JPS5917831B2 - electrophotographic equipment - Google Patents

Description

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

The present invention can be applied to copying machines and recording devices, and will be described in detail below using an electrophotographic copying machine that employs a slit exposure method as an example.

Conventionally, the following method has been considered in order to prevent areas other than the required image area from being visualized on a photoreceptor or transfer paper in an electrophotographic copying machine.

That is, in the (i) charging step, charging of unnecessary image areas on the photoreceptor is prevented.

(il) In the development process, development of unnecessary image areas on the photoreceptor is prevented.

(In the transfer step 110, transfer of unnecessary image areas on the photoreceptor is prevented.

I-off: After the charging process and before the developing process, a plurality of lamps are blinked to prevent or eliminate charging of unnecessary image areas.

(V) A movable light-shielding plate is provided for each of the lamps disposed at both ends of the photoreceptor, and the charge is erased with light not blocked by the light-shielding plate before the developing process.

However, these methods (1) to (1) require partial blocking of charging, development, or transfer action in order to prevent unnecessary image areas from being visualized.

Therefore, in the method (i), the boundary area between the charged side and the non-charged side of the photoreceptor becomes unclear due to the shielding member interposed between the corona discharge electrode and the photoreceptor, and the desired image area is sharpened. This makes it impossible to form images that are distinguished by distinct border areas. Furthermore, in the methods (4) and (111), there is a risk that toner particles adhering to the shielding member may contaminate the transfer material, photoreceptor, etc. The methods Q'S7) and (V) do not have the above drawbacks. However, (1V method selectively and frequently blinks the lamp, which affects its lifespan, and the disadvantage that the width of the required image area cannot be changed finely, and (V method), the width of the required image area cannot be changed. However, it is an object of the present invention to provide an electrophotographic apparatus that can solve the above-mentioned drawbacks of the prior art.

Examples of the present invention will be described in detail below. A drum-shaped photoreceptor 1 rotating in the direction of the arrow in FIG. 1 is composed of a conductive layer and a photoconductive layer, and is first charged by a corona discharger 2. As shown in FIG.

Next, the original image 4 on the document table 3 is illuminated from below by the illumination lamp 5, and the image is reflected by the reflecting mirrors 6, 7 and the lens 8.
An image is formed on a photoreceptor 1 through an optical system, and as a result, an electrostatic latent image is formed on the photoreceptor. At this time, in order to erase the electrostatic latent image in the unnecessary image area on the photoreceptor 1, control light for the image area is irradiated from the light source 9 for controlling the image area, and the mask members 10a and 10b are overlapped. The control light is controlled depending on the area, and the electrostatic latent image in the unnecessary image area on the photoreceptor 1 is erased. The electrostatic latent image in the necessary image area on the photoreceptor 1, which has been formed by erasing the electrostatic latent image in the unnecessary image area, then enters the developing device 11 and is developed into a developed image, and then in the transfer section 12 on the transfer paper. Transferred to 13. Thereafter, the transfer paper 13 is fixed by a fixing device (not shown) and is discharged from the apparatus. 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 shows the principle of the invention.

2 is a partial diagram showing a mechanism for controlling control light in an image area by a mask member to control formation of an electrostatic latent image on a photoreceptor, and corresponds to the image exposure section in FIG. 1. FIG. In the figure, the light sources 9 for controlling the image area are either point light sources sufficient to uniformly illuminate the entire width of the photoreceptor 1, or light sources sufficient to illuminate the entire width of the photoreceptor 1 in the axial direction. It is a line light source with a wide irradiation width. The light source 9 also irradiates the image area with control light 16 for controlling the formation of an electrostatic latent image, and irradiates the photosensitive member 1 with control light 16.
Erases the electrical charges in the unnecessary latent image area above. The light source 9 is installed in the light source frame 15 so as to be substantially horizontal 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 control light 16 matches the irradiation width d of the exposure light 17 of the original image. Mask members 10a, 10
b is provided on the optical path of the control light 16 when necessary. Furthermore, the mask members 10a and 10b block the control light 16 by overlapping each other, and prevent the control light 16 from reaching the photoreceptor 1. Therefore, the image remains without being erased. However, in places where the above members do not overlap, the control light 16
is transmitted, 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 according to the principle of the present invention. The figure shows polarizing plates 10c and 10.
3 is a view of the overlapping state of d as viewed from above (arrow view 1) in FIG. 1. The control light 20 in the image area is transmitted through the polarizing plate 10c.
, 10d, the light is completely blocked, or at least is blocked to such an extent that the photoconductive layer on the surface of the photoreceptor is not electrically conductive, and thus the electrical charges on the photoreceptor are not erased. on the other hand,
The single polarizing plate portions (non-overlapping portions) on both sides transmit at least enough control light 20 to completely erase the charges on the surface of the photoreceptor. Therefore, as shown in the figure, an electrostatic latent image 22 (indicated by 10 charges) remains on the photoreceptor 21 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 does not require that the polarization directions be orthogonal to each other as long as the control light can block light to such an extent that the charges on the photoreceptor soil are not erased.

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 master 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 overlaid, 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, a filter that divides the wavelength range so that the amount of light is equal may be superimposed, and (b) a filter that has a wavelength range that is divided into two layers so that the amount of light is the same, or (b) a filter that has a Large 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 (
between d and c) is the width of the required image area B, and between a and d (between b and
c) 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-V/line), and the right-hand diagram shows a polarizing plate that covers the irradiation area of the control light of the image area with respect to the exposure light of the original image on the photoreceptor 1. FIG. 3 is a diagram illustrating how the control is performed. In the left side diagram of FIG. 5, the solid line and dotted line along the drum-shaped photoreceptor 1 are as follows:
This is an image I to be formed from an original image as shown in FIG. 4 on the surface of the photoreceptor 1, and it advances on the photoreceptor soil in synchronization with the rotation of the photoreceptor 1 in the direction of the arrow. In image I, the solid line portion corresponds to the necessary image area (area B in FIG. 4), and the dotted line portion corresponds to the 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 control light 16 of the image area with respect to the exposure light 17 of the original image. As shown in FIG. 5 1, until the original image is scanned and the position of the leading edge a-b of the required image area in the image reaches the light irradiation area 23, the polarizing plates 10e and 10f are used to control the control light of the image area. It is completely out of the optical path of 16.

As a result, the light irradiation area 23 on the photoreceptor 1 receives the control light 16 over the entire surface, and the electric charges in the area are erased. Therefore, the electrostatic latent image in the area from the tip of image I to position ab is completely erased, and when trying to obtain a copy as shown in Figure 4, the part corresponding to the above area is erased. The image will appear white and no image will be formed. Next, the positions a-d shown in image I progress to the light irradiation area 23.
When the polarizing plate 10e, 1 is reached, as shown in FIG.
0f remains in an overlapping state, and the lower end begins to descend in the direction of the arrow in synchronization with the progression from position a to b. Subsequently, the polarizing plates 10e and 10f descend until they completely block the control light 16, and then stop. This state is maintained until the position of the rear end cmd of the required image area shown in image I reaches the light irradiation area 23. Therefore, in the light irradiation area 23, the control light 16 is prevented from irradiating the area corresponding to the overlapping portion 24 of the polarizing plates 10e and 10f, and the electrostatic latent image in the area is not erased. remain. On the other hand, the control light 16 is irradiated to a region of the irradiation region 23 corresponding to the non-overlapping portion of the polarizing plates, and the electrostatic latent image in the region is erased. Furthermore, the position cmd shown in image I is
When the light advances and reaches the light irradiation area 23, as shown in FIG. The light starts to move, and eventually descends to a position where it is completely out of the optical path of the control light 16, and then stops.

The above position is maintained until the image 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. In this way, an image of only area B in FIG. 4 can be formed. When scanning of the original image is completed, the polarizing plates 10a and 10b are raised in the direction of the arrow in FIG. 5 and returned to their original positions shown in FIG. 51.

The above is an example showing the operation of a polarizing plate for obtaining a necessary image according to the present invention.

It will be understood that by doing this, it is possible to accurately and easily obtain an image of area B, excluding the peripheral portion of the original image, which is indicated by diagonal lines in FIG. Further, operation examples of other polarizing plates will be described later. 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 further meshes with a gear 29 attached to the rotating shaft of the motor 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 side 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, reflection mirrors 40, 41 . Screen 42, indicators Xl, X2, Y,
, 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
The position signal selected by I and 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). In other words, the index Y1 independently specifies one end line b-c of the width of the required image area, and the index Y2 independently designates the other end line a-d of the width of the required image area. 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 Figure 7, screen 4
2 The required image area (the diagonal area surrounded by Abcd) of the original image 4 projected onto the soil is selected by index buttons Xl, X2, Yl, Y2 that can arbitrarily move the index rails 43 and 44 soil. . 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 coincidence circuit Cc. 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. The signal is sent to the matching circuit CCl. This matching circuit CCl compares the position signal of the photoreceptor 45 with the position signal from the index button X1,
If they match, a signal is sent to the motor control circuit MCX. This signal activates the motor control circuit MCX, and the motor M operates to move the polarizing plates 10g and 10h in the X-axis direction. Similarly, the position signal of the index button X2 is sent to the coincidence circuit CC2 via the potentiometer PMX2 and the AD 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 Y, which selects the width of the required image area (between a and b), is detected by the potentiometer PMYl as a voltage drop value or resistance value from the reference line Ys on the index rail 44, and is detected by the AD converter. ADY, is converted into a digital signal.

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, the pulse motor M2 is operated to move the polarizing plate 10h in the Y'-axis direction. In other words, the polarizing plates 10g and 10h are moved independently of each other based on the position designation by the index buttons Yl and Y2, respectively, and a necessary portion of the original image 4 at a necessary position can be copied in the width direction. As a result, electrostatic latent images a'b/c'd' corresponding to the required image area Abcd of the original image 4 are formed on the photoreceptor 45.

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, the tip position a-b of the required image area in the image I to be formed from the original image corresponds to the irradiation area 2 of the control light 16 of the image area with respect to the exposure light 17.
3, one polarizing plate 10e is completely out of the optical path of the control light 16 in the image area.

However, the other polarizing plate 10f is located in the optical path in such a manner as to completely block the control light 16. Then position a-b
When the polarizing plate 10e advances and reaches the light irradiation area 23, the lower end of the polarizing plate 10e starts to descend in the direction of the arrow in synchronization with the progression from position a to b, as shown in FIG. 8 and 2. Next, polarizing plate 10
e 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. Above position cmd
When the polarizing plate 10e reaches the area 23, as shown in FIG. begins to descend in the direction of The polarizing plate 10f completely deviates from the optical path of the final control light 16 and stops. This state is maintained until the scanning of the original image is completed, and then the polarizing plate 10
e and 10f both rise in the direction of the arrow in FIG.
Return to the position shown in the figure. From the above, it can be understood that, as in the operation example shown in FIG. 5, an area of the original image as shown in FIG. 4 with the peripheral portion omitted can be obtained as an image. 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.

In this example, one of the polarizers always has the control light 16 in the image area.
It is fixed to the optical path of the polarizing plate, and is characterized by being a one-sided moving type in which only the other polarizing plate moves. In FIG. 9, the polarizing plate 10f is fixed in such a manner that it completely covers the control light 16 in the image area.

First, as shown in FIG. 9 1, the polarizing plate 10e remains 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 control light 16 for the exposure light 17. is completely out of the optical path of the control light 16. Next, the position a-b advances and the light irradiation area 23
When the polarizing plate 10e reaches this point, the lower end of the polarizing plate 10e begins to move downward in the direction of the arrow in synchronization with the movement from position a to b, as shown in FIG. 92. Subsequently, the polarizing plate 10e descends until it completely overlaps the other fixed polarizing plate 10f and the light irradiation area 23, and then stops. This state is image I
The position cmd of the rear end of the required image area in is maintained until it reaches the light irradiation area 23. When the position cmd reaches the light irradiation area 23, the upper end of the polarizing plate 10e starts to descend in the direction of the arrow in synchronization with the progression of the position cmd, as shown in FIG. 9. The polarizing plate 10e finally leaves the optical path of the control light 16 completely and stops. This state is maintained until the scanning of the original image is completed, and then the polarizing plate 10e is
It rises in the direction of the arrow in FIG. 4 and returns to the position shown in FIG. 91. From the above, similar to the operation examples in FIGS. 5 and 8, the fourth
As shown in the figure, an area of the original image with the peripheral portion omitted can be obtained as an image.

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 a necessary image area D indicated by diagonal lines in the original image 47.

The original image 47 advances in the direction of mark loss and is scanned one application at a time with a slit exposure width. In the figure, 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 Dobe polarizing plates 101 and 10j.

For example, if the diagonal lines in the figure indicate the polarization direction, the polarizing plates 101 and 10k, 10j and 10k1, and 101
and 10j have their polarization directions perpendicular to each other. That is,
The left and right sides of the center 48 (dotted chain line) of the polarizing plate 10k are configured to have different polarization directions (orthogonal to each other). In the figure, the portions 49 and 50 where the diagonal lines intersect are the overlapping portions of the polarizing plates 101 and 10k and 10j and 10k, respectively. 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,
This is the view from Hijikata in Figure 11.1. 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 control light 51 in the image area, or at least erases the electrical charge on the surface of the photoreceptor. Block out light to the extent that it does not.

On the other hand, the single portion of the polarizing plate 10k that does not overlap transmits at least the control light 51 sufficient 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 52, and the control light 51 on the photoreceptor is transmitted. In some areas, the electrostatic latent image is erased. Next, an example of the operation of the polarizing plate to obtain the required image area D as shown in FIG. 10 will be described. If the polarizing plates 101 and 10j are considered as one set among the three polarizing plates as shown in FIG.
It is possible to operate in the same manner as the operation example of the two-ply polarizing plate shown in FIG. 8 or 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 Fig. 5, which moves up and down at the same time, (:i) Alternate movement type, similar to the example in Fig. 8, which moves alternately, (111) Either one of the image area control lights It is possible to perform a movement operation in which one side is fixed on the optical path and the other side is moved, similar to the example shown in FIG. In addition, the first
If you want to leave the entire image, such as the area from the leading edge of the original image to position e-f in Figure 0, and from position h-g to the rear edge of the original image, use a light-shielding member such as the frame of the polarizing plate unit. It is sufficient to block the above control light. Furthermore, the polarizing plates 101 and 10J in FIG. 11 are replaced with the polarizing plates 10e and 10 in FIG. 5, respectively.
If it corresponds to
0e, 10j, and 10f as shown in FIG. 5 to obtain an image like that shown in FIG.
Add 0k, polarizing plates 101, 10e, 10j, 10f
If the polarizing plates are operated in the same manner as in the example shown in FIG. 5, the above-mentioned (1) simultaneous movement type in a three-ply polarizing plate will be obtained.

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 the photoreceptor 52.Also, in FIG.
Electrostatic latent images 53, 54 can be obtained thereon.

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 this time, in each embodiment, an example was shown in which the control light for the image area that erases the electrical charge on the photoreceptor is irradiated onto the photoreceptor at the same time as the exposure light for the original image. However, it is not necessarily necessary to irradiate the control light at the same time as the exposure light. That is, if it is between the electrostatic latent image forming steps,
The control light may be applied to any position on the photoconductor, either before the exposure position or after the exposure position. Furthermore, when using a photoreceptor with a three-layer structure as described in Japanese Patent Publication No. 42-23910 by the applicant of this patent, it is possible to irradiate the photoreceptor with the control light at the same time as the exposure light of the original image. Although it is desirable, if the control light is irradiated at a position before the exposure position on the photoreceptor only during the time when the photoconductive layer irradiated with light retains conductivity, the same result as above can be obtained. It is something that can be obtained. Furthermore, by irradiating the above-mentioned control light after the exposure position on the three-layer photoreceptor, the following effects can be obtained.

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 59, and an electrostatic latent image is formed on the surface of the photoreceptor 54. This embodiment attempts to prevent the formation of an electrostatic latent image in an unnecessary image area by controlling the area of the entire surface exposed during the above-mentioned entire surface exposure.

In the figure, a light source 60 for controlling the image area is a light source that irradiates image area control light 61 onto the photoreceptor 54, and plays the role of full-surface exposure in place of the full-surface exposure light source 59.

The overlapping positions of the polarizing plates 101 and 10m are controlled as described above, and the polarizing plates 101 and 10m move across the optical path of the control light 61 like the polarizing plates shown in FIGS. 5, 8, and 9. 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 using the principle of the present invention, which controls the control light in the image area by overlapping polarizing plates as described above. This is what is shown. In the figure, the control light 62 in the image area is blocked in the overlapping portion of the polarizing plates 10n and 10q, and is transmitted in the single polarizing plate portion.

In the step of forming an electrostatic latent image on a three-layer photoreceptor, if the photoreceptor is not irradiated with light after simultaneous AC static elimination and exposure, no electrostatic contrast will occur and no electrostatic latent image will be formed. Therefore, as shown in the figure, no electrostatic latent image is formed on the light-shielded portions of the three-layer photoreceptor 63, and electrostatic latent images 64, 65 ( (indicated by positive charge)
is formed. Furthermore, as shown in FIG. 14, by adding a polarizing plate 10p to the polarizing plates 10n and 10q in FIG.
7, the electrostatic latent image 68 forms the latent image 64 in FIG.
, 65 are formed in the opposite shape. Furthermore, as is clear from a comparison of Fig. 13, Fig. 3, Fig. 3, Fig. 3, Fig. 3, Fig. 14, and Fig. 11, Fig. method (Fig. 3 2, 11)
In the case of FIG. 2), the pattern of formation of the electrostatic latent image is completely opposite even though the same polarizing plate is used. Who is this person?
Previously, we showed an example of adding a polarizing plate when leaving a partial area of the original image and when erasing the same area, but it is also possible to use a combination of the above two methods. also shows that similar results can be obtained. FIG. 15 shows an example of a method for leaving or erasing a selected image area by changing the irradiation position of the control light for the image area on the three-layer photoreceptor.

When trying to obtain an image such as region B in FIG.
The control light 70a of the image area controlled by the polarizing plates 10g and 10r composed of two sheets is applied to the photoreceptor 5 at the same time as the exposure light 71 of the original image.
is irradiated to erase 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 direction of irradiation of the control light 70a is changed to the direction of the dotted arrow 70b, and the polarizing plates 10q,
10r may be superimposed to block the control light 70b and prevent the formation of an electrostatic latent image on the photoreceptor 54. 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 deflecting plates 10q and 10r shown in the example, a three-ply deflecting plate such as the polarizing plates 10n, 10q, and 10p in FIG. 14 may be used, and in this case, the control 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.

Furthermore, if the slit 72 of the light source frame in FIG. 15 is set to open and close like a shutter mechanism, there is no need to synchronize the polarizing plate with the progression of the original image and move the control light across the image area. . That is, when the control light is irradiated onto the photoreceptor at the same time as the exposure light of the original image, the polarizing plate is fixed so as to cover the control light. The slit is kept closed until the original image shown in FIG. 10 is scanned and reaches the position e-f, and when the original image reaches the position e-f, the slit is opened. In this state, when scanning the original image, h-
Hold it until it reaches the g position, and when it reaches the h-g position,
Close the slit. Therefore, since the slit is closed from the leading edge of the original image to the position e-f and from the position h-g to the rear edge of the original image, the control light for the image area is not irradiated at all, and the entire area is not irradiated as an image. remain. On the other hand, from position e-f to h-g
Up to the position, the control light is irradiated onto the photoreceptor through the three-ply polarizing plate, and all charges in the photoreceptor area corresponding to the area C surrounded by Efgh in FIG. 10 are erased. is,
Therefore, no image will be formed in this area. Furthermore, when the direction of the control light in the image area is changed and the photoconductor soil is irradiated in the dotted line direction 70b shown in FIG. 15, the above-mentioned light as shown in FIG. The opposite image is obtained. According to this method, the length direction of the required image can be controlled without moving the polarizing plate at all in the optical path of the control light, and the control means becomes extremely simple. Note that instead of the three-ply polarizing plate shown in FIG. 11, a light-shielding member having a predetermined controllable aperture width may be used, and by controlling the aperture width of this light-shielding member, the three-ply polarizing plate described above may be used. As in the case of a polarizing plate, an electrostatic latent image as shown in FIG. 11 or 14 can be obtained.

Therefore, if the light shielding member is disposed at the position of the polarizing plate shown in FIG. 15, it is possible to form an image similar to that of the three-layered polarizing plate described above. As described above, the present invention uses a simple mechanism that includes a light source that controls the image forming area and a mask member that controls the light from the light source by overlapping the mask member to control the light from the original image. This allows the area to be obtained as an image. The width of the required image area is controlled by overlapping the mask members, and the length of the area is controlled by moving a polarizing plate in synchronization with the progression of the original image, or by using a slit that opens and closes like a shutter. I'll pull over and do it. This eliminates the blurring of the image boundary area, which conventional image forming methods have, and has the effect of obtaining accurate and clear image boundary areas. Furthermore, by using a monitor mechanism having arbitrarily selectable image positioning means, it is possible to select the necessary area while observing the original image, eliminating the drawbacks of conventional methods and simplifying the operation. This method has the effect of being easy to perform.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a copying machine having an image area control mechanism and a monitor mechanism used in an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. In an electrophotographic apparatus having a movable electrophotographic photoreceptor, a charging means, an image exposure means, and a developing means, a light source for illuminating the photoreceptor, and a light source located in the optical path between the light source and the photoreceptor. , a light shielding means for substantially shielding light from the light source means to an image forming area or a non-image area of the photoreceptor, the at least first light shielding means substantially blocking passage of light in mutually overlapping areas;
and a second mask member, a specifying means for specifying the necessary width for copying of the original image, the specifying means for independently specifying one end and the other end of the necessary width for copying, and the first and second mask members. 2
the mask members are moved independently from each other, and the overlapping width of the first and second mask materials in a direction perpendicular to the direction of movement of the photoreceptor is set in accordance with the necessary copying width specified by the specifying means. An electrophotographic apparatus comprising: a control means for changing. 2. The electrophotographic apparatus according to claim 1, wherein the first mask material is a band-shaped body, and is moved by a winding shaft to change the overlapping width. 3. The electrophotographic apparatus according to claim 2, wherein the second mask member is a band-shaped member, and is moved by a winding shaft to change the overlapping width. 4. The electrophotographic apparatus according to any one of claims 1 to 3, wherein the first and second mask members are polarizing plates arranged such that their polarization directions intersect with each other.