JPS6152673A - Picture transfer device - Google Patents

Abstract

PURPOSE:To eliminate the color staggering of a multi-colored picture by giving a charge of the same polarity as a toner on the rear 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 exposed 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 rear 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 positive 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 a multicolor image by performing multiple transfers on a photographic material in the same image.

[Prior art]

Various methods and apparatuses have been proposed for the purpose of producing multicolor images using electrophotography. After developing with color) toner, it is transferred to a transfer material such as paper, and the same process is performed with tjS2. Third, it is most common to repeatedly transfer a plurality of color toner images onto the same transfer material in a superimposed manner according to the number of required color separations to obtain a multicolor image. 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. Many transfer devices are used that are designed to always maintain a constant relative position. Generally, a mechanical locking means (gripper) is provided 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.

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, JP-A-55-18653
The publication 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, the transfer material is electrostatically attracted to the transfer material support.
Therefore, it is said that the 11 precepts for locking the transfer material are not necessarily necessary, but the screen-shaped transfer material support has a small contact area with the transfer material, so it is necessary to securely hold and fix the transfer material. It is still necessary to lock it to a support.

However, when a locking section is provided on the transfer drum, it becomes complicated to automatically lock, release, and separate the transfer material. The speed and sequence of copying operations are restricted due to waiting for the locking position, etc., the locking part is loose, and a blank is created at the leading edge of the transfer material that is locked to the locking part. Many problems have arisen, such as the need for a mechanism to avoid the gripper part in the cleaning device for the holding drum, 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, which has a simple structure and can reliably transfer multiple toner images onto a transfer material without color misregistration.

[Structure of the invention]

The above object is to provide a charge applying means for applying an electric charge of the same polarity as that of the toner, a transfer drum having an insulating surface, and a transfer drum having an insulating surface. This has been achieved by an image transfer device characterized by having a charge applying means for applying a charge of opposite polarity to the charge of the toner to the surface of the transfer drum provided opposite to the drum.

In other words, a charge of the same polarity as that of the toner is applied from the back side of the transfer material, and the transfer drum, which has an insulating surface and previously given a charge of the opposite polarity to the charge of the toner, is adsorbed and held by the city electricity. According to the above, it is possible to fix the transfer material on the transfer drum without any kind of locking means such as a gripper to fix the transfer material, and it is possible to fix the transfer material on the transfer drum without causing various problems such as overlapping, and to prevent color misalignment. Nona (・Multiple transfer of toner can be performed.

At this time, the transfer material is charged with the same polarity as the toner, creating a repulsive force, but the transfer drum is charged with a charge having the same polarity as the toner.
Since an electric charge is applied to the transfer material, if the amount of charge applied to the transfer material is set to a low value, the electrostatic 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. 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 transfer drum, and are not particularly limited, but a corona discharger is particularly preferably used as one. . 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 using a corona discharger, the applied voltage is 1
The force varies depending on the properties of the clay image carrier and the toner (normally, a range of 4 to 7 KV with the same polarity as the toner is appropriate. Also, the charge applied to the transfer drum is such that its surface potential is the same as that of the toner). The voltage applied to the transfer drum charging corona discharger is preferably 5 to 8 KV, which is the opposite polarity to the toner.

The transfer drum may be configured such that an insulating layer is provided on the surface of the conductive convex body and the four electrically conductive parts are grounded (1'), but the transfer drum presses the transfer material onto the image bearing surface and transfers the toner. In view of the necessity of carrying out this process, it is preferable that the surface thereof has a suitable degree of elasticity, and therefore it is preferable to have a structure in which a conductive elastic layer is provided on a conductive substrate, and an insulating layer is further provided on the surface of the conductive elastic layer.

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 taloloprene-based conductive rubbers. These conductive elastomers have a rubber hardness of 40° to 70” and a resistance of 108Ω.
- It is preferable to have a volume resistivity of ctn or less, and the layer thickness on the conductive w body is preferably about 1 to 10 mm.

The insulating layer is made of various insulators such as polyester, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, methacrylic resin, acrylic U.
(It can be constructed using resin, polystyrene, silicone, styrene-butadiene copolymer, various other polymers or copolymers, rubber, etc.). The insulating layer may be formed into an absolute M layer by applying it directly to the surface of a conductive elastic body, directly to the surface of a conductive substrate, or by covering it as a heat-shrinkable tube and heat-shrinking it.The thickness of the insulating layer is IO to 100. It is preferable to set it as tn.

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 denotes an image bearing drum consisting of a conductive substrate 1 and a photoconductive photosensitive layer 2, and the shadow denotes a conductive substrate 3 and a conductive elastic layer 4. , insulation IvI
6, which is a more powerful transfer drum than 5, shows a case in which 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 negatively charged by a transfer drum charging corona discharger 6. 7
A positive voltage is applied by a transfer material charging corona discharger provided opposite to the image bearing drum.

The image bearing drum L and the transfer drum are brought into pressure contact with the transfer section, and during operation, they rotate in the directions of arrows B and C, respectively (the figure schematically represents the state during transfer, so there is no space between the two drums). pictured).

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

The transfer material 10 (its length is 1 to 3) is advanced in the direction of the arrow by a feeding means not shown in the figure.
- is given a negative charge of the same polarity as the toner by the corona discharger 7 from its back side and enters the transfer section where the image bearing drum L and the transfer material holding drum are in contact. 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 fP4i toner image.

When the transfer material comes out of the pressing parts of both drums, electrostatic attraction from both drums is applied to the transfer material, but the negatively charged transfer material 1
0 is strongly attracted to the transfer drum, which has been positively charged in advance by the transfer drum charging corona discharger 6, and is wound and fixed on the surface of the transfer drum. 1, the photographic material is in full contact with the transfer drum and is strongly adsorbed, so it will not shift during subsequent processes. As the drum L rotates, the transfer material 10 wrapped around the transfer drum L advances to the transfer section again f5.
The second toner image is transferred. The corona discharger 6 operates the switch S to stop its operation at the point where 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 negative charge applied to the back surface of the transfer material is maintained without attenuation because the surface of the transfer drum is insulative, and the transfer material is held securely.

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 constant R1 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 separated from the drum L and advances in the direction of arrow E. When J1 is to be used for color copying, if it is set in this mode from the beginning, the transferred transfer material is immediately discharged in the direction of arrow E, making it possible to perform high-speed and continuous copying. This is an advantage that can only be obtained in the image transfer device of the present invention, which does not have a transfer material locking portion on the transfer drum and can be used in any position. 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, the functions and effects are the same, except that the polarities of the electrostatic charges are all reversed.

Also, in Figure 1, the transfer drum main is shown as being grounded.
By applying an appropriate bias voltage, sufficient transfer, winding and separation performance can be obtained.

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 the three-color negative method or, for example, to the Japanese Patent Publication No. 48-34
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 Laid-open No. 770 and Japanese Patent Application Laid-Open No. 56-5561. . Further, various known paper feeding and fixing means can be used as a paper feeding means for supplying a transfer material such as paper to this apparatus, a fixing means for fixing an image transferred by this apparatus, etc. .

〔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. ``Figure 2 shows an image forming section of a color copying machine using an image transfer device according to the present invention,
FIG. 3 is a schematic diagram of an image transfer section. In this figure as well, members having the same functions 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. Scan is 3
The filters FR (red) and F are repeated several times each time.

(green) and FB (blue) are alternately inserted into the optical path to perform color separation exposure. The figure shows a state in which the blue filter FB is not inserted into the optical path.

For L, a selenium-based photoreceptor constructed in the same manner as the image bearing drum shown in FIG. 1 was used (in this example, a Se/Te photoreceptor with a relative dielectric capacity of '4' and a thickness of 60 Jra was used). A photosensitive drum that rotates in the direction of the arrow and a corona discharger 2.
After the entire surface is given a positive charge by 0, the image is exposed by light from the optical path. First, a blue filter is placed in the optical path and exposed to light to form an electrostatic image on the photosensitive drum L, which is then developed by a developing device 21Y loaded with a negatively charged yellow developer to form a yellow toner image. The photosensitive drum carrying the yellow toner image is neutralized by the pre-transfer static eliminating lamp 22 and advances to the transfer position A.

On the other hand, the transfer paper 10 fed through the paper feed roller 23 has a negative charge (-2X10-'C/c) on its back surface by the discharger 7.
TI12) is sent to the transfer position A, and the yellow toner image is transferred by being pinched between the photosensitive drum L and the transfer drum 1, but before the transfer drum L comes into contact with the transfer material 10, the temperature is +8
A positive charge is applied in advance by a transfer drum charging corona discharger 6 so that a surface potential of 00 to +100 OV is obtained. The transfer drum has the same structure as that shown in FIG. 1, but the details are omitted in this figure.

The conductive rubber layer of the transfer drum -β- in this example has a thickness of 2 m1.
11. The hardness was 50°, the volume resistance was 105ΩcTII, and the insulating layer was made of polyester having a relative dielectric constant of 3 and a thickness of 12.5 μm. The transfer material 10 that has been transferred is wound around and held by the positively charged transfer drum L, 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 io held in the shadow of the transfer drum advances as the drum 3 rotates, and its position is read by the sensor 26, and in synchronization with this position, the 52nd exposure operation is started. Furthermore, at the point where the sensor 26 detects the leading edge of the transfer material, the voltage application to the transfer drum charge (11) and the corona discharger is stopped, and the negative discharge damages the negatively charged toner image transferred to the surface of the transfer material. to prevent

The second exposure uses a green filter FG, and development is performed by a developing device 21M loaded with a negatively charged magenta developer. The obtained magenta toner image is transferred overlappingly onto the yellow image on the transfer paper 10 held on the transfer drum and entering point A.

The it color toner is absorbed by the positive charge of the transfer drum, and the image may be distorted during overlapping transfer, and the photosensitive drum L111+
It will not be retransferred to 1.

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 transfer paper static elimination corona discharger 27, and the separation claw 11
is lowered to the transfer drum L side, separated from the drum L surface, and sent to a heat roller fixing device (not shown) to be fixed. The three color toners transferred onto the transfer paper 10 are fixed and melted and mixed to reproduce a color image by the subtractive color method.

``The transfer drum L from which the paper has been separated is neutralized by a transfer drum static eliminator 28, and is further removed by a transfer drum cleaner 29.
The toner adhering to the surface is removed and the toner is prepared for a large copy operation cycle.6 When making monochrome copies using this device, only one developing unit is operated, the separating claw 11 is placed in the lowered position, and the static eliminator 27 is continuously operated. By operating the printer continuously, copies can be made continuously and at high speed.

In addition, the above example is for normal three colors p! Although the case of color copying using f-filters and yellow, magenta, and cyan toners has been described, the colors and numbers of color separation filters and toners, the number of developing devices, etc. are not limited to these. Of course it's sticky.

〔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 +Le photo drum carrier can be kept in pressure contact at all times. It 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. f5i is a schematic diagram showing the operation of the image transfer apparatus according to the present invention, and FIG. L...Image bearing drum 3...Transfer drum 3...
- Conductive base 4... Conductive elastic layer 5... Insulating layer

Claims (2)

[Claims] (1) In an image transfer device that transfers a charged toner image formed on an image carrier onto a transfer material, the charge of the toner is transferred from the back side of the transfer material, which is provided opposite to the image carrier. a transfer material charge applying means for applying an electric charge of the same polarity as the toner, a transfer drum having an insulating surface, and applying an electric charge of the opposite polarity to the electric charge of the toner to the surface of the transfer drum, which is provided opposite to the transfer drum. An image transfer device characterized by having a transfer drum charge 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.