JP2004151220A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which solves the problem of image defects caused by dielectric breakdown of an amorphous silicon photoreceptor and in which occurrence of image defects is effectively prevented particularly even when a toner image is transferred using a transfer roller. <P>SOLUTION: The quantity Q (C/m<SP>2</SP>) of electric charges flowing from a transfer roller into the above photoreceptor during transfer of a toner image to a sheet of paper is set within a range of 6.5×10<SP>-4</SP><Q<2.1×10<SP>2</SP>/(the number of sheets on which printing is assured by the photoreceptor). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming an image by an electrophotographic method, and more particularly, to an image forming apparatus using an amorphous silicon photoconductor as a photoconductor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, and a facsimile, an image is formed by an electrophotographic method.
That is, the photoreceptor is uniformly charged in a predetermined polarity, and is image-exposed by light irradiation based on predetermined image information to form an electrostatic latent image. Next, a developing device supplies a developer to the surface of the photoreceptor to develop an electrostatic latent image to form a toner image on the surface of the photoreceptor. The toner image is formed using a transfer roller or a corona charger for transfer. The image is transferred to a predetermined sheet (transfer sheet). The transfer paper on which the toner image has been transferred is introduced into a fixing device, and the toner image is fixed on the surface of the transfer paper by heat and pressure. On the other hand, after the end of the transfer, the toner remaining on the surface of the photoreceptor is cleaned, and if necessary, static elimination is performed. Thereby, one cycle of the image forming process is completed, and the next image is formed. .
[0003]
As a photoreceptor used for such an image forming apparatus, an OPC (organic photoreceptor) has been widely adopted because it is inexpensive and has high productivity. However, the OPC photoconductor has a soft surface, is easily worn by a cleaning blade, toner, and paper, and has a problem in durability. Therefore, the surface of the photoconductor is harder than the OPC photoconductor, and amorphous silicon photoconductors are widely used in consideration of wear resistance, durability, function retention (maintenance), and environmental considerations. (For example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-1-315772
[Problems to be solved by the invention]
However, the volume resistance of the amorphous silicon photoconductor is 10 ^{9 to 11} (Ω · cm), which is lower than the volume resistance of the OPC photoconductor (10 ¹³ Ω · cm). A large amount of current flows into the photoconductor at the time of (negative), and as a result, there is a disadvantage that a black spot image is easily generated due to dielectric breakdown.
Further, in the manufacturing process of the amorphous silicon photoconductor, film defects such as abnormal growth of the film and pinholes are generated, so that a charging or transfer current is concentrated on the portion and dielectric breakdown may be caused.
[0006]
Further, when a transfer roller is used as a transfer unit for transferring the toner image formed on the photoreceptor surface to a predetermined paper surface, discharge of ozone, NOx, or the like is performed as in the case of using a corona charger. Almost no product is generated, which is environmentally advantageous. However, if a transfer roller is used when an amorphous silicon photoconductor is used, the roller directly contacts the film defect of the amorphous silicon photoconductor, so that the transfer current concentrates on the film defect, and the image defect ( There is a problem that a black point image) is more likely to occur.
[0007]
The amorphous silicon photoconductor has an amorphous silicon-based photoconductive layer on a conductive substrate. In order to avoid the problem of dielectric breakdown due to a film defect, the photoconductive layer such as SiC is formed on the photoconductive layer. It is common practice to form a surface protection layer having a higher C content than the layer. However, particularly when a transfer roller is used as the transfer means, the repetition of the transfer process lowers the resistance of the surface protective layer and lowers the charging ability, so that it is difficult to obtain an image with an appropriate density. There was a problem of becoming.
[0008]
Accordingly, an object of the present invention is to solve the problem of image defects caused by dielectric breakdown of an amorphous silicon photoconductor in an image forming apparatus using the above-described amorphous silicon photoconductor, and particularly to transfer a toner image using a transfer roller. It is another object of the present invention to provide an image forming apparatus in which such image defects are effectively prevented.
[0009]
[Means for Solving the Problems]
According to the present invention, an image is formed by using an amorphous silicon photoreceptor and transferring a toner image obtained by developing an electrostatic latent image formed on the photoreceptor surface to a predetermined sheet by a transfer roller. In the image forming apparatus to be performed,
The charge amount Q (C / m ² ) flowing from the transfer roller to the photoconductor when transferring the toner image onto one sheet of paper is
An image forming apparatus is provided, wherein the value is set within a range of 6.5 × 10 ⁻⁴ <Q <2.1 × 10 ² / guaranteed number of photoconductors.
In the present specification, the guaranteed number of printed sheets of the photoconductor means that, when a user exchanges an image forming purchase with a photoconductor, if the photoconductor causes any abnormality in an image, the maker can charge the photoconductor free of charge. It is the upper limit number that guarantees that the body is replaced.
[0010]
In the present invention,
1. The transfer roller is formed on the shaft and the shaft having conductivity composed of a foamed rubber layer, it is and has a volume resistivity of 10 ⁵ to 10 ⁹ Omega · cm,
2. The foamed rubber layer has a rubber hardness (Asker C) of 20 to 50 °,
3. The amorphous silicon photoreceptor has a three-layer structure in which a carrier blocking layer, a photoconductive layer, and a surface protective layer are formed in this order on a conductive substrate;
4. The surface protection layer is made of amorphous silicon carbide (SiC) and has a thickness of 2 μm or less;
5. The surface protective layer has a thickness of 0.5 to 1.5 μm,
6. The total thickness of the carrier blocking layer, photoconductive layer and surface protective layer is in the range of 10 to 20 μm,
7. The inflowing charge amount Q is set to 1.4 × 10 ⁻³ (C / m ² ) or less;
Is preferred.
[0011]
That is, in the present invention, by setting the transfer current so that the current flowing from the transfer roller to the surface of the photoconductor when printing (image formation) on one sheet is within the above range, the surface of the amorphous silicon photoconductor is Deterioration of the formed surface protective layer (Si-C layer) is effectively suppressed, and it is possible to effectively prevent the occurrence of image defects (black spot images) before the number of photoconductors reaches the guaranteed number of prints. It becomes.
[0012]
For example, see FIG. FIG. 3 shows the relationship between the number of black spots generated in one sheet and the number of printed sheets when a large number of images are repeatedly formed in an experimental example described later (detailed conditions are given in the experimental example). 3), it can be seen from FIG. 3 that the surface protective layer deteriorated after printing 150,000 sheets and the number of black spots sharply increased.
[0013]
On the other hand, FIG. 4 shows a transfer bias waveform applied to the transfer roller when the above-described image formation is performed. In FIG. 4, the two-stage transfer voltage on the minus side is that the positive / negative switching is performed inside and outside the paper, and when the minus voltage is switched at the position where there is no paper, the constant current control of -65 μA is performed. This is because the resistance value between the photoconductor and the transfer roller increases during paper passing, and thus the voltage limit is set at -2.1 kV before reaching -65 μA. Therefore, the total charge amount per 1 cm ^{2 of} the photoconductor is calculated by integrating the negative transfer current portion in FIG. 4 with time and dividing by the total area between the photoconductor and the transfer roller. The relationship between the total charge amount thus calculated and the number of printed sheets is shown in FIG.
[0014]
By the way, as shown in FIG. 3, the deterioration of the surface protective layer starts from 150,000 sheets, and the total charge amount after printing 150,000 sheets is 2.1 × 10 ² C / m ² from FIG. It turns out that there is. Therefore, assuming that the guaranteed number of printed sheets of the photoconductor is Y, the total charge amount Q (C / m ² ) flowing into the photoconductor in one-sheet printing is:
Q <2.1 × 10 ² / Y
It can be understood that, when the range is set, the surface protection layer is prevented from deteriorating until the photosensitive member warranty life, and the occurrence of image defects (black spots) can be reliably prevented.
[0015]
That is, when the photoconductor warranty life is set to 150,000 sheets, the charge amount Q flowing into the photoconductor in one-sheet printing is 2.1 × 10 ² /150000=1.4×10 ⁻³ (C / m ² ). It is set in the following range. For example, the waveform of the transfer bias applied to the transfer roller is changed as shown in FIG. 6, and the amount of charge Q flowing into the photoreceptor per print is set to 9.8 × 10 ⁻⁴ so as to satisfy the above condition. Assuming that (C / m ² ), the relationship between the number of black spots generated in one sheet and the number of printed sheets is as shown in FIG. From FIG. 7, it is understood that the number of printed sheets at which the deterioration of the surface protective layer starts is 200,000 or more, and the deterioration of the surface protective layer is effectively suppressed.
[0016]
Further, in the present invention, it is necessary that the charge amount X flowing into the photoconductor per one sheet of printing is larger than 6.5 × 10 ⁻⁴ (C / m ² ). That is, if the amount X of electric charge flowing in is less than the above range, it becomes difficult to effectively transfer the toner image, and transfer failure occurs.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
In FIG. 1 showing a schematic structure of the image forming apparatus of the present invention, a main charger 12, an exposing unit 13, a developing unit 14, a transfer roller 15, a cleaning unit are provided around an amorphous silicon photosensitive drum 11 along the rotation direction thereof. Means 16 and static elimination means 17 are provided.
[0018]
In the present invention, as shown in FIG. 2, the amorphous silicon photosensitive drum 11 has a structure in which an amorphous silicon photosensitive layer indicated by 30 is formed on a conductive substrate 21. The layer 30 preferably comprises a carrier blocking layer 20, an amorphous silicon-based photoconductive layer 19, and a surface protection layer 18.
[0019]
The material for forming the photoconductive layer 19 in the photosensitive layer 30 is not particularly limited as long as it is amorphous silicon (a-Si). Preferred materials include a-Si, a-SiC, and a-SiO. , A-SiON and the like. Among these materials, a-SiC (amorphous silicon carbide) has particularly high resistance, and is more suitable as a photosensitive layer material in the present embodiment because it has better charging ability, abrasion resistance, and environmental resistance. is there.
It is preferable to use a-SiC having a specific atomic ratio of Si to C (carbon). For example, represented by a-Si _1-X C _X ,
0.3 ≦ X <1,
Preferably, 0.5 ≦ X ≦ 0.95
Particularly preferably, 0.85 ≦ X ≦ 0.95
Those that satisfy the conditions of Such a-SiC has a particularly high resistance of 10 < ¹² > to 10 < ¹³ > [Omega] cm, has a small flow of latent image charges in the direction of the surface of the photoreceptor, and has excellent ability to maintain an electrostatic latent image and excellent moisture resistance. Because it is.
[0020]
Such an amorphous silicon-based photoconductive layer 19 can be formed by a glow discharge decomposition method, a sputtering method, an ECR method, a vapor deposition method, or the like. In general, at the time of film formation, hydrogen (H) or halogen is used for dangling bond termination. The element is contained at 1 to 40 atomic%. Further, in order to obtain desired characteristics such as electric characteristics such as dark conductivity and photoconductivity, and optical hand gap, a group IIIa element or a group Va element of the periodic table can be contained. Depending on the composition, elements such as nitrogen (N) and oxygen (O) can be contained.
[0021]
The carrier blocking layer 20 prevents the carrier from being injected from the conductive substrate 21 into the photoconductive layer 19 when the developer comes into contact with the surface of the drum 11 in a state where the developing bias voltage is applied. It is provided to increase the electrostatic contrast with the non-exposed area, increase the image density, and reduce the fog in the background area.
[0022]
Accordingly, such a carrier blocking layer 20 is formed from a high-resistance material, for example, an amorphous silicon-based material, a polyester resin such as polyethylene terephthalate, a fluorine-containing resin such as polytetrafluoroethylene and polyfluoroethylene propylene, It is formed of an organic material such as polyimide, urethane resin, epoxy resin, polycarbonate resin, and cellulose acetate resin.
[0023]
The above-mentioned carrier blocking layer 20 may be formed by a vacuum deposition method, an active reaction deposition method, an RF sputtering method, a DC sputtering method, an RF magnetron sputtering method, a DC magnetron sputtering method, a thermal CVD method, or a plasma CVD method, depending on the material for forming the carrier blocking layer. It is formed by a method, a spray method, a coating method, a dipping method, or the like.
The thickness of such a carrier blocking layer 20 is generally in the range of 0.01 to 5 μm, preferably 0.1 to 3 μm.
[0024]
The surface protection layer 18 is formed of amorphous silicon carbide (a-SiC) having a higher C content than the photoconductive layer 19. For example, represented by a-Si _1-X C _X ,
0.85 ≦ X <0.95
It is good to be formed from what satisfies. That is, the surface protection layer 18 has a higher volume resistance than the photoconductive layer 19, thereby avoiding dielectric breakdown due to a film defect.
[0025]
Such a surface protective layer 18 can be formed by a method similar to that of the photoconductive layer 19 described above. For example, the surface protective layer 18 is formed continuously with the photoconductive layer 19 by appropriately changing the carbon concentration in the source gas. be able to. In this case, when the carrier blocking layer 20 is formed of a-SiC, the carrier blocking layer 20, the photoconductive layer 19, and the surface protection layer 18 are continuously and collectively changed by appropriately changing the carbon concentration in the source gas. Can be formed.
[0026]
It is preferable that the surface protective layer 18 has a thickness of 2 μm (20,000 °) or less, particularly 0.5 to 1.5 μm. For example, if the thickness of the surface protection layer 19 is too small, the withstand voltage characteristic is reduced with respect to the inflow of negative current from the transfer, and as a result, the surface protection layer 19 is deteriorated at an early stage (for example, 15,000 sheets or less). There is a possibility that it will. Also, if the surface protection layer 19 is thicker than necessary, the film formation time becomes longer, which is disadvantageous in cost.
[0027]
In the present invention, the photosensitive layer 30 including the carrier blocking layer 20, the photoconductive layer 19, and the surface protective layer 18 described above is preferably a thin film as a whole, and in particular, charging ability, withstand voltage, dark decay characteristics, manufacturing cost, The thickness is preferably in the range of 10 to 20 μm depending on quality and the like.
That is, when the thickness of the photosensitive layer 30 is less than 10 μm, the charging ability of the photosensitive member is low, and it is difficult to obtain a predetermined surface potential. (Depends on the conductive layer 19), so that dielectric breakdown occurs due to repeated charging, and a black dot image is generated. In addition, the irregular reflection of the laser light on the surface of the conductive substrate 21 causes a problem that interference fringes occur in the half pattern. On the other hand, if the thickness of the photosensitive layer 30 exceeds 20 μm, the moving speed of the heat carrier increases, so that the dark decay characteristic deteriorates. As a result, the flow of the latent image toward the surface of the photosensitive member occurs. It becomes easy and causes a decrease in resolution. Also, in terms of cost, as the film thickness of the photosensitive layer 30 is larger, the film formation time is longer, the probability of adhesion of foreign matter and the like is higher, and the yield is lower. Therefore, in terms of cost and quality, the thickness of the photosensitive layer 30 is preferably 20 μm or less.
[0028]
The conductive substrate 21 having the photosensitive layer 30 on its surface is made of a metal or alloy material such as aluminum, stainless steel, Ti, Ni, Au, or Ag, or a resin substrate or the like in which a conductive film is formed on an insulating substrate surface. However, in general, those made of aluminum are used.
[0029]
The above-mentioned amorphous silicon-based photoconductor drum 11 is uniformly charged to a positive polarity by the main charger 12. At this time, the charging potential on the surface of the drum 11 is preferably in the range of +200 to +500 V, particularly +200 to +300 V. If the charging potential is smaller than the above range, the developing electric field becomes insufficient, and it becomes difficult to secure image density. On the other hand, if the charging potential is higher than the above range, depending on the thickness of the photosensitive layer 30, the charging ability is insufficient, black spots are easily generated due to dielectric breakdown, or the amount of generated ozone is increased. This is because there is a fear.
[0030]
As the main charger 12, a corona charger such as a corotron or a scorotron, or a conductive roller is used. When a scorotron is used, the distance between the grid and the surface of the drum 11 is preferably in the range of 0.4 to 0.8 mm. If this interval is too small, there is a risk of spark discharge, and if it is too large, it becomes difficult to perform charging effectively.
[0031]
After the main charging, image exposure is performed by irradiating the exposure device 13 with light such as laser light based on predetermined image information. By this light irradiation, the potential of the light-irradiated portion is reduced, and an electrostatic latent image is formed.
[0032]
The electrostatic latent image formed on the surface of the photoconductor drum 11 is developed by the developing device 14, and a toner image is formed on the surface of the photoconductor drum.
The development by the developing device 14 may be performed by a so-called regular development method or a reversal development method. In the case of performing the development by the reversal development method, a light irradiation part by the image exposure becomes an image part, and a part not irradiated with light becomes a background part of an image. In a normal development, the pattern is reversed.
[0033]
As the developer used for the development, a one-component developer composed of a non-magnetic or magnetic toner and a two-component developer composed of a non-magnetic or magnetic toner and a magnetic carrier (for example, iron powder or ferrite) are used. The developer is supplied to the surface of the photoreceptor by the developing device 14, so that the positively charged toner in the reversal development and the negatively charged toner in the regular development adhere to the electrostatic latent image forming portion, thereby performing the development. Then, a toner image is formed.
The development may be performed by so-called contact development in which the developer is brought into contact with the surface of the photoconductor drum 11, or may be performed by jumping development in which the developer and the surface of the photoconductor drum 11 are not in contact with each other. .
[0034]
The toner image formed as described above is transferred onto a sheet passing between the drum 11 and the transfer roller 15 by the transfer roller 15 to which a transfer bias is applied. That is, the toner image is transferred from the surface of the drum 11 to the surface of the sheet by the electric field formed between the drum 11 and the transfer roller 15 by the transfer bias. Therefore, when the charge polarity of the toner image is positive (in the case of reversal development), a negative transfer bias is applied to the transfer roller 15, and when the charge polarity of the toner image is negative (in the case of regular development). , A positive transfer bias is applied to the transfer roller 15.
[0035]
The transfer roller 15 is preferably in contact with the photosensitive drum 11 and driven by the drum 11, and rotates with a linear speed difference of 3% to 5% with respect to the drum 11. This is because if it is less than 3%, the transferability tends to decrease and the problem of hollowing out tends to occur, and if it is more than 5%, the slip between the transfer roller 15 and the drum 11 increases and jitter increases. .
[0036]
The transfer roller 15 preferably has a conductive shaft provided with a layer of foamed rubber (for example, foamed EPDM). This is because the use of the foam prevents the toner contaminated at the time of paper jam or the like from entering the bubbles of the foam, thereby preventing the back stain on the first paper after the restart of the operation. Further, by providing the foamed rubber layer, it is not necessary to clean the transfer roll, and the cost can be reduced.
The surface height of the transfer roller 15, that is, the hardness (Asuka C) of the foamed rubber layer is preferably in the range of 20 to 50 °, particularly preferably 30 to 40 °. If the hardness is lower than this range, transfer failure occurs. If the hardness is higher than this range, the nip between the photoconductor drum 11 and the photoconductor drum 11 becomes small, and the paper conveyance force may be reduced.
Further, in order to apply a predetermined transfer bias, the volume resistance of the transfer roller 15 is preferably in the range of 10 ^{5 to} 10 ⁹ Ω · cm. Therefore, it is preferable to disperse conductive powder such as carbon black and metal powder in the foamed rubber layer, and to adjust the volume resistance within the above range.
[0037]
As described above, the transfer of the toner image by applying the transfer bias to the transfer roller 15 is such that the charge amount Q (C / m ² ) flowing from the transfer roller 15 to the photosensitive drum 11 during printing of one sheet is
6.5 × 10 ⁻⁴ <Q <2.1 × 10 ² / Number of photoconductor guaranteed prints, especially 6.5 × 10 ⁻⁴ <Q ≦ 1.4 × 10 ⁻³
The transfer bias waveform is adjusted so as to satisfy the following condition. Thereby, the deterioration of the surface protective layer of the amorphous silicon photosensitive drum 11 described above can be effectively suppressed, and generation of a black spot image due to dielectric breakdown can be prevented for a long time.
[0038]
After the transfer of the toner image onto the sheet by the transfer roller 15, the sheet having the transferred toner image is introduced into a fixing device (not shown), and the toner image is fixed on the sheet surface by heat and pressure. After that, it is discharged out of the device.
On the other hand, after the transfer by the transfer roller 15 is completed, the toner remaining on the surface of the drum 11 is removed by the cleaning unit 16, and the remaining charge is removed by the charge remover 17. As the cleaning means 16, a rubber blade made of polyurethane or the like is usually used by being pressed against the surface of the drum 11, but if necessary, a fur brush or the like may be used. As the static eliminator 17, an LED or the like is used, and static elimination is performed by light irradiation. However, a charging roller, a corona charger, or the like may be used.
[0039]
【Example】
The present invention is described in the following experimental examples.
In the following experimental examples, printers having the following specifications were used.
[Photoconductor drum]
φ30 positively charged amorphous silicon photosensitive drum surface protective layer (1 μm):
Photoconductive layer (8 μm):
Carrier blocking layer (6 μm):
Conductive substrate: Aluminum tube [Main charger]
Scorotron circumferential charging width: 12.0 mm
Drum axial charging width: 242mm
Grid-wire distance: 5.8 mm
Drum-grid distance: 1.0 mm
Drum charging potential: 250V
[exposure]
Laser exposure [development]
Reversal contact developing developer: two-component magnetic developer developing bias: 200V
[Transfer roller]
Foam EPDM roller hardness (Asuka C):
Volume resistance: 1 × 10 ⁷ Ω · cm
Linear velocity difference with drum: + 15%
[cleaning]
Blade cleaning [static elimination]
LED static elimination [feeding speed]
16 sheets / minute (97 mm / s) with A4
[0040]
Experimental example 1
Using the printer described above, an image is formed by applying a transfer bias having the waveform shown in FIG. 4 to the transfer roller at A4 lengthwise continuous paper passing and a printing rate of 4%, and the number of black spots generated on the image is measured. FIG. 3 shows the relationship between the number of black spots and the number of printed sheets.
From FIG. 3, it can be seen that the number of black spots sharply increases from the point in time when the number of printed sheets reaches 150,000 sheets, and that the deterioration of the surface protective layer of the photoreceptor has begun.
Further, the total charge amount flowing from the transfer roller to the photosensitive drum is calculated from the negative integral value of the transfer bias waveform in FIG. 4 and the total area between the drum and the transfer roller, and the relationship between the number of printed sheets and the total charge amount is calculated. As shown in FIG.
FIG. 5 shows that the total charge amount when the number of printed sheets is 150,000 is 2.1 × 10 ² C / m ² .
From the above results, the amount of charge flowing into the drum when printing one sheet is:
2.1 × 10 ² /150000=1.4×10 ⁻³ (C / m ² )
Is calculated.
Therefore, by setting the amount of charge flowing into the drum during one-sheet printing to be smaller than the above value, it is expected that the number of printed sheets whose surface protective layer is deteriorated can be increased.
[0041]
Experimental Example 2:
Based on the results of Experimental Example 1, the waveform of the transfer bias was changed as shown in FIG. 6, and the amount of charge flowing into the drum during one-sheet printing was set to 9.8 × 10 ⁻⁴ (C / m ² ). An image was read out in the same manner as in Example 1, the number of black spots generated on the image was measured, and the relationship between the number of black spots and the number of printed sheets was shown in FIG.
As shown in FIG. 7, the number of printed sheets in which the surface protective layer is deteriorated has greatly increased to 200,000 or more.
[0042]
【The invention's effect】
According to the present invention, image defects such as black spots caused by dielectric breakdown of an amorphous silicon photoconductor can be suppressed for a long period of time.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic structure of an image forming apparatus of the present invention.
FIG. 2 is a diagram illustrating an example of a layer configuration of an amorphous photosensitive drum used in the present invention.
FIG. 3 is a diagram showing the relationship between the number of printed sheets and the number of black spots measured in Experimental Example 1.
FIG. 4 is a diagram showing a transfer bias waveform employed in Experimental Example 1.
FIG. 5 is a diagram showing the relationship between the total amount of charge flowing into the photosensitive drum calculated from the result of Experimental Example 1 and the number of printed sheets.
FIG. 6 is a diagram showing a transfer bias waveform employed in Experimental Example 2.
FIG. 7 is a diagram showing the relationship between the number of printed sheets and the number of black spots measured in Experimental Example 2.
[Explanation of symbols]
11: Photoreceptor drum 12: Main charger 13: Exposure device 14: Developing device 15: Transfer roller 16: Cleaning means 17: Static eliminator 18: Surface protective layer 19: Photoconductive layer 20: Carrier blocking layer 21: Conductive substrate 30: photosensitive layer

Claims (8)

Using an amorphous silicon photoreceptor, in an image forming apparatus that performs image formation by transferring a toner image obtained by developing an electrostatic latent image formed on the photoreceptor surface to a predetermined sheet by a transfer roller,
The charge amount X (C / m ² ) flowing from the transfer roller to the photosensitive member when transferring the toner image onto one sheet of paper is
An image forming apparatus, wherein the value is set in a range of 6.5 × 10 ⁻⁴ <Q <2.1 × 10 ² / number of guaranteed photoconductors. 2. The image according to claim 1, wherein the transfer roller includes a conductive shaft and a foamed rubber layer formed on the shaft, and has a volume resistance of 10 ^{5 to} 10 ⁹ Ω · cm. Forming equipment. The image forming apparatus according to claim 2, wherein the foamed rubber layer has a rubber hardness (Asker C) of 20 to 50 °. 4. The image forming apparatus according to claim 1, wherein the amorphous silicon photoconductor has a three-layer structure in which a carrier blocking layer, a photoconductive layer, and a surface protective layer are formed on a conductive substrate in this order. 5. apparatus. The image forming apparatus according to claim 4, wherein the surface protection layer is made of amorphous silicon carbide (a-SiC) and has a thickness of 2 m or less. The image forming apparatus according to claim 5, wherein the surface protection layer has a thickness of 0.5 to 1.5 μm. The image forming apparatus according to claim 4, wherein a total thickness of the carrier blocking layer, the photoconductive layer, and the surface protective layer is in a range of 10 to 20 m. ^2. The image forming apparatus according to claim 1, wherein the inflow charge amount Q is set to 1.4 × 10 ⁻³ (C / m ² ) or less.

Images