Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-10-28
2001-06-26
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06250741
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an image forming apparatus which forms images on a recording medium by causing the developer to jump thereto and in particular relates to an image forming apparatus in which a sufficient amount of toner can be secured for neighboring gates, to thereby prevent degradation of the image.
(2) Description of the Related Art
Conventionally, as a technology to produce a visual image in accordance with an image signal onto a recording medium such as paper and the like, a configuration has been known in which an image is formed directly on the recording medium whilst the passage of charged particles jumping through gates is controlled.
For example, Japanese Patent Application Laid-Open Hei 6 No. 344, 588 discloses an image forming apparatus in which charged particles are placed in an electric field so that they will jump by electric force whilst the potential being applied to the control electrode, having a number of passage holes and located in the jump path, is being varied, to thereby make the charged particles adhere to the recording medium, thus forming a visual image on the recording medium, directly.
In image forming apparatuses of this type, represented by this prior art, either the jumping or non-jumping of toner is selected by controlling the electric field formed between the gates and the toner support, so that the toner is made to reach to the paper surface as a recording medium by a strong electric field generated by the opposing electrode.
However, in a configuration in which the control electrode is spaced about 100 &mgr;m for example, from the toner support, the area on the toner support from which toner has jumped is usually greater than the area of the gate provided on the control electrode. In other words, when the toner is caused to jump through a certain gate, toner jumps toward the gate from an area greater than that of the gate. Therefore, when taking into consideration a plurality of gates neighboring each other, there occur cases in which the area on the toner support opposing each gate may have an insufficiency of toner.
In this way, if a sufficient amount of toner cannot be secured for neighboring gates, dots having a predetermined diameter and a predetermined density cannot be formed, resultantly producing degradation of the image. In particular, when a monochrome solid image in which a certain density of a color is printed uniformly (hereinbelow referred to as ‘solid image’) needs to be formed, areas with a lower amount of toner will appear as white lines. On the other hand, when a multi-color image is taken into consideration, out of registration occurs so that it is impossible to reproduce the correct original colors.
If this problem is tried to be solved by increasing the amount of toner on the support, or by increasing the conveyed amount or the packing density of toner, it becomes more difficult to form a stable toner layer as the packing density or the conveyed amount is increased more and more because of the fact that the characteristic values of the toner cannot be controlled independently.
On the other hand, even if the voltage to be applied to the gates to cause jumping of the toner is increased or if the pulse width of the voltage to be applied is made greater toward the downstream side, this method is only effective within a markedly limited range of applications and is not practicable to a real situation, because such defects do not always occur at the specified gates.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an image forming apparatus which, when forming an image on a recording medium by controlling the passage of the charged toner particles jumping through gates, can secure a sufficient amount of toner for neighboring gates, to thereby solve the above problems and prevent degradation of the image.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the invention, an image forming apparatus at least comprises:
a supplying means having a developer support carrying a developer;
an opposing electrode disposed facing the developer support;
a high voltage power source supplying a high voltage to generate a potential difference between the developer support and the opposing electrode;
a control electrode comprising:
an insulative substrate disposed between the developer support and the opposing electrode;
a plurality of gates formed in the insulative substrate;
one or more electrode groups provided around the plural gates; and
a control means imparting plural levels of potential states to each electrode group of the control electrode, wherein the control means controls the passage of the developer through gates by applying the designated voltage to the electrode groups so as to form an image on the surface of a recording medium which is being conveyed over the opposing electrode, and is characterized in that, the control means controls the developer supported at the positions corresponding to the gates or in the vicinity thereof on the developer support such that only the developer facing the gates and residing in the topmost layer or in the vicinity thereof jumps through the gates.
In accordance with the second aspect of the invention, the image forming apparatus having the above first feature is characterized in that, when a developer existing at an area of the surface of the developer support is allowed to jump through neighboring plural number (m) of gates provided in the control electrode, the control means controls the jumping of the developer such that the amount of the developer jumping through each of the neighboring gates, qn(1≦n≦m) and the amount of the developer originally existing at the area, Q, satisfy the formula:
Q
≧
∑
n
=
1
m
qn
(
1
)
In accordance with the third aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the control means controls the application time of the voltage applied to the control electrode so as to apply the voltage to cause the developer supported on the developer support to jump through the plural gates.
In accordance with the fourth aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the control means controls the potential level of the voltage applied to the control electrode so as to apply the voltage for causing the developer supported on the developer support to jump through the plural gates.
In accordance with the fifth aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the control means applies the voltage for causing the developer supported on the developer support to jump through the plural gates based on the positional relationship between the developer support and the control electrode.
In accordance with the sixth aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the control means controls the electric field generated by the control electrode and the opposing electrode to apply the voltage for causing the developer supported on the developer support to jump through the plural gates.
In accordance with the seventh aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the control means, based on the shapes or sizes of the electrodes provided for the control electrode, applies the voltage for causing the developer supported on the developer support to jump through the plural gates.
In accordance with the eighth aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the control means comprises using at least one electrode capable of revealing a shielding characteristic and capable of being imparted a potential for controlling jumping or non-jumping of the developer through t
Nakano Nobuhiko
Wakahara Shirou
Barlow John
Conlin David G.
Dike Bronstein Roberts & Cushman IP Group
Gordon Raquel Yvette
Sharp Kabushiki Kaisha
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