JPH03126960A - Image forming device - Google Patents

Abstract

PURPOSE:To form an image with a clean base and a sharp contrast by developing a body to be developed adhering to an electrostatic latent image carrier on which an electrostatic latent image is formed, and removing reversed polarity toner adhering to a non-image part on the body to be developed on which a toner image is formed. CONSTITUTION:The toner image corresponding to the electrostatic latent image on the electrostatic latent image carrier 101 is formed on the body to be developed 102 closely overlapped to the electrostatic latent image carrier 101 so as to cover it. A reversed polarity toner carrier 109 is provided on the side of toner image formed surface on the body to be developed 102 without coming into contact with the toner image, and a counter electrode is provided on a position corresponding to the reversed polarity toner carrier 109 of the opposite surface side of the body to be developed 102, with contacting with the body to be developed 102, and an electrical bias is applied between the reversed polarity toner carrier 109 and the counter electrode. Therefore, the reversed polarity toner is attracted to the reversed toner carrier 109 by the action of a generated electric field, and completely removed from the non-image part on the body to be developed 102. Thus, an image with a clean base and a sufficient contrast is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus used in printers, copying machines, and the like.

(Prior art) Conventionally, when forming images with printers, copying machines, etc., an electrophotographic recording method based on the Carlson method has generally been used (Electrophotographic Technology Akebono, ``Fundamentals and Applications of Electrophotographic Technology'' (1988). Published by Coronasha on June 15th) P28.
46.47).

FIG. 5 is a conceptual diagram of an image forming apparatus using the electrophotographic recording method based on the Carlson method.

In the figure, an image on a document read by an optical means is first exposed by an exposure device 3 on a photosensitive drum 2 which is charged by corona discharge from a corona discharger 1, and then the image on the document is read by an optical means.
Formed as a latent image. This electrostatic latent image is developed by a developing device 4, transferred onto a recording medium 8 by a transfer device 5, and fixed by a fixing device 6 to form an image.

Since the photosensitive drum 2 is used repeatedly, residual toner after transfer is cleaned by a cleaning device 7.

However, the conventional image forming apparatus described above has a poor transfer rate because it uses a transfer process based on electrostatic action, and requires a process for cleaning residual toner on the photoreceptor drum 2 after transfer. Maintenance work is required to dispose of the collected toner.

Furthermore, when the toner is disposed of, there are problems such as staining the body or clothing or scattering the toner inside and outside the device.

Further, there are many processes from forming the electrostatic latent image to fixing the toner image on the recording medium 8, which causes problems in that the apparatus not only becomes complicated but also large in size. Therefore, an image forming apparatus is provided that does not require a cleaning device on the photoreceptor drum 2 and can be made compact.

FIG. 6 is a schematic diagram of an image forming apparatus that does not require a cleaning device on a photosensitive drum.

In the figure, a drum-shaped electrostatic latent image carrier 501 comprising a photoconductive layer provided on a conductive support is rotated at a constant circumferential speed in the direction of the arrow by a driving means (not shown). 502
is an endless body to be developed, which is stretched between an electrostatic latent image carrier 501 and a pressure roll 503. The object to be developed 50
2 has an insulating property and is formed into a film shape, and moves in the direction of the arrow due to frictional force with the static N latent image carrier 501.

Next, the operation of the image forming apparatus having the above configuration will be explained.

First, the electrostatic latent image carrier 501 is uniformly charged using a charging device 504 provided opposite to the surface thereof. Then, between the charging process and the exposure process, the object to be developed 5
02 moves at a constant speed in close contact with the electrostatic latent image carrier 501.

Next, an exposure device 505 irradiates the electrostatic layer image carrier 501 with light that passes through the object 502 and corresponds to the image signal, thereby forming an electrostatic latent image.

The developing device 506 is disposed to face the object to be developed 502 that is in close contact with the electrostatic latent image 501, and attracts toner 508 onto the toner carrier 507 and conveys it in the direction of the arrow. The object to be developed 5 corresponds to the electrostatic latent image formed thereon.
02. At this time, in the space between the toner carrier 507 and the object to be developed 502, lines of electric force accompanying the electrostatic latent image formed on the electrostatic latent image carrier 501 penetrate through the object to be developed 502 and are generated. Therefore, the charged toner 508 on the toner carrier 507 is transferred to the object to be developed 502 due to electrostatic force.
It is deposited on top and developed to form a toner image.

Thereafter, the electrostatic latent image carrier 501 and the separated development object 5
02 is conveyed to a transfer/fixing section composed of a pressure roll 503 and a heating roll 510. A developing object 502 on which a toner image is formed and a paper feed roll 51 from a paper feed cassette 513
The final recording support 514 sent through 6 is stacked here, heated and pressurized. The heat from the heat generating roll 510 is applied to the toner 5 on the object to be developed 502 via the final recording support 514.
08 is melted and penetrates between the fibers of the final recording support 514 by pressure action, and transfer and fixing are performed simultaneously.

According to the above method, the toner 508 is transferred to the electrostatic latent image carrier 50.
1. In other words, no cleaning device is required because no particles are deposited on the photoreceptor. Further, since the transfer is performed using heat and pressure, the transfer rate is very high, the amount of residual toner after transfer is extremely small, and there is virtually no need to collect waste toner, making maintenance easy. Moreover, since the transfer and fixing are performed simultaneously in the same process, the apparatus can be downsized and simplified.

(Problems to be Solved by the Invention) However, in the conventional image forming apparatus described above, the electrostatic latent image carrier 5011. : After forming a toner image corresponding to the electrostatic latent image on the developing object 502 in close contact with the developing object 502, when the toner image on the developing object 502 is transferred and fixed onto the final recording support 514 at the same time, the image area is Toner 50 attached to
In addition to 8, toner adhering to non-image areas, called "fogging", is also transferred at the same time.

Since the transfer efficiency at this time is very high compared to the conventional electrostatic transfer method, a lot of fogging toner 508 adheres to the non-image area on the final recording support 514, and the base becomes dirty and the image area and non-image area There is a problem with the image quality that the contrast of the image becomes poor.

This will be explained with reference to FIG.

FIG. 7 is a diagram showing a developing process and a transfer/fixing process in a conventional apparatus, FIG. 7(A) is a diagram showing a developing process, and FIG. 7(B) is a diagram showing a transfer/fixing process.

In this development process, a reversal development method is shown in which toner is attached to areas where charges have been erased, but it can also be applied to a regular development method in which toner is attached to areas where charges remain. In the developing device 506, the toner 508 is positively charged by a charging member (not shown) (for example, carrier particles in a two-component developing method, and an 11!11' charging blade in a -component developing method). In this embodiment, the main electrical polarity of the toner 508 is positive.

However, as seen in the figure, some toner 50
8" is negatively charged with the opposite polarity. This is a carrier,
This is because the toner 508 does not have sufficient friction with a frictional charge imparting member such as a blade, or because friction occurs between the toners 508 and one is charged positively while the other is negatively charged. When the object to be developed 502 is developed with the positive toner 508 and the negative toner 508' attached to the toner carrier 509 in this way, the positive toner 508 with the main polarity causes static electricity to appear in the image area where the charge has been erased. However, the negative toner 508' of opposite polarity adheres to the non-image area where the charge remains.

Then, the developed object 502 is transported to a transfer/fixing process, where it is superimposed on a final recording support 514, heated and pressurized, and the positive toner 508 attached to the image area is separated from the non-image area. Adhered negative toner 508'
and are transferred to the final recording support 514 and fixed at the same time. Therefore, the image formed on the final recording support 514 has toner 508' (fogging) attached to the non-image area.
There are an extremely large number of problems, which is a drawback in image quality.

An object of the present invention is to solve the problems of the conventional image forming apparatus described above, and to provide an image forming apparatus that can form an image with less toner adhesion to non-image areas, a clean base, and sufficient contrast. With the goal.

(Means for Solving the Problems) For this purpose, in the image forming apparatus of the present invention, a developing object is closely stacked so as to cover an electrostatic latent image carrier on which an electrostatic latent image is formed. In an image forming apparatus that forms a toner image corresponding to an electrostatic latent image on an electrostatic latent image carrier, overlaps the toner image with a final recording support, and fixes the toner image on the final recording support at the same time as the transfer. In order to form a toner image on the developed portion of the object to be developed, a toner carrier of opposite polarity, that is, a fog toner removing roll is disposed in a non-contact state with the toner image.

Also, at a position corresponding to the opposite polarity toner carrier on the opposite side of the developing object, it contacts the developing object and faces the opposite polarity toner carrier! A pole is provided.

Then, the counter electrode is grounded, and a potential opposite to the electrical polarity of the opposite polarity toner is applied to the opposite polarity toner carrier, and an electric bias is applied between them.

The opposite polarity toner carrier may be a conductive support of an electrostatic latent image carrier.

(Function) According to the present invention, as described above, a toner carrier of opposite polarity is provided on the toner image forming surface side of the portion after development on the to-be-developed object in a non-contact state with the toner image, and A counter electrode is provided in contact with the object to be developed at a position corresponding to the opposite polarity toner carrier on the opposite surface side, and an electric bias is applied between the opposite polarity toner carrier and the counter electrode.

Because the toner of opposite polarity is attracted to the toner carrier of opposite polarity by the action of the electric field generated by the application of this electric bias,
The particles adhering to the non-image area on the object to be developed are completely removed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the image forming process of the image forming apparatus of the present invention, FIG. 1(A) is a diagram showing the developing process, and FIG.
B) is a diagram showing the fog removal process, and FIG. 1(C) is a diagram showing the transfer/fixing process.

In the figure, a developing device 106 positively charges toner 108 and causes it to adhere to the image area of the object to be developed 102, but there is also toner 108' that is negatively charged, and this toner 108' adheres to the non-image area. do.

In order to improve this, a means is provided to remove the negative toner 108' adhering to the non-image area after development, as shown in FIG. 1(B). That is, a toner carrier of opposite polarity, that is, a fog toner removing roll 109 is provided on the side of the toner image-formed surface of the object to be developed 102 without contacting the toner image. On the opposing surface side, a counter electrode roll 101C as a counter electrode is provided in contact with the object to be developed 102 and at a position facing the dusting toner removal roll 109.

The counter electrode roll 10IC is grounded, and a potential opposite to the electrical polarity of the toner 108' is applied to the fog toner removing roll 109. At this time, the gap between the object to be developed 102 and the fog toner removing roll 109 is approximately 10-
It is appropriate to apply a potential of 100 to 1500 V to the 500 μm 1 toner removal roll 109, and if the electric field between the gaps is set to 106 sh/m or more, the toner 108' attached to the non-image area will be removed by electrostatic action. The toner particles fly between the body 102 and the fog toner removing roll 109 and adhere to the fog toner removing roll 109, thereby being able to remove the fog on the object to be developed 102.

The developing object 102 from which the fog has been removed is stacked on the final recording support 114, heated and pressurized in a transfer/fixing process, and the toner image is transferred and fixed onto the final recording support 114. The toner image thus obtained on the final recording support 114 can provide good image quality with very little fog and strong contrast.

FIG. 2 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention.

In the figure, an electrostatic latent image carrier 10 formed in a drum shape
1 is rotated at a constant circumferential speed in the direction of the arrow by a driving means (not shown). This electrostatic latent image carrier 101 is one in which a photoconductive N tolb is provided on a conductive support 101a, and a selenium photoreceptor, an organic photoreceptor, a zinc oxide photoreceptor, an amorphous silicon photoreceptor, etc. can be used. be able to. In this embodiment, a positively charged organic photoreceptor is used in which a charge transport layer and a charge generation layer are sequentially laminated as a photoconductive layer 101b on a conductive support 101a.

102 is an endless object to be developed; this object to be developed 102
is stretched over an electrostatic latent image carrier 101, a pressure roll 103, and a tension roll 11]. The object to be developed 102 moves in the direction of the arrow due to the frictional force of the electrostatic latent image carrier 101 . A tension mechanism (not shown) is applied to the tension roll 111 to exert an appropriate tension on the developing object 102 so that the developing object 102 moves at the same speed as the electrostatic latent image carrier 101 .

The object to be developed 102 used here needs to have translucency suitable for the wavelength of the light source during exposure, insulation during development, and heat resistance during transfer and fixing. Films made of materials such as polyimide, polyetherimide, polyether sulfone, and polyether ether ketone are used.

Next, the image forming process in this embodiment will be explained.

First, the electrostatic layer image carrier 101 is uniformly charged by a charging device 104 as a charging means provided opposite to the surface thereof. As the charging device 104, a corona charger as shown is generally used, but a brush charger or the like can also be used.

Between this charging process and the next exposure process, the object to be developed 10
Reference numeral 2 is a sidewall that comes into close contact with the electrostatic latent image carrier 101 .

In the exposure process, an exposure device 105 serving as an exposure unit irradiates the electrostatic latent image carrier 101 with light corresponding to an image signal via the developing object 102, thereby forming an electrostatic latent image. In addition to the exposure device that combines the LED array and Cellphone Cleanse (trade name) used here, any combination of a laser and an imaging optical system can be used.

Next, a developing device 106 is provided facing the developing object 102 which is closely stacked so as to cover the electrostatic layer image bearing member 101, and this developing device 106 is connected to the toner-bearing member 1 (
The toner 10B is attracted onto the toner 17 and conveyed in the direction of the arrow, and is developed on the developing object 102 in close contact with the electrostatic latent image. In this embodiment, reversal development is used, and a bias potential is applied between the conductive support 101a of the electrostatic latent image 101 and the toner carrier 10.

With this configuration, lines of electric force are generated in the space between the toner carrier 107 and the object to be developed 102 due to the electrostatic latent image formed on the electrostatic latent image carrier 101 through the object to be developed 102. do. Therefore, the charged toner +08 on the toner carrier 107 adheres to the object to be developed +02 due to electrostatic force, and is developed to form a toner image. The developing device may be a two-component magnetic brush developer, a -component magnetic brush developer, a -component non-magnetic developer, or the like.

In close proximity to the electrostatic latent image carrier i01, a minute gear knob is provided on a portion of the developing object 102 after development, and a fog toner removing means, that is, a fog toner removing roll 109 is provided. The fog toner removing roll 109 can be made of a conductive support or a thin insulating layer coated on the conductive support.

A positive high potential is applied to this fog toner removing roll 109, and in this embodiment, the conductive support 101a of the electrostatic latent image carrier 101 is connected to the counter electrode roll 101c.
(Figure 1) Here, the negative toner 108' adhering to the non-image area on the object to be developed 102 is attracted to the dust toner removing roll 109 by the action of static electricity.

Toner 108 attached to fog toner removal roll 109
' is scraped off by a scraping scraper 110 provided with one end in contact with the fog toner removing roll 109, and stored in the fog toner storage tank 122.

An AC corona charger 112 is provided where the electrostatic latent image carrier 101 and the object to be developed 102 are separated, and removes the electric charge on the object to be developed 102 and removes the toner generated by discharge when they are separated. Prevent image distortion.

After that, the electrostatic latent image carrier 101 and the separated development object 1
02 is conveyed to a transfer/fixing section where it is heated by a pressure roll 103 and a heating roll 113.

On the other hand, the final recording support 1 accommodated in the paper cassette 120
14 is taken out via a paper feed roll 115 and sent to a paper feed roll 116 whose rotation has been stopped to correct the skew. At this time, the paper feed roll 116 is started, and the final recording support 114 is sent to the transfer/fixing section, superimposed on the developing object 102 on which the toner image has been formed, and heated and pressurized.

The heat from the heating roll 113 is transferred to the final recording support 114 to melt the toner on the object to be developed 102, and penetrates between the fibers of the final recording support 114 due to the pressure action, thereby performing transfer and fixing at the same time. be exposed. The transferred and fixed final recording support 114 is delivered to the outside of the apparatus by a paper delivery roll 117.

On the other hand, a small amount of toner 108 may remain on the developing object 102 after being transferred and fixed, but it is removed by the fixing cleaner 118 provided so as to press against the developing object 102 on the pressure roller 103. . Toner 108 at this time
Since 71j is still in a molten state in the fixing section, it can be easily removed.

On the other hand, the electrostatic latent image carrier 101 is separated from the object to be developed 102 after the development process, and the entire surface thereof is irradiated with light by a charge removal lamp 119 serving as a charge removal means to remove residual charges. In this way, the electrostatic latent image (holder 101) is used repeatedly.

FIG. 3 is a schematic configuration diagram of an image forming apparatus showing a second embodiment of the present invention.

In this embodiment, the fog toner removing roll 109
is provided at a position after the object to be developed 102 is separated from the electrostatic latent image carrier 101. In this case, a counter electrode roll 121 is provided on the opposite side of the toner image on the object to be developed 102 and in contact with the object to be developed 102 .

FIG. 4 is a schematic configuration diagram of an image forming apparatus showing a third embodiment of the present invention.

In this embodiment, unlike the first embodiment, the object to be developed 202 is not endless but has an end shape, and is configured to be sent from a supply roll 203 to a take-up roll 204 and collected. The object to be developed 202 used here can be the same as that used in the first embodiment. Here, as the object to be developed 202, a polyester film is used in consideration of economic efficiency.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As explained in detail above, according to the present invention, static 1t'
The structure in which the ftl image carrier and the object to be developed are partially in contact makes it quiet!
Developing a latent image on a developing object that is in close contact with an electrostatic latent image carrier, and removing toner of opposite polarity attached to a non-image area on the developing object on which a toner image is formed. As a result, the image formed on the final recording support has extremely little toner adhesion to non-image areas, has a clean base, and has an extremely strong contrast with the toner image adhered to the image areas.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the image forming process of the image forming apparatus of the present invention, FIG. 1(A) is a diagram showing the developing process, and FIG.
B) is a diagram showing a fog removal process, FIG. 1(C) is a diagram showing a transfer/fixing process, FIG. 2 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention, and FIG. 3 is a diagram showing an embodiment of the present invention. the second of
FIG. 4 is a schematic configuration diagram of an image forming apparatus showing a third embodiment of the present invention;
FIG. 5 is a conceptual diagram of an image forming apparatus using an electrophotographic recording method based on the Carlson method, FIG. 6 is a schematic diagram of an image forming apparatus that does not require a cleaning device on a photoreceptor, and FIG.
7(A) is a diagram showing the developing process and FIG. 7(B) is a diagram showing the transfer/fixing process in a conventional apparatus. 101.501... Electrostatic latent image carrier, 101c...
Counter electrode roll, 102, 202. 502... Developed object, 104, 504... Charging device, 108, 108
', 508, 508'... Toner, 109... Fogging toner removal roll, 114... Final recording support.

Claims (1)

[Scope of Claims] The electrostatic latent image on the electrostatic latent image bearing member is placed on a developing object that is closely stacked so as to cover the electrostatic latent image bearing member on which the electrostatic latent image is formed. In an image forming apparatus that forms a corresponding toner image, overlaps the toner image with a final recording support, and fixes the toner image on the final recording support at the same time as the transfer, (a) a toner image of a portion after development on a member to be developed; (b) A toner carrier of opposite polarity is provided on the forming surface side without contacting the toner image, and (b) a toner carrier of opposite polarity is provided on the opposite side of the object to be developed in a position corresponding to the toner carrier of opposite polarity in contact with the object to be developed. (c) Applying an electric bias between the opposite polarity toner carrier and the opposite electrode to carry the opposite polarity toner that has adhered to the non-image area on the object to be developed by the action of the electric field. An image forming device characterized by suction and removal from the body.