JPH09281813A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a deterioration in a photoreceptor caused by the catching of developer carriers in the nip between the photoreceptor and an intermediate transfer means and the sticking of toner to the intermediate transfer means by providing an elastic layer on the intermediate transfer means and fixing a fine grain whose diameter is specified with respect to the diameter of a toner grain and a grain whose diameter is equal to or less than that of the toner grain and larger than that of the fine grain, on the surface. SOLUTION: The intermediate transfer means 5a is provided with the elastic layer 5b and at least two or more kinds of fine grains having different grain diameters of the fine grain 5c whose diameter is <=1/10 that of the toner grain and the grain 5d whose diameter is equal to or less than that of the toner grain and larger than that of the fine grain are fixed on the surface of the intermediate transfer means. For the material of the fine grain 5c, preferably, hydrophobic silica obtained in such a manner that a silica grain surface is replaced with a hydrophobic functional group such as a methyl group and an ethyl group is suitable. In the larger grain 5d, a thing not stuck to the toner such as silica, silicone resin, polyester resin, acrylic resin and fluororesin is used as a base material.

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 using electrophotography.

[0002]

2. Description of the Related Art An image forming an image by transferring a toner image formed on a photoconductor to an intermediate transfer unit before transferring the toner image to the recording medium and transferring the toner image from the intermediate transfer unit to the recording medium. The forming method is used in a color image forming apparatus such as a color copying machine because a multicolor image can be easily formed.

In the above-mentioned intermediate transfer body system, various characteristics are required for the intermediate transfer means for intermediately holding the toner image. However, when the intermediate transfer means is provided with the elastic layer, the developer is provided in the nip portion with the photoconductor. The damage to the photoconductor that occurs when the carrier is bitten is reduced, which is effective in extending the life of the photoconductor.

Further, as an advantage of providing an elastic layer, Japanese Patent Laid-Open No.
As described in Japanese Patent Laid-Open No. 1-198773, there is also an effect that a nip between the photoconductor and the transfer point of the intermediate transfer means is stably secured. Further, by providing an elastic layer on the surface layer of the intermediate transfer means, the lowermost layer of the toner adheres to the surface of the intermediate transfer means, which lowers the transfer efficiency of the toner.
As disclosed in Japanese Patent Laid-Open No. 7-234592, it has been proposed to fix fine particles having a particle diameter of ½ or less of the toner particle diameter on the surface of the intermediate transfer means.

[0005]

As in the above-mentioned prior art, it is an effective means to provide the intermediate transfer means with an elastic layer, and fixing fine particles to the surface of the intermediate transfer means improves the transfer efficiency. Is effective for.

However, since the fine particles each have a small absolute mass, they tend to float in the air, and it is extremely difficult to fix them to the surface of the elastic body. This point is not mentioned.

Further, if the fine particles are only partially adhered to the surface of the elastic body, it is possible to press the fine particles onto the surface of the intermediate transfer member, but it is to be uniformly adhered to the entire surface of the intermediate transfer member. Is extremely difficult.

If the adhesion of the fine particles is non-uniform, the transfer efficiency of the toner becomes non-uniform in the whole image, and transfer unevenness occurs. Therefore, image defects such as density unevenness and characters, thin lines, and other image defects occur. However, various image defects such as non-uniform line thickness will occur.

[0009]

SUMMARY OF THE INVENTION The present invention has been devised to solve the above-mentioned problems. In order to obtain a uniform surface with good releasability from toner, the intermediate transfer means has elasticity. , The intermediate transfer means has an elastic layer, and the fine particles having a particle diameter of 1/10 or less of the toner particle diameter on the surface of the intermediate transfer means and the particle diameter equal to or smaller than the toner particle diameter and larger than the fine particles. At least two kinds of fine particles different in particle size from particles are fixed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of an image forming apparatus using the present invention. The structure of the apparatus will be described with reference to the drawing.

A controller (not shown) for controlling the printer is provided on the inner side of the main body. An image signal processing unit and a print command control unit are built in this controller.

A belt-shaped photosensitive member 1 stretched around three rotatable shafts is provided in the central portion on the right side of the main body.

The photosensitive belt 1 has a photosensitive layer (for example, OPC) on the surface and a conductive layer (for example, aluminum) under the photosensitive layer.
It has a two-layer structure with and.

The photoconductor belt 1 is designed to run in the X direction, and in the vicinity of the photoconductor belt 1, the charger 2, the exposing means 3, the developing means 4a, 4b, and the developing means 4 are sequentially arranged along the X direction.
4c, 4d, an intermediate transfer drum 5, an erase lamp 6, and a photoconductor cleaner 7 are provided.

The intermediate transfer drum 5 also includes a cleaner 8
And a pre-transfer charger 9 are provided.

The charger 2 is a corotron charger and charges the photoconductor by discharging the corotron wire.

The exposing means 3 comprises a laser diode, a polygon mirror, an fθ lens and a case containing them.

The four developing devices of the developing means 4a, 4b, 4c and 4d are of the same type, but toners of different colors, for example, yellow, magenta, cyan and black are stored, and each color is stored. develop. In addition, each is designed to operate independently.

The intermediate transfer drum 5 has a diameter of 80 to 150 mm.
Cylinder, conductive cylindrical substrate (eg aluminum drum)
And a surface layer that covers it (details will be described later).

The electrically conductive cylindrical substrate is connected to ground. The intermediate transfer drum 5 is pressed against the photoconductor belt 1 with an appropriate pressure and contacts with the nip width of 5 to 20 mm, and the toner image formed on the photoconductor belt 1 receives the photoconductor belt at this nip portion. It is transferred onto the intermediate transfer drum 5 by the voltage applied to the first conductive layer.

Both the photosensitive belt 1 and the intermediate transfer drum 5 may be driven, or one of them may be driven by the other.

The erase lamp 6 removes the residual potential on the photosensitive belt 1 after the transfer by light irradiation.

The photoconductor cleaner 7 removes the residual toner remaining on the photoconductor belt 1 after the transfer.

Similarly, the cleaner 8 removes the toner remaining on the intermediate transfer drum 5 after transferring the recording medium.

The cleaner 8 retreats upward while the toner image is formed on the intermediate transfer drum 5.

The pre-transfer charger 9 has a function of making the potential of the surface of the toner on the intermediate transfer drum 5 constant and improving the transfer.

Below the photosensitive belt 1, there is a paper cassette 1
1 is provided. A pickup roller 12 is provided above the paper cassette 11, whereby the recording medium 10 is pulled out from the paper cassette 11 and discharged through the registration roller 13, the transfer roller 14, the static eliminator 15, and the fixing device 16.

The registration roller 13 is for aligning the leading ends of the recording medium 10.

The transfer roller 14 is for transferring the toner image formed on the intermediate transfer drum 5 onto the recording medium 10, and has a metal shaft and an appropriate resistance value (1 k to 10 GΩ).
Of the elastic layer.

An appropriate voltage for transfer is applied to the metal shaft to transfer the toner image. In addition, the transfer roller 1
The toner image 4 is retracted so that it does not come into contact with the intermediate transfer drum 5 while the toner image is formed on the intermediate transfer drum 5.

The static eliminator 15 neutralizes the recording medium 10 and the fixing device 16 fixes the toner on the recording medium 10.

Next, the surface layer of the intermediate transfer drum 5 of the present invention will be described in detail.

FIG. 2 is a schematic structural view of the surface of the intermediate transfer drum 5 used in this embodiment.
The elastic layer 5b is formed on a, and the fine particles 5c and 5d are fixed to the surface of the elastic layer 5b.

As described above, by covering the surface of the elastic layer with the fine particles, the adhesiveness of the elastic layer is lowered.

This is to suppress the adhesive force of the toner with the above-mentioned surface constitution so that the adhesive property disappears when sand is adhered to the surface of the adhesive tape.

Further, as the surface characteristics of the fine particles, if particles having a small surface energy such as hydrophobic silica are used, the adhesiveness with the toner is further lowered, and a further effect can be obtained.

Next, the characteristics of each layer will be described in detail. The intermediate transfer drum substrate 5a is a cylindrical raw tube made of metal (such as aluminum).

The elastic layer 5b has a thickness of about 0.1 to 3 mm so that the photoreceptor belt 1 is not easily scratched even when the developer carrier is caught in the nip between the photoreceptor belt 1 and the intermediate transfer drum 5. is there.

As the material, polyurethane rubber, chloroprene rubber, nitrile rubber, epichlorohydrin rubber, silicone rubber, acrylic rubber, fluorine rubber, etc. are used. The reason why such a great variety of materials can be selected is that the adhesion of the fine particles 5c and 5d to the surface eliminates the tackiness of the surface.

Incidentally, the elastic layer 5b does not necessarily have to be formed as a single layer. For example, polyurethane rubber has the property of being deteriorated under the influence of ozone generated from the charger 2.

Therefore, when urethane rubber is used as the material of the elastic layer 5b, in order to prevent this deterioration, the elastic layer 5b has a two-layer structure and the surface is made of a layer of another material (for example, fluororubber or fluororesin). It is better to have a structure covered with dispersed fluororubber).

FIG. 3 is a schematic sectional view of the surface of the intermediate transfer drum 5 in which an intermediate layer 5e for covering the surface is added to the elastic layer 5b. The layer forming the upper layer portion of the elastic layer 5b as in this example is preferably made of an elastic material.

Further, in order to control the resistance value of the intermediate transfer drum 5, a layer for adjusting the resistance is provided inside the elastic layer 5b (for example, in the case of a high resistance layer, a layer such as a blocking layer used as a base of the photosensitive member or For a medium resistance material such as PET, a rubber material such as the above-mentioned fluororubber or a semiconductive plastic may be used, and a material may be selected according to the resistance value of the elastic layer 5b and other layers). .

FIG. 4 shows that the insulating layer 5 is formed below the elastic layer 5b.
The schematic sectional drawing of the surface of the intermediate transfer drum 5 which has f is shown.

In this case, the structure in which the resistance layer is formed on the lowermost layer portion of the elastic layer 5b does not necessarily have elasticity, but when it is formed on the middle portion and the upper layer portion of the elastic layer 5b, elasticity is not formed. I need.

The fine particles 5c have an average particle size of 10
Use one that is less than 1 /.

In this embodiment, a toner having an average particle size of 7 μm was used, but the present invention is not limited to this, and the average particle size is 3 to 3.
20 μm toner may be used.

The material of the fine particles 5c is silica (Si
O ₂ ), silicone resin, polyester resin, acrylic resin, fluororesin, etc. that do not adhere to the toner are used as the base material, but more preferably the silica particle surface is hydrophobic such as methyl group or ethyl group. Hydrophobic silica substituted with the functional group of (3) is suitable because of its low adhesion to the toner.

Particles 5d having a particle size equal to or smaller than the toner particle size and larger than the fine particles 5c are the above-mentioned silica particles.
(SiO ₂ ), silicone resin, polyester resin, acrylic resin, fluororesin, etc. that do not adhere to the toner are used as the base material. Among these base materials, the silicone resin has a low surface energy and therefore has a low adhesiveness to the toner. It was low and suitable.

The large particles 5d are preferably spherical in shape. By adhering at least one or more kinds of fine particles made of these materials to the surface of the intermediate transfer drum 5, the adhesive force with the toner can be reduced, but two kinds of fine particles having different particle diameters can be used. By using particles, it is possible to increase the pressure contact force for fixing these fine particles.

Specifically, as shown in FIG. 5, the pressing member 1
When pressure is applied to the fine particles 5c and 5d at 7, the presence of the larger particles 5d makes it possible to concentrate the stress applied to the fine portion, and the fixing force of the fine particles 5c also increases.

Further, by making the shape of the larger particles 5d spherical, and performing the pressure contact while sliding, the larger particles 5d play the role of rollers, so that the surface of the intermediate transfer means is smooth. Fine particles 5c without scratching,
The 5d can be adhered well to the entire surface.

These two kinds of fine particles 5 having different sizes
As for the mixing ratio of c and 5d, since the fine and uniform particles 5c are adhered uniformly and densely to improve the releasability of the toner,
It is desirable to increase the blending amount of the particles 5c that are smaller than the larger particles 5d. Preferably, the compounding amount of the large particles 5d was 3 to 50 wt.% With respect to the total amount of the fine particles 5c and the large particles 5d.

Here, a method for fixing the fine particles 5c and 5d to the surface of the intermediate transfer drum 5 will be briefly described.

Apply a friction member to the surface of the intermediate transfer drum 5,
The fine particles 5c and 5d are mixed in the contact portion, and a speed difference is applied to cause friction, and the fine particles 5c and 5d are fixed to the surface of the intermediate transfer drum 5 by frictional contact.

At this time, if the particles 5d having a larger particle size than the fine particles 5c are mixed and brought into frictional contact with each other, the fixing can be performed in a relatively short time.

The fine particles 5c and 5d may be dispersed in a solvent. Examples of the solvent include alcohols (eg ethyl alcohol, isopropyl alcohol etc.), ethers (eg dimethyl ether, diethyl ether etc.), Ketones (eg acetone, 2-butanone, etc.), hydrocarbons (eg hexane, heptane,
Cyclohexane, etc.), aromatics (eg, toluene, xylene, etc.), or organic solvents such as mixed solvents using at least one of these, or water-based solvents to which a dispersant or emulsifier is added It is also possible to apply fine particles 5c and 5d dispersed in these solvents to the surface of the transfer drum 5 by spraying or the like, and then frictionally contact and fix them.

The fine particles 5c, 5 fixed in this way
Since d sticks to the intermediate transfer drum 5 relatively firmly,
Almost no matter if it is wiped with a solvent such as alcohol, the intermediate transfer drum 5 can be reused for cleaning.

In the above example, the intermediate transfer means is a drum-shaped device. However, even if the intermediate transfer means is belt-shaped, fine particles can be fixed to the surface as in the above example. It is obvious that good characteristics can be obtained with.

The method of fixing fine particles to the surface as described above is effective not only when applied to the intermediate transfer drum 5 but also to a member which comes into contact with toner and requires elasticity.

For example, when the surface of the transfer roller or the transfer belt is subjected to the surface treatment as in the present embodiment, the contamination of the toner on the roller or the belt is reduced and the cleaning of those members is facilitated.

Further, by fixing fine particles which are stable against heat to the surface of the fixing roller, there was also an effect of reducing the offset.

Such an application is an example applicable not only to the intermediate transfer type image forming apparatus of this embodiment, but also to other type image forming apparatuses.

The operation of the electrophotographic apparatus configured as above will be described below.

First, when a print command from the computer is input to the controller, the photosensitive belt 1 starts to move, and the photosensitive belt 1 charged by the charger 2 is exposed by the exposing means 3 to form a latent image. To be done. This latent image is first developed by the developing means 4a.

The developed toner image is transferred onto the intermediate transfer drum 5. Next, the photosensitive belt 1 is charged and exposed again, and this time, development is performed by the developing means 4b.

Then, the developed toner image is transferred onto the intermediate transfer drum 5 so as to be superimposed on the previous image.

This process is repeated thereafter with the developing means 4c and 4d to form toner images of a plurality of colors on the intermediate transfer drum 5. The toner images formed on the intermediate transfer drum 5 are made uniform in potential by the pre-transfer charger 9, and are transferred at once by the transfer roller 14 to the recording medium 10 pulled out from the paper cassette 11 by the pickup roller 12.

Then, the recording medium 10 is discharged and stripped by the static eliminator 15 and sent to the fixing device 16 to be fixed.

At this time, when the intermediate transfer drum 5 having the fine particles 5c and 5d fixed to the surface, which has been described in detail above, is used, the surface of the intermediate transfer drum 5 has elasticity, and therefore the developer is formed in the nip with the photosensitive belt 1. The photoreceptor belt 1 is not damaged even when foreign matter such as the carrier is bitten in, and the life of the photoreceptor belt 1 deteriorated after about 1000 sheets of paper passed, but up to 20,000 sheets it is possible to print without any problem in image quality. became.

Further, since the adhesive force between the surface of the intermediate transfer drum 5 and the toner is lowered, the transfer efficiency from the intermediate transfer drum 5 to the recording medium 10 is increased by up to 5%, which is a great effect for improving the image density. .

Further, voids in characters and thin lines were reduced to a level where they were barely visible to the naked eye, which greatly contributed to the improvement of image quality. Further, after the toner is transferred onto the recording medium 10, the amount of the toner remaining on the intermediate transfer drum 5 is reduced due to the increased transfer efficiency, and the cleaning efficiency of the cleaner 8 is also improved. , The stain on the next image is almost gone.

As described above, by using the present invention, an image forming apparatus with high image quality and low maintenance is realized.

[0075]

As in the present invention, the intermediate transfer means is provided with the elastic layer, and the surface of the intermediate transfer means has fine particles having a particle diameter of 1/10 or less of the toner particle diameter, and the particle diameter is the toner particle diameter. By fixing particles that are equal to or smaller than the above-mentioned fine particles and are smaller than the fine particles, it is possible to prevent deterioration of the photoconductor due to the developer carrier being caught in the nip between the photoconductor and the intermediate transfer unit, and to prevent the toner from being transferred to the intermediate transfer unit. The stickiness also disappears.

Further, the adherence of these fine particles to the intermediate transfer means becomes uniform and dense.

As a result, the photoconductor has a long life, high-efficiency transfer of toner to the recording medium is realized, image uniformity is high, and image defects and stains due to hollow defects and poor cleaning of the intermediate transfer unit are caused. An image forming apparatus in which a high-quality image having no quality is formed is obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram illustrating a surface structure of an intermediate transfer drum.

FIG. 3 is a diagram illustrating another embodiment of the surface structure of the intermediate transfer drum.

FIG. 4 is a diagram illustrating another embodiment of the surface structure of the intermediate transfer drum.

FIG. 5 is a diagram illustrating a method of fixing fine particles to the surface of an intermediate transfer drum.

[Explanation of symbols]

1 ... Photosensitive belt, 2 ... Charging device, 3 ... Exposure means, 4a,
4b, 4c, 4d ... Developing means, 5 ... Intermediate transfer drum, 5
a ... Intermediate transfer drum substrate, 5b ... Elastic layer, 5c, 5d ...
Fine particles, 5e ... Intermediate layer, 5f ... Insulating layer, 6 ... Erase lamp, 7 ... Photoconductor cleaner, 8 ... Cleaner, 9 ... Pre-transfer charger, 10 ... Recording medium, 11 ... Paper cassette, 12
... Pickup roller, 13 ... Registration roller, 14 ...
Transfer roller, 15 ... Static eliminator, 16 ... Fixing device, 17 ... Pressure member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masashi Yamamoto, Inventor Masashi Yamamoto, 1-1-1, Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. (72) Inventor, Tetsuo Ishikawa 1-chome, Higashitaga-cho, Hitachi City, Ibaraki Prefecture No. 1 Company, Hitachi Ltd., Electrical Appliances Division, Taga Headquarters (72) Inventor Hiroyuki Onodera 1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture, Ltd. Hitachi Ltd., Electrical Appliances Division, Taga Headquarters (72) Invention Person Masahiro Nakano 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki, Ltd. Inside the Taga Headquarters, Electric Equipment Division, Hitachi, Ltd.

Claims (7)

[Claims] 1. An image forming apparatus for transferring a toner image on a photoconductor to an intermediate transfer means and transferring the toner image on the intermediate transfer means to a recording medium to form an image, wherein the intermediate transfer means is an elastic layer. And at least particles having a particle size equal to or less than 1/10 of the toner particle size on the surface of the intermediate transfer means, and particles having a particle size equal to or smaller than the toner particle size and larger than the particle size. An image forming apparatus characterized in that two or more kinds of fine particles having different particle sizes are fixed. 2. The image forming apparatus according to claim 1, wherein two or more elastic layers are formed. 3. The image forming apparatus according to claim 1, wherein the two kinds of fine particles having different particle diameters are silica (Si
O ₂ ), a silicone resin, a polyester resin, an acrylic resin, or a fluororesin as a base material, and at least one kind of them is fixed to the surface of the intermediate transfer means. apparatus. 4. The image forming apparatus according to claim 1, wherein at least one of the two or more kinds of fine particles having different particle sizes is a particle having silica (SiO ₂ ) as a base material,
Further, the image forming apparatus is characterized in that the silica is a hydrophobic silica in which the particle surface is substituted with a hydrophobic functional group. 5. The image forming apparatus according to claim 1 or 2, wherein, of the two or more kinds of fine particles having different particle diameters, at least the larger particle diameter is a particle having a silicone resin as a base material. An image forming apparatus characterized by. 6. The image forming apparatus according to claim 1, wherein among the two or more kinds of fine particles having different particle sizes that are fixed, at least the larger particle has a shape close to a sphere. An image forming apparatus characterized by the above. 7. The image forming apparatus according to claim 1, wherein the elastic layer or the outermost surface layer of the elastic layer is made of fluororubber or fluororubber in which fluororesin is dispersed.