JPH0317671A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a developing roller hardly sclatched on its surface and capable of impressing a developing bias stable for a long time by forming a conductive layer on the peripheral surface of a metal shaft through an elastic body layer and bringing the surface of the conductive layer with the surface of the metal shaft into contact through a conductive member. CONSTITUTION:The developing roller 1 is constituted of the metal shaft 2, the elestic body layer 3 provided on the peripheral surface of the metal shaft 2, the conductive layer 4 formed on the peripheral surface of the elastic body layer 3, and the conductive members 5,5 provided so as to bring both edges of the conductive layer 4 into contact with the metal shaft 2 through it. As for the developing roller 1, a prescribed elastic force can be obtained by the elastic body layer 3, and a bias voltage can be stably supplied to the conductive layer 4, which is formed on the periphery surface of the elastic body layer, from the metal shaft 2 through the conductive member 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device for visualizing an electrostatic latent image used in an electrophotographic device, an electrostatic recording device, or the like.

(Prior Art) A pressure development method is known as a development method using a one-component developer. This method is characterized in that the electrostatic latent image and toner particles are brought into contact with each other such that the relative circumferential speed of the photoreceptor drum, which is the electrostatic 7Is latent image holder, and the developing roller, which is the toner carrier, is substantially constant. There is.

Since this method does not require a magnetic material, it has many advantages such as the ability to downsize and simplify the device.

However, in the pressure development method, development is performed by pressing or contacting the developing roller with the photoreceptor drum, so the developing roller needs to have elasticity and conductivity.

In particular, in order to prevent the photosensitive drum from being scratched, it is essential that the developing roller be made of an elastic material. Further, in order to obtain the Piias effect or the developing electrode effect, it is necessary to provide a conductive layer at least on the surface of the roller or in the vicinity of the surface of the roller so that a bias voltage can be applied.

Therefore, in conventional developing devices of this kind, in order to apply a developing bias to the developing roller, the developing roller itself is made of a conductive elastic roller, or power is supplied by bringing an electrode into direct contact with the surface of the roller. A method was taken.

Another method has been to supply electricity by forming a conductive layer on the surface of the elastic roller and also providing a conductive layer on the side surface of the elastic roller and connecting it to a metal shaft.

However, if the developing roller is made of a conductive elastic material, it is necessary to use rubber or sponge which is made into a low resistance material by dispersing conductive carbon or the like. Since these rubbers and sponges lack flexibility, they suffer from large permanent deformation due to compression and may cause developing defects due to roller deformation. Further, the rubber or sponge subjected to the above-mentioned conductive treatment becomes expensive in terms of price. Furthermore, if power is supplied by bringing an electrode into direct contact with the conductive layer on the roller surface, the electrode may scratch the roller surface, resulting in poor development, or if used for a long period of time, the electrode may scratch the roller surface. There was a problem in that toner entered between the roller surfaces and the conduction between the electrode and the conductive layer became unstable.

Furthermore, if the conductive layer on the roller surface is also provided on the side surface of the roller and power is supplied from the metal shaft of the developing roller, the connection between the conductive layer and the metal shaft is fragile and may peel off after long-term use. This may cause unstable conductivity, or may cause poor conductivity due to peeling at the connection between the conductive layer on the side of the roller and the conductive layer on the surface of the roller, so it is necessary to obtain a voltage with a stable developing bias. There was a problem that it was not possible to

(Issue 8 to be Solved by the Invention) As described above, in the past, the surface of the roller was scratched and a stable developing bias voltage could not be applied.
There was a problem that good developing operation could not be performed.

The present invention has been made based on the above circumstances, and aims to provide a developing bias that is simple and inexpensive, does not damage the surface of the developing roller, and is stable over a long period of time. It is possible to apply voltage,
It is an object of the present invention to provide a developing device that can perform stable and good developing operations over a long period of time.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a developing roller having elasticity disposed opposite to an electrostatic latent image holding member that holds an electrostatic latent image; and a toner layer forming means for forming a thin toner layer on the surface of a developing roller, the developing device visualizing the electrostatic latent image by bringing the thin toner layer into contact with an electrostatic latent image holder, the developing device comprising: The roller is brought into contact with a metal shaft, an elastic layer provided on the outer peripheral surface of the metal shaft, a conductive layer formed on the outer peripheral surface of the elastic layer, and the surface of the conductive layer and the surface of the metal shaft. The structure includes a conductive member.

(Function) That is, an elastic layer is formed on the outer peripheral surface of the metal shaft, a conductive layer is formed on the outer peripheral surface of the elastic layer, and the surface of the conductive layer and the surface of the metal shaft are made conductive. Since the developing roller is constructed by making contact with the member, a predetermined elastic force can be secured by the elastic layer, and by bringing the electrode into direct contact with the metal shaft or the conductive member, the outer peripheral surface of the elastic layer can be A bias voltage can be stably supplied to the conductive layer formed on the substrate.

This allows the material of the elastic layer to be freely selected.
It is possible to obtain a developing roller that is inexpensive, has high flexibility, and has little deformation, and is unlikely to cause image density unevenness caused by deformation of the developing roller, and even if deformation or eccentricity occurs for some reason, It is possible to easily set a developing nip width sufficient to cover such fluctuations. In addition, there is no occurrence of ground force blur, scratches on the roller surface, peeling of the conductive layer, etc. due to poor bias conduction, and it is possible to obtain high-quality images without density unevenness, ground force blur, etc. over a long period of time.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows a developing roller 1 as a toner carrier used in the present invention.

The developing roller l includes a metal shaft 2, an elastic layer 3 provided on the outer circumferential surface of the metal shaft 2, a conductive layer 4 formed on the outer circumferential surface of the elastic layer 3, and a conductive layer 4 formed on the outer circumferential surface of the elastic layer 3. The conductive member 5.5 is provided in contact with both ends of the metal shaft 2.

The metal shaft 2 was made of stainless steel and had a diameter of 8 mm.

The elastic layer 3 is made of NBR rubber, and is made of JI
It has a hardness of 20 to 40 degrees on the A type hardness tester of S standard K 6301, and the outer diameter is 20.2 mm.

The electrical resistance value of NBR rubber is determined by placing an NBR rubber roller in parallel to contact with a stainless steel roller of the same shape, and applying 1. The result was calculated by measuring the current observed when a potential difference of O O V was provided, and the result was 3.5×10''Ω·.

The conductive layer 4 is made by dispersing conductive carbon particles in a polyurethane resin to give it a conductivity of 106 Ω·cm, and is made by applying a conductive polyurethane paint to the NBR rubber surface, drying it, and then heat-treating it. formed.

The conductive member 5 is formed of urethane foam impregnated with carbon or the like, has a volume resistivity of 106Ω, and has an annular flange portion 5a with an outer diameter of 22 mm, an inner diameter of approximately 8 mm, and a thickness of 7 mm. has.

The conductive member 5 is fitted onto the metal shaft 2, and the flange 5a is placed over the outer circumferential surface of the end of the conductive layer 4, so that the inner circumferential surface thereof is brought into contact with the conductive member 5. Moreover, the conductive members 5, 5
is adhered to the outer circumferential surface of the end portion of the conductive layer 4 and the outer circumferential surface of the metal shaft 2 with a conductive adhesive.

FIG. 2 shows a developing device 8 that employs this developing roller.Inside the device main body 10, there is a developing roller 1, a toner supply roller 11, a doctor 12 as a toner layer forming member, and a glue cover blade for preventing toner spillage. 13, a toner stirring member 14, and the like are incorporated.

Further, the developing roller 1 is in a state in which a part of its circumferential surface is in light pressure contact with the photosensitive drum 15 as an electrostatic latent image holder, and the above-mentioned doctor 1 is provided on the upper part of the developing roller 1.
2, the recovery blade l3 is disposed at the bottom.

Further, the toner supply roller 11 is provided below the developing roller 1 and at a position facing the bottom of the toner container 16, and the toner stirring member 14 is provided in the toner container 16 for stirring the toner t, which is a developer material. is now installed.

Further, the doctor 12 is formed by molding the tip of silicone rubber with a thickness of 2.0 mm into a semicircle with a radius of 1 ++ uw, and is arranged so that the center of the arc presses against the surface of the developing roller 1 with a predetermined pressure. There is.

The recovery blade 13 prevents the toner t stored in the toner container]-6 from spilling out of the developing device 8, and at the same time removes the undeveloped toner t on the surface of the developing roller 1.
It has a function of collecting the toner into the toner container 16 without spilling it, and in this embodiment, a urethane rubber sheet 13a having a thickness of 0.5 mm is bonded onto a sponge 13b.

The upper surface of the urethane rubber sheet 13a except for both ends is lightly pressed against the developing roller 1.

The toner supply roller 11 is made of soft polyurethane foam with a density of 75 kg/rn3 and a number of foam cells of 80/25 m, and its contact depth with the developing roller 1 is 0.5 m.
m, and the rotational circumferential speed is set to be 1/2 that of the developing roller 1.

The toner t used here is a negatively charged insulating different color toner in which carbon black is dispersed in a polyester resin, and the toner t is charged mainly by friction with the doctor 12, which is a thin toner layer forming member. There is.

Next, a developing device 8 equipped with the above-described developing roller 1
When we applied this to a laser beam printer, which uses a laser beam to illuminate an organic photoreceptor drum with a negatively charged surface to form a latent image and visualize it using a reversal development method, we obtained the following results. was gotten.

The potential of the image area, that is, the potential of the exposed area is -40V, the potential of the non-image area, that is, the potential of the unexposed area is -500V, and the developing bias (
When reversal development was performed with the voltage applied to the shaft 2 being -175 V and the contact width between the photosensitive drum 15 and the developing roller 1 being 1.5 mm, the image density was 1.4 and there was no fogging at all.
A printed sample with an extremely sharp line image was obtained.

Furthermore, a life test of 10,000 sheets was conducted using this developing device 8, and even at the end of the life test, toner t was left on the contact surface between the conductive members 5, 5 of the developing roller 1 and the conductive layer 4.
The state remained the same as the initial state without any occurrence of intrusion or peeling of the conductive layer 4.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and may be constructed, for example, as a developing port roller 1' as shown in FIGS. 4 and 5.

This involves forming an elastic layer 3 made of NBR rubber on the outer periphery of the metal shaft 2, and forming 45 degree cut portions 3a, 3a at the corners between both end faces and the periphery. Further, a conductive material is applied to cover the circumferential surface and both end surfaces of the elastic layer 3 to form the conductive layer 4. At this time, 45 degree cut portions 4a, 4a are formed at the corners between both end surfaces (both side surfaces) and the peripheral surface of the conductive layer 4.

In this embodiment, since the conductive layer 4 is also formed on both end surfaces of the elastic layer 3, the conductive member 5'5' is attached to both end surfaces of the conductive layer 4 and the outer peripheral surface of the metal shaft 2 using a conductive adhesive. It is glued to. At this time, a 45 degree cut portion 4a formed at the corner between both end surfaces (both side surfaces) and the peripheral surface of the conductive layer 4
, 4a have tapered flange portions 5a-, 5a of the conductive members 5, 5.
Glue. As a result, the conductive layer 4 and the conductive member 5',
5- can be made the same outer diameter. Note that the materials and the like are the same as those of the developing roller 1 shown in FIG.

) This developing roller 1' was attached to the developing device 8 shown in FIG. 2, and a life test was conducted under the same conditions as in the previous example. An extremely sharp line image with no fog was obtained at an image density of 1.4.

Furthermore, the adhesive surface between the conductive member 5''.5- and the conductive layer 4 remained in the same state as the initial state without any intrusion of toner t or peeling of the conductive layer 4.

For comparison with the present invention, an experiment was conducted on a developing roller not according to the present invention, in which a conductive layer 4 was formed on the circumferential surface and both end surfaces of the elastic layer 3 shown in FIG. (
(Other conditions were the same as in the previous example.) As for the initial image, a good image equivalent to that of the above-mentioned developing device was obtained. However, in a life test, the conductive layer 4 on both end surfaces of the elastic layer 3 began to peel off after approximately 2,000 sheets.
The conductivity state was lost after about 1,000 copies, and the image was blurred.

In addition, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various modifications without departing from the gist.

[Effects of the Invention] As explained above, according to the present invention, it is possible to apply a developing bias voltage stably over a long period of time without damaging the surface of the developing roller, while having a simple and inexpensive configuration. It is possible to provide a developing device that can stably form high-quality images without density unevenness, background blur, etc.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
Fig. 1 is a partially cutaway perspective view of the main part of the developing roller, Fig. 2 is a schematic configuration diagram of the developing device, Fig. 3 is a sectional view of the main part of the developing roller, and Figs. The drawings show another embodiment of the present invention; FIG. 4 is a partially cutaway perspective view of the main part of the developing roller, and FIG. 5 is a sectional view of the main part of the developing roller. 1...Developing roller, 2...Metal shaft, 3...
Elastic layer, 4... Conductive layer, 5.5''... Conductive member, 8... Developing device, 12... Toner layer type member (doctor), 15... Electrostatic latent image Holder (photosensitive drum),
t...Developer (toner). Figure 1 R Figure 2 Figure 3 Figure 5' 4a Figure 5

Claims (1)

[Scope of Claims] A developing roller having elasticity disposed opposite to an electrostatic latent image holding member that holds an electrostatic latent image, and a toner layer forming means for forming a thin toner layer on the surface of the developing roller. In a developing device that visualizes the electrostatic latent image by bringing the thin toner layer into contact with an electrostatic latent image holder, the developing roller includes a metal shaft and an elastic roller provided on the outer peripheral surface of the metal shaft. A body layer, a conductive layer formed on the outer peripheral surface of the elastic body layer, and a conductive member that is brought into contact with the surface of the conductive layer and the surface of the metal shaft. developing device.