JPH0623900B2 - 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) and a laser printer.

2. Description of the Related Art Generally, a transfer belt used in a PPC (plain paper copying machine) has functions of conveying a sheet, transferring an image to the sheet, and separating the transferred sheet. , A conductive sheet made of EPDM or polyurethane rubber containing a conductive filler such as carbon black and having a volume resistivity of 10 ⁶ Ω · cm or less on the inside,
On the other hand, a dielectric film having a volume resistivity of 10 ¹⁴ Ω · cm or more and having an insulating property is placed outside, and the both are bonded, and both ends of a composite sheet having a required length after bonding are joined to form an endless shape. It was manufactured by

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a conventional transfer belt, it is necessary to remove the electric charge remaining on the surface of the belt by a static eliminator after transfer. Also, in the conventional transfer belt, there is a step at the joint part of the composite sheet,
When cleaning with a blade, toner remained on the stepped portion, resulting in poor cleaning. If the joint of the transfer belt is not sufficiently joined, the transfer belt will break,
There is a problem that the durability of the transfer belt is very poor, such as the use of the copying machine must be interrupted.

Therefore, in order to solve the above-mentioned problems, conventionally, in a case where a toner image is transferred from an image carrier on which a toner image is formed to a transfer target, an insulating layer (outer dielectric) having a specific resistance of 10 ¹⁰ Ω · cm or more is used. Layer) and a conductive layer (inner conductor layer) having a specific resistance of 10 ⁸ Ω · cm or less, and a transfer device provided with a contact charger (for example, JP-A-56).
(See Japanese Patent Publication No. 154772).

According to such a conventional transfer device of the prior proposal, the charge characteristic (charge acceptability) is good in the transfer area, and therefore, the image can be transferred well from the photoconductor drum and the transfer which contacts the photoconductor is performed. The belt nip width can be made large, the applied voltage can be suppressed to a low level, and the endless ring shape does not have the seams or steps as in conventional products, resulting in poor cleaning or breakage during use. It had an advantage that it was excellent in durability.

The object of the present invention is to provide a transfer belt as described above,
Further, the charge characteristic (charge acceptability) of the outer dielectric layer is increased, the holding time of the charging potential becomes longer, and the holding time of the charging potential can be freely controlled. An object of the present invention is to provide a transfer belt for use in an image forming apparatus, which has improved slipperiness due to curing, requires only a small rotational torque of the transfer belt, and reduces power cost for driving the transfer belt.

Means for Solving the Problems In order to achieve the above object, the present invention comprises a thermoplastic elastomer or an ionomer with or without a conductive filler and has a volume resistivity of 10 ⁷ to 10 ¹² Ω · cm. Made of an inner semiconductive layer and a thermoplastic elastomer or an ionomer, and is 10 ¹² to 10 ¹⁶ Ω.
cm and an outer dielectric layer having a volume resistivity higher than the volume resistivity of the inner semiconductive layer, and
A transfer belt used in an image forming apparatus is characterized in that a surface of an outer dielectric layer is subjected to an isocyanate treatment in a transfer belt in which both layers are integrally bonded in an endless ring shape.

In the above, the inner semiconductive layer and the outer dielectric layer are made of different or the same kind of thermoplastic elastomer or ionomer, and a conductive filler is mixed in the inner semiconductive layer as necessary.

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

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 fiber and metal fiber.

The content of the conductive filler is usually 5 to 20% by weight.

As the thermoplastic elastomer or ionomer constituting the outer dielectric layer, a linear polymer is preferable in terms of molecular structure, and the longer the linear chain, the better the retention of the charging potential. For example, it is preferable to use a polyamide-based thermoplastic elastomer, which is represented by the following formula.

HO - [[CO-NH- _{(CH 2) p] m -CO- (CH 2) 12 -CO-} - [O- _{(CH 2) 4] n] Q} -OH where at p = 5 or 11 is there.

The thickness of the outer dielectric layer is 10 to 100 μm, preferably 20 to 60 μm. Here, if the thickness of the outer dielectric layer exceeds 100 μm, during charging due to corona discharge,
The charging voltage becomes low, which may cause transfer failure.
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 thickness of the inner semiconductor layer is used in the range of 200 μm to 1 mm. The inner diameter of the inner semiconductive layer is, for example, 100
~ 150 mm.

The inner semiconductive layer has a volume resistivity of 10 ⁷ to 10 ¹² Ω · cm, and the outer dielectric layer has a volume resistivity of 10 ¹² to 10 ¹⁶ Ω · cm.
In addition to having a volume resistivity of cm, the latter has a higher volume resistivity than the former.

An adhesive layer is optionally interposed between the inner semiconductive layer and the outer dielectric layer. Here, as the adhesive layer, an appropriate one is used depending on the types of the thermoplastic elastomer or ionomer constituting the base material of the inner semiconductive layer and the thermoplastic elastomer or ionomer constituting the outer dielectric layer.

In order to reinforce the entire transfer belt, organic fibers such as polyamide fiber and polyester fiber, or glass fiber, asbestos, especially on the inner semiconductive layer side of the boundary portion between the inner semiconductive layer and the outer dielectric layer. Inorganic fibers such as the above, and fiber layers such as yarns and woven fabrics made of these fibers may be embedded.

The transfer belt is made by molding the inner semiconductive layer, the outer dielectric layer, and optionally the intermediate adhesive layer simultaneously and integrally, for example by extrusion blow molding.

That is, a spiral mandrel die with two or three layers (when an intermediate adhesive layer is provided) is set, and the inner layer material is put into this die with an extruder with a diameter of 50 mm and a diameter of 32 mm, for example.
The outer layer material is extruded at the same time with the extruder, thereby obtaining a tubular molded product in which the inner semiconductive layer and the outer dielectric layer are integrated, and the die outlet is provided with an air ring to keep the shape constant, and thereafter Cool to solidify the resin in both layers,
It is cut into a certain size.

The transfer belt according to the present invention is obtained by further treating the surface of the outer dielectric layer with an isocyanate solution to isocyanate the constituent polymer on the surface of the outer dielectric layer.

Isocyanate treatment such as this
A solution containing 20 to 20% by weight of the solution is applied to the surface of the outer dielectric layer of the transfer belt by a method such as a dipping method, a spray method or a tube coating method.
It is carried out by heating at 0 to 150 ° C. for 0.5 to 3 hours.

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 ¹² to 10
^The latter has a volume resistivity of ¹⁶ Ω · cm and the latter has a higher volume resistivity than the former. Therefore, when the outer dielectric layer of this transfer belt is positively charged by a charger, it is charged to a potential of a required height,
This is maintained for the fixed time required for transfer.

In the transfer belt according to the present invention in which the outer dielectric layer is isocyanated, the charge characteristic (charge acceptability) of the outer dielectric layer is increased and the holding time of the charging potential becomes longer. Therefore, by appropriately setting the conditions for the isocyanate treatment, it is possible to control the decay time of the charging potential. This is considered to be because when the polyamide-based thermoplastic elastomer of the above formula is used as the material for the outer dielectric layer, the CN group reacts with the terminal OH group to block the conductivity of electric charge.

In addition, the surface of the outer dielectric layer is hardened by the isocyanate treatment, so that the slipperiness is improved, and therefore the contact resistance with the cleaning blade is reduced, and the rotational torque of the transfer belt is small, which in turn drives the transfer belt. Power costs are reduced.

Further, in the transfer belt, after the transfer, the electric charge is transferred 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 electric charge disappears. Therefore, after transfer, it is not necessary to remove the electric charge remaining on the surface of the transfer belt by a static eliminator as in the conventional case, and the conventional static eliminator is completely unnecessary.

In addition, the transfer belt is an endless loop and has no seams or steps as in conventional products, so there is no possibility that cleaning failure will occur due to residual toner during cleaning, or there will be no breakage during use. It has excellent properties.

Embodiment Next, an embodiment of the present invention will be described with reference to 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 horizontally arranged under the photoconductor drum (1), which is wound around a pair of front and rear rotary drive rollers (5) and (6). , Photoconductor drum (1)
It is made to rotate in synchronization with. (7) (7) is a transfer belt (2)
Timing roll for paper feeding, which is located near the beginning of the
Reference numeral (8) is a charger, and reference numeral (9) is a cleaning blade disposed below the end portion of the transfer belt (2).

The transfer belt (2) comprises 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 50 mm.
μm. Here, the properties of the inner semiconductive layer (3) and the outer dielectric layer (4) are as follows.

The transfer belt (product of the present invention) according to the present invention comprises an outer dielectric layer (4) of the transfer belt (2) (referenced to this).
The surface of is treated with isocyanate as follows. That is, the above reference product was added to a solution of 10% by weight of isocyanate and 90% by weight of methyl ethyl ketone.
Soak for 10 seconds, let it air dry in the room for 30 minutes, then
It was kept in a thermostatic chamber at 0 ° C. for 1 hour and dried to obtain a transfer belt (invention product) having an outer dielectric layer that was isocyanated.

Inner Semiconductive Layer (3) Hardness (JISA) 80 ° C Breaking Strength 430kg / cm ² Breaking Elongation 550% Tear Strength 90kg / cm Volume Resistivity 1.6 × 10 ¹¹ Ωcm Thickness 300μm Inner Diameter 115mm Outer Dielectric Layer (4) Hardness (Shore D) 62 ° Breaking strength 400 kg / cm ² Breaking elongation 300% Dielectric constant 3 Volume resistivity 1 × 10 ¹³ Ω · cm Thickness 50 μm The transfer belt of the present invention (the present invention) and the outside Dielectric layer
In order to compare a reference transfer belt (reference product) in which (4) was not isocyanated with a conventional transfer belt (conventional product), charging characteristics were tested. That is, the applied voltage is 7.5 KV, and the humidity is 40% R at room temperature (25 ° C).
H and 100% RH were measured for their respective charged states immediately after humidification, and the obtained results are shown in FIGS. 3 and 4.

Referring to FIG. 3, when the humidity is 40% RH, the reference product is
A charge of +1000 V was generated, which was maintained for 1.7 seconds, then gradually decreased, and the charge disappeared after 4 seconds. On the other hand, in the product of the present invention, a charge of +1200 V occurred, which was held for 2.6 seconds, then gradually attenuated and the charge disappeared after 7 seconds. On the other hand, in the case of the conventional product, + 1500V was charged, which was maintained as it was.

Referring to FIG. 4, under the bad condition of the humidity of 100% RH, the reference product is charged with +750 V, which is 1.3%.
After being held for a second, the charge gradually decayed and the charge disappeared after 2 seconds. On the other hand, in the product of the present invention, a charge of +1200 V occurred, which was held for 2.2 seconds, then gradually decreased and the charge disappeared after 6 seconds. On the other hand, the conventional product is +15
A charge of 00 V was generated, which was maintained unchanged.

As is apparent from the results shown in FIGS. 3 and 4, according to the conventional product, it is necessary to remove the electric charge remaining on the transfer belt surface after transfer by using a static eliminator. On the other hand, according to the product of the present invention and the reference product, the charge potential is gradually attenuated after the transfer, and the charge disappears. Therefore, when the paper is separated from the transfer belt, it is not necessary to perform the charge removal, and thus the conventional method is used. A static eliminator such as is unnecessary. It should be noted that the product of the present invention, which has been subjected to the isocyanate treatment, has better charge characteristics than the reference product, and has a longer charge retention time. Further, by changing the conditions of the isocyanate treatment, it is possible to easily control the charge characteristics and the charge retention time.

Although the present invention is applied to the transfer belt of a PPC (plain paper copying machine) in the above embodiment, the present invention is of course applicable to a transfer belt used in a laser printer or the like. .

EFFECTS OF THE INVENTION The present invention, as described above, comprises an inner semiconductive layer made of a thermoplastic elastomer or an ionomer with or without a conductive filler and having a volume resistivity of 10 ⁷ to 10 ¹² Ω · cm; An outer dielectric layer made of a plastic elastomer or an ionomer and having a volume resistivity of 10 ¹² to 10 ¹⁶ Ω · cm and higher than that of the inner semiconductive layer, and both layers are endless ring-shaped. In the transfer belt that is integrally bonded to the transfer belt, the surface of the outer dielectric layer is subjected to isocyanate treatment. When the outer dielectric layer of the transfer belt is positively charged by a charger, the required height is increased. It is charged to an electric potential and is held for the fixed time required for transfer. Therefore, in the transfer area, the charge characteristic (charge acceptability) is good, and the image can be transferred from the photosensitive drum to the paper very well.

Further, in the transfer belt according to the present invention in which the outer dielectric layer is made into isocyanate, the charge characteristic (charge acceptability) of the outer dielectric layer is further increased, and the holding time of the charging potential becomes longer. Therefore, by appropriately setting the conditions of the isocyanate treatment, the holding time of the charging potential can be freely controlled. Further, the surface of the outer dielectric layer is hardened by the isocyanate treatment, so that the slipperiness is improved, so that the contact resistance with the cleaning plate is reduced, the rotational torque of the transfer belt is small, and the transfer belt is driven. There is an effect that the power cost of is reduced.

Further, in the transfer belt, after the transfer, the electric charge is transferred 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 electric charge disappears. Therefore, after transfer, it is not necessary to remove the electric charge remaining on the surface of the transfer belt by a static eliminator as in the conventional case, and the conventional static eliminator is completely unnecessary. In addition, the transfer belt is an endless loop and has no seams or steps as in conventional products, so there is no possibility that cleaning failure will occur due to residual toner during cleaning, or there will be no breakage during use. It has the advantage of being excellent in nature.

[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, FIG. 2 is a partially enlarged sectional view of the transfer belt, and FIGS. 3 and 4 show the results of the charging characteristic test. It is a curve figure respectively shown. (1) …… Photosensitive drum, (2) …… Transfer belt, (3) ……
Inner semi-conducting layer, (4) ... Outer dielectric layer.

Claims (3)

[Claims] 1. A thermoplastic elastomer or ionomer with or without a conductive filler and 10
An inner semiconductive layer having a volume resistivity of ⁷ to 10 ¹² Ω · cm, a thermoplastic elastomer or an ionomer, and a volume resistivity of 10 ¹² to 10 ¹⁶ Ω · cm, which is based on the volume resistivity of the inner semiconductive layer. And an outer dielectric layer having a high volume resistivity, both layers being integrally bonded in an endless ring shape, wherein the surface of the outer dielectric layer is subjected to isocyanate treatment. A transfer belt used in an image forming apparatus. 2. A thermoplastic elastomer used as a material for the inner semiconductive layer and the outer dielectric layer is a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, or polybutadiene. At least one selected from the group consisting of thermoplastic thermoplastic elastomers, thermoplastic polyamide elastomers, thermoplastic ethylene-vinyl acetate thermoplastic elastomers, thermoplastic thermoplastic polyethylenes, thermoplastic thermoplastic fluorines, and thermoplastic thermoplastic polyvinyl chlorides One of the thermoplastic elastomers, the conductive filler contained in the inner semiconductive layer is at least one conductive material selected from the group consisting of carbon black, metal powder, carbon fiber and metal fiber. A transfer belt in the range set forth in claim 1, wherein the those consisting of quality claims. 3. The isocyanate treatment comprises applying a solution containing 1 to 20% by weight of isocyanate to the surface of the outer dielectric layer and then heating at 80 to 150 ° C. for 0.5 to 3 hours. The transfer belt according to claim 1.