JPH11119571A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality without disturbing a transferred toner image on a recording medium by providing a transfer device and a fixing device which fixes the toner image transferred to the recording medium, and covering the surface of the transfer device with an insulating thin-film pattern having an insulating part. SOLUTION: The device is equipped with a developing device 14 for forming a toner image by developing an electrostatic latent image on an image carrier, the transfer device for transferring the toner image to a recording medium, the fixing device 27 for fixing the toner image transferred to the recording medium, and other devices. The surface of the transfer device is covered with the insulating thin-film pattern having the insulating part. In the case, the insulating thin-film pattern causes a part where a potential difference for the transfer of the toner image to the recording medium is sufficiently made and a part where the potential difference for the transfer of the toner image to the recording medium is not sufficiently made. Thus, the toner image is prevented from being disturbed when the toner image formed on the image carrier is transferred to the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile machine or the like using an electrophotographic recording system, a photosensitive drum having a uniformly and uniformly charged surface has a laser, an LED head and the like. Exposure by the exposure device, to form an electrostatic latent image on the photosensitive drum, develop the electrostatic latent image to form a toner image, transfer the toner image to a recording paper as a recording medium, It has become established.

When a corona transfer device is used as a transfer device for transferring the toner image onto recording paper, it is necessary to apply a high voltage of 5 to 10 [kv] to the corona transfer device. A power supply is required, which increases the cost of the image forming apparatus. In addition, the corona transfer unit has low stability to the environment, and particularly, the transfer efficiency changes when the humidity changes. Further, since the corona transfer device generates ozone by utilizing the corona discharge phenomenon, the ozone significantly deteriorates the photosensitive drum.

On the other hand, it is considered that an ozone absorption / decomposition filter is provided in the image forming apparatus to absorb ozone. However, since the ozone absorption / decomposition filter has low durability, it is frequently replaced. Must be done, and the work is cumbersome. Therefore, a transfer roller composed of a semiconductive sponge roller is used as a transfer device, and the transfer roller and the photosensitive drum are brought into contact with each other via a recording sheet to apply a DC transfer voltage to the semiconductive sponge roller. Japanese Patent Application Laid-Open No. 6-19276 discloses a technique in which a toner image on a photosensitive drum is transferred onto a recording sheet.

[0005]

However, in the above-described conventional image forming apparatus, when the transfer voltage applied to the transfer roller is increased, discharge occurs between the photosensitive drum and the transfer roller, and toner is scattered. And adhere to the white background of the recording paper. Therefore, disturbance occurs in the toner image transferred to the recording paper, and the image quality deteriorates.

The present invention solves the above-mentioned problems of the conventional image forming apparatus, and provides an image forming apparatus capable of improving the image quality without disturbing the toner image transferred to the recording medium. The purpose is to provide.

[0007]

For this purpose, in the image forming apparatus of the present invention, an image bearing member, a charging device for uniformly and uniformly charging the surface of the image bearing member, and an image bearing member on the image bearing member are provided. An exposure device for forming an electrostatic latent image on the recording medium; a developing device for developing the electrostatic latent image to form a toner image; a transfer device for transferring the toner image to a recording medium; and a transfer device for transferring the toner image to the recording medium. And a fixing device for fixing the toner image.

Then, the surface of the transfer device is covered with an insulating thin film pattern having an insulating portion.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. In the figure, reference numeral 11 denotes a photosensitive drum as an image carrier which is formed in a drum shape and is rotated in the direction of arrow A by a driving means (not shown).
Is formed by covering the photoconductive layer 11b on the conductive support 11a. In the present embodiment, the photoconductive layer 1
An organic photoreceptor was used as 1b. In addition, a selenium photoreceptor, a zinc oxide photoreceptor, an amorphous silicon photoreceptor, or the like can be used instead of the organic photoreceptor.

Reference numeral 12 denotes a charging roller as a charging device which is brought into contact or pressure contact with the surface of the photosensitive drum 11 and is rotated in the direction of arrow B. Reference numeral 13 denotes a charging roller which rotates in the rotation direction of the photosensitive drum 11. Downstream,
The exposure device is provided so as to face the photoconductor drum 11. In the present embodiment, the exposure device 13 is
An LED array head formed by combining an LED array (not shown) and a SELFOC lens (trade name) was used. Instead of the LED array head, a combination of a laser and an image forming optical system can be used.

A reference numeral 14 denotes a downstream side of the exposure device 13 in the rotation direction of the photosensitive drum 11, which is provided in contact with the photosensitive drum 11 or with a small space from the photosensitive drum 11. The developing device has a developing roller 15 disposed therein and a toner 16 stored therein. As the developing device 14, a two-component magnetic brush developing device, a one-component magnetic brush developing device, a one-component non-magnetic developing device, or the like can be used.

The developing roller 15 is rotated in the direction of arrow C while adsorbing the toner 16, and
The electrostatic latent image formed above is developed (reversal development). Therefore, when a bias voltage is applied between the conductive support 11a and the developing roller 15, lines of electric force are generated corresponding to the electrostatic latent images. The toner 16 is non-magnetic, has insulating properties, and has an average volume particle size of 8 to 12.
[Μm] styrene-based or polyester-based resin is used. In the present embodiment, since the polarity with which the photoconductor drum 11 is charged is negative, the toner 16 is made negatively charged by filling a negative charge control agent. Further, as the toner 16, a magnetic toner or the like obtained by adding a magnetic powder such as iron or ferrite to a resin can be used.

Reference numeral 17 denotes a paper cassette, 18 denotes recording paper as a recording medium, 19 denotes a paper feed roller, 20 denotes a paper feed roller, and 24 denotes a downstream side of the developing device 14 in the rotation direction of the photosensitive drum 11. , A transfer roller as a transfer device that is disposed in pressure contact with the photosensitive drum 11. The transfer roller 24 is formed of a semiconductive sponge roller, and the conductive shaft 21 has a rubber resistance layer 22.
And an insulating thin film mesh 23 as an insulating thin film pattern. The transfer roller 24 is rotated in the direction of arrow D by driving means (not shown). Then, the peripheral speed of the transfer roller 24 and the peripheral speed of the photosensitive drum 11 are made different.

In place of the transfer roller 24, an oven fixing device, a flash fixing device or the like can be used. Further, as the transfer roller 24, the conductive shaft 21
A semi-conductive rubber roller, a semi-conductive sponge roller, or the like having a three-layer structure or a four-layer structure in which a resistance layer, an intermediate layer, an elastic layer, a surface layer, and the like are covered.

Reference numeral 25 denotes a heating roller, reference numeral 26 denotes a pressing roller, reference numeral 27 denotes a fixing device including the heating roller 25 and the pressing roller 26, and reference numeral 28 denotes a downstream side of the transfer roller 24 in the rotation direction of the photosensitive drum 11. , A cleaner device disposed in contact with the photosensitive drum 11, and the cleaner device 28 is configured to remove the toner 1 remaining on the photosensitive drum 11.
Remove 6.

Next, the operation of the image forming apparatus having the above configuration will be described. First, the surface of the photoconductor drum 11 is uniformly and uniformly charged by the charging roller 12, and the exposure device 13 irradiates the photoconductor drum 11 with light corresponding to an image signal. To form an electrostatic latent image. Next, the developing device 14 forms the toner image by attaching the toner 16 charged on the developing roller 15 to the photosensitive drum 11 by electrostatic force and developing the electrostatic latent image.

Thereafter, the recording paper 18 stored in the paper cassette 17 is fed out one by one by a paper feed roller 19 and sent to a stopped paper feed roller 20 to correct the skew. Next, the paper feed roller 20 is rotated, and the recording paper 18 is sent to a transfer section formed between the photosensitive drum 11 and the transfer roller 24, and the transfer roller 2
4 transfers the toner image on the photosensitive drum 11 to the recording paper 18.

Thereafter, when the recording paper 18 on which the toner image has been transferred is sent to the fixing device 27, the heating roller 2
The toner 16 is melted by the heat of 5, and the toner 16 penetrates between the fibers of the recording paper 18 by the pressurization by the pressure roller 26. Thus, the toner image is fixed on the recording paper 18. Then, recording paper 1 after fixing
8 is discharged out of the image forming apparatus.

On the other hand, a small amount of toner 16 may remain on the photosensitive drum 11 after the transfer, and the toner 16 is removed by the cleaner device 28. In this way, the photosensitive drum 11 is repeatedly used. next,
The transfer roller 24 will be described. FIG. 2 is a front view of the transfer roller according to the first embodiment of the present invention, and FIG. 3 is an enlarged perspective view of the insulating thin film mesh according to the first embodiment of the present invention.

As shown in the figure, a transfer roller 24 has a conductive shaft 21 covered with a rubber resistance layer 22, and a mesh opening 23 a and an insulating part 2 on the rubber resistance layer 22.
It is formed by further covering the insulating thin film mesh 23 made of 3b. In the present embodiment,
Urethane rubber contains alkali metal, and resistance value is 3 ×
The urethane foam adjusted to 10 ⁸ [Ω] was used as the rubber resistance layer 22, and the Asker C hardness of the rubber resistance layer 22 was 35.
[°], and the pressing force against the photosensitive drum 11 (FIG. 1) was set to 2000 [gf].

A DC power supply (not shown) is connected between the conductive shaft 21 and the conductive support 11a of the photosensitive drum 11, and the DC power supply connects the conductive shaft 21 to about 3000 [V]. Is applied. In this case, since the negatively charged toner 16 is used, the polarity of the transfer voltage applied to the transfer roller 24 from the DC power supply is made positive. The positively charged toner 16
Is used, the polarity of the voltage applied from the DC power supply to the transfer roller 24 is made negative.

Next, the dimensions of the transfer roller 24 will be described. A stainless steel shaft having a diameter of 8 [mm] is used as the conductive shaft 21, and a foamed semiconductive urethane rubber obtained by adding an alkali metal to urethane rubber is molded as the rubber resistance layer 22. The finished outer diameter is 18 mm.
[Mm], the longitudinal dimension of the rubber resistance layer 22 is 220
[Mm].

The thickness of the insulating thin film mesh 23 covering the rubber resistance layer 22 is preferably not more than 50% of the thickness of the toner layer formed on the photosensitive drum 11, One side of the section 23a is set to about 80% of the basic resolution interval of the image forming apparatus. For example, as shown in FIG. 3, when the resolution of the image forming apparatus is 600 [dpi], since the basic resolution interval is 42.3 [μm], one side of each mesh opening 23a is about 34 [μm]. ]
become.

Further, since the insulating portion 23b of 8.3 [μm], which is obtained by subtracting the mesh interval from the basic resolution interval, is formed between the mesh openings 23a, the toner image can be recorded on the recording paper 1.
8, a white streak occurs in a portion corresponding to the insulating portion 23b. However, in general, each of the toners 16 of the toner image becomes 1.2 to 1.5 times as large as the recording paper 18 passing through the fixing device 27.
The width of 3b is accordingly reduced to a value of 20% or less. As a result, generation of white streaks can be prevented.

The insulating thin film mesh 23 is formed by applying an insulating film on the entire surface of the rubber resistance layer 22 and then performing an etching process to form a mesh, or by directly forming the rubber resistance layer 22 by screen printing. Is done. The longitudinal dimension of the rubber resistance layer 22 covered with the insulating thin film mesh 23 is determined by the longitudinal dimension of the photoconductive layer 11b of the photoconductor drum 11.

In this case, in manufacturing the photosensitive drum 11, it is difficult to form the photoconductive layer 11b on the circumference of both ends in the longitudinal direction of the photosensitive drum 11.
Therefore, the length of the rubber resistance layer 22 in the longitudinal direction is slightly shorter than the length of the photoconductive layer 11b so that the current from the DC power supply does not leak to the photosensitive drum 11.

The conductive shaft 21 includes:
A metal shaft such as stainless steel, steel, or aluminum is used. The rubber resistance layer 22 is made of a rubber material such as butyl rubber, chloroprene rubber, urethane rubber, silicone rubber, nitrile rubber, styrene rubber, butadiene rubber, fluorine rubber, ethylene propylene rubber, graphite, ferrite, aluminum powder, copper powder. , A conductive powder such as bronze powder, stainless steel powder, titanium oxide, tin oxide or the like, a metal powder, a metal fiber or the like, and molded into a foam. The rubber resistance layer 22 can be formed in a solid shape.

It is preferable that the resistance value of the rubber resistance layer 22 falls within the range of 10 ⁶ to 10 ⁹ [Ω] as a result of experiments. In this case, when the resistance value of the rubber resistance layer 22 is smaller than the above range, when there is a defect such as a pinhole in the photoconductive layer 11b, the transfer voltage applied from the DC power supply to the transfer roller 24 is applied to the photosensitive drum 11. Easier to leak,
Improper transfer occurs. Further, when the resistance value is larger than the above range, poor transfer is likely to occur.

Further, the transfer roller 24 and the photosensitive drum 1
In the case of the foam-shaped rubber resistance layer 22, the Asker C hardness is set to 20 to 60 [°], and the solid rubber resistance layer 2 is formed.
In the case of 2, the JIS A hardness is preferably 30 [°] or less. The pressing force of the transfer roller 24 against the photosensitive drum 11 depends on the hardness of the rubber resistance layer 22, but is
When the value is set to 00 to 4000 [gf], a dropout of the transfer or the like does not occur.

The transfer voltage applied to the conductive shaft 21 depends on the resistance value of the rubber resistance layer 22.
When the voltage is set to 0 to 5000 [V], good transfer can be performed. The insulating thin film mesh 23 is made of a fluororesin,
It is formed of polyimide, polyethylene resin, polystyrene resin, polycarbonate resin, or the like, and has a resistance value that is at least two orders of magnitude higher than the resistance value of the rubber resistance layer 22, for example, about 10 ⁸ to 10 ¹¹ [Ω]. .

Next, a transfer method when the insulating thin film mesh 23 having the above structure is used for the transfer roller 24 will be described. When the toner image formed on the photoreceptor drum 11 is sent to the transfer unit, the negatively charged toner 16 constituting the toner image is charged with the positive polarity applied to the transfer roller 24. Is attracted to the recording paper 18 by the electric potential,
Transcribed.

At this time, since the surface of the transfer roller 24 is covered with the insulating thin film mesh 23, the photosensitive drum 1
A uniform rectangular electric field is formed between the transfer roller 1 and the transfer roller 24 by the transfer voltage. Therefore, even if a discharge occurs between the photosensitive drum 11 and the transfer roller 24, the toner 16 does not scatter, so that the toner 1
6 can be prevented from adhering to a white background of the recording paper 18.

As a result, the toner image transferred to the recording paper 18 is not disturbed, and the image quality can be improved. FIG. 4 is a first diagram illustrating the operation of the transfer unit according to the first embodiment of the present invention. FIG. 5 is a first distribution diagram of the toner before transfer according to the first embodiment of the present invention. FIG. 3 is a first distribution diagram of toner after transfer according to the first embodiment of the present invention.

As shown in FIG. 4, when the insulating thin film mesh 23 is coated on the rubber resistance layer 22, the mesh opening 23 a has a potential (+1.5) in a form in which the transfer voltage leaks.
[KV]), the insulating portion 23b becomes 0 [V], a rectangular transfer portion potential distribution is formed, and the photosensitive drum 1
1 and the transfer roller 24 (FIG. 1). On the other hand, the surface potential of the photosensitive drum 11 is -7.
An electrostatic latent image potential distribution is formed by the 00 [V] portion and the 0 [V] portion, and the toner 16 is sucked into the 0 [V] portion.

In this case, a sufficient potential difference for transferring the toner image to the recording paper 18 is formed in the mesh opening 23a, whereas the toner image is transferred to the recording paper 18 in the insulating part 23b. Is not sufficiently formed, the toner 16 is attracted only to the mesh opening 23a and not to the insulating part 23b. Moreover, the lines of electric force generated by the rectangular electric field concentrate on the mesh openings 23a.

Therefore, when the toner image formed on the photosensitive drum 11 is transferred to the recording paper 18, FIG.
As shown in FIG. 3, the toner 1 adhering to the photosensitive drum 11
6, only the portion corresponding to the mesh opening 23a of the recording paper 18 is adhered to the insulating portion 2 as shown in FIG.
Since the toner image does not adhere to the portion corresponding to 3b, no disturbance occurs in the toner image. As a result, image quality can be improved.

The photosensitive drum 11 and the transfer roller 24
Even if a discharge occurs between the recording paper 18 and the toner, the toner 16 does not scatter, and the toner 16 can be prevented from adhering to a white background of the recording paper 18. Next, a case where the toner image on the photosensitive drum 11 is displaced from the insulating thin film mesh 23 in the longitudinal direction of the photosensitive drum 11 will be described.

FIG. 7 is a second diagram illustrating the operation of the transfer unit according to the first embodiment of the present invention, and FIG. 8 is a second distribution diagram of the toner before transfer according to the first embodiment of the present invention. , FIG. 9
FIG. 5 is a second distribution diagram of the toner after transfer according to the first embodiment of the present invention. As shown in FIG.
2 is covered with the insulating thin film mesh 23, the mesh opening 23a has a potential (+1.5
[KV]), the insulating portion 23b becomes 0 [V], a rectangular transfer portion potential distribution is formed, and the photosensitive drum 1
1 and the transfer roller 24 (FIG. 1). On the other hand, the surface potential of the photosensitive drum 11 is -7.
An electrostatic latent image potential distribution is formed by the 00 [V] portion and the 0 [V] portion, and the toner 16 is sucked into the 0 [V] portion. When the toner image on the photosensitive drum 11 is displaced from the insulating thin film mesh 23 in the longitudinal direction of the photosensitive drum 11, the toner image is transferred to the recording paper 1.
The toner 16 is sucked only in the mesh opening 23a in which the potential difference for transferring to the toner image 8 is formed, and the toner 16 is not sucked in the insulating portion 23b.

Therefore, when the toner image formed on the photosensitive drum 11 is transferred to the recording paper 18, FIG.
As shown in FIG. 3, the toner 1 adhering to the photosensitive drum 11
As shown in FIG. 9, the adhesive 6 adheres only to the portion of the recording paper 18 corresponding to the mesh opening 23 a, and
It does not adhere to the portion corresponding to 3b. In this case, the toner 16 is separated into two parts, but no disturbance occurs in the toner image. As a result, image quality can be improved.

Incidentally, even if the toner image on the photosensitive drum 11 is displaced from the insulating thin film mesh 23 in the circumferential direction of the photosensitive drum 11, the toner 16 is separated into two parts. No disturbance occurs in the toner image. Next, a second embodiment of the present invention will be described. FIG. 10 is an enlarged view of the insulating layer according to the second embodiment of the present invention.

In the figure, 53 is a rubber resistance layer, and 54 is an insulating thin film formed on the surface of the rubber resistance layer 53 with a width (8.3 [μm]) smaller than the basic resolution interval in a spot shape. It is an insulating layer as a pattern. In this case, since the image can be continuously formed in a portion (34 [μm]) other than the insulating layer 54, the image quality can be improved.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0043]

As described above in detail, according to the present invention, in an image forming apparatus, an image carrier, a charging device for uniformly and uniformly charging the surface of the image carrier, and An exposure device for forming an electrostatic latent image on an image carrier, a developing device for developing the electrostatic latent image on the image carrier to form a toner image, and a transfer device for transferring the toner image to a recording medium And a fixing device for fixing the toner image transferred to the recording medium.

Then, an insulating thin film pattern having an insulating portion is coated on the surface of the transfer device. In this case, the insulating thin film pattern causes a portion where a potential difference for transferring the toner image to the recording medium is sufficiently formed and a portion where the potential difference for transferring the toner image to the recording medium is not sufficiently formed. When the toner image formed on the image carrier is transferred to a recording medium, disturbance of the toner image does not occur. As a result, image quality can be improved.

Further, since the toner does not scatter,
It is possible to prevent toner from adhering to a white background of the recording medium.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a front view of the transfer roller according to the first embodiment of the present invention.

FIG. 3 is an enlarged perspective view of an insulating thin film mesh according to the first embodiment of the present invention.

FIG. 4 is a first diagram illustrating an operation of the transfer unit according to the first embodiment of the present invention.

FIG. 5 is a first distribution diagram of toner before transfer according to the first embodiment of the present invention.

FIG. 6 is a first distribution diagram of toner after transfer according to the first embodiment of the present invention.

FIG. 7 is a second diagram illustrating the operation of the transfer unit according to the first embodiment of the present invention.

FIG. 8 is a second distribution diagram of the toner before transfer according to the first embodiment of the present invention.

FIG. 9 is a second distribution diagram of the toner after transfer according to the first embodiment of the present invention.

FIG. 10 is an enlarged view of an insulating layer according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 photoconductor drum 12 charging roller 13 exposing device 14 developing device 18 recording paper 23 insulating thin film mesh 23 a mesh opening 23 b insulating portion 24 transfer roller 27 fixing device 54 insulating layer

Claims (2)

[Claims] 1. An image carrier, (b) a charging device for uniformly and uniformly charging the surface of the image carrier, and (c)
An exposure device for forming an electrostatic latent image on the image carrier,
(D) a developing device that develops the electrostatic latent image to form a toner image; (e) a transfer device that transfers the toner image to a recording medium; and (f) a toner image that is transferred to the recording medium. An image forming apparatus comprising: a fixing device for fixing; and (g) an insulating thin film pattern provided with an insulating portion on a surface of the transfer device. 2. An insulating thin film mesh comprising an insulating portion and a mesh opening.
An image forming apparatus according to claim 1.