JPH0251168A - Cleaningless electrophotographic printing method - Google Patents

Abstract

PURPOSE:To obtain a cleaningless printer by equalizing the electrostatic charging polarity of an electrostatic charging part to that of toner and shaping materials of both dry toner particles and carriers spherically. CONSTITUTION:The electrostatic charging polarity of the electrostatic charging part 2 is equalized to that of the toner, so toner particles are prevented from flocculating into lumps and the materials of both the toner and carriers are made spherical. Smooth motion and high flowability are generated between the toner and carriers to improve the contact electrostatic charging between the toner and carriers and remaining toner is attracted by carriers to carry out cleaning operation at a development part 4 simultaneously. Consequently, the printer which has no cleaning device is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to a method for realizing a printer that is employed in a printer and lacks a cleaning device, which has conventionally been installed as an indispensable condition.

(Prior Art) Conventionally, in an electrophotographic copying machine, it has been considered an essential condition to wipe off toner remaining on the surface of a photoreceptor after transfer, and this has actually been the case. The process of wiping off residual toner is considered to be more than 20% important among all processes in electrophotographic equipment, and can be performed by brushing, blade, or changing the polarity of the bias applied to the developer every other rotation. Many types of cleaning devices have been devised, including the so-called two-turn method for use as a cleaner. It has been a dream of electrophotography to be able to eliminate this cleaning part.

(Problems to be Solved by the Invention) The present invention aims to provide a cleaning-less printer that realizes the above-mentioned dream.

1. Refinement of the invention (means for solving the problem) In order to achieve the above-mentioned goal, the present invention has fully analyzed the unique operation of printers, investigated how each part, especially the developing part, works, and developed the present invention. The goal of the invention was to basically determine the desired state of the material, and this was realized using a specific device.

The first thing we focused on was the theoretical difference between conventional so-called copying machines and printers. The first point of view is that in the case of a so-called copying machine, for example, in the case of a Se photoreceptor, the photoreceptor is (+
), the white part of the image loses its charge due to the light image,
A so-called positive visualization method is used, which takes advantage of the inability of toner to adhere and visualizes using (-) charged toner. The portion of the photoreceptor that is irradiated with light discharges and reduces the surface charge, which is used to cause toner to adhere to this portion. It uses a so-called negative development method.

The fact that the behavior of the toner in these two types of methods is vastly different has not been well understood or utilized in the past.

At the basis of the present invention, attention was paid to the significance of the residual toner always passing through the main discharge region for charging the surface of the photoreceptor. That is, for example, in the case of a printer using a (+) type photoreceptor, the surface thereof is charged with a (+) charge, then loses charge at the light irradiated area due to light image irradiation, and the area where the charge has been lost becomes (+). ) is visualized by toner with a charge of . This means that the cycle repeats. In this case, even if the toner, which originally has the property of being charged (+), undergoes a transfer process in which it is exposed to (-) corona, it will always end up being charged up (+).

In other words, the first point to note is that the residual toner, when entering the next cycle, strongly depends on the charged polarity that it should originally have. The significance of this point of view is important.

In the case of positive development as in a copying machine, when the residual toner enters the next cycle, it is always forcibly charged to a polarity opposite to what it should originally have. In such a state where two types of polarity toners are mixed in the next cycle, the toners will flocculate together and form a spirit, which not only loses its original toner function but also causes electrostatic charge. It throws the entire mechanism of the system out of order.

The next problem is that it interferes with the irradiation of the light image in the next cycle from residual I to Luna.

Transfer efficiency is generally said to be 70% to 80%. Of course, this low transfer rate may change depending on the improvement of the toner, but even if residual toner exists, it must be ensured that the optical effect of the irradiated light image is not diminished. Of course, the average particle size of toner in a printer is nearly an order of magnitude smaller due to the optical dots irradiated.
For example, even if 20% to 30% of the residual toner exists, 70% to 80% of the surface will receive the average light irradiation, and the amount of exposure will be sufficient.

However, in reality, the quality of the image is greatly influenced by the properties of the toner used. Determining the quality of this toner is the third important element of the present invention.

Next, in the cleaning-less method of the present invention, cleaning of transfer residual toner generated in the previous cycle must proceed at the same time as development. For this purpose, it is desirable that the effective surface area of the developer, especially the carrier, is sufficiently large and that it rolls well during the development operation. This is the second most important point.

Selecting materials and systems that satisfy the above conditions is a necessary condition for realizing a cleaning-less system.

The concepts for realizing a cleaning-less method are as follows: (1) Printers that perform negative development are fundamentally different from copiers and are moving toward a cleaning-less system, but conventional materials and systems cannot be used insensitively. It's not enough.

(2) The developing device and developer must have smooth movement and high fluidity so that cleaning and development can be performed at the same time.

(3) It is desirable that the toner has as high a transfer efficiency as possible, and that even if it remains, it has little optical shielding effect.

(4) It is better to avoid cases where the toner is charged with opposite polarity.

It was narrowed down to four points. Needless to say, the above (1) to (4)
) are listed according to their importance.

(Example) Embodiments of the present invention will be described below based on the drawings.

Example 1 A commercially available laser beam printer using a Se-based photoreceptor was used with some adjustments. The diameter of the photosensitive drum is 8
0mmφ, process speed is 11A lTln
1/SeC. First, remove the cleaning device installed on this machine. Next, we improved the rotating direction and speed of the developing machine as well as the surface of the magnetic roller so that the developer to be used can touch the developing surface most smoothly.
Adjusted so that the developer rolls. Furthermore, the timing of the transfer corona is adjusted, and the time when the transfer paper is not being fed is
Improved so that the transfer corona does not work.

Carrier used as a developer: The surface is nitrided with spherical iron powder manufactured by Tetsuhara Co., Ltd. with an average particle size of 50 μm.

Toner A spherical toner made by Nippon Paint with an average particle size of 7μ, and one surface of the toner is coated with a polar polymer.

Do not use. All other conditions remain the operating conditions of the original printer.

As a result, even if the cleaning section is completely absent, it does not produce any antecedent, and it can continuously provide a complete printout result, whether it is running a few prints continuously or intermittently. Furthermore, within the range of relative humidity 20% to 80%,
Furthermore, it has been known that even when the atmosphere is varied within the temperature range of 0° C. to 30° C., it can stably provide perfect printing results without any prior history.

The properties of the developer used in the above examples are characterized by its manufacturing method. Regarding the carrier, this iron powder is based on spherical iron powder generated in the carbon removal process of the steel manufacturing process, and its surface is nitrided or coated with an anion resin. Its features are that it has an almost perfect spherical shape and that it is made of nearly 100% iron. Naturally, its surface is extremely smooth. The toner is also spherical, and its structure is made by uniformly coating six spheres obtained by polymerization containing color elements with a much finer amount of cationic resin.

The fact that both the carrier and the toner are spherical is a factor in that the developer exhibits extremely homogeneous characteristics as a whole, and at the same time exhibits extremely good fluidity. Furthermore, the spherical shape means that it has the widest active area, and since it is uniform over the entire surface, it means that a stable charging state will occur no matter what state the toner and carrier meet. do.

Conventionally, spherical toner has been found to be difficult to clean; for example, as seen in Japanese Patent Publication No. 63501040, the surface of spherical toner has been intentionally made to have unevenness.
There are even techniques to improve cleaning efficiency.

However, the present invention does not address such problems at all. Toner is uniformly charged, and its particle size is homogeneous, for example, 7μ±1μ.
The toner surface is selected to be 100% covered with cationic resin. The carrier surface is also homogeneous and smooth.

In particular, the characteristics of the toner were carefully selected so that almost no toner would be charged to the opposite polarity. If there are toner particles that are charged with opposite characteristics, the toner will flocculate with these toner particles as nuclei, and agglomerates will be generated. This results in the same result as if toner particles with extremely different particle sizes were generated, resulting in a decrease in resolution and at the same time causing uneven transfer. If an attempt is made to increase the average transfer efficiency, transfer defects tend to occur in the part where the particles accumulate, and the residual toner causes interference with the optical image and a defect in cleaning that progresses simultaneously with development.

Of course, it is not an absolute requirement to use spherical toner. However, amorphous toner based on the conventional pulverization method has poor fluidity, large particle size, and so-called CC.
Large variations in charging characteristics due to poor dispersion of D (charge control agent) can easily become a disaster.

If a toner with satisfactory fluidity, charging characteristics, particle size, etc. can be obtained, there is no need to insist on using this type of toner.

Of course, the carrier is not limited to the iron powder used in Example 1.

For example, there are many ferrite carriers that can be used.

As described above, the corona whistle of opposite polarity added during transfer has the opposite effect for the present invention. A method for eliminating this adverse effect will be described in Example 2.

Embodiment 2 FIG. 1 is a diagram schematically showing the configuration of Embodiment 2. In the figure, 1 is the photosensitive drum, 2 is the corona charger, 3 is the input signal light, 4 is the developer, 5 is the transfer belt,
Reference numeral 6 indicates a corona charger for charging the surface of the transfer belt 5, 7 indicates a transfer paper, and 8 indicates a fixing device.

FIG. 2 is a cross-sectional model diagram of the transfer belt 5 shown in FIG. 1 for explaining some details of the belt. In the figure, numeral 9 indicates a conductive rubber lining, and numeral 10 indicates an insulating thin layer.

Basically, the second embodiment differs from the first embodiment only in the transfer system composed of 5.6.

As shown in FIG. 2, the transfer belt 5 has a laminated structure of a conductive visible member 9 and an insulating visible member 10. The insulating surface of the insulating flexible member 10 is charged by the corona charger 6 shown in FIG. 1 to a polarity opposite to that of the toner. The degree of charging is, for example, when the surface potential of the insulating layer is 20
It is about 00 volts.

The thickness of the insulating flexible member layer 10 is typically 20μ to 70μ.
That's about it. The operating principle of this transfer method is that the toner is transferred from the surface of the photoreceptor to the transfer paper by the electric field created by the electric charges existing on the transfer belt surface, unlike conventional methods in which corona discharge is performed from the back side of the transfer paper. It is very different from that.

First, the transfer by the transfer belt is static;
No excessive charge is injected into the toner. Furthermore, since the transfer belt has a homogeneous and smooth structure, the electric field from this surface is perpendicular and of equal strength at each point. As a result, so-called transfer residual toner is extremely reduced. The amount of charge of opposite polarity injected into the toner existing on the surface of the photoreceptor remains the same regardless of the presence or absence of transfer paper. It does not cause any problem even if it is carried out continuously regardless of the feeding of the paper.

Sites other than transcription are completely the same as in Example 1.

What is shown in Example 2 describes the futility of unnecessarily charging the toner present on the surface of the photoreceptor to the opposite polarity using the opposite polarity corona during transfer. Basically, there is a need for a method in which ions due to the opposite polarity corona are not bombarded directly at the transfer section.
The present invention is not limited to the transarbelt of the second embodiment, but a relatively high-resistance Bell I, or a system in which an electric field is applied from the back surface of the transfer portion of an insulating belt using a corona or a roller may also be adopted.

The functionally separated transfer belt of Example 2 was selected from the viewpoint of its most stable operation.

When the method of the present invention is adopted, since the original cleaning section disappears, it is of course functionally simplified, but the cleaning section, which has conventionally made electrophotographic systems complicated. In addition to eliminating the problems of processing the toner that accumulates in the developer and the mechanism that returns the accumulated toner to the developing device, the toner return rate is 100%.

Therefore, the amount of toner wasted is zero.

As an additional note, the factor that causes the most mechanical damage to the photoreceptor in the conventional method is the cleaning part, and eliminating this will directly lengthen the life of the photoreceptor, and using a spherical carrier will make it even worse. is encouraging.

Here, we define the concept of an electrophotographic printer.

Basically, the activated surface of the photoreceptor is irradiated with a light image by being charged to a certain specific polarity, for example, a positive polarity, and the electrostatic latent image created as a result is transferred to the activated surface of the photoreceptor. A general term for systems that have a basic process of visualization using toner charged to the same specific polarity (for example, positive polarity). Of course, logically, there may be a method in which the charged polarities of the photoreceptor and the toner are reversed. However, my invention does not extend to that scope.

However, recently in the field of copying machines, a method has also been realized in which the optical image of a subject is electrically decomposed and reproduced as a copy using a printer method. Such a system is also included in the concept of a printer in the present invention.

C0 Detailed Description of the Invention According to the present invention, there is provided a unique electrophotographic method that completely eliminates the conventionally required cleaning section and allows the developing operation and the cleaning operation to proceed at exactly the same time. It is effective.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing the basic configuration of an electrophotographic printer that implements the method of the present invention. FIG. 2 is an enlarged sectional view schematically showing the transfer belt in the same as above. 1: Photoreceptor 3: Input signal 4; Developing section 8: Fixing device

Claims (3)

[Claims] (1) In an electrophotographic method comprising a photoconductor, a light image irradiation section, a developing section using dry toner and carrier, and a transfer section, the polarity of the charge that charges the surface of the photoconductor;
An electrophotographic method characterized in that the charged polarities of the toners are the same, and the cleaning portion is omitted, and the cleaning operation proceeds simultaneously in the developing section. (2) The electrophotographic method according to claim (1), characterized in that a transfer belt is used in the transfer section. (3) The electrophotographic method according to claim (1), characterized in that a spherical toner and a spherical carrier are used in the developing section.