JPH0699053B2 - Anti-static endless belt - Google Patents

Description

TECHNICAL FIELD The present invention relates to an antistatic endless belt, which is suitably used for an electrophotographic copying machine, a transfer separation device of an optical printer, a phenomenon machine, and the like. The present invention relates to antistatic endless belts.

[Prior Art] A rotating body coated with an endless belt or a cylindrical endless belt that electrostatically supports or conveys a transfer target or conveys a phenomenon agent by applying a voltage to an electrophotographic copying machine or an optical printer. It is used to improve the reliability and speed of equipment. As an example, as a transfer separation belt that attracts the transfer target by applying a voltage to the belt that conveys the transfer target to the transfer position and separates it from the image carrier, the volume resistivity is 10 ¹⁶ Ωcm.
An endless transfer belt comprising an insulating layer made of a polyester film and a conductive layer having a resistance of 10 ⁸ Ω · cm or less has been proposed (JP-A-49-31326, 52-42125).

This proposal is to ensure that the charge is applied to the insulating layer of the transfer belt so that the charge is saturated and a constant charge potential is maintained, and the transfer paper and the transfer paper are reliably separated from each other. However, since the residual toner adhering to the surface of the polyester film is removed, it cannot be sufficiently cleaned by a cleaning means such as a fur brush. Therefore, it is preferable to periodically rub the surface of the belt with a cleaning agent such as aluminum oxide fine powder. In addition, 5-8KV continuously on the polyester film surface by corona charger as a charger
When a high voltage is applied, the ozone surface and the peroxynitride will deteriorate the polyester surface layer, and the low molecular weight oxides and oxynitrides generated will lower the resistance value and lower the charging potential on the belt surface. There is a problem to do.

Polyvinylidene fluoride is known as a material having excellent toner cleaning properties and corona resistance, and a high dielectric constant (JP-A-54-58034 and JP-A-62-251779).
issue).

However, polyvinylidene fluoride has a large crystallinity, and large spherulites are easily generated in the process of cooling and solidifying from a molten state, so that there is a drawback that the appearance tends to be cloudy, and the impact resistance is low and it is easy to tear. There is a problem that distortion is likely to remain. Regarding the spherulites, by performing a quenching operation during film formation, it is possible to prevent the formation of large spherulites, but the drawbacks of polyvinylidene fluoride cannot be improved. .

Therefore, when a polyvinylidene fluoride film is used as an endless belt base material, it easily tears, and when both film end faces are heat-sealed or when this film and another thermoplastic resin film are heat-bonded, polyvinylidene fluoride is used. There is a problem that directional shrinkage wrinkles occur on the film surface, and it is difficult to produce a belt having a smooth surface.

[Problems to be Solved by the Invention] The present invention was devised in view of the above-mentioned drawbacks of the prior art, and the purpose thereof is to easily adjust the surface potential, the charge decay time, the charge charge amount, and the like. Another object of the present invention is to obtain an endless belt excellent in cleaning property, corona resistance and flatness.

[Means for Solving the Problems] The object of the present invention is achieved by the following configurations.

1. An antistatic endless belt composed mainly of a film made of a copolymer obtained by copolymerizing 99 to 70 mol% of vinylidene fluoride with 1 to 30 mol% of hexafluoropropene.

2. The antistatic endless belt according to the above item, wherein the film has a cylindrical shape.

The above item 1 or 2 in which three or more films are laminated.
Antistatic endless belt as described.

4 The preceding paragraph 1 in which the copolymer contains a conductive filler
An anti-static endless belt that is any of item 3.

5. The antistatic endless belt according to 1 or 2 above, which has on the surface thereof a conductive layer comprising a thermoplastic resin (A) and a conductive filler and having a volume resistivity of 5 × 10 ¹⁴ Ω · cm or less.

Examples of the thermoplastic resin (A) used in the present invention include acrylic copolymers, polyether ester copolymers, polyester ester copolymers, polyether amide copolymers, polyvinyl acetates, vinyl acetate copolymers, At least one selected from the group of olefin copolymers, ionomers, polyurethanes, styrene elastomers, vinyl chloride copolymers, vinyl chloride graft copolymers, fluorine resins, fluorine elastomers, polyether sulfones, polysulfones and chlorinated polyethylenes. One or more or a mixture of these is used.

Further, a thermoplastic resin film having a thickness of 5 to 50 μm as a surface layer, preferably a thermoplastic resin film forming the surface layer is polyethylene terephthalate, polyether ether ketone, polycarbonate, ethylene tetrafluoroethylene copolymer, vinyl chloride copolymer. , An antistatic endless belt or an antistatic cylindrical endless belt made of at least one or more thermoplastic resins (B) selected from polyvinylidene chloride and an acrylic copolymer, or a volume resistivity of 5 × on the inner surface. An antistatic endless belt having a conductive layer of 10 ⁸ Ω · cm or less can also achieve the object of the present invention.

In the antistatic endless belt or the antistatic cylindrical endless belt of the present invention, the film constituting the belt is obtained by copolymerizing 99 to 70 mol% of vinylidene fluoride with 1 to 30 mol% of hexafluoropropene. It is important to form a vinylidene fluoride copolymer with improved crystallinity, which makes it excellent in impact strength, tear resistance, flexibility, heat processability, etc., as well as corona resistance, toner removability, and toner. It is possible to surely impart slipperiness and the like to the removing blade.

The polymerization method of the vinylidene fluoride copolymer, emulsion polymerization, suspension polymerization, bulk polymerization, it is possible to use a usual method such as liquid polymerization, the composition ratio of hexafluoropropene in the copolymer is 30 mol%. If it exceeds the above range, the strength and melting point are reduced, and the processed endless belt has a problem that the elastic recovery is poor when the belt is stretched and it is difficult to drive the belt.
It is not preferable because the surface vibrates greatly when the belt is driven.
On the other hand, if the composition ratio of hexanefluoropropene in the copolymer is less than 1 mol%, the crystallinity becomes strong, and when heat-treated into a belt, shrinkage and wrinkles are generated on the belt surface and the belt tends to tear and the belt life is shortened, which is not preferable .

As the conductive filler used in the present invention, carbon black, graphite, carbon fibers, metal powder, conductive metal oxides, organometallic compounds, organometallic salts,
It is preferable to use at least one selected from a conductive polymer and a polyethylene glycol copolymer, or a mixture thereof. Among these, particularly preferable are conductive carbon, conductive tin oxide added with a small amount of antimony, metal salt of dodecylben sulfonic acid, and polyether ester amide copolymer.

When the conductive filler is added to the copolymer, preferably with respect to 100 parts by weight of the copolymer, it is preferable to add in the range of 40 parts by weight or less, if the addition amount exceeds 40 parts by weight, inorganic type The conductive filler of (1) has a drawback that the rigidity of the belt becomes large and loses flexibility, and the organic conductive filler has a drawback of lowering the belt strength and shortening the belt life.

A belt made of a single layer (thickness: 25 to 200 μm) of a film made of a vinylidene fluoride copolymer having the composition defined in the present invention or a film having a conductive layer having a body specific resistance of 5 × 10 ⁸ Ω × cm or less bonded to its inner surface The transfer / transport belt used for the base material has a suction force of 100 g or more on the copy paper when a voltage of 5-8 KV is applied to the belt and the surface potential of the belt is in the range of 1.0-3 KV. Has desirable performance as.

However, in the case of this mode, in order to separate the transfer paper from the belt and prevent the belt surface potential from rising, a static eliminator or a static eliminator that applies a DC voltage or an AC voltage to the applied voltage and the reverse electrode for each revolution of the belt. Is desirable.

On the other hand, a conductive filler is kneaded and dispersed in a vinylidene fluoride copolymer to give a volume resistivity of 5 × 10 ⁸ Ω · cm to 5 × 10 5.
Monolayer film adjusted to ¹⁴ Ω · cm or 2
A flexible film in which more than two layers are laminated, or a conductive filler is mixed in the surface or in the middle of these films to adjust the volume resistivity to the range of 5 × 10 Ω ⁸ · cm to 5 × 10 ¹⁴ Ω · m. Since the applied electric charge is saturated in a short time and the charging potential is attenuated in a short time, the belt joined with the film made of the thermoplastic resin (A) having The transfer paper can be separated without peeling discharge and can be easily peeled from the endless belt. Since this endless belt has a self-attenuation characteristic of electric charge, there is no problem that the belt potential rises to a high potential even if the voltage is repeatedly applied without removing the static electricity. Therefore, the device is simplified and the reliability is improved. Further, it is possible to improve image performance and the like.

A monolayer film made of the vinylidene fluoride copolymer specified in the present invention or a conductive filler is kneaded and dispersed to adjust the volume resistivity to a range of 5 × 10 ⁸ Ω · cm to 5 × 10 ¹⁴ Ω · cm. A cylindrical endless belt made of a vinylidene chloride copolymer film is coated on a frame to form a transfer drum, and a toner image formed on an image carrier is transferred onto a transfer target supported on the transfer drum. A multi-color electrophotographic apparatus of the transfer type or a toner carrier that covers an elastic conductive rubber roller and supplies the developer to the image carrier to develop the image, and a toner supply member that supplies the developer to the toner carrier. It is also effective when used on a machine.

When it is necessary to impart flexibility to the cylindrical endless belt, a film made of a thermoplastic resin (A) having flexibility is laminated on the surface of the monolayer film, or two monolayer films are laminated. It is preferable to provide a film made of the thermoplastic resin (A) having the flexibility in the middle of, and when rigidity is required for the cylindrical endless belt,
The object can be achieved by joining a film made of the thermoplastic resin (B) to the above single layer film or a laminated film thereof.

Further, when the above-mentioned antistatic endless belt is used in a transfer separation device to remove toner with an elastic blade, in order to reduce frictional resistance between the elastic blade and the antistatic endless belt, The surface roughness Rmax of the endless belt is preferably in the range of 1 to 20 μm, whereby the rotational running property of the antistatic endless belt can be remarkably improved. Here, the surface roughness Rmax is JI
It is measured according to SB0601-1976.

The endless belt or the cylindrical endless belt of the present invention can be formed by a known method by cutting both ends of an endless belt base material obtained by cutting a single layer or a composite film or sheet formed by extrusion molding by a T-die method into a certain size. It can be made by bonding and bonding, but the latter bonding method is not so preferable because toner accumulates on the bonding surface and toner stains adhere to the transferred material as black streaks.

As an example of forming a cylindrical endless belt, a single layer, two layers, or three layers (when an intermediate adhesive layer or a conductive layer is provided) are integrally formed by extrusion molding of a tubular product from a coextrusion die, After obtaining the above, it can be manufactured by cutting into a predetermined size.

Next, the case where the antistatic endless belt of the present invention is used in a transfer separation device will be described.

That is, in FIG. 1, 1 is an image carrier, 2 is a transfer separation device, 3 is its endless belt, and this endless belt 3 has, for example, a vinylidene fluoride-hexafluoropropene copolymer (copolymer) on its surface layer. A 30 μm thick cylindrical film with a polymerization molar ratio of 96-4) was used, on the inner surface of which vinyl chloride graft ethylene vinyl acetate copolymer was blended with polyether ester amide and sodium dodecylbenzene sulfonate. Is 8 ×
The volume resistivity of the entire belt is set to 1 × 10 ¹³ Ω · cm by joining the inner surface layers of 10 ¹¹ Ω · cm and the thickness of 300 μm. A toner image is formed on the image carrier 1 by a known method. The toner image is transferred and separated by the transfer device 2.
Is transferred to the transferred material 4 conveyed by the endless belt 3 under the voltage application of the charger 6 connected to the DC power supply 5, and the transferred material 4 is transferred by the attraction force of the electric charges charged on the belt. It is separated from the image carrier 1, conveyed by the endless belt 3, and moved to a fixing device (not shown).

The thickness of the antistatic endless belt of the present invention is usually 1 mm or less, preferably 0.1 to 0.6 mm.

The antistatic endless belt of the present invention has a volume resistivity of 5 × 10 ¹⁴ Ω · cm or less, preferably 5 × 10 ^{8 to} 5 × 10 ¹⁴ Ω · cm, and obtains a good transferred image. Since a surface potential of 1 KV or more can be repeatedly applied, the transfer separation device of FIG. 1 using this endless belt has a good separation property without the transferred material sticking to the image carrier, The image is not disturbed by the above, and the transferred material can be easily separated from the endless belt.

Further, FIG. 2 shows an example in which the endless belt 3 is conveyed to the transfer target material, and thereafter, the charge is removed by the charge eliminator 7 of the endless belt, which is reverse to the charging electrode, and is rotated to the transfer position again. In this case, as the endless belt, for example, a cylindrical film having a thickness of 30 μm made of vinylidene fluoride-hexafluoropropene copolymer (copolymerization molar ratio 96-4) is used for the surface layer, and vinyl chloride-grafted ethylene acetate is used on the inner surface thereof. The volume resistivity of the entire belt is 1 × 10 ¹⁴ Ω ・ cm by joining the conductive layer of vinyl copolymer and conductive carbon with volume resistivity of 3 × 10 ³ Ω ・ cm and thickness of 150 μm. You can use the one that

The antistatic endless belt of this aspect with the conductive layer makes use of the characteristics of the vinylidene fluoride copolymer, which has a high dielectric constant, and holds a high electric charge on the belt surface. Although it has a strong carrying force for the material, it is preferable to provide a static eliminator as shown in FIG.

In the antistatic endless belt of the present invention, the surface layer is formed by a dielectric layer made of a specific vinylidene fluoride copolymer having good corona resistance, and a conductive layer is formed on the inner surface of the dielectric layer, so that the voltage generated by the charger is increased. The application can be performed extremely stably.

When the antistatic endless belt or cylindrical endless belt of the present invention is used in a developing device, an electrostatic image is formed on the image bearing member by a known electrophotographic process or electrostatic recording method.

That is, in this developing device, for example, a one-component non-magnetic toner is contained in a developer container, and a conductive rotating body is provided below the container as a conductive rotating body on the peripheral surface of a urethane or silicone conductive rubber roller. A conductive roller having a flexible cylindrical endless belt coated and fixed thereto is provided, and a voltage is applied to the conductive roller. The toner adhering to the conductive roller is conveyed after the adhering amount is adjusted by the regulating piece.

Further, below the conductive roller, the antistatic endless belt of the present invention is rotated through a pair of rollers as a developer supply means, and one of the rollers is applied with a voltage higher than a power source. , The endless belt is charged. Therefore, the developer electrostatically adheres to the endless belt, flies toward the image carrier at a position facing the image carrier with the movement of the belt, and adheres to the electrostatic latent image on the image carrier. be able to. In this case, in order to ensure the flight of the developer, a clearer image can be obtained by applying a DC voltage or an AC bias voltage between the one roller and the opposite electrode to the other roller for rotating the belt. it can.

As a developer supplying means for the developing device, a conductive rotating body is placed on a urethane or silicone conductive rubber roller,
The antistatic cylindrical endless belt of the present invention is composed of a conductive roller that is fixed in a cylindrical shape by coating, and an alternating voltage is applied to this by a power source to transfer the developer on the conductive roller to an electrostatic latent image on the image carrier. It is also possible to fly to an image.

Since the pinylidene fluoride copolymer used in the present invention has non-adhesiveness, the developer can be easily scraped off from the developer endless belt, so that a reliable developing device can be provided.

Furthermore, by imparting a surface roughness Rmax of 10 to 30 μm to the surface of the antistatic cylindrical endless belt, it is possible to improve the toner transportability and reduce the fog.

As an application example of the antistatic endless belt or the cylindrical endless belt of the present invention, an example applied to a transfer separation device and a developing device has been described. In addition to this, a charged antistatic endless belt of the present invention can be used as an image. It is also possible to prevent damage to the image carrier and to perform reliable and uniform continuous charging by frictionally contacting the carrier and applying a voltage to continuously and uniformly charge the image carrier. Further, the visible image on the image bearing member obtained by the development is repeated by using the antistatic endless belt of the present invention as an intermediate image transfer belt and repeating transferring the intermediate image on the belt to a transfer paper. The image transfer can be efficiently performed. In addition, the antistatic endless belt of the present invention can be used as a belt for electrostatically attracting and transporting the transfer paper from the dish, and can be effectively used for various purposes.

[Examples] Comparative Examples 1 to 3 and Examples 1 to 4 (1) Raw materials were charged into a polymerization apparatus at the raw material blending ratios shown in Table 1, and after nitrogen substitution, the polymerization temperature was raised to 95 ° C and self-made pressure. The polymerization was carried out for 12 hours.

After the completion of the polymerization reaction, the produced latex was taken out by a known method to add a salt to coagulate it, followed by washing with water and drying, and then two kinds of vinylidene fluoride copolymers, that is, 4 mol% hexafluoropropene-96 mol% vinylidene fluoride. Ride copolymer (hereinafter abbreviated as VdF-4HFP) and 25 mol% hexafluoropropene-75 mol% vinylidene fluoride copolymer (hereinafter abbreviated as VdF-25HFP) were obtained.

Regarding the polymerization ratio of hexafluoropropene in the vinylidene fluoride copolymer, the copolymer composition was confirmed by nuclear magnetic resonance analysis (NMR) and infrared absorption analysis. That is, the obtained copolymer VdF-4HFP molar ratio of VdF / HFP molar is 96/4, Vd
It was 75/25 for F-25HFP. The physical properties of each polymer are shown in Table 2.

(2) The raw materials shown in Table 3 were blended at the compounding ratio shown in Table 4 and kneaded and extruded by an extruder according to a conventional method, and the obtained pellets were extruded by heating from a T die of a film extruder. An unstretched film having the thickness shown in was obtained.

Table 3 Raw materials used Polyethylene terephthalate film (“Lumirror” manufactured by Toray Industries, Inc.) Polyvinylidene fluoride copolymer (obtained by the above method) Polyvinylidene fluoride homopolymer (“Kynan” 720 manufactured by Penwalt) Vinyl chloride grafted ethylene -Vinyl acetate copolymer (“Smedica” V4142E manufactured by Sekisui Chemical Co., Ltd.) Polyether ester amide * (self-produced) Ethylene / methacrylic acid copolymer (“Nucrel” 1027c manufactured by Du Pont) Conductive carbon (Tokai Carbon ( Co., Ltd. "Cast" so) Sodium dodecylbenzene sulfonate (Kao Co., Ltd.) Conductive tin oxide (Mitsubishi Metal Co., Ltd. conductive fine powder T-1) *: Polyether ester amide is nylon 6 polyamide Block copolymer with polyethylene glycol (number average molecular weight 4000) and terephthalic acid is there.

According to the combinations shown in Table 4, the obtained films were heat-laminated at a temperature 20 ° C. higher than the lowest melting point in the film of each constitution while sandwiching them between two release papers to obtain an endless belt base material.

The single layer endless belt substrate was not subjected to the thermal laminating step.

Both ends of the cut sheet cut into a predetermined size from the above endless belt base material were joined by using a high frequency bonding machine to obtain an antistatic endless belt.

The volume resistivity of the obtained antistatic endless belt was measured using an insulation resistance meter (R-503 manufactured by Kawaguchi Electric Co., Ltd.) (applied voltage 100V, 20 ° C., 33% RH).

For toner cleaning properties, see FIGS.
Using the device shown in the figure, the toner was directly transferred onto the belt without supplying the transfer target paper, and then the belt surface was rubbed with a urethane cleaning blade to observe and judge the residual toner on the belt surface. .

On the other hand, regarding the belt life, using the transfer device shown in Fig. 1 and Fig. 2, a notch of 1 mm was made at one point on the end face of the belt, and the belt surface speed was 15 at a belt tension of 20 g / mm.
Continuously rotate at 0 mm / sec, 10 mm from the belt end surface after 7 hours
The life of the belt was determined by the presence or absence of tearing.

As is clear from Table 4, Examples 1 to 1 satisfying the present invention
It can be seen that the antistatic endless belt of No. 4 is a reher satisfying not only the cleaning property of the toner but also the surface smoothness after belt processing and the belt life, and is remarkably superior to Comparative Examples 1 to 3.

The dielectric constant of the vinylidene fluoride copolymer used in this example is 9.3 (1 KHz) for VdF-4HFP and 8.0 (1 KH for VdF-25HFP.
z), which is more than twice as high as the dielectric constant of polyethylene terephthalate, 3.2. Therefore, in the case of the same thickness as the belt made of polyethylene terephthalate film, the electrostatic capacity of the belt of the present invention should be more than double. You can

Therefore, due to the high capacitance, it is possible to improve the belt conveyance force and transfer efficiency.

Examples 5 to 6 The raw materials shown in Table 3 were used, and kneading and pelletizing were performed at the raw material blending ratios shown in Examples 5 and 6 of Table 4.

Each of the vinylidene fluoride copolymer forming the surface layer and the blend polymer forming the inner surface layer is extruded into a cylindrical shape from a single-screw extruder through a two-layer coextrusion die, and by introducing compressed air from the center of the die. The cylindrical film was made uniform in shape, cooled, and then cut into a predetermined size to obtain a seamless antistatic endless belt.

This belt was mounted on the transfer device shown in FIGS. 1 and 2 and evaluated for use as a transfer separation belt.

The toner cleaning property, the surface smoothness after belt processing, and the belt life were satisfactory. Further, since this belt is seamless and seamless, there is no occurrence of stains on the transfer paper due to toner accumulation.

The vinylidene fluoride copolymer containing 25 mol% of hexafluorofuropene used as the inner surface layer of Example 6 as a monomer ratio has a rubber-like flexibility of JIS hardness 60A, and thus the belt of Example 6 Has no stop mark and can be imparted with a desired flexibility as a belt.

[Effect of the Invention] The antistatic endless belt of the present invention is obtained by copolymerizing vinylidene fluoride with a specific amount of hexafluoropropene as described above, and if necessary, by appropriately incorporating a conductive filler in the copolymer. In addition, since a combination of the constituent layers of the belt is used as the base material, the surface potential, the charge decay time, the charge charge amount, etc. can be appropriately adjusted and designed according to the device used. It is possible to reliably obtain an endless belt excellent in cleaning property, corona resistance and flatness.

Therefore, as compared with the conventional endless belt system, the transfer separation device of the electrophotographic copying machine, the developing device and the like can be simplified and the performance can be improved.

[Brief description of drawings]

FIG. 1 and FIG. 2 are schematic diagrams for explaining examples of use of the antistatic endless belt of the present invention. 1: Image carrier, 2: Transfer separation device, 3: Endless belt, 4: Transfer material, 5: DC power supply, 6: Charger, 7: Static eliminator.

Claims (11)

[Claims] 1. An antistatic endless belt comprising a film mainly composed of a copolymer obtained by copolymerizing 99 to 70 mol% of vinylidene fluoride with 1 to 30 mol% of hexafluoropropene. 2. The antistatic endless belt according to claim 1, wherein the film has a cylindrical shape. 3. The antistatic endless belt according to claim 1, wherein the film is formed by laminating two or more layers. 4. The antistatic endless belt according to claim 1, wherein the copolymer contains a conductive filler. 5. The antistatic endless according to claim 1 or 2, wherein the surface has a conductive layer made of a thermoplastic resin (A) and a conductive filler and having a volume resistivity of 5 × 10 ¹⁴ Ω · cm or less. belt. 6. The antistatic endless belt according to claim 3, further comprising a conductive layer which is composed of a thermoplastic resin (A) and a conductive filler and has a volume resistivity of 5 × 10 ¹⁴ Ω · cm or less in the middle. 7. The thermoplastic resin (A) is an acrylic copolymer, a polyether ester copolymer, a polyester ester copolymer, a polyetheramide copolymer, polyvinyl acetate, a vinyl acetate copolymer, an olefin copolymer. At least one selected from the group consisting of polymers, ionomers, polyurethanes, styrene elastomers, vinyl chloride copolymers, vinyl chloride graft copolymers, fluororesins, fluoroelastomers, polyether sulfones, polysulfones and chlorinated polyethylenes. The antistatic endless belt according to claim 5 or 6 as described above. 8. A surface layer made of a thermoplastic resin film having a thickness of 5 to 50 μm is further provided.
Alternatively, the antistatic endless belt according to 2. 9. The thermoplastic resin film forming the surface layer is selected from polyethylene terephthalate, polyether ether ketone, polycarbonate, ethylene tetrafluoroethylene copolymer, vinyl chloride copolymer, polyvinylidene chloride and acrylic copolymer. At least 1
The antistatic endless belt according to claim 7, comprising at least one thermoplastic resin (B). 10. The volume resistivity is further 5 × 10 ⁸ Ωc on the inner surface.
The antistatic endless belt according to claim 1, which has a conductive layer of m or less. 11. The antistatic endless belt according to claim 1, wherein the surface roughness Rmax of the surface layer is in the range of 1 to 30 μm.