JP2532523B2 - Transfer / transport equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transfer in which a transfer material is electrostatically supported / conveyed and a toner image on a toner image carrier is transferred to the transfer material by a physical or chemical means. -Regarding the transport device.

2. Description of the Related Art In electrophotographic copying machines and electrophotographic printers, in order to make transfer material transfer more reliable, a belt is composed of an insulating member such as a dielectric material, and the transfer material is electrostatically adhered to it for transfer. The means to do so are known.

U.S. Pat. No. 3,357,325 uses a corona charger for adsorption and transfer of a transfer material, and proposes a method using a belt of a single dielectric layer. FIG. 2 shows a schematic diagram of the proposed example. Reference numeral 21 is a drum-shaped toner image carrier, 22 is a dielectric single-layer belt, and 23 and 24 are rolls for supporting and extending the dielectric belt 22 to rotate. 25 is a roll for guiding the transfer material 26. 27 is a transfer material 26 which is a dielectric belt by electrostatic force.
Reference numeral 28 is a corona charger for adsorbing the toner image on 22, and 28 is a corona charger for transferring the toner image from the image support 21 to the transfer material 26.

Japanese Unexamined Patent Publication No. 54-58034 discloses a proposal for deleting the corona charger for adsorbing the transfer material in the above example. The content of the proposal is divided into two according to the resistance value of the belt constituent material. One is the resistance value range of 10 ⁸ to 10 ¹³ Ω · cm.
In the other cases, the resistance value range is 10 ¹³ Ω · Cm or more, the belt thickness is 150 μ or less, and the saturated charging potential is 2500 V or less. FIG. 3 shows a schematic diagram of the proposed example. The drum 30 charged by the corona charger 29 is exposed by the optical system 31 to form a latent image, and the developing device 32 forms a toner image. The toner image is a transfer material conveyed by the belt 34 of the separation belt device 33.
It is transferred to 35 by a transfer corona charger 37 connected to a DC power supply 36. After the transfer material 35 is conveyed, the belt 34 is discharged by an alternating current or a corona charger 38 having a polarity opposite to the belt charging polarity. Then, in order to assist the separation property of the transfer material from the drum, as shown in FIG.
1 to 10 KV AC power supply 39 in series with the DC power supply of the above, or as shown in FIG. 5, the transfer corona charger 37 is a DC power supply of AC or reverse polarity to the charging polarity on the belt running downstream side. Separate corona charger 41 connected to power supply 40
Shows how to place.

Problems to be Solved by the Invention However, in the proposal of US Pat. No. 3,357,325, the belt is a single dielectric layer, and there is a limit to the amount of charge that can be charged if a practical belt thickness is secured. If the permittivity is ε and the belt thickness is d, the capacitance C of the belt is
Since the capacity C per unit area is given by C = ε / d, if a capacity of about 100 pF is to be obtained as a capacity equivalent to the surface capacity of the photosensitive drum serving as a toner image holding member, a normal organic belt material ( ε = 2-4), the thickness is 20-40
It becomes μ. With this thickness, the practical strength of the conveyor belt is weak, and therefore, a belt with a thickness of several 100μ cannot hold sufficient capacity, and since the amount of charge held on the belt is small, it cannot be transferred to the transfer position. Although it has a corona charger exclusively for transfer, it has a weak point in transfer ability. This point is as described in JP-A-54-58034, and when continuously used, the belt surface potential rises, which also causes the drawbacks described in JP-A-54-58034. Is not practical. In addition, when an organic material is irradiated with corona discharge for a long time, an altered layer is generated in the molecular structure of the surface layer, and when moisture is absorbed, the surface resistance drops significantly and the charge retention is lost, so this is also a weak point. It is a method. On the other hand, the proposal of Japanese Laid-Open Patent Publication No. 54-58034 proposes that when the resistance value range is 10 ¹³ or more, the belt thickness is 150 μ or less, and the saturation charging potential is 2500 V or less, the belt surface potential rises in continuous use. Is protected by a corona charger for static elimination, but in the example shown in FIG.
Transfer current flowing from drum to drum 31 is belt 35 → transfer material 36 →
The attraction force between the drum 31 and the belt and the transfer material exhibits the same attraction force as the attraction force between the transfer material and the drum, and therefore, there is no factor that causes the force that the transfer material is easily separated from the drum. If the separation is performed, the rigidity is such that the transfer material is not bent against the curvature of the drum, and if the rigidity of the transfer material is small or the diameter of the transfer material is large, the probability of separation is halfway. For this reason, the proposals shown in FIG. 4 and FIG. 5 have been made in order to assist the separability, but all of these proposals are directed to reduce the transferability of the toner image. However, when moisture is absorbed and the resistance value is lowered, transfer failure is caused. Even when the resistance value range is 10 ⁸ to 10 ¹³ Ωcm, the separation property of the transfer material is similar to the above, there is no particularly excellent element, and the resistance value range is 10 ¹³ Ωcm or more and the belt thickness is It is the same as the case of 150μ or less.

In view of the above problems, the present invention effectively uses the charging characteristics of the conveyor belt to realize strong separation / conveyance of the transfer material without using any special means in the charging device, and uses a complicated high-voltage power supply. Another object is to provide a transfer / conveyance device that obtains a transfer image of high quality.

Means for Solving the Problems The present invention has a volume resistivity of 10 in order to solve the above problems.
An endless transfer material transport belt composed of a conductor of ¹¹ to 10 ¹³ Ω ・ Cm, a means for supporting and extending this transfer material transport belt, and rotating it in a fixed direction, and a transfer material transport belt on the surface side. The toner image carrier that is installed, the transfer material that is sandwiched between the toner image carrier and the transfer material transport belt, and the toner that forms a toner image on the back surface side of the transfer material transport belt at the sandwiched portion of the transfer material A transfer unit having a transfer corona charger to which a high voltage is applied from a first DC power source having a polarity, for electrostatically transferring the toner image to the transfer material; and a grounding unit for grounding a part of the transfer material transport belt. A member that is in conductive contact with the transfer material, which is arranged on the upstream side of the transfer site where the transfer means of the transfer material transport belt is located, further downstream of the ground site where the grounding means is located, and on the surface side of the transfer material transport belt. , At the position facing the conductive contact member, Before the transfer material is conveyed to the transfer portion, a corona charger for adhering the transfer material, to which a high voltage is applied from a second DC power source having a polarity opposite to that of the toner image carrier, is attached to the back side of the transfer material conveyance belt. In addition, a transfer material contact means for applying a charge having the same polarity as that of the toner image carrier to the transfer material surface in advance by an injection charge from the conductive contact member and electrostatically contacting the transfer material and the transfer material transport belt is provided. According to the present invention, by adopting the above-described configuration, first, the current is transferred from the transfer material contacting corona charger provided on the upstream side of the transfer portion where the transfer means is located to the transfer material → conductive contact member through the conveyor belt. To give a charge of the same polarity as the toner image carrier to the surface of the transfer material in advance from the conductive contact member, and also a sufficient charge between the transfer material and the transfer material transport belt to electrostatically Since the transfer material is attached and then transferred to the transfer portion, the electrostatic adhesion between the transfer belt and the transfer material is always kept higher than the electrostatic adhesion between the toner image carrier and the transfer material. The separability of the transfer material from the toner image carrier of the transfer material becomes highly reliable.

Embodiment Hereinafter, a transfer / conveyance apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an electrophotographic printer equipped with a transfer / conveyance device according to the present invention. In FIG. 1, reference numeral 1 denotes a rotatable drum-shaped toner image carrier (hereinafter simply referred to as a drum), which is a photosensitive dielectric layer such as selenium on a drum-shaped conductor support such as aluminum. Is provided. Usually this conductor support is grounded. First, the drum 1 is uniformly charged by the corona charger 2 for charging the drum, and the light corresponding to the print original is exposed by means of a corona charger 2 for the next stage, such as a semiconductor laser, an LED array, a liquid crystal shutter array, lens optics. An image is formed on the drum 1 through a system or the like. At this time, the charge on the surface of the drum, which is uniformly charged, 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 printing. A charge pattern corresponding to the original, that is, a latent image is formed. This latent image is visualized in the subsequent developing section 4 by attaching fine insulating charged particles (hereinafter referred to as toner) by electrostatic force. The toner image thus obtained on the drum 1 is electrostatically transferred by the transfer means 5 to the transfer material 8 which is conveyed in time with the toner image, and the residual toner on the drum 1 is cleaned by the cleaning unit 6. After being wiped by means such as a blade at
The static elimination unit 7 irradiates uniform static elimination light to eliminate static electricity on the drum 1 to prepare for the next printing process.

Next, transfer / transfer of a transfer material such as paper according to the present invention applied to the printing process using the generally known toner described above.
The transport device will be described in detail. In FIG. 1, the conveyor belt 9 is composed of a conductor layer having a volume resistivity of 10 ¹¹ to 10 ¹³ Ω · Cm. In this embodiment, the thickness is 1 mm and the volume resistivity is 5 × 10 ^12.
A carbon-dispersed polyurethane resin of Ω · Cm molded endlessly with a peripheral length of 380 mm was used. As described above, the charge discharge time constant of the conveyor belt is C = ε / d for the capacitance component and R = ρd for the resistance component R, where ρ is the resistivity, and thus the time constant CR = ερ, The time constant of the conveyor belt used here is about 1.3 seconds when ε = 3. Therefore,
If it takes 1.3 seconds, 70% or more of the charged electric charge will be discharged, so if the same portion of the belt does not pass the transfer means 5 within this time, the corona charger for static elimination is not required. On the other hand, when the volume resistivity is 10 ¹⁰ Ω · Cm or less, the discharge time constant is too small and the problems described later occur. The belt 9 has rolls 10 and 11
And is stretched by means such as a spring (not shown) by tension. The surface of each of these rolls is formed of a conductor and is grounded through the inside of the belt 9. An appropriate bias may be applied to this depending on the situation. The belt 9 is a roll 10 or a rotary drive means (not shown)
By driving 11, the direction of rotation at the transfer portion where the transfer means 5 is located is the same as that of the drum 1 and the peripheral speed is made to coincide with each other. Here, the drum peripheral speed is 160 mm / sec. Therefore, the belt goes around in about 2.4 seconds. A transfer corona charger 12 is installed on the back side of the transfer portion of the conveyor belt 9, and a high voltage is applied from a first DC high-voltage power supply 13 having a polarity opposite to that of the toner to transfer the toner to the transfer material 8. For example, if the toner is positively charged, the transfer corona charger 12 is a negative electrode, and a transfer current flows to give a positive charge to the negative charge on the back surface of the belt 9, and the transfer of this positive charge occurs. Based on this, the toner on the surface of the drum 1 is transferred to the transfer material 8 existing on the surface side of the belt 9. As mentioned above, in the case of a belt with a high electric resistance or a belt with a large discharge time constant, if there is sufficient charge transfer to charge the capacitive component of the belt, then transfer current will not flow and transfer will be impossible. In the belt according to the present invention, the resistance component causes discharge after passing through the transfer portion, and at the transfer portion, the transfer current flows through the resistance component to assist the transfer.

However, recently, in a printer using an electrophotographic process such as a laser printer shown in FIG. 1, since a latent image is often developed by reversal development, a transfer corona charger having a polarity opposite to that of the drum 1 is used. Therefore, for example, in a selenium photosensitive member, if the transfer corona charger 12 charges the negative electrode due to its rectifying property, an excessive transfer current may flow to cause deterioration of the drum, but the belt according to the present invention is sandwiched in the middle. When it is electrified, it is possible to reduce the transfer current by the buffering effect of the resistance component of the belt. To make this effect work, it is preferable that the belt is thick, and 0.4 mm or more is desirable. On the other hand, if it is too thick, the surface stress will increase during mechanical transportation, so that surface deterioration and minute irregularities in the transportation speed tend to occur, and therefore should be suppressed to about 1.5 mm. More desirably, 0.6 mm to 1.0
mm. According to the present invention, the following configuration should be added essentially. That is, on the upstream side of the transfer site where the transfer means 5 of the transfer material conveying belt is located, and on the roll.
A member 14 disposed on the downstream side of the grounding portion of 11 for electrically conducting contact with the transfer material 8 existing on the front surface side of the belt 9 and a member provided on the rear surface side of the transfer material transport belt 9 at a position facing the electrically conductive contact member 14. In the case of using the reversal development method shown in this embodiment, transfer to a conveyor belt including a transfer material contacting corona charger 15 connected to a second DC high-voltage power source 16 having the same polarity as the transfer corona charger 12 This is a structure that serves as a material contact means.
The electrically conductive contact member 14 may be formed of, for example, a stainless steel wire bundled into a brush shape, a carbon fiber bundled into a brush shape, an electrically conductive roll supported by a fulcrum, or the like. Here, a brush-shaped stainless thin wire was used to rub against the surface of the transfer material 8 for grounding. The conductive contact member 14 may be applied with an appropriate bias. With this added structure, charges are injected into the transfer material and the belt in the same polarity as that of the toner image carrier before the transfer material is transferred to the transfer portion, so that the transfer belt and the transfer material are not charged. The electrostatic adhesive force can be always kept larger than the adhesive force between the toner image carrier and the transfer material. However, in order to maintain the effect, the transfer material contacting corona charger 15 transfers the transfer material transport belt 9 → transfer material 8 →
The current flowing through the conductive contact member 14 is the transfer corona charger 12
To transfer material conveying belt 9 → transfer material 8 → toner image carrier 1
At least 20% of the current flowing into is required. In particular, the belt is running when the distance between the transfer site and the conductive contact member is large, but the charge injected until reaching the transfer site is discharged due to the time constant of the belt.
The current flowing from the transfer material contacting corona charger 15 to the conveyor belt 9 → transfer material 8 → conductive contact member 14 should be made larger to prevent the effect from decreasing. Here, this distance is set to 25 mm. As described above, if the discharge time constant of the belt 9 is too small, the effect of the present invention is difficult to obtain because the electric charge discharge here is large. Therefore, the lower limit of the electric resistance of the belt material is suppressed. The current flowing from the transfer material contacting corona charger 15 is controlled by grounding the conductive contact member 14 through a resistor, applying a bias to the conductive contact member 14, or adjusting the voltage of the second DC high-voltage power supply 16. By doing so, the state is set to satisfy the above value. 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. According to the present invention, the diameter of the belt supporting roll 11 is made smaller, the rigidity of the transfer material is utilized, or the belt support roll 11 is opposed to the roll 11 in order to neutralize and inject the charge injected into the transfer material. The transfer material separating corona charger 17 connected to the third high-voltage DC power supply 18 may be installed. In this embodiment, the first DC high voltage power supply 13
Since the DC high-voltage power supply 16 and the third DC high-voltage power supply 18 have the same polarity, they are supplied separately from the same high-voltage power supply.
Even if the power supply is simplified, the effect of the present invention is not impaired.

The transfer / conveyance apparatus according to the present invention has the above configuration. An electrophotographic printer using a semiconductor laser scanner as an optical system equipped with the present apparatus was subjected to the following experiment under the environment of 20 ° C. and 65% temperature and humidity to confirm the effect of the present invention. That is, the electrophotographic printer to which the present transfer / conveyance device is applied can be mounted on the transfer / conveyance device in a state where the A4 size transfer material is laterally fed. In this printer, the photosensitive drum that serves as the toner image carrier is a positively charged selenium / tellurium photosensitive member with a diameter of 150 mm, the weekly speed of the photosensitive drum and the transfer material transport speed on the transport belt are as described above.
160 mm / sec., The latent image on the photoconductor is visualized by the toner charged to the positive polarity by the reversal phenomenon method, and the first high-voltage DC power supply 13 is the negative electrode on the transfer material 8 by the transfer corona charger 12 It was transcribed. The toner transferred onto the transfer material 8 was fixed by the heating roll fixing device 19. The linear pressure of the heating roll and the backup roll of the fixing device was 1.5 kg / cm, the heating roll temperature was 180 ° C, and the transfer material was A4 size. The fiber direction is perpendicular to the longitudinal direction of the transfer material, paper with a basis weight of 56 g and a moisture content of 7% is used, and the conductive contact member 14 and the corona charger 15 are not added first, and continuous single sided twice. Output 100 sheets and output tray 2
It was collected at 0. At this time, 5 in the second print on one side
Transfer material separation failure from 6 drums 1 occurred. At this time, the transfer current flowing from the belt to the drum was 40 μA at the time of the first printing, and at the second time, the water content of the transfer paper was decreased at the time of heat fixing and the resistance value was increased to 32 μA. Next, the conductive contact member 14 and the transfer material contacting corona charger 1
5. A second high-voltage DC power supply 16 was added, and continuous single-sided twice printing was performed 100 sheets in the same manner, and the sheets were collected in the 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 almost the same value as the above, but the current flowing from the conveyor belt 9 to the grounded conductive contact member 14 is 15 μA at the time of the first printing because the second DC high-voltage power supply 16 has the negative electrode. At the time of the second printing, it was 12 μA. Next, a transfer material conveying belt of a metal oxide dispersion type polyester resin having a volume resistivity of 5 × 10 ¹³ Ω · Cm and a thickness of 0.3 mm was prepared, and the separated state of the transfer material was observed under the same conditions as above. As a result, there were no separation defects, but the transfer current decreased during continuous printing, and transfer defects were recognized, which was not a desirable result on the image. This is because the time constant of the above belt is about 10
It is assumed that this is a phenomenon caused by the accumulation of electric charges during continuous printing. On the other hand, the volume resistivity is 5 × 10 ⁹ Ω
As a result of observing the separation state of the transfer material under the same conditions as above, creating a transfer material conveying belt of carbon dispersion type polyurethane resin having a thickness of 1.0 mm in Cm, 68 sheets when the conductive contact member 14 is not added, 60 if conductive contact means is added
The transfer material separation failure of one sheet occurred and reliable separation property was not obtained. This is because although the distance between the transfer site and the conductive contact means is short because the time constant of the transfer belt drops to about 0.001 seconds, the charge injected between the transfer material and the transfer belt from the conductive contact means is immediately discharged. It is speculated that the effect was not obtained. Therefore, in order to obtain the effect of the present invention as described above, it is necessary to select the condition of the transfer material conveying belt in accordance with the condition of the printing process in which the transfer / conveying device according to the present invention is mounted. The optimum volume resistance value range is 10 ¹¹ to 10 ¹³ Ω · Cm.

Effects of the Invention According to the present invention, a current is passed from the transfer material contacting corona charger provided on the upstream side of the transfer portion where the transfer means is located to the transfer material to the conductive contact member through the conveyor belt, and the photosensitive member is sufficiently preliminarily charged. An electrostatic charge is applied to the surface of the transfer material in the same polarity as the drum to electrostatically adhere the transfer material and the transfer material conveyance belt, and then the transfer material is conveyed to the transfer site. The electrostatic adhesive force between the transfer belt and the transfer material is always kept higher than the electrostatic adhesive force, so the transfer material transferability from the toner image carrier is highly reliable, and the transfer material transferability is extremely stable. There are those that have the great industrial value as well as those that have the effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrophotographic printer equipped with a transfer / conveyance device according to the present invention, and FIGS. 2, 3, 4, and 5 show a known transfer material utilizing electrostatic force. It is the schematic of a conveying apparatus. 1 ... Drum, 4 ... Developing section, 5 ... Transfer means, 8 ...
Transfer material, 9 ... Transport belt, 12 ... Transfer corona charger, 13, 16, 18 ... DC high voltage power supply, 14 ... Conductive contact member.

Claims (2)

(57) [Claims] 1. An endless transfer material transport belt composed of a conductor having a volume resistivity of 10 ¹¹ to 10 ¹³ Ω · cm, and a means for supporting and extending the transfer material transport belt to rotate in a fixed direction. ,
The toner image carrier placed on the front surface side of the transfer material transport belt, the transfer material sandwiched between the toner image carrier and the transfer material transport belt, and the back surface side of the transfer material transport belt at the portion sandwiching the transfer material. A transfer means for electrostatically transferring the toner image onto the transfer material, which has a transfer corona charger to which a high voltage is applied from a first DC power source having a polarity opposite to that of the toner forming the toner image; Grounding means for grounding a part, upstream of the transfer site where the transfer means of the transfer material transport belt is located, further downstream of the ground site where the grounding means is located, and on the surface side of the transfer material transport belt, A member that is in conductive contact with the transfer material, and a second member having a polarity opposite to that of the toner image carrier at a position facing the conductive contact member and on the back surface side of the transfer material transport belt.
A corona charger for adhering the transfer material, to which a higher voltage is applied from the DC power source, is attached to the toner image carrier by the charge injected from the conductive contact member to the surface of the transfer material before the transfer material is conveyed to the transfer site. A transfer / conveyance apparatus comprising: a transfer material contact unit that applies an electric charge of the same polarity and electrostatically adheres the transfer material and the transfer material transfer belt. 2. The transfer / conveying apparatus according to claim 1, wherein the transfer material conveying belt has a thickness of 0.4 mm to 1.5 mm.