JPS6152672A - Picture transfer device - Google Patents

Abstract

PURPOSE:To eliminate the color staggering of a multi-colored picture by giving a charge of a polarity reverse to a toner on the surface of a transfer material and impressing a voltage of the same polarity on the surface of a transfer drum so as to fix the transfer material. CONSTITUTION:An electrostatic image is exposed on, for instance, a selenum 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. On the surface of the transfer drum 30 a negative voltage is impressed 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, the surface of said material is positively 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 transfer material 10 and transferred. On the other hand, the positive transfer material 10 is attracted to the negative transfer drum 30 to be wound strongly. Consequently even if colors of the toner are sequentially charged, the multi-colored picture without 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 d suitable for obtaining multicolor images by performing multiple transfers on the same transfer material.

[Prior art]

Various methods and devices have been proposed for the purpose of producing multicolor images using electrophotography. After developing with the first color toner, it is transferred to a transfer material such as paper, and the same process is repeated according to the number of required color separations to create multiple colors on the same transfer material. The most common method is to transfer toner images in sequence, one on top of the other, to obtain a multicolor image. It is extremely important to align the transfer material, and if it is inaccurate, the image will not be able to withstand color misregistration.

As means for accurately positioning the transfer material relative to the image carrier by one square inch, a transfer drum is provided in contact with the image carrier;
A type of copying device is widely used in which a transfer material is fixed on the drum and rotated in synchronization with the image carrier so that the transfer material always maintains a constant position relative to the image carrier. A locking means (gripper) is installed on the transfer drum to automatically lock the leading edge of the material being fed by a feed roller or the like and fix it on the drum. is normal.

When transferring the toner image on the image carrier to a transfer material, an electrostatic process such as applying an electric charge to the transfer material is required in order to move the toner onto the transfer material, and the image carrier also does not have an electric charge. Due to the complicated electrostatic force acting on the transfer material, the transfer material tends to shift easily due to the force from the image carrier or transfer drum. 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 an i1g photographic material support consisting of a mesh screen having an insulating surface in contact with an image bearing drum.

Here, since the transfer material is absorbed by the transfer material support by electrostatic force In order to reliably hold and fix the photographic material with a small contact area, it is necessary to lock it to the support.

However, when a locking portion is provided on the transfer drum, complicated grooves are required for automatic locking, unlocking, and separation of the transfer material, and the speed of copying operation is reduced due to waiting for the locking position, etc. The sequence is restricted, the locking part becomes dirty, a blank is created at the leading edge of the transfer material that is locked in the locking part, a groove is required in the cleaning device of the transfer material holding drum to avoid the gripper part, etc. Due to these problems, it was desired to develop a simpler and more extensive 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 transfer drum having an insulating surface, a transfer material charge applying means for applying a charge of opposite polarity to the charge of the toner to the surface of the 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 the same polarity as the toner to the surface of the transfer drum, which is provided opposite to the transfer drum.

In other words, the transfer material is placed on a transfer drum that has been charged with the same polarity as the toner charge, and then a charge of the opposite polarity is applied to the surface of the drum, so that the transfer material is attracted and held by the transfer drum l by electrostatic force. This device then performs i1g copying of the toner image, and this device does not require any locking means such as a gripper to fix the transfer material on the transfer drum, and can be used in various ways as described above. Multiple toner transfer without color misregistration can be performed without any problems.

Further, since the transfer material has a charge of opposite polarity to that of the toner, toner can be transferred with high efficiency.

The two charge applying means used in the present invention are not particularly limited as long as they can apply charges to the surface of the transfer drum, but a corona discharger is particularly preferably used. The polarity of the charge applied depends on the charge polarity of the transferred toner (determined according to the polarity of the electrostatic image formed on the image bearing member), and the polarity of the charge applied to the transfer material is the opposite of that of the toner, The transfer drum has the same polarity as the toner. When using a corona discharger as a charge imparting means, the voltage applied to the discharger varies depending on the properties of the image carrier, toner, etc.;
It is preferable to set the polarity to 1 to 8 (the polarity is opposite to that of the toner). The transfer drum has a surface potential of 100 to 300V (
It is preferable to apply a charge so that the li property is the same as that of the toner), and therefore it is preferable to apply a voltage of 4 to 6 KV (the polarity is the same as that of the toner) to the transfer drum charging corona discharger.

The transfer drum may have a configuration in which an insulating layer is provided on the surface of the conductive substrate and the conductive portion is grounded, but the transfer drum must transfer the toner by pressing the transfer material against the image bearing surface. Moreover, it is preferable that the surface has appropriate elasticity, and for this reason, 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.

As the conductive substrate, it is preferable to use metal such as aluminum, for example. Preferred examples of the conductive elastic body include conductive rubber such as silicone-based or chloroprene-based conductive rubber. These tetraelectric elastic bodies have a rubber hardness of 40° to 70° and a resistance of 10'Ω
・The insulating layer preferably has a volume resistivity of 1 cm or less, and the layer thickness on the conductive substrate is preferably about 1 to 10 mm. It can be constructed using polyvinyl chloride, polyvinyl acetate, methacrylic resin, acrylic resin, borisnarene, silicone 8I resin, fluororesin, styrene-butadiene copolymer, and various other polymers or copolymers, rubber, etc. These insulators have a conductive elastic surface,
Alternatively, the insulating layer may be formed by applying it directly to the surface of the conductive W body, or by covering it with a heat-shrinkable tube and heat-shrinking it. Absolute kk Jr! ll7) The thickness should be 10 to 100 μm.

is preferable.

The functions of the image transfer device of the present invention will be explained below. 0
'S1 is a schematic diagram of the image transfer device of the present invention, and L
6 is an image bearing drum consisting of a conductive substrate 1 and a photoconductive photosensitive layer 2, L is a transfer drum consisting of a conductive substrate 3, a conductive elastic body WJ4, and an insulating layer 5. Figure 6 is a selenium-based or amorphous silicone drum. The case is shown in which a photosensitive layer that forms a positively charged electrostatic image is used.

The transfer drum a- is grounded, and its surface is given a negative charge by a transfer drum charging corona discharger 6. Reference numeral 7 denotes a corona discharger for applying a charge to the transfer material, which is provided opposite to the transfer drum, and a positive voltage is applied thereto.

The image carrier drum L and the transfer drum L are pressed against each other in the transfer section A, and during operation, they rotate in the directions of arrows B and C, respectively (the figure schematically represents the state during transfer, so both drums are opened). pictured).

The electrostatic image formed on the image bearing drum L is developed by a developing device (not shown in the figure) 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), which advances in the direction of the arrow by a feeding means not shown in the figure, is reversed from the toner by a discharger 7 cored on its surface. It is charged with a positive polarity and enters the transfer section where the image bearing drum L and the transfer material holding drum are in contact with each other. The negatively charged toner particles are attracted by the positive charges on the surface of the transfer material and move toward the transfer material, completing the transfer of the first toner image. When the transfer material exits from the pressure contact portion of both drums, electrostatic attraction from both drums is applied to the transfer material. It is strongly attracted to the surface of L and is wrapped around and fixed to that surface. The transfer material beam is in full contact with the photo drum and is strongly adsorbed, so it will not shift during subsequent processes. Transfer material 1 wrapped around transfer drum L
0 again advances to the transfer section A as the drum L rotates, and a second toner image is transferred thereto. The corona discharger 6 is deactivated by actuating the switch SW at the point at which the III transfer drum rotates so that no discharge is applied to the transfer material. Thereafter, the same transfer process is repeated as many times as necessary to complete a multicolor image on the transfer material 10. During this time, the positive charge applied to the back surface of the transfer material is maintained without being lost 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. 1 in the diagram
1 is a separation claw, and by rotating this to the position indicated by the dotted line, the transfer material 10 is separated from the drum. - Separate and move in the direction of arrow E. If you are making single-color copies, if you set this mode from the beginning, the transfer material that has been transferred will be directly marked with arrow E.
It is possible to make 11 copies at high speed and continuously by ejecting the paper in the direction shown in FIG. This is the stamp I on the transfer drum L.
Only in the image transfer device 1 of the present invention, which does not have an L section and the drum can be used at any position; an advantage that can be obtained is that the drum can be positioned at any position even in the case of monochrome copying in the device with a locking section. It is difficult to increase the speed because alignment, locking, and locking operations are required.

All of the above explanations are based on the case where a photosensitive layer that forms a positively charged electrostatic image, such as selenium-based or amorphous silicon, is used. Even when a 1'I type photosensitive layer is used, the functions and effects are the same, except that the polarities of the electrostatic charges mentioned above are all reversed. Various shapes such as a belt shape can be used.

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. 70 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, and the like.

〔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, components with the same specificity as those in Figure 1 are indicated by the same numbers.In Figure 6, the arrows indicate scanned images of original images sent from an optical system not shown in the figure. This is the optical path for exposure. The scanning is repeated three times, and each time filters FR (red), F6 (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.

1 i is a photosensitive drum configured similarly to the image bearing drum shown in FIG.
A Se T (!) photoreceptor is used. The drum rotates in the direction of the arrow, and after its entire surface is given a positive charge by the corona discharger 2o, it is exposed to image by light from the optical path -. After the Zrt color film is placed in the optical path and exposed to light to form a photosensitive drum L, a yellow toner image is developed by a developing device 21Y loaded with a negative A:7 electrostatic yellow developer. .) The photosensitive drum carrying the 1° color toner image is neutralized by the pre-transfer static elimination lamp 2Z and advances to the 1-degree copying position A.

On the other hand, the transfer paper 1o fed through the paper feed roller 23 is
By saving power, the transfer drum L, which has been negatively charged in advance by the transfer drum charge applying corona discharger 6 to have a surface potential of -zoov, is adsorbed, and further, the transfer material is charged on its surface by the transfer material charge applying corona discharger 7. 10-'C
/ m2 positive charge is given. As a result, the transfer material IO is strongly attracted and held by the transfer drum L, moves to the transfer position, is pinched between the photosensitive drum 1 and the transfer drum 1, and the yellow toner image is transferred.

Since the surface of the transfer material is positively charged, negatively charged toner transfers extremely well.

The transfer drum L has the same structure as that shown in FIG. 1, but the details are omitted in the figure. The diameter of the transfer drum 3 is 150
mm, the conductive elastic layer is made of conductive rubber with a thickness of 2II1 m, a hardness of 50°, and a volume resistivity of 105Ωa, and the absolute I & layer is rI'! , dl=10In, ratio A electric rate t
It was composed of polyester with d=3.

The transfer material 10 that has been transferred is transferred to the negatively charged transfer drum 3t.
y>#Wound and held by electric power to move.

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 before being reused.

The transfer paper 10 held on the IV photo drum 3- advances as it rotates with the drum, and its position is read by the sensor Z6, and the second exposure operation is started in synchronization with this position. .

The second exposure uses a green filter FG, and the development is performed using a developing device 21M loaded with a negative electric magenta developer.
It is carried out by The obtained magenta toner image is held on the transfer drum and transferred to the transfer paper IO entering point A.
It is duplicated and transferred to the yellow image above.

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

Furthermore, through the same process, a cyan toner image obtained by exposure through a red filter FR and development by a developing device 21C loaded with cyan developer is transferred in a double FM manner. After the transfer of the cyan toner image is completed t2, the transfer paper 10 is charged with an alternating current corona discharge from the transfer machine charge-eliminating corona discharger 27, and is separated from the drum surface by lowering the separating claw 11 toward the transfer drum L side. The three color toners transferred onto the transfer paper 10 are sent to a silent roller fixing device (not shown) and fixed thereon, and as they are fixed, they are melted and mixed to reproduce a color image using a subtractive color method.

The transfer drum L from which the transfer paper has been separated is transferred to a transfer drum static eliminator 2.
The transfer drum cleaner 29 removes the toner adhering to the surface of the transfer drum 29 to prepare for the copy 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〕

In the image transfer apparatus 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 constantly pressed against each other. This provides many advantages, such as eliminating the need for 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 main recording device with reliable image transfer, no color shift, and simple structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the operation of the image transfer device according to the present invention, and FIG. tjS2 is a schematic diagram of a color copying machine using the image transfer device according to the present invention. L... Image bearing drum L... Transfer drum 3...
Conductive base 4... Conductive elastic layer 5... Insulating layer

Claims (2)

[Claims] (1) An image transfer device that transfers a charged toner image formed on an image carrier onto a transfer material, including a transfer drum having an insulating surface, and the transfer drum provided opposite to the transfer drum. a transfer material charge applying means for applying a charge of opposite polarity to the charge of the toner to the surface of the material; and a transfer drum charge for applying a charge of the same polarity as 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.