JPS63141081A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent an image from tailing, blurring, and voiding by providing a screen member which has a specific aperture rate and an alkaline film consisting of alkali metal silicate and a conductive material on the photosensitive body side of a corona electrostatic charger. CONSTITUTION:The screen member 3 which has a 45-75% aperture rate and the alkaline film consisting of alkali metal silicate and a conductive material is provided to the corona charger 2 on the photosensitive body side. When the aperture rate is made small, an electrostatic charging potential becomes too low and when the aperture rate is too large, the amount of NOx reaching the surface of the photosensitive body increases and the reduction effect of NOx is lessened greatly. The effective aperture rate is preferably 60-70% and the film thickness is 75-100mum. Consequently, Nox produced by negative corona discharging is adsorbed efficiently, chemically, and fixed to charge the surface of the photosensitive body electrostatically with negative ions which are free from NOx, thereby eliminating the tailing, blurring, white absence, etc., of the image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application] The present invention relates to an electrophotographic apparatus using a negatively charged electrophotographic photoreceptor. More specifically, by removing discharge products generated from the corona charger used for charging the negative-polarity photoreceptor, transferring the developed image, separating the transfer paper, and cleaning residual developer, blurring of the image can be prevented. The present invention relates to an electrophotographic device that prevents image quality defects such as blurred images, blurred images, and white spots.

[Prior Art] In recent years, the development of organic photoconductors has been remarkable, and they are now being used in medium-speed electrophotographic devices and printers, where inorganic photoconductors such as 3e-based photoconductors have traditionally been used. It has become. Along with the development of highly sensitive organic pigments, CG
This is due to improvements in the structure of photoreceptors, which are typified by the functionally separated type L (charge generation layer) and CTL (charge transport layer). Most of these functionally separated organic photoreceptors are used with negative polarity charging;
This is because there are very few charge transport materials used in TLs that have electron transport properties. Corona chargers used to charge the photoreceptor include corotrons, dicorotrons, and scorotrons, but it is known that when these are used with negative polarity, large amounts of 03 and NOx are generated. These 03 and NOx oxidize the surface of the photoreceptor, lower the electrical resistance, and make it easier for surface charges to leak, causing defects such as blurred images, image blurring, and self-destruction. . For this reason, in electrophotographic devices and printers that use negatively charged photoreceptors, conventional methods are used to prevent these gases from reaching the surface of the photoreceptor, such as by suctioning or ventilating the 03 and NOx generated from the corona charger. In addition, measures are taken to reduce the amount of 03 and NOx released by coating the inside of the case of the charger with a substance that absorbs 03 and NOx, or by plating with gold or the like.

However, all of these methods complicate the structure of the device itself, causing an increase in device cost.

Furthermore, methods of gold plating the inner surface of the discharger or absorbing and fixing NOx were not necessarily effective.

[Problems to be Solved by the Invention] In view of the above circumstances, an object of the present invention is to efficiently chemically adsorb and fix NOx generated from negative polarity corona discharge, and to produce a negative polarity containing almost no NOx. An object of the present invention is to provide an electrophotographic apparatus in which defects such as image blur, image deletion, and white spots do not occur by charging the surface of a photoreceptor with ions.

[Means for Solving the Problems] As a result of extensive research, the present inventors have achieved the above object by providing a mesh member having a coating made of a material that adsorbs and fixes NO8 on the photoreceptor surface side of the corona charger. The present invention was completed based on the discovery that the following can be achieved.

That is, the present invention provides an electrophotographic apparatus equipped with a photoreceptor and a corona charger disposed on the circumferential surface of the photoreceptor, in which an alkali metal silicate and a conductive substance are placed on the photoreceptor surface side of the corona charger. It has an alkaline coating consisting of an aperture ratio of 4.
This is an electrophotographic apparatus characterized in that a screen member of 5 to 75% is provided.

Hereinafter, the present invention will be explained based on the accompanying drawings.

FIG. 1 shows the configuration of the main parts of the present invention.

In the figure, 1 is a photoreceptor for negative polarity charging, 2 is a corona discharger for charging, and 3 is a screen for NO and adsorption.

FIG. 2(A) is a perspective view of an example of the screen member of FIG. 1 before a coating is provided, and FIG. 2(B) is a sectional view of the screen member with a coating provided on (A>).

-4 to 7 KV to the discharge wire of the corona discharger (2a in Figure 1)
When a voltage of negative polarity is applied to the discharger case (FIG. 2b), corona discharge occurs around the discharge wire. The negative polar ions generated at this time are released from the opening of the case 2b of the discharger facing the photoreceptor, and flow toward the photoreceptor surface due to an electric field defined by the potential of the discharge line, the potential of the screen, and the potential of the photoreceptor surface. . At this time, the negative polarity ions pass through the openings 3b of the screen.

The screen is made of a material (such as graphite) dispersed in water glass containing an alkali metal as a material for adsorbing and fixing NOx on the surface of a grid base material 3a having openings as shown in FIG. 2(B). For example, Electrodag (trade name) manufactured by Acheson Colloids Co., Ltd. in the United States has a dry film thickness of 5.
The thickness is 5 μm or more.

When the water glass containing alkali metals is dried, it is thought that NOx is adsorbed and fixed in the K part of 20" For example, it can be provided by overcoating by repeating several times the operation of spraying a coating liquid and then drying it by heating (150° C., about 20 minutes) to dehydrate the water glass.

When NOx in the negative ions from the corona discharger passes through the screen opening, it is adsorbed by the substance and chemically fixed, so NOx in the negative ions that have passed through the screen
The amount of x decreases drastically. That is, the surface of the photoreceptor 1 is charged with negative polarity ions with less NOx.

Previously, it was thought that NOx caused solid matter to precipitate on the inside of the discharger case, which would fall and adhere to the photoconductor surface, reducing the surface resistance, but in reality, NOx would further reach the photoconductor surface. It has also become clear that surface leakage can occur. According to the present invention, since NOx, which causes surface leakage, is prevented from reaching the photoreceptor surface, the object of the present invention can be achieved more effectively.

[Example] An embodiment of the invention is shown in FIG.

Figure 3 shows the screen on the photoreceptor surface side of the corona charger, and this example is a stainless steel frame with a thickness of 110C1 on which grids 3a with a width of 95 μm are arranged at 1M intervals at an angle of 45 degrees. It is coated with Electrodag (RW-22932) manufactured by Acheson Colloid Co., USA.

The number of applications and the viscosity of the coating solution are as follows: The thickness of the coating after drying is 75%.
It was made to be on the order of μm. In this case, the aperture ratio of the screen was approximately 75%. It is desirable that this screen is insulated from the corona discharger and placed as close to the discharger as possible so as to cover the opening of the discharger. It was attached to a frame made of insulating material supported by the framework of an electrophotographic device at a position of ~10 m, and 800 V, which is almost the surface potential of the negatively charged organic photoreceptor, was applied to the stainless steel plate of the screen. The surface was uniformly charged to about 780-795 .mu.m.

It has been found that the Electrodag applied to the surface of the photoreceptor preferably has a volume resistance of 10 to 10 Ω·cm. This value can be adjusted by the amount of graphite included in Electrodag. If the amount of graphite is small and the volume resistivity exceeds the above value, the surface potential of the photoreceptor becomes high, causing uneven charging.

The aperture ratio of the screen is extremely important; if the aperture ratio is too small, the charging potential will become too low, and if the aperture ratio is too large, the amount of NO that will reach and cover the photoreceptor surface will increase, significantly reducing the NOx reduction effect. It turns out. It has been found that the effective aperture ratio is 45-75%, preferably 60-70%, and the film thickness is 75-100 μm. An example of the effects of the present invention is shown in FIG. 4 when NO3 is accumulated on the surface of a negatively charged organic photoreceptor (the surface of a photoreceptor using polycarbonate as a binder polymer).

As is clear from FIG. 4, when the screen according to the present invention is used, the amount of NO3 accumulated on the surface of the photoreceptor is reduced by 1/4 to 1/4.
It was found that the number of cases decreased to 115.

Further, when actual copying was carried out using the electrophotographic apparatus according to the present invention, it was confirmed that no image blurring, image blurring, or image loss occurred in a continuous copying test of more than 150,000 sheets.

In the above embodiments, stainless steel is used as the material for the screen, but the base of the screen does not need to be made of stainless steel, and an insulating material (such as plastic) can also be used.

In this case, it is necessary to maintain the coating film itself on the screen at a predetermined potential (necessary charging potential of the photoreceptor surface).

Further, the photoreceptor is not limited to an organic photoreceptor; of course, a similar effect can be obtained with conventional inorganic photoreceptors for negative polarity charging, but the effect is greater in organic photoreceptors whose surfaces are easily damaged. This is because molding products, paper dust, etc. adhere to the scratches, which tends to cause image blurring, image blurring, and unwhitening.

[Effects of the Invention] The present invention provides an electrophotographic apparatus having a screen coated with a substance that adsorbs and fixes NOx in the middle of the moving direction of a negative corona that charges a photoreceptor. Since the photoreceptor is fixed by suction, it is possible to prevent the occurrence of image retention, blurring of the image, or unwhitened image due to No. 2, and the maintenance such as cleaning of the photoreceptor can be greatly omitted.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the basic configuration of the invention, Fig. 2 (A) is a perspective view of an example of the screen before the coating for NOx adsorption and fixation is provided, and (B) is the state in which the coating is provided on the screen of (A>). 3 shows the shape of the screen used in one embodiment of the present invention, and FIG. 4 shows the N of the photoreceptor surface in the present invention and the conventional apparatus.
This is a graph showing the amount of O3 accumulated. Symbols in the figure: 1... Photoreceptor: 2... Corona charger; 2a...
- Discharge wire; 2b...Charger case; 3...Screen; 3a...Screen grid portion; 3b...Screen frontage portion; 3G...NO8 adsorption coating film. Figure 1 Figure 2 (A) Figure 2 (B)

Claims (1)

[Claims] In an electrophotographic apparatus equipped with a photoreceptor and a corona charger disposed around the photoreceptor, an alkaline coating made of an alkali metal silicate and a conductive substance is applied to the photoreceptor surface side of the corona charger. An electrophotographic apparatus comprising a screen member having an aperture ratio of 45 to 75%.