Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2002-01-18
2004-04-06
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S140000, C430S110300
Reexamination Certificate
active
06717602
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image forming method as well as an image forming apparatus which carries out digital exposure, and an electrostatic latent image developing toner employed by the same.
BACKGROUND OF THE INVENTION
In recent years, high quality images have been increasingly demanded of image forming apparatuses such as copiers, printers, and the like which carry out digital exposure. Further, digital imaging has progressed in which electrostatic latent images are formed employing digital exposure and subsequently developed.
In common images, the ratio of an area, to which a toner is practically applied to carry out printing, is no more than 30 percent with respect to the entire image area. In digital exposure, being different from analogue exposure, it is easy to carry out exposure in which image information signals are reversed. Accordingly, from the viewpoint of print speed as well as minimization of the fatigue of a photoreceptor, it is advantageous that parts of an image are subjected to exposure and to reversal development. However, the reversal development is unstable as the development method, compared to the normal development, and as a result, it is difficult to carry out stable reversal development.
Prior to the development of a digital image, image exposure is carried out by controlling light intensity as well as the exposure time employing a semiconductor laser, LED, and the like, to form latent image dots. Accordingly, laser dots are composed of electrical potentials distributed in a normal distribution-like state. However, when the latent image dots formed in such a state are developed, it is required that the size and shape of dots in the original document are the same as those in the developing image. Specifically, when halftone, and the like, is printed, image quality is determined depending on the degree of matching the dots of the developing image to those of the original document.
When a common toner is employed, it is impossible to carry out stable development with high reproducibility for electric potential having a semi-normal distribution when such a distribution exists at development. The reasons for this are as follows. In commonly employed toner, which is prepared employing a pulverization method, fractures exist on its surface, and minute toner particles, which remain unclassified, exist, or minute toner particles, generated by stress in a development unit, remain. Accordingly, the distribution of electrostatic potential is widened, and toner having low electrostatic potential or toner components having reverse polarity, are adhered onto the edge portion of dots. Thus, it is impossible to form dots having uniform size as well as shape.
SUMMARY OF THE INVENTION
The present invention has been accomplished to provide a means to overcome the aforementioned problems.
Namely, it is an object of the present invention to provide an image forming method as well as an image forming apparatus which exhibits excellent dot reproducibility and is capable of forming high quality images, and an electrostatic latent image developing toner which is employed by the same. The invention and the embodiment thereof are described.
An image forming method wherein a latent image formed on a latent image forming body employing exposure having a exposure diameter A (in &mgr;m) in the primary scanning direction is subjected to reversal development employing a developer comprising toner to form an image, and the relationship between the exposure diameter A (in &mgr;m) in the primary scanning direction and the development diameter B (in &mgr;m) in the primary scanning direction of the developed image is hold.
1.1
≦B/A≦
1.5
The toner is prepared preferably by fusing at least the resin particles in a water based medium.
It is preferred that the reversal development is carried out by the contact development, and ratio (Vs/Vp) of line velocity of a latent image forming body (Vp) to line velocity of developer carrying device (Vs) is 1.1 to 3.0.
It is preferred that the exposure diameter in the primary scanning direction is between 20 and 100 &mgr;m.
It is preferred that the exposure diameter in the secondary scanning direction is between 20 and 100 &mgr;m.
It is preferred that the toner is prepared by fusing at least the resin particles having weight average diameter of between 50 and 2000 nm in a water based medium.
It is preferred that the water based medium comprises at least 50 percent by weight and organic solvents of methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone or tetrahydrofuran.
It is preferred that after reversal development, said obtained toner image is transferred onto an image support, and subsequently fixed.
It is preferred that content ratio of said electrostatic latent image developing toner particles, having a volume average particle diameter of 3 to 9 &mgr;m, a shape coefficient of 1.3 to 2.2 in the formula described below, and a shape coefficient of 1.3 to 2.0, is at least 80 percent in terms of the number of particles.
Shape coefficient=(maximum diameter/2)
2
×&pgr;/projection area
An image forming apparatus comprising a means to uniformly charge the surface of a latent image forming body, a means to carry out digital exposure corresponding to an image to form an electrostatic latent image, a means to carry out reversal development employing a developer comprising a toner, a means to transfer an obtained toner image onto an image support, and a means to fix said toner image, wherein said toner is prepared by fusing at least the resin particles in a water based medium.
An image forming apparatus comprising a means to uniformly charge the surface of a latent image forming body, a means to carry out digital exposure corresponding to an image to form an electrostatic latent image, a means to carry out reversal development employing a developer comprising a toner, a means to transfer an obtained toner image onto an image support, and a means to fix said toner image, wherein said toner is prepared by fusing at least the resin particles in a water based medium.
An electrostatic latent image developing toner employed in an image forming method in which after uniformly charging the surface of a latent image forming body, digital exposure corresponding to an image is carried out; a formed electrostatic latent image is subjected to reversal development employing a developer comprising a toner; and an obtained toner image is transferred onto an image support and subsequently fixed, wherein the latent image developing toner is prepared by fusing at least the resin particles in a water based medium.
It is preferable that the content ratio of said electrostatic latent image developing toner particles, having a volume average particle diameter of 3 to 9 &mgr;m, a shape coefficient of 1.3 to 2.2 in the formula described below, and in addition, a shape coefficient of 1.3 to 2.0, is at least 80 percent in terms of the number of particles.
Shape coefficient=[(maximum diameter/2)
2
×&pgr;]/projection area
It is preferable that in said-electrostatic latent image developing toner, the content ratio of minute toner particles, having a particle diameter of no more than 3.0 &mgr;m, is no more than 20 percent in terms of the number of particles.
It is preferable that the content ratio of minute toner particles, having a particle diameter of no more than 2.0 &mgr;m, is no more than 10 percent in terms of the number of particles.
An image forming method wherein a latent image formed on a latent image forming body employing exposure having a exposure diameter A (in &mgr;m) in the primary scanning direction is subjected to reversal development employing a developer comprising toner to form an image, and the relationship between the exposure diameter A (in &mgr;m) in the primary scanning direction and the development diameter B (in &mgr;m) in the primary scanning direction of the developed image, as described below, is held.
1.1
≦B/A≦
1.5
DETAILED DESCRIPTION OF THE INVENTION
Kouno Shigenori
Shirose Meizo
Yamada Hiroyuki
Yamazaki Hiroshi
Konica Corporation
Muserlian Lucas and Mercanti
Pendegrass Joan
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