JPH0194357A - Developing method for electrophotography - Google Patents

Abstract

PURPOSE:To prevent disturbance of narrow lines of an image by setting the magnetic body content of magnetic toner particles to a specific value and setting the average particle size of this magnetic toner in a specific range. CONSTITUTION:A photosensitive body is electrostatically charged by a primary charger, and first and second electrostatic latent images are formed by a laser beam 3, a secondary charger 11, a laser beam 4, etc., and are developed with negative-charged red nonmagnetic toner and positively-charged a black magnetic toner respectively to form first and second toner images. The magnetic body content of this magnetic toner is set to 30-50wt.%, and the average particle size of magnetic toner is set to 4-8mu. Thus, the disturbance of narrow line parts of the image is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides two first images formed on an image carrier based on different image information. The present invention relates to an electrophotographic developing method for obtaining a two-color image by developing a second electrostatic latent image with a non-magnetic toner and a magnetic toner, respectively.

(Prior Art) Currently, electrostatic recording methods using electrophotography are often applied to printers serving as terminal devices for information equipment such as computers, facsimiles, and CAD.

These printers use laser beam, LED, LCD
An information signal is written as an electrostatic latent image on a photoreceptor (image carrier) by a developer, etc., this electrostatic latent image is visualized by a developing device, this visualized image is transferred to a transfer paper, and further A recorded image is obtained by fixing the transferred image on a transfer paper, and this recorded image is generally of a single color, for example, black.

However, if, for example, calculated values or data values are formed in a color different from the format color, or a part of a drawing output by CAD is formed in a different color, and the image is distinguished by two colors,
The image becomes clearer and the content becomes easier to understand. Distinguishing images using two colors in this way is an effective means for better understanding information. Therefore, a developing method for forming a two-color image using an electrostatic recording method has been proposed, but this method has the drawback that the two-color toners tend to mix. The reason for this is that the developing device used for electrophotography is a so-called two-component developing device that uses iron powder as a carrier and a two-component developer mixed with approximately 10% by weight of toner. When the second developing device is a two-component developing device, the toner image of the first color developed by the first developing device may be rubbed off when the first electrostatic latent image is rubbed on the photoreceptor. Also, if the carrier has deteriorated or the ratio of toner in the developer has changed, please use the first method. Second
Toner becomes difficult to adhere to the photoreceptor in any of the developing devices, and the toner image of the first color is more likely to be damaged when the second developing device rubs the photoreceptor.

Conventionally, the above drawbacks have been solved. A method of developing a first electrostatic latent image with a jumping developing device using a one-component developer made of non-magnetic toner, and developing a second electrostatic latent image with a jumping developing device using a one-component magnetic developer made of magnetic toner. is proposed.

(Problems to be Solved by the Invention) However, with the above-mentioned developing method, there has been a problem that fine line portions of the image are disturbed due to toner scattering.

(Objective) The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a developing method that does not cause disturbances in the fine line portions of an image.

[Summary of the Invention] In order to solve the above problems, the present invention provides two first images formed on an image carrier based on different image information.
In a developing method for obtaining a two-color image by developing a second electrostatic latent image with a non-magnetic toner and a magnetic toner, the content of the magnetic material in the magnetic toner is set to 30 to 50 percent by weight, and The average particle size of the magnetic toner is 4 to 8 microns.

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

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus for carrying out the method of the present invention. In the figure, 1 is a photoreceptor (image carrier) that forms an electrostatic latent image; 1000V
1 to be charged to the potential Vp (see (I) in Figure 2)
The next charger 3 is a laser beam or the like that irradiates light onto the surface of the photoreceptor 1 other than those to be developed, for example, in red.The surface of the photoreceptor 1 irradiated with this laser beam 3 has approximately zero potential. (See (■) in Fig. 2.) 11 is a secondary charger having a control grid G, which charges the photoreceptor 1.
The zero potential portion of the surface is brought to an intermediate potential Vs of about 500V (see (m) in Figure 2), and this is controlled by the control grid G to prevent fluctuations in the sensitivity of the photoreceptor l, fluctuations in the irradiation intensity of the laser beam, etc. This makes it possible to compensate for the factors and perform stable development. Reference numeral 4 denotes a laser beam or the like that irradiates light onto a portion of the surface of the photoreceptor 1 to be developed in black to form a second electrostatic latent image.By irradiating this laser beam 4, the irradiated portion has a potential of about 100V. Down ((■) in Figure 2)
reference).

Further, in the figure, reference numeral 5 denotes a jumping developer (first developer) that develops the first electrostatic latent image with negatively charged red non-magnetic toner, and the developing sleeve 5a of this developer 5 has an intermediate potential V
s is applied as a bias potential, and therefore,
The negatively charged red toner is transferred to the area of potential Vp (iooov) as shown in FIG. 2(V), and develops the first electrostatic latent image. 6 is a positively charged black magnetic toner;
Jumping developer (second developer) that develops the electrostatic latent image
An intermediate potential Vs of 5oov is applied as a bias potential to the developing sleeve 6a of the developing device 6, and therefore, the positively charged black toner has a potential of 100 V as shown in (1) in FIG. The second electrostatic latent image is developed by transferring the second electrostatic latent image to the second electrostatic latent image. 7 is the first. A post charger 8 that aligns the polarity of a red toner image (first toner image) and a black toner image (second toner image) formed by the second developing devices 5 and 6;
1 is a transfer charger that transfers the red and black toner images with the same polarity onto the transfer paper 9, and 1O is a cleaning blade that removes residual toner on the surface of the photoreceptor 1.

Next, the following experiment was conducted using the electrophotographic apparatus described above. The experiment will be explained below.

(Experiment 1) The photoreceptor 1 was charged with a primary charger, and the laser beam was 3.2-banded. A 1st and 2nd electrostatic latent image is formed using the L/-the beam 4, etc., and these 1st and 2nd electrostatic latent images are formed. The second electrostatic latent image is developed with negatively charged red non-magnetic toner and positively charged black magnetic toner to form first and second toner images. And the first. After the second toner image is uniformly negatively charged by the post charger 7, the first and second toner images are transferred to the transfer paper 9 by the transfer charger 8. As a result, the black color transferred to the transfer paper 9 is Disturbances caused by toner scattering occurred in the fine line portions of images formed with magnetic toner. on the other hand,
No disturbance occurred in the fine M portion of the image formed with the red non-magnetic toner. When the above experiment was carried out in a lower humidity environment, the disturbance in the fine line portions of the black magnetic toner image became even more noticeable and exceeded the practical limit.

However, when the charging polarity of the post charger 7 was changed from negative to positive, the disturbance in the thin line portion of the black magnetic toner image was reduced to a practical level, and the disturbance in the red non-magnetic toner image did not occur. . From this, it can be said that positive polarity is suitable for the charging polarity by the post charger 7.

(Experiment 2) When the red toner used in Experiment 1 was changed to a magnetic toner and the black toner was changed to a non-magnetic toner, toner scattering was not a problem when the charging polarity by the post charger 7 was negative. When the value is positive, the image becomes an image with many disturbances in the fine line portions due to toner scattering.

From the above experiment 1.2, it was found that the magnetic toner was easily disturbed by the post charger 7. Therefore, it is preferable that the polarity of charging by the post charger 7 be the same as the polarity of the magnetic toner.

(Experiment 3) In Experiment 1, under conditions in which the positively charged black magnetic toner scatters, that is, under conditions in which the charging polarity by the post charger 7 is made negative, the magnetic roller (not shown) in the developing sleeve 6a of the second developing device 6 is When the second electrostatic latent image was developed in a configuration in which no magnetic field was generated in the developing area between the photoreceptor l and the developing sleeve 6a, sharpness and fogging of the image occurred, but due to toner scattering. The disturbance of fine lines in the image has become extremely small. This revealed that the disturbance of fine lines in images is a phenomenon that tends to occur when magnetic toner is developed in a magnetic field.

Therefore, when observing the toner image, we find that in the case of non-magnetic toner, the toner adhering to the photoreceptor l is densely and flatly adhered, as shown in A in FIG. As shown in B, they are attached in the form of spikes, and
It can be seen that both the toner brush on the photoreceptor l and the brush on the developing sleeve are formed with toner having a larger particle size at its center. When the toner adhering to the photoconductor 1 reaches the transfer area of the transfer charger 8, it is easily scattered by the so-called corona wind blowing from the transfer charger 8 toward the photoconductor 1. Also, observe the disturbance of fine lines in the image. It can be seen that many large toner particles are scattered. By the way, if the charging polarity of the post charger 7 is opposite to that of the toner, the leading edge of the spiked toner tends to adhere to the non-latent image area due to the repulsive force, resulting in more disturbances in fine lines in the image, and furthermore, in the case of low humidity. At times, the toner moves more easily, so it seems that the number of fine lines becomes more disordered.

From the above, in order to reduce the disturbance of fine lines in the image, it is necessary to remove large particle size, that is, coarse toner, and also to take into account the force that acts on a single magnetic toner so as not to impair the development characteristics. It is necessary to reduce the force between each toner and to move each toner independently.

The magnetic toner used in experiments 1 to 3 was 35QfJ-
Contains % magnetite, average particle size 12 in air flow
The particle size distribution of particles classified as JLm is from full size to 17.
Approximately 95% of the particles are distributed in the #Ls range.

(Experiment 4) Therefore, when a magnetic toner was used in which the component composition of magnetite was kept as it was and the average particle size was reduced to 6JL, the disturbance of fine lines in the image due to toner scattering became extremely small. Further experiments revealed that when the average particle size of the magnetic toner ranged from 4JL to 81L, it was possible to obtain an appropriate image without fogging or disturbance of fine lines in the image, and when the average particle size was reduced to 4JL or less. Then, the fog increases, and 8
It was also found that if the setting is set to 1 or higher, the effect of suppressing the disturbance of fine lines in the image becomes smaller.

(Experiment 5) When the average particle size of the magnetic toner was fixed at 6 µm and the relationship between the magnetite content and the image was investigated, it was found that when the magnetite content was increased to 60% by weight, the fine lines in the image were not disturbed. Occurred. Furthermore, when the content was reduced to 30% by weight, fog became noticeable. From these results, it was found that the appropriate content of magnetite is from 30% by weight to 50% by weight.

And, the average particle size is 4 ~
8JL11. When the toner image formed by developing the second electrostatic N3 image with a magnetic toner having a magnetite content of 30 to 50 percent by weight was observed, the spiked state was suppressed as shown in C in FIG. It has become less susceptible to the effects of the coronavirus.

Note that although the above embodiment describes a developing method using toners of different polarities, it is also applicable to a developing method using toners of the same polarity. Further, although the first developer uses a one-component non-magnetic toner, a two-component developer may be used.

(Effects of the Invention) As explained above, the present invention provides two images: 51. In a developing method for obtaining a two-color image by developing a second electrostatic latent image with a non-magnetic toner and a magnetic toner, the content of the magnetic material in the magnetic particles is set to 30 to 50 percent by weight, and Since the average particle size of the magnetic toner is 4 to 8 microns, it has the effect of preventing fine lines in the image from being disturbed.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an electrophotographic apparatus that implements the method of the present invention, FIG. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 5...1st developing device, 6...-2nd developing device.

Claims (1)

[Claims] 2 images formed on the image carrier based on different image information
In a developing method for obtaining a two-color image by developing two first and second electrostatic latent images with a non-magnetic toner and a magnetic toner, the content of the magnetic substance in the magnetic toner is set to 30 to 50% by weight. and an electrophotographic developing method characterized in that the average particle size of the magnetic toner is 4 to 8 microns.