JPH07271204A - Transfer belt - Google Patents

Abstract

PURPOSE:To suppress the variance of electrical resistance and the secular change thereof in a transfer belt by using hydrin rubber as the rubber material of the transfer belt. CONSTITUTION:A resist roller 16 is arranged in front of a photoreceptuve drum 1 and the transfer belt 2 is arranged to abut on the drum 1. The belt 2 is spread between a driving roller 3 and a driven roller 4. Then, the dual structure of an inside layer 2a consisting of the hydrin rubber being the rubber material whose electrical resistance is medium and a dielectric layer 2b made of urethane formed on the layer 2a as a surface layer is used for the belt 2. The roller 3 is formed by winding a rubber layer round the outside circumferential surface of a metallic roller in order to enhance friction coefficient between the belt 2. The roller 4 is constituted of the metallic roller. Then, a bias roller 5 is made to abut on A position the inside circumferential surface of the belt 2 at a prescribed distance away from a nip part 17 between the drum 1 and the belt 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer belt which is used in a transfer section of a copying machine, a printer, a facsimile or the like, for transferring a toner image on an image carrier to a sheet or for conveying the sheet.

[0002]

2. Description of the Related Art Generally, a transfer belt used in a transfer belt device such as a copying machine serves to convey a sheet, transfer a toner image onto the sheet, and separate the sheet after the transfer. In the transfer belt device, a corona discharge method is often used for charging the transfer belt.
However, recently, there is a transfer belt device (Ricoh FT550) that directly applies a bias roller or the like. According to such a system, ozone generation is 1/10 of that of the conventional system.
It is possible to reduce the concentration to 1/20.

[0003]

However, in the above-mentioned conventional transfer belt, when the above-mentioned direct application method is used, transfer is performed by the current flowing through the inside of the transfer belt to the photosensitive member, so that the method using corona discharge is used. In comparison, the change in the electric resistance of the transfer belt has a greater effect on the image. In other words, when the resistance in the transfer belt varies greatly, the current flowing in the photoconductor also varies, so uneven density occurs in the transferred toner image, and when the resistance value increases with time, the transfer The current becomes insufficient and a blank image occurs. As a countermeasure, there is a method of controlling by appropriately changing the output voltage of the power supply so that the transfer current becomes constant.However, when the resistance in the transfer belt varies widely, the change in the output voltage of the power supply causes a change in the resistance value. There was a problem that a constant transfer current could not be supplied or the transfer current became insufficient without keeping up with the fluctuation.

Further, the transfer belt based on EDPM uses a material in which carbon is added to rubber in order to obtain medium resistance. However, in the rubber in which conductivity is obtained by dispersing carbon, the structure state of carbon is used. Greatly affects the electrical resistance, and if the carbon structure is not evenly distributed in one transfer belt, the resistance value of the transfer belt may vary and the electrical conductivity due to the carbon structure may change over time. It was difficult to avoid the problem that the values change over time. Therefore, the present invention solves the above-mentioned conventional problems and can suppress variations in electric resistance in the transfer belt and changes over time as much as possible, and can stably obtain a good image. The challenge is to provide.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is a double structure in which a rubber material having a medium resistance is used as an inner layer and a urethane dielectric layer is formed on the inner layer. The hydrin rubber is used as the rubber material in the transfer belt having the functions of transferring the sheet, conveying the sheet, or both.

[0006]

Therefore, since the hydrin rubber used for the inner layer of the transfer belt can obtain a medium resistance without dispersing carbon, variations in resistance value and changes with time that occur when carbon is dispersed can be suppressed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. A transfer belt device according to the present invention is shown in FIG. 1, in which a registration roller 16 is arranged in front of a photosensitive drum 1 and a transfer belt 2 is arranged in contact with the photosensitive drum 1 respectively. The belt 2 is stretched around a driving roller 3 and a driven roller 4, and is an inner layer 2a made of hydrin rubber, which is a rubber material having a medium electric resistance.
Then, a dielectric layer 2b (surface resistance 10 ¹² Ω) made of urethane is formed as a surface layer on the inner layer 2a to form a double structure. The drive roller 3 is formed by winding a rubber layer around the outer peripheral surface of a metal roller for increasing the friction coefficient with the transfer belt 2, and the driven roller 4 is a metal roller.
Then, the bias roller 5 for applying a voltage is brought into contact with the inner peripheral surface of the transfer belt 2 at a position separated from the nip portion 17 between the photosensitive drum 1 and the transfer belt 2 toward the drive roller 3 by a predetermined distance. Further, a contact plate 6 is arranged between the bias roller 5 and the driving roller 3 so as to be in contact with the inner peripheral surface of the transfer belt 2. This bias roller 5
Is a metal roller, which rotates following the rotation of the transfer belt 2, and the contact plate 6 is a metal plate, both of which are connected to the power source 7 (the contact plate 6 is connected via the transfer control plate 8). )ing.

A fixing device 15 including a fixing roller 13 and a pressure roller 14 is arranged at a position separated from the rear end of the transfer belt 2 by a predetermined distance.

By the way, as an example of the structure of the transfer belt 2,
As described above, the double structure that has been conventionally used can be cited. It has a medium resistance EPDM as an inner layer, and this EPDM is formed to have a thickness t = 0.5 (mm) through the steps of kneading rubber, extruding, vulcanizing and polishing in this order.
20μm of urethane resin spray coated on the surface of DM
Was getting a film. In this embodiment, the same manufacturing method is adopted, and the hydrin rubber (inner layer 2a) is used instead of the conventional EPDM. Urethane is the product name C-23
100 parts by weight of 0 u main agent (manufactured by Hirono Chemical Co., Ltd.) and 30 parts by weight of C-230u curing agent (manufactured by Hirono Chemical Co., Ltd.) were used.

In the above structure, first, the sheet 8 conveyed by the registration rollers 16 is placed on the transfer belt 2. By applying a voltage from the power supply 7 via the bias roller 5, a current flows to the photoconductor drum 1 and the contact plate 6 side. Here, as shown in FIG. 3, when the applied current output from the power source 7 is I ₁ and the feedback current flowing from the contact plate 6 to the ground side through the transfer belt 2 is I ₂ , this feedback current I ₂ The value of the applied current I ₁ is controlled by detecting and changing the voltage of the power supply 7 so that I ₁ −I ₂ = Iout becomes constant. In this embodiment, Iout = 40 μA.
The toner image on the photosensitive drum 1 is transferred onto the sheet 8 by this method and is conveyed on the transfer belt 2. Next, the sheet 8 is peeled off from the transfer belt 2 due to the curvature of the driving roller 3, and the fixing roller 13 and the pressure roller 14 fix the toner.

Next, a comparative example of a transfer belt using hydrin rubber and EPDM will be described. First, hydrin rubber as an inner layer was prepared with the formulations shown in Tables 1 and 2.

[0012]

[Table 1]

[0013]

[Table 2]

As described above, these materials are blended and kneaded with rubber, extruded, vulcanized, and ground to obtain a thickness t = 0.
On the surface of the 5 (mm) hydrin rubber belt, urethane resin
(The same material as the material applied to the surface of the EDPM belt described above) was spray-coated to manufacture a transfer belt 2 ₁ (composition of Table 1) and a transfer belt 2 ₂ (composition of Table 2). The transfer belts 2 ₁ and 2 ₂ based on the above two types of hydrin rubber and EDPM in which carbon black is dispersed are used as an inner layer, and urethane resin (the same as the material applied to the surface of the EDPM belt described above) is spray-coated on the surface thereof. the transfer belt 2 ₀ was,
In the volume resistivity measurement system shown in FIG. 4, the resistance value of each belt was randomly measured at five points, and this was converted into volume resistivity to obtain the results in Table 3. (In FIG. 4, 20 and 21 are voltage application electrodes, and 22 is a grid electrode.)

[0015]

[Table 3]

As apparent from Table 3, the resistance value of the transfer belt 2 ₀ EDPM is 1 month, whereas has increased about one order, transfer of hydrin rubber belt 2
₁ and 2 ₂ of the resistance value change was both increased following half order.

Further, since regard to variations in the resistance in one transfer belt, in the case of the transfer belt 2 ₀ of EDPM belt variation is about one order, Ricoh FT55
When the image was output at 00, a blank image was generated.
However, the transfer belts 2 ₁ and 2 ₂ of hydrin rubber had almost no variation in resistance, and a good image could be obtained.
The transfer belt 2 ₁ and 2 ₂ of this embodiment is not limited to only the transfer belt apparatus of a system configuration shown in FIG. 1, for example, sufficiently effectively used in apparatus configuration of using a corona discharge to charge or charge removal You can Further, needless to say, the present invention can be used not only for a transfer belt that uses both transfer and transport functions, but also for a transfer belt that has only a single transfer or transport function.

[0018]

As described above, according to the present invention, since hydrin rubber is used as the rubber material of the inner layer of the transfer belt, a medium resistance can be obtained without mixing an additive, and carbon is dispersed as compared with the case of dispersing carbon. As a result, it is possible to suppress variations in the resistance value in the belt and changes with time as much as possible. Therefore, it is possible to stably obtain a good image and a good carrying property at the same time without controlling the output voltage of the power source on the device side.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram showing an embodiment of a transfer belt device according to the present invention.

FIG. 2 is a sectional view showing a double structure of the transfer belt of the present invention.

FIG. 3 is an enlarged view showing a transfer portion of the transfer belt device.

FIG. 4 is a plan view and a side view showing a volume resistivity measuring system.

[Explanation of symbols]

 1 image carrier 2 transfer belt 2a inner layer (hydrin rubber) 2b urethane dielectric layer 8 paper

Claims (1)

[Claims] 1. A double structure in which a rubber material of medium resistance is used as an inner layer and a urethane dielectric layer is formed on the inner layer, and a toner image on an image carrier is transferred to a sheet or conveyed, or A transfer belt having both functions, wherein hydrin rubber is used as the rubber material.