JP2007132980A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor, capable of suppressing the degradation in image quality due to crazing and film peeling between a ground and a surface layer with respect to the electrophotographic photoreceptor that uses magnesium fluoride in the surface layer. <P>SOLUTION: The electrophotographic photoreceptor with at least a photoconductive layer and the surface layer laminated, in this order, is characterized in that the tensile stress of the surface layer is in the range of 1.0×10<SP>6</SP>to 5.0×10<SP>8</SP>N/m<SP>2</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic photoreceptor.

  Conventionally, electrophotographic photoreceptors having various layer configurations have been proposed in accordance with various performance requirements. Among them, the surface layer has an abrasion resistance, charge retention, and resistance to electrophotographic photoreceptors. It is recognized as an important layer for obtaining various properties such as environmental properties and light transmittance.

  In recent years, due to the demand for improved durability, the internal stress of the surface layer is kept small, so even if it is affected by mechanical stress or thermal cycle in the image forming process, the increase in strain due to the change of internal stress is small, and cracks Therefore, characteristics that maintain a state where peeling or peeling does not occur have been demanded.

As described above, as an example of an electrophotographic photoreceptor having a protective layer having a small internal stress, the protective layer is composed of a first layer showing tensile stress and a second layer showing compressive stress. There has been disclosed a structure in which the internal stress is nearly zero in the entire protective layer by canceling each other (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 01-200288

  In recent years, with the increase in color of electrophotographic apparatuses, there has been a demand for further extension of the life of electrophotographic photoreceptors in accordance with higher definition for forming finer images. Under such circumstances, there are still problems to be solved in the electrophotographic photoreceptor in which the internal stress of the surface layer is suppressed to be small.

  One of the problems is image defects during repeated use. In the electrophotographic apparatus, since most of the charging process of the photosensitive member uses discharge, the surface of the photosensitive member is always exposed to a discharge environment. In particular, there is a problem that charging deterioration is more likely to occur in a high humidity environment than in a normal humidity environment. One of the deteriorations in charging is that cracks occur in the surface layer during repeated use, and further, the adhesion with the underlying layer decreases, resulting in peeling, and cracks and peeling marks appear on the image.

  As a result of conducting research in view of the above circumstances, it has been found that the compressive stress of the surface layer gradually accumulates and the strain energy increases in the charging process. For this reason, it was found that cracks in the surface layer and peeling from the base occur in order to release the accumulated strain energy during repeated use.

  The degree of cracking depends on the amount of accumulated strain energy, so the degree of cracking ranges from very slight to large. Cracks with a very small degree do not affect the characteristics of the surface layer, but cracks with a large degree appear on the image and may cause peeling from the underlayer.

  In the state where internal stress is accumulated, due to friction with the separation claw for separating the copy paper from the surface of the electrophotographic photosensitive member and mechanical stress such as a cleaning blade that scrapes off the toner remaining on the photosensitive member, It was also found that the internal strain of the film increased and scratches were likely to occur.

  In addition, even when the internal stress is not large enough to cause cracking or film peeling on the surface layer, the travelability of the optical carrier deteriorates due to the accumulation of compressive stress and tensile stress, resulting in ghost abnormalities. I understood that.

  The present invention has been made in view of the above-mentioned problems, and its object is to balance the internal stress of the surface layer at the time of repeated use, so that there is no film peeling and the electrophotographic photosensitive material has excellent durability. To provide a body.

In order to achieve the above object, the present invention provides an electrophotographic photoreceptor in which at least a photoconductive layer and a surface layer are sequentially laminated on a conductive substrate of a surface layer, and the stress of the surface layer is 1.0 × 10 ⁶ to 5. The tensile stress is 0 × 10 ¹⁰ N / m ² .

The surface layer of the electrophotographic photoreceptor can suppress cracking during film formation by setting the internal stress of the surface layer to 1.0 × 10 ^{6 to} 5.0 × 10 ¹⁰ N / m ^2. By balancing the internal stress of the surface layer during repeated use, film peeling can be suppressed and an electrophotographic photoreceptor excellent in durability can be provided.

  EMBODIMENT OF THE INVENTION The form for implementing 1st invention based on this application is demonstrated using drawing.

In the first invention according to the present application, in the electrophotographic photoreceptor in which at least a photoconductive layer and a surface layer are sequentially laminated on a conductive substrate, the stress of the surface layer is 1.0 × 10 ^{6 to} 5.0 × 10 ^{6. By} setting the tensile stress to ¹⁰ N / m ² , the above effect can be obtained.

  Generally, when the internal stress in the surface layer is large, the strain energy of the surface layer is large. Therefore, a crack is generated in the surface layer, or it is triggered by the crack to cause peeling from the base, thereby attempting to release the energy.

  In addition, when mechanical stress is applied to the membrane from the outside, the strain becomes larger, and the scratches are more likely to occur. Therefore, in order to suppress cracks and peeling from the base, it is desirable to keep the internal stress small before and after repeated use in order to maintain a state that does not reach the strain energy necessary for generating cracks and peeling.

  However, when the characteristics as the surface layer are examined, as a result of being exposed to the discharge environment during the charging process, a compressive stress is accumulated during repeated use. For this reason, in the case of a surface layer with low internal stress during film formation, compressive stress gradually accumulates during repeated use, resulting in cracks and peeling from the substrate, or mechanical stresses such as cleaning blades and separation nails. It was found that scratches may occur due to repeated application.

  Therefore, by maintaining a tensile stress that is the internal stress opposite to the compressive stress during film formation, it is possible to balance the internal stress during repeated use and maintain it within a range where cracks do not occur. Therefore, durability can be improved.

As a result of conducting research in view of the above circumstances, by making the internal stress of the surface layer a tensile stress of 1.0 × 10 ⁶ N / m ² or more, it is possible to achieve a balance of internal stress during repeated use, It was found that cracks, film peeling from the substrate, and scratches due to mechanical stress can be suppressed.

Even during film formation, cracks and peeling of the film from the base may occur due to the large internal stress. In order to prevent them, the internal stress is preferably suppressed to a tensile stress of 5.0 × 10 ¹⁰ N / m ² or less.

  FIG. 1 is a diagram schematically showing an example of the layer structure of the electrophotographic photoreceptor in the first invention according to the present application.

  An electrophotographic photoreceptor 100 shown in FIG. 1 includes a conductive substrate 103, a photoconductive layer 102 sequentially stacked on the surface of the conductive substrate 103, and a surface layer 101.

  The conductive substrate 103 is not particularly limited as long as it can hold the photoconductive layer 102 and the surface layer 101 formed on the surface, and may be any one. For example, metals such as aluminum, iron, nickel, and alloys thereof, and those obtained by conducting a conductive treatment on at least the surface of the electrically insulating support on which the photoconductive layer 102 is formed can be used as the conductive substrate. .

  The photoconductive layer 102 exhibits at least photoconductivity and may be any one as long as it has characteristics that can be used as an electrophotographic photoreceptor. For example, an organic semiconductor, selenium, amorphous silicon, or the like can be used as the material.

  The surface layer 101 protects the surface of the photoconductive layer from the surface of the electrophotographic photoreceptor, and also imparts moisture resistance, repeated use characteristics, electrical pressure resistance, use environment characteristics, and durability to the electrophotographic photoreceptor. As long as it has, it may be any.

The second invention according to the present application is characterized in that the surface layer has a tensile stress of 1.0 × 10 ^{7 to} 2.0 × 10 ⁸ N / m ² . When the tensile stress is increased from 1.0 × 10 ⁷ N / m ² , it is possible to effectively relieve the accumulation of compressive stress after repeated use, so that the durability can be further improved. The internal stress after use can be suppressed to a compressive stress within a range where the ghost cannot be visually confirmed. Moreover, even if the internal stress during film formation is large enough not to cause cracks, ghosts may be generated. Therefore, in order to suppress the ghost, it is effective to make the internal stress smaller than the tensile stress of 2.0 × 10 ⁸ N / m ² .

  The third invention according to the present application is characterized in that a metal fluoride is used as the surface layer. When metal fluoride is used as a material for the surface layer, durability is improved, and there is a tendency that cracks and peeling from the base are unlikely to occur. This is because the bonding strength of metal fluoride is large, and as a result, compression stress is difficult to accumulate during repeated use. As a result, scratches are less likely to occur even when subjected to mechanical stress from a cleaning blade, etc., improving durability. It is to do.

  The fourth invention according to the present application is characterized in that the metal fluoride is composed of magnesium fluoride containing magnesium and fluorine as main components. When magnesium fluoride is used as the material for the surface layer, among metal fluorides, there is a tendency that durability is further improved and cracks and peeling from the base are unlikely to occur. This is because magnesium fluoride is relatively hard among metal fluorides and has a high bonding force, so that it is difficult to accumulate compressive stress during repeated use, resulting in mechanical stress from a cleaning blade or the like. However, the scratches are less likely to occur, and the durability is further improved.

  The fifth invention according to the present application is characterized in that the photoconductive layer is made of amorphous silicon. Since amorphous silicon has a high hardness, when used as a photoconductive layer as an underlayer, it has good adhesion to the surface layer and is effective in suppressing film peeling.

  Next, embodiments of the present invention and effects thereof will be described in detail with reference to the drawings.

  A manufacturing procedure when amorphous silicon is used for the photoconductive layer and magnesium fluoride is used for the surface layer will be described.

  First, a method for forming an amorphous silicon layer will be described.

  Examples of the forming method include glow discharge methods (DC or AC CVD methods, etc.), sputtering methods, vacuum deposition methods, ion plating methods, photo CVD, thermal CVD methods, and the like. These deposited film forming methods can be appropriately selected depending on the manufacturing conditions, investment load, manufacturing scale, desired characteristics, etc., but the condition control for forming the amorphous silicon layer having the desired characteristics is relatively easy. Therefore, a glow discharge method, particularly a high-frequency glow discharge method using a power supply frequency such as an RF band, a VHF band, and a μW band is preferable.

  In order to form the photoconductive layer 102 by the glow discharge method, basically, as is well known, a source gas for supplying Si that can supply silicon atoms (Si) and an H supply that can supply hydrogen atoms (H). At least one of the raw material gas and the raw material gas for supplying X capable of supplying halogen atoms (X) is introduced in a desired gas state into a reaction vessel in which the inside can be depressurized. A layer made of a-Si: H, X may be formed on a predetermined conductive substrate 103 that is preliminarily set in a predetermined position by causing discharge to decompose the introduced source gas.

  In order to compensate for dangling bonds of silicon atoms and improve layer quality, particularly photoconductivity and charge retention characteristics, the photoconductive layer 102 must contain at least one of hydrogen atoms and halogen atoms. However, the content of hydrogen atoms or halogen atoms, or the total content of hydrogen atoms and halogen atoms is 10 atom% or more, particularly 15 atom%, based on the sum of silicon atoms, hydrogen atoms, and halogen atoms. The above is preferable, and 30 atomic% or less, particularly 25 atomic% or less is preferable with respect to the sum of silicon atoms, hydrogen atoms, and halogen atoms.

Specific examples of the halogen compound that can be preferably used in the present invention include halogen compounds such as fluorine gas (F ₂ ), BrF, ClF, ClF ₃ , BrF ₃ , BrF ₅ , IF ₃ , and IF _7. Can do. Specific examples of silicon compounds containing halogen atoms, so-called silane derivatives substituted with halogen atoms, include silicon fluorides such as SiF ₄ and Si ₂ F ₆ .

  In the present invention, the photoconductive layer 102 preferably contains atoms for controlling conductivity as required. The atoms for controlling the conductivity may be contained in the photoconductive layer 102 in a uniformly distributed state, or a portion containing a non-uniformly distributed portion in the layer thickness direction. There may be.

  Examples of atoms that control conductivity include so-called impurities in the semiconductor field, and atoms belonging to Group 13 of the periodic table that give p-type conduction characteristics (hereinafter abbreviated as “Group 13 atoms”) or n-type conduction. An atom belonging to Group 15 of the periodic table giving characteristics (hereinafter abbreviated as “Group 15 atom”) can be used.

  Specific examples of the Group 13 atom include boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), and B, Al, and Ga are particularly preferable. . Specific examples of the Group 15 atom include phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi), and P and As are particularly preferable.

The content of atoms controlling the conductivity contained in the photoconductive layer 102 is 1 × 10 ⁻² atom ppm or more, particularly 5 × 10 ⁻² atom ppm or more, and further 1 × 10 ⁻¹ atom ppm or more. In addition, it is preferably 1 × 10 ⁴ atom ppm or less, particularly 5 × 10 ³ atom ppm or less, more preferably 1 × 10 ³ atom ppm or less.

  In order to structurally introduce an atom for controlling conductivity, for example, a group 13 atom or a group 15 atom, a source material for introducing a group 13 atom or a group 15 atom for introducing a group 15 atom during the layer formation. The source material may be introduced into the reaction vessel in a gas state together with other gases for forming the photoconductive layer 102. As a source material for introducing a Group 13 atom or a source material for introducing a Group 15 atom, a material that is gaseous at normal temperature and pressure, or a material that can be easily gasified at least under layer formation conditions is adopted. It is preferable to do.

In addition, if necessary, these raw material materials for introducing atoms for controlling conductivity may be diluted with H ₂ or He.

Further, in the present invention, it is also effective that the photoconductive layer 102 contains one or more of carbon atoms, oxygen atoms, and nitrogen atoms. The content (total amount) of carbon atoms, oxygen atoms and nitrogen atoms is 1 × 10 ⁻⁵ atom% or more, particularly 1 × 10 ⁻⁴ atoms, based on the sum of silicon atoms, carbon atoms, oxygen atoms and nitrogen atoms. % Or more, preferably 1 × 10 ⁻³ atom% or more, and 10 atom% or less, particularly 8 atom% or less, more preferably 8 atom% or less with respect to the sum of silicon atom, carbon atom, oxygen atom and nitrogen atom. Is preferably 5 atomic% or less. Carbon atoms, oxygen atoms and nitrogen atoms may be uniformly contained in the photoconductive layer, or have a non-uniform distribution in which the content varies in the thickness direction of the photoconductive layer. There may be parts.

  In the present invention, the layer thickness of the photoconductive layer 102 is appropriately determined as desired from the viewpoints of obtaining desired electrophotographic characteristics and economic effects, but is preferably 15 μm or more, particularly preferably 20 μm or more. Also, it is preferably 60 μm or less, particularly 50 μm or less, and more preferably 40 μm or less. If the layer thickness of the photoconductive layer 102 is less than 15 μm, the amount of current passing through the charging member increases and the deterioration tends to be accelerated. When the layer thickness of the photoconductive layer 102 exceeds 60 μm, the abnormal growth site of the a-Si photosensitive member may become large, specifically 50 to 150 μm in the horizontal direction and 5 to 20 μm in the height direction. Damage to a member that rubs can not be ignored and may cause an image defect.

  An example of an apparatus for producing a silicon photoreceptor will be described. FIG. 2 is a diagram schematically showing an example of a photoconductor deposition apparatus by RF plasma CVD using a high frequency power source.

  This apparatus is roughly composed of a deposition apparatus 2100 having a reaction vessel 2110, a source gas supply apparatus 2200, and an exhaust device (not shown) for depressurizing the inside of the reaction container 2110.

  In the reaction vessel 2110 in the deposition apparatus 2100, a conductive substrate 2112 connected to the ground, a conductive substrate heating heater 2113, and a source gas introduction pipe 2114 are installed, and a high-frequency power source is connected via a high-frequency matching box 2115. 2120 is connected.

The source gas supply device 2200 includes source gas cylinders 2221 to 2226 such as SiH ₄ , H ₂ , CH ₄ , NO, B ₂ H ₆ , and CF ₄ , valves 2231 to 2236, pressure regulators 2261 to 2266, and inflow valves 2241 to 2246. The gas cylinder filled with each raw material gas is connected to a raw material gas introduction pipe 2114 in the reaction vessel 2110 via an auxiliary valve 2260. The outflow valves 2251 to 2256 and the mass flow controllers 2211 to 2216 are connected to each other.

  First, the reaction vessel 2110 is fixed, and a conductive substrate 2112 that has been degreased and washed in advance is placed in the reaction vessel 2110 via a cradle 2123. Next, an exhaust device (not shown) is operated to exhaust the reaction vessel 2110. While viewing the display of the vacuum gauge 2119, when the pressure in the reaction vessel 2110 reaches a predetermined pressure of, for example, 1 Pa or less, power is supplied to the substrate heating heater 2113, and the conductive substrate 2112 is set at, for example, 50 ° C to 350 ° C. To the desired temperature. At this time, an inert gas such as Ar or He can be supplied from the gas supply device 2200 to the reaction vessel 2110 and heated in an inert gas atmosphere.

  Next, a gas used for forming a deposited film is supplied from the gas supply device 2200 to the reaction vessel 2110. That is, the valves 2231 to 2236, the inflow valves 2241 to 2246, and the outflow valves 2251 to 2256 are opened as necessary, and the flow rate is set in the mass flow controllers 2211 to 2216. When the flow rate of each mass flow controller is stabilized, the main valve 2118 is operated while viewing the display of the vacuum gauge 2119 to adjust the pressure in the reaction vessel 2110 to a desired pressure. When a desired pressure is obtained, high-frequency power is applied from the high-frequency power source 2120 and simultaneously the high-frequency matching box 2115 is operated to generate plasma discharge in the reaction vessel 2110. Thereafter, the high frequency power is quickly adjusted to a desired power, and a deposited film is formed.

  When the formation of the predetermined deposited film is finished, the application of the high frequency power is stopped, the valves 2261 to 2266, the inflow valves 2241 to 2246, the outflow valves 2251 to 2256, and the auxiliary valve 2260 are closed, and the supply of the raw material gas is finished. At the same time, the main valve 2118 is opened, and the reaction vessel 2110 is evacuated to a pressure of 1 Pa or less.

  The formation of the deposited layer is completed as described above. However, when a plurality of deposited layers (for example, a lower charge injection blocking layer and a photoconductive layer) are formed, the above procedure is repeated to form each layer again. The intermediate layer can also be formed by changing the raw material gas flow rate, pressure and the like to the conditions for forming the photoconductive layer in a certain time.

  After all the deposited films are formed, the main valve 2118 is closed, an inert gas is introduced into the reaction vessel 2110 to return to atmospheric pressure, and then the conductive substrate 2112 is taken out.

  Next, a method for forming a surface layer made of magnesium fluoride will be described.

  Examples of the method for forming the surface layer of the present invention include vacuum thin film forming methods such as vacuum deposition and sputtering. The conditions for forming the magnesium fluoride film as the surface layer are not particularly limited, and may be determined as appropriate. Here, a formation method by a sputtering method will be described.

  FIG. 3 is a schematic cross-sectional view of an example of a DC magnetron sputtering apparatus used for forming the surface layer of the present invention. As shown in this figure, the sputtering apparatus is provided with a vacuum vessel 301 for maintaining the inside in a substantially vacuum state. A cooling box 302 is provided at the center of the bottom of the vacuum vessel 301. The cooling box 302 cools the target by storing a magnet inside and circulating cooling water supplied from outside. A cathode electrode 303 is disposed on the upper surface of the cooling box 302, and a high purity Mg metal target 304 is fixed on the upper surface of the electrode 303. The target material may be a target made of a fluorine-added metal or the like. An anode electrode 305 disposed outside with a predetermined gap between the target 304 and the target 304 is fixed to the vacuum vessel 301. Note that an insulating material 306 is disposed between the anode electrode 305 and the cathode electrode 303.

  Further, a moving mechanism (not shown) is provided on the upper portion of the vacuum vessel 301 so that the cylindrical base 307 is movably transferred between the base support mechanism 308 and the load lock chamber 310 via the gate valve 309. It has been. A shutter 311 is provided between the target substrate 307 and the target 304 so that no film adheres to the target substrate 307 until the discharge is stabilized. This shutter can be opened and closed at high speed by a moving mechanism (not shown). Further, during the processing, the base 307 is rotated via the rotation shaft 317 by a rotation mechanism (not shown). In addition, although it does not attach | subject a code | symbol in particular, in order to prevent the leak in the vacuum vessel 301, the sealing member is provided in the suitable place.

  The substrate 307 is installed at a position not facing the target 304 and is not directly affected by negative ions generated on the target surface and accelerated by the target sheath.

Further, it is configured such that F ₂ gas diluted with Ar can be introduced by a gas supply system including a sputtering gas introduction port 313 and a mass flow controller. Here, the flow rate, purity, and pressure of the introduced gas are limited to high precision and can be held at a constant value. As an inert gas for diluting F ₂ , a gas such as He, Ne, Kr, or Xe is required in addition to Ar, and as a gas containing fluorine, a gas such as CF ₄ or NF ₃ is required in addition to F ₂ gas. According to the configuration, it can be switched and introduced.

  The target cooling water is adjusted to a desired temperature by a chiller (not shown), the flow rate is kept constant, and the target surface temperature is kept constant.

The vacuum vessel 301 is evacuated to a vacuum by the exhaust system 312. After that, when F ₂ / Ar gas is introduced and a DC voltage is applied to the cathode electrode 303 from the DC power source 314, F ₂ and Ar gas are ionized by discharge, and a magnetic field by the magnet 316 is formed above the target 304. Therefore, electrons are trapped in the magnetic field, and magnetron plasma is generated on the target surface. A sheath is formed on the surface of the target by the discharge, positive ions in the plasma are accelerated by the sheath and collide with the target 304, and particles such as Mg, F, and MgF sputtered from the target 304 are released.

In addition, examples of parameters that change the internal stress of the thin film to be formed include gas pressure, gas flow rate, and applied power. However, the internal stress ranges from 1 × 10 ^{6 to} 5 × under any formation conditions. Any conditions may be used as long as the tensile stress is 10 ¹⁰ N / m ² .

  The sputtered particles react with molecules containing active F atoms in the plasma and on the substrate surface, and a magnesium fluoride thin film is deposited on the substrate 307 to be processed. After the film formation is completed, the shutter is closed and the discharge is stopped. Here, the substrate is carried out to the atmosphere via the load lock chamber 310.

  In this method, a control device 315 is installed that can constantly monitor the target voltage from the DC power source and control the DC power source output and the reactive gas flow rate according to the voltage fluctuation. The film formation rate can be made constant by forming the film while keeping this voltage constant, and the film thickness can be controlled by controlling the opening and closing time of the shutter.

  By the way, depending on conditions, fluoride of an insulator may be formed on the target surface, and abnormal discharge may be noticeably generated on and near the target surface. This abnormal discharge is a breakdown due to ions or electrons charged in the insulator. When this abnormal discharge occurs, foreign matter may be mixed in the film, resulting in a film having a rough surface. Thus, by further superimposing the AC voltage on the DC voltage, the charge can be canceled and abnormal discharge can be prevented.

  When superimposing a high frequency, since the substrate self-bias voltage increases due to the high frequency discharge and the film may be damaged by cations incident on the substrate, it is preferable to superimpose a low frequency of 500 kHz or less, In particular, it is preferable to superimpose a voltage having a frequency of 50 kHz or less.

  In the present invention, the film thickness of the surface layer is preferably 0.1 μm or more because desired electrophotographic characteristics and sufficient mechanical strength can be obtained, and the effects of the present invention can be sufficiently obtained. Further, the thickness of the surface layer is preferably 3 μm or less, particularly 1 μm or less because it is easy to form a uniform film, the residual potential can be sufficiently reduced, and desired electrophotographic characteristics can be obtained.

  The magnesium fluoride of the surface layer may not have a stoichiometric composition, and the surface layer may contain O, H, C, N, etc. in addition to magnesium fluoride, but absorbs light. In order to obtain a small film, it is more preferable that the content of these impurities is small.

  As shown in FIG. 5, the electrophotographic photoreceptor of the present invention has a buffer layer 504 between the surface layer 501 and the photoconductive layer 502, and a charge injection blocking layer 505 between the photoconductive layer 502 and the conductive substrate 503. Is preferably provided.

  The buffer layer 504 is a layer having the ability to block the injection of electric charges from the surface to the photoconductive layer 503 and the ability to protect the surface of the photoconductive layer 503, and contains hydrogen and / or halogen and contains silicon atoms as a base material. The amorphous silicon (a-Si (H, X)) is used as a base and is made of a non-single-crystal material further containing at least one atom selected from a carbon atom, a nitrogen atom and an oxygen atom. Examples of such a non-single crystal material include amorphous silicon carbide, amorphous silicon nitride, and amorphous silicon oxide.

  In this case, the composition of the buffer layer 504 can be continuously changed from the photoconductive layer 502 toward the surface layer 501, which is effective for preventing interference. Further, the buffer layer 504 can be doped with a dopant such as a group 13 element or a group 15 element to control the conductivity type and to have an upper blocking ability to block the injection of charged carriers from the surface.

  As the source gas used for the buffer layer 504 in the present invention, the following can be preferably cited.

Examples of substances that can serve as a carbon supply gas include hydrocarbons that can be gasified or gasified such as CH ₄ , C ₂ H ₆ , C ₃ H ₈ , and C ₄ H _10. .

As a substance that can be used as a nitrogen or oxygen supply gas, a compound in a gas state such as NH ₃ , NO, N ₂ O, NO ₂ , O ₂ , CO, CO ₂ , N ₂ , or the like that can be gasified is effectively used. To be mentioned.

  The buffer layer 504 can be formed by a plasma CVD method, a sputtering method, an ion plating method, or the like. In addition, any frequency can be used as a discharge frequency used in the plasma CVD method when forming the buffer layer 504, and an industrial frequency of 1 MHz or more and less than 50 MHz called an RF frequency band is 50 MHz called a VHF band. As described above, even a high frequency of 450 MHz or less can be suitably used.

  The conductive substrate temperature when depositing the buffer layer 504 is preferably adjusted to 50 to 450 ° C., more preferably 100 to 300 ° C.

  The charge injection blocking layer 505 blocks charge injection from the conductive substrate 505 to the photoconductive layer 503. Generally, the charge injection blocking layer 505 is based on a-Si (H, X) and is based on a group 13 element or group 15 The conductivity type is controlled by adding a dopant such as an element. In this case, if necessary, the stress can be adjusted by containing at least one atom selected from a carbon atom, a nitrogen atom and an oxygen atom, and a function of improving the adhesion of the photoconductive layer can be provided.

[Examples and Comparative Examples]
Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to these examples.

[Example 1 and Comparative Example 1]
In this example, an electrophotographic photoreceptor having a layer structure shown in FIG. 5 was used. A conductive substrate made of aluminum having a diameter of 80 mm, a length of 358 mm, and a thickness of 3 mm is used as the substrate, and the CVD apparatus shown in FIG. An amorphous silicon layer and a buffer layer were sequentially stacked as the conductive layer. A power source having a frequency of 13.56 MHz was used.

  After the buffer layer was laminated, a surface layer made of amorphous silicon nitride was sequentially laminated under the conditions shown in Table 2 using the CVD apparatus shown in FIG. 2 to produce an electrophotographic photoreceptor.

  The internal stress evaluation will be described. First, a method for producing a measurement sample will be described. In the CVD apparatus shown in FIG. 2, a substrate in which a strip type Corning optical glass substrate of 5 × 20 × 0.2 mm in thickness was mounted on an aluminum cylinder having a diameter of 80 mm and a length of 358 mm was mounted. An amorphous silicon nitride single film having a thickness of 1.0 μm was formed under the same conditions as the respective examples and comparative examples shown in Table 1.

  FIG. 4 shows a state where the surface layer single film 402 formed on the substrate 401 is bent by tensile stress. One end of the obtained measurement sample was fixed, and the deflection deformation δ of the substrate 401 and the surface layer single film 402 due to film formation was measured using a double-scan high-precision laser measuring instrument LT-9010M (manufactured by Keyence). Here, the deflection amount is the amount of deformation from the midpoint M of the points A and B shown in FIG. 4 to the intersection of the perpendicular bisector of the reference line 403 connecting the points A and B and the film. is there. The internal stress value σ was calculated by the Stoney-Hoffman equation using the deflection amount δ.

  As shown in FIG. 4, the internal stress that the surface layer single film 402 formed on the substrate 401 has when bent in a direction having a small radius of curvature with respect to the substrate is called tensile stress. On the contrary, the internal stress possessed when the formed surface layer single film 402 is bent in a direction having a large curvature with respect to the substrate 401 is referred to as a compressive stress.

σ = Eb ² δ / 3 (1-ν) dl ²
σ: Internal stress value E: Young's modulus of substrate (N / m ² )
b: thickness of substrate (mm)
δ: Deflection amount (μm)
ν: Poisson's ratio of substrate d: Thin film thickness (μm)
l: Length of substrate (mm)

In the present invention, the internal stress was obtained by calculating with the Young's modulus E of the substrate being 6.4 × 10 ¹⁰ N / m ² and the Poisson's ratio ν of the substrate being 0.2.

  Table 2 shows the formation conditions of the amorphous silicon nitride surface layer and the internal stress obtained from the amorphous silicon nitride single film formed under each condition.

  The electrophotographic photoreceptors of Example 1 and Comparative Example 1 manufactured under the above conditions were evaluated as follows.

(Surface condition and image evaluation during film formation)
The surface of the electrophotographic photoreceptor taken out from the film forming furnace was observed, and the presence or absence of cracks was examined with a microscope.

  Further, the electrophotographic photosensitive member was mounted on a digital copying machine (a modified model of iR6000 manufactured by Canon Inc.). A halftone chart (halftone chart) was placed on the document table of the copying machine to output a halftone image, and the presence or absence of scratches on the image was visually inspected. The evaluation was evaluated according to the following criteria: ◎, ○, Δ, ×.

◎ ・ ・ ・ When there are no cracks on the surface of the electrophotographic photoreceptor ○ ・ ・ ・ When there is a slight crack on the surface of the electrophotographic photoreceptor, but it does not appear on the image △ ・ ・ ・ Electronic When cracks occur on the surface of the photoconductor, and the cracks appear only on the halftone image, but there is no problem in light and practical use × ... Cracks occur on the surface of the electrophotographic photoreceptor, and the image If not practical as

(Ghost evaluation during film formation)
An electrophotographic photosensitive member is installed in the copying machine, and the reflection density is applied to the edge of the original printed with a halftone having a reflection density of 0.5 measured by a reflection densitometer D200-II (manufactured by Macbeth). Is placed on the platen in the direction that becomes the leading edge of the image. This image is output, and the reflection density of the halftone part and the reflection density of the ghost part by the circular paper are measured, and the difference is compared and evaluated according to the following three evaluation criteria: ○, △, × It was.

○ ・ ・ ・ When the difference between the reflection density of the halftone part and the reflection density of the ghost part is 0.5 or less and the ghost part cannot be confirmed on the image △ ・ ・ ・ The reflection density of the halftone part and the reflection of the ghost part When the difference in density is 0.5 to 0.9, and the ghost part is slight and practically not problematic ×: The difference between the reflection density of the halftone part and the reflection density of the ghost part is 1.0 or more, When the ghost part is noticeable and is not practical as an image

(Surface condition and image evaluation after endurance test)
As an endurance test, the peeling of the surface layer from the crack and the base after repeated use of 3 million sheets and 5 million sheets in an environment of 35 ° C. and 85% RH was examined with a microscope, and the image was evaluated.

  As the image evaluation, the same procedure as the image evaluation at the time of film formation was performed, and the evaluation was made in the following four evaluation criteria: ◎, ○, Δ, ×.

◎ ・ ・ ・ When there is no scratch due to mechanical stress and the image is good ○ ・ ・ ・ When a scratch due to mechanical stress occurs but does not appear on the image △ ・ ・ ・ Scratch due to mechanical stress Scratches appear on the image only in the halftone image, but it is very slight and has no problem in practical use × ・ ・ ・ Scratches due to mechanical stress have occurred, appear on the image, and cannot be used practically If it is

(Ghost evaluation after endurance test)
After repeated use of 3 million sheets and 5 million sheets in an environment of 35 ° C. and 85% RH, the ghost evaluation after the durability test was performed by the same procedure and the same standard as the ghost evaluation.

  In Example 1 and Comparative Example 1, Table 3 shows the internal stress, the surface condition, the image and the ghost evaluation results at the time of film formation and after durability of 3 million sheets.

From Table 3, when the internal stress of the surface layer of the electrophotographic photoreceptor is a tensile stress of 1.0 × 10 ⁶ N / m ^{2 to} 5.0 × 10 ¹⁰ N / m ² , As a result, it was possible to suppress film peeling and to suppress film peeling and deterioration in image quality after the endurance test of 3 million sheets.

Further, when the internal stress is a tensile stress of less than 1.0 × 10 ⁶ N / m ² , scratches are likely to appear in the surface condition and the image quality after the endurance test of 3 million sheets, and 5.0 × 10 ¹⁰ N / When the tensile stress was larger than m ^2, it was found that scratches were likely to appear in the surface condition and image quality during film formation.

On the other hand, when the tensile stress is 1.0 × 10 ⁷ N / m ² or more, the ghost after durability of 3 million sheets may be better than when the tensile stress is less than 1.0 × 10 ⁷ N / m ^2. all right. This is presumably because, when the film has a small tensile stress at the time of film formation, the compressive stress gradually accumulates during repeated use, and as a result, the compressive stress is such that a ghost appears after the endurance of 3 million sheets.

In addition, when the tensile stress is within a range of 2.0 × 10 ⁸ N / m ² or less, the ghost during film formation is better than when it is larger than 2.0 × 10 ⁸ N / m ^2. Results were obtained.

[Example 2 and Comparative Example 2]
In this example, using the CVD apparatus shown in FIG. 2 under the same conditions as in Example 1, a charge injection blocking layer, an amorphous silicon layer as a photoconductive layer, and a buffer layer were sequentially laminated. Thereafter, a surface layer made of lanthanum fluoride was laminated under the conditions shown in Table 4 using the sputtering apparatus shown in FIG.

  A flat lantern having a length of 120 mm in the central axis direction of the substrate and a width of 80 mm was used as the target. And it installed so that the distance of the sputtering surface of a board | substrate and a target might be set to 120 mm. In addition, as a condition for forming the lanthanum fluoride film, in order to change the internal stress, the pressure in the processing vessel was appropriately changed in the range of 0.05 to 3.0 Pa.

  The fluorine gas used was diluted to 10% with argon gas. At this time, the film thickness of the surface layer was set to 1 μm.

  Further, the internal stress was measured by the same procedure as in Example 1. The measurement sample was mounted on the sputtering apparatus shown in FIG. 3 by mounting a strip type Corning optical glass substrate of 5 × 20 × 0.2 mm thickness on an aluminum cylinder having a diameter of 80 mm and a length of 358 mm as a substrate. . A lanthanum fluoride single film having a thickness of 1 μm was formed thereon under the same conditions as those of the lanthanum fluoride surface layer in each of the examples and comparative examples shown in Table 4.

  Table 4 shows the formation conditions of the lanthanum fluoride surface layer and the internal stress obtained from the lanthanum fluoride single film formed under each condition.

  In the electrophotographic photoreceptors of Example 2 and Comparative Example 2 manufactured under the above conditions, the same procedure and evaluation criteria as in Example 1 were used, and the film surface state and images at the time of film formation, ghost, and 3 million sheets, The film surface state, image and ghost after the 5 million sheet durability test were evaluated.

  The durability test was performed in an environment of 35 ° C. and 85% RH in the same manner as in Example 1. The evaluation criteria are the same as those in Example 1.

  These evaluation results and respective stress measurement results in the lanthanum fluoride surface layer are shown in Table 5, and the internal stress values in the amorphous silicon nitride surface layer of Example 1 and the endurance evaluation of 5 million sheets are shown in Table 6.

  As can be seen from Tables 5 and 6, when lanthanum fluoride, which is a metal fluoride, is used as the material for the surface layer, electrons after a durability test of 5 million sheets in a wider stress range than when the SiN surface layer is used. The result was that the surface state of the photographic photoreceptor and the image and ghost were good. This is because the bonding strength of the metal fluoride is large, and as a result, it becomes difficult to accumulate compressive stress during repeated use. It is to do.

[Example 3, Comparative Example 3]
In this example, using the CVD apparatus shown in FIG. 2 under the same conditions as in Example 1, a charge injection blocking layer, an amorphous silicon layer as a photoconductive layer, and a buffer layer were sequentially laminated. Thereafter, using the sputtering apparatus shown in FIG. 3, a surface layer made of magnesium fluoride was laminated under the conditions shown in Table 7.

  As the target, plate-shaped magnesium having a length in the central axis direction of the substrate of 120 mm and a width of 80 mm was used. And it installed so that the distance of the sputtering surface of a board | substrate and a target might be set to 120 mm. Further, as a condition for forming the magnesium fluoride film, the pressure in the processing vessel was appropriately changed in the range of 0.5 to 3.0 Pa in order to change the internal stress.

  The fluorine gas used was diluted to 10% with argon gas. At this time, the film thickness of the surface layer was set to 1 μm.

  Further, the internal stress was measured by the same procedure as in Example 1. The sample for measuring the internal stress was manufactured in the same manner as in Example 2 by using a strip type Corning 5 × 20 × 0.2 mm thick on an aluminum cylinder having a diameter of 80 mm and a length of 358 mm as a substrate in the sputtering apparatus shown in FIG. Mounted with an optical glass substrate attached. A magnesium fluoride single film having a thickness of 1 μm was formed thereon under the same conditions as those for the magnesium fluoride surface layer in each of the examples shown in Table 7.

  Table 7 shows the conditions for forming the magnesium fluoride surface layer and the internal stress obtained from the magnesium fluoride single film formed under each condition.

  In the electrophotographic photoreceptors of Example 3 and Comparative Example 3 manufactured under the above conditions, the film surface state and images, ghosts, and 3 million sheets at the time of film formation, using the same procedures and evaluation criteria as in Example 1, The surface condition of the film and the image and ghost evaluation after the endurance test of 5 million sheets were performed.

  The durability test was performed in an environment of 35 ° C. and 85% RH in the same manner as in Example 1. The evaluation criteria are the same as those in Example 1.

  These evaluation results are shown in Table 8 together with the stress measurement results.

  As can be seen from Table 7, in comparison with Tables 5 and 6, when magnesium fluoride is used as a material for the surface layer, the surface condition and image after 5 million sheets durability are excellent in a wider stress range. Obtained. This is because magnesium fluoride is relatively hard among metal fluorides, so that compressive stress is difficult to accumulate through durability, and it maintains a state where cracks, peeling from the substrate, and scratches due to mechanical stress are unlikely to occur. It is thought that.

It is a figure which shows an example of the laminated constitution of the electrophotographic photoreceptor which concerns on this invention. It is the figure which showed the schematic diagram of an example of the plasma CVD method apparatus used in order to form the photoconductive layer which has an amorphous silicon as a main component. It is the figure which showed the schematic diagram of an example of the sputtering device used in order to form the surface layer which consists of magnesium fluoride. It is the figure which showed the schematic diagram in case the internal stress of the thin film on a board | substrate turns into tensile stress. It is a figure which shows an example of the laminated constitution of the electrophotographic photoreceptor which concerns on the Example of this invention.

Explanation of symbols

100,500 Photoconductors for electrophotography 101,501 Surface layers 102,502 Photoconductive layers 103,503 Conductive substrate 301 Vacuum vessel 302 Cooling box 303 Cathode electrode 304 Target 305 Anode electrode 306 Insulating material 307 Substrate 308 Substrate support mechanism 309 Gate valve 310 Load lock chamber 311 Shutter 312 Exhaust system 313 Sputter gas introduction port 314 DC power supply 315 Calculation and control device 316 Magnet 317 Base rotating shaft 401 Substrate 402 Surface layer single film 403 Reference line 504 Buffer layer 505 Charge injection blocking layer 2110 Reaction vessel 2111 Cathode electrode 2112 Conductive substrate 2113 Heater 2114 for substrate heating Gas introduction tube 2115 High-frequency matching box 2116 Gas piping 2117 Leak valve 2118 Main valve 2 19 gauge 2120 high-frequency power source 2121 insulating material 2123 cradle 2200 gas supply apparatus 2211 to 2216 mass flow controllers 2221 to 2226 bomb 2231-2236 valves 2241-2246 inflow valve 2251 to 2256 outflow valves 2260 auxiliary valve 2261 to 2266 pressure regulators

Claims (5)

In an electrophotographic photoreceptor in which at least a photoconductive layer and a surface layer are sequentially laminated on a conductive substrate, the stress of the surface layer is a tensile stress of 1.0 × 10 ⁶ to 5.0 × 10 ¹⁰ N / m ^2. An electrophotographic photoreceptor characterized by the above. ^2. The electrophotographic photoreceptor according to claim 1, wherein the surface layer has a tensile stress of 1.0 × 10 ⁷ to 2.0 × 10 ⁸ N / m ² .   The electrophotographic photoreceptor according to claim 1, wherein the surface layer is made of a metal fluoride.   4. The electrophotographic photoreceptor according to claim 3, wherein the metal fluoride is composed of magnesium fluoride containing magnesium and fluorine as main components.   The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer is made of amorphous silicon.

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