Method for non-impact printing utilizing a multiplexed matrix of controlled electrode units and device to perform method

#This invention relates to electrographical printing devices and, more particularly, to an improved direct electrostatic printing device utilizing a multiplexed matrix of control electrode units and a method of using the device to form a clear image at a reduced manufacturing cost.

#Of the various electrostatic printing techniques, the most familiar and widely utilized is that of xerography wherein latent electrostatic images formed on a charge retentive surface, such as a roller, are developed by a suitable toner material to render the images visible, the images being subsequently transferred to plain paper. This process is called an indirect or transfer processes because it first forms a visible image on an intermediate photoreceptor and then transfers that image to a paper surface.

#Another form of electrostatic printing is one that has come to be known as direct electrostatic printing (DEP). This form of printing differs from the aforementioned xerographic form in that pigmented particles (i.e. toner or developing material) are deposited directly onto a plain (i.e. not specially treated) information carrier to form a visible image. In general, this type of printing device uses electrostatic fields controlled by addressable electrodes for allowing passage of pigment particles through selected apertures in a printhead structure. A separate electrostatic field is provided to attract the pigment particles to an imaging substrate in image configuration.

#FIG. 1a is a schematic perspective view of a section through one embodiment of the invention.

#FIG. 1b is an enlargement of the matrix of control electrode units shown in FIG. 1a.

#FIG. 2 is a section through the print zone of FIG. 1.

#FIG. 1 shows a printer using a preferred embodiment of the invention. A container 1 for pigment particles 2, e.g., toner, also acts as a mounting surface for a control electrode matrix 3. A particle carrier, e.g., developing roller 4 within container 1 encloses a multiple magnet core 5 for attraction of pigment particles 2 toward developing roller 4.

#FIG. 1b shows the control electrode unit matrix 3 composed of an array of individual control electrode units 7 (delineated by a dashed circle), each surrounding an aperture 10, all arranged in a pattern of rows and columns. A substrate 6, such as an etched circuit board, supports the control electrode units 7 of control electrode matrix 3 and includes the apertures 10. Each control electrode unit 7 in the matrix 3 is composed of preferably four, but at least two electrode segments 11 connected through connection layers 12 (FIG. 4) beneath the visible top layer of the substrate 6.

#The electrode segments 11 are preferably constructed to circumscribe the aperture 10. Thus, in the embodiment shown, the segments 11 comprise quarter arcs with four segments spaced around and substantially surrounding the round apertures. The present invention, however, is not limited to round apertures nor to a specific number of segments. It is contemplated that the apertures 10 may take any number of geometric forms, although shapes having symmetry about a central axis are advantageous due to the uniform distribution of pigment therethrough. Likewise, there may be only two electrode segments 11 or more than four, wholly depending on design criteria.