JP2003228187A - Electrophotographic photoreceptor and electrophotographic device equipped with the photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor causing no failure such as decrease in sensitivity in a low electric field region and increase in residual potential due to repeated use and having low transfer memory potential. <P>SOLUTION: In the electrophotographic photoreceptor, the charge generating layer contains oxytitanylphthalocyanine and vinyl chloride resin by 0.8 to 2.0 weight ratio (phthalocyanine/resin) and the charge transfer layer contains a charge transfer material having the ionization potential (Ip (CTM)) (eV) satisfying the relation of Ip(CGM)≤Ip(CTM)≤Ip(CGM)+0.3, wherein Ip (CGM) (eV) is the ionization potential of oxytitanylphthalocyanine. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member and an electrophotographic apparatus including the photosensitive member, and more specifically, to an electrophotographic photosensitive member including at least a charge generation layer and a charge transport layer, and the photosensitive member. The present invention relates to an electrophotographic apparatus such as an electrophotographic printer, a facsimile, and a copying machine, in which an image is formed by a reversal development method.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member has a basic structure having a photosensitive layer having a photoconductive function on a conductive substrate.

The photoreceptor is required to have a function of retaining surface charges in a dark place, a function of receiving light to generate charges, and a function of transporting the generated charges, and a single layer having these functions together. A so-called single-layer type photoreceptor having a photosensitive layer of
A charge generation layer mainly responsible for the charge generation function at the time of receiving light,
There is a so-called function-separated layered type photoreceptor in which a function-separated layered type photoreceptor is layered so as to be function-separated with a charge-transporting layer having a function of retaining surface charges in a dark place and a function of transporting charges generated in a charge-generating layer.

In recent years, many laminated electrophotographic photoconductors have been invented which use organic compounds and take advantage of the versatility, high productivity and safety of the materials to share charge generation and transport functions. It has been put to practical use and has become the mainstream type of photoconductor and electrophotographic apparatus using this photoconductor on the market.

The electrophotographic apparatus using these photoconductors has the same polarity in the applied voltage in the charging step and the transfer step and develops the unexposed portion in the normal rotation developing method, and the polarity is opposite to each other. Therefore, it is roughly classified into a reversal development method for developing the exposed portion. Conventionally, the normal development method has been mainly used for copying machines, and the reversal development method has been mainly used for printers and facsimiles. The development method is the mainstream.

In the reversal development method, since transfer toner having a polarity opposite to that of the charging step is transferred from the back side of the transfer paper in order to transfer the toner image on the surface of the photoreceptor to the paper in the transfer step, the presence or absence of the transfer paper (that is, The difference between the paper area and the paper area) or the presence or absence of a toner image is recorded as the potential difference on the surface of the photoconductor,
At the next charging, a so-called transfer memory occurs in which the difference is not canceled and is manifested as a gray level difference on a halftone image or the like. At least for the negative charging type photoconductor in which the charge transport layer is laminated on the charge generating layer, this transfer memory phenomenon is caused by the positive charge having the opposite polarity to the charge being injected from the surface of the charge transport layer into the film at the transfer portion. When a charge transport material having a sufficiently large ionization potential with respect to the charge generating material is used, the injection of positive charges from the surface into the film is blocked as described above. Gives good results.

[0007]

However, when a charge transporting material having a sufficiently large ionization potential is used, charge injection from the charge generating layer into the charge transporting layer cannot be carried out smoothly, so that particularly in a low electric field region. Problems such as a decrease in sensitivity and an increase in residual potential due to repeated use have newly occurred, and improvements have been demanded.

On the other hand, in Japanese Patent Laid-Open No. 11-265081, charge generation is performed in order to achieve the object of obtaining a good image with high sensitivity and small fluctuations of the charging potential and residual potential even after repeated use. Layer and a charge transport layer, the charge generation layer contains a phthalocyanine compound and a vinyl chloride resin binder, and the phthalocyanine / vinyl chloride resin has a weight ratio of 0.3 to 0.8. Although there is a description of the invention, the transfer memory is not considered at all, and not only the charge transport material combined with the phthalocyanine of the charge generation material is different from the present invention, and the relationship of their ionization potential values is also different from the present invention. There is.

Japanese Patent Application Laid-Open No. 11-249333 discloses a function-separated type organic photoconductor containing a charge transporting material suitable for combination with a charge generating material in terms of injection efficiency and having an ionization potential of 5.3 or less. However, there is no description and no suggestion about specifying the relationship of the ionization potential with a specific charge generation layer.

Further, in JP-A-6-250421, in order to provide an image forming method capable of stably obtaining an excellent image even when it is repeatedly used at high speed, the photosensitive layer contains oxytitanium phthalocyanine and charge transport. The work function of the oxytitanium phthalocyanine (W
There is a description of the invention that one of the requirements is that the work function (WFCT) of the FCG) and the charge transport material satisfies the following expression 0.2 <WFCG−WFCT ≦ 0 (eV). But,
Since the transfer memory is not considered in the same manner as described above, the polyvinyl butyral resin corresponding to the binder resin of the comparative example described later in the present invention is used as the binder resin of the charge generation layer in the embodiment.

Further, in Japanese Patent Laid-Open No. 10-63015, it is an object to provide an electrophotographic photosensitive member capable of stabilizing the charging potential of an electrophotographic copying machine and shortening the time until the first copy becomes possible. As the ionization potential IpG (eV) of the charge generating material in the charge generating layer and the ion potential IpT of the charge transporting material in the charge transporting layer.
(EV) and the hole mobility μ (cm ² / volt · second) of the charge transport layer are represented by the following formula: 0 ≦ (IpG−IpT) ≦ 1.2
There is a description to the effect that the electrophotographic photosensitive member satisfies +0.15 log (μ). However, since the transfer memory is not taken into consideration, the charge transport material is different from that of the present invention described later, and the configuration thereof is different from that of the present invention.

In view of the above-mentioned problems, the present invention provides an electrophotographic photosensitive member having a small transfer memory potential without causing problems such as a decrease in sensitivity in a low electric field region and an increase in residual potential due to repeated use. To aim.

Still another object of the present invention is to provide an electrophotographic apparatus in which a transfer memory image does not occur and a good printed image can be obtained in the reversal development system.

[0014]

According to the invention of claim 1 or 2, the object is an electrophotographic photosensitive member comprising a conductive substrate and at least a charge generating layer and a charge transporting layer laminated on the conductive substrate. Is 0.8 to 2.0, preferably 1.0 to oxytitanyl phthalocyanine and vinyl chloride resin.
The weight ratio (the phthalocyanine / the resin) is in the range of 2.0 to 2.0, and the charge transport layer satisfies the relational expression (1) below with the ionization potential (eV) of the oxytitanyl phthalocyanine. It is achieved by providing an electrophotographic photosensitive member containing a charge transport material having an ionization potential (eV).

[0015]

[Equation 2]

According to the third aspect of the present invention, the object is that oxytitanyl phthalocyanine has a Bragg angle (2θ ± 0.2 °) of 7.5 °, 12.3 °, 16 in a CuKα-X-ray diffraction spectrum. .3 °, 25.3 °, 2
8.7 ° (α-type oxytitanyl phthalocyanine) or 9.5 °, 9.7 °, 11.7 °, 15.0 °, 23.
The electrophotographic photoreceptor according to claim 1 or 2, which has major peaks at 5 °, 24.1 °, and 27.3 ° (commonly known as Y-type oxytitanyl phthalocyanine).

According to a fourth aspect of the present invention, the object has the electrophotographic photosensitive member according to any one of the first to third aspects and at least a charging mechanism, an exposure mechanism, a developing mechanism, and a transfer mechanism. This is achieved by providing an electrophotographic apparatus having a configuration in which an image is formed by the reversal development method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electrophotographic photosensitive member according to the present invention and an electrophotographic apparatus using the photosensitive member will be described in detail below with reference to the drawings. The present invention is not limited to the description of the embodiments described below. FIG. 1 is a schematic cross-sectional view of an essential part showing an electrophotographic photosensitive member 10 according to the present invention, in which an intermediate layer 2, a charge generation layer 3, a charge transport layer 4, and a protective layer 5 are sequentially laminated on a conductive substrate 1. It is a function-separated laminated type photoreceptor 10 having the above configuration. In the present invention, the intermediate layer 2 and the protective layer 5 are layers added as needed. FIG. 2 shows an electrophotographic apparatus 100 according to the present invention.
2 is a schematic configuration diagram of FIG. FIG. 3 is a schematic configuration diagram of a photoconductor surface potential measuring device according to the present invention.

The conductive substrate 1 shown in FIG. 1 serves not only as an electrode of the photoconductor but also as a support for each functional layer constituting the photoconductor, and has any shape such as a cylindrical shape, a plate shape, or a film shape. However, as the material, a metal such as aluminum, stainless steel, or nickel, or a material such as glass or resin whose surface is subjected to a conductive treatment is used. It is preferably cylindrical, and the material is aluminum (including alloy)
Is preferred.

The intermediate layer 2 is composed of a layer containing an organic resin as a main component or a metal oxide film such as alumite, for controlling the injection of charges from the conductive substrate to the photosensitive layer (charge generation layer and charge transport layer). Alternatively, it is provided as necessary for the purpose of covering defects on the surface of the substrate and improving the adhesion between the photosensitive layer and the conductive substrate. As the resin material used for the intermediate layer,
Examples include insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, and cellulose, and conductive polymers such as polythiophene, polypyrrole, and polyaniline. These resins can be used alone or in admixture in an appropriate combination. . Further, these resins may contain metal oxide fine particles such as titanium dioxide and zinc oxide. In order to improve the dispersibility of these metal oxide fine particles in the resin material, Japanese Patent Publication No. 6-59397 is used.
It is preferable that aminosilane treatment or the like is performed according to the method described in the publication.

The charge generation layer 3 is mainly composed of an organic charge generation material and a resin binder. In the present invention, an oxytitanyl phthalocyanine pigment is used as the charge generating material. As the resin binder, vinyl chloride resin may be used alone or as a main component mixed with vinyl acetate, vinyl alcohol, polyvinyl acetal, polycarbonate, polyester, polyamide and other resins.

A resin binder containing a vinyl chloride resin is used for the charge generation layer 3 when the coating liquid in the coating tank contains the vinyl chloride resin, even if the coating operation is repeated for a long period of time. As a result of a part of the product not sticking to the tank wall due to crystallization, etc., there is a large merit in industrial production that the appearance defect of the coating film due to redeposition of the film that has peeled off from the tank wall as in the case of sticking is eliminated. This is because.

The charge transport layer 4 is mainly composed of a charge transport material and a resin binder. As the charge transport material, a hydrazone compound, a butadiene compound, a diamine compound, an indole compound, an indoline compound, a stilbene compound, a distilbene compound, or the like is used, and the formula (1) is used between the ionization potential (eV) of the oxytitanyl phthalocyanine according to the present invention. The compounds having the ionization potential (eV) satisfying the relational expression (1) are selected and used alone or in combination. As the resin binder, polycarbonate resins such as bisphenol A type, bisphenol Z type, bisphenol A type-biphenyl copolymer, polystyrene resins, polyphenylene resins and the like are used alone or in combination. Further, hereinafter, when simply referred to as a photosensitive layer, it means a charge generation layer and a charge transport layer.

Further, in each functional layer, an electron-accepting substance, an antioxidant, and the like may be added, if necessary, for the purpose of improving sensitivity, reducing residual potential, improving environment resistance and stability against harmful gas and light. A light stabilizer or the like can be added. Examples of the compound used for such purpose include chromal derivatives such as tocopherol and etherified compounds, esterified compounds, polyarylalkane compounds, hydroquinone derivatives, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds,
Examples thereof include a phenylenediamine derivative, a phosphonic acid ester, a phosphite ester, a phenol compound, a hindered phenol compound, a linear amine compound, and a hindered amine compound.

Further, the photosensitive layer may contain a leveling agent such as silicone oil or a fluorine-containing additive for the purpose of improving the leveling property of the formed coating film and imparting further lubricity.

If necessary, a surface protective layer may be provided on the surface of the photosensitive layer for the purpose of improving mechanical strength.
The surface protective layer is made of a material having excellent durability against mechanical stress, and it is desired that the surface protective layer has a property of transmitting light, which is sensitive to the charge generation layer, with as low loss as possible.

FIG. 2 is a schematic configuration diagram of a reversal development type electrophotographic apparatus 100 according to the present invention, which has a charging mechanism, an exposure mechanism, a developing mechanism and a transfer mechanism, and uses a corona charging method by a scorotron for the charging mechanism. . Using this figure,
The electrophotographic apparatus according to the present invention will be described below.

The electrophotographic apparatus 100 includes a charging mechanism including a scorotron charging member 21 on the outer peripheral edge of the cylinder of the electrophotographic photosensitive member 10 shown in FIG. 1, and a high voltage power source 22 for supplying a voltage to the charging member, and a charging mechanism. An exposure mechanism 23, a developing mechanism 24, a paper feed roller and a paper feed guide 25, a transfer charging mechanism 26 by a corotron, a cleaning device 27, and the like are sequentially arranged, and an image is formed by a reversal development method.

The charging mechanism shown in FIG. 2 is a scorotron charging member, but it is a corotron charging system or a charge injection charging system by contact with a charging roller, a charging brush or the like.
In addition, according to the present invention, since the transfer memory potential is small, a good image can be obtained even with a mechanism in which the application power source section is simplified by applying only the DC component.

Further, according to the present invention, in a method of charging by superimposing DC and AC components by a normal scorotron charging method or a charge injection charging method such as a normal charging roller or a charging brush, like an OHP sheet or thick paper. A good image without a memory image can be obtained even under image forming conditions where a memory image is likely to appear, such as when a significantly increased transfer current is required.

In the image forming method, first, the voltage supplied from the high voltage power source 22 is applied to the scorotron charging member 21 arranged on the electrophotographic photosensitive member 10, and the photosensitive member 10 is subjected to the image forming.
The surface is charged, and an image corresponding to the original is imagewise exposed on the photoconductor 10 by the image exposure mechanism 23 to form an electrostatic latent image.

Next, the toner in the developing mechanism 24 is transferred to the photosensitive member 1.
By making it adhere to 0, the electrostatic latent image on the photoconductor 10 is developed (visualized).

Further, the toner image formed on the photosensitive member 10 is transferred by a corotron transfer charging mechanism 26 onto a transfer material such as paper supplied through a paper feed roller and a paper feed guide 25. At this time, especially when the transfer material is different from a normal printing paper such as an OHP sheet and has a large thickness, the transfer current may have to be significantly increased. Then, in the gap with the next OHP sheet,
Since the surface of the photoreceptor is charged with a voltage higher than usual, the surface potential of the previous cycle is likely to appear as the transfer memory potential without being canceled in the charging step of the cycle of the next electrophotographic process. According to the present invention, a good image can be obtained without causing a transfer memory even in such a case.

Next, the cleaning member 27 collects the residual toner remaining on the photoconductor 10 without being transferred to the transfer material.

On the other hand, the transfer material such as paper on which the toner image is formed is sent to a fixing device (not shown) by a carrying unit (not shown), and the toner image is fixed and output.

In the electrophotographic apparatus 100, the light source of the image exposure mechanism 23 is a halogen light, a fluorescent lamp, an LED,
Laser light or the like can be used. Also, other auxiliary processes may be added if necessary.

As such an electrophotographic apparatus 100,
In addition to copiers, there are laser beam printers, facsimiles, electrophotographic plate making systems, etc.

FIG. 3 is a schematic configuration diagram of a surface potential measuring device used for measuring the surface potential of the electrophotographic photosensitive member in each main process in the electrophotographic process in the examples described below.

In this surface potential measuring instrument, light from the scorotron charging mechanism 12, the surface potential measuring probe 11-1 and the exposure source 18 is applied to the outer peripheral edge of the cylindrical electrophotographic photosensitive member 78.
An optical filter 17 that selects only a wavelength of 0 nm, an exposure mechanism 13 including an exposure member 16 that supplies light to the surface of the photoconductor through an optical shutter 20 that opens and closes light, a surface potential measurement probe 11-2, and a transfer corotron charging mechanism 15. Are arranged in this order at a peripheral angle of 45 degrees, and further 90
An exposure mechanism (for static elimination), which is located at a peripheral angle of 4 degrees, is composed of an exposure source 18, an optical filter 19 for selecting a wavelength of 630 nm, and an exposure member 14 for supplying light via an optical shutter 20, is arranged. The surface potential measurement probe 11-3 is arranged at a circumferential angle.

When the photoconductor 10 rotates in the direction of the arrow in FIG. 3, the surface of the photoconductor charged to a predetermined negative potential by the scorotron charging mechanism 12 is the surface potential measuring probe 11-1.
The surface potential is measured at the position of, and exposed when the position of the exposure member 16 is reached, and the surface potential measuring probe 11 is further exposed.
The surface potential after exposure is measured at the position -2. Subsequently, at the position of the transfer corotron charging member 15, a positive charge having a reverse polarity for transfer is received. When this transfer charging is ON and OFF
The absolute value of the difference between the surface potential values measured by the surface potential measurement probe 11-3 at each time is the transfer memory potential.

[0041]

EXAMPLES As for the present invention, since the photoconductor according to the present invention has a lower transfer memory potential than that of the comparative example, the transfer memory is generated even in the reversal development type electrophotographic apparatus in which the transfer memory is likely to occur. It is clarified from a comparative experiment that it is difficult to obtain good print and image.
It goes without saying that the present invention is not limited to the electrophotographic photosensitive member and the electrophotographic apparatus specifically described in the following examples.

Example 1 An aluminum cylindrical substrate having a diameter of 30 mm was washed and dried, and then an intermediate layer coating solution having the following composition was applied by dip coating and dried at 100 ° C. for 30 minutes to obtain a film thickness of about A 1 μm intermediate layer was formed. Alcohol-soluble polyamide resin (CM-8000: manufactured by Toray Industries, Inc.) 5 parts by weight Aminosilane-treated titanium oxide fine particles 5 parts by weight Methanol / dichloromethane mixed solvent (6 parts by weight / 4 parts by weight) 90 parts by weight

Next, a charge generation layer dispersion having the following composition was applied by dip coating and dried at 80 ° C. for 15 minutes to give a film thickness of about 0.2 μm.
m charge generating layer was formed. α-type oxytitanyl phthalocyanine 1.2 parts by weight Vinyl chloride resin (MR-110: Nippon Zeon Co., Ltd.) 0.8 parts by weight Dichloromethane / 1,2-dichloroethane mixed solvent (7 parts by weight / 3 parts by weight) 98 parts by weight Department

Next, a charge transport layer coating solution having the following composition was applied by dip coating and dried at 90 ° C. for 60 minutes to give a film thickness of about 20 μm.
Was formed on the charge transport layer. The following compound 3 was used as the charge transport material (CTM material 1). Compound 3 (the following structural formula 3) 9 parts by weight Bisphenol A-biphenyl copolymerized polycarbonate (Tafuzet B-500 / manufactured by Idemitsu Kosan Co., Ltd.) 11 parts by weight 2,6-di-tert-butyl-4-methylphenol (Takeda Yakuhin Kogyo Co., Ltd. 0.5 parts by weight Dichloromethane 100 parts by weight The electrophotographic photoreceptor of Example 1 was prepared with a layer structure of 100 parts by weight or more.

Example 2 The α-type oxytitanyl phthalocyanine of Example 1 was changed to Y-type oxytitanyl phthalocyanine, and the phthalocyanine / resin ratio was 1.0 (1 part by weight Y-type oxytitanyl phthalocyanine / 1 part by weight vinyl chloride resin). Part) and two kinds of C instead of the compound 3
Example 2 was the same as Example 1 except that the TM materials 1 and 2 were changed to 4.5 parts by weight of compound 1 (the following structural formula 1) and compound 2 (the following structural formula 2), respectively. An electrophotographic photoreceptor was produced.

Example 3 Example 3 is the same as Example 2 except that the CTM material 1 is replaced by the compound 3 (the following structural formula 3) instead of the compound 1 and the compound 2 in the charge transport layer, and only 9 parts by weight is used. An electrophotographic photosensitive member of Example 3 was manufactured in the same manner as in 2.

Example 4 The same as Example 2 except that the phthalocyanine / resin ratio was 0.8 (0.8 parts by weight of Y-type oxytitanyl phthalocyanine / 1 part by weight of vinyl chloride resin). Thus, an electrophotographic photosensitive member of Example 4 was produced.

Example 5 Example 5 was carried out in the same manner as in Example 2 except that the phthalocyanine / resin ratio was 2.0 (2 parts by weight of Y-type oxytitanyl phthalocyanine / 1 part by weight of vinyl chloride resin). An electrophotographic photosensitive member of Example 5 was produced.

Comparative Example 1 Comparative Example 1 was carried out in the same manner as in Example 1 except that the polyvinyl chloride resin in the charge generation layer of Example 1 was changed to polyvinyl butyral resin (BM-1 manufactured by Sekisui Chemical Co., Ltd.). An electrophotographic photoreceptor was produced.

(Comparative Example 2) Of the charge generation layers of Example 2,
An electrophotographic photosensitive member of Comparative Example 2 was produced in the same manner as in Example 2 except that the polyvinyl chloride resin was changed to polyvinyl butyral resin (BX-1 manufactured by Sekisui Chemical Co., Ltd.).

(Comparative Example 3) Of the charge transport layers of Example 2,
Instead of compound 1 and compound 2, CTM material 1 was compound 4 (the following structural formula 4) alone in 9 parts by weight, and vinyl chloride resin was polyvinyl butyral resin (B manufactured by Sekisui Chemical Co., Ltd.).
An electrophotographic photoreceptor of Comparative Example 3 was produced in the same manner as in Example 2 except that X-1) was used.

Comparative Example 4 The same as Example 2 except that the phthalocyanine / resin ratio was 0.6 (0.6 parts by weight of Y-type oxytitanyl phthalocyanine / 1 part by weight of vinyl chloride resin). To prepare an electrophotographic photosensitive member of Comparative Example 4.

(Comparative Example 5) The same as Example 2 except that the phthalocyanine / resin ratio was 2.2 (2.2 parts by weight of Y-type oxytitanyl phthalocyanine / 1 part by weight of vinyl chloride resin). An electrophotographic photosensitive member of Comparative Example 5 was produced.

(Comparative Example 6) In Example 3, instead of Compound 3 in the charge transport layer, Compound 5 was used as a CTM material.
An electrophotographic photosensitive member of Comparative Example 6 was produced in the same manner as in Example 3 except that (the following structural formula 5) was changed to 9 parts by weight.

(Comparative Example 7) In Example 3, instead of Compound 3 in the charge transport layer, Compound 6 was used as a CTM material.
An electrophotographic photosensitive member of Comparative Example 7 was produced in the same manner as in Example 3 except that (the following structural formula 6) was changed to 9 parts by weight.

Differences in materials and compositions between the above Examples 1 to 5 and Comparative Examples 1 to 7 are listed in Table 1 below. In Table 1, CGL and CTM represent a charge generation layer and a charge transport material, respectively, and α-TiOPc,
Y-TiOPc and Pc represent the above α-type oxytitanyl phthalocyanine, Y-type oxytitanyl phthalocyanine and phthalocyanine, respectively. Further, "vinyl chloride" means vinyl chloride resin.

[0057]

[Table 1]

[0058]

[Chemical 1]

[0059]

[Chemical 2]

[0060]

[Chemical 3]

[0061]

[Chemical 4]

[0062]

[Chemical 5]

[0063]

[Chemical 6]

(Evaluation) Examples 1 to 5 and Comparative Example 1
For each of the photoconductors prepared in Nos. 7 to 7, the surface potential measurement probe shown in FIG. 3 is used to measure the surface potential value when the transfer mechanism is turned ON / OFF (operation / skip).
1-3, and the transfer memory potential was determined from the difference between the surface potential values. The transfer memory potential value is shown in Table 2. If this transfer memory potential has a large value, a transfer memory image is likely to occur.

Separately, each of phthalocyanine and charge transport material (material 1 and material 2 or material 1) measured with a powder sample using a surface analyzer AC-1 manufactured by Riken Keiki Co., Ltd. with a light amount of 50 nw. Ionization potential (eV)
Value of IP (CGM), IP (CTM material 1), IP (C
The TM material 2) is shown for Examples 1-5 and Comparative Examples 1-7 in Table 2, respectively.

The surface potential of each of the photoconductors after irradiation with light having a light intensity of 2.5 μJ / cm ² was measured by the surface potential measuring device (the smaller the value, the higher the sensitivity of the photoconductor), and Using a commercially available digital copying machine (reversal development method) equipped with each of the photoconductors prepared in Examples 1 to 5 and Comparative Examples 1 to 7, a transfer memory before and after a printing test of 10,000 A4 sheets of OHP sheets was used. Table 3 below shows the presence or absence of an image and the results of black solid density measurement before and after the printing test on 10,000 sheets. It is preferable that the black solid density (ID) does not change before and after printing 10,000 sheets, and if the black solid density (ID) is small or the ID value changes after printing 10,000 sheets, the low electric field area It means that problems such as decreased sensitivity and increased residual potential occur at.

[0067]

[Table 2]

[0068]

[Table 3]

In Examples 2, 4, and 5, the weight ratio of phthalocyanine / vinyl chloride resin in the charge generation layer was 0.8.
To 2.0, the transfer memory potential and the surface potential of the photoconductor after light irradiation with a light intensity of 2.5 μJ / cm ² are small (initial sensitivity is good) from Tables 2 and 3, and repeated (10,000 times). Since the change in print density before and after use is small,
It can be seen that the electrophotographic photoreceptor has no deterioration in sensitivity in the low electric field region, does not cause a failure such as an increase in residual potential due to repeated use, and does not generate a transfer memory image.

Even when the same charge generating material and charge transporting material are combined in the same weight ratio as in Example 1 and Comparative Example 1, and in Example 2 and Comparative Example 2, charge generation is performed. When the binder resin of the layer was changed from the vinyl chloride resin of Examples 1 and 2 to the polyvinyl butyral resin of Comparative Examples 1 and 2, respectively, the initial sensitivities (2.
Although the surface potential of the photoconductor after irradiation with light of 5 μJ / cm ² ) and the black solid density characteristic (ID) after repeated use are good, the transfer memory potential is 20 as in Examples 1 and 2.
Compared with V and 22V, Comparative Examples 1 and 2 have higher voltages of 46V and 45V, respectively, and transfer memory images are also generated from the initial stage. Therefore, the vinyl chloride resin binders of Examples 1 and 2 are superior. I understand.

In Example 3, the charge generation layer was the same in material and weight ratio as in Example 2, and the charge transport material of the charge transport layer was formed of compounds 1 and 2 (ionization potentials of 5.23 eV and 5.12 eV). Compound 3 (with an ionization potential of 5.40 eV) was changed to a material larger by +0.3 than the ionization potential of oxytitanyl phthalocyanine of 5.10 eV. In this case, the photoconductor is within the scope of the present invention, and the transfer memory potential is 1
The voltage is 8 V, which is smaller than those in Examples 1 and 2, and no memory image is generated.

Further, in the case of Comparative Example 3, the material (+) having an ionization potential (5.60 eV) of the charge transport material is sufficiently larger than the ionization potential (5.10 eV) of the oxytitanyl phthalocyanine according to the present invention.
0.5) is used, the transfer memory value (15V) is small as shown in Tables 2 and 3 to prevent the transfer memory image, but as shown in Table 3, the light intensity is 2.5 μJ /
Surface potential of photoconductor after irradiation with light of cm ² (80V)
Is high (low initial sensitivity), the black solid density is as low as 1.20 from the initial stage, which means that it is not practical.

Furthermore, from Comparative Example 4, when the weight ratio of oxytitanyl phthalocyanine / vinyl chloride resin was 0.6, which is outside the range of the present invention, the transfer memory potential was initially as small as 22 V, and the transfer memory image was Although not seen, the black solid density was lowered (1.35 to 1.18) and the occurrence of a transfer memory image was observed after printing 10,000 sheets after repeated use.

Further, in Comparative Example 5, the initial sensitivity and the black solid density after printing 10,000 sheets were good, and there was almost no decrease in sensitivity after repeated use, but the transfer memory was as large as 40 V and the transfer memory image Occurred from the beginning.

In Comparative Example 6, as the charge transport material, its ionization potential was smaller than the ionization potential of oxytitanyl phthalocyanine, which was 5.10 eV, 4.8.
This is the case where the compound 5 of 7 eV was used, and the case where the law relating to the ionization potential well known in the prior art for the negatively charged laminated electrophotographic photosensitive member was followed. The injection property of the charges generated in the charge generation layer into the charge transport layer is extremely good, and therefore the initial sensitivity (light intensity 2.5 μJ /
The surface potential of the photoconductor after irradiation with light of cm ² is as good as 30 V from Table 3, but the transfer memory value is large at 55 V, and a transfer memory image is generated from the initial stage.

In Comparative Example 7, as the charge transport material, the compound 6 having an ionization potential of 5.50 eV, which is larger than the ionization potential of oxytitanyl phthalocyanine of 5.10 eV by a value (+0.4) exceeding the range according to the present invention, is used. In this case, although the transfer memory is small as in Comparative Example 3, the initial sensitivity is low, the black solid density at the initial stage is low, and the sensitivity decrease and the transfer memory after repeated use (10,000 sheets) are also observed. It turns out that it is not practical.

Although not shown in the experimental example, the weight ratio of oxytitanyl phthalocyanine / vinyl chloride resin was comparative example 5.
When it was larger, the surface potential decreased (reduction of the holding ratio) as it increased, and the charging potential could be charged only below a predetermined standard specification value.

As can be seen from Tables 2 and 3, the photoconductors according to the present invention have a small transfer memory potential, and thus are of the scorotron charging type or the DC-AC superposed contact charging type, and are similar to OHP sheets. The surface potential after transfer tends to remain without being canceled by the next charging mechanism, such as the condition that the transfer current is greatly increased in response to the case where the thickness and material are different from those of normal printing paper (that is, transfer memory image occurs It is understood that the effect is particularly suitably exerted in an electrophotographic apparatus that forms an image by an electrophotographic process.

Further, in the electrophotographic apparatus for forming an image by an electrophotographic process in which the surface potential after transfer is likely to remain without being canceled by the next charging mechanism, such as a corotron or a charge injection charging method in which only direct current is applied. It was found to have the same effect as in.

[0080]

According to the present invention, in an electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer laminated on a conductive substrate, the charge generation layer contains oxytitanyl phthalocyanine and vinyl chloride resin in an amount of 0.8 to 0.8. 2.0, preferably in a weight ratio of 1.0 to 2.0 (the phthalocyanine / the resin), and the charge transport layer comprises an ionization potential (e) of the oxytitanyl phthalocyanine.
V), the electrophotographic photosensitive member contains a charge transport material having an ionization potential (eV) satisfying the relational expression (1), so that the sensitivity decreases in the low electric field region and the residual potential due to repeated use. (EN) An electrophotographic apparatus which can provide an electrophotographic photosensitive member having a small transfer memory potential without causing an obstacle such as a rise, and can further obtain a good printed image without generating a transfer memory image in the reversal development method. You can

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of essential parts of an electrophotographic photosensitive member according to the present invention.

FIG. 2 is a schematic configuration diagram of an electrophotographic apparatus according to the present invention.

FIG. 3 is a schematic configuration diagram of a photoconductor surface potential measuring device.

[Explanation of symbols]

1 Conductive substrate 2 Middle class 3 Charge generation layer 4 Charge transport layer 5 protective layer 10 Electrophotographic photoreceptor 21 Charging member 23 Exposure mechanism 24 Development mechanism 26 Transfer mechanism 100 electrophotographic device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mikio Yamazaki             Fujiden, 4-18-1 Chikuma, Matsumoto City, Nagano Prefecture             Machine Image Device Co., Ltd. F term (reference) 2H068 AA13 AA19 AA20 BA11 BA13                       BA39 BB12

Claims (4)

[Claims] 1. An electrophotographic photosensitive member comprising a conductive substrate and at least a charge generation layer and a charge transport layer laminated on the conductive substrate, wherein the charge generation layer contains oxytitanyl phthalocyanine and vinyl chloride resin in a range of 0.8 to 2.0. A weight ratio (the phthalocyanine / the resin) is included, and the charge transport layer has an ionization potential (eV) satisfying the relational expression of the following formula (1) with the ionization potential (eV) of the oxytitanyl phthalocyanine. An electrophotographic photoreceptor comprising the charge transport material having [Equation 1] 2. The charge generation layer comprises at least oxytitanyl phthalocyanine and vinyl chloride resin in an amount of 1.0 to 2.0.
The electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member is contained in a weight ratio (the phthalocyanine / the resin) in the range of. 3. Oxytitanyl phthalocyanine is CuK.
In the X-ray diffraction spectrum of α, the Bragg angle (2θ ±
0.2 °) is 7.5 °, 12.3 °, 16.3 °, 2
5.3 °, 28.7 ° or 9.5 °, 9.7 °, 1
1.7 °, 15.0 °, 23.5 °, 24.1 °, 2
The electrophotographic photosensitive member according to claim 1 or 2, which has a main peak at 7.3 °. 4. The electrophotographic photosensitive member according to claim 1, at least a charging mechanism, an exposure mechanism,
An electrophotographic apparatus comprising a developing mechanism and a transfer mechanism, and having a structure for forming an image by a reversal developing method.