JPH07120112B2 - Toner layer forming device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a toner layer forming apparatus applied to an electrophotographic developing apparatus for developing using a magnetic toner, and in particular, developing while being carried on a toner carrier. The present invention relates to an improvement in an apparatus for forming a toner layer by regulating the layer thickness of a toner moving in a position direction by a toner layer thickness regulating member that is in contact with a toner carrier, and then applying magnetic force lines to the toner layer whose layer thickness is regulated.

“Prior Art” As a toner layer forming device conventionally applied to an electrophotographic developing device, a thin plate material called “Mylar” is brought into contact with a toner carrier that conveys toner to a developing position, and the toner layer thickness is changed by the contact pressure. There are those which regulate the toner layer thickness and those which arrange a toner layer thickness regulating member called a doctor blade on the toner carrier so as to face each other, and regulate the toner layer thickness by the distance between them.

However, in the former case, since the toner layer is formed by the contact pressure, the toner layer surface is likely to have streak unevenness. In the latter case, the spacing between the doctor blade and the carrier is extremely small according to the toner layer regulation thickness. Therefore, there is a problem in that toner agglomeration or clogging is likely to occur in the spacing, and extremely high mechanical precision is required for setting the minute spacing.

As a result of intensive studies conducted by the present inventors in order to solve the drawbacks of the prior art, first, the toner layer thickness regulating member for contacting the toner carried on the toner carrier and moving in the developing position direction with the toner carrier is contacted. After the layer thickness is regulated by the method described above, the magnetic field lines are applied to the toner layer whose layer thickness is regulated to form the toner layer, thereby simplifying the structure and forming a uniform toner layer without particularly requiring assembly accuracy. We have proposed a device that enables thinning. (Japanese Patent Application No. 59-268441) "Problems to be Solved by the Invention" The present invention further embodies such an apparatus and proposes an apparatus for more stable formation and uniformization of a toner layer.

That is, for example, the electrostatic latent image holding member is arranged on the downstream side of the toner layer forming position so as to face it, and the toner is selected by the electric field of the electrostatic latent image without directly contacting the toner layer with the electrostatic latent image holding surface. In the so-called flight developing method, in which the toner is selectively fly-transferred by the action of the electric field formed on the latent image holding surface, the toner required for the flight transfer is previously transferred. It is necessary to perform sufficient charging (charge injection).

For this reason, in the above-mentioned prior art, etc., this kind of charging is performed on the upstream side of the toner layer thickness regulation position or at the same time as the toner layer thickness regulation, and at the same time, the charge injection of toner is performed by frictional charging or corona discharge. In an apparatus for controlling the layer thickness by bringing the layer thickness regulating member into contact with the toner carrier as in the case of the prior art, since the sufficiently charged toner is rubbed at the contact position, the layer thickness regulating member side The electric charge becomes high, and as a result, the toner adheres to the regulating member side, and the toner adheres to cause toner aggregation and streak unevenness. For example, such kind of agglomeration and streak unevenness is unraveled by the magnetic action on the downstream side. However, it may not be solved, and may adversely affect development.

Moreover, the electric charge of the toner becomes unstable due to the rubbing,
After all, development may be adversely affected.

An object of the present invention is to provide a toner layer forming apparatus suitable for an apparatus that carries out development by transferring the toner in flight, but the present invention is not limited to this.
It can also be applied to an apparatus that develops by rubbing toner on the latent image holding surface.

[Technical Means for Solving the Problem] In the present invention, the toner that is carried on the toner carrier and moves in the developing position direction is regulated by a toner layer thickness regulating member that is in contact with the toner carrier through the toner. rear,
In a toner layer forming apparatus for unraveling toner by applying magnetic force lines to the toner layer whose layer thickness is regulated, a pair of fixed magnetic bodies of the same polarity are arranged on the back side of the toner carrier located in the toner unraveling region, A toner layer thickness formed of a non-magnetic conductive member that forms a repulsive magnetic field on the toner carrier and is grounded on the upstream side of the repulsive magnetic field formation region in the toner carrier rotation direction A technical means is proposed in which the regulating member is brought into contact with the toner layer thickness regulating member so that the surface potential of the toner layer thickness regulating member at the contact position is smaller than the absolute value of the image portion voltage of the electrostatic latent image holding surface.

By setting the surface resistance of the conductive member to 10 ⁹ Ω / cm ² or less, the surface potential can be set smaller than the absolute value of the image portion voltage of the electrostatic latent image holding surface, and Preferably, by setting the surface resistance to 10 ⁵ Ω / cm ² or less, the surface potential of the conductive member can be maintained substantially equal to the surface potential of the toner carrier.

Here, “substantially equivalent to the surface potential of the toner carrier” means
It means that the surface potential of the conductive member is set to be the same as the surface potential of the toner carrier or less than the toner binding potential of the toner carrier.

Further, the image portion voltage of the electrostatic latent image holding surface specifically refers to the maximum voltage of the latent image voltage formed in the image portion, and the reason why it is described as smaller than the absolute value is that the polarity of the toner causes This is because the voltage of the image portion becomes a positive voltage or a negative voltage.

That is, when the toner polarity is positive, it is preferable to maintain the relationship of Vg <Vm ≦ Vs, and when the toner polarity is negative, it is preferable to maintain the relationship of Vg> Vm ≧ Vs.

Vg: image area (maximum) potential Vm: conductive member surface potential Vs: toner carrier surface potential "action" According to such technical means, the toner layer thickness regulating member in contact with the toner carrier controls the layer thickness of the charged toner. While being regulated, since the side of the toner layer thickness regulating member that contacts the toner carrier is composed of a non-magnetic conductive member that is grounded, the charged toner has a toner layer thickness regulating member and a toner carrier. Even if the layer thickness is regulated while being rubbed between the bodies, the surface potential of the toner layer thickness regulating member is smaller than the absolute value of the image portion voltage of the electrostatic latent image holding surface, preferably substantially the surface potential of the toner carrier. It is possible to maintain the same as above, and as a result, it is possible to suppress the aggregation and streaking of the toner without the charged toner adhering to the toner layer thickness regulating member side.

Since the toner layer thickness regulating member is non-magnetic, it is possible to smoothly regulate the layer thickness without causing unnecessary magnetic attraction with the fixed magnet body that forms a repulsive magnetic field through the toner carrier. Can be done.

Further, in this case, since the side of the toner layer thickness regulating member that comes into contact with the toner carrier, that is, the sliding side of the charged toner is made of a conductive member that is grounded, an unnecessary charge is injected into the charged toner. The stable toner charging potential is maintained without being charged.

Then, the toner of which the layer thickness is regulated is subsequently released in the repulsive magnetic field forming region formed on the downstream side by the repulsive force of both fixed magnets, and the toner is unraveled and slightly lifted from the carrier. After maintaining the aerial swimming state, the toner having a coarse toner density is rearranged in a uniform and dense state on the toner carrier by the fixed magnet on the downstream side, and an extremely thin toner thin layer can be formed.

In the present invention, by applying a pulse voltage formed by switching to the ground potential to the toner layer thickness regulating member, a potential between the conductive member and the toner carrier facing each other via the magnetic toner is applied. A unidirectional pulsed electric field is generated in the magnetic field. As a result, the magnetic toner vibrates at a predetermined frequency and the layer thickness is regulated, so that a more uniform layer thickness regulation becomes possible.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be exemplarily described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only thereto, but merely illustrative examples. Nothing more than.

The drawings show a schematic configuration of a developing device to which the present invention is applied.

Reference numeral 1 is a photosensitive drum having a photoconductive layer formed on its surface, and 2 is a non-magnetic sleeve containing a fixed magnet assembly 3. Both members 1 and 2 have a space between them at a developing position (closest position).
The photosensitive drums 1 are arranged so as to face each other at 200 μ, and the non-magnetic sleeve 2 rotates in the clockwise direction, and the non-magnetic sleeve 2 rotates in the counterclockwise direction at the same peripheral speed, for example, 100 rpm.

In the photoconductor drum 1, the electrostatic latent image potential carried on the photoconductive layer formed on the surface of the photoconductor drum 1 is changed by the charging device and the exposure device (both not shown) arranged on the upstream side of the image portion 500.
V is set to be 50V in the non-image portion, and is set to be larger than the toner binding potential (about 120V: experimental value) on the non-magnetic sleeve 2 side in the image portion and smaller than the toner binding potential in the non-image portion. I am configuring.

On the other hand, the non-magnetic sleeve 2 has a voltage generating circuit 9 connected to the DC power source 8 and the ground potential, and has a voltage of 0 V (valley side potential) to
A voltage of 300 V (mountain side potential) is configured to be applied intermittently at a cycle of 1 KHz, and the bottom side of the sleeve 2 is arranged at the toner accumulation position below the hopper 11.

The fixed magnet assembly 3 contained in the non-magnetic sleeve 2 is arranged in parallel on the outer peripheral surface on the upstream side of the developing position along the axial direction with the fixed magnets 4a and 4b of the same polarity spaced apart by a predetermined distance and adjacently arranged. A repulsive magnetic field is formed on the non-magnetic sleeve 2 by the fixed magnets 4a and 4b.

The fixed magnets 4a and 4b are integrally formed on the opposite polarity side in order to facilitate the positioning of the separation distance, and the magnetic flux strengths thereof are set so that the maximum magnetic flux density on the surface of the non-magnetic sleeve 2 is 600 gausses. At the same time, the spacing between the fixed magnets 4a and 4b is set so that the amount of magnetic flux drop at the intermediate position between the fixed magnets 4a and 4b is 100 gauss or more.

On the non-magnetic sleeve 2 between the fixed magnets 4a and 4b, a magnet blade 6 having a polarity opposite to that of the fixed magnets 4a and 4b is arranged at a predetermined distance from each other, and the tip surface of the magnet blade 6 is located in the repulsive magnetic field forming region. To be located at. Specifically, the magnet blade 6 is located within the distance between the fixed magnets 4a and 4b, has its tip formed in a rectangular shape, and has a wall thickness of 0.3.
The range is set to ~ 2mm.

Further, on the downstream side wall surface of the magnet blade 6 in the toner conveying direction,
A toner layer thickness regulating member 7 is attached, and its free end side is extended to the upstream side of the magnet blade 6, and is located slightly inward of the free end at a position corresponding to the one fixed magnet 4a. It is configured so as to contact the surface of the magnetic sleeve 2.

The toner layer thickness regulating member 7 is formed of, for example, a non-magnetic thin plate having a wall thickness of about 100 μ, has a constant elastic force so as to obtain a predetermined contact pressure, and at least a contact side with the non-magnetic sleeve 2 is provided. A conductive member 7a having a surface resistance of 10 ⁵ Ω / cm ² or less is arranged, and the base end of the conductive member 7a is grounded via the resistor 10.

As a result, not only the surface potential on the side in contact with the non-magnetic sleeve 2 is maintained substantially equal to the surface potential on the non-magnetic sleeve 2 side, but also the non-magnetic sleeve 2 has ground potentials 0V and 300V. Since a pulse voltage switched between the non-magnetic sleeve 2 and the conductive member 7a facing each other through the magnetic toner is applied, a pulse electric field formed by potential switching, in other words, An oscillating electric field in one direction is generated, and as a result, the magnetic toner vibrates at a predetermined frequency (1 KHz) and the layer thickness is regulated. Therefore, the layer thickness can be regulated more uniformly.

Regarding the toner layer thickness regulating member 7, for example, copper,
A strip of aluminum or the like is thinned to a thickness of about 100 μ and integrally formed with the conductive member 7a, or a conductive thin film of aluminum or the like is vapor-deposited on a resin film such as a polyester film to separate the conductive member 7a. Any of those formed in the above may be used.

Further, the thickness of the layer thickness regulating member 7 is not necessarily limited to 100 μm, and is appropriately determined depending on the relationship between the elastic force and the separation distance from the non-magnetic sleeve 2.

The toner used in this example is composed of polystyrene resin, magnetic material (ferrite), carbon black, and a charge control agent, and the magnetic material contains 30 to 40 parts by weight. Use the one that is charged.

Next, a developing procedure based on such a configuration will be described.

By rotating the non-magnetic sleeve 2 together with the photosensitive drum 1,
After the toner is tribo-charged to the positive polarity in the hopper 11 on the upstream side of the layer thickness regulating member 7, the toner is held on the non-magnetic sleeve 2 and is placed at the layer thickness regulating position formed with the layer thickness regulating member 7. Reach

Since the surface potential of the layer thickness regulating member 7 is maintained substantially equal to the surface potential of the non-magnetic sleeve 2, the toner does not adhere to the layer thickness regulating member 7 side and the layer potential regulating member 7 has a ground potential. The magnetic toner vibrates in one direction at a predetermined frequency (1 KHz) with a pulsed electric field that is swung in a switching manner to regulate the layer thickness, so that a uniform toner layer is formed in the repulsive magnetic field formation region on the downstream side. Be transported.

Then, in the repulsive magnetic field forming region, the restraint of the non-magnetic sleeve 2 is released by the repulsive force of both the fixed magnets 4a and 4b, and the non-magnetic sleeve 2 is slightly lifted from the sleeve 2 to maintain the aerial swimming state,
After the toner having a coarse toner density is adjusted by the magnet blade 6, it is rearranged in a uniform and dense state on the non-magnetic sleeve 2 by the fixed magnet 4b on the downstream side, and an extremely thin toner thin layer. Can be formed.

In order to confirm the effect of this example, a conductive film (trade name, manufactured by Toray Industries, Inc.) obtained by vapor-depositing aluminum on one side surface of a polyester film having a thickness of 100 μ is formed on the toner layer thickness regulating member 7. High beam) and insulating polyester film without aluminum deposition (Toray Industries, Inc.)
The product using Lumirror was used as it was, but when using the product using Lumirror, agglomeration due to toner adhesion occurred and streaky unevenness occurred on the transfer paper. With the product name High Beam,
Until the toner in the toner hopper was completely consumed, a stable toner layer was obtained, and the streaky unevenness did not occur on the transfer paper at all.

[Advantages of the Invention] As described above, according to the present invention, the prior art is further embodied to enable more stable formation and uniformization of the toner layer, and in particular, the toner is fly-transferred for development. A toner layer forming apparatus suitable for the apparatus can be provided.

[Brief description of drawings]

The drawing is an overall schematic view of a developing device according to an embodiment of the present invention. 2: Toner carrier, 7: Toner layer thickness control member 1: Electrostatic latent image holder, 7a: Conductive member

Claims (3)

[Claims] 1. A toner layer thickness regulating member, which is carried on a toner bearing member and moves in a developing position direction, is regulated by a toner layer thickness regulating member which is in contact with the toner bearing member through the toner, and then is regulated. In a toner layer forming apparatus for detangling toner by applying magnetic force lines to the toner layer, a pair of fixed magnetic members of the same polarity are arranged on the back side of the toner carrier located in the toner unraveling region, A repulsive magnetic field is formed, and a toner layer thickness regulating member made of a non-magnetic conductive member is grounded on the upstream side of the repulsive magnetic field forming region in the rotation direction of the toner carrier, and the side in contact with the toner carrier is grounded. A toner layer forming apparatus, characterized in that the surface potential of the toner layer thickness regulating member at the contact position is maintained to be smaller than the absolute value of the image portion voltage of the electrostatic latent image holding surface. 2. The toner layer forming apparatus according to claim 1, wherein the surface resistance of the conductive member is set to 10 ⁹ Ω / cm ² or less. 3. A pulsed electric field that is switched between the toner layer thickness regulating member and the ground potential is applied to the contact position of the toner layer thickness regulating member.
Item or the toner layer forming apparatus according to item 2.