JP4534898B2 - Method for producing electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to a method for producing an electrophotographic photoreceptor having a surface protective layer used in an electrophotographic copying machine, an image forming apparatus, and the like, and an electrophotographic photoreceptor.

  Photoreceptors having a photosensitive layer made of an organic material are widely used in copying machines, image forming apparatuses, and the like because they can be easily formed, are inexpensive, and have high safety. However, the photosensitive layer is fragile because it is formed of an organic material, and is easily worn by sliding with, for example, a charging roller or a cleaning blade, and is inferior in mechanical durability. Due to the recent increase in environmental problems, it has become necessary to increase the life of photoconductors made of organic materials, that is, to improve durability or high printing durability, and to provide a surface protective layer on the surface of the photosensitive layer. Is being studied. The surface protective layer includes an organic material and an inorganic material. The inorganic surface protective layer is typically amorphous carbon, for example, and is formed on the surface of the photosensitive layer by various methods such as plasma CVD, thermal CVD, sputtering, and vapor deposition. In particular, the film formation of the surface protective layer by the plasma CVD method can easily obtain homogeneous amorphous carbon at a relatively low temperature. However, during the film formation, the photosensitive layer is directly irradiated with plasma. There is a problem that the photosensitive characteristics deteriorate due to damage.

  To remedy this problem, developed a technology to form a surface protective layer made of hard carbon after forming a protective layer mainly composed of carbon on the surface of the photosensitive layer by sputtering, plasma CVD, coating, etc. For example, it is disclosed in (Patent Document 1).

In addition, in order to form a diamond-like thin film with high hardness, transparent to near-infrared light, and high resistance without any defects such as cracks without deteriorating the photosensitive layer of organic material, direct current is applied to the conductive support. A technique for forming a surface protective layer by applying a voltage and blowing a gas as a material for the surface protective layer onto the photosensitive layer as an ultrafast molecular beam has been developed, for example, disclosed in (Patent Document 2). In the technique of (Patent Document 2), a negative voltage is applied to the conductive support, and the material gas that is made into plasma as an ultrafast molecular beam and sprayed is accelerated on its positive ions and formed on the photosensitive layer. The characteristics of the surface protective layer are improved by colliding with the diamond thin film.
JP-A-3-135571 Japanese Patent No. 2532803

  However, the above conventional techniques have the following problems.

  (1) Although the technology of (Patent Document 1) can prevent deterioration of the photosensitive layer during the formation of the protective layer, it cannot obtain sufficient adhesion strength between the protective layer and the photosensitive layer. Even when a hard carbon film is used as the surface protective layer, the protective layer peels off from the photosensitive layer during use, resulting in a lack of printing durability.

  (2) With the technology of (Patent Document 2), the characteristics of the surface protective layer are improved, but it is difficult to avoid the deterioration of the photosensitive layer of the organic material during the formation of the protective layer, thereby deteriorating the image characteristics. In addition, it is necessary to provide an injection hole (nozzle) so as to correspond to each photoconductor, and in the case of mass production, there is a problem that equipment becomes large and productivity is lacking.

  The present invention solves the above-mentioned conventional problems, and the adhesion strength between the photosensitive layer and the surface protective layer is reduced by the plasma CVD method excellent in mass productivity without causing deterioration of the photosensitive layer that deteriorates image characteristics. It is an object of the present invention to provide a method for producing an electrophotographic photosensitive member which forms a sufficiently strong surface protective layer and is excellent in printing durability and productivity.

In the present invention, a pulse high-frequency voltage and a negative pulse bias voltage having the same repetition period and pulse width are applied to a substrate in which a charge generation layer composed of an organic material and a charge transport layer are sequentially laminated on a conductive support. A method for producing a photosensitive member for electrophotography comprising a surface protective layer forming step of forming a surface protective layer made of amorphous carbon on the surface of the photosensitive layer using a plasma CVD method applied in an overlapping manner, The surface protective layer forming step is set within a range of 0.5 kV or more and 4 kV or less in absolute value using a cleaning step of cleaning the charge transport layer by irradiation of hydrogen plasma using hydrogen gas as an operating gas and methane gas as an operating gas. a first surface protective layer forming step of forming the first protective surface layer by irradiation of a hydrocarbon plasma by applying a first bias voltage pulse, followed by the absolute value the Second second protective surface layer forming step of pulse bias voltage is applied to form a second protective surface layer by irradiation of the hydrocarbon plasma that is set by a pulse bias voltage greater than 3kV or 15kV following range The main feature is that

  According to the present invention, a high-hardness surface protective layer having excellent wear resistance can be obtained by sufficiently increasing the adhesion strength between the photosensitive layer and the surface protective layer without deteriorating the characteristics of the photosensitive layer. Since it can be formed on the surface, it is possible to provide a method for producing an electrophotographic photoreceptor capable of easily mass-producing an electrophotographic photoreceptor excellent in printing durability and image characteristics.

  The present invention forms a surface protective layer having a sufficiently strong adhesion strength between the photosensitive layer and the surface protective layer without causing the deterioration of the photosensitive layer that deteriorates the image characteristics by the plasma CVD method having excellent mass productivity. A first surface protective layer forming step of forming a first surface protective layer by applying a first pulse bias voltage for the purpose of providing a method for producing an electrophotographic photoreceptor excellent in printing durability and productivity. And a second surface protective layer forming step of forming a second surface protective layer by subsequently applying a second pulse bias voltage that is equal to or higher than the first pulse bias voltage in absolute value. .

  In addition, the plasma CVD method, which is excellent in mass productivity, forms a surface protective layer with a sufficiently strong adhesion strength between the photosensitive layer and the surface protective layer without causing deterioration of the photosensitive layer that deteriorates image characteristics. In order to provide an electrophotographic photoreceptor excellent in productivity and productivity, a first surface protective layer formed by applying a first pulse bias voltage and an absolute value equal to or higher than the first pulse bias voltage And a second surface protective layer formed on the first surface protective layer by applying a second pulse bias voltage.

  A first invention made to solve the above-described problem is that an amorphous film is formed using a plasma CVD method in which a pulse high-frequency voltage and a negative pulse bias voltage are superimposed and applied to a conductive support on which a photosensitive layer is formed. A method for producing an electrophotographic photoreceptor comprising a surface protective layer forming step of forming a surface protective layer made of carbonaceous material on the surface of a photosensitive layer, wherein the surface protective layer forming step applies a first pulse bias voltage. The first surface protective layer forming step of forming the first surface protective layer, and then applying the second pulse bias voltage that is equal to or higher than the first pulse bias voltage in absolute value to thereby form the second surface protective layer And a second surface protective layer forming step for forming the structure.

  This configuration has the following effects.

  (1) Forming a hard surface protective layer with excellent wear resistance on the surface of the photosensitive layer without degrading the characteristics of the photosensitive layer and sufficiently increasing the adhesion strength between the photosensitive layer and the surface protective layer Therefore, an electrophotographic photoreceptor excellent in printing durability and image characteristics can be easily mass-produced.

  (2) Since the first surface protective layer and the second surface protective layer can be continuously formed in the same vacuum vessel, chamber, etc., the adhesion strength between the first surface protective layer and the second surface protective layer Can be strong enough.

  (3) By setting the second pulse bias voltage to an absolute value equal to or higher than the first pulse bias voltage, the second surface protective layer is made to be a hard film having more excellent wear resistance. Even if the pulse bias voltage is increased, damage to the photosensitive layer can be prevented by the already formed first surface protective layer.

  A second invention made to solve the above-described problem has a configuration in which, in the first invention, the first pulse bias voltage has an absolute value of not less than 0.5 kV and not more than 4 kV.

  With this configuration, in addition to the operation of the first invention, the following operation is provided.

  (1) By setting the first pulse bias voltage to 0.5 kV or more and 4 kV or less, the adhesion strength between the photosensitive layer and the first surface protective layer is sufficiently increased, and deterioration of the photosensitive layer is prevented. The second pulse bias voltage can be set higher so that the second surface protective layer becomes a harder film.

  A third invention made to solve the above-described problems has a configuration in which the second pulse bias voltage is 3 kV or more and 15 kV or less in absolute value in the first or second invention.

  With this configuration, in addition to the functions of the first or second invention, the following functions are provided.

  (1) By setting the second pulse bias voltage to 3 kV or more and 15 kV or less, a harder film can be formed and the wear resistance can be improved. Thus, deterioration of image characteristics can be prevented.

  A fourth invention made to solve the above-mentioned problems is that, in any one of the first to third inventions, the thickness of the first surface protective layer is 10 nm or more and 50 nm or less, and the second surface protection The thickness of the layer is 100 nm or more and 3000 nm or less.

  With this configuration, in addition to the operation of any one of the first to third inventions, the following operation is provided.

  (1) Since the thickness of the second surface protective layer is from 100 nm to 3000 nm, the wear resistance can be improved with a harder film, and the thickness of the first surface protective layer is from 10 nm to 50 nm. Even if a high second pulse bias voltage is applied so that the second surface protective layer becomes a harder film, the photosensitive layer is not damaged by this, and the first surface protective layer and the photosensitive layer are exposed to light. The layer and adhesion strength can be made sufficiently strong.

  A fifth invention made to solve the above-described problem is a conductive support, a photosensitive layer formed on the conductive support, and a pulse high frequency voltage and a negative pulse bias voltage superimposed on the conductive support. And a surface protective layer made of amorphous carbon formed on the surface of the photosensitive layer using a plasma CVD method to be applied, wherein the surface protective layer is a first pulse. A first surface protective layer formed by applying a bias voltage and a second surface bias layer formed on the first surface protective layer by applying a second pulse bias voltage that is equal to or greater than the first pulse bias voltage in absolute value. 2 surface protective layers.

  This configuration has the following effects.

  (1) Forming a hard surface protective layer with excellent wear resistance on the surface of the photosensitive layer without degrading the characteristics of the photosensitive layer and sufficiently increasing the adhesion strength between the photosensitive layer and the surface protective layer By doing so, the printing durability is excellent and the image characteristics are excellent.

  (2) Since the first surface protective layer and the second surface protective layer can be continuously formed in the same vacuum vessel, chamber, etc., the adhesion strength between the first surface protective layer and the second surface protective layer Can be strong enough.

  (3) By setting the second pulse bias voltage to an absolute value equal to or higher than the first pulse bias voltage, the second surface protective layer is made to be a hard film having more excellent wear resistance. Even if the pulse bias voltage is increased, damage to the photosensitive layer can be prevented by the already formed first surface protective layer.

  A sixth invention made in order to solve the above-mentioned problem is that, in the fifth invention, the photosensitive layer is formed by sequentially laminating at least a charge generation layer and a charge transport layer, and at least the charge transport layer is formed of an organic material. It has the structure which was made.

  With this configuration, in addition to the operation of the fifth invention, the following operation is provided.

  (1) Since the surface protective layer made of amorphous carbon begins to precipitate with the dangling bonds of the carbon as the nucleus during the precipitation process to the underlying charge transport layer, the bond with the charge transport layer is tightly coupled Therefore, the adhesion strength between the surface protective layer and the charge transport layer can be further increased.

  (2) As the surface protective layer, amorphous carbon having excellent characteristics in terms of electrical characteristics and mechanical characteristics can be used, and image characteristics can be improved.

  7th invention made | formed in order to solve the said subject WHEREIN: 5th or 6th invention WHEREIN: The thickness of a 1st surface protective layer is 10 nm or more and 50 nm or less, and the thickness of a 2nd surface protective layer is 100 nm. The structure is 3000 nm or less.

  With this configuration, in addition to the functions of the fifth or sixth invention, the following functions are provided.

  (1) Since the thickness of the second surface protective layer is from 100 nm to 3000 nm, the wear resistance can be improved with a harder film, and the thickness of the first surface protective layer is from 10 nm to 50 nm. Even if a high second pulse bias voltage is applied so that the second surface protective layer becomes a harder film, the photosensitive layer is not damaged by this, and the first surface protective layer and the photosensitive layer are exposed to light. The layer and adhesion strength can be made sufficiently strong.

Eighth aspect of which has been made to solve the above problems, organic in any one invention of the fifth to seventh, the structure dynamic hardness of the surface protective layer is 80 kgf / mm ² or more 200 kgf / mm ² or less is doing.

  With this configuration, in addition to the operation of any one of the fifth to seventh inventions, the following operation is provided.

(1) The dynamic hardness of the surface protective layer by a 80 kgf / mm ² or more 200 kgf / mm ² or less, it is possible to improve a more film hard can be formed abrasion resistance, electrical resistance of the surface protective layer Therefore, it is possible to easily eliminate static electricity and prevent deterioration of image characteristics.

  A ninth invention made to solve the above-described problems has a structure in which the peel strength of the surface protective layer is 6 gf or more and 15 gf or less in any one of the fifth to eighth inventions.

  With this configuration, in addition to the operation of any one of the fifth to eighth inventions, the following operation is provided.

  (1) By setting the peel strength of the surface protective layer to 6 gf or more and 15 gf or less, the wear resistance can be improved, the electrical resistance of the surface protective layer can be lowered, the charge can be easily removed, and the deterioration of the image characteristics can be prevented.

In a tenth aspect of the present invention made to solve the above-mentioned problem, in any one of the fifth to ninth aspects, the electrical resistance of the surface protective layer is 1 × 10 ¹² Ω or more and 1 × 10 ¹⁴ Ω or less. It has a configuration.

  With this configuration, in addition to the operation of any one of the fifth to ninth inventions, the following operation is provided.

(1) By setting the electrical resistance of the surface protective layer to 1 × 10 ¹² Ω or more and 1 × 10 ¹⁴ Ω or less, the electrostatic latent image is not blurred and remains after a series of printing steps. It is possible to reliably remove charges and prevent deterioration of image characteristics.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the main part of the electrophotographic photoreceptor in the first exemplary embodiment.

  In the figure, reference numeral 1 denotes an electrophotographic photosensitive member according to the first embodiment. On the outer peripheral surface of a conductive support 2 formed in a cylindrical shape or the like, a charge generation layer 3, a charge transport layer 4, and a surface protective layer 5 are provided. Are sequentially stacked. 2 is a conductive support for mechanically maintaining the shape of the electrophotographic photoreceptor 1, 3 is a charge generation layer that generates charges in response to incident light from the outside, and 4 is generated in the charge generation layer 3. A charge transport layer 5 for transporting charges to the surface is a surface protective layer composed of a first surface protective layer 6 on the inner peripheral side and a second surface protective layer 7 on the outer peripheral side. The first surface protective layer 6 prevents deterioration of the charge transport layer 4 under film formation conditions that improve the abrasion resistance during film formation of the second surface protective layer 7, and 2 is a layer for obtaining good adhesion strength with the surface protective layer 2. The second surface protective layer 7 is formed on the outermost peripheral portion of the electrophotographic photoreceptor 1, and is a layer for preventing wear of the charge transport layer 4 in the image forming process and improving printing durability. . Reference numeral 8 denotes a photosensitive layer composed of the charge generation layer 3 and the charge transport layer 4, and 9 denotes a substrate composed of the conductive support 2 and the photosensitive layer 8.

  A method for manufacturing the electrophotographic photoreceptor 1 in the first embodiment configured as described above will be described below with reference to FIGS.

  FIG. 2 is a schematic configuration diagram of the plasma CVD apparatus.

  In the figure, 10 is a plasma CVD apparatus, 11 is a vacuum container for modifying the surface of the substrate 9 or forming a film, 11a is for controlling the exclusion of air in the vacuum container 11 or the gas pressure of the working gas. Vacuum pump, 12 is a gas pipe for guiding the working gas to the reaction chamber, 13 is a flow meter for controlling the flow rate of the working gas, 14 is a working gas source, 15 is a pulse high-frequency power source for generating a pulse high-frequency voltage, and 16 is A pulse bias voltage power source that generates a pulse bias voltage, 17 is a superimposing device that superimposes a pulse high-frequency voltage and a pulse bias voltage, 18 holds a base 9, and a pulse high-frequency voltage and a pulse bias voltage are superimposed on the base 9 A base holder for applying a voltage. Note that the pulse high frequency power supply 15 and the pulse bias voltage power supply 16 are electrically connected to the conductive support 2 of the substrate 9 set on the substrate holder 18 via the superimposing device 17.

  First, the base 9 is prepared. The substrate 9 is formed by forming a photosensitive layer 8 formed of an organic material or the like on the surface of a conductive support 2 formed in a cylindrical shape with a conductive metal or the like. As the material of the conductive support 2, aluminum that is conductive, lightweight, and easy to process is used. In addition, it is possible to use an alumite-treated surface or an aluminum surface with an undercoat layer made of titanium oxide and polyamide.

  As the material of the charge generation layer 3 of the photosensitive layer 8, a material having absorption in the wavelength region of the semiconductor laser, for example, a material in which a charge generation material such as phthalocyanine is dispersed in a binder resin such as butyral resin is used. Is about 0.2 μm and formed on the conductive support 2. The charge transport layer 4 is made of a material that transports holes, for example, a material in which an electron donor such as a triphenylamine compound is dispersed in a binder resin such as polycarbonate, and has a thickness of about 20 μm. Those formed on the charge generation layer 3 are used. The materials or thicknesses of the conductive support 2, the charge generation layer 3, and the charge transport layer 4 are not limited to those described above, and various metals, organic materials, etc. that are generally used as photosensitive layers Various thicknesses can be used as appropriate.

  Next, the surface protective layer 5 composed of the first surface protective layer 6 and the second surface protective layer 7 is formed on the surface of the substrate 9 having the prepared photosensitive layer 8 using the plasma CVD apparatus 10. The surface protective layer 5 is formed as follows. That is, the surface protective layer forming step includes a step of cleaning the surface of the charge transport layer 4, a step of forming the first surface protective layer 6, and a step of forming the second surface protective layer 7.

First, the substrate 9 is set on the substrate holder 18 in the vacuum vessel 11 of the plasma CVD apparatus 10. Next, in order to prevent the generated plasma from being affected by a gas other than the operating gas such as air, the air in the vacuum vessel 11 is exhausted using the vacuum pump 11a. After exhausting until the degree of vacuum in the vacuum container 11 becomes 1 × 10 ⁻³ Pa, for example, the working gas is introduced into the vacuum container 11. As the working gas, hydrogen gas is selected as a gas not containing hydrocarbons, and the introduction amount of the working gas and the opening of the exhaust valve (not shown) of the vacuum pump 11a are set so that the gas pressure in the vacuum vessel 11 becomes 10 Pa. Adjust. After the gas flow is stabilized, the pulse high-frequency voltage output from the 13.56-MHz pulse high-frequency power supply 15 is intermittently input at a predetermined cycle and a predetermined pulse width to the substrate 9 and from the start of input of the pulse high-frequency voltage. A pulse bias voltage of a predetermined voltage output from the pulse bias voltage power supply 16 is applied with a predetermined pulse width after a predetermined time, for example, about 100 μsec has elapsed. In this cleaning step and first and second surface protective layer forming steps described later, for example, a pulse high frequency voltage having a repetition period of about 1000 Hz, a pulse width of about 100 μsec and about 300 W is used, and the repetition period is about A pulse bias voltage of 1000 Hz and a pulse width of about 100 μsec is used. The magnitude of the pulse bias voltage will be described later.

The pulse high-frequency voltage and the pulse bias voltage are superimposed by the superimposing device 17, then transmitted to the base 9 set in the base holder 18 in the vacuum container 11, and hydrogen is transferred between the vacuum container 11 and the ground potential. Discharge using gas as working gas occurs. By this discharge, the hydrogen gas is ionized to form a hydrogen plasma containing chemically active hydrogen radicals. On the other hand, a pulse bias voltage is applied to the substrate 9, and the positively charged substance in the hydrogen plasma is accelerated toward the substrate 9 by the negative pulse bias voltage and is irradiated to the substrate 9. . By irradiating the substrate 9 with hydrogen plasma, the surface of the substrate 9 is changed to an active surface (cleaning step). Here, the active surface is a clean surface that can be physically or chemically bonded to the CH ₄ decomposition product to be formed later, or the chemical bonding of the resin layer constituting the photosensitive layer 8 is interrupted. The surface on which the hand appears. Although the specific change process in this step is unknown, contaminants such as fats and oils remaining on the surface of the charge transport layer 4 on the surface of the substrate 9 are removed and subjected to physical or chemical changes. It is thought to be due to this. Here, since hydrogen gas is used as the working gas, the impact applied to the charge transport layer 4 is small, the occurrence of characteristic deterioration of the charge transport layer 4 can be suppressed, and new deposition is performed on the surface of the charge transport layer 4. It does not form things.

  The reason why the organic material is used for the charge transport layer 4 is that amorphous carbon is used as the surface protective layer 5 (first surface protective layer 6), and the surface is improved in terms of electrical characteristics and mechanical characteristics. The amorphous carbon having excellent characteristics as the protective layer 5 (first surface protective layer 6) is formed by removing the dangling bonds of the underlying carbon during the deposition process on the underlying layer (charge transport layer 4) of the amorphous carbon film. Since the precipitation starts with nuclei, by using an organic material having carbon dangling bonds on the surface, the bond between the amorphous carbon film and the substrate can be tightly coupled. This is because the adhesion strength of the crystalline carbon film can be further increased. In general, the photosensitive layer 8 is made of an organic material, and it is desirable from the viewpoint of productivity if high printing durability can be achieved only by applying the surface protective layer 5 thereto.

  Next, the surface protective layer 5 is formed. As the surface protective layer 5, an amorphous carbon film is used because hardness, peel strength, and electric resistance can be easily optimized depending on the manufacturing conditions, and the friction characteristics of the film, that is, the friction characteristics of the surface of the surface protective layer 5 can be reduced. The surface protective layer 5 is composed of a first surface protective layer 6 and a second surface protective layer 7, and both the first surface protective layer 6 and the second surface protective layer 7 are amorphous carbon. Formed with a film.

  First, after completion of the process of cleaning the surface of the charge transport layer 4, the supply of hydrogen gas is stopped and the exhaust valve of the vacuum pump 11a is fully opened to discharge the hydrogen gas in the vacuum vessel 11. After evacuation for a predetermined time, methane gas is selected from hydrocarbon-based gas as an operation gas for forming the surface protective layer 5 made of amorphous carbon, and the gas pressure in the vacuum vessel 11 is set to a predetermined gas pressure. The amount of gas introduced and the opening of the exhaust valve of the vacuum pump 11a are adjusted so that After the gas flow is stabilized, a pulsed high-frequency voltage is intermittently input to the substrate 9 at a predetermined cycle and a predetermined pulse width, and a predetermined pulse bias voltage (the first voltage) is applied after a predetermined time has elapsed from the start of input of the pulsed high-frequency voltage. 1 pulse bias voltage) is applied at the same repetition period and a predetermined pulse width as the pulse high-frequency voltage. The pulse high-frequency voltage and the pulse bias voltage are applied to the substrate 9 after being superimposed by the superimposing device 17, and a discharge using methane gas as an operating gas is generated between the pulsed high-frequency voltage and the pulse bias voltage. By this discharge, methane gas is decomposed and ionized, and a hydrocarbon plasma containing chemically active hydrocarbon radicals is formed. On the other hand, a pulse bias voltage is applied to the substrate 9, and the positively charged substance in the hydrocarbon plasma is accelerated toward the substrate 9 by the negative pulse bias voltage and irradiated to the substrate 9. Become. By irradiating the substrate 9 with hydrocarbon plasma, an amorphous carbon film (first surface protective layer 6) is formed on the surface of the charge transport layer 4 on the surface of the substrate 9 (first surface protective layer formation). Process). Note that the film thickness is adjusted by the film formation time so as to obtain a desired film thickness.

  Next, the second surface protective layer 7 is formed. The second surface protective layer 7 is formed by continuously changing the pulse bias voltage after the first surface protective layer forming step, and the first surface protective layer forming step except that the pulse bias voltage is changed. (Second surface protective layer forming step). The film thickness of the second surface protective layer 7 is also adjusted according to the film formation time so as to obtain a desired film thickness.

  In this manner, the surface protective layer 5 made of amorphous carbon composed of the first surface protective layer 6 and the second surface protective layer 7 is formed on the surface of the substrate 9.

  In the first embodiment, the surface of the charge transport layer 4 is modified by the plasma generated by the discharge between the base 9 set on the base holder 18 and the vacuum vessel 11 held on the ground. Although the formation is performed, the surface protective layer 5 may be formed by arranging a cylindrical conductor held on the ground around the base 9 set on the base holder 18. In this case, the surface protective layer 5 is formed by plasma generated by discharge between the base 9 set on the base holder 18 and the cylindrical conductor held on the ground. Since the ground electrode is arranged around the substrate 9, the discharge is stable and the working gas flows along the cylindrical conductor, so that the thickness of the surface protective layer 5 tends to be uniform and excellent. A characteristic film is obtained. The entire surface of the cylindrical conductor may be a conductor, or may be formed in a mesh shape for the purpose of facilitating evacuation.

  Next, in the same manner as described above, the first surface protective layer 6 and the second surface protective layer 7 are changed on the base material 9 of the same material and size by changing the pulse bias voltage and the film thickness. A plurality of test bodies of the electrophotographic photoreceptor 1 were produced. The first surface protective layer 6 receives a pulse high frequency voltage of 300 W, changes the pulse bias voltage in the range of 0 V to −10 kV, and changes the film pressure in the range of 0 to 200 nm by adjusting the film formation time. Formed. The second surface protective layer 7 receives a pulse high frequency voltage of 300 W, changes the pulse bias voltage in the range of 0 V to −20 kV, and adjusts the film formation time to adjust the film pressure in the range of 0 to 5000 nm. Changed and formed. Note that the gas pressure of methane gas as the working gas in the first surface protective layer forming step and the second surface protective layer forming step was both 50 Pa.

  Moreover, the test about an image characteristic was done about each test body produced as mentioned above. In the test, a predetermined number of printing durability tests were performed using an image forming apparatus, and the image characteristics at that time were visually evaluated. The image forming apparatus used for the test will be described with reference to FIG.

  FIG. 3 is a schematic configuration diagram of the image forming apparatus.

  In the figure, A is an image forming apparatus, 19 is a charging unit, 20 is an exposure unit, 21 is a development unit, 22 is a transfer unit, and 23 is a cleaning unit. The image forming apparatus A is configured such that a charging unit 19, an exposure unit 20, a developing unit 21, a transfer unit 22, and a cleaning unit 23 are disposed in the vicinity of the outer peripheral portion of the electrophotographic photoreceptor 1. The electrophotographic photoreceptor 1 has a drive mechanism (not shown) and is driven to rotate in the direction of the arrow in FIG. The charging unit 19 uniformly charges the surface of the electrophotographic photoreceptor 1. The exposure unit 20 exposes the surface of the charged electrophotographic photoreceptor 1 with a laser beam to form a latent image on the surface of the electrophotographic photoreceptor 1. The developing unit 21 supplies a non-magnetic developer to the electrophotographic photoreceptor 1 by a built-in developing roller 24 and attaches a certain amount of toner to the latent image formed on the surface of the electrophotographic photoreceptor 1. The transfer unit 22 transfers the toner attached to the latent image to the recording paper 26 conveyed by the conveyance roller 25. A cleaning unit 23 is disposed on the downstream side of the transfer unit 22 to remove the toner remaining on the surface of the electrophotographic photoreceptor 1 after the transfer of the toner to the recording paper 26. The cleaning unit 23 includes a cleaning blade 27 that directly contacts and removes toner remaining on the surface of the electrophotographic photoreceptor 1.

  The image forming apparatus A configured as described above is subjected to a printing durability test in which a test body of the produced electrophotographic photoreceptor 1 is incorporated and a change in image characteristics is evaluated after printing a predetermined number of sheets. It was.

  Table 1 shows the evaluation results of the image characteristics after printing 10,000 sheets for typical test specimens produced by changing the pulse bias voltage. In (Table 1), the thickness of the first surface protective layer 6 was 50 nm and the thickness of the second surface protective layer 7 was 200 nm in any of the test bodies. The pulse bias voltage is obtained from the maximum amplitude of the voltage waveform measured between the superimposing device 17 and the vacuum vessel 11. The evaluation method of image characteristics was “good” when no blur, fogging, streaks or the like occurred in the image, and “bad” in other cases.

As shown in Table 1, the first pulse bias voltage is in the range of −4 kV to −0.5 kV and the absolute value of the second pulse bias voltage is greater than or equal to the absolute value of the first pulse bias voltage. In the range, good image characteristics were shown. Further, as a result of visually observing the surface of each test specimen after the end of the printing durability test, peeling or abrasion of the surface protective layer 5 was not observed in the test specimen showing good image characteristics. This is because a sufficient adhesion strength of the film is obtained between the charge transport layer 4 and the first surface protective layer 6 by increasing the first pulse bias voltage so as not to damage the charge transport layer 4. This is because the second pulse bias voltage can be set higher so that the second surface protective layer 7 becomes a harder film. Even if the pulse bias voltage is set high when the second surface protective layer 7 is formed, the charge transport layer 4 is not damaged because the first surface protective layer 6 has already been formed. Further, since the first surface protective layer 6 and the second surface protective layer 7 can be continuously formed in the same chamber, it is sufficient even between the first surface protective layer 6 and the second surface protective layer 7. Film adhesion strength can be obtained.

It should be noted that in the case where the first pulse bias voltage is in the range of −0.2 kV to 0 kV, the second
Even when the pulse bias voltage was increased, good image characteristics could not be obtained. However, as a result of observing the surface of these specimens after the end of the printing durability test, partial peeling of the surface protective layer 5 was observed. This is considered to be the cause. In the case where the first pulse bias voltage is −5 kV, the second
The image characteristics were poor regardless of the pulse bias voltage, but in this case, the image characteristics were already poor before the 10,000 plate life test was performed. This is probably because the charge transport layer 4 was damaged by the -5 kV pulse bias voltage. Also, when the second pulse bias voltage was −2 kV, good image characteristics could not be obtained, but as a result of surface observation of these specimens after the end of the printing durability test, irregularities due to wear of the surface protective layer 5 were observed. Unevenness is observed, which is considered to be the cause. In addition, the image characteristics were poor in the specimen having the first pulse bias voltage of −4 kV and the second pulse bias voltage of −3 kV. As a result, partial peeling of the surface protective layer 5 was observed, which is considered to be the cause. When the surface protective layer 5 is formed by applying a pulse bias voltage lower than that of the first surface protective layer 6 to the second surface protective layer 7, it is considered that the second surface protective layer 7 is likely to be peeled off due to film stress or the like. In addition, when the second pulse bias voltage is −20 kV, the image characteristics are already poor before the 10,000 plate life test is performed, but this is because the electric resistance of the second surface protective layer 7 becomes too high. As a result, it is considered that the charge removal cannot be easily performed, thereby deteriorating the image characteristics.

From the above results, the formation of the surface protective layer 5 made of amorphous carbon has the first pulse bias voltage in the range of 0.5 kV to 4 kV in absolute value, and the second bias voltage in absolute value as the first value.
In this case, the surface protective layer 5 has excellent peeling resistance and wear resistance, and the charge transport layer 4 is not damaged. It was found that an electrophotographic photoreceptor suitable for printing can be obtained.

  Next, (Table 2) shows evaluation results of image characteristics after printing 10,000 sheets of representative test specimens prepared by changing the thicknesses of the surface protective layers 6 and 7. In (Table 2), the first pulse bias voltage was set to −1 kV and the second pulse bias voltage was set to −4 kV for any of the specimens. Note that the evaluation method of image characteristics was the same as in the case of (Table 1).

  As shown in (Table 2), the film thickness of the first surface protective layer 6 is in the range of 10 nm to 50 nm and the film thickness of the second surface protective layer 7 is in the range of 100 nm to 3000 nm. The image characteristics are shown. Further, as a result of visually observing the surface of each test specimen after the end of the printing durability test, peeling or abrasion of the surface protective layer 5 was not observed in the test specimen showing good image characteristics. Even if a second pulse bias voltage higher than the first pulse bias voltage is applied so that the second surface protective layer 7 becomes a harder film, the film thickness of the first surface protective layer 6 is as follows. The film thickness is such that the charge transport layer 4 is not damaged, and the film thickness is sufficient to obtain a sufficient adhesion strength between the charge transport layer 4 and a high pulse bias voltage. This is probably because the second surface protective layer 7 formed by application also has a sufficient thickness. In addition, since the first surface protective layer 6 and the second surface protective layer 7 can be continuously formed in the same vacuum vessel 11, the first surface protective layer 6 and the second surface protective layer 7 are interposed. However, sufficient film adhesion strength can be obtained.

Note that the image characteristics of the test specimen in which the film thickness of the first surface protective layer 6 was in the range of 0 nm to 5 nm were poor. In this case, however, the image characteristics were already poor before the 10,000 plate life test was performed. Therefore, it is considered that this is because the charge transport layer 4 was damaged by the second pulse bias voltage of −4 kV when the second surface protective layer 7 was formed. That is, when a large bias voltage is applied when the second surface protective layer 7 is formed, if the thickness of the first surface protective layer 6 is 0 nm to 5 nm, it is sufficient to prevent damage to the charge transport layer 4. It is not a thickness. In addition, the image characteristics were poor in the specimen having the thickness of the first surface protective layer 6 of 100 nm, but this was due to the surface observation of these specimens after the printing durability test. Exfoliation is observed, which is considered to be the cause. When the first surface protective layer 6 is formed, the first pulse bias voltage is as low as −1 kV, and therefore there are many fragile portions of the film. It is probable that peeling occurred. Further, the image characteristics are poor even when the second surface protective layer 7 is an 80 nm test piece, but as a result of observing the surface of these test pieces after the printing durability test, partial wear of the surface protective layer 5 is observed. Recognized and believed to be the cause. The second pulse bias voltage at the time of forming the second surface protective layer 7 is a large voltage of −4 kV. However, when the film thickness is about 80 nm, sufficient film hardness is not obtained. It is believed that there is. In addition, even when the second surface protective layer 7 is 4000 nm, the image characteristics are poor. In this case, the image characteristics were already bad before the 10,000 printing tests were performed. This is considered to be because the electrostatic latent image formed on the surface protective layer 5 was blurred because the surface protective layer 7 of No. 2 was as thick as 4000 nm.

  From the above results, the surface protective layer 5 made of amorphous carbon is formed by setting the thickness of the first surface protective layer 6 in the range of 10 nm to 50 nm and the thickness of the second surface protective layer 7 being 100 nm. When the thickness is in the range of 3000 nm or less, an electrophotographic photoreceptor 1 that is excellent in peeling resistance and abrasion resistance of the surface protective layer 5 and suitable for high printing durability without damage to the charge transport layer 4 is obtained. I found out that Even if the thickness of the second surface protective layer 7 is as thick as 3000 nm, there is no problem in image characteristics, but it takes a long time to form the surface protective layer 5, which is not appropriate in terms of productivity. Even if the film thickness of the second surface protective layer 7 is about 100 nm to 500 nm, there is no problem in printing durability, so that this film thickness can be said to be the optimum film thickness in consideration of productivity and the like.

  Next, the film hardness, the adhesion strength of the film, and the electric resistance of the surface protective layer 5 made of amorphous carbon were examined as follows for the prepared test body.

  The film hardness was determined by measuring the dynamic hardness. Using a dynamic microhardness meter (DUH-200) manufactured by Shimadzu Corporation, the hardness measured when a triangular pyramid-shaped stylus with a ridge angle of 115 degrees penetrated 50 nm from the surface was measured.

  The peel strength of the film was evaluated by using a scanning scratch tester (SST-101) manufactured by the same company and the load corresponding to the position of scratches observed when scratched with a stylus having a tip curvature of 50 μm. .

In addition, the electric resistance is obtained by taking two electrodes with a distance of 10 mm with a conductive adhesive tape having a width of about 10 mm and a length of about 5 mm on the surface of the substrate 9 on which the surface protective layer 5 is formed, and using a DC power source between the two electrodes. When a voltage of 20V is applied, the pA meter detects the minute current that flows and the time change of the minute current is applied after applying a voltage obtained from an equivalent circuit in which an electric resistance and a capacitor are arranged in series with respect to the DC power supply. Fitting was made to (Equation 1) of the time change of the flowing current, and the coefficient was calculated from the coefficient.

  For test specimens that were produced in the same manner as the specimens produced by changing the pulse bias voltage and the film thickness and were not subjected to the printing durability test, the film hardness, the peel strength of the film, and the electrical resistance were examined, and then the printing durability A test was conducted. Tables 3 to 5 show the results of associating these characteristics with the image characteristics after the printing test described above.

  Table 3 shows the results of film hardness and image characteristics after the printing test, Table 4 shows the results of film peeling strength and image characteristics after the printing test, and Table 5 shows the electrical resistance. And the results of image characteristics after the printing durability test. Note that (Table 1) to (Table 5) are tabulated by selecting representative characteristics for each characteristic, and are not necessarily shown for the same specimen in each table.

As shown in (Table 3), the dynamic hardness of the surface protective layer 5 made of amorphous carbon with 80 kgf / mm ² or more 200 kgf / mm ² or less of the range, the image characteristics after printing test was good. Although the image characteristics were poor in the test specimen having a dynamic hardness of 60 kgf / mm ² , as a result of observing the surface of the specimen after the printing durability test, inhomogeneous wear of the surface protective layer 5 was observed. It is considered that the image characteristics after the printing durability test were deteriorated due to the uneven wear. That is, when the dynamic hardness of the surface protective layer 5 is 60 kgf / mm ² , the hardness of the surface protective layer 5 is too small. On the other hand, even with a specimen having a dynamic hardness of 250 kgf / mm ² , the image characteristics are poor. However, in this case, since the wear of the printing test was not recognized, there is no problem as printing characteristics. Such high hardness is obtained in the case of amorphous carbon because the proportion of sp ³ bonds of carbon atoms (single bonds typified by diamond) is increased, and the electrical resistance increases accordingly. Therefore, it is considered that the image characteristics are deteriorated because the surface protective layer 5 is not easily neutralized. From the above results, it dynamic hardness of the surface protective layer 5 made of amorphous carbon is in the range of 80 kgf / mm ² or more 200 kgf / mm ² or less, without the occurrence of wear in the surface protective layer 5 in printing durability test It was found that good image characteristics can be obtained.

Further, as shown in Table 4, the image properties after the printing durability test were good when the peel strength of the surface protective layer 5 made of amorphous carbon was in the range of 6 gf to 15 gf. Although the image characteristics were poor in the test specimen having a dynamic hardness of 4 gf, as a result of observing the surface of the specimen after the printing durability test, inhomogeneous peeling of the surface protective layer 5 was observed. It is considered that the image characteristics after the printing durability test deteriorated due to non-uniform peeling of the surface protective layer 5. That is, when the peel strength of the surface protective layer 5 is 4 gf, the peel strength of the surface protective layer 5 is too small. On the other hand, the image characteristics are poor even in the specimen having a peel strength of 18 gf. However, in this case, no peeling of the surface protective layer 5 was observed after the printing durability test, so there is no problem with the printing durability characteristics. However, in the case of amorphous carbon, such a high peel strength is obtained because of an increase in the proportion of sp ³ bonds of carbon atoms, and as a result, the electrical resistance increases, and the surface protective layer It is considered that the image characteristics were deteriorated because it was difficult to remove the charge 5. From the above results, when the peel strength of the surface protective layer 5 made of amorphous carbon is in the range of 6 gf or more and 15 gf or less, the surface protective layer 5 is free from wear even in the printing durability test, and good image characteristics are obtained. I found out that I could do it.

Also, as shown in Table 5, the surface protection layer 5 made of amorphous carbon has good image characteristics after the printing durability test when the electrical resistance is in the range of 1 × 10 ¹² Ω to 1 × 10 ¹⁴ Ω. Met. The test specimens with electrical resistance of 1 × 10 ¹⁰ Ω and 1 × 10 ¹¹ Ω have poor image characteristics, but these have poor image characteristics before the printing durability test, and the electrostatic latent image is blurred. This is thought to be due to this. That is, in order to form a good electrostatic latent image on the surface protective layer 5, the electrical resistance of the surface protective layer 5 is too small at 1 × 10 ¹¹ Ω. On the other hand, even with a test specimen having an electrical resistance of 1 × 10 ¹⁵ Ω, the image characteristics are poor. In this case, the electrostatic latent image is not blurred, but the electrostatic latent image is formed, the toner is developed, In the process of static charge removal after a series of printing processes such as transfer to recording paper, cleaning, etc., the electric resistance is too high, the movement of the charge is bad, and the charge removal is incomplete. It has deteriorated. From the above results, it can be seen that when the electrical resistance of the surface protective layer 5 made of amorphous carbon is in the range of 1 × 10 ¹² Ω to 1 × 10 ¹⁴ Ω, good image characteristics can be obtained. It was.

  As described above, since the electrophotographic photoreceptor 1 and the manufacturing method thereof according to Embodiment 1 are configured, the following effects are obtained.

  (1) The second surface protective layer 7 having excellent wear resistance and high hardness can be formed without deteriorating the characteristics of the charge transport layer 4, and the charge transport layer 4 and the first surface protective layer 6 The adhesion strength of can be made sufficiently strong.

  (2) The surface protective layer 5 having both high wear resistance and high adhesion and prevention of deterioration of the photosensitive layer during production can be easily formed on the substrate 9 having a photosensitive layer formed of an organic material, and printing durability is improved. In addition, the electrophotographic photoreceptor 1 having excellent image characteristics can be easily mass-produced.

  (3) Since the first surface protective layer 6 and the second surface protective layer 7 can be formed using the same vacuum vessel 11 and the operating gas is the same, for example, methane gas, the first surface protective layer The adhesion strength between 6 and the second surface protective layer 7 can be sufficiently increased, and the productivity can be improved because there is no need to switch the apparatus or replace the gas.

  The present invention relates to a method for producing an electrophotographic photoreceptor having a surface protective layer used in an electrophotographic copying machine, an image forming apparatus, and the like, and the electrophotographic photoreceptor, and particularly according to the present invention, is excellent in mass productivity. The plasma CVD method forms a surface protective layer with a sufficiently strong adhesion strength between the photosensitive layer and the surface protective layer without causing deterioration of the photosensitive layer that degrades the image characteristics, and is excellent in printing durability and productivity. A method for producing an electrophotographic photoreceptor and an electrophotographic photoreceptor are obtained.

Sectional view of the main part of the electrophotographic photosensitive member according to the first embodiment. Schematic configuration diagram of plasma CVD equipment Schematic configuration diagram of an image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 2 Conductive support 3 Charge generation layer 4 Charge transport layer 5 Surface protective layer 6 First surface protective layer 7 Second surface protective layer 8 Photosensitive layer 9 Substrate 10 Plasma CVD apparatus 11 Vacuum container 11a Vacuum pump 12 Gas pipe 13 Flow meter 14 Operating gas source 15 Pulse high frequency power source 16 Pulse bias voltage power source 17 Superimposing device 18 Substrate holder 19 Charging unit 20 Exposure unit 21 Development unit 22 Transfer unit 23 Cleaning unit 24 Development roller 25 Transport roller 26 Recording Paper 27 Cleaning blade A Image forming device

Claims (2)

Applying a pulse high-frequency voltage with the same repetition period and pulse width and a negative pulse bias voltage superimposed on a substrate in which a charge generation layer composed of an organic material and a charge transport layer are sequentially laminated on a conductive support A method for producing an electrophotographic photoreceptor comprising a surface protective layer forming step of forming a surface protective layer made of amorphous carbon on the surface of the photosensitive layer using a plasma CVD method,
The surface protective layer forming step is set in a cleaning step of cleaning the charge transport layer by irradiation of hydrogen plasma using hydrogen gas as an operating gas, and in an absolute value range of 0.5 kV to 4 kV using methane gas as an operating gas. first a first surface protective layer forming step of applying a pulse bias voltage to form a first protective surface layer by irradiation of the hydrocarbon plasma that subsequently greater than the first pulse bias voltage in absolute value A second surface protective layer forming step of forming a second surface protective layer by applying a second pulse bias voltage set in a range of 3 kV to 15 kV and irradiating the hydrocarbon plasma. A method for producing an electrophotographic photoreceptor characterized by the above. 2. The electrophotographic photoreceptor according to claim 1 , wherein the thickness of the first surface protective layer is from 10 nm to 50 nm, and the thickness of the second surface protective layer is from 100 nm to 3000 nm. Production method.

Images