Developing method using (alternating electric field and) a developer of the field-dependent type and an apparatus therefor

A developing method for developing a latent image formed on an image bearing member, comprising:

• forming a layer of one-component magnetic developer on a developer supporting sleeve, wherein said layer has a thickness which is less than a clearance, at a developing station, between the image bearing member and the supporting sleeve, and wherein said developer is selected as having a volume resistivity which varies with variations in an electric field to which it is subjected;
• conveying said layer of one-component magnetic developer to the developing station by a relative rotation between said sleeve and a magnet enclosed in said sleeve;
• applying an alternating electric field between said developer layer supporting sleeve and said latent image bearing member at the developing station, whereby said alternating electric field causes transition of said developer from said developer supporting sleeve to both the image and non-image areas of said image bearing member and back transition of said developer from said image bearing member to said supporting sleeve;
• and
• reducing the intensity of said alternating electric field to thereby cause said back transition at least in the non-image areas and leave a developed image on said image bearing member.