JP2012042777A - Electrophotographic image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus, which is free of problems such as decrease in image density or generation of a transfer memory even when a great number of sheets are printed at a high speed, and which can continuously give high-quality printed images.SOLUTION: The electrophotographic image forming apparatus includes at least first charging means 1, exposure means 2, developing means 3, transfer means 4, second charging means 5 which imparts a potential in an opposite polarity to the potential given by the first charging means to a photoreceptor 10, after a toner image is transferred to a transfer medium 30, and cleaning means 7 cleaning a transfer residue toner on the photoreceptor. The photoreceptor includes a photosensitive layer and a surface protective layer, sequentially formed in this order on a conductive support, and the surface protective layer contains at least inorganic fine particles and a resin having a crosslinked structure.

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In an electrophotographic image forming apparatus using an electrophotographic system, a reversal developing unit that develops toner using toner having the same polarity as that applied to a photoreceptor is the mainstream, and is widely used in digital image forming apparatuses.

  The transfer current applied to the photoconductor by the transfer means is usually not applied directly to the photoconductor, but is applied via the transfer body or the intermediate transfer body. As the image quality progresses year by year, the toner tends to have a smaller particle size, and in association with this, the transfer current flowing to the photosensitive member is often set higher (see, for example, Patent Document 1). ).

  This is because the toner having a smaller particle size has a stronger cohesive force, making transfer difficult.

  On the other hand, a problem when the transfer current is set high is the generation of a transfer memory.

  The transfer current is uniformly applied to the toner adhering portion and the toner non-adhering portion on the photosensitive member. That is, the surface of the photosensitive member to which a transfer current is applied via the toner and the surface of the photosensitive member to which a direct transfer current is applied can be formed, and a difference in the transfer current flowing depending on the portion of the photosensitive member can be made.

  In the case of a negatively charged photoreceptor, the polarity of the current applied by the transfer means is positive, so that positive space charge remains on the surface of the photoreceptor to which a positive current is applied. Generally, the positive space charge is erased in the next charging means.

  However, when the transfer current increases, there is an excess of positive space charge, and even if it is negatively charged by the next charging means, the potential is lowered due to the effect of space charge, and further appears as a sensitivity difference in the developing means. In the print image, a so-called transfer memory image is generated in which the portion becomes black.

  These tend to become more prominent when the transfer voltage is increased when transferring a toner having a smaller particle diameter. On the other hand, when the transfer current is lowered, transfer failure occurs and the toner cannot be transferred sufficiently.

  In addition, in an electrophotographic image forming apparatus using electrophotographic technology, development of an image forming apparatus having excellent durability has been demanded.

  In order to increase the durability of the image forming apparatus, it is necessary to extend the life of the photoreceptor. As means for extending the life of the photoreceptor, studies have been made to improve the abrasion resistance by providing a surface protective layer on the photosensitive layer constituting the photoreceptor (see, for example, Patent Document 2).

JP 2006-220812 A JP 11-95473 A

  However, when the photosensitive member provided with the surface protective layer disclosed above is loaded into a high-speed (for example, 65 sheets / 1 minute, A4 size lateral feed) image forming apparatus and printing is performed, a transfer memory is generated in the printed image. However, there has been a problem that the print quality is deteriorated.

  The object of the present invention is that even when a large number of sheets (for example, 1 million sheets) are printed at a high speed (for example, 65 sheets / minute, A4 size lateral feed), the image density is lowered or a transfer memory is generated. An object of the present invention is to provide an electrophotographic image forming apparatus (hereinafter also simply referred to as an image forming apparatus) that can continuously obtain a high-quality print image.

  The object of the present invention is achieved by the following configurations.

1. First charging means for charging at least the surface of the photoreceptor;
Exposure means for irradiating the surface of the photoreceptor charged by the first charging means with light to form an electrostatic latent image;
Developing means for visualizing the electrostatic latent image with toner to form a toner image on a photoreceptor;
Transfer means for transferring the toner image on the photosensitive member to a transfer medium;
Electrophotographic image forming comprising: a second charging unit that applies a potential opposite to that of the first charging unit to the photosensitive member after the toner image is transferred to the transfer medium; and a cleaning unit that cleans residual toner on the photosensitive unit. A device,
The photoreceptor is formed by sequentially forming a photosensitive layer and a surface protective layer on a conductive support,
The electrophotographic image forming apparatus, wherein the surface protective layer contains at least a resin having an inorganic fine particle and a crosslinked structure.

  2. 2. The electrophotographic image forming apparatus according to 1 above, wherein the inorganic fine particles have a reactive group on the surface thereof.

  3. 3. The electrophotographic image forming apparatus as described in 1 or 2 above, wherein the electrophotographic image forming apparatus has a light neutralizing unit between the second charging unit and the first charging unit.

  In the image forming apparatus of the present invention, even when a large number of sheets (for example, 1,000,000 sheets) are printed at a high speed (for example, 65 sheets / minute, A4 size lateral feed), the image density or the transfer rate is decreased. In addition, there is no problem that a transfer memory is generated, and there is an excellent effect that a high-quality print image can be obtained continuously.

FIG. 2 is a schematic diagram illustrating an example of an image forming unit of the image forming apparatus of the present invention. It is a schematic diagram showing how the charge on the photoreceptor changes when a conventional image forming apparatus is used. FIG. 6 is a schematic diagram showing how the charge on the photoreceptor changes when the image forming apparatus of the present invention is used. It is a schematic diagram which shows an example of the laminated constitution of the photoreceptor used by this invention.

  In an image forming apparatus using electrophotographic technology, development of an image forming apparatus having excellent durability is desired.

  In order to realize an image forming apparatus having excellent durability, it is necessary to make a photosensitive member having inferior durability compared to other members highly durable.

  As a highly durable photoreceptor, for example, a photoreceptor provided with a surface protective layer containing a resin having inorganic fine particles and a curable compound has been studied.

  However, a photoreceptor provided with a surface protective layer containing inorganic fine particles and a resin having a cross-linked structure has a problem that a transfer memory is easily generated as compared with a photoreceptor provided with no surface protective layer.

  The present inventors use a highly durable photoconductor, and even when a large number of sheets (for example, 1 million sheets) are printed, the image density decreases, the transfer rate decreases, and a transfer memory is generated. An image forming apparatus that does not perform is studied.

  As a result of various studies, it has been found that even when a highly durable photoconductor is used, the generation of a transfer memory can be reduced by providing a second charging unit that performs charging with a polarity opposite to that of the charging unit after transfer. It was. Furthermore, it has been found that the occurrence of transfer memory can be further reduced by forming an image using an image forming apparatus provided with a light neutralizing means downstream of the second charging means.

  In the photoreceptor having the surface protective layer, a negative electric field is applied to the surface layer side because the toner adhesion portion has a negative potential after the transfer. When light is removed in this state, holes are generated and moved, and hole traps occur in the surface protective layer, resulting in an increase in potential after exposure in the next process. As a result, a transfer memory is generated.

  In the present invention, the transfer memory can be prevented by positively charging the second charging means after the transfer and preventing the generation of holes when the light is discharged.

  Note that a photoconductor without a surface protective layer generates holes even if it is photocharged without being positively charged after transfer, but a transfer memory is unlikely to occur because hole traps are unlikely to occur.

  The transfer memory referred to in the present invention means that after printing a character image continuously (for example, 100 sheets) and then printing a halftone image, the previously printed character image appears black in the halftone image portion, or halftone. A phenomenon that appears as white spots in the image area.

  The present invention will be described below.

<Image forming apparatus>
The image forming apparatus of the present invention includes:
First charging means for charging at least the surface of the photoreceptor;
Exposure means for irradiating the surface of the photoreceptor charged by the first charging means with light to form an electrostatic latent image;
Developing means for visualizing the electrostatic latent image with toner to form a toner image on a photoreceptor;
Transfer means for transferring the toner image on the photosensitive member to a transfer medium;
The image forming apparatus includes a second charging unit that applies a potential opposite to that of the first charging unit to the photosensitive member after the toner image is transferred to the transfer medium, and a cleaning unit that cleans transfer residual toner on the photosensitive member. .

  In the present invention, the second charging unit may be provided between the transfer unit and the cleaning unit, or may be provided between the cleaning unit and the first charging unit, and can be selected depending on the installation space of the image forming apparatus.

  Furthermore, the image forming apparatus of the present invention may further include a light neutralizing unit between the second charging unit and the first charging unit, if necessary.

  FIG. 1 is a schematic diagram illustrating an example of an image forming unit of an image forming apparatus according to the present invention.

  In FIG. 1, 1 is a first charging unit, 2 is an exposure unit, 3 is a developing unit, 4 is a transfer unit, 5 is a second charging unit, 6 is a light neutralizing unit, 7 is a cleaning unit, 10 is a photoconductor, 20 Denotes a toner, 21 denotes a transfer residual toner, and 30 denotes a transfer material (transfer medium).

  In the image forming section of FIG. 1A, the first charging unit 1, the exposure unit 2, the developing unit 3, the transfer unit 4, the second charging unit 5, the photostatic unit 6, and the cleaning unit 7 are exposed in this order. It is provided in the direction of rotation of the body 10.

  The second charging unit 2 is disposed between the transfer unit 4 and the cleaning unit 7.

  The light neutralizing unit 6 is disposed between the second charging unit 2 and the cleaning unit 7.

  In the image forming section of FIG. 1B, each of the units is photosensitive in the order of the first charging unit 1, the exposure unit 2, the developing unit 3, the transfer unit 4, the second charging unit 5, the photostatic unit 6, and the cleaning unit 7. It is provided in the direction of rotation of the body 10.

  The second charging unit 2 is disposed between the cleaning unit 7 and the first charging unit 1.

  The light neutralizing unit 6 is disposed between the second charging unit 2 and the first charging unit 1.

  As the second charging means, it is preferable to use a strip electrode, a conductive film, or a conductive roller, and a conductive roller is more preferable in consideration of downsizing of the apparatus and dirt due to toner.

  Note that the image forming apparatus of the present invention can be applied to an image forming apparatus that directly transfers a toner image to a transfer material as described above, or an image forming apparatus that transfers a toner image to a transfer medium after being transferred to a transfer medium. .

  FIG. 2 is a schematic diagram showing how the charge on the photoreceptor changes in each step when a conventional image forming apparatus is used.

  In FIG. 2, 1 is a first charging process, 2 is an exposure process, 3 is a development process, 4 is a transfer process, 5 is a photostatic process, 7 is a cleaning process, 1 'is a first charging process that is repeatedly performed, and 9 is The latent image, 11 is a conductive support, 14 is a charge generation layer, 15 is a charge transport layer, 16 is a surface protective layer, 20 is a toner particle, + is a positive charge, and-is a negative charge.

  FIG. 2 schematically shows the role of each process and the change in charge on the photoreceptor.

1: The surface of the photoreceptor is negatively charged by the charging means (first charging step)
2: The negatively charged photoconductor is irradiated with light, the negative charge of the irradiated portion is erased, and an electrostatic latent image is formed (exposure process)
3: Toner adheres to the portion (electrostatic latent image portion) from which the negative charge is erased (development process)
4: Toner adhering to the electrostatic latent image portion is transferred to a transfer medium (transfer process)
6: Photostatic discharge of entire surface of photoconductor (photostatic discharge process)
7: Transfer residual toner on the photoreceptor remaining without being transferred is removed by a cleaning member (cleaning step).
1 ': The surface of the photosensitive member is negatively charged by the repeated charging means (first charging step).
After the first charging process 1 'repeated, the processes from 2 to 4, 6, and 7 are repeated, and printing is performed continuously.

  From this schematic diagram, it can be seen that, after the cleaning process, negative charges remain in the latent image portion, and even after the first charge, positive charges remain in the electrostatic latent image portion in the charge transport layer. As a result, excessive toner adheres to the portion where the positive charge remains in the developing process, thereby forming a transfer memory.

  FIG. 3 is a schematic diagram showing how the charge on the photoreceptor changes in each step when the image forming apparatus of the present invention is used.

  In FIG. 3, 1 is a first charging process, 2 is an exposure process, 3 is a development process, 4 is a transfer process, 5 is a second charging process, 6 is a photostatic process, 7 is a cleaning process, and 1 'is repeated. First charging step, 11 is a conductive support, 9 is a latent image, 14 is a charge generation layer, 15 is a charge transport layer, 16 is a surface protective layer, 20 is toner particles, + is a positive charge,-is a negative charge Show.

1: The surface of the photoreceptor is negatively charged by the charging means (first charging step)
2: The negatively charged photoconductor is irradiated with light, the negative charge of the irradiated portion is erased, and a latent image is formed (exposure process).
3: Toner adheres to the portion (latent image portion) from which the negative charge has been erased (development process)
4: The toner adhering to the latent image portion is transferred to the transfer medium (transfer process).
5: The surface of the photoreceptor is positively charged by the charger (second charging step)
6: Photostatically remove the entire surface of the positively charged photosensitive member (photostatic elimination process)
7: Transfer residual toner on the photoreceptor remaining without being transferred is removed by a cleaning member (cleaning step).
1 ': The surface of the photosensitive member is negatively charged by the repeated charging means (first charging step).
After the first charging step 1 ′ that is repeated, the steps 2 to 7 are repeated, and printing is performed continuously.

  From this schematic diagram, when the second charging step is charged with the opposite polarity to that of the first charging step, the charge in the electrostatic latent image portion and the charge in the other portion are at the same level. It can be seen that no negative charge remains in the portion, and when it is first charged again, it becomes a uniform charge. As a result, toner uniformly adheres in the development process, and no transfer memory is generated.

<Photoconductor>
The photoreceptor used in the present invention has a multilayer structure in which a photosensitive layer and a surface protective layer are provided in this order on a conductive support, and the surface protective layer contains at least a resin having inorganic fine particles and a crosslinked structure. is doing.

  FIG. 4 is a schematic view showing an example of the layer structure of the photoreceptor used in the present invention.

  In FIG. 4, 11 is a conductive support, 12 is an intermediate layer, 13 is a photosensitive layer, 14 is a charge generation layer, 15 is a charge transport layer, 16 is a surface protective layer, 17 is a resin having a crosslinked structure, and 18 is inorganic. Shows fine particles.

  First, the member which a surface protective layer contains is demonstrated.

《Inorganic fine particles》
Examples of the inorganic fine particles used in the present invention include inorganic fine particles such as titanium oxide (TiO ₂ ), zinc oxide (ZnO), and tin oxide (SnO ₂ ). Among these, tin oxide and titanium oxide are preferable. .

  Furthermore, preferred examples of the inorganic fine particles used in the present invention include those in which the inorganic fine particles are surface-treated and have a reactive acryloyl group or a reactive methacryloyl group on the surface thereof.

  If the surface of the inorganic fine particles has a reactive acryloyl group or a reactive methacryloyl group, when the curable compound is cured, the reactive acryloyl group or the reactive methacryloyl group reacts with the curable compound to make it more durable. An excellent surface protective layer can be formed, which is preferable.

  The inorganic fine particles preferably have a number average primary particle size of 5 to 300 nm, more preferably 10 to 200 nm.

  Here, the number average primary particle size is a value obtained by observing 100 particles as primary particles at random by magnifying the particles 100000 times by observation with a transmission electron microscope and performing image analysis.

  Examples of the transmission electron microscope (TEM) include “H-9000NAR” (manufactured by Hitachi, Ltd.), “JEM-200FX” (manufactured by JEOL Ltd.), and the like.

  The observation method using a transmission electron microscope is performed by a normal method performed when measuring the particle size of the particles. For example, the procedure is as follows. First, materials for observation are prepared. The inorganic oxide particles are sufficiently dispersed in a room temperature curable epoxy resin, and then embedded and cured to produce a block. The prepared block is cut into a thin piece having a thickness of 80 to 200 nm using a microtome equipped with diamond teeth to produce a measurement sample.

  Next, using a transmission electron microscope (TEM), the image is magnified 100000 times to photograph inorganic fine particles. Next, the image information of 100 inorganic fine particles photographed by the image processing apparatus “Luzex F” (manufactured by Nicole) is arithmetically processed to obtain the number average primary particle size.

  Inorganic fine particles having a number average primary particle size in the above range can be uniformly dispersed in the resin forming the coating film, prevent formation of aggregated particles and generation of large irregularities on the surface, and the aggregated particles serve as charge traps. As a result, it is possible to form a good printed matter free from black spots, transfer memory, and black spots due to the large unevenness. Further, the inorganic fine particles are difficult to settle in the coating solution, and the dispersion stability of the solution is also excellent.

  Hereinafter, the surface-treated inorganic fine particles used in the present invention will be described in detail using tin oxide particles having a reactive acryloyl group or methacryloyl group as an example.

  The tin oxide particles having a reactive acryloyl group or methacryloyl group used in the present invention can be produced, for example, by reacting a compound represented by the following general formula (1) with tin oxide particles.

(Wherein R ³ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 1 to 10 carbon atoms, R ⁴ is an organic group having a reactive acryloyl group or methacryloyl group, X is a halogen atom, an alkoxy group) An acyloxy group, an aminoxy group, or a phenoxy group, and n is an integer of 1 to 3.)
Examples of the compound represented by the general formula (1) will be given below.

_{S-1 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-2 CH 2 = CHCOO (} CH 2) 2 Si (OCH 3) 3
_{S-3 CH 2 = CHCOO (} CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-4 CH 2 = CHCOO (} CH 2) 3 Si (OCH 3) 3
_{S-5 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) Cl 2
_{S-6 CH 2 = CHCOO (} CH 2) 2 SiCl 3
_{S-7 CH 2 = CHCOO (} CH 2) 3 Si (CH 3) Cl 2
_{S-8 CH 2 = CHCOO (} CH 2) 3 SiCl 3
_{S-9 CH 2 = C (} CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-10 CH 2 = C (} CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-11 CH 2 = C (} CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-12 CH 2 = C (} CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-13 CH 2 = C (} CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-14 CH 2 = C (} CH 3) COO (CH 2) 2 SiCl 3
_{S-15 CH 2 = C (} CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-16 CH 2 = C (} CH 3) COO (CH 2) 3 SiCl 3
_{S-17 CH 2 = CHCOOSi (} OCH 3) 3
_{S-18 CH 2 = CHCOOSi (} OC 2 H 5) 3
_{S-19 CH 2 = C (} CH 3) COOSi (OCH 3) 3
_{S-20 CH 2 = C (} CH 3) COOSi (OC 2 H 5) 3
_{S-21 CH 2 = C (} CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
_{S-22 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) 2 (OCH 3)
_{S-23 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) (OCOCH 3) 2
_{S-24 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) (ONHCH 3) 2
_{S-25 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) (OC 6 H 5) 2
_{S-26 CH 2 = CHCOO (} CH 2) 2 Si (C 10 H 21) (OCH 3) 2
_{S-27 CH 2 = CHCOO (} CH 2) 2 Si (CH 2 C 6 H 5) (OCH 3) 2
These silane compounds can be used alone or in admixture of two or more.

(Production method of tin oxide particles having reactive groups)
The tin oxide particles having a reactive acryloyl group or methacryloyl group used in the present invention can be obtained by surface-treating the tin oxide particles using the silane compound represented by the general formula (1) or the like. . In carrying out the surface coating treatment, a wet media dispersion type apparatus is used with 100 to 100 parts by mass of tin oxide particles, using 0.1 to 100 parts by mass of a silane compound as a surface treating agent and 50 to 5000 parts by mass of a solvent. It is preferable to do.

  Hereinafter, a surface treatment method for producing tin oxide particles that are uniformly and more finely surface-coated with a silane compound will be described.

  That is, by subjecting a slurry (suspension of solid particles) containing tin oxide particles and a silane compound to wet pulverization, the surface treatment of the tin oxide particles proceeds at the same time as the tin oxide particles are refined. Then, since the solvent is removed and powdered, tin oxide particles surface-treated with a uniform and finer silane compound can be obtained.

  The wet media dispersion type apparatus, which is a surface treatment apparatus used in the present invention, is agglomeration of tin oxide by filling beads in a container as media and rotating a stirring disk mounted perpendicularly to the rotation axis at high speed. It is an apparatus having a step of crushing and pulverizing / dispersing particles, and as its configuration, there is no problem if the tin oxide particles are sufficiently dispersed when performing surface treatment on the tin oxide particles and can be surface treated. For example, various types such as a vertical type, a horizontal type, a continuous type, and a batch type can be adopted. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersion-type devices are pulverized and dispersed by impact crushing, friction, shearing, shear stress, etc., using a grinding medium (media) such as balls and beads.

  As the beads used in the sand mill, balls made of glass, alumina, zircon, zirconia, steel, flint stone and the like can be used, but those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 1 to 2 mm are usually used, but in the present invention, those having a diameter of about 0.3 to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, the disk and container inner wall made of ceramic such as zirconia or silicon carbide are particularly used. Is preferred.

  By the wet treatment as described above, tin oxide particles having a reactive acryloyl group or methacryloyl group can be obtained by surface treatment with the silane compound of the general formula (1).

  Here, having a reactive acryloyl group or methacryloyl group means that a compound having a hydroxyl group and a silyl group on the surface of the inorganic fine particles forms a chemical bond by a hydrolysis reaction.

  Thereby, the reactive organic group in the silane compound such as the general formula (1) becomes inorganic fine particles existing on the particle surface.

  The tin oxide particles having the reactive group form a protective layer by a reaction with a compound having a polymerizable group described below.

<Resin having a crosslinked structure>
The resin having a crosslinked structure is a resin formed by polymerizing a curable compound.

  Examples of the curable compound used for forming the resin having a crosslinked structure include a compound having a reactive methacryloyl group.

  That is, as the curable compound having a reactive methacryloyl group, it is preferable to use a compound that reacts with the reactive acryloyl group or methacryloyl group of the tin oxide particles.

  In the present invention, the curable compounds may be used alone or in combination.

  Examples of the curable compound used in the present invention are shown below.

In the present invention, the methacryloyl compound is a compound having a methacryloyl group (CH ₂ ═C (CH ₃ ) CO—). Moreover, the number of Ac groups referred to below represents the number of methacryloyl groups.

  However, in the above, R is shown below.

  In the present invention, the curable compound preferably has 2 or more functional groups. The methacryloyl-based compound is preferably a compound having a ratio of the molecular weight M of the compound having a methacryloyl group to the number Ac of the methacryloyl group (Ac / M, methacryloyl group number / molecular weight) greater than 0.005.

  Use of a curable compound having an Ac / M greater than 0.005 is preferable because the crosslink density is increased, the abrasion resistance of the photoreceptor is improved, and the occurrence of image flow and image blur is prevented.

  As for the upper limit of Ac / M, as the value increases, the number of crosslinks in the resin increases, so the hardness of the surface protective layer increases and the wear resistance of the photoreceptor improves. However, since the hardness is too high, cracks in the surface protective layer or an adverse effect on the life of the coating solution at the time of manufacture are likely to occur, and the occurrence of image flow and image blur may tend to increase. Therefore, it is rather desirable that Ac / M is smaller than 0.05. Further, Ac / M is particularly preferably 0.01 or less.

  In the present invention, two or more curable compounds having different functional group densities may be mixed and used.

  The resin having a crosslinked structure can be formed by applying a coating liquid containing a polymerization initiator as necessary in addition to the curable compound to form a film, and then reacting.

  When the curable compound is reacted, a method of reacting by electron beam cleavage, a method of reacting with light or heat by adding a radical polymerization initiator or a cationic polymerizable initiator, and the like are used. As the polymerization initiator, either a photopolymerization initiator or a thermal polymerization initiator can be used. Further, both light and heat initiators can be used in combination.

As a radical polymerization initiator of these photocurable compounds, a photopolymerization initiator is preferable, and among them, an alkylphenone compound or a phosphine oxide compound is preferable. In particular, a compound having an α-hydroxyacetophenone structure or an acylphosphine oxide structure is preferable. The compound that initiates cationic polymerization, e.g., diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds such as phosphonium ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 - , CF ₃ SO ₃ ^- ionic polymerization initiator or sulfonic acid sulfonated materials that generate a such as salts, halides or generates hydrogen halide, can be mentioned nonionic polymerization initiator such as iron arene complex. In particular, a sulfonate that generates a sulfonic acid that is a nonionic polymerization initiator and a halide that generates a hydrogen halide are preferable.

  The photoinitiator used preferably below is illustrated.

  Examples of α-aminoacetophenone series

  Examples of α-hydroxyacetophenone compounds

  Examples of acylphosphine oxide compounds

  Examples of other radical polymerization initiators

  Nonionic polymerization initiator

  Ionic polymerization initiator

  Next, production of the photoreceptor used in the present invention will be described.

<< Production of photoconductor >>
<Conductive support>
As the conductive support used in the present invention, for example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel formed into a drum or a sheet, or a metal foil such as aluminum or copper is laminated on a plastic film. Metal, aluminum, indium oxide, zinc oxide and the like deposited on a plastic film, a metal, a plastic film and paper provided with a conductive layer by applying a conductive substance alone or with a binder resin.

<Intermediate layer>
In the present invention, an intermediate layer having a barrier function and an adhesive function may be provided between the conductive layer and the photosensitive layer.

  The intermediate layer can be formed by dip coating or the like by dissolving a binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane and gelatin in a known solvent. Of these, an alcohol-soluble polyamide resin is preferred.

  As the solvent used for the intermediate layer, a solvent in which inorganic particles are well dispersed and the polyamide resin is dissolved is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are excellent in solubility and coating performance of the polyamide resin. In addition, examples of co-solvents that can be used in combination with the above-described solvent to obtain favorable effects in order to improve storage stability and particle dispersibility include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

  The density | concentration of binder resin is suitably selected according to the film thickness and production rate of an intermediate | middle layer.

  When the inorganic particles are dispersed, the mixing ratio of the inorganic particles to the binder resin at the time is preferably 20 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  As a means for dispersing the inorganic particles, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The method for drying the intermediate layer can be appropriately selected according to the type of solvent and the film thickness, but thermal drying is preferred.

  The thickness of the intermediate layer is preferably from 0.1 to 15 μm, more preferably from 0.3 to 10 μm.

<Photosensitive layer>
The photosensitive layer is not particularly limited, but a so-called laminated type photosensitive layer having a charge generation layer and a charge transport layer is preferable.

(Charge generation layer)
The charge generation layer preferably contains a charge generation material and a binder resin, and is formed by dispersing and coating the charge generation material in a binder resin solution.

  Examples of the charge generation material include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and phthalocyanine pigments. It is not something. These charge generating substances can be used alone or in a form dispersed in a known resin.

  As the binder resin of the charge generation layer, a known resin can be used, for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacryloyl resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, Polyurethane resins, phenol resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (eg, vinyl chloride-vinyl acetate copolymer resins, chlorides) Vinyl-vinyl acetate-maleic anhydride copolymer resin) and poly-vinylcarbazole resin, but are not limited thereto.

  The charge generation layer is formed by dispersing a charge generation material in a solution in which a binder resin is dissolved in a solvent using a disperser to prepare a coating solution, and applying the coating solution to a certain film thickness using a coating device. It is preferable to prepare the film by drying.

  Solvents for dissolving and coating the binder resin used in the charge generation layer include, for example, toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, Examples include butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine, but are not limited thereto.

  As a means for dispersing the charge generating material, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The mixing ratio of the charge generating material to the binder resin is preferably 1 to 600 parts by weight, more preferably 50 to 500 parts by weight based on 100 parts by weight of the binder resin. The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating. The pigment can also be formed by vacuum deposition.

(Charge transport layer)
The charge transport layer contains a charge transport material and a binder resin, and is formed by dissolving and coating the charge transport material in a binder resin solution.

  Examples of charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds Oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1- Two or more kinds of vinylpyrene and poly-9-vinylanthracene may be mixed and used.

  As the charge transport material (CTM), it is preferable to use a charge transport material having an atomic weight ratio of N atoms of less than 4.5%. As the basic structure of the charge transport material, a triphenylamine derivative, a styryl compound, a benzidine compound, a butadiene compound, and the like can be used, and among them, a styryl compound is preferable.

  A known resin can be used as the binder resin for the charge transport layer, and polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylic ester resin, and styrene-methacrylic acid. Examples include ester copolymer resins, and polycarbonate is preferred. Further, BPA, BPZ, dimethyl BPA, BPA-dimethyl BPA copolymer and the like are preferable in terms of crack resistance, wear resistance, and charging characteristics.

  The charge transport layer is preferably formed by dissolving the binder resin and the charge transport material to prepare a coating solution, applying the coating solution to a certain film thickness with a coating machine, and drying the coating film.

  Examples of the solvent for dissolving the binder resin and the charge transport material include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, and tetrahydrofuran. 1,4-dioxane, 1,3-dioxolane, pyridine, diethylamine, and the like, but are not limited thereto.

  The mixing ratio of the charge transport material to the binder resin is preferably 10 to 500 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the binder resin.

  The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  An antioxidant, an electronic conductive agent, a stabilizer and the like may be added to the charge transport layer. As the antioxidant, those described in JP-A No. 2000-305291 and the electronic conductive agent as described in JP-A Nos. 50-137543 and 58-76483 are preferable.

<Surface protective layer>
The surface protective layer is formed by applying a coating solution containing at least a member necessary for forming a resin having a crosslinked structure with inorganic fine particles (such as a curable compound and a polymerization catalyst) on the charge generation layer. Thereafter, the coating film can be formed by reacting the curable compound by irradiating the coating film with active rays.

  As the coating method, a known method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, and a slide hopper method can be used as in the case of the intermediate layer and the photosensitive layer. .

  The photoreceptor used in the present invention is polymerized by generating radicals by irradiating the coating film to be the surface protective layer by irradiating active rays, and is cured by forming a cross-linking bond between molecules and within the molecule, It is preferable to produce a resin having a crosslinked structure. As the active ray, ultraviolet rays and electron beams are particularly preferable.

As the ultraviolet light source, any light source that generates ultraviolet light can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, or the like can be used. Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 5 to 500 mJ / cm ² , preferably 5 to 100 mJ / cm ² . The power of the lamp is preferably 0.1 kW to 5 kW, particularly preferably 0.5 kW to 3 kW.

  As an electron beam source, there is no particular limitation on the electron beam irradiation apparatus, and generally, an electron beam accelerator for electron beam irradiation is a curtain beam type that is relatively inexpensive and can provide a large output. Used. The acceleration voltage during electron beam irradiation is preferably 100 to 300 kV. The absorbed dose is preferably 0.5 to 10 Mrad.

  The irradiation time for obtaining the necessary irradiation amount of active rays is preferably 0.1 second to 10 minutes, and more preferably 0.1 second to 5 minutes from the viewpoint of work efficiency.

  As the actinic radiation, ultraviolet rays are easy to use and are particularly preferable.

  In the present invention, drying can be performed before and after irradiation with active rays and during irradiation with active rays, and the timing of drying can be appropriately selected by combining them.

  Drying conditions can be appropriately selected depending on the type of solvent, film thickness, and the like. The drying temperature is preferably room temperature to 180 ° C, particularly preferably 80 to 140 ° C. The drying time is preferably 1 to 200 minutes, particularly preferably 5 to 100 minutes.

  The thickness of the surface protective layer is preferably 0.2 to 10 μm and more preferably 0.5 to 6 μm.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.

<Preparation of inorganic fine particles>
<Preparation of inorganic fine particles 1>
Tin oxide particles having a number average primary particle size of 30 nm were prepared as “inorganic fine particles 1”.

<Preparation of inorganic fine particles 2>
100 parts by mass of tin oxide particles having a number average primary particle size of 30 nm, 30 parts by mass of “Exemplary Compound S-17” and 1000 parts by mass of methyl ethyl ketone as a surface treatment agent are placed in a wet sand mill (alumina beads having a diameter of 0.5 mm), and 30 ° C. Then, methyl ethyl ketone and alumina beads were separated by filtration, and dried at 60 ° C. to prepare surface-treated tin oxide fine particles having reactive acryloyl groups, which were prepared as “inorganic fine particles 2”.

<Preparation of inorganic fine particles 3>
100 parts by mass of titanium oxide particles having a number average primary particle size of 35 nm, 30 parts by mass of “Exemplary Compound S-17” as a surface treatment agent, and 1000 parts by mass of methyl ethyl ketone are placed in a wet sand mill (alumina beads having a diameter of 0.5 mm), and 30 ° C. Then, methyl ethyl ketone and alumina beads were separated by filtration, dried at 60 ° C. to prepare surface-treated titanium oxide fine particles having reactive acryloyl groups, and this was prepared as “inorganic fine particles 3”.

<< Production of photoconductor >>
A photoreceptor was prepared as follows.

<Preparation of Photoreceptor 1>
(Conductive support)
The surface of a cylindrical aluminum support (length: 360 mm) having a diameter of 60 mm was cut to prepare a conductive support having a surface roughness Rz = 1.5 (μm).

(Middle layer)
A dispersion having the following composition was diluted twice with the same mixed solvent, and allowed to stand overnight, followed by filtration (filter; using a lime mesh 5 μm filter manufactured by Nippon Pole Co., Ltd.) to prepare an intermediate layer coating solution.

Composition Polyamide resin CM8000 (manufactured by Toray Industries, Inc.) 1 part by mass Titanium oxide SMT500SAS (manufactured by Teika) 3 parts by mass Methanol 10 parts by mass In addition, the dispersion is carried out for 10 hours in a batch manner using a sand mill as a disperser. Prepared.

  The said coating liquid was apply | coated by the dip coating method so that it might become a dry film thickness of 2.0 micrometers on the said support body, and the intermediate | middle layer was formed.

(Charge generation layer)
The following compositions were mixed and dispersed for 10 hours using a batch-type sand mill to prepare a charge generation layer coating solution. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.

Composition Charge generation material: titanyl phthalocyanine pigment (titanyl phthalocyanine pigment having a maximum diffraction peak at a position of at least 27.3 ° by Cu-Kα characteristic X-ray diffraction spectrum measurement) 20 parts by mass Polyvinyl butyral resin (# 6000-C: electricity 10 parts by mass t-butyl acetate 700 parts by mass 4-methoxy-4-methyl-2-pentanone 300 parts by mass (charge transport layer)
The following composition was mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer using a circular slide hopper coating machine and dried at 110 ° C. for 60 minutes to form a charge transport layer having a dry film thickness of 20 μm.

Composition Charge transport material (4,4′-dimethyl-4 ″-(β-phenylstyryl)
Triphenylamine) 225 parts by weight Binder: Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 300 parts by weight Antioxidant (Irganox 1010: manufactured by Ciba Geigy Japan) 6 parts by weight Tetrahydrofuran 1600 parts by weight Toluene 400 parts by weight Silicone oil (KF-54) : Shin-Etsu Chemical Co., Ltd.) 1 part by mass (surface protective layer)
The following compositions were mixed and dispersed for 10 hours using a batch type sand mill to prepare a surface protective layer coating solution. This coating solution was coated on the charge transport layer using a circular slide hopper coating machine. After coating, a metal halide lamp was used to irradiate ultraviolet rays for 1 minute to form a surface protective layer having a dry film thickness of 2.0 μm, and “Photoreceptor 1” was produced.

  The dry film thickness was measured using an eddy current type film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO).

Composition Inorganic fine particles (inorganic fine particles 2) 8 parts by mass Curable compound (Exemplary compound 1) 10 parts by mass Polymerization initiator (Exemplary compound 1-5) 10 parts by mass 1-propyl alcohol 40 parts by mass <Production of photoreceptors 2 to 4 >
“Photoconductors 2 to 4” were prepared in the same manner except that the inorganic fine particles used in the production of the photoconductor 1, the resin having a crosslinked structure, and the curing conditions were changed as shown in Table 1.

  However, the photoconductor 4 was subjected to a heat treatment at 120 ° C. for 60 minutes instead of the ultraviolet irradiation after coating the surface protective layer.

<Preparation of photoconductor 5> (for comparison)
The following surface protective layer was formed on the charge transport layer formed in the preparation of the photoreceptor 1 to prepare “Photoreceptor 5”.

(Surface protective layer)
The following composition was mixed and dissolved to prepare a surface protective layer coating solution. This coating solution was applied onto the charge transport layer formed in the preparation of the photoreceptor 1 using a circular slide hopper coating machine. After the application, a surface protective layer having a dry film thickness of 2.0 μm was formed by irradiating with an ultraviolet ray for 1 minute using a metal halide lamp.

Composition Curing Compound (Exemplary Compound 1) 10 parts by mass Polymerization initiator (Exemplary Compound 1-5) 10 parts by mass 1-propyl alcohol 40 parts by mass <Preparation of Photoreceptor 6> (for comparison)
The following surface protective layer was formed on the charge transport layer formed in the preparation of the photoreceptor 1 to prepare “Photoreceptor 6”.

(Surface protective layer)
The following components were mixed and dispersed for 10 hours using a batch-type sand mill to prepare a surface protective layer coating solution. This coating solution was applied onto the charge transport layer formed in the preparation of the photoreceptor 1 using a circular slide hopper coating machine. After coating, the film was dried at 100 ° C. to form a surface protective layer having a dry film thickness of 2.0 μm.

Composition Surface-treated tin oxide particles 8 parts by weight Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 20 parts by weight 1-propyl alcohol 40 parts by weight <Preparation of photoreceptor 7> (for comparison)
The surface protective layer formed in the production of the photoconductor 1 was not provided, and the one formed up to the charge transport layer was produced as “photoconductor 7”.

  Table 1 shows the inorganic fine particles, the resin having a crosslinked structure, and the curing conditions used in the production of the photoreceptors 1 to 7.

<Evaluation>
<Evaluation image forming apparatus>
As an image forming apparatus for evaluation, a commercially available image forming apparatus “bizhub PROC6500” (printing speed 65 sheets / 1 minute, A4 size lateral feed) (manufactured by Konica Minolta Business Technologies) (FIG. 1A: No. 1) FIG. 1 (B): the second charging means and the light neutralizing means are attached between the cleaning means and the first transmission means. A modified machine was prepared. The evaluation was performed for the following items by sequentially loading the photoconductors produced above into the modified machine, turning on and off the power of the second charging unit and the photostatic unit. In addition, the evaluation is ◎ and ○.

(Transfer memory)
For the evaluation of the transfer memory, using the above-mentioned modified machine, a chart having a 2 cm square solid image and a halftone image having a density of 0.4 was continuously printed with cyan toner, and the 1st and 5000th prints were printed. In addition, a transfer memory in which a history of a solid image of 2 cm square was seen in a cyan halftone image was visually determined.

◎: Transfer memory is not observed and good ○: Transfer memory is confirmed, but there is no problem in practical use ×: Transfer memory is confirmed to be practically problematic.

(Photoconductor durability)
The durability of the photoreceptor was evaluated by using the above-described modified machine, printing a solid image after printing 1 million sheets after the initial printing, and evaluating the density difference between the initial printing image and the printed image after completion of printing 1 million sheets. The density of the printed image was measured at random 12 points using a reflection densitometer “RD-918 (manufactured by Macbeth)”, and the average value was used as the image density.

Evaluation Criteria A: Good when the density difference between the initial printed image after printing 1 million sheets is 0.1 or less. O: The density difference between the initial printed image after printing 1 million sheets exceeds 0.1. No problem in practical use at 3 or less. X: The density difference between the initial printed image and the printed image after printing 1 million sheets exceeds 0.3, and there is a practical problem.

(Coating film wear)
The amount of coating film depletion on the photoreceptor was evaluated by the difference between the initial film thickness and the film thickness after printing 1 million sheets using the above-mentioned remodeling machine. Measure the film thickness of the photoconductor film at 10 locations at random (excluding at least 3 cm at both ends because the film thickness tends to be nonuniform at both ends of the photoconductor), and measure the average value. Let it be the film thickness of the body coating.

  The coating film depletion amount was measured using an eddy current type film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO). The coating film depletion amount is 0.10 or less.

  Table 2 shows the evaluation results.

  From Table 2, it can be seen that “Evaluation 4, 5, 7, 9, 10, 14”, which is an example, is excellent in evaluating transfer memory, durability of the photoconductor, and amount of wear of the coating film. On the other hand, “Evaluations 1 to 3, 6, 8, 11 to 13” as comparative examples are not excellent in all evaluation items, and it is understood that the object of the present invention has not been achieved.

DESCRIPTION OF SYMBOLS 1 1st charging means 2 Exposure means 3 Developing means 4 Transfer means 5 Second charging means 6 Photostatic means 7 Cleaning means 10 Photoconductor 20 Toner 30 Transfer material (transfer medium)

Claims (3)

First charging means for charging at least the surface of the photoreceptor;
Exposure means for irradiating the surface of the photoreceptor charged by the first charging means with light to form an electrostatic latent image;
Developing means for visualizing the electrostatic latent image with toner to form a toner image on a photoreceptor;
Transfer means for transferring the toner image on the photosensitive member to a transfer medium;
Electrophotographic image forming comprising: a second charging unit that applies a potential opposite to that of the first charging unit to the photosensitive member after the toner image is transferred to the transfer medium; and a cleaning unit that cleans residual toner on the photosensitive unit. A device,
The photoreceptor is formed by sequentially forming a photosensitive layer and a surface protective layer on a conductive support,
The electrophotographic image forming apparatus, wherein the surface protective layer contains at least a resin having an inorganic fine particle and a crosslinked structure. The electrophotographic image forming apparatus according to claim 1, wherein the inorganic fine particles have a reactive group on a surface thereof. 3. The electrophotographic image forming apparatus according to claim 1, wherein the electrophotographic image forming apparatus includes a light neutralizing unit between the second charging unit and the first charging unit.

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