Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-12-19
2001-07-10
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06257708
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to direct electrostatic printing methods in which charged toner particles are transported in accordance with an image information from a particle source to an image transfer member to form a toner image which is subsequently transferred onto an information carrier.
BACKGROUND TO THE INVENTION
According to a direct electrostatic printing method, such as that disclosed in U.S. Pat. No. 5,036,341, a background electric field is produced between a developer sleeve and a back electrode to enable the transport of charged toner particles therebetween. A printhead structure, such as an electrode matrix provided with a plurality of selectable apertures, is interposed in the background electric field and connected to a control unit which converts an image information into a pattern of electrostatic control fields which selectively open or close the apertures, thereby permitting or restricting the transport of toner particles from the developer sleeve. The modulated stream of toner particles allowed to pass through opened apertures impinges upon an information carrier, such as paper, conveyed between the printhead structure and the back electrode, to form a visible image.
According to such a method, each single aperture is utilized to address a specific dot position of the image in a transverse direction, i.e. perpendicular to paper motion. Thus, the transversal print addressability is limited by the density of apertures through the printhead structure. For instance, a print addressability of 300 dpi requires a printhead structure having 300 apertures per inch in a transversal direction.
A new concept of direct electrostatic printing, hereinafter referred to as dot deflection control (DDC), was introduced in U.S. patent application Ser. No. 08/621,074. According to the DDC method each single aperture is used to address several dot positions on an information carrier by controlling not only the transport of toner particles through the aperture, but also their transport trajectory toward a paper, and thereby the location of the obtained dot. The DDC method increases the print addressability without requiring a larger number of apertures in the printhead structure. This is achieved by providing the printhead structure with at least two sets of deflection electrodes connected to variable deflection voltages which, during each print cycle, sequentially modify the symmetry of the electrostatic control fields to deflect the modulated stream of toner particles in predetermined deflection directions.
For instance, a DDC method performing three deflection steps per print cycle, provides a print addressability of 600 dpi utilizing a printhead structure having 200 apertures per inch.
An improved DDC iaethodr disclosed in U.S. patent application Ser. No. 08/759,481, provides a simultaneous dot size and dot position control. This later method utilizes the deflection electrodes to influence the convergence of the modulated stream of toner particles thus controlling the dot size. According to the method, each aperture is surrounded by two deflection electrodes connected to a respective deflection voltage D
1
, D
2
, such that the electrode field generated by the control electrodes remains substantially symmetrical as long as both deflection voltages D
1
, D
2
have the same amplitude. The amplitudes of D
1
and D
2
are modulated to apply converging forces on toner to obtain smaller dots. The dot position is simultaneously controlled by modulating the amplitude difference between D
1
and D
2
. Utilizing this improved method enables 60 &mgr;m dots to be obtained utilizing 160 &mgr;m apertures.
It can be considered a drawback of current DDC methods that the properties of the information carrier, e.g. paper properties, can influence the accuracy of the dot size and dot position control. For instance, when printing directly onto paper, the deflection, and thus the dot positions become dependent on paper thickness, conductivity, triboelectric charge concentration, humidity etc. Therefore, there seems to still exist a need to improve the current DDC method.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of and device for improving the accuracy of dot deflection control in direct electrostatic printing methods.
A further object of the present invention is to provide a method of direct electrostatic printing which is substantially unaffected by the physical properties of the information carrier onto which an image is to be recorded.
Still a further object of the present invention is to provide a method of and a device for reducing scattering in direct electrostatic printing methods.
Yet a further object of the present invention is to provide a method of and a device for preventing clogging of passages through which toner particles pass in direct electrostatic printing methods.
Another object of the present invention is to provide a method of and device for reducing or eliminating the influence of the electrostatic field used for toner particle transport on anything other than the intended toner particles in direct electrostatic printing methods.
Still another object of the present invention is to provide a method of and a device for trajecting toner particles to predetermined positions, in view of an image which is to be recorded, substantially unaffected by a wide range of environmental conditions and unaffected by the physical properties of the information carrier onto which an image is to be recorded.
Yet another object of the present invention is to provide a method of and a device for trajecting toner particles to predetermined positions, in view of an image which is to be recorded, substantially unaffected of uneven feed due to speed variations caused for example by mechanical imperfections.
Said objects are achieved according to the invention by providing an intermediate image receiving medium whose properties do not alter the accuracy of the dot deflection control, in order to thereby first form a toner image on the intermediate image receiving medium and thereafter transfer that image to an information carrier.
Said objects are also achieved according to the invention by an image recording device and method for recording an image onto an information carrier. The image recording device comprises a pigment particle source, a voltage source, a printhead structure, and an intermediate image receiving member. The pigment particle source provides pigment particles. The intermediate image receiving member and the printhead structure move relative to each other during recording. The intermediate image receiving member has a first face and a second face. The printhead structure is placed in between the pigment particle source and the first face of the intermediate image receiving member. The voltage source is connected to the pigment particle source and the back electrode thereby creating an electrical field for transport of pigment particles from the pigment particle source toward the first face of the intermediate image receiving member. The printhead structure includes control electrodes to thereby be able to selectively open or close passages/apertures through the printhead structure to permit or restrict the transport of pigment particles to thereby enable the formation of a pigment image on the first face of the intermediate image receiving member, which pigment image is subsequently transferred to an information carrier. Where according to the method and device of the invention the first face of the intermediate image receiving member is substantially evenly coated with a layer of bouncing reduction agent thus providing a surface on the first face of the intermediate image receiving member that the pigment particles transported through the print head structure substantially adhere to substantially without bouncing.
Suitably the bouncing reduction agent is a liquid having adhesion properties suitable for the adhesion of pigment particles to the first face of the intermediate image receiving member and also suitably
Array Printers AB
Barlow John
Gordon Raquel Yvette
Knobbe Martens Olson & Bear LLP
LandOfFree
Direct electrostatic printing apparatus and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Direct electrostatic printing apparatus and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Direct electrostatic printing apparatus and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469095