JPH0473592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an image forming apparatus having a rotatably supported photosensitive drum and a process element that comes into pressure contact with the surface of the drum.

Prior Art A conventional photosensitive drum has a support made of a rigid body and a photosensitive layer supported by the support, and is rotatably supported by the main body of an image forming apparatus. During an image forming operation, an electrostatic latent image is formed on the photosensitive layer of the drum, and this latent image is visualized by a developing device. However, if the photosensitive drum is made of a rigid body as in the past, it cannot avoid the following drawbacks, for example.

That is, as a developing device, a one-component developer (hereinafter referred to as toner) is supported on a developer carrier consisting of, for example, a developing roller, and is conveyed, and during the conveyance, toner particles are transferred to, for example, the developing roller. When the toner particles are charged to a predetermined polarity by contact with the developing roller and the thus charged toner particles are attached to the electrostatic latent image on the photoreceptor drum, in order to uniformly charge the toner, the toner particles on the developing roller are charged to a predetermined polarity. It is desirable to make the thickness extremely thin, and ideally to form a toner layer with a thickness of one toner particle on the developing roller. This is because if the toner on the developing roller is thick, it will not be possible to charge the toner uniformly over the thickness direction, which may reduce the quality of the visible image.

On the other hand, a thin toner layer is formed on the developing roller,
In order to transfer the toner particles to the electrostatic latent image on the photoreceptor drum and obtain a high-quality visible image, the toner on the roller is transferred to the surface of the photoreceptor drum in the area where the developing roller and the photoreceptor drum face each other. It is necessary to bring the toner into contact with the drum surface, or to oppose the toner and the drum surface with a small gap between them. However, if the photosensitive drum is made of a rigid body, it is not easy to bring the extremely thin toner layer on the developing roller into contact with the drum surface or to make them face each other with a small gap between them. If the photoreceptor drum and the developing roller are pressed against each other or are placed very close to each other, the surface of the photoreceptor drum or the developing roller may be slightly distorted, especially if the surface of the developing roller is made of a rigid body.
Even if these outer diameters are slightly inaccurate due to manufacturing variations, a large gap may form between the drum and the developing roller, or conversely, they may press against each other with excessive force, causing the photoreceptor drum to This is because there is a risk of scratches on the surface. It is difficult to manufacture a developing roller or a photoreceptor drum with such high precision as to completely eliminate surface distortion or variation in the outer diameter thereof. In order to eliminate this inconvenience, a photoreceptor belt is used instead of the photoreceptor drum, and by pressing the developing roller against this belt and bending the belt, the toner on the developing roller comes into contact with the photoreceptor belt. It is also possible to do so. However, when a photoreceptor belt is used, at least two rollers are required to support it, which not only complicates the structure and increases costs, but also increases the size of the copying machine.

Therefore, if a photoreceptor drum whose surface is elastically deformable is used, and a developing roller is pressed against the drum to elastically deform the surface of the photoreceptor drum, the surfaces of the photoreceptor drum and the developing roller can be It is possible to reliably bring the toner on the roller into contact with the photoreceptor drum, or to place the toner and the photoreceptor drum facing each other with a small gap, while suppressing inconveniences such as damage to the photoreceptor. The disadvantage of increasing the size of the device, as in the case of using a belt, can also be avoided. However, when the surface of the photoreceptor drum is configured to be recessed and deformable in this way, when a process element, such as a developing roller, which is in pressure contact with the surface of the photoreceptor drum deforms the drum, the drum is affected by the deformation of the drum. The surface in other parts may also be significantly deformed in its radial direction, which may lead to unfavorable results in forming an image on the photoreceptor drum or transfer paper. For example, when exposing the surface of a photoreceptor drum to form an electrostatic latent image on it, if the surface of the photoreceptor drum in the exposed area is distorted and deformed, the image cannot be correctly focused on the exposed area. This makes it difficult to do this, resulting in a blurred image. Although configuring the surface of the photoreceptor drum to be elastically deformable in this manner provides favorable results in developing a latent image, other drawbacks may arise as a result.

Object The object of the invention is to provide an image forming device of the type mentioned at the outset, which eliminates the above-mentioned drawbacks.

Embodiment FIG. 1 shows an example of an electronic copying machine according to the present invention, and in order to understand the present invention, first, its overall structure and its operation will be explained.

The electronic copying machine shown in FIG. 1 has a photosensitive drum 1 rotatably supported by the copying machine body, and various process elements arranged around it. Of these, a developing roller 9, which will be described in detail later, and a cleaning blade 5 are in pressure contact with the surface of the photosensitive drum 1.

The photosensitive drum 1 includes a shaft 2, an elastic material layer 3 supported by the shaft 2 and capable of elastic deformation, and this material layer 3.
around the outer layer 4, usually in the form of a sleeve, which is fitted without movement, and the elastic material layer 3.
is filled between the shaft 2 and the outer layer 4 without forming a substantial gap therebetween. In this example, the elastic material layer 3 is integrally fixed to a shaft 2, which is rotatably supported by the main body of the copying machine and is drivingly connected to a drive device (not shown). When an external force is applied to the surface of the photoreceptor drum 1, it elastically deforms as will be described later, but in a free state where no external force is applied, the surface of the photoreceptor drum 1 is separated from the elastic material layer 3 as shown in FIGS. 2 and 3. The layer 4 has a cylindrical shape concentric with the axis 2. As clearly shown in FIG. 4, the outer layer 4 consists of a photoreceptor support layer 5 and a thin photosensitive layer 6 formed on the surface of the support layer 5 by, for example, coating. The photosensitive layer 6 supported by such a photosensitive member support layer 5 is made of, for example, OPC, zinc oxide, selenium, etc., like the photosensitive layer in a conventional photosensitive drum.
It is composed of a photoconductive material made of an inorganic or organic substance such as an amorphous material. Photoreceptor support layer 5
The photoreceptor support layer 5 in this example is made of an elastically deformable thin plate made of metal or the like, and the photoreceptor support layer 5 in this example is electrically conductive (usually
The specific volume resistivity is approximately 10 ⁹ Ω-cm or less. The elastic material layer 3 is made of an elastic material such as a non-foamed material made of rubber or the like, or a foamed material (including sponge) made of an appropriate material. In this way, the photoreceptor drum 1 has an elastically deformable outer layer 4.
and the elastic material layer 3, the surface can be elastically deformed when an external force is applied to the surface as described above.

During a copying operation, the photosensitive drum 1 is rotated clockwise in FIG. 4 by a drive device (not shown). At this time, as in a normal electronic copying machine, the photosensitive layer 6 of the drum 1 is charged to a predetermined polarity by the charger 7, and this charged portion is
At the exposure section C, light 8 from a document (not shown) is irradiated, and an electrostatic latent image corresponding to the image of the document is formed.

On the other hand, in the developing device 9, a thin layer 11 of toner (one-component developer) supplied from a tank (not shown) is formed on the circumferential surface of the developing roller 10 serving as the developing polarity. While being supported on the surface of the developing roller 10, it is conveyed, for example, in the direction of arrow A as the roller 10 rotates.
The toner transported in this manner is charged to a predetermined polarity (usually a polarity opposite to that of the photosensitive layer 6) by contact with the surface of the developing roller. At this time, the thickness of the toner layer 11 on the developing roller 10 is extremely thin;
Since the thickness is about one or two fine toner particles with a particle size of about 5 to 10 μm, it is charged uniformly over the entire thickness direction. The charged toner reaches the area where the photoreceptor drum 1 and the developing roller 10 face each other, and the toner on the developing roller side contacts the photoreceptor drum 1 and electrostatically transfers to the electrostatic latent image on the drum. Then, the latent image is visualized.
In this case, the developing roller 10 is pressed against the photoreceptor drum 1, and therefore, the drum 1 It is elastically deformed in a concave state in the radial direction. Therefore, although the toner on the developing roller 10 is extremely thin, it reliably contacts the surface of the photoreceptor drum.

As a structure for conveying the toner carried on the developing roller 10, for example, a magnet (not shown) may be installed inside the roller 10, or the toner may be conveyed by using the frictional force with the surface toner of the roller 10. As is well known, in the former case, the toner needs to be made of a magnetic material, but in the latter case, a non-magnetic toner can also be used. It is also well known that when a magnet is installed inside the developing roller, the magnet may be rotated instead of rotating the developing roller, or the developing roller and the magnet may be rotated together, and the direction of rotation may be changed as appropriate. You can choose.

The visible image formed on the photoreceptor drum 1 as described above is transferred to the transfer paper 12 supplied to the surface of the drum 1.
The transfer paper 12 is then separated from the surface of the drum 1 by a separation charger 14, for example, as shown. It goes without saying that a separation claw (not shown) may be used in place of or together with the separation charger 14 to separate the transfer paper.
D in FIG. 1 indicates a transfer/separation section where the above-described transfer and separation are performed.

The toner remaining on the surface of the photoreceptor drum after the visible image has been transferred is removed by a cleaning plate 15 that is pressed against the surface of the drum 1, for example, as shown in the figure. Static electricity is removed. Naturally, a magnetic brush, a fur brush, etc. may be used instead of the cleaning blade.

The photosensitive drum 1 is pressed by the developing roller 10 and the blade 15, and the drum portion is deformed, but the deformation is kept within the elastic deformation limit.
The pressing state of the roller 10 and the plate 15 against the drum 1 is set. In order to bring the toner layer on the developing roller 10 into uniform and stable contact with the photoreceptor drum, the amount by which the developing roller 10 deforms the surface of the drum 1 in the radial direction (indentation amount) is usually determined.
ΔZ may be, for example, about 0.1 to 0.5 mm, and the blade 15 can also keep the amount of deformation ΔZ' to 0.5 mm or less, for example. If a magnetic brush or fur brush is used instead of the blade 15,
The amount of deformation of the drum surface can be reduced compared to when a blade is used.

According to the above-described configuration, the surface of the photoreceptor drum 1 is elastically deformable, and the developing roller 10 can be pressed against the photoreceptor drum 1 to deform the drum surface in its radial direction. Therefore, the circumferential surfaces of the photoreceptor drum 1 and the developing roller 10 may be slightly eccentric with respect to their central axes, or there may be slight manufacturing variations in their outer diameters, or the surface of the developing roller 10 may be made of a rigid body. The developing roller 10 and photoreceptor drum 1 can be easily removed without causing any inconvenience such as damaging the drum surface or the developing roller.
The toner on the roller 10 in the area facing the drum 1 can be brought into contact with the drum 1 more reliably and stably than before. Therefore, it is possible to suppress the deterioration in the quality of the visible image due to the formation of a large gap between the toner on the developing roller 10 and the surface of the drum 1. Further, when the developing roller 10 is not pressed against the surface of the drum 1 via toner, but is configured to be opposed to each other with a small gap between them, it is possible to prevent the gap between them from becoming too large. When the drum 1 and the roller 10 are arranged close to each other, even if a portion of them comes into contact with each other through the toner, the drum 1 will only be elastically deformed, and the drum 1 or the roller 10 will be damaged. For there is no fear.

If the surface of the photosensitive drum 1 is configured to be elastically deformable as described above, favorable results can be obtained in visualizing a latent image. However, if parts other than the surface area of the photoreceptor to which an external force is applied or the areas near it are also affected by the external force and are greatly deformed as shown in FIG. 5, the photoreceptor drum or transfer paper may be deformed. An undesirable situation occurs when forming an image. That is, as described above, if the portion of the photosensitive drum in the exposure section C is deformed as shown in FIG. 5, an image cannot be correctly formed on this portion. Further, when the transfer charger 13 and the separation charger 14 are used as a device for transferring the transfer paper 12 and a device for separating it as in the illustrated embodiment, if the transfer/separation portion D is unevenly deformed, the transfer or separation may occur. Wire 13 for corona discharge of separation chargers 13, 14
a, 14a to the surface of the drum 1 becomes inconsistent, the visible image cannot be transferred reliably, and the visible image on the transfer paper is disturbed, or the transfer paper 1
There is also a risk of causing a separation error in step 2. In this way, the photoreceptor drum 1 has a portion on which external pressure is applied;
Either the drum should be constructed so that only the parts near it are deformed so that other parts are not affected by the external pressure acting on the drum, or even if they are, the amount of deformation in the radial direction of the drum is at most 0.1 to 0. 0.5
It is desirable to keep it below mm.

In the present invention, based on the above-mentioned novel recognition, when an external force is applied to the surface of the drum by a process element of an electronic copying machine arranged around the photoconductor drum, the photoconductor drum to which the external force is applied The outer layer and the elastic material layer are configured so that the surface portion of the photoreceptor drum other than the surface portion or the portion near the surface portion is not deformed at all or hardly.

The above structure can be embodied in various forms, and as an example, when the outer layer 4 and the elastic material layer 3 are separated and an external force is applied to each of them in the diametrical direction, A specific example of deformation as shown in FIG. 7 will be explained.

Now, as shown in FIG. 6, an external force F _A is applied to the single outer layer 4 from the outside in the diametrical direction by the pressure member 16, and the part to which this external force is applied is
Assume that the photosensitive drum is elastically deformed by an amount ΔZ that is normally compressed. At this time, if the outer layer 4 is made of metal, for example, the outer layer 4 to which the external force F _A is applied changes as a whole, and its cross-sectional shape changes as shown by the dashed line in FIG. It is usually approximately oval in shape. When the external force F _A is removed, the outer layer 4 returns to its original sleeve shape.

On the other hand, both ends of the shaft 2 shown in FIG. 7 are fixedly supported,
A pressure member 1 is placed on the elastic material layer 3 from which the outer layer has been removed.
6, an external force F _B is applied in the diametrical direction from the outside, and that part is compressed and deformed in the radial direction by ΔZ, the same as in the case of FIG. In this case, since the elastic material layer 3 is made of a non-foamed or foamed elastic material such as rubber, the external pressure F _B
Normally, only the portion to which the stress is applied and the portions in its vicinity deform, and the other portions do not deform substantially. In this case, the forces F _A and F _B required to deform the outer layer 4 and the elastic material layer 3 by the same amount ΔZ are F _A
The outer layer 4 and the elastic material layer 3 are configured so as to satisfy the relationship: ≦F _B , preferably F _A <F _B . In other words, if the outer layer 4 is made more elastically deformable than the elastic material layer 3, the photosensitive drum 1 (the first
When pressure is applied to (Fig.), its outer layer 4 becomes
The drum 1 is deformed to follow the elastic material layer 3 as shown in FIG. 1, but the circumferential surface of the drum 1 is not deformed as a whole as shown in FIG. Conversely, the same amount of deformation ΔΖ
If F _A > F _B to obtain , the drum 1 may be deformed as shown in FIG.

In this way, the surfaces of the exposure section that exposes the photoreceptor drum, the transfer section that transfers the visible image formed on the drum to the transfer paper, and the separation section that separates the transfer paper from the photoreceptor drum are completely or hardly deformed. By arranging it in the photoreceptor drum part, the above-mentioned disadvantages can be prevented, and in this case, the exposure part,
Even if the photoreceptor drum surface in the transfer section and separation section deforms in the drum radial direction, the amount of deformation can be reduced to 0.5 mm.
It is possible to suppress it to below.

Examples of the material of the outer layer 4, more precisely, the photoreceptor support layer 5, which can satisfy the above-mentioned relationship F _A ≦ F _B include nickel, stainless steel, aluminum, and the like. in this case,
Since nickel and stainless steel have relatively high yield strength and longitudinal elastic modulus, when the photoreceptor support layer 5 is made from these materials, it is desirable to set the thickness to 100 μm or less. If this thickness is set larger than 100μ, it becomes difficult to deform the outer layer 4 unless the external pressure applied to the photoreceptor drum 1 is increased, and the elastic material layer 3 that satisfies F _A ≦ F _B as described above becomes difficult to deform. As a result, the photoreceptor drum tends to deform into an undesirable state as shown in FIG. 5. Also, the outer layer 4
When the photoreceptor support layer 5 is made of aluminum, the yield strength and modulus of longitudinal elasticity of aluminum are smaller than those of nickel or stainless steel, so it is preferable to make the thickness slightly thicker.
It was advantageous to set it to 200μ or less. Although it is desirable that the thickness of the photoreceptor support layer 5 be quite thin, it is important that the outer layer 4 completely restores its original sleeve-like shape when the external force acting on it is removed. Therefore, no matter what material the photoreceptor support layer 5 is made of, the thickness should be set so that the thickness of the photoreceptor support layer 5 does not become too thin and cause plastic deformation. Of course it should be.

Further, if the material as exemplified above is used as the photoreceptor support layer 5 of the outer layer 4 and the thickness is selected as described above, the elastic material layer 3 that satisfies the above-mentioned condition F _A ≦ F _B can be formed. As for the material, a wide variety of materials can be used, such as ordinary non-foamed rubber or appropriate foamed materials. In that case, the elastic material layer 3
When external pressure is applied to , as shown in Figure 7,
The external pressure is absorbed by that part or the parts near it, and the force is not only difficult to transmit to other elastic material layer parts, but also when a predetermined amount of elastic deformation is obtained, when the external pressure is removed. , elastic material layer 3
It goes without saying that it is desirable to select a material that has the property of being able to return to its original cylindrical shape and that will not undergo permanent deformation even if external pressure is applied to the elastic material layer 3 for a long time. According to experiments, favorable results were obtained when a polyurethane foam manufactured by Rogert Corporation in the United States under the trade name Microcell Rubber was used as the material for the elastic material layer 3.
The hardness was 20 degrees using a JIS C type rubber hardness tester. This microcell rubber was compressed to 50% of its thickness and left at a temperature of 158〓 for 22 hours, and then when the pressure was released, the initial 10% permanent compression strain was However, this is considerably smaller than the permanent compressive strain of ordinary foam, which is about 30%, and shows that this rubber is an excellent material suitable for the elastic material layer 3.

Further, the outer layer 4 using the sleeve-shaped photoreceptor support layer 5 made of nickel with a thickness of 50 μm is fitted to the cylindrical elastic material layer 3 made of the above-mentioned microcell rubber. The outer diameter of the material layer 3 is set to be 1 mm larger than the inner diameter of the outer layer 4, and the elastic material layer 3 after fitting is compressed by 0.5 mm in the radial direction over its entire circumference to produce a prototype photoreceptor drum 1. death,
When this was installed in a copying machine as shown in FIG. 1 and an experiment was carried out, it was possible to obtain a desirable deformed state of the drum as shown in FIG.

In another experiment, microcell rubber with a hardness (C type) of 5 degrees was used as the elastic material layer 3, and the thickness of the photoreceptor support layer 5 made of nickel was determined.
By making it as thin as 25μ and making it easier to deform, the deformation pattern of the drum as shown in FIG. 1 was obtained. In this way, the photoreceptor support layer 5
The hardness of the elastic material layer 3 can be lowered by reducing the thickness of the elastic material layer 3. However, if this hardness is reduced too much, the thickness of the photoreceptor support layer 5 must also be made extremely thin. On the contrary, if the hardness of the elastic material layer 3 is made too high, there is a risk of plastic deformation.
In practice, the hardness (C type) of the elastic material layer 3 should be set at 5 to 5 to prevent the photoreceptor drum 1 from deforming.
It was advantageous to set the angle to about 50 degrees.

The basic embodiments of the present invention have been described above, but
It goes without saying that the present invention can be constructed by variously modifying the above configuration. For example, in the above specific example, the case where the photoreceptor support layer 5 is made of metal or the like and its individual deformed state is as shown in FIG. 6 has been described.
The support layer 5 may be made of a suitable material other than metal, such as conductive rubber. In addition, although the photoreceptor drum is composed of only the elastic material layer and the outer layer, appropriate layers or members other than these layers may be added as necessary as long as the drum surface can be deformed. . In addition, the outer layer is not composed only of a photosensitive layer and its photoreceptor support layer;
As shown in the figure, an intermediate layer 17 of a conductive material having a specific volume resistivity of, for example, 10 ⁹ Ω ^- cm or less is provided between the photosensitive layer 6 and the photoreceptor support layer 5, and the intermediate layer 17 is made of a conductive material, as is well known per se. A reduction in sensitivity of layer 6 may be suppressed. As the intermediate layer 17, the photoreceptor support layer 5
Vapor deposited aluminum or other suitable inorganic or organic materials can be used.

Further, as is well known, in order to form an electrostatic latent image on the photoreceptor drum, it is necessary to ground the photoreceptor support layer 5 or the intermediate layer 17. For this purpose, the photoreceptor drum 1 is The photoreceptor support layer 5 or the intermediate layer 17 can be grounded via a conductor (not shown) so as not to inhibit deformation. In that case, the shaft 2 may be made of a conductor, and the shaft 2 and the photoreceptor support layer 5 or the intermediate layer 17 may be connected to each other with a conductor made of thin wire or foil to ground them. It is also possible to embed it in the elastic material layer 3 in a deformable state. Also,
When the elastic material layer is made of a conductor, for example, conductive rubber, the intermediate layer or photoreceptor support layer can be grounded without using the above-mentioned thin wire or foil.
Furthermore, as can be seen from the above, if the intermediate layer 17 made of a conductive material is provided and grounded, the photoreceptor support layer itself can be made of an insulator such as insulating rubber. is also possible.

Further, the outer layer may be fixed to the elastic material layer with an adhesive or the like, but if the outer layer 4 is removably attached to the elastic material layer, there is an advantage that the outer layer can be replaced. In this case, when the photoreceptor drum is used, the sum ΣF of the external force exerted on the drum in the tangential direction of the drum by, for example, the developing roller, cleaning blade, separating claw, etc., and the friction acting on the elastic material layer and the outer layer. The force f should satisfy the relationship f>ΣF so that the outer layer does not shift relative to the elastic material layer. To meet this condition,
In addition to increasing the coefficient of friction between the elastic material layer and the outer layer, as shown in the previous experimental example, the outer diameter of the elastic material layer before fitting the elastic material layer and the outer layer is smaller than the inner diameter of the outer layer. It is also advantageous to be able to make it larger. Furthermore, the elastic material layer may be rotatably supported on a shaft via, for example, a ring, the shaft may be fixed to the main body of the copying machine, and the outer layer and the elastic material layer may be rotatably supported with respect to the shaft. It is possible. Further, when the elastic material layer is fixed to the shaft as in the illustrated embodiment, it may be fixed with an adhesive or the like, but it can also be fixed to the shaft integrally when molding the elastic material layer.

Effects According to the present invention, since the surface of the photoreceptor drum can be elastically deformed, the thin layer of developer on the developer carrier in the opposing area between the developer carrier and the photoreceptor drum can be easily and reliably applied than before. The developer is brought into contact with the photoreceptor drum, or the developer and the photoreceptor drum are
It became possible to easily create a minute gap and close the gap. In addition, the part of the photoreceptor surface to which external force is applied, or this part, the part near it, and the part of the photoreceptor drum surface other than the part near it, will not be deformed at all or most of the time. , it is possible to eliminate inconveniences in image formation.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional explanatory diagram showing an example of an electronic copying machine according to the present invention, FIG. 2 is a cross-sectional view of the photoconductor drum when no external force is applied to the photoconductor drum, and FIG.
4 is an enlarged sectional view taken along the line - in FIG. 2, FIG. 5 is an explanatory diagram similar to FIG. The figure is an explanatory sectional view showing an example of a deformed state when an external force acts only on the outer layer, and Figure 7 shows an example of a deformed state when an external force acts on the elastic material layer with the outer layer removed. The explanatory diagram, FIG. 8, is a sectional view similar to FIG. 4 in another embodiment, and shows the photosensitive drum, outer layer, or elastic material layer in FIGS. 1, 5, 6, and 7. The deformed state is exaggerated. DESCRIPTION OF SYMBOLS 1... Photoreceptor drum, 2... Shaft, 3... Elastic material layer, 4... Outer layer, 5... Photoreceptor support layer, 6...
...Photosensitive layer, 12...Transfer paper, C...Exposed area, D...
...Transfer/separation section.

Claims (1)

[Scope of Claims] 1. An image forming apparatus including a rotatably supported photoreceptor drum and a process element that is in pressure contact with the surface of the drum, the photoreceptor drum comprising a shaft and a shaft supported by the shaft,
and an elastic material layer that is elastically deformable and has a cylindrical shape in a free state, and an outer layer that is attached around the elastic material layer, and the outer layer includes an elastically deformable photoreceptor support layer, and an elastic material layer that is elastically deformable and has a cylindrical shape. and a photosensitive layer supported by a support layer, and has a cylindrical shape in a free state, and the elastic material layer is filled between the shaft and the outer layer without substantially forming a gap. and the outer layer is formed such that a portion of the surface of the photoreceptor drum other than a portion of the surface of the photoreceptor drum to which an external force is applied by the process element, or a portion of the surface of the photoreceptor drum other than the portion and a portion in the vicinity thereof, is not deformed at all or hardly deforms. and an elastic material layer. 2. A photoreceptor whose surface does not undergo any or almost no deformation; The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged in a drum portion. 3. The image forming apparatus according to claim 2, wherein the amount of deformation of the surface of the photosensitive drum in the exposure section, transfer section, and separation section in the drum radial direction is 0.5 mm or less. 4 External force F _A is applied diametrically from the outside to a single outer layer, and external force F _B is applied diametrically from the outside to the elastic material layer from which the outer layer has been removed.
When adding and obtaining the same amount of radial deformation,
The image forming apparatus according to any one of claims 1 to 3, wherein the outer layer and the elastic material layer are configured such that the relationship F _A ≦ F _B is obtained.