JP3748452B2 - Single layer type electrophotographic photoreceptor - Google Patents

Description

The present invention relates to a single layer type electrophotographic photosensitive member, and more particularly to a single layer type electrophotographic photosensitive member used for an electrophotographic copying machine, a facsimile, a laser beam printer, and the like.

  More specifically, the present invention relates to a single-layer electrophotographic photosensitive member that does not generate a memory image even when used in a reversal development type digital image forming apparatus that does not have a charge eliminating step.

  Organic photoconductors are easier to manufacture than conventional inorganic photoconductors, are less expensive, have a wide range of options for photoconductor materials such as charge transport agents, charge generators, and binder resins. Has been widely used in recent years.

  The organic photoreceptor includes a single-layer type photoreceptor in which a charge transport agent (a hole transport agent, an electron transport agent) is dispersed in the same photosensitive layer together with a charge generator, a charge generation layer containing the charge generator, and a charge. There are laminated photoconductors with a charge transport layer containing a transport agent, which has advantages such as a simple layer structure and excellent productivity, and improved optical characteristics because there are few interfaces between layers. In recent years, it has been in the spotlight.

  On the other hand, an image forming apparatus using an electrophotographic system charges a photosensitive member (main charging step), exposes an image to form an electrostatic latent image (exposure step), and develops the electrostatic latent image with a developing bias voltage. The toner is developed in the applied state (development process), and the formed toner image is transferred to transfer paper (transfer process) and fixed to perform image formation. The residual toner on the photoconductor is cleaned by a urethane blade or the like (cleaning process), and the residual charge on the photoconductor is erased by an LED or the like (static elimination process).

  Various attempts have been made to omit the above-described cleaning process and static elimination process in order to reduce the size of the image forming apparatus and reduce the initial cost.

  In addition, image forming apparatuses using electrophotography include digital and analog copying machines, facsimiles, laser beam printers, and the like, and in particular, using toner having the same polarity as the charging voltage applied to the photoreceptor in the charging process. A reversal developing method for developing is widely used in digital image forming apparatuses.

<Transfer memory>
When the electrophotographic photosensitive member is used in a reversal development type digital image forming apparatus, the transfer voltage applied to the photosensitive member in the transfer step is usually applied via a transfer medium (paper) without being directly applied to the photosensitive member, It is not applied when the transfer medium does not pass through the transfer process.

  However, the transfer voltage on / off timing is very difficult, and a portion that is directly applied to the photoreceptor often occurs at the front and rear end portions of the transfer medium. That is, the transfer voltage starts to be applied before the leading edge of the transfer medium covers the transfer device, and the transfer voltage continues to be applied even if a part of the transfer device is exposed due to the passage of the rear end of the transfer medium. In this portion, the transfer voltage is directly applied to the photoconductor.

  For this reason, for example, in the case of a positively charged single layer type photoreceptor, since the polarity of the voltage applied by the transfer device is negative, negative space charges remain on the photoreceptor portion to which a negative voltage is applied. In general, a single-layer type photoreceptor has sensitivity in both polarities, so that negative space charges are erased in the next static elimination step.

  However, when the above-mentioned positively charged single-layer type photoreceptor is very insensitive to the negative polarity (the mobility of the electron transfer agent is extremely small), or when used in an image forming apparatus that does not have a charge eliminating step. The negative space charge is not sufficiently erased, and even if it is positively charged in the next charging step, the potential drop is caused by the effect of the space charge, and further, a sensitivity difference appears in the development step, and the portion in the image The problem arises that the image becomes black (memory image).

<Exposure memory>
For example, a positively charged single layer type photoreceptor is normally positively charged in the next charging step after the positive charge on the surface of the photosensitive member is erased uniformly in the static elimination step after the exposure step and the development step. .

  However, as in the case of the transfer memory, when the sensitivity to the negative polarity of the positively charged single layer type photoreceptor described above is poor, or when used in an image forming apparatus that does not have a charge eliminating step, the exposed portion is better. Compared with the non-exposed portion, the negative space charge density is large, a potential difference is generated in the next charging step, and a memory image is easily generated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a single-layer electrophotographic photosensitive member that does not generate a memory image even when used in a reversal development type digital image forming apparatus that does not have a charge eliminating step.

  As a result of diligent research, the inventors of the present invention have found a single-layer type electrophotographic photosensitive member that is used by being charged to a positive polarity in a reversal development type digital image forming apparatus that does not have a static elimination process in order to achieve the above-described object. A photosensitive layer is formed on a conductive substrate, the photosensitive layer contains a phthalocyanine compound as a charge generator, a hole transport agent, and an electron transport agent in a binder resin, and the content of the phthalocyanine compound is a binder resin. The photosensitive layer thickness is 10 to 35 μm, the charging potential is set to 800 V, the exposure wavelength is 780 nm, and the exposure energy is 1.0 μJ / cm. ² Single layer type electrophotographic photosensitive member in which the absolute value difference between the positive and negative polarities measured after elapse of 500 msec is 312 V or less and the absolute value of the positive polarity is smaller than the absolute value of the negative polarity However, the present inventors have found that a memory image is not generated even in a reversal development digital image forming system that has very small exposure memory and transfer memory and does not have a charge eliminating step.

That is, the absolute value difference between the positive polarity and negative polarity sensitivity measured after elapse of 500 msec under the conditions of the exposure wavelength of 780 nm and the exposure energy of 1.0 μJ / cm ² is 312 V or less, and the absolute value of the positive polarity sensitivity is negative. When a single layer type electrophotographic photosensitive member having a smaller polarity sensitivity is used , the exposure memory and the transfer memory are very small. This is presumably because the smaller the absolute value difference between the positive and negative polarities, the better the transport balance between holes and electrons generated in the photosensitive layer and the smaller the memory.

  In the single-layer electrophotographic photosensitive member of the present invention, the content of the phthalocyanine compound as a charge generator is preferably in the range of 0.1 to 4 wt% with respect to the binder resin weight. When the content of the phthalocyanine compound exceeds 4 wt%, the memory becomes large. That is, since it is considered that the memory is generated as a residual carrier by entering the trap in the photosensitive layer, the number of generated carriers becomes excessive and the number of remaining carriers also increases. On the other hand, when the content is less than 0.1 wt%, the photosensitivity is insufficient and actual use becomes difficult.

  In the single-layer electrophotographic photoreceptor of the present invention, the thickness of the photosensitive layer is preferably in the range of 10 to 35 μm. When the film thickness exceeds 35 μm, the memory becomes large. That is, as the photosensitive layer thickness increases, the dark decay increases and the charging ability decreases, making it more susceptible to memory, or the increase in the absolute amount of photosensitive layer constituent material increases traps. It is thought that. On the other hand, when the film thickness is less than 10 μm, the sensitivity is greatly deteriorated due to film shaving, and actual use becomes difficult.

  In addition, as a single-layer electrophotographic photosensitive member of the present invention, it is difficult to design a material for an electron transport agent having a high mobility, and the mobility of the electron transport agent is small compared to the mobility of a hole transport agent. It is preferable to use a positively charged type because the absolute value of the positive polarity sensitivity is smaller than the absolute value of the negative polarity sensitivity, for example, because ozone generation in the apparatus is extremely small.

  In the single-layer electrophotographic photosensitive member of the present invention, it is preferable to contain a compound represented by the general formula (1) as a hole transport agent. This is because reducing the content of phthalocyanine compounds and the film thickness to reduce memory deteriorates the initial sensitivity of the positively charged single-layer type electrophotographic photosensitive member. This is because sufficient initial sensitivity can be obtained.

  The single-layer electrophotographic photosensitive member of the present invention may contain at least one compound represented by the general formula (2), (3), (4) or (5) as an electron transport agent. preferable. This is because the use of the above-described compound having a high electron transporting capability provides a sufficient initial sensitivity and is very effective in reducing memory.

[First Embodiment]
The first embodiment is a single-layer electrophotographic photosensitive member that is used by being charged with a positive polarity in a reversal development type digital image forming apparatus that does not have a static elimination step, and a photosensitive layer is formed on a conductive substrate. The photosensitive layer contains a phthalocyanine compound as a charge generator, a hole transport agent, and an electron transport agent in a binder resin, and the content of the phthalocyanine compound is 0.1 to 4 wt% with respect to the binder resin weight. The positive polarity and the negative polarity measured after 500 msec have elapsed under the conditions that the photosensitive layer thickness is 10 to 35 μm, the charging potential is set to 800 V, the exposure wavelength is 780 nm, and the exposure energy is 1.0 μJ / cm ^2. In the single-layer type electrophotographic photosensitive member, the absolute value difference of the sensitivity is 312 V or less and the absolute value of the positive polarity sensitivity is smaller than the absolute value of the negative polarity sensitivity. That.
Various materials used for the single-layer electrophotographic photosensitive member of the present invention will be described in detail.

<Charge generator>
In a digital image forming apparatus, when a laser is used as a light source, semiconductor lasers and LEDs are often used from the viewpoints of small size, low cost, and simplicity. Therefore, an organic photoreceptor having sensitivity in a wavelength region of at least 700 to 850 nm is necessary. As charge generators used in organic photoreceptors that satisfy such requirements, for example, polycyclic quinone compounds, pyrylium compounds, squalium compounds, phthalocyanine compounds, azo compounds and the like have been proposed or put into practical use. Various phthalocyanine compounds are used for the single-layer electrophotographic photoreceptor used in the image forming method.

  In general, phthalocyanine compounds include metal-free phthalocyanine (CGM-1) having no central metal, titanyl phthalocyanine (CGM-2), which has been actively researched and developed in recent years, and aluminum phthalocyanine and vanadium phthalocyanine. Central metals such as cadmium phthalocyanine, antimony phthalocyanine, chromium phthalocyanine, copper 4-phthalocyanine, germanium phthalocyanine, iron phthalocyanine, chloroaluminum phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, magnesium phthalocyanine, dialkyl phthalocyanine, tetramethyl phthalocyanine, tetraphenyl phthalocyanine Metal phthalocyanines having α-type, β-type, γ-type, δ-type, ε-type, σ-type, x-type, τ There is a thing of the crystal type and the like.

<CGM-1>

<CGM-2>

  In addition, metal-free phthalocyanine or titanyl phthalocyanine is preferably used as the phthalocyanine compound in the single-layer electrophotographic photosensitive member used in the image forming method of the present invention. Moreover, it is preferable to contain 0.1-4 wt% of phthalocyanine type compounds with respect to the binder resin weight as mentioned above.

<Hole transport agent>
As the hole transporting agent used in the single layer type electrophotographic photosensitive member of the present invention, a stilbene compound represented by the general formula (1) is particularly preferably used.

  Moreover, when using this stilbene type compound as a hole transport agent, what is necessary is just to contain individually or at least 1 sort (s) or more. That is, various hole transport agents may be contained together with the stilbene compound.

  Examples of various hole transport agents include oxadiazole compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, and 9-4 (-diethylaminostyryl). Styryl compounds such as anthracene, carbazole compounds such as polyvinyl carbazole, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3 (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, indole compounds Examples thereof include nitrogen-containing cyclic compounds such as compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

  Further, the content of the hole transport agent is preferably 5 to 500 wt%, more preferably 25 to 200 wt%, based on the weight of the binder resin.

<Electron transport agent>
In addition, as the electron transfer agent used in the single-layer electrophotographic photosensitive member of the present invention, a quinone compound represented by the general formula (2), (3), (4) or (5) is particularly preferably used. The

  Moreover, when using this quinone type compound as an electron transport agent, what is necessary is just to contain individually or at least 1 sort (s) or more. That is, various electron transport agents may be contained together with the quinone compound.

  Examples of various electron transfer agents include pyrene compounds, carbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, tetracyanoethyl. Tetracyanoquinodimethane, chloroanil, bromoanil, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone Examples thereof include electron-withdrawing substances such as 2,4,5,7-tetranitroxanthone and 2,4,8-trinitrothioxanthone, or polymers obtained by polymerizing these electron-withdrawing substances.

  Further, the content of the electron transport agent is preferably 5 to 100 wt%, more preferably 10 to 80 wt%, based on the weight of the binder resin.

<Binder resin>
In addition, as the binder resin for dispersing the above-described components, various resins conventionally used in the photosensitive layer can be used.

  For example, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene , Polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, etc. Resin such as thermoplastic resin, silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, other cross-linkable thermosetting resin, epoxy acrylate, urethane acrylate, etc. It is. These binder resins can be used alone or in combination of two or more.

  Particularly suitable resins are bisphenol Z-type polycarbonates derived from bisphenol Z-type monomers and phosgene such as Panlite manufactured by Teijin Chemicals Ltd. and PCZ manufactured by Mitsubishi Gas Chemical Company, Inc.

  The weight average molecular weight of the binder resin mentioned in the above example is preferably 5,000 to 200,000, more preferably 15,000 to 100,000.

  In addition to the above-described components, the single-layer type electrophotographic photosensitive member of the present invention includes various conventionally known additives such as antioxidants and radical scavengers as long as the electrophotographic characteristics are not adversely affected. Agent, singlet quencher, anti-degradation agent such as UV absorber, softener, plasticizer, surface modifier, extender, thickener, dispersion stabilizer, wax, acceptor, donor, etc. . In order to improve the sensitivity of the photosensitive layer, for example, a known sensitizer such as terphenyl, halonaphthoquinone, and acenaphthylene may be used in combination with the charge generator.

  In the single-layer electrophotographic photosensitive member of the present invention, a barrier layer may be formed between the conductive substrate and the photosensitive layer as long as the characteristics of the photosensitive member are not impaired.

  The single-layer type electrophotographic photosensitive member of the present invention has a single photosensitive layer provided on a conductive substrate. This photosensitive layer is formed by dissolving or dispersing a charge generator, a hole transport agent, an electron transport agent, a binder resin, etc. in an appropriate solvent, coating the resulting coating solution on a conductive substrate, and drying. The

  In addition, as the conductive substrate on which the above-described photosensitive layer is formed, various conductive materials can be used. For example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, Examples thereof include simple metals such as cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, plastic materials on which the above metals are deposited or laminated, glass coated with aluminum iodide, tin oxide, indium oxide, and the like. .

  Further, the shape of the conductive substrate may be any of a sheet shape, a drum shape, or the like in accordance with the structure of the image forming apparatus to be used. The substrate itself is conductive or the surface of the substrate is conductive. As long as it has. The conductive substrate preferably has sufficient mechanical strength when used.

  When the photosensitive layer is formed by a coating method, the hole transporting agent, charge generating agent, electron acceptor, binder resin, and the like exemplified above together with an appropriate solvent are combined with a known method such as a roll mill. A dispersion is prepared by dispersing and mixing using a ball mill, an attritor, a paint shaker, an ultrasonic disperser or the like, and this is applied by a known means and dried.

  Moreover, as a solvent for producing the above-mentioned dispersion liquid, various organic solvents can be used, for example, alcohols such as methanol, ethanol, isopropanol and butanol, and aliphatics such as n-hexane, octane and cyclohexane. Hydrocarbons, aromatic hydrocarbons such as benzene, toluene, xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc. Ethers, acetone, methyl ethyl ketone, cyclohexanone and other ketones, ethyl acetate, methyl acetate and other esters, dimethylformaldehyde, dimethylformamide, dimethylsulfone Examples include xoxide. These solvents are used alone or in combination of two or more.

  Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the hole transporting agent, charge generating agent, electron acceptor, and surface of the photosensitive layer.

  Hereinafter, the present invention will be described with reference to examples and comparative examples. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Examples 1-7 , Reference Example 8 ]
As a charge generating agent, 2.0 parts by weight of X-type metal-free phthalocyanine (CGM-1), 70 parts by weight of a hole transport agent (HTM-1) represented by the general formula (1), general formulas (2) and (3), (4), 40 parts by weight of the electron transporting agent (ETM-1 to ETM-8) shown in (5), 100 parts by weight of a bis-Z type polycarbonate resin having a weight average molecular weight of 30,000 as a binder resin, and tetrahydrofuran 800 Weight parts were dispersed or dissolved in a ball mill for 24 hours to prepare a single-layer photosensitive layer coating solution. Then, this coating solution is applied on an aluminum base tube as a support by a dip coating method, followed by hot air drying at 125 ° C. for 30 minutes, and a single-layer photoreceptor having a single photosensitive layer with a thickness of 20 μm. Was made.

[Comparative Examples 1-3]
Single layer type photoreceptors were prepared in the same manner as in Examples 1 to 7 except that ETM-9 to ETM-11 were used as the electron transporting agent.

<HTM-1>

<ETM-1>

<ETM-2>

<ETM-3>

<ETM-4>

<ETM-5>

<ETM-6>

<ETM-7>

<ETM-8>

<ETM-9>

<ETM-10>

<ETM-11>

[Examples 9 to 15, Reference Example 16 ]
Single layer type photoreceptors were prepared in the same manner as in Examples 1 to 7 and Reference Example 8 except that titanyl phthalocyanine (CGM-2) was used as the charge generating agent.

[Comparative Examples 4 to 6]
Single layer type photoreceptors were prepared in the same manner as in Comparative Examples 1 to 3, except that titanyl phthalocyanine (CGM-2) was used as the charge generator.

[Comparative Example 7]
A single-layer photoreceptor was prepared in the same manner as in Example 1 except that 4.5 parts by weight of X-type metal-free phthalocyanine (CGM-1) was contained as a charge generator.

[Comparative Example 8]
A single layer type photoreceptor was prepared in the same manner as in Example 1 except that a photosensitive layer having a thickness of 40 μm was obtained.

[Comparative Example 9]
A monolayer type photoreceptor was produced in the same manner as in Example 9 except that 4.5 parts by weight of titanyl phthalocyanine (CGM-2) was contained as a charge generating agent.

[Comparative Example 10]
A single-layer type photoreceptor was produced in the same manner as in Example 9 except that a photosensitive layer having a thickness of 40 μm was obtained.

  The following characteristics were evaluated for the single-layer electrophotographic photoreceptors of the above Examples and Comparative Examples. The evaluation results are shown in Tables 1 and 2. Of these data, the relationship between the transfer memory potential / exposure memory potential and the absolute value difference between the positive polarity sensitivity and the negative polarity sensitivity is shown in FIG.

<Positive polarity sensitivity evaluation>
An applied voltage was applied to the electrophotographic photosensitive member of each example and comparative example using a drum sensitivity tester (product name Gentec Cynthia 30M) manufactured by GENTEC, and the surface was charged to + 800V. . Next, monochromatic light having a wavelength of 780 nm (half-value width 20 nm, light intensity 20 μW) extracted from the white light of a halogen lamp, which is an exposure light source of the testing machine, using a band-pass filter is applied to the surface of the charged photoreceptor. Exposure (exposure time 100 msec) was performed (exposure energy was 1.0 μJ / cm ² ). Then, the surface potential after 500 msec from the exposure start time was measured as a post-exposure potential V _LP (V). That is, the smaller the post-exposure potential, the higher the sensitivity of the photoreceptor.

<Negative polarity sensitivity evaluation>
Using a drum sensitivity testing machine (product name Gentec Cynthia 30M) manufactured by GENTEC, an applied voltage is applied to the electrophotographic photosensitive member of each example and comparative example, and the surface is charged to -800V. Except for the above, the surface potential at the time when 500 msec had elapsed from the start of exposure was measured as the post-exposure potential V _LN (V) in the same manner as in the above <Positive polarity sensitivity evaluation>.

<Evaluation of transfer memory potential>
The multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which the static elimination lamp has been removed, is mounted with the electrophotographic photosensitive member of each example and comparative example, and the surface potential when no transfer bias is applied, and when the transfer bias is applied. The surface potential after the next charging step was measured, and the difference was taken as the transfer memory potential. As for the transfer memory potential, 45 V or less at which no transfer memory image was generated was allowed, and when it was greater than 45 V, it was not allowed.

<Evaluation of exposure memory potential>
The multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which the static elimination lamp has been removed, is mounted with the electrophotographic photosensitive member of each example and comparative example, and the surface potential at the time of unexposed and after the next charging step at the time of exposure. The surface potential was measured and the difference was taken as the exposure memory potential. As for the exposure memory potential, 45 V or less at which no exposure memory image is generated is allowed, and when it is higher than 45 V, the transfer memory potential is not allowed.

<Evaluation of transfer memory image>
Whether or not a transfer memory image is generated by mounting the electrophotographic photosensitive member of each example and comparative example on the multi-function printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which the static elimination lamp has been removed, and performing a printing test. It was judged visually. As shown in FIG. 6, the transfer memory image means that the surface potential of the photosensitive member at the portion to which the transfer bias is applied when a printing test is performed using a front gray (Munsell value: N = 6.5) document. An image in which a black horizontal band is generated in the drum longitudinal direction due to the decrease is shown.

<Exposure memory image evaluation>
Whether or not an exposure memory image is generated by mounting the electrophotographic photosensitive member of each example and comparative example on the multifunction printer Antico40 manufactured by Kyocera Mita Co., Ltd., from which the static elimination lamp has been removed, and performing a printing test. It was judged visually. The exposure memory image means that when a printing test is carried out using a document as shown in FIG. 7, the ghost image of the exposed portion is changed to a gray portion due to a decrease in the photosensitive member surface potential of the strongly exposed portion (solid black portion). The generated image is shown.

  From Tables 1 and 2 and FIG. 1, it is clear that when the absolute value difference between the positive and negative polarities is 500 V or less, both the transfer memory potential and the exposure memory potential are 45 V or less, and no memory image is generated. became.

  FIG. 2 shows the relationship between the X-type metal-free phthalocyanine addition amount of the single-layer electrophotographic photosensitive member produced in Example 6 and the transfer memory potential / exposure memory potential, and FIG. 3 shows the X-type photosensitive member. The relationship between the addition amount of metal-free phthalocyanine and the absolute difference in sensitivity between positive polarity and negative polarity was shown.

  2 and 3, when the X-type metal-free phthalocyanine addition amount is 4 wt% or less with respect to the binder resin weight, the absolute value difference between the positive polarity and the negative polarity sensitivity is 500 V or less, both the transfer memory potential and the exposure memory potential. Became 45V or less.

  4 shows the relationship between the photosensitive layer thickness of the single-layer electrophotographic photosensitive member produced according to Example 6 and the transfer memory potential / exposure memory potential, and FIG. 5 shows the photosensitive layer thickness of the photosensitive member. And the relationship between the positive and negative polarity sensitivity difference.

  4 and 5, when the film thickness of the photosensitive layer is 35 μm or less, the absolute value difference between the positive polarity and the negative polarity sensitivity is 500 V or less, and both the transfer memory potential and the exposure memory potential are 45 V or less.

6 is a graph showing the relationship between the transfer memory potential / exposure memory potential of single layer type electrophotographic photosensitive member of each example and comparative example, and the absolute value difference in sensitivity between positive polarity and negative polarity. 6 is a graph showing the relationship between the addition amount of X-type metal-free phthalocyanine and the transfer memory potential / exposure memory potential of a single layer type electrophotographic photosensitive member. It is a graph which shows the relationship between the addition amount of X-type metal-free phthalocyanine of a single layer type electrophotographic photosensitive member, and the absolute value difference of the sensitivity of positive polarity and negative polarity. 6 is a graph showing the relationship between the photosensitive layer thickness of a single-layer type electrophotographic photosensitive member and the transfer memory potential and exposure memory potential. It is a graph which shows the relationship between the photosensitive layer film thickness of a single layer type electrophotographic photosensitive member, and the absolute value difference of the sensitivity of plus polarity and minus polarity. It is a figure which shows the original for transfer memory image evaluation, and a transfer memory image. It is a figure which shows the original for exposure memory image evaluation, and an exposure memory image.

Claims (6)

  In a reversal development type digital image forming apparatus having no charge eliminating step, a single layer type electrophotographic photosensitive member used by being charged to a positive polarity,
  A photosensitive layer is formed on a conductive substrate, and the photosensitive layer contains a phthalocyanine compound as a charge generator, a hole transport agent, and an electron transport agent in a binder resin, and the content of the phthalocyanine compound is a binder resin. The photosensitive layer thickness is 10 to 35 μm, the charging potential is set to 800 V, the exposure wavelength is 780 nm, the exposure energy is 1.0 μJ / cm. ² The absolute value difference between the positive polarity and negative polarity sensitivity measured after elapse of 500 msec is 312 V or less, and the absolute value of the positive polarity sensitivity is smaller than the absolute value of the negative polarity sensitivity. Type electrophotographic photoreceptor. 2. The monolayer electrophotographic photoreceptor according to claim 1, wherein the phthalocyanine compound in the monolayer electrophotographic photoreceptor contains metal-free phthalocyanine having no central metal or titanyl phthalocyanine . 3. The single-layer electrophotographic photosensitive member according to claim 1, comprising a compound represented by the general formula (1) as a hole transport agent in the single-layer electrophotographic photosensitive member.
General formula (1):

(In the general formula (1), R ¹ and R ³ are the same or different, and may have an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. An aralkyl group or an alkoxy group, wherein R ² and R ⁴ are the same or different and each represents a hydrogen atom, an alkyl group or an alkoxy group which may have a substituent, provided that the substitution positions of R ² and R ⁴ are In the para position, R ² and R ⁴ are hydrogen atoms.) The electron transport agent in the single-layer type electrophotographic photosensitive member contains at least one compound represented by the general formula (2), (3), (4) or (5). The single-layer electrophotographic photosensitive member according to any one of 1 to 3 .
General formula (2):

(In the general formula (2), R ⁵ represents a halogen atom, an alkyl group or an aryl group which may have a substituent, and R ⁶ may have an alkyl group or an aryl group, or group: .R ^6a showing a -O-R ^6a may have a substituent, an alkyl group or an aryl group).
General formula (3):

(In the general formula (3), R ⁷ and R ⁸ are the same or different and are an alkyl group, halogenated alkyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, aralkyloxy group, acyl group, alkoxycarbonyl group. An aryloxycarbonyl group, an aralkyloxycarbonyl group or a nitro group, n represents an integer of 0 to 3.)
General formula (4):

(In the general formula (4), R ^9a , R ^9b , R ^9c and R ^9d are the same or different and each represents a hydrogen atom or an alkyl group or an aryl group which may have a substituent.)
General formula (5):

(In the general formula (5), R ¹⁰ and R ¹¹ are the same or different and are an alkyl group, halogenated alkyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, aralkyloxy group, acyl group, alkoxycarbonyl group. An aryloxycarbonyl group, an aralkyloxycarbonyl group or a nitro group, n represents an integer of 0 to 3.) 5. The bisphenol Z-type polycarbonate having a weight average molecular weight of 15,000 to 100,000 is contained as a binder resin in the single-layer type electrophotographic photosensitive member. Single layer type electrophotographic photoreceptor. 6. The single-layer electrophotographic photosensitive member according to claim 1, wherein an exposure memory and a transfer memory in the single-layer electrophotographic photosensitive member have a value of 45 V or less .

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