JPH01172988A - Transfer/carrier equipment - Google Patents

Abstract

PURPOSE:To powerfully separate and carry a transfer material to obtain a transfer image of high quality without a complicated high voltage power source by effectively using electrification characteristics of a carrying belt and the transfer material. CONSTITUTION:A current flows to a transfer material 8 and a conductive contact member 14 through a carrying belt 9 from a transfer corona charger 12 as a transfer material close contacting means provided above a transfer position and the electric charge is preliminarily sufficiently given to the transfer material 8 and the belt 9 to closely bring them into contact with each other, and thereafter, the transfer material 8 is carried to the transfer position. Consequently, the electrostatic attraction strength between the carrying belt 9 and the transfer material 8 is always kept higher than that between a toner image holding body and the transfer material 8. Thus, the transfer material 8 is separated from the toner image holding body with a high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a transfer method in which a toner image on a toner image carrier is transferred to a transfer material by physical or chemical means by electrostatically supporting and transporting a transfer material. - Concerning the conveyance device.

Conventional technology In electrophotographic copying devices and electrophotographic printers, insulating materials such as dielectric materials or conductive materials are used to ensure transferability of the transfer material and separation of the transfer material from the toner image carrier. There is known a method of conveying a transfer material such as paper by electrostatically adhering it to the belt.

US Pat. No. 3,357,325 uses a corona charger to attract and transfer a transfer material, and proposes a method using a dielectric single-layer belt. Figure 2 shows a schematic diagram of a proposed example. 23 is a drum-shaped toner image carrier, 24 is a dielectric single-layer belt, and 25 and 26 are rolls for supporting, stretching, and rotating the dielectric belt 24. 27 is transfer material 2
This is a roll to lead to an 8.

29 transfers the transfer material 28 to the dielectric belt 24 by electrostatic force.
a corona charger 30 for adsorption to the image support 23;
This is a corona charger for transferring a toner image from to a transfer material 28.

Japanese Patent Laid-Open No. 54-58034 discloses a proposal in which the corona charger for adsorbing a transfer material in the above-mentioned example is deleted. The content of the proposal is divided into two depending on the resistance value of the belt constituent material.
iX:,”, it! range is 101Ω・1 or more, belt thickness is 150μ or less, and saturation charging potential is 2500
This is a case of V or less. FIG. 3 shows a schematic diagram of a proposed example. A drum 32 charged by a corona charger 31 is exposed to light by an optical system 33 to form a latent image, and a toner image is formed by a developer 34. The toner image is transferred onto a transfer material 37 conveyed by a belt 36 of a separation belt device 35 by a transfer corona charger 39 connected to a DC power source 38 .

After conveying the transfer material 37, the belt 36 is neutralized by an alternating current or a corona charger 40 having a polarity opposite to that of the belt.

In order to assist the separation of the transfer material from the drum, as shown in FIG. As shown in FIG. 5, a method is shown in which a separate corona charger 43 connected to a separate power source 42, which is an AC power source or a DC power source with a polarity opposite to that of the charging polarity, is arranged downstream of the transfer corona charger 39 as the belt travels.

Problems to be Solved by the Invention However, in the proposal of U.S. Pat. There are limits. The capacitance C of the belt is given by the dielectric constant ε and the belt thickness d, then the capacitance C per unit area is C= a / d
Since it is given by
If you want to obtain a certain capacity, you should use ordinary organic belt material (ε=
2 to 4), the thickness is 20 to 40μ.

This thickness does not have enough strength for practical use as a conveyor belt.
Therefore, if the belt is several hundred micrometers thick, it will not be possible to obtain sufficient capacity, and the amount of charge held by the belt will be small. There are weaknesses in his abilities. This point is also stated in the above-mentioned Japanese Patent Application Laid-Open No. 54-58034, and when used continuously, the belt surface potential increases,
This also has the disadvantages shown in Japanese Patent Application Laid-Open No. 54-58034, and is not practical for transfer purposes.

Furthermore, when the belt surface potential increases, the adsorption force of the transfer material also decreases in proportion to it.Furthermore, from the perspective of transfer ability, the polarity of the corona charger for adsorbing the transfer material to the belt surface is Since the charging polarity is the same as that of the toner, when the resistance value decreases due to moisture absorption etc. of the transfer material (
When the transfer material is plain paper, the volume resistivity changes in the range of approximately 10@~1QL4Ω・value due to the influence of environmental humidity)
Transferability is greatly inhibited because a charging current flows through the transfer material. In addition, when an organic material is irradiated with corona discharge for a long time, a modified layer is generated in the molecular structure of the surface layer, and when it absorbs moisture, the surface resistance drops significantly and the charge retention property is lost, so there are also weaknesses in this respect. This is a method that allows On the other hand, the proposal in Japanese Patent Application Laid-open No. 54-58034 is that the resistance value range is above 10I3Ω, the belt thickness is 150μ or less,
Regarding the case where the saturated charging potential is 2.500V or less, the increase in belt surface potential during continuous use can be prevented by installing a corona charger, but 1. In the example shown in Fig. 3, the transfer current flowing from the corona charger 37 to the drum 30 flows from the belt 34 to the transfer material 35 to the drum 30. The ax exhibits the same force as that of the ax, and there is no element of force that could easily cause the transfer material to separate from the drum. If separation occurs, the stiffness of the transfer material that resists the drum's milt is Φ, and if the stiffness of the transfer material is small or the drum diameter is large, the probability of separation is high. Become. Furthermore, even if the transfer material is thick and has high rigidity, monochrome copying devices, which have recently begun to be widely used, are paper-based and when color composite copying is performed multiple times on the same copying surface, this Due to the influence of the heated roll type fixing device used in seed copying machines, the moisture on the copying surface of the transfer material on the heated roll side, on which the toner image is placed, is less than the moisture on the back surface of the transfer material on the backup roll side, resulting in a decrease in surface resistance. As a result, the adhesion between the drum and the transfer material becomes greater than the adhesion between the belt and the transfer material, which often results in poor separation during multiple copies. For this reason, the proposals shown in Figures 4 and 5 have been made to assist in separability, but these proposals all aim to reduce the transferability of toner images, especially when the transfer material is If the paper absorbs moisture and its resistance value decreases, this will lead to poor transfer. Furthermore, when an AC power source is used, it is economically disadvantageous due to the high cost of the power source. In addition, even when the resistance value range is 108 to 1013Ω・value, there is no particularly excellent factor regarding the separability of the transfer material as described above. Same as in case.

In view of the above-mentioned problems, the present invention effectively utilizes the charging characteristics between the conveyor belt and the transfer material without using any special means for the charging device to realize strong separation and conveyance of the transfer material. In order to solve the above-mentioned problems, the present invention provides a transfer/conveying device that obtains high-quality transferred images without using a high-voltage power source.The present invention aims to solve the above problems by supporting and stretching an endless transfer material conveying belt made of a conductor. The toner image is transferred to the transfer material by means of rotating means for rotating in the direction of the transfer material, and a transfer corona charger on the back side of the transfer material conveyance belt while holding the transfer material between the toner image holder and the transfer material conveyance belt on the front side of the transfer material conveyance belt. a grounding means for grounding a part of the transfer material conveyance belt; and a grounding means for grounding a part of the transfer material conveyance belt, and conductive contact with the transfer material at a position upstream of the transfer site where the transfer means is located and close to the toner holding body. and has a grounded conductive contact member, and injects electric charge into the transfer material and the transfer material conveyance belt inserted between the conductive contact member and the transfer material conveyance belt by passing a current from the corona charger to the conductive contact member. and a transfer material adhesion means for bringing the transfer material into close contact with the transfer material conveying belt by electrostatic force.

By adopting the above-mentioned structure, the present invention first supplies a current from the transfer corona charger, which serves as a means for adhering the transfer material provided on the upstream side of the transfer site, to the transfer material-conductive contact member through the conveyor belt. Since the transfer material and the belt are charged and brought into close contact with each other, and then the transfer material is transported to the transfer site, the electrostatic force between the transport belt and the transfer material is reduced by the electrostatic adhesion between the toner image carrier and the transfer material. It becomes possible to maintain a high adhesion force at all times, and the separability of the transfer material from the toner image carrier becomes extremely reliable.

Embodiments Hereinafter, a transfer/conveyance apparatus of the present invention will be described with reference to drawings showing embodiments. FIG. 1 shows a cross section of an electrophotographic printer equipped with a transfer/conveyance device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a drum-shaped toner image carrier (hereinafter simply referred to as a drum) having a rotatable curvature. It has a body layer. Usually this conductor support is grounded. First, the drum 1 is uniformly charged by the main corona charger 2, and the exposure optical system 3 in the next stage emits light that matches the original using means (not shown), such as a semiconductor laser, an LED array, a liquid crystal shutter array, a lens optical system, etc. and is imaged onto the drum l. At this time, the charge on the portion of the drum surface exposed to light, which is charged in a negative manner, disappears by being neutralized with the opposite polarity charge induced in the conductive support on the back of the photosensitive layer, and the original A pattern of charges, that is, a latent image, corresponding to the brightness and darkness of the image is formed. This latent image is visualized in the subsequent developing section 4 by adhering fine A-edge charged particles (hereinafter referred to as toner) by electrostatic force. The toner image thus obtained on the drum 1 is electrostatically transferred by a transfer means 5 to a transfer material 8 that is conveyed in synchronization with the toner image, and the remaining toner on the drum 1 is transferred to a cleaning section 5. After being wiped away by means such as a blade, the drum 1 is irradiated with --like static eliminating light in the static eliminating section 7 to eliminate static electricity from the drum 1, and is ready for the next process.

Next, a transfer/transport device for a transfer material such as paper according to the present invention, which is applied to the above-described generally known electrophotographic printing process, will be described in detail. In FIG. 1, the conveyor belt 9 is an endless belt with a circumference of 380 mm and a layer thickness of 0.6 fi made of carbon-dispersed polyurethane resin made of a conductor with a volume resistivity of 4' x 10'' Ω. As mentioned above, the charge discharge time constant of the conveyor belt 9 is given by the capacitance component C-a/d and the resistance component R as R=ρd, where ρ is the resistivity, so the time constant CR = εp, and the time constant of the conveyor belt used here is approximately 0.1 seconds as ε-3. Therefore, in 0.1 seconds, more than 70% of the charged charge is discharged, so the same part of the belt is If it does not pass through the transfer means 5 within this time, there is no need for a corona charger for static elimination, which is seen in conventional examples.The resistivity of the conveyor belt is set within a range where this time constant does not practically require a static neutralization charger. It is determined by the range in which the discharge time constant described below is too short and the effects of the present invention are not impaired.
The belt structure may be the single-layer belt described above, or a polyester resin or fluorine resin with a low coefficient of friction may be used to make it easier to clean if unnecessary toner adheres to the belt surface layer due to some trouble. However, the discharge time constant of the belt needs to be selected in consideration of the above points.

The transfer material conveying belt 9 is supported by rolls 10.11 and stretched by means (not shown) using tension such as a spring. The surfaces of these rolls are made of a conductor and are grounded through the back side of the belt 9. An appropriate bias may be applied to this depending on the situation. The belt 9 is rotated by driving the roll IO or 11 by a rotational drive means (not shown) so that the direction of rotation and traveling at the transfer site where the transfer means 5 is located is the same as that of the drum 1, and the circumferential speed is the same. Here, the drum circumferential speed is 160 mm/
Seconds. Therefore, the belt completes one rotation in approximately 2.4 seconds.

A transfer corona charger 12 is installed inside the transfer area of the transfer material conveyance belt 9, and a DC high voltage power source 1 with a polarity opposite to that of the toner is installed.
3, a high voltage is applied to transfer the toner onto the transfer material 8. For example, if the toner is positively charged, the transfer corona charger 12 is a negative electrode, and the belt 9 is a negative electrode.
A transfer current flows to positively charge the negative charge on the back side of the drum 1, and the toner on the surface of the drum 1 is transferred to the belt 9 side based on the movement of this positive charge. As mentioned earlier, in the case of a dielectric belt, if enough charge moves to charge the capacitance component of the belt, transfer becomes impossible because no transfer current flows, but in the conductive belt used in the present invention, transfer becomes impossible. Since a discharge is generated according to a time constant and a transfer current flows through a resistance component when passing through the transfer means, transfer can be assisted.

Recently, in printers using electrophotographic processes, a corona charger for transfer is used with a polarity opposite to that of the drum 1 in order to perform reversal development. Therefore, if the drum is negatively charged, excessive drum current will flow and may cause drum deterioration.
When the transfer material conveyance belt used in the present invention is sandwiched between the belts and charged, it is possible to reduce the drum current due to the buffering effect of the belt's resistance component, and in order to make this effect work, the belt must be thick. is more preferable, 0.4
− or more is desirable. On the other hand, if it is too thick, the surface stress increases during mechanical conveyance, which tends to cause surface deterioration and minute disturbances in the conveyance speed. Therefore, the thickness should be kept to about 1.5 times. More preferably i is 0.6+n-1, □n
It is.

According to the present invention, the following configuration essentially needs to be added. In other words, the member 14 is arranged upstream of the transfer means 5 of the transfer material conveying belt 9 and very close to the transfer means, and is in electrical contact with the transfer material 8. By disposing the conductive contact member 14 at the position described above, the conveyor belt is ejected from the transfer corona charger and a current is applied to the transfer material-conductive contact member, and as a result, the transfer from the conductive contact member 14 is carried out. It serves as a transfer material adhesion means that injects charge into the material 8 and the transfer material conveyance belt 9 and brings the transfer material 8 and the transfer material conveyance belt 9 into close contact with each other by electrostatic force. The transfer material is brought into close contact with the transfer material conveying belt by this transfer material adhesion means and then conveyed to the transfer site, but this adhesion force gradually decreases due to the influence of the discharge time constant of the belt. . On the other hand,
When the transfer material 8 is conveyed to the transfer site by the running of the belt 9, the drum 1 is moved by the action of the transfer corona charger 12.
The charge is again injected into the transfer material 8-belt 9, and the transfer material 8
The adhesion force of the belt 9 increases. However, at the same time, adhesion force also occurs between the drum 1 and the transfer material 8, and if the latter adhesion force becomes large, defective separation of the transfer material will inevitably occur. The adhesion force between the transfer material 8 and the conveyor belt 9 due to charge injection from the drum 1 is approximately equal to the adhesion force between the transfer material 8 and the drum 1. Therefore, in order to reliably separate the transfer material from the drum 1, it is necessary to The adhesion force applied by the transfer material adhesion means until the material is conveyed to the transfer site must be sufficiently large. For this purpose, the transfer material 8-
The condition is that the charge injected into the belt 9 is not discharged at least up to the transfer site,
For this reason, it is not preferable that the discharge time constant of the belt is too small. However, in the present invention, since the distance between the transfer site and the conductive contact member 14 is small, the range in which the resistance value of the belt can be selected is wide, and therefore the degree of freedom in the belt configuration is also large. In addition, in order to increase the adhesion force by the former transfer material adhesion means, the corona charger 1
2 to the belt-to-transfer material, but for this purpose, the installation position of the corona charger must be moved to the upstream side of the transfer site, or the corona charger 12 may be used to charge &, When two ? The adhesion force can always be maintained higher than that of 8, and the reliability of separation of the transfer material from the drum 1 can be greatly improved.The conductive contact member 14 may be made of, for example, a brush-shaped bundle of thin stainless steel wires. Alternatively, it may be composed of a brush-like material made by bundling carbon fibers.Here, the stainless steel wire made into a brush-like material was used to rub against the surface of the transfer material 8 and ground it. Increasing the current flowing from the charger 12 to the conductive contact member 14 may affect the transfer current.
The current flowing into the conductive contact member 14 may be controlled by grounding the conductive contact member 14 through a resistor, applying a bias, or the like. The volume resistivity of the conveyor belt 9 is determined in order to set the discharge time constant to a desired value and maintain transfer material separability. There is a possibility that the discharge time constant will increase and it will be necessary to provide a static eliminating means. On the other hand, if it is low, the time constant becomes small and the transfer current flowing to the drum is interrupted, resulting in poor transfer. Also, the back side facing the corona charger deteriorates due to corona discharge, and the resistance value decreases when moisture is absorbed. Since it is descending, you can take these things into consideration when making decisions.

As described above, when the adhesion of the transfer material 8 to the belt 9 increases, the separability of the transfer material from the belt 9 becomes a problem.

To solve this problem, the diameter of the belt support roll 11 can be made smaller, or the belt support roll 11 can be connected to a high-voltage electric conductor A117 opposite to the roll 11 in order to neutralize and separate the charges injected into the transfer material. A corona charger 16 may also be installed.

Note that since the high voltage power supplies 13 and 17 have the same polarity, the effects of the present invention will not be impaired even if they are supplied separately from the same high voltage power supply to simplify the power supply.

Note that, from the viewpoint of transferability of the transfer material, the charge retention property of the transfer material itself, in other words, the discharge time constant is also an important factor. As mentioned earlier, when the transfer material is a general paper, the resistance value fluctuates significantly, and the discharge time constant also changes accordingly. Even if the charge retention property of the transfer belt side is slightly decreased, sufficient conveyance performance can be obtained, but if the resistance value of the transfer material is decreased, the transfer performance cannot be relied on due to the charge retention capacity of the conveyor belt side because the transfer material has no charge retention capacity. I have no choice but to. Therefore, taking these points into consideration, the volume resistivity of the conveyor belt or the corona charger 1
It is necessary to set the applied current from 2 to the transfer material-conductive contact member 14.

The transfer/conveyance device according to the present invention has the above configuration. In this device, the following experiment was conducted in an environment of temperature and humidity of 20° C. and 65%, and the effects of the present invention were confirmed. That is, the present transfer/conveyance device is applied to an electrophotographic printer that uses a laser beam scanner as an exposure optical system, and is capable of loading an A4 size transfer material onto the transfer/conveyance device while being fed horizontally. In this printer, the photoreceptor drum serving as the toner image holding member is a selenium-tellurium photoreceptor with a diameter of 150fi, and the circumferential speed of the photoreceptor drum and the transfer material conveyance speed of the conveyor belt are 160cm/sec as described above.
c. The latent image on the photoreceptor was visualized with positive toner by a reversal development method, and the high-voltage DC power supply 13 was set at -6.3 KV, and the latent image was transferred onto the transfer material by the corona charger 12.

At this time, the earthed outer shell member 18 is attached to the transfer corona charger 12.
A double corotron was used in which the opening was 28 mm and the charging wire 15 was two 70μ tungsten wires installed in the hand side. The position is such that the center of the ground case of the transfer corona charger 12 is located on a line connecting the contact point 19 on the traveling upstream side of the contact portion between the drum 1 and the transfer material conveying belt 9 and the center of curvature 20 of the drum 1. set.

On the other hand, the conductive contact member was set upstream from the contact point 19. This distance □ is a distance that can sufficiently hold the charge based on the discharge time constant of the belt. The toner transferred onto the transfer material was fixed by a heating fixing device 21, and the linear pressure between the heating roll and backup roll of the fixing device was 1.5 kg/cat, the heating roll temperature was 180° C.
The transfer material is A4 size paper with the grain direction perpendicular to the longitudinal direction of the transfer material, weighing 130 g, and moisture content 18.5%. 100 sheets were printed twice and collected on the paper discharge tray 22.

At this time, during the second one-sided printing, failure to separate the transfer material from the drum occurred for 68 sheets. The transfer current flowing from the drum to the belt at this time was 45 .mu.A during the first printing, and 30 .mu.A during the second printing because moisture in the transfer decreased during heat fixing and the resistance value increased. Next, an electrically conductive contact member 14 serving as a means for adhering the transfer material is added to the continuous one-sided surface.
100 sheets were printed in the same manner and collected on a paper discharge tray. At this time, there was no defective separation of the transfer paper from the drum. The transfer current to the drum is approximately the same value as above, but the corona charger 1 is connected to the grounded conductive contact member 14.
The current applied from No. 2 was 18 μA during the first printing and 12 μA during the second printing. At this time, if the conductive contact member 14 is not added, the donor is transferred before the transfer material 8 and the drum 1 are not completely in contact with each other due to the influence of the corona charger 12 just before the transfer material 8 is conveyed to the transfer means 5. Toner flying to the material and appearing on the image was observed, but when the conductive contact member 14 is added, charges are injected into the transfer material, the potential of the transfer surface of the transfer material increases, and the contact with the drum 1 increases. Since the potential difference was reduced, the above-mentioned toner flying was not observed.

Next, a transfer material conveying belt made of metal oxide dispersed polyester resin with a volume resistivity of 5 x 10'3 and a thickness of 0.3 mm was made, and the separation state of the transfer material was observed under the same conditions as above. Although there were no separation defects, the transfer current decreased during continuous printing and transfer defects were observed, which was not a desirable result in terms of images. This phenomenon is presumed to be due to the fact that the time constant of the belt is approximately 10 seconds and that charge is accumulated during continuous printing.

On the other hand, the volume resistivity is 5X10' and the thickness is 1 Omm.
A transfer material conveying belt made of carbon-dispersed polyurethane resin was prepared and the separation state of the transfer material was observed under the same conditions as above.As a result, □88 sheets were transferred when the conductive contact member 14 was not added, and 1f-contact means. Due to the addition of 56 sheets of transfer material, defective separation of the transfer material occurred and reliable separation could not be obtained. Although this is close to the distance force between the transfer site and the conductive contact means because the time i number of the conveyance belt falls to about 0.001 seconds, the electric charge injected between the transfer material and the conveyance belt from the conductive contact means is It is presumed that this effect could not be obtained because the discharge occurred immediately.

Effects of the Invention According to the present invention, a conductive contact member is provided at 41 on the upstream side of the transfer site.
□According to the configuration that can be realized extremely easily, the transfer material-conductive contact member and ttt are passed from the transfer corona charger to the conductive contact member through the conveyor belt, and the The transfer material and the belt are charged and brought into close contact with each other, and then the transfer material is conveyed to the transfer means. The adhesion force is always maintained higher than the adhesion force, and the separation of the transfer material from the toner image carrier is highly reliable.It has the effect of making the conveyance of the transfer material extremely stable, and has great industrial value. There is something big.

[Brief explanation of the drawing]

- FIGS. 4 and 5 are schematic diagrams of a known transfer material conveyance device that utilizes electrostatic force. DESCRIPTION OF SYMBOLS 1... Toner image holding body, 4... Development section, 5... Transfer means, 8... Transfer material, 9
... Transfer material conveyance belt, 12 ... Corona charger, 13 ... DC high voltage power supply, 14 ...
...Conductive contact member. Name of agent Patent attorney Toshio Nakao 1 person 1-m-drum 8- copy 9-・-fube) Reto 1st figure 2--
Transfer force corona charger 13-11 Proper flow high voltage Jft source 14- Computer contact member 25 24, jo 26

Claims (1)

[Claims] A means for supporting and stretching an endless transfer material conveying belt made of a conductive material and rotating it in a fixed direction, and a means for holding the transfer material between a toner image holder and the transfer material conveying belt on the surface side of the transfer material conveying belt. a transfer means that has a transfer corona charger on the back side and transfers the toner image to the transfer material, a grounding means that grounds a part of the transfer material conveyance belt, and a transfer site where the transfer means of the transfer material conveyance belt is located. On the upstream side of the
and a conductive contact member that is in conductive contact with the transfer material and grounded at a position close to the toner holding body, and the corona is inserted between the conductive contact member and the transfer material conveyance belt and the transfer material conveyance belt. 1. A transfer/conveying device comprising a transfer material adhering means for injecting electric charge by passing a current from a charger to a conductive contact member and adhering the transfer material to a transfer material conveying belt by electrostatic force.