JP7183552B2 - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus.

Patent Document 1 discloses a conductive substrate and an organic photosensitive layer provided on the conductive substrate, wherein the layer constituting the surface contains a charge transport material, a binder resin, silica particles, and a silicone compound. An electrophotographic photoreceptor comprising an organic photosensitive layer and an inorganic protective layer provided on the organic photosensitive layer is described.

JP 2017-146562 A

An object of the present invention is to provide an electrophotographic photoreceptor having an inorganic protective layer in which cracking of the inorganic protective layer is suppressed as compared with the case where the inorganic protective layer is provided directly on the charge transport layer containing silica particles. to provide.

The invention according to claim 1 comprises a conductive substrate, a charge transport layer provided on the conductive substrate and containing a charge transport material, a binder resin and silica particles, and an inorganic protective layer provided on the charge transport layer. A crack suppression layer sandwiched between the charge transport layer and the inorganic protective layer, which does not hinder the movement of charges transported from the charge transport layer and the charge transport layer of the inorganic protective layer. a crack suppression layer that suppresses cracking of the side surface, the crack suppression layer contains silica particles, and the density of the silica particles in the crack suppression layer is equal to the density of the silica particles in the charge transport layer. The crack suppression layer has a volume resistivity of 0.3 to 2 times the volume resistivity of the charge transport layer, and the surface of the crack suppression layer on the inorganic protective layer side The electrophotographic photoreceptor has a height difference of 0.05 μm or less . The invention according to claim 2 comprises a conductive substrate, a charge transport layer provided on the conductive substrate and containing a charge transport material, a binder resin and silica particles, and an inorganic protective layer provided on the charge transport layer. A crack suppression layer sandwiched between the charge transport layer and the inorganic protective layer, which does not hinder the movement of charges transported from the charge transport layer and the charge transport layer of the inorganic protective layer. and a crack suppression layer that suppresses cracking of the surface of the charge transport layer, the crack suppression layer contains silica particles, and the volume average particle size of the silica particles contained in the crack suppression layer is equal to that of the charge transport layer. The crack suppression layer has a volume resistivity smaller than the volume average particle diameter of the silica particles contained therein, and a volume resistivity of the crack suppression layer that is 0.3 to 2 times the volume resistivity of the charge transport layer. The height difference of the inorganic protective layer side surface of is 0.05 μm or less .

The invention according to claim 3 is the electrophotographic photoreceptor according to claim 1 or 2 , wherein the thickness of the crack suppression layer is larger than the volume average particle diameter of the silica particles contained in the charge transport layer. .

The invention according to claim 4 is the invention according to claim 3 , wherein the thickness of the crack suppression layer is more than 1 time and 10 times or less the volume average particle diameter of the silica particles contained in the charge transport layer. It is an electrophotographic photoreceptor.

The invention according to claim 5 is the electrophotographic photoreceptor according to any one of claims 1 to 4 , wherein the crack suppression layer has a thickness of 0.08 μm or more and 0.8 μm or less.

The invention according to claim 6 is the electrophotographic photoreceptor according to any one of claims 1 to 5, wherein the content of the silica particles in the crack suppression layer is 30% by mass or less.

The invention according to claim 7 is the electrophotographic photoreceptor according to any one of claims 1 to 6 , wherein the height difference of the surface of the crack suppression layer on the inorganic protective layer side is 0.01 μm or less.

The invention according to claim 8 is the electrophotographic photoreceptor according to any one of claims 1 to 7 , wherein the inorganic protective layer has a thickness of 1 μm or more and 6 μm or less.

According to a ninth aspect of the invention, there is provided a process cartridge which includes the electrophotographic photosensitive member according to any one of the first to eighth aspects and which is detachable from an image forming apparatus.

The invention according to claim 10 is an electrophotographic photoreceptor according to any one of claims 1 to 8 ,
The electrophotographic photosensitive member is charged by charging means for charging the surface of the electrophotographic photosensitive member, electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member, and developer containing toner. The image forming apparatus includes developing means for developing an electrostatic latent image formed on the surface of a body to form a toner image, and transfer means for transferring the toner image to the surface of a recording medium.

According to the invention of claim 1 or 2 , in the electrophotographic photoreceptor having an inorganic protective layer, cracking of the inorganic protective layer is suppressed compared to the case where the inorganic protective layer is provided directly on the charge transport layer containing silica particles. An electrophotographic photoreceptor is provided.

According to the inventions according to claims 3 and 4 , cracks in the inorganic protective layer are less likely to occur than when the thickness of the crack suppression layer is equal to or less than the volume average particle diameter of the silica particles contained in the charge transport layer. Inhibited electrophotographic photoreceptors are provided.

According to the fifth aspect of the invention, there is provided an electrophotographic photoreceptor in which cracking of the inorganic protective layer is suppressed as compared with the case where the thickness of the cracking suppression layer is less than 0.08 μm.

According to the first aspect of the invention, cracks in the inorganic protective layer are more likely to occur than when the density of the silica particles in the crack suppression layer exceeds 30% of the density of the silica particles in the charge transport layer. Inhibited electrophotographic photoreceptors are provided. According to the sixth aspect of the present invention, there is provided an electrophotographic photoreceptor in which cracking of the inorganic protective layer is suppressed as compared with the case where the content of the silica particles in the cracking suppression layer exceeds 30% by mass. be.

According to the first aspect of the invention, there is provided an electrophotographic photoreceptor in which cracking of the inorganic protective layer is suppressed as compared with the case where the height difference of the surface of the crack suppressing layer on the inorganic protective layer side exceeds 0.05 μm. be done. Further, according to the invention of claim 7 , the electrophotographic photoreceptor suppresses cracking of the inorganic protective layer as compared with the case where the height difference of the surface of the crack suppressing layer on the inorganic protective layer side exceeds 0.01 μm. is provided.

According to the eighth aspect of the invention, there is provided an electrophotographic photoreceptor in which cracking of the inorganic protective layer is suppressed as compared with the case where the thickness of the inorganic protective layer is less than 1 μm or exceeds 6 μm. be.

According to the inventions of claims 9 and 10 , in the electrophotographic photoreceptor having an inorganic protective layer, the inorganic protection of the electrophotographic photoreceptor is improved compared to the case where the inorganic protective layer is provided directly on the charge transport layer containing silica particles. A process cartridge or an image forming apparatus in which cracking of layers is suppressed is provided.

1 is a schematic cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor of the present exemplary embodiment; FIG. FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor of the exemplary embodiment; FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor of the exemplary embodiment; 1 is a schematic diagram showing an example of a film forming apparatus used for forming an inorganic protective layer of an electrophotographic photoreceptor of the present exemplary embodiment; FIG. 1 is a schematic diagram showing an example of a plasma generator used for forming an inorganic protective layer of an electrophotographic photoreceptor of the present exemplary embodiment; FIG. It is a figure which shows the measurement result of the surface shape of the coating film with a laser microscope. This is a model of an electrophotographic photoreceptor used for simulation analysis. It is a figure which shows the result of simulation analysis. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to an embodiment; FIG. FIG. 2 is a schematic configuration diagram showing another example of the image forming apparatus according to the embodiment;

Hereinafter, embodiments of the present invention will be described in detail.

[Electrophotographic photoreceptor]
The electrophotographic photoreceptor according to the present embodiment comprises a conductive substrate, a charge transport layer provided on the conductive substrate, an inorganic protective layer provided on the charge transport layer, a charge transport layer and an inorganic protective layer. and a crack suppression layer sandwiched between. The charge-transporting layer contains a charge-transporting material, a binder resin, and silica particles. Suppresses cracks on the transport layer side surface.

Conventionally, a technique for forming an inorganic protective layer on an organic photosensitive layer including a charge transport layer is known. Since the charge transport layer contains a charge transport material and a binder resin, it tends to be flexible and easily deformed, while the inorganic protective layer is hard and tends to be inferior in toughness. Therefore, if the charge transport layer, which is the underlying layer of the inorganic protective layer, is deformed, cracks may occur in the inorganic protective layer. It is considered that such a phenomenon is likely to occur because the electrophotographic photosensitive member is likely to be subjected to a mechanical load from a member (for example, an intermediate transfer member) arranged in contact with the surface thereof.

Therefore, by forming the charge transport layer constituting the surface of the organic photosensitive layer to contain silica particles in addition to the charge transport material and the binder resin, the silica particles function as a reinforcing material for the charge transport layer and charge transport. Since the layer becomes difficult to deform, cracking of the inorganic protective layer is thought to be suppressed.

On the other hand, due to the silica particles contained in the charge transport layer, on the surface ^of the charge transport ^layer on the inorganic protective layer side, ) was found to be generated. When minute unevenness occurs on the surface of the charge transport layer on the inorganic protective layer side, the unevenness is transferred to the surface of the inorganic protective layer on the charge transport layer side, which is in contact with the surface of the charge transport layer on the inorganic protective layer side. Conceivable. If unevenness is formed on the surface of the inorganic protective layer on the side of the charge transport layer, for example, when the toner image formed on the surface of the electrophotographic photosensitive member is primarily transferred to the surface of the intermediate transfer member, the inorganic protective layer is mechanically affected. It was found that there is a possibility that the inorganic protective layer cracks starting from the concave portions (cracks) of the unevenness when a load is applied.

Cracking of the inorganic protective layer caused by irregularities on the surface of the inorganic protective layer can be suppressed by increasing the thickness of the inorganic protective layer. However, when the film thickness of the inorganic protective layer becomes thick, the image quality may be deteriorated, and it takes time and cost to form the inorganic protective layer. It is considered that the deterioration of the image quality due to the thickening of the inorganic protective layer is caused by the damage to the charge transport layer caused by plasma irradiation during film formation of the inorganic protective layer.

In contrast, the electrophotographic photoreceptor of the present embodiment includes a crack-suppressing layer that does not hinder the movement of charges transported from the charge-transporting layer and suppresses cracking of the charge-transporting-layer-side surface of the inorganic protective layer. , By providing between the charge transport layer and the inorganic protective layer, compared with the case where the inorganic protective layer is directly provided on the charge transport layer containing silica particles, the unevenness generated on the surface of the inorganic protective layer on the charge transport layer side is reduced. reduce the difference in height. As a result, cracking of the inorganic protective layer can be suppressed, and deterioration of image quality and cost increase due to thickening of the inorganic protective layer can be suppressed.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted.

[Electrophotographic photoreceptor]
FIG. 1 is a schematic cross-sectional view showing an example of an electrophotographic photoreceptor according to this embodiment. As shown in FIG. 1, the electrophotographic photoreceptor according to the present embodiment includes a conductive substrate 4, a charge transport layer 3 provided on the conductive substrate 4, and an inorganic protective layer provided on the charge transport layer 3. It comprises a layer 5 and a crack suppression layer 6 sandwiched between the charge transport layer 3 and the inorganic protective layer 5 . The charge transport layer 3 contains a charge transport material, a binder resin, and silica particles, and the crack suppression layer 6 does not hinder the movement of charges transported from the charge transport layer 3, and is inorganic protective. It suppresses cracking of the surface of the layer 5 on the charge transport layer 3 side.

The electrophotographic photoreceptor 7A shown in FIG. 1 is a so-called function-separated photoreceptor (or laminated photoreceptor). It has a structure in which a generation layer 2, a charge transport layer 3 and a crack suppression layer 6 are sequentially formed.

2 and 3 are schematic cross-sectional views showing other examples of the electrophotographic photoreceptor according to this embodiment, respectively.

The electrophotographic photoreceptor 7B shown in FIG. 2 is functionally separated into the charge generation layer 2 and the charge transport layer 3, and has a plurality of layers corresponding to the charge transport layer 3 in the electrophotographic photoreceptor 7A shown in FIG. It is a function-separated photoreceptor in which functions are separated into (charge-transporting layer 3B and charge-transporting layer 3A). That is, in the electrophotographic photoreceptor 7B shown in FIG. 2, the undercoat layer 1 is provided on the conductive substrate 4, and thereon the charge generation layer 2, the charge transport layer 3B, the charge transport layer 3A, and the crack suppression layer. 6 and an inorganic protective layer 5 are sequentially formed.

In the electrophotographic photoreceptor 7B, the charge transport layer 3A, the charge transport layer 3B, the charge generation layer 2 and the crack prevention layer 6 constitute an organic photosensitive layer. The charge transport layer 3A contains a charge transport material, a binder resin and silica particles. The charge transport layer 3B contains at least a charge transport material, and may or may not contain silica particles. Thus, when the charge transport layer is composed of two or more layers, at least one of the two or more charge transport layers is on the surface opposite to the conductive substrate 4 and adjacent to the crack suppression layer 6. A layer comprises a charge transport material, a binder resin and silica particles.

In the electrophotographic photoreceptor 7C shown in FIG. 3, the undercoat layer 1 is provided on the conductive substrate 4, and the charge generation/charge transport layer 3C, the crack suppression layer 6 and the inorganic protective layer 5 are successively formed thereon. have a structure. In the electrophotographic photoreceptor 7C shown in FIG. 3, the charge generation/charge transport layer 3C contains a charge generation material, a charge transport material, a binder resin and silica particles. In this way, by including the charge generation material together with the charge transport material, the charge generation/charge transport layer 3C in the electrophotographic photoreceptor 7C is similar to the charge generation layer 2 and the charge generation layer 2 in the electrophotographic photoreceptor 7A shown in FIG. It functions as a layer having both functions of the charge transport layer 3 .

Hereinafter, based on the electrophotographic photoreceptor 7A shown in FIG. 1 as a representative example, each element constituting the electrophotographic photoreceptor 7A will be described. It should be noted that the reference numerals may be omitted in the description.

(Conductive substrate)
Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). is mentioned. Examples of conductive substrates include paper, resin films, belts, etc., coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. is also mentioned. Here, "conductivity" means having a volume resistivity of less than 10 ¹³ Ωcm.

When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate has a center line average roughness Ra of 0.04 μm or more and 0.5 μm for the purpose of suppressing interference fringes generated when laser light is irradiated. It is preferable that the surface is roughened to the following. When non-interfering light is used as the light source, roughening is not particularly necessary to prevent interference fringes, but it is suitable for longer life because it suppresses the occurrence of defects due to irregularities on the surface of the conductive substrate.

Surface roughening methods include, for example, wet honing in which an abrasive is suspended in water and sprayed against the conductive substrate, and centerless grinding in which the conductive substrate is pressed against a rotating grindstone and continuously ground. , anodizing, and the like.

As a roughening method, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate without roughening the surface of the conductive substrate. A method of roughening with particles dispersed in a layer is also included.

In the surface roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate by anodizing a metal (eg, aluminum) conductive substrate as an anode in an electrolytic solution. Examples of electrolyte solutions include sulfuric acid solutions and oxalic acid solutions. However, the porous anodic oxide film formed by anodic oxidation is chemically active as it is, is easily contaminated, and has large resistance fluctuations depending on the environment. Therefore, the micropores of the porous anodized film are closed with pressurized steam or boiling water (metal salts such as nickel may be added) by volume expansion due to hydration reaction, and hydration with lower activity is performed. It is preferable to perform a pore-sealing treatment to convert to an oxide.

The film thickness of the anodized film is preferably 0.3 μm or more and 15 μm or less, for example. When this film thickness is within the above range, there is a tendency for the film to exhibit barrier properties against injection, and the increase in residual potential due to repeated use tends to be suppressed.

The conductive substrate may be treated with an acidic treatment liquid or treated with boehmite. The treatment with an acidic treatment liquid is performed, for example, as follows. First, an acidic treatment liquid containing phosphoric acid, chromic acid and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment liquid is, for example, phosphoric acid in the range of 10% by mass to 11% by mass, chromic acid in the range of 3% by mass to 5% by mass, and hydrofluoric acid in the range of 3% by mass to 5% by mass. It is preferable that the total concentration of these acids is in the range of 0.5 mass % or more and 2 mass % or less, and the range of 13.5 mass % or more and 18 mass % or less. The treatment temperature is preferably 42° C. or higher and 48° C. or lower, for example. The film thickness of the coating is preferably 0.3 μm or more and 15 μm or less.

The boehmite treatment is performed, for example, by immersing the substrate in pure water at a temperature of 90° C. or higher and 100° C. or lower for 5 to 60 minutes, or by contacting the substrate with heated steam at a temperature of 90° C. or higher and 120° C. or lower for 5 to 60 minutes. The film thickness of the coating is preferably 0.1 μm or more and 5 μm or less. This is further anodized using an electrolytic solution with lower film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate. good too.

(Undercoat layer)
The undercoat layer is, for example, a layer containing inorganic particles and a binder resin. In addition, in the electrophotographic photoreceptor according to the exemplary embodiment, the undercoat layer may or may not be provided.

Examples of inorganic particles include inorganic particles having a powder resistance (volume resistivity) of 10 ² Ωcm or more and 10 ¹¹ Ωcm or less. Among these, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles are preferable as the inorganic particles having the above resistance value, and zinc oxide particles are particularly preferable.

The specific surface area of the inorganic particles by the BET method is preferably 10 m ² /g or more, for example. The volume average particle diameter of the inorganic particles is preferably, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

The inorganic particles may be surface-treated. Two or more kinds of inorganic particles having different surface treatments or different particle diameters may be mixed and used.

Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

Silane coupling agents having an amino group include, for example, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-amino Examples include, but are not limited to, propylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and the like.

You may use a silane coupling agent in mixture of 2 or more types. For example, a silane coupling agent having an amino group and another silane coupling agent may be used in combination. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycol sidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-( aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, etc., but are not limited thereto. not a thing

The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

The treatment amount of the surface treatment agent is preferably 0.5% by mass or more and 10% by mass or less with respect to the inorganic particles, for example.

Here, the undercoat layer preferably contains an electron-accepting compound (acceptor compound) together with the inorganic particles, from the viewpoint of enhancing long-term stability of electrical properties and carrier-blocking properties.

Examples of electron-accepting compounds include quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, and the like. fluorenone compounds; 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4- Oxadiazole compounds such as oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4 oxadiazole; xanthone compounds; thiophene compounds; 3,3′,5,5′ tetra- electron-transporting substances such as diphenoquinone compounds such as t-butyldiphenoquinone; A compound having an anthraquinone structure is particularly preferable as the electron-accepting compound. As the compound having an anthraquinone structure, for example, hydroxyanthraquinone compounds, aminoanthraquinone compounds, aminohydroxyanthraquinone compounds, etc. are preferable, and specifically, for example, anthraquinone, alizarin, quinizarin, anthrafin, purpurin, etc. are preferable.

The electron-accepting compound may be dispersed in the undercoat layer together with the inorganic particles, or may be attached to the surfaces of the inorganic particles.

Examples of the method of adhering the electron-accepting compound to the surface of the inorganic particles include a dry method and a wet method.

In the dry method, for example, an electron-accepting compound dissolved in an organic solvent is added dropwise while stirring inorganic particles with a mixer having a large shearing force, and the electron-accepting compound is sprayed with dry air or nitrogen gas. It is a method of adhering to the surface of inorganic particles. Dropping or spraying of the electron-accepting compound is preferably carried out at a temperature not higher than the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be further performed at 100° C. or higher. Baking is not particularly limited as long as the temperature and time are such that electrophotographic properties can be obtained.

In the wet method, for example, by stirring, ultrasonic waves, sand mill, attritor, ball mill, etc., while inorganic particles are dispersed in a solvent, an electron-accepting compound is added, stirred or dispersed, and then the solvent is removed to obtain electrons. This is a method of adhering a receptive compound to the surface of inorganic particles. Solvent removal methods include distilling off by filtration or distillation. After removing the solvent, baking may be further performed at 100° C. or higher. Baking is not particularly limited as long as the temperature and time are such that electrophotographic properties can be obtained. In the wet method, the water contained in the inorganic particles may be removed before adding the electron-accepting compound, examples of which include a method of removing while stirring and heating in a solvent, and a method of removing by azeotroping with a solvent. mentioned.

Attachment of the electron-accepting compound may be performed before or after the surface treatment with the surface treatment agent is applied to the inorganic particles, or attachment of the electron-accepting compound and surface treatment with the surface treatment agent may be performed together.

The content of the electron-accepting compound is, for example, preferably 0.01% by mass or more and 20% by mass or less, preferably 0.01% by mass or more and 10% by mass or less, relative to the inorganic particles.

Examples of binder resins used in the undercoat layer include acetal resins (for example, polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, and unsaturated polyesters. Resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, Urethane resins, alkyd resins, known polymer compounds such as epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; Examples of the binder resin used in the undercoat layer include charge-transporting resins having a charge-transporting group, conductive resins (eg, polyaniline, etc.), and the like.

Among these, resins that are insoluble in the coating solvent of the upper layer are suitable as the binder resin used in the undercoat layer. thermosetting resins such as resins, alkyd resins and epoxy resins; at least one resin selected from the group including polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins and polyvinyl acetal resins; Resins obtained by reaction with a curing agent are preferred. When two or more of these binder resins are used in combination, the mixing ratio is set according to need.

The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality. Examples of the additive include known materials such as electron-transporting pigments such as polycyclic condensed and azo-based pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. be done. The silane coupling agent is used for the surface treatment of the inorganic particles as described above, and may be added to the undercoat layer as an additive.

Silane coupling agents as additives include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3- glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2- (Aminoethyl)-3-aminopropylmethylmethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like.

Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, zirconium acetylacetonate butoxide, ethyl zirconium butoxide acetoacetate, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, zirconium isostearate butoxide and the like.

Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-normal butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt. , titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, polyhydroxytitanium stearate, and the like.

Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

These additives may be used alone or as mixtures or polycondensates of multiple compounds.

The undercoat layer preferably has a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer is 1/(4n) (n is the refractive index of the upper layer) to 1/2 of the exposure laser wavelength λ used to suppress moiré images. should be adjusted to Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. Further, the surface of the undercoat layer may be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

Formation of the undercoat layer is not particularly limited, and a well-known formation method is used. and, if necessary, by heating.

Solvents for preparing the undercoat layer-forming coating liquid include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents, Solvents, ester solvents and the like can be mentioned. Specific examples of these solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, Ordinary organic solvents such as n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene and toluene can be used.

Examples of the method for dispersing the inorganic particles when preparing the undercoat layer-forming coating solution include known methods such as a roll mill, ball mill, vibrating ball mill, attritor, sand mill, colloid mill, and paint shaker.

Examples of methods for applying the undercoat layer-forming coating liquid onto the conductive substrate include blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating. Ordinary methods such as

The thickness of the undercoat layer is, for example, desirably 15 μm or more, more desirably 20 μm or more and 50 μm or less.

(middle layer)
Although not shown, an intermediate layer sandwiched between the undercoat layer and the organic photosensitive layer may be further provided. The intermediate layer is, for example, a layer containing resin. Examples of resins used for the intermediate layer include acetal resins (for example, polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, Polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, melamine resins and other high-molecular compounds can be mentioned. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used for the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese and silicon. These compounds used for the intermediate layer may be used singly or as a mixture or polycondensate of a plurality of compounds.

Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

Formation of the intermediate layer is not particularly limited, and a well-known forming method is used. It is done by heating according to. As the coating method for forming the intermediate layer, usual methods such as dip coating, thrust coating, wire bar coating, spray coating, blade coating, knife coating and curtain coating can be used.

The film thickness of the intermediate layer is preferably set within a range of 0.1 μm or more and 3 μm or less, for example. Note that the intermediate layer may be used as an undercoat layer.

(Charge generation layer)
The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Also, the charge generation layer may be a deposited layer of a charge generation material. The deposited layer of the charge generating material is suitable for use with non-coherent light sources such as LEDs (Light Emitting Diodes) and organic EL (Electro-Luminescence) image arrays.

Examples of charge-generating materials include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments;

Among these, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generation material in order to cope with laser exposure in the near-infrared region. Specifically, for example, hydroxygallium phthalocyanine disclosed in JP-A-5-263007 and JP-A-5-279591; chlorogallium phthalocyanine disclosed in JP-A-5-98181; -140472, JP-A-5-140473, etc., and titanyl phthalocyanine disclosed in JP-A-4-189873, etc. are more preferable.

On the other hand, in order to cope with laser exposure in the near-ultraviolet region, charge-generating materials include condensed aromatic pigments such as dibromoanthanthrone; thioindigo pigments; porphyrazine compounds; zinc oxide; Bisazo pigments disclosed in JP-A-2004-78147 and JP-A-2005-181992 are preferred.

The above-mentioned charge generation material may also be used when using a non-coherent light source such as an LED or an organic EL image array having an emission central wavelength of 450 nm or more and 780 nm or less. Here, from the viewpoint of resolution, when a thin film of 20 μm or less is used for the photosensitive layer, the electric field strength in the photosensitive layer becomes high, and charging deterioration due to charge injection from the substrate tends to cause image defects called black spots. This becomes remarkable when a charge-generating material such as trigonal selenium, phthalocyanine pigment, or the like, which is a p-type semiconductor and tends to generate dark current, is used.

On the other hand, when n-type semiconductors such as condensed aromatic pigments, perylene pigments, and azo pigments are used as the charge generation material, dark current is less likely to occur, and image defects called black spots can be suppressed even if the film is formed into a thin film. . Examples of n-type charge generation materials include compounds (CG-1) to (CG-27) described in paragraphs [0288] to [0291] of JP-A-2012-155282. It is not limited. The n-type is determined by the time-of-flight method, which is usually used, and the polarity of the photocurrent that flows.

The binder resin used in the charge generation layer is selected from a wide range of insulating resins, and the binder resin is selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene and polysilane. You may choose. Examples of binder resins include polyvinyl butyral resins, polyarylate resins (polycondensates of bisphenols and aromatic divalent carboxylic acids, etc.), polycarbonate resins, polyester resins, phenoxy resins, vinyl chloride-vinyl acetate copolymers, Polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin and the like can be mentioned. Here, “insulating” means having a volume resistivity of 10 ¹³ Ωcm or more. These binder resins may be used singly or in combination of two or more.

The mixing ratio of the charge-generating material and the binder resin is preferably in the range of 10:1 to 1:10 in mass ratio.

The charge generation layer may contain other known additives.

Formation of the charge-generating layer is not particularly limited, and a well-known formation method is used. and, if necessary, by heating. The charge generation layer may be formed by vapor deposition of a charge generation material. Formation of the charge-generating layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or perylene pigment is used as the charge-generating material.

Solvents for preparing the charge-generating layer-forming coating solution include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, and n-acetic acid. -butyl, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like. These solvents are used singly or in combination of two or more.

Examples of the method for dispersing particles (for example, charge-generating material) in the coating liquid for forming the charge-generating layer include media dispersing machines such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, stirring, and ultrasonic dispersing machines. , roll mills, high-pressure homogenizers, and other medialess dispersers are used. Examples of high-pressure homogenizers include a collision system in which a dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration system in which a fine flow path is penetrated and dispersed in a high-pressure state. In this dispersion, it is effective to set the volume average particle size of the charge generation material in the coating liquid for forming the charge generation layer to 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.15 μm or less. be.

Examples of the method for applying the charge generation layer forming coating liquid onto the undercoat layer (or onto the intermediate layer) include blade coating, wire bar coating, spray coating, dip coating, bead coating, and air knife coating. conventional methods such as coating method, curtain coating method, and the like.

The film thickness of the charge generation layer is set, for example, preferably in the range of 0.1 μm to 5.0 μm, and more preferably in the range of 0.2 μm to 2.0 μm.

(Charge transport layer)
-Composition of charge transport layer-
The charge transport layer contains a charge transport material, a binder resin, and silica particles.

Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanyl and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; ; cyanovinyl-based compounds; and electron-transporting compounds such as ethylene-based compounds. Charge transport materials also include hole-transporting compounds such as triarylamine-based compounds, benzidine-based compounds, arylalkane-based compounds, aryl-substituted ethylene-based compounds, stilbene-based compounds, anthracene-based compounds, and hydrazone-based compounds. These charge transport materials may be used singly or in combination of two or more, but are not limited to these.

From the viewpoint of charge mobility, the charge transport material is preferably a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2).

In structural formula (a-1), Ar ^T1 , Ar ^T2 and Ar ^T3 each independently represent a substituted or unsubstituted aryl group, —C ₆ H ₄ —C(R ^T4 )=C(R ^T5 )(R ^T6 ), or -C ₆ H ₄ -CH=CH-CH=C(R ^T7 )(R ^T8 ). R ^T4 , R ^T5 , R ^T6 , R ^T7 and R ^T8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of substituents for the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Moreover, as a substituent of each said group, the substituted amino group substituted with the C1-C3 or less alkyl group is also mentioned.

In structural formula (a-2), R ^{1 T91} and R ^{2 T92} each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. R ^T101 , R ^T102 , R ^T111 and R ^T112 are each independently substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 2 carbon atoms. a substituted or unsubstituted aryl group, —C(R ^T12 )=C(R ^T13 )(R ^T14 ), or —CH=CH—CH=C(R ^T15 )(R ^T16 ); R ^T12 , R ^T13 , R ^T14 , R ^T15 and R ^T16 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1 and Tn2 each independently represent an integer of 0 or more and 2 or less. Examples of substituents for the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Moreover, as a substituent of each said group, the substituted amino group substituted with the C1-C3 or less alkyl group is also mentioned.

Here, among the triarylamine derivative represented by the structural formula (a-1) and the benzidine derivative represented by the structural formula (a-2), in particular, “—C ₆ H ₄ —CH=CH—CH= A triarylamine derivative having “C(R ^T7 )(R ^T8 )” and a benzidine derivative having “—CH═CH—CH═C(R ^T15 )(R ^T16 )” are preferred from the viewpoint of charge mobility.

As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester polymer charge transport materials disclosed in JP-A-8-176293 and JP-A-8-208820 are particularly preferred. The polymer charge transport material may be used alone, or may be used in combination with a binder resin.

Examples of silica particles used in the charge transport layer include dry silica particles and wet silica particles. Dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound and deflagration silica obtained by explosively burning metallic silicon powder. Wet-process silica particles include wet-process silica particles obtained by a neutralization reaction between sodium silicate and mineral acid (precipitation silica particles synthesized and aggregated under alkaline conditions, gel-process silica particles synthesized and aggregated under acidic conditions), and acidic silicic acid. Examples include colloidal silica particles (silica sol particles) obtained by alkalinizing and polymerizing, and sol-gel method silica particles obtained by hydrolyzing an organic silane compound (eg, alkoxysilane).

Among these, silica particles have fewer silanol groups on the surface and have a lower void structure from the viewpoint of suppressing image defects due to generation of residual potential and deterioration of other electrical properties (suppression of deterioration of fine line reproducibility). Combustion silica particles are preferred.

The volume average particle diameter of the silica particles is, for example, preferably 20 nm or more and 200 nm or less, desirably 40 nm or more and 150 nm or less, more desirably 50 nm or more and 120 nm or less, and still more desirably 50 nm or more and 110 nm or less.

When silica particles having a volume-average particle diameter within the above range and a binder resin having a viscosity-average molecular weight of less than 50000 are used in combination, image smearing can be more easily suppressed.

The volume average particle diameter of the silica particles is obtained by separating the silica particles from the layer, observing 100 primary particles of the silica particles with a SEM (Scanning Electron Microscope) device at a magnification of 40,000 times, and analyzing the image of the primary particles. Measure the longest diameter and shortest diameter for each, and measure the equivalent sphere diameter from the intermediate value. The 50% diameter (D50v) in the cumulative frequency of the obtained sphere equivalent diameters is obtained, and this is measured as the volume average particle diameter of the silica particles.

The silica particles are preferably surface-treated with a hydrophobizing agent. This reduces the number of silanol groups on the surface of the silica particles, making it easier to suppress the generation of residual potential. Hydrophobizing agents include well-known silane compounds such as chlorosilanes, alkoxysilanes and silazanes. Among these, a silane compound having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group is preferable as the hydrophobizing agent from the viewpoint of facilitating suppression of residual potential. That is, the silica particles preferably have a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group on their surfaces.

Silane compounds having a trimethylsilyl group include, for example, trimethylchlorosilane, trimethylmethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane and the like. Silane compounds having a decylsilyl group include, for example, decyltrichlorosilane, decyldimethylchlorosilane, and decyltrimethoxysilane. Silane compounds having a phenyl group include triphenylmethoxysilane and triphenylchlorosilane.

The condensation rate of silica particles that have been hydrophobized (ratio of Si—O—Si in bonds of SiO ₄ — in silica particles: hereinafter also referred to as “condensation rate of hydrophobizing agent”) is, for example, the surface of silica particles is preferably 96% or more, preferably 97% or more, and more preferably 98% or more, with respect to the silanol groups of . When the condensation ratio of the hydrophobizing agent is within the above range, the silanol groups of the silica particles are further reduced, and the generation of residual potential is easily suppressed.

The condensation ratio of the hydrophobizing agent indicates the ratio of condensed silicon to all possible silicon bonding sites in the condensed portion detected by NMR, and is measured as follows. First, silica particles are separated from the layer. The separated silica particles were subjected to Si CP/MAS NMR analysis with Bruker's AVANCE III 400 to determine the peak area corresponding to the number of SiO substitutions, and the respective disubstituted (Si(OH) ₂ (0-Si) ₂ -), 3-substituted (Si(OH)(0-Si) ₃ -), and 4-substituted (Si(0-Si) ₄ -) are defined as Q2, Q3, and Q4, and the condensation rate of the hydrophobizing agent is expressed by the formula : Calculated by (Q2×2+Q3×3+Q4×4)/4×(Q2+Q3+Q4).

The volume resistivity of the silica particles is, for example, preferably 10 ¹¹ Ω·cm or more, preferably 10 ¹² Ω·cm or more, and more preferably 10 ¹³ Ω·cm or more. When the volume resistivity of the silica particles is within the above range, deterioration in electrical properties is suppressed.

The volume resistivity of silica particles is measured as follows. The measurement environment is assumed to have a temperature of 20° C. and a humidity of 50% RH. First, silica particles are separated from the layer. Separated silica particles to be measured are placed on the surface of a circular jig on which an electrode plate of 20 cm ² is arranged so as to have a thickness of about 1 mm or more and 3 mm or less to form a silica particle layer. Another 20 cm ² electrode plate is placed on top of this to sandwich the silica particle layer. In order to eliminate voids between silica particles, a load of 4 kg is applied to the electrode plate placed on the silica particle layer, and then the thickness (cm) of the silica particle layer is measured. Both electrodes above and below the silica particle layer are connected to an electrometer and a high-voltage power generator. A high voltage is applied to both electrodes so that the electric field has a predetermined value, and the current value (A) that flows at this time is read to calculate the volume resistivity (Ω·cm) of the silica particles. The formula for calculating the volume resistivity (Ω·cm) of silica particles is as shown below.
In the formula, ρ is the volume resistivity of the silica particles (Ω cm), E is the applied voltage (V), I is the current value (A), _I0 is the current value at the applied voltage of 0 V (A), L is Each represents the thickness (cm) of the silica particle layer. In this evaluation, the volume resistivity at an applied voltage of 1000V was used.
・ Formula: ρ = E × 20 / (II ₀ ) / L

From the viewpoint of suppressing the occurrence of cracks in the inorganic protective layer, the content of the silica particles is, for example, preferably 30% by mass or more, preferably 40% by mass or more, preferably 50% by mass, with respect to the entire charge transport layer. % or more is more desirable. Although the upper limit is not particularly limited, it is preferably 70% by mass or less, preferably 65% by mass or less, and more preferably 60% by mass or less from the viewpoint of ensuring the properties of the charge transport layer. .

The charge transport layer may contain a silicone compound together with the charge transport material, the binder resin and the silica particles. When the charge-transporting layer contains silica particles, although the elasticity of the charge-transporting layer is improved, the elasticity of the charge-transporting layer may vary due to the deterioration of the dispersibility of the silica particles. If the elastic modulus of the charge-transporting layer containing silica particles varies, the charge-transporting layer will have a mixture of portions with a relatively high elastic modulus and portions with a relatively low elastic modulus. Cracks (including dents) tend to occur easily in inorganic protective layers provided on relatively low portions. The decrease in dispersibility of the silica particles in the charge transport layer is considered to be due to the low affinity between the binder resin in the charge transport layer and the silica particles. For example, when silica particles are hydrophobized, the dispersibility in the charge transport layer is likely to be improved. However, a decrease in dispersibility may occur.

On the other hand, in the charge transport layer containing a silicone compound together with silica particles, the variation in the elastic modulus of the charge transport layer is suppressed, the elastic modulus of the entire charge transport layer is improved, and cracking of the inorganic protective layer is prevented. Suppressed. Although the reason for this is not clear, it is considered as follows. Since the silica particles and the silicone compound contain silicon in their chemical structures, the affinity between the silicone compound and the silica particles is high. In addition, since silicone compounds have many hydrophobic groups (eg, methyl groups) in their chemical structure, they have high affinity with binder resins. Therefore, the silicone compound acts to increase the affinity between the binder resin and the silica particles. That is, the interaction between the silica particles and the silicone compound suppresses the deterioration of the dispersibility of the silica particles in the charge transport layer. As a result, it is believed that variations in the elastic modulus of the charge transport layer are suppressed, the elastic modulus of the entire charge transport layer is improved, and cracking of the inorganic protective layer is suppressed.

The silicone compound used in the charge transport layer is a compound having a siloxane skeleton, and from the viewpoint of suppressing cracking of the inorganic protective layer, for example, silicone oil (straight silicone oil or modified silicone oil) can be used. A silicone oil with lower reactivity is desirable.

Examples of silicone compounds include straight silicone oils such as dimethyl silicone oil, methylphenyl silicone oil and diphenyl silicone oil; phenyl-modified silicone oil, aralkyl-modified silicone oil, alkyl-modified silicone oil, fluoro-modified silicone oil; modified silicone oils such as fluoroalkyl-modified silicone oils, polyether-modified silicone oils, polyol-modified silicone oils, polyester-modified silicone oils, fatty acid ester-modified silicone oils, and acrylic-modified silicone oils;

The content of the silicone compound is desirably 0.0033% by mass or more and 0.033% by mass or less based on the solid content of the charge transport layer. More desirably, it is 0.0066% by mass or more and 0.02% by mass or less. By using the silicone compound within this range, the dispersibility of the silica particles can be easily improved.

The content of the silicone compound in the charge transport layer is measured as follows. First, after peeling off the inorganic protective layer from the photoreceptor to be measured, the photosensitive layer to be measured is exposed, and a part of the photosensitive layer is scraped off to prepare a sample for measurement. Next, the content of the silicone compound is determined by subjecting the measurement sample to nuclear magnetic resonance (NMR) analysis or the like.

Although the binder resin used in the charge transport layer is not particularly limited, it preferably has a viscosity-average molecular weight of 50,000 or less, for example, from the viewpoint of further suppressing cracking of the inorganic protective layer. It is preferably 45,000 or less, more preferably 35,000 or less. The lower limit of the viscosity-average molecular weight is preferably 20,000 or more from the viewpoint of maintaining properties as a binder resin.

Here, the following one-point measurement method is used to measure the viscosity-average molecular weight of the binder resin. First, after peeling off the inorganic protective layer from the photoreceptor to be measured, the photosensitive layer to be measured is exposed. Then, a part of the photosensitive layer is scraped out to prepare a measurement sample. Next, the binder resin is extracted from the measurement sample. 1 g of the extracted binder resin is dissolved in 100 cm ³ of methylene chloride, and the specific viscosity ηsp is measured with an Ubbelohde viscometer under a measurement environment of 25°C. Then, the intrinsic viscosity [η] (cm 3 /g) was obtained from ^the relational expression ηsp/c=[η]+0.45[η] ² c (where c is the concentration (g/cm ³ )). The viscosity-average molecular weight Mv is obtained from the relation [η]=1.23×10 ⁻⁴ ×Mv ^0.83 given by Schnell.

Specific examples of binder resins include polycarbonate resins (homopolymerization type of bisphenol A, bisphenol Z, bisphenol C, bisphenol TP, etc., or copolymerization types thereof), polyarylate resins, polyester resins, methacrylic resins, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl acetate resin, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-acrylic copolymer, acetylene-alkyd resin, poly-N-vinylcarbazole resin, polyvinyl butyral resin, Examples include polyphenylene ether resins. These binder resins are used singly or in combination of two or more. The mixing ratio of the charge transport material and the binder resin is preferably from 10:1 to 1:5 in mass ratio.

Among the binder resins described above, polycarbonate resins (homopolymerization type of bisphenol A, bisphenol Z, bisphenol C, bisphenol TP, etc., or copolymerization type thereof) are preferable from the viewpoint of further suppressing the occurrence of image deletion. Polycarbonate resin may be used individually by 1 type, and may be used in combination of 2 or more types. From the same point of view, it is more preferable to include a bisphenol Z homopolymerization type polycarbonate resin among the polycarbonate resins.

-Characteristics of charge transport layer-
The elastic modulus of the charge transport layer is, for example, preferably 5 GPa or higher, preferably 6 GPa or higher, more preferably 6.5 GPa or higher, and even more preferably 7 GPa or higher. When the elastic modulus of the charge transport layer is within the above range, cracking of the inorganic protective layer is easily suppressed. Although the upper limit of the elastic modulus is not particularly limited, it is preferably 20 GPa or less, for example. In order to set the elastic modulus of the charge transport layer within the above range, for example, a method of adjusting the particle size and content of silica particles, and a method of adjusting the type and content of the charge transport material can be used. Moreover, when the charge transport layer contains a silicone compound, a method of adjusting the type and content of the silicone compound can be used.

Further, the elastic modulus of the charge transport layer has a standard deviation of 0.1 or more and 0.65 or less (preferably 0.2 or more and 0.62 or less, more preferably 0.2 or more and 0.62 or less, more preferably is 0.2 or more and 0.60 or less). As described above, the standard deviation of the elastic modulus of the charge transport layer can be reduced by including the silica particles and the silicone compound in the charge transport layer.

The elastic modulus of the charge transport layer is measured as follows. First, after peeling off the inorganic protective layer, the layer to be measured is exposed. Then, a portion of the layer is cut out with a cutter or the like to obtain a measurement sample. For this measurement sample, using Nano Indenter SA2 manufactured by MTS Systems, a depth profile is obtained by the continuous stiffness method (CSM) (U.S. Pat. No. 4,848,141), and from the measured value of the indentation depth of 30 nm to 100 nm Measure using the average value obtained.

The film thickness of the charge transport layer is, for example, preferably 10 μm or more and 40 μm or less, preferably 10 μm or more and 35 μm or less, and more preferably 15 μm or more and 30 μm or less. When the film thickness of the charge transport layer is within the above range, cracking of the inorganic protective layer and occurrence of residual potential are easily suppressed.

-Formation of charge transport layer-
Formation of the charge transport layer is not particularly limited, and a well-known formation method is used. , by heating if necessary.

Examples of methods for applying the charge transport layer-forming coating liquid onto the charge generation layer include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like. The usual method of

When particles (for example, silica particles or fluororesin particles) are dispersed in the coating liquid for forming the charge transport layer, examples of dispersion methods include media dispersion using a ball mill, vibrating ball mill, attritor, sand mill, horizontal sand mill, and the like. In addition, medialess dispersers such as agitators, ultrasonic dispersers, roll mills, and high-pressure homogenizers are used. Examples of high-pressure homogenizers include a collision system in which a dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high pressure state, and a penetration system in which a fine flow path is penetrated and dispersed in a high pressure state.

(Crack suppression layer)
-Composition of crack suppression layer-
The crack suppression layer does not hinder the movement of charges transported from the charge transport layer and suppresses cracks on the surface of the inorganic protective layer on the charge transport layer side.

The crack suppression layer according to the present embodiment does not directly provide an inorganic protective layer on the charge transport layer having unevenness on the surface, and provides a layer that is less likely to form unevenness on the surface than the charge transport layer. It suppresses cracking of the surface of the protective layer on the charge transport layer side. As a specific example of the crack suppression layer according to the present embodiment, for example, the charge transport layer contains at least a charge transport material and a binder resin, and the density of silica particles contained in the crack suppression layer is layer having a density lower than that of the silica particles contained therein. Another example of the crack-suppressing layer includes a charge-transporting material, a binder resin, and silica particles, and the volume-average particle diameter of the silica particles contained in the crack-suppressing layer is the silica contained in the charge-transporting layer. Layers smaller than the volume average particle size of the particles are included. It is considered that the unevenness formed on the surface of each of these layers has a smaller height difference than the unevenness formed on the surface of the charge transport layer on the inorganic protective layer side.

The cracking prevention layer may contain, for example, a charge transport material, a binder resin, and silica particles, or may contain a charge transport material and a binder resin without silica particles. . As the charge transport material, the binder resin and the silica particles constituting the cracking prevention layer, the charge transport material, the binder resin and the silica particles described as the materials constituting the charge transport layer may be used.

When the crack-suppressing layer contains silica particles, the density of the silica particles in the crack-suppressing layer is preferably lower than the density of the silica particles in the charge-transporting layer from the viewpoint of suppressing cracking of the inorganic protective layer. It is more preferably 30% or less, still more preferably 10% or less, relative to the density of silica particles in the layer. Also, the content of silica particles contained in the crack-suppressing layer is preferably, for example, 30% by mass or less, more preferably 20% by mass or less, relative to the entire crack-suppressing layer. The lower limit of the crack suppression layer is not particularly limited, and the unevenness (height difference) of the inorganic protective layer side surface of the crack suppression layer is reduced to further suppress the occurrence of cracks on the charge transport layer side surface of the inorganic protective layer. From a viewpoint, it is particularly preferable if the crack suppression layer does not contain silica particles (the content of silica particles is below the detection limit).

In addition, when the crack suppression layer contains silica particles, from the viewpoint of crack suppression of the inorganic protective layer, the volume average particle diameter of the silica particles contained in the crack suppression layer is equal to the volume of the silica particles contained in the charge transport layer. It is preferably smaller than the average particle size. From this point of view, the volume average particle diameter of the silica particles contained in the crack suppression layer is more preferably 110 nm or less, and even more preferably 100 nm or less. The lower limit of the volume average particle diameter of the silica particles contained in the crack suppression layer is not particularly limited. A thickness of 50 nm or more is preferable.

In addition, with regard to the crack suppression layer according to the present embodiment, the phrase "does not hinder the movement of charges transported from the charge transport layer" means that the difference in electrical resistivity between the crack suppression layer and the charge transport layer is small. The volume resistivity of the crack suppression layer is, for example, preferably 0.3 times or more and 2 times or less, and preferably 0.5 times or more and 1.5 times or less, that of the charge transport layer. If the crack-transporting layer has too high a volume resistivity, it may be difficult to generate a potential difference when forming an electrostatic latent image, resulting in a low image density. On the other hand, if the volume resistivity of the crack transport layer is too low, charges may flow in the in-plane direction, deteriorating the graininess (resolution) of the image.

The volume resistivity of the crack-suppressing layer may be adjusted, for example, by adjusting the types and contents of the charge-transporting material, the binder resin, and the silica particles that constitute the crack-suppressing layer. For example, without changing the composition of the charge transport layer except for changing the content and type of silica particles, i.e., using the charge transport material and binder resin used in the charge transport layer, A crack-preventing layer formed without changing the blending ratio of the charge-transporting material and the binder resin is preferable because the change in volume resistivity from the charge-transporting layer is small and image deterioration can be suppressed. However, the charge-transporting material and the binder resin that constitute the crack-suppressing layer may be the same as or different from the charge-transporting material and the binder resin that constitute the charge-transporting layer.

When the crack-suppressing layer contains silica particles, the crack-suppressing layer may further contain a silicone compound from the viewpoint of suppressing cracking of the inorganic protective layer. As the silicone compound, the silicone compound contained in the charge transport layer may be used.

-Characteristics of the crack suppression layer-
From the viewpoint of suppressing cracking of the inorganic protective layer, the height difference of the surface of the crack suppressing layer on the inorganic protective layer side is preferably 0.05 μm or less, more preferably 0.01 μm or less. Here, the height difference of the surface of the crack-suppressing layer on the side of the inorganic protective layer means the maximum height difference of unevenness in the surface shape of the crack-suppressing layer measured using a laser microscope. The height difference of the inorganic protective layer side surface of the crack suppression layer is measured by the following method. First, the inorganic protective layer is peeled off from the electrophotographic photoreceptor to expose the crack suppression layer. Then, as a laser microscope, for example, using a product name "VK9510" (manufactured by Keyence Corporation), using a 150-fold objective lens, scanning pitch: 0.01 μm. .1 mm width is observed. Next, by calculating the maximum height difference of the unevenness in the surface shape of the observed region, the height difference of the inorganic protective layer side surface of the crack suppression layer is obtained. The lower limit of the height difference of the surface of the crack-suppressing layer on the side of the inorganic protective layer is not particularly limited, and may be equal to or lower than the detection limit.

The thickness of the crack suppression layer is not particularly limited as long as it has the function of suppressing cracking of the inorganic protective layer. It is more preferably more than 1 time and 10 times or less, more preferably 2 times or more and 8 times or less, the volume average particle diameter of . If the crack-preventing layer is too thin, it will be difficult to obtain the effect of reducing the height difference on the surface of the charge transport layer on the side of the inorganic protective layer. From the above viewpoint, the thickness of the crack suppression layer is preferably 0.08 μm or more and 0.8 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. The thickness of the crack suppression layer may be measured using, for example, an interference film thickness meter.

- Formation of crack suppression layer -
Formation of the crack suppression layer is not particularly limited, and may be formed according to the method of forming the charge transport layer described above. For example, a coating film is formed from a coating solution for forming a crack-preventing layer in which a charge transport material and a binder resin are added to a solvent, and the coating film is dried and, if necessary, heated. The method of applying the coating solution for forming the crack-preventing layer onto the charge generation layer and the method of dispersing particles such as silica particles in the coating solution for forming the crack-suppressing layer may also be carried out according to the method for the charge transport layer. .

(Inorganic protective layer)
- Composition of inorganic protective layer -
The inorganic protective layer is a layer containing an inorganic material. Examples of the inorganic material include oxide-based, nitride-based, carbon-based, and silicon-based inorganic materials from the viewpoint of having mechanical strength and translucency as a protective layer.

Examples of oxide-based inorganic materials include metal oxides such as gallium oxide, aluminum oxide, zinc oxide, titanium oxide, indium oxide, tin oxide, and boron oxide, and mixed crystals thereof. Examples of nitride-based inorganic materials include metal nitrides such as gallium nitride, aluminum nitride, zinc nitride, titanium nitride, indium nitride, tin nitride, and boron nitride, and mixed crystals thereof. Carbon-based and silicon-based inorganic materials include, for example, diamond-like carbon (DLC), amorphous carbon (aC), hydrogenated amorphous carbon (aC:H), hydrogen/fluorinated amorphous carbon (aC :H), amorphous silicon carbide (a-SiC), hydrogenated amorphous silicon carbide (a-SiC:H) amorphous silicon (a-Si), hydrogenated amorphous silicon (a-Si:H), etc. . The inorganic material may be a mixed crystal of oxide-based and nitride-based inorganic materials.

Among these inorganic materials, metal oxides are excellent in mechanical strength and translucency, particularly have n-type conductivity, and are excellent in conductivity controllability. Oxides of group 13 elements (preferably gallium oxide) are preferred. That is, the inorganic protective layer preferably contains at least a Group 13 element (particularly gallium) and oxygen, and may contain hydrogen as necessary. By containing hydrogen, the physical properties of the inorganic protective layer containing at least a group 13 element (especially gallium) and oxygen can be easily controlled. For example, in an inorganic protective layer containing gallium, oxygen, and hydrogen (for example, an inorganic protective layer made of gallium oxide containing hydrogen), the composition ratio [O]/[Ga] is changed from 1.0 to 1.5. By doing so, it becomes easier to control the volume resistivity in the range of 10 ⁹ Ω·cm or more and 10 ¹⁴ Ω·cm or less.

The sum of the element composition ratios of the group 13 element, oxygen and hydrogen with respect to all the elements constituting the inorganic surface layer is preferably 90 atomic % or more. When the sum of the above element composition ratios is 90 atomic % or more, for example, when group 15 elements such as N, P, and As are mixed, the influence of these elements bonding with gallium is suppressed, and the inorganic surface layer. It becomes easier to find an appropriate range of oxygen and gallium composition ratio (oxygen/gallium) that can improve hardness and electrical properties. From the above viewpoint, the sum of the above element composition ratios is more preferably 95 atomic % or more, further preferably 96 atomic % or more, and particularly preferably 97 atomic % or more.

Also, the element composition ratio of oxygen and the group 13 element (oxygen/group 13 element) is preferably 1.1 or more and 1.5 or less. When the elemental composition ratio (oxygen/group 13 element) is 1.1 or more, the hardness of the inorganic surface layer is ensured, mechanical damage is suppressed, and a decrease in electrical resistance is suppressed. Flow of the electrostatic latent image in the in-plane direction is reduced, making it easier to obtain image resolution. On the other hand, when it is 1.5 or less, residual potential can be suppressed. The element composition ratio (oxygen/group 13 element) is more preferably 1.1 or more and 1.4 or less.

In addition to the above inorganic materials, the inorganic protective layer may contain one or more elements selected from C, Si, Ge, and Sn in the case of n-type, for example, to control the conductivity type. Further, for example, in the case of p-type, it may contain one or more elements selected from N, Be, Mg, Ca, and Sr.

Here, when the inorganic protective layer contains gallium, oxygen, and optionally hydrogen, it is preferable from the viewpoint of excellent mechanical strength, translucency, flexibility, and excellent conductivity controllability. The element composition ratio is as follows.

The element composition ratio of gallium is, for example, preferably 15 atomic % or more and 50 atomic % or less, preferably 20 atomic % or more and 40 atomic % or less, more preferably 20 atomic %, with respect to all constituent elements of the inorganic protective layer. % or more and 30 atomic % or less. The element composition ratio of oxygen is, for example, preferably 30 atomic % or more and 70 atomic % or less, preferably 40 atomic % or more and 60 atomic % or less, more preferably 45 atoms, based on all the constituent elements of the inorganic protective layer. % or more and 55 atomic % or less. The elemental composition ratio of hydrogen is, for example, preferably 10 atomic % or more and 40 atomic % or less, preferably 15 atomic % or more and 35 atomic % or less, more preferably 20 atoms, based on all constituent elements of the inorganic protective layer. % or more and 30 atomic % or less. On the other hand, the atomic number ratio [oxygen/gallium] is preferably more than 1.50 and 2.20 or less, preferably 1.6 or more and 2.0 or less.

Here, the element composition ratio, atomic number ratio, etc. of each element in the inorganic protective layer, including the distribution in the thickness direction, can be obtained by Rutherford-back scattering (hereinafter referred to as "RBS"). In the RBS, NEC's 3SDH Pelletron is used as an accelerator, CE&A's RBS-400 is used as an end station, and 3S-R10 is used as a system. For the analysis, CE&A's HYPRA program or the like is used. The RBS measurement conditions are a He ⁺⁺ ion beam energy of 2.275 eV, a detection angle of 160°, and a grazing angle of 109° with respect to the incident beam.

Specifically, the RBS measurement is performed as follows. First, a He ⁺⁺ ion beam is incident normal to the sample, the detector is set at 160° to the ion beam, and the backscattered He signal is measured. The composition ratio and film thickness are determined from the detected energy and intensity of He. Spectra may be measured at two detection angles to improve the accuracy of composition ratio and film thickness determinations. Accuracy is improved by measuring and cross-checking at two detection angles with different depth resolution and backscattering dynamics. The number of He atoms backscattered by a target atom is determined by three factors: (1) the atomic number of the target atom, (2) the energy of the He atom before scattering, and (3) the scattering angle. The density is assumed by calculation from the measured composition and used to calculate the thickness. Density error is within 20%.

The element composition ratio of hydrogen is obtained by hydrogen forward scattering (hereinafter referred to as "HFS"). In the HFS measurement, NEC's 3SDH Pelletron is used as an accelerator, CE&A's RBS-400 is used as an end station, and 3S-R10 is used as a system. The HYPRA program from CE&A is used for the analysis. The HFS measurement conditions are as follows.
・He ⁺⁺ ion beam energy: 2.275 eV
・Detection angle: Grazing angle 30° with respect to 160° incident beam

HFS measurements pick up the signal of hydrogen scattered in front of the sample by setting the detector at 30° to the He ⁺⁺ ion beam and the sample at 75° from normal. At this time, the detector should be covered with aluminum foil to remove He atoms scattered with hydrogen. Quantification is performed by normalizing the hydrogen counts of the reference sample and the sample to be measured by the stopping power and then comparing them. A sample obtained by implanting H ions into Si and muscovite mica are used as reference samples. Muscovite is known to have a hydrogen concentration of 6.5 atomic percent. The H adsorbed on the outermost surface is corrected by, for example, subtracting the amount of H adsorbed on the clean Si surface.

-Characteristics of the inorganic protective layer-
Depending on the purpose, the inorganic protective layer may have a composition ratio distribution in the thickness direction, or may have a multilayer structure.

The inorganic protective layer is desirably a non-single-crystal film such as a microcrystalline film, polycrystalline film, or amorphous film. Among these, amorphous films are particularly desirable from the viewpoint of surface smoothness, and microcrystalline films are more desirable from the viewpoint of hardness. The growth section of the inorganic protective layer may have a columnar structure, but from the viewpoint of slipperiness, a highly flat structure is desirable, and an amorphous structure is desirable. Crystallinity and amorphousness are determined by the presence or absence of dots and lines in a diffraction image obtained by RHEED (reflection high energy electron diffraction) measurement.

The volume resistivity of the inorganic protective layer is preferably 10 ⁶ Ω·cm or more, preferably 10 ⁸ Ω·cm or more. When the volume resistivity is within the above range, the charge is suppressed from flowing in the in-plane direction, and good electrostatic latent image formation can be easily realized. This volume resistivity is calculated based on the electrode area and the sample thickness from the resistance value measured under the conditions of a frequency of 1 kHz and a voltage of 1 V using an LCR meter ZM2371 manufactured by nF. The sample to be measured was a sample obtained by forming a film on an aluminum substrate under the same conditions as when the inorganic protective layer to be measured was formed, and forming a gold electrode on the film by vacuum deposition. Alternatively, it may be a sample obtained by peeling the inorganic protective layer from the electrophotographic photoreceptor after production, partially etching the sample, and sandwiching the sample between a pair of electrodes.

The elastic modulus of the inorganic protective layer is preferably 30 GPa or more and 80 GPa or less, preferably 40 GPa or more and 65 GPa or less. When the elastic modulus is within the above range, the inorganic protective layer is likely to be prevented from forming recesses (dents), peeling off, and cracking.

The elastic modulus of the inorganic protective layer is measured from 30 nm to 100 nm depth profile by continuous stiffness method (CSM) (U.S. Pat. No. 4,848,141) using Nano Indenter SA2 manufactured by MTS Systems. Use the average value obtained from The following are the measurement conditions.
・Measurement environment: 23°C, 55% RH
Indenter used: diamond regular triangular pyramid indenter (Berkovic indenter) triangular pyramid indenter Test mode: CSM mode The measurement sample is a sample formed on a substrate under the same conditions as the formation of the inorganic protective layer to be measured. Alternatively, it may be a sample obtained by removing the inorganic protective layer from the manufactured electrophotographic photosensitive member and partially etching it.

The thickness of the inorganic protective layer may be, for example, 0.2 μm or more and 10 μm or less, preferably 1 μm or more and 6 μm or less, and more preferably 1 μm or more and 4 μm or less. If the inorganic protective layer is too thin, the effect of protecting the organic photosensitive layer including the charge transport layer is reduced, and the inorganic protective layer may be easily damaged or cracked. If the inorganic protective layer is too thick, as described above, the image quality may deteriorate, and it may take time and cost to form the inorganic protective layer. The thickness of the inorganic protective layer may be measured using, for example, an interference film thickness meter.

-Formation of inorganic protective layer-
For the formation of the protective layer, for example, known vapor phase film formation methods such as plasma CVD (Chemical Vapor Deposition) method, metalorganic vapor deposition method, molecular beam epitaxy method, vapor deposition, and sputtering are used.

Hereinafter, the formation of the inorganic protective layer will be described with specific examples while showing an example of a film forming apparatus in the drawings. Although the following description shows a method for forming an inorganic protective layer containing gallium, oxygen, and hydrogen, it is not limited to this, and a well-known forming method can be selected depending on the composition of the target inorganic protective layer. should be applied.

FIG. 4 is a schematic diagram showing an example of a film forming apparatus used for forming an inorganic protective layer of an electrophotographic photoreceptor according to the present embodiment, and FIG. 4(A) is a side view of the film forming apparatus. 4B is a schematic cross-sectional view of the film forming apparatus shown in FIG. 4A between A1 and A2. In FIG. 4, 210 is a film formation chamber, 211 is an exhaust port, 212 is a substrate rotating part, 213 is a substrate support member, 214 is a substrate, 215 is a gas introduction pipe, and 216 is a gas introduced from the gas introduction pipe 215 to inject. 217 is a plasma diffusion portion; 218 is a high frequency power supply portion; 219 is a plate electrode; 220 is a gas introduction pipe; and 221 is a high frequency discharge tube portion.

In the film forming apparatus shown in FIG. 4, an exhaust port 211 connected to a vacuum exhaust device (not shown) is provided at one end of the film forming chamber 210, and the side of the film forming chamber 210 provided with the exhaust port 211 is provided. A plasma generator composed of a high-frequency power supply unit 218 , a plate electrode 219 and a high-frequency discharge tube unit 221 is provided on the opposite side. This plasma generator includes a high-frequency discharge tube portion 221, a flat plate electrode 219 disposed in the high-frequency discharge tube portion 221 and having a discharge surface on the exhaust port 211 side, and a flat plate electrode 219 disposed outside the high-frequency discharge tube portion 221. It is composed of a high-frequency power supply section 218 connected to the discharge surface of the electrode 219 and the opposite surface. A gas introduction pipe 220 for supplying gas into the high-frequency discharge tube portion 221 is connected to the high-frequency discharge tube portion 221, and the other end of the gas introduction pipe 220 is connected to a first gas supply.

Note that the plasma generator shown in FIG. 5 may be used instead of the plasma generator provided in the film forming apparatus shown in FIG. FIG. 5 is a schematic diagram showing another example of a plasma generator used in the film forming apparatus shown in FIG. 4, and is a side view of the plasma generator. In FIG. 5, 222 represents a high frequency coil, 223 represents a quartz tube, and 220 represents a gas introduction tube as shown in FIG. This plasma generator comprises a quartz tube 223 and a high-frequency coil 222 provided along the outer peripheral surface of the quartz tube 223. One end of the quartz tube 223 is a film forming chamber 210 (not shown in FIG. 5). is connected with A gas introduction pipe 220 for introducing gas into the quartz tube 223 is connected to the other end of the quartz tube 223 .

In FIG. 4, a rod-shaped shower nozzle 216 extending along the discharge surface is connected to the discharge surface side of the plate electrode 219, and one end of the shower nozzle 216 is connected to a gas introduction pipe 215. The introduction pipe 215 is connected to a second gas supply source (not shown) provided outside the film forming chamber 210 . A substrate rotating part 212 is provided in the film forming chamber 210, and a cylindrical substrate 214 is provided with a substrate support member so that the longitudinal direction of the shower nozzle 216 and the axial direction of the substrate 214 face each other. 213 to be attached to the base rotating part 212 . During film formation, the substrate rotating part 212 rotates to rotate the substrate 214 in the circumferential direction. As the substrate 214, for example, a photosensitive member having an organic photosensitive layer laminated in advance is used.

Formation of the inorganic protective layer is carried out, for example, as follows. First, oxygen gas (or helium (He) diluted oxygen gas), helium (He) gas, and optionally hydrogen (H ₂ ) gas are introduced into the high-frequency discharge tube section 221 from the gas introduction tube 220, A radio wave of 13.56 MHz is supplied from the high frequency power supply unit 218 to the plate electrode 219 . At this time, the plasma diffusion portion 217 is formed so as to spread radially from the discharge surface side of the flat plate electrode 219 toward the exhaust port 211 side. Here, the gas introduced from the gas introduction pipe 220 flows through the film forming chamber 210 from the flat plate electrode 219 side to the exhaust port 211 side. The plate electrode 219 may be an electrode surrounded by an earth shield.

Next, trimethylgallium gas is introduced into the film formation chamber 210 through the gas introduction pipe 215 and the shower nozzle 216 located downstream of the flat plate electrode 219 serving as activation means, so that gallium and oxygen are formed on the surface of the substrate 214. A non-single-crystal film containing hydrogen is formed. As the base 214, for example, a conductive base on which the charge transport layer and the crack prevention layer according to the present embodiment are formed is used.

Since an organic photoreceptor having an organic photosensitive layer is used, the temperature of the surface of the substrate 214 when forming the inorganic protective layer is preferably 150° C. or lower, more preferably 100° C. or lower, and particularly preferably 30° C. or higher and 100° C. or lower. . Even if the temperature of the surface of the substrate 214 is 150° C. or less at the beginning of film formation, if the temperature rises above 150° C. due to the influence of plasma, the organic photosensitive layer may be thermally damaged. It is desirable to control the surface temperature of the substrate 214 using a The temperature of the surface of the substrate 214 may be controlled by heating means, cooling means (not shown in the figure) or the like, or may be left to the natural temperature rise during discharge. When heating the substrate 214 , a heater may be installed outside or inside the substrate 214 . When cooling the substrate 214 , cooling gas or liquid may be circulated inside the substrate 214 . If it is desired to avoid an increase in the temperature of the substrate 214 surface due to discharge, it is effective to adjust the high-energy gas flow hitting the substrate 214 surface. In this case, conditions such as gas flow rate, discharge output and pressure are adjusted so as to obtain the required temperature.

Alternatively, instead of trimethylgallium gas, an aluminum-containing organometallic compound or a hydride such as diborane may be used, and two or more of these may be mixed. For example, in the initial stage of forming the inorganic protective layer, trimethylindium is introduced into the film forming chamber 210 through the gas inlet pipe 215 and the shower nozzle 216 to form a film containing nitrogen and indium on the substrate 214. This film then absorbs the ultraviolet rays that are generated during continuous deposition and that degrade the organic photosensitive layer. Therefore, damage to the organic photosensitive layer due to the generation of ultraviolet rays during film formation is suppressed.

As a method of doping dopants in film formation, SiH ₃ and SnH ₄ are used for n-type, and biscyclopentadienylmagnesium, dimethyl calcium, dimethylstrontium, etc. are used in gaseous state for p-type. do. In order to dope the dopant element into the surface layer, a known method such as a thermal diffusion method or an ion implantation method may be employed. Specifically, for example, by introducing a gas containing at least one or more dopant elements into the film formation chamber 210 through the gas introduction pipe 215 and the shower nozzle 216, a conductivity type such as n-type or p-type is introduced. An inorganic protective layer is obtained.

In the film forming apparatus described with reference to FIGS. 4 and 5, the active nitrogen or active hydrogen formed by the discharge energy may be independently controlled by providing a _{plurality of} active apparatuses. A gas containing hydrogen atoms may also be used. Additional _H2 may be added. In addition, conditions under which active hydrogen is liberated from the organometallic compound may be used. By doing so, activated carbon atoms, gallium atoms, nitrogen atoms, hydrogen atoms, etc. exist on the surface of the substrate 214 in a controlled state. Then, the activated hydrogen atoms have the effect of desorbing hydrogen atoms of hydrocarbon groups such as methyl groups and ethyl groups constituting the organometallic compound as molecules. Therefore, a hard film (inorganic protective layer) that forms a three-dimensional bond is formed.

The plasma generation means of the film forming apparatus shown in FIGS. 4 and 5 uses a high-frequency oscillator, but is not limited to this. or a helicon plasma system may be used. Moreover, in the case of a high-frequency oscillator, either an inductive type or a capacitive type may be used. Furthermore, two or more of these devices may be used in combination, or two or more of the same type of devices may be used. A high-frequency oscillator is desirable for suppressing temperature rise on the surface of the substrate 214 due to plasma irradiation, but a device for suppressing heat irradiation may be provided.

When two or more different plasma generators (plasma generating means) are used, it is desirable that the discharge be generated at the same pressure at the same time. Also, a pressure difference may be provided between the discharging region and the film forming region (the portion where the substrate is installed). These devices may be arranged in series with respect to the gas flow formed in the film forming apparatus from the portion into which the gas is introduced to the portion from which the gas is discharged. You may arrange|position so that it may oppose.

For example, when two types of plasma generating means are installed in series with respect to the gas flow, taking the film forming apparatus shown in FIG. 2 plasma generator. In this case, for example, a high-frequency voltage is applied to the shower nozzle 216 through the gas introduction pipe 215 to cause discharge in the film formation chamber 210 using the shower nozzle 216 as an electrode. Alternatively, instead of using the shower nozzle 216 as an electrode, a cylindrical electrode is provided between the substrate 214 in the film forming chamber 210 and the flat plate electrode 219, and this cylindrical electrode is used to operate the film forming chamber 210. cause an internal discharge.

In addition, when two different types of plasma generators are used under equal pressure, for example, when a microwave oscillator and a high-frequency oscillator are used, the excitation energy of the excited species can be greatly changed, which is effective for film quality control. is. Also, the discharge may be performed at around atmospheric pressure (70000 Pa or more and 110000 Pa or less). It is desirable to use He as a carrier gas when discharging near atmospheric pressure.

For forming the inorganic protective layer, for example, the substrate 214 having the organic photosensitive layer formed thereon is placed in the film forming chamber 210, and mixed gases having different compositions are introduced to form the inorganic protective layer.

As for film forming conditions, for example, in the case of high-frequency discharge, the frequency is preferably in the range of 10 kHz or more and 50 MHz or less in order to form a good film at a lower temperature. Although the output depends on the size of the substrate 214, it is desirable that the output be in the range of 0.01 W/cm ² or more and 0.2 W/cm ^{2 or} less with respect to the surface area of the substrate. The rotational speed of the substrate 214 is desirably in the range of 0.1 rpm to 500 rpm.

An example of an electrophotographic photoreceptor in which the organic photosensitive layer is of the function-separated type and the charge transport layer is of the single-layer type has been described above. In the case where the charge transport layer is of a multi-layer type), for example, the charge transport layer 3A in contact with the crack suppression layer 6 has the structure of the charge transport layer 3 of the electrophotographic photoreceptor 7A shown in FIG. The charge transport layer 3B not in contact with 6 may have a structure of a known charge transport layer. Here, the film thickness of the charge transport layer 3A may be, for example, 1 μm or more and 15 μm or less, and the film thickness of the charge transport layer 3B may be, for example, 15 μm or more and 29 μm or less.

On the other hand, in the case of the electrophotographic photoreceptor 7C shown in FIG. 3 (an example provided with a charge generation/charge transport layer 3C), the charge generation/charge transport layer 3C is, for example, as shown in FIG. 1 except that it further contains a charge generation material. may be configured according to the charge transport layer 3 of the electrophotographic photoreceptor 7A shown in FIG. At this time, the content of the charge generation material may be, for example, 25% by mass or more and 50% by mass or less with respect to the entire charge generation/charge transport layer 3C. Also, the film thickness of the charge generation/charge transport layer 3C may be, for example, 15 μm or more and 30 μm or less.

The effects of the electrophotographic photoreceptor according to this embodiment will be described below.

FIG. 6 shows the surface profile of a coating film formed using a coating liquid containing a charge transport material and a binder resin added to a solvent, measured using a laser microscope (trade name: "VK9510", manufactured by Keyence Corporation). The measurement results are shown. FIG. 6A shows 25 parts by mass of charge transport material, 25 parts by mass of binder resin, 50 parts by mass of silica particles (0.08 μm in volume average particle diameter, hydrophobized with trimethoxysilane), and 250 parts by mass of tetrahydrofuran solvent. shows the surface shape of a coating film formed using a coating liquid composed of, and FIG. 6B shows the surface shape of a coating film formed in the same manner except that silica particles are not used.

As a result of surface shape measurement with a laser microscope, the coating film shown in FIG. A height difference of 0.01 μm was measured. As shown in FIG. 6, when the charge transport layer contains silica particles, fine irregularities are formed on the surface of the charge transport layer on the inorganic protective layer side due to the silica particles. When the charge transport layer containing silica particles and the inorganic protective layer are in direct contact, the irregularities formed on the surface of the charge transport layer facing the inorganic protective layer are thought to be transferred to the surface of the inorganic protective layer facing the charge transport layer. .

The effect of the unevenness formed on the surface of the inorganic protective layer on the charge transport layer side on the cracking characteristics of the inorganic protective layer was analyzed by simulation using the FEM analysis program ABAQUS for the charge transport layer based on the destruction mechanism of the plastic material. . Here, the "FEM analysis program ABAQUS" is a technical calculation program for analyzing the stress of structures or machines using the finite element method, which is a kind of numerical analysis method.

FIG. 7 shows a model of the electrophotographic photoreceptor 7 used for simulation analysis. In the model shown in FIG. 7, in the electrophotographic photosensitive member 7 in which the inorganic protective layer 5 is formed on the charge transport layer 3, the carrier C sandwiched when passing through the primary transfer nip portion causes the electrophotographic photosensitive member 7 to This is a model of how the inorganic protective layer 5 receives a load. As shown in FIG. 7, a recess (crack) having a length a is formed on the surface of the inorganic protective layer 5 having a width W on the charge transport layer 3 side. In the simulation analysis, the Young's modulus and Poisson's ratio of the inorganic protective layer 5 were set to 80 GPa and 0.3, respectively, and the Young's modulus, Poisson's ratio and thickness of the charge transport layer 3 were set to 8 GPa, 0.4 and 24 μm, respectively. .

In the simulation analysis, the stress intensity factor around the tip of the recess was calculated using the following brittle fracture model formula.
・K=F×σ×(πa) ^1/2
・F = 1.12 - 0.231 x ε + 10.55 x ε ² + 10.55 x ε ³ - 21.72 x ε ³ + 30.39 x ε ⁴
・ε=a/W
In each formula, K indicates the stress intensity factor, σ indicates tensile stress, a indicates the length of the recesses formed in the inorganic protective layer 5 , and W indicates the thickness of the inorganic protective layer 5 . When the stress intensity factor K calculated by the above formula exceeds the fracture toughness value specific to the material forming the inorganic protective layer 5, the fracture progresses at the tip of the concave portion, and eventually the inorganic protective layer 5 cracks. Therefore, the smaller the stress intensity factor K, the greater the effect of suppressing cracking of the inorganic protective layer 5 .

FIG. 8 shows the results of a simulation analysis in which the tensile stress σ is assumed to be constant and the thickness W of the inorganic protective layer 5 and the length a of the recesses are changed. As shown in FIG. 8, as a result of simulation analysis, when the thickness W of the inorganic protective layer 5 is the same, the shorter the length a of the recess formed on the surface of the inorganic protective layer 5, the smaller the stress intensity factor. Also, it was found that the smaller the thickness W of the inorganic protective layer 5, the larger the stress intensity factor when the length a of the concave portion of the inorganic protective layer 5 is the same.

As described above, the electrophotographic photoreceptor according to the present embodiment is configured such that an inorganic protective layer is not directly provided on a charge transport layer containing silica particles, but a crack suppression layer is sandwiched therebetween. According to this configuration, when the inorganic protective layer is in direct contact with the charge transport layer, the height difference of the unevenness formed on the charge transport layer side surface of the inorganic protective layer corresponding to the surface shape of the crack suppression layer on the inorganic protective layer side is can be reduced compared to As a result, as shown by the above simulation analysis results, the stress intensity factor is lowered, so cracking of the inorganic protective layer can be suppressed. In other words, in the electrophotographic photoreceptor according to the present embodiment, by providing the crack suppression layer sandwiched between the charge transport layer and the inorganic protective layer, an increase in the stress intensity factor is suppressed and the crack suppression effect of the inorganic protective layer is improved. While maintaining the above, by thinning the inorganic protective layer, it is possible to improve the image quality and reduce the film-forming cost of the inorganic protective layer.

[Image forming apparatus (and process cartridge)]
An image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, and an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member. means, developing means for developing an electrostatic latent image formed on the surface of an electrophotographic photosensitive member with a developer containing toner to form a toner image, and transfer means for transferring the toner image onto the surface of a recording medium; Prepare. As an electrophotographic photoreceptor, the electrophotographic photoreceptor according to the present embodiment is applied.

The image forming apparatus according to the present embodiment includes fixing means for fixing a toner image transferred to the surface of a recording medium; direct transfer for directly transferring a toner image formed on the surface of an electrophotographic photosensitive member to a recording medium. Apparatus of this type: Intermediate transfer that primarily transfers the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the intermediate transfer member, and then secondarily transfers the toner image transferred on the surface of the intermediate transfer member to the surface of the recording medium. A device equipped with a cleaning means for cleaning the surface of the electrophotographic photosensitive member before charging after transferring the toner image; A known image forming apparatus, such as an apparatus equipped with a static eliminating means for eliminating static electricity by means of an electrophotographic photosensitive member; and an apparatus equipped with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred, and a primary transfer means for primarily transferring a toner image formed on the surface of an electrophotographic photosensitive member to the surface of the intermediate transfer body. A configuration having transfer means and secondary transfer means for secondarily transferring the toner image transferred on the surface of the intermediate transfer member to the surface of the recording medium is applied.

The image forming apparatus according to the present embodiment may be either a dry developing type image forming apparatus or a wet developing type image forming apparatus (a developing type using a liquid developer).

In addition, in the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to this embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include, for example, at least one selected from the group including charging means, electrostatic latent image forming means, developing means, and transfer means.

An example of the image forming apparatus according to the present embodiment will be shown below, but the present invention is not limited to this. Note that the main parts shown in the drawings will be explained, and the explanation of the others will be omitted.

FIG. 8 is a schematic configuration diagram showing an example of an image forming apparatus according to this embodiment. As shown in FIG. 8, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photosensitive member 7, an exposure device 9 (an example of electrostatic latent image forming means), and a transfer device 40 (primary a transfer device) and an intermediate transfer member 50 . In the image forming apparatus 100 , the exposure device 9 is arranged at a position where the electrophotographic photosensitive member 7 can be exposed through the opening of the process cartridge 300 , and the transfer device 40 transfers the image to the electrophotographic photosensitive member 7 via the intermediate transfer member 50 . 7 , and the intermediate transfer member 50 is arranged so that a portion of the intermediate transfer member 50 is in contact with the electrophotographic photosensitive member 7 . Although not shown, it also has a secondary transfer device for transferring the toner image transferred to the intermediate transfer member 50 onto a recording medium (for example, paper). Note that the intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of transfer means.

A process cartridge 300 in FIG. 8 integrates an electrophotographic photosensitive member 7, a charging device 8 (an example of charging means), a developing device 11 (an example of developing means), and a cleaning device 13 (an example of cleaning means) in a housing. supported by The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131 , and the cleaning blade 131 is arranged so as to contact the surface of the electrophotographic photosensitive member 7 . The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131 , and may be used alone or in combination with the cleaning blade 131 .

FIG. 8 shows, as an image forming apparatus, a fibrous member 132 (roll-like) that supplies the lubricant 14 to the surface of the electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-like) that assists cleaning. are shown, but these are placed as needed.

Each configuration of the image forming apparatus according to the present embodiment will be described below.

- Charging device -
As the charging device 8, for example, a contact type charger using a conductive or semi-conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, or the like is used. In addition, a known charger such as a non-contact roller charger, a scorotron charger using corona discharge, a corotron charger, or the like may also be used.

-Exposure equipment-
Examples of the exposure device 9 include an optical device that exposes the surface of the electrophotographic photosensitive member 7 to light such as semiconductor laser light, LED light, and liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity region of the electrophotographic photosensitive member. As for the wavelength of semiconductor lasers, near-infrared light having an oscillation wavelength near 780 nm is predominant. However, the wavelength is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm or more and 450 nm or less may also be used. A surface emitting laser light source capable of outputting multiple beams is also effective for color image formation.

- Developing device -
As the developing device 11, for example, a general developing device that develops by contacting or non-contacting a developer can be used. The developing device 11 is not particularly limited as long as it has the functions described above, and is selected according to the purpose. For example, a known developing device having a function of adhering a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, a roller, or the like can be used. Among them, it is preferable to use a developing roller holding a developer on its surface.

The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and carrier. Also, the developer may be magnetic or non-magnetic. As these developers, well-known ones are applied.

－Cleaning device－
As the cleaning device 13, a cleaning blade type device having a cleaning blade 131 is used. In addition to the cleaning blade method, a fur brush cleaning method and a simultaneous development cleaning method may be employed.

-Transfer device-
As the transfer device 40, for example, a known transfer charger such as a contact type transfer charger using a belt, a roller, a film, a rubber blade, etc., a scorotron transfer charger using corona discharge, a corotron transfer charger, or the like can be used. mentioned.

-Intermediate transfer body-
As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, or the like is used. Further, as the form of the intermediate transfer body, a drum-shaped one may be used instead of the belt-shaped one.

FIG. 10 is a schematic configuration diagram showing another example of the image forming apparatus according to this embodiment. The image forming apparatus 120 shown in FIG. 10 is a tandem type multicolor image forming apparatus in which four process cartridges 300 are mounted. In the image forming apparatus 120, four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used for each color. Note that the image forming apparatus 120 has a configuration similar to that of the image forming apparatus 100, except that it is a tandem system.

Note that the image forming apparatus 100 according to the present embodiment is not limited to the configuration described above. A configuration in which a first static elimination device for aligning the polarity of residual toner and facilitating removal with a cleaning brush may be provided on the upstream side of the rotation direction of the electrophotographic photosensitive member from 13 , or from the cleaning device 13 . A second neutralization device for neutralizing the surface of the electrophotographic photosensitive member 7 may be provided on the downstream side in the rotational direction of the electrophotographic photosensitive member and upstream of the charging device 8 in the rotational direction of the electrophotographic photosensitive member. .

Further, the image forming apparatus 100 according to the present embodiment is not limited to the above-described configuration, and may be a known configuration, for example, a direct transfer type image forming apparatus that directly transfers a toner image formed on the electrophotographic photosensitive member 7 onto a recording medium. may be adopted.

1 Undercoat layer 2 Charge generation layer 3, 3A, 3B Charge transport layer 3C Charge generation/charge transport layer 4 Conductive substrate 5 Inorganic protective layer 7, 7A, 7B, 7C Electrophotographic photoreceptor 8 Charging Device 9 Exposure Device 11 Developing Device 13 Cleaning Device 14 Lubricant 40 Transfer Device 50 Intermediate Transfer Body 100, 120 Image Forming Device 131 Cleaning Blade 132 Fibrous Member (Roll) 133 Fiber Shaped member (flat brush shape), 210 deposition chamber, 211 exhaust port, 212 substrate rotation unit, 213 substrate support member, 214 substrate, 215, 220 gas introduction pipe, 216 shower nozzle, 217 plasma diffusion unit, 218 high-frequency power supply Section 219 Flat plate electrode 221 High frequency discharge tube section 222 High frequency coil 223 Quartz tube 300 Process cartridge C Carrier.

Claims (10)

a conductive substrate;
a charge transport layer provided on the conductive substrate and containing a charge transport material, a binder resin and silica particles;
an inorganic protective layer provided on the charge transport layer;
A crack suppression layer sandwiched between the charge transport layer and the inorganic protective layer, which does not hinder the movement of charges transported from the charge transport layer, and the surface of the inorganic protective layer on the charge transport layer side A crack suppression layer that suppresses cracking of
with
The crack suppression layer contains silica particles, and the density of the silica particles in the crack suppression layer is 30% or less of the density of the silica particles in the charge transport layer,
The crack suppression layer has a volume resistivity of 0.3 to 2 times the volume resistivity of the charge transport layer,
An electrophotographic photoreceptor , wherein the difference in height of the crack-suppressing layer on the side of the inorganic protective layer is 0.05 μm or less . a conductive substrate;
a charge transport layer provided on the conductive substrate and containing a charge transport material, a binder resin and silica particles;
an inorganic protective layer provided on the charge transport layer;
A crack suppression layer sandwiched between the charge transport layer and the inorganic protective layer, which does not hinder the movement of charges transported from the charge transport layer, and the surface of the inorganic protective layer on the charge transport layer side A crack suppression layer that suppresses cracking of
with
The crack suppression layer contains silica particles, and the volume average particle diameter of the silica particles contained in the crack suppression layer is smaller than the volume average particle diameter of the silica particles contained in the charge transport layer,
The crack suppression layer has a volume resistivity of 0.3 to 2 times the volume resistivity of the charge transport layer,
An electrophotographic photoreceptor , wherein the difference in height of the crack-suppressing layer on the side of the inorganic protective layer is 0.05 μm or less . 3. The electrophotographic photoreceptor according to claim 1, wherein the crack suppression layer has a thickness larger than the volume average particle diameter of the silica particles contained in the charge transport layer. 4. The electrophotographic photoreceptor according to claim 3, wherein the thickness of the crack suppression layer is more than 1 time and 10 times or less the volume average particle diameter of the silica particles contained in the charge transport layer. The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein the crack suppression layer has a thickness of 0.08 µm or more and 0.8 µm or less. 6. The electrophotographic photoreceptor according to claim 1, wherein the content of the silica particles in the crack suppression layer is 30% by mass or less. 7. The electrophotographic photoreceptor according to claim 1 , wherein the height difference of the surface of the crack suppression layer on the inorganic protective layer side is 0.01 μm or less. 8. The electrophotographic photoreceptor according to claim 1, wherein the inorganic protective layer has a thickness of 1 μm or more and 6 μm or less. A process cartridge, comprising the electrophotographic photoreceptor according to any one of claims 1 to 8 , and detachable from an image forming apparatus. The electrophotographic photoreceptor according to any one of claims 1 to 8 ;
charging means for charging the surface of the electrophotographic photosensitive member;
an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
developing means for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
a transfer means for transferring the toner image onto the surface of a recording medium;
An image forming apparatus comprising:

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