JP4850033B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that performs an image forming operation using an electrophotographic process, and is applied to a copying machine, a facsimile, a laser printer, a direct digital plate making machine, and the like.

The electrophotographic photoreceptors used in electrophotographic apparatuses applied to copying machines, laser printers, etc. have been mainly used for inorganic photoreceptors such as selenium, zinc oxide, cadmium sulfide, and so on. Organic photoreceptors (OPC), which are more advantageous than inorganic photoreceptors from the viewpoint of reducing load, reducing costs, and increasing design freedom, are widely used.
This organophotoreceptor can be classified by layer structure. Single layer type, charge generation in which a charge generating material and a charge transporting material are contained in a single layer on a conductive support and formed with a binder resin. It is broadly classified into a laminated type constituted by laminating a charge generation layer mainly composed of a substance and a charge transport layer mainly composed of a charge transport material. In the case of a stacked type, there are a structure in which a charge transport layer is provided on a charge generation layer and a structure opposite to this structure. The former is generally used and the latter is particularly referred to as a reverse layer. However, the reverse layer type is not practically used because the charge generation layer usually provided as a thin layer is on the surface layer, and its durability due to wear is weak. On the other hand, the single-layer type requires less coating and film forming steps due to its layer structure, and is excellent in productivity. In addition, since the charge generating material is dispersed in the photosensitive layer, it is possible to generate charges from the vicinity of the surface layer, and there is little charge diffusion, which is advantageous for high resolution. In addition, there is little change in sensitivity due to wear.
It can be said that the photoconductor structure is suitable for obtaining a high-quality and stable image forming apparatus which is a major requirement as an image forming apparatus in recent years.
However, in an image forming apparatus that forms an image at a high density in order to achieve a high image quality using such a single layer photoconductor, there is a case in which image deterioration called “afterimage” is caused as a side effect in repeated use. However, in reality, a stable high-quality output image cannot be obtained over a long period of time as required at present.

Here, the afterimage phenomenon will be described.
In an electrophotographic apparatus for forming an image by an electrophotographic method, for example, if a halftone image is printed after the creation of a clear and dark image as shown in FIG. 7, the halftone image is not originally uniform and uniform. There are cases in which an image pattern printed before a halftone image appears in an image that does not become clear. This schematic diagram is shown in FIG. Such image deterioration is referred to as “positive afterimage” or “positive ghost”, and in particular, in a high-quality full-color electrophotographic apparatus, it is necessary to suppress this image deterioration. On the contrary, image degradation in which the image pattern printed before this is identified with a low density in the halftone image area is called “negative afterimage” or “negative ghost”, and this image degradation is similarly suppressed. There is a need to. This schematic diagram is shown in FIG.

There are several mechanisms for the afterimage phenomenon, and one of them is interpreted as being caused by fluctuations in the surface potential of the photoreceptor as described in, for example, Patent Document 1 (paragraph numbers: [0002] to [0006]). be able to. For this explanation, FIG. 10 schematically shows changes in the photoreceptor surface potential in each step after latent image formation, development, and transfer.
In this case, when the latent image shown in FIG. 10A is formed, the surface of the photosensitive member is uniformly charged to −700 V, and then the image information is exposed (the arrow indicates the exposed portion). The potential of the exposed portion is approximately 0V. Then, at the time of development in FIG. 10B, the toner is attached to the surface of the photoconductor and developed according to the potential difference between the development potential and the surface of the photoconductor. Next, at the time of transfer, the print paper side is charged positively to transfer the toner image from the photoconductor to the print paper. As shown in FIG. 10C, when a reverse bias is applied to the photosensitive member by the transfer unit, the surface potential of the photosensitive member after the transfer transitions in the positive direction as a whole, and the potential of the exposed portion exceeds 0V. Eventually, the polarity is reversed and becomes a positive potential (+10 V in the figure). Of course, the principle is the same because only positive and negative are switched even when the charging polarity is reversed.
If this phenomenon is repeated, even if the surface of the photoconductor is negatively charged uniformly before the image exposure by the charging means, the portion of the photoconductor surface that has become close to the positive side has a positive charge potential. It will be close. As a result, the portion that has shifted in the positive direction has a larger development potential difference than the other portions, so that apparent sensitization occurs and a dark toner image is formed. This portion is identified as a positive afterimage.

As shown in Patent Document 2 (paragraph number [0017]), an afterimage is obtained even in a method of processing the density of an image with or without dots (binary), such as a printing method widely used in an ink jet printer. Will occur. The beam spot for writing the dot shape has a slight illuminance distribution. For this reason, if the beam spot is irradiated to the part where the charging potential has shifted to the plus side, the contour of the dot that can be developed will be widened by the offset of the surface potential to the low potential side, resulting in an increase in the dot diameter. End up.
The dot image that has become unnecessarily large is felt dark when viewed as a whole image, and this is also an image in which a positive afterimage is identified. In this case, for example, the degree of afterimage is felt stronger as the image is output at a higher resolution of 1200 dpi than 600 dpi. Therefore, when the resolution of an electrophotographic apparatus that forms an image by an electrophotographic method is increased, the degree of seriousness of this problem Becomes larger.

  The cause of the fluctuation of the photoreceptor surface potential is understood to be mainly caused by the accumulation of space charges in the photosensitive layer as described in, for example, Patent Document 3 (paragraph numbers: [0011] to [0012]). Yes. Therefore, in order to eliminate the occurrence of the afterimage, a means for preventing the accumulation of space charge is required.

The prior art for afterimage prevention is described below.
[(1) Improvement of photoreceptor surface layer]
Patent Document 4 proposes that the surface layer of the photoreceptor contains a polyarylate resin and the dielectric constant is specified to be 2.3 or more. Since the mechanism for the effect is under investigation (described in paragraph [0038]), the description of the mechanism is omitted, but the effect has been confirmed by the examples.
As a proposal similar to this, Patent Document 5 proposes that the photosensitive layer contains an azo pigment and that the photoreceptor surface layer contains a polyarylate resin. According to this publication, the polyarylate resin has high crystallinity and is presumed to orient the charge transport material to some extent due to its properties. By combining the orientation and a specific charge generation material (azo pigment), the injection interface It is considered that the photo memory is reduced as a result (described in paragraph [0036]).
Patent Document 6 proposes that in an electrophotographic apparatus having an intermediate transfer member, a surface layer of an electrophotographic photosensitive member having a layered structure having a charge generation layer containing a phthalocyanine compound contains a bisphenol type polycarbonate. . Although the explanation of the mechanism for the effect is not found, the effect is confirmed by the examples. The effect seems to be due to the selected material.
In Patent Document 7, in an electrophotographic apparatus having an intermediate transfer member, a surface layer of an electrophotographic photosensitive member having a charge generation layer containing a phthalocyanine compound contains a charge transport material made of a polymer. Has been proposed. Although the explanation of the mechanism for the effect is not found, the effect is confirmed by the examples. The effect seems to be due to the selected material.
In Patent Document 8, in an electrophotographic apparatus having an intermediate transfer member, an electrophotographic photosensitive member having a charge generation layer containing a phthalocyanine compound has a semiconductive property including an insulating property and at least a resistance adjusting material. It has been proposed to provide any surface protective layer. Although the explanation of the mechanism for the effect is not found, the effect is confirmed by the examples. The effect seems to be due to the selected material.
Patent Document 9 proposes that injection of reverse polarity charges from the surface layer side can be prevented by using a copolymer polycarbonate of bisphenol A and a specific arylene group for the photoreceptor surface layer such as a charge transport layer. Yes.
Patent Document 10 proposes that the constituent material of the surface layer includes surface-treated metal oxide particles, an alcohol-soluble resin, and an alcohol-soluble charge transport material. In this publication, as the binder resin for the surface layer, the thermoplastic resin is not suitable because it has insufficient strength, and the solvent that dissolves the resin during coating is a solvent that easily dissolves the resin. It has been pointed out that a method of dissolving the photosensitive layer cannot be adopted because it must be used (described in paragraph [0009]). Although the explanation of the mechanism for the effect is unknown, it is interpreted from the description in the examples that the generation of an afterimage can be prevented by using an alcohol-soluble charge transport material as a combination of these materials.
Patent Document 11 proposes that an electrophotographic photosensitive member having a photosensitive layer and a protective layer contains at least one of an alkali metal element or an alkaline earth metal element in the protective layer. By containing these elements in the protective layer, it is interpreted as a means for imparting ionic conductivity and achieving both durability and accumulation elimination of residual potential. In this publication, it is pointed out that the residual potential can be lowered by including a charge transport material in the protective layer, but there is a problem that the wear amount due to durability increases (described in paragraph [0019]). .)

(2) Improvement of photosensitive layer In Patent Document 12, the charge transport material contained in the electrophotographic photoreceptor contains at least one selected from a chlorogallium phthalocyanine compound and a hydroxygallium phthalocyanine compound, and hydrazone is used as the charge transport material. It has been proposed to include at least one specific compound having a skeleton. This publication proposes that there is always a more preferable combination between the charge generation material that transfers charges and the charge transport material, and if these are preferable combinations, the transfer memory and the photo memory can be improved. Although it is difficult to predict the law of compatibility of these combinations at present, the above combinations are considered to be appropriate (described in paragraphs [0017] to [0021]).
Patent Document 13 proposes that an azo pigment is contained in a photosensitive layer in an electrophotographic apparatus that irradiates a photoreceptor with a short-wavelength semiconductor laser beam having a wavelength of 380 to 500 nm. Although no explanation of the mechanism for the effect can be found, the examples confirm that many of the azo pigments have a smaller photomemory than the α-type titanyl phthalocyanine.
In Patent Document 14, in an electrophotographic photoreceptor containing a charge generation material and a charge transport material, the charge transport material has a calculated value of polarizability by structure optimization calculation using semi-empirical molecular activation calculation using PM3 parameters. A compound having a wavelength greater than 70% and a calculated dipole moment smaller than 1.8D and a wavelength having a transmittance of 50% on the longer wavelength side than the wavelength at which the transmittance of the charge transport material is 50% It has been proposed to contain. It is considered that the latter compound improves the photomemory property because it absorbs extra light irradiated to the photoreceptor (described in paragraph [0071]).

(3) Improvement of charge transport layer In Patent Document 15, in the multilayer photoreceptor, the charge generation layer contains oxytitanium phthalocyanine, the charge transport layer contains two or more kinds of charge transport materials, and individual charge transport materials. It has been proposed to define the oxidation potential difference of 0.04V or less. Although the explanation of the mechanism for the effect is unclear, it is possible to smoothly hop the charge carriers between the charge transport materials by matching the energy level of the charge transport material, and to reduce the trapping of the charge transport material, thereby transferring the charge transport material. It is considered that afterimages are prevented because the absolute amount of electrons excited by reverse polarity charging by means is reduced (described in paragraphs [0021] to [0022]).
In Patent Document 16, in an electrophotographic photoreceptor to be mounted in a back-exposure type high-speed electrophotographic process (the time from the exposure unit to the development unit is about 10 to 150 msec), the charge mobility of the charge transport layer is expressed as the electric field strength 2. It has been proposed to specify 1 × 10 ⁻⁶ cm ² / V · sec or more under the condition of × 10 ⁶ V / cm. When the dynamic sensitivity of the photoreceptor is slow, latent image formation is not completed before development, and it has been pointed out that repeated use increases afterimages. The above measures ensure dynamic sensitivity characteristics and prevent afterimage formation. (Described in paragraphs [0010] and [0043] to [0044]).
In Patent Document 17, in an electrophotographic apparatus having an intermediate transfer member, a triphenylamine compound and N, N, N, N are formed in a charge transport layer of an electrophotographic photosensitive member having a stacked structure having a charge generation layer containing a phthalocyanine compound. It has been proposed to include a charge transport material selected from '-tetraphenylbenzidine compounds. Although the explanation of the mechanism for the effect is not found, the effect is confirmed by the examples. The effect seems to be due to the selected material.

(4) Improvement of charge generation layer In Patent Document 18, the thickness of the charge generation layer is increased to 0.25 μm or more, or the content of the charge generation material in the charge generation layer is increased to 50% by weight or more. There has been proposed a means for increasing the charge trapping of this layer and, as a result, making the ghost inconspicuous.
Patent Document 19 proposes that a triarylamine compound having a xylyl group is contained in a charge generation layer in an electrophotographic photoreceptor having a laminated structure. According to this publication, it is described that a carrier transport barrier is formed at the interface between the charge generation layer and the charge transport layer, and charge carriers are trapped therein. Since the trap carriers reduce the space electric field in the charge generation layer, the potential of the halftone image portion does not drop, and an afterimage occurs at this portion. Thus, by mixing a charge transport agent (triarylamine compound having a xylyl group) in the charge generation layer, the generated carriers are quickly injected into the charge transport agent and moved to the charge transport layer. As a result, it is said that accumulation of trapping carriers can be prevented and generation of afterimages is improved (described in paragraphs [0011] to [0012]).
In Patent Document 20, in an electrophotographic photosensitive member having at least a photosensitive layer and a surface protective layer in this order on a conductive support, a diffraction angle (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction as a charge generating substance in the photosensitive layer. ) Contain oxytitanium phthalocyanine having strong peaks at 9.5 °, 24.1 ° and 27.3 °. Although the explanation of the mechanism for the effect is not found, the effect is confirmed by the examples. The effect seems to be due to the selected material.
In Patent Document 21, the constituent material of the charge generation layer is composed of hydroxygallium phthalocyanine and the binder resin is composed of an acetalized portion, an acetyl group portion, and a hydroxyl portion, and has a butyralization degree of 62 mol% or more and a weight average molecular weight (Mw). ) Is 2.0 × 10 ⁵ or more and the number average molecular weight is 5.0 × 10 ⁴ or more. It is presumed that the amount of residual photocarriers in the photosensitive layer is reduced and the afterimage is improved by the effect of the butyral resin having the above specific composition (for example, the influence of the number of hydroxyl groups).

(5) Rules for Matching between Charge Generation Layer and Charge Transport Layer In Patent Document 22, for an electrophotographic photoreceptor having a laminated structure, the charge generation layer contains a specific azo pigment, and the charge transport layer has a fluorene skeleton. It has been proposed to contain a charge transport material. The explanation of the mechanism for the effect is not found, but the effect of suppressing light fatigue is confirmed by the examples. The effect seems to be due to the selected material.
In Patent Document 23, a negative-type photosensitive member having high gamma characteristics has a stacked structure in which a charge generation layer containing a phthalocyanine compound and a P-type charge transport layer are provided on a conductive support, and P-type charge transport is provided. It has been proposed to use a material selected from the group consisting of an inorganic P-type semiconductor, fine powder of t-Se, and a charge transporting polymer for the layer. In this publication, the P-type charge transport layer is characterized by not including hole transport molecules, thereby preventing the hole transport molecules from diffusing into the charge generation layer. Thus, it is explained that the suppression of traps and the reduction of afterimages by phthalocyanine pigments were achieved (described in paragraphs [0003] and [0012]).

(6) Improvement of undercoat layer Patent Document 24 proposes to provide an undercoat layer prepared using a silane coupling agent and an inorganic pigment as an electrophotographic photosensitive member. As a result, an afterimage is not generated as a result of smoothly flowing out charges to be discharged to the support (base) side (described in paragraph [0017]).
In Patent Document 25, a photoreceptor having an undercoat layer (intermediate layer) may contain a specific polyamic acid or polyamic acid ester structure, a polyimide structure resin having a specific structure, and a resin having a cyanoethyl group in the undercoat layer. Proposed. The explanation of the mechanism for the effect is not found, but the effect of suppressing light fatigue is confirmed by the examples. The effect seems to be due to the selected material.
In Patent Document 26, it is introduced that a crosslinkable resin having a small change in resistance value due to a change in external humidity has been used for the undercoat layer (intermediate layer) (described in paragraph [0004]). . In this publication, as a proposal for reducing afterimage generation, an example in which polycyclic quinone, perylene and the like are contained in the undercoat layer (Patent Document 27), an example using a metallocene compound, an electron-withdrawing compound, and a melamine resin (Patent Document 28). ), Examples using metal oxide fine particles and a silane coupling agent (Patent Document 21), examples using metal oxide fine particles surface-treated with a silane coupling agent (Patent Document 29), etc. It is shown.
In the case of a high-sensitivity type electrophotographic photoreceptor using oxytitanium phthalocyanine as a charge generation layer, the high sensitivity causes a large number of excited molecules and generated carriers, which causes charge separation in an electrophotographic process in which charging and exposure are repeated. It has been pointed out that non-excited species, electrons, holes and the like are likely to remain in the photoreceptor (described in paragraph [0010]). On the other hand, the publication proposes that the constituent material of the undercoat layer includes a polyamide resin and a zirconium compound, or a polyamide resin and a diketone compound such as zirconium alkoxide and acetylacetone. Similarly, Patent Document 30 proposes using a cellulose resin as the resin for the undercoat layer and containing a zirconium compound or zirconium alkoxide and a diketone compound.
In Patent Document 31, in an electrophotographic photosensitive member containing an undercoat layer, a charge generation material, and a charge transport material, the charge transport material is a polarizability obtained by structure optimization calculation using semi-empirical molecular activation calculation using PM3 parameters. A titanium oxide particle having a calculated value of greater than 70% and a calculated dipole moment of less than 1.8D, or a specific arylamine compound, and an undercoat layer coated with an organosilicon compound; It has been proposed to contain a polyamide having a diamine component having a specific structure as a constituent component. In this publication, it has been confirmed that the photo memory characteristics are improved by providing the undercoat layer, but this mechanism is considered to make it easier to escape the staying carriers in the photosensitive layer by providing the undercoat layer. (Described in paragraph [0075].)
In Patent Document 32, a multilayer photoreceptor having an undercoat layer (intermediate layer) is set such that the volume resistivity of the undercoat layer is set to 10 ¹⁰ to 10 ¹² Ωcm, the film thickness of the charge transport layer is set to 18 μm or less, and static elimination is performed. A method of omitting the means has been proposed. By eliminating the charge removal means (charge removal light), photo-fatigue of the photoconductor is prevented, and the resistance of the undercoat layer is regulated to control the charge injection from the support to the photoconductor, thereby accumulating space charge. (It is described in paragraph numbers [0005] and [0025] to [0029].)

(7) Compounding of additive In Patent Document 3, in an electrophotographic apparatus having an intermediate transfer body, at least a hindered phenol structure is formed on the surface layer of the electrophotographic photosensitive member having a charge generation layer containing a phthalocyanine compound. It has been proposed to contain units. Although the explanation of the mechanism for the effect is not found, the effect is confirmed by the examples. The effect seems to be due to the selected material.
Patent Document 33 proposes that a charge generation layer using a phthalocyanine pigment contains a dithiobenzyl compound. Although the explanation of the mechanism for the effect is omitted, the embodiment shows the improvement of the accumulation of the photo memory and the positive ghost.

(8) Device for electrophotographic process In Patent Document 34, it is proposed that a photoconductor is charged with a polarity opposite to that of normal charging (plus) and used under a certain condition. In the case of a photoreceptor having a highly sensitive charge transport layer, there are many photoinduced charge carriers generated by exposure. As the photo-induced charge carriers, the same number of electrons as holes injected into the charge transport layer are generated. However, if the electrons do not quickly escape to the support, electrons remain in the charge generation layer, thereby generating an afterimage. Therefore, by positively charging positively, electrons are injected from the support and an electron trap is held inside the charge generation layer. When the photosensitive member is exposed in this state, it is interpreted that the difference between the electron traps of the exposed portion and the non-exposed portion is small, and the ghost image becomes inconspicuous (described in paragraphs [0016] to [0022]). .
Patent Document 35 proposes means for applying a direct current in which an alternating current is superimposed on the support side of the photosensitive member. It is interpreted as a means that the electrons trapped in the charge generation layer are emitted by applying a reverse bias to the support side. It is described that the aim of superimposing alternating current is to increase the amount of current and promote the reverse charge bias effect (described in paragraphs [0019] to [0021]).
In Patent Document 36, an electrophotographic photosensitive member having a layered structure containing a charge generation layer containing a phthalocyanine compound is charged other than the main charge, then subjected to photostatic discharge, and the first charged electron. Image formation can be performed in a state where the space charge in the photoconductor is released and extinguished by performing main charging from the time when the portion of the photoconductor enters the position facing the main charging means. It has been proposed that afterimage formation at the initial stage of image formation can be suppressed (described in paragraphs [0012] and [0020]).
In Patent Document 37, a control unit that controls a transfer current from a transfer unit flowing into the photoconductor to a constant level is provided for an electrophotographic photoconductor having a stacked structure having a charge generation layer containing a phthalocyanine compound. Proposed. According to this publication, the occurrence of afterimages depends on the transfer current, and when the transfer current increases, negative afterimages appear strongly. This is because holes are injected into the non-exposed area (non-image area) of the photoreceptor during transfer, and the holes are trapped at the substrate-side interface of the charge generation layer or charge transport layer, and the next charge It is estimated that the dark decay increases (apparently sensitization) when released during the process, and a negative afterimage occurs. Therefore, if the transfer current value is controlled to be constant, the charge injected to the photoreceptor can be controlled to be constant, and as a result, the afterimage can be suppressed (described in paragraph [0012]).
Patent Document 38 proposes a means for defining a writing light wavelength or a neutralizing light wavelength from an action spectrum of a pre-charging optical memory ratio with respect to sensitivity.
In Patent Document 39, an electrophotographic photosensitive member having a layered structure containing a charge generation layer containing a phthalocyanine compound is exposed to light before transfer so that the charged potential of the non-exposed portion is reduced to 1/3 of that before the exposure. It has been proposed that the afterimage can be suppressed by making the above. Although the explanation of the mechanism for the effect is not described in detail, if the exposure is performed before the transfer, the gap difference between the exposed portion potential and the non-exposed portion potential becomes small, so that the afterimage cannot be identified. Seem.
In Patent Document 40, regarding an electrophotographic apparatus using an electrophotographic photosensitive member having a photosensitive layer and a protective layer containing a photocurable resin (acrylic resin), it is proposed to provide a humidity sensor near the surface of the electrophotographic photosensitive member. ing. The humidity sensor controls the current value of the AC component applied to the charging member. In this publication, there is a description related to a mechanism for reducing image blur and image blur due to the installation of a humidity sensor, but a description of the mechanism for effects relating to photomemory reduction is omitted. However, in the embodiment, it has been confirmed that the photo memory is reduced by installing the humidity sensor.
In Patent Document 41, as a measure for preventing the ghost image output of the S-shaped photoconductor, the half time of the photoconductor charging potential due to exposure calculated from the xerographic TOF method reaches from the exposure unit of the electrophotographic apparatus to the development unit. It has been proposed to define the time as 1/10 or less of the time (hereinafter, for the sake of simplicity, this may be referred to as “exposure-development time”).
Further, as described in the section of improving the undercoat layer, Patent Document 32 proposes a method for preventing light fatigue of the photosensitive member by omitting the charge removal means (charge removal light).
In Patent Document 2, the time T from charging to exposure, the charging potential on the surface of the photoconductor is VH, the dark decaying potential is V1 until 10T after charging, and after charging and image exposure, charging is performed again. It has been proposed to satisfy the relationship of | (V1−V2) / VH | <0.020, where V2 is the dark decay potential until 10T later. As an actual means, in the embodiment, it is shown that the dark decay time is shortened by increasing the process speed or the charging potential is reduced.
Regarding the prevention of afterimage generation, we tried to apply the above-mentioned prior art, but the results are not sufficient for application to electrophotographic photoreceptors and electrophotographic apparatuses that are highly durable, high-speed, and intended for high-quality prints. It was all over. In other words, the current state of the art is not yet solved by the conventional technology.

Japanese Patent Laid-Open No. 11-133825 JP 2002-123067 A JP-A-10-177261 JP-A-10-115946 JP-A-11-184135 Japanese Patent Laid-Open No. 10-177263 JP-A-10-177264 Japanese Patent Laid-Open No. 10-177269 JP 2000-147803 A JP 2001-235889 A JP 2002-6528 A JP 2000-75521 A JP 2000-105478 A JP 2001-305762 A Japanese Patent Application Laid-Open No. 7-92701 JP-A-8-152721 Japanese Patent Laid-Open No. 10-177262 JP-A-6-313972 JP-A-10-69104 JP-A-10-186696 JP 2002-107972 A JP 7-43920 A Japanese Patent Laid-Open No. 9-211876 JP-A-8-22136 JP-A-11-184127 JP 2000-112162 A Japanese Patent Application Laid-Open No. 8-14639 Japanese Patent Laid-Open No. 10-73942 JP 9-258469 A JP 2001-51438 A JP 2001-305763 A JP 2002-107983 A JP 2000-292946 A JP 7-13374 A JP 7-44065 A JP-A-10-123802 Japanese Patent Laid-Open No. 10-123855 JP 2000-231246 A JP-A-10-123856 Japanese Patent Laid-Open No. 10-246997 JP 2001-117244 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus excellent in durability and image quality stability that does not generate abnormal images, particularly afterimages, even when used repeatedly over a long period of time. It is to provide.

In order to achieve the above object, the present inventors have achieved a highly durable, high-quality image that does not cause abnormal images without impairing basic electrophotographic characteristics even when photoconductor wear occurs during repeated use over a long period of time. As a result of intensive studies on the forming device, the photosensitive member, a charging device that uniformly charges the surface of the photosensitive member, an image exposure device that forms an electrostatic latent image by performing image exposure after uniform charging, and the electrostatic device described above. A developing device for developing a latent image, a transfer device for applying a transfer bias having a polarity opposite to the charging polarity of the charging device for transferring the developed image to a transfer material, and a device for applying a bias having a polarity opposite to that of the transfer device And a static eliminator that neutralizes residual charges on the photoconductor, wherein the photoconductor is represented on a conductive substrate by at least a charge generating material, a hole transport material, and the following general formula (I): With electron transport materials An image forming apparatus comprising a control layer for controlling an output of a preliminary static eliminator configured to include a photosensitive layer including a single layer, and to apply a bias having a polarity opposite to that of the transfer device; The present inventors have found that an image forming apparatus capable of outputting a good image without generating an abnormal image such as an afterimage can be obtained even when the above-mentioned problems are solved and used repeatedly for a long period of time.

The electron transport material represented by the following general formula (I) used for the photoreceptor used in the present invention has excellent electron transport ability and is very stable against oxidizing gases such as ozone and NOx. High nature. In the electrophotographic system, ozone generation is unavoidable although there is some amount at the time of charging, so that it is a stable substance against such an oxidizing gas, in order to obtain a high-quality output image over a long period of time. It becomes very important.
Further, the photoconductor is slightly worn after repeated use over a long period of time. If the wear progresses significantly, the surface of the photoconductor cannot be charged to the desired charging potential by the charging device, and image formation becomes impossible. As the characteristics change, the image processing process conditions (charging conditions, development conditions, transfer conditions, static elimination conditions, etc.) optimized for the initial photoconductor film thickness deviate from appropriate conditions as wear progresses. It becomes a factor of abnormal images. In particular, afterimages may occur from a stage where wear does not proceed relatively, and it is understood that this is mainly caused by the accumulation of space charges in the photosensitive layer as described above due to repeated use. Therefore, control according to the wear of the photoreceptor is required.
In general, to eliminate afterimages, it is effective to equalize the potential difference between the exposed and unexposed areas on the surface of the photoreceptor by uniformly irradiating light before the charging step. The side effect that the electrical characteristics of the photoreceptor deteriorate due to repeated uniform light irradiation is caused.
In order to equalize the potential difference between the exposed portion and the non-exposed portion on the surface of the photoreceptor, it is necessary to irradiate a relatively strong light amount, but this causes a contradiction that this side effect becomes strong.
In order to prevent this, in order to ensure that neutralization is sufficiently performed by weak light irradiation, a preliminary neutralization device that applies a charge having a polarity opposite to the transfer bias applied by the transfer device at the stage prior to irradiation with the neutralization light. Becomes effective. By providing such a preliminary static eliminating device, it is very effective to remove the history due to the transfer bias. However, if the application by this apparatus is also optimized in accordance with the initial film thickness of the photoreceptor, it will deviate from the appropriate value as described above as the wear progresses. Therefore, output control according to the wear of the photoreceptor becomes effective.
Specifically, the film thickness of the photoconductor is sufficient in the initial state, and electrostatic fatigue does not occur. Therefore, the output of the device is small, and the output is increased during repeated use. It is what controls. The use state of the photoconductor is detected, sent to the control unit, and the output is changed from the control unit based on the information stored in the storage unit in advance (a conceptual diagram of this control is shown in FIG. 3). Show.)

As a means for detecting the usage state of the photoconductor, various means such as performing based on potential information from a surface potentiometer or the like can be used, but a method for detecting the rotation speed of the photoconductor is preferable. It is known that the wear amount of the photoconductor increases in proportion to the rotation speed of the photoconductor. When the rotation speed of the photoconductor and the wear amount of the photoconductor at the rotation speed are plotted, a linear relationship is shown. (FIG. 5).
Therefore, if a device for detecting the total number of revolutions of the photoconductor is provided in advance and the output is varied in accordance with the information on the number of revolutions, the control can be performed within an appropriate range according to the thickness of the photoconductor. In other words, the control means for controlling the output of the device that applies a bias having a polarity opposite to that of the transfer device performs control according to the number of rotations of the photoconductor, whereby a more stable image forming apparatus can be obtained (this control). Is shown in FIG. 4).

In addition, as a transfer device that applies a reverse polarity to the charging bias when transferring to a transfer material (mainly transfer paper), it is possible to transfer the whole surface with high adhesion by contact transfer and through a medium resistance roller that generates less ozone. A transfer roller system in which a voltage is directly applied to transfer paper to perform transfer is more preferable. Various methods such as a corona charger and a contact charger can be selected as a preliminary charge eliminating device that applies a bias having a polarity opposite to that of the transfer device. Among them, a corotron charger is more preferable, among which a mechanism is simple and the size can be reduced. Examples of the static eliminator include those commonly used. Among them, a light-emitting diode (LED) that consumes less power and has a long life is preferable. Among these, those having an emission wavelength of 600 nm or more are particularly preferable from the viewpoint of reducing light fatigue of the photoreceptor. In addition, by using phthalocyanine as the charge generating material used in the photosensitive layer, it has excellent sensitivity characteristics for light sources in a relatively long wavelength region such as a laser diode (LD) used in an exposure part that forms a latent image. Can be obtained. Phthalocyanine is known in many types due to the presence of its central metal and crystal structure, but by using titanyl phthalocyanine in particular, it has excellent responsiveness and stable potential characteristics even during repeated use. Image formation with little deterioration in image quality is possible even when used for a long time. In particular, among titanyl phthalocyanine, it has a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα (wavelength 1.542 mm). Furthermore, titanyl phthalocyanine has a CuKα ray (wavelength). As a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to 1.542 mm, it has a maximum diffraction peak at least 27.2 ° and is further dominant at 9.4 °, 9.6 °, and 24.0 °. And a peak at 7.3 ° as the lowest diffraction peak, and no peak between the 7.3 ° peak and the 9.4 ° peak. This makes it possible to form a more stable image.
Furthermore, it is possible to form a color image by arranging a plurality of these image forming apparatuses in parallel and forming an image of a single color toner (for example, cyan, magenta, yellow, etc.) in each image forming apparatus and then sequentially superimposing them. That is, as an image forming group called a so-called tandem system having a plurality of image forming apparatuses in one apparatus, one image forming apparatus capable of forming a different color toner image for each unit and obtaining a full color image in one cycle. It becomes possible.

That is, according to the present invention, the following image forming apparatus is provided.

(1) A photosensitive member, a charging device that uniformly charges the surface of the photosensitive member, an image exposure device that performs image exposure after uniform charging to form an electrostatic latent image, and develops the electrostatic latent image A developing device, a transfer device for applying a transfer bias having a polarity opposite to the charging polarity of the charging device to transfer the developed image to a transfer material, a preliminary charge eliminating device for applying a bias having a polarity opposite to that of the transfer device, An image forming apparatus comprising a static eliminator for neutralizing residual charges on a photoconductor, wherein the photoconductor has at least a charge generating material, a hole transport material, and an electron transport material represented by the following general formula (I) on a conductive substrate: And a control means for controlling the output of the preliminary static eliminator.

（式中、Ｒ１、Ｒ２は、それぞれ独立に水素原子、置換又は無置換のアルキル基、置換又は無置換のシクロアルキル基、置換又は無置換のアラルキル基からなる群より選ばれる基を表し、Ｒ３、Ｒ４、Ｒ５、Ｒ６、Ｒ７、Ｒ８、Ｒ９、Ｒ１０、Ｒ１１、Ｒ１２、Ｒ１３、Ｒ１４はそれぞれ独立に水素原子、ハロゲン原子、シアノ基、ニトロ基、アミノ基、水酸基、置換又は無置換のアルキル基、置換又は無置換のシクロアルキル基、置換又は無置換のアラルキル基からなる群より選ばれる基を表し、ｎは繰り返し単位であり、０から１００までの整数を表す。）
（２）前記転写装置と逆極性のバイアスを印加する装置の出力を制御する制御手段が前記感光体の回転数に応じて該逆極性のバイアスを印加する装置の出力制御をおこなうものであることを特徴とする前記第（１）項に記載の画像形成装置。
（３）前記転写装置が転写ローラ方式のものであることを特徴とする前記第（１）項または第（２）項に記載の画像形成装置。
（４）前記転写装置と逆極性のバイアスを印加する装置がコロトロン帯電器であることを特徴とする前記第（１）項乃至第（３）項の何れかに記載の画像形成装置。
（５）前記除電装置が発光ダイオードであることを特徴とする前記第（１）項乃至第（４）項の何れかに記載の画像形成装置。
（６）前記感光層に少なくとも電荷発生物質としてフタロシアニンを含有することを特徴とする前記第（１）項乃至第（５）項の何れかに記載の画像形成装置。
（７）前記フタロシアニンがチタニルフタロシアニンであることを特徴とする前記第（６）項に記載の画像形成装置。
（８）前記フタロシアニンがＣｕ−Ｋα線（波長１．５４２Å）に対するブラッグ角２θの回折ピーク（±０．２゜）として、少なくとも２７．２°に最大回折ピークを有し、更に９．４゜、９．６゜、２４．０゜に主要なピークを有し、かつ最も低角側の回折ピークとして７．３゜にピークを有し、７．３゜のピークと９．４゜のピークの間にピークを有さない結晶型を有するチタニルフタロシアニンであることを特徴とする前記第（７）項に記載の画像形成装置。
（９）前記第（１）項乃至第（８）項の何れかに記載の画像形成装置を複数並列に具備し、それぞれの画像形成装置において単色のトナー画像を順次重ね合わせてカラー画像を形成することを特徴とする画像形成装置。

Wherein R 1 and R 2 each independently represent a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, and R 3 , R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14 are each independently a hydrogen atom, halogen atom, cyano group, nitro group, amino group, hydroxyl group, substituted or unsubstituted alkyl group Represents a group selected from the group consisting of a substituted or unsubstituted cycloalkyl group and a substituted or unsubstituted aralkyl group, n is a repeating unit, and represents an integer of 0 to 100.)
(2) The control means for controlling the output of the device that applies a reverse polarity bias to the transfer device controls the output of the device that applies the reverse polarity bias according to the rotational speed of the photosensitive member. The image forming apparatus according to item (1), wherein:
(3) The image forming apparatus according to (1) or (2), wherein the transfer device is of a transfer roller type.
(4) The image forming apparatus according to any one of (1) to (3), wherein the apparatus for applying a bias having a reverse polarity to the transfer apparatus is a corotron charger.
(5) The image forming apparatus according to any one of (1) to (4), wherein the static eliminator is a light emitting diode.
(6) The image forming apparatus according to any one of (1) to (5), wherein the photosensitive layer contains at least phthalocyanine as a charge generating substance.
(7) The image forming apparatus as described in (6) above, wherein the phthalocyanine is titanyl phthalocyanine.
(8) The phthalocyanine has a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to Cu—Kα rays (wavelength 1.542 mm), and further 9.4 °. , 9.6 °, 24.0 °, and the lowest angle diffraction peak at 7.3 °, 7.3 ° and 9.4 ° The image forming apparatus as described in (7) above, wherein the image forming apparatus is titanyl phthalocyanine having a crystal type having no peak therebetween.
(9) A plurality of image forming apparatuses according to any one of (1) to (8) are provided in parallel, and color images are formed by sequentially superimposing single-color toner images in the respective image forming apparatuses. An image forming apparatus.

  As is apparent from the following detailed and specific description, the present invention is extremely excellent in that an image forming apparatus excellent in durability and image quality stability that does not cause abnormal images even when used repeatedly over a long period of time can be obtained. It is effective.

Next, the photoreceptor used in the image forming apparatus of the present invention will be described below.
In the photoreceptor used in the image forming apparatus of the present invention, as a conductive support, a conductor or an insulator subjected to a conductive treatment, for example, a metal such as Al, Fe, Cu, Au, or an alloy thereof, polyester, polycarbonate, A material in which a thin film of a metal such as Al, Ag, or Au or a conductive material such as In ₂ O ₃ or SnO ₂ is formed on an insulating substrate such as polyimide or glass, paper that has been subjected to conductive treatment, or the like can be used. The shape of the conductive support is not particularly limited, and either a drum shape or a belt shape can be used.

Next, the photosensitive layer of the photoreceptor used in the image forming apparatus of the present invention will be described.
The photosensitive layer in the present invention is of a single layer type and comprises a photosensitive layer comprising a single layer containing at least a charge generating material, a hole transporting material and an electron transporting material represented by the general formula (I) ( FIG. 6).

The electron transport material used in the present invention is represented by the aforementioned general formula (I). By incorporating the compound represented by the general formula (I) into the photosensitive layer, long-term electrostatic stability that is impossible with conventional electrophotographic apparatuses, that is, the difference between the charged potential and the exposed portion potential, As a result, it is possible to realize an electrophotographic apparatus that can improve the electrical durability that keeps the so-called electrostatic contrast stable, and can stably obtain a high-quality image even in repeated use over a long period of time.
In addition, the electron transport material represented by the general formula (I) is very stable against an active gas such as ozone or nitrogen oxide gas, and is used in an electrophotographic apparatus in which such an active gas is generated from a charger. It is very advantageous to use. This is considered to be resistant to the gas as described above because of its strong N-basic molecular structure. That is, it is possible to obtain an electrophotographic apparatus that is very excellent in terms of chemical durability in addition to the mechanical durability and electrical durability described above. Therefore, when designing various electrophotographic image forming apparatuses, it is possible to prevent an increase in size and cost, and it is possible to provide an image forming apparatus that is inexpensive and easy to install.

  In the formula of the compound represented by the general formula (I) used herein, R1 and R2 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, substituted or unsubstituted. R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, and R14 are each independently a hydrogen atom, a halogen atom, a cyano group, or a nitro group. Represents a group selected from the group consisting of a group, an amino group, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, n is a repeating unit, Represents an integer up to 100.

The substituted or unsubstituted alkyl group is an alkyl group having 1 to 25 carbon atoms, preferably 1 to 10 carbon atoms, specifically a methyl group, an ethyl group, an n-propyl group, an n- Linear groups such as butyl group, n-pentyl group, n-hexyl group, n-peptyl group, n-octyl group, n-nonyl group, n-decyl group, i-propyl group, s-butyl group, t -Branched group such as butyl group, methylpropyl group, dimethylpropyl group, ethylpropyl group, diethylpropyl group, methylbutyl group, dimethylbutyl group, methylpentyl group, dimethylpentyl group, methylhexyl group, dimethylhexyl group, alkoxy Alkyl group, monoalkylaminoalkyl group, dialkylaminoalkyl group, halogen-substituted alkyl group, alkylcarbonylalkyl group, Kishiarukiru group, alkanoyloxy group, an aminoalkyl group, esterified optionally alkyl group substituted with a carboxyl group which have an alkyl group substituted by a cyano group are exemplified. The substitution position of these substituents is not particularly limited, and a group in which a part of carbon atoms of the substituted or unsubstituted alkyl group is substituted with a hetero atom (N, O, S, etc.) is also substituted. Included in the alkyl group.
The substituted or unsubstituted cycloalkyl group includes a cycloalkyl ring having 3 to 25 carbon atoms, preferably 3 to 10 carbon atoms, specifically, a homocyclic ring from cyclopropane to cyclodecane, methylcyclo Those having an alkyl substituent such as pentane, dimethylcyclopentane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, tetramethylcyclohexane, ethylcyclohexane, diethylcyclohexane, t-butylcyclohexane, alkoxyalkyl groups, monoalkylaminoalkyl groups, dialkylamino Alkyl group, halogen-substituted alkyl group, alkoxycarbonylalkyl group, carboxyalkyl group, alkanoyloxyalkyl group, aminoalkyl group, halogen atom, amino group, esterified Which may be a carboxyl group, a cycloalkyl group substituted by a cyano group and the like. The substitution position of these substituents is not particularly limited, and a group in which a part of carbon atoms of the substituted or unsubstituted cycloalkyl group is substituted with a hetero atom (N, O, S, etc.) is also substituted. It is included in the cycloalkyl group.
Examples of the substituted or unsubstituted aralkyl group include groups in which an aromatic ring is substituted on the above-described substituted or unsubstituted alkyl group, and an aralkyl group having 6 to 14 carbon atoms is preferable. More specifically, benzyl group, perfluorophenylethyl group, 1-phenylethyl group, 2-phenylethyl group, terphenylethyl group, dimethylphenylethyl group, diethylphenylethyl group, t-butylphenylethyl group, 3- Examples thereof include a phenylpropyl group, a 4-phenylbutyl group, a 5-phenylpentyl group, a 6-phenylhexyl group, a benzhydryl group, and a trityl group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the method for producing the electron transport material represented by the general formula (I) can be exemplified by the following two synthesis methods.
(N is a repeating unit and represents an integer from 0 to 100.)

  Specific examples of the synthesis and production method of the starting material for producing the electron transport material represented by the general formula (I) include the following methods. That is, naphthalenecarboxylic acid is synthesized from the following reaction formula according to a known synthesis method (for example, US Pat. No. 6,794,102, Industrial Organic Pigments 2nd edition, VCH, 485 (1997)).

「式中、ＲｎはＲ３、Ｒ４、Ｒ５、Ｒ６を表し、ＲｍはＲ５、Ｒ６、Ｒ７、Ｒ８を表す。」

“In the formula, Rn represents R3, R4, R5, and R6, and Rm represents R5, R6, R7, and R8.”

  The electron transporting material represented by the general formula (I) used in the present invention is a method of reacting the above naphthalenecarboxylic acid or its anhydride with amines to monoimidize, or using a buffer solution for naphthalenecarboxylic acid or its anhydride. It is obtained by a method of adjusting pH and reacting with diamines. Monoimidization is carried out without solvent or in the presence of a solvent. The solvent is not particularly limited, but it does not react with raw materials or products such as benzene, toluene, xylene, chloronaphthalene, acetic acid, pyridine, methylpyridine, dimethylformamide, dimethylacetamide, dimethylethyleneurea, dimethylsulfoxide, and the like. It is good to use what can be made to react at the temperature of -250 degreeC. For pH adjustment, a buffer solution prepared by mixing a basic aqueous solution such as lithium hydroxide or potassium hydroxide with an acid such as phosphoric acid is used. Carboxylic acid derivative dehydration reaction obtained by reacting carboxylic acid with amines or diamines is carried out in the absence of a solvent or in the presence of a solvent. Although there is no restriction | limiting in particular as a solvent, It is good to use what reacts at the temperature of 50 to 250 degreeC, without reacting with raw materials and products, such as benzene, toluene, chloronaphthalene, bromonaphthalene, and acetic anhydride. Any reaction may be carried out without a catalyst or in the presence of a catalyst, and is not particularly limited. For example, molecular sieves, benzenesulfonic acid, p-toluenesulfonic acid and the like can be used as a dehydrating agent.

In the formula of the electron transport material represented by the general formula (I), it is a repeating unit and is an integer of 0 to 100. The repeating unit n is obtained from the weight average molecular weight (Mw). For example, the repeating unit n can be obtained by dividing the weight average molecular weight (Mw) in terms of standard polystyrene measured by GPC (gel permeation chromatography) by the molecular weight of the repeating unit. it can. In other words, this electron transport material exists in a state having a distribution in molecular weight. When n exceeds 100, the molecular weight of the electron transport material is increased and the solubility in various solvents is lowered. In particular, a dimer having n of 0 is preferable because of excellent compatibility and photoreceptor characteristics.
On the other hand, for example, when n is 1, it is a trimer of naphthalene carboxylic acid, but excellent electron transfer characteristics can be obtained even for oligomers by appropriately selecting substituents for R1 and R2. In this way, a wide range of naphthalenecarboxylic acid derivatives from oligomers to polymers are synthesized depending on the number of repeating units n.
In the range where the molecular weight of the oligomer region is small, monodispersed compounds can be obtained by stepwise synthesis. In the case of an electron transport material having a large molecular weight, a material having a distribution in molecular weight can be obtained.

More specifically, the electron transport material represented by the general formula (I) can be specifically exemplified as follows (however, in each of the formulas, the terminal groups Me at both ends represent methyl groups).

（ｎは、前記繰り返し単位）

(N is the repeating unit)

  In the electrophotographic characteristics, the electron transport materials represented by the above formulas (2) to (9) are particularly preferable from the viewpoints of the charging potential during repeated use and the stability of the exposed portion potential.

The content of the electron transport material represented by the general formula (I) is preferably 10 wt% to 70 wt%, more preferably 30 wt% to 60 wt%, based on the total solid content of the entire photosensitive layer. If the added amount is too large, problems such as a decrease in wear resistance, a decrease in electric potential resistance, and an increase in dark decay may appear. If the added amount is too small, sufficient electrostatic contrast cannot be obtained, or abnormal There may be a problem that the image suppression effect is not sufficiently exhibited.
In addition, as the electron transport material, known electron transport materials other than those represented by the general formula (I) can be used in combination. For example, chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7- Tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-trinitrodibenzothiophene-5 An electron-accepting substance such as 5-dioxide is used. These electron transport materials can be used alone or as a mixture of two or more.

  Further, in addition to the electron transport material, it is necessary to use a hole transport material that transports holes. Any known material can be used as the hole transporting substance, and in particular, an oxazole derivative, an oxadiazole derivative (described in JP-A Nos. 52-139065 and 52-139066), an imidazole derivative, and a triphenylamine derivative. (Described in Japanese Patent Application No. 1-77839), benzidine derivatives (described in Japanese Patent Publication No. 58-32372), α-phenylstilbene derivatives (described in Japanese Patent Application Laid-Open No. 57-73075), hydrazone derivatives (Japanese Patent Application Laid-Open No. 57-73075). No. 55-154955, No. 55-156554, No. 55-52063, No. 56-81850, etc.), triphenylmethane derivatives (described in JP-B No. 51-10983), anthracene derivatives ( JP-A 51-94829), styryl derivatives (JP-A 56-948) 9245 JP, described in JP 58-198043), described in JP-carbazole derivatives (JP-58-58552), pyrene derivatives (described in Japanese Patent Application No. 2-94812) is preferred.

In addition, a known material can be used as the charge generation material essential for the photoreceptor used in the present invention. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorenone skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Jigoido based pigments, and bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.
Among them, in particular, a titanyl phthalocyanine as shown in the following structural formula (1) having titanium as a central metal can make a photosensitive layer with particularly high sensitivity, and the electrophotographic apparatus can be further reduced in size and speed. It is possible to measure.

References relating to the synthesis method and electrophotographic properties of titanyl phthalocyanine include, for example, JP-A-57-148745, JP-A-59-36254, JP-A-59-44054, and JP-A-59-31965. JP, 61-239248, JP, 62-67094, A, etc. are mentioned. In addition, various crystal systems are known for titanyl phthalocyanine. JP-A 59-49544, JP-A 59-166959, JP-A 61-239248, JP-A 62-67094. JP-A-63-366, JP-A-63-116158, JP-A-64-17066, JP-A-2001-19871, etc. each describe a titanyl phthalocyanine having a different crystal form. .
Of these crystal forms, titanyl phthalocyanine having a maximum diffraction peak at 27.2 ° with a Bragg angle 2θ exhibits particularly excellent sensitivity characteristics and potential stability during repeated use, and does not increase the potential of the exposed area. Therefore, it is used well. In particular, it has a maximum diffraction peak at 27.2 ° described in JP-A-2001-19871, and further has main peaks at 9.4 °, 9.6 °, and 24.0 °, In addition, by using titanyl phthalocyanine having a peak at 7.3 ° as the diffraction peak on the lowest angle side and having no peak between the 7.3 ° peak and the 9.4 ° peak, Without losing sensitivity, it is possible to obtain a stable electrophotographic photosensitive member that does not cause a decrease in chargeability even when it is repeatedly used and does not cause an increase in potential of the exposed portion.
In addition, by using the titanyl phthalocyanine crystal having an average particle size of 0.60 μm or less, it is possible to obtain a stable electrophotographic photosensitive member that does not cause deterioration in chargeability even after repeated use without losing high sensitivity. The background dirt property can be remarkably improved.
This is because when the average particle size is larger than 0.60 μm, the contact area is lowered and the charge generation efficiency is lowered.

  As a binder resin (also referred to as a binder resin) used to form the above-mentioned substance as a photosensitive layer, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, Polyvinyl ketone, polystyrene, poly-N-vinyl carbazole, polyacrylamide and the like are used. These binder resins can be used singly or as a mixture of two or more. Among them, polycarbonate resins having excellent wear resistance are preferred in view of their properties.

Examples of the method for forming the photosensitive layer include a casting method from a solution dispersion system. In order to provide a photosensitive layer by the casting method, the above-described charge generating material is first dispersed by a ball mill, an attritor, a sand mill or the like using a binder resin and a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, or butanone as necessary. After appropriately diluting the dispersion, it is dissolved and coated with a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone, etc. together with an electron transport material, a hole transport material, a binder resin, etc. It is formed. The coating can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.
10-100 micrometers is suitable for the film thickness of the photosensitive layer provided as mentioned above, Preferably it is 10-35 micrometers.

The photoreceptor used in the image forming apparatus of the present invention can be provided with an intermediate layer (sometimes referred to as an undercoat layer) as appropriate between the conductive support and the photosensitive layer.
Although it is an intermediate layer that can be used, an intermediate layer is generally used that has a resin as a main component, but considering that these resins are coated with a photosensitive layer using a solvent, It is desirable that the resin is highly resistant to dissolution in general organic solvents. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, alkyd resin, melamine resin, and epoxy resin. And a curable resin that forms a three-dimensional network structure. In addition, metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide, etc., or fine powders such as metal sulfides and metal nitrides are added as fillers in the intermediate layer for further stability. The charged property can be maintained. These intermediate layers can be formed by using an appropriate solvent and a coating method, and the film thickness is 0.1 to 20, preferably 0.5 to 10 μm.

The electrophotographic photoreceptor of the present invention may be provided with a protective layer having a composition and composition ratio different from that of the photosensitive layer on the photosensitive layer for the purpose of protecting the photosensitive layer and improving printing durability. .
Materials used for the protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, Polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride And resins such as epoxy resins. In the protective layer, a material in which an inorganic material such as titanium oxide, tin oxide, potassium titanate, or alumina is dispersed can be added. As a method for forming the protective layer, a normal coating method is employed. The thickness of the protective layer is suitably about 0.1 to 20 μm, preferably about 1 to 7 μm.

Next, the image forming apparatus used in the present invention will be described with reference to the drawings. In any of the drawings, the photoconductor satisfies the requirements of the present invention.
FIG. 1 is a schematic diagram for explaining an example of an image forming element of an image forming apparatus according to the present invention, and modifications as described below also belong to the category of the present invention.
In FIG. 1, a photoreceptor (1) is a photoreceptor that satisfies the requirements of the present invention.
The photosensitive member (1) has a drum shape, but may be a sheet or an endless belt.
As the charging device (2), known means such as a corotron, a scorotron, a solid state charger (solid state charger), and a charging roller are used.
(3) represents an exposure apparatus, and a semiconductor laser (LD), a light emitting diode (LED), or the like can be used. In some cases, various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range. .
(4) is a developing device, and the toner (10) developed on the photoconductor by (4) is transferred to the image receiving medium (11).
As the transfer means (5), generally known ones can be used, but transfer can be performed by directly applying voltage to the transfer paper via a medium resistance roller that can transfer the entire surface with high adhesion by contact transfer and generates less ozone. A transfer roller system that performs the above is more preferable.
The toner (10) developed on the photoconductor by the developing device (4) is transferred to the image receiving medium (11), but not all is transferred, and some toner remains on the photoconductor. Such toner is removed from the photoreceptor by the cleaning device (7). As the cleaning means, a rubber cleaning blade, a brush such as a fur brush, a mag fur brush, or the like can be used.

(8) is a device for applying a bias having a polarity opposite to that of the transfer device. Various devices such as a corona charger and a contact charger can be selected as a device for applying a bias having a polarity opposite to that of the transfer device, but a corona charger is preferable because a charge can be imparted to the surface of the photoreceptor in a non-contact manner. Of these, a corotron charger that has a simple mechanism and can be miniaturized is more preferable. The application by a device that applies a bias having a polarity opposite to that of the transfer device is variable. This is because if it is optimized according to the initial film thickness of the photosensitive member, it will deviate from an appropriate value as described above as wear progresses. Therefore, output control according to the usage state of the photoconductor becomes effective. Specifically, the film thickness of the photoconductor is sufficient in the initial state, and electrostatic fatigue does not occur. Therefore, the output of the device is small, and the output is increased during repeated use. It is what controls. The use state of the photoconductor is detected, sent to the control unit, and the output is changed from the control unit based on the information stored in the storage unit in advance. As a means for detecting the usage state of the photoconductor, various means such as performing based on potential information from a surface potentiometer or the like can be used, but a method for detecting the rotation speed of the photoconductor is preferable. It is known that the wear amount of the photoconductor increases in proportion to the rotation speed of the photoconductor. When the rotation speed of the photoconductor and the wear amount of the photoconductor at the rotation speed are plotted, a linear relationship is shown. (FIG. 5). Therefore, if a device for detecting the total number of revolutions of the photoconductor is provided in advance and the output is varied in accordance with the information on the number of revolutions, the control can be performed within an appropriate range according to the thickness of the photoconductor. That is, it is possible to obtain a more stable image forming apparatus by controlling the output of the apparatus that applies a bias having a polarity opposite to that of the transfer apparatus according to the rotational speed of the photosensitive member.
Conceptual diagrams regarding such control are shown in FIGS.

(9) is a static elimination means. Examples of the light source include fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium lamps, light-emitting diodes (LEDs), semiconductor lasers (LDs), and electroluminescence (ELs). A light emitting diode (LED) having a small and long life is preferable. Among these, those having an emission wavelength of 600 nm or more are particularly preferable from the viewpoint of reducing light fatigue of the photoreceptor.
When the electrophotographic photosensitive member is positively (negatively) charged and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member. If this is developed with toner of negative (positive) polarity (electrodetection fine particles), a positive image can be obtained, and if developed with toner of positive (negative) polarity, a negative image can be obtained. A known method is applied to such developing means, and a known toner is used.

In the present invention, a plurality of image forming elements as shown in FIG. 1 may be provided, and in such a case, a plurality of these image forming elements are arranged horizontally or obliquely to be used (FIG. 2).
FIG. 2 shows an example of the entire image forming apparatus supporting full color according to the present invention. This image forming apparatus is a type using four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) as toner, and an image forming unit is provided for each color. A photoconductor (1Y, 1M, 1C, 1Bk) for each color is provided. The photoreceptors (1Y, 1M, 1C, 1Bk) for each color used in this image forming apparatus are electrophotographic photoreceptors that satisfy the requirements of the present invention. Around each photosensitive member (1Y, 1M, 1C, 1Bk), similarly to the image forming apparatus of FIG. 1, the charging device (2Y, 2M, 2C, 2Bk), the exposure device (3Y, 3M, 3C, 3Bk), developing device (4Y, 4M, 4C, 4Bk), transfer device (5Y, 5M, 5C, 5Bk), cleaning device (7Y, 7M, 7C, 7Bk), device for applying a bias of reverse polarity to the transfer device (8Y, 8M, 8C, 8Bk) and a static eliminator (9Y, 9M, 9C, 9Bk) are provided.
Note that the fixing device (6) in FIG. 2 is disposed at the last position of the receiving medium (11) in order to fix the toner images of the respective colors formed on the four image forming devices at once.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not restrict | limited by an Example. All parts are parts by weight.
First, a photoreceptor for use in each example was prepared as follows.

<Preparation of Photoconductor for Reference Example 1>
(Photosensitive layer coating solution)
A photosensitive layer coating solution was prepared by the following procedure.
27 parts by weight of X-type metal-free phthalocyanine (Fastogen Blue 8120BS: manufactured by Dainippon Ink & Chemicals, Inc.) as a charge generating substance was dispersed together with 1015 weight of cyclohexane non in a ball mill apparatus for 120 minutes to obtain a charge generating substance dispersion.
Separately, 340 parts by weight of tetrahydrofuran, 48 parts by weight of a polycarbonate resin (Z-type polycarbonate, viscosity average molecular weight: 50000, manufactured by Teijin Chemicals Ltd.), an electron transport material 27 of the formula (2) synthesized by the method described above Part by weight, 34 parts by weight of the charge transport material represented by the following structural formula (A), and 0.1 part by weight of silicone oil (KF50-100CS manufactured by Shin-Etsu Chemical Co., Ltd.) are dissolved, and the charge generation material dispersion described above is dissolved in this. 57.6 parts by weight of the solution was added and stirred to obtain a photosensitive layer coating solution.

次いで、φ１００ｍｍ、長さ３６０ｍｍのアルミニウムドラム上に、上記感光層用塗工液を浸漬塗工法にて塗工速度を調節することにより２９μｍの感光層を形成し１２０℃において１５分乾燥し、参考例１用感光体を作製した。

Then, 100 mm in diameter, on the aluminum drum length 360 mm, dried for 15 minutes in the formation to 120 ° C. The light-sensitive layer of 29μm by adjusting the coating speed of the photosensitive layer coating solution by a dip coating method, reference A photoreceptor for Example 1 was prepared.

<Preparation of Photoconductor for Reference Example 2>
In the photoreceptor for Reference Example 1, in place of X-type metal-free phthalocyanine which is a charge generating material used in the photosensitive layer coating solution, it was synthesized by Synthesis Example 2 described in JP-B-7-97221. A photoconductor for reference example 2 was produced in the same manner as the photoconductor for reference example 1 except that

<Preparation of Photoconductor for Example 1 >
Reference Example 1 except that the titanyl phthalocyanine pigment produced according to the method of Synthesis Example 1 shown below was used in place of the metal-free phthalocyanine pigment which is the charge generation material used in the photosensitive layer coating solution in the photoreceptor for Reference Example 1. A photoconductor for Example 1 was produced in the same manner as the photoconductor.
(Synthesis Example 1 of titanyl phthalocyanine used in the photosensitive member for Example 1)
A pigment was prepared according to Japanese Patent Application Laid-Open No. 2001-19871. That is, 29.2 g of 1,3-diiminoisoindoline and 200 ml of sulfolane are mixed, and 20.4 g of titanium tetrabutoxide is added dropwise under a nitrogen stream. After completion of the dropwise addition, the temperature was gradually raised to 180 ° C., and the reaction was carried out by stirring for 5 hours while maintaining the reaction temperature between 170 ° C. and 180 ° C. After completion of the reaction, the mixture was allowed to cool and then the precipitate was filtered, washed with chloroform until the powder turned blue, then washed several times with methanol, further washed several times with hot water at 80 ° C. and dried, Crude titanyl phthalocyanine was obtained. Dissolve the crude titanyl phthalocyanine in 20 times the amount of concentrated sulfuric acid, add dropwise to 100 times the amount of ice water with stirring, filter the precipitated crystals, and then repeat washing with water until the washing solution becomes neutral (ion-exchanged water after washing). PH value was 6.8), and a titanyl phthalocyanine pigment wet cake (water paste) was obtained. 40 g of the obtained wet cake (water paste) was put into 200 g of tetrahydrofuran, stirred for 4 hours, filtered and dried to obtain titanyl phthalocyanine powder. This is designated as Pigment 1.
The solid content concentration of the wet cake was 15 wt%. The weight ratio of the crystal conversion solvent to the wet cake is 33 times.
The obtained titanyl phthalocyanine powder was subjected to X-ray diffraction spectrum measurement under the following conditions. As a result, the Bragg angle 2θ with respect to the characteristic X-ray of Cu—Kα (wavelength: 1.542 mm) was 27.2 ± 0.2 ° with the maximum peak. Has a peak at the lowest angle of 7.3 ± 0.2 °, no peak between 7.3 ° peak and 9.4 ° peak, and no peak at 26.3 ° A titanyl phthalocyanine powder was obtained. The result of the X-ray diffraction is shown in FIG.
(X-ray diffraction spectrum measurement conditions)
X-ray tube: Cu
Voltage: 50kV
Current: 30mA
Scanning speed: 2 ° / min Scanning range: 3 ° -40 °
Time constant: 2 seconds The average particle size in the charge generation layer coating solution using titanyl phthalocyanine was measured with CAPA-700 manufactured by Horiba, Ltd. and found to be 0.31 μm.

<Preparation of Photoconductor for Example 2 >
In the photoreceptor for Example 1, the photosensitive layer represented instead of the electron transporting material in the coating liquid using equation (2), except for using the electron transporting material represented by the formula (3) Example 1 In the same manner as the photoconductor for Example 2 , a photoconductor for Example 2 was produced.

<Preparation of Photoconductor for Example 3 >
In the photoreceptor for Example 1, the photosensitive layer represented instead of the electron transporting material in the coating liquid using equation (2), except for using the electron transporting material represented by the formula (4) Example 1 In the same manner as the photoconductor for Example 3 , a photoconductor for Example 3 was produced.

<Preparation of Photoconductor for Example 4 >
Example 1 except that the electron transport material represented by formula (5) was used in place of the electron transport material represented by formula (2) used in the photosensitive layer coating solution in the photoreceptor for Example 1. In the same manner as the photoconductor for Example 4 , a photoconductor for Example 4 was produced.

<Preparation of Photoconductor for Example 5 >
Example 1 except that the electron transport material represented by formula (6) was used instead of the electron transport material represented by formula (2) used in the photosensitive layer coating solution in the photoreceptor for Example 3. In the same manner as the photoconductor for Example 5 , a photoconductor for Example 5 was produced.

<Preparation of Photoconductor for Example 6 >
Example 1 except that the electron transport material represented by formula (7) was used in place of the electron transport material represented by formula (2) used in the photosensitive layer coating solution in the photoreceptor for Example 1. In the same manner as the photoconductor for Example 6 , a photoconductor for Example 6 was produced.

<Preparation of Photoconductor for Example 7 >
In the photoreceptor for Example 1, the photosensitive layer represented instead of the electron transporting material in the coating liquid using equation (2), except for using the electron transporting material represented by the formula (8) Example 1 A photoconductor for Example 7 was produced in the same manner as the photoconductor for photopolymer.

<Preparation of Photoconductor for Example 8 >
Example 1 except that the electron transport material represented by the formula (9) was used in place of the electron transport material represented by the formula (2) used in the photosensitive layer coating solution in the photoreceptor for Example 1. In the same manner as the photoconductor for Example, a photoconductor for Example 8 was produced.

<Preparation of Photoconductor for Comparative Example 1>
In the photoreceptor for Example 1 , instead of the charge transport material represented by the formula (2) used in the charge transport layer coating solution, a charge transport material represented by the following structural formula (C) was used. in the same manner as the photoreceptor for example 1, to manufacture a photoconductor for Comparative example 1.

<Preparation of Photoconductor for Comparative Example 2>
In the photoreceptor for Example 1 , instead of the charge transport material represented by the formula (2) used in the charge transport layer coating solution, a charge transport material represented by the following structural formula (D) was used. A photoconductor for Comparative Example 2 was produced in the same manner as the photoconductor for Example 1 .

<Preparation of Photoconductor for Comparative Example 3>
In the photoreceptor for Example 1 , instead of the charge transport material represented by the formula (2) used in the charge transport layer coating solution, a charge transport material represented by the following structural formula (E) was used. A photoconductor for Comparative Example 3 was produced in the same manner as the photoconductor for Example 1 .

[ Reference Examples 1 and 2, Examples 1 to 8 and Comparative Examples 1 to 3]
After the photoconductors for Reference Examples 1 and 2, the photoconductors for Examples 1 to 8 and the photoconductor for Comparative Examples 1 to 3 thus produced were used for mounting, the digital multifunction machine Imagio MF7070 [Rico Co., Ltd.] -Made] image, with a corotron charger that applies a bias of reverse polarity to the transfer device before irradiation with static elimination light (using a 660 nm LED), and a power pack that has been modified to change the toner polarity to positive charge Attached to the forming apparatus. The corotron charger is equipped with a control device that varies the output in accordance with the rotation speed information based on information from a device that detects the total rotation speed of the photoconductor. Control the output of the charger.
Using such an image forming apparatus, A4 size (horizontal) test charts having an image area ratio of 6% were continuously printed (printed) up to 250,000 sheets.
The following items were evaluated at the initial stage (at the start of printing), after printing 50,000 sheets, and after printing 250,000 sheets.

<Photoconductor exposure area potential>
Evaluation was made on the exposed portion potential in the developing portion when writing the entire black solid image when the surface potential (charging potential) of the photosensitive member at the time of printing 250,000 copies was set to +800 V after printing 50,000 copies at the initial stage.
<Afterimage evaluation>
Regarding the presence or absence of afterimages for images output after printing at the initial stage, after printing 50,000 sheets, and after printing 250,000 sheets
Evaluation items such as image quality other than afterimages for images output after printing 50,000 sheets at the initial stage and after printing 250,000 sheets, for example, changes in image density of solid black parts, presence or absence of blurring of characters, presence or absence of image flow, etc. In addition to the above, it was evaluated comprehensively from all aspects including afterimages.

[Comparative Example 4]
In Example 1 , the same evaluation as in Example 1 was performed except that a corotron charger for applying a bias having a polarity opposite to that of the transfer device was not applied before the neutralizing light irradiation, and Comparative Example 4 was obtained.

[Comparative Example 5]
In Reference Example 1, the corotron charger that applies a reverse polarity bias to the transfer device provided before the neutralizing light irradiation does not have a variable control mechanism and applies a reverse polarity bias to the transfer device with a constant output from the beginning. Except for the above, the same evaluation as in Example 1 was performed to obtain Comparative Example 5.

  These evaluation results are shown in Table 1.

[Production of Photosensitive Materials for Reference Examples 3 and 4 and Examples 9 to 16 and Photoconductors for Comparative Examples 6 to 8]
A photoconductor for Reference Example 3 was prepared in the same manner as Reference Example 1 except that a photosensitive layer was provided on an aluminum drum having a diameter of 30 mm and a length of 256 mm when the photoconductor for Reference Example 1 was prepared.
Similarly to the photoconductors for Reference Example 2, Examples 1 to 8 , and Comparative Examples 1 to 3, except that a photosensitive layer was provided on an aluminum drum having a diameter of 30 mm and a length of 256 mm, for Reference Example 2 , examples 1 to photoreceptor and Similarly respectively for example 4 for 8, for examples 9-16, and a photoreceptor for Comparative example 6-8. In addition, photosensitive members for Comparative Examples 9 and 10 as described below were prepared.
After the electrophotographic photoreceptors for Reference Examples 3 and 4 thus prepared , Examples 9 to 16 and Comparative Examples 6 to 10 were used for mounting, the IPCIO CX400 [Full Color Printer having a tandem mechanism] Rico Co., Ltd.] as a base, a corotron charger that applies a bias of reverse polarity to the transfer device before irradiation with static elimination light (using a 660 nm LED) was added, and the power pack was remodeled to correct the toner polarity. The image forming apparatus was changed to charging and mounted. The corotron charger is equipped with a control device that varies the output in accordance with the rotation speed information based on information from a device that detects the total rotation speed of the photoconductor. Control the output of the charger.
Using such an image forming apparatus, up to 50,000 sheets of A4 size (vertical) test charts in which the image area ratio is 5% for each of black, cyan, magenta, and yellow are printed (printed). did.
The following items were evaluated at the initial stage (at the start of printing), after printing 10,000 sheets, and after printing 50,000 sheets.

<Photoconductor exposure area potential>
Evaluation was made on the exposed portion potential at the developing portion when writing the entire solid black image when the photoreceptor surface potential (charged potential) was +550 V at the initial stage, after printing 10,000 sheets, and after printing 50,000 sheets.
<Afterimage evaluation>
The image output after the initial printing, after printing 10,000 sheets, and after printing 50,000 sheets was evaluated for the occurrence of afterimages.
<Comprehensive evaluation of image quality>
Evaluation items such as image quality other than afterimages for images output after initial printing and after printing 50,000 sheets, for example, changes in image density of solid black parts, presence or absence of blurring of characters, presence or absence of image flow, etc. In addition to the above, it was evaluated comprehensively from all aspects including afterimages.

[Comparative Example 9]
In Example 9 , the same evaluation as in Example 9 was performed except that a corotron charger for applying a bias having a polarity opposite to that of the transfer device was not applied before the neutralizing light irradiation, and Comparative Example 9 was obtained.

[Comparative Example 10]
In the ninth embodiment, the corotron charger that applies a reverse polarity bias to the transfer device provided before the neutralizing light irradiation does not have a variable control mechanism, and applies a reverse polarity bias to the transfer device with a constant output from the beginning. Except for the above, the same evaluation as in Example 9 was performed to obtain Comparative Example 10.

  These evaluation results are shown in Table 2.

  As described above, according to the present invention, it is possible to obtain an image forming apparatus excellent in durability and image quality stability in which abnormal images are not generated even during repeated use over a long period of time.

1 is a schematic cross-sectional view illustrating an example of an image forming apparatus according to the present invention. It is a schematic cross section which shows another example of the image forming apparatus which concerns on this invention. FIG. 5 is a diagram illustrating a control example of an apparatus that applies a bias having a reverse polarity to the transfer apparatus of the image forming apparatus according to the present invention. It is a figure which shows another example of control of the apparatus which applies the bias of reverse polarity with the transfer apparatus of the image forming apparatus which concerns on this invention. It is a figure which shows the general correlation of a photoreceptor speed and photoreceptor wear amount. FIG. 2 is a diagram illustrating a layer configuration of a photoreceptor of the image forming apparatus according to the present invention. It is a figure which shows an example of the image pattern in the past. It is a schematic diagram which shows the example of the conventional positive afterimage. It is a schematic diagram which shows the example of the conventional negative afterimage. It is a figure explaining the electric potential state of the photoreceptor surface potential at the time of each process of the conventional electrophotographic apparatus. It is a figure which shows the result of the X-ray diffraction of the titanyl phthalocyanine used for the photoreceptor for Example 3. FIG.

Explanation of symbols

1, 1Y, 1M, 1C, 1Bk ... photosensitive member 2, 2Y, 2M, 2C, 2Bk ... charging device 3, 3Y, 3M, 3C, 3Bk ... exposure device 4, 4Y, 4M, 4C, 4Bk: Development device 5, 5Y, 5M, 5C, 5Bk ... Transfer device 6 ... Fixing device 7, 7Y, 7M, 7C, 7Bk ... Cleaning device 8, 8Y, 8M, 8C, 8Bk ..Apparatus for applying a bias of reverse polarity to the transfer device 9, 9Y, 9M, 9C, 9Bk ... Static eliminating device 10, 10Y, 10M, 10C, 10Bk ... Toner 11 ... Image receiving medium

Claims (4)

A photoconductor, a charging device that uniformly charges the surface of the photoconductor, an image exposure device that forms an electrostatic latent image by performing image exposure after uniform charging, and a developing device that develops the electrostatic latent image A transfer device that applies a transfer bias having a polarity opposite to the charging polarity of the charging device in order to transfer the developed image onto a transfer material, a preliminary static elimination device that applies a bias having a polarity opposite to that of the transfer device, and the preliminary slow charge In an image forming apparatus comprising a control means for controlling the output of the apparatus and a static eliminator for neutralizing residual charges on the photoconductor, the photoconductor has at least a charge generating material, a hole transport material, and A photosensitive layer comprising a single layer containing an electron transporting material represented by formula (I), wherein the charge generating material has a Bragg angle 2θ diffraction peak with respect to Cu—Kα rays (wavelength 1.542Å) ( Less than ± 0.2 °) Has a maximum diffraction peak at 27.2 °, and further has major peaks at 9.4 °, 9.6 °, and 24.0 °, and the diffraction peak at the lowest angle is 7.3 °. A titanyl phthalocyanine having a crystal form having a peak and having no peak between a peak at 7.3 ° and a peak at 9.4 °, the preliminary static eliminator is a corotron charger, and the preliminary static eliminator image forming apparatus control means for controlling the output of characterized der Rukoto performs control to output to a bias of the reverse polarity in accordance with the rotational speed of the photosensitive member.

Wherein R 1 and R 2 each independently represent a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, and R 3 , R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14 are each independently a hydrogen atom, halogen atom, cyano group, nitro group, amino group, hydroxyl group, substituted or unsubstituted alkyl group Represents a group selected from the group consisting of a substituted or unsubstituted cycloalkyl group and a substituted or unsubstituted aralkyl group, n is a repeating unit, and represents an integer of 0 to 100.) The image forming apparatus according to claim 1 , wherein the transfer device is of a transfer roller type. The image forming apparatus according to claim 1 or 2, wherein the discharging device is a light emitting diode. The image forming apparatus according to any one of claims 1 to 3, the photosensitive member, a charging device, an image exposing device, a developing device, a transfer device, the unit comprising a pre-discharging device and discharging device in parallel a plurality, in each unit An image forming apparatus that forms a color image by sequentially superimposing monochromatic toner images.

Images