JPS6162079A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a developed picture having high picture quality and prevented from environmental change and a change with the lapse of time by providing a reaction generating means of an electrostatic force generating a reverse reaction against the flying direction of a developer so as to control the flying in a developing area of a contactless developing device using a one-component developer. CONSTITUTION:A single developer layer of the developer 7 is formed on a developer carrier 5 to carry the developer 7 to a developing area. Under an electric field formed by a developing bias 10 and a latent image potential between an electrostatic latent image carrier 1 and the developer carrier 5, charge having reverse polarity against an electrostatic latent image 2 is induced and the developer 7 is transferred only to a picture part. To control the flying of the developer itself, developing reaction based upon electrostatic force is applied to the developing area by a developing reaction applying means 8 and a holding bias 9 in the reverse direction against the flying direction of the developer by the induced charge. Consequently, the developed picture can be prevented from disturbance, defect of picture quality such as uneven density or the generation of fog, and a developed picture having high picture quality and prevented from environmental change with the lapse of time can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a developing device, and particularly to a developing device using a -component developer.

[Conventional technology]

Conventionally, in fields such as electrophotography and electrostatic recording, it is widely known that electrostatic latent images are developed using colored fine powder.

Among them, in recent years, developers that do not use carriers, so-called -
One-component development methods using component developers have been actively proposed. As a developing method using such a one-component developer,
■ A method in which developer is formed in the form of a spike on a developer carrier and then developed by rubbing the electrostatic latent image (contact development method), and ■ Developer that maintains a minute gap from the electrostatic latent image. These methods can be roughly divided into methods in which an electrostatic latent image is developed by flying or elongating the developer from above the carrier (non-contact development method).

The first contact development method can be further divided into a conductive toner contact development method and an insulating (high resistance) toner contact development method.

"Problems to be Solved by the Invention" This conductive toner contact developing method is, for example,
As proposed in Japanese Patent No. 4532, a magnetic brush of magnetic conductive toner is formed on a magnetic roll and brought into sliding contact with the electrostatic latent image, and a charge of opposite polarity is applied to the magnetic brush according to the charge of the electrostatic latent image. In this method, development is performed by injecting (inducing) This method has less fog and can perform development faithfully, but since the magnetic brush comes into contact with the photoreceptor, the latent image charge may leak and development may not be possible, or it may adhere to the photoreceptor. The toner is further rubbed with a magnetic brush,
This method has the disadvantage that the developed image is disturbed.

The insulating toner contact development method is a method in which development is carried out by rubbing the toner with a magnetic brush, which has been charged in advance by frictional charging, against the photoreceptor. It has advantages such as no charge leakage and easy transfer. However, since this method applies a charge to the toner in advance, it is difficult to apply a uniform charge to the toner, and the amount of charge fluctuates over time or due to the influence of temperature and humidity, causing density unevenness and unevenness in the developed image. It has the disadvantage that fogging etc. occur.

In addition, as a second non-contact developing method, for example,
No. 1-9475, patent application No. 52-109237-1092
No. 42, JP-A No. 49-104639, etc., the electrostatic latent image carrier maintains a minute gap where the developer layer formed on the developer carrier does not come in direct contact with the developer. The developer, which has been given a charge in advance, is
This is a method of developing an electrostatic latent image by flying or elongating it.

In this method, unlike the former developing method, the developer does not come into contact with the electrostatic latent image carrier indiscriminately, and the developer flies or extends only in the image area, thereby preventing the fogging phenomenon. Almost eliminates outbreaks.

In order to make the developer sufficiently fly to the electrostatic latent image area, it is necessary to apply charge to the developer by some method. , a method of applying a triboelectric charge using a triboelectric charging member or the like has been proposed.

The charge injection method is a method in which a voltage is applied to an electrode provided close to a developer carrier and in contact with the developer to impart a charge to the developer.In many cases, the electrode is attached to the toner layer. Also serves as a thickness regulating member. This method has a simple structure, and by selecting the polarity of the voltage applied to the electrode, it is possible to apply 1! to the developer. ) has the advantage that the polarity of the charges can be set arbitrarily.

However, only the upper layer of the developer layer can be charged, and in the inner layer, opposite polarity developers generated by friction between the developers are mixed in the developer layer. This developer of opposite polarity may fly and adhere to non-image areas, causing fog, or developers of different polarities may adhere to each other to form a chain, which is then flown and developed as a chain. There is a problem that the resulting image becomes less sharp.

On the other hand, in the frictional charging method using a frictional charging member, etc.,
There have been proposed methods for increasing the triboelectric charging efficiency by using friction between the developer and the developer carrier or by using a separately provided triboelectric charging member.

However, such a developer charging process is affected by various surface changes over time that contribute to charging, such as a decrease in triboelectric charging efficiency due to developer adhering to the charging member, and a decrease in flight rate due to insufficient developer charge. This may cause a decrease in the
Because triboelectric charging efficiency fluctuates significantly due to environmental changes,
This fluctuation has the disadvantage that it becomes difficult to control the phenomenon. Furthermore, since the developers are also triboelectrically charged, opposite polarity developers exist in the developer layer, which appears as defects in image quality as described above. Furthermore, since the amount of charge of each developer particle contributes to development, a certain amount of charge must be imparted to each developer particle, but since the charge injection probability and contact probability of developer particles differ, There is a problem in that the charge amount of the particles varies, and when development is performed with such a developer, image quality defects such as uneven development occur.

As a result of research on such conventional one-component development methods, the present inventors found that the following drawbacks of the conventional method are: (1) There is variation in the amount of charge on each side of the toner particles, and (2) The amount of charge on each side of the toner particles varies over time. It was found that this is due to the following: - The number of toner particles transferred to the latent image surface is not constant when the toner particles are transferred to the latent image surface.

The present invention was made based on this elucidation result,
There is no variation in the amount of charge on each side of the toner particles, and it does not change with time or environment, etc., and it is possible to transfer a constant number of toner particles at all times.As a result, compared to conventional one-component development methods, It is an object of the present invention to provide a developing device which can prevent various drawbacks such as disturbances in developed images, fogging, density unevenness, and variations thereof over time and environment.

"Means and effects for solving the problems" The present invention relates to a developing device, and in particular, to a novel developing device using a -component developer. A conductive developer is held in a layer on the developer carrier, and then this developer is transported to a development area so as not to be in contact with the electrostatic latent image carrier or the electrode, and the electrostatic latent image is formed. An electrostatic latent image or a charge of the opposite polarity to the voltage applied to the electrode is induced in the developer in an electric field formed by the carrier or electrode and the developer carrier, and the developer is flown only to the image area, thereby developing. The developing device is provided with a drag generating means for generating a drag in a direction opposite to the flying direction so as to control the flying of the developer in the developing area, and the drag generating means is based on electrostatic force. It is characterized by

"Example" Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a developing device according to an embodiment of the present invention.

In FIG. 1, an electrostatic latent image 2 is formed on a latent image carrier 1 by a means not shown, while a developer 7 is formed in a single layer on a developer carrier 5, and is developed. transported to the area. In the development area, the space between the latent image carrier 1 and the developer carrier 5 is such that the developer layer 4 formed on the developer carrier 5 is out of contact with the latent image carrier 1. In order to maintain a certain gap,
The developer is transferred only to the image area and a developing action is performed.

More specifically, the developer 7 in the present invention is a conductive toner, is formed into a single developer layer on the developer carrier 5, and is conveyed to a development area, where it is static. Between the electrostatic latent image carrier 1 and the developer carrier 5, an electric charge having a polarity opposite to that of the electrostatic latent image 2 is induced under an electric field formed by the developing bias 10 and the latent image potential. As a result, the developer 7 is transferred only to the image area, and the development process is completed. Note that the reference numeral 3 is a developer, and the reference numeral 6 is a developer holding member.

Further, in the development area, in order to control the flight of the developer itself, a development drag applying means 8 is provided in the development area in the opposite direction to the direction in which the developer tends to fly due to the induced charge. Developing resistance is applied by the holding bias 9 and the holding bias 9 by a method described later.

Note that the latent image forming method is not limited to ordinary electrophotography; for example, as shown in FIG. Any method can be used, such as a method of forming by electrostatic induction. In addition, in Fig. 13,
Reference numeral 26 is an image signal.

Further, the latent image carrier 1 is not limited to a photoconductor, and may be made of, for example, a dielectric material.

According to the method with such a configuration, there is no variation in the amount of charge between the toner particles as described above, and there is no change over time.
There is no fluctuation in the amount of charge due to environmental changes, etc., and therefore it is possible to transfer a sufficient amount of developer at all times. Therefore, various drawbacks of conventional one-component development methods, such as disturbances in developed images, occurrence of fog, density unevenness, etc., as well as changes in these over time and environment can be prevented.

Next, to explain the development resistance in detail, in the present invention,
The electric charge held by the toner is determined by the developing electric field, and if the force for flying the conventional pre-charged toner is expressed as 10 F = Q - En Fad, then (0 is the charge amount of the toner, En is the developing electric field, Fad
is the force that holds the toner on the developer carrier), and in the case of the present invention, O is E. The reason why the toner is supported on the developer carrier includes non-electrostatic force, but basically the mutual force is electrostatic force, which also includes mirror image force. Basically, it is expressed by the following formula.

F=Q (En) −En −Fad'(Pad'
; Adhesive force that can be expressed by the n-th equation of Q) In such a case,
An electric field is generated between the toner, donor, and developer carrier, but this electric field can be divided into cases where it is lost during development and cases where it can exist.

In the former case, during non-development (or in the non-development area), it is the F-0TE that holds the developer on the carrier.
(-Fa(1)<0.

(QT;) Electric charge induced under E electric field due to toner adhesion, force F; Flying direction is assumed to be positive.

For example, when the carrier is made of a semiconductor to prevent charge from escaping, the donor (developer carrier) is usually carried to the development area, so that F=Q(Eo) ・En (Fad) <0 Development can be carried out by changing to

In the latter case, the force applied to the toner is F=Q (
En) ・En −KO2(−Fad) (or F = Q (En) ・Eo−K(Q(Bo))
2-Fad), and when this force F is positive, the toner flies, but since Q itself has a limit of guidance and is equal to 1, that is, as shown in Figure 2. It is necessary that a region like this can exist. In other words, it must be QTII < QI4AM. (Here, QllI: flight threshold, QMxx: maximum induced charge amount, however, it is not charged up to Q)IAX) The important point is that in the present invention, the toner charge required for development is reduced using a charging member, etc. Since it is not applied artificially, the number of control factors can be reduced by one, and since electrostatic force is used as the development drag force, flying is controlled by density unevenness due to variations in Q, changes in Q over time, etc. There is no density variation, and it is possible to develop images that are faithful to the latent image.

This development by electric charge will be explained in more detail based on FIGS. 3 to 6.

In FIG. 3, 14 is an insulating substrate with microelectrodes embedded in its surface, and the holding electrodes 13 are all at a common potential (ground potential in this case), and the toner 7 is transferred from the electrode 8. Bamboo provides an electric charge to be retained on the donor (developer carrier) 5. In this case, the toner charge loses its charge over time, but the toner carried to the development position is induced to fly by the latent image electric field in the non-image area 11. In this case, the toner 7 is carried on the donor and does not fly away due to the electrostatic force of the retained charges. Note that the reference numeral 15 indicates the process direction.

Note that, although the same applies to the following figures, the polarity of the charge is not limited to that shown in the drawings, and may be the opposite polarity to that shown in the drawings.

FIG. 4 shows an example in which the polarity of the electrode 13 of the image area 11 is changed in the development area. First, a negative charge, for example, is induced in the toner 7 by the electrode 8 . This toner 7 is transported as it is to the development area, and in the image area 11, when the polarity of the holding electrode 13 is made the same as the toner charge, the toner 7 is transferred to the image area 11. However, in the non-image area 12, the toner 7 is held on the developer carrier 5 by the electrostatic force caused by the charge on the toner.

With this configuration, it is possible to control the flying of the toner 7 to the image area 11 and the non-adhesion of the toner 7 to the non-image area 12, and as described above, it is possible to perform development faithful to the latent image 2. In the configuration example shown in FIG. 4, for example, one effective means is to provide the developer with rectifying properties. For example, by selecting the material of the toner itself or the electrode so that only negative charges (or positive charges) can be induced in a conductive toner, if the toner has such a rectifying property, it will be possible to improve the image area. It becomes easy to provide flight drag by electrostatic force.

FIG. 5 shows a case where the polarity of the electrode 13 and the polarity of the latent image 2 are the same, and in the development area, the electrode 1 of the image area 11
The potential of No. 3 is made to be different from the potential of the latent image, and a negative (or positive) charge is induced by the electric field generated by the potential difference between the two, and the toner 7 flies to the image area 11 to perform development. In this case, the important point is that during development, toner flying to the image area 11 can also be controlled by electrostatic force. ) This also makes it possible to prevent overdevelopment.

FIG. 6 shows an example in which the flying drag during development is controlled by toner polarization.

The toner 7 placed on the substrate 14 is polarized by applying a bias to the electrodes 13 embedded in the insulating substrate 14 so that the cathodes have opposite polarities, and the toner 7 placed on the substrate 14 is polarized by the moment due to polarization. It is supported and given development resistance.

(See FIG. 6(a)) In the image section 11,
The electric field formed by the electrode 13 and the latent image 11 induces electrostatic charges necessary for flight, thereby causing flight.

(See FIG. 6(b)) In this case, the development resistance applying means 8 is not required, and it becomes possible to apply the development resistance with a simple configuration.

In the above configuration, it is important that the charge given as a development drag can act as a sufficient drag even during development, and the donor material is not necessarily limited to an electrode embedded in an insulator. . For example, Aβ, F
e, a semiconductor may be coated on a metal such as Ni5SO3 or an alternative conductive member, or a conductive member may be coated or laminated with an insulator in which conductive fine powder such as metal is dispersed. . Further, in order to improve the conveyance property, it is also possible to apply a method of providing minute irregularities on one surface. Moreover, these shapes may be any shape such as a cylindrical shape or a belt shape.

For example, FIGS. 11 and 12 show an example of the developer carrier 5. As shown in FIG.

11(a) shows a columnar or cylindrical support for the conductor 210, FIG. 11(b) shows an example in which a protective layer 22 of a semiconductor layer or an insulator is provided on the conductor 21, and FIG. 11(C) shows a protective layer on the conductor 21. An example in which conductive fine particles 23 are dispersed in 22, (d) and conductor 21
An example in which microelectrodes 13 are embedded in the upper laminated member 22 is shown.

FIG. 12(a) shows an example in which fine surface irregularities are provided on the developer carrier 5, which can be obtained, for example, by polishing the metal surface with a fine file. or,(
b) shows an example in which a porous laminated member 24 is laminated and fixed or coated on the surface of the carrier 5, and it is also possible to use the porous material itself as the developer carrier. Next, (C) is an example in which a recessed portion is provided on the surface of the developer carrier 5 to the extent that the developer particles are buried therein, thereby further improving the conveyance.

In addition, as will be described later, by controlling the conductivity of the toner itself, it is possible to prevent charge leakage at least to the extent that the development resistance is not lost until development is performed after the development layer is formed, or the leakage of charge can be prevented in a timely manner. If it can be maintained, for example, TC > τ0゛ (TC; time for toner to be transported to the developing section, τゎ”
The toner carrier may be electrically conductive as long as the time required for electric charge to leak from the developer to the carrier.

Further, as shown in FIG. 7, by rotating the insulating belt 16 and the conductive belt 17 in opposite directions so that their boundary surfaces are in contact with each other, a completely insulating developer carrier can be used.

In this case, the toner 7 is conveyed from the insulating belt 16 to the development area by transferring to the conductive belt 17. In addition, the code|symbol 18 is a roller, and 19 is a counter electrode.

FIG. 8 shows another modification, in which a three-phase alternating current is applied between adjacent electrodes 13, and the toner is vibrated and transported along the electric field formed by the adjacent electrodes 13. in this case,
This is an example in which both conveyance and development resistance can be provided at the same time, and in this case, it is possible to provide the toner with sufficient development resistance due to electrostatic force. In addition, the code|symbol 20 is a three-phase alternating current power supply.

The developer used in such a configuration is an electrically conductive developer and has a volume resistivity of 1O12 Ωcm or less, and as described above, the developer has a volume resistivity that is such that the charge as a development drag is not lost until the time of development. It is also necessary to keep in mind that a time constant of . Basically, resins such as polyvinyl chloride, polystyrene, polyethylene,
Coloring materials such as pigments or dyes are added to polymers and copolymers such as polypropylene, phenol resins, and epoxy resins, singly or in combination, and the conductive particles are made of metal or magnetic materials such as magnetite. By adding any amount of particles, carbon black, etc., it is possible to obtain a conductive toner having any desired volume resistivity.

In addition, the surface potential development bias of the latent image on the latent image carrier must be set so that the developer electric field is set to several hundred V/mm or more.
, or may be one in which AC is superimposed on DC.

As mentioned above, the present invention is not limited to the development of ordinary electrophotography or electrostatic recording, but can also be applied to, for example, methods such as contrastography or modified electrophotography using intermediates. It is possible.

FIG. 9 shows a modification of the present invention, in which numeral 31 is an image signal generating section, 32 is an image signal electrode, and a signal wave voltage corresponding to the image signal is applied to the image signal electrode 32 at the same time. An electric field is formed between the image signal electrode 32 and the developer carrier 5, and the developer has an induced charge due to the mechanism described above, and flies to and adheres to the recording paper 33. The image thus formed becomes a permanent image through a fixing process (not shown). In addition,
A charge having a polarity opposite to that of the voltage applied to the electrode 32 is induced in the developer.

FIG. 10 is a diagram showing still another modification, in which an electrostatic latent image is applied to the latent image carrier 1 by a method not shown in the drawings, for example, a multi-stylus or the like. An electric field is formed between the latent image carrier 1 and the developer carrier 5 via the intermediate transfer member 34, and the developer is electrostatically induced by the electric field and flies onto the intermediate transfer member 34. adhere to. The developed image thus obtained is heat-transferred and fixed onto the transfer member 35 by a transfer roll 36 to become a fixed image 38 to obtain a permanent image. In addition, the code|symbol 37 is a press roll.

As described above, the present invention holds a conductive developer in a single layer on an electrostatic latent image carrier or a developer carrier facing an electrode, and then applies this developer to an electrostatic latent image. The developer is transported to a developing area so as not to be in contact with the carrier or electrode, and in an electric field formed by the electrostatic latent image carrier or electrode and the developer carrier, the developer is transferred to the electrostatic latent image or the electrode. A developing device for developing by inducing a charge of opposite polarity to the applied voltage and causing the developer to fly only to the image area, the developing device having a direction of flight and a direction so as to control the flight of the developer in the development area. The present invention relates to a developing device characterized in that it is provided with a drag force generating means for generating a drag force in the opposite direction, and the drag force generating means is based on electrostatic force.

Before such a developing device, (1) the toner particles themselves can be developed into almost a single layer; (2) the amount of charge on each side of the toner particles is faithful to the corresponding latent image;
There is no variation for a latent image with the same potential. ■ The amount of charge on each side of the toner particles is not affected by changes over time or environmental changes. ■ The amount of transferred toner particles is always constant for a latent image with the same potential. 1. The toner does not fly or adhere to non-image areas; 2. The developed toner image does not move into or around the image, and does not peel off from the image area. .

Therefore, the developed image may be distorted, rough, or have uneven density.
The present invention relates to a developing device that can prevent the occurrence of image quality defects such as scratches, fog, etc., and can obtain high-quality developed images that do not change over time or in the environment.

Finally, specific examples will be explained in detail to facilitate understanding of the present invention.

Example I Add carbon black and magnetite as conductive powder to an epoxy resin, knead it, then crush it with a jet mill, then add carbon black, heat treat it, and classify the adsorbed material on the surface to determine the average particle size. A conductive toner having a thickness of 10.5 μm was obtained. When the volume resistivity of the toner was measured under an electric field of 5 x 103 V/cm, it was found to be 3 x 1060 c.
It showed a volume resistivity of m. On the other hand, 25 on the aluminum pipe
After forming a photoreceptor layer made of selenium with a thickness of μm and uniformly charging the photoreceptor, a light image is applied to the photoreceptor so that the image potential increases.
The electrostatic latent image of V is (1.

Further, a single layer of low-thickness toner is rolled in a toner holding container on an aluminum cylinder held at a distance of 9.3 mm from the latent image by a spacer roller and laminated with an insulating layer with microelectrodes embedded on the surface. Then, parallel plate electrodes at ground potential were placed on the layer, and a voltage of +200 cm was applied to the embedded electrode.

Next, this is placed opposite to the electrostatic latent image, the embedded electrode is set to ground potential, and the developed new image has a high density of 1.3, has no density unevenness, has a sharp image, and has no fog. I was able to obtain a developed image.

Example 2 A single layer of toner was formed in the same manner as described above, the embedded electrodes were alternately maintained at +200V and 0V, and a latent image similar to that described above was developed. I was able to obtain high-quality developed images with no unevenness.

"Effects of the Invention" As explained above, by using the present invention, it is possible to obtain high-quality images that do not change over time or in the environment.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a developing device according to an embodiment of the present invention, FIG. 2 is a graph diagram showing the relationship between charge Q and force F, and FIGS. 3, 4, 5, and 6 ( a) and (b) are explanatory views showing the developing action of the embodiment of the present invention, Fig. 7.8 is an explanatory view showing a modification of the developer carrier, and Figs. 9 and 10 are explanatory views showing the modification of the present invention. Explanatory diagrams showing examples, Figures 11 (a), (b), (C), (d), Figure 12 (
a), (b), and (C) are explanatory views of the developer carrier, and FIG. 13 is an explanatory view showing the latent image forming method. ■...Latent image carrier, 2...Latent image, 3.
...Development, 4...Developer layer, 5...
...Developer carrier, 6...Developer holding member, 7
. . . Developer, 8 . . . Development drag imparting means, 9 . . . Development bias. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure 4 Figure 7 Figure 8 Figure 9 Figure 1O Figure

Claims (1)

[Claims] (1) A conductive developer is held in a single layer on a developer carrier facing an electrostatic latent image carrier or an electrode, and then this developer is kept in a non-contact state with the electrostatic latent image carrier or electrode. The developer is transported to a developing area in such a manner that the developer is charged with a charge of opposite polarity to the voltage applied to the electrostatic latent image or electrode in an electric field formed by the electrostatic latent image carrier or electrode and the developer carrier. induce,
A developing device that performs development by causing developer to fly only in the image area, and includes a drag force generating means for generating a drag force in a direction opposite to the flying direction so as to control the flying of the developer in the development area. A developing device, characterized in that the drag generating means is based on electrostatic force.