JP3147623B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image bearing member (image forming member) such as an electrophotographic photosensitive member, an electrostatic recording dielectric or a magnetic recording magnetic material.
A transferable image (toner image) corresponding to the target image information is formed and carried by an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, a magnetic recording process, and the like.
A transfer roller for transferring a recording medium such as a transfer material and a recording material to the image carrier.
The present invention relates to a transfer-type image forming method (or apparatus) for transferring a transferable image on the image carrier side to a recording medium side by pressing and contacting with a key.

[0002]

2. Description of the Related Art FIG. 5 shows a schematic diagram of an example of a conventional transfer type image forming apparatus. The apparatus of this embodiment is a copying machine or a laser beam printer using a transfer type electrophotographic process.

[0003] Reference numeral 20 denotes a drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which comprises a conductive drum base 21 made of aluminum or the like and a photosensitive layer 22 formed on the outer peripheral surface thereof. It is driven to rotate at a predetermined process speed (peripheral speed) in the clockwise direction indicated by the arrow.

During the rotation of the photosensitive drum 20, the corona charger 3 as a primary charging means uniformly performs a primary charging process to a predetermined polarity and potential, and then performs an image exposure means (not shown). Means, laser scanner, etc.)
, An electrostatic latent image corresponding to the target image information is formed on the peripheral surface.

The latent image is developed as a toner image 9 by a developing device 5. Then, at a transfer portion 6A, which is a press-contact nip portion between the photosensitive drum 20 and a transfer roller 6 as a contact transfer member pressed against the photosensitive drum, one sheet is transferred from a paper supply unit (not shown) at a predetermined timing. The toner image 9 on the photosensitive drum 20 side is transferred to the transferred transfer material 8 as a recording medium.

The transfer roller 6 is an elastic roller composed of a conductive cored bar 6a and an elastic layer 6b of silicon rubber or the like formed concentrically and integrally with the outer periphery of the conductive cored bar 6a. The photosensitive drum 20 is pressed against with a pressing force, and is rotated in the forward direction with the rotation of the photosensitive drum 20.

The photosensitive drum 20 is a rigid body having substantially no elastic deformation, and the transfer roller 6 is an elastic roller. When the transfer roller 6 is pressed against the photosensitive drum 20, the elastic layer of the transfer roller 6 is pressed. 6b is elastically deformed and comes into contact with the photosensitive drum 20 to form a pressure contact nip portion having a predetermined width as the transfer portion 6A.

The transfer roller 6 is supplied with a transfer electric field (transfer bias) by a power source 6B, and a predetermined transfer is performed until the leading end of the transfer material 8 reaches the transfer portion 6A and the rear end of the transfer material 8 passes through the transfer portion 6A. A bias is applied.

The transfer material 8 fed to the transfer portion 6A is nipped and conveyed between the rotary photosensitive drum 20 and the rotary transfer roller 6, so that the transfer roller 6 presses the transfer material against the photosensitive drum 20 and transfers the transfer material. The electric field causes the photosensitive drum 2
The 0 side toner image 9 is transferred (transferred) to the transfer material 8 side.

The transfer material 8 to which the toner image 9 has been transferred through the transfer portion 6A is separated from the surface of the photosensitive drum 20, conveyed to a fixing device (not shown), and subjected to a toner image fixing process to form an image. It is output as an object (copy / print).

[0011] 10 after passing through the transfer portion, the photosensitive drum transfer material 8, will be transported wound around the photosensitive drum 20 2
It is a separation claw to be separated from the 0 plane.

On the other hand, the surface of the photosensitive drum 20 after the transfer of the toner image onto the transfer material 8 is cleaned by the cleaner 7 to remove the adhered contaminants such as residual toner, and is repeatedly used for image formation.

[0013]

In a transfer type image forming apparatus using a contact transfer member as in the above example,
The toner of the toner image 9 as a transferable image aggregates between the image carrier 20 and the recording medium 8 due to the pressing force of the transfer member 6 on the image carrier 20 and the central portion of the character or line image is transferred. So-called "missing"
An image defect called a phenomenon is likely to occur.

In order to improve the image defect, conventionally, a slight difference is made between the rotational movement speed of the photosensitive drum 20 as an image carrier and the conveyance speed of the transfer material 8 as a recording medium.
A method of generating a so-called peripheral speed difference has been used.

In this case, however, a speed difference is generated between the toner image 9 on the photosensitive drum 20 and the transfer material 8, so that toner scatters during transfer, and the contour of the toner image transferred to the transfer material 8 side. Blurry and obscured,
It was easy for the whole image to lack sharpness.

When a peripheral speed difference is made between the photosensitive drum 20 and the contact transfer member 6, the photosensitive drum 2 is moved by the peripheral speed difference.
Magnification changes between the toner image 9 on the transfer sheet 8 and the toner image transferred on the transfer material 8, and there is also a problem that a means for correcting the change is required.

The present invention also relates to a transfer type image forming method using a contact transfer member. However, the present invention has solved the above-mentioned problems, that is, it does not cause a defect in a transferred image and has a sharpness. It is an object of the present invention to provide a technique capable of executing good image transfer without reducing the image quality and without requiring a magnification correction process.

[0018]

The present invention is an image forming method characterized by the following constitution.

(1) Rotating drum type image carrier and rotation
Paper through the pressure nip with the transfer roller
Transferable image formed and carried on the image carrier by nipping and conveying
In the transfer type image forming method of transferring the image to the recording medium side, both the image carrier and the transfer roller are provided with elastic deformation properties, and are pressed against the image carrier and the transfer roller.
The press-contact nip portion having a predetermined width is formed by the image carrier and the transfer roller.
Rollers in the recording medium transport direction due to mutual elastic deformation
Of the image carrier and the transfer roller so that
An image forming method characterized in that both elastic deformation amounts are set .

(2) The image forming method according to (1), wherein a transfer electric field is applied to the transfer roller .

[0021]

[0022]

[0023]

[0024]

When the image carrier is provided with elastic deformation, and the image carrier is brought into contact with a recording medium while the image carrier is elastically deformed by the pressing force of the transfer member, the image transfer is performed. Due to the surface distortion, the releasability of the transferable image from the surface of the image carrier is improved, and the image transfer without the hollow phenomenon can be performed without making a difference in peripheral speed between the image carrier and the recording medium.

Since there is no need to make a difference in peripheral speed between the image carrier and the recording medium, there is no decrease in the sharpness of the transferred image.
Also, there is no need for magnification correction. Then, it is transferred to the image carrier.
The image bearing roller is provided with elastic deformation
Pressure of predetermined width formed by pressure contact with carrier and transfer roller
The contact nip is the elastic deformation of the image carrier and the transfer roller.
It becomes almost flat in the recording medium conveyance direction depending on the shape
The elastic deformation of both the image carrier and the transfer roller is set.
Pressure nip without deforming the recording medium
To transfer by holding and transferring the part (transfer site)
OHP sheets that make it difficult for the recording medium to deform
Even if the paper is thick paper, postcard paper, etc.
You can make a copy.

[0026]

Embodiment Reference Example 1 (FIG. 1) FIG. 1 is a schematic configuration model diagram of an image forming apparatus of the present reference example . This is a copying machine or a laser beam printer using a transfer type electrophotographic process, which has substantially the same configuration as the apparatus shown in FIG. 5, and the same components and portions are denoted by the same reference numerals, and the description thereof will not be repeated.

The difference from the apparatus of FIG. 5 is that the photosensitive drum 2 having elastic deformation is used as an image carrier in the apparatus of this embodiment.

The photosensitive drum 2 of this embodiment has a conductive support layer (drum substrate) 2-1 made of a conductive rigid material such as iron or aluminum, and a conductive material such as carbon formed on the outer periphery thereof dispersed therein. Urethane rubber, silicone rubber, E
An elastic layer 2-2 made of a rubber material such as PDM (ethylene propylene diene rubber) or a sponge-like elastic material obtained by foaming them, and an OPC formed on the outer periphery thereof
(Organic optical semiconductor) a-Si (amorphous silicon)
It is composed of a photoconductor layer 2-3 such as a photoconductor and a selenium-based photoconductor.
At the interface between the elastic layer 2-2 and the photoreceptor layer 2-3, an adhesive layer for improving the adhesion between the two layers and the conductivity may be formed.

The photosensitive drum 2 has an elastic layer 2 between a support layer 2-1 of a conductive rigid material and an outermost photosensitive layer 2-3.
The presence of -2, that is, the presence of the elastic layer below the photoreceptor layer, has the property that the outer surface portion subjected to the external force is elastically deformed against the elasticity of the elastic layer 2-2.

The transfer roller 6 comprises a conductive core (conductive support layer) 6a and an elastic layer 6b formed concentrically and integrally with the outer periphery of the roller. The elastic layer 6b disperses a conductive material such as carbon and has a volume resistance of 105 to 1010 Ω.
cm, urethane rubber, silicone rubber, EPD
It is a resistance layer using a rubber material such as M.

In this embodiment , when the transfer roller 6 is disposed in pressure contact with the photosensitive drum 2 with a predetermined pressing force, the transfer roller contact portion of the photosensitive drum 2 resists the elasticity of the elastic layer 2-2. The hardness of the transfer roller 6 is relatively smaller than the hardness of the photosensitive drum 2 so that a press-contact nip portion having a predetermined width as the transfer portion 6A is formed in a state where the recess is formed by elastic deformation as shown in FIG. There is as high.

The transfer of the toner image 9 to the transfer material 8 as a recording medium is performed by the transfer roller 6 as described above.
The transfer material 8 is introduced into the transfer portion 6A of the photosensitive drum 2 in a state where the elastically deformed dent is generated due to the pressure contact, and is nipped and conveyed between the photosensitive drum 2 and the transfer roller 6, so that the photosensitive drum 2 This is performed by the transfer material pressing force against the drum 2 and the transfer electric field applied to the transfer roller 6.

In this embodiment , when the photosensitive drum 2 and the transfer roller 6 are pressed against each other, the surface of the photosensitive member is elastically deformed as described above. As the amount of elastic deformation increases, it becomes more difficult for “transmissive image defect”, which is a transferred image defect, to occur. This is because the surface of the photosensitive drum on which the toner image 9 is adhered is elastically deformed, thereby causing surface distortion. This distortion reduces the adhesive force between the toner and the surface of the photosensitive drum, and causes "transfer missing" Is suppressed.

The effect of reducing the adhesive force is that the distortion of the elastic layer 2-2 of the photosensitive drum 2 is released in the vicinity of the transfer material outlet at the press-contact nip portion between the photosensitive drum 2 and the transfer roller 6 which is the transfer portion 6A. It is considered that a shift occurs instantaneously at the interface between the photoconductor and the toner, and this shift greatly reduces the adhesive force.

The minute image shift generated by this method is different from the method of generating a shift at the entire transfer portion (pressing nip portion) due to the peripheral speed difference used in the conventional example, and is different from the elastic layer 2 of the photosensitive drum 2. Transcription site 6 where distortion of 2 is released
Since the toner image is generated only in the vicinity of the transfer material outlet of A, blurring and scattering of the toner image, which are problems in the conventional method, are eliminated.

In the conventional method in which a peripheral speed difference is provided between the photosensitive drum 2 and the transfer roller 6, the magnification between the toner image on the photosensitive drum 2 and the toner image on the transfer paper 8 is determined by the peripheral speed difference. Is changed, and a means for correcting the change is required. However, the apparatus of the present embodiment has an advantage that no change in magnification occurs because there is no peripheral speed difference.

<Example> (FIG. 2) An example of the present invention. This embodiment is a modification of the image of Reference Example 1 described above.
In the image forming apparatus, the elastic deformation of the transfer roller 6 pressed against the photosensitive drum 2 is close to that of the elastic layer 2-2 of the photosensitive drum 2. As a result, as shown in FIG. 2, the press-contact nip portion between the photosensitive drum 2 and the transfer roller 6, which is the transfer portion 6A, has a substantially flat form, and the transfer portion is not deformed at the transfer portion 6A without deforming the transfer material 8. The transfer can be performed by nipping and conveying, and even if the transfer material is not easily deformed, such as an OHP sheet, a thick paper, or a postcard, the image can be transferred by passing the paper without any trouble. In this case, as in the case of the first embodiment, good image transfer can be performed without a hollow phenomenon due to the elastic deformation of the photosensitive drum 2.

[0038]

Reference Example 2 (FIG. 3) In the conventional apparatus as shown in FIG. 5, the transfer material 8 is electrostatically attracted to the photosensitive drum 20 after the transfer step, and the photosensitive drum 20 as shown by a two-dot chain line. There was a case where a problem of poor separation, that is, winding around the 20 side, occurred. In order to avoid this, it was necessary to install the separation claw 10 in front of the cleaner 7. However, it is assumed that the photosensitive drum 20 is damaged by the separation claw 10 and an image defect occurs.
You.

The image the photosensitive drum 2 as a bearing member that has an elastic deformability, since the photosensitive drum 2 is elastically deformed at the transfer site 6A is a press nip between the transfer member,
The curvature of the photosensitive drum 2 in the latter half of the transfer portion 6A increases, and as a result, the transfer material 8 does not wrap around the photosensitive drum 2 on the principle called curvature separation.

[0041] Therefore, a problem that separation failure is hardly generated, so that the apparatus of FIG. 3, the separation pawl (1
0) was not required, and stable image formation could always be performed.

Reference Example 3 (FIG. 4) This reference example is an image forming apparatus using a flexible endless belt photoconductor as an image carrier.

That is, in FIG. 4A, reference numeral 2A denotes a flexible endless belt photoreceptor, which is composed of three belt suspension rollers 11 and an elastically deformable elastic roller 12 arranged in parallel with each other. And is rotationally driven at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow. The endless belt photoconductor 2A is obtained by forming a photoconductor layer on the outer peripheral surface of a flexible base belt.

An image forming process device such as a corona charger 3, an image information exposing unit 4, a developing unit 5, a transfer roller 6, and a cleaner 7 as primary charging means is provided around the endless belt photoreceptor 2A. It is.

The transfer roller 6 is pressed against the elastic roller 12 with a predetermined pressing force by sandwiching the belt photoreceptor 2A between the transfer roller 6 and the elastic roller 12. As shown in FIG. The transfer roller contact portion of the photoreceptor 2A is deformed against the elasticity of the elastic roller 12 so as to form a nip portion having a predetermined width as a transfer portion 6A in a state where the transfer roller contact portion has a dent. The hardness is relatively higher than the hardness of the elastic roller 12.

The belt photoreceptor 2A for the transfer material 8
The transfer of the toner image on the side is performed by the transfer roller 6 as described above.
Photoreceptor 2A in a state in which an elastic deformation dent is generated by pressure contact of
The transfer material 8 is introduced into the transfer portion 6A of the transfer roller 6 by the pressing force of the transfer roller 6 on the belt photosensitive member 2A and the transfer electric field applied to the transfer roller 6.

In the present embodiment , the belt photoreceptor 2A is replaced by the elastic roller 12 as a backup roller, and the transfer roller 6 is replaced by the same logic as in the apparatus of the first embodiment.
The image is deformed by being elastically deformed by the pressing force, so that a good image transfer can be performed without a hollow phenomenon.

In the above embodiments and Reference Examples 1 to 3, the image bearing member is an electrophotographic photosensitive member. It is to include a resiliently deformable to carrier, thereby satisfactorily perform image transfer without image defects hollow defect such as when to be transferred to the image carrier to form a supported transfer roller over the recording medium transferable image was be able to.

[0049]

The application of a transfer electric field to the transfer roller is not essential, and the present invention can be effectively applied to image transfer (pressure transfer) mainly based on the pressing force of the transfer roller against the image carrier of the recording medium. .

[0051]

As described above, according to the present invention, the transfer row
The image forming method of the transfer system using a color, an image bearing
Make both the body and the transfer roller elastically deformable.
Is formed by pressing against the image bearing member and the transfer roller.
The width of the pressure contact nip is the mutual contact between the image carrier and the transfer roller.
It is almost flat in the recording medium conveyance direction due to elastic deformation.
Elastic deformation of both the image carrier and the transfer roller
By performing the image transfer by setting the amount, the releasability of the transferable image from the image carrier surface is improved due to the surface distortion of the image carrier, so that there is no difference in peripheral speed between the image carrier and the recording medium. Since it is possible to execute image transfer without a hollow phenomenon, and it is not necessary to make a peripheral speed difference between the image carrier and the recording medium,
There is no reduction in the sharpness of the transferred image, and there is no need for magnification correction. In addition, the image carrier and transfer
The press nip between the transfer roller and the transfer roller
The recording medium is hardly deformed because
HP sheets, cardboard, and postcards can be passed without any problems.
Image transfer can be performed on paper.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the configuration of an apparatus according to Reference Example 1 .

FIG. 2 is a schematic diagram of an apparatus according to an embodiment.

FIG. 3 is a schematic diagram of a schematic configuration of an apparatus of Reference Example 2 .

FIG. 4 (a) is a schematic configuration diagram of an apparatus of Reference Example 3 (b) is a partially enlarged view of a main part.

FIG. 5 is a schematic configuration diagram of a conventional device.

[Explanation of symbols]

2, 2A, 20 Image carrier (drum type or belt type electrophotographic photoreceptor) 2-1 Conductive support layer 2-2 Elastic layer 2-3 Photoreceptor layer 3 Corona charger 4 Image exposure 5 Developing device 6 Transfer Member (transfer roller) 7 Cleaner 8 Recording medium (transfer material) 10 Separation claw 12 Elastic roller

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 21/00 350

Claims (2)

(57) [Claims] 1. A rotating drum-type image carrier and a rotating image carrier
Pass the recording medium through the pressure nip with the transfer roller
The image forming method of the transfer method in which a transferable image is formed and borne on an image bearing member by lifting the conveyed transfer to the recording medium side, is provided with an elastic deformability in both the transfer roller and the image carrier, the image Formed by pressure contact with carrier and transfer roller
The press-contact nip portion with a predetermined width
Due to the mutual elastic deformation, almost fluctuates in the recording medium conveyance direction.
Of both the image carrier and the transfer roller so that
An image forming method, wherein an amount of sexual deformation is set . 2. The image forming method according to claim 1, wherein a transfer electric field is applied to the transfer roller .