CN101846894B - Electrophototgraphic photoreceptor and image forming device - Google Patents

Abstract

The present invention provides an electrophotographic photoreceptor capable of effectively suppressing the occurrence of whitening in formed images, and an image forming apparatus including the electrophotographic photoreceptor. The electrophotographic photoreceptor of the present invention comprises a cylindrical substrate and a photosensitive layer disposed around the substrate, wherein the contour line representing the surface shape of the photosensitive layer in the axial cross-section of the substrate has a connection with The first straight line at both ends of the photosensitive layer is a concave portion that is depressed toward the axis side.

Description

Electrophotographic photoreceptor and image forming device

technical field

The present invention relates to an electrophotographic photoreceptor and an image forming device. In particular, it relates to an electrophotographic photoreceptor and an image forming apparatus capable of effectively suppressing the occurrence of whitening in formed images.

Background technique

At present, in image forming apparatuses using electrophotography such as copiers and printers, a cylindrical electrophotographic photoreceptor and a similarly cylindrical developing roller are arranged in parallel, and the electrostatic potential formed on the electrophotographic photoreceptor is reduced. The image is developed by the toner supplied from the developing roller.

On the other hand, the pressure contact force (when using contact development) or the distance (when using non-contact development) between the electrophotographic photoreceptor and the developing roller tends to change depending on various factors, and there is a problem that it is difficult to maintain a constant distance.

Furthermore, if the pressure contact force or pitch is too uneven, the movement of the toner from the developing roller to the electrophotographic photoreceptor becomes uneven, and image defects such as whitening (whitening) tend to occur as a result.

Therefore, in order to solve such a problem, an electrophotographic photoreceptor provided with thick protrusions on both end edges of a substrate is disclosed (for example, Patent Document 1).

That is, it is disclosed that by providing thick protrusions at both ends of the base, when the flanges are inserted into both ends of the base, the expansion of the two ends of the base to the outside can be suppressed, and the gap caused by the expansion of the base is less likely to occur. Changing electrophotographic photoreceptors.

In addition, an electrophotographic photoreceptor for the purpose of making the contact pressure between the electrophotographic photoreceptor and the cleaning blade uniform is disclosed, but the outer diameter of the electrophotographic photoreceptor gradually decreases from the vicinity of the center in the direction of the generatrix to both ends in the direction of the length. A photographic photoreceptor (Patent Document 2).

Patent Document 1: Japanese Patent Application Laid-Open No. 10-48904

Patent Document 2: Japanese Patent Laid-Open No. 2000-98642

However, since the electrophotographic photoreceptors disclosed in Patent Documents 1 and 2 do not take the bending of the developing roller into consideration at all, there is a problem that it is difficult to stably maintain the contact force or the gap between the electrophotographic photoreceptor and the developing roller.

That is, in Patent Documents 1 and 2, it is difficult to stably maintain the relationship between the electrophotographic photoreceptor and the developing roller due to the possibility that the central portion of the developing roller may be bent so as to be extruded to the electrophotographic photoreceptor side by the pressing member at all, since no consideration is taken at all. The crimping force or spacing between the rollers.

Specifically, in Patent Document 1, the surface shape of the photosensitive layer forming region of the electrophotographic photoreceptor is still flat, and in Patent Document 2, on the contrary, it has convex portions on the developing roller side.

Therefore, since the pressing force between the electrophotographic photoreceptor and the developing roller becomes too small at both end portions of the electrophotographic photoreceptor, or the gap becomes too large, there is a problem that the toner is difficult to develop to this part, and the formation of an image is difficult. Easy to produce whitening problem.

Contents of the invention

That is, an object of the present invention is to provide an electrophotographic photoreceptor and an image forming apparatus capable of effectively suppressing occurrence of whitishness in formed images.

The present invention provides an electrophotographic photoreceptor comprising a cylindrical substrate and a photosensitive layer disposed around the substrate, wherein the surface shape of the photosensitive layer is shown in a cross-section in the axial direction of the substrate. The contour line has a concave portion that is recessed toward the axis side than the first straight line connecting both ends of the photosensitive layer, thereby solving the above-mentioned problem.

That is, the contour line representing the surface shape of the photosensitive layer has a concave portion that is recessed on the axial side compared with the first straight line connecting both ends of the photosensitive layer, so that even when the developing roller bends due to pressing, etc., Regardless of contact development or non-contact development, it is possible to stably suppress the pressure contact force between the end portion of the electrophotographic photoreceptor and the end portion of the developing roller from becoming too small or the pitch from becoming too large.

Thereby, it is possible to effectively suppress the occurrence of whitening at the portion corresponding to the end portion of the electrophotographic photoreceptor in the formed image.

Furthermore, another aspect of the present invention is an image forming apparatus including: the electrophotographic photoreceptor; and a developing member that develops an electrostatic latent image formed on the electrophotographic photoreceptor with a developer. , thereby forming a developer image on the electrophotographic photoreceptor; and a transfer member that transfers the developer image formed on the electrophotographic photoreceptor by the developing member to a prescribed recording medium.

That is, since the electrophotographic photoreceptor having the predetermined concave portion is provided, even when the developing roller bends due to pressing, etc., the pressing force between the end portion of the electrophotographic photoreceptor and the end portion of the developing roller can be stably suppressed. If the pitch is too small or the pitch is too large, it is possible to effectively suppress the occurrence of whitishness of the formed image caused by this.

Description of drawings

FIG. 1 is a diagram illustrating the structure of an electrophotographic photoreceptor of the present invention;

FIG. 2 is a diagram illustrating a mechanism of occurrence of bending of a developing roller;

(a) to (b) of FIG. 3 are diagrams illustrating the effects of the electrophotographic photoreceptor of the present invention;

(a) to (b) of FIG. 4 are another diagram illustrating the structure of the electrophotographic photoreceptor of the present invention;

5 is still another diagram illustrating the structure of the electrophotographic photoreceptor of the present invention;

FIG. 6 is a diagram illustrating an image forming apparatus of the present invention;

FIG. 7 is a diagram for explaining a method using rollers for pitch regulation;

FIG. 8 is a view showing the surface shape of an electrophotographic photoreceptor in Examples.

Detailed ways

[first embodiment]

Hereinafter, the electrophotographic photoreceptor according to the first embodiment of the present invention will be specifically described for each constituent element.

1. Shape

As shown in FIG. 1 , the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor 41 provided with a cylindrical substrate 22 and a photosensitive layer 14 arranged around the substrate 22 , and is characterized in that the The cross-section, that is, the contour line 4 (indicated by a thick line in the figure) representing the surface shape of the photosensitive layer 14 in the cross-section including the axis shown in FIG. The concave portion 12 is curved toward the axis 2 side compared with the imaginary straight line 10 (first straight line) shown by a hollow circle).

The reason for this is that since the contour line 4 representing the surface shape of the photosensitive layer 14 has the concave portion 12 bent toward the axial side compared with the imaginary straight line 10 connecting the two ends 6 of the photosensitive layer 14, even if it is developed due to extrusion, When the roller bends, it is possible to stably suppress the contact force between the end of the electrophotographic photoreceptor and the end of the developing roller from becoming too small or the gap from becoming too large regardless of contact development or non-contact development.

Thus, it is thereby possible to effectively suppress the occurrence of whitening at a portion where an image is formed corresponding to the end portion 6 of the electrophotographic photoreceptor 41 .

In addition, “both ends of the photosensitive layer” in the present invention refer to both ends 6 in the axial direction of the photosensitive layer 14 formed on the substrate 22 .

On the other hand, when the tip of the flange is pressed into a portion of the base 22 corresponding to the region where the photosensitive layer 14 is formed, the portion where the flange avoids the expansion of the base 22 and the photosensitive layer 14 is referred to as "photosensitive layer 14". Both ends of the layer".

That is, "both ends of the photosensitive layer" at this time refers to a predetermined position defined within a range of, for example, 5 to 20 mm from the tip of the flange toward the center in the axial direction.

More specifically, as shown in FIG. 2 which is a schematic diagram of the electrophotographic photoreceptor 41 and the developing member 44, usually on the developing roller 40, supply rollers 48a, 48b, and a thin-layer plate 49 for thinning the toner on the developing roller 40 while triboelectrically charging it.

At this time, as shown in (a) to (b) of FIG. 3, the force F generated by the above-mentioned pressing is applied to the developing roller 40, and the central part thereof is extruded toward the electrophotographic photoreceptor 41', 41 side. , prone to bending. Moreover, (a) of FIG. 3 shows a general electrophotographic photoreceptor 41' in which the surface shape of the photosensitive layer 14' is flat, and (b) of FIG. The electrophotographic photoreceptor 41 of the present invention.

It was confirmed that the above-mentioned bending is particularly likely to occur when the core material or the shaft member of the developing roller 40 is made of a weak material, or when the shaft diameter is small.

On the other hand, the electrophotographic photoreceptors 41 ′, 41 arranged in parallel to the developing roller 40 are precision components requiring strict uniformity in various characteristics such as charging characteristics and sensitivity characteristics.

Therefore, using a member having predetermined strength, such as an aluminum tube, as the bases 22', 22 hardly causes bending.

As a result, as shown in (a) of FIG. 3, when non-contact development is employed, the distance between the electrophotographic photoreceptor 41' and the developing roller 40 becomes relatively small in the center of the electrophotographic photoreceptor 41', and the other On the one hand, it becomes larger at the end portion of the electrophotographic photoreceptor 41'.

Then, at the end of the electrophotographic photoreceptor 41 ′ where the pitch is relatively large, the movement of the toner from the developing roller 40 becomes insufficient, and image defects such as whitening tend to occur as a result.

In addition, although not shown, in the case of contact development, the pressure contact force between the electrophotographic photoreceptor and the developing roller becomes relatively large at the center of the electrophotographic photoreceptor, and on the other hand becomes larger at the ends of the electrophotographic photoreceptor. be smaller.

As a result, image defects such as whitening tend to occur at the edge of the electrophotographic photoreceptor similarly to non-contact development.

In addition, in the following, for the convenience of illustration, non-contact image development is mainly used as an example for description.

Regarding this problem, since the electrophotographic photoreceptor 41 of the present invention has the above-mentioned predetermined shape, as shown in FIG. The distance between the photoreceptor 41 and the developing roller 40 is controlled so that there is no excessive difference in the central portion and the end portions 6 of the electrophotographic photoreceptor 41 .

Therefore, the electrophotographic photoreceptor 41 of the present invention can effectively suppress the occurrence of whitening at the portion corresponding to the end portion of the electrophotographic photoreceptor where an image is formed.

Furthermore, as shown in (a) of FIG. 4 , it is preferable that the slope of the contour line 4 near the end portion 6 is gentler than the slope of the contour line 4 near (the lowest point 8 of) the concave portion 12 . Furthermore, the slope is defined as the inclination of the tangent line at the site.

The reason for this is that, with such a configuration, the contact force or the distance between the electrophotographic photoreceptor 41 and the developing roller 40 can be maintained more stably.

That is, as shown in (b) of FIG. 4 , since both end portions 6 of the developing roller 40 are positioned by bearings, the curvature of the central portion is larger than that of the end portions 6, and the slope near the lowest point 8 of the concave portion 12 is related to the photosensitive When the slope near the end portion 6 of the layer 14 is the same, the pressure contact force between the developing roller 40 and the electrophotographic photoreceptor 41 on both end portions 6 sides of the photosensitive layer 14 becomes too large, or the pitch becomes too small. possibility.

In addition, when the steep slope and the gentle slope are set as described above, as shown in (a) of FIG. The slope of the straight line (the third straight line) at the lowest point 8) is gentle, wherein the midpoint 16 is the end portion 6 (represented by a hollow circle in the figure. The lowest point 8 and the midpoint 16 of the concave portion 12 are also the same) and the concave portion 12 (The lowest point of 8) is the midpoint between. Furthermore, in (a) of FIG. 4 , the length L1 corresponds to the distance between (the lowest point 8 of) the concave portion 12 and the midpoint 16 and the distance between the end portion 6 and the midpoint 16 in the axial direction.

The reason for this is that, with such a configuration, the contact force or the distance between the electrophotographic photoreceptor 41 and the developing roller 40 can be maintained more stably.

That is, as described above, since the end portions 6 on both sides of the developing roller 40 are positioned by the bearings, the curvature of the central portion is larger than that of the end portions 6. With such a configuration, the shape and curvature of the electrophotographic photoreceptor 41 can be developed The shape of the roller 40 corresponds more stably.

In addition, in the above description, the second straight line is defined as the straight line connecting the midpoint 16 between the end portion 6 and (the lowermost point 8 of) the concave portion 12 and the end portion 6, and the third straight line is defined as the straight line connecting the midpoint 16. A straight line with (the lowest point 8 of) the concave portion 12, but the specification of the second straight line and the third straight line is not limited thereto. For example, by replacing the midpoint 16 with a point near the midpoint 16 (hereinafter referred to as a nearby point), the straight line connecting the nearby point and the end 6 can also be defined as the second straight line, connecting the nearby point and the bottom of the recess 12 ( The straight line at point 8) is defined as the third straight line. More specifically, the near point is preferably within a range of 0 to 50 mm from the midpoint 16, and more preferably within a distance of 0 to 30 mm.

In addition, as shown in FIG. 1 , it is preferable that all the contour lines 4 representing the surface shape of the photosensitive layer 14 are located on the axis 2 side of the virtual straight line 10 connecting both ends 6 of the photosensitive layer 14 .

This is because, with such a configuration, the surface of the electrophotographic photoreceptor 41 effectively follows the curvature of the developing roller 40 , and the contact force or distance between the electrophotographic photoreceptor 41 and the developing roller 40 can be stably maintained.

In addition, as shown in FIG. 5 , it is preferable that the outer diameter A (mm) of the electrophotographic photoreceptor 41 at the end portion 6 of the photosensitive layer 14 and the outer diameter B (mm) of the electrophotographic photoreceptor 41 at the lowermost point 8 of the concave portion 12 The following relational expression (1) is satisfied.

2(μm)＜A-B＜50(μm) (1)

The reason for this is that by making the difference between the outer diameter A of the end portion 6 of the photosensitive layer 14 and the outer diameter B of the lowermost point 8 of the recess 12 within such a range, the surface of the electrophotographic photoreceptor 41 effectively follows the developing roller 40 Therefore, the pressure contact force between the electrophotographic photoreceptor 41 and the developing roller 40, or the gap can be stably maintained.

That is, if the value of (A-B) is less than 2 μm, the concave portion 12 becomes too shallow, and the contact force between the electrophotographic photoreceptor 41 and the developing roller 40 present at the end portion 6 of the electrophotographic photoreceptor 41 becomes too small. , or the possibility that the pitch at the end portion 6 of the electrophotographic photoreceptor 41 becomes too large. On the other hand, if the value of (A-B) exceeds a value of 50 μm, the concave portion 12 becomes too deep, and the contact force between the electrophotographic photoreceptor 41 and the developing roller 40 present at the end portion 6 of the electrophotographic photoreceptor 41 becomes low. Too large, or the pitch at the center of the electrophotographic photoreceptor 41 may become too small.

Therefore, the outer diameter A of the electrophotographic photoreceptor 41 at the end portion 6 of the photosensitive layer 14 and the outer diameter B of the electrophotographic photoreceptor 41 at the lowermost point 8 of the concave portion 12 more preferably satisfy the following relational expression (1′), further It is preferable to satisfy the following relational expression (1").

3(μm)＜A-B＜40(μm) (1′)

4(μm)＜A-B＜15(μm) (1″)

In addition, it is preferable to set the outer diameter A within a range of 20 to 40 mm.

The reason for this is that, by making the outer diameter A of the electrophotographic photoreceptor 41 at the end portion 6 of the photosensitive layer 14 within such a range, the concave portion 12 can be uniformly formed.

Therefore, it is more preferable to set the outer diameter A within a range of 23 to 35 mm.

In addition, although the length L2 of the portion where the photosensitive layer 14 is formed in the axial direction of the electrophotographic photoreceptor 41 in FIG. within range.

In addition, as shown in FIG. 5 , the outer diameter C (mm) and the outer diameter B of the electrophotographic photoreceptor 41 at the midpoint 16 between the end portion 6 of the photosensitive layer 14 and the lowermost point 8 of the concave portion 12 preferably satisfy the following Relational formula (2).

2(μm)＜C-B＜40(μm) (2)

This is because the difference between the outer diameter C of the midpoint 16 between the end 6 of the photosensitive layer 14 and the lowermost point 8 of the concave portion 12 and the outer diameter B of the lowermost point 8 of the concave portion 12 falls within such a range. Therefore, the surface of the electrophotographic photoreceptor 41 can more effectively follow the curvature of the developing roller 40 , and the contact force or distance between the electrophotographic photoreceptor 41 and the developing roller 40 can be further stably maintained.

That is, if (C-B) is less than 2 μm, the slope near the lowest point 8 of the concave portion 12 becomes too gentle, and it may be difficult to follow the curvature of the developing roller 40 . On the other hand, if (C-B) exceeds 40 μm, the slope near the lowest point 8 of the concave portion 12 becomes too steep, and it may be difficult to make the surface of the electrophotographic photoreceptor 41 follow the curvature of the developing roller 40 .

Therefore, the outer diameter C of the electrophotographic photoreceptor 41 at the middle point 16 between the end portion 6 of the photosensitive layer 14 and the lowermost point 8 of the concave portion 12 is the same as the outer diameter of the electrophotographic photoreceptor 41 at the lowermost point 8 of the concave portion 12 . B more preferably satisfies the following relational expression (2'), and further preferably satisfies the following relational expression (2").

3(μm)＜C-B＜30(μm) (2′)

3(μm)＜C-B＜10(μm) (2″)

2. Matrix

Various materials can be used as a constituent material of the base body 22 of the present invention.

Examples include substrates made of metals such as iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass; plastics on which the above metals are vapor-deposited or laminated. A substrate formed of a material; or a substrate made of glass covered with aluminum iodide, anodized aluminum, tin oxide and indium oxide, etc.

That is, the substrate itself may have conductivity, or the surface of the substrate may have conductivity, and in addition, it may have sufficient mechanical strength for use.

In addition, as shown in FIG. 5 , the outer diameter a (mm) of the position corresponding to the end portion 6 of the photosensitive layer 14 of the base body 22 is the same as the outer diameter b (mm) of the position corresponding to the lowest point 8 of the concave portion 12 of the base body 22 . ) preferably satisfy the following relational formula (3).

2(μm)＜a-b＜50(μm) (3)

This is because the difference between the outer diameter a of the base 22 corresponding to the end 6 of the photosensitive layer 14 and the outer diameter b of the base 22 corresponding to the lowermost point 8 of the recess 12 falls within such a range. , the concave portion 12 can be formed without adjusting the film thickness of the photosensitive layer 14 .

That is, as shown in FIG. 1 and the like, the shape of the substrate 22 is made into a predetermined shape, thereby forming the photosensitive layer 14 with a uniform film thickness only on the substrate 22, and an electrophotographic photoreceptor 41 having predetermined concave portions 12 can be obtained.

Therefore, the outer diameter a of the base 22 corresponding to the end portion 6 of the photosensitive layer 14 and the outer diameter b of the base 22 corresponding to the lowermost point 8 of the concave portion 12 more preferably satisfy the following relational expression (3′) , and further preferably satisfy the following relational expression (3").

5(μm)＜a-b＜40(μm) (3′)

5(μm)＜a-b＜30(μm) (3″)

In addition, from the same point of view, as shown in FIG. The outer diameter b preferably satisfies the following relational expression (4), and more preferably satisfies the following relational expression (4').

3(μm)＜c-b＜25(μm) (4)

5(μm)＜c-b＜20(μm) (4′)

Furthermore, the thickness L3 of the base body 22 is preferably within a range of 0.1 to 5 mm, more preferably within a range of 0.3 to 2 mm.

In addition, the axial length L4 of the base body 22 is preferably within a range of 230 to 500 mm, more preferably within a range of 240 to 380 mm.

Furthermore, it is preferable that the base body 22 is obtained by cutting.

This is because the predetermined concave portion 12 can be uniformly and easily formed on the base 22 by cutting.

As such a cutting method for the base body 22, it is preferable to first fix the base body 22 to a lathe on which the diamond turning tool is fixed, and then appropriately move the base body 22 in the axial direction and the circumferential direction while rotating, and contact the diamond turning tool to perform cutting. .

3. Photosensitive layer

The photosensitive layer 14 is not particularly limited, and may be an inorganic photosensitive layer such as an amorphous silicon photosensitive layer, or a single-layer or laminated organic photosensitive layer in which an organic photosensitive material is dispersed in a resin.

In addition, the composition of the photosensitive layer 14 is not particularly limited, and may be a conventionally known composition.

Furthermore, the film thickness of the photosensitive layer 14 is not particularly limited, but from the viewpoint of ensuring predetermined electrical characteristics, for example, in the case of an amorphous silicon photosensitive layer, it is preferably in the range of 15 to 50 μm, more preferably in the range of 20 to 35 μm. within range.

Moreover, in the case of a single-layer organic photosensitive layer, it is preferably in the range of 20 to 50 μm, more preferably in the range of 25 to 40 μm.

Furthermore, in the case of a laminate type organic photosensitive layer, it is preferably in the range of 15 to 50 μm, more preferably in the range of 20 to 40 μm.

[Second Embodiment]

The second embodiment is an image forming apparatus equipped with the electrophotographic photoreceptor of the first embodiment.

Hereinafter, the second embodiment will be specifically described focusing on points different from those described in the first embodiment.

For the image forming apparatus of the present invention, for example, the tandem image forming apparatus 30 shown in FIG. 6 can be preferably used. The image forming apparatus 30 includes an intermediate transfer belt 51 . In addition, a magenta developing unit 37M, a cyan developing unit 37C, a yellow developing unit 37Y, and a black developing unit 37Bk are disposed above the intermediate transfer belt 51 along the moving direction of the intermediate transfer belt 51 .

Further, electrophotographic photoreceptors 41 are respectively arranged facing the developing rollers 40 . In addition, a charging member 75 for charging the surface of the electrophotographic photoreceptor 41 , an exposure member 76 for forming an electrostatic latent image on the surface of the electrophotographic photoreceptor 41 , and the like are disposed around the electrophotographic photoreceptor 41 .

Accordingly, the electrostatic latent images formed on the electrophotographic photoreceptors 41 corresponding to the respective colors are respectively developed by the developing rollers 40 corresponding to the respective colors.

Further, primary transfer members 56 for transferring the developer images of the respective colors are sequentially arranged on the opposite side of the respective electrophotographic photoreceptors 41 through the intermediate transfer belt 51 on the intermediate transfer belt 51 .

Further, a secondary transfer member 52 for transferring the developer image formed on the intermediate transfer belt 51 onto a recording medium is arranged at the most downstream portion in the moving direction of the intermediate transfer belt 51 .

Furthermore, a fixing member 34 for fixing the developer image transferred on the recording medium to the recording medium is disposed at the lower left in the drawing.

Here, the development of the electrostatic latent image formed on the electrophotographic photoreceptor 41 by the developing roller 40 will be described more specifically.

That is, as shown in FIG. 2 , based on the electrostatic latent image formed on the electrophotographic photoreceptor 41 , the developing roller 40 disposed at the opening of the developing member 44 adheres toner as a developer for development, whereby A toner image is formed on the surface of the electrophotographic photoreceptor 41 .

At this time, forces (Fb, Fc, Fa) are applied to the developing roller 40 disposed at the opening of the developing member 44 by being pressed by the first supply roller 48a, the second supply roller 48b, and the thin-layer plate 49 or the like.

As a result, since the developing roller 40 bends so as to be extruded to the side of the electrophotographic photoreceptor 41, it is difficult to stably maintain the contact force between the electrophotographic photoreceptor 41 and the developing roller 40 in a general electrophotographic photoreceptor, or spacing.

With regard to this problem, since the electrophotographic photoreceptor mounted in the image forming apparatus of the present invention is an electrophotographic photoreceptor having the prescribed recesses described in the first embodiment, it is possible to stably suppress the electrophotographic photoreceptor in this case. The pressure contact force between the end of the developing roller and the end of the developing roller, or the gap becomes too large. Accordingly, occurrence of whitishness of the formed image can be effectively suppressed.

Also, the distance of the gap between the electrophotographic photoreceptor and the developing roller may be the same as conventionally known distances.

In addition, in order to maintain this gap more stably, it is preferable to interpose a rotatable gap regulating roller 50 between the electrophotographic photoreceptor 41 and the developing roller 40 as shown in FIG. 7 .

[Example]

The present invention will be specifically described below with reference to Examples and Comparative Examples.

[Example 1]

1. Manufacture of electrophotographic photoreceptor

(1) Cutting of the substrate

First, a substrate made of an aluminum alloy having an outer diameter of 30 mm, an axial length of 254 mm, and a thickness of 0.75 mm was prepared.

Then, after the base body is fixed to the lathe on which the diamond turning tool is fixed, it is rotated while moving appropriately in the axial direction and the circumferential direction of the base body, and comes into contact with the diamond turning tool to perform cutting.

(2) Measurement of the outer diameter of the substrate

Next, the outer diameter of the base was measured.

That is, using LS-5040R manufactured by KEYENCE Co., Ltd., the outer diameter a1 (mm) at the position of 20 mm from one end of the substrate obtained by cutting, the outer diameter c1 (mm) at the position of 72.5 mm, and the outer diameter at the position of 125 mm The diameter b (mm), the outer diameter c2 (mm) at the position of 177.5 mm, and the outer diameter a2 (mm) at the position of 230 mm were measured. In addition, a1-b (μm), c1-b (μm), c2-b (μm), and a2-b (μm) were calculated from the measured values. The obtained results are shown in Table 1.

(3) Formation of photosensitive layer

Next, a coating liquid for a single-layer photosensitive layer containing a charge generating agent, a hole transport agent, an electron transport agent, a binder resin, and an organic solvent is coated on the obtained substrate to form a single-layer photosensitive layer having a film thickness of 30 μm. Photosensitive layer.

Also, the photosensitive layer was formed so that the uncoated width from the end of the substrate was 5.5 mm at both ends.

(4) Press-fitting of the flange

Next, flanges were pressed into both ends of the substrate on which the photosensitive layer was formed to a depth of 10 mm from both end portions of the substrate, thereby obtaining an electrophotographic photoreceptor.

(5) Measurement of the outer diameter of the electrophotographic photoreceptor

Next, the outer diameter of the electrophotographic photoreceptor was measured.

That is, in the same manner as the outer diameter of the base, the outer diameters A1 (mm), C1 (mm), and B (mm) of the electrophotographic photoreceptor at each position of the outer diameters a1, c1, b, c2, and a2 of the base were measured. ), C2(mm) and A2(mm) were measured. In addition, A1-B (µm), C1-B (µm), C2-B (µm), and A2-B (µm) were calculated from the measured values. The obtained results are shown in Table 1.

2. Evaluation of whitening

Next, using the obtained electrophotographic photoreceptor, the occurrence of whitening during image formation was evaluated.

That is, a gray image was formed by contact development in a state where the obtained electrophotographic photoreceptor was mounted on a printer (manufactured by Kyocera Mita Co., Ltd., FS-C5016N modified machine). Then, after visually confirming occurrence of whitishness in the obtained gray image, evaluation was performed according to the following criteria. The obtained results are shown in Table 1.

In addition, the shaft member of the developing roller used at this time was made of SUS.

As a result, it was found that the central portion of the developing roller was bent by 50 μm on the electrophotographic photoreceptor side.

⊚: No whitishness was observed at all.

◯: There is slight whitishness at the positions corresponding to both ends of the electrophotographic photoreceptor, but it is within a practically non-problematic range.

×: Significant whitening occurs at positions corresponding to both end portions of the electrophotographic photoreceptor.

[Examples 2 to 6 and Comparative Examples 1 to 3]

In Examples 2 to 6 and Comparative Examples 1 to 3, the surface shape of the substrate was changed by changing the cutting conditions when cutting the substrate, thereby changing the surface shape of the photosensitive layer, and the electrophotographic film was produced in the same manner as in Example 1. photoreceptors and evaluated. The obtained results are shown in Table 1.

In addition, the surface states of the electrophotographic photoreceptors produced in Examples 2, 5 and Comparative Example 1 are represented by characteristic curves A to C in FIG. 8 , respectively.

[Table 1]

In this way, according to the electrophotographic photoreceptor and image forming apparatus of the present invention, the surface shape of the electrophotographic photoreceptor is made into a predetermined shape, so that the electrophotographic photoreceptor can be stably held even when the developing roller bends due to pressing. The contact force or distance between the developing roller and the developing roller.

Thereby, occurrence of whitishness of the formed image can be effectively suppressed.

Therefore, the electrophotographic photoreceptor and image forming apparatus of the present invention are expected to significantly contribute to the improvement of the quality of various image forming apparatuses such as copiers and printers.

Claims (9)

1. An electrophotographic photoreceptor comprising a cylindrical substrate and a photosensitive layer disposed around the substrate, wherein: A contour line representing the surface shape of the photosensitive layer in an axial cross-section of the substrate is recessed toward the axial side over the entire area compared with a first straight line connecting both ends of the photosensitive layer. The slope of the contour line near the end portion is gentler than the slope of the contour line near the concave portion. 2. The electrophotographic photoreceptor according to claim 1, wherein a slope of a second straight line connecting a midpoint between the end portion and the concave portion and the end portion is greater than a slope of a second straight line connecting the midpoint. The slope of the third straight line with the concave portion is gentle. 3. The electrophotographic photoreceptor according to claim 1, wherein all of the contour lines are located below the first straight line. 4. The electrophotographic photoreceptor according to claim 1, wherein an outer diameter A of the electrophotographic photoreceptor at the end portion and an outer diameter B of the electrophotographic photoreceptor at the concave portion satisfy The above relationship (1), 2(μm)<A-B<50(μm) (1). 5. The electrophotographic photoreceptor according to claim 4, wherein the outer diameter C and the outer diameter B of the electrophotographic photoreceptor at a midpoint between the end portion and the concave portion satisfy The following relationship (2), 2(μm)<C-B<40(μm) (2). 6. The electrophotographic photoreceptor according to claim 4, wherein the outer diameter A is in the range of 20 to 40 mm. 7. The electrophotographic photoreceptor according to claim 1, wherein the outer diameter a of the base at the end and the outer diameter b of the base at the recess satisfy the following relational expression (3) , 2(μm)<a-b<50(μm) (3). 8. The electrophotographic photoreceptor according to claim 1, wherein the substrate is obtained by cutting. 9. An image forming apparatus, comprising: The electrophotographic photoreceptor according to any one of claims 1 to 8; a developing member that develops the electrostatic latent image formed on the electrophotographic photoreceptor with a developer, thereby forming a developer image on the electrophotographic photoreceptor; and A transfer member that transfers the developer image formed on the electrophotographic photoreceptor by the developing member to a prescribed recording medium.

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