JPH01277261A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a sharp image in which sensitivity can be improved and fogging is prevented from being generated by forming an electrostatic latent image on the image carrier of an organic photoconductor to be electrified to a positive value by image exposing stage, and applying whole image exposure on a stage between an image exposure stage and a developing stage at the time of developing the electrostatic latent image by the developing stroke. CONSTITUTION:The electrostatic latent image is formed on the photosensitive drum 1 of the organic photoconductor 1a to be electrified to the positive value by the image exposure stroke, and at the time of developing the electrostatic latent image by the developing stage, the whole image exposure is applied on the surface of the organic photoconductor 1a at the stage between the image exposure stroke and the developing stage by an exposure means 3. Thereby, an electric charge remaining in the neighborhood of the boundary of the electric charge generating layer and the electric charge migrating layer of the organic photoconductor 1a is moved to a substrate side, and ground potential is decreased, and the sensitivity of a 1/10 exposure quantity can be increased. In such a way, it is possible to prevent the fogging due to the splash of a developer 5a from being generated, and to form a satisfactory image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus that is applied as, for example, a copying machine or a laser printer.

(Prior art) Copying machines and laser printers are equipped with a photoreceptor inside the main body of the device.The role of this photoreceptor is to hold the charge generated by corona discharge for a certain period of time, and to store the charge generated in the photoreceptor by image exposure. Either one of the electron-hole pairs neutralizes the surface charge.

At this time, an electrostatic latent image is formed on the surface of the photoreceptor,
This electrostatic latent image is made visible by attaching toner charged with the opposite sign to the charge on the surface of the photoreceptor using Coulomb force.

This visualized image is transferred onto a sheet of paper and discharged outside the main body of the apparatus.

By the way, the photoreceptor mentioned above is Se, 5e-Te type, A
S 2 S e 3 or ZnO is used.

However, since the Se-based photoreceptor has low hardness,
It has a short lifespan, is harmful to the human body, and has a low softening point.

In addition, the AS2Se3 photoreceptor has a large difference in charging ability, sensitivity, etc. due to optical fatigue, and has poor temperature characteristics.
There are also problems such as being harmful to the human body.

In addition, the ZnO photoreceptor has a problem with printing durability.Recently, amorphous silicon (a-Si) or amorphous silicon (OPC) photoreceptors have been developed to solve the above problem. It has attracted attention.

Amorphous silicon (a-Si) photoreceptors have a wide absorption wavelength range, are golden in color, have high sensitivity, and have high Vickers hardness, so they have advantages such as excellent printing durability.

However, this amorphous silicon (a-St) photoreceptor has the drawbacks of low charging ability, easy image deletion, and high cost per photoreceptor.

For this reason, it has been used in high-speed equipment because of its advantages in terms of printing durability and sensitivity, but it has been difficult to apply to medium- to low-speed equipment due to its high cost.

On the other hand, the organic photoconductor photoreceptor (OPC) is cheaper than the amorphous silicon (a-SL) photoreceptor, and the selection of materials greatly improves printing durability and sensitivity. In particular, positively charged OPCs have been studied as an alternative to photoreceptors.

(Problem to be Solved by the Invention) However, the OPC has the same sensitivity at a half exposure as compared to Se, but the sensitivity is inferior at an exposure of 1/1o, so toner scatters during image formation and fog occurs. There was a problem.

The present invention has been made in view of the above-mentioned circumstances, and its object is to provide an image forming apparatus which eliminates the drawbacks of positively charged photoconductor image carriers and enables good images to be obtained. Our goal is to provide the following.

[Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention forms an electrostatic latent image on a positively charged organic photoconductor image carrier through an image exposure process, and In an apparatus in which an electrostatic latent image is developed by a development process, the apparatus is characterized by being equipped with a full-surface exposure means for performing full-surface exposure between the image exposure process and the development process.

(Function) By performing full-surface exposure between the image exposure process and the development process, the organic photoconductor is pre-excited, the charge generation efficiency is increased, and the sensitivity of the organic photoconductor can be improved.

(Example) The present invention will be described below with reference to an example shown in the drawings.

In the figure, reference numeral 1 denotes a photosensitive drum coated with an organic photoconductor 1a. The photosensitive drum 1 is rotatably provided and is driven to rotate in the direction of the arrow by a drive means (not shown).

Further, around the photosensitive drum 1, a charging charger 2, a full surface exposure means 3, a developing device 5, a pre-transfer static eliminator 6, a transfer charger 7, a peeling charger 8, a static eliminator charger 9, Cleaning device 1
0 and a static elimination lamp 11 are provided.

The organic photoconductor 1a of the photosensitive drum 1 has a charge generation layer (C
GL layer) and a charge transport layer (CTL layer).

Further, as the exposure means 3, a green light emitting diode (LED) made of a pigment and a CT agent is used.

When forming an image, the surface of the photosensitive drum 1 is first charged by the charging charger 2, and the charged surface of the photosensitive drum 1 is irradiated with information light 12 as shown by the arrow to expose the image. and forms an electrostatic latent image. Thereafter, the surface of the photosensitive drum 1 is fully exposed by the full surface exposure means 3, and the electrostatic latent image is sent to the developing device 5 by the rotation of the photosensitive drum 1, and the developer 5a supplied from the developing device 5 is
It is visualized by This visualized image is transferred to the paper P by the action of the transfer charger 7 after the excess charge after development is erased by the pre-transfer static eliminator 11. Next, the paper P is separated from the photosensitive drum 1 by a peeling charger 8, and is sent to a fixing device (not shown), where the image is fixed.

On the other hand, the untransferred toner remaining on the photosensitive drum 1 is mechanically removed and collected by the blade 10a of the cleaning section 10 while the electric charge is erased by the charge eliminating charger 9. The surface of the photosensitive drum 1 is covered with a static eliminating lamp 11.
The entire surface is exposed, the residual potential is erased, and the second copy cycle begins.

By the way, at the time of image formation, the surface of the organic photoconductor 1a is entirely exposed by the exposure means 3 between the image exposure process and the development process as described above, so the charge generation layer (CG
Charges remaining near the boundary between the L layer) and the charge transport layer (CTL layer) move toward the substrate, lowering the white background potential and increasing the sensitivity by 1/10 of the exposure amount. By increasing the sensitivity by 1/10 of the exposure amount, fog caused by scattering of the developer 5a is prevented, and a good image is formed.

In order to eliminate fog, it is possible to lower the black background surface potential (Vs) or increase the developing bias, but in the former case, the organic photoconductor photoreceptor (OP
) is undesirable because the black ground surface potential (Vs) decreases during repetition and the image density (Id) decreases due to large photofatigue; in the latter case, the capacitance of the transformer increases, which is undesirable.

In the above example, a green light-emitting diode (LED) 3 was used from the pigment and the CT agent, but the present invention is not limited to this, and yellow-green or yellow light-emitting diodes (LED) may be used. .

Further, as the exposure means 3, a light emitting diode (LED) 3 is used.
However, the present invention is not limited to this, and cold cathode tubes, halogen lamps, neon lamps, etc. may be used.

[Effects of the Invention] As explained above, according to the present invention, since the entire surface of the image carrier is exposed between the image exposure process and the development exposure process, the sensitivity can be increased, fog can be prevented, and clear images can be obtained. This has the effect of being able to obtain the following.

FIG.

1a... Organic photoconductor, 1... Photosensitive drum (image carrier), 2... Charging means, 12... Information light (image exposure), 3... Light emitting diode (exposure means).

Applicant's agent: Patent attorney Takehiko Suzue

Claims (1)

[Claims] An electrostatic latent image is formed on a positively charged organic photoconductor image carrier by an image exposure process, and this electrostatic latent image is developed by a development process. An image forming apparatus characterized by comprising a full-surface exposure means for performing exposure.