JP6799776B2 - Charging roller and its manufacturing method - Google Patents

Description

The present invention relates to a charging roller used by being incorporated in an image forming apparatus using an electrophotographic method, such as a laser printer, an electrostatic copier, a plain paper facsimile machine, or a combination machine thereof, and a method for manufacturing the same. is there.

Incorporated in the image forming apparatus, is a charging roller for uniformly charging the surface of the photoreceptor, typically, the charging roller was crosslinked by molding the rubber composition to impart semiconductive properties to the shape of the roller Is used.

The charging roller is used in a state in which the shaft made of metal or the like through-hole in the center is fixed is inserted.
In the rubber composition that is the basis of the charging roller , for example, an ion conductive rubber such as epichlorohydrin rubber is blended as a rubber component to impart ion conductivity, or a conductive carbon black or the like is blended to impart electron conductivity. It is common to give it.

Also in the above rubber composition, together with the ionic-conductive rubber or the like, in combination with diene based rubber as the rubber component, or to improve the mechanical strength and durability of the charging roller, the characteristics of the rubber to the charging roller, That is, it is also common to impart characteristics such as flexibility, small compression set, and less occurrence of settling.
Fine particles such as silica and titanium oxide are externally added to the toner as an external additive in order to adjust the fluidity, chargeability and other characteristics of the toner.

However, these external additives and debris in which toner particles are finely pulverized (hereinafter, may be collectively referred to as "external additives, etc.") generated when image formation is repeated are exposed to light, especially with a cleaning blade or the like. It cannot be removed cleanly from the surface of the body. And after repeated image formation, an external additive or the like which can not be removed, gradually accumulated in particular adhered to the outer peripheral surface surface that has constant contact with the corresponding photosensitive member of the charging roller.

The accumulated external additive or the like affects the charging characteristics of the photoconductor or adheres to the formed image, which causes an image defect.
In particular, when the charged roller is formed by forming the semi-conductive rubber composition into a tubular shape and cross-linking the composition, and then polishing the outer peripheral surface thereof to finish the surface roughness to a predetermined surface, for example. When the outer peripheral surface is formed with fine irregularities of the polished eyes and image formation is repeated, an external additive or the like adheres to and accumulates on the polished eyes, and the above problem is likely to occur.

Therefore, it is conceivable to coat the outer peripheral surface of the charging roller with a coating film made of, for example, a urethane resin or the like to improve the slipperiness to the toner or the external additive and suppress the adhesion of the external additive or the like. Be done.
However, the coating film is generally formed by applying a liquid coating agent, which is the basis thereof, to the outer peripheral surface of the charging roller by a coating method such as a spray method or a dipping method, and then drying the coating film. In the process, various defects such as foreign matter such as dust and uneven thickness are likely to occur.

When the above-mentioned defects occur, the surface of the photoconductor cannot be uniformly charged when the charging roller is used, and there is a problem that image defects such as density unevenness are likely to occur in the formed image. is there.
In addition, an organic solvent is required to prepare a coating agent, but the use of an organic solvent has a large burden on the environment, and there is a problem that it goes against the recent trend toward low VOC (volatile organic compounds). ..

Therefore, instead of the coating film, it has been studied to form a large number of independent recesses sufficiently larger than the polished grain on the outer peripheral surface of the charging roller by various forming methods such as laser processing (for example, Patent Document). See 1-3 etc.).
In this case, for example, by arranging a large number of the recesses while crushing finer polished eyes by forming recesses, the surface roughness and electrical characteristics of the outer peripheral surface are made uniform, and the surface of the photoconductor at the time of image formation is formed. It is expected that the contact area and contact pressure can be adjusted to alleviate the stress applied to the outer peripheral surface and the toner during image formation, and to prevent the adhesion and accumulation of external additives and various problems caused by them. Has been done.

Japanese Unexamined Patent Publication No. 2008-116869 Japanese Unexamined Patent Publication No. 2006-243374 Japanese Unexamined Patent Publication No. 2006-2433375

However, according to the study of the inventor, in each of the inventions described in Patent Documents 1 to 3, a large number of recesses are formed so as to be separated from each other so that the opening edges do not overlap each other, and the region between the recesses is formed. Is left in an unprocessed state with polished marks, so that the surface texture tends to vary between the inner surface of the recess and the unprocessed region between the recesses. Further, the boundary between the peripheral edge of the recess and the unprocessed area is a sharp edge.

In particular, the polishing eyes left in the unprocessed area between the recesses or the edge portion of the peripheral edge of the recesses are likely to adhere and accumulate the external additive or the like. It is not possible to sufficiently suppress the occurrence of problems due to this.
An object of the present invention, without forming a coating film having various problems, a charging roller which issues adhesion and accumulation and by it, such as the external additive can be better prevented from occurring, such a charging roller The purpose is to provide a manufacturing method.

The present invention comprises a non-porous, single-layered tubular body of a semi-conductive rubber composition, directly on the outer peripheral surface thereof, in at least a part of the circumferential method and the axial direction of the outer peripheral surface. It is a charging roller provided with a large number of recesses that overlap each other (excluding the coating film that covers the outer peripheral surface) .
The present invention also includes a tubular inner layer made of a porous body of a semi-conductive rubber composition and an outer layer made of a semi-conductive seamless thermoplastic elastomer tube provided on the outer periphery of the inner layer. The overall Asker C-type hardness is 30 ° or more and 60 ° or less, and a large number of layers overlap each other on the outer peripheral surface of the outer layer in at least a part of the circumferential method and the axial direction of the outer peripheral surface. A charging roller provided with a recess (excluding the coating film that covers the outer peripheral surface).
Further, the present invention is a step of forming a large number of recesses on the outer peripheral surface of the charging roller by laser processing so as to overlap each other in at least a part of the circumferential direction and the axial direction of the outer peripheral surface. It is a manufacturing method of the charging roller of this invention including.

According to the present invention, a charging roller capable of better suppressing the adhesion and accumulation of external additives and the occurrence of problems due to the adhesion and accumulation without forming a coating film having various problems, and a charging roller A manufacturing method can be provided.

It is a stereomicrograph which shows a part of an example of the outer peripheral surface of the charging roller of this invention in an enlarged manner. FIG. (A) is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. 1, FIG. (B) is a sectional view taken along line BB of FIG. 1 (a), and FIG. It is a cross-sectional view taken along the line CC. It is a stereomicrograph which shows the part of the other example of the outer peripheral surface of the charging roller of this invention enlarged. It is a figure explaining the arrangement of the recess on the outer peripheral surface of the example of FIG. It is a stereomicrograph which shows the part of the outer peripheral surface of the charge roller of this invention by enlargement. It is a figure explaining the arrangement of the recess on the outer peripheral surface of the example of FIG. It is a stereomicrograph which shows the part of the outer peripheral surface of the charge roller of this invention by enlargement. It is a figure explaining the arrangement of the recess on the outer peripheral surface of the example of FIG. It is a stereomicrograph which shows the part of the outer peripheral surface of the charge roller of this invention by enlargement. It is a figure explaining the arrangement of the recess on the outer peripheral surface of the example of FIG. It is a stereomicrograph which shows the part of the outer peripheral surface of the charge roller of this invention by enlargement. It is a figure explaining the arrangement of the recess on the outer peripheral surface of the example of FIG. It is a stereomicrograph which shows the part of the outer peripheral surface of the charge roller of this invention by enlargement. It is a figure explaining the arrangement of the recess on the outer peripheral surface of the example of FIG. It is a perspective view which shows an example of the whole appearance of the charging roller of this invention. FIG. (A) is a perspective view showing another example of the overall appearance of the charging roller of the present invention, and FIG. (B) is an end view of the charging roller of the above example. FIG. (A) is a perspective view showing an example of the process of manufacturing the charging roller of FIGS. 16 (a) and 16 (b), FIG. (B) is an end view of the inner layer used in the above process, and FIG. It is an end view of the tube which is the base of the outer layer. It is a stereomicrograph which shows the part of the outer peripheral surface of the conventional charging roller enlarged. It is a stereomicrograph which shows the part of the outer peripheral surface of the charging roller of the Example of this invention enlarged. It is a stereomicrograph which shows the part of the outer peripheral surface of the charging roller of the Example of this invention enlarged. It is a stereomicrograph which shows the part of the outer peripheral surface of the charging roller of the Example of this invention enlarged. It is a stereomicrograph which shows the part of the outer peripheral surface of the charging roller of the Example of this invention enlarged.

The present invention comprises a non-porous, single-layered tubular body of a semi-conductive rubber composition, directly on the outer peripheral surface thereof, in at least a part of the circumferential method and the axial direction of the outer peripheral surface. It is a charging roller provided with a large number of recesses that overlap each other (excluding the coating film that covers the outer peripheral surface) .
The present invention also includes a tubular inner layer made of a porous body of a semi-conductive rubber composition and an outer layer made of a semi-conductive seamless thermoplastic elastomer tube provided on the outer periphery of the inner layer. The overall Asker C-type hardness is 30 ° or more and 60 ° or less, and a large number of layers overlap each other on the outer peripheral surface of the outer layer in at least a part of the circumferential method and the axial direction of the outer peripheral surface. A charging roller provided with a recess (excluding the coating film that covers the outer peripheral surface).
Further, the present invention is a step of forming a large number of recesses on the outer peripheral surface of the charging roller by laser processing so as to overlap each other in at least a part of the circumferential direction and the axial direction of the outer peripheral surface. It is a manufacturing method of the charging roller of this invention including.

According to the present invention, as described above, a large number of recesses are provided on the outer peripheral surface of the charging roller so as to overlap each other in at least a part of at least one of the circumferential direction and the axial direction of the outer peripheral surface. The unprocessed area remaining between them and the edge of the peripheral edge of the recess can be made as small as possible.
Therefore, it is possible to improve the slipperiness of the outer peripheral surface without forming a coating film having various problems, and to satisfactorily suppress the adhesion and accumulation of the external additive and the like and the resulting problems.

In particular, the recess is formed by laser processing, that is, the semi-conductive rubber composition or the like forming the outer peripheral surface is selectively melted by heat generated by laser irradiation focused on the opening shape of the recess, and at least a part thereof is evaporated. By doing so, the polished eyes can be crushed even in the area between the adjacent recesses, and the adjacent recesses can be connected by a continuous smooth curved surface together with the inside of the recess so as not to generate an edge. ..

This is because a large number of recesses are formed in close proximity to each other so that some of them overlap each other. Therefore, when the recesses are formed by laser machining, the heat transferred from the recesses causes half of the area between the recesses. This is because the conductive rubber composition and the like can also be melted.
Therefore, the slipperiness of the outer peripheral surface can be further improved, and the adhesion and accumulation of the external additive and the like and the occurrence of problems due to the adhesion can be further suppressed.

<< Recess on the outer peripheral surface (Example 1) >>
FIG. 1 is a stereomicrograph showing a part of an example of the outer peripheral surface of the charging roller of the present invention in an enlarged manner. 2 (a) is a view for explaining the arrangement of the recesses on the outer peripheral surface of the example of FIG. 1, FIG. 2 (b) is a sectional view taken along line BB of FIG. 2 (a), and FIG. 2 (c) is. , FIG. 2 (a) is a sectional view taken along line CC.
With reference to FIGS. 1 and 2 (a), a large number of recesses 2 having an elliptical opening shape [shown by a solid line in FIG. 2 (a)] are formed on the outer peripheral surface 1 of the charging roller . ..

Each of the recesses 2 is a semi-conductive rubber composition that forms, for example, the outer peripheral surface 1 of the charging roller by irradiating the outer peripheral surface 1 with a laser squeezed in an elliptical shape corresponding to the opening shape of the recess 2. It is formed by selectively melting (in the case of the example of FIG. 15) or a thermoplastic elastomer (in the case of the example of FIGS. 16 (a) and 16 (b)) and evaporating at least a part thereof.
In the case of the example in the figure, the recesses 2 are formed in a matrix in the circumferential direction and the axial direction of the outer peripheral surface 1, and the recesses 2 overlap each other in the circumferential direction and the axial direction. It is formed together.

Further, in the case of the example in the figure, each recess 2 is formed to have the same size, and the amount of overlap between adjacent objects is set to be small in the circumferential direction and large in the axial direction, whereby the recesses 2 are adjacent to each other in the circumferential direction. The convex portion 3 between the matching concave portions 2 is formed so as to project higher than the convex portion 4 between the adjacent concave portions 2 in the axial direction [FIGS. 2 (b) and 2 (c)].
Therefore, as shown in FIG. 1, the outer peripheral surface 1 is formed with the higher convex portions 3 connected in parallel in the axial direction as ridges, and the lower convex portions 4 are parallel in the circumferential direction and described above. It is in a state of being continuously formed as ridges so as to connect the ridges formed by the ridges 3. Further, the intersection position of the two convex stripes farthest from the four concave portions 2 is a convex portion 5 higher than the convex portion 3.

Further, the outer peripheral surface 1 is convex with the concave portion 2 as well as the polished eyes are crushed (in the case of the example of FIG. 15) by melting the semi-conductive rubber composition or the like by the heat generated by the above-mentioned laser irradiation. The portions 3 to 5 have a curved surface shape that is smoothly connected so as not to generate an edge.
In the example shown in the figure, the recesses 2 are formed in a matrix in the circumferential direction and the axial direction of the outer peripheral surface 1, respectively. By doing so, the machining is set and the machining itself is performed. This is because it can be facilitated, the processing accuracy can be maintained, and the uniformity of the surface texture of the outer peripheral surface 1 can be ensured.

Further, when the charging roller is driven, the outer peripheral surface 1 rotates while being in uniform contact with each other. Therefore, it is said that randomly forming the recesses 2 is more effective than forming the recesses 2 in a matrix. It's also because it's hard to think of. The same applies to other examples described later.
The size of each of the above parts is not particularly limited, but the depth of the recess 2 is preferably 0.5 μm or more, particularly preferably 1 μm or more, and more preferably 100 μm or less, particularly 50 μm or less, particularly 30 μm or less.

If the depth of the recess 2 is less than this range, the surface becomes close to the surface on which the recess is not formed, and the effect of forming a large number of recesses 2 on the outer peripheral surface 1 cannot be sufficiently obtained, and the external additive or the like adheres. And the accumulation and the resulting problems may not be adequately controlled.
On the other hand, if the depth of the concave portion 2 exceeds the above range, too large irregularities in the outer peripheral surface 1, it is impossible to charge the surface of the sensitive light body uniformly and sufficiently, based charging failure image It may be prone to defects.

In the present invention, the depth of the concave portion 2 is represented by, for example, the difference in height from the highest point of the outer peripheral surface 1, that is, the highest point of the convex portion 5 to the lowest point in the concave portion 2 in the example of the figure. ..
The classification of the concave portion 2 and the convex portion 3 to 5 is defined in the International Organization for Standardization Standard ISO 25178-2: 2012 "Geometrical Characteristic Specifications (GPS) of Product-Surface Texture-Part 2: Terms, Definitions and Surface Texture Parameters". In the volume parameter graph (load curve), the region where the load area ratio exceeds 10% is defined as the concave portion 2, and the region where the load area ratio is 10% or less is defined as the convex portion 3 to 5.

When the maximum height Sz specified in ISO 25178-2: 2012 is in the range of 0.5 μm or more and 30 μm or less, the outer peripheral surface 1 has an interface development area ratio Sdr specified in the same standard of 5 or less. It is preferable to have it.
The developed area ratio Sdr of the interface is an index showing how much the developed area (surface area) of the defined region is increased with respect to the area of the defined region (for example, 50,000 μm ² ), and a completely flat surface is developed. The area ratio Sdr becomes 0.

By setting the developing area ratio Sdr to 5 or less, the adjacent concave portions 2 and the convex portions 3 to 5 between them are connected as smoothly as possible to form a curved surface, and the slipperiness to toner, an external additive, or the like can be improved.
The developed area ratio Sdr is preferably 0.5 or more, and preferably 3 or less, even in the above range, in consideration of further improving the above effect.
However, the developed area ratio Sdr is not limited to the above range when the area of the definition region and the maximum height Sz are different.

<< Recess on the outer peripheral surface (Example 2) >>
FIG. 3 is a stereomicrograph showing a part of another example of the outer peripheral surface of the charging roller of the present invention in an enlarged manner, and FIG. 4 is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. ..
With reference to both figures, in this example, as shown by a solid line in FIG. 4, recesses 2 having an elliptical opening shape and randomly different in size are formed in the circumferential direction and the axial direction of the outer peripheral surface 1. They are formed in a matrix in rows.

Then, by randomly changing the size of each recess 2, the amount of overlap of the adjacent recesses 2 is randomly changed, and as shown in FIG. 3, the convex portions are randomly formed on the outer peripheral surface 1 in the circumferential direction and the axial direction. It is said that the ridges are arranged.
Further, on the outer peripheral surface 1, the semi-conductive rubber composition is melted by the heat generated by the above-mentioned laser irradiation, so that the polished eyes are crushed (in the case of the example of FIG. 15) and the concave portion 2 is formed.
And, the convex portion and the convex stripe are formed into a curved surface shape in which the protrusions and the protrusions are smoothly connected so as not to generate an edge.

<< Recess on the outer peripheral surface (Example 3) >>
FIG. 5 is a stereomicrograph showing a part of the outer peripheral surface of the charging roller of the present invention in an enlarged manner, and FIG. 6 is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. is there.
With reference to both figures, in this example, as shown by a solid line in FIG. 6, each recess 2 is formed in an elliptical opening shape of the same size, and adjacent objects are large in the circumferential direction. Although they overlap, they are formed so as not to overlap in the axial direction, so that the convex portions between the concave portions 2 adjacent to each other in the axial direction are formed as continuous protrusions in the circumferential direction as shown in FIG. ing.

Further, on the outer peripheral surface 1, the semi-conductive rubber composition is melted by the heat generated by the above-mentioned laser irradiation, so that the polished eyes are crushed (in the case of the example of FIG. 15), and the concave portions 2 and the ridges are formed. However, it has a curved surface that is smoothly connected so as not to generate edges.
<< Recess on the outer peripheral surface (Example 4) >>
FIG. 7 is a stereomicrograph showing a part of the outer peripheral surface of the charging roller of the present invention in an enlarged manner, and FIG. 8 is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. is there.

With reference to both figures, in this example, as shown by a solid line in FIG. 8, each recess 2 is formed in an elliptical opening shape having the same size, and adjacent objects overlap each other in the axial direction. They are formed so as not to overlap in the circumferential direction of the object.
Then, as shown in FIG. 7, the region between the concave portions 2 adjacent to each other in the axial direction remains in a continuous unprocessed state parallel to the axial direction with remaining polishing marks, and the concave portions 2 in each row and the unprocessed region remain. The boundary with and is edge-shaped.

Even in the above state, since the other regions of the outer peripheral surface 1 are connected by a smooth curve, it is possible to suppress the adhesion and accumulation of the external additive and the like on the outer peripheral surface 1 and the occurrence of problems due to the adhesion and accumulation. However, as is clear from the results of the examples described later, in consideration of further improving the above effect, the unprocessed areas and edges are eliminated as much as possible, and the outer peripheral surface is as in other examples such as FIG. It is preferable to connect substantially the entire surface of 1 with a continuous curved surface.
In any of the examples of FIGS. 3, 5 and 7, it is preferable that the recesses 2 and the like satisfy the above-mentioned size. That is, the depth of the recess 2 is preferably 0.5 μm or more and 100 μm or less.

Further, when the maximum height Sz of the outer peripheral surface 1 is 0.5 μm or more and 30 μm or less, it is preferable that the development area ratio Sdr of the interface is 5 or less. However, as described above, this does not apply when the area of the definition area and the maximum height Sz are different. The reasons for these are as described above.
<< Recess on the outer peripheral surface (Example 5) >>
FIG. 9 is a stereomicrograph showing an enlarged part of another example of the outer peripheral surface of the charging roller of the present invention, and FIG. 10 is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. is there.

Referring to both FIGS., As indicated by a solid line in FIG. 10 in this example, for example, a plurality of rows in the axial direction for each column in the circumferential direction in the example of FIG. 1, the amount that plurality has been formed, the charge A plurality of one recess 2 having a length extending over the entire length in the axial direction of the roller is provided parallel to each other in the circumferential direction.
Each of the recesses 2 irradiates , for example, the outer peripheral surface 1 of the charging roller in the axial direction while scanning a laser in a linear shape having a constant width corresponding to the recess 2, thereby forming the outer peripheral surface 1. It is formed by selectively melting a sex rubber composition (in the case of the example of FIG. 15) or a thermoplastic elastomer (in the case of the example of FIGS. 16A and 16B) and evaporating at least a part thereof.

Each recess 2 is formed by overlapping both side portions of adjacent recesses 2 in the circumferential direction, whereby the convex portion between the adjacent recesses 2 is formed as a convex portion in the axial direction as shown in FIG. It is said that it is formed in a row.
Further, on the outer peripheral surface 1, the semi-conductive rubber composition is melted by the heat generated by the irradiation of the laser, so that the polished eyes are crushed (in the case of the example of FIG. 15), and the recesses 2 and the ridges are formed. , It has a curved surface that is smoothly connected so as not to generate edges.

<< Recess on the outer peripheral surface (Example 6) >>
FIG. 11 is a stereomicrograph showing an enlarged part of another example of the outer peripheral surface of the charging roller of the present invention, and FIG. 12 is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. is there.
Referring to both FIGS., As indicated by a solid line in the figure 12, in this example, for example, a plurality of rows in the circumferential direction in each axial row in the example of FIG. 1, the amount that plurality has been formed, the charge A plurality of one recess 2 extending over the entire circumference of the roller in the circumferential direction is provided parallel to each other in the axial direction.

Further, a plurality of rows and a plurality of rows are formed in the axial direction for each row in the circumferential direction, and a plurality of one recess 2 extending over the entire length in the axial direction of the charging roller is provided parallel to each other in the circumferential direction. There is.
Each of the recesses 2 irradiates , for example, the outer peripheral surface 1 of the charging roller in the circumferential direction while scanning the laser in a linear shape having a constant width corresponding to the recess 2, and then also corresponds to the recess 2 in the axial direction. A semi-conductive rubber composition (in the case of the example of FIG. 15) or a thermoplastic elastomer (FIG. 16 (a)) that irradiates the laser while scanning the laser in a linear shape having a constant width to form the outer peripheral surface 1. It is formed by selectively melting (in the case of the example of (b)) and evaporating at least a part of it.

The circumferential recesses 2 are formed so as to be separated from each other so that adjacent objects do not overlap in the axial direction, and the axial recesses 2 are also separated from each other so that the adjacent objects do not overlap in the circumferential direction. It is formed. Each recess is formed in a matrix in the circumferential direction and the axial direction.
Further, the formation pitch of each recess is wider in the axial direction than in the circumferential direction, so that the region between the recesses 2 is substantially rectangular, which is longer in the axial direction than the circumferential direction, as shown in FIG. It remains in an unprocessed state, and the boundary between the region and each recess 2 is edge-shaped.

However, the other region of the outer peripheral surface 1 has a smooth curve because the semi-conductive rubber composition is melted by the heat generated by the irradiation of the laser and the polished eyes are crushed (in the case of the example of FIG. 15). Since they are connected, it is possible to suppress the adhesion and accumulation of the external additive or the like on the outer peripheral surface 1 and the occurrence of problems due to the adhesion.
<< Recess on the outer peripheral surface (Example 7) >>
FIG. 13 is a stereomicrograph showing an enlarged part of another example of the outer peripheral surface of the charging roller of the present invention, and FIG. 14 is a diagram illustrating the arrangement of recesses on the outer peripheral surface of the example of FIG. is there.

Referring to both FIGS., As indicated by a solid line in the figure 14, in this example, for example, a plurality of rows in the circumferential direction in each axial row in the example of FIG. 1, the amount that plurality has been formed, the charge A plurality of one recess 2 extending over the entire circumference of the roller in the circumferential direction is provided parallel to each other in the axial direction.
Each of the recesses 2 is, for example, a semi-conductive rubber composition that irradiates the outer peripheral surface 1 of the charging roller with a laser scanning linearly with a constant width corresponding to the recess 2 to form the outer peripheral surface 1. It is formed by selectively melting an object (in the case of the example of FIG. 15) or a thermoplastic elastomer (in the case of the example of FIGS. 16A and 16B) and evaporating at least a part thereof.

Each recess 2 is formed so that adjacent recesses 2 in the axial direction overlap each other on both sides, whereby the convex portion between the adjacent recesses 2 is convex in the circumferential direction as shown in FIG. It is said that it is formed in a row.
Further, on the outer peripheral surface 1, the semi-conductive rubber composition is melted by the heat generated by the irradiation of the laser, so that the polished eyes are crushed (in the case of the example of FIG. 15), and the recesses 2 and the ridges are formed. , It has a curved surface that is smoothly connected so as not to generate edges.

When each recess 2 is formed to have a length of a plurality of rows as shown in FIGS. 9, 11, and 13, the number of laser irradiations and the irradiation time are significantly reduced to improve the productivity of the charging roller. There is an advantage that it can be done.
In any of the examples of FIGS. 9, 11 and 13, it is preferable that the recess 2 and the like satisfy the above-mentioned size. That is, the depth of the recess 2 is preferably 0.5 μm or more and 100 μm or less.

Further, when the maximum height Sz of the outer peripheral surface 1 is 0.5 μm or more and 30 μm or less, it is preferable that the development area ratio Sdr of the interface is 5 or less. However, as described above, this does not apply when the area of the definition area and the maximum height Sz are different. The reasons for these are as described above.
In the examples of FIGS. 9, 11 and 13, as is clear from the results of Examples and Comparative Examples described later, the depth of the recess 2 is deep in consideration of making image defects due to poor charging even less likely to occur. The width is preferably 50 μm or less, and the width of each recess 2 is preferably 100 μm or less.

Further, considering that the adhesion and accumulation of the external additive or the like on the outer peripheral surface 1 and the occurrence of problems due to the adhesion and accumulation thereof are further suppressed, the recess 2 is formed as in the examples of FIGS. 9 and 11. It is preferable to form the outer peripheral surface 1 parallel to the axial direction.
<< Charging roller (1) >>
FIG. 15 is a perspective view showing an example of the overall appearance of the charging roller of the present invention in which the recess is formed on the outer peripheral surface.

With reference to FIG. 15, the charging roller 6 of this example is formed in a non-porous, single-layered tubular shape by a semi-conductive rubber composition as in the conventional case, and has a shaft in a through hole 7 at the center thereof. 8 is inserted and fixed.
The shaft 8 is integrally formed of a metal such as iron, aluminum, an aluminum alloy, or stainless steel.

The shaft 8 is electrically bonded to and mechanically fixed to the charging roller 6 via, for example, a conductive adhesive, or the shaft 8 has an outer diameter larger than the inner diameter of the through hole 7. By press-fitting into, it is electrically joined to the charging roller 6 and mechanically fixed and rotated integrally.
An oxide film 9 may be formed on the outer peripheral surface 1 of the charging roller 6 as shown in an enlarged manner in FIG.

When the oxide film 9 is formed, the oxide film 9 functions as a dielectric layer, and the dielectric loss tangent of the charging roller 6 can be reduced.
Moreover, oxidation film 9 functions as a low friction layer, can be more satisfactorily suppress the adhesion and accumulation of such an external additive.
Moreover, since the oxide film 9 can be easily formed by, for example, irradiating with ultraviolet rays in an oxidizing atmosphere, it is possible to suppress a decrease in the productivity of the charging roller 6 and a high production cost. However, the oxide film 9 does not have to be formed.

In order to manufacture the charging roller 6 of the above example, first, a predetermined semi-conductive rubber composition is extruded into a tubular shape using an extrusion molding machine, and then pressurized and heated in a vulcanizing can to be crosslinked. , A tubular body as a precursor of the charging roller 6 is formed.
Next, the formed tubular body is heated in an oven or the like for secondary cross-linking, cooled, cut to a predetermined length, and polished to a predetermined outer diameter.

The shaft 8 can be inserted into and fixed in the through hole 7 at any time from after cross-linking to after polishing.
However, after cross-linking, it is preferable to first perform secondary cross-linking to polishing with the shaft 8 inserted through the through hole 7.
This makes it possible to prevent the tubular body from warping or deforming due to expansion and contraction during secondary cross-linking. Further, by polishing while rotating around the shaft 8, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 1 can be suppressed.

As described above, the shaft 8 is inserted into the tubular body before the secondary cross-linking via a thermosetting adhesive having conductivity, or has an outer diameter larger than the inner diameter of the through hole 7. It may be press-fitted into the through hole 7.
In the former case, the tubular body is secondarily crosslinked by heating in the oven, and at the same time, the thermosetting adhesive is cured, and the shaft 8 is electrically bonded to the tubular body and mechanically. Is fixed to.

In the latter case, electrical joining and mechanical fixing are completed at the same time as press fitting.
Next, the outer peripheral surface 1 after polishing is irradiated with a laser focused on the opening shape of the predetermined recesses 2 as described above while scanning according to the arrangement to form a large number of recesses 2, and then, if necessary. By forming the oxide film 9, the charging roller 6 of the above example is manufactured.
It is preferable that the oxide film 9 is formed by irradiating the outer peripheral surface 1 of the charging roller 6 with ultraviolet rays as described above because it can be easily and efficiently formed. That is, the oxide film 9 is formed by oxidizing the semi-conductive rubber composition itself constituting the outer peripheral surface 1 of the charging roller 6 by irradiating it with ultraviolet rays having a predetermined wavelength for a predetermined time in an oxidizing atmosphere.

Moreover, since the semi-conductive rubber composition itself constituting the outer peripheral surface 1 of the charging roller 6 is formed by being oxidized by irradiation with ultraviolet rays as described above, the oxide film 9 is formed by applying a conventional coating agent. It does not cause problems like the formed coating layer, and is excellent in uniformity such as thickness and surface shape.
The wavelength of the ultraviolet rays to be irradiated is preferably 100 nm or more, particularly 400 nm or less, considering that the semi-conductive rubber composition is efficiently oxidized to form the oxide film 9 having the above-mentioned excellent function. It is preferably 300 nm or less. The irradiation time is preferably 30 seconds or longer, particularly preferably 1 minute or longer, and preferably 30 minutes or shorter, particularly 20 minutes or shorter.

However, the oxide film 9 may be formed by another method such as ozone exposure, or may be omitted as described above.
The shore A hardness of the charging roller 6 in the above example is preferably 60 ° or less, particularly 55 ° or less.
The charging roller 6 having a shore A hardness exceeding this range lacks flexibility, and may not be able to charge the photoconductor satisfactorily and efficiently by ensuring a wide nip width. In addition, the surface of the photoconductor may be damaged.

In the present invention, the shore A hardness is measured by the micro rubber hardness tester MD ₁ manufactured by Polymer Meter Co., Ltd. under the condition of a temperature of 23 ± 2 ° C. according to the measurement method described in Japanese Industrial Standards JIS K6253-3: 2012. It shall be expressed by the value measured using.
Examples charging roller 6 semiconductive rubber composition consisting under in FIG 15, it is possible to impart semi-conductivity for example of the order of 108Ω or less to the charging roller 6, on the outer peripheral surface 1, by laser processing, etc. Any of the various rubber compositions capable of forming the recess 2 can be used.

The following is an example of a semi-conductive rubber composition in which ionic conductivity is imparted by containing epichlorohydrin rubber, which is an ionic conductive rubber, as a rubber component, but the composition of the semi-conductive rubber composition is not necessarily the same. It is not limited to.
<Epichlorohydrin rubber>
Among the rubber components, as the epichlorohydrin rubber, various polymers containing epichlorohydrin as a repeating unit and having ionic conductivity can be used.

Examples of such epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allylglycidyl ether binary copolymer, and epichlorohydrin-ethylene oxide. -Allyl glycidyl ether ternary copolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether ternary copolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, etc. The above can be mentioned.

Of these, copolymers containing ethylene oxide, particularly ECO and / or GECO, are preferred.
The ethylene oxide content of both of the above copolymers is preferably 30 mol% or more, particularly preferably 50 mol% or more, and preferably 80 mol% or less.
Ethylene oxide works to reduce the roller resistance of the charging roller . However, if the ethylene oxide content is less than this range, such an action cannot be sufficiently obtained, so that the roller resistance value may not be sufficiently reduced.

On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs and the segment movement of the molecular chain is hindered, so that the roller resistance value tends to increase. Further, the charged roller after cross-linking may become too hard, or the viscosity of the semi-conductive rubber composition before cross-linking at the time of heating and melting may increase and the workability may decrease.
The epichlorohydrin content in ECO is the remaining amount of ethylene oxide content. That is, the epichlorohydrin content is preferably 20 mol% or more, preferably 70 mol% or less, and particularly preferably 50 mol% or less.

The allyl glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly preferably 2 mol% or more, and preferably 10 mol% or less, particularly 5 mol% or less.
The allyl glycidyl ether itself functions as a side chain to secure a free volume, thereby suppressing the crystallization of ethylene oxide and lowering the roller resistance value of the charging roller . However, if the allyl glycidyl ether content is less than this range, such an action cannot be obtained, so that the roller resistance value may not be sufficiently reduced.

On the other hand, allyl glycidyl ether functions as a cross-linking point when cross-linking GECO. Therefore, when the allyl glycidyl ether content exceeds the above range, the cross-linking density of GECO becomes too high, which hinders the segment movement of the molecular chain. On the contrary, the roller resistance value tends to increase.
The epichlorohydrin content in GECO is the remaining amount of ethylene oxide content and allyl glycidyl ether content. That is, the epichlorohydrin content is preferably 10 mol% or more, particularly preferably 15 mol% or more, and preferably 69.5 mol% or less, particularly 48 mol% or less.

As GECO, in addition to the copolymer in a narrow sense obtained by copolymerizing the three types of monomers described above, the epichlorohydrin-ethylene oxide copolymer (ECO) is modified with allylglycidyl ether. Monomers are also known, and such modified products can also be used as GECOs.
The blending ratio of epichlorohydrin rubber is preferably 15 parts by mass or more, particularly 50 parts by mass or more, and particularly 80 parts by mass or less, in the combined system with diene rubber described below, per 100 parts by mass of the total amount of rubber. It is preferably 70 parts by mass or less.

<Diene rubber>
As the rubber content, a diene-based rubber may be used in combination with the epichlorohydrin rubber.
Diene rubber, or improve the mechanical strength and durability of the charging roller 6 as described above, the characteristics of the rubber to the charging roller 6, that is flexible, yet less likely the compression set is small permanent set properties It functions to give etc.

Further, it is mainly a diene rubber that is oxidized when the outer peripheral surface 1 of the charging roller 6 is irradiated with ultraviolet rays to form an oxide film 9 on the outer peripheral surface 1.
The diene rubber is at least selected from the group consisting of, for example, styrene butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butadiene rubber (BR), natural rubber, and isoprene rubber (IR). One type can be mentioned.

Of these, it is preferable to use NBR alone as the diene rubber, or to use CR and NBR in combination, and the latter combination system is particularly preferable.
That is, as the rubber content, it is preferable to use epichlorohydrin rubber, CR and NBR in combination. As the three types of rubber, two or more types of rubber having different grades may be used in combination.

In such a combined system, since CR contains a large amount of chlorine atoms in the molecule, it also functions to improve the charging characteristics of the charging roller of the present invention in addition to the function as the diene rubber described above. Further, since CR is a polar rubber, it also functions to finely adjust the roller resistance value of the charging roller .
CR is synthesized by emulsion polymerization of chloroprene, and is classified into sulfur-modified type and non-sulfur-modified type according to the type of molecular weight modifier used at that time.

Of these, the sulfur-modified type CR is synthesized by plasticizing a polymer obtained by copolymerizing chloroprene and sulfur as a molecular weight modifier with thiuram disulfide or the like to adjust the viscosity to a predetermined value.
Further, the non-sulfur modified type CR is classified into, for example, a mercaptan modified type, a xanthate modified type and the like.

Of these, the mercaptan-modified type CR is synthesized in the same manner as the sulfur-modified type CR except that alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and octyl mercaptan are used as molecular weight modifiers. ..
Further, the xanthate-modified type CR is also synthesized in the same manner as the sulfur-modified type CR except that the alkylxanthate compound is used as a molecular weight modifier.

Further, CR is classified into a slow crystallization rate type, a moderate crystallization rate type, and a high crystallization rate type based on the crystallization rate.
In the present invention, any type of CR may be used, but among them, a non-sulfur-modified type CR having a slow crystallization rate is preferable.
Further, as CR, a copolymer of chloroprene and another copolymerization component may be used. Examples of such other copolymerization components include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylic nitrile, isoprene, butadiene, acrylic acid, and acrylic acid ester. , Methacrylic acid, and methacrylic acid ester and the like.

Still CR, there are those of the non-oil-extended type is not added to that of the oil extended type to adjust the flexibility by adding extender oil, Hiabura extended type in order to prevent contamination of the sensitive light body, especially It is preferable to use the CR of.
NBR is excellent in the function as the above-mentioned diene rubber.
As the NBR, low nitrile NBR, medium nitrile NBR, medium high nitrile NBR, high nitrile NBR, and extremely high nitrile NBR classified according to the acrylonitrile content can be used.

As also NBR, there are those of the non-oil-extended type is not added to those of adjusting the flexibility by adding extender oil oil extended type, Hiabura exhibition type in order to prevent contamination of the sensitive light body, especially It is preferable to use NBR of.
In a system in which three types of rubber, epichlorohydrin rubber, CR and NBR, are used in combination, the proportion of CR is preferably 5 parts by mass or more per 100 parts by mass of the total amount of rubber, and 30 parts by mass or less, particularly 20 parts by mass. It is preferably less than or equal to a portion.

If the blending ratio of CR is less than this range, the above-mentioned effect of blending the CR, that is, the effect of improving the charging characteristics of the charging roller and the effect of finely adjusting the roller resistance value may not be sufficiently obtained. ..
On the other hand, if the proportion of the CR exceeds the above range, since the relatively epichlorohydrin rubber is reduced, it may become impossible to impart good good semi conducting the charging roller.

The blending ratio of NBR is the remaining amount of epichlorohydrin rubber and CR. That is, the blending ratio of NBR may be set so that the total amount of rubber is 100 parts by mass when the blending ratios of epichlorohydrin rubber and CR are set to predetermined values.
<Crossing component>
As the cross-linking component, a thiourea-based cross-linking agent for cross-linking epichlorohydrin rubber, a sulfur-based cross-linking agent for cross-linking GECO among diene-based rubber and epichlorohydrin rubber, and an accelerator for both cross-linking agents are used in combination. Is preferable.

(Chiolea cross-linking agent and accelerator)
As the thiourea-based cross-linking agent, various compounds having a thiourea group in the molecule and capable of mainly functioning as a cross-linking agent for epichlorohydrin rubber can be used.
The thiourea-based cross-linking agent, such as tetramethyl thiourea, trimethyl thiourea, ethylene thiourea: shown (also known as 2-mercapto imidazoline), the number of _{(C n H 2n + 1 NH} ) 2 C = S wherein, n represents 1 to 10 .. ], One or more of the thiourea and the like. Ethylenethiourea is particularly preferable.

The blending ratio of the thiourea-based cross-linking agent is preferably 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber, and preferably 1 part by mass or less.
Examples of the accelerator for the thiourea-based cross-linking agent include guanidine-based promotion such as 1,3-diphenylguanidine (D), 1,3-di-o-tolylguanidine (DT), and 1-o-tolylbiguanide (BG). One or more of the agents and the like can be mentioned. In particular, 1,3-di-o-tolylguanidine (DT) is preferable.

The blending ratio of the accelerator is preferably 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber, and preferably 1 part by mass or less.
(Sulfur-based cross-linking agent and accelerator)
Examples of the sulfur-based cross-linking agent include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, and organic sulfur-containing compounds such as tetramethylthium disulfide and N, N-dithiobismorpholin. Can be mentioned.

However, sulfur is preferable as the sulfur-based cross-linking agent.
The blending ratio of sulfur is preferably 1 part by mass or more and preferably 2 parts by mass or less per 100 parts by mass of the total amount of rubber.
When, for example, oil-treated powdered sulfur, dispersible sulfur, or the like is used as sulfur, the above-mentioned compounding ratio is the ratio of sulfur itself as an active ingredient contained therein.

When a sulfur-containing cross-linking agent is used as the cross-linking agent, the blending ratio should be adjusted so that the mass part of the sulfur contained in the molecule per 100 parts by mass of the total amount of rubber is within the above range. preferable.
Examples of the accelerator for the sulfur-based cross-linking agent include a sulfur-containing accelerator containing sulfur in the molecule, such as a thiazole-based accelerator, a thiuram-based accelerator, a sulfenamide-based accelerator, and a dithiocarbamate-based accelerator. One type or two or more types can be mentioned.

Of these, it is preferable to use a thiazole-based accelerator and a thiuram-based accelerator in combination.
Examples of the thiazole-based accelerator include 2-mercaptobenzothiazole (M), di-2-benzothiazolyl disulfide (DM), zinc salt of 2-mercaptobenzothiazole (MZ), and cyclohexylamine of 2-mercaptobenzothiazole. One or two salts (HM, M60-OT), 2- (N, N-diethylthiocarbamoylthio) benzothiazole (64), 2- (4'-morpholinodithio) benzothiazole (DS, MDB), etc. The above can be mentioned. Particularly, di-2-benzothiazolyl disulfide (DM) is preferable.

Examples of the thiuram-based accelerator include tetramethylthiuram monosulfide (TS), tetramethylthiuram disulfide (TT, TMT), tetraethylthiuram disulfide (TET), tetrabutylthiuram disulfide (TBT), and tetrakis (2-ethylhexyl) thiuram. One or more of disulfide (TOT-N), dipentamethylene thiuram tetrasulfide (TRA) and the like can be mentioned. Particularly, tetramethylthiuram monosulfide (TS) is preferable.

In the combined system of the above two types of sulfur-containing accelerators, the blending ratio of the thiazole-based accelerator is preferably 1 part by mass or more per 100 parts by mass of the total amount of rubber, and preferably 2 parts by mass or less. .. The blending ratio of the thiuram-based accelerator is preferably 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber, and preferably 1 part by mass or less.
<Ion salt>
The semi-conductive rubber composition also preferably contains a salt (ionic salt) of an anion having a fluoro group and a sulfonyl group in the molecule and a cation.

By including such an ionic salt, even better semiconductivity can be imparted to the charging roller .
Examples of anions having a fluoro group and a sulfonyl group in the molecule constituting the ionic salt include one or two types such as fluoroalkyl sulfonic acid ion, bis (fluoroalkyl sulfonyl) imide ion, and tris (fluoroalkyl sulfonyl) methide ion. The above can be mentioned.

Among these, examples of the fluoroalkyl sulfonic acid ion include one or more of CF ₃ SO ^3- , C ₄ F ₉ SO ^{3- and the} like.
Examples of the bis (fluoroalkylsulfonyl) imide ion include (CF ₃ SO ₂ ) 2N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) N ⁻ , and so on. (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) N ⁻ , (C ₈ F ₁₇ SO ₂ ) (CF ₃ SO ₂ ) N ⁻ , (CF ₃ CH ₂ OSO ₂ ) ₂ N ⁻ , (CF ₃ CF) ₂ CH ₂ OSO ₂ ) ₂ N ⁻ , (HCF ₂ CF ₂ CH ₂ OSO ₂ ) ₂ N ⁻ , [(CF ₃ ) ₂ CHOSO ₂ ] ₂ N ^−, etc.

Further, examples of the tris (fluoroalkylsulfonyl) methide ion include one or more types such as (CF ₃ SO ₂ ) ₃ C ⁻ and (CF ₃ CH ₂ OSO ₂ ) ₃ C ⁻ .
The cations include, for example, alkali metal ions such as sodium, lithium and potassium, Group 2 element ions such as beryllium, magnesium, calcium, strontium and barium, transition element ions, amphoteric element cations and fourth cations. Examples thereof include one or more types such as a class ammonium ion and an imidazolium cation.

As the ionic salt, a lithium salt using lithium ion as a cation and a potassium salt using potassium ion as a cation are particularly preferable.
Among them, (CF ₃ SO ₂ ) ₂ NLi [lithium bis (trifluoromethanesulfonyl) imide], in terms of the effect of improving the ionic conductivity of the semi-conductive rubber composition and lowering the roller resistance value of the charging roller , And / or (CF ₃ SO ₂ ) ₂ NK [potassium bis (trifluoromethanesulfonyl) imide] is preferred.

The blending ratio of the ionic salt is preferably 0.5 parts by mass or more and preferably 5 parts by mass or less per 100 parts by mass of the total amount of rubber.
If the compounding ratio of the ionic salt is less than this range, the effect of improving the ionic conductivity of the charging roller and lowering the roller resistance value may not be sufficiently obtained.
On the other hand, even if it exceeds the range, not only no further effect can be obtained, but also excess ionic salts bloom on the outer peripheral surface of the charging roller to contaminate the photoconductor, or to form an oxide film by irradiation with ultraviolet rays. It may interfere.

<Others>
Various additives may be further added to the semi-conductive rubber composition, if necessary. Additives include, for example, cross-linking aids, acid receivers, plasticizers, processing aids, deterioration inhibitors, fillers, scorch inhibitors, lubricants, pigments, antistatic agents, flame retardants, neutralizers, nucleating agents. , Co-crosslinking agent and the like.
The type and blending ratio of these additives may be set while paying particular attention to the balance between the resistance value of the charging roller and the effect of suppressing the adhesion and accumulation of the external additive or the like on the outer peripheral surface.

Examples of the cross-linking aid include metal compounds such as zinc oxide; fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more of other conventionally known cross-linking aids.
The blending ratio of the cross-linking aid is preferably 3 parts by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
The antacid functions to prevent the chlorine-based gas generated from epichlorohydrin rubber and CR during cross-linking of the rubber component from remaining in the charged roller , thereby inhibiting cross-linking and contaminating the photoconductor. To do.

As the acid receiving agent, various substances that act as acid receptors can be used, and among them, hydrotalcites or magsalats having excellent dispersibility are preferable, and hydrotalcites are particularly preferable.
Further, when hydrotalcites and the like are used in combination with magnesium oxide and potassium oxide, a higher acid receiving effect can be obtained, and contamination of the photoconductor can be prevented even better.

The blending ratio of the antacid is preferably 3 parts by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the plasticizer include various plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), and tricresyl phosphate, and various waxes such as polar wax. Examples of the processing aid include fatty acid metal salts such as zinc stearate.

The blending ratio of the plasticizer and / or the processing aid is preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the deterioration inhibitor include various antioxidants and antioxidants.
Of these, the anti-aging agent works to reduce the environmental dependence of the roller resistance value of the charging roller and to suppress an increase in the roller resistance value during continuous energization. Examples of the anti-aging agent include nickel diethyldithiocarbamate [NEC-P manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.] and nickel dibutyl dithiocarbamate [Nocrack NBC manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.]. And so on.

The blending ratio of the anti-aging agent is preferably 0.3 parts by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the filler include one or more of zinc oxide, silica, carbon, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide and the like.

By blending the filler, the mechanical strength of the charging roller can be improved.
The mixing ratio of the filler is preferably 5 parts by mass or more, and preferably 20 parts by mass or less per 100 parts by mass of the total amount of rubber.
Further, a conductive filler such as conductive carbon black may be blended as the filler to impart electronic conductivity to the charging roller .

Examples of the conductive carbon black include acetylene black and the like.
The blending ratio of the conductive carbon black is preferably 1 part by mass or more per 100 parts by mass of the total amount of rubber, and preferably 5 parts by mass or less.
Examples of the scorch inhibitor include one or more of N-cyclohexylthiophthalimide, phthalic anhydride, N-nitrosodiphenylamine, 2,4-diphenyl-4-methyl-1-pentene and the like. .. In particular, N-cyclohexylthiophthalimide is preferable.

The blending ratio of the scorch inhibitor is preferably 0.1 part by mass or more per 100 parts by mass of the total amount of rubber, and preferably 1 part by mass or less.
The co-crosslinking agent refers to a component having a function of cross-linking itself and cross-linking with a rubber component to polymerize the whole.
Examples of the co-crosslinking agent include ethylenically unsaturated monomers represented by methacrylic acid esters, metal salts of methacrylic acid or acrylic acid, and polyfunctional polymers using functional groups of 1,2-polybutadiene. Alternatively, one kind or two or more kinds such as dioxime can be mentioned.

Among these, examples of the ethylenically unsaturated monomer include one or more of the compounds represented by the following (a) to (h).
(a) Monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid.
(b) Dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid.
(c) Esters or anhydrides of unsaturated carboxylic acids of (a) and (b).

(d) Metal salts of (a) to (c).
(e) Aliphatic conjugated diene such as 1,3-butadiene, isoprene, 2-chlor-1,3-butadiene.
(f) Aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, ethylvinylbenzene and divinylbenzene.

(g) A vinyl compound having a heterocycle, such as triallyl isocyanurate, triallyl cyanurate, and vinylpyridine.
(h) In addition, vinyl cyanide compounds such as (meth) acrylonitrile or α-chloroacrylonitrile, acrolein, formylsterol, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone.

Further, as the ester of the unsaturated carboxylic acid of (c), the ester of the monocarboxylic acid is preferable.
Examples of the ester of monocarboxylic acids include one or more of the following various compounds.
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, n-pentyl (meth) ) Acrylate, i-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) ) Alkyl esters of (meth) acrylic acids such as acrylates, tert-butylcyclohexyl (meth) acrylates, decyl (meth) acrylates, dodecyl (meth) acrylates, hydroxymethyl (meth) acrylates, hydroxyethyl (meth) acrylates.

Aminoalkyl esters of (meth) acrylic acids, such as aminoethyl (meth) acrylates, dimethylaminoethyl (meth) acrylates, and butylaminoethyl (meth) acrylates.
A (meth) acrylate having an aromatic ring, such as benzyl (meth) acrylate, benzoyl (meth) acrylate, and allyl (meth) acrylate.

A (meth) acrylate having an epoxy group, such as glycidyl (meth) acrylate, metaglycidyl (meth) acrylate, and epoxycyclohexyl (meth) acrylate.
A (meth) acrylate having various functional groups such as N-methylol (meth) acrylamide, γ- (meth) acrylic oxypropyltrimethoxysilane, and tetrahydrofurfuryl methacrylate.

Polyfunctional (meth) acrylates such as ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene dimethacrylate (EDM), polyethylene glycol dimethacrylate, and isobutylene ethylene dimethacrylate.
(Preparation of semi-conductive rubber composition)
The semi-conductive rubber composition containing each component described above can be prepared in the same manner as before.

First, the rubber content is mixed in a predetermined ratio and kneaded, then the ionic salt and various additives other than the cross-linking component are added and kneaded, and finally the cross-linking component is added and kneaded to make the semi-conductive rubber. The composition is obtained.
For kneading, for example, a closed kneader such as an intermix, a Bambali mixer, a kneader, an extruder, or an open roll can be used.

<< Charging roller (2) >>
FIG. 16 (a) is a perspective view showing another example of the overall appearance of the charging roller of the present invention in which the above-mentioned recess is formed on the outer peripheral surface, and FIG. 16 (b) is an end face of the charging roller of the above example. It is a figure.
17 (a) is a perspective view showing an example of the process of manufacturing the charging roller of FIGS. 16 (a) and 16 (b), and FIG. 17 (b) is an end view of the inner layer used in the above process, FIG. 17 (c). ) Is an end view of the tube that is the basis of the outer layer.

With reference to FIGS. 16A and 16B, the charging roller 6 of this example provides semiconductivity to the outer peripheral surface 11 of the inner layer 10 formed in a tubular shape by the porous body of the semiconductive rubber composition. The outer layer 12 made of a seamless thermoplastic elastomer tube is laminated.
A shaft 8 is inserted and fixed in the through hole 13 at the center of the inner layer 10.

Similar to the previous example, the shaft 8 is integrally formed of a metal such as iron, aluminum, aluminum alloy, or stainless steel, and is electrically bonded to the inner layer 10 via, for example, a conductive adhesive. It is mechanically fixed, or by press-fitting an outer diameter larger than the inner diameter of the through hole 13 into the through hole 13, it is electrically joined to the inner layer 10 and is mechanically fixed and integrally rotated. Will be done.

The overall Asker C-type hardness of the charging roller 6 is limited to 30 ° or more and 60 ° or less.
When the overall Asker C-type hardness is less than this range, the inner layer 10 is press-fitted into the tube 14 (see FIGS. 17 (a) to 17 (c)) which is the source of the outer layer 12, and the charging roller is described. When 6 is manufactured, the tightening force of the outer layer 12 on the inner layer 10 is insufficient, and the outer layer 12 tends to shift with respect to the inner layer 10 at the time of image formation, for example.

On the other hand, when if the entire Asker-C hardness exceeds the above range, which reduces the flexibility of the charging roller 6, was used is brought into contact with the field sensitive optical member even contact against the photoreceptor Since a sufficient area cannot be secured, there is a possibility that the photoconductor may be poorly charged and the density of the formed image may decrease accordingly.
On the other hand, by setting the overall Asker C-type hardness of the charging roller 6 within the above range, the charging roller 6 is imparted with appropriate flexibility and is exposed to light without causing deviation of the outer layer 12. It is possible to satisfactorily suppress poor charging of the body and the accompanying decrease in the density of the formed image.

Considering that the effect is further improved, the hardness of the entire Asker C type of the charging roller 6 is preferably 45 ° or more, and preferably 50 ° or less even in the above range.
In the present invention, the overall Asker C-type hardness of the charging roller 6 is measured in the measurement method described in the Japan Rubber Association standard SRIS 0101 "Physical test method for expanded rubber" under the condition of a temperature of 23 ± 2 ° C. It is expressed by the value measured according to this.

With reference to FIGS. 17 (a) to 17 (c), in the manufacturing method of this example, the tube 14 of the semi-conductive seamless thermoplastic elastomer which is the basis of the outer layer 12 and the center passage in advance. An inner layer 10 having an outer diameter D ₁ larger than the inner diameter D _{2 of the} tube 14 to which the shaft 8 is inserted and fixed to the hole 13 is prepared, and the inner layer 10 is press-fitted into the tube 14.
Then, the inner layer 10 and the tube 14 are electrically joined and mechanically fixed to form the outer layer 12 composed of the tube 14.

After that, the outer peripheral surface 1 which is the surface of the outer layer 12 is irradiated with a laser focused on the opening shape of the predetermined recess 2 as described above while scanning according to the arrangement to form a large number of recesses 2. Then, the charging roller 6 of the above example is manufactured.
The thickness T of the tube 14 is 100μm or more, while being limited to 400 [mu] m or less, interference represented by the difference _D 1 -D ₂ and the inner diameter _{D 2} of the outer diameter _{D 1} and the tube 14 of the inner layer 10 is 100μm or more, 400 [mu] m Limited to:

The thickness T of the tube 14 is limited to 100 μm or more and 400 μm or less for the following reasons.
That is, if the thickness T is less than this range, it is not easy to form the tube 14 having a uniform thickness.
On the other hand, when the thickness T of the tube 14 exceeds the above range, the hardness of the entire Asker C type exceeds 60 °, the flexibility of the charging roller 6 decreases, and as described above, the photoconductor There is a possibility that poor charging of the image and the accompanying decrease in the density of the formed image may occur.

On the other hand, by setting the thickness T of the tube 14 to the above range, the thickness of the outer layer 12 made of the tube 14 is made as uniform as possible, and the overall Asker C-type hardness is flexible to satisfy the range of 60 ° or less. It is possible to manufacture a charging roller 6 which has properties and can satisfactorily suppress poor charging of the photoconductor and the accompanying decrease in density of the formed image.
Further, the tightening allowance of the outer layer 12 with respect to the inner layer 10 represented by D _{1 to} D ₂ is limited to 100 μm or more and 400 μm or less for the following reasons.

That is, if the tightening allowance is less than this range, the tightening force of the inner layer 10 by the outer layer 12 cannot be sufficiently obtained, so that the outer layer 12 tends to shift with respect to the inner layer 10.
On the other hand, when the tightening allowance exceeds the above range, the tightening of the inner layer 10 by the outer layer 12 is too strong, the flexibility of the charging roller 6 is reduced, and the overall Asker C-type hardness exceeds 60 °. As described above, there is a possibility that the photoconductor may be poorly charged and the density of the formed image may decrease accordingly. Further, for example, when the outer layer 12 is thin, the outer layer 12 is likely to be broken at the time of image formation.

On the other hand, by setting the tightening allowance within the above range, the outer layer 12 is less likely to shift or break during image formation, and the overall Asker C-type hardness has the flexibility to satisfy the range of 60 ° or less. Therefore, it is possible to manufacture the charging roller 6 which can satisfactorily suppress the charging failure of the photoconductor and the accompanying decrease in the density of the formed image.
The inner layer 10 and the outer layer 12 constituting the charging roller 6 in the example of FIGS. 16A and 16B can be formed of various materials.

However, the inner layer 10 is formed of a porous body of a semi-conductive rubber composition containing ethylene propylene rubber and paraffin oil, and the outer layer 12 is a seamless polyamide-based thermoplastic elastomer tube having semi-conductive property. It is preferably formed by 14.
According to such a combination, at least the ethylene propylene rubber having excellent affinity and compatibility with paraffin oil is selected as the rubber component of the semi-conductive rubber composition which is the basis of the inner layer 10, and the paraffin is used. By blending the system oil, the semi-conductive rubber composition can be foamed and crosslinked in a state where the melt viscosity is lowered and the foamability is improved. Therefore, the foaming ratio of the foam of the semi-conductive rubber composition is increased. , The flexibility of the inner layer 10 made of the foam can be improved from the present level.

Further, the outer layer 12 is formed by a tube of a polyamide-based thermoplastic elastomer that functions as a barrier layer for the paraffin-based oil because it has low affinity and compatibility with ethylene propylene-based rubber and paraffin-based oil, whereby the inner layer 10 is formed. It is possible to prevent the paraffin-based oil blended in the above from bleeding onto the outer peripheral surface 1 of the charging roller 6 and contaminating the photoconductor.

Therefore, according to the present invention, the combination of the inner layer 10 and the outer layer 12 has the flexibility to satisfy the range in which the overall Asker C-type hardness is 60 ° or less without causing contamination of the photoconductor. The charging roller 6 can be formed.
<Inner layer 10>
(Ethylene propylene rubber)
Examples of the ethylene propylene rubber that forms the inner layer 10 include ethylene propylene rubber (EPM), which is a copolymer of ethylene and propylene, and ethylene propylene diene rubber (EPDM), which is a copolymer of ethylene, propylene, and diene. Both can be used, and EPDM is particularly preferable.

Further, as EPDM, various copolymers obtained by copolymerizing ethylene, propylene, and diene can be used. Examples of the diene include ethylidene norbornene (ENB) and dicyclopentadiene (DCPD).
Among these, EPDM in which diene is ENB includes, for example, Esprene (registered trademark) EPDM 501A manufactured by Sumitomo Chemical Co., Ltd. [Moony viscosity ML1 + 4 (100 ° C.): 44, ethylene content: 52%, diene content: 4.0%. ], 505A [Moony viscosity ML1 + 4 (100 ° C.): 47, ethylene content: 50%, diene content: 9.5%] and the like.

Examples of EPDM in which diene is DCDP include Esplen EPDM 301A manufactured by Sumitomo Chemical Co., Ltd. [Moonie viscosity ML1 + 4 (100 ° C.): 44, ethylene content: 50%, diene content: 5.0%], 301 [Moonie. Viscosity ML1 + 4 (100 ° C): 55, ethylene content: 62%, diene content: 3.0%], 305 [Moony viscosity ML1 + 4 (100 ° C): 60, ethylene content: 60%, diene content: 7.5%] One kind or two or more kinds such as.

Further, as the EPDM, in addition to the non-oil-extended EPDM exemplified above, an oil-extended EPDM extended with a spreading oil is also known. In the present invention, among the oil-extended EPDMs, the spreading oil is a paraffin-based oil. Can also be used as a substitute for EPDM + paraffinic oil.
Examples of EPDM include one or more of the above-exemplified types.
(Other rubber)
Considering that the effect described above can be further improved by combining ethylene propylene rubber, paraffin oil, and polyamide thermoplastic elastomer, only ethylene propylene rubber is used as the rubber component forming the inner layer 10. It is preferable to use it alone (including the case where two or more kinds of ethylene propylene rubbers are used in combination).

However, other rubbers may be used in combination as long as the above effects are not impaired.
Examples of such other rubbers include one or more types such as natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, and chloroprene rubber.
The blending ratio of the other rubber is preferably 20 parts by mass or less, particularly preferably 10 parts by mass or less, based on 100 parts by mass of the total amount of rubber.

(Paraffin oil)
As the paraffin oil, various paraffin oils having good compatibility with ethylene propylene rubber can be used.
Examples of the paraffin-based oil include one or more of various oils of the Diana (registered trademark) process oil PW series manufactured by Idemitsu Kosan Co., Ltd.

The blending ratio of the paraffin-based oil is preferably 20 parts by mass or more, and preferably 100 parts by mass or less per 100 parts by mass of the total amount of the rubber containing at least ethylene propylene-based rubber.
When the blending ratio of the paraffin-based oil is less than this range, the foaming of the foam is improved by lowering the melt viscosity of the semi-conductive rubber composition described above by blending the paraffin-based oil. There is a possibility that the effect of increasing the magnification and improving the flexibility of the inner layer 10 and eventually the charging roller 6 cannot be sufficiently obtained. That is, there is a possibility that the charging roller 6 cannot be provided with high flexibility that satisfies the range in which the overall Asker C-type hardness is 60 ° or less.

On the other hand, when the blending ratio of the paraffin-based oil exceeds the above range, the excess paraffin-based oil seeps out to the interface with the outer layer 12 and inhibits the electrical conduction between the outer layer 12 and the inner layer 10. There is a risk of reducing the semiconductivity of the charging roller 6. In addition, the outer layer 12 may easily shift with respect to the inner layer 10.
On the other hand, by setting the blending ratio of the parafi-based oil in the above range, the semi-conductive rubber composition is foamed while suppressing the decrease in the semi-conductive property of the charging roller 6 and the displacement of the outer layer 12. By improving the properties and increasing the foaming ratio to improve the flexibility of the inner layer 10, it is possible to impart high flexibility to the charging roller 6 that satisfies the range of the overall Asker C-type hardness of 60 ° or less.

In consideration of further improving the effect, the blending ratio of the paraffin oil is preferably 40 parts by mass or more, and 60 parts by mass or less per 100 parts by mass of the total amount of rubber even in the above range. It is preferable to have it.
Further, as described above, when oil-extended EPDM in which the spreading oil is a paraffin-based oil is used as EPDM, oil-extended EPDM having an oil spreading amount per 100 parts by mass of EPDM within the above range should be selected and used. Just do it.

If the amount of oil spread is insufficient, paraffin-based oil may be added, and if the amount of oil spread is excessive, non-oil-extended EPDM or the like may be added.
The semi-conductive rubber composition that forms the basis of the inner layer 10 has a rubber component containing at least ethylene propylene rubber, a cross-linking component for cross-linking the rubber component with paraffin oil, and an inner layer 10 having a porous structure. It can be prepared by blending a foaming component for foaming as much as possible, a conductive agent for imparting semiconductivity to the inner layer 10, and the like in a predetermined ratio.

(Crosslink component)
Examples of the cross-linking component for cross-linking the ethylene propylene rubber include a cross-linking agent and an accelerator.
Among these, examples of the cross-linking agent include one or more of sulfur-based cross-linking agents, thiourea-based cross-linking agents, triazine derivative-based cross-linking agents, peroxide-based cross-linking agents, and various monomers.

Examples of the sulfur-based cross-linking agent include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, and organic sulfur-containing compounds such as tetramethylthiuram disulfide and N, N-dithiobismorpholine. Can be mentioned.
Examples of the thiourea-based cross-linking agent include tetramethylthiourea, trimethylthiourea, ethylenethiourea, and (CnH2n + 1NH) 2C = S [in the formula, n represents a number of 1 to 10. ], One or more of the thiourea and the like.

Further, examples of the peroxide cross-linking agent include benzoyl peroxide and the like.
When the ethylene propylene rubber is EPDM, sulfur is preferable as the cross-linking agent.
The blending ratio of sulfur is preferably 0.5 parts by mass or more and preferably 3 parts by mass or less per 100 parts by mass of the total amount of the rubber containing at least the ethylene propylene rubber.

When, for example, oil-treated powdered sulfur, dispersible sulfur, or the like is used as sulfur, the above-mentioned compounding ratio is the ratio of sulfur itself as an active ingredient contained therein.
When a sulfur-containing cross-linking agent is used as the cross-linking agent, the blending ratio should be adjusted so that the mass part of the sulfur contained in the molecule per 100 parts by mass of the total amount of rubber is within the above range. preferable.

Examples of the accelerator include one or more kinds of inorganic accelerators such as slaked lime, magnesia (MgO) and litharge (PbO), and organic accelerators.
Examples of the organic accelerator include guanidine-based accelerators such as 1,3-di-o-tolylguanidine, 1,3-diphenylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salt of dicatecholborate. Thiazol-based accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; sulfenamide-based accelerators such as N-cyclohexyl-2-benzothiazil sulfenamide; tetramethylthiurammono Thiuram-based accelerators such as sulfide, tetramethylthiuram disulfide, tetraethyltiuram disulfide, dipentamethylene thiuram tetrasulfide; one or more of thiourea-based accelerators can be mentioned.

Since the functions of the accelerators differ depending on the type, it is preferable to use two or more types of accelerators in combination.
The blending ratio of each accelerator can be arbitrarily set depending on the type, but usually, it is preferably 0.5 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the total amount of rubber. ..

(Foam component)
As the foaming component, various foaming agents that decompose by heating to generate gas can be used.
Examples of such foaming agents include one or more of azodicarbonamide (ADCA), 4,4'-oxybis (benzenesulfonyl hydrazide) (OBSH), N, N-dinitrosopentamethylenetetramine (DPT) and the like. Can be mentioned.

The blending ratio of the foaming agent is preferably 3 parts by mass or more, and preferably 8 parts by mass or less per 100 parts by mass of the total amount of rubber.
If the blending ratio of the foaming agent is less than this range, the foaming ratio of the inner layer 10 is insufficient, the hardness of the Asker C type as a whole of the charging roller 6 exceeds 60 °, the flexibility is lowered, and the photoconductor is charged. Defects and the accompanying decrease in the density of the formed image may occur.

On the other hand, when the blending ratio of the foaming agent exceeds the above range, the foaming ratio of the inner layer 10 becomes too high, and the Asker C-type hardness of the entire charging roller 6 becomes less than 30 °, for example, image formation. Occasionally, the outer layer tends to shift with respect to the inner layer.
When the foaming agent is ADCA, for example, a urea-based foaming aid that acts to lower the decomposition temperature of the ADCA and promote the decomposition may be used in combination.

The blending ratio of the foaming aid can be arbitrarily set according to the type of foaming agent to be combined, but it is preferably 1 part by mass or more per 100 parts by mass of the total amount of rubber, and preferably 3 parts by mass or less. ..
(Conducting agent)
Examples of the conductive agent include an electron conductive conductive agent and / or an ionic conductive conductive agent. In particular, an electron conductive conductive agent is preferable.

Examples of the electron conductive conductive agent include various types of carbon black having electron conductivity, and one or more kinds such as graphite.
The blending ratio of the electronically conductive conductive agent is preferably 30 parts by mass or more, and preferably 60 parts by mass or less per 100 parts by mass of the total amount of rubber.
If the blending ratio of the electronically conductive conductive agent is less than this range, the resistance value of the inner layer 10 becomes too high, and sufficient semiconductivity cannot be imparted to the entire charging roller 6, for example, the solid black density of the formed image decreases. There is a risk of

On the other hand, if the proportion of the electron-conductive agent is more than the above range, even if the inner layer 10 even when blended with paraffin oil, thus charging roller 6 becomes hard, the whole of the Asker-C of the charging roller 6 The hardness exceeds 60 °, the flexibility is lowered, and there is a possibility that the photoconductor may be poorly charged and the density of the formed image may be lowered accordingly.
(Other additives)
Various additives may be further added to the semi-conductive rubber composition, if necessary. Examples of the additive include a cross-linking aid, a deterioration inhibitor, a filler, a scorch inhibitor, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, a co-crosslinking agent and the like.

As these additives, any of the above-exemplified additives can be used.
(Preparation of semi-conductive rubber composition)
The semi-conductive rubber composition containing each component described above can be prepared in the same manner as before.
First, the rubber component is kneaded, then the paraffin oil and the conductive agent are added and kneaded with various additives other than the cross-linking component and the foaming component, and finally the cross-linking component and the foaming component are added and kneaded. A semi-conductive rubber composition is obtained.

For kneading, for example, a closed kneader such as an intermix, a Bambali mixer, a kneader, an extruder, or an open roll can be used.
(Preparation of inner layer 10)
In order to prepare the inner layer 10, the semi-conductive rubber composition is first extruded into a tubular shape using an extrusion molding machine, then cut to a predetermined length, pressurized and heated in a vulcanization can. Foam and crosslink.

Then foaming, the tubular body was crosslinked, by heating using an oven or the like to secondary crosslinking, polished to a predetermined outer diameter D ₁ After cooling.
<Shaft 8>
The shaft 8 can be inserted into the through hole 13 and fixed at any time from after the tubular body is cut to after the inner layer 10 is press-fitted into the tube 14.

However, after cutting, it is preferable that the shaft 8 is first inserted into the through hole 13 and fixed, and then secondary cross-linking, polishing, and press fitting into the tube 14 as shown in FIG. 17 (a) are performed.
As a result, it is possible to prevent warpage and deformation of the tubular body → inner layer 10 due to expansion and contraction during secondary cross-linking. Further, by polishing while rotating around the shaft 8, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 11 can be suppressed. Further, workability when the inner layer 10 is press-fitted into the tube 14 can be improved.

As described above, the shaft 8 is electrically bonded to the inner layer 10 via a conductive adhesive and is mechanically fixed, or has an outer diameter larger than the inner diameter of the through hole 13. By press-fitting into the through hole 13, it is electrically joined to the inner layer 10 and mechanically fixed, and is rotated integrally with the inner layer 10.
In the former case, the tubular body is secondarily crosslinked by heating in the oven, and at the same time, the thermosetting adhesive is cured, and the shaft 8 is electrically bonded from the tubular body to the inner layer 10. It is also mechanically fixed.

In the latter case, electrical joining and mechanical fixing are completed at the same time as press fitting.
<Outer layer 12>
The outer layer 12 is composed of a seamless thermoplastic elastomer tube 14 having semiconductivity as described above.
Tube 14 is fabricated by extrusion molding the elastomer composition containing the thermoplastic elastomer in a cylindrical shape having a predetermined thickness T, and an inner diameter D _2.

As the thermoplastic elastomer that forms the basis of the tube 14, when the inner layer 10 is formed of ethylene propylene rubber containing paraffin-based oil, a polyamide-based thermoplastic elastomer is preferable as described above.
Examples of the polyamide-based thermoplastic elastomer include one or more block copolymers containing polyamide as a hard segment, a polyether, a polyester, a polypropylene glycol, a polytetramethylene ether glycol, or the like as a soft segment. ..

In order to impart semiconductivity to the tube 14, an electronically conductive conductive agent and / or an ionic conductive conductive agent may be added to the elastomer composition on which the tube 14 is based. In particular, an electronically conductive conductive agent is preferable from the viewpoint of preventing contamination of the photoconductor drum, toner, or peripheral members by bleeding.
Examples of the electronically conductive conductive agent include one or more of the above-mentioned various carbon blacks and graphites having electron conductivity, and carbon fibrils such as carbon nanotubes.

In particular, considering the cost and the characteristics of the developing roller, carbon black having a large DBP oil absorption amount, which can form a conductive circuit with a small amount of addition and can adjust the resistance, is preferable.
The blending ratio of carbon black is preferably 30 parts by mass or less, particularly preferably 15 parts by mass or less, per 100 parts by mass of the polyamide-based thermoplastic elastomer.
If the blending ratio of carbon black exceeds this range, the outer layer 12 may become hard and the toner may be easily deteriorated. It may also lead to cost increase.

The lower limit of the blending ratio of carbon black is not particularly limited, but in order to impart appropriate semiconductivity to the tube 14, 0.5 parts by mass or more, particularly 1 part by mass or more per 100 parts by mass of the polyamide-based thermoplastic elastomer. Is preferable.
The configuration of the present invention is not limited to that of the example of the figure described above.
For example, the charging roller 6 in the example of FIG. 15 is not limited to the single layer (excluding the oxide film 9) described above, and includes two rubber layers, an outer layer on the outer peripheral surface 1 side and an inner layer on the shaft 8 side. It may be formed in a laminated structure.

The charging roller of the present invention can be used les over Heather printer, an electrostatic copying machine, a plain paper facsimile apparatus, or the such as the MFP these, the image forming apparatus using an electrophotographic method.

<Example 1-1>
(Preparation of semi-conductive rubber composition)
The following rubber components were blended.
(A) ECO [Epicromer (registered trademark) D manufactured by Osaka Soda Co., Ltd., ethylene oxide content: 61 mol%] 15 parts by mass
(B) GECO [Epion (registered trademark) -301L, EO / EP / AGE = 73/23/4 (molar ratio) manufactured by Osaka Soda Co., Ltd.] 45 parts by mass
(C) CR [Showa Denko Co., Ltd. Showpren (registered trademark) WRT] 10 parts by mass
(D) NBR [JSR N250 SL manufactured by JSR Corporation, low nitrile NBR, acrylonitrile content: 20%] 30 parts by mass The rubber content of (A) to (D) above is 100 parts by mass using a Bambari mixer. While kneading, first, among the components shown in Table 1 below, other than the cross-linking component was added and kneaded, and finally, the cross-linking component was added and further kneaded to prepare a semi-conductive rubber composition.

Each component in Table 1 is as follows. The parts by mass in the table are parts by mass per 100 parts by mass of the total amount of rubber.
Ionic salt: Potassium bis (trifluoromethanesulfonyl) imide [EF-N112 manufactured by Mitsubishi Materials Denshi Kasei Co., Ltd.]
Antacid: Hydrotalcites [DHT-4A (registered trademark) -2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Cross-linking aid: Zinc oxide 2 types [Mitsui Mining & Smelting Co., Ltd.]
Filler: Conductive carbon black [acetylene black, Denka black (registered trademark) manufactured by Denki Kagaku Kogyo Co., Ltd., granular]
Processing aid: Zinc stearate [SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd.]
Anti-aging agent: Nickel dibutyldithiocarbamate [Nocrack (registered trademark) NBC manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.]
Thiourea-based cross-linking agent: Ethylene thiourea [2-mercaptoimidazoline, Axel (registered trademark) 22-S manufactured by Kawaguchi Chemical Industry Co., Ltd.]
Accelerator DT: 1,3-di-o-tolylguanidine [guanidine-based accelerator, Sunseller (registered trademark) DT manufactured by Sanshin Chemical Industry Co., Ltd.]
Dispersible sulfur: Cross-linking agent [trade name Salfax PS manufactured by Tsurumi Chemical Industry Co., Ltd., sulfur content: 99.5%]
Accelerator DM: Di-2-benzothiazolyl disulfide [thiazole-based accelerator, Noxeller (registered trademark) DM manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.]
Accelerator TS: Tetramethylthiuram Monosulfide [Thiuram-based accelerator, Sunseller TS manufactured by Sanshin Chemical Industry Co., Ltd.]
(Manufacturing of charging rollers )
The semi-conductive rubber composition is supplied to a φ60 extrusion molding machine, extruded into a tubular shape having an outer diameter of φ11.0 mm and an inner diameter of φ5.0 mm, mounted on a temporary shaft for cross-linking, and inside a vulcanization can. The mixture was crosslinked at 160 ° C. for 30 minutes.

The crosslinked tubular body was reattached to a metal shaft having an outer diameter of φ6 mm coated with a conductive thermosetting adhesive (polyamide type) on the outer peripheral surface, and heated in an oven at 150 ° C. for 60 minutes. After adhering to the metal shaft and cutting both ends, the outer peripheral surface was dry-polished using a wide polishing machine until the outer diameter became φ9.5 mm.
The outer peripheral surface 1 after polishing is wiped with alcohol and then laser-processed, and a large number of recesses 2 are formed on the outer peripheral surface 1 as shown in FIGS. 1 and 2 (a) in the circumferential direction and the axial direction of the outer peripheral surface 1. Each recess 2 was formed in a matrix, and each recess 2 was formed so as to overlap each other in the circumferential direction and the axial direction.

Each recess 2 was formed to have the same size, and the forming interval was set to 50 to 80 μm in both the circumferential direction and the axial direction.
Further, the aperture shape of the laser was adjusted so that the amount of overlap between the adjacent recesses 2 was small in the circumferential direction and large in the axial direction.
As shown in FIG. 1, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are connected by a continuous curved surface.

Next, after the outer peripheral surface 1 after laser processing is wiped with alcohol again, the distance from the UV light source to the outer peripheral surface is set to 50 mm, set in a UV processing apparatus, and the oxide film 9 is irradiated with ultraviolet rays for 15 minutes while rotating at 300 rpm. It was formed to manufacture a charging roller 6.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was defined as 22 μm. The development area ratio Sdr of the interface at the area of the region = 50,000 μm ² was 0.6.

<Example 1-2>
Examples except that the diaphragm shape of the laser is adjusted so that the adjacent recesses 2 are separated from each other so as to overlap in the axial direction but not in the circumferential direction as shown in FIGS. 7 and 8. The charging roller 6 was manufactured in the same manner as in 1-1.
Each recess 2 was formed to have the same size, and the forming interval was 50 to 80 μm in both the circumferential direction and the axial direction.

The region between the recesses 2 of each row adjacent to each other in the axial direction remains in an unprocessed state with a width of about 20 μm parallel to the axial direction and with polished marks, and the peripheral edge of the recesses 2 in each row and the unprocessed region. The boundary with was a sharp edge.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured in the same manner as in Example 1-1, the maximum height Sz of the outer peripheral surface 1 was 30 μm, and the development of the interface at the defined area area = 50,000 μm ^2. The area ratio Sdr was 1.3.

<Comparative Example 1-1>
No recess is formed on the outer peripheral surface 1 after polishing by laser processing, and as shown in FIG. 18, immediately wet polishing with # 400 paper using a wet paper polishing machine, wiping with alcohol, and then irradiating with ultraviolet rays. The charging roller 6 was manufactured in the same manner as in Example 1-1 except that the oxide film 9 was formed.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured in the same manner as in Example 1-1, the maximum height Sz of the outer peripheral surface 1 was 25 μm, and the area of the defined region = 50,000 μm ^2. The area ratio Sdr was 5.6.

<Comparative Example 1-2>
The charging roller 6 is formed in the same manner as in Example 1-1 except that the diaphragm shape of the laser is adjusted so that the adjacent recesses 2 are formed independently so that they do not overlap at all in the axial direction and the circumferential direction. Manufactured.
Each recess 2 was formed to have the same size, and the forming interval was 50 to 80 μm in both the circumferential direction and the axial direction.

The region between each of the independent recesses 2 remained in an unprocessed state with polished marks remaining, and the boundary between the peripheral edge of each recess 2 and the unprocessed region had a sharp edge shape.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured in the same manner as in Example 1-1, the maximum height Sz of the outer peripheral surface 1 was 46.2 μm, and the interface at the defined region area = 50,000 μm ^2. The unfolded area ratio Sdr of was 8.2.

<Actual machine test>
A genuine charging roller of a photoconductor unit [manufactured by Lexmark International] that has a photoconductor and a charging roller that is arranged in constant contact with the surface of the photoconductor and is removable from the laser printer body. Instead, the charging rollers manufactured in Examples and Comparative Examples were incorporated.

Then, the assembled photoconductor unit was loaded into a color laser printer [Color Laser Printer CS510 manufactured by Lexmark International Co., Ltd.], and after passing 2000 sheets / day for 5 days, the charging roller was taken out and placed on the outer peripheral surface. The presence or absence of adhesion and accumulation of external additives was evaluated.
That is, by visually observing the outer peripheral surface of the charging roller , the one whose entire surface is whitened by the adhesion of an external additive or the like is "x", the one which is partially whitened but is at a practical level is "△", and is completely white. Those that have not been converted are marked with "○".

In addition, the outer peripheral surface of the charging roller before and after the paper passing test was measured with a spectrophotometer, and the presence or absence of adhesion or accumulation of an external additive or the like was evaluated according to the following criteria.
◯: The color difference ΔE * a * b * before and after the paper passing test was 3 or less.
Δ: The color difference ΔE * a * b * before and after the paper passing test exceeded 3 and was 7 or less.
X: The color difference ΔE * a * b * before and after the paper passing test exceeded 7.

The results are shown in Table 2.

From the results of Examples 1-1 and 1-2 in Table 2, Comparative Example 1-1 which does not form the recesses by forming a large number of recesses on the outer peripheral surface so as to overlap each other in the circumferential direction and the axial direction. It was found that whitening due to adhesion and accumulation of an external additive or the like on the outer peripheral surface can be satisfactorily suppressed as compared with Comparative Example 1-2 in which a large number of recesses are formed independently.
Further, from the results of Examples 1-1 and 1-2, by connecting substantially the entire surface of the outer peripheral surface 1 with a continuous curved surface, whitening due to adhesion and accumulation of an external additive or the like on the outer peripheral surface can be further suppressed. I found out.

<Example 2-1>
As the rubber content, EPDM [Esplen EPDM 505A manufactured by Sumitomo Chemical Co., Ltd., Mooney viscosity ML1 + 4 (100 ° C.): 47, ethylene content: 50%, diene content: 9.5%] is used among ethylene propylene rubbers. There was.
As the paraffin oil, Diana process oil PW-380 manufactured by Idemitsu Kosan Co., Ltd. was used.

While kneading 100 parts by mass of EPDM using a rubber mixer, 60 parts by mass of paraffin oil and components other than the cross-linking component and foaming component among the components shown in Table 3 below are added and kneaded, and then the cross-linking component and foaming component are added. In addition, it was further kneaded to prepare a semi-conductive rubber composition as a base for the inner layer.

Each component in Table 3 is as follows. The mass part in the table is a mass part per 100 parts by mass of EPDM as a rubber component.
Filler: Heavy calcium carbonate, BF-300 manufactured by Shiraishi Calcium Co., Ltd.
Crosslinking aid I: Zinc oxide type 2 manufactured by Mitsui Metal Mining Co., Ltd. Crosslinking aid II: Stearic acid, trade name manufactured by Nichiyu Co., Ltd. Made of seast 6
Foaming agent: ADCA, Vinihole AC # 3 manufactured by Eiwa Kasei Kogyo Co., Ltd.
Foaming aid: Urea-based cell paste 101 manufactured by Eiwa Kasei Kogyo Co., Ltd.
Cross-linking agent: Sulfur with 5% oil, Accelerator TS manufactured by Tsurumi Chemical Industry Co., Ltd .: Tetramethyl thiuram monosulfide, Thiram-based accelerator, Sunseller (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd.
Accelerator MBTS: Di-2-benzothiazolyl disulfide, thiazole-based accelerator, Sunseller DM manufactured by Sanshin Chemical Industry Co., Ltd.
The semi-conductive rubber composition is supplied to an extrusion molding machine, extruded into a tubular shape having an outer diameter of φ11 mm and an inner diameter of φ5 mm, mounted on a temporary shaft for cross-linking, and cross-linked in a vulcanization can at 160 ° C. for 1 hour. , And foamed.

Next, the crosslinked tubular body was reattached to a shaft having an outer diameter of φ6 mm coated with a conductive thermosetting adhesive on the outer peripheral surface, heated to 160 ° C. in an oven, and then adhered to the shaft. The outer peripheral surface was polished using a cylindrical polishing machine to finish it so that the outer diameter D ₁ = 9.5 mm, and further washed with water to prepare an inner layer integrated with the shaft.
The tube that forms the basis of the outer layer is a semi-conductive, seamless polyamide-based thermoplastic elastomer tube with a thickness of T = 100 μm and an inner diameter of D ₂ = 9.3 mm [SLV made by Gunze Co., Ltd., conductive. Sex nylon sleeve] was prepared. Interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.

Then, after the inner layer is press-fitted into the tube, both ends are cut, and the outer peripheral surface of the tube is further laser-processed to form a large number of recesses 2 on the outer peripheral surface 1 as shown in FIGS. 1 and 2 (a). , The peripheral surface 1 was formed in a matrix in the circumferential direction and the axial direction, and the recesses 2 were formed so as to overlap each other in the circumferential direction and the axial direction to manufacture the charging roller 6.

Each recess 2 was formed to have the same size, and the forming interval was set to 50 to 80 μm in both the circumferential direction and the axial direction.
Further, the aperture shape of the laser was adjusted so that the amount of overlap between the adjacent recesses 2 was small in the circumferential direction and large in the axial direction.
As shown in FIG. 1, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are connected by a continuous curved surface.

When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured in the same manner as in Example 1-1, the maximum height Sz of the outer peripheral surface 1 was 22 μm, and the area of the defined region = 50,000 μm ^2. The area ratio Sdr was 0.6.
Further, the hardness of the entire Asker C type of the charging roller 6 was measured at a load of 1 kg according to the above-mentioned measuring method and found to be 32 °.

<Example 2-2>
The charging roller 6 was manufactured in the same manner as in Example 2-1 except that the amount of ADCA as a foaming agent to be blended in the semi-conductive rubber composition was 5 parts by mass.
The thickness T of the tube underlying the outer layer is 100 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.

The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 45 ° ..
<Example 2-3>
The outer diameter D _{1 of the} inner layer is 9.3 mm, and the inner diameter D ₂ of the SLV manufactured by Gunze Co., Ltd. is used as a tube made of a semi-conductive, seamless polyamide-based thermoplastic elastomer that is the basis of the outer layer. The charging roller 6 was manufactured in the same manner as in Example 2-1 except that the material having a thickness of 9.1 mm and a thickness T of 200 μm was used.

The thickness T of the tube underlying the outer layer interference represented by the difference _D 1 -D ₂ in 200 [mu] m as described above, the outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 47 ° ..

<Example 2-4>
The outer diameter D _{1 of the} inner layer is 8.9 mm, and the inner diameter D ₂ of the SLV manufactured by Gunze Co., Ltd. is used as a tube made of a semi-conductive, seamless polyamide-based thermoplastic elastomer that is the basis of the outer layer. The charging roller 6 was manufactured in the same manner as in Example 2-1 except that the material having a thickness of 8.7 mm and a thickness T of 400 μm was used.

The thickness T of the tube underlying the outer layer interference represented by the difference _D 1 -D ₂ of 400μm as mentioned above, the outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 55 ° ..

<Example 2-5>
The charging roller 6 was manufactured in the same manner as in Examples 2-3 except that the amount of paraffin oil to be blended in the semi-conductive rubber composition was 40 parts by mass and the amount of ADCA as a foaming agent was 4 parts by mass. ..
The thickness T of the tube underlying the outer layer is 200 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.

The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 58 ° ..
<Example 2-6>
The amount of 40 parts by weight of paraffin oil to be blended to the semi-conductive rubber composition, as well as 5 mass parts of the amount of ADCA as a blowing agent, except that the outer diameter D ₁ of the inner layer was 9.2mm performed The charging roller 6 was manufactured in the same manner as in Example 2-3.

The thickness T of the tube underlying the outer layer is 200 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 100 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 45 ° ..

<Example 2-7>
The amount of 40 parts by weight of paraffin oil to be blended to the semi-conductive rubber composition, as well as 5 mass parts of the amount of ADCA as a blowing agent, except that the outer diameter D ₁ of the inner layer was 9.5mm performed The charging roller 6 was manufactured in the same manner as in Example 2-3.
The thickness T of the tube underlying the outer layer is 200 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 400 [mu] m.

The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 48 ° ..
<Example 2-8>
The charging roller 6 was manufactured in the same manner as in Examples 2-3 except that the amount of paraffin oil to be blended in the semi-conductive rubber composition was 40 parts by mass and the amount of ADCA as a foaming agent was 5 parts by mass. ..

The thickness T of the tube underlying the outer layer is 200 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 45 ° ..

<Example 2-9>
Examples except that the diaphragm shape of the laser is adjusted so that the adjacent recesses 2 are separated from each other so as to overlap in the axial direction but not in the circumferential direction as shown in FIGS. 7 and 8. The charging roller 6 was manufactured in the same manner as in 2-8.
Each recess 2 was formed to have the same size, and the forming interval was 50 to 80 μm in both the circumferential direction and the axial direction.

The region between the recesses 2 of each row adjacent to each other in the axial direction remains in an unprocessed state with a width of about 20 μm parallel to the axial direction and with polished marks, and the peripheral edge of the recesses 2 in each row and the unprocessed region. The boundary with was a sharp edge.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured in the same manner as in Example 1-1, the maximum height Sz of the outer peripheral surface 1 was 30 μm, and the development of the interface at the defined area area = 50,000 μm ^2. The area ratio Sdr was 1.3.

The overall Asker C-type hardness of the charging roller 6 was 45 °.
<Comparative Example 2-1>
The amount of paraffin-based oil blended in the semi-conductive rubber composition was 50 parts by mass, and the non-foaming semi-conductive was the same as in Example 2-1 except that the foaming agent and foaming aid were not blended. A rubber composition was prepared.

Then, in the same manner as in Example 2-1 except that this semi-conductive rubber composition was used and the outer layer was not formed, the non-porous and single-layer charged with an outer diameter D ₁ of 9.5 mm. Roller 6 was manufactured. The outer peripheral surface of the charging roller is the arithmetic mean roughness of the contour curve specified in Japanese Industrial Standard JIS B0601: 2013 "Geometric characteristic specifications (GPS) of product-Surface texture: Contour curve method-Terms, definitions and surface texture parameters". The surface was mirror-polished so that Ra was 1 μm.

The overall Asker C-type hardness of the charging roller was 50 °.
<Comparative Example 2-2>
The charging roller 6 was manufactured in the same manner as in Example 2-4 except that the amount of paraffin oil to be blended in the semi-conductive rubber composition was 50 parts by mass and the amount of ADCA as a foaming agent was 2 parts by mass. ..

The thickness T of the tube underlying the outer layer is 400 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 65 ° ..

<Comparative Example 2-3>
The charging roller 6 was manufactured in the same manner as in Example 2-1 except that the amount of paraffin oil to be blended in the semi-conductive rubber composition was 50 parts by mass and the amount of ADCA as a foaming agent was 8 parts by mass. ..
The thickness T of the tube underlying the outer layer is 100 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 200 [mu] m.

The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 25 ° ..
<Comparative Example 2-4>
50 parts by weight the amount of the paraffin oil to be blended to the semi-conductive rubber composition, together with a 6 parts by weight the amount of ADCA as a blowing agent, except that the outer diameter D ₁ of the inner layer was 9.6mm performed The charging roller 6 was manufactured in the same manner as in Example 2-3.

The thickness T of the tube underlying the outer layer is 200 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 500 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 55 ° ..

<Comparative Example 2-5>
The amount of 40 parts by weight of paraffin oil to be blended to the semi-conductive rubber composition, together with a 4 parts by weight the amount of ADCA as a blowing agent, except that the outer diameter D ₁ of the inner layer was 9.16mm performed The charging roller 6 was manufactured in the same manner as in Example 2-3.
The thickness T of the tube underlying the outer layer is 200 [mu] m, interference represented by the difference _D 1 -D ₂ with an outer diameter _{D 1} and the inner diameter _{D 2} was 60 [mu] m.

The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 58 ° ..
<Comparative Example 2-6>
The amount of 40 parts by weight of paraffin oil to be blended to the semi-conductive rubber composition, together with a 6 parts by weight the amount of ADCA as a blowing agent, the outer diameter D ₁ of the inner layer and 8.6 mm, even yet the outer layer becomes bets, that a polyamide-based thermoplastic elastomer tube seamless with semiconductive inner diameter D ₂ of the SLV manufactured by Gunze Ltd. was used 8.5 mm, what thickness T is 500μm The charging roller 6 was manufactured in the same manner as in Example 2-1 except for the above.

The thickness T of the tube underlying the outer layer interference represented by the difference _D 1 -D ₂ of 500μm as mentioned above, the outer diameter _{D 1} and the inner diameter _{D 2} was 100 [mu] m.
The outer peripheral surface 1 of the charging roller 6 The shape and arrangement of the recess 2, as well as surface properties of the outer peripheral surface 1 are the same as in Example 2-1, the overall Asker-C hardness of the charging roller 6 was 62 ° ..

<Actual machine test>
A genuine charging roller of a photoconductor unit [manufactured by Lexmark International] that has a photoconductor and a charging roller that is arranged in constant contact with the surface of the photoconductor and is removable from the laser printer body. Instead, the charging rollers manufactured in Examples and Comparative Examples were incorporated.

Immediately after the assembled photoconductor unit was loaded into a color laser printer [color laser printer CS510 manufactured by Lexmark International Co., Ltd.], a solid image was formed and the presence or absence of density decrease was evaluated.
That is, by visually observing the formed solid image, the one with a reduced density is "x", the one with a slight decrease in density but at a practical level is "△", and the one with no decrease in density is "○". And said.

Further, after loading the photoconductor unit into a color laser printer and passing 2000 sheets / day for 5 days, the charging roller was taken out to evaluate the presence or absence of adhesion and accumulation of an external additive or the like on the outer peripheral surface.
That is, by visually observing the outer peripheral surface of the charging roller , the one whose entire surface is whitened by the adhesion of an external additive or the like is "x", the one which is partially whitened but is at a practical level is "△", and is completely white. Those that have not been converted are marked with "○".

Furthermore, the state of the outer layer was observed.
The above results are shown in Tables 4 to 6.

From the results of Examples 2-1 to 2-9 and Comparative Example 2-1 of Tables 4 to 6, the developing roller has a two-layer structure consisting of an inner layer having a porous structure and an outer layer composed of a tube, and has an outer peripheral surface thereof. It was found that by forming a large number of recesses so as to overlap each other in the circumferential direction and the axial direction, whitening due to adhesion and accumulation of an external additive or the like on the outer peripheral surface can be satisfactorily suppressed.
However, from the results of Examples 2-1 to 2-9 and Comparative Examples 2-2, 2-3, and 2-6, in order to obtain the above effect without causing displacement or whitening of the outer layer, the above 2 It was found that the overall Asker C-type hardness of the layered developing roller needs to be 30 ° or more and 60 ° or less.

Further, from the results of Examples 2-1 to 2-9 and Comparative Examples 2-4 to 2-6, in order to manufacture a developing roller which does not cause breakage or misalignment of the outer layer and is excellent in the above effects. , above 100μm thickness T of the tube underlying the outer layer, and 400μm or less, and yet the inner layer of the outer diameter _{D 1} and the 100μm or more interference represented by the difference _D 1 -D ₂ and the inner diameter _{D 2} of the tube, It was found that it was necessary to make it 400 μm or less.

Further, from the results of Examples 2-1 to 2-9, in order to further improve the above effect, the overall Asker C-type hardness is preferably 45 ° or more, preferably 50 ° or less. It is preferable that the blending ratio of the paraffin oil is 20 parts by mass or more, particularly 40 parts by mass or more, and 100 parts by mass or less, particularly 60 parts by mass or less, based on 100 parts by mass of the total amount of rubber. Was found to be preferable.

Then, from the results of Examples 2-8 and 2-9, it was found that by connecting the adjacent recesses with a continuous curved surface, whitening due to adhesion and accumulation of an external additive or the like on the outer peripheral surface can be suppressed more satisfactorily. It was.
<Example 3-1>
Irradiating the outer peripheral surface 1 in the axial direction while scanning the laser in a linear shape having a constant width, as shown in FIGS. 9 and 10, a plurality of recesses 2 having a length extending over the entire length in the axial direction of the charging roller are formed. The charging roller 6 was manufactured in the same manner as in Example 1-1 except that it was formed parallel to each other in the circumferential direction.

Each recess 2 was formed to have the same width of 80 μm and depth of 20 μm.
As shown in FIG. 9, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are connected by a continuous curved surface.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 37.8 μm. The development area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 3.9.

<Example 3-2>
By adjusting the scanning width and intensity of the laser, as shown in FIG. 19, a plurality of recesses 2 having the same width of 40 μm and depth of 5 μm, each having the same length over the entire length in the axial direction of the charging roller , are formed in the circumferential direction. The charging roller 6 was manufactured in the same manner as in Example 3-1 except that it was formed in parallel.
As shown in FIG. 19, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are connected by a continuous curved surface.

When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 19.8 μm. The development area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 1.2.

<Example 3-3>
Irradiating the outer peripheral surface 1 in the circumferential direction while scanning the laser in a linear shape with a constant width, as shown in FIGS. 13 and 14, a plurality of recesses 2 extending in the circumferential direction of the charging roller are provided in the axial direction. The charging roller 6 was manufactured in the same manner as in Example 3-1 except that the charged rollers 6 were formed parallel to each other.
Each recess 2 was formed to have the same width of 40 μm and depth of 5 μm.

As shown in FIG. 13, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are all connected by a continuous curved surface.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 11.5 μm. The developed area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 0.4.

<Example 3-4>
By adjusting the scanning width and intensity of the laser, as shown in FIG. 20, a plurality of recesses 2 having the same width of 60 μm and depth of 15 μm, each having the same length over the entire length in the axial direction of the charging roller , are formed in the circumferential direction. The charging roller 6 was manufactured in the same manner as in Example 3-1 except that it was formed in parallel.

As shown in FIG. 20, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are connected by a continuous curved surface.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 21.9 μm. The developed area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 3.8.

<Example 3-5>
By adjusting the scanning width and intensity of the laser, as shown in FIG. 21, a plurality of recesses 2 having the same width of 80 μm and depth of 60 μm, each having the same length over the entire length in the axial direction of the charging roller , are formed in the circumferential direction. The charging roller 6 was manufactured in the same manner as in Example 3-1 except that it was formed in parallel.

As shown in FIG. 21, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are all connected by a continuous curved surface.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 90.3 μm. The development area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 24.

<Example 3-6>
By adjusting the scanning width and intensity of the laser, as shown in FIG. 22, a plurality of recesses 2 having the same width of 110 μm and a depth of 40 μm, each having the same length over the entire length in the axial direction of the charging roller , are formed in the circumferential direction. The charging roller 6 was manufactured in the same manner as in Example 3-1 except that it was formed in parallel.

As shown in FIG. 22, the outer peripheral surface 1 after laser machining has a three-dimensional shape in which adjacent recesses 2 are connected by a continuous curved surface.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 58.0 μm. The development area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 11.

<Example 3-7>
Irradiating the outer peripheral surface 1 in the axial direction and the circumferential direction while scanning the laser in a linear shape having a constant width, respectively, as shown in FIGS. 11 and 12, a plurality of recesses 2 extending over the entire circumference of the charging roller in the circumferential direction are formed. Each piece is formed so as to be parallel to each other in the axial direction and separated from each other so as not to overlap each other, and a plurality of recesses 2 extending over the entire length in the axial direction are formed so as to be parallel to each other in the circumferential direction and separated from each other so as not to overlap each other. The charging roller 6 was manufactured in the same manner as in Example 3-1 except for the above.

The substantially rectangular region between the recesses 2 formed in a matrix shape remained in an unprocessed state in which the polishing marks remained, and the boundary between the region and each recess 2 had a sharp edge shape.
When the surface texture of the outer peripheral surface 1 of the manufactured charging roller 6 was measured using a shape analysis laser microscope [VK-X150 / 160 manufactured by KEYENCE CORPORATION], the maximum height Sz of the outer peripheral surface 1 was 36.0 μm. The development area ratio Sdr of the interface at the defined area area = 50,000 μm ² was 4.0.

<Processing time evaluation>
For Examples 3-1, 3-3, and 3-7, the time required to form the recess 2 on the entire surface of the outer peripheral surface 1 by laser machining was measured. The results are shown in Table 7 together with the results of Example 1-1.

From the table, by forming the recesses 2 in a length extending over a plurality of rows in the circumferential direction or the axial direction of the outer peripheral surface 1, the number of laser irradiations and the irradiation time can be significantly reduced, and the productivity of the charging roller can be improved. It turned out that it could be improved.

<Actual machine test>
A genuine charging roller of a photoconductor unit [manufactured by Lexmark International] that has a photoconductor and a charging roller that is arranged in constant contact with the surface of the photoconductor and is removable from the laser printer body. Instead, the charging rollers manufactured in Examples and Comparative Examples were incorporated.

Immediately after the assembled photoconductor unit was loaded into a color laser printer [color laser printer CS510 manufactured by Lexmark International Co., Ltd.], a solid image was formed and the presence or absence of density decrease was evaluated.
That is, by visually observing the formed solid image, the one with a reduced density is "x", the one with a slight decrease in density but at a practical level is "△", and the one with no decrease in density is "○". And said.

Further, after loading the photoconductor unit into a color laser printer and passing 2000 sheets / day for 5 days, the charging roller was taken out to evaluate the presence or absence of adhesion and accumulation of an external additive or the like on the outer peripheral surface.
That is, by visually observing the outer peripheral surface of the charging roller , the one whose entire surface is whitened by the adhesion of an external additive or the like is "x", the one which is partially whitened but is at a practical level is "△", and is completely white. Those that have not been converted are marked with "○".
The results are shown in Tables 8 and 9 together with the results of Example 1-1.

From the results of Examples 3-1 to 3-7 in Tables 8 to 9, even when a linear recess is formed on the outer peripheral surface 1, good image density is maintained as in Example 1-1 and the like. However, whitening due to adhesion and accumulation of an external additive or the like on the outer peripheral surface can be satisfactorily suppressed, and as is clear from the results in Table 7 above, the number of laser irradiations and the irradiation time are significantly reduced. It was found that the productivity of the charging roller can be improved.

However, from the results of Examples 3-1 to 3-7, in order to further improve the above effect, it is preferable that the depth of the linear recess 2 is 50 μm or less and the width is 100 μm or less. It has been found that the recesses are preferably formed at least parallel to the axial direction of the outer peripheral surface 1.

2 Concave 3 to 5 Convex 6 Charging roller 7 Through hole 8 Shaft 9 Oxidation film 10 Inner layer 11 Outer surface 12 Outer layer 13 Through hole 14 Tube D ₁ Outer diameter D ₂ Inner diameter T Thickness

Claims (13)

A large number of semi-conductive rubber compositions composed of a non-porous, single-layered tubular body that overlaps each other directly on the outer peripheral surface in at least one of the circumferential methods and axial directions of the outer peripheral surface. A charging roller provided with a recess (excluding the coating film that covers the outer peripheral surface). The charging roller according to claim 1, further comprising an oxide film on the outer peripheral surface. The entire Asker C is provided with a tubular inner layer made of a porous body of a semi-conductive rubber composition and an outer layer made of a semi-conductive seamless thermoplastic elastomer tube provided on the outer periphery of the inner layer. A charging roller having a mold hardness of 30 ° or more and 60 ° or less, and having a large number of recesses provided on the outer peripheral surface of the outer layer (excluding the coating film covering the outer peripheral surface). The charging roller according to any one of claims 1 to 3, wherein each recess has a depth of 0.5 μm or more and 100 μm or less. The item according to any one of claims 1 to 4, wherein the region of the volume parameter graph (load curve) in which the load area ratio exceeds 10% is the concave portion, and the region in which the load area ratio is 10% or less is the convex portion. Charging roller. The charging roller according to any one of claims 1 to 5 , wherein the outer peripheral surface has a maximum height Sz of 0.5 μm or more and 30 μm or less, and an interface development area ratio Sdr of 5 or less. The charging roller according to any one of claims 1 to 6, wherein the large number of recesses are provided in rows in the circumferential direction and the axial direction, respectively. The charging roller according to claim 7, wherein at least a part of the large number of recesses is formed in a length extending over a plurality of rows in the circumferential direction or the axial direction. The charging roller according to claim 8, wherein each of the recesses has a depth of 0.5 μm or more, 50 μm or less, a width of 100 μm or less, and the outer peripheral surface has an interface development area ratio Sdr of 5 or less. The charging roller according to any one of claims 1 to 9, wherein the adjacent recesses are connected by a continuous curved surface. The claim includes a step of forming a large number of recesses on the outer peripheral surface of the charging roller by laser processing so as to overlap each other in at least a part of at least one of the circumferential direction and the axial direction of the outer peripheral surface. The method for manufacturing a charging roller according to any one of 1 to 10. The large number of recesses are formed in rows in the circumferential direction and the axial direction, respectively, and at least a part of the large number of recesses is formed in a length extending over the plurality of rows in the circumferential direction or the axial direction. The method for manufacturing a charging roller according to claim 11. In the tube having a thickness T of 100 μm or more and 400 μm or less, which is the basis of the outer layer, the outer diameter D ₁ is larger than the inner diameter D _{2 of the} tube, and the outer diameter D ₁ and the inner diameter D ₂ interference is 100μm or more, represented by the difference _D 1 -D _2, comprising the step of press-fitting the inner layer is 400μm or less, the manufacturing method of the charging roller according to claim 3.