having a charge transporting ability, such as selenium, amorphous silicon, or amorphous silicon carbide, can also be used. Examples of the charge transporting polymer compound include a polymer compound having a group having a charge transporting ability in a side chain, such as polyvinyl carbazole, JP-A-5-232727.
And high-molecular compounds having a group having a charge transporting ability as a main chain, polysilanes, and the like, as disclosed in Japanese Patent Application Laid-Open Publication No. H10-157, and the like.

As the uniform charge transporting layer in the present invention,
In particular, it is preferable to use a charge transporting polymer compound in production. That is, when the heterogeneous charge transport layer and the uniform charge transport layer are formed into a multilayer film, when the charge transport low molecular compound is used for the uniform charge transport layer, the charge transport low molecular compound is mixed into the heterogeneous charge transport layer. In other words, the insulating property for the main charge of the electrically inactive matrix of the heterogeneous charge transporting layer is reduced, so that the S-shaped property is impaired, or the mixed molecules become charge traps, the residual potential increases, the transportability decreases, and Failures such as a decrease in light sensitivity occur. This problem is particularly prominent when each layer is formed by a wet coating method. Of course, these problems can be solved by selecting a solvent that hardly dissolves and swells the lower layer as the coating solvent for the upper layer, or by selecting an inactive matrix that is incompatible with the charge-transporting low-molecular compound as the electrically inert matrix. , It is possible to avoid.

However, it is known that it is common for polymers to undergo phase separation without being compatible with each other. When a charge-transporting polymer compound is used as a uniform charge-transporting layer, nonuniformity occurs. Since the phase separation is performed without being compatible with the electrically inert matrix resin of the charge transport layer, the problem of the above-mentioned mixing hardly occurs, and the advantage that the restriction on the selection of the material and the manufacturing method is eliminated. Have.
For the above reasons, in the case of a uniform charge transporting layer composed of a charge transporting polymer, it is desirable that the layer does not contain 5% or more of a charge transporting compound having a molecular weight of 1,000 or less.

Further, as the charge transporting polymer compound,
When a charge transporting resin containing at least one or more of the structures represented by the following general formula (1) as a repeating unit is used, it is particularly preferable since it has high charge transporting ability and excellent mechanical properties. .

[0051]

Embedded image (R _{1 to} R ₆ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a substituted amino group, a halogen atom, or a substituted or unsubstituted aryl group, and X represents a substituted or unsubstituted aromatic ring 2 T represents a divalent hydrocarbon group or a heteroatom-containing hydrocarbon group, and T represents a divalent hydrocarbon group or a heteroatom-containing hydrocarbon group having 1 to 20 carbon atoms and optionally having a branched or cyclic structure; And l
Represents an integer of 0 or 1, respectively. )

In the uniform charge transport layer, there may be electrically inactive regions surrounded by the charge transporting matrix. For example, insulating particles or the like can be contained for the purpose of reducing surface friction, abrasion, or surface deposits. In addition, the uniform charge transporting layer can include charge transporting fine particles and the like in order to improve transportability. The thickness of the uniform charge transport layer used in the present invention is 1
５０50 μm, preferably 5-30 μm. As the coating method, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like can be used. In addition, those capable of vapor phase film formation can be directly formed by a vacuum evaporation method or the like. The layer thickness of the entire charge transport layer in the invention is usually 5
５０50 μm is appropriate, and preferably set in the range of 10-40 μm.

In the present invention, since the charge transport layer exists between the charge generation layer and the exposure light source, the charge transport layer is substantially exposed to light of the exposure wavelength in order to prevent a reduction in effective photosensitivity. Desirably, it is transparent. The transmittance of light used for exposure through the charge transport layer is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. However, if use at low sensitivity is desired, the effective light sensitivity can be adjusted using a charge transport layer that effectively absorbs light at the exposure wavelength. However, when the S-shaped charge transporting layer absorbs light and the non-uniform charge transporting layer has a charge generating ability, the S-shaped property tends to be impaired. Desirably, it is substantially transparent to light of the wavelength. The absorptance of light used for exposure in the heterogeneous charge transport layer is preferably 30% or less, more preferably 20% or less, and further preferably 10% or less. The light absorptance means the original absorptivity of the film excluding reflection and scattering.

A protective layer may be further provided on the photoconductive layer comprising the charge generation layer and the charge transport layer of the electrophotographic photosensitive member used in the present invention, if necessary. This protective layer,
Protects the photoconductive layer from chemical stress such as ozone, oxidizing gas, and ultraviolet light generated from the charging member, and mechanical stress caused by contact with a developer, paper, a cleaning member, and the like. Is effective to improve the real life of In a layer configuration using a thin charge generation layer as an upper layer, the effect of providing a protective layer is particularly remarkable.

The protective layer is formed by including a conductive material in a suitable binder resin. Examples of the conductive material include, but are not limited to, metallocene compounds such as dimethylferrocene, and metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and ITO. . As the binder resin, known resins such as polyamide, polyurethane, polyester, polycarbonate, polystyrene, polyacrylamide, silicone resin, melamine resin, phenol resin, and epoxy resin can be used. Also, a conductive inorganic film such as amorphous carbon can be used as the protective layer.

The electric resistance of the protective layer is 10 ⁹ to 10 ¹⁴ Ω ·
cm. When the electric resistance is higher than this range, the residual potential increases. On the other hand, when the electric resistance is lower than this range, the charge leakage in the creeping direction cannot be ignored and the resolution decreases. The thickness of the protective layer is 0.5 to 2
0 μm is appropriate, and preferably set in the range of 1 to 10 μm. When a protective layer is provided, a blocking layer for preventing leakage of electric charge from the protective layer to the photosensitive layer can be provided between the photosensitive layer and the protective layer, if necessary. As the blocking layer, a known layer can be used as in the case of the protective layer.

In the electrophotographic photosensitive member used in the present invention, for the purpose of preventing deterioration of the photosensitive member due to ozone or oxidizing gas generated in the electrophotographic apparatus, or light or heat,
An antioxidant, a light stabilizer, a heat stabilizer and the like can be added to each layer or the uppermost layer. As the antioxidant, known ones can be used, for example, hindered phenol, hindered amine, paraphenylenediamine, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds and the like. Can be Further, as the light stabilizer, known ones can be used, for example, benzophenone,
Derivatives such as benzotriazole, dithiocarbamate, and tetramethylpiperidine, and electron-withdrawing or electron-donating compounds that can deactivate a photoexcited state by energy transfer or charge transfer are exemplified. Further, insulating particles such as a fluororesin may be dispersed in the outermost surface layer for the purpose of reducing surface wear, improving transferability, improving cleanability, and the like.

A conventional multi-layer electrophotographic photoreceptor in which a charge generation layer or a charge transport layer has a plurality of layers,
Alternatively, those having a photoconductive undercoat layer or a protective layer are known, but these electrophotographic photoreceptors are merely J-shaped laminated photoreceptors, and their photosensitivity, photosensitive wavelength The purpose is to improve the range or response speed. The present inventors conducted additional tests using the above-mentioned conventional laminated photoreceptor. As a result, none of the photoreceptors having the S-characteristic of _E50% / E10 _{% of} less than 3 which is preferable in the present invention does not exist. It was confirmed. The essential difference between these conventional laminated photoreceptors and the electrophotographic photoreceptor used in the present invention lies in the difference in the charge transport path structure of the layer located between the most distant charge generating layer and the charge transport layer. . That is, in the conventional laminated electrophotographic photoreceptor, the structure of the charge transport path of the layer located between the most distant charge generating layer and the charge transport layer achieves a smooth electric field movement essential for the J-shaped characteristic. As described above, uniform or substantially uniform (due to the fact that the volume ratio of the transportable domains is too high and the charge-transporting material is mixed and the insulating property of the electrically inert matrix is reduced). This does not include a substantially non-uniform structure that causes the S-shaped phenomenon of the present invention.

The image forming apparatus of the present invention equipped with the above-described electrophotographic photosensitive member preferably uses an electrophotographic apparatus that performs exposure based on digitally processed image signals. An apparatus that performs exposure based on a digitally processed image signal means that a light source such as a laser or an LED is used.
This is an electrophotographic device that exposes with multi-valued light by performing binarization or pulse width modulation or intensity modulation, and for the purpose of initializing the photoconductor after development or stabilizing the electrophotographic characteristics. An electrophotographic apparatus having a light source for static elimination, and having means for irradiating at least a light wavelength at which the charge transporting domain can generate charges, and specific examples thereof include an LED printer, a laser printer, and a laser exposure type digital copier. And the like.

[0060]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples and the like. However, the present invention is not limited to the following examples, and those skilled in the art can modify the following examples based on known knowledge of electrophotographic technology. Production Example 1 Aluminum drum (diameter 40 mm, length 318.5 m)
m), a zirconium alkoxide compound (trade name:
A solution consisting of 10 parts by weight of ORGATICS ZC540, manufactured by Matsumoto Pharmaceutical Co., Ltd., 1 part by weight of a silane compound (trade name: A1110, manufactured by Nippon Unicar), 40 parts by weight of isopropanol, and 20 parts by weight of butanol was applied by dip coating. At 150 ° C. for 10 minutes to form an undercoat layer having a thickness of 0.1 μm. Next, 4 parts by weight of chlorogallium phthalocyanine microcrystals were mixed with a vinyl chloride-vinyl acetate copolymer (trade name: UCAR Solution Vinyl Resin VMCH, manufactured by Union Carbide).
Parts by weight, 67 parts by weight of xylene and 33 parts by weight of butyl acetate, and the mixture was dispersed with 1 mmφ glass beads by a sand grinder for 2 hours. The obtained coating solution was applied on the undercoat layer by a dip coating method. And
Heat and dry at 100 ° C for 10 minutes, 0.2μm thick
Was formed.

Next, 15 parts by weight of hexagonal selenium microcrystals, 8 parts by weight of a vinyl chloride-vinyl acetate copolymer (trade name: UCAR Solution Vinyl Resin VMCH, manufactured by Union Carbide) and 100 parts by weight of isobutyl acetate were mixed with 3 parts by weight.
Dispersion treatment was performed for 8 days with an attritor using mmφ stainless steel beads. The obtained dispersion was applied on the charge generation layer by a dip coating method, and then 135
The resultant was dried by heating at 10 ° C. for 10 minutes to form a non-uniform charge transport layer (S-shaped charge transport layer) having a thickness of 1 μm. The volume ratio of hexagonal selenium in the obtained S-shaped charge transport layer was about 35%
Met.

Next, as a polymer charge transporting material, 15 parts by weight of a polymer compound having a repeating unit represented by the following general formula (2) (molecular weight: 120,000) was used:
A coating solution dissolved in 5 parts by weight was applied on the S-shaped charge transport by dip coating, and dried by heating at 135 ° C. for 1 hour to form a uniform charge transport layer having a thickness of 20 μm. An electrophotographic photoreceptor having the layer configuration shown in FIG. 4 was produced.

[0063]

Embedded image

The electrophotographic photoreceptor thus obtained was measured for the surface potential with respect to the exposure amount while changing the ND filter using the photoreceptor evaluation apparatus shown in FIG. , 40% RH), the surface of the photoreceptor was charged to -750 V, and a potential decay curve was measured. At this time, as exposure light, a halogen lamp light transmitted through a bandpass filter having a center wavelength of 780 nm and split into near-infrared light, and 60% as static elimination light.
Halogen lamp light transmitted through a band-pass filter having a center wavelength of 0 nm and separated into red light was used. The light amount of the static elimination light is one of the light amounts at which the photoconductor completely completes the light attenuation.
It was about 0 times. In FIG. 6, reference numeral 11 denotes a photoconductor,
13 is a charging scorotron, 19 is a band pass filter, 20 is an ND filter, 21 is a halogen lamp, 2
2 is an electrometer.

When measured using the above-described evaluation apparatus, the obtained electrophotographic photosensitive member showed an S-shaped photoinduced potential decay as shown in FIG. From this photoinduced potential decay curve, the E _{50 %} value was calculated to be 4.5 erg / cm ² , and the E _50% / E _10% value was calculated to be 1.5. At this time, the transmittance of the entire charge transport layer for light of 780 nm was 90%. The absorptance of the non-uniform charge transport layer with respect to light at 780 nm was 9%. In addition, the transmittance | permeability of the whole charge transport layer measured the nonuniform charge transport layer and the uniform charge transport layer on a glass plate using the same conditions, and using the Hitachi automatic recording spectrophotometer U-4000. The absorptance of the S-shaped charge transport layer was measured by using a Hitachi automatic recording spectrophotometer U-4000 after preparing a heterogeneous charge transport layer on a glass plate under the same conditions (black on the back of the sample). Plate) and the transmittance were determined by the following equation. (Absorptance) = 1-[(transmittance) + (reflectance)]

Reference Example 1 An electrophotographic photosensitive member was produced in the same manner as in Production Example 1, except that the non-uniform charge transport layer was not applied. When the electrophotographic characteristics of the obtained electrophotographic photoreceptor were evaluated by the same method as in Production Example 1, the photoinduced potential decay curve was as shown in FIG. 1 and was not S-shaped. Was. Also, the E
_{The 50%} / E _10% value was calculated to be 5.5. Reference Example 2 An electrophotographic photosensitive member was produced in the same manner as in Production Example 1, except that the charge generation layer was not applied. When the electrophotographic characteristics of the obtained electrophotographic photoreceptor were evaluated by the same method as in Preparation Example 1, no photosensitivity was exhibited. Production Example 1 and Reference Examples 1 to
Comparing with No. 2, it is clear that the non-uniform charge transport layer develops an S-shape without contributing to charge generation.

Preparation Example 2 Hydroxygallium phthalocyanine microcrystals were used in place of chlorogallium phthalocyanine microcrystals, and monochlorobenzene was used in place of xylene and butyl acetate as a solvent for dispersing the same. An electrophotographic photoreceptor was produced in the same manner as in Example 1. The obtained electrophotographic photoreceptor was evaluated in the same manner as in Production Example 1. The photoinduced potential decay characteristic was such that the E _50% value was 4.0 e.
rg / cm ² and an E _50% / E _10% value of 1.5
Was S-shaped.

Production Example 3 Titanyl phthalocyanine microcrystals were used in place of chlorogallium phthalocyanine microcrystals, and xylene and butyl acetate were used as a solvent for dispersing the same in place of xylene and butyl acetate.
An electrophotographic photoreceptor was produced in the same manner as in Production Example 1, except that only butyl acetate was used. When the obtained electrophotographic photoreceptor was evaluated in the same manner as in Production Example 1, the photoinduced potential decay characteristics were as follows: E _50% value was 3.7 erg / cm ² , and E _50% / E It was an S-shape with a _10% value of 1.3.

Production Example 4 First, an undercoat layer was formed in the same manner as in Production Example 1. Next, 5 parts by weight of dibromant anthrone microcrystals were mixed with 1 part by weight of polyvinyl butyral resin (trade name: BM-S, manufactured by Sekisui Chemical Co., Ltd.) and 100 parts by weight of cyclohexanone, and mixed with 1 mmφ glass beads using a sand grinder. after dispersed by time processing, the resulting coating liquid immersion co
The computing method is applied on the undercoat layer described above,
Heat and dry at 130 ° C. for 10 minutes, thickness 0.5 μm
Was formed.

Next, 11 parts by weight of chlorogallium phthalocyanine microcrystals, 11 parts by weight of a vinyl chloride-vinyl acetate copolymer (trade name: UCAR Solution Vinyl Resin VMCH, manufactured by Union Carbide) and 100 parts by weight of normal butyl acetate were The mixture was dispersed with a 1 mmφ glass bead using a sand grinder for 4 hours. Next, the obtained coating solution is applied on the above-mentioned charge generating layer by a dip coating method,
After heating and drying for 1 minute, a heterogeneous charge transport layer (S-shaped charge transport layer) having a thickness of 1 μm was formed. The volume ratio of chlorogallium phthalocyanine in the obtained S-shaped charge transport layer was about 30%. Next, a uniform charge transport layer was formed in the same manner as in Preparation Example 1, whereby a photoconductor for electrophotography having the layer configuration shown in FIG. 4 was prepared.

The photoconductor for electrophotography obtained in this manner was measured for the surface potential with respect to the exposure amount while changing the ND filter using the photoconductor evaluation apparatus shown in FIG. , 40% RH), the surface of the photoreceptor was charged to -750 V, and a potential decay curve was measured. At this time, as the exposure light, a halogen lamp light transmitted through a band-pass filter having a center wavelength of 500 nm and split into blue-green light, and 780 as a neutralization light
through a bandpass filter with a center wavelength of nm,
Halogen lamp light separated into near infrared light was used. The light amount of the static elimination light is one of the light amounts at which the photoconductor completely completes the light attenuation.
It was about 0 times.

When measured using the above-described evaluation apparatus, the obtained electrophotographic photosensitive member showed an S-shaped photoinduced potential decay as shown in FIG. From this photo-induced potential decay curve, the E _50% value was 3.5 erg / cm ² , and the E _50% / E _10%
The value was calculated to be 1.5. At this time, the transmittance of the entire charge transport layer for light of 500 nm was 90%, and the absorptivity of the non-uniform charge transport layer for light of 500 nm was 9%. This measurement was performed in the same manner as in Production Example 1.

Reference Example 3 An electrophotographic photosensitive member was produced in the same manner as in Production Example 4, except that the non-uniform charge transport layer was not applied. When the electrophotographic characteristics of the obtained electrophotographic photoreceptor were evaluated by the same method as in Production Example 4, the photoinduced potential decay curve was as shown in FIG. 1 and was not S-shaped. Was. The value of E _50% / E _10% was calculated to be 5.5. Reference Example 4 An electrophotographic photoconductor was prepared in the same manner as in Preparation Example 4, except that the charge generation layer was not applied. When the electrophotographic characteristics of the obtained electrophotographic photoreceptor were evaluated by the same method as in Production Example 4, only an extremely low photosensitivity was exhibited. Production Example 4
By comparing Reference Examples 3 and 4, it is clear that the heterogeneous charge transport layer develops an S-shape without contributing to charge generation.

Preparation Example 5 In place of the charge generation layer formed using dibromoanthanthrone, 5 parts by weight of hexagonal selenium microcrystals were replaced with a vinyl chloride-vinyl acetate copolymer (trade name: UCAR Solution Vinyl Resin VMCH, 2 parts by weight of Union Carbide), 100 parts by weight of isobutyl acetate
24 with an attritor using stainless steel beads
Time treated and dispersed. Next, the obtained coating solution is applied on the undercoat layer by a dip coating method, and dried by heating at 100 ° C. for 10 minutes to form a 0.2 μm-thick charge generating layer. A photoreceptor was produced. When the obtained electrophotographic photoreceptor was evaluated in the same manner as in Production Example 4, the photoinduced potential decay characteristics were such that the E _50% value was 1.5 erg / cm ² and the E _50% / E _{The 10%} value was 1.5 S-shaped.

Example 1 The photoconductors for electrophotography obtained in Production Examples 1 to 3 were mounted on a laser printer (Laser Press 4105, manufactured by Fuji Xerox Co., Ltd.) and subjected to a printing test. At this time, in order to obtain the optimal exposure amount, ND
I put the filter. FIG. 10 shows a schematic configuration diagram of the laser printer used for this printing test. FIG. 10 shows that a static elimination light source (red LED: emission center 600 nm) 12, a charging scorotron 13, an exposure laser beam 14, a developing unit 15, a transfer corotron 16 and a cleaning blade 17 are provided around a photosensitive drum 11. They are arranged in the order of the process. The exposure laser beam 14 is
An exposure laser diode having a transmission wavelength of 780 nm is provided, and emits light based on a digitally processed image signal. The emitted laser light is configured to expose the photoreceptor while being scanned by a polygon mirror (not shown) and a plurality of lenses and mirrors. Reference numeral 18 denotes a sheet. When the print quality of the image obtained using the laser printer shown in FIG. 10 was confirmed, the electrophotographic photoreceptors obtained in Production Examples 1 to 3 exhibited uniform image quality without any ghost. Obtained.

Comparative Example 1 Evaluation was made in the same manner as in Example 1 except that a halogen lamp light that passed through a band-pass filter having a center wavelength of 550 nm and was separated into green light was used as exposure light. The evoked potential decay curve had the shape shown in FIG. 8, and did not have a clear S-shape. Also, its E _50% / E
_{The 10%} value was calculated to be 3.8. By comparing Example 1 and Comparative Example 1, when the hexagonal selenium microcrystals were used as the charge transporting domain, as shown in FIG.
It can be understood that the absorption of the exposure light having a wavelength of 550 nm and the generation of charges cause the loss of the performance as a non-uniform charge transport layer, and the light-induced potential decay curve does not become S-shaped.

Comparative Example 2 A light source (green LED: light emission center 500n)
Except for using m), the print quality was confirmed in the same manner as in Example 1. As a result, a ghost in which the exposure history in the previous cycle was visualized occurred. It can be understood that, when the light has a wavelength of 500 nm, chlorogallium phthalocyanine in the charge generation layer does not generate a charge and a ghost is generated. Comparative Example 3 A light source (red LED: luminescence center 680 n
Except for using m), the print quality was confirmed in the same manner as in Example 1. As a result, a ghost in which the exposure history in the previous cycle was visualized occurred. It can be understood that, with the light of 680 nm, the hexagonal selenium fine particles in the S-shaped charge transporting layer do not generate charges, and ghosts are generated.

Example 2 A light source (green LED: emission center 500n)
m) and a light source (red LED: emission center: 680 nm), and the print quality was confirmed in the same manner as in Example 1. As a result, uniform image quality without ghost was obtained. FIG. 11 shows a schematic configuration diagram of the laser printer used for this printing test. FIG. 11 is the same as that shown in FIG. 10 except that FIG. 10 has two static elimination light sources 12.

Comparative Example 4 In the same manner as in Production Example 1, an undercoat layer and a charge generation layer were formed.
Next, JP-A-6-83077 (U.S. Pat.
N-vinylcarbazole and n-methacrylic acid prepared according to Example 1 described in JP-A-6,586) containing 64 mol% of N-vinylcarbazole monomer units.
8 parts by weight of the multi-block copolymer of dodecyl is dissolved in 90 parts by weight of methylene chloride and 10 parts by weight of monochlorobenzene, applied on the charge generation layer by a dip coating method, and dried by heating at 115 ° C. for 30 minutes. hand,
An S-shaped charge transport layer having a thickness of 4 μm was formed. Next, a uniform charge transport layer was formed in the same manner as in Preparation Example 1, and a photoconductor for electrophotography having the layer configuration shown in FIG. 4 was prepared.

When the electrophotographic photoreceptor thus obtained was evaluated in the same manner as in Production Example 1, the photoinduced potential decay characteristic was such that the E _50% value was 6.3 erg / cm ² . It was an S-shape having an E _50% / E _10% value of 2.3. 78 of the entire charge transport layer measured in the same manner as in Production Example 1
The transmittance for 0 nm light was 90%, and the absorptance for the 780 nm light of the heterogeneous charge transport layer was 3%. In this example, the N-vinylcarbazole structure, which is a charge transporting domain, has no charge generating ability for light in a wavelength region of 400 to 900 nm. When the printing quality of this electrophotographic photoreceptor was checked in the same manner as in Example 1, a ghost in which the exposure history in the previous cycle was visualized occurred.

Example 3 The electrophotographic photosensitive member obtained in Production Examples 4 and 5 was used in Example 1.
The laser printer (L
printer press 4105, manufactured by Fuji Xerox Co., Ltd.) to perform a printing test. The exposure laser beam 14 is a microminiature YA excited by a semiconductor laser.
SH with fundamental wavelength of 1060nm emission wavelength of G laser
A laser having an exposure laser of 530 nm by G and emitting light based on a digitally processed image signal was used. The emitted laser light is configured to expose the electrophotographic photosensitive member while being scanned by a polygon mirror (not shown) and a plurality of lenses and mirrors. In addition, by changing the exposure light source from the 780 nm semiconductor laser to the above laser, the spot diameter of the light beam is reduced to about 2/3. When the print quality of the image obtained using the laser printer shown in FIG. 10 was confirmed, the electrophotographic photoreceptors obtained in Production Examples 4 to 5 exhibited uniform image quality without ghost. Obtained.

Comparative Example 5 Production Example 4 was performed in the same manner as in Example 1 except that a halogen lamp light, which passed through a band-pass filter having a center wavelength of 780 nm and was split into near infrared light, was used as exposure light. When the electrophotographic photoreceptor was evaluated, the photoinduced potential decay curve was as shown in FIG. 13 and was not clearly S-shaped. The E _50% / E _10% value was calculated to be 3.8. By comparing Example 3 with Comparative Example 5, when chlorogallium phthalocyanine microcrystals were used as the charge transporting domain, as shown in FIG. 14, it absorbed the exposure light dispersed at 780 nm, It can be understood that the photoinduced potential decay curve does not become S-shaped.

Comparative Example 6 A light source (near infrared LED: emission center 700
When the print quality of the electrophotographic photosensitive member of Production Example 4 was confirmed in the same manner as in Example 3 except for using (nm), a ghost in which the exposure history in the previous cycle was visualized occurred.
With 700 nm light, it can be understood that dibromant anthrone in the charge generation layer does not generate charge, and ghost occurs.

Comparative Example 7 A light source (blue-green LED: emission center 500
When the print quality of the electrophotographic photosensitive member of Production Example 4 was confirmed in the same manner as in Example 3 except for using (nm), a ghost in which the exposure history in the previous cycle was visualized occurred.
It can be understood that chlorogallium phthalocyanine in the charge generation layer does not generate a charge and generates a ghost with light of 500 nm.

Example 4 A light source (blue-green LED: emission center 500
nm) and light source (near infrared LED: emission center 700 nm)
When the print quality of the electrophotographic photosensitive member of Production Example 4 was confirmed in the same manner as in Example 3 except that the two light sources were used, uniform image quality without ghost was obtained. For this printing test, a laser printer shown in FIG. 11 was used.

[0086]

The image forming apparatus of the present invention uses a novel electrophotographic photosensitive member exhibiting an S-shaped photoinduced potential decay characteristic, and performs exposure based on a digitally processed image signal. By controlling the light quality of the static elimination light, an excellent effect that no ghost is generated and an image having excellent stability of printing quality and image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an exposure amount and a surface potential in a J-shaped electrophotographic photosensitive member.

FIG. 2 is a graph showing a relationship between an exposure amount and a surface potential in an S-shaped electrophotographic photosensitive member.

FIG. 3 is a schematic sectional view showing an example of an electrophotographic photosensitive member used in the present invention.

FIG. 4 is a schematic sectional view showing another example of the electrophotographic photosensitive member used in the present invention.

FIG. 5 is a schematic sectional view showing an example of a conventional electrophotographic photosensitive member.

FIG. 6 is a schematic configuration diagram of a photoconductor evaluation device used for evaluating an electrophotographic photoconductor.

FIG. 7 is a graph showing light-induced potential decay characteristics of the electrophotographic photosensitive member obtained in Production Example 1.

FIG. 8 is a graph showing light-induced potential decay characteristics of the electrophotographic photosensitive member obtained in Comparative Example 1.

FIG. 9 is a graph showing the spectral absorption of hexagonal selenium used in Preparation Example 1.

FIG. 10 is a schematic configuration diagram of an image forming apparatus of the present invention that performs exposure based on a digitally processed image signal.

FIG. 11 is a schematic configuration diagram of another image forming apparatus of the present invention that performs exposure based on a digitally processed image signal.

FIG. 12 is a graph showing a photo-induced potential decay characteristic of the electrophotographic photosensitive member obtained in Production Example 4.

FIG. 13 is a graph showing a photo-induced potential decay characteristic of the electrophotographic photosensitive member obtained in Comparative Example 5.

FIG. 14 is a graph showing the spectral absorption of chlorogallium phthalocyanine microcrystals used in Comparative Example 5.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Charge generation layer, 2 ... Charge transport layer, 3 ... Conductive support,
4 undercoat layer, 5 S-shaped charge transport layer (non-uniform charge transport layer), 6 uniform charge transport layer, 11 photoconductor drum, 12
... Characterization light source, 13 ... Charging scorotron, 14 ... Exposure laser beam, 15 ... Developer, 16 ... Transfer corotron,
17 cleaning blade, 18 paper, 19 bandpass filter, 20 ND filter, 21 halogen lamp, 22 electrometer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G03G 15/043 (72) Inventor Ryosaku Igarashi 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (56) References 6-83077 (JP, A) JP-A-1-169454 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 5/043 G03G 5/047 G03G 5/08 101

Claims (10)

(57) [Claims] 1. A charge generating layer or an electrically inactive matrix having a charge transporting domain capable of generating charges for light in a wavelength range of 400 to 900 nm dispersed on a conductive substrate. An electrophotographic photoreceptor provided with a uniform charge transport layer and a uniform charge transport layer comprising a charge transporting matrix in this order, and exposure light corresponding to an image signal digitally processed based on image data; An exposure light source that scans the electrophotographic photoreceptor that has selected a wavelength region where the transmittance of exposure light passing through the uniform charge transport layer is 70% or more, and the charge transport domains and the charge generation layer generate charges. An image forming apparatus comprising: a charge elimination light source for irradiating a charge elimination light having a wavelength. 2. The image forming apparatus according to claim 1, wherein the exposure amount required for the 50% potential attenuation is less than three times the exposure amount required for the 10% potential attenuation. . 3. The image forming apparatus according to claim 1, wherein the charge transporting domain comprises hexagonal selenium fine particles. 4. The non-uniform charge transport layer has an electric resistivity of 10 ¹³
Ωcm or more of a binder resin and a volume ratio of 20 to
The image forming apparatus according to claim 1, further comprising hexagonal selenium fine particles having an average particle diameter of 0.5 μm or less dispersed at 50%. 5. The transmittance of the non-uniform charge-transporting layer, wherein the transmittance of the charge-removing light is 5 to 95%.
5. The image forming apparatus according to claim 4. 6. The image forming apparatus according to claim 1, wherein the charge generation layer contains a phthalocyanine compound as a charge generation material. 7. The image forming apparatus according to claim 1, wherein the charge transporting domain comprises phthalocyanine-based compound fine particles. 8. The non-uniform charge transport layer has an electric resistivity of 10 ¹³
Ωcm or more of a binder resin and a volume ratio of 20 to
2. The image forming apparatus according to claim 1, further comprising phthalocyanine-based compound fine particles having an average particle diameter of 0.5 μm or less dispersed at 50%. 9. The charge generation layer according to claim 5, wherein the charge generation material is 45%.
The image forming apparatus according to claim 1, wherein the image forming apparatus includes one having a charge generating ability for light in a wavelength range of 0 to 550 nm. 10. A charge removing light source comprising: a first charge removing light source having a transmittance of 50% or less for a charge removing light passing through a non-uniform charge transport layer; 5
2. The image forming apparatus according to claim 1, further comprising a second static elimination light source having an emission wavelength of 0% or more and an absorption wavelength range of the charge generation layer.