JP5595081B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Conventionally, an image forming apparatus using 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 the image forming apparatus having the electrophotographic photosensitive member having such a configuration, the reflected light at the interface between the surface layer and the photoconductive layer interferes with the 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, when the same image is output in large quantities, for example, in units of hundreds of thousands, the surface layer is worn, and the film thickness of the surface layer changes immediately after the start of printing and at the end of printing. Sometimes.

  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 an image forming apparatus intended to reduce the influence of the interference in an electrophotographic photosensitive member. In Patent Document 1, an intermediate layer is provided between the surface layer and the photoconductive layer, and a photoconductor in which the refractive index of the intermediate layer is gradually increased from the surface layer toward the photoconductive layer is accurately described. The point which produces and comprises an image forming apparatus using this is disclosed.

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 image forming apparatus 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 of the photoreceptor is sufficiently suppressed to a level that meets the recent demand for higher image quality. May not be possible.

  Further, in the configuration described in Patent Document 1, the thickness of the intermediate layer of the photoconductor 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, 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 the electrophotographic photosensitive member An image forming apparatus comprising: a developing unit that supplies toner and forms a toner image corresponding to the latent image on the electrophotographic photosensitive member; and a transfer unit that transfers the toner image onto a transfer material. The photographic photoreceptor includes a conductive substrate, a photoconductive layer 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, and the light An intermediate layer provided in a gap between the conductive layer and the surface layer, and a virtual refractive index of a laminate composed of the photoconductive layer and the intermediate layer with respect to a peak wavelength of the exposure light, The refractive index of the surface layer substantially matches the peak wavelength of the exposure light. To provide an image forming apparatus according to claim and.

1 is a diagram illustrating a configuration of an electrophotographic photoreceptor provided in an embodiment of an image forming apparatus of the present invention. 2A and 2B are diagrams for explaining the electrophotographic photosensitive member shown in FIG. 1, wherein FIG. 2A is a schematic sectional view, and FIG. 2B is a diagram showing a refractive index distribution in the vicinity of a surface layer. 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. It is a graph which shows the change of the value of a refractive index with respect to C atom concentration (atom number ratio) in a layer about an amorphous silicon layer containing a carbon atom (C). 2A and 2B are diagrams illustrating another embodiment of an electrophotographic photosensitive member that can be used in the image forming apparatus of the present invention, where FIG. 1A is a schematic cross-sectional view, and FIG. 2B is a refractive index distribution in the vicinity of a surface layer. FIG. 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 photoreceptor shown in FIG. It is sectional drawing explaining the LED head mounted in the image forming apparatus shown in FIG. FIG. 8 is a schematic cross-sectional view of an electrophotographic photosensitive member mounted on the image forming apparatus shown in FIG. 7.

  Hereinafter, an image forming apparatus according to an embodiment 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 used in the image forming apparatus 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 including an amorphous silicon material formed on the conductive substrate 10, and an intermediate layer including an amorphous silicon material formed on the photoconductive layer 14. 16 and a surface layer 18 containing an amorphous silicon-based material formed on the intermediate layer 16.

  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. The term “substantially coincides” means that the difference (Ng−n1) between the virtual refractive index Ng and the refractive index n1 of the surface layer 18 is 10% or less, more preferably 5% or less of the refractive index n1 of the surface layer 18. The range.

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−ika, 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, the surface layer of the laminate L (β) has the same refractive index N _g as the laminate L (β).
_When the structure L (γ) in which the layer Ld having _(β) is stacked is considered, there is no difference in refractive index between the stacked body L (β) and the layer Ld. 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 diminished. 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, a part of the component of the exposure light that has not been reduced by the interference between R1 and R2 is reflected at the interface between the first partial intermediate layer 16e1 and the second partial intermediate layer 16e2, and becomes reflected light R3. Reflected at the interface between the two-part intermediate layer 16e2 and the photoconductive layer 14 becomes 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. .

  As described above, the charge injection blocking layer is formed of an amorphous silicon-based material such as amorphous silicon (a-Si) (hereinafter sometimes referred to as an a-Si-based material). It is preferable to use an amorphous silicon material of an alloy to which N, O, or the like is added.

  Use of amorphous silicon materials of alloys with addition of C, N, O, etc. provides stable electrophotographic characteristics such as high photoconductivity, high-speed response, repeat stability, heat resistance, and durability. In addition, it is excellent in consistency with the surface layer formed of the amorphous silicon-based material.

  Here, as an a-Si material of an alloy obtained by adding C, N, O, etc. to a-Si, a-SiC, a-SiN, a-SiO, a-SiGe, a-SiCN, a-SiNO , A-SiCO and a-SiCNO.

  The charge injection blocking layer made of these a-Si materials is formed by, for example, a glow discharge decomposition method, various sputtering methods, various vapor deposition methods, ECR method, photo CVD method, catalytic CVD method, and reactive vapor deposition method. In forming the film, hydrogen (H) or halogen element (F or Cl) is added in the range of 1 to 40 atomic% when the entire film is 100 atomic% for dangling bond termination. Can be formed.

  Further, in forming the charge injection blocking layer, in order to obtain desired characteristics of the electrical characteristics such as dark conductivity and photoconductivity and optical band gap of each layer, elements in the periodic table group 13 (hereinafter referred to as “elements”) , "Group 13 element") or Periodic Table Group 15 element (hereinafter abbreviated as "Group 15 element"), or adjusting the content of elements such as C, N, O, etc. Thus, the above-described characteristics can be adjusted.

  In addition, as a group 13 element and a group 15 element, boron (B) and phosphorus (P) are excellent in terms of being excellent in covalent bonding and capable of sensitively changing semiconductor characteristics, and in obtaining excellent photosensitivity. It is desirable to use it.

  When the group 13 element and the group 15 element are contained together with elements such as C and O, the content of the group 13 element is 0.1 to 20000 ppm, and the content of the group 15 element is 0.1 to 10,000. Preference is given to ppm.

  When elements such as C and O are not contained or contained in a small amount, the content of the group 13 element is 0.01 to 200 ppm, and the content of the group 15 element is 0.01 to 100 ppm. Preferably there is.

  Further, these elements may be provided with a gradient in the layer thickness direction, and in this case, the average content of the entire layer may be within the above range.

  For the a-Si-based materials described above, the charge injection blocking layer contains group 13 elements or group 15 elements to adjust conductivity, or contains more C, N, and O than the photoconductive layer. To increase the resistance.

  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 photoconductive layer (first layer) 14 is mainly composed of an amorphous silicon-based material containing at least Si, and is made of a photoconductive material. Therefore, it is preferable to contain at least one element selected from the group consisting of, for example, a hydrogen atom and a halogen atom in addition to the amorphous silicon-based material. That is, by adding such atoms, the charge mobility in the photoconductive layer can be accurately controlled within a predetermined range.

  Further, as in the case of the charge injection blocking layer described above, an a-Si based material of an alloy obtained by adding C, N, O or the like to a-Si is used as necessary, or a group 13 element or a group 15 element is contained. Electrical characteristics such as conductivity and photoconductivity, optical band gap, and the like can also be adjusted.

  Further, for the photoconductive layer, microcrystalline silicon (μc-Si) may be included in the a-Si-based material, and when this μc-Si is included, dark conductivity and photoconductivity are increased. Therefore, there is an advantage that the degree of freedom in designing the photoconductive layer is increased. Such μc-Si can be formed by adopting the film formation method described above and changing the film formation conditions.

  For example, in the glow discharge decomposition method, it can be formed by setting the temperature and high-frequency power of the conductive substrate to be higher and increasing the flow rate of hydrogen as a dilution gas. Further, an impurity element similar to that described above may be added to the photoconductive layer containing μc-Si.

  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 intermediate layer 16 preferably includes a-SiC: H containing an amorphous silicon-based material, carbon atoms, and hydrogen atoms. By using such an intermediate layer, it is possible to obtain an a-Si photosensitive member that has excellent resolution and a low image flow even when a heaterless system is adopted due to a synergistic effect with the surface layer described later. This is because it can.

  The refractive index of the intermediate layer 16 varies depending on, for example, the content of silicon atoms, the content of carbon atoms, the film formation state (bonding state of each atom in the intermediate layer, etc.), and the like. For example, by adjusting the mixing ratio of the silicon atom supply gas and the carbon atom supply gas, the reaction vessel (the gas pressure in the film formation chamber, the discharge power, the temperature of the substrate, etc. during the formation of the intermediate layer, The refractive index distribution in the intermediate layer 16 can be controlled.

  For example, FIG. 5 is a graph plotting changes in the value of the refractive index with respect to the C atom concentration (atomic ratio) in the carbon atom (C) -containing amorphous silicon layer. The graph shown in FIG. 5 shows an amorphous silicon layer manufactured by a CVD method. In such an amorphous silicon layer, the refractive index decreases as the C atom concentration in the layer increases. When the surface layer and the intermediate layer are formed under these conditions, the C atom concentration of the surface layer 18 is smaller than that of the first partial intermediate layer 16e1, and the second partial intermediate layer 16e2 is compared with the first partial intermediate layer 16e1. The C atom concentration of is higher.

  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. Alternatively, the photoconductor can be cut, the cross section can be subjected to component analysis for each layer using, for example, XPS, and the analysis result can be identified based on a known relationship as shown in FIG.

  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.

  Various materials can be used for the intermediate layer in addition to amorphous silicon carbide (a-SiC). 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. Even when a-SiN film, a-SiO film, a-SiCo film, a-SiNO film or the like is used, by adjusting the composition ratio of materials in each layer, the size and distribution of refractive index in the intermediate layer Can be controlled. The distribution of the composition ratio and the like can be controlled relatively easily by adjusting the raw material ratio (gas pressure ratio, etc.) at the time of forming each layer.

  These are formed by the same thin film forming means as a-Si. In forming the film, hydrogen or halogen (F, Cl) is used in the film for dangling bond termination or for adjusting the hardness or resistance value. It is preferable to contain 1 to 160 atomic% with respect to the total number of silicon atoms and carbon atoms.

  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 reduction in sensitivity and generation of a residual potential, and to maintain a high print quality such as density reduction and fogging. 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.

  Similar to the intermediate layer, the surface layer 18 can be formed using various materials other than amorphous silicon carbide (a-SiC). 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%.

The reason for this is that by including such other elements in the surface layer, the surface hardness (kgf / mm 2) or mobility value in the surface layer may be more easily controlled.

  FIGS. 6A and 6B are diagrams for explaining a photoconductor 1 ′ which is another embodiment of the photoconductor used in the image forming apparatus of the present invention. FIG. 6A is a schematic sectional view, and FIG. 6B is a surface layer. It is a figure which shows distribution of the refractive index in the vicinity. In FIG. 6A, 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. 6, 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. 6, the refractive index of the intermediate layer 16 gradually increases from the surface layer 18 toward the photoconductive layer 14 in the first region E1. 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. 6, 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. In the embodiment shown in FIG. 6 as well, 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 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. 6, it is possible to maintain a relatively high ratio of light components (exposure energy) incident on the photoconductive layer 14.

  The photoconductor 1 ′ shown in FIG. 6 can also be configured with the same configuration as the photoconductor 1 shown in FIGS. Also in the intermediate layer 16 of the photoreceptor 1 ′ shown in FIG. 6, the gas flow rate conditions at the time of film formation are changed in time series, or the applied voltage at the time of film formation is changed in time series. What is necessary is just to form a desired refractive index distribution by changing the time condition. The electrophotographic photoreceptor 1 and the photoreceptor 1 ′ described above are an example, but can be manufactured by appropriately setting numerical conditions of film forming parameters so as to obtain desired characteristics by a vacuum deposition film forming method. .

As such a vacuum deposited film forming method, specifically, an AC discharge plasma CVD method such as a glow discharge method (low frequency plasma CVD), a high frequency plasma CVD method, or a microwave plasma CVD method is employed. DC discharge plasma CVD method, DC pulse plasma CVD
A method, an ECR plasma CVD method, a sputtering method, a vacuum deposition method, an ion plating method, a photo CVD method, a catalytic CVD (HOT wire CVD) method, or the like may be used.

  When the vacuum deposited film forming method is carried out, it is generated from an active species (A) generated by decomposing the source gas and a film-forming chemical substance that chemically interacts with the active species (A). A method (hereinafter abbreviated as “HRCVD method”) is employed in which the active species (B) are separately introduced into a film forming space for forming a deposited film and chemically reacted with each other. May be. Alternatively, the source gas and a halogen-based oxidizing gas (for example, F 2, Cl 2, etc.) having a property of oxidizing the source gas are separately introduced into the film forming section, and these are chemically reacted to separately deposit films. A method of forming (hereinafter abbreviated as “FOCVD method”) is also selected as appropriate.

  These vacuum deposited film forming methods are appropriately selected and employed depending on factors such as manufacturing conditions, manufacturing scale, and desired characteristics of the first layer (photoconductive layer). However, the glow discharge method, the sputtering method, the ion plating method, the HRCVD method, and the FOCVD method are preferable because the manufacturing conditions can be controlled relatively easily.

  7 and 8 are a schematic view 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. 9 is a diagram for explaining an LED head as a light source.

  First, as shown in FIGS. 7 and 8, 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. 7, 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. 7 and 8 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. 7, the reflected light is guided onto the surface of the electrophotographic photosensitive member 121 via 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.
While being transferred to the transfer material, it is separated from the electrophotographic photosensitive member 121 side.

  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. 10, 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.

Experimental example

  Examples of experiments performed using the image forming apparatus of the present invention will be described below.

  As the conductive substrate, an outer peripheral surface made of an aluminum alloy having an outer diameter of 84 mm, a length of 360 mm, and a thickness of 2.0 mm was mirror-finished and cleaned.

  This was set in a glow discharge decomposition apparatus, a rectangular wave pulse voltage of 33 KHz was applied to the substrate, and a charge injection blocking layer, a photoconductive layer, an intermediate layer, and a surface layer were sequentially laminated according to the film forming conditions shown in Table 1 below. A plurality of samples (Experimental Examples 1 and 2 and Comparative Examples 1 to 4) were prepared. Each sample has a different layer structure of the intermediate layer. The composition of the intermediate layer of each sample and the film formation conditions are as shown in Tables 2 and 3 below. Comparative Example 1 is a sample in which no intermediate layer is formed. In each sample, the refractive index of the photoconductive layer was 4.2 and the film thickness was 20 μm, the refractive index of the surface layer was 2, and the film thickness was 0.6 μm.

  Experimental example 1 is a sample corresponding to the embodiment shown in FIG. 2, and experimental example 2 corresponds to the embodiment shown in FIG.

〔Evaluation test〕
A sample of the produced photoreceptor was incorporated into an electrophotographic photoreceptor having the configuration shown in FIG. 8, and the following evaluation test was performed. The peak wavelength of the exposure light was 685 nm.

  In the initial state, the reflectance, the absorptance, and the intermediate sensitivity were measured. Moreover, the sensitivity fluctuation | variation in the process in which the surface layer was etched away from the initial state was measured.

The intermediate sensitivity is an initial value (the thickness shown in Tables 2 and 3). The photosensitive member is charged to 600 V with a charger and then irradiated with light having a wavelength of 685 nm. The exposure amount (μJ / cm ² ) (half exposure amount) that becomes / 2 (= 300 V).

  The sensitivity fluctuation means the magnitude of the difference between the maximum value and the minimum value of the measured value of the intermediate sensitivity when the intermediate sensitivity is measured every time the surface layer is etched every 200 nm. When the surface layer is etched away, the influence of the absorption of the surface layer is reduced, and the intermediate sensitivity is reduced. However, this rate of change is not simply proportional to the etching time (= surface layer film thickness), and the intermediate sensitivity increases or decreases with a certain film thickness cycle. It can be said that the magnitude of the sensitivity fluctuation indicates the degree of contribution of the surface layer thickness to the sensitivity of the photoreceptor. That is, it can be said that the sensitivity distribution with respect to the film thickness distribution of the surface layer is small in the sample with small sensitivity fluctuation, and the sensitivity distribution with respect to the film thickness distribution of the surface layer is large in the sample with large sensitivity fluctuation.

  Etching was used as an alternative to wear reduction evaluation by placing a photoconductor in the vacuum layer and etching with Ar plasma. The gas pressure was 60 Pa, and pulse discharge with a voltage of −500 V was applied. The etching amount was adjusted by the etching time.

  The evaluation results are shown in Table 4 below.

  As can be seen from Table 4.

  In Experimental Examples 1 and 2, the reflectance is suppressed to be relatively low, and the absorption rate in the intermediate layer + surface layer is suppressed to be low. On the other hand, in Comparative Examples 1 to 4, even when the absorption in the intermediate layer + surface layer is kept low, the reflectance is high overall, and the energy of the exposure light reaching the photoconductive layer is small. Yes.

  In Experimental Examples 1 and 2, the intermediate sensitivity is relatively small, and the amount of light incident on the photoconductive layer is relatively large. In addition, the sensitivity fluctuation is relatively small, and the influence of interference in the surface layer portion on the film thickness fluctuation of the surface layer is also small.

  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 (7)

An electrophotographic photoreceptor;
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;
An image forming apparatus comprising: a transfer unit that transfers the toner image to a transfer material;
The electrophotographic photoreceptor is
A conductive substrate;
A photoconductive layer 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 virtual refractive index of the laminate composed of the photoconductive layer and the intermediate layer with respect to the peak wavelength of the exposure light substantially matches the refractive index of the surface layer with respect to the peak wavelength of the exposure light ,
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 image forming apparatus comprising: a. At least a portion, claim 1 Symbol placing the image forming apparatus, characterized in that partial intermediate layer each having a substantially constant refractive index is formed by laminating the intermediate layer. 3. The image forming apparatus according to claim 1, wherein in the first region, the refractive index of the intermediate layer gradually increases as the surface layer approaches the photoconductive layer. In the second region, toward the the photoconductive layer from the surface layer, the image forming apparatus according to any one of claims 1 to 3, characterized in that the refractive index of the intermediate layer gradually decreases . The image forming apparatus according to any one of claims 1 to 4, wherein the thickness of the intermediate layer is 65nm or less. The image forming apparatus according to any one of claims 1 to 5, the thickness of the surface layer, characterized in that fluctuates along the central axis of said electrophotographic photosensitive member. 7. The image forming apparatus 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.