JP2007010959A - Organophotoreceptor, image forming method and apparatus, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organophotoreceptor having high-speed properties and activated gas resistance and capable of producing a good electrophotographic image, a process cartridge, an image forming method and an image forming apparatus. <P>SOLUTION: The organophotoreceptor has a photosensitive layer containing a charge transport material and a compound represented by a general formula (1), wherein the charge transport material is a compound having a triarylamine group and also having at least one or more carbon atoms of which the value of HOMO electron density distribution obtained by semiempirical molecular orbital calculation using an AM1 parameter is ≥0.009 on a carbocyclic group which links up indirectly with the N atom of the triarylamine group and exists farthest, and the dipole moment of the compound obtained by the semiempirical molecular orbital calculation is ≤0.7 debye. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic photoreceptor, an image forming method, and an image forming apparatus that can be applied to an electrophotographic copying machine and printer, and an organic photoreceptor, an image forming method, and an image forming apparatus that can produce an electrophotographic image at high speed. And a process cartridge.

  2. Description of the Related Art Conventionally, in a copying machine using the Carlson method, which is the most typical electrophotographic method, after a photoreceptor is uniformly charged, charges are erased imagewise by exposure to form an electrostatic charge latent image. This electrostatic charge latent image is developed and visualized with toner, and then the toner is transferred to paper or the like and then fixed to form an image.

  Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having an inorganic photoconductive substance such as selenium, zinc oxide, cadmium or the like as a main component of a photosensitive layer has been widely used. However, these inorganic photoreceptors are often harmful and have problems in terms of environmental measures.

  Therefore, in recent years, organic photoreceptors using non-polluting organic substances have been actively developed and widely used. In particular, a function-separated type photoconductor, in which a charge generation function and a charge transport function are assigned to different substances and a compound having desired characteristics can be selected from a wide range, has been actively developed.

  In recent years, the image forming method using the electrophotographic method has been accelerated by writing by digital signal processing, and a copying machine or printer using a cut sheet has a printing speed of 100 sheets or more per minute. And printers have been developed.

  However, organic photoreceptors applied to such copying machines and printers have, for example, electrophotographic characteristics capable of printing 1 million sheets, that is, high-speed and stable electrophotographic characteristics such as high-speed sensitivity characteristics and charging stability. Desired.

  As a technology to achieve such high-speed and stable electrophotographic characteristics, structural optimization calculation is performed using semi-empirical molecular orbital calculation using PM3 parameters, and polarizability and dipole moment are specified within a specific range. An electrophotographic photosensitive member using the prepared charge transport material has been proposed (Patent Document 1 and Patent Document 2).

  However, as high-speed characteristics are pursued, the chemical structure of the charge transport material tends to become chemically unstable, and in particular, when producing an electrophotographic image, an active gas such as NOx or ozone generated from a charging member or the like. Due to these characteristic deteriorations, there is a problem that image blurring occurs, the residual potential increases, and the image density decreases.

As a technology for preventing the deterioration of properties due to these active gases, a technology for adding an antioxidant to the charge transport layer is known, but the effect of the antioxidant on the charge transport material developed in pursuit of high-speed properties. However, the problem that image blur occurs on an organic photoreceptor having high speed characteristics, the residual potential increases, and the image density decreases cannot be sufficiently solved.
Japanese Patent Laid-Open No. 10-312071 JP 2001-305763 A

  An object of the present invention is to provide an organic photoreceptor capable of producing a good electrophotographic image using a charge transport material having a high speed characteristic and an active gas resistance characteristic. It is to provide an organic photoreceptor excellent in the above. Another object of the present invention is to provide an organic photoreceptor capable of maintaining stable sensitivity and stable potential characteristics at a high process speed, and to provide a process cartridge, an image forming method and an image forming apparatus using the organic photoreceptor. It is.

As a result of detailed examination of the above problems, the present inventors have found a specific relationship between the chemical structure of the charge transport material and the electron density distribution that can achieve both high speed characteristics and gas resistance characteristics, and completed the present invention. did. That is, the charge transporting substance having a specific relationship with the HOMO electron density distribution obtained by the semi-empirical molecular orbital calculation using the AM1 parameter at the same time as the spread of the electron cloud is shown by the following general formula (1). The present inventors have found that an organic photoreceptor having excellent gas resistance while maintaining high speed characteristics can be obtained by using the above compound together, and the present invention has been completed. That is, the above object of the present invention is achieved by using the following configuration.
(Claim 1)
In an organic photoreceptor for use in an image forming method in which a uniform charge is imparted on an organic photoreceptor in a charging process, an electrostatic latent image is formed in an image exposure process, and the electrostatic latent image is visualized as a toner image in a development process. A photosensitive layer containing at least a charge generation material and a charge transport material on a conductive substrate, the photosensitive layer having a triarylamine group and indirectly linked to the N atom of the triarylamine group; In addition, on the farthest carbocyclic group, it has at least one carbon atom having a HOMO electron density distribution value of 0.009 or more determined by semiempirical molecular orbital calculation using the AM1 parameter, And an organic photoreceptor comprising a charge transport material having a dipole moment of 0.7 debye or less obtained by the semi-empirical molecular orbital calculation and a compound represented by the following general formula (1): .

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3)
(Claim 2)
2. The organophotoreceptor according to claim 1, wherein the carbocyclic group is a phenyl group.
(Claim 3)
3. The organic photosensitive according to claim 1, wherein the photosensitive layer has a structure in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material laminated thereon are laminated. body.
(Claim 4)
The organophotoreceptor according to claim 1, wherein the charge generation material is a Y-type titanyl phthalocyanine pigment.
(Claim 5)
The organophotoreceptor according to claim 1, wherein the charge transport material has an ionization potential of 7.6 to 7.9 eV.
(Claim 6)
In an image forming method, a uniform charge is imparted on an organic photoreceptor in a charging step, an electrostatic latent image is formed in an image exposure step, and the electrostatic latent image is visualized as a toner image in a development step. Has a photosensitive layer containing at least a charge generating material and a charge transporting material on a conductive substrate, the photosensitive layer has a triarylamine group and is indirectly linked to the N atom of the triarylamine group, In addition, on the farthest carbocyclic group, it has at least one carbon atom having a HOMO electron density distribution value of 0.009 or more determined by semiempirical molecular orbital calculation using the AM1 parameter, An image forming method comprising: a charge transport material having a dipole moment determined by the semi-empirical molecular orbital calculation of 0.7 debye or less and a compound represented by the following general formula (1): .

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3)
(Claim 7)
The image forming method according to claim 6, wherein the process speed is 400 mm / sec or more.
(Claim 8)
An organic photoreceptor, a charger for uniformly charging the organic photoreceptor, an image exposure unit for forming an electrostatic latent image on the organic photoreceptor, and a developer for developing the electrostatic latent image into a toner image In the image forming apparatus, the organic photoreceptor has a photosensitive layer containing at least a charge generation material and a charge transport material on a conductive substrate, the photosensitive layer has a triarylamine group, and the triarylamine group The value of the HOMO electron density distribution obtained by the semi-empirical molecular orbital calculation using the AM1 parameter is 0.009 or more on the carbocyclic group that is indirectly linked to the N atom of A charge transport material having at least one carbon atom and having a dipole moment of 0.7 debye or less determined by the semi-empirical molecular orbital calculation and a compound represented by the following general formula (1): contains An image forming apparatus comprising and.

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3)
(Claim 9)
The image forming apparatus according to claim 8, wherein a process speed is 400 mm / sec or more.
(Claim 10)
An organic photoreceptor, a charger for uniformly charging the organic photoreceptor, an image exposure unit for forming an electrostatic latent image on the organic photoreceptor, and a developer for developing the electrostatic latent image into a toner image A process cartridge for use in an image forming apparatus having a photosensitive layer containing at least a charge generating substance and a charge transporting substance on a conductive substrate, the photosensitive layer having a triarylamine group, and the triarylamine group The value of the HOMO electron density distribution obtained by the semi-empirical molecular orbital calculation using the AM1 parameter is 0.009 or more on the carbocyclic group that is indirectly linked to the N atom of A charge transport material having at least one carbon atom and having a dipole moment determined by the semi-empirical molecular orbital calculation of 0.7 debye or less and represented by the following general formula (1): An organic photoreceptor containing a compound and at least one of charging means, latent image forming means, developing means, transfer means, charge eliminating means, and cleaning means are integrally supported and can be detachably attached to the image forming apparatus main body. Process cartridge characterized by being.

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3)

  By using the organophotoreceptor of the present invention, an organophotoreceptor that can be sufficiently adapted to a high-speed copying machine and excellent in active gas resistance can be provided, and an electrophotographic image with sufficient image density and good sharpness can be provided. In addition, an image forming method, an image forming apparatus, and a process cartridge using the organic photoreceptor can be provided.

  The organophotoreceptor of the present invention is an image in which uniform charge is imparted on the organophotoreceptor in the charging process, an electrostatic latent image is formed in the image exposure process, and the electrostatic latent image is visualized into a toner image in the development process. An organic photoreceptor used in the forming method has a photosensitive layer containing at least a charge generating substance and a charge transporting substance on a conductive substrate, the photosensitive layer has a triarylamine group, and N of the triarylamine group A carbon atom having a HOMO electron density distribution value of 0.009 or more obtained by semi-empirical molecular orbital calculation using the AM1 parameter on the farthest carbocyclic group that is indirectly linked to the atom. A charge transport material having a dipole moment of 0.7 debye or less obtained by the semi-empirical molecular orbital calculation and a compound represented by the general formula (1) That And butterflies.

  Due to the organic photoreceptor having the above-described configuration, the process speed is 400 mm / sec or more, and even when a large number of prints or copies are made, high-speed sensitivity characteristics and stable potential characteristics are exhibited. The increase in the residual potential due to the gas is small, the occurrence of image blur and the decrease in image density can be prevented, and an electrophotographic image with good sharpness can be stably produced.

  Hereinafter, the constitution of the organic photoreceptor of the present invention will be described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor configured to have an organic compound having either a charge generation function or a charge transport function essential for the configuration of the electrophotographic photoconductor, It contains all known organic electrophotographic photoreceptors such as a photoreceptor composed of a known organic charge generating material or organic charge transport material, a photoreceptor composed of a polymer complex with a charge generating function and a charge transport function.

  The layer structure of the organic photoreceptor of the present invention preferably has a charge generation layer and a charge transport layer on a conductive support, and the charge transport layer is preferably formed of a plurality of layers. Moreover, it is preferable to provide an intermediate layer between the conductive support and the charge generation layer, which can block the entry of free carriers from the support. Hereinafter, preferred configurations of the organic photoreceptor of the present invention are shown.

Conductive Support The conductive support used in the photoreceptor of the present invention may be either a sheet or a cylinder, but in order to design an image forming apparatus in a compact manner, a cylindrical conductive support is used. Is preferred.

  Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity is within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. A support is preferred. Exceeding the roundness and shake range makes it difficult to form a good image.

As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.

  As the conductive support used in the present invention, one having an alumite film that has been sealed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing treatment in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / L, the aluminum ion concentration is 1 to 10 g / L, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.

Intermediate Layer In the present invention, it is preferable to provide an intermediate layer that can block the entry of free carriers from the support between the conductive support and the photosensitive layer.

  In the present invention, in order to improve the adhesion between the conductive support and the photosensitive layer, or to prevent charge injection from the support, an intermediate layer (including an undercoat layer) is provided between the support and the photosensitive layer. Including) can also be provided. Examples of the material for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more of these resin repeating units. Of these subbing resins, a polyamide resin is preferable as a resin capable of reducing the increase in residual potential due to repeated use. The film thickness of the intermediate layer using these resins is preferably 0.01 to 0.5 μm.

  Examples of the intermediate layer preferably used in the present invention include an intermediate layer using a curable metal resin obtained by thermosetting an organic metal compound such as a silane coupling agent or a titanium coupling agent. As for the film thickness of the intermediate | middle layer using curable metal resin, 0.1-2 micrometers is preferable.

  An intermediate layer preferably used in the present invention includes an intermediate layer in which inorganic particles are dispersed in a binder resin. The average particle diameter of the inorganic particles is preferably 0.01 to 1 μm. In particular, an intermediate layer in which N-type semiconductive fine particles subjected to surface treatment are dispersed in a binder is preferable. For example, an intermediate layer in which titanium oxide having an average particle size of 0.01 to 1 μm, which has been surface-treated with silica / alumina treatment and a silane compound, is dispersed in a polyamide resin. The film thickness of such an intermediate layer is preferably 1 to 20 μm.

  The N-type semiconducting fine particles are fine particles having the property of using conductive carriers as electrons. That is, the property that the conductive carrier is an electron is that the N-type semiconducting fine particles are contained in an insulating binder to effectively block hole injection from the substrate, and to convert electrons from the photosensitive layer into electrons. On the other hand, it has the property which does not show blocking property.

Specific examples of the N-type semiconductive fine particles include fine particles such as titanium oxide (TiO ₂ ) and zinc oxide (ZnO). In the present invention, titanium oxide is particularly preferably used.

  The average particle diameter of the N-type semiconducting fine particles used in the present invention is preferably in the range of 10 nm to 500 nm in the number average primary particle diameter, more preferably 10 nm to 200 nm, and particularly preferably 15 nm to 50 nm. .

  The intermediate layer using N-type semiconducting fine particles whose number average primary particle size is within the above range can be finely dispersed in the layer, has sufficient potential stability, and generates black spots. Has a prevention function.

  For example, in the case of titanium oxide, the number-average primary particle size of the N-type semiconducting fine particles is magnified 10,000 times by observation with a transmission electron microscope, and 100 particles are randomly observed as primary particles. It is measured as the number average diameter.

  The shape of the N-type semiconducting fine particles used in the present invention includes dendritic, needle-like, and granular shapes. For example, in the case of titanium oxide particles, the N-type semiconductive fine particles have a crystalline form. There are anatase type, rutile type and amorphous type, but any crystal type may be used, or two or more crystal types may be mixed and used. Of these, the rutile type is the best.

  One of the hydrophobizing surface treatments performed on the N-type semiconducting fine particles is a plurality of surface treatments, and the last surface treatment is a surface treatment with a reactive organosilicon compound. Is to do. In addition, at least one of the surface treatments is at least one surface treatment selected from alumina, silica, and zirconia, and finally the surface treatment of the reactive organosilicon compound is performed. It is preferable.

  Alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of the N-type semiconductive fine particles. Alumina, silica, and zirconia deposited on these surfaces include alumina, silica, Zirconia hydrates are also included. The surface treatment of the reactive organosilicon compound means using a reactive organosilicon compound in the treatment liquid.

  In this way, the surface treatment of the N-type semiconductive fine particles such as titanium oxide particles was performed at least twice, so that the surface of the N-type semiconductive fine particles was uniformly coated (treated), and the surface treatment was performed. When N-type semiconducting fine particles are used in the intermediate layer, a good photoconductor having good dispersibility of N-type semiconductive fine particles such as titanium oxide particles in the intermediate layer and causing no image defects such as black spots. You can get it.

Photosensitive Layer The photosensitive layer configuration of the organic photoreceptor of the present invention has a photosensitive layer containing at least a charge generating substance and a charge transporting substance on a conductive substrate. The photosensitive layer may be composed of a photosensitive layer in which the charge generation material and the charge transport material are present in the same layer, but more preferably, a charge generation layer (CGL) containing a charge generation material on a conductive support and A stacked structure of a charge transport layer (CTL) containing a charge transport layer is preferred. Hereinafter, the organic photoreceptor of the present invention will be described focusing on the layer structure of the laminated structure.

Charge generation layer Charge generation layer: The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.

  A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments. For example, CGM such as titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu-Kα ray and benzimidazole perylene having a maximum peak at 2θ of 12.4 has little deterioration due to repeated use. Potential increase can be reduced.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.

Charge Transport Layer The charge transport layer according to the present invention has a triarylamine group and is indirectly linked to the N atom of the triarylamine group, and further, on the farthest carbocyclic group, the AM1 parameter Having at least one carbon atom having a HOMO electron density distribution value of 0.009 or more determined by semi-empirical molecular orbital calculation using a dipole, and a dipole moment determined by the calculation of 0.7 debye or less The charge transport material of the compound is used in combination with the compound of the general formula (1). That is, in the charge transport material of the present invention, the HOMO electron density distribution value is indirectly linked to the N atom of the triarylamine group, and 0.009 or more carbon atoms are present on the farthest carbocyclic group. Have at least one. Further, the value of the HOMO electron density distribution is in the range of 0.009 to 0.03, which is chemically most stable (is a chemically stable structure that is unlikely to be an attack site such as NOx) and high-speed transport of charge carriers. A chemical structure that satisfies the characteristics can be obtained.

  Here, the compound having a triarylamine group is a compound having at least a triarylamine group in the molecular structure. For example, a compound represented by the following general formula (2) is preferably used.

[In General Formula (2), R ¹ , R ² , R ³ , R ⁴ , R ⁵ are each a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group. Ar ¹ represents a hydrogen atom or a substituted or unsubstituted aromatic group, and Ar ² represents a substituted or unsubstituted aromatic group. ]
In general formula (2), the structure of the triarylamine group is composed of three phenyl groups linked to the N atom.

  Many of the compounds represented by the general formula (2) have a cis-cis, cis-trans, or trans-trans stereoisomeric structure, and satisfy the conditions of the HOMO electron density and the dipole moment. Many of these compounds have a trans-trans stereoisomeric structure. When the compound of the above general formula (2) is used as the charge transport material of the present invention, a compound having a trans-trans stereoisomeric structure may be used. preferable.

  The compounds having these three-dimensional structures preferably contain 50% by mass or more of compounds having a three-dimensional structure that satisfies the above conditions of HOMO and dipole moment after separating these three-dimensional structures once.

  Moreover, the synthesis example of the compound of the general formula (2) and the separation method thereof (cis-cis, cis-trans, trans-stereoisomer separation method) are described in JP-A No. 2003-280221. Can be separated under the liquid chromatography measurement conditions (separation conditions) described above, and separated from this, indirectly linked to the N atom of the triarylamine group and on the farthest carbocyclic group. It is preferable to select a compound which is a compound having at least one carbon atom of 009 or more and a dipole moment obtained by the calculation of 0.7 debye or less.

Measuring machine: Shimadzu LC6A (manufactured by Shimadzu Corporation)
Column: CLC-SIL (manufactured by Shimadzu Corporation)
Detection wavelength: 290 nm
Mobile phase: n-hexane / dioxane = 10-500 / 1
Mobile phase flow rate: about 1 ml / min
Sample solvent: n-hexane / dioxane = 10/1
Sample: 3 mg / solvent 10 ml
The farthest carbocyclic group that is indirectly linked to the N atom is a carbocyclic group that is indirectly connected to the N atom of the triarylamine group via another group, and A carbocyclic group having the farthest distance in the molecule from the N atom centering on the N atom is shown, and in the following compound (CTM-2), it corresponds to a phenyl group surrounded by circles of P1 and P2.

  Examples of the carbocyclic group include monocyclic carbocyclic groups (saturated carbocyclic groups and aromatic carbocyclic groups), condensed polycyclic carbocyclic groups, and the like. In the present invention, carbocyclic groups such as phenyl groups are used. Is preferably used.

  The HOMO electron density distribution and dipole moment obtained by semiempirical molecular orbital calculation using the AM1 parameter were obtained by semiempirical molecular orbital calculation as follows.

  That is, in the molecular orbital method, a wave function used in the Schrodinger equation is approximated by a slater determinant composed of molecular orbitals represented by linear combination of atomic orbitals, and the molecular orbits constituting the wave function are in a consistent field (self). Various physical quantities can be calculated as the total energy, wave function, and expected value of the wave function by using an approximation of -consistent field (abbreviated as SCF). The semi-empirical molecular orbital method shortens the calculation time by parameterizing and approximating the integral calculation, which requires a long calculation time, using various experimental values when calculating the molecular orbital by approximating the appropriate field. In the present invention, the AM1 parameter set was used as a semi-empirical parameter, and the calculation was performed using a version MOPAC 93 of a semi-empirical molecular orbital calculation program MOPAC (for PM3 and MOPAC, JJ P Stewart, Journal of Computer-Aided Molecular Design, 4, 1 (1990) and references cited therein).

  HOMO electron density distribution obtained by semi-empirical molecular orbital calculation using a AM1 parameter, which is a compound having a triarylamine group, indirectly linked to the N atom of the triarylamine group and present farthest Specific examples of the compound in which at least one carbon atom of 0.009 or more is present on the carbocyclic group and the dipole moment obtained by the above calculation is 0.7 debye or less include the following compounds: Is mentioned.

  The compounds shown in the specific examples can be selected from the compounds represented by the general formula (2), and all of the compounds of the general formula (2) are the conditions of the electron density distribution and the dipole moment. It is necessary to select a compound satisfying the above conditions from the compound of the general formula (2).

Among the compounds represented by the general formula (2), a compound having an alkyl group having 1 to 4 carbon atoms in at least one of R ^{1 to} R ⁵ satisfies the above conditions of electron density distribution and dipole moment. In particular, a compound having an alkyl group having 1 to 4 carbon atoms in R ₂ is preferable for satisfying the above conditions.

  As a charge transport material according to the present invention, it is a necessary condition to use the above-mentioned compounds. However, these compounds can be used together with a charge transport material that does not satisfy the above conditions. However, even when used in combination, it is preferable to use a charge transport material satisfying the above conditions as the main charge transport material (50% or more by mass ratio of the total charge transport material).

  It is preferable that the ionization potential (ionization potential obtained by semiempirical molecular orbital calculation using the AM1 parameter) of the charge transport material according to the present invention is 7.6 to 7.9 eV.

  In particular, when a titanyl phthalocyanine pigment having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to the Cu—Kα ray is used as the charge generating material, by applying a compound having an ionization potential in the above range as a charge transporting material, Even in a high-speed process of 400 mm / sec or more, an increase in residual potential is suppressed to a small level, and an electrophotographic image having a high density and good sharpness can be produced.

  The charge transport layer according to the present invention contains the compound of the general formula (1). In the general formula (1), A is a phosphate group, and a phosphate group represented by the following structure is most preferable.

In the above formula, each R ₃ represents an alkyl group having 1 to 5 carbon atoms. Most preferred R ₃ is an ethyl group.

In the general formula (1), R ₁ and R ₂ are each an alkyl group having 1 to 5 carbon atoms, and a t-butyl group (t-Bu) is particularly preferable. The metal atom M is preferably an atom capable of forming a divalent metal ion. Particularly preferred is a Ca atom.

  Examples of the compound of the general formula (1) according to the present invention include the following compounds.

  Among the above compounds, bis (3,5-di-t-butyl-4-hydroxybenzylphosphonate) calcium of AO-1 can effectively exhaust the active gas that is easily adsorbed in the surface layer. Are particularly preferably used.

  The charge transport layer according to the present invention may be composed of one layer or may be composed of two upper and lower layers. When the charge transport layer is composed of two layers, the charge transport material of the present invention is preferably used for the upper charge transport layer. That is, by using the charge transport material of the present invention in the charge transport layer constituting the surface layer, an organic photoreceptor satisfying both high speed characteristics and active gas resistance can be obtained. The content of the charge transport material in the charge transport layer is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  The total thickness of the first charge transport layer is preferably 10 to 25 μm.

  When preparing the charge transport layer according to the present invention, a dispersion of the charge transport layer is prepared. As a solvent for the charge transport layer dispersion, a non-halogen solvent having a small environmental load is used. Non-halogen solvents include acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, etc. Can be mentioned.

  The solvent for the charge transport layer dispersion is not limited to these, but toluene, tetrahydrofuran (THF), dioxolane and the like are particularly preferably used. These solvents may be used alone or as a mixed solvent of two or more.

  As a coating processing method for producing the organic photoreceptor of the present invention, a coating processing method such as dip coating, spray coating, circular amount regulation type coating or the like is used, but the upper layer side coating processing of the photosensitive layer is a lower layer film. In order to achieve a uniform coating process, it is preferable to use a coating process method such as spray coating or circular amount regulation type (a circular slide hopper type is a typical example). The spray coating is described in detail in, for example, JP-A-3-90250 and JP-A-3-269238, and the circular amount-regulating coating is described in detail in, for example, JP-A-58-189061. Yes.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an image forming apparatus according to the present invention will be specifically described below with reference to the accompanying drawings, and specific examples of forming an image using the image forming apparatus and the developing device of the embodiments will be given. As will be described, it is clarified that the developing method of the present invention can provide a good image with sufficient gradation and image density without black spots and fog.

  FIG. 1 is a cross-sectional view of an image forming apparatus as an example of the image forming method of the present invention.

  In FIG. 1, reference numeral 50 denotes a photosensitive drum (photosensitive member) which is an image bearing member, which is a photosensitive member of the present invention having an organic photosensitive layer coated on the drum, and is grounded and rotated clockwise. Reference numeral 52 denotes a scorotron charger, which uniformly charges the circumferential surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, the peripheral surface of the photosensitive member may be discharged by performing exposure by the pre-charging exposure unit 51 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.

  After uniform charging of the photoreceptor, image exposure based on the image signal is performed by the image exposure unit 53. The image exposure unit 53 in this figure uses a laser diode (not shown) as an exposure light source. Scanning on the photosensitive drum is performed by the light whose optical path is bent by the reflection mirror 532 through the rotating polygon mirror 531 and the fθ lens, and an electrostatic latent image is formed.

  Here, the unexposed portion potential of the photoreceptor of the present invention means the photoreceptor surface potential in a region where the surface of the photoreceptor is uniformly charged by the charger 52 and image exposure is not performed. The exposed portion potential means the photoreceptor surface potential in a region where image exposure has been performed. The potential is measured by providing a potential sensor 547 at the development position as shown in FIG.

The electrostatic latent image is then developed using a developing device 54 in a development process. A developing device 54 containing a developer composed of toner and carrier is provided on the periphery of the photosensitive drum 50, and development is performed by a developing sleeve 541 that contains a magnet and rotates while holding the developer. The inside of the developing device 54 is composed of developer agitating / conveying members 544 and 543, a conveying amount regulating member 542, and the like, and the developer is agitated and conveyed and supplied to the developing sleeve. Controlled by member 542. The amount of the developer transported varies depending on the linear velocity of the applied organic electrophotographic photosensitive member and the specific gravity of the developer, but is generally in the range of ^{20 to} 200 mg / cm ² .

  The developer includes, for example, a carrier in which the above ferrite is used as a core and an insulating resin is coated around the carrier, a colorant such as carbon black, a charge control agent, and the low molecular weight polyolefin of the present invention, which is mainly composed of the above styrene acrylic resin. The developer is made up of a toner obtained by externally adding silica, titanium oxide or the like to the colored particles, and the developer is transported to the development zone with the layer thickness regulated by the transport amount regulating member, and development is performed. At this time, development is usually performed by applying a DC bias voltage to the developing sleeve 541 and, if necessary, an AC bias voltage. Further, the developer is developed in contact with or not in contact with the photoreceptor.

  The recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 57 when the transfer timing is ready after the image formation.

  In the transfer area, a transfer electrode (transfer device) 58 is pressed against the peripheral surface of the photosensitive drum 50 in synchronization with the transfer timing, and the fed recording paper P is sandwiched and transferred.

  Next, the recording paper P is neutralized by a separation electrode (separator) 59 brought into a pressure contact state almost simultaneously with the transfer roller, separated by the peripheral surface of the photosensitive drum 50, conveyed to the fixing device 60, and pressed against the heat roller 601. After the toner is welded by heating and pressurizing the roller 602, the toner is discharged to the outside of the apparatus via the discharge roller 61. The transfer electrode 58 and the separation electrode 59 are retracted away from the peripheral surface of the photosensitive drum 50 after the recording paper P has passed to prepare for the next toner image formation.

  On the other hand, after the recording paper P is separated, the photosensitive drum 50 is subjected to removal and cleaning of residual toner by pressure contact of the blade 621 of the cleaning device 62, and after receiving charge removal by the pre-charge exposure unit 51 and charging by the charger 52 again. The image forming process is entered.

  Reference numeral 70 denotes a detachable process cartridge in which a photoconductor, a charger, a transfer device, a separator, and a cleaning device are integrated.

  FIG. 2 is an enlarged view of the configuration of charge potential control of the photosensitive drum 50 of FIG.

  Hereinafter, a method of measuring the unexposed portion potential and a charging potential adjustment process for the purpose of correcting the unexposed portion potential will be described with reference to FIG.

  First, the photosensitive member 50 is uniformly charged by a charger (charging step) 52. An unexposed area that is not digitally exposed is formed on the charged photosensitive member by an image exposure device (image exposure step) 53 of a laser diode. The surface potential (unexposed portion potential) of the unexposed region is detected by the potential sensor 547, and the detected potential signal is transmitted to the process control unit 63 in FIG. The process control unit 63 is a process controller that controls the band electrode based on the potential signal from the potential sensor 547. The controller compares the potential signal from the potential sensor with the target potential signal, corrects the difference, and determines a correction signal that achieves the target potential. The high-voltage control unit 64 is a high-voltage control unit that receives a control signal from the process control unit 63 and supplies current and voltage to the charger 52. Based on the determined correction signal, a correction signal for charging current and charging grit voltage is output from the process controller to the high voltage control unit, and then corrected from the high voltage control unit to the corona wire 521 and scorotron grit 522 of the charger 52, respectively. The charged current and charged grit voltage are output. By repeating this process several times, the photosensitive member potential (unexposed portion potential) at the potential sensor position can be corrected to the target potential.

  The organic photoreceptor of the present invention is preferably applied to an image forming method having a process speed (linear speed of the photoreceptor during image formation) of 400 mm / sec or more. When the process speed is 400 mm / sec or more, the photoconductor that is repeatedly rotated for image formation tends to be unstable in potential stability such as a charging potential and a residual potential. However, the charge transport material and the general formula ( By using the compound 1) in combination, these problems can be solved, and at the same time, the deterioration of the active gas resistance that easily occurs when a high-speed charge transport material (CTM) is used can be prevented, and image blurring can be prevented. be able to.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. However, “part” in the following text indicates “part by mass”.

Examples Photoconductors used for evaluation were produced as follows.

Preparation of photoreceptor 1 Intermediate layer The following intermediate layer coating solution is applied by a dip coating method onto a cleaned cylindrical aluminum substrate (10-point surface roughness Rz defined by JISB-0601 by cutting): 0.81 μm) And dried at 120 ° C. for 30 minutes to form an intermediate layer having a dry film thickness of 1.0 μm.

  The following intermediate layer dispersion is diluted twice with the same mixed solvent, and is allowed to stand overnight and then filtered (filter; rigesh mesh filter made by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 microns, pressure: 50 kPa). Produced.

(Preparation of intermediate layer dispersion)
Binder resin: (Exemplary polyamide N-1) 1 part (1.00 volume part)
2. Rutile-type titanium oxide A1 (primary particle size 35 nm; a surface treatment using a copolymer of methylhydrogensiloxane and dimethylsiloxane (molar ratio 1: 1) in an amount of 5% by mass of the total mass of titanium oxide) 5 parts (1.0 part by volume)
Ethanol / n-propyl alcohol / THF (= 45/20/30 mass ratio) 10 parts The above components were mixed and dispersed in a batch system for 10 hours using a sand mill disperser to prepare an intermediate layer dispersion. .

Charge generation layer The following components were mixed and dispersed using a sand mill disperser to prepare a charge generation layer coating solution. This coating solution was applied by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm on the intermediate layer.

Titanyl phthalocyanine pigment (Titanyl phthalocyanine pigment having a maximum diffraction peak at 27.3 ° at the Bragg angle (2θ ± 0.2 °) of the characteristic X-ray diffraction spectrum of Cu-Kα) 20 parts Silicone-modified polyvinyl butyral 10 parts 4 -Methoxy-4-methyl-2-pentanone 700 parts t-butyl acetate 300 parts <Charge transport layer (CTL)>
Charge transport material (CTM-1) 100 parts Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 100 parts Antioxidant (exemplary compound AO-1) 6 parts THF / toluene (mass ratio: 7/3) 1000 parts Silicon oil ( KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part was mixed and dissolved to prepare a charge transport layer coating solution 1. This coating solution was applied onto the charge generation layer with a circular slide hopper type applicator and dried at 110 ° C. for 70 minutes to form a charge transport layer having a dry film thickness of 22.0 μm.

Production of photoconductors 2 to 7 Photoconductors 2 to 7 were produced in the same manner as the photoconductor 1 except that the type of the charge transport material in the charge transport layer was changed as shown in Table 1.

In Table 1,
The maximum electron density is the HOMO electron density distribution of each CTM obtained by semi-empirical molecular orbital calculation using AM1 parameters, and is indirectly connected to the N atom of the triarylamine group and exists farthest away. It means the maximum electron density of a carbon atom on a carbocyclic group.

  The dipole moment and IP (ionization potential) were also determined by semiempirical molecular orbital calculation using the AM1 parameter as described above.

  In Table 1, CTMR-1 and CTMR-2 represent the following compounds.

  AOR-1, AOR-2 and AOR-3 represent the following compounds.

<< Evaluation 1 >>
A digital copying machine Konica “Sitos” 7085 (manufactured by Konica Minolta Business Technologies Co., Ltd.), a scorotron charger, a semiconductor laser image exposure device, and a reversal developing means, which basically has the structure shown in FIGS. A copy experiment was conducted.

《Image evaluation》
Attach each photoconductor to the above digital copier and copy the original image with A4 paper, 1 million text images, white solid image, black solid image in high temperature and high humidity (30 ° C, 80% RH) environment, The copied image was taken out at the start and every 100,000 copies, and the following image evaluation was performed.

Other conditions for image formation Process speed: 420 mm / sec
Charging conditions: A scorotron band electrode was used as the band electrode, and the grit voltage of the band electrode was set to 650V.

  Developer: A two-component developer containing carrier and toner was used.

(Potential stability)
At the start and every 100,000 copies, a potential sensor was installed at the position of the developing unit for the above-mentioned digital copy image, and the potential holding property and residual potential of the photosensitive member were evaluated.

  A: From the start to 1 million sheets, the change in the charging potential is in the range of less than 650 ± 50V, the stability of the charging potential is good, and the increase in the residual potential is also good at less than 50V.

○: From the start to 1 million sheets, the change in the charging potential is within a range of 650 ± 100 V, and the increase in the residual potential is 50 V or more and 100 V or less. (There is practicality)
X: From the start to 1 million sheets, the change in charging potential is larger than 650 ± 100V, and the increase in residual potential is also larger than 100V. (There is a problem with practicality)
(Image density)
A black solid image of a copied image was measured using a Macbeth RD-918. Measured with relative reflection density with paper reflection density set to “0” (image density)
A: From the start to 1 million sheets, the black solid image density is 1.3 or higher and the image density is high.

  ○: From the start to 1 million sheets, the black solid image density is 1.0 or more, which is a practically sufficient image density.

Δ: Black solid image density of 0.7 to less than 1.0 occurred between 1 million sheets from the start (re-examination required for practical use)
×: Black solid image density of less than 0.7 occurs between 1 million sheets from the start (There is a problem in practical use)
(Fog)
Using a Macbeth reflection densitometer “RD-918”, the density of copy paper (white paper) is measured at 20 locations at absolute image density, and the average value is defined as the white paper density. Next, 20 white solid images of the copied image were similarly measured at the absolute image density, and the value obtained by subtracting the white paper density from the average density was evaluated as the fog density.

A: From the start to 1 million sheets, white solid image density is 0.005 or less (good)
○: From the start to 1 million sheets, the white solid image density is 0.01 or less (a level that is not a problem for practical use)
×: fogging with a solid white image density greater than 0.01 between the start and 1 million sheets (obviously, there is a practical problem)
(Active gas resistance)
The above digital copying machine Konica “Sitos” 7085 is installed in an environment of low temperature and low humidity (10 ° C., 10% RH). After continuous copying of 1000 sheets, it is stopped for 20 minutes, and then a halftone image is copied and directly under the band electrode. The occurrence of image blur was observed and evaluated according to the following evaluation criteria.

A: No blurring is observed in the halftone image (good)
○: Image unevenness having a density difference of less than 0.15 occurs in the halftone image, but the density difference is not so noticeable in the halftone image. (Practical problem level)
X: An image blur having a density difference of 0.15 or more occurs in the halftone image, and the density difference is clear in the halftone image. (There are practical problems)

  As is clear from Table 2, the photoreceptors 1 to 5 in which the charge transport layer and the charge transport material satisfying the conditions of the present invention and the compound of the general formula (1) are used together have good potential stability. In addition, good evaluation results were obtained in all evaluations of image density and fog. Also, the evaluation of the active gas is good, and as a result, the occurrence of image blur is prevented, and an electrophotographic image with good sharpness can be formed.

  On the other hand, the photoreceptor 6 using the charge transport material other than the present invention has a large deterioration in the active gas resistance, and the photoreceptor 7 has a great potential stability and image density degradation.

  Further, all of the photoconductors 8 to 10 using the antioxidant other than the general formula (1) have deteriorated potential stability and image density, and the photoconductor 9 has also deteriorated fog evaluation.

1 is a cross-sectional view of an image forming apparatus as an example of an image forming method of the present invention. FIG. 2 is an enlarged view of a configuration of charge potential control of the photosensitive drum in FIG. 1.

Explanation of symbols

50 photoconductor drum (or photoconductor)
DESCRIPTION OF SYMBOLS 51 Pre-charge exposure part 52 Charging device 53 Image exposure device 54 Developer 541 Development sleeve 542 Conveyance amount regulating member 543 Developer agitation conveyance member 544 Developer agitation conveyance member 547 Potential sensor 57 Feed roller 58 Transfer electrode 59 Separation electrode (separation) vessel)
60 Fixing device 61 Paper discharge roller 62 Cleaning device 70 Process cartridge

Claims (10)

In an organic photoreceptor for use in an image forming method in which a uniform charge is imparted on an organic photoreceptor in a charging process, an electrostatic latent image is formed in an image exposure process, and the electrostatic latent image is visualized as a toner image in a development process. A photosensitive layer containing at least a charge generation material and a charge transport material on a conductive substrate, the photosensitive layer having a triarylamine group and indirectly linked to the N atom of the triarylamine group; In addition, on the farthest carbocyclic group, it has at least one carbon atom having a HOMO electron density distribution value of 0.009 or more determined by semiempirical molecular orbital calculation using the AM1 parameter, And an organic photoreceptor comprising a charge transport material having a dipole moment of 0.7 debye or less obtained by the semi-empirical molecular orbital calculation and a compound represented by the following general formula (1): .

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3) 2. The organophotoreceptor according to claim 1, wherein the carbocyclic group is a phenyl group. 3. The organic photosensitive according to claim 1, wherein the photosensitive layer has a structure in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material laminated thereon are laminated. body. The organophotoreceptor according to claim 1, wherein the charge generation material is a Y-type titanyl phthalocyanine pigment. The organophotoreceptor according to claim 1, wherein the charge transport material has an ionization potential of 7.6 to 7.9 eV. In an image forming method, a uniform charge is imparted on an organic photoreceptor in a charging step, an electrostatic latent image is formed in an image exposure step, and the electrostatic latent image is visualized as a toner image in a development step. Has a photosensitive layer containing at least a charge generating material and a charge transporting material on a conductive substrate, the photosensitive layer has a triarylamine group and is indirectly linked to the N atom of the triarylamine group, In addition, on the farthest carbocyclic group, it has at least one carbon atom having a HOMO electron density distribution value of 0.009 or more determined by semiempirical molecular orbital calculation using the AM1 parameter, An image forming method comprising: a charge transport material having a dipole moment determined by the semi-empirical molecular orbital calculation of 0.7 debye or less and a compound represented by the following general formula (1): .

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3) The image forming method according to claim 6, wherein the process speed is 400 mm / sec or more. An organic photoreceptor, a charger for uniformly charging the organic photoreceptor, an image exposure unit for forming an electrostatic latent image on the organic photoreceptor, and a developer for developing the electrostatic latent image into a toner image In the image forming apparatus, the organic photoreceptor has a photosensitive layer containing at least a charge generation material and a charge transport material on a conductive substrate, the photosensitive layer has a triarylamine group, and the triarylamine group The value of the HOMO electron density distribution obtained by the semi-empirical molecular orbital calculation using the AM1 parameter is 0.009 or more on the carbocyclic group that is indirectly linked to the N atom of A charge transport material having at least one carbon atom and having a dipole moment of 0.7 debye or less determined by the semi-empirical molecular orbital calculation and a compound represented by the following general formula (1): contains An image forming apparatus comprising and.

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3) The image forming apparatus according to claim 8, wherein a process speed is 400 mm / sec or more. An organic photoreceptor, a charger for uniformly charging the organic photoreceptor, an image exposure unit for forming an electrostatic latent image on the organic photoreceptor, and a developer for developing the electrostatic latent image into a toner image A process cartridge for use in an image forming apparatus having a photosensitive layer containing at least a charge generating substance and a charge transporting substance on a conductive substrate, the photosensitive layer having a triarylamine group, and the triarylamine group The value of the HOMO electron density distribution obtained by the semi-empirical molecular orbital calculation using the AM1 parameter is 0.009 or more on the carbocyclic group that is indirectly linked to the N atom of A charge transport material having at least one carbon atom and having a dipole moment determined by the semi-empirical molecular orbital calculation of 0.7 debye or less and represented by the following general formula (1): An organic photoreceptor containing a compound and at least one of charging means, latent image forming means, developing means, transfer means, charge eliminating means, and cleaning means are integrally supported and can be detachably attached to the image forming apparatus main body. Process cartridge characterized by being.

(In General Formula (1), A represents a phosphate group, R ₁ and R ₂ each represent an alkyl group having 1 to 5 carbon atoms, M represents a metal atom, and n represents an integer of 1 to 3)

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