JPS6333771A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent the generation of a ghost by providing a destaticizing light source, which can emit light having plural spectrum characteristics, and a light quantity determining means which determines the quantity of light of each spectrum to be emitted from the destaticizing light source in accordance with the spectrum characteristic of light emitted from an exposure light source. CONSTITUTION:A destaticizer 17 has two destaticizing light sources 20 and 21, and a mode I is set when an original irradiating light source 12 is selected as the light source for image exposure, and a mode II is set when the LED array of an optical writing device 14 is selected as it. In the mode I, adjusting resistances VR11 and VR21 are selected for stabilized power sources 25 and 26 respectively; and in case of the mode II, adjusting resistance VR12 and VR22 are selected for stabilized power sources 25 and 26 respectively. The ratio of the quantity of light of the destaticizing light source 20 to that of the destaticizing light source 21 is 3:1 in case of the mode I to effectively prevent the generation of a ghost, and this ratio is 1:1 in case of the mode II to effectively prevent the generation of the ghost. Thus, electrophotographic images of less ground stain and density variance are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an electrophotographic apparatus having a plurality of functions, and more specifically, an image exposure means has a plurality of spectral characteristics corresponding to the functions. The present invention relates to an electrophotographic apparatus equipped with an exposure light source that can selectively emit light with spectral characteristics ranging from 1 to 3.

[Prior Art 1] Conventionally, in order to improve the added value of electrophotographic copying machines, various electrophotographic devices have been proposed in which, for example, a printer function is added to the functions of the copying machine (Japanese Patent Application Laid-Open No. 54-3
0039, JP-A No. 56-89166, etc.).

This electrophotographic device having multiple functions uses the electrophotographic process as is even in its printer function. That is, the processes of charging, image exposure, development, transfer, cleaning, and neutralization are performed in the same way, centering on the photoreceptor.

However, in this case, the method of image exposure for forming an electrostatic latent image on the surface of the photoreceptor in a charged state is different. Specifically, in order to be suitable for dot recording, for example, a flying spot optical system may be constructed using a laser light source to irradiate sub-light onto the photoreceptor surface, or an LE light source for one line may be constructed.
A D array is used to irradiate spot light corresponding to dots. Then, the laser light source and the LED array are controlled on and off in accordance with the character information and image information.

The exposure light source used in electrophotography is a halogen lamp or the like, and its spectral characteristics are continuous and cover the sensitivity bands of conventionally used selenium-based and selenium-tellurium-based photoreceptors. However, when realizing the above printer function, a laser light source used as an exposure light source,
Looking at the light sources currently in practical use for LED arrays, many of them have center spectra located on the longer wavelength side than the sensitivity bands of selenium-based and selenium-tellurium-based photoreceptors (for example, He-Ne laser r630 nm, L E
D array is 660 nm, etc.). Therefore, in order to realize the multifunctional electrophotographic device, it is necessary to use a selenium-arsenic (5e-AS) photoreceptor, which has a sensitivity band on the longer wavelength side than a selenium-based or selenium-tellurium-based photoreceptor. need to use. This selenium-arsenic photoreceptor is more suitable for an electrophotographic apparatus that realizes the multiple functions in that it has higher sensitivity than selenium-based or selenium-tellurium-based photoreceptors.

[Problems to be Solved by the Invention] By the way, as mentioned above, a method that has two or more types of light sources, such as a halogen lamp or a laser light source, and selectively emits light with one spectral characteristic from among a plurality of spectral characteristics. With conventional electrophotographic equipment that has an exposure light source that can emit light, the electrophotographic image (visible) obtained when imagewise exposed to light with certain spectral characteristics has a lot of background smudges and density unevenness. It ends up. This phenomenon becomes particularly noticeable when the above-mentioned selenium-arsenic photoreceptor is used.

The occurrence of scumming and density unevenness in the electrophotographic image is due to the following reasons.

The background smudge and density unevenness are ghost phenomena in electrophotographic images. This ghost phenomenon is a phenomenon in which the image of the latent image previously formed on the surface of the photoreceptor is duplicated on the current electrophotographic image. Specifically, regarding development by positive exposure, for example, as shown in FIG. 8, the previous line image I (FIG. 8 (a)) overlaps the halftone solid part H, and is created as a negative ghost Gn with black and white reversed. (FIG. 8(b)), or as a positive ghost Gp that does not invert black and white. Furthermore, with respect to reversal development using negative exposure, in addition to the ghost of the halftone solid portion of development using positive exposure, a ghost also occurs in the ground portion, causing fogging and the like.

The cause of the ghost is that, as shown in FIG. 9, the surface potential of the photoconductor Vl during the current halftone solid exposure is This is explained as a difference in development density due to a difference in chargeability between the so-called non-exposed area and the exposed area, where V2 (unexposed area) and V2 (exposed area) are different. This difference in chargeability is thought to be related to optical fatigue of the photoreceptor material (for example, selenium-arsenic type). This optical fatigue of the photoreceptor is a phenomenon in which electrons with low mobility are trapped inside the photoreceptor due to static elimination and charging during the electrophotographic cycle, and negative space charges are accumulated. As this negative space charge accumulates, the internal electric field becomes stronger, so charge injection from the surface of the photoreceptor tends to occur, and the charging potential at the development position decreases. Further, this optical fatigue exhibits a phenomenon that is resolved by irradiation with light having a specific spectrum. This is because the irradiated light penetrates into the photoreceptor, and the penetrating light excites the trapped electrons, releasing the trapped state.

Therefore, in the electrophotographic cycle, the occurrence of ghosts due to the above-mentioned photofatigue depends on how the light irradiated during image exposure affects the steady increase/decrease of the negative space charge accumulated by light irradiation during static elimination. It is determined by whether the

This means that the occurrence of ghosts can be prevented by appropriately selecting the spectra of the light source for image exposure and the light source for static elimination.

Here, in a normal electrophotographic device, the spectral characteristics of the exposure light source and the spectral characteristics of the static elimination light source are selected as characteristics that are effective in preventing ghost generation. Therefore, in an electrophotographic apparatus equipped with an exposure light source that can emit light with one spectral characteristic out of a plurality of spectral characteristics, it is difficult to select Depending on the spectral characteristics of the exposure light source used, it may be difficult to prevent the occurrence of ghosts.

Therefore, it is an object of the present invention to make it possible to determine the spectral characteristics of a static elimination light source that are effective in preventing ghost generation based on the spectral characteristics of the exposure light source, even if the spectral characteristics of the exposure light source are arbitrarily selected. be.

[Means for Solving the Problems] As shown in FIG. The image exposing means 2 includes a static eliminating means 3 for removing electric charge on the surface of the photoreceptor 1 after developing and subsequent transfer processing is performed on the electrostatic latent image formed on the surface, and the image exposing means 2 has a The present invention is based on an electrophotographic apparatus equipped with an exposure light source 4 that selectively emits light having spectral characteristics of 1 to 3. In this electrophotographic apparatus, the technical means for solving the above problem is that the static eliminating means 3 has a plurality of spectral characteristics predetermined in relation to the spectral characteristics of the light that the exposure light source 4 can emit. It is equipped with a static elimination light source 5 that can emit light, and a light amount determining means 6 that determines the amount of light of each spectrum to be emitted from the static elimination light source 5 according to the spectral characteristics of the light emitted from the exposure light source 4. It is something.

[Function] The basic processes are the same as in the case of intra-film electrophotography: charging of the photoreceptor 1, image exposure by the 8'R light means 2, development, transfer, cleaning, and static elimination by the static elimination means 3. .

In the course of the above process, the static eliminating means 3
The light amount determining means 3 determines the amount of light of each spectrum to be emitted from the static elimination light source 5. Then, in the static elimination process, light of each spectrum is irradiated from the static elimination light source 5 at the determined light amount.

The amount of light of each spectrum of the static elimination light source 5 is 1 t of exposure light! It is determined based on the spectral characteristics of the light irradiated from 4 to be effective in preventing the occurrence of ghosts.

The mode of determining the light amount of each spectrum of the static elimination light source 5 will be specifically explained.

For example, as shown in FIG. 2, the static eliminating light source 5 has a center wavelength λ1. λ2. Three types of spectral characteristics Ql, Q2. of λ3.
In the case where monochromatic light of Q3 can be emitted, the spectral characteristics of the light irradiated from the exposure light source 4 are as shown in FIG.
Assume that In this case, as shown in FIG. 3, the longer the center wavelength of the light emitted from the static elimination light source 5 is than the center wavelength of the light emitted from the exposure light source 4, the higher the ghost potential indicating the degree of ghost occurrence becomes. (The ghost potential here refers to the potential that remains on the photoreceptor after the photoreceptor is irradiated with a light source for static elimination). Therefore, in order to prevent the occurrence of ghosts, the potential from ghost 1 to °°O'' is
In order to make it close to each other, the amount of light of each spectrum in the static elimination light source 5 can be determined as follows.

(2) Light with characteristic Q2 is irradiated at a predetermined amount of light, and neither light with characteristics Q1 and Q3 is irradiated (light amount "0").

■ Light with characteristic Q1 and light with characteristic Q3 are irradiated at a predetermined ratio of light intensity, and light with characteristic Q2 is not irradiated (light intensity "o")
>.

As in case (2) above, light with a center wavelength λ1 (characteristic Q1) having a shorter wavelength than the center wavelength λ4 of the light emitted from the exposure light source 4, and light with a center wavelength λ3 having a longer wavelength than the same wavelength λ4.
By combining the light with the center wavelength λ2 (characteristic Q3), it is possible to achieve the same effect as the light with the center wavelength λ2 (characteristic Q2) in preventing ghost occurrence.

Further, as shown in FIG. 4, the spectral characteristics of the static elimination light source 5 are left unchanged (same as in FIG. 2), and the exposure light [4
Assume that the spectral characteristics of the light irradiated from the light source have a characteristic Q5 in which a predetermined long wavelength band (longer wavelength side than the wavelength near the wavelength λ2) of the continuous spectral characteristic is cut.

In this case as well, static elimination using each monochromatic light (wavelengths λ1, λ2, λ3) is as shown in Figure 5, as described above (see Figure 3).
becomes a ghost potential. As a result, the amount of light of each spectrum in the static elimination light source 5 can be determined in the same manner as in (1) and (2) above.

Note that the spectral characteristics of the static elimination light source 5 and the exposure light source 4 are for convenience of explanation and are not to be interpreted in a limited manner.

Essentially, the spectral characteristics of the exposure light source 4 can be arbitrarily determined, and the spectral characteristics of the static elimination light source 5 are effective in preventing ghost generation in relation to the spectral characteristics of the exposure light source 4. It can be viewed as appropriate.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 6 is a diagram schematically showing an example of the structure of a mechanical section of an electrophotographic apparatus according to the present invention.

This example combines the functions of a copying machine and a printer using an electrophotographic method.

In FIG. 6, numeral 10 is a photoreceptor drum, and 11 is a uniform charger, and the surface of the rotating photoreceptor 10 is uniformly positively charged by the discharge action of the uniform charger 11. This photoreceptor drum 10 uses a selenium-arsenic material (5% arsenic by weight and a ratio) as its photoreceptor material. 12 is an original irradiation light source that irradiates the original 35 on the original platen 30; 13 is an imaging optical system so that an optical image corresponding to the image drawn on the original 30 is formed on the surface of the photoreceptor drum 10; (Compatible with copier functions).

This document irradiation light source 12 is composed of a halogen lab and a long wavelength band cut filter, and the cut wavelength is, for example, sson.
The light source corresponds to the continuous spectrum characteristic of m (sox value), that is, the characteristic Q5 in FIG. 4.

Reference numeral 14 denotes an optical writing device in which light irradiation is controlled based on printer input signals corresponding to image information or character information (corresponding to printer functions);
4 has an LED array for one line serving as a light source and an imaging optical system formed of an optical fiber bundle. For example, the LED array has a center wavelength λ0 = 660 nm and a half width of 49 nm.
m, that is, a monochromatic light source corresponding to the characteristic Q4 in FIG.

Photosensitive drum 10 based on the light from document irradiation light source 12
The electrostatic latent image formed on the surface is a so-called positive latent image in which the potential of the background part is low and the potential of the image part is high.In addition, in the optical writing device 14, the reliability and lifespan of the LED array serving as the light source are taken into consideration. Then, LED writing is performed on the image area, and a negative latent image is formed by lowering the potential of the image area.

15 is a developing device that electrostatically attaches toner to the electrostatic latent image formed on the surface of the photoreceptor drum 10; 16 is the photoreceptor drum 1;
This is a transfer device that transfers the toner attached to the surface of the recording paper 40 to the recording paper 40 by electrostatic attraction. The above developing device 1
In order to develop the above-mentioned positive latent image and negative latent image, No. 5 uses a bipolar developer as a developer, and an exposure light source, that is,
When the LED arrays in the document irradiation light source 12 and the optical writing device 12 are switched, the developing bias thereof is switched. Further, regarding the transfer device 16 as well, the polarity of the transfer charge is switched in accordance with switching of the developing bias in the developing device 15.

17 is a static eliminator, and this static eliminator 17 has two types of static eliminator light sources 20 and 21. Each light source 20.21 is L
It becomes a monochromatic light source by ED, and one light source 20 has a spectral characteristic of a center wavelength λ0=610no+ and a half-value width of 401'llB (corresponding to the characteristic 'Q1 in FIGS. 2 and 4), and the other light source 21 has a center wavelength Wavelength λO=700nm
, has a spectral characteristic (corresponding to characteristic Q3 in FIGS. 2 and 4) with a half-width of 40 rv.

In FIG. 6, 18 is a cleaning device for removing toner remaining on the surface of the photoreceptor drum 10 after transfer, and 19 is a cleaning device for peeling off the transferred recording paper 4o adsorbed on the photoreceptor drum 10. This is a detack.

A circuit for adjusting the amount of light from each of the static elimination light sources 20 and 21 is shown in FIG. 7, for example.

That is, the LED serving as the static elimination light source 20 is connected to the stabilized power supply 25, and the current flowing through this LED is connected to the adjustment resistor V R1.
1 or V R12, and the static elimination light source 2
1 is connected to the stabilized power supply 26, and this LED
The current flowing through D is determined by adjusting resistor VR21 or VR22. Then, when the light source for image exposure is selected as the original irradiation light source 12, the mode (I> is selected).
When the light source is selected for the LED array of the optical writing device 14, the adjustment resistors VR11 and VR12 for the stabilized power source 25 are switched and the stabilized power source is switched by the operation of the switch 27, which is switched by the selection signal corresponding to the mode (It), respectively. Adjustment resistors VR21° and VR22 with respect to 26 can be switched respectively. Specifically, in mode (I), the adjustment resistor VR1 is connected to the stabilized power supply 25.
1, the adjusting resistor VR21 is selected for the stabilized power source 26, while in mode (U), the adjusting resistor VR12 is selected for the stabilized power source 25, and the adjusting resistor VR22 is selected for the stabilized power source 26. are selected respectively.

As described above, the document irradiation light source 12 has the characteristic Q5 in FIG. 4, the LED array of the optical writing device 14 has the characteristic Q4 in FIG. When the other static elimination light source 21 has a spectrum characteristic corresponding to the characteristic Q3 in FIG. 2,
In mode (I), the light intensity ratio between the static elimination light source 20 and the same light source 21 is 3:1, which is effective in preventing ghost generation, while in mode (II), the static elimination light source 20 and the same light source 2
A light amount ratio of 1:1 is effective in preventing ghost generation. Therefore, each adjustment resistor VR11°VR12,V
R21 and VR22 are adjusted so that the above-mentioned optical ffi ratio is 1i5L and each light source 20.21 is energized.

When performing the electrophotographic process under the above conditions, the charging potential of 800 V at the development position is reduced to 100 V by image exposure.
Assuming that, the ghost potential can be reduced to 10 V or less in both the case of the tIA function of the copying machine using the original irradiation light source 12 and the case of the printer function using the light immersion device 14.

For reference, when the spectral characteristics of the static eliminating light source in the static eliminating device 17 are made approximately the same as those of the LED of the optical writing device 14 (center wavelength λ0-650nllll), the optical writing device 14
When exposed with the original irradiation light source 12, the ghost potential becomes 10 V or less, but when exposed with the original irradiation light source 12, the ghost potential becomes about 50 V.

From the above results, the spectral distribution of at least one type of static elimination light source that can emit light with two or more types of spectral characteristics is on the longer wavelength side than the spectral distribution of a plurality of image exposure light sources, and , when the spectral distribution of at least one other type of static elimination light source is relatively on the shorter wavelength side than the spectral distribution with the least spread toward the long wavelength side among the spectral distributions of the plurality of light sources for weighted light, It can be seen that the generation of ghosts can be prevented by switching the amount of light of each spectrum of the static elimination light source according to the spectral characteristics of the selected image exposure light source.

As mentioned above, in this embodiment, each adjustment resistor VR11
, VR12, R21, VR22f7) By adjusting the resistance value, it is possible to adjust the light amount of the static elimination light source in accordance with the ghost characteristics such as optical fatigue of each photoreceptor drum 10.

Further, when the photoreceptor drum 10 is made of selenium-arsenic,
Since the charging potential depends on the light quality and light intensity of the static elimination light source,
The charging potential can also be controlled by controlling the amount of light from the static eliminating light source. (Conventionally, this charging potential was controlled by switching the charging potential of a uniform charger.) Note that the charge eliminating light source is not limited to one using a plurality of monochromatic light sources as in the above embodiment. For example, a plurality of light sources having spectral characteristics such as those with long wavelength components removed (see characteristic Q5 in FIG. 4) may be used, or a monochromatic light source may be used in combination, in any manner. Further, in order to obtain predetermined spectral characteristics, various filters may be used for the light source having continuous spectral characteristics.

[Effects of the Invention] As described above, according to the present invention, even if the spectral characteristics of the exposure light source are arbitrarily selected, a static elimination light source that is effective in preventing ghost generation with respect to the spectral characteristics can be used. It becomes possible to determine the spectral characteristics, and electrophotographic images with less background smear and less moisture can be obtained no matter which exposure light source is used to perform the process depending on the function.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing an example of the spectral characteristics of an exposure light source and a static elimination light source, and FIG. 3 is an illustration of the middle color spectrum shown in FIG. 2. Figure 4 shows an example of the spectral characteristics of the exposure light source and the static elimination light source, and Figure 5 shows the wavelength dependence of the ghost potential of the monochromatic spectrum static elimination light source with respect to the exposure light source. A diagram showing the wavelength dependence of the ghost potential of a monochromatic spectrum static elimination light source with respect to an exposure light source, FIG. 6 is a diagram schematically showing an example of the configuration of the mechanical part of the electronic copying apparatus according to the present invention, and FIG. 7 is a diagram showing the static elimination light source. FIG. 8 is a diagram showing a state in which a ghost occurs, and FIG. 9 is a diagram showing a surface potential state of a photoreceptor that causes the occurrence of a ghost. 1... Photoreceptor 2... Image exposure means 3... Static elimination means 4... Light source for exposure 5... Light source for weight removal 6... Light amount determining means Patent applicant Agent of Fuji Xerox Co., Ltd.
Patent attorney Tomohiro Nakamura (2 others) 1. Ki E Buddha 2! 3 Static elimination + station box 2 Fig. 3 λ1 λ2

Claims (1)

[Claims] An image exposure means for forming an electrostatic latent image on a uniformly charged photoreceptor, and a charge on the surface of the photoreceptor after development and subsequent transfer processing are performed on the electrostatic latent image formed on the surface of the photoreceptor. In an electrophotographic apparatus, the image exposure means includes an exposure light source capable of selectively emitting light having one spectral characteristic from among a plurality of spectral characteristics, wherein the image exposure means has a , a static elimination light source that can emit light with a plurality of predetermined spectral characteristics in relation to the spectral characteristics of the light that can be emitted by the exposure light source; 1. An electrophotographic apparatus comprising: a light amount determining means for determining the amount of light of each spectrum to be emitted from a light source.