JPH0863042A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device where image fogging does not occur because the rise of the potential of a light part is restrained even in the case of endurance. CONSTITUTION: In this image forming device using a contact type electrifying system; a body to be electrified 1 is a photoreceptor 1a having a photoreceptive layer on an aluminum supporting body 1G whose surface is processed to be anodized, and an electrifying member 2 is controlled in terms of DC constant voltage and DC current amount in accordance with the layer thickness of the body to be electrified at such a time is detected when the electrifying member 2 corresponds to the image non-forming area of the body to be electrified 1, and it is controlled in terms of DC constant voltage at DC voltage in accordance with the detected DC current amount when it corresponds to the image forming area of the body to be electrified 1, then light irradiation amount is also controlled in accordance with the detected DC current amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a contact type charging device which charges a surface of a photosensitive member by bringing a charging member to which a voltage is applied into contact with the photosensitive member as a charging processing means of the photosensitive member.

[0002]

2. Description of the Related Art In the image forming apparatus as described above, a corona discharge device has been widely used as a device for charging the surface of an image bearing member as a member to be charged.

The corona discharge device is effective as a means for uniformly charging the surface of an object to be charged such as an image carrier to a predetermined potential. However, there is a problem that a high voltage power source is required and undesirable ozone is generated due to corona discharge.

In contrast to such a corona discharge device, a contact type charging device for charging the surface of the body to be charged by contacting the surface of the body to be charged with a charging member to which a voltage is applied as described above can reduce the power supply voltage. In addition, since it has advantages such as a small amount of ozone generated, for example, in an image forming apparatus, instead of a corona discharge device, a photoconductor, an image carrier such as a dielectric, and a charging process for other surfaces to be charged. It has attracted attention as a means, and research for its practical application is underway.

For example, the present applicant has previously proposed (Japanese Patent Application No.
No. 51492, No. 62-230334, etc.), a vibration having a peak-to-peak voltage that is more than twice the charging start voltage of the member to be charged when a DC voltage is applied to the charging member in the contact type charging device. Forming an electric field (alternating electric field, an electric field (voltage) whose voltage value periodically changes with time) between a charging member and a body to be charged, and further, using a charging member having a high resistance layer as a surface layer. As a result, it is possible to achieve uniform charging of the charged body, prevention of pinholes on the surface of the charged body such as the photoconductor, and leakage due to scratches.

Further, a conductive member (conductive potential maintaining member) such as a conductive fiber brush or a conductive elastic roller is brought into contact with the member to be charged as a charging member, and a DC voltage is applied from the outside to the member to be charged. There is also one in which electric charge is directly injected into the surface to charge the surface of the body to be charged to a predetermined potential.

[0007]

However, when the charging means is a contact type DC voltage application, it is greatly affected by the capacitance change of the photoconductor. That is, when the number of times image formation is used increases and the film thickness of the photoconductor decreases, the direct current flowing through the charging roller increases and the surface potential of the outer peripheral surface of the photoconductor rises. Further, when the film thickness of the photoconductor is decreased and the surface potential is increased, the development contrast is increased and the development image density is increased, and at the same time, sufficient reverse contrast cannot be obtained with respect to the potential of the white image. However, there was a problem in that it was thinly developed and became a "fog" image.

That is, when the film thickness of the photoconductor is reduced, the surface potential is increased and the bright portion potential of the surface potential is also increased accordingly. Further, since the sensitivity of the photoconductor decreases as the film thickness decreases, the surface potential corresponding to the white original, that is, the light portion potential does not drop sufficiently. Due to the above-mentioned two phenomena, the potential of the bright part is greatly increased, and the surface potential contrast between the black original and the white original is narrowed. The contrast was not obtained, and there was a problem that the light potential portion was thinly developed with the developer to form a “fog” image.

Even when it is adjusted so as not to be covered by the developing bias or the exposure lamp voltage (= the exposure amount of the light image irradiation), it is necessary to secure a wide adjustment range, so that the adjustment range is wide. Therefore, it was a factor of increasing the cost of power supplies.

Therefore, when the charging member corresponds to the non-image forming area of the photoconductor, the charging member is subjected to direct current constant voltage control, and the amount of direct current corresponding to the photoconductor layer thickness at that time is detected, When the charging member corresponds to the image forming area of the photoconductor, the charging member is controlled to a constant DC voltage by a DC voltage corresponding to the detected DC current amount, and the light is output according to the detected DC current amount. An image forming apparatus characterized by controlling the exposure amount of image irradiation has been proposed.However, even in this case, if the potential increase of the bright portion of the photosensitive member is too large, the above-mentioned limit of the DC constant voltage control is exceeded. It becomes difficult to obtain a good image.

An object of the present invention is to eliminate the above problems.

[0012]

That is, the present invention provides an image forming apparatus for performing image formation by applying an image forming process including a step of charging the surface of a charged body to the charged body. The body is a photoreceptor having a photosensitive layer on an aluminum support whose surface is anodized, and the charging means of the body to be charged is charged by bringing a charging member to which a voltage is applied into contact with the body to be charged. A contact type charging device for charging a body surface, wherein the charging member is subjected to direct current constant voltage control when the charging member corresponds to a non-image forming region of the charging target, and the charging target layer thickness at that time is controlled. Detecting a direct current amount according to the charging member, when the charging member corresponds to the image forming area of the member to be charged, the charging member is controlled to a constant DC voltage with a DC voltage according to the detected DC current amount, In addition, light is emitted according to the amount of DC current detected above. And to control the injection amount, it is an image forming apparatus according to claim.

The present invention will be described in detail below.

Materials generally used as a support for the latent image holding member are aluminum, iron, stainless steel, copper,
Examples thereof include zinc, nickel, electroconductive plastics, and glass. Among them, aluminum is widely used because it is relatively inexpensive, lightweight, has good workability, and does not impair electrical characteristics.

Usually, when aluminum is used as a drum-shaped support, an aluminum buret is processed into an extruded tube by a porthole method, a mandrel method or the like, and subsequently, a drum having a predetermined wall thickness and an outer size is formed. It can be made by drawing, impacting, ironing, etc. However, for example, since the extrusion process is usually performed under high temperature and high pressure, the surface of the aluminum drum is roughened, precipitation of dissimilar metals occurs during cooling, and various defects are formed on the surface of the drum as it is, It's difficult to make something satisfying. For this reason, the surface is further cut or, in some cases, another conductive layer is provided on the drum surface and used, but it still has a uniform enough surface for practical use. It can not be said.

The aluminum support used in the present invention can be obtained in a desired shape by the above-mentioned processes such as drawing, impacting and ironing. Furthermore, mirror finishing by cutting is performed if necessary. The aluminum support is preferably degreased by various degreasing cleaning methods such as acid, alkali, organic solvent, surfactant, emulsion and electrolysis before anodizing treatment.

The anodizing treatment is usually carried out in an acidic bath of, for example, chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but the anodizing treatment in sulfuric acid gives the best results. . In the case of anodic oxidation in sulfuric acid, the sulfuric acid concentration is 50 to 400 g / l and the dissolved aluminum concentration is 2 to 20.
g / l, liquid temperature is 10 to 40 ° C., electrolysis voltage is 5 to 30 V,
The current density is preferably set within the range of 0.5 to ² A / dm ² .

The average film thickness of the anodized film is 0.1.
It is preferably formed with a thickness of about 20 μm. More preferably, it is 1 to 10 μm. The anodized film thus formed contains, for example, a low-temperature sealing treatment in which it is immersed in an aqueous solution containing nickel fluoride as a main component or, for example, nickel acetate as a main component, in order to enhance the stability of the film. It is preferable to perform a high-temperature sealing treatment in which it is immersed in an aqueous solution, or other sealing treatment such as steam sealing or boiling water sealing.

The concentration of the nickel fluoride aqueous solution used in the low-temperature sealing treatment can be appropriately selected, but it is most effective when it is used in the range of 2 to 10 g / l. Further, in order to smoothly proceed with the sealing treatment, the treatment temperature is 1
5-40 degreeC, Preferably it is 25-35 degreeC, pH of nickel fluoride aqueous solution is 4.5-6.5, Preferably it is 5.5.
It is better to process within the range of 6.0. In this case, oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia, etc. can be used as the pH adjusting agent. The processing time is preferably within a range of 1 to 3 minutes per 1 μm of the film thickness. In order to further improve the film properties, cobalt fluoride, cobalt acetate, nickel sulfate, a surfactant and the like may be added to the nickel fluoride aqueous solution. Next, it is washed with water and dried to complete the low-temperature sealing treatment.

As the sealing agent in the case of the high temperature sealing treatment, an aqueous solution of a metal salt of nickel acetate, cobalt acetate, lead acetate, nickel acetate-cobalt, barium nitrate or the like can be used, but nickel acetate is particularly used. Is preferred. The concentration when using an aqueous nickel acetate solution is 3 to 20.
It is preferably used within the range of g / l. Processing temperature is 6
The treatment is preferably performed at 5 to 100 ° C., preferably 80 to 98 ° C., and the pH of the aqueous nickel acetate solution is in the range of 5.0 to 6.5. Here, ammonia water, sodium acetate, or the like can be used as the pH adjuster.

The treatment time is 10 minutes or longer, preferably 20 minutes or longer. Also in this case, sodium acetate, an organic carboxylate, an anionic surfactant, a nonionic surfactant and the like may be added to the nickel acetate aqueous solution in order to improve the physical properties of the coating. Then, after washing with water and drying, the high-temperature sealing treatment is completed.

An undercoat layer having a barrier function and an adhesive function can be provided between the support substrate and the photosensitive layer.

The layer is casein, polyvinyl alcohol,
Nitrocellulose, ethylene-acrylic acid copolymer,
It can be formed of polyamide (nylon, nylon 6, nylon 66, nylon 610, copolymerized nylon, etc.), polyurethane, gelatin, aluminum oxide and the like.

The thickness of the undercoat layer is 5 μm or less, preferably 0.5 to 3 μm. It is desirable that the specific resistance is 10 ⁷ Ωcm or more in order to exert the function as a barrier layer well.

The photosensitive layer is formed by coating a phthalocyanine pigment, an azo pigment or the like with a binder into a coating material.

When an organic photoconductor is used, a photosensitive layer composed of a charge generation layer which generates charge carriers upon exposure and a charge transport layer which transports the generated charge carriers can be effectively used.

As the charge generation layer, azo pigments such as Sudan Red, Diane Blue, and Genus Green B, quinone pigments such as Argol Yellow, pinone quinone, indanthrene brilliant violet RR, quinocyanine pigments, perylene pigments, indigo, thioindigo pigments, etc. 1 to 2 of indigo pigments, bisbenzimidazole pigments such as Indian fast orange toner, phthalocyanine pigments such as copper phthalocyanine, and quinacdrine pigments
It is formed by vapor deposition of one or more kinds, or by dispersion coating with an appropriate binder if necessary.

The binder can be selected from an insulating resin or an organic photoconductive polymer.

For example, as the insulating resin, polyvinyl butyral, polyarylate (polycondensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin,
Polyacrylamide resin, polyamide, polyvinylpyridine, cellulosic resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, polyvinylpyrrolidone and the like, and organic photoconductive polymers include carbazole, polyvinylanthracene, polyvinylpyrene and the like. .

The thickness of the charge generation layer is 0.01 to 15 μm,
It is preferably 0.05 to 5 μm, and the weight ratio of the charge generation layer to the binder is 10: 1 to 1:20.

The solvent used for the charge generation layer coating material is selected from the solubility and dispersion stability of the resin and charge transport material used, and specifically, alcohols such as methanol, ethanol and isopropanol, acetone, Sulfoxides such as methyl ethyl ketone, cyclohexanone, N, N-diethylformamide, N, N-dimethylacetamide, ethers such as tetrahydrofuran, dioxane, ethylene glycol, monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride. It is possible to use aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, and trichloroethylene, and aromatic compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene.

The coating can be carried out by a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a curtain coating method or the like.

The charge transport layer is formed by dissolving the charge transport layer in a film-forming resin.

Organic charge transport materials include pyrene and N-
Ethylcarbazole, N-isopropylcarbazole,
N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,
N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, N, N-diphenylhydrazino-
3-methylidene-10-ethylphenoxazine, P-diethylaminobenzaldehyde-N, N-diphenylhydrazone, P-diethylaminobenzaldehyde-N-
α-naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde-N, N-diphenylhydrazone,
Hydrazones such as 1,3,5-trimethylindolenine-ω-aldehyde-N, N-diphenylhydrazone and P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 2,5-bis (P- Diethylaminophenyl) -1,3,4-oxadiazole, 1
-Phenyl-3- (P-diethylaminostyryl) -5
-(P-diethylaminoethylphenyl) pyrazoline,
1- [quinolyl (2)]-3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (P-diethylaminostyryl) -5- (P -Diethylaminophenyl)
Pyrazoline, 1- [6-methoxy-pyridyl (2)]-
3- (P-diethylaminostyryl) -5- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (3)]-3- (P
-Diethylaminostyryl) -5- (P-diethylaminophenyl) pyralisone, 1- [lepidil (2)]-3
-(P-diethylstyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3
-(P-diethylaminostyryl) -4-methyl-5-
(P-diethylaminostyryl) pyrazoline, 1- [pyridyl (2)]-3- (α-methyl-P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1-phenyl-3- (P-diethylamino) Pyrazolines such as styryl) -4-methyl-5- (P-diethylaminophenyl) pyrazoline, 1-phenyl-3- (α-benzyl-P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline and spirpyramisone, 2- (P-diethylaminostyryl) -6
-Oxazole compounds such as diethylaminobenzoxazole, 2- (P-diethylaminophenyl) -4- (P-diethylaminophenyl) -5- (2-chlorophenyl) oxazole, 2- (P-diethylaminostyryl) -6-diethylaminobenzo Thiazole-based compounds such as thiazole, triallylmethane-based compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane, 1,1-bis (4-N, N-dimethylamino-)
Polyallyl alkanes such as 2-methylphenyl) ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, biren-formaldehyde resin, ethylcarbazoleformaldehyde resin , Or the like can be used alone or in combination of two or more.

As the charge transport layer, phenoxy resin, polyacrylamide, polyvinyl butyral, polyarylate, polysulfone, polyamide, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin,
Vinyl acetate resin, phenol resin, epoxy resin, polyester, alkyd resin, polycarbonate, polyurethane, or a copolymer containing two or more of repeating units of these resins, for example, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene. And maleic acid copolymers. Also,
It can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene and the like.

The thickness of the charge transport layer is 5 to 50 μm, preferably 10 to 30 μm, and the weight ratio with the binder is 5:
1, preferably about 3: 1 to 1: 3.

For the coating, a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a curtain coating method or the like can be used.

Dyes, pigments, organic charge transporting substances, etc. are generally vulnerable to stains by ultraviolet rays, ozone, oils, etc., metals, etc. Therefore, a protective layer may be provided if necessary.

As the protective layer, polyvinyl butyral,
Polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate,
Resins such as polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, and styrene-acrylonitrile copolymer are dissolved in a suitable organic solvent,
This is applied on the photosensitive layer and dried to form.

The thickness of the protective layer is usually 0.05 μm to 20 μm.
μm, and an ultraviolet absorber or the like may be further added.

In the image forming apparatus of the present invention, even if there is a change in the capacity of the charged body due to a decrease in the thickness of the charged body as the image carrier of the image forming apparatus due to an increase in the number of times of image formation, the capacity of the charged body changes each time. By detecting the voltage-current characteristic according to the capacitance with respect to the thickness of the body to be charged, the optimum correction applied voltage at that time can be applied to the charging member. Further, optimum correction exposure can be performed on the charged body.

According to this, as the thickness of the member to be charged decreases, the amount of detected current when the non-image area constant voltage is applied increases,
In order to add the voltage decrease correction to the image part applied voltage value according to the increase amount and the increase correction of the exposure lamp voltage,
The charging process and the image formation in the optimum state are always executed.

When the resistance value of the resistance layer of the charging member increases due to environmental humidity fluctuations and durability fluctuations, the amount of detected current decreases, voltage increase correction is applied to the image area applied voltage value, and the exposure lamp is used. Since the voltage drop is corrected or a constant voltage is used, sufficient image density and image quality can always be obtained without insufficient charging.

[0044]

EXAMPLES The present invention will be described below with reference to examples. [Embodiment 1] FIG. 1 shows a schematic configuration of an example of an image forming apparatus according to the present invention.

Reference numeral 1 denotes an image bearing member as a member to be charged. In this example, a drum having a conductive support 1b of anodized aluminum and a photosensitive layer 1a formed on the outer peripheral surface thereof as a basic constituent layer. Type electrophotographic photoreceptor. It is rotationally driven around the support shaft 1d at a predetermined peripheral speed (process speed) in the clockwise direction in the drawing.

Reference numeral 2 denotes a contact charging member which is in contact with the surface of the photoconductor 1 to uniformly perform a primary charging process on the photoconductor surface to a predetermined polarity and potential. In this example, a contact type charging member is a roller type (charging roller). The charging roller 2 is composed of a central core metal 2c, a conductive layer 2b formed on the outer periphery thereof, and two resistance layers 2a ₂ and 2a ₁ sequentially formed on the outer periphery thereof, and both ends of the core metal 2c are not shown. The bearing member is rotatably rotatably arranged in parallel with the drum type photoconductor 1 and is pressed against the surface of the photoconductor 1 by a pressing means (not shown) with a predetermined pressing force to rotate the photoconductor 1. Along with the rotation.

A predetermined direct current (DC) bias is applied to the core metal 2c from the power source 3 through the sliding contact 3a, so that the peripheral surface of the rotary photosensitive member 1 is contact-charged to a predetermined polarity and potential. (Primary charging).

The surface of the photosensitive member 1 which has been uniformly charged by the charging member 2 is then subjected to the exposure L of the target image information (exposure slit exposure of the original image, laser beam scanning exposure, etc.) by the exposure means 10. An electrostatic latent image corresponding to the target image information is formed on the peripheral surface.

The exposing means 10 in the apparatus of this embodiment is a known original table fixed-optical system moving type original image forming slit exposing means. In the exposure means 10, 20 is a fixed original platen glass, O is an original document placed and set on the original platen glass with the image surface facing downward, 21 is an original pressing plate, 22 is an original illumination lamp (exposure lamp), 23 is a slit plate, 24 to
26 is a movable first to third mirror, 27 is an imaging lens, 28
Is a fixed mirror. The lamp 22, the slit plate 23, and the moving first mirror 24 move the lower surface of the platen glass 20 from one end to the other end at a predetermined speed V, and the moving second and third mirrors 25 and 26 have a speed of V / 2. Is moved and driven, and the downward document surface on the document table glass 20 is scanned from one end side to the other end side, and a document image is imaged on the surface of the rotary photoconductor 1 by slit exposure L.
To be done.

The latent image formed on the surface of the photosensitive member 1 is then developed by the developing means 1.
By 1, the toner images are sequentially visualized.
The toner image is then conveyed from the sheet feeding section (not shown) by the transfer section 12 to the transfer section between the photoreceptor 1 and the transfer section 12 at an appropriate timing in synchronization with the rotation of the photosensitive body 1. The images are sequentially transferred onto the surface of the transfer material 14. The transfer unit 12 in this example is a transfer roller, and the toner image on the surface of the photosensitive member 1 is transferred to the surface of the transfer material 14 by charging the transfer material 14 from the back with a polarity opposite to that of the toner.

The transfer material 14 to which the toner image has been transferred is separated from the surface of the photosensitive member 1 and conveyed to an image fixing means (not shown) to be subjected to image fixing and output as an image-formed product. Alternatively, when the image is formed on the back side, the image is conveyed to the re-conveying unit to the transfer unit.

After the image transfer, the surface of the photosensitive member 1 is cleaned by the cleaning means 13 to remove adhering contaminants such as untransferred toner, and is then cleaned by a discharging and exposing device 15 to remove the charge.
It is repeatedly used for image formation.

(1) Examples of Various Forms of Charging Member 2 The roller type charging member 2 may be driven to rotate according to the photosensitive member 1 as a member to be surface-driven and to be charged, or may be non-rotating. Alternatively, the photosensitive member 1 may be positively rotationally driven in the forward or reverse direction of the surface moving direction at a predetermined peripheral speed.

Besides the roller type, the charging member 2 can be constructed in a blade type, a block type, a rod type, a belt type or the like.

FIG. 2A shows a schematic cross-sectional view of an example of the blade type. In this case, the direction of the blade-shaped charging member 2 contacting the surface of the photoconductor 1 may be either forward or reverse to the surface movement direction of the surface of the photoconductor 1.

FIG. 2B shows a schematic cross-sectional view of an example of a block or rod shape.

In each type of charging member 2, 2c is a conductive core metal member, 2b is a conductive layer, and 2a is a resistance layer.

The block-shaped or rod-shaped one is a rotatable roller type one without a power-supplying sliding contact 3a required for applying a bias voltage to the core-metal member 2c. The lead wire leading to the power source 3 can be directly connected to the member 2c, and the electric noise that may be generated from the power feeding sliding contact 3a can be eliminated, and the space can be saved. It is also possible to adopt a configuration in which the cleaning blade of 1 is also used.

(2) Sequence FIG. 3 shows an example of an operation sequence of the apparatus shown in FIG. This example is 2
The case of continuous printing on one sheet is shown.

.. Based on the print (copy) start signal, the rotation drive of the photosensitive member 1 (hereinafter, referred to as a drum) of the apparatus which has been in the standby state until then is started to start the pre-rotation period. At the same time when the rotation of the drum 1 is started, the static elimination exposure 15 is turned on, and static electricity is discharged from one peripheral surface or more of the drum 1 in the section A1.

.. Next, the charging roller 2 which is a contact charging member
The DC bias, which is the primary charging bias for, is turned on.

.. This primary charging bias begins with section B
1, constant voltage control is performed, DC current is detected during that period, and then charging roller DC corresponding to the detected DC current is detected.
Constant voltage control is performed.

The period before the image formation starts is the pre-rotation period of the drum 1, and the surface of the drum 1 during that period is the non-image forming area surface, and therefore the charging roller 2 corresponds to the non-image forming area surface of the drum 1. The charging roller DC constant voltage control is performed in the section B1 of the pre-rotation period, and the DC current at this time is detected, the primary voltage is corrected (the primary charging bias of the charging roller 2 is corrected), and the image exposure amount is corrected.

.. When the charging roller DC constant voltage control is started with the primary correction voltage, the first image is formed by image exposure (image forming slit exposure of the original image). The charging roller 2 corresponds to the image forming area surface of the drum 1, and the surface of the drum 1 is charged under the DC constant voltage control state.

.. A so-called drum surface between sheets until the image formation for the first print is completed and the image formation for the next second print is started is a non-image formation area surface. Then, the DC constant voltage control, the DC current detection, the DC constant voltage control, and the image exposure control of the charging roller 2 are executed again during this sheet interval.

That is, when the printing of the first sheet is completed, the primary charging bias is again set to the charging roller DC constant voltage control in the section B2 between the sheets, and the DC current detection is executed.
Next, the charging roller constant voltage control according to the detected DC current is executed, the image exposure control is further executed, and the image formation for the second print is executed.

Even when three or more sheets are continuously printed, the charging roller DC constant voltage control / DC current detection / DC constant voltage control / image exposure control sequence is similarly performed between the respective sheets.

.. When the image formation of the final print is completed, the drum 1 enters the post-rotation period, and in the section A2 of the post-rotation period, the static elimination exposure 15 on one circumferential surface or more of the drum 1 is performed.
Is removed and the charge is removed, and the rotation of the drum 1 and the charge removal exposure are OF
The status becomes F, and the apparatus enters the standby state until the next print start signal is input.

In the above structure, when the surface of the drum is scraped due to the durability and the film thickness of the photosensitive member is thinned, the DC constant performed when the charging roller 2 corresponds to the surface of the non-image forming area of the drum 1 is determined. Detection D of voltage control period B1 or B2
The C current becomes high, and the charging process for the image forming area surface of the drum 1 is performed by the charging roller 2 and the image exposure under the charging roller DC constant voltage control and the image exposure amount control with the reduction correction voltage according to the detected DC current. And the image formation is executed.

Further, in a low humidity environment, the resistance of the charging roller 2 is particularly lowered, and the detected DC current of the charging roller DC constant voltage control in the vapor periods B1 and B2 is lowered. Since the charging roller 2 performs the charging process on the image forming area surface of the drum 1 under the constant voltage control of the charging roller DC with the increased correction voltage according to the detected DC current, the charging roller 2 performs the image formation. The charging potential of the drum 1 is made constant regardless of the resistance fluctuation in the environment.

Next, the photoconductor used in the present invention will be described.

The extruded aluminum tube was ironed to a wall thickness of 0.8 mm, an outer diameter of 30 mm, and a length of 357.
A 5 mm aluminum cylinder was prepared.

This aluminum cylinder is treated with a degreasing agent NG
6 in a 30 g / l aqueous solution of # 30 (Kizai Co., Ltd.)
Degreasing cleaning was performed at 0 ° C. for 5 minutes. Subsequently, after washing with water, it was immersed in 7% nitric acid at 25 ° C. for 1 minute. After further washing with water,
180 g / l sulfuric acid electrolyte (dissolved aluminum concentration 7
g / l) at an electric current density of 1.0 A / dm ² to form an anodic oxide film having an average film thickness of 6 μm. Then, after washing with water, a high-temperature sealing agent Top Seal DX-500 (manufactured by Okuno Chemical Industries Co., Ltd.) containing nickel acetate as a main component was used.
It was immersed in an aqueous solution of 0 g / l at 90 ° C. for 20 minutes to perform a sealing treatment. Then, after washing with water, it was immersed in a pure water hot water bath at 95 ° C. for 10 minutes, taken out and dried.

Next, copolymer nylon (trade name: CM80
00, manufactured by Toray Industries, Inc., 4 parts (parts by weight, the same applies hereinafter) and 4 parts of type 8 nylon (trade name: Lackamide 5003, manufactured by Dainippon Ink and Chemicals), 50 parts of methanol and n-
It was dissolved in 50 parts of butanol and applied to the anodized cylinder described above to form an undercoat layer having a thickness of 0.5 μm.

10 parts of a disazo pigment having the following structural formula,

[0076]

Embedded image And 10 parts of polyvinyl butyral resin (trade name: S-REC BM2, manufactured by Sekisui Chemical Co., Ltd.) were dispersed in a sand mill for 10 hours together with 120 parts of cyclohexanone.

To this dispersion, 30 parts of methyl ethyl ketone was added and coated on the undercoat layer to form a charge generation layer having a thickness of 0.6 μm.

Further, the following structural formula,

[0079]

Embedded image Solution of 15 parts of stilbene compound and 10 parts of polycarbonate resin (Panlite L-1250, Teijin Kasei Co., Ltd.) dissolved in 50 parts of dichloromethane and 10 parts of monochlorobenzene was coated on the charge generation layer to give a thickness of 25 μm. A charge transport layer was formed.

The photosensitive member is attached to the above-mentioned image forming apparatus,
A durability test was conducted. FIG. 4 shows changes in the dark portion potential and changes in the bright portion potential at this time.

[Embodiment 2] A mirror-finished surface having a thickness of 0.
A durability test was conducted in the same manner as in Example 1 except that an aluminum cylinder having a diameter of 8 mm, an outer diameter of 30 mm, and a length of 357.5 mm was used.

FIG. 5 shows changes in the dark part potential and changes in the bright part potential at this time.

Example 3 The same durability test was conducted as in Example 1 except that the charge generating material of the photoconductor of Example 1 was changed to the one having the following structural formula.

[0084]

[Chemical 3] FIG. 6 shows changes in the dark portion potential and changes in the bright portion potential at this time.

Comparative Example 1 The same as Example 1 except that the cylinder of the photoreceptor of Example 1 was not anodized.
A similar durability test was conducted.

FIG. 7 shows changes in the dark portion potential and changes in the bright portion potential at this time.

The image characteristics of Examples 1 to 4 and Comparative Example 1 are shown in Table 1.

[0088] ○: Good △: Some fog, but practically no problem ×: Fogging, unusable × ×: Fogging is remarkable

[0089]

As described above, according to the present invention, an image forming apparatus for charging a charged body as an image carrier by using a contact charging means, and further, image information on the charged body surface is charged. In an image forming apparatus that executes an image forming process by applying an image forming process including a step of irradiating a light image containing light, it is possible to control so that image fogging does not occur by suppressing a bright portion potential rise due to endurance. It will be possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first exemplary embodiment.

FIG. 2A and FIG. 2B are schematic cross-sectional views of contact charging members of forms other than the roller type.

FIG. 3 is an operation sequence diagram of the image forming apparatus according to the first exemplary embodiment.

FIG. 4 is a diagram showing potential changes in Example 1.

FIG. 5 is a diagram showing potential changes in Example 2.

FIG. 6 is a diagram showing a potential change of Example 3.

FIG. 7 is a diagram showing potential changes in Example 4.

[Explanation of symbols]

 1 Charged Member (Photosensitive Member) 2 Charging Roller 3 Charging Bias Applying Power Supply 10 Image Exposure Means 11 Developing Means 12 Transfer Means 13 Cleaning Means 14 Transfer Materials

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akira Yoshida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. An image forming apparatus for performing image formation by applying an image forming process including a step of charging a surface of a body to be charged to the body to be charged, wherein the body to be charged is anodized aluminum. A photoreceptor having a photosensitive layer on a support, wherein the charging means for charging the charged body is a contact type charging device for charging the surface of the charged body by bringing a charging member to which a voltage is applied into contact with the charged body. Yes, when the charging member corresponds to the non-image forming area of the charged body, the charging member is subjected to DC constant voltage control, and the amount of DC current according to the thickness of the charged body layer at that time is detected, When the charging member corresponds to the image forming area of the member to be charged, the charging member is controlled to a constant DC voltage with a DC voltage corresponding to the detected DC current amount, and the charging current is detected according to the detected DC current amount. The light irradiation amount is controlled. An image forming apparatus comprising.