JPH1184858A - Developing sleeve and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent production of a ghost by development, to increase adhesion property of a coating layer, and to avoid such problems that a developing sleeve can not be used due to production of bubbles under the coating film by forming a base coating layer on the surface of a carrying body and then forming a coating film. SOLUTION: As a raw tube 1 as a carrier body of a sleeve, metals such as aluminum and stainless steel can be used. The surface of the metal tube 1 may be roughened by sand-blasting. After a base coating layer 12 is formed on the tube 1, a coating film 3 is formed. The base coating layer 12 may be formed at least on both ends of the raw tube. The coating film 3 is preferably prepared by dispersing an inorg. powder 4 in a binder, and the polarity of triboelectrification of the inorg. powder 4 to a toner is opposite to the polarity of the binder. Therefore, when the triboelectric charges between the toner 5 and the coating film 3 begin to increase with repetition of friction. positive charges are locally present in the toner because of the presence of the inorg. powder 4 having electrification property in the opposite polarity in the coating film 3. This compensate the increase in the triboelectric charges and suppress to a specified level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing sleeve used for a developing device of an electrophotographic apparatus such as a copying machine and a printer, and an image forming method using the developing sleeve.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, an electrostatic latent image formed on a photosensitive drum is developed with toner, and the toner image is transferred to paper to obtain an image. FIG. 4 is a schematic sectional view of a developing device using one-component magnetic toner. The toner 15 is supplied from the toner hopper 13 onto the rotating cylindrical developing sleeve 12, the thickness of the toner layer is made uniform by the charging blade 14, and the toner is frictionally charged, and the toner flies onto the surface of the photosensitive drum 16 to perform development. Do.

A portion of the developing sleeve 17 where the toner has been consumed is supplied with new toner by the rotation of the developing sleeve 1, and the toner is subjected to frictional charging by the charging blade 14 only once. On the other hand, the unconsumed portion of the toner 18 on the developing sleeve 1 is subjected to triboelectric charging. For this reason, the toner on the developing sleeve 12 has a different charge amount according to the development history.

[0004] In development, an amount of toner corresponding to the electrostatic potential of the drum flies from the developing sleeve. However, the difference in the amount of charge between the toner having a small particle diameter and the toner having a high charging ability is high. Or the amount of charge varies depending on the history of toner development, so that the toner does not fly according to the potential of the latent image. If the circumferential length of the developing sleeve is shorter than the length of the sheet, the developing sleeve rotates repeatedly to develop one sheet of paper. The phenomenon occurs.

In order to prevent the occurrence of such a development ghost, it is important to eliminate a difference in charge amount between newly supplied toner and toner not consumed and remaining on the developing sleeve. Become. That is, it is important that the toner on the developing sleeve has a constant charge amount regardless of the rotational speed of the sleeve.

In order to prevent development ghosts, Japanese Patent Application Laid-Open
JP-A-276174, JP-A-1-277265, JP-A-2-105183, and the like, a resin layer containing conductive fine particles such as carbon is formed on the surface of a developing sleeve, and unevenness and fine particles on the surface are formed. There has been proposed a method of appropriately controlling the amount of toner supplied on the developing sleeve and the charging property by using conductivity.

[0007] Also, Japanese Patent Application Laid-Open No. Hei 3-11380 discloses that
There has been proposed a developing sleeve in which a film containing molybdenum disulfide is formed on the surface. It is reported that this coating prevents fine powder toner from adhering and suppresses the occurrence of toner charge memory.

When the above-mentioned coating is formed, the coating must be adhered to the carrier, but depending on the type of resin used, there are some which have poor adhesion. When the adhesion of the coating film is reduced, not only may there be a risk of peeling during use, but also the flow of charges at the interface is obstructed and residual charges may accumulate at the interface. Then, the development characteristics change,
This is not preferable because the image density fluctuates.

In particular, a seal material for preventing the toner from spilling, a roller for keeping the position with the drum and maintaining the rotation accuracy, etc. may come into contact with both ends of the developing sleeve, so that the film is peeled off. There is even more concern. In addition, when a coating is formed after the surface of the carrier is roughened by a method such as sandblasting, there is also a problem that if the adhesion of the coating is reduced, irregularity defects are likely to appear.

[0010]

Accordingly, the present invention solves the above-mentioned problems, improves the adhesion between the surface of the sleeve carrier and the coating, prevents the occurrence of development ghosts, and suppresses the peeling of the coating. It is intended to provide a developing sleeve.

[0011]

The present invention has succeeded in solving the above-mentioned problems by employing the following constitutions. (1) A developing sleeve having a coating on a carrier, wherein a coating is formed after forming an undercoat layer on the surface of the carrier. (2) The developing sleeve according to (1), wherein the coating is a uniform dispersion of a binder and an inorganic powder whose triboelectric charging polarity with respect to toner is opposite. (3) The developing sleeve according to (2), wherein the coating is polished before use to expose the inorganic powder on the surface.

(4) The developing sleeve according to (1), wherein the carrier is an aluminum or stainless steel tube. (5) The developing sleeve according to (4), wherein the surface of the base tube is roughened.

(6) The undercoat layer is formed of one or more organometallic compounds selected from the group consisting of a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, a zirconium chelate compound, a zirconium alkoxide compound, and an aluminum silicate compound. The developing sleeve according to the above (1), wherein the developing sleeve is manufactured by the following. (7) The developing sleeve according to (6), wherein the undercoat layer has a thickness in a range of 0.05 to 0.5 μm.

(8) The developing sleeve according to (6) or (7), wherein the undercoat layer is formed only on both ends of the carrier. (9) The developing sleeve according to (8), wherein the undercoat layer is formed in a range of 5 to 20 mm in width from an end of the carrier.

(10) a step of forming an electrostatic latent image on the electrostatic latent image carrier, a step of developing the latent image using a developer on a developer carrier, and a step of transferring the developed toner image to a transfer member An image forming method having a step of transferring onto the upper surface, wherein the developing sleeve according to any one of (1) to (9) is used as the developer carrier.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a developing sleeve having a coating on the surface of a carrier such as a metal pipe or the like, by forming an undercoat layer such as a coupling agent on the surface of the carrier and then forming the coating. Thus, the present invention succeeded in preventing peeling of the film and suppressing generation of development ghost.

FIG. 1 is an enlarged sectional view of the developing sleeve of the present invention. Metal such as aluminum or stainless steel can be used for the raw tube 1 which is a carrier of the sleeve. The surface of the metal pipe may be roughened by sandblasting. After forming the undercoat layer 12 on the raw tube, the coating 3 is formed. The undercoat layer may be formed at least at both ends of the tube. The coating 3 is preferably formed by dispersing an inorganic powder 4 having a triboelectric charge polarity with respect to the toner 5 opposite to that of the binder in the binder.

It is important for the undercoat layer to ensure adhesion to the sleeve carrier, but the undercoat layer has a resistivity of 10 ¹²
It is also necessary that the residual charge is not accumulated below Ωcm, the durability of the coating applied thereon to the solvent, and the adhesion to the coating are also required.

Materials used for the undercoat layer include various coupling agents such as silane coupling agents, titanate coupling agents, aluminum coupling agents, zirconium chelate compounds such as zirconium tetraacetylacetonate, and tributoxy zirconium acetylacetate. Organometallic compounds such as zirconium alkoxide compounds such as silicates and aluminum silicate compounds are preferred. When these compounds are applied to the metal surface of the sleeve carrier, they have a characteristic of firmly adhering to the metal by a curing reaction upon drying. In addition, resin materials such as copolymerized nylon, alkoxymethylated nylon, and casein can be used. These materials are used alone or in combination. The preferred thickness of the undercoat layer is 0.05 to 0.5 μm.
m.

In general, the coating on the developing sleeve is easily peeled off from both ends where the contact member comes into contact with the developing sleeve. Therefore, it is not necessary to apply the undercoat layer to the entire surface of the metal pipe, and the formation region is limited to both ends. May be. The length of the undercoat layer at both ends may be set to be about 5 to 20 mm inward from the portion where the contact member contacts. Since the thickness of the undercoat layer is extremely small, even if a film is formed thereon, there is almost no step. In order to form the undercoat layer only on both ends of the raw tube, the ends may be immersed and applied to the raw material solution one by one.

The coating of the present invention contains an inorganic powder having a triboelectric charge polarity for the toner opposite to that of the binder. The reason that this film can prevent the development ghost from occurring is that when the amount of triboelectric charge between the toner 5 and the film 3 tends to increase as the number of friction increases in FIG.
Since the negatively polarizable inorganic powder 4 is present in the toner, positive charges (+ in the figure) partially exist in the toner,
The increase in the triboelectric charge can be offset and suppressed to a certain level.

The inorganic powder used in the coating of the present invention includes:
Molybdenum disulfide (MoS ₂ ), tungsten disulfide,
Examples include boron nitride, silicon carbide, and graphite. Although a negatively chargeable toner is used in a laser printer, MoS ₂ is most suitable as the oppositely chargeable powder. MoS ₂ is semiconductive with a powder specific resistance of 10 ⁵ Ωcm to 10 ⁷ Ωcm, and the coating in which it is dispersed also becomes semiconductive, and the opposite polarity charge of the toner generated on the developing sleeve side is accumulated in the coating. Can be prevented. In addition, since MoS ₂ has a solid lubricating property, the abrasion of the coating film can be suppressed.

The binder resin used in the film of the present invention needs to triboelectrically charge the toner to its original negative polarity. Specifically, acrylic resins such as polymethyl methacrylate (PMMA), polyethyl methacrylate, and copolymers thereof;
Thermoplastic resins such as polyacrylamide and polyamide; and thermosetting resins such as melamine resin, epoxy resin and urethane resin. The weight average molecular weight Mw of the binder resin is 10,000 to 200,000, preferably 40,000 to
A range of 150,000 is appropriate. If the Mw is too small, the wear of the coating layer increases, and the life of the developing sleeve is shortened.
Conversely, if Mw is too large, the solution viscosity will be extremely high, and application may be difficult.

By appropriately selecting the content of the inorganic powder and the type and amount of the binder resin, the toner charge amount of the entire coating film can be made suitable for development. The weight mixing ratio (PB ratio) of the inorganic powder and the binder resin cannot be specified unconditionally because it depends on the chargeability of the toner, the binder resin and the inorganic powder, but from the viewpoint of film strength and production stability. From 1: 5 to 2:
1, preferably in the range of 1: 4 to 1: 1. Dispersion of the inorganic powder is possible by a usual method.

The formation of the undercoat layer and the coating on the sleeve tube is selected from a ring coating method, a dip coating method, a spray coating method and the like. The thickness of the coating depends on the amount of the inorganic powder, but is 0.5 to 30 μm, preferably 2 to 20 μm.
Is appropriate.

On the other hand, when the developing sleeve is used repeatedly, the film is worn and the exposed area of the inorganic powder changes. As a result, the charge amount of the toner may change, and if necessary, the development density may change, or a memory or a development ghost may occur. In particular, immediately after the coating layer is formed, the exposure ratio of the inorganic powder is small, and development ghost is likely to occur.

Therefore, in order to suppress the change in the exposed area of the inorganic powder, as shown in the sectional view of FIG. 2, before using the developing sleeve, the surface of the coating is polished in advance to expose the inorganic powder. When the formed surface 6 is formed, the change of the exposed area thereafter becomes small.

Examples of the polishing method include buff polishing and dry or wet polishing using a fine sandpaper or tape-shaped polishing member. The tape-shaped polishing member is a film in which an abrasive such as aluminum oxide, cerium oxide, magnesium oxide, diamond, silicon carbide, etc. is applied to the surface of a plastic film such as polyester, and as shown in FIG. By pressing and polishing by the pressing roll 9 while sequentially feeding the roll from the roll 10 to the take-up roll 11, the polishing can always be performed on a new surface.

As another method of exposing the inorganic powder, the surface of the coating can be treated with a solvent that dissolves the binder resin of the coating. Such a solvent may be any solvent that dissolves the binder resin, other than the same solvent as the coating solvent. Specific methods for treating the surface of the film with a solvent include a method of immersing the film in a solvent for a short time, a method of spraying and wiping the solvent, and a method of wiping with a cloth or paper to which the solvent is adhered. By such processing,
The thin layer on the coating surface is removed, the exposed area of the powder increases,
The same effect as the above polishing can be obtained.

The life of the developing sleeve depends on the diameter of the base tube, and
The rotation speed is about 100,000 to 500,000 rotations, depending on the type of toner and the method of use. If the base tube is made of stainless steel, there is no decrease in dimensional accuracy, no deformation, no scratch on the surface, no contamination or corrosion by the solvent, and the used developing sleeve is collected together with the developing device or cartridge and developed. After removal from the vessel, the coating layer can be peeled off with an appropriate solvent and regenerated. The undercoat layer remains on the raw tube after the coating layer is peeled off, but after further washing, the coating may be applied again.

[0031]

【Example】

Example 1 An aluminum tube having a diameter of 20 mmφ, a length of 322 mmL, and a thickness of 0.4 mmt was used, and γ-aminopropyltriethoxysilane (A1100, manufactured by Nippon Unicar Co., Ltd.) as a silane coupling agent was applied on the surface thereof. -Diluted 3 times with butanone and applied by ring coating. Next, it was dried at 115 ° C. for 10 minutes to form an undercoat layer having a thickness of about 0.05 μm.

On the other hand, flaky MoS ₂ powder having a major axis of about 0.8 μm and a minor axis of about 0.1 μm whose surface was treated with high-grade paraffin having an Mw of about 1500 was mixed with PMMA (Mitsubishi Rayon Co., Ltd., B
R80) to a 2-butanone solution at a weight ratio of 1: 2,
It was dispersed in a sand mill and made into a paint. This was applied on the undercoat layer by a ring coating method, and dried at 115 ° C. for 40 minutes to form a coating layer having a thickness of 11 μm.

After the coating was formed, a tape-shaped polishing member (Lapping film # 2500, manufactured by Sumitomo 3M Co., Ltd.) obtained by applying diamond abrasive grains on a polyester film was used.
Polishing was performed by a polishing apparatus as shown in FIG. In the polishing, the developing sleeve 1 was rotated at 100 rpm, and the wrapping tape 20 was moved from the feeding roller 22 to the winding roller 23 at a speed of 20 mm / min. Polishing for about 0.2 μm was achieved by polishing for 8 seconds. If the coating came into contact with anything during the polishing process, it did not peel. The adhesion strength of the coating film was 100/100 as determined by the Gobang test method of the adhesive tape, and was strong.

The obtained developing sleeve was transferred to a magnetic one-component negatively-charged toner (Fuji Xerox Co., Ltd., XP-20 toner,
Built in a laser printer (Fuji Xerox Co., XP-20, output at 20 sheets per minute) that performs reversal development using a volume average particle diameter of 7 μm, at 10 ° C. and 15% in a low-temperature and low-humidity environment where development ghosts are likely to occur. When an image evaluation test was carried out at RH, no development ghost was generated, and good image quality was obtained with a solid black density of 1.4 or more. Even if a durability test was continuously performed on 8,000 sheets using this developing sleeve, there was no problem.
In addition, both ends of the developing sleeve had a structure in which a sealing material made of a polyester film was contacted over 8 mm from the end to prevent toner spillage.

Comparative Example 1 A developing sleeve was produced in the same manner as in Example 1 except that the undercoat layer was omitted, and the same test as in Example 1 was carried out. It is presumed that the coating came into contact with something during the process of assembling it into the container, but there was a peeled part. When the adhesion strength of the coating was examined, it was 10/100, which was insufficient. In addition, during the durability test, the coating layer was peeled off at both ends of the developing sleeve at the time of printing 6,000 sheets, and the peeled pieces were mixed into the toner to cause poor development, and further use was difficult.

Example 2 In Example 1, the solution of the undercoat layer was placed in a container so as to have a depth of 2 cm, and the base tubes were immersed one by one to form an undercoat layer of 2 cm at each end. Next, a film was formed in the same manner as in Example 1, and a durability test was performed in the same manner as in Example 1. However, no peeling of the film occurred, and good results were obtained as in Example 1.

Example 3 In Example 1, a 50% toluene solution of tributoxyzirconium acetylacetonate (ZC540 manufactured by Matsumoto Kosho Co., Ltd.) was diluted and applied twice as an undercoat layer, and then heated at 115 ° C. A developing sleeve was produced in the same manner as in Example 1 except that the developing sleeve was dried to a thickness of about 0.05 μm for 10 minutes, and an exploration test was conducted in the same manner as in Example 1. As in Example 1, good results were obtained.

Example 4 In Example 1, the surface of the aluminum tube was subjected to sand blasting to obtain a surface roughness Ra1.
The surface was roughened to 2 μm. Next, an undercoat layer and a coating were formed in the same manner as in Example 1, and then the coating surface was polished. Using the obtained developing sleeve, an image evaluation test was performed in the same manner as in Example 1. As a result, no developing ghost was generated and a solid black density of 1.5 or more and a good image quality was obtained.
By making the surface of the coating rough by roughening the base tube,
It is considered that the amount of toner transported during development increased, and the image density increased.

[Comparative Example 2] In Example 4, the formation of the undercoat layer was omitted, and the coating was directly formed on the roughened tube. Bubbles were generated and could not be used as a developing sleeve. This is because, when the surface of the raw tube is sandblasted, small holes are partially generated by the impact of the sand,
This is probably because the air in the pores expanded as a result of applying the coating thereon and heating and drying. After applying the undercoat layer,
The material of the undercoat layer easily penetrates into the pores on the surface of the base tube, and so-called plugging treatment can be performed.

[0040]

According to the present invention, by adopting the above structure and forming a coating after forming an undercoat layer on the surface of the sleeve carrier, development ghost can be prevented and the adhesion of the coating layer can be improved. Even if there is a problem during the manufacturing process or during use, bubbles are generated under the coating even if the carrier surface is roughened to increase the image density, even if the carrier layer is roughened to increase the image density. As a result, the developing sleeve cannot be used.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a film of a developing sleeve of the present invention.

FIG. 2 is a schematic sectional view of the developing sleeve of the present invention after surface polishing.

FIG. 3 is an explanatory view of a polishing method using a polishing film.

FIG. 4 is a schematic sectional view of a developing device.

Claims (3)

[Claims] 1. A developing sleeve having a coating on a carrier, wherein a coating is formed after forming an undercoat layer on the surface of the carrier. 2. The developing sleeve according to claim 1, wherein the undercoat layer is formed only on both ends of the carrier. 3. A step of forming an electrostatic latent image on an electrostatic latent image carrier, a step of developing the latent image using a developer on a developer carrier, and a step of applying the developed toner image to a transfer member. 3. An image forming method comprising the step of transferring to a developing device, wherein the developing sleeve according to claim 1 or 2 is used as the developer carrying member.