JP2001117244A - Digital electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital electrophotographic device by which a defective image quality so-called ghost is not caused, miniaturization is attained and an excellent image quality is obtained even when an S-shaped photoreceptor is used in an electrophotographic device which does not have an exposure means for destaticization. SOLUTION: Relating to the digital electrophotographic device that is provided with at least an electrophotographic sensitive body 11 in which exposure required for the potential attenuation of 50% is less than five times of the exposure required for the potential attenuation of 10%, an electrifying means 13, an electrostatic latent image forming exposure means 14, a developing means 15 and a transferring means 16 and in which a means to expose the body 11 is only the means 14, the potential attenuation time of 50% (T50) for the flash exposure of the body 11 and time required from the means 14 and the next means 13 (time between exposure and electrification) has the relation of T50 <=(the time between the exposure and the electrification)/10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital electrophotographic apparatus capable of forming a high quality image.

[0002]

2. Description of the Related Art In recent years, electrophotographic technology has played a central role in the fields of copiers, printers, facsimile machines and the like because of its advantages such as high speed and high printing quality.

A conventional analog type electrophotographic copying machine that optically forms an image on an electrophotographic photosensitive member (hereinafter, may be simply referred to as a “photosensitive member”) and exposes the image is based on a density gradation. In order to improve the reproducibility of halftone, a photoconductor having a photo-induced potential decay characteristic as shown in FIG. Body ”).

On the other hand, digital electrophotographic apparatuses, which have been actively researched and developed in response to recent demands for higher image quality, higher added value, networking, etc., generally use a gray scale based on an area ratio of dots or the like. To adopt the area gradation method
Rather, as shown in FIG. 2, light-induced potential decay (hereinafter, sometimes simply referred to as “potential decay”) is not performed until a certain exposure amount is reached, and a steep potential decay occurs when the exposure amount is exceeded. The use of a photoreceptor having an S-shaped photo-induced potential decay characteristic (hereinafter, referred to as “S-shaped photoreceptor”, and the property of the photoreceptor is referred to as “S-shaped property”) makes it possible to sharpen pixels. It is desirable because the degree can be increased.

[0005] This S-shaped photoinduced potential decay characteristic is based on ZnO
This is a known phenomenon in a single-layer type photoconductor in which an inorganic pigment such as phthalocyanine or an organic pigment such as phthalocyanine is dispersed in a resin. M. Schaffert: "Ele
crophotography ", Focal Pr
ess, p. 344 (1975); W. Weig
1, J .; Mammino, G .; L. Whitake
r, R. W. Radler, J .; F. Byrne; "C
current Problems in Electr
ophotography ", Walter de G
ruyter, p. 287 (1972)]. In particular, a large number of single-layer photoreceptors for laser exposure in which a phthalocyanine-based pigment having photosensitivity in the near-infrared region, which is the wavelength of a semiconductor laser that is widely used at present, is dispersed in a resin has been proposed (for example, Nguyen・ Chan Kae, Aizawa: Journal of the Chemical Society of Japan, p. 393 (1986), JP-A-1-1694
Nos. 54, 2-207258, 3-318
No. 47, 5-313337].

[0006] D. M. Pai et al., In a laminated photoreceptor comprising a charge generation layer and a charge transport layer, include, as a charge transport layer, at least two charge transport regions and one electrically inactive region, wherein the charge transport regions are in contact with each other. It has been reported that an S-shaped photo-induced potential decay characteristic can be realized by using a non-uniform charge transport layer formed with a convoluted charge transport path in combination with an arbitrary charge generation layer [Japanese Unexamined Patent Application Publication No. No. 83077 (U.S. Pat.
No. 86)].

Further, the present inventors have found that a photoconductor having a three-layer structure comprising a charge generation layer, a non-uniform charge transport layer, and a uniform charge transport layer exhibits an S-shaped photoinduced potential decay characteristic. 9-96914), and the above-mentioned D.C. M. Pai
From these inventions, we succeeded in further increasing the degree of function separation and stabilizing it.

On the other hand, in a digital electrophotographic apparatus, a contact-type charger having a low ozone generation amount is frequently used instead of a corona charger having a large ozone generation amount such as a corotron or a scorotron. In a digital electrophotographic apparatus using a contact-type charger having high charge uniformity, generally, there is no exposure means for static elimination in order to reduce cost and size.

Even when a J-shaped photoreceptor is used in such an electrophotographic apparatus having no exposure means for static elimination, a so-called ghost image defect occurs in which a previous exposure image appears in a developed image after the next exposure. Was not. However, if an S-shaped photoreceptor is used in an electrophotographic apparatus having no exposing means for static elimination, an image quality defect called a ghost may occur, which has been a problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object of the present invention is to provide an electrophotographic apparatus having no exposure means for static elimination in an S-shape. Even if a photoconductor is used, image quality defects called ghosts do not occur, miniaturization is possible, and
An object of the present invention is to provide a high quality digital electrophotographic apparatus.

[0011]

SUMMARY OF THE INVENTION The inventors of the present invention have been made to provide a high-quality digital electrophotographic apparatus which does not have a charge removing light, can be miniaturized, and has an S-shaped photosensitive member mounted thereon. Has found that the above problem can be avoided by making the photoinduced potential decay time of the electrophotographic photosensitive member mounted in the device sufficiently shorter than the time between exposure and charging of the device, and arrived at the present invention.

That is, the present invention provides an electrophotographic photoreceptor in which the exposure amount (E _50% ) required for 50% potential decay is less than 5 times the exposure amount (E _10% ) required for 10% potential decay,
Charging means for charging the electrophotographic photoreceptor; exposure means for forming an electrostatic latent image by performing exposure based on a digitally processed image signal; and toner for developing the electrostatic latent image A digital type including a developing unit for obtaining an image, and a transfer unit for transferring the toner image to a transfer material, and wherein the unit for exposing the electrophotographic photosensitive member is only the electrostatic latent image forming exposure unit. In an electrophotographic apparatus, a 50% potential decay time (T
_50% ) and the time from the exposure means for forming an electrostatic latent image to the next charging means (exposure-charging time) has a relationship represented by the following equation 1. is there. T _50% ≤ (exposure-charge time) / 10 (Equation 1)

According to the present invention, in an electrophotographic apparatus having no exposure means for static elimination, the exposure amount required for 50% potential attenuation (E _50% ) is less than five times the exposure amount required for 10% potential attenuation (E _10% ). Even if the S-shaped photoreceptor is used, it is possible to provide a digital electrophotographic apparatus which can be miniaturized without causing an image quality defect called a ghost, and which has high image quality.

In the present invention, it is preferable that the charging means is a contact charging means to which a voltage obtained by superimposing a DC voltage and an AC voltage is applied. By using a contact type charging means applying a voltage obtained by superimposing a DC voltage and an AC voltage,
A high-quality digital electrophotographic apparatus in which image defects called ghosts are less likely to occur can be provided.

Further, in the present invention, the exposure amount (E _50% ) required for 50% potential decay in the electrophotographic photosensitive member.
Is more preferably three times or less the exposure amount (E _10% ) required for 10% potential decay. By using a photoreceptor having a high S-characteristic, higher image quality can be achieved.

In the present invention, a 50% potential decay time (T
_50% ) and the time from the exposure means for forming the electrostatic latent image to the next charging means (exposure-charge time) is more preferably in the relationship of the following formula 2. T _50% ≦ (exposure-charge time) / 20 (Equation 2) The 50% potential decay time for flash exposure is the time from the exposure means for forming an electrostatic latent image to the next charging means (exposure-charge time) By using a photoreceptor of 1/20 or less of ()), higher image quality can be achieved.

In the present invention, the 50% potential decay time (T _50% ) of the electrophotographic photosensitive member with respect to the flash exposure.
Is desirably 0.05 sec or less.
50% potential decay time for flash exposure (T _50% )
Is shortened to 0.05 sec or less, the speed and the image quality can be further improved, and the degree of freedom in designing the digital electrophotographic apparatus of the present invention can be increased.

The electrophotographic photosensitive member according to the present invention includes:
It is preferable that a charge generation layer and a non-uniform charge transport layer in which charge transport domains are dispersed in an electrically inert matrix are provided on the surface of the conductive support. If the electrophotographic photosensitive member of the present invention has such a configuration, the digital electrophotographic apparatus of the present invention can be easily manufactured. In addition, the electrophotographic photoreceptor having such a configuration is
Since it has high stability, the digital electrophotographic apparatus of the present invention can have high stability.

The heterogeneous charge transporting layer in which the charge transporting domains are dispersed in the electrically inert matrix includes a phase-separable layer containing a charge transporting block and an insulating block (charge transporting inactive block). Desirably, it is formed from a block copolymer or a graft copolymer. Since the heterogeneous charge transport layer having such a configuration has high stability, the digital electrophotographic apparatus of the present invention can have high stability.

In the electrophotographic photoreceptor of the present invention, in addition to the charge generation layer and the non-uniform charge transport layer,
Further, it is desirable to provide a uniform charge transport layer. By providing the uniform charge transport layer, the thickness of the non-uniform charge transport layer that determines the response speed of the electrophotographic photoreceptor can be reduced, and the speed of the digital electrophotographic apparatus of the present invention can be increased.

Regarding the mechanism of the S-shaped photoinduced potential decay characteristics, the trap theory [for example, Kitamura, Komon: Journal of the Society of Electrophotography, Vol. 20, p. 60 (1982)];
M. Although there are some proposals such as the convolutional conduction theory proposed by Pai et al. In the above-mentioned document, there is no established theory yet.
However, the above-mentioned pigment resin dispersion type single-layer photoreceptor, which has been reported as an S-shaped photoreceptor, M. Pa
In the laminated photoreceptor comprising the charge generation layer and the heterogeneous charge transport layer, and the laminated photoreceptor comprising the charge generation layer, the heterogeneous charge transport layer and the uniform charge transport layer,
It can be recognized that at least the charge transport path of the charge transport region adjacent to the charge generation region has a non-uniform structure in which charge transport domains are dispersed in an electrically inert matrix. In addition, the electrical inertness here means that the transport energy level is largely different from the transport energy level of the charge transport domain, and at a normal electric field intensity, the transport charge is substantially not injected, It means that the transport charge is in a practically electrically insulating state.

According to the convolutional conduction theory of Pai et al., It is estimated that the process in which the S-shaped photoinduced potential decay occurs is as follows. First, in the heterogeneous charge transport layer, it is considered that the charge transport domains dispersed in the electrically inert matrix are in contact with each other to form a spiral charge transport path. In this case, when the electrophotographic photoreceptor is charged and a high electric field is applied to the photosensitive layer, the charges generated in the charge generation layer by exposure are transferred from the charge generation layer to the non-uniform charge transport layer by the Coulomb force due to the electric field. And moves in the direction of the electric field in the charge transporting domain. However, when reaching the terminal convex portion of the charge transporting domain, it encounters a barrier of an electrically inactive matrix, and the movement direction is regulated by the electric field, so that the movement of the charge is temporarily stopped here. .

If the moving distance during this period is sufficiently small with respect to the total film thickness of the photosensitive layer, the potential decay at this time becomes negligible. After charges corresponding to almost all the surface charges have been injected, the local electric field perpendicular to the surface near the injected charges becomes negligibly small, and the stopped charges escape from the electric field binding to the surface. It is possible to diffuse in a direction other than the vertical direction, and reaches a deeper position than the place where it first stopped following a spirally connected path. At this depth, as before, the charge is again exposed to a sufficiently high electric field, travels in the charge transporting domain along the direction of the electric field, again encounters the barrier of the electrically inert matrix, and stops moving. However, as the electric field strength is reduced by similar charge transfer, more charge passes through the convoluted charge transport path to the next insulating barrier. Thus, charge transfer occurs in a cascade, resulting in an S-shaped photoinduced potential decay.

Here, the terminal convex portion of the charge transporting domain whose movement direction is regulated by the electric field can be regarded as a kind of trap (hereinafter, referred to as “structural trap”). In a trap caused by a general energy level difference (hereinafter, referred to as an “energy trap”), the probability of escape from the trap increases with an increase in electric field strength due to the Poole-Frenkel effect. The mechanism described in (1) is characterized in that the escape probability increases as the electric field intensity decreases.

Further, as is apparent from the above mechanism, the bulk transport of charges in the non-uniform charge transport layer is not a mere electric-field-assisted drift movement observed in the uniform charge transport layer, but a drift movement in a domain. And diffusive escape from structural traps. Therefore, the photoinduced potential decay rate is determined by the photoinduced charge generation rate and the drift mobility in the J-shaped photoreceptor having no nonuniform charge transport layer, whereas the nonuniform charge transport layer In the case of the S-shaped photoreceptor having the above-mentioned structure, it is governed not only by the photoinduced charge generation speed and the drift mobility but also by the diffusion escape speed from the structural trap. Since escape from the structural trap is a thermal diffusion process with the potential potential as a barrier, Einstein's relation between drift mobility and diffusion coefficient
The escape speed will be approximately proportional to the drift mobility.

Conventionally, the drift mobility of the charge transport layer is determined by charging the charge transport layer (xerographic TOF).
Method) or voltage application (electrode TOF method), and a flash light (here, "flash light" refers to a pulse light that is negligible compared to the drift time) near the surface is compared with the electric field intensity by flash light. The light is generated in the form of a sheet, and the time required for the sheet charge to move to the opposite surface is determined. The time has been calculated by the following equation (3). m = L / (t · F) Formula (3) where m is the drift mobility, L is the film thickness of the charge transport layer, and t is
Denotes a drift time, and F denotes an electric field intensity. The reason why the amount of generated light is negligible compared to the electric field strength is to suppress the fluctuation of the electric field strength due to the movement of the electric charge to be negligible.

If the above-described drift mobility measurement method is applied to the non-uniform charge transport layer, if the amount of photogenerated charge is negligible compared to the electric field intensity, it cannot escape from the structural trap and cannot move. Becomes infinite, and the drift mobility becomes zero.

In the case of a J-shaped photoreceptor, the potential decay rate due to the flash light is governed only by the drift mobility and does not depend much on the exposure amount. The effective electric field strength tends to decrease and the potential decay rate generally tends to slightly decrease.) In the case of the S-shaped photoreceptor, the diffusion escape speed from the structural trap strongly depends on the exposure amount. , The potential decay rate also strongly depends on the exposure amount. That is, the potential decay rate is very slow when the exposure amount is small,
The speed increases exponentially as the exposure amount increases.

In the case of the S-shaped photoreceptor, the photoreceptor is charged, and thereafter, a charge equal to or more than the charging electric field intensity is generated by flash light, and the charge potential is attenuated by the photo-generated charge. The light-induced potential decay time described above can be represented by the time during which the surface potential of the body decays to 50% (this is referred to as the 50% potential decay time for flash light (T _50% )).

The "flash light" in the present invention is a pulse light having a half width of 0.01 second or less whose wavelength is substantially the same as the wavelength of the exposure means for forming a latent image of an electrophotographic apparatus. The exposure amount of the flash light required for measuring the 50% potential decay time (T _50% ) with respect to the flash light is 3 times or more and 6 times or less of the half-life exposure amount (E _50% ) of the electrophotographic photosensitive member to be measured. .

An electrophotographic apparatus having no exposing means for static elimination,
Even if a J-shaped photoreceptor is used, there is no image quality defect called a ghost in which a previous exposure image appears in a developed image (toner image) after the next exposure. The reason for the occurrence of the image quality defect referred to as above is presumed as follows.

In the J-shaped photoreceptor, the electric charge existing on the outermost layer of the electrophotographic photoreceptor is canceled out, and by uniformly charging, the history of the exposed portion and the non-exposed portion is almost completely canceled out. Does not affect the formation of a latent image.
In the portion of the S-shaped photoreceptor where the exposure is strong, the charge generated by the exposure moves without being trapped, cancels the charged charge and attenuates the potential. On the other hand, in the weakly exposed portion, the charge generated by the exposure is trapped by the above-described structural trap, and the charge cannot move. Therefore, the potential does not attenuate in a weakly exposed portion, and an S-shaped potential decay curve is realized in this manner.

When charging is performed without static elimination by static elimination light,
The trapped charge at the weakly exposed portion that has not been attenuated is charged as it is without being released. In the next image forming cycle, the trapped charges behave in the same manner as charges generated by exposure for forming a new latent image. Therefore, it is considered that the exposure history of the previous image forming cycle is reflected on the latent image of the next image forming cycle, and ghost occurs. As described above, it is generally considered that the S-shaped photoreceptor requires static elimination light during the process.

On the other hand, it is not always clear why the ghost does not occur according to the present invention, but it is estimated as follows. As described above, the potential decay rate of the S-shaped photoreceptor changes depending on the amount of exposure, and when exposure is weak, it takes much time for potential decay. That is, if there is sufficient time even in a weakly exposed portion, the electric charge trapped in the structural trap is released and the potential is attenuated. In other words, if the S-shaped photoreceptor has a potential decay rate sufficiently faster than the time from the exposure to the next charge, most of the charges trapped in the structural trap at the part of the light exposure are almost the next. Can be expected to be released from the trap by the time of charging. If the amount of the electric charge trapped in the structural trap is small, it is the same as that of the J-shaped photoconductor, and no ghost is generated.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention. In the present invention, the 50% potential decay time (T _50% ) of the electrophotographic photosensitive member with respect to flash light is 1/10 or less of the time between exposure and charging in a digital electrophotographic apparatus equipped with the same.

FIG. 8 shows an electrophotographic photosensitive member according to the present invention.
An example (Example 1 described later) of the result of photo-induced potential decay time-resolved measurement for flash light is shown. In measuring the 50% potential decay time (T _50% ) of the electrophotographic photosensitive member with respect to flash light, first, the photosensitive member is charged to a desired charging potential and irradiated with flash light. Thereafter, the change of the surface potential is measured in a time-resolved manner, and after a predetermined time has passed, the electricity is removed by a huge amount of light. When the measurement operation is repeatedly performed while increasing the amount of flash light, the charging on the potential decay curve (curve in FIG. 8) in which the potential decay curve does not substantially change even if the amount of flash light is further increased. The time required for 50% of the potential to decay (point A in FIG. 8) is the 50% potential decay time for flash exposure. Further, as a guide of the amount of exposure of the flash light at which the potential decay curve does not substantially change even if the amount of the flash light is further increased, the half-exposure amount (E _50% ) of the electrophotographic photosensitive member is three times or more and six times The following is assumed. In the example of FIG. 8, the exposure amount is about five times.

In FIG. 8, the measured 50% potential decay time (T _50% ) of the electrophotographic photosensitive member with respect to the flash light was measured.
Is determined to be 0.03 seconds (point A). The cause of the inflection point in the potential decay curve is unknown, but as described above, the decay rate certainly increases as the exposure amount increases.

From the viewpoint of achieving stable use at high speed, the 50% potential decay time (T _50% ) of the electrophotographic photosensitive member used for the present invention with respect to flash light is determined by the exposure means for forming an electrostatic latent image. It is 1/10 or less of the time until the next charging means (time between exposure and charging) (that is, the above-described formula 1), preferably 1/20 or less, more preferably 1/30 or less.

The electrophotographic photosensitive member used in the present invention is S
A photoreceptor, that is, the exposure (E _50% ) required for 50% potential decay is less than 5 times the exposure (E _10% ) required for 10% potential decay (ie, E _50% / E _10%). <5)
Is essential.

Here, E _50% is an exposure amount required for the surface potential of the electrophotographic photosensitive member to be reduced by 50%, and E _10%
The term “exposure amount” means an exposure amount required for the surface potential of the electrophotographic photosensitive member to be reduced by 10%. The E _50% / E _10% value needs to be less than 5 when actually developed in the electrophotographic apparatus of the present invention. Therefore, E _50% and E _10% of the electrophotographic photoreceptor are exposed from the electrophotographic photoreceptor and exposed to the electrostatic latent image forming means to developing means for developing the electrostatic latent image to obtain a toner image. (Time between exposure and development) must be measured.

The value of E _50% / E _10% is used as a measure of the S-shaped potential decay characteristic of the electrophotographic photosensitive member. In an ideal J-shaped photoreceptor, the potential decay is proportional to the amount of exposure,
The value of E _{50 %} / E _10% is 5. In a general J-shaped photoreceptor, the charge generation efficiency and / or the charge transport ability decrease with a decrease in the electric field strength, so that the E50 _% / E10 _% value exceeds 5. On the other hand, an ideal S-shaped photoreceptor shows a stepwise potential decay curve in which the potential does not attenuate at all up to a certain exposure amount, but abruptly decreases to the residual potential level at that exposure amount, so that E _50% / E _{The 10%} value is 1. Therefore, the S-shaped photoreceptor is defined as having an E _{50 %} / E _10% value of 1 or more and less than 5, and the closer the E _50% / E _10% value becomes 1,
It means that the S-shaped property is high.

The electrophotographic photoreceptor used in the present invention may have an S-shaped photoreceptor, that is, an E50 _% / E10 _% value of less than 5, but it can sufficiently exhibit digital characteristics and exhibit fine line reproducibility. In terms of assurance and the like, the value of E _50% / E _10% is preferably 3 or less, and more preferably 2 or less.

In the present invention, the 50% potential decay time (T _50% ) of the electrophotographic photosensitive member with respect to the flash exposure.
Is preferably 0.05 sec or less,
More desirably, it is 0.03 sec or less. The 50% potential decay time (T _50% ) for flash exposure is set to 0.
By shortening the time to less than 05 sec, the speed is further increased,
The image quality can be improved, and the degree of freedom in designing the digital electrophotographic apparatus of the present invention can be increased.

The electrophotographic photoreceptor used in the present invention is not particularly limited in constitution as long as it satisfies the above conditions, and either a single-layer photoreceptor or a laminated photoreceptor can be used. An electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer laminated on the body surface is preferable. Among them, in terms of repetition stability, environmental stability, and the like, a charge generation layer and a function-separated laminated structure in which a non-uniform charge transport layer in which charge transport domains are dispersed in an electrically inert matrix are provided. Things are desirable. Further, it is more preferable that a uniform charge transport layer is provided in addition to the charge generation layer and the non-uniform charge transport layer. For example, JP-A-6-83
No. 077 (US Pat. No. 5,306,586),
An electrophotographic photosensitive member having a structure described in JP-A-9-96914 is preferable.

FIGS. 3 to 6 are schematic diagrams showing a cross section of a part of the surface of the electrophotographic photosensitive member suitably used in the present invention. In FIG. 3, a charge generation layer 2 is provided on the surface of the conductive support 1, and has a function of imparting an S-shape thereon (hereinafter referred to as “S-shape”) and charge transport. A non-uniform charge transport layer 3 is provided. In FIG. 4, a charge generation layer 2 is provided on the surface of a conductive support 1, a non-uniform charge transport layer 3 for forming an S-shape is provided thereon, and a uniform charge for performing main charge transport is further provided thereon. A transport layer 4 is provided. In FIG. 5, a non-uniform charge transport layer 3 is provided on a conductive support 1, and a charge generation layer 2 is provided thereon. In FIG. 6, a uniform charge transport layer 4 is provided on the surface of the conductive support 1, a non-uniform charge transport layer 3 is provided thereon, and a charge generation layer 2 is provided thereon.

These electrophotographic photoreceptors can further include an undercoat layer, a protective layer, an intermediate layer, and / or a diffuse reflection layer, if desired.

As described above, the moving distance between the time when the charge generated in the charge generation layer encounters the obstacle of the electrically inactive matrix of the heterogeneous charge transport layer and the first stop is determined by the total thickness of the photosensitive layer. , The potential decay during that time is negligible and shows a more ideal S-shaped characteristic. In other words, the closer the charge generation layer and the non-uniform charge transport layer for S-shaping, the higher the S-shape. However, an appropriate intermediate layer may be provided between the charge generation layer and the heterogeneous charge transport layer for the purpose of injecting charges and assisting the generation of charges. Further, by inserting a uniform charge transporting layer between the charge generating layer and the heterogeneous charge transporting layer and changing the thickness of the uniform charge transporting layer, the value of E _50% / E _{10 %} is 1 or more and less than 5. Can be set to any value within the range.

Examples of the material of the non-uniform charge transporting layer responsible for the formation of the S-shape include a material in which fine particles having a charge transporting property are dispersed in a binder resin, and a charge transporting block and an insulating block (incompatible with each other). Charge-transporting inert block) and a phase-separable block copolymer or a graft copolymer containing the same can be used. However, in terms of the pot life of the coating solution, homogeneity of the coating film, etc. A phase-separable block copolymer or graft copolymer is particularly preferred.

Examples of the phase-separated charge transporting block copolymer or graft copolymer include known poly (vinyl carbazole-b-dodecyl methacrylate).
From the viewpoint of improving overall performance, it is composed of a vinyl polymer and a charge transport block having a triarylamine structure, a hydrazone structure, an alkoxy-substituted condensed polycyclic structure, a tetraarylbutadiene structure, or a silylene structure in a main chain or a side chain. It is preferable to use a block or graft copolymer containing an insulating block.

The phase-separable block copolymer or graft copolymer containing a charge-transporting block and an insulating block which are incompatible with each other and which is preferably used in the present invention is a block copolymer or a graft copolymer. As long as they are united, any combination of the constituent blocks may be used. That is, assuming that the charge transporting block is A and the insulating block is B, AB type, ABA type, BAB type, (AB)
_n- type, (AB) _n A-type, and B (AB) _n- type block copolymers; graft copolymers having a charge transporting block as a main chain and an insulating block as a side chain; and an insulating block as a main chain And a graft copolymer having a charge transporting block as a side chain. Further, the above-mentioned copolymers include those which are both block copolymers and graft copolymers. For example, A is added to the side chain of a block copolymer such as ABA type.
And / or a block-graft copolymer obtained by grafting B.

The method of synthesizing the copolymer used in the present invention is described in “Experimental Chemistry Lecture, 4th Edition, 28 Polymer Synthesis (Maruzen, 19
92), "Macromonomer Chemistry and Industry (IPC, 1990)", "Polymer Compatibilization and Evaluation Technology (Technical Information Association, 1992)", "Polymer New Material One P
oint 12 polymer alloy (Kyoritsu, 198
8) "," Angew. Macromol. Che
m. , 143 pp. 1-9 (1986) "," Journal of the Adhesion Society of Japan, 26, pp. 112-118 (199
0) ", Macromolecules, 28, pp.
4893-4898 (1995) "" J. Am. Che
m. Soc. , 111, pp. 7641-7643 (1
989) "," Japanese Patent Application Laid-Open No. 6-83077 "," New Materials, p. 37-41 (1997) "and any suitable synthetic method that can provide a block or graft copolymer can be used.

For example, a desired block copolymer can be obtained by separately synthesizing a charge-transporting polymer and an insulating polymer in advance and reacting and bonding the obtained polymers. Further, when the polymerization mode of the monomer forming the charge transporting block and the monomer forming the insulating block are the same, and the reactivity of the two is greatly different, simply polymerizing a mixture of the monomers firstly After the monomer having higher reactivity is polymerized and consumed, the monomer having lower reactivity is polymerized to obtain a desired block copolymer.

Further, a polymer of one monomer is synthesized in advance, and polymerization of azo, peroxyester, peroxy, dithiocarbamate, alkali metal alcoholate, alkali metal alkyl or the like is initiated at the terminal and / or side chain of the polymer. A desired block copolymer or graft copolymer can also be obtained by introducing a polymerization initiator containing a functional group and polymerizing the other monomer with the macropolymerization initiator. According to this method, a block copolymer or a graft copolymer comprising a polycondensation or polyaddition polymer and an addition polymerization or ring-opening polymerization polymer can be easily obtained.

Further, a compound containing a plurality of groups having a polymerization initiating ability such as azo, peroxyester, peroxy, etc. in a molecule is used. First, one monomer is polymerized from a part of the polymerization initiating groups, and then the remaining one is polymerized. The desired block copolymer can also be obtained by polymerizing the other monomer from the polymerization initiating group. In this case, in particular, those having a polymerization initiating group having a different polymerization initiating temperature first polymerize the monomer by a polymerization initiating group which starts polymerization at a lower temperature in one monomer, and removes unreacted monomer. Thereafter, the other monomer is added, the temperature is increased, and the other monomer is polymerized by a polymerization initiating group which starts polymerization at a higher temperature, whereby a desired block copolymer can be obtained with good control.

The desired block copolymer can also be obtained by sequentially polymerizing each monomer by a living polymerization method such as a cationic living polymerization method, an anion living polymerization method, or a radical living polymerization method.
The living polymerization method has an advantage that the molecular weight of each block can be easily controlled and a polymer having a narrow molecular weight distribution can be obtained. In addition, immortal polymerization method, Iniferte
The desired block copolymer can also be obtained by sequentially polymerizing each monomer by the r method or the like.

Furthermore, a desired graft copolymer can be obtained by synthesizing a macromonomer in which the other monomer has been introduced into the terminal of the polymer of one monomer in advance and polymerizing the macromonomer.

The molecular weight of the phase-separable block copolymer or graft copolymer containing a charge transporting block and an insulating block suitably used in the present invention may be any value. In order to exhibit high polymer properties such as separability, it is desirable that the molecular weight be 2000 or more.
It is more preferably 10,000 or more, and still more preferably 20,000 or more. When forming a film by a wet coating method, the upper limit of the molecular weight needs to be within a range that gives an appropriate solution viscosity, and is generally preferably 5,000,000 or less.

In the present invention, the phase separation state is generally well known in the field of polymer blends and polymer alloys, and includes macro phase separation (a macro phase separation having a phase separation scale of several μm or more) and It includes both microphase separation (phase separation in which the phase separation state is composed of fine domains of submicron or less).

In general, different polymers are incompatible with each other, and their mixtures, block copolymers or graft copolymers take a phase-separated state. Usually, a mere mixture, i.e., a polymer blend, results in macrophase separation, whereas a block copolymer and a graft copolymer, in which each component is covalently linked, usually results in microphase separation.

It is known that the scale of phase separation in the block copolymer and the graft copolymer is generally about the same as the average length of each block, and is substantially proportional to the molecular weight. In general, the phase separation property increases as the molecular weight increases, and as the difference between the solubility parameters increases.
high.

In the heterogeneous charge transport layer made of a phase-separable copolymer, the formation of the convoluted charge transport path depends on the stochastic contact between the charge transport domains. If the probability of the contact is too large, the charge transport path will not be convoluted and the S-shaped property will decrease, and if the probability of the contact is too small, a continuous charge transport path cannot be formed through the entire transport layer, This causes an increase in the residual potential. The contact of the charge transporting domains with each other does not necessarily have to be in direct contact, and a very thin insulating layer between the charge transporting domains can allow the charge to jump over that gap and negligible trapping there. If so, its existence is acceptable. Here, the convoluted charge transport path is a charge transport path that is formed such that the movement of charges is reversed at least once in the film thickness direction.

When the heterogeneous charge transporting layer is a phase-separating copolymer, the composition ratio of the charge-transporting block and the insulating block in the copolymer depends on the charge-transporting domain obtained as a result of the phase separation. The volume ratio is set arbitrarily within the range of 10/1 to 1/10, more preferably 2/1 to 1/2.

When the volume ratio of the charge transporting domains is larger than the above range, the charge transporting domains come into close contact with each other or the charge transporting blocks become a matrix,
A charge transport path having a substantially uniform structure is formed, and the non-uniform structure of the charge transport path, which is indispensable for the development of the S-shaped photoinduced potential decay characteristic, tends to be lost, and the S-shaped property tends to be lost. On the other hand, when the volume ratio of the charge-transporting domain is smaller than the above range, the charge-transporting path is divided, which tends to cause troubles such as an increase in residual potential and a decrease in response speed.

The phase separation structure of the heterogeneous charge transport layer is as follows:
Any structure may be adopted as long as the above-described convoluted charge transport path is formed, but the phase composed of the charge transport block is a spherical or rod-shaped island, and the phase composed of the insulating block is the sea. When a phase-separated structure (sea-island structure) is adopted, better S-shaped characteristics can be obtained. Also, when a modulation structure obtained by spinodal decomposition is adopted, preferable S
Characteristic is obtained. Further, even when a complicated lamella structure is adopted, a preferable S-shaped property can be obtained.

The problem here is how to control the phase separation state. The phase separation state has a thermodynamically most stable structure depending on the type and molecular weight of the constituent blocks. In the copolymer composed of the A block and the B block, it depends only on the A / B composition ratio without depending on the connection type,
As the A / B ratio increases, A is a spherical domain, B is a matrix, A is a rod-shaped domain, B is a matrix, A / B
Alternating layers, B is a rod-shaped domain, A is a matrix, B is a spherical domain, and A is systematically transformed into a matrix.

However, when a film is formed by a wet coating method, the phase separation state can be arbitrarily controlled depending on the solvent used, the drying speed, and the like. For example, A / B
Even when the ratio is large and thermodynamically the B-sphere A matrix is used, the A-sphere B matrix structure can be obtained by selecting a solvent that is a good solvent for B and a poor solvent for A as the coating solvent. . Also, using good solvents of both A and B,
When the solvent is rapidly removed, a phase separation structure (modulation structure) frozen in a spinodal decomposition state can be obtained. In addition, when a polymer having a large A / B ratio and having a thermodynamically B-sphere A matrix and a polymer compatible only with B is added, A becomes compatible with only the sphere, B and B. It is also possible to obtain a phase separation structure in which a certain polymer serves as a matrix.

The thickness of the heterogeneous charge transporting layer used in the present invention is suitably from 0.1 to 50 μm, but is preferably from 0.1 to 10 μm, more preferably from the viewpoint of increasing the response speed. It is set in the range of 0.5 to 5 μm. If the thickness is smaller than the above range, the S-shaped property tends to decrease.
The upper limit of the film thickness is limited by the charge transporting ability of the S-shaped charge transporting layer to be used, and the response speed, the residual potential, and the like are set within allowable ranges.

Further, the average diameter of the charge transporting domain is preferably from 0.005 to 3 μm, more preferably from 0.05 to 3 μm.
The range is from 1 to 1 μm, particularly preferably from 0.02 to 0.5 μm. When the average diameter of the charge transporting domain is larger than the above range, the formation of a non-uniform structure of the charge transporting path necessary for forming the S-shape within the preferable thickness range is stochastically reduced, and the S-shaped property is reduced. Will be. On the other hand, when the average diameter of the charge transporting domain is smaller than the above range, the charge transporting path approaches a uniform structure, and also in this case, the S-shaped property is reduced.

Into the heterogeneous charge transport layer, a compound capable of transporting only charges of the opposite polarity to the main transport charge can be added. By adding such a compound, effects such as a decrease in residual potential and an improvement in repetition stability can be obtained.

Further, a charge transporting polymer and / or an insulating polymer may be added to the heterogeneous charge transporting layer. When a charge transporting polymer is added, the charge transporting polymer preferably has compatibility with the block in the heterogeneous charge transporting layer or the charge transporting block of the graft copolymer. When an insulating polymer is added, it is preferable to have compatibility with the insulating block of the block or the graft copolymer.

The method of applying the heterogeneous charge transporting layer includes a blade coating method, a wire bar coating method,
Conventional methods such as spray coating, dip coating, bead coating, air knife coating, curtain coating, and ring coating can be used. As the coating liquid, a solution in which a polymer is uniformly dissolved, a solution forming micelles, or the like can be used. Solvents for preparing such a solution include chlorobenzene, tetrahydrofuran, methylene chloride, toluene, cyclohexanone and the like.

The electroconductive support of the electrophotographic photoreceptor of the present invention can be selected from any materials used in the art as electroconductive supports, and those which are opaque or substantially transparent can be selected. Examples are aluminum,
Metals such as nickel and stainless steel; aluminum, titanium, nickel, chromium, stainless steel, gold, platinum, zirconium, vanadium, tin oxide, indium oxide, I
Plastic, glass and ceramics provided with a thin film such as TO; paper coated or impregnated with a conductivity-imparting agent,
Examples include plastic, glass, and ceramics.

These conductive supports can be used in an appropriate shape such as a drum shape, a sheet shape, a plate shape, a belt shape and the like.

Further, if necessary, the surface of the conductive support can be subjected to various treatments. For example, oxidation treatment, chemical treatment, coloring treatment, or mechanical surface roughening treatment such as graining, honing, and rough cutting can be performed. Oxidation treatment and mechanical roughening treatment of the support surface not only roughens the support surface, but also controls the surface shape of the layer applied thereon, and coherent such as laser as the light source for exposure. The surface of the support and / or which are problematic when using a light source
Alternatively, the effect of preventing the occurrence of interference fringes due to regular reflection at the lamination interface is exhibited.

The electrophotographic photoreceptor of the present invention may be provided with one or more subbing layers. The undercoat layer functions as an adhesive layer for integrally bonding and holding the photosensitive layer to the conductive support, or, in some cases, acts to prevent specular reflection of light that causes interference fringes, and the like. And a function of preventing charge injection from the conductive support into the photosensitive layer during charging of the photosensitive layer.

As the undercoat layer, known ones can be used. For example, polyethylene resin, acrylic resin, methacrylic resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polyurethane resin, polyimide resin, Resins such as vinylidene chloride resin, polyvinyl acetal resin, polyvinyl alcohol resin, water-soluble polyester resin, alcohol-soluble nylon resin, nitrocellulose, polyacrylic acid, polyacrylamide and copolymers thereof, or zirconium alkoxide compounds, titanium alkoxide compounds And a curable metal organic compound such as a silane coupling agent may be used alone or in combination of two or more. Further, a material capable of transporting only charges having the same polarity as the charged polarity can be used as the undercoat layer.

The undercoat layer is formed by dissolving or dispersing these materials in an appropriate solvent, or by applying a dry method to the surface of a conductive support. As the method of applying the undercoat layer, use a normal method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, a ring coating method, or the like. Can be. The thickness of the undercoat layer is suitably from 0.01 to 10 μm, preferably from 0.1 to 10 μm.
It is in the range of 0.5 to 5 μm.

The charge generation layer in the present invention has a J-shape, S
Regardless of the character shape, it can be selected from any one that can be used as a charge generation layer in a laminated electrophotographic photoreceptor.
For example, amorphous selenium, selenium-tellurium alloy, selenium-
Inorganic photoconductive materials such as arsenic alloys, other selenium compounds and alloys, zinc oxide, titanium oxide, a-Si, a-SiC; phthalocyanine, squarium, anthantrone, perylene, azo, anthraquinone And organic pigments and dyes of pyrene type, pyrylium salt type and thiapyrylium salt type. These charge generating materials can be used alone or in combination of two or more.

In particular, phthalocyanine compounds are emission wavelengths of LEDs and laser diodes which are currently widely used as light sources in digital electrophotographic devices.
Since it has an excellent light sensitivity of 600 to 850 mm, it is particularly preferable as the charge generation material in the present invention.

As the phthalocyanine-based compound, metal-free phthalocyanine, metal phthalocyanine, and derivatives thereof can be used. As the central metal of the metal phthalocyanine, Cu, Ni, Zn, Co, Fe, V, Si, A
1, Sn, Ge, Ti, In, Ga, Mg, Pb, Li
And the like, and oxides, hydroxides, halides, alkylated compounds, alkoxylated compounds and the like of these central metals can also be used. Specific examples include titanyl phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, vanadyl phthalocyanine, chloroindium phthalocyanine, dichlorotin phthalocyanine, dimethoxysilicon phthalocyanine, and the like.

Further, substituted phthalocyanines in which an arbitrary substituent is introduced into the phthalocyanine ring of the above compound can also be used. Further, azaphthalocyanines in which an arbitrary carbon atom in the phthalocyanine ring of the above compound is substituted with a nitrogen atom are also effective. As the form of these phthalocyanine-based compounds, amorphous or all crystalline forms can be used.

Among these phthalocyanine compounds,
Metal-free phthalocyanine, titanyl phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, and dichlorotin phthalocyanine have particularly excellent photosensitivity, and are particularly preferred as charge generation materials used in the present invention.

While most phthalocyanine compounds have the property of a p-type semiconductor having holes as the main transport charge, dichlorotin phthalocyanine, phthalocyanines having an electron-withdrawing group and azaphthalocyanines are Since it is an n-type semiconductor having electrons as main transport charges, a charge generation layer containing these phthalocyanine compounds as a charge generation material and a non-uniform charge transport layer having a hole transport property are sequentially laminated on a conductive substrate. The S-shaped photoreceptor, when used with negative charge, has the advantage that the injection of holes from the conductive support is suppressed and the amount of dark charge is suppressed to a very low level.

Also, hexagonal selenium pigments, anthraquinone pigments, azo pigments and perylene pigments can be preferably used as a charge generation material because of their excellent charge generation efficiency. Since the beam diameter of the laser beam can be reduced as the transmission wavelength becomes shorter, studies have been made on shortening the wavelength of the exposure laser in order to further improve image quality. Since it has photosensitivity, it can be particularly preferably used as a charge generation material for a short wavelength laser. In particular, anthraquinone-based pigments, azo-based pigments and perylene-based pigments are n-type semiconductors, and a charge generation layer containing these pigments as a charge generation material and a non-uniform charge transport layer having a hole transporting property are sequentially formed on a conductive substrate. The stacked S-shaped photoreceptor has the advantage that when it is used with negative charge, the injection of holes from the conductive support is suppressed and the amount of dark charge is suppressed to a very low level.

The charge generation layer is formed by directly forming a film of the charge generation material by a vacuum evaporation method, or by dispersing or dissolving the charge generation material in a binder resin, and applying this by a wet or dry method. it can. When using a binder resin for the charge generation layer, the type of the binder resin is not particularly limited, for example, polyvinyl butyral resin, polyvinyl formal resin, partially modified polyvinyl acetal resin,
Polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinyl acetate resin, polyvinyl acetate resin, silicone resin, phenol resin, polyvinyl carbazole resin and the like are used. These binder resins may be block, random or alternating copolymers, and these binder resins may be used alone or in combination of two or more.
Further, the charge transporting block or the graft copolymer in the present invention is also effective as a binder resin for the charge generation layer.

The mixing ratio (volume ratio) of the charge generation material and the binder resin is preferably in the range of 10: 1 to 1:10. More preferably, it is set in the range of 3: 1 to 1: 1. It is difficult to obtain a uniform film by the wet coating method in which the mixing ratio of the charge generation material to the binder resin is larger than the above range.
On the other hand, if it is smaller than the above range, problems such as a decrease in photosensitivity and an increase in residual potential occur.

The thickness of the charge generating layer used in the present invention is generally from 0.05 to 3 μm, preferably from 0.1 to 1 μm, and more preferably from 0.1 to 1 μm. It is set in the range of 0.3 μm. When the film thickness is large, the amount of dark charge generally tends to increase. When a charge generation material having a high dark charge density is used, the thickness is preferably set to 0.3 μm or less.

Examples of the method for applying the charge generating layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, curtain coating, and ring coating. A method can be used.

The electrophotographic photosensitive member used in the present invention includes:
Further, a uniform charge transport layer can be provided. By providing the uniform charge transport layer, the thickness of the non-uniform charge transport layer, which determines the response speed of the photoreceptor, can be reduced while maintaining a sufficient thickness for the performance of the entire charge transport layer. It is more preferable in terms of speeding up.

The uniform charge transporting layer can be selected from any known in the art as a charge transporting layer in a J-shaped laminated photoreceptor. For example, benzidine compounds,
Triarylamine-based compounds, hydrazone-based compounds, stilbene-based compounds, diphenoquinone-based compounds and the like may be used alone or in combination of two or more to form an insulating resin (for example, polycarbonate, polyarylate, polyester, polysulfone, polymethylmethacrylate, etc.). ) Can be used as a solid solution film in which molecules are uniformly dispersed. Alternatively, it is also possible to use a polymer compound or the like which itself has charge transporting ability. In addition, an inorganic substance having a charge transporting ability such as selenium, a-Si, or a-SiC can also be used. Above all, it is preferable in production to use a polymer compound having a charge transporting property itself as the uniform charge transporting layer.

Examples of the charge-transporting polymer compound include a polymer compound having a group having a charge-transporting ability in a side chain as disclosed in JP-A-2-304456 and the like. For example, a polymer compound having a group having a charge transporting ability in a main chain, such as a polycarbonate having a triarylamine skeleton, and a polysilylene can be used, as disclosed in Japanese Patent No. 232727. .

When a heterogeneous charge transporting layer and a uniform charge transporting layer are laminated and formed, if the charge transporting low molecular weight compound is used for the uniform charge transporting layer, the charge transporting low molecular weight compound is mixed into the heterogeneous charge transporting layer. May be. As a result, the insulating property for the main charge of the electrically inert matrix of the heterogeneous charge transporting layer is reduced, so that the S-shaped property is impaired or the charge transporting small molecules mixed into the heterogeneous charge transporting layer are reduced. It becomes a charge trap in the heterogeneous charge transport layer, and causes problems such as an increase in residual potential, a decrease in transport ability, and a decrease in photosensitivity. This problem is particularly remarkable when each layer is formed by a wet coating method. (Of course, these problems are caused by selecting a solvent that hardly dissolves and swells the lower layer as a coating solvent for the upper layer, or a non-uniform charge. This can be avoided by making the transport layer cross-linkable and curable so that dissolution and swelling by the upper layer coating solvent do not occur.

However, as described above, it is generally known that polymers cause phase separation without being compatible with each other. When a charge transporting polymer compound is used as a uniform charge transporting layer, Since the phase is separated without being compatible with the resin of the heterogeneous charge transport layer, the problem of the above-mentioned mixing hardly occurs, and there is an advantage that restrictions on selection of a material and a manufacturing method are eliminated.

Incidentally, in the uniform charge transport layer, there may be an electrically inactive region surrounded by a charge transporting matrix. For example, insulating particles having a low surface energy can be contained for the purpose of reducing the surface frictional force, reducing the abrasion, or reducing the adhesion of foreign substances to the surface.

Charge transporting fine particles can be added to the uniform charge transporting layer for the purpose of improving the charge transporting ability and the like. Further, as the uniform charge transporting layer, a charge transporting copolymer composed of a charge transporting block and an insulating block can be used as long as it is compatible. Furthermore, as described above, in the uniform charge transport layer, there may be an electrically inactive region surrounded by the charge transport matrix, so that the charge transport block is the matrix and the insulating block is the domain. Copolymers in a microphase-separated state can also be used as a uniform charge transport layer.

The uniform charge transporting layer can be obtained by dry or wet coating the above-mentioned materials. As the application method,
Conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, curtain coating, and ring coating can be used. In addition, a material such as selenium that can be formed in a vapor phase can be directly formed by a vacuum evaporation method or the like. The thickness of the uniform charge transport layer used in the present invention is 50 μm.
m, preferably 30 μm or less.

In the configuration in which the charge transport layer (including both the non-uniform and uniform charge transport layers) is the outermost layer, the three-dimensional cross-linkable charge transport layer formed using a cross-linking curable material from the viewpoint of mechanical strength. Preferably, a layer is used.

In the present invention, the total thickness of the charge transport layer including the heterogeneous charge transport layer and the uniform charge transport layer is 5
１００100 μm is suitable, preferably 10-40 μm
Is set in the range. More preferably, 15 to 35μ
m.

When the charge transport layer is present between the charge generation layer and the exposure light source, it is desirable that the charge transport layer is substantially transparent to light of the exposure wavelength in order to prevent a reduction in effective photosensitivity. Preferably, the transmittance of light used for exposure in the charge transport layer is 50% or more. It is more preferably at least 70%, further preferably at least 90%. However, if use at low sensitivity is desired, a substance that absorbs light at the exposure wavelength can be added to adjust the effective light sensitivity.

In the present invention, the provision of the protective layer on the photosensitive layer can be achieved by chemical stress such as ozone or oxidizing gas generated from the charging member, ultraviolet light or the like, or
This is effective for protecting the photosensitive layer from mechanical stress caused by contact with a developer, paper, a cleaning member, and the like, and improving the substantial life of the photosensitive layer. In particular, the effect is remarkable in a layer configuration using a thin charge generation layer as an upper layer.

The protective layer is formed by including a conductive material in a suitable binder resin and applying the same.
Examples of the conductive material include, but are not limited to, metallocene compounds such as dimethylferrocene, and metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and ITO. As the binder resin, known resins such as polyamide, polyurethane, polyester, polycarbonate, polystyrene, polyacrylamide, silicone resin, melamine resin, phenol resin, and epoxy resin can be used. Also, a semiconductive inorganic film such as amorphous carbon can be used as the protective layer.

The electric resistance of these resistance control type protective layers must be in the range of 10 to 10 ¹⁴ Ω · cm. When the electric resistance is higher than this range, the residual potential increases. On the other hand, when the electric resistance is lower than this range, the charge leakage in the creeping direction cannot be ignored and the resolution is reduced.
The thickness of the protective layer is suitably from 0.5 to 20 μm, and is preferably set in the range from 1 to 10 μm.

When a protective layer is provided, a blocking layer for preventing leakage of electric charge from the protective layer to the photosensitive layer can be provided between the photosensitive layer and the protective layer, if necessary. As the blocking layer, a known layer can be used as in the case of the protective layer.

In the electrophotographic photosensitive member used in the present invention, ozone or oxidizing gas generated in the electrophotographic apparatus,
Alternatively, an antioxidant, a light stabilizer, a heat stabilizer, or the like can be added to each layer or the uppermost layer for the purpose of preventing the photoconductor from being deteriorated by light or heat. These additives may be incorporated as components of the insulating block of the copolymer in the present invention in addition to simply adding and mixing.

As the antioxidant, known ones can be used. For example, hindered phenol, hindered amine, paraphenylenediamine, hydroquinone,
Spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds and the like can be mentioned.

Known light stabilizers can be used. For example, derivatives such as benzophenone, benzotriazole, dithiocarbamate, tetramethylpiperidine, and the like can deactivate the photoexcited state by energy transfer or charge transfer. Examples thereof include an electron-withdrawing compound and an electron-donating compound. Furthermore, insulating particles having a low surface energy such as a fluororesin may be dispersed in the outermost surface layer for the purpose of reducing surface wear, improving transferability, improving cleanability, and the like.

The digital electrophotographic apparatus of the present invention includes at least the S-shaped electrophotographic photosensitive member described above,
Charging means for charging the electrophotographic photosensitive member to a predetermined potential; and electrostatic means for exposing the charged electrophotographic photosensitive member based on digitally processed image signals to form an electrostatic latent image. Latent image forming exposure means, developing means for developing the electrostatic latent image to obtain a toner image, transfer means for transferring the toner image to a transfer material such as recording paper, an intermediate transfer body, It is necessary that the means for exposing the electrophotographic photosensitive member comprises only the exposure means for forming an electrostatic latent image.

The exposing means for exposing based on the digitally processed image signal means using a light source such as a laser or an LED to perform exposure with multi-valued light by performing binarization or pulse width modulation or intensity modulation. It is an exposure means, and examples of the electrophotographic apparatus having the exposure means include an LED printer, a laser printer, a laser exposure type digital copying machine, and the like.

As the charging means for charging the electrophotographic photosensitive member, any conventionally known charging means such as a corotron, a scorotron, a charging roll, a charging blade, a charging brush, and a wet charger can be used. However, in order to uniformly charge without performing static elimination, a contact-type charger is preferable. The voltage applied to the contact charger is preferably a DC voltage to which an AC voltage is applied. In addition, the control of the voltage applied by the contact-type charger may be any control such as constant voltage control or constant current control.However, the control method is to control the DC voltage at a constant voltage and control the AC voltage at a constant current. Is preferred.

Further, a cleaning means for cleaning the toner and the like remaining after the transfer may be provided, and a corotron before the transfer and a corotron after the transfer may be provided.

FIG. 7 schematically shows a preferred example of the digital electrophotographic apparatus of the present invention. This device is a laser exposure type digital copying machine, and is a contact type charger which can apply a voltage obtained by superimposing an AC voltage on a DC voltage around a photoreceptor drum (electrophotographic photoreceptor) 11. A charging roller 13, a laser optical system 14 as an exposure unit for forming an electrostatic latent image, which performs exposure based on a digitally processed image signal, a developing unit 15 as a developing unit, and a transfer roller as a transfer unit And the cleaning blade 17 are sequentially arranged so as to be in a process order.

The laser optical system 14 has a transmission wavelength of 780 m.
m, which emits light based on digitally processed image signals. The emitted laser light 14a is scanned by a polygon mirror, a plurality of lenses, and mirrors (not shown) while the photosensitive drum 1 is scanned.
It is configured to expose one surface. Reference numeral 18 denotes a sheet.

The process until an image is formed by the digital electrophotographic apparatus shown in FIG. 7 will be described below. First, the photosensitive drum 11 is charged by a charging roller 13 which is a contact type charger.
Are uniformly charged. Next, the photosensitive drum 11 is irradiated with light (exposure) at a predetermined position by the image signal digitally processed by the laser optical system 14. The charged charge on the exposed portion is removed, and an electrostatic latent image is formed on the charge remaining portion. Subsequently, the electrostatic latent image is exposed to the toner in the developing device 15, and the toner adheres to the latent image by an electrostatic force, and becomes a visible image. Next, the visible image is transferred to the sheet 18 by the transfer roller 16 by opposing the sheet 18 to which a charge having a polarity opposite to the charge polarity of the toner is applied. The toner remaining on the photosensitive drum 11 after the transfer is removed by the cleaning blade 17.

The charging means, the exposing means for forming an electrostatic latent image, the developing means, and the transferring means are not limited to the above-mentioned constitutions, and any constitutions conventionally used can be used. Digital electrophotographic devices are generally produced and sometimes traded for each of the units that make up such devices (eg, repair parts, etc.). Therefore, when manufacturing or maintaining the digital electrophotographic apparatus of the present invention, an apparatus unit is manufactured so as to constitute the digital electrophotographic apparatus of the present invention.

[0115]

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples, and those skilled in the art can modify the following examples based on known knowledge such as polymer chemistry and electrophotographic technology.

[Synthesis Example 1] N, N'-bis (p, m-dimethylphenyl) -N, N'-bis [p- (2-methoxycarbonylethyl) phenyl]-[3,3'-dimethyl- 1,1′-biphenyl] -4,4′-diamine 3k
g, 9 kg of ethylene glycol, and 25 g of tetrabutoxytitanium were heated and refluxed for 6 hours under a nitrogen stream.
The atmosphere was reduced to 0.5 mmHg, heated to 235 ° C. while distilling off ethylene glycol, and the reaction was further continued for 6 hours. Thereafter, the mixture was cooled to room temperature, and 30 kg of toluene was added to dissolve the produced resin.
After removing the insoluble matter with a FE filter, 150 kg of methyl ethyl ketone was added, and the precipitated polymer component was separated.

This was reprecipitated from tetrahydrofuran / isopropanol to obtain 2.0 kg of a charge transporting polymer (1) having hydroxy groups at both ends and represented by the following structural formula. When the weight average molecular weight of the obtained charge transporting polymer (1) was measured by GPC analysis, it was 9.8.
× 10 ⁴ (in terms of polystyrene). The components having a molecular weight of 10,000 or less accounted for 1.1% of the whole.

[0118]

Embedded image

[Synthesis Example 2] The above charge transporting polymer (1)
1000 g and 10 g of triethylamine were dissolved in 3.4 L of toluene and cooled to 0 ° C. Here, 4,4 '
200 g of -azobis (4-cyanovaleric chloride) were added. The temperature was raised to 35 ° C., and the reaction was performed for 6 hours. This was added dropwise to methanol, and the mixture was stirred for 1 hour and filtered off. Further, reprecipitation treatment with toluene / methanol was repeated twice to obtain 900 g of a charge transporting polymer having an azo type polymerization initiating group at a terminal.

Into 13.2 L of toluene was dissolved 700 g of the obtained charge transporting polymer having an azo-type polymerization initiating group at the end, 2400 g of styrene and 200 g of methacrylic acid were added, and the mixture was purged with nitrogen and heated at 65 ° C. for 70 hours. . This was dropped into methanol, and the precipitated solid was separated by filtration. When the filtrate was analyzed, styrene, methacrylic acid, and a styrene-methacrylic acid copolymer were detected. Next, 800 g of the filtered solid was finely pulverized, put into 7.2 L of xylene, stirred for 24 hours, and then mixed with 3.5 parts of cyclohexane.
L was added, and the mixture was separated into insoluble and soluble components.

As a result of ¹ H-NMR spectrum and GPC analysis, the soluble matter was a block copolymer rich in the unreacted charge transporting polymer and the charge transporting block, and the insoluble content was changed to the target structural formula shown below. And a charge transporting block copolymer (2). In addition, in the following structural formulas, the notation in parentheses at both ends (charge transport inactive block) indicates that a styrene unit and a methacrylic acid unit are randomly polymerized.

[0122]

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From the analysis of the ¹ H-NMR spectrum, the weight composition ratio of the charge transporting block and the charge transporting inactive block of the charge transporting block copolymer (2) was about 32:68. The weight ratio of styrene units to methacrylic acid units in the charge transport inert block was about 80:20.

[Synthesis Example 3] In Synthesis Example 2, the amount of styrene added was changed from 2400 g to 5000 g, and
Synthesis and purification were carried out in the same manner as in Synthesis Example 2 except that the amount of the added methacrylic acid was changed from 200 g to 530 g, to obtain a charge transporting block copolymer (3). The charge transporting block copolymer (3) can be represented by the same structural formula as the charge transporting block copolymer (2).

From the analysis of the ¹ H-NMR spectrum, the weight composition ratio of the charge transporting block and the charge transporting inactive block of the charge transporting block copolymer (3) was approximately 24:76. The weight ratio of styrene units to methacrylic acid units in the charge transport inert block was about 80:20.

In the above Synthesis Examples 2 and 3, the charge transporting polymer (1) having the same structure as the charge transporting block in the charge transporting block copolymer, and the same structure as the charge transporting inactive block were used. And a styrene-methacrylic acid copolymer having the following formulas (2) and (3):
And (3) have a microphase-separated structure.

[Example 1] <Preparation of undercoat layer> Zirconium alkoxide compound ("Orgatic ZC540", manufactured by Matsumoto Pharmaceutical Co., Ltd.)
20 parts by weight, a silane coupling agent ("A1100",
A solution comprising 2 parts by weight of Nippon Unicar Co., 0.5 parts by weight of polyvinyl butyral resin (“S-LEC BM-S”, manufactured by Sekisui Chemical Co., Ltd.), 20 parts by weight of isopropanol, and 30 parts by weight of n-butanol was prepared This was used as a coating liquid for forming an undercoat layer.

Ra = 0.18 μm by honing treatment
The coating liquid for forming an undercoat layer is applied by dip coating onto a 30 mm-diameter aluminum drum (conductive support) surface roughened so that
The resultant was dried by heating for 5 minutes to form an undercoat layer having a thickness of 0.6 μm.

<Preparation of Charge Generation Layer> In an X-ray diffraction spectrum using CuKα as a source, at least the Bragg angle (2θ ± 0.2 °) is 7.4 °, 16.6 °,
4 parts by weight of chlorogallium phthalocyanine microcrystals having strong diffraction peaks at 5.5 ° and 28.3 ° were mixed with 2 parts by weight of a vinyl chloride-vinyl acetate copolymer (UCAR Solution Vinyl Resin VMCH, manufactured by Union Carbide), The mixture was mixed with 67 parts by weight of xylene and 33 parts by weight of n-butyl acetate, and dispersed together with glass beads by a paint shake method for 5 hours to obtain a coating solution for forming a charge generation layer. The obtained coating solution for forming a charge generation layer is applied on the undercoat layer by a dip coating method,
After heating and drying for 0 minutes, a charge generation layer having a thickness of 0.2 μm was formed.

<Preparation of Non-Uniform Charge Transport Layer> Synthesis Example 2
And the weight ratio of the charge transporting block copolymers (2) and (3) obtained in Synthesis Example 3 to (2) :( 3) = 1: 1.
7 parts by weight of the mixture mixed in
It was dissolved in a solvent consisting of 5 parts by weight, 56 parts by weight of toluene, and 9 parts by weight of isopropyl alcohol to obtain a coating liquid for forming a heterogeneous charge transport layer. The obtained coating solution for forming a heterogeneous charge transport layer is applied on the charge generation layer by a dip coating method, and then dried by heating at 135 ° C. for 7 minutes to form a heterogeneous charge transport layer having a thickness of 2 μm. Formed. The weight composition ratio of the charge transporting block and the charge transporting inactive block of the heterogeneous charge transporting layer is approximately 27:73.

<Preparation of Uniform Charge Transporting Layer> 24 parts by weight of the charge transporting polymer (1) obtained in Synthesis Example 1 was added to toluene 7
The solution was dissolved in 6 parts by weight, and 0.015 parts by weight of dimethyl silicone oil (Shin-Etsu Silicone KP-340, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to obtain a coating solution for forming a uniform charge transport layer. The obtained coating solution for forming a uniform charge transport layer is applied by a dip coating method, and dried by heating at 135 ° C. for 30 minutes to form a uniform charge transport layer having a thickness of 18 μm. An electrophotographic photosensitive member J-1 (drum shape) was produced.

Further, an aluminum plate (length 40 mm × width 2)
Each layer was formed on the surface (4 mm × 1 mm thick) by the same operation as above to produce an electrophotographic photosensitive member J-1 ′. The obtained plate-shaped electrophotographic photosensitive member J-1 'was subjected to an electrostatic copying paper tester (Electrostatic Analyzer E).
Using PA-8100 (manufactured by Kawaguchi Electric Works), the electrophotographic characteristics were evaluated in the following manner under the environment of normal temperature and normal humidity (20 ° C., 40% RH).

First, the corona discharge voltage was adjusted,
After charging the surface of photoconductor J-1 'to -450V, interference
Filtering wavelengths other than 700 nm to 800 nm through a filter
If the potential decay rate of the cut halogen lamp light fluctuates,
The electronic exposure, which is sufficiently higher than the
The light intensity on the surface of the true photoconductor J-1 'is 2000 mW / m. ^Two
And adjust the shutter exposure to 1/125
For 50 seconds, and calculate the 50% potential decay time from the start of exposure.
Was.

In the same manner, the electrophotographic photosensitive member J-
The potential at 0.18 seconds after exposure was determined while changing the light intensity on the 1 'surface, and the flash-induced potential decay time-resolved measurement of the electrophotographic photoreceptor J-1' was performed. Obtained. From FIG. 8, the 50% potential decay time T
_50% is calculated as 0.03 seconds. Further, the electrophotographic photoreceptor J-1 ′ of this example exhibited an S-shaped photoinduced potential decay,
_{The 50%} / E _10% value was 2.5.

Example 2 The mixing ratio of the charge transporting block copolymers obtained in Synthesis Examples 2 and 3 in <Preparation of heterogeneous charge transporting layer> in Example 1 was determined by weight. S-shaped electrophotographic photosensitive members J-2 (drum-shaped) and J-2 '(plate-shaped) in the same manner as in Example 1 except that the ratio (2) :( 3) = 1: 3. Was prepared. The weight composition ratio of the charge-transporting block and the charge-transporting inactive block of the heterogeneous charge-transporting layers in the electrophotographic photoreceptors J-2 and J-2 'is about 26:74.

The obtained electrophotographic photosensitive member J-2 'was evaluated for electrophotographic characteristics in the same manner as in Example 1. The E _50% / E _10% value of the electrophotographic photosensitive member J-2 ′ is 2.0
And the 50% potential decay time was 0.04 seconds.

[Example 3] The mixing ratio of the charge transporting block copolymers obtained in Synthesis Examples 2 and 3 in <Preparation of heterogeneous charge transporting layer> in Example 1 was determined by weight. S-shaped electrophotographic photosensitive members J-3 (drum-shaped) and J-3 '(plate-shaped) in the same manner as in Example 1, except that the ratio (2) :( 3) = 1: 7. Was prepared. The weight composition ratio of the charge-transporting block and the charge-transporting inactive block in the heterogeneous charge-transporting layers in such electrophotographic photoreceptors J-3 and J-3 'is about 25:75.

The obtained electrophotographic photosensitive member J-3 'was evaluated for electrophotographic characteristics in the same manner as in Example 1. The E50 _% / E10 _% value of the electrophotographic photosensitive member J-3 'is 1.8.
And the 50% potential decay time was 0.08 seconds.

Example 4 The procedure of Example 1 was repeated, except that the thickness of the heterogeneous charge transport layer to be formed was 1 μm and the thickness of the uniform charge transport layer was 19 μm. , S-shaped electrophotographic photosensitive members J-4 (drum shape) and J-4 '(plate shape) were produced.

The obtained electrophotographic photosensitive member J-4 'was evaluated for electrophotographic characteristics in the same manner as in Example 1. The E50 _% / E10 _% value of the electrophotographic photosensitive member J-4 'is 2.8.
And the 50% potential decay time was 0.02 seconds.

Example 5 An undercoat layer and a charge generation layer were formed on the surface of a conductive support in the same manner as in <Preparation of an undercoat layer> and <Preparation of a charge generation layer> in Example 1. Next, 22 parts by weight of a mixture obtained by mixing the charge transporting block copolymers (2) and (3) obtained in Synthesis Examples 2 and 3 in a weight ratio of (2) :( 3) = 3: 1. Was dissolved in a solvent consisting of 28 parts by weight of cyclohexanone, 56 parts by weight of toluene and 9 parts by weight of isopropyl alcohol to obtain a coating liquid for forming a heterogeneous charge transport layer. The obtained coating solution for forming a heterogeneous charge transport layer is applied on the charge generation layer by a dip coating method, and then dried by heating at 135 ° C. for 30 minutes to form a heterogeneous charge transport layer having a thickness of 20 μm. Formed. The weight composition ratio of the charge-transporting block and the charge-transporting inactive block of the heterogeneous charge-transporting layer is as follows:
It is about 30:70. Thus, S-shaped electrophotographic photosensitive members J-5 (drum-like) and J-5 '(plate-like) having the layer configuration shown in FIG. 3 were produced.

The obtained electrophotographic photosensitive member J-5 'was evaluated for electrophotographic characteristics in the same manner as in Example 1. The value of E _50% / E _{10% of the} electrophotographic photosensitive member J-5 ′ is 1.6.
And the 50% potential decay time was 0.09 seconds.

[Comparative Example 1] The mixing ratio of each charge transporting block copolymer obtained in Synthesis Example 2 and Synthesis Example 3 in <Preparation of heterogeneous charge transporting layer> in Example 1 was determined by weight. S-shaped electrophotographic photosensitive members h-1 (drum-shaped) and h-1 '(plate-shaped) in the same manner as in Example 1, except that the ratio (2) :( 3) = 0: 1. Was prepared.

The obtained electrophotographic photosensitive member h-1 ′ was evaluated for electrophotographic characteristics in the same manner as in Example 1. The value of E _50% / E _{10% of the} electrophotographic photosensitive member h-1 ′ is 1.8.
And the 50% potential decay time was 0.15 seconds.

[Comparative Example 2] In Example 1, the heterogeneous charge transport layer was not provided, but the thickness of the uniform charge transport layer was changed to 2
A J-shaped electrophotographic photosensitive member h-2 (drum shape) and h-2 ′ were formed in the same manner as in Example 1 except that the thickness was set to 0 μm.
(Plate shape).

Further, the obtained electrophotographic photosensitive member h-2 'was evaluated for electrophotographic characteristics in the same manner as in Example 1. The E _50% / E _10% value of the electrophotographic photosensitive member h-2 ′ is 5.2.
And the 50% potential decay time was 0.01 seconds or less.

The drum-shaped electrophotographic photosensitive members J-1 to J-5 and h-1 to h-2 obtained as described above were
Laser exposure printer (“Laser Press”
4161II ", manufactured by Fuji Xerox Co., Ltd.), and a printing test was conducted in which the obtained printing quality was visually evaluated for sensory evaluation.

The rotation speed of the drum (photoconductor for electrophotography) of the laser exposure type printer is 58 rpm, and the light source for forming an electrostatic latent image (exposure means for forming an electrostatic latent image) has an oscillation wavelength of 780.
nm laser diode, charger (charging means) is a contact-type roller charger in which an AC voltage is superimposed on a DC voltage, the time between exposure and charging is 0.97 seconds, and the time between exposure and development is 0.18 seconds. It is.

The electrophotographic photosensitive member J- of Examples 1 to 5
When the results of the printing test using 1 to J-5 and the results of the printing test using the electrophotographic photoreceptor h-1 of Comparative Example 1 were compared, in Comparative Example 1, ghosts were severely generated. On the other hand, in Examples 1 and 4, no ghost was generated, and in Examples 3 and 5, ghost was slightly generated, but at an acceptable level, and in Example 2, the ghost was intermediate. In addition, the evaluation of the ghost is such that the halftone exposure image is
Judgment was made based on whether or not the same portion of the electrophotographic photosensitive member appeared in the developed halftone image after the next exposure. In addition, the reproducibility of the fine line was all good.

The results of a printing test using the electrophotographic photosensitive members J-1 to J-5 of Examples 1 to 5 and Comparative Example 2
Comparing the results of the printing test using the electrophotographic photoreceptor h-2 with Examples, Examples 1 to 5 were superior in the printing quality in terms of reproducibility of fine lines and the like. In Comparative Example 2, no ghost occurred.

As described above, the digital electrophotographic apparatus using the S-shaped photoreceptor has higher image quality than the digital electrophotographic apparatus using the J-shaped photoreceptor, and has no digital erasing light. In the type electrophotographic apparatus, by using an S-shaped photoreceptor having a potential decay rate sufficiently faster than the time between exposure and charging (and / or
It can be seen that a high quality image free from image defects can be obtained by taking a sufficient time between charging times.

[0152]

The digital electrophotographic apparatus equipped with the S-shaped photoreceptor according to the present invention and having no exposure means for static elimination has a 50% potential decay time (T _{50%) with} respect to flash exposure of the electrophotographic photoreceptor. ) Is 1/1 of the time (exposure-charging time) from the exposure unit for forming an electrostatic latent image to the next charging unit.
By setting the value to 0 or less, there is an excellent effect that it is possible to provide a digital electrophotographic apparatus which can be miniaturized and has high image quality without causing image quality defects called ghost.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an exposure amount and a surface potential in a J-shaped electrophotographic photosensitive member.

FIG. 2 is a graph showing a relationship between an exposure amount and a surface potential in an S-shaped electrophotographic photosensitive member.

FIG. 3 is a schematic cross-sectional view illustrating an example of an electrophotographic photosensitive member according to the present invention.

FIG. 4 is a schematic cross-sectional view showing another example of the electrophotographic photosensitive member according to the present invention.

FIG. 5 is a schematic cross-sectional view illustrating another example of the electrophotographic photosensitive member according to the invention.

FIG. 6 is a schematic cross-sectional view illustrating another example of the electrophotographic photosensitive member according to the invention.

FIG. 7 is a schematic configuration diagram illustrating an example of an electrophotographic apparatus of the present invention that performs exposure based on a digitally processed image signal.

FIG. 8 is a time-resolved measurement result of photoinduced potential decay of the electrophotographic photosensitive member of Example 1 with respect to flash light.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 conductive support 2 charge generation layer 3 heterogeneous charge transport layer (S-shaped charge transport layer) 4 uniform charge transport layer 11 photoconductor drum (electrophotographic photoconductor) 13 charging roll (charging means) 14 exposure laser Optical system (exposure means for forming an electrostatic latent image) 15 Developing device (developing means) 16 Roll for transfer (transfer means) 17 Cleaning blade 18 Paper

Claims (1)

[Claims] 1. An electrophotographic photoreceptor in which the exposure amount (E _50% ) required for 50% potential decay is less than 5 times the exposure amount (E _10% ) required for 10% potential decay. Charging means for charging the body, exposure means for forming an electrostatic latent image by performing exposure based on a digitally processed image signal, and developing to obtain a toner image by developing the electrostatic latent image And a transfer means for transferring the toner image to a transfer material, and wherein the means for exposing the electrophotographic photosensitive member is only the electrostatic latent image forming exposure means. A 50% potential decay time (T _50% ) with respect to the flash exposure of the electrophotographic photoreceptor, a time from the electrostatic latent image forming exposure means to the next charging means (exposure-charge time),
Has a relationship represented by the following equation (1). T _50% ≤ (exposure-charge time) / 10 (Equation 1)