JPS629904B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for developing an electrostatic latent image using a one-component toner, and is applicable to electrophotographic copying machines, electrostatic recording devices, and the like.

Development methods using one-component toner are broadly classified depending on whether the one-component toner is non-magnetic or magnetic. Further, the method differs depending on whether the one-component toner has high resistance or low resistance. The present invention particularly relates to a method of developing an electrostatic latent image using a high-resistance one-component toner.

Conventionally, developing devices using non-magnetic high-resistance toner are disclosed in Japanese Patent Application Laid-open No. 47-13088 and Japanese Patent Publication No. 51-36070.
No. 1, in which an electrostatic latent image is developed by charging toner on a conductive elastic roller with a plurality of triboelectric charging blades. Furthermore, a method has been proposed in which the toner is charged using a charge injection electrode to which a voltage is applied instead of the frictional charging blade. This kind of developing device does not use magnetic attraction force to adhere toner to the developing roller, so toner easily adheres to the developing roller.
That is, since a material with high surface energy is used, toner is strongly adhered by a force other than electrostatic adhesion, resulting in poor reproducibility of low-contrast images and gradation reproducibility. Therefore, it is possible to coat the surface of the developing roller with a dielectric material with low surface energy, but this makes it difficult for the toner to adhere to the developing roller. When trying to remove excess toner from
Since the adhesion of the toner to the developing roller is weak, it is difficult to form a uniform toner layer, which causes uneven development. Furthermore, in those employing a toner charging method using a charge injection electrode, the amount of toner charge is reduced due to the presence of a dielectric layer, and there is a risk that development, such as a decrease in image density, may occur.

The present invention solves the above-mentioned drawbacks by combining a toner donor member to which toner easily adheres and a developing roller to which toner does not adhere easily, thereby achieving low contrast reproduction and gradation reproduction that are difficult to obtain with one-component toner. The object of the present invention is to provide a developing device that makes it possible to perform the following steps.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the invention. Reference numeral 1 denotes a photoreceptor drum, and a photoreceptor made of an organic photoconductor is used. Other materials such as zinc oxide, selenium, and cadmium sulfide can be used as the photoreceptor. The photosensitive drum 1 is rotating clockwise at a constant speed. The developing device is comprised of a portion that takes out one-component toner from the hopper and charges it to a predetermined polarity, and a portion that receives the charged toner and brings it into contact with the latent image surface. The roller 2 as a toner supplying member is a roller having elasticity and excellent toner adhesion. Materials used for this include silicone rubber, nitrile rubber, etc., and the following are particularly preferred. It has a volume resistivity of 10 ⁵ Ωcm to 10 ⁸ Ωcm, a hardness of 40 to 50 HS, and a surface roughness of 5 μ or less. Roller 2 is rotating clockwise. A toner hopper 3 is disposed above the roller 2, and contains a one-component nonmagnetic toner 4 therein. The toner is a high resistance toner having a volume resistivity of 10 ¹⁴ Ωcm or more. A charge injection electrode 5 is attached to the outlet side wall 3a of the toner hopper 3, and is pressed against the roller 2 by a spring 6 with a predetermined pressure. The charge injection electrode 5 may be made of any conductive material, but hard aluminum is used. The tip of the charge injection electrode 5 has a sharp edge and also serves as a doctor for regulating the thickness of the toner layer on the roller 2. Further, a voltage Va (positive in this case) is applied to the charge injection electrode 5 from a power source 7. A developing roller 8 is disposed between the roller 2 and the photosensitive drum 1 and rotates counterclockwise. That is, the contact portion with the roller 2 is moving in the same direction.
And their movement speeds are set almost the same. The developing roller 8 is composed of a semiconductive elastic body 9 and a dielectric layer 10 coated on the surface thereof. As for the material of the elastic body 9, conductive rubber such as silicone rubber or nitrile rubber is used as in the roller 2 described above, but a semiconductive member without elasticity can also be used. The dielectric layer 10 differs greatly from the surface characteristics of the roller 2 in the following points. That is, the roller 2 has a surface to which the toner easily adheres since it conveys the one-component toner. In other words, it is made of a material that has a high surface energy relative to the toner. On the other hand, the dielectric layer 10 is the opposite,
The material used is a material that has a property that makes it difficult for toner to adhere to it, that is, a material that has a low surface energy with respect to toner. For example, Teflon (trade name), polyethylene, polypropylene, etc. are preferably used. It should be noted that such a dielectric material has a high resistance value and may reduce the effect of the bias voltage applied to the developing roller. Therefore, its thickness cannot be increased too much. When the bias voltage Vb of the power supply 11 connected to the developing roller 8 was set to 200 to 300 V, there was no adverse effect as long as the thickness of the dielectric layer 10 was 2 to 5 μm.

Next, the operation of this developing device will be explained.

A roller 2 serving as a toner supply member deposits the one-component toner 4 on its surface and carries it out of the toner hopper 3. When passing under the charge injection electrode 5 provided at the outlet of the toner hopper 3, the monocomponent toner is positively charged. Since this charge injection electrode 5 also serves as a doctor, the thickness of the toner layer on the roller 2 is made uniform. The one-component toner on roller 2 is then transferred to developer roller 8. The reason why the toner is transferred to the developing roller 8 is that the developing roller 8
A potential difference is formed between the developing roller 8 and the roller 2, and a voltage having a polarity opposite to the charged polarity of the toner is applied to the developing roller 8.
It is considered that this one-component toner is electrostatically transferred. The surface of the developing roller 8 is a dielectric layer 10 with low surface energy.
Therefore, the one-component toner adheres more easily to the roller 2 than to the developing roller 8. The one-component toner on the developing roller 8 is brought into contact with the photoreceptor drum 1.
The photoreceptor drum 1 and the developing roller 8 are moving in the same direction and at approximately the same speed in opposing parts. A potential of the same polarity as the background potential of the photosensitive drum 1 or slightly higher is applied to the developing roller 8 by a power source 11 . Therefore, the one-component toner on the developing roller 8 is electrostatically attracted by the electric field of the electrostatic latent image on the photoreceptor drum 1, but the one-component toner is attracted to the background part by the electrostatic force in the opposite direction. is sucked toward the developing roller 8 side. In normal development, there is another large force that attracts the toner toward the developing roller during development, but in this embodiment, it will be noticed that this suction force is made as small as possible. Therefore, the photoreceptor drum 1
The upper electrostatic latent image is made into a visible image.

Next, another embodiment of the present invention will be described with reference to FIG. This example differs greatly in that a magnetic toner is used as the one-component toner. In this embodiment, parts having the same functions as the devices or members shown in FIG. 1 will be described with the same reference numerals. In FIG. 2, a one-component magnetic toner 12 is contained in a toner hopper 3. As shown in FIG. This magnetic toner also has a high resistance value, similar to the first embodiment. The magnetic roller 13 as a toner donor member includes a magnet 14 whose N pole and S pole are alternately magnetized.
and a non-magnetic sleeve 15 rotating around it. This non-magnetic sleeve 15 is made of a non-magnetic and conductive material such as aluminum, and is grounded. Therefore, the one-component magnetic toner 12 carried out from the toner hopper 3 by the magnetic attractive force of the magnet 14 and the movement of the non-magnetic sleeve 15 is transported by the electric potential difference between the charge injection electrode 5 and the non-magnetic sleeve 15. When passing under the charge injection electrode 5, it is charged. The thickness of the toner layer on the magnetic roller 13 is 30 mm due to the charge injection electrode 5.
The thickness is regulated to 50μ. Developing roller 16
Like the magnetic roller 13, the magnet 17 is composed of a magnet 17 whose north and south poles are alternately magnetized, and a non-magnetic sleeve 18 which rotates around the magnet. magnet 14
At the portions of the magnets 17 that are close to each other and opposite each other, different poles are arranged to face each other. As a result, the charged one-component magnetic toner is transferred from the magnetic roller 13 to the developing roller 16, as described in FIG. It also ensures efficient transfer by magnetic attraction. A dielectric layer 20 with low surface energy is formed on the conductive cylinder 19 of the nonmagnetic sleeve 16. The same material as that explained in FIG. 1 can be used for this material. The non-magnetic sleeve 15 of the magnetic roller 13 and the non-magnetic sleeve 18 of the developing roller 16 rotate in opposite directions, and the one-component magnetic toner 12 transferred from the magnetic roller 13 is transferred to the non-magnetic sleeve 18 by the magnetic attraction force of the magnet 17. The photoreceptor drum 1 is transported toward the photoreceptor drum 1. Therefore, the magnetic poles 17-1, 17-2, 17-3 of the magnet 17 are 1
This is necessary for attracting and transporting the component magnetic toner, and thereby prevents toner from scattering from the developing roller 16, which has a dielectric layer 20 with low surface energy to which toner does not easily adhere. On the other hand, the magnetic pole 17-4 facing the photosensitive drum 1 has extremely weak magnetic force, and may be zero. In other words, there may be no magnetic pole. In this case, the one-component magnetic toner is positively charged, and the toner is prevented from adhering to the surface of the photosensitive drum 1 by the action of the bias voltage. Developing roller 16
The non-magnetic sleeve 20 is moving in the same direction and at approximately the same speed at the portion facing the photoreceptor drum 1. In other words, this means that the moving speed of the photosensitive drum 1 and the moving speed of the toner (one-component magnetic toner) are almost the same. Thus, the electrostatic latent image on the photosensitive drum 1 is visualized.

In the above-mentioned embodiments, a case was explained in which a roller was used as a toner donor and a developing means, but it goes without saying that an equivalent endless belt can also be used. In place of the photoreceptor, other materials capable of carrying an electrostatic latent image, such as a dielectric material, may be used, and the shape thereof is not limited to a drum, but may be a belt or a flat plate. When using the electric body, a well-known image forming method of an electrostatic recording device may be employed.

As described above, according to the present invention, since the force acting on the toner in the direction opposite to the direction toward the latent image surface of the toner during development is reduced, reproduction of low contrast images is improved in development using single-component toner. This is possible, and since the toner is sufficiently charged, gradation can be reproduced and image quality can be improved. Since a one-component toner is used, there is no need to detect the toner concentration, and the developer has the advantage that it is cheaper than a two-component developer and can provide image quality comparable to that of a two-component developer.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device showing one embodiment of the present invention, and FIG. 2 is a sectional view of a developing device showing another embodiment of the present invention. 1... Photosensitive drum, 2... Roller, 5...
Charge injection electrode, 8, 16...Developing roller, 1
0,20...Dielectric layer, 13...Magnetic roller,
14, 17... Magnet, 15, 18... Non-magnetic sleeve.

Claims (1)

[Claims] 1. A toner supplying member that adheres to the surface of the toner supplying member and conveys the one-component high-resistance toner supplied from the toner supplying means; a charging member that charges the one-component high-resistance toner on the toner supplying member to a predetermined polarity; a developing roller or belt that moves at the same speed and in the same direction as the toner donating member at a contact portion with the toner donating member, and has a surface having a lower surface energy than that of the toner donating member, and the developing roller or belt means for applying a bias voltage having a polarity opposite to that of the charged one-component high-resistance toner to create a potential difference between the toner donor member and the developing roller or belt; 1
A one-component toner developing device, characterized in that a component-based high-resistance toner is transferred from a toner supply member to a developing roller or belt to develop an electrostatic latent image.