JP2007271949A - Image-forming device and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image-forming device which causes no deterioration in cleaning properties and filming, even if a durability-excellent photoreceptor is used, and restrains the occurrence of abnormal images due to a residual potential to give high-quality images for a long period of time. <P>SOLUTION: The image-forming device is provided with: a photoreceptor which keeps a conductive base material sequentially overlaid with at least an electric charge-generating layer, an electric charge-conveying layer and a crosslink-type electric charge-conveying layer; a charging means; an exposing means; a developing means; a transferring means; and a cleaning means, the means being all arranged in the vicinity of the surface of the photoreceptor. In addition, the crosslink-type electric charge-conveying layer is formed by the reaction of a radically polymerizable monomer, which has three or more functional groups and at least has no electric charge-conveying structure, with a radically polymerizable compound which has one functional group and electric charge-conveying structure. Further, a precharging means, which precharges the surface of the photoreceptor prior to the start of charging to eliminate the residual potential of the photoreceptor, is arranged on the upstream side of the cleaning means and the downstream side of the transferring means to the rotational direction of the photoreceptor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system, and a process cartridge used in the image forming apparatus. More particularly, the present invention relates to an image forming apparatus and a process cartridge that can stably supply high-quality images over a long period of time despite the use of a highly durable photoconductor.

  As a photoconductor of an image forming apparatus using an electrophotographic process, the cost is lower, the toxicity is scarce, and the film formability is easier than an inorganic photoconductor produced by vacuum deposition of a conventional selenium film. For many merits, so-called organic photoreceptors have become mainstream. Among these organic photoreceptors, a laminate type in which a so-called charge generation layer and charge transport layer are laminated on a conductive substrate is mainly employed.

  However, organic photoconductors are prone to scraping of the photoconductor due to repeated use, and as the photoconductive layer progresses, the photoconductor surface potential decreases, photosensitivity deteriorates, and the surface of the photoconductor becomes scratched. Since there is a strong tendency to promote dirt, image density reduction, or image quality deterioration, it has been desired to improve the abrasion resistance and scratch resistance of the photosensitive layer.

  Furthermore, in recent years, it is indispensable to improve the wear resistance of the photoreceptor due to the speedup, full color, and maintenance-free movement due to the increase in the speed of the electrophotographic apparatus or the reduction in the diameter of the photoreceptor accompanying the downsizing of the apparatus. It has become a thing. Therefore, in an organic electrophotographic photosensitive member, it has been cited as the most important issue particularly to achieve both high image quality and high durability.

In order to solve such problems, attempts have been made to improve the physical properties of the photoreceptor surface by adding various substances in the charge transport layer and to improve the durability as an image quality.
For example, Patent Document 1 and Patent Document 2 include an epoxy compound and a hindered amine compound having a specific structure or a hindered phenol compound having a specific structure in the photosensitive layer, so that the charging potential can be repeatedly used. Further, it is disclosed that an electrophotographic photoreceptor excellent in durability in which electrical characteristics such as residual potential do not change and image characteristics such as sensitivity, character thickening, and image blurring do not change stably can be obtained.

Patent Document 3 discloses that a surface layer of a photosensitive layer contains polytetrafluoroethylene powder as a lubricant, has a di-lower alkylaminophenyl group, and has (C ₆ H ₅ ) ₂ (C ₆ By incorporating 4,4-diphenyl-1,1-di (P-di-lower alkyl-substituted aminophenyl) -butadiene having the structural formula of H ₅ P—NR ₂ ) ₂ as a charge transport material, An electrophotographic photosensitive member having durability against the occurrence of abrasion, scratches, etc. and capable of obtaining a high-quality image free from image blur, as well as a surface of the photosensitive member with good cleaning properties It is disclosed that an electrophotographic photosensitive member having high durability with no toner adhesion to the layer can be obtained.

  Further, in Patent Document 4, an electrophotographic photosensitive member formed by sequentially forming a protective layer containing at least a photosensitive layer and a filler on a conductive support, the photosensitive layer contains an organic sulfur compound, and By including a compound having both a hindered amine structure and a hindered phenol structure in the protective layer, there is no residual potential increase or abnormal image such as image blurring even after repeated use. It is disclosed that a highly durable photoreceptor that can be obtained stably can be obtained.

However, all of these known techniques prevent the charging potential of the photoreceptor from being lowered, the photosensitivity from being deteriorated, the contamination due to scratches on the surface of the photoreceptor, the reduction in image density, or the deterioration in the image quality. It was insufficient in terms of compatibility.
For example, in the method described in Patent Document 3, since the polytetrafluoroethylene powder is a low surface energy polymer, it is insoluble in a solvent and its dispersibility is poor, so that a smooth photoreceptor surface is obtained. Is difficult. In addition, although the dispersibility can be improved with a dispersant or the like, the obtained coating film has a problem that light scattering is likely to occur due to a low refractive index, resulting in degradation of the latent image, and image blurring is also caused. Likely to happen.
Further, although the method described in Patent Document 4 has an effect on enhancing the durability of the image quality, it is not sufficient as compared with the photoconductor used in the image forming apparatus corresponding to the high image quality shown in the present invention. Especially, the image quality deteriorates severely under high temperature and high humidity.

On the other hand, techniques for improving the abrasion resistance of the photosensitive layer include (1) using a curable binder in the crosslinkable charge transport layer (see, for example, Patent Document 5), and (2) a polymer charge transport material. Examples thereof include those used (for example, see Patent Document 6), (3) those in which an inorganic filler is dispersed in a crosslinked charge transport layer (for example, see Patent Document 7), and the like.
Among these technologies, those using the curable binder (1) have poor compatibility with the charge transport material, and the residual potential increases due to impurities such as polymerization initiators and unreacted residues, resulting in decreased image density. Tends to occur. In addition, although the polymer charge transport material (2) can improve the abrasion resistance to some extent, the durability required for the organic photoreceptor is not fully satisfied. Not reached. In addition, polymer charge transport materials are difficult to polymerize and purify, and it is difficult to obtain a high-purity material. Therefore, it is difficult to stabilize electrical characteristics between materials. Furthermore, production problems such as high viscosity of the coating solution may occur. The dispersion of the inorganic filler (3) exhibits higher abrasion resistance than a photoreceptor in which a normal low molecular charge transport material is dispersed in an inert polymer, but the charge present on the surface of the inorganic filler. The residual potential increases due to the trap, and the image density tends to decrease. In addition, when the unevenness of the inorganic filler and the binder resin on the surface of the photoconductor is large, defective cleaning may occur, which may cause toner filming and image flow.
As described above, in the techniques (1) to (3), the total durability including the electrical durability, mechanical durability, and image quality durability required for the organic photoreceptor is sufficient. Not satisfied with the minute.

Furthermore, a photoreceptor containing a polyfunctional acrylate monomer cured product for improving the abrasion resistance and scratch resistance of (1) is also known (see Patent Document 8). However, in this photoreceptor, although there is a description that the polyfunctional acrylate monomer cured product is contained in the protective layer provided on the photosensitive layer, the protective layer may contain a charge transport material. However, there is a problem of compatibility with the cured product when a cross-linked charge transport layer contains a low-molecular charge transport material. As a result, precipitation of a low-molecular charge transport material and white turbidity occur, and not only the image density is lowered but also the mechanical strength is lowered due to the increase of the exposed portion potential.
In addition, since this photoreactor specifically reacts with the monomer in a state containing a polymer binder, the three-dimensional network structure does not proceed sufficiently, and the cross-linking density becomes dilute, resulting in dramatic wear resistance. Has not yet been able to demonstrate.

As an alternative to the wear resistance technology of the photosensitive layer, a charge transport layer formed by using a coating liquid comprising a monomer having a carbon-carbon double bond, a charge transport material having a carbon-carbon double bond, and a binder resin is used. It is known to provide (for example, refer to Patent Document 9).
This binder resin is thought to play a role of improving the adhesion between the charge generation layer and the curable charge transport layer, and further mitigating the internal stress of the film during thick film curing, and has a carbon-carbon double bond. These are broadly classified into those having reactivity with the charge transfer agent and those having no reactivity with the double bond.
This photoreceptor is noticeable because it has both wear resistance and good electrical characteristics, but when a non-reactive binder resin is used, the binder resin, the monomer and the charge transport agent are used. The compatibility with the cured product produced by this reaction is poor, and phase separation occurs in the cross-linked charge transport layer, which may cause scratches and sticking of external additives and paper powder in the toner.
In addition, as described above, the three-dimensional network structure does not proceed sufficiently and the cross-linking density becomes dilute, so that it has not reached the point where dramatic wear resistance can be exhibited. In addition, what is specifically described as the monomer used in this photoreceptor is bifunctional, and from these reasons, it has not yet been satisfactory in terms of wear resistance. Even when a reactive binder is used, although the molecular weight of the cured product is increased, the number of intermolecular crosslinks is small, and it is difficult to achieve a balance between the amount of the charge transport material and the crosslink density. Abrasion was not sufficient.

  A photosensitive layer containing a compound obtained by curing a hole transporting compound having two or more chain polymerizable functional groups in the same molecule is also known (see, for example, Patent Document 10). This photosensitive layer has high hardness because the crosslink density can be increased, but since the bulky hole transporting compound has two or more chain polymerizable functional groups, distortion occurs in the cured product and internal stress increases. In some cases, the crosslinked surface layer is liable to crack or peel off when used for a long period of time.

  Further, it is also known to produce a polymer having a hole transporting compound having two or more chain polymerizable functional groups in the same molecule and having a photosensitive layer thickness in the range of 5 to 15 μm. (See Patent Document 11). However, the reason for limiting the film thickness is related to the stability of the photoreceptor electrostatic characteristics such as a decrease in charging potential and an increase in residual potential in repeated use, in addition to wear resistance and scratch resistance, and related to image quality. No description / effect is described. Further, there is no description about the combination with the writing light source.

  Furthermore, in order to increase the durability of the photoreceptor, it has been studied to use a resin obtained by curing a compound having a chain polymerizable functional group on the surface layer by polymerization or crosslinking (for example, Patent Document 12, Patent Document). 13, Patent Document 14).

  In addition, it has been put to practical use to provide a highly durable organosilicon binder resin-containing photosensitive layer or surface protective layer for improving abrasion resistance, but the organosilicon binder is easy to absorb moisture, resulting in a decrease in image quality. In particular, defects such as image blur and image flow due to filming also occur.

  On the other hand, in the electrophotographic apparatus, since the surface of the photoreceptor cannot be sufficiently cleaned only by mechanically scraping the residual toner by the cleaning device, the residual toner is discharged by the AC corona discharger before cleaning, and the cleaning by the cleaning device is performed. It is generally known to improve the performance, and the frequency and voltage applied to the static eliminator can be adjusted, or the output of the static eliminator can be changed according to the amount of use of the cleaning device. However, it has not been studied yet from the viewpoint of the problem of the cleaning property of the above-mentioned highly durable photoconductor.

The reason why it is difficult to achieve both high image quality and high durability as described above is considered as follows.
As described above, many attempts have been made so far to achieve high wear resistance, and as a result, dramatic improvement in wear resistance of organic electrophotographic photoreceptors has been realized. However, as the life of the photoconductor is extended, a problem that an abnormal image is noticeably generated over time due to the residual potential of the photoconductor and poor cleaning has become apparent. This is considered to be caused mainly by a decrease in cleaning performance due to an increase in the residual potential of the photoconductor and deterioration of the cleaning blade due to an increase in the use period as the wear resistance of the photoconductor is improved. Therefore, it is important to suppress an increase in the residual potential of the photoconductor for a long period of time and to maintain a cleaning performance and stably supply a high-quality image for a long period of time.
JP-A-10-198053 JP-A-10-301303 JP-A-8-160648 JP 2002-139659 A JP 56-48637 A JP-A 64-1728 JP-A-4-281461 Japanese Patent No. 3262488 Japanese Patent No. 3194392 JP 2000-66425 A JP 2001-166501 A JP 2004-302450 A JP 2004-302451 A JP 2004-302452 A JP 2005-77654 A

  The present invention has been made in view of the above-described circumstances. In spite of the use of a highly durable photoconductor, there is no deterioration in cleaning property or filming, and an abnormal image due to the residual potential of the photoconductor is not generated. An object of the present invention is to provide an image forming apparatus and a process cartridge capable of stably generating a high-quality image over a long period while suppressing the occurrence.

The above problems are solved by the following inventions (1) to (10) (hereinafter referred to as the present invention 1 to 10).
(1) A photoreceptor in which at least a charge generation layer, a charge transport layer, and a crosslinkable charge transport layer are sequentially laminated on a conductive support, a charging unit, an exposure unit, a developing unit, and a transfer unit that are disposed close to the surface of the photoreceptor. And an image forming apparatus provided with a cleaning means, wherein the image forming apparatus further comprises a precharge means, and the cross-linked charge transport layer has at least a trifunctional or higher-functional radical polymerizability having no charge transport structure. The precharge means is formed by reacting a monomer and a radical polymerizable compound having a monofunctional charge transporting structure, and precharges the surface of the photoreceptor before charging starts to remove the residual potential of the photoreceptor. An image forming apparatus, wherein the image forming apparatus is installed upstream of the cleaning unit and downstream of the transfer unit with respect to the rotation direction of the photoconductor.
(2) The image forming apparatus according to (1), wherein the radical polymerizable functional group of the radical polymerizable monomer or the radical polymerizable compound is at least one of an acryloyloxy group and a methacryloyloxy group.
(3) The image forming apparatus according to (1) or (2), wherein the precharge unit is not in contact with the photoconductor.
(4) The image forming apparatus according to any one of (1) to (3), wherein the precharge unit has a roller shape.
(5) The precharging means is an AC charging method that precharges the surface potential of the photosensitive member by applying a voltage in which an alternating current component is further superimposed on a direct current component, and (1) to (4) ).
(6) The image forming apparatus according to (5), wherein the AC voltage applied to the precharge means is controlled by a current value flowing from the photoconductor to the ground.
(7) The ON / OFF timing of charging by the precharge means is turned ON at the timing when the leading end of the exposure means in the photosensitive member charging area enters the precharging means or at a timing earlier than the leading end enters, and the exposure area on the photosensitive body The image forming apparatus according to any one of (1) to (6), wherein the rear end of the image forming apparatus is turned off at a timing after the rear end passes through the precharge means or at a later timing than after the rear end passes through the precharge means. .
(8) The image forming apparatus according to any one of (1) to (7), wherein the cross-linkable charge transport layer has a thickness of 1 μm or more and 10 μm or less.
(9) The cross-linked charge transport layer has a 10-point average surface roughness (Rz) in the range of 0.05 to 1.0 μm, according to any one of (1) to (8), Image forming apparatus.
(10) An electrophotographic photosensitive member and a precharge unit used in the image forming apparatus according to any one of (1) to (9), a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit. A process cartridge comprising a combination of at least one of them and being detachably installed in an image forming apparatus main body.

As described above, the present inventors can reduce the influence of charging hazard due to repeated use by using a cross-linked charge transport layer as the photoconductor of the image forming apparatus. It has been found that the adhesion energy with the body can be reduced and sustained, and that the cross-linked charge transport layer has excellent wear resistance.
In order to prevent a cleaning failure due to deterioration of the cleaning blade caused by using such a highly durable photoconductor for a long period of time, a precharge means for removing the residual potential of the photoconductor is installed before the charging process. As a result, the electrostatic adhesion between the residual toner on the photosensitive member and the photosensitive member can be reduced to improve the cleanability, and further, the generation of a residual image due to the residual potential of the photosensitive member can be suppressed. In addition, it has been found that by combining them, a high-quality image can be stably supplied over a long period of time.
The precharger method uses a method that generates significantly less ozone and NOx than the corona charging method, and reduces the influence of ozone and NOx gas by minimizing the precharge drive timing. Further, by placing the charging member close to the photosensitive member, the influence of the contamination of the charging member and the image quality deterioration derived therefrom is reduced.

  According to the image forming apparatus of the first aspect of the present invention, a precharge for removing the residual potential of the photoconductor by using a photoconductor having a cross-linked charge transport layer having a specific configuration and precharging the surface of the photoconductor before starting charging. Since the means is installed on the upstream side of the cleaning means and on the downstream side of the transfer means, the residual potential of the photoconductor over time can be eliminated even if a highly durable photoconductor is used. Provided is an image forming apparatus in which the occurrence of afterimages as a cause is prevented and the electrostatic adhesion between the toner and the photoreceptor is weakened to improve the cleaning property, and a high-quality image can be stably obtained over a long period of time. be able to.

  According to the image forming apparatus of the present invention 2, since the radical polymerization functional group of the radical polymerizable compound is an acryloyloxy group and / or a methacryloyloxy group, the wear resistance of the cross-linked charge transport layer is improved. Can do.

  According to the image forming apparatus of the third aspect of the invention, since the precharge unit is of a non-contact type, it can be used without residual toner or foreign matter on the photoconductor contaminating the precharge unit.

  According to the image forming apparatus of the fourth aspect of the present invention, since the precharge means is formed in a roller shape, it is possible to reduce the size, the cost, the applied bias, and the ozone generation amount as compared with the corona discharger. it can.

  According to the image forming apparatus of the fifth aspect of the invention, since the precharge means is an AC charging system, uniform and stable charging can be performed regardless of the environment.

  According to the image forming apparatus of the present invention 6, since the control (bias control) of the AC voltage applied to the precharge means is performed with the current value flowing from the photoconductor to the ground, the discharge to the photoconductor is prevented from being excessive. It is possible to control the discharge of the photoconductor and the adhesion of foreign matter from the photoconductor to the precharge means. Further, since the current is controlled by the current from the photoconductor to the ground, the discharge to the photoconductor can be made uniform, so that the photoconductor can be charged stably.

  According to the image forming apparatus of the present invention 7, since the precharge timing on the photoconductor is optimized, the area requiring precharge on the photoconductor can be efficiently charged without unevenness. Deterioration of the photoreceptor can be minimized. Further, useless energy consumption can be suppressed and energy consumption of the image forming apparatus can be reduced.

  According to the image forming apparatus of the present invention 8, since the crosslinkable charge transport layer has a thickness of 1 μm or more and 10 μm or less, the wear resistance of the crosslinkable charge transport layer can be improved and stabilized. .

  According to the image forming apparatus of the ninth aspect, the crosslinkable charge transport layer has a 10-point average surface roughness (Rz) of 0.05 to 1.0 μm, so that the cleaning property of the photoreceptor can be improved. .

  According to the process cartridge of the present invention 10, since the photoconductor having the cross-linked charge transport layer having a specific configuration and the precharge means are provided, even if a highly durable photoconductor is used, the cleaning property is deteriorated or abnormal with time. It is possible to provide a process cartridge that suppresses image generation and stably obtains high-quality images over a long period of time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows the layout of each means in the image forming apparatus of the present invention. As shown in FIG. 1, the image forming apparatus of the present invention includes a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit arranged around the cylindrical photosensitive member in the vicinity of the surface of the photosensitive member. Charging means is provided.
The image forming apparatus of the present invention includes the precharge unit as described above, so that the residual potential of the photoconductor can be neutralized, the occurrence of an afterimage caused by the residual potential is prevented, and a highly durable photoconductor is provided. Even if it is used, the occurrence of abnormal images over time can be suppressed, and high-quality images can be stably obtained over a long period of time.

  In the present invention, as a highly durable photoconductor, at least a charge generation layer, a charge transport layer and a crosslinkable charge transport layer are sequentially laminated on a conductive support, and the crosslinkable charge transport layer has at least a charge transport structure. It was formed by curing a radically polymerizable compound having a trifunctional or higher functional radical and a monofunctional charge transporting structure that does not have.

  Examples of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, HPA (alkylene) -modified trimethylolpropane triacrylate, EO (ethylene). (Oxy) -modified trimethylolpropane triacrylate, PO (propyleneoxy) -modified trimethylolpropane triacrylate, caprolactone-modified trimethylolpropane triacrylate, HPA-modified trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETTA), Glycerol triacrylate, ECH (epichlorohydrin) modified glycerol triacrylate EO modified glycerol triacrylate, PO modified glycerol triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), caprolactone modified dipentaerythritol hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkyl modified dipentaerythritol Pentaacrylate, alkyl-modified dipentaerythritol tetraacrylate, alkyl-modified dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, EO-modified phosphate triacrylate, 2,2,5,5-tetra Such as hydroxymethylcyclopentanone tetraacrylate It is. These can be used individually by 1 type or in combination of 2 or more types. The reason for the modification is to lower the viscosity of the monomer and make it easier to handle.

  Examples of the radical polymerizable compound having a monofunctional charge transport layer structure include hole transport structures such as triarylamine, hydrazone, pyrazoline, carbazole, condensed polycyclic quinone, diphenoquinone, cyano group, and nitro group. A compound having an electron transport structure such as an electron-withdrawing aromatic ring having a single radical polymerizable functional group. As the radical polymerizable functional group, acryloyloxy group and methacryloyloxy group are particularly useful. As the charge transporting structure, a triarylamine structure is highly effective.

  Next, the precharge means is preferably non-contact in order to prevent contamination. By using a non-contact method, the remaining toner or foreign matter on the photoreceptor can be used without contaminating the precharge means.

  In addition, the precharge means applies a voltage in which an alternating current component is superimposed on a direct current component in order to stabilize the precharge on the surface of the photoreceptor, and performs an AC charging method for precharging the surface potential of the photoreceptor. It is preferable that By using the AC charging method, uniform and stable charging can be performed regardless of the environment.

  Further, the precharge means preferably has a roller shape in order to reduce the size and cost of the charge means, reduce the applied bias, and reduce the amount of ozone generated. By using a roller shape, it is possible to reduce the size, the cost, and the applied bias as compared with the corona discharger, and further reduce the amount of ozone generated.

  Further, the precharge means prevents the occurrence of an afterimage due to the photoreceptor residual potential and improves the cleaning performance on the photoreceptor, as shown in FIG. 1, with respect to the rotation direction of the photoreceptor. It is preferable to be installed on the upstream side of the transfer unit and on the downstream side of the transfer means. By using such an installation location, the residual potential on the photoconductor after transfer is removed, and the generation of an afterimage is prevented. Further, since the residual potential of the photoconductor is removed before cleaning, the electrostatic adhesion between the toner and the photoconductor can be weakened to improve the cleaning performance.

In addition, the precharge means controls the AC voltage applied to the precharge means by a current value flowing from the photoreceptor to the ground in order to suppress deterioration of the photoreceptor due to discharge and contamination on the precharge means. Is preferred.
FIG. 2 shows the current control method. The current flowing from the photosensitive drum to the ground is measured so that the target current value is obtained, and the applied AC potential to the precharging roller is controlled.
By controlling the bias control with the value of the current flowing to the photoconductor, the discharge to the photoconductor can be controlled so as not to be excessive, and the discharge of the photoconductor and the adhesion of foreign matter from the photoconductor to the precharge means are suppressed. Can do.

The ON / OFF timing of charging by the precharge means is ON when the leading end of the exposed portion of the photosensitive member charging area enters the precharging portion or at a timing earlier than the leading end enters, and the exposure area on the photosensitive member It is preferable that the rear end of the rear end passes through the precharge portion or that the rear end is turned off at a later timing than after the precharge portion passes.
FIG. 3 shows the ON / OFF timing of the precharge means.
The charging start of the precharge means is the timing when the exposure start portion on the photoconductor passes through the precharge portion at the latest, and the charging end is the timing when the exposure end portion on the photoconductor passes through the precharge portion at the earliest. The actual ON / OF timing is based on the time T for entering the precharge unit from the exposure unit calculated from the distance between the exposure unit and the precharge unit / process linear velocity. The precharge is controlled to be completed T seconds after the exposure is completed.
When the precharge timing on the photoconductor is optimized, an area on the photoconductor that requires precharge can be efficiently charged, and deterioration of the photoconductor due to discharge is minimized. Further, useless energy consumption can be suppressed and energy consumption of the image forming apparatus can be reduced.

The cross-linked charge transport layer has a thickness of 1 μm or more and 10 μm or less, preferably 2 μm or more and 8 μm or less in order to improve and stabilize the wear resistance of the cross-linkable charge transport layer.
When the cross-linked charge transport layer is thicker than 10 μm, cracks and film peeling tend to occur. When the thickness is 8 μm or less, the margin for cracks and film peeling is improved, the crosslinking density can be increased, and further, material selection and curing conditions can be set to enhance wear resistance.
When the surface layer is 1 μm or less, the radical polymerization reaction tends to be inhibited by oxygen, that is, the surface in contact with the air does not easily proceed or become non-uniform due to the influence of radical trapping by oxygen.
The cross-linked charge transport layer has good wear resistance and scratch resistance at a film thickness of 1 μm or more. However, when a part that is locally scraped to the lower charge transport layer is formed in repeated use, wear of the part increases. However, the density unevenness of the halftone image is likely to occur due to chargeability and sensitivity fluctuations. Therefore, in order to achieve a longer life and higher image quality, it is desirable that the thickness of the cross-linked charge transport layer be 2 μm or more. .

The cross-linked charge transport layer preferably has a 10-point average surface roughness (Rz) of 0.05 to 1.0 μm in order to improve the cleaning properties of the photoreceptor.
When the surface roughness Rz is more than 1.0 μm, minute toner slips out easily in the cleaning blade, which causes background stains and streaky images. When the surface roughness Rz is less than 0.05, the slip stick of the cleaning blade becomes excessive, and cleaning failure occurs due to the reversal of the blade or the vibrational slipping of the toner accompanying the slip stick.

In addition, the radical polymerizable functional group of the tri- or higher functional radical polymerizable monomer having no charge transport structure used in the cross-linked charge transport layer and the radical polymerizable compound having a monofunctional charge transport structure is acryloyloxy. It is preferably a group and / or a methacryloyloxy group.
By using a monomer or compound having an acryloyloxy group and / or methacryloyloxy group in the uppermost cross-linked charge transport layer after reaction (polymerization reaction, etc.), a three-dimensional network structure is developed and the degree of crosslinking is very high. A high hardness surface layer is obtained, and high wear resistance can be achieved.

In addition to the above-described image forming apparatus invention, the present invention includes the above-described photoreceptor and precharge means, and a combination of at least one of charging means, exposure means, developing means, transfer means, and cleaning means. The invention also includes an invention of a process cartridge that can be formed and detachably attached to the apparatus body.
According to such a process cartridge, since the precharge means is provided, the residual potential of the photosensitive member can be eliminated, and the cleaning property is improved by weakening the electrostatic adhesion between the toner and the photosensitive member. Generation of afterimages due to residual potential can be prevented, and high-quality images can be stably obtained over a long period of time.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. In addition, this invention is limited and interpreted by the Example shown below. Unless otherwise specified, parts means parts by weight.

A 5% methanol solution of polyamide resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) is applied on an aluminum cylinder with a diameter of 30 mm x 340 mm (diameter 30 mm, length 340 mm) by a dipping method to provide a subbing layer of 0.3 μm thickness. It was. The aluminum cylinder was subjected to a cutting process so that moire was not generated.
Next, 10 oxytitanium phthalocyanine pigments having strong peaks at 9.0 °, 14.2 °, 23.9 °, and 27.1 ° at diffraction angles 2θ ± 0.2 ° in X-ray diffraction using CuKα were used. Part, 10 parts of polycarbonate Z resin (weight average molecular weight 28,000) and 60 parts of cyclohexane were dispersed in a sand mill apparatus using 1φ glass beads for 20 hours. A solution obtained by adding 100 parts of methyl ethyl ketone to this dispersion was applied onto the undercoat layer and dried to form a charge generation layer. This film thickness was 0.12 μm.

  Next, 7 parts of a triarylamine compound represented by the following formula (1) and 3 parts of a styryl compound represented by the following formula (2) were added to 10 parts of a polycarbonate Z resin (weight average molecular weight 80,000) and 60 parts of monochlorobenzene. Dissolved. This solution was applied onto the charge generation layer and dried to form a charge transport layer. The film thickness after drying was 20 μm.

Furthermore, after spray-coating a coating liquid for a crosslinking charge transport layer having the following composition on the charge transport layer and naturally drying for 20 minutes, a metal halide lamp: 160 W / cm, irradiation distance: 120 mm, irradiation intensity: 500 mW / Light irradiation was performed under conditions of cm ² and irradiation time: 60 seconds to cure the coating film. Further, drying was performed at 130 ° C. for 20 minutes to provide a cross-linked charge transport layer having a thickness of 5.3 μm to obtain an electrophotographic photoreceptor of the present invention.
[Coating liquid for cross-linked charge transport layer]
10 parts of the following acrylate was used as a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure.
Trimethylolpropane triacrylate (Nippon Kayaku KAYARAD TMPTA,
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99)
Radical polymerizable compound having a monofunctional charge transporting structure (compound of the following structural formula (3)) 10 parts

光重合開始剤 １部
１−ヒドロキシ−シクロヘキシル−フェニル−ケトン
（イルガキュア１８４、チバ・スペシャルティ・ケミカルズ製）
テトラヒドロフラン １００部

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts

  An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the film thickness of the crosslinked charge transport layer in Example 1 was changed to 1.3 μm.

  An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the film thickness of the crosslinked charge transport layer in Example 1 was changed to 7.7 μm.

A radical having a monofunctional charge transporting structure is replaced with the following monomer instead of the trifunctional or higher radical polymerizable monomer having no charge transporting structure contained in the coating liquid for the crosslinkable charge transporting layer of Example 1. An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the polymerizable compound was changed to 10 parts of the compound of the following structural formula (4) and the thickness of the cross-linked charge transport layer was changed to 5.4 μm.
10 parts of the following acrylate was used as a radical polymerizable monomer of a tri- or higher functional radical polymerizable monomer having no charge transporting structure.
Pentaerythritol tetraacrylate (SR-295 manufactured by Kayaku Sartomer,
(Molecular weight: 352, number of functional groups: tetrafunctional, molecular weight / number of functional groups = 88)
Radical polymerizable compound having monofunctional charge transport structure

  An electrophotographic photosensitive member was produced in the same manner as in Example 4 except that the film thickness of the crosslinked charge transport layer in Example 4 was changed to 1.4 μm.

  An electrophotographic photosensitive member was produced in the same manner as in Example 4 except that the film thickness of the crosslinked charge transport layer in Example 4 was changed to 7.7 μm.

(Comparative Example 1)
An electrophotographic photosensitive member of Comparative Example 1 was produced in the same manner as in Example 1 except that the cross-linked charge transport layer was not provided and the charge transport layer thickness was 25 μm.

(Comparative Example 2)
In Example 1, a crosslinkable charge transport layer was not provided on the charge transport layer, and 25 parts of an acrylic curable monomer represented by the following structural formula (5), 2.0 parts of 2-methylthioxanthone and 300 parts of toluene were added. The mixed solution was spray-coated, dried, and then exposed to ultraviolet light at a light intensity of 800 mW / cm ² for 20 seconds with a high-pressure mercury lamp, and a protective layer having a thickness of 2.0 μm was formed as in Example 1. An electrophotographic photosensitive member of Comparative Example 2 was produced.

(Comparative Example 3)
In Example 1, a charge transporting layer was prepared, and an adhesive layer coating solution having the following composition was applied onto the charge transporting layer, followed by heat treatment at 100 ° C. for 30 minutes to form an adhesive layer having a thickness of 0.3 μm. did.
[Coating liquid for adhesive layer]
Silyl acrylate (PC-7A: manufactured by Shin-Etsu Chemical Co., Ltd.) 6 parts 2-butanone 200 parts Further, a protective layer was provided on the adhesive layer as follows.
<Protective layer>
The molecular sieve 4A was added to a methanol solution of polysiloxane composed of 80 mol% of methylsiloxane units and 20 mol% of methyl-phenylsiloxane units, and allowed to stand for 15 hours for dehydration treatment. 10 parts of this solution was dissolved in 10 parts of toluene, and 1 part of methyltrimethoxysilane and 0.2 part of dibutyltin acetate were added thereto to make a uniform solution.
This solution was applied as a protective layer having a dry film thickness of 3 μm and heat-cured at 120 ° C. for 1 hour to produce an electrophotographic photoreceptor of Comparative Example 3.

(Comparative Example 4)
The radical polymerizable compound having a monofunctional charge transporting structure contained in the coating liquid for a crosslinkable charge transporting layer of Example 1 is a radical polymerizable compound having a bifunctional charge transporting structure represented by the following structural formula (6). An electrophotographic photoreceptor of Comparative Example 4 was produced in the same manner as in Example 1 except that 10 parts of the compound was changed.
10 parts of a radically polymerizable compound having a bifunctional charge transporting structure

The electrophotographic photosensitive members 1 to 6 of the examples and the electrophotographic photosensitive members 1 to 4 of the comparative example manufactured as described above were prepared with a precharge unit provided between the transfer process and the cleaning process as shown in FIG. It was mounted on a modified IPSIO CX400 machine and image evaluation was performed.
As a modification of the precharge means, a PET tape having a thickness of 50 μm was wound around and fixed to both ends (non-image forming areas) of the charging roller, and the charging member was disposed close to the photoreceptor. Further, the precharge charging roller is supplied with AC (1.35 kHz, 2.0 kV (peak to peak)) + DC (0 V) at which the current value flowing from the photosensitive member to the ground becomes 300 μA from the leading end of the exposed portion of the photosensitive member. Applied across the edge.

  For image evaluation, a total of 60,000 sheets are printed continuously with or without precharge means. After printing 60,000 sheets, the images are evaluated in an environment of 25 ° C. and 50% RH and 30 ° C. and 90% RH. Went. Moreover, the 10-point average surface roughness (Rz) of the bridge | crosslinking surface layer which is the uppermost layer in the initial stage was evaluated.

  The average surface roughness Rz of the crosslinked surface layer is a 10-point average roughness measured according to JIS B0601-1994 standard, and was measured using Surfcom 1400D (manufactured by Tokyo Seimitsu) in the present invention.

These results are shown in Tables 1 and 2. The image level was classified according to the following symbols.
◎: Good level without image quality degradation ○: Level without image quality degradation but no problem △: Level where image quality degradation can be clearly confirmed ×: Level where image quality degradation is significant and image discrimination is difficult

From the above table, it can be seen that according to the image forming apparatus using the photoconductor of the example and provided with the precharge means, a good image can be obtained without image quality deterioration even after printing 60,000 sheets. Further, the 10-point average surface roughness (Rz) of the photoconductor is less than 0.7 μm, and it can be seen that there is no occurrence of minute toner slipping in the cleaning blade.
In addition, AC (1.35 kHz) + DC (0 V) with an output from the power pack of 2.0 kV (peak to peak) was applied to the precharge charging roller, and the same evaluation as described above was performed. The occurrence of filming becomes remarkable under high humidity (because the gap between the charging roller and the photosensitive member becomes narrow due to the expansion of the charging roller, resulting in excessive discharge). Furthermore, the charging of the surface of the photoconductor was not stable with respect to changes in the environment (because the gap between the charging roller and the photoconductor changed depending on the environment), and the image quality was uneven. Further, when the precharge charging application timing was synchronized with ON / OFF of the photosensitive member drive, the occurrence of filming became more remarkable.

FIG. 5 is a layout diagram illustrating a place where precharge means is installed in the image forming apparatus of the present invention. It is a figure for demonstrating the electric current control method of the pre-charge means in the image forming apparatus of this invention. FIG. 4 is a diagram for explaining ON / OFF timing of a precharge unit in the image forming apparatus of the present invention.

Claims (10)

A photosensitive member in which at least a charge generation layer, a charge transport layer, and a cross-linked charge transport layer are sequentially laminated on a conductive support, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit disposed in proximity to the surface of the photosensitive unit An image forming apparatus comprising means,
The image forming apparatus further includes a precharge unit,
The cross-linked charge transport layer is formed by reacting at least a trifunctional or higher functional radical polymerizable monomer having no charge transport structure with a radical polymerizable compound having a monofunctional charge transport structure, and starts charging. The precharge means that precharges the surface of the photoconductor to remove the residual potential of the photoconductor before is installed upstream of the cleaning means and downstream of the transfer means with respect to the rotation direction of the photoconductor. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the radical polymerizable functional group of the radical polymerizable monomer or the radical polymerizable compound is at least one of an acryloyloxy group and a methacryloyloxy group.   The image forming apparatus according to claim 1, wherein the precharge unit is not in contact with the photosensitive member.   4. The image forming apparatus according to claim 1, wherein the precharge unit has a roller shape.   5. The AC charging method according to claim 1, wherein the precharge means is an AC charging system that precharges the surface potential of the photoconductor by applying a voltage in which an AC component is further superimposed on a DC component. Image forming apparatus.   6. The image forming apparatus according to claim 5, wherein the AC voltage applied to the precharge means is controlled by a current value flowing from the photoconductor to the ground.   The ON / OFF timing of charging by the precharge means is ON at a timing when the leading end of the exposure means in the photosensitive member charging area enters the precharging means or at a timing earlier than the leading edge enters, and the trailing end of the exposure area on the photosensitive member 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is turned off at a timing after passing through the precharge means or at a timing when the rear end is later than after passing through the precharge means.   The image forming apparatus according to claim 1, wherein the cross-linked charge transport layer has a thickness of 1 μm or more and 10 μm or less.   The image forming apparatus according to claim 1, wherein the cross-linked charge transport layer has a 10-point average surface roughness (Rz) in a range of 0.05 to 1.0 μm.   10. The electrophotographic photosensitive member and precharge means used in the image forming apparatus according to claim 1, and at least one of charging means, exposure means, developing means, transfer means, and cleaning means. And a process cartridge that is detachably installed in the main body of the image forming apparatus.

Images