JPH07295334A - Electrifying member and its production - Google Patents

Abstract

PURPOSE:To provide a production method for an electrifying member stable in qualities, less in the limitation of the material, uniform in thickness and high in productivity, and to provide an electrifying member obtd. by this method. CONSTITUTION:This electrifying member is produced by uniaxially stretching at least one of polyolefin thermoplastic resin, thermoplastic polyester resin, thermoplastic polyamide resin and thermoplastic polyurethane resin having vol. resistivity controlled to 10<5>-10<12>OMEGAcm to form a hollow endless film, heating the hollow endless film, and adhering the film on a conductive supporting body or on a member having a conductive elastic layer on the supporting body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member and a method for manufacturing the same, and a charging member for applying an oscillating electric field (a DC voltage is superposed with an AC voltage) to bring the surface of the photosensitive member into contact with or in proximity to the surface of the photosensitive member. A member and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, contact charging has been widely used in which a roller-shaped charging member is brought into contact with a photoconductor to charge the surface of the photoconductor. The contact charging member has advantages such as a simple structure and an extremely small amount of ozone generated.

The charging member is generally manufactured by the following method. A) A conductive elastic layer is formed along the outer circumference of a metal conductive support (core bar), and a resistance layer and a surface layer are thinly coated along the outer circumference by a dipping method or a roll coating method. B) In addition, a method is also used in which the inner diameter of a semi-conductive tube whose resistance has been adjusted in advance is made smaller than that of the conductive elastic layer, and the conductive elastic layer is press-fitted therein. C) More recently, a method has also been proposed in which a shrink tube made of a conductive fluororesin is heated and adhered to form a surface layer.

[0004]

However, the method A) has the following problems. 1) The material of each layer must be dissolved in an organic solvent to form a coating material, which limits the material. 2) The productivity is low because the lower layer is dried and then the surface layer is applied and dried. 3) Unless the solubility coefficient of each layer is changed, the respective layers will be dissolved and the function of each layer will be impaired. 4) Since the solubility coefficients are different, the adhesion of each layer is poor and floating or wrinkling may occur. In addition, a primer may be used to improve the adhesion, which is likely to cause a cost increase. 5) Thickness unevenness is likely to occur in each layer.

The method B) also has the following problems. 1) High accuracy is required to keep the difference between the inner diameter of the tube and the outer diameter of the conductive elastic layer constant. 2) Since a large force is applied to join the two, there is a risk that the tube may break or the wall thickness may become uneven.

Further, in the method C), 1) it is difficult to uniformly disperse the conductive pigment in the fluororesin. 2) Since the workability of the fluororesin is poor, it is difficult to stretch it, and thus it is difficult to obtain a shrink tube having a uniform thickness. Have problems such as.

[0007]

[Means for Solving the Problems] That is, according to the present invention, a polyolefin-based thermoplastic resin, a thermoplastic polyester resin, a thermoplastic polyamide resin and a thermoplastic polyurethane having a volume resistivity adjusted to a range of 10 ⁵ to 10 ¹² Ωcm. At least one kind of resin is uniaxially stretched to form a hollow endless film, and then the hollow endless film is heated to be adhered onto a conductive support or a member having a conductive elastic layer on the conductive support. It is a method of manufacturing a charging member that is characteristic.

Further, the present invention is a charging member obtained by the above manufacturing method.

The present invention will be described in detail below.

The characteristic of the thermoplastic resin is that its shape can be freely changed by heating. Particularly in the case of a thin film, it can be heated and stretched by an external force. Stretching means aligning the constituent polymers in a certain manner. Biaxial stretching (longitudinal / horizontal direction) can enhance the polymer orientation in both directions, so that a film with excellent heat resistance can be produced. On the other hand, in the case of uniaxial stretching, it has a characteristic of returning to the original length when heated again (shrinkage). The charging member according to the present invention utilizes this contracting property.

In the present invention, at least one selected from the group consisting of thermoplastic polyolefin resins, thermoplastic polyester resins, thermoplastic polyamide resins and thermoplastic polyurethane resins is selected and used.

Since these resins have stable structures,
Little deterioration due to heating, so there is little deterioration in physical properties even after the steps of kneading, extrusion, and stretching. No special plasticizer is required so that the surface of the photoconductor is not contaminated, ozone is less likely to deteriorate, and energization deterioration occurs even when a high voltage is applied. No, because it has excellent environmental stability, the change in electrical resistance is small under each environment.Especially compared to fluororesin, the conductive pigment is easier to disperse, it can be stretched at low temperature, and its processing temperature range is wide. It has the advantage that the uneven thickness of the obtained film is extremely small. These properties make it the most suitable resin for the charging member of the present invention. Volume resistivity of 10 ⁵ to 10 ¹² Ω
The reason for adjusting to cm is that if there is a defect (pinhole) on the surface of the photoconductor below 1 × 10 ⁵ Ωcm, the concentration of current generated during charging cannot be prevented and the periphery of the defect is not charged. Abnormal on top. On the other hand, 1 × 10 ¹² Ω
This is because when the voltage exceeds cm, the applied voltage is distributed in the resistance layer to cause a voltage drop and sufficient charging cannot be performed.

The thickness is preferably 10 μm or more. If the thickness is less than 10 μm, uneven thickness is likely to occur and the accuracy of the thickness cannot be compensated. The upper limit is not particularly limited, but when it is used as a charging member in contact with the photoconductor, care must be taken because the hardness of the film affects the hardness of the charging member when the thickness exceeds 200 μm.

The process will be described in more detail with reference to the process chart (FIG. 1).

First, a conductive pigment is mixed with a thermoplastic resin to prepare pellets having a volume resistivity in the range of 1 × 10 ⁵ to 1 × 10 ¹² Ωcm. At this time, in order to disperse the conductive pigment in a sufficiently uniform manner, it is desirable to use a kneading means such as a kneader or a Brabender, and then thread it with an extruder and pelletize with a cutter.

The thermoplastic resin used may be polyethylene, polypropylene, polyester, ethylene vinyl acetate, polyamide, polyurethane or the like, and the conductive pigment may be conductive carbon, conductive titanium oxide, conductive tin oxide or aluminum powder. Etc. can be used alone or in combination.

The pellets thus obtained are melt-extruded by an extruder equipped with an inflation valve at the tip thereof and formed into a hollow endless film along with a cylindrical first outer diameter regulating guide cooled by air blown into the inflation valve. To do.

At the tip of the first cylindrical outer diameter regulating guide, there is a conical stretching guide whose diameter gradually increases. The conical stretching guide is heated to a predetermined temperature, and the hollow endless film is stretched in the direction in which its diameter is expanded along with the conical stretching guide by the air heated and blown therein. That is, it is uniaxially stretched here.

Thereafter, the stretched hollow endless film is cooled along with the cooled cylindrical second outer diameter regulating guide to adjust its shape.

Then, it is wound by a roll.

What is important here is that the inner diameter of the cylindrical first outer diameter regulating guide is the outer diameter or the approximate diameter on the conductive support to be used or on the member having the conductive elastic layer on the conductive support. And the cylindrical second outer diameter regulating guide must be designed to be larger than these outer diameters or the approximate size.

Preferably, the inner diameter of the cylindrical second outer diameter regulating guide is 1.5 to 5 times the inner diameter of the cylindrical first outer diameter regulating guide.
Double range is good. If the ratio of the two is less than 1.5 times, the shrinkage due to heating is not sufficient and a gap or a wrinkle is likely to be formed between the conductive support and the conductive support. On the other hand, if the ratio of the both exceeds 5, the uneven thickness of the hollow endless film may occur, which may cause uneven resistance after being adhered to the conductive support or may be broken at the time of adhesion. When two or more materials are used, each may be a uniaxially stretched hollow endless film, but a plurality of extruders may be connected to an inflation valve to simultaneously uniaxially stretch a hollow endless film. Also good.

The charging member according to the present invention is a hollow endless film uniaxially stretched by the above-mentioned method and covers a conductive support or a member provided with a conductive elastic layer on the conductive support at a predetermined temperature. After heating for a time, the hollow endless film is heat-shrinked to be brought into close contact with each supporting member to form its outer shape.

[0024] The uniaxially stretched hollow endless film is continuously produced, so that the cost is very low. Since it is a simple method, once each condition is set, a film with stable quality can always be obtained.

Unlike the method A) described in the prior art, there is no need to make it into a paint, and there is no restriction on the material of each layer.
Molding with an inflation valve has little thickness unevenness. In addition, above all, the product can be brought into close contact by simply heating and shrinking it, resulting in extremely high productivity.

Similarly, unlike the method B), high precision is not required, and since the resin itself contracts, a large force such as press fitting is not applied, so that the member does not break or have uneven thickness.

[0027]

The present invention will be described with reference to the following examples. Example 1 The productivity of the charging member according to the present invention will be described.

Conductive carbon of 5 wt% was dispersed in ethylene vinyl acetate (EVA; vinyl acetate content of 25 wt%), and pellets adjusted to have a volume resistivity of 2 × 10 ⁸ Ωcm were prepared using the apparatus shown in FIG. It is designed to have an inner diameter of 10 mm before uniaxial stretching, an inner diameter of 20 mm after uniaxial stretching (draw ratio of 2), and a thickness of 100 μm. The temperature of the conical stretching guide part is 150 ° C. and the pressure of air is 6 k.
A hollow endless film was prepared at g / cm ² .

Separately from this, 7 wt% of conductive carbon was mixed on the outer circumference of a metal core (SUS φ6), and an SBR having a volume resistivity of 5 × 10 ⁴ Ωcm was molded and added to have a thickness of 3 mm. Vulcanized The obtained electroconductive elastic member has an outer diameter of 12 mm and a length of 250 mm.

Then, the conductive elastic member is passed through the hollow endless film and heated at 160 ° C. for 1, 3, 5,
The adhesion with the conductive elastic member was examined by changing the time from 7, 10, 15, 20, 30 seconds.

As a result, in 5 seconds or less, due to insufficient heating, it floated between the conductive elastic members and wrinkled, but in 7 seconds or more, no problem occurred. No particular difference was observed between 10 seconds and 30 seconds. Therefore, in this case, it was confirmed that sufficient adhesion can be obtained by heating for 10 seconds even in consideration of safety.

After that, it is left for 12 hours or longer in an environment of temperature: 23 ° C., humidity: 55%, an aluminum sheet of 10 mm width is wound around a predetermined position of the charging member as shown in FIG. 2, and a DC voltage of 500 v is applied for 10 seconds. The subsequent resistance (Ω) was measured and found to be 4 × 10 ⁵ Ω.

When the resistance (Ω) is measured by the method shown in FIG. 2, the good range is 1 × 10 ⁴ to 1 × 10 ⁸ Ω.
This is because when the resistance is lower than 1 × 10 ⁴ , pinhole leakage is caused, and when it exceeds 1 × 10 ⁸ , charging failure is caused.

Comparative Example 1 Alcohol-soluble nylon resin was dissolved in methanol so that the solid content was 10 wt% on the outer periphery of the same conductive elastic member as in Example 1, and 30 wt% of the conductive titanium oxide was based on the solid content. And the viscosity of which is 150 cps is applied to the paint by using a dipping device and the moving speed is 100, 20.
The coating was changed to 0, 300, 400, 500 mm / min, and the surface condition under each condition was observed.

The thickness of the central portion at 100 mm / min is 5 μm.
m, the thickness of the central part at 200 mm / min is 8 μm, 300
The thickness of the central part in mm / min was 12 μm. 300
There is a problem that the upper part is thin and the lower part is thick up to mm / min, but there is no problem such as wrinkles on the coating film. But 400mm
When the speed was increased up to / min, thickness unevenness occurred and wrinkles were also seen on the surface of the member. Furthermore, it became even worse at 500 mm / min.

From these results, it was found that the dipping method has a limit in the coating speed. Incidentally, when the dipping speed is 300 mm / min, the time required for coating the conductive elastic member (length 250 mm) is 250 m.
It becomes 50 seconds from m ÷ 300 mm × 60 seconds.

Comparative Example 2 Using the paint prepared in Comparative Example 1, the moving speed of the roll coater was set to 10 on the outer periphery of the same conductive elastic member as in Example 1.
Coating was performed while changing the coating amount to 0, 200, 300, 400, 500, 600 mm / min, and the surface condition under each condition was observed. The rotation speed of the roll was constant at 100 rpm.

As a result, a uniform surface could be formed up to 500 mm / min, but thickness unevenness occurred at 600 mm / min. The fastest coating speed in this case is 250mm ÷ 500m
It becomes 30 seconds from m × 60 seconds.

Comparative Example 3 Resin having 5 wt% of conductive carbon dispersed in polyurethane and having a volume resistivity of 5 × 10 ⁸ Ωcm adjusted to an inner diameter of 11 m
m, a length of 250 mm, and a thickness of 100 μm were molded by an extruder, and the speed of pushing into the outer periphery of the same conductive elastic member as in Example 1 was 100 mm / min, 250 mm /
Min, 500 mm / min, 750 mm / min, 1000 mm /
I pressed in instead of the minute.

As a result, no problem occurred up to 500 mm / min, but the conductive elastic member was deformed at 750 mm / min. Further, at 1000 mm / min, the pipe broke. Therefore, the fastest speed in this method is 500 mm / min, and the production speed at that time is 250 mm ÷ 500 mm ×
It will be 30 seconds from 60 seconds.

From the results of Example 1 and Comparative Examples 1 to 3 described above, the use of the uniaxially stretched hollow endless film according to the present invention has very high productivity, and a charging member can be stably obtained. confirmed.

Example 2 The charging member manufactured in Example 1 was applied to the position of the primary charger of the electrophotographic cartridge shown in FIG. 3 at a contact pressure of 10 g with the photosensitive member (width between the photosensitive member and the charging roller was 1 cm). Of the aluminum sheet of scissors)
DC voltage; AC voltage 2kv at -670v and frequency 470
Superimposition was applied at Hz, and the durability of 6000 sheets was evaluated under the environment of temperature of 23 ° C. and humidity of 55%.

As a result, there was almost no change in the image at the initial stage and after the durability test, and no fusion of the developer to the photosensitive member was observed. From this result, it was confirmed that the charging member according to the present invention can obtain its charging performance without being inferior to the member that can be produced by the conventional method. Example 3 65 wt% of conductive titanium oxide was dispersed in polypropylene, and pellets adjusted to have a volume resistivity of 5 × 10 ⁸ Ωcm were prepared using the apparatus shown in FIG. 1 with an inner diameter of 15 mm before uniaxial stretching. A hollow endless film was prepared at a temperature of the conical stretching guide portion of 180 ° C. and a pressure of air of 6 kg / cm ^{2 so} that the inner diameter after uniaxial stretching was 45 mm (three times the stretching ratio) and the thickness was 500 μm.

The obtained hollow endless film was passed through a metallic (SUS) blade having an outer circumference of about 20 mm as shown in FIG. The obtained charging member floated and had no wrinkles, and was firmly adhered.

Then, spacers made of PTFE are attached to both ends of the charging member, and as shown in FIG. 5, adjustment is made so that the minimum distance from the photosensitive member is 80 μm at the position of the primary charger of the electrophotographic cartridge, Installed at a position where the distance between the two gradually increases with respect to the rotation direction, a DC voltage of -670V and an AC voltage of 2kV are superimposed and applied at a frequency of 200Hz, and the durability of 6000 sheets is evaluated under constant temperature and humidity (23C, 55%) environment. went. If the charging member is blade-shaped as in the present embodiment, the discharge area is expanded, so that uniform charging is possible even if the applied frequency is lowered.

As a result, there was almost no image change at the initial stage and after the endurance test, and no fusion of the developer to the photosensitive member was observed. Further, since it did not come into contact with the photoconductor, the photoconductor surface was scarcely scraped.

From this result, it was confirmed that a blade-shaped charger can be manufactured very easily and the performance thereof is extremely excellent.

[0048]

Industrial Applicability The uniaxially stretched hollow endless film is continuously produced, so that the cost is very low. Since it is a simple method, once each condition is set, a film with stable quality can always be obtained.

There is no need to form a coating like dipping or roll coating, and there is no restriction on the material of each layer. Molding with an inflation valve has little thickness unevenness.

In addition, above all, the product can be brought into close contact with each other only by heating and shrinking, so that the productivity is very high.

Further, high precision such as press-fitting of a pipe is not required, and since the resin itself contracts, a large force is not applied, so that the member does not break or have uneven thickness.

[Brief description of drawings]

FIG. 1 is a schematic process diagram of a method of the present invention.

FIG. 2 is a diagram showing a resistance measuring method of a charging roller.

FIG. 3 is a schematic view of an electrophotographic cartridge having a charging member of the present invention.

FIG. 4 is a schematic view showing a state in which a hollow endless film is attached to a blade-shaped member.

FIG. 5 is a schematic view showing a state in which the charging member of the present invention is charged in proximity to a photoconductor.

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Claims (4)

[Claims] 1. A hollow obtained by uniaxially stretching at least one of a thermoplastic polyolefin resin, a thermoplastic polyester resin, a thermoplastic polyamide resin and a thermoplastic polyurethane resin, the volume resistivity of which is adjusted to a range of 10 ⁵ to 10 ¹² Ωcm. A method for producing a charging member, characterized in that a continuous endless film is formed, and then the hollow endless film is heated to adhere onto a conductive support or a member having a conductive elastic layer on the conductive support. 2. A charging member obtained by the method according to claim 1. 3. The charging member according to claim 2, wherein the charging member is charged in contact with or in proximity to the electrophotographic photosensitive member. 4. The charging member according to claim 2, wherein the photosensitive member is charged by the charging member to which an oscillating electric field in which a DC voltage is superimposed with an AC voltage is applied.