JP2005053052A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a stabilized electrostatic latent image by preventing occurrence of contact corrosion on the interface even when the conductive fine particles of an image carrier and a writing electrode are composed of different metals. <P>SOLUTION: A metal composing the conductive fine particles 2c<SB>1</SB>of an image carrier 2 is different from a metal composing a writing electrode 3a. The conductive fine particles 2c<SB>1</SB>and the writing electrode 3a are held to touch each other when an image is formed and to separate from each other when an image is not formed. Since contact time of the conductive fine particles 2c<SB>1</SB>and the writing electrode 3a is shortened, occurrence of contact corrosion due to contact of different kinds of metal is minimized. Even when the conductive fine particles 2c<SB>1</SB>of the image carrier 2 and the writing electrode 3a are composed of different metals, contact corrosion is retarded on the interface and a stabilized electrostatic latent image can be formed. Consequently, good image formation can be ensured over a long term. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has an independent floating electrode portion composed of a large number of conductive fine particles dispersed electrically independently from each other in a dielectric layer, and writing to the conductive fine particles exposed on the surface of the independent floating electrode portion. The present invention relates to a technical field of an image forming apparatus and an image forming method for forming an electrostatic latent image on an image bearing member by causing an electrode to contact and transfer charges.

  2. Description of the Related Art Conventionally, an image forming apparatus such as an electrostatic copying machine or a printer is provided with an image carrier having a large number of conductive fine particles dispersed electrically independently in a dielectric layer, and writing in a writing head unit. An image forming apparatus that forms an electrostatic latent image on an image carrier using electrodes has been proposed (see, for example, Patent Document 1). As shown in FIG. 5A, the image forming apparatus a includes conductive fine particles exposed on the surface of the dielectric layer c among the conductive fine particles d dispersed in the dielectric layer c of the image carrier b. An electrostatic latent image is written on the image carrier b by the writing electrode e coming into contact with d and the charge moving between the conductive fine particles d and the writing electrode e.

On the other hand, in general, when different metals are placed in contact with each other, due to the difference in ionization tendency of these metals, one metal is in an excessive electron state, and the other metal is in an insufficient electron state. In that case, if the metal atoms at the interface run short of electrons, an anodic phenomenon occurs in which the ions are separated from the metal and dissolved when there is no electron supply. Cathode phenomenon occurs where electrons are received and returned to metal. And it is known that the dissolved metal or the activated metal is likely to cause contact corrosion by reacting with a gas in the atmosphere (see, for example, Non-Patent Document 1).
JP 2002-225332 A. Internet literature, various aspects of corrosion, Mamoru Yanagihara, Osaka Prefectural Industrial Technology Research Institute, June 08, 2000, URL: http://www.tri.pref.osaka.jp/group/surface/Post/Yanagihara/Y4 .pdf, website access date: July 14, 2003.

In the image forming apparatus a described above, when the metal used for the conductive fine particles d of the image carrier b and the metal used for the writing electrode e are different metals, the conductive fine particles d and If the state of contact with the write electrode e is maintained for a certain period of time, the contact corrosion described above may occur at the contact interface as shown in FIG. When this contact corrosion occurs at the contact portion between the conductive fine particles d and the write electrode e, an impurity film f is formed at these contact portions. When such an impurity film f is not formed at the contact portion between the conductive fine particle d and the write electrode e, the electrical resistance (hereinafter referred to as contact resistance) due to the contact between the conductive fine particle d and the write electrode e. ) Is relatively small. For this reason, as shown in FIG. 5B, with respect to the head applied voltage A (solid line) applied to the write electrode e, the drum surface potential B of the conductive fine particles d exposed on the surface of the dielectric layer c ( The dotted line) has good responsiveness, rises relatively quickly following the head applied voltage A, and quickly approaches the head applied voltage A. However, when the impurity film f is formed at the contact portion between the conductive fine particle d and the write electrode e, the contact resistance between the conductive fine particle d and the write electrode e becomes relatively large. Therefore, as shown in FIG. 6B, the drum surface potential B (dotted line) of the conductive fine particles d is poor in response to the head applied voltage A (solid line) and does not follow the head applied voltage A quickly. The rise is relatively slow and does not readily approach the head applied voltage A.
As described above, when the impurity film f is formed, the contact resistance between the write electrode e and the conductive fine particle d is large at the time of image writing, that is, at the time of contact between the write electrode e and the conductive fine particle d. As a result, the latent image formation time is delayed (time constant delay), or the unevenness of the gas compound film on the image carrier b and the writing electrode e causes unevenness of the electrostatic latent image. It occurs. For this reason, the electrostatic latent image is formed in an unstable manner, and the toner image may be shaded to cause image formation failure.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide contact corrosion at the interface even when the conductive fine particles of the image carrier and the writing electrode are made of different metals. It is an object to provide an image forming apparatus and an image forming method capable of forming a stable electrostatic latent image in such a manner as to prevent the occurrence of the above.

  In order to solve the above-described problem, an image forming apparatus according to the first aspect of the present invention includes a plurality of conductive fine particles dispersed in a dielectric layer electrically independently of each other and a part of these conductive fine particles. At least an image carrier having an independent floating electrode part in which fine particles are exposed on the surface, and a writing head part having a writing electrode for writing an electrostatic latent image in contact with the conductive fine particles exposed on the surface In the image forming apparatus, the metal used for the conductive fine particles and the metal used for the writing electrode are different from each other, and the writing electrode is provided in contact with and separated from the independent floating electrode portion. The image forming apparatus includes a control unit that holds the write electrode in a state of being separated from the independent floating electrode portion during non-image formation in which image formation is not performed.

  Further, in the image forming apparatus according to the second aspect of the present invention, the independent floating electrode portion is provided radially inward (depth direction) from the surface of the dielectric layer and is provided over the entire circumference of the dielectric layer. A part of the conductive fine particles is located on the circumference at any position in the radial direction of the dielectric layer.

  Further, the image forming method of the invention of claim 3 is a method in which the conductive layer is exposed on the surface in an independent floating electrode portion in which a large number of conductive fine particles are electrically dispersed in the dielectric layer of the image carrier. In an image forming method for forming an image by writing an electrostatic latent image by bringing a writing electrode of a writing head into contact with a conductive fine particle, the conductive fine particle and the writing electrode use different metals. After the non-image formation in which image formation is not performed, the write electrode is held away from the independent floating electrode portion, and after the write electrode is brought into contact with the independent floating electrode portion during image formation The image is formed by writing the electrostatic latent image by bringing the writing electrode into contact with the conductive fine particles exposed on the surface of the independent floating electrode portion.

  According to the image forming apparatus according to the first and second aspects of the invention and the image forming method according to the third aspect of the invention, the metal used for the conductive fine particles of the image carrier and the writing are written. Although the metals used for the electrodes are different from each other, these conductive fine particles and the writing electrode are in contact with each other during image formation and are kept separated from each other during non-image formation. As a result, the contact time between the conductive fine particles and the write electrode is shortened, and the occurrence of the above-described contact corrosion due to the contact of different metals can be suppressed to the minimum. Therefore, even if the conductive fine particles of the image carrier and the writing electrode are made of different metals, contact corrosion hardly occurs at the interface between them, and a stable electrostatic latent image can be formed. As a result, good image formation can be performed over a long period of time, and a high-quality image can be obtained.

  In particular, according to the second aspect of the present invention, a part of the conductive fine particles is located on the circumference at any position in the radial direction of the dielectric layer. Even if contact corrosion occurs at the contact portion with the buried electrode, the surface of the new conductive fine particles can be surely exposed by scraping the surface layer of the independent floating electrode portion of the image carrier. Thereby, even if contact corrosion occurs, formation failure of an electrostatic latent image can be prevented, and a high-quality image can be obtained more reliably.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1A and 1B schematically show the best mode for carrying out the image forming apparatus of the present invention. FIG. 1A is a diagram showing a state in which a writing head unit is in contact with an image carrier, and FIG. FIG. 2 is a partially enlarged view showing a portion around the contact portion of the writing head portion shown in FIG. 1A that is in contact with the image carrier. It is.

  As shown in FIG. 1A, the image forming apparatus 1 includes an insulating dielectric layer (insulator layer) made of a conductive material such as aluminum and provided on the outer periphery of a grounded substrate 2a. An image carrier 2 having 2b, a write head unit 3 for writing an electrostatic latent image on the dielectric layer 2b of the image carrier 2, a flexible substrate 4 for supporting the write head unit 3, A developing device 5 having a developing roller 5a that is a developer carrying member, a developer layer thickness regulating member 5b that regulates a layer thickness of the developer (toner) on the developing roller 5a, and a transfer device 6 having a transfer roller 6a. At least.

As shown in FIG. 2, in the dielectric layer 2b of the image carrier 2, an independent floating electrode portion 2c to which an electrostatic latent image is written faces radially inward (depth direction) from the surface of the dielectric layer 2b and It is provided over the entire circumference of the dielectric layer 2b. The independent floating electrode portion 2c has a large number of conductive fine particles 2c ₁ dispersed electrically independently from each other in the dielectric layer 2b. Part of the fine particles 2c ₁ of these conductive fine particles 2c ₁ are arranged in a sea-island structure exposed on the surface of the dielectric layer 2b, thereby constituting an independent floating electrode. In that case, at least a part of the conductive fine particle 2c ₁ is positioned at the circumference at any position in the radial direction of the dielectric layer 2b. Therefore, as will be described later, even if the dielectric layer 2b and the conductive fine particles 2c ₁ exposed on the surface are cut and the previously cut conductive fine particles 2c ₁ disappear, the conductive fine particles 2c ₁ Part of the fine particles 2c ₁ are always exposed on the surface.

The material of the dielectric layer 2b includes polycarbonate resin, acrylic resin, styrene resin, polyester resin, polyarylate resin, polysulfone, polyphenylene oxide, epoxy resin, polyurethane resin, alkyd resin, phosphazene resin, polyamide resin, vinyl chloride-acetic acid A material having characteristics as a dielectric material such as vinyl copolymer resin and silicone resin is used.
As a material of the conductive fine particles _{2c 1, Cu, Al, Ni} , Ag, C, Mo, fine metal particles such as W is used.

  The substrate 4 that supports the writing head unit 3 has a high electrical insulation property such as FPC (abbreviation of Flexible Print Circuit, hereinafter referred to as FPC) or PET (abbreviation of polyethylene terephthalate, hereinafter referred to as PET), and is relatively. It is composed of a flexible material that is soft and elastic. And this base material 4 is attached by the cantilever which the one end part is fixed to the fixing | fixed part 8, and the other end is a free end. The fixing portion 8 is rotatably supported by the image forming apparatus main body and is rotationally driven by the writing head portion driving means 7.

The write head unit 3 has a predetermined number of write electrodes 3a made of a metal such as Cu, for example, and these write electrodes 3a are aligned with the free end of the substrate 4 in the main scanning direction. Arranged and supported. In the image forming apparatus 1 of this example, different metals are used for the conductive fine particles 2c ₁ and the writing electrode 3a.
Each writing electrode 3a is lightly pressed onto the dielectric layer 2b of the image carrier 2 by a weak elastic restoring force due to the bending of the base material 4, and is brought into surface contact with each other, so that the independent floating electrode in the dielectric layer 2b is obtained. The electrostatic latent image is written on the independent floating electrode made of the conductive fine particles 2c ₁ exposed on the surface of the portion 2c.

  Further, as shown in FIG. 1, a write head drive means 7 such as a motor for rotating the fixed portion 8 is provided. As shown in FIG. 3, the write head drive means 7 is connected to the control device 10. The control device 10 uses a central processing unit (CPU) for image formation of the image forming apparatus 1, and performs a drive motor 11 for rotating the image carrier 2 and an image forming operation, for example, image formation. An image forming operation means 12 such as an image forming operation key provided on the operation panel of the apparatus is also connected to the control device 10. Note that, as the control device 12, a dedicated control device for controlling the rotation of the fixing unit 8 may be used instead of the CPU for image formation of the image forming apparatus 1.

  Then, when the image forming operation signal from the image forming operation means 12 is not input, the control device 10 determines that the image forming operation is not performed and the writing is performed as shown in FIG. The write head unit driving means 7 is driven and controlled so that the write electrode 3a of the insertion head unit 3 is set at a position away from the surface of the independent floating electrode unit 2c of the image carrier 2. Further, when the image forming operation signal is input from the image forming operation unit 12, the control device 10 determines that the image forming is performed, and first, as shown in FIG. The write head drive means 7 is driven and controlled so that the write electrode 3 a of the write head 3 is in contact with the surface of the independent floating electrode 2 c of the image carrier 2. The contact control device 10 rotates the image carrier drive motor 11 before and after the contact of the writing electrode 3a with the independent floating electrode portion 2c. Thereafter, latent image writing by the writing electrode 3a is started and a series of image forming operations are performed. Note that the control device 10 determines when an image is formed or when a non-image is formed, instead of determining when an image is formed or when a non-image is formed, depending on whether an image forming operation signal is input from the image forming operation unit 12. It goes without saying that other methods can be used as long as they can.

In a series of image forming operations by the image forming apparatus 1, the image carrier 2 rotates clockwise as shown in FIGS. 1 and 2, and the dielectric layer 2b of the image carrier 2 is brought into a uniform charge state. after write writing voltage is applied via the driver IC9 of writing electrode 3a to the electrode 3a, mainly, in contact with the image bearing member 2 of the conductive book of particles 2c ₁ and the write head portion 3 to each other The electrostatic latent image is written on the independent floating electrode portion 2c in the dielectric layer 2b of the image carrier 2 by charge transfer (for example, charge injection) with the embedded electrode 3a. Then, the electrostatic latent image on the independent floating electrode portion 2c of the image carrier 2 was conveyed by the developing roller 5a whose layer thickness was regulated by the developer layer thickness regulating member 5b of the developing device 5 and rotated in the clockwise direction. Developed with developer. The developer image on the image carrier 2 is transferred to a recording medium (not shown) such as paper by a transfer roller 6a to which a transfer voltage is applied and rotates clockwise.

The metal used for the conductive fine particles 2c ₁ of the image carrier 2 and the metal used for the writing electrode 3a are different from each other. The conductive fine particles 2c ₁ and the writing electrode 3a are different in image formation. At times, they are in contact with each other, and are kept separated from each other at the time of non-image formation. As a result, the contact time between the conductive fine particles 2c ₁ and the write electrode 3a is shortened, and the occurrence of the above-described contact corrosion due to the contact of different metals can be suppressed to the minimum. As a result, since the surfaces of the conductive fine particles 2c ₁ and the write electrode 3a of the independent floating electrode portion 2c are both surfaces without the aforementioned impurity film, the contact resistance is relatively small. Therefore, as shown in FIG. 5B, the responsiveness of the drum surface potential B (dotted line) of the conductive fine particles 2c ₁ to the head applied voltage A (solid line) applied to the write electrode 3a is good. .
Thus, even if the conductive fine particles 2c ₁ of the image carrier 2 and the writing electrode 3a are made of different metals, contact corrosion hardly occurs at the interface between them, and a stable electrostatic latent image is formed. be able to. As a result, good image formation can be performed over a long period of time.

Further, since the conductive fine particles 2c ₁ are at least partly located on the circumference at any position in the radial direction of the dielectric layer 2b, the conductive fine particles 2c ₁ and the write electrode 3a Even if contact corrosion occurs at the contact portion, the surface of the new conductive fine particle 2c ₁ can be exposed by scraping the surface layer of the independent floating electrode portion 2c of the image carrier as shown in FIG. Thereby, even if contact corrosion occurs, formation failure of an electrostatic latent image can be prevented, and a high-quality image can be obtained reliably.

  The image forming apparatus and the image forming method of the present invention can be suitably used for an image forming apparatus and an image forming method for forming an electrostatic latent image on an image carrier such as an electrophotographic, electrostatic copying machine, printer, or facsimile. it can.

1 is a diagram schematically illustrating a best mode for carrying out an image forming apparatus of the present invention. FIG. 2 is a partially enlarged view showing a part of the vicinity of a contact part of the writing head part shown in FIG. FIG. 6 is a block diagram for controlling the operation of the write head unit. FIG. 3 is a partially enlarged view similar to FIG. 2, showing a state in which the image carrier has been scraped by a predetermined amount. (A) is a diagram schematically showing the contact portion between the image carrier 2 and the writing electrode 3a when no oxide film is formed, and (b) shows the rise of the surface potential of the conductive fine particles in this case. FIG. (A) is a diagram schematically showing the contact portion between the image carrier 2 and the writing electrode 3a when an oxide film is formed, and (b) shows the rise of the surface potential of the conductive fine particles in this case. FIG.

Explanation of symbols

1 ... image forming apparatus, 2 ... image bearing member, 2a ... substrate, 2b ... dielectric layer, 2c ... independent floating electrode portion, 2c ₁ ... conductive particles 3 ... write head, 3a ... writing electrodes, DESCRIPTION OF SYMBOLS 4 ... Base material, 5 ... Developing device, 5a ... Developing roller, 6 ... Transfer device, 6a ... Transfer roller, 7 ... Writing head part drive means, 8 ... Fixed part, 9 ... Driver IC, 10 ... Control device (CPU) 11... Image carrier driving motor, 12.

Claims (3)

An image carrier having an independent floating electrode part in which a large number of conductive fine particles are electrically dispersed in a dielectric layer and a part of the conductive fine particles are exposed on the surface; In an image forming apparatus comprising at least a write head unit having a write electrode for writing an electrostatic latent image in contact with conductive fine particles exposed on the surface,
The metal used for the conductive fine particles and the metal used for the write electrode are different from each other,
Control means for providing the write electrode so as to be in contact with and separated from the independent floating electrode portion, and holding the write electrode in a state separated from the independent floating electrode portion when non-image formation is not performed. An image forming apparatus comprising the image forming apparatus. The independent floating electrode portion is provided inward in the radial direction (depth direction) from the surface of the dielectric layer and over the entire circumference of the dielectric layer, and the circumference at any position in the radial direction of the dielectric layer. The image forming apparatus according to claim 1, wherein a part of the conductive fine particles is located. The write electrode of the write head unit is applied to the conductive fine particles exposed on the surface of the independent floating electrode part in which a large number of conductive fine particles are dispersed electrically and independently in the dielectric layer of the image carrier. In an image forming method of forming an image by writing an electrostatic latent image in contact,
The conductive fine particles and the write electrode use different metals from each other,
During non-image formation in which image formation is not performed, the write electrode is held in a state of being separated from the independent floating electrode portion, and at the time of image formation, the write electrode is brought into contact with the independent floating electrode portion, An image forming method comprising: forming an image by writing an electrostatic latent image by bringing the writing electrode into contact with conductive fine particles exposed on a surface of the independent floating electrode portion.

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