JPS5918703B2 - electrophotographic equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electrophotographic apparatus.

Conventionally, in an electrophotographic apparatus, in order to prevent the non-image forming area of a photoreceptor from being visualized, light is irradiated to the non-image forming area to erase the electrical charge or prevent charging.

Incidentally, the boundary between the image forming area and the non-image forming area moves in the direction of movement as the photoreceptor moves. Conventionally, the boundary between the image forming area and the non-image forming area moves in the direction of movement of the photoreceptor. The two areas are divided by turning on or off the lamp when the person exits the area.
However, in this method, since the rise and fall of the lamp is relatively slow, it is not possible to produce the above-mentioned boundary sufficiently sharply, and the light enters the vicinity of the above-mentioned boundary of the image forming area, causing the image to be distorted. If the image is erased, or if sufficient light is not provided near the boundary of the non-image forming area,
There was an inconvenience that it would be visualized. The main objective of the present invention is to solve the above-mentioned disadvantages.

Embodiments of the present invention will be described below with reference to the drawings.

A drum-shaped photoreceptor 1 rotating in the direction of the arrow in FIG.
The structure consists of a conductive layer and a photoconductive layer, and is first charged by a corona discharger 2. Subsequently, the original image 4 on the document table 3 is illuminated from below by the illumination lamp 5, and the image is formed on the photoreceptor 1 through an optical system of reflection mirrors 6, 7 and a lens 8, and as a result, the above-mentioned photoreceptor An electrostatic latent image is formed on the body. At this time, light is irradiated from the light source 9 to erase the electrostatic latent image in the non-image forming area on the photoreceptor 1, but the light from the light source 9 is directed to the image forming area by the mask member 10a, It is shielded by the overlapping portion of 10b. The electrostatic latent image formed in the image forming area on the photoreceptor 1 by erasing the electrostatic latent image in the non-image forming area in this way then enters the developing device 11 and is developed, and is then transferred in the transfer section 12. The image is transferred onto paper 13. Thereafter, the image transferred to the transfer paper 13 is fixed by a fixing device (not shown), and the image transferred to the transfer paper 13 is fixed by a fixing device (not shown).
is ejected outside the device. On the other hand, the photoreceptor 1 is cleaned of residual toner after transfer by the cleaning blade 14, and the above cycle is repeated again. FIG. 2 is a partial diagram showing a mechanism for controlling the light from the light source 9 using a mask member to control division of the image forming area and non-forming area on the photoreceptor. handle. In the figure,
The light sources 9 are point light sources with a sufficient number to evenly illuminate the entire width of the photoreceptor 1, or line light sources with a sufficient irradiation width to illuminate the entire photoreceptor 1 in the axial direction. The light source 9 is installed in the light source frame 15 so as to be substantially parallel to the photoreceptor 1 in order to make the illuminance uniform on the surface of the photoreceptor 1. Further, a slit 18 is provided in the light source frame 15 so that the irradiation width of the light 16 matches the irradiation width d of the exposure light 17 of the original image. Mask member 10a
, 10b move onto the optical path of the control light 16 when necessary to block this light from the image forming area. Note that the mask members 10a and 10b block the light 16 by overlapping each other, and prevent the light 16 from reaching the photoreceptor 1. Therefore, the image remains without being erased. However, the light 16 is transmitted where the members do not overlap, and the charges on the photoreceptor 1 are erased. As a result, unnecessary images will be deleted. FIG. 3 is a diagram showing overlapping of mask members.

In this embodiment, an example in which a polarizing plate is used as a mask member will be shown in the following description. In FIG. 3 1, the mask member 10
C and 10d are polarizing plates configured such that their polarization directions are perpendicular to each other, and a shaded region 19 indicates a portion where the polarizing plates are overlapped.

The polarizing plates 10c and 10d can be independently changed in the direction of the arrow shown in the figure by a control means (not shown), thereby changing the overlapping area 19 of the polarizing plates.
can be set continuously and arbitrarily. Figure 3 2
shows an example in which an electrostatic latent image is formed only in an arbitrary region of a photoreceptor. The figure shows how the polarizing plates 10c and 10d are superimposed, viewed from above in FIG. 31. The light 16 is completely blocked at the overlapping portion of the polarizing plates 10c and 10d, or at least is blocked to such an extent that it does not conduct through the photoconductive layer on the surface of the photoreceptor and therefore does not erase the charges on the photoreceptor.
On the other hand, the single polarizing plate portions (non-overlapping portions) on both sides transmit at least enough light 16 to completely erase the charges on the surface of the photoreceptor. Therefore, as shown in the figure, an electrostatic latent image 22 (indicated by a positive charge) remains on the photoreceptor 1 only in the light-shielded portion, and the latent image is erased in the light-transmitted portion. Note that the configuration of the polarizing plate is such that if it can block light to the extent that the charges on the photoreceptor are not erased by the light,
The polarization directions do not need to be orthogonal to each other.

Further, the mask member is not limited to a polarizing plate, but may be any other member as long as the above-mentioned functions and effects can be achieved by overlapping the mask member.

In other words, the mask member is a member that has the function of producing at least a light-shielding effect to the extent that it does not erase the electrical charges on the photoreceptor when overlapped, and that alone can transmit enough light to erase the electrical charges. If there is, then anything is fine. For example, in addition to the polarizing plate, (a) depending on the spectral sensitivity of the photoreceptor, it is also possible to superimpose a filter that divides the wavelength range so that the amount of light is the same, or (b) a filter with a large absorption coefficient for light. Materials may also be used. Furthermore, (c) the above-mentioned light transmission and light blocking effects can be obtained by overlapping a polarizing plate and a liquid crystal and changing the orientation of the liquid crystal. FIG. 4 shows the entire area A of the original image.

In the figure, the shaded area (the area surrounded by Abcd) represents the necessary image area B, and the other parts (white areas) represent the unnecessary image area. The original image A advances in the direction of the arrow and is sequentially scanned with the slit exposure width. Between a and b in the figure (
d-C) is the width of the required image area B, and a-d (b-
e) corresponds to the length. Figure 5 is the original image A of Figure 4.
FIG. 4 is a diagram showing an example of the operation of a polarizing plate in order to obtain a required image area B from .

The left side diagrams of FIGS. 1 to 4 each show the polarizing plate 10e,
10f is a cross-sectional view cut along the overlapping portion (V-line), and the right-hand figure explains how the polarizing plate controls the irradiation area of the light 16 with respect to the exposure light of the original image on the photoreceptor 1. This is a diagram. In the diagram on the left side of FIG. 5, the solid and dotted lines on the drum-shaped photoreceptor 1 are the image I to be formed from the original image as shown in FIG. 4 on the surface of the photoreceptor 1, and It advances on the photoreceptor in synchronization with the rotation in the direction of the arrow 1. In the image 1, the solid line portion corresponds to a necessary image area (area B in FIG. 4), and the dotted line portion corresponds to an unnecessary image area (white area in FIG. 4). Further, in the figure on the right, an area 23 surrounded by a dotted line indicates an irradiation area of the light 16 with respect to the exposure light 17 of the original image. 5. As shown in FIG. 1, the original image is scanned until the position of the tip a-b (boundary between the image forming area and non-image forming area) of the required image area in the image I reaches the irradiation area 23 of the light 16. In this case, the polarizing plates 10e and 10f are completely out of the optical path of the light 16. As a result, the light irradiation area 23 on the photoreceptor 1 receives the light 16 over its entire surface, and the electrical charges in the area are erased. Therefore, from the tip of image I, a
The electrostatic latent image in the area up to position -b is all erased, and the fourth
When attempting to obtain a copy as shown in the figure, the portion corresponding to the above area will be blanked out and no image will be formed. Next, when the positions a and b shown in image I progress and reach the light irradiation area 23, as shown in FIG.
The lower ends of the polarizing plates 10e and 10f begin to descend in the direction of the arrow in synchronization with the movement from position a-b while remaining in an overlapping state. Subsequently, the polarizing plates 10e and 10f descend until they completely block the light 16, and then stop. This state is maintained until the position of the rear end ed (boundary between the image forming area and non-image forming area) of the required image area shown in image I reaches the light irradiation area 23. Therefore, within the light irradiation area 23, the polarizing plate 1
Irradiation of the light 16 is blocked to the region corresponding to the overlapping portion 24 of 0e and 10f, and the electrostatic latent image in the region remains without being erased. On the other hand, in the irradiation area 23, the area corresponding to the non-overlapping portion of the polarizing plate is irradiated with the light 16, and the electrostatic latent image in the area is erased.
Therefore, when attempting to obtain a copy as shown in FIG. 4, an image will be formed only in area B indicated by diagonal lines.
Furthermore, when the position cmd shown in image I advances and reaches the light irradiation area 23, the polarizing plates 10e and 10f remain in an overlapping state and their upper ends are at the position cmd, as shown in FIG. 5. It begins to descend in the direction of the arrow in synchronization with its progress, and eventually descends to a position where it is completely out of the optical path of the light 16, and then stops.

The above position is maintained until the image I completely passes through the light irradiation area 23, that is, until the scanning of the original image is completely completed. Therefore, the electrostatic latent image in the area from the position cmd to the rear end of the image is erased, and the image remains in the area of the copy corresponding to the above-mentioned area in the same way as the area from the leading edge to positions a-b. Not formed at all. When scanning of the original image is completed, the polarizing plates 10a and 10b move upward in the direction of the arrow in FIG. 5 and return to their original positions shown in FIG. 51.

FIG. 6 is a perspective view showing an embodiment of a polarizing plate unit having two polarizing plates arbitrarily overlapping each other and a control means for controlling the polarizing plates.

The right end of the polarizing plate 24 on the front side is wound up by a spool 25 on which back tension is applied, and the back tension of the spool is performed by a spring or the like. On the other hand, a transparent film 26 is continuously connected to the left end of the polarizing plate 24 (position M in the figure), and another spool 27 for winding this transparent film 26 is connected to the spool 25 described above. installed in a parallel position. A gear 28 is installed on the rotating shaft of the spool 27, and this gear 28 meshes with a gear 29 attached to the rotating shaft of the Mimo 1/30. The set position of the polarizing plate 24 is determined by the amount of rotation of the motor 30. Similarly, another polarizing plate 31 whose polarization direction is perpendicular to that of the polarizing plate 24 is arranged parallel to or close to the polarizing plate 24 .

The left end portion of the polarizing plate 31 is wound up by a spool 32 having the same structure as the spool 25 described above.
On the other hand, a transparent film 33 is continuously connected to the right end of the polarizing plate 31 (position N in the figure) in the same way as described above, and another spool 34 is connected to the polarizing plate 31 on which the transparent film 33 is wound.
is installed in parallel at a position facing the spool 32. A gear 35 is installed on the rotating shaft of the spool 34, and this gear 35 further meshes with a gear 36 attached to a motor 37. With the above configuration, the set position of the polarizing plate 31 is determined by the amount of rotation of the motor 37. Polarizing plate 24
is pulled out from the spool 25 to position M in the figure,
Furthermore, when the polarizing plate 31 is pulled out from the spool 32 located on the opposite side of the spool 25 to the position N in the figure, the polarizing plates 24 and 31 block light between MN where they overlap, and other than the above The polarizing plate alone transmits enough light to erase the charges on the photoreceptor.

Next, a mechanism for selecting a necessary image area (hereinafter referred to as a monitor mechanism) will be explained.

FIG. 1 shows an embodiment of an electronic copying machine having a monitor mechanism.

The monitor mechanism includes an illumination lamp 38, a lens 39, reflective mirrors 40, 41, a screen 42, and indicators Xl, X2, Yl.
, Y2, etc. When the document table 3 on which the original image 4 is placed is positioned above the illumination lamp 38, the illuminated image is projected onto the screen 42 via an optical system consisting of a lens 39 and reflection mirrors 40, 41. A necessary image area is selected from the image on the screen 42 using the indices Xl, X2, Yl, and Y2. Among the above indices, the indices Xl and X2 are the length of the required image area (a-
d or b-c). Above indicator X
, , X2 is transmitted to the control means for controlling the vertical movement of the polarizing plate in FIG. 5 mentioned above. Indices Yl and Y2 are used to select the width of the required image area (between a and b or between d and c in FIG. 4). A position signal of the width of the area selected by the indicators Yl and Y2 is transmitted to a control means that sets the overlapping position of the polarizing plates. Next, a positioning means having these indicators and selecting a necessary image area will be explained in detail with reference to an embodiment.

In FIG. 7, the necessary image area (hatched area surrounded by ABCd) of the original image 4 projected onto the screen 42 is as follows:
The selection is made by index buttons X, , X2, Y, , Y2 that can be moved arbitrarily on the index rails 43 and 44. The position signal of the index button X1 on the index rail 43 for selecting the length of the required image area (between a and d) is determined by a voltage drop value or resistance value from the reference line Xs on the index rail 43 by a potentiometer PMXl. is detected, converted into a digital signal by the AD converter ADXl, and sent to the matching circuit C.
Sent to C. On the other hand, a position signal of the photoreceptor 45 detected as a clock pulse by an optical or magnetic device from a clock plate 46 rotating in the direction of the arrow in synchronization with the drum-shaped photoreceptor 45 is also transmitted to the photoreceptor 45 via the pulse counter PC. Coincident rotation CC, is sent. This coincidence circuit CCl
Now, the position signal of the photoreceptor 45 and the previous index button X1
The position signals are compared, and if they match, a signal is sent to the motor control circuit MCX. This signal causes the motor control circuit MCX to actuate, and the motor M operates to operate the polarizing plate 10.
g, 10h in the X-axis direction. Similarly, the position signal of the index button
It is sent to the coincidence circuit CC2 via the D converter ADX2.
When the above signal and the signal from the clock plate 46 match, the motor M is activated and the polarizing plates 10g and 10h are moved to predetermined positions in the X-axis direction. The position signal of the index button Y1 for selecting the width of the required image area (between a and b) is sent to the reference line Ys on the index rail 44 by the potentiometer PMYl.
It is detected as a voltage drop value or resistance value from , and is converted into a digital signal by an AD converter ADYl.

This digital signal is further sent to the motor control circuit MCYl, converted into pulses, and operates the pulse motor M1. As a result, the polarizing plate 10g is moved to a predetermined position in the Y-axis direction by the operation of the pulse motor. Similarly, the position signal of index button Y2 is output from potentiometer PMY2.
, AD converter ADY2, and motor control circuit MCY2 to operate the pulse motor M2 to move the polarizing plate 10h in the Y-axis direction. With the above, the original image 4 is placed on the photoreceptor 45.
Electrostatic latent image a′b′c corresponding to the required image area Abcd of
'd' is formed.

Next, regarding the movement of the mask member for controlling the length direction of the required image area, other embodiments other than the example shown in FIG. 5 will be described in detail.

FIG. 8 shows another example of the operation of a polarizing plate as a mask member.

The configuration of each part is the same as that in Figure 5, but unlike the simultaneous movement type in which the polarizing plates in Figure 5 overlap and move up and down together, in this example, each polarizing plate moves up and down together. It is characterized by being an alternating movement type that moves alternately. First, as shown in FIG. 8, one of the polarizing plates 1 is
0e is completely out of the optical path of the light 16.

However, the other polarizing plate 10f is located in the optical path in such a manner as to completely block the light 16. Next, when the position a-b advances and reaches the light irradiation area 23, as shown in FIG. Begin to. Subsequently, the polarizing plate 10e descends until it completely overlaps the other polarizing plate 10f and the light irradiation area 23, and then stops. This state is maintained until the position cmd of the rear end of the required image area in image I reaches the light irradiation area 23. When the position cmd reaches the area 23, as shown in FIG. 8, the polarizing plate 10e remains on the optical path of the light 16, and the upper end of the other polarizing plate 10f synchronizes with the progress of the cmd. and start descending in the direction of the arrow. The polarizing plate 10f finally transmits the light 16
completely out of the optical path and stop. This state is maintained until the scanning of the original image is completed, and then the polarizing plates 10e and 10f
Both rise in the direction of the arrow in FIG. 8 and return to the position shown in FIG. As described above, as in the operation example shown in FIG.
It will be understood that an image is obtained by omitting the peripheral part of the original image as shown in the figure.

Moreover, in this example, it is not necessary to move two polarizing plates at the same time, so it is easier to synchronize the ends of the polarizing plates and the progress of the image. Note that the polarizing plates 10e and 10f may be operated in the reverse order of the above example. FIG. 9 shows yet another example of the operation of the polarizing plate, and the configuration of each part is the same as that in FIGS. 5 and 8.

This example is characterized by being a one-sided moving type in which one of the polarizing plates is always fixed on the optical path of the light 16 and only the other polarizing plate moves. In FIG. 9, polarizing plate 1
Of is fixed in such a way that it completely covers the light 16.

First, as shown in FIG. 9 1, the polarizing plate 10e does not control the optical path of the light 16 until the tip position a-b of the required image area in the image I to be formed from the original image reaches the irradiation area 23 of the light 16. It's completely out of place. Next, when the position a-b advances and reaches the light irradiation area 23, the lower end of the polarizing plate 10e moves in the direction of the arrow in synchronization with the progress of the position a-b, as shown in FIG. begins to descend. Next, the polarizing plate 10
e descends until it completely overlaps with the other fixed polarizing plate 10f and the light irradiation area 23, and then stops. This state is maintained until the position cmd of the rear end of the required image area in image I reaches the light irradiation area 23. When the position cmd reaches the light irradiation area 23, the ninth
As shown in FIG. 3, the upper end of the polarizing plate 10e begins to descend in the direction of the arrow in synchronization with the progression of the position cmd. The polarizing plate 10e finally leaves the optical path of the light 16 completely and stops. This state is maintained until the scanning of the original image is completed, and then the polarizing plate 10e rises in the direction of the arrow in FIG.
Return to the position shown in Figure 1. From the above, similarly to the operation examples shown in FIGS. 5 and 8, it is possible to obtain an image of the area of the original image as shown in FIG. 4, with the peripheral portion omitted.

Furthermore, in this example, only one polarizing plate moves, so the structure of the means for controlling movement is simplified. Note that, contrary to the above example, the polarizing plate 10e may be fixed and the polarizing plate 10f may be moved. Next, a method for obtaining an image having a shape opposite to that shown in FIG. 4 will be explained in detail.

FIG. 10 shows an unnecessary image area C surrounded by Efgh and five necessary image areas D indicated by diagonal lines in the original image 47.

The original image 47 advances in the direction of the arrow and is sequentially scanned with the slit exposure width. In the figure, the distance between e and f (between h and g) corresponds to the width of the unnecessary image area C, and the distance between e and h (between f and g) corresponds to the length. FIG. 11 is a diagram showing how polarizing plates are stacked to obtain the required image area D as shown in FIG. 10.

In FIG. 11, polarizing plates 101 and 10j are configured such that their polarization directions are orthogonal to each other, and further, polarizing plates 10
k is configured such that its polarization direction is orthogonal to each of the upper polarizing plates 101 and 10j.

For example, if the diagonal lines in the figure are the polarization directions, the polarizing plates 101 and 10k, 10j and 10k, and 101
and 10j are orthogonal to each other in their polarization directions. That is, the polarizing plate 10k is configured such that its polarization directions are different (orthogonal) on the left and right sides of the center 48 (dotted chain line). In the figure, the portions 49 and 5 where the diagonal lines intersect
0 are polarizing plates 101 and 10k, and 10j and 10, respectively.
This is the overlapping part of k. FIG. 11 shows an example in which an electrostatic latent image is formed only in an arbitrary area on a photoreceptor according to the principle of the present invention.

The figure shows the overlapping of polarizing plates 101, 10j and 10k,
FIG. 11 is a view from above of 1. 3. Similar to the example in FIG. 2, the overlapping portion of the polarizing plates 101 and 10k or 10j and 10k completely blocks the light 16 in the image area, or
Alternatively, light is blocked at least to the extent that the charges on the surface of the photoreceptor are not erased. On the other hand, the single portion of the polarizing plate 10k that does not overlap transmits at least enough light 16 to completely erase the above-mentioned charges. Therefore, as shown in the figure, electrostatic latent images 53 and 54 (indicated by positive charges) remain only on the light-shielded portions of the photoreceptor 1, and on the portions of the photoreceptor 1 through which the light 16 is transmitted. Then, the silent latent image is erased. Next, the 10th
An example of the operation of the polarizing plate to obtain the required image area D as shown in the figure will be described.

Among the three-ply polarizing plates as shown in FIG. 11, the polarizing plate 101
If 10j and 10j are considered as one set, it is possible to operate in the same manner as the operation example of the two-ply polarizing plate shown in FIG. 5, FIG. 8, or FIG. 9.

That is, the pair of polarizing plates 101 and 10j and the polarizing plate 10k are
(!) Simultaneous movement type, similar to the example in Figure 5, in which they are moved underground at the same time; (4) Alternate movement type, similar to the example in Figure 8, in which they are moved alternately; It is possible to perform a one-side movement type movement operation similar to the example of Fig. 9, in which one is fixed on the optical path and the other is moved.In addition, from the tip of the original image to position e-f in Fig. 10, position h-
If the entire image is to be left, such as the area from g to the rear end of the original image, the light 16 may be blocked by a light blocking member such as a frame of a polarizing plate unit. Furthermore, the polarizing plate 10 in FIG.
1 and 10j respectively correspond to the polarizing plates 10e and 10f in FIG.
), 10j (10f) as shown in FIG. 5 to obtain an image like that shown in FIG.
0k is added and polarizing plates 101 (10e), 10j (10f
) and operate in the same manner as in the example shown in FIG. 5, it becomes the above-mentioned (1) simultaneous movement type in a three-ply polarizing plate.

In other words, depending on whether or not to add one more polarizing plate to the same polarizing plate, it is possible to leave a part of the original image or erase the same area.With a simple combination of polarizing plates, It is possible to control a wide range of image formation as described above. In addition, in FIG. 11, polarizing plates 101 and 10j
with the same polarization direction, and the entire polarizing plate 10k is
01, 10j may be configured to be perpendicular to the polarization direction of 01 and 10j. Also, in FIG. Electrostatic latent images 53 and 54 can be obtained.

Above, an embodiment of an image forming method for obtaining a necessary image area by erasing the electrical charges in an unnecessary image area on a photoreceptor has been described in detail.

At that time, in each of the examples, an example was shown in which the photoreceptor was irradiated with light for erasing charges on the photoreceptor at the same time as the exposure light of the original image. However, it is not necessarily necessary to irradiate the above light simultaneously with the exposure light. That is,
As long as it is between the electrostatic latent image forming steps, the light may be irradiated to any position on the photoreceptor described above, before or after the exposure position.

In addition, when using a photoreceptor with a three-layer structure as described in Japanese Patent Publication No. 42-23910 by the applicant of this patent,
The photoreceptor may be irradiated with the above light simultaneously with the exposure light of the original image.

Furthermore, the above-mentioned light can be irradiated after the exposure position on the three-layer photoreceptor as so-called whole-surface exposure light for producing latent image contrast.

FIG. 12 is an example showing the formation of an electrostatic latent image when a three-layer photoreceptor consisting of a conductive layer, a photoconductive layer and a surface insulating layer is used.

In the figure, a drum-shaped three-layer photoreceptor 54 rotating in the direction of the arrow is first charged to + by a corona discharger 55 of positive polarity. Subsequently, when reaching the exposure section 56, the AC corona discharger 58 simultaneously generates the exposure light 57 of the original image.
undergoes static electricity removal. Next, the entire surface is exposed by the entire surface exposure light source 60, and an electrostatic latent image is formed on the surface of the photoreceptor 54. The present embodiment attempts to prevent the formation of an electrostatic latent image in the non-image forming area by controlling the area exposed on the entire surface during the above-mentioned overall exposure.

In the figure, the overlapping positions of the polarizing plates 101 and 10m are controlled as described above, and the polarizing plates 101 and 10m are
It moves across the optical path of the light 61 like the polarizing plate in the figure.

By the light blocking effect of these polarizing plates, the formation of an electrostatic latent image can be controlled in the same way as the method of erasing charges on a photoreceptor. However, the latent image formation results are different between the method of controlling full-surface exposure and the method of erasing the charged charges. Next, electrostatic latent image formation in the method of controlling full-surface exposure will be explained in detail. FIG. 13 shows an example in which an electrostatic latent image is formed only in an arbitrary area of a three-layer photoreceptor during full-surface exposure, based on the principle of the present invention in which the control light in the image area is controlled by overlapping polarizing plates as described above. This is what is shown.

In the figure, light 61 is blocked in the overlapping portion of the polarizing plates 10n and 100, and is transmitted in the single polarizing plate portion.

In the electrostatic latent image formation process on the three-layer photoconductor, the temperature is
If the photoreceptor is not irradiated with light after the simultaneous exposure and static elimination, no electrostatic contrast will occur and no electrostatic latent image will be formed. Therefore, as shown in the figure, no electrostatic latent images are formed on the light-shielded portions of the three-layer photoconductor 54, and electrostatic latent images 64, 65 (+ ) is formed. Furthermore, as shown in FIG. 14, if a polarizing plate 10p is added to the polarizing plates 10n and 100 in FIG. are formed in a form opposite to that of the latent images 64 and 65 in FIG. Moreover, as is clear from comparing FIG. 13 with FIG. 3 2 and FIG. 14 with FIG. 11 2,
The method of controlling full-surface exposure (FIGS. 13 and 14) and the method of erasing charged charges (FIG. 3 2 and FIG. 11 2) are as follows:
Even though polarizing plates with the same configuration are used, the pattern of electrostatic latent image formation is completely reversed. We have shown examples of whether or not to add a polarizing plate when leaving a partial area of the original image and when erasing the same area. This shows that similar results can be obtained using a combination of methods. FIG. 15 shows an example of a method for leaving or erasing a selected image area by changing the irradiation position of the image area on the three-layer photoreceptor.

When trying to obtain an image like the area B in FIG.
The photoreceptor 54 is irradiated with the light 70a controlled to r at the same time as the exposure light 71 of the original image, thereby erasing the electrical charge on the unnecessary area on the photoreceptor. Furthermore, when trying to obtain an image such as the area D in FIG. 10, which is completely opposite to the area B, the light 70
Change the irradiation direction of a to the direction of the dotted arrow 70b, and
The light 70b may be blocked by the superposition of 0q and 10r, and formation of an electrostatic latent image on the photoreceptor 54 may be prevented. This makes it possible to select an image area without changing the configuration of the polarizing plate. In addition, in FIG. 15, instead of the polarizing plates 10q and 10r in the above example, three-ply polarizing plates such as the polarizing plates 10n, 100, and 10p in FIG. 14 may be used (in this case, In this case, the result is exactly the same as in the above example, except that the way the image is formed depending on the direction of light irradiation is reversed.

As described above, according to the present invention, since the mask means moves in synchronization with the movement of the boundary between the image forming area and the non-image forming area, the boundary between the two areas can be clearly formed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a copying machine used in an embodiment of the present invention. FIG. 2 is an explanatory diagram of the control process of the image forming area range. FIG. 3 is an explanatory diagram showing how polarizing plates are stacked together. FIG. 3 is an explanatory diagram of latent image formation when the above polarizing plate is used. FIG. 4 is an explanatory diagram of the required image area. 5.1 to 5.4 are explanatory diagrams of movement of the polarizing plate. FIG. 6 is a perspective view showing an embodiment of the polarizing plate unit. FIG. 7 is an explanatory diagram of the positioning means of the monitor mechanism. FIGS. 81 to 84 and FIGS. 91 to 94 are further explanatory diagrams of the movement of the polarizing plate. FIG. 10 is an explanatory diagram of the required image area in a form opposite to that of FIG. 4. Figure 11 1 and Figure 11 2 are 3
An explanatory diagram showing an example of overlapping of polarizing plates having a structure of sheets, and an explanatory diagram for forming a latent image thereof. FIG. 12 is an explanatory diagram of the control process of the image forming area range when a three-layer photoreceptor is used. FIG. 13 is an explanatory diagram of latent image formation when a two-ply polarizing plate is used during full-surface exposure. FIG. 14 is an explanatory diagram of latent image formation when three polarizing plates are used during full-surface exposure. FIG. 15 is an explanatory diagram showing that an image forming area is selected by changing the light irradiation position.
In the figure, 1 is a photoreceptor, 3 is a document table, 4 is an original image, and 9
10 is a polarizing plate, 42 is a screen, 54 is a three-layer photoreceptor,
60 is a light source for controlling the image forming area range; 16;
Reference numeral 61 indicates control light for the image forming area range.

Claims (1)

[Claims] 1. In an electrophotographic device that exposes an image while moving it onto a moving electrophotographic photoreceptor, a light source that illuminates the photoreceptor to prevent the non-image forming area of the photoreceptor from becoming visible; mask means for blocking light from the light source to the image forming area or the non-image forming area, the mask unit moving in synchronization with the movement of the image forming area and the non-image forming area as the photoreceptor moves; An electrophotographic device comprising: