JP2001215802A - Magnetic developing roller and image forming apparatus using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic developing roller which can be manufactured with a simple procedure, besides, of which work accuracy is improved, and also, capable of easily attaining a desired surface shape. SOLUTION: As for the magnetic developing roller constituted by arranging a magnetic roller in a sleeve, the sleeve is a hollow cylindrical sleeve constituted of resin compound containing synthetic resin and conductive agent, and also, having a volume resistivity <=105 Ω.cm, and a surface roughness <=15 μm as for the spot mean roughness Rz of JIS10, and whose thickness is <=1.5 mm at 25 deg.C, and as for the dimensional accuracy of the cylindrical sleeve, the magnetic developing roller is characteristic of the deviation of <=50 μm, the straightness of <=45 μm, and the circularity of 50 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic developing roller and an image forming apparatus using the same, and more particularly, to a copier,
A developing roller for visualizing an electrostatic latent image on a latent image holding member such as a photosensitive drum in an electrophotographic apparatus such as a laser printer or a facsimile or an electrostatic recording apparatus.
The present invention relates to a magnetic developing roller capable of easily expressing desired surface properties and having good dimensional accuracy and excellent practicality, and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as a copying machine, a printer, a facsimile or an electrostatic recording apparatus, a rotating roller as a developing roller for visualizing an electrostatic latent image on a latent image holding member such as a photosensitive drum is used. A magnet roller formed by a bonded magnet is provided in a free sleeve, and the magnetic developer (toner) held on the surface of the sleeve flies or transfers onto the latent image holding member depending on the magnetic force characteristics of the magnet roller. A method of visualizing an electrostatic latent image by supplying a magnetic developer to the surface of a latent image holding member by a jumping phenomenon is known. A conventional magnetic developing roller used for visualizing the electrostatic latent image has a structure in which a magnet roller is disposed in a rotatably disposed sleeve. The sleeve is usually formed from a metal such as aluminum. Therefore, it is necessary to coat the sleeve surface with a resin coating layer or to perform various surface treatments to impart a predetermined surface property, and in some cases, to prevent surface oxidation of a sleeve made of a metal such as aluminum. In some cases, there are various problems such as the dimensional accuracy of the obtained sleeve is not always sufficient.

[0003]

SUMMARY OF THE INVENTION According to the present invention, desired surface properties can be easily expressed under such circumstances,
It is an object of the present invention to provide a magnetic developing roller which has good dimensional accuracy and excellent reliability and can be manufactured at low cost.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the sleeve of the magnetic developing roller has been formed using a conductive resin composition containing a synthetic resin and a conductive agent. It has been found that, when formed by molding, it is possible to form with extremely high dimensional accuracy and to freely adjust its resistance value and surface roughness. The present invention has been completed based on such findings. That is, the present invention relates to a magnetic developing roller having a magnet roller disposed in a sleeve, wherein the sleeve is made of a resin composition containing a synthetic resin and a conductive agent, and has a volume resistivity at 25 ° C. of 10 ⁵ Ω.・ C
m and a hollow cylinder having a surface roughness of 15 μm or less in terms of JIS 10 point average roughness (Rz), wherein the thickness of the cylinder is 1.5 mm or less, and the dimensional accuracy is 50 μm Below, straightness 45μm or less and roundness 50μm
The present invention provides a magnetic developing roller characterized by the following. Further, the present invention also forms a thin film by carrying a magnetic developer on the surface, in contact with or in proximity to the image forming body,
By supplying a magnetic developer to the surface of the image forming body,
Another object of the present invention is to provide an image forming apparatus equipped with a magnetic developing roller for forming a visible image, wherein the above magnetic developing roller is used as the magnetic developing roller.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the sleeve of the magnetic developing roller of the present invention is formed into a hollow cylindrical shape using a conductive resin composition containing a synthetic resin and a conductive agent as a material. Since the sleeve in the present invention is made of a conductive resin composition containing a synthetic resin and a conductive agent, by selecting the type and the mixing ratio of the synthetic resin and the conductive agent,
Desired resistance and surface roughness can be appropriately adjusted. In the sleeve of the present invention, the volume resistivity at 25 ° C. is 10 ⁵ Ω · cm or less, preferably 10 ³ Ω · cm or less, and the surface roughness is 15 μm or less in JIS 10-point average roughness (Rz), preferably 10 to 1 μm. Here, if the volume resistivity is too large, fogging or the like tends to occur. The surface roughness is JIS 10 point average roughness (Rz)
If it exceeds 15 μm, the amount of developer carried may be small, and the image may be unclear. In the present invention, since the sleeve of the developing roller is made of the above-described conductive resin composition, the above properties can be easily exhibited without performing a special treatment on the surface or forming a film. However, if desired, a coating layer may be provided on the sleeve surface.

Further, the magnetic developing roller of the present invention is characterized in that the dimensional accuracy of the cylindrical shape of the sleeve is extremely good. This is because the constituent material of the sleeve is the conductive resin composition described above, so that the shrinkage is small and the shape has high thermal stability. Here, the dimensional accuracy is evaluated based on runout, straightness and roundness. First, the run-out is measured with an outer diameter / run-out measuring machine “Laser Scan Micrometer” (manufactured by Mitutoyo Corporation).
In the sleeve of the present invention, it is 50 μm or less, preferably 30 μm or less.
μm or less. Next, the straightness is measured by a roundness / cylindrical shape measuring device “Round Test RA-726” (manufactured by Mitutoyo Corporation).
Or less, preferably 40 μm or less, particularly preferably 20 μm
m or less. Further, the roundness is measured by a roundness / cylindrical shape measuring device “Round Test RA-726” (manufactured by Mitutoyo Corporation).
Or less, preferably 30 μm or less. The thickness of the sleeve of the present invention is 1.5 mm or less, preferably 0.5 mm.
〜1.0 mm.

The conductive resin composition used in the present invention contains a synthetic resin and a conductive agent, and may further contain a fibrous material and / or a whisker if desired. As a synthetic resin used in this case, while having an appropriate strength,
It is not particularly limited as long as it can be molded by injection molding or the like, and may be appropriately selected from general-purpose resin, general-purpose engineering plastic, or super-engineering plastic. Here, general-purpose engineering plastics or super-engineering plastics include polyacetal, polyamide 6, polyamide 6.6, polyamide 12, and polyamide 4
6, polyamide 6,10, polyamide 6,12, polyamide 11, polyamide MXD6, polybutylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polyethersulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, polyetheretherketone , Polyethylene terephthalate, polyarylate, liquid crystal polymer or various fluorine resins (for example, polytetrafluoroethylene). In addition, as a general-purpose resin,
Examples include polypropylene, ABS (acrylonitrile-butadiene-styrene) resin, polystyrene, and polyethylene. In addition, melamine resin, phenol resin, silicone resin and the like can also be mentioned.
Among them, polyamide resins (polyamide 6, polyamide 6.6, etc.), polyacetal, polybutylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polycarbonate and the like are preferable because they are thermoplastic and have excellent moldability and excellent mechanical strength. . Among them, polyamide 6.6 and polyamide MXD6
A mixed resin of (polyamide obtained from meta-xylylenediamine and adipic acid) is particularly preferred.

Next, as the conductive agent in the conductive resin composition, various ones can be used as long as they can be uniformly dispersed in the resin composition. Carbur black powder, graphite powder, Powders such as metal powders such as aluminum, copper, and nickel, metal oxide powders such as tin oxide, titanium oxide, and zinc oxide, and conductive glass powders are preferably used. The amount of the conductive agent may be appropriately selected depending on the situation, but is preferably 5 to 40% by weight, particularly preferably 5 to 20% by weight, based on the whole composition.

In addition, various fibrous materials and whiskers can be added to the conductive resin composition for the purpose of reinforcing and increasing the amount thereof, if desired. Here, examples of the fibrous material or whiskers include various conductive or non-conductive fibers or whiskers such as carbon fibers, inorganic filler whiskers (such as potassium titanate whiskers), and glass fibers. The blending amount of these fibrous materials and whiskers depends on the length and diameter of the fibrous materials and whiskers used.
Alternatively, the amount varies depending on the type of the synthetic resin and the like, and may be appropriately selected depending on the situation.

The method of forming the magnetic developing roller of the present invention varies depending on the type of synthetic resin and the like, but is usually performed by injection molding using the above-described conductive resin composition. Note that normal molding conditions such as molding temperature and injection pressure may be selected according to the type of synthetic resin used. The magnetic developing roller of the present invention is manufactured using the conductive resin composition as described above, but in some cases, a sleeve body and a flange portion at one end thereof may be integrally formed. Further, a gear, a shaft hole, a support shaft, or the like can be provided integrally with the flange portion.

The magnetic developing roller of the present invention is used by being incorporated in an image forming apparatus such as a developing apparatus in an electrophotographic apparatus. Here, there are various types of image forming apparatuses to which the magnetic developing roller of the present invention is mounted, but a magnetic developer is supported on the surface to form a thin film thereof, and the thin film is brought into contact with or close to the image forming body, Any material that forms a visible image by supplying a magnetic developer to the surface of the image forming body may be used. Examples of the developer (toner) carried on the magnetic developing roller of the present invention include a magnetic type developer, for example, a one-component magnetic developer and a two-component magnetic developer.

[0012]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Examples 1 to 5 Using a conductive resin composition having the composition shown in Table 1 below, a hollow cylindrical sleeve (outer diameter 30 mm, length 275 m) was formed by injection molding at a molding temperature of 290 ° C. and a molding pressure of 150 MPa.
m, thickness 1.5 mm). The surface roughness, conductivity, and dimensional accuracy of this sleeve were measured by the following methods. The results are shown in Table 1. (1) Measurement of Surface Roughness The JIS 10-point average roughness (Rz) was measured using a surface roughness profile measuring machine “Surfcom 470” (manufactured by Tokyo Seimitsu Co., Ltd.).
It was measured according to B0601. (2) Conductivity measurement Four-probe resistance meter "Loresta IP" MCP-T25
0 (manufactured by Mitsubishi Chemical Corporation) was used to measure the volume resistivity. (3) Measurement of Dimensional Accuracy Measurement was performed using a three-dimensional coordinate measuring machine “XYZAX RVA600” (manufactured by Tokyo Seimitsu Co., Ltd.) to evaluate run-out, straightness and roundness.

[0013]

[Table 1]

[0014]

[Table 2]

* 1: Polyamide 6.6 * 2: Polyamide obtained from meta-xylylenediamine and adipic acid * 3: Whisker of potassium titanate

[0016]

As described above, the magnetic developing roller of the present invention can easily exhibit desired surface properties,
It has good dimensional accuracy and excellent reliability and can be manufactured at low cost, and its practical value is extremely high.

Claims (9)

[Claims] 1. A magnetic developing roller comprising a sleeve and a magnet roller disposed therein, wherein the sleeve is made of a resin composition containing a synthetic resin and a conductive agent, and has a volume resistivity at 25 ° C. of 10 ⁵ Ω. A hollow cylindrical article having a JIS 10-point average roughness (Rz) of 15 μm or less and a wall thickness of 1.5 mm or less and a dimensional accuracy of the cylindrical article of less than 15 cm; A magnetic developing roller having a straightness of 50 μm or less, a straightness of 45 μm or less, and a roundness of 50 μm or less. 2. The magnetic developing roller according to claim 1, wherein the dimensional accuracy is 50 μm or less in run-out, 40 μm or less in straightness and 50 μm or less in roundness. 3. The magnetic developing roller according to claim 1, wherein the synthetic resin is at least one synthetic resin selected from the group consisting of a general-purpose resin, a general-purpose engineering plastic, and a super-engineering plastic. 4. A general engineering plastic or a super engineering plastic is polyacetal, polyamide 6, polyamide 6.6, polyamide 1
2, polyamide 4,6, polyamide 6,10, polyamide 6,12, polyamide 11, polyamide MXD6, polybutylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polyethersulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, 4. The magnetic developing roller according to claim 3, wherein the roller is a polyether ether ketone, polyethylene terephthalate, polyarylate, liquid crystal polymer or polytetrafluoroethylene. 5. The conductive material according to claim 1, wherein the conductive agent is at least one selected from the group consisting of carbon black, graphite, tin oxide, titanium oxide, zinc oxide, nickel, aluminum and copper. Magnetic developing roller. 6. The magnetic developing roller according to claim 1, wherein the resin composition further contains a fibrous material and / or a whisker. 7. The magnetic developing roller according to claim 1, wherein the sleeve has a coating layer on the surface. 8. The magnetic developing roller according to claim 1, wherein the sleeve is formed by integrally forming a flange with a sleeve main body and one end thereof. 9. A visible image is formed by carrying a magnetic developer on the surface to form a thin film thereof, and contacting or approaching the image forming body and supplying the magnetic developing agent to the surface of the image forming body. An image forming apparatus provided with a magnetic developing roller, wherein the magnetic developing roller according to claim 1 is used as the magnetic developing roller.