JPH09127806A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably carry a transfer material after being separated from an image carrier and to prevent 'tailing edge curling', irregularities in an image caused by the fact and the generation of a drop of water caused by a failure in removement of static charge by arranging an electrostatic attracting means and a static charge removing member in a transfer material carrying path on the downstream side in the carrying direction of the transfer material from a transfer part, in order. SOLUTION: The image forming device is provided with the electrostatic attracting member 23, the destaticization member 14 and an electrostatic attracting/carrying member 24 in order in the carrying direction of the transfer material, on the transfer material exit side of a transfer nip part N. In order words, the electrostatic attracting member 23 is interposed between the transfer part N and the destaticization member 14, so that the part of the transfer material after passing through the transfer part N is forcibly separated from the surface of the image carrier 1 by the member 23, 'the curling of the tailing edge part' of the transfer material after passing through the transfer part is prevented by attracting force of the member 23 and the irregularities in the image due to the curling of the tailing edge' can be prevented as well. Since the static charge of the transfer material part is removed by the charge removing member 14 just behind the member 23, the irregularities in the image such as 'the drop of water' due to the approaching of the transfer material which carries an excessive transfer charge, because of the failure in he destaticization, to a low resistance member in the carrying path can be prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member.
Forming and carrying a transferable image of desired image information by applying an appropriate image forming process such as electrophotographic process, electrostatic recording process, magnetic recording process to image carrier such as electrostatic recording dielectric / magnetic recording magnetic substance The present invention relates to an image forming apparatus such as a copier or a printer of an electrostatic transfer system in which the transferable image is transferred onto the surface of a transfer material by a transfer member to which a back surface of the transfer material is contacted and a voltage is applied.

[0002]

2. Description of the Related Art Conventionally, in an electrostatic transfer type image forming apparatus, as a transfer means for transferring a transferable image from an image carrier to a transfer material, a corona discharge transfer type using a corona discharger, a transfer roller There is also a roller transfer system using.

In the corona discharge transfer system, a corona discharge device is disposed so as to face an image carrier, and a transfer material is introduced and conveyed between the image carrier and the corona discharge device so that the back surface of the transfer material is corona-charged. The transferable image on the side of the image carrier is electrostatically transferred to the surface side of the transfer material by exposing the transferable image on the side of the image carrier to the opposite polarity to the charge polarity of the transferable image on the side of the image carrier.

In the roller transfer system, the transfer roller is brought into contact with the image carrier, and the transfer material is introduced into the contact nip portion to be nipped and conveyed, and a transfer bias is applied to the transfer roller to apply the transfer bias to the image carrier. The transferable image is electrostatically transferred to the surface of the transfer material.

FIG. 16 shows a schematic view of a roller transfer type transfer means.

Reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member, which is indicated by an arrow R.
It is rotationally driven in the clockwise direction of 1 at a predetermined peripheral speed (process speed). As a transferable image of desired image information on an image forming process device (not shown) on the surface of the photosensitive drum,
In this example, a toner image having a negative charging polarity is formed.

Reference numeral 6 denotes a transfer roller, which comprises a cored bar 6a and a medium resistance layer 6b integrally formed on the outer periphery of the cored bar and abutted against the photosensitive drum 1 with a predetermined pressing force to form a transfer nip portion N. The photosensitive drum 1 rotates in the forward direction.

Reference numeral 26 is a high voltage power source for transfer.
A transfer bias is applied from 6 to the core metal 6 a of the transfer roller 6.

In the process in which the transfer material P is introduced into the transfer nip portion N, and the nip portion is nipped and conveyed,
A positive voltage of 1 to 10 kV is applied to the transfer roller 6,
As a result, a positive charge is given to the transfer material portion passing through the transfer nip portion N, and the photosensitive drum 1 is transferred to the transfer nip portion N.
The upper toner image is transferred and transferred to the surface side of the transfer material P by electrostatic attraction. The portion of the transfer material that has passed through the transfer nip portion N is separated from the surface of the photosensitive drum 1 and is conveyed and introduced into an image fixing unit (not shown).

This roller transfer type transfer means produces a significantly smaller amount of undesirable ozone than the corona discharge type transfer means.

A transfer bias V _T necessary for transferring a toner image is applied to the transfer roller 6 via a core metal 6a by a power source 26, and a transfer nip portion N between the photosensitive drum 1 and the transfer roller 6 is formed. The toner image on the photosensitive drum 1 is transferred onto the transfer material P by applying an electric charge to the transfer material P passing therethrough, and after the transfer, the voltage applied to the transfer roller 6 is controlled by the low voltage control so that the transfer weak bias _VL is applied. By switching to (OFF or a weak bias lower than the transfer bias),
Drum memory and paper marks are prevented during non-transfer.

A transfer material P passing through the transfer nip portion N
The so-called curvature separation method utilizing the curvature of the photosensitive drum 1 is often used for the separation from the surface of the photosensitive drum 1. In the curvature separation method, since it is not necessary to apply a separation bias or the like, the device configuration can be easily simplified, and the cost can be further reduced. In the case of the curvature separation method, a charge elimination needle 14 is disposed immediately after the transfer material outlet side of the transfer nip portion N as a separation assisting means to remove excess transfer charge, thereby smoothing the separation, and a charge of 60 g / m ² or less. Even thin transfer materials can be separated.

[0013]

[Problems to be solved by the invention]

(1) In the image forming apparatus adopting the conventional curvature separation method, so-called “rear end bounce” occurs when the rear end of the transfer material P passes through the transfer nip portion N, and an unfixed image is formed inside the device. There is a possibility that an edge of the transfer material P may be touched by an object, and the trailing edge of the transfer material P may be smeared or the image of the trailing edge may be rubbed.

When the trailing edge bounces, the trailing edge of the transfer material becomes far from the neutralizing needle 14, so that sufficient charge removal is not performed, and excessive transfer charge at the trailing edge of the transfer material causes a low resistance between transfer and fixing. There is a possibility that an abnormal image called "polka dots" may occur in which the toner is discharged in a circular shape by discharging the toner to the conveying member.

As shown in FIG. 17, the above-mentioned trailing edge bounce is caused by the transfer material P
After the trailing edge P2 passes through the transfer nip portion N, the trailing edge P2 is not separated from the photosensitive drum 1 by the electrostatic attraction force of the photosensitive drum 1 and is attracted and moved in the rotation direction R1 of the photosensitive drum 1 and jumped up as shown by an arrow f. It occurs because it ends up. Reference numeral 13 is a fixing device.

Further, in order to prevent the trailing edge bouncing, in the conventional image forming apparatus, the trailing edge P2 of the transfer material P passes through the transfer nip portion N as shown in FIGS. Immediately before the end, the applied bias to the transfer roller 6 is changed from the transfer bias V _T for transferring the toner image, which has been applied until then, to the bias V _{N having the} opposite polarity.
By applying the voltage under constant voltage control after switching to, the photosensitive drum 1 is moved from the rear end P2 of the transfer material P to the rear end of the transfer material in the non-image area of the transfer material P after passing through the transfer nip portion N.
A method for forcibly separating from the surface by electrostatic repulsive force a is proposed in Japanese Patent Laid-Open No. 05-224541. Reference numeral t is a toner image in the image area transferred from the photosensitive drum 1 side to the transfer material P side.

However, in the method of applying the reverse bias V _N to the rear end portion of the transfer material, for example, when the transfer material P left for a long time in a high humidity environment of 80% or more in humidity is used, the transfer material on the first surface is used. Therefore, when a reverse bias is applied to the trailing edge of the first surface, a charge having a polarity opposite to the toner holding charge is applied to the entire surface of the transfer material P whose resistance has been reduced, and the toner of the transfer material P is applied. The holding force is reduced and electrostatic offset occurs.

The reverse bias V _N is applied at the transfer material P by a resist sensor (not shown) disposed in the transfer material conveying path upstream of the transfer nip portion N in the transfer material conveying direction.
The time at which the rear end of the transfer material P arrives at the transfer nip portion N is calculated from the time when the rear end passes, the distance between the registration sensor and the transfer nip portion N, and the transfer material conveyance speed, and the application timing is calculated. Although it has been decided, there is some variation in the distance between the registration sensor and the transfer nip portion N due to machine differences, and the transfer material transport speed is slightly affected by the transfer roller outer diameter, paper type, printing ratio, etc. Therefore, when these variations are summed up, the application point of the reverse bias may deviate by several mm from the target. Therefore, when the reverse bias application point is displaced from the rear end of the transfer material, a sufficient effect cannot be obtained, and conversely, when the reverse bias is displaced from the inner side of the transfer material, image disturbance occurs at the rear end of the transfer material. I was afraid.

(2) In the conventional roller transfer system, the transfer bias is applied from the core metal 6a of the transfer roller 6 to the sponge portion 6b of medium resistance to supply the transfer charge onto the transfer material P. In this case, since the electric field on the transfer roller surface is uniform, the toner image formed on the photosensitive drum 1 is transferred onto the transfer roller 6 even at a position (front position) before the transfer nip portion N where the photosensitive drum 1 and the transfer roller 6 contact each other. The force that pulls the toner to the side works, and the toner flies toward the transfer roller, so that a so-called “scattering” image occurs in which the toner is scattered around the character without faithful transfer.

Therefore, in the conventional image forming apparatus, a guide member for bringing the transfer material P into close contact with the photosensitive drum 1 at a position before the transfer nip N is provided, and the transfer material P is fixed before the transfer electric field is affected. For example, it makes contact with the toner image above to prevent scattering.

However, the conventional guide member is the photosensitive drum 1.
However, there is a problem in that, when the surface of the transfer material is brought close to the surface of the transfer material, dirt such as toner or paper powder adheres to the surface of the transfer material.

The present invention eliminates the above-mentioned problems in the transfer type image forming apparatus, that is, "transfers the transfer material after separation from the image carrier stably" to cause "rear end bounce".
"Dot" due to image distortion caused by it and poor charge removal
To prevent "scattering" by eliminating the influence of the transfer electric field on the upstream side of the transfer nip portion, and to prevent back stain on the transfer material.

[0023]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) In an image forming apparatus in which a transferable image formed and carried on an image carrier is transferred to a surface of a transfer material by a transfer member to which a back surface of the transfer material is contacted and a voltage is applied, An image forming apparatus characterized in that an electrostatic attraction member and a charge eliminating member are sequentially arranged in a transfer material conveying path on the downstream side in the transfer material conveying direction.

(2) In an image forming apparatus in which a transferable image formed and carried by an image carrier is transferred to a surface of a transfer material by a transfer member to which a back surface of the transfer material is contacted and a voltage is applied, An image forming apparatus characterized in that an electrostatic attraction member, a charge eliminating member, and an electrostatic attraction transport member are sequentially arranged in a transfer material transport path on the downstream side in the transfer material transport direction.

(3) The image forming apparatus according to (2), characterized in that the electrostatic attraction transfer member is a transfer material transfer belt in which high resistance rubber is formed on the inner and outer surfaces of a grounded metal thin belt.

(4) In an image forming apparatus in which a transferable image formed and carried on an image carrier is transferred to the front surface of a transfer material by a transfer roller to which a back surface of the transfer material is contacted and a voltage is applied,
An outer peripheral electrode that abuts on an outer peripheral surface of the transfer roller on the downstream side in the transfer material conveyance direction, and a voltage applying unit that applies a voltage to the outer peripheral electrode, and supply a transfer charge to the transfer roller via the outer peripheral electrode. An image forming apparatus characterized by.

(5) The image forming apparatus according to (4), wherein the outer peripheral electrode is a conductive roller member, and the outer peripheral electrode roller drives the outer periphery of the transfer roller.

(6) In an image forming apparatus in which a transferable image formed and carried on an image carrier is transferred to a surface of a transfer material by a transfer roller to which a back surface of the transfer material is contacted and a voltage is applied,
An image forming apparatus comprising: a transfer material guide rotating body that is in contact with a transfer roller and rotationally drives the transfer roller in a forward direction.

(7) When a bias having a polarity opposite to that of the transfer bias is applied to the transfer roller, the bias having the same potential as that of the transfer roller is applied to the transfer material guide rotating body. Image forming device.

(8) The image forming apparatus according to (6), wherein the transfer material guide rotating body is a rotating body in which a release layer having a surface energy smaller than that of the transfer roller is formed on the surface of the insulating base material. apparatus.

<Operation> A) An image forming apparatus adopting a curvature separation system in which the transfer material that has passed through the transfer portion is separated from the image carrier by the curvature of the image carrier and the separation by the charge eliminating member. In this configuration, the electrostatic attraction member and the static eliminator are sequentially arranged in the transfer material conveying path on the downstream side of the transfer portion in the transfer material conveying direction. Are sequentially separated by the curvature of the image carrier and the assistance of the static eliminating member. In this case, since the electrostatic attraction member is present between the transfer portion and the static elimination member, the transfer is performed by this electrostatic attraction member. The portion of the transfer material that has passed through the portion is forcibly separated from the surface of the image carrier, and the trailing edge of the transfer material that has exited the transfer portion is also prevented from "rear end bounce" by the attractive force of this electrostatic attraction member. Image distortion due to splashing is prevented.

The portion of the transfer material separated from the image carrier through the transfer portion is neutralized by the static elimination member immediately after the electrostatic attraction member, so that the transfer material holding the excessive transfer charge due to poor static elimination is conveyed. The image disturbance such as "polka dots" that occurs when the image is near the low resistance member is prevented.

Further, an electrostatic adsorption conveyance member is arranged next to the above-mentioned static elimination member, that is, a range in which there is a member for electrostatic adsorption of the transfer material on the printing surface side downstream of the static elimination member in the transfer material conveyance direction. By disposing an electrostatic attraction transport member that has a stronger electrostatic attraction force than the printing surface side member on the entire area of the non-printing surface side, the image disturbance caused by the transfer material printing surface rubbing against the structural material in the transport path Can be prevented.

B) In the image forming apparatus adopting the roller transfer system for supplying the transfer charge to the transfer roller which is in contact with the image carrier, the power is supplied to the transfer roller by the outer periphery of the transfer roller on the downstream side in the transfer material conveying direction. By doing so, it is possible to eliminate the influence of the transfer electric field on the upstream side of the transfer material in the transfer section and prevent the scattering.

Further, at least in front of the transfer portion, a transfer material guide rotating body (roller) which is in contact with the transfer roller and rotates in the forward direction with the transfer roller is provided, and the transfer material is guided by the rotating body to the image carrier. By transporting incident light to prevent scattering, and by transferring dirt on the surface of the rotating body for the transfer material guide to the transfer roller and cleaning via the image carrier,
It is possible to obtain an image-formed product with no stain on the back.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 4) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus of this example is a laser beam printer that uses an electrostatic transfer type electrophotographic process and has a process cartridge removable type.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (photosensitive drum) as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow R1 at a predetermined peripheral speed (process speed).

Reference numeral 2 is a charging roller as a primary charging device that uniformly charges the peripheral surface of the photosensitive drum 1 to a predetermined polarity and potential. In this example, the charging process is performed to about -600 V (dark area potential V _D ).

Reference numeral 3 denotes a laser scanner as an image exposing means, which outputs a laser beam modulated corresponding to a time series electric digital pixel signal of target image information to scan and expose the surface of the rotary photosensitive drum. As a result, an electrostatic latent image of desired image information is formed on the surface of the rotary photosensitive drum 1.

A reversal developing device 5 develops the electrostatic latent image formed on the surface of the rotating photosensitive drum 1 with negative toner (negative toner) (toner adheres to the exposed bright portion of the electrostatic latent image). A thin layer of toner is coated on the sleeve 5a rotatably attached to the developing device 5, and the toner is negatively charged. The sleeve 5a bias voltage V _B between the dark portion potential V _D of the photosensitive drum 1 and the exposure light potential V _L (|
(V _D |> | V _B |> | V _L |) is supplied by an external power source (not shown), the toner on the sleeve 5 a is transferred only to the portion of the photosensitive drum 1 at the exposure bright portion potential V _L. The electrostatic latent image is visualized.

Reference numeral 6 denotes a transfer roller as a transfer member which is brought into contact with the photosensitive drum 1. The transfer roller 6 is composed of a core metal 6a and a sponge layer 6b of a medium resistance formed concentrically and integrally on the outer periphery of the core metal 6a. The transfer nip portion N is formed by abutting with a pressing force, and the photosensitive drum 1 rotates in the forward direction. 26 is a high voltage power source for transfer.
A transfer bias is applied to the core metal 6a of the transfer roller 6 from the above.

Reference numeral 22 denotes a paper cassette, and the paper feed roller 21 is driven by a paper feed start signal, the transfer material P in the paper cassette 22 is fed out one by one, and the paper is fed into the printer A1. 21a, skew feed roller pair 1
7, registration roller pair 11, registration sensor 11a,
Paper is fed to the transfer nip portion N through the path of the transfer guide 10 at a predetermined control timing.

A positive voltage of 1 to 10 kV is applied to the transfer roller 6 in the process of introducing the transfer material P into the transfer nip portion N and nipping and transporting the transfer material nip portion. A positive charge is applied to the transfer material portion, and the toner image on the photosensitive drum 1 is transferred and transferred to the surface side of the transfer material P by electrostatic attraction at the transfer nip portion N.

The portion of the transfer material that has passed through the transfer nip portion N is separated from the surface of the photosensitive drum 1 and is conveyed to the fixing device 13 via the conveying guide 12, and the toner image is fixed by the fixing device 13 to form an image-formed product (print). , Copy) is discharged and conveyed B1.

After the toner image is transferred onto the transfer material P, the surface of the photosensitive drum 1 is subjected to removal of residual toner by the cleaning device 7 and is repeatedly used for image formation.

In the printer of this example, a photosensitive drum 1, a charging roller 2, a developing device 5, and a cleaning device 7 are collectively constituted as a process cartridge 30 which is attachable to and detachable from the printer body.

(2) Electrostatic attracting member / static eliminating member / electrostatic attracting / conveying member As shown in FIGS. 2 and 3, the conveying guide 12 is sequentially arranged in the transfer material conveying direction at the transfer material outlet side of the transfer nip N. Electrostatic attracting member (transfer material attracting member) 23, static eliminating member (static eliminating needle)
14. An electrostatic adsorption transfer member (transfer sheet metal member) 24 is provided.

Transfer material attracting member 23 as an electrostatic attracting member
Is arranged in the vicinity of the transfer material outlet side of the transfer nip portion N, the charge elimination needle 14 as a charge eliminating member is arranged immediately next to the transfer material attracting member 23, and the carrying sheet metal member 24 as an electrostatic attraction carrying member is neutralized. It is arranged next to the needle 14.

The transfer material attracting member 23 is for forcibly separating from the photosensitive drum 1 by attracting the transfer material portion immediately after passing through the transfer nip portion N with an electrostatic attraction force. For example, A1 and SUS. A member made of a metal conductive material is arranged over the entire sheet passing area between the transfer roller 6 and the charge elimination needle 14, and the potential thereof is grounded or a voltage having a polarity opposite to that of the transfer bias is applied.

The transport sheet metal member 24 attracts the transfer material after the transfer separation from the non-printing surface to the lower side of the transport path by electrostatic attraction to stably transport the transfer material. It is arranged on the entire downstream side of the sheet passing width facing the surface on which the structural material for electrostatically adsorbing the transfer material such as CRG is located on the transfer material printing surface side, and the potential is grounded or has a polarity opposite to the transfer bias. Is applied. An abnormality that occurs on the surface of the transfer sheet metal member 24 facing the transfer material, which reduces transfer resistance of the transfer material, and causes transfer charge to leak or discharge due to direct contact or proximity of the transfer path attracting member with low resistance. In order to prevent an image, a conveyance rib 25 made of a high resistance resin material such as PC (polycarbonate) or ABS resin is provided.

Before and after the static elimination needle 14, openings are provided so that the electric field is easily concentrated from the transfer material P to the static elimination needle.

Transfer material P nipped and conveyed at the transfer nip portion N
After passing through the transfer nip N while holding the transfer charge, is attracted in the direction C1 (FIG. 2) of the transfer material adsorbing member 23 by the electrostatic adsorbing force of the transfer material adsorbing member 23, and is forced from the photosensitive drum 1. To be separated.

The transfer material attracting member 23 is arranged on the surface of the photosensitive drum facing the photosensitive drum 1 with respect to the tangent line of the photosensitive drum 1-transfer roller 6 (any place within the area A surrounded by the diagonal lines in FIG. 4). By arranging in such a position, a sufficient "rear end bounce" prevention effect is obtained, and at the same time, the transfer material P
Does not directly contact the transfer material attracting member 23,
The image distortion caused thereby can be avoided.

When a transfer material holding an excessive transfer charge approaches a peripheral member in the conveyance path, image disturbance tends to occur due to abnormal discharge or abnormal charging of the peripheral member. A static elimination needle 14 is arranged immediately after the member 23 to eliminate excessive electric charges almost at the same time as the transfer material comes close to the conveyance path surface, so that a good image without image disturbance can be obtained.

Further, when there is a member for electrostatically adsorbing the printing surface side of the transfer material in the transfer material conveying path on the downstream side of the charge removal needle 14, the transfer material adsorbing member 23 forcibly separates it from the photosensitive drum. Even with the transfer material, after the charge is removed, the print surface side is rubbed against the peripheral member and conveyed, so that the image is deformed. Further, when the transfer material printing surface side is electrostatically adsorbed by the peripheral member and conveyed, the transfer material P is in a direction away from the transfer material adsorbing member 23, so that the electrostatic adsorbing force of the adsorbing member weakens and the transfer material P is transferred again to the photosensitive drum 1. A re-adsorption phenomenon occurs in which the material is adsorbed. Further, since the transfer material is away from the charge removal needle 14, there is a possibility that charge removal failure may occur and an abnormal image due to charging or discharging may occur, but there is a member that electrostatically attracts the printing surface as in this example. By providing the conveying sheet metal member 24 having a stronger electrostatic attraction force over the entire area to be protected, it is possible to prevent the occurrence of an abnormal image due to the rubbing of the image, the trailing edge bouncing due to the re-adhesion to the photosensitive drum, and the lack of charge removal.

(3) Execution Example a) Transfer material P 64 g / m ² , thickness 90 μm, A4 size (paper grain is parallel to the conveying direction), process speed 100 mm /
It was transported in sec.

B) Transfer roller 6 outer diameter: φ18.0 (conductive EPDM layer 6b on core metal 6a of φ6) Resistance value: 8.0 × 10 ⁸ [Ω] (temperature 23 ° C., humidity 6
(Measured value when 2.0 kV is applied under 0% environment) The strong transfer bias V _T when this transfer roller is used is V _T = 3.2 kV in an environment of temperature 23 ° C. and humidity 60%.
Met.

[0059] c) the photosensitive drum 1 material and outer diameter: OPC, 0 30 image portion potential V _L: -100 V non-image portion potential V _D: at -600V above conditions, while grounding the transfer material adsorbing member 23,
Occurrence frequency (experimental example 1) of abnormal images (rear edge edge stains, image rubs, and rear edge polka dots) due to "rear edge bounce" when the first and second sides are printed, and the transfer material adsorbing member Table 1 shows the frequency of occurrence of the above-mentioned image problem (Experimental Example 2) when a bias of -300 V was applied to No. 23. As a comparative example, the occurrence frequency when the transfer material attracting member 23 is not provided (Comparative Example 1) and when the transport sheet metal member 24 is not provided (Comparative Example 2) is also shown.

The experiment was carried out in a low humidity environment (humidity 10% RH) where trailing edge bounce is likely to occur, and shows the number of abnormal images generated during continuous printing of 100 sheets.

[0061]

[Table 1] In Comparative Example 1, since there is no force to forcibly separate the transfer material P from the photosensitive drum 1 immediately after the transfer, trailing edge bounce occurs and trailing edge dirt, image rubbing, and polka dots have a particularly high resistance value of the transfer material P. It occurs frequently on the second side.

On the other hand, in both Experimental Example 1 and Experimental Example 2 according to the present invention, the trailing edge bounce is not likely to occur even in the second-side printing in which the trailing edge bounce is likely to occur, and the trailing edge edge stain caused by the trailing edge bounce and It was confirmed that abnormal images such as edge image rubbing and trailing edge polka dots did not occur at all.

Further, in Comparative Example 2, since the conveying sheet metal member 24 is removed, the force for pulling the transfer material P downward is eliminated between the transfer and the fixing, and the transfer material P is floated and conveyed. The printing surface side holding the unfixed image is rubbed against the surface side member (bottom part of the cartridge 30 in FIG. 1), and the transfer material is again attracted to the photosensitive drum to cause the trailing edge bounce and the image is disturbed. doing. In this case, the image distortion occurs not only on the rear edge but on the entire surface.

As described above, according to this embodiment, the transfer material attracting member 23 and the discharging needle 14 are provided immediately after the transfer nip portion N, so that the trailing edge bounce and the trailing edge image rubbing caused by the trailing edge bounce, It is possible to prevent the occurrence of image problems such as water drops, and by providing the transport sheet metal member 24 on the downstream side of the static elimination needle, the print surface side is rubbed by the member in the transport path and the transfer material is exposed to light. It is also possible to prevent an abnormal image due to a trailing edge bouncing due to re-adsorption on the drum and a defective charge removal.

<Embodiment 2> (FIGS. 5 and 6) This embodiment is an example in which the present invention is applied to an image forming apparatus having a transfer material conveying mechanism using a belt after transfer, and conveys in order to reduce the number of parts. In this example, the belt has the same effect as that of the transport sheet metal member (electrostatic adsorption transport member).

FIG. 5 is a schematic view of the configuration example, and the same reference numerals are given to the component parts common to the device of the first embodiment and the repetitive description will be omitted.

Reference numeral 51 is a conveyor belt for conveying a small-sized transfer material, which is shorter than the distance between transfer and fixing. As shown in the side view of FIG. 6A and the plan view of FIG. 6B, the conveyor belt 51 has a conductive adsorption layer 51b made of a thin metal E
It is a belt sanded with a base rubber base layer 1a made of a rubber material such as PDM and ribs 51c, and is a drive roller pair 52.
It is rotationally driven in the downstream side D1 direction at substantially the same speed as the process speed by a.52b. Conductive adsorption layer 51
b is grounded or a voltage having a polarity opposite to the transfer bias is applied. Other configurations are similar to those of the first embodiment, and the transfer material adsorbing member 23 and the charge eliminating needle 14 are arranged immediately after the transfer nip portion N.

The transfer material P that has passed through the transfer nip portion N is forcibly separated from the photosensitive drum 1 by the transfer material adsorbing member 23 as in the first embodiment, and the excess transfer charge is removed by the charge removing needle 14. , The adsorption layer 51 of the conveyor belt 51
It is conveyed along the conveyor belt 51 by the suction force of b.

As described above, by providing at least one suction layer 51b on the transfer belt 51 after transfer, the same effect as the case where the transfer sheet metal member 24 of Embodiment 1 is provided can be obtained, and the rear end bounce can be prevented. It becomes possible to do.

<Embodiment 3> (FIGS. 7 and 8) In this embodiment, the transfer bias is supplied to the transfer roller 6 from the downstream side of the transfer roller to eliminate the transfer electric field on the upstream side of the transfer roller and scatter. That is, a good image is obtained.

The transfer roller 7 is formed by disposing carbon or the like on the core material 6a and forming an EPDM rubber layer 6b whose resistance is adjusted, and having a resistance value of about 5 × 10 ^{7 to} 5 × 10 ⁹ Ω ( Resistance value when a voltage of 2 kV is applied after being left in an environment of room temperature of 23 ° C and humidity of 60% RH for 48 hours)
Is suitable. As the core material 6a of the transfer roller 6, a metal cored bar is used as a float, or a shaft made of an insulating material such as ceramic or resin is used.

An outer peripheral electrode 71 made of a conductive brush or a metal plate is in contact with the entire outer periphery of the sheet passing area on the outer periphery of the transfer roller 6 on the downstream side. Transfer charge is supplied to N.

FIG. 8 schematically shows the state of the electric field in the vicinity of the transfer nip portion N.

The transfer charges supplied from the outer peripheral electrode 71 to the photosensitive drum 1 flow in the direction E1 from the surface where the outer peripheral electrode 71 contacts the transfer roller 6 to the surface where the transfer roller 6 contacts the photosensitive drum 1. Since the transfer charge does not flow to the upstream side of the transfer nip portion N, an electric field is prevented from being generated on the upstream side of the transfer nip portion N. It is possible to prevent the occurrence of a “scattered” image in which the toner image is pre-transferred and scattered around the characters.

The same transfer material P as in the execution example of the first embodiment,
The transfer roller 6 and the photosensitive drum 1 are used, the transfer bias is controlled at a constant current of 2.0 μA, and the printing environment is room temperature 23 °.
Under a condition of C / humidity of 60% RH, a transfer bias is applied to the outer periphery of the transfer downstream side using a brush electrode 71 (Experimental Example 3) and a transfer bias is applied from the transfer roller core metal 6a (Comparative Example 3). As a result of comparison of the splattering levels of No. 3, it was confirmed that the splattering was Δ level in Comparative Example 3, whereas the splattering was improved to ◯ level in Experimental Example 3.

<Embodiment 4> (FIGS. 9 and 10) In the present embodiment, the transfer bias is supplied to the transfer roller 6 via a roller-shaped electrode provided on the downstream side of the transfer roller.
By eliminating the transfer electric field on the upstream side of the transfer roller to obtain a good image without scattering and by driving the transfer roller to the outer circumference by using the roller-shaped electrode, a stable image is provided for a long term use.

Reference numeral 91 is an electrode roller provided on the outer circumference on the downstream side of the transfer roller. Power is supplied to the transfer roller 6 by the electrode roller 9
Through 1. As a result, the effect of preventing scattering can be obtained as in the third embodiment.

In this example, the transfer roller 6 is driven by the electrode roller 91 on the outer circumference. As the transfer roller 6, as described in the above-mentioned embodiment, it is common to use a sponge roller in which a resistance-adjusted EPDM foam is formed on the core metal, but this type of transfer roller has an outer diameter dimension. It is difficult to make it with high precision, and there is a problem that the outer diameter is reduced by passing the paper for a long time. In the roller transfer type image forming apparatus, the transfer material is conveyed by the transfer roller before and after the transfer nip portion.

FIG. 10 shows the relationship between the outer diameter of the transfer roller and the sub-scanning magnification. From this, it can be seen that when the outer diameter of the transfer roller changes, the transfer material conveying speed in the transfer nip portion N changes at the same time, and the magnification of the image on the transfer material in the sub-scanning direction changes accordingly.

According to this example, the transfer roller 6 is connected to the roller electrode 9
By driving the outer circumference at 1, the outer peripheral speed of the transfer roller 6 becomes constant regardless of the outer diameter of the transfer roller 6, and the sub-scanning magnification can be made constant.

<Embodiment 5> (FIGS. 11 and 12) In this embodiment, a transfer bias is supplied to the transfer roller from the downstream side of the transfer roller, and a shield electrode member is provided on the outer periphery of the upstream side of the transfer roller. By eliminating the transfer electric field on the upstream side of the transfer roller, a good image without scattering can be obtained.

That is, as in the third embodiment, an outer peripheral electrode 71 made of a conductive brush or a metal plate is in contact with the outer periphery of the transfer roller 6 on the downstream side in the entire paper passing area, and a high voltage power source 72 is used. Transfer charges are supplied to the transfer nip portion N via the outer peripheral electrode 71.

A conductive brush or a shield electrode 111 made of a metal plate is in contact with the outer periphery of the transfer roller 6 on the upstream side over the entire area of the sheet passing area, and a voltage of the opposite polarity to the ground or the transfer bias is applied. It's

FIG. 12 schematically shows the state of the electric field in the vicinity of the transfer nip portion N.

The transfer charge supplied from the outer peripheral electrode 71 to the photosensitive drum 1 flows in the direction E1 from the surface where the outer peripheral electrode 71 contacts the transfer roller 6 to the surface where the transfer roller 6 contacts the photosensitive drum 1. At this time, when the transfer roller 6 having a relatively low resistance is used, there is a current flowing in the direction F1 that goes around the transfer roller sponge portion 6b, but this leakage current is cut by the shield electrode 111.

Under the same conditions as in the first embodiment, when the transfer bias is applied using the brush electrode 71 on the outer periphery of the transfer downstream side in the configuration of this example (the shield electrode 111 is grounded) (Experimental example 5), the transfer downstream is obtained. As a result of comparing the scattering level between the case where the transfer bias is applied from the outer circumference and the shield electrode is not provided (Experimental Example 3) and the case where the transfer bias is applied from the transfer roller core metal 6a (Comparative Example 3), the Comparative Example It was confirmed that the splatter in Example 3 was Δ level, and the splatter that was ◯ level in Experimental Example 3 became ⊚ level in Experimental Example 5.

As described above, the outer periphery of the transfer roller is grounded on the upstream side,
Alternatively, by providing a shield electrode 111 to which a voltage having a polarity opposite to that of the transfer bias is applied and applying a transfer bias from an outer peripheral electrode 71 provided on the transfer downstream side outer circumference, the transfer electric field in front of the transfer nip portion is completely cut. It is possible to prevent the occurrence of “scattered” images.

<Embodiment 6> (FIG. 13) In this embodiment, immediately before the transfer nip portion N, the transfer roller 6 is placed in contact with the photosensitive drum 1 and in the same direction as the transfer roller 6. By providing a guide roller (rotating body for transfer material guide) 131 that is rotationally driven on the transfer material P, the transfer material P is introduced and conveyed from the photosensitive drum 1 to prevent scattering.

The guide roller 131 comprises a POM (polyacetal), PC (polycarbonate), PBT (polyptyrene terephthalate), a core metal such as A1 and SUS,
An insulating surface layer made of a resin such as modified PPO (modified polyphenylene oxide) is formed.

The guide roller 131 is abutted and supported by a spring (not shown) on the surface of the transfer roller 6 upstream of the transfer nip portion N at a light pressure of 1 kgf or less, and guide roller driving means (not shown). Are driven to rotate in the same direction as the transfer roller 6 at substantially the same speed as the process speed.

The transfer material P fed from the paper feeding portion is guided to the surface of the photosensitive drum 1 upstream of the transfer nip portion N by the guide roller 131 and is in contact with the toner image formed on the photosensitive drum 1. Is conveyed to the transfer nip portion N.

Toner attached on the guide roller 131
Dirt such as paper dust is scraped off by the transfer roller 6 and cleaned via the photosensitive drum 1. The guide roller 131 is grounded during the printing operation (switch 132b / OF
F, switch 133 / ON), the switch 133 is turned OFF only when the cleaning bias is output from the transfer high-voltage power supply 132 to the transfer roller 6 (switch 132b /
When the transfer roller 6 is controlled, a bias is applied so that the same potential as that of the transfer roller 6 is applied.
The reverse transfer onto 31 is prevented.

In the experiment, the same transfer material P, transfer roller 6, and photosensitive drum 1 as those in the execution example of the first embodiment were used, the transfer bias was constant voltage control of 3.2 kV, and the real environment was room temperature 23.
It was conducted under the conditions of ° C and humidity of 60% RH.

In Table 2, the guide roller 131 is used to make the transfer material photosensitive drum incident point (transfer nip N) on the transfer upstream side.
Change of the splattering level when the distance from the transfer roller is changed, and the occurrence of stains on the backside of the transfer material (Experimental example 6), and when a transfer roller non-contact fixing member is used as a pre-transfer guide as a comparative example (Comparative example). The result of 6) is shown.

[0095]

[Table 2] From this result, it is understood that as the photosensitive drum entrance point of the transfer material P moves further upstream than the transfer nip portion N, the scattering level improves. Further, when the transfer roller non-contact fixing member is used, the back stain level becomes worse as the photosensitive drum incident point of the transfer material approaches the transfer nip portion N (the transfer roller non-contact fixing member approaches the photosensitive drum). On the other hand, in the case of the guide roller 131, backside contamination does not occur because the guide roller 131 is always cleaned via the transfer roller 6.

As described above, according to this embodiment, by using the guide roller 131 that comes into contact with the transfer roller 6 and is rotationally driven in the same direction as the transfer roller 6 as the transfer material guide member, the guide roller is prevented in order to prevent scattering. Even when 131 is brought close to the photosensitive drum 1, it is possible to obtain a good image without stains on the back side of the transfer material due to stains on the guide.

<Embodiment 7> (FIG. 14) In this embodiment, a guide roller 131, which is arranged in contact with the transfer roller 6 and in the vicinity of the photosensitive drum 1, is driven to rotate in the same direction as the transfer roller 6. 131 is provided before and after transfer to prevent scattering.

The guide rollers 131, 131 are rollers having the same structure as that of the sixth embodiment in which a resin surface layer is formed on the cored bar. In this example, as in the sixth embodiment, the bias having the same potential as that of the transfer roller 6 is applied to both guide rollers 131, 131 only when the transfer cleaning bias is applied.

In this way, the guide rollers 131, 131 are arranged before and after the transfer nip portion N, and the transfer material P is conveyed in a state of being in contact with the photosensitive drum 1 even after passing through the transfer nip portion, thereby passing through the transfer nip portion. Post transfer in which the transfer residual toner on the photosensitive drum 1 flies onto the transfer material later can also be prevented, and an image more faithful to the toner image on the photosensitive drum can be obtained.

<Embodiment 8> (FIG. 15) In this embodiment, as a guide roller which is in contact with the transfer roller 6 and is arranged in proximity to the photosensitive drum 1, the guide roller is driven to rotate in the same direction as the transfer roller 6. This is an example in which a roller 151 whose surface is made of a high release material is used.

The high releasability guide roller 151 is a roller in which an insulating material such as resin or rubber is coated with a high release layer (release layer having a small surface energy) such as PFA or PTFE.

In this example, instead of applying a bias to the guide rollers 151, 151, the transfer rollers 6 are guided to the guide rollers 151. 1 by utilizing the difference in releasability from the transfer rollers 6.
In order to transfer the deposits on the transfer roller 6 to the transfer roller 6, the surface of the guide roller is made of a material having a higher releasability than the transfer roller.

Specifically, the high releasability guide roller 151.
The contact angle of the surface of the transfer roller 6 with respect to water is made larger than the contact angle of the surface of the transfer roller 6 with respect to the water.
The cleaning of 1.151 can be performed smoothly.

By thus forming the surface of the guide roller 151 with a material having a high mold release property, it is not necessary to provide a mechanism for applying a special bias to the guide roller 151, and the scattering due to the pre-transfer and the post-transfer can be achieved with a simple structure. Can be prevented.

The shape of the guide roller (rotating body for transfer material guide) is not limited to the roller shape, but any rotating body such as rollers provided in the longitudinal direction of the transfer material may be used in this example and the above. The effects described in the examples can be similarly obtained.

[0106]

As described above, according to the present invention, in the image forming apparatus of the transfer system, the "transfer of the transfer material after separation from the image carrier is stably carried out, so that" the trailing edge bounce "and the image caused by it It is possible to prevent the occurrence of “drops” due to disturbance and poor charge removal, to prevent “scattering” by eliminating the influence of the transfer electric field on the upstream side of the transfer nip portion, and to prevent the back stain of the transfer material.

That is, in the image forming apparatus adopting the curvature separation system in which the transfer material that has passed through the transfer section is separated from the image carrier by the curvature of the image carrier and the separation by the charge eliminating member, With the configuration in which the electrostatic attraction member and the static eliminator are sequentially arranged in the transfer material conveying path on the downstream side of the transfer material in the transfer material conveying direction, the transfer material portion passing through the transfer portion is transferred from the image carrier surface to the image carrier. Are sequentially separated by the curvature of and the assist of the static elimination member. In this case, since the electrostatic attraction member is present between the transfer unit and the static elimination member, the electrostatic attraction member passes through the transfer unit. The transfer material portion is forcibly separated from the surface of the image carrier, and the rear end portion of the transfer material that has passed through the transfer portion is also prevented from "rear end bounce" by the pulling force by the electrostatic attraction member, and is caused by the rear end bounce. Image distortion is prevented.

The portion of the transfer material separated from the image carrier through the transfer portion is neutralized by the neutralization member immediately after the electrostatic attraction member, so that the transfer material holding excessive transfer charge due to poor static elimination is conveyed. Distortion of an image such as a "polka dot" that occurs due to the proximity of the above member is prevented.

Further, an electrostatic adsorption conveyance member is arranged next to the above static elimination member, that is, a range in which there is a member that electrostatically adsorbs the transfer material on the printing surface side downstream of the static elimination member in the transfer material conveyance direction. By disposing an electrostatic attraction transport member that has a stronger electrostatic attraction force than the printing surface side member on the entire area of the non-printing surface side, the image disturbance caused by the transfer material printing surface rubbing against the structural material in the transport path Can be prevented.

In the image forming apparatus adopting the roller transfer system for supplying the transfer charge to the transfer roller in contact with the image carrier, the power is supplied to the transfer roller by the outer periphery of the transfer roller on the downstream side in the transfer material conveying direction. By doing so, it is possible to eliminate the influence of the transfer electric field on the upstream side of the transfer material in the transfer section and prevent the scattering.

Further, at least in front of the transfer portion, a transfer material guide rotating body (roller) which comes into contact with the transfer roller and rotates in the forward direction with the transfer roller is provided, and the transfer material is guided by the rotating body to the image carrier. By transporting incident light to prevent scattering, and by transferring dirt on the surface of the rotating body for the transfer material guide to the transfer roller and cleaning via the image carrier,
It is possible to obtain an image-formed product with no stain on the back.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 2 is a configuration diagram of a transfer material transport path portion on the downstream side of the transfer nip portion in the transfer material transport direction.

FIG. 3 is a plan view of the same portion.

FIG. 4 is an explanatory diagram of an arrangement area of a transfer material attracting member.

FIG. 5 is a configuration diagram of a transfer material transport path portion on the downstream side in the transfer material transport direction with respect to the transfer nip portion of the apparatus according to the second exemplary embodiment.

FIG. 6A is a side model view of a transfer material transport belt as an adsorption transport member, and FIG. 6B is a plan view.

FIG. 7 is a main part diagram of an apparatus according to a third embodiment.

FIG. 8 is a diagram schematically showing a state of an electric field in the vicinity of a transfer nip portion.

FIG. 9 is a main part diagram of an apparatus according to a fourth embodiment.

FIG. 10 is a graph showing a relationship between a transfer roller outer diameter and a sub-scanning magnification in a conventional image forming apparatus.

FIG. 11 is a main part diagram of an apparatus according to a fifth embodiment.

FIG. 12 is a diagram schematically showing a state of an electric field in the vicinity of a transfer nip portion.

FIG. 13 is a main part diagram of an apparatus according to a sixth embodiment.

FIG. 14 is a main part diagram of an apparatus according to a seventh embodiment.

FIG. 15 is a main part diagram of the device according to the eighth embodiment.

FIG. 16 is an explanatory diagram of a roller transfer type transfer means.

FIG. 17 is an explanatory diagram of occurrence of trailing edge of transfer material.

FIG. 18 is an explanatory diagram of a conventional transfer material trailing edge bounce prevention method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 image carrier (photosensitive drum) 6 transfer roller 24 static elimination member (static elimination needle) 23 electrostatic attraction member 24 electrostatic attraction transport member (transport metal plate member) 41 transport belt 61 outer peripheral electrode 81 electrode roller 101 transfer material transport rotator (Guide roller) 121 High release guide roller

Front page continuation (72) Inventor Hiroshi Kataoka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yozo Horita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (8)

[Claims] 1. An image forming apparatus for transferring a transferable image formed and carried by an image carrier onto a surface of a transfer material by a transfer member to which a back surface of the transfer material is contacted and a voltage is applied. An image forming apparatus characterized in that an electrostatic attraction member and a static eliminator member are sequentially arranged in a transfer material conveying path on the downstream side in the material conveying direction. 2. An image forming apparatus for transferring a transferable image formed and carried by an image carrier onto a surface of a transfer material by a transfer member to which a back surface of the transfer material is contacted and a voltage is applied. An image forming apparatus characterized in that an electrostatic attraction member, a charge eliminating member, and an electrostatic attraction transport member are sequentially arranged in a transfer material transport path on the downstream side in the material transport direction. 3. The image forming apparatus according to claim 2, wherein the electrostatic attraction conveyance member is a transfer material conveyance belt in which high resistance rubber is formed on the inner and outer surfaces of a grounded metal thin belt. 4. An image forming apparatus for transferring a transferable image formed and carried by an image carrier onto a surface of a transfer material by a transfer roller which is in contact with the back surface of the transfer material and to which a voltage is applied. An image characterized by having an outer peripheral electrode in contact with the outer peripheral surface on the downstream side in the transport direction and a voltage applying means for applying a voltage to the outer peripheral electrode, and supplying a transfer charge to the transfer roller via the outer peripheral electrode. Forming equipment. 5. The image forming apparatus according to claim 4, wherein the outer peripheral electrode is a conductive roller member, and the outer peripheral electrode roller drives the outer periphery of the transfer roller. 6. An image forming apparatus for transferring a transferable image formed and carried on an image carrier to a surface of a transfer material by a transfer roller to which a back surface of the transfer material is applied and a voltage is applied. An image forming apparatus comprising: a transfer material guide rotating body that is rotationally driven in a forward direction on the transfer roller. 7. The bias according to claim 6, wherein when a bias having a polarity opposite to that of the transfer bias is applied to the transfer roller, a bias having the same potential as that of the transfer roller is applied to the rotating body for the transfer material guide. Image forming apparatus. 8. The image forming apparatus according to claim 6, wherein the transfer material guide rotating body is a rotating body in which a release layer having a surface energy smaller than that of the transfer roller is formed on the surface of the insulating base material. .