JP2007047564A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which rise of residual potential in repetitive use of an electrostatic latent image carrier is suppressed, and by which high-definition image formation is made possible with high durability, and an image forming method. <P>SOLUTION: The image forming apparatus comprises: the electrostatic latent image carrier having on a support a photosensitive layer composed of a charge generating layer containing at least one naphthalenetetracarboxylic acid diimidazole pigment represented by a specific formula and a charge transport layer; an electrostatic latent image forming means; a developing means; a transfer means; a fixing means; and a charge eliminating means for photo-eliminating residual charges on the electrostatic latent image carrier (a light source which illuminates light having a shorter wavelength than 500 nm: a charge eliminating lamp (2)). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly, to a static layer having a photosensitive layer composed of a charge generation layer containing a naphthalene tetracarboxylic acid diimidazole pigment represented by a specific chemical formula and a charge transport layer. The present invention relates to an image forming apparatus including at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, a transfer unit, a fixing unit, and a charge eliminating unit that emits light having a wavelength shorter than 500 nm, and an image forming method using the image forming apparatus. . Hereinafter, the electrostatic latent image carrier may be referred to as an “electrophotographic photosensitive member”, a “photosensitive member”, or a “photoconductive insulator”.

  In recent years, there has been a remarkable development of information processing system machines using electrophotography. In particular, an optical printer that converts information into a digital signal and records information by light is markedly improved in print quality and reliability. This digital recording technique is applied not only to printers but also to ordinary copying machines, and so-called digital copying machines have been developed. In addition, since a variety of information processing functions are added to a conventional copying machine equipped with this digital recording technology for analog copying, the demand is expected to increase in the future. Furthermore, with the spread of personal computers and the improvement in performance, the progress of digital color printers for performing color output of images and documents is rapidly progressing.

  Most of such digital image forming apparatuses employ negative / positive development. This is because most of the images (originals) output by the conventional image forming apparatus are centered on characters, and the writing rate is low with respect to the output image (paper) and is about 5 to 10%. caused by.

  It can be said that the conversion from analog to digital has shifted from positive / positive development to negative / positive development. A major difference in this conversion is that the entire surface of the document is irradiated with light and the photosensitive member is irradiated with light so that only necessary information such as characters is written on the photosensitive member. It is done. That is, in the case of digital, since the writing rate is low for the output image as described above, only the document information portion (about 10% or less of the whole) is used in consideration of the life of the writing light source. Then, the fact that the output time of the light source is 1/10 is used.

  In an image forming apparatus using negative / positive development, a portion not written by a writing light source (non-image portion, background portion) is an electrostatic latent image carrier (hereinafter referred to as “electrophotographic photosensitive member”) after development and transfer. The surface charge of the “body”, “photosensitive body”, and “photoconductive insulator” may remain, which may affect the next charging, and the charge removal is performed. For static elimination, light is used to generate photocarriers to cancel surface charges (photo static elimination), a method in which a conductive brush or the like is brought into contact with the photoconductor to leak charges, or a reverse bias is applied. A method of canceling the surface charge is used.

  In recent years, image forming apparatuses have been improved in image quality and color, and relatively high-definition writing and development are possible. Information (originals) input to the image forming apparatus has also changed somewhat. As described above, characters have mainly been used in past manuscripts, but photographic images, colored pictures, graphs, and the like have been input. When such various patterns of input signals exist, the next image formation may be affected unless the history of the previous cycle in image formation is erased. In many cases, an abnormal image called an afterimage is generated.

  The afterimage is an area where the photoconductor is in a non-uniform state when the photoconductor is charged in the image forming process and a history of the photoconductor charge state before charging is left and a non-uniform state has already been formed. When writing is performed uniformly on the entire surface, particularly in the case of halftone, the charge potential after writing is essentially uniform, whereas the charge distribution is non-uniform. In this state, an electrostatic latent image is formed, and when this is developed by the developing unit, non-uniform development is performed, and the latent image formed in the previous image forming cycle remains as it is. It is what produces.

There are two possible causes for the afterimage. One is that image formation has become very fast, so the capacity (charging ability) of the charger tends to be insufficient, and if the surface charge of the photoconductor before charging is not uniform, the history is picked up at the next charging. This is because it is impossible to ensure uniform charge. The other is that the use of the charging roller has increased due to the compactness of the image forming apparatus or the tandemization of color.
That is, the charging roller causes a discharge phenomenon with the photoconductor and charges the surface of the photoconductor due to a bias difference between the two, but the surface charge on the photoconductor before charging is non-uniform. The history will be left at the next charging.

Therefore, the key is how to uniformize the surface potential (surface charge) of the photoreceptor before charging, and the charge removal process has played a very important role in improving image quality.
Among the static elimination methods described above, methods other than the optical static elimination have the following problems. The method of charge leakage using a conductive brush or the like requires a member that makes contact with the surface of the photoconductor, and wear of the photoconductor and the contact member occurs, and high durability cannot be desired. In addition, the effect of the charge leakage method may be reduced due to contamination of the surface of the photoreceptor or the contact member. Further, when the speed is increased, a sufficient effect cannot be expected in consideration of the charge transfer time.

  In the method of applying the reverse bias, uniformization is not sufficiently performed when the bias application condition is too weak, and when the bias application condition is too strong, the surface of the photosensitive member is reversely charged. Since a normal photoconductor can move only with a positive charge, it cannot be canceled when the surface is charged with a positive charge. Accordingly, when negative charging is performed at the next charging, the positive charge is first canceled and then negative charging is performed. This further creates a shortage of charger capacity. Further, when positively charged, it becomes easy to form a trap in the photosensitive layer, and it becomes easy to generate a residual potential of the photosensitive member, and as a result, the life of the photosensitive member is shortened.

From the above, it can be said that the use of optical static elimination is the best choice at the present time for the static elimination process in the image forming apparatus. As described above, in recent years, digital image forming apparatuses have become mainstream, and for the reasons described above, negative / positive development is used as a developing method used at that time. Compared with the case of positive / positive development in the analog method used conventionally, the meaning in charge removal is very different.
That is, in the positive / positive development, in the photostatic discharge after transfer, the entire surface of the photosensitive member is usually irradiated with light, but only the area corresponding to the writing portion of characters or the like is substantially discharged. For this reason, the area is at most about 10% with respect to the entire area of the photosensitive member.

  On the other hand, in negative / positive development, the non-exposed portion of the photoconductor (the portion where writing is not performed) is substantially neutralized, so if the document is the same as above, it is close to 90% of the total area of the photoconductor. The area will be substantially neutralized. As used herein, “substantially charge removal” means that the photoconductor has a surface charge at the place where photostatic discharge is performed, and light irradiation of the charge removal member generates photocarriers inside the photoconductor, thereby This means that the surface charge of the photoreceptor is canceled out.

  In other words, the positive / positive development and the negative / positive development that have been used in the past mean that the surface charge cancellation ratio of the photoconductor is completely different (resulting in a reverse history). Compared to the above, the effect of static elimination differs by at least about 10 times. However, studies on the influence (especially the neutralization light wavelength) on the photosensitive member in the static elimination process have not been made so much, and the actual situation is that it has been used as it is.

Prevention of light fatigue and charging fatigue by irradiating with appropriate charge-removing light including short-wavelength light in an image forming apparatus using an inorganic photoreceptor (Se-based, a-Si) There has been proposed a technique for performing (see, for example, Patent Documents 1 and 2).
However, the photoconductor used in Patent Document 1 or Patent Document 2 is an inorganic photoconductor, and the photocarrier generation mechanism is essentially different from a photoconductor using an organic charge generating material as described later. For this reason, inorganic technology (photostatic discharge) cannot be used (horizontal development) as it is for an organic photoreceptor. Further, the development system used is of an era corresponding to positive / positive development, and the degree of influence of light neutralization is completely different from that of negative / positive development. Further, the wavelength of the static elimination light includes wavelength light in a region of 500 nm or more.
In addition, as a result of performing an experiment by applying the technique of Patent Document 1 or Patent Document 2, the effect of suppressing the increase in residual potential was not sufficient.

As another example, the residual potential is obtained by performing exposure at a wavelength that approximately matches the intrinsic photosensitive wavelength of the dye-sensitized photoconductor, in other words, by performing neutralization using a wavelength in a region where the sensitizing dye does not absorb. There has been proposed a technique for removing (see, for example, Patent Document 3).
However, the original material (for example, polyvinyl carbazole) or the like of a photosensitized photoreceptor subjected to dye sensitization has no absorption in the visible range, and is sensitized with a dye having absorption in the visible range. Therefore, in the above technique, the dye is not absorbed and the charge is removed in a wavelength region having absorption in polyvinyl carbazole.
In this case, since the generation efficiency of the optical carrier in this wavelength band is low and the charge removal cannot be performed efficiently, there is a case where it cannot necessarily be an effective means because it causes photodegradation of polyvinylcarbazole. Further, the development system used is of an era corresponding to positive / positive development, and the degree of influence of light neutralization is completely different from that of negative / positive development. For this reason, when it is used for negative / positive development which is the subject of the present invention, the effect is not sufficient.

Alternatively, a photosensitizer that has photosensitivity at long wavelengths and low sensitivity or short photosensitivity on the short wavelength side can be used to eliminate sensitivity deterioration due to light fatigue by eliminating charges with short-wavelength light. A technique has been proposed (see, for example, Patent Document 4).
However, in a relatively high-speed image forming apparatus, when neutralization is performed with light in a region with low sensitivity or substantially no photosensitivity, the neutralization function is insufficient and abnormal images cannot be suppressed. Occurs. It is important to have sufficient photosensitivity for the static elimination light, and the technique of Patent Document 4 cannot cope with current image forming measures. In Patent Document 4, the neutralization wavelength is not specified.

In addition, a method has been proposed in which a positively charged photoreceptor having a charge generation layer laminated on a charge transport layer is subjected to charge removal by irradiating light with a wavelength of 620 nm or less to reduce the residual potential (for example, patents). (Ref. 5, 6).
However, the wavelength of the static elimination light includes wavelength light in the region of 500 nm or more. As a result of conducting an experiment by applying the technique of Patent Document 5 or 6, the effect of suppressing the increase in residual potential was not sufficient.

Alternatively, a method has been proposed in which neutralization is performed by simultaneously irradiating two types of light emitting diodes to prevent a residual potential from increasing under high temperature and high humidity (see, for example, Patent Document 7). As the wavelength of the static elimination light, wavelength light in a region of 500 nm or more is included.
However, as a result of conducting an experiment by applying the technique of Patent Document 7, the effect of suppressing the increase in residual potential was not sufficient.

Further, in the charge removal of a single-layer photoconductor containing an organic pigment, a method has been proposed in which charge removal is efficiently performed by irradiating light in a range including a wavelength region that is equal to or greater than the half-value width of the maximum absorbance of the photosensitive layer (for example, , See Patent Document 8).
However, since a practical organic pigment usually has an absorption peak in the visible region, the technique of Patent Document 8 cannot obtain a sufficient effect of suppressing the increase in residual potential.

Alternatively, a method is proposed in which the residual potential is reduced and ghosting is suppressed by selecting a wavelength at which the sensitivity of the photoconductor at the neutralization wavelength is higher than the sensitivity of the photoconductor in the writing light and using it for the neutralization light. (For example, refer to Patent Document 9).
In this technique, the charge eliminating wavelength varies depending on the photosensitive material used, and the charge eliminating wavelength cannot be specified. In addition, organic pigments usually have an absorption peak in the visible region, and a spectral sensitivity peak is also present in the visible region. For this reason, in the technique of patent document 9, the static elimination technique by the wavelength of 500 nm or less is not produced.

Furthermore, a method of irradiating light with a wavelength having a relatively low spectral absorptivity of the photoconductor in the charge removal of the image forming apparatus using the photogenerating material (single-layer photoconductor) is proposed ( For example, refer to Patent Document 10.)
This technique is performed in order to remove residual charges generated in the bulk of the photosensitive layer when the single-layer photosensitive member is repeatedly used. That is, in the case of a single-layer photoconductor, the charge generating material is uniformly dispersed in the bulk, and the irradiation light is absorbed near the surface of the photosensitive layer at a wavelength having a high absorption rate. The high resolution of single-layer photoconductors uses this phenomenon, and writing light is used to reduce the irradiation energy by using a wavelength with a high absorption rate of the photosensitive layer, and photocarriers are generated only near the surface of the photosensitive layer. Let

  For this reason, the movement distance of the charge having the opposite polarity to the polarity charged on the surface of the photosensitive member is small, and the diffusion due to the Coulomb repulsion is prevented by reducing the movement distance of the charge. On the other hand, since the irradiation light hardly reaches the inside of the bulk, when the charge having the same polarity as that charged on the surface of the photosensitive member is trapped in the photosensitive layer bulk and becomes a residual potential, it can be canceled. Can not. For this reason, in the static elimination light, light with a wavelength that penetrates deep into the bulk is used to cancel the light by generating optical carriers in the deep part of the bulk (near the electrode, near the center of the photosensitive layer, etc.). To do.

  On the other hand, the charge generation layer of the laminated photoreceptor is very thin, unlike the single-layer photosensitive layer. Further, the absorptance with respect to writing light is 90% or less even at the maximum absorption wavelength. In other words, the writing light passes through the charge generation layer by 10% or more. For this reason, even if the wavelength of the writing light is different, there is no change in the essence that charge generation occurs in the entire charge generation layer bulk. Therefore, in the case of a laminated photoreceptor, the effect described in Patent Document 10 does not occur.

In addition, a method has been proposed in which the phthalocyanine compound is subjected to light irradiation on the Soret band to eliminate static electricity. In this publication, it is described that a fluorescent lamp is used as a static elimination light source in order to realize this (for example, see Patent Document 11).
As yet another example, it is described that a static electricity is removed from a photoreceptor containing a phthalocyanine compound with a fluorescent lamp (for example, see Patent Document 12).

For reference, FIG. 1 shows a spectral emission spectrum of a fluorescent lamp.
Fluorescent lamps contain several bright lines, but in addition to this, there is a large light emission from 500 to 650 nm. Since the light irradiation amount (light emission amount) depends on the area of FIG. 1, the light of the fluorescent lamp irradiated on the photosensitive member is mainly light in the above wavelength range (500 to 650 nm). It will be irradiated.
In Patent Documents 11 and 12, charge removal by 680 nm red LED light and charge removal by fluorescent lamp irradiation are compared. From the spectrum of FIG. 1, the comparison between the two means that the charge removal by the red LED light of 680 nm and the charge removal by the light emission from 500 to 650 nm are compared. Since the light corresponding to the phthalocyanine Sore band is not zero, it is true that the Sore band is irradiated with light. It will be big.

  In the situation where various proposals have been made as described above, printers and copiers are required to have higher image quality and higher durability, including colorization. There are two problems in improving image quality in digital machines, one is how to form an electrostatic latent image uniformly with minute dots, and the other is how to reduce various abnormal images. . Further, with regard to high durability, extending the life of the photoreceptor is the most effective method.

  There are various approaches to solve these problems, but what can be said in common to both is how to reduce the deterioration due to electrostatic fatigue of the photoreceptor used in these image forming apparatuses. Specifically, it is how to suppress an increase in residual potential (exposure portion potential) during repeated use.

  As a countermeasure for increasing the residual potential, the development so far has been performed by devising the design (prescription, configuration, etc.) of the photoreceptor. However, the electrostatic fatigue of the photoreceptor varies greatly depending on the photoreceptor formulation or process conditions, and when considered from the development side of the photoreceptor, it is necessary to cope with each process condition. Under such circumstances, little study has been made on the electrostatic fatigue of the photoreceptor from the process conditions.

A naphthalene tetracarboxylic acid diimidazole pigment is mentioned as an example of a preferable electron accepting pigment in a laminated electrophotographic photoreceptor provided with a charge generation layer comprising an electron donating pigment layer and an electron accepting pigment layer. (For example, refer to Patent Document 13).
However, when used for recent negative / positive development and aiming for very high durability, the process conditions to be used are not established, and the superiority of the material is not necessarily fully drawn out. There wasn't.

JP 60-88981 A JP-A-62-87981 JP-A 61-36784 JP-A-62-38491 JP-A-1-217490 JP-A-1-274186 JP-A-4-17489 Japanese Patent No. 3460285 JP 2002-287382 A Japanese Patent Laying-Open No. 2005-31110 JP 2004-45996 A JP 2004-45997 A JP 7-13354 A

An object of the present invention is to solve the conventional problems and achieve the following objects.
That is, the present invention provides an image forming apparatus and an image forming method capable of suppressing an increase in residual potential in repeated use of an electrostatic latent image carrier (photoconductor) and capable of forming a highly durable and high-definition image. Objective.

The present inventor has examined how the process conditions influence the electrostatic fatigue of the photoreceptor, particularly the increase in the residual potential.
That is, the examination method is as follows.
In a state of repeated use in an image forming apparatus, a state where development, transfer and cleaning members are removed and only charging, writing and static elimination are applied so as not to affect the shape and physical properties other than the electrostatic characteristics of the photoreceptor as much as possible. Then, the electrostatic fatigue test of the photoreceptor was performed as follows.

(A) The writing rate by the writing light was changed, and the amount of charge passing through the photoreceptor was measured.
(B) The surface charge was erased only by static elimination light without writing, and the passing charge amount of the photoreceptor was measured.
Measurement was performed under the conditions (a) and (b) above to evaluate the residual potential of the photoreceptor, and the following knowledge was obtained.

(1) The increase in the residual potential of the photoconductor depends on the amount of charge passing through the photoconductor. Even when the writing rate is changed, the amount of increase in residual potential is evenly arranged by arranging the amount of passing charges.
(2) The passing charge amount of the photoreceptor depends on the light irradiation amount in one cycle of image formation. Regardless of writing and static elimination, it depends on the light irradiation amount (more precisely, the light absorption amount of the photosensitive member).
(3) In the case of negative / positive development, most of the light irradiation amount is given by light neutralization.

Further, an experiment similar to the above was performed with a transfer member attached so that a reverse bias could be applied to the photoreceptor before the charge removal step. The surface potential of the photoconductor before neutralization can be measured and the reverse bias is changed so that the surface potential of the photoconductor before neutralization becomes substantially the same as the surface potential after neutralization in the experiments (1) to (3). The reverse bias can be applied under such conditions.
When the electrostatic fatigue test was carried out in this state, the amount of increase in the residual potential of the photoconductor became very small and became a magnitude depending on the writing rate, and the influence of static elimination did not appear at all.

From the above, the following can be said.
(4) If the photoreceptor surface potential is lowered before static elimination, the residual potential is unlikely to increase. In other words, if the surface potential of the photosensitive member is low at the time of charge removal, irradiation with charge removal light does not contribute to an increase in residual potential.
(5) Even when a reverse bias is applied and the surface potential of the photoconductor is lowered before static elimination, the amount of increase in residual potential can be organized by the amount of charge passing through the photoconductor as in (1) above.
From (1) to (5), although the increase in the residual potential depends on the amount of charge passing through the photoconductor, most of it is generated in the static elimination process, and how to control the static elimination process depends on the increase in the residual potential. One key to control.

  The passing charge amount shown in (1) is the passing charge amount per unit surface area of the photoreceptor in one cycle of image formation, and depends on the amount of photocarrier generated. Therefore, the image forming conditions depend on the charging potential (applied electric field strength to the photosensitive member), the exposure amount, the exposure area, the electrostatic capacitance (film thickness) of the photosensitive member, the carrier generation efficiency, and the like. However, the target image forming apparatus cannot have such a large change with respect to these items.

For example, greatly changing the charging potential brings about the following changes.
When the charging potential is greatly increased, the hazard to the photoreceptor increases. In the case of a large decrease, the background potential (photosensitive member charging potential-developing bias) decreases or the developing potential (developing bias-photosensitive portion exposed portion potential) decreases, and image forming conditions (especially developing conditions). Becomes very narrow and the margin of the system becomes small.
Changing the exposure amount greatly brings about the following changes.
When the exposure amount is reduced, there are cases where the image density is insufficient or the contrast cannot be obtained. On the other hand, when the exposure amount is increased, the phenomenon occurs when the dots are crushed.

The electrostatic capacity (film thickness) and carrier generation efficiency of the photoconductor do not change significantly unless the photoconductor material itself is changed significantly, but it is used for current high-speed, high-durability, and high-stability image forming devices. There are limits to the main materials (charge generating substances and charge transporting substances) that can be produced, and it is extremely difficult to change them to completely different materials.
Accordingly, the passing charge amount of the photoconductor mounted on the target image forming apparatus does not change significantly, and greatly depends on the light irradiation amount.

However, the light irradiation amount referred to here is the light irradiation amount to the photosensitive member in one cycle of image formation (charging, writing, developing, transferring, discharging). The image formation includes a fixing step, but is not directly in contact with the photoconductor, and therefore is omitted from the description here. That is, it can be seen that light irradiation to the photosensitive member consists of two types of writing light and static elimination light.
As described above, in general, an image forming apparatus that performs digital writing currently uses negative / positive development, which is because most of the actual writing ratio of an original is 10% or less. The purpose is to reduce stress.
However, from the viewpoint of the photoconductor side, if the surface potential of the photoconductor is not canceled (smoothed) before the next image forming cycle, it will be affected at the time of the next charging. The surface potential of the photoreceptor is reduced as much as possible before charging in the next step.

As described above, since the writing rate is about 10%, 90% or more of the surface of the photoconductor enters the charge removal process with surface charge on it. Here, the remaining charge is erased by irradiating the surface potential of the photoreceptor remaining after the transfer with a charge-removing light and generating a photocarrier. That is, 90% or more of the charge passing through the photoreceptor generated in one cycle of the image forming process is generated in the static eliminating process.
Up to this point, this is the normal state of an image forming apparatus using negative / positive development, and basically all negative / positive images are output except when only originals that are continuously written on the entire surface are output. This is true for image forming apparatuses that use development. However, as described above, the actual situation is that the analysis from the process side regarding the electrostatic fatigue of the photoreceptor has not been performed so much.

  The present inventor examined the control by process conditions for the increase in the residual potential (exposure portion potential) in the repeated use of the photoreceptor. As described above, the static elimination process in image formation has a great influence. Was revealed. Furthermore, examination was repeated regarding the conditions (mainly light wavelength) of static elimination light.

The neutralizing light exhibits its function as long as the photoconductor (charge generation layer) has a wavelength with absorption.
In general, a light source such as an LED array or a fluorescent lamp is used to irradiate substantially uniform light in the longitudinal direction of the photoreceptor. In the past, fluorescent lamps have been mainly used, but have the following problems because they include light in an area where the charge transport layer has absorption.
(1) Since a part of light is absorbed by the charge transport layer, there is a case where sufficient light does not reach the charge generation layer, and there is a case where the amount of light needs to be very large.
(2) As a result of the charge transporting material absorbing the static elimination light, the charge transporting material may deteriorate and affect the electrostatic characteristics of the photoreceptor.

  In order to overcome such a problem, a red LED (having a wavelength on the order of 600 nm) has generally been used. At the wavelength of this red LED, normally used charge transport materials have no absorption, the above-mentioned two problems can be cleared, and many charge generation materials have a large absorption, so that the charge removal is carried out efficiently. In addition, the fact that the cost of the LED is relatively low is also a great advantage of using this member.

  The present inventor questioned whether the neutralization by irradiating light of a relatively long wavelength such as the red LED is optimal for repeated use of the photoreceptor, and examined the wavelength dependence of the neutralization light. Specifically, various wavelengths were produced by combining a monochromatic laser beam or an appropriate light source and a filter, and studies were made on the increase in residual potential in repeated use of the photoreceptor.

  As a result, it has been found that red static elimination, which has been considered to be good in the past, raises the residual potential rather than irradiating light with a shorter wavelength. Further, when looking closely at the wavelength dependence, it has been found that an increase in the residual potential can be significantly suppressed by performing static elimination with light having a wavelength shorter than 500 nm. In this experiment, the amount of charge passing through the photoconductor per unit time at the time of static elimination is adjusted, so the amount of static elimination light applied to the photoconductor is determined by the spectral absorption spectrum profile of the photoconductor (charge generation material). Although it changes, the light absorption amount of the photosensitive layer does not change. Therefore, it was understood that the above result was due to the influence of the wavelength dependency of the static elimination light.

It has been found that the increase in residual potential can be suppressed by the process-side control technology (means) in image formation as described above. However, if the photoreceptor used has poor durability against electrostatic fatigue, The effect is not fully demonstrated.
The present inventor has found that the use of a specific charge generating substance (naphthalene tetracarboxylic acid diimidazole pigment) can greatly control the deterioration of electrostatic characteristics in the repeated use of a photoreceptor using the same.
That is, as a result of intensive studies to solve the above problems, the present inventor has found that the charge generation layer in the electrostatic latent image carrier having at least a laminated photosensitive layer composed of at least a charge generation layer and a charge transport layer. It has been found that the above-mentioned problems can be solved by using a light source having a wavelength shorter than 500 nm as a static elimination light source, which contains a ring quinone pigment and phthalocyanine, and has completed the present invention. The specific solution is as follows.

That is, the present invention relates to an electrostatic latent image carrier having a photosensitive layer composed of a charge generation layer and a charge transport layer on a support, an electrostatic latent image forming unit, a developing unit, a transfer unit, and a fixing unit. And an image forming apparatus having at least a static eliminating unit for static eliminating the residual charge of the electrostatic latent image carrier,
The static elimination means has a light source that emits light having a wavelength shorter than 500 nm,
In the image forming apparatus, the charge generation layer contains at least one of naphthalenetetracarboxylic acid diimidazole pigments represented by any one of the following general formulas (1) and (2).

(In general formulas (1) and (2), A represents an optionally substituted divalent aromatic hydrocarbon group or divalent nitrogen-containing heterocyclic group.)

  In the image forming apparatus, the naphthalene tetracarboxylic acid diimidazole pigment represented by the general formula (1) is a naphthalene tetracarboxylic acid diimidazole pigment represented by the following formula (3). Features.

  Furthermore, in the image forming apparatus according to the present invention, the naphthalenetetracarboxylic acid diimidazole pigment represented by the general formula (2) is a naphthalenetetracarboxylic acid diimidazole pigment represented by the following formula (4). Features.

  According to the present invention, in any one of the above image forming apparatuses, the charge transporting layer transmits at least 30% of the irradiation light for photostatic discharge.

  In the image forming apparatus according to any one of the above aspects, the charge transport layer includes a charge transport material having a triarylamine structure.

  Furthermore, the present invention is characterized in that, in the image forming apparatus, the charge transport material is a charge transport material represented by the following formula (5).

In the formula, R ₃₀₁ , R ₃₀₃ and R ₃₀₄ are a hydrogen atom, an amino group, an alkoxy group, a thioalkoxy group, an aryloxy group, a methylenedioxy group, an unsubstituted alkyl group, a halogen atom, or a substituted or unsubstituted aryl group. R ₃₀₂ represents a hydrogen atom, an alkoxy group, a substituted or unsubstituted alkyl group or halogen. K, l, m and n are integers of 1, 2, 3 or 4, and when each is an integer of 2, 3 or 4, the R ₃₀₁ , R ₃₀₂ , R ₃₀₃ and R ₃₀₄ are the same or different. May be.

  In the image forming apparatus according to any one of the above, the charge transport layer may include a polycarbonate containing a triarylamine structure in at least one of a main chain and a side chain.

  Furthermore, according to the present invention, in any one of the above image forming apparatuses, a protective layer is provided on the charge transport layer.

  Furthermore, the present invention is characterized in that, in the image forming apparatus, the protective layer transmits at least 30% of the light for light neutralization.

In the image forming apparatus according to any one of the above, the protective layer includes at least one selected from an inorganic pigment or a metal oxide having a specific resistance of 10 ¹⁰ Ω · cm or more.

  In the image forming apparatus according to any one of the above, the protective layer includes a radical polymerizable monomer having at least a trifunctional radical polymerizable monomer having no charge transporting structure and a radical polymerization having a monofunctional charge transporting structure. It is formed by curing a functional compound.

  Furthermore, in the image forming apparatus according to the present invention, the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (6) or (7). It is characterized by.

In formulas (6) and (7), R ₁ is a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or an aryl which may have a substituent. Group, cyano group, nitro group, alkoxy group, —COOR ₇ (R ₇ may be a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents a good aryl group.), A halogenated carbonyl group or —CONR ₈ R ₉ (R ₈ and R ₉ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or a substituent. Represents an aralkyl group or an aryl group which may have a substituent, and may be the same or different from each other. Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, and It may or may not be. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3.

  According to the present invention, in any one of the above image forming apparatuses, the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (8). Features.

In the formula, each of o, p, and q is an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent substituents other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, The case may be different. s and t represent an integer of 0 to 3. Za represents a single bond, a methylene group, an ethylene group, or the following formula (a), (b) or (c). )
In the formula, each of o, p, and q is an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent substituents other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, The case may be different. s and t represent an integer of 0 to 3. Za represents a single bond, a methylene group, an ethylene group, or the following formula (a), (b) or (c).

  In the image forming apparatus according to any one of the above aspects, the protective layer curing means may be heating or light energy irradiation means.

  According to the present invention, in the electrostatic latent image carrier of any of the above image forming apparatuses, an intermediate layer is provided between the support and the charge generation layer, and the intermediate layer is formed from the support to the photosensitive layer. It is characterized by comprising a charge blocking layer for preventing charge injection and a moire preventing layer for preventing the occurrence of moire inside the photosensitive layer.

  In the image forming apparatus, the charge blocking layer is made of an insulating material, and the film thickness is less than 2.0 μm and 0.3 μm or more.

  Further, according to the present invention, in any one of the above image forming apparatuses, the moire preventing layer contains an inorganic pigment and a binder resin, and the volume ratio of the inorganic pigment and the binder resin is in a range of 1/1 to 3/1. It is characterized by that.

  In the image forming apparatus according to any one of the above, the light source wavelength of the image writing light used for the electrostatic latent image forming unit is a light source having a wavelength shorter than 450 nm.

  According to the present invention, any one of the above image forming apparatuses includes a plurality of image forming elements each having at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, a transfer unit, and a charge eliminating unit. Features.

  Further, according to the present invention, in any one of the above image forming apparatuses, the electrostatic latent image carrier and one or more means selected from an electrostatic latent image forming unit, a developing unit, a discharging unit, and a cleaning unit are integrated. Thus, a process cartridge that is detachable from the apparatus main body is mounted.

And, the present invention comprises an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier having a photosensitive layer comprising a charge generation layer and a charge transport layer on a support;
Developing the electrostatic latent image with toner to form a visible image;
A transfer step of transferring the visible image to a recording medium;
A fixing step of fixing the transferred image transferred to the recording medium;
An image forming method comprising at least a static elimination step of photostaticizing residual charges of the electrostatic latent image carrier,
The charge removing step is a step of discharging by irradiating light having a wavelength shorter than 500 nm, and the charge generation layer of the electrostatic latent image carrier on which an electrostatic latent image is formed in the electrostatic latent image forming step. Contains at least one naphthalene tetracarboxylic acid diimidazole pigment represented by either of the following general formulas (1) or (2).

  In general formulas (1) and (2), A represents an optionally substituted divalent aromatic hydrocarbon group or divalent nitrogen-containing heterocyclic group.

  In the image forming method, the present invention is characterized in that the light source wavelength of the image writing light used in the electrostatic latent image forming step is a light source having a wavelength shorter than 450 nm.

  Furthermore, the present invention is characterized in that the image forming method of any one of the above images comprises a plurality of image forming steps including the electrostatic latent image forming step, the developing step, the transferring step, and the charge eliminating step.

The photosensitive layer of the latent electrostatic image bearing member (laminated type of charge generating layer and charge transporting layer) is used for the light neutralizing means having a wavelength shorter than 500 nm, which greatly improves the neutralizing effect applied to the image forming apparatus of the present invention. If the charge generation layer in the layer) contains a naphthalenetetracarboxylic acid diimidazole pigment represented by a specific structural formula, there is little electrostatic fatigue even when used repeatedly, and the increase in residual potential is suppressed.
Further, if the charge transport layer contains a charge transport material having a triarylamine structure, the charge removal characteristics are suitably maintained, and excellent characteristics such as wear resistance can be obtained. Furthermore, if a protective layer is provided on the charge transport layer, the durability is further improved, an electrostatic latent image bearing member having high sensitivity and no abnormal defects can be obtained, and high-speed output and downsizing of the apparatus can be achieved.
The electrostatic latent image carrier, the electrostatic latent image forming unit, the developing unit, the transfer unit, the fixing unit, and the residual charge of the electrostatic latent image carrier are subjected to light neutralization using an irradiation light source having a wavelength shorter than 500 nm. If the structure has at least static elimination means, an image forming apparatus capable of suppressing the increase in the residual potential and causing no afterimage even when the electrostatic latent image bearing member is repeatedly used, and capable of highly durable and stable image output. Is provided.
Further, by the image forming method using the image forming apparatus, a high-definition and high-quality image can be stably obtained for a long period of time even in repeated use.

[Image Forming Apparatus and Image Forming Method]
As described above, the image forming apparatus of the present invention is a charge generator containing at least one naphthalene tetracarboxylic acid diimidazole pigment represented by either the general formula (1) or (2) on a support. An electrostatic latent image carrier having a photosensitive layer (laminated photosensitive layer) composed of a layer and a charge transport layer, an electrostatic latent image forming unit, a developing unit, a transfer unit, a fixing unit, and a residual of the electrostatic latent image carrier And at least a static elimination unit having a light source with a wavelength shorter than 500 nm for photostatic elimination of charges, and further having other means appropriately selected as necessary, for example, a cleaning unit, a recycling unit, a control unit, etc. It becomes.
In the image forming apparatus, the electrostatic latent image forming unit forms an electrostatic latent image on the electrostatic latent image carrier, and the developing unit develops the electrostatic latent image with toner to form a visible image. The transfer means transfers the visible image to the recording medium, the fixing means fixes the transferred image transferred to the recording medium, and the static elimination means electrostatically uses a light source having an emission spectrum in a region shorter than 500 nm. Irradiate the latent image carrier with static elimination light.

In addition, the image forming method of the present invention includes a charge generation layer containing at least one naphthalene tetracarboxylic acid diimidazole pigment represented by either the general formula (1) or (2) on a support, and a charge. An electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier having a photosensitive layer comprising a transport layer;
Developing the electrostatic latent image with toner to form a visible image;
A transfer step of transferring the visible image to a recording medium;
A fixing step of fixing the transferred image transferred to the recording medium;
At least a charge eliminating step for discharging the residual charge of the latent electrostatic image bearing member by irradiating light with a wavelength shorter than 500 nm, and further selecting other steps as necessary, for example, a cleaning step, recycling A process, a control process, and the like.

  The image forming method of the present invention can be preferably carried out by the image forming apparatus of the present invention, the electrostatic latent image forming step can be performed by the electrostatic latent image forming means, and the developing step is the developing The transfer step can be performed by the transfer unit, the neutralization step can be performed by the neutralization unit, the fixing step can be performed by the fixing unit, and the other steps. Can be performed by the other applicable means.

According to the inventor's study, when the irradiation light is finely decomposed, the increase in the residual potential can be suppressed as the short wavelength light is irradiated, and when long wavelength light of 500 nm or more is mixed, the long wavelength light is long. A residual potential increase was observed depending on the amount of wavelength light mixed. Therefore, the method described in Patent Document 1 is still insufficient as a technique for suppressing the increase in residual potential in consideration of high durability and high image quality.
Therefore, the neutralizing light having a wavelength shorter than 500 nm in the present invention indicates that the light does not include light having a wavelength longer than 500 nm (hereinafter, it may be referred to as a neutralizing light of less than 500 nm). .

Although a detailed mechanism that can suppress an increase in the residual potential in repeated use of the photoreceptor by using charge removal light of less than 500 nm has not been clarified, at present, the mechanism is considered as follows.
For the sake of explanation, the photocarrier generation mechanism of an organic material is shown in FIG. Most known photocarrier generation mechanisms of organic materials are based on a reaction consisting of two steps (photoexcitation → intermediate generation → free carrier generation) as shown in FIG. At this time, although the charge generation material absorbs light and is excited to a higher excited state, the formation of the intermediate occurs from a certain energy level. This constant energy level is the lowest excited singlet state (S ₁ ). When irradiated with energy (long wavelength light) smaller than that between the ground state (S ₀ ) and the lowest excited singlet state (S ₁ ), almost no optical carrier is generated.

On the other hand, when irradiated with energy (short wavelength light) larger than between the ground state (S ₀ ) and the lowest excited singlet state (S ₁ ), the energy level (S *) higher than S _1. And is immediately relaxed to the S ₁ state, and an intermediate is formed from S ₁ . At this time, the energy corresponding to the energy difference between the S * and S ₁ is thermally relaxed (in the figure, shows surplus energy). This model is supported by the result that there is no wavelength dependency of the photocarrier generation efficiency of the organic photoreceptor.

  When the electrophotographic photosensitive member is repeatedly used, the residual potential increases due to the positive and negative photocarriers generated by the generation of photocarriers due to the action of the electric field applied to the photosensitive member. In the case of a body, the negative charge is on the surface side of the photoreceptor). At this time, the optical carrier falls into a certain trap and forms a residual potential. Since the depth of this trap is larger than the activation energy given by room temperature, it cannot be detrapped under normal use and is accumulated as a residual potential.

  By the way, when most of the optical carriers generated in one cycle of image formation are generated by static elimination light having a wavelength shorter than 500 nm as in the present invention, the state of large surplus energy shown in FIG. 2 is repeated. For this reason, it is thought that this surplus energy can suppress a rise in residual potential by acting on detrapping.

  On the other hand, a schematic diagram of a photocarrier generation mechanism of an inorganic photoreceptor is shown in FIG. In general, since a band model is applied in the case of an inorganic material, a model composed of a valence band and a conduction band as shown in FIG. 3 is submitted.

As shown in FIG. 3, electrons that have obtained energy corresponding to a band gap by photoexcitation can move freely in the valence band and exist as free carriers. In this case, the conduction band region is characterized by being directly ionized to become free carriers. Therefore, when energy larger than the energy gap is obtained as shown in FIG. 2, the carrier generation efficiency (ion dissociation efficiency) is improved, but no surplus energy is generated. This point is greatly different from the photocarrier generation mechanism of the organic photoreceptor.
Such an inorganic model is supported by the result that the carrier generation efficiency of the inorganic photoconductor shows the wavelength dependence on the excitation light.

Considering the difference in the photocarrier generation mechanism between the organic photoconductor and the inorganic photoconductor, the difference in the effect on the charge elimination light wavelength in the present invention can be considered.
That is, in the photocarrier generation in the static elimination process as described above, in the case of an organic photoconductor, the amount of generated carriers with respect to the static elimination light wavelength does not change (there is no wavelength dependence of quantum efficiency), but when one carrier is generated. The surplus energy has wavelength dependency. That is, the shorter the neutralization wavelength, the greater the amount of surplus energy generated inside the photoreceptor.

On the other hand, in the case of an inorganic photoconductor, the quantum efficiency depends on the wavelength, so that the shorter the static elimination wavelength, the more carriers are generated, but no surplus energy is produced. Energy corresponding to the surplus energy is distributed to improve carrier generation efficiency.
Accordingly, when the neutralization light having a wavelength shorter than 500 nm is irradiated as in the present invention, the amount of generated carriers is not changed in the organic photoreceptor as compared with the conventional case where the neutralization in the visible light region is performed. However, a lot of surplus energy can be acquired. This surplus energy is used as activation energy for detrapping the charges trapped in the photosensitive layer.

  On the other hand, in the case of an inorganic photoreceptor, only the amount of carriers generated is increased as described above, and no surplus energy is generated, so that charges trapped in the photosensitive layer cannot be detrapped. This is a major difference based on the difference in the carrier generation mechanism depending on the material constituting the photosensitive layer. For this reason, even if a short wavelength neutralization is performed with an inorganic photoconductor, the effect as in the present invention cannot be obtained, and even if there is a similar configuration, the idea, purpose, and effect are similar to those of the present application. Are completely different.

  That is, by the image forming apparatus and the image forming method having the above-described configuration of the present invention, even when the electrostatic latent image carrier is repeatedly used, the increase in residual potential is suppressed, the durability is excellent, and high-definition image formation is achieved. Is possible.

[Electrostatic latent image carrier]
As the electrostatic latent image carrier, it is essential that the charge generation layer contains at least one naphthalene tetracarboxylic acid diimidazole pigment represented by either the general formula (1) or (2). There is no restriction | limiting in particular about the material, a shape, a structure, a magnitude | size, etc. except, and it can select suitably from well-known things. As the support, a conductive support having conductivity is preferable.
The electrostatic latent image carrier (electrophotographic photosensitive member) used in the present invention will be described in detail with reference to the drawings.

  FIG. 4 is a cross-sectional view showing a configuration example of the electrophotographic photosensitive member used in the present invention, and on the support (31), at least one of the general formulas (1) and (2) as a charge generating substance. A charge generation layer (35) mainly composed of at least one naphthalenetetracarboxylic acid diimidazole pigment represented by the formula, and a charge transport layer (37) mainly composed of a charge transport material are laminated. I'm taking it.

  FIG. 5 is a cross-sectional view showing another structural example of the electrophotographic photosensitive member used in the present invention. On the support (31), an intermediate layer (39) and at least the general formula (1) as a charge generating substance are shown. ) Or (2) a charge generation layer (35) containing at least one naphthalenetetracarboxylic acid diimidazole pigment as a main component, and a charge transport layer (37) containing a charge transport material as a main component Are in a stacked configuration.

  FIG. 6 is a cross-sectional view showing still another structural example of the electrophotographic photosensitive member used in the present invention. The intermediate layer (39) is composed of a charge blocking layer (43) and a moire preventing layer (45). A charge generation layer (35) comprising, as a main component, at least one naphthalenetetracarboxylic acid diimidazole pigment represented by at least one of the general formulas (1) and (2) as a charge generation material on the layer; The charge transport layer (37) mainly composed of a transport material has a laminated structure.

  FIG. 7 is a cross-sectional view showing another structural example of the electrophotographic photosensitive member used in the present invention. On the support (31), an intermediate layer (39) and at least the general formula (39) as a charge generating substance are used. A charge generation layer (35) containing at least one naphthalenetetracarboxylic acid diimidazole pigment represented by either 1) or (2) as a main component, and a charge transport layer (37) containing a charge transport material as a main component And a protective layer (41) is further provided on the charge transport layer (photosensitive layer).

<Conductive support>
Examples of the conductive support (31) include those having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, oxidation A method of extruding and drawing metal oxides such as indium by film deposition or sputtering, or film or cylindrical plastic, paper or aluminum, aluminum alloy, nickel, stainless steel, etc. After forming the tube, it is possible to use a tube subjected to surface treatment such as cutting, superfinishing or polishing. Endless nickel belts and endless stainless steel belts can also be used as the conductive support.

  In addition, the conductive support dispersed in a suitable binder resin on the support can be used as the conductive support of the present invention. Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, and silver, or metal oxide powder such as conductive tin oxide and ITO. It is done.

The binder resin used simultaneously includes polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. Copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin , Thermoplastic resins such as melamine resin, urethane resin, phenol resin, and alkyd resin, thermosetting resin, or photocurable resin.
Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.

  Furthermore, it is electrically conductive by a heat shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer can also be used favorably as the conductive support of the present invention.

  Of these, a cylindrical support made of aluminum, which can be easily subjected to the anodic oxide film treatment, can be most preferably used. As used herein, aluminum includes both pure aluminum and aluminum alloys. Specifically, JIS 1000 series, 3000 series, and 6000 series aluminum or aluminum alloy is most suitable. The anodized film is obtained by anodizing various metals and various alloys in an electrolyte solution. Among them, a film called anodized aluminum or an aluminum alloy that has been anodized in an electrolyte solution is used in the present invention. Is the most suitable. In particular, it is excellent in preventing point defects (black spots, background stains) that occur when used in reversal development (negative and positive development).

The anodizing treatment is performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid. Of these, treatment with a sulfuric acid bath is most suitable. For example, sulfuric acid concentration: 10 to 20%, bath temperature: 5 to 25 ° C., current density: 1 to 4 A / dm ² , electrolytic voltage: 5 to 30 V, treatment time: treatment in the range of about 5 to 60 minutes However, the present invention is not limited to this. Since the anodic oxide film produced in this way is porous and has high insulation, the surface is very unstable. For this reason, there is a change with time after fabrication, and the physical property value of the anodized film is likely to change. In order to avoid this, it is preferable to further seal the anodized film.

Examples of the sealing treatment include a method of immersing the anodized film in an aqueous solution containing nickel fluoride and nickel acetate, a method of immersing the anodized film in boiling water, and a method of treating with pressurized steam. Among these, the method of immersing in the aqueous solution containing nickel acetate is the most preferable.
Subsequent to the sealing treatment, the anodic oxide film is washed. The main purpose of this is to remove excess metal salts and the like attached by the sealing treatment. If this remains excessively on the surface of the support (anodized film), it not only adversely affects the quality of the coating film formed on this surface, but also generally low resistance components remain, resulting in the occurrence of soiling. It can also be a cause. Cleaning may be performed with pure water only once, but usually, multistage cleaning is performed. At this time, it is preferable that the final cleaning liquid is as clean (deionized) as possible. Moreover, it is preferable to perform physical rubbing cleaning with a contact member in one of the multi-stage cleaning processes. The thickness of the anodized film formed as described above is preferably about 5 to 15 μm. If it is thinner than this, the effect of the barrier property as an anodic oxide film is not sufficient, and if it is thicker than this, the time constant as an electrode becomes too large, resulting in the generation of residual potential and the response of the photoreceptor. There is a case.

<Intermediate layer>
Next, the intermediate layer (39) will be described.
The intermediate layer generally contains a resin as a main component, but these resins are preferably resins having a high solvent resistance with respect to a general organic solvent in consideration of applying a photosensitive layer thereon with a solvent. .
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, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin.

  Further, fine powder pigments of metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the intermediate layer in order to prevent moire and reduce residual potential. Among these, when titanium oxide is contained in the intermediate layer, the effect of the present invention becomes remarkable and can be used most effectively. In addition, when the intermediate layer containing titanium oxide is present in contact with the charge generation layer described below, the effect is most remarkable, and the photoreceptor structure is most appropriate.

These intermediate layers can be formed using an appropriate solvent and coating method as in the photosensitive layer described later. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the intermediate layer of the present invention. In addition, in the intermediate layer of the present invention, Al ₂ O ₃ is provided by anodic oxidation, organic matter such as polyparaxylylene (parylene), SiO ₂ , SnO ₂ , TiO ₂ , ITO, CeO _2, etc. Those provided with an inorganic material by a vacuum thin film forming method can also be used favorably. In addition, known ones can be used. The thickness of the intermediate layer is suitably from 0 to 5 μm.

  The intermediate layer (39) has a function of preventing injection of a reverse polarity charge induced on the electrode side into the photosensitive layer when the photosensitive member is charged, and a function of preventing moire generated when writing with coherent light such as laser light. It has at least two functions. A function separation type intermediate layer in which this function is separated into two or more layers is an effective means for the photoreceptor used in the present invention. The function-separated intermediate layer of the charge blocking layer (43) and the moire prevention layer (45) will be described below.

<Charge blocking layer>
The charge blocking layer (43) is a layer having a function of preventing the reverse polarity charge induced in the electrode (conductive support (31)) during charging of the photosensitive member from being injected into the photosensitive layer from the support. .
In the case of negative charging, it has a function of preventing hole injection, and in the case of positive charging, it has a function of preventing electron injection.
The charge blocking layer includes an anodized film typified by an aluminum oxide layer, an inorganic insulating layer typified by SiO, a layer formed from a glassy network of metal oxide, a layer made of polyphosphazene, an aminosilane reaction Examples thereof include a layer made of a product, a layer made of an insulating binder resin, a layer made of a curable binder resin, and the like. Among them, a layer composed of an insulating binder resin or a curable binder resin that can be formed by a wet coating method can be used favorably.

Since the charge blocking layer is formed by laminating a moiré preventing layer and a photosensitive layer thereon, when these are provided by a wet coating method, the charge blocking layer must be composed of a material or a structure that does not attack the coating film by these coating solvents. Is essential.
Usable binder resins include thermoplastic resins such as polyamide, polyester, vinyl chloride-vinyl acetate copolymer, and thermosetting resins such as active hydrogen (—OH group, —NH ₂ group, —NH group, etc.). A thermosetting resin obtained by thermally polymerizing a compound containing a plurality of (hydrogen) and a compound containing a plurality of isocyanate groups and / or a compound containing a plurality of epoxy groups can also be used.

  In this case, examples of the compound containing a plurality of active hydrogens include acrylic resins containing active hydrogen such as polyvinyl butyral, phenoxy resin, phenol resin, polyamide, polyester, polyethylene glycol, polypropylene glycol, polybutylene glycol, and hydroxyethyl methacrylate groups. System resin and the like. Examples of the compound containing a plurality of isocyanate groups include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and their prepolymers. Examples of the compound having a plurality of epoxy groups include bisphenol A type epoxy resins. Can be mentioned. Among these, polyamide is most preferably used from the viewpoint of film formability, environmental stability, solvent resistance, and the like.

  In addition, a thermosetting resin obtained by thermally polymerizing an oil-free alkyd resin and an amino resin such as a butylated melamine resin, a polyurethane having an unsaturated bond, a resin having an unsaturated bond such as an unsaturated polyester, and thioxanthone A photocurable resin such as a combination with a photopolymerization initiator such as a methyl compound or methylbenzyl formate can also be used as the binder resin. Further, a function of suppressing charge injection from the substrate may be provided by adding a conductive polymer having a rectifying property or an acceptor (donor) resin / compound in accordance with the charging polarity.

  The film thickness of the charge blocking layer is 0.1 μm or more and less than 2.0 μm, preferably 0.3 μm or more and less than 2.0 μm. When the charge blocking layer becomes thick, the residual potential rises remarkably at low temperature and low humidity due to repeated charging and exposure, and when the film thickness is too thin, the blocking effect is reduced, and the charge blocking layer 5 is necessary. Add chemicals, solvents, additives, curing accelerators, etc. necessary for curing (crosslinking) according to the conventional method, and apply to the substrate by blade coating, dip coating, spray coating, beat coating, nozzle coating, etc., using conventional methods. Formed. After the coating, it is dried or cured by a curing process such as drying, heating, or light.

<Moire prevention layer>
The moiré prevention layer 45 is a layer having a function of preventing the generation of a moiré image due to light interference inside the photosensitive layer when writing with coherent light such as laser light. Basically, it has a function of causing light scattering of the writing light. In order to exhibit such a function, it is effective that the anti-moire layer has a material having a large refractive index. In general, an inorganic pigment and a binder resin (binder resin) are contained, and the inorganic pigment is dispersed in the binder resin. In particular, white pigments are effectively used among inorganic pigments, and for example, titanium oxide, calcium fluoride, calcium oxide, silicon oxide, magnesium oxide, aluminum oxide, and the like are favorably used. Among these, titanium oxide having a large hiding power can be most effectively used.

  Even when the intermediate layer is composed of the charge blocking layer and the moire preventing layer, the effect of the present invention is most remarkably exhibited when the moire preventing layer contains titanium oxide. Further, when the moire preventing layer containing titanium oxide is brought into contact with the charge generation layer, the effect is further remarkably enhanced, and is the most effective photoconductor structure.

  Further, in the photoconductor having the function separation type intermediate layer, the charge blocking layer prevents the charge injection from the support (31), so in the moire prevention layer, at least the charge charged on the surface of the photoconductor From the viewpoint of preventing residual potential, it is preferable to have a function of moving charges of the same polarity. For this reason, for example, in the case of a negatively charged type photoreceptor, it is desirable to impart electronic conductivity to the moire prevention layer, and the inorganic pigment to be used is one that has electronic conductivity, or one that is conductive. It is desirable. Alternatively, the use of an electron conductive material (for example, an acceptor) or the like for the moire preventing layer makes the effect of the present invention more remarkable.

Although the same resin as the charge blocking layer can be used as the binder resin, in consideration of laminating the photosensitive layer (33) (charge generation layer (35), charge transport layer (37)) on the moire prevention layer, It is important that the photosensitive layer (charge generation layer and charge transport layer) is not affected by the coating solvent.
As the binder resin, a thermosetting resin is preferably used. In particular, alkyd / melamine resin mixtures are best used. At this time, the mixing ratio of alkyd / melamine resin is an important factor for determining the structure and characteristics of the moire prevention layer. A range in which the ratio (weight ratio) between the two is 5/5 to 8/2 can be cited as a good mixing ratio range. If the melamine resin is richer than 5/5, volume shrinkage is increased during thermosetting, and coating film defects are likely to occur, or the residual potential of the photoreceptor is increased. Further, if the alkyd resin is richer than 8/2, it is effective in reducing the residual potential of the photoreceptor, but it is not desirable because the bulk resistance becomes too low and the soiling becomes worse.

  In the anti-moire layer, the volume ratio between the inorganic pigment and the binder resin determines an important characteristic. For this reason, it is important that the volume ratio of the inorganic pigment to the binder resin is in the range of 1/1 to 3/1. When the volume ratio of the two is less than 1/1, not only the moire prevention ability is lowered, but there is a case where the increase of the residual potential in repeated use becomes large. On the other hand, in the region where the volume ratio exceeds 3/1, not only the binding ability of the binder resin is inferior, but also the surface property of the coating film is deteriorated, which may adversely affect the film forming property of the upper photosensitive layer. This effect can be a serious problem when the photosensitive layer is a laminated type and a thin layer such as a charge generation layer is formed. When the volume ratio exceeds 3/1, there are cases where the binder resin cannot cover the surface of the inorganic pigment, and the direct contact with the charge generation material increases the probability of heat carrier generation, resulting in soiling. It may have an adverse effect on it.

Furthermore, by using two types of titanium oxides having different average particle diameters for the moire prevention layer, it is possible to improve the concealing power to the conductive substrate and suppress moire and to cause a pin that causes an abnormal image. The hole can be eliminated. For this purpose, it is important that the ratio of the average particle diameters of the two types of titanium oxide used is within a certain range (0.2 <D2 / D1 ≦ 0.5).
When the particle size ratio is outside the range specified in the present invention, that is, when the ratio of the average particle size of the other titanium oxide (T2) to the average particle size of the titanium oxide (T1) having a large average particle size is too small (0. In the case of 2 ≧ D2 / D1), the activity on the titanium oxide surface is increased, and the electrostatic stability of the electrophotographic photosensitive member is significantly impaired. Further, when the ratio of the average particle diameter of the other titanium oxide (T2) to the average particle diameter of one titanium oxide (T1) is too large (D2 / D1> 0.5), the hiding power to the conductive substrate is lowered. In addition, the suppression of moiré and abnormal images is reduced. The average particle size mentioned here is obtained from a particle size distribution measurement obtained when strong dispersion is performed in an aqueous system.

  Further, the average particle size (D2) of titanium oxide (T2) having a smaller particle size is an important factor, and it is important that 0.05 μm <D2 <0.20 μm. When the thickness is 0.05 μm or less, the hiding power is reduced, and moire may be generated. On the other hand, when the thickness is 0.20 μm or more, the filling rate of titanium oxide in the moire preventing layer is lowered, and the background stain suppressing effect cannot be sufficiently exhibited.

  The mixing ratio (weight ratio) of the two types of titanium oxide is also an important factor. When T2 / (T1 + T2) is smaller than 0.2, the filling rate of titanium oxide is not so large and the effect of suppressing soiling cannot be sufficiently exhibited. On the other hand, when it is larger than 0.8, the concealing power is reduced, and moire may be generated. Therefore, it is important that 0.2 ≦ T2 / (T1 + T2) ≦ 0.8.

  The thickness of the moire preventing layer is 1 to 10 μm, preferably 2 to 5 μm. If the film thickness is less than 1 μm, the effect is small, and if it exceeds 10 μm, residual potential is accumulated, which is not desirable.

  The inorganic pigment is dispersed together with a solvent and a binder resin by a conventional method, for example, a ball mill, a sand mill, an attrier, etc., and if necessary, a chemical, a solvent, an additive, a curing accelerator, etc. necessary for curing (crosslinking) are added. In general, it is formed on the substrate by blade coating, dip coating, spray coating, beat coating, nozzle coating or the like. After the coating, it is dried or cured by a curing process such as drying, heating, or light.

<Photosensitive layer>
Next, the photosensitive layer will be described.
The photosensitive layer in the present invention is composed of a laminated structure of a charge generation layer (35) and a charge transport layer (37).
That is, the charge generation layer (35) is a layer mainly composed of at least one of naphthalenetetracarboxylic acid diimidazole pigments represented by the general formula (1) or (2) as a charge generation material. . Using one of the naphthalenetetracarboxylic acid diimidazole pigments represented by the general formula (1) or (2) in a suitable solvent together with a binder resin, if necessary, using a ball mill, attritor, sand mill, ultrasonic wave, etc. It is formed by coating and dispersing on a conductive support or an intermediate layer and drying.

  The binder resin used in the charge generation layer as necessary includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, and poly-N-vinyl. Examples include carbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, and the like. . The amount of the binder resin is suitably 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generating material.

  Examples of the solvent used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like. . As a coating method for the coating solution, a dip coating method, spray coating, beat coating, nozzle coating, spinner coating, ring coating, or the like can be used. The thickness of the charge generation layer is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm.

  At least one of the naphthalenetetracarboxylic acid diimidazole pigments represented by the above general formula (1) or (2) is described in Patent Document 13 described above.

In the general formula (1) or (2), examples of the divalent aromatic hydrocarbon group represented by A and B include groups such as o-phenylene, o-naphthylene, perinaphthylene, and 1,2-anthrylene. Examples of the nitrogen-containing heterocyclic group include divalent groups such as 3,4-pyrazolediyl, 2,3-pyridinediyl, 4,5-pyridinediyl, 6,7-imidazolediyl and 6,7-quinolinediyl. .
Examples of the substituent that the above group may have include alkyl groups such as methyl, ethyl, propyl and butyl, alkoxy groups such as methoxy, ethoxy and propoxy, halogen atoms such as fluorine atom, chlorine atom and bromine atom, dimethylamino And a dialkylamino group such as diethylamino, a hydroxyl group, a nitro group, a cyano group, and a halomethyl group.

  Tables 1 and 2 below show at least one suitable example of the naphthalenetetracarboxylic acid diimidazole pigment represented by either the general formula (1) or (2) used as the charge generation material of the present invention.

In at least one of the charge generating materials contained in the electrophotographic photosensitive member of the present invention, that is, the naphthalene tetracarboxylic acid diimidazole pigment represented by the general formula (1) or (2), charge generation is performed. The effect is expressed by making the average particle size of the substance finer, and the average particle size is preferably 0.25 μm or less, more preferably 0.2 μm or less. The manufacturing method is shown below.
The method for controlling the average particle size of the charge generating material contained in the photosensitive layer is a method of removing coarse particles larger than 0.25 μm after dispersing the charge generating material.

The average particle size referred to here is a volume average particle size and is determined by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba, Ltd.). At this time, the particle diameter (Median diameter) corresponding to 50% of the cumulative distribution was calculated.
However, this method may not be able to detect a minute amount of coarse particles, and in order to obtain more details, it is important to directly observe the charge generating material powder or dispersion with an electron microscope and obtain the size. It is.

  As a result of further observation of the dispersion and examination of micro defects, the above phenomenon was understood as follows. Usually, in the method of measuring the average particle size, when an extremely large particle is present in several% or more, the presence can be detected, but it is about 1% or less of the whole. When the amount is too small, the measurement is below the detection limit. As a result, the presence of coarse particles is not detected only by measuring the average particle size, making it difficult to interpret the above minute defects.

  FIG. 8 and FIG. 9 show photographs observing the state of two types of dispersions in which only the dispersion time is changed while fixing the dispersion conditions. A photograph of a dispersion liquid having a short dispersion time under the same conditions is shown in FIG. 8, and it is observed that coarse particles remain as compared with FIG. 9 having a long dispersion time. Black particles in FIG. 8 are coarse particles.

The average particle size and particle size distribution of these two types of dispersions were measured according to a known method using a commercially available particle size distribution measuring device (manufactured by Horiba: ultracentrifugal automatic particle size distribution measuring device, CAPA700).
The result is shown in FIG. “A” in FIG. 10 corresponds to the dispersion shown in FIG. 8, and “B” corresponds to the dispersion shown in FIG. When both are compared, there is almost no difference in the particle size distribution. In addition, the average particle diameter values of the two are “A” of 0.29 μm and “B” of 0.28 μm, and taking into account measurement errors, there is no difference between the two.
Accordingly, it is understood that the remaining of a minute amount of coarse particles cannot be detected only by the definition of the known average particle size (particle size), and it is not possible to cope with the recent high-resolution negative / positive development. The presence of such a minute amount of coarse particles can be recognized for the first time by observing the coating solution at the microscope level.

Next, a method of removing coarse particles after dispersing a charge generating material (at least one of naphthalenetetracarboxylic acid diimidazole pigments represented by either general formula (1) or (2)) will be described.
For the preparation of the dispersion, a general method is used, and at least one of the naphthalene tetracarboxylic acid diimidazole pigments represented by either the general formula (1) or (2) is optionally combined with a binder resin. It can be obtained by dispersing in a suitable solvent using a ball mill, attritor, sand mill, bead mill, ultrasonic wave or the like. At this time, the binder resin may be selected depending on the electrostatic characteristics of the photoreceptor, and the solvent may be selected depending on the wettability to the pigment, the dispersibility of the pigment, and the like.

That is, it is a method in which a dispersion liquid with as fine a particle as possible is prepared and then filtered through an appropriate filter. This method is a very effective means from the viewpoint that even a minute amount of coarse particles that cannot be visually observed or that cannot be detected by particle size measurement can be removed, and that the particle size distribution is uniform.
Specifically, the dispersion prepared as described above is filtered through a filter having an effective pore size of 5 μm or less, more preferably 3 μm or less, thereby completing the dispersion. Also by this method, a dispersion containing only pigment particles having a small particle size (0.25 μm or less, preferably 0.2 μm or less) can be produced, and a photoconductor using the dispersion is mounted on an image forming apparatus. This makes the effect of the present application more remarkable.

  At this time, if the particle size of the dispersion to be filtered is too large or the particle size distribution is too wide, the loss due to filtration may increase, or clogging may occur and filtration may become impossible. There is a case. For this reason, in the dispersion before filtration, it is desirable to perform dispersion until the average particle size reaches 0.3 μm or less and the standard deviation reaches 0.2 μm or less. When the average particle size is 0.3 μm or more, the loss due to filtration increases, and when the standard deviation is 0.2 μm or more, there may be a problem that the filtration time becomes very long.

  The charge generation material used in the present invention has an extremely strong intermolecular hydrogen bonding force, which is a feature of the charge generation material exhibiting highly sensitive characteristics. For this reason, the interaction between the dispersed pigment particles is very strong. As a result, there is a great possibility that the charge generation material particles dispersed by a disperser or the like will re-aggregate due to dilution or the like. Such agglomerates can be removed. At this time, since the dispersion is in a thixotropic state, particles having a size smaller than the effective pore size of the filter to be used are removed. Or the liquid which shows structural viscosity can also be changed into the state close | similar to Newton property by a filter process. In this way, the effect of the present invention is remarkably improved by removing the coarse particles of the charge generation material.

  The filter for filtering the dispersion varies depending on the size of coarse particles to be removed, but according to the study by the present inventors, as a photoreceptor used in an electrophotographic apparatus that requires a resolution of about 600 dpi. The presence of coarse particles of at least 3 μm affects the image. Therefore, a filter with an effective pore size of 5 μm or less should be used. More preferably, a filter having an effective pore size of 3 μm or less is used.

  As for the effective pore size, the finer the particle, the more effective the removal of coarse particles. However, if the particle size is too fine, the necessary pigment particles themselves are also filtered, and therefore there is an appropriate size. In addition, if it is too fine, it takes time for filtration, clogging of the filter, and too much load when liquid is sent using a pump or the like. As a matter of course, a material having resistance to the solvent used in the dispersion to be filtered is used as the material of the filter used here.

<Charge transport layer>
The charge transport layer (37) can be formed by dissolving or dispersing a charge transport material and a binder resin in a suitable solvent, and applying and drying the solution on the charge generation layer. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.
Charge transport materials include hole transport materials and electron transport materials.

  Examples of hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc., bis-stilbene derivatives, enamine derivatives, etc. Knowledge materials are mentioned. These charge transport materials may be used alone or in combination of two or more.

  Examples of the electron transport material include chloroanil, bromanyl, 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] thiophen-4-one, 1,3,7- Examples thereof include electron-accepting substances such as trinitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives.

As the binder resin, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, Polyvinylidene chloride, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol Examples thereof include thermoplastic or thermosetting resins such as resins and alkyd resins.
The amount of the charge transport material is appropriately 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the charge transport layer is preferably about 5 to 100 μm.

  As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used. Among them, the use of a non-halogen solvent is desirable for the purpose of reducing the environmental load. Specifically, cyclic ethers such as tetrahydrofuran, dioxolane and dioxane, aromatic hydrocarbons such as toluene and xylene, and derivatives thereof are preferably used.

  This is not a problem when the photosensitive layer has a single layer structure or when a charge generation layer is formed on the charge transport layer, but in the case of a photosensitive layer that forms a charge transport layer on the charge generation layer, an appropriate charge transport material is used. If is not selected, there are cases where the static elimination light does not reach the charge generation layer sufficiently and the static elimination action does not work clearly. In addition, there is a case where the charge transport material is easily deteriorated by absorbing the static elimination light, and conversely, a residual potential rise is generated. For this reason, in the case of the laminated structure of the present invention, the charge transport layer has a transmittance of 30% or more, preferably 50% or more, and more desirably 85% or more.

In order to set the charge transport layer to such a condition, it is important to select a charge transport material appropriate for the static elimination light and form the charge transport layer. Among the charge transport materials described above, a charge transport material having a triarylamine skeleton is suitable as a charge transport material for use in the photoreceptor of the present invention because it easily transmits static elimination light of less than 480 nm and has high mobility. It is.
Among charge transport materials having a triarylamine skeleton, a charge transport material represented by the following general formula (5) is particularly effectively used. A method for synthesizing this material is described in JP-A-2-36156. Moreover, it is possible to use the material illustrated by the gazette.

In the formula, R ₃₀₁ , R ₃₀₃ and R ₃₀₄ are a hydrogen atom, an amino group, an alkoxy group, a thioalkoxy group, an aryloxy group, a methylenedioxy group, an unsubstituted alkyl group, a halogen atom, or a substituted or unsubstituted aryl group. R ₃₀₂ represents a hydrogen atom, an alkoxy group, a substituted or unsubstituted alkyl group or halogen. K, l, m and n are integers of 1, 2, 3 or 4, and when each is an integer of 2, 3 or 4, the R ₃₀₁ , R ₃₀₂ , R ₃₀₃ and R ₃₀₄ are the same or different. May be.

  In addition, a polymer charge transport material having a function as a charge transport material and a function of a binder resin is also preferably used for the charge transport layer. The charge transport layer composed of these polymer charge transport materials is excellent in wear resistance. As the polymer charge transport material, known materials can be used, and in particular, a polycarbonate containing a triarylamine structure in the main chain and / or side chain is preferably used. Among these, the polymer charge transport materials represented by the following general formulas (I) to (X) exemplified below are preferably used.

[Wherein R ₁ , R ₂ and R ₃ are each independently a substituted or unsubstituted alkyl group or a halogen atom, R ₄ is a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₅ and R ₆ are substituted or Unsubstituted aryl group, o, p and q are each independently an integer of 0 to 4, k and j represent a composition, 0.1 ≦ k ≦ 1, 0 ≦ j ≦ 0.9, and n is a repeating unit It represents a number and is an integer from 5 to 5000. X is an aliphatic divalent group, a cycloaliphatic divalent group, or the following general formula (I-1):

[Wherein, R ₁₀₁ and R ₁₀₂ each independently represents a substituted or unsubstituted alkyl group, aryl group or halogen atom. l and m are integers of 0 to 4, Y is a single bond, a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, —O—, —S—, —SO—, —SO ₂ —. , -CO-, -CO-O-Z-O-CO- (wherein Z represents an aliphatic divalent group) or the following general formula (I-2):

(Wherein, a represents an integer of 1 to 20, b represents an integer of 1 to 2000, R ₁₀₃ and R ₁₀₄ represent a substituted or unsubstituted alkyl group or an aryl group). The divalent group represented by this is represented. Here, R ₁₀₁ and R ₁₀₂ , and R ₁₀₃ and R ₁₀₄ may be the same or different.

  In the general formula (I), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₇ and R ₈ represent a substituted or unsubstituted aryl group, and Ar ₁ , Ar ₂ , and Ar ₃ represent the same or different arylene groups. X, k, j and n are the same as those in the general formula (I).
In the general formula (II), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₉ and R ₁₀ represent a substituted or unsubstituted aryl group, and Ar ₄ , Ar ₅ and Ar ₆ represent the same or different arylene groups. X, k, j and n are the same as those in the general formula (I).
In the general formula (III), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₁ and R ₁₂ are substituted or unsubstituted aryl groups, Ar ₇ ,
Ar ₈ and Ar ₉ are the same or different arylene groups, and p represents an integer of 1 to 5. X, k, j and n are the same as those in the general formula (I).
In the general formula (IV), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₃ and R ₁₄ are substituted or unsubstituted aryl groups, Ar ₁₀ , Ar ₁₁ and Ar ₁₂ are the same or different arylene groups, X ₁ and X ₂ are substituted or unsubstituted ethylene groups, or substituted or unsubstituted Represents a substituted vinylene group. X, k, j and n are the same as those in the general formula (I).
In the general formula (V), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ are substituted or unsubstituted aryl groups, Ar ₁₃ , Ar ₁₄ , Ar ₁₅ and Ar ₁₆ are the same or different arylene groups, and Y ₁ , Y ₂ and Y ₃ are A single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group may be the same or different. X, k, j and n are the same as those in the general formula (I). In the general formula (VI), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₉ and R _{20 each} represent a hydrogen atom or a substituted or unsubstituted aryl group, and R ₁₉ and R ₂₀ may form a ring. Ar ₁₇ , Ar ₁₈ , Ar ₁₉ represent the same or different arylene groups. X, k, j and n are the same as those in the general formula (I).
In the general formula (VII), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₂₁ represents a substituted or unsubstituted aryl group, and Ar ₂₀ , Ar ₂₁ , Ar ₂₂ , and Ar ₂₃ represent the same or different arylene groups. Y represents a divalent alkylene group.
X, k, j and n are the same as those in the general formula (I).
In the general formula (VIII), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₂₂ , R ₂₃ , R ₂₄ and R ₂₅ represent a substituted or unsubstituted aryl group, and Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ and Ar ₂₈ represent the same or different arylene groups. X, k, j and n are the same as those in the general formula (I).
In the general formula (IX), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₂₆ and R ₂₇ represent a substituted or unsubstituted aryl group, and Ar ₂₉ , Ar ₃₀ and Ar ₃₁ represent the same or different arylene groups. X, k, j and n are the same as those in the general formula (I).
In the general formula (X), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

  Further, as the polymer charge transport material used in the charge transport layer, in addition to the polymer charge transport material described above, in the state of the monomer or oligomer having an electron donating group at the time of film formation of the charge transport layer, A polymer having a two-dimensional or three-dimensional crosslinked structure is finally included by carrying out a curing reaction or a crosslinking reaction.

Furthermore, a charge transport layer having a crosslinked structure is also effectively used as the charge transport layer.
Regarding the formation of a cross-linked structure, a reactive monomer having a plurality of cross-linkable functional groups in one molecule is used to cause a cross-linking reaction using light or thermal energy to form a three-dimensional network structure. is there. This network structure functions as a binder resin and exhibits high wear resistance.

  Moreover, it is a very effective means to use a monomer having a charge transporting ability in whole or in part as the reactive monomer. By using such a monomer, a charge transport site is formed in the network structure, and the function as the charge transport layer can be sufficiently expressed. A reactive monomer having a triarylamine structure is effectively used as the monomer having charge transporting ability.

  The charge transport layer having such a network structure has high wear resistance, but has a large volume shrinkage during the crosslinking reaction, and if it is too thick, cracks may occur. In such a case, the charge transport layer has a laminated structure, the lower layer (charge generation layer side) uses a low molecular dispersion polymer charge transport layer, and the upper layer (surface side) has a cross-linked structure. It may be formed.

A charge transport layer composed of a polymer having these electron donating groups or a polymer having a crosslinked structure is excellent in wear resistance.
Usually, in the electrophotographic process, since the charging potential (unexposed portion potential) is constant, if the surface layer of the photoreceptor is worn by repeated use, the electric field strength applied to the photoreceptor increases accordingly. As the electric field strength increases, the occurrence frequency of scumming increases. Therefore, the high wear resistance of the photosensitive member is advantageous for scumming.
The charge transport layer composed of a polymer having these electron donating groups is a polymer compound, so it has excellent film-forming properties and has a charge transport site compared to a charge transport layer composed of a low molecular weight dispersed polymer. It can be configured with high density and has excellent charge transport capability. For this reason, the photoconductor having the charge transport layer 8 using the polymer charge transport material can be expected to have high-speed response.

  As other polymers having electron donating groups, copolymers of known monomers, block polymers, graft polymers, star polymers, cross-linked polymers having electron donating groups, and the like can be used. It is.

In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer.
As the plasticizer, those used as general plasticizers such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is suitably about 0 to 30% by weight based on the binder resin.
As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain are used, and the amount used is 0 to 0 with respect to the binder resin. 1% by weight is suitable.
Even in the charge transport layer containing the polymer charge transport material as described above, it is important to transmit the static elimination light at 30% or more, preferably 50% or more.

<Protective layer>
In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. In recent years, computers have been used on a daily basis, and there has been a demand for miniaturization of devices as well as high-speed output by printers. Therefore, by providing a protective layer and improving the durability, it is possible to use the photosensitive member of the present invention with high sensitivity and no abnormal defects.

The effective protective layer used in the present invention is roughly classified into two types. One is a configuration in which a filler is added to the binder resin. The other one uses a cross-linking binder.
First, a configuration in which a filler is added to the protective layer will be described.
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, polyarylate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polychlorinated Examples thereof include resins such as vinyl, polyvinylidene chloride, and epoxy resin. Of these, polycarbonate or polyarylate can be most preferably used.

  Other protective layers include fluorine resins such as polytetrafluoroethylene, silicone resins, and inorganic fillers such as titanium oxide, tin oxide, potassium titanate, and silica for the purpose of improving wear resistance. What disperse | distributed the filler etc. can be added.

  Among the filler materials used for the protective layer of the photoreceptor, examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, a-carbon powder, and the like. Metal powders such as copper, tin, aluminum and indium, metal oxides such as silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, tin oxide doped with antimony, tin-doped indium oxide And inorganic materials such as potassium titanate. In particular, it is advantageous to use an inorganic material among them from the viewpoint of the hardness of the filler. In particular, inorganic pigments and metal oxides are preferable, and silica, titanium oxide, and alumina can be used effectively.

  The filler concentration in the protective layer varies depending on the type of filler used and also on the electrophotographic process conditions using the photoconductor, but the ratio of filler to the total solid content on the outermost layer side of the protective layer is preferably 5% by weight or more, preferably It is 10% by weight or more and 50% by weight or less, preferably about 30% by weight or less. Moreover, the volume average particle diameter of the filler to be used is preferably in the range of 0.1 μm to 2 μm, and preferably in the range of 0.3 μm to 1 μm. In this case, if the average particle size is too small, the wear resistance is not sufficiently exhibited, and if it is too large, the surface property of the coating film is deteriorated or the coating film itself cannot be formed.

  The average particle size of the filler in the present invention is a volume average particle size unless otherwise specified, and was determined by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba, Ltd.) as described above. Is. At this time, the particle diameter (Median diameter) corresponding to 50% of the cumulative distribution was calculated. In addition, it is important that the standard deviation of each particle measured simultaneously is 1 μm or less. If the standard deviation is larger than this, the particle size distribution may be too wide, and the effects of the present invention may not be obtained remarkably.

  Further, the pH of the filler used in the present invention greatly affects the resolution and the dispersibility of the filler. One possible reason is that hydrochloric acid or the like remains in the filler, particularly the metal oxide, during production. When the remaining amount is large, the occurrence of image blur is unavoidable, and depending on the remaining amount, the dispersibility of the filler may be affected.

Another reason is due to the difference in chargeability on the surface of the filler, particularly the metal oxide. Usually, particles dispersed in a liquid are charged positively or negatively, and ions having opposite charges gather to try to keep it electrically neutral, and an electric double layer is formed there. The dispersed state of the particles is stabilized. The potential (zeta potential) gradually decreases with increasing distance from the particle, and the potential in a region that is sufficiently away from the particle and electrically neutral is zero. Therefore, the stability increases as the repulsive force of the particles increases due to the increase in the absolute value of the zeta potential, and the particles tend to aggregate and become unstable as they approach zero.
On the other hand, the zeta potential varies greatly depending on the pH value of the system, and at a certain pH value, the potential becomes zero and has an isoelectric point. Therefore, the dispersion system is stabilized by increasing the absolute value of the zeta potential as far as possible from the isoelectric point of the system.

In the configuration of the present invention, the filler having a pH at the isoelectric point of at least 5 is preferably from the viewpoint of image blur suppression, and the more basic the filler, the higher the effect. It was confirmed that there was. A filler exhibiting basicity having a high pH at the isoelectric point has a higher zeta potential when the system is acidic, thereby improving dispersibility and its stability.
Here, the pH of the filler in the present invention is the pH value at the isoelectric point from the zeta potential. At this time, the zeta potential was measured with a laser zeta potentiometer manufactured by Otsuka Electronics Co., Ltd.

Further, as a filler that is less likely to cause image blur, a filler having a high electrical insulation property with a specific resistance of 10 ¹⁰ Ω · cm or more is preferable, and a filler having a pH of 5 or more, or a dielectric constant of the filler of 5 or more. Can be used particularly effectively.
In addition, a filler having a pH of 5 or more or a filler having a dielectric constant of 5 or more can be used alone, or two or more fillers having a pH of 5 or less and a filler having a pH of 5 or more can be mixed. It is also possible to use a mixture of two or more fillers having a dielectric constant of 5 or less and a filler having a dielectric constant of 5 or more. Among these fillers, α-type alumina, which has high insulation properties, high thermal stability, and high wear resistance, is a hexagonal close-packed structure, from the viewpoint of suppressing image blur and improving wear resistance. It is particularly useful.

The specific resistance of the filler used in the present invention is defined as follows. Since the specific resistance value of a powder such as a filler varies depending on the filling rate, it is necessary to measure under certain conditions.
In the present invention, the specific resistance value of the filler was measured using an apparatus having the same configuration as the measuring apparatus disclosed in JP-A-5-113688 (FIG. 1), and this value was used. In the measuring apparatus, the electrode area is 4.0 cm ² . Prior to the measurement, a load of 4 kg is applied to the electrode on one side for 1 minute, and the sample amount is adjusted so that the distance between the electrodes is 4 mm. At the time of measurement, the measurement is performed with the upper electrode weight (1 kg) loaded, and the applied voltage is measured at 100V. The area of 10 ⁶ Ω · cm or higher was measured with a HIGH RESISTER METER (Yokogawa Hewlett Packard), and the area below it was measured with a digital multimeter (Fluk). The specific resistance value thus obtained is defined as the specific resistance value in the present invention.

  The dielectric constant of the filler was measured as follows. Using a cell similar to the measurement of the specific resistance as described above, after applying a load, the capacitance was measured, and the dielectric constant was determined from this. For the measurement of the capacitance, a dielectric loss measuring device (Ando Electric) was used.

  Further, these fillers can be surface-treated with at least one kind of surface treatment agent, and it is preferable from the viewpoint of dispersibility of the fillers. Lowering the dispersibility of the filler not only increases the residual potential, but also lowers the transparency of the coating film, causes defects in the coating film, and lowers the abrasion resistance. It can develop into a big problem to hinder.

As the surface treatment agent, all conventionally used surface treatment agents can be used, but a surface treatment agent capable of maintaining the insulating properties of the filler is preferable.
For example, titanate coupling agents, aluminum coupling agents, zircoaluminate coupling agents, higher fatty acids, etc., or mixed treatments of these with silane coupling agents, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Silicone, aluminum stearate, or the like, or a mixture thereof is more preferable from the viewpoint of filler dispersibility and image blur.
The treatment with the silane coupling agent is strongly influenced by image blur, but the influence may be suppressed by performing a mixing treatment of the surface treatment agent and the silane coupling agent.

The surface treatment amount varies depending on the average primary particle size of the filler used, but is preferably 3 to 30 wt%, more preferably 5 to 20 wt%. If the surface treatment amount is less than this, the filler dispersion effect cannot be obtained, and if it is too much, the residual potential is significantly increased. These filler materials may be used alone or in combination of two or more. The surface treatment amount of the filler is defined by the weight ratio of the surface treatment agent to be used with respect to the filler amount as described above.
These filler materials can be dispersed by using an appropriate disperser. Further, from the viewpoint of the transmittance of the protective layer, it is preferable that the filler used is dispersed to the primary particle level and has less aggregates.

Further, the protective layer may contain a charge transport material for reducing residual potential and improving responsiveness.
As the charge transport material, the materials described in the description of the charge transport layer can be used. When a low molecular charge transport material is used as the charge transport material, a concentration gradient in the protective layer may be provided. In order to improve wear resistance, it is an effective means to reduce the concentration of the surface side.
The concentration here means the ratio of the weight of the low-molecular charge transporting substance to the total weight of all the materials constituting the protective layer, and the concentration gradient is a gradient that lowers the concentration on the surface side in the above weight ratio. It shows that. The use of a polymer charge transport material is very advantageous in terms of enhancing the durability of the photoreceptor.

In addition, as the binder resin for the protective layer, the polymer charge transport material described in the section of the charge transport layer can also be used. As the effect when this is used, the effect of improving the wear resistance and the high-speed charge transport can be obtained as described in the section of the charge transport layer.
As a method for forming such a protective layer, a normal coating method is employed. In addition, about 0.1-10 micrometers is suitable for the thickness of the protective layer mentioned above.

Next, a protective layer having a crosslinked structure will be described as a binder structure of the protective layer (hereinafter referred to as a crosslinked protective layer).
Regarding the formation of a cross-linked structure, a reactive monomer having a plurality of cross-linkable functional groups in one molecule is used to cause a cross-linking reaction using light or thermal energy to form a three-dimensional network structure. is there. This network structure functions as a binder resin and exhibits high wear resistance.

  Moreover, it is a very effective means to use a monomer having a charge transporting ability in whole or in part as the reactive monomer. By using such a monomer, a charge transporting site is formed in the network structure, and the function as a protective layer can be sufficiently expressed. A reactive monomer having a triarylamine structure is effectively used as the monomer having charge transporting ability.

The protective layer having such a network structure has high wear resistance, but has a large volume shrinkage during the crosslinking reaction, and if it is too thick, it may cause cracks. In such a case, the protective layer may be a laminated structure, a low molecular dispersion polymer protective layer may be used for the lower layer (photosensitive layer side), and a protective layer having a crosslinked structure may be formed on the upper layer (surface side). Good.
Among the crosslinked protective layers, a protective layer having the following specific structure is particularly effectively used.

The specific crosslinkable protective layer is a protection formed by curing at least a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. Is a layer.
The specific cross-linkable protective layer has a cross-linked structure obtained by curing a tri- or higher-functional radical polymerizable monomer, so that a three-dimensional network structure is developed, and a high hardness and high elasticity surface layer having a very high cross-linking density is obtained. In addition, it is uniform and smooth, and high wear resistance and scratch resistance are achieved.
As described above, it is important to increase the crosslink density on the surface of the photoreceptor, that is, the number of crosslink bonds per unit volume. However, since a large number of bonds are instantaneously formed in the curing reaction, internal stress due to volume shrinkage occurs. This internal stress increases as the thickness of the crosslinkable protective layer increases. Therefore, when the entire protective layer is cured, cracks and film peeling tend to occur. Even if this phenomenon does not appear initially, it may be likely to occur over time due to repeated use in the electrophotographic process and the influence of charging, development, transfer, cleaning hazards and thermal fluctuations.

As a method for solving this problem, (1) a polymer component is introduced into the crosslinked layer and the crosslinked structure, (2) a large amount of monofunctional and bifunctional radically polymerizable monomers are used, and (3) a flexible group is introduced. Although the directionality which makes a cured resin layer soft, such as using the polyfunctional monomer which has, is mentioned, the crosslink density of a bridge | crosslinking layer becomes thin in any case, and remarkable wear resistance is not achieved.
On the other hand, the photoreceptor of the present invention is preferably provided with a cross-linking protective layer having a high cross-linking density in which a three-dimensional network structure is developed on the charge transport layer, preferably with a film thickness of 1 μm or more and 10 μm or less. Cracks and film peeling do not occur, and very high wear resistance is achieved. By making the film thickness of the crosslinkable protective layer 2 μm or more and 8 μm or less, in addition to further improving the margin for the above problem, it is possible to select a material for increasing the crosslink density that leads to further improvement in wear resistance. It becomes possible.

The reason why the photoconductor of the present invention can suppress cracks and film peeling is that the crosslinkable protective layer can be made thin, so that the internal stress does not increase, and the lower layer has a photosensitive layer or charge transport layer, so that the surface is a crosslinkable protective layer. This is because the internal stress can be relaxed.
For this reason, it is not necessary to contain a large amount of polymer material in the crosslinkable protective layer, and the polymer material and radical polymerizable composition (radical polymerizable monomer or radical polymerizable compound having a charge transporting structure) generated at this time. Scratches and toner filming due to incompatibility with the cured product resulting from this reaction are unlikely to occur.

  Furthermore, when the thick film over the entire protective layer is cured by irradiation with light energy, the light transmission from the absorption by the charge transporting structure is limited, and the curing reaction may not sufficiently proceed. In the crosslinkable protective layer of the present invention, preferably a thin film having a thickness of 10 μm or less causes a uniform curing reaction to proceed to the inside, and high wear resistance is maintained inside as well as the surface. In addition, in the formation of the crosslinkable protective layer of the present invention, in addition to the trifunctional radical polymerizable monomer, a radical polymerizable compound having a monofunctional charge transporting structure is contained, which is the trifunctional or higher functional group. These radically polymerizable monomers are incorporated into the cross-linking during curing.

  On the other hand, when a low molecular charge transport material having no functional group is contained in the crosslinked surface layer, precipitation of low molecular charge transport material and white turbidity occur due to its low compatibility, and Mechanical strength also decreases. On the other hand, when a bifunctional or higher-functional charge transporting compound is used as the main component, the crosslink structure is fixed by a plurality of bonds and the crosslink density is further increased. Becomes very large, which increases the internal stress of the crosslinked protective layer.

Furthermore, the photoconductor of the present invention has good electrical characteristics, and therefore has excellent repetitive stability, realizing high durability and high stability.
This is because a radical polymerizable compound having a monofunctional charge transporting structure is used as a constituent material of the crosslinkable protective layer and is immobilized in a pendant shape between the crosslinks.
As described above, the charge transport material having no functional group causes precipitation and clouding phenomenon, and the electrical characteristics are remarkably deteriorated in repeated use such as a decrease in sensitivity and an increase in residual potential. When a bifunctional or higher-functional charge transporting compound is used as the main component, it is fixed in the crosslinked structure with a plurality of bonds, so the intermediate structure (cation radical) during charge transport cannot be kept stable, Sensitivity decreases due to traps and residual potential increases. Such deterioration of the electric characteristics appears as an image such as a decrease in image density and thinning of characters. Further, in the photoreceptor of the present invention, the high charge mobility design with less charge trapping of the conventional photoreceptor can be applied as the lower charge transport layer, and the electrical side effects of the crosslinked protective layer can be minimized. .

Furthermore, in the formation of the above-mentioned crosslinkable protective layer of the present invention, particularly rapid wear resistance is exhibited by making the crosslinkable protective layer insoluble in an organic solvent.
The crosslinkable protective layer of the present invention is formed by curing a tri- or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure as described above. The layer as a whole has a three-dimensional network structure and a high crosslink density, but contains other than the above components, such as mono- or bifunctional monomers, polymer binders, antioxidants, leveling agents, plasticizers, etc. Depending on the additive and the components mixed and dissolved from the lower layer and the curing conditions, the crosslink density may become locally dilute or may be formed as an aggregate of minute cured products cross-linked with high density. Such a crosslinkable protective layer is weak in bonding strength between cured products and is soluble in organic solvents, and is repeatedly used in the electrophotographic process. Desorption in units tends to occur.
However, by making the crosslinkable protective layer insoluble in an organic solvent as in the present invention, the original three-dimensional network structure develops and has a high degree of crosslinking, and the chain reaction proceeds in a wide range and cures. Since the material has a high molecular weight, a dramatic improvement in wear resistance is achieved.

Next, the constituent material of the crosslinking type protective layer coating solution of the present invention will be described.
The trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the present invention is, for example, a hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole, or the like, for example, condensed polycyclic quinone or diphenoquinone. And a monomer having no electron transport structure such as an electron-withdrawing aromatic ring having a cyano group or a nitro group and having three or more radically polymerizable functional groups. The radical polymerizable functional group may be any group as long as it has a carbon-carbon double bond and is capable of radical polymerization. Examples of these radical polymerizable functional groups include 1-substituted ethylene functional groups and 1,1-substituted ethylene functional groups.

Examples of the 1-substituted ethylene functional group include a functional group represented by the following general formula (10).
CH ₂ = CH-X _1- (10)

In Formula 10, X ₁ is an arylene group such as an optionally substituted phenylene group or naphthylene group, an alkenylene group optionally having a substituent, a —CO— group, a —COO— group. , —CON (R ₁₀ ) — group (R ₁₀ represents an alkyl group such as hydrogen, methyl group or ethyl group, an aralkyl group such as benzyl group, naphthylmethyl group or phenethyl group, or an aryl group such as phenyl group or naphthyl group. Or -S- group.

  Specific examples of these functional groups include vinyl group, styryl group, 2-methyl-1,3-butadienyl group, vinylcarbonyl group, acryloyloxy group, acryloylamide group, vinylthioether group and the like.

Examples of the 1,1-substituted ethylene functional group include a functional group represented by the following general formula (11).
CH ₂ = C (Y) -X _2- (11)

However, in formula (11), Y represents an alkyl group which may have a substituent, an aralkyl group which may have a substituent, a phenyl group which may have a substituent, a naphthyl group, and the like. Aryl group, halogen atom, cyano group, nitro group, alkoxy group such as methoxy group or ethoxy group, -COOR ₁₁ group [R ₁₁ is a hydrogen atom, an optionally substituted methyl group, ethyl group, etc. An alkyl group, an aralkyl group such as benzyl or phenethyl group which may have a substituent, an aryl group such as a phenyl group or naphthyl group which may have a substituent, or -CONR ₁₂ R ₁₃ (R ₁₂ And R ₁₃ represents a hydrogen atom, an alkyl group such as an optionally substituted methyl group or an ethyl group, an aralkyl group such as an optionally substituted benzyl group, naphthylmethyl group, or phenethyl group. , Ma It is a phenyl group which may have a substituent, an aryl group such as a naphthyl group, a mutually identical or may be different.). ] Is represented. X ₂ represents the same substituent, single bond, and alkylene group as X _{1 in the} formula (10). However, at least one of Y and X ₂ is an oxycarbonyl group, a cyano group, an alkenylene group, or an aromatic ring.

Specific examples of these functional groups include an α-acryloyloxy chloride group, a methacryloyloxy group, an α-cyanoethylene group, an α-cyanoacryloyloxy group, an α-cyanophenylene group, and a methacryloylamino group.
In addition, examples of the substituent further substituted with the substituent for X ₁ , X ₂ , and Y include, for example, a halogen atom, a nitro group, a cyano group, a methyl group, an alkyl group such as an ethyl group, a methoxy group, and an ethoxy group. And aryloxy groups such as phenoxy group, aryl groups such as phenyl group and naphthyl group, and aralkyl groups such as benzyl group and phenethyl group.

  Among these radical polymerizable functional groups, acryloyloxy group and methacryloyloxy group are particularly useful, and a compound having three or more acryloyloxy groups is, for example, a compound having three or more hydroxyl groups in the molecule and an acrylic group. It can be obtained by using an acid (salt), an acrylic acid halide, or an acrylic ester to cause an ester reaction or a transesterification reaction. A compound having three or more methacryloyloxy groups can be obtained in the same manner. Further, the radical polymerizable functional groups in the monomer having three or more radical polymerizable functional groups may be the same or different.

Specific examples of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure include the following, but are not limited to these compounds.
That is, examples of the radical polymerizable monomer used in the present invention include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, trimethylolpropane alkylene-modified triacrylate, trimethylolpropane ethyleneoxy-modified (hereinafter referred to as EO-modified). ) Triacrylate, trimethylolpropane propyleneoxy modified (hereinafter PO modified) triacrylate, trimethylolpropane caprolactone modified triacrylate, trimethylolpropane alkylene modified trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETTA), glycerol triacrylate Glycerol epichlorohydrin modified (hereinafter ECH modified) tria Relate, glycerol EO modified triacrylate, glycerol PO modified triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), dipentaerythritol caprolactone modified hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkylated di Pentaerythritol pentaacrylate, alkylated dipentaerythritol tetraacrylate, alkylated dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, phosphoric acid EO-modified triacrylate, 2, 2, 5, 5 , -Tetrahydroxymethylcyclopentanone tetraacrylate And the like, which can be used in combination either alone or in combination.

  The trifunctional or higher functional radical polymerizable monomer having no charge transport structure used in the present invention has a molecular weight relative to the number of functional groups in the monomer in order to form a dense crosslink in the crosslinkable protective layer. The ratio (molecular weight / functional group number) is preferably 250 or less. On the other hand, if this ratio is larger than 250, the crosslinked protective layer tends to be soft and wear resistance tends to decrease somewhat. Therefore, among the monomers exemplified above, monomers having modifying groups such as EO, PO, caprolactone, etc. In this case, it is not preferable to use a compound having an extremely long modifying group alone.

  In addition, the proportion of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the crosslinkable protective layer is 20 to 80% by weight, preferably 30 to 70% by weight, based on the total amount of the crosslinkable protective layer. It is. When the monomer component is less than 20% by weight, the three-dimensional crosslink density of the crosslinkable protective layer is small, and it is difficult to achieve a dramatic improvement in wear resistance as compared with the case of using a conventional thermoplastic binder resin. On the other hand, when it exceeds 80% by weight, the content of the charge transporting compound is lowered, and the electrical characteristics tend to be deteriorated. The electrical characteristics and abrasion resistance required vary depending on the process used, and the thickness of the cross-linked protective layer of the photoconductor also varies accordingly. A weight percent range is most preferred.

  The radically polymerizable compound having a monofunctional charge transporting structure used in the crosslinked protective layer of the present invention is a hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole, etc., such as a condensed polycyclic quinone. , A compound having an electron transport structure such as diphenoquinone, an electron-withdrawing aromatic ring having a cyano group or a nitro group, and having one radical polymerizable functional group.

  Examples of the radical polymerizable functional group include those shown in the above radical polymerizable monomer, and acryloyloxy group and methacryloyloxy group are particularly useful. Further, as a charge transporting structure, a triarylamine structure has a high effect, and in particular, when a compound represented by the structure of the following general formula (6) or general formula (7) is used, the electrical properties such as sensitivity, residual potential, etc. The mechanical properties are well maintained.

{In Formulas (6) and (7), R ₁ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Aryl group, cyano group, nitro group, alkoxy group, —COOR ₇ (R ₇ has a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. An aryl group), a halogenated carbonyl group or CONR ₈ R ₉ (R ₈ and R ₉ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or a substituent. Represents an aralkyl group or an aryl group which may have a substituent, and may be the same or different from each other. Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, and It may or may not be. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3.

Specific examples of general formulas (6) and (7) are shown below.
In the general formulas (6) and (7), in the substituent of R ₁ , examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group include a phenyl group and a naphthyl group. However, examples of the aralkyl group include a benzyl group, a phenethyl group, and a naphthylmethyl group, and examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. These include a halogen atom, a nitro group, a cyano group, and a methyl group. Group, alkyl group such as ethyl group, alkoxy group such as methoxy group and ethoxy group, aryloxy group such as phenoxy group, aryl group such as phenyl group and naphthyl group, aralkyl group such as benzyl group and phenethyl group, etc. It may be. Among the substituents of R _1, particularly preferred are a hydrogen atom, a methyl group.

Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group. In the present invention, the aryl group includes a condensed polycyclic hydrocarbon group, a non-condensed cyclic hydrocarbon group, and a heterocyclic group, and examples thereof include the following groups.
The condensed polycyclic hydrocarbon group preferably has 18 or less carbon atoms forming a ring, for example, a pentanyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptaenyl group, a biphenylenyl group, an as-indacenyl group. , S-indacenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylyl group, pyrenyl group , A chrycenyl group, a naphthacenyl group, and the like.

Examples of the non-fused cyclic hydrocarbon group include monovalent groups of monocyclic hydrocarbon compounds such as benzene, diphenyl ether, polyethylene diphenyl ether, diphenyl thioether and diphenyl sulfone, or biphenyl, polyphenyl, diphenylalkane, diphenylalkene, diphenylalkyne, Monovalent groups of non-condensed polycyclic hydrocarbon compounds such as triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane, and polyphenylalkene, or ring assemblies such as 9,9-diphenylfluorene And monovalent groups of hydrocarbon compounds.
Examples of the heterocyclic group include monovalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.

The aryl group represented by Ar ₃ or Ar ₄ may have a substituent as shown below, for example.

(1) Halogen atom, cyano group, nitro group and the like.

(2) Alkyl groups, preferably C _{1 to} C _12, especially C _{1 to} C ₈ , more preferably C _{1 to} C ₄ linear or branched alkyl groups, and these alkyl groups further include a fluorine atom , a hydroxyl group, a cyano group, an alkoxy group of C ₁ -C _4, a phenyl group or a halogen atom, which may have a phenyl group substituted by an alkoxy group C ₁ -C ₄ alkyl or C ₁ -C ₄ Good.
Specifically, methyl group, ethyl group, n-butyl group, i-propyl group, t-butyl group, s-butyl group, n-propyl group, trifluoromethyl group, 2-hydroxyethyl group, 2-ethoxyethyl Group, 2-cyanoethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, 4-phenylbenzyl group and the like.

(3) Alkoxy group (—OR ₂ ). R ₂ represents the alkyl group defined in (2).
Specifically, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, t-butoxy group, n-butoxy group, s-butoxy group, i-butoxy group, 2-hydroxyethoxy group, benzyloxy group And a trifluoromethoxy group.

(4) Aryloxy group.
Examples of the aryl group include a phenyl group and a naphthyl group. It may contain an alkoxy group having C ₁ -C _4, alkyl group, or a halogen atom C ₁ -C ₄ as a substituent.
Specific examples include a phenoxy group, a 1-naphthyloxy group, a 2-naphthyloxy group, a 4-methoxyphenoxy group, and a 4-methylphenoxy group.

(5) Alkyl mercapto group or aryl mercapto group.
Specific examples include a methylthio group, an ethylthio group, a phenylthio group, and a p-methylphenylthio group.

(6) An amino group represented by the following general formula (d).

In the formula, R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group defined in (2) above, or an aryl group. Examples of the aryl group include a phenyl group, biphenyl group or a naphthyl group, and these may contain an alkoxy group of C ₁ -C _4, alkyl group, or a halogen atom C ₁ -C ₄ as a substituent. R ₃ and R ₄ may form a ring together.

  Specifically, amino group, diethylamino group, N-methyl-N-phenylamino group, N, N-diphenylamino group, N, N-di (tolyl) amino group, dibenzylamino group, piperidino group, morpholino group And pyrrolidino group.

(7) An alkylenedioxy group or an alkylenedithio group such as a methylenedioxy group or a methylenedithio group.

(8) A substituted or unsubstituted styryl group, a substituted or unsubstituted β-phenylstyryl group, a diphenylaminophenyl group, a ditolylaminophenyl group, and the like.

The arylene group represented by Ar ₁ or Ar ₂ is a divalent group derived from the aryl group represented by Ar ₃ or Ar ₄ .

X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group.
The substituted or unsubstituted alkylene group is a C _{1 to} C ₁₂ , preferably C _{1 to} C ₈ , more preferably a C _{1 to} C ₄ linear or branched alkylene group, and these alkylene groups include a fluorine atom, a hydroxyl group, a cyano group, an alkoxy group of C ₁ -C _4, a phenyl group or a halogen atom, a phenyl group substituted with an alkyl group or a C ₁ -C ₄ alkoxy group C ₁ -C ₄ It may be.
Specifically, methylene group, ethylene group, n-butylene group, i-propylene group, t-butylene group, s-butylene group, n-propylene group, trifluoromethylene group, 2-hydroxyethylene group, 2-ethoxyethylene Group, 2-cyanoethylene group, 2-methoxyethylene group, benzylidene group, phenylethylene group, 4-chlorophenylethylene group, 4-methylphenylethylene group, 4-biphenylethylene group and the like.

The substituted or unsubstituted cycloalkylene group is a C _{5 to} C ₇ cyclic alkylene group, and these cyclic alkylene groups include a fluorine atom, a hydroxyl group, a C _{1 to} C ₄ alkyl group, and a C _{1 to} C ₄ alkyl group. It may have an alkoxy group. Specific examples include a cyclohexylidene group, a cyclohexylene group, and a 3,3-dimethylcyclohexylidene group.

  The substituted or unsubstituted alkylene ether group represents ethyleneoxy, propyleneoxy, ethylene glycol, propylene glycol, diethylene glycol, tetraethylene glycol, tripropylene glycol, alkylene ether group alkylene group is hydroxyl group, methyl group, ethyl group, etc. You may have the substituent of.

  Examples of the vinylene group include those represented by the following general formula (e) or (f).

In formulas (b) and (c), R ₅ is hydrogen, an alkyl group (the same as the alkyl group defined in (2) above), an aryl group (the same as the aryl group represented by Ar ₃ or Ar ₄ above). , A represents 1 or 2, and b represents an integer of 1 to 3.

Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group.
Examples of the substituted or unsubstituted alkylene group include the same alkylene groups as those described above for X.
Examples of the substituted or unsubstituted alkylene ether divalent group include the alkylene ether divalent group of X.
Examples of the alkyleneoxycarbonyl divalent group include a caprolactone divalent modifying group.

  Further, the radically polymerizable compound having a monofunctional charge transporting structure of the present invention is more preferably a compound having the structure of the following general formula (8).

  In the formula, each of o, p, and q is an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent substituents other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, The case may be different. s and t represent an integer of 0 to 3. Za represents a single bond, a methylene group, an ethylene group, or the following formula (a), (b) or (c).

  As the compound represented by the above general formula, compounds having a methyl group or an ethyl group as substituents for Rb and Rc are particularly preferable.

The radical polymerizable compound having a monofunctional charge transporting structure represented by the general formulas (6) and (7), particularly (8) used in the present invention has a carbon-carbon double bond opened on both sides. In order to polymerize, it does not become a terminal structure, but is incorporated in a chain polymer and crosslinked by polymerization with a tri- or higher-functional radically polymerizable monomer, present in the main chain of the polymer, And it exists in the bridge | crosslinking chain | strand between main chains-main chains.
This cross-linked chain was polymerized between one polymer and another intermolecular cross-linked chain between the other polymer, a portion of the main chain folded in one polymer, and a position away from it in the main chain. There are intramolecular crosslinked chains that are crosslinked with other sites derived from the monomer.
And whether it is present in the main chain or in the cross-linked chain, the triarylamine structure suspended from the chain portion has at least three aryls arranged radially from the nitrogen atom. It has a group and is bulky, but because it is not directly bonded to the chain part and hangs from the chain part via a carbonyl group etc., it is fixed in a state that is flexible in three-dimensional positioning. These triarylamine structures can be arranged spatially adjacent to each other in the polymer, have little structural distortion in the molecule, and when used as a surface layer of an electrophotographic photoreceptor, a charge transport route. It is presumed that it can adopt an intramolecular structure that is relatively free from disconnection.

  Specific examples of the radically polymerizable compound having a monofunctional charge transporting structure of the present invention are shown below, but are not limited to the compounds having these structures.

  Further, the radical polymerizable compound having a monofunctional charge transporting structure used in the present invention is important for imparting the charge transporting performance of the crosslinkable protective layer, and this component is 20 to 80 with respect to the crosslinkable protective layer. % By weight, preferably 30 to 70% by weight. If this component is less than 20% by weight, the charge transport performance of the cross-linked protective layer cannot be sufficiently maintained, and repeated use tends to cause deterioration of electrical characteristics such as a decrease in sensitivity and an increase in residual potential. On the other hand, when the content exceeds 80% by weight, the content of the trifunctional monomer having no charge transporting structure is lowered, and the crosslink density is lowered and high wear resistance tends to be hardly exhibited. The electrical characteristics and abrasion resistance required vary depending on the process used, and accordingly the film thickness of the crosslinked protective layer of the photoreceptor in the present invention also differs. A range of ˜70% by weight is most preferred.

  The crosslinkable protective layer constituting the electrophotographic photoreceptor of the present invention cures at least a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. In addition to this, monofunctional and bifunctional radically polymerizable monomers for the purpose of imparting functions such as viscosity adjustment during coating, stress relaxation of the cross-linkable protective layer, lower surface energy and reduced friction coefficient, A functional monomer and a radical polymerizable oligomer can be used in combination. Known radical polymerizable monomers and oligomers can be used.

  Examples of the monofunctional radical monomer include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-ethylhexyl carbitol acrylate, 3-methoxybutyl acrylate, benzyl acrylate, and cyclohexyl acrylate. , Isoamyl acrylate, isobutyl acrylate, methoxytriethylene glycol acrylate, phenoxytetraethylene glycol acrylate, cetyl acrylate, isostearyl acrylate, stearyl acrylate, styrene monomer, and the like.

  Examples of the bifunctional radical polymerizable monomer include 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1, Examples include 6-hexanediol dimethacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A-EO modified diacrylate, bisphenol F-EO modified diacrylate, neopentyl glycol diacrylate, and the like.

  Examples of the functional monomer include those substituted with a fluorine atom such as octafluoropentyl acrylate, 2-perfluorooctylethyl acrylate, 2-perfluorooctylethyl methacrylate, 2-perfluoroisononylethyl acrylate, No. 60503, JP-B-6-45770, siloxane repeating units: 20-70 acryloyl polydimethylsiloxane ethyl, methacryloyl polydimethylsiloxane ethyl, acryloyl polydimethylsiloxane propyl, acryloyl polydimethylsiloxane butyl, diacryloyl polydimethylsiloxane Examples include vinyl monomers having a polysiloxane group such as diethyl, acrylates and methacrylates.

Examples of the radical polymerizable oligomer include epoxy acrylate, urethane acrylate, and polyester acrylate oligomers.
However, when a large amount of monofunctional and bifunctional radically polymerizable monomers and radically polymerizable oligomers are contained, the three-dimensional crosslink density of the crosslinkable protective layer is substantially reduced, resulting in a decrease in wear resistance. For this reason, the content of these monomers and oligomers is more preferably 50 parts by weight or less, preferably 30 parts by weight or less, based on 100 parts by weight of the tri- or higher functional radical polymerizable monomer.

  The crosslinked protective layer of the present invention is obtained by curing at least a trifunctional or higher-functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. Accordingly, a polymerization initiator may be contained in the crosslinking type protective layer coating solution in order to allow the curing reaction to proceed efficiently.

  Examples of the thermal polymerization initiator include 2,5-dimethylhexane-2,5-dihydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di ( Peroxybenzoyl) hexyne-3, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) B) Peroxide-based initiators such as propane, azo-based compounds such as azobisisobutylnitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 4,4′-azobis-4-cyanovaleric acid Initiators are mentioned.

Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2- Acetophenone-based or ketal-based photopolymerization initiators such as methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether Benzoin ether photopolymerization initiators such as benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether, acrylated benzophenone, Benzophenone photopolymerization initiators such as 1,4-benzoylbenzene, thioxanthones such as 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone And photopolymerization initiators.
Other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine Examples thereof include oxide, bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine compound, triazine compound and imidazole compound. .

  Moreover, what has a photopolymerization acceleration effect can also be used individually or in combination with the said photoinitiator. Examples include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, ethyl (2-dimethylamino) benzoate, 4,4'-dimethylaminobenzophenone, and the like.

  These polymerization initiators may be used alone or in combination of two or more. The content of the polymerization initiator is 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight with respect to 100 parts by weight of the total content having radical polymerizability.

Furthermore, the coating liquid for forming a crosslinkable protective layer of the present invention includes various plasticizers for the purpose of stress relaxation and adhesion improvement, leveling agents, and low molecular charge transport having no radical reactivity as necessary. Additives such as substances can be included.
As these additives, known ones can be used, and as the plasticizer, those used in general resins such as dibutyl phthalate and dioctyl phthalate can be used. The amount used is 20% by weight or less, preferably 10% by weight or less, based on the total solid content of the coating liquid.
As leveling agents, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain can be used, and the amount used is based on the total solid content of the coating liquid. 3% by weight or less is appropriate.

The crosslinkable protective layer according to the present invention includes a coating liquid containing at least a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. It is formed by coating and curing on the charge transport layer.
When the radically polymerizable monomer is a liquid, such a coating liquid can be applied by dissolving other components in the liquid, but is diluted with a solvent as required.

  Solvents used at this time include alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, tetrahydrofuran, dioxane and propyl ether. And ethers such as dichloromethane, dichloroethane, trichloroethane and chlorobenzene, aromatics such as benzene, toluene and xylene, cellosolves such as methyl cellosolve, ethyl cellosolve and cellosolve acetate. These solvents may be used alone or in combination of two or more. The dilution ratio with the solvent varies depending on the solubility of the composition, the coating method, and the target film thickness, and is arbitrary. The application can be performed by dip coating, spray coating, bead coating, ring coating, or the like.

In the present invention, after the application of such a crosslinkable protective layer coating solution, energy is applied from the outside and cured to form a crosslinkable protective layer. The external energy used at this time is heat, light, radiation, etc. There is.
The heat energy is applied by heating from the coating surface side or the support side using a gas such as air or nitrogen, steam, various heat media, infrared rays or electromagnetic waves. The heating temperature is preferably 100 ° C. or higher and 170 ° C. or lower. If the heating temperature is lower than 100 ° C., the reaction rate is slow and the curing reaction tends not to be completed completely. At a high temperature exceeding 170 ° C., the curing reaction proceeds non-uniformly, and large strains, a large number of unreacted residues, and reaction termination terminals are generated in the crosslinked protective layer.
In order to advance the curing reaction uniformly, it is also effective to complete the reaction by heating at a relatively low temperature of less than 100 ° C. and then heating to 100 ° C. or more.

As the energy of light, UV irradiation light sources such as high-pressure mercury lamps and metal halide lamps that mainly have an emission wavelength in the ultraviolet light region can be used, but the visible light source can be adjusted according to the absorption wavelength of radically polymerizable substances and photopolymerization initiators. Is also possible.
Irradiation light amount, 50 mW / cm ² or more, preferably 1000 mW / cm ² or less, it takes time for the curing reaction is less than 50 mW / cm ^2. If it is higher than 1000 mW / cm ² , the reaction progresses unevenly, local flaws occur on the surface of the crosslinked protective layer, and a large number of unreacted residues and reaction termination ends occur. In addition, internal stress increases due to rapid crosslinking, which causes cracks and film peeling.

  Examples of radiation energy include those using electron beams. Among these energies, those using heat and light energy are useful because of the ease of reaction rate control and the simplicity of the apparatus.

The film thickness of the crosslinked protective layer of the present invention is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less.
If it is thicker than 10 μm, cracks and film peeling are likely to occur as described above, and if it is 8 μm or less, the margin is further improved, so that the crosslink density can be increased, and material selection and curing that further increases wear resistance. Conditions can be set.
On the other hand, radical polymerization reactions are susceptible to oxygen inhibition. That is, on the surface in contact with the atmosphere, crosslinking is not promoted due to the influence of radical trapping by oxygen, and unevenness tends to occur. This effect appears remarkably when the surface layer is less than 1 μm, and the crosslinkable protective layer having a thickness less than this thickness is liable to cause a decrease in wear resistance or uneven wear.
In addition, when the crosslinkable protective layer is applied, the lower charge transport layer component is mixed.In particular, if the coating thickness of the crosslinkable protective layer is thin, the contaminants spread throughout the layer, inhibiting the curing reaction and reducing the crosslink density. Bring about a decline.

  For these reasons, the crosslinkable protective layer of the present invention has a good abrasion resistance and scratch resistance at a film thickness of 1 μm or more, but if it can be locally scraped to the lower charge transport layer in repeated use, The wear of the portion increases, and the density unevenness of the halftone image tends to occur due to the charging property and sensitivity fluctuation. Therefore, it is desirable that the thickness of the cross-linking protective layer is 2 μm or more for a longer life and higher image quality.

  In the structure in which the charge blocking layer, the moire prevention layer, the photosensitive layer (charge generation layer, charge transport layer), and the crosslinkable protective layer of the electrostatic latent image carrier of the present invention are sequentially laminated, When the crosslinkable protective layer is insoluble in an organic solvent, it is characterized in that dramatic wear resistance and scratch resistance are achieved.

As a method for testing the solubility in an organic solvent, a drop of an organic solvent having high solubility in a polymer substance, for example, tetrahydrofuran, dichloromethane or the like, is dropped on the surface layer of the photoreceptor, and the surface shape of the photoreceptor is dried after natural drying. It can be determined by observing the change with a stereomicroscope.
That is, a highly soluble photoconductor has a phenomenon in which the central part of the droplet becomes concave and the surroundings swell up in reverse, a phenomenon that the charge transport material precipitates and white turbidity or cloudiness occurs due to crystallization, and the surface swells and then shrinks. Changes such as the phenomenon that occurs. In contrast, an insoluble photoconductor does not exhibit the above-described phenomenon, and does not change at all as before dropping.

  In the constitution of the present invention, in order to make the crosslinkable protective layer insoluble in the organic solvent, (1) composition of the crosslinkable protective layer coating solution, adjustment of the content ratio thereof, (2) coating of the crosslinkable protective layer Dilution solvent of working solution, adjustment of solid content concentration, (3) Selection of coating method of crosslinkable protective layer, (4) Control of curing conditions of crosslinkable protective layer, (5) Difficult dissolution of lower charge transport layer It is important to control factors such as sexification, but it is not achieved by controlling a single factor.

  The composition of the crosslinkable protective layer coating solution includes radical polymerization in addition to the above-described trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. When a large amount of additives such as binder resin, antioxidant, plasticizer, etc. that do not have a functional functional group is contained, the crosslinking density is reduced, and the cured product resulting from the reaction and the above-mentioned additive are phase separated, resulting in organic It tends to be soluble in solvents.

  Specifically, it is important to suppress the total content of the additives to 20% by weight or less with respect to the total solid content of the coating liquid. Further, in order not to dilute the crosslinking density, the total content of monofunctional or bifunctional radical polymerizable monomers, reactive oligomers, and reactive polymers is 20% by weight or less based on the trifunctional radical polymerizable monomers. It is desirable. Further, when a large amount of a radically polymerizable compound having a bifunctional or higher-functional charge transporting structure is contained, a bulky structure is fixed in the crosslinked structure by a plurality of bonds, so that distortion is likely to occur. It is easy to become an aggregate. This can cause solubility in organic solvents. Although different depending on the compound structure, the content of the radical polymerizable compound having a bifunctional or higher functional charge transporting structure is preferably 10% by weight or less based on the radical polymerizable compound having a monofunctional charge transporting structure.

As for the diluting solvent of the crosslinkable protective layer coating solution, when a solvent with a slow evaporation rate is used, the remaining solvent may hinder the curing, or increase the amount of mixing of the lower layer components. Reduces the cured density. For this reason, it tends to be soluble in organic solvents.
Specifically, tetrahydrofuran, a mixed solvent of tetrahydrofuran and methanol, ethyl acetate, methyl ethyl ketone, ethyl cellosolve and the like are useful, but are selected according to the coating method. Further, regarding the solid content concentration, if it is too low for the same reason, it tends to be soluble in an organic solvent. On the contrary, the upper limit concentration is restricted by the limitation of the film thickness and the coating solution viscosity. Specifically, it is desirable to use in the range of 10 to 50% by weight.

  As a coating method for the cross-linked protective layer, for the same reason, the solvent content at the time of forming the coating film, a method of reducing the contact time with the solvent is preferable, specifically, the spray coating method, the amount of coating liquid A regulated ring coat method is preferred. Also, in order to suppress the amount of the lower layer component mixed in, a polymer charge transport material is used as the charge transport layer, and a crosslinkable protective layer is applied between the photosensitive layer (or charge transport layer) and the crosslinkable protective layer. It is also effective to provide an intermediate layer insoluble in the solvent.

As the curing conditions for the cross-linkable protective layer, if the energy of heating or light irradiation is low, the curing is not completely completed and the solubility in the organic solvent is increased. On the other hand, when cured with very high energy, the curing reaction becomes non-uniform, which tends to increase the number of uncrosslinked parts and radical stopping parts, and to form an aggregate of minute cured products. For this reason, it may become soluble in an organic solvent. To insolubilize in an organic solvent, the heat curing conditions are preferably 100 to 170 ° C. and 10 minutes to 3 hours, and the curing conditions by UV light irradiation are 50 to 1000 mW / cm ² and 5 seconds to 5 minutes. In addition, it is desirable to control the temperature rise to 50 ° C. or less to suppress non-uniform curing reaction.

An example of a method for making the cross-linkable protective layer constituting the electrophotographic photoreceptor of the present invention insoluble in an organic solvent will be described.
For example, when an acrylate monomer having three acryloyloxy groups and a triarylamine compound having one acryloyloxy group are used as the coating liquid, the usage ratio thereof is 7: 3 to 3: 7. The polymerization initiator is added in an amount of 3 to 20% by weight based on the total amount of these acrylate compounds, and a solvent is further added to prepare a coating solution.
For example, in the charge transport layer that is the lower layer of the cross-linked protective layer, when a triarylamine donor is used as the charge transport material, polycarbonate is used as the binder resin, and the surface layer is formed by spray coating, As the solvent, tetrahydrofuran, 2-butanone, ethyl acetate and the like are preferable, and the use ratio thereof is 3 to 10 times the total amount of the acrylate compound.

Next, for example, the prepared coating solution is applied by spraying or the like on a photoreceptor in which an intermediate layer, a charge generation layer, and the charge transport layer are sequentially laminated on a support such as an aluminum cylinder. Then, it is naturally dried or dried at a relatively low temperature for a short time (25 to 80 ° C., 1 to 10 minutes) and cured by UV irradiation or heating.
In the case of UV irradiation, uses a metal halide lamp, illuminance 50 mW / cm ² or more, 1000 mW / cm ² or less, preferably about 5 minutes 5 seconds as the time, the drum temperature not to exceed 50 ° C. Control.
In the case of thermosetting, the heating temperature is preferably 100 to 170 ° C. For example, when a blow type oven is used as the heating means and the heating temperature is set to 150 ° C., the heating time is 20 minutes to 3 hours.
After the curing is completed, the photosensitive material of the present invention is obtained by heating at 100 to 150 ° C. for 10 to 30 minutes to reduce the residual solvent.

  Moreover, well-known materials, such as a-C and a-SiC formed with the vacuum thin film preparation method other than the protective layer containing the filler described above and a bridge | crosslinking type protective layer, can be used as a protective layer.

  As described above, when a protective layer is formed on the photosensitive layer, there is a case where the neutralizing light does not sufficiently reach the photosensitive layer unless the appropriate protective layer is selected, and the static eliminating action does not work clearly. In addition, the protective layer absorbs the static elimination light, so that it tends to deteriorate, and conversely, there is a case where a residual potential rise is generated. Therefore, in any of the protective layers described above, the transmittance for the static elimination light is 30% or more, preferably 50% or more, and more desirably 85% or more.

  As described above, using a polymer charge transport material for the charge transport layer in the photosensitive layer or providing a protective layer on the surface of the photoreceptor only increases the durability such as the wear resistance of each photoreceptor. In addition, when used in a tandem type full-color image forming apparatus as will be described later, a new effect not found in the monochrome image forming apparatus is also produced.

  In the present invention, in order to improve environmental resistance, in order to prevent a decrease in sensitivity and an increase in residual potential, in particular, in each layer such as a protective layer, a charge transport layer, a charge generation layer, a charge blocking layer, and a moire prevention layer. The following antioxidants can be added.

(Phenolic compounds)
2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol), 4, 4'-thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3-tris- (2-methyl-4 -Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene- -(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] Crycol esters, tocopherols, etc.

(Paraphenylenediamines)
N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N, N'- Di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine and the like.

(Hydroquinones)
2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl) ) -5-methylhydroquinone and the like.

(Organic sulfur compounds)
Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like.

(Organic phosphorus compounds)
Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

  These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained. The addition amount of the antioxidant in the present invention is 0.01 to 10% by weight based on the total weight of the layer to be added.

In the case of a full-color image, various types of images are input, but on the contrary, a fixed image may also be input. For example, the presence of a seal in a Japanese document or the like. Something like indicia is usually located towards the edge of the image area, and the colors used are also limited. In a state in which a random image is always written, image writing, development, and transfer are performed on the photoconductor in the image forming element on average. When many image formations are repeated or only a specific image forming element is used, the durability balance is lost. When a photoconductor having a low surface durability (physical / chemical / mechanical) is used in such a state, this difference becomes prominent and easily causes an image problem.
On the other hand, when the photoconductor is made highly durable, the amount of such local change is small, and as a result, it becomes difficult to appear as a defect on the image, so that high durability is achieved and the stability of the output image is improved. This is very effective.

[Electrostatic latent image forming means]
The formation of the electrostatic latent image can be performed, for example, by uniformly charging the surface of the electrostatic latent image carrier and then performing imagewise exposure, and is performed by the electrostatic latent image forming unit. be able to.
The electrostatic latent image forming means includes, for example, at least a charger that uniformly charges the surface of the electrostatic latent image carrier and an exposure device that exposes the surface of the electrostatic latent image carrier imagewise. Prepare.

  The charger is not particularly limited and may be appropriately selected depending on the purpose. For example, a known contact charging device including a conductive or semiconductive roll, brush, film, rubber blade, etc. And non-contact chargers using corona discharge such as corotrons, corotrons and scorotrons. The non-contact charger includes a proximity type non-contact charger having a gap of 100 μm or less between the surface of the photoreceptor and the charger.

The electric field strength applied to the electrostatic latent image carrier by the charger is preferably 20 to 60 V / μm, and more preferably 30 to 50 V / μm. The higher the electric field strength applied to the photoconductor, the better the dot reproducibility. However, if the electric field strength is too high, problems such as dielectric breakdown of the photoconductor and carrier adhesion during development may occur.
The electric field strength is expressed by the following mathematical formula (1).
Electric field strength (V / μm) = SV / G (1)
In Equation (1), SV represents the surface potential (V) at the unexposed portion of the electrostatic latent image carrier at the development position. G represents the film thickness (μm) of the photosensitive layer including at least the photosensitive layer (charge generation layer and charge transport layer).

  The exposure can be performed, for example, by exposing the surface of the latent electrostatic image bearing member imagewise using the exposure device. The type of the exposure device is not particularly limited and may be appropriately selected according to the purpose. For example, various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system. Is mentioned. In the present invention, a back light system in which imagewise exposure is performed from the back side of the electrostatic latent image carrier may be employed.

As the light source of the exposure device, a light source capable of ensuring high luminance such as a light emitting diode (LED), a semiconductor laser (LD), or electroluminescence (EL) is used.
Depending on the resolution of the light source (write light) to be used, the resolution of the electrostatic latent image and thus the toner image to be formed is determined, and the higher the resolution, the clearer the image. However, if writing is performed at a higher resolution, writing takes longer, so writing with one writing light source is limited by the drum linear speed (process speed). Therefore, when there is one writing light source, a resolution of about 2400 dpi is the upper limit. When there are a plurality of write light sources, each of them only needs to bear the write area, and the upper limit is substantially “2400 dpi × number of write light sources”. Among these light sources, light emitting diodes and semiconductor lasers have high irradiation energy and are used favorably.

Further, since a finer electrostatic latent image is formed by using a light source having a wavelength shorter than 450 nm as the light source wavelength of the exposure device, it is effectively used in the present invention. Examples of a technique for causing laser oscillation in such a wavelength range include a method of halving the wavelength of laser light using second harmonic generation (SHG) and a method using a wide gap semiconductor.
In recent years, LDs that oscillate in the wavelength region of 400 to 410 nm have also been developed, and optical systems using these have been developed, and can be beneficially used in the present invention. The lower limit of the wavelength that can be used for the current writing light is about 350 nm, although it varies depending on the materials constituting the charge transport layer and the protective layer. With the development of new materials and lasers, this lower limit will be shortened.

[Development means]
The development can be performed by developing the electrostatic latent image with toner to form a visible image. As the toner, toner having the same polarity as the charged polarity of the photoreceptor is used, and the electrostatic latent image is developed by reversal development (negative / positive development). There are two methods, a one-component method in which development is performed with toner alone and a two-component method in which a two-component developer comprising a toner and a carrier is used. Either method can be used favorably.

[Transfer means]
The transfer means is a means for transferring the visible image onto a recording medium. The transfer means can be transferred onto the intermediate transfer body using a method of directly transferring the visible image from the surface of the photoreceptor to the recording medium and an intermediate transfer body. There is a method in which a visual image is primarily transferred and then the visible image is secondarily transferred onto the recording medium. Either aspect can be used satisfactorily, but the former (direct transfer) method with a small number of transfers is preferred when the adverse effect of the transfer is great when the image quality is improved.

  The transfer can be performed, for example, by charging the latent electrostatic image bearing member (photoconductor) of the visible image using a transfer charger, and can be performed by the transfer unit. The transfer unit is not particularly limited, and can be appropriately selected from known transfer units according to the purpose. For example, a transfer conveyance belt that can simultaneously convey a recording medium can be preferably cited. It is done.

  The primary transfer unit and the secondary transfer unit include at least a transfer unit that peels and charges the visible image formed on the electrostatic latent image carrier (photoconductor) to the recording medium side. Is preferred. There may be one transfer means or two or more transfer means. Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device. The recording medium is not particularly limited and can be appropriately selected from known recording media (recording paper).

  As the transfer charger, a transfer belt or a transfer roller can be used, but it is desirable to use a contact type such as a transfer belt or a transfer roller that generates less ozone. As a voltage / current application method at the time of transfer, either a constant voltage method or a constant current method can be used, but the transfer charge amount can be kept constant, and a constant voltage with excellent stability can be used. The current method is more desirable. As such a transfer member, a known member can be used as long as the structure of the present invention can be satisfied.

As described above, the amount of charge passing through the photoconductor per cycle of image formation varies greatly depending on the surface potential of the photoconductor after transfer (the surface potential of the difference entering the charge eliminating portion). The larger this is, the greater the influence on the electrostatic fatigue of the photoreceptor in repeated use. This passing charge amount corresponds to the amount of charge flowing in the film thickness direction of the photoreceptor.
As an operation in the image forming apparatus of the photoconductor, the main charger is charged to a desired charging potential, and optical writing is performed based on an input signal corresponding to the original. In most cases, the charging potential is negatively charged.
At this time, photocarriers are generated in the portion where writing is performed, and the surface charge is neutralized (potential decay). At this time, the amount of charge depending on the amount of generated photocarriers flows in the direction of the photoreceptor film thickness. On the other hand, the region where the optical writing is not performed (non-writing portion) proceeds to the static elimination process through the development process and the transfer process (a cleaning process is performed before that if necessary). Here, when the surface potential of the photoconductor is close to the potential applied by main charging (excluding dark decay), the amount of charge is almost the same as that in the area where optical writing is performed. Will flow into. Generally, since the current original document has a low writing rate, this method means that the current passing through the photoconductor in repetitive use is mostly current. If the writing rate is 10%, the current flowing in the static elimination process accounts for 90% of the total.

This passing electric charge greatly affects the electrostatic characteristics of the photoconductor, for example, causing deterioration of the material constituting the photoconductor. As a result, depending on the amount of passing charge, the residual potential of the photoreceptor increases in particular.
When the residual potential of the photoconductor is increased, the image density is lowered in the negative and positive development used in the present invention, which is a serious problem. Therefore, there is a problem of how to reduce the passing charge amount of the photosensitive member in order to extend the life (high durability) of the photosensitive member in the image forming apparatus.

On the other hand, there is a way of thinking that the photostatic discharge is not performed, but if the main charger is not sufficiently charged, the charging cannot be stabilized and a problem such as an afterimage may occur.
The passing charge of the photoconductor is generated by the movement of the generated optical carrier by light irradiation by the electric potential (the electric field generated thereby) charged on the surface of the photoconductor. Therefore, if the photoreceptor surface potential can be attenuated by means other than light, the amount of passing charge per rotation of the photoreceptor (one cycle of image formation) can be reduced.

  For this purpose, it is effective to adjust the charge passing through the photosensitive member by adjusting the transfer bias in the transfer process. That is, a non-writing portion that is charged by main charging and does not perform writing enters the transfer process in a state close to the charged potential except for the dark attenuation amount. At this time, the absolute value on the polarity side charged by the main charger is reduced to 100 V or less, so that almost no photocarrier is generated even if the subsequent charge removal process is entered, and no passing charge is generated. This value is preferably closer to 0V.

Furthermore, by adjusting the transfer bias, by applying a transfer bias so that the surface potential of the photosensitive member is charged to a polarity opposite to the charging polarity applied by the main charging, it is more preferable because no optical carrier is generated. . However, under transfer conditions that charge to a reverse polarity, there may be cases where a large amount of transfer dust occurs or the main charge of the next image forming process (cycle) cannot catch up. In that case, since a problem such as an afterimage may occur, the absolute value of the reverse polarity is preferably 100 V or less.
Adding the control as described above can effectively use the effect of the present invention as a remarkable effect.

[Fixing means]
The fixing may be performed each time the visible image transferred to the recording medium is fixed by using a fixing device and transferred to the recording medium for each color toner, or the toner is stacked on each color toner. May be performed simultaneously at the same time.
There is no restriction | limiting in particular as said fixing device, Although it can select suitably according to the objective, A well-known heating-pressing means is suitable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt. The heating in the heating and pressing means is usually preferably 80 ° C to 200 ° C. In the present invention, for example, a known optical fixing device may be used together with or in place of the fixing step and the fixing unit depending on the purpose.

[Static elimination means]
The neutralization means only needs to have a wavelength of less than 500 nm (preferably less than 480 nm, more preferably less than 450 nm), and can neutralize the electrostatic latent image carrier. For example, a semiconductor laser (LD), electroluminescence (EL), and the like are preferable.
For light sources such as semiconductor lasers (LD) and electroluminescence (EL), semiconductor lasers (LD) and electroluminescence (EL) having an oscillation wavelength of less than 500 nm, or fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium A combination of a lamp, a xenon lamp, or the like with an appropriate optical filter that can limit light emission to less than 500 nm can be used.
The optical filter includes various types 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 in order to irradiate only light in a desired wavelength range (less than 500 nm). A filter can also be used.

There are several techniques for causing laser oscillation in such a wavelength range. One is to use a non-linear optical material and to halve the wavelength of the laser light by using second harmonic generation (SHG) (for example, Japanese Patent Laid-Open Nos. 9-275242 and 9). No. 189930, JP-A-5-313033, etc.). This system can use a GaAs LD or YAG laser that has already established technology and is capable of high output as a primary light source.
The other is a method using a wide gap semiconductor, and the size of the apparatus can be reduced as compared with a device using SHG. LD using a ZnSe-based semiconductor (see JP-A-7-321409, JP-A-6-334272, etc.) or a GaN-based semiconductor (see JP-A-8-88441, JP-A-7-335975, etc.) However, because of its high luminous efficiency, it has been the subject of many studies. Also, as a relatively recent technology, Nichia Chemical Industries has put into practical use LD (405 nm oscillation) using a GaN-based semiconductor, and has developed a writing system far more advanced than the above-mentioned technology. It can be used beneficially.
In addition, LED lamps using the above materials are on the market, and these can also be used effectively.

  On the other hand, at the present time, the lower limit is determined by the following problem. That is, as a material constituting the photoconductor such as a charge transport layer and a protective layer existing on the writing light incident side, a charge transport material can be mentioned. Among charge transport materials having high mobility and usable at a practical level. That is, there is no material that is sufficiently transparent with respect to light having a shorter wavelength than about 350 nm. This is because most of the charge transport materials currently developed have a triarylamine structure, and the absorption edge on the long wavelength side of this material is approximately 300 to 350 nm. Accordingly, if further shortening of the wavelength of the light source for static elimination and further transparency of the charge transport material, that is, shortening of the wavelength of absorption is realized, the adjustment of the oscillation wavelength of the light source that can be used in the present invention is further shortened. It will extend to.

Hereinafter, other means will be described.
[Cleaning means]
The cleaning means is not particularly limited as long as it can remove the electrophotographic toner remaining on the electrostatic latent image carrier, and can be appropriately selected from known cleaners. Suitable examples include brush cleaners, electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, and the like.

[Recycling means]
The recycling unit is a step of recycling the electrophotographic color toner removed by the cleaning unit to the developing unit, and examples thereof include a known conveyance unit.

[Control means]
The control means is a process for controlling the respective steps, and can be suitably performed by the control means. The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

Next, one aspect of the image forming apparatus of the present invention will be described with reference to FIG.
FIG. 11 is a schematic diagram for explaining the image forming apparatus and the electrophotographic process of the present invention, and modifications as described later also belong to the category of the present invention.

  In FIG. 11, the photoreceptor (1) as an electrostatic latent image carrier is at least one of naphthalene tetracarboxylic acid diimidazole pigments represented by at least one of the general formulas (1) and (2) on a support. And a multilayer photosensitive layer comprising a charge transport layer and a charge transport layer. The photoreceptor (1) has a drum shape, but may be a sheet shape or an endless belt shape.

  As the charger (charging member) (3), a wire-type charger or a roller-shaped charger is used. When high-speed charging is required, a scorotron charger is preferably used. In a compact or tandem image forming apparatus that uses a plurality of photoconductors described later, acid gas (NOx, SOx, etc.) A roller-shaped charger that generates less ozone is effectively used. Although the photosensitive member is charged by this charger, the higher the electric field strength applied to the photosensitive member, the better the dot reproducibility. Therefore, it is desirable to apply an electric field strength of 20 V / μm or more. . However, there is a possibility that problems such as dielectric breakdown of the photosensitive member and carrier adhesion during development occur, and the upper limit is approximately 60 V / μm or less, more preferably 50 V / μm or less.

In addition, the image exposure unit (5) can ensure high brightness such as a light emitting diode (LED), a semiconductor laser (LD), and electroluminescence (EL), and can be written at a high resolution (600 dpi or more). Is used. Depending on the resolution of the light source (writing light), the resolution of the formed electrostatic latent image, and thus the toner image, is determined. The higher the resolution, the clearer the image. However, if writing is performed at a higher resolution, writing takes longer, so writing with one writing light source is limited by the drum linear speed (process speed). Therefore, when there is one writing light source, a resolution of about 1200 dpi is the upper limit. When there are a plurality of writing light sources, each of them only has to bear a writing area, and “1200 dpi × number of writing light sources” is practically the upper limit. Among these light sources, light emitting diodes and semiconductor lasers have high irradiation energy and are used favorably.
Further, as described above, it is an effective means to use laser light having an oscillation wavelength shorter than 450 nm.

The developing unit (6) which is a developing means has at least one developing sleeve.
In the developing unit (6), toner having the same polarity as the charged polarity of the photoreceptor is used, and the electrostatic latent image is developed by reversal development (negative / positive development). Depending on the light source used in the previous image exposure unit, in the case of a digital light source used in recent years, there is generally a reversal development method in which toner development is performed on the writing portion in response to a low image area ratio. This is advantageous in view of the life of the light source. There are two methods, a one-component method in which development is performed with toner alone and a two-component method in which a two-component developer comprising a toner and a carrier is used. Either method can be used favorably.

The transfer charger (10) may be a transfer belt or a transfer roller, but it is desirable to use a contact type such as a transfer belt or transfer roller that generates less ozone.
As a voltage / current application method at the time of transfer, either a constant voltage method or a constant current method can be used. However, the transfer charge amount can be kept constant, and the constant voltage method has excellent stability. The current method is more desirable. In particular, by subtracting the current that flows from the power supply member (high-voltage power supply) that supplies electric charge to the transfer member and does not flow into the photosensitive member, the current to the photosensitive member is subtracted. A method of controlling the value is preferred.

  The transfer current is a current based on the amount of charge required to peel off the toner electrostatically attached to the photosensitive member and transfer it to a transfer target (transfer paper or intermediate transfer member). In order to avoid transfer defects such as transfer residue, it is sufficient to increase the transfer current. However, in the case of using negative and positive development, charging with a polarity opposite to the charging polarity of the photosensitive member is given. As a result, the electrostatic fatigue of the photoconductor becomes remarkable.

  The larger the transfer current, the more advantageous it is because the charge amount exceeding the electrostatic adhesion force between the photoconductor and the toner can be given. As a result, the developed toner image is scattered. For this reason, the upper limit is a range in which this discharge phenomenon does not occur. This threshold varies depending on the gap (distance) between the transfer member and the photoconductor, the material constituting the both, and the like, but the discharge phenomenon can be avoided by using it at about 200 μA or less. Therefore, the upper limit value of the transfer current is about 200 μA.

Further, the toner image formed on the photoconductor is transferred onto the transfer paper to become an image on the transfer paper. At this time, there are two methods. One is a method of directly transferring a toner image developed on the surface of a photoreceptor as shown in FIG. 11 to the transfer paper, and the other is that the toner image is once transferred from the photoreceptor to an intermediate transfer body, and this is transferred to the transfer paper. It is the method of transferring to. Either case can be used in the present invention.
As such a transfer member, a known member can be used as long as the structure of the present invention can be satisfied.
Further, by controlling the transfer current as described above, reducing the photoreceptor surface potential after transfer (the unexposed portion of the writing light) reduces the amount of charge passing through the photoreceptor per one cycle of image formation. Can be used effectively in the present invention.

A light source such as a static elimination lamp (2) has a wavelength of less than 500 nm (preferably less than 480 nm, more preferably less than 450 nm), and is only required to be able to eliminate static electricity on the electrostatic latent image carrier. The static eliminator can be appropriately selected, and for example, a semiconductor laser (LD), electroluminescence (EL), and the like are preferable.
For light sources such as semiconductor lasers (LD) and electroluminescence (EL), semiconductor lasers (LD) and electroluminescence (EL) having an oscillation wavelength of less than 500 nm, or fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium A combination of a lamp, a xenon lamp, or the like with an appropriate optical filter that can limit light emission to less than 500 nm can be used. The optical filter includes various types 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 in order to irradiate only light in a desired wavelength range (less than 500 nm). A filter can also be used.
The lower limit of the wavelength used varies depending on the transmittance of the charge transport layer and the protective layer used in the photoreceptor, but the lower limit is about 300 to 350 nm.
In FIG. 11, reference numeral 8 denotes a registration roller, 11 denotes a separation charger, and 12 denotes a separation claw.

  In addition, the toner developed on the photoreceptor (1) by the developing unit (6) is transferred to the transfer paper (9), but when toner remaining on the photoreceptor (1) is generated, a fur brush ( 14) and the blade (15). Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.

FIG. 12 is a schematic diagram for explaining the tandem type full-color image forming apparatus of the present invention, and the following modifications also belong to the category of the present invention.
In FIG. 12, reference numerals (16Y), (16M), (16C), and (16K) are drum-shaped photoconductors, and the photoconductors are at least the above general formulas (1), (2), and ( A laminated photosensitive layer comprising a charge generation layer containing at least one polycyclic quinone pigment represented by 3) and a phthalocyanine and a charge transport layer is provided.

  The photoconductors (16Y), (16M), (16C), and (16K) can rotate in the direction of the arrow in FIG. 12, and around them, at least in the order of rotation, chargers (charging members) (17Y), (17M) , (17C), (17K), developing means (19Y), (19M), (19C), (19K) having at least one developing sleeve, cleaning members (20Y), (20M), (20C), (20K) ), Static elimination means (27Y), (27M), (27C), and (27K) for irradiating light having a wavelength shorter than 500 nm (preferably less than 480 nm, more preferably less than 450 nm). The chargers (17Y), (17M), (17C), and (17K) are chargers that constitute a charging device for uniformly charging the surface of the photoreceptor. Exposure from the surface of the photoreceptor between the chargers (17Y), (17M), (17C), (17K) and the developing means (developing member) (19Y), (19M), (19C), (19K) (Exposure section) (18Y), (18M), (18C), and (18K) are irradiated with laser light, and electrostatic latent images are formed on the photoreceptors (16Y), (16M), (16C), and (16K). Is to be formed.

  Then, the four image forming elements (25Y), (25M), (25C), and (25K) centering on such photoconductors (16Y), (16M), (16C), and (16K) serve as transfer materials. They are juxtaposed along the transfer conveyance belt (22) which is a conveyance means. The transfer / conveying belt (22) includes developing means (19Y), (19M), (19C), (19K) and a cleaning member (20Y) of the image forming units (25Y), (25M), (25C), (25K). , (20M), (20C), and (20K) are in contact with the photosensitive member (16Y), (16M), (16C), and (16K), and contact the back side of the photosensitive member side of the transfer conveyance belt (22). Transfer chargers (21Y), (21M), (21C), and (21K) for applying a transfer bias are arranged on the surface (back surface). Each of the image forming elements (25Y), (25M), (25C), and (25K) is different in the color of the toner inside the developing device, and the others are the same in configuration.

  In the full-color image forming apparatus having the configuration shown in FIG. 12, the image forming operation is performed as follows. First, in each of the image forming elements (25Y), (25M), (25C), and (25K), an electrostatic latent image is formed on the photoconductors (16Y), (16M), (16C), and (16K). It has become. Then, the photoreceptors (16Y), (16M), (16C), and (16K) rotate, and the photoreceptors are charged by the chargers (17Y), (17M), (17C), and (17K). The At this time, in order to form a high-definition latent image, charging is performed so that the electric field strength of the photosensitive member is 20 V / μm or more (60 V μm or less, preferably 50 V / μm or less).

Next, writing is performed by writing at a resolution of 1200 dpi or more, preferably 2400 dpi or more by laser light at the exposed portions (18Y), (18M), (18C), and (18K) arranged outside the photoreceptor. An electrostatic latent image corresponding to each color image is formed. As the writing light source, as described above, a light source suitable for an arbitrary photoconductor is used. In this case as well, 2400 dpi writing is generally the upper limit for one writing light source. Also in this case, it is an effective means to use laser light having an oscillation wavelength shorter than 450 nm as described above.
The latent image is developed by developing means (19Y), (19M), (19C), and (19K) to form a toner image. Developing means (19Y), (19M), (19C), and (19K) are developing means for developing with toners of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The toner images of the respective colors formed on the two photoconductors (16Y), (16M), (16C), and (16K) are superimposed on the transfer paper.

The transfer paper (26) is fed out from the tray by a paper feeding roller (not shown), temporarily stopped by a pair of registration rollers (23), and transferred and conveyed (22) in synchronization with the image formation on the photosensitive member. ). The transfer paper (26) held on the transfer / conveying belt (22) is conveyed and contacts each photoconductor (16Y), (16M), (16C), (16K), that is, each color at the transfer portion. The toner image is transferred.
The toner image on the photoconductor is transferred to the transfer chargers (21Y), (21M), (21C), and (21K) and the photoconductors (16Y), (16M), (16C), and (16K). Is transferred onto the transfer paper (26) by an electric field formed from the potential difference between the first transfer sheet and the second transfer sheet. Then, the recording paper (26) on which the four color toner images are passed through the four transfer sections is conveyed to the fixing device (24), where the toner is fixed, and is discharged to a paper discharge section (not shown).
Further, residual toner remaining on each of the photoconductors (16Y), (16M), (16C), and (16K) without being transferred by the transfer unit is removed from the cleaning devices (20Y), (20M), (20C), ( 20K).

Subsequently, excess residual charges on the photosensitive member are removed by the charge removal members (27Y), (27M), (27C), and (27K) having a light source having a wavelength shorter than 500 nm. Thereafter, charging is performed uniformly by the charger, and the next image formation is performed.
In the example of FIG. 12, the image forming elements are arranged in the order of Y (yellow), M (magenta), C (cyan), and K (black) from the upstream side to the downstream side in the transfer paper conveyance direction. However, it is not limited to this order, and the color order is arbitrarily set. Further, when creating a black-only document, it is particularly effective to use the present invention to provide a mechanism that stops image forming elements other than black ((25Y), (25M), (25C)). .
Further, as described above, the surface of the photoreceptor after transfer is preferably charged to 100 V or less on the polarity side charged by the main charger, more preferably charged to the reverse polarity side, and to the reverse polarity side. It is particularly preferable to charge to 100 V or less. As a result, an increase in residual potential due to repeated use of the photoreceptor can be reduced.

The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. A process cartridge is a single device (part) that contains a photoconductor and further includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a neutralizing unit, and the like.
There are many shapes and the like of the process cartridge, but a typical example is shown in FIG. The photoreceptor (101) is a laminated photosensitive film comprising a charge generation layer containing at least one of naphthalenetetracarboxylic acid diimidazole pigments represented by the general formula (1) or (2) on a support and a charge transport layer. A layer is provided.
As described above, a light source capable of writing with a resolution of 600 dpi or higher is preferably used for the image exposure unit (103), and an arbitrary charger is used for the charger (charging unit) (102). . In FIG. 13, 104 is a developing means having at least one developing sleeve, 105 is a transfer member, 106 is a transfer means, 107 is a cleaning means, and 108 is a wavelength shorter than 500 nm (preferably less than 480 nm, more preferably 450 nm). Less than) light source.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example at all. All parts are parts by mass.

Dispersion was performed according to the formulation and conditions of the following composition to prepare a dispersion as a charge generation layer coating solution.
(Dispersion Preparation Example 1)
<composition>
Naphthalene tetracarboxylic acid diimidazole pigment represented by the following structural formulas (3) and (4) (mixture of cis and trans isomers): 5 parts Polyvinyl butyral (manufactured by Sekisui Chemical: BM-S): 4 parts Tetrahydrofuran: 100 Part

  Use a PSZ ball with a diameter of 1 mm in a bead mill disperser, add all of the solvent in which polyvinyl butyral is dissolved and the naphthalenetetracarboxylic acid diimidazole pigment, disperse for 3 hours, add 100 parts of cyclohexanone, and dilute the dispersion. Was made (dispersion liquid 1).

(Dispersion preparation example 2)
A dispersion was prepared in the same manner as dispersion preparation example 1 except that the naphthalenetetracarboxylic acid diimidazole pigment used in dispersion preparation example 1 was changed to that of the following structural formula (9) (referred to as dispersion liquid 2). .

(Dispersion preparation example 3)
The dispersion 2 prepared in Dispersion Preparation Example 1 was filtered using a cotton wind cartridge filter, TCW-3-CS (effective pore size 3 μm) manufactured by Advantech. During filtration, a pump was used and filtration was performed under pressure (referred to as dispersion 3).

(Dispersion preparation example 4)
Except for changing the filter used in Dispersion Preparation Example 3 to Advantech Co., Ltd., Cotton Wind Cartridge Filter, TCW-5-CS (effective pore size 5 μm), pressure filtration was performed in the same manner as Dispersion Preparation Example 4, A dispersion was prepared (referred to as dispersion 4).

  The particle size distribution of the pigment particles in the dispersion prepared as described above was measured by HORIBA, Ltd .: CAPA-700. The results are shown in Table 3 below.

Next, a photoreceptor having the following configuration was produced.
(Photoreceptor Preparation Example 1)
On an aluminum drum (JIS 1050) with a diameter of 30 mm, an intermediate layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution having the following composition were sequentially applied and dried to obtain a 3.5 μm intermediate layer, 0 A 0.5 μm charge generation layer and a 25 μm charge transport layer were formed to produce a laminated photoreceptor (referred to as electrophotographic photoreceptor 1).

<Intermediate layer coating solution>
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm): 112 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.]: 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals, Inc.]: 18.7 parts 2-butanone: 260 parts

<Charge generation layer coating solution>
Dispersion 1 prepared above was used as the charge generation layer coating solution.

<Charge transport layer coating solution>
Polycarbonate (TS2050: manufactured by Teijin Chemicals): 10 parts Charge transport material of the following structural formula (g): 7 parts Methylene chloride: 80 parts

Example 1
The electrophotographic photosensitive member 1 produced as described above is mounted on the image forming apparatus as shown in FIG. 11, the image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, A transfer belt was used as the transfer member, and a 428 nm LED (Rohm: half-value width: 65 nm) was used as the static elimination light source. Process conditions before the test were set as follows, and a chart with a writing rate of 6% (characters equivalent to 6% as an image area are written on the entire A4 surface) was continuously 30,000. Sheet printing was performed.

<Process conditions>
Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Surface potential after neutralization (unexposed area of writing light): −100V

The evaluation was performed by measuring the photosensitive member exposed portion potential before and after printing 30,000 images.
As a measuring method, a surface potential meter is mounted at the position of the developing portion shown in FIG. 11, and after charging the photosensitive member to −900 V, solid writing is performed with the semiconductor laser, and the surface potential of the unexposed portion and the exposure at the developing portion are measured. The partial potential was measured. The results are shown in Table 4 below.
Further, in order to measure the transmittance of the charge transport layer, only the charge transport layer in the electrophotographic photoreceptor 1 is formed on a φ30 mm aluminum drum wound with a polyethylene terephthalate film under the same conditions as in the electrophotographic photoreceptor 1. did. This was cut out to an appropriate size, and the transmittance at a static elimination wavelength was measured using a commercially available spectrophotometer (Shimadzu: UV-3100) using a polyethylene terephthalate film without a charge transport layer as a comparison object. . The results are shown in Table 4.

(Example 2)
Evaluation was performed in the same manner as in Example 1 except that the light source in Example 1 was changed to a 472 nm LED (manufactured by Seiwa Denki: full width at half maximum of 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 1. The results are shown in Table 4 below.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 except that the neutralization light source in Example 1 was changed to 502 nm LED (manufactured by Seiwa Denki: full width at half maximum of 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 1. The results are shown in Table 4 below.

(Comparative Example 2)
Evaluation was performed in the same manner as in Example 1 except that the static elimination light source in Example 1 was changed to 591 nm LED (Rohm: full width at half maximum: 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 1. The results are shown in Table 4 below.

(Comparative Example 3)
Evaluation was performed in the same manner as in Example 1 except that the static elimination light source in Example 1 was changed to 630 nm LED (Rohm: half width 20 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 1. The results are shown in Table 4 below.

(Comparative Example 4)
Evaluation was performed in the same manner as in Example 1 except that the static elimination light source in Example 1 was changed to a fluorescent lamp (having the emission spectrum shown in FIG. 1). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 1. The results are shown in Table 4 below.

(Comparative Example 5)
Except for changing to irradiate substantially the same amount of light simultaneously using two 428 nm LEDs (made by ROHM: half-value width: 65 nm) and 630 nm LEDs (made by ROHM: half-value width: 20 nm) as the static elimination light source in Example 1. Evaluation was performed in the same manner as in 1. The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 1. The results are shown in Table 4 below.

From Table 4, when the wavelength of the static elimination light is less than 500 nm (Examples 1 and 2), the exposure after repeated use is compared with the case where a longer wavelength is used (Comparative Examples 1 to 3). It can be seen that the increase in the partial potential is small. In particular, when the thickness is less than 450 nm (Example 1), it can be seen that the effect is more remarkable than Example 2.
In addition, in the case where the emission distribution is wide and a component of long wavelength light of 500 nm or more is included (Comparative Example 4), a clear effect as in the example is not obtained. In addition, when two types of light sources having different exposure wavelengths are used (Comparative Example 5), it can be seen that the effect of charge removal by the short wavelength light source is reduced.

(Photoreceptor preparation example 2)
In Photoconductor Preparation Example 1, a photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that Dispersion 2 prepared above was used as the charge generation layer coating solution (referred to as electrophotographic photoconductor 2). .

(Example 3)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member 2 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 5 below.

Example 4
In Example 2, evaluation was performed in the same manner as in Example 2 except that the electrophotographic photosensitive member 2 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 5 below.

(Comparative Example 6)
In Comparative Example 1, evaluation was performed in the same manner as in Comparative Example 1 except that the electrophotographic photosensitive member 2 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 5 below.

(Comparative Example 7)
In Comparative Example 2, evaluation was performed in the same manner as in Comparative Example 2 except that the electrophotographic photosensitive member 2 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 5 below.

(Comparative Example 8)
In Comparative Example 3, evaluation was performed in the same manner as in Comparative Example 3 except that the electrophotographic photosensitive member 2 was used instead of the used electrophotographic photosensitive member 1. The results are shown in Table 5 below.

(Comparative Example 9)
In Comparative Example 4, evaluation was performed in the same manner as in Comparative Example 4 except that the electrophotographic photosensitive member 2 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 5 below.

  From Table 5, when the wavelength of the static elimination light is less than 500 nm (Examples 3 and 4), the exposure after repeated use is compared with the case where a longer wavelength is used (Comparative Examples 6 to 8). It can be seen that the increase in the partial potential is small. In particular, when the thickness is less than 450 nm (Example 3), it can be seen that the effect is more remarkable than Example 4. Further, when the emission distribution is wide and a component of long wavelength light of 500 nm or more is included (Comparative Example 9), a clear effect as in the example is not obtained.

(Photoreceptor Preparation Example 3)
In Photoconductor Preparation Example 1, a photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that a charge transport layer coating solution having the following composition was used as the charge transport layer coating solution (electrophotographic photoconductor 3 and To do).

<Charge transport layer coating solution>
Polycarbonate (TS2050: manufactured by Teijin Chemicals): 10 parts Charge transport material of the following structural formula (h): 7 parts Methylene chloride: 80 parts

(Example 5)
The electrophotographic photosensitive member 3 produced as described above is mounted on an image forming apparatus as shown in FIG. 11, and an image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, a transfer member A transfer belt was used as a member, and the following was used as a static elimination light source. The process conditions before the test were set as follows, and continuous 30,000 sheets were printed using a chart with a writing rate of 6%.

<Process conditions>
Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Surface potential after neutralization (unexposed area of writing light): −100V
Neutralizing light source: A monochromatic light of 461 nm was made by combining a xenon lamp with a spectroscope, which was guided to an image forming apparatus by an optical fiber, and slit-like light was irradiated to the surface of the photoreceptor at a static eliminating portion.

The evaluation was performed by measuring the photosensitive member exposed portion potential before and after printing 30,000 images.
As a measuring method, a surface potential meter is mounted at the position of the developing portion shown in FIG. 11, and after charging the photosensitive member to −900 V, solid writing is performed with the semiconductor laser, and the surface potential of the unexposed portion and the exposure at the developing portion are measured. The partial potential was measured. The results are shown in Table 6 below.
Further, after the potential measurement was performed after outputting 30,000 sheets, a chart as shown in FIG. 14 (the front half was a stripe and the rear half was a halftone) was output, and the unevenness of the image in the halftone portion was observed.
Further, in order to measure the transmittance of the charge transport layer, only the charge transport layer in the electrophotographic photoreceptor 3 is formed on a φ30 mm aluminum drum wound with a polyethylene terephthalate film under the same conditions as in the electrophotographic photoreceptor 4. did. This was cut out to an appropriate size, and the transmittance at a static elimination wavelength was measured using a commercially available spectrophotometer (Shimadzu: UV-3100) using a polyethylene terephthalate film without a charge transport layer as a comparison object. . The results are shown in Table 6.

(Example 6)
Evaluation was performed in the same manner as in Example 5 except that the static elimination light wavelength in Example 5 was changed to 443 nm by a spectroscope. The results are shown in Table 6 below.

(Example 7)
Evaluation was performed in the same manner as in Example 5 except that the static elimination light wavelength in Example 5 was changed to 437 nm by a spectrometer. The results are shown in Table 6 below.

(Example 8)
Evaluation was performed in the same manner as in Example 5 except that the static elimination light wavelength in Example 5 was changed to 433 nm by a spectrometer. The results are shown in Table 6 below.

Example 9
Evaluation was performed in the same manner as in Example 5 except that the static elimination light wavelength in Example 5 was changed to 429 nm by a spectrometer. The results are shown in Table 6 below.

As can be seen from Table 6, when the transmittance of the charge transport layer with respect to static elimination light is less than 30%, the effect is slightly reduced.
In the chart output of FIG. 14, the halftone portions of Examples 5 to 7 formed a completely normal image. However, in Examples 8 and 9, the level was not a problem, but the halftone portion was striped. A slight afterimage corresponding to was observed. This degree was worse in Example 9 than in Example 8.
From the above results, it is possible to suppress an increase in the potential of the exposed area after repeated use by irradiating the charge removal light of less than 500 nm, but when the transmittance of the charge transport layer to the charge removal light is less than 30%, It can be seen that there may be side effects.

(Photosensitive member production example 4)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge generation layer coating solution (dispersion 1) in Photoconductor Preparation Example 1 was changed to Dispersion 3 (referred to as electrophotographic photoconductor 4). .

(Photoreceptor Preparation Example 5)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge generation layer coating solution (Dispersion 1) in Photoconductor Preparation Example 1 was changed to Dispersion 4 (referred to as electrophotographic photoconductor 5). .

(Example 10)
Evaluation was performed using the electrophotographic photosensitive member 4 instead of the electrophotographic photosensitive member 1 under the same conditions as in Example 1. In addition, after outputting 30,000 images, a solid white image was output to evaluate background stains. The results are shown in Table 7 below together with the results of Example 1.

(Example 11)
Evaluation was performed using the electrophotographic photosensitive member 5 instead of the electrophotographic photosensitive member 1 under the same conditions as in Example 1. In addition, after outputting 30,000 images, a solid white image was output to evaluate background stains. The results are shown in Table 7 below.

  For the background dirt evaluation, a rank evaluation was performed from the number and size of sunspots generated on the background. The ranking was performed in four stages, and very good ones were indicated by ◎, good ones by ○, slightly inferior by Δ, and very bad by ×.

  From Table 7, when the average particle diameter of the coating solution used for the charge generation layer is 0.25 μm or less (Examples 11 and 12), the surface potential of the exposed portion in the initial state of the photoreceptor can be lowered and repeatedly used. Later, it can be seen that the occurrence of background contamination can be suppressed without affecting the increase in potential of the exposed portion.

(Photosensitive member preparation example 6)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge transport layer coating solution in Photoconductor Preparation Example 1 was changed to one having the following composition (referred to as electrophotographic photoconductor 6).

<Charge transport layer coating solution>
Polymer charge transport material of the following structural formula (i): 10 parts (weight average molecular weight: about 140000)

  Additive of structural formula (j) below: 0.5 part

  Methylene chloride: 100 parts

(Photoreceptor Preparation Example 7)
In the same manner as in the photoreceptor preparation example except that the thickness of the charge transport layer in the photoreceptor preparation example 1 is 22 μm, a protective layer coating solution having the following composition is applied and dried on the charge transport layer, and a 3 μm protection layer is provided. A photoconductor was prepared (referred to as electrophotographic photoconductor 7).

<Protective layer coating solution>
Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.): 10 parts Charge transport material of the following structural formula (g): 7 parts Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm,
Average primary particle size: 0.4 μm): 4 parts cyclohexanone 500 parts tetrahydrofuran 150 parts

(Photoreceptor Preparation Example 8)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 7 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 7 were changed to the following (referred to as electrophotographic photoconductor 8).
Titanium oxide fine particles: 4 parts (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.5 μm)

(Photoreceptor Preparation Example 9)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 7 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 7 were changed to the following (referred to as electrophotographic photoconductor 9).
Tin oxide-antimony oxide powder: 4 parts (specific resistance: 10 ⁶ Ω · cm, average primary particle size 0.4 μm)

(Photoreceptor Preparation Example 10)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 7 except that the protective layer coating solution in the photosensitive member preparation example 7 was changed to the one having the following composition (referred to as an electrophotographic photosensitive member 10).

<Protective layer coating solution>
Polymer charge transport material of the following structural formula (i): 17 parts (weight average molecular weight: about 140000)
Alumina fine particles: 4 parts (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm)
Cyclohexanone: 500 parts Tetrahydrofuran: 150 parts

(Photoreceptor Preparation Example 11)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member manufacturing example 7 except that the protective layer coating solution in the photosensitive member manufacturing example 7 was changed to the one having the following composition (referred to as an electrophotographic photosensitive member 11).

<Protective layer coating solution>
Methyltrimethoxysilane: 100 parts 3% acetic acid: 20 parts Charge transporting compound of the following structural formula (k): 35 parts Antioxidant (Sanol LS2626: Sankyo Chemical Co., Ltd.): 1 part Curing agent (dibutyltin acetate): 1 part 2-propanol: 200 parts

(Photoconductor Preparation Example 12)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 7 except that the protective layer coating solution in the photosensitive member preparation example 7 was changed to one having the following composition (referred to as an electrophotographic photosensitive member 12).

<Protective layer coating solution>
Methyltrimethoxysilane: 100 parts 3% acetic acid: 20 parts Charge transporting compound of the following structural formula (k): 35 parts Alumina fine particles: 15 parts (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size : 0.4μm)
Antioxidant (Sanol LS2626: Sankyo Chemical Co., Ltd.): 1 part Polycarboxylic acid compound BYK P104: Big Chemie Co .: 0.4 part Curing agent (dibutyltin acetate): 1 part 2-propanol: 200 parts

(Photoreceptor Preparation Example 13)
An electrophotographic photosensitive member was prepared in the same manner as the photosensitive member preparation example 7 except that the protective layer coating solution in the photosensitive member preparation example 7 was changed to the one having the following composition (referred to as an electrophotographic photosensitive member 13).

<Protective layer coating solution>
Trifunctional or higher functional radical polymerizable monomer having no charge transport structure: 10 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku Co., Ltd.) Molecular weight: 296, functional group number: trifunctional, molecular weight / functional group number = 99 }
Radical polymerizable compound having a monofunctional charge transport structure of the following structural formula (No. 54): 10 parts Photopolymerization initiator: 1 part [1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, Ciba Specialty) Chemicals)]
Tetrahydrofuran: 100 parts

The protective layer is naturally dried for 20 minutes after spray coating, and then the coating film is cured by light irradiation under conditions of a metal halide lamp: 160 W / cm, irradiation intensity: 500 mW / cm ² , irradiation time: 60 seconds. I let you.

(Photoreceptor Preparation Example 14)
In Photoconductor Preparation Example 13, all the examples of photoconductor preparation except that the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure contained in the protective layer coating solution was changed to the following radical polymerizable monomer. An electrophotographic photosensitive member was produced in the same manner as in Example 13 (referred to as an electrophotographic photosensitive member 14).
Trifunctional or higher functional radical polymerizable monomer (*) having no charge transporting structure (*): 10 parts (*) [pentaerythritol tetraacrylate (SR-295, manufactured by Kayaku Sartomer), molecular weight: 352, number of functional groups: tetrafunctional , Molecular weight / number of functional groups = 88]

(Photoreceptor Preparation Example 15)
A trifunctional or higher-functional radical polymerizable monomer having no charge transporting structure contained in the protective layer coating solution of Photoreceptor Preparation Example 13 was converted into a bifunctional radical polymerizable monomer having no following charge transporting structure. Except for changing to 10 parts, an electrophotographic photosensitive member was manufactured in the same manner as in the photosensitive member manufacturing example 13 (referred to as an electrophotographic photosensitive member 15).
Bifunctional radically polymerizable monomer having no charge transporting structure (*): 10 parts (*) [1,6-hexanediol diacrylate (manufactured by Wako Pure Chemical Industries), molecular weight: 226, number of functional groups: bifunctional, Molecular weight / number of functional groups = 113]

(Photoreceptor Production Example 16)
In Photoconductor Preparation Example 13, photoconductor preparation was performed except that the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure contained in the protective layer coating solution was replaced with the following radical polymerizable monomer. An electrophotographic photosensitive member was produced in the same manner as in Example 13 (referred to as an electrophotographic photosensitive member 16).
Trifunctional or higher functional radical polymerizable monomer (*) having no charge transporting structure (*): 10 parts (*) [caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-120, manufactured by Nippon Kayaku Co., Ltd.), molecular weight: 1947, functional Number of groups: 6 functions, molecular weight / number of functional groups = 325]

(Photoreceptor Preparation Example 17)
Radical polymerization having a bifunctional charge transporting structure represented by the following structural formula (m) is converted to a radically polymerizable compound having a monofunctional charge transporting structure contained in the protective layer coating solution of Photoreceptor Preparation Example 13. An electrophotographic photoconductor was prepared in the same manner as in Photoconductor Preparation Example 13 except that the photosensitive compound was replaced with 10 parts (referred to as electrophotographic photoconductor 17).

(Photoreceptor Preparation Example 18)
In Photoconductor Preparation Example 13, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 13 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 18).

<Protective layer coating solution>
Trifunctional or more radically polymerizable monomer having no charge transport structure: 6 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku Co., Ltd.), molecular weight: 296, functional group number: trifunctional, molecular weight / functional group number = 99}
Radical polymerizable compound having a monofunctional charge transport structure of the following structural formula (No. 54): 14 parts Photopolymerization initiator: 1 part [1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, Ciba Specialty) Chemicals)]
Tetrahydrofuran: 100 parts

(Photoreceptor Preparation Example 19)
In Photoconductor Preparation Example 13, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 13 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 19).

<Protective layer coating solution>
Trifunctional or more radical polymerizable monomer having no charge transport structure: 14 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku Co., Ltd.), molecular weight: 296, functional group number: trifunctional, molecular weight / functional group number = 99}
Radical polymerizable compound having a monofunctional charge transport structure of the following structural formula (No. 54): 6 parts Photopolymerization initiator: 1 part [1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, Ciba Specialty) Chemicals)]
Tetrahydrofuran: 100 parts

(Photoreceptor Preparation Example 20)
In Photoconductor Preparation Example 13, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 13 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 20).

<Protective layer coating solution>
Trifunctional or more radical polymerizable monomer having no charge transport structure: 2 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku Co., Ltd.), molecular weight: 296, functional group number: trifunctional, molecular weight / functional group number = 99}
Radical polymerizable compound having a monofunctional charge transport structure of the following structural formula (No. 54): 18 parts Photopolymerization initiator: 1 part [1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, Ciba Specialty) Chemicals)]
Tetrahydrofuran: 100 parts

(Photoconductor Preparation Example 21)
In Photoconductor Preparation Example 13, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 13 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 21).

<Protective layer coating solution>
Trifunctional or higher radical polymerizable monomer having no charge transport structure: 18 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku Co., Ltd.), molecular weight: 296, functional group number: trifunctional, molecular weight / functional group number = 99}
Radical polymerizable compound having a monofunctional charge transport structure of the following structural formula (No. 54): 2 parts Photopolymerization initiator: 1 part [1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, Ciba Specialty, Chemicals)]
Tetrahydrofuran: 100 parts

(Example 12)
The electrophotographic photosensitive member 1 produced as described above is mounted on an image forming apparatus as shown in FIG. 11, the image exposure light source is a 655 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, a transfer member A transfer belt was used as a member, and 472 nm (manufactured by Seiwa Electric Co., Ltd .: full width at half maximum of 15 nm) was used as a static elimination light source. The process conditions before the test were set as follows, and 50,000 sheets were continuously printed using a chart with a writing rate of 6%.

<Process conditions>
Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Surface potential after neutralization (unexposed area of writing light): −100V

<Evaluation items>
(1) Measurement of surface potential Evaluation was made by measuring the potential of a photosensitive member exposed part before and after printing 50,000 images.
As a measuring method, a surface potential meter is mounted at the position of the developing portion shown in FIG. 11 and the photosensitive member is charged to −900 V, and then solid writing is performed with the semiconductor laser. The exposed area potential was measured. The results are shown in Table 8 below.

(2) Soil evaluation Further, after outputting 50,000 images (after the completion of the surface potential measurement), a solid white image was output to evaluate the soil (22 ° C.-50% RH). The background dirt evaluation was performed by the above-described four-level rank evaluation. The results are shown in Table 8 below.

(3) Evaluation of cleaning property Further, after evaluation of soiling, under a low temperature and low humidity environment (10 ° C., 15% RH), using a test chart as shown in FIG. The image was output in the direction from solid to white, 50 sheets were continuously printed, and the cleaning property was evaluated. At this time, the image of the 50th white solid portion was visually evaluated.
Evaluation is performed in 4 stages, ◎ for very good (no cleaning failure at all), ◯ for good (level with slight black streaks, 1 to 2 in the longitudinal direction), slightly inferior (slightly) The level at which black streaks enter, 3 to 4 places in the longitudinal direction) is represented by Δ, and the very bad one (level at which black streaks enter clearly) is represented by x. The results are shown in Table 8 below.

(4) Dot reproducibility evaluation Subsequent to the previous cleaning test, a further sheet passing test (used with the previous 6% char) was conducted in a high temperature and high humidity environment (30 ° C.-90% RH). A one-dot image evaluation (outputting an image in which independent dots were written) was performed after passing the sheet. A one-dot image was observed with an optical microscope, and the clarity of the dot outline was ranked. The rank evaluation was performed in four stages. Very good ones were indicated by ◎, good ones were indicated by ○, slightly inferior ones were indicated by Δ, and very bad ones were indicated by ×. The results are shown in Table 8 below.

(5) Wear amount evaluation The initial film thickness of the photoconductor was measured, and the film thickness was measured again after completing the above tests (1) to (4). The difference in film thickness (amount of wear) before and after all tests was evaluated. The film thickness was measured at intervals of 1 cm, excluding 5 cm at both ends in the longitudinal direction of the photoreceptor, and the average value was taken as the film thickness. The results are shown in Table 8 below.
Further, in order to measure the transmittance of the charge transport layer, only the charge transport layer in the electrophotographic photoreceptor 1 is formed on a φ30 mm aluminum drum wound with a polyethylene terephthalate film under the same conditions as in the electrophotographic photoreceptor 3. did. This was cut out to an appropriate size, and the transmittance at a static elimination wavelength was measured using a commercially available spectrophotometer (Shimadzu: UV-3100) using a polyethylene terephthalate film without a charge transport layer as a comparison object. . The results are shown in Table 8.

(Examples 13 to 28)
Under the same conditions as in Example 12, the electrophotographic photoreceptors 6 to 21 produced as described above were evaluated. When the surface layer of the electrophotographic photosensitive member was a protective layer, the protective layer transmittance was determined as follows. Only the protective layer in the electrophotographic photoreceptors 6 to 21 was formed on a φ30 mm aluminum drum wound with a polyethylene terephthalate film under the same conditions as in the electrophotographic photoreceptors 6 to 21. This was cut out to an appropriate size, and the transmittance at a static elimination wavelength was measured using a commercially available spectrophotometer (Shimadzu: UV-3100) using a polyethylene terephthalate film having no protective layer as a comparison target.
The transmittance of the protective layer was measured in the same manner as in Example 12.
The results are shown in Table 8 below. Table 8 below also describes the electrophotographic photosensitive member numbers used corresponding to the example numbers.

Table 8 shows the following.
Even in the case where a protective layer is provided, the effect of preventing the residual potential from rising can be recognized by performing static elimination with a light source having a wavelength shorter than 500 nm.
By providing a charge transport layer containing a polymer charge transport material (polycarbonate having a triarylamine structure in the main chain or side chain) (Example 13), the wear resistance is lower than that of a low molecular dispersion system (Example 12). improves. By providing the protective layer (Examples 14 to 28), the wear resistance is improved as compared with the case where the protective layer is not provided (Example 12). Among the cases where a protective layer containing an inorganic pigment (metal oxide) is provided (Examples 14 to 16), by containing an inorganic pigment (metal oxide) having a specific resistance of 10 ¹⁰ Ω · cm or higher, The dot reproducibility does not decrease so much even under high humidity (Examples 14 and 15).
By having the crosslinked structure in the protective layer, the wear resistance is improved as compared with the case where it is not present. Furthermore, when using a protective layer formed by curing a radically polymerizable monomer having three or more functional groups having no charge transporting structure and a radically polymerizable compound having a monofunctional charge transporting structure, Higher wear resistance is obtained (Examples 20, 21, 23, 25-28).
In the case of using a protective layer formed by curing a tri- or more functional radical polymerizable monomer having no charge transporting structure and a radical polymerizable compound having a monofunctional charge transporting structure. Also, the cleaning property is good.

(Comparative Example 10)
The exposed portion potential and the protective layer transmittance were measured and evaluated in the same manner as in Example 20 except that the neutralization light source in Example 20 was changed to 502 nm LED (manufactured by Seiwa Denki: half-value width 15 nm).
The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 20. The results are shown in Table 9 below.

(Comparative Example 11)
The exposed portion potential and the protective layer transmittance were measured and evaluated in the same manner as in Example 20 except that the static elimination light source in Example 20 was changed to a 591 nm LED (Rohm: half width: 15 nm).
The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 20. The results are shown in Table 9 below.

(Comparative Example 12)
Except for changing to a 630 nm LED (made by ROHM: half-value width 20 nm) as the static elimination light source in Example 20, the exposed portion potential and the protective layer transmittance were measured and evaluated in the same manner as in Example 20.
The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 20. The results are shown in Table 9 below.

(Comparative Example 13)
Except for changing to a fluorescent lamp (having the emission spectrum shown in FIG. 1) as the charge removal light source in Example 20, the exposed portion potential and protective layer transmittance were measured and evaluated in the same manner as in Example 20.
The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 20. The results are shown in Table 9 below.

From Table 9, when the wavelength of the static elimination light is less than 500 nm (Example 20), compared to the case where a longer wavelength is used (Comparative Examples 10 to 12), the exposed portion potential after repeated use It can be seen that the rise in is small.
Further, in the case where the emission distribution is wide and a component of long wavelength light of 500 nm or more is included (Comparative Example 13), the clear effect as in the example is not obtained.

(Example 29)
The electrophotographic photosensitive member 13 produced as described above is mounted on an image forming apparatus as shown in FIG. 11, and an image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, a transfer member A transfer belt was used as a member, and the following was used as a static elimination light source. The process conditions before the test were set as follows, and 50,000 sheets were continuously printed using a chart with a writing rate of 6%.

<Process conditions>
Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Surface potential after neutralization (unexposed area of writing light): −100V
Neutralizing light source: A monochromic light of 450 nm was made by combining a xenon lamp with a spectroscope, which was guided to an image forming apparatus by an optical fiber, and slit-shaped light was applied to the surface of the photoreceptor at a static eliminating portion.

Evaluation was made by measuring the potential of the photosensitive member exposed area before and after printing 50,000 images.
As a measuring method, a surface potential meter is mounted at the position of the developing portion shown in FIG. 11 and the photosensitive member is charged to −900 V, and then solid writing is performed with the semiconductor laser. The exposed area potential was measured. The results are shown in Table 10 below.
Further, after the potential measurement was performed after outputting 50,000 sheets, a chart as shown in FIG. 14 (the front half was a stripe and the rear half was a halftone) was output, and the unevenness of the image in the halftone portion was observed.
Further, in order to measure the transmittance of the protective layer, only the protective layer in the electrophotographic photoreceptor 13 was formed on a φ30 mm aluminum drum wrapped with a polyethylene terephthalate film under the same conditions as in the electrophotographic photoreceptor 13. This was cut out to an appropriate size, and the transmittance at a static elimination wavelength was measured using a commercially available spectrophotometer (Shimadzu: UV-3100) using a polyethylene terephthalate film having no protective layer as a comparison target. The results are shown in Table 10.

(Example 30)
Evaluation was performed in the same manner as in Example 29 except that the static elimination light wavelength in Example 29 was changed to 400 nm by a spectrometer. The results are shown in Table 10 below.

(Example 31)
Evaluation was performed in the same manner as in Example 29 except that the static elimination light wavelength in Example 29 was changed to 393 nm by a spectrometer. The results are shown in Table 10 below.

(Example 32)
Evaluation was performed in the same manner as in Example 29 except that the static elimination light wavelength in Example 29 was changed to 390 nm by a spectrometer. The results are shown in Table 10 below.

(Example 33)
Evaluation was performed in the same manner as in Example 29 except that the static elimination light wavelength in Example 29 was changed to 385 nm by a spectrometer. The results are shown in Table 10 below.

As can be seen from Table 10, when the transmittance of the protective layer against the static elimination light is less than 30%, the effect is slightly reduced.
In the chart output of FIG. 14, the halftone portions of Examples 29 to 31 formed a completely normal image. However, in Examples 32 and 33, the level was not a problem, but the halftone portion was striped. A slight afterimage corresponding to was observed. This degree was worse in Example 33 than in Example 32.
From the above results, it is possible to suppress the exposure portion potential increase after repeated use by irradiating the charge-removing light of less than 500 nm, but when the transmittance of the protective layer to the charge-removing light is less than 30%, It can be seen that side effects may occur.

(Photoconductor Preparation Example 22)
The intermediate layer in the photoreceptor preparation example 1 has a laminated structure of a charge blocking layer and a moire preventing layer. Photoconductor Preparation Example 1 except that the charge blocking layer coating solution and the moire prevention layer coating solution having the following composition were applied and dried to obtain a 1.0 μm charge blocking layer and a 3.5 μm moire prevention layer. Similarly, a photoconductor was prepared (referred to as electrophotographic photoconductor 22).

<Charge blocking layer coating solution>
N-methoxymethylated nylon (Lead City: Fine Resin FR-101): 4 parts Methanol: 70 parts n-Butanol: 30 parts

<Moire prevention layer coating solution>
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm): 126 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.]: 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dai Nippon Ink Chemical Co., Ltd.]: 18.7 parts 2-butanone: 100 parts

With the above composition, the volume ratio of the inorganic pigment to the binder resin is 1.5 / 1.
The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

(Photoconductor Preparation Example 23)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 22 except that the thickness of the charge blocking layer was 0.3 μm in Photoconductor Preparation Example 22 (referred to as electrophotographic photoconductor 23).

(Photoconductor Preparation Example 24)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 22 except that the thickness of the charge blocking layer was 1.8 μm in Photoconductor Preparation Example 22 (referred to as electrophotographic photoconductor 24).

(Photoconductor Preparation Example 25)
In Photoconductor Preparation Example 22, a photoconductor was prepared in the same manner as Photoconductor Preparation Example 22 except that the charge blocking layer coating solution was changed to one having the following composition (referred to as electrophotographic photoconductor 25).

<Charge blocking layer coating solution>
Alcohol-soluble nylon (Toray: Amilan CM8000): 4 parts Methanol: 70 parts n-butanol: 30 parts

(Photoconductor Preparation Example 26)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 22 except that the moire-preventing layer coating solution was changed to one having the following composition in Photoconductor Preparation Example 22 (referred to as electrophotographic photoconductor 26).

<Moire prevention layer coating solution>
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm): 252 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.]: 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dai Nippon Ink Chemical Co., Ltd.]: 18.7 parts 2-butanone: 100 parts

With the above composition, the volume ratio of the inorganic pigment to the binder resin is 3/1.
The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

(Photoconductor Preparation Example 27)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 22 except that the moire-preventing layer coating solution was changed to one having the following composition in Photoconductor Preparation Example 22 (referred to as electrophotographic photoconductor 27).

<Moire prevention layer coating solution>
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm): 84 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.]: 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dai Nippon Ink Chemical Co., Ltd.]: 18.7 parts 2-butanone: 100 parts

In the above composition, the volume ratio of the inorganic pigment to the binder resin is 1/1.
The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

(Examples 34 to 39)
The electrophotographic photosensitive member produced as described above was subjected to a running test of 50,000 sheets under the same conditions as in Example 12 (same evaluation method and items). The results are shown in Table 11 below in comparison with Example 12.

  From the results shown in Table 11, it can be seen that the durability against soiling is improved by configuring the intermediate layer as a charge blocking layer and a moire preventing layer.

(Example 40)
The previously prepared electrophotographic photosensitive member 1 is mounted on a process cartridge as shown in FIG. 13, mounted in an image forming apparatus as shown in FIG. 12, and an image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror). ), A contact roller charger was used as the charging member, a transfer belt was used as the transfer member, and a 428 nm LED (manufactured by ROHM: full width at half maximum: 65 nm) was used as the charge eliminating light source. Process conditions before the test were set as follows, and a chart with a writing rate of 6% (characters equivalent to 6% as an image area are written on the entire A4 surface) was continuously 30,000. Sheet printing was performed.

<Process conditions>
Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Surface potential after neutralization (unexposed area of writing light): −100V

The evaluation was performed by measuring the potential of the photosensitive member exposed portion before and after printing 30,000 images (black station).
As a measuring method, a surface potential meter is mounted at the developing portion position shown in FIG. 12, and after charging the photosensitive member to −900 V, solid writing is performed with the semiconductor laser, and the surface potential of the unexposed portion at the developing portion and the exposure are measured. The partial potential was measured. The results are shown in Table 12 below.
Further, before and after printing 30,000 sheets, an ISO / JIS-SCID image N1 (portrait) was output to evaluate the color color reproducibility.
Further, in order to measure the transmittance of the charge transport layer, only the charge transport layer in the electrophotographic photoreceptor 1 is formed on a φ30 mm aluminum drum wound with a polyethylene terephthalate film under the same conditions as in the electrophotographic photoreceptor 3. did. This was cut out to an appropriate size, and the transmittance at a static elimination wavelength was measured using a commercially available spectrophotometer (Shimadzu: UV-3100) using a polyethylene terephthalate film without a charge transport layer as a comparison object. . The results are shown in Table 12.

(Example 41)
Evaluation was performed in the same manner as in Example 40, except that the charge removal light source in Example 40 was changed to a 472 nm LED (manufactured by Seiwa Denki: full width at half maximum of 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 40. The results are shown in Table 12 below.

(Comparative Example 14)
Evaluation was performed in the same manner as in Example 40, except that the static elimination light source in Example 40 was changed to a 502 nm LED (manufactured by Seiwa Denki: full width at half maximum of 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 40. The results are shown in Table 12 below.

(Comparative Example 15)
Evaluation was performed in the same manner as in Example 40 except that the static elimination light source in Example 40 was changed to a 591 nm LED (Rohm: half width: 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 40. The results are shown in Table 12 below.

(Comparative Example 16)
Evaluation was performed in the same manner as in Example 40, except that the static elimination light source in Example 40 was changed to 630 nm LED (Rohm: half width 20 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 40. The results are shown in Table 12 below.

(Comparative Example 17)
Evaluation was performed in the same manner as in Example 40 except that the static elimination light source in Example 40 was changed to a fluorescent lamp (having the emission spectrum shown in FIG. 1). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 40. The results are shown in Table 12 below.

(Comparative Example 18)
Except for changing to irradiate substantially the same amount of light simultaneously using two 428 nm LEDs (Rohm: half width 65 nm) and 630 nm LEDs (Rohm: half width 20 nm) as the static elimination light source in Example 40 Evaluation was carried out in the same manner as in No.40. The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 40. The results are shown in Table 12 below.

From Table 12, when the wavelength of the static elimination light is less than 500 nm (Examples 40 and 41), exposure after repeated use is compared with the case of using a longer wavelength (Comparative Examples 14 to 16). It can be seen that the increase in the partial potential is small. Furthermore, when it is less than 450 nm (Example 40), it turns out that the effect is further remarkable.
Further, in the case where the emission distribution is wide and a component of long wavelength light of 500 nm or more is included (Comparative Example 17), the clear effect as in the example is not obtained. In addition, when two types of light sources having different exposure wavelengths are used (Comparative Example 18), it can be seen that the effect of charge removal by the short wavelength light source is reduced.
From the results of the test chart, in the case of Examples 40 and 41, an image almost the same as the initial image was output even after printing 30,000 sheets, but in the case of Comparative Examples 14 to 18, after printing 30,000 sheets , The image was slightly out of color balance.

It is a spectrum emission spectrum figure of a fluorescent lamp. It is a conceptual diagram of the optical carrier generation | occurrence | production mechanism of an organic material. It is a conceptual diagram of the optical carrier generation | occurrence | production mechanism of an inorganic material. It is a figure showing the layer structure of the electrophotographic photosensitive member used for this invention. It is a figure showing another layer structure of the electrophotographic photosensitive member used for this invention. It is a figure showing another layer structure of the electrophotographic photosensitive member used for this invention. It is a figure showing another layer structure of the electrophotographic photosensitive member used for this invention. It is a figure which shows the state of the dispersion liquid when dispersion time is short. It is a figure which shows the state of the dispersion liquid when dispersion time is long. It is a figure which shows an average particle diameter and a particle size distribution about the dispersion liquid of FIG. 1 is a schematic diagram for explaining an image forming apparatus and an electrophotographic process of the present invention. 1 is a schematic view for explaining a tandem-type full-color image forming apparatus of the present invention. FIG. FIG. 4 is a diagram for explaining a process cartridge for an image forming apparatus according to the present invention. 18 is a test chart used in Example 15. 22 is a test chart used in Example 22. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Static elimination lamp 3 Charger (charging member)
5 Image exposure unit 6 Developing unit 8 Registration roller 9 Transfer paper 10 Transfer charger 11 Separation charger 12 Separation claw 14 Fur brush 15 Cleaning blades 16Y, 16M, 16C, 16K Photoconductors 17Y, 17M, 17C, 17K Charger (charging member)
18Y, 18M, 18C, 18K Exposure unit (exposure section)
19Y, 19M, 19C, 19K Developing means (developing member)
20Y, 20M, 20C, 20K Cleaning member 21Y, 21M, 21C, 21K Transfer brush 22 Transfer conveyance belt 23 Registration roller 24 Fixing device 25Y, 25M, 25C, 25K Image forming element 26 Transfer paper 27Y, 27M, 27C, 27K Static elimination member 101 photoconductor 102 charger (charging means)
Reference Signs List 103 Image exposure unit 104 Developing unit 105 Transfer body 106 Transfer unit 107 Cleaning unit 108
31 Conductive Support 35 Charge Generation Layer 37 Charge Transport Layer 39 Intermediate Layer 41 Protective Layer 43 Charge Blocking Layer 45 Moire Prevention Layer

Claims (23)

An electrostatic latent image carrier having a photosensitive layer comprising a charge generation layer and a charge transport layer on a support, an electrostatic latent image forming means, a developing means, a transfer means, a fixing means, and an electrostatic latent image In an image forming apparatus having at least a static elimination means for photostaticizing residual charges on a carrier,
The static elimination means has a light source that emits light having a wavelength shorter than 500 nm,
The image forming apparatus, wherein the charge generation layer contains at least one naphthalene tetracarboxylic acid diimidazole pigment represented by any one of the following general formulas (1) and (2).
(In general formulas (1) and (2), A represents an optionally substituted divalent aromatic hydrocarbon group or divalent nitrogen-containing heterocyclic group.) The image forming apparatus according to claim 1, wherein the naphthalenetetracarboxylic acid diimidazole pigment represented by the general formula (1) is a naphthalenetetracarboxylic acid diimidazole pigment represented by the following formula (3): .
The image forming apparatus according to claim 1, wherein the naphthalenetetracarboxylic acid diimidazole pigment represented by the general formula (2) is a naphthalenetetracarboxylic acid diimidazole pigment represented by the following formula (4). .
  4. The image forming apparatus according to claim 1, wherein the charge transport layer transmits at least 30% of irradiation light for photostatic discharge. 5.   The image forming apparatus according to claim 1, wherein the charge transport layer contains a charge transport material having a triarylamine structure. 6. The image forming apparatus according to claim 5, wherein the charge transport material is a charge transport material represented by the following formula (5).
Wherein R ₃₀₁ , R ₃₀₃ and R ₃₀₄ are a hydrogen atom, an amino group, an alkoxy group, a thioalkoxy group, an aryloxy group, a methylenedioxy group, an unsubstituted alkyl group, a halogen atom or a substituted or unsubstituted aryl. R ₃₀₂ represents a hydrogen atom, an alkoxy group, a substituted or unsubstituted alkyl group or halogen, and k, l, m and n are integers of 1, 2, 3 or 4, each of which is 2, 3 Or when R is an integer of 4, R ₃₀₁ , R ₃₀₂ , R ₃₀₃ and R ₃₀₄ may be the same or different.)   The image forming apparatus according to claim 1, wherein the charge transport layer contains a polycarbonate containing a triarylamine structure in at least one of a main chain and a side chain.   The image forming apparatus according to claim 1, further comprising a protective layer on the charge transport layer.   The image forming apparatus according to claim 8, wherein the protective layer transmits at least 30% of the light for light neutralization. The image forming apparatus according to claim 8, wherein the protective layer includes at least one selected from an inorganic pigment or a metal oxide having a specific resistance of 10 ¹⁰ Ω · cm or more.   The protective layer is formed by curing at least a trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. The image forming apparatus according to claim 8, wherein the image forming apparatus is an image forming apparatus. 12. The image formation according to claim 11, wherein the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formulas (6) and (7). apparatus.
[In the formulas (6) and (7), R ₁ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Aryl group, cyano group, nitro group, alkoxy group, —COOR ₇ (R ₇ has a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. A carbonyl halide group or —CONR ₈ R ₉ (R ₈ and R ₉ may be a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or a substituent. An aralkyl group or an aryl group which may have a substituent, which may be the same or different from each other.), Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group and are the same Or different. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3. ] 13. The image forming apparatus according to claim 11, wherein the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (8).
(Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represent an integer of 0 to 3. Za represents a single bond, a methylene group, an ethylene group, or the following formula (a), (b) or (c).
  The image forming apparatus according to claim 11, wherein the protective layer curing means is heating or light energy irradiation means.   In the latent electrostatic image bearing member, an intermediate layer is provided between the support and the charge generation layer, and the intermediate layer includes a charge blocking layer for preventing charge injection from the support to the photosensitive layer, and an inner layer of the photosensitive layer. 15. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises a moire preventing layer that prevents the occurrence of moire.   The image forming apparatus according to claim 15, wherein the charge blocking layer is made of an insulating material and has a film thickness of less than 2.0 μm and 0.3 μm or more.   The image formation according to claim 15 or 16, wherein the moire preventing layer contains an inorganic pigment and a binder resin, and a volume ratio of the inorganic pigment and the binder resin is in a range of 1/1 to 3/1. apparatus.   18. The image forming apparatus according to claim 1, wherein a light source wavelength of image writing light used for the electrostatic latent image forming unit is a light source having a wavelength shorter than 450 nm.   19. The image according to claim 1, comprising a plurality of image forming elements each having at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, a transfer unit, and a charge eliminating unit. Forming equipment.   The electrostatic latent image carrier and one or more means selected from an electrostatic latent image forming means, a developing means, a charge eliminating means, and a cleaning means are integrated, and the apparatus main body and a detachable process cartridge are mounted. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier having a photosensitive layer comprising a charge generation layer and a charge transport layer on a support;
Developing the electrostatic latent image with toner to form a visible image;
A transfer step of transferring the visible image to a recording medium;
A fixing step of fixing the transferred image transferred to the recording medium;
An image forming method comprising at least a static elimination step of photostaticizing residual charges of the electrostatic latent image carrier,
The charge removing step is a step of discharging by irradiating light having a wavelength shorter than 500 nm, and the charge generation layer of the electrostatic latent image carrier on which an electrostatic latent image is formed in the electrostatic latent image forming step. Contains at least one naphthalene tetracarboxylic acid diimidazole pigment represented by either of the following general formulas (1) or (2).
(In the general formulas (1) and (2), A represents a divalent aromatic hydrocarbon group or a divalent nitrogen-containing heterocyclic group which may be substituted.)   The image forming method according to claim 21, wherein a light source wavelength of image writing light used in the electrostatic latent image forming step is a light source having a wavelength shorter than 450 nm. 23. The image forming method according to claim 21, further comprising a plurality of image forming steps including the electrostatic latent image forming step, the developing step, the transfer step, and the charge eliminating step.