JP2002357982A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of image quality in a step for final transfer onto a transfer material in an electrophotographic transfer system. SOLUTION: A particle coater is disposed, which coats coating particles that comprise a polyester resin, styrene-acrylic resin, polyurethane resin, polyamide resin or the like and become substantially transparent after fixation on a transfer material before a toner image is transferred, and the transferability of the toner to the transfer material is improved by the coating particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an electrostatic latent image on an image carrier such as a photoreceptor in an electrophotographic apparatus or an electrostatic printer, and developing the electrostatic latent image to obtain an image. And an image forming apparatus for transferring and fixing the image.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, after forming an electrostatic latent image on a photoreceptor, a developer is electrostatically attached to the electrostatic latent image to form a developer image, and the developer image is transferred. The image is transferred to transfer paper by an apparatus. As this type of transfer device, electrostatic means such as a corona transfer method and a roller transfer method are known.

[0003] The electrophotography system has evolved from a copying machine, and has a wider range of applications such as page printers and facsimile outputs. In addition, it has evolved from an analog system to a digital system. Is growing.

At present, in most electrophotographic apparatuses, as described above, a toner image on a photosensitive member is transferred to plain paper by an electric means. However, image deterioration at the time of transfer is very large. It is a major cause of inferior technology.

[0005] It has been really shocking that the image quality has been dramatically improved by changing the ink jet paper to special specialty paper in fields other than the electrophotographic field recently.

[0006] On the other hand, there is no special paper which specializes in electrophotography and has such a dramatic improvement in image quality.

[0007]

In the electrophotographic transfer system, image deterioration occurs in the process of finally transferring the image onto transfer paper, which is a bottleneck in the image quality of the electrophotographic system. The image deterioration in the transfer is mainly caused by the unevenness of the paper, and the image is inevitably a rough image corresponding to the unevenness of the paper.

[0008]

Therefore, in the present invention, an electrostatic latent image forming means for forming an electrostatic latent image on an image carrier and developing the electrostatic latent image to transfer a developer image to a transfer material. An image forming apparatus including a transfer unit, wherein a particle coating apparatus for applying coating particles before transferring the toner image onto the transfer material is provided.

[0009]

FIG. 1 shows a full-color printer according to a first embodiment of the present invention. In this full-color printer, a laser is irradiated from the laser irradiation unit 4 to the photosensitive drum 1 in accordance with an image signal (not shown). The image signal may be from a computer or, if a scanner is connected, a color copier.

A photosensitive drum 1 as an image carrier is uniformly charged to about -700 V by a corona charger 2, and receives a laser beam L according to an image signal. As a result, an electrostatic latent image is formed on the photosensitive drum 1, and the latent image is developed by a developing device of the rotary developing unit 3 using toner as a developer, and a toner image is formed on the photoconductor 1.

The rotary developing unit 3 is provided with four developing units containing toners of four colors shifted from each other by 90 degrees. The rotary developing unit rotates and develops so as to face the photoconductor at the time of forming an image of each color.

The intermediate transfer member 6 has a metal drum with a medium resistance rubber layer on the surface, and a transfer bias is applied to the metal drum.

In the present invention, the particles are applied onto the transfer material T before the full-color toner image is transferred from the intermediate transfer member to the transfer material T. The particle coating device 10 has a configuration similar to a developing device, and faces the transfer material T so as to be separated therefrom.

FIG. 2 shows the particle coating apparatus 10. The particle coating device 10 has a coating roller 11,
Reference numeral 1 denotes a non-magnetic sleeve including a magnet roller. Screws 12 and 13 are provided on the container side, and the screw conveys and agitates the coating agent and supplies the coating agent to the coating sleeve. The coating agent is a mixture of coated particles and magnetic fine particles.

In the present embodiment, the coating particles have a particle size of 2
Pulverized particles obtained by adding a known charge control agent and the like to a polyester of μm are used. The color is white in powder and transparent when melted. The particle size is not limited to this, and can be used from submicron to about 20 μm.

If the particle size is about the same as or larger than the toner, it is easy to use in terms of handling, but the image quality tends to be slightly deteriorated. Therefore, the particle size is preferably smaller than that of the toner. In the present embodiment, 2 μm is used.

As the coating particles, resins other than polyester such as styrene acrylic resin, polyurethane resin and polyamide resin can be used. In addition, not only resins but also inorganic materials such as titanium oxide and zinc oxide can be used.

As the magnetic fine particles, those obtained by applying a very thin resin coating on the surface of magnetic particles are preferably used, and those having an average particle diameter of 40 μm are used. A mixture of the coated particles and the magnetic fine particles at a volume weight ratio of about 5: 100 is used as a coating agent. In the present embodiment, the applied particles are negatively charged by frictional charging with the magnetic fine particles.

During the coating operation, the coating roller 11 of the particle coating apparatus 10 is opposed to the transfer material T while maintaining a gap of 500 μm, and a ground electrode E is provided on the back surface of the transfer material T. A voltage is applied from a power supply (not shown) to the application roller 11 of the particle pre-applying device 10 to give a potential difference of −300 V with respect to the ground electrode E, and the application particles negatively charged by the potential difference transfer the transfer material T. Applied on top.

The transfer material T coated with the coating particles as described above
As described above, the full-color toner image formed on the intermediate transfer body 6 is transferred onto transfer paper by a bias applied to a transfer roller 7 as a secondary transfer unit, and is thermally fixed by a fixing unit 8. The transfer residual toner on the photosensitive drum 1 is cleaned by contact with 9A.

Here, the effect of the present embodiment will be described. The feature of the present embodiment is that the application particles are applied on the transfer material T in advance, and the multicolor toner on the intermediate transfer body 6 is collectively transferred from above.

However, the transfer from the intermediate transfer member to the paper may be accompanied by image quality deterioration. In the present embodiment, the transferability is greatly improved by applying the coating particles on the transfer material T in advance and smoothing the unevenness of the surface of the transfer material T.

Furthermore, it has been surprisingly observed that the phenomenon of toner scattering at the time of transfer is greatly reduced.

Further, even when the coated particles are transferred to a transfer material, they are substantially colorless and transparent when melted at the fixing temperature of the toner image, so that there is no adverse effect on the image.

With this configuration, a high-quality image with excellent transfer efficiency, which has not been obtained conventionally, can be obtained.

Further, even for a transfer material which cannot be fixed with normal toner, by using a material having an enhanced fixability for the coated particles which are not related to image formation, the material functions as a binder between the toner and the transfer material. Since it can be fixed, the range of the electrophotographic medium can be greatly expanded.

In this embodiment, the applied particles have the same negative charge as the toner, but it is of course possible to use positively charged particles. It just needs to be able to be applied to the transfer material.

[Second Embodiment] FIG. 3 shows a second embodiment.
In the present embodiment, the photosensitive drum 1, the developing device 3, the cleaner 9
And four units of the charger 2 are arranged side by side along the transfer belt 16. The units are Y, M, C, and K, and there are yellow, magenta, cyan, and black units, respectively.

The photosensitive member 1 is charged by a corona charger 2 and
The exposure is performed by the ED unit 14 according to the image signal. The formed electrostatic latent image is developed by the developing device 3 as a toner image using toner. On the other hand, the transfer material T is previously coated with particles by the particle coating device 17.

FIG. 4 shows a particle coating apparatus according to the second embodiment.
One example of the application particles G is the same pulverized particles of 2 μm polyester resin as in the first embodiment, and the application particles G are coated in a thin layer by rubbing the surface of the transfer material T with the fur brush 21.

The yellow toner image on the photoreceptor 1 is transferred onto a transfer material T on which the coating particles G are applied by a roller 15 as transfer means.

In the next M units, magenta toner, cyan, black and the transfer material T are successively transferred. In this way, on the transfer material T, the coated particles are transferred to the lowermost layer, and the toner image of yellow, magenta, cyan, black and the toner is multiplex-transferred thereon. With this configuration, a high-quality image with excellent transfer efficiency, which could not be obtained conventionally, could be obtained, just like the first embodiment.

The configuration as in the second embodiment can perform high-speed output.

[0034]

As described above, according to the present invention,
By applying the coating particles on the transfer material in advance, one layer of the coating particles in contact with the transfer material is prevented from contacting the toner with the transfer material. Highly efficient transfer can be performed without producing, and a high quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing Embodiment 1 of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating a particle coating apparatus according to a first embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a diagram showing Embodiment 2 of the image forming apparatus according to the present invention.

FIG. 4 is a diagram showing a particle coating apparatus according to a second embodiment of the image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Developing device 6 Intermediate transfer body 7 Secondary transfer roller 8 Fixing device 10, 17 Particle coating device 11 Application roller 15 Transfer roller 16 Transfer belt 21 Fur brush T Transfer material

Claims (3)

[Claims] 1. An image forming apparatus comprising: an electrostatic latent image forming unit that forms an electrostatic latent image on an image carrier; and a transfer unit that develops the electrostatic latent image and transfers a developer image to a transfer material. At
An image forming apparatus, comprising: a particle coating device for applying coating particles before transferring a toner image onto the transfer material. 2. The image forming apparatus according to claim 1, wherein the coating particles are formed of a material that becomes substantially transparent after fixing the toner image. 3. The image forming apparatus according to claim 1, wherein the coating particles are formed of any one of a polyester resin, a styrene acrylic resin, a polyurethane resin, and a polyamide resin.