JPS5824164A - Electrostatic latent image developing method - Google Patents

Abstract

PURPOSE:To obtain a 2-color image by use of the same developing machine, by using a mixed developer consisting of an insulating magnetic toner, and a high resistance magnetic toner having photoconductivity and a color which is different from the former, and selectively charging an electrostatic latent image formed on the surface of a photosensitive body. CONSTITUTION:A developing device 20 is formed by covering the outside circumference of a roller-like magnet 13 with an electrically conductive carrier 14, and placing a developing layer control plate 22, a developer charging charger 15 and a developer exposure source 16. A black insulating magnetic toner TB(>=10<15>OMEGAcm) is mixed with a red toner TR having photoconductivity and high resistance magnetism (dark resistance 10<8>-10<11>OMEGAcm), by which a magnetic toner De is obtained. It is magnetically adsorbed like one layer by the control plate 22, and is charged 15 and is exposed 16. The black TB is charged, but the red TR is not charged. On a photosensitive body surface 11a, an electromagnetic latent image of an original is formed, and at first, the black TB is transferred. Subsequently, a bias electric power supply 18 is applied to a photosensitive body substrate 11a, and the red TR is transferred to the latent image which has passed through a red light absorbing filter 17, by which a copied image having 2 colors is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electrostatic latent image developing method in which an electrostatic latent image carried on the surface of an electrostatic latent image carrier can be visualized using toners of different tones. . For more details, please refer to the 2 different color tones.
The present invention relates to an electrostatic latent image developing method for developing the electrostatic latent image using a novel developer made of a mixture of different types of toners.

Prior Art In order to provide an electronic copying machine with the function of changing the tone of a copied image from black to red or from red to black, it is necessary to install a black developing device and a red developing device in the copying machine. Therefore, it is inevitable that the copying machine itself will become larger. On the other hand, in a two-color electronic copying machine as well, it is necessary to install two developing devices in order to carry out two-color development, and there is a problem with increasing the size of the copying machine itself.

OBJECTS OF THE INVENTION An object of the present invention is to provide an electrostatic latent image developing method that allows an electronic copying machine to have the above-mentioned functions without substantially increasing the number of developing devices installed. Another object of the present invention is to provide an electrostatic latent image developing method that can improve the problem of increasing the size of the two-color electronic copying machine.

SUMMARY OF THE INVENTION The gist of the present invention is to provide a method for developing an electrostatic latent image according to the present invention, in which a magnetic toner comprising a mixture of an insulating magnetic toner and a high-resistance magnetic toner having photoconductivity but having a different color tone from the toner is used. The developer is used to develop the electrostatic latent image carried on the surface of the electrostatic latent image carrier. More specifically, prior to the development of the electrostatic latent image, the magnetic developer is magnetically attracted to the surface of the conductive carrier in a single layer, and the magnetic developer magnetically attracted to the surface of the conductive carrier is The reason is that charging and exposure are performed.

In the electrostatic latent image developing method according to the present invention, when developing the electrostatic latent image, an insulating magnetic toner or a high-resistance magnetic toner in the magnetic developer is used depending on the charging polarity in the charging and exposure. Either one of them is electrostatically attracted to the electrostatic latent image, and as a result, the electrostatic latent image is visualized with toner of a different tone depending on the charging polarity.

EXAMPLE In order to specifically explain an example of the electrostatic latent image developing method according to the present invention, a two-color electrophotographic copying process to which the electrostatic latent image developing method according to the present invention is applied will be described below. Note that the third step in the two-color electrophotographic copying process shown below.
In step 4 and step 7.8, the electrostatic latent image development method according to the present invention is carried out.゛ Fig. 1 is a diagram schematically showing the first step in the process, in which an electrophotographic photoreceptor (1) is formed by placing an electrophotographic photoreceptor (1b) on a grounded conductive substrate (1a). It's layered. In this first step, this photoreceptor (1) is moved relative to the charger (2) in the direction of the arrow in the figure.
) is uniformly charged with ←) polarity, and its surface is ←)
It will hold a polar charge.

Note that the charging polarity of the photoreceptor (1) may be (g) polarity depending on its characteristics. Subsequently, the photoreceptor after being charged (
1), in the second step schematically shown in FIG.
Except for the part indicated by (B) in the figure, the (-) polar charge held on the surface is dissipated, and a first electrostatic latent image corresponding to the original image is formed on the surface. become. The electrostatic latent image thus formed is visualized in step 8.4, which is schematically shown in FIG. 3.4, while being supported on the surface of the photoreceptor (1).

FIG. 3 is a drawing schematically showing the eighth step in the process, in which a magnetic developer (Da) is mixed with a black toner (Tu) that has both insulation and magnetism, and a black toner (Tu) that has a high resistance value. , a red toner (T
R). The black toner (TB)
indicates the resistance value of 1o Ω・σ, and the red toner (TiQ has a resistance value of 1o 10Ω・m1 in the dark and 10Ω in the light).
・It shows the resistance value of α. Note that the two-color electrophotographic copying process shown here is intended to copy an original image in two different tones, black and red, so each color in the magnetic developer (De) is Although the toners have black and red tones, each toner can have a different tone if necessary. Regarding the resistance value of each toner, if the resistance value of black toner (TB) is 1014 Ω・m or more, and on the other hand, the resistance value of red toner (TR) in a dark place is 108 to 1011 Ω・m, then the electrostatic latent image The conductive carrier (4) is grounded by the magnetic action of the magnet (8).
magnetically adsorbed in a single layer on the surface. A charger for charging the developer (5) and a light source for exposing the developer (5) are moved relative to the magnetic developer (De) magnetically attracted to the surface of the conductive carrier (4) in the direction of the arrow in the figure. 6), charging and exposure are performed simultaneously. The charging polarity at this time is (g) polarity, which is opposite to the polarity of the first electrostatic latent image. Therefore, the black toner (TB) in the magnetic developer (De) is charged to a polarity opposite to the polarity of the first electrostatic latent image, and holds the charge of the (g) polarity. On the other hand, the red toner (TR) loses charge retention ability because it becomes conductive upon exposure by the light source (6), and is not charged by the charger (5). TR) does not hold any charge. That is, in this third step, only the black toner (TB) is selectively charged. Note that charging and exposure in the eighth step (same as the seventh step described later) do not necessarily have to be performed simultaneously, and exposure may be performed after charging is completed. Further, the two-color electrophotographic copying process shown here is based on the first
In order to visualize the electrostatic latent image with the black toner (TB), the charging polarity in the third step is set to be opposite to the polarity of the first electrostatic latent image. In order to visualize the image using TR), the charged polarity may be reversed.

In the fourth step in the process, a first step is applied to the surface.
A photoreceptor (1) carrying an electrostatic latent image and a conductive carrier (4) having a magnetic developer (De) magnetically adsorbed on its surface
The conductive carriers (4) are closely opposed to each other with a minute gap of 00 to 800 μm maintained, and are relatively moved in the direction of the arrow in the figure. As a result, an electrostatic attraction force is generated between the (c) polar charge of the first electrostatic latent image and the (g) polar charge of the black toner (TB), and the black toner (TB) is attracted to the magnet ( 8), it is electrostatically attached to the first electrostatic latent image by the magnetic adsorption force. That is, the first electrostatic latent image is visualized by black toner (TB). In addition, at this time, the red toner (TR) does not hold an electric charge, and the magnet (
Since it is magnetically attracted to the surface of the conductive carrier (4) by the magnetic action of 3), it does not adhere to the photoreceptor (1) side.

However, when the potential of the first electrostatic latent image is high, red toner (TR) often adheres to the first electrostatic latent image. In order to avoid this, the potential, i.e.
The 4th position of the charger (2) on the photoreceptor (1) is -5
It is desirable to suppress the voltage to about 00V.

After the completion of the fourth step, in the fifth step schematically shown in FIG. ) is re-charged to polarity. At this time, although the surface portion of the photoreceptor (1) on which the black toner (TB) is attached, that is, the portion indicated by ω in the figure, is also charged, the black toner (TB)
), the charging potential of the surface portion is extremely low compared to the charging potential of other surface portions. Also, at this time,
In order that the (g) polar charge held by the black toner (TO) is not neutralized and the black toner (TB) can still hold the (g) polar charge even after the completion of this fifth step, The charge amount of the black toner (TB) charged by the charger (5) and the charge amount charged by the charger (2) are each adjusted. The charging polarity of the photoreceptor (1) in this fifth step may be opposite to that in the first step. However, in that case, since the polarity of the second electrostatic latent image becomes (g) polarity, the charging polarity of the black toner (TB) in the seventh step described below needs to be ←) polarity.

Subsequently, in the sixth step schematically shown in FIG. 6, the charged photoreceptor (1) is subjected to image exposure using the same copy original again in exactly the same manner as in the second step. receive. However, at this time, unlike in the second step, the image exposure is performed through a red light absorption filter (7). As a result, the surface portions of the photoreceptor (1) corresponding to the black and red portions of the copy original, that is, the sixth
Except for the parts indicated by (B) and (R) in the figure, the ←) polar charges held on the surface are dissipated, and a second electrostatic latent image corresponding to the original image is formed on the surface. will be formed.

This second electrostatic latent image actually corresponds to both the black and red images of the document, but as explained above, the second electrostatic latent image is formed on the photoreceptor (1) to which black toner (TB) is attached. The potential of the surface portion, that is, the portion indicated by (B) in the figure, is (6) in the figure.
), this second electrostatic latent image substantially corresponds only to the red image of the document. The second electrostatic latent image formed in this way is visualized in steps 7 and 8, which are schematically shown in FIGS. 7 and 8 while being supported on the surface of the photoreceptor (1). be done. Of course, the second electrostatic latent image is visualized in a different tone from the first electrostatic latent image.

In the seventh step, in order to visualize the second electrostatic latent image with red toner (TR), unlike in the third step, black toner (TB) is used in the second electrostatic latent image. It is selectively charged to the same polarity as that of the latent image, that is, (→ polarity. Seventh
The method of selectively charging the black toner (TB) in the step is exactly the same as that in the third step.

After completing the seventh step, in the eighth step, a second layer is applied to the surface.
The photoconductor (1) carrying the electrostatic latent image and the conductive carrier (4) on which the magnetic developer (D) is magnetically adsorbed are brought into close proximity in the same way as in the fourth step. However, in this eighth step, the conductive substrate (
1a), a developing bias voltage having the same polarity as that of the second electrostatic latent image is applied. For this reason, conductive carrier (4)
From a different point of view, there is an electric field between the black toner (TB) and the photoreceptor (1), which directs the black toner (TB) toward the conductive carrier (4).
An electric field is created which substantially increases the potential of the electrostatic latent surface.

As a result, a charge of (g) polarity is induced in the red toner (to)) by the charge of the ←) polarity of the second electrostatic latent image, and the red toner (TR) is attracted by the magnetic attraction force of the magnet (3). It overcomes and electrostatically adheres to the second electrostatic latent image. Note that because the potential of the portion to which the black toner (TB) is attached is extremely low, the red toner (TR) does not adhere to the portion to which the black toner (TB) is attached. The developing bias power source (8) is used in the eighth step to compensate for the difficulty in inducing the electric charge in the red toner (TR) due to the proximity of the second electrostatic latent image. 1 changes the charging position of the photoreceptor (1) in the fifth step to the first
If the potential of the second electrostatic latent image itself is made sufficiently high, such as by setting it to a sufficiently high value compared to that in the step (2), it is not necessary to use it. On the other hand, in this eighth step, the black toner (TB) holds charges of the same polarity as the polarity of the second electrostatic latent image.
It electrostatically repels the second electrostatic latent image and is magnetically attracted to the conductive carrier (4), and does not adhere to the photoreceptor (1) side.

In this way, through steps 1 to 8, a two-color toner image of black and red corresponding to the original image is formed on the surface of the photoreceptor (1), and this toner image is transferred to transfer paper. However, in order to further fix the image and finally obtain a copy, a ninth step schematically shown in FIG. 9 is required in the two-color electrophotographic copying process shown here. This ninth step is to facilitate the electrostatic transfer of black toner (TB) and red toner (TR) to the transfer paper.
B) This is a step in which both red toner (TR) are charged to the same polarity by a charger (9) that moves relatively in the direction of the arrow in the figure. In addition, in FIG. 9, both the black toner (To) and the red toner (TR) are (T).
Although shown as being charged in a polar manner, it is of course possible to be charged in a polar manner.

Next, with reference to FIG. 10, an example of a two-color electrophotographic copying machine suitable for continuously carrying out the two-color electrophotographic copying process will be described below.

Although the copying machine described below is a two-color electrophotographic copying machine, it is equipped with only one developing device α, and the copying machine itself is made more compact.

A detailed explanation of the operation of the copying machine shown in FIG. 10 will be omitted, but in this copying machine, the first to fourth steps are performed sequentially while the drum-shaped photoreceptor (11) rotates once or twice. The fifth to ninth steps are sequentially executed during two to three rotations, and one two-color copying of the original image is completed. For this reason, each element in this copying machine is adjusted as described below.

In FIG. 10, a drum-shaped photoreceptor (11) is formed by laminating an electrophotographic photosensitive layer (llb) on a conductive substrate (lla), and when the copying operation starts, the drum-shaped photoreceptor (11) moves in the direction of arrow (a). By rotating approximately three times, the two-color copying of the original image is completed once, and then stopped. On the other hand, the charger (12) uniformly charges the surface of the photoreceptor (11) to ←) polarity, and performs the first step in the first rotation of the photoreceptor (11) and in the second rotation. The fifth step is executed sequentially. Further, the slit (21) constitutes a part of an optical system for sequentially projecting a light image corresponding to the original image onto the surface of the photoreceptor (11). )
The second step is executed in the first to second rotations of the first rotation.
An electrostatic latent image of (
b) Yes. Note that this optical system includes a red light absorption filter (17) that is provided so as to be movable back and forth in the direction of the arrow Sakaki. (17) is allowed to enter.

The developing device (20) has a sleeve-shaped, grounded, electrically conductive carrier (14) with a roller-shaped magnet (13) inside. This conductive carrier (14) is rotated integrally with the magnet (13) in the direction of arrow (C) at a peripheral speed greater than that of the photoreceptor (11) during electrostatic latent image development. There is also a developer-regulating plate (22) around it.
, a charger for charging the developer (15), and a light source for exposing the developer (16). The regulation plate (22)
is the amount of developer magnetically adsorbed on the surface of the conductive carrier (14), specifically, the amount of magnetic developer (De) consisting of a mixture of black toner (TB) and red toner (TR). It is regulated by On the other hand, the charger (
15) is a developer (Do ) to the (g) polarity, and the developing device ff1 (20)
Prior to developing the second electrostatic latent image, the developer (De) is charged to (c) polarity in order to carry out the seventh step in the 21st to 8th rotations of the photoreceptor (11). Mr,
Charge polarity is automatically switched at appropriate times. Also,
The light source (16) is for exposing the developer (De) when performing the steps 3 and 7 above. A developing bias power source (18) is connected to the conductive substrate (lla) of the photoreceptor (11), and when the second electrostatic latent image is developed, that is, the eighth step is executed. During this process, a (-) polarity bias voltage is applied to the substrate (lla). However, the substrate (lla) is grounded except when the eighth step is executed.

The charger (19) collects black toner (TB) and red toner (TR) attached to the surface of the photoreceptor (11).
It is charged with polarity, and is activated only during the second to eighth rotations of the photoreceptor (11) to carry out the ninth step. In addition, the transfer charger (29) is
The photoconductor (11) is rotated in the direction of the arrow (d) in synchronization with the movement of the surface of the photoconductor (11) after the second electrostatic latent image development to the transfer section.
This is to electrostatically transfer the black toner (TB) and red toner (TR) adhering to the surface of the transfer paper (23) to the surface of the transfer paper (23). The transfer charger (29) is also the same as the charger (19), and the photoreceptor (11) is
It is designed to be activated for the first time in the third rotation.

Of course, the transfer paper (23) also covers 2 to 3 of the photoreceptors (11).
The image is conveyed to the transfer section only at the turn of rotation.

Black toner (Th) attached to the surface of the photoreceptor (11)
Transfer paper (28) after transferring red toner (TR)
is an AC operated in synchronization with the transfer charger (25).
Separate charger (JX&
It is peeled off from the surface of the light body (11) and the arrow (e)
The image is ejected to the outside of the copying machine via a fixing device by a conveyor belt (26) which is rotated in the direction shown in FIG. On the other hand, transfer black toner (TB) and red toner (TR) to transfer paper (23).
The surface of the photoreceptor (11) after being transferred to the surface of
As the photoreceptor (11) is rotated in the direction of arrow (a), it reaches a position facing the cleaning device (28). At this position, the black toner (TB) and red toner (TR) remaining on the surface of the photoreceptor (11) without being completely transferred to the surface of the transfer paper (23) are removed from the photoreceptor by a cleaning blade (28). (11) is scraped off and collected from the surface of the cleaning blade) (2).
8a) is provided so as to be swingable in the direction of arrow (f), and the surface of one photoreceptor (11) with black toner (TB) and red toner (TR) remaining on the surface is cleaned. Only when passing through the device M (28) is the photoreceptor (11
) The tip of the blade (28a) is pressed against the surface of the blade (28a) to perform the above function. Note that the eraser lamp (29) is used to erase charges remaining on the surface of the photoreceptor (11) before forming a latent image next time.
1) This is to provide uniform exposure to both.

Effects of the Invention In the electrostatic latent image developing method according to the present invention, when an electrostatic latent image is developed using a developer consisting of a mixture of two types of toners with different tones, the electrostatic latent image is Since it is possible to arbitrarily select whether or not to develop a latent image, it is possible to provide an electronic copying machine with a function of changing the tone of a copied image without substantially increasing the number of developing devices installed. Furthermore, since the developing device in the two-color electronic copying machine can be reduced to one, the problem of increasing the size of the copying machine itself in the two-color electronic copying machine is also improved.

[Brief explanation of drawings]

1 to 9 are drawings each schematically showing steps 1 to 9 of a two-color electrophotographic copying process to which the electrostatic latent image developing method according to the present invention is applied, and FIG. 10 is a drawing showing the φ 1 is a drawing schematically showing essential parts of a two-color electrophotographic copying machine suitable for carrying out a process. 1.11... Electrophotographic photoreceptor 3,13... Magnet 4.
14 Conductive carrier 5, 15... Charger for charging developer 6, 16... Light source for exposing developer 7, 17...
Red light absorption filter 8, 18...Development bias power supply De...Magnetic developer TB...Black toner (insulating magnetic toner) TR...Red toner (high resistance magnetic toner) Applicant Minolta Camera Co., Ltd. Figure 6 Figure 7 Figure 9

Claims (1)

[Claims] 1. A magnetic developer consisting of a mixture of an insulating magnetic toner and a high-resistance magnetic toner having photoconductivity but having a different color tone from the toner is formed in a single layer on the surface of a conductive carrier. The electrostatic latent image carried on the surface of the electrostatic latent image carrier is transferred into the magnetic developer by magnetically adsorbing the electrostatic latent image carried on the surface of the electrostatic latent image carrier by charging and exposing the magnetic developer magnetically adsorbed to the surface of the conductive carrier. When the image is visualized with an insulating magnetic toner, the insulating magnetic toner is selectively charged to a polarity opposite to that of the electrostatic latent image, and when an image is visualized with a high-resistance magnetic toner, the insulating magnetic toner is selectively charged to a polarity opposite to that of the electrostatic latent image. An electrostatic latent image developing method, characterized in that the insulating magnetic toner is selectively charged to the same polarity as the electrostatic latent image. 2. The resistance value of the insulating magnetic toner is 10 Ω・m
2. The electrostatic latent image developing method according to claim 1, wherein the resistance value of the high-resistance magnetic toner in a dark place is 10 to 10 Ω. & When the electrostatic latent image is visualized with the high-resistance magnetic toner in the magnetic developer, the insulating magnetic toner is placed between the conductive carrier and the electrostatic latent image carrier in a direction toward the conductive carrier. An electrostatic latent image developing method according to claim 1 or 2, characterized in that an electric field of: