JP2000293045A - Endless belt for electrophotographic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit drive and travel while sufficiently suppressing the warp which occurs inevitable in molding by affixing tensile force tapes to both transverse ends of a seamless belt of a synthetic resin film. SOLUTION: The seamless belt 1 of the synthetic resin film molded by a centrifugal molding method, etc., warps to a trumpet shape at both ends due to the bending moment m based on the residual stress at the time of molding. The tensile force tapes 2 are affixed to both transverse ends of the seamless belt 1. The tensile force tapes 2 may be affixed to both transverse ends on the rear surface or both surfaces of the seamless belt 1. The thickness of the tensile force tapes 2 is usually 1 to 200 μm, more preferably 5 to 100 μm and the width thereof is usually 5 to 50 mm, more preferably 10 to 40 mm. The material of the tensile force tapes 2 may be any materials, insofar as the material can satisfy the heat resistance required for an endless belt, more particularly an intermediate transfer belt for electrophotographic devices. Tacky adhesive tapes of an acrylic system, etc., satisfying the required heat resistance for an adhesive and a base material are preferably used for affixation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt for an electrophotographic apparatus, and is useful, for example, as an intermediate transfer belt.

[0002]

2. Description of the Related Art In an electrophotographic recording apparatus such as a laser printer, a copying machine or a video printer, an image developed on an image carrier such as a photosensitive drum via a recording material such as toner is usually used. Is directly fixed on a print sheet.

However, recently, in order to avoid early damage due to paper jam of the photosensitive drum or the like, the toner image on the photosensitive drum is temporarily transferred to an intermediate transfer endless belt, and the transferred image is recorded on a recording sheet. An indirect method of fixing on top is being developed. The intermediate transfer method includes a method in which a toner image is transferred to an intermediate transfer endless belt by pressing, and a method in which a toner image is transferred to an intermediate transfer endless belt by using an electrostatic induction phenomenon. The belt is made conductive by the addition of carbon or the like in order to escape the charge of the belt (having the same polarity as the charge of the toner image), which becomes free due to electrostatic attraction of the toner image to the transfer endless belt. Usually, a film-shaped seamless belt formed by the same molding method is used for both. For example, a centrifugal molding method of supplying a resin liquid into a cylindrical mold, forming a film on the inner peripheral surface of the mold by centrifugal force by rotating the mold, drying and curing the film, and then releasing the mold is used. I have.

[0004]

The inventors of the present invention have conducted intensive studies on the manufacture and driving and running of the intermediate transfer endless belt. As a result, both ends of the seamless belt are warped in a trumpet shape, and the roll is rolled. It has been found that when the vehicle is hung and driven, the warp causes the seamless belt and the drive roll to interfere with each other, so that the seamless belt often cracks.

[0005] The cause of the warpage of the seamless belt is the inevitable nonuniformity of the cooling rate of the inner and outer surfaces during the formation of the seamless belt. That is, the inner surface side of the seamless belt is first cooled and solidified by air cooling and thermally contracts. At this time, the outer surface side is still in a heat-softened state and does not substantially generate stress without substantially resisting contraction on the inner side. Next, when the outer surface side is cooled and solidified and heat shrinks, the inner surface side is already solidified and acts to prevent shrinkage on the outer surface side, resulting in a compressive stress on the inner surface side and a tensile stress on the outer surface side. A bending moment acts to make the belt surface of the seamless belt convex toward the inner surface. Even under the action of the bending moment, when the width of the seamless belt is larger than the caliber, for example, in the case of a long tubular body such as an endless belt of a roll-belt type fixing device, the bending is performed. The above-mentioned warpage does not occur as a result of the bending stiffness of the pipe body being smaller than that of the moment, but the above-mentioned warpage occurs in the case of the intermediate transfer endless belt because the width is smaller than the diameter. Leads to the occurrence.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an endless belt for an electrophotographic apparatus which can drive and drive an intermediate transfer endless belt while sufficiently suppressing warpage inevitably occurring in the formation of the endless belt.

[0007]

An endless belt for an electrophotographic apparatus according to the present invention is characterized in that a tensile tape is attached to both ends of a synthetic resin film seamless belt. A polyimide film is used as the synthetic resin film, and a polyethylene terephthalate tape, a polyethylene tape, a polypropylene tape, a polytetrafluoroethylene tape or the like can be used as the tensile strength tape.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view showing the endless belt according to the present invention, FIG. 1B is a front view thereof, and FIG.
FIG. In FIG. 1, reference numeral 1 denotes a seamless belt made of a synthetic resin film formed by a centrifugal molding method or the like, and both ends are warped in a trumpet shape due to a bending moment m based on a residual stress during molding. For this seamless belt, for example, a solution of polyamic acid obtained by polymerizing tetracarboxylic dianhydride or a derivative thereof with a diamine in a solvent such as N-methyl-2-pyrrolidone is used by using a rotating cylindrical mold. After forming a film by centrifugal force, drying and forming the film, the molded product is heated and imidized, and a polyimide film seamless belt obtained by releasing the mold can be used. Reference numerals 2 and 2 denote tensile strength tapes adhered to both ends of the width of the seamless belt 1.

The endless belt shown in FIG. 1 is not hung and both ends are warped in a trumpet shape due to bending moment based on residual stress during molding.

FIG. 2 shows a driving and running state of the endless belt. The endless belt A according to the present invention is suspended between a driving roller 21 and a driven roller 22, and the driving roller 2 is driven.
The endless belt A is running in the direction of the arrow by one rotation drive. In this case, the driven Russia - Le tensile force F ₁ to becomes the load belt tension side, acts tensile force F ₂ on the belt slack side respectively, the effective winding angle of the belt theta, belts and Russia - between Le of When the friction coefficient is μ,

[ ^Formula 1] F ₁ / F ₂ = e ^μθ holds.

Since the endless belt has a tensile strength tape attached to both ends of the width thereof, the above-mentioned tensile force F
_1, the distribution of tensile stress per unit width along the belt width F ₂ is as shown in FIG. 3, the larger the width end portions. In FIG. 3, w is the width of the tensile tape.
If the thickness of the seamless belt is t, the Young's modulus is e, the thickness of the tensile strength tape is t ', and the Young's modulus is e',

The following holds: δ / δ ′ = te / (te + t′e ′) Therefore, the tension F ₂ of the belt slack side be small, resulting to concentrate sufficient tensile stress to the belt width end portions, it can be prevented better floating of the belt end portions on the roll, an endless belt of the previous year The vehicle can run without the appearance of warpage.

In the above, a tensile tape may be attached to both ends of the width on the back side of the seamless belt. Further, it is also possible to attach a tensile strength tape to both ends of the width of both sides of the seamless belt.

In the above, if the tensile strength tape is too thick, the step between the belt surface and the tape surface becomes large and hinders smooth running of the endless belt. If the tensile tape is too thin, the above-mentioned warpage suppressing effect is insufficient. And the durability also decreases.
Therefore, the thickness of the tensile strength tape is usually 1 to 200 μm,
Preferably it is 5 to 100 μm.

As the width of the tensile strength tape is increased, the effect of suppressing the warpage is more advantageous. However, the effective width of the belt is reduced due to the tensile strength tape, and the belt width must be increased accordingly. If the width is too large, it is disadvantageous in terms of compactness of the apparatus. Therefore, the width of the tensile strength tape is usually 5 to 50 mm, preferably 10 to 40 mm.
It is said.

The material of the tensile strength tape may be any material which can satisfy the heat resistance (80 to 100 ° C.) required for an endless belt for an electrophotographic apparatus, particularly, an intermediate transfer endless belt. -Tape, polyethylene tape, polypropylene tape, polytetrafluoroethylene tape and the like can be used.

In order to attach the above-described tensile strength tape, it is preferable to attach an acrylic or silicone-based adhesive tape which satisfies the above-mentioned heat resistance for both the adhesive and the substrate. It is also possible to attach a high-strength tape with an adhesive or a hot-melt adhesive, or to heat-seal the high-strength tape.

The above-mentioned seamless belt can be formed by a method other than the centrifugal forming method. For example, a polymer solution is applied to the inner surface of a cylindrical mold, and the polymer solution is vertically supported, and the core mold is dropped and run to spread the coating solution on the inner surface to a uniform thickness.
It is also possible to use a method of performing drying and solidification or imide conversion.

As described above, the warping deformation due to the bending moment based on the residual stress at the time of forming the seamless belt is as follows.
It depends on the ratio between the belt width and the caliber. In the endless belt for an electrophotographic apparatus according to the present invention, (belt width) /
(Aperture) is usually 0.5 to 2.0.

The endless belt according to the present invention is particularly suitably used for an intermediate transfer endless belt. FIG. 4 shows an example of an intermediate transfer type electrophotographic apparatus, in which the endless belt according to the present invention is used as an intermediate transfer endless belt. In FIG. 4, reference numeral 5 denotes a photosensitive member for forming an electrostatic latent image by exposure, and a toner of opposite polarity is attached to the electrostatic latent image by a normal image method (or a reversal developing method) by a suction force (or the same polarity). This is a photosensitive drum that develops by charging a toner to a non-charged portion by a repulsive force. Reference symbol A denotes an endless belt according to the present invention, which is suspended between a driving roll 21 and a driven roll 22, and is a low-resistance body formed by blending conductive particles such as carbon. The charged toner image is suction-transferred by the electrostatically induced charge on the endless belt A at the contact portion of the contact belt, and the charge released by the transfer is released to the ground at the ground roll 23. Reference numeral 6 denotes a fixing roll for fixing the intermediate transfer toner image to the print sheet 7.

Examples of the conductive particles that make the endless belt low-resistance include carbon black such as Ketjen black and acetylene black, metal powder (eg, aluminum and nickel), and semiconductive powder (eg, tin oxide). Metal oxide compounds such as, for example, potassium titanate) conductive polymers (eg, polyaniline) can also be used, and can be dispersed in a solvent before the preparation of the polyamic acid solution or in a polyamic acid solution.

[0021]

EXAMPLES Example 1 N-methyl-2-pyrrolidone 1
To a dispersion obtained by mixing 16.1 g of carbon black dried to 67 g with a ball mill at room temperature for 6 hours, 3
Dissolve 294.2 g of 3 ', 4,4'-biphenyltetracarboxylic dianhydride and 108.2 g of p-phenylenediamine and carry out a polymerization reaction while stirring at room temperature for 4 hours in a nitrogen atmosphere to obtain a polyamic acid solution. I got This polyamic acid solution is applied to the inner peripheral surface of a cylindrical mold having an inner diameter of 300 mm and a length of 500 mm with a dispenser to a thickness of approximately 400 μm, and rotated at 1500 rpm for 10 minutes to form a spread film having a uniform thickness, and then rotated at 250 rpm. While blowing hot air at 60 ° C. from the outside of the mold for 30 minutes,
After heating at 60 ° C x 60 minutes, the heating rate was 2 ° C / min.
The temperature was raised to 00 ° C., and the temperature was maintained for 30 minutes to remove the solvent, remove the dehydrated ring-closing water, and convert to imide, then cooled to room temperature, released from the mold, and trimmed at both ends of the width. Thickness 75μm, outer diameter 300mmφ, width 300m
m was obtained. The base material is a polyethylene terephthalate film having a thickness of 25 μm, and the pressure-sensitive adhesive layer having a thickness of 3
20 μm wide adhesive tape that is 0 μm acrylic adhesive
The endless belt according to the present invention was prepared by attaching the belt to both ends of the outer surface of the seamless belt.

Example 2 The adhesive tape was a polytetrafluoroethylene film having a thickness of 50 μm as a base material and a silicone-based adhesive having a thickness of 30 μm as a pressure-sensitive adhesive layer.
An endless belt according to the present invention was produced in the same manner as in Example 1, except that a silicone-based adhesive tape of 5 mm was used.

Comparative Example The seamless belt in Example 1 was used as an endless belt, and the application of the tensile strength tape was omitted.

With respect to each of the product of the example and the product of the comparative example, an endless belt was suspended in tension between two rolls each having an outer diameter of 45 mmφ with a center-to-center distance of 400 mm. The roll was driven to rotate and the endless belt was run at 20 m / min, and the floating amount (maximum value) between the drive roll surface and the inner surfaces at both ends of the width of the endless belt was measured. In the first embodiment, 0.6
mm, and 1.0 mm in Example 2. In the endless belt according to the present invention, the endless belt was able to run while substantially suppressing the appearance of warpage.
Further, in the comparative example product, the end portion was broken relatively early after driving, but no abnormality was observed in both the example products 1 and 2.

[0025]

As described above, the endless belt for an electrophotographic apparatus according to the present invention suppresses the warpage in a driving and running state even if the endless belt for an electrophotographic apparatus is warped in a non-hanging state due to a bending moment based on a residual stress during molding. The smooth running of the endless belt can be ensured, damage such as breakage or cracking of the endless belt can be eliminated, and damage to the photosensitive drum can be avoided.

[Brief description of the drawings]

FIG. 1 is a view showing an endless belt for an electrophotographic apparatus according to the present invention.

FIG. 2 is a view showing a driving state of the endless belt according to the present invention.

FIG. 3 is a drawing showing a distribution state of tensile stress in the running state shown in FIG.

FIG. 4 is a view showing an intermediate transfer type electrophotographic apparatus using the endless belt according to the present invention.

[Explanation of symbols]

 1 Seamless belt of synthetic resin film 2 Tensile tape

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiko Tomita 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 2H032 BA09 BA18

Claims (3)

[Claims] 1. An endless belt for an electrophotographic apparatus, wherein a tensile tape is attached to both ends of a width of a seamless belt made of a synthetic resin film. 2. The endless belt for an electrophotographic apparatus according to claim 1, wherein the synthetic resin film is a polyimide film. 3. The tensile strength tape is made of polyethylene terephthalate.
Tope, polyethylene tape, polypropylene tape
3. An endless belt for an electrophotographic apparatus according to claim 1, wherein the endless belt is one of a tape and a polytetrafluoroethylene tape.