Electricity: electrical systems and devices – Electric charging of objects or materials – By charged gas irradiation
Patent
1982-01-12
1984-02-07
Moose, Jr., Harry E.
Electricity: electrical systems and devices
Electric charging of objects or materials
By charged gas irradiation
361235, H01T 1900
Patent
active
044306865
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a charger for electrophotographic surfaces, to a method of charging such surfaces, and to the surfaces to be charged.
THE PRIOR ART
It is customary in electrophotography to have a surface on which is a layer of photosensitive material which is energized by first charging the surface and then light-bleeding the surface to produce an image and to then develop the surface with particles which are attracted to the surface according to the charge pattern.
This charging may be carried out prior to the actual exposure but it is necessary to then hold the charged surface in dark conditions to avoid bleeding away of the overall charge from the surface, but according to some systems the charging and exposure is carried out simultaneously, the latter being particularly required in what is termed a "one-shot" system, that is a system in which all colours are simultaneously developed as opposed to "step-wise" development according to which there is an exposure to a particular colour and a development of that colour and then an exposure to another colour and development in accordance with that colour and so on until a complete colour rendition exists.
In all of these methods however it is highly important to have an adequate form of charging of the surface and this has been one of the major problems in electrophotography in that the charging systems as known heretofore lack certain characteristics such as the maintaining of the surface in the condition where artifacts and spurious development is avoided which is caused extensively according to the present known systems due to the field from a corona puncturing the surface containing the photoconductor and thereby causing spots or absence of development according to whether a negative or positive development is used.
The problems associated with charging have been known for a long time and considerable prior art exists which teaches the problem of charge imperfection. Amongst the prior art documents is for instance the specification of Australian Letters Patent No. 462,918 Alan J. Brock, assigned to Repco Research Pty. Ltd., or the corresponding U.S. Pat. No. 3,942,079, in which various devices were suggested which resulted in a devious path of flow of the ions and electrons in a corona field to try and avoid ions reaching the sensitive area where puncturing and other problems are then caused. According to one form suggested the corona was formed between a point source and a remote electrode surface, and a stream of air was blown through the corona field on to an independent area which was to be charged, the basis being that the more acceptable components of the corona would be diverted by the airstream to charge the surface, the surface itself not receiving a direct charge.
A reference to three earlier patents number respectively Australian Letters Patent No. 478,069, Kenneth A. Metcalfe, Alwin S. Clements and Brian J. Horrocks, Australian Letters Patent No. 412,176, Ian E. Smith and Kenneth A. Metcalfe, and Australian Letters Patent No. 412,769 Kenneth Archibald Metcalfe, Frank Cecil Gillespie and Ian Edward Smith, all assigned to The Commonwealth of Australia, shows that it is well known that a corona contains bands of differing characteristic, and it was shown that there are bands of differing polarities in a corona outwardly from the centre of the corona. The above patent specifications teach that if certain precautions are taken it is possible to exclude harmful parts of the corona from the area being charged, but that was achieved at a considerable sacrifice to the simplicity of the mechanism by means of which the charging is carried out and only partly achieved the results aimed at.
One of the objects of the present invention is to provide an arrangement wherein a selected part of the corona only is available for charging a surface, a further object being to achieve this in a simple manner and with reliable operation, using charging wires extending across the area to be charged and having relative motion between the wires and area to
REFERENCES:
patent: 1207862 (1916-12-01), Chapman
patent: 3076092 (1963-01-01), Mott
patent: 3383624 (1968-05-01), Fiala
patent: 3581149 (1971-05-01), Tanaka et al.
patent: 3942079 (1976-03-01), Brock
Brock Alan J.
Clements Alwin S.
Horrocks Brian J.
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