JP2631402B2 - Cleaning device for image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer, and particularly to a cleaning apparatus for the image forming apparatus. is there.

(Prior art and problems to be solved) The toner image electrostatically formed on the surface of the moving photoconductor is
In a well-known image forming apparatus in which a process of electrostatically transferring to a sheet-like transfer material such as paper is repeatedly performed, it is essential to sufficiently remove residual toner remaining on a photoreceptor for each transfer to obtain a high-quality image. Condition.

As cleaning means for this purpose, various means such as a fur brush, a cleaning blade, and cleaning wear have been conventionally proposed. Among these known cleaning means, the cleaning blade has a simple configuration and a small size. It is well known that the method is widely used because of its cost advantage and excellent toner removing function.

However, on the surface of the photoreceptor after transfer, not only toner but also fine paper powder generated from paper as a transfer material, deposited rosin and talc and other deposits, and corona due to the presence of high-pressure members in the apparatus. Various foreign substances such as products are mixed, and if these foreign substances adhere to the photoreceptor, there is a regret that they cannot be sufficiently removed by the cleaning blade. Thus, the electrostatic latent image was disturbed, and the image quality was degraded.

In order to avoid such a problem, in a cleaning device, a magnet roller is arranged near a cleaning blade at an appropriate distance from a photoreceptor, and toner collected in the device is supplied to the magnet roller to supply the toner to the surface thereof. A magnetic brush is formed on the surface of the photoreceptor by the magnetic brush (for example, Japanese Patent Application No.
-104970), or an elastic cleaning roller such as a sponge is arranged upstream of the cleaning blade,
Japanese Patent Application No. 55-100585 (Japanese Patent Application No. 55-100585) has been proposed to remove the above-mentioned foreign substances by rubbing the surface of the photoreceptor.

FIG. 2 schematically shows an example of the former device, in which a cleaning blade 6a disposed in a cleaning device C disposed close to a cylindrical photoconductor 1 rotating in the direction of the arrow in FIG. Magnetic roller M on the upstream side when viewed in the direction
Is disposed at an appropriate distance from the photoreceptor 1 and is also rotated in the direction of the arrow shown in the figure to transport the toner collected by the blade 6a to the reservoir on the back side of the cleaning device, and to connect the scraper S to an appropriate position. The distance between the scraper S and the magnetic roller and the distance between the magnetic roller M and the photoconductor 1 are, for example, 0.3 to 0.7 mm for the former and 0.8 mm for the latter.
The magnetic brush formed at a position beyond the scraper S rubs the surface of the photoconductor 1.

With this configuration, it is possible to effectively remove paper dust and the like having a relatively low adhesion to the photoreceptor of about 0.1 to 1 mm, which are mixed in the residual toner, but still cannot remove corona products and the like. Was enough.

Further, in the above-described apparatus using the elastic cleaning roller, the magnetic roller is disposed at the position of the magnetic roller. However, since such a roller has a strong rubbing force, rosin, talc, corona product, etc. However, the photosensitive member may be damaged, or the electrostatic latent image may be disturbed due to charging due to friction between the cleaning roller and the photosensitive member.

In order to avoid such a drawback, a means for removing the collected toner is provided on the surface of the elastic cleaning roller, and the surface of the cleaning roller is set at a position higher than the potential of the photosensitive member at the portion where the roller contacts the photosensitive member. There has also been proposed a device that positively removes foreign matter on the photoreceptor side by charging to a high potential.

Although these proposals have achieved certain effects,
Particularly in the case of an electrophotographic apparatus using an organic photoreceptor, the cleaning roller charged to a high potential is in contact with the photoreceptor even when the operation is stopped. Injection of electric charge into the photoreceptor causes a decrease in the surface potential of the photoreceptor during the next primary charging, resulting in a defect that an image defect is caused by the charging memory.

The present invention has been made in order to cope with such a situation, and in a cleaning device provided with an elastic cleaning roller, the cleaning roller is maintained at a high potential during operation, and the potential of the roller is reduced during non-operation. It is an object of the present invention to provide a cleaning device that removes toner, effectively cleans toner and other foreign matters on the photoconductor side, prevents generation of charging memory, and can always stably perform good cleaning. Things.

(2) Configuration of the Invention (Technical Means for Solving the Problems and the Function thereof) In order to achieve the above object, the present invention provides a cleaning method for removing foreign matters such as residual toner on the surface of the image carrier by rubbing against the image carrier. Means for maintaining the surface potential of the cleaning roller at the pressure contact rubbing portion higher than the surface potential of the image carrier at the portion during the cleaning operation, when the cleaning operation is not performed, A cleaning device (1) comprising means for removing the surface potential of the cleaning roller so as to make the surface potential of the cleaning roller at the rubbed portion lower than the surface potential of the image carrier; or (1) 5), wherein the photosensitive layer of the image carrier is an organic photoconductor.

With this configuration, in the image forming apparatus in which the cleaning roller is pressed against the image bearing member, it is possible to preferably prevent the occurrence of the charging memory at the pressed portion and always perform good cleaning.

(Explanation of Embodiment) FIG. 1 is a main portion showing an embodiment in which the present invention is applied to a copying machine having an organic photoconductive layer formed on a surface thereof and having a cylindrical photoreceptor rotating in the direction of arrow A in the drawing. FIG. 2 is a schematic side view of the cleaning device, in which a cleaning device 2 is disposed in parallel with a photoconductor 1 having an axis perpendicular to the paper surface.

A cleaning blade 3 is provided in the cleaning device 2.
Is made of an insulating elastic material on the upstream side of the photosensitive member in the running direction, and is shown in the direction of the arrow shown in the figure (or the opposite direction).
And a cleaning roller 4 that rotates at an appropriate relative speed with respect to the surface of the photoconductor 1.

At a transfer site (not shown), the photosensitive member 1 does not contribute to the transfer.
Residual toner and various foreign substances as described above
The photoreceptor 1 is brought to the position of the cleaning device with the rotation thereof, and is usually removed by the cleaning roller 4 which is in pressure contact with the photoreceptor with a nip width of about 2 mm.
The toner is then scraped off and falls on the cleaning roller 4, which is further removed by the scraper 5 to reach the toner reservoir in the apparatus, and further discharged to the outside by the transport screw 6 as necessary.

Around the photosensitive member 1, a primary charger for uniformly charging the surface, an image signal applying means for forming an electrostatic latent image thereon, and a toner for supplying the formed electrostatic latent image are provided. Needless to say, a developing device for forming a toner image, a transfer means for transferring the toner image to a transfer material, and other members necessary for image formation are provided. They are all omitted because they have no relation.

By appropriately setting the state of contact of the scraper 5 with the cleaning roller 4, at a position beyond the scraper 5, the surface of the cleaning roller 4 is almost free of the various foreign substances as described above, 50 to 100 μm. After the toner layer is formed, the photoreceptor 1 and the cleaning roller 4 are rubbed with each other through the toner layer to remove foreign substances, and triboelectric charging occurs due to the contact between the scraper 5 and the cleaning roller. .

Here, the relationship between the surface potential of the photosensitive member 1 and the cleaning roller 4 at the portion where the photosensitive member 1 is in pressure contact with the cleaning roller 4 indicates that the surface potential of the photosensitive member is maintained lower than that of the cleaning roller. Even when a transfer material having a large amount of precipitates such as rosin and talc is used in a high-temperature and high-humidity environment, the latent image is disturbed due to a decrease in the surface resistance of the photoreceptor until 10,000 sheets are passed. No image quality deterioration was observed.

On the other hand, if the cleaning roller is set at a lower potential than the photosensitive member surface potential, about several thousand sheets pass,
The latent image was disturbed, resulting in a remarkable deterioration of the image quality.

The polarity of the surface potential of the cleaning roller will be described. For example, by using silicon rubber for the cleaning roller 4 and methyl methacrylate, mylar, metal, urethane rubber, or the like for the scraper 5, the surface potential of the cleaning roller is actually set to a negative polarity. Can be charged to -700V to -1500V. In particular, in the case of Mylar or metal, the voltage becomes -1000 to -1500 V or more, and when the photoconductor enters the cleaning roller position, its surface potential is -500 to
It can be maintained at a potential sufficiently higher than -800V.

Further, by using silicon rubber for the cleaning roller and Teflon or polyethylene for the scraper, the surface potential of the cleaning roller can be made positive, and these may be used as appropriate.

In order to remove electricity from the charged cleaning roller at the end of the cleaning process, a power source B1 is connected to the cleaning roller 4 to apply an AC bias. If the scraper is made of metal, a power source B2 connected to the power source B1 is used. Appropriate means such as applying an AC bias to the scraper or grounding it can be used.

Hereinafter, the structure of an image carrier having an organic photosensitive layer applicable to the present invention will be described.

The photosensitive layer is provided on a conductive substrate, and the substrate itself has conductivity, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, Gold, platinum, etc. can be used.

In addition, on the surface of a plastic substrate such as polyethylene, polypropylene, polyvinyl chloride, acrylic resin, and polyfluoroethylene, aluminum, an aluminum alloy, indium oxide, a generalized tin alloy, etc., are formed by vacuum evaporation, carbon black, Plastics or paper impregnated with conductive particles such as tin oxide particles together with an appropriate binder, plastics having a conductive binder, and the like can be used.

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive layer and the photosensitive layer.

The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylate copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon), polyurethane, gelatin, aluminum oxide, or the like. Its film thickness is 5μ, preferably 0.5-3.
μ is appropriate. It is desirable that the volume resistance is 10 ⁷ Ωcm or more to exhibit the function as a barrier layer.

The photosensitive layer is formed by coating a photoconductor such as a phthalocyanine pigment or an azo pigment together with a binder as necessary. When an organic photoconductor is used, a photosensitive layer composed of a combination of a charge generation layer that generates charge carriers by exposure and a charge transport layer that transports the generated charge carriers can also be effectively used.

As the charge generation layer, azo pigments such as Sudan Red, Diane Blue, Genus Green B, argon yellow, pinone quinone, quinone pigments such as indathrene brilliant violet RRP, quinone cyanine pigments,
Either one or two or more kinds of charge generating layers, such as perylene pigments, indigo pigments, indigo pigments such as thioindigo pigments, hisbenzimidazole pigments such as Indian First Orange toner, phthalocyanine pigments such as copper phthalocyanine, and quinacodrine pigments are deposited or required. It is dispersed with a suitable binder according to the above and formed by coating.

The binder can be selected from a wide range of insulating resins or organic photoconductive polymers.

Examples of the insulating resin include polyvinyl butyral, polyarylate (polycondensate of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, cellulose resin. , Urethane resin, epoxy resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone and the like.

Examples of the organic photoconductive polymer include carbazole and polyvinyl anthracene polyvinylpyrene.

The thickness of the charge generation layer is 0.05 to 15 μ, more preferably 0.05
To 5μ, and the weight ratio of the charge generation layer to the binder is 1
0: 1 to 1:20.

Solvents used for forming the charge generation layer paint, the solubility of the material,
It is selected in consideration of dispersion stability, etc.
Examples of the organic solvent include alcohols such as methanol, ethanol and isopropanol, and sulfoxides such as acetone, methyl ethyl ketone, cyclohexanone N <N-dimethylformamide and NN-dimethylacetamide;
Ethers such as tetrahydrofuran, dioxane, ethylene glycol, monomethyl ether, etc., esters such as methyl acetate, ethyl acetate, chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, aliphatic halogenated hydrocarbons such as trichloroethylene or Aromatic compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene can be used.

Coating is dip coating, spray coating, spinner coating, bead coating,
Coating methods such as a Meyer bar coating method, a blade coating method, a roller coating method, and a curtain coating method can be used.

The charge transport layer is formed by dissolving a charge transport material in a film-forming resin.

Materials suitable for use in the present invention include pyrene,
N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, NN-diphenylhydrazino-3-methylidene-9-ethylcarbazole,
NN-diphenylhydrazino-3-methylidene-10-
Ethylphenothiazine, NN-diphenylhydrazino-
3-methylidene-10-ethylphenoxazine, P-ethylaminobenzaldehyde-NN-diphenylhydrazine, P-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde-NN-diphenylhydrazone, 1.3. Hydrazones such as 5-diethylbenssealdehyde-3-methylbenzthiazoline-2-hydrazone, 2.5-bis (P-diethylaminostyryl) -5- (P-diethylaminostyryl) pyrazoline, 1- [quinolyl (2)}
-3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (P-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazolin, 1- [6
-Methoxy-pyridyl (2)]-3- (P-diethylaminophenyl) pyrazolin, 1- [pyridyl (3)]-
3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (P-diethylstyryl) -5- (P-
Diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (P-diethylaminostyryl) -4-
Methyl-5- (P-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (α-methyl-P-
Diethylaminostyryl) -5- (diethylaminophenyl) pyrazolin, 1-phenyl-3- (P-diethylaminostyryl) -4-methyl-5- (P-diethylaminophenyl) pyrazolin, 1-phenyl-3- (α-
Benzyl-P-diethylaminostyryl) -5- (P-
Pyrazolines such as diethylaminophenyl) pyrazolin and spirpyrazoline, 2- (P-diethylaminostyryl) -4- (P-diethylaminophenyl) -5
Oxazole-based compounds such as (2-chlorophenyl) oxazole, 2- (P-diethylaminostyryl) -6
Thiazole compounds such as diethylaminobenzothiazole, triallylmethane compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane, 1.1-bis (4-N> N-dimethylamino-2-methylphenyl) Polyallylalkanes such as ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene,
Examples thereof include polyvinyl acridine, poly-9-vinylphenylanthracene, a pyrene-formaldehyde resin, and an ethyl carbazole formaldehyde resin. These charge transporting substances can be used alone or in combination of two or more.

As the binder used for the charge transport layer, phenoxy resin, polyacrylamide, polyvinyl butyral, polyarylate, polysulfone, polyamide, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy resin, Polyester, alkyd resin, polycarbonate,
Polyurethane or a copolymer containing two or more repeating units of these resins, for example, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and the like can be mentioned.

It can also be selected from organic photoconductive polymers such as poly-N-vinyl carbazole, polyvinyl anthracene, polyvinyl pyrene.

The film of the charge transport layer is 5 to 50μ, preferably 8 to 20μ,
The weight ratio of the charge transport material to the binder is about 5: 1 to 1: 5, preferably about 3: 1 to 1: 3.

For the coating, various coating means similar to those for the charge generation layer described above can be used.

In general, a coloring layer, a pigment, a charge transporting substance, and the like may be stained by ultraviolet rays, ozone, oil, or the like, a metal, or the like. Therefore, a protective layer may be formed on the surface. This protective layer desirably has a surface resistivity of 10 ¹¹ Ω or more in order to form an electrostatic latent image thereon.

As the protective layer, a resin such as polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer or the like is used as a suitable organic solvent. By dissolving, coating and drying.

The thickness of the protective layer is in the range of 0.05 to 20 μm, and may contain an ultraviolet absorber or the like as necessary.

 Next, examples of the present invention will be described.

Example 1 An aluminum cylinder having a thickness of 0.5 mm, a diameter of 80 mm, and a length of 360 mm was prepared as a conductive substrate.

Copolymer nylon (trade name CM8000: manufactured by Toray Industries, Inc.) 4
Part and type 8 nylon (trade name Lackamide 5003:
4 parts of Dainippon Ink Co., Ltd.) are dissolved in 50 parts of methanol and 50 parts of n-butanol, and are dip-coated on the surface of the substrate.
An undercoat layer having a thickness of 0.6 μ was formed.

10 parts of disazo pigment of the following structural formula, Polyvinyl butyral resin (trade name ESREC BM2:
10 parts of Sekisui Chemical Co., Ltd.) and 120 parts of cyclohexanone were dispersed in a sand mill for 10 hours. A dispersion obtained by adding 30 parts of methyl ethyl ketone to this dispersion was applied to the undercoat layer to form a 0.15 μ thick charge generation layer.

In addition, the following structure 15 parts of stilbene compound and 10 parts of polycarbonate resin (Panlite L-1250 manufactured by Teijin Chemicals Limited) in dichloromethane
A solution dissolved in 50 parts of monochlorobenzene and 10 parts of monochlorobenzene was applied on the charge generation layer to form a 20 μm thick charge transport layer.

Using such an organic photoreceptor, in the apparatus shown in FIG. 1, a silicon rubber roller is used as an elastic cleaning roller, a metal scraper is used, and a metal core of the cleaning roller is used at the same time when the cleaning process is completed. The roller was configured to apply an AC bias to the roller to remove the charge from the roller.

With this apparatus, 1000 sheets were passed, and the image was evaluated after a 30-minute pause (Table 1).

Example 2 The same photosensitive member as in Example 1 was used, and a silicon rubber roller was used as a cleaning roller in the apparatus shown in FIG. 1. The scraper was made of metal. Was evaluated by a device capable of removing static electricity as described above (Table 1).

Comparative Example 1 The same photosensitive member as in Example 1 was used, no bias was applied to the cleaning roller, and the same sheet-passing as in Example 1 was performed except for the evaluation (Table 1).

Comparative Example 2 The same photoreceptor as in Example 1 was used, no bias was applied to the scraper, and the same paper-passing as in this example was carried out, except for the evaluation (Table 1).

Comparative Example 3 The same photoconductor as in Example 1 was used, and the same paper passing as in Example 1 was performed except that the scraper was grounded, and the evaluation was performed (Table 1).

As described above, according to the example apparatus, it is possible to suppress the occurrence of the cleaning failure, the charging memory, and the like, and to always obtain the stable and poor cleaning action.

(3) Effects of the Invention As described above, according to the present invention, the surface of the photoreceptor is rubbed using an elastic cleaning roller and a scraper is brought into contact with the roller. In a cleaning device in which the potential at the contact portion with the body is higher than that of the photoreceptor, by removing the surface potential of the cleaning roller at the end of the cleaning process, the action of removing residual toner and other foreign substances is improved, and Image defects due to the residual potential of the roller are also prevented, and good cleaning is always possible, which greatly contributes to obtaining high-quality images.

[Brief description of the drawings]

FIG. 1 is a side view of a main part showing a cleaning device of an image forming apparatus to which the present invention is applied, and FIG. 2 is a schematic side view showing an example of a known cleaning device. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Cleaning device, 3 ... Cleaning blade, 4 ... Elastic cleaning roller, 5 ...
... Scraper, 6 ... Conveying screw.

Claims (2)

(57) [Claims] An image forming apparatus comprising a cleaning roller for removing foreign matters such as toner remaining on the surface of the image bearing member by rubbing against the image carrier. Means for maintaining the surface potential higher than the surface potential of the image carrier at the site; and a cleaning roller for lowering the surface potential of the cleaning roller at the rubbing portion when the cleaning operation is not performed. A cleaning device comprising means for removing a surface potential. 2. The cleaning device according to claim 1, wherein the photosensitive layer of the image carrier is made of an organic photoconductor.