JPS6152674A - Picture transfer device - Google Patents

Abstract

PURPOSE:To eliminate the color staggering by giving a charge of the same polarity as a toner on the surface of a transfer material and impressing a voltage of the reverse polarity on the surface of a transfer drum to fix the transfer material. CONSTITUTION:For instance, an electrostatic image is expored on a selenium photosensitive drum 10 to form an image of a negatively charged toner 9. A transfer drum 30 is so constituted to provide a conductive elastic layer 4 and an insulating layer 5 on a conductive base body 3. A positive voltage is impressed on the surface of the transfer drum 30 by a corona discharge device 6, and said drum 30 is brought into contact with the photosensitive drum 10 at a contact part A. The transfer material 10 is advanced as shown by an arrow D, and the surface of the transfer material 10 is negatively charged by a corona discharge device 7. At the contact part A of the drums 10 and 30 the negative toner 9 is attracted to the positive transfer drum 30 to be transferred on the transfer material 10. On the other hand, the negative transfer material 10 is attracted to the transfer drum 30 to be strongly wound. Consequently, even if colors of the toner are sequentially charged, the multi-colored picture without the color staggering can be obtained since the transfer material is fixed on the transfer drum.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an image transfer device for transferring a toner image formed by electrophotography or the like onto a transfer material such as paper.
More specifically, the present invention relates to an image transfer device suitable for obtaining multicolor images by performing multiple transfers onto the same transfer material.

[Prior art]

Various methods and apparatuses have been proposed in the United States for the purpose of obtaining multicolor images using electrophotography. After developing with a second image, it is transferred to a transfer material such as paper, and the same process is carried out with a second image. 3. Repeat the same process depending on the number of color separations required.
Multiple color toner images are sequentially transferred onto a transfer material,
It is most common to obtain polychromatic images. In the method of sequentially overlapping color images on a transfer material, the alignment of the transfer material with respect to the image carrier is extremely important, and if this is inaccurate, color misregistration may occur, making the image unusable. It becomes.

As a means for accurately regulating the position of the transfer material relative to the image carrier, a transfer drum is provided in contact with the image carrier, and the transfer material is fixed on the drum and rotated in synchronization with the image carrier, so that the transfer material is aligned with the image carrier. A transfer device that always maintains a constant relative position is often used. Usually, a mechanical locking means (grip/pa) is installed on the transfer drum to automatically lock the leading edge of the transfer material fed by a feed roller or the like and fix it on the drum. be.

When transferring the toner image on the image carrier to a transfer material, an electrostatic process such as applying a charge to the transfer material is required to move the toner onto the transfer material, and the image carrier is also charged. Complex electrostatic forces act on the transfer material, such as having The current situation is that

For example, US Pat. No. 3,729,311 discloses a color copying machine having a transfer material holding drum in contact with an image bearing drum, and the transfer material holding drum is provided with a gripper for fixing the transfer material. Also vP Kaisho 55-1885
No. 3 discloses a color copying machine having a transfer material support made of a mesh screen having an insulating surface in contact with an image bearing drum.

Here, since the transfer material is electrostatically attracted to the transfer material support, it is said that mechanical means for locking the transfer material is not necessarily necessary, but the screen-shaped transfer material support is In order to securely hold and fix the photographic material, it is necessary to lock it to the support body.

However, when a locking section is provided on the transfer drum, it requires a complicated mechanism for automatically locking, unlocking, and separating the transfer material. There are many restrictions, such as dirt on the locking part, blank space at the leading edge of the transfer material that is locked in the locking part, and the need for a mechanism to avoid the gripper part in the cleaning device for the transfer material holding drum. This problem has arisen, and it has been desired to develop a simpler and more reliable transfer material fixing means.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image transfer device for a multicolor electrostatic recording device 6, which has a simple structure and can reliably transfer multiple toner images onto a transfer material without causing color misregistration. be.

[Structure of the invention]

The above object is to provide a transfer drum having an insulating surface, a transfer material charge f'NIL5 means for applying a charge of the same polarity as the charge of the toner to the surface of a transfer material provided opposite to the transfer drum, and This was achieved by an image transfer apparatus having a transfer drum charge applying means for applying a charge of opposite polarity to the iiM toner to the surface of the transfer drum provided opposite to the drum.

In other words, the transfer material is placed on the transfer drum, which has been given a charge of 7% the same polarity as the toner charge, and the transfer material is attracted and held onto the transfer drum by electrostatic force by applying a charge of the same polarity as the toner from its surface. After that, the toner image is transferred. According to this device, there is no need for any locking means such as a gripper for fixing the ++g photographic material on the transfer drum. Multiple transfer of toner without color misregistration can be performed without causing problems.

At this time, since the transfer material is charged with the same polarity as the toner, a repulsive force will be generated between the toner and the transfer material, but the transfer drum Since an electrostatic charge is applied, if the amount of charge applied to the transfer material is set to a low value, the electric field generated by the charge on the transfer drum will overcome the charge on the transfer material and attract the toner together with the transfer material toward the transfer drum. Toner transfer and retention are performed well.

Furthermore, since the electric charges of the toner and the transfer material are both opposite in polarity to the electric charge of the transfer drum, the adsorption of the transfer material to the transfer drum becomes extremely strong.

The transfer material charge applying means and the transfer drum charge applying means used in the present invention may be any means as long as they can respectively apply charges to the transfer material or the copying drum, and are not particularly limited, but a corona discharger is particularly preferably used. . The polarity of the charge applied to the transfer material is the same as the charge of the toner depending on the polarity of the charge of the toner to be transferred (determined according to the polarity of the electrostatic image formed on the image carrier). Set it like this. When a corona discharger is used, the applied voltage varies depending on the properties of the image carrier and the toner, but it is usually appropriate to range from 4 to 7 KVn, which has the same polarity as the toner. Furthermore, it is preferable that the charge applied to the transfer drum has a surface potential of 0.5 to 1.5 K +/, which is opposite in polarity to the toner. Therefore, the voltage applied to the transfer drum charge imparting corona discharger is It is appropriate to set the voltage to 5 to 8 KV with the opposite polarity.

The transfer drum may have a structure in which an insulating layer is provided on the surface of the conductive substrate and the conductive portion can be grounded, but the transfer drum must transfer the toner by pressing the transfer material onto the image carrier surface. Above, it is preferable that the surface has appropriate elasticity,
For this reason, it is preferable to use conductive Ji (having a structure in which a conductive elastic layer is provided on the body and an insulating layer is further provided on the surface thereof).

As the conductive substrate, it is preferable to use metal such as aluminum, for example. Preferred examples of the conductive elastic body include conductive rubbers such as silicone-based or chloroprene-based conductive rubbers. These conductive elastic bodies now have a rubber hardness of 0° to 70°, and a resistance of 108Ω.
- It is preferable to have a volume resistivity of c'm or less, and the layer thickness on the conductive substrate is preferably about 1 to 10 m+++.

The insulating layer may be made of various insulators such as polyester,
Polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, methacrylic U (fat, acrylic resin, polystyrene, silicone 8 (fat, fluororesin, styrene-butadiene copolymer, and various other polymers or copolymers), These insulators can be constructed using rubber, etc. These insulators can be applied to the surface of a conductive elastic body, or directly to the surface of a conductive substrate, or can be covered with a heat-shrinkable tube and heat-shrinked to form an insulating layer. The thickness of the insulating layer is preferably from 10 to 100 mm.

The functions of the image transfer device of the present invention will be explained below. FIG. 1 is a schematic diagram of an image transfer apparatus of the present invention, in which L is an image bearing drum consisting of a conductive substrate 1 and a photoconductive photoreceptor R1I2, L is a conductive substrate 3, a conductive elastic layer 4, Insulating layer 5
This is a transfer drum consisting of. The figure shows a case where a photosensitive layer that forms a positively charged electrostatic image, such as selenium-based or amorphous silicon, is used.

The transfer drum L is grounded, and its surface is positively charged by a transfer drum charging corona discharger 6. 7
A negative voltage is applied by a transfer material charging corona discharger provided opposite to the transfer drum.

Image carrier drum L and transfer drum -? - is in pressure contact with the transfer portion, and rotates in the directions of arrows B and C, respectively, during operation (in the figure, the space between the two drums is shown as being open to schematically represent the state during transfer).

The electrostatic image formed on the image bearing drum L is developed by a developing device (not shown) loaded with negatively charged toner to form a toner image. 9 is a toner forming a toner image.

The transfer material 10 (its length is shorter than the circumference of the transfer material holding drum L), which is advanced in the direction of the arrow by a feeding means not shown in the figure, is coated with the same polarity as the toner by a corona discharger 7 on its surface. It is given a negative charge and enters the transfer section where the image bearing drum L and the transfer material holding drum L are in contact with each other. The negatively charged toner particles are attracted by the positive charge on the surface of the transfer drum and migrate to the transfer material, completing the transfer of the first toner image. When the transfer material comes out of the pressure contact portion of both drums, electrostatic attraction from both drums is applied to the transfer material, but the negatively charged transfer material 10 is transferred to the transfer material 10 that has been positively charged in advance by the transfer drum charging corona discharger 6. It is more strongly attracted to the surface of the drum L and is wound and fixed on that surface.

The transfer material is in full contact with the transfer drum and is strongly adsorbed, so it will not shift during subsequent processes. The transfer material 10 wound around the transfer drum L advances to the transfer section again as the drum L rotates, and the second toner image is transferred thereto.

The corona discharger 6 operates a switch to stop its operation when the transfer drum has made one rotation so that no discharge is applied to the transfer material. Thereafter, the same transfer process is repeated as many times as necessary, and a multicolor image is completed on the transfer material 10. During this time, the positive charge applied to the surface of the transfer drum is maintained without being destroyed because the surface of the transfer drum is insulating, and the toner is transferred smoothly.

After the transfer is completed, the transfer material may be separated from the transfer material holding drum using a separation means such as a separation claw and sent to the fixing process. In the figure, reference numeral 11 denotes a separation claw, and by rotating this to the position indicated by the dotted line, the transfer material 10 is further separated from the drum and advances in the direction of arrow E. If you are making monochrome copies, if you set this mode from the beginning, the transfer material will be immediately moved to the arrow E when the transfer is completed.
It is possible to perform high speed and continuous copying by ejecting the paper in the same direction. This is an advantage that can only be obtained in the image transfer device of the present invention in which there is no transfer material locking portion on the transfer drum L and the drum is used at an arbitrary position. However, it is difficult to increase the speed because positioning, locking, and locking operations of the drum are required.

All of the above explanations have been made using photosensitive layers that form positively charged electrostatic images such as selenium-based or amorphous silicon, but negatively charged types such as zinc oxide, cadmium sulfide, and various organic photoreceptors are used. Even when using a photosensitive layer, all the polarities of the above-mentioned nodal charges are simply reversed, and 8! The ability and effect are the same.

Although the transfer drum L is shown grounded in FIG. 1, sufficient transfer, winding and separation performance can be obtained by applying an appropriate bias voltage.

In addition to the transfer material separation means, the image transfer device of the present invention includes:
Transfer material static eliminator, transfer material holding drum static eliminator,
Additional devices such as a transfer material holding drum cleaner and positioning sensor can be added.

The image transfer device of the present invention can be applied to various known color image forming means using a three-color separation method, or for example, to the Japanese Patent Publication No. 48-347
It can be used in combination with various multicolor image forming means such as known two-color image forming means including a black image erasing process as disclosed in Japanese Patent Application Laid-Open No. 56-5561. 6. Also, a paper feeding means for supplying a transfer material such as paper to this apparatus, by this apparatus.

As the fixing means for fixing the transferred image, any of various known paper feeding and fixing means can be used.

〔Example〕

An example in which the image transfer device according to the present invention is used in a color copying machine using a three-color separation method will be described below.

FIG. 2 is a schematic diagram of an image forming section and an image transfer section of a color copying machine using an image transfer device according to the present invention. In this figure, members of the same age as those in FIG. 1 are indicated by the same numbers. In the figure, the arrow indicates the optical path of image exposure that scans the original image sent from an optical system not shown in the figure. The scanning is repeated three times, and each time filters FR (red), FG (green), and FB (blue) are alternately inserted into the optical path to perform color separation exposure. The figure shows a state in which a blue filter FB is placed in the optical path.

The knee was constructed in the same manner as the image bearing drum shown in FIG.
The photosensitive drum (using a photosensitive member made of 0n Se/Te) rotates in the direction of the arrow and is image-exposed by light from the light path after the entire surface is positively charged by a corona discharger 20. Ru. 5'Q Two color filters are placed in the optical path and exposed to light to form an electrostatic image on the photosensitive drum 1, which is then developed with a developing device 21Y loaded with a negatively charged yellow developer to form a yellow toner image. The photosensitive drum carrying the six-color toner image is first neutralized by a pre-photographing static eliminating lamp 22, and then advances to a transfer position.

On the other hand, the eaves copy paper 10 fed via the paper feed roller 23 is statically placed on the transfer drum L, which has been positively charged in advance by the transfer drum charge-applying corona discharger 6 so that its surface potential is +800V to +1000V. The transfer material is adsorbed by electric power, and a negative charge is applied to the surface thereof by a transfer material charge applying corona discharger 7 so that -I x 10-'C/CTl12. As a result, the transfer material 10 is strongly attracted and held by the transfer drum L, moves to the transfer position, and moves to the photosensitive drum L.
The yellow toner image is transferred by being pinched between the transfer drum L and the transfer drum L. The surface of the transfer material is negatively charged, but due to the strong positive power saving field of the transfer drum, the negatively charged toner transfers smoothly. It is omitted in Figure 2.

The conductive rubber layer of the transfer drum L in this embodiment has a thickness of 2'I,
The insulating layer was made of polyester having a hardness of 50° and a volume resistivity of 105 Ωcm and a thickness of 1265 μm and a dielectric constant of 3.

The transfer material 10 that has been transferred is wound around and held by the positively charged transfer drum 3, which saves power, and moves.

After the photosensitive drum has been transferred, the toner remaining on the surface of the drum is removed by a cleaning device 24, and the residual charge is removed by a charge removal lamp 25, and then the photosensitive drum is reused.

The transfer paper lO held on the transfer drum L moves along with the rotation of the drum shadow, and its position is read by the sensor 26, and the f52nd exposure operation is started in synchronization with this position. Furthermore, at the point when the sensor 26 detects the leading edge of the transfer material, the voltage application to the transfer material charge imparting front discharge device is stopped, and the negative discharge damages the negatively charged toner image transferred to the surface of the transfer material. prevent.

The second exposure is performed using the green filter FG1, and the development is performed by the developing device 21M loaded with a negatively charged magenta developer. The obtained magenta toner image is held on the transfer drum, enters point A, and is transferred to overlap the yellow image on the transfer paper 10.

The yellow toner is attracted by the positive charge on the transfer drum, and the image is not blurred or retransferred to the photosensitive drum L side.

Furthermore, through the same process, a cyan toner image obtained by exposure through the red filter FR and development by the developing device 21C loaded with cyan developer is transferred overlappingly. After the transfer of the cyan toner image has been completed, the transfer paper 10 is charged with alternating current corona discharge from the static eliminator Frona discharger 27, and the separation claw 1
1 is lowered to the side of the transfer drum L, separated from the surface of the drum 3, and sent to a heat roller fixing device (not shown) to be fixed. The three color toners transferred onto the IIE paper 10 are fixed and melted and mixed to reproduce a color image by the subtractive color method.

The separated transfer drum shadow on the transfer paper is removed by the transfer drum static eliminator 2.
8, the transfer drum cleaner 29 removes toner adhering to the surface of the drum, and prepares for the next copying operation cycle.

When making monochrome copies using this apparatus, only one developing unit is operated, the separating claw 11 is placed in a lowered position, and the static eliminator 27 is continuously operated, thereby making it possible to obtain copies continuously and at high speed.

In the above embodiment, the case of color copying using yellow, magenta, and cyan toners using a normal three-color separation filter was explained.
Of course, the number of developing devices is not limited to this.

〔Effect of the invention〕

With the image transfer device of the present invention, which does not require a transfer material locking means on the transfer drum, the transfer material holding drum can be used at any position because there is no locking means, and the transfer drum and image carrier are kept in pressure contact at all times. This has many advantages, such as eliminating the need for mechanisms such as pressure release or positioning to avoid the locking means hitting the image carrier, and easy cleaning of the transfer drum. It is possible to obtain a multicolor electrostatic recording device that is reliable, has no color shift, and has a simple structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the operation of an image transfer apparatus according to the present invention, and FIG. 2 is a schematic diagram showing color copying using the image transfer apparatus according to the present invention. L... Image bearing drum -3-... Transfer drum 3.
...Conductive base 4...Conductive elastic layer 5...
Insulating layer 6...Transfer drum charge imparting corona discharger 7...Transfer material charge imparting corona discharger Agent Patent attorney No 1) Father-in-law Figure 2

Claims (2)

[Claims] (1) An image transfer device that transfers a charged toner image formed on an image carrier to a transfer material, including a transfer drum having an insulating surface, and a transfer drum provided opposite to the transfer drum. a transfer material charge applying means for applying a charge of the same polarity as the charge of the toner to the surface of the material; and a transfer drum charge applying a charge of the opposite polarity to the toner to the surface of the transfer drum provided opposite to the transfer drum. An image transfer device comprising: a applying means. (2) The transfer drum having an insulating surface includes a conductive drum base, a conductive elastic layer provided on the base,
The image transfer device according to claim 1, further comprising an insulating layer provided on the surface of the conductive elastic layer.