PHOTOCONDUCTOR DRUM HAVING A LAYER

BACKGROUND

[0001] An image forming apparatus performs image forming on a print medium. For example, an image forming apparatus performs forming an image using a photoconductor drum to generate electrostatic pattern as a latent image for the image. The image forming apparatus may use printing material to form the image on a surface such as a surface of a print medium. For example, the printing material may be supplied to the electrostatic pattern such as the latent image to form the image that is visible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a diagram of an example of an image forming apparatus including a photoconductor drum.

[0003] FIG. 2 is a diagram of a photoconductor drum in an example process to form an electrophotographic image, according to an example.

[0004] FIGS. 3A through 3C illustrate a cross-sectional view of the layer in the photoconductive body or photoconductor drum according to an example.

[0005] FIG. 4 illustrates an example process of forming the layer on the substrate 510, such as a substrate drum, according to an example.

[0006] FIG. 5 illustrates an example of the cross-sectional thickness and alignment of a substrate drum and a layer formed on the substrate drum.

[0007] FIG. 6 illustrates examples of uneven layer thickness of the layer along the circumference of the photoconductor drum.

[0008] FIG. 7 illustrates an example cause for a varying or uneven thickness during a dip coating process according to an example.

[0009] FIG. 8 illustrates example alignments of the substrate drum during a dipping coating process, according an example. [0010] FIG. 9 illustrates an example of a degraded image quality due to an uneven thickness of the layer or a misalignment of the substrate.

[0011] FIG. 10 illustrates examples of a cleaning blade to clean the surface of the photoconductor drum.

[0012] FIG. 11 illustrates a circumferential thickness profile along a circumference of the photoconductor drum at an initial stage and after 200,000 (200K) times of image forming operations, according to an example.

[0013] FIG 12 illustrates an example of determining a thickness variation of the layer along a circumference of the photoconductor drum according to an example.

[0014] FIG. 13 illustrates examples of the layer having the maximum thickness and the minimum thickness around a circumference of the photoconductor drum, according to an example.

[0015] FIG. 14 illustrates example longitudinal positions where circumferential thickness variation as discussed above can be determined at or measured at, according to an example.

[0016] FIG. 15 illustrates different types of cleaning blades applying a force onto the photoconductor drum to detach printing material from the surface of the photoconductor drum according to an example.

[0017] FIG. 16 indicates the flow diagram of a control system regarding a cartridge couplable to an image forming device, according to an example.

DETAILED DESCRIPTION

[0018] In this disclosure, when the specification states that one constituent element is "connected to" another constituent element, it includes a case in which the two constituent elements are connected to each other with another constituent element intervened therebetween as well as a case in which the two constituent elements are directly connected to each other. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

[0019] Further, the expression "image forming apparatus" as used herein includes an apparatus that processes image forming data generated at a terminal such as a computer communicating through a wired connection or wirelessly, which may be a computer for personal and/or business use, a remote server communicating data across a network or the internet, and/or a wireless mobile device such as a smartphone or tablet, to perform image forming. Examples of the image forming apparatus may include particulatebased image forming apparatuses.

[0020] As an example of an image forming apparatus, electrophotographic image forming apparatuses may be used to form an image, such as hardcopy documents, from electronic data. Toner-based image forming apparatuses may be an example. In an electrophotographic image forming apparatus, a pattern of electric charges is formed corresponding to the image to be printed. Printing material such as charged toner particles is then attracted to the image pattern to develop the image. The image can then be transferred to a print medium, such as a sheet of paper. The toner can then be securely attached to the print medium.

[0021] According to an example, an image forming apparatus may include some or all of the features described in this disclosure.

[0022] According to an example, FIG. 1 is a diagram of an example of an image forming apparatus 1000 including a photoconductor durm 300. According to an example, FIG. 2 is a diagram of the photoconductor drum 300 to form an electrophotographic image. According to an example, the image forming apparatus 1000 may include a body 1 without a cartridge 2 or a body 1 and an image forming cartridge 2 that is attachable to and detachable from the body 1 . According to an example, the cartridge 2, such as cartridges containing toners of different colors, may be couplable to the plurality of cartridge receiving parts of the image forming apparatus 1000. The cartridge 2 may be coupled to or removed from the body 1 through an opening to the inside of the image forming apparatus. [0023] In a toner-based image forming apparatus, for example, uniform coverage of charges may be initially formed on a photoconductor drum 300. The light L or light beam L such as a laser and LED is scanned over the surface of the cylindrical photoconductor drum 300 according to the image to be printed. Where the light illuminates the surface of the photoconductor drum 300, a partially discharged area is formed. These charged and discharged areas together compose a pattern corresponding to the image to be printed.

[0024] Charged toner is then applied to the photoconductor drum 300. The charged toner is then driven by electric fields in the latent electrostatic image to the discharged areas on the drum 300, thereby developing the image to be printed. The toner image can then be transferred to a print medium 120, such as a transfer belt or a sheet of paper as showin in FIGS. 1 and/or 2, to produce the desired hardcopy document.

[0025] According to an example, FIG. 2 is a diagram of the manner by which an electrophotographic image forming can be accomplished, according to an example.

[0026] According to an example, at least a part of this electrophotographic mechanism may include in an image forming apparatus 1000. The electrophotographic image forming mechanism may include a photoconductor drum 300, which is made from highly photoconductive material that is discharged by light photons. The photoconductor drum 300 may also be referred to as a photoreceptor drum 300, photosensitive drum 300, photosensitive body 300, a photoconductor 300, an optical photoconductor 300, or an organic photoconductor 300. Initially, the photoconductor drum 300 is given a total positive charge or negative charge via a charge roller 110. The charge roller 110 is in contact with the drum 300 during image formation on the print medium 120 for precise alignment of the image to be formed on the print medium 120.

[0027] As the photoconductor drum 300 revolves, the image forming mechanism shines a light beam such as a laser beam or a LED light beam emanating from the light beam source 102, through a light travel path and onto the surface 106 of the photoconductor drum 300 to discharge certain points in accordance with an image. In this way, the light beam draws, or scans, the image to be printed as a pattern of electrical charges, which can be referred to as an electrostatic image. The photoconductor drum 300 may rotate, as indicated by the arrow 112. After the pattern as the electrostatic image has been set, the image forming mechanism coats the drum 300 with toner, which is a fine powder. For example, the toner also may have a positive charge or negative charge, so the toner clings to the discharged areas of the drum 300, but not to the positively or negatively charged background.

[0028] According to an example, referring to Figs. 1 and 2, the toner may be transferred to the photoconductive drum 300 by a developer roller 114 that rotates, as indicated by the arrow 116, against the photoconductor drum 300, after having rotated through the toner container 118 to pick up toner. According to an example, the toner may be transfrred to the developer roller 114 by the supply roller 115 from the toner container. The developer roller 114 may be in contact with the photoconductor drum 300 during image formation on the print medium 120 for alignment of the image to be formed on the print medium 120. At other times, during non-use, the developer roller 114 may be separated from the photoconductor drum 300. With the powder pattern affixed, the drum 300 rolls over a sheet of print medium 120, which moves in the direction indicated by the arrow 122. Before the print medium 120 rolls under the drum 300, it may be given a negative charge or a positive charge by the transfer roller 124. This charge is stronger than the charge of the electrostatic image, so the print medium 120 pulls the powder away from the drum 300. Since it is moving at the same speed as the drum 300, the print medium 120 picks up the image pattern exactly.

[0029] The image forming mechanism 100 finally passes the print medium 120 through the fuser 130, which can be a pair of heated rollers 132 and 134 that move in the opposite direction. As the print medium 120 passes through these heated rollers 132 and 134, the loose toner powder melts, fusing with the fibers in the print medium 120. The fuser 130 rolls the print medium 120 to an output tray, providing a printed page.

[0030] According to an example, at least some components of the electrophotographic-image forming mechanism as illustrated in FIG. 2 may be encased within a removable cartridge 2 that can be replaced. For example, at least some components of the electrophotographic-image forming mechanism as illustrated in FIG. 2 may be encased within different removable cartridges 2 that can be replaced. A variety of cartridge structures may be included in the cartridge 2. For example, the removable cartridge 2 can be a toner cartridge 2 containing toner and replaceable when the toner supply of the toner cartridge 2 has been depleted. For example, the removable cartridge 2 may include a drum. According to an example, the drum may be the photoconductor drum 300, the developer roller 114, and the charge roller 110, or any roller usable to perform a function for the image forming apparatus 1000 or the cartridge 2. According to an example, the toner container 118 or a corresponding component thereto, the photoconductor drum 300, the developer roller 114, and the charge roller 110 may all be encased within a removable toner cartridge 2. As such, when the toner supply present in the toner container 118 or the corresponding component thereto has been depleted, the toner cartridge 2 is replaced with a new, fresh toner cartridge 2 to continue forming images on print medium 120. According to an example, the cartridge 2 may be an image forming cartridge 2 that includes a developing portion in which the photoconductor drum 300 and the developing roller 114 are mounted, a waste container receiving waste toner removed from the photoconductor drum 300, and a toner containing portion connected to the developing portion and containing toner.

[0031] According to an example, the photoconductor drum 300 may comprise a substrate 310 such as a substrate drum 310 and a layer 320. According to an example, the layer 320 may include a photosensitive layer 321 , which may also be referred as a photoconductive layer 321 or photoconductor layer 321. According to an example, the layer 320 may include a plurality of layers 320, such as different types of layers 320.

[0032] According to an example, FIGS. 3A through 3C illustrate cross-sectional views of types of the layer in the photoconductive body according to an example. [0033] According to an example, referring to FIG. 3A, the photosensitive body 300 may include a support 310 such as a substrate 310 or substrate drum 310, and the layer 320 including a photosensitive layer 321 . [0034] According to an example, referring to FIG. 3B, the photosensitive body 300 may include a support 310 such as a substrate 310 or substrate drum 310, and the layer 320 that may include a charge generation layer 325 (“CGL”) and/or a charge transfer layer 327 (“CTL”).

[0035] According to an example, referring to FIG. 3B, the photosensitive body 300 may include a support 310 such as a substrate 310 or substrate drum 310, and the layer 320 that may include an undercoat layer 323 (“UCL”), a charge generation layer 325 (“CGL”) and/or a charge transfer layer 325 (“CTL”).

[0036] According to an example, the electrically conductive substrate 310 may be in the form of a plate, disc, sheet, belt, drum, or the like which may include any conductive material, for example, a metal or an electrically conductive polymer. For example, referring to FIG. 3, the shape of the substrate 310 may be, for example, a drum being a cylindrical shape having a circular or a substantially circular cross-sectional shape.

[0037] According to an example, the substrate 310 such as a substrate drum 310 may include a conductive material. For example, the conductive material may include metal materials such as aluminum, an aluminum alloy, vanadium, nickel, copper, zinc, silver, gold, stainless steel, palladium, indium, tin, platinum, titanium, or the like. For example, the electrically conductive material may include a polymer such as a polyester resin, a polycarbonate resin, a polyamide resin, a polyimide resin, and any mixture thereof, or a copolymer of monomers used in preparing the resins described above in which an electrically conductive material such as metal particles, a conductive carbon, tin oxide, indium oxide, or the like may be dispersed. For example, an organic polymer sheet or glass sheet on which a metal is deposited or a metal sheet is laminated may be used as the electrically conductive substrate. For example, the conductive material may be obtained by laminating or depositing a metal film such as films of aluminum, an aluminum alloy, copper, zinc, silver, gold, stainless steel or titanium, or depositing or coating a layer of a conductive metal oxide such as a conductive polymer, tin oxide, indium oxide or indium tin oxide, on the surface of polyester such as polyethylene terephthalate, nylon such as nylon 6 and nylon 66, and polymer materials such as polystyrene, polycarbonate, a phenol resin and polyimide, hard paper, glass, or the like, may be used. For example, a conductive path formed by including the particles of the metal material or the conductive metal oxide in the polymer material may be used.

[0038] The surface of the substrate 310 such as a substrate drum 310 may, for example, undergo a positive electrode oxide coat treatment, surface treatment by chemicals, hot water or the like, coloring treatment, or diffuse treatment such as roughening the surface, to the extent not affecting image quality. In the electrophotographic process using a light exposure source such as a laser or a LED, incident light and reflected light in an organic photosensitive body such as a photoconductor drum 300 may cause interference, and an interference pattern by this interference occurs on the image to cause an image defect. By carrying out the above-described treatment on the surface of the substrate 310 such as a substrate drum 310, the image defect by the interference of laser light may be reduced or suppressed.

[0039] According to an example, an intermediate layer, such as a undercoat layer 323 shown in FIG. 3C, may be further included to maintain the electrical properties of the photoconductor body 300 between the photosensitive layer 321 and the substrate 310 such as a substrate drum 310. For example, The intermediate layer, such as the undercoat layer 323, may be formed on the substrate 310 such as a substrate drum 310, and may serve to improve image characteristics by hole injection inhibition, improve adhesion of the substrate 310 such as a substrate drum 310 and the photosensitive layer 321 , prevent damages such as dielectric breakdown of the photosensitive layer 321 .

[0040] According to an example, as shown in FIGS. 3B or 3C, the photosensitive layer 321 may be formed of a structure including a charge generation layer 325 containing a charge generating material, and a charge transport layer 327 containing a charge transporting material. As such, each of these layer may be responsible for a charge generation function and a charge transport function, based on materials for charge generation and charge transport.

[0041] According to an example, the charge generation layer 325 may contain a charge generating material to generate charge. [0042] As a material that can be effective for the charge generating material, a variety of material types may be implemented, such as an azo-based pigment such as a monoazo-based pigment, a bisazo-based pigment and a trisazo-based pigment; an indigo-based pigment such as indigo and thioindigo; a perylene- based pigment such as perylene imide and perylenic acid anhydride; a polycyclic quinone-based pigment such as anthraquinone and pyrenequinone; a phthalocyanine-based pigment such as metal phthalocyanine and non-metal phthalocyanine; a squarylium coloring agent; pyrylium dyes and thiopyrylium dyes; a triphenylmethane-based coloring agent; inorganic materials such as selene and amorphous silicon. According to an example, these charge generating materials may be used alone or in combination of two or more.

[0043] According to an example, the photosensitive layer 321 or the charge transport layer 327 may contain a charge transport material having a transport ability by accepting charge generated in the charge generating material.

[0044] According to an example, the charge transport layer 327 may include a charge transporting material and a binder compound to hold or bind the charge transporting material, such as a binder resin. According to an example, the charge transporting material may be to function to form an electrostatic latent image by transferring holes generated from the charge generation layer to a surface of the charge transport layer through a conductive path formed in the charge transport layer by light exposure. According to an example, the charge transporting material may include a hole transporting material for transporting holes and/or an electron transporting material for transporting electrons. When the laminate type photoreceptor may be used as a negatively charged type, the hole transporting material may be used as a major component of the charge transporting material. In this case, a small amount of the electron transporting material may be added thereto in order to prevent a hole trap. A content of the electron transporting material may be in a range of about 0 to 50 parts by weight, for example, about 5 to 30 parts by weight.

[0045] According to an example, a variety of types of materials can be used to optimize or increase the performance of the charge transporting material. For example, the charge transporting material may include the hole transporting material which may be included in the charge transport layer, which may be nitrogen containing cyclic compounds or condensed polycyclic compounds such as a hydrazone-based compound, a butadiene-based compound, a benzidine- based compound, a stilbene-based compound, a bisazo-based compound, a pyrene-based compound, a carbazole-based compound, an arylmethane-based compound, a thiazol-based compound, a styryl-based compound, a pyrazoline- based compound, an arylamine-based compound such as a diphenylamine- based compound and triphenylamine-based compound, an oxazole-based compound, an oxadiazole-based compound, a pyrazoline-based compound, a pyrazolone-based compound, a polyaryl alkane-based compound, a polyvinylcarbazole-based compound, a N-acrylamide methylcarbazole copolymer, a triphenylmethane copolymer, a styrene copolymer, polyacenaphthene, polyindene, a copolymer of acenaphthylene and styrene, a formaldehyde-based condensed resin, and/or a high molecular weight compound having substituents of the above compounds in a main chain or a side chain. For example, the charge transport material may include a carbazole derivative, a butadiene derivative, an oxazole derivative, an oxadiazole derivative, a thiazole derivative, a thiadiazole derivative, a triazole derivative, an imidazole derivative, an imidazolone derivative, an imidazolidine derivative, a bisimidazolidine derivative, a styryl compound, a hydrazone compound, a polycyclic aromatic compound, an indole derivative, a pyrazoline derivative, an oxazolone derivative, a benzimidazole derivative, a quinazoline derivative, a benzofuran derivative, an acridine derivative, a phenazine derivative, an aminostilbene derivative, a triarylamine derivative, a triarylmethane derivative, a phenylenediamine derivative, a stilbene derivative, a benzidine derivative, and the like may be listed. In addition, a polymer having a moiety derived from these compounds in a straight chain or branched chain, for example, poly-N-vinyl carbazole, poly-1 -vinylpyrene, poly-9-vinylanthracene and the like may be used. According to an example, the above-listed hole transporting material compound may be used alone or in combination of two or more. [0046] For example, the charge transporting material may include N,N'-(((1 E,1'E)- 1 ,4-phenylenebis(ethene-2, 1 -d iy I )) bis(4 , 1 -phenylene))bis(2,4-dimethyl-N-(p- tolyl)aniline).

[0047] According to an example, when the electron transporting material is included in the charge transporting material, a variety of types of a usable electron transporting material can be implemented for the performance of the photosensitive body. According to an example, the electron transporting material may include low molecular weight compounds for electron transporting such as a benzoquinone-based compound, a naphthoquinone-based compound, an anthraquinone-based compound, a malononitrile-based compound, a diphenoquinone-based compound, a fluorenone-based compound, a cyanoethylene-based compound, a cyanoquinodimethane-based compound, a xanthone-based compound, a phenanthraquinone-based compound, a phthalic anhydride-based compound, a thiopyran-based compound, a dicyanofluorenonebased compound, a naphthalenetetracarboxylic acid diimide compound, a benzoquinoneimine-based compound, a stilbenequinone-based compound, a diiminoquinone-based compound, a dioxotetracenedione compound, and a pyran sulfide-based compound. In addition, an electron transporting polymer compound or a pigment having n-type semiconductor characteristics may be used. The foregoing electron transporting materials may be used alone or in combination of two or more.

[0048] Examples of the hole transporting material may include 1 ,1-bis-(para- diethylaminophenyl)-4,4-diphenyl-1 ,3-butadiene, N,N'-bis(ortho,para- dimethylphenyl)-N,N'-diphenylbenzidine, 3,3'-dimethyl-N,N,N',N'-tetrakis-4- methylphenyl-(1 ,1'-biphenyl)-4,4'-diamine, N-ethyl-3-carbozolylaldehyde-N,N'- diphenylhydrazone, 4-(N,N-bis(para-toluyl)amino)-betaphenylstilbene, N,N,N',N'- tetrakis(3-methylphenyl)-1 ,3-diaminobenzene, N,N- diethylaminobenzaldehydediphenyl-hydrazone, N,N- dimethylaminobenzaldehydediphenyl-hydrazone, 4-dibenzylamino-2- methylbenzaldehydediphenylhydrazone, 2,5-bis(4-aminophenyl)-

[1 ,3,4]oxadiazole, (2-phenylbenzo[5,6-b]-4H-thiopyran-4-ylidene)- propanedinitrile-1 ,1 -dioxide, 4-bromo-triphenylamine, 4,4'-(1 ,2-ethanediylidene)- bis(2,6-dimethyl-2,5-cyclohexadiene-1-one), 3,4,5-triphenyl-1 ,2,4-triazole, 2-(4- methylphenyl)-6-phenyl-4H-thiopyran-4-ylidene-propanedinitri le-1 , 1 -dioxide, 4- dimethylamino-benzaldehyde-N,N-diphenylhydrazone, 9-ethylcarbazole-3- aldehyde-N-methyl-N-phenylhydrazone, 5-(2-chlorophenyl)3-[2-(2- chlorophenyl)ethenyl]-1 -phenyl-4,5-dihydro-1 H-pyrazole, 4-diethylamino- benzaldehyde-N,N-diphenylhydrazone, N-biphenylyl-N-phenyl-N-(3- methylphenyl)amine, 9-ethylcarbazole-3-aldehyde-N,N-diphenylhydrazone, 3,5- bis(4-tert-butylphenyl)4-phenyltriazole, 3-(4-biphenylyl)-4-phenyl-5-tert- butylphenyl-1 ,2,4-triazole, 4-diphenylamino-benzaldehyde-N,N- diphenylhydrazone, 5-(4-diethylaminophenyl)-3-[2-(4-diethylaminophenyl)- ethenyl]-1-phenyl-4,5-dihydro-1-pyrazole, N,N'-di(4-methylphenyl)-N,N'- diphenyl-1 ,4-phenylenediamine, 4-dibenzylaminobenzaldehyde-N,N- diphenylhydrazone, 4-dibenzylamino-3-methylbenzaldehyde-N,N- diphenylhydrazone, 4,4'-bis(carbazole-9-yl)biphenyl, N,N,N',N'- tetraphenylbenzidine, N,N'-bis(4-methylphenyl)-N,N'-bis(phenyl)-benzidine, N,N'- bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine, N,N,N',N'-tetrakis(4- methylphenyl)bezidine, N,N,N',N'-tetrakis(3-methylphenyl)bezidine, di(4- dibenzylaminophenyl)ether, N,N'-di(naphthalene-2-yl)-N,N'-diphenylbezidine, N,N'-di(naphthalene-1-yl)-N,N'-diphenylbezidine, 1 ,3-bis(4(4- diphenylamino)phenyl-1 ,3,4-oxadiazole-2-yl)benzene, N,N'-di(naphthalene-2- yl)N,N'-di(3-methylphenyl)bezidine, N,N'-di(naphthalene-1-yl)-N,N'-di(4- methylphenyl)bezidine, N,N'-di(naphthalene-2-yl)-N,N'-di(3- methylphenyl)bezidine, 1 , 1 -bis(4-bis(4-methylphenyl)aminophenyl)cyclohexane, 4,4',4"-tris(carbazole-9-yl)-triphenylamine, 4,4',4"-tris(N,N-diphenylamino)- triphenylamine, N,N'-bis(biphenyl-1-yl)-N,N'-bis(naphth-1-yl)benzidine, 4, 4', 4"- tris(N-3-methylphenyl-N-phenylamino)triphenylamine, N,N,N',N'- tetrakis(biphenyl-4-yl)benzidine, 4,4',4"-tris(N-(1-naphthyl)-N- phenylamino)triphenylamine, and 4,4',4"-tris(N-(2-naphthyl)-N- phenylamino)triphenylamine. According to an example, these hole transporting materials may be used alone or in combination of two or more. [0049] If the charge transporting material itself has film-forming characteristics, the charge transporting layer may be formed without the binder resin, but usually low molecular materials do not have film-forming characteristics. Therefore, the charge transporting material may be dissolved or dispersed with a binder resin in a solvent to prepare a coating composition (solution or dispersion) for forming a charge transport layer, and then the solution or the dispersion may be coated on the charge generation layer and dried to form the charge transport layer. Examples of the binder resin which may be used for the charge transport layer of the electrophotographic photoreceptor according to an example may include an insulation resin capable of forming a film, such as polyvinyl butyral, polyacrylate (a condensed polymer of bisphenol A and phthalic acid, and so on), polycarbonate, polysulfone, a polyester resin, a phenoxy resin, polyvinyl acetate, an acrylic resin, a polyacrylamide resin, polyamide, polyvinyl pyridine, a cellulose- based resin, a urethane resin, an epoxy resin, a silicone resin, polystyrene, polyketone, polyvinyl chloride, a vinyl chloride-vinyliacetate copolymer, polyvinyl acetal, polyacrylonitrile, a phenolic resin, a melamine resin, casein, polyvinyl alcohol, and polyvinyl pyrrolidone; and an organic photoconductive polymer, such as poly N-vinyl carbazole, polyvinyl anthracene, polyvinyl pyrene, and so on. For example, a polycarbonate resin may be used as the binder resin for a charge transport layer. For example, among the polycarbonate resin, polycarbonate-A derived from bisphenol A or polycarbonate-C derived from methylbisphenol-A, and polycarbonate-Z derived from cyclohexylidene bisphenol may be used. Polycarbonate-Z may have a high wear resistance. These binder resins may be used alone or in combination of two or more.

[0050] A solvent used in preparation of a coating composition for forming a charge transport layer may vary according to a type of the used binder resin, and may preferably be selected in such a way that it does not affect the charge generation layer formed underneath. Examples of the solvent may be, for example, hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, xylene, ligroin, monochlorobenzene, and dichlorobenzene; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, and isopropanol; esters such as ethyl acetate and methyl cellosolve; halogenated aliphatic hydrocarbons such as carbon tetrachloride, chloroform, dichloromethane, dichloroethane, and trichloroethylene; ethers such as tetrahydrofuran (THF), dioxane, dioxolan, ethylene glycol, and monomethyl ether; amides such as N,N-dimethyl formamide, N,N-dimethyl acetamide; and sulfoxides such as dimethyl sulfoxide. The foregoing solvents may be used alone or in combination of one or two.

[0051] According to an example, a protective layer may be formed on the photosensitive layer 321 or the charge transport layer 327 to protect the photosensitive layer 321 or the charge transport layer 327.

[0052] According to an example, a variety of methods of processes may be used to form the layer 320 on the substrate 310, such as painting, coating, and/or spraying. FIG. 4 illustrates an example process of forming the layer 320 on the substrate 310, such as a substrate drum 310.

[0053] According to an example, referring to FIG. 4, the layer 320 can be formed on the substrate 310 using a dip-coating method. For example, the substrate 310 may be dipped into a coating solution and pulled out to form the coating layer 320. In doing so, the rate of pulling the substrate from the coating solution may influence or may be a factor for the thickness of the coating layer 320. For example, a precise controlling may be needed to maintain the rate to be constant enough to form the layer 320.

[0054] According to an example, a manufacturer has been producing a photoconductor drum 300 to have a consistent or even thickness of the coating layer 320 and/or by aligning the substrate drum 310 and the layer 320 to be centered and/or symmetrical according to the cross-sectional center of the substrate drum 310. For example, the manufacturer has been producing a photoconductor drum 300 to have the thickness of the layer 320 to be within an effective range indicating a substantial uniformity in the thickness and/or the alignment. For example, the alignment between the substrate drum 310 has been controlled to be within an effective range indicating a substantially centered and alignment, such as a parallel alignment along the axis of the substrate drum 310 in a cylindrical form. For example, FIG. 5 illustrates the cross-sectional thickness and alignment being within the corresponding effective ranges according to the manufacturer’s product quality standard. [0055] However, forming the consistent thickness of the layer 320 and/or the alignment to be aligned, centered, or symmetrical according to the cross-sectional center of the substrate drum 310 may increase production cost, add complexity to the process, and/or generate higher frequency of defects and/or higher amounts of wastes.

[0056] On the other hand, if the thickness consistency and/or the alignment between the substrate drum 310 and the layer 320 deviates from the corresponding effective ranges, a degradation in the quality of the image formed or being formed may occur. For example, when the thickness consistency and/or the alignment between the substrate drum 310 and the layer 320 deviates from the corresponding effective ranges, inconsistencies such as an uneven surface, uneven formation of an electrostatic pattern or image, and/or a disruption in transferring printing material to an electrostatic pattern or image or forming an image with the printing material may occur.

[0057] For example, FIG. 6 illustrates examples of uneven layer thickness types of the layer 320 along a circumference of the photoconductor drum 300.

[0058] For example, referring to FIG. 6, there may be a region of the layer 320 where the thickness of the layer 320 varies. For example, a surface unevenness may occur during the formation of the layer 320, for example, during a dip coating process, such as an indentation, a blob, or varied layer thicknesses. For example, the thickness along a circumference of the photoconductor drum 300 may vary. For example, referring to FIG. 6, a cross-sectional area of the photoconductor may indicate varying thicknesses.

[0059] According to an example, a varying thickness or uneven thickness of the layer 320 may occur depending on causes during the layer forming process, which may affect a part of an image forming process by the photoconductor drum 300.

[0060] According to an example, FIG. 7 illustrates an example cause for a varying or uneven thickness during a dip coating process. Referring to FIG. 7, the substrate 310 may be dipped into a coating solution 351 contained in a coating cylinder 350 or a coating container 350 in a cylinder shape, and the layer 320 during the dip coating process is formed with respect to the axis, center, or axial center of the substrate 310 being dipped. For example, the layer 320 may be formed symmetrically or substantially symmetrically with respect to the axis, center, or axial center of the substrate 310. When the layer 320 is being formed substantially asymmetrical to or deviating from the axis, center or axial center of the substrate 310, a varying thickness or uneven thickness of the layer 320 may occur.

[0061] According to an example, FIG. 8 illustrates example alignments of the substrate drum 310 during the dip coating process, which may result in a varying thickness or an uneven thickness of the layer 320 according an example. Referring to FIG. 8, the alignment of the substrate 310 may not be aligned with respect to the coating cylinder 350 or the coating solution container 350 in a cylinder shape and containing coating solution 351 , and a resulting thickness over a substrate drum 310 or along a circumference of the photoconductor drum 300 may vary along circumferential direction. For example, the center or the axis of the substrate 310 may be off-centered or not aligned parallel with respect to the center or the axis of the photoconductor drum 300. For example, the off-centered substrate 310 or the misaligned substrate 310 may result in a varying thickness or an uneven thickness of the layer 320. According to an example, the varying thickness or the uneven thickness may be relative to an orientation of the photoconductor drum 300, due to, for example, its rotation with respect to an axis of the photoconductor drum 300.

[0062] According to an example, an uneven thickness of the layer 320 or misalignment of the substrate 310 or the layer 320 with respect to an axis or center of the photoconductor drum 300 may cause a degradation in the image quality of an image forming apparatus or the operation of the image forming apparatus. For example, the uneven thickness of the layer 320 or the misaligned substrate 310 or the misaligned layer 320 may cause uneven pressing force or pressure onto a surface exerted by the photoconductor drum 300, may cause additional friction on a portion of the photoconductor drum causing an uneven wear and tear, may place additional or excessive load to a motor rotating the photoconductor drum, and/or may cause a degraded, inferior or inconsistent quality of an image being formed by the photoconductor drum 300.

[0063] For example, FIG. 9 illustrates an example of a degraded image quality due to an uneven thickness of the layer 320 or misalignment of the substrate 310. Referring to FIG. 9, due to the uneven thickness of the layer 320, the degraded image with inconsistent color density occurred as shown.

[0064] According to an example, an effect of uneven thickness of the layer 320 of the photoconductor 300 may present or persist for a period such as a lifespan of the photoconductor drum.

[0065] According to an example, a variety of different types of cleaning blades may be used to detach printing materials from the surface of the photoconductor drum 300. For example, FIG. 10 illustrates examples of a cleaning blade to clean the surface of the photoconductor drum 300. Referring to FIG. 10, different types of cleaning blades may include a screw type cleaning blade on the left in FIG. 10 and a spring type cleaning blade on the right in FIG. 10.

[0066] According to an example, over a time period of usage, the layer 320 may get thinner or worn due to repeated contacts or frictions when contacting another surface such as a cleaning blade. An effect of uneven thickness of the layer 320 may present or persist over the time period of usage and after the layer 320 gets thinner or worn after repeated uses.

[0067] For example, FIG. 11 illustrates a circumferential thickness profile along a circumference of the photoconductor drum 300 at an initial stage (e.g., before the photoconductor drum is initially used for an image forming operation) and after 200,000 (200K) times of image forming operations (e.g., forming an image on a print medium 200,000 times). Referring to FIG. 11 , after 200K times of image forming operations, while the thickness of the layer 320 along a circumference of the photoconductor drum 300 became thinner, the overall uneven thickness profile along the circumference of the photoconductor remained comparable or similar.

[0068] Due to an effect of uneven thickness of the layer 320 or a misaligned substrate 310 with respect to the center or the axis of a photoconductor drum, a photoconductor drum 300 has been produced to have even thickness or substantially even thickness of the layer 320 and/or to have symmetrically aligned or substantially symmetrically aligned substrate 310 with respect to the center or the axis of the photoconductor drum, to avoid the effect of the uneven thickness of the layer 320 or the misaligned substrate 310.

[0069] Producing a photoconductor drum having the even thickness or the substantially even thickness of the layer 320 and/or the aligned or substantially aligned substrate 310 demands a relatively higher level of a precise and/or complex control of different variables and/or parameters. As a result, producing a photoconductor drum having the even thickness or the substantially even thickness of the layer 320 and/or the aligned or substantially aligned substrate 310 may incur relatively higher production cost and result in a relatively higher error rate or defect rate and may result in relatively higher number of photoconductor drums with the thickness evenness or unevenness and/or the substrate alignment or misalignment. For example, a defect rate of photoconductor drums under a standard based on the even thickness or the substantially even thickness of the layer 320 and/or the aligned or substantially aligned substrate 310 may be about 40% to about 60% of a total produced batch of photoconductor drums 300. As a result, from about 40% to about 60% of the photoconductor drums may be regarded as defective photoconductor drums and may be discarded, which makes the production of a photoconductor drum costly and generates high volumes of wastes that may not be preferable for the environment.

[0070] According to an example, it has been unexpectedly found that producing a photoconductive drum having a certain pattern of varied thickness of the layer 320 and/or a certain pattern of varied alignment of the substrate with respect to the center or the axis of a photoconductor drum 300 may mitigate, overcome, or suppress the effect of uneven thickness of the layer 320 or a misaligned substrate 310 and may preserve a level of image quality being formed. According to an example, it has been unexpectedly found that producing a photoconductive drum which may not have as the even thickness or as the substantially even thickness of the layer 320 and/or as the aligned or as the substantially aligned substrate 310 as anticipated, but which may have a certain pattern of varied thickness of the layer 320 and/or a certain pattern of varied alignment of the substrate with respect to the center or the axis of a photoconductor drum 300, may mitigate, overcome, or suppress the effect of uneven thickness of the layer 320 or a misaligned substrate 310 and preserve a level of image quality being formed. According an example, it has been unexpectedly found that producing a photoconductive drum having a certain pattern of varied thickness of the layer 320 and/or a certain pattern of varied alignment of the substrate with respect to the center or the axis of a photoconductor drum 300 may not demand the level of precision or complexity in producing the photoconductor drum with the even coating thickness the substrate 310 alignment. Accordingly, it has been unexpectedly found that producing a photoconductor drum 300 that may have the certain pattern of varied thickness of the layer 320 and/or the certain pattern of varied alignment of the substrate 310 may increase the production efficiency and may reduce a defect rate. For example, the defect rate in the batch of photoconductor drums may be reduced from the about 40% to about 60 % of the batch to about 10% or less of the batch when photoconductor drums 300 are produced to have the certain pattern of varied thickness of the layer 320 and/or the certain pattern of varied alignment of the substrate 310.

[0071] According to an example, evenness or unevenness of thickness of the layer 320 over the substrate 310, or alignment or misalignment of the substrate 310 with respect to an axis or center of the photoconductor drum 300, may be determined or estimated in a variety of ways. For example, the alignment of or the misalignment, or the evenness or the unevenness, may be determined or estimated by measuring thicknesses along a length of the photoconductor drum 300, and/or in a longitudinal direction or an axial direction of the photoconductor drum. For example, the alignment of or the misalignment, or the evenness or unevenness, may be determined or estimated by measuring thicknesses along a circumference or in a circumferential direction of the photoconductor drum 300. For example, the alignment of or the misalignment, or the evenness or unevenness, may be determined or estimated by measuring thicknesses at an interval along a length of the photoconductor drum 300, and/or in a longitudinal direction or an axial direction of the photoconductor drum. For example, the alignment of or the misalignment, or the evenness or the unevenness may be determined or estimated by measuring thicknesses at an interval along a circumference or in a circumferential direction of the photoconductor drum 300. [0072] According to an example, an image forming apparatus 1000 may include a cartridge 2 decouplably coupled to the image forming apparatus 1000, the cartridge 2 including a photoconductor drum 300 having a substrate drum 310 and a layer 320 formed on a surface of the substrate drum 310, wherein a difference between a maximum thickness and a minimum thickness among thicknesses of the layer 320 over a length along a circumference of the photoconductor drum 300 starting from each respective position of a plurality of positions on the layer 320 located consecutively at an interval around the circumference may be less than about 2 micrometer (pm). For example, the difference between the maximum thickness and the minimum thickness among the thicknesses of the layer 320 over the length along the circumference of the photoconductor drum 300 starting from each respective position of the plurality of positions on the layer 320 located consecutively at the interval around the circumference may be equal to or less than about 1 .8 micrometer (pm).

[0073] According to an example, the difference between the maximum thickness and the minimum thickness may be more than about 0.3 pm.

[0074] According to an example, a thickness difference between a thickest thickness and a thinnest thickness around the circumference of the photoconductor drum 300 may be from about 0.3 pm to about 3.0 pm.

[0075] According to an example, a thickness difference between a thickest thickness and a thinnest thickness around the circumference of the photoconductor drum 300 may be more than about 3.0 pm, and the difference between the maximum thickness and the minimum thickness may be equal to or less than about 0.9 pm.

[0076] According to an example, the length along the circumference is proportional to a central angle of about 45° corresponding to the circumference. [0077] According to an example, the interval may be proportional to a central angle of about 15° corresponding to the circumference. [0078] According to an example, a longitudinal position of the circumference on the photoconductor drum 300 may be at least one position among: a center longitudinal position of the photoconductor drum 300; a right longitudinal position at a distance in a right direction from the center longitudinal position; or a left longitudinal position at the distance in a left direction from the center longitudinal position.

[0079] According to an example, the distance may be based on a maximum size of a print medium onto which the image forming apparatus 1000 is to form an image.

[0080] According to an example, a cartridge 2 coupleable to an image forming apparatus 1000 may comprise a photoconductor drum 300 having a substrate drum 310 and a layer 320 formed on a surface of the substrate drum 310, where a difference between a maximum thickness and a minimum thickness among thicknesses of the layer 320 over a length along a circumference of the photoconductor drum 300 starting from each respective position of a plurality of positions on the layer 320 located consecutively at an interval around the circumference may be from about 0.3 micrometer (pm) to about 2 pm. For example, the difference between the maximum thickness and the minimum thickness among the thicknesses of the layer 320 over the length along the circumference of the photoconductor drum 300 starting from each respective position of the plurality of positions on the layer 320 located consecutively at the interval around the circumference may be from about 0.3 micrometer (pm) to about 1.8 pm.

[0081] According to an example, a thickness difference between a thickest thickness and a thinnest thickness around the circumference of the photoconductor drum 300 may be from about 0.3 pm to about 3.0 pm. According to an example, the thickness difference between the thickest thickness and the thinnest thickness around the circumference of the photoconductor drum 300 may more than about 3.0 pm, and the difference between the maximum thickness and the minimum thickness may be equal to or less than about 0.9 pm. [0082] According to an example, the length along the circumference may be proportional to a central angle of about 45° corresponding to the circumference, and the interval may be proportional to a central angle of about 15° corresponding to the circumference.

[0083] According to an example, a longitudinal position of the circumference on the photoconductor drum 300 may be at least one position among: a center longitudinal position of the photoconductor drum 300; a right longitudinal position at a distance in a right direction from the center longitudinal position; or a left longitudinal position at the distance in a left direction from the center longitudinal position, where the distance is based on a maximum size of print medium 120 onto which the image forming apparatus 1000 is to form an image. [0084] According to an example, a method, such as a method of producing a cartridge 2 or a method of assembling a cartridge 2 may include disposing a photoconductor drum 300 in a cartridge 2 coupleable to an image forming apparatus 1000 to develop an image on a print medium 120, the photoconductor drum 300 including a substrate drum 310 and a layer 320 formed on a surface of the substrate drum 310, when the photoconductor drum 300 satisfies a first threshold where a difference between a maximum thickness and a minimum thickness among thicknesses of the layer 320 over a length along a circumference of the photoconductor drum 300 starting from each respective position of a plurality of positions on the layer 320 located consecutively at an interval around the circumference from about 0.3 micrometer (pm) to about 2 pm. For example, the difference between the maximum thickness and the minimum thickness among the thicknesses of the layer 320 over the length along the circumference of the photoconductor drum 300 starting from each respective position of the plurality of positions on the layer 320 located consecutively at the interval around the circumference may be from about 0.3 micrometer (pm) to about 1 .8 pm.

[0085] According to an example, the disposing the photoconductor drum 300 in the cartridge 2 further comprises disposing the photoconductor drum 300 in the cartridge 2 when the photoconductor drum satisfies a second threshold where a thickness difference between a thickest thickness and a thinnest thickness around the circumference of the photoconductor drum 300 is from about 0.3 pm to about 3.0 pm, or disposing the photoconductor drum 300 in the cartridge 2 when the photoconductor drum 300 satisfies a third threshold where the thickness difference between the thickest thickness and the thinnest thickness around the circumference of the photoconductor drum 300 is more than about 3.0 pm, and the difference between the maximum thickness and the minimum thickness is equal to or less than about 0.9 pm.

[0086] According to an example, the method may further include identifying the photoconductor drum 300 as being defective to be placed in the cartridge 2 when the photoconductor drum 300 satisfies a fourth threshold where the difference between the maximum thickness and the minimum thickness is more than about 2 pm, when the thickness difference between the thickest thickness and the thinnest thickness around the circumference of the photoconductor drum 300 is from about 0.3 pm to about 3.0 pm, or the difference between the maximum thickness and the minimum thickness is more than about 0.9 pm, when the thickness difference between a thickest thickness and a thinnest thickness around the circumference of the photoconductor drum 300 is more than about 3.0 pm.

[0087] According to an example, different methods of determining thickness variations of the layer 320 can be implemented in producing or identifying photoconductor drums that can be acceptable or sufficiently functional for an operation of the photoconductor drum while not demanding a relatively higher level of precisions or complex controls of forming the layer 320 to achieve overly symmetrical alignment of the substrate 310 or even thickness of the layer 320, thereby increasing production efficiency and/or decreasing the amount of wasted photoconductor drums identified as defective photoconductor drums, which is considered as green technology. According to an example, a variation range of the thickness of the layer 320 along a circumference of the photoconductor drum 300 may be determined by measuring or determining a thickness variation in circumferential sub-sections of the circumference. According to an example, a variation range of the thickness along a circumference of the photoconductor drum 300 may be determined by measuring or determining thickness variations along lengths of the circumferential segments along the circumference.

[0088] According to an example, a plurality of positions on a surface of the layer 320 along a circumference of the photoconductor drum 300 can divide the circumference into equal subsections having the equal central angle of the circumference ora cross-sectional area that is substantially circular in shape, and thickness variations based on a subsection or a position, such as a single subsection or subsections, can be measured, analyzed, estimated or determined to determine the acceptability or the operability of the photoconductor drum. For examplethe plurality of positions on the surface of the layer 320 and along a circumference of the photoconductor drum 300 may divide the circumference into subsections at an interval corresponding to the central angle. Then the thickness variation of the layer 320 over a circumferential length corresponding to a subsection, such as a single subsection or subsections, may be measured or determined.

[0089] For example, FIG 12 illustrates an example of determining a thickness variation of the layer 320 along a circumference of the photoconductor drum 300 according to an example. Referring to FIG. 12, the plurality of positions at 0° (360°), 15°, 30°, 45°, 60°, 75°, 90°, 90° to 105°, 105° to 120°, 135°, 150°, 165°, 180°, 195°, 210°, 225°, 240°, 255°, 270°, 285°, 300°, 315°, 330°, 345° on the surface of the layer 320 and along a circumference of the photoconductor drum 300 may divide the circumference into the following subsections at an interval corresponding to the central angle of 15°: 0° to 15°, 15° to 30°, 30° to 45°, 45° to 60°, 60° to 75°, 75° to 90°, 90° to 105°, 105° to 120°, 120° to 135°, 135° to 150°, 150° to 165°, 165° to 180°, 180° to 195°, 195° to 210°, 210° to 225°, 225° to 240°, 240° to 255°, 255° to 270°, 270° to 285°, 285° to 300°, 300° to 315°, 315° to 330°, 330° to 345° and 345° to 360° (0°). Then the thickness variation of the layer 320 over a circumferential length corresponding to a subsection, such as a single subsection or subsections, may be measured or determined. For example, the thickness variation of the layer 320 over 0° to 15°, 0° to 30°, 0° to 45°, 0° to 60°, or more can be measured or determined. For example, referring to FIG. 12, the thickness variation over the following circumferential segments or lengths may be measured: The thickness variation over the circumferential segment or length of 0°(360°) to 45°, the thickness variation over the circumferential segment or length of 15° to 60°, the thickness variation over the circumferential segment or length of 30° to 75°, the thickness variation over the circumferential segment or length of 45° to 90°, the thickness variation over the circumferential segment or length of 60° to 105°, the thickness variation over the circumferential segment or length of 75° to 120°, the thickness variation over the circumferential segment or length of 90° to 135°, the thickness variation over the circumferential segment or length of 105° to 150°, the thickness variation over the circumferential segment or length of 120° to 165°, the thickness variation over the circumferential segment or length of 135° to 180°, the thickness variation over the circumferential segment or length of 150° to 195°, the thickness variation over the circumferential segment or length of 165° to 210°, the thickness variation over the circumferential segment or length of 180° to 225°, the thickness variation over the circumferential segment or length of 195° to 240°, the thickness variation over the circumferential segment or length of 210° to 255°, the thickness variation over the circumferential segment or length of 225° to 270°, the thickness variation over the circumferential segment or length of 240° to 285°, the thickness variation over the circumferential segment or length of 255° to 300°, the thickness variation over the circumferential segment or length of 270° to 315°, the thickness variation over the circumferential segment or length of 285° to 330°, the thickness variation over the circumferential segment or length of 300° to 345°, the thickness variation over the circumferential segment or length of 315° to 360° (0°), the thickness variation over the circumferential segment or length of 330° to 15°, and the thickness variation over the circumferential segment or length of 345° to 30°.

[0090] For example, a difference (5) between the maximum thickness of the layer 320 in each respective segment or length listed above can be measured or determined as follows:

1. SA: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 0°(360°) to 45°, bB Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 15° to 60°, bC: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 30° to 75°, bD: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 45° to 90°, bE: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 60° to 105°, bF: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 75° to 120°, bG: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 90° to 135°, bH: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 105° to 150°, bl: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 120° to 165°, bJ: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 135° to 180°, bK: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 150° to 195°, bL: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 165° to 210°, bM: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 180° to 225°, bN: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 195° to 240°, SO: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 210° to 255°, bP: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 225° to 270°, bQ: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 240° to 285°, SR: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 255° to 300°, bS: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 270° to 315°, bT : Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 285° to 330°, bll: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 300° to 345°, 22. bV: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 315° to 360° (0°),

23. bW: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 330° to 15°, and

24. bX: Difference between the maximum thickness and minimum thickness of the layer 320 over the circumferential segment or length of 345° to 30°.

[0091] For example, referring to FIG. 12, layer thicknesses at the plurality of positions on the layer surface corresponding to 0°, 15 °, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, 165°, 180°, 195°, 210°, 225°, 240°, 255°, 270°, 285°, 300°, 315°, 330°, 345, and 360° (0°), and a difference between the maximum thickness and the minimum thickness among a plurality of consecutive position thicknesses, such as four consecutive position thickness, can be determined. For example, referring to FIG. 12, the thickness differences can be determined as follows:

1. bA: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 0°(360°) to 45°,

2. bB Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 15° to 60°,

3. bC: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 30° to 75°,

4. bD: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 45° to 90°,

5. bE: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 60° to 105°, bF: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 75° to 120°, bG: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 90° to 135°, bH: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 105° to 150°, bl: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 120° to 165°, bJ: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 135° to 180°, bK: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 150° to 195°, bL: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 165° to 210°, bM: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 180° to 225°, bN: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 195° to 240°, bO: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 210° to 255°, 16. bP: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 225° to 270°,

17. bQ: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 240° to 285°,

18. SR: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 255° to 300°,

19. bS: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 270° to 315°,

20. ST : Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 285° to 330°,

21 . bll: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 300° to 345°,

22. bV: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 315° to 360° (0°),

23. bW: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 330° to 15°, and

24. bX: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 345° to 30°.

[0092] According to an example, a thickness difference between the thickest thickness and the thinnest thickness among the thickness of the layer 320 along a circumference of the photoconductor drum 300 may be measured and determined to further determine the operability of the photoconductor drum 300. [0093] For example, FIG. 13 illustrates examples of the layer 320 having the maximum thickness and the minimum thickness around a circumference of the photoconductor drum 300. For example, referring to FIG. 13, in an example A1 , the thickest thickness of the layer 320 may be at about the 90° position and the thinnest thickness may be at about the 270° position. A thickness difference between the thicknesses at about the 90° position and at about the 270° position may be obtained in Example A1 of FIG. 13. Similarly, a thickness difference between the thickest thickness and the thinnest thickness at corresponding positions in examples A2 through A8 may be obtained, according to the example. [0094] According to an example, determining thickness variations along a circumference of the photoconductor drum 300, as discussed above, can be determined or measured over a circumference at a longitudinal position of the photoconductor drum 300.

[0095] For example, FIG. 14 illustrates example longitudinal positions, in which the circumferential thickness variation as discussed above can be determined at or measured at. For example, referring to FIG. 14, the longitudinal position P2 is a longitudinal center or middle position where the circumferential thickness variation along a circumference can be determined or measured at one of the longitudinal positions. For example, P1 and/or P3 are the right end position or the left end position of an effective image forming area, where the photoconductor drum 300 is operated to form an image. For example, P1 position and/or P3 position can be determined based on a size of a print medium, such as the width of the print medium 120 that is to pass by the photoconductor drum 300. For example, the size, such as the width, can be determined based on the maximum size of the print medium 120 the image forming apparatus 1000 can process to form an image onto.

[0096] According to an example, FIG. 15 illustrates different types of cleaning blades applying a force onto the photoconductor drum 300 to detach printing material from the surface of the photoconductor drum 300.

[0097] For example, referring to FIG. 15, an amount of normal force (N/F) for a screw type cleaning blade can be determined or calculated using the following equation below: N/F = E*d ³ *t/4L ³ where, N/F represents Normal force, E represents Young’s Modulus, d represents a degree of the NIP formation, t represents the thickness of the cleaning blade, and L represents Free Length before the NIP is being formed. 0 represents the blade setting angle and a represents the working angle.

[0098] For example, referring to FIG. 15, a free length (Fz) for a spring type cleaning blade can be determined or calculated using the following equation below:

Fx = Fs*Ls/Lb where, Fx represents the free length, Fs represents the spring force, Ls represents the distance between the lever and the spring, and Lb represents the distance between lever and the tip of the cleaning blade.

[0099] According to an example, referring to FIG. 16, the image forming apparatus 1000 may be controlled to form an image on an image forming apparatus. According to an example, the image forming apparatus 1000 may include a controller 3000 to control to output information. For example, a message may be presented on a screen of the user interface 1010 regarding the status of an image forming operation and/or the status of the cartrige 2 including the photoconductor drum 300. Further the output may be in any form of feedback presented through the user interface 1010, or a sound generated by the user interface 1010 or the output device 1020 including a speaker, which may also provide a user information regarding the coupling status or the cartridge coupling status of the separation of the cartridge 2 from the cartridge receiving part 20. The user interface 1010 and output device 1020 may be combined as a single device where the user interface 1010 includes the output device 1020 or vice versa.

[00100] Hereinafter, as an example, experimental procedures and experimental results are described.

[00101] For the experiments photoconductor drums 300 having an aluminum drum as the substrate drum 310 and the layer 320 including the undercoat layer 323, the charge generation layer 325, and the charge transport layer 327 were prepared. [00102] For the substrate drum 310, an aluminum drum (a cylindrical drum having a diameter of 30 mm and a length of 360 mm) was used as a conductive support 310 or as the substrate drum 310.

[00103] For the undercoat layer 323, with respect to the weight of the slurry for the undercoat layer 323 formation, 5 parts by weight of nylon resin (trade name; CM8000, manufactured by Toray Industries, Inc.), which dissolves in alcohol, was dissolved in 90 parts by weight of methanol, and then, mixed with 5 parts by weight of titanium oxide (TiCk) treated with aminosilane. The mixture was subjected to sand-milling for 2 hours and then, dispersed with ultrasonic waves. The obtained solution was dip-coated on the aluminum drum and then dried at a temperature of 80° C for 20 minutes to prepare the undercoat layer 323 having a thickness of about 3.0 pm.

[00104] For the charge generation layer 325, with respect to the weight of the slurry for the charge generation layer 325 formation, 20 parts by weight of a charge-generating material (y-TiOPc, titanyloxy phthalocyanine), 13 parts by weight of polyvinyl butyral resin (trade name; S-LEC BX-1 , manufactured by Sekisui Chemical Co., Ltd.) that was used as a binder resin for a charge generation layer 325, and 635 parts by weight of solvent (tetrahydrofurane) were mixed by sand-milling for 2 hours and then dispersed with ultrasonic waves to prepare a slurry for forming a charge generation layer. The slurry for forming a charge generation layer was dip-coated on the drum with an undercoat layer 323 coated thereon, and then dried at a temperature of 120°C for 20 minutes to form a charge generation layer 325 having a thickness of about 0.3 pm.

[00105] For the charge transport layer 327, with respect to the weight of the slurry for the charge transport layer 327 formation, 30 parts by weight of charge transport material (Trade name : CT-204S, manufactured by IT-Chem Co., Ltd.) and 40 parts by weight of the first binder resin (trade name; H-500, manufactured by Idemitsu Kosan) and 10 parts by weight of the second binder resin (trade name; EH-503, manufactured by Idemitsu Kosan) were dissolved in 360 parts by weight of a THF/toluene co-solvent (a weight ratio of 4:1) to prepare a coating composition for forming a charge transport layer. [00106] CT-204S by IT-Chem is N,N'-(((1 E,1'E)-1 ,4-phenylenebis(ethene-2,1- diyl))bis(4,1-phenylene))bis(2,4-dimethyl-N- (p-tolyl)aniline) and may have the following molecular structure:

[00107] The first binder resin (trade name; H-500, manufactured by Idemitsu Kosan) may have the following molecular structure:

[00108] The second binder resin (trade name; EH-503, manufactured by

Idemitsu Kosan) may have the following molecular structure:

[00109] The conductive support including the charge generation layer obtained according to the above-discussed layer formation process was dip-coated in the coating composition for forming a charge transport layer to coat the coating composition on the conductive support, and then, dried at a temperature of 120°C for 30 minutes to form a charge transport layer.

[00110] When the substrate drum 310 was coated, the distance between the center of the coating cylinder 350 and the center of the substrate drum 310 was set at 1 mm, 2mm, and 3mm respectively. [00111] Thicknesses of the layer 320 (including the undercoat layer 323, the charge generation layer 325 and the charge transport layer 327) was measured. [00112] Thicknesses of the layer 320 manufactured by the above process was measured using Fisher's FMP40. The same pressure was applied using a motor-driven jig to reduce the measurement error that occurs when measured by human.

[00113] The average axial thickness was calculated based on the measurements taken at respective positions at every 5 mm interval in the longitudinal or axial direction corresponding to the width of the paper as the print medium. The thickensses along the circumferential direction was measured at respective positions every 15 degree along circumferences at the three points P1 , P2, P3 corresponding to the print medium width as discussed above as an example referring to FIG. 14.

[00114] The thickness difference between the thickest thickness and the thinnest thickness were measured along the corresponding circumference at 180° point and assigned one of the following Align Level 1 , 2, or 3. In other words, the thickness difference is expressed in level by measuring the thickness of the position at 180 degrees for the position where the maximum thickness measured in P1 , P2, and P3.

Align Level 1 = about 0.3 pm ~ about 1 ,2pm;

Align Level 2 = about 1 ,3pm ~ about 2.2pm;

Align Level 3 = about 2.3pm ~ about 3.0pm; and Align Level 4 = over about 3.0pm.

[00115] At P1 , P2, P3, the following differences SA through bX were measured and the maximum value among SA through bX at P1 , P2, and P3 was obtained:

1. bA: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 0°(360°) to 45°, bB: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 15° to 60°, bC: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 30° to 75°, bD: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 45° to 90°, bE: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 60° to 105°, bF: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 75° to 120°, bG: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 90° to 135°, bH: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 105° to 150°, bl: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 120° to 165°, bJ: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 135° to 180°, bK: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 150° to 195°, bL: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 165° to 210°, bM: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 180° to 225°, bN: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 195° to 240°, SO: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 210° to 255°, bP: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 225° to 270°, bQ: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 240° to 285°, SR: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 255° to 300°, bS: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 270° to 315°, bT : Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 285° to 330°, bll: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 300° to 345°, 22. bV: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 315° to 360° (0°),

23. bW: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 330° to 15°, and

24. bX: Difference between the maximum thickness and minimum thickness of the layer 320 among the four position thicknesses as shown in FIG. 12 at 345° to 30°.

[00116] Based on the methods above, Examples 1 through 62 and Comparative Examples 1 through 57 were obtained.

[00117] Measurement results of Examples 1 through 62 and Comparative Examples 1 through 57 in accordance with the above were as follows:

[00118] Based on the produced examples and comparative examples (Examples 1 through 62 and Comparative Examples 1 through 57), the following tests were performed.

[00119] [Test 1] [00120] Referring to FIG. 15, The HP COLOR LASERJET MANAGED MFP E87660 equipped with each of the examples and comparative examples as a drum-unit assembled with a screw-type cleaning blade was used to print 200,000 sheet of 1 % coverage images. Then 40% grey-tone images were printed to determine whether there are any image defects. The screw type cleaning blade was assembled with the same left (L) and right(R) force.

[00121] [Test 2]

[00122] Except for a drum unit being assembled with a spring-type cleaning blade, assembled with the same left (L) and right (R) forces, the test was carried out as shown in Test 1 .

[00123] [Test 3]

[00124] Except for a drum unit with a screw-type cleaning blade assembled with the left (L) =20gf/cm and right(R) =30gf/cm forces, the test was carried out as shown in Test 1.

[00125] [test 4]

[00126] Except for a drum unit with a spring-type cleaning blade assembled with the left (L) =20gf/cm and right(R) =30gf/cm forces, the test was carried out as shown in Test 1.

[00127] [Evaluation of the image quality for assigning Ranks A, B, C, or D] [00128] A printed gray tone image was used to determine the defect level based on the following criteria.

[00129] An image density was measured by spectrophotometer manufactured by X-RITE MODEL EXACT STANDARD. Based on the measurement results, one of the following image quality ranks to each test example or comparative example:

[00130] Rank A : No defect of the photoconductor cycle detected by the spectrophotometer.

[00131] Rank B: Can slightly observe defect of the photoconductor cycle by human eye, but no difference in image density when measured by the spectrophotometer. [00132] Rank C: Can observe defect of the photoconductor cycle by human eye and 0.01-0.1 difference of image density when measured by the spectrophotometer.

[00133] Rank D: Can observe defect of the photoconductor cycle by human eye and 0.1 -0.3 difference of image density when measured by the spectrophotometer.

[00134] Rank E: Can observe defect of the photoconductor cycle by human eye and more than 0.3 difference of image density when measured by the spectrophotometer.

[00135] Test results of Examples 1 through 62 and Comparative Examples 1 through 57 in accordance with the above were as follows:

[00136] As shown above, In Examples 1 through 62, the axial average thickness was about 28 pm, about 33 pm, about 36 pm, respectively. When the alignment level was 1 through 3, and when the maximum value among SA through bX at P1 , P2, and P3 positions was equal to or less than about 1 .8 pm, the Examples did not exhibit image defects under spring type test 1 conditions and screw type test 2 cleaning conditions, tests 3 conditions, and test 4 conditions. When the alignment level was 4, and when the maximum value among SA through bX at P1 , P2, and P3 positions was equal to or less than 0.9 pm, the Example images did not exhibit image defects under spring type test 1 conditions and screw type test 2 cleaning conditions, tests 3 conditions, and test 4 conditions.

[00137] In Examples 63 through 72, even when the alignment level was 4, when the maximum value among bA through bX at P1 , P2, and P3 positions was equal to or less than 1 .8 pm, the image quality rank was mostly Rank C or better.

[00138] In contrast, In Comparative Examples 1 to 48, with axial average thicknesses of about 28 pm, about 33 pm, about 36 pm, respectively, when Alignment Levels were Level 1 , 2 or, 3, and when the maximum value among SA through bX at P1 , P2, and P3 positions was about 2.0 pm or more, and when Alignment Level was 4 and the maximum value among SA through bX at P1 , P2, and P3 positions was about 1 pm or more level, counter example images exhibited image defects. In particular, under the test 3 and 4 conditions with different left and right cleaning forces have more severe image defects. [00139] While various examples have been described with reference to the drawings, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.