JPH05100553A - Screen device for electrophotographic device - Google Patents

Abstract

PURPOSE:To keep a copy density constant and further, to prevent the damage on a film surface by preventing the bending of a screen filter caused by a change in humidity, etc., and keeping a distance between the screen filter and the photosensitive body constant. CONSTITUTION:In this screen device provided on an electrophotographic device for exposing the photosensitive body with reflected light from an original optically scanned by a light source lamp, to develop and visualize an electrostatic latent image formed on the photosensitive body, having the screen filter 24 for improving the gradation of an image, on the optical path of the reflected light reaching the photosensitive body from the original, and provided with a transparent film base 41 and a coating film 42 provided on the transparent film base 41, and having the formation of a prescribed opaque pattern, on the screen filter 24, hard transparent plates 43 are provided on the upper and back surfaces of the screen filter 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen device for an electrophotographic apparatus such as a full-color copying machine provided with a screen filter arranged in an exposure light path to a photoconductor to improve gradation of an image. ..

[0002]

2. Description of the Related Art Electrophotographic devices such as full-color copying machines
The photoconductor is exposed by the reflected light from the document optically scanned by the light source lamp, whereby the electrostatic latent image formed on the photoconductor is developed and visualized to obtain a copy image.

In the above-mentioned full-color copying machine, in order to faithfully reproduce a photographic original or an original requiring gradation, a screen filter for improving gradation is provided on the surface of the photosensitive member in the exposure light path to the photosensitive member. Some include a screen device that can be arranged in close proximity to each other.

A screen filter 60 used in a screen device of a conventional full-color copying machine is formed of a photographic film of silver salt, and as shown in FIG. 6, a transparent film base 61 made of polyester, for example, and a photosensitive layer 6.
It has a two-layer structure with 2. On the photosensitive layer 62, transparent portions 63 ... And opaque portions 64 ... Which are patterned in a dot shape, a linear shape, or a mesh shape are continuously formed. The screen filter 60 is used to precisely form the pattern of the opaque portions 64 ... With the silver salt photographic film.

[0005]

However, since the screen filter 60 used in the conventional full-color copying machine has a two-layer structure of the transparent film base 61 and the photosensitive layer 62, as shown in FIG. In addition, when the vicinity of the screen filter 60 is dried due to environmental conditions such as humidity, the photosensitive layer 62 may become transparent to the transparent film base 61.
And the screen filter 60 bends. When the screen filter 60 is curved in this manner, the photoconductor 6
5 changes the distance between the screen filter 60 and the screen filter 60, and the projected image of the screen filter 60 formed on the photoconductor 65 becomes blurry and faint or becomes distinctly dark, resulting in a change in copy density. have.

[0006]

In order to solve the above-mentioned problems, a screen device of an electrophotographic apparatus according to a first aspect of the present invention, in which a photoconductor is caused by reflected light from a document optically scanned by a light source lamp. It is provided in an electrophotographic apparatus that is exposed, and thereby the electrostatic latent image formed on the photoconductor is developed and visualized, and in the optical path of the reflected light from the document reaching the photoconductor,
An electrophotographic apparatus having a screen filter for improving the gradation of an image, the screen filter including a transparent film base and a coating provided on the transparent film base and having a predetermined opaque pattern formed therein. In the screen device, a hard transparent plate is provided on the upper surface and the lower surface of the screen filter.

In order to solve the above-mentioned problems, in the screen device of the electrophotographic apparatus according to the second aspect of the present invention, the photoconductor is exposed by the reflected light from the document optically scanned by the light source lamp, whereby the photoconductor is exposed. Equipped with an electrophotographic device that develops and visualizes the electrostatic latent image formed on the body, a screen filter is provided in the optical path of the reflected light from the document to reach the photoconductor to improve the gradation of the image. The screen filter of the electrophotographic apparatus, wherein the screen filter includes a transparent film base and a predetermined opaque pattern portion provided on the transparent film base, wherein the screen filter includes a transparent film base and a transparent film base. And a predetermined opaque pattern portion provided on the.

[0008]

According to the structure of the first aspect, since the hard transparent plate is provided on the upper surface and the lower surface of the screen filter, the screen filter is reinforced by the hard transparent plate. Therefore, it is possible to prevent the screen filter from being curved due to changes in environmental conditions such as humidity, and it is possible to always keep the distance between the screen filter and the photoconductor constant. As a result, the copy density can be kept constant. Moreover, since the film surface of the screen filter is protected by the transparent plate, the film surface is not damaged even if the finger is touched by mistake.

According to the second aspect of the invention, since the screen filter is composed of the transparent film base and the predetermined opaque pattern portion provided on the transparent film base, the opaque pattern portion becomes discontinuous, The area of the opaque pattern portion is smaller than the area of the transparent film base, for example, about 30%. Therefore, even if environmental conditions such as humidity change around the screen filter, the stretching force of the opaque pattern portion is about 30 times the stretching force of the conventional continuous film.
%, The curving of the screen filter is suppressed. Therefore, the distance between the screen filter and the photoconductor is always kept substantially constant, and the copy density is also kept substantially constant.

[0010]

【Example】

[Embodiment 1] One embodiment of the present invention will be described with reference to FIGS.
The explanation is based on the following.

As shown in FIG. 2, a full-color copying machine (hereinafter referred to as a "copying machine") as an electrophotographic apparatus of this embodiment has a transparent original placing table 1 on the upper surface thereof. An exposure optical system 2 that exposes a photoconductor 3 described below by optically scanning a document 11 placed on the document placing table 1 is disposed below the document placing table 1. The exposure optical system 2 includes a light source lamp 2a for irradiating the original 11 with light, and the original 11
A plurality of reflecting mirrors 2b for guiding the reflected light from the photoconductor 3 to the photoconductor 3 as shown by the one-dot chain line in the figure, an imaging lens 2c arranged in the exposure light path of the reflected light to the photoconductor 3, and a blue Green and red 3
And a filter device 2d having a primary color separation filter.

A screen device 21 having a screen filter 24 for improving the gradation of a copy image is disposed at a position below the exposure optical system 2 and close to the photoconductor 3, and the screen filter 24 has a screen filter 24. As shown by the alternate long and two short dashes line in FIG. 2, it can be inserted into and removed from the exposure optical path.

The screen filter 24 is formed of, for example, a photographic film of silver salt, and as shown in FIG. 1, a transparent film base 41 made of, for example, a transparent polyester film, and a coating provided on the transparent film base 41. Photosensitive layer 42. On the photosensitive layer 42, a transparent portion 42b and an opaque portion 42a ... As an opaque pattern patterned by baking a plurality of thin lines are continuously formed. This thin line
For example, they are formed at a rate of about 125 Line / inch (line width: about 60 μm, line spacing: about 80 μm), and the ratio of the opaque portion 42a made of the thin lines is about 30%. In addition,
The screen filter 24 uses a silver salt photographic film to accurately form the opaque portion 42a. Further, on the upper surface and the lower surface of the screen filter 24, that is, the transparent film base 41 and the photosensitive layer 42.
Hard transparent plates 43, 43 made of, for example, glass that transmits light are provided on both sides of the. This transparent plate 43
Each 43 is, for example, 37 mm × 320 mm × 1 m
It has a size of m.

As shown in FIG. 3, both ends 24a, 24a in the longitudinal direction of the screen filter 24 are attached to the screen holding member 25. The screen holding member 25 is attached to a rotary shaft 28 rotatably supported by a screen device body 27 so that the screen filter 24 can be inserted into or retracted from the exposure optical path. It is rotatable as a fulcrum.

The photosensitive member 3 is provided on the opposite side of the rotating shaft 28 at the rising portions at the left and right ends of the screen holding member 25.
And a roller 33, which is in contact with, and holds the screen holding member 25 and the photoconductor 3 at a constant distance.
In addition, the spring fixing portions 25a.
5a is projectingly provided, and this spring fixing portion 25a
The respective end portions of the screw coil springs 34, 34 are attached to the spring fixing portions 27a, 27a provided on both side walls of the screen device main body 25a and the screen fixing device 25a. When the screen filter 24 is inserted, the torsion coil springs 34, 34 are used for the screen holding member 2
5 is elastically urged in the direction of pressing the photoconductor 3 while the screen filter 24 is retracted so as to maintain the retracted state.

The screen device 21 includes a pulse motor 35 for rotating the screen holding member 25 attached to the rotary shaft 28. A gear 36 is attached to the drive shaft of the pulse motor 35, and the drive force of the pulse motor 35 is applied to the rotary shaft 28 via the gear 36 and the gear 37 attached to one end of the rotary shaft 28. It is being transmitted. Further, the screen device main body 27 is provided with a light transmission type position sensor 38 including, for example, a light emitting element and a light receiving element, and the position sensor 38 has a convex portion 25 b formed on the rising portion of the screen holding member 25. By blocking the light from the light emitting element of the position sensor 38, it is possible to detect that the screen filter 24 is in the retracted position.

Further, the present copying machine has a screen filter 2
4 has a control unit (not shown) that controls the rotational driving operation of the pulse motor 35 for inserting and removing the pulse motor 4. That is,
When inserting the screen filter 24 in the retracted position into the exposure optical path, the control unit stops the pulse motor 35 at a predetermined number of rotation steps from the time when the convex portion 25b is no longer detected by the position sensor 38. It has become. When the screen filter 24 is retracted from the insertion position in the exposure light path to the retracted position outside the exposure light path, the pulse motor 35 is stopped when the position sensor 38 detects the convex portion 25b. Is becoming

Further, the operation section of the copying machine is provided with an exposure mode switching key (not shown), and a screen mode in which the screen filter 24 is inserted into the exposure light path and the screen filter 24 is retracted from the exposure light path. Two exposure modes, the normal mode and the exposure mode, can be selected.

On the other hand, as shown in FIG. 2, a correction device 29 having a correction glass plate 30 for correcting the optical path length of the screen filter 24 is provided above the screen device 21. The correction glass plate 30 has different optical path lengths depending on the refractive index of the transparent plates 43, 43 depending on whether the screen filter 24 is inserted in the exposure optical path or not, and therefore the transparent plate 43. 43 of 2
It is made of glass with the same thickness as the sheet. Therefore, when the screen filter 24 is not inserted in the exposure optical path, the correction device 29 inserts the correction glass plate 30 in the exposure optical path as shown by the chain double-dashed line in FIG. When inserted inside, the correction glass plate 30 is retracted out of the exposure optical path as shown by the solid line in the figure. Then, the insertion and withdrawal operations of the correction glass plate 30 are interlocked with the insertion / removal control of the screen filter 24 in the control unit,
It is designed to be performed by a driving device (not shown).

Below the screen device 21, a belt-shaped photosensitive member 3 is provided. The photosensitive member 3 is rotatably driven by being stretched over two rollers 12a and 12b arranged at regular intervals. Around the photoconductor 3, a charging charger 7 that charges the photoconductor 3, a cleaning device 13 that removes toner remaining on the photoconductor 3, a transfer intermediate device 17, a developing device 4, and the like are provided.

The developing device 4 comprises three developing tanks 4a-4a.
c, and is arranged in a non-contact state with the photoconductor 3. In this developing device 4, toners as color developers of yellow, magenta, and cyan, which are complementary colors of the blue, green, and red filters in the filter device 2d, are individually stored in the developing tanks 4a to 4c.

The transfer intermediate device 17 is provided with a belt-shaped transfer intermediate 5 that is pressed against the photosensitive member 3, and three rollers 14a to 14c that support and rotate the transfer intermediate 5. Around the transfer intermediate 5, a transfer roller 8a that transfers the toner image on the photoconductor 3 to the transfer intermediate 5, and a transfer roller 8 that transfers the toner image on the transfer intermediate 5 to a transfer sheet.
b, a cleaning device 9 and the like are arranged.

Paper feed cassettes 6a and 6b of different sizes are arranged vertically in the paper feed direction with respect to the transfer intermediate device 17, and the conveyor belt 16 is provided in the paper output direction of the transfer intermediate device 17.
Further, a fixing device 10 for thermally fixing the toner on the transfer paper to the transfer paper is provided.

As described above, the screen filter 24 of the screen device 21 of this embodiment is provided with the hard transparent plates 43, 43 on both sides of the transparent film base 41 and the photosensitive layer 42 on which a predetermined opaque pattern is formed. Therefore, the screen filter 24 has the hard transparent plate 43.
It is reinforced by 43. Therefore, it is possible to prevent the screen filter 24 from being curved due to changes in environmental conditions such as humidity, and it is possible to always keep the distance between the screen filter 24 and the photoconductor 3 constant. As a result, the copy density can be kept constant. Further, since the correction glass plate 30 protects the film surface of the screen filter 24, the film surface is not damaged even if the finger is touched by mistake.

The operation of the copying machine in the above-mentioned configuration when the exposure mode is set to the screen mode in which the screen filter 24 is used for copying will be described below.

First, when the exposure mode switching key is operated so that the exposure mode becomes the screen mode, the control section sets the screen holding member 25 on the photoconductor 3 by the detection signal from the position sensor 38. Or
Determine if it is in the retracted position.

Here, when the position sensor 38 detects the convex portion 25b of the screen holding member 25, the control unit determines that the screen holding member 25 is at the retracted position and sets the screen holding member 25 to the photosensitive member 3. A drive signal is applied to the pulse motor 35 so that the pulse motor 35 is rotated in the direction. Then, the pulse motor 35 starts to rotate, and this rotational driving force is transmitted to the rotary shaft 28 via the gear 36 and the gear 37, and the rotary shaft 28 rotates so that the screen holding member 25 moves toward the photoconductor 3 direction. Start turning. After that, the control unit controls the pulse motor 35 in a predetermined number of steps from the time when the convex portion 25b is no longer detected by the position sensor 38.
To stop. Further, the correction glass plate 30 of the correction device 29 retracts out of the exposure light path in conjunction with the insertion operation of the screen filter 24 into the exposure light path.

As a result, the screen holding member 25 comes to be positioned on the photoconductor 3. At this time, roller 33
33 contacts the photoconductor 3 and the screen holding member 25 is urged toward the photoconductor 3 by the screw coil springs 34, 34.
The contact state with the photoconductor 3 is always maintained.

When the copy start button is operated in this state, as shown in FIG. 2, the light source lamp 2 of the exposure optical system 2 is operated.
The light a irradiates the original 11 placed on the original placing table 1 with light, and scanning is performed a plurality of times.

As a result, the reflecting mirrors 2b ...
The reflected light passing through is separated into each color component via the imaging lens 2c and the filter device 2d. Then, the light for each color component for each scanning is applied to the photoconductor 3 through the screen filter 24, and the photoconductor 3 is exposed. As a result, an electrostatic latent image for each color component corresponding to the image of the original 11 is sequentially formed on the photoconductor 3.

The latent images for the respective color components formed in order as described above are formed by the developers of yellow, magenta, and cyan, which are the complementary colors of the filters of the respective color filters of the filter device 2d, accommodated in the developing tanks 4a to 4c. After being developed, they are sequentially transferred to the transfer intermediate 5 by the transfer charger 8a. As a result, one color toner image is formed by superimposing the toner images for the respective color components on the transfer intermediate body 5. The color toner image is transferred from either one of the paper feed cassettes 6a and 6b and transferred by the transfer charger 8b to the transfer paper 15 which is in contact with the lower surface of the transfer intermediate 5. After that, the transfer paper 15 is introduced into the fixing device 10 through the conveyance path 16 and fixed as a full-color copy image.

Next, the exposure mode is changed to the screen filter 2.
The operation of the copying machine when copying is performed in the normal mode in which No. 4 is not used will be described below.

First, when the exposure mode switching key is operated so that the exposure mode becomes the normal mode, the control section sets the screen holding member 25 on the photoconductor 3 by the detection signal from the position sensor 38. Judgment whether it is present or in the retracted position. Here, if the position sensor 38 does not detect the convex portion 25b of the clean holding member 25, the control unit determines that the screen filter 24 is inserted on the photoconductor 3 and retracts the screen filter 24. Pulse motor 3 so that it is retracted to the position
A drive signal is given to 5. As a result, the pulse motor 3
5 starts rotating, the rotational driving force of the pulse motor 35 is transmitted from the gear 36 to the gear 37, the rotating shaft 28 rotates, and the screen holding member 25 starts rotating in the retracted position direction.

After that, the control unit stops the pulse motor 35 when the position sensor 38 detects the convex portion 25b. As a result, the screen holding member 25 moves to the retracted position, and the screen filter 24 separates from the exposure optical path. Further, in conjunction with this detachment, the correction device 29
The correction glass plate 30 is inserted in the exposure optical path.

When the copy start button is operated in this state, the screen filter 24 is not inserted in the exposure light path, but the correction glass 29 is inserted, so
The optical path length is kept constant. Regarding other operations, as in the screen mode described above, an electrostatic latent image for each color component corresponding to the image of the original 11 is formed on the photoconductor 3. After that, similarly, the development in the developing tanks 4a to 4c,
A copy image is obtained through the steps of transfer to the transfer intermediate 5, transfer to the transfer paper 15, and fixing by the fixing device 10.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIGS. 4 and 5. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

The screen filter 50 of this embodiment is formed of a non-silver salt film, and as shown in FIG. 4, a transparent film base 5 made of transparent polyester, for example.
1 and an opaque portion 52 composed of thin lines as a plurality of opaque pattern portions provided on the transparent film base 51.
... has only. Therefore, there is no transparent portion formed in the past, and therefore the opaque portion 52 ...
Are discontinuous on the transparent film base 51.

The fine lines are formed, for example, at a rate of about 125 Line / inch (line width about 60 μm, line interval about 80 μm), and the ratio of the opaque portions 52 ..
It is 0%. Opaque part 5 in the above non-silver film
2 is formed, the photosensitive layer provided on the transparent film base 51 is irradiated with light corresponding to a fine line to expose the photosensitive layer to form a pattern. Then, the photosensitive portion of the patterned photosensitive layer is cured to black after development, while the non-cured portion of the non-photosensitive portion is washed away when washed with water, and only the photosensitive portion cured to black remains on the transparent film base 51.
The screen filter 50 having a discontinuous pattern is formed.

As shown in FIG. 5, one end 24a of the screen filter 50 in the longitudinal direction is attached to the screen holding member 25, and the other end 24b is pulled by the tension spring 26, so that the screen holding member does not hang down. Tensioned flat on 25. The other structure is the same as that of the copying machine.

In the above structure, the screen filter 50 of the screen device 21 of this embodiment is composed of only the transparent film base 51 and the predetermined opaque portions 52 provided on the transparent film base 51.
Are discontinuous and the area of the opaque portions 52 is smaller than the area of the transparent film base 51, for example, about 30%. Therefore, even if environmental conditions such as humidity change around the screen filter 50, the stretching force of the opaque portions 52 becomes as small as about 30% of the stretching force of the conventional continuous film, so that the screen filter 50 is curved. Is suppressed.
Therefore, the distance between the screen filter 50 and the photoconductor 3 is always kept substantially constant, and the copy density is always kept substantially constant. Further, during the manufacture of the screen filter 50, the photosensitive portions that become the opaque portions 52 ... Are cured to black by development and remain, while the uncured portions of the non-photosensitive portions are washed away. Therefore, the screen filter 50 having a discontinuous opaque pattern can be easily formed.

The other operations are the same as those of the above copying machine.

[0042]

As described above, the screen device of the electrophotographic apparatus according to the first aspect of the present invention has a structure in which hard transparent plates are provided on the upper surface and the lower surface of the screen filter.

As a result, it is possible to prevent the screen filter from being curved due to changes in environmental conditions such as humidity.
The distance between the screen filter and the photoconductor can always be kept constant. Therefore, the copy density can be kept constant. Moreover, since the film surface of the screen filter is protected by the transparent plate, the film surface is not damaged even if the finger is touched by mistake.

Further, in the screen device of the electrophotographic apparatus according to the second aspect of the present invention, as described above, the screen filter includes only the transparent film base and the predetermined opaque pattern portion provided on the transparent film base. It is a composition.

As a result, the predetermined opaque pattern portion is discontinuous, and the area of the opaque pattern portion is smaller than the area of the transparent film base. Therefore, even if environmental conditions such as humidity around the screen filter change,
Since the stretching force of the opaque pattern portion is smaller than the stretching force of the conventional continuous film, the screen filter is prevented from being curved. Therefore, there is an effect that the distance between the screen filter and the photoconductor is always kept substantially constant, and the copy density is also kept substantially constant.

[Brief description of drawings]

FIG. 1 is a side view showing a screen filter in a screen device of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a full-color copying machine including the screen filter shown in FIG.

FIG. 3 is a perspective view schematically showing a screen device including the screen filter shown in FIG.

FIG. 4 is a side view showing a screen filter in a screen device of an electrophotographic apparatus according to another embodiment of the present invention.

5 is a perspective view showing an outline of a screen device including the screen filter shown in FIG.

FIG. 6 is a side view showing a screen filter in a screen device of a conventional electrophotographic apparatus.

FIG. 7 is a vertical cross-sectional view showing a curved state of the screen filter.

[Explanation of symbols]

 24 Screen Filter 41 Transparent Film Base 42 Photosensitive Layer (Coating) 42a Opaque Part (Opaque Pattern) 43 Transparent Plate 50 Screen Filter 51 Transparent Film Base 52 Opaque Part (Opaque Pattern Part)

Claims (2)

[Claims] 1. An electrophotographic apparatus in which a photoconductor is exposed by reflected light from a document optically scanned by a light source lamp, and an electrostatic latent image formed on the photoconductor is developed and visualized. , A screen filter for improving the gradation of the image is provided in the optical path of the reflected light from the original to the photoconductor, and the screen filter is provided on the transparent film base and the predetermined opacity. A screen device for an electrophotographic apparatus, comprising a film having a pattern formed thereon, wherein a hard transparent plate is provided on an upper surface and a lower surface of the screen filter. 2. An electrophotographic apparatus in which a photoconductor is exposed by reflected light from a document optically scanned by a light source lamp to develop and visualize an electrostatic latent image formed on the photoconductor. , A screen filter for improving the gradation of the image is provided in the optical path of the reflected light from the document to the photoconductor, and the screen filter is provided with a transparent film base and a predetermined opacity provided on the transparent film base. In a screen device of an electrophotographic apparatus having a pattern portion, the screen filter is a transparent film base, and a predetermined opaque pattern portion provided on the transparent film base of the electrophotographic apparatus, characterized in that Screen device.