JP3315933B2 - Conductive seamless belt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive seamless belt, and more particularly, to a sheet material in an image forming apparatus such as a copying machine, a facsimile, and a printer for forming an image by an electrophotographic method or an electrostatic printing method. Conveyor belt, transfer belt, intermediate transfer belt, fixing belt, developing belt,
The present invention relates to a conductive seamless belt used for a belt for a photoreceptor substrate or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming a toner image by an electrophotographic method or an electrostatic printing method such as a copying machine, a facsimile, and a printer, a sheet material conveying belt, a transfer belt, an intermediate transfer belt, A conductive seamless belt is used for a fixing belt, a developing belt, a belt for a photoreceptor substrate, and the like.

For example, in a transfer area, a conductive seamless belt is generally called a transfer belt, and is used, for example, in a form as shown in FIG. That is, the transfer belt 1 is set in a stretched state by two or more (two in the figure) pulleys 2, and is driven to rotate and move in the longitudinal direction of the belt (the arrow X direction in the figure) by driving the pulleys 2. . Then, a sheet material 4 such as paper is carried and conveyed on the upper linear portion 3 of the rotating belt 1. on the other hand,
The photoreceptor 10 moves in synchronization with the conveyance of the sheet material 4 by an arrow Y in the drawing.
The toner T on the photoconductor 10 is conveyed to a position close to or in contact with the surface of the sheet material 4. Also,
A charging unit 6 such as an electrode and a charging roller is in contact with the linear portion 5 on the lower side of the transfer / transport belt 1 that rotates, and the charging unit 6 causes the surface of the transfer / transport belt 1 to be charged with the toner T. The toner T is charged to the opposite polarity (when the charge of the toner T is plus (+), the charge is minus (-), and when the charge of the toner T is plus (-), the charge is plus (+)). Therefore, when the toner T on the photoreceptor 10 approaches or comes into contact with the surface of the sheet material 4, the toner T is attracted to the charge of the transfer belt 1 charged to the opposite charge to the toner T, and
Is transferred to the surface of

As described above, the transfer belt is set in a stretched state by two or more pulleys, and is rotated by driving the pulleys. Therefore, in order to obtain good transfer characteristics over a long period of time, the transfer belt is required to run stably without being stretched even in a stretched state for a long period of time. This is because when the transfer belt is stretched, rotation unevenness occurs, making it difficult to move the sheet material at a constant speed and in a constant running state, and the toner on the photoconductor transferred to the sheet material is originally transferred. Out of position to be done,
This is because a so-called transfer deviation occurs.

In an image forming apparatus that forms a toner image by an electrophotographic system or an electrostatic printing system, for example,
There is an apparatus using a one-component developing method in which a thin toner layer is formed on a developing sleeve surface by a blade, such as a jumping developing method, and the thin toner layer is brought into close proximity to or in contact with the surface of the electrostatic latent image holding member to perform development. In recent years, as shown in FIG. 2, instead of using a developing sleeve, an elastic seamless belt 20 mainly made of rubber is rotated by pulleys 21a and 21b in a stretched state, and the rotating belt (developing belt) is rotated. A method is used in which a thin toner layer 23 is formed on the surface of a photoreceptor 20 by a blade 22 and is brought close to or in contact with a photoreceptor 24 for development. In a one-component developing system in which development is performed using a thin layer of toner alone without using such a magnetic carrier, it is important to form a thin toner layer having a uniform thickness in order to obtain good development characteristics. Therefore, when a developing belt is used, in order to form a thin toner layer having a uniform thickness, it is required that the developing belt does not stretch even in a stretched state and the belt runs stably without waving.

In the fixing area, the conductive seamless belt is generally called a fixing belt. In many cases, the conductive seamless belt is stretched by two or more pulleys at a position facing a heating means (for example, a heating roll) in the same manner as the transfer belt. When the pulley is in a suspended state, it is rotated by the drive of the pulley, and the sheet material on which the toner has been transferred is carried on the upper surface thereof, conveyed, and the transferred toner on the sheet material is fixed on the sheet material. . Therefore, even in such a fixing region, in order to obtain good fixing performance for a long period of time, the conductive seamless belt is required to run stably without stretching even in a stretched state for a long period of time.

In a so-called belt-shaped photosensitive member,
A photosensitive layer is formed on the conductive seamless belt as a conductive substrate. The photoreceptor is for forming an electrostatic latent image on the surface of the photosensitive layer at the initial stage of the image forming process. Therefore, a belt-shaped photoreceptor, that is, a conductive seamless It is required that the belt run stably without stretching.

On the other hand, in an image forming apparatus for forming a full-color image, as shown in FIG. 3, a toner image formed on a photoreceptor 10 or the like is primarily transferred to an intermediate transfer belt 11 made of an elastic seamless belt, Then, an operation of secondarily transferring the toner transferred to the intermediate transfer belt 11 to the sheet material 4 is performed. That is, while the photoreceptor 10 rotates in the direction of arrow A, the intermediate transfer belt 11 is stretched by the three pulleys 7, 8, 9, and the pulleys 7, 8, 9
, The toner image formed on the surface of the photoconductor 10 is transferred to the intermediate transfer belt 11 at the contact portion between the surface of the photoconductor 10 and the linear portion 11A of the intermediate transfer belt 11, The primary-transferred toner image is secondarily transferred to the sheet material 4 inserted between the pulley 9 and the transfer roller 12. In the drawing, 13 is an optical system for exposure, 1
4 is a charger, 15 is a developing device, 16 is a cleaning brush for a photoreceptor, and 17 is a transfer charger provided inside the intermediate transfer belt 11. In this transfer process, the toner images of different hues are transferred to the intermediate transfer belt and superimposed, and the superimposed toner images are collectively transferred to the sheet material. The complicated operation of transferring the toner to the sheet material by transporting the toner to an area close to the sheet material is eliminated. The intermediate transfer belt 11 does not carry a sheet material on a belt like the transfer belt or the fixing belt, and conveys the toner image onto the belt. It is secondary transfer to the material, but belt elongation is fatal even in such an intermediate transfer belt,
The transfer of the toner (the toner is transferred to a position shifted from the original transfer position of the belt) and the poor transfer of the toner (the transfer omission where the toner to be transferred is not transferred) occur due to the belt elongation. An image cannot be formed.

[0009]

The conductive seamless belt used in the image forming apparatus includes, for example, a thermoplastic resin such as a polycarbonate resin or a fluorine-based resin mixed with a conductive filler such as carbon black. In addition, there is known a rubber in which a reinforcing filler such as silica or magnesium oxide is blended with a conductive filler together with a conductive filler, and these are relatively hard to elongate even when rotated in a stretched state. However, since the flexibility is poor and the spring constant in the thickness direction is high, for example, in a transfer belt (intermediate transfer belt), the nip amount with the photoconductor cannot be increased.
In some cases, the transfer efficiency is reduced, and the nip amount of the fixing belt with the heating roll cannot be increased, so that good fixing properties cannot be obtained.

In a belt using the above rubber as a polymer material, a crosslinked rubber may be used in order to adjust the elastic modulus of the belt. In this case, a vinyl monomer such as an unsaturated carboxylic acid and an organic rubber are used as the rubber. Although a rubber is cross-linked by adding a cross-linking agent such as a peroxide, the cross-linking agent and unreacted monomers may bleed out when the belt is used, and contaminate the photoreceptor and the like.

On the other hand, in recent years, the spread of image forming apparatuses has been remarkable, and a higher level of image quality of toner images obtained by image forming apparatuses has been demanded. For this reason, conductive seamless belts used in various processes such as sheet conveyance, transfer, development, and fixing have been required to have more stable running. When vibrations are applied, the vibration is rapidly attenuated, and the contacted member such as the photoconductor is required to have a soft and uniform contacting flexibility. For example, running with the belt vibrating,
When the ability to follow the photoreceptor or the like is reduced, even if the transfer deviation is at a level that is not a problem in a monocolor image (monochromatic toner image), the full color image (cyan toner, yellow toner, magenta toner, and black toner) In the case of a (superimposed image of color toners), a color shift occurs, and image deterioration is conspicuous.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and is rotated in a stretched state by at least two or more pulleys in an image forming apparatus that forms an image by an electrophotographic method or an electrostatic printing method. This is a conductive seamless belt that is used by moving.It does not contaminate the photoreceptor, etc., has appropriate flexibility in the thickness direction, and elongates in the length direction even after continuous operation for a long time. Not to mention
It is an object to provide a conductive seamless belt having excellent vibration damping properties.

[0013]

In order to solve the above-mentioned problems, the present invention provides a method in which a volume resistivity value is from 1 × 10 ⁴ to 1 × 10 ^4.
A conductive seamless belt having a conductive base layer in a range of ¹² Ω · cm, wherein the conductive base layer is obtained by dispersing a conductive filler in a polyester polyether resin having a melting point of 160 to 210 ° C. 23 ℃, 10H
The present invention provides a conductive seamless belt having a loss tangent (tan δ) in the range of 0.1 to 0.2 when measured under measurement conditions of z and elongation strain of 4%.

The conductive seamless belt of the present invention may be constituted by a single conductive base layer, or the conductive base layer may be provided on the surface of the conductive base layer in order to impart better surface characteristics to the belt. A surface layer made of a material different from the above may be formed. In this case, the thickness of the surface layer is an extremely thin thickness such that the volume resistivity of the belt in which the surface layer is laminated on the conductive base layer is almost the same as the volume resistivity of the conductive base layer alone.

The conductive base layer is kept at 23.degree.
It is preferable that the dynamic elastic modulus measured under the measurement conditions of Hz and elongation strain of 4% is in the range of 2.5 × 10 ^{8 to} 2.0 × 10 ¹¹ dyn / cm ² .

The loss tangent (tan δ) and dynamic elastic modulus are values measured using a viscoelastic spectrum meter manufactured by Rheology Co., Ltd.

The conductive seamless belt of the present invention has a moderate flexibility in the thickness direction by forming a seamless belt by adding a conductive filler to a polyester polyether resin having a specific melting point in a specific range. In addition, a seamless belt that does not easily stretch in the length direction and has excellent vibration properties is obtained. Thus, for example, when used as a transfer belt (intermediate transfer belt), good transfer performance can be obtained over a long period of time without causing transfer deviation or transfer failure. Further, when used for a sheet conveying belt, a developing belt, a fixing belt, a base belt of a belt-shaped photoreceptor, etc., it is possible to obtain better performance than before, and as a result, to achieve high image quality. .

When a polyester polyether resin having a melting point lower than 160 ° C. is used, the loss tangent (tan δ) of the conductive base layer becomes larger than 0.2 because the proportion of the polyester which is a hard segment is too small. When a tensile force acts on the conductive base layer (belt) for a long period of time, stress relaxation is caused and belt elongation occurs. When a polyester polyether resin having a melting point higher than 210 ° C. is used, the crystallinity becomes too high, the loss tangent (tan δ) of the conductive base layer (belt) becomes smaller than 0.1, and vibration occurs on the belt. When the vibration is applied, the vibration does not attenuate quickly. Further, the elastic modulus of the belt becomes too high, the flexibility in the thickness direction of the belt is impaired, and the followability of the belt to the contact surface such as the surface of the photoreceptor is deteriorated. Therefore, it is preferable to use a polyester polyether resin having a melting point in the range of 170 to 200 ° C.

As described above, in the present invention, the conductive base is used.
Under the measurement conditions of 23 ° C., 10 Hz and 4% elongation strain of the base layer
Dynamic elastic modulus when measured is 2.5 × 10⁸~ 2.0 × 1
0¹¹dyn / cm^TwoIs preferably within the range. this
Has a dynamic elastic modulus of 2.5 × 10 ⁸ dyn / cm^TwoAbove
When there is, the conductive base layer
Although the elongation is less likely to occur, the dynamic elastic modulus is 2.0 × 1
0¹¹dyn / cm^TwoWhen it exceeds
Elasticity in the thickness direction of the conductive base layer (belt thickness direction)
Too high, the ability of the belt to follow the surface of the photoreceptor
Is to show a tendency to decrease.

Examples of the conductive filler include metal oxides such as carbon black, tin oxide, and titanium oxide (including those coated with tin oxide), or conductive silica, copper, iron, nickel, and the like. Metal powder such as aluminum can be used. These fillers may be used alone or in combination of two or more.

As the carbon black, for example, various carbon blacks such as channel black, furnace black and acetylene black can be used, and those having an average particle diameter in the range of 18 to 120 nm, especially 22 to 90 nm are preferably used. Can be

The required amount of the conductive filler is determined in the range of 10 to 50 parts by weight, preferably 10 to 35 parts by weight, based on 100 parts by weight of the polyester polyether resin. That is, the volume resistivity of the conductive seamless belt in the image forming apparatus is generally 1 × 10 ⁴ to 1 × 10 ^4.
The value is set within the range of ¹² Ω · cm according to the application process. Therefore, also in the present invention, a conductive filler is blended within the above range with respect to the polyester polyether resin so that the volume resistivity of the conductive base layer is 1 × 10 5
Within the range of ⁴ to 1 × 10 ¹² Ω · cm, a value corresponding to the application process is obtained, and the loss tangent (t) of the conductive base layer is
and an δ) is adjusted to fall within the range of 0.1 to 0.2 described above. The volume specific resistance here is JIS K69
11 is the volume resistivity ρ _V determined according to the method described in “5.13 Resistivity”.

In addition to the conductive filler, for example, calcium carbonate, silica,
Reinforcing fillers such as clay, talc, barium sulfate, and diatomaceous earth may be blended. However, when such a reinforcing filler is compounded, the loss tangent (tan δ) of the rubber composition
Is a compounding amount that does not increase beyond the above-mentioned numerical range or that the workability at the time of production is not reduced.

In order to increase the flexibility of the conductive base layer, the polyester polyether resin may contain, for example, a fatty acid such as stearic acid or lauric acid, or a softening agent such as cottonseed oil, tall oil, asphalt substance, or paraffin wax. You may mix. Further, as a plasticizer, for example, phthalic acid compounds such as dimethyl phthalate and dibutyl phthalate, adipic acid compounds such as dioctyl adipate,
A sebacic acid compound such as dibutyl sebacate, a benzoic acid compound, or the like may be blended. Further, in order to improve the durability of the conductive base layer, for example, 2
Imidazoles such as mercaptobenzimidazole,
Phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, N-phenyl-N ′
Amines such as -isopropyl-p-phenylenediamine, phenols such as di-t-butyl-p-cresol and styrenated phenol may be blended.

The thickness of the conductive base layer is 0.1 to 1.0.
mm, preferably 0.3 to 0.7 mm.
This is because if the thickness is smaller than the above range, the tension of the belt is low, and the slip tends to occur between the pulley and the belt, and if the thickness is larger than the above range, the tension of the belt is high and the pulley has a high tension. This is because a load is applied to the drive system.

When a surface layer is provided on the surface of the conductive base layer, it is preferable to form a thin film of, for example, urethane resin, fluorine resin, or the like. The thin film is coated on the surface of the conductive base layer using an electrostatic coating machine or the like. Forming a thin film of the urethane resin, fluororesin, etc., improves the chemical stability of the belt surface and stabilizes the surface resistivity,
Further, the cleaning property of the toner attached to the belt surface is improved. The thickness of the surface layer is usually as thin as 1 to 10 μm, preferably about 5 μm.

In the present invention, the method for producing the conductive base layer is not particularly limited, but usually, a conductive filler or the like is kneaded with a polyester polyether resin, and the kneaded product is formed into a seamless belt shape. . Kneading is performed by an open roll, a kneader, a closed kneader, a single-screw extruder, a twin-screw extruder, or the like, and the kneaded composition is subjected to injection molding, press molding,
It is formed into a seamless belt shape (endless belt shape) by a conventionally known forming method such as extrusion.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments (examples) and comparative examples. Raw materials having the composition described in the upper row of Table 1 below are kneaded with a kneader, and the kneaded material is 180 ° C, 360 mm in width, 100 mm in inner diameter,
After pouring into a cylindrical mold having a thickness of 1.5 mm, it was cooled to room temperature and demolded. The surface of the cylindrical molded product is polished using a cylindrical grinder to adjust the thickness of the cylindrical molded product to 0.5 mm,
Apply urethane resin to the polished surface with an electrostatic coating machine,
A surface layer having a thickness of 5 μm was formed to complete the conductive seamless belts of Examples and Comparative Examples.

[0029]

[Table 1]

The numerical values in the upper row of Table 1 are all parts by weight.
DCP in the upper part of Table 1 is dicumyl peroxide.

With respect to the conductive seamless belts of the respective Examples and Comparative Examples produced as described above, the specific volume resistance was measured, and the elongation strain was measured at 23 ° C., 10 Hz, and at 4 ° C. using a viscoelastic spectrum meter manufactured by Rheology Co., Ltd. %, The loss tangent (tan δ) and the dynamic elastic modulus were measured.

In addition, the presence or absence of stress relaxation due to long-term elongation in the conductive seamless belts of the examples and comparative examples,
Tests were performed to determine whether or not there was a transfer deviation, whether or not toner transfer was poor, and whether or not there was contamination of the photoconductor.

(Presence / absence of stress relaxation due to long-term elongation) A belt was stretched by a pulley, and the stress after 2 hours was measured while maintaining the initial elongation when a stress of 18 kg / cm ² was applied. Is measured by the following formula (1). When the reduction rate (%) of the stress is 30% or less, the result is passed (○), and when the reduction rate of the stress is more than 30%, the test is failed (×). ).

Reduction rate (%) = [1− (stress after 2 hours / initial stress)] × 100 (1)

(Existence of Transfer Deviation) The belt is mounted on a commercially available electrophotographic copying machine as an intermediate transfer belt, as shown in FIG. A reference line is drawn, and a copy is made on an A4 transfer sheet using a document in which a linear marking line running in the short direction is drawn at a position 270 mm away from the reference line toward the other end in the longitudinal direction, The image deviation of the copy in the belt driving direction was examined. That is, the ideal copy position of the actual mark line copy position (a position 270 mm away from the reference line copy position)
The gap from was investigated. 5 deviations from ideal copy position
A case of less than 0 micron was regarded as pass (○), and a case of 50 microns or more was rejected (x).

(Presence or absence of defective transfer of toner) Using a solid black original, copying is performed on A4 transfer paper using a commercially available electrophotographic copying machine, the copy is visually checked, and a visible transfer loss (white Part) was checked. A case where there was no visible transition missing (white portion) was judged as pass (○), and a case where visible transition missing (white portion) occurred was judged as failed (×).

(Presence or absence of contamination of photoreceptor) A belt obtained by cutting a belt having a size of 3 × 5 mm was pasted on a photoreceptor of a commercially available electrophotographic copying machine, and left at 40 ° C. and 90% for 1 week. The copy was removed and a copy was made using a halftone original, and the copy image was visually observed to check whether unnecessary stains had occurred on the copy image.

The above test results are shown in the lower part of Table 1 together with the physical properties of the belt. In all of the examples and comparative examples, there was no contamination of the photoreceptor as in the case where a belt was formed with a conventional crosslinked rubber.

However, the melting point of Comparative Example 1 was 217 ° C.
In the case of using the polyester polyether resin, the loss tangent (tan δ) was too small than 0.1, the dynamic elastic modulus increased to 3.0 × 10 ¹¹ dyn / cm ² , and vibration was applied to the belt. Vibration does not decay quickly,
Further, since the flexibility in the thickness direction of the belt is poor, the followability of the belt to the photoreceptor surface is poor, and poor toner transfer occurs.

In Comparative Example 2 using a polyester polyether resin having a melting point of 154 ° C., the loss tangent (t
anδ) was larger than 0.2, which caused stress relaxation and transfer deviation.

On the other hand, in Examples 1 to 5 using a polyester polyether resin having a melting point in the range of 163 ° C. to 196 ° C., the loss tangent (tan δ) is in the range of 0.1 to 0.17, and Elastic modulus is also 8 × 10 ^{8 to} 1.2 × 10
^In the range of ¹¹ dyn / cm ² , all of them do not cause stress relaxation, have excellent vibration damping property of the belt and flexibility in the thickness direction of the belt, and do not cause transfer deviation and toner transfer failure.
Good quality images could be obtained.

Here, the case where the conductive seamless belt is used as the intermediate transfer belt has been described.
The same polyester polyether resin as the belts of Examples 1 to 5 was used, and the amount of the conductive filler was changed and the dimensions of the belts were adjusted. The resulting belt was used as a transfer belt, a fixing belt, and a developing belt. In addition, good results with improved performance were obtained.

[0043]

As is apparent from the above description, according to the conductive seamless belt of the present invention, the belt has appropriate flexibility in the thickness direction and can be rotated in a stretched state by a pulley. Does not grow,
In addition, the vehicle runs stably without significant vibration. Therefore,
The transfer performance, the sheet conveyance performance, the fixing performance, the developing performance, and the like are improved as compared with the related art, and a high-quality image can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a state in which a conductive seamless belt is used as a transfer belt in an image forming apparatus.

FIG. 2 is a schematic plan view illustrating a state in which a conductive seamless belt is used as a developing belt of a developing device in the image forming apparatus.

FIG. 3 is a schematic plan view illustrating a state in which a conductive seamless belt is used as an intermediate transfer belt in the image forming apparatus.

[Explanation of symbols]

 7, 8, 9 Pulley 10 Photoconductor 11 Intermediate Transfer Belt 12 Transfer Roller 13 Exposure Optical System 14 Charger 15 Developing Device 16 Cleaning Brush for Photoconductor 17 Transfer Charger

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI G03G 15/20 102 G03G 15/20 102 (58) Investigated field (Int.Cl. ⁷ , DB name) B65H 5/02 G03G 5 / 10 G03G 15/00 G03G 15/08 501 G03G 15/16 G03G 15/20 102

Claims (2)

(57) [Claims] 1. A volume specific resistance value of 1 × 10 ⁴ to 1 × 10
A conductive seamless belt having a conductive base layer in a range of ¹² Ω · cm, wherein the conductive base layer is obtained by dispersing a conductive filler in a polyester polyether resin having a melting point of 160 to 210 ° C. And a loss tangent (tan δ) of 0.1 to 0.2 when measured under measurement conditions of 23 ° C., 10 Hz, and 4% elongation strain.
The conductive seamless belt according to any one of the preceding claims. 2. The conductive base layer has a temperature of 23.degree.
^2. The conductive seamless belt according to claim 1, wherein the dynamic elastic modulus measured under the measurement conditions of z and elongation strain of 4% is in a range of 2.5 × 10 ^{8 to} 2.0 × 10 ¹¹ dyn / cm ^2. .