JPH01276181A - Electrode component and toner transfer device - Google Patents

Abstract

PURPOSE:To obtain desired elasticity and resistivity independently by using the electrode component formed by laminating a resistance layer, a conductive layer, and an elastic layer from the side facing a transfer material. CONSTITUTION:A transfer roller 5 which is the electrode component used for a toner transfer device is composed of the resistance layer 1, the conductive layer 2, the elastic layer 3 which deforms elastically, and a metallic shaft 4 from the side facing the transfer material. The volume resistance value of the layer 1 is preferably 10<8>-10<15>OMEGA.cm and, specially, a range of 10<9>-10<12>OMEGA.cm is most preferably. The volume resistance value is easily controlled by varying the mixing rate of conductive particulates materials to resin or rubber. Further, the layer 2 is preferably as thick as possible so as to maintain the flexibility of the layer 3, and the thickness sum of the layers 1 and 2 is preferably <=1/10 as large as the thickness of the layer 3. Consequently, the influence of environmental humidity is small and elastic force characteristics and electric characteristics are controlled independently.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a toner transfer device.

(Prior Art) Devices that electrostatically transfer toner from a toner image carrier to a transfer material include devices that use a corona charger and devices that use a conductive roller or drum to apply a voltage from the outside.

Devices using a corona charger have a simple device configuration, so they are widely used in general monochrome copying machines. In this device, a corona charger generates charges from the back side of the transfer material, and an electric field formed by the charges attached to the transfer material transfers toner from the toner image carrier to the transfer material. In this device, even if the amount of charge generated by the corona charger is the same, the amount of charge attached differs depending on the electrical resistance of the transfer material, and the strength of the electric field changes. Therefore, the toner transfer efficiency also changes. The electrical resistance of plain paper, which is generally used as a transfer material, changes greatly depending on the environmental humidity, so when color is expressed by overlapping color toners as in color recording, the color balance is disrupted and stable color recording cannot be achieved. It was difficult to maintain. Also, even in monochrome recording,
Inter-image density changes often occurred due to environmental humidity.

Further, when the transfer material comes into contact with the toner image carrier and leaves the toner image bearing member, a gas discharge occurs due to the charge on the transfer material, causing the toner transferred to the transfer material to scatter, resulting in a problem that the image is disturbed. These are problems even in monochrome recording, but in color recording in particular, even if the electrical resistance of the recording paper that is the transfer material changes due to environmental humidity, the transfer efficiency of each color toner is stable, and the toner image of each color is not disturbed. There is a strong demand for the ability to overlap with high precision without any problems. In order to solve these problems, the following first-order proposals have been made. A corona discharge is performed from the back side of the insulating mesh attached to the hollow drum (the opposite side of the mesh in contact with the transfer material) to charge the transfer material and bring it into soft contact with the toner image carrier, and
After the toner is transferred, the insulating mesh is given an appropriate time constant to leak charge and prevent gas discharge (Japanese Patent Laid-Open No. 56
However, this method also does not solve the problem that the transfer efficiency changes due to the electrical resistance of the transfer material, which changes depending on the environmental humidity.

There is also a method that uses a soft conductive rubber roller (see Japanese Patent Laid-Open No. 50-22640). This method uses a foamed conductive rubber roller to apply an electric field between the transfer material and the toner image carrier. As a result, the transfer material is not charged, and therefore stable transfer efficiency can be maintained against environmental humidity. In addition, as the conductive roller is compressed, its electrical resistance decreases continuously, so the electrical resistance of the conductive roller is lowest at the point of contact between the conductive roller and the toner image carrier (toner transfer point). The transfer electric field becomes strong enough,
Since the electrical resistance increases before the two contact and when they separate, the electric field becomes weaker and gas discharge between the conductive roller and the toner image carrier is prevented.

(Problems to be Solved by the Invention) However, it has been difficult to accurately manufacture the shape of the foamable conductive rubber roller. In addition, in order to give conductivity to a foamed rubber roller, conductive particles such as conductive carbon black are generally mixed in, but depending on the mixing rate,
The elasticity of the rollers also varied, so that the desired elasticity was often not achieved. Further, there are problems such as discharge occurring within the bubbles inside the foamable conductive rubber roller, shortening the life of the foaming conductive rubber roller, and deteriorating the image quality due to this discharge.

Therefore, this invention was made in view of the above problems.
The purpose is to create an electrode structure for use in toner transfer devices that is less affected by environmental humidity and can independently obtain the desired elasticity and resistance. An object of the present invention is to provide a transfer device.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention provides, from the side facing the transfer material, a resistive layer whose resistance value does not change due to external pressure, a conductive layer, and an elastic layer that is elastically deformable. By using an electrode structure with a laminated structure, it has a mechanical function that allows soft contact between the transfer material and the toner image carrier, and an electrical function that is stable under the usage environmental conditions and that can provide the desired transfer voltage. The functions are separated and can be controlled independently so that each function can be fully achieved. In addition, this electrode structure is pressed against a toner image carrier with a transfer material in between, and a transfer voltage applying means supplies electricity to the conductive layer of the electrode structure to electrostatically transfer the toner to the transfer material. Configure the device.

(Function) By using the electrode structure of the present invention, elastic properties and electrical properties can be controlled independently. Further, an electrode structure having no air chambers and having excellent elasticity can be formed. Further, by using the toner transfer device of the present invention, a sufficient transfer voltage can be applied while elastically contacting the toner image carrier without applying high pressure.

(Example) Hereinafter, this invention will be explained in detail using the drawings.

FIG. 1 schematically shows a cross section of a transfer roller which is an embodiment of the electrode structure according to the present invention. 1 is a resistive layer, 2 is a conductive layer, 3 is an elastically deformable elastic layer, 4
is a metal shaft. The resistive layer 1 is made of resin such as polyester, polyethylene, or vinyl chloride, or rubber in which conductive fine particles such as conductive carbon, copper, or nickel fine metal particles are dispersed, or a flexible material such as conductive polymer resin. Excellent resistive sheets can be used.

The volume resistance value is 101 to 101 sΩ・l as described later.
A range of 10''-10''Ω·1 is particularly preferred. This type of volume resistance control is
This can be easily achieved by changing the mixing ratio of the conductive fine particles to the resin or rubber. In addition, it is desirable that the volume resistance value of the resistive layer does not change or changes only slightly in response to changes in external pressure and/or environmental conditions such as temperature and humidity.The resin sheet structure has an air chamber inside. Since it does not have a foam structure, its resistance value is stable against humidity compared to a foam structure. By having such characteristics,
Even if transfer materials of different thicknesses, such as paper or envelopes and postcards, come between the toner image carrier and the transfer roller, which are in pressure contact,
Alternatively, electrical toner transfer conditions can be maintained the same regardless of temperature and humidity. In addition, it is desirable that the surface of the resistive layer 1 be smooth. If unnecessary toner accumulates on the surface of the resistive layer 1, it will stain the back surface of the transfer material. The smoother the surface, the easier it is. The thickness of the resistive layer 1 is preferably as thin as possible in order not to impair the flexibility of the elastic N3, and is in the range of 0.02 to 21
A range of 111 is good. The conductive material M2 can be made of a conductive resin such as polyester with conductive fine particles such as conductive carbon dispersed therein, a thin sheet of metal, or a conductive adhesive, and must have conductivity and flexibility. The volume resistivity must be lower than that of resistive layer 1, 10'
It is Ω・1 or less. Furthermore, the thickness of the conductive layer 2, which must ensure electrical connection between the conductive layer 2 and the resistive layer 1, is preferably as thin as possible in order not to impair the flexibility of the elastic layer 3. By making the sum of the thicknesses of the resistive layer 1 and the conductive layer 2 less than 1/10 of the thickness of the elastic layer 3, the function of the elastic layer 3 is maintained. The elastic layer 3 that can be elastically deformed can be made of an elastic body that can be compressed and deformed, such as foamed rubber sponge, foamed polyethylene, or foamed urethane. Since the transfer roller 5 is used with a part of the toner image carrier in pressure contact, the elastic layer 3 must be flexibly deformed during the pressure contact and quickly return to its original shape when the pressure is released, and this process must be repeated. However, it is necessary to operate stably. In other words, a material with excellent creep resistance and plastic deformation resistance is desirable. The foam structure is a continuous first cell (open cell) structure.

Although any structure such as a closed cell structure can be used, the open cell structure is stable in shape regardless of the ambient temperature, so it can be preferably used. Foamed structure 2 Any desired structure can be obtained by changing the degree of foaming, and a hardness equal to or lower than the sponge rubber hardness of 30 for the closed cell structure is preferably used.

Furthermore, a part of the elastic layer 3 can be made into the conductive elastic layer 6 by subjecting the elastic layer 3 to conductive treatment from the end. Conductive elastic layer 6
electrically connects the conductive layer 2 and the shaft 4;
By supplying power to the resistive layer 1, it becomes possible to apply a voltage to the resistive layer 1. Furthermore, as shown in FIG. 2, it is also possible to expose a part of the conductive layer 2 and supply power from that part.
If the thickness of the elastic layer 3 is too thin, the flexible structure will not function, so it is necessary to have a thickness of 2 m or more. The manufacturing method of the transfer roller shown in FIG. 1 will be briefly explained. Foamed urethane with a rubber hardness of 20 was cast to a thickness of 10+ om around an SOS shaft with a diameter of 81 mm. A conductive treatment was applied to both ends of this sponge roller to form a conductive sponge layer having a volume resistivity of 104 Ω·l and having a width of about 5 mm at both ends of the urethane foam. Furthermore, on top of this, a conductive layer with a volume resistivity of 104Ω・1 and a resistive layer with a volume resistance of 1010Ω・G made by dispersing conductive force-bonds in a polyester resin are placed, each with a thickness of 0.1 m. It was cast and formed.

Next, the operation of an embodiment of the toner transfer device according to the present invention using the transfer roller shown in FIG. 1 will be described with reference to FIG. 3.

The toner image 8 on the toner image carrier 7 is transferred to the toner transfer portion (B-C section) according to the rotation of the toner image carrier (in the direction of the arrow).
will be transferred to. At the toner transfer section, the toner image 8 is pressed against plain paper 9, which is a transfer material.

During this time, a high transfer voltage of approximately 1 kV to 3 kV having a polarity opposite to the charge (negative polarity in this figure) of the toner image supplied from the high voltage generation circuit 10 acts on the toner image 8, and the toner image 8 is electrostatically The image is transferred onto plain paper 9 to form an image 11 on the plain paper 9. In the toner transfer section (B-C section), the toner image carrier 7 is elastically deformed by the elastic layer 3 of the transfer roller 5.
and plain paper are in close contact.

Forms a wide nip width. In this region, the flexible structure of the elastic layer 3 allows the transfer pressure to be kept almost constant 3. Furthermore, since the volume resistivity of the resistive layer 1 has almost no pressure dependence, it is possible to obtain uniform transfer conditions over the entire nip width region.

In roller transfer, if the transfer pressure is too high, a phenomenon occurs in which the toner in the center of the toner image is not transferred to the transfer material.For example, in character recording, only blank characters, that is, only the irregularities of the character shape are recorded. FIG. 5 shows the relationship between the transfer pressure and the rate of occurrence of voids when the toner transfer device of FIG. 3 is used. The proportion of hollow spots was expressed by transferring a square isolated toner image and calculating the proportion of the white background portion of the resulting transferred image to the overall image. If the percentage of hollow spots is 10% or less, a transferred image with no practical problems can be obtained. However, if the transfer pressure is too low, the nip width becomes narrow and the transfer density decreases. In the toner transfer device according to this invention, 20 to 30
A transfer pressure in the range 0 g/aJ is suitable, preferably a transfer pressure of 20 to 200 g/aJ is used. If the rubber hardness of the elastic layer of the transfer roller is 30 or less, the relationship shown in Figure 5 is maintained, but if the rubber hardness exceeds 30, the ability to elastically deform is reduced, and the transfer The pressure must be small 6 For example, rubber hardness approx. 4
5, the transfer pressure can only be used in the range of 20 to 50 g/i. Figure 6 shows the relationship between the volume resistance value of the resistive layer of the transfer roller and the toner transfer efficiency using environmental humidity as a parameter. The toner transfer efficiency is expressed as a percentage of the amount of toner transferred to the transfer material (referred to as the amount of transferred toner) to the sum of the amount of transferred toner and the amount of toner remaining on the toner image bearing member.

The resistive resin sheet forming the resistive layer can be designed with emphasis only on electrical properties. If the volume resistance value of the resistive layer is too low, when a transfer voltage is applied, discharge occurs between the layer and the toner image carrier, or toner of opposite polarity is generated due to charge injection, resulting in a significant reduction in transfer efficiency. Furthermore, if the volume resistance value is too high, the transfer voltage distributed to the toner layer will be low, and the transfer efficiency will be reduced. As shown in FIG. 6, the volume resistance value of the resistive layer of the transfer roller of the toner transfer device according to the present invention is preferably in the range of 101 to 101 sΩ・−, especially l
A range of 0″ to 10 12 Ω·d can be suitably used.

As described above, in the toner transfer device according to the present invention, the transfer conditions are mechanical, l! Since it is easy to maintain an electrically stable state and a toner transfer efficiency of 80% or more can be obtained even when the environmental humidity is 80% or more, good images can be obtained.

The electrode structure according to this invention may have a structure in which a conductive rubber layer 3' is provided between a conductive resin sheet 2 and a foamed rubber sponge layer 3, as shown in FIG. This configuration is used when it is necessary to strengthen the adhesive force between the polyester resin sheet 2 and the foamed rubber sponge 3. 1 is a resistive polyester resin sheet layer, 4 is a metal shaft,
6 is a foamed rubber sponge that has been treated to be electrically conductive.

Next, an embodiment in which the toner transfer device according to the present invention is applied to an electrophotographic device will be described with reference to FIG. This figure shows an electrophotographic apparatus incorporating a reversal developing device. A charger (102) is used to give a negative charge (103) to an organic photoreceptor (hereinafter referred to as OPC) (101), and an optical signal (10
4) to form an inverted electrostatic latent image. This electrostatic latent image is developed with a developer (106) having negative polarity toner biased (105) with a negative voltage of 600V, which is about the same as the surface potential on O20, and a visible image (107) is formed on O20.
Form on top. On the other hand, the transfer paper (108) is conveyed between the photoreceptor and the transfer roller (109), and is transferred by the transfer roller to which a positive voltage (110) of around 2 kV is applied, forming a toner image (111) on the transfer paper. . - The toner (112) remaining on the photoconductor is cleaned by a cleaner device (113), and the static charge on the photoconductor is erased by an erase lamp (114), so that the photoconductor can be used again. In the above-mentioned electrophotographic apparatus, the toner in the unnecessary image area on the photoreceptor, which is larger than the inside of the transfer paper, is directly transferred onto the transfer roller, causing the transfer roller to become stained. Furthermore, if a transfer error occurs in the transfer paper, the toner image portion on the photoreceptor will adhere to the transfer roller. Furthermore, even when the device is operating normally, the transfer roller becomes dirty due to adhesion of floating toner. Part 8 about how to remove toner stains on the transfer roller
This will be explained using figures. FIG. 8(,) is a schematic diagram when the transfer roller voltage is used to remove the toner adhered to the transfer roller and the toner is retransferred to the photoreceptor. This toner stain (121) on the transfer roller not only causes stains on the back side of the transfer paper, but also causes uneven transfer due to the insulating toner adhering to the transfer roller. In order to remove this toner, the negative polarity toner adhering to the transfer roller is passed through a polarity control charger (122) capable of applying a positive voltage of 5.5 kV in the direction of arrow B to make it positive. This toner (123) changed to positive polarity is reversely transferred onto the photoreceptor (101) by the same power source (124) as the transfer voltage of 600 V applied to the transfer roller. The toner (125) reversely transferred onto the photoconductor is removed by a cleaning device (11) installed around the photoconductor.
3), the photoreceptor returns to its initial state. Further, after the toner has been reversely transferred onto the photoreceptor, the toner is removed from the transfer roller and it can be used again. The residual potential on the photoreceptor in this series of steps may exist around 100V, but
A smaller potential is desirable. During the transfer roller cleaning process described above, the image forming process is not performed, and the cleaning is completed while the photoreceptor is moved one rotation. By stopping the operation of the developing device during this time, toner will not adhere to the photoreceptor, and the cleaning effect will be improved. Same figure (
b) is a method in which the toner adhered on the transfer roller is reversely transferred onto the photoreceptor without applying voltage to the transfer roller.

After completing the image forming process and cleaning, the cleaned photoreceptor (101) is given a surface potential of -600V by a main charger (102) with a negative charge (126) of the same polarity as that of the image forming process. This photoreceptor is a transfer roller (10
9) Transported to the department. On the other hand, the negative polarity adhering toner on the transfer roller is converted to positive polarity by a toner polarity control charger installed around the transfer roller, and the toner is reversed by adhering to a photoconductor having a negative surface potential. The photo ends. At this time, it is not necessary to apply a positive voltage to the transfer roller.

〔Effect of the invention〕

According to this invention, unlike charger transfer, no electric charge acts directly on the transfer material, so toner transfer can be performed with less influence from environmental humidity. Furthermore, since the toner image bearing member and the transfer material can be brought into soft and uniform contact, good toner transfer can be achieved without image smearing due to voiding or image deterioration due to toner scattering. Furthermore, since the transfer nip width is wide and a constant electric field strength can be maintained in that region, toner transfer with high transfer efficiency can be obtained. Furthermore, since there are no air bubbles in the resistive layer,
There is no air discharge inside the electrode structure, and a stable electrode structure with a long life can be provided. Furthermore, it is possible to obtain an electrode structure whose electrical properties and elastic properties can be designed independently and arbitrarily.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a transfer roller which is an embodiment of the electrode structure according to the present invention, FIG. 2 is a schematic cross-sectional view of a transfer roller which is a modified example of the electrode structure according to the present invention, and FIG.
The figure is a schematic explanatory diagram of one embodiment of the toner transfer device according to the present invention, FIG. 4 is a schematic cross-sectional view of a transfer roller which is another modification of the electrode structure according to the present invention, and FIG. FIG. 6 is a diagram for explaining the relationship between the transfer pressure and transfer characteristics in a toner transfer device using an electrode structure, and FIG. 6 is a diagram for explaining the relationship between the volume resistance value of the resistive layer of the transfer roller and the transfer characteristics. 7 is a schematic illustration of an electrophotographic recording apparatus incorporating a toner transfer device according to the present invention, and FIG. 8 is a diagram for explaining one method for removing toner adhering to a transfer roller. 1... Resistive layer 2... Conductive layer 3... Elastically deformable elastic layer 3'... Conductive rubber layer 5... Transfer roller 6.
...Conductive elastic layer 7...Toner image carrier 9...
Transfer material 10...Transfer voltage generation circuit agent
Patent Attorney Noriyuki Chika Ken Yudo Mitsuyuki Matsuyama Figure 1 Figure 2 Figure 4 Figure 5 4ρ2 □ Outside 1 resistance (n, c-) Figure 6 9Q-

Claims (5)

[Claims] (1) An electrode used in a toner transfer device that supplies power to an electrode structure that is placed in pressure contact with a toner image carrier across a transfer material, and electrostatically transfers toner from the toner image carrier to the transfer material. In the structure, from the side facing the transfer material,
An electrode structure characterized by having a laminated structure of a resistive layer/conductive layer/elastic layer that can be elastically deformed. (2) Volume resistivity of the resistive layer is 10^■ ~ 10^1^5
Ω・cm, preferably 10^9 to 10^1^2 Ω・c
The electrode structure according to claim 1, wherein the electrode structure is m. (3) The electrode structure according to claim 1, wherein the sum of the thicknesses of the resistive layer and the conductive layer is 1/10 or less of the thickness of the elastically deformable elastic layer. (4) In a toner transfer device that electrostatically transfers toner from a toner image carrier to a transfer material, it is provided so as to be in pressure contact with the toner image carrier across the transfer material, and is more resistant than the opposite side of the transfer material. A toner transfer device comprising: an electrode assembly in which a layer/conductive layer/an elastically deformable elastic layer are laminated; and a transfer voltage applying means for supplying a voltage to the electrode assembly. (5) 300g/cm^ of the electrode structure on the toner image carrier
5. The toner transfer device according to claim 4, wherein the pressure contact is made with a pressure of 2 or less.