JP2015055758A - Charging apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging apparatus configured to prevent an abnormal image from being formed by setting charging characteristics according to an environmental change even if states on a surface and on the inside are changed differently with respect to the environmental change.SOLUTION: A charging apparatus 40 includes a charging member 41 to be used for uniformly charging a surface of a latent image carrier 10, and is configured to charge the surface of the latent image carrier 10 with a predetermined polarity and a predetermined image forming potential by applying a voltage to the charging member 41 during image formation. The charging apparatus includes detection means 403 for detecting a change of state in the charging member 41 with respect to a use environment of the charging member 41, and controls the voltage to be applied to the charging member 41 according to a detection result of the detection means 403, to charge the surface with a predetermined image forming potential.

Description

  The present invention relates to a charging device and an image forming apparatus, and more particularly to charging characteristic control with respect to environmental fluctuations.

In addition to a configuration using an image forming unit for a single color image, an image forming apparatus using an electrophotographic system can receive a multicolor image such as a full color image by using an image forming unit capable of forming a multi-color image. There are configurations to form.
The image forming unit is provided with a charging device for uniformly charging the latent image carrier. However, the charging member used in the charging device is configured so as to be in contact with the surface of the latent image carrier or in close proximity. A configuration that maintains a contact state is known.

In the contact charging method in which charging is performed while bringing a charging member into contact with the surface of the latent image carrier, a configuration is known in which a charging roller in which an elastic layer made of conductive rubber is provided on a core metal is used as the charging member.
At the time of charging by the charging member having the above configuration, the surface of the latent image carrier can be charged to a predetermined potential by applying a bias to the core of the charging roller as the charging member.

However, the conductive rubber elastic layer used for the charging roller is a member whose bias condition changes under the influence of a change in use environment.
In other words, the bias condition may change due to the influence of the temperature and humidity, particularly moisture, included in the usage environment of the material that can be used for the charging roller.
For example, when the amount of water contained in the conductive rubber elastic layer used in the charging roller changes, the resistance value and dielectric constant also change, and the set bias conditions cannot be maintained and charging irregularities and abnormal images are generated. There is a risk of inviting.

On the other hand, it takes a certain amount of time for the amount of water contained in the conductive rubber elastic layer used in the charging roller to change. For this reason, even when the bias condition is changed corresponding to the temperature and humidity change in the usage environment, the bias condition on the charging roller is different depending on the difference between the bias condition and the amount of water actually contained in the conductive rubber elastic layer. May not match. As a result, even when the applied voltage for charging, which is one of the charging characteristics, is controlled based on the temperature and humidity in the usage environment, a deviation occurs from the required charging potential on the photoreceptor, and the photosensitive The charged potential on the body surface cannot be set to a predetermined value.
If the charged potential on the surface of the photoconductor deviates from a predetermined value in this way, there is a concern about the occurrence of abnormal images due to background contamination, carrier adhesion, insufficient charging, or excessive charging.

Conventionally, regarding the control of charging conditions according to changes in the usage environment, a configuration has been proposed in which the temperature of the charging roller surface is detected, and the applied voltage is changed in accordance with the result of comparing the detection result with a preset voltage application condition. (For example, Patent Document 1).
On the other hand, a configuration in which the change in the amount of water contained in the conductive rubber layer described above is monitored by the optical detection means separately from the temperature of the charging roller, and the applied voltage is changed according to the optical change from the charging roller by the optical detection means. Has also been proposed (for example, Patent Document 2).

In each of the configurations disclosed in each patent document, since it is assumed that the surface state of the charging roller is monitored, a change in the amount of water inside the charging roller that does not readily respond to environmental changes is not monitored. .
For this reason, it is not possible to determine a change in charging characteristics due to a change in the amount of water inside the conductive rubber elastic layer used in the charging roller, so that charging characteristics are not controlled when a sudden environmental change is reported. become.

For example, when air conditioning is resumed at the end of the week from a state where the air conditioning is left off, the ambient temperature and humidity change in about several tens of minutes, while the temperature inside the charging roller changes after several hours and May not be stable for more than a day. The same phenomenon occurs when the image forming apparatus is moved to a place where the usage environment is greatly different.
Even if a charging roller that does not respond quickly to changes in the usage environment performs control of charging characteristics for changes on the surface that directly contacts the usage environment, changes in the charging roller are charged by controlling the charging characteristics. The characteristics may not be met.
In other words, even when the applied voltage corresponding to the environmental change is set, if the temperature and water content inside the charging roller are different from the surface, the resistivity and dielectric constant inside the charging roller may be different from the surface. In some cases, the charged potential on the surface cannot be obtained.

  The object of the present invention is to provide a charging device having a configuration capable of preventing the occurrence of abnormal images by setting charging characteristics in accordance with the environmental change even when the state change is different between the surface and the interior with respect to the environmental change. An apparatus and an image forming apparatus are provided.

  In order to achieve this object, the present invention includes a charging member used for uniformly charging the surface of the latent image carrier, and the surface of the latent image carrier is applied by applying a voltage to the charging member during image formation. A charging device having a configuration for charging to a predetermined polarity and a predetermined image forming potential, comprising: a detecting unit that detects a change in the state of the charging member with respect to a change in the usage environment of the charging member; In the charging device, the image forming potential is charged to a predetermined potential by controlling a voltage applied to the charging member in accordance with a detection result.

  According to the present invention, since a change in state inside the charging member can be detected, it is one of charging characteristics for the charging member according to a result of detecting a change in state in the charging member that does not respond immediately to environmental changes. The voltage to be applied can be determined. As a result, even if the environment does not immediately respond to changes in the environment, an applied voltage corresponding to the actual state change in the charging member is applied so that the charging potential for image formation is set to a predetermined potential on the latent image carrier side. be able to. As a result, it is possible to prevent the occurrence of uneven charging and abnormal images on the surface of the latent image carrier.

1 is a schematic diagram for explaining a configuration of an image forming apparatus using a charging device according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a configuration of a process cartridge used in an image forming unit of the image forming apparatus shown in FIG. 1. FIG. 3 is a diagram for explaining a layer structure of a photoconductor equipped in the process cartridge shown in FIG. 2. FIG. 3 is a diagram illustrating an example of a configuration of a charging roller used in the process cartridge illustrated in FIG. 2. FIG. 5 is a diagram illustrating a modification example of a main part of the charging roller illustrated in FIG. 4. FIG. 3 is a view for explaining a characteristic part of a charging device used in the process cartridge shown in FIG. 2. FIG. 6 is a diagram for explaining the relationship between the voltage applied to the charging roller and the charging potential of the photosensitive member by the difference in temperature and humidity. It is a block diagram for demonstrating the structure of the control part used for the characteristic part shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to illustrated embodiments.
FIG. 1 is a diagram illustrating a configuration of a printer 100 that is one of image forming apparatuses using a charging device according to an embodiment of the present invention.
The printer 100 shown in the figure includes a configuration capable of forming a full-color image by including a plurality of color image forming units. That is, the printer 100 includes an image forming unit 120 including a plurality of image forming units, an intermediate transfer device 160, and a paper feeding unit 130 as main parts.
In the image forming unit 120, process cartridges 121 constituting a plurality of image forming units are arranged along the extending direction of an intermediate transfer belt 162 used in an intermediate transfer device 160 described later. Note that the subscripts Y, C, M, and K attached to the numerals shown in the figure mean yellow, cyan, magenta, and black, and the process cartridge 121 of each image forming unit has a different color image. It shows that it can be formed.
Details of the process cartridge 121 will be described later with reference to FIG.

The intermediate transfer device 160 is provided with an intermediate transfer belt 162 that is wound around a plurality of support rollers and is movable in the direction of the arrow shown in the drawing.
A primary transfer roller 161 that sequentially transfers an image formed on the photoreceptor 10 provided in each image forming unit to the intermediate transfer belt 162 at a position facing each image forming unit in the extended portion of the intermediate transfer belt 162. Has been placed.
A secondary transfer roller 165 is disposed on one side of the intermediate transfer belt 162 in the extending direction to collectively transfer the superimposed image transferred to the intermediate transfer belt 162 onto a transfer sheet used as a recording medium.
The intermediate transfer belt 162 can move in the direction indicated by the arrow using one of the support rollers as a drive roller, and moves in synchronization with the movement of the photoconductor 10 provided in each image forming unit.
The primary transfer roller 161 is disposed to face the photoreceptor 10 provided in each image forming unit with the intermediate transfer belt 162 interposed therebetween, and a toner image formed on the photoreceptor 10 is placed on the intermediate transfer belt 162. Transcript. The primary transfer roller 161 is configured to contact the intermediate transfer belt 162 with a weak pressure against the photoreceptor 10.

The intermediate transfer belt 162 is in contact with or separated from the photoreceptors 10 (Y, C, M) other than the image forming unit that forms a black (K) color image among the image forming units by an unshown contact / separation mechanism. can do. Accordingly, when forming a single color image of only black (K), it is possible to move away from the photoconductor 10 of the image forming unit that forms an image of another color.
Regarding the contact / separation of the intermediate transfer belt 162, a mechanism for contacting / separating the primary transfer roller 161 or a mechanism for swinging the other support roller side with a support roller positioned on the black (K) image forming unit side as a swing fulcrum. Etc. are used.

  The intermediate transfer device 160 has a unit structure or the like, and is configured to be detachable from the main body of the printer 100. Specifically, the front cover (not shown) on the front side of the paper in FIG. 1 covering the image forming unit 120 of the printer 100 is opened to take out to the outside. Is executed.

In FIG. 1, reference numeral 167 denotes a belt cleaning device that removes untransferred toner remaining on the intermediate transfer belt 162 after the batch transfer by the secondary transfer roller 165 is completed. The belt cleaning device 167 is configured to be attachable to and detachable from the apparatus main body together with the intermediate transfer belt 162. Further, the untransferred toner collected by the belt cleaning device 167 can be returned to a developing device 50 in a process cartridge described later, or can be transported toward a waste toner tank (not shown).
In FIG. 1, reference numerals 159 (Y, C, M, and K) indicate toner cartridges that store replenishment toner for the developing device 60. Toner is supplied from the toner cartridge 159 when the toner density in the developing device 60 decreases.

  In FIG. 1, reference numeral 140 denotes a writing apparatus that irradiates the photosensitive member 10 with writing light for each image forming unit. The writing device 140 forms an electrostatic latent image on the photosensitive member 10 by irradiating the photosensitive member 10 with writing light corresponding to image information transmitted from a control unit (not shown). In the present embodiment, the electrostatic latent image portion is formed by reducing the potential of the photosensitive member by about −100 V to −100 V by irradiation of the writing light by the writing device 140.

In FIG. 1, a paper feeding unit 130 is disposed below the writing device 140.
The paper feed unit 130 includes a plurality of paper feed cassettes 131, and transfer paper is fed from each paper feed cassette 131 toward the conveyance path by a feed roller 132. The transfer sheet fed to the transport path is transported toward the position of the secondary transfer roller 165 after the registration timing is set by the registration rollers 133 arranged in the transport path, and is carried on the intermediate transfer belt 162. The superimposed images are transferred at once.
The transfer paper after the batch transfer is discharged toward the paper discharge tray via the paper discharge roller 90.

FIG. 2 is a diagram showing a configuration of the process cartridge 121 used for each image forming unit.
Since the configuration of the process cartridge 121 is the same in each image forming unit, in the following description, the symbols Y, C, M, and K that indicate the type of color are omitted.
In the figure, a photosensitive member 10 as a latent image carrier is disposed in a process cartridge 121, and a charging device 40 that executes image forming processing along the moving direction of the photosensitive member 10 around the photosensitive member 10. A developing device 50 and a cleaning device 30 are arranged. The cleaning device 30 is used for cleaning the photoreceptor 10 after the transfer of the visible image.
The charging device 40 is a device used to uniformly charge the surface of the latent image carrier, that is, the surface of the photosensitive member, and a charging roller 41 is used as a main part.

In the case of this embodiment, the photosensitive drum 10 uses a rotatable drum, has at least a photosensitive layer on a conductive support, and inorganic fine particles are dispersed on the surface thereof.
Hereinafter, each layer structure of the photoconductor 10 (hereinafter, the photoconductor may be expressed as an image carrier for convenience) will be described.

  FIG. 3A shows an example in which a photosensitive layer 92 containing inorganic fine particles is provided in the vicinity of the surface on a conductive support 91. FIG. 3B shows an example in which a surface layer 93 containing a photosensitive layer 92 and inorganic fine particles is provided on a conductive support 91. FIG. 3C shows an example in which a charge generation layer 921, a photosensitive layer 92 in which a charge transport layer 922 is stacked, and a surface layer 93 containing inorganic fine particles are provided on a conductive support 91. FIG. 3D shows an example in which an undercoat layer 94 is provided on a conductive support 91, a photosensitive layer 92 in which a charge generation layer 921, a charge transport layer 922 are stacked, and a surface layer 93 containing inorganic fine particles are provided. Show.

The photoreceptor 10 shown in FIG. 3 only needs to have a structure having at least the photosensitive layer 92 and the surface layer 93 on the conductive support 91, and other layers and the like may be arbitrarily combined.
As the conductive support 91, a material having a volume resistance of 1010 Ω · cm or less, for example, the following material is used.
A metal or metal oxide such as aluminum, nickel, chromium, nichrome, copper, gold, silver or platinum, or metal oxide such as tin oxide or indium oxide coated with film or cylindrical plastic or paper by vapor deposition or sputtering, Alternatively, a plate made of aluminum, an aluminum alloy, nickel, stainless steel, or the like, and a tube subjected to surface treatment such as cutting, superfinishing, polishing, or the like after being formed into a raw pipe by a method such as extrusion or drawing can be used.
Further, an endless nickel belt or an endless stainless belt can be used as the conductive support 91 as a latent image carrier instead of the photosensitive member 10.

In addition to this, as the configuration of the conductive support 91, it is also possible to use a conductive powder dispersed on an appropriate binder resin and coated on the surface. The conductive powder used in this case is carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, silver, or metal oxide powder such as conductive tin oxide, ITO, etc. Examples include the body.
The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin.

Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.
Furthermore, it is electrically conductive by a heat-shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer can also be used favorably as the conductive support 91 of the present invention.

Next, the photosensitive layer 92 will be described.
The photosensitive layer 92 may be a single layer or a stacked layer. For convenience of explanation, the photosensitive layer 92 is first described from the case where it is composed of the charge generation layer 921 and the charge transport layer 922 (configuration shown in FIG. 3C).
The charge generation layer 921 is a layer mainly composed of a charge generation material. A known charge generation material can be used for the charge generation layer 921, and representative examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, and quinone condensed polycycles. Examples thereof include compounds, squalic acid dyes, other phthalocyanine pigments, naphthalocyanine pigments, and azulenium salt dyes. These charge generation materials may be used alone or in combination of two or more.

In this embodiment, in particular, azo pigments and / or phthalocyanine pigments are effectively used.
Especially azo pigments and titanyl phthalocyanine (especially titanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.514α) of CuKα) Can be used effectively.
The charge generation layer 921 is dispersed in a suitable solvent together with a binder resin as necessary using a ball mill, attritor, sand mill, ultrasonic wave, etc., and this is applied onto the conductive support 91 and dried. It is formed by.
As the binder resin used for the charge generation layer 921 as necessary, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly-N -Vinylcarbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, etc. Can be mentioned. The amount of the binder resin is suitably 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generating material.

Examples of the solvent used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like. In particular, ketone solvents, ester solvents, and ether solvents are preferably used.
As a coating method for the coating solution, a dip coating method, spray coating, beat coating, nozzle coating, spinner coating, ring coating, or the like can be used.
The thickness of the charge generation layer 921 is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm.
The charge transport layer 922 can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, and applying and drying the solution on the charge generation layer 921.
Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.
Charge transport materials include hole transport materials and electron transport materials.

Examples of the charge transport material include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron-accepting substances such as nitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives.
Examples of the hole transport material include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc., bisstilbene derivatives, enamine derivatives, etc. Other known materials may be mentioned. These charge transport materials may be used alone or in combination of two or more.

As the binder resin, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, Polyvinylidene chloride, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol Examples thereof include thermoplastic or thermosetting resins such as resins and alkyd resins.
The amount of the charge transport material is appropriately 20 to 300 parts by weight, preferably 40 to 150 parts by weight with respect to 100 parts by weight of the binder resin.
The thickness of the charge transport layer 922 is preferably 25 μm or less from the viewpoint of resolution and responsiveness.
Regarding the lower limit, although it differs depending on the system to be used (particularly the charging potential), it is preferably 5 μm or more.
As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used.

In the case of the image carrier in this embodiment, a plasticizer or a leveling agent may be added to the charge transport layer 922.
As the plasticizer, those used as general plasticizers such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is suitably about 0 to 30% by weight based on the binder resin.
As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain are used, and the amount used is 0 to 0 with respect to the binder resin. 1% by weight is suitable.
In the case where the charge transport layer 922 is an outermost layer, the charge transport layer 922 contains inorganic fine particles. Inorganic fine particles include metal powders such as copper, tin, aluminum, indium, silicon oxide, silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, tin oxide doped with antimony, tin Metal oxides such as indium oxide, and inorganic materials such as potassium titanate. In particular, metal oxides are good, and silicon oxide, aluminum oxide, titanium oxide and the like can be used effectively.
The average primary particle size of the inorganic fine particles is preferably 0.01 to 0.5 μm from the viewpoint of the light transmittance and wear resistance of the surface layer 93.
When the average primary particle size of the inorganic fine particles is 0.01 μm or less, it causes a decrease in wear resistance and a dispersibility. Or toner filming may occur.
The higher the amount of inorganic fine particles added, the better the wear resistance and the better. However, when the amount is too high, the residual potential increases and the write light transmittance of the protective layer decreases, which may cause side effects. Therefore, it is generally 30% by weight or less, preferably 20% by weight or less, based on the total solid content.
The lower limit is usually 3% by weight.

Further, these inorganic fine particles can be surface-treated with at least one kind of surface treatment agent, and it is preferable from the viewpoint of dispersibility of the inorganic fine particles.
A decrease in the dispersibility of inorganic fine particles not only increases the residual potential, but also decreases the transparency of the coating film, the occurrence of coating film defects, and a decrease in wear resistance. It can develop into a big problem to hinder.

Next, the case where the photosensitive layer 92 has a single layer structure will be described.
An image carrier in which the above-described charge generating material is dispersed in a binder resin can be used.
The single-layer photosensitive layer 92 can be formed by dissolving or dispersing a charge generation material, a charge transport material, and a binder resin in an appropriate solvent, and applying and drying the solution.
Further, when the single photosensitive layer 92 becomes the surface layer 93, the inorganic fine particles are contained. Further, the photosensitive layer 92 may be a function separation type to which the above-described charge transport material is added, and can be used satisfactorily.
Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.
As the binder resin, the binder resin previously mentioned in the charge transport layer 922 may be used as it is, or the binder resin mentioned in the charge generation layer may be mixed and used.
The amount of the charge generating material with respect to 100 parts by weight of the binder resin is preferably 5 to 40 parts by weight, and the amount of the charge transporting material is preferably 0 to 190 parts by weight, and more preferably 50 to 150 parts by weight.
The single-layer photosensitive layer 92 is formed by immersing a coating solution in which a charge generating material and a binder resin are dispersed together with a charge transporting material, if necessary, using a solvent such as tetrahydrofuran, dioxane, dichloroethane, and cyclohexane with a disperser or the like. It can be formed by spray coating or bead coating. The film thickness of the single photosensitive layer 92 is suitably about 5 to 25 μm.

In the image carrier in this embodiment, an undercoat layer 94 can be provided between the conductive support 91 and the photosensitive layer 92.
The undercoat layer 94 generally contains a resin as a main component. However, considering that the photosensitive layer 92 is applied with a solvent thereon, these resins are resins having high solvent resistance with respect to general organic solvents. It is desirable.
Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin.
Further, in order to prevent moire and reduce residual potential, the undercoat layer 94 may be added with fine powder pigments of metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like. Good.
The undercoat layer 94 can be formed using an appropriate solvent and coating method like the photosensitive layer 92 described above.
Further, in this embodiment, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer 94.
In addition, the undercoat layer 94, and those in which a Al2O3 with anodic oxidation, polyparaxylylene (parylene) or the like of the organic substances and _{SiO 2, SnO 2, TiO 2} , ITO, an inorganic material such as CeO ₂ vacuum Those provided by the thin film preparation method can also be used favorably. In addition, known ones can be used. The thickness of the undercoat layer 94 is suitably 0 to 5 μm.

In the image carrier in this embodiment, a surface layer 93 containing inorganic fine particles can be provided on the outermost surface of the photosensitive layer 92.
The surface layer 93 is composed of at least inorganic fine particles and a binder resin. As the binder resin, a thermoplastic resin such as polyarylate resin or polycarbonate resin, or a crosslinked resin such as urethane resin or phenol resin is used.
As the fine particles, organic fine particles and inorganic fine particles are used. Examples of the organic fine particles include fluorine-containing resin fine particles and carbon-based fine particles. Metal powder such as copper, tin, aluminum, indium, silicon oxide, silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, tin-doped indium oxide, etc. Inorganic materials such as metal oxide and potassium titanate can be mentioned. In particular, metal oxides are good, and silicon oxide, aluminum oxide, titanium oxide and the like can be used effectively.
The average primary particle size of the inorganic fine particles is preferably 0.01 to 0.5 μm from the viewpoint of the light transmittance and wear resistance of the surface layer 93.
When the average primary particle size of the inorganic fine particles is 0.01 μm or less, it causes a decrease in wear resistance and a dispersibility. Or toner filming may occur.
The higher the concentration of the inorganic fine particles in the surface layer 93, the higher the wear resistance and the better. .
Therefore, it is approximately 50% by weight or less, preferably 30% by weight or less, based on the total solid content.
The lower limit is usually 5% by weight.
Further, these inorganic fine particles can be surface-treated with at least one kind of surface treatment agent, and it is preferable from the viewpoint of dispersibility of the inorganic fine particles.
A decrease in the dispersibility of inorganic fine particles not only increases the residual potential, but also decreases the transparency of the coating film, the occurrence of coating film defects, and a decrease in wear resistance. It can develop into a big problem to hinder.

As the surface treatment agent, a conventionally used surface treatment agent can be used, but a surface treatment agent capable of maintaining the insulating properties of the inorganic fine particles is preferable.
For example, a titanate coupling agent, an aluminum coupling agent, a zircoaluminate coupling agent, a higher fatty acid, etc., or a mixing treatment of these with a silane coupling agent, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Silicone, aluminum stearate, or the like, or a mixture thereof is more preferable from the viewpoint of dispersibility of inorganic fine particles and image blur.
The treatment with the silane coupling agent is strongly influenced by image blur, but the influence may be suppressed by performing a mixing treatment of the surface treatment agent and the silane coupling agent.
The surface treatment amount varies depending on the average primary particle size of the inorganic fine particles used, but is preferably 3 to 30 wt%, more preferably 5 to 20 wt%.

If the surface treatment amount is less than this, the dispersion effect of the inorganic fine particles cannot be obtained, and if it is too much, the residual potential is significantly increased.
These inorganic fine particles (materials) are used alone or in combination of two or more. The thickness of the surface layer 93 is preferably in the range of 1.0 to 8.0 μm.
An image carrier that is used repeatedly over a long period of time is mechanically durable and hardly wears.
However, ozone, NOx gas, and the like are generated from the charging member or the like in the actual machine and adhere to the surface of the image carrier. If these deposits are present, image flow occurs.
In order to prevent this image flow, it is necessary to wear the photosensitive layer 92 at a certain speed or higher.
For that purpose, it is preferable that the surface layer 93 has a film thickness of at least 1.0 μm or more in consideration of long-term repeated use.

Further, when the thickness of the surface layer 93 is larger than 8.0 μm, it is considered that the residual potential is increased and the fine dot reproducibility is decreased.
These inorganic fine particles (materials) can be dispersed in a dispersion with a binder resin by using an appropriate disperser.
The average particle size of the inorganic fine particles in the dispersion is preferably 1 μm or less, and preferably 0.5 μm or less from the viewpoint of the transmittance of the surface layer 93.
As a method of providing the surface layer 93 on the photosensitive layer 92, a dip coating method, a ring coating method, a spray coating method, or the like is used.
Among these, a general method for forming the surface layer 93 is to form a coating film by ejecting paint from a nozzle having a minute opening and depositing fine droplets generated by atomization on the photosensitive layer 92. A spray coating method is used.
As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used.
The surface layer 93 may contain a charge transport material for reducing residual potential and improving responsiveness. As the charge transport material, the materials described in the description of the charge transport layer can be used.
When a low molecular charge transport material is used as the charge transport material, it may have a concentration gradient in the surface layer 93.
For the surface layer 93, a polymer charge transport material having a function as a charge transport material and a function of a binder resin is also preferably used.

The surface layer 93 composed of these polymer charge transport materials is excellent in wear resistance.
A known material can be used as the polymer charge transport material, but at least one polymer selected from polycarbonate, polyurethane, polyester, and polyether is preferable. In particular, a polycarbonate containing a triarylamine structure in the main chain and / or side chain is preferable.
It is preferable that the image carrier surface layer 93 has a Martens hardness of 190 N / mm 2 or more and an elastic work rate (We / Wt value) of 37.0% or more. The Martens hardness and the elastic power increased here are measured under the following conditions.
Evaluation device: Fisherscope H-100
Test method: Load unloading repetition (one time) test Indenter: Micro Vickers indenter Maximum load: 9.8 mN
Load (unloading) time: 30 seconds Holding time: 5 seconds

When the Martens hardness is less than 190 N / mm 2, there is a problem that the toner adheres to the surface of the photoreceptor. Also, when the elastic power (We / Wt value) is less than 37.0%, there is a problem that the wear speed of the photoconductor changes and wear unevenness occurs, for example, when the image area ratio changes in the photoconductor axis direction. Arise.
For this reason, hardness and elastic work rate are controlled by the addition amount of inorganic fine particles and the resin type. Resins such as polycarbonate and polyarylate are improved in hardness and elastic power by incorporating a rigid structure into the resin skeleton. Further, by adopting the polymer charge transport material, the hardness and elastic power are improved.
Fine irregularities are formed on the surface of the photoreceptor by the addition of inorganic fine particles. For this reason, the adhesion force to the photosensitive member is reduced, and filming of the toner base material and the external additive to the photosensitive member is less likely to occur. The surface roughness of the photoreceptor is preferably about Rz = 0.3 to 1.0 μm. The surface roughness is measured with Surfcom 1400D (manufactured by Tokyo Seimitsu).

Returning to FIG. 2, the developing device 50 can perform visible image processing on the electrostatic latent image on the photoconductor 10 by supplying toner to the surface of the photoconductor 10.
The developing device 50 is provided with a developing tank capable of containing a developer, and a developing roller 51 capable of carrying the developer is disposed inside the developing tank so as to face the photoreceptor.
In the developing tank, the supply screw 52 supplied while stirring and conveying the developer toward the developing roller 51 and the developer in the developing tank are stirred and conveyed, and the replenished toner is mixed and stirred in the developer. A screw 53 is arranged.
In the developing device 50, the developer supplied from the supply roller 52 to the developing roller 51 is supplied toward the photoconductor 10 after the layer thickness is regulated by a doctor blade (not shown). The developer causes toner to be attracted to the electrostatic latent image by the electrostatic attraction force from the electrostatic latent image and the developing bias applied to the developing roller 50 to make the electrostatic latent image visible.
In this embodiment, the developing bias is set to −550 V for the electrostatic latent image carried on the photoconductor 10, so that the potential difference with respect to the photoconductor is set to −550 to −100 V. Then, the negatively charged toner is electrostatically moved to perform visible image processing of the electrostatic latent image.

The cleaning device 30 that removes untransferred toner from the photoconductor 10 is provided with a charge eliminating device 60 that neutralizes the transferred photoconductor 10 and a cleaning blade 5 that contacts the surface of the photoconductor 10.
After the transfer, the photoreceptor 10 is charged with residual charges by the static eliminator 60 and then scraped off foreign matters such as untransferred toner by the cleaning blade 5. A urethane rubber material is used for the cleaning blade 5.

On the other hand, the toner used in the developing device 50 is obtained by the method described below. The term “parts” used in the following description indicates “parts by mass”.
<Product of [Toner 1]>
Synthesis of [Ester Wax 1] A fatty acid component and an alcohol component are put together with a catalyst (effective amount) in a reaction vessel and subjected to esterification reaction at 240 ° C. under a nitrogen stream to synthesize [Ester Wax 1].

Synthesis of [Crystalline Polyester Resin 1] In a 5-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple, 2,120 g of 1,10-decanoic acid, 1520 g of 1,8-octanediol, , 6-hexanediol 1200g, hydroquinone 4.9g. Then, after reacting at 180 ° C. for 10 hours, the temperature is raised to 200 ° C. and reacted for 3 hours, and further reacted at 8.3 kPa for 2 hours to obtain [Crystalline Polyester Resin 1].

Synthesis of [Amorphous Polyester Resin 1] In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 67 parts of bisphenol A ethylene oxide 2 mol adduct, 84 parts of bisphenol A propion oxide 3 mol adduct, terephthalate 274 parts of acid and 2 parts of dibutyltin oxide are added. And it is made to react at 230 degreeC under a normal pressure for 8 hours. Next, this reaction solution is reacted for 5 hours under a reduced pressure of 10 to 15 mmHg to synthesize [Amorphous Polyester Resin 1].
[Non-crystalline polyester resin 1] thus obtained had a number average molecular weight (Mn) of 2100, a mass average molecular weight (Mw) of 5600, and a glass transition temperature (Tg) of 55 ° C.

Preparation of [Masterbatch] (MB) 1000 parts of water, 540 parts of carbon black (Printex 35; manufactured by Degussa, DBP oil absorption = 42 mL / 100 g, PH = 9.5), and 1200 parts of the unmodified polyester resin were added to Henschel. Mix using a mixer (Mitsui Mining Co., Ltd.). This mixture is kneaded for 30 minutes at 150 ° C. with two rolls, rolled and cooled, and pulverized with a pulverizer (manufactured by Hosokawa Micron) to prepare a [masterbatch].

Preparation of [Crystalline Polyester Resin Dispersion] 100 g of [Crystalline Polyester Resin 1] and 400 g of ethyl acetate are placed in a 2 L container made of metal, dissolved by heating at 70 ° C., and then 20 ° C./min in an ice-water bath. Quench quickly at speed. After cooling, 100 g of [Crystalline Polyester Resin 1] is dissolved in the dispersion, 500 mL of glass beads (3 mmφ) are added thereto, and pulverized for 10 hours while maintaining the average liquid temperature at 24 ° C. with a batch type sand mill device (Kampehapio). I do. Then, [Crystalline polyester resin dispersion 1] having a volume average particle size of 0.3 μm is obtained.

Synthesis of [Polyester Prepolymer 1] The following materials were placed in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, reacted at 230 ° C. for 8 hours under normal pressure, and further under reduced pressure of 10 to 15 mmHg. Reaction is performed for 5 hours to obtain [Intermediate polyester 1]. Bisphenol A ethylene oxide 2-mole adduct 682 parts, bisphenol A propylene oxide 2-mole adduct 81 parts, terephthalic acid 283 parts, trimellitic anhydride 22 parts, and dibutyltin oxide 2 parts.
[Intermediate polyester 1] thus obtained had a number average molecular weight of 2100, a mass average molecular weight of 9500, Tg of 55 ° C., an acid value of 0.5 and a hydroxyl value of 51.

Next, 410 parts of [Intermediate Polyester 1], 89 parts of isophorone diisocyanate, and 500 parts of ethyl acetate are placed in a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, and reacted at 100 ° C. for 5 hours. [Polyester prepolymer 1] is obtained.
The amount of free isocyanate of [Polyester Prepolymer 1] thus obtained was 1.53% by mass.

Preparation of [Pigment / WAX Dispersion 1] (Oil Phase) In a container equipped with a stirring rod and a thermometer, 378 parts of [Amorphous Polyester Resin 1], 110 parts of [Ester Wax 1] and 947 parts of ethyl acetate were added. The temperature was raised to 80 ° C. and stirred and held at 80 ° C. for 5 hours, and then cooled to 30 ° C. over 1 hour. Next, 500 parts of [Masterbatch] and 500 parts of ethyl acetate were charged in a container and mixed for 1 hour to obtain [Material solution 1].
Next, 1324 parts of [Raw Material Solution 1] was transferred to a container, and 3 passes, carbon black and wax were dispersed under the following conditions using a bead mill (Ultra Visco Mill, manufactured by Imex Corporation). The conditions are a liquid feed speed of 1 kg / hr, a disk peripheral speed of 6 m / s, and 80% by volume of 0.5 mm zirconia beads.

Next, 1042.3 parts of a 65% ethyl acetate solution of [Amorphous Polyester Resin 1] was added, followed by one pass with a bead mill under the above conditions to obtain [Pigment / WAX Dispersion 1].
The thus obtained [Pigment / WAX Dispersion 1] had a solid content concentration (130 ° C., 30 minutes) of 50%.

Synthesis of [Fine Particle Dispersion 1] (Organic Fine Particle Emulsion) In a reaction vessel equipped with a stirrer and a thermometer, 683 parts of water, sodium salt of ethylene oxide methacrylate adduct sulfate (Eleminol RS-30 = Sanyo Chemical Industries, Ltd.) 11 parts), 138 parts of styrene, 138 parts of methacrylic acid, and 1 part of ammonium persulfate are charged.
And after stirring for 15 minutes at 400 rotation / min and obtaining a white emulsion, it heats up to 75 degreeC inside system temperature, and is made to react for 5 hours.

Further, 30 parts of 1% ammonium persulfate aqueous solution was added, and the mixture was aged at 75 ° C. for 5 hours, and an aqueous dispersion of vinyl resin (styrene salt copolymer of styrene-methacrylic acid-methacrylic acid ethylene oxide adduct sulfate) [ A fine particle dispersion 1] is obtained.
The [fine particle dispersion 1] thus obtained had a volume average particle size (measured with LA-920) of 0.14 μm.
Then, the -part of [fine particle dispersion 1] is dried to isolate the resin component.

Preparation of [Aqueous Phase 1] 990 parts of water, 83 parts of [fine particle dispersion 1], 37 parts of 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7 = manufactured by Sanyo Chemical Industries), 90 parts of ethyl acetate Are mixed and stirred to obtain a milky white liquid. This is designated as [Aqueous Phase 1].

Preparation of [dispersion slurry 1] (emulsification)
[Pigment / WAX Dispersion 1] 664 parts, [Prepolymer 1] 109.4 parts, [Crystalline Polyester Resin Dispersion 1] 73.9 parts, [Ketimine Compound 1] 4.6 parts are put in a container, and TK is added. Mix for 1 minute at 5000 rpm using a homomixer (manufactured by Tokushu Kika). Thereafter, 1200 parts of [Aqueous phase 1] is added to the container, and mixed with a TK homomixer (5 minutes at a rotational speed of 11000 rpm) to obtain [Emulsified slurry 1].
Next, [Emulsion slurry 1] is charged into a container equipped with a stirrer and a thermometer, and after removing the solvent at 30 ° C. for 8 hours, aging is performed at 45 ° C. for 4 hours to obtain [dispersed slurry 1].

[Toner base particle B] (cleaning and drying)
The following operations (1) to (4) are performed on the filter cake obtained by subjecting 100 parts of [Dispersion Slurry 1] to filtration under reduced pressure.

(1) Add 100 parts of ion-exchanged water to the filter cake, mix with a TK homomixer (rotation speed 12000 rpm for 10 minutes), and then filter.
(2) Next, 100 parts of a 10% aqueous solution of sodium arsenate is added and mixed with a TK homomixer (30 minutes at a rotational speed of 12000 rpm), and then filtered under reduced pressure.
(3) Next, 100 parts of 10% hydrochloric acid is added, mixed with a TK homomixer (rotation speed: 12000 rpm for 10 minutes), and then filtered.
(4) Next, 300 parts of ion-exchanged water is added and dried at 45 ° C. for 48 hours with a hot air dryer to obtain [Mother toner particles B].

Production of [Toner 1] (external treatment)
To 100 parts of the above “toner base particle B”, 1.5 parts of silica A (UFP-35, manufactured by Nippon Denki Kagaku Kogyo Co., Ltd.) is added, and 1 at a peripheral speed of 13 m / s by a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.). Mix for 1 minute, then mix for 10 minutes at a peripheral speed of 40 m / s. To this, 0.5 part of titanium oxide having a volume average particle size of 20 nm is added, mixed for 1 minute at a peripheral speed of 13 m / s by a Henschel mixer, and then mixed for 10 minutes at a peripheral speed of 40 m / s. To this, 2.0 parts of silica B (H1303, manufactured by Clariant Japan) is added, mixed for 1 minute at a peripheral speed of 13 m / s by a Henschel mixer, and then mixed for 10 minutes at a peripheral speed of 40 m / s. To this, 0.2 part of fatty acid metal salt particles (zinc stearate 1) is added, mixed for 1 minute at a peripheral speed of 13 m / s by a Henschel mixer, and then mixed for 10 minutes at a peripheral speed of 40 m / s.

The powder after mixing is passed through a mesh having an opening of 500 μm, coarse powder is removed, and [toner 1] is prepared by externally adding a fatty acid metal salt and inorganic fine particles.
The toner outflow start temperature (Tfb: measured with a flow tester), wax melting point (Tm1: measured with DSC), and crystalline polyester melting point (Tm2: measured with DSC) obtained as described above. It was measured. The measurement results of [Toner 1] were Tfb = 80.2 ° C., Tm1 = 67.9 ° C., and Tm2 = 64.3 ° C.

<Production of [Carrier]>
To 100 parts of toluene, 100 parts of silicone resin organostraight silicone, 5 parts of γ- (2-aminoethyl) aminopropyltrimethoxysilane and 10 parts of carbon black are added and dispersed with a homomixer for 20 minutes. A coating solution is prepared.
Next, using a fluidized bed type coating apparatus, the resin layer coating solution is applied to the surface of 1000 parts of spherical magnetite having a volume average particle size of 50 μm to produce [Carrier].
<Production of [Developer 1]>
Using a ball mill, 5 parts of [Toner 1] and 95 parts of [Carrier] are mixed to produce [Developer 1].

The characteristics of this embodiment will be described below for the image forming apparatus having the above configuration.
The present embodiment is characterized in that when the voltage applied to the charging roller is adjusted according to the change in the usage environment, the voltage is controlled based on the state change for the elastic layer used in the charging roller.
Thereby, it is possible to prevent the occurrence of uneven charging and abnormal images on the charging roller by setting the image forming potential according to the state change in the roller where a time lag exists with respect to the state change on the surface layer of the charging roller.

Hereinafter, configurations of the charging device 40 and the cleaning unit will be described.
As shown in FIG. 2, the charging device 40 mainly includes a charging roller 41 as a charging member and a pseudo charging roller 400 as a pseudo charging member that is disposed in the vicinity of the charging roller 41 and has the same configuration as the charging roller 41. As a part.
Although not shown, the charging roller 41 is provided with a cleaning roller that removes foreign matter adhering to the surface of the charging roller 41 by moving in contact with the surface of the charging roller 41.
As the cleaning roller, a brush roller having a brush using a sponge layer of polyurethane or melamine resin or a fiber such as conductive or insulating polyamide (nylon), acrylic acid resin, or polyester resin on a core metal is used. The cleaning roller can be removed by applying a mechanical force to the surface of the charging roller 41 by selecting a case where the cleaning roller is interlocked with the charging roller 41 or a case where the cleaning roller is rotationally driven.

The charging roller 41 is a member to which a constant DC voltage is applied as a charging bias, and as shown in FIG. 5, a conductive elastic layer having a conductive rubber layer is provided on a cored bar.
By applying a constant DC voltage as a charging bias to the charging roller 41, the load on the photoconductor can be reduced, the amount of wear of the photoconductor during discharge is reduced, and the life of the photoconductor can be extended. .

The conductive elastic layer has a surface roughness Rz made of irregularities adjusted to about 15 μm.
The surface roughness Rz using unevenness is obtained by a large number of dispersed particles, and the particle diameter is set to 10 μm or more, preferably about 15 μm.
When the surface roughness is 10 μm or less and the unevenness becomes small, it becomes easy to obtain an abnormal image in which horizontal streaks or the like occur, and since the unevenness becomes small, current flows easily along the surface of the charging roller, and current leakage occurs. There is a possibility that a horizontal streak is likely to occur due to the phenomenon. On the contrary, if the surface roughness Rz is too large, unevenness unevenness may be reflected in the halftone image as it is and appear as density unevenness. For this reason, as an upper limit of surface roughness, it is desirable to suppress to about 20 micrometers.

FIG. 4 is a view showing an example of the charging roller 41. The charging roller 41 shown in FIG. 4 includes a conductive elastic layer and a base layer and a surface layer corresponding to the surface layer. In the configuration shown in FIG. 4, a hydrin rubber layer, which is one of rubber elastic layers, is used as a base layer, and a surface layer made of nylon resin is provided on the hydrin rubber layer.
A large number of particles 41A ′ having a particle size of about 15 μ are dispersed in the surface layer. An uneven portion is formed on the surface by the particles 41A ′. The surface roughness Rz was measured with Surfcom 1400D (manufactured by Tokyo Seimitsu).
In the charging roller 41 having a surface layer on which uneven portions are formed using particles, the surface layer prevents the exudation component from the base layer, that is, the rubber component, from contaminating the photoreceptor to which the charging roller 41 contacts. In addition to preventing this, the contact area with the photoreceptor 10 is reduced.
By reducing the contact area with the photoconductor, the contact portion and the non-contact portion (gap portion) are appropriately distributed, and the discharge opportunity can be increased to stabilize the charging. In particular, when the linear velocity is high, the effect of charging stability is increased, and contamination of the photosensitive member 10 due to bleeding of the rubber component from the base layer or toner contamination from the photosensitive member 10 toward the charging roller 41 is caused. Can be deterred.

FIG. 5 shows an example in which the uneven portion shown in FIG. 4 is configured without using particles.
The charging roller 41 shown in the figure is randomly provided with uneven polishing portions 41A formed along the circumferential direction with polishing paper or the like on the surface of a single rubber layer. The polishing unit 41A is obtained by bringing the polishing paper into contact with the charging roller 41 while rotating.
In this case, the surface treatment liquid is dried and cured by immersing or coating the surface treatment liquid on the surface of a single hydrin rubber layer to form the surface treatment layer. Thus, the surface treatment layer prevents the rubber component from exuding from the rubber layer.

By the way, the surface layer of the charging roller 41 can prevent the rubber component from seeping out and prevent the photoreceptor 10 from being contaminated. However, there is little change in the state of moisture content or the like in response to changes in the use environment. State change tends to be delayed.
Accordingly, when the charging bias potential corresponding to the image forming potential is adjusted for the state change on the surface of the charging roller 41, the state change inside the charging roller 41 may not be supported.

Thus, in this embodiment, the voltage applied to the charging roller 41 is adjusted based on the state change inside the charging member, that is, inside the charging roller 41, instead of detecting the state change on the surface layer of the charging roller. As a result, the charging condition using the applied voltage on the charging roller 41 side can be changed so that the image forming potential on the photoconductor 10 becomes a predetermined potential.
As a configuration for this purpose, in this embodiment, as shown in FIG. 2, a pseudo charging roller 42 as a pseudo charging member having a configuration similar to that of the charging roller 41 is provided in the vicinity of the charging roller 41.
The configuration of the pseudo charging roller 42 is shown in FIG.
In FIG. 6, the pseudo charging roller 42 has a base layer 401 and a surface layer 402 laminated on the core metal 400 in the same manner as the charging roller 41, and is maintained in a non-rotating state unlike the charging roller 41. Yes.
In the hydrin rubber layer used for the base layer 401, a temperature sensor S1 as a temperature detection member, which is one of the state change detection members 403, is embedded.

On the other hand, a cavity 404 surrounded by an elastic layer is provided in the base layer 401 of the pseudo-charging roller 42, and the humidity in the cavity can be detected in the cavity 404 as another state change detection member. A humidity sensor S2 is disposed as a humidity detection member.
Since the pseudo charging roller 42 is a member that can determine the change that occurs inside the charging roller 41 when an environmental change occurs, the pseudo charging roller 42 does not necessarily require an axial length similar to that of the charging roller 41 or a cored bar. However, only the material of the base layer and the surface layer may be used.

The reason for detecting the state change in the charging roller 41 corresponds to the actual state change in the charging roller 41 due to the presence of a time lag in the state change in the surface layer and the state change in the inside as described above. The application voltage can be set.
FIG. 7 is a diagram showing the results of experiments in which the relationship between the voltage applied to the charging roller 41 and the charging potential on the photoconductor 10 is matched to the environmental change.
The result shown in the figure is a result when the charging roller 41 is left for two days or more when each environment changes. Due to this standing period, a state in which the influence of the change in use environment is sufficiently achieved can be obtained inside the charging roller 41.
In FIG. 7, when the temperature and humidity are 23 ° C. and 50%, when a negative DC voltage of −1350 V is applied to the charging rotor 41, a charging potential of about −700 V is obtained on the surface of the photoreceptor.
On the other hand, when the temperature / humidity was changed to 10 ° C. and 15%, in order to charge the photoconductor to the same −700 V, a result of −1390 V was obtained.

From this, for example, assuming that the temperature and humidity drop to 15 ° C. and 15% in the indoor environment on the weekend in winter, and the temperature and humidity rises to 23 ° C. and 50% during the day by turning on air conditioning at the beginning of the week, the following is assumed.
In the charging roller, the influence of the weekend state still remains (in the extreme example, if the charging roller is still at a temperature of 10 ° C. and 15%), the charging roller tries to be charged to −700 V based on the indoor environment to be −1350 V. Apply. The charging potential at this time is about −660 V, and charging is insufficient. For this reason, the image density may deviate from the aim, and an abnormal image such as background stains may occur. Changes due to the environment of the charging roller may take more than two days to stabilize.

  As described above, there is a time lag between the change in the surrounding environment and the state of the charging roller, but in this embodiment, the image density is appropriately adjusted to the charging potential even for a sudden environmental change by detecting the temperature and humidity inside the charging roller. It can be adjusted so that an abnormal image does not occur.

FIG. 8 is a block diagram showing a configuration of a control unit for adjusting the voltage applied to the charging roller 41 in accordance with the state change.
In the figure, the control unit 1000 uses a control unit that executes an image forming sequence program. As a configuration related to the present embodiment, a state change detection member barrel temperature sensor S1 and a humidity sensor S2 are connected to the input side. ing.
On the other hand, an applied voltage driving unit 1001 for setting an applied voltage to the charging roller 41 is connected to the output side of the control unit 1000.
The control unit 1000 corrects a preset applied voltage to the charging roller 41 based on the detection result using the temperature sensor S1 and the humidity sensor S2 in the charging roller 41 based on environmental changes.
In the correction, the applied voltage is adjusted so that the voltage applied to the charging roller 41 does not become insufficient or excessive from the result shown in FIG.

In the above embodiment, even when the usage environment of the charging roller 41 changes and there is a time lag in the state change that affects the inside of the charging roller 41, the applied voltage is adjusted based on the state change inside the charging roller. As a result, the charging potential can be maintained at a predetermined potential.
In particular, in order to determine the state change inside the charging roller, the actual state change inside the charging roller can be accurately determined by using the pseudo charging roller 42 having the same configuration as the charging roller.
As a result, it is possible to prevent the occurrence of abnormal images such as uneven charging on the surface of the photosensitive member and background stains due to insufficient voltage applied to the charging roller according to environmental changes over a long period of time.

DESCRIPTION OF SYMBOLS 10 Photoconductor 40 Charging device 41 Charging roller 42 Pseudo charging roller 400 Core metal 401 Base layer 402 Surface layer 403 State change detection member 1000 Control unit 1001 Applied voltage drive unit S1 Temperature sensor S2 Humidity sensor

Japanese Patent Laid-Open No. 04-186381 JP 09-114200 A

Claims (10)

A charging member used to uniformly charge the surface of the latent image carrier is provided, and the surface of the latent image carrier is charged to a predetermined polarity and a predetermined image forming potential by applying a voltage to the charging member during image formation. A charging device having a configuration of
Detection means for detecting a change in the internal state of the charging member with respect to a change in the usage environment of the charging member, and controlling the voltage applied to the charging member according to the detection result of the detection means, thereby controlling the image forming potential. A charging device that is charged to a predetermined potential.   As the charging member, a charging roller having a conductive elastic layer provided on a core metal is used, and the detecting means is a pseudo-charging member having the same configuration as the charging member in the vicinity of the charging member and an environmental change. A state change detecting member capable of detecting a state change in the conductive elastic layer in the pseudo-charging member based on, and controlling the voltage applied to the charging member according to the state change in the pseudo-charging member The charging device according to claim 1, wherein the image forming potential is charged to a predetermined potential.   3. The temperature detection member capable of detecting a state change targeting a temperature of a conductive elastic layer provided in the pseudo-charging member is used as the state change detection member. Charging device.   4. The humidity detection member capable of detecting a state change targeting humidity in a cavity provided in the pseudo-charging member is used as the state change detection member. 5. The charging device according to claim 1.   The state change detection member is connected to a control unit that determines a voltage to be applied to the charging member, and the control unit determines a voltage to be applied to the charging member according to a detection result from the state change detection member. The charging device according to claim 1 or 2, characterized in that   The charging device according to claim 1, wherein the voltage applied to the charging member is a DC voltage.   The charging member includes a base layer and a surface layer in an elastic layer provided on a cored bar, and the surface layer prevents the contamination due to a component exuding from the base layer. 6. The charging device according to claim 1.   8. The charging device according to claim 7, wherein a rubber elastic layer is used for the base layer, and a resin layer is used for the surface layer.   7. The charging member according to claim 1, wherein the charging member includes a single rubber layer disposed on a metal core, and the rubber layer is surface-treated to form a surface layer. The charging device according to claim 1.   The charging device, a latent image carrier whose surface is uniformly charged by the charging device, a developing device for performing visible image processing of the latent image formed on the latent image carrier, and cleaning the latent image carrier after visible image transfer. An image forming apparatus comprising: a process cartridge including at least one of cleaning devices to be included in an image forming unit.

Images