JPH0782270B2 - Transfer / transport device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer / conveyance device that electrostatically supports / conveys a transfer material and transfers the transfer material onto the transfer material by physical or chemical means.

2. Description of the Related Art In copying machines and printers, in order to make transfer material transfer more reliable, a belt is composed of an insulating member such as a conductor, and the transfer material is electrostatically adhered to the belt material and transferred. There are already some known examples.
For example, in U.S. Pat. No. 2567882, a conductive belt and a dielectric member are bonded together to form a two-layered structure to form a conveyor belt, and the transfer material is supplied between the conveyor belt and the charging member. Therefore, it can be regarded as a method in which the transfer material is charged and is attracted to the belt, rather than the transfer material being attracted to the belt that is charged in advance. Therefore, the belt dielectric layer and the transfer material are charged to the same polarity. This embodiment is shown in FIG. Reference numeral 81 is a dielectric belt, which is supported and stretched by rollers 82 and 83. 84 is a metal belt supported by rollers 86 and 87. A metal foil 85 is opposed to the metal belt 84 with the dielectric belt 81 sandwiched therebetween. The transfer material 88 is charged by the bias applied between the metal belt 84 and the metal foil 85. 89 is for short-circuiting the metal foil 85 and the transfer material 88. Reference numeral 810 is a guide plate that guides the transfer material 88 to the belt 81.

In U.S. Pat. No. 3,357,325, a corona discharger is used for attracting and transferring a transfer material, and a dielectric single layer belt is used. FIG. 9 shows a schematic view of the embodiment. 91 is a drum-shaped image support, 92 is a dielectric single layer belt 93, 94 is a dielectric belt 92
It is a roller for supporting, stretching and rotating. Reference numeral 95 is a roller for guiding the transfer material 96. Reference numeral 97 is a corona discharger for attracting the transfer material 96 to the dielectric belt 92 by electrostatic force, and 98 is a corona discharger for transferring the charged powder image from the image support 91 to the transfer material 96.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in US Pat. No. 3,357,325, the belt is a dielectric single layer, but the corona discharger electrostatically charges the transfer material and adsorbs it on the dielectric belt. When performing transfer, it is necessary to provide a plurality of independent corona dischargers for transfer only at the transfer position. Also, in US Pat. No. 2,576,882, it is possible to transfer and convey the charging devices as a unit.
Due to its structure, as in the former U.S. Pat.No. 3357325, when the transfer belt and transfer material are charged to the extent that sufficient transfer force is obtained, static electricity is applied to the transfer material when the transfer material and transfer belt are separated. It is very likely that the electrically-charged insulating particles that have been transferred are disturbed and adversely affect the transferred image. For this reason, in the conventional transfer device using the transfer / conveyance belt, it is indispensable to remove the electric charges existing on the belt and the transfer material at the separation position between the transfer material and the conveyance belt. However, it is very difficult to completely remove all the electric charges existing on the transport belt and the transfer material without excess or deficiency, and therefore, use another discharger connected to a special power source for static elimination. What must be done is shown in US Pat. No. 3244083 and the like. US Pat. No. 3,717,801 discloses the use of a special discharger and a power source as a method of charging the conveyor belt and the transfer material, but it is hard to say that it is a preferable means in view of economic reasons. Further, in US Pat. No. 2,576,882, if the transfer material is curled, the transportability becomes uneasy. In view of the above problems, the present invention realizes a strong transfer property of a transfer material by effectively using the charged electric charge of the transfer belt without using any special means in a charging device, and can achieve a high quality without a complicated static elimination operation. It is to provide a transfer / conveyance device that obtains a transfer image of.

Means for Solving the Problems In order to solve the above problems, according to the present invention, a transfer belt is charged between a conveying belt and a grounded conductive member which is provided opposite to the transfer belt prior to the transfer position. The charging device for charging the belt is arranged at a position where the transfer material and the transport belt are separated from each other.

Effect of the Invention With the above-described structure of the present invention, first, the charge having the opposite polarity to the charge accumulated on the surface of the dielectric material at the time of charging the transfer material transport belt is transferred from the conductive member installed facing the vicinity of the dielectric material. The electrostatic transfer between the strong transfer material and the conveyor belt is realized by transferring this to the electric charge on the surface of the dielectric material, and the transfer material can be stably conveyed without deviation during transfer. is there. Further, the charging device for charging the transfer belt, which is installed at the separation position between the transfer material and the transfer belt, has the function of removing the electric charge having the opposite polarity to that of the transfer belt applied to the transfer material at the separation position, thus preventing image disturbance. can do. Further, this charger also serves as a precharger for cleaning the belt.

Further, since the transfer material is pressed against the belt and brought into close contact with the belt by electrostatic force, curling of the transfer material does not cause a big problem.

Embodiment Hereinafter, a transfer / conveyance apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section of a transfer / conveyance apparatus in an embodiment of the present invention. In FIG. 1, 11 is a rotatable drum-shaped image holding member (hereinafter, referred to as
It is simply called a drum. ), And a photosensitive dielectric layer such as selenium is provided on a drum-shaped conductor support such as aluminum. Usually this conductor support is grounded. First, the drum 11 is uniformly charged by the charger 12, and the light corresponding to the original is imaged on the drum 11 through a means (not shown), such as a lens, at the next exposed portion 13. At this time, the charge on the surface of the drum that is uniformly charged and exposed to light disappears by neutralizing the charge of the opposite polarity induced on the conductor support on the back surface of the photosensitive layer, and A charge pattern corresponding to light and dark, that is, a latent image is formed. This latent image is visualized in the subsequent developing section 14 by attaching fine insulating charged particles (hereinafter referred to as toner) by electrostatic force. The toner image thus obtained on the drum 11 is electrostatically transferred at the transfer position 15 to a transfer material 117 (hereinafter, referred to as paper) which is conveyed in time with the toner image, and the drum 11 is transferred. After the residual toner on the upper part is wiped by means such as a blade in the cleaning section 16, the static elimination section 17 irradiates the static elimination light uniformly to eliminate the static electricity in the drum 11 to prepare for the next process.

Here, the portion A is a transfer / conveyance device for paper or the like according to the present invention. The belt 111 has a dielectric layer 112 on the outer side and a conductive layer 11 on the inner side.
It consists of two layers. In this example, a double-layered sheet in which aluminum was vapor-deposited on one surface of a polyester film having a thickness of 90 μm was cut into a predetermined size and the ends were ultrasonically welded. Of course, the outside is nylon, Teflon, etc.
If it is a dielectric, it does not matter, the required electrical resistance is
It is 10 ¹³ Ω · cm or more, preferably 10 ¹⁴ Ω · cm or more. The thickness is 200 μm or less, preferably 10 to 100 μm. The electric resistance of the inner layer is preferably 10 ⁶ Ω · cm or less as long as it is a conductor. The thickness of the conductor layer may be arbitrarily determined according to the mechanical strength required for the belt including the dielectric layer. Further, even if a belt is formed as a single sheet by laminating a sheet of a dielectric and a conductor, etc., a seamless endless conductive belt may be formed by coating, laminating, dipping or the like with a dielectric layer. Alternatively, there is no problem in practice even if a belt having a two-layer structure of a dielectric layer and a conductor layer is simultaneously molded by injection-molding a conductor member and a dielectric member. Further, even if an adhesive layer was present between the dielectric layer and the conductor layer, there was no functional problem.

The belt 111 is supported by rollers 114 and 115 and stretched by a not-shown means such as a spring with tension. The surface of the roller 115 is formed of a conductor, and the conductor layer 113 inside the belt 111 is grounded through the roller 115. This may be applied with an appropriate bias depending on the situation. The belt 111 is a roller 1 by a rotating means (not shown).
By driving 15, the direction of movement of the transfer portion 15 is the same as that of the drum 11 and the peripheral speed is made to coincide with that of the drum 11.
The surface of the dielectric portion 112 on the outer side of the conveyor belt is charged by the charging corotron 116 in the opposite polarity to the toner. This is because, for example, if the toner is negatively charged, the dielectric portion of the belt 111 is positively charged, and the toner on the surface of the drum 11 is electrostatically transferred to the belt 111 side by the electric field based on this positive charge. is there.

Here the paper 117 is in time with the drum 11 and the roller 1
It is fed between 14 and the conductive roller 118 which is grounded. In this embodiment, the conductive roller 118 has an electric resistance of about 10 ⁶ Ω between the surface of the member and the grounded position.
The belt 111 is strongly pressed against the scissors roller 114 by means not shown. Therefore, the paper 117 can be pressed against the belt 111 even if the paper 117 is curled.

In FIG. 1, at the contact portion between the charged belt dielectric layer 112 and the dielectric roller 118, the electric field in this portion is reduced because the spatial distance between the charged belt dielectric surface and the electrostatically grounded dielectric roller is narrowed. The strength becomes very strong.
Therefore, when the potential difference between the belt dielectric layer and the surface of the dielectric roller is larger than about 700 V, a discharge phenomenon occurs due to dielectric breakdown of air.

The principle of paper conveyance by this method is to positively utilize this discharge phenomenon. The electrostatic action of the electrostatic paper and the paper transport / transfer belt will be described below with reference to the drawings. FIG. 2 shows a discharge situation when, for example, the belt dielectric layer is positively charged and a conductive and electrostatically grounded member is closely opposed to the belt dielectric layer. In this figure, the grounded dielectric member has the shape of a roller,
The belt dielectric layer is mechanically adhered with a certain pressure. However, in order to generate the discharge phenomenon, this conductive member does not necessarily have to be in the shape of a roller, and even a brush-shaped member that easily causes discharge has no change in the effect of discharge. Further, it is not necessary that the electrically conductive member, which is grounded, and the charged belt dielectric layer are in contact with each other in order to generate the discharge. This is because the electric potential of the surface of the belt dielectric layer is equal to that of the electrically conductive member and the belt dielectric. It may be higher than the discharge start voltage determined by the layer interval. This discharge starting voltage can be easily obtained from the curve of the Pacshen air breakdown voltage. In Figure 2, when the charged belt dielectric surface approaches a grounded conductive roller, Pacs
Discharge starts at a point exceeding the discharge breakdown voltage described by the Hen curve, and when the conductive member is in close contact with the belt dielectric layer, as in this example, finally direct charge transfer occurs. Accompanied by. FIG. 3 illustrates this discharge development using an equivalent circuit. Since the belt dielectric layer has a material having a very high volume resistivity (10 ¹⁴ Ω · cm or more), it can be considered that the capacitance between the belt dielectric 112 and the belt conductor layer 113 is ideal. Call this C ₁ . On the other hand, since the movement of charge, that is, the current flows between the belt dielectric 112 and the conductor roller 118 which is grounded, the charged capacitance C ₁ is discharged through the resistor R ₁ in the discharge area. become.

Next, consider the case where the paper rushes into the discharge area between the belt dielectric layer 112 and the conductive roller 118. FIG. 4 schematically shows this state. Generally, when an object with high electric resistance is inserted in a place where air discharge is generated, the discharge is stopped. It can be considered that this is because the electric field strength in the discharge region is weakened by the polarization action, and the electric resistance of the object becomes an obstacle to the movement of the charges. Inrush of paper reduces the dielectric breakdown of air. However, basically, paper can be considered as a conductor when viewed electrostatically. Therefore, the paper 117 sandwiched between the belt dielectric layer 112 and the conductive roller 118 receives the negative charge induced in the conductive roller 118 by the charged electric charge on the belt dielectric surface. This allows the paper to be negatively charged by passing it between a substantially positively charged belt dielectric layer and a grounded conductive member. It is clear from the above reason that if the charging polarity of the belt dielectric is negative, the charging polarity of the paper will be positive. How much the paper is charged is important when evaluating the paper transportability, and this can be understood by considering an equivalent circuit as shown in FIG. The reason why the electric charge is not neutralized between the conductor paper 117 and the belt dielectric layer 112 is that a thin air layer is interposed therebetween, and the charge is not negatively charged between the belt dielectric layer 112 and the belt dielectric layer 112 which are positively charged. Since the charged paper 117 faces each other across the air gap, it can be placed with a single capacitance. Let this capacity be C ₂ . Further, since the electric resistance of the paper is added to the movement of the electric charge, the discharge resistance becomes larger than the discharge resistance R _{1 in} FIG.

This is represented by R ₂ . According to the equivalent circuit of FIG. 5, when the electric resistance of the paper is small, the current flowing through the circuit should not be large, but when the paper with high water content is passed, the current flowing through the conductive roller 118 is large. We support the validity of this model. For example, the current flowing through the conductive roller having a width of 315 mm was 12 μA when the water content was 7.5%, but the current of 17.6 μA flowed when the paper containing 12% water was passed under the same conditions.

No matter how low the electrical resistance of the paper is, there will not be enough current to cancel all the charges on the charged belt dielectric layer 112. Even in the state shown in FIG. 2, the surface potential of the belt dielectric layer does not become zero even after passing through the discharge area, and is +500.
It shows a potential of ~ 600V. Therefore, even if the paper is negatively charged, an excess positive charge still exists in the belt dielectric layer.
Even in the equivalent circuit of FIG. 5, it is clear that only negative charges that can be divided into C ₁ and C ₂ can flow into the paper.
Therefore, it is possible to electrostatically transfer the toner image by negatively charging the paper and realizing strong suction by electrostatic force between the paper and the positive charge of the belt dielectric layer.

The electrostatically transferred toner image is constrained by a positive charge in excess of the amount of charge on the paper present in the belt dielectric layer. The uneven charge corresponding to the image portion and the non-image portion is adjusted by the negative charge induced in the belt conductor layer. This is because, for example, in the portion of the paper where the negative charge is high, the negative charge induced in the belt dielectric layer is decreased, and the number of electric lines of force from the belt dielectric layer to the paper is increased, so that the electric line of force as a whole is increased. This is to keep the balance of. This is the reason why the two-layer structure belt is used, and thereby a high quality transferred image can be obtained. After the transfer, due to the suction force of the paper 117 and the belt 111 and the rigidity of the paper 117 itself, the paper 117 is separated from the drum without any special device, and the paper 117 is separated from the belt 111.
The transfer is completed while keeping close contact with.

After that, the belt 111 and the paper 117 are combined with the curvature of the roller 115 and the paper 117.
After being separated by its own rigidity, it is delivered to the fixing guide 119, passed through the fixing device 120, and conveyed to a paper discharge tray (not shown) to complete copying. U.S. Pat.
When the belt 111 is separated from the belt 111, a problem is caused in which an image disturbance occurs in which toner is scattered backward in the traveling direction. As a countermeasure against this, in US Pat. No. 3,717,801, a special operation is performed on the charging method. Also, some methods have been proposed in which the paper, the dielectric, and the charge are removed at the position where the paper and the belt are separated.

The image disturbance when separating the paper 117 and the transfer / conveying belt 111 in this method is remarkable especially when the electric resistance of the paper is large. The reason for this can be considered as follows. First, the positive charge on the surface of the belt dielectric layer, the negative charge on the paper, and the negative charge on the toner form one capacitance. Here, as the paper 117 and the transfer / conveyance belt are separated, the value of the electrostatic capacitance C ₂ becomes smaller. Therefore, as the paper holding a constant charge is separated from the transfer / conveyance belt, the electric potential of the paper 117 increases as the distance from the belt 111 increases. This state is schematically shown in FIG. 6 by an equivalent circuit. When the surface resistance R ₃ of the paper 117 is small, the electric charge flows from the X-Y direction in the X-Y direction due to the potential difference between the X-Y resulting from the change in the electrostatic capacitance, so that the electric potential difference between the X-Y is canceled. However, if the resistance R ₃ is large, the electric charge cannot flow from the X direction to the Y direction and the potential at the X point is increased. Therefore, a potential difference is generated between XY and an electrostatic force is exerted on the toner. This is a cause of image distortion on paper with high electrical resistance.

Therefore, if a charger is provided at the separation position between the paper 117 and the belt 111 and the negative charge in the paper can be canceled, no potential difference will occur between XY. Here, the charge polarity of the transfer / transport belt is positive, and the polarity of the charger required to cancel the negative charge of the paper is also positive. Therefore, both of these can be integrated with the belt charging charger and the image disturbance preventing charger. This is also an effect because the charging polarity of the paper is opposite to the charging charge of the belt dielectric layer. For example, in U.S. Pat. No. 2,576,882, if the belt is positively charged, the charger for static elimination must have a negative polarity and integration is impossible. However, the biggest obstacle to the integration of the charger was the problem of the cleaning performance of the transfer / transport belt.

In FIG. 1, a belt cleaning device 121 electrostatically removes toner by applying a bias having a polarity opposite to that of the toner to a conductive fur brush, for example. When cleaning the toner attached to the belt 111, the relationship between the charging potential of the belt 111 and the potential of the brush 121 is important, and precharging the toner before the cleaning brush is effective for efficient cleaning. is there. It is considered that the polarity of the precharge and the polarity of the brush are opposite to each other. For this reason, when the precharger is applied with a positive polarity, the belt charged with a negative polarity is discharged by the cleaning brush, and a new charging means is required thereafter. However, in the actual cleaning test, it was found that the output of the precharger and the voltage of the cleaning brush satisfied the cleaning property with a certain relation. FIG. 7 shows an example of the result of the cleaning property of the one-component toner. As a result, even if the polarity of the precharge is positive, it is not necessary to make the voltage applied to the cleaning brush negative, and the inconvenience that the cleaning brush 121 removes the positive charge charged by the charger 116 is avoided. It is clear from FIG. 7 that this does not matter whether the charging polarity of the belt dielectric layer is positive or negative. Therefore, the configuration of FIG.
Has the three functions of a charging / charging function of the transfer / transport belt 111, a paper discharging corotron for preventing the disturbance of the transferred image, and a precharger for cleaning the belt. This is the paper 117 that is being attracted to the transfer / transport belt 111 by the charger 116.
It can be realized by grounding at a position where is separated. However, when cleaning with a blade, the charger
The main purpose of 116 is to prevent the disorder of the transferred image and to charge the belt. However, the toner is easily cleaned by the precharger, and a sufficient effect can be expected in the blade cleaning.

In the embodiment shown in FIG. 1, the paper 117 is configured to pass above the drum 11, but it may be configured to pass laterally or below the drum 11. Further, in FIG. 1, the conductor portion of the belt 111 is kept in the grounded state, but an appropriate bias may be applied to this.

EFFECTS OF THE INVENTION As described above, the present invention is provided so as to face a belt consisting of two layers of a dielectric material charged on paper or the like and a conductor grounded or biased, and prior to a transfer position. By feeding the transfer material between the conductive material in the grounded state and the conductive material in the grounded state, the electric charge is transferred from the conductive material in the grounded state, the transfer material is strongly adsorbed, and stable conveyance without deviation is ensured. Transfer is performed, and by installing a charger for belt charging at the position where the paper and transfer / conveyor belt are separated, a good belt and transfer material that does not disturb the image are separated without installing a special static eliminator. The toner attached to the belt can be efficiently cleaned.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining a discharge condition from the transfer material transport belt of the present invention, and FIG. 3 is a schematic view of the transfer material transport belt of the present invention. FIG. 4 is a model diagram for explaining the discharge condition, FIG. 4 is a schematic diagram for explaining the transfer material transport principle of the present invention, and FIG. 5 is a model diagram for explaining the transfer material transport principle of the present invention. FIG. 7 is a model diagram for explaining an image disturbance that occurs when the transfer material transport belt and the transfer material are separated, and FIG. 7 shows a change in cleaning property due to a change in the applied voltage of the conductive fur brush and the output of the precharger. FIGS. 8A and 8B are cross-sectional views of a known transfer material conveying device utilizing static electricity, and FIG. 9 is a cross-sectional view of a known transfer material conveying device utilizing static electricity. 111 …… Conveyor belt, 112 …… Belt dielectric layer, 113 ……
Belt conductor layer, 116 ... Charger, 117 ... Transfer material, 118
…… Conductive roller, 121 …… Conductive cleaning fur brush.

Claims (2)

[Claims] 1. A means for supporting and extending an endless transfer material conveying belt composed of a dielectric on the surface in contact with the transfer material and two layers of conductors on the back surface and rotating in a fixed direction. Means for grounding the conductor portion of the transfer material conveying belt or applying an arbitrary bias thereto and means for charging the dielectric portion are corona chargers, and the charging point is the transfer material and the transfer material conveying belt. As a separating position, the transfer material is configured to be supplied between a transfer material conveying belt and a conductive member in a grounded state which is arranged in front of the transfer position so as to face the transfer material conveying belt. Transfer / transport device. 2. The transfer / conveyance apparatus according to claim 1, wherein the cleaning means for the transfer material conveyance belt is a conductive fur brush to which a voltage is applied.