JP2010237555A - Single-layer electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single-layer electrophotographic photoreceptor which effectively suppresses the occurrence of void even under the existence of oxidative gas, and at the same time, effectively suppresses the occurrence of a black spot due to a leakage current, and an image forming apparatus. <P>SOLUTION: The single-layer electrophotographic photoreceptor is used in an image forming apparatus provided with a roller cleaning system, and the image forming apparatus uses the single-layer electrophotographic photoreceptor, wherein a photosensitive layer containing at least a charge generating agent, a hole transport agent, an electron transfer agent, and a binder resin is provided on a base without an oxide film due to anodic oxidation. The binder resin is a polycarbonate resin having a viscosity average molecular weight of 10.000 to 40,000, and the photosensitive layer has a layer thickness of 20 to 45 &mu;m, and an absolute value of a positive/negative breakdown voltage of the single-layer electrophotographic photoreceptor, measured according to JIS C 2110 is &ge;6 kV. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a single layer type electrophotographic photosensitive member and an image forming apparatus. In particular, even in the presence of an oxidizing gas, it is possible to effectively suppress the occurrence of white spots, while also effectively suppressing the occurrence of black spots due to leakage currents and images. The present invention relates to a forming apparatus.

Conventionally, in an electrophotographic machine such as a copying machine or a laser printer, an electrostatic latent image is formed on an electrophotographic photosensitive member by a charging process and an exposure process. Then, after the formed electrostatic latent image is developed with toner in a development process, the developed toner image is transferred to a recording medium by a transfer process, and finally fixed by a fixing process. .
Of the above-described steps, particularly in the charging step and the transfer step, a charge is applied to the electrophotographic photosensitive member and the recording medium by utilizing a discharge phenomenon generated by applying a predetermined voltage to a predetermined member. The method is widely practiced.

On the other hand, since the speed of image formation has been increasing in recent years, in order to obtain the charging potential and the transfer potential at the conventional level, the applied voltage in the charging step and the transfer step is increased to increase the discharge amount. There is a need.
However, the case of increasing the discharge amount in this manner, the amount of the oxidizing gas such as ozone and NO _x generated with the discharge increases, the organophotoreceptor consists in particular organic material, the photosensitive The layer surface is likely to be oxidized and deteriorated.
When the surface of the photosensitive layer is oxidized and deteriorated, there is a problem that white spots are likely to occur in a portion corresponding to that portion in the formed image.

Therefore, in order to solve such a problem, a method of polishing and removing a portion of the photosensitive layer surface which has been oxidized and deteriorated by a roller cleaning system is disclosed (for example, Patent Document 1).
That is, Patent Document 1 discloses a cleaning device including a cleaning roller whose surface is made of an elastic material.

JP 2003-43889 A (Claims)

However, as in Patent Document 1, when a roller cleaning system is simply used, the occurrence of white spots can be suppressed to some extent, but this time, there is a problem that black spots are likely to occur.
That is, when the roller cleaning system is used, the photosensitive layer gradually wears, and accordingly, the withstand voltage of the photosensitive layer is lowered, and a leak current is likely to occur.
As a result, black spots are likely to occur in the formed image corresponding to the location where such leakage current occurs.
Therefore, there has been a demand for an electrophotographic photosensitive member that can effectively suppress the occurrence of white spots even in the presence of an oxidizing gas, while also effectively suppressing the occurrence of black spots due to leakage current.

Therefore, as a result of intensive studies, the present inventors have determined that a polycarbonate resin having a viscosity average molecular weight within a predetermined range as a binder resin in a single layer type electrophotographic photosensitive member used in an image forming apparatus equipped with a roller cleaning system. In addition, the inventors have found that the above-mentioned problems can be solved by using a single-layer electrophotographic photosensitive member within a predetermined range.
That is, the object of the present invention is a single layer type that can effectively suppress the occurrence of white spots even in the presence of an oxidizing gas, and can also effectively suppress the occurrence of black spots due to leakage current. An object is to provide an electrophotographic photosensitive member and an image forming apparatus.

According to the present invention, there is provided a single-layer electrophotographic photosensitive member used in an image forming apparatus equipped with a roller cleaning system, wherein at least a charge generating agent and a positive electrode are formed on a substrate having no oxide film formed by anodization. A photosensitive layer containing a hole transporting agent, an electron transporting agent and a binder resin is provided, and the binder resin is a polycarbonate resin having a viscosity average molecular weight in the range of 10,000 to 40,000. The absolute value of the positive / negative withstand voltage of the single-layer electrophotographic photosensitive member measured according to JIS C 2110 is set to a value within the range of 20 to 45 μm, and the value is 6 kV or more. A single-layer electrophotographic photosensitive member is provided, which can solve the above-described problems.
That is, since the single-layer electrophotographic photosensitive member of the present invention uses a polycarbonate resin having a predetermined molecular weight as the binder resin for the photosensitive layer, the formation of voids in the photosensitive layer is suppressed. Further, it is possible to effectively suppress the oxidative deterioration of the photosensitive layer surface.
Further, since the roller cleaning system is employed, even if the photosensitive layer surface is oxidized and deteriorated, the oxidized and deteriorated portion can be effectively polished and removed.
Therefore, even in the presence of an oxidizing gas, it is possible to effectively suppress the occurrence of white spots due to oxidative degradation of the photosensitive layer surface.
The single-layer electrophotographic photosensitive member of the present invention has a positive and negative withstand voltage (hereinafter sometimes referred to as a reference withstand voltage) measured under predetermined conditions while the photosensitive layer has a predetermined thickness. Since the absolute value of is a value within a predetermined range, even when the photosensitive layer is worn, the generation of leakage current in the charging step and the transfer step can be effectively suppressed.
Therefore, the occurrence of black spots due to the leakage current can be effectively suppressed.

  In constituting the single-layer electrophotographic photosensitive member of the present invention, the binder resin contains a polycarbonate resin represented by at least one general formula selected from the following general formulas (1) to (2). preferable.

(In the general formula (1), the plurality of substituents Ra and Rb are each independently an hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. A substituted aryl group, the subscripts p and q are each independently an integer of 0 to 4, and the substituents Rc and Rd are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms. W is a single bond, —O—, —CO—, —CH ₂ —, and the subscripts k and l are molar ratios satisfying a relational expression of 0 ≦ l / (k + 1) <0.6. .)

(In the general formula (2), the plurality of substituents Re and Rf are each independently an hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. A substituted aryl group, the subscripts r and s are each independently an integer of 0 to 4, W is a single bond, —O—, —CO—, —CH ₂ —, and the subscripts m and n are The molar ratio satisfies the relational expression 0 ≦ n / (n + m) <0.6.)

  By comprising in this way, the oxidative degradation of the photosensitive layer surface can be suppressed more effectively.

In constituting the single-layer electrophotographic photosensitive member of the present invention, the charge generator is preferably a titanyl phthalocyanine crystal having the following characteristics (A) and (B).
(A) The CuKα characteristic X-ray diffraction spectrum has main peaks at Bragg angles 2θ ± 0.3 ° = 9.5 and 27.2 °.
(B) In the differential scanning calorimetry spectrum, it has one peak in the range of 270 to 400 ° C. in addition to the peak accompanying vaporization of adsorbed water.
With this configuration, the formation efficiency of the electrostatic latent image by exposure can be significantly improved.

In forming the single-layer electrophotographic photosensitive member of the present invention, an intermediate layer is provided on a substrate, and the intermediate layer includes a binder resin and titanium oxide fine particles, and the titanium oxide fine particles The content of is preferably set to a value in the range of 50 to 500 parts by weight with respect to 100 parts by weight of the binder resin, and the film thickness of the intermediate layer is preferably set to a value in the range of 0.1 to 10 μm. .
With this configuration, it becomes easier to adjust the absolute value of the reference withstand voltage of the single-layer electrophotographic photosensitive member to a value within a predetermined range.

Another aspect of the present invention is an image forming apparatus including any one of the above-described single-layer type electrophotographic photoconductors, and a charging unit, an exposure unit, An image forming apparatus comprising: a developing unit, a transfer unit, and a cleaning unit; and a roller cleaning system as the cleaning unit.
That is, the image forming apparatus of the present invention includes a predetermined single-layer type electrophotographic photosensitive member and a roller cleaning system, so that white spots are effectively generated even in the presence of an oxidizing gas. On the other hand, generation of black spots due to leakage current can be effectively suppressed.

Further, in constituting the image forming apparatus of the present invention, it is preferable that the charging polarity by the charging means is a positive polarity.
By comprising in this way, generation | occurrence | production of the oxidizing gas from a charging means can be suppressed compared with the case of negative polarity.

In configuring the image forming apparatus of the present invention, it is preferable that the peripheral speed of the single-layer electrophotographic photosensitive member is set to a value of 120 mm / sec or more.
With this configuration, the voltage applied in the charging unit and the transfer unit increases, and the amount of oxidizing gas generated increases. However, according to the present invention, white spots are effectively generated. Can be suppressed.

In configuring the image forming apparatus of the present invention, it is preferable that the charging unit is a scorotron and the voltage applied to the scorotron is set to a value in the range of 5 to 10 kV.
With this configuration, even when high-speed image formation is performed, a predetermined charged potential can be stably maintained, while white spots due to an oxidizing gas are effectively suppressed. can do.

In configuring the image forming apparatus of the present invention, it is preferable that the transfer unit is a roller or a belt type via a roller.
With this configuration, even when high-speed image formation is performed, the predetermined transfer potential can be stably maintained, and the occurrence of white spots due to the oxidizing gas can be effectively suppressed. can do.

In constructing the image forming apparatus of the present invention, when the single-layer electrophotographic photosensitive member is charged to 700 V and exposed at a wavelength of 780 nm at 0.5 μJ / cm ² , the surface potential after 0.34 seconds has elapsed. Is preferably 160 V or less.
With this configuration, excellent sensitivity characteristics can be exhibited even when high-speed image formation is performed.

FIGS. 1A to 1B are views for explaining the configuration of the single-layer electrophotographic photosensitive member of the present invention. FIG. 2 is a diagram provided for explaining the relationship between the viscosity average molecular weight of the polycarbonate resin and the oxidative deterioration of the photosensitive layer. FIG. 3 is a diagram provided for explaining the outline of the reference withstand voltage measuring apparatus. FIG. 4 is a diagram for explaining the relationship between the absolute value of the reference withstand voltage and the leakage current. FIG. 5 is a diagram for explaining the image forming apparatus of the present invention. 6 is a CuKα characteristic X-ray diffraction spectrum of a titanyl phthalocyanine crystal (stored in tetrahydrofuran for 7 days) used in Example 1. FIG. FIG. 7 is a differential scanning calorimetry chart of the titanyl phthalocyanine crystal used in Example 1.

[First Embodiment]
The first embodiment is a single-layer type electrophotographic photosensitive member used in an image forming apparatus equipped with a roller cleaning system, and has at least a charge generating agent on a substrate that does not have an anodized oxide film, A photosensitive layer containing a hole transport agent, an electron transport agent and a binder resin is provided, and the binder resin is a polycarbonate resin having a viscosity average molecular weight in the range of 10,000 to 40,000, Positive / negative withstand voltage (hereinafter referred to as a reference withstand voltage) of a single-layer type electrophotographic photoreceptor measured in accordance with JIS C 2110, with the thickness of the photosensitive layer being in the range of 20 to 45 μm. The single-layer electrophotographic photosensitive member is characterized in that the absolute values of both are 6 kV or more.
Hereinafter, the single-layer electrophotographic photosensitive member as the first embodiment will be specifically described for each component.

1. Basic Configuration As shown in FIG. 1A, the electrophotographic photosensitive member of the present invention has a single-layer photosensitive layer 114 comprising a base 112 and a charge generating agent, a charge transporting agent, and a binder resin. It is a single layer type electrophotographic photosensitive member 71 provided with
The reason for this is that, in the case of a single-layer electrophotographic photosensitive member, it is easy to set the charging polarity of the electrophotographic photosensitive member to a positive polarity. It is because it can suppress.
Further, this is because a single-layer electrophotographic photosensitive member has an advantage that excellent sensitivity characteristics can be obtained even though the configuration is simple.
The single-layer electrophotographic photosensitive member of the present invention is a single-layer electrophotographic photosensitive member in which an intermediate layer 116 is formed between the photosensitive layer 114 and the substrate 112 as shown in FIG. It can also be the body 71 '.

2. Substrate Moreover, various materials can be used as the constituent material of the substrate.
For example, a substrate formed of a metal such as iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, or the above-described metal is deposited or deposited. Examples include a substrate made of a laminated plastic material, or a glass substrate coated with aluminum iodide, tin oxide, indium oxide, or the like.
That is, it is sufficient that the substrate itself has conductivity, or the surface of the substrate has conductivity, and it is sufficient that the substrate has sufficient mechanical strength when used.

3. Intermediate Layer Further, as illustrated in FIG. 1B, it is also preferable to provide an intermediate layer 116 containing a binder resin, inorganic fine particles, and the like on the substrate 112.
This is because the provision of such an intermediate layer makes it easy to adjust the absolute value of the reference withstand voltage of the single-layer electrophotographic photoreceptor measured under a predetermined condition to a value greater than or equal to a predetermined value. is there.
Therefore, the intermediate layer includes, for example, the binder resin and the titanium oxide fine particles, and the content of the titanium oxide fine particles is a value within the range of 50 to 500 parts by weight with respect to 100 parts by weight of the binder resin. It is preferable that
The reason for this is that it becomes easier to adjust the absolute value of the reference withstand voltage of the single-layer type electrophotographic photosensitive member to a value within a predetermined range by such a configuration.
That is, by setting the content of the titanium oxide fine particles in such a range, the resistance of the intermediate layer can be easily adjusted to a predetermined range, and the dispersibility of the titanium oxide fine particles can be improved to reduce the resistance of the intermediate layer. This is because it can be made uniform.
Therefore, the content of the titanium oxide fine particles is more preferably set to a value in the range of 100 to 400 parts by weight with respect to 100 parts by weight of the binder resin, and is set to a value in the range of 150 to 300 parts by weight. Further preferred.

Further, it is preferable that the titanium oxide fine particles have been subjected to a surface treatment with alumina, silica and an organosilicon compound.
This is because the surface treatment can adjust the resistance of the intermediate layer to a suitable range while further improving the dispersibility of the titanium oxide fine particles in the intermediate layer.
That is, the basic dispersibility of the titanium oxide fine particles in the intermediate layer can be improved by subjecting the titanium oxide fine particles to a surface treatment with alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). .
In addition, after the surface treatment with alumina and silica, the surface treatment with an organosilicon compound can further improve the dispersibility of the titanium oxide fine particles, and also by changing the surface treatment amount. This is because the conductivity of the titanium oxide fine particles can be easily adjusted.

In addition, as an organosilicon compound that is preferably used, an alkylsilane compound, an alkoxysilane compound, a vinyl group-containing silane compound, a mercapto group-containing silane compound, an amino group-containing silane compound, or a polysiloxane compound that is a condensation polymer thereof. Is mentioned. More specifically, siloxane compounds such as methyl hydrogen polysiloxane and dimethyl polysiloxane are preferable, and methyl hydrogen polysiloxane is particularly preferable.
And as addition amount of an alumina and a silica, it is preferable to set it as the value within the range of 1-30 weight part with respect to 100 weight part of titanium oxide fine particles, and setting it as the value within the range of 5-20 weight part. More preferred. Further, the addition amount of the organosilicon compound is preferably a value within the range of 1 to 15 parts by weight with respect to 100 parts by weight of the titanium oxide fine particles, and is preferably within a range of 5 to 10 parts by weight. More preferred.

Moreover, it is preferable to make the average primary particle diameter (number average primary particle diameter, the same applies hereinafter) of the titanium oxide fine particles within a range of 5 to 30 nm.
The reason for this is that by setting the average primary particle diameter of the titanium oxide fine particles to a value in the range of 5 to 30 nm, the dispersibility in the intermediate layer becomes good and the resistance of the intermediate layer can be made uniform. It is.
That is, when the average primary particle diameter of the titanium oxide fine particles is less than 5 nm, not only is it difficult to accurately produce such titanium oxide fine particles, but the particles may easily aggregate. . On the other hand, when the average primary particle diameter of the titanium oxide fine particles exceeds 30 nm, the dispersibility in the intermediate layer is lowered, and the resistance in the intermediate layer may be nonuniform.
Therefore, the average primary particle diameter of the titanium oxide fine particles is more preferably set to a value within the range of 10 to 20 nm, and further preferably set to a value within the range of 10 to 15 nm.
The average primary particle diameter of the titanium oxide fine particles can be measured by combining an electron micrograph and an image processing apparatus.

Moreover, it is preferable to make the film thickness of an intermediate | middle layer into the value within the range of 0.1-10 micrometers.
This is because when the thickness of the intermediate layer is less than 0.1 μm, the resistance of the intermediate layer becomes excessively small and it may be difficult to form a uniform thickness. On the other hand, when the film thickness of the intermediate layer exceeds 10 μm, the resistance of the intermediate layer may become excessively high or exposure memory may be easily generated.
Therefore, the thickness of the intermediate layer is more preferably set to a value within the range of 1 to 8 μm, and further preferably set to a value within the range of 1 to 6 μm.

  The binder resin in the intermediate layer is, for example, at least one selected from the group consisting of polyamide resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl formal resin, vinyl acetate resin, phenoxy resin, polyester resin, and acrylic resin. Resin can be used.

4). Photosensitive layer (1) Binder resin In the single-layer electrophotographic photosensitive member of the present invention, the binder resin is a polycarbonate resin having a viscosity average molecular weight in the range of 10,000 to 40,000. Features.
The reason for this is that if the polycarbonate resin has a viscosity average molecular weight within the range of 10,000 to 40,000, the formation of voids in the photosensitive layer can be suppressed, and the surface of the photosensitive layer can be prevented. This is because oxidation deterioration can be effectively suppressed.
That is, when the viscosity average molecular weight of the polycarbonate resin is less than 10,000, the density of the photosensitive layer is lowered, and the wear amount by the cleaning roller may be excessively increased. On the other hand, when the viscosity average molecular weight of the polycarbonate resin exceeds 40,000, the polycarbonate resin molecules become excessively long, and voids are easily generated in the photosensitive layer, which may be easily influenced by the oxidizing gas. Because there is. As a result, the surface of the photosensitive layer is likely to be oxidized and deteriorated by the oxidizing gas, and white spots may easily occur in the formed image.
Accordingly, the viscosity average molecular weight of the polycarbonate resin is more preferably set to a value within the range of 15,000 to 40,000, and further preferably set to a value within the range of 20,000 to 35,000.
The viscosity average molecular weight of the polycarbonate resin may be adjusted by mixing a plurality of polycarbonate resins having different structural units and molecular weights.
In addition, as a method for measuring the viscosity average molecular weight, a sample was dissolved in purified methylene chloride so as to have a constant concentration (0.2 g / 40 ml), and a specific viscosity (at a temperature of 20 ° C. using an Ubbelohde viscometer ( ηsp) is measured. The intrinsic viscosity [η] is a calibration curve obtained by plotting ηsp / C against C at sample concentrations [C] of 0.4, 0.6, 0.8, and 1.0 g / l using BisA-PC as a sample. Obtained from extrapolated values at a concentration of 0 g / l. And the viscosity average molecular weight (BisA-PC conversion) is calculated | required from following Formula.
[Η] = 1.23 × 10 ⁻⁵ Mv ^0.83

The above-described “white spot” generation mechanism is as follows.
That is, when the surface of the photosensitive layer is oxidized and deteriorated by the oxidizing gas generated from the charging means or the like in a high humidity environment, moisture in the air is easily adsorbed to the oxidized and deteriorated portion.
As a result, due to the influence of moisture, the toner is difficult to be developed in the portion of the photosensitive layer surface that has been oxidized and deteriorated, and white spots occur in the formed image.

(1) Binder resin
The type of binder resin used in the electrophotographic photosensitive member of the present invention is not particularly limited. For example, polycarbonate resin, polyester resin, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer are used. Polymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, ionomer, vinyl chloride-acetic acid Vinyl copolymers, alkyd resins, polyamides, polyurethanes, polysulfones, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyether resins, and other thermoplastic resins, silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, etc. Bridge thermosetting resin, epoxy acrylate, urethane - resin such as photocurable resin such as acrylate can be used.

  In addition, among the resins described above, it is particularly preferable to include a polycarbonate resin, and among the polycarbonate resins, it particularly includes at least one polycarbonate resin represented by the following general formulas (1) to (2). Is preferred.

(In the general formula (1), the plurality of substituents Ra and Rb are each independently an hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. A substituted aryl group, the subscripts p and q are each independently an integer of 0 to 4, and the substituents Rc and Rd are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms. Wherein W is a single bond, —O—, —CO—, —CH ₂ —, and the subscripts k and l are 0 ≦ l / (k + l) <0. (The molar ratio satisfies the relational expression of 6.)

(In the general formula (2), the plurality of substituents Re and Rf are each independently an hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. A substituted aryl group, the subscripts r and s are each independently an integer of 0 to 4, W is a single bond, —O—, —CO—, —CH ₂ —, and the subscripts m and n are The molar ratio satisfies the relational expression 0 ≦ n / (n + m) <0.6.)

This is because these polycarbonate resins can improve the compatibility with the charge generating agent and the charge transporting agent.
As a result, it is difficult for the oxidizing gas to penetrate into the photosensitive layer, and the gas resistance in the photosensitive layer can be further improved.
In addition, as a substituent in the substituent shown in General formula (1), (2), a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C6-C30 aryl group, etc. are mentioned. .
In addition, the subscripts k to n in the general formulas (1) and (2) represent the molar ratio of the copolymerization component. For example, when k is 85 and l is 15, the molar ratio is 85:15. Represents. Such a molar ratio can be calculated by, for example, NMR.

  Here, specific examples of the polycarbonate resin represented by the general formula (1) include polycarbonate resins (Resin-1 to 4) represented by the following formulas (3) to (6).

  Specific examples of the polycarbonate resin represented by the general formula (2) include polycarbonate resins (Resin-5 to 6) represented by the following formulas (7) to (8).

Next, the relationship between the viscosity average molecular weight of the polycarbonate resin and the oxidative deterioration of the photosensitive layer surface will be described with reference to FIG.
That is, in FIG. 2, the horizontal axis represents the viscosity average molecular weight (−) of the polycarbonate resin composed of the structural unit (Resin-5), and the left vertical axis represents the image using the corresponding single layer type electrophotographic photoreceptor. A characteristic curve A is shown in which an evaluation (relative value) of white spots in the case of formation is taken.
On the right vertical axis, there is shown a characteristic curve B in which the change (V) of the charging potential before and after exposing the corresponding single layer type electrophotographic photosensitive member to ozone.
Note that as the oxidative deterioration of the photosensitive layer surface progresses, the evaluation value of white spots decreases and the change in charging potential increases.
In addition, the relative evaluation of white spots was performed by quantifying according to the following criteria.
4: No white spots were confirmed.
3: Slight white spots were confirmed.
2: Streaky white spots less than the charger width were confirmed.
1: Streaky white spots larger than the charger width were confirmed.

In addition, the absolute value of the reference withstand voltage of the single-layer electrophotographic photosensitive member used as a sample was 6 kV or more, and the film thickness of the photosensitive layer was 30 μm.
The details of other configurations of the single-layer type electrophotographic photosensitive member, the method of measuring the charged potential, and the like will be described in the examples.

First, it can be understood from the characteristic curve A that when the value of the viscosity average molecular weight of the polycarbonate resin is increased, the evaluation value of white spots is lowered accordingly.
More specifically, it can be understood that when the value of the viscosity average molecular weight of the polycarbonate resin is 40,000 or less, the white evaluation value can be maintained at 3 or more.
On the other hand, when the value of the viscosity average molecular weight of the polycarbonate resin exceeds 40,000, the evaluation value of white spots decreases to 2 or less, and it becomes difficult to effectively suppress white spots. I understand that.

Next, it is understood from the characteristic curve B that when the value of the viscosity average molecular weight of the polycarbonate resin is increased, the value of the change in the charging potential is increased accordingly.
More specifically, it can be seen that if the value of the viscosity average molecular weight of the polycarbonate resin is a value of 40,000 or less, the value of change in charging potential can be maintained at a value of 50 V or less.
On the other hand, when the value of the viscosity average molecular weight of the polycarbonate resin exceeds 40,000, the change value of the charging potential continues to increase to a value of 50 V or more, and the change of the charging potential is effectively suppressed. It turns out that it becomes difficult.

  Therefore, it can be understood from the characteristic curves A and B that the oxidation degradation of the photosensitive layer surface can be critically suppressed by setting the viscosity average molecular weight of the polycarbonate resin to a value of 40,000 or less.

(2) Charge generator (2) -1 type Examples of the charge generator include phthalocyanine pigments such as metal-free phthalocyanine and titanyl phthalocyanine, perylene pigments, bisazo pigments, metal-free naphthalocyanine pigments, and metal naphthalocyanine. Organic photoconductors such as pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, cyanine pigments, pyrylium pigments, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments Alternatively, conventionally known charge generating agents such as inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon can be used.
More specifically, it is more preferable to use phthalocyanine pigments (CGM-1 to 4) represented by the following formulas (9) to (12).
This is because a photoreceptor having sensitivity in a wavelength region of 600 to 800 nm or more is required when used in a digital optical image forming apparatus such as a laser beam printer or a facsimile provided with a semiconductor laser as a light source. It is.
When used in an analog optical image forming apparatus such as an electrostatic copying machine equipped with a white light source such as a halogen lamp, a photosensitive member having sensitivity in the visible region is required. A pigment, a bisazo pigment, or the like can be preferably used.

Among the phthalocyanine pigments described above, it is particularly preferable to use a titanyl phthalocyanine crystal having the following characteristics (A) and (B).
(A) In a CuKα characteristic X-ray diffraction spectrum, it has a main peak at a Bragg angle of 2θ ± 0.2 ° = 27.2 °.
(B) In differential search calorimetric analysis, it has one peak in the range of 270 to 400 ° C. in addition to the peak accompanying vaporization of adsorbed water.
This is because the formation efficiency of the electrostatic latent image by exposure can be remarkably improved by using the titanyl phthalocyanine crystal having such predetermined characteristics.
That is, because the titanyl phthalocyanine crystal has the characteristic (A), its crystal stability, charge generation ability and dispersibility can be remarkably improved.
Further, the titanyl phthalocyanine crystal has the characteristic (B), so that its crystal stability, charge generation ability and dispersibility can be further improved.
In addition, it is more preferable that one peak appearing in the range of 270 to 400 ° C. other than the peak accompanying vaporization of the adsorbed water appears in the range of 290 to 400 ° C., and the range of 300 to 400 ° C. More preferably, it appears within.

In order to obtain a titanyl phthalocyanine crystal having the characteristics (A) and (B) described above, the amount of titanium alkoxide such as titanium tetrabutoxide or titanium tetrachloride added as a material substance when synthesizing a titanyl phthalocyanine compound To a value within the range of 0.40 to 0.53 moles per mole of o-phthalonitrile or a derivative thereof, or 1,3-diiminoisoindoline or a derivative thereof as another material substance Is preferable, and a value within the range of 0.42 to 0.50 mol is more preferable.
Further, it is preferable to synthesize the titanyl phthalocyanine compound in the presence of the urea compound. In this case, the amount of the urea compound added is o-phthalonitrile or a derivative thereof, or 1,3-diiminoisoindoline or It is preferable to set it as the value within the range of 0.1-0.95 mol with respect to 1 mol of the derivatives, and it is more preferable to set it as the value within the range of 0.2-0.8 mol.

(1) -2 Content The content of the charge generating agent is preferably set to a value in the range of 0.1 to 50 parts by weight with respect to 100 parts by weight of the binder resin described later.
This is because the charge generator can efficiently generate charges when the photosensitive layer surface is exposed by setting the content of the charge generator within such a range. .
That is, when the content of the charge generating agent is less than 0.1 part by weight with respect to 100 parts by weight of the binder resin, the amount of charge generated is insufficient to form an electrostatic latent image on the surface of the photosensitive layer. This is because there is a case of becoming. On the other hand, if the content of the charge generating agent exceeds 50 parts by weight with respect to 100 parts by weight of the binder resin, it may be difficult to uniformly disperse in the coating solution for the photosensitive layer. It is.
Therefore, the content of the charge generating agent with respect to 100 parts by weight of the binder resin is more preferably set to a value within the range of 0.2 to 40 parts by weight, and a value within the range of 0.5 to 30 parts by weight. Is more preferable.

(3) Charge transport agent (3) -1 type As the charge transport agent (hole transport agent and electron transport agent) used in the charge transport layer, 2,5-bis (p-diethylaminophenyl) -1,3 Oxadiazole derivatives such as 1,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) ) Aromatic tertiary amino such as pyrazoline derivatives such as pyrazoline, triphenylamine, tri (p-methyl) phenylamine, N, N-bis (3,4-dimethylphenyl) biphenyl-4-amine, dibenzylaniline Aromatic tertiary diamino compounds such as compounds, N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1-biphenyl] -4,4'-diamine 1,2,4-triazine derivatives such as 3- (4′-dimethylaminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzaldehyde-1 , Hydrazone derivatives such as 1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, p- (2 , 2-diphenylvinyl) -N, N-diphenylaniline and other α-stilbene derivatives, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, hole transport materials such as poly-N-vinylcarbazole and derivatives thereof; chloranil, Quinone compounds such as bromoanil and anthraquinone, tetracyanoquinodimethane , Fluorenone compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, xanthone compounds, thiophene compounds, diphenoquinone compounds and other electron transport materials; One kind or a combination of two or more kinds of polymers having a group to be formed in the main chain or side chain can be mentioned.

(3) -2 Content The content of the hole transport agent is preferably set to a value in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. A value within the range of parts by weight is preferred.
Further, the content of the electron transport agent is preferably a value within the range of 10 to 100 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer, and a value within the range of 20 to 70. Is more preferable.

(4) Additives In addition, for the purpose of preventing deterioration of the photoreceptor due to ozone, oxidizing gas, or light and heat generated in the electrophotographic apparatus, an antioxidant, a light stabilizer, and heat stability in the photoreceptor layer. It is preferable to add an agent or the like.
For example, as the antioxidant, hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds, and the like are used. Examples of the light stabilizer include derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine.

(5) Film thickness The film thickness of the photosensitive layer is set to a value in the range of 20 to 45 μm.
This is because, when the thickness of the photosensitive layer is less than 20 μm, the pressure resistance tends to be excessively decreased and the sensitivity characteristics are likely to be excessively decreased. On the other hand, when the thickness of the photosensitive layer exceeds 45 μm, voids are likely to occur in the photosensitive layer, and it may be difficult to form a uniform layer.
Accordingly, the thickness of the photosensitive layer is more preferably set to a value within the range of 20 to 40 μm, and further preferably set to a value within the range of 25 to 40 μm.

5). Reference Withstand Voltage In the present invention, the absolute value of the positive / negative withstand voltage (reference withstand voltage) of a single layer type electrophotographic photosensitive member measured according to JIS C 2110 is set to a value of 6 kV or more. It is characterized by.
The reason is that by setting the absolute value of the reference withstand voltage within a predetermined range, it is possible to effectively suppress the occurrence of leakage current in the charging step and the transfer step even when the photosensitive layer is worn. Because.
That is, the single-layer electrophotographic photoreceptor of the present invention uses a polycarbonate resin having a relatively small viscosity average molecular weight as a binder resin for the photosensitive layer in order to suppress oxidative deterioration of the surface of the photosensitive layer, and It is used in an image forming apparatus provided with a roller cleaning system.
Therefore, in the single layer type electrophotographic photosensitive member of the present invention, the photosensitive layer is relatively easily worn, and as a result, the withstand voltage of the single layer type electrophotographic photosensitive member tends to decrease.
Therefore, in the single layer type electrophotographic photosensitive member of the present invention, even if the photosensitive layer is worn and the withstand voltage of the photosensitive layer is lowered, the withstand voltage of the entire single layer type electrophotographic photosensitive member is maintained, In order to effectively suppress the occurrence of leakage current and black spots caused by the leakage current, the positive / negative withstand voltage measured under predetermined measurement conditions is defined within a predetermined range.

That is, when the absolute value of the reference withstand voltage is less than 6 kV, the withstand voltage may be excessively lowered and black spots may be easily generated at the stage where the life of the photosensitive layer still remains due to wear of the photosensitive layer. Because there is. On the other hand, if the absolute value of the reference withstand voltage is excessively large, charges are likely to be excessively accumulated in the photosensitive layer, and it may be difficult to sufficiently suppress the occurrence of exposure memory.
Therefore, the absolute value of the reference withstand voltage of the single-layer electrophotographic photosensitive member is more preferably set to a value within the range of 7 to 15 kV, and further preferably set to a value within the range of 8 to 15 kV.
The reference withstand voltage in the present invention is, for example, a single-layer electrophotographic photosensitive member when the photosensitive layer has a film thickness of 22 μm, if the photosensitive layer has a film thickness of 22 μm. The standard withstand voltage of

Moreover, an example of the measurement conditions of the reference withstand voltage measured according to JIS C 2110 is shown below.
FIG. 3 shows a schematic diagram of a measuring apparatus 200 for measuring the reference withstand voltage.
The measuring apparatus 200 basically includes a V-rail stand 203 on which the electrophotographic photosensitive member 71 is placed, a linear slider 201 that can move in the axial direction of the single-layer electrophotographic photosensitive member 71, and a linear slider. A cotton needle 202 fixed to 201 is provided.
In addition, a conductive wire is connected to the base of the single layer type electrophotographic photosensitive member 71 placed on the cotton needle 202 and the V rail base 203, and a voltage can be applied by the high voltage power source 203.
Photosensitive layer thickness: 20 to 45 μm
Electrode: Cotton needle No. 3 (manufactured by Clover, length: 51.5 mm,
(Diameter: 0.84mm)
Distance between electrode and photosensitive layer: 1mm
Voltage rise pattern: 0.1 kV / sec.
Applied voltage type: Current value when judging positive and negative DC potential leakage phenomenon: 0.5 mA
Leak phenomenon measurement environment: temperature 20 ° C., relative humidity 50%, dark place high voltage power supply / leak phenomenon measurement device: high voltage power supply TREK 610E (manufactured by TREK)

Next, the relationship between the reference withstand voltage and the leakage current of the single layer type electrophotographic photosensitive member will be described with reference to FIG.
That is, in FIG. 4, the absolute value (kV) of the reference negative withstand voltage is taken on the lower horizontal axis, and the black dots in the case where image formation is performed using the corresponding single-layer electrophotographic photosensitive member on the vertical axis. A characteristic curve taking the number of occurrences (pieces / A4) is shown.
As the leak current is generated, the number of black spots generated increases.

Further, as the binder resin in the single layer type electrophotographic photosensitive member used as a sample, a polycarbonate resin having a viscosity average molecular weight in the range of 10,000 to 40,000 was used.
Further, as a cleaning means, a roller cleaning system is used, and the number of black spots generated after 5000 durable printing is used.
Details of other configurations of the single-layer electrophotographic photosensitive member, a method for measuring the number of black spots, and the like are described in the examples.

That is, it can be understood from the characteristic curve shown in FIG. 4 that the value of the number of black spots generated decreases as the absolute value of the reference negative withstand voltage increases.
More specifically, in the range where the absolute value of the reference negative withstand voltage is less than 6 kV, as the value increases, the number of sunspot occurrences rapidly increases from a value of 100 / A4 or more to around 50 / A4. It is understood that it is decreasing.
On the other hand, when the absolute value of the reference negative withstand voltage is in the range of 6 kV or more, the number of sunspots gradually decreases as the value increases, and the level of 40 / A4 or less can be stably maintained. Is done.
Therefore, the characteristic curve shown in FIG. 4 indicates that the absolute value of the reference negative withstand voltage of the single-layer electrophotographic photosensitive member is set to 6 kV or less, and the roller cleaning system is used and durable printing is performed. However, it is understood that the generation of leakage current can be suppressed critically.
It has been confirmed that similar results can be obtained even when the reference positive withstand voltage is taken on the horizontal axis.

[Second Embodiment]
The second embodiment is an image forming apparatus including the single-layer electrophotographic photosensitive member described as the first embodiment, and a charging unit, an exposing unit, An image forming apparatus comprising: a developing unit, a transfer unit, and a cleaning unit; and a roller cleaning system as the cleaning unit.
Hereinafter, the image forming apparatus as the second embodiment will be specifically described for each component.

1. Basic Configuration FIG. 5 is a diagram showing an example of a tandem image forming apparatus according to the present invention.
The image forming apparatus 1 includes an intermediate transfer belt 11. Further, on the upper side of the intermediate transfer belt 11, a magenta developing unit 7M, a cyan developing unit 7C, a yellow developing unit 7Y, and a black developing unit 7K are arranged along the moving direction of the endless belt 11, respectively. ing.
In addition, an electrophotographic photoreceptor 71 is disposed so as to face the developing roller 72. Further, around these electrophotographic photoreceptors 71, charging means 75 for charging the surface of the electrophotographic photoreceptor 71 and exposure means 76 for forming an electrostatic latent image on the surface of the electrophotographic photoreceptor 71, respectively. Is arranged.
Therefore, the electrostatic latent image formed on the electrophotographic photosensitive member 71 corresponding to each color is developed by the developing means 72 corresponding to each color.
Further, primary transfer means 16 for sequentially transferring the respective color developer images onto the intermediate transfer belt 11 is disposed on the opposite side of each electrophotographic photoreceptor 71 via the intermediate transfer belt 11.
Further, a secondary transfer unit 12 for transferring a developer image formed on the intermediate transfer belt 11 onto a recording medium is disposed at the most downstream portion in the moving direction of the intermediate transfer belt 11.
Further, a fixing means 4 for fixing the developer image transferred onto the recording medium to the recording medium is arranged at the lower left in the drawing.
Hereinafter, the electrophotographic photosensitive member, the charging unit, the exposure unit, the developing unit, the transfer unit, and the cleaning unit will be specifically described.

2. Electrophotographic Photoreceptor As the electrophotographic photoreceptor 71 shown in FIG. 5, the predetermined single-layer type electrophotographic photoreceptor described in the first embodiment is used.
This is because, even in the presence of an oxidizing gas, the occurrence of white spots can be effectively suppressed, while the occurrence of black spots due to leakage current can also be effectively suppressed.

The peripheral speed of the single layer type electrophotographic photosensitive member is preferably set to a value of 120 mm / sec or more.
The reason for this is that by setting the peripheral speed of the single-layer electrophotographic photosensitive member within such a range, the voltage applied in the charging means and the transfer means increases, and as a result, the amount of oxidizing gas generated increases. However, according to the present invention, the occurrence of white spots can be effectively suppressed.
That is, when the peripheral speed of the single-layer electrophotographic photosensitive member is less than 120 mm / sec, it is difficult to realize high-speed image formation that has been required in recent years, although the generation amount of oxidizing gas can be reduced. On the other hand, if the peripheral speed of the single-layer type electrophotographic state becomes excessively large, the amount of oxidizing gas generated excessively increases and sufficiently suppresses the oxidative deterioration of the photosensitive layer surface. And it may be difficult to sufficiently suppress the occurrence of white spots.
Therefore, the peripheral speed of the single-layer electrophotographic photosensitive member is more preferably set to a value within the range of 120 to 300 mm / sec, and further preferably set to a value within the range of 120 to 250 mm / sec.

3. Cleaning means The cleaning means is installed on the most downstream side of the electrophotographic photosensitive member 71, and is a means for polishing and removing residual toner, an oxidizing substance, and the like fixed on the surface of the electrophotographic photosensitive member 71. .
Here, a roller cleaning system is used as the cleaning means in the present invention.
This is because, in the case of a roller cleaning system, even if the photosensitive layer surface is oxidized and deteriorated, the oxidized and deteriorated portion can be effectively polished and removed.
Therefore, even in the presence of an oxidizing gas, the occurrence of white spots due to oxidative deterioration of the photosensitive layer surface can be more effectively suppressed.
The roller cleaning system preferably has an elastic layer on the surface, and the elastic layer may be made of an elastic material such as polyurethane rubber, silicon rubber, butadiene rubber, carbon black, titanium, What disperse | distributed electroconductive fine particles which consist of metal oxides, such as aluminum, and an ionic conductive agent is used suitably.
Further, as the hardness of the elastic layer, the Asuka C hardness is preferably set to a value within the range of 0.5 to 70 degrees.
Further, the rotation direction of the roller is generally the rotation and forward direction of the photoconductor, and the rotation speed is preferably substantially equal to that of the photoconductor.

4). Charging Unit The charging unit 75 shown in FIG. 5 is installed above the electrophotographic photosensitive member 71 and is a unit for uniformly charging the electrophotographic photosensitive member 71.
The type of the charging means is not particularly limited, but is preferably scorotron.
This is because, with a scorotron, a predetermined charged potential can be stably maintained even when high-speed image formation is performed.
Moreover, it is preferable to make the applied voltage with respect to this scorotron into the value within the range of 5-10 kV.
This is because when the applied voltage to the scorotron is less than 5 kV, it may be difficult to stably maintain a predetermined charged potential when high-speed image formation is performed. On the other hand, when the applied voltage to the scorotron exceeds 10 kV, the amount of oxidizing gas generated excessively increases, making it difficult to sufficiently suppress the oxidative deterioration of the photosensitive layer surface, or generating leakage current. This is because it may be difficult to suppress the above.
Therefore, the voltage applied to the scorotron is more preferably a value within the range of 6 to 10 kV, and even more preferably a value within the range of 6 to 8 kV.

Moreover, it is preferable that the charging polarity by the charging means is a positive polarity.
This is because, if the polarity is positive, the generation of oxidizing gas from the charging means can be suppressed compared to the case of the negative polarity.
Further, it is preferable to set the charging potential in the electrophotographic photosensitive member to a value in the range of 600 to 1000V.
This is because it may be difficult to form a clear electrostatic latent image when the value of the charging potential is less than 600V. On the other hand, when the value of the charged potential exceeds 1000 V, the amount of oxidizing gas generated excessively increases, making it difficult to sufficiently suppress oxidative deterioration of the surface of the photosensitive layer, or generating leakage current. This is because it may be difficult to suppress the above.
Therefore, the charging potential in the electrophotographic photosensitive member is more preferably set to a value within the range of 650 to 900V, and further preferably set to a value within the range of 700 to 900V.

5). Exposure Unit The exposure unit 76 shown in FIG. 5 is a unit for forming an electrostatic latent image on the electrophotographic photosensitive member 71 based on a document image read from an image data input unit (not shown).
Here, since the single layer type electrophotographic photosensitive member in the present invention can effectively suppress the oxidative deterioration of the surface of the photosensitive layer, the formation efficiency of the electrostatic latent image by exposure is remarkably improved.
Therefore, even when the exposure amount per unit area when the single-layer electrophotographic photosensitive member is exposed is reduced, image formation can be performed without any practical problem, and the energy saving effect can be improved. .
Accordingly, the exposure amount per unit area is preferably set to a value within the range of 0.2 to 0.8 μJ / m ² on the single-layer type electrophotographic photosensitive member, and 0.3 to 0.6 μJ / m ^2. It is more preferable to set the value within the range.
As a specific level of sensitivity characteristics, 0.34 seconds have elapsed when a single-layer electrophotographic photosensitive member is charged to 700 V and light having a wavelength of 780 mm is exposed to 0.5 μJ / cm ^2. The subsequent surface potential is preferably 160 V or less, and more preferably 130 V or less.

6). Developing Unit The developing unit 72 shown in FIG. 5 is a unit that forms a toner image by supplying toner to the surface of the electrophotographic photoreceptor 71 on which the electrostatic latent image is formed.

7). The transfer means 16 shown in FIG. 5 is installed below the electrophotographic photosensitive member 71 and transfers the toner image formed on the electrophotographic photosensitive member 71 to the recording medium or the intermediate transfer belt. It is a means for transferring.
The type of the transfer means is not particularly limited, but is preferably a roller or a belt type via a roller.
This is because these transfer means can stably maintain a predetermined transfer potential even when high-speed image formation is performed.

  Hereinafter, the present invention will be described in more detail by way of examples.

[Example 1]
1. Production of electrophotographic photoreceptor (1) Preparation of substrate An aluminum substrate having a diameter of 30 mm and a length of 254 mm was prepared.

(2) Formation of intermediate layer Using a bead mill, 300 parts by weight of titanium oxide fine particles (manufactured by Teika Co., Ltd., SMT-02), 100 parts by weight of copolymerized polyamide resin (manufactured by Daicel Degussa Co., Ltd., X1010), as a solvent 1000 parts by weight of methanol and 250 parts by weight of n-butanol were mixed and dispersed for 5 hours, and further filtered through a 5 micron filter to prepare an intermediate layer coating solution.
Next, one end of a substrate (supporting substrate) prepared in advance was placed on the top and immersed in the obtained intermediate layer coating solution at a rate of 5 mm / sec to apply the intermediate layer coating solution. Then, the hardening process was performed on 130 degreeC and the conditions for 30 minutes, and the intermediate | middle layer with a film thickness of 3 micrometers was formed.
The titanium oxide fine particles described above were surface-treated with alumina and silica and then surface-treated with methyl hydrogen polysiloxane, and the number average primary particle size was 10 nm.

(3) Formation of photosensitive layer Next, in the container is a Y-type crystal of titanyl phthalocyanine (CGM-2) represented by the formula (10) as a charge generating agent produced by the production method described later, 3 parts by weight of crystals having A) and (B) (K-TiOPc), 50 parts by weight of a hole transport agent (HTM-1) represented by the following formula (13), and an electron represented by the following formula (14) 30 parts by weight of a transport agent (ETM-1), 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 10,000 consisting of a structural unit (Resin-1) represented by the formula (3) as a binder resin, and tetrahydrofuran as a solvent 800 parts by weight were accommodated to obtain a mixture thereof. Next, this mixture was mixed and dispersed for 50 hours using a ball mill to obtain a photosensitive layer coating solution.
Next, the obtained coating solution for the photosensitive layer is applied on the above-described intermediate layer by a dip coating method, and then dried with hot air at 100 ° C. for 40 minutes to form a photosensitive layer having a thickness of 30 μm. Thus, a single layer type electrophotographic photosensitive member was obtained.

(4) Manufacture of titanyl phthalocyanine crystal In addition, the crystal | crystallization (K-TiOPc) of the titanyl phthalocyanine (CGM-2) represented by Formula (10) as a charge generator was manufactured as follows.

(4) -1 Synthesis of crude titanyl phthalocyanine crystal First, in an argon-substituted flask, 22 g (0.17 mol) of o-phthalonitrile, 25 g (0.073 mol) of titanium tetrabutoxide, 300 g of quinoline, urea 2. 28g (0.038mol) was added, and it heated up to 150 degreeC, stirring.
Next, the temperature of the system was raised to 215 ° C. while distilling off the vapor generated from the reaction system, and the mixture was further stirred for 2 hours while maintaining this temperature.
Then, after the reaction is completed, when the reaction mixture is cooled to 150 ° C., the reaction mixture is taken out of the flask, filtered through a glass filter, and the resulting solid is washed successively with N, N-dimethylformamide and methanol and then vacuum-dried. Then, 24 g of a blue-violet solid as a crude titanyl phthalocyanine crystal was synthesized.

(4) -2 Pre-acid treatment step 10 g of the blue-violet solid obtained in the production of the above-mentioned titanyl phthalocyanine compound is added to 100 ml of N, N-dimethylformamide and heated to 130 ° C. with stirring for 2 hours. The stirring process was performed.
Next, the heating was stopped when 2 hours passed, and further the stirring was stopped when the temperature was cooled to 23 ± 1 ° C. In this state, the liquid was allowed to stand for 12 hours for stabilization treatment. The stabilized supernatant was filtered off with a glass filter, and the resulting solid was washed with methanol and then vacuum dried to obtain 9.83 g of a crude crystal of a titanyl phthalocyanine compound.

(4) -3 Acid treatment step 5 g of the crude crystals of titanyl phthalocyanine obtained in the above-mentioned pre-acid treatment step were added to 100 ml of concentrated sulfuric acid and dissolved.
Next, this solution was added dropwise to ice-cooled water, stirred for 15 minutes at room temperature, and then allowed to stand at about 23 ± 1 ° C. for 30 minutes for recrystallization.
Next, the liquid described above was filtered off with a glass filter, and the obtained solid was washed with water until the washing liquid became neutral, and then dispersed in 200 ml of chlorobenzene in the presence of water without drying. The mixture was heated to 0 ° C. and stirred for 10 hours.
Next, the liquid was filtered off with a glass filter, and the obtained solid was vacuum-dried at 50 ° C. for 5 hours to obtain 4.1 g of unsubstituted titanyl phthalocyanine crystals (blue powder) represented by the formula (10). Got.

(4) -4 Evaluation of titanyl phthalocyanine crystal (X-ray diffraction measurement)
0.3 g of the obtained titanyl phthalocyanine crystal was dispersed in 5 g of tetrahydrofuran, stored in a closed system for 24 hours under conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50 to 60%, and then the tetrahydrofuran was removed. The measurement was performed by filling a sample holder of an X-ray diffractometer (RINT1100 manufactured by Rigaku Corporation). The obtained spectrum chart is shown in FIG. Further, since the spectrum chart has a characteristic that it has a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and does not have a peak at 26.2 °, the obtained titanyl was obtained. It was confirmed that the phthalocyanine crystal had the characteristic (A).
Note that a spectrum chart similar to that shown in FIG. 6 was also measured before the dispersion in tetrahydrofuran.
The measurement conditions for the X-ray diffraction were as follows.
X-ray tube: Cu
Tube voltage: 40 kV
Tube current: 30 mA
Start angle: 3.0 °
Stop angle: 40.0 °
Scanning speed: 10 ° / min

(Differential scanning calorimeter measurement)
Moreover, differential scanning calorimetry of the obtained titanyl phthalocyanine crystal was performed using a differential scanning calorimeter (TAS-200 type, DSC8230D manufactured by Rigaku Corporation). The obtained differential scanning analysis chart is shown in FIG. Moreover, in this chart, since one peak exists at 296 ° C. in addition to the peak accompanying vaporization of adsorbed water, it was confirmed that the obtained titanyl phthalocyanine crystal has the characteristic (B). .
The measurement conditions were as follows.
Sample pan: Aluminum heating rate: 20 ° C / min

2. Evaluation of electrophotographic photoreceptor (1) Evaluation of withstand voltage (1) -1 Measurement of reference negative withstand voltage In accordance with JIS C 2110, the negative withstand voltage of a single layer type electrophotographic photoreceptor was measured.
That is, as shown in FIG. 3, a cotton needle No. 3 (manufactured by Clover, length: 51.5 mm, diameter: 0.84 mm) is connected to a high-voltage power source (manufactured by TREK Co., Ltd., 610E) It was made to oppose so that a needle point might be 1 mm from the surface of a single layer type electrophotographic photosensitive member.
Next, under normal temperature and normal humidity conditions (temperature: 20 ° C., relative humidity: 50%, dark place), 0.1 kV / sec. The applied voltage (minus DC potential) was increased at, and the voltage at the time when the current of 0.5 mA was measured was read as the reference withstand voltage (kV). The absolute values are shown in Table 1.

(1) -2 Measurement of standard positive withstand voltage Moreover, the positive withstand voltage of the single-layer type electrophotographic photosensitive member was measured according to JIS C2110.
That is, the measurement was performed in the same manner as the measurement of the reference withstand voltage except that the polarity of the applied voltage was changed to the positive polarity. The obtained results are shown in Table 1.

(2) Evaluation of Oxidative Degradation (2) -1 Evaluation of White-Spotted Image formation was performed using the obtained single-layer electrophotographic photosensitive member, and the occurrence of white-out spots was evaluated.
That is, the obtained single-layer type electrophotographic photosensitive member was printed on a printer with a peripheral speed of 140 mm / sec (manufactured by Kyocera Mita Co., Ltd., FS-1010 modified machine, cleaning means: roller cleaning system, charging means: scorotron (charging potential 850 V ), Transfer means: roller system), and a white paper image (Fuji Xerox Co., Ltd., high quality PPC) 5000 in a high temperature and high humidity environment (temperature: 35 ° C., relative humidity: 85% RH) 5000 Printed continuously.
Next, after the printer was left for 6 hours, a gray image was printed on A4 paper, and whether or not white spots occurred was visually confirmed and evaluated according to the following criteria. The obtained results are shown in Table 1.
A: No white spots were confirmed.
○: Slight white spots were confirmed.
Δ: Streaky white spots less than the charger width were confirmed.
X: Streaky white spots larger than the charger width were confirmed.

(2) -2 Evaluation of ozone resistance Further, the obtained single layer type electrophotographic photosensitive member was exposed to ozone. The change of the charging potential before and after that was evaluated.
That is, using a drum sensitivity tester (manufactured by GENTEC), the single-layer electrophotographic photosensitive member is charged by rotating it four times under a current condition of 8 μA (circumferential speed 31 rpm), and the average surface on the third round The potential was measured as the initial charging potential.
Next, the average surface potential immediately after the single layer type electrophotographic photosensitive member was exposed at room temperature for 6 hours in an atmosphere having an ozone concentration of 10 ppm was measured in the same manner as a charging potential immediately after the exposure.
Next, ΔV0 was calculated from the following equation, and ozone resistance was evaluated according to the following criteria. It can be said that the smaller the ΔV0, the better the ozone resistance of the photoreceptor. The obtained results are shown in Table 1.
(Initial charging potential)-(charging potential immediately after exposure) = ΔV0
A: Less than 30V ○: Less than 30-60V Δ: Less than 60-90V x: 90V or more

(3) Evaluation of Leakage Current Further, an image was formed using the obtained single layer type electrophotographic photosensitive member, and the occurrence of black spots caused by the leakage current was evaluated.
That is, the obtained single-layer type electrophotographic photosensitive member was printed on a printer with a peripheral speed of 140 mm / sec (manufactured by Kyocera Mita Co., Ltd., FS-1010 modified machine, cleaning means: roller cleaning system, charging means: scorotron (charging potential 850 V ), Transfer means: roller system), 1% printed image in high-temperature high-humidity environment (temperature: 35 ° C., relative humidity: 85% RH), A4 paper (Fuji Xerox Co., Ltd., high-quality PPC) ) 5000 sheets were printed continuously.
Next, after leaving the printer for one day, ten blank images were printed on A4 paper, and the number of black spots generated in the tenth blank image was visually counted and evaluated according to the following criteria. The obtained results are shown in Table 1.
A: The number of black spots generated was less than 20 / A4.
○: The number of black spots generated was 20 to 50 / A4 or less.
Δ: The number of black spots generated was 50 to 80 / A4 or less.
X: The number of black spots generated was 80 / A4 or more.

(4) Evaluation of sensitivity The bright potential of the obtained electrophotographic photosensitive member was measured.
That is, using a drum sensitivity tester (manufactured by GENTEC), the surface potential of the single-layer type electrophotographic photosensitive member was charged to 700V.
Next, monochromatic light having a wavelength of 780 nm (half-width: 20 nm, light intensity: 0.5 μJ / cm ² ) extracted from white light using a band pulse filter was exposed on the surface of the electrophotographic photosensitive member (irradiation time: 50 msec). .
Next, the potential after 350 msec after exposure was measured to obtain a sensitivity potential and evaluated according to the following criteria. The obtained results are shown in Table 1.
A: The value of the sensitivity potential was less than 120V.
(Circle): The value of the sensitivity potential was a value less than 120-160V.
(Triangle | delta): The value of the sensitivity potential was a value below 160-200V.
X: The value of the sensitivity potential was 200 V or more.

(5) Comprehensive evaluation Moreover, comprehensive evaluation of each evaluation mentioned above was performed along the following reference | standard. The obtained results are shown in Table 1.
A: All evaluations were A.
○: There was one or more evaluations of ○, but there was no evaluation of Δ and ×.
Δ: There was one or more evaluations of Δ, but there was no evaluation of ×.
X: There was one or more evaluations of x.

[Examples 2-3]
In Examples 2 to 3, electrophotographic photosensitivity was the same as in Example 1 except that when the photosensitive layer was formed, the viscosity average molecular weights of the polycarbonate resin as the binder resin were 30,000 and 40,000, respectively. The body was manufactured and evaluated. The obtained results are shown in Table 1.

[Example 4]
In Example 4, when the photosensitive layer was formed, a polycarbonate resin having a viscosity average molecular weight of 25,000 composed of the structural unit (Resin-2) represented by the formula (4) was used as the binder resin. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1.

[Example 5]
In Example 5, when the photosensitive layer was formed, a polycarbonate resin having a viscosity average molecular weight of 24,000 consisting of a structural unit (Resin-3) represented by the formula (5) was used as the binder resin. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1.

[Example 6]
In Example 6, when the photosensitive layer was formed, a polycarbonate resin having a viscosity average molecular weight of 20,000 composed of the structural unit represented by formula (6) (Resin-4) was used as the binder resin. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1.

[Example 7]
In Example 7, when forming the photosensitive layer, a polycarbonate resin having a viscosity average molecular weight of 30,000 consisting of the structural unit (Resin-5) represented by the formula (7) was used as the binder resin. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1.

[Examples 8 to 28]
In Examples 8 to 28, when forming the photosensitive layer, a polycarbonate resin having a viscosity average molecular weight of 32,000 composed of the structural unit (Resin-6) represented by the formula (8) is used as the binder resin. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that hole transporting agents (HTM-2 to 21) represented by the following formulas (15) to (34) were used as hole transporting agents, respectively. evaluated. The obtained results are shown in Table 1.

[Examples 29 to 32]
In Examples 29 to 32, when forming a photosensitive layer, a polycarbonate resin having a viscosity average molecular weight of 32,000 consisting of a structural unit (Resin-6) represented by the formula (8) is used as a binder resin, and an electron is used. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that hole transport agents (ETM-2 to 5) represented by the following formulas (35) to (38) were respectively used as transport agents. did. The obtained results are shown in Table 1.

[Examples 33 to 34]
In Examples 33 to 34, when forming the photosensitive layer, a polycarbonate resin having a viscosity average molecular weight of 32,000 composed of the structural unit (Resin-6) represented by the formula (8) is used as the binder resin. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that the layer thicknesses were changed to 25 and 35 μm, respectively. The obtained results are shown in Table 1.

[Example 35]
In Example 35, when the electrophotographic photosensitive member is produced, the intermediate layer is not formed, and when the photosensitive layer is formed, as the binder resin, from the structural unit (Resin-6) represented by the formula (8). An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that the polycarbonate resin having a viscosity average molecular weight of 32,000 was used and the film thickness of the photosensitive layer was changed to 38 μm. The obtained results are shown in Table 1.

[Example 36]
In Example 36, when forming the photosensitive layer, a polycarbonate resin having a viscosity average molecular weight of 32,000 consisting of the structural unit (Resin-6) represented by the formula (8) is used as the binder resin, and the charge generating agent is used. As a Y-type crystal of titanyl phthalocyanine (CGM-2) represented by the formula (10), which has the characteristic (A) but does not have the characteristic (B), that is, a conventionally used crystal An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that a typical Y-type crystal (Y-TiOPc) was used. The obtained results are shown in Table 1.

[Example 37]
In Example 37, the formation of the photosensitive layer was carried out except that a polycarbonate resin having a viscosity average molecular weight of 25,000 composed of the structural unit (Resin-2) represented by the formula (4) was used as the binder resin. An electrophotographic photoreceptor was produced and evaluated in the same manner as in Example 36. The obtained results are shown in Table 1.

[Example 38]
In Example 38, when the electrophotographic photosensitive member was produced, the intermediate layer was not formed, and when forming the photosensitive layer, the binder resin was obtained from the structural unit (Resin-6) represented by the formula (8). An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 36 except that the polycarbonate resin having a viscosity average molecular weight of 32,000 was used and the thickness of the photosensitive layer was changed to 38 μm. The obtained results are shown in Table 1.

[Example 39]
In Example 39, when forming a photosensitive layer, a polycarbonate resin having a viscosity average molecular weight of 32,000 consisting of a structural unit (Resin-6) represented by the formula (8) is used as a binder resin, and a charge generating agent is used. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that an x-type crystal (xH ₂ Pc) of metal-free phthalocyanine (CGM-1) represented by the formula (9) was used. The obtained results are shown in Table 1.

[Example 40]
In Example 40, the formation of the photosensitive layer was carried out except that a polycarbonate resin having a viscosity average molecular weight of 25,000 composed of the structural unit (Resin-2) represented by the formula (4) was used as the binder resin. An electrophotographic photoreceptor was produced and evaluated in the same manner as in Example 39. The obtained results are shown in Table 1.

[Example 41]
In Example 41, when the electrophotographic photosensitive member was produced, the intermediate layer was not formed, and when forming the photosensitive layer, the structural unit (Resin-1) represented by the formula (3) was used as the binder resin. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 39 except that a polycarbonate resin having a viscosity average molecular weight of 30,000 was used. The obtained results are shown in Table 1.

[Comparative Examples 1-2]
In Comparative Examples 1 and 2, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the viscosity average molecular weight of the binder resin was changed to 60,000 and 80,000, respectively, when forming the photosensitive layer. And evaluated. The obtained results are shown in Table 1.

[Comparative Example 3]
In Comparative Example 3, an electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that when forming the photosensitive layer, the thickness of the photosensitive layer was changed to 15 μm. The obtained results are shown in Table 1.

[Comparative Example 4]
Comparative Example 4 was the same as Comparative Example 3 except that the intermediate layer was not formed when the electrophotographic photosensitive member was produced, and the photosensitive layer thickness was changed to 20 μm when forming the photosensitive layer. An electrophotographic photosensitive member was manufactured and evaluated. The obtained results are shown in Table 1.

[Comparative Example 5]
In Comparative Example 5, when forming the photosensitive layer, the viscosity average molecular weight of the binder resin was changed to 60,000, and a Y-type crystal of titanyl phthalocyanine (CGM-2) represented by the formula (10) as a charge generator. In Example 1, except that a crystal having the characteristic (A) but not the characteristic (B), that is, a general Y-type crystal (Y-TiOPc) conventionally used is used. In the same manner as described above, an electrophotographic photoreceptor was produced and evaluated. The obtained results are shown in Table 1.

[Comparative Example 6]
In Comparative Example 6, when forming the photosensitive layer, the viscosity average molecular weight of the binder resin was changed to 60,000, and the x-type of metal-free phthalocyanine (CGM-1) represented by the formula (9) as a charge generator. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that the crystal (x-H ₂ Pc) was used. The obtained results are shown in Table 1.

[Comparative Example 7]
In Comparative Example 7, when the photosensitive layer was formed, a comparison was made except that a polycarbonate resin having a viscosity average molecular weight of 62,000 consisting of a structural unit (Resin-4) represented by the formula (6) was used as the binder resin. An electrophotographic photoreceptor was produced and evaluated in the same manner as in Example 6. The obtained results are shown in Table 1.

[Comparative Example 8]
In Comparative Example 8, an electrophotographic photosensitive member was produced and evaluated in the same manner as in Comparative Example 7, except that the thickness of the photosensitive layer was changed to 15 μm when forming the photosensitive layer. The obtained results are shown in Table 1.

According to the single layer type electrophotographic photosensitive member and the image forming apparatus according to the present invention, in the single layer type electrophotographic photosensitive member used in the image forming apparatus provided with the roller cleaning system, the viscosity average molecular weight is predetermined as the binder resin. In addition to using the polycarbonate resin in the range of 1, and by setting the withstand voltage of the single-layer electrophotographic photosensitive member to a predetermined range, it is possible to achieve both gas resistance of the photosensitive layer and suppression of leakage current. .
As a result, it is possible to effectively suppress the occurrence of white spots even in the presence of an oxidizing gas, while also effectively suppressing the occurrence of black spots due to leakage current.
Therefore, the single-layer electrophotographic photosensitive member and the image forming apparatus using the same according to the present invention are expected to significantly contribute to the improvement in quality and cost in image forming apparatuses such as copying machines and printers.

1: color image forming apparatus, 72: developing means, 71: electrophotographic photosensitive member, 75: charging means, 76: exposure means, 16: transfer means, 21: paper feed cassette, 4: fixing means, 71: single layer type Latent image carrier, 112: substrate, 114: single-layer photosensitive layer, 116: intermediate layer, 200: measuring device

Claims (10)

A single-layer electrophotographic photosensitive member used in an image forming apparatus provided with a roller cleaning system,
A photosensitive layer containing at least a charge generator, a hole transport agent, an electron transport agent and a binder resin is provided on a substrate that does not have an oxide film formed by anodization,
The binder resin is a polycarbonate resin having a viscosity average molecular weight in the range of 10,000 to 40,000;
The film thickness of the photosensitive layer is set to a value in the range of 20 to 45 μm, and
A single layer type electrophotographic photosensitive member, characterized in that the absolute value of the positive / negative withstand voltage of the single layer type electrophotographic photosensitive member measured in accordance with JIS C 2110 is 6 kV or more. 2. The single-layer electrophotographic photosensitive member according to claim 1, wherein the binder resin includes a polycarbonate resin represented by at least one general formula selected from the following general formulas (1) to (2): .

(In the general formula (1), the plurality of substituents Ra and Rb are each independently an hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. A substituted aryl group, the subscripts p and q are each independently an integer of 0 to 4, and the substituents Rc and Rd are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms. W is a single bond, —O—, —CO—, —CH ₂ —, and the subscripts k and l are molar ratios satisfying a relational expression of 0 ≦ l / (k + 1) <0.6. .)

(In the general formula (2), the plurality of substituents Re and Rf are each independently an hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. A substituted aryl group, the subscripts r and s are each independently an integer of 0 to 4, W is a single bond, —O—, —CO—, —CH ₂ —, and the subscripts m and n are The molar ratio satisfies the relational expression 0 ≦ n / (n + m) <0.6.) 3. The single-layer electrophotographic photosensitive member according to claim 1, wherein the charge generating agent is a titanyl phthalocyanine crystal having the following characteristics (A) and (B).
(A) The CuKα characteristic X-ray diffraction spectrum has main peaks at Bragg angles 2θ ± 0.3 ° = 9.5 and 27.2 °.
(B) In the differential scanning calorimetry spectrum, it has one peak in the range of 270 to 400 ° C. in addition to the peak accompanying vaporization of adsorbed water.   An intermediate layer is provided on the substrate, and the intermediate layer includes a binder resin and titanium oxide fine particles, and the content of the titanium oxide fine particles is 100 parts by weight of the binder resin. The value is in the range of 50 to 500 parts by weight, and the film thickness of the intermediate layer is set to a value in the range of 0.1 to 10 µm. Single layer type electrophotographic photoreceptor. An image forming apparatus comprising the single-layer electrophotographic photosensitive member according to claim 1,
A charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit are arranged around the single layer type electrophotographic photosensitive member,
An image forming apparatus comprising a roller cleaning system as the cleaning unit.   The image forming apparatus according to claim 5, wherein a charging polarity by the charging unit is a positive polarity.   7. The image forming apparatus according to claim 5, wherein a peripheral speed of the single layer type electrophotographic photosensitive member is set to a value of 120 mm / sec or more.   The image forming apparatus according to claim 5, wherein the charging unit is a scorotron, and an applied voltage to the scorotron is set to a value within a range of 5 to 10 kV.   The image forming apparatus according to claim 5, wherein the transfer unit is a roller or a belt type via a roller. The surface potential after elapse of 0.34 seconds is 160 V or less when the single-layer electrophotographic photosensitive member is charged to 700 V and exposed at a wavelength of 780 nm at 0.5 μJ / cm ^2. The image forming apparatus according to 5 to 9.