JPH0749604A - Operating method of conductive member - Google Patents

Abstract

PURPOSE:To surely reproduce an excellent image over a long period, without increasing the resistance value of an electric conductive member even if it is operated for a long time by applying a current to reverse the positive and negative of tame current flowing in the conductive member by a specific charge amount at each prescribed interval. CONSTITUTION:The roller-like conductive member (electrifying roller) 1 is brought into contact with a body to be electrified 2, to apply a voltage between the electrifying roller 1 and the body to be electrified 2 by a power source 3 and genet-ate an electric field between the body 2 and the roller 1. Thus, when the body to be electrified 2 is electrified, electrifying operation is repeated while the positive and negative of ant applied current are reversed by the specific charge amount at each prescribed interval. At this time, it is preferable that the integrated value of the current in the reverse direction by the reverse is set 25-175% of an integrated current value in the forward direction. It is ideally preferable that the current in the reverse direction substantially having the same quantity as that in the forward direction is imparted. In other words, the conductive member 1 is operated by a cycle that the integrated current value in the reverse direction only for suppressing the rising rate of resistance by the application of the voltage is applied, the rising of the resistance value of the conductive member 1 can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a conductive member, particularly a conductive member used as a charging member, a phenomenon member, a transfer member in an electrophotographic process.

[0002]

2. Description of the Related Art In recent years,
A conductive member made of an elastic material (hereinafter simply referred to as a conductive member) has been attracting attention as a contact charging member for a photoconductor, a transfer material, and a toner of a dry electrophotographic apparatus. It is used for etc.

The conductive member is made of an elastic material such as a polymer elastomer material such as rubber or urethane or a polymer foam material, and is brought into direct contact with a member to be charged such as a photosensitive member so that a voltage is applied between the member and the member to be charged. Is applied, an electric field is generated between the member to be charged and the member to be charged is charged or discharged. Further, such a conductive member has an advantage that a required charging potential can be applied to the photoconductor at a lower power supply voltage, as compared with the conventionally used corotron charger.

The conductive member used for such a purpose is
It is necessary to set a constant electric resistance value in order to uniformly charge the surface potential of the photoconductor, but due to the inclusion of carbon black etc., a medium resistance region of 1 [MΩ] to 100 [GΩ] required for the electrophotographic process. It is difficult to manufacture with a constant resistance value, and a member having a constant resistance in the above-mentioned medium resistance region is manufactured by mixing an ion conductive substance such as sodium perchlorate.

However, when such a member is continuously operated for a long time, the resistance gradually increases, and there is a problem that an image defect occurs when it is used for electrophotography.

The present invention has been made in view of the above circumstances, and does not increase the resistance value of the conductive member even when it is operated for a long time, and when used for electrophotography, it is good for a long time. It is an object of the present invention to provide a method for operating a conductive member that can reliably reproduce various images.

[0007]

In order to achieve the above object, the present inventor first examined the mechanism of increasing the resistance value of the conductive member in the conventional operating method. As a result, although not always clear, the conductive member usually expresses or adjusts its conductivity by the addition of an ionic substance such as sodium perchlorate as described above. It was considered that when a polar current was continuously applied, the ionic substance was dissociated and polarized, and the current hardly flowed, so that the resistance value increased.

In fact, as shown in an experimental example described later, a voltage having a constant polarity is continuously applied to a conductive member to which sodium perchlorate is added, and the inner portion (central portion) of the conductive member having an increased resistance value. When the amount of sodium and the amount of perchloric acid in the outer part (surface part) were quantified, the amount of sodium decreased and the amount of perchloric acid increased in the inner part compared to the standard sample without voltage application. Conversely, sodium increased in the outer part. From this, dissociation and polarization of sodium perchlorate by voltage application were recognized.

Therefore, the inventor of the present invention corrects such dissociation / polarization of the ionic substance and prevents the resistance value of the conductive member from rising, and is capable of continuously performing the charging operation. As a result of further examination of the driving method of
During the operation cycle of the conductive member, in which the conductive member is brought into contact with the member to be charged and an electric current is applied, and the member to be charged is repeatedly charged, the positive and negative of the current flowing through the conductive member is inverted at predetermined intervals at a predetermined interval. It was found that the charging operation can be performed while preventing the resistance value of the conductive member from increasing by repeating the charging operation while applying the current to correct the dissociated / polarized ionic substance by this reversal current. The present invention has been completed.

Therefore, according to the present invention, a conductive member having ionic conductivity is brought into contact with a member to be charged, and a current is applied between the conductive member and the member to be charged to charge the member to a predetermined polarity. The present invention provides a method for operating a conductive member, which comprises inverting the positive / negative of an applied current at a predetermined interval at the time of removing static electricity.

The present invention will be described in more detail below. In the method for operating a conductive member according to the present invention, for example, as shown in FIG. 1, a conductive member formed in a roller shape (charging roller).
1 is brought into contact with an object to be charged 2, a voltage is applied between the charging roller 1 and the object to be charged 2 by a power source 3, and an electric field is generated between the object to be charged 2 and the charging roller 1. When the charged body 2 is charged, the charging operation is repeated while inverting the positive and negative of the applied current at a predetermined charge amount at predetermined intervals.

Here, the conductive member 1 is usually one in which a conductive material layer is formed around a core metal (not shown),
This conductive material layer uses a polymer elastomer such as rubber or urethane or a polymer foam material as a base material, and by mixing an ionic conductive material into the base material, the conductivity is 1 [M
Ω] to 100 [GΩ] in the medium resistance region.

The urethane used as the base material of the conductive material layer is, as a polyhydroxyl compound, a polyol used in the production of general flexible polyurethane foams and urethane elastomers, that is, a polyether polyol having a polyhydroxyl group at the terminal, In addition to polyester polyols and polyether polyols, which are copolymers of both, there can be used general polyols such as so-called polymer polyols obtained by polymerizing ethylenically unsaturated monomers in the polyols. Further, as the polyisocyanate compound, similarly, a polyisocyanate used in the production of general flexible polyurethane foams and urethane elastomers, that is, tolylene diisocyanate (TDI), crude TDI, 4,4-diphenylmethane diisocyanate (MDI), crude MDI. , C2-18 aliphatic polyisocyanate, C4-15
The alicyclic polyisocyanate and a mixture or modified product of these polyisocyanates, for example, a prepolymer obtained by partially reacting with a polyol or the like are used.

The rubber used as the base material of the conductive material layer is usually natural rubber, nitrile butadiene rubber, chloroprene rubber, styrene butadiene rubber, butadiene rubber, ethylene propylene rubber, isoprene rubber, polynorbornene rubber or the like. Rubbers or thermoplastic rubbers such as styrene-butadiene-styrene (SBS) and styrene-butadiene-styrene water additive (SEBS) can be used, and liquid polyisoprene rubber can be mixed with these rubbers. it can. Further, a foamed product of these rubbers or a copolymer rubber of epichlorohydrin and ethylene oxide may be used.

As the ionic conductive substance added to these base materials, inorganic ionic conductive substances such as sodium perchlorate, calcium perchlorate, sodium chloride and the like, and further modified aliphatic dimethylethylammonium ethosulfate and stearyl. Examples of organic ionic conductive substances such as ammonium acetate, lauryl ammonium acetate, octadecyl trimethyl ammonium perchlorate,
Generally, sodium perchlorate is often used.

As described above, in the method for operating a conductive member of the present invention, when a current is applied between the conductive member 1 and the body 2 to be charged, the positive / negative sign of the applied current is applied at a predetermined interval for a predetermined time. The amount is reversed. In this case, it is preferable that the integrated value of the reverse current due to the reversal is 25 to 175%, particularly 60 to 140% of the forward integrated current value, and ideally, the reverse current of substantially the same amount as the forward current. Is preferably given. That is, the rate of increase in resistance due to voltage application can be expressed as a function of the applied integrated current value. Therefore, if operating in a cycle in which a reverse direction integrated current value is applied to suppress it, the increase in the resistance value of the conductive member is suppressed. It is what is done.

Since it is substantially impossible to perform the charging operation when the reverse current is applied, it is preferable to make the reverse current application time as short as possible. Therefore, the reverse current is applied in the forward direction. It is preferable to control so that a larger current than the current is applied for a short time from the viewpoint of charging treatment efficiency. Specifically, as in Example 1 to be described later, a reverse current of −48 μA is applied for 1 sec every time a forward current of 4 μA is applied for 12 sec, and a reverse direction equal to the forward integrated current value is applied. An integrated current value can be applied.

Further, there is no particular limitation on the method of applying the reverse integrated current, and a rectangular wave, a pulse wave, a sine wave, a triangular wave, etc. are preferably applied.

The method of operating a conductive member according to the present invention is suitable for driving a photosensitive member charging portion, an electrostatic image phenomenon portion, a toner transfer portion, etc. in an electrophotographic apparatus. It can be preferably used if the contact charging operation using is performed. Although the roller-shaped conductive member is used in FIG. 1 here, the conductive member may have a brush shape, a plate shape, a block shape, or another shape, and the material of the conductive member is ion conductive. Any material may be used as long as it is of a sex.

[0020]

According to the method of operating a conductive member of the present invention,
Even if it is operated for a long time, the resistance value of the conductive member is not increased, and when it is used for electrophotography, it is possible to reliably reproduce a good image for a long time.

[0021]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Prior to Examples and Comparative Examples, experimental examples of the mechanism of increasing the resistance value of the conductive member due to voltage application will be shown.

Experimental Example Preparation of Conductive Member (Sample) A compound having an isocyanate group consisting of 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate, and propylene oxide in glycerin. And ethylene oxide are added to give a molecular weight of 5000
100 parts (weight part, the same applies hereinafter) consisting of the polyether polyol described above, 1.65 parts of 1,4-butanediol, 3.6 parts of a silicone-based surfactant, 0.007 part of dibutyltin dilaurate, 0.02 parts of 33% diethylene glycol monomethyl ester solution of sodium chlorate was bubbled with a foaming pouring machine manufactured by MONDOMIX, and the mixture was poured into a mold having a roller cored bar in the central part and cured at 80 ° C. for 12 hours. After curing, it was buffed to a predetermined size to obtain a roller-shaped conductive member.
The diameter of the conductive roller was 16.5 mm.

An aluminum drum having a diameter of 30 mm for voltage application is used as a counter electrode, and the TRE is used.
A Model 610C power supply manufactured by CK was used to apply a voltage of +1,000 V to the core of the conductive roller for 8 hours.
The environment at the time of voltage application was a temperature of 28 ° C. and a humidity of 85%. The resistance value of the conductive roller was about 2 × 10 ⁷ Ω in the initial resistance, but it increased with the voltage application, and after 8 hours, it was about 1 ×.
The resistance value increased to about 10 ⁸ Ω.

Measurement of polarization shift of ionic substance 0.5 g of a sample obtained by cutting a portion of the roller from the cored bar to a thickness of 2 mm (hereinafter referred to as inner side) and a sample of a surface portion of the roller cut to a thickness of 2 mm. (Hereinafter referred to as the outside)
0.5g and 0.5g of standard sample without voltage
Each of them was immersed and extracted in 1.4 ml of distilled water for 24 hours, and the amount of sodium and the amount of perchloric acid were quantified by ion chromatography. The equipment used was the Toyo Soda CCPD pump,
Waters U-6K injector, Wescan conductivity detector, Shimadzu IC-A1 (for anion analysis) or IC-G1 (for cation analysis) column, flow rate 3 m
1 / min. As a mobile phase, a phthalate buffer solution (4 mM, pH 6.2) was used for anion analysis, and a nitric acid aqueous solution (2 mM) was used for cation analysis. The analysis results are shown in Table 1.

[0025]

[Table 1]

From the results shown in Table 1, it is recognized that the ion conductive substance (sodium perchlorate) in the conductive member undergoes dissociation / polarization due to the voltage application, and this dissociation / polarization causes an increase in resistance value. Presumed to be.

Example 1 A roller-shaped conductive member was prepared in the same manner as in the above experimental example, and the apparatus shown in FIG. 1 was constructed using this conductive member. In this case, in the apparatus of FIG. 1, the electrically conductive roller having a diameter of 16.5 mm is used as one charging member, the aluminum drum having a diameter of 30 mm is used for the second portion, and the rotation speed of the aluminum drum is 17 mm.
It was set to be rpm.

Next, TRECK is used as a constant current generating power source.
The Model 610C manufactured by the company and a function generator were used to apply the rectangular wave low current shown in FIG. The voltage value at this time was observed and the roller resistance was calculated from the conversion with the current value. FIG. 3 shows the results plotted against the energization time.

As is apparent from FIG. 3, almost no increase in roller resistance was observed, indicating that good continuous operation was possible. Under this application condition, the reverse current integrated value is equal to the forward current integrated value.

[Comparative Example] An experiment was conducted in the same manner as in Example 1 except that the current was applied in only one continuous direction as shown in FIG. 4, and the change in resistance of the conductive roller with time was measured. The result is shown in FIG. In this case, what had an initial resistance of about 2 × 10 ⁷ Ω increased with the voltage application, and after 8 hours, the resistance value increased to about 1 × 10 ⁸ Ω. Therefore, in order to secure a current amount equivalent to the initial value, it is necessary to apply a voltage about 10 times the initial value.

[Embodiment 2] An experiment was conducted in the same manner as in Embodiment 1 except that the rectangular wave as shown in FIG. 6 was used as the current application condition, and the change with time of the conductive roller resistance was measured. The result is shown in FIG. 7. In this case, although a slight increase in resistance was observed, a sufficient improvement effect was confirmed as compared to continuous homopolarity application (Comparative Example). In this case, the reverse current integrated value corresponds to 62.5% of the forward current integrated value.

[Embodiment 3] An experiment was conducted in the same manner as in Embodiment 1 except that the rectangular wave as shown in FIG. 8 was used as the current application condition, and the change in the resistance of the conductive roller with time was measured. The result is shown in FIG. In this case, although it is inferior to Examples 1 and 2, the effect of suppressing the increase in resistance was confirmed. In this case, the reverse current integrated value corresponds to 17% of the forward current integrated value.

[Example 4] Propylene oxide and ethylene oxide were added to glycerin to give a molecular weight of 6,0.
00 polyether polyol (made by Asahi Glass Co., Ltd.,
Exenol 828) 100 parts, urethane modified M
DI (Sumitomo Bayer Urethane Co., Ltd., Sumidule P
F) 25 parts, 1,4-butanediol 2.9 parts, a silicone-based surfactant (manufactured by Nippon Yunika Co., Ltd., L-52).
0) 1.5 parts, dibutyltin dilaurate 0.01
, Modified aliphatic dimethylethylammonium ethosulfate (PPG Industries, Inc.
Manufactured by Larostat 264A anhydro
s) 0.5 part was bubbled with a foaming and pouring machine manufactured by MONDOMIX, and the mixture was poured into a mold in which a roller cored bar was arranged at the center, and cured at 80 ° C for 12 hours. After curing, it was buffed to a predetermined size to obtain a roller-shaped conductive member.
The conductive roller obtained had a diameter of 16.5 mm and a resistance value (initial resistance) of about 1.0 × 10 ⁷ Ω.

The same experiment as in Example 1 was conducted on the obtained conductive roller. As a result, the resistance value hardly increased due to energization even after 8 hours, and good continuous operation was possible.

Example 5 100 parts of polyester polyol (Nipporan 2200 manufactured by Nippon Polyurethane Industry Co., Ltd.) and 16.3 parts of TDI (Coronate T-80 manufactured by Nippon Polyurethane Industry Co., Ltd.) 1,4 -3 parts of butanediol, 1.5 parts of a silicone-based surfactant (L-520 manufactured by Nippon Unica Co., Ltd.), 0.01 part of dibutyltin dilaurate, stearyl ammonium acetate (manufactured by NOF Corporation) 0.3 parts of acetamine 86) was bubbled with a foaming and pouring machine manufactured by MONDMIX, and the mixture was poured into a mold having a roller cored bar in the center, and 80
It was cured at ℃ for 12 hours. After curing, it was buffed to a predetermined size to obtain a roller-shaped conductive member. The conductive roller thus obtained had a diameter of 16.5 mm and a resistance value (initial resistance) of about 2.0 × 10 ⁷ Ω.

The same experiment as in Example 1 was conducted on the obtained conductive roller. As a result, the resistance value hardly increased due to energization even after 8 hours, and good continuous operation was possible.

Example 6 Polyether polyol (manufactured by Sumitomo Bayer Urethane Co., Desmophen 1915)
U) 100 copies, TDI (Sumitomo Bayer Urethane Co., Ltd.)
Manufactured by Sumidur T-80), 12.3 parts by weight, 1,4-butanediol by 3 parts by weight, silicone surfactant (L-520 manufactured by Nippon Unica Co., Ltd.) by 1.5 parts, dibutyltin dilaurate. 0.01 part and lauryl ammonium acetate (Nippon Oil and Fats Co., Ltd., Acetamine 24) 0.3 part are bubbled by a foaming and pouring machine manufactured by MONDMIX, and the mixture is poured into a mold having a roller cored bar in the central part. Then 8
It was cured at 0 ° C for 12 hours. After curing, it was buffed to a predetermined size to obtain a roller-shaped conductive member. The conductive roller obtained had a diameter of 16.5 mm and a resistance value (initial resistance) of about 0.8 × 10 ⁷ Ω.

The same experiment as in Example 1 was conducted on the obtained conductive roller. As a result, the resistance value hardly increased due to energization even after 8 hours, and good continuous operation was possible.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for carrying out a method for operating a conductive member according to the present invention.

FIG. 2 is a waveform diagram of a current applied in Example 1.

FIG. 3 is a graph showing a change in resistance value of a conductive member in an operation test of Example 1.

FIG. 4 is a waveform diagram of a current applied in a comparative example.

FIG. 5 is a graph showing a change in resistance value of a conductive member in an operation test of a comparative example.

FIG. 6 is a waveform diagram of a current applied in Example 2.

FIG. 7 is a graph showing a change in resistance value of a conductive member in an operation test of Example 2.

FIG. 8 is a waveform diagram of a current applied in Example 3.

FIG. 9 is a graph showing a change in resistance value of a conductive member in an operation test of Example 3.

[Explanation of symbols]

 1 conductive member 2 charged body 3 power supply

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Claims (2)

[Claims] 1. When a conductive member having ionic conductivity is brought into contact with a member to be charged and a current is applied between the conductive member and the member to be charged so as to charge the member to a predetermined polarity, or static elimination is performed. In this case, the operating method of the conductive member is characterized in that the positive and negative of the applied current is inverted by a predetermined charge amount at predetermined intervals. 2. The method of operating a conductive member according to claim 1, wherein the backward integrated current value is 25% to 175% of the forward integrated current value.