Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
1998-09-03
2001-02-06
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C399S227000, C399S233000
Reexamination Certificate
active
06184909
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a recording apparatus for recording data after a density gradation process for every pixel, and in particular relates to a recording apparatus which develops a latent image including a halftone with a high degree of loyalty by using liquid developer so as to obtain an image of high quality with the use of microparticle toner.
For example, Japanese Laid-Open Patent No. H7-334004 discloses a conventional apparatus in which wet-type liquid developer is circulated through a feed pipe and a return pipe so as to prevent build-up and deposition of the liquid developer in order to prevent the tone from varying through the development and to effect an agitating function.
Further, Japanese Laid-Open Patent No. H5-35117 discloses another conventional recording apparatus in which a developer bottle is shifted left and right in order to agitate developer having a high density.
A conventional wet-type developing device using electrostatic liquid developer has been well-known as is disclosed in “Basic and Applied Electrophotographic Technology” edited by Electrophotographing Association, pages 288 to 277, issued in 1998 by Corona Co.
That is, there have been well-known liquid type developing apparatuses having a dish development system in which an image bearing medium carrying a latent image is dipped in liquid developer filled in a developing dish for developing the latent image, a roller development system in which a developing roller formed on its outer peripheral surface with a thin film of electrostatic liquid developer is approached by an image bearing medium carrying a latent image for developing the latent image, and a slit development system in which an image bearing medium is sucked by grooves formed in opposite end parts of a developing part and connected to a vacuum source, and liquid developer is drawn from a slit formed in the center part of an electrode so as to be circulated between the electrode and the image bearing medium for developing a latent image thereon when negative pressure is effected in the developing part. The above-mentioned wet-type developing apparatus requires in general a liquid developer circulating system for feeding and retrieving liquid developer, causing a disadvantage in that the developing device using liquid developer becomes large-sized and complicated.
Meanwhile, there has been known a rotary developing apparatus using dry type developer, in which a plurality of developing units circumferentially arranged and carried are rotated cicumeferentially, and the circumferential rotation of each of the developing units is stopped at a developing position where the developing unit faces an image bearing medium so that the developing unit located at the developing position develops a latent image carried on the image bearing medium.
For example, Japanese Laid-open Patent No. H8-305119 discloses a rotary type developing device having such a feature that there is in particular provided means for rotating a developer carrier in a developing unit at a position other than a developing position.
In the above-mentioned conventional technologies, a toner liquid developer having a weight rate of less than 1% can easily be circulated by using a pump so as to possibly redisperse the toner. However, the higher the toner density, the more the circulation would become difficult, and the toner having deposited, can hardly be drawn up even though it is sucked up by a pump using a pipe. Further, if the toner density is low, there is offered such a problem that a fine image can not be obtained.
Meanwhile, in the case of liquid developer having a high density, which require oscillating a developer bottle left and right, the redispersion of toner which have once deposited onto the bottom of the bottle is difficult, and acceleration during movement is required for enhancing the effect of the redispersion while it is moved left and right. This causes a problem of requiring a high power drive source for vibrating and moving the apparatus.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a recording apparatus incorporating a liquid developing unit using a high density liquid developer and being capable of printing a highly fine color image.
To the end according to the present invention, cartridges containing therein liquid developers having a high density of 5 to 35%, and a developing roller are arranged on a rotary base, and color developing units are positioned by rotating the rotary base for developing while supplying and recovering liquid developer.
In particular, after a long stand-by time or a long interruption, the rotary base is rotated by at least a half-turn just before initiation of recording.
Accordingly, by rotating a rotary body attached thereto four color developing units using high density liquid developers containing 5 to 35 wt. % of toner just before recording, the toner which has even precipitated and agglutinated in the liquid developers, depositing on the bottoms of the cartridges, can be redispersed in the liquid developers since the cartridges become once upside down, that is, the bottom surfaces of the cartridges are once turned into the top surfaces through the rotation by a half-turn, thereby it is possible to satisfactorily disperse the toner in the liquid developer during recording. Simultaneously, a predetermined quantity of liquid developer can be supplied to the developing roller part while the liquid developer remaining on the developing roller part can be recovered.
Further, developing parts and cleaning parts are provided outside of but adjacent to a circumscribed circle depicted by the color developing units during rotation while the color developing units are stopped, as necessary, at the positions of the developing parts and the cleaning parts. In the case of the four color developing units arranged at angular intervals of 90 deg. on the rotary base, each of the color developing units can be shifted from the associated developing part to the associated cleaning part through the rotation by a quarter turn, and further, the recovery of the liquid developer and the closing of developer tanks are carried out in relation to the rotating positions of the developing units. With this arrangement, the developing can be reliably made even with high density liquid developer, and by rotating the rotary base, the developing, the cleaning and the recovery of liquid developer can be selectively made, thereby it is possible to provide an inexpensive developing device.
By the way, in the case of a developing device in which no liquid developer is circulated, and which has no density control mechanism, it is necessary to set a toner density in accordance with an averaged printing rate. The ratio between a toner adhering area and a printing area on a recording medium, which corresponding to the averaged printing rate, is estimated to 3 to 30% in the case of printing a photographic tone image, the density of the liquid developer can be set such that the degree of solvent consumption in the liquid developer is substantially equal to the degree of toner consumption with this printing rate.
REFERENCES:
patent: 4728987 (1988-03-01), Diola et al.
patent: 5832334 (1998-11-01), Corn et al.
Kamio Keiji
Matsumoto Shogo
Matsuno Jun-ichi
Mori Akira
Suzuki Mitsuo
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Pendegrass Joan
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