JP3423143B2 - Charging member and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in electrophotographic copying machines, PPCs, laser printers, facsimiles, etc., for uniform charging of a charge carrying medium or for transferring a visible image to an image carrier. The present invention relates to a charging member of a contact charging device.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, a corona discharger has been widely used as a means for uniformly charging a photoreceptor. Since the corona discharger is not in contact with the photoconductor, it is less affected by the type of the photoconductor and the usage environment, and the photoconductor can be uniformly charged to a predetermined potential. However, there is a problem that the device is complicated and that ozone generated by the discharge deteriorates the photoconductor and peripheral members. In addition, the suppression of ozone generation as an environmental problem has been a market demand.

A contact roller charger has been introduced here. However, charging unevenness is likely to occur, and it is necessary to apply a superimposed voltage of DC (direct current) and AC (alternating current) in order to make it uniform. . As a result of a detailed examination of the cause of uneven charging when only a DC voltage is applied, it is found that the elastic layer is a dispersion layer of rubber and carbon,
By replacing this with a medium resistance epichlorohydrin rubber, it was made possible to eliminate electrical non-uniformity and eliminate charging unevenness that occurs when only a DC voltage is applied.

As an example of this, a roller charging device disclosed in Japanese Patent Laid-Open No. 7-49602 has a DC charging roller.
In a roller charging device that applies only a voltage to uniformly charge the surface of a photosensitive member, the charging roller is made of epichlorohydrin rubber, and the roller hardness of the charging roller is 42 (JIS.
Or more (according to A type hardness tester). In addition, JP-A-1-
205180 proposes a charging member having a surface layer containing N-alkoxymethylated nylon.

[0005]

However, the medium resistance (1
As a practical problem of a charging roller composed of an epichlorohydrin rubber elastic layer (thickness: 1 to 5 mm) of 0 ⁷ to 10 ⁹ Ω · cm, the roller surface is easily soiled, and the charging potential fluctuates greatly due to environmental fluctuations. Therefore, a surface layer of a non-adhesive resin covering the surface of the elastic layer is required.
In the method disclosed in Japanese Patent Application Laid-Open No. 1-205180, the N-alkoxymethylated nylon surface layer has excellent non-adhesiveness and environmental characteristics, but the film strength is weak and durability as a charging roller is a problem. is there. Japanese Patent Laid-Open No. 7-4960
The charging member disclosed in Japanese Patent Publication No. 2 is a polyamide resin (film thickness 5
Although a fluororesin-based surface layer containing 4% of carbon, which has a large humidity dependency, is used as the surface layer, the dispersibility of the carbon and the fluororesin is poor and the charging uniformity is poor.

A charging roller provided with a surface layer made of acetylene black having a low structure which is easily dispersible in methanol and a copolymerized nylon resin soluble in methanol on the surface of the elastic layer of epichlorohydrin has (1) a photoreceptor and It is characterized by good non-adhesiveness with toner, (2) small humidity dependence, and (3) good charge uniformity.

However, in order to reduce fluctuations in the charging potential due to environmental fluctuations, if too much conductive carbon is added to the surface layer, the surface resistance of the charging roller becomes too low, and the surface of the photoconductor that is contact-charged is damaged. If there is a defect such as the above, there is a new problem that charge leakage occurs, and not only the scratched portion on the surface of the photoconductor but also the non-charged portion expands like a horizontal stripe.

The present invention aims to remedy this type of problem.

[0009]

Means for Solving the Problems ( 1 ) The core metal of the present invention
A charging member having two layers, an elastic layer covering the surface and a surface layer covering the surface, has acetylene black and hydrophobic silica dispersed in a copolymerized nylon resin, and the closer the elastic layer is to the elastic layer, the more dispersed acetylene black is. It is characterized in that it has a surface layer in which the amount of silica dispersed is larger than that of acetylene black as it is farther from the elastic layer. ( 2 ) In the present invention, the surface of the elastic layer covering the surface of the core metal is
A plurality of times with different solutions of acetylene black and silica blend ratio to a copolymer nylon resin, silica
A solution with a high blending ratio that contains a large amount of polyacetylene black
With more silica than acetylene black
The surface ratio layer is formed by overcoating with a solution having a specific ratio in this order .

[0010]

DETAILED DESCRIPTION OF THE INVENTION

EXAMPLES Comparative Example 1 FIG. 1 shows a charging roller 1 of Comparative Example 1 . Charging roller 1
Is a core metal 101 having a diameter of 8 mm (diameter 8 mm), an epichlorohydrin rubber elastic layer 102 having a thickness of 3 mm formed thereon, and a surface layer 103 formed on the surface of the elastic layer 102. The electric resistance of the elastic layer 102 is 1.2 × 10 ⁸ Ω · cm, the rubber hardness is 42 (JISA), and the average surface roughness Rz is 5.5 μm.
Is.

The coating solution A is applied onto the peripheral surface of the elastic layer 102 by spraying, and the surface layer 10 having a thickness of 10 μm after drying is applied.
Formed 3. This charging roller 1 of Comparative Example 1 is referred to as Comparative Sample 1: Coating solution A: Copolymerized nylon resin (Daiamide T171, Daicel-Schuls) 100 (weight, the same applies hereinafter) Acetylene black (HS- 100 Denka) 10 Hydrophobic silica 10 Methanol 1200 dispersed in a Hommonizer for 20 minutes.

Further, a coating liquid B is prepared by removing silica from the coating liquid A, spray-coated, and the thickness after drying is 10 μm.
The surface layer of was formed. The charging roller thus obtained (Comparative Example 2 ) is referred to as Comparative Sample 2 .

[0013] - Example - on the circumferential surface of the elastic layer 102 produced in Comparative Example 1, the following table 1
The coating solution and the coating solution shown in (3) were successively applied by spraying to form a surface layer 103 having a thickness of 10 μm after drying. Charging b of this example - La 1 is referred to as sample.

[0014]

[Table 1]

Both the coating solution and the coating solution were dispersed for 20 minutes by a Hommonizer after preparation.

FIG. 2 shows an experimental apparatus for evaluating the charging characteristics of the charging roller 1. 1 is a charging roller to be evaluated, 101 is a core metal of the charging roller 1, and 2 is the charging roller 1.
A power source for applying a DC voltage Va to the core bar 101, 3 is a photoconductor drum, 5 is a discharge lamp, and 4 is an electrometer for measuring the charging potential Vs of the surface of the photoconductor drum 3.

FIG. 3 shows a roller charging type image forming apparatus using the charging roller 1. In FIG. 3, the photoconductor on the surface of the photoconductor drum 3 is uniformly charged by the charging roller 1.
Image light 6 is projected onto the charged surface by an exposing unit (not shown), and an electrostatic latent image is formed on the photosensitive member. The electrostatic latent image is visualized by the developing device 7 and becomes a toner image. This toner image is transferred onto the recording paper 9 by the transfer belt 8. The recording paper 9 onto which the toner image has been transferred is sent to a fixing device (not shown), where the toner image is heated and pressed and fixed to the recording paper 9. The recording paper exiting the fixing device is discharged to the outside of the apparatus. After the transfer, the surface of the photoconductor is cleaned by the drum cleaner 10 and discharged by the discharge lamp 5.

In order to test the characteristics of the charging roller 1 of the present invention, a photosensitive drum having two defects (scratches) on its surface was used as the photosensitive drum 3, and the charging roller 1 was used. Image formation was performed.

Comparative sample 1 of the above-mentioned charging roller 1 ( ratio
Compare Example 1), sample (Example) and the charging characteristics in the three environments (temperature and humidity) of Comparative Sample 2 (Comparative Example 2) (using the experimental apparatus of FIG. 2) as well as image characteristics (in FIG. 3 (Using an image forming apparatus) is shown in Table 2 .

[0020]

[Table 2]

[0021] By the above-described image forming experiment, the charging roller according to the present invention (sample) is compared to the charging roller before improvement (Comparative Sample 2), in pairs environmental characteristics of the charge position slightly charged with low temperature and low humidity There was no problem at all in the generation of the abnormal image of the drum pitch due to the defect of the photoconductor while maintaining the non-adhesiveness and the uniformity of the charging property at the same level or higher except the low rank. It turned out that this problem has been greatly improved.

[0022]

The material for the surface layer of the charging member of the present invention, acetylene black having a low structure which is easily dispersible in methanol and the copolymerized nylon resin which is soluble in methanol, have extremely good dispersibility and are electrically uniform. It is effective for forming a smooth surface layer, and since the nylon resin has a good film forming property, the non-adhesiveness of the roller surface to OPC and toner is also improved. However, acetylene black has a higher purity (more carbon content) than carbon black, and has a low hydrogen content, and therefore has good conductivity (small electrical resistance). Therefore,
Although the electrical resistance changes greatly with a small amount of addition to the resin component, silica is added as a filler to the surface layer of the charging member of the present invention in order to mitigate this change. This silica was extremely effective in adjusting the electric resistance.

In the surface layer of the charging member of the present invention, the closer it is to the surface of the charging member, the larger the amount of dispersion of silica having high resistance and the smaller the amount of dispersion of acetylene black having good conductivity. The surface resistance is suppressed to a high level, and even if the surface of the photoconductor that is contact-charged is scratched, there is no leakage of charge or an abnormal image is generated.

Since the surface layer is divided into a plurality of times with solutions having different blending ratios of acetylene black and silica and overcoated, a desired electric resistance distribution in the thickness direction of the surface layer can be stably obtained.

[Brief description of drawings]

Charging of the embodiment of the present invention; FIG Russia - is a cross-sectional view showing a structure of La 1.

FIG. 2 is a transverse cross-sectional view showing a schematic configuration of an experimental apparatus for evaluating the charging characteristics of the charging roller 1.

FIG. 3 is a cross-sectional view schematically showing the configuration of a roller charging type image forming apparatus.

[Explanation of symbols]

1: charging roller 101: core metal 102: Elastic layer 2: Power supply 3: Photoconductor drum 4: Electrometer 5: Static elimination lamp 6: Image exposure 7: Developing device 8: Transfer belt 9: Recording paper 10: Drum Greena

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-64378 (JP, A) JP-A-5-116790 (JP, A) JP-A-6-149010 (JP, A) JP-A-6- 250496 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103 G03G 15/08 501

Claims (2)

(57) [Claims] 1. A charging member having two layers, an elastic layer covering the surface of a cored bar and a surface layer covering the surface, wherein acetylene black and hydrophobic silica are dispersed in a copolymerized nylon resin, and the closer to the elastic layer A charging member having a surface layer in which the amount of acetylene black dispersed is larger than that of silica, and the amount of silica dispersed is larger than that of acetylene black as it is farther from the elastic layer. 2. On the surface of the elastic layer covering the surface of the core metal, a solution having a different blend ratio of acetylene black and silica to the copolymerized nylon resin is divided into a plurality of times, and the solution is separated from the silica.
A solution with a high blending ratio and
Blend ratio with more silica dispersion than acetylene black
A method for producing a charging member, characterized in that the surface layer is formed by applying the solution of 1. above in this order .