JP2002072699A - Intermediate transfer belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt which is capable of preventing the increase of electric resistance and can make residual potential smaller even when the belt is used for a long period. SOLUTION: The intermediate transfer belt of a four-layered structure used by being tented on tenting rollers 1 has a layer 2 which comes into contact with the tenting rollers 1 and is formed of a resin composition containing a conducting agent. The compounding ratio of this conducting agent is set at <=5 pts.wt. per 100 pts.wt. resin and the specific dielectric constant over the entire part of the intermediate transfer belt is set at <=23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate transfer belt used as an intermediate transfer member for copying a toner image on a photosensitive member in an apparatus employing an electrophotographic technique such as a full-color copying machine and a full-color printer.

[0002]

2. Description of the Related Art As an intermediate transfer member used in a full-color copying machine or the like, an intermediate transfer belt having a single layer or a multilayer structure is often used. Since the intermediate transfer belt is preferably semiconductive from the viewpoint of static elimination and the like, usually,
2. Description of the Related Art Conductive agents such as carbon black, metal oxides, and ionic conductive agents are blended in a binder of a layer other than the surface layer.

[0003]

However, if the intermediate transfer belt is subjected to image forming for a long period of time, the inner peripheral surface of the belt is worn by sliding contact with the tension roller, and the conductive agent may fall off. In addition, there is a problem that the electrical properties of the inner circumferential surface of the belt fluctuate with time (electric resistance increases) due to wear of the conductive agent itself, and image quality deteriorates.

Further, when the intermediate transfer belt is once stopped, a residual potential is generated at a contact portion between the belt and the photosensitive member, and a large amount of toner is developed at the portion when the intermediate transfer belt is reused. Band image unevenness (black band unevenness)
There is also a problem that occurs.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an intermediate transfer belt capable of preventing an increase in electric resistance and reducing a residual potential even when used for a long period of time. I do.

[0006]

In order to achieve the above object, an intermediate transfer belt of the present invention is formed by a resin composition containing a conductive agent having a single-layer or multilayer structure and used by being stretched over a stretching roller. Wherein the compounding ratio of the conductive agent in the layer in contact with the stretching roller is
A configuration is employed in which the relative dielectric constant of the entire intermediate transfer belt is set to 23 or less, and the relative dielectric constant of the entire intermediate transfer belt is set to 23 or less.

The inventor can prevent an increase in electric resistance,
In addition, intensive studies have been made to obtain an intermediate transfer belt capable of reducing the residual potential. In the process, the change in the electrical characteristics of the intermediate transfer belt due to the loss of the conductive agent or the wear of the conductive agent itself is due to the relatively large amount of the conductive agent in the layer contacting the tension roller. Was obtained.
Also, since the residual potential is proportional to the relative permittivity,
It has been found that, when the relative dielectric constant is set to be low, the residual potential is reduced and the occurrence of band-like image unevenness can be suppressed. Based on these findings, as a result of repeated experimental research, a resin composition in which the compounding ratio of the conductive agent was set to a specific range was used as the material for forming the layer that comes into contact with the tension roller of the intermediate transfer belt, and the ratio of the entire belt was It has been found that the desired object can be achieved by setting the dielectric constant to a specific range, and the present invention has been achieved.

[0008]

Next, an embodiment of the present invention will be described.

The intermediate transfer belt of the present invention is, for example, shown in FIG.
As shown in FIG. 1, the layer 2 that contacts the stretching roller 1, the first intermediate layer 3 adjacent thereto, the second intermediate layer 4 adjacent to the first intermediate layer 3, and the second intermediate layer 4 It consists of an adjacent surface layer 5. The drawing shows a state where the intermediate transfer belt is stretched over four stretching rollers 1.

The layer 2 (hereinafter referred to as "contact layer 2") which comes into contact with the stretching roller 1 is formed of a resin composition containing a conductive agent.

The resin in the resin composition is not particularly limited, and examples thereof include a fluororesin and a polycarbonate (P
C), polyethylene terephthalate (PET), vinyl chloride resin (vinyl chloride-vinyl acetate copolymer, etc.), A
Examples include BS resin, polymethyl methacrylate (PMMA), polyamide (PA), and the like. These may be used alone or in combination of two or more. Among these, a fluororesin is preferably used because it is excellent in both strength and flex fatigue.

As the fluororesin, for example, vinylidene fluoride-ethylene tetrafluoride copolymer [Poly (V
dF-TFE)], ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (P
CTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (P
FA) and the like. Among these, Poly
(VdF-TFE) is preferably used.

The conductive agent used together with the above resin includes metal powders such as aluminum powder and stainless steel powder;
_{c-ZnO, c-TiO 2} , c-Fe 3 O 4, c-Sn
Conductive metal oxides such as O _2, quaternary ammonium salts, phosphate esters, sulfonates, aliphatic polyhydric alcohols,
Examples include ionic conductive agents such as aliphatic alcohol sulfate salts, such as graphite, carbon black, and conductive carbon black. These may be used alone or in combination of two or more. Among these, conductive carbon black is preferred in that stable electrical properties can be obtained even with a small amount of compounding.

Examples of the conductive carbon black include commercially available products such as Denka Black HS-100 (manufactured by Denki Kagaku Kogyo) and Ketjen Black EC (Ketjen Black International).

[0015] The mixing ratio of the conductive agent is as follows.
It must be set to 5 parts or less for 00 parts by weight (hereinafter abbreviated as "part"). This is because by using such a small amount, the conductive agent is effectively prevented from falling off, and the electric resistance does not fluctuate greatly. The mixing ratio is 2 in consideration of the volume resistivity of the entire belt and the surface resistivity of the contact layer 2.
It is preferable to set it in the range of up to 4 parts.

The above resin composition may be blended with an antistatic agent, a crosslinking agent and the like, if necessary.

The material for forming the first intermediate layer 3 adjacent to the contact layer 2 is not particularly limited, and polyamide resins such as N-methoxymethylated nylon, nylon 12, and copolymer nylon are preferably used. These may be used alone or in combination of two or more.

The materials for forming the first intermediate layer 3 include:
If necessary, a conductive agent, an antistatic agent, a crosslinking agent and the like may be added.

The second intermediate layer 4 adjacent to the first intermediate layer 3
There is no particular limitation on the material for forming the above, and rubber, resin, and thermoplastic elastomer (hereinafter abbreviated as “TPE”) are preferably used.

The above rubber is not particularly limited, but for example, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber (SBR), butyl rubber, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM) ), Chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, acrylonitrile-butadiene rubber (NBR), urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, acrylic rubber, silicone rubber,
Fluorine rubber, polynorbornene rubber, hydrogenated nitrile rubber and the like can be mentioned. These may be used alone or in combination of two or more.

The above resin is not particularly limited. For example, fluorine resin, polypropylene, polycarbonate, polyimide, polyetheretherketone, A
BS resin and the like. These may be used alone or in combination of two or more.

The TPE is not particularly limited, but includes, for example, polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyamide, polyester and the like. These may be used alone or in combination of two or more.

The material for forming the second intermediate layer 4 includes:
If necessary, a conductive agent, an antistatic agent, a crosslinking agent and the like may be contained.

The material for forming the surface layer 5 adjacent to the second intermediate layer 4 is not particularly limited, and a fluorine-modified acrylic resin, silicone resin, fluorine resin, or the like is preferably used. These may be used alone or in combination of two or more. Above all, a fluorine-modified acrylic resin is preferred from the viewpoint of excellent toner releasability and the like.

The fluorine-modified acrylic resin is obtained by substituting part or all of the hydrogen atoms in the acrylic resin with fluorine atoms. For example, a perfluoroalkyl group having 1 to 20 carbon atoms is added to the side chain of the acrylic resin. Alternatively, it can be obtained by introducing a fluorine atom-containing group such as a partially fluorinated alkyl group by a conventionally known method.

The material for forming the surface layer 5 may contain an antistatic agent, a crosslinking agent, and the like, if necessary.

The intermediate transfer belt of the present invention can be manufactured using the above-described materials, for example, as follows. That is, first, a resin composition containing a conductive agent, which is a material for forming the contact layer 2, and a solvent are appropriately blended, kneaded with a ball mill or the like, and then stirred,
A coating liquid for forming the contact layer 2 is prepared. Similarly,
A coating liquid for forming the first intermediate layer 3, a coating liquid for forming the second intermediate layer 4, and a coating liquid for forming the surface layer 5 are prepared. In order to form each layer with high accuracy, it is preferable that the solvents used for preparing each coating liquid are different from each other. Then, the concentration of each coating liquid is appropriately set according to the thickness of the layer.

Next, each of the above coating liquids is accommodated in a tank 6, a tank 7, a tank 8 and a tank 9 as shown in FIG. On the other hand, a metal shaft (for example, aluminum, stainless steel, etc.) 10 is prepared, and the shaft 10 is set upright.
First, it is repeatedly immersed in the coating liquid contained in the tank 6. Then, after repeating the immersion a predetermined number of times,
The shaft body 10 is pulled up from the coating liquid. afterwards,
The same operation is performed to form a coating liquid layer composed of four layers. Then, after drying and removing the solvent, a heat treatment (for example, 60 to 150 ° C. × 60 minutes) is performed, and the shaft body 10 is extracted to obtain an intermediate transfer belt having a four-layer structure.

The intermediate transfer belt can be obtained by a method such as extrusion molding, spray coating, inflation, and blow molding other than the above-mentioned production method.

The relative dielectric constant of the entire intermediate transfer belt thus obtained must be set to 23 or less. By setting the relative dielectric constant low in this way, the residual potential after the charge is applied is reduced, and band-like image unevenness corresponding to the contact portion with the photoconductor is not generated. The relative dielectric constant is more preferably set in a range of 15 to 20 in consideration of the volume resistivity of the entire belt.

The volume resistivity of the intermediate transfer belt is preferably in the range of 1 × 10 ^{8 to} 5 × 10 ¹³ Ω · cm, and particularly preferably in the range of 1 × 10 ⁹ to 1 × 10 ¹³ Ω · cm. is there. That is, the volume resistivity is 1 × 10 ⁸ Ω · c
If it is less than m, the charge may decay too quickly and the capacity of the power supply may need to be increased, resulting in 5 × 10 ¹³ Ω · cm
This is because if it exceeds 300, the decay of the electric charges is too slow, and a system for removing electricity may be required. The volume resistivity is
It was measured with Mitsubishi Yuka's Hiresta.

Further, the surface resistivity of the contact layer 2 of the intermediate transfer belt is preferably in the range of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω / □, particularly preferably 1 × 10 ⁸ to 1 × 10 ¹⁰ Ω.
/ □ range. That is, the surface resistivity is 1 × 10 ⁶
If it is less than Ω / □, the charge may decay too quickly and the capacity of the power supply may need to be increased, and the surface resistivity may be 1 ×.
If it exceeds 10 ¹⁰ Ω / □, the charge decay is too slow, and there is a possibility that a static elimination system may be required. In addition, the surface resistivity was measured with Mitsubishi Yuka's Hiresta.

The thickness of each layer of the intermediate transfer belt is appropriately set according to the copying machine to be incorporated.
The contact layer 2 is 50 to 300 μm, and the first intermediate layer 3 is 1 to 50 μm.
μm, the second intermediate layer 4 is 50 to 300 μm, and the surface layer 5 is 0.1 μm.
It is set to 2 to 30 μm.

The intermediate transfer belt of the present invention is not limited to the four-layer structure as shown in FIG.
If a resin composition in which the blending ratio of the conductive agent is set in a specific range is used as the forming material of the belt and the relative dielectric constant of the entire belt is set in a specific range, a two-layer structure, a three-layer structure, or the like may be used. Or a single-layer structure.

The intermediate transfer belt of the present invention is mainly used for a transfer belt of a full-color copying machine, a full-color printer or the like, but may be used for a monochromatic electrophotographic copying machine which is not a full color.

Next, examples will be described together with comparative examples.

[0037]

Example 1 [Preparation of coating liquid for forming contact layer]
Poly (VdF-TFE) (Kynar SL, Elf
After dissolving 100 parts of Atochem Japan in acetone, conductive carbon black (DENKA BLACK HS-
100 parts, manufactured by Denki Kagaku Kogyo Co., Ltd.), and the mixture was stirred and dispersed by a sand mill to prepare a coating solution for forming a contact layer.

[Preparation of Coating Solution for Forming First Intermediate Layer] 100 parts of a polyamide resin (Toresin EF-30T, manufactured by Teikoku Chemical Industry Co., Ltd.) is mixed with a mixed solvent of water and methanol (water / methanol = 1/3). After dissolution, c-SiO
₂ (Conductive tin oxide T-1, manufactured by Mitsubishi Materials Corporation) 60
Part by adding, stirring and dispersing with a sand mill,
A coating liquid for forming a first intermediate layer was prepared.

[Preparation of Coating Solution for Forming Second Intermediate Layer] After dissolving 100 parts of Poly (VdF-TFE) (Kynar SL, manufactured by Elf Atochem Japan) in acetone, c-TiO ₂ (titanium black) 13M, manufactured by Mitsubishi Materials Corporation) and stirred with a sand mill.
By dispersing, a coating liquid for forming a second intermediate layer was prepared.

[Preparation of Coating Solution for Forming Surface Layer] Fluorine-modified acrylic resin (a copolymer mainly composed of a partially fluorinated alkyl ester of acrylic acid and methyl methacrylate, the content ratio of both being in the entire copolymer 75 parts by weight) and 400 parts of acetone were mixed and stirred to prepare a coating solution for forming a surface layer.

[Preparation of Intermediate Transfer Belt] First, the coating liquids for forming the respective layers were stored in separate tanks (see FIG. 2). Then, according to the method described above, a contact layer, a first intermediate layer, a second intermediate layer, and a coating liquid layer serving as a surface layer were sequentially formed around the aluminum shaft. Then, after the coating liquid layer was dried to remove the solvent, a heat treatment (60 to 150 ° C. × 60 minutes) was performed to form each layer. Then, by extracting the shaft body, an intermediate transfer belt having a four-layer structure was manufactured.

[0042]

Example 2 The amount of conductive carbon black was changed to 3.5.
A coating solution for forming a contact layer was prepared in the same manner as in Example 1 except that the parts were changed to parts. Then, using this coating liquid, an intermediate transfer belt having a four-layer structure was produced in the same manner as in Example 1.

[0043]

Example 3 The amount of conductive carbon black was 2.2.
A coating solution for forming a contact layer was prepared in the same manner as in Example 1 except that the parts were changed to parts. Then, using this coating liquid, an intermediate transfer belt having a four-layer structure was produced in the same manner as in Example 1.

[0044]

Example 4 A coating solution for forming a contact layer was prepared in the same manner as in Example 1 except that the amount of the conductive carbon black was changed to 5 parts. Then, using this coating liquid, an intermediate transfer belt having a four-layer structure was produced in the same manner as in Example 1.

[0045]

Example 5 In place of using conductive carbon black, TYPAKE ET-500W (manufactured by Ishihara Sangyo Co., Ltd.) was used.
In the same manner as in Example 1, a coating solution for forming a contact layer was prepared. Then, using this coating liquid, an intermediate transfer belt having a four-layer structure was produced in the same manner as in Example 1.

[0046]

Example 6 An intermediate transfer belt having a single-layer structure consisting of a contact layer was produced in the same manner as in Example 1 except that the first intermediate layer, the second intermediate layer, and the surface layer were not formed.

[0047]

Comparative Example 1 A coating liquid for forming a contact layer was prepared in the same manner as in Example 1 except that the amount of the conductive carbon black was changed to 30 parts. Then, using this coating liquid, an intermediate transfer belt having a four-layer structure was produced in the same manner as in Example 1.

[0048]

Comparative Example 2 A coating liquid for forming a contact layer was prepared in the same manner as in Example 1 except that the amount of the conductive carbon black was changed to 10 parts. Then, using this coating liquid, an intermediate transfer belt having a four-layer structure was produced in the same manner as in Example 1.

[0049]

Comparative Example 3 Ketjen Black EC (manufactured by Ketjen Black International) was used as a conductive agent, and the amount was 5 parts.
A coating solution for forming a contact layer was prepared. Then, using this coating liquid, 4
An intermediate transfer belt having a layer structure was manufactured.

The intermediate transfer belts of the examples and the comparative examples thus obtained were obtained according to the following criteria.
Each characteristic was evaluated. The results are shown in Tables 1 to 3 below.

[Relative Dielectric Constant] As shown in FIG. 3, platinum was deposited on the outer peripheral surface and the inner peripheral surface of the intermediate transfer belt to produce electrodes (shaded portions), and DC was measured using a YHP 4276A LCZ meter. The capacitance C [F] was measured under the conditions of the applied OFF, the applied AC voltage of 1 V, and the frequency of 1 KHz, and the relative dielectric constant ε was calculated by the following equation (α).

[0052]

[Number 1] _{ε = C × d / ε 0} × S ... (α) { wherein, d is the distance between the electrodes [m] (in this case, the thickness of the belt) indicates, epsilon ₀ is the vacuum dielectric constant (8 .855 × 10
⁻¹² [F / m]), and S represents the electrode area [m ² ]. ｝

[Volume resistivity] Using a resistivity meter Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd. and an attached HRS probe, the probe was pressed against the outer peripheral surface of the intermediate transfer belt with a constant load, and the applied voltage was 100 V and the application time was 10 seconds. , Volume resistivity was measured.

[Surface Resistivity of Contact Layer] After measuring the surface resistivity (initial) of the contact layer of the intermediate transfer belt immediately after the production, the intermediate transfer belt is incorporated in a commercially available full-color copying machine, and is used to continuously print 10,000 full-color images. Was done. Thereafter, the surface resistivity of the contact layer in the intermediate transfer belt after printing was measured. Then, a change in the surface resistivity of the contact layer from the initial stage (the initial stage was 1) was calculated. In the above measurement,
Mitsubishi Yuka's Hiresta IP resistivity meter and attached HR
Using an S probe, the probe is pressed against the surface of the contact layer (the inner peripheral surface of the intermediate transfer belt) with a constant load, and an applied voltage of 50
The measurement was performed at 0 V and an application time of 10 seconds.

[Residual Potential] The intermediate transfer belt was incorporated in a commercially available full-color copying machine, and an image was formed. Then, using a surface voltmeter, the residual potential immediately after the completion of the image output (initial residual potential) and the residual potential after being left for a certain time (one hour) were measured. Then, the fluctuation of the residual potential from the initial stage (the initial stage was set to 1) was calculated.

[Copy Image] * 1: Full-Color Image Quality The intermediate transfer belt was incorporated in a commercially available full-color copying machine, and 10,000 full-color images were continuously printed. The evaluation criteria were set as follows. ：: A good image was obtained without any color shift, no fine line insect biting, no background dirt, etc. Δ: A good image was obtained although color shift, biting of fine lines, background stains and the like were slightly observed. ×: Color shift, biting of fine lines, background stains, etc. occurred, and a good image could not be obtained. * 2: Presence or absence of black belt unevenness After 10,000 sheets of continuous printing, the sheet was left for several hours. Thereafter, a full-color image was printed again. The evaluation criteria were set as follows. ：: No horizontal black band unevenness occurred in the initial image. X: Black band unevenness in the horizontal direction occurred in the initial image.

[0057]

[Table 1]

[0058]

[Table 2]

From the results shown in Tables 1 and 2, it can be seen that the intermediate transfer belt of the example product has a small variation in electric resistance, a small residual potential, and a good image. On the other hand, the product of Comparative Example 1 has a large amount of the conductive agent and a large relative dielectric constant.
Moreover, it can be seen that the residual potential is large. Comparative Example 2
It can be seen that the product has a large variation in electrical resistance because of the large amount of the conductive agent. It can be seen that the product of Comparative Example 3 has a large residual potential because of a large relative dielectric constant.

[0060]

As described above, in the intermediate transfer belt of the present invention, the layer in contact with the tension roller is formed of the resin composition in which the conductive agent is mixed at a specific mixing ratio. The relative dielectric constant of the whole is set in a specific range. Therefore, the electric resistance does not increase due to the drop of the conductive agent or the like, and the residual potential does not increase. Therefore, when the intermediate transfer belt of the present invention is incorporated in an actual machine and used, an excellent image can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating an example of an intermediate transfer belt of the present invention.

FIG. 2 is an explanatory view showing an example of a method for producing an intermediate transfer belt of the present invention.

FIG. 3 is an explanatory diagram illustrating a method of measuring a relative dielectric constant of an intermediate transfer belt.

[Explanation of symbols]

 1 Stretch roller 2 Layer in contact with stretch roller

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H032 AA15 BA09 BA23 4J002 BB101 BD041 BD081 BD121 BD141 BD151 BG061 BN151 CF061 CG001 CL001 DA026 DA036 DA086 DA096 DE096 DE106 DE116 DE136 EC026 EN136 EV186 EV256 EW046 FD116 GM01

Claims (3)

[Claims] 1. An intermediate transfer belt formed of a resin composition containing a conductive agent having a single-layer or multi-layer structure, which is used by being stretched over a stretching roller, wherein the conductive agent in a layer in contact with the stretching roller is provided. Is set to 5 parts by weight or less with respect to 100 parts by weight of the resin, and the relative dielectric constant of the entire intermediate transfer belt is set to 23 or less. 2. The volume resistivity of the entire intermediate transfer belt is 1
× 10⁸~ 5 × 10 ¹³2. The method of claim 1, wherein the resistance is Ω · cm.
Transfer belt. 3. The intermediate transfer belt according to claim 1, wherein the layer in contact with the stretching roller has a surface resistivity of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω / □.