Electrophotographic products such as copying machines and laser beam printers make use of an electrically charged photosensitive drum to generate images. The conventional corona discharge method employed in such machines involves the application of voltages ranging from 5 to 10 kV, which creates ozone that can result in an unpleasant odor and may have adverse effects on skin. Remedying this problem required the introduction of an ozone filter, coupled with an airflow structure that reliably directs ozone to the filter.

Canon, however, adopted a new approach through the development of an innovative roller charging system, which charges the photosensitive drum by applying a voltage generated through the superposing of an AC voltage over a DC voltage to a conductive roller. Compared to the corona discharge method, this new method reduces ozone generation to about 1/1000 or less, and voltage to about one-fifth of previous levels.

Overview of ozone-free electrical charging

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