JPH10186885A - Intermediate transferring body and electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transferring body for a smaller size electrophotographic image forming device, capable of forming an excellent image with less color slippage or scattering by adopting a metallic belt for a base material of a tubular rotary body, as for a charged powder image transferred on the tubular rotary body by potential of a power feeding member located on a rear side of the tubular rotary body. SOLUTION: This intermediate transferring body is composed of the curvature variable tubular rotary body, the tubular rotary body carries the charged powder image on a surface thereof, which is successively transferred in company with its rotation, and the charged powder image is transferred on the rear side or the surface of the tubular rotary body by the potential of the power feeding member located on the rear side of the tubular rotary body. Then, the metallic belt is adopted as the base material of tubular rotary body. By this intermediate transferring body, expansion and contraction sideways corresponding to driving tension becomes small, the surface expansion and contraction is prevented even in a section on which curvature varies, and the electrophotographic device adopting this can realize the image of the excellent quality, miniaturize and prolong the life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intermediate transfer member and an electrophotographic image forming apparatus using the intermediate transfer member.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus using an intermediate transfer member, there is known a color image forming apparatus in which an electrophotographic method as shown in FIG. 5 is applied to a full color printer.

A photosensitive drum 11 rotates in the direction of the arrow, is uniformly charged by a primary charger 12, and is modulated by an image information signal sent from a host computer.
An electrostatic latent image is formed on the photosensitive drum 11 by the laser light from the third. The intensity of the laser light and the irradiation spot diameter are appropriately set according to the resolution of the image forming apparatus and the desired image density, and the electrostatic latent image on the photosensitive drum 11 is a portion irradiated with the laser light. the light portion potential V _L, otherwise portion is formed by being held in the dark potential V _D which has been charged by the primary charger 12. The electrostatic latent image reaches a portion facing the developing device 14 by the rotation of the photosensitive drum 11, and powder (toner) charged to the same polarity is supplied to be visualized.

A full-color image forming apparatus generally includes four color developing units 1401 to 1404 for supplying yellow, magenta, cyan and black toners, respectively. The full-color image forming apparatus described here synthesizes a toner image on a belt that is an intermediate transfer member.
The electrostatic latent image on the photosensitive drum 11 is visualized for a single color toner.

First, toner of a first color (yellow) is applied to the photosensitive drum 11 from a first developing device 1401 in accordance with an electrostatic latent image. At this time, the second to fourth developing devices 1402 to 14
04 is off, the visual image of the first color reaches the transfer nip between the belt 1 as the intermediate transfer member and the photosensitive drum 11 without being affected by the second to fourth developing devices 1402 to 1404, The toner image of the first color is formed on the belt 1 by an electric field formed in the transfer nip area by a voltage having a polarity opposite to that of the toner of the first color applied to the conductive roller 1501 in contact with the back surface of the belt 1. Is transferred intermediately.

The surface of the photosensitive drum 11 on which the transfer of the first color toner image has been completed is cleaned by the drum cleaning device 16, and then the image forming process for the second color (magenta) is started. In the process of the second color, only the second developing device 1402 is operated, and the other developing devices 1401, 1403, and 1404 are turned off.
A color toner image is intermediately transferred onto the belt 1.

[0007] Intermediate transfer of a third color (cyan) and a fourth color (black) is sequentially performed on the belt 1.
A color superimposed color image is formed. During this time,
The cleaning device 1503 for the belt 1 has been released,
The image on the belt 1 is not disturbed.

Next, the recording material P is set to 1
The sheet is taken out and inserted into the transfer nip area. At this time, a voltage having a polarity opposite to that of the toner is applied to the conductive roller 1502, and the toners of the first to fourth colors are transferred from the belt 1 to the recording material P.

The recording material P on which an unfixed color image has passed the transfer nip area reaches the fixing device 17 and is heated and pressed to obtain a permanent fixed image. The cleaning device 1503 operates to clean the surface of the belt 1 on which the toner images of the first to fourth colors have been transferred onto the recording material P.

As the belt 1 as an intermediate transfer material, it is known to use a dielectric film such as polyester, polyethylene, nylon, or the like, or to use a two-layer film with a conductor lined on the back surface. Also, an intermediate transfer drum in which a dielectric material is coated on a core metal such as aluminum as an intermediate transfer member has been devised.

However, the apparatus using the above-mentioned intermediate transfer member has the following disadvantages.

Since the belt-shaped intermediate transfer member needs to be given a certain tension in order to rotate smoothly, the dielectric layer as a base material is elongated by long-term use, and the accuracy of image formation is reduced. In addition, it may cause color misregistration. Although the permanent elongation described above is reduced by using male rubber or the like for the belt, the toner image on the belt may be disturbed and the image may be scattered because the image forming operation is performed while constantly expanding and contracting. When the thickness of the base material is increased to reduce the elongation, the shrinkage of the surface increases with the change in the curvature, and the scattering also worsens. When resin or elastic material is used for the base material of the belt,
Belt shift occurs with rotation, belt wrinkles,
Problems such as poor rotation have occurred.

In the case of a drum-shaped intermediate transfer body, the above problem is reduced, but it is necessary to carry at least one recording paper image. Therefore, there is a problem that the diameter of the drum is increased and the size of the apparatus is increased as a result.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an intermediate transfer member for use in a smaller electrophotographic image forming apparatus capable of forming a high quality image with less color shift and scattering, and an electrophotographic image forming apparatus. It is to provide.

[0015]

SUMMARY OF THE INVENTION The present invention comprises a tubular rotary body having a variable curvature, and the tubular rotary body carries a charged powder image on its surface by being sequentially transferred with its own rotation. The charged powder image is transferred to the back surface of the tubular rotating body or the surface of the tubular rotating body by a potential of a power supply member placed on the back surface, and is applied to a base material of the tubular rotating body. The intermediate transfer member is characterized by using a metal belt.

In the above-described structure, the base material of the metal belt has an effect of reducing the expansion and contraction in the horizontal direction even when the thickness is reduced, and reducing the expansion and contraction of the surface in the portion where the curvature changes by reducing the thickness.

The intermediate transfer member of the present invention may have a nonmetallic resistance layer of 20 to 100 μm on the surface.

In the above structure, the resistance layer has an effect of adjusting the voltage and current at the transfer portion while suppressing expansion and contraction of the surface when the curvature changes.

In the intermediate transfer member of the present invention, in addition to the above-described structure of the present invention, nickel electroforming of 20 to 60 μm can be used as a base material.
It may have a non-metallic resistance layer of １００100 μm.

In the above configuration, the nickel electroforming has an effect of easily forming the tubular rotating body and improving the processing accuracy.

Further, the intermediate transfer member of the present invention can use a tubular rotating body whose base material is a metal belt having different peripheral lengths at both ends in addition to the structure of the present invention. It is possible to use a nickel layer which has a resistance layer and the above-mentioned nickel electroforming.

In the above configuration, the tubular rotating body has a function of generating a shift force by generating a peripheral speed difference between both ends.

The present invention also provides an electrophotographic photosensitive member, an image forming means for forming a charged powder image on the electrophotographic photosensitive member, and a method for rotating the charged powder image formed on the electrophotographic photosensitive member by a plurality of rotations. An intermediate transfer member for carrying a composite transfer image formed by copying, a first voltage supply means for transferring the charged powder image onto the intermediate transfer member, and recording the composite transfer image on the intermediate transfer member The material is formed of a tubular rotating body having a variable curvature, and the tubular rotating body has a surface on which a charged powder image is sequentially transferred and carried along with its own rotation, and the charged powder image is A back surface of the tubular rotator or an intermediate transfer member using a metal belt as a base material of the tubular rotator, which is transferred to the surface of the tubular rotator by a potential of a power supply member placed on the back surface. It comprises an electrophotographic image forming apparatus characterized in that it is used. .

In the above arrangement, when the expansion and contraction in the horizontal direction with respect to the driving tension is small, the expansion and contraction of the surface is suppressed even in the portion where the curvature changes, and the potential potential for restraining the charged powder image on the surface of the intermediate transfer member is small. However, it has the effect of suppressing scattering and improving running stability with respect to rotational driving, and an electrophotographic image forming apparatus using this can realize high image quality, downsizing and long life of the apparatus.

The intermediate transfer member having the above construction is, of course,
The intermediate transfer member of the present invention is used.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described by way of examples.
This will be described in detail.

[0027]

【Example】

Embodiment 1 FIG. 1 shows a layer configuration of an intermediate transfer belt showing the features of the present invention.
FIG. 2 is a schematic sectional view of a full-color electrophotographic image forming apparatus using this belt.

The intermediate transfer belt 1 has a thickness of 30 μm
Nickel electroforming with a thickness of 20 μm
It is covered with a resistance layer 102 made of urethane resin having a thickness of m. The intermediate transfer belt 1 operates by being suspended by three rollers as shown in the image forming apparatus shown in FIG. 1
Reference numeral 501 denotes a medium resistance (in this example, when 1 KV is applied) for supplying a charge from the back surface of the intermediate transfer belt 1 when transferring the toner image on the photosensitive drum 11 onto the intermediate transfer belt 1 to form a transfer electric field. A voltage is applied to the metal core from a power supply (not shown) by a primary transfer roller composed of a conductive sponge having a real resistance of 10 ⁷ Ω in the nip formation.

As described above, since the intermediate transfer body needs to hold an image of at least one page of the recording paper, the circumference must be as long as the length of the maximum recording size. In this example, since the A4 size is set to the maximum size of the recording paper, the circumference of the intermediate transfer belt 1 needs to be about 300 mm. Actually, the base material 101 of the electroformed belt manufactured by using a cylindrical matrix having a diameter of 100 mm is used. Used. The base material 101 does not necessarily need to be a seamless belt made of nickel, and using a belt made of other circular pipe forming means using a metal such as aluminum or brass does not change the essence of the present invention. The electroforming method is used in the present example because it is easy to obtain a thin circular tube suitable for the present example in a small number of steps, and nickel is a metal suitable for the electroforming method.

The resistance layer 102 on the surface is formed by coating the base material 101 by a known technique such as a spray method or a dipping method. The resistance layer 102 is not limited to a urethane resin, but may be a fluororesin, a nylon resin, or the like, or a resistance material in which carbon or conductive powder is dispersed therein, such as 10 ⁶ to 10 ¹³ Ω in volume resistivity. Cm, it can be used by selecting an appropriate film thickness.

The thickness of the resistive layer 102 is important in determining the relationship between the transfer current and the applied voltage. When the thickness is large with a high volume resistivity, the transfer current cannot flow, and the transfer failure is likely to occur. Also, if the volume resistivity is low and the film thickness is reduced, the transfer voltage cannot be applied and the transfer efficiency is reduced. It is also important to select a transfer voltage within a range that does not cause insulation breakdown. In this example, the urethane resin used was 10 ¹² Ω · cm, the withstand voltage of 120 KV / mm, and the maximum voltage applied to the front and back of the intermediate transfer belt 1 was about 2 KV.

The toner image on the intermediate transfer member is different from that on the photoreceptor, and is not merely maintained by the potential potential on the surface, but is merely due to stacking. Therefore, the image is formed by mechanical external force such as vibration or bending. There is a problem that it is easily disturbed. In particular, this problem is remarkable when the intermediate transfer member is formed of a belt as in this example. When the thickness of the belt is increased, each time the curvature of the belt changes with rotation, the belt receives the above mechanical stress to reduce the image quality. It has been found that it worsens. On the other hand, when the thickness of the belt is reduced, the expansion and contraction of the belt itself is increased by the above-described drive tension, and the image quality is also deteriorated. As described above, the toner image on the belt is easily disturbed due to a small binding force due to the potential potential. Since the toner image is in a state different from the toner image on the photosensitive member, the base material is made of metal instead of resin. This produces a unique effect in the intermediate transfer member.

That is, in general, a metal base material has an elastic modulus 100 times or more larger than that of a resin base material. Even when the metal base material is thin, the elongation with respect to a tensile load can be suppressed extremely small. In the intermediate transfer belt having a large value, the mechanical stress applied to the toner image can be minimized, and the toner image not maintained by the potential potential on the surface is not disturbed.

Further, since the metal base material has a high tensile strength, permanent distortion hardly occurs even when used for a long time, and there is an advantage that driving stability is high and image accuracy can be maintained.

Further, the feature that the intermediate transfer belt using the metal base material has a small elastic deformation facilitates the shift control when performing the rotational drive. In other words, when a resin belt or a rubber belt is used, the elastic deformation of the resin belt itself is easy, so that wrinkles in the circumferential direction are apt to occur, and it is difficult to transmit the tension for deviation control, but a metal base material is used. Even if the belt is thin, the running of the entire belt can be adjusted by regulating a part of the belt because the rigidity is high even when the belt is thin.

The following is a comparative example that summarizes these features.

[Table 1] ○: good △: normal ×: bad

As is clear from Table 1, the intermediate transfer belt using the metal base material is excellent overall.
The items in Table 1 relate to a general belt and are an additional effect in the present invention, but are effects in the case of an image bearing member. This shows that the effect is obtained.

Embodiment 2 FIG. 3 is a sectional view of an intermediate transfer belt according to another embodiment of the present invention.

In this embodiment, a nickel base material 101 having a thickness of 30 μm is covered with a urethane rubber layer 103 of 50 μm, and a resistance layer 102 of a urethane resin layer, which is a medium resistance layer, is further coated with a thickness of 20 μm. .

In this construction, the base material 101 made of nickel regulates expansion and contraction in the plane direction. The urethane rubber layer 103 as the coating layer and the resistance layer 1 as the urethane resin layer are used.
As the thickness of 02 increases, the expansion and contraction of the surface at the point of curvature change increases. In such a case, scattering of the toner image may be observed in the belt-shaped intermediate transfer body. Therefore, it is preferable that the total thickness of the resistance layer 102 and the urethane rubber layer 103, which are the coating layers, be 100 μm or less.

The urethane rubber layer 103 has a function of improving the adhesion by providing elasticity to the contact between the intermediate transfer belt and the photosensitive drum or the contact between the intermediate transfer belt and the recording paper, thereby improving the transfer efficiency. In this example, since a metal base material is used,
An intermediate layer which can increase the strength in the plane direction and can provide an elastic layer thinly in a range not disturbing the toner image on the intermediate transfer belt to have elasticity in the thickness direction and rigidity in the plane direction. A transfer belt can be realized.

Embodiment 3 FIG. 4 is a schematic perspective view of an intermediate transfer unit showing another embodiment of the present invention.

The intermediate transfer belt 1 is formed by driving holes H having a diameter of 4 mm at intervals of 15 μm in the circumferential direction in the belt described in the first embodiment.
Driving projections provided on the flange 501 are engaged with the driving holes H. As described above, in the present embodiment, the intermediate transfer belt 1
Since nickel electroforming is used as a base material of the above, it is possible to form such a driving hole with extremely high precision.

In the present embodiment, the flange of the primary transfer roller 1501 is driven to rotate from the outside while being driven by the driving projection 1501B while being engaged with the driving hole H of the intermediate transfer belt 1.

When similar processing is performed on a belt made of a resin as a base material as in the related art, rotation accuracy and the like are likely to occur due to low accuracy. Due to the low tear strength, there was a problem that the drive hole was damaged when stress was applied.However, in this example, the above method enables stable drive and does not cause problems such as belt deviation or wrinkles. There is. In this example, drive holes H are provided at both ends.
However, when the thickness of the nickel electroformed base material is set to 40 μm or more, it may be provided on only one side and driven.

The drive hole is preferably circular or elliptical so that stress concentration does not occur. If the interval is too small, the strength of the belt decreases, and if it is too wide, the running becomes unstable, so the hole diameter is 2 to 5 mm. The distance is preferably about 5 to 15 mm depending on the hole diameter.

Embodiment 4 As still another embodiment of the present invention, an intermediate transfer belt in which the peripheral length of the metallic base material is different at both ends can be cited. The effect of this shape is that a difference in peripheral speed can be provided between both ends of the belt so that the direction of the belt can be shifted in one direction. In other words, when one of the peripheral lengths of the belt end is φ ₁ , the other is φ ₂ , and any position other than the longitudinal end of the belt is φ _X , by setting φ ₁ ≦ φ _X <φ ₂ , so it can be restricted to one direction deviation force is generated in a direction having a circumferential length of phi _1. The deviation force increases in accordance with the difference in the circumference, but if it is too large, the side plate may be rubbed against the side plate and may be damaged. In this example, one perimeter is 300 mm and the other perimeter is 30 mm.
By setting the distance to 1 mm, a moderate deviation regulating force could be obtained.

The nickel electroformed seamless belt can be manufactured by using a cylindrical matrix. The base material of the intermediate transfer belt according to the present embodiment uses a conical shape having a reduced diameter in one direction in the matrix. It can be easily manufactured in a similar process using a trapezoidal matrix. Furthermore, there is an advantage that, since the precision is higher and the elongation with respect to the driving tension is smaller than that of resin, rubber, or the like, the biasing force can be kept constant, and problems such as meandering and wrinkling do not occur.

[0049]

According to the intermediate transfer member of the present invention, the expansion and contraction in the horizontal direction with respect to the drive tension is reduced, and the expansion and contraction of the surface is suppressed even in the portion where the curvature changes, and the charged powder image on the surface of the intermediate transfer member is suppressed. Has the effect of suppressing scattering even when the potential potential constraining is small and improving the running stability with respect to rotational driving. With an electrophotographic image forming apparatus using this, it is possible to improve image quality and reduce the size of the apparatus. This has a remarkable effect that a longer life can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a layer configuration of an intermediate transfer belt used in Embodiment 1 of the present invention.

FIG. 2 is a schematic sectional view of a full-color electrophotographic image forming apparatus using an intermediate transfer belt used in Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a layer configuration of an intermediate transfer belt used in Embodiment 2 of the present invention.

FIG. 4 is a schematic perspective view of an intermediate transfer unit used in Embodiment 3 of the present invention.

FIG. 5 is a schematic sectional view of an electrophotographic image forming apparatus using an intermediate transfer belt in a conventional example.

[Explanation of symbols]

1: Intermediate transfer belt 101: Base material 102: Resistive layer 103: Urethane rubber layer 11: Photosensitive drum 12: Primary charger 13: Scanner 14: Developing device, developing device 1401: First developing device 1402: Second developing device 1403: Third developing device 1404: Fourth developing device 1501: Primary transfer roller 1501B: Driving projection provided on a flange of primary transfer roller 1501 1502: Conductive roller 1503: Cleaning device 1504: Tension roller Roller 1505: Secondary transfer facing roller 16: Drum cleaning device 17: Fixing device H: Drive hole P: Recording material

Claims (8)

[Claims] 1. A tubular rotating body having a variable curvature, the tubular rotating body carrying a charged powder image sequentially transferred on its surface with its own rotation, and carrying the charged powder image. The image is transferred to the back surface of the tubular rotating body or the surface of the tubular rotating body by a potential of a power supply member placed on the back surface, and a metal belt is used as a base material of the tubular rotating body. Characteristic intermediate transfer member. 2. The intermediate transfer member according to claim 1, which has a nonmetallic resistance layer of 20 to 100 μm on the surface. 3. The intermediate transfer member according to claim 1, wherein a nickel electroforming of 20 to 60 μm is used as a base material. 4. The intermediate transfer member according to claim 1, wherein a tubular rotator having metal belts having different peripheral lengths at both ends as a base material is used. 5. An electrophotographic photosensitive member, image forming means for forming a charged powder image on the electrophotographic photosensitive member, and transferring the charged powder image formed on the electrophotographic photosensitive member a plurality of times. An intermediate transfer member carrying the synthetic transfer image formed by the first transfer device, a first voltage supply means for transferring the charged powder image onto the intermediate transfer member, and a synthetic transfer image on the intermediate transfer member as a recording material. A tubular rotating body having a variable curvature, the tubular rotating body having a charged powder image sequentially transferred and carried on its surface along with its own rotation, and the charged powder image is formed by the tubular rotating body. The intermediate transfer body using a metal belt as a base material of the tubular rotating body, which is transferred to the surface of the tubular rotating body by the potential of a power supply member placed on the back side of the body or the back side. An electrophotographic image forming apparatus. 6. The electrophotographic image forming apparatus according to claim 5, wherein an intermediate transfer member having a nonmetallic resistance layer of 20 to 100 μm on its surface is used. 7. The electrophotographic image forming apparatus according to claim 5, wherein an intermediate transfer member using nickel electroforming of 20 to 60 μm as a base material is used. 8. An intermediate transfer body using a tubular rotating body whose base material is a metal belt having different peripheral lengths at both ends.
8. The electrophotographic image forming apparatus according to 6 or 7.