JP4533189B2 - Electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to an electrophotographic photoreceptor.

  As one of element members used for an electrophotographic photoreceptor, a non-single crystal deposited film containing silicon atoms as a main component, for example, an amorphous silicon (hereinafter referred to as a-Si) deposited film compensated with hydrogen and / or halogen is used. Proposed as high-performance, high-durability, non-polluting photoconductors, some of which have been put into practical use.

  Such a-Si electrophotographic photoreceptors have been proposed having various layer configurations in accordance with various required performances. Above all, the surface layer is recognized as an important layer for obtaining various characteristics such as wear resistance, charge retention, environment resistance, and light transmittance of the electrophotographic photoreceptor.

  In recent years, with the progress of higher definition of copying machines, it is planned to shorten the wavelength of image exposure light, and the surface layer is required to have a characteristic of having a wide band gap with little absorption of exposure light of short wavelength in particular. It has become like this.

  As a material that satisfies the above characteristics, magnesium fluoride has attracted attention as a material for the electrophotographic photoreceptor surface layer, and an example in which the surface layer of the electrophotographic photoreceptor is actually magnesium fluoride has been proposed ( For example, Patent Document 1).

By using this magnesium fluoride as a surface layer, it is possible to obtain excellent characteristics such as suppression of occurrence of image blur and image flow and almost no potential fluctuation due to wear.
JP 2003-29437 A

  However, in recent years, with the increase in speed of electrophotographic apparatuses, with the increase in color, high definition for forming finer images has rapidly progressed, and as a photoconductor for electrophotography, higher quality images have been developed. A member that can be formed is required, and it is required to have excellent image quality and durability.

  Under such circumstances, there are still problems to be solved even with an electrophotographic photoreceptor using magnesium fluoride having excellent characteristics as a surface layer as described above.

  One of them is the problem of tenderness. Crushing refers to a phenomenon in which scratch-like white spots or black streaks appear on an image due to local mechanical stress on the surface of the electrophotographic photoreceptor.

  Although the pressure scar is not scratched on the surface of the electrophotographic photoreceptor, it is easily noticeable in the halftone image. In addition, although slight injuries do not appear on the image by heating the electrophotographic photoreceptor at about 200 ° C. for about 1 hour, such a response is not possible in the market, and the occurrence is not possible in advance. It cannot be predicted.

  Another problem is the occurrence of a so-called ghost in which an afterimage of the previous image is generated when image formation is repeated. This has been found to cause ghosting by causing fluctuations in the surface potential by accumulating charges generated by image formation inside the electrophotographic photoreceptor.

  These problems have become conspicuous in an electrophotographic process using a short wavelength laser as image exposure light so that a higher-definition image can be formed as compared with the prior art. Further, when a surface layer of magnesium fluoride is applied to a negatively charged electrophotographic photoreceptor generally used in a full-color electrophotographic apparatus, it may be particularly noticeable.

  Due to the above background, the surface layer of magnesium fluoride is required to have further improved performance.

  The present invention has been made to solve the above-mentioned problems, and its object is to improve the durability against mechanical stress by controlling the orientation of the magnesium fluoride crystals. An object of the present invention is to provide an electrophotographic photoreceptor that suppresses the generation of scratches and effectively suppresses the generation of ghosts to form high-quality images over a long period of time.

  The present invention is an electrophotographic photoreceptor having at least a photoconductive layer and a surface layer made of magnesium fluoride on a substrate, and has a plane orientation 101 obtained by X-ray diffraction as viewed from the surface side of the electrophotographic photoreceptor. The ratio of the peak value of the reflection intensity is 0 to 0.8 with respect to the peak value of the reflection intensity in the plane orientation 110.

  The electrophotographic photoreceptor of the present invention can effectively suppress the occurrence of pressure flaws and ghosts.

  FIG. 1 is a cross-sectional view schematically showing an example of the electrophotographic photoreceptor of the present invention.

  In FIG. 1A, an electrophotographic photoreceptor 10 of the present invention includes a conductive base 13 made of a conductive material such as aluminum, and light sequentially stacked on the surface of the conductive base 13. It consists of a conductive layer 12 and a surface layer 11. In FIG. 1B, a lower charge injection blocking layer 14 and an upper charge injection blocking layer 15 are further provided between the conductive substrate 13 and the photoconductive layer 12.

  The surface layer of the present invention is made of magnesium fluoride, and the peak value of the reflection intensity in the plane orientation 101 obtained by X-ray diffraction viewed from the surface of the electrophotographic photoreceptor becomes the peak value of the reflection intensity in the plane orientation 110. On the other hand, it is 0-0.8, More preferably, it is 0-0.6.

  In general, a magnesium fluoride thin film tends to be a crystalline film. In light of the above-mentioned problems, the present inventor examined the relationship with the crystal orientation of the surface layer of magnesium fluoride.

  In general, a thin film for crystal growth having a single crystal structure with a certain plane orientation is expected to exhibit good characteristics.

  However, it is actually difficult to grow only crystals having a single plane orientation on the surface of a curved electrophotographic photosensitive member, and it becomes a mixture of crystal components having other plane orientations in a certain ratio. There are many cases.

  In view of this, the present inventor paid attention to the relationship between the magnesium fluoride surface layer having various crystal orientations formed under various conditions and the characteristics of the electrophotographic photoreceptor.

  As a result, there is a correlation between the degree of growth of the surface orientation 110 and the surface orientation 101 (hereinafter simply referred to as the surface orientation 110 and the surface orientation 101) and the electrophotographic photoreceptor characteristics when viewed from the surface of the electrophotographic photoreceptor. I found out.

  That is, the generation of crushing and ghosting can be effectively prevented by setting the plane orientation 110 as the main crystal growth plane and reducing the growth ratio of the plane orientation 101.

  At present, there is no clear reason why the characteristics of the electrophotographic photoreceptor may deteriorate if the growth ratio of the plane orientation 101 to the plane orientation 110 is large. However, when the plane orientation 101 grows greatly, it is presumed that crystals with various plane orientations tend to grow in the same manner and are often randomly oriented.

  In such a film, the internal structure becomes complicated and various grain interfaces are formed, and at the same time, it seems that voids are formed inside the film, but this phenomenon leads to the occurrence of crushing and ghosting. Presumed to be.

  According to the study of the present inventor, other surface orientations when viewed from the surface of the electrophotographic photoreceptor depending on conditions, for example, the surface orientations 111, 210, 211, 220, etc. grow to a certain extent with respect to the surface orientation 110. There is also. However, they may grow independently of each other, and the growth of these plane orientations does not immediately lead to growth with random orientation, and therefore there is also a significant correlation with the characteristics of electrophotographic photoreceptors. There wasn't. Further, among the studies conducted by the present inventors, the main crystal growth is the plane orientation 110, and there is no condition for the main growth of crystal planes having other orientations. Even when the reflection intensity does not become the main peak, the electrophotographic photoreceptor characteristics change corresponding to the peak value of the reflection intensity of the plane orientation 101 with respect to the peak value of the reflection intensity of the plane orientation 110. The result seems to be obtained.

  From the above knowledge, the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 is set to 0.8 or less, more preferably 0.6 or less. The present inventors have found that it can be improved and have completed the present invention.

  In the present invention, the effect is obtained by setting the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 of the crystal to 0.8 or less, more preferably 0.6 or less. I can. As a method for forming such a surface layer, any method can be used as long as this can be achieved. For example, a known method such as an evaporation method, an ion plating method, or a sputtering method can be adopted. Among these, the reactive sputtering method using a fluorine-containing gas as a reactive gas and magnesium as a target is preferable because the composition can be easily controlled and a uniform deposited film having a relatively large area can be easily obtained.

In this case, NF ₃ or CF ₄ can be used as the reactive gas in addition to F ₂ (fluorine). Moreover, what diluted these with rare gas, such as Ar, Ne (neon), He (helium), and Kr (krypton), can also be used.

  As a gas for sputtering the target, a rare gas such as Ar, Ne, or Kr can be preferably used.

  On the surface of a curved electrophotographic photosensitive member, it is actually difficult to grow only a crystal having a single plane orientation, which may result in a mixture of crystal components having other plane orientations at a certain ratio. Since there are many, the lower limit is not particularly specified, but when a crystal that is completely oriented in the plane orientation 110 is obtained, the reflection intensity in the plane orientation 101 becomes 0, and the peak value of the reflection intensity in the plane orientation 110 Thus, the ratio of the peak values of the reflection intensity in the plane orientation 101 can be zero, but even in this case, there seems to be no problem.

  In order to set the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 to be 0.8 or less, it is necessary to change the formation conditions for each of the above formation methods. Obtainable. However, for example, when the reactive sputtering method described above is used, crystal orientation is not uniquely determined under a single condition. For example, conditions such as pressure, substrate temperature, discharge power, power frequency, gas flow rate, etc. Crystal growth changes by acting organically.

  However, in the present invention, the ratio of the peak value of the reflection intensity at the plane orientation 101 to the peak value of the reflection intensity at the plane orientation 110 of the crystal when viewed from the surface of the electrophotographic photoreceptor is 0.8 or less. It is important that any formation method and formation condition can be achieved.

  In the present invention, the reflection intensity of each plane orientation by X-ray diffraction was performed by the following method.

  First, the electrophotographic photoreceptor to be measured is cut out to a size of about 30 mm square to prepare a measurement sample. This is installed in an X-ray diffractometer. Since the surface of the electrophotographic photoreceptor is curved, the surface of the measurement point (hereinafter referred to as the measurement surface) is approximately parallel to the reference measurement surface. It is necessary to install.

  The angle of the X-ray source and the detector (counter tube) with respect to the surface of the sample placed in this way is measured by a method of scanning in conjunction with each other so as to be symmetric with respect to the normal of the measurement surface. This method is called a 2θ / θ scan method because the X-ray incident angle θ on the measurement surface and the X-ray reflection angle (that is, the detector angle) 2θ change simultaneously.

  In the 2θ / θ scan method, the crystal plane that causes diffraction is always parallel to the measurement surface and does not change depending on the value of 2θ. Therefore, the crystal orientation when viewed from the measurement surface, that is, the surface of the electrophotographic photoreceptor is directly measured. it can.

  For the measurement by the above method, a powder X-ray diffractometer using a normal concentrated optical system can be used, and any general X-ray diffractometer capable of obtaining sufficient reflection intensity for measurement can be used.

  FIG. 2 shows the above procedure using a RINT-1500 X-ray diffractometer manufactured by Rigaku Corporation. Both the diverging and scattering slits are 0.5 degrees, the receiving slit is 0.15 mm, the scanning speed is 1 degree per minute, and the step angle is 0. It is an example of the result of X-ray diffraction measured at 0.02 degree. In this example, a slight undulation is observed in the background due to the influence of the photoconductive layer formed of amorphous silicon as the lower layer of the surface layer, and at the same time, the reflection intensity peak that appears due to the aluminum crystals used as the substrate Appear around 38.5 and 44.7 degrees.

  In the example as shown in FIG. 2, the peak value of the reflection intensity in each plane orientation is obtained by subtracting the background intensity from the measured peak.

  FIG. 3 shows an outline of the peak value calculation method. As shown in FIG. 3, an arbitrary point is extracted from the background and sampled. For example, a fitting line is created by using a spline function or the like, and a base line is virtually generated at a point where a reflection intensity peak is obtained. To form. At each angle, the reflection intensity by the magnesium fluoride crystal lattice can be obtained by subtracting the virtual baseline value from the measurement value of the reflection intensity.

  In addition, if a reflection intensity peak derived from the type of substrate or the material of the lower layer appears near the plane orientation of the target magnesium fluoride, as described above, electrons are formed on the crystalline substrate. A magnesium fluoride film may be formed under the same conditions as those for forming the surface layer of the photographic photoreceptor, and this may be measured and evaluated.

  However, an electrophotography in which a photoconductive layer or the like as a lower layer is formed of an amorphous layer formed of general amorphous silicon (hereinafter referred to as a-Si), amorphous silicon nitride (hereinafter referred to as a-SiN), or the like. In the case of a photoconductor, the result measured on the electrophotographic photoconductor as described above may be adopted.

  At this time, as the crystalline substrate, the substrate material and the surface orientation in which the peak of the reflection intensity derived from the substrate does not appear near the peak of the reflection intensity due to the plane orientation of the target magnesium fluoride are appropriately selected. Must be selected.

  In general, in the 2θ / θ scanning method, the sensitivity tends to decrease when 2θ is larger than when 2θ is small. Also, depending on the sample to be measured, it may be difficult to obtain the reflection intensity depending on the plane orientation.

  In this case, sensitivity correction is required in addition to the above-described correction for reducing the background.

  In order to correct the sensitivity, a correction coefficient can be obtained by measuring a powder made of magnesium fluoride crystals.

  That is, a sample made of magnesium fluoride powder having an arbitrary particle size and made into a pellet is prepared. This is measured by the aforementioned 2θ / θ scan, and the peak value of the reflection intensity in each plane orientation is obtained. Since all surface orientations are randomly arranged at almost the same ratio in the powder sample, the peak values of the reflection intensity appear as they are as a difference in sensitivity, so correction is made so that the peak values of the reflection intensity of each surface orientation are the same. What is necessary is just to determine a coefficient.

  In the above example, the electrophotographic photosensitive member is cut out, but this is due to the limitation of the measuring device. If there is no limitation on the measuring device, there is no problem in the measurement even if it is not cut out.

Magnesium fluoride takes an ionic crystal in which magnesium ions, which are divalent cations, and fluorine ions, which are monovalent anions, are combined, so the theoretical stoichiometric composition is MgF ₂ . However, the magnesium fluoride of the present invention is not limited to this range, and can be used as long as a peak of reflection intensity that can be identified by X-ray diffraction can be obtained even if the composition ratio deviates from the stoichiometric composition. it can.

  In the present invention, the film thickness of the surface layer may be in a range where desired electrophotographic characteristics and sufficient mechanical strength can be obtained. Specifically, it is preferably 0.05 μm or more, and more preferably 0.1 μm or more. In addition, when the film thickness is too thick, a residual potential may be generated, and from the viewpoint of economy and the like, it is preferably 3 μm or less, and more preferably 1 μm or less.

  In the present invention, the photoconductive layer 12 may be any one as long as it exhibits at least photoconductivity and has characteristics that can be used as an electrophotographic photoreceptor. For example, an organic semiconductor, selenium, amorphous silicon (a-Si), or the like can be used as a material for the photoconductive layer.

  Among these, a-Si is preferable as the photoconductive layer. This will be described later when the magnesium fluoride deposited film of the present invention is formed on the photoconductive layer. Usually, a vacuum process such as sputtering using a magnesium metal target is used. In addition to being less contaminated by degassing and the like, and having little influence on the formation of the magnesium fluoride deposited film, when the photoconductive layer is a-Si, its hardness is relatively high, and image formation was repeated over a long period of time. Even in this case, the durability is sufficient.

  When a-Si is employed as the photoconductive layer, it can be formed by a known method such as plasma CVD, sputtering, or ion plating.

  For example, in order to form the photoconductive layer 12 by a plasma CVD method, basically, as is well known, a silicon atom (Si) source gas and a hydrogen atom (H) source gas are mixed in a reaction vessel whose inside is reduced in pressure. In a gas state, a glow discharge is generated in the reaction vessel, the introduced source gas is decomposed, and a layer made of a-Si is deposited on the conductive substrate 13 installed at a predetermined position. That's fine.

  The a-Si deposited film generates dangling bonds only with Si, which causes problems in layer quality, particularly photoconductivity, charge retention characteristics, and the like. Is preferably compensated. For example, when hydrogen atoms are included, the content is preferably 10 atomic% or more, particularly 15 atomic% or more, and preferably 30 atomic% or less, particularly 25 atoms, based on the sum of silicon atoms and hydrogen atoms. % Or less is preferable.

In the present invention, silanes such as silane (SiH ₄ ) and disilane (Si ₂ H ₆ ) can be suitably used as the Si source gas. In addition to these silanes, hydrogen gas (H ₂ ) can also be suitably used as a hydrogen atom source gas in the photoconductive layer.

In the present invention, a halogen atom (X) can be used in addition to H in order to compensate for dangling bonds of Si. Examples of the halogen atom include fluorine (F), bromine (Br), chlorine (Cl) and the like. Specific examples of compounds for introducing these include fluorine gas (F ₂ ), BrF, ClF, Mention may be made of halogen compounds such as ClF ₃ , BrF ₃ , BrF ₅ , IF ₃ and IF ₇ . Also, silicon compounds containing halogen atoms, so-called silane derivatives substituted with halogen atoms can be used, and specific examples include silicon fluorides such as SiF ₄ and Si ₂ F _6. .

  In the present invention, it is preferable that the photoconductive layer 12 contains an atom for controlling conductivity as required. The atoms for controlling the conductivity may be contained in the photoconductive layer 12 in a uniformly distributed state, or there are portions containing in a non-uniform distribution state in the layer thickness direction. Also good.

  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”) and 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 group 13 atoms include boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl), with B, Al, and Ga being particularly preferred. 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 the atoms for controlling the conductivity contained in the photoconductive layer 12 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 the atoms for controlling the conductivity, the photoconductive layer 12 is formed in the gaseous state of the Group 13 atom introduction source material or the Group 15 atom introduction source material when forming the layer. The other raw material gas may be introduced into the reaction vessel. 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.

For example, when B is used as an atom for controlling conductivity, halides such as BF ₃ and BCl ₃ can be used in addition to diborane (B ₂ H ₆ ). When P is used as an atom for controlling conductivity, phosphine (PH ₃ ) or the like can be used.

If necessary, these raw material materials for atom introduction for controlling conductivity may be diluted with H ₂ or He.

Furthermore, in the present invention, it is also effective that the photoconductive layer 12 contains one or more of carbon atoms, oxygen atoms, and nitrogen atoms. The content (total) of carbon atoms, oxygen atoms and nitrogen atoms is 1 × 10 ⁻⁵ atom% or more, particularly 1 × 10 ⁻⁴ atom%, based on the sum of silicon atoms, carbon atoms, oxygen atoms and nitrogen atoms. In addition, it is preferably 1 × 10 ⁻³ atom% or more, and is preferably 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, It 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.

Substances that introduce these carbon, oxygen, and nitrogen atoms include methane (CH ₄ ), acetylene (C ₂ H ₂ ), carbon dioxide (CO ₂ ), oxygen (O ₂ ), nitrogen (N ₂ ), ammonia ( NH ₃ ), nitric oxide (NO), or the like can be used.

  In the present invention, the layer thickness of the photoconductive layer 12 is appropriately determined from the viewpoint of obtaining desired electrophotographic characteristics, economic effects, etc., but is preferably 15 μm or more, more preferably 20 μm or more. Moreover, 60 micrometers or less are preferable, 50 micrometers or less are more preferable, and it is still more preferable to set it as 40 micrometers or less.

  The conductive substrate 13 is not particularly limited as long as it can hold the photoconductive layer 12 and the surface layer 13 formed on the surface, and may be any one. Examples thereof include metals such as Al, Cr, Mo, Au, In, Nb, Te, V, Ti, Pt, Pd, and Fe, and alloys thereof such as Al alloy and stainless steel. In addition, the surface on the side on which at least the photoconductive layer is formed of an electrically insulating support such as a synthetic resin film or sheet such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene or polyamide, glass or ceramic. The conductive substrate 13 can also be used as the conductive substrate 13.

  In the present invention, the layer structure of the electrophotographic photoreceptor is appropriately formed with a lower charge injection blocking layer 14 below the photoconductive layer 12 and an upper charge injection blocking layer 15 above the photoconductive layer 12 as appropriate. can do. These materials are preferably formed based on the material constituting the photoconductive layer 12. For example, when a-Si is selected as the photoconductive layer, the dangling bond is generally terminated by a hydrogen atom (H) or a halogen atom (X) as described above, and a group 13 element or a group 15 element. By adding a dopant such as those having a conductivity type controlled and having a carrier injection blocking ability, a dopant can be used. In particular, the lower charge injection blocking layer 14 has a function of adjusting the stress by containing at least one atom selected from a carbon atom, a nitrogen atom and an oxygen atom as necessary, and improving the adhesion of the photoconductive layer. It can also be made.

  In addition to these layers, an intermediate layer in which the composition is continuously changed between the layers may be formed. Further, these layers may be formed by appropriately selecting according to the characteristics required for the electrophotographic photoreceptor.

  Next, a method for forming the photoconductive layer 12 when a-Si is employed as the photoconductive layer 12 will be described by taking a plasma CVD method as an example.

  FIG. 4 is a schematic view of an example of a deposited film forming apparatus that can be used for forming the photoconductive layer 12 in the present invention.

  The apparatus shown in FIG. 4 is roughly composed of a deposited film forming container 100, an exhaust apparatus 200, and a source gas supply means 300.

  The source gas supply means 300 includes cylinders 301 to 305, supply valves 306 to 310, pressure regulators 311 to 315, primary valves 316 to 320, mass flow controllers 321 to 325, and secondary valves 326 to 330. The cylinders 301 to 305 are filled with a raw material gas for a vacuum processing process, and are adjusted to a pressure of, for example, about 0.2 MPa by pressure regulators 311 to 315 through supply valves 306 to 310.

  An exhaust device 200 is further connected to the deposited film forming container 100 through an exhaust pipe 405, a throttle valve 406, and an exhaust valve 407. The exhaust device 200 includes a mechanical booster pump 201 and a rotary pump 202, and evacuates the inside of the deposited film forming container 100. In addition to the mechanical booster pump 201 and the rotary pump 202, the exhaust device 200 may include an oil diffusion pump, a turbo molecular pump, or the like as necessary.

  FIG. 5 is a longitudinal sectional view schematically showing an example of the deposited film forming container 100 of FIG. FIG. 6 is a cross-sectional view schematically showing the container of FIG.

  The deposited film forming container 100 includes a base plate 136 and a vacuum container 101 on a frame 121. A holding member 123 for holding the base 122 is provided at the approximate center in the vacuum vessel 101, and a heater 124 is provided on the holding member 123 so that the base 122 can be heated from the inside. Further, after the substrate 122 is placed on the holding member 123 of the deposited film forming apparatus 100, a cap 125 is provided on the substrate so that the heater 124 inside the substrate 122 is not exposed to plasma.

  The vacuum vessel 101 is coupled by an upper lid 126, a base plate 136, and a seal member (not shown) so that the inside can be vacuum-sealed. Around the vacuum vessel 101, a plurality of electrodes 127 are provided concentrically with the vacuum vessel 101, a matching box 423 is connected via a branch plate 128, and further connected to a high frequency introduction cable 422 and a high frequency power source 421. .

  The vacuum vessel 101 is formed of a ceramic member such as alumina, and also serves as a window member that transmits high-frequency power into the vacuum vessel 101.

  The high frequency power radiated from the electrode 127 is transmitted into the vacuum vessel 101 and causes glow discharge in the vacuum vessel 101. Further, a high frequency shield 129 is provided around the electrode 127 to prevent high frequency from leaking to the periphery.

  An exhaust port 130 is provided on the base plate 136 on the same circumference with the base 122 as a center, and these are assembled and connected to the exhaust pipe 405.

  The source gas introduction pipe 131 is provided outside the arrangement circle of the exhaust port 130 on the same circumference with the base 122 as the approximate center, and is connected to the source gas supply means 300 via the source gas supply path 404. . The source gas introduction pipe 131 is provided with a plurality of gas discharge holes (not shown) to supply the source gas into the vacuum vessel 101.

  Next, a procedure for forming a deposited film using the apparatus shown in FIGS. 4 to 6 will be specifically described.

  First, the vacuum vessel 101 is fixed to the base plate 136 installed on the gantry 121 via a seal member (not shown), and the base 122 that has been degreased and washed in advance is placed in the vacuum vessel 101 via the holding member 123. After installing the cap 125 at the same time, the upper lid 126 is installed in the vacuum container 101 via a seal member (not shown).

  Next, the exhaust device 200 is operated, the valve 407 is opened, and the inside of the vacuum vessel 101 is exhausted. While viewing the display of the vacuum gauge 111, when the pressure in the vacuum vessel 101 reaches a predetermined pressure of 1 Pa or less, for example, power is supplied to the heater 124 and the base 122 is heated to a predetermined temperature of 50 to 350 ° C., for example. To do. At this time, an inert gas such as Ar, He or the like can be supplied from the source gas supply means 300 to the vacuum vessel 101 to perform heating in an inert gas atmosphere.

  Next, the source gas used for forming the deposited film is supplied from the source gas supply means 300 to the vacuum vessel 101. That is, the supply valves 306 to 310, the primary valves 316 to 320, and the secondary valves 326 to 330 are opened as necessary, and the flow rate is set in the mass flow controllers 321 to 325. When the flow rate of each mass flow controller is stabilized, the throttle valve 406 is operated while viewing the display of the pressure gauge 111 to adjust the pressure in the vacuum vessel 101 to a desired pressure.

  When a predetermined pressure is obtained, high-frequency power is applied from the high-frequency power source 421 and simultaneously the matching box 423 is operated to generate plasma discharge in the vacuum vessel 101. Thereafter, the high-frequency power is quickly adjusted to the predetermined power. Then, 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 supply valves 306 to 310, the primary valves 316 to 320, the secondary valves 326 to 330, and the valves 402 and 403 are closed, Simultaneously with the completion of the supply, the throttle valve 406 is opened, and the inside of the vacuum vessel 101 is exhausted 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, the lower charge injection blocking layer and the photoconductive layer) are formed, the above procedure is repeated again to form each layer. 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, a leak valve (not shown) is opened, and the substrate 122 having the photoconductive layer is taken out with the inside of the vacuum vessel 101 set to atmospheric pressure.

  Next, a method for forming a surface layer made of magnesium fluoride will be described taking a sputtering method as an example.

  FIG. 7 is a diagram schematically showing an example of a deposited film forming apparatus using a sputtering method that can be used to form a surface layer.

  This deposited film forming apparatus is roughly composed of a reaction furnace 5100 and a charging furnace 5200. The reaction furnace 5100 includes a reaction vessel 5108, a reactive gas nozzle 5103, a rotating shaft 5104, a sputter gas introduction pipe 5105, and a cathode 5102.

  The reaction vessel 5108 is connected to an exhaust device (not shown) through a valve 5117 so that the inside can be evacuated. The substrate 122 (having at least a photoconductive layer formed by the above procedure) is installed on the rotating shaft 5104 via the holder 5113, and the rotating shaft 5104 is rotatably supported by the rotating shaft seal 5119 and connected to the motor 5118. The

  The reactive gas nozzle 5103 includes a gas discharge hole 5116 and is connected to a source gas supply means (not shown) through a valve 5115. As the source gas supply means, the same source gas supply means 300 as shown in FIG. 5 can be used.

  The cathodes 5102 are respectively supported by the reaction vessel 5108 via insulating members 5107, and the outer periphery thereof is isolated from the plasma by a shield 5111. Further, the cathode 5102 can be cooled from outside through the cooling water pipes 5131 and 5132 during the sputtering process.

  The cathode 5102 is connected to a power source 5109 outside the reaction vessel 5108. The power source 5109 is shown as a direct current power source as an example, but this may be a power source having a function of periodically reversing the applied polarity. Further, a low frequency power source having a frequency of about 10 kHz to 500 kHz and a high frequency power source having a frequency of about 13.56 MHz may be used. Note that when a high-frequency power source is used, it is desirable to provide a matching unit (not shown) between the power source 5109 and the cathode 5102 as necessary.

  The cathode 5102 includes a target 5106, and has a configuration in which so-called magnetron sputtering is performed in which a permanent magnet 5129 is installed in pairs so as to form a magnetic field parallel to the target 5106.

  A sputtering gas introduction pipe 5105 is installed near the cathode 5102 and connected to a sputtering gas supply means (not shown) via a valve 5110 to introduce a sputtering gas such as argon (Ar).

  The input furnace 5200 includes a vacuum vessel 5201, an actuator 5203, and a door 5202, and the vacuum vessel 5201 communicates with the reaction vessel 5108 through a gate valve 5101. Further, the vacuum vessel 5201 can be evacuated separately from the reaction vessel 5108 by an exhaust device (not shown) connected via a valve 5205.

  The actuator 5203 has a shaft 5207 supported by the vacuum vessel 5201 by a vacuum seal 5206. The shaft 5207 is provided with a chucking mechanism 5208. The base 122 is held in a vacuum, the gate valve 5101 is opened, and the shaft 5207 is expanded and contracted to convey the base 122 between the reaction furnace 5100 and the input furnace 5200.

  The vacuum container 5201 can be opened to the atmosphere by a valve 5204.

  Next, the procedure for forming the surface layer when the apparatus shown in FIG. 7 is used will be specifically described.

  First, after setting a target 5106 made of a metal necessary for forming a deposited film in the reaction vessel 5108, the valve 5117 is opened and the inside of the reaction vessel 5108 is exhausted by an exhaust device. At the same time, for example, the base body 122 on which the photoconductive layer is formed is set to the chucking mechanism 5208 in the charging furnace 5200 through the door 5202. Next, the door 5202 is closed, the valve 5205 is opened, and the inside of the charging furnace 5200 is exhausted.

  When both the reaction vessel 5108 and the inside of the charging furnace 5200 have a sufficient degree of vacuum, for example, 0.1 Pa or less, the valve 5101 is opened, the actuator 5203 is operated, the shaft 5207 is extended, and the substrate 122 is placed in the reaction vessel 5108. It is installed in the holder 5113, the chucking mechanism 5208 is opened, and the base body 122 is left on the holder 5113.

  Thereafter, the shaft 5207 is contracted, the chucking mechanism 5208 is returned into the charging furnace 5200, and the gate valve 5101 is closed.

  Next, sputter gas and reactive gas are supplied into the reaction vessel 5108 from the sputtering gas and reactive gas supply means (not shown) by opening the valves 5110 and 5115, respectively, and a vacuum gauge connected to the reaction vessel 5108. (Not shown), when a predetermined pressure is reached, power is applied from the power source to the cathode 5102 to cause glow discharge.

  At this time, the rotating film 5104 is rotated by the motor 5118, whereby a deposited film can be obtained uniformly in the circumferential direction of the substrate 122.

  When a predetermined deposited film is formed, the supply of power from the power source 5109 is stopped, and the formation of the deposited film is finished.

  At the same time, the valves 5110 and 5115 are closed, the supply of the reactive gas and the sputtering gas is finished, the inside of the reaction vessel 5108 is once evacuated to a pressure of, for example, 0.1 Pa or less, and the gate valve 5101 is opened.

  Here, the actuator 5203 is operated, the shaft 5207 is extended, the base 122 is held by the chucking mechanism 5208, and then the shaft 5207 is contracted again. When the base 122 is accommodated in the charging furnace 5200, the gate valve 5101 is closed. .

  After confirming that the gate valve 5101 is closed, the valve 5204 is opened, the inside of the vacuum vessel 5201 is at atmospheric pressure, the door 5202 is opened, the substrate 122 is taken out, and the formation of the electrophotographic photoreceptor is finished.

  In the example of the procedure for forming the electrophotographic photoreceptor described above, the electrophotographic photoreceptor formed using the deposited film forming apparatus by the plasma CVD method shown in FIGS. 4 to 6 is once taken out into the atmosphere. The procedure was put into the deposited film forming apparatus by sputtering shown in FIG. 7, but this procedure is not particularly specified. For example, a transport apparatus capable of transporting the vacuum connecting both apparatuses is installed, and the electrophotographic photoreceptor is transported in vacuum. May be performed.

  Hereinafter, the present invention will be described with reference to examples.

(Example 1 and Comparative Example 1)
According to the above procedure, the lower charge injection blocking layer 14, the photoconductive layer 12, and the upper charge injection blocking layer 15 were formed on the substrate 13 by the plasma CVD method, and then the magnesium fluoride surface layer 11 was formed by the sputtering method.

  In this embodiment, a cylinder having a mirror-finished surface made of an aluminum material having a diameter of 80 mm, a length of 358 mm, and a thickness of 3 mm was used as the conductive substrate 13.

  Table 1 shows the formation conditions by the plasma CVD method.

  In this example, the substrate temperature was changed from room temperature (about 20 ° C.) to 300 ° C. in the surface layer formation conditions. Here, high-frequency power having a frequency of 13.56 MHz is used as power applied to the cathode 5102.

  Table 2 shows the conditions for forming the surface layer.

The F ₂ flow rate in Table 2 indicates the F ₂ effective flow rate in the gas diluted with Ar to a concentration of 5%.

  The electrophotographic photosensitive member formed in this way was modified using a Canon copier iR6000 for negative charging system evaluation, and the wavelength of the laser for image exposure was changed to 405 nm. Evaluation of ghosts and pressure injuries was performed. Moreover, the crystal orientation by X-ray diffraction was evaluated using the electrophotographic photoreceptor subjected to the above evaluation.

  Each item was evaluated by the following method.

(Chargeability)
First, an electrophotographic photosensitive member is set in the copying machine, image exposure (laser) is performed, and a high voltage of −6 kV is applied to the charger to perform corona charging. At this time, the surface potential (that is, dark portion charging potential) generated on the electrophotographic photosensitive member was measured by installing a sensor of a surface potential meter (Model 334 manufactured by TREK) at a position corresponding to the developing unit. The unit of charging ability is measured by voltage (V).

(Light sensitivity)
An electrophotographic photoreceptor is installed in the copying machine, and the charging current applied to the charger is adjusted so that the dark portion charging potential at the position of the developing device is -450V. While maintaining this charging current, image exposure (laser) was performed by adjusting the intensity of the laser beam so that the bright portion surface potential at the developing unit position was -50V. The intensity of the laser beam at this time was defined as photosensitivity. The unit of photosensitivity is measured by the amount of light (lux · sec).

(ghost)
A ghost chart is created by pasting a 10 mm diameter circular paper printed with a reflection density of 1.1 on the edge of a document having a halftone with a reflection density of 0.5 printed on the entire surface. Place it on the platen in the direction where the pasted image will be the leading edge of the image.

  Using this manuscript, a copy image was output, and the reflection density of the halftone part and the reflection density of the ghost part by circular paper were measured, and the difference was compared and evaluated.

(Crush)
Using a surface property test apparatus (manufactured by HEIDON), a constant load is applied to a diamond needle having a curvature of 0.8 mm in diameter and brought into contact with the surface of the electrophotographic photoreceptor. In this state, the diamond needle is moved at a constant speed of 50 mm / min in the generatrix direction (longitudinal direction) of the electrophotographic photoreceptor. The moving distance may be arbitrarily set, but is preferably about 10 mm.

  This operation is repeated while changing the load (g) applied to the diamond needle. In this case, it goes without saying that the position on the electrophotographic photoreceptor where the needle is brought into contact is changed.

  After observing the surface of the electrophotographic photoreceptor subjected to the surface property test with a microscope and confirming that no scratches are generated, the surface is placed in the above-described electrophotographic apparatus, and a document on which a halftone is printed is obtained. Used to output a copy image having a halftone with a reflection density of 0.5. The above procedure was performed on all the electrophotographic photoreceptors to be evaluated, and each electrophotographic photoreceptor was evaluated by comparing the minimum load at which the pressure was recognized on the image.

  In the above measurement, the reflection density was measured using a reflection densitometer D200-II manufactured by Gretag Macbeth.

(Crystal orientation)
The electrophotographic photosensitive member is cut out in a size of about 30 mm square at the central position, and X-ray diffraction is measured by the above-described method, and the peak value of the reflection intensity in each plane direction as viewed from the surface of the electrophotographic photosensitive member is obtained. It was measured.

  Table 3 shows the peak values of the reflection intensities in the respective plane orientations obtained with the respective electrophotographic photoreceptors, taking the plane orientations 110, 101, 111, 211, and 220 as examples. These plane orientations appear in the vicinity of 27.3 degrees, 35.2 degrees, 40.4 degrees, 53.5 degrees, and 56.3 degrees as values of 2θ, respectively. This angle varies slightly depending on the measurement device, adjustment on the sample installation, and the state of the sample, but all are derived from the substrate and the lower layer in the measurement on the electrophotographic photoreceptor formed in this example. The peak of the reflection intensity is not in the vicinity and can be easily identified.

  In addition, the peak of the reflection intensity of the plane orientation 210 is also observed relatively prominently, but this is excluded because the reflection intensity peak due to the aluminum substrate used appears close and may be difficult to separate in some cases. It does not matter.

  In Table 3, the peak value of the reflection intensity in each plane orientation is shown as a ratio to the peak value of the reflection intensity of 110 in each sample. According to Table 3, as the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 increases, the peak intensity of each plane orientation also increases, and the crystal is oriented in a random direction. You can see that

  After performing the above evaluation, the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 is compared. Table 4 shows the results of arranging those exceeding as Comparative Example 1.

  The results in Table 4 are shown in FIG. 8 for charging ability, photosensitivity, and ghost, and in FIG. 9 for wounds. In Table 4 and FIGS. 8 and 9, the values of charging ability, photosensitivity, crushing, and ghost are shown by relative comparison with the electrophotographic photoreceptor of Sample 6 as 1.00. In this case, the charging ability and the pressure wound are better as the numerical value is larger. In addition, light sensitivity and ghost indicate that the smaller the numerical value, the better.

  In the above comparison, the numerical value of each item was evaluated according to the following criteria in actual use.

(Chargeability)
0.95 or more ···································· 0.90 to 0.95 ···················· 0.80 to 0.90 ··· Practical problems Has a charging capacity of less than 0.80 ..... Practical problems due to insufficient charging capacity (Photosensitivity)
1.00 or less ···············································································. Has no photosensitivity 1. Less than 30 ... Practical problems due to insufficient photosensitivity (ghost)
2.00 or less ···································· 2.00 to 3.00 ················ ... Ghosts can be identified on the image but are minor and have no practical problems. Exceeding 4.00 ... Ghosts on the image are prominent and affect image interpretation (injuries)
More than 1.00 ... very excellent durability 0.95-1.00 ... excellent durability 0.75-0.95 ... practical problems It has no durability. Less than 0.75 ..... It is easy to generate crushing and practical durability cannot be obtained.

  The “peak intensity ratio” in Table 4 indicates the ratio of the reflection intensity peak value in the plane orientation 101 to the peak intensity reflection value in the plane orientation 110, and the same notation is used in the following tables.

  The electrophotographic photoreceptors of Example 1 and Comparative Example 1 both had excellent characteristics in the range of variation in chargeability and photosensitivity, but the surface orientation 101 with respect to the reflection intensity of the surface orientation 110 was excellent. When the ratio of reflection intensities is 0.8 or less, both ghost and pressure injury are improved. It can also be seen that ghosts and injuries are particularly improved when the ratio of the reflection intensity of the plane orientation 101 to the reflection intensity of the plane orientation 110 is 0.6 or less.

(Example 2 and Comparative Example 2)
After forming a lower layer composed of the lower charge injection blocking layer 14, the photoconductive layer 12, and the upper charge injection blocking layer 15 under the same conditions as in Example 1, a surface layer was formed by reactive sputtering.

  In this example, as in Example 1, the substrate temperature was changed from room temperature (about 20 ° C.) to 300 ° C. in the surface layer formation conditions. Here, a high frequency power source having a frequency of 13.56 MHz was used as the power applied to the cathode 5102.

  Table 5 shows the formation conditions of the surface layer.

The F ₂ flow rate in Table 5 is the F ₂ effective flow rate in the gas diluted with Ar to a concentration of 5%.

  The electrophotographic photoreceptor thus formed was evaluated in the same manner as in Example 1.

  Table 6 shows the peak value of the reflection intensity in each plane orientation.

  Under the conditions of this example and the comparative example, the peak value of the reflection intensity in the plane orientation 220 is higher than that in the case of the first example. Thus, even if the substrate temperature is changed, the tendency changes depending on other conditions.

  After performing the above evaluation, the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 is compared. Table 7 shows the results of arranging the excess as Comparative Example 2.

  The results of Table 7 are shown in FIG. 10 for charging ability, photosensitivity, and ghost, and in FIG. 11 for wounds.

  From the results of Table 7, FIG. 10, and FIG. 11, improvement of ghost and pressure flaws was recognized corresponding to the peak value of the reflection intensity of the plane orientation 101 with respect to the peak value of the reflection intensity of the plane orientation 110.

  In the comparison of Table 7, each item corresponds to the evaluation criteria of Example 1 and Comparative Example 1.

  When combined with the results in Table 6, the peak values of the reflection intensity of the surface orientation 220 relative to the peak value of the reflection intensity of the surface orientation 110 are higher in the samples 11 and 12 than in the sample 7. The characteristics of ghosts and pressure injuries are improved.

  This is probably because even if the reflection intensity of the plane orientation 220 is high, the reflection intensity of the plane orientations 101, 111, and 211 may be low, and the orientation is not consistent with the tendency to be in a random direction. However, even in this case, it can be seen that there is a correlation between the ratio of the peak value of the reflection intensity of the surface orientation 101 to the surface orientation 110, and the ghost and the injuries.

(Example 3 and Comparative Example 3)
After forming a lower layer composed of the lower charge injection blocking layer 14, the photoconductive layer 12, and the upper charge injection blocking layer 15 under the same conditions as in Example 1, a surface layer was formed by reactive sputtering.

In this example, hydrogen (H ₂ ) was added in addition to the raw material gas, and the flow rate was changed from 0 to 200 ml / min (normal).

  Table 8 shows the conditions for forming the surface layer.

The F ₂ flow rate in Table 8 indicates the F ₂ effective flow rate in a gas diluted with Ne to a concentration of 5%.

  The electrophotographic photoreceptor thus formed was evaluated in the same manner as in Example 1.

  Table 9 shows the peak value of the reflection intensity in each plane orientation.

  Under the conditions of the present example and the comparative example, as compared with the case of Example 1, the ratio of the peak value of the reflection intensity of the plane orientation 111 to the peak value of the reflection intensity of the plane orientation 110 was not significantly changed. After performing the above evaluation, the ratio of the peak value of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 is compared. Table 10 shows the result of arranging the product as Comparative Example 3.

  The results of Table 10 are shown in FIG. 12 for charging ability, photosensitivity, and ghost, and in FIG. 13 for wounds.

  From the results of Table 10, FIG. 10, and FIG. 11, improvement in ghost and pressure flaws was recognized corresponding to the peak value of the reflection intensity of the plane orientation 101 with respect to the peak value of the reflection intensity of the plane orientation 110.

  In the comparison of Table 10, each item corresponds to the evaluation criteria of Example 1 and Comparative Example 1.

  As described above, in the present example and the comparative example, the peak value of the reflection intensity of the plane orientation 111 with respect to the peak value of the reflection intensity of the plane orientation 110 did not change greatly, but the peak value of the reflection intensity of the plane orientation 110 does not change. This is probably because the orientation of the surface orientation 211 and the surface orientation 220 advances corresponding to the peak value of the reflection intensity of the surface orientation 101, and as a result, it becomes close to random surface growth.

FIG. 2 is a diagram schematically showing a layer configuration of the electrophotographic photoreceptor of the present invention. It is an example of the measured value by an X-ray diffractometer. It is the figure which showed typically the method of calculating | requiring the peak value of the reflection intensity of X-ray diffraction by this invention. 1 is a configuration diagram schematically showing an example of a deposited film forming apparatus that can be used for forming a photoconductive layer of an electrophotographic photoreceptor of the present invention. It is the longitudinal cross-sectional view which showed typically the example of the deposition film formation container by plasma CVD method in the deposition film formation apparatus of FIG. FIG. 6 is a transverse sectional view schematically showing the deposited film forming container of FIG. 5. It is the longitudinal cross-sectional view which showed typically the example of the deposition film formation container by sputtering method which can be used for formation of the surface layer of the electrophotographic photoreceptor of this invention. It is the figure which showed the result of the charging ability in Example 1 and the comparative example 1, photosensitivity, and a ghost. It is the figure which showed the result of the pressure wound in Example 1 and Comparative Example 1. It is the figure which showed the result of the charging ability in Example 2 and the comparative example 2, photosensitivity, and a ghost. It is the figure which showed the result of the pressure wound in Example 2 and Comparative Example 2. It is the figure which showed the result of the charging ability in Example 3 and the comparative example 3, photosensitivity, and a ghost. It is the figure which showed the result of the pressure wound in Example 3 and Comparative Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrophotographic photoreceptor 11 Surface layer 12 Photoconductive layer 13 Conductive substrate 14 Lower charge injection blocking layer 100 Deposited film formation vessel 101 Vacuum vessel 111 Pressure gauge 121 Base 122 Base 123 Holding member 124 Heater 125 Cap 126 Upper lid 127 Electrode 128 Branch plate 129 High-frequency shield 130 Exhaust port 131 Gas introduction pipe 136 Base plate 200 Exhaust device 201 Mechanical booster pump 202 Rotary pump 300 Raw material gas supply means 301 to 305 Raw material gas cylinders 306 to 310 Supply valves 311 to 315 Pressure regulators 316 to 320 Primary valve 321 to 325 Mass flow controller 326 to 330 Secondary valve 401, 403 Valve 402 piping 404 Raw material gas supply path 405 Exhaust piping 406 Throttle valve 4 07 Exhaust valve 421 High frequency power supply 422 High frequency introduction cable 423 Matching box 5100 Reactor 5101 Gate valve 5102 Cathode 5103 Reactive gas nozzle 5104 Rotating shaft 5105 Sputter gas introduction pipe 5106 Target 5108 Reaction vessel 5109 Power supply 5110 Valve 5111 Shield 5117 Gas release hole 5117 Valve 5118 Motor 5119 Rotating shaft seal 5131, 5132 Cooling water piping 5129, 5130 Permanent magnet 5200 Charge furnace 5201 Vacuum vessel 5202 Door 5203 Actuator 5204 Valve 5205 Valve 5206 Vacuum seal 5207 Shaft 5208 Chucking mechanism

Claims (3)

On a conductive substrate a electrophotographic photoreceptor having at least a photoconductive layer and a surface layer composed of magnesium fluoride, the conjunction surface layer also has a crystal structure with smaller, electrophotographic photosensitive member surface A ratio of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 obtained by X-ray diffraction of the crystal structure as viewed from the side is 0 to 0.8. The ratio of the reflection intensity of the plane orientation 101 to the peak value of the reflection intensity of the plane orientation 110 obtained by X-ray diffraction of the crystal structure seen from the surface of the electrophotographic photoreceptor is 0 to 0.6. The electrophotographic photoreceptor according to claim 1 . The electrophotographic photoreceptor according to claim 1, wherein at least the photoconductive layer contains amorphous silicon as a main component.

Images