JPH06230653A - Corona discharge device - Google Patents

Abstract

PURPOSE:To obtain a corona discharge device having little deterioration of discharging performance and capable of uniformly and efficiently performing discharge and saving space by possessing an electrode including a conductive fiber sheet and setting the peak value of applied superposed voltage within a specified range. CONSTITUTION:An electrode of conductive fiber sheet is provided, and the peak value of the superposed voltage of DC voltage and AC voltage, which is applied on the electrode, is twice or more times as high as discharge start voltage at the time of applying DC on the electrode, and set within the range equal to or under spark discharge start voltage. The sheet formed out of conductive fiber, such as a fiber which has been worked to be conductive, metallic fiber or carbon fiber is good to be used, and the sheet obtained by forming the fiber sheet from a synthetic fiber or inorganic fiber and working the sheet to be conductive is also good as the conductive fiber sheet. Since the electrode easily performs discharge at a low voltage, toner, paper powder and dust are hardly electrostatically stuck, the deterioration of discharging performance is little, and discharging efficiency is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge device for charging or discharging a photoconductor of a copying machine.

[0002]

2. Description of the Related Art Conventionally, wires such as corotron have been used as electrodes in corona discharge devices for charging or discharging a photoconductor of a copying machine. However, when such a wire is used, it is necessary to apply a high voltage of 4 to 8 kilovolts to discharge the wire, and thus toner, paper powder, dust, and the like are liable to be electrostatically attached, and the discharge is generated as the wire is used. There has been a problem that the dischargeability is greatly reduced, such as unevenness. In addition, in order to improve the dischargeability from this wire, it is common to provide a shield electrode so as to surround this wire, but since this shield electrode also discharges, the discharge current that actually flows to the photoconductor is 5
It was as low as about 30%, and there was a problem in terms of discharge efficiency.
Further, as described above, since a high voltage is applied, the power source becomes large and a shield electrode needs to be provided so as to surround the wire, so that the space occupied by the corona discharge device is large and the copying machine is There was also the problem that it could not be miniaturized.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and provides a corona discharge device in which the deterioration of the discharge property is small, the discharge can be performed uniformly and efficiently, and the space can be saved. The purpose is to do.

[0004]

The present invention has an electrode containing a conductive fiber sheet, and the peak value of the superimposed voltage of a DC voltage and an AC voltage applied to this electrode is such that a DC voltage is applied to this electrode. The corona discharge device is set within a range that is at least twice the discharge starting voltage when applied and is below the spark discharge starting voltage.

[0005]

The corona discharge device of the present invention has an electrode containing a conductive fiber sheet, and since this electrode is easily discharged at a low voltage, toner, paper dust, dust, etc. are less likely to be electrostatically attached, Little decrease in dischargeability. Further, even if the shield electrode is not used, the discharge is easily performed to the photoconductor in the vicinity of the electrode, so that the discharge efficiency is excellent. As described above, in the corona discharge device of the present invention, since the discharge is easily generated at a low voltage, it is possible to reduce the power supply, and since it is not necessary to provide the shield electrode, the space can be saved.

Furthermore, the peak value of the superimposed voltage of the DC voltage and the AC voltage applied to this electrode is more than twice the discharge starting voltage when DC is applied to this electrode and is less than the spark discharge starting voltage. Since it is set within the range, it is possible to discharge more uniformly.

The conductive fiber sheet of the present invention may be a sheet formed from conductive fibers such as metal plated, conductive fibers such as metal fibers, carbon fibers and metal ion mixed fibers, regenerated fibers, semi-fibers, etc. Synthetic fiber, synthetic fiber,
It may be obtained by forming a fiber sheet from fibers such as inorganic fibers, vegetable fibers, animal fibers, and mineral fibers, and then subjecting this fiber sheet to conductive processing.

In the present invention, the fiber density of the conductive fiber sheet is preferably 3,500 m / cm ³ or more. This is because when the fiber density is less than 3,500 m / cm ^3, it is difficult to discharge and it is difficult to uniformly charge the photoconductor even if discharged. It is more preferably 4,000 m / cm ³ or more, and most preferably 4,500 m / cm ³ or more.
The fiber density is the length occupied by the fibers per cm ³ , and when the fibers constituting the conductive fiber sheet are short fibers, it is the sum of the lengths of the individual short fibers,
It is a value obtained by the following formula. ρ: Specific gravity of fiber, r: Radius of fiber (cm)

When the fiber diameter of these fibers is 14 μm or less, more preferably 10 μm or less, discharge is more likely to occur, and therefore it can be suitably used. However, if the fiber diameter is less than 0.1 μm, durability is poor, and therefore 0.1 μm. Above, more preferably 1μ
It is preferably m or more. A fiber having a fiber diameter within this range is divided by performing a mechanical and / or chemical treatment, or is spun from a nozzle and at the same time an air flow is applied to reduce the fiber diameter, generally a microspun bond. It can also be obtained by the method called law.

The fiber diameter of these fibers is the length of a straight line which can be taken longest in the fiber cross section. For example, when the fiber cross section is elliptical, it is the length of the long axis,
If the fiber cross section is triangular, it is the longest side length,
In the case of a quadrangle, it is the length of the longer diagonal. When fibers having various fiber diameters are mixed, the fibers are averaged according to their existing ratios. For example, in the case of a fiber sheet in which 70% of fibers having a fiber diameter of 20 μm and 30% of fibers having a fiber diameter of 10 μm are mixed, 17 (= 20 ×
0.7 + 10 × 0.3) μm.

The above-mentioned fibers that can be divided include, for example,
A sea-island type fiber with a cross section in which other components are arranged in an island shape in one component, a multi-bimetal type fiber with a cross section in which different components are alternately laminated in layers, or a cross section in which one component is radially arranged in another component There are also chrysanthemum type fibers. Examples of the combination of resin components constituting the divisible fiber include polyamide-based resin and polyester-based resin, polyamide-based resin and polyolefin-based resin, polyester-based resin and polyolefin-based resin, polyester-based resin and polyacrylonitrile-based resin, and polyamide. Resins and polyacrylonitrile resins, polyolefin resins and polyacrylonitrile resins, and the like.

The conductive fiber sheet of the present invention includes woven fabrics such as plain weave, twill weave and satin weave, knitted fabrics, thread laces, nets,
A flat braid, a non-woven fabric, or the like may be used, and the non-woven fabric is not particularly limited. Among them, the non-woven fabric can densely arrange the fibers, and many fibers can act on the photoconductor, so that it is easy to discharge, It can be preferably used.

As a method of manufacturing this non-woven fabric, for example,
The fiber web obtained by the card method, the air-laying method, the wet method, the spunbond method, etc. is entangled with each other by the action of a water stream or a needle, the method of bonding with an adhesive, the bonding of the constituent fibers by fusion. There are ways to do it. Among these, a nonwoven fabric obtained by entanglement of a web of fibers obtained by a wet method with a water stream has fibers uniformly arranged and has a high fiber density, and thus can be suitably used. It should be noted that the use of the above-mentioned splittable fibers has an advantage in the manufacturing process that the fibers can be split at the same time as the fibers are entangled with each other by a water stream or a needle punch.

When non-conductive fibers are used among the fiber sheets obtained as described above, the fiber sheet is subjected to conductive processing to obtain a part or all of the electrodes.

The surface resistance of this conductive fiber sheet is 1 × 1.
It is preferably from 0 ⁰ to 1 × 10 ⁹ Ω / □. If the surface resistance is less than 1 × 10 ⁰ Ω / □, partial spark discharge is likely to occur, and uniform and stable discharge is unlikely to occur.
^If it exceeds ⁹ Ω / □, it is necessary to apply a high voltage, so toner, paper powder, dust, etc. tend to adhere, which not only reduces the dischargeability, but also if the conductive fiber sheet is defective. This is because if foreign matter is attached, spark discharge may occur. The more preferable surface resistance is 1 × 10 ² to 1 × 10 ⁶ Ω / □, and the most preferable surface resistance is 1 × 10 ² to 1 × 10 ⁴ Ω / □.

Examples of the conductive processing method for the fiber sheet or fiber include, for example, coating treatment with an electron conjugated polymer, metal plating treatment, vapor deposition treatment, sputtering treatment,
Ion plating treatment, metal spray treatment, etc. are available.
The coating treatment with the electron-conjugated polymer can be preferably used because it is easy to make the surface resistance of the conductive fiber sheet within the above range.

As a method of imparting conductivity with this electron-conjugated polymer, for example, a solution containing an oxidizing agent such as iron (III) chloride or copper (II) chloride is impregnated into a fiber sheet or fibers, and then the monomer is added. There is a method of polymerizing by contacting with. Further, the method of contacting with the monomer is to impregnate, coat or spray the fiber sheet or fibers to which the oxidant is attached when the monomer is in a liquid state. The fiber sheet or fiber to which the oxidant is attached may be placed in the filled container.

Examples of the monomer to be polymerized include pyrrole, acetylene, benzene, aniline, phenylacetylene, furan, thiophene, indole and derivatives of these monomers. Among these,
Pyrrole is particularly suitable for use because it has excellent conductivity and polymerizability and can impart conductivity evenly.

The conductive fiber sheet obtained as described above forms an electrode in a form processed into a sheet shape, a roll shape, a thread shape or the like, or a shape bonded to a conductive base material such as a metal roll. .

The corona discharge device of the present invention includes the electrode as described above, and the peak value of the superimposed voltage of the DC voltage and the AC voltage applied to this electrode is the discharge start when DC is applied to this electrode. It is more than twice the voltage and is set within the range of the spark discharge starting voltage or less. If the peak value of this superimposed voltage is less than twice the discharge start voltage, the photoreceptor is insufficiently charged, so in the reversal developing system, too much toner is attached overall and there are many black spots and a clear image. No image can be obtained. On the other hand, if the spark discharge start voltage is exceeded, the photoreceptor is charged too much.Therefore, in the reversal development system, there is little toner as a whole and there are many white spots, and a clear image is obtained. Because there is no.

The discharge start voltage when a direct current is applied to the electrode means that when the electrode containing the conductive fiber sheet is installed with a gap between the photosensitive member and the direct current voltage, the direct current voltage is gradually increased. The spark discharge start voltage means the voltage when the current first flows through the body, and the spark discharge start voltage means the voltage when the DC current is applied to similarly installed electrodes and the current flowing through the photoconductor rapidly increases. Therefore, the discharge start voltage and the spark discharge start voltage vary depending on the electrode used, but the electrode including the conductive fiber sheet as in the present invention starts discharge at a low voltage and starts spark discharge at a low voltage. Therefore, the deterioration of the discharge property is small and the discharge efficiency is excellent. In addition, since the discharge is performed at a low voltage, the amount of ozone generated is extremely small, and there is an advantage that the photoconductor and peripheral parts are oxidatively deteriorated and the human body is not adversely affected.

Examples of the waveform of the AC voltage include a sine wave, a rectangular wave, and a pulse wave.

Examples of the present invention will be described below, but the invention is not limited to the following examples. The surface resistance is a value measured by a four-terminal method using a surface resistance meter (Loresta AP manufactured by Mitsubishi Petrochemical Co., Ltd.).

[0024]

【Example】

(Examples 1 to 3 and Comparative Examples 1 and 2) 100% of polyester fibers (fiber diameter 3.2 μm, fiber length 5 mm) were formed by a wet method, and then entangled with a water flow of water pressure 95 kg / cm ^2. A non-woven fabric having a basis weight of 100 g / m ² and a thickness of 0.6 mm was obtained.
After impregnating this non-woven fabric with iron (III) chloride at a concentration of 30%, the whole non-woven fabric was coated with 3.5 g / m ² of polypyrrole by bringing the pyrrole solution into contact with the vaporized pyrrole monomer gas. Obtained. The fiber density of this conductive nonwoven fabric was 15,000 m / cm ³ and the surface resistance was 1.3 × 10 ² Ω / □.

This conductive non-woven fabric was flatly wound on a metal roll shaft having a diameter of 8 mm to form an electrode, and the electrode was made 0.5 m from the photoconductor.
The laser beam printer was installed at a distance of m.
A combination of a DC voltage and an AC voltage (DC voltage (V), AC voltage (peak to peak value, V)) is (-800, 400) (-600, 600) (-60
0, 800) (-500, 400) (-900, 60)
0) superimposed voltage (in the order of Example 1, Example 2, Example 3,
Comparative Examples 1 and 2) were applied to form an image, and the image was visually judged to be superior or inferior. The results show that, as shown in Table 1, the corona discharge device of the present invention discharges uniformly even at a low voltage and can uniformly charge the photoconductor.
The discharge start voltage of the electrode was -400 V and the spark discharge start voltage was -1,100 V.

[0026]

[Table 1]

(Examples 4 to 6 and Comparative Examples 3 to 4) A polyester component was the main component, and the polyester component was separated into 8 sections by a polyamide component radially extending from the axis of the fiber. Denier, fiber length 38
mm) 100% is carded into a fibrous web, which is then entangled with a water flow at a water pressure of 95 kg / cm ² to give a basis weight of 85 g /
A nonwoven fabric with m ² and a thickness of 0.45 mm was obtained. The fiber diameter of this nonwoven fabric was a value measured based on an electron micrograph, and the polyester component had an average of 6 μm and the polyamide component had an average of 7 μm, and the average fiber diameter was 6.1 μm. Then, this non-woven fabric was treated in exactly the same manner as in Example 1 and the whole non-woven fabric was treated with 3.
A conductive non-woven fabric was obtained by coating with 0 g / m ² of polypyrrole.
The fiber density of this conductive non-woven fabric is 4,800 m / cm ³ ,
The surface resistance was 2.0 × 10 ² Ω / □.

This conductive non-woven fabric was installed in a laser beam printer as in Example 1, and a combination of DC voltage and AC voltage (DC voltage (V), AC voltage) was applied to this electrode.
(Peak to peak value, V) is (-1,00)
0, 200) (-1,000, 400) (-700, 1,
000) (-700, 400) (-1,000, 80
0) superimposed voltage (Example 4, Example 5, Example 6,
An image was formed by applying Comparative Examples 3 and 4), and the image was visually judged to be superior or inferior. This result also shows that, as shown in Table 1, the corona discharge device of the present invention discharges uniformly even at a low voltage and can uniformly charge the photoconductor.
The discharge start voltage of the electrode was -500 V and the spark discharge start voltage was -1,300 V.

[0029]

The corona discharge device of the present invention has an electrode containing a conductive fiber sheet. Since this electrode is easily discharged at a low voltage, the deterioration of the discharge property is small. In addition, the discharge efficiency is excellent because the discharge is easily performed without using the shield electrode. As described above, in the corona discharge device of the present invention, since the discharge is easily generated at the low voltage, the power source can be made small, and the shield electrode is not required. Therefore, the space can be saved.

Further, the peak value of the superimposed voltage of the DC voltage and the AC voltage applied to the electrode of the corona discharge device of the present invention is more than twice the discharge starting voltage when DC is applied to this electrode, Since it is set within the range below the spark discharge starting voltage, more uniform discharge can be achieved.

Claims (1)

[Claims] 1. An electrode including a conductive fiber sheet is provided, and a peak value of a superimposed voltage of a DC voltage and an AC voltage applied to the electrode is a discharge start voltage when DC is applied to the electrode. A corona discharge device characterized in that it is set to a value not less than twice and not higher than a spark discharge starting voltage.