JPS6137629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an image forming apparatus using a short focus small imaging element array as an optical system for forming a desired light image on an electrophotographic photoreceptor in order to form an electrostatic latent image on the photoreceptor. The present invention relates to a forming device.

Compared to image forming devices such as electrophotographic copying machines that use so-called monocular long focus through lenses or in-mirror lenses, devices that use a compound eye short focus small imaging element array as the imaging optical system have the extremely small size of the device. On the other hand, since the output end surface of the array and the photoreceptor surface, or the input end surface and the surface of the original to be copied are brought close to each other, the end surface,
In particular, it also has the disadvantage that dust tends to adhere to the output end face and cause stains. That is, for example, a considerable amount of developing toner is floating in the air near the surface of the electrophotographic photoreceptor, but this is mechanically attached to the output end face of the array, or the floating toner is charged. On the other hand, since the array is made of materials that easily charge, such as glass or synthetic resin, it can easily become charged due to friction with other parts or other causes, and in this case, the floating toner mentioned above is electrostatically attracted to the output end surface. Because of this, contamination tends to occur on the output end face of the array. In addition, gaseous ion particles generated due to charging of the photoreceptor surface or corona discharge used for transfer, etc., exist in the atmosphere inside the device, but these ion particles may cause airborne silicon, calcium, It combines with substances such as magnesium, and the compound mechanically and electrostatically adheres to the input and output end faces of the small imaging element array, resulting in stains. In particular, as mentioned above, when the small imaging element array is charged, If the ion particles are present, the ion particles are attracted to the small imaging element array by electrostatic attraction and enter the array, promoting contamination of the output end face. Furthermore, various other types of dust in the air are also a source of contamination, and this dust mechanically and electrostatically adheres to the input and output end faces of the array as contamination, especially when the small imaging element array is charged. and when the dust is combined with ion particles, the dust is attracted to the small imaging element array by electrostatic attraction and adheres to the element end face 3, and enters.
Promotes contamination of the output end face. When dirt adheres to the end face of the small imaging element array due to these causes, the effect on image formation is greater than when dirt adheres to the surface of a normal large-diameter, monocular through lens, or in-mirror lens. Significant. In other words, since each of the imaging elements in the small imaging element array has a very small aperture, and because it has a compound eye configuration, not the entire array but some imaging elements are involved in forming one image point. Therefore, compared to the case where the same size of dirt adheres to the through lens or in-mirror lens, the rate of light ray blocking for one image point due to dirt is large, and the illuminance of the image point corresponding to the dirty area is large. The decrease becomes significant, and if the dirt distribution is uneven, the illuminance of the entire image will not decrease uniformly, but the illuminance distribution of the image will also become uneven.

The present invention has been made to solve the above-mentioned disadvantages, and focuses on the fact that most of the floating dust that adheres to the end face of the array and becomes dirt is charged. Alternatively, an electrode for forming a dust-proof electric field is disposed near the output end face to form a dust-proof electric field near the end face to prevent dust from adhering to the end face. Embodiments of the present invention will be described below with reference to the drawings.

First, an outline of the short focus small imaging element array will be explained. The one shown in FIG. 1A is a condensing optical fiber light guide element 1 whose refractive index decreases in a parabolic curve from the center toward the outside in the radial direction. This is disclosed in Japanese Patent Application No. 47-28058, etc., and has an imaging effect and forms an erect optical image I of the same size of the object 0 by making it of an appropriate length. The item shown in Figure 1B is
In the bar lens system 2 as shown in specification No. 52-81571 (Japanese Unexamined Patent Publication No. 54-17029), the bar lens 2'
to form the image I of the aerial image I' of the object 0, and re-image the image I of the image I' by the bar lens 2''. Lenses 2', 2''
If both have the same focal length and are placed symmetrically with respect to the image point I', an erect real image of the object can be formed. The element array used in the present invention consists of the above-described elements 1 and 2 arranged densely in a straight line with the optical axes of the elements parallel to each other, as shown in FIG. 2A. In Figure 2A, the bales are stacked in two tiers, but they may be stacked in three or more tiers or only one tier. A suitable fixing frame 4 is fitted around the outer periphery of the array 3. If such a short-focus small imaging element array 3 is used, it will function as a compound eye imaging system, and in the same-magnification imaging relationship, it will produce a same-magnification erect optical image I of an object 0 that is approximately the same size as the incident surface of the array. can be formed. This is shown in Figure 2B.

Next, the copying process of an electrostatographic copying apparatus to which the present invention is applied, which uses a short-focus small imaging element array as an imaging optical system, will be outlined with reference to FIG. A photoreceptor, that is, a grounded conductive drum 5' rotating in the direction of the arrow in the figure.
A photosensitive drum having a photoconductive layer 5 thereon is first uniformly charged on its surface by a corona charger 6 and reaches an exposure area. Here, the image light of the original 9 on the original platen 8 (which is moved at the same speed as the circumferential speed of the drum in the direction of the arrow when forming a latent image) illuminated by the illumination light source 7 is formed by a short focus small imaging element which is an imaging optical system. The light is introduced to the surface of the photoreceptor through the array 3, and the original light image is exposed to the photoreceptor in a slit exposure manner. As a result, an electrostatic latent image corresponding to the original image is formed on the surface of the photoreceptor. This electrostatic latent image is visualized by a dry developing device 10 that supplies charged toner to the photoreceptor, and then this toner image is transferred onto a transfer paper 12 by a corona transfer charger 11. Thereafter, the surface of the photoreceptor is cleaned by an elastic blade 13 that is pressed against the surface of the photoreceptor.
Move on to the next copy process.

Fig. 3 shows an electrophotographic copying machine that uses the so-called Carlson process; however, it is an electrophotographic process that uses a conductive base layer, a photoconductor layer, and a transparent insulating layer layered in this order as a photoreceptor, for example, −
The processes described in Publication No. 23910, Publication No. 43-24748, etc. can also be adopted. In this case, the output end face of the short-focus small imaging element array is disposed in a corona discharger that attenuates the surface charge of the photoreceptor at the same time as the light image is exposed, so as mentioned above, the array output end face is particularly susceptible to dirt, and such The present invention is particularly useful in these cases.

FIG. 4 is an explanatory diagram of essential parts of an example in which the present invention is applied to the apparatus shown in FIG. 3. In FIG. 4a, reference numerals 14 and 15 are conductive plates made of metal or the like, which are integrally fixed to the array 3 on the output end surface 3' side of the array 3, and the lower end of each serves as a shield for the imaging light flux. It protrudes further toward the photoreceptor side than the cross section 3' within a range that does not occur. The protruding lower portions of the conductive plates 14 and 15 are opposed to each other. This conductive plate 1
4 and 15 are connected to the other end of a DC power supply 16 whose unipolar connection is grounded as shown in the figure. As a result, an electric field approximately parallel to the optical axis of the elements of the array 3 is formed between the photoreceptor and the charged dust floating in or near the photoreceptor. It is electrostatically attracted to the side of the plates 14, 15 which act as electrodes. The direction in which this dust is attracted is determined by the charged polarity of the dust and the direction of the electric field. Assuming that the dust is toner, the surface of the photoreceptor is negatively charged, the toner is positively charged, and the electrode plate 14,
When a positive potential is applied to 15 as shown in the figure, dusty toner is attracted to the photoreceptor side by the above-mentioned dustproof electric field.

Incidentally, as long as the dirt does not accumulate on the photoreceptor, the amount of dirt adhering to the photoreceptor is very small, so that its influence on image formation can be ignored. Since the photoreceptor is cleaned every cycle of the image forming process, the dirt caused by the above-mentioned dust does not accumulate.

The potentials applied to the electrodes 14 and 15 and their polarities are preferably determined by the distribution of charge polarity of dust floating near the emission end face of the array 3. In other words, if there is a lot of positively charged dust, there is a factor that causes the dust of that polarity to move away from the output end face of the array 3, or in other words, to contaminate the end face 3' of the array 3. It is desirable to apply a potential to the electrodes 14 and 15 that moves as much as possible toward the photoreceptor.

In FIG. 4a, a positive DC voltage is applied to the dust-proof electrodes 14 and 15, but an AC voltage may be applied as in FIG. 4b, or they may be grounded as in FIG. 4c. When grounded, when floating charged dust approaches, a mirror image charge of opposite polarity is induced in the electrode, and this dust is attracted to the electrode.

In addition, in Fig. 4 a, b, and c, two dust-proof electrodes 1
4 and 15 were set at the same potential, but voltages of different polarities were applied to the dust-proof electrodes 14 and 15, respectively, as shown in Fig. 4d, or one was grounded and a positive or negative voltage was applied to the other. Alternatively, a low voltage of the same polarity as the other may be applied to one. In any case, in this way, an electric field is formed between the electrodes 14 and 15 that crosses the output optical path of the array 3 almost perpendicularly, so that the output end surface 3' of the array 3 It is completely shielded from dust by the lower part and the above electric field. That is, charged dust that passes between the electrodes 14 and 15 and reaches the array end face 3' is attracted to either the electrodes 14 or 15 depending on its charging polarity.

Figure 5 shows the present invention as disclosed in Japanese Patent Publication No. 42-23910.
This shows the main part of an embodiment applied to a copying apparatus using a short-focus small imaging element array, which employs an electrophotographic process using an electrophotographic photoreceptor having an insulating layer on its surface, as described in Publication No. 43-24748, etc. It is. That is, the output end face 3' of the array 3 has a corona discharge wire 17 connected to an AC or DC high voltage source and a grounded conductive shield 1 surrounding the discharge wire 17.
8 and is arranged in a corona discharger. This corona discharger applies corona discharge to an electrophotographic photoreceptor having a transparent insulating layer 5'' on its surface at the same time as the light image of the original 9 is irradiated by the array 3. After this simultaneous exposure and static elimination step, the entire surface of the photoreceptor is uniformly exposed to form a high-contrast electrostatic latent image.

As shown in FIG. 5, in this embodiment as well, conductive plates 14 and 15 are provided integrally with the array 3 on the output end surface 3' side of the array 3, as shown in FIG. The lower end portions of the plates 14 and 15 project further toward the photoreceptor side from the output end surface 3' of the array 3, and the projecting portions are opposed to each other. Plate 14,1
Voltages as shown in Fig. 4 a, b, c, and d are applied to the plate 1 as shown in Fig. 4 a.
A positive equal voltage is applied to both 4 and 15.
In this case, a dustproof electric field is formed between the plates 14 and 15 and the photoreceptor and between the shield member 18. The charged dust moves in this electric field according to its charged polarity, and is exposed to the electrodes 14 and 15 side and the shield member 18.
side, and is electrostatically attracted to the photoreceptor side. In order to prevent spark discharge between the discharge wire 17 and the electrodes 14, 15, the electrodes 14, 15 are coated with an insulating material, for example, a coating 19 of synthetic resin.

The above is an example of preventing contamination of the output end face 3' of the short-focus small imaging element array 3, but to prevent contamination of the input end face 3'', for example, the steps shown in FIGS. 6a and 6b may be used. In FIGS. 6a and 6b, conductive plates 20 and 21 are provided integrally with the short-focus small imaging element array 3 on the incident end surface 3'' side thereof. The upper end sides of the plates 20 and 21 are projected further toward the original than the incident end surface 3'' within a range that does not eclipse the light beam from the original entering the array 3, and the respective protruding surfaces are opposed to each other. In FIG. 6a, conductive plates 22 and 23 are disposed close to the lower surface of the document table 8 and opposite to the upper end surfaces of the plates 20 and 21, respectively. is also used to form an optical slit that limits the document facing area of the array 3. In FIG. 6a, the plates 22 and 23 forming this slit are grounded, while the plate body 20,2
1 is connected to the other pole of one grounded DC power supply 24. In this way, electric fields are formed between the electrodes 20 and 22 and between the electrodes 21 and 23, which are substantially parallel to the optical axis of each element of the array 3. This electric field acts as a dust prevention electric field as described above, and charges floating dust to the electrodes 20, 21 or 2 depending on its charging polarity.
It adsorbs to 2 and 23.

In FIG. 6b, the electrode 20 is grounded and a positive voltage is applied to the electrode 21. In FIG. An electric field substantially perpendicular to the optical axis of each imaging element of the array 3 is formed between the opposing surfaces of the electrodes 20 and 21, and charged dust that is about to pass between the electrodes 20 and 21 is caused by this electric field to strike the array entrance end surface. The dust is prevented from directing toward the direction 3'' and is attracted to either the electrodes 20 or 21 depending on the charged polarity of the dust.

The means shown in FIGS. 6a and b are shown in FIGS.
b, c, d may be combined with the embodiments of FIG.

In each of the above embodiments, the dust-proof electrode plate is the seventh
It goes without saying that it is desirable to have a length equal to or longer than the length of the output end face and/or the input end face of the short focus small imaging element array 3 as shown in the figure, and to cover the end face. Furthermore, in the above-mentioned embodiment, the dust-proof electrode was integrally provided in the array 3, but
It is also possible to arrange them separately.

As can be seen from the above description, according to the present invention, the output of the short focus small imaging element array and/or
Since a dustproof electric field is formed near the input end face to prevent dirt on the end face, the structure is simple and compact, and therefore the purpose of miniaturizing the device using a short-focus small imaging element array is not impaired, and the end face of the array is prevented from becoming dirty. It is highly effective in preventing
It is possible to stably form high-quality images, etc.
It has various useful effects.

[Brief explanation of the drawing]

Figures 1A and B, Figures 2A and B show a short focus small imaging element array, Figure 3 shows an example of an electrophotographic copying apparatus to which the present invention can be applied, and Figures 4a, b, c, d, Fifth
6a, b, and 7 show embodiments of the present invention,
They are diagrams for explaining each. 3 is a short focus small imaging element array, 14, 15, 2
0 and 21 are dust-proof electrodes.

Claims (1)

[Claims] 1 Charging department, exposure department, developing department, transfer department,
In order to form an electrostatic latent image on the electrophotographic photoreceptor that moves through the cleaning section in this order, a short-focus small imaging element array is used as an optical system to form a desired light image on the photoreceptor in the exposure section. In the image forming apparatus used, first and second dust-proofing electrodes are provided near the output end face of the short-focus small imaging element array and facing each other across the optical path; a power supply that applies a DC voltage of the same polarity to the electrodes (this polarity is opposite to the polarity of charging the photoreceptor in the charging section, and the same polarity as the polarity of charging the toner supplied to the photoreceptor in the developing section); An image forming apparatus comprising: