Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-02-21
2004-02-24
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108700, C430S110400, C430S111410, C430S125320, C430S126200, C430S108600
Reexamination Certificate
active
06696211
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a developer used in image forming apparatus, such as electrophotographic apparatus, electrostatic recording apparatus, and magnetic recording apparatus, an image forming method using the developer, and a process-cartridge incorporating the developer. More specifically, the present invention relates to a developer used in image forming apparatus, such as copying machines, printers, facsimile apparatus, and plotters, wherein a toner image is first formed on an image-bearing member and a recording medium such as a transfer(-receiving) material; an image forming method using the developer and the image forming apparatus; and a process-cartridge including the developer.
Hitherto, image forming methods, such as electrophotography, electrostatic recording, magnetic recording, and toner jetting have been known. In the electrophotography, for example, an electrical latent image is formed on a latent image-bearing member which is generally a photosensitive member comprising a photoconductor material by various means, the electrostatic image is developed with a toner to form a visible toner image, and the toner image is, after being transferred onto a recording medium, such as paper, as desired, followed by fixing of the toner image onto the recording medium under application of heat, pressure or heat and pressure to form a fixed image.
Various methods are known, regarding the step of forming a visible image with a toner. For example, as methods for visualizing electrical latent images, there have been known, e.g., the cascade developing method, the pressure developing method, and the magnetic brush developing method using a two-component developer comprising a carrier and a toner. Further, there are also known a non-contact mono-component developing method wherein a toner carried on a toner-carrying member free from contact with a latent image-bearing member is caused to jump onto the latent image-bearing member; a magnetic mono-component developing method wherein a magnetic toner carried on a rotating sleeve containing therein a magnetic field generating means including magnetic poles is caused to jump between the sleeve and a photosensitive member and also a contact mono-component developing method; wherein a toner carried on a toner-carrying member in pressure contact with a latent image-bearing member is transferred under an electric field.
As the developers for visualizing latent images, there are known a two-component(-type) developer comprising a (particulate) carrier and a toner; a mono-component type developer (inclusive of a magnetic toner and a non-magnetic toner) not necessitating a (particulate) carrier. The toner is charged triboelectrically principally owing to friction between the carrier and the toner in the two-component developer, and principally owing to friction between the toner and a charging member, such as a developing sleeve in the mono-component developer.
Further, it has been proposed and widely practiced to use inorganic fine powder as an additive externally added to toner particles in order to improve the flowability or/and triboelectrification characteristic of the toner in both the two-component developer and the mono-component developer.
For example, Japanese Laid-Open Patent Application (JP-A) 5-66608 and JP-A 4-9860 have disclosed a method of adding inorganic fine powder which has been hydrophobized (i.e., hydrophobicity-imparted) and optionally further treated with silicone oil, to toner particles. Further, JP-A 61-249059, JP-A 4-264453 and JP-A 5-346682 have disclosed a method of adding both hydrophobized inorganic fine powder and inorganic fine powder treated with silicone oil.
Further, it has been also proposed to add electroconductive fine powder as an external additive to a developer. For example, it has been widely known to use carbon black as an example of electroconductive fine powder in a form of being attached or stuck onto the surfaces of toner particles, for the purpose of imparting electroconductivity to the toner, or for suppressing an excessive charge of the toner to provide a uniform triboelectric charge distribution. Further, JP-A 57-151952, JP-A 59-168458 and JP-A 60-69660 have disclosed to use electroconductive fine powders, such as tin oxide, zinc oxide and titanium oxide as external additives to high-resistivity magnetic toner particles. JP-A 56-142540 has proposed a developer formed by externally adding electroconductive magnetic particles of, e.g., iron oxide, iron powder or ferrite, to high-resistivity magnetic toner particles so as to satisfy developing performance and transferability by promoting charge induction to the magnetic toner particles with the electroconductive magnetic particles. Further, JP-A 61-275864, JP-A 62-258472, JP-A 61-141452, and JP-A 2-120865 have disclosed the addition of graphite, magnetite, polypyrrole conductor particles and polyaniline conductor particles, respectively, to the toner.
Various methods are also known as methods of forming latent images on image bearing members, such as an electrophotographic photosensitive member and an electrostatic recording dielectric member. In the electrophotography, for example, it is a general practice to uniformly charge a photosensitive member comprising a photoconductor as a latent image-bearing member in a desired polarity and at desired potential, and then subject the photosensitive member to imagewise pattern exposure to form an electrical latent image.
Hitherto, a corona charger (or corona discharger) has been generally used as a charging device for uniformly charging (including a case for charge removal) a latent image-baring member to desired polarity and potential.
A corona charger is a non-contact-type charging device comprising a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode while leaving a discharge opening, and the device is disposed in no contact with an image-bearing member as a member to be charged so that the discharge opening is directed to the image-bearing member for a prescribed charging operation wherein a high voltage is applied between the discharge electrode and the shield electrode to cause a discharge current (corona shower), to which the image-bearing member surface is exposed to be charged to a prescribed potential.
In recent years, a contact charging device has been proposed and commercialized as a charging device for a member to be charged such as a latent image-bearing member because of advantages, such as low ozone-generating characteristic and a lower power consumption, than the corona charging device.
A contact charging device is a device comprising an electroconductive charging member (which may also be called a contact charging member or a contact charger) in the form of a roller (charging roller), a fur brush, a magnetic brush or a blade, disposed in contact with a member-to-be-charged, such as an image-bearing member, so that the contact charging member is supplied with a prescribed charging bias voltage to charge the member-to-be-charged to prescribed polarity and potential.
The charging mechanism (or principle) during the contact charging may include (1) discharge (charging) mechanism and (2) direct injection charging mechanism, and may be classified depending on which of these mechanism is predominant.
(1) Discharge Charging Mechanism in the Contact Charging
This is a mechanism wherein a member is charged by a discharge phenomenon occurring at a minute gap between the member and a contact charging member. As a certain discharge threshold is present, it is necessary to apply to the contact charging member a voltage which is larger than a prescribed potential to be provided to the member-to-be-charged. Some discharge product occurs wile the amount thereof is remarkably less than in a corona charger, and active ions, such as ozone, occur though the amount thereof is small.
(2) Direct Injection Charging Mechanism in the Contact Charging
This is a mechanism wherein a member surface is charged wit
Tanikawa Hirohide
Yoshida Satoshi
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