Image forming device

Abstract

To provide an image forming device in which occurrence of density unevenness caused by the arrangement relation between the center axis of a lens array, a photoconductor drum, and a light-emitting chip that uses an organic EL element is suppressed.SOLUTION: An exposure head includes a light-emitting board 202, and a rod lens array 206. The light-emitting board 202 includes a light-emitting chip in which a plurality of light-emitting elements are arranged, and the light-emitting elements are organic EL elements. The wavelength of strongest peak of the light-emission spectrum of the organic EL elements is 370 nm to 780 nm inclusive, and the reflectance on surface of a photoconductor drum 103 at the wavelength of strongest peak of the light-emission spectrum of the organic EL elements is 10% or less. The rod lens array 206 includes a plurality of rod lenses. The plurality of light-emitting chips are arranged along a first direction 1 and alternately arranged in a second direction 2. An angle 5 of a center axis 4 of the rod lenses relative to a third direction s is more than 0° and 3° or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] In electrophotographic image forming devices such as laser beam printers and digital copiers, a commonly known method is to expose a photosensitive drum (a drum-shaped electrophotographic photosensitive member) to light using an exposure head that uses LEDs or organic electroluminescence (EL) elements to form a latent image. The exposure head is composed of a row of light-emitting elements arranged along the longitudinal direction of the photosensitive drum and a rod lens array that focuses light from the row of light-emitting elements onto the photosensitive drum. The LEDs and organic EL elements are known to have a surface-emitting configuration in which the direction of light emitted from the light-emitting surface is the same as the direction of the rod lens array (hereinafter referred to as a surface-emitting element array). Image forming devices using such exposure heads use fewer components than laser scanning image forming devices that deflect and scan a laser beam using a polygon motor, making it easier to reduce the size and cost of the device. Patent documents 1 and 2 describe such exposure heads, each of which has a light-emitting chip with a row of light-emitting elements formed on a compound semiconductor substrate and arranged on a printed circuit board.

[0003] Patent Document 1 shows an example in which a compound semiconductor substrate on which a row of light-emitting elements is formed is used as a light-emitting chip. The light-emitting chip has a long, thin rectangular shape and has wire bonding pads on both sides of the row of light-emitting elements. Since there are no light-emitting elements in the wire bonding pad area when the light-emitting chips are arranged in a row, parts of the light-emitting chips are arranged alternately in a direction perpendicular to the longitudinal direction, so that the light-emitting elements are arranged without interruption in the longitudinal direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-183436 [Patent Document 2] Patent Publication No. 2021-30565 Summary of the Invention [Problem to be solved by the invention]

[0005] Light from the light-emitting chip passes through the rod lens and is imaged on the photosensitive drum, but the light imaged on the photosensitive drum is reflected on the surface and inside of the photosensitive drum, and the light reflected again by the rod lens is imaged on the photosensitive drum.

[0006] The rod lens is disposed so that its central axis is tilted to a certain extent with respect to the direction connecting the light emitting chip and the photosensitive drum.

[0007] In this case, the light from the light-emitting chips arranged alternately is reflected differently due to the different image formation on the photosensitive drum caused by the inclination of the rod lens, resulting in differences in the latent image formation on the photosensitive drum. Differences in latent image formation result in differences in image density, which can cause uneven image density depending on the arrangement of the light-emitting chips.

[0008] An object of the present disclosure is to suppress the occurrence of such image density unevenness. [Means for solving the problem]

[0009] According to the present disclosure a photosensitive drum rotatable around a rotation axis; Exposure head, An image forming apparatus having the exposure head has a light emitting substrate and a rod lens array; the light-emitting substrate has a plurality of light-emitting chips for emitting exposure light to irradiate the surface of the photosensitive drum; The light-emitting chip has a plurality of light-emitting elements arranged in a plurality of rows, the rod lens array has a plurality of rod lenses for condensing the exposure light emitted from the light-emitting element onto the surface of the photosensitive drum; the rod lenses are aligned in the direction of the rotation axis, the light-emitting element is an organic EL element, the wavelength of the most intense peak in the emission spectrum of the organic EL element is 370 nm or more and 780 nm or less; When the longitudinal direction of the light emitting substrate is defined as a first direction, the lateral direction of the light emitting substrate is defined as a second direction, and a direction perpendicular to the light emitting substrate is defined as a third direction, The rotation axis is parallel to the first direction, The plurality of light emitting chips are arranged along a first direction and alternately arranged in a second direction; the angle of the central axis of the rod lens with respect to the third direction is greater than 0° and is not more than 3°; the reflectance of the surface of the photosensitive drum at the wavelength of the most intense peak in the emission spectrum of the organic EL element is 10% or less; An image forming apparatus characterized by the above features is provided. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an image forming apparatus in which the occurrence of uneven image density is suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] 2 is a schematic diagram showing a first direction, a second direction, and a third direction in the present disclosure. FIG. [Figure 2] 1 is a schematic diagram illustrating an example of an image forming apparatus having a photosensitive drum according to the present disclosure. [Figure 3] 1 is a schematic diagram illustrating an example of a printed circuit board on which a group of light-emitting elements is arranged in the present disclosure. [Figure 4] FIG. 2 is a schematic diagram showing an example of a cross-sectional view of an exposure head according to the present disclosure. [Figure 5] FIG. 2 is a diagram illustrating an example of a photosensitive drum used in the present disclosure. [Figure 6] FIG. 2 is a diagram showing an example of an emission spectrum of an organic EL element used in the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] the light-emitting element is an organic EL element, The wavelength of the largest peak in the emission spectrum of the organic EL element is within the range of 370 to 780 nm, When the longitudinal direction of the light emitting substrate is defined as a first direction, the lateral direction of the light emitting substrate is defined as a second direction, and the direction perpendicular to the light emitting substrate is defined as a third direction, A plurality of light-emitting chips each consisting of a plurality of light-emitting elements are arranged on a plane, The light emitting chips are arranged along a first direction and alternately arranged in a second direction; the angle of the central axis of the rod lens with respect to the third direction is greater than 0° and less than or equal to 3°; The reflectance of the surface of the photosensitive drum to the exposure light at the wavelength of the most intense peak in the emission spectrum of the organic EL element is 10% or less. This can suppress unevenness in image density.

[0013] The first direction, second direction, and third direction in this disclosure are defined with reference to FIG. 1(a).

[0014] The longitudinal direction of the light emitting substrate 202 is defined as a first direction 1 , the lateral direction of the light emitting substrate is defined as a second direction 2 , and the direction perpendicular to the light emitting substrate 202 is defined as a third direction 3 .

[0015] As shown in FIG. 1(b), the angle 5 of the central axis 4 of the rod lens with respect to the third direction 3 is greater than 0° and is equal to or smaller than 3°.

[0016] The present inventors speculate as follows as to why the image forming apparatus of the present disclosure is excellent in the effect of suppressing the occurrence of image density unevenness.

[0017] Because the central axes of the rod lenses arranged between the light-emitting chips and the photosensitive drum are angled with respect to the third direction in this disclosure, the angle of light incident on the rod lenses from the light-emitting chips arranged in two rows staggered along the first direction differs for each row. As a result, the angle of incidence of light that forms an image from the rod lenses on the photosensitive drum also differs, resulting in differences in reflection on the surface and inside of the drum. This is thought to result in differences in latent image formation on the photosensitive drum at locations corresponding to the arrangement of the two rows of light-emitting chips, causing density unevenness.

[0018] As a result of investigations by the inventors, it was found that the occurrence of image density unevenness can be suppressed by setting the reflectance of the surface of the photosensitive drum to 10% or less for light with the wavelength having the greatest peak in the emission spectrum of the organic EL element.

[0019] The present inventors speculate as follows about the reason why the image forming apparatus of the present disclosure is excellent in the effect of suppressing the occurrence of density unevenness corresponding to the positions of the light-emitting chips arranged alternately.

[0020] The density unevenness is caused by differences in the formation of latent images on the photosensitive drum, which occurs when light is reflected on the surface and inside the photosensitive drum, reflected by the rod lens, and then incident on the photosensitive drum again.We believe that the differences in latent image formation corresponding to the arrangement of the two rows of light-emitting chips are suppressed by promoting the absorption of light inside the photosensitive drum and the scattering of light on the surface and inside.

[0021] The present disclosure will be described in detail below by way of preferred embodiments.

[0022] [Image forming device] 2 includes four image forming units 102Y, 102M, 102C, and 102K that form toner images of yellow, magenta, cyan, and black, respectively. The image forming units 102Y, 102M, 102C, and 102K include photosensitive drums 103Y, 103M, 103C, and 103K that can rotate around their respective rotation axes. Chargers 104Y, 104M, 104C, and 104K, exposure heads 105Y, 105M, 105C, and 105K, and developers 106Y, 106M, 106C, and 106K are provided around the photosensitive drums.

[0023] <Image formation process> The photosensitive drums 103Y, 103M, 103C, and 103K, which are uniformly charged by the chargers 104Y, 104M, 104C, and 104K, are exposed by the exposure heads 105Y, 105M, 105C, and 105K to form electrostatic latent images. The electrostatic latent images are visualized as toner images of the respective colors by the developers 106Y, 106M, 106C, and 106K, and transferred to the intermediate transfer belt 107 at the primary transfer portions Ty, Tm, Tc, and Tk.

[0024] The toner images of each color superimposed on the intermediate transfer belt 107 are transferred at once by a secondary transfer roller 109 at a secondary transfer section T2 onto a recording sheet P transported from a paper feed section 101. The recording sheet P onto which the toner images have been transferred is transported to a fixing device 110, where the toner images are fixed by heat and pressure, and then the recording sheet is discharged from a paper discharge section 111.

[0025] <Organic EL element> The light emitting element of the exposure head 201 used in the present disclosure is an organic EL element having an emission spectrum with the most intense peak wavelength of 370 nm or more and 780 nm or less.

[0026] In the present disclosure, the peak with the highest intensity refers to the peak with the highest intensity when there is only one peak. When there are multiple peaks, the peak with the highest emission intensity at the peak wavelength in the emission spectrum of the organic EL device of the present disclosure is referred to. The peak wavelength and the wavelength of the peak refer to the wavelength at the top of the peak (peak top).

[0027] The emission spectrum of the organic EL element of the present disclosure may have multiple peaks in the range of 370 nm to 780 nm. When multiple peaks are present, it is preferable that the emission peak intensity at the wavelength of the most intense peak of the organic EL element is at least three times the emission peak intensity at the wavelength of the second most intense peak.

[0028] Instead of an exposure head having a light-emitting substrate with a plurality of organic EL elements arranged on an array of light-emitting chips each having a peak intensity of 370 nm or more and 780 nm or less in the emission spectrum, the following exposure head can also be used in the present disclosure. That is, an exposure head having a peak intensity of 370 nm or more and 780 nm or less in the emission spectrum. Even when an exposure head having a peak intensity of 370 nm or more and 780 nm or less is used, there may be multiple peaks in the range of 370 nm or more and 780 nm or less. When there are multiple peaks, it is preferable that the emission peak intensity at the wavelength of the exposure head's most intense peak is at least three times the emission peak intensity at the wavelength of the second most intense peak.

[0029] In the present disclosure, the description of the emission spectrum of an organic EL element is the same even if the organic EL element is replaced with the exposure head in parts where the organic EL element can be replaced with the exposure head.

[0030] In the present disclosure, the peak with the highest intensity refers to the peak at which the emission intensity at the peak wavelength is the greatest in the emission spectrum of the organic EL device of the present disclosure.

[0031] The emission peak intensity of the emission spectrum of an organic EL element is determined as follows: The emission spectrum intensity is calculated from the difference between the emitting state and the non-emitting state, and the intensity at the peak wavelength is taken as the emission peak intensity.

[0032] An example of the emission spectrum of an organic EL element is shown in Figure 6. The wavelength of the most intense peak 301 is 600 nm, and the emission peak intensity 303 at the wavelength of the most intense peak is indicated by the arrow. The wavelength of the second most intense peak 302 is 650 nm, and the emission peak intensity 304 at the wavelength of the second most intense peak is indicated by the arrow.

[0033] The wavelength of the most intense peak in the emission spectrum of the organic EL element of the present disclosure is 370 nm or more and 780 nm or less as follows: That is, among a plurality of organic EL elements (=light-emitting elements), it is preferable that the wavelength of the most intense peak in the emission spectrum of 80% or more of the organic EL elements falls within the range of 370 nm or more and 780 nm or less, more preferably 90% or more by number, even more preferably 95% or more by number, and most preferably 100% by number.

[0034] Examples of light-emitting materials used in the organic EL device of the present disclosure, which are primarily involved in the light-emitting function, include fused ring compounds (e.g., fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives, rubrene, etc.), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organoaluminum complexes such as tris(8-quinolinolato)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylenevinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives. Among these, perylene derivatives are preferred. Specific examples of compounds used as light-emitting materials are listed below, but the present invention is not limited to these.

[0035] [ka]

[0036] [ka]

[0037] Specific examples of the host or assist contained in the light-emitting layer include, but are not limited to, aromatic hydrocarbon compounds or derivatives thereof, carbazole derivatives, azine derivatives, xanthone derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organoaluminum complexes such as tris(8-quinolinolato)aluminum, and organic beryllium complexes. Specific examples are shown below.

[0038] [ka]

[0039] <Configuration of exposure head board> 3 shows the light emitting substrate 202 on which the light emitting chip group 401 and the connectors 305 are arranged. Fig. 3(a) shows the surface opposite to the surface on which the light emitting chip group 401 is mounted (hereinafter referred to as the light emitting element non-mounted surface), and Fig. 3(b) shows the surface on which the light emitting chip group 401 is mounted (hereinafter referred to as the light emitting element mounted surface).

[0040] The light-emitting chip group 401 is configured by arranging a plurality of light-emitting chips 400 in a staggered manner. The light-emitting chips 400-a, 400-b, 400-c, etc. are arranged in order in the first direction, 400-a, 401-c, 401-e, etc. are arranged in a line along the first direction 1, and the light-emitting chips 400-b, 401-d, 401-f, etc. are arranged in a line along the first direction 1 at different positions in the second direction 2. In other words, the light-emitting chips 400-a, 400-b, 400-c, etc. are arranged in order in the first direction and staggered in the second direction.

[0041] On the surface where the light-emitting chips are not mounted, there is arranged a connector 305 which connects a control signal that controls the light-emitting chips from an image controller unit (not shown) and a power supply line, and each light-emitting chip is driven via the connector 305.

[0042] <Exposure head> FIG. 4 shows a cross-sectional view of an example of an exposure head 201. In some cases, the exposure head is also referred to as a solid-state exposure head. The first axis is parallel to the rotation axis of the photosensitive drum. A light-emitting substrate 202, on which multiple light-emitting chips are mounted and aligned in a first direction, and a rod lens array 206, on which multiple cylindrical gradient index lenses are aligned in the same direction, are held in a housing 205. The light-emitting substrate 202 has multiple light-emitting elements for emitting exposure light to irradiate the surface of the photosensitive drum. The housing 205 is made of a zinc-plated steel plate or cold-rolled steel plate that has been plated afterward. The rod lens array 206 has a light-incident surface facing the light-emitting elements and a light-exiting surface facing the photosensitive drum. It is composed of multiple lenses aligned in the direction of the rotation axis to focus the exposure light emitted from the light-emitting elements onto the surface of the photosensitive drum. The rod lens array 206 forms a 1:1 erect image of the light beam emitted from the light-emitting point 203 on the photosensitive drum 102. At this time, the distance from the light emitting point to the incident surface of the rod lens array 206 and the distance from the exit surface of the rod lens array 206 to the surface of the photosensitive drum 103 are approximately equal.

[0043] In the present disclosure, the angle of the central axis of the rod lens array 206 with respect to the third direction is greater than 0° and not greater than 3°. The rod lens array is a collection of rod lenses, and the angle of the central axis of each rod lens with respect to the third direction is determined by finding the angles of the rod lenses located at both ends of the rod lens array in the longitudinal direction and using the average value of the angles.

[0044] The distance between the light-emitting point 203 and the incident surface of the rod lens array 206 must be highly accurate on the order of μm, and after this distance is precisely adjusted, the light-emitting substrate 202 and the rod lens array 206 are fixed to the housing 205 by adhesive. The light-emitting substrate 202, rod lens array 206, and housing 205 integrated into one unit is called the exposure head 201.

[0045] <Photosensitive drum> As an example of the photosensitive drum 103 used in the electrophotographic image forming apparatus of the present disclosure, a support and a laminated photosensitive drum formed on the support are shown in Fig. 5. In Fig. 5, 501 is the support, 502 is an undercoat layer, 503 is a charge generation layer, 504 is a charge transport layer, and 505 is a protective layer.

[0046] In the present disclosure, the outermost layer is referred to as the “surface layer.” When a protective layer is provided, the protective layer is the surface layer, and when no protective layer is provided, the charge transport layer is the surface layer.

[0047] A method for manufacturing the photosensitive drum of the present disclosure includes preparing a coating liquid for each layer described below, coating the desired layers in order, and drying the coating liquid. Examples of methods for applying the coating liquid include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.

[0048] <Support> The support of the photosensitive drum is preferably conductive (conductive support). The support of the present disclosure has a drum (cylindrical) shape. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like.

[0049] The support is preferably made of a metal, a resin, or a glass.

[0050] Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support using aluminum is preferred.

[0051] It is also preferable to impart electrical conductivity to the resin or glass by processing such as mixing or coating with an electrically conductive material.

[0052] <Conductive layer> A conductive layer may be provided on the support, which can conceal scratches and irregularities on the surface of the support and control light reflection on the surface of the support.

[0053] The conductive layer preferably contains conductive particles and a resin.

[0054] Examples of materials for the conductive particles include metal oxides, metals, and carbon black.

[0055] Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, strontium titanate, magnesium oxide, antimony oxide, bismuth oxide, etc. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, silver, etc.

[0056] Among these, it is preferable to use metal oxide particles as the conductive particles, and it is particularly preferable to use titanium oxide particles, tin oxide particles, or zinc oxide particles.

[0057] When metal oxide particles are used as the conductive particles, the surfaces of the metal oxide particles may be treated with a silane coupling agent or the like, or the metal oxide particles may be doped with an element such as phosphorus or aluminum or an oxide thereof.

[0058] The conductive particles may have a layered structure including a core particle and a coating layer covering the core particle. Examples of the core particle include titanium oxide particles, barium sulfate particles, and zinc oxide particles. Examples of the coating layer include metal oxide particles such as tin oxide.

[0059] When metal oxide particles are used as the conductive particles, the volume average particle size thereof is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0060] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin.

[0061] The conductive layer may further contain silicone oil, resin particles, a masking agent such as titanium oxide, and the like.

[0062] The conductive layer can be formed by preparing a coating solution for the conductive layer containing the above-mentioned materials and solvent, forming this coating film on a support, and drying it. Examples of solvents used in the coating solution for the conductive layer include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of dispersion methods for dispersing the conductive particles in the coating solution for the conductive layer include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision-type high-speed disperser.

[0063] The thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.

[0064] <Undercoat layer> In the present disclosure, an undercoat layer may be provided on the support or the conductive layer. By providing an undercoat layer, adhesion between layers can be improved and a charge injection blocking function can be imparted.

[0065] The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

[0066] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, and cellulose resin.

[0067] Examples of the polymerizable functional group contained in the monomer having a polymerizable functional group include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group, a metal alkoxide group, a hydroxy group, an amino group, a carboxy group, a thiol group, a carboxylic acid anhydride group, and a carbon-carbon double bond group.

[0068] Furthermore, for the purpose of improving electrical properties, the undercoat layer may further contain an electron transport material, metal oxide particles, metal particles, a conductive polymer, etc. Among these, it is preferable to use an electron transport material or metal oxide particles.

[0069] Examples of the electron transport substance include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, an aryl halide compound, a silole compound, a boron-containing compound, etc. An electron transport substance having a polymerizable functional group may be used as the electron transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the electron transport substance with the above-mentioned monomer having the polymerizable functional group.

[0070] Examples of metal oxide particles include particles of indium tin oxide, tin oxide, indium oxide, titanium oxide, strontium titanate, zinc oxide, and aluminum oxide. Silicon dioxide particles can also be used. Examples of metal particles include particles of gold, silver, and aluminum.

[0071] The metal oxide particles contained in the undercoat layer may be surface-treated with a surface treatment agent such as a silane coupling agent.

[0072] The surface treatment of the metal oxide particles can be carried out by a common method, such as a dry method or a wet method.

[0073] In the dry method, metal oxide particles are stirred in a mixer capable of high-speed stirring, such as a Henschel mixer, and an alcohol aqueous solution, organic solvent solution, or aqueous solution containing a surface treatment agent is added to the metal oxide particles to uniformly disperse them, followed by drying.

[0074] In the wet method, metal oxide particles and a surface treatment agent are stirred in a solvent or dispersed in a sand mill using glass beads or the like, and the solvent is then removed by filtration or vacuum distillation. After the solvent is removed, the mixture is preferably baked at 100°C or higher.

[0075] The undercoat layer may further contain additives, such as known materials such as metal particles such as aluminum particles, conductive material particles such as carbon black, charge transport materials, metal chelate compounds, and organometallic compounds.

[0076] The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming the coating film on the support or the conductive layer, and drying and / or curing it.

[0077] Examples of solvents used in the coating liquid for the undercoat layer include organic solvents such as alcohols, sulfoxides, ketones, ethers, esters, halogenated aliphatic hydrocarbons, aromatic compounds, etc. In the present disclosure, it is preferable to use alcohol-based and ketone-based solvents.

[0078] Dispersion methods for preparing the coating liquid for the undercoat layer include methods using a homogenizer, ultrasonic disperser, ball mill, sand mill, roll mill, vibration mill, attritor, and liquid collision type high-speed disperser.

[0079] The thickness of the undercoat layer is preferably from 0.1 μm to 30 μm, and particularly preferably from 0.3 μm to 5 μm.

[0080] The thickness of the undercoat layer is preferably such that the ratio of the thickness of the undercoat layer to the total thickness of all layers on the support is 1. This range makes it possible to suppress reflection of exposure light inside the photosensitive drum.

[0081] <Charge generation layer> The charge generating layer preferably contains a charge generating material and a resin.

[0082] Examples of charge-generating materials include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, titanyl phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.

[0083] The content of the charge generating material in the charge generating layer is preferably 40% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less, based on the total mass of the charge generating layer.

[0084] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is more preferred.

[0085] The charge generating layer may further contain additives such as antioxidants and ultraviolet absorbers, etc. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0086] The charge generating layer can be formed by preparing a coating solution for the charge generating layer containing the above-mentioned materials and solvent, forming a coating film of this on the undercoat layer, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0087] The thickness of the charge generating layer is preferably 0.1 μm or more and 1 μm or less, and more preferably 0.15 μm or more and 0.4 μm or less.

[0088] <Charge transport layer> The charge transport layer preferably contains a charge transport material and a binder material.

[0089] When a protective layer, which will be described later, is not provided, the charge transport layer becomes the surface layer of the photosensitive drum.

[0090] Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, triarylamine compounds are preferred.

[0091] The content of the charge transport material in the charge transport layer is preferably 25% by mass to 70% by mass, and more preferably 30% by mass to 55% by mass, based on the total mass of the charge transport layer.

[0092] As the binding material, a thermoplastic resin (hereinafter also referred to as "resin") is used.

[0093] Examples of thermoplastic resins include polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins. Among these, polycarbonate resins and polyester resins are preferred. As the polyester resin, polyarylate resins are particularly preferred.

[0094] The content ratio (mass ratio) of the charge transport material to the resin is preferably 4:10 to 20:10, and more preferably 5:10 to 12:10.

[0095] The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, and leveling agents, including hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, and silicone oils.

[0096] The charge transport layer may contain additive particles. By containing additive particles in the charge transport layer, the reflectance of the photosensitive drum can be reduced. This effect is particularly evident when the charge transport layer is a surface layer.

[0097] Examples of the additive particles include silicone resin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles, and fluorine atom-containing resin particles.

[0098] Among these, organic resin particles are preferred from the viewpoint of dispersibility, and fluorine atom-containing resin particles are more preferred.

[0099] Examples of resins contained in the fluorine atom-containing resin particles include polytetrafluoroethylene resin, polychlorotrifluoroethylene resin, polytetrafluoroethylenepropylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, and polydichlorodifluoroethylene resin. It is also preferable to use particles containing multiple types of the above resins. Among the above, from the viewpoint of improving dispersibility, it is more preferable that the fluorine atom-containing resin particles be polytetrafluoroethylene (PTFE) resin.

[0100] The content of the additive particles in the charge transport layer is preferably 5% by mass to 40% by mass, and more preferably 5% by mass to 30% by mass, based on the total mass of the charge transport layer.

[0101] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvent, forming a coating film of this on the charge generation layer, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents and aromatic hydrocarbon-based solvents are preferred.

[0102] The thickness of the charge transport layer is preferably from 5 μm to 50 μm, more preferably from 8 μm to 40 μm, and particularly preferably from 10 μm to 30 μm.

[0103] <Protective layer> In the present disclosure, a protective layer may be provided on the photosensitive layer, which can improve durability.

[0104] When a protective layer is provided, the protective layer becomes the surface layer of the photosensitive drum.

[0105] The protective layer preferably contains a polymer of a compound having a polymerizable functional group.

[0106] The protective layer may be formed as a cured film by polymerizing a composition containing, for example, a monomer having a polymerizable functional group, which is a raw material for the binder material. Examples of the reaction include thermal polymerization, photopolymerization, and radiation polymerization. Examples of the polymerizable functional group possessed by the monomer having the polymerizable functional group include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylmethylol group, an epoxy group, a metal alkoxyl group, a hydroxyl group, an amino group, a carboxyl group, a thiol group, a carboxylic anhydride group, and a group containing a carbon-carbon double bond. Examples of the group containing a carbon-carbon double bond include an acryloyl group and a methacryloyl group. A monomer having charge transport capability may be used as the monomer having the polymerizable functional group.

[0107] Here, the cured product of the monomer having a polymerizable functional group is the binder material of the protective layer.

[0108] The polymerizable functional group is preferably a chain-polymerizable functional group. As the monomer having a polymerizable functional group, it is preferable to use a hole transporting compound having a chain-polymerizable functional group.

[0109] The hole transporting compound having a chain-polymerizable functional group is more preferably a compound represented by the following formula (CT-1) or (CT-2).

[0110] [ka]

[0111] In the formula (CT-1), Ar 11 ~Ar 13 are each independently a substituted aryl group or an unsubstituted aryl group. The substituent that the substituted aryl group may have is an alkyl group having from 1 to 6 carbon atoms, or a monovalent functional group represented by any one of the following formulae (P-1) to (P-3). However, the compound represented by formula (CT-1) has at least one monovalent functional group represented by any one of the following formulae (P-1) to (P-3).

[0112] [ka]

[0113] In the formula (CT-2), Ar 21 ~Ar 24 each independently represents a substituted aryl group or an unsubstituted aryl group, Ar 25 represents a substituted arylene group or an unsubstituted arylene group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms, or a monovalent functional group represented by any of the following formulae (P-1) to (P-3). The substituent that the substituted arylene group may have is an alkyl group having 1 to 6 carbon atoms, or a monovalent functional group represented by any of the following formulae (P-1) to (P-3). However, the compound represented by formula (CT-2) has at least one monovalent functional group represented by any of the following formulae (P-1) to (P-3).

[0114] [ka]

[0115] In the formula (P-1), Z 11 represents a single bond or an alkylene group having 1 to 6 carbon atoms, and X 11 represents a hydrogen atom or a methyl group.

[0116] [ka]

[0117] In the formula (P-2), Z 21 represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0118] [ka]

[0119] In the formula (P-3), Z31 represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0120] The protective layer may contain additive particles, which can reduce the reflectance of the photosensitive drum.

[0121] The content of the additive particles in the protective layer is preferably 5% by mass or more and 40% by mass or less, and more preferably 25% by mass or more and 35% by mass or less, based on the total mass of the protective layer.

[0122] Examples of the additive particles include silicone resin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles, and fluorine atom-containing resin particles.

[0123] Among these, organic resin particles are preferred, and fluorine atom-containing resin particles are more preferred from the viewpoint of dispersibility.

[0124] Examples of resins contained in the fluorine atom-containing resin particles include polytetrafluoroethylene resin, polychlorotrifluoroethylene resin, polytetrafluoroethylenepropylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, and polydichlorodifluoroethylene resin. It is also preferable to use particles containing multiple types of the above resins. Among the above, from the viewpoint of improving dispersibility, it is more preferable that the fluorine atom-containing resin particles be polytetrafluoroethylene (PTFE) resin.

[0125] In cross-sectional observation of the surface layer, the additive particles preferably have an arithmetic mean of the major axes of the primary particles (average primary particle size) measured from a secondary electron image taken with a scanning electron microscope of 150 nm to 300 nm in order to improve dispersibility and suppress potential fluctuations. Furthermore, the resin particles more preferably have an average primary particle size of 180 nm to 250 nm.

[0126] The protective layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, etc. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, polystyrene resin particles, polyethylene resin particles, and boron nitride particles.

[0127] The protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned materials and solvent, forming a coating film of this on the photosensitive layer, and drying and / or curing it. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0128] The thickness of the protective layer is preferably 0.50 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

[0129] As described above, the protective layer may have charge transport capability. When the photosensitive layer is a laminated photosensitive layer having a charge generation layer and a charge transport layer, the protective layer having charge transport capability may also be called a second charge transport layer.

[0130] <Photosensitive drum surface treatment> In the present disclosure, the surface of the photosensitive drum may be processed.

[0131] Surface processing methods include pressing a mold with convex portions onto the surface of the photosensitive drum to transfer the shape, and mechanical polishing to create a concave-convex shape (e.g., multiple grooves formed in the approximate circumferential direction of the peripheral surface of the photosensitive drum). Another method involves roughening the surface by colliding powder with the surface of the photosensitive drum. In this way, providing concave or convex portions on the surface layer of the photosensitive drum can reduce the surface reflection of exposure light on the photosensitive drum surface.

[0132] The recesses or protrusions may be formed over the entire surface of the photosensitive drum or may be formed on only a part of the surface of the photosensitive drum. When the recesses or protrusions are formed on only a part of the surface of the photosensitive drum, it is preferable that the recesses or protrusions are formed over at least the entire image forming area.

[0133] When forming recesses, a mold having protrusions corresponding to the recesses is pressed against the surface of the photosensitive drum to transfer the shape, thereby forming the recesses on the surface of the photosensitive drum. [Example]

[0134] The technology of the present disclosure will be described in more detail below with reference to Production Examples and Examples, but is not limited thereto. Note that the number of parts in the following formulations is by mass unless otherwise specified.

[0135] [Photosensitive drum manufacturing example] <Production example of photosensitive drum 1> (Support 1) A cylindrical aluminum cylinder (JIS-A3003, aluminum alloy, outer diameter 30 mm, length 357.5 mm, wall thickness 0.7 mm) was used as the support (conductive support). It was ultrasonically cleaned in a cleaning solution containing pure water and detergent (product name: Chemicol CT, manufactured by Tokiwa Chemical Co., Ltd.), and after the cleaning solution was rinsed off, it was further ultrasonically cleaned in pure water and degreased. This was designated Support 1.

[0136] (Undercoat layer 1) Zinc oxide particles (specific surface area: 19 m 2 / g, powder resistance: 4.7×10 6 100 parts of the sol-gel (Ω·cm) was mixed with 500 parts of toluene and stirred, to which 0.8 parts of a silane coupling agent (compound name: N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, product name: KBM602, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 6 hours. Thereafter, the toluene was distilled off under reduced pressure, and the particles were dried by heating at 130°C for 6 hours to obtain surface-treated zinc oxide particles A.

[0137] Next, 15 parts of butyral (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) as a polyol and 15 parts of blocked isocyanate (trade name: Duranate TPA-B80E, nonvolatile content 80% by mass, manufactured by Asahi Kasei Chemicals Corp.) were dissolved in a mixed solvent of 73.5 parts of methyl ethyl ketone and 73.5 parts of 1-butanol. To this solution, 80.8 parts of surface-treated zinc oxide particles A and 0.81 parts of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the mixture was dispersed in a sand mill using glass beads with a diameter of 0.8 mm in an atmosphere of 23±3°C for 3 hours.

[0138] After the dispersion process, 0.01 parts of silicone oil (trade name: SH28PA, manufactured by Toray Dow Corning Co., Ltd. (formerly Toray Dow Corning Silicones Co., Ltd.)) and 5.6 parts of cross-linked polymethyl methacrylate (PMMA) particles (trade name: Techpolymer SSX-103, manufactured by Sekisui Plastics Co., Ltd., average primary particle size: 3 μm) were added and stirred to prepare a coating solution for the undercoat layer.

[0139] The obtained coating liquid for undercoat layer was dip-coated onto the support 1 to form a coating film, and the coating film was dried at 160° C. for 30 minutes to form an undercoat layer 1 with a film thickness of 18 μm.

[0140] (Charge generation layer 1) Four parts of hydroxygallium phthalocyanine crystals (charge generating material) in a crystalline form having strong peaks at Bragg angles 2θ±0.2° (7.4° and 28.1°) in CuKα characteristic X-ray diffraction and 0.04 parts of a compound represented by the following formula (K) were added to a solution prepared by dissolving 2 parts of polyvinyl butyral (trade name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.) in 100 parts of cyclohexanone. The mixture was then dispersed for 1 hour in a sand mill using 1 mm diameter glass beads in an atmosphere of 23±3°C, and after the dispersion process, 100 parts of ethyl acetate was added to prepare a coating solution for a charge generating layer.

[0141] This charge generating layer coating liquid was dip coated onto the undercoat layer 1, and the resulting coating was dried at 90° C. for 10 minutes to form a charge generating layer 1 having a thickness of 0.15 μm.

[0142] [ka]

[0143] (Charge transport layer 1) A coating solution for a charge transport layer was prepared by dissolving 60 parts of a compound represented by the following formula (L), 30 parts of a compound represented by the following formula (M), 10 parts of a compound represented by the following formula (N), 100 parts of a bisphenol Z-type polycarbonate resin (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering-Plastics Corporation), and 0.2 parts of a polycarbonate having a structural unit represented by the following formula (O) (viscosity average molecular weight Mv: 20,000) in a mixed solvent of 272 parts of o-xylene, 256 parts of methyl benzoate, and 272 parts of dimethoxymethane.

[0144] This charge transport layer coating liquid was dip coated onto the charge generating layer 1 to form a coating film, and the resulting coating film was dried at 115° C. for 50 minutes to form a charge transport layer 1 having a thickness of 18 μm.

[0145] [ka]

[0146] [ka]

[0147] [ka]

[0148] [ka]

[0149] (In formula (O), 0.95 and 0.05 are the molar ratios (copolymerization ratios) of the two structural units.) (Protective layer 1) A dispersant solution was prepared by dissolving 2.20 parts of a resin (weight average molecular weight: 130,000) having a structural unit represented by the following structural formula (A) in a mixed solvent consisting of 100 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeorora H, manufactured by Nippon Zeon Co., Ltd.) and 100 parts of 1-propanol.

[0150] To the obtained dispersant solution, 40 parts of polytetrafluoroethylene resin microparticles (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) were added, and the mixture was passed through a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics, Inc., USA) to obtain a polytetrafluoroethylene resin microparticle dispersion.

[0151] [ka]

[0152] (In formula (A), 0.5 is the molar ratio (copolymerization ratio) of the two structural units.)

[0153] [ka]

[0154] To the obtained polytetrafluoroethylene resin microparticle dispersion, 75.4 parts of the hole transport compound represented by the above structural formula (B) and 100 parts of 1-propanol were added and mixed, and the mixture was filtered through a Polyflon filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.) to prepare a polytetrafluoroethylene resin microparticle dispersion (surface layer coating material).

[0155] This protective layer coating solution was dip-coated onto the charge transport layer 1 to form a coating film, and the resulting coating film was dried at 40°C for 5 minutes. After drying, the coating film was irradiated with an electron beam for 1.6 seconds under a nitrogen atmosphere at an acceleration voltage of 70 kV and an absorbed dose of 15 kGy. Then, a heat treatment was performed for 15 seconds under a nitrogen atmosphere to bring the coating film temperature to 135°C. The oxygen concentration from the electron beam irradiation to the 15-second heat treatment was 15 ppm. Next, the coating film was naturally cooled in the atmosphere to 25°C, and then heat-treated for 1 hour under conditions to bring the coating film temperature to 105°C, forming a protective layer 1 with a thickness of 5 μm.

[0156] In this way, a photosensitive drum 1 having a support and a surface layer before surface polishing was produced.

[0157] <Surface treatment of photosensitive drum 1> Before surface polishing, the photosensitive drum surface was provided with a circumferentially streaked surface. Both ends of the photosensitive drum were gripped, and the drum was rotated in the circumferential direction, and polished by pressing an abrasive sheet against it. The abrasive sheet used was GC3000 manufactured by Riken Corundum Co., Ltd.

[0158] By the above-described polishing, a plurality of grooves were formed in the approximately circumferential direction on the peripheral surface of the photosensitive drum. The same applies to the photosensitive drums 6 to 10 described later.

[0159] The surface shape of the photosensitive drum after surface polishing was measured. The maximum height Rmax according to JIS B 0601 1982 was measured using a surface roughness measuring instrument, Surfcorder SE3500, manufactured by Kosaka Laboratory Co., Ltd., and the Rmax was found to be 0.75 μm.

[0160] <Production example of photosensitive drum 2> Photosensitive drum 2 was produced in the same manner as photosensitive drum 1, except that protective layer 1 was changed to protective layer 2 formed as follows.

[0161] (Protective layer 2) 16.25 parts of the compound represented by formula (B), 8.75 parts of a hole-transporting compound represented by formula (D) below, and 0.1 parts of a siloxane-modified acrylic compound (trade name: US270, manufactured by Toagosei Co., Ltd.) were dissolved in a mixed solvent consisting of 12 parts of 1-propanol and 27 parts of cyclohexane, and the mixture was stirred. The mixture was then filtered through a Polyflon filter (trade name: FP-022, manufactured by Sumitomo Electric Fine Polymer Co., Ltd.) to prepare a coating solution for a protective layer.

[0162] This protective layer coating solution was dip-coated onto the charge transport layer 1 to form a coating film, which was then dried at 40°C for 5 minutes. After drying, the coating film was irradiated with an electron beam for 1.6 seconds under a nitrogen atmosphere at an acceleration voltage of 70 kV and an absorbed dose of 15 kGy. The coating film was then heat-treated for 15 seconds under a nitrogen atmosphere to a temperature of 135°C. The oxygen concentration from the electron beam irradiation to the 15-second heat treatment was 15 ppm. The coating film was then naturally cooled in the atmosphere to a temperature of 25°C, and then heat-treated for 1 hour to a temperature of 105°C, forming a protective layer 3 with a thickness of 5 μm.

[0163] [ka]

[0164] <Production example of photosensitive drum 3> Photosensitive drum 3 was produced in the same manner as photosensitive drum 1, except that no protective layer was provided.

[0165] <Production example of photosensitive drum 4> Undercoat layer 1 was changed to undercoat layer 2 and undercoat layer 3 formed as follows, and protective layer 1 was changed to protective layer 5 formed as follows. Except for these, photosensitive drum 4 was produced in the same manner as photosensitive drum 1.

[0166] (Undercoat layer 2) Five parts of N-methoxymethylated nylon (FR101, manufactured by Lead City Co., Ltd.), 70 parts of methanol, and 30 parts of n-butanol were mixed together to prepare a coating liquid for an undercoat layer.

[0167] This coating solution for undercoat layer 2 was dip-coated onto the support 1 to form a coating film, and the resulting coating film was dried by heating at 130° C. for 10 minutes to form an undercoat layer 2 with a thickness of 0.7 μm.

[0168] (Undercoat layer 3) 24 parts of alkyd resin (Beckolite M6401-50, manufactured by DIC Corporation), 16 parts of melamine resin (Amidia L-150-60, manufactured by DIC Corporation), 160 parts of titanium oxide particles (CR-EL, manufactured by Ishihara Sangyo Kaisha, Ltd.), and 500 parts of methyl ethyl ketone were mixed. The mixture was then dispersed for 10 hours using a sand mill equipped with 0.8 mm diameter glass beads to prepare a coating solution for an undercoat layer. This coating solution for an undercoat layer was dip-coated onto the undercoat layer 2 to form a coating film. The resulting coating film was then dried by heating at 130°C for 20 minutes to form an undercoat layer 3 with a thickness of 3.5 μm.

[0169] (Protective layer 3) A coating solution for a protective layer was prepared by mixing 14.5 parts of a hole transporting compound represented by the following formula (G), 5.5 parts of a compound represented by the following formula (H), 0.20 parts of a compound represented by the following formula (I), 0.5 parts of a photopolymerization initiator 1-hydroxycyclohexyl phenyl ketone, and 80 parts of tetrahydrofuran.

[0170] [ka]

[0171] [ka]

[0172] [ka]

[0173] This protective layer coating solution was dip-coated onto the charge transport layer 1 to form a coating film, which was then dried for 5 minutes at 60°C. After drying, the coating film was irradiated with ultraviolet light at an irradiation intensity of 700 mW / cm2 for 120 seconds using a metal halide lamp with an output of 160 W / cm. This was followed by a heat treatment at 130°C for 30 minutes to form a protective layer 3 with a thickness of 5.0 μm.

[0174] <Production example of photosensitive drum 5> (Support) A cylindrical aluminum cylinder (JIS-A3003, aluminum alloy, outer diameter 30 mm, length 357.5 mm, wall thickness 0.7 mm) was used as a support (conductive support). It was ultrasonically cleaned in a cleaning solution containing pure water and detergent (product name: Chemicol CT, manufactured by Tokiwa Chemical Co., Ltd.), and after the cleaning solution was rinsed off, it was further ultrasonically cleaned in pure water for degreasing, and this was used as a support.

[0175] (Undercoat layer 4) Zinc oxide particles (average particle size: 70 nm, specific surface area: 15 m 2 Sixty parts of zinc oxide (60 parts by weight / g) were mixed with 500 parts of tetrahydrofuran and stirred. To this was added 0.75 parts of a silane coupling agent (compound name: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, product name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.), and the mixture was stirred for 2 hours. Thereafter, the tetrahydrofuran was distilled off under reduced pressure, and the mixture was dried by heating at 120°C for 3 hours to obtain surface-treated zinc oxide particles.

[0176] Next, 25 parts of butyral (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) as a polyol and 22.5 parts of blocked isocyanate (trade name: Sumidur BL-3173, manufactured by Sumitomo Bayer Urethane Co., Ltd.) were dissolved in 142 parts of methyl ethyl ketone. To this solution, 100 parts of zinc oxide particles that had been surface-treated as described above and 1 part of alizarin were added, and the mixture was dispersed for 5 hours in a sand mill using glass beads with a diameter of 1 mm.

[0177] After the dispersion treatment, 0.008 parts of dioctyltin dilaurate and 6.5 parts of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicones) were added and stirred to prepare a coating liquid for an undercoat layer.

[0178] The obtained coating liquid for undercoat layer was dip-coated onto the support to form a coating film, and the coating film was dried at 190° C. for 24 minutes to form an undercoat layer 4 with a thickness of 20 μm.

[0179] (Charge generation layer 2) Next, 15 parts of chlorogallium phthalocyanine crystals (ionization potential 5.5 eV) having strong diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.4°, 16.6°, 25.5°, and 28.3° relative to CuKα characteristic X-rays, 10 parts of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Union Carbide Co., Ltd.), and 300 parts of n-butyl alcohol were mixed. This mixture was dispersed for 4 hours in a sand mill using 1 mm diameter glass beads to prepare a coating solution for the charge generating layer.

[0180] This charge generating layer coating liquid was dip coated onto the undercoat layer described above, and the resulting coating was dried at 150° C. for 5 minutes to form a charge generating layer 2 having a thickness of 0.2 μm.

[0181] (Charge transport layer 2) 3 kg of commercially available polytetrafluoroethylene resin particles (average primary particle size 210 nm, average circularity 0.85) were placed in a stainless steel container with a width of 400 mm, a depth of 400 mm, and a height of 50 mm, and dried at 150°C for 3 hours in a high-temperature incubator (model: SPH-102, manufactured by Espec Corporation) to obtain dried polytetrafluoroethylene resin particles.

[0182] Next, 10 parts of the dried polytetrafluoroethylene resin particles, 0.50 parts of the graft copolymer represented by the above formula (A), and 50 parts of tetrahydrofuran were mixed and stirred for 48 hours while maintaining the liquid temperature at 20°C to obtain preparation B.

[0183] Next, 10 parts of a compound represented by the following formula (CT-3), 50 parts of a compound represented by the formula (L), 65 parts of bisphenol Z-type polycarbonate resin (viscosity average molecular weight 40,000) as a binder material, and 1.4 parts of 2,6-di-t-butyl-4-methylphenol as an antioxidant were mixed, and 250 parts of tetrahydrofuran was added to dissolve the mixture, thereby obtaining a preparation C.

[0184] Preparation B was added to Preparation C and mixed with stirring, and then passed through a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics, Inc., USA) to obtain a dispersion.

[0185] Thereafter, fluorine-modified silicone oil (product name: FL-100, manufactured by Shin-Etsu Silicones Co., Ltd.) was added to the dispersion to a concentration of 5 ppm, and the mixture was filtered through a Polyflon filter (product name: PF-040, manufactured by Advantech Toyo Co., Ltd.) to prepare a coating liquid for the charge transport layer.

[0186] This charge transport layer coating liquid was dip coated onto the charge generation layer to form a coating film, and the resulting coating film was dried at 130° C. for 45 minutes to form a charge transport layer 2 having a thickness of 30 μm.

[0187] In this way, a photosensitive drum 5 was obtained.

[0188] [ka]

[0189] <Production example of photosensitive drum 6> The thickness of the undercoat layer 1 was changed to 13 μm, and the thickness of the charge transport layer 1 was changed to 24 μm. A photosensitive drum 6 was produced in the same manner as the photosensitive drum 1 except for these.

[0190] <Production example of photosensitive drum 7> The thickness of the undercoat layer 1 was changed to 30 μm, and the thickness of the charge transport layer 1 was changed to 15 μm. A photosensitive drum 7 was produced in the same manner as the photosensitive drum 1 except for these.

[0191] <Production example of photosensitive drum 8> In forming the protective layer 1, the amount of the resin having the structural unit represented by the structural formula (A) was changed from 2.2 parts to 0.3 parts, the amount of the polytetrafluoroethylene resin fine particles was changed from 40 parts to 5 parts, and the amount of the hole transport compound represented by the structural formula (B) was changed from 75.4 parts to 94 parts. Except for these changes, the photosensitive drum 8 was prepared in the same manner as the photosensitive drum 1.

[0192] <Production example of photosensitive drum 9> Photosensitive drum 9 was prepared in the same manner as photosensitive drum 1, except that in forming protective layer 1, the amount of the hole transporting compound represented by the structural formula (B) was changed from 75.4 parts to 58 parts.

[0193] <Manufacturing example of photosensitive drum 10> The protective layer 1 was changed to a protective layer 4 formed as follows. Otherwise, a photosensitive drum 10 was produced in the same manner as the photosensitive drum 1.

[0194] (Protective layer 4) 3.31 parts of 1H,1H,2H,2H-perfluorohexyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 180 parts of a macromonomer (number average molecular weight 6,000) represented by the following formula (A-1), 8.51 parts of 1,1'-azobis(1-acetoxy-1-phenylethane) (trade name: OTAZO-15, manufactured by Otsuka Chemical Co., Ltd.), and 900 parts of n-butyl acetate were mixed in a glass flask at 20°C under a nitrogen atmosphere for 30 minutes. The reaction mixture was then heated to 85-90°C and reacted for 5 hours. The reaction was stopped by cooling with ice, and 4500 parts of 2-propanol were added to obtain a precipitate. The precipitate was washed with a mixed solvent of n-butyl acetate and 2-propanol at a ratio of 1:5 and dried at 50°C under a reduced pressure of 1325 Pa or less for 2 hours to obtain graft copolymer X. The glass flask is equipped with a stirrer, a reflux condenser, a nitrogen gas inlet tube, a thermostatic bath, and a thermometer.

[0195] [ka]

[0196] The resulting graft copolymer X was subjected to GPC measurement by the following method, and the weight average molecular weight (Mw) was calculated to be Mw 250,000.

[0197] (Weight average molecular weight measured by GPC) The weight average molecular weight according to the present disclosure is measured by gel permeation chromatography (GPC) as follows.

[0198] First, the sample is dissolved in tetrahydrofuran (THF) at room temperature for 24 hours. The resulting solution is then filtered through a solvent-resistant membrane filter "Maesholidisc" (manufactured by Tosoh Corporation) with a pore size of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of components soluble in THF is approximately 0.8 mass%. This sample solution is used for measurements under the following conditions. Apparatus: HLC8120 GPC (detector: RI) (Tosoh Corporation) Column: Shodex KF-801, 802, 803, 804, 805, 806, 807 (7 columns, manufactured by Showa Denko Co., Ltd.) Eluent: tetrahydrofuran (THF) ·Flow rate: 1.0ml / min Oven temperature: 40.0℃ Sample injection volume: 0.10 ml To calculate the molecular weight of a sample, a molecular weight calibration curve prepared using standard polystyrene resins (e.g., trade names "TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500", manufactured by Tosoh Corporation) is used.

[0199] A dispersant solution was prepared by dissolving 2.8 parts of the graft copolymer X in a mixed solvent consisting of 100 parts of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (product name: AE-3000, manufactured by AGC Corporation) and 100 parts of 1-propanol.

[0200] To the resulting dispersant solution, 40 parts of polytetrafluoroethylene resin particles (average primary particle size 210 nm, average circularity 0.85) were added, and the mixture was passed through a high-pressure disperser (product name: Microfluidizer M-110EH, manufactured by Microfluidics, Inc., USA) to obtain a polytetrafluoroethylene resin particle dispersion.

[0201] To the obtained polytetrafluoroethylene resin particle dispersion, 75.4 parts of a hole transport compound represented by the above formula (B), 21.9 parts of a compound represented by the following formula (C), and 100 parts of 1-propanol were added. Then, the mixture was filtered with a Polyflon filter (trade name: PF-040, manufactured by Advantec Toyo Co., Ltd.) to prepare a polytetrafluoroethylene resin particle dispersion (coating liquid for protective layer).

[0202] [ka]

[0203] This protective layer coating solution was dip-coated onto the charge transport layer to form a coating film, and the resulting coating film was dried at 40°C for 5 minutes. After drying, the coating film was irradiated with an electron beam for 1.6 seconds under a nitrogen atmosphere at an acceleration voltage of 70 kV and an absorbed dose of 15 kGy. Then, under a nitrogen atmosphere, the coating film was heat-treated for 15 seconds to a temperature of 135°C. The oxygen concentration from the electron beam irradiation to the 15-second heat treatment was 15 ppm. Next, the coating film was naturally cooled in the atmosphere to a temperature of 25°C, and then heat-treated for 1 hour to a temperature of 105°C to form a surface layer (protective layer) with a thickness of 5 μm.

[0204] <Manufacturing example of the photosensitive drum 11> The thickness of the undercoat layer 1 was changed to 12 μm, the thickness of the charge transport layer 1 was changed to 24 μm, and the protective layer 1 was changed to a protective layer 5 formed as follows. Except for these, a photosensitive drum 11 was produced in the same manner as the photosensitive drum 1.

[0205] (Protective layer 5) A surface layer coating material was prepared by dissolving 110 parts of the hole transport compound represented by the above structural formula (B) in a mixed solvent consisting of 100 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeorora H, manufactured by Nippon Zeon Co., Ltd.) and 200 parts of 1-propanol.

[0206] This protective layer coating solution was dip-coated onto the charge transport layer 1 to form a coating film, and the resulting coating film was dried at 40°C for 5 minutes. After drying, the coating film was irradiated with an electron beam for 1.6 seconds under a nitrogen atmosphere at an acceleration voltage of 70 kV and an absorbed dose of 15 kGy. Then, a heat treatment was performed for 15 seconds under a nitrogen atmosphere to bring the coating film temperature to 135°C. The oxygen concentration from the electron beam irradiation to the 15-second heat treatment was 15 ppm. Next, the coating film was naturally cooled in the atmosphere to 25°C, and then heat-treated for 1 hour under conditions to bring the coating film temperature to 105°C, forming a protective layer 5 with a thickness of 5 μm.

[0207] [Example 1] The manufactured photosensitive drum 1 was subjected to the measurement of reflectance of the photosensitive drum described below in advance.

[0208] A modified Canon Inc. multifunction printer (product name: imageRUNNER ADVANCE C5870F) was used, with the exposure head described above installed in the area where the exposure section had been removed. An organic EL element using a perylene derivative as the light-emitting material was used as the light-emitting element for the light-emitting substrate of the solid-state exposure head. The modified machine was equipped with a pre-exposure process.

[0209] The organic EL element used had an emission spectrum with the most intense peak wavelength at 600 nm and the second most intense peak wavelength at 650 nm, and the emission peak intensity at 600 nm was three times that at 650 nm.

[0210] As shown in FIG. 3, the light emitting chips are arranged along the first direction in the present disclosure and alternately in the second direction.

[0211] The exposure head was positioned so that the lens array was at an angle of 1.5° with respect to the third direction in this disclosure.

[0212] The exposure head configured as described above had an emission spectrum with the most intense peak wavelength at 600 nm and the second most intense peak wavelength at 650 nm. The emission peak intensity at 600 nm was three times that at 650 nm.

[0213] [Evaluation 1: Reflectance measurement of photosensitive drum] The reflected light spectrum of the photosensitive drum was measured in the visible light region (370 nm to 780 nm) using a multichannel spectrophotometer (Otsuka Electronics Co., Ltd., product name: MCPD-2000). In measuring the reflected light spectrum, halogen light was irradiated perpendicularly onto the surface of the photosensitive drum with a spot diameter of 2 mm, and the specular reflected light spectrum was measured. Note that the aluminum cylinder of the support 1 was used as a reference, and the measurement was performed after correcting the specular reflected light spectrum of the reference so that the reflectance was 100% across the entire visible light region.

[0214] From the obtained spectrum, the reflectance at 600 nm, the wavelength at which the intensity of the organic EL element is strongest, was determined, and the average value of 44 points, measured at positions 30 mm, 60 mm, 90 mm, 120 mm, 150 mm, 180 mm, 210 mm, 240 mm, 270 mm, 300 mm, and 330 mm from the longitudinal end of the photosensitive drum and at positions rotated 90 degrees from each of these points in the direction of rotation of the drum, was taken as the reflectance of the photosensitive drum of this example.

[0215] [Evaluation 2: Image density unevenness measurement] The drum cartridge equipped with the photosensitive drum 1 was placed in the cyan station of the image forming apparatus, and the conditions of the charging device and the exposure device were set so that the charging potential of the photosensitive drum was −600 V and the exposure potential was −200 V in an environment of 30° C. / 80% RH. The conditions of the developing device were also set so that the development potential was −420 V.

[0216] When a single full-page halftone image with a density of 30% in monochromatic cyan was output as the pattern image, it was evaluated whether density differences occurred in the direction of the rotation axis of the photosensitive drum (corresponding to the first direction in this disclosure). The output image was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.

[0217] (Evaluation criteria for image density unevenness) A: No difference in concentration occurs B: A concentration difference occurs to a level that cannot be determined. C: Slight density difference occurs D: A clear difference in concentration occurs

[0218] [Table 1]

[0219] [Examples 2 to 12, Comparative Example 1] The image forming apparatus was evaluated in the same manner as in Example 1, except that the type of photosensitive drum, whether or not the surface of the photosensitive drum was treated, and the angle formed by the lens array of the exposure head and the third direction were changed as shown in Table 3. The evaluation results are shown in Table 1.

[0220] (Configuration 1) a photosensitive drum rotatable around a rotation axis; An exposure head; An image forming apparatus having the exposure head has a light emitting substrate and a rod lens array; the light-emitting substrate has a plurality of light-emitting chips for emitting exposure light to irradiate the surface of the photosensitive drum; The light-emitting chip has a plurality of light-emitting elements arranged in a plurality of rows, the rod lens array has a plurality of rod lenses for condensing the exposure light emitted from the light-emitting element onto the surface of the photosensitive drum; the rod lenses are aligned in the direction of the rotation axis, the light-emitting element is an organic EL element, the wavelength of the most intense peak in the emission spectrum of the organic EL element is 370 nm or more and 780 nm or less; When the longitudinal direction of the light emitting substrate is defined as a first direction, the lateral direction of the light emitting substrate is defined as a second direction, and a direction perpendicular to the light emitting substrate is defined as a third direction, The rotation axis is parallel to the first direction, The plurality of light emitting chips are arranged along the first direction and are arranged alternately in the second direction; the angle of the central axis of the rod lens with respect to the third direction is greater than 0° and is not more than 3°; the reflectance of the surface of the photosensitive drum at the wavelength of the most intense peak in the emission spectrum of the organic EL element is 10% or less; An image forming apparatus characterized by:

[0221] (Configuration 2) 2. The image forming apparatus according to claim 1, wherein the emission peak intensity at the wavelength of the most intense peak of the organic EL element is at least three times the emission peak intensity at the wavelength of the second most intense peak.

[0222] (Configuration 3) the photosensitive drum has a support, an undercoat layer on the support, a charge generating layer on the undercoat layer, and a charge transport layer on the charge generating layer; the charge transport layer is a surface layer of the photosensitive drum, the ratio of the thickness of the undercoat layer to the total thickness of all layers on the support is 1 is 0.3 or more and 0.6 or less; 3. The image forming apparatus according to claim 1 or 2.

[0223] (Configuration 4) the photosensitive drum has a surface layer containing particles, the content of the particles in the surface layer is 5% by mass or more and 40% by mass or less with respect to the total mass of the surface layer; 4. The image forming apparatus according to any one of the first to third aspects.

[0224] (Configuration 5) 5. The image-forming apparatus according to any one of configurations 1 to 4, wherein the particles are organic resin particles.

[0225] (Configuration 6) 6. The image forming apparatus according to any one of configurations 1 to 5, wherein a plurality of grooves are formed on the peripheral surface of the photosensitive drum in the approximately circumferential direction of the peripheral surface.

[0226] (Configuration 7) the photosensitive drum has a protective layer, the protective layer is a surface layer of the photosensitive drum, the protective layer contains a polymer of a compound having a polymerizable functional group; 7. The image forming apparatus according to any one of configurations 1 to 6.

[0227] (Configuration 8) 8. The image-forming apparatus according to any one of configurations 1 to 7, wherein the compound having a polymerizable functional group is a compound represented by the following formula (CT-1) or (CT-2):

[0228] [ka]

[0229] (In the formula (CT-1), Ar 11 ~Ar 13 are each independently a substituted aryl group or an unsubstituted aryl group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms, or a monovalent functional group represented by any one of the following formulas (P-1) to (P-3). However, the compound represented by the formula (CT-1) has at least one monovalent functional group represented by any one of the following formulas (P-1) to (P-3).

[0230] [ka]

[0231] (In the formula (CT-2), Ar 21 ~Ar 24each independently represents a substituted aryl group or an unsubstituted aryl group. 25 represents a substituted arylene group or an unsubstituted arylene group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms or a monovalent functional group represented by the following formulas (P-1) to (P-3), and the substituent that the substituted arylene group may have is an alkyl group having 1 to 6 carbon atoms or a monovalent functional group represented by the following formulas (P-1) to (P-3). However, the compound represented by formula (CT-2) has at least one monovalent functional group represented by any of the following formulas (P-1) to (P-3).

[0232] [ka]

[0233] (In the formula (P-1), Z 11 represents a single bond or an alkylene group having 1 to 6 carbon atoms, and X 11 represents a hydrogen atom or a methyl group.

[0234] [ka]

[0235] (In the formula (P-2), Z 21 represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0236] [ka]

[0237] (In the formula (P-3), Z 31 represents a single bond or an alkylene group having 1 to 6 carbon atoms. (Configuration 9) 9. The image-forming apparatus according to any one of configurations 1 to 8, wherein the compound having a polymerizable functional group is a compound represented by formula (CT-1). [Explanation of symbols]

[0238] 1 First direction 2 Second direction 3 Third direction 4. Center axis of rod lens 5 Angle of the central axis of the rod lens with respect to the third direction 102 Image forming unit 103 Photosensitive drum 104 Charger 106 Developer 107 Intermediate transfer belt 109 Secondary transfer roller 110 Fixing unit 111 Paper output section 201 Exposure head 202 Light-emitting substrate 203 Luminous Point 205 Housing 206 Rod Lens Array 301 Most intense peak 302 Second most intense peak 303 Emission peak intensity at the wavelength of the most intense peak 304 Emission peak intensity at the wavelength of the second most intense peak 400 light-emitting chips 400 light-emitting chips 401 Light-emitting chip group 501 Support 502 Undercoat layer 503 Charge generation layer 504 Charge transport layer 505 Protective layer

Claims

1. a photosensitive drum rotatable around a rotation axis; An exposure head; An image forming apparatus having: the exposure head has a light emitting substrate and a rod lens array; the light-emitting substrate has a plurality of light-emitting chips for emitting exposure light to irradiate the surface of the photosensitive drum; The light-emitting chip has a plurality of light-emitting elements arranged in a plurality of rows, the rod lens array has a plurality of rod lenses for condensing the exposure light emitted from the light-emitting element onto the surface of the photosensitive drum; the rod lenses are aligned in the direction of the rotation axis, the light-emitting element is an organic EL element, the wavelength of the most intense peak in the emission spectrum of the organic EL element is 370 nm or more and 780 nm or less; When the longitudinal direction of the light emitting substrate is defined as a first direction, the lateral direction of the light emitting substrate is defined as a second direction, and a direction perpendicular to the light emitting substrate is defined as a third direction, The rotation axis is parallel to the first direction, The plurality of light emitting chips are arranged along the first direction and are arranged alternately in the second direction; the angle of the central axis of the rod lens with respect to the third direction is greater than 0° and is equal to or less than 3°; the reflectance of the surface of the photosensitive drum at the wavelength of the most intense peak in the emission spectrum of the organic EL element is 10% or less; An image forming apparatus characterized by:

2. 2. The image forming apparatus according to claim 1, wherein the emission peak intensity at the wavelength of the most intense peak of said organic EL element is at least three times the emission peak intensity at the wavelength of the second most intense peak.

3. the photosensitive drum has a support, an undercoat layer on the support, a charge generating layer on the undercoat layer, and a charge transport layer on the charge generating layer; the charge transport layer is a surface layer of the photosensitive drum, the ratio of the thickness of the undercoat layer to the total thickness of all layers on the support is 1 is 0.3 or more and 0.6 or less; 3. The image forming apparatus according to claim 1.

4. the photosensitive drum has a surface layer containing particles, the content of the particles in the surface layer is 5% by mass or more and 40% by mass or less with respect to the total mass of the surface layer; 3. The image forming apparatus according to claim 1.

5. 5. The image forming apparatus according to claim 4, wherein the particles are organic resin particles.

6. 3. The image forming apparatus according to claim 1, wherein a plurality of grooves are formed on the peripheral surface of the photosensitive drum in a substantially circumferential direction of the peripheral surface.

7. the photosensitive drum has a protective layer, the protective layer is a surface layer of the photosensitive drum, the protective layer contains a polymer of a compound having a polymerizable functional group; 3. The image forming apparatus according to claim 1.

8. 8. The image-forming apparatus according to claim 7, wherein the compound having a polymerizable functional group is a compound represented by the following formula (CT-1) or (CT-2): 【Chemical 1】 (In the formula (CT-1), Ar １１ ~Ar １３ each independently represents a substituted aryl group or an unsubstituted aryl group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms, or a monovalent functional group represented by any one of the following formulas (P-1) to (P-3). However, the compound represented by formula (CT-1) has at least one monovalent functional group represented by any one of the following formulas (P-1) to (P-3). 【Chemistry 2】 (In the formula (CT-2), Ar ２１ ~Ar ２４ each independently represents a substituted aryl group or an unsubstituted aryl group. ２５ represents a substituted arylene group or an unsubstituted arylene group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms, or a monovalent functional group represented by the following formulas (P-1) to (P-3), and the substituent that the substituted arylene group may have is an alkyl group having 1 to 6 carbon atoms, or a monovalent functional group represented by the following formulas (P-1) to (P-3). However, the compound represented by formula (CT-2) has at least one monovalent functional group represented by any of the following formulas (P-1) to (P-3). 【Chemistry 3】 (In the formula (P-1), Z １１ represents a single bond or an alkylene group having 1 to 6 carbon atoms; X １１ represents a hydrogen atom or a methyl group. 【Chemistry 4】 (In the formula (P-2), Z ２１ represents a single bond or an alkylene group having 1 to 6 carbon atoms. 【Chemistry 5】 (In the formula (P-3), Z ３１ represents a single bond or an alkylene group having 1 to 6 carbon atoms.

9. 9. The image-forming apparatus according to claim 8, wherein the compound having a polymerizable functional group is a compound represented by formula (CT-1).

Images