JP2013097221A - Organic photoreceptor, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic photoreceptor and an image forming apparatus for suppressing the occurrence of density unevenness in an image to be formed, and the occurrence of image defects such as black dots and fogging.SOLUTION: An organic photoreceptor has an intermediate layer on a conductive support, and an organic photosensitive layer is laminated on the intermediate layer. The intermediate layer contains a binder resin and titanium oxide particles, and the organic photosensitive layer contains a butyral resin. The titanium oxide particles have been subjected to a surface treatment with a silane coupling agent represented by the following general formula (1).

Description

  The present invention relates to an organic photoreceptor used in an electrophotographic image forming method and an image forming apparatus including the organic photoreceptor.

In recent years, there has been a demand for higher image quality in image forming apparatuses such as electrophotographic copying machines and printers.
Specifically, the demand for higher image quality includes improving density unevenness within a page or between pages.

  Here, as a photoreceptor used in an image forming apparatus such as a copying machine or a printer, an organic photoreceptor having an organic photosensitive layer containing an organic photoconductive material as a main component is widely used. Examples of such organic photoreceptors include those having an organic photosensitive layer having a single layer structure including a charge generation material and a charge transport material, and charge transport layers including a charge generation layer including a charge generation material and a charge transport material. Those having an organic photosensitive layer having a laminated structure in which layers are laminated are known. Among these, organic photoreceptors having an organic photosensitive layer having a laminated structure, particularly negatively charged organic photoreceptors that negatively charge the surface of the photoreceptor are excellent in electrophotographic characteristics and durability, and have a high degree of design freedom. Because of this, it has been widely put into practical use.

In an organic photoreceptor having a negatively charged laminated structure, an intermediate layer and an organic photosensitive layer in which a charge transport layer is formed on a charge generation layer are usually laminated on a conductive support.
In the organic photoreceptor having such a negatively charged layered structure, when the surface is negatively charged and then exposed, a charge is generated in the charge generation layer, of which negative charges (electrons) are intermediate. The holes move through the layer to the conductive support, while the holes move through the charge transport layer to the surface of the organophotoreceptor, canceling the negative charges on the surface and forming an electrostatic latent image. Therefore, the intermediate layer has an electron transporting property (moves electrons generated in the charge generation layer to the conductive support quickly) and has a hole blocking property (from the conductive support to the organic photosensitive layer). To suppress the injection of holes into the substrate).

  As a method of improving the density unevenness, it is conceivable to increase the electron transport property of the intermediate layer. However, simply increasing the electron transport property of the intermediate layer cannot sufficiently suppress the injection of holes from the conductive support to the organic photosensitive layer, that is, sufficient hole blocking property cannot be obtained. In the case where a highly sensitive charge generation material contained in the charge generation layer is used, carrier leakage generated by thermal excitation occurs, which partially reduces the surface potential of the organophotoreceptor. There is a problem that image defects such as black spots and fog occur.

On the other hand, as a method for suppressing the occurrence of image defects such as black spots and fog, for example, Patent Documents 1 and 2 disclose surface treatment agents such as aminosilane coupling agents for metal oxide particles contained in the intermediate layer. It has been proposed to carry out a surface treatment by using the
However, according to the above method, although the hole blocking property is increased and the occurrence of image defects can be suppressed, the electron transport property is decreased, and the occurrence of density unevenness within a page or between pages can be suppressed. There is a problem that you can not.

Japanese Patent Laid-Open No. 11-15184 JP 2007-57820 A

  The present invention has been made based on the above circumstances, and its purpose is to suppress the occurrence of density unevenness in the formed image and also to suppress the occurrence of image defects such as black spots and fog. An organic photoreceptor and an image forming apparatus are provided.

The organic photoreceptor of the present invention has an intermediate layer on a conductive support, and the organic photoreceptor is formed by laminating an organic photosensitive layer on the intermediate layer.
The intermediate layer contains a binder resin and titanium oxide particles,
The organic photosensitive layer contains butyral resin,
The titanium oxide particles are surface-treated with a silane coupling agent represented by the following general formula (1).

[In General Formula (1), R ¹ represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms or an acetyl group, R ² represents a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, R ³ represents a hydrogen atom or a methyl group. n shows the integer of 1-3. When n is an integer of 2 or more, two or more R ^{1 s} may be the same as or different from each other. ]

  In the organic photoreceptor of the present invention, the titanium oxide particles preferably have a number average primary particle size of 10 to 20 nm.

  In the organic photoreceptor of the present invention, the organic photosensitive layer is not added with a Y-type titanyl phthalocyanine, a 2,3-butanediol-added titanyl phthalocyanine, or a 2,3-butanediol-added titanyl phthalocyanine as a charge generating substance. It is preferable that the mixture with this titanyl phthalocyanine is contained.

  In the organic photoreceptor of the present invention, the organic photosensitive layer is preferably formed by forming a charge transport layer containing a charge transport material on a charge generation layer containing a charge generation material and a butyral resin. .

  In the organic photoreceptor of the present invention, the binder resin constituting the intermediate layer is preferably a polyamide resin.

  An image forming apparatus according to the present invention includes the above-described organic photoreceptor.

  According to the organophotoreceptor of the present invention, the titanium oxide particles contained in the intermediate layer are surfaced by a silane coupling agent represented by the general formula (1) (hereinafter also referred to as “specific silane coupling agent”). By being processed and containing the butyral resin in the organic photosensitive layer, the occurrence of density unevenness in the formed image is suppressed, and the occurrence of image defects such as black spots and fog is suppressed.

  According to the image forming apparatus of the present invention, by having the above organic photoreceptor, the occurrence of density unevenness in the formed image is suppressed, and the occurrence of image defects such as black spots and fog is suppressed.

It is sectional drawing for description which shows an example of the layer structure of the organic photoreceptor of this invention. 1 is a cross-sectional view illustrating an example of a configuration of an image forming apparatus according to the present invention. The chart used in an Example is shown.

  Hereinafter, the present invention will be described in detail.

<Organic photoconductor>
The organic photoreceptor of the present invention is a negatively charged organic photoreceptor, having an intermediate layer on a conductive support, and an organic photosensitive layer laminated on the intermediate layer.
In the present invention, the organic photosensitive layer has a function of generating charges by exposure and a function of transporting the generated charges (holes) to the surface of the photoreceptor. The organic photosensitive layer according to the present invention may have a single layer structure in which the charge generation function and the charge transport function are performed in the same layer, and a stacked structure in which the charge generation function and the charge transport function are performed in different layers. However, in order to suppress an increase in residual potential due to repeated use, it is preferable to have a stacked structure of a charge generation layer and a charge transport layer.

The layer structure of the organophotoreceptor of the present invention is not particularly limited, but specific examples include the following (1) and (2) layer structures.
(1) A laminated structure in which an intermediate layer is provided on a conductive support, and a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated on the intermediate layer in this order. A layer structure in which an organic photosensitive layer is laminated and the charge transport layer is the outermost surface layer.
(2) An organic photosensitive layer having a single layer structure containing a charge generation substance and a charge transport substance is laminated on the conductive support on the conductive support, and the organic photosensitive layer (single layer) ) Is the layer structure that becomes the outermost surface layer.
In the organic photoreceptor of the present invention, a protective layer may be formed on the organic photosensitive layer.

  In the present invention, the organic photoreceptor means a structure in which at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoreceptor is exhibited by an organic compound. Includes all known organic photoreceptors such as a photoreceptor having a photosensitive layer composed of a generating material or an organic charge transport material, and a photoreceptor having a photosensitive layer in which a charge generating function and a charge transport function are composed of a polymer complex Say.

  Hereinafter, the case where the organophotoreceptor of the present invention has the layer configuration (1) will be specifically described.

FIG. 1 is an explanatory sectional view showing an example of the layer structure of the organic photoreceptor of the present invention.
In this organic photoreceptor 10, an organic photosensitive layer 17 in which a charge generation layer 16 and a charge transport layer 18 are laminated in this order via an intermediate layer 14 is formed on a conductive support 12.

  In the organic photoreceptor 10, when the surface of the organic photoreceptor 10 is negatively charged and then exposed, charges are generated in the charge generation layer 16. Among the charges generated in the charge generation layer 16, negative charges (electrons) move to the conductive support 12 through the intermediate layer 14, and holes move to the surface of the organic photoreceptor 10 through the charge transport layer 18 and become organic. By canceling the negative charge on the surface of the photoconductor 10, an electrostatic latent image is formed on the surface of the organic photoconductor 10.

  In the present invention, since the titanium oxide particles contained in the intermediate layer 14 are surface-treated with a specific silane coupling agent, the titanium oxide particles and the butyral resin contained in the charge generation layer 16 Since the familiarity is improved and the electron transport property is increased, the occurrence of density unevenness is suppressed, and no defects are generated at the interface between the intermediate layer 14 and the charge generation layer 16, so that image defects such as black spots and fog are generated. It is thought that it can be suppressed. In addition, since the titanium oxide particles have a uniform coating with a specific silane coupling agent, it is considered that the fog transport resistance can be improved without impairing the electron transport property.

[Conductive support]
The conductive support constituting the organophotoreceptor of the present invention is not particularly limited as long as it is cylindrical or sheet-like and has conductivity. For example, aluminum, copper Metals such as chrome, nickel, zinc, and stainless steel are formed into drums or sheets. Metal foils such as aluminum and copper are laminated on plastic films. Aluminum, indium oxide, tin oxide, etc. are deposited on plastic films. Examples thereof include metals, plastic films, and papers each having a conductive layer applied alone or together with a binder resin.

  The surface of the conductive support may be subjected to sealed alumite treatment (anodization treatment) in order to suppress interference fringes (moire) generated by exposure. The alumite treatment can be usually carried out in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but is preferably carried out in a sulfuric acid bath. The alumite treatment in the sulfuric acid bath is preferably performed under the conditions of a sulfuric acid concentration of 100 to 200 g / l, an aluminum ion concentration of 1 to 10 g / l, a liquid temperature of 20 ° C., and an applied voltage of about 20V. The average film thickness of the alumite-treated film is usually preferably 20 μm or less, and more preferably 10 μm or less.

[Middle layer]
The intermediate layer constituting the organic photoreceptor of the present invention contains a binder resin (hereinafter also referred to as “binder resin for intermediate layer”) and titanium oxide particles.
The titanium oxide particles contained in the intermediate layer are those that are surface-treated with a silane coupling agent having a methacrylic structure or an acrylic structure represented by the general formula (1), that is, titanium oxide particles (hereinafter referred to as raw materials). And the surface of the "untreated titanium oxide particles") is treated with the silane coupling agent represented by the general formula (1), whereby the coating with the silane coupling agent represented by the general formula (1) Is attached.

  The intermediate layer may contain other components such as a dispersant, an antioxidant, and a leveling agent together with the binder resin for the intermediate layer and the titanium oxide particles.

(Titanium oxide particles)
The untreated titanium oxide particles used as the raw material for the titanium oxide particles according to the present invention may be of any crystal type such as anatase type, rutile type, amorphous type, etc., in order to increase the dispersibility in the intermediate layer. The rutile type is preferable.
The untreated titanium oxide particles may have any shape such as dendritic shape, needle shape, and granular shape, but in order to improve the dispersibility in the intermediate layer, the granular shape is preferable.

In the present invention, the reason why the intermediate layer contains titanium oxide particles surface-treated with a specific silane coupling agent is not necessarily clear, but is considered as follows.
That is, by using a specific silane coupling agent having a methacrylic structure or an acrylic structure, the familiarity between the titanium oxide particles and the butyral resin contained in the charge generation layer is improved, and the electron transport property is increased. Image defects such as black spots and fogging are suppressed because the occurrence of unevenness is suppressed, and because the titanium oxide particles contained in the intermediate layer are uniformly dispersed, no defects occur at the interface between the intermediate layer and the charge generation layer. It is considered that the occurrence of the occurrence can be suppressed. Moreover, since the surface of untreated titanium oxide particles can be uniformly coated with a thin film by using a specific silane coupling agent, it is considered that the fog transport resistance can be improved without impairing the electron transport property. .

In the general formula (1), R ¹ represents an aliphatic hydrocarbon group or an acetyl group having 1 to 3 carbon atoms, preferably a methyl group, an ethyl group.

R ² represents a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, preferably a divalent aliphatic hydrocarbon group having 2 to 4 carbon atoms.

R ³ represents a hydrogen atom or a methyl group, preferably a methyl group.

n shows the integer of 1-3. When n is an integer of 2 or more, two or more R ^{1 s} may be the same or different from each other.

  Specific examples of such a specific silane coupling agent include 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyl. Examples include triethoxysilane, 2-methacryloxyethyltrimethoxysilane, 3-methacryloxybutylmethyldimethoxysilane, and 3-acryloxypropyltrimethoxysilane.

  In order not to impair the electron transport property of the intermediate layer, the adhesion amount of the specific silane coupling agent to the untreated titanium oxide particles is preferably 20% by mass or less based on the untreated titanium oxide particles, and 15% by mass. % Or less is more preferable. Moreover, in order to suppress fogging, the adhesion amount of the specific silane coupling agent is preferably 2% by mass or more, and more preferably 5% by mass or more with respect to the untreated titanium oxide particles.

The adhesion amount of the specific silane coupling agent can be determined from the amount of decrease in the mass of the titanium oxide particles in the ignition loss test of the surface-treated titanium oxide particles.
The ignition loss test can be performed, for example, under conditions of heating at 700 to 800 ° C. in an electric muffle furnace.

The surface treatment method using a specific silane coupling agent is not particularly limited, and wet treatment or dry treatment can be employed.
Specifically, as a surface treatment method by wet treatment, a solution in which untreated titanium oxide particles and a specific silane coupling agent are dispersed in a solvent is mixed and stirred at a predetermined temperature, and then the solvent is removed. Then, the surface-treated titanium oxide particles can be obtained by annealing.
The temperature during mixing and stirring is preferably about 30 to 150 ° C., and the mixing and stirring time is preferably 0.5 to 10 hours. The annealing treatment temperature can be set to 120 to 220 ° C., for example.

In the surface treatment method as described above, the addition amount of the specific silane coupling agent is 2 to 20 parts by mass with respect to 100 parts by mass of the untreated titanium oxide particles, and the addition amount of the solvent is 100% of the untreated titanium oxide particles. It is preferable that it is 5-15 mass parts with respect to a mass part.
When the amount of the specific silane coupling agent is too small, sufficient surface treatment is not performed on the untreated titanium oxide particles, and the hole blocking property of the intermediate layer is lowered, thereby causing black spots and fog. The occurrence of image defects such as these may not be sufficiently suppressed. On the other hand, when the amount of the specific silane coupling agent added is excessive, the silane coupling agents react with each other, and a uniform film is not attached to the surface of the untreated titanium oxide particles. There is a risk.

In the present invention, the titanium oxide particles are preferably those in which the surface of the untreated titanium oxide particles is completely covered with a coating with a silane coupling agent represented by the general formula (1).
In addition, since the surface of the untreated titanium oxide particles is directly surface-treated with a specific silane coupling agent, the coating with the specific silane coupling agent is directly applied to the surface of the untreated titanium oxide particles. As long as it has been adhered, it may be further subjected to surface treatment with another surface treatment agent so that a film with the other surface treatment agent is adhered thereto. That is, the titanium oxide particles may have a structure in which coatings of the plurality of surface treatment agents are laminated by being surface-treated with a plurality of surface treatment agents. The film in contact with the surface of the treated titanium oxide particles may be formed of a specific silane coupling agent.

Preferable examples of other surface treatment agents include inorganic compounds, reactive organosilicon compounds other than specific silane coupling agents, and the like.
Examples of the inorganic compound include alumina, silica, zirconia and hydrates thereof.
Examples of the reactive organosilicon compound include alkoxysilanes such as methyltrimethoxysilane, n-butyltrimethoxysilane, n-hexyltrimethoxysilane, and dimethyldimethoxysilane; and methylhydrogenpolysiloxane.
The surface treatment with the reactive organosilicon compound can effectively enhance the dispersibility of the titanium oxide particles.

The surface treatment method using another surface treatment agent can be performed by a known method.
For example, in the surface treatment with a reactive organosilicon compound, titanium oxide particles are added to a solution in which the reactive organosilicon compound is dispersed in water or an organic solvent, mixed and stirred, and the resulting solution is filtered and dried. Can be done.

The titanium oxide particles preferably have a number average primary particle size of 10 to 20 nm.
When the number average primary particle diameter of the titanium oxide particles is less than 10 nm, the generation of image defects such as black spots and fog cannot be sufficiently suppressed because the electron transport property becomes too high or the dispersibility is impaired. There is a fear. On the other hand, when the number average primary particle diameter of the titanium oxide particles exceeds 20 nm, there is a possibility that the occurrence of density unevenness cannot be sufficiently suppressed because the electron transport property is impaired.

In the present invention, the number average primary particle diameter of the titanium oxide particles is measured as follows.
That is, a TEM (transmission electron microscope) image of titanium oxide particles is observed at a magnification of 100,000, and 100 particles are randomly selected as primary particles. The average diameter in the ferret direction of these primary particles is measured by image analysis, and the average value thereof is obtained as “number average primary particle diameter”.

(Binder resin for intermediate layer)
Examples of the intermediate layer binder resin include polyamide resin, vinyl chloride resin, and vinyl acetate resin. Among these, from the viewpoint of suppressing dissolution of the intermediate layer when applying a coating solution for forming the charge generation layer on the intermediate layer, a polyamide resin is preferable, and alcohol-soluble such as methoxymethylolated polyamide resin is preferable. A polyamide resin is more preferable.

The volume ratio (T / B) of the volume (T) of the titanium oxide particles surface-treated with a specific silane coupling agent and the volume (B) of the binder resin for the intermediate layer is 0.6 to 1.3. It is preferable that it is 0.6 to 1.1.
In the case where the volume ratio (T / B) is less than 0.6, there is a possibility that the occurrence of density unevenness cannot be sufficiently suppressed due to a decrease in the electron transport property of the intermediate layer. On the other hand, when the volume ratio (T / B) exceeds 1.3, the occurrence of image defects such as black spots and fog cannot be sufficiently suppressed due to a decrease in the hole blocking property of the intermediate layer. There is a fear.

The volume ratio (T / B) can be measured by TGA (calorimeter measuring device) by the following method.
(1) The specific gravity of the titanium oxide particles is measured using a true specific gravity meter (Micropycnometer, manufactured by STEC Co.). The specific gravity of the intermediate layer binder resin is determined by measuring the weight of the molded piece and then measuring the excluded volume by placing the molded piece in water of known volume.
(2) On the other hand, a mixture of titanium oxide particles and an intermediate layer binder resin is prepared as a measurement sample. Next, 5 mg of a measurement sample was weighed in an aluminum sample pan, and using a differential thermogravimetric simultaneous measurement apparatus “TG / DTA6200” (manufactured by Seiko Instruments Inc.), under a nitrogen gas atmosphere (introduction amount: 150 to 200 ml / min), The amount of reduction is measured with a heating weight reduction curve at a temperature elevation temperature of 20 ° C./min. The weight of the binder resin for the intermediate layer is determined from the first stage heating weight reduction amount, and the titanium oxide particle weight is determined from the residual weight at that time.
(3) From the specific gravity obtained in (1) and the weight obtained in (2) of the titanium oxide particles and the binder resin for the intermediate layer, the volumes of the titanium oxide particles and the binder resin for the intermediate layer were respectively determined. calculate. Thereby, the volume ratio (T / B) is calculated.

The thickness of the intermediate layer is preferably 0.5 to 15 μm, and more preferably 1 to 7 μm.
When the film thickness of the intermediate layer is too small, the entire surface of the conductive support cannot be covered, and the injection of holes from the conductive support cannot be sufficiently blocked. The occurrence of image defects such as fog and fog may not be sufficiently suppressed. On the other hand, when the film thickness of the intermediate layer is excessive, the electrical resistance increases, so that sufficient electron transportability cannot be obtained, so that the occurrence of density unevenness may not be sufficiently suppressed. .

[Organic photosensitive layer]
(Charge generation layer)
The charge generation layer in the organic photosensitive layer constituting the organic photoreceptor of the present invention comprises a charge generation material and a butyral resin as a binder resin.

(Charge generating material)
Examples of the charge generating substance include phthalocyanine pigments, azo pigments, perylene pigments, and azulenium pigments.
The charge generation material may be selected according to the sensitivity to the oscillation wavelength of the exposure light source, but a phthalocyanine pigment is preferable in order to increase the sensitivity to the oscillation wavelength of the exposure light source in the digital copying machine.

  As the phthalocyanine pigment, it is preferable to use Y-type titanyl phthalocyanine or butanediol-added titanyl phthalocyanine in order to increase sensitivity to the oscillation wavelength of the exposure light source, for example, a wavelength of 780 nm.

  Y-type titanyl phthalocyanine has a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-rays.

  Examples of the butanediol-added titanyl phthalocyanine include 2,3-butanediol-added titanyl phthalocyanine. The structure of this 2,3-butanediol-added titanyl phthalocyanine is schematically shown in the following formula (1).

  2,3-butanediol-added titanyl phthalocyanine can take different crystal forms depending on the addition ratio of butanediol. In order to obtain good sensitivity, a crystalline type obtained by reacting 1 mol of butanediol compound with 1 mol or less of 1 mol of titanyl phthalocyanine is preferable. The 2,3-butanediol-added titanyl phthalocyanine having such a crystal form has a characteristic peak in a powder X-ray diffraction spectrum at least at a Bragg angle (2θ ± 0.2 °) of 8.3 °. This 2,3-butanediol-added titanyl phthalocyanine has peaks at 24.7 °, 25.1 °, and 26.5 ° in addition to 8.3 °.

  The butanediol-added titanyl phthalocyanine may be included alone or may be included together with the non-added titanyl phthalocyanine.

  As the charge generation material, a mixture of 2,3-butanediol-added titanyl phthalocyanine and non-added titanyl phthalocyanine can also be used. Absorbance Abs (780) at a wavelength of 780 nm and absorbance Abs at a wavelength of 700 nm of the organic photosensitive layer obtained by conversion from the relative reflection spectrum of an organic photoreceptor having an organic photosensitive layer (charge generation layer) containing this mixture. )) (Abs (780) / Abs (700)) is preferably 0.8 to 1.1.

The absorbance ratio (Abs (780) / Abs (700)) can be determined as follows.
(1) First, a photoreceptor sample is prepared in which an organic photosensitive layer containing a mixture of 2,3-butanediol-added titanyl phthalocyanine and non-added titanyl phthalocyanine is formed on an aluminum support. Then, the absorption spectrum of the relative reflected light of the photoconductor sample is measured. The absorption spectrum of the reflected light can be measured using an optical film thickness measuring device “Solid Lambda Thickness” (Spectra Corp.).
That is, first, the reflection intensity of the aluminum support at each wavelength is measured as a baseline. Next, the reflection intensity of the photoreceptor sample at each wavelength is measured. A value obtained by dividing the reflection intensity of the photosensitive member sample at each wavelength by the reflection intensity of the aluminum support at each wavelength is defined as “relative reflectance (R _λ )”. Thereby, a relative reflection spectrum is obtained.
(2) Next, the relative reflection spectrum of the obtained photoreceptor sample is converted into an absorbance spectrum by the following formula (A).
Formula (A): Absλ = −log (R _λ )
[In formula (A), R _λ represents a relative reflectance obtained by dividing the reflection intensity of the photosensitive member sample at the wavelength λ by the reflection intensity of the aluminum support at the wavelength λ. ]
(3) Next, in order to remove unevenness due to interference fringes, the absorbance spectrum data converted in (2) above is approximated to a second order polynomial in each of the wavelength region 765 to 795 nm and the wavelength region 685 to 715 nm.
(4) Then, the absorbance Abs (780) at a wavelength of 780 nm and the absorbance Abs (700) at a wavelength of 700 nm in an approximated second order polynomial are obtained. Thereby, the absorbance ratio (Abs (780) / Abs (700)) is calculated.

Butanediol-added titanyl phthalocyanine is obtained by conversion from the relative reflection spectrum of an organic photoreceptor provided with an organic photosensitive layer (charge generation layer) containing the same. Absorbance Abs (780) and wavelength at a wavelength of 780 nm of the organic photosensitive layer. The absorbance ratio (Abs (780) / Abs (700)) to the absorbance Abs (700) at 700 nm is preferably 0.8 to 1.1. When the absorbance ratio (Abs (780) / Abs (700)) of the organic photosensitive layer containing butanediol-added titanyl phthalocyanine is within the above range, the pigment crystals are easily stabilized by an appropriate dispersion share, Image characteristics by repeated exposure are stabilized.
The absorbance ratio of the organic photosensitive layer containing butanediol-added titanyl phthalocyanine can be measured in the same manner as described above.

(Butyral resin)
Examples of the butyral resin include polyvinyl butyral resin and silicone-modified butyral resin. Two or more different butyral resins may be mixed. In addition to the butyral resin, a polyvinyl acetal resin or the like may be contained, but the content of the other resin is preferably 40% by volume or less with respect to the butyral resin.
The degree of butyralization of the butyral resin is preferably 50 mol% or more.
Although there is no restriction | limiting in particular as molecular weight of a butyral resin, It is preferable that it is 10,000-150,000, More preferably, it is 15000-100,000.

The content of the charge generation material is preferably 20 to 600 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the butyral resin.
When the content of the charge generation material is too small, sufficient charge cannot be generated by exposure, and the sensitivity of the organic photosensitive layer (charge generation layer) may be reduced. On the other hand, when the content of the charge generation material is excessive, the sensitivity of the organic photosensitive layer (charge generation layer) becomes excessively high, so that the residual potential tends to increase with repeated use.

  The layer thickness of the charge generation layer varies depending on the characteristics of the charge generation material, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm.

(Charge transport layer)
The charge transport layer in the organic photosensitive layer constituting the organic photoreceptor of the present invention is composed of a charge transport material and a binder resin (hereinafter also referred to as “binder resin for charge transport layer”).

(Charge transport material)
Examples of the charge transport material include a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, and a butadiene compound as a material that transports charges (holes).

(Binder resin for charge transport layer)
The binder resin for charge transport layer may be a thermoplastic resin or a thermosetting resin. Specific examples include polyester resin, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and the like. Among these, a polycarbonate resin is preferable because the water absorption is low and the charge transport material can be dispersed well.

  The charge transport layer may contain other components such as an antioxidant as necessary.

The content of the charge transport material is preferably 10 to 200 parts by weight and more preferably 20 to 100 parts by weight with respect to 100 parts by weight of the charge transport layer binder resin.
When the content of the charge transporting material is too small, the charge transporting property is not sufficient, so that the charge generated in the charge generation layer may not be sufficiently transported to the surface of the organic photoreceptor. On the other hand, when the content of the charge transport material is excessive, an increase in residual potential due to repeated use tends to be remarkable.

  The thickness of the charge transport layer is not particularly limited, but can be about 10 to 40 μm.

[Protective layer]
In the organic photoreceptor of the present invention, when a protective layer is formed, the protective layer is composed of inorganic particles and a binder resin (hereinafter referred to as “binder resin for protective layer”), and if necessary. In addition, other components such as antioxidants and lubricants may be contained.

  Inorganic particles contained in the protective layer include silica, alumina, strontium titanate, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony and tantalum-doped oxide. Particles such as tin and zirconium oxide can be preferably used. In particular, hydrophobic silica, hydrophobic alumina, hydrophobic zirconia, fine powder sintered silica and the like whose surface has been hydrophobized are preferable.

The inorganic particles preferably have a number average primary particle size of 1 to 300 nm, particularly preferably 5 to 100 nm.
The number average primary particle diameter of the inorganic particles is magnified 10,000 times with a transmission electron microscope, 300 particles are randomly observed as primary particles, and the measured value is calculated as the number average diameter of the ferret diameter by image analysis. The obtained value.

  The binder resin for the protective layer may be a thermoplastic resin or a thermosetting resin. For example, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin and the like can be mentioned.

  Examples of the lubricant contained in the protective layer include resin fine powder (for example, fluorine resin, polyolefin resin, silicone resin, melamine resin, urea resin, acrylic resin, styrene resin, etc.), metal oxide fine powder (for example, , Titanium oxide, aluminum oxide, tin oxide, etc.), solid lubricant (eg, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, zinc stearate, aluminum stearate, etc.), silicone oil (eg, dimethyl silicone) Oil, methylphenyl silicone oil, methyl hydrogen polysiloxane, cyclic dimethylpolysiloxane, alkyl-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, fluorine-modified silicone oil, amino-modified silicone Corn oil, mercapto-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, higher fatty acid-modified silicone oil, etc.), fluorine-based resin powder (for example, tetrafluoroethylene resin powder, trifluorinated ethylene chloride resin powder) , Hexafluoroethylene propylene resin powder, vinyl fluoride resin powder, vinylidene fluoride resin powder, fluorinated ethylene chloride resin powder and copolymers thereof, polyolefin resin powder (for example, polyethylene) Homopolymer resin powder such as resin powder, polypropylene resin powder, polybutene resin powder, polyhexene resin powder, copolymer resin powder such as ethylene-propylene copolymer, ethylene-butene copolymer, hexene and the like Terpolymers of these, as well as Fin-based resin powder, etc.) and the like.

  The molecular weight of the resin used as the lubricant and the particle size of the powder are appropriately selected. The particle size of the resin is particularly preferably 0.1 μm to 10 μm. In order to disperse these lubricants uniformly, a dispersant may be further added to the protective layer binder resin.

[Method for producing organic photoreceptor]
The organic photoreceptor of the present invention can be produced, for example, by the following steps (1) to (2).
(1) Step of forming the intermediate layer In the step of forming the intermediate layer, a coating solution for forming the intermediate layer is prepared by adding titanium oxide particles to a solution obtained by dissolving the binder resin for the intermediate layer in the solvent. The coating liquid for forming is applied to the conductive support by, for example, a dip coating method to form a coating film, and this coating film is dried to form an intermediate layer.

  Examples of the solvent used for forming the intermediate layer include alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol, and the like. From the viewpoints of solubility and coating properties, it is particularly preferable. Examples of the co-solvent that can be used in combination with the above-described solvent in order to improve the storage stability and the dispersibility of the titanium oxide particles include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

(2-1) Step of forming a charge generation layer constituting an organic photosensitive layer In the step of forming a charge generation layer, a charge generator is dispersed by using a disperser in a solution in which a butyral resin is dissolved in a solvent. A coating solution for generating the generation layer is prepared, and the coating solution for forming the charge generation layer is applied onto the intermediate layer by, for example, a dip coating method to form a coating film, and the coating layer is formed by drying the coating film. Is done.

  Examples of the solvent used for forming the charge generation layer include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, Examples include, but are not limited to, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, diethylamine and the like.

  The means for dispersing the charge generating material is not particularly limited, and examples thereof include a dispersing machine such as an ultrasonic dispersing machine, a ball mill, a sand grinder, and a homomixer.

(2-2) Step of forming a charge transport layer constituting an organic photosensitive layer In the step of forming a charge transport layer, a charge transport layer forming coating solution is prepared by dissolving a charge transport layer binder resin and a charge transport material in a solvent. The charge transport layer forming coating solution is applied onto the charge generation layer by, for example, a dip coating method to form a coating film, and the coating film is dried to form the charge transport layer.

  Examples of the solvent used for forming the charge transport layer include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, 1 , 4-dioxane, 1,3-dioxolane, pyridine, diethylamine and the like, but are not limited thereto.

  In addition to the dip coating method, a coating method using a slide hopper type coating device or a coating method such as spray coating can be adopted as a coating method of various coating solutions for producing the organic photoreceptor of the present invention. . A coating method using a slide hopper type coating apparatus is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.

As described above, according to the organic photoreceptor of the present invention, the titanium oxide particles contained in the intermediate layer are surface-treated with a specific silane coupling agent, and the organic photosensitive layer contains a butyral resin. As a result, the occurrence of density unevenness in the formed image is suppressed, and the occurrence of image defects such as black spots and fog is suppressed.

<Image forming apparatus>
The image forming apparatus of the present invention has at least the organic photoreceptor of the present invention.
FIG. 2 is an explanatory sectional view showing an example of the configuration of the image forming apparatus of the present invention.
The image forming apparatus 100 is a tandem type color image forming apparatus, and includes four sets of image forming units 110Y, 110M, 110C, and 110Bk, an endless belt-shaped intermediate transfer body unit 130, a paper feeding / conveying means 150, Fixing means 170. A document image reading device SC is arranged on the upper part of the main body of the image forming apparatus 100.

  The image forming units 110Y, 110M, 110C, and 110Bk are arranged side by side in the vertical direction. The image forming units 110Y, 110M, 110C, and 110Bk include organic photoreceptors 111Y, 111M, 111C, and 111Bk that are first image carriers, and charging units 113Y and 113M that are sequentially arranged around the periphery in the rotation direction of the drum. 113C, 113Bk, exposure means 115Y, 115M, 115C, 115Bk, developing means 117Y, 117M, 117C, 117Bk, and cleaning means 119Y, 119M, 119C, 119Bk. Then, yellow (Y), magenta (M), cyan (C), and black (Bk) toner images can be formed on the organic photoreceptors 111Y, 111M, 111C, and 111Bk, respectively. Since the image forming units 110Y, 110M, 110C, and 110Bk are configured in the same manner except that the colors of toner images formed on the organic photoreceptors 111Y, 111M, 111C, and 111Bk are different, the image forming unit 110Y will be described below. To do.

  The organophotoreceptor 111Y is an organophotoreceptor according to the present invention, and an intermediate layer constituting the organophotoreceptor contains titanium oxide particles surface-treated with a specific silane coupling agent, The photosensitive layer contains a butyral resin.

The charging unit 113Y is a unit that applies a uniform potential to the organic photoreceptor 111Y.
In the present embodiment, a corona discharge type charger is preferably used as the charging means 113Y.

  The exposure unit 115Y performs exposure based on an image signal (yellow image signal) on the organic photoreceptor 111Y to which a uniform potential is applied by the charging unit 113Y, and generates an electrostatic latent image corresponding to the yellow image. Has the function of forming. The exposure means 115Y can be composed of an LED in which light emitting elements are arrayed in the axial direction of the organic photoreceptor 111Y and an imaging element, or a laser optical system.

  The exposure light source is preferably a semiconductor laser or light emitting diode whose oscillation wavelength is in the range of 50% or more of the maximum absorbance of the charge generating material used. For example, when a mixture of 2,3-butanediol-added titanyl phthalocyanine and non-added titanyl phthalocyanine is used as the charge generating material, the thickness is preferably 650 to 800 nm. By using these exposure light sources, the exposure dot diameter in the writing direction is narrowed to 10 to 100 μm, and digital exposure is performed on the photosensitive member, so that 600 dpi (dpi: number of dots per 2.54 cm) to 2400 dpi or more The above high-resolution electrophotographic image can be formed.

The exposure dot diameter indicates the length of the exposure beam in the main scanning direction (Ld: measured at the maximum position) in the region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The developing unit 117Y is configured to supply toner to the organic photoreceptor 111Y and develop the electrostatic latent image formed on the surface of the organic photoreceptor 111Y.
The cleaning unit 119Y may have a roller or a blade that is in pressure contact with the surface of the organic photoreceptor 111Y.

  The endless belt-shaped intermediate transfer body unit 130 is provided so as to be in contact with the organic photoreceptors 111Y, 111M, 111C, and 111Bk. The endless belt-shaped intermediate transfer body unit 130 includes an endless belt-shaped intermediate transfer body 131 that is a second image carrier, and primary transfer rollers 133Y, 133M, and 133C disposed in contact with the endless belt-shaped intermediate transfer body 131. 133Bk and a cleaning means 135 for the endless belt-shaped intermediate transfer member 131.

  The endless belt-shaped intermediate transfer member 131 is wound around a plurality of rollers 137A, 137B, 137C, and 137D and is rotatably supported.

  In this image forming apparatus 100, the above-mentioned organic photoreceptor 111Y, developing means 117Y, cleaning means 119Y and the like are a process cartridge (image forming unit) which is integrally coupled and detachably attached to the apparatus main body. Also good. Alternatively, a process cartridge (image forming unit) in which one or more members selected from the group consisting of a charging unit 113Y, an exposure unit 115Y, a developing unit 117Y, a primary transfer roller 133Y, and a cleaning unit 119Y and the organic photoreceptor 111Y are integrally formed. Unit).

  The process cartridge 200 includes a casing 201, an organic photoreceptor 111 </ b> Y, a charging unit 113 </ b> Y, a developing unit 117 </ b> Y, a cleaning unit 119 </ b> Y accommodated therein, and an endless belt-shaped intermediate transfer body unit 130. The apparatus main body is provided with support rails 203L and 203R as means for guiding the process cartridge 200 into the apparatus main body. Thereby, the process cartridge 200 can be attached to and detached from the apparatus main body. These process cartridges 200 can be a single image forming unit configured to be detachable from the apparatus main body.

  The sheet feeding / conveying means 150 is provided so that the transfer material P in the sheet feeding cassette 211 can be conveyed to the secondary transfer roller 217 via a plurality of intermediate rollers 213A, 213B, 213C, 213D and a registration roller 215.

  The fixing unit 170 fixes the color image transferred by the secondary transfer roller 217. The paper discharge roller 219 is provided so as to be able to be placed on a paper discharge tray 221 provided outside the image forming apparatus with the transfer material P subjected to fixing processing interposed therebetween.

  In the image forming apparatus 100 configured as described above, an image is formed by the image forming units 110Y, 110M, 110C, and 110Bk. Specifically, the charging means 113Y, 113M, 113C, and 113Bk charge the surface of the organic photoreceptors 111Y, 111M, 111C, and 111Bk by corona discharge to be negatively charged. Next, the surface of the organic photoreceptors 111Y, 111M, 111C, and 111Bk is exposed based on the image signal by the exposure means 115Y, 115M, 115C, and 115Bk, and an electrostatic latent image is formed. Next, toner is applied to the surface of the organic photoreceptors 111Y, 111M, 111C, and 111Bk by the developing means 117Y, 117M, 117C, and 117Bk, and developed.

  Next, primary transfer rollers (primary transfer means) 133Y, 133M, 133C, and 133Bk are brought into contact with the rotating endless belt-shaped intermediate transfer member 131. As a result, each color image formed on each of the organic photoreceptors 111Y, 111M, 111C, and 111Bk is sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 131 to transfer the color image (primary transfer). . During the image forming process, the primary transfer roller 133Bk is always in contact with the organic photoreceptor 111Bk. On the other hand, the other primary transfer rollers 133Y, 133M, and 133C are in contact with the corresponding organic photoreceptors 111Y, 111M, and 111C, respectively, only during color image formation.

  Then, after separating the primary transfer rollers 133Y, 133M, 133C, and 133Bk and the endless belt-shaped intermediate transfer body 131, the toner remaining on the surfaces of the organic photoreceptors 111Y, 111M, 111C, and 111Bk is cleaned with the cleaning units 119Y and 119M. 119C and 119Bk. In preparation for the next image formation, the surfaces of the organic photoreceptors 111Y, 111M, 111C, and 111Bk are neutralized by a neutralizing unit (not shown) as necessary, and then negatively charged by the charging units 113Y, 113M, 113C, and 113Bk. Charge.

  On the other hand, a transfer material P (for example, a support for carrying a final image such as plain paper or a transparent sheet) accommodated in a paper feed cassette 211 is fed by a paper feed / conveying means 150, and a plurality of intermediate rollers 213A and 213B are fed. 213C, 213D, and registration rollers 215, and then conveyed to a secondary transfer roller (secondary transfer means) 217. Then, the secondary transfer roller 217 is brought into contact with the rotating endless belt-shaped intermediate transfer body 131 to transfer the color image on the transfer material P in a lump (secondary transfer). The secondary transfer roller 217 contacts the endless belt-shaped intermediate transfer body 131 only when performing secondary transfer on the transfer material P. Thereafter, the transfer material P on which the color images are collectively transferred is separated at a portion where the curvature of the endless belt-shaped intermediate transfer body 131 is high.

  The transfer material P onto which the color images have been transferred in this way is fixed by the fixing unit 170 and then sandwiched by the paper discharge roller 219 and placed on the paper discharge tray 221 outside the apparatus. Further, after separating the transfer material P onto which the color image has been collectively transferred from the endless belt-shaped intermediate transfer body 131, the residual toner on the endless belt-shaped intermediate transfer body 131 is removed by the cleaning unit 135.

As described above, the intermediate layers of the organic photoreceptors 111Y, 111M, 111C, and 111Bk included in the image forming apparatus 100 of the present embodiment have sufficient electron transport properties. for that reason,
An increase in the residual potential on the surface of the organic photoconductors 111Y, 111M, 111C, and 111Bk can be suppressed, and the density unevenness of the image can be reduced. Furthermore, the intermediate layers of the organic photoreceptors 111Y, 111M, 111C, and 111Bk included in the image forming apparatus 100 have high hole blocking properties. Therefore, even in the organic photoconductors 111Y, 111M, 111C, and 111Bk having a particularly sensitive charge generation layer, unnecessary holes are injected from the conductive support and unnecessary thermally excited carriers are moved from the charge generation layer. Image defects such as black spots and fog can be suppressed.

  According to the image forming apparatus 100 of the present invention, by having the organic photoconductors 111Y, 111M, 111C, and 111Bk of the present invention, the occurrence of density unevenness in the formed image is suppressed, and black spots, fog, etc. Generation of image defects is suppressed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example.

[Organic photoconductor production example 1]
By the following procedure, an organic photoreceptor [1] having a laminated structure in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially formed on a conductive support was produced.

(1) Production of conductive support An aluminum alloy element tube having a length of 362 ± 0.2 mm is mounted on an NC _lathe , and an outer diameter of 59.95 ± 0.04 mm and a surface Rz _jis with a diamond sintered tool. Was cut to a thickness of 1.2 ± 0.2 μm to produce a conductive support [1].

(2) Production of Titanium Oxide Particles 100 parts by mass of rutile titanium oxide particles having a number average primary particle size of 15 nm are mixed with 500 parts by mass of toluene, and 3-methacryloxy is used as a silane coupling agent represented by the general formula (1). 9.5 parts by mass of propyltrimethoxysilane “KBM-503” (manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred at 50 ° C. for 2 hours. Thereafter, toluene was distilled off under reduced pressure and baked at 130 ° C. for 3 hours to obtain titanium oxide particles [1] surface-treated with the silane coupling agent represented by the general formula (1). The true specific gravity of the titanium oxide particles [1] was 3.8. Moreover, it confirmed that the number average primary particle diameter of this titanium oxide particle [1] was 16 nm from the TEM image.

(3) Formation of intermediate layer 1 part by mass of a polyamide resin represented by the following formula (N-1) as a binder resin was mixed with a mixed solvent 20 of ethanol / n-propyl alcohol / tetrahydrofuran (volume ratio; 45/20/35). In addition to parts by mass, the mixture was stirred and mixed at 20 ° C. To this solution, 3.4 parts by mass of titanium oxide particles [1] was added and dispersed by a bead mill with a mill residence time of 4 hours. And after leaving this solution still for a whole day and night, the intermediate layer forming coating solution [1] was prepared by filtering. Filtration was performed under a pressure of 50 kPa using a “rigid mesh filter” (manufactured by Nippon Pole Co., Ltd.) having a nominal filtration accuracy of 5 μm as a filtration filter. The intermediate layer-forming coating solution [1] thus obtained is applied to the outer periphery after washing the conductive support [1] by a dip coating method to form a coating film. An intermediate layer [1] having a layer thickness of 2 μm was formed by drying at 30 ° C. for 30 minutes. In the obtained intermediate layer [1], the volume ratio (T / B) between the titanium oxide particles [1] and the binder resin was 0.8.

(4) Formation of charge generation layer (4-1) Synthesis of charge generation material Crude titanyl phthalocyanine was synthesized from 1,3-diiminoisoindoline and titanium tetra-n-butoxide. A solution in which the obtained crude titanyl phthalocyanine was dissolved in sulfuric acid was poured into water to precipitate crystals. After filtering this solution, the obtained crystals were sufficiently washed with water to obtain a wet paste product. Next, the wet paste product was frozen in a freezer, thawed again, filtered and dried to obtain amorphous titanyl phthalocyanine.
The obtained amorphous titanyl phthalocyanine and (2R, 3R) -2,3-butanediol have an equivalent ratio of (2R, 3R) -2,3-butanediol to amorphous titanyl phthalocyanine of 0.6. As such, it was mixed in orthodichlorobenzene (ODB). The obtained mixture was heated and stirred at 60 to 70 ° C. for 6 hours. The resulting solution was allowed to stand overnight, and methanol was further added to precipitate crystals. After filtering this solution, the obtained crystal was washed with methanol to obtain a charge generating material [CGM-1] containing (2R, 3R) -2,3-butanediol-added titanyl phthalocyanine.
As a result of measuring the X-ray diffraction spectrum of the charge generation material [CGM-1], peaks were observed at 8.3 °, 24.7 °, 25.1 °, and 26.5 °. This charge generation material [CGM-1] was estimated to be a mixture of a 1: 1 adduct of titanyl phthalocyanine and (2R, 3R) -2,3-butanediol and titanyl phthalocyanine (non-adduct). .

(4-2) Formation of Charge Generation Layer The following components were mixed, and a circulating ultrasonic homogenizer “RUS-600TCVP” (manufactured by Nippon Seiki Seisakusho Co., Ltd., 19.5 kHz, 600 W) at a circulating flow rate of 40 L / H was set to 0.00. The coating solution [1] for forming a charge generation layer was prepared by dispersing for 5 hours. Then, the coating solution [1] for forming the charge generation layer is applied onto the intermediate layer [1] by the dip coating method to form a coating film, and the coating film is dried to generate a charge having a layer thickness of 0.5 μm. Layer [1] was formed.
Charge generation material: Charge generation material [CGM-1] 24 parts by mass Binder resin: Polyvinyl butyral resin “ESREC BL-1” (manufactured by Sekisui Chemical Co., Ltd.)
12 parts by mass Solvent: methyl ethyl ketone / cyclohexanone (volume ratio; 4/1) 400 parts by mass

(5) Formation of charge transport layer The following components were mixed to prepare a charge transport layer forming coating solution [1]. The charge transport layer forming coating solution [1] is applied onto the charge generation layer [1] by a dip coating method to form a coating film, and the coating film is dried to form a charge transport layer [1] having a thickness of 25 μm. Formed.
Charge transport material: Compound represented by the following formula (CTM-1) 225 parts by mass Binder resin: Polycarbonate “Z300 (manufactured by Mitsubishi Gas Chemical)” 300 parts by mass Antioxidant: “Irganox 1010” (manufactured by Ciba Geigy Japan) 6 mass Part Solvent: Tetrahydrofuran / toluene mixture (volume ratio; 3/1) 2000 parts by mass Leveling agent: Silicone oil “KF-54” (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass

The relative reflection spectrum of the produced organic photoreceptor [1] was measured by the following procedure using an optical film thickness measuring device “Solid Lambda Thickness” (manufactured by Spectra Corp.).
(1) First, the reflection intensity of the aluminum support at each wavelength was measured as a baseline. Next, the reflection intensity of the organic photoreceptor sample at each wavelength was measured. Then, a relative reflection spectrum was obtained by setting a value obtained by dividing the reflection intensity of the organic photoreceptor sample at each wavelength by the reflection intensity of the aluminum support as “relative reflectance (Rλ)”.
(2) The relative reflection spectrum of the obtained organic photoreceptor sample was converted to an absorbance spectrum by the following formula (A).
Formula (A): Absλ = −log (R _λ )
[In formula (A), R _λ represents a relative reflectance obtained by dividing the reflection intensity of the photosensitive member sample at the wavelength λ by the reflection intensity of the aluminum support at the wavelength λ. ]
(3) Next, in order to remove unevenness due to interference fringes, the absorbance spectrum data converted in (2) above was approximated to a second order polynomial in each of the wavelength region 765 to 795 nm and the wavelength region 685 to 715 nm.
(4) Absorbance Abs (780) at a wavelength of 780 nm and absorbance Abs (700) at a wavelength of 700 nm in an approximated second-order polynomial were obtained, and the absorbance ratio (Abs (780) / Abs (700)) was calculated. The obtained absorbance ratio (Abs (780) / Abs (700)) was 0.99.

[Organic photoconductor production example 2]
In the production of titanium oxide particles in (2) production of the organic photoreceptor, “rutile titanium oxide particles having a number average primary particle diameter of 15 nm” were changed to “rutile titanium oxide particles having a number average primary particle diameter of 35 nm”. Further, titanium oxide particles [2] were obtained in the same manner except that the amount of 3-methacryloxypropyltrimethoxysilane added was changed to 8 parts by mass, and (3) intermediate layer in Production Example 1 of the organic photoconductor The organophotoreceptor [2] was prepared in the same manner except that “titanium oxide particles [1] 3.4 parts by mass” was changed to “titanium oxide particles [2] 3 parts by mass”.

[Organic photoconductor production example 3]
The organic photoreceptor [3] was prepared in the same manner as in (3) Formation of the intermediate layer in Production Example 1 of the organic photoreceptor, except that the titanium oxide particles [1] were changed to the titanium oxide particles [3] shown below. Produced.

(Preparation of titanium oxide particles [3])
(2) 500 parts by mass of titanium oxide particles (1) obtained in the production of titanium oxide particles in Production Example 1 of the organic photoreceptor, 30 parts by mass of methyl hydrogen polysiloxane (MHPS), and 1500 parts by mass of toluene. After stirring and mixing, wet crushing treatment was performed with a bead mill under conditions of a mill residence time of 25 minutes and a temperature of 35 ± 5 ° C. Toluene was separated and removed from the slurry obtained by the wet crushing treatment by vacuum distillation using a kneader (bath temperature: 110 ° C., product temperature: 30 to 60 ° C., vacuum degree: about 100 Torr). The obtained dried product was baked with methylhydrogenpolysiloxane at 120 ° C. for 2 hours. The powder obtained after the baking treatment was cooled to room temperature and then pulverized with a pin mill to obtain titanium oxide particles [3] surface-treated with the silane coupling agent represented by the general formula (1) and MHPS. .

[Production Examples 4 to 6 of the organic photoreceptor]
In the production of the titanium oxide particles in (2) Production of organic photoreceptor 1 in Example 1, except that “3-methacryloxypropyltrimethoxysilane 9.5 parts by mass” is changed to those shown in Table 1 and the addition amount. Titanium oxide particles [4] to [6] were obtained, and in the formation of the intermediate layer (3) in Production Example 1 of the organic photoreceptor, the titanium oxide particles [1] were changed to titanium oxide particles [4] to [6], respectively. Organic photoreceptors [4] to [6] were prepared in the same manner except that the above was changed.

[Organic photoconductor production example 7]
(4) In formation of the charge generating layer in Production Example 1 of the organophotoreceptor, except that the charge generating layer forming coating solution [1] was changed to the charge generating layer forming coating solution [2] shown below. Thus, an organic photoreceptor [7] was produced.

(Preparation of charge generation layer forming coating solution [2])
The following components are mixed and dispersed in a circulating ultrasonic homogenizer “RUS-600TCVP” (manufactured by Nippon Seiki Seisakusho Co., Ltd., 19.5 kHz, 600 W) for 0.5 hour at a circulating flow rate of 40 L / H for charge generation layer formation. A coating solution [2] was prepared.
Charge generation substance: Y-type titanyl phthalocyanine (Titanyl phthalocyanine having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray) 20 parts by mass Binder resin : Polyvinyl butyral resin “BM-1” (manufactured by Sekisui Chemical Co., Ltd.) 10 parts by mass Solvent: 700 parts by mass of methyl ethyl ketone Solvent: 300 parts by mass of cyclohexanone

[Organic photoconductor production example 8 (for comparison)]
(4) In the formation of the charge generating layer in Production Example 1 of the organic photoreceptor, the charge generating layer forming coating solution [1] was changed to the charge generating layer forming coating solution [3] shown below. Thus, an organic photoreceptor [8] was produced.

(Preparation of charge generation layer forming coating solution [3])
The following components are mixed and dispersed in a circulating ultrasonic homogenizer “RUS-600TCVP” (manufactured by Nippon Seiki Seisakusho Co., Ltd., 19.5 kHz, 600 W) for 0.5 hour at a circulating flow rate of 40 L / H for charge generation layer formation. A coating solution [3] was prepared.
Charge generating material: Charge generating material [CGM-1] 24 parts by mass Binder resin: Phenoxy resin “PKHH” (manufactured by InChem) 12 parts by mass Solvent: Methyl ethyl ketone 500 parts by mass Solvent: Cyclohexanone 100 parts by mass

[Organic photoconductor production example 9 (for comparison)]
In the preparation of the titanium oxide particles in (2) production of the organic photoreceptor 1 in the production example 1, “3-methacryloxypropyltrimethoxysilane” was changed to “N-2- (aminoethyl) -3-aminopropyltrimethoxysilane“ KBM603 ”( Titanium oxide particles [9] were obtained in the same manner except that the product was changed to “Shin-Etsu Chemical Co., Ltd.)”, and titanium oxide particles [1] ] Was changed to titanium oxide particles [9] to produce an organic photoreceptor [9].

[Organic photoconductor production example 10 (for comparison)]
In the production of the organic photoreceptor (2) in the production of the titanium oxide particles, “the rutile type titanium oxide particle having a number average primary particle size of 15 nm” is referred to as “the rutile type titanium oxide particle having a number average primary particle size of 15 nm (silica and alumina coated Article) Titanium oxide particles [10] were obtained in the same manner except that it was changed to “MT-100SA” (manufactured by Teica). In (3) formation of the intermediate layer in Production Example 1 of the organic photoreceptor, oxidation was performed. An organophotoreceptor [10] was prepared in the same manner except that the titanium particles [1] were changed to titanium oxide particles [10].

[Examples 1-7 and Comparative Examples 1-3]
The surface potential and image quality (density unevenness, fogging) of the obtained organic photoreceptors [1] to [10] before and after printing (after printing the first and 100,000th sheets) were evaluated as follows. The evaluation results are shown in Table 2.

[Evaluation of surface potential]
The difference between the initial potential (after 0 seconds) and the potential after 30 seconds (potential fluctuation ΔVi) at a temperature of 10 ° C. and a humidity of 15% RH on each surface of the obtained organic photoreceptors [1] to [10]. ) Was measured with an electrical property measuring device. The surface potential fluctuation was measured by repeating charging and exposure under conditions of a grid voltage of −800 V and an exposure amount of 0.5 μJ / cm ² while rotating the organic photoreceptor at 130 rpm. ΔVi was evaluated based on the following criteria.
A: 20V or less before and after printing, B: 20V or less before printing, more than 20V and 30V or less after printing C: More than 20V before printing, 30V or less, or 30V or less before printing and 30V after printing Super D: More than 30V before printing

[Evaluation of image quality]
Using the image forming apparatus “bizhub PRO C6501” (manufactured by Konica Minolta Business Technologies), the following image quality was evaluated under a temperature of 30 ° C. and a humidity of 80% RH.

(1) Density unevenness Each of the organic photoreceptors [1] to [10] was mounted on a black (BK) image forming unit. Then, the transfer current was changed from 20 μA to 100 μA, and the chart shown in FIG. 3 was output. An image formed on the transfer material was visually observed using a transfer material “POD gloss coat (A3 size, 100 g / m ² )” (manufactured by Oji Paper Co., Ltd.). The density unevenness of the image was evaluated according to the following criteria.
A: Density unevenness is not observed even when the transfer current is 60 μA or more B: Slight density unevenness is observed when the transfer current is 60 μA or more, but there is no practical problem C: Concentration unevenness is slightly observed when the transfer current is 40 to 50 μA However, there is no problem in practical use (however, it is a problem level when forming high-quality images)
D: Level where the density unevenness is clearly seen even when the transfer current is less than 40 μA, causing a practical problem.

(2) Fog (sensory evaluation)
The organic photoreceptors [1] to [10] were each mounted on a black (BK) image forming unit. A transfer material “POD gloss coat (A3 size, 100 g / m ² )” (produced by Oji Paper Co., Ltd.) with no image formed thereon was prepared, and this transfer material was transported to the black position, where the grid voltage was −800V, A solid image (solid white image) was formed under the condition of developing bias of −650V. Then, the presence or absence of fog on the obtained transfer material was evaluated.
Similarly, a transfer material “POD gloss coat (A3 size, 100 g / m ² )” (produced by Oji Paper Co., Ltd.) on which a yellow solid image was formed was prepared instead of the transfer material on which no image was formed. . Then, the transfer material was conveyed to the position of black (BK), and a solid image (yellow solid image) was formed in the same manner as described above. Then, the presence or absence of fog on the obtained recording paper was evaluated. The evaluation of the presence or absence of fog was performed based on the following criteria.
A: No fogging B: Slight fogging is observed when zoomed in, but there is no practical problem C: Slight fogging is visually observed, causing practical problems D: Fog is conspicuous

(3) Fog (concentration evaluation)
In the evaluation of (2) above, the fog density of the transfer material after the plain image was formed on the part where the image was not formed was measured with a Macbeth densitometer “RD-918” (manufactured by Macbeth). Specifically, it measured by the following procedures.
(A) The absolute image density of 20 arbitrary positions of the transfer material (white paper) on which no image was formed was measured, and the average value thereof was defined as “white paper density before image formation”.
(B) Each of the organic photoreceptors [1] to [10] was mounted on a black (BK) image forming unit, and a solid image was formed on the transfer material (2). Absolute image densities at 20 arbitrary positions of the obtained transfer material were measured, and the average value thereof was defined as “white paper density after plain image formation”.
(C) The blank paper density obtained in the above (a) and (b) was obtained as the fog density based on the following formula (B).
Formula (B): fog density = (white paper density after plain image formation) − (white paper density before image formation)
The fog density was evaluated based on the following criteria.
A: Fog is good when fog density is 0.003 or less B: Fog is good when fog density is more than 0.003 and less than 0.006 C: Fog density is more than 0.006 and less than 0.01 Level D: The fog density is over 0.01, which is a practical problem.

  As shown in Table 2, the titanium oxide particles surface-treated with the silane coupling agent represented by the general formula (1) are directly used for the untreated titanium oxide particles, and the butyral resin is included in the charge generation layer. In the organic photoreceptors [1] to [7] according to Examples 1 to 7, the surface potential ΔVi is as low as 20 V or less before printing and 30 V or less after printing and suppresses both density unevenness and fogging. It was confirmed that it was possible. On the other hand, the organophotoreceptor [8] according to Comparative Example 1 which does not contain a butyral resin in the charge generation layer, and Comparative Example 2 in which the titanium oxide particles surface-treated with the silane coupling agent represented by the general formula (1) were not used The organophotoreceptor [9] according to the comparative example 3 using the titanium oxide particles not directly treated with the silane coupling agent represented by the general formula (1) on the surface of the untreated titanium oxide particles [9] 10] was confirmed to be unable to achieve both density unevenness and fogging.

DESCRIPTION OF SYMBOLS 10 Organic photoreceptor 12 Conductive support 14 Intermediate layer 16 Charge generation layer 17 Organic photosensitive layer 18 Charge transport layer 100 Image forming apparatus 110Y, 110M, 110C, 110Bk Image forming unit 111Y, 111M, 111C, 111Bk Organic photoreceptor 113Y, 113M, 113C, 113Bk Charging means 115Y, 115M, 115C, 115Bk Exposure means 117Y, 117M, 117C, 117Bk Developing means 119Y, 119M, 119C, 119Bk Cleaning means 130 Endless belt-like intermediate transfer body unit 131 Endless belt-like intermediate transfer body 133Y 133M, 133C, 133Bk Primary transfer roller (transfer means)
135 Cleaning means 137A, 137B, 137C, 137D Roller 150 Paper feed conveyance means 170 Fixing means 200 Process cartridge 201 Housing 203R, 203L Support rail 211 Paper feed cassette 213A, 213B, 213C, 213D Intermediate roller 215 Registration roller 217 Secondary transfer Roller (transfer means)
219 Paper discharge roller 221 Paper discharge tray P Transfer material SC Document image reading device

Claims (6)

In an organic photoreceptor having an intermediate layer on a conductive support and an organic photosensitive layer laminated on the intermediate layer,
The intermediate layer contains a binder resin and titanium oxide particles,
The organic photosensitive layer contains butyral resin,
An organic photoreceptor, wherein the titanium oxide particles are surface-treated with a silane coupling agent represented by the following general formula (1).

[In General Formula (1), R ¹ represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms or an acetyl group, R ² represents a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, R ³ represents a hydrogen atom or a methyl group. n shows the integer of 1-3. When n is an integer of 2 or more, two or more R ^{1 s} may be the same as or different from each other. ]   The organophotoreceptor according to claim 1, wherein the titanium oxide particles have a number average primary particle diameter of 10 to 20 nm.   The organic photosensitive layer contains, as a charge generating material, Y-type titanyl phthalocyanine, 2,3-butanediol-added titanyl phthalocyanine, or a mixture of 2,3-butanediol-added titanyl phthalocyanine and non-added titanyl phthalocyanine. The organophotoreceptor according to claim 1, wherein the organophotoreceptor is provided.   The organic photosensitive layer is formed by forming a charge transport layer containing a charge transport material on a charge generation layer containing a charge generation material and a butyral resin. The organophotoreceptor according to any one of the above.   The organic photoreceptor according to any one of claims 1 to 4, wherein the binder resin constituting the intermediate layer is a polyamide resin.   An image forming apparatus comprising the organic photoreceptor according to claim 1.