JP2006154620A - Charging member and system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging member having excellent C set nature at high foaming low stiffness and excellent in pouring electrostatic charging property and a system using the same. <P>SOLUTION: A shape coefficient (K-1) of a cell of a foaming body is defined as 110≤K-1≤500. Thus, in order to control the shape coefficient, it is necessary to appropriately control balance of curing speed and foaming speed. Furthermore, it is more preferable that the shape coefficient (K-2) is 105≤K-2≤280. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used in an electrophotographic apparatus such as a copying machine, a printer, and a fax machine, and an apparatus using the same, and is particularly suitable for an electrophotographic apparatus having a charging method that does not substantially involve discharge. Is.

  In electrophotographic apparatuses, conductive members are used for various purposes / uses. A typical example is a charging member that makes a member to be charged have a predetermined polarity and potential in the charging step. The charging member has a shape such as a roller, a blade, a brush, a belt, a film, a sheet, and a chip. It is used by applying a superimposed voltage of voltage and AC voltage.

  Regardless of contact / contact, the charging member is preferably used in the form of a roller (charging roller) from the viewpoint of stable productivity, and as a support, a polymer compound such as at least rubber, elastomer, resin, etc. around the core metal A configuration in which a layer mainly composed of is provided is common. In particular, in contact-type charging members, the layer mainly composed of a polymer compound is made of a solid or sponge of relatively low hardness for the purpose of improving the uniformity of the contact state (static / dynamic) with the photoreceptor. A configuration having an elastic layer is common. As a charging member used for these, various studies have been made on the premise of a configuration having at least an elastic layer and a surface layer. For example, Patent Document 1 proposes a configuration using a foam as an elastic body.

  As a charging method used for image formation of an electrophotographic apparatus, there are a method in which only a DC voltage is applied to a charging member and a method in which a superimposed voltage of a DC voltage and an AC voltage is applied. As described above, in particular, the charging member for charging the photosensitive member as the member to be charged has a structure having an elastic layer having a relatively low hardness from the viewpoint of improving the uniformity of the contact state (static / dynamic) with the photosensitive member. It is desirable, but if the hardness is lowered, the C set (permanent deformability at the time of compression) will decrease (deteriorate), and the contact part of the charging member will be deformed if left in contact with the photoreceptor for a long time. It may end up.

  In recent years, in order to reproduce an original image as faithfully as possible, studies on an electrophotographic apparatus having high resolution and high developability are in progress. In such a high-performance electrophotographic apparatus, there is no conventional problem. Even if the amount of deformation of the charging member abutting portion is not uniform, charging unevenness due to that portion is faithfully reflected in the image, and as a result, there is a problem in that an image defect due to density unevenness may occur. This tendency is particularly remarkable in the charging method in which only a DC voltage is applied.

  Considering these charging methods from the charging mechanism, both the method of applying only the DC voltage and the method of applying the superimposed voltage of the DC voltage and the AC voltage are relatively high for the charging member having the characteristics as a dielectric. By applying a voltage, the photosensitive member is charged to a predetermined potential by using a discharge generated in the minute gap. These methods are excellent in view of easily obtaining good chargeability. However, since a relatively high voltage is required, improvement has been desired from the viewpoint of efficient use of energy.

  As a new technology to cope with this, the characteristics of the charging member as a semiconductor are utilized, a relatively low voltage is applied to the charging member, and the charge is directly transferred from the charging member to the photoreceptor (that is, using discharge). Various methods for charging the photosensitive member to a predetermined potential have been studied. According to this method, it is possible to stably obtain good chargeability by increasing the opportunity to transfer the charge from the charging member to the photoreceptor (that is, the opportunity to contact the photoreceptor) and ensuring the state over a long period of time. Therefore, it becomes an important factor.

  Examples of charging members studied by this method include a magnetic brush charging method in which a semiconductive magnetic material is formed into a brush shape using a magnet, a conductive fur brush, and a fiber brush in which the roller is formed into a roller shape. There are a charging method, an elastic roller charging method using a conductive elastic body, and the like. In the magnetic brush charging method, inorganic fine powders such as magnetite and ferrite are generally used. Therefore, it is easy to obtain the characteristics as a semi-conductor, and the surface of the charging member is formed of powder, which increases the chance of contact with the photoreceptor. Have advantages in these aspects. However, since these inorganic powder pairs are extremely hard compared to the photoreceptor, there is a problem that the photoreceptor is likely to be scraped or scratched, and may be restricted when used for a long period of time. On the other hand, the fiber brush charging method imparts semiconductivity by adding a conductivity-imparting material to a polymer compound, so the effect on the photoconductor is small because the hardness is lower than that of a magnetic material, but as a fiber As a result, Tg and Tm must be very high, and as a result, there is a problem that the hair tends to fall down, and furthermore, there is a limit to the fiber flocking density, resulting in insufficient density There was a problem that charging failure occurred due to insufficient contact opportunity.

  On the other hand, in the elastic roller charging method, it is important to increase the relative nip area between the charging member and the photosensitive member in order to obtain good chargeability. For this purpose, the charging member has a low hardness. In addition, it is necessary to increase the contact pressure. However, even if the contact force of the conventional charging member is made very large and contacted with the photosensitive member, the effect of increasing the contact opportunity is not sufficient and the charging performance is not good. Furthermore, increasing the contact pressure is a direction in which the C set of the elastic body is likely to be caused, and in many cases causes an image defect due to the C set portion. That is, in particular, in the elastic roller charging method, it is indispensable to develop an elastic body having low hardness, good C setting property and good charging performance. As a technique corresponding to this, as disclosed in Patent Document 2, for example, a method for defining the cell diameter and the number of cells has been proposed. However, in this method, even if a good image is obtained at the very beginning, it is not durable and cannot be used stably.

Against this backdrop, using the characteristics of the charging member as a semiconductor, a relatively low voltage is applied to the charging member, and the charge is transferred directly from the charging member to the photoreceptor (ie, no discharge is used). Therefore, there has been a demand for the development of an optimal technique relating to a charging method for stably charging a photoconductor to a predetermined potential over a long period of time.
Japanese Patent Laid-Open No. 2001-72806 Japanese Patent Laid-Open No. 2001-42605

  An object of the present invention is to provide a charging member having an elastic body having both low hardness and good C set, and an apparatus using the charging member.

  Another object of the present invention is to provide a charging member having excellent chargeability even in a charging system in which only a DC voltage is applied, and an apparatus using the same.

  Furthermore, another object of the present invention is to charge the photosensitive member to a predetermined potential by applying a relatively low voltage to the charging member and transferring the charge directly from the charging member to the photosensitive member without substantially utilizing discharge. It is an object of the present invention to provide a charging member that can be used and an apparatus using the same.

  In order to solve these problems, the present inventors have intensively studied, and as a result, the following problems have been solved.

That is, the present invention is a conductive member having at least a foam and having an electric resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less, and a cell shape factor K-1 represented by Formula-1 is 110 ≦ K−1 ≦ 500.

（式中、MXLNGはセルの絶対最大長、AREAはセルの投影面積を示す）
本発明において、K-1はセルの丸さの度合いを示し、数字が大きいほどセル形状が真球（２次元すなわち断面形状では真円である。今後の説明においては簡便のため真円という表現を使う。したがって、特に断らない限り、２次元表現である真円と３次元表現である真球は同義である。）からズレが大きく、不定形であることを示す。このような構成とすることによって低硬度と良Ｃセットを両立することを見出したものである。

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)
In the present invention, K-1 indicates the degree of roundness of the cell, and the larger the number, the more the cell shape is a true sphere (two-dimensional, that is, a perfect circle in a cross-sectional shape. Therefore, unless otherwise specified, a perfect circle that is a two-dimensional representation and a true sphere that is a three-dimensional representation are synonymous.) It has been found that such a configuration makes it possible to achieve both low hardness and good C set.

  In general, a foam is formed of a space (cell) and a wall (solid), and factors affecting the hardness of the foam include the volume ratio of the space (cell) in the unit volume. The hardness of the wall (solid) can be increased. Accordingly, when viewed from the viewpoint of the hardness of the foam, the larger the volume ratio of the space portion, the lower the hardness of the wall, and the lower the hardness of the foam.

  In order to increase the volume ratio of the space portion in the unit volume, the cell diameter may be increased. However, if it is too large, an image defect due to charging failure occurs in that portion. Furthermore, the fact that there are many spaces means that there are few solid parts having elastic force, so that the deformation recovery force also decreases, and as a result, C set deteriorates. Due to these problems, there is a limit to the increase in cell diameter.

  On the other hand, in order to reduce the hardness of the wall, it is necessary to add a large amount of a plasticizing material such as a plasticizer or a softening agent. However, these materials generally exhibit fluidity at room temperature, causing bleed and the like. Not only will this lead to a worsening of the C set. It is practically difficult to greatly reduce the hardness when the addition amount is within a range where these phenomena do not occur.

  In view of such a situation, as a result of analyzing conventional foams, it has been found that these phenomena are caused by the cell shape being a perfect circle or close to it (FIG. 3). That is, if the cell cross-sectional shape is close to a perfect circle like a conventional foam, even if the cell diameter is increased, a wall having a thickness distribution in a shape that theoretically follows the shape of the circle will be created. The thick (L1) and thin (L2) parts coexist on the wall (FIG. 4), and it is difficult to make the wall thin uniformly. If the hardness is measured in this state, the influence of the thick part of the wall becomes dominant, so the hardness is not lowered as expected. Furthermore, when stress is applied to the foam, stress concentrates on the thin part of the wall, and therefore, the phenomenon that the C set is lowered due to concentration of deformation on the thin part tends to occur. In order to alleviate these phenomena, it is preferable to distribute the cell diameter so that the cells are packed most closely, so that the cell diameter has an appropriate distribution at an arbitrary cut surface. Even so, as long as the cell cross-sectional shape is close to a perfect circle, the wall thickness distribution cannot be essentially improved, and there is a limit to precisely controlling the cell size and distribution.

  In order to dramatically improve such essential problems, it is effective to make the cell shape irregular. As shown in FIG. 1, by making the cell shape irregular, the wall can be made to have a fairly uniform thickness. When the hardness of the foam is measured, there is no influence of the thick part of the wall, so that the hardness can be reduced. In addition, when stress is applied to this foam, there is no influence of the thin part of the wall, so the stress is moderately distributed throughout the wall without concentrating on the part, and deformation is also averaged over the entire wall. Since this occurs, it is possible to reduce both an increase in the amount of local deformation and an increase in local stress, and it is estimated that the C set is improved.

  That is, the gist of the present invention is to uniformly control the wall thickness by making the foam cell shape indefinite within a predetermined range. In the present invention, if the cell shape factor K-1 is 110 ≦ K-1 ≦ 500, a good effect is obtained, but if 120 ≦ K-1 ≦ 400, an excellent effect is obtained, which is preferable. 130 ≦ K−1 ≦ 300 is more preferable because a very excellent effect can be obtained. When K-1 is less than 110, since the cell shape is close to a perfect circle, the effect of the present invention cannot be obtained. On the other hand, if K-1 is larger than 500, low hardness and good C set can be obtained, but it is not preferable because dents in a wide range are often generated when surface polishing, and it tends to cause image defects.

  Moreover, it is preferable that the cell diameter in an arbitrary cross section has a certain distribution. This is because, when the cell diameter distribution is appropriate, the cells are easily packed most closely, and as a result, the cell wall thickness and variations thereof are reduced, and the effects of the present invention are more easily obtained. In this case, if the number of cells having a true circle equivalent cell diameter of 30 μm or more and 300 μm or less obtained from the projected area of the cell is 50% or more and 97% or less of the total number of cells, a further effect can be obtained. In particular, it is preferable that cells in the range of 50 μm or more and 150 μm or less have a number of 50% or more and 95% or less of the total number of cells because a further effect can be obtained.

  In addition, the wall thickness is preferably 0.1 μm or more and 50 μm or less because a greater effect can be obtained, more preferably 0.5 μm or more and 30 μm or less, and even more preferably 1 μm or more and 25 μm or less. If possible, it is desirable that the wall thickness is smaller than the true circle equivalent diameter of the cell, and if the wall thickness is 1/5 or less of the true circle equivalent diameter of the cell, a very excellent synergistic effect will be exhibited. desirable. If the wall is thin, the strength is lowered, and therefore, when the surface of the charging member is polished, it must be carefully performed and the productivity is lowered. In particular, if the thickness of the wall is less than 0.1 μm, the wall portion is easily broken during polishing, and if it is thicker than 50 μm, it is disadvantageous for reducing the hardness.

  The charging member thus obtained has a good C set while being highly foamed and low in hardness. That is, the specific gravity can be 0.4 or less as well as 0.45 or less, and in some cases 0.3 or less, and the Asker C hardness is 40 ° or less and 30 ° or less. Even if it is less than or equal to °, C set can be improved. In the present invention, C set is the amount of residual deformation measured after 12 hours after compressing the foam part of the charging member 4% and leaving it at 40 ° C 95% RH for 1 week, then releasing the pressure at 23 ° C 60% RH. This means that even under these conditions, an excellent result that the deformation amount is 125 μm or less can be obtained.

  The charging member of the present invention can be suitably used for any charging method or charging method, but preferably has a powder on the surface. By adopting such a configuration, it is possible to reduce the adhesiveness on the surface of the charging member or reduce the coefficient of friction between the charging member and the photosensitive member. And uniformity of rotation (no rotation unevenness such as stick-slip or minute chatter) is obtained, so durability (longer life by reducing wear and reducing damage to the power transmission system) and image quality Not only does it contribute to improvement (there is no unevenness in the surface of the photoreceptor due to unevenness in rotation, resulting in a uniform charge state), but also the developer component, photoreceptor component, and transferred material component on the charging member surface that accompanies use It is possible to reduce the amount of adhesion (such as paper powder, transfer material surface treatment agent and surface coating agent component), etc., as well as to reduce adhesion unevenness. Nabata For it is possible to improve the durability can be eliminated.

Furthermore, the charging member of the present invention is particularly useful when used in a method of charging a photosensitive member to a predetermined potential by applying a relatively low voltage to the charging member and transferring the charge directly from the charging member to the photosensitive member. According to this method, the charge is directly charged from the charging member to the photosensitive member via the nip portion so that the photosensitive member is charged to a predetermined voltage, and discharge from the charging member to the photosensitive member is not substantially generated. In this method, the voltage applied to the charging member may be a direct current alone or may be an oscillating voltage on which an alternating voltage having a peak-to-peak voltage less than twice the discharge start voltage is superimposed. It is preferable from the viewpoints of overall size reduction, energy saving, cost reduction, and the like. In order to cope with this method, it is desirable to reduce the resistance of the outermost layer of the photoconductor to some extent, and it is possible to obtain a photoconductor dark part potential substantially equal to the DC voltage applied to the charging member. In this method, in order to improve the charging performance, a powder having an electric resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less in the so-called medium resistance region used around the charging member is used. It is necessary. This is because the powder on the surface of the charging member plays a role of promoting charge transfer. Therefore, as the frequency of contact between the powder on the surface of the charging member and the photosensitive member increases, better charging characteristics can be obtained. For this purpose, a predetermined amount of powder in the middle resistance region is always present on the surface of the charging member, and a large contact area (nip area) between the charging member and the photosensitive member (approximately 1.5 times that when using discharge). The above is important, and further, increasing the relative speed difference between the surface of the charging member and the surface of the photosensitive member leads to further improvement in charging performance, which is preferable. The means for increasing the relative speed difference is not particularly limited, but it is most preferable to reversely rotate the charging member and the photosensitive member because they are relatively easy in terms of mechanism.

  In such a state, the charging member has characteristics that are easily deformed to increase the contact area (that is, low hardness) and small permanent deformation (that is, good C set), which is far superior to the conventional charging member. It is clear that a level is required. Since the charging member of the present invention has a particularly excellent balance between low hardness and good C set, the charging member exhibits particularly good effects when used under such conditions.

However, when the charging member and the photosensitive member are rotated in reverse, the powder that exists between them is subjected to great stress, so that the physical characteristics, chemical characteristics, electrical characteristics, etc. of the powder itself deteriorate. This may cause a problem that it is difficult to use for a long time. In order to solve this, it is preferable that the powder on the surface of the charging member is appropriately replaced. In other words, the charging member is required to have both a certain level of powder retention and a certain level of powder falling off. As a result of intensive studies, it has been found that the surface property of the charging member (that is, the cell shape that appears on the surface of the charging member) is greatly related to this conflicting demand. The reason for this is not clear yet, but is generally estimated as follows. Although powder is present in the walls and cells, pay particular attention to the cells. Here, a cross section of one cell (assuming that it has become half after polishing) will be described as a model. As shown in FIG. 7, when the cell shape is close to a perfect circle (with radius r), the cell forms a semicircle with radius r. Area of the space (cell unit) is πr ^2/2, the opening is 2r. The powder that has entered the inside through the cell opening is gradually pressed and filled into the cell. In other words, the distance of the arbitrary powder in the cell varies depending on the location (powder particle size is ignored) as represented by r · sin θ from the surface of the charging member (FIG. 8). Therefore, even if an external force (such as a bias) is applied for detachment, those that are likely to detach (close to the surface, that is, θ is small) preferentially detach but are difficult to detach (distant from the surface, that is, θ is Large ones do not detach. As a result, it is considered that a state in which things that are easily replaced are replaced and items that are difficult to replace are not replaced is accumulated. In such a case, fresh powder and powder that has been used for a long time are mixed, and the difference tends to increase with long-term use. It is considered a thing.

  On the other hand, if the cell shape is indefinite (FIG. 5) as in the present invention, the distance from the charging member surface to the powder may be at a relatively similar position (h) (FIG. 6). Therefore, when an external force (such as a bias) is applied for detachment, the powder is easily removed evenly at any location. Therefore, since the powder is appropriately replaced as a whole, it is considered that stable charging characteristics can be maintained over a long period of time. In order to further enhance such an effect, it is preferable to have a system that initially attaches powder to the surface of the charging member and supplies the powder from the outside in the long term.

  By the way, in the charging member of the present invention, it is important to control the value of K-1 within a predetermined range, and in particular, the charging member having the medium resistance region powder adhered to the surface is pressed against the photoreceptor, When charging the photosensitive member by applying only a relatively low DC voltage while rotating in reverse, the contact area between the charging member and the photosensitive member can be increased because both low hardness and C set can be achieved. In addition, as described above, it is very preferable because the charging performance can be further improved and the durability can be improved by the effect of promoting and stabilizing the powder appropriately. However, in the range where the value of K-1 is large (130 ≦ K-1 ≦ 500), the detachability of the powder tends to increase. If the detachability becomes too large, the powder may move onto the photoreceptor during image formation. In such a case, since the powder having sufficient charging ability is detached and collected, it is necessary to increase the amount of powder supplied from the outside. In addition, when the detachability is particularly large, a system is required that controls the amount of the powder that is detached from the charging member to an extent that does not affect the image. A higher-resolution electrophotographic apparatus is more susceptible to the influence of powder on the photoreceptor, so a more precise system is required, and a higher-speed electrophotographic apparatus tends to promote this phenomenon. Since these all cause high costs, it is desirable to improve the level.

  In order to improve this, the cell diameter on the surface preferably has a certain distribution. This is because the effect of promoting and stabilizing an appropriate replacement of the powder can be enhanced depending on the degree of cell diameter distribution on the surface. By the way, when the surface is formed by polishing, the degree of cell diameter distribution on the surface can be substituted with the degree of cell diameter distribution on an arbitrary cross section. In other words, in an arbitrary cross section, if the number of cells in the range where the round circle equivalent cell diameter determined from the projected area of the cell is 30 μm or more and 300 μm or less is 50% or more and 97% or less of the total number of cells, an appropriate powder This is preferable because the effect of promoting and stabilizing the replacement can be further obtained, and particularly if the number of cells in the range of 50 μm to 150 μm is 50% to 95% of the total number of cells, a further effect can be obtained. It is very preferable.

  In order to obtain further effects, it is desirable that the cell shape factor K-2 satisfies 105 ≦ K-2 ≦ 280. The cell shape factor K-2 is a measure of the unevenness of the cell surface, and the larger the K-2, the larger the surface unevenness of the cell (the larger the surface area).

（式中、AREAはセルの投影面積、PERIMEはセルの周囲長を示す）
K-2の値を本発明の範囲に制御することによって、セル内面の表面積を適度に大きくすることができるため、粉体の保持性が向上する。このような効果によって、特にK-1の値が大きい範囲（130≦K-1≦500）においても脱離性と保持性のバランスを取ることが可能となるのである。このような観点から、110≦K-2≦250であればより好ましく、120≦K-2≦200であればなおさら好ましい。K-2が105未満ではこの効果は小さく、また280より大きいと逆に奥に押し込まれた粉体が保持されやすくなりすぎるため入れ替わりにくくなることがある。

(In the formula, AREA indicates the projected area of the cell and PERIME indicates the perimeter of the cell)
By controlling the value of K-2 within the range of the present invention, the surface area of the cell inner surface can be increased appropriately, so that the powder retention is improved. Such an effect makes it possible to balance the detachability and the retentivity even in the range where the value of K-1 is particularly large (130 ≦ K−1 ≦ 500). From such a viewpoint, 110 ≦ K−2 ≦ 250 is more preferable, and 120 ≦ K−2 ≦ 200 is even more preferable. When K-2 is less than 105, this effect is small, and when K-2 is greater than 280, the pressed-in powder tends to be retained too easily and may not be easily replaced.

  FIG. 2 shows a cross-sectional SEM photograph showing an example of the cell shape of the charging member of the present invention.

  In the present invention, the cell shape factors K-1 and K-2 are measured as follows. First, an arbitrary portion of the charging member is cut to create a cut surface of the foam. Next, after obtaining image information and photographs magnified to a predetermined magnification with an electron microscope or optical microscope, etc., introduce them into an image analyzer and analyze them, and define the values obtained from Equations 1 and 2 above. To do. In the present invention, as a means for easily expressing such a three-dimensional cell shape, it is made two-dimensional by observing the cell cross section, and the surface irregularity (surface area) is expressed as the perimeter, as a sphere as a circle. is there.

  Further, the true circle equivalent cell diameter obtained from the projected area of the cell is obtained by using the projected area (AREA) obtained when measuring the shape factors K-1 and K-2.

  In the present invention, the cell shape and cell diameter may have a distribution in the thickness direction of the foam. For example, the cell shape is preferably configured such that the lower portion has a larger K-1 or / and K-2 than the upper portion, or the lower portion has a larger cell diameter than the upper portion.

  Further, the thickness of the cell wall is similarly obtained from image information and a photograph of an arbitrary foam cut surface.

  Within the scope of the present invention, the cells may be open cells or closed cells, and they may exist in a mixed state. It is preferable to appropriately control the state and form of the cell by a process unique to the electrophotographic apparatus, and it is important to pay attention to the blending surface and the manufacturing method so as to be optimal. In the present invention, open cells and closed cells are defined as the maximum cell length in any cross section regardless of the shape and form, and open cells are cells whose maximum length is 300 μm or more and closed cells. The case where the maximum cell length is less than 300 μm. The maximum cell length is the maximum length when any two points on the cell periphery are connected by a straight line as shown in FIG. 9A. The straight line crosses the cell wall. It was decided not to worry. In the figure, arbitrary points are indicated by black points, and four arbitrary points are set as an example. In this case, it is obvious that the line connecting the two points facing each other is longer than the line connecting the two adjacent points. Therefore, the longer of the two lines connecting the two points facing each other is the maximum length of this cell. Since n1> n2 in this figure, the maximum length is n1. Representative examples are shown in FIGS.

As described above, when the charging member of the present invention is used in a method of charging a photosensitive member to a predetermined potential by applying a relatively low voltage to the charging member and transferring the charge directly from the charging member to the photosensitive member, It is very preferable that a powder in a so-called medium resistance region having a volume resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less adheres to the surface of the member. If a powder with a volume resistance of less than 1 × 10 ³ Ωcm is used, the charging performance will be good, but if there is a pinhole in the photoconductor, leakage will occur from that part and the image will be defective. Because there is. In addition, when powder in the low resistance region is used, the current is very easy to flow. Because of concentration, there may be a shortage of current in the part where the adhesion is relatively small. As described above, the uneven adhesion of the powder causes current unevenness, and as a result, an adverse effect such as uneven density of the image may occur, which is not preferable. On the other hand, if a powder with a volume resistance exceeding 1 × 10 ¹⁰ Ωcm is used, the charging performance is insufficient. Process restrictions such as having to make the rotation speed of the member very fast may occur, or it may not be possible to cope with it. In addition, when the applied voltage is set very high, it becomes sensitive to defects on the photoconductor, which is disadvantageous to leakage, and when the rotation speed of the charging member is very high, the charging member or Since the wear of the photoreceptor is promoted, it is not preferable. On the other hand, if the powder is in the middle resistance region, a good image can be obtained by combining with appropriate process conditions. At this time, it is preferable that the electrical resistance value of the charging member after powder adhesion is higher than the electrical resistance value of the charging member before powder adhesion. In addition, a combination in which the volume resistivity of the powder is sufficiently high is desirable.

  Further, from the viewpoint of further improving the charging performance, the particle size and shape of the powder can be mentioned. If the average particle size (primary particle size) of the powder is 0.001 μm or more and 10 μm or less, desirably 0.01 μm or more and 1 μm or less, the contact frequency is greatly increased and good results can be obtained. If possible, it is even more preferable that the particle diameter is smaller than the wavelength of the laser to be irradiated to form an electrostatic latent image on the photoreceptor, and preferably 0.1 μm or less. Furthermore, the flat or irregular shape is also preferable because the contact area with the photoreceptor increases.

  Furthermore, if the charging member surface has powder as in the present invention, the photosensitive member and the charging member may move or rotate in the reverse (counter) direction, or the charging member may have an independent drive mechanism. Even in such a case, the friction coefficient between the charging member and the photosensitive member can be reduced, so that the load in the rotating mechanism can be reduced and the rotation can be uniform (rotation unevenness such as stick-slip and minute chatter does not occur). Therefore, durability of the device itself (longer life by reducing wear and damage to the power transmission system) and improvement of image quality (there is no unevenness in the potential of the photoreceptor surface due to uneven rotation, resulting in a uniform charged state) Also effective. From these surfaces, the shape of the powder is not particularly limited, but it is preferable that the slidability, lubricity, and rolling properties are large.

  On the other hand, the powder adhering to the surface of the charging member rubs the photoconductor, which promotes the abrasion of the photoconductor. In order to reduce this, the particle size of the powder is preferably small, and the average particle size (primary particle size) of the powder is preferably 0.001 μm to 10 μm, more preferably 0.01 μm to 1 μm. The shape and state of the powder also affect the photoconductor scraping. That is, it is preferable that the coefficient of friction is low, and a powder having good sliding properties (sliding properties) and rolling properties is preferable. Examples of good slipperiness (slidability) include surface-treated powder and amorphous powder, and examples of good rollability include spherical powder. Among these, the most preferable is a powder having excellent sliding property (sliding property) and having a property of stably existing on the surface of the charging member. For this purpose, the powder is particularly indefinite. desirable. As an index indicating such irregularity, there is K-H1 represented by Formula-3. In the present invention, 110 ≦ K−H1 ≦ 250 is preferable. If K-H1 is less than 110, the effect is small, and if it is greater than 250, it tends to stick.

（式中、MXLNGはセルの絶対最大長、AREAはセルの投影面積を示す）
このような不定形の粉体は粉砕によって得ることができる。品質的な安定性からは粉体の粒度分布は小さい方が望ましいので、粉砕後分級を行なうほうが良い。この場合、いわゆる粗粉カットあるいは微粉カットだけでなく、ほぼ正規分布を有しなおかつシャープであることが好ましい。

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)
Such an amorphous powder can be obtained by pulverization. Since it is desirable that the particle size distribution of the powder is small from the viewpoint of quality stability, it is better to perform classification after pulverization. In this case, it is preferable that not only so-called coarse powder cut or fine powder cut, but also a substantially normal distribution and sharp.

  Furthermore, the degree of unevenness of the powder itself can be cited as a factor governing the detachability of the powder. As an index representing the degree of unevenness of the powder itself, there is K-H2 represented by Formula-4.

（式中、PERIMEはセルの周囲長、AREAはセルの投影面積を示す）
K-H2が大きいほど粉体の表面凹凸が大きい（表面積が大きい）ということを意味し、本発明においては、105≦K-H2≦230であることが望ましい。

(In the formula, PERIME indicates the perimeter of the cell, and AREA indicates the projected area of the cell)
It means that the larger the K-H2, the larger the surface irregularity of the powder (the larger the surface area). In the present invention, it is desirable that 105≤K-H2≤230.

  In addition, there is an optimal relationship between the shape factor of the cell and the shape factor of the powder. That is, the relationship of K-1 <K-H1 or / and K-2 <K-H2 is very preferable because the balance of stable retention / desorption of powder is further improved.

  In the present invention, the kind of powder that is preferably used on the surface of the charging member is not particularly limited, and inorganic substances, organic substances, mixtures thereof, hybridized substances, and the like can be used. As a specific example, the surface resistance of a medium resistance substance (for example, metal oxide) powder or conductive powder (for example, carbon black, graphite, metal, etc.) is appropriately surface-treated to obtain a predetermined volume resistance value. Resin fine powder prepared by mixing conductive powders, resin, etc., and kneading and then pulverizing the powder adjusted to the range, the surface of the insulating powder conductive, and the volume resistance value adjusted to the predetermined range Examples thereof include resin fine powders prepared by mixing a polymer and a monomer with a conductivity-imparting material and then polymerizing. These may be composed of a plurality of materials, and may be a laminated structure or a mixture. Furthermore, you may use together.

  Since the powder on the surface of the charging member is subjected to external stress such as pressure and electric power, the problem of internal heat generation cannot be ignored. In addition, since friction with the photosensitive member is also generated, it is also affected by frictional heat. It is important that the characteristics and shape of the powder do not change due to these effects, and the powder preferably has a thermally stable structure. Therefore, the higher the melting point and the decomposition temperature, the more preferable the powder. Usually, the melting point and decomposition temperature may be 100 ° C. or higher, preferably 200 ° C. or higher, more preferably 300 ° C. or higher.

  Furthermore, since the powder comes into contact with a developer component present on the photoreceptor, a component derived from the outermost layer of the photoreceptor, or the like, it is more preferable that these are difficult to adhere to the powder surface. An example of achieving this object is, for example, surface treatment of powder. The surface treatment means is not particularly limited. For example, chemical treatment such as various coupling agent treatments (silane, titanium, aluminum, etc.), silicone treatment, isocyanate treatment, halogen treatment, etc., plasma There are physical treatments such as irradiation, electron beam treatment, etc.

  From this point of view, metal oxides are most preferable, and typical examples include tin oxide, titanium oxide, zinc oxide, antimony oxide, and the like, which can be used regardless of the crystal structure, the presence / absence or type of doping, and the like. However, among these, oxygen deficient tin oxide is most preferable, and the surface treatment with a silicone compound is more preferable in order to impart fluidity.

  These powders are preferably attached to the surface of the charging member in advance. There are no particular restrictions on the means for attachment, but it is important that the attachment be as uniform as possible. However, in order to maintain stable charging performance over a long period of time, it is necessary to appropriately replace the powder as described above. That is, it is necessary that the powder adhering to the surface of the charging member is detached and a new powder is supplied instead, and the repetition is continued stably. For this purpose, it is preferable to have a mechanism for supplying powder to the charging member. The mechanism for supplying the powder is not particularly limited and may be an independent mechanism for the main purpose of supply. However, since the apparatus tends to be large, a method using a developing machine is preferable. That is, it is desirable that the powder to be supplied is stored in the developing machine and is supplied to the electrophotographic conductive member with use. The powder may exist independently in the developing machine, but it is most desirable if it is configured as a developer component because it can be simplified, enhanced in function and stable in terms of apparatus and electrophotographic process. . In this way, in order to adhere the supplied powder to the surface of the charging member as uniformly as possible, the powder attached to or around the charging member is physically or electrostatically leveled. It is desirable to provide a means to do this.

  It is preferable that the powder adhering to the surface of the charging member in advance and the powder supplied from the developing machine are the same, but they may be different. If they are different, it is preferable that the various properties and materials such as shape, particle size, particle size distribution, and resistance are closer.

The charging member of the present invention only needs to have at least a layer made of a foam, and there are no particular restrictions on other configurations, materials, and shapes, but the contact state stability (static and dynamic) and From the viewpoint of production stability, a roller shape (charging roller) is common. For example, in a charging roller, it is common to provide a layer mainly composed of one or more polymer compounds directly or via an adhesive around a core bar as a support. The value is adjusted to 1 × 10 ³ Ω or more and 1 × 10 ¹⁰ Ω or less. An apparatus for measuring the electrical resistance value of the charging roller of the present invention is shown in FIG. The measurement is allowed to stand for 12 hours or more in the environment (temperature, humidity) and let it fully adapt. Then, under the environment, the charging roller is pressed against the metal drum with a specified load, while rotating at a specified speed and with a specified voltage. And the current flowing is recorded in a chart for a predetermined time as time passes. At this time, it is desirable that the outer diameter of the metal drum, the load, the applied voltage, the rotation speed of the metal drum and the charging roller, etc., be performed under the conditions of the electrophotographic apparatus using the charging roller. Therefore, the metal drum is made of stainless steel (the surface 10-point average roughness Rz is 5 μm or less), the outer diameter is 30 mm, the load Fd is 500 g on one side (1 kg in total), the rotation speed of the metal drum is 30 rpm, the rotation of the charging member Is driven by a metal drum and applied with a predetermined voltage (DC-500 V. The current value 30 seconds after the voltage application is read, and I (A) is taken, and the resistance value (Ω) of the charging roller is Rs = | V / I | = | −500 / I |

Although there is no restriction | limiting in particular as a support body, It is preferable if the electrical resistance is lower than the electrical resistance of layers other than a support body, and the intensity | strength is larger than the intensity | strength of layers other than a support body. In general, the electrical resistance value required for the support is 1 × 10 ¹ Ωcm or less. Of course, a lower value is preferable because power loss is reduced. Examples of such a support include metals such as iron, aluminum, stainless steel, copper, nickel, and chromium (preferably, metal plating such as chromium and nickel is applied on these) and conductive resins ( Any of those having conductivity in structure, those obtained by mixing a conductivity-imparting material with an insulating resin, etc. may be used.

  Further, the layer mainly composed of the polymer compound is not particularly limited as long as it is within the scope of the present invention. However, it is desirable that at least the outermost layer has a substantially foamed shape. The meaning of the substantially foamed shape means, for example, that the outermost layer of a layer mainly composed of a polymer compound is a foam, a film is formed on the surface of the foam, or the surface This refers to the case where the foamed shape of the foam is relatively reflected even after the treatment (FIG. 11).

  The foam is formed by generating bubbles by a physical or chemical foaming technique using a polymer compound such as rubber, thermoplastic elastomer, or resin. A foaming agent is added to form by a chemical foaming method. In order to form by physical foaming method, bubbles are generated mechanically in the raw material, but if it is left as it is, it tends to become a spherical shape, so external force that deforms the bubbles by rotating the roller itself, etc. It is also preferable to carry out at the same time. In this case, it is particularly suitable when the raw material is liquid, and it is necessary to adjust the additional external force in consideration of the viscosity of the raw material. In this way, in the case of the physical foaming method, additional means are required at the time of molding, whereas in the case of chemical foaming, the cells can be made amorphous by dealing with the material, so the equipment From the viewpoint of simplifying the processing machine, it is preferable to employ a chemical foaming technique. In any case, as necessary, conductivity imparting agents, vulcanizing (crosslinking) agents, chain extenders, anti-aging agents, stabilizers, plasticizers, softeners, various auxiliaries, catalysts, activators, and other various types. Add material and use.

  There are no particular restrictions on the means for making the cell shape irregular as in the charging member of the present invention, but typical examples include a method for controlling the shape of the foaming agent, the foaming speed and the vulcanization (crosslinking) speed. And a method of adjusting the balance.

  As a method for controlling the shape of the foaming agent, an amorphous foaming agent may be used, or the foaming agent may be dispersed in a state where it is secondarily aggregated to some extent. These blowing agents are desirably dispersed uniformly. However, it is generally quite difficult to uniformly disperse the foaming agent that has undergone secondary aggregation to some extent while maintaining the state as it is. That is, if the secondary agglomeration is to be maintained, the kneading must be soft, and as a result, the secondary agglomerates are likely to be poorly dispersed. If hard kneading is performed to sufficiently disperse the secondary agglomerates, Since the secondary agglomerates collapse and approach the primary particles, it is difficult to obtain the effects of the present invention. In order to improve such a phenomenon, it is necessary to set the kneading conditions in a balanced manner, but differences in the raw material lot and kneading environment (temperature and humidity), variations in the kneading process itself (time, pressure pattern, There is a case where it is inevitably influenced by the tolerance (mixing amount, etc.), leading to a variation in quality. In order to solve such a problem, it is preferable to perform a surface treatment of the foaming agent. If the surface treatment is performed in a state of a certain amount of secondary agglomerates, the surface treatment has a shape retention effect, so that the secondary agglomerates are uniformly dispersed while maintaining the shape of the secondary agglomerates in the kneading step. Can do. The surface treatment method is not particularly limited as long as the shape retention is improved, for example, coupling agent treatment or oil baking treatment, treatment with a silazane compound, treatment with a compound that reacts with active hydrogen such as isocyanate, fatty acid treatment, In view of versatility, various coupling agent treatments (silane-based, titanium-based, aluminum-based, etc.) and fatty acid treatments are preferred, but silane coupling agents are particularly desirable. Of these, aminosilane coupling agents are most preferred. In these methods, in addition to the kneading step, for example, even when the kneaded product has a share such as extrusion and injection, it is necessary to carefully select the processing conditions and the blending method so as to make the share as small as possible. As such a method, for example, a method of imparting slip property by dispersing a foaming agent in oil in advance to form a paste can be mentioned. According to this method, since the slip property can be imparted by the oil present around the foaming agent, an excessive load is not applied to the foaming agent at the time of kneading as compared with the case where the foaming agent is added as a powder as it is. It is preferable because the history of heat and pressure can be reduced, the initial shape can be easily maintained, and a phenomenon such as a decrease in decomposition temperature due to an excessive processing history can be reduced. In this method, it is preferable that the oil has a high viscosity because slip properties are easily obtained. Moreover, since the plasticizing effect becomes smaller as the oil generally has a higher viscosity, there is an advantage that, for example, the rate of decrease in hardness and strength can be reduced.

  Moreover, in order to obtain an amorphous foaming agent, it can be made irregular by optimizing the pulverizing means or the like in the powder forming process, or by heating and aggregating the primary particles. It goes without saying that the surface treatment may be applied to the amorphous foaming agent thus obtained. Furthermore, after the surface treatment is performed at the primary particle stage, it may be agglomerated by pressure or heating to form an irregular shape. Of course, it is needless to consider that the decomposition temperature is set high so that decomposition does not occur by heating, or the heating temperature is set low.

  In the method of adjusting the balance between the foaming speed and the vulcanization (crosslinking) speed, it is necessary to control the foaming speed and the vulcanization (crosslinking) speed, respectively, and to adjust both of them optimally. In the present invention, controlling the vulcanization (crosslinking) speed has two meanings: controlling the time until the rise of the torque rise in the rheometer or curast meter, and controlling the slope of the rise. In addition, controlling the foaming speed has two meanings: controlling the time until foaming starts and controlling the slope of rising. In order for both to be optimal, it is important that vulcanization (crosslinking) starts moderately earlier than the decomposition of the blowing agent, and that the slope of the curve after the rise is moderately greater for vulcanization than for foaming. The meaning of the curve of such a pattern is that the change in the torque increase with respect to the time change being heated is reasonably large. Even if heated at a certain temperature, partial temperature distribution is likely to occur, and the position and distance from the heat source, hot air flow path, The roller tends to have a temperature distribution due to the heat capacity of the heat medium. Accordingly, a difference in the degree of vulcanization (that is, viscosity) is likely to occur according to the temperature distribution. In such a state, an irregular cell shape is easily obtained as described above.

  The fact that vulcanization (crosslinking) starts moderately earlier than foaming means that a three-dimensional (vulcanization, cross-linking) reaction takes place to some extent before the decomposition of the foaming agent begins. This means that there is a part where the chemical reaction is occurring (or progressing) and a part where it is not occurring (or lagging). From a microscopic viewpoint, there are a high viscosity part and a low viscosity part. It means to coexist. This phenomenon can be caused by the way heat is transmitted (for example, the shape and thickness of the molded product, the surrounding heat medium, thermal conductivity, the state of contact with a good heat conductor such as metal), and the molecular structure (for example, vulcanization / Although it is affected by the reactivity, dispersion state, etc., where there is a crosslinking site, it always occurs during the period of transition from unvulcanized (crosslinked) to complete vulcanized (crosslinked). On the other hand, the foaming agent is decomposed by heating to generate a large amount of gas and generate bubbles in the rubber. Normally, when the foaming agent decomposes, the generated gas increases in volume at a stretch, but expands in volume while applying equal force around the foaming agent. In other words, in the state where the microscopic viscosity part and the low part coexist moderately, a state in which volume expansion occurs due to decomposition of the foaming agent appears. Even if it is applied, the amount of deformation varies due to the difference in microscopic viscosity of the surrounding rubber. In other words, the resistance increases in the portion having high viscosity against the pressure generated by the decomposition of the foaming agent, so that the amount of deformation decreases. In the portion having low viscosity, the resistance decreases, so the amount of deformation increases. As a result, the cell shape tends to be indefinite, and the cell wall thickness is likely to be uniform and thin, so that it is possible to obtain a foam having a low C hardness and a good C setting property. For this reason, the greater the difference in viscosity of the rubber around the foaming agent and the finer dispersion of parts with different viscosity differences, the greater the degree of irregularity, and the more irregularities there are, the more irregular the degree of irregularity. The degree increases. In addition, if vulcanization (crosslinking) starts moderately earlier than the decomposition of the foaming agent, the overall (macro) viscosity will also increase at the start of foaming, so the generated gas will be difficult to escape and foaming will occur. Since the cell diameter is large and the degree is high, a foam having a lower hardness can be obtained. In addition, the fact that the slope of the curve after the rise is moderately larger than the foaming of the vulcanization means that the generated gas is more difficult to escape, which is very preferable because it has the effect of further increasing the foaming degree. .

  As a measure of vulcanization (crosslinking) and decomposition of the blowing agent, it can be roughly judged from the rheometer characteristics of the kneaded product as shown in FIG. That is, it is necessary that the difference (tc−tv) between the rise time (tv) of the torque increase due to vulcanization and the rise time (tc) of the foaming pressure rise at a certain temperature T ° C. Usually, when T = 160 ° C., 5 (min) <tc-tv <20 (min) is desirable, and when T = 150 ° C., 7 (min) <tc-tv <40 ( Min), when T = 170 ° C., it is highly desirable if 1 (min) <tc−tv <15 (min) is also satisfied. In addition, it is more preferable that tc is smaller than the time when the vulcanization torque becomes maximum.

  On the other hand, if the decomposition of the foaming agent starts earlier than the vulcanization (cross-linking) or without much difference, the rubber around the foaming agent is unvulcanized and has low viscosity and good gas permeability. The generated gas is easy to escape. Therefore, the degree of foaming becomes small and the foam becomes hard, which is not suitable.

  In addition, when vulcanization (crosslinking) starts much earlier than decomposition of the blowing agent, vulcanization (crosslinking) has progressed considerably at the time when decomposition of the blowing agent occurs. It is presumed that the partial viscosity difference is small. In this state, if the foaming agent decomposes and expands while applying equal force to the surroundings, the variation in resistance force is reduced, and as a result, the cells are liable to be spherical, which is not preferable. Furthermore, foaming after vulcanization (crosslinking) has progressed too much is not preferable because the elongation of the vulcanization (crosslinking) portion cannot follow the volume expansion and may lead to tearing of the foam.

  In addition, if the slope of the rise of vulcanization (crosslinking) is too large, vulcanization (crosslinking) proceeds at a stretch, so that the vulcanization (crosslinking) proceeds fairly uniformly at the time of decomposition of the foaming agent. As a result, the same problem as in the case where vulcanization (crosslinking) starts much earlier than the decomposition of the blowing agent occurs.

  In order to obtain torque increasing characteristics suitable for the present invention, a system using sulfur as a vulcanizing agent and an organic vulcanization accelerator is preferable. In this case, it is important that the amount of sulfur is greater than 0 parts by weight and 1 part by weight or less (unless otherwise noted, it means the added part by weight relative to 100 parts by weight of rubber. The same applies hereinafter) A low sulfur vulcanization system in which the amount of sulfur is 0.1 to 0.5 parts by weight is very desirable. As the organic vulcanization accelerator, for example, thiuram, carbamate, thiazole, etc. are used, and it is desirable to adjust the vulcanization speed by appropriately combining a plurality of these. The addition amount of the organic vulcanization accelerator is preferably 0.1 to 5 parts by weight, and it is necessary that the total amount is 1.5 parts by weight or more and 10 parts by weight or less. When the amount of sulfur is 1.5 parts by weight or more, the inclination of the vulcanization rise becomes too large, and even if the amount of the vulcanization accelerator is adjusted, it cannot be controlled and the cell becomes spherical, which is not suitable. From this point of view, the foams disclosed in JP-A-2001-42605 and JP-A-2001-72806 are not preferable because the cell shape is spherical (K-1 <110). Moreover, when there is too much addition amount of a vulcanizing agent or a vulcanization accelerator, it tends to produce bloom and is not preferable.

  As another means, a method of using a plurality of polymer compounds and making a difference in viscosity and vulcanization (crosslinking) speed can be mentioned. For example, a technique of mixing a rubber, an elastomer, or a resin with different viscosities or types to form a sea-island structure may be used. In this case, it is preferable that the viscosity difference is larger and the compatibility is smaller. The blending of the sea part and the island part may be the same or different, but it is more preferable if the vulcanization speed and the foaming speed are controlled as described above in each of the sea part and the island part. Furthermore, for example, a combination of a low sulfur vulcanization system (or a sulfur-free vulcanization system, that is, 0 part by weight of sulfur) and a high sulfur vulcanization system, that is, a sulfur content of 0 part by weight, or sulfur vulcanization And other reaction forms (for example, a combination of peroxide crosslinking and urethanization reaction, etc.), etc., may be combined with different vulcanization (crosslinking) speeds and mechanisms.

  In addition, as another means, there is a method of increasing the activity of vulcanization (crosslinking). Alkylene glycols have the effect of activating and accelerating vulcanization, and are therefore suitable for adjusting the vulcanization (crosslinking) rate. Representative examples of alkylene glycols include diethylene glycol (DEG) and polyethylene glycol (PEG). PEG has various degrees of polymerization, and there are various types from a liquid to a solid at room temperature. In general, the activation effect tends to decrease as the degree of polymerization increases. DEG and PEG with a relatively low degree of polymerization have a large active effect, but are difficult to handle because they are liquid at room temperature. A large amount of PEG having a relatively high degree of polymerization needs to be blended. PEG having a molecular weight of 2000 to 6000 has a good balance between ease of handling and activation effect. In particular, this means is effective when an acidic additive as described above is used.

  When controlling vulcanization, it is necessary to pay attention to the pH of the compound. A compound is a mixture obtained by adding various additives to a raw material polymer compound, but vulcanization (crosslinking) is generally promoted in a basic atmosphere and inhibited in an acidic atmosphere. Therefore, although depending on the amount added, if an acidic additive is used, vulcanization becomes too slow and it becomes difficult to control the balance with foaming. For example, although carbon black and silica range from acidic to basic, adding 10 parts by weight or more of the acidic type causes an effect. In such cases, a method of increasing the activity of vulcanization (crosslinking) is also used. Sufficient attention is required such as

  On the other hand, in order to control the foaming speed, the type of foaming agent, shape, decomposition temperature, particle size, particle size distribution, presence / absence of surface treatment and degree of treatment, type of surface treatment agent, foaming aid, foaming promotion or delay effect It is necessary to consider the combined use of materials having There are no particular restrictions on the blowing agent used, and known materials (for example, azo compounds, nitroso compounds, hydrazine derivatives, semicarbazide compounds, azide compounds, tetrazole compounds, isocyanate compounds, bicarbonates, carbonates, nitrites, hydrogens) However, it is preferable to contain at least an azo compound because the foaming speed can be easily controlled. A typical example of the azo compound is azodicarbonamide (ADCA). Of course, other foaming agents include inorganic foams (for example, sodium bicarbonate, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, etc.), nitroso compounds, sulfonyl hydrazides (typically p, p'-oxybis (benzene) Sulfonyl hydrazide), which is referred to as OBSH), water, etc. may be used in combination, but ADCA is preferred (the amount of ADCA added is the largest in the foaming agent), preferably ADCA Alone is most preferred. Further, it is preferable to use a foaming agent having a small particle size when attempting to increase the cell diameter, and to use a foaming agent having a large particle size when attempting to reduce the cell diameter. Further, it is preferable to use a foaming agent having a large particle size distribution when increasing the cell diameter distribution, and using a foaming agent having a small particle size distribution when reducing the cell diameter distribution. Moreover, when performing surface treatment, there is no restriction | limiting in particular in the kind of surface treating agent, a surface treatment method, etc. Types of surface treatment agents include, for example, coupling agent treatment, oil baking treatment, treatment with silazane compounds, treatment with compounds that react with active hydrogen such as isocyanate, fatty acid treatment, etc. Ring agent treatment (silane-based, titanium-based, aluminum-based, etc.) and fatty acid treatment are preferred, but silane coupling agents are particularly desirable. Of these, aminosilane coupling agents are most preferred. Examples of the surface treatment method include a wet treatment and a dry treatment, and the treatment is performed under appropriate conditions, but the dry treatment is generally preferable from the viewpoint of anisotropy of foaming. That is, in the wet processing method, since the surface of the powder (foaming agent) is processed relatively uniformly, the processing agent is coated relatively uniformly, whereas in the dry processing method, the powder (foaming agent) This is because the surface treatment state tends to be relatively uneven, and a portion coated with the treatment agent and a portion not covered with the treatment agent are likely to be formed. When heat is transmitted from the outside in such a state, the temperature of the foaming agent does not rise so much in the coated part because the coated part acts as a cushioning material, whereas in the uncoated part, heat is directly applied. Temperature is easy to rise to be transmitted. That is, the high temperature portion and the low temperature portion coexist on the foam surface, and even if the high temperature portion reaches the decomposition temperature and decomposes, the low temperature portion does not decompose. Therefore, the pressure to the surroundings accompanying the decomposition of the foaming agent is partially different slightly. Furthermore, since the force that suppresses volume expansion by the reinforcing effect of the treatment agent works toward the inside in the covering portion, the force exerted on the outside is relatively smaller than that in the uncovered portion. Due to these effects, even if the foaming agent is decomposed, the force exerted on the surroundings is not necessarily equal (foaming anisotropy), and as a result, the shape of the cell tends to be irregular.

  It is also effective to use additives that affect the foaming rate. In general, by using various foaming aids, the foaming speed can be adjusted to increase. Some metal oxides also affect the foaming rate. Typical examples of such metal oxides include zinc oxide and magnesium oxide. Among them, since zinc oxide is usually added in a certain amount as a vulcanization acceleration aid, the foaming temperature after compounding is lower than the decomposition temperature of the foaming agent alone. Although the degree of reduction varies depending on the type of foaming agent, in the case of ADCA, it often falls by 20 ° C or more. Utilizing this phenomenon, the foaming rate can be adjusted by adjusting the amount of zinc oxide added. Increasing the amount of zinc oxide increases the foaming speed, and decreasing it decreases it.

  However, as already mentioned many times, it is difficult to achieve the effect of the present invention by controlling only with the foaming agent or controlling only with the vulcanizing system. An optimal combination is required.

The polymer compound used for the foam of the charging member of the present invention is not particularly limited, but preferably ethylene propylene rubber (EPM, EPDM), silicone rubber, epichlorohydrin rubber, nitrile rubber (NBR), urethane compound, main chain Among them, a polymer compound having an ether bond can be exemplified, and EPDM is particularly preferred. Since EPDM is a non-polar rubber, it is compatible with developer components (toners, external additives, carriers, etc.), photoreceptor components (substances caused by scraping of the outermost layer) and media components (paper dust). As a result, the adhesion of these substances to the surface of the charging member is reduced, so that it can be used for a long time. Furthermore, since EPDM has a stable chemical structure, it is highly resistant to ultraviolet rays, ozone, and by-products resulting from these, and can be used for a longer period of time. In addition, because it is inexpensive and excellent in workability, it can lead to downsizing and simplification of construction equipment and improvement of productivity, so that stable quality can be supplied, which is suitable for cost reduction. EPDM is a general term for a copolymer of ethylene, propylene and a third component (such as ethylidene norbornene or dicyclopentadiene). The content of ethylene and propylene, the type and content of the third component, the molecular weight after polymerization / There are various grades depending on molecular weight distribution / molecular structure. In order to make the shape of the cell amorphous in the foam using EPDM, the higher the content of the third component (iodine value) or the higher the reactivity of the third component, the better. The higher the iodine value, or the higher the reactivity, the sharper the start of vulcanization (the greater the slope). Therefore, as described above, the difference in viscosity due to the difference in the progress of vulcanization increases. This is because there is a further effect on the amorphous form. Further, such EPDM has a manufacturing advantage that vulcanization tends to be tight, so that it is suitable for improvement of C set, high cycle vulcanization is possible and high productivity is suitable. Further, in order to achieve fine foaming in a foam using EPDM, the higher the Mooney viscosity of the raw material EPDM used or the kneaded product, the better. The higher the Mooney viscosity, the easier it is to obtain a high expansion ratio because the air bubbles are more easily taken into the interior when foaming, and it is easy to obtain a high expansion ratio. This is because the cell becomes small due to the strong resistance, and in combination, high foaming ratio / fine foaming can be obtained. To obtain this effect, use ethylidene norbornene as the third component, EPDM with an iodine value of 20 or more, Mooney viscosity (ML _{1 + 4} (100 ° C)) of 50 or more, and propylene content of 45% by weight or less. It is most appropriate to do.

  There is no restriction | limiting in particular in the manufacturing method of the foam used for the electroconductive member of this invention, A well-known method may be sufficient. For example, the rubber is formed into a tube shape using an extruder and the core metal is inserted after vulcanization, or when the rubber is extruded, the core metal is supplied at the same time to form a rubber layer around the core metal and then added. There are a method of vulcanizing, a method of using a mold, etc., and the rubber layer may be one layer or two or more layers. In particular, when manufacturing using an extruder, EPDM having a high ethylene content and a composition distribution is suitable, and it is preferable to set the extrusion conditions at a high temperature within a range that does not affect vulcanization. Examples of vulcanization means include vulcanization can vulcanization, continuous vulcanization, press vulcanization, injection, etc., and energy sources include heat, electron beam, microwave, (near) ultraviolet, (far) infrared, etc. Various means can be used. Of course, it is not limited to these.

  Since the charging member manufactured in this manner has stable characteristics over a long period of time, it is suitable for reuse. In particular, in the configuration where the powder adheres to the surface, the powder exists between the charging member and the photosensitive member, so that it acts as a kind of buffer material, and the physical and chemical influence on the charging member can be reduced. This has the advantage of further extending the life of the charging member and, as a result, facilitates repeated use and recycling.

The charging member of the present invention is not limited by the charging method or method, but in particular, the surface of the charging member has a so-called medium resistance region having an electric resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less. Extremely effective when used in electrophotographic devices that charge a photosensitive member to a predetermined potential by applying powder and applying a relatively low voltage to the charging member to transfer the charge directly from the charging member to the photosensitive member. Can be obtained. In this electrophotographic apparatus, when the absolute value of the DC voltage (V) applied to the charging member is | Vc | and the absolute value of the dark portion potential (V) of the photoreceptor is | Vd |, 0 <| Vc | ≦ The photosensitive member starts charging at 100, and 0.7 ≦ | Vd | / | Vc | <1.3 when 100 <| Vc | ≦ 1500. That is, it is suitable for a charging method that does not have a clear discharge threshold. In such an electrophotographic apparatus, it is preferable to reversely rotate the charging member and the photoreceptor in order to improve charging performance.

There is no limitation on the photoreceptor used in the present invention, and either an inorganic photoreceptor or an organic photoreceptor can be used, but there is a preferable form particularly in combination with a charging method. That is, in the charging method having no clear discharge threshold as described above, it is important to reduce the volume resistance of the outermost layer of the photoreceptor. In such a charging method, since the charge moves from the charging member through the contact portion between the charging member and the photoconductor, the volume resistance value of the outermost layer of the photoconductor is 5 × 10 5 in order to obtain good charging performance. It is preferably ¹¹ Ωcm or more and 5 × 10 ¹³ Ωcm or less, and more preferably 1 × 10 ¹² Ωcm or more and 1 × 10 ¹³ Ωcm or less. In order to obtain such a photoreceptor, the outermost layer contains 5 to 200 parts by weight of powder having an electric resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less to 100 parts by weight of the binder resin. It is desirable that the average particle size is 0.0001 μm or more and 0.1 μm or less. Although there is no restriction | limiting in particular in such powder, For example, oxides, such as a titanium oxide, a zinc oxide, a tin oxide, and an antimony oxide, are preferable, and especially a tin oxide is the most preferable. It is preferable to impart hydrophobicity to this powder by coupling treatment, silicone treatment or the like because environmental fluctuations can be reduced. These powders are represented by Formula-6, and the shape factor K-D1 of the powder contained in the outermost layer of the photoreceptor represented by Formula-5 is 110 ≦ K-D1 ≦ 250. The shape factor K-D2 of the powder contained in the outermost layer of the photoreceptor is preferably 105 ≦ K-D2 ≦ 230, since better charging performance can be obtained.

（式中、MXLNGはセルの絶対最大長、AREAはセルの投影面積を示す）

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)

（式中、PERIMEはセルの周囲長、AREAはセルの投影面積を示す）
感光体最外層に含有する粉体の電気抵抗値が5×10¹¹Ωｃｍ未満であると高湿度環境において潜像流れによる画像不良が発生するので好ましくない。一方、5×10¹³Ωｃｍより高い抵抗値では、放電を利用した場合においては特に問題はないが、上述したような明確な放電閾値を有さない帯電方法に用いる場合には、帯電が不十分になるので好ましくない。

(In the formula, PERIME indicates the perimeter of the cell, and AREA indicates the projected area of the cell)
If the electric resistance value of the powder contained in the outermost layer of the photoreceptor is less than 5 × 10 ¹¹ Ωcm, image defects due to the latent image flow occur in a high humidity environment, which is not preferable. On the other hand, with a resistance value higher than 5 × 10 ¹³ Ωcm, there is no particular problem when using discharge, but charging is insufficient when used in a charging method that does not have a clear discharge threshold as described above. This is not preferable.

  Although the reason is unknown, there is a preferable combination between the powder contained in the outermost layer of the photoreceptor and the powder adhering to the surface of the charging member from the viewpoint of improving the long-term stability of the charging performance. For example, 0.5 ≦ K-1 / K-D1 ≦ 2, 0.5 ≦ K-2 / K-D2 ≦ 2, the particle size (G-1) of the powder around the charging member and the powder contained in the outermost layer of the photoreceptor The average particle size (G-D1) is 0.1 ≦ G-1 / G-D1 ≦ 10, the electric resistance value of the powder around the charging member (ρ-1) and the electric power of the powder contained in the outermost layer of the photoconductor It is preferable that the resistance value (ρ−D1) has a relationship of 0.1 ≦ ρ−H1 / ρ−D1 ≦ 10. Of course, it is most preferable that both are the same kind.

On the other hand, the thinner outermost layer of the photoreceptor is suitable for refining the latent image. Specifically, the thickness is preferably 0.001 μm or more and 10 μm or less. However, in particular, a powder in a so-called medium resistance region having an electric resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less is adhered to the surface of the charging member, and a relatively low voltage is applied to the charging member to charge the charging member. In order to use the method in which the photosensitive member is charged to a predetermined potential by directly moving the charge from the member to the photosensitive member, the relative contact area (or contact frequency) of the contact portion between the charging member and the photosensitive member is increased. This is an important factor for obtaining good initial charging characteristics. For this purpose, it is desirable to reversely rotate the charging member and the photosensitive member, but on the other hand, the frictional force increases, so that the wear of the photosensitive member is promoted. Thus, there is a tendency that the wearability and the subtlety of the latent image are contradictory. In order to solve these problems, it is highly desirable to increase the hardness of the outermost layer of the photoreceptor. There are various means for increasing the hardness, but there is an advantage that it has a wide range of options and the state can be easily controlled. In order to perform three-dimensional crosslinking, a reaction energy may be imparted using a polymer, oligomer, or monomer having a reaction site. There are no particular restrictions on the reaction site, structure, or reaction mode, but it is preferable that the crosslinking is tight and the degree of freedom of the crosslinking chain is small. The reaction energy to be applied is not particularly limited, and various materials such as heat, ultraviolet rays, infrared rays, and electron beams can be used. However, heat and electron beams are most preferable from the viewpoint of simplicity. On the other hand, from the viewpoint of productivity, it is important to obtain a predetermined cross-linked state in a short time. For this purpose, it is desirable to use a catalyst and a reaction accelerator in combination. From such a viewpoint, it is most suitable that the outermost layer of the photoreceptor is mainly composed of an acrylic resin.

  The toner used in the electrophotographic apparatus of the present invention is not particularly limited, and known toners (either magnetic / nonmagnetic, spherical / indeterminate, polymerization / pulverization) can be used. In particular, when a charging member having a structure in which powder is attached around the charging member and rotating in the counter direction with the photosensitive member, a combination of the conductive member of the present invention and a new effect that the width of toner to be used is widened. Remarkably obtained. That is, the following features are manifested by setting the cell shape within the scope of the present invention. First, since a sponge having a lower hardness than before can be obtained, the pressure applied from the charging member can be further reduced. In addition, since there is a foamed portion on the surface of the charging member, the toner hardly adheres to the surface of the charging member due to an air layer present in the foamed portion. Furthermore, especially in the configuration having powder on the surface, not only is this effect more effective, but also uneven adhesion can be reduced. Such effects synergistically make it possible to use even low Tg toners that were difficult to use in the past. Specifically, any toner having a Tg of 35 ° C. or higher and 90 ° C. or lower can be used in combination with the conductive member of the present invention, so that an electrophotographic apparatus excellent in low-temperature fixability can be obtained. . That is, an electrophotographic apparatus suitable for energy saving could be realized. Such toner preferably has a weight average particle size of 10 μm or less, more preferably 8 μm or less, and even more preferably 5.5 μm or less. Especially, it is optimal when a magnetic toner is used. This is because the magnetic toner contains iron oxide inside and thus is hard to some extent and is difficult to be deformed even when pressure is applied from the charging member. From such a viewpoint, the toner is preferably indefinite. That is, in the case of a spherical toner, the toner characteristics are likely to change when deformed by pressure, but in the case of an indefinitely shaped toner from the beginning, it is presumed that the influence is relatively small even if the shape is further changed by pressure. The

  As an index indicating the shape of the toner, there are a toner shape factor K-T1 represented by Formula-7 and a toner shape factor K-T2 represented by Formula-8, and 120 ≦ K−T1 ≦ 240, 115 ≦ K−T2 ≦ 230 is preferable.

（式中、MXLNGはセルの絶対最大長、AREAはセルの投影面積を示す）

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)

（式中、PERIMEはセルの周囲長、AREAはセルの投影面積を示す）
加えて、帯電部材表面の粉体とトナーとの組み合わせで、0.5≦K-H1／K-T1≦2、0.5≦K-H2／K-T2≦2、帯電部材表面の粉体の粒径（G-1）と現像材の粒径（G-T1）とが、0.01≦G-H1／G-T1≦0.5、等の関係にあるとより長期にわたって使用できるので更に好ましい。

(In the formula, PERIME indicates the perimeter of the cell, and AREA indicates the projected area of the cell)
In addition, by combining the powder on the charging member surface with the toner, 0.5 ≦ K−H1 / K−T1 ≦ 2, 0.5 ≦ K−H2 / K−T2 ≦ 2, the particle size of the charging member surface powder ( It is more preferable that the relationship between G-1) and the particle size (G-T1) of the developer is 0.01 ≦ G-H1 / G-T1 ≦ 0.5 because it can be used for a longer period of time.

  Such shape stability is better as the magnetic material is uniformly dispersed. In the case of a toner manufactured by a polymerization method, a resin layer (a layer containing no or a small amount of magnetic material) is likely to be formed on the surface, whereas in a toner manufactured by a pulverization method, a magnetic material appears on the surface. A toner produced by a pulverization method is more preferable because it can be said to be more uniform.

  The material of the toner is not particularly limited, but a toner mainly composed of a styrene acrylic resin can be cited as an example that can provide an excellent effect in combination with the charging member of the present invention. The same applies to other physical properties of the toner. For example, the acid value, MI, viscoelastic properties, specific gravity, bulk density, fluidity and the like are not particularly limited.

  Further, there is no particular limitation on the developing method, and it can be suitably used for both a contact type and a non-contact type. In general, a contact developing system using an elastic roller is used for an electrophotographic apparatus for printing a color, but the mechanism is complicated. On the other hand, a jumping development system is suitable for an electrophotographic apparatus that prints only black because of its simplicity. In this case, magnetic toner is used. In any of these cases, the charging member of the present invention can exhibit an excellent effect. However, in particular, when a jumping development method is used, an irregularly shaped toner is often used, and physical properties of the toner are not limited. Therefore, it is more preferable that a toner having a lower Tg can be used.

  In addition, the transfer member is not particularly limited, and can be suitably used for both a contact type and a non-contact type. As a typical contact type, there is a method using a transfer roller made of solid or sponge, but any method can be used. A soft sponge roller is preferable from the viewpoint of reducing physical damage to the toner in the transfer. On the other hand, since the transfer roller also has a role of transporting the material to be transferred, solid is preferable in order to obtain stable transportability over a long period of time. In particular, when the material to be transferred is a slippery material such as an OHP film, it is desirable to use a material that can provide a firm grip, and wear resistance (especially if magnetic toner is used, it will wear out). From this point of view, it is desirable to use a sponge that is easy to secure a nip, and the outermost part is solid (solid or less foamed than the inner part). Is most preferred. Of course, it is needless to say that the electroconductive member of the present invention can be suitably used in an electrophotographic apparatus employing an intermediate transfer system.

  Further, there is no limitation on the cleaning method for removing the residue (for example, developer component or transfer material component) on the member to be charged. Recently, an independent cleaning mechanism such as a cleaning blade (for example, a cleaning blade or a cleaning roller) is contacted with a photosensitive member to remove a residue on the photosensitive member physically or electrostatically to reduce the size of the apparatus. (A so-called cleaner-less system) and a mechanism for collecting with a developing machine (so-called simultaneous development cleaning) has been studied. In the cleanerless system, the residue on the charged body is larger than that in the case where there is a cleaning blade. Therefore, if the charging process is started as it is, it becomes a deposit on the surface of the charging member. In order to reduce this, it is effective to attach the powder to the surface of the charging member. By adopting such a configuration, the adhering material once attached to the charging member can be discharged again onto the object to be charged. It becomes easy. At this time, by adjusting the potential of the adhering substance to a predetermined value with a predetermined bias, it is possible to collect it by the developing device. As described above, the charging member of the present invention is particularly useful for an electrophotographic apparatus using a cleaner-less system. Further, it is more preferable to add a function of separating the collected material in the developing machine because the powder supplied from the developing machine can be reused.

  In addition, there is no particular limitation in the fixing process. Fixing part such as light pressure fixing system that reduces the pressure on the toner, softening of the fixing member such as sponge, belt or film, shortening the fixing nip passage time by improving thermal conductivity, etc. In the electrophotographic apparatus in which the pressure factor is reduced, it contributes to further lowering the toner Tg, which is preferable because it can contribute to further energy saving. Among these, a fixing method using a film is particularly preferable because it is effective in shortening the time required to reach a predetermined temperature and effectively using heat.

  For members that may apply pressure to the toner, such as charging members, developing members, transfer members, cleaning members, fixing members, etc., if various surface treatments are performed to improve releasability and slipping, preferable.

  The electrophotographic apparatus or process cartridge of the present invention can use a plurality of the charging members of the present invention, but it is important to combine them with optimum process conditions so that the function of the charging member can be sufficiently exhibited.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these.

  As described above, according to the present invention, it is possible to obtain an elastic body having both high foaming, low hardness, and good C set. Accordingly, it is possible to obtain a charging member having a very excellent charging performance and an apparatus using the same, in any charging system.

  In addition, when the charging member of the present invention has a powder adhered to the surface, a good exchangeability of the powder can be stably obtained.

  Therefore, in particular, a method in which a relatively low voltage is applied to the charging member and the charge is directly transferred from the charging member to the photoconductor without substantially utilizing discharge, and a cleanerless method or a cleanerless method. It is most suitable for an electrophotographic apparatus. Further, in such a system, the relative rotation ratio between the photoconductor and the charging member can be reduced, so that the durability is improved and the degree of freedom in mechanical design is increased, which is very preferable.

  The charging member, the powder adhering to the charging member surface, the electrophotographic apparatus, the photosensitive member, and the developer used in this example were prepared as follows.

(Charging member)
<Charging member-1>
First, a compound for a charging member was prepared.

  100 parts by weight of EPDM (EP65 made by JSR), 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 12 parts by weight of conductive carbon black (Ketjen Black EC made by Lion), SRF carbon black (Shiest S made by Tokai Carbon Co., Ltd.) ) 55 parts by weight, 5 parts by weight of specially treated calcium oxide (VESTA-BS manufactured by Inoue Lime), 2 parts by weight of PEG6000, 75 parts by weight of paraffin softener (Diana Process Oil PW-150, manufactured by Idemitsu Kosan Co., Ltd.) The mixture was kneaded with a kneader to obtain EPDM batch-1. This was left to stand overnight in a cool dark place maintained at 20 ° C. for aging, and then a vulcanization system and a foaming system were added and sufficiently kneaded using a sufficiently cooled open roll to obtain a compound (E-1).

  In Charging Member-1, the vulcanization system is 0.25 parts by weight of sulfur, 2.5 parts by weight of Noxeller (registered trademark) M, 1.5 parts by weight of Noxeller (registered trademark) BZ, 1.5 parts by weight of Noxeller (registered trademark) TRA, and Noxeller (registered trademark). ) 1.5 parts by weight of TS, and the foaming system was 45 parts by weight of surface-treated ADCA paste. The surface-treated ADCA paste was prepared as follows. First, treatment agent A was prepared by diluting a silane coupling agent (γ-aminopropyltriethoxysilane) with acetone so that the weight ratio would be 10%. Next, 650 g of the processing agent A was uniformly sprayed while stirring 1 kg of the foaming agent ADCA (Vinole AC # 3 manufactured by Eiwa Kasei Kogyo Co., Ltd.) in a rotary mixer, and then heated to 60 ° C. and dried. Furthermore, after being kept rotating at 30 ° C. for 6 hours, it was taken out from the mixer to obtain a surface-treated ADCA. The decomposition temperature after the surface treatment was measured and found to be 205 ° C.

  Finally, the surface-treated ADCA was dispersed in a high-viscosity oil paraffin softener (Diana Process Oil PW-430 manufactured by Idemitsu Kosan Co., Ltd.) at a weight ratio of 1: 1 to obtain a surface-treated ADCA paste. The main combinations of the materials used are shown in Table-1 and Table-2.

  Next, a conductive adhesive was applied to a metal core (nickel plated on iron) having a length of 252 mm and a diameter of 6 mm. The application range of the conductive adhesive is 230 mm, and both ends are 11 mm uncoated portions. While extruding the rubber compound 1 to an outer diameter of 20 mm with an extruder, the unvulcanized roller having the rubber compound 1 extending over a length of 240 mm around the core metal by supplying the core metal coated with a conductive adhesive in advance and simultaneously extruding it. Got. At this time, both ends of the rubber compound 1 are located outside the adhesive application portion, and the core metal is exposed at both ends of 6 mm.

  The unvulcanized roller is left in an oven at 160 ° C. for 30 minutes for primary vulcanization, then taken out and cooled once. Then, it is left in an oven at 165 ° C. for 30 minutes for secondary vulcanization. This further strengthens the adhesion. After standing for one day, both ends were cut and removed to adjust the rubber to 230 mm. Since both ends were not coated with an adhesive on the core, removal after cutting was easy. Next, the circumference | surroundings of rubber | gum were grind | polished and the outer diameter was set to 18.0 mm and the charging member 1 which has a foam was obtained. Since the used grindstone has a width of 280 mm and is longer than the roller length, the grindstone can be polished once without traversing the grindstone. However, in order to reduce stress and chatter, the shape was stabilized by reciprocating about 20 mm left and right 5 times just before the grindstone was separated from the roller. The rotation direction of the grindstone surface is opposite to the rotation direction of the roller and abuts in the counter direction. Therefore, as a grinding | polishing state of a roller surface, it has the grinding | polishing shape which fluttered in the downstream direction with respect to the direction where a roller rotates with a grinding machine. The peripheral speed of the grindstone surface is preferably faster than the peripheral speed of the roller surface.

  The characteristics of the charging member 1 thus obtained were measured as follows.

(A) Cell shape factor (K-1, K-2)
An arbitrary portion of the charging member foam part is cut to create a cut surface of the foam. At this time, there is no particular limitation on the cutting method, but it is preferable to cool below the glass transition point (Tg) of the foam because the work is easy. Next, using FE-SEM (S-800) manufactured by Hitachi, Ltd., 40 cell images in which the cross section of the foam was magnified 1000 times were randomly sampled, and the image information was manufactured by Nicole via the interface. Analysis was performed by introducing the image analysis apparatus (Luzex III), and values obtained from the above-described Expression-1 and Expression-2 were defined. In the present invention, as a means for easily expressing such a three-dimensional cell shape, it is made two-dimensional by observing the cell cross section, and the surface irregularity (surface area) is expressed as the perimeter, as a sphere as a circle. is there.

（式中、MXLNGはセルの絶対最大長、AREAはセルの投影面積を示す）

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)

（式中、AREAはセルの投影面積、PERIMEはセルの周囲長を示す）
のようにして得られた、40個のK-1およびK-2を単純（算術）平均して、帯電部材のK-1、K-2とした。その結果、帯電部材-1のK-1は130、K-2は125であった。表-4に示す。

(In the formula, AREA indicates the projected area of the cell and PERIME indicates the perimeter of the cell)
The 40 K-1 and K-2 obtained as described above were simply (arithmetic) averaged to obtain charging members K-1 and K-2. As a result, K-1 of charging member-1 was 130, and K-2 was 125. It is shown in Table-4.

(B) Perfect Circle Equivalent Cell Diameter and Ratio The projected circle equivalent cell diameter obtained from the projected area of the cell uses the projected area (AREA) obtained when measuring the shape factors K-1 and K-2. Assuming that the diameter with an area of (AREA) is the equivalent circle diameter (L _ss ), π × (L _ss / 2) ² = (AREA) and L _ss = 2 × ((AREA) / π) ^Obtained at ^1/2 . In the 40 L _ss thus obtained, the numbers in the range of 30 μm to 300 μm or less and 50 μm to 150 μm were counted, and the number% of each was determined. Specifically, 2 for L _ss = 20 μm, 2 for L _ss = 40 μm, 6 for L _ss = 60 μm, 16 for L _ss = 90 μm, 8 for L _ss = 130 μm, and L _ss = 160 μm Since there were two L _ss = 190μm and two L _ss = 250μm, the ratio of 30μm to 300μm in charging member-1 is (38/40) × 100 = 95% The ratio of 50 μm to 150 μm was (30/40) × 100 = 75% by number. Shown in Table-4.

(C) Cell wall thickness Similarly, the cell wall thickness was obtained from the image information obtained by randomly sampling around 40 cell images magnified 1000 times. Note that the value of one cell wall is expressed by a simple average of the maximum value and the minimum value, and the cell wall of the charging member is obtained by simply averaging the values of the 40 cell walls. As a result, the thickness of the cell wall of the charging member-1 was 10 μm. It is shown in Table-4.

<Charging member-2-7>
Charging members-2 to 8 were obtained in the same manner as the charging member-1, except that the compounds (E-2 to 7) were used instead of the compound (E-1) used for the charging member-1. Details are shown in Tables 1 and 2.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member -8-15>
Charging members -8 to 15 were obtained in the same manner as charging member-1, except that the vulcanization temperature or / and the foaming system were changed. Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member -16-19>
Charging members -16 to 19 were obtained in the same manner as the charging member-1, except that the primary vulcanization method was changed from oven heating to vulcanization can vulcanization and / or the treatment of the foaming agent was changed. Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging members -20, 21>
Charging members -20 and 21 were obtained in the same manner as the charging member-16 except that the type of EPDM was changed. Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-22>
Charging members -20 and 21 were obtained in the same manner as the charging member-16 except that the amount of zinc oxide added was changed to 10 parts by weight. Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-23>
Propylene oxide and ethylene oxide were randomly added to glycerin to produce a polyether polyol having an oxyethylene unit content of 14% by weight, a functional group number of substantially 3, a weight average molecular weight of 5000, and an OH value of 60 mgKOH / g. This polyether polyol and a polytetramethylene ether glycol having a weight average molecular weight of 3000 and an OH value of 60 mgKOH / g were mixed in an equivalent amount by weight to prepare a mixed polyol. To 100 parts by weight of this mixed polyol, 5 parts by weight of conductive carbon black (Ketjen Black EC manufactured by Lion Corporation) and 35 parts by weight of SRF carbon black (Shiest S manufactured by Tokai Carbon Co., Ltd.) are sufficiently dispersed and mixed with carbon. A polyol was obtained.

  Next, diphenylmethane diisocyanate and urethane-modified diphenylmethane diisocyanate were mixed in an equivalent amount by weight to prepare mixed isocyanate (isocyanate group content 30 wt%).

  Further, 150 parts by weight of a carbon dispersion mixed polyol, 100 parts by weight of a mixed isocyanate, and 20 parts by weight of a silicone-based foam stabilizer composed of a dimethylpolysiloxane-polyoxyalkylene copolymer are mixed while being foamed by mechanical stirring, and the mixture is mixed. Is cast into a cylindrical mold centered on the same core as used for charging member-1, and then heated at 150 ° C for 2 hours while rotating on a rotating stand while keeping the cylindrical mold horizontal. Cured to obtain a conductive roller having a foam having a urethane rubber length of 230 mm and an outer diameter of 18.0 mm. Since the surface of this conductive roller was in a state where the skin layer was formed very thin and was partially broken, the surface was acid-treated to completely remove the skin layer. As a result, a charging member -23 having foam cells on the surface was obtained. Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-24>
83 parts by weight of Nipol DN002 (NBR manufactured by Nippon Zeon, 53% bonded nitrile), 17 parts by weight of Nipol DN601 (liquid NBR manufactured by Nippon Zeon), 5 parts by weight of zinc oxide, 2 parts by weight of stearic acid, conductive carbon black ( Lion Ketjen Black EC) 6 parts by weight, SRF Carbon Black (Tokai Carbon Co., Ltd. Seest S) 30 parts by weight, specially treated calcium oxide (Inoue Lime VESTA-BS) 5 parts by weight, PEG6000 2 parts by weight, aging A kneader in which 1 part by weight of inhibitor A (Nouchi (registered trademark) MB manufactured by Ouchi Shinsei Co., Ltd.), 0.5 part by weight of anti-aging agent B (Nocrak (registered trademark) NBC manufactured by Ouchi Shinsei Co., Ltd.), and 25 parts by weight of DOP are cooled sufficiently. By kneading, NBR batch-1 was obtained. This is left to stand overnight in a cool dark place kept at 20 ° C. for aging, and then using a sufficiently cooled open roll, 0.3 parts by weight of sulfur and vulcanization accelerator A (Noxer (registered trademark) CZ made by Ouchi Shinsei Co., Ltd.) 1 weight Part, 1 part by weight of vulcanization accelerator B (Noxeller (registered trademark) TS manufactured by Ouchi Shinsei Co., Ltd.) and 40 parts by weight of the same surface-treated ADCA paste as used in charging member-1 were added, kneaded thoroughly, and compound ( N-1) was obtained.

  Next, 70 parts by weight of compound (E-1) used in charging member-1 and 30 parts by weight of compound (N-1) were mixed using a sufficiently cooled open roll to obtain compound (NE-1). It was.

  A charging member -24 was obtained in the same manner as the charging member -16 except that the compound (NE-1) was used instead of the compound (E-1). Details are shown in Table-1.

<Charging member-25>
100 parts by weight of SBR (JSR SBR1502, bound styrene content 23.5%), 5 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 6 parts by weight of conductive carbon black (Ketjen Black EC by Lion), SRF carbon black ( Tokai Carbon Co., Ltd. Seest S) 30 parts by weight, specially treated calcium oxide (Inoue Lime Co., Ltd. VESTA-BS) 5 parts by weight, PEG6000 2 parts by weight, anti-aging agent A (Ouchi Shinsei Co., Ltd. Nocrack (registered trademark) MB) 1 part by weight, anti-aging agent B (Nocrack (registered trademark) NBC manufactured by Ouchi Shinsei Co., Ltd.) 0.5 part by weight, and DOP 25 part by weight were kneaded in a sufficiently cooled kneader to obtain SBR Batch-1. This is left to stand overnight in a cool dark place kept at 20 ° C. for aging, and then using a sufficiently cooled open roll, 0.3 parts by weight of sulfur and vulcanization accelerator A (Noxer (registered trademark) CZ made by Ouchi Shinsei Co., Ltd.) 1 weight Part, 1 part by weight of vulcanization accelerator B (Noxeller (registered trademark) TS manufactured by Ouchi Shinsei Co., Ltd.) and 40 parts by weight of the same surface-treated ADCA paste as used in charging member-1 were added, kneaded thoroughly, and compound ( S-1) was obtained.

  Next, 100 parts by weight of styrene / ethylene butylene / olefin crystal block copolymer (DYNARON4600P by JSR, styrene content 20%), 2.5 parts by weight of zinc stearate, 5 parts by weight of conductive carbon black (Ketjen Black EC by Lion) , 25 parts by weight of SRF carbon black (Shiest S manufactured by Tokai Carbon Co., Ltd.) and 5 parts by weight of specially treated calcium oxide (VESTA-BS manufactured by Inoue Lime Co., Ltd.) were kneaded in a kneader heated to 160 ° C to obtain a compound (S-2) It was. The compound (S-2) was sufficiently cooled, pulverized and classified to obtain a compound (S-2) powder having an average particle size of 5 μm.

  Compound (SS-1) was obtained by mixing 100 parts by weight of compound (S-1) with 20 parts by weight of compound (S-2) powder using a sufficiently cooled open roll.

  A charging member -25 was obtained in the same manner as the charging member-16 except that the compound (SS-1) was used instead of the compound (E-1). Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-26>
Add 4 parts by weight of dicumyl peroxide, 4 parts by weight of triallyl isocyanurate, and 40 parts by weight of the same surface-treated ADCA paste as used for charging member-1 to EPDM batch-1 used in charging member-1. The compound (E-0) was obtained by kneading.

  Compound (E-18) was obtained by mixing 100 parts by weight of compound (E-1) with 100 parts by weight of compound (E-0) using a sufficiently cooled open roll.

  A charging member -26 was obtained in the same manner as the charging member-16 except that the compound (E-18) was used instead of the compound (E-1). Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-27>
Epichlorohydrin rubber (Daiso Epichromer (registered trademark) CG102) 100 parts by weight, zinc oxide 5 parts by weight, stearic acid 1 part by weight, conductive carbon black (Lion Corporation Ketjen Black EC) 12 parts by weight, SRF carbon black ( Tokai Carbon Co., Ltd. Seest S) 55 parts by weight, specially treated calcium oxide (Inoue Lime Co., Ltd. VESTA-BS) 5 parts by weight, PEG6000 2 parts by weight, naphthenic softener (Diana Process Oil NM-280, Idemitsu Kosan Co., Ltd.) 10 Part by weight and 10 parts by weight of a polymerizable plasticizer (Adekasizer (registered trademark) PN-350, manufactured by Asahi Denka Co., Ltd.) were kneaded with a sufficiently cooled kneader to obtain hydrin rubber batch-1. This was left to stand overnight in a cool dark place maintained at 20 ° C. for aging, and then using a sufficiently cooled open roll, 0.5 parts by weight of sulfur, 2.5 parts by weight of Noxeller (registered trademark) DM, 1 part by weight of Noxeller (registered trademark) TS, 45 parts by weight of the surface-treated ADCA paste used for charging member-1 was added and sufficiently kneaded to obtain compound (H-1).

  Compound (NH-1) was obtained by mixing 70 parts by weight of compound (N-1) with 30 parts by weight of compound (H-1) using a sufficiently cooled open roll.

  A charging member-27 was obtained in the same manner as the charging member-16 except that the compound (NH-1) was used instead of the compound (E-1). Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-28>
Instead of 55 parts by weight of SRF carbon black (Shiest S manufactured by Tokai Carbon Co., Ltd.), 25 parts by weight of SRF carbon black (Shiest S manufactured by Tokai Carbon Co., Ltd.) and 20 parts by weight of hydrous silicic acid (Nipsil VN3 manufactured by Nippon Silica Co., Ltd.) were used in combination. A charging member-28 was obtained in the same manner as the charging member-16 except that. Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

<Charging member-29>
100 parts by weight of EPDM (EP11 made by JSR), 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 12 parts by weight of conductive carbon black (Ketjen Black EC made by Lion), SRF carbon black (Shiest S made by Tokai Carbon Co., Ltd.) ) 55 parts by weight, 5 parts by weight of specially treated calcium oxide (VESTA-BS manufactured by Inoue Lime), 2 parts by weight of PEG6000, 75 parts by weight of paraffin softener (Diana Process Oil PW-150, manufactured by Idemitsu Kosan Co., Ltd.) By kneading with a kneader, EPDM batch-2 was obtained. After being aged in a cool dark place kept at 20 ° C. for 24 hours, dicumyl peroxide 4 parts by weight, triallyl isocyanurate 4 parts by weight, and charging member-1 using a sufficiently cooled open roll 40 parts by weight of the same surface-treated ADCA paste was added and sufficiently kneaded to obtain a compound (E-20).

  A charging member-29 was obtained in the same manner as the charging member-16 except that the compound (E-20) was used instead of the compound (E-1). Details are shown in Table-1.

  The cell shape factor (K-1, K-2), the equivalent circle cell diameter and ratio, and the cell wall thickness were also measured in the same manner as the charging member 1. The results are summarized in Table-4.

[Powder adhering to charging member surface]
<Powder 1>
Powder 1 was obtained using tin oxide. The volume resistance value of the powder 1 was 1 × 10 ⁷ Ωcm, and the particle size was 0.02 μm. Further, when the shape factor of the powder 1 was measured according to the method of measuring the shape factor of the cell of the charging member 1, K-H1 = 110 and K-H2 = 105. The results are shown in Table-3.

  In addition, the volume resistance value measurement of the powder 1 used the apparatus shown in FIG. The electrode is composed of an upper electrode, a middle electrode, and a lower electrode. The height of the middle electrode is 5 mm, and a hole with a diameter of 5 mm penetrates vertically. After filling the hole 1 with the powder 1, the upper and lower electrodes are brought into close contact with a pinch load of 1 kg. In this state, a predetermined voltage (DC-500 V was applied. When a current value 30 seconds after the voltage application was read and taken as I (A), the resistance value (Ω) of the powder 1 was Rs = | V / I | = | -500 / I | The powder is left to stand for 12 hours or more in an environment of 23 ° C. and 60% RH before use. The resistance value was determined as follows.

Volume resistance value = resistance value × cross-sectional area / thickness The particle size is determined by measuring the true circle equivalent cell diameter and ratio of the foam using a FE-SEM (S-800) manufactured by Hitachi, Ltd. The diameter was magnified 10,000 times, and the equivalent circle diameter was obtained to obtain the particle diameter of one powder. In this example, 40 powders were randomly sampled to obtain a simple average of each equivalent circle diameter, and this was used as the particle size of the powder 1.

<Powder 2>
Powder 1 was surface-treated with a coupling agent to obtain Powder 2.

  As the surface treatment agent, a 20% MEK solution was prepared using a silane coupling agent (vinyltrichlorosilane). This was sprayed on the powder 1 by spraying several times and dried by heating to obtain a powder 2. The properties of powder 2 are summarized in Table-3.

<Powder 3>
Powder 1 was surface-treated with a coupling agent to obtain Powder 2.

  As the surface treating agent, a mixed solution of a silane coupling agent and a resin was used. As a silane coupling agent, a 20% MEK solution of vinyltrichlorosilane was used. As a resin component, a methyl isobutyl ketone (MIBK) solution of acrylic polyol (acrylic polyol content 40% by weight) and an isophorone diisocyanate (IPDI) trimer butanone oxime block are mixed so that OH / NCO = 1/1. The solution used was used. These were mixed at a weight ratio of 8: 2, and then sprayed onto the powder 1 by spraying several times and dried by heating to obtain a powder 3. Table 3 summarizes the characteristics of the powder 3.

<Powder 4>
Powder 4 was obtained in the same manner as Powder 2, except that instead of Powder 1, a surface of tin oxide doped with antimony oxide was used. Table 3 summarizes the characteristics of the powder 4.

<Powder 5>
A powder 5 was obtained in the same manner as the powder 4, except that γ-aminopropyltriethoxysilane was used as the silane coupling agent. The properties of powder 5 are summarized in Table-3.

<Powder 6>
Powder 6 was prepared in the same manner as Powder 2 except that conductive ZnO powder was used instead of powder 1 and γ-methacryloxypropyltrimethoxysilane was used instead of vinyltrichlorosilane as the silane coupling agent. Obtained. Table 3 summarizes the characteristics of powder 6.

<Powder 7>
Powder 7 was prepared in the same manner as Powder 3 except that conductive ZnO powder was used instead of Powder 1 and γ-methacryloxypropyltrimethoxysilane was used instead of vinyltrichlorosilane as the silane coupling agent. Obtained. Table 3 summarizes the characteristics of the powder 7.

<Powder 8>
A powder 8 was obtained in the same manner as the powder 4 except that silicone oil was used as the surface treatment agent instead of the coupling agent. Table 3 summarizes the characteristics of the powder 8.

  As the surface treating agent, dimethyl silicone oil was used to prepare a 20% MEK solution. This was sprayed onto the powder 1 in several sprays and baked at 400 ° C.

<Powder 9>
Powder 9 was obtained in the same manner as Powder 2, except that nickel zinc ferrite having an average particle diameter of 1.0 μm was used instead of Powder 1 and silicone oil was used instead of the coupling agent as the surface treatment agent. Table 3 summarizes the characteristics of the powder 9.

<Powder 10>
Predetermined amounts of an aqueous Na ₃ PO ₄ solution and an aqueous CaCl ₂ solution were added to ion-exchanged water and stirred to obtain an aqueous medium containing calcium phosphate.

  Next, 100 parts by weight of styrene, 12.5 parts by weight of n-butyl acrylate, 23 parts by weight of ester wax, and 7 parts by weight of conductive carbon black are heated and dissolved and dispersed sufficiently uniformly using a granulator. Here, 6 parts by weight of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

  The polymerizable monomer composition was put into the aqueous medium, heated and stirred in a nitrogen atmosphere to granulate the polymerizable monomer composition, and then polymerized. Thereafter, the residual monomer was distilled off, and after cooling, hydrochloric acid was added to dissolve the calcium phosphate salt, followed by filtration, washing with water and drying to obtain a resin powder, which was designated as powder 10. Table 3 summarizes the characteristics of the powder 10.

[Electrophotographic equipment]
<Electrophotographic device 1>
A digital laser beam printer (manufactured by Canon Inc., LBP-1660) was prepared as an electrophotographic apparatus. The outline of this apparatus is a contact-type charging device using a charging roller as a photosensitive member charging unit, a one-component developing device employing a one-component jumping development method as a developing unit, a contact-type transfer device using a transfer roller as a transfer unit, It includes blade cleaning means, a fixing device using a heating method, and the like. The photosensitive member charging means will be described in detail. A charging roller having an outer diameter of 12 mm is pressed against the photosensitive member with a predetermined pressure, and the charging member is rotated (driven) as the photosensitive member rotates. It does not have an independent drive for rotation. In this state, when a voltage is applied to the charging roller, the photosensitive member is charged to a predetermined potential via the charging roller. In addition, the photosensitive member charging unit, the cleaning unit, and the photosensitive member are integrated units. This printer was modified as follows to obtain an electrophotographic apparatus 1.

First, the housing of the unit is removed as necessary, and a charging roller having an outer diameter of 18 mm can be incorporated as the photosensitive member charging means, and the spring is adjusted so that the contact force between the charging roller and the photosensitive member becomes a predetermined pressure. (Length, spring constant).
Next, a motor for driving the charging roller was prepared, and the rotation of the motor could be directly transmitted to the charging roller by a joint or the like. Therefore, by controlling the rotation of the motor, it has become possible to freely control the rotation speed and rotation direction of the charging roller.

  Furthermore, a power source for applying a voltage from the outside to the charging roller was connected. Thereby, a direct current component and an alternating current component can be controlled freely.

<Electrophotographic device 2>
The cleaning blade was removed from the unit used in the electrophotographic apparatus 1 to obtain a cleanerless copying apparatus. This was designated as an electrophotographic apparatus 2.

[Photoreceptor]
<Photoreceptor 1>
Four functional layers were provided on a φ30 mm aluminum cylinder.

  The first layer is a conductive layer, and is a layer made of conductive fine particle dispersed resin having a thickness of about 20 μm, which is provided to smooth out defects of the aluminum cylinder and to prevent the generation of moire due to reflection of exposure. .

The second layer is a positive charge injection preventing layer, serves to prevent canceling the negative charge positive charge injected from the aluminum cylinder was charged photoreceptor surface, 10 by a solvent-soluble polyamide resins such as ⁶ This is a medium resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about Ωcm.

  The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a phthalocyanine pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.

  The fourth layer is a charge transport layer, which is obtained by dispersing hydrazone in a polycarbonate resin, and is a P-type semiconductor. Accordingly, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor. The thickness was 18 μm.

In the photoreceptor 1, the charge transport layer was a surface layer, and the volume resistance value of the photoreceptor surface layer was 3 × 10 ¹⁵ Ωcm.

<Photoreceptor 2>
Five functional layers are provided on an aluminum cylinder with a diameter of 30 mm.

The first layer, the second layer, and the third layer were prepared in the same manner as the photoreceptor 1, and the thickness of the fourth layer was adjusted to 15 μm by finely adjusting the coating conditions. Further, a charge injection layer is formed thereon as a fifth layer. This charge injection layer is obtained by dispersing SnO ₂ ultrafine particles in a photocurable acrylic resin. Specifically, SnO ₂ particles having a particle size of about 0.03 μm, doped with antimony and reduced in resistance, are 170 parts by weight with respect to 100 parts by weight of resin, and further 20 parts by weight of tetrafluoroethylene resin particles are dispersed. The agent is dispersed in 1.2 parts.

In the photoreceptor 2, the charge injection layer was a surface layer, and the volume resistance value of the photoreceptor surface layer was 4 × 10 ¹² Ωcm. Further, when the shape factor of SnO ₂ used for the charge injection layer was measured in the same manner as that of the powder 1, it was K-D1 = 110 and K-D2 = 105.

(Developer)
First, 100 parts by weight of a polyester resin, 2.5 parts by weight of a metal-containing azo dye, 3.5 parts by weight of a low molecular weight polypropylene, and 90 parts by weight of magnetite were dry mixed and then kneaded in a twin-screw kneading extruder set at 150 ° C. did. The obtained kneaded product was cooled, finely pulverized by an airflow type pulverizer, and then classified by air to obtain a toner composition having an adjusted particle size distribution. Developer 1 having a weight average particle size of 6.0 μm was prepared by externally adding 1.5 wt% of hydrophobized titanium oxide and 1.0 wt% of hydrophobic silica to the toner composition. When the shape factor of the toner was measured, K-T1 = 150 and K-T2 = 140.

Example 1
The following evaluation was performed using the charging member 1.

<Hardness>
The hardness was measured using an Asker C hardness meter, and the load Fk was measured at 500 g per side (1 kg in total) using the apparatus shown in FIG. There were a total of three measurement locations at both ends and the center, and the simple (arithmetic) average of these was used as the Asker C hardness of the charging member 1. When measured in this manner, the left end portion is 22 °, the central portion is 24 °, and the right end portion is 23 °. The simple average of 23 ° is the Asker C hardness of the charging member-1. Shown in Table-4.

<C set>
The residual deformation amount measured 12 hours after leaving the pressure at 23 ° C. and 60% RH after leaving the foam part of the charging member at 40 ° C. and 95% RH for 1 week while maintaining the compression ratio (FIG. 14) at 4%. This means that the smaller the number, the better the C setting property. In this example, the wall thickness of the foam portion of the charging member is 6 mm, so that it was deformed by 0.24 mm using a flat plate.

  The outer diameter before and after leaving the environment was measured using a laser, and the difference was defined as C set. In charging member-1, the thickness was 110 μm. Shown in Table-4.

<Specific gravity>
A sample was cut out from the foam, and the weight in air and the weight in water were measured and calculated. Since the foam of the present invention floats in water, a metal weight was used to completely submerge it in water. That is, as shown in FIG. 15, first, the weight in the air was measured with a metal weight attached to the sample, and W (g) was measured, and then the weight in water was measured as it was to obtain Ww (g). Further, only the weight of the metal was used to measure the weight in the air and the weight in water by the same method, and were set as W0 and Ww0, respectively. Therefore, the specific gravity (SG) of the foam is represented by SG = (W−W0) / (W−W0) − (Ww−Ww0). In this example, W0 and Ww0 are almost the same, so W0 = Ww0. That is, SG = (W−W0) / (W−Ww). Thus, when the specific gravity of the foam of charging member-1 was determined, it was 0.25.

(Examples 2 to 4)
Evaluation was performed in the same manner as in Example 1. These results are summarized in Table-4.

  In Examples 1 to 4, the charging member of the present invention has an Asker C hardness of 40 ° or less, preferably 30 ° or less, more preferably 25 ° or less, a C set of 125 μm or less, preferably 120 μm or less, and a specific gravity of 0. .45 or less, preferably 0.4 or less, more preferably 0.3 or less, respectively. As is clear from Examples 1 to 4, the charging member of the present invention can obtain an excellent effect that the C set is good while being highly foamed and low in hardness. Depending on the combination of the polymer compound and the vulcanization system, bloom may occur on the surface of the charging member. Although there is a difference in the degree of bloom, there is no particular problem because none of them affects the characteristics, but it is preferable that there is no bloom in terms of appearance.

(Example 5)
17 to 19 show an example of the electrophotographic apparatus used in this embodiment.

  FIG. 17 shows an example in which the charging member rotates with the photosensitive member (driven), and AC / DC is applied as the bias.

  FIG. 18 shows an example in which the charging member rotates with the photoreceptor (driven), and DC is applied as the bias.

  FIG. 19 shows an example of rotation of the charging member in the reverse direction of FIGS. 17 and 18, DC is applied as a bias, and an independent drive mechanism (not shown) is provided.

  The charging member of the present invention was attached to the photosensitive member charging unit of the unit in which the photosensitive member charging unit, the cleaning unit, and the photosensitive unit were integrated. In this state, the sample was stored in an environment of 40 ° C. and 95% RH for 1 month, and then taken out and evaluated in an environment of 23 ° C. and 60%.

  For the image evaluation, the electrophotographic apparatus 1 was used, and the evaluation was performed by changing the charging member, its driving condition, and the voltage applied from the outside. In Examples 5-1 and 5-2, charging member-1 was used, and in Example 5-3, charging member-30 was used. The charging member-30 is obtained by uniformly attaching the powder 1 to the surface of the charging member-1. Details of evaluation conditions and results are shown in Table-5.

  As a result, it was found that the effect of applying a relatively low voltage to the photosensitive member to a predetermined voltage (Example 5-3) is likely to appear in the image even if the deformation amount of the charging member is the same. . However, it has been found that the charging member of the present invention can be used even in such a strict charging system.

(Example 6)
In this example, the electrophotographic apparatus 1 was used to evaluate various powders by applying a relatively low voltage to charge the photoreceptor to a predetermined voltage. The charging member was rotated counter to the photosensitive member by an external driving force. The ratio of absolute values of speed was 3. That is, | the rotational speed of the charging member | / | the rotational speed of the photosensitive member | = 3. The absolute value is expressed because the rotation direction is opposite, and when one is +, the other is-.

  Further, in this example, a dedicated device for supplying the same powder as the powder adhered to the charging member surface to the charging member is provided. This is because even if the powder is attached to the surface of the charging member in advance, it may be detached due to physical or electrical influence with use and the charging performance may be lowered. This powder supply device has at least a container for storing powder, a stirring device, a supply port, and a leveling member. The powder in the container is homogenized by a stirrer and supplied to the surface of the charging member through the supply port. The supplied powder can be uniformly adhered to the surface of the charging member by the leveling member in contact with the charging member.

  The evaluation was carried out using a 3% image of a halftone image (one dot and two spaces), a solid black, and a solid white every predetermined number of continuous images of a 4% printed image in an environment of 23 ° C. and 60% RH.

  As a result, in the solid black and solid white images, good images were obtained from the initial stage up to 6000 sheets. Some halftone images (one dot and two spaces) showed changes in image quality.

Judging comprehensively from these results, the powder having the characteristics as used in this example is good in an electrophotographic apparatus adopting a method in which a relatively low voltage is applied to charge the photosensitive member to a predetermined voltage. It can be seen that it can be used. The metal oxide is particularly preferably a metal oxide. In particular, when tin oxide is used, scratches and fusion to the photoreceptor do not occur, and even when rubbed against the charging member, it may cause wear of the charging member. It is very preferable because it is not. It was found that there was a difference in the degree of change in the charging member resistance value before and after durability depending on the volume resistance value of the powder. Of course, the smaller the resistance value change of the charging member before and after the endurance, the better, and the lower the volume resistance value of the powder tends to be advantageous for the above problem, but on the other hand, leaks associated with the endurance occur. Therefore, it is desirable to set the volume resistance within a proper range. Furthermore, when the particle size of the powder and K-H1 were small, a tendency that the powder was easily embedded (filled) in the cell was observed. From the viewpoint of durability and stability, such a phenomenon is preferably small.
The combinations and results used for the evaluation are shown in Table-6.

(Example 7)
FIG. 20 shows an example of the electrophotographic apparatus used in this embodiment. It has an independent drive mechanism (not shown) and is cleanerless. In this example, the electrophotographic apparatus 2 was used, and various charging members were evaluated by applying a relatively low voltage to charge the photoreceptor to a predetermined voltage. The charging member was rotated counter to the photosensitive member by an external driving force. The ratio of absolute values of speed was 3.5. That is, | the rotational speed of the charging member | / | the rotational speed of the photosensitive member | = 3.5. The absolute value is expressed because the rotation direction is opposite, and when one is +, the other is-.

  In this example, a developing device was used without providing a dedicated device for supplying powder. That is, a predetermined amount of powder is added and mixed in advance in the developer, and the electrostatic latent image is moved onto the photosensitive member together with the developer during development of the electrostatic latent image without being transferred or scraped off from the photosensitive member. It moves to the charging member. Therefore, it is attached (supplied) to the surface of the charging member by contacting with the charging member. The powder is positioned like an external additive of the developer. Therefore, in this example, it is necessary to have at least a mechanism for physically scraping the substance on the photoreceptor, so-called cleanerless system. Suitable for. In this example, powder 1 or 2 was added at 2% by weight with respect to the developer.

  The evaluation was carried out using a three-tone image of a halftone image (one dot and two spaces), a solid black, and a solid white every predetermined number of continuous images of a 4% printed image in an environment of 23 ° C. and 60% RH.

  As a result, in the solid black and solid white images, good images were obtained from the initial stage up to 6000 sheets, but in the halftone image (1 dot 2 spaces), there were some that showed a change in image quality. It was. As a change in the image quality, fog and spots may appear on the image.

  Although the level of fogging deteriorates as durability progresses, the spots often appear or disappear depending on the point of checking the image, and there are many differences in levels. On the other hand, when the resistance value of the charging member after the endurance was measured, it was found that when the fog was generated, the resistance was considerably increased, whereas when the spot was generated, the increase was small. Therefore, when the details of charging were enlarged and observed with a CCD camera, there was a difference in the behavior of the powder. That is, the following tendencies were generally observed. When fog occurs, there are few powders detached from the surface of the charging member. In other words, there is little replacement of the powder adhering to the charging member surface in advance, and the supplied powder often passes through the charging member surface as it is. That is, since the same powder is used over a long period of time, the resistance of the powder increases, leading to an increase in the resistance of the charging member, and as a result, fogging is considered to occur. However, in some cases, as in Comparative Example 9, the rising width is not so large. In this case, it is considered as follows. That is, it is presumed that the resistance of the powder is increased but not so much as to affect the resistance value of the entire charging member. In this charging method, it is estimated that the increase in the resistance of the powder causes microscopic charging failure. Therefore, fog becomes worse with durability. This phenomenon is conspicuous when the value of K-1 is less than 110, and it is thought that the closer the cell diameter is to a spherical shape, the deeper the depth is pushed and the freedom of movement of the powder is lost. On the other hand, when the spots occur, it is considered that the presence state of the powder on the surface of the charging member is unstable. When the powder is supplied from the outside and is accumulated up to a certain amount on the surface of the charging member, it suddenly falls off on the photoconductor in a lump without being touched. Even if the charged state on the photoconductor is uniformized at the nip portion, if the powder falls off the nip downstream as viewed from the photoconductor rotation direction, the potential is disturbed due to the influence of the powder resistance value (medium resistance region). This is thought to be a point-like image defect. In other words, it suddenly occurs, and if a lump is left as it is on the photoconductor, it will always be a patchy image, but if it is removed from the photoconductor for some reason, it will return to a good image. This phenomenon is presumed to be a sudden problem. This phenomenon is not a problem in an electrophotographic apparatus having a cleaner. This is because the material on the photoreceptor is scraped off. In other words, this is a problem unique to the cleanerless system.

  In addition, when there is no change in image quality, the supply and desorption of the powder on the surface of the charging member is reasonably balanced, so that the powder can always exist in a fresh state and has sufficiently good charging performance. For this reason, it is considered that there is no sudden dropout because it does not accumulate until it becomes a lump. These are influenced by the shape factor of the foam cell, and moreover, the shape factor of the powder tends to be related. Therefore, it is very preferable if the shape factor of the cell and the shape factor of the powder are within the scope of the present invention.

  Table 7 shows the combinations and results used for the evaluation.

(Example 8)
The same electrophotographic apparatus as in Example 7 was used, and | the rotational speed of the charging member | / | the rotational speed of the photoconductor | = 2. In this example, powder 8 was added at 1.5% by weight with respect to the developer.
The combinations and results used for the evaluation are shown in Table-8.

  As apparent from Examples 5 to 8, the charging member of the present invention is suitable for a system in which a relatively low voltage is applied to charge the photoreceptor to a predetermined voltage or a cleanerless type electrophotographic apparatus.

  Examples of other electrophotographic apparatuses are shown in FIGS.

Sectional drawing which shows an example of the cell shape of the charging member of this invention. 2 is a cross-sectional SEM photograph showing an example of a cell shape of the charging member of the present invention. Sectional drawing which shows an example of the cell shape of the conventional charging member. Sectional drawing which shows an example of thickness distribution of the cell wall in FIG. The model figure of the cell shape of the charging member of this invention. FIG. 6 is a model diagram of the presence state of the powder (2a-3) in FIG. 5. The model figure of the cell shape of the conventional charging member. The model figure of the presence state of the powder (2a-3) in FIG. An example which shows the maximum length (arrow part) of the cell which consists of various indefinite shapes. Schematic of the apparatus which measured the electrical resistance value of the charging member of this invention. Sectional drawing which shows another example of the cell shape of the charging member of this invention. The rheometer characteristic which shows an example of the vulcanization | cure state and foaming state of the compound used for the charging member of this invention. A shows the change with time of vulcanization progress (torque), and B shows the change with time of foaming progress (foaming pressure). tv represents the rise time of the torque increase due to vulcanization, and tc represents the rise time of the foaming pressure rise. 1 is a schematic view of an Asker C hardness measuring device for a charging member according to the present invention. The schematic of the apparatus contact | abutted by predetermined compression rate for C set measurement of the charging member of this invention. In order to obtain a predetermined compression rate, the flat plate is brought into contact with a load of one side Fs (2 Fs in total). Schematic which shows the procedure which measures the specific gravity of the foam of the charging member of this invention. A is a weight measurement in the air, B is a weight measurement in water. Schematic of the apparatus which measures the volume resistance value of the powder adhering to the surface of the charging member of this invention. 6 is an example of an electrophotographic apparatus used in Example 5. The charging member rotates with the photoreceptor (followed). Bias is AC / DC applied. 6 shows another example of the electrophotographic apparatus used in Example 5. The charging member rotates with the photoreceptor (followed). Bias is DC applied. FIG. 6 shows still another example of the electrophotographic apparatus used in Example 5. FIG. The charging member rotates in the reverse direction of Figs. Bias is DC applied. It has an independent drive mechanism (not shown). An example of the electrophotographic apparatus used in Examples 7 and 8. It has an independent drive mechanism (not shown) and is cleanerless. Examples of other electrophotographic apparatuses. Examples of other electrophotographic apparatuses. Examples of other electrophotographic apparatuses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging member 2a Foam 2a-1 Cell 2a-2 Cell wall 2a-3 Powder 2a-4 Coating layer 2a-5 Surface treatment layer 3 Image exposure 4 Developer 5 Transfer paper 6 Transfer device 7 Fixing device DESCRIPTION OF SYMBOLS 8 Cleaning apparatus 9 Powder supply apparatus 10 Scraping stirring brush 11 Control blade 12 Powder supply roller 100 Metal drum 101-103 Electrode 200 Power supply 300 Ammeter

Claims (12)

A charging member having at least a foam and an electrical resistance value of 1 × 10 ³ Ω or more and 1 × 10 ¹⁰ Ω or less, and a shape factor K-1 of the cell represented by Formula-1 is 110 ≦ K−1 A charging member, wherein ≦ 500.

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)   The cell having a perfect circle equivalent cell diameter of 30 μm or more and 300 μm or less obtained from the projected area of the cell in an arbitrary cross section of the foam has a number of 50% to 97% of the total number of cells. 1. The charging member according to 1.   3. The charging member according to claim 1, wherein the thickness of the cell wall is 0.1 μm or more and 50 μm or less in any cross section of the foam. 4. The charging member according to claim 1, wherein a shape factor K-2 of the cell represented by Formula-2 satisfies 105 ≦ K-2 ≦ 280.

(In the formula, PERIME indicates the perimeter of the cell, and AREA indicates the projected area of the cell) 5. The charging member according to claim 1, wherein the charging member has a powder having a volume resistance value of 1 × 10 ³ Ωcm or more and 1 × 10 ¹⁰ Ωcm or less on the surface. 6. The charging member according to claim 5, wherein a shape factor K-H1 of the powder represented by Formula-3 is 110 ≦ K−H1 ≦ 250.

(In the formula, MXLNG indicates the absolute maximum length of the cell and AREA indicates the projected area of the cell)   At least a charging step of charging the photosensitive member with a charging device to which a voltage is applied, a step of forming an electrostatic latent image by image exposure, a developing device for visualizing the electrostatic latent image with toner, and the visualization An electrophotographic apparatus having a transfer device for transferring an electrostatic latent image onto a transfer material, wherein the charging member according to claim 1 is used. When the absolute value of the DC voltage (V) applied to the charging member is | Vc | and the absolute value of the dark portion potential (V) of the photosensitive member is | Vd |, the photosensitive member is charged when 0 <| Vc | ≦ 100. Start
Furthermore, when 100 <| Vc | ≦ 1500, 0.7 ≦ | Vd | / | Vc | <1.3
The electrophotographic apparatus according to claim 7, wherein: 9. The electrophotographic apparatus according to claim 8, further comprising a mechanism for supplying powder having a volume resistance value of 1 × 10 ³ Ωcm to 1 × 10 ¹⁰ Ωcm to the charging member.   The electrophotographic apparatus according to claim 7, wherein the particle size of the developer is 0.5 μm or more and 10 μm or less.   The electrophotographic apparatus according to claim 7, which does not have an independent cleaning mechanism.   A process cartridge detachably attachable to an electrophotographic apparatus, wherein at least the charging member according to claim 1 and an electrophotographic photosensitive member are integrally supported.

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