JPH0131606B2 - - 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.

Therefore, in the development method using a one-component developer, there is essentially no change in toner concentration, which simplifies the configuration of the developing device, and the characteristics of the developer do not deteriorate over a long period of time. Although it is superior to systems using two-component developers in that it is possible to stably obtain images without any image formation, it has the serious drawback of not being able to form stable images. This is because it is difficult to charge the developer to the required state and to cause the developer to act on the electrostatic image support in the required state during development.

In other words, in order to obtain a good visible image using the dry development method, it is necessary to charge the toner so that it has a polarity opposite to that of the electrostatic charge image to be developed and a charge amount of an appropriate amount. In the system using a two-component developer, the toner is triboelectrified by mechanically stirring the toner and carrier, so by selecting the characteristics of the carrier, stirring conditions, etc. It is possible to control charge polarity and charge amount to a considerable extent. However, in a single-component developer consisting only of toner, such a carrier does not exist, so
It is very difficult to control the toner charge polarity and charge amount.

Conventionally, known methods for charging one-component developers include a frictional charging method using mechanical force, a charge injection charging method using an injection electrode, and a charging method using a corona discharger.

However, in the frictional charging method using mechanical force, the toner is charged by friction between the toner and the stirrer or container wall, or friction between toner particles, so the amount of charge is generally small and it is difficult to control the size. However, as a matter of course, there is a drawback that some toner is charged to a polarity opposite to the required polarity.

In the charge injection charging method, if the developer is insulating, it is difficult to inject the charge, whereas if the developer is conductive, leakage occurs and a large amount of charge cannot be obtained.

Further, the charging method using a corona discharger has the disadvantage that the developer cannot be charged uniformly and the corona wire becomes dirty.

On the other hand, a means (hereinafter referred to as "means") for making a charged one-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 (referred to as "developing means") are known, including a contact developing method such as an impression method in which the developer is brought into contact with the entire surface of the electrostatic image support;
There are two types of developing methods: non-contact developing methods such as jumping methods and touch-down methods, in which the developer is not brought into contact with the entire surface of the electrostatic image support.
The developing means according to the present invention employs a contact development method in which an insulating one-component developer is used and the developer is brought into contact with the entire surface of the electrostatic image support.

The contact development method is preferable in that the toner 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 toner held on the developer carrier be uniform, and in addition, in the impression method, etc., the thickness and surface condition of the layer formed by the toner must be uniform. If these are not sufficient, a phenomenon occurs in which toner also adheres to non-image areas on the electrostatic image support, making it impossible to obtain a clear visible image.

Furthermore, regardless of the contact development method or the non-contact development method, in development using a one-component developer, the development area, that is, the area where the charged one-component developer is applied to the electrostatic image support, contains the necessary components for development. It is desirable that the developer be carried in in the minimum amount required, and this is because, unlike a two-component developer, all of the developer has the possibility of participating in development. The minimum amount required is the amount in which several layers of developer particles are deposited.

However, in the past, as mentioned above, not only is it not possible to obtain the required charge state such as charge polarity and charge amount for a one-component developer, but also it is difficult to carry the developer charged in a preferable state into the development area. Therefore, it has been difficult to stably form a good visible image.

The present invention has been made based on the above circumstances, and provides an electrostatic image developing method that can stably form a good visible image by a contact development method using an insulating one-component developer. There is something to do.

The above purpose is to regulate the developer amount of the insulating one-component developer on the cylindrical developer transport member, and then arrange the insulating one-component developer on the cylindrical developer transport member and to The amount of developer is regulated in a charging space in which an alternating electric field is formed between a plate-shaped charging member whose ends in the direction are rounded and covered with an insulating material and the developer conveying body. A method for developing an electrostatic image, comprising: introducing a developer, vibrating the developer using the alternating electric field to charge the developer, and using the charged developer to develop an electrostatic image by a contact development method. It is achieved by doing so.

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. A rotating sleeve 2 is disposed, a developer hopper 3 for supplying an insulating one-component developer (hereinafter simply referred to as "toner") T is provided on the sleeve 2, and the developer hopper 3 and the photoreceptor 1 are connected to each other.
Along the rotational direction of the sleeve 2,
A toner amount regulating member 4 and a charging member 5 having a configuration described later are provided in this order, and the charging member 5 has a uniform thickness between it and the outer peripheral surface of the sleeve 2, as shown in FIG. For example, the charging members 5 are arranged facing each other so that a charging space 6 is formed.
An alternating current power source V or an alternating current power source V and a positive or negative DC power source E for toner adhesion prevention with a voltage of about 0 to 300 V are connected to generate an alternating electric field in the charging space 6. .

As shown in FIG. 4, the charging member 5 has both end portions 5A, 5A in the circumferential direction of the sleeve 2, which is a plate-shaped conductor, rounded and further covered with an insulating material. 7,7.

In the present invention, an electrostatic charge image is developed in the following manner using 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 toner T filled in the developer hopper 3 is supplied onto the sleeve 2. The amount of toner T regulated by the toner amount regulating member 4 is introduced into the charging space 6 where an alternating electric field is generated by the AC power source V, and a toner cloud is formed in the charging space 6. Each particle of the toner T is vibrated to be charged.

In this way, as will be described later, the charged toner 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 are in contact with each other, and in this developing area D, , the charged toner is brought into contact with the photoreceptor 1 through the sleeve 2, whereby the electrostatic charge 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. Although the sleeve 2 may be rotated in opposite directions, preferable results can be obtained if the sleeves 2 are rotated in the same direction. 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 1KV and a frequency of 50Hz to 50K.
Applying an AC bias voltage of about Hz,
This is effective in improving developability and preventing fogging. B in the figure is this DC bias power supply. Further, the sleeve 2 elastically contacts the photoreceptor 1,
It is preferable that the material does not damage the photoreceptor 1.

The method of the present invention is as described above, and the toner is charged by passing through the charging space 6, and the mechanism thereof is thought to be as follows. That is, since the toner T is in the form of powder particles, it is slightly charged even in its natural state, and even if it is not charged at all, the toner T is charged until it is introduced into the charging space 6. The particles become electrically charged due to friction between particles or friction with instruments, vessel walls, etc.

However, since the toner T is electrically charged, even if only slightly, a Coulomb force acts on the toner T when an electric field acts on it, and in the present invention, an alternating electric field acts on the toner T in the charging space 6. As a result, the toner T vibrates in accordance with the alternating vibration of the electric field. That is, in a half cycle of the AC power source V, 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 become charged. It collides with the member 5 or the sleeve 2, and this process is repeated. In this state, a toner cloud is formed. The toner particles are charged mainly due to friction when they collide with the sleeve 2 or the charging member 5, or further due to friction between the toner particles during flight or the like. In this way, the sleeve 2 acts as one of the charging members.

The charging polarity of the toner T is determined by the relative relationship between the materials of the sleeve 2 and the charging member 5 and the toner T in the triboelectric charging order. By establishing a relative order relationship necessary for the toner T to be charged, the toner T is charged with a polarity corresponding to this. The charged toner is then attracted to the surface of the sleeve 2 or the charging member 5 in a layered manner due to the electrostatic force. Therefore, as described above, by superimposing a DC voltage on an AC voltage for forming an alternating electric field, the toner T charged to a certain amount of charge can be charged using attractive force or repulsive force. In addition to being able to reliably attract and hold the toner particles on the sleeve 2, no further charging action is performed on the attracted toner particles, and the toner ends up being charged with a constant amount of charge.

It is practically necessary that at least a part of the sleeve 2 and the charging member 5 be made of an electrically conductive material, so that the sleeve 2 or the charging member 5 is free from electricity caused by collision with the toner T. 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, it is preferable that the sleeve 2 and the charging member 5 are made of metal and used as an electrode plate. It can also be formed by twisting.

Further, in the charging space 6, the toner T is vibrated and charged by the action of the alternating electric field, so that the toner particles introduced into the charging space 6 are subjected to a substantially uniform action. As a result, all the toner T is 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.

Furthermore, in the above charging process, the number of collisions and collision speed of the toner particles against the sleeve 2 or the charging member 5 per unit time depend on the frequency and voltage of the AC power supply 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 charge in a certain charging time, and the sufficient amount of charge required in the subsequent development process can be obtained in a short time. be able to.

Furthermore, in the above-described charging process, the charged toner T can be made to adhere to the outer peripheral surface of the sleeve 2 by its electrostatic force, and the adhered toner T forms a layer of uniform thickness. This is because, as described above, a uniform charging action is performed within the charging space 6, and the toner T is charged to a uniform amount of charge. Of course, it is desirable that the amount of toner T introduced into the charging space 6 is always a constant amount, and the toner amount regulating member 4 is used for this purpose. It is not necessary for the toner T to be formed into a layer of uniform thickness by the toner amount regulating member 4. This is because toner particles are charged as they fly, and the charging action in the charging space 6 is uniform, so even if the layer of introduced toner T is not uniform, the charged toner T is uniform. This is because it adheres to the sleeve 2 in layers.

This charged toner layer is then conveyed to the development area D, where it is brought into contact with the photoreceptor 1, thereby causing it to adhere to the electrostatic charges on the photoreceptor 1 by electrostatic attraction, resulting in the static A charge image is developed.

In the present invention, as described above, the toner carried into the development area D is particularly uniform and has a sufficiently large amount of charge, and the charged toner on the sleeve 2 is in the form of a layer with a uniform thickness. Since the surface is flat, the toner is uniformly distributed 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.

In addition, since the amount of charge of the toner can be made uniform, most of the toner carried into the development area D is used for development, and therefore, the amount of toner being carried into the development area D is controlled by the toner amount regulating member 4. The thickness, ie, the amount, of the charged toner layer to be applied can be controlled to a sufficient amount necessary for development, and the occurrence of fog can be suppressed, resulting in a clear visible image.

Furthermore, since the necessary charging of the toner 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 1 KV and a frequency of about 50 Hz to 50 KHz in the developing means, even higher speed development can be fully realized. It becomes possible to do so.

The charging member 5 has a structure in which both end portions 5A, 5A of the conductor sleeve 2 in the circumferential direction are rounded, and the both end portions 5A, 5A are further covered with insulating materials 7, 7. This prevents electrical discharge or lightning strikes from occurring between the end and the sleeve 2.

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

Further, in the charging step, since it is necessary for the toner T to fly, it may be effective to mix in the toner T an additive such as fine silica powder that prevents or releases the aggregation of the toner.

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 larger than that necessary for the toner particles to vibrate is required, and in practical terms, the range is ±5×
10 ⁴ to 5×10 ⁶ V/m is preferred. 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 a range of 50Hz to 50KHz that the toner particles can follow. range, but 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 toner introduced therein is preferably such that the layer thickness is about 1 to 500 microns.

As for the charging member 5, as shown in FIG. It is also effective to make the radius R of the sleeve 2 larger than the radius R' of the sleeve 2 at a distance from the center O' in order to prevent electric discharges and lightning strikes.

Furthermore, in order to prevent the toner T flying in the charging space 6 from scattering to the outside and going behind the charging member 5, a toner amount regulating member 4 is provided.
It is preferable to provide a shielding plate that covers the space between the charging member 5 and the charging member 5.

The toner is conveyed by the sleeve 2 by using the suction force due to frictional electrification of the toner, by making the surface of the sleeve 2 rough and utilizing the frictional force, by using a brush, or by using a brush, or by using the friction force generated by the frictional electrification of the toner, or by using a brush.
This is carried out using the method described in No. 3866574. In this conveyance, it may be effective to apply a DC or AC voltage to the sleeve 2.

FIG. 5 shows another apparatus which can be used in the method of the invention, in this example a toner tank 12 is used instead of the developer hopper 3. B is a developing bias power supply.

FIG. 6 shows an example in which an AC power source 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 power source V is connected to the sleeve 2 in place of the charging member 5. In addition to V, a bias power supply B can be superimposed as necessary.

As the toner amount regulating member 4, one having a knife edge is usually used, but in addition to this, there are
A toner amount regulating member 4 as shown in FIGS. 7 to 10 can be used. The one in FIG. 7 shows a configuration in which a plate-like body has a large number of notches 20 formed at its tip edge, and the one in FIG. . The one in FIG. 9 has a spiral thread 23 on the outer periphery of the rotating rod 22, and the one in FIG.
It has a configuration in which a protrusion 24 extending in the length direction is formed on the outer circumferential surface of the two, and these two are rotated to regulate the amount of toner introduced.

As described in detail above, according to the present invention, it is possible to easily and reliably develop an electrostatic charge image by using a contact developing method using an insulating one-component developer, and to obtain a good visible image. Images can be stably formed.

[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 FIG. 3 is an explanatory diagram showing a preferable example of the charging member. 4 are explanatory diagrams showing the configuration of the charging member, FIGS. 5 and 6 are explanatory diagrams showing configuration examples of other devices that can be used in the method of the present invention, and FIGS. FIG. 10 is an explanatory diagram showing a specific example of the toner amount regulating member. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Sleeve, 3... Developer hopper, 4... Toner amount regulating member, 5... Charging member, 6... Charging space, 7... Insulating material, V...
...AC power supply, T...Insulating one-component developer, 12...
... Toner tank, 20 ... Notch, 21 ... Net body, 22 ... Rotating rod, 23 ... Spiral strip, 24
... Projection, D... Development area, B... Bias power supply, E... DC power supply.

Claims (1)

[Scope of Claims] 1. After regulating the developer amount of the insulating one-component developer on the cylindrical developer transport member, the developer transport member is placed facing the developer transport member and A charging space in which an alternating electric field is formed between a plate-shaped charging member whose both ends in the circumferential direction are rounded and covered with an insulating material and the developer transport body;
The method is characterized in that a developer whose amount is regulated is introduced, the developer is vibrated and charged by the alternating electric field, and the charged developer is used to develop an electrostatic image by a contact development method. Electrostatic image development method. 2. Claims characterized in that development is carried out in a state where a DC or AC voltage is applied between the developer conveying member and the electrostatic image support supporting the electrostatic image to be developed. 2. The electrostatic image developing method according to item 1.