JP2012237886A - Electrophotographic photoreceptor and image forming apparatus including the electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of filming on a surface of a photoreceptor drum.SOLUTION: A photosensitive layer 72 for forming an electrostatic latent image is formed on a surface of a photoreceptor drum 30. The photosensitive layer 72 includes a charge generating layer 72a essentially comprising a charge generating substance and a charge transporting layer 72b essentially comprising a charge transporting substance and a binder resin on a conductive support body 70. As the photosensitive layer 72 is formed to have a surface smoothness of 0.30 to 0.90 [N] and Vickers hardness of 26.7 to 34.2 [gf μm] on the surface, the photoreceptor drum 30 is free from generation of filming.

Description

  The present invention relates to an electrophotographic photosensitive member for forming an electrostatic latent image, and an image forming apparatus provided with the electrophotographic photosensitive member.

  2. Description of the Related Art Conventionally, electrophotographic technology is widely used not only in the field of copying machines but also in various printer fields because high-quality images can be obtained immediately. Organic materials are widely used as the photoconductive material of the photoreceptor, which is the core of the electrophotographic technology.

  In an organic photoreceptor using such an organic photoconductive material, a function-separated photoreceptor in which a charge generation layer and a charge transport layer are laminated is widely used. Function-separated type photoconductors can obtain highly sensitive photoconductors by combining highly efficient charge generating materials and charge transport materials, respectively, and can provide highly safe photoconductors with a wide selection of materials. Furthermore, since the productivity of coating is high and it is relatively advantageous in terms of cost, it has become the mainstream of photoreceptors.

  The mechanism of electrostatic latent image formation in the function-separated type photoreceptor is as follows. That is, after charging the photoconductor, the photoconductor is irradiated with light. This light passes through the charge transport layer and is absorbed by the charge generation material in the charge generation layer to generate a charge. This charge is injected into the charge transport layer at the interface between the charge generation layer and the charge transport layer. The injected charge further moves toward the outermost surface in the charge transport layer by an electric field, and neutralizes the surface charge of the photoreceptor to form an electrostatic latent image.

  In recent years, in the electrophotographic process, there has been an increasing demand for higher image quality of formed images and higher speed of the electrophotographic forming apparatus. In order to realize this high image quality and high speed, the toner has been improved in terms of materials, and since it is necessary to achieve chargeability control, fluidity imparting, and transfer efficiency improvement, the toner must be made of silica or the like. Additives are now included.

JP 2007-183403 A

  However, in the conventional electrophotographic photosensitive member, since an external additive such as silica is included in the toner, there is a filming problem that silica adheres to the surface of the photosensitive drum used in the electrophotographic process. It has surfaced. Until now, measures such as controlling the BET specific surface area (surface area per unit weight) of the toner have been taken, but since the toner contains silica as a toner external additive that causes filming, It was difficult to prevent filming only by improving the toner.

In the electrophotographic photoreceptor of the present invention, a photosensitive layer 72 that generates and transports charges is formed on a conductive support 70. The photosensitive layer 72 is formed by laminating a plurality of layers, and the slip property of the surface of the outermost layer in the photosensitive layer 72 is 0.30 to 0.90 [N], and the surface of the photosensitive layer 72 The Vickers hardness is 26.7 to 34.2 [gf · μm ⁻² ].

  The image forming apparatus of the present invention includes the electrophotographic photosensitive member, a charging device that charges the electrophotographic photosensitive member, and an exposure device that forms an electrostatic latent image by exposing the surface of the charged electrophotographic photosensitive member. A developing device for developing the electrostatic latent image to form a visible image, and a transfer device for transferring the visible image to a transfer medium.

  According to the electrophotographic photosensitive member and the image forming apparatus of the present invention, the values of both the slipperiness and the Vickers hardness of the electrophotographic photosensitive member are defined, so that a high-quality image without filming can be obtained. it can.

FIG. 1 is a cross-sectional view showing a layer structure in the vicinity of the surface of the photosensitive drum in Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram of the image forming apparatus in Embodiment 1 of the present invention. FIG. 3 is a sectional view showing the structure of the photosensitive drum in FIG. FIG. 4 is a perspective view showing the gear and the drive gear in FIG. FIG. 5 is a schematic configuration diagram of an apparatus for measuring the slipperiness of the photosensitive drum in FIG. FIG. 6 is a view showing a Vickers indenter and indentations formed on the photosensitive layer in FIG. FIG. 7 is a diagram showing measurement results and evaluation of slipperiness, film scraping amount, hardness, and filming of each sample in Example 1 of the present invention. FIG. 8 is a diagram showing the relationship between the slipping property and the film scraping amount shown in FIG. FIG. 9 is a diagram showing the relationship between the slipperiness and Vickers hardness shown in FIG. FIG. 10 is a diagram showing measurement results and evaluation of slipperiness, film scraping amount, hardness, and filming of each sample in Example 2 of the present invention. FIG. 11 is a diagram showing the relationship between the slipping property and the film scraping amount shown in FIG. FIG. 12 is a diagram showing the relationship between the slipperiness and Vickers hardness shown in FIG.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Example 1)
FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the first embodiment of the present invention.

  The image forming apparatus is, for example, an electrophotographic printer, and a paper cassette 1 is provided in the uppermost stream in the transport direction of a transfer medium (for example, paper) P. The paper cassette 1 has a hopper stage 2 on which the paper P is loaded and a spring 3 provided below the hopper stage 2. The spring 3 is disposed so as to press the uppermost sheet P against the feeding roller 4. The feeding roller 4 has a function of feeding the paper P to the paper transport path 5 one by one.

  The paper transport path 5 is provided with transport rollers 6a and 6b for transporting the fed paper P to the vicinity of the image forming cartridge 20 for forming an image. A fixing device 7 is provided on the downstream side of the paper conveyance path 5. The fixing device 7 includes a heating roller 7 a that heats the paper P on which the developer (for example, toner) T is transferred and a pressure roller 7 b that presses the paper P, and has a function of fixing the toner image on the paper P. have. On the downstream side of the fixing device 7, discharge rollers 8a and 8b for carrying out the paper P after fixing out of the apparatus are provided.

  A cover 9 is provided on the upper portion of the image forming apparatus 1 so as to be rotatable about a fulcrum 10. A support member 11 is provided below the cover 9. A light emitting diode (hereinafter referred to as “LED”) head 13 as an exposure apparatus is attached to the support member 11 via a spring 12. The LED head 13 includes an LED array composed of a plurality of LEDs, a substrate on which a driver integrated circuit (hereinafter referred to as “driver IC”) for driving the LED array is mounted, a rod lens array that collects light from the LED, and the like. have.

  The LED head 13 has a function of selectively causing the LED to emit light in response to an image data signal transmitted from the outside under the control of a control unit (not shown) to form an electrostatic latent image on the photosensitive drum 30. doing. When the cover 9 is closed, the LED head 13 is biased toward the image forming cartridge 20 by the spring 12.

  A transfer device (for example, a transfer roller) 14 is provided below the image forming cartridge 20. The transfer roller 14 has a function of transferring the toner T on the photosensitive drum 30 onto the paper P.

  The image forming cartridge 20 is integrally formed by a cartridge case 21. In the cartridge case 21, an electrophotographic photosensitive member (for example, a photosensitive drum) 30 that forms an electrostatic latent image, a charging device (for example, a charging roller) 22 that charges the photosensitive drum 30, and the photosensitive drum 30. A developing device (for example, a developing unit) 50 that develops the upper electrostatic latent image and a cleaning unit 23 that scrapes off the toner T on the surface of the photosensitive drum 30 are provided.

  The charging roller 22 has a function of charging the surface of the photosensitive drum 30, and is attached so as to be rotatable in contact with the photosensitive drum 30. The cleaning unit 23 includes a cleaning blade 23a and a spiral screw 23b. The cleaning blade 23 a has a function of scraping off the toner T remaining on the surface of the photosensitive drum 30. The spiral screw 23b has a function of conveying the scraped toner T to a toner box (not shown).

  The developing unit 50 has a function of developing an electrostatic latent image formed on the surface of the photosensitive drum 30 by supplying toner T to the surface of the photosensitive drum 30. The developing unit 50 supplies a developing roller 51 that supplies toner T to the photosensitive drum 30, a developing blade 52 that charges the surface of the developing roller 51 with a thin layer of toner T, and supplies the toner T to the developing roller 51. The toner supply roller 53 and the stirring member 54 that stirs the toner T and conveys the toner T to the toner supply roller 53 are provided. A detachable toner cartridge 55 is mounted on the top of the developing unit 50.

  The developing roller 51 is configured by forming a semiconductive elastic body on a conductive shaft. The toner supply roller 53 is configured by forming a semiconductive elastic body on a conductive shaft.

  The developing roller 51 and the photosensitive drum 30 are rotatably arranged, and are configured to obtain a toner image by bringing the developing roller 51 into contact with the photosensitive drum 30. The toner T is a non-magnetic one-component toner, which is a pulverized toner containing 3 to 4% of a pigment in a polyester resin, and silica is used as an external additive. The image forming apparatus according to the first embodiment employs a non-magnetic one-component contact development method.

FIG. 3 is a cross-sectional view showing a configuration of the photosensitive drum 30 in FIG.
Inside the photosensitive drum 30, a metal shaft 31 made of a conductor is disposed. A flange 32 is press-fitted into one end portion inside the photosensitive drum 30 and fixed with a non-conductive adhesive. As the material of the flange 32, a synthetic resin such as polyamide, polycarbonate, ABS resin, polyacetal or the like is used. These synthetic resins are used by making them conductive by blending conductive powders such as metal powder, carbon black, and graphite. The flange 32 is rotatably attached to the shaft 31.

  A support member 33 is provided on the opposite side of the flange 32 on the inner side of the photosensitive drum 30. The support member 33 is rotatably attached to the shaft 31 and is fixed to the inside of the photosensitive drum 30. A gear 34 is fixed to the outside of the support member 33 with an adhesive. The gear 34 rotates the photosensitive drum 30 and meshes with the drive gear 35. The drive gear 35 is rotatably supported by a fixed shaft 36 that is fixedly supported by the apparatus frame 15b. When the drive gear 35 is driven by a drive source (not shown), the photosensitive drum 30 is configured to rotate via the gear 34.

  The shaft 31 and the photosensitive drum 30 are attached to the cartridge case 21 of the image forming cartridge 20. Bearing holes 21a and 21b are formed in the cartridge case 21, and both end portions of the shaft 31 pass through these bearing holes 21a and 21b. A collar 37 is provided between the left cartridge case 21 and the flange 32. The collar 37 is made of a conductive metal and is configured to be rotatable with respect to the shaft 31 and movable in the axial direction of the shaft 31. The collar 37 is disposed so as to contact the flange 32 and the cartridge case 21.

  The cartridge case 21 including the shaft 31 and the photosensitive drum 30 is mounted on the apparatus frames 15a and 15b. Slots 38 and 39 are formed in the device frames 15a and 15b, respectively, and both end portions of the shaft 31 are locked to these slots 38 and 39, respectively. Thus, the cartridge case 21 is configured to be attached to the apparatus frames 15a and 15b. At this time, one end 21a of the shaft 31 protrudes from the device frame 15a.

  A conductive spring member 40 is attached to the outside of the device frame 15a by a pin 41. The spring member 40 is connected to the ground and is arranged to have a biasing force in the inner direction. When the image forming cartridge 20 is not mounted, the spring member 40 is located slightly inside the position shown in FIG. 3, but the upper end of the spring member 40 is inclined outward, so that the image from above is displayed. The forming cartridge 20 is configured to be mountable. In the mounted state, the shaft 31 and the spring member 40 are configured to be in pressure contact with each other.

FIG. 4 is a perspective view showing the gear 34 and the drive gear 35 in FIG.
In FIG. 4, the gear 34 and the drive gear 35 are formed by helical gears, and the torsion angles of the teeth are set in opposite directions. Due to this helical gear structure, the gear 34 is urged to the left in FIG. 3 so that the contact between the one end portion 31a of the shaft 31 and the spring member 40 becomes good.

  FIG. 1 is a cross-sectional view showing a layer structure in the vicinity of the surface of the photosensitive drum 30 in Embodiment 1 of the present invention.

  The vicinity of the surface of the photosensitive drum 30 has a conductive support 70 and a photosensitive layer 72 formed thereon. The conductive support 70 is made of a metal material such as aluminum, stainless steel, copper, and nickel, or a polyester film or paper having a conductive layer such as aluminum, copper, palladium, tin oxide, and indium oxide formed on the surface. It is comprised by the insulating support body.

  A known undercoat layer 71 may be formed between the conductive support 70 and the photosensitive layer 72. The undercoat layer 71 includes, for example, an inorganic layer such as an aluminum anodized film, aluminum oxide, and aluminum hydroxide, polyvinyl alcohol, casein, polyvinyl pyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, and It is composed of an organic layer such as polyamide.

  Specific configurations of the photosensitive layer 72 of Example 1 include a laminated photosensitive layer, an inverted two-layer photosensitive layer, and a dispersion type photosensitive layer. In the multilayer photosensitive layer, a charge generation layer 72a mainly composed of a charge generation material and a charge transport layer 72b mainly composed of a charge transport material and a binder resin are sequentially stacked on a conductive support 70. It is configured.

  In the reverse two-layer type photoreceptor, a charge transport layer 72b mainly composed of a charge transport material and a binder resin and a charge generation layer 72a mainly composed of a charge generation material are sequentially laminated on a conductive support 70. It has been configured. The dispersion type photosensitive layer has a structure in which a charge generation material is dispersed in a layer containing a charge transport material and a binder resin laminated on the conductive support 70.

  When the photosensitive layer 72 is a laminated type photosensitive layer or an inverted two-layer type photosensitive layer, the charge generation material used for the charge generation layer 72a includes selenium, a selenium alloy, an arsenic selenide compound, cadmium sulfide, zinc oxide, and other Various organic pigments and dyes such as inorganic photoconductive substances, phthalocyanines, azo dyes, quinacridones, polycyclic quinones, pyrylium salts, thiapyrylium salts, indigo, thioindigo, anthanthrone, pyranthrone, and cyanine can be used.

  Among them, metal-free phthalocyanine, copper indium chloride, gallium chloride, tin, oxytitanium, zinc, vanadium and other metals or oxides thereof, phthalocyanines coordinated with chloride, monoazo, bisazo, trisazo, polyazo, etc. The azo pigments are preferred.

  The charge generation layer 72a is formed by binding fine particles of the charge generation material described above with a binder resin. Examples of the binder resin include polyester resin, polyvinyl acetate, polyacrylate ester, polymethacrylate ester, polyester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin, cellulose ester, And cellulose ether.

  The use ratio in this case is used from the range of 30 to 500 parts by weight of the charge generating material with respect to 100 parts by weight of the binder resin, and the film thickness is usually 0.1 to 2 μm. The charge generation layer 72a may contain various additives such as a leveling agent, an antioxidant, and a sensitizer for improving coating properties as necessary. The charge generation layer 72a may be a vapor deposition film of the charge generation material.

  Examples of the charge transport material used for the charge transport layer 72b include heterocyclic compounds such as carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, and thiadiazole. Furthermore, the charge transport material may be an electron donating material such as an aniline derivative, a hydrazone compound, an aromatic amine derivative, a stilbene derivative, or a polymer having a group composed of these compounds as a main chain or a side chain. .

  Binder resins used for the charge transport layer 72b generally include vinyl polymers such as polycarbonate, polymethyl methacrylate, polystyrene, and polyvinyl chloride. Further, the binder resin may be polyester, polyester carbonate, polysulfone, polyimide, phenoxy, epoxy, silicone resin, and a copolymer thereof. Alternatively, a partially crosslinked cured product or the like may be used alone or as a mixture. In Example 1, polyester is used.

  The charge transport layer 72b may contain various additives such as an antioxidant and a sensitizer as necessary. The thickness of the charge transport layer 72b is usually 10 to 30 μm. In the case where the photosensitive layer 72 is a dispersion type photosensitive layer, the above-described charge generating material is dispersed in the charge transport medium having the above blending ratio by the combination of the binder resin and the charge transport material. In this case, the particle size of the charge generation material needs to be sufficiently small, and is used at 1 μm or less. If the amount of the charge generating material dispersed in the photosensitive layer 72 is too small, sufficient sensitivity cannot be obtained. If the amount is too large, there are adverse effects such as a decrease in chargeability and a decrease in sensitivity. Used in the range of%.

  As a method for forming the charge generation layer 72a and the charge transport layer 72b, a known method such as sequentially applying a coating solution obtained by dissolving or dispersing a substance contained in the layer in a solvent can be applied.

  The charge transport material contained in the charge transport layer 72b has a charge mobility that realizes a surface potential of 60 [−V] or less at an exposure-development time of 50 msec in an environment of a temperature of 10 ° C. and a humidity of 20%. The photosensitive drum 30 can operate at a very high rotational speed, corresponding to 346 mm / sec. This corresponds to 59 PPM when A4 size paper is conveyed vertically when the outer diameter of the photosensitive drum 30 is 30 mm.

  The binder resin contained in the charge transport layer 72b of the photosensitive drum 30 has a printing durability capable of printing 40,000 sheets of A4 size paper P by vertical conveyance in intermittent printing which repeats an operation of stopping for 10 seconds after printing three sheets. doing.

(Operation of Image Forming Apparatus of Example 1)
A host device (not shown) issues an instruction to start printing to the image forming apparatus shown in FIG. 2, and image data is sent to the image forming apparatus. A control unit (not shown) of the image forming apparatus drives the feeding roller 4 to feed out the paper P. The fed paper P is conveyed between the photosensitive drum 30 and the transfer roller 14 by the conveyance rollers 6a and 6b.

  A control unit (not shown) drives the LED head 13 based on the sent image data to selectively cause the LEDs to emit light, and the charging roller 22 exposes the surface of the photosensitive drum 30 that has already been charged. Thereby, an electrostatic latent image corresponding to the image data is formed. The photosensitive drum 30 rotates in the direction of the arrow, and when the electrostatic latent image comes to a position facing the developing unit 50, the toner T on the developing roller 51 adheres to the electrostatic latent image by electrostatic force. As a result, a toner image is formed on the photosensitive drum 30, and the toner image moves to a contact position with the transfer roller 14.

  The toner image reaches the position of the transfer roller 14 at the timing when the paper P reaches between the photosensitive drum 30 and the transfer roller 14, and the toner image is transferred onto the paper P by the transfer roller 14. The sheet P on which the toner image is transferred is further conveyed and conveyed to the fixing device 7. In the fixing device 7, the toner image on the paper P is heated and pressed by the heating roller 7 a and the pressure roller 7 b to be fixed. The sheet P after fixing is carried out of the apparatus by the discharge rollers 8a and 8b.

(Evaluation of Photosensitive Drum 30)
Regarding the evaluation of the photoconductor drum 30, (A) the preconditions for the evaluation, (B) the measurement of the slipperiness of the surface of the photoconductor drum 30, (C) the measurement of the hardness of the surface of the photoconductor drum 30, (D) the photoconductor The description will be divided into measurement of the amount of film scraping on the surface of the drum 30, (E) evaluation of filming, (F) relationship between slipperiness and film scraping amount, and (G) relationship between hardness and filming.

(A) Prerequisites for Evaluation A plurality of samples of the photosensitive drum 30 are prepared for the relationship between the amount of film scraping and filming and the slipperiness and hardness of the surface of the photosensitive drum 30 in the photosensitive drum 30 of FIG. And evaluated.

  In Example 1, a multilayer photoreceptor is used as a sample. The charge generation layer 72a is formed by using a bisazo compound as a charge generation material and binding with polyvinyl butyral which is a binder resin. The charge generation material is 50% by weight with respect to the binder resin, and the film thickness of the charge generation layer 72a is 0.5 μm. A vidrazone compound is used as the charge transport material of the charge transport layer 72b, and polyester is used as the binder resin. The structural formula of this polyester is shown in chemical formula (1).

  In the chemical formula (1), X represents a single bond, a sulfur atom, an oxygen atom, a sulfonyl group, or a cycloalkyl group. W represents a divalent aromatic group which may be substituted or a divalent hydrocarbon group which may be substituted. R1 to R8 each independently represents a hydrogen atom, an alkyl group, an aryl group, a halogen tomb, or an alkoxyl group.

  In Example 1, the structure represented by the chemical formula (2) among the structures represented by the general formula (1) represented by the general formula was used.

  The average molecular weight of the binder resin is about 30000. The initial film thickness of the charge transport layer 72b was 14 μm. The ratio of the charge transporting material in the binder resin was changed in the range of 34 to 55% by weight, and the charge transporting material production conditions and coating conditions were changed to prepare a total of 12 types of samples A to L. About these 12 types of samples, the slip property and hardness were measured, and the amount of film scraping and filming were evaluated.

(B) Measurement of slipperiness of surface of photoconductor drum 30 FIG. 5 is a schematic configuration diagram of an apparatus for measuring the slipperiness of the photoconductor drum 30 in FIG.

In the following (1) to (5), a method for measuring slipperiness will be described.
(1) The photosensitive drum 30 is set in the slip measuring device, and the force gauge 61 is adjusted so as to indicate 0 in a state where there is no load.

  (2) Width 10 mm, thickness 0. A weight 63 of 50 g is applied to the lower end side of the 1 mm PET film 62, and a force gauge 61 is set on the upper end side of the PET film 62. At this time, the angle formed between the line extending the PET film 62 connecting the force gauge 61 and the photosensitive drum 30 shown in FIG. 5 and the line extending the PET film 62 connecting the weight 63 and the photosensitive drum 30 is θ. When this is done, the PET film 62 is set so that the angle θ is 90 °. As the PET film 62 to be used, # 100 of type S10 which is a standard grade of a general industrial film “Lumirror” manufactured by Toray Industries, Inc. was used.

  (3) After the value of the force gauge 61 is stabilized, the photosensitive drum 30 is rotated in the arrow direction R shown in FIG. 5. At this time, the tangential speed between the photosensitive drum 30 and the PET film 62 is 78.5 mm. / Sec.

  (4) With the photoconductor drum 30 rotated, the rubbing force between the photoconductor drum 30 and the PET film 62 is measured with the force gauge 61.

  (5) The value when the rotation of the photosensitive drum 30 is stabilized and the variation of the value of the force gauge 61 becomes ± 0.1 N is defined as the slipperiness value.

(C) Measurement of surface hardness of photosensitive drum 30 FIGS. 6A and 6B are views showing a Vickers indenter and indentations formed on the photosensitive layer 72 in FIG.

A method for measuring the hardness of the surface of the photosensitive drum 30 will be described.
A hardness measurement method uses Vickers hardness. Vickers hardness (hereinafter simply referred to as “hardness”) is an index of plasticity of a material, and is obtained according to Japanese Industrial Standard JISZ2244. FIG. 6A shows the bottom surface of the Vickers indenter 81. FIG. 6B is a diagram showing indentations when the Vickers indenter 81 is pressed against the photosensitive layer 72 on the surface of the photosensitive drum 30.

The shape of the Vickers indenter 81 is a regular square pyramid having a facing angle γ of 136 °, and this is pushed into the surface of the photosensitive layer 72 with a load F [N]. F / S divided by the surface area S [mm ² ] obtained from the length d [mm] is defined as hardness Hv. That is, the hardness is expressed by the following formula.
Hv = F / S = 2Fsin (γ / 2) / d ²

  In Example 1, MVK-E manufactured by Akashi Seisakusho was used for the Vickers hardness tester, and the load F was measured at 10 gf.

(D) Measurement of the amount of film abrasion on the surface of the photosensitive drum 30 A method for measuring the amount of film abrasion of the photosensitive layer 72 of the photosensitive drum 30 is shown.

  The evaluation was performed by incorporating a photoconductor drum 30 as a sample in the image forming apparatus shown in FIG.

  The continuous test is performed in an environment of a temperature of 10 ° C. and a humidity of 20%. The paper P is an A4 size paper using Fuji Xerox P thick paper, and a print pattern with a print area of 0.3% is used to print 40000 sheets. Continuous printing was performed.

  The outer diameter of the photosensitive drum 30 as an evaluation sample was measured before and after continuous printing using a roller automatic measuring device RM-202 manufactured by Apollo Seiko Co., Ltd., and the amount of film scraping was calculated from the outer diameter difference before and after printing.

  The criteria for determining the amount of film scraping were determined to be image quality free of background stains when fogging that could be determined as a cause of film scraping due to image evaluation or when the photosensitive drum 30 was not soiled with a period. In the first embodiment, when the average film scraping amount exceeds the threshold value of 4.0 μm, fogging or dirt occurs. Therefore, when the average film scraping amount is equal to or less than the threshold value of 4.0 μm, the image quality without background dirt is set. .

(E) Filming Evaluation A filming evaluation method will be described.

  The paper P was A4 size, Fuji Xerox P thick paper, and 20000 sheets were continuously printed using a print pattern with a print area of 50%. Thereafter, a solid pattern was printed, and the presence or absence of whitening caused by filming was visually observed. When the whitening can be confirmed visually, it is determined that filming has occurred. When the whitening cannot be visually confirmed, it is determined that filming does not occur.

  The image forming apparatus shown in FIG. 2 was used for evaluation. In a low-temperature and low-humidity environment, the cleaning blade 23a formed of urethane rubber contracts slightly more than at room temperature, so that the pressing pressure between the cleaning blade 23a and the photosensitive drum 30 is weakened. For this reason, filming that adheres to the surface of the photosensitive layer 72 slips through the cleaning blade 23a, and filming is likely to occur. Therefore, the continuous test was performed in an environment of a temperature of 10 ° C. and a humidity of 20%.

(F) Relationship between slipperiness and film scraping amount FIG. 7 is a diagram showing the measurement results and evaluation of slipperiness, film scraping amount, hardness, and filming of each sample in Example 1 of the present invention. In the filming column of FIG. 7, samples that are determined not to have filming are indicated by ◯, and samples that are determined to have filming are indicated by ×. In the image evaluation column of FIG. 7, a sample with an afterimage or a sample with background contamination is indicated by ×. FIG. 8 is a diagram showing the relationship between the slipperiness and the film scraping amount shown in FIG. In FIG. 8, white circles indicate samples without background stains or afterimages, and black circles indicate samples with background stains or afterimages.

  According to FIG. 8, the film scraping amount increases substantially linearly with the increase in slipperiness. In FIG. 7, the samples whose film shaving amount exceeds the threshold value of 4.0 μm are the sample K whose film shaving amount is 4.15 μm and the sample L whose film shaving amount is 4.15 μm. The slipperiness of sample K is 0.95 [N], and the slipperiness of sample L is 1.00 [N]. Among the remaining samples A to J, samples with a large film scraping amount are Sample I and Sample J, and the film scraping amounts are 3.85 [μm] and 3.80 [μm], respectively.

  The film scraping amounts of Samples I and J are sufficiently smaller than the threshold value 4.0 [μm]. Of the remaining samples A to J, the sample with the maximum slipperiness is sample J, and the slipperiness is 0.90 [N]. Since the film scraping amount increases almost linearly with the increase in slipperiness, if the slipperiness is 0.90 [N] or less, the film scraping amount is the background stain threshold 4.0 [μm]. ] Is judged to be less than.

  On the other hand, when the slip property is remarkably reduced, the rubbing force between the cleaning blade 23a and the surface of the photosensitive drum 30 is almost eliminated. For this reason, the transfer residual toner T cannot be scraped off by the cleaning blade 23a. As a result, an afterimage due to the transfer residual toner pattern is likely to occur. As shown in FIG. 7, sample B, which has the second smallest slipperiness, has a slipperiness of 0.30 [N], and no afterimage due to the transfer residual toner pattern is generated. In the sample A having a slipperiness of 0.26 [N] and the smallest slipperiness value, an afterimage is generated. Since the slipperiness and the amount of film scraping are substantially linear, the lower limit of the slipperiness at which no afterimage is generated is determined to be 0.30 [N]. From the above, it can be seen that by setting the slipping property to 0.30 to 0.90 [N], the image forming apparatus can obtain an image quality in which no background contamination occurs and no afterimage occurs.

(G) Relationship Between Hardness and Filming FIG. 9 is a diagram showing the relationship between slipperiness and hardness shown in FIG.

  In FIG. 9, white circles indicate samples with good image quality, and black circles indicate samples with poor image quality. As described above, by setting the slipping property to 0.30 to 0.90 [N], the image forming apparatus can obtain an image quality in which background contamination is not generated and an afterimage is not generated. Actually, according to FIG. 9, samples K and L in which background contamination occurs are plotted in a region where the slipperiness is greater than 0.9 [N]. In a region where the slip property is smaller than 0.3 [N], a sample A in which an afterimage is generated is plotted.

Next, regarding hardness, there is variation between slipperiness and hardness, but linearity is generally observed. Samples C and F in which filming has occurred are plotted in a region where the hardness is lower than the hardness 26.7 [gf · μm ⁻² ] of sample D, which has good image quality. Filming does not occur in the sample D having a hardness of 26.7 [gf · μm ⁻² ] or more. Therefore, in order to prevent filming, the hardness needs to be 26.7 [gf · μm ⁻² ] or more.

In the region where the hardness is higher than the hardness 34.2 [gf · μm ⁻² ] of the sample I which has a high image quality, the sample L in which the background contamination is generated is plotted. As shown in FIG. 9, when the hardness is increased, the slipping property tends to increase. For example, if the hardness is 35.0 [gf · μm ⁻² ], which is the hardness of the sample L, the slipping property is 1.0 [N], and background contamination is caused as described in the explanation of FIG. It becomes the area that has occurred. Therefore, the upper limit of the sample in which the slipping property is in the range of 0.30 [N] to 0.90 [N] and no filming occurs is 34.2 [gf · μm ⁻² ] of Sample I. . In summary, the hardness is preferably 26.7 to 34.2 [gf · μm ⁻² ].

(Effect of Example 1)
According to the photosensitive drum 30 and the image forming apparatus of the first embodiment, since both the slipperiness and hardness of the photosensitive drum 30 are defined, a high-quality image without filming can be obtained. it can.

  According to the method for measuring the slipperiness of the surface of the photosensitive drum 30 of the first embodiment, the following effects (1) to (4) are obtained.

  (1) When developing the photosensitive layer 72, it is possible to obtain a high-quality photosensitive drum 30 by measuring the slipperiness and hardness of the surface of the photosensitive layer 72, so that a reduction in development cost can be expected.

  (2) Since the surface of the photosensitive drum 30 and the PET film 62 are in contact with each other, the reproducibility of the measurement is very good as compared with the case where the friction coefficient is measured using the cleaning blade 23a.

  (3) When the friction coefficient is measured using the photosensitive drum 30 and the cleaning blade 23a, the photosensitive drum 30 and the cleaning blade 23a used for the measurement can be used only once. However, in the slippage measuring method according to the first embodiment, since the PET film 62 having a width of 10 mm is used, the photosensitive drum 30 can be used a plurality of times at different measurement locations. For this reason, reduction of development cost can be expected.

  (4) Since the PET film 62 is less expensive than the cleaning blade 23a, a reduction in development cost can be expected.

(Configuration of Example 2)
The configurations of the image forming apparatus and the photosensitive drum 30 in the second embodiment of the present invention are the same as those in the first embodiment. The configuration of the photosensitive layer 72 of the second embodiment is almost the same as that of the first embodiment, and the materials constituting the conductive support 70, the undercoat layer 71, and the charge generation layer 72a are the same as those of the first embodiment. . The material constituting the charge transport layer 72b of the second embodiment is different from that of the first embodiment.

  In Example 2, the binder resin of the charge transport layer 72b is made of polycarbonate and polyester. Among them, 5 to 20% of polyester is contained, and the remainder is polycarbonate. The general formula of the polycarbonate bottle is represented by the chemical formula (3). In Example 2, the one represented by the chemical formula (4) is used.

  As in the case of Example 1, the polyester represented by the chemical formula (2) is used. Among various binder resins, polycarbonate has comprehensively excellent characteristics, and thus various polycarbonate resins have been developed so far. However, since the mechanical strength is not sufficient, the printing durability is slightly inferior. Therefore, an electrophotographic photoreceptor excellent in both mechanical characteristics and electrical characteristics can be realized by adding a certain amount of polyester having good printing durability.

  Also in Example 2, the ratio of the charge transport material in the binder resin was changed in the range of 34 to 55% by weight, and the charge transport material production conditions and application conditions were changed to obtain a total of 12 types of samples M to X. A sample was made. About these 12 types of samples, the slip property and hardness were measured, and the amount of film scraping and filming were evaluated.

  FIG. 10 is a diagram showing measurement results and evaluation of slipperiness, film scraping amount, hardness, and filming of each sample in Example 2 of the present invention. FIG. 11 is a diagram showing the relationship between the slipping property and the film scraping amount shown in FIG. In FIG. 11, white circles indicate samples without background stains or afterimages, and black circles indicate samples with background stains or afterimages.

  According to FIG. 11, the film scraping amount increases substantially linearly with the increase in slipperiness. In FIG. 10, the sample whose film scraping amount exceeds the threshold value of 4.0 μm includes the sample U with the film scraping amount of 4.25 μm, the sample V with the film scraping amount of 4.45 μm, and the film scraping amount of 4.90 μm. Sample W and Sample X with a film scraping amount of 5.00 μm. The sliding property of sample U is 0.96 [N], the sliding property of sample V is 1.01 [N], the sliding property of sample W is 1.07 [N], and the sliding property of sample X is 1.11 [N].

  Among the remaining samples M to T, the sample with a large film scraping amount is the sample T, and the film scraping amount is 3.95 [μm]. Among the remaining samples M to T, the sample having the maximum slipperiness is the sample T, and the slipperiness is 0.91 [N]. Since the film scraping amount increases almost linearly with the increase in slipperiness, if the slipperiness is 0.91 [N] or less, the film scraping amount is the background stain threshold 4.0 [μm]. ] Is judged to be less than.

  On the other hand, when the slip property is remarkably reduced, the rubbing force between the cleaning blade 23a and the surface of the photosensitive drum 30 is almost eliminated. For this reason, the transfer residual toner T cannot be scraped off by the cleaning blade 23a. As a result, an afterimage due to the transfer residual toner pattern is likely to occur. As shown in FIG. 10, the sample N having the second smallest slipperiness has a slipperiness of 0.56 [N], and no afterimage due to the transfer residual toner pattern is generated. In the sample A having the smallest slip value, the slip property is 0.51 [N], and an afterimage is generated. Since the slipperiness and the amount of film scraping are substantially linear, the lower limit of the slipperiness that does not cause an afterimage is determined to be 0.56 [N]. From the above, it can be seen that by setting the slipperiness to 0.56 to 0.91 [N], the image forming apparatus can obtain an image quality in which no background contamination occurs and no afterimage occurs.

FIG. 12 is a diagram showing the relationship between the slipperiness and Vickers hardness shown in FIG.
In FIG. 12, white circles indicate samples with high image quality, and black circles indicate samples with poor image quality. Here, looking at the relationship between hardness and filming, there is variation between slipperiness and hardness, but linearity is generally observed. Samples N, O, Q, and R in which filming has occurred are plotted in a region where the hardness is lower than the hardness 27.7 [gf · μm ⁻² ] of the sample P that has high image quality. Filming does not occur in the sample having a hardness of 27.7 [gf · μm ⁻² ] or higher in the sample P in a range where the slip property is 0.64 to 0.91 [N]. Therefore, in order to prevent the occurrence of filming, the hardness needs to be 27.7 [gf · μm ⁻² ] or more.

In a region where the hardness is higher than the hardness 29.2 [gf · μm ⁻² ] of the sample S, which has a high image quality, the slipperiness exceeds 0.91 [N], and background contamination occurs. For this reason, a good image cannot be obtained. That is, samples U, V, W, and X exceeding the film scraping threshold 4.0 are plotted in a region where the hardness is higher than 29.2 [gf · μm ⁻² ]. Therefore, the hardness of the upper limit sample in which the slipping property is in the range of 0.64 [N] to 0.91 [N] and no filming is generated is 29.2 [gf · μm ⁻² ] of the sample S. Become. In summary, the hardness is preferably 27.7 to 29.2 [gf · μm ⁻² ].

(Effect of Example 2)
According to the photoconductor drum 30 and the image forming apparatus of the second embodiment, the charge transport layer 72b is configured by adding polyester to polycarbonate so that the photoconductor drum 30 that does not cause filming as in the first embodiment can be obtained. In addition, it is possible to realize an electrophotographic photoreceptor excellent in both mechanical characteristics and electrical characteristics.

  The effect of the method for measuring the slipperiness of the surface of the photosensitive drum 30 of the second embodiment is the same as that of the first embodiment.

(Modification)
The present invention is not limited to the above-described embodiments, and various usage forms and modifications are possible. For example, in the first and second embodiments, the electrophotographic printer is described as an example of the image forming apparatus using the photosensitive drum 30, but the present invention is applicable to all image forming apparatuses using an electrophotographic photosensitive member such as a copying machine and a facsimile machine. It is possible.

13 LED Head 14 Transfer Roller 22 Charging Roller 30 Photosensitive Drum 50 Developing Unit 61 Force Gauge 62 PET Film 63 Weight 70 Conductive Support 72 Photosensitive Layer 72a Charge Generation Layer 72b Charge Transport Layer 81 Vickers Indenter

Claims (7)

An electrophotographic photosensitive member in which a photosensitive layer for generating and transporting a charge is formed on a conductive support,
The photosensitive layer is formed by laminating a plurality of layers,
The slip property of the surface of the outermost layer in the photosensitive layer is 0.30 to 0.90 [N],
The electrophotographic photosensitive member is characterized in that the surface of the photosensitive layer has a Vickers hardness of 26.7 to 34.2 [gf · μm ⁻² ].   2. The electrophotographic photosensitive member according to claim 1, wherein the outermost layer of the photosensitive layer is formed of a binder resin having polyester. The electrophotographic photosensitive member according to claim 1,
The value of the slip property of the surface of the outermost layer in the photosensitive layer is 0.64 to 0.91 [N],
The electrophotographic photosensitive member is characterized in that the surface of the photosensitive layer has a Vickers hardness of 27.7 to 29.2 [gf · μm ⁻² ]. The outermost layer of the photosensitive layer is formed of a binder resin made of polycarbonate and polyester,
The electrophotographic photosensitive member according to claim 3, wherein the polyester is 5 to 20 [wt%] in the binder resin. The slipperiness of the surface of the photosensitive layer 72 is
A polyethylene terephthalate film having a width of 10 [mm] and a thickness of 0.1 [mm] is placed in contact with the surface of the photosensitive layer 72, and force gauges are provided at both ends of the polyethylene terephthalate film. 50 [g] is applied, and is defined by the value of the force gauge when the tangential speed between the surface of the photosensitive layer and the polyethylene terephthalate film is moved at 78.5 [mm / sec]. The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein The Vickers hardness is
The electrophotographic photosensitive member according to any one of claims 1 to 5, wherein the electrophotographic photosensitive member is obtained from a size of a thickness mark when a Vickers indenter is pushed into the surface of the photosensitive layer with a weight of 10 [gf]. body. The electrophotographic photosensitive member according to any one of claims 1 to 6,
A charging device for charging the electrophotographic photoreceptor 30;
An exposure device 13 for exposing the charged surface of the electrophotographic photosensitive member 30 to form an electrostatic latent image; and
A developing device for developing the electrostatic latent image to form a visible image;
A transfer device for transferring the visible image to a transfer medium;
An image forming apparatus comprising:

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