JPH0440714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a printing device, and more particularly to a reversal development process and cleaning in an electrostatic printing device using an electrophotographic method or the like.

(b) Prior Art and Problems Figure 1 is a diagram showing the configuration of an electrostatic printing device using an electrophotographic method, which is the object of the present invention, in which 1 indicates a photoreceptor as an image carrier, indicated by an arrow. Rotate in two directions. 3 is a charger, and 4 is a document which is irradiated with an image lamp 5 (in the case of a printer, a laser beam, an OFT light, etc. is used) and passes through a lens 6 to form a latent image on the photosensitive surface of the photoconductor 1. A forming means is provided, and the latent image is developed in a developing means 7. This electrostatic printing device uses a so-called reversal development process in which toner of the same polarity as the charge is attached to the charge wells on the surface of the photoreceptor to form a visible image.
The printing paper 8 is transferred in the direction of the arrow 9 below. A transfer means 10 is installed below the photoreceptor 1 and on the back side of the paper, and the toner 1 attached to the surface of the photoreceptor 1 is
1 is transferred according to the image. The transferred unfixed toner 12 is fixed when the paper to which the image has been transferred passes through a fixing means 13. The fixing means can fix unfixed toner 12 on paper 8 through a filter 15 using a xenon lamp 14 to obtain an image.

When it is necessary to use toner with a low melting point in such a device due to the fixing method,
When the surface of the photoreceptor 1 is rubbed by the cleaner brush 20 in the cleaning process, the toner is fused to the surface of the photoreceptor 1, causing a filming phenomenon and impairing light transmission.

Due to such a filming phenomenon, the formation of a latent image becomes sharp and a good image cannot be obtained.

As a countermeasure against such a phenomenon, the circumferential speed of the cleaner brush has conventionally been set in an area where cleaning efficiency is high.

Conventionally, as a countermeasure against the above-mentioned filming, methods have been used such as increasing the melting point of the toner or mixing additives into the toner or developer.

However, even with the above-mentioned conventional method, there was a problem in that the filming phenomenon could not be sufficiently prevented.

(c) Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and its purpose is to prevent the filming phenomenon from occurring on the surface of an image bearing member such as a photoreceptor even when a low melting point toner is used, and to provide a good product. It is an object of the present invention to provide a printing device that allows the user to obtain beautiful images.

(d) Structure and operation of the invention According to the present invention, a latent image forming means, a developing means, and a transfer means are sequentially arranged at least around an image bearing member, and the latent image forming means forms an image on the surface of the image bearing member. In a structure in which a visible image is formed by depositing toner of the same polarity as the surface charge on the charge well in the latent image using a developing means and then transferred to a recording paper using a transfer means, the toner is charged during the operation of the developing means. The bias voltage is applied such that a bias voltage of opposite polarity is applied, and the potential difference between the well potential and the bias voltage is smaller than the potential difference between the surface potential of the charge part of the image carrier excluding the well and the potential of the well. is achieved by being chosen. Further, according to the present invention, a latent image forming means, a developing means, and a transfer means are sequentially arranged at least around the image bearing member, and the developing means is applied to charge wells in the latent image formed on the surface of the image bearing member by the latent image forming means. In a structure in which a visible image is formed by depositing toner with the same polarity as the surface charge and is transferred to recording paper by a transfer means, a bias voltage with a polarity opposite to the charged polarity of the toner is applied to the developing means during its operation. , and the bias voltage is selected so that the potential difference between the well potential and the bias voltage is smaller than the potential difference between the surface potential of the portion of the image carrier excluding the charge well and the well potential, and A cleaner brush is provided at the rear of the transfer means, and the brush is rotated at a circumferential speed within a range where toner does not form on the surface of the image carrier and where toner begins to remain on the surface of the photoreceptor. The cleaning process is then more complete.

That is, when toner is attached to the charge wells on the surface of the image carrier, the charge remaining on the surface of the image carrier is removed by applying a bias voltage of opposite polarity to the toner to the developing means using the improved reversal development method according to the present invention. The toner other than the well portion is strongly attracted to the developing means due to the large potential difference between the surface of the image carrier and the developing means, and is completely removed.

In addition, in the improved reversal development method according to the present invention, a cleaner brush is further provided at the rear of the transfer means, and depending on the circumferential speed in that case, some of the toner remains, but the toner does not reach the surface of the image carrier. Filming is prevented, so that the first cleaning step is carried out with this cleaner brush, and the subsequent complete cleaning is achieved with the improved reversal development method of the present invention.

(e) Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing the relationship between the circumferential speed of the cleaner brush and the cleaning efficiency. shows the relationship between the peripheral speed of the cleaner brush and the cleaning efficiency, and the dotted curve 17 shows the relationship between the peripheral speed of the cleaner brush and the amount of filming.

As shown by the curve in the figure, when the circumferential speed of the cleaner brush is set to the region arrow 21 where the cleaning efficiency is sufficiently high, the amount of filming is large and the deterioration of the image is large. Furthermore, if the peripheral speed of the cleaner brush is lowered in order to suppress the amount of filming, the cleaning efficiency will also be lowered, and in this case, the residual image from the previous cycle will be transferred or the fogging phenomenon will increase on the image.

According to the present invention, the toner is a low melting point toner (having positive polarity) suitable for non-contact type fixing such as xenon lamp flash fixing and halogen fixing.
The circumferential speed of the photoreceptor as an image carrier is set to 150
The circumferential speed of the cleaner brush is 3.0 m/sec in mm/sec.
sec.

In the present invention, as a prerequisite for adding such a cleaner brush, a bias voltage of -300V, which has a polarity opposite to the charged polarity of the toner, is applied to the developing means. The relationship between the circumferential speed of the cleaner brush and the cleaning efficiency at this time is the application area 22 in the curve shown by the solid line 16 in FIG. The toner filming phenomenon on the body disappears.

Figure 3A shows the conventional reversal development method, and Figure 3A shows the conventional reversal development method.
FIG. 2 is a diagram illustrating the development principle and cleaning action of the improved reversal development method according to the present invention.

In electrostatic printing, regular development and reversal development are used. In the regular development method, the surface of a photoreceptor as an image carrier is uniformly charged by a charger, and then a latent image is formed on the surface of the photoreceptor by a latent image forming member. In that case, the charge on the area exposed to the light disappears and a well of charge is formed, and a visible image is formed by applying toner with the opposite polarity to the remaining charge using the developing means. It is formed.

On the other hand, in the reversal development method, a negative original image is turned into a positive visible image by attaching toner having the same polarity as the charge polarity of the charged surface to the charge well portion of the latent image. In this case, the toner receives a Coulomb repulsive force from the charges on the charged surface, is guided by lines of electric force, and adheres to the low potential area, which is a charge well, to form a visible image. In this method, a bias voltage having the same polarity as the charge on the charged surface of the photoreceptor, that is, the polarity of the toner, is generally applied to the developing means.

The developing function and cleaning function of such a conventional reversal development method will be further explained with reference to FIG. 3A.

In the figure, 19 is a photoreceptor as an image carrier, 1
Reference numeral 8 indicates a developing means, 11 indicates toner attached to the latent image, and 11' indicates residual toner attached during the previous development and not removed by subsequent cleaning. In this conventional reversal development method, the photoreceptor is
The charge well portion, which is uniformly charged with 600V and exposed to light, has a voltage of +100V, and this 500V potential difference becomes the contrast potential. In addition, since a bias voltage of +300V is applied to the developing means, toner of the same polarity in the developing means is attracted from the charge on the surface of the photoreceptor by the lines of electric force corresponding to the contrast potential of the charge well, especially at the edges. The charge adheres to the well and forms a visible image.

However, the residual toner 11' in this conventional reversal development method is weak because electric lines of force based on the 300V difference between the potential on the surface of the photoconductor and the bias potential of the developing means act on it, and the residual toner 11' remains on the surface of the photoconductor. This results in insufficient suction by the developing means.

FIG. 3B is a diagram illustrating the improved reversal developing method according to the present invention, in which the bias voltage applied to the developing means is -300V, which is the opposite polarity to that of the conventional method.

In this case, the surface potential of the photoreceptor as an image carrier, excluding the charge wells, is +600V, while at the center of the charge wells, it is +100V.

Therefore, on the surface of the photoreceptor except for the charge wells, the developing means 1 is used for toner having positive charge polarity.
A suction force is acting on the 8 side. However, the potential difference between the potential of the photoconductor surface excluding the charge well and the potential of the charge well is 500V, while the potential difference between the charge well potential and the bias voltage is 400V. Electric lines of force are generated along the edges of the toner to the well, thereby drawing the toner into the well. That is, in the reversal development method, the contrast potential of the charge well, particularly at the edge portions, attracts toner, but in the improved reversal development method of the present invention, this edge effect acts even more strongly.

Thereby, the developing means can develop the electrostatic latent image on the photoreceptor even if a bias voltage having a polarity opposite to that of the toner is applied during its operation.

On the other hand, in this improved reversal development method, the +
Toner 1 remaining in the area with a charge of 600V
1', electric lines of force due to a potential difference of 900V act strongly. Therefore, according to the present invention, the attraction force for the residual toner, which was not sufficient with the conventional bias voltage of +300V, becomes a strong attraction force, and all the residual toner is transferred to the developing means, and cannot be removed by the conventional reversal development method. This means that the toner that could not be cleaned will be cleaned.

Therefore, by adding a cleaner brush to the improved reversal developing method according to the present invention, and setting the peripheral speed of the cleaner brush within a range that does not cause toner filming and at a peripheral speed at which toner begins to remain on the photoreceptor. Then, the toner is cleaned after the development transfer, and in that case, the remaining toner is removed by the reversal development method according to the present invention, thereby achieving complete cleaning.

(f) Effect As explained above, in the printing apparatus of the present invention, the cleaner brush is set at a peripheral speed within a range where the toner does not cause filming and at which the toner begins to remain on the latent image forming body. In addition, since a bias voltage with a polarity opposite to the charged polarity of the toner is applied to the developing means during its operation, no filming phenomenon occurs on the drum surface even when a low melting point toner is used, and cleaning is completely performed. This makes it possible to obtain good printing, and the effect is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the configuration of an electrostatic printing device, Fig. 2 is a diagram showing the relationship between the circumferential speed of the cleaner brush and cleaning efficiency, and Figs. 3 A and B are the conventional reversal development method and the improved reversal development method of the present invention. FIG. 3 is a diagram illustrating the developing function and cleaning action of the developing method. In the figure, 1 is a photoreceptor as an image carrier, 2
is the rotation direction of the photoreceptor, 3 is the charger, 4 is the original, 5
1 is an image lamp (laser light source), 6 is a lens, 7 is a developing means, 8 is paper, 9 is a paper transport direction, 10 is a transfer means, 11 is toner attached to a latent image, 11'
is the remaining toner, 12 is the unfixed toner, 13 is the fixing means, 14 is the halogen lamp, 15 is the filter, 18 is the developing means, 19 is the surface of the photoreceptor, X is the peripheral speed of the cleaner brush, Y is the cleaning efficiency and filming Indicate quantity.

Claims (1)

[Scope of Claims] 1. A latent image forming means, a developing means, and a transfer means are sequentially arranged at least around the image bearing member, and a latent image forming means, a developing means, and a transfer means are arranged in sequence, and the charge wells in the latent image formed on the surface of the image bearing member by the latent image forming means are In a configuration in which a developing means deposits toner with the same polarity as the surface charge to form a visible image, and a transfer means transfers it to recording paper, a bias with a polarity opposite to the charged polarity of the toner is applied to the developing means during its operation. A voltage is applied, and the value of the bias voltage is selected so that the potential difference between the well potential and the bias voltage is smaller than the potential difference between the surface potential of a portion of the image carrier excluding the charge well and the well potential. A printing device featuring: 2. A latent image forming means, a developing means, and a transfer means are sequentially arranged at least around the image bearing member, and the developing means generates a surface charge in the charge well in the latent image formed on the surface of the image bearing member by the latent image forming means. In a structure in which toner of the same polarity is deposited to form a visible image and transferred to recording paper by a transfer means, a bias voltage with a polarity opposite to the charge polarity of the toner is applied to the developing means during its operation, and a well The value of the bias voltage is selected so that the potential difference between the potential of the image carrier and the bias voltage is smaller than the potential difference between the surface potential of the part of the image carrier excluding the charge wells and the potential of the well, and A cleaner brush is provided at the rear of the transfer means, and the brush is rotated at a circumferential speed such that the toner does not form on the surface of the image carrier, and the toner does not remain on the surface of the image carrier. Characteristic printing device.