Electrophotographic photoreceptor and method for manufacturing the same

Abstract

To reduce unevenness of sensitivity in an electrophotographic photoreceptor.SOLUTION: An electrophotographic photoreceptor comprises: a base body; and a first layer to fifth layer. The first layer is located on the base body, and includes main amorphous silicon and an n-type dopant. The second layer is located on the first layer, and includes the main amorphous silicon. The third layer is located on the second layer, and includes the main amorphous silicon, nitrogen, oxygen, carbon and boron. The fourth layer is located on the third layer layer, and includes an amorphous material containing the silicon and carbon as a main component. The fifth layer is located on the fourth layer, and includes an amorphous material containing an amorphous carbon, or the carbon and silicon as a main component. The third layer includes a first area in contact with the second layer, and a second area in contact with the fourth layer. The first area has a tendency in which, as separating from the second layer, a content rate of the silicon reduces, and each content rate of the boron, nitrogen and oxygen increases. The second area has a tendency in which, as getting closer to the fourth layer, each content rate of the boron, nitrogen and oxygen reduces, and the content rate of the carbon increases.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic photoreceptor and a method for manufacturing an electrophotographic photoreceptor. [Background technology]

[0002] There is an electrophotographic image forming apparatus equipped with an electrophotographic photosensitive member (see, for example, the description in Patent Document 1). The electrophotographic photosensitive member has, for example, a cylindrical substrate having electrical conductivity (also referred to as a conductive support) and a photosensitive layer formed on the outer peripheral surface of this substrate. The photosensitive layer has, for example, a laminated structure that allows the surface of the photosensitive layer to bear a negative charge (also referred to as a negative surface charge). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-62674 Summary of the Invention [Problem to be solved by the invention]

[0004] Regarding electrophotographic photosensitive members, there is room for improvement in terms of reducing unevenness (nonuniformity) in sensitivity. [Means for solving the problem]

[0005] An electrophotographic photoreceptor and a method for manufacturing the electrophotographic photoreceptor are disclosed.

[0006] One embodiment of an electrophotographic photoreceptor comprises a conductive substrate and a first, second, third, fourth, and fifth layers. The first layer is located on the substrate and contains amorphous silicon as a main component and an n-type dopant. The second layer is located on the first layer and contains amorphous silicon as a main component. The third layer is located on the second layer and contains amorphous silicon as a main component and nitrogen, oxygen, carbon, and a p-type dopant, boron. The fourth layer is located on the third layer and contains an amorphous material containing silicon and carbon as a main component. The fifth layer is located on the fourth layer and contains amorphous carbon as a main component or an amorphous material containing carbon and silicon as a main component, and has a surface exposed to the external space. The third layer includes a first region in contact with the second layer and a second region located closer to the fourth layer than the first region and in contact with the fourth layer. The first region has a tendency that the silicon content decreases, the boron, nitrogen, and oxygen contents increase, and the carbon content does not increase with increasing distance from the second layer. The second region has a tendency that the boron, nitrogen, and oxygen contents decrease, and the carbon content increases with increasing distance from the fourth layer. The fourth layer has a tendency that the silicon content decreases and the carbon content increases with increasing distance from the fifth layer.

[0007] One embodiment of a method for manufacturing an electrophotographic photoreceptor includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first layer containing amorphous silicon as a main component and an n-type dopant is formed on a conductive substrate in a reaction chamber. In the second step, a second layer containing amorphous silicon as a main component is formed on the first layer in the reaction chamber. In the third step, a third layer containing amorphous silicon as a main component and nitrogen, oxygen, carbon, and a p-type dopant, boron, is formed on the second layer in the reaction chamber. In the fourth step, a fourth layer containing an amorphous material containing silicon and carbon as a main component is formed on the third layer in the reaction chamber. In the fifth step, a fifth layer containing amorphous carbon as a main component or an amorphous material containing carbon and silicon as a main component is formed on the fourth layer in the reaction chamber. The second, third, fourth, and fifth steps are sequentially performed in the reaction chamber using plasma enhanced chemical vapor deposition. In the second step, a silicon-based gas is introduced into the reaction chamber. The third step includes a third step (3A) and a third step (3B) performed after the third step (3A). In the third step (3A), the amount of the silicon-based gas introduced into the reaction chamber per unit time is decreased while the amount of each of the diborane gas and the nitrogen oxide gas introduced into the reaction chamber per unit time is increased. In the third step (3B), the amount of the carbon-based gas introduced into the reaction chamber per unit time is increased while the amount of the silicon-based gas introduced into the reaction chamber per unit time is decreased. In the fourth step (4), the amount of the silicon-based gas introduced into the reaction chamber per unit time is increased while the amount of the carbon-based gas introduced into the reaction chamber per unit time is decreased. In the fifth step, the carbon-based gas is introduced into the reaction chamber, or the silicon-based gas is introduced into the reaction chamber while the carbon-based gas is being introduced into the reaction chamber. [Effects of the Invention]

[0008] It is possible to reduce unevenness in sensitivity in the electrophotographic photosensitive member. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of an electrophotographic photosensitive member according to the first embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a portion II in FIG. 1, showing a schematic example of the configuration. [Figure 3] FIG. 3 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements in the photosensitive layer according to the first example of the first embodiment. [Figure 4] FIG. 4 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index of the photosensitive layer according to the first example of the first embodiment. [Figure 5] FIG. 5 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements in the photosensitive layer according to the second example of the first embodiment. [Figure 6] FIG. 6 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index of a photosensitive layer according to a second example of the first embodiment. [Figure 7] FIG. 7 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements in the photosensitive layer according to the first reference example. [Figure 8] FIG. 8 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index of the photosensitive layer according to the first reference example. [Figure 9] FIG. 9 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements in the photosensitive layer according to the second reference example. [Figure 10] FIG. 10 is a diagram schematically showing the relationship between the refractive index and the distance from the outermost surface in the thickness direction of the photosensitive layer according to the second reference example. [Figure 11] FIG. 11 is a cross-sectional view schematically showing the configuration of the photosensitive layer according to the first and second reference examples. [Figure 12]FIG. 12 is a cross-sectional view schematically showing an example of the configuration of a film forming apparatus for forming a photosensitive layer of an electrophotographic photosensitive member. [Figure 13] FIG. 13 is a diagram schematically illustrating an example of a change over time in the amount of each raw material gas introduced into the reaction chamber per unit time when forming a photosensitive layer according to the first example of the first embodiment. [Figure 14] FIG. 14 is a diagram schematically illustrating an example of the change over time in the amount of each raw material gas introduced into the reaction chamber per unit time when forming a photosensitive layer according to the second example of the first embodiment. [Figure 15] FIG. 15 is a diagram showing an example of a change over time in the amount of each raw material gas introduced into the reaction chamber per unit time when forming the photosensitive layer according to the first reference example. [Figure 16] FIG. 16 is a diagram showing an example of a change over time in the amount of each raw material gas introduced into the reaction chamber per unit time when forming a photosensitive layer according to the second reference example. [Figure 17] FIG. 17 is a cross-sectional view schematically illustrating an example of the configuration of an image forming apparatus including the photosensitive layer according to the first embodiment. [Figure 18] FIG. 18 is a diagram showing the relationship between the time taken for sputtering from the outermost surface in the thickness direction and the ratio of the four elements silicon, nitrogen, oxygen, and carbon, as a result of ESCA analysis of the photosensitive layer of Example 1. [Figure 19] FIG. 19 is a diagram showing the relationship between the time taken for sputtering from the outermost surface in the thickness direction and the ratio of four elements, silicon, nitrogen, oxygen, and carbon, as a result of ESCA analysis of the photosensitive layer of Reference Example 1. [Figure 20] FIG. 20 is a diagram showing the measurement results of the distribution in the axial direction of the total film thickness of the three layers on the surface side of the electrophotographic photosensitive member of Reference Example 1 before and after etching. [Figure 21] FIG. 21 is a diagram for explaining a method for measuring unevenness in sensitivity in an electrophotographic photosensitive member. [Figure 22]FIG. 22 is a diagram showing the measurement results of the distribution of the surface potential in the axial direction as an index relating to the intermediate sensitivity for each of Example 1 and Reference Example 1 before and after etching. [Figure 23] FIG. 23 is a diagram showing intermediate sensitivity axial unevenness as an index showing unevenness in the intermediate sensitivity in the axial direction for Example 1 before and after etching, and intermediate sensitivity axial unevenness as an index showing unevenness in the intermediate sensitivity in the axial direction for Reference Example 1 before and after etching. [Figure 24] FIG. 24 is a cross-sectional view schematically showing the structure of a photosensitive layer in a negatively charging electrophotographic photosensitive member according to one reference example. DETAILED DESCRIPTION OF THE INVENTION

[0010] 2. Description of the Related Art Electrophotographic image forming apparatuses equipped with electrophotographic photosensitive members are known.

[0011] An electrophotographic photoreceptor has, for example, a cylindrical substrate having conductivity and a photoreceptor layer formed on the outer peripheral surface of the substrate. Electrophotographic photoreceptors include negatively charged electrophotographic photoreceptors (also called negatively charged electrophotographic photoreceptors) in which the surface of the photoreceptor layer can be negatively charged (also called negative surface charge).

[0012] FIG. 24 is a cross-sectional view schematically illustrating the structure of a photoreceptor layer in a negative-charging electrophotographic photoreceptor according to a reference example. In a negative-charging electrophotographic photoreceptor, for example, as shown in FIG. 24, a photoreceptor layer 90b has a structure (also referred to as a laminated structure) in which a lower charge injection blocking layer 901, a photoconductive layer 902, an upper charge injection blocking layer 903, and a surface protective layer 904 are laminated in this order on the outer peripheral surface of a cylindrical substrate 90a. The lower charge injection blocking layer 901 serves to block the injection of positive charges (also referred to as positive charges) from the substrate 90a into the photoconductive layer 902. The photoconductive layer 902 serves to generate carriers in response to irradiation with light (also referred to as exposure light), such as laser light or LED (light-emitting diode) light, from outside the negative-charging electrophotographic photoreceptor. The upper charge injection blocking layer 903 serves to block the injection of negative charges carried on the surface of the photoreceptor layer 90b into the photoconductive layer 902. The surface protection layer 904 has the role of protecting the photosensitive layer 90b from the surface side.

[0013] An electrophotographic image forming apparatus equipped with a negatively charged electrophotographic photosensitive member can form an image on a recording medium such as paper by performing a series of steps, for example, a charging step, an exposure step, a development step, a transfer step, a fixing step, a cleaning step, and a de-electrification step, in the order listed.

[0014] In the charging step, substantially the entire surface of the photosensitive layer 90b is negatively charged.

[0015] In the exposure process, exposure light is applied to the photosensitive layer 90b based on an image signal. Here, in the area of ​​the surface of the photosensitive layer 90b irradiated with the exposure light, electrons (negative charges) carried on the surface of the photosensitive layer 90b are eliminated by holes (positive charges) generated in the photoconductive layer 902, and the negative polarity potential is attenuated. As a result, an electrostatic image (also referred to as an electrostatic latent image) is formed on the photosensitive layer 90b. Here, the electrons (negative charges) generated in the photoconductive layer 902 are discharged via the lower charge injection blocking layer 901 and the substrate 90a.

[0016] In the developing process, a toner image (also referred to as a toner image) is formed by developing the electrostatic latent image on the photosensitive layer 90b. Here, for example, in the case of reversal development, negatively charged toner adheres to areas of the surface of the photosensitive layer 90b where the negative potential is attenuated. Here, for example, in normal development, positively charged toner may adhere to areas of the surface of the photosensitive layer 90b that are negatively charged.

[0017] In the transfer process, the surface of the recording medium opposite the photosensitive layer 90b (also called the non-recording surface) is charged with a polarity opposite to that of the toner, and the toner image on the photosensitive layer 90b is transferred by electrostatic attraction onto the surface of the recording medium facing the photosensitive layer 90b (also called the recording surface).

[0018] In the fixing process, the recording medium is passed between a pair of fixing rollers, and the toner image is fixed onto the recording medium by applying heat and pressure to the recording medium by the pair of fixing rollers.

[0019] In the cleaning step, the toner remaining on the surface of the photosensitive layer 90b after the transfer step is removed by a cleaning blade or the like.

[0020] In the charge removal step, the photosensitive layer 90b is irradiated with charge removal light to eliminate the negative charges remaining on the surface of the photosensitive layer 90b, thereby removing the electrostatic latent image.

[0021] Meanwhile, in the exposure step, the exposure light passes through the surface protective layer 904 and the upper charge injection blocking layer 903 and reaches the photoconductive layer 902 along an optical path including an interface between the surface protective layer 904 and the upper charge injection blocking layer 903, and an interface between the upper charge injection blocking layer 903 and the photoconductive layer 902. The presence of these interfaces can cause optical interference in the exposure light due to multiple reflections.

[0022] Here, assume that the thicknesses of the surface protection layer 904 and the upper charge injection blocking layer 903 vary depending on the location. In this case, even if the photosensitive layer 90b is irradiated with exposure light of the same intensity, the intensity of the exposure light incident on the photoconductive layer 902 may vary depending on the location due to optical interference. That is, sensitivity unevenness may occur in the electrophotographic photosensitive member. If the sensitivity of the electrophotographic photosensitive member varies uniformly across the entire surface, this can be addressed by offset adjustment or the like, but if sensitivity unevenness occurs, this cannot be addressed by offset adjustment or the like. Furthermore, in an electrophotographic image forming apparatus equipped with an electrophotographic photosensitive member, sensitivity unevenness in the electrophotographic photosensitive member may cause unevenness in the density of the toner image fixed on a recording medium.

[0023] Differences in thickness (also referred to as thickness variations) depending on the location in each of the surface protective layer 904 and the upper charge injection blocking layer 903 can occur, for example, when the surface protective layer 904 and the upper charge injection blocking layer 903 are formed. Furthermore, thickness variations in the surface protective layer 904 can also occur, for example, due to wear of the surface protective layer 904 during use of the electrophotographic photosensitive member. Electrophotographic photosensitive members generally have an elongated shape with the longitudinal direction aligned with the axial direction of the cylindrical substrate 90a. Therefore, it is conceivable that the thicknesses of the surface protective layer 904 and the upper charge injection blocking layer 903 will vary in the axial direction of the cylindrical substrate 90a.

[0024] Therefore, there is room for improvement in reducing unevenness in sensitivity of electrophotographic photosensitive members. From another perspective, there is room for improvement in reducing unevenness in density (non-uniformity) in images formed by the above-mentioned series of steps in electrophotographic image forming apparatuses equipped with electrophotographic photosensitive members.

[0025] Therefore, the inventors of the present disclosure have created a technology that can reduce unevenness in sensitivity in an electrophotographic photosensitive member.

[0026] In the following, various embodiments will be described with reference to the drawings. In the drawings, parts having the same or similar configurations and functions are designated by the same reference numerals, and duplicated explanations will be omitted in the following description. The drawings are schematic.

[0027] 1. First Embodiment <1-1. Structure of Electrophotographic Photoreceptor> Fig. 1 is a cross-sectional view schematically showing an example of the configuration of an electrophotographic photoreceptor (also referred to as a photoreceptor) 10 according to the first embodiment. Fig. 2 is a cross-sectional view schematically showing an example of the configuration by enlarging a portion II in Fig. 1.

[0028] The photoreceptor 10 is a component mounted in, for example, an electrophotographic image forming apparatus 100 (see FIG. 17). On the surface of the photoreceptor 10 mounted in the image forming apparatus 100, for example, an electrostatic latent image and a toner image are formed based on an image signal. For example, when a flange 10f is fixed to the photoreceptor 10, the photoreceptor 10 is mounted in the image forming apparatus 100 rotatably via the flange 10f.

[0029] 1 and 2, the photoreceptor 10 includes a substrate 10a and a photoreceptor layer 10b. The photoreceptor layer 10b is located on the substrate 10a.

[0030] <1-1-1. Base> The substrate 10a is a member that supports the photosensitive layer 10b. The shape of the substrate 10a may be, for example, a cylindrical shape or an endless belt shape. In the example of Fig. 1, the shape of the substrate 10a is cylindrical.

[0031] The substrate 10a may be conductive throughout the entire substrate 10a, or at least the surface of the substrate 10a facing the photosensitive layer 10b may be conductive. In other words, the substrate 10a is conductive. Therefore, the substrate 10a may be referred to as a conductive substrate.

[0032] More specifically, the base 10a may be, for example, a member in which the entire base 10a is made of a conductive material (also referred to as a conductive material), or a member having a configuration in which a conductive film (also referred to as a conductive film) is formed on the surface of a base material made of an insulator. The conductive material may be, for example, one or more materials selected from metals and alloys containing metals. The insulator may be, for example, one or more insulating materials selected from synthetic resins, glasses, and ceramics. The conductive film may be, for example, one or more layers selected from a film made of metal (also referred to as a metal film) and a film made of a transparent conductive material (also referred to as a transparent conductive material) (also referred to as a transparent conductive film).

[0033] The metal constituting the substrate 10a may be one or more of aluminum (Al), stainless steel (Steel Use Stainless: SUS), zinc (Zn), copper (Cu), iron (Fe), titanium (Ti), nickel (Ni), chromium (Cr), molybdenum (Mo), indium (In), niobium (Nb), tellurium (Te), vanadium (V), palladium (Pd), tantalum (Ta), tin (Sn), platinum (Pt), gold (Au), and silver (Ag). The synthetic resin constituting the base material of the substrate 10a may be one or more of polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene, and polyamide. The transparent conductive material may be one or more of indium tin oxide (ITO) and tin dioxide (SnO).

[0034] Here, when the portion of the photoreceptor layer 10b in contact with the substrate 10a mainly contains an amorphous silicon-based material, the adhesion between the photoreceptor layer 10b and the substrate 10a can be improved by making the surface of the substrate 10a facing the photoreceptor layer 10b, for example, an Al-Mn alloy, an Al-Mg alloy, or an Al-Mg-Si alloy. The term "main" refers to the component with the highest content among the components (also referred to as constituent components) constituting a substance such as a layer. The main component may also refer to the majority of the components of a substance such as a layer, excluding small amounts of impurities or additives. The Al-Mn alloy may be an aluminum alloy containing mainly manganese (Mn) added to aluminum. The Al-Mg alloy may be an aluminum alloy containing mainly magnesium (Mg) added to aluminum. The Al-Mg-Si alloy may be an aluminum alloy containing mainly magnesium (Mg) and silicon (Si) added to aluminum.

[0035] The surface of the substrate 10a on which the photosensitive layer 10b is formed (the surface to be formed) is subjected to a surface treatment using, for example, lathe processing. The surface treatment may involve one or more of mirror finishing and linear groove processing. Furthermore, the surface treatment may involve a roughening treatment such as blasting or liquid honing to obtain a desired surface roughness. The surface to be formed may be the outer peripheral surface of the substrate 10a.

[0036] <1-1-2. Photoreceptor layer> The photoreceptor layer 10b is located, for example, on the outer peripheral surface of the substrate 10a. The photoreceptor layer 10b has a thickness (also referred to as layer thickness) of, for example, 15 micrometers (μm) or more and 90 μm or less.

[0037] 2, the photoreceptor layer 10b includes, for example, a lower charge injection blocking layer (also referred to as a lower blocking layer) 101 as a first layer, a photoconductive layer 102 as a second layer, an upper charge injection blocking layer (also referred to as an upper blocking layer) 103 as a third layer, a surface gradient layer (also referred to as a gradient layer) 104 as a fourth layer, and a surface protection layer (also referred to as a surface layer) 105 as a fifth layer. In other words, the photoreceptor 10 includes a substrate 10a, the lower blocking layer 101, the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105.

[0038] The lower blocking layer 101 is located on the substrate 10a. The photoconductive layer 102 is located on the lower blocking layer 101. The upper blocking layer 103 is located on the photoconductive layer 102. The gradient layer 104 is located on the upper blocking layer 103. The surface layer 105 is located on the gradient layer 104. In other words, the photoreceptor 10 has a configuration in which the lower blocking layer 101, the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105 are stacked in this order on the substrate 10a. The surface layer 105 has a surface exposed to the space outside the photoreceptor 10 (also referred to as the external space) Ex1. In other words, the surface layer 105 constitutes the surface of the photoreceptor layer 10b.

[0039] <<Lower charge injection blocking layer (lower blocking layer) 101>> The lower blocking layer 101 has the role of preventing injection of charges from the substrate 10a into the photoconductive layer 102. More specifically, the lower blocking layer 101 has the function of preventing injection of holes (positive charges) from the substrate 10a into the photoconductive layer 102 when the surface of the photoreceptor layer 10b is negatively charged.

[0040] The lower blocking layer 101 mainly contains amorphous silicon (Si). In other words, the base material as the main constituent element of the lower blocking layer 101 is silicon. The lower blocking layer 101 may be made of, for example, a non-single-crystal material mainly containing amorphous silicon. Here, the non-single-crystal material means a material that includes a polycrystalline, microcrystalline, or amorphous portion.

[0041] The lower blocking layer 101 also contains an n-type dopant. An n-type dopant is an impurity element that, when added to a semiconductor, supplies electrons having a negative charge (also referred to as "negative charge") as carriers and thus functions as a donor to turn the semiconductor into an n-type semiconductor. More specifically, the lower blocking layer 101 contains, for example, a Group 15 element of the periodic table (also referred to as "Group 15 element") as the n-type dopant. In the lower blocking layer 101, the Group 15 element may be distributed substantially uniformly or non-uniformly in the thickness direction of the lower blocking layer 101. The atomic concentration of the Group 15 element may be lower in the region of the lower blocking layer 101 closer to the substrate 10a than in the region of the lower blocking layer 101 closer to the photoconductive layer 102. In this case, the adhesion of the lower blocking layer 101 to the substrate 10a may be improved. In the lower blocking layer 101, if the atomic concentration of the Group 15 element is substantially uniform in the direction along the outer peripheral surface of the substrate 10a (also called the in-plane direction), the characteristics of the lower blocking layer 101 can be more uniform in the in-plane direction.

[0042] The number of atoms of the Group 15 element per unit volume in the lower blocking layer 101 is, for example, 5×10 17 atoms / cubic centimeter 3 ) or more and 5 x 10 19 atoms / cm 3 The voltage is set to be equal to or less than 0.05 V. This sufficiently increases the withstand voltage of the lower blocking layer 101 against positive charges, and also maintains the residual potential of the photoreceptor layer 10b at a sufficiently low level. The sufficiently low residual potential of the photoreceptor layer 10b may be, for example, a state in which the residual potential of the photoreceptor layer 10b is −20 volts (V) or less.

[0043] The Group 15 element may be any of nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). If nitrogen or phosphorus is used as the Group 15 element, it may be easier to control the concentration of the Group 15 element introduced (also called the doping concentration) when the lower blocking layer 101 is formed by, for example, a glow discharge decomposition method, which is a type of plasma-enhanced chemical vapor deposition (PECVD) method. Nitrogen is easy to handle and dispose of.

[0044] The lower block layer 101 may contain at least one of oxygen (O) and an element of Group 15. When the lower block layer 101 contains oxygen, the adhesion of the lower block layer 101 to the substrate 10a can be improved.

[0045] Furthermore, the lower blocking layer 101 may further contain, for example, carbon (C). If the lower blocking layer 101 contains carbon, the adhesion of the lower blocking layer 101 to the substrate 10a can be improved, and the function of the lower blocking layer 101 to block injection of holes (positive charges) from the substrate 10a into the photoconductive layer 102 can be improved.

[0046] When forming the lower blocking layer 101, a gas containing silicon (also called a silicon-based gas) is used as a raw material for introducing silicon into the lower blocking layer 101. Examples of the silicon-based gas include monosilane (SiH4) gas, disilane (Si2H6) gas, trisilane (Si3H8) gas, and tetrasilane (Si4H 10The gaseous source material is referred to as a source gas. For example, if monosilane gas and / or disilane gas is used as the source gas for introducing silicon during the formation of the lower blocking layer 101, the efficiency of silicon supply can be improved. Furthermore, hydrogen (H) in the source gas can terminate and compensate for dangling bonds of silicon in the formed non-single-crystal silicon, resulting in a film with favorable properties as a semiconductor material. Furthermore, monosilane gas and disilane gas are easy to handle. The source gas for introducing silicon into the lower blocking layer 101 during the formation of the lower blocking layer 101 may be diluted with one or more dilution gases selected from hydrogen (H) gas and helium (He) gas, if necessary.

[0047] During the formation of the lower blocking layer 101, the source gas for introducing a Group 15 element into the lower blocking layer 101 may be, for example, one or more of nitrogen (N2) gas, ammonia (NH3) gas, nitrogen oxide gas (also called nitrogen oxide gas), phosphine (PH3) gas, phosphorus trifluoride (PF3) gas, phosphorus pentafluoride (PF5) gas, and arsine (AsH3) gas. The nitrogen oxide gas may be one or more of nitric oxide (NO) gas and dinitrogen oxide (NO) gas (also called nitrous oxide gas).

[0048] As a source gas for introducing oxygen into the lower blocking layer 101 during the deposition of the lower blocking layer 101, for example, one or more types of gases selected from oxygen (O2) gas and nitrogen oxide gas are used. The above-mentioned gases are used as the nitrogen oxide gas.

[0049] A gas containing carbon (also called a carbon-based gas) is used as a source gas for introducing carbon into the lower blocking layer 101 during the formation of the lower blocking layer 101. Examples of the carbon-based gas include methane (CH4) gas, acetylene (C2H2) gas, ethane (C2H6) gas, propane (C3H8) gas, and butane (C4H 10) gases, such as one or more hydrocarbon-based gases (also called hydrocarbon-based gases), are used.

[0050] In the lower blocking layer 101, any of the additive elements, oxygen, Group 15 elements, and carbon, may be distributed substantially uniformly or non-uniformly in the thickness direction of the lower blocking layer 101. For example, when the additive element is distributed non-uniformly in the thickness direction of the lower blocking layer 101, the residual charge in the photoreceptor layer 10b can be maintained at a sufficiently low level if the atomic concentration of the additive element is higher in the region of the lower blocking layer 101 closer to the substrate 10a than in the region of the lower blocking layer 101 closer to the photoconductive layer 102. In the lower blocking layer 101, if the atomic concentration of the additive element is substantially uniform in the in-plane direction along the outer peripheral surface of the substrate 10a, the characteristics of the lower blocking layer 101 can be more uniform in the in-plane direction.

[0051] The lower blocking layer 101 has a thickness (layer thickness), for example, of 0.1 μm or more and 10 μm or less. This allows the lower blocking layer 101 to fully perform its role of preventing charge injection from the substrate 10a into the photoconductive layer 102, and reduces the generation of residual charge in the photoreceptor layer 10b, thereby improving memory characteristics. Furthermore, excessive increases in the formation time of the lower blocking layer 101 and increases in the amount of material required to form the lower blocking layer 101 are reduced, thereby reducing the cost required to manufacture the photoreceptor 10.

[0052] <<Photoconductive layer 102>> The photoconductive layer 102 generates carriers upon irradiation with light (exposure light) such as laser light or LED light. Carriers include holes and electrons. For example, when the photoreceptor 10 is mounted in an image forming apparatus 100, holes (positive charges) generated in the photoconductive layer 102 upon irradiation with exposure light pass through the upper blocking layer 103, the gradient layer 104, and the surface layer 105, eliminating at least a portion of the negative charges present on the surface of the surface layer 105 and attenuating the negative potential on the surface of the surface layer 105. Furthermore, electrons (negative charges) generated in the photoconductive layer 102 upon irradiation with exposure light are discharged via the lower blocking layer 101 and the substrate 10a.

[0053] The photoconductive layer 102 primarily contains amorphous silicon. In other words, the base material, which is the main constituent element of the photoconductive layer 102, is silicon. From another perspective, the photoconductive layer 102 may be composed of, for example, a non-single-crystal material primarily containing amorphous silicon. If the photoconductive layer 102 contains microcrystalline silicon, the dark conductivity and photoconductivity can be increased. This can increase the design flexibility of the photoconductive layer 102. Microcrystalline silicon can be formed by changing the conditions for forming the photoconductive layer 102. For example, when forming the photoconductive layer 102 using glow discharge decomposition, microcrystalline silicon can be formed by setting the temperature of the substrate 10a and the pulsed DC voltage relatively high and increasing the supply amount of dilution gas (e.g., hydrogen).

[0054] If the photoconductive layer 102 contains, for example, at least one of hydrogen and a halogen element, termination of dangling bonds of silicon with at least one of hydrogen and a halogen element can be realized. Here, in the photoconductive layer 102, for example, the total content of hydrogen and halogen elements may be set to 1 atomic percent (at%) or more and 40 at% or less with respect to the total content of silicon, hydrogen, and halogen elements. For example, amorphous silicon can be stabilized by performing a process (also called hydrogenation) to bond hydrogen to dangling bonds of amorphous silicon. Hydrogenated amorphous silicon is called hydrogenated amorphous silicon (also called hydrogenated amorphous silicon).

[0055] A silicon-based gas, for example, is used as a source gas for introducing silicon into the photoconductive layer 102 during deposition of the photoconductive layer 102. The silicon-based gas may be, for example, one or more silicon hydride gases (silane-based gases) selected from monosilane gas, disilane gas, trisilane gas, and tetrasilane gas. If monosilane gas and / or disilane gas is used as the source gas for introducing silicon during deposition of the photoconductive layer 102, the efficiency of silicon supply can be improved.

[0056] A gas containing fluorine (also referred to as a fluorine-based gas), for example, is used as a raw material gas for introducing a halogen element into the photoconductive layer 102 during deposition of the photoconductive layer 102. The fluorine-based gas may be, for example, one or more of fluorine (F2) gas, bromine fluoride (BrF) gas, chlorine fluoride (ClF) gas, chlorine trifluoride (ClF3) gas, bromine trifluoride (BrF3) gas, bromine pentafluoride (BrF5) gas, iodine trifluoride (IF3) gas, iodine heptafluoride (IF7) gas, silicon tetrafluoride (SiF4), and disilicon hexafluoride (Si2F6) gas.

[0057] The source gas for introducing silicon into the photoconductive layer 102 during deposition of the photoconductive layer 102 may be diluted with one or more dilution gases selected from hydrogen gas and helium gas, as necessary. When the photoconductive layer 102 is deposited by glow discharge decomposition, the contents of hydrogen and halogen elements in the photoconductive layer 102 can be controlled by adjusting one or more parameters, for example, the temperature of the substrate 10a, the amount of source gas introduced per unit time for introducing each element into the photoconductive layer 102, and discharge power.

[0058] The photoconductive layer 102 may also contain an element for controlling the conductivity of the photoconductive layer 102 (also referred to as a conductivity control element). The conductivity control element may be, for example, one or more of a Group 13 element acting as an acceptor for imparting p-type conductivity to a semiconductor and a Group 15 element acting as a donor for imparting n-type conductivity to a semiconductor. When boron (B) is used as the Group 13 element and / or when phosphorus is used as the Group 15 element, the semiconductor's properties such as sensitivity and photosensitivity can be maintained or improved. The use of a Group 13 element as the conductivity control element may bring the photoconductive layer 102 closer to an intrinsic (i-type) semiconductor. When the photoconductive layer 102 is formed by the glow discharge decomposition method, the conductivity control element can be introduced into the photoconductive layer 102 by supplying a raw material gas for introducing the conductivity control element into the photoconductive layer 102 into a reaction chamber during the formation of the photoconductive layer 102 together with the raw material gas for introducing the main constituent elements into the photoconductive layer 102.

[0059] During the deposition of the photoconductive layer 102, one or more types of gases containing boron (also referred to as boron-based gases) are used as source gases for introducing boron, a Group 13 element serving as a conductivity control element, into the photoconductive layer 102. Examples of the one or more types of boron-based gases include one or more types of boron hydride gases (also referred to as boron hydride gases) and / or one or more types of boron halide gases (also referred to as boron halide gases). Examples of the one or more types of boron hydride gases include diborane (B2H6) gas and tetraborane (B4H 10) gases are used. The one or more boron halide gases may be, for example, one or more of boron trifluoride (BF3) gas, boron trichloride (BCl3) gas, and boron tribromide (BBr3) gas. The source gas for introducing other Group 13 elements, which are conductivity control elements, into the photoconductive layer 102 during deposition of the photoconductive layer 102 may be, for example, one or more of aluminum chloride (AlCl3) gas, gallium chloride (GaCl3) gas, trimethylgallium (Ga(CH3)3) gas, indium chloride (InCl3) gas, and thallium chloride (TlCl3) gas.

[0060] As a raw material gas for introducing a Group 15 element, which is a conductivity control element, into the photoconductive layer 102 during film formation of the photoconductive layer 102, for example, one or more gases selected from the group consisting of nitrogen gas, ammonia gas, oxynitride gas such as nitric oxide gas and / or nitrous oxide gas, phosphine gas, phosphorus trifluoride gas, phosphorus pentafluoride gas, and arsine gas are used.

[0061] In addition, the raw material gas for introducing the conductivity control element into the photoconductive layer 102 during the deposition of the photoconductive layer 102 may be diluted with one or more dilution gases selected from hydrogen gas, helium gas, argon (Ar) gas, and neon (Ne) gas, as necessary.

[0062] In the photoconductive layer 102, the concentration of the conductivity control element may vary in the thickness direction of the photoconductive layer 102. When the photoconductive layer 102 is formed by glow discharge decomposition, this configuration can be achieved by changing over time the amount of source gas introduced per unit time and / or the amount of dilution gas introduced per unit time for introducing the conductivity control element into the reaction chamber. Here, the concentration of the conductivity control element in the photoconductive layer 102 may be set such that the average concentration of the conductivity control element throughout the photoconductive layer 102 is within a predetermined range.

[0063] Furthermore, the photoconductive layer 102 may contain one or more elements of carbon, oxygen, and nitrogen. In this case, the photoconductive layer 102 has a silicon, carbon, oxygen, and nitrogen content of 1×10 or less. -5 It may be set to 10 at % or more and 10 at % or less.

[0064] The photoconductive layer 102 has a thickness (layer thickness) of, for example, 5 μm or more and 100 μm or less. This ensures sufficient charging ability and photosensitivity in the photoreceptor layer 10b, and can reduce excessive increases in the time required to form the photoconductive layer 102 and the amount of material used to form the photoconductive layer 102. As a result, the cost required to manufacture the photoreceptor 10 can be reduced.

[0065] <<Top charge injection blocking layer (top blocking layer) 103>> The upper blocking layer 103 has a role of preventing negative charges carried by the charger 11 (see FIG. 17) on the surface of the photoreceptor layer 10b from being injected into the photoconductive layer 102 when the photoreceptor 10 is mounted on the image forming apparatus 100. The surface of the photoreceptor layer 10b may be the surface of the surface layer 105.

[0066] The upper blocking layer 103 mainly contains amorphous silicon and also contains nitrogen, oxygen, carbon, and a Group 13 element that is a p-type dopant.

[0067] In the upper blocking layer 103, the Group 13 element transforms amorphous silicon into a p-type semiconductor, thereby providing the upper blocking layer 103 with the function of blocking injection of negative charges carried on the surface of the photoreceptor layer 10b into the photoconductive layer 102. In the upper blocking layer 103, nitrogen and oxygen widen the band gap of amorphous silicon, thereby increasing the energy barrier for blocking injection of negative charges carried on the surface of the photoreceptor layer 10b into the photoconductive layer 102 and improving the transmittance of exposure light from outside the photoreceptor 10 through the upper blocking layer 103. In other words, the characteristics of the photoreceptor 10 can be improved.

[0068] In the upper blocking layer 103, the concentrations of nitrogen, oxygen, and Group 13 elements vary in the thickness direction of the upper blocking layer 103. If the atomic concentration of each constituent element in the upper blocking layer 103 is substantially uniform in the direction along the outer peripheral surface of the base 10a (in-plane direction), the characteristics of the upper blocking layer 103 can be made more uniform in the in-plane direction.

[0069] The number of atoms of the Group 13 element per unit volume in the upper blocking layer 103 is, for example, 5×10 17 atoms / cm 3 Above and 5 x 10 19 atoms / cm 3 This makes it possible to sufficiently prevent negative charges from being injected into the photoconductive layer 102 from the surface layer 105 side, and also reduces the generation of residual charges in the photosensitive layer 10b, thereby improving memory characteristics.

[0070] The upper blocking layer 103 may include one or more of boron, aluminum, gallium, indium, and thallium as the Group 13 element. The Group 13 element contained in the upper blocking layer 103 may be boron. In this case, when the upper blocking layer 103 is formed by glow discharge decomposition, it may be easier to control the concentration (doping concentration) of the Group 13 element introduced into the upper blocking layer 103.

[0071] A silicon-based gas, for example, is used as a source gas for introducing silicon into the upper blocking layer 103 during deposition of the upper blocking layer 103. The silicon-based gas may be, for example, one or more silicon hydride gases (silane-based gases) selected from the group consisting of monosilane gas, disilane gas, trisilane gas, and tetrasilane gas. If monosilane gas and / or disilane gas is used as the source gas for introducing silicon during deposition of the upper blocking layer 103, the efficiency of silicon supply can be improved. The source gas for introducing silicon into the upper blocking layer 103 during deposition of the upper blocking layer 103 may be diluted with one or more dilution gases selected from the group consisting of hydrogen gas and helium gas, as necessary.

[0072] A boron-based gas is used as a source gas for introducing boron (B), a Group 13 element, into the upper blocking layer 103 during deposition of the upper blocking layer 103. The boron-based gas may be, for example, one or more boron hydride gases and / or one or more boron halide gases. The one or more boron hydride gases may be, for example, one or more diborane gases and tetraborane gases. The one or more boron halide gases may be, for example, one or more boron trifluoride gases, boron trichloride gases, and boron tribromide gases.

[0073] As a raw material gas for introducing other Group 13 elements into the upper blocking layer 103 during the formation of the upper blocking layer 103, for example, one or more of aluminum chloride gas, gallium chloride gas, trimethylgallium gas, indium chloride gas, and thallium chloride gas may be used.

[0074] The source gas for introducing the Group 13 element into the upper blocking layer 103 during deposition of the upper blocking layer 103 may be diluted with one or more dilution gases selected from the group consisting of hydrogen gas, helium gas, argon gas, and neon gas, as necessary. When the upper blocking layer 103 is deposited by glow discharge decomposition, the source gas for introducing the Group 13 element can be introduced into the upper blocking layer 103 by supplying into the reaction chamber the source gas for introducing the main constituent elements into the upper blocking layer 103.

[0075] A carbon-based gas, for example, is used as a source gas for introducing carbon into the upper blocking layer 103 during the formation of the upper blocking layer 103. The carbon-based gas may be, for example, one or more hydrocarbon gases selected from the group consisting of methane gas, acetylene gas, ethane gas, propane gas, and butane gas.

[0076] In the upper blocking layer 103, the maximum value of the total content of nitrogen, oxygen, and carbon relative to the total content of silicon, nitrogen, oxygen, and carbon may be set to, for example, 10 at % or more and 70 at % or less. Furthermore, in the upper blocking layer 103, the maximum value of the content of carbon relative to the total content of silicon and carbon may be set to 10 at % or more and 70 at % or less. The carbon content in the upper blocking layer 103 may be lower than the carbon content in the gradient layer 104 and the surface layer 105. This allows the residual potential in the photosensitive layer 10b to be maintained at a sufficiently low level.

[0077] The upper blocking layer 103 has a thickness (layer thickness) of, for example, 0.01 μm or more and 1 μm or less, which allows the upper blocking layer 103 to fully perform the role of preventing charge injection from the surface layer 105 side into the photoconductive layer 102, and reduces the generation of residual charge in the photoreceptor layer 10b, thereby improving memory characteristics.

[0078] The upper blocking layer 103 includes a first region 103a and a second region 103b. The first region 103a is a region in contact with the photoconductive layer 102. The second region 103b is a region located closer to the gradient layer 104 than the first region 103a and in contact with the gradient layer 104. The first region 103a and the second region 103b may be in contact with each other, or a region (also referred to as a third region) that is significantly thinner than each of the first region 103a and the second region 103b may exist between the first region 103a and the second region 103b. When the third region exists, the thickness of the third region may be 20% or less, 10% or less, or 5% or less of the thickness of each of the first region 103a and the second region 103b.

[0079] In the first region 103a, the concentrations of nitrogen, oxygen, and a Group 13 element (e.g., boron) vary in the thickness direction of the upper blocking layer 103. Here, for example, when the upper blocking layer 103 is formed by glow discharge decomposition, the first region 103a can be formed by changing over time the amount per unit time of each source gas for introducing silicon, nitrogen, oxygen, and a Group 13 element (e.g., boron) into the reaction chamber.

[0080] In the second region 103b, the concentrations of silicon, nitrogen, oxygen, carbon, and a Group 13 element (e.g., boron) vary in the thickness direction of the upper blocking layer 103. Here, for example, when the upper blocking layer 103 is formed by glow discharge decomposition, the second region 103b can be formed by changing over time the amount per unit time of each source gas for introducing silicon, nitrogen, oxygen, carbon, and a Group 13 element (e.g., boron) into the reaction chamber.

[0081] The thickness of the first region 103a may be, for example, 40% or more and 80% or less of the thickness of the upper blocking layer 103, and the thickness of the second region 103b may be, for example, 20% or more and 60% or less of the thickness of the upper blocking layer 103. If the third region is present, the concentrations of nitrogen, oxygen, carbon, and Group 13 elements (e.g., boron) in the third region may not vary substantially in the thickness direction of the upper blocking layer 103.

[0082] FIG. 3 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements for a photoreceptor layer 10b according to a first example of the first embodiment. FIG. 4 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index for a photoreceptor layer 10b according to a first example of the first embodiment. FIG. 5 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements for a photoreceptor layer 10b according to a second example of the first embodiment. FIG. 6 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index for a photoreceptor layer 10b according to a second example of the first embodiment. FIG. 7 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements for a photoreceptor layer 10bA according to a first reference example (see FIG. 11). FIG. 8 is a diagram schematically showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index for a photoreceptor layer 10bA according to a first reference example. FIG. 9 is a diagram showing the relationship between the distance from the outermost surface in the thickness direction and the ratio of the four elements for a photoreceptor layer 10bA according to a second reference example. FIG. 10 is a diagram showing the relationship between the distance from the outermost surface in the thickness direction and the refractive index for a photoreceptor layer 10bA according to a second reference example. FIG. 11 is a cross-sectional view showing the configuration of a photoreceptor layer 10bA according to a first reference example and a second reference example. As shown in FIG. 11, the photoreceptor layers 10bA according to the first and second reference examples differ from the photoreceptor layer 10b described above in that the upper blocking layer 103 is an upper blocking layer 103A that does not include the first region 103a and the second region 103b.

[0083] Here, the outermost surface is the surface of the surface layer 105. The four elements are silicon, nitrogen, oxygen, and carbon. The element ratios (also referred to as elemental ratios) are the atomic ratios of the four elements in the photoreceptor layers 10b and 10bA. In each of FIGS. 3, 5, 7, and 9, the horizontal axis represents the distance from the outermost surface in the thickness direction of the photoreceptor layers 10b and 10bA, and the vertical axis represents the atomic ratios. In each of FIGS. 3, 5, 7, and 9, the atomic ratio of silicon is represented by multiple black circles and a thick dashed line, the atomic ratios of nitrogen and oxygen are represented by multiple black diamonds and a thick dashed line, and the atomic ratio of carbon is represented by multiple black triangles and a thick dashed line. In the photoreceptor layers 10b and 10bA, the content of Group 13 elements (e.g., boron) is significantly lower than the content of the four elements (silicon, nitrogen, oxygen, and carbon). Therefore, although the element ratios of Group 13 elements are not shown in FIGS. 3, 5, 7, and 9, the trends in the increase and decrease of the Group 13 element content in the upper blocking layers 103 and 103A are the same or similar to the trends in the increase and decrease of the nitrogen and oxygen content. The element content may be expressed as atomic concentration. The line graphs showing changes in refractive index shown in FIGS. 4, 6, 8, and 10 are line graphs showing predicted changes in refractive index based on the refractive index measured for multiple samples with appropriately changed ratios of the four elements and the ratios of the four elements in the photoreceptor layer 10b. 3 to 10, the sections corresponding to the photoconductive layer 102, the upper blocking layers 103 and 103A, the gradient layer 104, and the surface layer 105 in the thickness direction are labeled with reference numerals. 3 to 6, the sections corresponding to the first region 103a and the second region 103b in the upper blocking layer 103 in the thickness direction are also labeled with reference numerals.

[0084] 7 and 9, the upper blocking layer 103A does not have the first region 103a or the second region 103b. The upper blocking layer 103A has a tendency that the silicon content rapidly decreases and the respective contents of the Group 13 elements, nitrogen, oxygen, and carbon rapidly increase with increasing distance from the photoconductive layer 102, and then, with increasing distance from the gradient layer 104, the respective contents of the Group 13 elements, nitrogen, and oxygen decrease and the carbon content increases.

[0085] In contrast, in the first embodiment, as shown in FIGS. 3 and 5, in the first region 103a, the silicon content decreases, the contents of the Group 13 elements, nitrogen, and oxygen increase, and the carbon content does not increase, with increasing distance from the photoconductive layer 102.

[0086] In this case, as shown in FIGS. 4, 6, 8, and 10, in the first embodiment, the change in refractive index in the thickness direction of the photosensitive layer 10b near the interface between the photoconductive layer 102 and the upper blocking layer 103 is significantly reduced compared to the first and second reference examples. In other words, the occurrence of abrupt changes in the refractive index in the thickness direction of the photosensitive layer 10b near the interface between the photoconductive layer 102 and the upper blocking layer 103 is reduced. This reduces the occurrence of light reflection at the interface between the upper blocking layer 103 and the photoconductive layer 102. In other words, the occurrence of a clear optical interface between the upper blocking layer 103 and the photoconductive layer 102 is reduced.

[0087] Here, in the first region 103a, the silicon content may decrease monotonically with increasing distance from the photoconductive layer 102, or may decrease roughly with small local increases and decreases. In other words, in the first region 103a, the silicon content may decrease continuously or almost continuously with increasing distance from the photoconductive layer 102. The decrease in the silicon content in the first region 103a according to the distance from the photoconductive layer 102 may be a decrease at a substantially constant rate, or may be a stepwise decrease at two or more rates. Note that the first region 103a may have a portion in which the silicon content is substantially constant in the thickness direction of the first region 103a.

[0088] In the first region 103a, the respective contents of the Group 13 element, nitrogen, and oxygen may increase monotonically with increasing distance from the photoconductive layer 102, or may increase roughly with small local variations. In other words, in the first region 103a, the respective contents of the Group 13 element, nitrogen, and oxygen may increase continuously or almost continuously with increasing distance from the photoconductive layer 102. The increase in the contents of the Group 13 element, nitrogen, and oxygen in the first region 103a with respect to the distance from the photoconductive layer 102 may be at a substantially constant rate or may be a stepwise increase of two or more rates. The first region 103a may have a portion in which the contents of one or more of the Group 13 element, nitrogen, and oxygen are substantially constant in the thickness direction of the first region 103a.

[0089] The first region 103a may contain no carbon or may contain a trace amount of carbon that is clearly smaller than the amounts of nitrogen and oxygen. In this case, the atomic concentration of carbon in the first region 103a may be 30% or less, 20% or less, or 10% or less of the atomic concentrations of nitrogen and oxygen.

[0090] In the first embodiment, as shown in FIGS. 3 and 5, the second region 103b tends to have a decreasing content of Group 13 elements, nitrogen, and oxygen, and an increasing content of carbon, toward the gradient layer 104. As a result, as shown in FIGS. 4 and 6, in the first embodiment, abrupt changes in the refractive index in the upper blocking layer 103 in the thickness direction of the photosensitive layer 10b are reduced. This reduces the occurrence of light reflection in the upper blocking layer 103. In other words, the occurrence of clear optical interfaces in the upper blocking layer 103 is reduced. This reduces the occurrence of light reflection in the optical path from the surface layer 105, the gradient layer 104, and the upper blocking layer 103 to the photoconductive layer 102.

[0091] In the second region 103b, the respective contents of the Group 13 element, nitrogen, and oxygen may decrease monotonically as the region approaches the gradient layer 104, or may decrease roughly with small local increases and decreases. In other words, in the second region 103b, the respective contents of the Group 13 element, nitrogen, and oxygen may decrease continuously or almost continuously as the region approaches the gradient layer 104. The decrease in the contents of the Group 13 element, nitrogen, and oxygen in the second region 103b according to the distance to the gradient layer 104 may be a substantially constant rate decrease, or may be a stepwise decrease of two or more rates. Note that the second region 103b may have a portion in the thickness direction of the second region 103b where the contents of one or more of the Group 13 element, nitrogen, and oxygen are substantially constant.

[0092] In addition, in the second region 103b, the carbon content may increase monotonically as the region approaches the gradient layer 104, or may increase roughly with small local increases and decreases. In other words, in the second region 103b, the carbon content may increase continuously or almost continuously as the region approaches the gradient layer 104. The increase in the carbon content in the second region 103b according to the distance to the gradient layer 104 may be an increase at a substantially constant rate, or may be an increase in two or more steps at different rates. Note that the second region 103b may have a portion in which the carbon content is substantially constant in the thickness direction of the second region 103b.

[0093] In addition, in second region 103b, the silicon content may gradually increase or decrease as it approaches gradient layer 104, or may be approximately constant regardless of the distance to gradient layer 104. The increase or decrease in silicon content in second region 103b according to the distance to gradient layer 104 may be an increase or decrease at an approximately constant rate, or may be an increase or decrease in two or more steps.

[0094] <<Surface gradient layer (gradient layer) 104>> The inclined layer 104 has the role of facilitating the transmission of exposure light from outside the photosensitive member 10 toward the upper blocking layer 103 and the photoconductive layer 102, and the role of facilitating the movement of positive charges from the photoconductive layer 102 toward the surface layer 105.

[0095] The gradient layer 104 mainly contains an amorphous material (also referred to as an amorphous material) containing silicon and carbon. As shown in FIGS. 3 and 5, the gradient layer 104 has a tendency for the silicon content to decrease and the carbon content to increase toward the surface layer 105. As shown in FIGS. 4 and 6, in the first embodiment, abrupt changes in refractive index between the upper blocking layer 103 and the surface layer 105 in the thickness direction of the photosensitive layer 10b are thereby reduced. This reduces the occurrence of light reflection between the upper blocking layer 103 and the surface layer 105. In other words, the occurrence of a clear optical interface between the upper blocking layer 103 and the surface layer 105 is reduced. This reduces the occurrence of light reflection in the optical path from the surface layer 105, the gradient layer 104, and the upper blocking layer 103 to the photoconductive layer 102.

[0096] Here, in the gradient layer 104, the silicon content may decrease monotonically as it approaches the surface layer 105, or may decrease roughly with small local increases and decreases. In other words, in the gradient layer 104, the silicon content may decrease continuously or almost continuously as it approaches the surface layer 105. The decrease in the silicon content in the gradient layer 104 according to the distance to the surface layer 105 may be a decrease at a substantially constant rate, or may be a stepwise decrease at two or more rates. Note that the gradient layer 104 may have a portion in which the silicon content is substantially constant in the thickness direction of the gradient layer 104.

[0097] Furthermore, in the gradient layer 104, the carbon content may increase monotonically as it approaches the surface layer 105, or may increase roughly with small local increases and decreases. In other words, in the gradient layer 104, the carbon content may increase continuously or almost continuously as it approaches the surface layer 105. The increase in the carbon content in the gradient layer 104 according to the distance to the surface layer 105 may be an increase at a substantially constant rate, or may be an increase in two or more steps at different rates. Note that the gradient layer 104 may have a portion in which the carbon content is substantially constant in the thickness direction of the gradient layer 104.

[0098] In the gradient layer 104, if the atomic concentrations of each of multiple constituent elements such as silicon and carbon are substantially uniform in the direction along the outer peripheral surface of the substrate 10a (in-plane direction), the characteristics of the gradient layer 104 can become more uniform in the in-plane direction.

[0099] A silicon-based gas is used as a source gas for introducing silicon into the gradient layer 104 during the formation of the gradient layer 104. The silicon-based gas may be, for example, one or more silicon hydride gases (silane-based gases) selected from monosilane gas, disilane gas, trisilane gas, and tetrasilane gas. If, for example, monosilane gas and / or disilane gas is used as the source gas for introducing silicon during the formation of the gradient layer 104, the efficiency of silicon supply can be improved.

[0100] As a raw material gas for introducing carbon into the gradient layer 104 during the deposition of the gradient layer 104, for example, one or more hydrocarbon gases selected from methane gas, acetylene gas, ethane gas, propane gas, and butane gas are used.

[0101] Here, for example, when the gradient layer 104 is formed by glow discharge decomposition, the gradient layer 104 can be formed by changing over time the supply amounts of raw material gases for introducing silicon and carbon, which are supplied into the reaction chamber.

[0102] <<Surface protective layer (surface layer) 105>> The surface layer 105 mainly serves to improve the moisture resistance of the photoreceptor 10, its ability to stably withstand repeated use (repeated use characteristics), its electrical pressure resistance, its ability to adapt to the use environment (use environment characteristics), and its durability.

[0103] The surface layer 105 mainly contains amorphous carbon or mainly contains an amorphous material containing carbon and silicon. In this specification, an amorphous material containing carbon and silicon is referred to as amorphous silicon carbide (a-SiC). In the photoreceptor layer 10b according to the first example of the first embodiment shown in FIGS. 3 and 4, the surface layer 105 mainly contains amorphous carbon (a-C). In the photoreceptor layer 10b according to the second example of the first embodiment shown in FIGS. 5 and 6, the surface layer 105 mainly contains an amorphous material containing carbon and silicon.

[0104] For example, when the surface layer 105 is made of amorphous silicon carbide, the carbon content may be set to 40 at % or more and 90 at % or less with respect to the total content of carbon and silicon in the amorphous silicon carbide.

[0105] If the surface layer 105 contains, for example, at least one of hydrogen and a halogen element, termination of silicon dangling bonds by at least one of hydrogen and a halogen element can be realized. Here, in the surface layer 105, for example, the hydrogen content may be set to 1 at% or more and 70 at% or less, or 1 at% or more and 45 at% or less, relative to the total content of the constituent elements. This satisfies the stabilization by termination of silicon dangling bonds, and the residual potential in the photoreceptor layer 10b can be maintained at a sufficiently low level by sufficiently reducing charge traps that occur when the surface of the surface layer 105 is irradiated with exposure light.

[0106] When the surface layer 105 is composed of hydrogenated amorphous silicon carbide (also called hydrogenated amorphous silicon carbide or a-SiC:H), the carbon content of the hydrogenated amorphous silicon carbide may be set to 55 at% or more and 93 at% or less, or 60 at% or more and 70 at% or less, relative to the total content of carbon and silicon.

[0107] The surface layer 105 may have a thickness (layer thickness) of, for example, 0.2 μm or more and 1.5 μm or less, or 0.5 μm or more and 1 μm or less, which allows the surface layer 105 to sufficiently realize the durability of the photoreceptor layer 10b and maintain the residual potential of the photoreceptor layer 10b at a sufficiently low level.

[0108] If the atomic concentrations of multiple constituent elements such as carbon and silicon in the surface layer 105 are substantially uniform in the direction along the outer peripheral surface of the substrate 10a (in-plane direction), the characteristics of the surface layer 105 can become more uniform in the in-plane direction.

[0109] As a raw material gas for introducing carbon into the surface layer 105 during the deposition of the surface layer 105, for example, a carbon-based gas such as one or more hydrocarbon gases selected from methane gas, acetylene gas, ethane gas, propane gas, and butane gas is used.

[0110] As a source gas for introducing silicon into the surface layer 105 during deposition of the surface layer 105, for example, a silicon-based gas such as one or more silicon hydride gases (silane-based gases) selected from monosilane gas, disilane gas, trisilane gas, and tetrasilane gas is used. If, for example, monosilane gas and / or disilane gas is used as the source gas for introducing silicon during deposition of the surface layer 105, the efficiency of supplying silicon can be improved. The source gas for introducing silicon into the surface layer 105 during deposition of the surface layer 105 may be diluted with one or more dilution gases selected from hydrogen gas and helium gas, as necessary.

[0111] As described above, in the first embodiment, the ratio of constituent elements does not change suddenly in the thickness direction of each layer near the interfaces of the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105, and in each of the upper blocking layer 103, the gradient layer 104, and the surface layer 105. Therefore, in the thickness direction of the photoreceptor layer 10b, a sudden change in refractive index is reduced near the interface between the photoconductive layer 102 and the upper blocking layer 103, near the interface between the upper blocking layer 103 and the gradient layer 104, and near the interface between the gradient layer 104 and the surface layer 105. This reduces the occurrence of light reflection in the optical path from the surface layer 105, the gradient layer 104, and the upper blocking layer 103 to the photoconductive layer 102. Therefore, for example, when the photoreceptor 10 is mounted in the image forming apparatus 100, even if the upper blocking layer 103, the inclined layer 104, and the surface layer 105 each have different thicknesses depending on the location (thickness variations), when the photoreceptor layer 10b is irradiated with exposure light of the same intensity, the occurrence of a defect in which the intensity of the exposure light incident on the photoconductive layer 102 varies depending on the location due to optical interference can be reduced. As a result, unevenness (non-uniformity) in the sensitivity of the photoreceptor 10 can be reduced.

[0112] The fact that the ratio of constituent elements does not change suddenly in the thickness direction of each layer near each interface between the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105, and in each of the upper blocking layer 103, the gradient layer 104, and the surface layer 105, can be confirmed by, for example, composition analysis in the depth direction of the photoreceptor layer 10b using X-ray photoelectron spectroscopy (XPS) and / or secondary ion mass spectrometry (SIMS). X-ray photoelectron spectroscopy (XPS) is also called ESCA (Electron Spectroscopy for Chemical Analysis).

[0113] <1-2. Film deposition equipment> FIG. 12 is a cross-sectional view schematically showing an example of the configuration of a film forming apparatus 300 for forming the photoreceptor layer 10b of the photoreceptor 10. As shown in FIG.

[0114] The film forming apparatus 300 can form the lower blocking layer 101, photoconductive layer 102, upper blocking layer 103, gradient layer 104 and surface layer 105 that constitute the photosensitive layer 10b on the substrate 10a in the order listed.

[0115] The film forming apparatus 300 includes a reaction chamber 20, a support mechanism 30, a DC voltage supply mechanism 40, a temperature control mechanism 50, a rotation mechanism 60, a gas supply mechanism 70, and an exhaust mechanism 80.

[0116] <<Reaction chamber 20>> The reaction chamber 20 has a space (also called a formation space) inside for forming deposited films that will become the layers of the photosensitive layer 10b on the substrate 10a. The formation space is a space surrounded by the cylindrical electrode 21, the pair of plates 22 and 23, and the insulating members 24 and 25 that constitute the reaction chamber 20.

[0117] The cylindrical electrode 21 has a cylindrical shape that laterally surrounds the formation space and serves as a second conductor when the substrate 10a serves as the first conductor for generating a glow discharge. The cylindrical electrode 21 is made of the same or similar conductive material as the substrate 10a. The cylindrical electrode 21 is integrated with a pair of plates 22 and 23 via insulating members 24 and 25. In the example shown in FIG. 12, the cylindrical electrode 21 is sized and positioned such that when the substrate 10a is supported by the support mechanism 30, the distance between the substrate 10a and the cylindrical electrode 21 is 10 millimeters (mm) or more and 100 mm or less. This stabilizes the discharge between the cylindrical electrode 21 and the support mechanism 30 and reduces the power required for this discharge.

[0118] The cylindrical electrode 21 has a gas inlet 21a and a plurality of gas outlet holes 21b. One end of the cylindrical electrode 21 is grounded. The cylindrical electrode 21 may not be grounded and may be connected to a reference power supply separate from a DC power supply 41 described below. When the cylindrical electrode 21 is connected to a reference power supply separate from the DC power supply 41, the potential (also referred to as a reference potential) applied to the cylindrical electrode 21 by the reference power supply is set to, for example, −1500 V or more and 1500 V or less.

[0119] The gas inlet 21a is an opening for introducing a cleaning gas or a raw material gas into the reaction chamber 20. The gas inlet 21a is connected to a gas supply mechanism .

[0120] The gas outlet holes 21b are openings for blowing cleaning gas or raw material gas introduced into the cylindrical electrode 21 toward the substrate 10a. In the example of FIG. 12, the gas outlet holes 21b are arranged, for example, at equal intervals in both the vertical and circumferential directions of the cylindrical electrode 21. The gas outlet holes 21b may have circular shapes of the same size. The diameter of the gas outlet holes 21b is set, for example, to be equal to or greater than 0.5 mm and equal to or less than 2 mm. The diameter, shape, and arrangement of the gas outlet holes 21b may be changed as appropriate.

[0121] The plate 22 is a member that can be attached to and detached from the cylindrical electrode 21 via an insulating member 24. When the plate 22 is attached to the cylindrical electrode 21 via the insulating member 24, the formation space of the reaction chamber 20 is closed (also referred to as a closed state). When the plate 22 is detached from the cylindrical electrode 21, the formation space of the reaction chamber 20 is opened (also referred to as an open state). In other words, by attaching and detaching the plate 22, the state of the reaction chamber 20 can be selectively switched between an open state and a closed state. For example, when the formation space of the reaction chamber 20 is opened, the support 31 can be inserted and removed from the formation space of the reaction chamber 20. The plate 22 is made of, for example, the same or similar conductive material as the substrate 10a. The insulating member 24 interposed between the plate 22 and the cylindrical electrode 21 serves to reduce the occurrence of arc discharge between the plate 22 and the cylindrical electrode 21. A shield plate 26 is attached to the underside of the plate 22. This reduces the formation of a deposition film on the plate 22. The deposition shield 26 may be interposed between the plate 22 and the cylindrical electrode 21. The deposition shield 26 may be made of the same or similar conductive material as the substrate 10a. The deposition shield 26 may be a member that can be attached to and detached from the plate 22.

[0122] The plate 23 serves as the base of the reaction chamber 20. The plate 23 is made of, for example, the same or similar conductive material as the substrate 10a. An insulating member 25 may be interposed between the plate 23 and the cylindrical electrode 21. The presence of this insulating member 25 reduces the occurrence of arc discharge between the cylindrical electrode 21 and the plate 23.

[0123] Each of the insulating members 24, 25 may be made of one or more of the following materials: glass, inorganic insulating materials (also referred to as inorganic insulating materials), and synthetic resin insulating materials (also referred to as synthetic resin insulating materials). Examples of the glass material include borosilicate glass, soda glass, and / or heat-resistant glass. Examples of the inorganic insulating material include ceramics, quartz, and / or sapphire. Examples of the synthetic resin insulating material include fluororesins such as polytetrafluoroethylene, polycarbonate, polyethylene terephthalate, polyester, polyethylene, polypropylene, polystyrene, polyamide, vinylon, epoxy, Mylar, and / or polyether ether ketone. The material of the insulating member 25 may be any material that has insulating properties, sufficient heat resistance at the operating temperature, and minimal outgassing even in a vacuum.

[0124] The plate 23 and the insulating member 25 are provided with gas exhaust ports 23a, 25a and a pressure gauge 27. The gas exhaust ports 23a, 25a serve to exhaust gas from inside the reaction chamber 20. The gas exhaust ports 23a, 25a are connected to an exhaust mechanism 80. The pressure gauge 27 can monitor the pressure inside the reaction chamber 20. Various known pressure gauges can be used as the pressure gauge 27.

[0125] <<Support mechanism 30>> The support mechanism 30 supports the substrates 10a and also serves as a first conductor for generating glow discharge. The support mechanism 30 includes a support 31, conductive supports 32, and an insulating material 33. In the example of FIG. 12, the support mechanism 30 has a length (dimension) sufficient to support two substrates 10a. The support mechanism 30 may have a configuration in which the support 31 is detachably attached to the conductive supports 32. This allows the two substrates 10a to be inserted and removed from the formation space of the reaction chamber 20 by inserting and removing the support 31 supporting the two substrates 10a into and from the formation space of the reaction chamber 20 without touching the surfaces of the two substrates 10a supported by the support mechanism 30.

[0126] The support 31 is a hollow member having a flange 31a at its lower end, and is entirely made of, for example, the same or similar conductive material as the base 10a.

[0127] The conductive pillar 32 is a cylindrical member having a conductive plate 32a. The entire conductive pillar 32 is made of, for example, the same or similar conductive material as the base 10a. The upper end of the conductive pillar 32 is in contact with the inner wall surface of the support 31.

[0128] The insulating material 33 serves to ensure electrical insulation between the conductive support posts 32 and the plate 23. The insulating material 33 is interposed between the conductive support posts 32 and the plate 23 approximately in the center of the reaction chamber 20.

[0129] <<DC voltage supply mechanism 40>> The DC voltage supply mechanism 40 is a mechanism that supplies a DC voltage to the conductive support columns 32. The DC voltage supply mechanism 40 includes a DC power source 41 and a control unit .

[0130] The DC power supply 41 serves to generate a DC voltage to be applied to the conductive support 32. The DC power supply 41 is connected to the conductive support 32 via the conductive plate 32a.

[0131] The control unit 42 has a role of controlling the operation of the DC power supply 41. The control unit 42 is connected to the DC power supply 41. For example, by controlling the operation of the DC power supply 41, the control unit 42 can apply a pulsed DC voltage to the support 31 via the conductive support 32 by the DC power supply 41.

[0132] <<Temperature control mechanism 50>> The temperature control mechanism 50 has a role of controlling the temperature of the substrate 10a and includes a ceramic pipe 51 and a heater 52.

[0133] The ceramic pipe 51 has the role of ensuring insulation and thermal conductivity. The ceramic pipe 51 is housed inside the conductive support 32.

[0134] The heater 52 serves to heat the substrate 10a. The heater 52 is housed inside the conductive support 32. The temperature of the substrate 10a can be controlled, for example, by on / off control of the heater 52 in response to the results of monitoring the temperature of the support 31 or the conductive support 32. The temperature of the support 31 or the conductive support 32 can be monitored by a thermocouple (not shown) attached to the support 31 or the conductive support 32. The temperature of the substrate 10a is maintained at a predetermined temperature (also referred to as a predetermined temperature) in a temperature range of, for example, 200 degrees Celsius (200°C) or higher and 400 degrees Celsius (400°C) or lower. The heater 52 may be, for example, a nichrome wire or a cartridge heater.

[0135] <<Rotation mechanism 60>> The rotation mechanism 60 serves to rotate the support 31. The rotation mechanism 60 has a rotary motor 61, a rotary lead-in terminal 62, an insulating shaft member 63, and an insulating flat plate 64. When the deposition films that will become the layers of the photosensitive layer 10b are formed on the base 10a while the support 31 supporting the base 10a is rotated by the rotation mechanism 60, the components of the raw material gas decomposed by glow discharge can be deposited approximately evenly on the outer periphery of the base 10a.

[0136] The rotary motor 61 has a role of applying a rotational force to the base body 10a. The rotary motor 61 can rotate the base body 10a at a constant rotation speed, for example, in the range of 1 revolution per minute (rpm) or more and 10 rpm or less. Various known rotary motors can be used as the rotary motor 61.

[0137] Rotary feedthrough 62 has the role of transmitting the rotational force generated by rotary motor 61 to insulating shaft member 63 while maintaining a predetermined degree of vacuum inside reaction chamber 20. A vacuum seal such as an oil seal or a mechanical seal having a double- or triple-structured rotary shaft can be applied to rotary feedthrough 62.

[0138] The insulating shaft member 63 and the insulating flat plate 64 have the role of transmitting the rotational force from the rotary motor 61 via the rotation lead-in terminal 62 to the support mechanism 30 while maintaining an insulating state between the support mechanism 30 and the plate 22. The insulating shaft member 63 and the insulating flat plate 64 are made of, for example, the same or similar insulating material as the insulating member 25.

[0139] The insulating plate 64 serves to reduce the adhesion of foreign matter, such as dust or dirt, that falls from the shielding plate 26 attached to the underside of the plate 22 to the base 10a when the plate 22 is removed from the cylindrical electrode 21. The presence of the insulating plate 64 can reduce the occurrence of abnormal discharge due to the adhesion of foreign matter to the base 10a. This can reduce the occurrence of defects in the deposited films that become the layers of the photosensitive layer 10b formed on the base 10a.

[0140] <<Gas supply mechanism 70>> The gas supply mechanism 70 includes a plurality of source gas tanks 71, 72, 73, and 74, a plurality of pipes 71a, 72a, 73a, and 74a, a plurality of valves 71b, 72b, 73b, 74b, 71c, 72c, 73c, and 74c, and a plurality of mass flow controllers 71d, 72d, 73d, and 74d. The gas supply mechanism 70 is connected to the inside of the cylindrical electrode 21 via a pipe 75 and a gas inlet 21a. For example, the source gas tank 71 is connected to the gas inlet 21a via a pipe 71a and a pipe 75, and valves 71b and 71c and a mass flow controller 71d are provided in the pipe 71a. For example, the source gas tank 72 is connected to the gas inlet 21a via a pipe 72a and a pipe 75, and valves 72b and 72c and a mass flow controller 72d are provided in the pipe 72a. For example, the source gas tank 73 is connected to the gas inlet 21a via pipes 73a and 75, and valves 73b and 73c and a mass flow controller 73d are provided in the pipe 73a. For example, the source gas tank 74 is connected to the gas inlet 21a via pipes 74a and 75, and valves 74b and 74c and a mass flow controller 74d are provided in the pipe 74a.

[0141] Each of the source gas tanks 71, 72, 73, and 74 is a tank filled with a source gas, such as monosilane gas, hydrogen gas, diborane gas, methane gas, nitrogen gas, or nitric oxide gas.

[0142] The plurality of valves 71b, 72b, 73b, 74b, 71c, 72c, 73c, 74c and the plurality of mass flow controllers 71d, 72d, 73d, 74d can adjust the amount of each source gas introduced per unit time, and the ratio and pressure of the source gases introduced into the reaction chamber 20. Note that in the gas supply mechanism 70, the type of source gas to be filled in each source gas tank 71, 72, 73, 74 and / or the number of the source gas tanks 71, 72, 73, 74 may be selected appropriately depending on the type and / or composition of a film to be formed on the substrate 10a.

[0143] <<Exhaust mechanism 80>> The exhaust mechanism 80 has a role of exhausting gas inside the reaction chamber 20 to the outside through the gas exhaust ports 23a and 25a. The exhaust mechanism 80 has, for example, a mechanical booster pump 81 and a rotary pump 82. The operation of these pumps 81 and 82 may be controlled according to the monitoring results of the pressure inside the reaction chamber 20 by the pressure gauge 27. In other words, the exhaust mechanism 80 can maintain the inside of the reaction chamber 20 at a predetermined vacuum state and set the pressure of the gas inside the reaction chamber 20 to a target value based on the monitoring results of the pressure inside the reaction chamber 20 by the pressure gauge 27. The pressure of the gas inside the reaction chamber 20 is set to, for example, 1 Pascal (Pa) or more and 100 Pa or less.

[0144] <1-3. Method for forming a photoreceptor layer using a film forming device> A method for forming the photoreceptor layer 10b using the film forming apparatus 300 will be described.

[0145] First, in the film formation apparatus 300, the plate 22 is detached from the cylindrical electrode 21 to open the formation space of the reaction chamber 20. A support 31 supporting a plurality of substrates 10a (two in FIG. 12) is set in the formation space of the reaction chamber 20. Then, the plate 22 is attached to the cylindrical electrode 21 via the insulating member 24 to close the formation space of the reaction chamber 20.

[0146] Here, the two bases 10a are supported by the support 31 by stacking the lower dummy base D1, the first base 10a, the middle dummy base D2, the second base 10a, and the upper dummy base D3 in this order on the flange portion 31a of the support 31. Each of the dummy bases D1, D2, and D3 may be made of, for example, a member having an overall conductive configuration, or a member having a conductive film formed on the surface of an insulator. Each of the dummy bases D1, D2, and D3 may be made of a member having the same or similar configuration as the base 10a. In other words, each of the dummy bases D1, D2, and D3 may be made of, for example, a cylindrical member.

[0147] The lower dummy substrate D1 mainly serves to adjust the position of the substrate 10a in the vertical direction. The intermediate dummy substrate D2 mainly serves to reduce the occurrence of non-uniform discharge between two adjacent substrates 10a in the vertical direction. For example, if the vertical length of the intermediate dummy substrate D2 is set to 1 centimeter (cm) or more, the occurrence of non-uniform discharge between the two substrates 10a can be sufficiently reduced. The corners of the outer peripheral surface of the intermediate dummy substrate D2 may be curved, for example, with a curvature radius of 0.5 mm or more, or may be chamfered. The axial and radial lengths of the portions of the intermediate dummy substrate D2 removed by chamfering may be set to 0.5 mm or more. The upper dummy substrate D3 mainly serves to reduce the formation of a deposited film on the support 31. The upper dummy substrate D3 is arranged so that its upper end protrudes above the top of the support 31.

[0148] Next, the temperature control mechanism 50 controls the temperature of the substrate 10a to be maintained at a predetermined temperature, and the exhaust mechanism 80 reduces the pressure inside the reaction chamber 20. The temperature of the substrate 10a is controlled by first raising the temperature of the substrate 10a to a temperature close to the predetermined temperature using heat from the heater 52, and then maintaining the temperature of the substrate 10a at the predetermined temperature by controlling the on / off of the heater 52. The temperature of the substrate 10a is appropriately set depending on the type and composition of the film to be formed on the surface of the substrate 10a. For example, when forming an amorphous silicon (a-Si)-based film, the temperature of the substrate 10a is set to a temperature range of 250°C or higher and 300°C or lower. Furthermore, the temperature of the substrate 10a may be set lower during the formation of the gradient layer 104 and the surface layer 105 than during the formation of the lower blocking layer 101, the photoconductive layer 102, and the upper blocking layer 103. In this case, when the upper blocking layer 103 is formed, the temperature of the substrate 10a may be gradually lowered over time.

[0149] The pressure inside the reaction chamber 20 is reduced by monitoring the pressure inside the reaction chamber 20 with the pressure gauge 27 and controlling the operation of the pumps 81 and 82 based on the results of this monitoring to discharge gas from the reaction chamber 20 through the gas discharge ports 23a and 25a. Note that, for example, before the source gas is introduced into the reaction chamber 20, if the pressure inside the reaction chamber 20 is 1×10 -3 The pressure is reduced to about Pa.

[0150] Next, while maintaining the temperature of the substrate 10a at a predetermined temperature and reducing the pressure inside the reaction chamber 20 to a predetermined pressure (also referred to as a "predetermined pressure"), the gas supply mechanism 70 supplies the source gas into the reaction chamber 20, and a pulsed DC voltage is applied between the cylindrical electrode 21 and the support 31 using the DC voltage supply mechanism 40. This generates a glow discharge between the cylindrical electrode 21 and the support 31. In other words, a glow discharge occurs between the cylindrical electrode 21 and the substrate 10a. The source gas is decomposed by the glow discharge, and the decomposed components of the source gas are deposited on the surface of the substrate 10a. Here, the exhaust mechanism 80 controls the operation of the pumps 81 and 82 based on the results of monitoring the pressure inside the reaction chamber 20 using the pressure gauge 27, thereby maintaining the pressure inside the reaction chamber 20 within a predetermined pressure range. The predetermined pressure range is set, for example, to be equal to or higher than 1 Pa and equal to or lower than 100 Pa. That is, the pressure inside the reaction chamber 20 is maintained within a predetermined range by the mass flow controllers 71d, 72d, 73d, and 74d in the gas supply mechanism 70 and the pumps 81 and 82 in the exhaust mechanism 80.

[0151] The supply of source gas into reaction chamber 20 is performed by appropriately controlling the open / close states of valves 71b, 72b, 73b, 74b, 71c, 72c, 73c, and 74c while controlling mass flow controllers 71d, 72d, 73d, and 74d. Source gases from multiple source gas tanks 71, 72, 73, and 74 are introduced into cylindrical electrode 21 at desired ratios and flow rates via pipes 71a, 72a, 73a, 74a, and 75 and gas inlet 21a. The source gas introduced into cylindrical electrode 21 is blown toward substrate 10a through multiple gas outlet holes 21b. The ratios and flow rates (also referred to as gas flow rates) of the plurality of source gases introduced into the reaction chamber 20 are appropriately changed by the plurality of valves 71b, 72b, 73b, 74b, 71c, 72c, 73c, and 74c and the plurality of mass flow controllers 71d, 72d, 73d, and 74d. Here, the flow rates (gas flow rates) of the respective source gases correspond to the amounts of the respective source gases introduced into the reaction chamber 20 per unit time.

[0152] Furthermore, for example, when the cylindrical electrode 21 is grounded, the application of a pulsed DC voltage between the cylindrical electrode 21 and the support 31 is performed in such a way that the potential of the support 31 becomes a negative pulsed DC potential V1 that is equal to or greater than −3000 V and equal to or less than −50 V, or equal to or greater than −3000 V and equal to or less than −500 V. For example, when the cylindrical electrode 21 is connected to a reference power supply (not shown), the application of a pulsed DC voltage between the cylindrical electrode 21 and the support 31 is performed in such a way that the potential of the support 31 generates a target potential difference ΔV relative to the reference potential, which is a potential V2 supplied from the reference power supply. The target potential difference ΔV is set, for example, to a range of −3000 V to −50 V. Here, when a negative pulsed DC voltage is applied to the support 31 (i.e., the substrate 10a), the potential V2 supplied from the reference power supply is set, for example, to a range of −1500 V to 1500 V. The control unit 42 controls the DC power supply 41 so that the frequency (1 / Tc1 [seconds]) of the DC voltage is 300 kHz or less and the duty ratio is 0.2 or more and 0.9 or less. Here, the duty ratio is defined as the ratio of the potential difference generation time Te1 to the time taken up by the potential difference generation time Te1, where Tc1 is the duration of one cycle of the pulsed DC voltage and Te1 is the period during which a target potential difference ΔV is generated between the cylindrical electrode 21 and the support 31 (also referred to as the potential difference generation time). The time Tc1 of one cycle is the time from the moment a potential difference of the DC voltage is generated between the base 10a and the cylindrical electrode 21 to the moment the next potential difference of the DC voltage is generated. For example, a duty ratio of 0.2 means that the potential difference generation time Te1 occupies 20% of the time Tc1 of one cycle when the pulsed DC voltage is applied.

[0153] In this manner, the lower blocking layer 101, the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105 are formed on the surface of the substrate 10a in this order. Here, for example, the lower blocking layer 101, the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105 can be formed in this order by changing the ratio of the multiple source gases supplied into the reaction chamber 20 while maintaining the generation of glow discharge by applying a pulsed DC voltage.

[0154] FIG. 13 is a diagram showing an example of temporal changes in the introduction amount (gas flow rate) per unit time of each raw material gas introduced into the reaction chamber 20 when forming the photosensitive layer 10b according to a first example of the first embodiment. FIG. 14 is a diagram showing an example of temporal changes in the introduction amount (gas flow rate) per unit time of each raw material gas introduced into the reaction chamber 20 when forming the photosensitive layer 10b according to a second example of the first embodiment. FIG. 15 is a diagram showing an example of temporal changes in the introduction amount (gas flow rate) per unit time of each raw material gas introduced into the reaction chamber 20 when forming the photosensitive layer 10bA according to a first reference example. FIG. 16 is a diagram showing an example of temporal changes in the introduction amount (gas flow rate) per unit time of each raw material gas introduced into the reaction chamber 20 when forming the photosensitive layer 10bA according to a second reference example.

[0155] 13 to 16, the horizontal axis represents the time required to form the photosensitive layers 10b and 10bA, and the vertical axis represents the amount (gas flow rate) of each of the source gases introduced into the reaction chamber 20 per unit time. The gas flow rates of the source gases correspond to the flow rates of the source gases in the mass flow controllers 71d, 72d, 73d, and 74d. In each of FIGS. 13 to 16, the flow rates of the silicon-based gases are indicated by thick dashed lines, the flow rates of the nitrogen oxide gases are indicated by thick lines, the flow rates of the carbon-based gases are indicated by thick broken lines, and the flow rates of the boron-based gases are indicated by thin solid lines. The silicon-based gas may be, for example, one or more silane-based gases selected from the group consisting of monosilane gas and disilane gas. The nitrogen oxide gas may be, for example, one or more nitric oxide gases and nitrous oxide gas. The carbon-based gas may be, for example, one or more hydrocarbon-based gases selected from the group consisting of methane gas, ethylene gas, and acetylene gas, and the boron-based gas may be, for example, diborane gas as a boron hydride gas.

[0156] Although the gas flow rate of the boron-based gas is actually much smaller than the gas flow rates of the silicon-based gas, nitrogen oxide gas, and carbon-based gas, for convenience, the gas flow rate of the boron-based gas is shown larger than the actual flow rate in Figures 13 to 16. In each of Figures 13 to 16, the photoconductive layer 102, the upper blocking layers 103 and 103A, the gradient layer 104, and the surface layer 105 are each indicated by a reference symbol. In each of Figures 13 and 14, the first region 103a and the second region 103b of the upper blocking layer 103 are also each indicated by a reference symbol.

[0157] A method for manufacturing the photoreceptor 10 according to the first embodiment by forming the photoreceptor layer 10b on the substrate 10a will be described with reference to FIGS.

[0158] The method for manufacturing the photoreceptor 10 according to the first embodiment includes steps 1, 2, 3, 4, and 5. In this case, steps 2, 3, 4, and 5 may be performed consecutively in sequence in the reaction chamber 20 using a glow discharge decomposition method, which is a type of PECVD method. For example, when forming the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105 using the glow discharge decomposition method, the gas flow rates and ratios of the multiple source gases introduced into the reaction chamber 20 are continuously changed while maintaining the generation of glow discharge by applying a pulsed DC voltage.

[0159] In the first step, a lower blocking layer 101 is formed on a conductive substrate 10a in a reaction chamber 20. The lower blocking layer 101 contains amorphous silicon as a main component and an n-type dopant. In the example of FIGS. 13 and 14, the first step is performed from time t0 to time t2. In this first step, for example, a silicon-based gas and a nitrogen oxide gas are introduced into the reaction chamber 20. Here, for example, the silicon-based gas is introduced as the main source gas, and nitrogen oxide gas is also introduced into the reaction chamber 20. More specifically, for example, from time t0 to time t1, the gas flow rates of the silicon-based gas and the nitrogen oxide gas are kept constant. Furthermore, for example, from time t1 to time t2, the gas flow rate of the silicon-based gas is continuously increased, and the gas flow rate of the nitrogen oxide gas is continuously decreased to zero or approximately zero.

[0160] During the period from time t0 to time t1, the gas flow rate of the silicon-based gas may be kept substantially constant or may be slightly increased or decreased rather than being kept completely constant.Furthermore, during the period from time t0 to time t1, the gas flow rate of the nitrogen oxide gas may be kept substantially constant or may be slightly increased or decreased rather than being kept completely constant.

[0161] During the period from time t1 to time t2, the gas flow rate of the silicon-based gas may be increased monotonically over time, or may be increased overall with slight increases and decreases. In other words, during the period from time t1 to time t2, the gas flow rate of the silicon-based gas may be increased continuously or almost continuously over time. During the period from time t1 to time t2, the gas flow rate of the silicon-based gas may be increased at a constant or approximately constant rate over time, or may be increased sequentially at two or more rates. Note that during the period from time t1 to time t2, there may be a time period during which the gas flow rate of the silicon-based gas is maintained at a constant or approximately constant rate.

[0162] Furthermore, during the period from time t1 to time t2, the flow rate of nitrogen oxide gas may be decreased monotonically over time, or may be decreased overall with slight increases and decreases. In other words, during the period from time t1 to time t2, the flow rate of nitrogen oxide gas may be decreased continuously or almost continuously over time. During the period from time t1 to time t2, the flow rate of nitrogen oxide gas may be decreased at a constant or approximately constant rate over time, or may be decreased sequentially at two or more rate increments. Note that during the period from time t1 to time t2, there may be a time period during which the flow rate of nitrogen oxide gas is maintained at a constant or approximately constant rate.

[0163] In the second step, a photoconductive layer 102 is formed on the lower blocking layer 101 in the reaction chamber 20. The photoconductive layer 102 mainly contains amorphous silicon. In this second step, a silicon-based gas is introduced into the reaction chamber 20. In the examples of FIGS. 13 and 14, the second step is performed during the period from time t2 to time t3. More specifically, for example, the gas flow rate of the silicon-based gas is kept constant during the period from time t2 to time t3. Note that in the second step, the gas flow rate of the silicon-based gas does not need to be kept completely constant, but may be approximately constant or may be slightly increased or decreased.

[0164] In the third step, an upper blocking layer 103 is formed on the photoconductive layer 102 in the reaction chamber 20. The upper blocking layer 103 mainly contains amorphous silicon and may also contain nitrogen, oxygen, carbon, and boron as a p-type dopant. In the examples of FIGS. 13 and 14, the third step is performed during the period from time t3 to time t5. The third step includes a step 3A and a step 3B performed after the step 3A. In the examples of FIGS. 13 and 14, the step 3A is performed during the period from time t3 to time t4, and the step 3B is performed during the period from time t4 to time t5.

[0165] In step 3A, for example, the amount (gas flow rate) of a silicon-based gas (e.g., monosilane gas) introduced per unit time into the reaction chamber 20 is decreased, while the amount (gas flow rate) of a boron-based gas (e.g., diborane gas) and a nitrogen oxide gas (e.g., nitric oxide gas) introduced per unit time into the reaction chamber 20 is increased. This results in the formation of a first region 103a in which, with increasing distance from the photoconductive layer 102, the silicon content decreases, the contents of boron, nitrogen, and oxygen as Group 13 elements increase, and the carbon content does not increase. As a result, the change in refractive index near the interface between the photoconductive layer 102 and the upper blocking layer 103 in the thickness direction of the photoreceptor layer 10b is significantly reduced. In other words, the occurrence of a sudden change in refractive index near the interface between the photoconductive layer 102 and the upper blocking layer 103 in the thickness direction of the photoreceptor layer 10b is reduced. This reduces the occurrence of light reflection at the interface between the upper blocking layer 103 and the photoconductive layer 102. In other words, it reduces the occurrence of a clear optical interface between the upper blocking layer 103 and the photoconductive layer 102. In step 3A, the gas flow rates of the boron-based gas and the nitrogen oxide gas into the reaction chamber 20 may be increased from zero or may be increased from a very small gas flow rate of approximately zero.

[0166] Here, during the period of step 3A, the gas flow rates of the boron-based gas and the nitrogen oxide gas may each be increased monotonically over time, or may be increased overall with slight increases and decreases. In other words, during the period of step 3A, the gas flow rates of the boron-based gas and the nitrogen oxide gas may each be increased continuously or almost continuously over time. During the period of step 3A, the gas flow rates of the boron-based gas and the nitrogen oxide gas may each be increased at a constant or approximately constant rate, or may be increased sequentially at two or more rates. Note that during the period of step 3A, there may be a time period during which the gas flow rates of the boron-based gas and the nitrogen oxide gas are each maintained at a constant or approximately constant rate.

[0167] Furthermore, during the period of the 3A step, the gas flow rate of the silicon-based gas may be decreased monotonically over time, or may be decreased overall with slight increases and decreases. In other words, during the period of the 3A step, the gas flow rate of the silicon-based gas may be decreased continuously or almost continuously over time. During the 3A step, the gas flow rate of the silicon-based gas may be decreased at a constant or approximately constant rate over time, or may be decreased sequentially at two or more rates. Note that during the 3A step, there may be a time period during which the gas flow rate of the silicon-based gas is maintained at a constant or approximately constant rate.

[0168] In step 3B, for example, the gas flow rate of the carbon-based gas into the reaction chamber 20 is increased while the gas flow rates of the boron-based gas and the nitrogen oxide gas into the reaction chamber 20 are decreased. In step 3B, for example, the gas flow rate of the silicon-based gas into the reaction chamber 20 may be decreased. In step 3B, for example, the gas flow rates of the boron-based gas and the nitrogen oxide gas into the reaction chamber 20 may be decreased to zero or to a very small gas flow rate of approximately zero. In step 3B, for example, the gas flow rate of the carbon-based gas into the reaction chamber 20 may be increased from zero or to a very small gas flow rate of approximately zero. As a result, the second region 103b is formed, which has a tendency that the content rates of the Group 13 elements of boron, nitrogen, and oxygen decrease and the content rate of carbon increases toward the gradient layer 104. As a result, the occurrence of abrupt changes in the refractive index in the upper blocking layer 103 in the thickness direction of the photoreceptor layer 10b is reduced. This reduces the occurrence of light reflection in the upper blocking layer 103. In other words, the occurrence of clear optical interfaces in the upper blocking layer 103 is reduced. This reduces the occurrence of light reflection in the optical path from the surface layer 105, the gradient layer 104, and the upper blocking layer 103 to the photoconductive layer 102.

[0169] Here, during the period of step 3B, the gas flow rates of the boron-based gas and the nitrogen oxide gas may each be decreased monotonically over time, or may be decreased overall with slight increases and decreases. In other words, during the period of step 3B, the gas flow rates of the boron-based gas and the nitrogen oxide gas may each be decreased continuously or almost continuously over time. During the period of step 3B, the gas flow rates of the boron-based gas and the nitrogen oxide gas may each be decreased at a constant or approximately constant rate over time, or may be decreased sequentially at two or more rates. Note that during the period of step 3B, there may be a time period during which the gas flow rates of the boron-based gas and the nitrogen oxide gas are each maintained at a constant or approximately constant rate.

[0170] Furthermore, during the period of step 3B, the gas flow rate of the carbon-based gas may be increased monotonically over time, or may be increased overall with slight increases and decreases. In other words, during the period of step 3B, the gas flow rate of the carbon-based gas may be increased continuously or almost continuously over time. During the period of step 3B, the gas flow rate of the carbon-based gas may be increased at a constant or almost constant rate over time, or may be increased sequentially at two or more rate increments. Note that during the period of step 3B, there may be a time period during which the gas flow rate of the carbon-based gas is maintained at a constant or almost constant rate. During the period of step 3B, the gas flow rate of the silicon-based gas may be decreased monotonically over time, or may be decreased overall with slight increases and decreases. In other words, during the period of step 3B, the gas flow rate of the silicon-based gas may be decreased continuously or almost continuously over time. During the period of step 3B, the gas flow rate of the silicon-based gas may be decreased at a constant or approximately constant rate over time, or may be decreased sequentially at two or more rates. Note that during the period of step 3B, there may be a time period during which the gas flow rate of the silicon-based gas is maintained at a constant or approximately constant rate.

[0171] Here, for example, there may be a period of several seconds to several tens of seconds between Step 3A and Step 3B. During this period, for example, the gas flow rates of the source gases may be maintained constant. Here, the gas flow rates of the source gases may not be kept completely constant, but may be approximately constant or may be slightly increased or decreased.

[0172] Here, for example, in step 3B, the timing at which the flow rates of the boron-based gas and the nitrogen oxide gas into the reaction chamber 20 begin to decrease is defined as the first timing. The timing at which the flow rate of the carbon-based gas into the reaction chamber 20 begins to increase is defined as the second timing. In this case, the first and second timings may be simultaneous or may be offset by several seconds to several tens of seconds. If the first and second timings are simultaneous, the occurrence of abrupt changes in the refractive index in the upper blocking layer 103 in the thickness direction of the photosensitive layer 10b is further reduced. This further reduces the occurrence of light reflection in the upper blocking layer 103. In other words, the occurrence of a clear optical interface in the upper blocking layer 103 is further reduced. This further reduces the occurrence of light reflection in the optical path from the surface layer 105, the gradient layer 104, and the upper blocking layer 103 to the photoconductive layer 102.

[0173] In the fourth step, a gradient layer 104 is formed on the upper blocking layer 103 in the reaction chamber 20. The gradient layer 104 is primarily composed of an amorphous material containing silicon and carbon. In the examples of FIGS. 13 and 14, the fourth step is performed from time t5 to time t6. In the fourth step, the flow rate of a silicon-based gas (e.g., monosilane gas) into the reaction chamber 20 is decreased while the flow rate of a carbon-based gas (e.g., methane gas) into the reaction chamber 20 is increased. This results in the formation of a gradient layer 104 in which the silicon content decreases and the carbon content increases with increasing distance from the upper blocking layer 103. In the example of FIG. 13, the flow rate of the silicon-based gas into the reaction chamber 20 is decreased to zero in the fourth step. In the example of FIG. 14, the flow rate of the silicon-based gas into the reaction chamber 20 is not decreased to zero in the fourth step.

[0174] Here, during the fourth step, the gas flow rate of the silicon-based gas may be decreased monotonically over time, or may be decreased overall with slight increases and decreases. In other words, during the fourth step, the gas flow rate of the silicon-based gas may be decreased continuously or almost continuously over time. During the fourth step, the gas flow rate of the silicon-based gas may be decreased at a constant or approximately constant rate over time, or may be decreased sequentially at two or more rates. Note that during the fourth step, there may be a time period during which the gas flow rate of the silicon-based gas is maintained at a constant or approximately constant rate.

[0175] Furthermore, during the fourth step, the gas flow rate of the carbon-based gas may be increased monotonically over time, or may be increased overall with slight increases and decreases. In other words, during the fourth step, the gas flow rate of the carbon-based gas may be increased continuously or almost continuously over time. During the fourth step, the gas flow rate of the carbon-based gas may be increased at a constant or approximately constant rate over time, or may be increased sequentially at two or more rate increments. Note that during the fourth step, there may be a time period during which the gas flow rate of the carbon-based gas is maintained at a constant or approximately constant rate.

[0176] In the fifth step, a surface layer 105 is formed on the gradient layer 104 in the reaction chamber 20. The surface layer 105 mainly contains amorphous carbon or mainly contains an amorphous material containing carbon and silicon. In the examples of FIGS. 13 and 14, the fifth step is performed during the period from time t6 to time t7. In the fifth step, a carbon-based gas (e.g., methane gas) may be introduced into the reaction chamber 20, or a silicon-based gas (e.g., monosilane gas) may be introduced into the reaction chamber 20 while introducing a carbon-based gas into the reaction chamber 20.

[0177] Here, in the fifth step, for example, if a carbon-based gas is introduced into the reaction chamber 20 without introducing a silicon-based gas, a surface layer 105 containing amorphous carbon as a main component is formed. In the example of FIG. 13, in the fifth step, the gas flow rate of the silicon-based gas into the reaction chamber 20 is set to zero. Then, for example, during the period from time t6 to time t7, the gas flow rate of the carbon-based gas is kept constant. In this case, during the fifth step, the gas flow rate of the carbon-based gas does not need to be kept completely constant, but may be kept approximately constant or may be slightly increased or decreased.

[0178] Furthermore, if both a carbon-based gas and a silicon-based gas are introduced into the reaction chamber 20 in the fifth step, a surface layer 105 containing an amorphous material containing carbon and silicon as a main component is formed. In the example of FIG. 14 , a carbon-based gas is introduced into the reaction chamber 20 as the main source gas, and a silicon-based gas is also introduced in the fifth step. More specifically, for example, the gas flow rates of the carbon-based gas and the silicon-based gas are kept constant during the period from time t6 to time t7. The ratio of the gas flow rates of the carbon-based gas and the silicon-based gas can be set depending on the ratio of the atomic concentration of carbon to the atomic concentration of silicon in the amorphous material to be formed, the ease of decomposition of the carbon-based gas in glow discharge decomposition, and the ease of decomposition of the silicon-based gas in glow discharge decomposition. During the fifth step, the gas flow rates of the carbon-based gas and the silicon-based gas may not be kept completely constant, but may be approximately constant or slightly increased or decreased.

[0179] In this manner, a photoreceptor 10 can be manufactured that includes a photoreceptor layer 10b in which the ratio of constituent elements changes gradually, rather than suddenly, near the interfaces between the photoconductive layer 102, the upper blocking layer 103, the gradient layer 104, and the surface layer 105, and in the upper blocking layer 103, the gradient layer 104, and the surface layer 105. This reduces the occurrence of abrupt changes in refractive index in the thickness direction of the photoreceptor layer 10b near the interface between the photoconductive layer 102 and the upper blocking layer 103, near the interface between the upper blocking layer 103 and the gradient layer 104, and near the interface between the gradient layer 104 and the surface layer 105. This reduces the occurrence of light reflection in the optical path that leads to the photoconductive layer 102 via the surface layer 105, the gradient layer 104, and the upper blocking layer 103. Therefore, for example, when the photoreceptor 10 is mounted in the image forming apparatus 100, even if the upper blocking layer 103, the inclined layer 104, and the surface layer 105 each have different thicknesses depending on the location (thickness variations), the occurrence of a defect in which the intensity of exposure light incident on the photoconductive layer 102 varies depending on the location due to optical interference when exposure light of the same intensity is irradiated onto the photoreceptor layer 10b can be reduced. As a result, unevenness in sensitivity in the photoreceptor 10 can be reduced.

[0180] Incidentally, as shown in Fig. 15, a photosensitive layer 10bA according to the first reference example can be formed on the substrate 10a by changing the gas flow rates of the respective raw material gases introduced into the reaction chamber 20 over time. Also, as shown in Fig. 16, a photosensitive layer 10bA according to the second reference example can be formed on the substrate 10a by changing the gas flow rates of the respective raw material gases introduced into the reaction chamber 20 over time.

[0181] More specifically, as shown in Figures 15 and 16, a process (time T0 to time T2) identical to the first process (time t0 to time t2) described above, and a process (time T2 to time T3) identical to the second process (time t2 to time t3) described above are successively performed in the order described, thereby forming a lower blocking layer 101 and a photoconductive layer 102 in sequence on the substrate 10a.

[0182] At time T3, the generation of glow discharge caused by the application of the pulsed DC voltage is stopped for a predetermined time, and the gas flow rate of the silicon-based gas (e.g., monosilane gas) into the reaction chamber 20 is reduced, and the gas flow rates of the boron-based gas (e.g., diborane gas) and nitrogen oxide gas (e.g., nitric oxide gas) into the reaction chamber 20 are increased (also referred to as a standby state). The predetermined time is set, for example, in the range of several minutes to several tens of minutes. At time T3, during the standby state for the predetermined time, no glow discharge is generated in the reaction chamber 20, and therefore no film formation is taking place. In other words, after the predetermined time has elapsed at time T3, the standby state is released, and the generation of glow discharge caused by the application of the pulsed DC voltage is resumed. For this reason, each of FIGS. 15 and 16 shows the time during which the photosensitive layer 10bA is formed, excluding the predetermined standby time.

[0183] Next, during the period from time T3 to time T4 when the standby state is released, the gas flow rate of the silicon-based gas into the reaction chamber 20 is reduced, while the gas flow rates of the boron-based gas and nitrogen oxide gas into the reaction chamber 20 are reduced, and the gas flow rate of the carbon-based gas (e.g., methane gas) into the reaction chamber 20 is increased. Here, for example, the gas flow rates of the boron-based gas and nitrogen oxide gas into the reaction chamber 20 may be reduced to zero or to a very small gas flow rate of approximately zero. As a result, the upper blocking layer 103A is formed on the photoconductive layer 102.

[0184] Next, during the period from time T4 to time T5, the gas flow rate of the silicon-based gas into the reaction chamber 20 is decreased while the gas flow rate of the carbon-based gas into the reaction chamber 20 is increased. As a result, the graded layer 104 is formed on the upper blocking layer 103A. Here, in the example of FIG. 15, the gas flow rate of the silicon-based gas into the reaction chamber 20 is decreased to zero. In the example of FIG. 16, the gas flow rate of the silicon-based gas into the reaction chamber 20 is not decreased to zero.

[0185] Next, during the period from time T5 to time T6, a surface layer 105 is formed on the gradient layer 104. Here, for example, as shown in FIG. 15 , if a carbon-based gas is introduced into the reaction chamber 20 without introducing a silicon-based gas during the period from time T5 to time T6, a surface layer 105 containing amorphous carbon as a main component is formed. In the example of FIG. 15 , the gas flow rate of the carbon-based gas is constant during the period from time T5 to time T6. Furthermore, for example, as shown in FIG. 16 , if both a carbon-based gas and a silicon-based gas are introduced into the reaction chamber 20 during the period from time T5 to time T6, a surface layer 105 containing an amorphous material containing carbon and silicon as a main component is formed. In the example of FIG. 16 , during the period from time T5 to time T6, a carbon-based gas is introduced into the reaction chamber 20 as the main source gas, and a silicon-based gas is also introduced. During the period from time T5 to time T6, the gas flow rates of the carbon-based gas and the silicon-based gas are kept constant.

[0186] In this manner, the photoreceptor layer 10bA according to the first and second reference examples, in which the ratio of the constituent elements changes suddenly at the interface between the photoconductive layer 102 and the upper blocking layer 103, can be formed.

[0187] <1-4. Image forming device> Fig. 17 is a cross-sectional view schematically illustrating an example of the configuration of an image forming apparatus 100 including a photoreceptor layer 10b according to the first embodiment. In the example of Fig. 17, the Carlson method, which is one of electrophotographic methods, is adopted as a method for forming an image in the image forming apparatus 100.

[0188] As shown in FIG. 17, the image forming apparatus 100 includes a photoreceptor 10, a charger 11, an exposure unit 12, a developing unit 13, a transfer unit 14, a fixing unit 15, a cleaning unit 16, and a static eliminator 17.

[0189] The charger 11 serves to negatively charge the outer peripheral surface of the photoreceptor 10. The charging voltage is set, for example, to a value between −1000 V and −200 V. The charger 11 may be, for example, a contact charger having a core metal coated with conductive rubber and polyvinylidene fluoride. Instead of a contact charger, a non-contact charger (for example, a corona charger) equipped with a discharge wire may also be used for the charger 11.

[0190] The exposure device 12 serves to form an electrostatic latent image on the charged photoconductor 10. More specifically, the exposure device 12 irradiates the photoconductor 10 with exposure light having a peak wavelength of a specific wavelength (also referred to as a first specific wavelength) in response to an image signal, thereby attenuating the potential of the portion of the photoconductor 10, whose outer circumferential surface is charged, that is irradiated with the exposure light (also referred to as an exposed portion), thereby forming an electrostatic latent image. The first specific wavelength may be, for example, a wavelength of 650 nanometers (nm) or more and 780 nm or less. The exposure light may be, for example, laser light. The exposure device 12 may be, for example, an LED head, which is a device configured with an array of multiple light-emitting diode (LED) elements. The peak wavelength of the light emitted by the LED elements is, for example, 680 nm. Instead of LED elements, the light source of the exposure device 12 may be a laser diode (LD) element capable of emitting laser light or a lamp capable of emitting white light. Therefore, a laser printer having a configuration in which an LD element and an optical system including a polygon mirror are combined may be realized, and a copying machine having a configuration in which a lamp and an optical system including a lens and a mirror that transmits light reflected from an original may be realized.

[0191] The developing unit 13 has a role of forming a toner image by developing the electrostatic latent image on the photoreceptor 10. In the example of Fig. 17, the developing unit 13 includes a magnetic roller 13a that can magnetically hold the developer 200.

[0192] The developer 200 is capable of forming a toner image on the outer peripheral surface of the photoreceptor 10, and is charged to a specific polarity by frictional charging in the developing device 13. As the developer 200, for example, a two-component developer containing a magnetic carrier and insulating toner, or a one-component developer containing magnetic toner is used.

[0193] The magnetic roller 13a serves to transport the developer 200 to the outer circumferential surface of the photoreceptor 10. The magnetic roller 13a transports the developer 200, which has been charged in the developing unit 13, in the form of a magnetic brush adjusted to a fixed spike length. The transported developer 200 adheres to the outer circumferential surface of the photoreceptor 10 due to the electrostatic attraction of the electrostatic latent image on the outer circumferential surface of the photoreceptor 10, thereby forming a toner image. This makes the electrostatic latent image visible. When an image is formed by normal development, the charge polarity of the toner image is opposite to the charge polarity of the outer circumferential surface of the photoreceptor 10. When an image is formed by reversal development, the charge polarity of the toner image is the same as the charge polarity of the outer circumferential surface of the photoreceptor 10.

[0194] In the example of FIG. 17, a dry development method is adopted in developing device 13, but a wet development method using a liquid developer may also be adopted.

[0195] The transfer device 14 transfers the toner image on the photoreceptor 10 to a recording medium 400 supplied to a transfer region between the photoreceptor 10 and the transfer device 14. The recording medium 400 is, for example, a sheet-like material such as paper or film. In the example shown in FIG. 17, the transfer device 14 includes a transfer discharger 14a and a separation discharger 14b. In the transfer device 14, the transfer discharger 14a charges the surface of the recording medium 400 opposite the photoreceptor 10 (also referred to as the back surface or non-recording surface) with a polarity opposite to that of the toner image. As a result, the toner image is transferred onto the surface of the recording medium 400 facing the photoreceptor 10 (also referred to as the top surface or recording surface) due to the electrostatic attraction between the charge (charge) carried by the charge on the back surface of the recording medium 400 and the toner image. In the transfer device 14, simultaneously with the transfer of the toner image, the separation discharger 14b removes the charge on the back surface of the recording medium 400 by AC discharge, and the recording medium 400 is quickly separated from the surface of the photoreceptor 10.

[0196] Alternatively, the transfer device 14 may be a transfer roller that rotates in response to the rotation of the photoreceptor 10 and is arranged with a small gap between it and the photoreceptor 10. The small gap is usually set to 0.5 mm or less. The transfer roller is configured to apply a transfer voltage using, for example, a DC power supply to attract the toner image on the photoreceptor 10 onto the recording medium 400. When a transfer roller is used, devices such as the separation discharger 14b that separates the recording medium 400 from the surface of the photoreceptor 10 (also called a transfer separation device) can be omitted.

[0197] The fixing device 15 has a role of fixing the toner image transferred onto the recording medium 400 to the recording medium 400. The fixing device 15 includes a pair of fixing rollers 15a and 15b. Each of the pair of fixing rollers 15a and 15b is, for example, a roller having a configuration in which the outer surface of a metal cylinder is coated with polytetrafluoroethylene or the like. In the fixing device 15, the pair of fixing rollers 15a and 15b can fix the toner image to the recording medium 400 by applying heat, pressure, and the like to the recording medium 400 passing between the pair of fixing rollers 15a and 15b.

[0198] The cleaning device 16 has a role of removing toner (also referred to as residual toner) remaining on the outer peripheral surface of the photoreceptor 10 after the toner image has been transferred to the recording medium 400. In the example of FIG. 17, the cleaning device 16 is equipped with a cleaning blade 16a. The cleaning blade 16a has a role of scraping off the residual toner from the outer peripheral surface of the photoreceptor 10. The cleaning blade 16a is made of, for example, a rubber material whose main component is polyurethane resin.

[0199] The static eliminator 17 serves to remove charge (also referred to as surface charge) remaining as an electrostatic latent image on the outer peripheral surface of the photoconductor 10. In the example of FIG. 17, the static eliminator 17 eliminates charge by exposing the photoconductor 10 to light. A device capable of emitting light having a peak wavelength of a specific wavelength (also referred to as a second specific wavelength) is used as the static eliminator 17. The second specific wavelength is, for example, a wavelength of 780 nm or more. The static eliminator 17 is configured to remove surface charge (remaining electrostatic latent image) on the outer peripheral surface of the photoconductor 10 by irradiating the entire outer peripheral surface of the photoconductor 10 in the axial direction with light using a light source such as an LED. [Example]

[0200] <Production of Electrophotographic Photoreceptor> Example 1 (also simply referred to as Example 1) of the electrophotographic photoreceptor 10 was fabricated using an aluminum alloy tube (also referred to as an aluminum alloy tube) having an outer diameter of 242 mm and an axial length of 382 mm as the cylindrical substrate 10a. Here, a photoreceptor layer 10b was formed on the outer peripheral surface of the aluminum alloy tube using a film-forming apparatus 300 shown in FIG. 12 under the conditions shown in Table 1. More specifically, a lower charge injection blocking layer (lower blocking layer) 101, a photoconductive layer 102, an upper charge injection blocking layer (upper blocking layer) 103, a surface gradient layer (gradient layer) 104, and a surface protective layer (surface layer) 105 were formed in this order on the outer peripheral surface of the aluminum alloy tube using the film-forming apparatus 300 shown in FIG. 12 under the conditions shown in Table 1. The photoreceptor layer 10b formed here corresponds to the photoreceptor layer 10b according to the first example of the first embodiment described above.

[0201] [Table 1]

[0202] As shown in Table 1, when forming the photoreceptor layer 10b of Example 1, the following source gases were used: monosilane gas, a silicon-based gas; hydrogen gas, a diluent gas; nitric oxide gas, a nitrogen oxide gas; diborane gas, a boron-based gas; and methane gas, a carbon-based gas. The pulsed DC voltage applied to the conductive support 32 by the DC power supply 41 had a frequency of 33 kHz and a duty ratio of 0.7. While maintaining the generation of glow discharge by applying the pulsed DC voltage, the flow rates and ratios of the source gases supplied to the reaction chamber 20 were changed to sequentially form the lower blocking layer 101, photoconductive layer 102, upper blocking layer 103, gradient layer 104, and surface layer 105, thereby producing Example 1 of the electrophotographic photoreceptor 10.

[0203] Table 1 lists the film formation time, gas flow rate, gas pressure, film formation voltage, substrate temperature, and film thickness. The film formation time is the time it takes for each layer to be formed. The gas flow rate is the amount of each of the multiple source gases introduced into the reaction chamber 20 introduced per unit time. The gas pressure is the pressure of the gas inside the reaction chamber 20 detected by the pressure gauge 27. The film formation voltage is a DC voltage applied between the cylindrical electrode 21 and the support 31. This film formation voltage corresponds to the DC voltage applied between the cylindrical electrode 21 and the substrate 10a. The substrate temperature is the temperature of the substrate 10a detected using a thermocouple in the temperature control mechanism 50. The film thickness is the target film thickness of each layer. The unit of film formation time is minutes (min). The unit of gas flow rate is the volumetric flow rate (Standard Cubic Centimeter per Minute: SCCM) at standard conditions of 1 atmosphere and 0°C, i.e., cubic centimeters per minute (cm) at standard conditions. 3 / min). The unit of gas pressure is pascal (Pa). The unit of film formation voltage is volt (V). The unit of substrate temperature is degree Celsius (°C). The unit of film thickness is micrometer (μm). In Table 1, the gas flow rate of diborane gas is shown as a ratio based on the gas flow rate of monosilane gas. For this reason, the unit of gas flow rate of diborane gas is percent per million (ppm) where the gas flow rate of monosilane gas is set to 1 million as the reference value. Note that because the amount of diborane gas introduced was small, diborane gas diluted with hydrogen gas was used.

[0204] In Table 1, a number with an upward arrow ("↑") to the right indicates that the gas flow rate will be increased by that number from the end of the previous period to the start of the next period. For example, if the monosilane gas flow rate is "370" for the previous period and "570↑" for the next period, it indicates that the monosilane gas flow rate will be increased from 370 SCCM to 570 SCCM from the start to the end of that period. In Table 1, a number with a downward arrow ("↓") to the right indicates that the gas flow rate will be decreased from the end of the previous period to the start of the next period. For example, if the monosilane gas flow rate is "570" for the previous period and "330↓" for the next period, it indicates that the monosilane gas flow rate will be decreased from 570 SCCM to 330 SCCM from the start to the end of that period.

[0205] As shown in Table 1, during the first 6 minutes of forming the photosensitive layer 10b of Example 1, the flow rate of monosilane gas was decreased from 570 SCCM to 330 SCCM, the flow rate of nitric oxide gas was increased from 0 SCCM to 30 SCCM, and the flow rate of diborane gas was increased from 0 ppm to 7500 ppm. The flow rate of hydrogen gas was also decreased from 330 SCCM to 0 SCCM as the flow rate of hydrogen-diluted diborane gas increased. During the next very short 0.25 minute period during which the upper blocking layer 103 was formed, the gas flow rate of monosilane gas was maintained at a constant 330 [SCCM], the gas flow rate of nitric oxide gas was maintained at a constant 30 [SCCM], and the gas flow rate of diborane gas was maintained at a constant 7500 [ppm]. During the next final 3 minute period during which the upper blocking layer 103 was formed, the gas flow rate of monosilane gas was decreased from 330 [SCCM] to 160 [SCCM], the gas flow rate of nitric oxide gas was decreased from 30 [SCCM] to 0 [SCCM], the gas flow rate of diborane gas was decreased from 7500 [ppm] to 0 [ppm], and the gas flow rate of methane gas was increased from 0 [SCCM] to 470 [SCCM]. Next, during the period in which the gradient layer 104 was formed on the upper blocking layer 103, the gas flow rate of the monosilane gas was decreased from 160 [SCCM] to 0 [SCCM], while the gas flow rate of the methane gas was increased from 470 [SCCM] to 690 [SCCM].

[0206] An electrophotographic photoreceptor (Reference Example 1) was fabricated using an aluminum alloy tube having an outer diameter of 242 mm and an axial length of 382 mm as the cylindrical substrate 10a. Here, a photoreceptor layer 10bA was formed on the outer peripheral surface of the aluminum alloy tube using the film-forming apparatus 300 shown in FIG. 12 under the conditions shown in Table 2. More specifically, a lower blocking layer 101, a photoconductive layer 102, an upper blocking layer 103A, a gradient layer 104, and a surface layer 105 were formed on the outer peripheral surface of the aluminum alloy tube in this order using the film-forming apparatus 300 shown in FIG. 12 under the conditions shown in Table 2. The photoreceptor layer 10bA formed here corresponds to the photoreceptor layer 10bA of the first Reference Example described above.

[0207] [Table 2]

[0208] As shown in Table 2, when forming the photosensitive layer 10bA of Reference Example 1, monosilane gas, hydrogen gas, nitric oxide gas, diborane gas, and methane gas were used as the source gases. The pulsed DC voltage applied to the conductive support 32 by the DC power supply 41 had a frequency of 33 kHz and a duty ratio of 0.7. During the 25-minute period between the deposition of the photoconductive layer 102 and the deposition of the upper blocking layer 103A, the glow discharge caused by the application of the pulsed DC voltage was stopped, and the flow rates of the monosilane gas were reduced, while the flow rates of the diborane gas and the nitric oxide gas were increased (a standby state). The flow rate of the hydrogen gas was reduced as the hydrogen-diluted diborane gas was introduced. During other periods, while maintaining the generation of glow discharge by applying a pulsed DC voltage, the gas flow rates and ratios of the multiple raw material gases supplied to the reaction chamber 20 were changed to sequentially form a lower blocking layer 101, a photoconductive layer 102, an upper blocking layer 103A, a gradient layer 104 and a surface layer 105, thereby producing Reference Example 1 of the electrophotographic photosensitive member.

[0209] Table 2, like Table 1, lists the deposition time, gas flow rate, gas pressure, deposition voltage, substrate temperature, and film thickness. Also in Table 2, like Table 1, a number with an upward arrow ("↑") to the right indicates that the gas flow rate is increased to that number from the end of the immediately preceding period to the start of the immediately following period. Also in Table 2, like Table 1, a number with a downward arrow ("↓") to the right indicates that the gas flow rate is decreased to that number from the end of the immediately preceding period to the start of the immediately following period.

[0210] As shown in Table 2, when forming the photosensitive layer 10bA of Reference Example 1, during a 25-minute period immediately after the completion of the deposition of the photoconductive layer 102, the generation of glow discharge by application of a pulsed DC voltage was stopped, the gas flow rate of monosilane gas was reduced to 330 [SCCM], the gas flow rate of nitric oxide gas was increased to 30 [SCCM], the gas flow rate of diborane gas was increased to 7500 [ppm], and the gas flow rate of hydrogen gas was reduced to 0 [SCCM] (standby state). Next, during the period for depositing the upper blocking layer 103, the gas flow rate of the monosilane gas was decreased from 330 [SCCM] to 160 [SCCM], the gas flow rate of the nitric oxide gas was decreased from 30 [SCCM] to 0 [SCCM], the gas flow rate of the diborane gas was decreased from 7500 [ppm] to 0 [ppm], and the gas flow rate of the methane gas was increased from 0 [SCCM] to 470 [SCCM]. Next, as shown in Table 2, during the period for depositing the gradient layer 104 on the upper blocking layer 103A, the gas flow rate of the monosilane gas was decreased from 160 [SCCM] to 0 [SCCM], and the gas flow rate of the methane gas was increased from 470 [SCCM] to 690 [SCCM].

[0211] <Changes in element ratios in the thickness direction> Using the same apparatus and the same conditions, ESCA was used to analyze the changes in the ratios of four elements (silicon, nitrogen, oxygen, and carbon) in the thickness direction of the photoreceptor layers 10b and 10bA of Example 1 and Reference Example 1, respectively. Here, the outer peripheral surface of the electrophotographic photoreceptor was abraded by sputtering using argon ions, while the changes in the ratios of the four elements in the thickness direction of the photoreceptor layers 10b and 10bA were analyzed. However, the rate at which the photoreceptor layers 10b and 10bA were abraded by sputtering also changed depending on the composition that changed in the thickness direction of the photoreceptor layers 10b and 10bA. Therefore, the relationship between the sputtering time (also referred to as sputtering time) and the ratios of the four elements (silicon, nitrogen, oxygen, and carbon) was analyzed for Example 1 and Reference Example 1 of the electrophotographic photoreceptor. It should be noted that boron was not included in the analysis because it is generally known that its presence in the photosensitive layers 10b and 10bA is very low compared to silicon, nitrogen, oxygen, and carbon, and that it has almost no effect on the change in refractive index in the photosensitive layer.

[0212] FIG. 18 is a diagram showing the relationship between the time taken for sputtering from the outermost surface in the thickness direction (also referred to as sputtering time) and the ratios of the four elements silicon, nitrogen, oxygen, and carbon, as a result of ESCA analysis of the photoreceptor layer 10b of Example 1. FIG. 19 is a diagram showing the relationship between the time taken for sputtering from the outermost surface in the thickness direction (sputtering time) and the ratios of the four elements silicon, nitrogen, oxygen, and carbon, as a result of ESCA analysis of the photoreceptor layer 10bA of Reference Example 1. In each of FIGS. 18 and 19, the horizontal axis represents the sputtering time, and the vertical axis represents the ratio of each element, where the total ratio of the four elements (silicon, nitrogen, oxygen, and carbon) is 100 percent (%). Here, the element ratios (element ratios) refer to the atomic ratios of the four elements in the photoreceptor layers 10b and 10bA. In each of Figures 18 and 19, the relationship between sputtering time and the silicon ratio is shown by a dotted line, the relationship between sputtering time and the nitrogen ratio is shown by a thick line, the relationship between sputtering time and the oxygen ratio is shown by a thin line, and the relationship between sputtering time and the carbon ratio is shown by a thick dashed line.

[0213] 18 and 19, it was confirmed that, compared to Reference Example 1, in Example 1, the ratios of the four elements did not change suddenly but changed gradually during the sputtering time estimated to correspond to the vicinity of the interface between the upper blocking layer 103 and the photoconductive layer 102. As a result, it was estimated that, compared to Reference Example 1, in Example 1, the occurrence of a sudden change in the refractive index in the thickness direction of the photosensitive layer 10b near the interface between the photoconductive layer 102 and the upper blocking layer 103 was reduced.

[0214] <Achieving thickness variation through etching> For each of Example 1 and Reference Example 1, in order to simulate thickness variations due to wear in the surface layer 105 and the inclined layer 104, the entire outer peripheral surface of each electrophotographic photosensitive member was etched by plasma etching under the same conditions using carbon tetrafluoride (CF4) gas in the same reaction chamber. Here, Example 1 of the electrophotographic photosensitive member before etching is referred to as "Example 1 before etching," Example 1 of the electrophotographic photosensitive member after etching is referred to as "Example 1 after etching," Reference Example 1 of the electrophotographic photosensitive member before etching is referred to as "Reference Example 1 before etching," and Reference Example 1 of the electrophotographic photosensitive member after etching is referred to as "Reference Example 1 after etching."

[0215] For each of Reference Example 1 before and after etching, an optical interference film thickness meter was used to measure the total film thickness of the three layers (also referred to as the three surface-side layers) located on the photoconductive layer 102: the upper blocking layer 103A, the gradient layer 104, and the surface layer 105. Here, one axial end of the outer peripheral surface of the electrophotographic photosensitive member was set as a reference position (also referred to as the reference position), and the total film thickness of the three surface-side layers was measured at five positions that were different distances from the reference position in the axial direction. The five different positions were a first position that was 28 mm away from the reference position in the axial direction, a second position that was 110 mm away from the reference position in the axial direction, a third position that was 191 mm away from the reference position in the axial direction, a fourth position that was 273 mm away from the reference position in the axial direction, and a fifth position that was 354 mm away from the reference position in the axial direction.

[0216] Fig. 20 shows the measurement results of the axial distribution of the total film thickness of the three surface-side layers for Reference Example 1 of the electrophotographic photosensitive member before and after etching. In Fig. 20, the horizontal axis represents the distance from a reference position in the axial direction of the electrophotographic photosensitive member, and the vertical axis represents the total film thickness of the three surface-side layers. Also in Fig. 20, the total film thickness of the three surface-side layers at five positions for Reference Example 1 before etching is shown by five open triangles connected by dashed lines, and the total film thickness of the three surface-side layers at five positions for Reference Example 1 after etching is shown by five filled triangles connected by solid lines.

[0217] As shown in FIG. 20 , in Reference Example 1 before etching, the total film thickness of the three surface-side layers was approximately 9050 angstroms (Å) (=905 nm) to approximately 9220 Å (=922 nm). On the other hand, in Reference Example 1 after etching, the total film thickness of the three surface-side layers was approximately 4210 Å (=421 nm) to approximately 7260 Å (=726 nm). Here, the magnitude of thickness variation was evaluated in comparison with a wavelength of 650 nm or more and 780 nm or less, which is the first specific wavelength that can be adopted as the peak wavelength of the exposure light irradiated to the electrophotographic photosensitive member by the above-mentioned exposure device 12. As a result, it was confirmed that for Reference Example 1 before etching, the difference in the total film thickness of the three surface-side layers (thickness variation) was small regardless of the difference in axial position. In contrast, it was confirmed that for Reference Example 1 after etching, the difference in the total film thickness of the three surface-side layers was somewhat large depending on the difference in axial position. In other words, it was confirmed that for Reference Example 1 of the electrophotographic photosensitive member, the difference in thickness (thickness variation) depending on the location in the three layers on the surface side was small before etching and somewhat large after etching.

[0218] It should be noted that even when an optical interference film thickness meter was used to measure the total film thickness of the three layers (the three surface-side layers) located on the photoconductive layer 102, namely, the upper blocking layer 103, the gradient layer 104, and the surface layer 105, both of which were measured for Example 1 before etching and Example 1 after etching. It was presumed that the refractive index did not change abruptly between the photoconductive layer 102 and the upper blocking layer 103, and that this prevented the total film thickness of the three surface-side layers from being measured due to optical interference. However, the three surface-side layers of the electrophotographic photoreceptor in Example 1 had compositions similar to those of the three surface-side layers of the electrophotographic photoreceptor in Reference Example 1. Therefore, it was presumed that, in Example 1 of the electrophotographic photoreceptor, as in Reference Example 1 of the electrophotographic photoreceptor, the difference in thickness (thickness variation) depending on the location of the three surface-side layers was small before etching and increased to a certain extent after etching.

[0219] Therefore, it was confirmed or estimated that in each of Example 1 and Reference Example 1, variations in thickness due to wear in surface layer 105 and gradient layer 104 could be simulated by etching.

[0220] <Changes in sensitivity before and after etching> Next, an experiment was conducted to evaluate unevenness (non-uniformity) in sensitivity for each of Example 1 before etching, Example 1 after etching, Reference Example 1 before etching, and Reference Example 1 after etching.

[0221] Fig. 21 is a diagram for explaining a method for measuring unevenness in sensitivity in an electrophotographic photosensitive member. As shown in Fig. 21, a charger 701, an exposure device 702, a surface potential measuring device 703, and a static eliminator 704 were arranged around the electrophotographic photosensitive member in this order in the circumferential direction.

[0222] The charger 701 was a scorotron, a type of corona charger. The power source for the scorotron was a Trek Model 610E-F high-voltage power supply. The scorotron included multiple gold-plated tungsten wires, each with a diameter of 150 μm, as grid wires, and multiple untreated tungsten wires, each with a diameter of 80 μm, as corona wires. The scorotron was configured such that an output current It from the high-voltage power supply passed through the multiple corona wires, generating a corona discharge. Much of the current generated by this corona discharge returned to the high-voltage power supply as a return current Ir through the multiple grid wires. Here, the relationship between the current Id (also referred to as the corona current or discharge current) involved in charging the outer peripheral surface of the electrophotographic photosensitive member, the output current It, and the return current Ir was Id = It - Ir.

[0223] An LED light source manufactured by our company, which emitted light with a peak wavelength of 630 nm, was used as the exposure device 702. A DC stabilized power supply, model number PMC35-2A manufactured by Kikusui Electronics Co., Ltd., was used as the power source for this LED light source.

[0224] The surface potential measuring instrument 703 used was a measuring instrument that combined a surface potential meter, model number 344-F, manufactured by Trek, with a probe, model number 6000B-7C, manufactured by Trek.

[0225] An LED light source manufactured by our company, which emitted light with a peak wavelength of 650 nm, was used as the static eliminator 704. A DC stabilized power supply of model number PMC35-2A manufactured by Kikusui Electronics Co., Ltd. was used as the power source for this LED light source.

[0226] In the above configuration, the electrophotographic photosensitive member was rotated around the central axis at a predetermined constant speed in the circumferential direction using a motor or the like. The direction of rotation was clockwise, as indicated by the arc-shaped arrow in Figure 21. The condition for the predetermined constant speed was a condition in which the moving speed (also referred to as linear speed) of the outer peripheral surface in the circumferential direction was 1.2 meters per second (m / s). This condition meant that the electrophotographic photosensitive member rotated around the central axis in the circumferential direction at 96 revolutions per minute. The temperature of the substrate 10a of the electrophotographic photosensitive member was maintained within a temperature range of 40°C or higher and 44°C or lower. Under this condition, the following processes [A] to [C] were carried out.

[0227] [A] While rotating the electrophotographic photosensitive member in the circumferential direction around the central axis at a predetermined constant speed (linear velocity of 1.2 m / s), a scorotron was used to charge substantially the entire outer peripheral surface of the electrophotographic photosensitive member to a negative polarity under conditions such that a surface potential measuring instrument 703 would detect a surface potential of −500 V on the outer peripheral surface of the electrophotographic photosensitive member if no exposure light was irradiated by the exposure device 702. In other words, −500 V was set as the initial surface potential of charging (also referred to as the initial surface potential of charging).

[0228] [B] The exposure device 702 applies 0.3 μJ / cm to the outer peripheral surface of the negatively charged electrophotographic photosensitive member. 2 The amount of exposure light was set to a value aimed at reducing the surface potential on the outer peripheral surface of the electrophotographic photosensitive member from −500 V, which is the initial surface potential of charging, to a surface potential (also referred to as intermediate surface potential) near the middle between −500 V, which is the initial surface potential of charging, and 0 V, which is the reference surface potential (also referred to as reference surface potential).

[0229] [C] The surface potential of the outer peripheral surface of the electrophotographic photosensitive member after being irradiated with the exposure light was detected using the surface potential meter 703. Here, the average value of the surface potential of the outer peripheral surface of the electrophotographic photosensitive member detected using the surface potential meter 703 during a period in which the electrophotographic photosensitive member made three rotations was obtained as the measurement result of the surface potential.

[0230] When the above processes [A] to [C] are performed, the static eliminator 704 is always used to apply 2 μJ / cm 2 to the outer peripheral surface of the electrophotographic photosensitive member. 2 The state in which light (also referred to as erase light) of this amount was irradiated was maintained. As a result, in the region of the outer circumferential surface of the electrophotographic photosensitive member facing the static eliminator 704, static elimination was performed by exposure, and the potential of the outer circumferential surface of the electrophotographic photosensitive member was set to the reference potential (0 V).

[0231] The surface potential obtained as a measurement result in the process [C] above can increase or decrease depending on the sensitivity of the electrophotographic photosensitive member to the exposure light, and therefore was obtained as an index for evaluating the sensitivity of the electrophotographic photosensitive member to the exposure light. This surface potential as an index was used as an index relating to the sensitivity of the electrophotographic photosensitive member to the exposure light of a light amount intended to reduce the surface potential on the outer peripheral surface of the electrophotographic photosensitive member from the initial surface potential (=-500) of charging to an intermediate surface potential (also referred to as intermediate sensitivity).

[0232] The above operations [A] to [C] were performed at five positions in the axial direction on the outer peripheral surface of the electrophotographic photosensitive member, which were the first to fifth positions described above.

[0233] FIG. 22 shows the measurement results of the axial distribution of surface potential as an index related to intermediate sensitivity for Example 1 and Reference Example 1 before and after etching. In FIG. 22, the horizontal axis represents the distance from a reference position in the axial direction of the electrophotographic photosensitive member, and the vertical axis represents the surface potential at the outer peripheral surface of the electrophotographic photosensitive member. Also in FIG. 22, the surface potential as an index related to intermediate sensitivity at five positions for Example 1 before etching is shown as a plot of five open circles connected by a thick dashed line, and the surface potential as an index related to intermediate sensitivity at five positions for Example 1 after etching is shown as a plot of five filled circles connected by a thick line. Also in FIG. 22, the surface potential as an index related to intermediate sensitivity at five positions for Reference Example 1 before etching is shown as a plot of five open triangles connected by a thin dashed line, and the surface potential as an index related to intermediate sensitivity at five positions for Reference Example 1 after etching is shown as a plot of five filled triangles connected by a thin line.

[0234] As shown in FIG. 22 , for Reference Example 1 before etching, the surface potential as an index related to intermediate sensitivity was −347 V to −374 V. For Reference Example 1 after etching, the surface potential as an index related to intermediate sensitivity was −233 V to −321 V. On the other hand, for Example 1 before etching, the surface potential as an index related to intermediate sensitivity was −356 V to −369 V. For Example 1 after etching, the surface potential as an index related to intermediate sensitivity was −314 V to −326 V. Here, for both Reference Example 1 and Example 1, the surface potential as an index related to intermediate sensitivity decreased after etching compared to before etching, regardless of the position in the axial direction. This decrease in surface potential was presumed to be due to a decrease in the amount of exposure light absorbed due to a decrease in the film thickness of the surface layer 105 and the gradient layer 104.

[0235] Furthermore, for each of Reference Example 1 before etching, Reference Example 1 after etching, Example 1 before etching, and Example 1 after etching, the difference between the maximum and minimum values ​​of the surface potential, which serves as an index of intermediate sensitivity, was calculated as intermediate sensitivity axial unevenness, which is an index showing unevenness in the intermediate sensitivity axial direction. The unit of intermediate sensitivity axial unevenness was volts (V).

[0236] 23 is a graph showing the intermediate sensitivity axis unevenness as an index showing the unevenness in the intermediate sensitivity axis direction for Example 1 before and after etching, and the intermediate sensitivity axis unevenness as an index showing the unevenness in the intermediate sensitivity axis direction for Reference Example 1 before and after etching. In Fig. 23, the vertical axis represents the intermediate sensitivity axis unevenness. In Fig. 23, from left to right, the intermediate sensitivity axis unevenness of Reference Example 1 before etching is shown by a bar graph with sandy hatching, the intermediate sensitivity axis unevenness of Reference Example 1 after etching is shown by a bar graph with diagonal hatching, the intermediate sensitivity axis unevenness of Example 1 before etching is shown by a bar graph with sandy hatching, and the intermediate sensitivity axis unevenness of Example 1 after etching is shown by a bar graph with diagonal hatching.

[0237] 23, the intermediate sensitivity axis unevenness of Reference Example 1 before etching was 27 V, while the intermediate sensitivity axis unevenness of Reference Example 1 after etching was 88 V. On the other hand, the intermediate sensitivity axis unevenness of Example 1 before etching was 13 V, while the intermediate sensitivity axis unevenness of Example 1 after etching was 12 V. Therefore, it was confirmed that the intermediate sensitivity axis unevenness of Reference Example 1 increased significantly by more than three times due to etching. In contrast, it was confirmed that the intermediate sensitivity axis unevenness of Example 1 before and after etching hardly changed within a small range.

[0238] In other words, it was confirmed that in Reference Example 1, the intermediate sensitivity axis unevenness increased significantly by more than three times due to the thickness variations occurring in the surface layer 105 and the gradient layer 104. In contrast, in Example 1, it was confirmed that the intermediate sensitivity axis unevenness hardly changed within a small range even when the thickness variations occurred in the surface layer 105 and the gradient layer 104.

[0239] As described above, in Reference Example 1, similar to the photoreceptor according to Reference Example 1, it was estimated that a rapid change in refractive index exists in the thickness direction of the photoreceptor layer 10bA near the interface between the photoconductive layer 102 and the upper blocking layer 103A. Therefore, in Reference Example 1, it was estimated that the thickness variations in the gradient layer 104 and the surface layer 105 caused the intensity of the exposure light incident on the photoconductive layer 102 to vary depending on the location due to optical interference, even when the photoreceptor layer 10bA was irradiated with exposure light of the same intensity, resulting in increased unevenness in the intermediate sensitivity. Furthermore, in Reference Example 1 of the electrophotographic photoreceptor, it was estimated that if the unevenness in the intermediate sensitivity increased, the negative surface potential would attenuate over a narrower area in areas with low intermediate sensitivity, and the negative surface potential would attenuate over a wider area in areas with high intermediate sensitivity, even when the same spot diameter and intensity of exposure light were irradiated. As a result, it was estimated that when Reference Example 1 of the electrophotographic photosensitive member is installed in an image forming apparatus, unevenness may occur in the diameter of the dots in the toner image fixed to the recording medium, and unevenness (irregularity) in the density of the toner image fixed to the recording medium may increase.

[0240] In contrast, as described above, in Example 1, similar to the photoreceptor 10 according to the first specific example, it was estimated that the occurrence of abrupt changes in refractive index was reduced in the thickness direction of the photoreceptor layer 10b near the interface between the photoconductive layer 102 and the upper blocking layer 103, near the interfaces between the upper blocking layer 103 and the gradient layer 104, and near the interfaces between the gradient layer 104 and the surface layer 105. Therefore, it was estimated that in Example 1, the occurrence of light reflection was reduced in the optical path leading to the photoconductive layer 102 via the surface layer 105, the gradient layer 104, and the upper blocking layer 103. As a result, it was estimated that in Example 1, even if the gradient layer 104 and the surface layer 105 have thickness variations, when exposure light of the same intensity is irradiated onto the photoreceptor layer 10b, the occurrence of light interference was reduced, thereby reducing the occurrence of a defect in which the intensity of exposure light incident on the photoconductive layer 102 varies depending on the location. That is, it was estimated that unevenness in intermediate sensitivity was reduced. In other words, it was estimated that unevenness in sensitivity was reduced for Example 1 of the electrophotographic photosensitive member. It was also estimated that if unevenness in intermediate sensitivity was reduced for Example 1 of the electrophotographic photosensitive member, then when exposure light of the same spot diameter and intensity was irradiated, the occurrence of increases and decreases in the size of the region where the negative surface potential attenuates would be reduced at any location on the electrophotographic photosensitive member. Therefore, it was estimated that when Example 1 of the electrophotographic photosensitive member is installed in an image forming apparatus, the occurrence of unevenness in the diameter size of dots in a toner image fixed on a recording medium can be reduced, and the occurrence of unevenness in the density of the toner image fixed on the recording medium can be reduced.

[0241] <2.Other> The present disclosure is not limited to the first embodiment described above, and various modifications and improvements are possible within the scope of the gist of the present disclosure. For example, although the electrophotographic photoreceptor and the method for manufacturing the electrophotographic photoreceptor have been described in detail above, the above description is merely an example in all respects, and the present disclosure is not limited thereto. Furthermore, the various examples described above can be applied in combination as long as they are not mutually contradictory. It is understood that countless examples not exemplified can be envisioned without departing from the scope of this disclosure. [Explanation of symbols]

[0242] 10 Electrophotographic photoreceptor (photoreceptor) 101,901 Lower charge injection blocking layer (lower blocking layer) 102,902 Photoconductive layer 103,103A,903 Upper charge injection blocking layer (upper blocking layer) 103a 1st area 103b 2nd area 104 Surface gradient layer (gradient layer) 105,904 Surface protective layer (surface layer) 10a,90a Base 10b,10bA,90b Photoreceptor layer 20 Reaction Chamber

Claims

1. a conductive substrate; a first layer located on the substrate, the first layer comprising primarily amorphous silicon and an n-type dopant; a second layer located on the first layer and containing amorphous silicon as a main component; a third layer located on the second layer, the third layer containing amorphous silicon as a main component and containing nitrogen, oxygen, carbon, and boron as a p-type dopant; a fourth layer located on the third layer and mainly composed of an amorphous material containing silicon and carbon; a fifth layer located on the fourth layer, the fifth layer containing mainly amorphous carbon or mainly an amorphous material containing carbon and silicon, and having a surface exposed to an external space; the third layer includes a first region in contact with the second layer, and a second region located closer to the fourth layer than the first region and in contact with the fourth layer; the first region has a tendency that, with increasing distance from the second layer, the silicon content decreases, the boron, nitrogen and oxygen contents increase, and the carbon content does not increase; the second region has a tendency that the content of each of boron, nitrogen, and oxygen decreases and the content of carbon increases toward the fourth layer, The fourth layer has a tendency that the silicon content decreases and the carbon content increases toward the fifth layer.

2. a first step of forming a first layer containing amorphous silicon as a main component and an n-type dopant on a conductive substrate in a reaction chamber; a second step of forming a second layer mainly containing amorphous silicon on the first layer in the reaction chamber; a third step of forming a third layer on the second layer in the reaction chamber, the third layer containing amorphous silicon as a main component and containing nitrogen, oxygen, carbon, and boron as a p-type dopant; a fourth step of forming a fourth layer mainly containing an amorphous material containing silicon and carbon on the third layer in the reaction chamber; a fifth step of forming, in the reaction chamber, a fifth layer on the fourth layer, the fifth layer comprising mainly amorphous carbon or an amorphous material containing carbon and silicon; The second step, the third step, the fourth step, and the fifth step are successively performed in this order in the reaction chamber by using a plasma enhanced chemical vapor deposition method; In the second step, a silicon-based gas is introduced into the reaction chamber; the third step includes a third step A and a third step B that is performed after the third step A, In the step 3A, the amount of the silicon-based gas introduced into the reaction chamber per unit time is decreased while the amount of the diborane gas and the amount of the nitrogen oxide gas introduced into the reaction chamber per unit time is increased; In the third step B, the amount of the diborane gas and the nitrogen oxide gas introduced into the reaction chamber per unit time is decreased while the amount of the carbon-based gas introduced into the reaction chamber per unit time is increased; In the fourth step, the amount of the silicon-based gas introduced into the reaction chamber per unit time is decreased while the amount of the carbon-based gas introduced into the reaction chamber per unit time is increased; In the fifth step, the carbon-based gas is introduced into the reaction chamber, or the silicon-based gas is introduced into the reaction chamber while the carbon-based gas is being introduced into the reaction chamber.

3. 3. A method for producing an electrophotographic photoreceptor according to claim 2, comprising: the timing at which the amount of each of the diborane gas and the nitrogen oxide gas introduced into the reaction chamber per unit time starts to decrease and the timing at which the amount of the carbon-based gas introduced into the reaction chamber per unit time starts to increase are simultaneous in the 3B step.

4. A method for producing an electrophotographic photoreceptor according to claim 2 or 3, comprising the steps of: the silicon-based gas includes one or more silane-based gases selected from monosilane gas and disilane gas, the carbon-based gas includes one or more hydrocarbon-based gases selected from the group consisting of methane gas, ethylene gas, and acetylene gas; The method for producing an electrophotographic photoreceptor, wherein the nitrogen oxide gas contains at least one gas selected from the group consisting of nitric oxide gas and dinitrogen monoxide gas.

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