Electrophotographic developer having a specific voltage-dependant index
AssigneeMita Industrial Co., Ltd.
InventorsTakahiro Ishihara, Kiyofumi Nakatsu
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Abstract
The present invention provides an electrophotographic developer comprising a magnetic carrier and a toner, wherein a certain voltage-dependent index Y of the developer and a number proportion X (%) of a certain non-charged toner in the total toner have a relation satisfying the following formula (3): Y>3X/400+1 (3). This developer can certainly prevent blur of the image, such as forward flow or backward flow, while maintaining a high image density.
Claims6
An electrophotographic developer comprising a magnetic carrier and a toner, wherein a voltage-dependent index Y of the developer, obtained from resistance values R.sub.500 (.OMEGA..multidot.cm) and R.sub.2500 (.OMEGA..multidot.cm), which are measured at electric field strengths of 500 V/cm and 2500 V/cm, respectively, in accordance with the formula (1):
- Y=log (R.sub.500)/log (R.sub.2500) (1)
- and
- a number proportion X (%), in the total toner, of a non-charged toner which is within a region of the formula (2):
- Q/D<0.2 (2)
- in a charged amount distribution of toner defined by a charged amount Q (femt. C) and a particle size D(.mu.m) of the toner,
- have a relation satisfying the following formula (3):
- Y>3X/400+1 (3).
A developing method which comprises the steps of:
- forming an electrostatic latent image on the surface of a photoconductor;
- forming a toner image by contacting electrophotographic developer with the surface of the photoconductor to adhere toner contained in the developer to the electrostatic latent image, the electrophotographic developer including a magnetic carrier and a toner, wherein a voltage-dependent index Y of the developer, obtained from resistance values R.sub.500 (.OMEGA..multidot.cm) and R.sub.2500 (.OMEGA..multidot.cm), which are measured at electric field strengths of 500 V/cm and 2500 V/cm, respectively, in accordance with the formula (1):
- Y=log (R.sub.500)/log (R.sub.2500) (1)
- and
- a number proportion X (%), in the total toner, of a non-charged toner which is within a region of the formula (2):
- Q/D<0.2 (2)
- in a charged amount distribution of toner defined by a charged amount Q (femt. C) and a particle size D(.mu.m) of the toner,
- have a relation satisfying the following formula (3):
- Y>3X/400+1 (3);
- and
- transferring and fixing the toner image on a medium.
Dependencies are inferred from the claim text.