JPH0869154A - Electrifying member, electrifying device, image forming device, and process cartridge - Google Patents

Abstract

PURPOSE: To eliminate defective electrification caused by a a ruggedness shape on the surface of conductive foaming body by setting a ratio of difference on the height of the ruggedness shape on the surface of the conductive foaming body to the film thickness of a resistant layer in a specified range. CONSTITUTION: The electrifying roller 1 of a process cartridge is constituted of a core bar 1a as a conductive supporting body, the conductive foamed body layer lb concentrically and integrally formed with the core bar 1a on the external peripheral surface of the core bar 1a in a roller state, and the resistant layer 1c formed on the external peripheral surface of the layer 1b. The ratio of the difference on the height of the ruggedness shape (surface roughness R) on the surface of the layer 1b to the film thickness (T) of the layer 1c', being T/R is <=0.65 to 150. In order to do that, the surface roughness of the conductive foamed body layer is lowered by grinding, and the film thickness of the resistant layer is adjusted according to the value. As a result, the defective electrification caused by the ruggedness shape on the surface of the foamed body is prevented, so that an image having high quality can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member, a charging device,
The present invention relates to an image forming apparatus and a process cartridge.

More specifically, a. A charging member that performs a charging process (including a destaticizing process) on the body to be charged b. Charging device having the charging member c. Image forming apparatus for image forming process including charging step d. The present invention relates to a process cartridge that includes at least an image carrier and a charging unit and is attached to and detached from a main body of an image forming apparatus.

[0003]

2. Description of the Related Art For the sake of convenience, an explanation will be given by taking as an example a charging process of a photoconductor, a transfer material and the like in an image forming apparatus such as an electrophotographic copying machine, a laser beam printer and an electrostatic recording apparatus.

In the image forming apparatus as described above, a step of uniformly charging a photoconductor or a dielectric as an image carrier to a predetermined polarity and potential, and a transferable image (toner) from the image carrier side to the transfer material side. It includes a step of charging the transfer material in order to electrostatically transfer the image).

A non-contact type corona charging device has been widely used as the charging device.
The corona charging device requires a high voltage, generates a lot of ozone, etc., and needs a corona wire cleaning means.
Such defects have been pointed out.

In order to eliminate such a drawback, a contact charging method has recently been put into practical use in which a charging member to which a voltage is applied is pressed against a member to be charged with a constant load so as to charge the member to be charged. The contact charging method is advantageous over the corona charging method in that it does not require a large power source and generates almost no ozone.

As a contact charging method, a charging member such as a charging roller to which a DC voltage is applied from the outside is brought into contact with an object to be charged such as a photoconductor to carry out charging (hereinafter referred to as DC charging).
And a method of applying an oscillating voltage, for example, a superimposed voltage of a DC voltage and an AC voltage to a charging member to perform charging (hereinafter referred to as AC charging).

In these contact charging methods, charging is performed by using a discharge mechanism in a minute air gap formed between a charging member and a photosensitive member as a member to be charged,
In DC charging, a voltage obtained by adding a discharge start threshold and a desired photoreceptor surface potential is applied to the contact charging member, and in AC charging, a DC voltage corresponding to the desired photoreceptor surface potential, Proper charging is performed by superimposing and applying an AC voltage having a peak-to-peak voltage that is at least twice the discharge start threshold voltage.

The charging member is generally a conductive support having at least a conductive elastic layer and a resistance layer formed thereon.

The conductive elastic layer of the charging member is, for example, NR,
IR, BR, SBR, EPM, EPDM, silicone rubber, CR, urethane rubber, epichlorohydrin rubber, and other rubbers, and conductive agents such as carbon black, metal oxides, quaternary ammonium salts, and perchlorates, and It is formed on the core metal by sufficiently mixing other additives and heat-molding. Further, a charging roller in which a resistance layer having conformability to the conductive elastic layer is coated thereon is often used.

The resistance layer is for preventing the charging member and the photoconductor from being damaged by the concentration of the charging current when a defect such as a pinhole occurs on the photoconductor. At the same time, it is also necessary to have a barrier effect for preventing surface migration of the plasticizer and the like contained in the elastic layer.

Materials used for the resistance layer include, for example, Japanese Patent Laid-Open Nos. 64-66674 and 64-6.
6676 proposes to use a nylon resin as a surface layer which is a resistance layer of a charging member, and US Pat. No. 4,967,231 discloses a charging member having a surface layer as a resistance layer made of urethane resin. It is disclosed, and conductive fine powder such as carbon black or metal oxide is dispersed in these resins and used.

In the charging roller, in order to obtain a uniform charging property, it is necessary to make the surface roughness of the surface facing the photosensitive member fine. Generally, the ten-point average roughness (Rz) in the JIS B0601 surface roughness standard is used. It is generally expressed by using the value, and its value is preferably about 1 μm to 50 μm.

However, when the AC charging is performed, an AC electric voltage is applied to the contact charging member, an oscillating electric field is generated between the contact charging member and the photosensitive member, and when they are attracted to each other, an abnormal noise called a charging sound is generated. This charging sound mainly has a frequency twice as high as the frequency applied to the contact charging member, and the charging sound frequency is several hundreds to several kilohertz at the charging frequency of several hundreds hertz which is usually used, and it feels very annoying. To be

In order to prevent this, the conductive elastic layer of the contact charging member needs to have a low hardness.

When the conductive elastic layer is solid, it is necessary to add a large amount of plasticizer / softening agent, but the amount added is naturally limited, and naturally there is a limit to the reduction of hardness of the conductive elastic layer. is there.

This is still effective in the case of low speed or low frequency, but it may be insufficient in order to cope with high speed or high frequency. In this case, the conductive elastic layer is used as a foam.

In this case, as the charging roller, 1 × 10
^As long as it has an electric resistance of ³ Ω or more and less than 1 × 10 ¹² Ω, it can be used without limitation on the constitution and material.

For the conductive foam, the materials used for the conductive elastic layer described above can be used, and further, ADCA,
A foaming agent such as OBSH, sodium hydrogen carbonate, and water, which is appropriately selected depending on the rubber, is added for use.

In a personal type image forming apparatus, a process cartridge in which such a charging roller, a toner container and a developing device are integrated is generally used. 8,
After printing about 000 sheets, the toner runs out, and the life of the cartridge is generally terminated at that point.

[0021]

However, when the image forming apparatus is required to have higher speed and higher image quality as in recent years, a large amount of current needs to be passed, which causes the problem of charging noise as described above. It is necessary to use a foam for the conductive elastic layer of the contact charging member, but in this case, there were the following problems.

That is, various methods such as an extrusion method and a die method can be used to produce a foam.
For example, when a method is used in which rubber is extruded into a tube shape, vulcanized and foamed, and then the surface is polished to obtain a predetermined outer diameter dimension, the foam roller surface is formed by polishing. Since a porous grindstone that rotates at a constant speed is contacted while rotating at a constant speed, especially in a soft foam, the surface rises as if it was torn, resulting in a rough surface.

In this state, even if a resistance layer is provided on the surface, the shape of the foam surface is reflected and the dripping of the resistance layer occurs at the peaks of the foam. When the film thickness becomes thin and high durability is required, there is a possibility that leakage may occur from that part during durability, and the barrier effect that prevents exudation of plasticizer etc. from the foam is insufficient. However, there is a drawback that the photoreceptor as a member to be charged is likely to deteriorate due to high humidity.

Further, as a matter of course, by performing the polishing, the foam cells appear on the surface, and that portion becomes a concave shape as a whole, which becomes the waviness of the roller and the contact of the roller with the photosensitive member. There is a drawback that unevenness in density is likely to cause an image defect during durability due to non-uniformity.

Therefore, an object of the present invention is to provide a charging member which has at least a conductive foam and a resistance layer thereon, on a conductive support, and which eliminates the above-mentioned drawbacks. .

That is, it is an object of the present invention to provide a charging member in an image forming apparatus, which is free from image defects and deterioration of the photosensitive member due to the unevenness of the foam surface of the charging member.

Another object of the present invention is to provide a charging member having a small resistance variation over the environment from high temperature and high humidity to low temperature and low humidity.

Another object of the present invention is to provide a charging member whose composition does not change even when charging and discharging are repeated.

Another object of the present invention is to provide a charging device capable of uniformly charging an object to be charged for a long period of time, and an image forming apparatus and a process cartridge capable of providing an excellent image for a long period of time, by achieving the above-mentioned object. It is in.

[0030]

SUMMARY OF THE INVENTION The present invention is a charging member characterized by the following configurations, a charging device using the charging member, an image forming apparatus using the charging device, and a process cartridge.

(1) In a charging member having at least a conductive foam and a resistance layer provided thereon on a conductive support, a difference in height of irregularities on the surface of the conductive foam ( Ratio of surface roughness R and film thickness T of the resistance layer T / R
Is greater than 0.65 and 150 or less.

(2) The charging member according to (1), characterized in that the surface of the conductive foam is polished.

(3) The charging member according to (1), wherein the conductive foam has an average cell diameter (cell diameter) of 30 μm or more and 300 μm or less.

(4) The binder resin of the resistance layer is a reaction product of a polymer component containing at least a carboxyl group-containing vinyl monomer and / or its derivative and a polymer component containing a urethane bond. The charging member as described in (1) above.

(5) In the binder resin, at least one end of the polymer component containing a urethane bond is bound to the polymer component containing at least a carboxyl group-containing vinyl monomer and / or its derivative. (4) The charging member according to (4).

(6) The charging member as described in (4) or (5), wherein the polymer component containing at least the carboxyl group-containing vinyl monomer and / or its derivative has a hydrophilic group.

(7) The charging member as described in (4) or (5), wherein the polymer component containing a urethane bond has a hydrophilic group.

(8) The charging member according to (4), wherein the binder resin is dispersed in water.

(9) Electric resistance of 1 × 10 ³ Ω or more 1 × 1
The charging member according to (1), which is less than 0 ¹² Ω.

(10) The charging member according to any one of (1) to (9), wherein the member to be charged is charged by applying a voltage to the charging member.

(11) The charging member according to (10), wherein the applied voltage is only a DC voltage.

(12) The charging member according to (10), wherein the applied voltage is an oscillating voltage.

(13) The charging member according to (12), wherein the oscillating voltage is a voltage obtained by superposing a DC voltage and an AC voltage.

(14) The charging member according to any one of (1) to (13), wherein the charging member is in contact with the surface of the body to be charged.

(15) The charging member according to any one of (1) to (14), wherein the charging member is a roller type.

(16) The charging member is a charging member for charging the image carrier in the image forming apparatus (1)
The charging member according to any of (15) to (15).

(17) The charging member according to (16), wherein the image carrier is an electrophotographic photosensitive member.

(18) The charging member according to any one of (1) to (15), characterized in that the charging member is a transfer charging member in an image forming apparatus.

(19) The charging member according to any one of claims 1 to 15, wherein the charging member is a charging member for static elimination charging in an image forming apparatus.

(20) A charging device having a charging member for applying a voltage to the charging target to bring it into contact with the charging target, wherein the charging member is any one of (1) to (19). The charging device is a charging member of.

(21) An image forming apparatus for an image forming process including a charging step, wherein the charging step means is the charging apparatus described in (20).

(22) In the image forming process, the step of uniformly charging the image carrier, the step of selectively eliminating the charge to form an electrostatic latent image, the step of developing the latent image with toner, (21) The image forming apparatus according to (21), which is a transfer type image forming process including a step of transferring a toner development image to a recording material.

(23) A process cartridge which includes at least an image carrier and a charging means and which is attached to and detached from the main body of the image forming apparatus, wherein the charging means (1) to (1)
A process cartridge comprising the charging member according to any one of 9) or the charging device according to claim 20.

[0054]

According to the present invention, in the charging member having at least the conductive foam and the resistance layer provided thereon on the conductive support, the uneven shape on the surface of the conductive foam is high. The difference between the thickness (surface roughness, R) and the film thickness (T) of the resistance layer, T / R is 0.65 or more and 150 or less, whereby the surface of the foam is formed by polishing. Even with rollers, not only can a smooth surface be obtained without the effect of surface fraying, but also the concave shape in the foamed cell part can be kept small, so waviness can also be reduced, and furthermore, the crests of the wrinkle part can be reduced. The film thickness of the resistance layer at the apex can also be made sufficiently thick.

That is, the surface condition is very good, sufficient pressure resistance and barrier effect are obtained even in long-term durability, and image defects such as density unevenness do not occur in the image forming apparatus or process cartridge. It is possible to obtain a charging member having a conductive foam made of a conductive elastic body, which has good characteristics for a long period of time.

T / R is preferably greater than 0.75 and 75 or less, more preferably greater than 0.9 and 30 or less.

The method of setting T / R to 0.65 or more and 150 or less is preferable because it is relatively easy to adjust the film thickness of the resistance layer. The resistance layer can be provided by coating such as dipping or roll coating, as is usually done. The thickness of the resistance layer can be adjusted by optimizing favorable coating conditions such as viscosity, solid content, pulling rate, and number of coatings of the coating.

The surface roughness of the foam is measured according to JIS B0.
Although the maximum height (Rmax) in the standard of 601 surface roughness may be used, the cross section of the roller is accurately observed by an electron microscope or the like because the influence of the foam cell cannot be ignored.
It is desirable to use a numerical value obtained from the difference in height between the concave portion and the convex portion at that time.

Usually, when the surface is formed by polishing, a foam having a foam diameter of about 30 μm to 300 μm often has a surface roughness (R) of about 20 μm to 160 μm (of course, it is not limited to this range). So good)
Depending on these values, the film thickness of the resistance layer may be adjusted so that T / R is 0.65 or more and 150 or less.

In this case, as the binder resin used for the resistance layer, conventionally used resins such as nylon resin and urethane resin can be used.
When a reaction product of a polymer component containing at least a carboxyl group-containing vinyl monomer and / or its derivative and a polymer component containing a urethane bond is used, environmental stability of resistance of the polymer component having a urethane bond is exhibited. The good weather resistance of the polymer component containing the carboxyl group-containing vinyl monomer and / or its derivative can be imparted without deteriorating the heat resistance, abrasion resistance and strength. It is preferable because resistance fluctuation due to resistance increase or environmental change can be reduced. At this time, if the content of nitrogen in the binder resin is 0.3% or more and 10% or less, the hydrolysis of the urethane bond can be suppressed, so that the photosensitivity due to the influence of the amine generated by the hydrolysis can be suppressed. It is very suitable because it can eliminate body deterioration. Furthermore, if a water-based paint is used, even if there are foam cells on the surface, the surface tension makes it difficult to penetrate into the foam cells, and it is easy to form a smooth surface even with a relatively thin film thickness. Since water is used as the solvent, it is more preferable than the solvent type in terms of environmental measures and safety, and is therefore more preferable.

When T / R is less than 0.65, the above effect is not sufficient, and when T / R is more than 150, there is an effect, but the film thickness becomes very thick, resulting in poor productivity. There is such a problem.

Naturally, it is also possible to use a foam whose surface is not polished.

Examples of the above-mentioned carboxyl group-containing vinyl monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and the like. Methyl) methacrylate, ethyl (meth) acrylate, (meth)
Examples thereof include (meth) acrylic acid esters such as n-butyl acrylate and lauryl (meth) acrylate, and hydroxyalkyl monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate. it can.

In the present invention, when a carboxyl group-containing vinyl monomer is used, for example, when a compound having an amino group is added, an intramolecular salt is formed and the dispersibility in water is improved, so that a water-based paint is obtained. Can also be used.

Further, the polymer component having a urethane bond is composed of isocyanate and polyol, and as the polyol, those which can be usually used for polyurethane are used. Examples include polyether polyols, polyester polyols, silicone glycols, polybutadiene glycols, castor oil, acrylic polyols, fluorine-containing polyols, polyol polymers and mixtures thereof.

As the isocyanate, those generally used for polyurethane are used. Examples thereof include aromatic isocyanates, alicyclic isocyanates, aliphatic isocyanates, isocyanate polymers, and mixtures thereof.

A polymer component having a urethane bond composed of these is selected from the repeating units of, for example, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amino group and ethylene oxide in its molecule. By having one kind or two or more kinds of hydrophilic groups, self-emulsification in water becomes possible and an aqueous paint can be obtained.

[0068]

【Example】

<First Embodiment> (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus that employs a contact charging device as a charging unit of an image carrier.

The image forming apparatus of this example is a transfer type copying machine or a laser beam printer using an electrophotographic process.

Reference numeral 2 denotes a drum type photosensitive member as an image bearing member (charged member), which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).

Reference numeral 1 denotes a roller-shaped charging member (charging roller) as a contact charging member, and in the case of this example, it rotates following the rotation of the photosensitive member 2.

Reference numeral 3 denotes a charging bias applying power source for the charging roller 1. By applying a predetermined charging bias from the power source 3 to the charging roller 1, the peripheral surface of the rotating photosensitive member 2 has a predetermined polarity and potential. Is subjected to primary charging treatment.

By subjecting the primary charging surface of the photoconductor 2 to exposure L of desired image information by exposing means (slit image forming exposing means for original image, laser beam scanning exposing means, etc.) not shown. , An electrostatic latent image is formed on the surface of the photoconductor 2.

The electrostatic latent image is developed as a toner image by the developing device 4. Reference numeral 5 is a developing bias application power source.

The toner image on the rotating photoconductor 2 is separately fed from a paper feed unit (not shown) to a transfer unit, which is a pressure contact nip between the photoconductor 2 and the transfer roller 6, and a predetermined pair is formed by a pair of registration rollers 8. The recording material P is transferred at a timing. Reference numeral 7 denotes a transfer bias application power source for the transfer roller 6.

The recording material P, to which the toner image has been transferred at the transfer portion, is separated from the rotating photoconductor 2 and introduced into a fixing device (not shown) to undergo a toner image fixing process, and is discharged to the discharge portion. Alternatively, in the case of the multiplex or double-sided image forming mode, the toner image is re-fed to the transfer portion by the recirculation feeding mechanism (not shown) and the toner image is transferred for the second time or the second surface, and separated from the rotating photoconductor 2. Is introduced to the fixing machine and undergoes fixing processing,
It is discharged to the discharge part.

After the transfer of the toner image to the recording material P, the rotary photosensitive member 2 is cleaned by the cleaner 9 to remove the residual adhering substances such as the transfer residual toner, and the eraser lamp 10 is used.
Thus, the static charge exposure 11 is received and the image is repeatedly formed.

The image forming apparatus of this example is a process cartridge mounting / demounting type apparatus. That is, the apparatus of this example includes the photoconductor 2,
The four process devices including the charging roller 1, the developing device 4, and the cleaner 9 are collectively configured as a process cartridge 12 that is detachable from the image forming apparatus main body.

Reference numeral 13 denotes a cartridge mounting guide member on the apparatus main body side. The process cartridge 12 is connected to the drive system and the electric system on the apparatus body side by being mounted in the apparatus body in a predetermined manner.

(2) Charging Roller 1 FIG. 2 is a schematic cross-sectional view showing the layer structure of the charging roller 1 as a contact charging member, and the core metal 1 as a conductive support.
a, a conductive foam layer 1b concentrically and integrally formed on the outer periphery of the core metal 1a in a roller shape, and a resistance layer 1c provided on the outer peripheral surface thereof.

A) Conductive foam layer 1b That is, the charging roller 1 serves as a conductive support.
An SBR rubber compound as shown below was extruded and molded to an outer diameter of 15 mm around a stainless steel core metal 1a having an outer diameter of 6 mm, which was previously coated with an adhesive, to form a roller-shaped molded product.

SBR rubber compound SBR 100 parts by weight Conductive carbon black 10 parts by weight DOP 40 parts by weight Zinc oxide 5 parts by weight Stearic acid 1 part by weight Sulfur 2 parts by weight Vulcanization accelerator 3 parts by weight Blowing agent 5 parts by weight Other additions Agent 5 parts by weight The formed roller-shaped product is left in an atmosphere of 160 ° C. for 2 hours to vulcanize and foam the rubber compound, and then peripheral polishing is performed to form a conductive foam layer 1b. 1
A 2.0 mm conductive foam roller was obtained.

The Rmax of this conductive foam roller was measured and found to be 63 μm. For Rmax, we used surfcorder SE-3300 manufactured by Kosaka Laboratory Ltd. and the feed rate was 0.5.
The measurement was performed under the conditions of mm / s, cutoff 0.8 mm, and measurement length 2.5 mm.

B) Resistance layer 1c Next, an acrylic resin component mainly composed of 2-ethylhexyl methacrylate, droxypropyl methacrylate, methacrylic acid, n-butyl acrylate and styrene, adipic acid, neopentyl glycol and dimethylol. A dispersion of a water-based acrylic composite polyurethane composed of a urethane resin component mainly composed of propionic acid and H6XDI (hydrogenated xylylene diisocyanate) was used. The parts were dispersed for 2 hours using a paint shaker to prepare a coating material (solid content: 35%) for the resistance layer.

Here, the content of N in the used acrylic composite polyurethane was measured according to the following procedure.

That is, a thin, water-based acrylic composite polyurethane dispersion was applied onto a glass plate, air-dried at room temperature for 14 days, and
Ultrasonic cleaning with acetone was used as a test amount. When this sample amount was subjected to CHN elemental analysis by using a CHN coder MT-3 type manufactured by Yanagimoto Seisakusho to measure the N content, 3.
It was 2%.

Next, the conductive foam roller is dipped twice into the coating for the resistance layer, and then 13
A resistance layer 1c is formed by drying in an oven at 0 ° C. for 1 hour, a conductive foam layer 1b is formed as a base layer, and a charging roller 1 having acrylic composite urethane as a resistance layer 1c.
I got

C) T / R The cross section of the charging roller 1 is magnified 100 times with an electron microscope to measure the film thickness T of the resistance layer 1c, the surface roughness R of the conductive foam layer 1b, and the foam cell diameter d. did. Figure 3 shows the foam layer 1b
FIG. 3 is an enlarged cross-sectional model view of an interface portion between a resistance layer 1c and a resistance layer 1c.

The film thickness of the resistance layer 1c was obtained by observing at arbitrary three points on the charging roller 1 to find the maximum and minimum at each point, and taking the simple average of them as the film thickness T. T was 78 μm.

Further, the surface roughness R of the foam layer 1b was observed at three arbitrary points on the charging roller 1 and was found as the average of the maximum differences of the uneven portions at each point.
It was m.

That is, T / R = 78/65 = 1.2.

Since the surface roughness R obtained here substantially matches the value of Rmax measured by a contact type roughness meter, Rmax can be used as a substitute for the surface roughness.

Further, the foam cells (air bubbles) 1 of the foam layer 1b.
The diameter d of d was 93 μm as calculated by the following formula, where three arbitrary 1 mm ² areas in the cross section were selected and the weighted average of the individual foam diameters d at that time was selected.

D = Σd _i · n _i / Σn _i d: foamed cell diameter, d _i : foamed cell diameter of _i , n _i : i
(3) Performance of the charging roller 1 The electric resistance of the charging roller 1 is set to a direct current between the conductive support 1a of the roller 1 and the metal electrode by bringing a metal electrode with a width of 1 cm into close contact with the outer circumference of the charging roller 1. Voltage (250V)
Apply a tester (HIOK 3116 DEGITAL MΩ HI TESTE
R), it was 3.6 × 10 ⁶ Ω in high temperature and high humidity environment (H / H environment, 32.5 ° C / 85%), and in low temperature and low humidity environment (L / L environment, 15 ° C / 10%). 4.3x
It was 10 ⁶ Ω and was found to be hardly affected by the difference in environment. The electric resistance was a value 5 seconds after the voltage was applied.

This charging roller 1 was installed in the position of the primary charging device of the LBP NX cartridge (manufactured by Canon Inc.), and as an applied charging bias, V _DC = -750V V _PP = 2KV _PP f = 650Hz was applied (AC charging), When the initial image and the charging noise were confirmed at a speed of 16 sheets per minute, the image was very good, and the charging noise was 50 dB and was quiet.

Furthermore, 100 is set in both H / H and L / L environments.
Durability was performed up to 00 sheets, but good images were obtained from the initial stage to 10000 sheets.

After the endurance, the electric resistance of the charging roller 1 was measured by the same method as in the initial stage described above.
2.3 × 10 ⁶ Ω in H environment, 5.0 × in L / L environment
It was 10 ⁶ Ω, and it was found that there was almost no change compared with the initial stage, and there was almost no difference due to the difference in the environment.

Next, the charging roller 1 is attached to the LBP NX.
The cartridge (manufactured by Canon Inc.) was installed in the position of the primary charging device, left as it was for 40 days in an environment of 40 ° C / 95% RH, and when the image was confirmed, no abnormalities occurred at all and it was high temperature and high humidity. It was also found to be suitable for long-term storage below.

The surface of the charging roller used for durability is M
After thoroughly washing with EK and methanol to remove the toners adhering to the roller surface, the toner was repeatedly used up to 10,000 sheets. After 10,000 sheets, very small black spots were found in the white image part of the black and white repeated image. However, it was found that the other images had no problem, had excellent durability even after solvent cleaning, and were suitable for repeated use.

That is, the charging roller 1 as the contact charging member of the embodiment is a charging roller which has a good charging property for a long period of time and an excellent storability without contamination of the photoconductor and has a small environmental fluctuation.

Second Embodiment A charging roller 1 was prepared by using the same conductive foam roller as that used in the first embodiment and the coating for the resistance layer, and dipping once. .

This charging roller 1 has T = 45 μm and R
= 65 μm, T / R = 45/65 = 0.69.

The electric resistance of this charging roller is 9.5 × 10 ⁵ Ω in the H / H environment and 1.2 × 10 ⁶ Ω in the L / L environment.
It was found that the fluctuation due to the environment was small.

Further, when the performance was confirmed in the same manner as in the first embodiment, good images were obtained from the initial stage to 10,000 sheets, and the electric resistance after endurance was 1.1 × 1 in H / H environment.
0 ⁶ Omega, 3.0 and × 10 ⁶ Omega in the L / L environment, hardly changed in comparison early and, also was found to be a difference due to environmental small.

The charging sound was also quiet at 52 dB.

Furthermore, when the image was confirmed after being left in an environment of 40 ° C./95% RH for 40 days, a minute black spot was generated at a portion corresponding to the photosensitive member portion which was in contact with the convex peak of the roller surface. However, after passing 5 sheets, the black dots disappeared, and it was found that there was no problem in practical use.

<Third Embodiment> A stainless steel core bar 1a having an outer diameter of 6 mm and having an adhesive applied thereto is
The SBR rubber compound used in the first example was formed into a roller shape by extrusion molding to prepare a roller-shaped molded product having an outer diameter of 11 mm.

This roller-shaped molded product was inserted into a cylindrical mold having an inner diameter of 12 mm, vulcanized and foamed at 160 ° C. for 1 hour, and then taken out from the mold to obtain a conductive film having an extremely thin skin layer. A conductive foam roller provided with the conductive foam layer 1b was obtained.

Next, the conductive foam roller was first coated with
The resistance roller coating material used in the above Example was used, dipping was performed 4 times, and then drying was performed in an oven at 130 ° C. for 1 hour, whereby a charging roller 1 was prepared.

The charging roller 1 has T = 151 μm,
R = 12 μm and T / R = 151/12 = 12.6.

The electric resistance of this charging roller 1 is H / H.
5.1 × 10 ⁶ Ω in environment, 7.0 × 10 ⁶ in L / L environment
It was found that the variation due to the environment was small.

Further, when the performance was confirmed in the same manner as in the first embodiment, good images were obtained from the initial stage to 10000 sheets, and the electric resistance after running was 5.0 × 1 in an H / H environment.
0 ⁶ Omega, and 7.2 × 10 ^{6 Ω} at the L / L environment, hardly changes compared early, also been found that even differences due to environmental small. The charging noise was 53 dB, which was a level at which there was no practical problem.

Further, after leaving it for 40 days in an environment of 40 ° C./95% RH, the image was confirmed and no abnormality occurred at all.

<Comparative Example 1> The resistance layer coating material used in the first embodiment has a solid content of 18% and a dipping frequency of 1
A charging roller was produced in the same manner as in the first example except that the rotation was repeated.

This charging roller has T = 38 μm and R =
It was 65 μm and T / R = 38/65 = 0.58.

The electric resistance of this charging roller is 1.0 × 10 ⁷ Ω in the H / H environment and 3.6 × 10 ⁷ Ω in the L / L environment.
It was found that the fluctuation due to the environment was small.

Further, when the performance was confirmed in the same manner as in the first embodiment, the charging sound was as good as 52 dB, a good image was obtained from the initial stage up to 10,000 sheets, and the electric resistance after endurance was H / H. 2.3 × 10 ⁶ Ω in the environment, 4.
It was found that the variation was 9 × 10 ⁶ Ω, which was small compared to the initial stage, but it was confirmed that the image after left for 40 days in the environment of 40 ° C / 95% RH showed a convex shape on the roller surface. It was found that a large number of minute black spots were generated at the portion corresponding to the photoconductor portion that was in contact with the peak portion of No. 3, and the black spots did not disappear even after 100 sheets of paper were passed, and there was a problem in the characteristics.

<Fourth Embodiment> A charging roller 1 was prepared in the same manner as in the third embodiment except that a nylon coating material was used in place of the resistance layer coating material used in the first embodiment. .

That is, the nylon-based coating used was prepared by dissolving methoxymethylated nylon in methanol (solid content 25%).
%), 30 parts by weight of conductive titanium oxide was added to 100 parts by weight of the solid content, and dispersed by a paint shaker for 5 hours.

Then, the conductive foam roller prepared in the third embodiment was dipped twice in this nylon-based resistance layer coating material and then dried at 130 ° C. for 1 hour.
It was created.

This charging roller 1 has T = 38 μm and R
= 12 μm and T / R = 3.2.

The electric resistance of this charging roller is 9.1 × 10 ⁴ Ω in the H / H environment and 1.0 × 10 ⁶ Ω in the L / L environment.
It was

Further, when the performance was confirmed in the same manner as in the first embodiment, the charging noise was 53 dB, which was a level at which there was no practical problem, and the halftone image after the endurance of 10,000 sheets from the initial stage was obtained. However, it was found that there was no problem in practical use.

The electric resistance of the charging roller after running was measured and found to be 2.2 × 10 ⁶ Ω in the H / H environment and 1.1 × 10 ⁷ Ω in the L / L environment, which is about one digit compared to the initial value. It turned out to be rising.

Furthermore, in an environment of 40 ° C./95% RH, 40
After standing for a day, the image was confirmed, and a small amount of methoxymethylated nylon, which was a material for the resistance layer of the charging roller, was attached to the photoconductor, but it was found that the image was good and practically no problem.

<Fifth Embodiment> As a metal mold, a cylindrical metal whose inner wall is precision-ground and then chrome-plated is used, and an SBR rubber compound is extruded into a roller shape having an outer diameter of 11 mm. Except for the above, the same procedure as in the third embodiment is carried out, and the surface has an ultrathin skin layer,
A conductive foam roller provided with a conductive foam layer 1b having a smooth surface was obtained.

Next, the conductive foam roller was first coated with the first
The resistance layer coating material used in the above Example was used, dipping was performed 6 times, and then drying was performed in an oven at 130 ° C. for 1 hour, to prepare a charging roller 1.

The charging roller 1 has T = 218 μm,
R = 2.1 μm and T / R = 218 / 2.1 = 104.

The electric resistance of this charging roller 1 is H / H.
8.6 × 10 ⁶ Ω in environment, 8.2 × 10 ⁶ in L / L environment
It was found that the variation due to the environment was small.

Further, when the performance was confirmed in the same manner as in the first embodiment, good images were obtained from the initial stage to 10,000 sheets, and the electric resistance after endurance was 7.2 × 1 in the H / H environment.
0 ⁶ Omega, and 4.9 × 10 ^{6 Ω} at the L / L environment, hardly changes compared early, also been found that even differences due to environmental small. The charging noise was 54 dB, which was at a level with no practical problem.

Further, after leaving it in an environment of 40 ° C./95% RH for 40 days, the image was confirmed and no abnormality occurred at all.

In each of the above embodiments, the charging member is of the roller type, but the present invention is not limited to this, and charging members of other shapes and forms such as blade type, pad type, rod type, wire type and the like. The same effect can be obtained by applying to a member.

The charging member of the present invention can also be used in the DC charging system in which the applied voltage is only the DC voltage.

Also, it can be used as a charging member for transfer charging and charge removal.

Further, the charging member is not limited to the charging member or the charging (static elimination) device for the charging (static elimination) step of the image forming apparatus, and is widely effective as a charging member or a charging (static elimination) device for the general charging (static elimination) of the body to be charged. Is.

[0136]

As described above, according to the present invention,
In a charging member having at least a conductive foam and a resistance layer provided thereon on a conductive support, a difference in height of irregularities on the surface of the conductive foam (surface roughness R) And the film thickness (T) of the resistance layer, T / R is 0.
By setting the ratio to be larger than 65 and not more than 150, it is possible to eliminate the charging failure due to the uneven shape of the surface of the foam layer, and to eliminate the image failure due to this in the image forming apparatus or the process cartridge. Thus, it is possible to provide a charging member suitable for high image quality.

By using a reaction product of a polymer component containing at least a carboxyl group-containing vinyl monomer and / or its derivative and a urethane bond-containing polymer component as the binder resin for the resistance layer, Charged body,
In an image forming apparatus or a process cartridge, there is provided a charging member having no deterioration of an image bearing member such as a photoconductor and having small environmental fluctuations from high temperature and high humidity to low temperature and low humidity and resistance fluctuation due to endurance, that is, high durability. Therefore, the charging member is excellent not only in high durability but also in reusability and resource saving.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 2A is an enlarged cross-sectional model view showing a layer structure of a charging roller as a charging member, and FIG. 2B is an enlarged cross-sectional model view of an interface portion between a foam layer and a resistance layer.

[Explanation of symbols]

 1 Charging Roller as Charging Member 1a Core Bar as Conductive Support 1b Conductive Foam Layer 1c Resistive Layer 1d Foam Cell R Surface Roughness of Foam Layer T Resistive Layer Thickness 2 Photoreceptor as Charged Body 3 Power supply for charging bias

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Jun Murata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshiaki Nishimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Naoki Shirai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (23)

[Claims] 1. In a charging member having at least a conductive foam and a resistance layer provided thereon on a conductive support, a difference in height of irregularities on the surface of the conductive foam (surface Roughness) R and resistance layer thickness T ratio T / R is
A charging member which is greater than 0.65 and 150 or less. 2. The charging member according to claim 1, wherein the surface of the conductive foam is polished. 3. The charging member according to claim 1, wherein the conductive foam has an average cell diameter (cell diameter) of 30 μm or more and 300 μm or less. 4. The binder resin of the resistance layer is a reaction product of a polymer component containing at least a carboxyl group-containing vinyl monomer and / or its derivative and a polymer component containing a urethane bond. The charging member according to claim 1. 5. The binder resin is such that at least one end of a polymer component containing a urethane bond is bound to a polymer component containing at least a carboxyl group-containing vinyl monomer and / or a derivative thereof. The charging member according to claim 4, which is characterized in that. 6. The charging member according to claim 4, wherein the polymer component containing at least the carboxyl group-containing vinyl monomer and / or its derivative has a hydrophilic group. 7. The charging member according to claim 4, wherein the polymer component containing a urethane bond has a hydrophilic group. 8. The charging member according to claim 4, wherein the binder resin is dispersed in water. 9. The electric resistance is 1 × 10 ³ Ω or more and 1 × 10 ¹²
The charging member according to claim 1, which is less than Ω. 10. The object to be charged is charged by applying a voltage to the charging member.
The charging member according to any one of 1. 11. The charging member according to claim 10, wherein the applied voltage is only a DC voltage. 12. The charging member according to claim 10, wherein the applied voltage is an oscillating voltage. 13. The charging member according to claim 12, wherein the vibration voltage is a voltage obtained by superposing a DC voltage and an AC voltage. 14. The charging member according to claim 1, wherein the charging member is in contact with the surface of the body to be charged. 15. The charging member according to claim 1, wherein the charging member is a roller type. 16. The charging member according to claim 1, wherein the charging member is a charging member for charging an image carrier in an image forming apparatus. 17. The charging member according to claim 16, wherein the image bearing member is an electrophotographic photosensitive member. 18. The charging member according to claim 1, wherein the charging member is a transfer charging charging member in an image forming apparatus. 19. The charging member according to claim 1, wherein the charging member is a charging member for static elimination charging in an image forming apparatus. 20. A charging device comprising a charging member for applying a voltage to contact an object to be charged to charge the object to be charged, wherein the charging member is the charging device according to any one of claims 1 to 19. A charging device, which is a member. 21. An image forming apparatus in an image forming process including a charging step, wherein the charging step means is the charging apparatus according to claim 20. 22. In the image forming process, a step of uniformly charging the image carrier, a step of selectively eliminating the charge to form an electrostatic latent image, a step of developing the latent image with toner, and a toner thereof. 22. The image forming apparatus according to claim 21, wherein the image forming process is a transfer type image forming process including a step of transferring a developed image to a recording material. 23. A process cartridge including at least an image carrier and a charging unit, which is attached to and detached from an image forming apparatus main body, wherein the charging unit is the charging member according to any one of claims 1 to 19. 21. A process cartridge comprising the charging device according to claim 20.