JP2016090687A - Image forming method and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method and an image forming apparatus that can maintain a state where appropriate images can be provided for a long period even when the sensitivity of a photoreceptor has changed through repetition of an image forming process and has exceeded a light intensity adjustment range in a pre-charging exposure step.SOLUTION: An image forming method includes a pre-charging exposure adjustment step of performing adjustment of pre-charging exposure conditions in a pre-charging exposure step, and the pre-charging exposure adjustment step includes adjusting the exposure intensity and exposure wavelength of pre-charging exposure light.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming method and an image forming apparatus.

  An image forming method and an image forming apparatus using the same are widely used as a copying machine, a laser beam printer, a facsimile machine, and a printing machine. In such an image forming apparatus, the surface of the photosensitive member provided with the photoconductive layer is uniformly charged and exposed by a laser or LED corresponding to the image information, whereby an electrostatic latent image is formed on the surface of the photosensitive member. Form. Then, a toner image is formed by attaching toner to the surface of the photoreceptor using the formed electrostatic latent image, and this is transferred to a transfer material such as paper. The toner remaining on the surface of the photoreceptor (transfer residual toner) is removed by a cleaning means including a rubber cleaning blade, a magnet roller, and a brush roller. Then, the photosensitive member is discharged by exposure with a laser, LED, or fluorescent lamp. By repeating these steps, image formation is repeated.

As a photoreceptor that can be suitably used in such an image forming apparatus, a photoreceptor having a photoconductive layer and a surface layer formed of a non-single crystal material containing silicon atoms as a main component (hereinafter referred to as a-Si photosensitive member). Abbreviated to body.). The a-Si photoreceptor has a very hard Vickers hardness of 1000 kgf / mm ² or more, and is excellent in durability, heat resistance, and environmental stability. Therefore, it is preferable in a high-speed machine that requires high reliability.

  However, even in an image forming apparatus using an a-Si photosensitive member having excellent durability, the surface of the photosensitive member is slightly worn by sliding with various members around the photosensitive member including the cleaning unit. In some cases, the photosensitive characteristics and the charging characteristics may change with such wear. As a countermeasure against such a case, a technique is disclosed in which the usage amount calculation means for calculating the usage status of the photoconductor is used to control the light amount of the light source in the pre-charging exposure process so that it is within a desired surface potential range. (Patent Document 1).

JP 2008-158024 A

  However, in Patent Document 1, the only item to be controlled to be within the desired surface potential range is the light amount of the light source in the pre-charging exposure process, and there is a large amount of change in sensitivity of the photoconductor, and the range in which the light amount can be adjusted. If it exceeds, the surface potential may not be set correctly. If the potential setting deviates from a predetermined value, it is difficult to form an optimal image, and there may be room for improvement because the dot may become thicker or thinner, or image defects such as fogging and density fluctuations may occur. It was.

In particular, in the case of an image forming apparatus using an a-Si photosensitive member, there is a strong demand for further extending the life of the main body of the image forming apparatus, and it is required to design the main body on the order of more than 10 million sheets. It has become. In order to achieve such a requirement, the surface layer has been made thicker as a photoconductor, and this allows the surface layer thickness at the initial stage of use and the surface layer thickness at the end of use to be reduced. The difference was getting bigger. A large change in the surface layer thickness means that the amount of light reaching the photoconductive layer changes greatly. Under such circumstances, it has been found that the amount of change in the sensitivity of the photoconductor becomes large, which may exceed the light amount adjustment range of the pre-charging exposure light, and there is room for improvement.
That is, the present invention provides an image forming method capable of correctly setting a potential even when the sensitivity of the photoconductor greatly fluctuates with the repetition of the image forming process and exceeds the light amount adjustment range in the pre-charging exposure process. It is another object of the present invention to provide an image forming apparatus.

The image forming method of the present invention that solves the above-mentioned problems includes a charging step for charging the surface of an electrophotographic photosensitive member having at least a photoconductive layer and a surface layer, and electrostatic latent image on the charged surface of the electrophotographic photosensitive member. A latent image forming step of forming an image, a developing step of transferring the toner carried on the toner carrying member to develop the electrostatic latent image, and forming a toner image on the surface of the electrophotographic photosensitive member; A transfer step of transferring the toner image from the surface of the electrophotographic photosensitive member to a transfer material; a cleaning step of removing transfer residual toner remaining on the surface of the electrophotographic photosensitive member from the electrophotographic photosensitive member; In the image forming method, the method includes a pre-charging exposure step for discharging the electrophotographic photosensitive member, and repeatedly forming an image until the film thickness of the surface layer is reduced by 50% or more with respect to the initial film thickness.
The method further comprises a pre-charge exposure adjustment step for adjusting pre-charge exposure conditions in the pre-charge exposure step, wherein the pre-charge exposure adjustment step adjusts the exposure intensity and exposure wavelength of the pre-charge exposure light. To do.

In addition, an image forming apparatus of the present invention that solves the above-described problems includes a charging unit that charges the surface of an electrophotographic photosensitive member having at least a photoconductive layer and a surface layer, and a static surface on the surface of the charged electrophotographic photosensitive member. A latent image forming means for forming an electrostatic latent image; and a developing means for transferring the toner carried on the toner carrying member to develop the electrostatic latent image to form a toner image on the surface of the electrophotographic photosensitive member. Transfer means for transferring the toner image from the surface of the electrophotographic photosensitive member to a transfer material; and cleaning means for removing transfer residual toner remaining on the surface of the electrophotographic photosensitive member from the electrophotographic photosensitive member; An image forming apparatus that repeatedly forms an image until the film thickness of the surface layer is reduced by 50% or more with respect to the initial film thickness.
A pre-charge exposure adjusting means for adjusting the pre-charge exposure conditions of the pre-charge exposure means;
The pre-charge exposure adjusting means is means for adjusting the exposure intensity and exposure wavelength of the pre-charge exposure light.

  In the image forming method and the image forming apparatus of the present invention, the sensitivity of the photoconductor greatly fluctuates with the repetition of the electrophotographic process, and even when the light amount adjustment range in the pre-charge exposure process is exceeded, a desired surface potential can be obtained. It becomes possible to set correctly within the range. For this reason, the image forming method and the image forming apparatus of the present invention have an effect that a state where a proper image can be obtained under a proper image forming condition can be maintained for a longer period of time. Further, by using the image forming method of the present invention, the photoconductor can be used for a longer period of time, so that an image forming apparatus having a longer life can be provided.

1 is a schematic cross-sectional view showing an example of a layer structure of an a-Si photosensitive member that can be suitably used in the image forming method and the image forming apparatus of the present invention. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus preferably used in the present invention. It is typical sectional drawing of the pre-charge exposure adjustment means when using the light source which can light-emit single wavelength light for the pre-charge exposure means. It is an example of the operation | movement flowchart of a pre-charging exposure adjustment process. 1 is a schematic cross-sectional view showing an example of an apparatus for producing a photoreceptor preferably used in the present invention. It is an example of the operation | movement flowchart of a pre-charging exposure adjustment process. It is an example of the operation | movement flowchart of a pre-charging exposure adjustment process. It is the model which showed the relationship between the number of printed sheets and image density.

  The present invention is suitable even when the electrophotographic photosensitive member has a large initial surface layer thickness, a large difference in surface layer thickness between the initial use and the end of use, and the sensitivity of the electrophotographic photosensitive member varies greatly. An object is to maintain a state where an appropriate image can be obtained under image forming conditions for a long period of time. The initial surface layer film thickness means the film thickness of the initial surface layer from which an electrophotographic photosensitive member (hereinafter also referred to as a photosensitive member) is manufactured and then used.

FIG. 8 is a schematic diagram showing the relationship between the number of printed sheets and the image density.
A line 801 shows the relationship between the image density and the number of printed sheets when the pre-charge exposure adjustment process of the present invention is performed to adjust the exposure intensity and exposure wavelength of the pre-charge exposure light. A line 802 shows the relationship between the image density and the number of printed sheets when the conventional pre-charge exposure adjustment process for adjusting only the exposure intensity of the pre-charge exposure light is provided. Note that a line 801 and a line 802 indicate a case where a photoconductor manufactured under the same conditions is used.

In line 801, the exposure intensity of the pre-charging exposure light is adjusted at the timing indicated by 806, and the exposure intensity of the pre-charging exposure light and the exposure wavelength are adjusted at the timing indicated by 807.
In line 802, the exposure intensity of the pre-charging exposure light is adjusted at the timing indicated by 805.
Reference numeral 803 denotes an upper limit of the allowable image density, and reference numeral 804 denotes a lower limit of the allowable image density. In line 802, the adjustment of the pre-charge exposure light is only the adjustment of the exposure intensity, so the light amount adjustment in the pre-charge exposure process exceeds the adjustable range and is allowed at the timing indicated by 808. It is below the lower limit 804 of the image density.

  Even in an image forming apparatus using an a-Si photosensitive member having excellent durability, the surface layer of the photosensitive member may be formed along with the repetition of the image forming process by rubbing with various members around the photosensitive member including a cleaner. Some wear. As the surface layer wears and its film thickness gradually decreases, the amount of pre-charge exposure light that reaches the photoconductive layer increases because the amount of pre-charge exposure light absorbed by the surface layer decreases. Become. As the amount of pre-charge exposure light that reaches the photoconductive layer increases, excess photocarriers generated in the photoreceptor increase.

  This excess photocarrier is discharged when the surface potential of the photosensitive member rises in the charging step, and causes dark decay to increase. For this reason, when the charging condition is constant, the surface potential at a specific position (for example, a position where the developing process is performed) is decreased by the amount of increase in dark attenuation. When a potential drop occurs at a position where such a development process is performed, a change in image density (in the case of FIG. 8, the density is lowered) occurs. For this reason, in the lines 801 and 802 in FIG. 8, the image density decreases as the number of printed sheets increases until the pre-charging exposure light is adjusted.

Until now, if there is a change that increases the amount of pre-charge exposure light that reaches the photoconductive layer, the potential can be set correctly by adjusting the exposure intensity of the pre-charge exposure light. The image density has been adjusted so as to be within an allowable range.
The reason why the potential can be set correctly and the image density falls within the allowable range by adjusting the exposure intensity of the pre-charging exposure light is considered as follows.

  When the exposure intensity of the pre-charging exposure light is weakened, the amount of pre-charging exposure light reaching the photoconductive layer is reduced. As a result, surplus photocarriers generated in the photoconductor are reduced, so that a decrease in surface potential due to dark decay is reduced. As a result, the surface potential at a specific position (for example, the position where the development process is performed) increases by the amount corresponding to the decrease in dark attenuation, so that correct potential setting can be performed, that is, the image density is within an allowable range. I think we can now adjust it to fit.

  However, when the image formation is repeated until the film thickness of the surface layer is reduced by 50% or more with respect to the initial film thickness in order to achieve a longer lifetime of the image forming apparatus, In some cases, the light amount adjustment in the pre-charge exposure process exceeds the adjustable range. This is presumably because the difference in the film thickness of the surface layer becomes large between the initial stage of use and the final stage of use, and therefore the fluctuation of the amount of pre-charging exposure light absorbed by the surface layer becomes large.

Therefore, the present inventors have made extensive studies on the adjustment of pre-charge exposure conditions in the pre-charge exposure process in order to solve the above-described problems. As a result, not only the exposure intensity of the pre-charging exposure light but also the exposure wavelength can be adjusted so that it can be set correctly within the desired surface potential range and the image density falls within the allowable range. I found out that it would be possible.
When there is a change that increases the amount of pre-charge exposure light that reaches the photoconductive layer, the exposure layer is adjusted along with the exposure intensity of the pre-charge exposure light, so that the surface layer film can be used at the beginning and end of use. The reason why the potential can be set correctly even when the difference in thickness is large will be described below.

  As described above, the surface potential can be increased by reducing the exposure intensity of the pre-charging exposure light. Similarly, it was found that the surface potential can be increased by shortening the exposure wavelength for the exposure wavelength of the pre-charging exposure light. This is because the pre-charge exposure light is usually irradiated from the surface layer side of the photoconductor. By shortening the exposure wavelength, all the pre-charge exposure light is exposed in a very shallow area on the surface layer side of the photoconductive layer. It seems to be absorbed.

  Absorption of all pre-charging exposure light in the very shallow region on the surface layer side of the photoconductive layer increases the recombination probability of excess photocarriers, resulting in a reduction in excess photocarriers. It seems to be made. Then, the decrease in the surface potential due to dark decay is reduced, and as a result, the surface potential seems to increase. In addition, photocarriers that have not been recombined are also generated in a very shallow region on the surface layer side of the photoconductive layer, so that they are close to the surface layer where charged charges are present and travel distance when discharged is shortened. .

  For this reason, the decrease in the surface potential due to dark decay after the charging step is reduced, and as a result, the surface potential is considered to increase. In FIG. 8, in the line 801, the exposure intensity and exposure wavelength of the pre-charging exposure light are adjusted at the timing indicated by 807. By adjusting the exposure wavelength in addition to the exposure intensity, the amount of increase in the surface potential increases, and the correct potential can be set after 807, that is, the image density is adjusted to be within the allowable range. I think I can do it now.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of an a-Si photosensitive member (hereinafter sometimes referred to as a photosensitive member) that can be suitably used in the image forming method and the image forming apparatus of the present invention. Represent.
A photoconductor 100 shown in FIG. 1A includes a base 101, a photoconductive layer 102 and a surface layer 103 that are sequentially provided on the base 101.

  Further, as shown in FIG. 1B, a lower charge injection blocking layer 104 is provided on the substrate 101 in order to block the injection of charges from the substrate side. A layer structure in which the conductive layer 102 and the surface layer 103 are sequentially provided may be employed. If necessary, a layer structure in which an upper charge injection blocking layer 105 is provided between the photoconductive layer 102 and the surface layer 103 in order to prevent charge injection from the surface side may be employed.

  If necessary, the photoconductive layer 102 may have a two-layer structure including a first layer region and a second layer region from the substrate 101 side. In addition, regarding the interface between the photoconductive layer 102 and the surface layer 103, the interface between the photoconductive layer 102 and the upper charge injection blocking layer 105, and the interface between the upper charge injection blocking layer 105 and the surface layer 103, the composition is continuously changed. You may provide the composition change layer to change.

The surface layer 103 is composed of hydrogenated amorphous silicon carbide, and the number of carbon atoms (C) relative to the sum of the number of silicon atoms (Si) and the number of carbon atoms (C) in the surface layer 103 is The ratio (C / (Si + C)) is 0.50 or more and 0.65 or less,
The sum of the atomic density of silicon atoms and the atomic density of carbon atoms in the surface layer 103 is 6.60 × 10 ²² atoms / cm ³ or more,
The ratio [alpha] 2 / [alpha] 1 of the absorption coefficient [alpha] 2 of the wavenumber 2890cm ^-1 for the absorption coefficient [alpha] 1 of the wave number 2960 cm ^-1 in the infrared absorption spectrum of the surface layer 103 is 0.50 or less,
The defect density measured by the electron spin resonance method of the surface layer 103 is 9.0 × 10 ¹⁸ (spins / cm ³ ) or more and 2.2 × 10 ¹⁹ (spins / cm ³ ) or less. It is more preferable from the viewpoint of wear resistance and high humidity flow suppression.

  In addition, by using the surface layer 103 having such characteristics, it is possible to obtain a photoconductor having a sensitivity enough to repeatedly form an image even if the surface layer 103 is laminated thickly. Further, since the surface layer 103 can be thickly laminated, a photoconductor having a lifetime exceeding 10 million sheets can be obtained. The film thickness of the surface layer 103 can be appropriately set depending on the desired sensitivity and the life of the photoreceptor.

  The photosensitive member is formed on the substrate by a generally known vacuum deposition method, sputtering method, ion plating method, thermal CVD method, photo CVD method, plasma CVD method, or the like on the substrate. ) And a layer structure as shown in FIG. Among these, the plasma CVD method in which RF gas or VHF band high-frequency power is applied to decompose the raw material gas by glow discharge and a deposited film is formed on the substrate can be preferably produced.

Next, an apparatus that can be used for manufacturing a photoreceptor suitable for the image forming apparatus of the present invention and a method for manufacturing the photoreceptor using the same will be described below.
FIG. 5 is a schematic cross-sectional view showing an example of an apparatus for manufacturing a photoreceptor by a high-frequency plasma CVD method (also abbreviated as RF-PCVD) using an RF band as a power supply frequency.

  This apparatus is roughly composed of a deposition apparatus 5100, a source gas supply system 5200, and an exhaust apparatus (not shown) for depressurizing the inside of the reaction vessel 5111. In a reaction vessel 5111 in the deposition apparatus 5100, a mounting table 5110 for mounting a cylindrical substrate 5112, a substrate heating heater 5113, and a source gas introduction pipe 5114 are installed. Further, a high frequency power source 5120 is connected to a cathode electrode also serving as a reaction vessel 5111 via a high frequency matching box 5115.

  The source gas supply device 5200 includes source gas cylinders 5221 to 5226, valves 5231 to 5236, 5241 to 5246, 5251 to 5256, and mass flow controllers 5211 to 5216. Each source gas cylinder is connected to a gas introduction pipe 5114 in the reaction vessel 5111 via a valve 5260.

Formation of the deposit film using this apparatus is performed by the following procedures, for example.
First, the cylindrical substrate 5112 is installed in the reaction vessel 5111, and the inside of the reaction vessel 5111 is evacuated by an exhaust device (not shown) such as a vacuum pump. Subsequently, the temperature of the cylindrical substrate 5112 is controlled to a predetermined temperature of 200 ° C. to 350 ° C. by the substrate heating heater 5113.
Next, the raw material gas for forming the deposited film is introduced into the reaction vessel 5111 by controlling the flow rate with the gas supply device 5200. Then, a predetermined pressure is set by adjusting the exhaust speed.
After the preparation for deposition is completed as described above, each layer is formed by the following procedure.

When the internal pressure is stabilized, the high frequency power source 5120 is set to a desired power and supplied to the cathode electrode through the high frequency matching box 5115 to cause high frequency glow discharge. An RF band of 1 to 30 MHz can be suitably used as a frequency used for discharge.
Each material gas introduced into the reaction vessel 5111 is decomposed by this discharge energy, and a deposited film containing a predetermined silicon atom as a main component is formed on the cylindrical substrate 5112. After the formation of the desired film thickness, the supply of high-frequency power is stopped, the valves of the gas supply device are closed, the inflow of each source gas into the reaction vessel 5111 is stopped, and the formation of the deposited film is completed.

  By repeating the same operation a plurality of times, a photosensitive layer having a desired multilayer structure is formed. In order to make the film formation uniform, it is also effective to rotate the cylindrical substrate 5112 at a predetermined speed by a driving device (not shown) during the layer formation. Furthermore, it goes without saying that the types of gas and the valve operations described above are changed according to the production conditions of each layer.

Next, an image forming apparatus suitably used in the present invention will be described below.
FIG. 2 is a schematic cross-sectional view showing an example of an image forming apparatus suitably used in the present invention.
In this image forming apparatus, an electrostatic latent image is formed on the surface, and a toner image is formed on the electrostatic latent image by transferring the toner carried on the toner carrying member to form a toner image. 201. Around the photoconductor 201, a charging unit 202 that uniformly charges the surface of the photoconductor 201 to a predetermined polarity and potential, and image exposure light 203 is applied to the surface of the charged photoconductor 201 to electrostatic latent image. A latent image forming unit (not shown) for forming an image is arranged.

  In addition, a first developing unit 204a for adhering black toner B is disposed on the formed electrostatic latent image as a developing unit for transferring and developing the toner carried on the toner carrying member. In addition, a rotary second developing unit 204b including a developing unit for depositing yellow toner Y, a developing unit for depositing magenta toner M, and a developing unit for depositing cyan toner C is disposed.

Further, a pre-transfer charging unit 205 is provided for making the charge of the toner forming the toner image on the surface of the photoconductor 201 uniform and performing stable transfer.
Further, after the toner image is transferred to the intermediate transfer belt 206 which is a part of the transfer means, the cleaning means 207 for removing the transfer residual toner remaining on the surface of the photoconductor 201 and the charge before discharging the photoconductor 201 are performed. An exposure means 208 is provided.

As an example of the pre-charging exposure means 208, an LED or a semiconductor laser capable of emitting single wavelength light, a fluorescent lamp, a halogen lamp, or a tungsten lamp capable of emitting continuous wavelength light can be used as a light source.
The pre-charge exposure means 208 of the present invention further includes a pre-charge exposure adjustment means (not shown) that adjusts pre-charge exposure conditions such as the exposure intensity and exposure wavelength of the pre-charge exposure light. Among the pre-charge exposure adjustment means, the exposure intensity adjustment means includes, for example, a power source capable of voltage control connected to the light source described above, and adjusting the exposure intensity by adjusting the voltage applied to the light source. Can do.

Further, when the light source capable of emitting single wavelength light is used as the exposure wavelength adjusting means, the exposure wavelength can be changed by preparing a plurality of light sources having different emission wavelengths.
FIG. 3 shows a schematic cross-sectional view of an example of the pre-charge exposure adjusting means when a light source capable of emitting single wavelength light is used for the pre-charge exposure means.

  The pre-charge exposure adjusting unit 301 includes a light source carrier 305 provided with a plurality of LEDs 303a, 303b, and 303c having different emission wavelengths. The light source carrier 305 is provided to be rotatable in the direction of the arrow in the drawing. The emission wavelength of each LED is, for example, 660 nm for LED 303a, 630 nm for 303b, and 590 nm for 303c, and is not particularly limited, and is appropriately determined so as to be within a desired surface potential range. .

  Then, only the LED (LED 303a in FIG. 3) at the position of the opening 304 provided at a position facing the photoconductor 302 emits light. When adjusting the exposure wavelength, the light source carrier 305 rotates, and the exposure wavelength can be adjusted by stopping any LED at the position of the opening 304. The exposure wavelength can be set to 630 nm by rotating the light source carrier 305 and disposing, for example, the LED 303b at the position of the opening 304.

When a light source capable of emitting continuous wavelength light is used, the exposure wavelength can be changed by preparing a plurality of optical filters each having a different maximum transmission wavelength.
The transfer means has the following configuration. The intermediate transfer belt 206 is disposed so as to be driven to the photosensitive member 201 via a contact nip portion, and on the inner side, a toner image formed on the photosensitive member 201 is transferred to the intermediate transfer belt 206. A primary transfer roller 209 is provided.

  The primary transfer roller 209 is connected to a bias power source (not shown) that applies a primary transfer bias for transferring the toner image on the photoconductor 201 to the intermediate transfer belt 206. Around the intermediate transfer belt 206, a secondary transfer roller 210 for further transferring the toner image transferred to the intermediate transfer belt 206 to the recording material 212 is provided so as to be in contact with the lower surface portion of the intermediate transfer belt 206. ing.

  The secondary transfer roller 210 is connected to a bias power source for applying a secondary transfer bias for transferring the toner image on the intermediate transfer belt 206 to the recording material 212. Also, an intermediate transfer belt cleaner 211 is provided for removing residual toner remaining on the surface of the intermediate transfer belt 206 after the toner image on the intermediate transfer belt 206 is transferred to the recording material 212.

  The image forming apparatus also includes a paper feed cassette 213 that holds a plurality of recording materials 212 on which an image is formed, and the recording material 212 that contacts the intermediate transfer belt 206 and the secondary transfer roller 210 from the paper feed cassette 213. And a transport mechanism for transporting through the nip portion. A fixing device 214 for fixing the toner image transferred onto the recording material 212 onto the recording material 212 is disposed on the conveyance path of the recording material 212. In the above-described configuration, the intermediate transfer belt 206 serves as a transfer material. However, a configuration in which the image is directly transferred to the recording material 212 without using the intermediate transfer belt 206 may be used. Becomes a transfer material.

As the charging unit 202 and the pre-transfer charging unit 205, a corona charger or a contact charger having magnetic particles arranged in contact with the photoreceptor 201 can be used.
The latent image forming means includes a color separation / imaging exposure optical system for a color original image, and a scanning exposure system using a laser scanner that outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of image information. Is used. With such an exposure system, an electrostatic latent image is formed on the surface of the photoreceptor by irradiating a light beam using a laser or LED as a light source for each pixel of a pixel matrix of a plurality of rows and a plurality of columns according to an image pattern. be able to.

  The image forming apparatus preferably used in the present invention stores a potential measuring unit 215 that measures the surface potential of the photoconductor 201 and an initial surface potential value of the photoconductor 201 measured by the potential measuring unit 215. It is preferable to provide initial potential storage means (not shown). By providing these means, a state in which an appropriate image can be obtained under an appropriate image forming condition can be maintained with high accuracy and for a long period of time. The potential measuring means 215 is not particularly limited as long as the surface potential of the photoreceptor can be measured, and a general surface potential meter can be used. The initial surface potential means an initial surface potential at which the photoreceptor is manufactured and thereafter used.

  Further, the image forming apparatus is preferably provided with a photoconductor usage amount detecting unit 216 that detects the usage amount of the photoconductor 201. As a result, a state in which an appropriate image can be obtained under an appropriate image forming condition can be maintained with high accuracy and for a long period of time. The amount used here means the integrated value of the amount used after the photoconductor is manufactured.

  The photoconductor usage amount detection means 216 detects the rotational speed of the photoconductor 201 using a pulse detector, detects the usage amount of the photoconductor from the rotational speed, and uses a spectrophotometer to detect the surface layer. A means for measuring the film thickness and detecting the amount of the photoreceptor used from the film thickness of the surface layer can be used. Further, when the surface layer thickness of the photoconductor 201 is measured and the usage amount of the photoconductor is detected, the initial surface layer thickness of the photoconductor 201 is further measured, and the value of the obtained surface layer thickness An initial film thickness storage means for storing can be provided.

Next, an image forming method of the present invention using this image forming apparatus will be described.
First, as indicated by an arrow in FIG. 2, the photosensitive member 201 is rotationally driven in a counterclockwise direction at a predetermined peripheral speed (process speed), and the intermediate transfer belt 206 is rotated in the clockwise direction at the same peripheral speed as that of the photosensitive member 201. Is driven to rotate.

  The photosensitive member 201 undergoes a charging process in which it is uniformly charged to a predetermined polarity and potential by the charging unit 202 during the rotation process. Next, the photosensitive member 201 forms a latent image on the surface of the photosensitive member 201 by image exposure 203 to form an electrostatic latent image corresponding to the first color component image (for example, magenta component image) of the target color image. Go through. Next, the second developing unit 204b rotates, the developing unit for attaching the magenta toner M is set at a predetermined position, and the electrostatic latent image is developed with the first color magenta toner M, and then undergoes a developing process. .

  Next, the photoconductor 201 undergoes a transfer process. In the transfer process, the primary transfer bias is applied to a bias power source (not shown) while the first color magenta toner image formed and supported on the photoconductor 201 passes through the nip portion between the photoconductor 201 and the intermediate transfer belt 206. ) To the primary transfer roller 209. Due to the electric field formed by this primary transfer bias, the magenta toner image of the first color is sequentially intermediately transferred onto the outer peripheral surface of the intermediate transfer belt 206.

Next, the photoconductor 201 that has finished transferring the first color magenta toner image to the intermediate transfer belt 206 is subjected to a cleaning process for removing transfer residual toner remaining on the surface of the photoconductor 201 by the cleaning unit 207.
Next, a pre-charging exposure process for removing the charge of the photosensitive member 201 is performed.
Thereafter, a second color toner image (for example, a cyan toner image) is formed on the surface of the photoconductor 201 in the same manner as the formation of the first color toner image, and the second color toner image is converted into the first color toner image. Is transferred onto the surface of the intermediate transfer belt 206 onto which the toner image is transferred. Similarly, a third-color toner image (for example, a yellow toner image) and a fourth-color toner image (for example, a black toner image) are sequentially superimposed and transferred onto the intermediate transfer belt 206, so that a color corresponding to the target color image is obtained. A toner image is formed.

  Next, the recording material 212 is fed from the paper feed cassette 213 to the nip portion between the intermediate transfer belt 206 and the secondary transfer roller 210 at a predetermined timing. Next, the secondary transfer roller 210 is brought into contact with the intermediate transfer belt 206 and a secondary transfer bias is applied to the secondary transfer roller 210 from a bias power source. The composite color toner image superimposed and transferred onto the intermediate transfer belt 206 is transferred to the recording material 212 as the second image carrier by the electric field generated by the secondary transfer bias.

After the transfer of the toner image onto the recording material 212 is completed, the residual toner on the intermediate transfer belt 206 is cleaned by the intermediate transfer belt cleaner 211. The recording material 212 onto which the toner image has been transferred is guided to a fixing device 214 where the toner image is heated and fixed on the recording material 212.
In the image forming method of the present invention, the above-described image formation is repeated until the film thickness of the surface layer of the photoreceptor is reduced by 50% or more with respect to the initial film thickness. The upper limit for the above-mentioned value can be appropriately determined depending on the intended use of the photoreceptor and the initial surface layer thickness, but is preferably up to 90% from the viewpoint of scratch resistance and environmental stability.

Next, the pre-charge exposure adjustment process of the present invention will be described below with reference to the drawings.
FIG. 7 shows an example of an operation flowchart of the pre-charging exposure adjustment process.
In FIG. 7, a pre-charging exposure adjustment process is performed (step S702) at a predetermined timing such as an integrated value of the operating time of the image forming apparatus (step S701).

In the pre-charge exposure adjustment process of the present invention, the exposure intensity of the pre-charge exposure light is adjusted (step S703), then the exposure wavelength of the pre-charge exposure light is adjusted (step S704), and then image formation is continued. (Step S705).
In FIG. 7, the exposure intensity of the pre-charging exposure light is adjusted first, but the exposure wavelength may be adjusted first. The exposure intensity of the pre-charging exposure light is adjusted by adjusting the voltage applied to the pre-charging exposure light source.

  Adjustment of the exposure wavelength of the pre-charging exposure light is performed by switching to another light source having a different emission wavelength when a light source capable of emitting single-wavelength light is used for the pre-charging exposure means. In addition, when a light source capable of emitting continuous wavelength light is used, it is performed by switching optical filters having different maximum transmission wavelengths.

  For adjusting the exposure intensity and exposure wavelength of the pre-charging exposure light, for example, the relationship between how the surface potential of the photoreceptor changes when the exposure intensity and the exposure wavelength are changed is acquired in advance. According to the relationship, it is made to fall within a desired surface potential range.

  By performing such adjustment, even in the case where the amount of exposure light exceeds the adjustment range in the pre-charging exposure step, it is possible to correctly set the desired surface potential within the range. As a result, even if image formation is repeated until the film thickness of the surface layer of the photoconductor is reduced by 50% or more with respect to the initial film thickness, a proper image can be obtained under appropriate image forming conditions. The state can be maintained for a longer period. Further, by using the image forming method of the present invention, the photoconductor can be used for a longer period of time, so that an image forming apparatus having a longer life can be provided.

Next, a pre-charge exposure adjustment process which is another example of the present invention will be described below with reference to the drawings.
FIG. 4 shows an example of an operation flowchart of the pre-charging exposure adjustment process.
First, an initial surface potential of the photosensitive member 201 is measured using the potential measuring unit 215, and an initial potential storing step of storing the obtained initial surface potential value in the initial potential storing unit is performed (step S401). . Then, normal image formation is performed (step S402).

Then, a potential measuring step for measuring the surface potential of the photoconductor 201 is performed using the potential measuring unit 215 (step S403). The surface potential measurement step may be always performed during image formation or may be performed only at a desired timing.
Next, a comparison is made as to whether the surface potential value obtained in the potential measurement step is within the desired surface potential range (step S404), and it is determined that the surface potential value is within the desired surface potential range. In this case, image formation is continued (step S413).
If it is determined that the surface potential is not within the desired range, the exposure intensity of the pre-charging exposure light is adjusted as a pre-charging exposure adjustment step (step S406).

Next, the surface potential of the photoconductor 201 is measured using the potential measuring unit 215 (step S407).
Next, a comparison is made as to whether it is within the desired surface potential range (step S408), and if it is determined that it is within the desired surface potential range, image formation is continued (step S413). ).
If it is determined that it is not within the desired surface potential range and is within the exposure intensity adjustment range, the adjustment of the exposure intensity of the pre-charging exposure light is repeated again (step S406). If the exposure intensity adjustment range is exceeded, the exposure wavelength of the pre-charging exposure light is adjusted (step S410). Then, the surface potential of the photosensitive member 201 is measured again using the potential measuring unit 215 (step S411).

Next, a comparison is made as to whether it is within the desired surface potential range (step S412). If it is determined that the surface potential is within the desired range, image formation is continued (step S413). ). If it is determined that the surface potential is not within the desired range, the process is repeated again from the adjustment of the exposure intensity of the pre-charging exposure light (step S406).
The range of the desired surface potential described here is an allowance that is appropriately determined from the intended purpose and environment of use of the image forming apparatus, centering on the initial surface potential of the photosensitive member 201 obtained in the initial potential storage step. The range of the surface potential reflecting the range is shown.

By doing so, appropriate image forming conditions at the start of use of the photoreceptor and the image forming apparatus can be maintained with high accuracy for a long period of time.
The pre-charge exposure adjustment step may be performed periodically during repeated image formation, or may be performed when the surface potential measurement step deviates from a desired surface potential range.

  Further, when the surface potential measured in the potential measurement step is compared with the initial surface potential stored in the initial potential storage step described above, and a surface potential deviated by 2% or more from the initial surface potential is measured. A pre-charging exposure adjustment step may be performed. In this case, the pre-charge exposure adjustment process may be performed according to an example of an operation flowchart of the pre-charge exposure adjustment process shown in FIG.

Based on FIG. 6, the pre-charge exposure adjustment process performed using the initial surface potential will be described.
First, the initial surface potential of the photoconductor 201 is measured using the potential measuring unit 215, and an initial potential storing step of storing the obtained initial surface potential value in the initial potential storing unit is performed (step S601). . Then, normal image formation is performed (step S602).

Then, a surface potential measuring step for measuring the surface potential of the photoconductor 201 is performed using the potential measuring unit 215 (step S603). The surface potential measurement step may be always performed during image formation or may be performed only at a desired timing.
Next, the surface potential measured in the surface potential measuring step in step S603 is compared with the initial surface potential (step S604).

If the surface potential value obtained in the surface potential measurement step in step S603 is not deviated by 2% or more from the initial surface potential value (YES in step S605), image formation is continued (step S616). .
When the surface potential value measured in the surface potential measurement process in step S603 deviates by 2% or more from the initial surface potential value (NO in step S605), the pre-charge exposure adjustment process is started (step S606). ). Then, the exposure intensity of the pre-charging exposure light is adjusted (step S607).

Next, the surface potential of the photoconductor 201 is measured using the potential measuring unit 215 (step S608).
Next, the surface potential measured in the surface potential measuring step in step S608 is compared with the initial surface potential (step S609).

If the surface potential value measured in the surface potential measurement step in step S608 is not deviated by 2% or more from the initial surface potential value (YES in step S610), image formation is continued (step S616). .
If the surface potential value measured in the surface potential measurement step in step S608 deviates by 2% or more from the initial surface potential value (NO in step S610), it is checked whether it is within the exposure intensity adjustment range (step S611). ).

If the exposure intensity is within the adjustment range (YES in step S611), the adjustment of the exposure intensity of the pre-charging exposure light is repeated again (step S607).
If the exposure intensity is not within the adjustment range (NO in step S611), the exposure wavelength of the pre-charging exposure light is adjusted (step S612). Then, again, the surface potential of the photoconductor 201 is measured using the potential measuring means 215 (step S613).

Next, the surface potential measured in the surface potential measuring step in step S613 is compared with the initial surface potential (step S614).
If the surface potential value measured in the surface potential measurement step in step S613 is not deviated by 2% or more from the initial surface potential value (YES in step S615), image formation is continued (step S616). .
When the surface potential value measured in the surface potential measurement step in step S613 deviates by 2% or more from the initial surface potential value (NO in step S615), the exposure intensity of the pre-charging exposure light in step S607 is determined. Repeat again from adjustment.

By doing so, appropriate image forming conditions at the start of use of the photoreceptor and the image forming apparatus can be maintained with high accuracy for a long period of time.
In addition, the method further includes a photoconductor usage amount detection step for detecting the usage amount of the photoconductor 201, and performs the pre-charge exposure adjustment process according to the usage amount of the photoconductor 201 obtained in the photoconductor usage amount detection step. It may be. In the photoconductor usage amount detection step, the rotational speed of the photoconductor 201 may be detected using a pulse detector, and the usage amount of the photoconductor may be detected from the rotational speed. Alternatively, the film thickness of the surface layer may be measured using a spectrophotometer, and the usage amount of the photoreceptor may be detected from the film thickness of the surface layer. When the surface layer thickness of the photoconductor 201 is measured and the usage amount of the photoconductor is detected from the thickness of the surface layer, the initial surface layer thickness of the photoconductor 201 is further measured, and the obtained surface layer You may have the initial film thickness memory | storage process which memorize | stores the value of a film thickness.

Then, every time the film thickness of the surface layer is reduced by 2% with respect to the initial film thickness of the surface layer, the pre-charging exposure adjustment step may be performed. For example, if the initial surface layer thickness is 1 μm, the pre-charge exposure adjustment step is performed every time the surface layer decreases, which is 0.02 μm, which is 2% of the initial surface layer thickness. Just do it. By doing so, appropriate image forming conditions at the start of use of the photoreceptor and the image forming apparatus can be maintained with high accuracy for a long period of time.
The pre-charge exposure adjustment step of the present invention may be performed during an image forming process such as a charging step, a latent image forming step, a development step, a transfer step, a cleaning step, or a pre-charge exposure step. You may perform as an adjustment process between an image process and an image formation process.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, the technical scope of this invention is not limited at all by these.
<Example 1>
Using the plasma CVD apparatus shown in FIG. 5, a photosensitive member having the layer structure shown in FIG. 1 (b) is formed on an aluminum cylinder (base) having a mirror finish of 84 mm in diameter under the conditions shown in Table 1. Made this book.

The obtained photoreceptor is based on an image forming apparatus iRC-6800 manufactured by Canon Inc., which is a color multifunction peripheral, and the means shown in FIG. 2 can be installed, and the charging polarity is modified to negative charging. Installed in the image forming apparatus.
In this embodiment, the potential measuring means 215, the initial potential storage means (not shown), and the photoconductor usage amount detecting means 216 in FIG. 2 are removed. The pre-charging exposure means 208 uses an LED as a light source. And, as the exposure intensity adjustment means among the pre-charge exposure adjustment means, the voltage applied to the light source can be adjusted, and as the exposure wavelength adjustment means, three LEDs having different emission wavelengths were installed, The pre-charge exposure adjusting means shown in FIG. 3 was installed. The wavelengths of the three LEDs were 660 nm, 630 nm, and 590 nm.

Then, the image formation including the charging process, latent image forming process, developing process, transfer process, cleaning process, pre-charge exposure process, and pre-charge exposure adjustment process is performed with respect to the initial surface layer film thickness. Repeated until 80% reduction.
Note that the pre-charging exposure adjustment process was performed at a predetermined timing in FIG. 7 every 30 minutes from the start of the image forming process according to the flowchart shown in FIG. The exposure intensity was adjusted by adjusting the voltage applied to the light source, and the exposure wavelength was adjusted by rotating the light source carrier 305 shown in FIG.
And the item shown below was evaluated. The results are shown in Table 5.

(Concentration variation)
As described above, when the image formation is repeated, the sensitivity of the photoconductor changes as the film thickness of the surface layer decreases, and the surface potential of the photoconductor changes. Further, as described above, the change in the potential of the photoconductor causes the change in the image density. Since the image forming method and the image forming apparatus of the present invention exert the effect of suppressing the above-described image density fluctuation by suppressing the above-described potential fluctuation, the density fluctuation was evaluated as an evaluation of the examples and comparative examples. .

  A photoconductor produced under the conditions shown in each example and each comparative example is installed in the image forming apparatus under the conditions shown in each example and each comparative example, and a black halftone image having a pixel density of 50% is obtained. An A3 size initial image was output. Next, an A4 size test chart consisting of two-point characters on a white background is placed on the manuscript table, and repeated copying is performed until the film thickness of the surface layer reaches the film thickness of the conditions shown in each example and each comparative example. It was. At this time, every time the film thickness of the surface layer decreased by 5% with respect to the initial film thickness, a black halftone image having a pixel density of 50% was output as an A3-size check image. In addition, a black single-color halftone image with a pixel density of 50% was output as an A3-sized check image even after repeated copying was completed.

  The obtained A3 size initial image and check image were measured for image density by a reflection densitometer (504 spectral densitometer manufactured by X-Rite Inc). The image density is measured in nine locations in the longitudinal direction of the image (9 locations in total: 0 mm, ± 50 mm, ± 100 mm, ± 150 mm, ± 200 mm, where the center of the longitudinal direction of the image is 0 mm) and in the lateral direction of the image. A total of 81 places were performed at 9 places (9 places (0 mm, ± 30 mm, ± 60 mm, ± 90 mm, ± 120 mm in total, with the center in the short direction of the image being 0 mm)). Then, the average value of the obtained 81 image densities was calculated and used as the density value of the initial image and each check image.

Then, the average density value, maximum density value, and minimum density value of the initial image and each check image were calculated. Then, the difference between the maximum density value and the minimum density value with respect to the average value of the density values of the initial image and each check image is calculated, respectively, and the larger difference is divided by the average value of the density values of the initial image and each check image, It was calculated as a concentration fluctuation value.
With respect to the obtained density fluctuation value, the value of Example 2-3 described later was used as a reference (100%), and rank determination was performed according to the following criteria.
In this evaluation item, it is determined that the smaller the density fluctuation value, the better the result.

AAA: 1% or more and less than 40% compared to the reference AA: 40% or more and less than 80% compared to the reference A: 80% or more and less than 120% compared to the reference B: 120% or more compared to the reference

(The number of printed sheets)
In the image forming apparatus under the conditions shown in each example and each comparative example, a photoconductor manufactured under the conditions shown in each example and each comparative example was installed. Next, a black monochrome A4 size halftone image with a pixel density of 30% is used until the film thickness of the surface layer reaches the film thickness of the conditions shown in the examples and comparative examples, or the allowable image density. The copy was repeated until it deviated. The number of copy images obtained up to any of the above conditions was defined as the number of prints.

The number of printed sheets obtained was determined by rank according to the following criteria, using the value of Example 2-3 described later as a reference (100%).
In this evaluation item, it is determined that the larger the number of printed sheets, the better the result.
AAA: greater than 250% compared to the reference AA: greater than 150% greater than the reference to 250% or less A: greater than 50% greater than the reference to 150% or less B: 50% or less compared to the reference

(Comprehensive evaluation)
Based on the score obtained by evaluating the density fluctuation and the number of printed sheets, the AAA rank is 3, the AAA rank is 2, the A rank is 1 point, and the B rank is 0 point as follows. Overall ranking was performed.
AA ... No B rank, 4 points or more A ... No B rank, 2 points or more, 3 points or less B ... B ranks, or 0 points or more, 1 point or less It is judged that the effect of the present invention is obtained at rank A or higher.

<Examples 2-1 to 2-3, Comparative Examples 1-1 to 1-2>
Five photoconductors were produced under the same conditions as in Example 1.
The photoconductor produced as described above was installed in an image forming apparatus under the same conditions as in Example 1, and the image formation was repeated until the film thickness of the surface layer reached the film thickness shown in Table 2. The image was formed under the same conditions as in No. 1. And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

  The film thickness of the surface layer was determined by irradiating light perpendicularly on the surface of the photoreceptor with a spot diameter of 2 mm, and performing spectroscopic measurement of reflected light using a spectrometer (manufactured by Otsuka Electronics: MCPD-2000). The measurement was performed at a total of 8 locations: 1 center in the axial direction of the photoconductor and 8 locations in the circumferential direction of the photoconductor (a point in the circumferential direction of the photoconductor was 0 ° and a total of 8 locations in 45 ° increments). . Then, the film thickness was calculated based on the obtained reflection waveform, and the average value of the film thickness obtained at 8 locations was defined as the surface layer film thickness. At this time, the wavelength range was 500 nm to 750 nm, and the refractive index of the surface layer used was a value obtained by spectroscopic ellipsometry measurement.

The refractive index of the surface layer was measured by spectroscopic ellipsometry as follows.
Under the same conditions as the photoconductors prepared in the examples and comparative examples, only the lower charge injection blocking layer is formed on the substrate, only the lower charge injection blocking layer and the photoconductive layer are formed, and the lower charge injection. A blocking layer, a photoconductive layer, and an upper charge injection blocking layer were formed. These were cut out with a 15 mm square at the center in the longitudinal direction to prepare a reference sample.

Next, for measuring the refractive index of the surface layer, a lower charge injection blocking layer, a photoconductive layer, and an upper charge injection blocking layer are formed on the substrate under the same conditions as in each of the examples and comparative examples. What formed the surface layer was produced. And it cut out similarly to a reference sample, and produced the sample for surface layer measurement.
The above-mentioned reference sample and surface layer measurement sample were measured by spectroscopic ellipsometry (manufactured by JA Woollam: high-speed spectroscopic ellipsometry M-2000) to determine the refractive index of the surface layer. Specific measurement conditions are incident angles: 60 °, 65 °, 70 °, measurement wavelength: 195 nm to 700 nm, analysis software: WVASE 32, beam diameter: 1 mm × 2 mm.

<Example 3>
One photoconductor was produced under the same conditions as in Example 1 except that the surface layer was produced under the conditions shown in Table 3.
The photoconductor produced in this way is installed in an image forming apparatus under the same conditions as in Example 1, image formation is performed under the same conditions as in Example 2-3, and evaluation is performed using the same method as in Example 1. went. The results are shown in Table 5.

Further, the surface layer prepared in Example 3, the ratio [alpha] 2 / [alpha] 1 of the absorption coefficient [alpha] 2 of the wavenumber 2890cm ^-1 for the absorption coefficient [alpha] 1 of the wave number 2960 cm ^-1 obtained from an infrared absorption spectrum, as measured by electron spin resonance defect The density was analyzed. The following items were also analyzed. The results are also shown in Table 4.
(Ratio of the number of carbon atoms (C) to the sum of the number of silicon atoms (Si) and the number of carbon atoms (C) (C / (Si + C)))

  The photoconductor was cut out at a central portion in the longitudinal direction and a size of 10 mm × 10 mm at an arbitrary position in the circumferential direction. Then, the number of silicon atoms and carbon atoms in the surface layer in the measurement area of RBS was measured by RBS (Rutherford backscattering method) (manufactured by Nissin High Voltage Co., Ltd .: backscattering measuring device AN-2500).

Then, C / (Si + C)) was calculated using the number of silicon atoms and carbon atoms in the surface layer in the RBS measurement area.
Specific measurement conditions for RBS are incident ion: 4He ⁺ , incident energy: 2.3 MeV, incident angle: 75 °, sample current: 35 nA, and incident beam length: 1 mm. The RBS detector was measured at a scattering angle of 160 ° and an aperture diameter of 8 mm.

(Sum of atomic density of silicon atoms and atomic density of carbon atoms)
The photoconductor was cut out at a central portion in the longitudinal direction and a size of 10 mm × 10 mm at an arbitrary position in the circumferential direction. Then, the number of silicon atoms and carbon atoms in the surface layer in the measurement area of RBS was measured by RBS (Rutherford backscattering method) (manufactured by Nissin High Voltage Co., Ltd .: backscattering measuring device AN-2500). Next, for the silicon atoms and carbon atoms obtained from the RBS measurement area, the Si atom density and C atom density are obtained using the surface layer thickness obtained by the above-described method, and the atomic density of carbon atoms and carbon atoms are obtained. The sum with the atomic density of was calculated. The specific measurement conditions of RBS were measured under the same conditions as described above.

<Example 4>
One photoconductor was prepared under the same conditions as in Example 3 except that the surface layer thickness was 1.0 μm.
The photoreceptor thus produced was installed in an image forming apparatus under the same conditions as in Example 1 except that the potential measuring means and the initial potential storage means were attached. Then, an image was formed under the same conditions as in Example 2-3 except that the potential measurement step and the initial potential storage step were added and the pre-charge exposure adjustment step was performed according to the flowchart shown in FIG.

In the pre-charging exposure adjustment process of this embodiment, “is it within the range of the desired surface potential?” In FIG. 4 is “95% or more and less than 105% when the initial surface potential is 100%? "
And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

<Example 5>
One photoconductor was produced under the same conditions as in Example 3 except that the surface layer thickness was 1.6 μm.
The photoreceptor thus produced was placed in an image forming apparatus having the same conditions as in Example 4. Then, image formation was performed under the same conditions as in Example 4 except that the pre-charge exposure adjustment step was performed according to the flowchart shown in FIG.
And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

<Example 6>
One photoconductor was produced under the same conditions as in Example 3 except that the surface layer thickness was 2.2 μm.
The photoreceptor thus produced was installed in an image forming apparatus under the same conditions as in Example 4 except that a pulse detector was attached as a photoreceptor usage amount detecting means. Then, image formation was performed under the same conditions as in Example 4 except that a photoconductor usage detection step was added and the pre-charge exposure adjustment step was performed according to the flowchart shown in FIG.

The pre-charge exposure adjustment process of this example was performed at the predetermined timing in FIG. 7 every time the photoconductor rotates 500,000, and the number of rotations of the photoconductor was detected using a pulse detector.
And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

<Example 7>
One photoconductor was produced under the same conditions as in Example 3 except that the surface layer thickness was 2.5 μm.
The photoconductor produced in this manner was implemented except that a spectrophotometer was attached as a photoconductor usage amount detecting means, a halogen lamp was used as a light source of the pre-charging exposure means, and a plurality of optical filters were used as the exposure wavelength adjusting means. The image forming apparatus was installed under the same conditions as in Example 1. Then, a photoconductor usage amount detection step and an initial film thickness storage step are added, and the pre-charge exposure adjustment step is performed at a predetermined timing in FIG. 7 with a film whose surface layer thickness is 2% of the initial surface layer thickness. Image formation was performed under the same conditions as in Example 2-3 except that the measurement was performed every time the thickness decreased. The exposure intensity was adjusted by adjusting the voltage applied to the light source, and the exposure wavelength was adjusted by switching a plurality of optical filters.
And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

<Comparative Example 2>
A photoconductor was manufactured under the same conditions as in Example 1.
The photoreceptor thus prepared was installed in an image forming apparatus under the same conditions as in Example 1 except that the 630 nm and 590 nm LEDs were removed. Then, image formation was performed under the same conditions as in Example 1 except that the pre-charge exposure adjustment step was performed only by adjusting the exposure intensity of the pre-charge exposure light. And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

<Comparative Example 3>
A photoconductor was manufactured under the same conditions as in Example 1.
The photoreceptor thus prepared was placed in an image forming apparatus under the same conditions as in Example 1 except that the exposure intensity adjusting means was removed. Then, image formation was performed under the same conditions as in Example 1 except that the pre-charge exposure adjustment step was performed only by adjusting the exposure wavelength of the pre-charge exposure light. And it evaluated by the method similar to Example 1. FIG. The results are shown in Table 5.

  From Table 5, in the pre-charge exposure process, the configuration of the present invention that adjusts the exposure intensity and the exposure wavelength of the pre-charge exposure light can maintain a state where a proper image can be obtained under a proper image forming condition for a long period of time. It became clear that we could do it. In addition, it has become clear that by using the image forming method of the present invention, the photoconductor can be used for a longer period of time, so that an image forming apparatus having a longer life can be provided.

In Examples 3 to 7, the surface layer is composed of hydrogenated amorphous silicon carbide, C / (Si + C) in the surface layer is 0.50 or more and 0.65 or less, and the atomic density of silicon atoms in the surface layer is The sum of the atomic density of carbon atoms is 6.60 × 10 ²² atoms / cm ³ or more, α2 / α1 in the surface layer is 0.50 or less, and the defect density of the surface layer is 9.0 × 10 ¹⁸ ( spins / cm ³ ) or more and 2.2 × 10 ¹⁹ (spins / cm ³ ) or less. By adopting such a surface layer, it is possible to obtain a photoconductor having a sensitivity enough to repeat image formation even when the surface layer is thickly laminated, and the photoconductor can be used for a longer period. It was revealed that an image forming apparatus having a long life can be provided.

Further, from Example 4, the potential measurement step and the initial potential storage step are added, and the pre-charge exposure adjustment step is performed so as to be close to the initial surface potential, thereby obtaining a state where a proper image can be obtained under a more proper image forming condition. It became clear that it could last for a long time.
In addition, it is clear from Example 5 that a state in which a proper image can be obtained under a more appropriate image forming condition can be maintained for a long period of time by performing the pre-charge exposure adjustment step when the deviation from the initial surface potential is 2% or more. became.

Further, from Example 6, a state where a proper image can be obtained under a more appropriate image forming condition can be obtained for a long time by adding a photoconductor usage detection step and performing a pre-charge exposure adjustment step according to the usage amount of the photoconductor. It became clear that it could be sustained.
Further, from Example 7, by adding a photoconductor usage amount detection step and an initial film thickness storage step, and performing the pre-charge exposure adjustment step every time the film thickness decreases by 2% with respect to the initial surface layer thickness, It has been clarified that a state where a proper image can be obtained under a more appropriate image forming condition can be maintained for a long time. Further, it has been clarified that the effect of the present invention can be exhibited even when the pre-charging exposure means is changed to a light source capable of emitting continuous wavelength light and a plurality of optical filters are used as the exposure wavelength adjusting means.

100, 201, 302 Photoconductor 101 Base 102 Photoconductive layer 103 Surface layer 104 Lower charge injection blocking layer 105 Upper charge injection blocking layer 202 Charging unit 203 Image exposure 204a First developing unit 204b Second developing unit 205 Pre-transfer charging unit 206 Intermediate transfer belt 207 Cleaning means 208 Pre-charge exposure means 209 Primary transfer roller 210 Secondary transfer roller 211 Intermediate transfer belt cleaner 212 Recording material 213 Paper feed cassette 214 Fixing device 215 Potential measurement means 216 Photoconductor usage detection means 301 Pre-charge exposure Adjustment means 303a, 303b, 303c LED
304 Opening 305 Light source carrier

Claims (11)

A charging step for charging the surface of the electrophotographic photosensitive member having at least a photoconductive layer and a surface layer; a latent image forming step for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member; A developing process for transferring the toner carried thereon to develop the electrostatic latent image to form a toner image on the surface of the electrophotographic photosensitive member; and a transfer material for transferring the toner image from the surface of the electrophotographic photosensitive member. A transfer process for transferring to the surface of the electrophotographic photosensitive member, a cleaning process for removing the transfer residual toner remaining on the surface of the electrophotographic photosensitive member from the electrophotographic photosensitive member, and a pre-charging exposure step for discharging the electrophotographic photosensitive member. In the image forming method in which image formation is repeatedly performed until the film thickness of the surface layer is reduced by 50% or more with respect to the initial film thickness,
Adjusting the pre-charge exposure conditions in the pre-charge exposure step, further comprising a pre-charge exposure adjustment step;
The image forming method, wherein the pre-charge exposure adjusting step adjusts an exposure intensity and an exposure wavelength of pre-charge exposure light. The surface layer is composed of hydrogenated amorphous silicon carbide, and the ratio of the number of carbon atoms (C) to the sum of the number of silicon atoms (Si) and the number of carbon atoms (C) in the surface layer ( C / (Si + C)) is 0.50 or more and 0.65 or less,
The sum of the atomic density of silicon atoms and the atomic density of carbon atoms in the surface layer is 6.60 × 10 ²² atoms / cm ³ or more,
The ratio [alpha] 2 / [alpha] 1 of the absorption coefficient [alpha] 2 of the wavenumber 2890cm ^-1 for the absorption coefficient [alpha] 1 of the wave number 2960 cm ^-1 in the infrared absorption spectrum is 0.50 or less in the surface layer,
2. The image according to claim 1, wherein a defect density of the surface layer measured by an electron spin resonance method is 9.0 × 10 ¹⁸ (spins / cm ³ ) or more and 2.2 × 10 ¹⁹ (spins / cm ³ ) or less. Forming method. Measuring an initial surface potential of the electrophotographic photosensitive member and further storing an initial potential storage step of storing the obtained surface potential value;
The image forming method according to claim 1, wherein the pre-charge exposure condition is adjusted so that the pre-charge exposure adjustment step approaches the initial surface potential stored in the initial potential storage step. Further comprising a potential measuring step for measuring a surface potential of the electrophotographic photosensitive member,
4. The image formation according to claim 3, wherein, in the potential measurement step, the pre-charge exposure adjustment step is performed when a surface potential that deviates by 2% or more from the initial surface potential stored in the initial potential storage step is measured. Method. Further comprising a photoconductor use amount detecting step for detecting the use amount of the electrophotographic photoconductor,
The image forming method according to any one of claims 1 to 3, wherein the pre-charge exposure adjustment step is performed according to a usage amount of the electrophotographic photosensitive member obtained in the photosensitive member usage amount detection step. Measuring the initial surface layer thickness of the electrophotographic photosensitive member, further having an initial film thickness storing step of storing the value of the obtained surface layer thickness;
The photoconductor usage detection step is a step of detecting the film thickness of the surface layer,
In the photoconductor usage amount detection step, the pre-charge exposure adjustment step is performed each time the film thickness decreases by 2% with respect to the initial surface layer thickness stored in the initial film thickness storage step. The image forming method according to claim 5. A charging means for charging the surface of the electrophotographic photosensitive member having at least a photoconductive layer and a surface layer; a latent image forming means for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; Developing means for transferring the toner carried thereon to develop the electrostatic latent image to form a toner image on the surface of the electrophotographic photosensitive member; and a transfer material for transferring the toner image from the surface of the electrophotographic photosensitive member A transfer means for transferring to the surface of the electrophotographic photosensitive member, a cleaning means for removing transfer residual toner remaining on the surface of the electrophotographic photosensitive member from the electrophotographic photosensitive member, and a pre-charging exposure means for discharging the electrophotographic photosensitive member. An image forming apparatus that repeatedly forms an image until the film thickness of the surface layer is reduced by 50% or more with respect to the initial film thickness,
A pre-charge exposure adjusting means for adjusting the pre-charge exposure conditions of the pre-charge exposure means;
The image forming apparatus, wherein the pre-charge exposure adjusting means is means for adjusting an exposure intensity and an exposure wavelength of the pre-charge exposure light. The surface layer is composed of hydrogenated amorphous silicon carbide, and the ratio of the number of carbon atoms (C) to the sum of the number of silicon atoms (Si) and the number of carbon atoms (C) in the surface layer (C / (Si + C)) is 0.50 or more and 0.65 or less,
The sum of the atomic density of silicon atoms and the atomic density of carbon atoms in the surface layer is 6.60 × 10 ²² atoms / cm ³ or more,
The ratio [alpha] 2 / [alpha] 1 of the absorption coefficient [alpha] 2 of the wavenumber 2890cm ^-1 for the absorption coefficient [alpha] 1 of the wave number 2960 cm ^-1 in the infrared absorption spectrum is 0.50 or less in the surface layer,
The image according to claim 7, wherein a defect density of the surface layer measured by an electron spin resonance method is 9.0 × 10 ¹⁸ (spins / cm ³ ) or more and 2.2 × 10 ¹⁹ (spins / cm ³ ) or less. Forming equipment. Initial potential storage means for storing the value of the surface potential obtained by measuring the initial surface potential of the electrophotographic photosensitive member;
The image forming apparatus according to claim 7 or 8, wherein the pre-charge exposure adjusting unit adjusts the pre-charge exposure condition so as to approach the initial surface potential stored in the initial potential storage unit. Further comprising a photoconductor use amount detecting means for detecting the use amount of the electrophotographic photoconductor,
The pre-charging exposure adjusting unit adjusts the pre-charging exposure condition according to the usage amount of the electrophotographic photosensitive member obtained by the photosensitive member usage detection unit. Image forming apparatus. An initial film thickness storage means for storing a value of the surface layer film thickness obtained by measuring the initial surface layer film thickness of the electrophotographic photosensitive member;
The photoconductor usage amount detecting means is means for detecting a surface layer thickness of the electrophotographic photoconductor,
According to the initial surface layer film thickness stored by the initial film thickness storage unit and the surface layer film thickness detected by the photoconductor usage amount detection unit, the pre-charge exposure adjustment unit performs pre-charge exposure conditions. The image forming apparatus according to claim 10, wherein the adjustment is performed.

Images