JP5421008B2 - Positively charged single layer type electrophotographic photosensitive member, image forming apparatus, and image forming method - Google Patents

Description

  The present invention relates to a positively charged single-layer type electrophotographic photosensitive member, an image forming apparatus, and an image forming method. The present invention relates to a photographic photoreceptor, an image forming apparatus including such a positively charged single layer type electrophotographic photoreceptor, and an image forming method.

Conventionally, in order to form a high-quality color image at a high speed, a method using a titanyl phthalocyanine crystal having excellent charge generation efficiency as a charge generation agent has been attempted.
Such titanyl phthalocyanine crystals are known to vary in dispersibility and crystal stability in the photosensitive layer depending on their crystal form, but in any case, the charge generation efficiency is higher than that of conventional charge generators. It is known that it is remarkably excellent (for example, patent document 1).
Accordingly, it has been expected that the use of titanyl phthalocyanine crystal as a charge generating agent can significantly improve the formation efficiency of an electrostatic latent image by exposure, and further increase in the speed of the image forming apparatus can be realized.

JP 2001-181531 A

However, when a titanyl phthalocyanine crystal is used as a charge generator, the current resistance phenomenon between the charging means and the electrophotographic photosensitive member (hereinafter simply referred to as the leakage phenomenon) due to its relatively low electrical resistance. There is a further problem that it is easy to occur.
In particular, in the case of a single layer type electrophotographic photosensitive member, there is a problem that a leak phenomenon is more likely to occur because the charge generating agent is also present near the surface of the photosensitive layer.

  Furthermore, an electrophotographic photoreceptor using a titanyl phthalocyanine crystal as a charge generating agent is prone to oxidative degradation of the photosensitive layer by an active gas such as ozone generated in the charging step, and it is difficult to obtain a sufficient charging potential. The problem of becoming was seen.

Therefore, the present inventors have conducted intensive studies. As a result, even when a titanyl phthalocyanine crystal is used as a charge generator, an antioxidant is used as an additive, and the positive withstand voltage of the electrophotographic photosensitive member is set to a predetermined value. It has been found that the occurrence of a leak phenomenon and a decrease in charging potential can be effectively suppressed by setting the above range.
That is, an object of the present invention is to provide a positively charged single layer type electrophotographic photosensitive member capable of effectively suppressing the occurrence of a leak phenomenon and a decrease in charging potential, and an image forming apparatus including such a positively charged single layer type electrophotographic photosensitive member. And providing an image forming method.

According to the present invention, there is provided a positively charged single layer type electrophotographic photoreceptor having a photosensitive layer on a substrate, the photosensitive layer containing titanyl phthalocyanine crystals as a charge generating agent, and an antioxidant as an additive. And the thickness of the photosensitive layer is in the range of 22 to 40 μm, and an intermediate layer is provided on the substrate, and the intermediate layer includes a binder resin and titanium oxide fine particles. The content of the titanium oxide fine particles is set to a value within 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 within the range of 0.3 to 10 μm. And a content of the titanyl phthalocyanine crystal in the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer, and a dispersant for adjusting the dispersion of the charge generator 100 parts by weight of the binder resin for the photosensitive layer The antioxidant is contained in a value within the range of 0.1 to 10 parts by weight, and the antioxidant is represented by the hindered phenol antioxidant represented by the following general formula (1) and the following general formula (2). An amine-based antioxidant, or one of them,
Provided is a positively charged single layer type electrophotographic photosensitive member characterized in that the positive withstand voltage of the positively charged single layer type electrophotographic photosensitive member measured in accordance with JIS C 2110 is a value of 8.2 kV or more , The problems described above can be solved.
That is, since the titanyl phthalocyanine crystal is used as the charge generating agent, the formation efficiency of the electrostatic latent image by exposure can be remarkably improved, and further increase in the speed of the image forming apparatus can be realized.
On the other hand, when a titanyl phthalocyanine crystal is used as a charge generating agent and durable printing is performed, the occurrence of a leak phenomenon and a decrease in charged potential are likely to occur.
In this respect, according to the present invention, by using an antioxidant as an additive and setting the positive withstand voltage of the electrophotographic photosensitive member within a predetermined range, the occurrence of a leak phenomenon and A decrease in charging potential can be effectively suppressed.
In addition, by configuring the antioxidant in this manner, even when the photosensitive layer surface is exposed to an active gas such as ozone in the charging step, the oxidative deterioration of the photosensitive layer surface is more effectively suppressed. Thus, a decrease in charging potential can be suppressed.
Further, by configuring the content of the titanyl phthalocyanine crystal in this way, it becomes easy to adjust the reference positive withstand voltage of the positively charged single layer type electrophotographic photosensitive member to a value higher than a predetermined value, while the amount of charge generation Can be secured stably.
Further, by configuring the intermediate layer in this way, it becomes easier to adjust the reference positive withstand voltage of the positively charged single layer type electrophotographic photosensitive member to a value equal to or higher than a predetermined value.

(In General Formula (2), R < ¹ > -R < ¹⁰ > is respectively independent, The carbon number of a hydrogen atom, a C1-C8 alkyl group, a C6-C20 aryl group, and an alkyl group part is 1. An alkylamino group of ˜8, or an arylamino group of 6 to 20 carbon atoms in the aryl group portion, and adjacent substituents may be bonded to form a naphthalene ring.)

Further, in constituting the positively charged single layer type electrophotographic photosensitive member of the present invention, the content of the antioxidant is in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. It is preferable to set the value of.
By comprising in this way, antioxidant can be effectively disperse | distributed in a photosensitive layer, fully exhibiting the oxidation degradation prevention effect by antioxidant.

Another embodiment of the present invention is an image forming apparatus comprising a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer on a substrate, wherein the photosensitive layer contains titanyl phthalocyanine crystals as a charge generating agent. In addition, an antioxidant is included as an additive, and the film thickness of the photosensitive layer is set to a value within the range of 22 to 40 μm. Further, an intermediate layer is provided on the substrate, and the intermediate layer is bound. A resin and titanium oxide fine particles, and the content of the titanium oxide fine particles is 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 set to a value in the range of 0.3 to 10 μm, and the content of the titanyl phthalocyanine crystal is set to a value in the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. Dispersant for adjusting the dispersion of the agent In the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer, and the antioxidant is a hindered phenol-based oxidation represented by the following general formula (1) An antioxidant and an amine-based antioxidant represented by the following general formula (2), or any one of them, and a positive withstand voltage of a positively charged single-layer type electrophotographic photoreceptor measured in accordance with JIS C 2110 An image forming apparatus having a value of 8.2 kV or more .
That is, since the image forming apparatus of the present invention includes a predetermined electrophotographic photosensitive member, even when durable printing is performed, the occurrence of a leak phenomenon and a decrease in charging potential are effectively suppressed. Thus, a high quality image can be stably formed.


(In General Formula (2), R < ¹ > -R < ¹⁰ > is respectively independent, The carbon number of a hydrogen atom, a C1-C8 alkyl group, a C6-C20 aryl group, and an alkyl group part is 1. An alkylamino group of ˜8, or an arylamino group of 6 to 20 carbon atoms in the aryl group portion, and adjacent substituents may be bonded to form a naphthalene ring.)

Further, in configuring the image forming apparatus of the present invention, the exposure amount per unit area when exposing the positively charged single layer type electrophotographic photosensitive member is a value within the range of 0.2 to 0.8 μJ / cm ^2. It is preferable to do.
With such a configuration, it is possible to sufficiently generate electric charges while suppressing the occurrence of a leak phenomenon, so that it is possible to realize further higher speed in image formation.

In constituting the image forming apparatus of the present invention, it is preferable to set the charging potential when charging the positively charged single layer type electrophotographic photosensitive member to a value in the range of 600 to 1000V.
Even in such a configuration, it is possible to realize a further increase in speed in image formation while effectively suppressing the occurrence of a leak phenomenon and a decrease in charging potential.

Yet another embodiment of the present invention is an image forming method using the above-described image forming apparatus.
That is, in the image forming method of the present invention, since a predetermined image forming apparatus is used, even when durable printing is performed, the occurrence of a leak phenomenon and a decrease in charged potential are effectively suppressed. Thus, a high quality image can be stably formed.

FIG. 1 is a diagram provided for explaining the relationship between the reference positive withstand voltage and the number of spots generated. FIG. 2 is a diagram for explaining the relationship between the content of the antioxidant and the decrease in the charging potential. FIG. 3 is a diagram for explaining the image forming apparatus of the present invention. FIGS. 4A to 4B are views for explaining a single layer type electrophotographic photosensitive member in the present invention. FIG. 5 is a diagram provided for explaining the outline of the reference positive withstand voltage measuring device. FIG. 6 is a diagram provided to explain the relationship between the content of the charge generating agent and the reference positive withstand voltage. FIG. 7 is a CuKα characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal used in Example 1 (after storage for 24 hours in tetrahydrofuran). FIG. 8 is a differential scanning calorimetry chart of the titanyl phthalocyanine crystal used in Example 1.

[First Embodiment]
The first embodiment is a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer on a substrate, the photosensitive layer containing titanyl phthalocyanine crystals as a charge generating agent, and an antioxidant as an additive And the photosensitive layer has a thickness in the range of 22 to 40 μm. Further, an intermediate layer is provided on the substrate, and the intermediate layer includes a binder resin and titanium oxide fine particles. In addition, the content of the titanium oxide fine particles is set to a value within 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 within the range of 0.3 to 10 μm. Value, and the content of the titanyl phthalocyanine crystal is a value within the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer, and the dispersion for adjusting the dispersion of the charge generating agent 100 weight of binder resin for photosensitive layer The hindered phenol-based antioxidant represented by the general formula (1) described later and the general formula (2) described later are contained in a value within the range of 0.1 to 10 parts by weight with respect to parts. ) Or an amine-based antioxidant represented by
A positively charged single layer type electrophotographic photosensitive member characterized in that a positive withstand voltage of a positively charged single layer type electrophotographic photosensitive member measured in accordance with JIS C 2110 is a value of 8.2 kV or more .
That is, as shown in FIG. 1, by setting the reference positive withstand voltage to a value of 8.2 kV or higher, even when the charging potential is higher than a predetermined value due to high-speed image formation (characteristic curve A), This is a positively charged single layer type electrophotographic photosensitive member capable of critically suppressing the occurrence of a leak phenomenon and thus suppressing the occurrence of spots in a formed image.
At the same time, as shown in FIG. 2, by containing an antioxidant in the photosensitive layer, for example, even when 2000 durable prints are performed, a decrease in the charging potential can be effectively suppressed. This is a positively charged single layer type electrophotographic photosensitive member.

1. Basic Configuration An electrophotographic photosensitive member 71 shown in FIG. 3 is a single-layer type photosensitive member comprising a charge generating agent, a charge transporting agent, and a binder resin on a substrate 112 as shown in FIG. It is a single-layer electrophotographic photosensitive member 71 provided with a layer 114.
Further, as illustrated in FIG. 4B, a single-layer electrophotographic photoreceptor 71 ′ in which an intermediate layer 116 is formed between the photosensitive layer 114 and the substrate 112 can be used.

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, alumite, 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.

Of these, it is particularly preferable to use a material substance containing aluminum, and it is preferable that an alumite layer having a thickness of 1 to 10 μm is provided on the outer peripheral surface of the substrate.
This is because the reference positive withstand voltage of the electrophotographic photosensitive member can be easily adjusted to a predetermined value or more by configuring in this way.
That is, if the thickness of the alumite layer is less than 1 μm, it may be difficult to give a sufficient reference positive withstand voltage to the electrophotographic photosensitive member. On the other hand, if the thickness of the alumite layer exceeds 10 μm, the reference positive withstand voltage of the electrophotographic photosensitive member may increase excessively and exposure memory may be easily generated.
Accordingly, the thickness of the alumite layer is more preferably set to a value within the range of 2 to 8 μm, and further preferably set to a value within the range of 3 to 7 μm.

3. Intermediate Layer Further, as illustrated in FIG. 4B, an intermediate layer 116 containing a binder resin, inorganic fine particles, and the like is provided on the substrate 112 .
This is because the provision of such an intermediate layer makes it easy to adjust the reference positive withstand voltage of the electrophotographic photosensitive member measured under a predetermined condition to a value greater than or equal to a predetermined value.
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 characterized by.
This is because it is easier to adjust the reference positive withstand voltage of the positively charged single layer type electrophotographic photosensitive member to a value equal to or higher than a predetermined value 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 further improved. .
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 ). .
Moreover, it is because the surface treatment amount by the organosilicon compound described later can be easily adjusted by subjecting the titanium oxide fine particles to a surface treatment with alumina and silica.
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 content 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 microparticles | fine-particles, and setting it as the value within the range of 5-20 weight part. More preferred. Further, the content of the organosilicon compound is preferably set to a value in 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 set to a value in the range of 5 to 10 parts by weight. More preferred.

Further, the titanium oxide fine particles were surface-treated with the titanium oxide fine particles surface-treated with alumina and silica as the first titanium oxide fine particles and the alumina and silica as the second titanium oxide fine particles. Thereafter, it is preferable to further use titanium oxide fine particles that have been surface-treated with methylhydrogenpolysiloxane.
This is because the reference positive voltage of the positively charged single-layer type electrophotographic photosensitive member is adjusted to a predetermined value or more by using the first titanium oxide fine particles and the second titanium oxide fine particles in combination at a predetermined ratio. This is because it becomes easier.

Moreover, it is preferable to make the average primary particle diameter (number average primary particle diameter, hereinafter the same) in 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.
Accordingly, 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 12 to 18 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, the film thickness of the intermediate layer is set to a value within the range of 0.3 to 10 μm .
This is because when the thickness of the intermediate layer is less than 0.3 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 0.5 to 8 μm, and further preferably set to a value within the range of 1 to 5 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) Charge generator The present invention is characterized in that a titanyl phthalocyanine crystal is used as a charge generator.
This is because the titanyl phthalocyanine crystal is excellent in charge generation efficiency, so that the formation efficiency of the electrostatic latent image by exposure can be remarkably improved, and an even higher speed can be realized in an image forming apparatus or the like. Because.

In addition, the titanyl phthalocyanine compound constituting the titanyl phthalocyanine crystal is preferably a compound represented by the following general formula (1).
This is because a titanyl phthalocyanine compound having such a structure can not only further improve the stability of the titanyl phthalocyanine crystal but also stably produce such a titanyl phthalocyanine crystal.
In particular, the structure of the titanyl phthalocyanine compound is preferably represented by the following general formula (2). Among them, an unsubstituted titanyl phthalocyanine compound represented by the following formula (3) is particularly preferable.
This is because a titanyl phthalocyanine crystal having more stable properties can be more easily produced by using a titanyl phthalocyanine compound having such a structure.

(In the general formula (1), X ¹ , X ² , X ³ and X ⁴ are the same or different substituents, and each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group. And the repeating numbers a, b, c and d each represent an integer of 1 to 4, and may be the same or different.

(In general formula (2), X represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and the repeating number e represents an integer of 1 to 4.)

(1) -1 Optical Characteristics In addition, the titanyl phthalocyanine crystal in the present invention preferably has a main peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° as an optical characteristic in a CuKα characteristic X-ray diffraction spectrum. (First optical characteristic).
In the CuKα characteristic X-ray diffraction spectrum, it is preferable that there is no peak at the Bragg angle 2θ ± 0.2 ° = 26.2 ° (second optical characteristic).
Furthermore, in the CuKα characteristic X-ray diffraction spectrum, it is preferable that there is no peak at the Bragg angle 2θ ± 0.2 ° = 7.2 ° (third optical characteristic).
The reason for this is that, when the first optical characteristic is not provided, the crystal stability, charge generation ability, and dispersibility tend to be remarkably reduced as compared with a titanyl phthalocyanine crystal having such an optical characteristic. It is. In other words, it is possible to improve crystal stability, charge generation ability and dispersibility by providing the first optical characteristic, more preferably the second optical characteristic and the third optical characteristic. .
Incidentally, by improving the dispersibility of the titanyl phthalocyanine crystal, it becomes easy to adjust the reference positive withstand voltage of the electrophotographic photosensitive member to a value equal to or higher than a predetermined value, and as a result, between the electrophotographic photosensitive member and the charging means. It is possible to suppress the occurrence of the leak phenomenon.

Further, in the CuKα characteristic X-ray diffraction spectrum measured after the titanyl phthalocyanine crystal is immersed in an organic solvent for 24 hours, it has a main peak at least at a Bragg angle of 2θ ± 0.2 ° = 27.2 °, and 26. It is preferable not to have a peak at 2 °.
This is because the titanyl phthalocyanine crystal has such characteristics, whereby the temporal stability and dispersibility in the photosensitive layer coating solution can be further improved.
That is, even when the titanyl phthalocyanine crystal is actually immersed in an organic solvent such as tetrahydrofuran for 24 hours, the crystal form does not transition to the α or β form, and the predetermined crystal form is maintained. This is because the crystal transition in the organic solvent can be reliably controlled because it can be confirmed.
In addition, immersion experiment evaluation in the organic solvent used as the reference | standard which evaluates the storage stability of a titanyl phthalocyanine crystal is the coating liquid for photosensitive layers (henceforth, coating liquid for photosensitive layers) for producing the electrophotographic photoreceptor, for example. Is preferably carried out under the same conditions as the actual storage conditions. Therefore, for example, it is preferable to evaluate the storage stability of titanyl phthalocyanine crystals in a closed system under conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50 to 60% RH.

The organic solvent for evaluating the storage stability of the titanyl phthalocyanine crystal is at least one member selected from the group consisting of tetrahydrofuran, dichloromethane, toluene, 1,4-dioxane, and 1-methoxy-2-propanol. preferable.
This is because the stability of the titanyl phthalocyanine crystal when such an organic solvent is used as the organic solvent in the photosensitive layer coating solution can be determined more reliably.

(1) -2 Thermal characteristics In addition, the titanyl phthalocyanine crystal according to the present invention has, as a thermal characteristic, one peak within a range of 270 to 400 ° C. in the differential scanning calorimetric analysis other than the peak accompanying vaporization of adsorbed water. It is preferable to have.
This is because a titanyl phthalocyanine crystal having such optical characteristics and thermal characteristics can further improve crystal stability, charge generation ability and dispersibility.
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 adsorbed water appears in the range of 280 to 390 ° C, and the range of 290 to 380 ° C. More preferably, it appears within.
In addition, a specific method for measuring the Bragg angle in the CuKα characteristic X-ray diffraction spectrum and a specific method for differential scanning calorimetry will be described in detail in Examples.

(1) -3 Production Method The titanyl phthalocyanine crystal in the present invention can be produced, for example, by the method shown below.
That is, o-phthalonitrile or a derivative thereof, or 1,3-diiminoisoindoline or a derivative thereof as a material for producing such a titanyl phthalocyanine crystal is reacted with titanium alkoxide or titanium tetrachloride in the presence of a urea compound. Thus, it is preferable to produce a titanyl phthalocyanine compound.
Therefore, it is preferable to carry out according to the following reaction formula (1) or the following reaction formula (2). In the reaction formulas (1) and (2), as an example, titanium tetrabutoxide represented by the formula (5) is used as the titanium alkoxide.

Further, the addition amount of titanium alkoxide such as titanium tetrabutoxide represented by formula (5) or titanium tetrachloride is represented by o-phthalonitrile represented by formula (4) or a derivative thereof, or formula (6). It is preferable to make it a value within the range of 0.40-0.53 mol with respect to 1 mol of 1,3-diiminoisoindoline or its derivative.
This is because the addition amount of titanium alkoxide such as titanium tetrabutoxide represented by formula (5) or titanium tetrachloride is changed to o-phthalonitrile represented by formula (4) or a derivative thereof, or formula (6). By adding an excess amount exceeding 1/4 molar equivalent to the 1,3-diiminoisoindoline represented or its derivative, interaction with the urea compound described later is effectively exhibited. It is.
Therefore, the addition amount of titanium alkoxide such as titanium tetrabutoxide represented by the formula (5) or titanium tetrachloride is changed to o-phthalonitrile represented by the formula (4) or 1,3 represented by the formula (6). -It is more preferable to set it as the value within the range of 0.42-0.50 mol with respect to 1 mol of diiminoisoindoline etc., and it is further set as the value within the range of 0.45-0.47 mol. preferable.

Moreover, it is preferable to perform the reaction represented by the reaction formulas (1) and (2) described above in the presence of a urea compound.
The reason for this is that by using a titanyl phthalocyanine compound produced in the presence of a urea compound, the interaction between the urea compound and titanium alkoxide or titanium tetrachloride is exerted, so that specific titanyl phthalocyanine crystals can be efficiently obtained. It is because it can do.
That is, such an interaction means that ammonia produced by the reaction between a urea compound and titanium alkoxide or titanium tetrachloride further forms a complex with titanium alkoxide or titanium tetrachloride, and these substances are represented by reaction formulas (1) and (2 ) Is a function that further promotes the reaction represented by. And by making a raw material react with such a promotion effect | action, even if it is in an organic solvent, a specific titanyl phthalocyanine crystal | crystallization can be manufactured efficiently.

The urea compound is preferably at least one member of the group consisting of urea, thiourea, O-methylisourea sulfate, O-methylisourea carbonate, and O-methylisourea hydrochloride.
The reason for this is that by using such a urea compound as the urea compound in the reaction formulas (1) and (2), ammonia generated in the course of the reaction more efficiently forms a complex with titanium alkoxide or titanium tetrachloride. This is because such a substance further promotes the reactions represented by the reaction formulas (1) and (2).
That is, this is because the ammonia produced by the reaction of titanium alkoxide or titanium tetrachloride as a raw material with a urea compound forms a complex compound with titanium alkoxide or the like more efficiently. Therefore, this complex compound further promotes the reactions represented by the reaction formulas (1) and (2).
It has been found that such a complex compound is likely to be produced specifically when reacted under a high temperature condition of 180 ° C. or higher. Therefore, among nitrogen-containing compounds having a boiling point of 180 ° C. or higher, for example, quinoline (boiling point: 237.1 ° C.), isoquinoline (boiling point: 242.5 ° C.), or a mixture thereof (weight ratio 10:90 to 90:10) It is more effective to implement in.
Also, urea is more preferably used among the above-mentioned urea compounds because ammonia as a reaction accelerator and complex compounds resulting therefrom are more likely to be produced.

Further, the amount of urea compound used in the reaction formulas (1) and (2) is set to 0.1 with respect to 1 mol of o-phthalonitrile or a derivative thereof, or 1,3-diiminoisoindoline or a derivative thereof. A value within the range of ˜0.95 mol is preferred.
This is because the above-described action of the urea compound can be more efficiently exhibited by setting the addition amount of the urea compound within the range.
Therefore, the addition amount of the urea compound is a value within the range of 0.2 to 0.8 mol with respect to 1 mol of o-phthalonitrile or a derivative thereof, or 1,3-diiminoisoindoline or a derivative thereof. It is more preferable to set it to a value within the range of 0.3 to 0.7 mol.

Examples of the solvent used in the reaction formulas (1) and (2) include hydrocarbon solvents such as xylene, naphthalene, methylnaphthalene, tetralin, and nitrobenzene, dichlorobenzene, trichlorobenzene, dibromobenzene, and chloronaphthalene. Halogenated hydrocarbon solvents such as hexanol, octanol, decanol, benzyl alcohol, ethylene glycol, and diethylene glycol, and other alcohol solvents, cyclohexanone, acetophenone, 1-methyl-2-pyrrolidone, and 1,3-dimethyl-2- Examples include one or two or more arbitrary combinations of the group consisting of ketone solvents such as imidazolidinone, amide solvents such as formamide and acetamide, and nitrogen-containing solvents such as picoline, quinoline, and isoquinoline.
In particular, in the case of a nitrogen-containing compound having a boiling point of 180 ° C. or higher, for example, quinoline or isoquinoline, ammonia produced by the reaction of titanium alkoxide or titanium tetrachloride as a raw material with a urea compound is more efficiently produced by titanium. This is a suitable solvent because it easily forms a complex compound with an alkoxide or the like.

Moreover, it is preferable to make reaction temperature in Reaction Formula (1) and (2) into 150 degreeC or more high temperature. This is because when the reaction temperature is less than 150 ° C., particularly 135 ° C. or less, titanium alkoxide or titanium tetrachloride as a raw material reacts with a urea compound, and it becomes difficult to form a complex compound. Therefore, it is difficult for the complex compound to further promote the reaction represented by the reaction formulas (1) and (2), and it becomes difficult to efficiently produce a specific titanyl phthalocyanine crystal. .
Therefore, the reaction temperature in the reaction formulas (1) and (2) is more preferably set to a value within the range of 180 to 250 ° C, and further preferably set to a value within the range of 200 to 240 ° C.

The reaction time in the reaction formulas (1) and (2) depends on the reaction temperature, but is preferably in the range of 0.5 to 10 hours. This is because when the reaction time is less than 0.5 hours, titanium alkoxide or titanium tetrachloride as a raw material reacts with a urea compound, and it becomes difficult to form a complex compound. Therefore, it is difficult for the complex compound to further promote the reaction represented by the reaction formulas (1) and (2), and it becomes difficult to efficiently produce a specific titanyl phthalocyanine crystal. . On the other hand, when the reaction time exceeds 10 hours, it is economically disadvantageous or the produced complex compound may be reduced.
Therefore, it is more preferable to set the reaction time in the reaction formulas (1) and (2) to a value in the range of 0.6 to 3.5 hours, and to a value in the range of 0.8 to 3 hours. Further preferred.

In addition, it is preferable to obtain a final titanyl phthalocyanine crystal by performing steps including the following steps (a) to (d) on the obtained titanyl phthalocyanine compound (crude titanyl phthalocyanine crystal).
(A) Step of obtaining a titanyl phthalocyanine solution by dissolving a crude titanyl phthalocyanine crystal in an acid to obtain a titanyl phthalocyanine solution in a poor solvent to obtain a wet cake (c) (D) A step of obtaining titanyl phthalocyanine crystals by heating and stirring the washed wet cake in a non-aqueous solvent.

(1) -4 Content Further, the content of the titanyl phthalocyanine crystal as the charge generating agent is set to a value within the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. It is characterized by.
The reason for this is that it is easy to adjust the reference positive withstand voltage of the positively charged single-layer type electrophotographic photosensitive member to a value higher than a predetermined value, while ensuring a stable charge generation amount. This is because it can be done.
That is, when the content of titanyl phthalocyanine crystal is less than 0.5 parts by weight, the amount of charge generation is excessively reduced, making it difficult to form an electrostatic latent image on the surface of the electrophotographic photosensitive member. Because there is.
On the other hand, when the content of the titanyl phthalocyanine crystal exceeds 4 parts by weight, it becomes difficult to uniformly disperse in the photosensitive layer, and the reference positive withstand voltage of the electrophotographic photosensitive member is set to a value higher than a predetermined value. This is because it becomes difficult to adjust.
Accordingly, the content of titanyl phthalocyanine crystals, relative to 100 parts by weight of the binder resin of the photosensitive layer, more preferably set to a value within the range of from 1 to 4 parts by weight, a value in the range from 2 to 4 parts by weight More preferably.

(2) Dispersant Further, in order to adjust the dispersion of the charge generating agent in the photosensitive layer, a dispersant is used in combination .
That is, the reference withstand voltage can be easily adjusted by adjusting the dispersion of the charge generating agent in the photosensitive layer using the dispersant.
Moreover, as this dispersing agent, PY128 represented by following formula (7) as a pigment is mentioned, for example.

Examples of other dispersants include PR254, PY110, and PY242 as pigments.
In addition, the content of the dispersant is a value within the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer , and is 0.5 to 5 parts by weight. More preferably, the value is within the range.

(3) Antioxidant In the present invention, an antioxidant is used as an additive.
The reason for this is that even when durable printing is performed, a decrease in charging potential can be effectively suppressed.
That is, in the present invention, as described above, since the titanyl phthalocyanine crystal is used as the charge generating agent, the formation efficiency of the electrostatic latent image by exposure can be remarkably improved, and the image forming apparatus can further increase the speed. Can be realized.
On the other hand, when a titanyl phthalocyanine crystal is used as a charge generating agent and durable printing is performed, the occurrence of a leak phenomenon and a decrease in charged potential are likely to occur.
In this respect, by containing an antioxidant as an additive to the photosensitive layer, it is possible to effectively suppress oxidative deterioration of the photosensitive layer due to an active gas such as ozone generated mainly in the charging step.
As a result, the latter can be effectively suppressed among the occurrence of the above-described leakage phenomenon and the decrease in the charged potential.

(3) -1 type Further , the antioxidant is a hindered phenol-based antioxidant and an amine-based antioxidant, or one of them.
The reason for this is that by using these compounds as antioxidants, even if the surface of the photosensitive layer is exposed to an active gas such as ozone in the charging step, the oxidative deterioration of the surface of the photosensitive layer is more effective. This is because a decrease in charging potential can be suppressed.

Moreover, the hindered phenolic antioxidant mentioned above contains the structure represented by following formula (1), It is characterized by the above-mentioned.

  This is because a hindered phenol antioxidant containing such a structure can more effectively suppress oxidative deterioration of the surface of the photosensitive layer and suppress a decrease in charging potential.

In addition, the amine-based antioxidant described above has a structure represented by the following general formula (2) .

(In General Formula (2), R < ¹ > -R < ¹⁰ > is respectively independent, The carbon number of a hydrogen atom, a C1-C8 alkyl group, a C6-C20 aryl group, and an alkyl group part is 1. An alkylamino group of ˜8, or an arylamino group of 6 to 20 carbon atoms in the aryl group portion, and adjacent substituents may be bonded to form a naphthalene ring.)

  This is because an amine-based antioxidant having such a structure can more effectively suppress oxidative deterioration of the surface of the photosensitive layer and suppress a decrease in charging potential.

Specific examples of the hindered phenol antioxidant include compounds (P-1 to 16) represented by the following formula (8).
Among these, those including the structure represented by the general formula (1) are P-1, 2, 3, 7, 14, and 15.

Specific examples of the amine-based antioxidant include compounds (P-17 to 27) represented by the following formula (9).
Of these, those having the structure represented by the general formula (2) are (P-17, 18, 21, 22, 24, 25, 26 and 27).

(3) -2 Content Further, the content of the antioxidant is preferably set to a value within the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer.
This is because, by setting the content of the antioxidant in such a range, it is possible to effectively disperse the antioxidant in the photosensitive layer while sufficiently exhibiting the effect of preventing the antioxidant deterioration due to the antioxidant. It is.
That is, when the content of the antioxidant is less than 0.1 parts by weight, it is difficult to sufficiently suppress the oxidative deterioration of the surface of the photosensitive layer when durable printing is performed, and the charging potential is increased. It is because it may become easy to fall too much. On the other hand, when the content of the antioxidant exceeds 10 parts by weight, the dispersibility of the antioxidant in the photosensitive layer is excessively decreased, and the dispersibility of the charge generating agent is easily decreased excessively. This is because it may be difficult to suppress the occurrence of the phenomenon or the sensitivity characteristics may be deteriorated.
Therefore, it is more preferable to set the content of the antioxidant to a value within the range of 0.5 to 7 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer, and within the range of 1 to 7 parts by weight. More preferably, the value is more preferably in the range of 2 to 5 parts by weight.

Next, the relationship between the content of the antioxidant in the photosensitive layer of the electrophotographic photosensitive member and the decrease in the charging potential will be described with reference to FIG.
That is, in FIG. 2, on the horizontal axis, 3,5-tert-butyl-4-hydroxytoluene (BHT) (P— The characteristic curve obtained by taking the content (part by weight) of 1) and taking the decrease in charge potential (V) after the initial and 2000-sheet durable printing is shown on the vertical axis.
The charging potential at this time was 850 V, and the image forming speed was 160 mm / s. Other image forming conditions, the configuration of the electrophotographic photosensitive member, and the like are described in the examples.

First, it can be read from the characteristic curve that the value (absolute value) of the potential decrease decreases, that is, the potential decrease is suppressed as the BHT content increases.
More specifically, when the content of BHT is 0.5 part by weight, the potential decrease value (absolute value) is about 50 V, but then the potential decreases as the BHT content increases. Is in a state of being stably suppressed.
When the BHT content is 2.5 parts by weight or more, the potential drop value (absolute value) can be stably suppressed to a value of 20 V or less.
Therefore, it can be seen from the characteristic curve that the content of the antioxidant typified by BHT needs to be a predetermined value or more particularly when image formation is performed with the charging potential being a predetermined value or more. .

(4) Hole transport agent The hole transport agent used in the electrophotographic photoreceptor of the present invention is not particularly limited, and any of various conventionally known hole transport compounds can be used. .
In particular, benzidine compounds, phenylenediamine compounds, naphthylenediamine compounds, phenanthrylenediamine compounds, oxadiazole compounds (for example, 2,5-di (4-methylaminophenyl) -1,3,4- Oxadiazole, etc.), styryl compounds (eg, 9- (4-diethylaminostyryl) anthracene, etc.), carbazole compounds (eg, poly-N-vinylcarbazole, etc.), organic polysilane compounds, pyrazoline compounds (eg, 1 -Phenyl-3- (p-dimethylaminophenyl) pyrazoline, etc.), hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds , Razole compounds, triazole compounds, butadiene compounds, pyrene-hydrazone compounds, acrolein compounds, carbazole-hydrazone compounds, quinoline-hydrazone compounds, stilbene compounds, stilbene-hydrazone compounds, and diphenylenediamine compounds Etc. are preferably used. These may be used alone or in combination of two or more.
Note that the reference positive withstand voltage can also be adjusted by changing the type of the hole transport agent.

Moreover, it is preferable to make content of a hole transport agent into the value within the range of 10-100 weight part with respect to 100 weight part of binder resin in a photosensitive layer.
The reason for this is that by setting the content of the hole transporting agent in such a range, excellent electrical characteristics can be obtained while effectively suppressing the crystallization of the hole transporting agent in the photosensitive layer. This is because it can.
That is, when the content of the hole transport agent is less than 10 parts by weight, the sensitivity is lowered, and there may be practical problems. On the other hand, when the content of the hole transport agent exceeds 100 parts by weight, the hole transport agent is excessively easily crystallized and it is difficult to form an appropriate film as a photosensitive layer. Because there is.
Therefore, the content of the hole transport agent is more preferably set to a value within the range of 20 to 90 parts by weight, and further preferably set to a value within the range of 30 to 80 parts by weight.

(5) Electron transport agent The electron transport agent used in the electrophotographic photoreceptor of the present invention is not particularly limited, and any of various conventionally known electron transport compounds can be used. Especially diphenoquinone derivatives, azoquinones, pyrene derivatives, benzoquinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, 3,4,5,7-tetranitro-9-fluorenone derivatives, dinitroanthracene derivatives, dinitroacridine derivatives , Nitroantharaquinone derivatives, dinitroanthraquinone derivatives, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromoanhydride One kind of maleic acid or a combination of two or more kinds may be mentioned.
Note that the reference positive withstand voltage can also be adjusted by changing the type of the electron transfer agent.

Moreover, it is preferable to make content of an electron transport agent into the value within the range of 10-100 weight part with respect to 100 weight part of binder resin.
This is because when the amount of the electron transport agent added is less than 10 parts by weight, the sensitivity is lowered and a practical problem may occur. On the other hand, when the addition amount of the electron transport agent exceeds 100 parts by weight, the electron transport agent is easily crystallized, and an appropriate film as a photosensitive layer may not be formed.
Therefore, it is more preferable to set the addition amount of the electron transfer agent to a value within the range of 20 to 80 parts by weight.

(6) Binder Resin The type of binder resin used in the electrophotographic photoreceptor of the present invention is not particularly limited. For example, polycarbonate resin, polyester resin, polyarylate resin, styrene-butadiene copolymer Polymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, Ionomer, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide, polyurethane, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, etc., silicone resin, epoxy resin, phenol resin, urea Resin, melami Resins such as vinyl resins, other cross-linkable thermosetting resins, and photo-curing resins such as epoxy acrylate and urethane acrylate can be used.

(7) Film thickness The film thickness of the photosensitive layer is set to a value in the range of 22 to 40 μm.
The reason for this is that the positive withstand voltage of the electrophotographic photosensitive member can be improved by setting the film thickness of the photosensitive layer in such a range, while the generation of residual charges is suppressed and the exposure memory is made more effective. This is because it can be suppressed.
That is, when the film thickness of the photosensitive layer is less than 22 μm, the positive withstand voltage of the electrophotographic photosensitive member tends to be excessively lowered, or the mechanical strength of the photosensitive layer becomes insufficient, so that it is easily peeled off from the substrate. This is because there is a case where it becomes.
On the other hand, if the film thickness of the photosensitive layer exceeds 40 μm, the generation of residual charges may be excessively increased.
Therefore, the film thickness of the photosensitive layer is more preferably set to a value within the range of 23 to 38 μm, and further preferably set to a value within the range of 25 to 35 μm.

5. Reference positive withstand voltage The positive withstand voltage (reference positive withstand voltage) of a positively charged single layer type electrophotographic photosensitive member measured in accordance with JIS C 2110 when the film thickness of the photosensitive layer is 22 to 40 μm. It is characterized by being a value of 8.2 kV or more.
This is because even when the reference positive withstand voltage is set to a predetermined value, a titanyl phthalocyanine crystal is used as the charge generating agent, and the charging potential is set to a predetermined high value as will be described later. This is because the occurrence of a leak phenomenon between the charging means and the electrophotographic photosensitive member can be effectively suppressed.
That is, when the reference positive withstand voltage is less than 8.2 kV, a leakage current flows between the charging means and the electrophotographic photosensitive member when the charging process is performed, and the photosensitive layer breaks down. This is because, eventually, spots corresponding to the leaked portion are always image-formed.
On the other hand, when the reference positive withstand voltage becomes an excessively large value, charges are likely to be excessively accumulated in the photosensitive layer, and it may be difficult to sufficiently suppress the generation of the exposure memory.
Therefore, it is more preferably a value within the range of the reference positive voltage resistance of 8.2 ～15KV of the electrophotographic photosensitive member, still more preferably a value within the range of 8.2 ~10kV.
The reference positive withstand voltage in the present invention is, for example, a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer thickness of 22 μm, and the electrophotographic photosensitive member itself when the photosensitive layer thickness is 22 μm. The standard positive withstand voltage of
For example, in the case of a positively charged single-layer type electrophotographic photosensitive member having a photosensitive layer thickness of 40 μm, it means the reference positive withstand voltage of the electrophotographic photosensitive member itself when the photosensitive layer thickness is 40 μm.

Moreover, an example of the measurement conditions of the reference | standard positive withstand voltage measured based on JISC2110 is as follows.
FIG. 5 shows a schematic diagram of a measuring apparatus 200 for measuring the reference positive withstand voltage.
That is, the measuring apparatus 200 basically includes a V-rail base 203 for placing the electrophotographic photosensitive member 71, a linear slider 201 that can move in the axial direction of the electrophotographic photosensitive member 71, and the linear slider 201. A fixed cotton needle 202 is provided.
Further, a conductive wire is connected to the base of the electrophotographic photosensitive member 71 placed on the cotton needle 202 and the V-rail stand 203, and a voltage can be applied by the high-voltage power source 203.
Photosensitive layer thickness: 25 μm
Electrode: Cotton needle No. 3 (manufactured by Clover, length: 51.5 mm, diameter: 0.84 mm)
Distance between electrode and photosensitive layer: 1mm
Voltage rise pattern: 0.1 kV / sec.
Type of applied voltage: Current value at the time of positive DC potential leakage phenomenon judgment: 0.5 mA
Leak phenomenon measurement environment: temperature 20 ° C., relative humidity 50%, dark place high voltage power supply and leak phenomenon measurement device: high voltage power supply TREK 610E (manufactured by TREK Co., Ltd.)

Next, the relationship between the reference positive withstand voltage of the electrophotographic photosensitive member and the occurrence of a leak phenomenon between the charging means and the electrophotographic photosensitive member will be described with reference to FIG.
That is, in FIG. 1, the horizontal axis represents the reference positive withstand voltage (kV) of the electrophotographic photosensitive member, and the vertical axis represents the formed image resulting from the occurrence of leakage between the charging means and the electrophotographic photosensitive member. Characteristic curves A and B taking the number of spots (number / (9.4 × 21) cm ² ) in FIG.
Here, the characteristic curve A is a characteristic curve when the charging potential by the charging unit is 850V, and the characteristic curve B is a characteristic curve when the charging potential by the charging unit is 450V.
The image forming speed was 160 mm / s in both the characteristic curves A and B. Other image forming conditions, the configuration of the electrophotographic photosensitive member, and the like are described in the examples.

First, it can be read from the characteristic curves A and B that the number of spots generated per unit area decreases as the value of the reference positive withstand voltage increases.
On the other hand, in the characteristic curves A and B, the rate of decrease in the number of spots generated as the reference positive withstand voltage increases is greatly different.
That is, in the characteristic curve A, when the reference positive withstand voltage value is 7 kV, the number of spots generated per unit area is about 70, but thereafter, the reference positive withstand voltage value increases. The number of spots is decreasing rapidly.
And when the value of the reference positive withstand voltage becomes a value of 8.2 kV or more, the number of spots generated per unit area can be stably suppressed to around 20.
On the other hand, in the characteristic curve B, even when the value of the reference positive withstand voltage is low, the number of spots generated per unit area is sufficiently suppressed, for example, when the value of the reference positive voltage is 7 kV. Even there are around 30.
Therefore, from the characteristic curves A and B, when image formation is performed with the charging potential being a predetermined value or more, it is necessary to specifically set the value of the reference positive band voltage to a value of 8.2 kV or more. Recognize.

In addition, as described above, the reference positive withstand voltage of the electrophotographic photosensitive member can be adjusted by forming an alumite layer on the substrate surface, providing an intermediate layer on the substrate, or the type of titanyl phthalocyanine crystal as a charge generating agent. The content can be changed or the film thickness of the photosensitive layer can be changed.
Hereinafter, an example of such adjustment will be described with reference to FIG.

That is, the case where the content of titanyl phthalocyanine crystal in the photosensitive layer is changed will be described with reference to FIG.
In FIG. 6, the horizontal axis represents the characteristic curve with the titanyl phthalocyanine crystal content (parts by weight) with respect to 100 parts by weight of the binder resin of the photosensitive layer and the vertical axis the standard positive withstand voltage (kV). .
Details of the configuration of the electrophotographic photosensitive member, the method of measuring the reference positive withstand voltage, and the like will be described later.

That is, it can be understood from the characteristic curve that the value of the reference positive withstand voltage can be decreased by increasing the content of the titanyl phthalocyanine crystal.
Conversely, it is understood that the value of the reference positive withstand voltage can be increased by reducing the content of the titanyl phthalocyanine crystal.
Therefore, it can be seen that the value of the reference positive withstand voltage can be finely adjusted by changing the content of the titanyl phthalocyanine crystal.

[Second Embodiment]
The second embodiment is an image forming apparatus provided with a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer on a substrate, the photosensitive layer containing a titanyl phthalocyanine crystal as a charge generating agent, As an additive, an antioxidant is included, and the film thickness of the photosensitive layer is set to a value within the range of 22 to 40 μm. Further, an intermediate layer is provided on the substrate, and the intermediate layer includes a binder resin, Titanium oxide fine particles, the content of the titanium oxide fine particles is set to a value within 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 set to 0. The value is within the range of 3 to 10 μm, and the content of the titanyl phthalocyanine crystal is within the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. Dispersing agent to adjust condition The hindered phenol-based antioxidant represented by the above general formula (1) is contained in a value within the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the layer, and A positive withstand voltage of a positively charged single-layer type electrophotographic photoreceptor measured in accordance with JIS C 2110 is 8.2 kV , which is either an amine-based antioxidant represented by the general formula (2) or any one of them. An image forming apparatus having the above values.
Hereinafter, the image forming apparatus as the second embodiment will be described in detail by dividing it into a basic configuration, an electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a charge eliminating unit.

1. Basic Configuration FIG. 3 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 7BK 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 exposing unit, the developing unit, and the neutralizing unit will be specifically described.

2. Electrophotographic Photoreceptor Since the content can be the same as that described in the first embodiment, description thereof is omitted here.

3. Charging Unit The charging unit 75 shown in FIG. 3 is installed above the electrophotographic photosensitive member 71 and is a unit for uniformly charging the electrophotographic photosensitive member 71.
As the type of the charging means, it is preferable to use a non-contact type charging means such as Scorotron, but a contact type charging means such as a charging roller may be used.

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, if the value of the charged potential exceeds 1000 V, the leakage phenomenon may be excessively likely to occur, or the photosensitive layer surface may be excessively easily oxidized and deteriorated.
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.

4). Exposure Unit The exposure unit 76 shown in FIG. 3 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, the electrophotographic photosensitive member in the present invention uses a titanyl phthalocyanine crystal having excellent charge generation efficiency as a charge generating agent, and the charging potential is set to a predetermined high value. The image formation efficiency is remarkably improved.
Therefore, even when the exposure amount per unit area when the electrophotographic photosensitive member is exposed is reduced, image formation can be performed without any practical problem, and the energy saving effect can be improved.
Therefore, the exposure amount per unit area is preferably set to a value within the range of 0.2 to 0.8 μJ / cm ² on the electrophotographic photosensitive member, and within the range of 0.3 to 0.6 μJ / cm ² . More preferably, the value of

5. Developing Unit The developing unit 72 shown in FIG. 3 is a unit that supplies toner to the surface of the electrophotographic photoreceptor 71 on which the electrostatic latent image is formed to form a toner image.
Further, it is preferable that the developing unit is a simultaneous development cleaning system in which the toner remaining on the surface of the electrophotographic photosensitive member is collected by the developing unit, whereby the surface of the electrophotographic photosensitive member is cleaned.
This is because the image forming apparatus of the present invention can downsize the configuration of each image forming unit while suppressing the occurrence of a leak phenomenon even when configured in this way. .
That is, when the simultaneous development cleaning method is adopted, the blade cleaner provided on the upstream side of the charging unit is usually omitted.
Accordingly, the transfer residual toner remains on the surface of the electrophotographic photosensitive member during charging and exposure.
In this regard, the electrophotographic photosensitive member of the present invention uses a titanyl phthalocyanine crystal having excellent charge generation efficiency as a charge generating agent, and the charging potential is set to a predetermined high value. This is because the image forming efficiency is remarkably improved, and even in such a case, the image can be formed without any practical problem.

6). Static elimination means Further, a static elimination means for removing residual charges remaining in the photosensitive layer of the electrophotographic photosensitive member may be provided upstream of the charging means.
On the other hand, in the case of the present invention, since the neutralization means is omitted and the occurrence of a leak phenomenon can be suppressed even if charging is performed in the next process without completely removing the residual charge, a static elimination-less system in which the neutralization means is omitted is adopted. Is preferred.

7). Developer In the present invention, it is preferable to use a non-magnetic one-component developer.
This is because a non-magnetic one-component developer does not need to contain magnetic powder in the developer, so that a vivid color image can be formed.
In addition, unlike the case of using a magnetic developer or a two-component developer, it is not necessary to use a magnet roll, which can contribute to the simplification and compactness of the developing device. This is because it can be configured as a cleaner-less color image forming apparatus in which the blade cleaner is omitted.

The binder resin used for the toner particles is not particularly limited, and for example, it is preferable to use a thermoplastic resin such as a styrene resin, an acrylic resin, and a styrene-acrylic resin.
Further, the colorant contained in the toner particles is not particularly limited. For example, carbon black, acetylene black, lamp black, aniline black, azo pigment, yellow iron oxide, ocher, nitro dye, oil-soluble It is preferable to use dyes, benzidine pigments, quinacridone pigments, copper phthalocyanine pigments, and the like.

Further, it is also preferable to use a charge control agent exhibiting positive charge characteristics such as nigrosine, a quaternary ammonium salt compound, or a resin type charge control agent in which an amine compound is bonded to the resin, for the toner particles. .
Furthermore, it is also preferable to use waxes such as polyethylene wax, polypropylene wax, fluororesin-based wax, Fischer-Tropsch wax, paraffin wax, ester wax, montan wax, and rice wax for the toner particles.
In order to adjust the flowability and charging characteristics of the developer, it is also preferable to add inorganic fine particles such as silica fine particles and titanium oxide fine particles to the toner particles to adjust the flowability and charging characteristics.

  Further, the volume average particle diameter of the toner particles is preferably set to a value in the range of 6 to 10 μm, and as a production method thereof, a conventionally known production method such as a pulverization method or a polymerization method can be used.

[Third Embodiment]
The third embodiment is an image forming method using the image forming apparatus described in the second embodiment.
Hereinafter, the contents overlapping with those of the second embodiment are omitted, and the characteristic contents of the image forming method according to the third embodiment are exemplified by the case where the simultaneous development cleaning method in which the blade cleaner is omitted is employed. This will be specifically described.

First, the image forming unit 3 includes an image forming unit 7, an intermediate transfer belt 11 on which a toner image is primarily transferred onto the surface (contact surface) by the image forming unit 7, and a developer on the intermediate transfer belt 11. Secondary transfer means 12 for secondary transfer of the image onto the recording medium P fed from the paper feed cassette 21 is provided.
The image forming unit 7 includes a black unit 7K, a yellow unit 7Y, a cyan unit 7C, and a magenta unit 7M, which are sequentially arranged from the upstream side (left side in FIG. 3) to the downstream side. It has.
In each of the units 7K, 7Y, 7C, and 7M, an electrophotographic photosensitive member 71 as an image carrier is arranged at the center position so as to be rotatable in the direction of an arrow (counterclockwise).
Further, around each electrophotographic photosensitive member 71, a charging unit 75, an exposure unit 76, a developing unit 72, and the like are arranged in order from the upstream side in the rotation direction.

The charging means 75 uniformly charges the peripheral surface of the electrophotographic photosensitive member 71 rotated in the direction of the arrow.
Examples of the charging unit 75 include a scorotron charger.
The exposure unit 76 is a so-called laser scanning unit, and irradiates the peripheral surface of the electrophotographic photosensitive member 71 uniformly charged by the charging unit 75 with laser light based on image data input from an image reading device or the like. Then, an electrostatic latent image based on the image data is formed on the electrophotographic photosensitive member 71.
The developing unit 72 supplies a developer to the peripheral surface of the electrophotographic photoreceptor 71 on which the electrostatic latent image is formed, thereby forming a developer image based on the image data.
Then, the formed developer image is primarily transferred to the intermediate transfer belt 11.

The intermediate transfer belt 11 is an endless belt-like rotating body, and includes a driving roller 13, a belt support roller 14, a backup so that the surface (contact surface) side is in contact with the peripheral surface of each electrophotographic photoreceptor 71. A plurality of rollers such as a roller 15, a primary transfer unit 16, and a tension roller 17 are spanned.
The intermediate transfer belt 11 is configured to rotate endlessly by the plurality of rollers in a state where the intermediate transfer belt 11 is pressed against the electrophotographic photosensitive member 71 by the primary transfer unit 16 disposed opposite to each electrophotographic photosensitive member 71. Yes.

Further, the primary transfer unit 16 applies a primary transfer bias (a polarity opposite to the charging polarity of the developer) to the intermediate transfer belt 11.
By doing so, the developer image formed on each electrophotographic photoreceptor 71 is moved between each electrophotographic photoreceptor 71 and the primary transfer means 16 by the driving roller 13 (arrow clockwise). The images are sequentially transferred (primary transfer) in an overcoated state to the intermediate transfer belt 11 that circulates in the direction.

Further, the secondary transfer unit 12 applies a secondary transfer bias having a polarity opposite to that of the developer image to the paper P.
By doing so, the developer image primarily transferred onto the intermediate transfer belt 11 is transferred onto the paper P between the secondary transfer means 12 and the backup roller 15, whereby a color transfer image is transferred onto the paper P. Is formed.

The fixing unit 4 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 3. The fixing unit 4 is disposed opposite to the heating roller 41 heated by the energized heating element, And a pressure roller 42 having a peripheral surface pressed against and in contact with the peripheral surface of the heating roller 41.
The transferred image transferred to the paper P by the secondary transfer roller 12 in the image forming unit 3 is subjected to a fixing process by heating when the paper P passes between the heating roller 41 and the pressure roller 42. To be established.
Further, the paper P subjected to the fixing process is discharged to a paper discharge unit.

With the above-described image forming method of the present invention, even if high-speed image formation is performed with a relatively high charging potential by using a predetermined image forming apparatus, leakage occurs and formation due to the leakage occurs. The occurrence of spots in the image can be effectively suppressed.
The high-speed image formation in the present invention means that image formation is performed at a value within the range of the drum rotation speed of 100 to 200 mm / s, and the image formation speed is a value within the range of 150 to 200 mm / s. More preferably.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it cannot be overemphasized and this invention is not limited to these description content without a particular reason.

[ Reference 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, the first titanium oxide fine particles (manufactured by Teika Co., Ltd., MT05) 160 parts by weight, the second titanium oxide fine particles (manufactured by Teika Co., Ltd., SMT02) 40 parts by weight, 100 parts by weight of a quaternary copolymerized polyamide resin (CM8000, manufactured by Toray Industries, Inc.), 1000 parts by weight of methanol as a solvent, and 250 parts by weight of n-butanol were mixed and dispersed for 5 hours, and further filtered with a 5 micron filter. The intermediate layer coating solution was prepared by filtration.
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 2 micrometers was formed.

In addition, the structure of the 1st titanium oxide microparticles | fine-particles mentioned above and the 2nd titanium oxide microparticles | fine-particles is as follows, respectively.
First titanium oxide fine particles (MT05)
Titanium oxide fine particles surface-treated with alumina and silica (manufactured by Teika Co., Ltd., number average primary particle size 10 nm)
Second titanium oxide fine particles (SMT02)
Titanium oxide fine particles surface-treated with alumina and silica and then surface-treated with methyl hydrogen polysiloxane (manufactured by Teika Co., Ltd., number average primary particle size: 10 nm)

(3) Formation of photosensitive layer Next, in a container, 3 parts by weight of titanyl phthalocyanine (CGM-1) crystal (TiOPc) represented by the formula (3) as a charge generating agent produced by a production method described later, As an antioxidant, 50 parts by weight of a hole transporting agent (HTM-1) represented by the following formula (10), 30 parts by weight of an electron transporting agent (ETM-1) represented by the following formula (11), and N-phenyl-naphthalen-1-amine (P-24) 2.5 parts by weight in formula (9), 100 parts by weight of a polycarbonate resin having an average molecular weight of 30,000 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 25 μm. Thus, a single layer type electrophotographic photosensitive member was obtained.

(4) Production of titanyl phthalocyanine A crystal (TiOPc) of titanyl phthalocyanine (CGM-1) represented by the formula (3) as a charge generating agent was produced 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 ° C and stirred for 10 hours.
Next, after the liquid was filtered off with a glass filter, 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 (3). Got.

(4) -4 Evaluation of titanyl phthalocyanine crystal (X-ray diffraction measurement)
After 0.3 g of the obtained titanyl phthalocyanine crystal was dispersed in 5 g of tetrahydrofuran and 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%, 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 a stable predetermined crystal form. This is because the peak at the Bragg angle 2θ ± 0.2 ° = 27.2 ° is a peak peculiar to the above-mentioned predetermined crystal type, and the peak at 26.2 ° is a peculiar peak to the β-type crystal. Because there is.
Note that a spectrum chart similar to that shown in FIG. 7 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. Further, in this chart, one peak was confirmed at 296 ° C. in addition to the peak accompanying vaporization of adsorbed water.
The measurement conditions were as follows.
Sample pan: Aluminum heating rate: 20 ° C / min

2. Evaluation of Electrophotographic Photoreceptor (1) Measurement of Standard Positive Withstand Voltage The positive withstand voltage of a positively charged single layer type electrophotographic photoreceptor was measured in accordance with JIS C2110.
That is, as shown in FIG. 5, a cotton needle No. 3 (manufactured by Clover, length: 51.5 mm, diameter: 0.84 mm) is connected to a high voltage power source (TREK Co., Ltd., 610E) The needle tips were opposed so as to be 1 mm from the surface of the 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 (plus 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 positive withstand voltage (kV). The obtained results are shown in Table 1.

(2) Evaluation of the number of spots generated Moreover, the number of spots generated was evaluated using the obtained electrophotographic photosensitive member.
That is, the obtained electrophotographic photosensitive member is applied to a black, cyan, magenta and yellow developer for a color image forming apparatus (Kyocera Mita Co., Ltd., KM-C3232 remodeling machine) adopting a tandem method and a cleanerless method. It was mounted as an electrophotographic photoreceptor corresponding to the above.
Next, under normal temperature and normal humidity conditions (temperature: 20 ° C., relative humidity: 50%), a color solid image using black, cyan, magenta and yellow developers uniformly in all colors and only the black developer were used. Monochrome solid images and 5,000 sheets are printed alternately, then a blank image is printed, and the number of spots in the area corresponding to one rotation (9.4 cm × 21 cm) of the image carrier (photosensitive member) is visually observed. Counted. The obtained results are shown in Table 1.
Other image forming conditions are as shown below.
Charging method: Scorotron charging method (charging potential: 850V)
Exposure method: Laser light source exposure method (exposure amount: 0.5 μJ / cm ² )
Developer: Non-magnetic one-component developer (polymerization method)
Transfer method: Intermediate transfer belt method Image forming speed: 160 mm / s

(3) Evaluation of charging potential Further, the charging potential of the obtained electrophotographic photosensitive member was evaluated.
In other words, except that the environmental conditions are set to a temperature of 10 ° C. and a relative humidity of 20%, the charging potential (before and after printing 2000 sheets of a 4% original image under the same conditions as in the evaluation of the number of spots generated as described above) V) were measured, and the initial charging potential was subtracted from the charging potential after printing 2000 sheets to calculate the decrease in charging potential (V). The obtained results are shown in Table 1.
Note that the environmental conditions of a temperature of 10 ° C. and a relative humidity of 20% are environmental conditions where ozone and NOx are more likely to be generated.

(4) Sensitivity evaluation Moreover, the sensitivity in the obtained electrophotographic photosensitive member was measured.
That is, using a drum sensitivity tester (manufactured by GENTEC) under normal temperature and normal humidity conditions (temperature: 20 ° C., relative humidity: 50%), it is charged so that the charging potential becomes 850 V, and then white light Then, monochromatic light having a wavelength of 780 nm (half width: 20 nm, exposure amount: 0.3 μJ / cm ² ) extracted from the surface of the electrophotographic photoreceptor was exposed (irradiation time: 50 msec). Next, the potential after 350 msec elapsed after exposure was measured and defined as sensitivity (V).

[ Reference Example 2]
In Reference Example 2, single layer type electrons were formed in the same manner as in Reference Example 1 except that 2.5 parts by weight of diphenylamine (P-17) in formula (9) was used as an antioxidant when forming the photosensitive layer. Photoconductors were manufactured and evaluated. The obtained results are shown in Table 1.

[ Reference Example 3]
In Reference Example 3, 2.5 parts by weight of 3,5-di-tert-butyl-4-hydroxytoluene (BHT) (P-1) in formula (8) as an antioxidant when forming the photosensitive layer A single-layer electrophotographic photosensitive member was produced and evaluated in the same manner as in Reference Example 1 except that was used. The obtained results are shown in Table 1.

[ Reference Example 4]
In Reference Example 4, when forming the photosensitive layer, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (P-3) 2 in formula (8) is used as an antioxidant. A single-layer electrophotographic photosensitive member was produced and evaluated in the same manner as in Reference Example 1 except that 0.5 part by weight was used. The obtained results are shown in Table 1.

[ Reference Example 5]
In Reference Example 5, pentaerythritol tetrakis-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (P-14) in formula (8) was used as an antioxidant when forming the photosensitive layer. ) A single-layer electrophotographic photosensitive member was produced and evaluated in the same manner as in Reference Example 1 except that 2.5 parts by weight were used. The obtained results are shown in Table 1.

[ Reference Examples 6 to 10]
In Reference Examples 6 to 10, the content of 3,5-di-tert-butyl-4-hydroxytoluene (BHT) (P-1) in the formula (8) as an antioxidant when forming the photosensitive layer A single-layer electrophotographic photosensitive member was produced and evaluated in the same manner as in Reference Example 3 except that the amount was changed to 0.5, 1.0, 1.5, 3.5 and 5.0 parts by weight, respectively. . The obtained results are shown in Table 1.

[Comparative Example 1]
In Comparative Example 1, a single-layer electrophotographic photosensitive member was produced and evaluated in the same manner as in Reference Example 1 except that the antioxidant was not included when forming the photosensitive layer. The obtained results are shown in Table 1.

[ Reference Examples 11 to 15 and Comparative Example 2]
In Reference Examples 11 to 15 and Comparative Example 2, when the intermediate layer is formed, the content of the second titanium oxide fine particles (SMT02) is 200 parts by weight, and the first titanium oxide fine particles (MT05) are not included. Otherwise, single layer type electrophotographic photoreceptors were produced and evaluated in the same manner as Reference Examples 1 to 5 and Comparative Example 1, respectively. The obtained results are shown in Table 1.

[ Reference Examples 16 to 20 and Comparative Example 3]
In Reference Examples 16 to 20 and Comparative Example 3, in manufacturing the electrophotographic photosensitive member, using a substrate formed with alumite layer having a thickness of 6μm to the surface, and, except that it did not form the intermediate layer, respectively reference example Similarly prepared an electrophotographic photosensitive member 1 to 5 and Comparative example 1 were evaluated. The obtained results are shown in Table 1.

[ Reference Examples 21 to 25 and Comparative Example 4]
In Reference Examples 21 to 25 and Comparative Example 4, a copolyamide resin (manufactured by Daicel Degussa Co., Ltd., X1010) is used as the binder resin when forming the intermediate layer, and the second titanium oxide fine particles (SMT02) In the same manner as in Reference Examples 1 to 5 and Comparative Example 1, except that the content of the first titanium oxide fine particles is 40 parts by weight and the thickness of the photosensitive layer is 28 μm. An electrophotographic photosensitive member was manufactured and evaluated. The obtained results are shown in Table 1.

[ Reference Examples 26 to 30 and Comparative Example 5]
In Reference Examples 26 to 30 and Comparative Example 5, an electrophotographic photosensitive member was produced in the same manner as Reference Examples 21 to 25 and Comparative Example 4, respectively, except that when forming the photosensitive layer, the film thickness of the photosensitive layer was set to 35 μm. And evaluated. The obtained results are shown in Table 1.

[ Reference Examples 31 to 35 and Comparative Example 6]
In Reference Examples 31 to 35 and Comparative Example 6, an electrophotographic photosensitive member was produced in the same manner as Reference Examples 21 to 25 and Comparative Example 4, respectively, except that when forming the photosensitive layer, the film thickness of the photosensitive layer was 33 μm. And evaluated. The obtained results are shown in Table 1.

[ Reference Examples 36 to 40 and Comparative Example 7]
In Reference Examples 36 to 40 and Comparative Example 7, an electrophotographic photosensitive member was produced in the same manner as Reference Examples 21 to 25 and Comparative Example 4, respectively, except that the thickness of the photosensitive layer was 23 μm when forming the photosensitive layer. And evaluated. 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 Comparative Example 7 except that no intermediate layer was provided and the film thickness of the photosensitive layer was 25 μm. The obtained results are shown in Table 1.

According to the present invention, in a positively charged single layer type electrophotographic photosensitive member, even when titanyl phthalocyanine crystal is used as a charge generating agent, an antioxidant is used as an additive, and the positive electrode of the electrophotographic photosensitive member is used. By setting the withstand voltage within a predetermined range, it is possible to effectively suppress the occurrence of a leak phenomenon and a decrease in the charging potential when performing durable printing with a high charging potential.
Therefore, the positively charged single layer type electrophotographic photosensitive member, the image forming apparatus, and the image forming method according to the present invention significantly contribute to high speed and stable quality in various image forming apparatuses such as copying machines and printers. There is expected.

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 (6)

A positively charged single layer type electrophotographic photosensitive member having a photosensitive layer on a substrate,
The photosensitive layer contains a titanyl phthalocyanine crystal as a charge generating agent, an antioxidant as an additive, and
The film thickness of the photosensitive layer is set to a value within the range of 22 to 40 μm, and
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 in the range of 0.3 to 10 μm,
The content of the titanyl phthalocyanine crystal is set to a value within the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer,
A dispersant for adjusting the dispersion of the charge generating agent is included at a value in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer,
The antioxidant is a hindered phenol-based antioxidant represented by the following general formula (1) and an amine-based antioxidant represented by the following general formula (2), or any one of them:
A positively charged single layer type electrophotographic photosensitive member, characterized in that the positive withstand voltage of the positively charged single layer type electrophotographic photosensitive member measured in accordance with JIS C 2110 is a value of 8.2 kV or more .


(In General Formula (2), R < ¹ > -R < ¹⁰ > is respectively independent, The carbon number of a hydrogen atom, a C1-C8 alkyl group, a C6-C20 aryl group, and an alkyl group part is 1. An alkylamino group of ˜8, or an arylamino group of 6 to 20 carbon atoms in the aryl group portion, and adjacent substituents may be bonded to form a naphthalene ring.)   2. The positive electrode according to claim 1, wherein the content of the antioxidant is set to a value within a range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. Charged single layer type electrophotographic photoreceptor. An image forming apparatus comprising a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer on a substrate,
The photosensitive layer contains a titanyl phthalocyanine crystal as a charge generating agent, an antioxidant as an additive, and
The film thickness of the photosensitive layer is set to a value within the range of 22 to 40 μm, and
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 in the range of 0.3 to 10 μm,
The content of the titanyl phthalocyanine crystal is set to a value within the range of 0.5 to 4 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer,
A dispersant for adjusting the dispersion of the charge generating agent is included at a value in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer,
The antioxidant is a hindered phenol-based antioxidant represented by the following general formula (1) and an amine-based antioxidant represented by the following general formula (2), or any one of them:
An image forming apparatus characterized in that a positive withstand voltage of a positively charged single layer type electrophotographic photosensitive member measured according to JIS C 2110 is a value of 8.2 kV or more .


(In General Formula (2), R < ¹ > -R < ¹⁰ > is respectively independent, The carbon number of a hydrogen atom, a C1-C8 alkyl group, a C6-C20 aryl group, and an alkyl group part is 1. An alkylamino group of ˜8, or an arylamino group of 6 to 20 carbon atoms in the aryl group portion, and adjacent substituents may be bonded to form a naphthalene ring.) According to claim 3, characterized in that a value within the range exposure amount of 0.2~0.8μJ / cm ² per unit area when exposing the positive charging single layer type electrophotographic photoconductor Image forming apparatus. 5. The image forming apparatus according to claim 3, wherein a charging potential when charging the positively charged single layer type electrophotographic photosensitive member is set to a value within a range of 600 to 1000V. An image forming method using the image forming apparatus according to claim 3 .