JP2011209360A - Electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress changes in an interference light, with respect to changes in the thickness of a surface layer, while maintaining the sensitivity of a photoreceptor to incident light to be relatively high.SOLUTION: An electrophotographic photoreceptor is provided, including a conductive substrate; a photoconductive layer formed on the conductive substrate and essentially comprising an organic compound; a surface layer formed on the photoconductive layer and having a refractive index smaller than that of the photoconductive layer; and an intermediate layer disposed in a gap between the photoconductive layer and the surface layer, wherein the intermediate layer includes a first region having a refractive index larger than that of the surface layer, and a second region at a position close to the photoconductive layer than the first region and having a refractive index smaller than that of the first region.

Description

  The present invention relates to an electrophotographic photoreceptor and an image forming apparatus.

  Conventionally, an electrophotographic photosensitive member having a structure in which a photoconductive layer and a surface layer are laminated on a substrate has been used. In an image forming apparatus using an electrophotographic photosensitive member having a laminated structure of a surface layer and a photoconductive layer, reflected light from the interface between the surface layer and the photoconductive layer interferes with reflected light from the surface. The degree of this interference varies depending on the film thickness and refractive index of the surface layer and the photoconductive layer. Because of this interference, it is known that the amount of light that is substantially incident on the photoconductive layer varies depending on the film thickness of the surface layer and the like. The degree of variation in the amount of incident light on the photoconductive layer due to the interference of these reflected lights is relatively large, and the subtle variation in the thickness of the surface layer leads to a relatively large variation in the amount of incident light on the photoconductive layer. There was a case to be connected.

  In an image forming apparatus such as a printing machine, when the same image is output in large quantities, for example, in units of hundreds of thousands, the surface layer is worn immediately after the start of printing and at the end of printing. Thickness may vary.

  In this case, when the degree of interference changes, the quality of the printed image, such as density unevenness, may change visibly as the number of printed sheets increases. In addition, when an in-plane distribution occurs in the wear amount of the surface layer, an in-plane distribution occurs in the substantial light transmission amount due to interference, and density unevenness may also occur in each printed image. there were.

  For example, Patent Document 1 below discloses a photoconductor intended to reduce the influence of the interference in the electrophotographic photoconductor. Patent Document 1 discloses a photoconductor in which an intermediate layer is provided between a surface layer and a photoconductive layer, and the refractive index of the intermediate layer is increased stepwise as it approaches the photoconductive layer from the surface layer. It describes how to make well.

JP 2010-37643 A

  In recent years, with the demand for higher image quality, the image density distribution in an output image is also required to be suppressed to be lower than before. In the electrophotographic photosensitive member described in Patent Document 1, the degree of change in the interference light with respect to a minute change in the thickness of the surface layer cannot be sufficiently suppressed to a level that meets the recent demand for higher image quality. There is a case.

  In the configuration described in Patent Document 1, the thickness of the intermediate layer needs to be relatively thick, for example, 200 nm or more as described in Patent Document 1. The thicker the intermediate layer, the greater the light absorption in this intermediate layer and the smaller the amount of light incident on the photoconductive layer. The conventional electrophotographic photoreceptor as described in Patent Document 1 has a problem that the sensitivity of image formation (latent image formation) with respect to incident light is relatively small.

  The present invention has been made for the purpose of solving such problems.

  In order to solve the above problems, a conductive substrate, a photoconductive layer mainly composed of an organic compound formed on the conductive substrate, and the photoconductive layer formed on the photoconductive layer A surface layer having a small refractive index, and an intermediate layer provided in a gap between the photoconductive layer and the surface layer, the intermediate layer having a first region having a refractive index larger than that of the surface layer; An electrophotographic photoreceptor comprising: a second region having a refractive index smaller than that of the first region, which is located closer to the photoconductive layer than the first region.

  An electrophotographic photosensitive member; exposure means for irradiating the electrophotographic photosensitive member with exposure light to form a latent image on the surface of the electrophotographic photosensitive member; and supplying toner to the electrophotographic photosensitive member; A developing unit that forms a toner image corresponding to a latent image on the electrophotographic photosensitive member, a transfer unit that transfers the toner image onto a transfer material, and a surface of the electrophotographic photosensitive member, and after the transfer, the electrophotographic Also provided is an image forming apparatus comprising a cleaning blade for removing toner remaining on the surface of the photoreceptor.

  According to the electrophotographic photoreceptor and the electrophotographic photoreceptor of the present invention, the in-plane distribution of image density in the formed image can be reduced. Even when used for a long period of time, the density variation of the formed image is small. Further, even when the sensitivity to incident light is relatively high and an image is formed at a relatively high speed, a high-definition image can be formed.

1 is a diagram illustrating a configuration of an electrophotographic photoreceptor that is an embodiment of the electrophotographic photoreceptor of the present invention. FIG. 2A and 2B are diagrams for explaining the electrophotographic photosensitive member shown in FIG. 1, in which FIG. 1A is a schematic cross-sectional view, and FIG. It is a model figure for demonstrating a virtual refractive index, (a)-(c) is a cross-sectional model figure of the photoreceptor which each has a different layer structure. FIG. 2 is a cross-sectional view schematically showing a path of exposure light in the photoreceptor shown in FIG. 1. FIG. 6 is a diagram for explaining another embodiment of the photoconductor of the present invention, in which (a) is a schematic cross-sectional view, and (b) is a diagram showing a refractive index distribution in the vicinity of a surface layer. FIG. 2 is a schematic cross-sectional view of an image forming apparatus configured to include the photoreceptor shown in FIG. 1. FIG. 2 is a partially enlarged view of a developing device including the photoconductor shown in FIG. 1. It is sectional drawing explaining the LED head mounted in the image forming apparatus shown in FIG. FIG. 7 is a schematic cross-sectional view of a photoreceptor mounted on the image forming apparatus shown in FIG. 6.

  Hereinafter, an embodiment of a photoreceptor and an image forming apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an electrophotographic photosensitive member 1 (photosensitive member 1) which is an embodiment of the electrophotographic photosensitive member of the present invention. 2A and 2B are diagrams for explaining the electrophotographic photosensitive member shown in FIG. 1, in which FIG. 2A is a schematic sectional view, and FIG. 2B is a diagram showing a refractive index distribution in the vicinity of the surface layer.

  The photoreceptor 1 includes a conductive substrate 10, a photoconductive layer 14 mainly formed of an organic compound formed on the conductive substrate 10, and an organic compound formed on the photoconductive layer 14 as a main component. The intermediate layer 16 and the surface layer 18 mainly composed of an organic compound formed on the intermediate layer 16 are provided.

As the organic compound constituting the photoconductive layer, known compounds conventionally used for photoreceptors can be used. For example, organic pigments and dyes such as phthalocyanine-based, squarylium-based, anthanthrone-based, perylene-based, azo-based, anthraquinone-based, pyrene-based, pyrylium salt, and thiapyrylium salt 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 materials described above, phthalocyanine compounds have excellent photosensitivity in the range of 600 to 850 nm of the emission wavelength of LEDs and laser diodes currently used as light sources for digital electrophotographic devices. Preferred as a material for the photoconductive layer of the present invention.

  The photoconductive layer of the present invention can be produced by vacuum-depositing the above-described charge generation material or by dispersing or dissolving the charge generation material in a binder resin. As the binder resin used for the charge generation layer, 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, vinyl chloride-acetic acid Examples include, but are not limited to, vinyl copolymers, silicone resins, phenol resins, poly-N-vinyl carbazole resins, and the like.

  These binder resins may be block copolymers, random copolymers or alternating copolymers, and can be used alone or in combination of two or more.

As the organic compound constituting the intermediate layer, known compounds that are both used as the charge transport layer in the conventional laminated photoreceptor can be used. For example, hole transporting low molecular compounds such as benzidine compounds, amine compounds, hydrazone compounds, stilbene compounds, carbazole compounds, or low electron transport properties such as fluorenone compounds, malononitrile compounds, diphenoxyquinone compounds, etc. A solid solution film in which molecular compounds are singly or mixed in two or more and dispersed uniformly in an insulating resin such as polycarbonate, polyarylate, polyester, polysulfone, polymethyl methacrylate, etc. Or a polymer compound having
The first charge transport layer of the present invention may contain insulating fine particles.

  As the insulating fine particles, silicone resin, acrylic resin, polyvinylidene fluoride resin, polyvinylidene chloride resin, insulating resin powder or beads such as Teflon (registered trademark) resin, and alumina, silica, titanium oxide, oxidation Inorganic fine particles or white pigments such as zinc, magnesium oxide, magnesium carbonate, zirconium oxide, lead titanate, barium sulfate, calcium carbonate, cadmium red, cadmium yellow, iron oxide, vermilion, red, yellow pigment, etc. However, it is not limited to these.

  Moreover, these charge transport materials can be used alone or in admixture of two or more. White, red, or yellow pigments are preferable because they do not substantially absorb light having a wavelength of 700 nm or more, which is the transmission wavelength of the laser diode.

  When the charge transporting fine particles and the insulating fine particles are used to roughen the first charge transporting layer, 1% by volume or more of the charge transporting fine particles and the insulating fine particles having a particle diameter of 0.5 μm or more are used. It is preferable to contain.

  In the intermediate layer 16, inorganic fine particles having a large refractive index, insulating particles such as white, red or yellow pigments, or charge transporting particles are dispersed and contained.

  In the electrophotographic photoreceptor 1, the refractive index n1 of the surface layer 18 is about 2.0, for example, and the refractive index n2 of the photoconductive layer 14 is about 4.2, for example. Compared to the refractive index, the refractive index of the surface layer 18 is made small. In the electrophotographic photosensitive member, the film thickness of the surface layer 18 is about 600 nm, for example, and the film thickness of the photoconductive layer 14 is about 20000 nm, for example.

  In the electrophotographic photoreceptor 1 of the present embodiment, the intermediate layer 16 has a first region E1 having a refractive index larger than that of the surface layer 18, and a first region E1 positioned on the photoconductive layer 14 side with respect to the first region E1. A second region E2 having a refractive index smaller than that of the first region E1.

In the present embodiment, the intermediate layer 16, a first partial intermediate layer 16e1 and 16 _e2 each having substantially constant refractive index, is formed by laminating. In the electrophotographic photoreceptor 1, the refractive index n _{e1 of} the first partial intermediate layer 16 _{e 1} is about 4.0, for example, and the refractive index n _{e2 of} the second partial intermediate layer 16 _{e 2} is about 2.0, for example. Further, the intermediate layer 16 is configured to be relatively thin with a film thickness of the first partial intermediate layer 16e1 of 14 nm, a film thickness of the second partial intermediate layer 16e2 of 27 nm, and the entire intermediate layer 16, for example, a film thickness of about 41 nm. ing.

  In the photoreceptor 1, the relatively thin intermediate layer 16 can relatively reduce the in-plane distribution of the image density in the image formed by the image forming apparatus. Further, even when a large number of images are output continuously by the image forming apparatus, the density variation of the formed image is small. Further, even when the sensitivity to incident light is relatively high and an image is formed at a relatively high speed, a high-definition image can be formed.

  Specifically, in the photosensitive member 1, the photoconductive layer 14 and the intermediate layer 16 (the first partial intermediate layer 16 e 1 and the second partial intermediate layer 16 e 2) each have a virtual refractive index Ng that is equal to the refractive index of the surface layer 18. The film thickness and the refractive index of each layer are set so as to substantially coincide with the size n1.

Here, the virtual refractive index Ng is a value representing the magnitude of the total refractive index when a plurality of stacked layers are regarded as one layer. The virtual refractive index will be described with reference to FIG. Consider a model in which light having a wavelength λ is incident from the surface of the Lb layer in the two-layer structure L (α) in which the Lb layer is stacked on the surface of the La layer shown in FIG. The virtual refractive index Ng _(α) = _{ng (α)} −ik _{g (α)} of this L (α) consisting of two layers is La complex refractive index Na = na−ica, Lb complex refractive index Nb When == nb−ikb, it is known that it is expressed by the following formula (1).

In addition, when the third layer Lc is laminated on the L (α) shown in FIG. 3B, the virtual refractive index N _{g (β} of the laminated body L (β) of L (α) and Lc is obtained. ₎ = Ng _(β) −ik _{g (β)} is obtained by replacing the refractive index Na of La in the above formula (1) with N _{g (α),} and changing the refractive index Nb of Lb in the above formula (1) to Lc It can be calculated by using the following formula (2) replaced by the complex refractive index Nc == nc−ikc.

As shown in FIG. 3C, a structure L (γ) in which a layer Ld having the same refractive index _{Ng (β)} as that of the laminate L (β) is laminated on the surface layer of the laminate L (β) is considered. In this case, the difference in refractive index between the laminate L (β) and the layer Ld disappears. In this model, there is no difference in refractive index at the interface between the laminate L (β) and the layer Ld (the interface between the layers Lc and Ld), and this interface when the wavelength λ is incident from the surface of the layer Ld. Thus, no reflection or refraction occurs due to the difference in refractive index.

  For example, in the photoreceptor 1, when the layer Ld is regarded as the surface layer 18, the layer Lc as the first partial intermediate layer 16e1, the layer Lb as the second partial intermediate layer 16e2, and the layer La as the photoconductive layer 14, the latent image is formed. Of the first partial intermediate layer 16e1, the second partial intermediate layer 16e2 and the photoconductive layer 14 at the interface between the surface layer 18 and the layered body L (β). The refractive indexes of the first partial intermediate layer 16e1 and the second partial intermediate layer 16e2 are adjusted so as to eliminate the difference in rate.

  In the photoreceptor 1, as described above, the intermediate layer 16 has a higher refractive index than the surface layer 18 while satisfying the virtual refractive index condition as described above, and the first region E 1. And a second region E2 having a refractive index smaller than that of the first region E1, which is located on the photoconductive layer 14 side.

  The action brought about by the configuration of the intermediate layer 16 in the photoreceptor 1 can be considered as follows. FIG. 4 is a diagram schematically showing a path of exposure light in the photoreceptor 1. In the image forming process, exposure light enters the photoreceptor 1 from the surface layer of the surface layer 18. Although this exposure light does not reflect as it is, there is also a component that passes through the intermediate layer 16 and reaches the photoconductive layer 14, but a part of the exposure light is reflected by the surface of the surface layer 18 and reflected light component R1. Become. Similarly, part of the exposure light is reflected at the interface between the surface layer 18 and the intermediate layer 16 to become a reflected light component R2. If the phases of the reflected light components R1 and R2 are shifted by λ / 2 (λ is the wavelength of the exposure light), the reflected light R1 and R2 cancel each other, and the reflected light becomes very small (theoretically). Reflection is zero). For example, in the initial state of use, the refractive index of the surface layer 18 and the first partial intermediate layer 16e1 and the film thickness of the surface layer 18 are set so that the path difference between R1 and R2 is λ / 2. ing.

  For example, when the image forming process is repeated, the surface layer 18 is worn and the film thickness of the surface layer 18 changes. In this case, the phase difference between R1 and R2 deviates from the set amount (that is, λ / 2), and the effect of reducing the reflected light component due to interference between R1 and R2 is reduced. Even when the film thickness of the surface layer 18 is distributed in the initial state, the distribution is generated on the surface of the photoconductor to the extent of interference of the reflected light.

  In the photoreceptor 1, the intermediate layer 16 is positioned on the photoconductive layer 14 side of the first region E1 (first partial intermediate layer 16e1) having a refractive index higher than that of the surface layer 18, and the first region E1. And a second region E2 (second partial intermediate layer 16e2) having a refractive index smaller than that of the first region E1.

For this reason, some of the components of the exposure light that have not been reduced by the interference between R1 and R2 are the first
Reflected at the interface between the partial intermediate layer 16e1 and the second partial intermediate layer 16e2 becomes reflected light R3, and reflected at the interface between the second partial intermediate layer 16e2 and the photoconductive layer 14 to become reflected light R4. Furthermore, each reflected light further repeats reflection at the interface of each layer (R2 ′, R3 ′, R4 ′, etc. in the figure). In the photoconductor 1, in addition to the interference between R1 and R3, the interference between R2 and R3, the interference between R3 and R4, and the interference of a plurality of re-reflected lights, and the interference corresponding to the number of combinations of a plurality of reflected lights. Occurs.

  In the photoreceptor 1, the intermediate layer 16 is positioned on the photoconductive layer 14 side of the first region E1 (first partial intermediate layer 16e1) having a refractive index higher than that of the surface layer 18, and the first region E1. And a second region E2 (second partial intermediate layer 16e2) having a refractive index smaller than that of the first region E1, and a configuration in which a plurality of reflections such as reflected light R3 and R4 and re-reflected light are likely to occur. . Further, since the refractive index of the first partial intermediate layer 16e1 is relatively large, the effective optical path length in the first partial intermediate layer 16e1 is relatively long, and even when the film thickness of the intermediate layer 16 is relatively thin. The path difference between the reflected lights traveling in the intermediate layer 16 is increased to such an extent that it contributes to the interference.

  In the photoconductor 1, the degree of interference between the reflected lights traveling inside the intermediate layer 16 other than the interference between R1 and R2 is relatively large. For example, the film thickness of the surface layer 18 varies (decreases). Even in this case, the reflected light component emitted from the surface layer 18 can be sufficiently reduced by the interference of each reflected light in the intermediate layer 16. Further, the intermediate layer 16 is configured to be relatively thin, and light loss in the intermediate layer 16 can also be suppressed. In the photoreceptor 1, the ratio of the light component (exposure energy) incident on the photoconductive layer 14 can be kept relatively high.

  Hereinafter, the configuration of the photoreceptor 1 shown in FIGS. 1 to 3 will be described in more detail.

  Although it does not restrict | limit especially as a constituent material of the electroconductive base | substrate 10, Metal materials, such as Al, SUS, Zn, Cu, Fe, Ti, Ni, Cr, Ta, Sn, Au, Ag, and those alloys It is preferable to make it from a material. Moreover, the material which carried out the electroconductive process by vapor-depositing transparent conductive materials, such as the metal mentioned above, ITO, and SnO2, on the surface of electrical insulators, such as resin, glass, and ceramics, can also be used. The use of an Al alloy is preferable in that the cost is reduced, the weight can be reduced, and the adhesion with a photoconductive layer or charge injection blocking layer, which will be described later, is improved and the reliability is improved.

  The charge injection blocking layer 12 is provided between the conductive substrate 10 and the first layer 14. The charge injection blocking layer 12 is not necessarily provided, but is preferably provided to prevent charge injection from the conductive substrate 10. The charge injection blocking layer 12 controls the flow of charges in a predetermined direction, and more precisely controls the lateral flow of electrons in the surface layer 18, whereby the electrophotographic photosensitive member 1 with further excellent resolution can be obtained. . The charge injection blocking layer may be formed using, for example, the material constituting the above-described photoconductive layer.

  The thickness of the charge injection blocking layer is preferably set to a value in the range of 0.5 to 12 μm. When the thickness of the charge injection blocking layer is 0.5 to 12 μm, the charge injection blocking effect on the conductive substrate is relatively high, and the charge injection blocking layer can be formed with a uniform thickness relatively easily. The film thickness of the charge injection blocking layer is more preferably set to a value within the range of 1 to 12 μm, and further preferably set to a value within the range of 2 to 7 μm.

  The film thickness of the photoconductive layer is preferably set to a value in the range of 1 to 100 μm. When the thickness of the photoconductive layer is set to a value within the range of 1 to 100 μm, the photoconductivity can be maintained and the film can be formed to have a relatively uniform thickness. The film thickness of the photoconductive layer is more preferably set to a value within the range of 1 to 100 μm, and further preferably set to a value within the range of 8 to 20 μm.

  The refractive index of the intermediate layer 16 can be adjusted by adjusting the content ratio of the inorganic fine particles. A charge transport layer made of an organic charge transport material and a resin or the like usually has a refractive index of usually about 1.4 to 1.7. The above are preferable, and more preferably 2.3 or more.

  The average particle size of the inorganic fine particle powder is preferably in the range of 0.001 to 2 μm, more preferably 1 μm or less, and still more preferably 0.5 μm or less. Since the refractive index of the layer can be increased even when the particle diameter is small, and the scattering effect by the particles can be ignored, a more uniform image can be obtained. Examples of the inorganic fine particles having a large refractive index include titanium zinc (refractive index 2.7), titanium oxide (refractive index 2.5 to 2.9), zirconium oxide (refractive index 2.4), and iron oxide (refractive index). 2.0), Bengala (refractive index 2.9), selenium (refractive index 2.5), cadmium sulfide (refractive index 2.4-2.7), and the like are used, but not limited thereto.

  The refractive index of each layer in the photosensitive layer may be measured by etching from the surface layer in order and using a known refractive index measuring device from the surface of each layer. Moreover, the sample sample of the bulk state taken out from each layer can also be measured using a well-known refractive index measuring apparatus. In addition, the photoconductor can be cut, and the refractive index at the measurement portion can be identified from component analysis of each section of this cross section using, for example, XPS.

  The thickness of the intermediate layer is preferably as small as possible from the viewpoint of reducing exposure light loss in the intermediate layer, and is preferably set to, for example, 100 nm or less, and more preferably 65 nm or less.

  The surface layer 18 preferably has a film thickness of 100 nm or more and less than 1.0 μm. By setting the film thickness of the surface layer 18 to 100 nm or more and less than 1.0 μm, it is possible to suppress a decrease in sensitivity and the occurrence of a residual potential, and to maintain a high print quality such as a decrease in density and fog. Even when the photoconductor is used for a long time, it is preferable that the film thickness of the surface layer is less than 1.0 μm in order to maintain a predetermined image quality.

  The surface layer 18 can be formed using various materials such as amorphous silicon carbide (a-SiC) in addition to the same organic compound as the intermediate layer. For example, as an a-Si-based material, amorphous silicon nitride (a-SiN), amorphous silicon oxide (a-SiO), amorphous silicon oxycarbide (a-SiCO), amorphous silicon oxynitride (a-SiNO), etc. A high resistance material may be used.

  These are formed by a thin film forming means similar to that of a-Si. In forming the film, hydrogen or halogen (F, Cl) is used in the film for dangling bond termination or for adjusting hardness or resistance value. It is good to contain -160 atomic%.

  FIGS. 5A and 5B are diagrams for explaining a photoreceptor 1 ′, which is another embodiment of the photoreceptor of the present invention. FIG. 5A is a schematic cross-sectional view, and FIG. It is a figure which shows distribution. In FIG. 5A, the same components as those in FIG. 2 are denoted by the same reference numerals as those in FIG.

In the embodiment shown in FIG. 5, as in the embodiment shown in FIG. 2, the intermediate layer 16 has a first region E1 having a higher refractive index than the surface layer 18, and the photoconductive layer 14 has a higher refractive index than the first region E1. And a second region E2 having a refractive index smaller than that of the first region E1. In the embodiment shown in FIG. 5, in the first region E1, the refractive index of the intermediate layer 16 gradually increases as it approaches the photoconductive layer 14 from the surface layer 18. On the other hand, in the second region, the refractive index of the intermediate layer 16 gradually decreases as the surface layer 18 approaches the photoconductive layer 14.

  Also in the embodiment shown in FIG. 5, the path of the reflected light in the intermediate layer 16 can be made relatively long, and the degree of interference of the reflected light can be made relatively large. Also in the embodiment shown in FIG. 5, for example, even when the film thickness of the surface layer 18 fluctuates (decreases), the reflected light component emitted from the surface layer 18 due to the interference of each reflected light in the intermediate layer 16 is reduced. It can be sufficiently reduced. Further, the intermediate layer 16 is configured to be relatively thin, and light loss in the intermediate layer 16 can also be suppressed. In the photoreceptor 1 ′ shown in FIG. 5, the ratio of the light component (exposure energy) incident on the photoconductive layer 14 can be kept relatively high.

  The photoconductor 1 ′ shown in FIG. 5 can also be configured with the same configuration as the photoconductor 1 shown in FIGS. In the intermediate layer 16 of the photoreceptor 1 ′ shown in FIG. 5, a refractive index distribution can be generated by distributing the mixing ratio of the inorganic fine particles in the layer.

  6 and 7 are a schematic diagram of the image forming apparatus 100 configured to include the photoconductor 1 and a partially enlarged view of the developing device 120 including the electrophotographic photoconductor 121. FIG. 8 is a diagram for explaining an LED head as a light source.

  First, as shown in FIGS. 6 and 7, the image forming apparatus 100 includes a developing device 120, an electrophotographic photosensitive member 121, a developing roller 122, a transfer roller 123, cleaners 125 and 126, a charger 127, a developing device 128, and a light source. (LED) 130, transfer material conveying means 112, and fixing means 113 are basically provided.

  As shown in FIG. 6, the LED head as the light source 130 includes a rod lens array 131, an LED array 132, a driver IC 133, a circuit board 134, and the like. The wavelength of the exposure light emitted from the light source 130 is not particularly limited, and for example, exposure light having a peak wavelength of 685 nm may be used. The wavelength of the exposure light is not particularly limited, and the layer configuration and refractive index of the intermediate layer may be appropriately adjusted according to the peak wavelength of the exposure light.

  The image forming apparatus 100 includes developing devices 120a, 120b, 120c, and 120d that correspond to four colors, and is an example of a tandem color printer.

  The basic operation of the image forming apparatus 100 (tandem color printer), that is, the image forming method will be specifically described. First, the electrophotographic photosensitive member 121 shown in FIGS. 6 and 7 is rotated in the direction of the arrow, and a uniform corona charging is performed on the surface of the electrophotographic photosensitive member 121 by the main charger 127. The irradiated light is irradiated to a document (not shown).

Next, as shown in FIG. 6, the reflected light is guided onto the surface of the electrophotographic photosensitive member 121 through a mirror system, a lens system, a filter, and the like, and is projected to form an electrostatic latent image.
Therefore, the toner image can be formed by supplying the toner 125 from the toner container 111 in the developing device 120 to the electrostatic latent image.

  On the other hand, the transfer material such as paper or plastic supplied to the electrophotographic photosensitive member 121 through the transfer material conveying means 112 including the transfer material passage and the registration roller is a transfer roller 123 having a transfer / separation charger, In the gap between the electrophotographic photosensitive members 121, an electric field having a polarity opposite to that of the toner is applied from the back surface. As a result, the toner image on the surface of the electrophotographic photosensitive member 121 is transferred to the transfer material and the electrophotographic photosensitive member 121 side. Separated from.

  Next, the separated transfer material reaches the fixing device 113 to fix the toner image, and the transfer material is discharged out of the device.

  Note that residual toner that does not contribute to the transfer and remains on the surface of the electrophotographic photosensitive member 121 at the transfer portion reaches the cleaners 125 and 126 and is cleaned by a cleaning blade or the like provided therein.

  In this way, the electrophotographic photosensitive member 121 renewed by the above cleaning is subjected to a static elimination exposure from a static elimination light source (not shown) and then subjected to the same cycle again.

  In the image forming apparatus 100, the surface of the electrophotographic photosensitive member 121 slides while a transfer material such as paper or plastic is pressed by the transfer roller 123. Further, a cleaning blade for removing residual toner and the like slides while being pressed against the surface of the electrophotographic photosensitive member 121. In general, the pressing force of the transfer material and the pressing force of the cleaning blade are relatively strong in the central portion of the surface of the electrophotographic photosensitive member 121 along the axial direction of the electrophotographic photosensitive member 121. In the electrophotographic photosensitive member 121, as shown in the cross-sectional view shown in FIG. 9, the film thickness of the surface layer 18 is distributed so as to be thickest in the central portion along the axial direction of the electrophotographic photosensitive member 121. In the image forming apparatus 100, since the surface layer 18 has such a film thickness distribution, even if the film thickness phenomenon in the central portion where the film thickness is most likely to occur is selectively advanced, the surface layer is maintained over a relatively long period. The film thickness of 18 can be kept at a usable size.

  In the electrophotographic photosensitive member 121 of this embodiment, even when the surface layer 18 has a film thickness distribution, the in-plane distribution of the image density in the formed image can be kept relatively small. By providing a distribution in the film thickness of the surface layer 18 of the electrophotographic photosensitive member 121, an image forming apparatus having a relatively high durability and a relatively small image density distribution in the formed image can be obtained.

  As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to the said embodiment, You may change variously in the range of invention.

10 conductive substrate 14 photoconductive layer 16 intermediate layer 18 surface layer 16e1 first partial intermediate layer 16e2 second partial intermediate layer 100 image forming apparatus 112 transfer material conveying means 113 fixing means 120 developing apparatus 121 electrophotographic photosensitive member 122 developing roller 123 Transfer roller 125, 126 Cleaner 127 Charger 128 Developer 130 Light source (LED)
131 Rod lens array 132 LED array 133 Driver IC
134 Circuit board

Claims (8)

A conductive substrate;
A photoconductive layer mainly composed of an organic compound formed on the conductive substrate;
A surface layer formed on the photoconductive layer and having a refractive index smaller than that of the photoconductive layer;
An intermediate layer provided in a gap between the photoconductive layer and the surface layer,
The intermediate layer includes a first region having a refractive index larger than that of the surface layer, a second region having a refractive index smaller than that of the first region, located closer to the photoconductive layer than the first region, An electrophotographic photosensitive member comprising:   2. The electrophotographic photoreceptor according to claim 1, wherein at least a part of the intermediate layer is formed by laminating partial intermediate layers each having a substantially constant refractive index.   3. The electrophotographic photosensitive member according to claim 1, wherein, in the first region, the refractive index of the intermediate layer is gradually increased from the surface layer toward the photoconductive layer. 4.   4. The electrophotographic photosensitive member according to claim 1, wherein in the second region, the refractive index of the intermediate layer gradually decreases from the surface layer toward the photoconductive layer. 5. body.   The electrophotographic photosensitive member according to claim 1, wherein the intermediate layer has a thickness of 65 nm or less.   The electrophotographic photosensitive member according to claim 1, wherein the film thickness of the surface layer varies along a central axis of the electrophotographic photosensitive member.   7. The electrophotographic photosensitive member according to claim 6, wherein the film thickness of the surface layer is the largest at a central portion along the central axis of the electrophotographic photosensitive member. The electrophotographic photosensitive member according to claim 1,
Exposure means for irradiating the electrophotographic photosensitive member with exposure light to form a latent image on the surface of the electrophotographic photosensitive member;
A developer for supplying toner to the electrophotographic photosensitive member and forming a toner image corresponding to the latent image on the electrophotographic photosensitive member;
A transfer portion for transferring the toner image onto a transfer material;
A cleaning blade that contacts the surface of the electrophotographic photosensitive member and removes toner remaining on the surface of the electrophotographic photosensitive member after the transfer;
An image forming apparatus comprising: