Electrophotography – Image formation – Development
Reexamination Certificate
2002-09-18
2004-03-30
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
C492S028000
Reexamination Certificate
active
06714754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a developing apparatus for developing an electrostatic latent image formed on an image bearing member, by adhering thereto a non-magnetic one-component toner formed in thin layer on a developing roller to render the electrostatic latent image visible as a toner image; a developing roller for electrophotography used in the developing apparatus; and an apparatus unit and an image-forming apparatus which make use of such a developing roller.
2. Related Background Art
As developers used in electrophotographic developing apparatus for forming black-and-white images, toners endowed with magnetic properties and comprised of a single component (magnetic one-component toners) are conventionally used. Toners having magnetic properties, however, are not suited for color toners. Accordingly, in currently available electrophotographic developing apparatuses for forming color images, toners having no magnetic properties and comprised of a single component (non-magnetic one-component toners) are chiefly used.
Electrophotographic developing apparatus are constructed in a little different ways depending on the types of toners used. In particular, the way in which the toner is carried on the surface of a developing roller (developer-carrying member) differs depending on whether toners are magnetic or non-magnetic. More specifically, in the case when the magnetic one-component toners are used, a magnet is provided within the developing roller so that the toner can be carried, and transported, on the developing roller chiefly by the aid of a magnetic force. On the other hand, in the case when the non-magnetic one-component toners, having no magnetic properties and comprised of a single component, the toner must be carried, and transported, on the surface of the developing roller chiefly by the charging of toner itself, in place of the magnetic force, by the aid of image force which is Coulomb force acting between electric charges on the toner and those generated on the roller surface by the charging. Accordingly, in the case when the non-magnetic one-component toner is used, the magnet is no longer required but instead a means by which the charge quantity necessary for producing the image force is imparted to the toner is required to make the toner carried on the developing roller.
As a commonly available example of a conventional electrophotographic developing apparatus making use of a non-magnetic one-component toner, a contact type developing apparatus is shown in FIG.
4
.
As shown in
FIG. 4
, a developing apparatus
101
has a developing roller
102
which comes into contact with a photosensitive drum (image bearing member)
100
rotated in the direction of X in the drawing to perform development while being rotated in the direction of Y in the drawing, a toner feed roller
104
which is rotated in the direction of Z to feed a non-magnetic one-component toner T′ to the developing roller
102
, a developing blade (toner regulation means)
103
which regulates the quantity of the toner T′ to be coated on the developing roller
102
and the charge quantity thereof, and an agitating member
105
which agitates the toner T′ and also feeds it to the toner feed roller
104
. In a contact type developing apparatus in which the photosensitive drum
100
is a rigid body and which performs development while bringing this drum and the developing roller
102
into contact with each other in the zone shown by S in
FIG. 4
, the developing roller
102
may preferably be a roller having an elasticity so that the photosensitive drum
100
and the developing roller
102
can be in close contact without any gap between them. In a developing apparatus having a developing roller
102
formed of a resin which is an elastic material, a developing blade
103
made of a metal, having a good performance of charging by friction, may preferably be used in order to control the quantity of charge to the non-magnetic one-component toner T′.
In the developing apparatus
101
, a DC component development bias is applied to the developing roller
102
from a power source (not shown) to form a development potential at the developing zone lying between the photosensitive drum
100
and the developing roller
102
, whereby the toner T′ is caused to adhere to the surface of the photosensitive drum
100
. More specifically, the toner T′ having been charged adheres to the surface of the photosensitive drum
100
by the aid of Coulomb force, in a pattern corresponding to an electrostatic latent image formed on the surface of the photosensitive drum
100
by an exposure means (not shown), and the electrostatic latent image is rendered visible as a toner image to effect development. The toner having not participated in the development and remained on the surface of the developing roller
102
is taken off by the toner feed roller
104
and is collected in the developing apparatus
101
.
This developing apparatus
101
uses an insulating non-magnetic one-component toner basically. For this toner T′ to be carried and transported on the developing roller
102
, it is necessary to charge the toner T′ to produce the image force between the toner T′ and the developing roller
102
.
Now, a method of carrying the toner T′ on the developing roller
102
will be more detailed below. The toner feed roller
104
feeds the toner T′ to the developing roller
102
and also triboelectically charge the toner T′ at the contact nip zone between this developing roller
102
and the toner feed roller
104
. More specifically, as the toner feed roller
104
is rotated, the toner T′ is guided to the contact nip zone between the developing roller
102
and the toner feed roller
104
, and is charged by its friction with the developing roller
102
. As the result, the charge quantity necessary for producing the image force by the aid of which the toner T′ is carried on the developing roller
102
is imparted to the toner T′. In that course, the quantity of the toner T′ to be fed to the developing roller
102
is controlled by appropriately setting a difference in peripheral speed between the developing roller
102
and the toner feed roller
104
.
In an image-forming apparatus where the above conventional developing apparatus is used, a spherical toner T′ having a uniformly round particle shape has come to be used in order to make reproduced images have a high quality. More specifically, when the toner T′ has an uneven particle shape as in the case of pulverization toners conventionally used, particles having different shapes move in different ways at the time of development, and hence part of the toner T′ may scatter and may adhere to non-image areas (to cause a phenomenon of what is called fog). Use of spherical toner T′ can make such an inconvenience less occur.
The pulverization toners have so high a frictional force of toner itself that, even when the developing roller
102
is constituted of a silicone rubber single layer as shown in
FIG. 5
, the intended charge quantity can be obtained by its friction with such a silicone rubber surface layer. When, however, the toner T′ is made to have a spherical particle shape, the toner T′ itself has a low frictional force, so that the charge quantity to be obtained by the friction between the toner T′ and the silicone rubber surface layer may lower to make it difficult to obtain the intended charge quantity.
A toner T′ having a core/shell structure encapsulating a wax having a low melting temperature also has come to be used in order to reduce heat energy required in the step of permanently fixing toner images transferred to a recording medium surface (to achieve what is called energy-saved fixing).
A spherical toner T′ having such wax-encapsulated core/shell structure tends to deteriorate because of stress. Accordingly, it has become necessary to lower the hardness of the developing r
Nonomura Makoto
Ozeki Yukihiro
Sakaizawa Katsuhiro
Sekiguchi Manami
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grainger Quana M.
LandOfFree
Developing roller for electrophotography, developing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Developing roller for electrophotography, developing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Developing roller for electrophotography, developing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3237504