Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-08-19
2001-11-27
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06322199
ABSTRACT:
RELATED APPLICATION
This application is based on Japanese Patent Application No.10-232755, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. [Field of the Invention]
The present invention relates to an apparatus for recording images on a recording sheet, such as paper, by allowing recording particles to jump and directly attach to the recording sheet.
2. [Description of the Related Art]
U.S. Pat. No. 5,477,250, issued on Dec. 19, 1995, discloses a recording apparatus. This recording apparatus comprises a cylindrical toner retaining member, which is rotatable, for retaining charged toner particles on its outer peripheral surface, and a back electrode spaced from the toner retaining member. The back electrode is electrically connected to a power source so that an electric field is formed to attract the charged toner particles on the toner retaining member toward the back electrode. An insulating plate provided with a plurality of apertures, through which the toner particles can pass, is disposed between the toner retaining member and the back electrode. In addition, the insulating plate is provided with a ring-shaped electrode surrounding each of the apertures.
In the above-mentioned recording apparatus, when a signal corresponding to image data is applied to the electrode, the toner particles existing at a position on the toner retaining member, where is opposed to the electrode, jump into the corresponding aperture. After passing through this aperture, the toner particles attach to a recording sheet, and an image corresponding to the image data is recorded on the recording sheet.
In the above-mentioned recording apparatus, the toner particles disperse while jumping, and attach to the recording sheet, thereby forming a dot that is blurred in outline and has a low density. A recorded image obtained in this way is therefore blurred in outline and lacks sharpness.
In order to solve this problem, a method is available wherein a guard electrode surrounding the aperture is provided on the back electrode side of the insulating plate with respect to the ring-shaped electrode, and a voltage having the same polarity as that of the charged toner particles is applied to this guard electrode so that the group of the toner particles jumping inside the aperture is biased by electric repulsion force to converge inwardly in the radial direction. With this method, a dot that is sharp in outline and has a high density can be formed, and an image having high definition can be obtained.
In the case of the above-mentioned recording apparatus without the guard electrode, the density of an image to be recorded is apt to rise as the application time of the signal to be applied to the ring-shaped electrode is prolonged. Therefore, in the case of carrying out gradation representation by using this recording apparatus, the application time of the signal to be applied to the ring-shaped electrode is generally prolonged to raise the image density.
However, in the recording apparatus with the guard electrode, it was found that the image density rises once as the application time of the signal to be applied to the ring-shaped electrode is prolonged, but lowers after the application time goes beyond a certain time, depending on the voltage potential applied to the guard electrode, in some cases. In these cases, it is impossible to perform gradation control by using the method of simply prolonging the application time of the signal to be applied to the ring-shaped electrode to raise the image density.
SUMMARY OF THE INVENTION
Accordingly, one feature of the present invention is to provide a recording apparatus capable of performing proper gradation control depending on the voltage potential to be applied to the guard electrode thereof.
To provide this feature, among other features of the present invention, the direct recording apparatus of the present invention includes:
a retaining member for retaining charged recording particles;
a back electrode opposed to the retaining member to electrostatically attract the recording particles;
a PC board disposed between the retaining member and the back electrode so as to form a passage with the back electrode, through which a recording sheet passes, and provided with apertures having a diameter through which the toner particles can pass;
a first electrode disposed near each of the apertures in the PC board, to which a first voltage is applied in order to more strongly attract the toner particles retained on the retaining member toward the back electrode; and
a second electrode disposed near each of the apertures and nearer the back electrode side than the first electrode in the PC board, to which a second voltage is applied so that a group of toner particles passing through the aperture converges;
wherein gradation of an image to be recorded are controlled by adjusting the application time of the first voltage to be applied to the first electrode depending on the second voltage to be applied to the second electrode.
In accordance with this direct recording apparatus of the present invention, the gradations of the image to be recorded are controlled by adjusting the application time of the first voltage to be applied to the first electrode depending on the second voltage applied to the second electrode. Therefore, gradation representation can be carried out properly, even when the characteristic in the relationship between the image density and the application time of the voltage to be applied to the first electrode changes depending on the potential of the second electrode.
In the direct recording apparatus of the present invention, the second voltage to be applied to the second electrode may be set so that the density of the image to be formed rises monotonically, or rises monotonically once and then becomes substantially constant as the application time of the first voltage is prolonged. In this case, the second voltage potential should only be 0 (zero) or a potential having the polarity opposite to the polarity of the charged toner particles.
In accordance with this direct recording apparatus of the present invention, the second voltage to be applied to the second electrode is set so that the density of the image to be formed rises monotonically, or rises monotonically once and then becomes substantially constant as the application time of the first voltage is prolonged. Therefore, the application time of the voltage to be applied to the first electrode should only be prolonged in the case of desiring to raise the image density, just as the conventional recording apparatus having only the first electrode. As a result, gradation control can be simplified.
Furthermore, in the direct recording apparatus of the present invention, the gradation of the image to be recorded may be controlled by setting the second voltage to be applied to the second electrode so that the density of the image to be formed rises once and then lowers gently as the application time of the first voltage is prolonged, and by using the first voltage application time period of an area wherein the image density lowers gently.
In accordance with this direct recording apparatus of the present invention, the gradation of the image to be recorded is controlled by setting the second voltage to be applied to the second electrode so that the density of the image to be formed rises once and then lowers gently as the application time of the first voltage is prolonged, and by using the first voltage application time period of the area wherein the image density lowers gently. In this case, since the gradation control is carried out using the time period of the area wherein the relationship between the image density and the voltage application time changes gently, the gradation can be produced more easily, and stable gradation control can be carried out accurately and easily.
REFERENCES:
patent: 5477250 (1995-12-01), Larson
patent: 5708464 (1998-01-01), Desie
patent: 6011944 (2000-01-01), Nilsson
patent: 6012801 (2000-01-01), Nilsson
patent: 6123418 (
Barlow John
Loper, Jr. Robert D
Minolta Co. , Ltd.
Morrison & Foerster / LLP
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