Image forming apparatus and image forming method

#The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus and an image forming method and more particularly to an image forming apparatus of the type causing colored particles to fly for forming an image on a paper sheet or similar recording medium.

#An electrophotographic process has been extensively applied to a copier, printer, facsimile apparatus or similar image forming apparatus. Typical of the electrophotographic process is a Carlson method (xerography). However, the problem with the Carlson method is that it needs a charging step, an exposing step, a developing step, an image transferring step, a fixing step and a cleaning step, i.e., six consecutive steps in total. Such a process is not practicable without resorting to a sophisticated, bulky construction. Japanese Patent 2,897,705 discloses a simple electrophotographic process that is a substitute for the Carlson method. The electrophotographic process taught in this document does not charge a photoconductive element and thereby reduces the number of steps (Prior Art 1 hereinafter).

#Japanese Patent No. 1,876,764 teaches an electrophotographic recording method directed toward a higher toner transfer speed and the obviation of fog (Prior Art 2 hereinafter). Prior Art 2 includes a toner carrying member made up of a transparent base, a transparent electrode, and a carrier transport layer. Toner formed of a carrier generating material is charged by friction and caused to deposit on the surface of the toner carrying member. Light selectively scans the toner via the transparent base of the toner carrying member in order to invert the polarity of the toner. A transfer electrode is positioned behind a paper sheet or similar recording medium and biased to negative polarity. The transfer electrode causes the toner inverted in polarity to electrostatically move toward the paper sheet.

#The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:

#FIG. 1 is a section showing a conventional image forming method;

#FIG. 2 is a section showing a first embodiment of the image forming apparatus in accordance with the present invention, particular a particle conveying body included therein;

#To better understand the present invention, brief reference will be made to the image recording method taught in accordance with Prior Art 1 stated earlier, shown in FIG. 1. As shown, a photoconductor unit 110 is included in a recording section and faces a paper sheet or similar recording medium, not shown, via a preselected gap. The photoconductor unit 110 includes a base 101 made of glass or similar light-transmitting material. A conductive, light-transmitting layer 102 and a photoconductive layer 109 are sequentially formed on the base 101. A porous, insulative screen 104 is formed on the photoconductive layer 109 and has a screen electrode or electrode layer 105 formed on its top.

#Before a recording medium faces the photoconductor unit 110, conductive, colored particles 106 that are charged to negative polarity by induction charging fill the pores of the insulative screen 110. A facing electrode, not shown, is positioned behind the recording medium. An electric field is formed between the facing electrode and the conductive layer 102 and causes positively charged particles to fly toward the recording medium. During recording, an LED (Light Emitting Diode) array, for example, selectively emits light 107 in accordance with an image signal. The light 107 is incident to the photoconductive layer 109 via the base 101 and conductive layer 102.

#The light 107 lowers the resistance of the photoconductive layer 109. As a result, the charge of the negatively charged particles 106 flows into the photoconductive layer 109, i.e., the particles 106 looses their charge. An electric field is formed between the conductive layer 102 and the screen electrodes 105. This electric field, coupled with the electric field formed between the conductive layer 102 and the facing electrode, charges the particles 106 close to the photoconductive layer 109 to negative polarity and charges the particles 106 remote from the same to positive polarity. The particles 106 with positive charge fly toward the facing electrode due to the electric field between the conductive layer 102 and the facing electrode. The particles 106 deposited on the recording medium are fixed thereon by a fixing process.