JPH0230012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic image developing method for developing an electrostatic image formed in electrophotography, electrostatic recording, electrostatic printing, or the like.

In general, there are two known methods for developing electrostatic images to form visible images: a wet developing method using a liquid developer, and a dry developing method using a powder developer. The latter method, which is superior in that it uses a carrier, is further divided into a method using a two-component developer consisting of a carrier and a toner, and a method using a single-component developer consisting only of toner.

In the development method using a two-component developer, the toner and carrier are mechanically stirred to triboelectrically charge the toner that adheres to the electrostatically charged image and visualizes it. Yes, by selecting carrier characteristics, stirring conditions, etc.
It is possible to control the charge polarity and charge amount of the toner to a considerable extent, and as a result, it is advantageous in that a relatively good visible image can be obtained, and is actually widely used.

However, when using this two-component developer, mechanical force has traditionally been used to stir the developer in order to charge it, and for this reason, only a large torque stirring mechanism is required. This is a serious drawback, especially when developing at high speed or when the developing process is repeated many times in succession. becomes.

On the other hand, a means (hereinafter referred to as "means") for making a charged two-component developer act on an electrostatic charge image support supporting an electrostatic charge image and essentially utilizing the electrostatic attraction of the electrostatic charge image to create a visible image (hereinafter referred to as Various types of developing means are known (referred to as "developing means"), and this developing means may be a cascade method in which the developer is brought into contact with the entire surface of the electrostatic image support, or a cascade method in which the developer is brought into contact with the entire surface of the electrostatic image support, or a method in which a carrier and toner are combined. Contact development methods such as the magnetic brush method, in which at least one side is magnetic, and non-contact development methods, such as the jumping method or the touch-down method, in which the developer is not brought into contact with the entire surface of the electrostatic image support. Broadly classified. The developing means according to the present invention particularly uses a two-component developer,
This is based on a contact development method in which the developer is brought into contact with the entire surface of the electrostatic image support.

The contact development method is preferable in that the developer can be reliably attached to the electrostatically charged image, but since the developer is also brought into contact with non-image areas where there is no electrostatic charge, toner is likely to adhere to these areas. Therefore, it is necessary that the amount of charge of the developer held on the developer carrier, especially the toner, be uniform, and furthermore, the thickness and surface condition of the layer formed by the charged developer must be uniform. If these are not sufficient, a phenomenon occurs in which toner also adheres to non-image areas of the electrostatic image support, making it impossible to obtain a clear visible image.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide an electrostatic image developing method capable of stably forming a good visible image by a contact development method using a two-component developer. be.

The above purpose is to control the developer amount of the two-component developer on the developer transport member, and then to charge Introducing a developer with a regulated amount into a charging space in which an alternating electric field is formed between the developer member and the developer transporting member, and causing the developer to vibrate and be charged by the alternating electric field; This is achieved by a method of developing an electrostatically charged image by a contact development method using this charged developer.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an example of an apparatus used for carrying out the method of the present invention. In this example, a developer conveying body is arranged so as to face the outer peripheral surface of a rotating drum type photoreceptor 1 constituting an electrostatic image support. A rotating metal sleeve 2 is disposed, and a developer hopper 3 for supplying a two-component developer P consisting of a carrier and toner, at least one of which is magnetic, is provided on the sleeve 2, and the developer hopper 3 and the photosensitive A developer amount regulating member 4 for regulating the amount of developer on the sleeve 2 and, for example, a conductive charging member 5 are provided in this order along the rotational direction of the sleeve 2 between the sleeve 2 and the sleeve 2. 2, a magnet M is provided to rotate in the same direction, and the charging member 5 is
As shown in the figure, the sleeve 2 is disposed so as to face the outer peripheral surface of the sleeve 2 so as to form a charging space 6 with a uniform thickness, and to be spaced apart from the developer whose amount is regulated, for example. The charging member 5 is supplied with an AC power supply V or an AC power supply V and a positive or negative voltage of 0 to 300V.
An alternating electric field is generated in the charging space 6 between the sleeve 2 and the charging member 5 by connecting a DC power source E with a voltage of about 100 volts to prevent toner adhesion.

In the present invention, an electrostatic charge image is developed in the following manner using, for example, the apparatus configured as described above.

That is, the sleeve 2 is rotated in the opposite direction to the photoreceptor 1 so that it advances in the same direction as the photoreceptor 1 in the developing area D, and the developer P filled in the developer hopper 3 is supplied onto the sleeve 2. The amount of developer P regulated by the developer amount regulating member 4 is conveyed by using the action of the magnet M, and the developer P is conveyed between the sleeve 2 and the charging member in which an alternating electric field is generated by the AC power supply V. The particles of the carrier C and the toner T are vibrated and charged so that a cloud is formed in the charging space 6.

In this way, as will be described later, the charged developer layer formed on the outer circumferential surface of the sleeve 2 is carried into the developing area D where the sleeve 2 and the photoreceptor 1 face each other, and the developing area D In this step, the charged developer is made to stand up like a spike on the sleeve 2 by the action of the magnet M and brought into contact with the photoreceptor 1, whereby the electrostatic image supported on the photoreceptor 1 is developed.

In this development, when the sleeve 2 is rotated in the direction in which it advances in the same direction as the photoreceptor 1 in the development area D, as in the illustrated example, the advancing speed of the sleeve 2 must be equal to or higher than that of the photoreceptor 1. This is effective for suppressing fog in the resulting visible image. The direction of rotation of the sleeve 2 may be reversed. In addition, the sleeve 2 is supplied with a positive or negative DC voltage of about 0 to 300V or a voltage of 0 to 2KV and a frequency of 50Hz to 50K.
Applying an AC bias voltage of about Hz,
This is effective in improving developability and preventing fogging. In the figure, B is this DC bias power supply.

The method of the present invention is as described above, and the developer is charged by passing through the charging space 6, and the mechanism thereof is thought to be as follows. That is, when the toner T or carrier C is insulating, the toner T and carrier C are in the form of powder and therefore are slightly charged even in their natural state, and even if they are not charged at all, Also, friction between the particles, friction between the particles, friction between the toner T and the carrier C, or friction between the toner T and the carrier C before the particles are introduced into the charging space 6
It becomes electrically charged due to friction when mixed with.

However, when an electric field acts, the toner T and carrier C are charged, even if only slightly, or if the carrier C is conductive, charges are injected into them. Coulomb force acts on the particles, and in the present invention, an alternating electric field acts on the developer particles in the charging space 6, so that the particles vibrate in accordance with the alternating oscillation of the electric field. That is, AC power supply V
In one half cycle, the carrier particles or toner particles fly through the charging space 6 toward the sleeve 2 or the charging member 5 and collide with them, and in the next half cycle, they fly in the opposite direction and collide with the charging member 5. Or it collides with the sleeve 2, and this repeats. In this state, a cloud is formed. The toner particles T are charged by friction when they collide with the sleeve 2 or the charging member 5 and by friction with the carrier particles C. In this way, the sleeve 2 also acts as one of the charging members.

Therefore, the charging polarity of the toner T depends on the materials of the sleeve 2, the charging member 5, and the carrier C, and the toner T.
This is determined by the relative relationship in the triboelectrification order with the toner, and therefore, by making these materials or the materials of the toner have the relative order relationship necessary for the toner to become electrically charged. The toner T becomes charged with a polarity corresponding to . The charged toner is attracted to the surface of the sleeve 2 or the charging member 5 together with the carrier C in a layered manner due to the electrostatic force. Therefore, as mentioned above, by superimposing a DC voltage on an AC voltage to form an alternating electric field, an attractive force or a repulsive force can be used to
In some cases, magnetic force can also be used to reliably attract and hold the toner T charged to a certain amount on the sleeve 2 together with the carrier C. In this case, no further charging is performed, and the toner ends up being charged with a constant amount of charge.

It is practically necessary that at least a part of the surface of the sleeve 2 and the charging member 5 or the carrier is made of a conductive material, so that by collision with the toner T, the sleeve 2 or the charging member Electrical balance can be maintained with the charges generated in the member 5 or the carrier C, and as a result, accumulation of charges therein is prevented and the intended behavior of the toner T is not restricted. From this point of view, when using an insulating carrier, such as glass beads, or a conductive carrier core with an insulating coating, the sleeve 2 and the charging member 5 may be made of metal. It is preferable to use these as electrode plates because the configuration of the device becomes simple. On the other hand, when a conductive material such as iron powder is used as the carrier, the amount of developer introduced into the charging space 6 is such that an effective electric field is generated between the sleeve 2 and the charging member 5. Appropriate measures are required, such as reducing the amount, increasing the density of the toner so that it becomes insulating as a developer, or making the surfaces of the sleeve 2 and charging member 5 insulating. becomes.

Furthermore, in the charging space 6, the toner T is transformed into a carrier C by the action of the alternating electric field.
As a result, the toner particles introduced into the charging space 6 are subjected to a substantially uniform action, and as a result, all the toner particles T
becomes charged with a high degree of uniformity.
If the charging member 5 is arranged parallel to the sleeve 2 and the thickness of the charging space 6 is made uniform, the same charging effect can be achieved in any region of the charging space 6. The amount of charge on the toner T can be reliably made uniform. Since the carrier and the toner are charged by friction due to electrical force, the charging is done softly and the developer is less likely to deteriorate.The toner is also charged uniformly and the toner is charged. is in a state where it has a stable charging potential.

In the above charging process, the number of collisions and collision speed of toner particles against the sleeve 2, the charging member 5, or the carrier particles per unit time depend on the frequency and voltage of the AC power source V that forms the alternating electric field in the charging space 6. By controlling this, it is possible to easily control the charging speed of the toner or the amount of charging in a certain charging time, and the sufficient amount of charging required in the subsequent development process can be achieved in a short period of time. You can get it at home.

Furthermore, in the above charging process, the charged toner T can be attached to the outer circumferential surface of the sleeve 2 together with the carrier C by its electrostatic force, and this attached developer can be made to have a uniform thickness. It becomes layered. This is because, as described above, a uniform charging action is performed within the charging portion 6, and each particle is charged to a uniform amount. The amount of developer P introduced into the charging space 6 is regulated by the developer amount regulating member 4. It is not necessary for the layer to be of uniform thickness. This is because the magnetic body M performs a mixing action, each particle flies, and is charged, and since the charging action in the charging space 6 is uniform, the layer of the introduced developer P is This is because even if the charged toner T is not uniform, the charged toner T forms a uniform layer with the carrier C and adheres to the sleeve 2.

This charged developer layer is then conveyed to the development zone D, where it is brought into contact with the photoreceptor 1, so that it adheres to the electrostatic charge on the photoreceptor 1 by electrostatic attraction, so that An electrostatic charge image is developed.

In the present invention, as described above, the toner carried into the developing area D is particularly uniform and has a sufficiently large amount of charge, and the charged toner on the sleeve 2 is uniformly charged on the photoreceptor 1. Since the electrostatic charge image on the photoreceptor 1 can be developed reliably and easily, a good visible image can be stably formed.

Furthermore, since the necessary charging of the developer can be carried out at high speed, high-speed development is possible, and in particular, by using a high-frequency voltage with a voltage of 0 to 2 KV and a frequency of about 50 Hz to 50 KHz in the developing means, even higher speed development can be achieved sufficiently. It becomes possible to realize this.

The toner of the two-component developer to which the method of the present invention is applied is required to have charge retention ability, and for this purpose, the toner T preferably has a specific resistance of 10 ¹⁰ Ω·cm or more.

In the charging step, since it is necessary for the developer P to fly, it may be effective to mix an additive such as fine silica powder in the developer to prevent or release the agglomeration.

Next, conditions suitable for carrying out the method of the present invention will be described. Considering the conditions in the developing process, it is preferable that the particle size of the toner T is usually in the range of 0.1 to 100 microns. In the charging space 6, an alternating electric field of a magnitude greater than that required to vibrate the carrier particles and toner particles is required, and in practical terms, the range is preferably ±5×10 ⁴ to 5×10 ⁶ V/m.
The voltage between the sleeve 2 and the charging member 5 should be lower than the voltage at which corona discharge occurs (generally about ±4KV), and the frequency should be within the range of 50Hz to 50KHz that each particle can follow. Although the range is
Preferably it is within the range of 300Hz to 5KHz.

The thickness of the charging space 6 may normally be about 0.1 to 10 mm, and the amount of developer introduced therein is preferably such that the thickness of the layer is about 0.1 to 5 mm.

Regarding the charging member 5, electric discharge or lightning strikes are likely to occur particularly between the ends of the charging member 5 and the sleeve 2, but in order to prevent this, as shown in FIG. Therefore, in order to further distance the charging member 5 from the sleeve 2, for example, the center O of the charging member 5 is set farther than the center O' of the sleeve 2, and its radius R is set as the radius of the sleeve 2.
R', or as shown in FIG.
It is effective to cover A with insulating materials 7, 7.

Further, in order to prevent the particles flying in the charging space 6 from scattering to the outside and going behind the charging member 5, a shielding plate is provided to cover the space between the developer amount regulating member 4 and the charging member 5. It is preferable.

FIG. 5 shows another device that can be used in the method of the invention, in this example, instead of the sleeve 2 in the device of FIG. 1, three rollers 10A, 10
A conductive belt 11 suspended between B and 10C is used. Also, as shown in Fig. 6, the sleeve 2
It is also possible to fix the magnet M at an appropriate position within the developer hopper 3, or to use a developer tank 12 instead of the developer hopper 3.

FIG. 7 shows an example in which an AC power supply V for forming an alternating electric field in the charging space 6 is connected to the sleeve 2 instead of the charging member 5. In such a configuration, the AC voltage is applied to the developing means. When applying , a bias power source B can be superimposed in addition to this AC power source V as necessary. Furthermore, as in this example, the magnet M may be rotated in the opposite direction to the sleeve 2.

As can be understood from the explanations of the above embodiments, when one or both of the carrier and the toner constituting the developer have magnetism, the developer can be transported by using the magnet M. Not only can this be easily achieved, but also a good charging effect can be obtained in the charging process, and the charged developer layer can be reliably retained, among other advantages. However, the method of the present invention is not limited to the use of such magnetic developers. In this case, the developer can be transported, for example, by using the suction force due to charging or the frictional force generated by roughening the surface of the sleeve 2. In this conveyance, it may be effective to apply a DC or AC voltage to the sleeve 2.

As the developer amount regulating member 4, one having a knife edge is usually used, but in addition to this, there are
A developer amount regulating member 4 as shown in FIGS. 8 to 11 can be used. The one in FIG. 8 is a plate-like body with a large number of notches 20 formed at its leading edge, and the one in FIG. 9 has a net 21 at the leading edge of the plate-like body. have 10th
The one in the figure has a spiral strip 23 on the outer periphery of the rotating rod 22, and the one in FIG. The two are rotated to regulate the amount of developer introduced. In addition, a magnetic blade (see Japanese Patent Publication No. 55-93177) can also be used.

Although the above description has focused on a developing means using a magnetic brush developing method, the present invention can also use a developing means using other contact developing methods, such as a cascade method, and in this case, the same method can be applied. Effects can be obtained.

As described in detail above, according to the present invention, it is possible to easily and reliably develop an electrostatic charge image using a contact development method using a two-component developer, and to produce a good visible image. It can be formed stably.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus that can be used in the electrostatic image developing method of the present invention, FIG. 2 is an explanatory diagram showing an enlarged part of the apparatus, and FIGS. 3 and 4 are preferred for charging members. Explanatory diagrams showing examples, Figures 5 to 7
The figures are explanatory diagrams showing configuration examples of other apparatuses that can be used in the method of the present invention, and FIGS. 8 to 11 are explanatory diagrams showing specific examples of developer amount regulating members. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 2...Sleeve, 3...Developer hopper, 4...Developer amount regulating member, 5...Charging member, 6...Charging space, 7...Insulating material, V...
...AC power supply, P...Two-component developer, T...Toner, C...Carrier, 10A, 10B, 10C...
... Roller, 11 ... Conductive belt, 12 ... Developer tank, 20 ... Notch, 21 ... Net, 22
...Rotating rod, 23...Spiral strip, 24...Protrusion strip, D...Development area, M...Magnet, B...Bias power supply, E...DC power supply.

Claims (1)

[Scope of Claims] 1. After regulating the developer amount of the two-component developer on the developer transport member, the developer is disposed opposite to the developer transport member and spaced apart from the developer whose developer amount is regulated. A developer with a regulated amount of developer is introduced into a charging space in which an alternating electric field is formed between the charging member and the developer conveying body, and the developer is vibrated by the alternating electric field and charged. A method for developing an electrostatic image, characterized in that an electrostatic image is developed by a contact development method using the charged developer.