JP2009086263A - Charging member - Google Patents

Abstract

The present invention relates to an image such as a ghost or a charged horizontal streak that has uniform electric characteristics, has sufficient charging ability, applies only a DC voltage, and uniformly charges a photoconductor without a pre-exposure means. Provided is a charging member that is free from defects and has no image defects or photoconductor contamination due to defects on the roller surface over a long period of use.
A charging member is formed of an elastic body layer comprising at least one layer on a conductive support and a surface layer comprising at least one layer on the elastic layer, and the surface layer of the charging member is formed. In an unformed state, the average value of the electrical resistance when applied at 200 V for 2 seconds in an environment of 23 ° C. and 50% RH is 3 × 10 ⁵ Ω or less, and the ratio between the maximum value and the minimum value in the circumferential direction of the electrical resistance is 2. The surface layer has a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω · cm, and the average thickness of the surface layer is 10 to 100 nm.
[Selection] Figure 1

Description

  The present invention relates to a charging member used in contact with a photoreceptor in an electrophotographic apparatus. In the following, details of the charging roller will be described as an example of the charging member, but the present invention is not limited to the charging roller.

  In image forming apparatuses such as electrophotographic apparatuses such as copying machines and optical printers and electrostatic recording apparatuses, a contact charging method has recently been adopted as means for charging an image carrier surface such as a photoreceptor or a dielectric. In the contact charging method, a charged member surface (also referred to as a charging member) to which a voltage is applied is brought close to or in contact with the surface of the object to be charged, and the surface of the object to be charged is generally charged. A rubber roller type charging roller having a semiconductive elastic layer formed on a gold shaft is used.

The charging roller needs to have moderate semiconductivity in order to prevent leakage caused by pinholes or scratches on the surface of a charged body such as a photoconductor. Further, in order to uniformly charge the object to be charged, it is important that the electric resistance value is uniform semiconductivity having a volume resistivity of about 1 × 10 ³ to 1 × 10 ⁹ Ω · cm. As such a charging roller, a protective layer made of a material such as fluorine resin or silicone resin is formed on a rubber elastic body layer obtained by adding carbon black to rubber such as EPDM or NBR to provide conductivity. Conductive rollers have been used.

  Conventionally, in the roller charging method, an AC voltage component (AC voltage) having a peak-to-peak voltage more than twice the charging start threshold (Vth) in a DC voltage (DC voltage) corresponding to a desired surface potential Vd to be charged. A charging method has been used in which a voltage on which a component is superimposed is applied to a contact charging member. This charging method is a so-called “AC / DC charging method”. This is because the potential of the object to be charged converges to the potential Vd which is the center of the peak of the AC voltage due to the leveling effect of the AC voltage, and charging is not affected by external conditions such as the environment. Contact charging method.

  However, in the AC / DC charging method, an AC power supply is required in addition to the DC power supply in order to superimpose a high-voltage AC voltage that is a peak-to-peak voltage more than twice the charging start voltage (Vth) when a DC voltage is applied, This increases the cost of the device itself. Furthermore, there has been a problem that the durability of the charging roller and the electrophotographic photosensitive member is reduced by consuming a large amount of alternating current. Therefore, recently, charging has been performed using only the DC voltage as the voltage applied to the charging roller.

  Further, conventionally, pre-exposure means for removing residual charges on the surface of the electrophotographic photosensitive member after image transfer using an LED chip array, a fuse lamp, a halogen lamp, a fluorescent lamp, or the like is provided upstream of the charging process. However, in recent years, demands for miniaturization and cost reduction of electrophotographic apparatuses have increased, and there is a demand for image formation without using this pre-exposure means.

  However, as described above, when only the DC voltage is applied to the charging roller and the photosensitive member is charged or when the pre-exposure operation is not performed, the surface potential of the photosensitive member, the first charge of the photosensitive member, and the charging are charged. There may be a potential difference between the second and subsequent saturation potentials (dark part potential VD). When this potential difference occurs, for example, in the case of the reversal development method, if a halftone image is continuously output immediately after forming a latent image of a character or a black figure, the character or black figure is faintly displayed on the image. A phenomenon (ghost) that causes an afterimage is likely to occur. In addition to the ghost, there also arises a problem that fine horizontal streak-like image defects (charging horizontal streaks) are likely to occur due to abnormal discharge from the charging roller.

  As a means for solving ghosts and charging horizontal stripes, it is known to reduce the electrical resistance of the charging roller and increase the charging ability. In particular, it is effective to reduce the electrical resistance of the rubber elastic layer described above and increase the electrical resistance of the protective layer to reduce the thickness.

As a charging roller having such a configuration, a charging roller has been proposed in which a high resistance material selected from the group consisting of melamine resin, silicone resin, epoxy resin, acrylic resin, polycarbonate resin, urethane resin, etc. is made into a thin film as the outermost layer. (Patent Document 1). In addition, a charging roller has been proposed in which a protective layer having a pencil hardness of 6H or more is formed of a material such as silicon oxide ceramic or silicon nitride ceramic (Patent Document 2).
JP-A-11-272042 Japanese Patent Registration No. 03028057

  However, in the method of thinning the high resistance material described in Patent Document 1 as the outermost layer, the strength of the resin material is small, and when used over a long period of time, defects in the outermost layer may occur and image defects may occur. . Moreover, it was difficult to obtain a uniform thin film of 100 nm or less.

  Further, when a protective layer having a pencil hardness of 6H or higher is formed, the protective layer is too hard, and image defects may occur due to the photoconductor being scraped.

  Therefore, the present invention has uniform electric characteristics and sufficient charging ability, and even without a pre-exposure means, the photoreceptor can be uniformly charged by applying only a DC voltage, and images such as ghosts and charged horizontal stripes can be obtained. It is an object of the present invention to provide a charging member that does not cause defects. It is another object of the present invention to provide a charging member suitable as a charging roller that is free from image defects due to roller surface defects or photoconductor scraping over a long period of use.

That is, the charging member according to the present invention is a charging member having a conductive support, an elastic layer formed on the conductive support, and a surface layer.
The average value of the electrical resistance of the elastic layer in the state where the surface layer is not formed is less than 3 × 10 ⁵ Ω when applied at 200V for 2 seconds in an environment of 23 ° C. and 50% RH, and the electrical resistance The ratio of the maximum value and the minimum value in the circumferential direction is 2.0 times or less,
The volume resistivity of the surface layer is 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω · cm,
The average thickness of the surface layer is 10 to 100 nm.

  According to the present invention, image defects such as ghosts and charged horizontal stripes can be suppressed. Further, by forming the surface layer with a sol-gel film made of polysiloxane having an oxyalkylene group, it is possible to form a highly durable surface layer that is uniform and thin. Further, since the friction coefficient of the surface layer is small, the photoconductor is not scraped, and image defects due to the photoconductor scraping do not occur.

  Hereinafter, the present invention will be described in more detail.

  FIG. 5 shows a schematic configuration of an electrophotographic apparatus having the charging member of the present invention. Reference numeral 51 denotes an image carrier as a member to be charged. This example is a drum-type electrophotographic photosensitive member having a conductive support 51b such as aluminum and a photosensitive layer 51a formed on the outer peripheral surface thereof as basic constituent layers. is there. It is rotationally driven at a predetermined peripheral speed in the clockwise direction in the drawing around the support shaft 51c.

  Reference numeral 10 denotes a charging member that is in contact with the surface of the photosensitive member 51 and uniformly charges the surface of the photosensitive member uniformly to a predetermined polarity and potential. This example is of a roller type. The charging roller 10 includes a central core metal 11, a lower elastic body layer 12 formed on the outer periphery thereof, and an upper surface coating layer 13 formed on the outer periphery thereof. As a result, the photoconductor 51 is driven to rotate.

  Thus, when the power source 53 applies a predetermined direct current (DC) bias or direct current + alternating current (DC + AC) bias of the metal core 11 from the rubbing power source 53a, the peripheral surface of the rotating photoconductor 51 has a predetermined polarity.・ Contact potential is charged. The surface of the photoreceptor 51 that has been uniformly charged by the charging roller 10 is then subjected to exposure of target image information (laser beam scanning exposure, slit exposure of a document image, etc.) by an exposure means 54, so An electrostatic latent image corresponding to the image information is formed.

  The latent image is sequentially visualized as a toner image by the developing means 55. The toner image is then transferred from the paper feeding means (not shown) by the transfer means 56 in synchronization with the rotation of the photoconductor 51 and conveyed to the transfer section between the photoconductor 51 and the transfer means 56 at an appropriate timing. The images are sequentially transferred to the 57th surface. The transfer means 56 in this example is a transfer roller, and the toner image on the surface of the photoconductor 51 is transferred to the front surface side of the transfer material 57 by charging the reverse polarity of the toner from the back of the transfer material 57.

  The transfer material 57 that has received the transfer of the toner image is separated from the surface of the photoconductor 51 and conveyed to an image fixing means (not shown) to receive image fixing and output as an image formed product. Alternatively, in the case of forming an image on the back side, it is conveyed to a re-conveying means to the transfer unit.

  The surface of the photoconductor 51 after the image transfer is cleaned by the cleaning means 58 after removal of adhering contaminants such as transfer residual toner and is repeatedly used for image formation.

  The charging roller 10 may be driven and driven by a surface-driven member 51 that is driven to move the surface, or may be non-rotating, or may be a predetermined direction in the forward or reverse direction of the surface of the charged member 51. You may make it actively rotate at a peripheral speed.

  Further, when the electrophotographic apparatus is used as a copying machine, the exposure is performed by reading a document with reflected light or transmitted light, scanning a laser beam based on this signal, driving an LED array, or This is done by driving a liquid crystal shutter array.

  Examples of the electrophotographic apparatus that can use the charging member of the present invention include electrophotographic application apparatuses such as a copying machine, a laser beam printer, an LED printer, or an electrophotographic plate making system.

  In addition to a charging member such as a charging roller, the charging member of the present invention can also be used as a conveying member such as a developing member, a transfer member, a charge eliminating member, and a paper feed roller.

The elastic body layer of the charging roller of the present invention has an average value of electrical resistance of less than 3 × 10 ⁵ Ω measured by applying a voltage of 200 V for 2 seconds in an environment of 23 ° C. and 50% RH. When the average value of the electrical resistance is 3 × 10 ⁵ Ω or more, the charging ability of the surface of the photoconductor is insufficient, and a ghost image and a charged horizontal stripe are generated.

  The ratio (circumferential unevenness) between the maximum value and the minimum value in the circumferential direction of the electric resistance of the elastic layer is 2.0 times or less. In the present invention, since a high resistance material is used for the surface layer and a thin film is formed, the electric resistance as a charging roller greatly depends on the characteristics of the elastic layer. Therefore, when the circumferential unevenness of the elastic layer is more than 2.0 times, the circumferential unevenness of the charging roller on which the surface layer is formed also becomes large. As a result, the photoreceptor surface potential becomes non-uniform and a halftone image is output. In this case, density unevenness of the charging roller pitch occurs.

  The circumferential unevenness of the electrical resistance of the elastic layer is either a value before forming the surface layer or a value measured after removing the surface layer by polishing or the like after forming the surface layer.

  As a method of obtaining a uniform elastic body layer with such a low electric resistance, it is preferable that the elastic body layer has a two-layer structure of a conductive layer and a resistance adjusting layer as shown in FIG.

  Examples of the raw rubber used for the conductive layer include the following. Natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene terpolymer rubber ( EPDM), silicone rubber. Conductive particles are blended in order to reduce the electrical resistance of these raw rubbers. Examples of the conductive particles include oxides such as carbon black, graphite, titanium oxide, and tin oxide; metals such as Cu and Ag; particles that are conductively coated with an oxide or metal on the surface, and the like. . Further, if necessary, two or more kinds of these conductive particles can be blended in an appropriate amount and used.

  The amount of the conductive particles as described above is generally 1 to 200 parts by mass with respect to 100 parts by mass of the raw rubber.

  As the conductive particles, carbon black is most preferred because of its high conductivity efficiency.

  In order to uniformly charge the photosensitive member, the charging roller preferably has a low hardness so as to ensure uniform contact with the photosensitive member in the roller axial direction. Therefore, the conductive layer may be made of foamed rubber. preferable.

  The example of the foaming agent for making a conductive layer into a foam contains the following. Organic foaming agents (dinitrosopentamethylenetetramine, azodicarbonamide, paratoluenesulfonylhydrazine, azobisisobutyronitrile, 4,4'-oxybisbenzenesulfonylhydrazine, etc.). Inorganic foaming agent (such as sodium bicarbonate).

  The resistance adjusting layer is preferably made of ion conductive rubber in order to make the electric resistance of the elastic layer uniform. Examples of ion conductive rubbers include: Epichlorohydrin homopolymer (CHC), epichlorohydrin-ethylene oxide copolymer (CHR), epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (CHR-AGE), acrylonitrile-butadiene copolymer (NBR), acrylonitrile-butadiene Rubber such as hydrogenated copolymer (H-NBR), chloroprene rubber (CR), acrylic rubber (ACM, ANM), urethane rubber (U). The above rubbers may be used alone or in a blend of two or more.

Further, for the purpose of adjusting electric resistance, an ionic conductive agent can be blended with the above ionic conductive raw rubber. Examples of ionic conductive agents include:
(B) Inorganic ionic substances such as lithium perchlorate, sodium perchlorate, calcium perchlorate;
(B) Cationic surface actives such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, trioctylpropylammonium bromide, modified aliphatic dimethylethylammonium ethosulphate Agent;
(C) Zwitterionic surfactants such as lauryl betaine, stearyl betaine, dimethylalkyl lauryl betaine;
(D) quaternary ammonium salts such as tetraethylammonium perchlorate, tetrabutylammonium perchlorate, and trimethyloctadecylammonium perchlorate;
(E) Organic acid lithium salts such as lithium trifluoromethanesulfonate.

  Conductive particles such as carbon black can be blended in the resistance adjusting layer to such an extent that the electric resistance does not become non-uniform.

  The thickness of the resistance adjustment layer is not particularly limited, but is preferably in the range of 1000 to 100 μm. When the thickness of the resistance adjustment layer is more than 1000 μm, even if the lower conductive layer is reduced in hardness, it may be difficult to reduce the surface hardness of the roller because the resistance adjustment layer is thick. In addition, if the thickness of the resistance adjustment layer is less than 100 μm, it may be difficult to uniformly form the thickness of the resistance adjustment layer, or the effect of reducing resistance unevenness of the lower conductive layer may be reduced. is there.

  Fillers, plasticizers, processing aids, cross-linking aids, cross-linking accelerators, cross-linking accelerators, cross-linking retarders, adhesives that are commonly used as rubber compounding agents as necessary for both the conductive layer and resistance adjusting layer An imparting agent or a dispersing agent can also be added.

  Examples of the mixing method of these raw materials include a mixing method using a closed mixer such as a Banbury mixer and a pressure kneader, and a mixing method using an open mixer such as an open roll.

  As a method for forming the elastic body layer, for example, an unvulcanized semiconductive rubber composition is extruded into a tube shape by an extruder, and a core metal is press-fitted into a product obtained by vulcanization molding with a vulcanization can, The method of grind | polishing the surface and making it a desired outer diameter can be mentioned. In addition, for example, the vulcanized semiconductive rubber composition is coextruded into a cylindrical shape around a core metal by an extruder equipped with a cross head, and fixed inside a mold having a desired outer diameter, heated, and molded. The method of obtaining a body can be mentioned.

  In FIG. 2, the outline | summary of the extruder used for shaping | molding is shown as an example which shape | molds the laminated body which made the elastic body layer 2 layer structure. The unvulcanized conductive layer rubber composition and the unvulcanized resistance adjusting layer composition are respectively fed using separate extruders shown in 21 and 22, and are laminated on the outer periphery of the cored bar in the extrusion head 23.

  FIG. 3 schematically shows a cross-sectional view of the extrusion head 23 of FIG. The unvulcanized conductive layer rubber composition follows the path indicated by the arrow 32 in the figure, and the unvulcanized resistance adjustment layer composition follows the path indicated by the arrow 31 in the figure, and on the outer periphery of the core metal inserted from the arrow 33 in the figure. Laminated.

  The outer diameter of the obtained cylindrical laminate can be adjusted to a desired thickness by changing the diameter of the die 34, and the thickness of the inner conductive layer and the outer resistance adjustment layer can be adjusted according to each extruder. It can be adjusted by the ratio of the rubber discharge amount (screw rotation speed).

  As an example of vulcanization molding of the obtained laminate using a molding die, FIG. 4 shows an example of a molding die to be used. As shown in FIG. 4, the unvulcanized laminate is inserted into a cylindrical molding die 42 having lids 41 at both ends for holding the core metal on the concentric shaft with the inner peripheral surface of the molding die, This is done by vulcanization and foaming. As a result, the foamed conductive layer rubber is formed on the outer peripheral surface of the core metal, and the non-foaming resistance adjusting layer is formed on the outer peripheral surface of the foamed conductive layer rubber.

The surface layer of the present invention is formed of a material having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω · cm. If the volume resistivity is less than 1 × 10 ⁸ Ω · cm, there is no effect of suppressing ghosts and charged horizontal stripes. If it exceeds 1 × 10 ¹⁴ Ω · cm, slight film thickness unevenness on the surface layer may cause an image defect. is there.

  The average film thickness of the surface layer is 10 to 100 nm. If it is less than 10 nm, it is difficult to obtain a uniform film thickness, and image defects may occur due to film thickness unevenness. On the other hand, if it exceeds 100 nm, the electrical resistance of the charging roller increases, and ghost / charging horizontal streaks may occur.

  The ratio between the maximum value and the minimum value of the surface layer thickness (film thickness unevenness) is within twice. When the film thickness unevenness is more than twice, the potential unevenness of the charged body may occur due to the film thickness difference of the surface layer. A preferred surface layer thickness is 10 to 50 nm.

  The surface layer preferably contains a polysiloxane having an oxyalkylene group, and more preferably contains a polysiloxane having an oxyalkylene group and a fluorinated alkyl group.

  Examples of the fluorinated alkyl group include those in which part or all of the hydrogen atoms of a linear or branched alkyl group are substituted with fluorine atoms. Among these, a linear perfluoroalkyl group having 6 to 31 carbon atoms is preferable.

  The oxyalkylene group is a divalent group having a structure represented by —O—R— (R: alkylene group) (sometimes referred to as “alkylene ether group”). As this R (alkylene group), a C1-C6 alkylene group is preferable.

  The content of the fluorinated alkyl group in the polysiloxane is preferably 5.0 to 50.0 mass% with respect to the total mass of the polysiloxane. Moreover, it is preferable that content of the oxyalkylene group in polysiloxane is 5.0-70.0 mass% with respect to polysiloxane total mass. Furthermore, it is preferable that content of the siloxane part in polysiloxane is 20.0-90.0 mass% with respect to polysiloxane total mass.

  The polysiloxane preferably further has an alkyl group and a phenyl group. The alkyl group is preferably a linear or branched alkyl group having 1 to 21 carbon atoms, and more preferably a methyl group, an ethyl group, an n-propyl group, a hexyl group, or a decyl group.

  When the polysiloxane further has an alkyl group and a phenyl group, the content of the fluorinated alkyl group in the polysiloxane is preferably 5.0 to 50.0% by mass with respect to the total mass of the polysiloxane. Moreover, it is preferable that content of the oxyalkylene group in polysiloxane is 5.0-30.0 mass% with respect to the polysiloxane total mass. Moreover, it is preferable that content of the alkyl group in polysiloxane is 5.0-30.0 mass% with respect to polysiloxane total mass. Moreover, it is preferable that content of the phenyl group in polysiloxane is 5.0-30.0 mass% with respect to polysiloxane total mass. Moreover, it is preferable that content of the siloxane part in polysiloxane is 20.0-80.0 mass% with respect to polysiloxane total mass.

  As a method for producing the polysiloxane, first, a hydrolyzable silane compound having a cationically polymerizable group and a hydrolyzable silane compound having a fluorinated alkyl group are condensed by hydrolysis to obtain a hydrolyzable condensate. . Next, the polysiloxane can be obtained by crosslinking the hydrolyzable condensate by cleaving the cationically polymerizable group.

  As the hydrolyzable silane compound having a group capable of cationic polymerization, a hydrolyzable silane compound having a structure represented by the following general formula (2) is preferable.

In the general formula (2), R ²¹ independently represents a saturated or unsaturated monovalent hydrocarbon group. R ²² independently represents a saturated or unsaturated monovalent hydrocarbon group. Z ²¹ represents a divalent organic group. Rc ²¹ represents a group capable of cationic polymerization. d is an integer of 0 to 2, e is an integer of 1 to 3, and d + e = 3.

The cationically polymerizable group Rc ²¹ of the general formula (2), means a cationic polymerizable organic group which forms an oxyalkylene group by cleavage, for example, cyclic ether groups such as an epoxy group and an oxetane group, or And vinyl ether groups. Among these, an epoxy group is preferable from the viewpoint of availability and reaction control.

Examples of the saturated or unsaturated monovalent hydrocarbon group represented by R ²¹ and R ^{22 in} the general formula (2) include an alkyl group, an alkenyl group, and an aryl group. Among these, a linear or branched alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.

Examples of the divalent organic group represented by Z ^{21 in} the general formula (2) include an alkylene group and an arylene group. Among these, an alkylene group having 1 to 6 carbon atoms is preferable, and an ethylene group is more preferable.

  E in the general formula (2) is preferably 3.

When d in the general formula (2) is 2, two R ²¹ may be the same or different.

When e in the general formula (2) is 2 or 3, two or three R ²² may be the same or different.

  Below, the specific example of the hydrolysable silane compound which has a structure shown by General formula (2) is shown.

(2-1): Glycidoxypropyltrimethoxysilane (2-2): Glycidoxypropyltriethoxysilane (2-3): Epoxycyclohexylethyltrimethoxysilane (2-4): Epoxycyclohexylethyltriethoxysilane Moreover, as a hydrolysable silane compound which has the said fluorinated alkyl group, the hydrolysable silane compound which has a structure shown by following General formula (3) is suitable.

In the general formula (3), R ³¹ independently represents a saturated or unsaturated monovalent hydrocarbon group. R ³² independently represents a saturated or unsaturated monovalent hydrocarbon group. Z ³¹ represents a divalent organic group. Rf ³¹ represents a linear perfluoroalkyl group having 1 to ³¹ carbon atoms. f is an integer of 0 to 2, g is an integer of 1 to 3, and f + g = 3.

Examples of the saturated or unsaturated monovalent hydrocarbon group represented by R ³¹ and R ^{32 in} the general formula (3) include an alkyl group, an alkenyl group, and an aryl group. Among these, a linear or branched alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group and an ethyl group are more preferable.

Examples of the divalent organic group for Z ^{31 in} the general formula (3) include an alkylene group and an arylene group. Among these, an alkylene group having 1 to 6 carbon atoms is preferable, and an ethylene group is more preferable.

The linear perfluoroalkyl group having 1 to ³¹ carbon atoms of Rf ^{31 in} the general formula (3) is particularly preferably a linear perfluoroalkyl group having 6 to ³¹ carbon atoms from the viewpoint of processability. .

  G in the general formula (3) is preferably 3.

When f in the general formula (3) is 2, two R ³¹ may be the same or different.

When g in the general formula (3) is 2 or 3, two or three R ³² may be the same or different.

  Below, the specific example of the hydrolysable silane compound which has a structure shown by General formula (3) is shown.

(3-1): CF ₃ — (CH ₂ ) ₂ —Si— (OR) ₃
(3-2): F (CF ₂ ) ₂ — (CH ₂ ) ₂ —Si— (OR) ₃
(3-3): F (CF ₂ ) ₄ — (CH ₂ ) ₂ —Si— (OR) _{3
(3-4): F (CF 2} ) 6 - (CH 2) 2 -Si- (OR) 3
(3-5): F (CF ₂ ) ₈ — (CH ₂ ) ₂ —Si— (OR) ₃
(3-6): F (CF ₂ ) ₁₀ — (CH ₂ ) ₂ —Si— (OR) ₃
R in the above (3-1) to (3-6) represents a methyl group or an ethyl group.

  Among the above (3-1) to (3-6), (3-4) to (3-6) are preferable.

  The hydrolyzable silane compound having a cationically polymerizable group and the hydrolyzable silane compound having a fluorinated alkyl group may be used alone or in combination of two or more.

In particular, when the hydrolyzable silane compound having the structure represented by the general formula (3) is used as the hydrolyzable silane compound having a fluorinated alkyl group, the following (A) and (B) are used in combination. May be.
(A) Rf ^{31 having} a carbon number nA (nA is an integer of 6 to ³¹ ).
(B) The number of carbon atoms is nB (nB is an integer of 6 to 31 and nB ≠ nA).

  As a result, a polysiloxane having perfluoroalkyl groups having different carbon numbers is obtained. The perfluoroalkyl group tends to be oriented toward the surface of the charging member. Therefore, if the polysiloxane contained in the surface layer of the charging member has perfluoroalkyl groups having different carbon numbers, the perfluoroalkyl groups having different lengths are oriented toward the surface of the charging member. . In this case, the concentration of fluorine atoms in the vicinity of the surface of the charging member is higher and the surface free energy of the charging member is lower than when a single length of perfluoroalkyl group is oriented toward the surface of the charging member. . Therefore, sticking of toner, external additives, and the like to the surface of the charging member when repeatedly used for a long time can be suppressed.

  When using 2 or more types of hydrolysable silane compounds which have a structure shown by General formula (3), it is preferable to select 2 or more types from said (3-4)-(3-6).

  As described above, as a method for producing the polysiloxane used in the charging member of the present invention, first, a hydrolyzable silane compound having a cationically polymerizable group and a hydrolyzable silane compound having a fluorinated alkyl group are hydrolyzed. To obtain a hydrolyzable condensate. It can then be obtained by crosslinking the hydrolyzable condensate by cleaving the cationically polymerizable group. In this case, from the viewpoint of controlling the surface properties of the charging member, when obtaining a hydrolyzable condensate, it is preferable to further use a hydrolyzable silane compound having a structure represented by the following general formula (1). .

In the general formula (1), R ¹¹ independently represents an alkyl group having a phenyl group as a substituent or an unsubstituted alkyl group, or an aryl group having an alkyl group as a substituent or an unsubstituted aryl group. R ¹² independently represents a saturated or unsaturated monovalent hydrocarbon group. a is an integer of 0 to 3, b is an integer of 1 to 4, and a + b = 4.

As the alkyl group of the phenyl group-substituted alkyl group or unsubstituted alkyl group represented by R ^{11 in} the general formula (1), a linear alkyl group having 1 to 21 carbon atoms is preferable.

As the aryl group of the alkyl group-substituted aryl group or unsubstituted aryl group of R ^{11 in} the general formula (1), a phenyl group is preferable.

  A in the general formula (1) is preferably an integer of 1 to 3, and more preferably 1.

  B in the general formula (1) is preferably an integer of 1 to 3, more preferably 3.

Examples of the saturated or unsaturated monovalent hydrocarbon group represented by R ^{12 in} the general formula (1) include an alkyl group, an alkenyl group, and an aryl group. Among these, a linear or branched alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group, an ethyl group, and an n-propyl group are more preferable.

When a in the general formula (1) is 2 or 3, two or three R ¹¹ may be the same or different.

When b in the general formula (1) is 2, 3 or 4, 2, 3 or 4 R ¹² may be the same or different.

  Below, the specific example of the hydrolysable silane compound which has a structure shown by General formula (1) is shown.

(1-1): Tetramethoxysilane (1-2): Tetraethoxysilane (1-3): Tetrapropoxysilane (1-4): Methyltrimethoxysilane (1-5): Methyltriethoxysilane (1- 6): methyltripropoxysilane (1-7): ethyltrimethoxysilane (1-8): ethyltriethoxysilane (1-9): ethyltripropoxysilane (1-10): propyltrimethoxysilane (1- 11): Propyltriethoxysilane (1-12): Propyltripropoxysilane (1-13): Hexyltrimethoxysilane (1-14): Hexyltriethoxysilane (1-15): Hexyltripropoxysilane (1- 16): Decyltrimethoxysilane (1-17): Decyltriethoxysilane (1-18): Decyl Rutripropoxysilane (1-19): Phenyltrimethoxysilane (1-20): Phenyltriethoxysilane (1-21): Phenyltripropoxysilane (1-22): Diphenyldimethoxysilane (1-23): Diphenyldi Ethoxysilane When a hydrolyzable silane compound having a structure represented by the general formula (1) and a hydrolyzable silane compound having a structure represented by the general formula (3) are used in combination, a in the general formula (1) is 1 It is preferable that it is an integer of -3, and b is preferably an integer of 1-3. Further, it is preferred that one of R ¹¹ of a number of R ¹¹ is a linear alkyl group of 1 to 21 carbon atoms. Furthermore, the carbon number of the linear alkyl group having 1 to 21 carbon atoms is n1 (n1 is an integer of 1 to ²¹ ), and the carbon number of Rf ³¹ in the general formula (3) is n2 (n2 is 1 to 1). It is preferable that n2-1 ≦ n1 ≦ n2 + 1. The linear alkyl group having 1 to 21 carbon atoms tends to be oriented toward the surface of the charging member, like the perfluoroalkyl group. However, when n1> n2 + 2, the effect of the perfluoroalkyl group of the hydrolyzable silane compound having the structure represented by the general formula (3) may be poor. On the other hand, when n1 <n2-2, the ghost may deteriorate.

Only 1 type of hydrolysable silane compound which has a structure shown by General formula (1) may be used, and may be used 2 or more types. When using 2 or more types, it is preferable to use together that whose R < ¹¹ > in General formula (1) is an alkyl group, and whose R < ¹¹ > in General formula (1) is a phenyl group. This is because the alkyl group is preferable from the viewpoint of controlling the surface properties of the charging member, and the phenyl group is preferable from the viewpoint of suppressing the ghost phenomenon.

  Hereinafter, a specific method for forming the surface layer containing the polysiloxane will be described.

  First, a hydrolyzable silane compound having a cationically polymerizable group and a hydrolyzable silane compound having a fluorinated alkyl group, and if necessary, hydrolyzing the other hydrolyzable silane compound in the presence of water. A hydrolyzable condensate is obtained by reacting.

  During the hydrolysis reaction, a hydrolyzable condensate having a desired degree of condensation can be obtained by controlling temperature, pH and the like.

  In the hydrolysis reaction, the degree of condensation may be controlled by using a metal alkoxide or the like as a catalyst for the hydrolysis reaction. Examples of the metal alkoxide include aluminum alkoxide, titanium alkoxide, zirconium alkoxide and the like, and complexes thereof (acetylacetone complex and the like).

  The mixing ratio of the hydrolyzable silane compound having a group capable of cationic polymerization and the hydrolyzable silane compound having a fluorinated alkyl group is such that the content of the fluorinated alkyl group in the obtained polysiloxane is based on the total mass of the polysiloxane. It is preferable to be 5.0 to 50.0% by mass.

  The same applies to the blending ratio of the hydrolyzable silane compound having a cationically polymerizable group, the hydrolyzable silane compound having a fluorinated alkyl group, and the hydrolyzable silane compound having a structure represented by the general formula (1).

  Moreover, it is preferable that the content of the oxyalkylene group is 5.0 to 70.0% by mass with respect to the total mass of the polysiloxane. Furthermore, it is preferable that the content of the siloxane portion is 20.0 to 90.0% by mass with respect to the total mass of the polysiloxane.

  Specifically, the hydrolyzable silane compound having a fluorinated alkyl group is preferably blended so as to be in the range of 0.5 to 20.0 mol% with respect to the total hydrolyzable silane compound, and in particular, 1 It is more preferable to mix | blend so that it may become the range of 0.0-10.0 mol%.

  Moreover, when using together the hydrolysable silane compound which has a structure shown by General formula (1), it is preferable to mix | blend so that it may become the following ranges. The molar ratio (MC: M1) of the hydrolyzable silane compound (MC) having a group capable of cationic polymerization and the hydrolyzable silane compound (M1) having the structure represented by the general formula (1) is 10: 1 to 1 : 10.

  Next, a surface layer coating solution containing the obtained hydrolyzable condensate is prepared, and the prepared surface layer coating solution is applied onto the charging roller elastic layer.

  When preparing the coating solution for the surface layer, an appropriate solvent may be used in addition to the hydrolyzable condensate in order to improve the coating property. Suitable solvents include, for example, alcohols such as ethanol and 2-butanol, ethyl acetate, methyl ethyl ketone, or a mixture thereof. Moreover, when applying the surface layer coating liquid onto the conductive elastic member, coating using a roll coater, dip coating, ring coating, or the like can be employed.

  Next, an active energy ray is irradiated to the applied coating liquid for the surface layer. Then, the cationically polymerizable group in the hydrolyzable condensate contained in the coating solution for the surface layer is cleaved, whereby the hydrolyzable condensate can be crosslinked. The hydrolyzable condensate is cured by crosslinking.

  As the active energy ray, ultraviolet rays are preferable. For irradiation with ultraviolet rays, a high-pressure mercury lamp, a metal halide lamp, a low-pressure mercury lamp, an excimer UV lamp, or the like can be used, and among these, an ultraviolet ray source rich in light having a wavelength of 150 to 480 nm is used.

  The integrated light quantity of ultraviolet rays is defined as follows.

UV integrated light quantity [mJ / cm ² ] = UV intensity [mW / cm ² ] × irradiation time [s]
The adjustment of the accumulated amount of ultraviolet light can be performed by the irradiation time, lamp output, distance between the lamp and the irradiated object, and the like. Moreover, you may give a gradient to integrated light quantity within irradiation time.

  In the case of using a low-pressure mercury lamp, the integrated light amount of ultraviolet rays can be measured using an ultraviolet integrated light amount meter UIT-150-A or UVD-S254 manufactured by USHIO INC. Further, when an excimer UV lamp is used, the integrated light amount of ultraviolet rays can be measured using an ultraviolet integrated light amount meter UIT-150-A or VUV-S172 manufactured by USHIO INC.

  In the crosslinking reaction, it is preferable that a cationic polymerization catalyst (polymerization initiator) is allowed to coexist from the viewpoint of improving the crosslinking efficiency. For example, since an epoxy group exhibits high reactivity with respect to an onium salt of a Lewis acid activated by an active energy ray, the above cationic polymerizable group is an epoxy group. It is preferable to use an onium salt of an acid.

  Examples of other cationic polymerization catalysts include borate salts, compounds having an imide structure, compounds having a triazine structure, azo compounds, and peroxides.

  Among various cationic polymerization catalysts, aromatic sulfonium salts and aromatic iodonium salts are preferable from the viewpoints of sensitivity, stability, and reactivity. In particular, a bis (4-tert-butylphenyl) iodonium salt, a compound having a structure represented by the following formula (Chemical Formula 4), or a compound having a structure represented by the following Formula (Chemical Formula 5) is preferable. The compound represented by Chemical Formula 4 is sold by ADEKA Corporation under the trade name: Adekaoptoma-SP150. The compound represented by Chemical formula 5 is sold by Ciba Specialty Chemicals under the trade name: Irgacure 261.

  It is preferable that the usage-amount of a cationic polymerization catalyst is 1-3 mass% with respect to a hydrolyzable condensate.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to these. In the examples, “part” means “part by mass”.

<Example 1>
(Production of rubber composition)
As raw rubber, the following materials were mixed with an open roll to obtain an unvulcanized rubber composition 1 for a conductive layer.
Acrylonitrile-butadiene copolymer (trade name: N250SL manufactured by JSR): 100 parts,
Processing aid: Zinc stearate (trade name: Zinc stearate manufactured by Nippon Oil & Fats): 1 part
Vulcanization accelerating aid: Zinc oxide (2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts,
Filler: SRF carbon black (Asahi # 35 manufactured by Asahi Carbon Co.): 30 parts
Conductive agent: Ketjen Black (trade name: Ketjen Black EC600JD, manufactured by Ketjen Black International): 10 parts,
Anti-aging agent: 2,2′-methylenebis (4-ethyl-6-tert-butylphenol) (trade name: NOCRACK NS-5 manufactured by Ouchi Shinsei Chemical Co., Ltd.): 2 parts,
Cross-linking agent: sulfur (trade name: Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.): 1.5 parts
Vulcanization accelerator: dibenzothiazolyl disulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 2 parts, tetrabenzylthiuram disulfide (trade name: Noxeller TBzTD, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 2 Part,
Foaming agent: azodicarbonamide (ADCA) (trade name: biphonyl AC # 3, manufactured by Eiwa Kasei Kogyo Co., Ltd.): 4 parts Foaming aid: urea (trade name: Cell Paste A, manufactured by Eiwa Kasei Kogyo Co., Ltd.): 4 parts As raw rubber The following materials were mixed with an open roll to obtain an unvulcanized rubber composition 2 for the resistance adjusting layer.
Epichlorohydrin rubber (trade name: Epion 301, manufactured by Daiso) 100 parts,
Vulcanization accelerator: Zinc stearate (trade name: Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd.): 1 part, Zinc oxide (2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts,
Filler: Calcium carbonate (trade name: Silver W manufactured by Shiroishi Kogyo Co., Ltd.): 40 parts,
Vulcanization accelerator: benzothiazolyl disulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 1.0 part, tetrabenzylthiuram disulfide (trade name: Noxeller TBzTD, manufactured by Ouchi New Chemical Co., Ltd.) : 2 parts Vulcanizing agent: Sulfur (trade name: Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.): 1.2 parts (production of rubber roller)
Two types of obtained unvulcanized rubber compositions were simultaneously extruded into a cylindrical shape coaxially with a cored bar (diameter 6 mm, length 252 mm) by extrusion molding using the crosshead shown in FIG. The end was cut. In this way, a charged shape was produced in which an unvulcanized conductive layer and a resistance adjusting layer were laminated on the outer periphery of the cored bar. The material having the prepared shape and the core metal integrated are fixed inside the molding die (crown shape having an inner diameter of 8.2 mm and an inner diameter of 8.5 mm) shown in FIG. Vulcanization was performed at 160 ° C. for 15 minutes. After demolding, secondary vulcanization was further performed in an electric furnace at 160 ° C. for 30 minutes, and then both ends were cut off. The length of the elastic layer was 228 mm, the end diameter was 8.2 mm, and the central part diameter was 8.5 mm. A rubber roller 1 having an elastic body layer having a crown shape was obtained. At this time, the thickness of the resistance adjusting layer measured from the cross section of the elastic layer was 400 μm.

(Roller electrical resistance measurement)
FIG. 6 shows a schematic diagram of an electrical resistance measuring apparatus. The rubber roller 64 is pressed against the cylindrical aluminum drum 61 having a diameter of 30 mm by pressing means (not shown) at both ends of the core metal 11, and rotates following the rotation of the aluminum drum 61. In this state, a DC voltage was applied to the cored bar portion 11 of the rubber roller 64 using the power source 62, and the electric resistance of the rubber roller 64 was calculated from the voltage applied to the resistor 63 connected in series to the 61 aluminum drum.

Rubber roller 1 electrical resistance is 23 ° C., 50% R.D. H. Under the environment (also referred to as N / N), the electrical resistance is obtained by using the apparatus of FIG. 6 and applying a voltage of DC 200V for 2 seconds between the core drum and the metal drum at a rotation speed of the aluminum drum of 30 rpm. It was. The electrical resistance was an average value for 2 seconds, simultaneously, the maximum value and the minimum value for 2 seconds were measured, and the maximum value / minimum value was expressed as circumferential unevenness. As a result, the electric resistance of the rubber roller 1 was 1.5 × 10 ⁵ Ω and the circumferential unevenness was 1.1 times.

(Preparation of surface layer)
Next, after the following materials were mixed, the mixture was stirred at room temperature and then heated to reflux (120 ° C.) for 24 hours to obtain a hydrolyzable silane compound condensate I.
37.44 g of phenyltriethoxysilane (PhTES) (0.156 mol (equivalent to 48.67 mol% with respect to the total amount of hydrolyzable silane compounds)),
21.68 g (0.078 mol) of glycidoxypropyltriethoxysilane (GPTES),
Hexyltrimethoxysilane (HeTMS) 13.21 g (0.064 mol)
Tridecafluoro-1,1,2,2, tetrahydrooctyltriethoxysilane (FTS, carbon number 6 of perfluoroalkyl group) 11.42 g (0.022 mol)
25.93 g of water
71.91 g of ethanol
The pH during the hydrolysis reaction was 5, and the Roh was 1.5. Here, Roh is
Roh = [H ₂ O] / [OR]
Means the value defined by. [H ₂ O] means the number of moles of water molecules, and [OR] means the number of moles of all alkoxy groups contained in the hydrolyzable silane compound.

  This condensate I was added to a mixed solvent of 2-butanol / ethanol to prepare a condensate-containing alcohol solution I having a solid content of 7% by mass.

  0.35 g of an aromatic sulfonium salt (trade name: Adekaoptomer SP-150, manufactured by Asahi Denka Kogyo Co., Ltd.) as a photocationic polymerization initiator for 100 g of this condensate-containing alcohol solution I was used as a condensate-containing alcohol. Added to Solution I. Subsequently, this was further diluted with ethanol to prepare a surface layer coating solution I having a solid content of 2% by mass.

  Next, the surface layer coating liquid I was ring-applied on the elastic layer of the rubber roller 1 (discharge amount: 0.008 ml / s (ring portion speed: 30 mm / s, total discharge amount: 0.064 ml).

Next, the coating solution I for surface layer is cured (crosslinking reaction) by irradiating the coating solution I for surface layer ring-coated on the elastic layer with ultraviolet light having a wavelength of 254 nm so that the integrated light quantity becomes 8500 mJ / cm ^2. Curing). Next, this cured product was left to dry for a few seconds (2 to 3 seconds) to form a surface layer. A low-pressure mercury lamp manufactured by Harrison Toshiba Lighting Co., Ltd. was used for ultraviolet irradiation.

  It is considered that the glycidoxy group of glycidoxypropyltriethoxysilane was cleaved by irradiation with ultraviolet rays, and the crosslinking reaction of condensate I occurred.

  As described above, the support, the elastic layer formed on the support, and the surface layer formed on the elastic layer (a layer containing polysiloxane formed using the surface layer coating liquid I) ) Was prepared.

(Measurement of volume resistivity of surface layer)
The surface layer coating solution I was formed on an aluminum sheet with a bar coater, irradiated with ultraviolet rays in the same manner as a roller, and cured, and the volume resistivity of the surface layer was measured from the sheet sample. The measurement was performed using a Hi-Lester (Mitsubishi Chemical Corporation), and the value after 30 seconds of voltage application was measured at an applied voltage of 100V. As a result, the volume resistivity of the surface layer I was 1 × 10 ¹³ Ω · cm.

(Measurement of surface layer thickness)
About 1 cm from the both ends of the elastic body layer of the charging roller-1 and the central part, samples were cut out at 2 places in the circumferential direction, a total of 6 places, and the film thickness of the surface layer was measured by electron microscope observation. The average film thickness at 6 locations was 30 nm, and the ratio of the maximum thickness to the minimum thickness at 6 locations was 1.5 times.

(Charge roller image evaluation)
The following image evaluation was performed using the charging roller 1 manufactured in the same manner as described above.

  First, the charging roller I and the electrophotographic photosensitive member were incorporated into a process cartridge that integrally supports them, and this process cartridge was mounted on a laser beam printer for vertical output of A4 paper. The developing method of this laser beam printer is a reversal developing method, the output speed of the transfer material is 47 mm / s, and the image resolution is 600 dpi.

  The electrophotographic photosensitive member incorporated in the process cartridge together with the charging roller 1 is an organic electrophotographic photosensitive member formed by forming an organic photosensitive layer having a layer thickness of 14 μm on a support. The organic photosensitive layer is a laminated photosensitive layer in which a charge generation layer and a charge transport layer containing a modified polyarylate (binder resin) are laminated from the support side. The charge transport layer is an electrophotographic photosensitive layer. It is the surface layer of the body.

  The toner used in the laser beam printer is a so-called polymerized toner having a glass transition temperature of 63 ° C. and a volume average particle diameter of 6 μm. The so-called polymerized toner includes, for example, silica fine particles and titanium oxide fine particles obtained by suspension polymerization of a polymerizable monomer system containing a wax, a charge control agent, a dye, styrene, butyl acrylate and an ester monomer in an aqueous medium. It is produced by adding.

  Image output is performed in a 15 ° C./10% RH environment, and a halftone image (an image in which a line with a width of 1 dot is drawn at intervals of 2 dots in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member) is formed on A4 paper. 3000 sheets were output at a process speed of 47 mm / s.

  As an adverse effect of the output image due to the deterioration of the electrical characteristics, the retransfer pattern (ghost) on the first round of the electrophotographic photosensitive member and the occurrence of charged horizontal stripes were observed.

  The output image was evaluated by visually observing the output image at the time of outputting one sheet (initial) and after outputting 3000 sheets (after durability).

  In addition, as an image defect after durability, evaluation of a black spot image due to uneven density of the charging roller pitch and a surface layer defect was also performed.

  The evaluation criteria are as follows.

  A: The above-mentioned image defect does not appear at all.

  B: The above-mentioned image defect occurred slightly.

  C: The above-mentioned image defect slightly occurred.

  D: The above-mentioned image defect clearly occurred.

  The above evaluation results are shown in Table 1.

<Example 2>
As raw rubber, the following materials were mixed with an open roll to obtain an unvulcanized rubber composition 3 for a resistance adjusting layer.
Acrylonitrile-butadiene copolymer (trade name: N230SV, manufactured by JSR): 100 parts,
Processing aid: Zinc stearate (trade name: Zinc stearate manufactured by Nippon Oil & Fats): 1 part
Vulcanization accelerating aid: Zinc oxide (2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts,
Filler: Calcium carbonate (trade name: Silver W manufactured by Shiroishi Kogyo Co., Ltd.): 20 parts
Conductive agent: carbon black (trade name: Toka Black # 7360SB manufactured by Tokai Carbon Co., Ltd.): 40 parts
Anti-aging agent: 2,2′-methylenebis (4-ethyl-6-tert-butylphenol) (trade name: NOCRACK NS-5 manufactured by Ouchi Shinsei Chemical Co., Ltd.): 2 parts,
Crosslinking agent: Sulfur (trade name: Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.): 1.2 parts
Vulcanization accelerator: Tetrabenzylthiuram disulfide (trade name: Noxeller TBzTD, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 4 parts The unvulcanized rubber composition 1 of Example 1 is a conductive layer, and the above-mentioned unvulcanized rubber composition A rubber roller 2 was produced in the same manner as in Example 1 using 3 as a resistance adjustment layer.

The electrical resistance of the rubber roller 2 was measured in the same manner as in Example 1. As a result, the electric resistance of the rubber roller 2 was 2.0 × 10 ⁴ Ω, and the circumferential unevenness was 1.4 times. Further, the thickness of the resistance adjustment layer at this time was 450 μm.

  Next, a surface layer was formed on the rubber roller 2 in the same manner as in Example 1 to obtain the charging roller 2. About the obtained charging roller 2, the film thickness of the surface layer was measured in the same manner as in Example 1. As a result, the average film thickness of the surface layer was 25 nm, and the ratio of the maximum film thickness to the minimum film thickness at six locations was 1.4 times.

  The charging roller 2 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

<Example 3>
As raw rubber, the following materials were mixed with an open roll to obtain an unvulcanized rubber composition 4.
Epichlorohydrin rubber (trade name: Epion 301, manufactured by Daiso Corporation): 100 parts,
Vulcanization accelerator: Zinc stearate (trade name: Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd.): 1 part, Zinc oxide (2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts,
Filler: Calcium carbonate (trade name: Silver W manufactured by Shiroishi Kogyo Co., Ltd.): 40 parts,
Ionic conductive agent: N-hexaoxyethylene-N, N, N-monododecyldimethylammonium perchlorate: 0.3 parts
Vulcanization accelerator: benzothiazolyl disulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 1.0 part, tetrabenzylthiuram disulfide (trade name: Noxeller TBzTD, manufactured by Ouchi New Chemical Co., Ltd.): 2 parts Vulcanizing agent: Sulfur (trade name: Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.): 1.2 parts The above unvulcanized rubber composition 4 is 9.4 mm in outer diameter and 5.4 mm in inner diameter with a rubber extruder. Was extruded into a cylindrical shape, cut to a length of 250 mm, and primary vulcanized with steam at 160 ° C. for 30 minutes in a vulcanizing can to obtain a primary vulcanized tube for an elastic layer.

  The above-mentioned primary vulcanization tube for elastic layer was press-fitted into the same metal core as in Example 1, and then secondary vulcanization was performed at 160 ° C. for 30 minutes. Next, both ends of the elastic layer portion are cut so that the axial width of the elastic layer portion is 228 mm, and then the surface of the conductive elastic layer portion is polished with a rotating grindstone so that the end diameter is 8.2 mm and the central portion A crown-shaped rubber roller 3 having a diameter of 8.5 mm was obtained.

The electrical resistance of the rubber roller 3 was measured in the same manner as in Example 1. As a result, the electric resistance of the rubber roller 3 was 3.0 × 10 ⁴ Ω and the circumferential unevenness was 1.1 times.

  Next, a surface layer was formed on the rubber roller 3 in the same manner as in Example 1 to obtain the charging roller 3. About the obtained charging roller 3, the film thickness of the surface layer was measured in the same manner as in Example 1. As a result, the average thickness of the surface layer was 30 nm, and the ratio of the maximum thickness to the minimum thickness at six locations was 1.5 times.

  The charging roller 3 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

<Example 4>
Using the unvulcanized rubber composition 3 of Example 2, extrusion, vulcanization and polishing were carried out in the same manner as in Example 3 to obtain a rubber roller 4.

The obtained rubber roller 4 was measured for electric resistance in the same manner as in Example 1. As a result, the electric resistance of the rubber roller 4 was 3.5 × 10 ⁴ Ω, and the circumferential unevenness was 1.3 times.

  Next, a surface layer was formed on the rubber roller 4 in the same manner as in Example 1 to obtain the charging roller 4.

  About the obtained charging roller 4, the film thickness of the surface layer was measured in the same manner as in Example 1. As a result, the average thickness of the surface layer was 25 nm, and the ratio of the maximum thickness to the minimum thickness at six locations was 1.3 times.

  The charging roller 4 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
As raw rubber, the following materials were mixed with an open roll to obtain an unvulcanized rubber composition 5.
Epichlorohydrin rubber (trade name: Epichromer CG102, manufactured by Daiso Corporation): 100 parts,
Vulcanization accelerator: Zinc stearate (trade name: Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd.): 1 part, Zinc oxide (2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts,
Filler: Calcium carbonate (trade name: Silver W manufactured by Shiroishi Kogyo Co., Ltd.): 40 parts,
Ionic conductive agent: N-hexaoxyethylene-N, N, N-monododecyldimethylammonium perchlorate: 0.3 parts
Vulcanization accelerator: benzothiazolyl disulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 1.0 part, tetrabenzylthiuram disulfide (trade name: Noxeller TBzTD, manufactured by Ouchi New Chemical Co., Ltd.): 2 parts and vulcanizing agent: sulfur (trade name: Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.) 1.2 parts Extruded, vulcanized and cured as in Example 3 using the obtained unvulcanized rubber composition 5 Polishing was performed to obtain a rubber roller 5.

The obtained rubber roller 5 was measured for electric resistance in the same manner as in Example 1. As a result, the electric resistance of the rubber roller 5 was 3.5 × 10 ⁵ Ω, and the circumferential unevenness was 1.1 times.

Next, the following materials were mixed and dispersed with a paint shaker for 70 hours.
Conductive tin oxide powder (trade name: SN-100P, manufactured by Ishihara Sangyo Co., Ltd.): 50 parts by mass of trifluoropropyltrimethoxysilane in 1% isopropyl alcohol: 500 parts by mass Glass beads having an average particle size of 0.8 mm: 300 Parts by mass,
This dispersion is filtered through a mesh of 500 mesh, and then the solution is heated in a 100 ° C. hot water bath while stirring with a Nauta mixer, the alcohol is blown off and dried, and a silane coupling agent is applied to the surface. A treated conductive tin oxide powder was obtained.

200 parts by mass of a lactone-modified acrylic polyol (trade name: Plaxel DC2009, manufactured by Daicel Chemical Industries) was dissolved in 500 parts by mass of MIBK (methyl isobutyl ketone) to obtain a solution having a polyol concentration of 20% by mass. The following (i) to (d) were added to 200 parts by mass of this acrylic polyol solution, placed in a 450 ml bottle, and dispersed for 15 hours using a paint shaker to prepare a dispersion.
(A) The surface-treated conductive tin oxide powder: 50 parts by mass
(B) Silicone oil (trade name: SH-28PA, manufactured by Toray Dow Corning Silicone): 0.01 parts by mass,
(C) Fine particle silica (primary particle size 0.02 μm) surface-treated with hexamethylene disilazane 1.2 parts by mass (d) Glass beads having a diameter of 0.8 mm: 200 parts by mass.

The following (e) and (f) were added to 370 parts by mass of the dispersion prepared above, and the mixture was stirred for 1 hour with a ball mill.
(E) Block type isocyanurate type trimer of isophorone diisocyanate (trade name: Bestanat B1370, manufactured by Degussa Huls): 33.5 parts by mass;
(F) Isocyanurate type trimer of hexamethylene diisocyanate (trade name: Duranate TPA-B80E, manufactured by Asahi Kasei Kogyo Co., Ltd.): 21.5 parts by mass.

  Thereafter, the solution was filtered through a mesh of 500 mesh, and further diluted with MIBK to prepare a surface layer coating solution II having a solid content ratio of 2% by mass.

  The surface layer coating solution II was ring-coated in the same manner as in Example 1, air-dried for 30 minutes, and then dried at 160 ° C. for 100 minutes to obtain a charging roller 5.

The surface layer coating solution II was formed on an aluminum sheet with a bar coater, air-dried for 30 minutes in the same manner as a roller, and then dried at 160 ° C. for 100 minutes, and the volume resistivity of the surface layer was measured from this sheet sample. did. The measurement was performed in the same manner as in Example 1. As a result, the volume resistivity of the surface layer II was 8 × 10 ¹³ Ω · cm.

  About the obtained charging roller 5, the film thickness of the surface layer was measured in the same manner as in Example 1. As a result, the average thickness of the surface layer was 90 nm, and the ratio of the maximum thickness to the minimum thickness at six locations was 1.8 times.

  The charging roller 5 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

<Comparative example 2>
As raw rubber, the following materials were mixed with an open roll to obtain an unvulcanized rubber composition 6.
Acrylonitrile-butadiene copolymer (trade name: N250SL manufactured by JSR): 100 parts,
Processing aid: Zinc stearate (trade name: Zinc stearate manufactured by Nippon Oil & Fats): 1 part
Vulcanization accelerating aid: Zinc oxide (2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts,
Filler: SRF carbon black (Asahi # 35 Asahi Carbon Co., Ltd.): 40 parts
Conductive agent: Ketjen Black (Ketjen Black EC600JD manufactured by Ketjen Black International): 6 parts
Anti-aging agent: 2,2′-methylenebis (4-ethyl-6-tert-butylphenol) (trade name: NOCRACK NS-5 manufactured by Ouchi Shinsei Chemical Co., Ltd.): 2 parts,
Crosslinking agent: Sulfur (trade name: Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.): 0.8 parts
Vulcanization accelerator: Dibenzothiazolyl disulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 1 part, Tetrabenzylthiuram disulfide (trade name: Noxeller TBzTD, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 2 Part Using the obtained unvulcanized rubber composition 6, extrusion, vulcanization and polishing were carried out in the same manner as in Example 3 to obtain a rubber roller 6.

The obtained rubber roller 6 was measured for electric resistance in the same manner as in Example 1. As a result, the electric resistance of the rubber roller 6 was 4.0 × 10 ⁴ Ω, and the circumferential unevenness was 2.2 times.

  Next, a surface layer was formed on the rubber roller 6 in the same manner as in Comparative Example 1 to obtain the charging roller 6.

  About the obtained charging roller 6, the film thickness of the surface layer was measured similarly to Example 1. As a result, the average thickness of the surface layer was 90 nm, and the ratio of the maximum thickness to the minimum thickness at six locations was 1.8 times.

  The charging roller 6 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 3>
In the preparation procedure of the surface layer coating liquid II of Comparative Example 1, the surface layer was the same except that the amount of the surface-treated conductive tin oxide powder was 150 parts by mass and the solid content concentration was 1.5% by mass. Coating solution III was prepared.

  Using the rubber roller 3 produced in Example 3, the surface layer coating solution III was applied by ring coating in the same manner as in Comparative Example 1, and then dried to obtain the charging roller 7.

The coating liquid III was formed on an aluminum sheet in the same manner as in Comparative Example 1, and the volume resistance was measured. As a result, the volume resistance of the surface layer III was 1 × 10 ⁷ Ω · cm.

  For the obtained charging roller 7, the thickness of the surface layer was measured in the same manner as in Example 1. As a result, the average thickness of the surface layer was 85 nm, and the ratio of the maximum thickness to the minimum thickness at six locations was 1.9 times.

  The charging roller 7 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

<Comparative example 4>
A surface layer was formed on the rubber roller 4 produced in Example 4 using the surface layer coating liquid II of Comparative Example 1 in the same manner as in Comparative Example 1 to obtain a charging roller 8.

  About the obtained charging roller 8, the film thickness of the surface layer was measured in the same manner as in Example 1. As a result, the average film thickness of the surface layer was 210 nm, and the ratio of the maximum film thickness to the minimum film thickness at six locations was 2.2 times.

The charging roller 8 was subjected to image evaluation in the same manner as in Example 1. The results are shown in Table 1.

  Table 2 shows a compounding table of rubber compositions used in Examples and Comparative Examples.

  As is apparent from Table 1, in Comparative Example 1, the electrical resistance of the elastic layer is high, and as a result, the charging lateral streaks during durability deteriorate. In Comparative Example 2, the unevenness of the electrical resistance of the elastic layer is large, and as a result, the unevenness of density (step unevenness) occurs during the durability. In Comparative Example 3, since the electrical resistance of the surface layer is low, a ghost image defect occurs. In Comparative Example 4, the thickness of the surface layer is large, and the ghost / charging horizontal streaks during durability deteriorate.

  Examples 1 to 4 are within the scope of the present invention, and in the image evaluation, good images are obtained with rank B or higher for all items both in the initial stage and after the endurance.

FIG. 3 is a schematic cross-sectional view for explaining an example of a charging roller in the present invention. It is a schematic diagram for demonstrating the example of the crosshead extruder in this invention. It is typical sectional drawing for demonstrating the example of the crosshead in this invention. It is typical sectional drawing for demonstrating the example of the shaping die in this invention. It is a typical sectional view for explaining an example of an electrophotographic apparatus in the present invention. It is a schematic diagram for demonstrating the resistance measurement example of the charging roller in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Charging roller 11 Core metal 12 Elastic body layer 121 Conductive layer 122 Resistance adjustment layer 13 Surface layer 21 Extruder 22 Extruder 23 Crosshead 31 Unvulcanized resistance adjustment layer path 32 Unvulcanized conductive layer path 33 Core metal insertion path 34 Die 41 Lid 42 Molding die 51 Image carrier 51a Photosensitive layer 51b Conductive support 51c Support shaft 53 Power supply 53a Sliding power supply 54 Exposure means 55 Development means 56 Transfer roller 57 Transfer material 58 Cleaning means 61 Aluminum drum 62 External power supply 63 Reference resistance 64 Rubber roller

Claims (7)

In a charging member having a conductive support, an elastic layer formed on the conductive support, and a surface layer,
The average value of the electrical resistance of the elastic body layer in the state where the surface layer is not formed is less than 3 × 10 ⁵ Ω when applied for 2 seconds at 200 V in an environment of 23 ° C. and 50% RH, The ratio of the maximum value and the minimum value in the circumferential direction of the resistor is 2.0 times or less,
The volume resistivity of the surface layer is 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω · cm,
The charging member, wherein the average thickness of the surface layer is 10 to 100 nm.   The charging member according to claim 1, wherein a ratio between a maximum value and a minimum value of the film thickness of the surface layer is within twice.   The charging member according to claim 1, wherein the surface layer contains polysiloxane having an oxyalkylene group.   The charging member according to claim 3, wherein the surface layer contains polysiloxane having a fluorinated alkyl group.   The charging member according to claim 1, wherein the elastic layer includes a conductive layer and a resistance adjustment layer formed on the conductive layer.   The charging member according to claim 5, wherein the conductive layer is a layer made of foamed rubber. The charging member according to claim 3, wherein the polysiloxane is a polysiloxane obtained through the following steps (I) to (III).
(I) Condensation step of condensing a hydrolyzable silane compound having a group capable of cationic polymerization and a hydrolyzable silane compound having a fluorinated alkyl group by hydrolysis (II) The hydrolysis obtained in the step (I) Step of forming a degradable condensate on the surface of the elastic body layer of the charging member (III) Hydrolysis of the thin film formed on the surface of the elastic body layer of the step (II) by cleaving the cationically polymerizable group A crosslinking step for crosslinking the degradable condensate.

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