JPS60166973A - Image recording device - Google Patents

Abstract

PURPOSE:To eliminate difference in image density due to irregularity of the potential of a photosensitive body by setting the quantity of preexposure nearly >=10 times the quantity of preexposure for obtaining the same potential as the mean potential of a light part of an electrostatic latent image as to a laser beam printer. CONSTITUTION:A photosensitive body 1 which is irradiated by a preexposure source 2 and charged electrostatically uniformly by an electrifier 3 is scanned with a laser beam L which is modulated with an image signal. The quantity of preexposure is set >= 10 times the quantity P0 of exposure required to obtain the light part potential of the electrostatic latent image after the image exposure. Consequently, a ghost is eliminate completely and the potential difference of the photosensitive body which is generated according to whether a transfer member is present or not is reduced, thereby obtaining an image having no density irregularity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image recording apparatus such as a laser beam printer.

In the electrophotographic method, images are created by repeating the process of charging φ image exposure, transfer and cleaning. It may not disappear even after printing, and a ghost may occur during the next development.

Therefore, in order to eliminate the ghost, pre-exposure may be performed to irradiate the photoreceptor with light before charging. In the case of normal electrophotography, the amount of light for this pre-exposure is generally 1 to 5 times the exposure required to obtain a bright area potential in the image exposure process, and this light tel- almost eliminates ghosts. disappear.

However, in image recording devices such as laser beam printers (LBPs), which have recently been widely used, ghosts may not be prevented even if pre-exposure is performed. Although the basic processes of photography and image formation 1- are the same, this is thought to be because the image exposure methods are different.

In other words, LBP scans a photoreceptor with a laser beam modulated according to an image signal, and the light intensity portion 41 of the laser beam spot has a nearly Gaussian distribution, so the IW radiation intensity is strong in some parts. . Therefore, it is considered that the pre-exposure amount of 11ff used in conventional copying machines cannot erase the memory completely and ghosts occur.

Therefore, the present invention aims to eliminate the drawbacks mentioned above in an image recording apparatus such as an LBP using a copying process, and at the same time eliminate image density differences due to non-uniform potential of a photoreceptor caused by the presence or absence of a transfer member during transfer charging. (=f).

The present invention will be explained in detail below. FIG. 1 is a diagram illustrating the process layout of an image recording apparatus in which the present invention is implemented. The photoreceptor 1 is irradiated with pre-exposure light from a pre-exposure light source 2, uniformly charged by a charger 3, and exposed and scanned by a laser beam L modulated by an image signal. The static latent image thus formed is then transferred to the charger 3 by the developer 4.
The developer 5 charged to the same polarity as that of the latent image is developed by attaching it to the 1jJ1 portion 7 of the latent image, and the developer on the photoreceptor is transferred to the transfer member by the transfer charger 6. the law of nature)
The toner remaining on the photoreceptor L without being transferred is cleaned by the cleaner 7. By the way, the following method is used as a guideline for determining the amount of light in the above-mentioned pre-exposure 2.

Now let Vo be the bright area potential of the electrostatic latent image formed in the process after image exposure, and let po be the exposure area required to obtain this bright area potential V0. P because it is less tiring and can erase ghosts.
It was thought to be 1 to 5 times that of O.

This value is considered appropriate for the conventional analog system in which the optical image of the original is projected onto a photoreceptor using a lens, but for LBP
In this case, it is not necessarily an appropriate value. That is LB
In P, the bright area potential V0 on the photoreceptor after image exposure is 882
As shown in Figures (A) and (c), the wavy potentials are averaged, with the minimum value and maximum value being the potential V2 above the center of the image foggy spot and the middle potential V2 between the adjacent spots, respectively. If the pre-exposure amount was set to 1 to 5 times the Po used in conventional analog copiers, the memory of the previous image exposure would not be completely erased by the pre-exposure, and ghosts would occur. This is because it becomes

Now, an embodiment of the present invention will be shown below, with a wavelength of 780 to 800.
In a laser beam printer using a nm semiconductor laser, an OPC (organic lead 7V) is used as the photoreceptor, and a white light lamp (wavelength 300 to 1200 nm) is used for pre-exposure.
)It was used. The potentials were set such that the dark area potential was 1600V, the bright area average potential was 1100V, and the developing bias was 1450V.

After charging the photoreceptor described in 1-, it was exposed using a pre-exposure lamp instead of laser beam exposure, and the required exposure amount P to set the bright area potential to I-100 V was approximately 209-
It was ux, sec. Therefore, as an experiment, (1) no pre-exposure, (2) pre-exposure i150 n ug, sec, (3
) When we compared the images in the case of 200 intersections tlK, sec, we found the following results.

1. As can be seen from the table of Z, there is no pre-exposure as shown in (+), or the photoconductor is exposed to light by laser light at 501 ux, sec, where the pre-exposure amount is about 2 to 3 times that of Po, as shown in (2). It is clear that it is not possible to completely erase the remaining optical memory. -The amount of manly exposure was made more than 10 times that of Po (3)
In this case, the optical memory can be completely erased by pre-exposure, and there will be no ghost.

Further, in this case, there is an advantage that there is almost no difference in image density (paper traces) due to a potential difference created on the photoreceptor due to the inactivity of the transfer member during transfer charging.

In order to extend the life of the photoreceptor as much as possible, it is best to apply pre-exposure only to the part of the photoreceptor that corresponds to the image area, and to cut or weaken the pre-exposure to areas other than the image area. This is preferable.

In the above embodiment, the pre-exposure was performed after cleaning and before charging, but the same effect can be expected even if the exposure is performed after transfer and before cleaning.

Also, a laser or LED whose spot diameter is larger than the image exposure spot size may be used as the pre-exposure source.

As explained above, it is possible to completely eliminate ghosts by irradiating the pre-exposure with an amount of light that is 10 times more than 10 times the light 11E, which has a potential obtained by image exposure. There is also the effect that the potential difference (paper trace potential difference) can be made smaller than in the past, and images with uniform density can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the process relationship of the image recording apparatus of the present invention, and Fig. 2 (A), (B), and (C) are the relationships between the image exposure amount and the photoreceptor potential when the laser is scanned on the photoreceptor. Diagram showing. 1 is a photoreceptor, 2 is a pre-exposure light source, 3 is a charger, L is a laser beam, 4 is a developer, 6 is a transfer charger, 7 is a cleaner,
■ is the photoreceptor potential, and P is the exposure light amount. WJ2 diagram Main support direction (C) → Banking two cypress E direction (A) → Sub fL survey direction Figure 1

Claims (1)

[Claims] (+) After pre-exposure and charging, the electrostatic latent image formed on the photoreceptor is developed by scanning with a laser beam modulated according to the image signal, and the developed image is transferred to a transfer material and fixed. An image recording device for recording an image, characterized in that the amount of light for the pre-exposure is approximately 10 times or more lx the amount of pre-exposure to obtain the same potential as the bright area average potential of the electrostatic latent image. Device.