JPH066455B2 - Transfer belt used in image forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a transfer belt used in an image forming apparatus such as a PPC (plain paper copying machine).

2. Description of the Related Art Generally, a transfer belt used in a PPC (plain paper copying machine) performs the functions of conveying a sheet, transferring an image to the sheet, and separating the transferred sheet. After the transfer, it is necessary to remove the electric charge remaining on the belt surface by a static eliminator, which causes a problem that the manufacturing cost of the printer is high.

Therefore, the present applicant has a good charge characteristic (charge acceptability) in the transfer area, and therefore can transfer an image from the photoconductor drum very well, and the charge potential is gradually attenuated after that, so that the charge Therefore, a transfer belt used in an image forming apparatus has been proposed, in which the conventional static eliminator is completely unnecessary, the number of components of the image forming apparatus is reduced accordingly, and the manufacturing cost is low. See Japanese Patent Application No. 61-46963).

However, with the transfer belt proposed in the above, the transfer and the separation of the paper are surely performed smoothly under the conditions of normal temperature and normal humidity. However, for example, when the transfer belt is exposed to high temperature and high humidity such as during the rainy season. Under the conditions, the surface of the transfer belt absorbs moisture,
There was a problem that the resistance was apparently lowered, the surface voltage required for the transfer was not obtained, and the transfer failure occurred. Therefore, in order to obtain the required voltage even under such high temperature and high humidity conditions, the resistance of the dielectric layer was increased, or the voltage itself applied to the transfer belt was increased. Under normal temperature and humidity conditions, the voltage on the belt surface becomes too high, transfer defects occur and the image is disturbed, or the charge is not neutralized due to the natural decay of the charge.
There was a problem that a static eliminator was needed.

An object of the present invention is to solve the above problems, the charging voltage on the belt surface is hardly reduced even under high temperature and high humidity conditions, and transfer and paper separation are performed extremely smoothly and stably. It is an object of the present invention to provide a transfer belt used in an image forming apparatus which does not use a static eliminator and which is very inexpensive to manufacture.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention comprises a thermoplastic elastomer containing a conductive filler, and 10 ⁷
An inner semiconductive layer having a volume resistivity of 10 ¹² Ω · cm;
Made of a thermoplastic elastomer containing a hydrophilic group and 10 ¹⁰
And an outer dielectric layer having a volume resistivity higher than that of the inner semiconductive layer and having a volume resistivity of 10 ¹⁶ Ω · cm to 10 ¹⁶ Ω · cm, and both layers are integrally joined in an endless annular shape,
The surface of the outer dielectric layer is treated with a solution containing a metal compound, whereby the hydrophilic group of the thermoplastic elastomer on the surface is bonded to the metal compound, and the hygroscopicity of the surface is reduced. The main point is a transfer belt used in an image forming apparatus.

In the above, the inner semiconductor layer is made of a thermoplastic elastomer and a conductive filler is mixed therein.

Here, the thermoplastic elastomer used as the material of the inner semiconductive layer is a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polybutadiene-based thermoplastic elastomer, or a polyamide-based thermoplastic elastomer. It is at least one thermoplastic elastomer selected from the group consisting of thermoplastic elastomers, ethylene-vinyl acetate thermoplastic elastomers, polyethylene thermoplastic elastomers, fluorine thermoplastic elastomers, and polyvinyl chloride thermoplastic elastomers.

The conductive filler contained in the inner semiconductive layer is made of at least one conductive substance selected from the group consisting of carbon black, metal powder, carbon fibers and metal fibers. The conductive filler content is usually 5 to 2
It is 0% by weight.

The thickness of the inner semiconductive layer is not particularly limited, but is usually 2
Used in the range of 00 μm to 1 mm. The inner diameter of the inner semiconductive layer is, for example, 100 to 150 mm.

On the other hand, the hydrophilic group contained in the thermoplastic elastomer forming the outer dielectric layer is -NHCO-, -NHCOO-,-.
COO-, -CO-, -NH-, -COOH-, -NH
It is at least one group selected from the group consisting of ₂ and —OH.

The thermoplastic elastomer used as the material for the outer semiconductive layer is selected from the group consisting of a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, and an ethylene-vinyl acetate-based thermoplastic elastomer. At least one thermoplastic elastomer.

The thermoplastic elastomer constituting the outer dielectric layer is preferably a linear polymer in terms of molecular structure, and the longer the linear chain, the better the charging potential retention rate. For example, it is preferable to use a polyamide-based thermoplastic elastomer,
This is expressed by the following equation.

HO {[CO-NH- (CH _{2) p] m CO- (CH 2) 12 -} CO- [O- (CH _{2) 4] n]} l} OH wherein a p = 5 or 11.

The thickness of the outer dielectric layer is usually 10 to 100 μm, preferably 20 to 60 μm. Here, if the thickness of the outer dielectric layer exceeds 100 μm, the charging voltage may be lowered during charging due to corona discharge, and transfer defects may occur. In addition, the corona discharge voltage must be increased, which increases power consumption, which is not preferable. On the other hand, if it is less than 10 μm, the durability of the transfer belt deteriorates due to abrasion of the outer dielectric layer due to contact with the photosensitive drum, which is not preferable.

The transfer belt has an inner semiconductive layer of 10 ⁷ to 10 ¹² Ω.
-Having a volume resistivity of cm and an outer dielectric layer of 10 ¹⁰ to 10
^The latter has a volume resistivity of ¹⁶ Ω · cm and the latter has a higher volume resistivity than the former.

Here, if the volume resistivity of the inner semiconductive layer is less than 10 ⁷ Ω · cm and the volume resistivity of the outer semiconductive layer is less than 10 ¹⁰ Ω · cm, the charge escapes from the inner semiconductive layer. This is not preferable because the charge is easily applied to the surface of the outer semiconductive layer and the charging voltage on the surface of the outer semiconductive layer becomes low, the charge necessary for transfer cannot be obtained, and transfer failure occurs. The volume resistivity of the inner semiconductor layer exceeds 10 ¹² Ω · cm, and the volume resistivity of the outer semiconductor layer is 10 ¹⁶ Ω · cm.
On the other hand, if the electric charge exceeds the range, on the contrary, the electric charge does not escape from the inner semiconductive layer, and the electric charge on the surface of the outer semiconductive layer is too large to have a high electric charge, and a strong electrostatic attraction works with the toner particles. Then, it becomes difficult to stably separate and remove the toner particles, and it becomes difficult to separate the paper after transfer, which is not preferable.

The outer dielectric layer of the transfer belt has a higher volume resistivity than the inner semiconductive layer, and by appropriately setting the volume resistivity within the above range, charging of the transfer belt and its charge By facilitating the disappearance, the transfer onto the copy paper and the separation after the transfer can be performed smoothly and stably.

Further, the metal compound for treating the surface of the outer dielectric layer includes Cr ⁶⁺ , Cr ³⁺ , A ³⁺ , Fe ³⁺ , Cu ²⁺ , Ag ⁺ ,
Zn ²⁺ , Hg ₊ , Ti ⁴⁺ , Pb ²⁺ , Bi ³⁺ , Ce ³⁺ , C
It is an oxide, halide, carbonate, sulfate or nitrate of a metal selected from the group consisting of e ⁴⁺ . Of these, especially CrO ₃ , AlO ₃ , Fe ₂ O ₃ , Al
It is preferable to use Cl ₃ , FeCl ₃ and CuCl ₂ .

In order to treat the surface of the outer dielectric layer of the transfer belt, both side openings of the endless annular belt are sealed in advance, and the belt is immersed in a solution containing 1 to 20% by weight of the metal compound for 1 to 2 hours. It is carried out by immersing it for a while and then rinsing it with water. As a result, the metal compound is bound (chelated) to the hydrophilic group contained in the outer dielectric layer on the belt surface, and the surface is made hydrophobic, so that the belt surface does not absorb moisture even under high temperature and high humidity conditions. The charging voltage does not decrease.

The belt composed of the inner semiconductive layer, the outer dielectric layer, and the intermediate adhesive layer as the case may be is formed by simultaneously and integrally molding by, for example, extrusion blow molding.

Further, in order to reinforce the entire transfer belt, of the boundary portion between the inner semiconductive layer and the outer dielectric layer, particularly on the inner semiconductive layer side, organic fibers such as polyamide fiber and polyester fiber, or glass fiber, Inorganic fibers such as asbestos, and fibers made of these fibers, such as woven fabric, may be embedded.

Therefore, when the outer dielectric layer of this transfer belt is charged to a positive charge by a charger by corona discharge, it is charged to a potential of a required height, and this is held for a fixed time required for transfer or the like. After that, the charges move to the inner semiconductive layer having a lower volume resistivity than the outer dielectric layer, so that the charging potential is gradually attenuated and the charges disappear. Therefore, it is not necessary to remove the electric charge remaining on the surface of the transfer belt after transfer by a static eliminator as in the conventional case. In the present invention, particularly, the surface of the outer dielectric layer of the transfer belt is treated with a solution containing a metal compound, whereby the hydrophilic group contained in the thermoplastic elastomer on the surface is bonded with the metal compound, Since the hygroscopicity is reduced,
Even under conditions of high temperature and high humidity, the transfer voltage and the separation of the paper are smoothly performed with almost no decrease in the charging voltage.

Embodiment Next, an embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a PPC using the transfer belt according to the present invention.
(Plain paper copying machine). In the figure,
(1) is a photoconductor drum, (2) is a transfer belt of the present invention horizontally arranged below the photoconductor drum (1), which is a pair of front and rear rotation drive rollers (5) (6) It is wound around and rotated in synchronization with the photosensitive drum (1). (7) (7) is the paper feed timing, which is located near the beginning of the transfer belt (2).
A roll, (8) is a charger, and (9) is a cleaning blade disposed below the end of the transfer belt (2).

The transfer belt (2) is composed of an inner semiconductive layer (3) made of a polyurethane thermoplastic elastomer (ester type) containing 10% by weight of carbon black as a conductive filler, and a polyamide (nylon 12) type thermoplastic elastomer. The outer dielectric layer (4) is integrally connected in an endless ring shape. The transfer belt (2) has an inner diameter of 115 mm and a width of 320 mm, and the outer dielectric layer (4) has a thickness of 30 mm.
μm. Here, the properties of the inner semiconductive layer (3) and the outer dielectric layer (4) are as follows. Inner semiconductive layer (3) Hardness (JISA) 80 ° Breaking strength 430Kg / cm ² Breaking elongation 550% Tear strength 90Kg / cm Volume resistivity 1.6 × 10 ¹⁰ Ω · cm Thickness 300μm Inner diameter 115mm Outer dielectric layer (4) Hardness (Shore D) 62 ° Breaking strength 400 Kg / cm ² Breaking elongation 300% Volume resistivity 1 × 10 ¹² Ω · cm Thickness 30 μm The surface of the outer dielectric layer (4) of the transfer belt (2) is It was treated with various metal compounds as described below. That is, first, both side openings of an endless annular belt composed of the inner semiconductive layer (3) and the outer dielectric layer (4), which are materials for the transfer belt (2), are sealed, and then this belt is treated with water. And a solution containing 1% by weight of various metal compounds in a solvent consisting of an equal mixture of methanol and methanol, respectively, and immersed for 1 to 2 hours to react the hydrophilic groups contained in the outer dielectric layer of the belt with the metal compounds. After that, the transfer belt (2) according to the present invention was manufactured by washing with water and releasing the sealing of the openings on both sides of the belt.

In order to compare the above-mentioned transfer belt of the present invention (product of the present invention) with an untreated transfer belt (untreated product), charging characteristics were tested. That is, with an applied voltage of 6.5 KV, room temperature and normal humidity (25 ° C, 60% RH) and high temperature and high humidity (33 ° C, 8%)
The charged state was measured under the condition of 0% RH), and the obtained results are summarized in the following table.

As is clear from the above table, according to the transfer belt of the present invention, the decrease in the charging voltage on the belt surface under high temperature and high humidity can be changed to about 100 V, while the transfer of the untreated product can be performed. According to the belt, the charging voltage is lowered by 400 to 500 V under high temperature and high humidity, which hinders transfer.

According to the transfer belt (2) of the present invention, high temperature
Even under bad conditions of high humidity, a high voltage can be charged on the belt surface. After the transfer, the charge potential is gradually attenuated and the charge disappears. Therefore, when the paper is separated from the belt, there is no need to remove the charge, and thus a charge remover like the conventional one is unnecessary.

As described above, the transfer belt used in the image forming apparatus of the present invention is made of a thermoplastic elastomer containing a conductive filler and has an inner semiconductivity having a volume resistivity of 10 ⁷ to 10 ¹² Ω · cm. A body layer and an outer dielectric layer made of a thermoplastic elastomer containing a hydrophilic group and having a volume resistivity of 10 ¹⁰ to 10 ¹⁶ Ω · cm and higher than that of the inner semiconductive layer. Both layers are integrally bonded in an endless ring shape, and the surface of the outer dielectric layer is treated with a solution containing a metal compound, whereby the hydrophilic group of the thermoplastic elastomer on the surface is bonded to the metal compound. ,
Since the hygroscopicity of the surface is lowered, the charging voltage on the surface of the belt is hardly reduced even under the condition of high temperature and high humidity, and the transfer is performed extremely smoothly and stably. Further, the outer dielectric layer of the transfer belt has a higher volume resistivity than the inner semiconductive layer, and by appropriately setting the volume resistivity within the above range, the transfer belt is charged and transferred after transfer. The charge can be lost smoothly, and transfer to copy paper and separation after transfer can be performed smoothly and stably, eliminating the need for a conventional static eliminator and reducing the number of components of the image forming apparatus. In addition, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic side view of a PPC (plain paper copying machine) using the transfer belt of the present invention, and FIG. 2 is a partially enlarged sectional view of the product of the present invention. (1) ... Photosensitive drum, (2) ... Transfer belt, (3) ... Inner semiconductive layer, (4) ... Outer dielectric layer.

Claims (4)

[Claims] 1. An inner semiconductive layer made of a thermoplastic elastomer containing a conductive filler and having a volume resistivity of 10 ⁷ to 10 ¹² Ω · cm, and a thermoplastic elastomer containing a hydrophilic group, and 10 ¹⁰ to The outer dielectric layer has a volume resistivity of 10 ¹⁶ Ω · cm and is higher than the volume resistivity of the inner semiconducting layer, and both layers are integrally joined in an endless annular shape. By treating the surface of the body layer with a solution containing a metal compound, the hydrophilic group of the thermoplastic elastomer on the surface is bonded to the metal compound,
Characterized in that the hygroscopicity of the surface is reduced,
A transfer belt used in an image forming apparatus. 2. The hydrophilic group contained in the thermoplastic elastomer forming the outer dielectric layer is --NHCO--, --NHCOO.
-, -COO-, -CO-, -NH-, -COOH,-
The transfer belt according to claim 1, which is at least one group selected from the group consisting of NH ₂ and —OH. 3. A thermoplastic elastomer used as a material for the outer dielectric layer is selected from the group consisting of a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, and an ethylene-vinyl acetate-based thermoplastic elastomer. The transfer belt according to claim 1, which is at least one thermoplastic elastomer selected from the group consisting of: 4. The metal compound is Cr ⁶⁺ , Cr ³⁺ , A ³⁺ , F.
e ³⁺ , Cu ²⁺ , Ag ⁺ , Zn ²⁺ , Hg ⁺ , Ti ⁴⁺ , Pb
The transfer according to claim 1, which is an oxide, halide, carbonate, sulfate or nitrate of a metal selected from the group consisting of ²⁺ , Bi ³⁺ , Ce ³⁺ and Ce ^4+. belt.