JPH02106775A - Toner transfer device - Google Patents

Abstract

PURPOSE:To stably and satisfactorily transfer at any time regardless of the degree that a sheet absorbs moisture by arranging a conductive electrode with polarity opposite to that for corona transfer a conductive electrode upstream side of a corona electrifier. CONSTITUTION:The conductive electrode 7 to which a voltage of polarity opposite to that for corona transfer is impressed is arranged upstream side of the corona charger. In this way, the resistance of a transfer sheet 6 falls under a high moisture so that an excess charge in a transfer position is attracted to the conductive electrode 7 through the transfer sheet 6; moreover, such thing that the charge passes through the sheet 6 and any leaks of the charge to a photosensitive body side 8 can be prevented. On the other hand, the resistance of the transfer sheet 6 becomes high when the sheet is dry, and therefore a charge does not flow inside the transfer sheet 6, and the voltage applied by the conductive electrode 7 does not influence transfer performance. Therefore, the stable and satisfactory transfer can be always attained regardless of the degree that a sheet absorbs moisture.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a toner image transfer device that can be used in a hard copy device such as a copying machine or a printer.

2. Description of the Related Art Currently, in electrophotographic devices widely used in copying machines and laser printers, after an electrostatic latent image is written on an electrostatic latent image carrier such as an electrophotographic photoreceptor, charged toner is A well-known method is to electrostatically adhere and develop the toner, and then perform corona transfer onto plain paper using a corona charger to which a voltage of opposite polarity to that of the toner is applied, thereby obtaining a toner image on the plain paper.

Problems to be Solved by the Invention In such a corona transfer method, it is known that a toner image transfer failure occurs when plain paper absorbs moisture in the air in a high humidity environment.

The reasons for this are as follows. In other words, since plain paper is mainly made of cellulose, it is an insulator under normal circumstances, but when the environmental humidity exceeds 70%, its moisture absorption exceeds 12%, and its resistance value is in the semiconductor region. It was found that the value decreased to less than cm. If you try to perform corona transfer from the back of the paper in this condition,
As shown in FIG. 2, a transfer corona charge 2 generated by a corona charger 1, which is a transfer device, passes through a transfer paper 3 to a photoreceptor 4.
It was found that the toner leaked to the upper toner 5, and the charging polarity of the toner was reversed from the initial charging polarity, and the toner was not electrostatically attracted to the paper, resulting in transfer failure. In such cases, it has been found that if the voltage applied to the transfer corona is set low enough to prevent the corona charge from leaking through the paper, good transfer can be achieved even with moisture-absorbing paper, but under such low corona voltage setting conditions, On the other hand, it was found that during drying, transfer defects occur due to insufficient transfer voltage.

In view of the above, the present invention is a toner transfer device that performs corona transfer of a toner image recorded on an electrostatic image carrier, and is capable of always performing stable and good transfer regardless of the degree of moisture absorption of paper. The purpose is to provide

Means for Solving the Problems The present invention provides a transfer device that corona-transfers the toner image onto a transfer paper by providing a corona charger at a position opposite to an electrostatic image holder carrying a toner image, the transfer device comprising: A conductive electrode to which a voltage with a polarity opposite to the corona transfer polarity is applied is placed on the world side of the corona charger at a position where the paper enters the opposing position and is brought into contact with the transfer paper. This is a toner transfer device.

Effect As mentioned above, when corona transfer is performed from the back side of plain paper during high humidity, the paper absorbs moisture in the air and its resistance decreases, causing the amount of transfer charge in the paper to exceed the appropriate amount, causing the paper to Through the toner, the toner leaks onto the photoconductor and the polarity of the toner is reversed. At this time, if a conductive electrode is placed in contact with a part of the paper and a voltage with a polarity opposite to that of corona transfer is applied to this conductive electrode, changes in the resistance value of the paper itself due to the environment can be reversed. It can be used to improve transfer at high humidity.

That is, as shown in FIGS. 3(a) and 3(b), when the conductive electrode 7 is brought into contact with the surface of the paper 6 and a voltage with a polarity opposite to that of the transfer corona is applied to the conductive electrode 7, When the humidity is high, the resistance of the transfer paper 6 decreases, so excess charge at the transfer position is drawn into the conductive electrode 7 through the transfer paper 6, and this charge is prevented from passing through the paper 6 and leaking to the photoreceptor 8 side. be able to.

On the other hand, when the transfer paper 6 is dry, the resistance of the paper increases because it does not absorb moisture, so even if a voltage is applied to the conductive electrode 7, no charge flows inside the transfer paper 6, and this conductive electrode The voltage applied by this method does not affect the transfer performance. In other words, if the transfer corona conditions are set according to the state of the paper when drying, the resistance of the paper will decrease when humidity is high and the effect of the conductive electrode will automatically appear, making the transfer conditions optimal for conditions at high temperatures. can be converted into Therefore, it is possible to obtain a transfer device in which transfer conditions are automatically optimized in dry and high humidity conditions without requiring any special humidity sensor or switch.

Furthermore, as shown in FIG. 4, when this conductive electrode 9 is applied to a method of corona transfer to a transfer paper 10 via a dielectric belt 11, 1) the above-mentioned transfer performance at high humidity is improved. 2) The transfer paper 10 is
is electrostatically attracted to the dielectric belt 11 before contacting the
A new effect occurs in that the transfer paper 10 is not attracted to the photoreceptor 12 and the separation performance from the photoreceptor 12 is improved.

In order to further improve the separation performance of the paper from the photoreceptor, which is the second effect, as shown in FIG.
A new adsorption corona charger 14 is installed inside the conductive electrode 15, and the voltage 1 applied to the conductive electrode 15 is applied to the corona charger 14.
It has been found that applying a voltage 17 of opposite polarity to that of 6 is effective. This is due to the electrostatic attraction between the paper 18 and the belt 13 because the transfer paper 18 and the dielectric belt 13 are in contact with each other while being sandwiched between the conductive electrode 15 and the corona charger 14 to which voltages of opposite polarity are applied. becomes extremely strong, and the photoreceptor 19
This is because the separation performance from

Furthermore, in the configuration shown in FIG. 5, the adhesion between the transfer paper 18 and the transfer belt 13 is improved, and an uneven air layer is removed between them, resulting in a new third effect. . This third effect is a significant improvement in toner transferability in color electrophotographic devices that create color images by superimposing toner images of multiple colors on a photoreceptor and transfer them all at once to paper. be. In such a device, the toner adhering to the photoreceptor continues to be charged with corona multiple times, so the toner on the photoreceptor changes to a different amount of charge depending on the order in which it is developed, and the optimum transfer is determined for each toner. The conditions were different. In extreme cases, under conditions where the toner developed first is transferred to the paper, the toner developed last will not be transferred, and conversely, under conditions where the toner developed last is transferred, the toner developed first will not be transferred. A phenomenon occurred where toner was not transferred.

In such a color electrophotographic apparatus, a corona charger 14 is installed inside the dielectric belt 13 as shown in FIG.
By sandwiching and transferring the toner and the dielectric belt 13, all toners can be transferred well under any environment.

Examples The electrostatic image carrier used in the present invention includes electrostatic recording paper,
There are electrophotographic photoreceptors in which a film of a photoconductive substance such as amorphous selenium, zinc oxide, or polyvinylcarbazole is formed on a conductive material such as aluminum.

The conductive electrode used in the present invention may be provided at any position on the downstream side or downstream of the transfer position where the toner developed on the electrostatic image carrier is corona-transferred to the transfer paper; On the downstream side, an unfixed toner image is already transferred to the "-" portion of the transfer paper, so if this position is rubbed with a conductive member, the toner image will be disturbed. Therefore, it is preferable to provide it on the opposite side of the corona transfer position.

In addition, in order to prevent excess corona charge from transferring to the photoreceptor during high humidity and to remove corona charge from the transfer paper, a power supply is applied to the conductive member that has come into contact with the transfer paper, applying a voltage with the opposite polarity to the polarity of the corona transfer. It is necessary to connect. At this time, if normal development is performed, for example, the photoreceptor becomes positive and the toner becomes negative, the corona transfer voltage becomes positive, and the voltage applied to the conductive electrode becomes negative. In the case of reversal development, for example, the photoreceptor becomes positive, the toner becomes positive, the corona transfer voltage becomes negative, and the voltage applied to the conductive electrode becomes positive.

In order to uniformly absorb charge from the paper, it is particularly effective to use a conductive brush as the conductive electrode. Suitable materials for the conductive brush include stainless steel fiber, carbon black-dispersed rayon fiber, and carbon fiber.

It is also effective to use a conductive roller 20 as the conductive electrode as shown in FIG. At this time, since the roller 20 rotates, no resistance occurs when the transfer paper 21 passes between the dielectric belt 22 and the roller 20, resulting in excellent paper conveyance. The roller 20 may be made of a material made of the conductive fur brush shaped into a roller, or a conductive rubber roller.

The range of voltage applied to the conductive electrode is 100 to 2 kV1
Preferably, the range is 200 to 1 kV.

At a voltage of 100 V or less, excessive transfer corona is sucked in at high temperatures, making it ineffective, and at 2 kV or higher, too much transfer corona is sucked in, resulting in poor transfer.

When the transfer device is a device that sandwiches transfer paper between a dielectric belt and a photoreceptor and performs corona transfer from the back side of the dielectric belt, the resistance value of not only the transfer paper but also the dielectric belt is affected by high humidity. The present invention becomes particularly effective in such cases, since the transfer efficiency is further reduced. The dielectric belt used for transfer at this time is, for example, an insulating belt made of fluorinated ethylene resin, polyester resin, glass fiber, or the like. Furthermore, a belt is used in which a layer of a high-resistance material such as polytetrafluoroethylene or polyethylene terephthalate is coated on the surface of conductive rubber in which carbon blank or the like is dispersed. If the conductive layer of this belt is made completely conductive, it will block the transfer electric field and transfer will not be possible, so it is desirable that its resistance value be in the range of 10@4 to IQI of 9 .OMEGA.cm. Further, the thickness of the transfer belt is preferably in the range of 200 μm to 2 mm.

By installing a corona charger that applies a voltage of opposite polarity to the voltage applied to the conductive electrode at a position opposite the conductive electrode inside the belt via the dielectric belt, the charge from the transfer paper to the conductive electrode can be absorbed. Not only can this be done more aggressively, but also because a large electric field is applied between the transfer paper and the dielectric belt, the degree of adhesion between the transfer paper and the dielectric belt increases, and the photoreceptor and the transfer paper come into contact with each other during transfer, causing the transfer. The paper is prevented from being electrostatically attracted to the photoreceptor, and the effect is that the separation between the photoreceptor and the transfer paper is improved.

Furthermore, for example, an image recording method is disclosed in Japanese Patent Application No. 60-212927, which uses toners of multiple colors to perform charging number exposure and
In an image recording method that repeats the development process to form a color image on a photoreceptor and then transfers the color image to paper, corona charging is repeated from the toner after the toner is developed on the photoreceptor. As a result, toners with various amounts of charge are mixed on the photoreceptor. Although it is difficult to uniformly transfer such a color image under the same conditions using conventional corona transfer methods, it is extremely easy to transfer such a color image using the transfer device of the present invention, which consists of a voltage-applied conductive electrode and a dielectric belt. become.

Note that although dry toner is used as the toner to be transferred, the same effect can be obtained even if wet toner is used.

Hereinafter, specific embodiments of the present invention will be described in more detail.

Example 1 A color image was formed using the apparatus shown in FIG.

The transfer belt 23 is composed of a conductive rubber belt in which carbon black is dispersed and whose surface is coated with Teflon, and its resistance value is 108 Ωcm and its thickness is 1 mm.
It is. The developing device 24.25.26 is a non-contact type non-magnetic one-component developing device that uses a DC electric field to scatter the toner, and the conductive fur brush 27.28.2 is in contact with the developing roller.
The toner is frictionally charged at 9, and a thin layer of toner is formed on the aluminum developing roller 3013L32j- by blades 33, 34, and 35. Developer 2
4 is yellow (Y), developing device 25 is magenta (M),
The developing device 26 contains cyan (C) insulating toner. The black developing device 36 is a contact type developing device containing a two-component developer consisting of an insulating toner and a magnetic carrier, which is widely used in electrophotographic devices. and developing roller 30.3
The developing devices were placed opposite to each other around the photoreceptor 38 with the gap (developing gap) between L 32.37 and the photoreceptor 38 being kept constant. Each developing device is attached with a separation mechanism that brings it close to the photoreceptor 38 during development and separates it when not developing.

The specifications and development conditions of the black developing device 36 and the physical properties of the toner are shown below.

Developing unit specifications and developing conditions Diameter of developing roller 37: 22 mm Peripheral speed of developing roller 37: 320 mm/S Second developer layer thickness of developing roller 37: 400 μm Rotation direction of developing roller 37: Opposite direction to photoreceptor 38 (Same traveling direction) Development gap (gap between the surface of the developing roller and the surface of the photoreceptor): 300 μm during development 2 m when not developed Developer physical properties Type of developer: Two-component developer consisting of toner and carrier Average particle size of carrier: Approximately 50 μm Carrier type: Teflon foot ferrite Toner charge amount: 115 μC/g Toner average particle size: 12 μm Toner dielectric constant: Approx. 2 The specifications and development conditions of yellow, magenta, and cyan developers, and the physical properties of the toner are as follows. show.

Developing device specifications and developing conditions Diameter of developing roller: 20 mm Peripheral speed of developing roller: IBO mrn/s Rotating direction of developing roller: Opposite direction to photoreceptor 38 (same traveling direction) Thickness of toner layer on developing roller: 30 μm Development gap(
Gap between the developing roller surface and the photoconductor surface: 150 μm during development, 2 m when not developing Toner physical properties Toner charge amount: +3 μC/g Average particle size: 12 μm Relative dielectric constant: Approx. 2 Long in the infrared region as a photoconductor Wavelength sensitized diameter 152.8
mm amorphous 5e-Te photoreceptor drum 38 (photosensitive layer thickness 63 μm 1 dielectric constant 7, functionally separated selenium photoreceptor sensitized to long wavelengths in the infrared region, half-exposure fi 0.6 tt J/ Cm2) was used and rotated at a circumferential speed of 160 mm/s. This photoreceptor 38
Charger 39 (Scorotron charger, corona voltage: +7
kV, grid voltage: 1kV), charging potential +9
It was charged to 00V. Next, the semiconductor laser 40 with a wavelength of 790 nm was emitted to perform exposure.

At this time, the light intensity on the photoreceptor surface was set to 1.5 mW. Using this semiconductor laser 40, a negative black signal was exposed onto the photoreceptor 38 to form an electrostatic latent image. After the latent image is reversely developed by the black developer 36 in the developing state in which +eoov is applied to the developing roller 37 to form a black toner image, the -degree photoreceptor 38 is charged to the AC corona charger 41 (applied AC voltage: 4
．． 5kVrms, DC bias component; +200V
) to eliminate static electricity.

The thickness of the black toner layer developed on the photoreceptor 38 is from 1 layer to 2 layers.
The toner layer had a thickness of 10 to 20 μm.

Next, the photoreceptor 38 was charged to +800V again using the corona charger 39 (Scorotron charger, corona voltage: +7 kV, grid voltage: +f300V).

At this time, the charged G potential of the photoreceptor 38 to which the black toner was attached became +600. Thereafter, the photoreceptor 38 was exposed to signal light corresponding to yellow by the semiconductor laser 40 to form a yellow electrostatic latent image. Here, the exposure amount of the semiconductor laser was set to 1.5 mW on the photoreceptor surface. Next, this photoconductor is applied to the developing roller 30 in the developing device 24 for yellow in a developing state, magenta in a non-developing state,
The toner was passed through a developer 25, a cyan developer 26, and a black developer 36 to form a yellow toner image. Next, this photoreceptor 38 is charged to an AC corona charger 41 (applied AC voltage: 4,
5kVrms, DC bias component; +200V)
to remove the static electricity, and then turn on the corona charger 39 (Scorotron charger, corona voltage: +7kV1, grid voltage: +940
The photoreceptor 38 was charged to +810V by V). At this time, the charged potential of the photoreceptor 38 to which the black and yellow toners were attached became +840V. After that, the semiconductor laser 4
0, a signal light corresponding to magenta was exposed to form a magenta electrostatic latent image. Next, the photoreceptor 38 was passed through a yellow developing device 24 in a non-developing state and a magenta developing device 25 in a developing state in which +800V was applied to the developing roller 31 to form a magenta toner image. At this time, the toner layer in the overlapping portion of yellow and magenta on the photoconductor 38' was 2 to 4 layers, and the thickness was 20 to 40 μm. Thereafter, the photoreceptor 38 was passed through the cyan developer 26 and the black developer 36 in a non-developing state.

Next, the photoreceptor 38 is charged with an AC corona charger 41 (applied AC voltage; 4.5 kVrms1 DC bias component;
+200V), and the photoreceptor 38 was charged again to +850V by the corona charger 39. At this time, the photoconductor 38 to which only black, yellow, and magenta toner has adhered
The charging potential of was +870■. Also, the charged potential of the photoreceptor 38 in the area where the yellow and magenta toners overlap is +
It became 780V. Thereafter, the semiconductor laser 40 was used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. Next, the photoreceptor 38 is transferred to the yellow developing device 2 in a non-developing state.
4 and magenta developing device 25, +8 to developing roller 32
The toner toner was passed through a cyan developing mold 36 in a developing state to which 30 V was applied to form a cyan toner image, thereby completing a color image on the photoreceptor 38.

The dielectric belt 23 is moved while the plain paper 42 is brought into contact with a stainless steel fur brush 43 to which a voltage of +1 kV is applied.
Paper adsorption charger 44 (applied voltage: -6 kV)
and was brought into close contact with the dielectric belt 23. The color toner image obtained on the photoreceptor 38 was transferred onto this paper 42 by a transfer charger 45 (applied voltage: -8 kV), and then the paper was charged by a paper separation charger 46 (applied voltage: -6 kV). After that, the paper is separated from the dielectric belt 23, passed between a pair of chargers consisting of a positive charger 47 (applied voltage: +13 kV) and a negative charger 48 (applied voltage: -+3 kV), and then charged by a fixing device. Heat fixing was carried out using No. 49.

On the other hand, after the transfer, the surface of the photoreceptor 38 was exposed to corona using an AC corona charger 41 (applied AC voltage: 4.5 kVrms, DC bias component: +800V) to remove static electricity from the photoreceptor. Thereafter, a conductive fur plan cleaner 50 (fur made of rayon fibers with carbon black dispersed therein and wrapped around a stainless steel rod) to which a voltage of -350 V was applied was brought into pressure contact with the photoreceptor 38 for cleaning.

As a result, moisture-absorbing paper (
Even when the toner (with a moisture absorption of 14%) was used, all of the black, yellow, magenta, and cyan toners were completely transferred to the paper, and a clear image was obtained. Furthermore, even in a dry state at 10° C. and 15% relative humidity, no transfer defects occurred. Furthermore, under high temperature environment 1
A paper conveyance test of oooo sheets was conducted, but there was no separation failure where the paper was wrapped around the photoreceptor.

Example 2 An experiment was conducted using the electrophotographic apparatus shown in FIG.

The photoreceptor 51 was an organic photoreceptor in which an azo pigment was dispersed in a polyester resin, rotated in the direction of the arrow at a speed of 100 mm/s, and charged to -800 V with a corona charger 52. Next, the reflected light of the original is exposed at the exposure position, and further +1
Developing was carried out using a two-component magnetic brush developer 53 containing l·ner charged to 0 μC/g.

Next, the transfer paper 54 is conveyed to a transfer position below the photoreceptor drum 51 while being in contact with a conductive fur brush 55 to which a voltage of +500V is applied, and a transfer corona provided at this transfer position is applied to a negative voltage. By 56,
The toner image developed on the photoreceptor 51 was transferred to a transfer paper 54.

As a result, even when using moisture-absorbing paper (moisture absorption: 14%) in an environment of 35° C. and 85% relative humidity, the toner was completely transferred to the paper and a clear image was obtained. Also, 10°C relative humidity 1
No transfer defects occurred even when drying at 0%.

Example 3 Next, an experiment was conducted using the apparatus shown in FIG.

An amorphous selenium photoreceptor is used as the photoreceptor 57, rotated at a speed of 150 mm/s in the direction of the arrow, and charged at +800 mm by the charger 58.
Charged to V. Next, at the exposure position, the original is exposed to the reflected light, and further contains 2
Developed using a component magnetic brush developer 59.

In the apparatus shown in FIG. 8, an insulating belt 60 made of polyester resin is placed in the transfer section so as to be in contact with the photosensitive drum 57. The transfer paper 61 is conveyed by the belt 60 to the transfer position of the photosensitive drum 57. The transfer paper 61 is brought into contact with a conductive fur brush 62 to which a voltage of 700 V is applied, and is attracted to the transfer belt 60''. , the toner image developed on the photoreceptor 57 is transferred to a transfer paper 61.
transcribed into.

As a result, even when using moisture-absorbing paper (moisture absorption: 14%) in an environment of 35° C. and 85% relative humidity, the toner was completely transferred to the paper and a clear image was obtained. Also, 10゛C relative humidity 1
No transfer defects occurred even when drying at 0%.

Effects of the Invention According to the present invention, in a device that performs corona transfer of a toner image recorded on an electrostatic image carrier, a toner transfer device that can always perform stable and good transfer regardless of the degree of moisture absorption of paper is provided. You can get the equipment.

[Brief explanation of the drawing]

FIG. 1 is a side view of a color electrophotographic apparatus using a toner transfer device according to an embodiment of the present invention, FIG. 2 is a diagram illustrating the main parts of a conventional transfer device, and FIG. FIG. 4, FIG. 5, and FIG. 6 are configuration diagrams of toner transfer devices according to different embodiments of the present invention. FIGS. 7 and 8 are diagrams showing toner transfer devices according to embodiments of the present invention. FIG. 7 is a side view of an electrophotographic apparatus according to another embodiment. 23...Dielectric belt, 24...Yellow developer, 2
5...Magenta developer, 26...Cyan developer, 3
6... Black developer, 38... Photoreceptor, 39... Corona charger, 40... Semiconductor laser, 43... Conductive far plan, 44... Adsorption corona charger, 45...・
・Transfer charger, 52...heat fixing device.

Claims (4)

[Claims] (1) A corona charger is provided at a position opposite to the electrostatic image holder carrying a toner image, and the toner image is corona-transferred to a transfer paper, and the transfer paper is located on a path that enters the opposing position. , and a toner transfer device in which a conductive electrode to which a voltage of polarity opposite to the corona transfer polarity is applied is placed in a position in contact with the transfer paper upstream of the corona charger with respect to the traveling direction of the transfer paper. . (2) The toner transfer device according to claim 1, further comprising a dielectric belt provided between the electrostatic image holder and the corona charger and in contact with the electrostatic image holder. (3) The toner transfer device according to claim 2, wherein the dielectric belt is a conductive rubber belt with a high resistance material layer provided on the surface thereof. (4) A second corona charger was provided at a position facing the conductive electrode via a dielectric belt, and a voltage of opposite polarity to the voltage applied to the conductive electrode was applied to the second corona charger. The toner transfer device according to claim 2.