JPS6153658A - Contactless developing method using insulating magnetic one-component developer - Google Patents

Abstract

PURPOSE:To form vivid images in the contactless developing method by providing a control electrode member in the gap between a developing roll and a carrying roll and generating an alternating electric field between the control electrode member and the carrying roll and generating a DC electric field between the control electrode member and the developing roll and developing a latent image with a magnetic developer without contacting. CONSTITUTION:A DC power source 13 is connected to a control electrode provided between a developing roll 3 and a carrying roll 4. A toner stuck to the carrying roll 4 in a developer hopper 2 is carried while controlling its layer thickness by a trimmer 6. The control electrode member 12 generates the alternating electric field between the carrying roll 4 and the member 12 itself by an AC bias voltage applied to the carrying roll and prevents this alternating electric field from being transmitted to the part between the control electrode member 12 and the developing roll 3, and the toner is electrified by the wire-shaped control electrode member 12 and passes this part and is supplied uniformly to the developing roll 3. The toner is flied to a latent image on a latent image carrier 1 by a DC bias voltage 9 applied to the developing roll 3 to develop the latent image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for developing an electrostatic latent image, and more particularly to a non-contact developing method using an insulating magnetic one-shot developer.

[Prior art]

In order to develop a latent image using an insulating magnetic component developer, the developer must be charged in advance in a direction opposite to the latent image charge polarity before the development process, and the developer must be uniformly supplied to the development area. There is a need.

Conventionally, known methods for charging an insulating magnetic component developer include a frictional charging method and a corona charging method.

In the triboelectric charging method, the developer is charged by contact friction with a developer layer thickness regulating member on the surface of the developing roll or with each other. The developer is susceptible to mechanical damage due to the application of heavy pressure. Therefore, the developer aggregation phenomenon tends to occur, making it difficult to achieve another condition for achieving good developability: "supplying a uniform developer layer to the developing section."

In addition, the corona charging method uses corona discharge from a corona discharge wire to charge the developer with the corona ions, but it generally has low charging efficiency and has drawbacks such as uneven charging due to dirt on the corona discharge wire. have.

Conventionally, as a method for forming a uniform developer layer, a blade-shaped or roll-shaped developer layer regulating material is provided close to the developing roll, and the developer conveyed on the developing roll is directly connected to the developing roll and the developer layer. There is a method of removing a portion of the developer layer exceeding the regulation thickness when passing between the regulation members, or a method of pressing the developer layer against the regulation member with a rubber blade.

However, this method has the disadvantage that foreign objects such as pieces of paper and agglomerated developer tend to get caught in the gap between the developing roll and the layer regulating member, and this causes streak-like gaps on the developing roll, which can appear in the developed image. have.

Furthermore, since the layer thickness of the developer is regulated by mechanical compression, the developer aggregates, resulting in the formation of visualization units with large particle sizes, resulting in a decrease in the clarity of the developed image.

On the other hand, a developing method in which a charged and layer-controlled developer acts on an electrostatic latent image on a latent image carrier to make it visible is a developing method in which the developer layer is brought into contact with the latent image carrier. There are two main types: a contact method, in which there is a gap even at the closest portion, and a non-contact method, in which development is performed by selectively flying the developer using a force such as electrical attraction.

In the non-contact method, a developer charged with a polarity different from that of the latent image is formed into a latent image according to the electric field formed by the latent image charge and the DC and AC developing biases applied between the latent image carrier and the developing roll. Let it fly to the department. In this case, the amount of charge on the developer needs to be not only charged to a certain polarity, but also to a certain degree and uniform. If the amount of electrical charge is low, the Coulomb force acting in the direction that makes the developer fly is weaker than the adhesion force acting between the developer and the developing roll, and the developer cannot fly, resulting in a low-density image. Put it away. Furthermore, if a bias voltage is applied to the developing roll to strengthen the developing electric field and promote the flying of the developer, the developer will spread not only to the image area but also to the non-image area.7. +1
This results in an image with significant fog. In this way, in the non-contact development method, it is very important to control the amount of charge on the developer, but in the conventional charging method as described above, sufficient charge m and its uniformity cannot be achieved. As a result, it has become difficult to obtain a clear image due to fogging or a decrease in image quality.

In addition, this non-contact development method is also a development method that is significantly affected by the uniformity of the layer thickness of the developer layer, the degree of softness and agglomeration of the layer, etc. In other words, the amount of developer flying toward the latent image surface is affected by the amount of developer on the developing roll.
If the developer layer is not uniform, the developer density will be uneven.

In addition, if a developer that has aggregated is used, the aggregated particles become flying units and image constituent units, so the edge g'I of the image
9. It may cause lines etc. to protrude or reduce the graininess of solid parts. Therefore, with the conventional developer charging method and layer thickness regulating method as described above, the above-mentioned problems occur and clear images cannot be produced by IM. In order to solve these problems, a method has been proposed in which a developing device as shown in FIG. 5 supplies developer to the latent image carrier.

Referring to FIG. 5, the latent image carrier 1 is composed of a rotatable drum, and a developer hopper 2 is installed adjacent to this drum. A developing roll 3 and a conveying roll 4 are arranged within the developer hopper 2 . The developing roll 3 is spaced apart from the latent image carrier 1 at a distance suitable for non-contact development, while the conveying roll 4 is arranged below the developing roll 3 with an appropriate gap. An insulating magnetic component developer 5 is deposited at the bottom of the developer hopper 2, and the lower half of the transport roll 4 is located in this deposited insulating magnetic component developer. The conveyance roll 4 consists of a rotating sleeve 4a and a fixed magnet 4b inside the rotating sleeve 4a.
The magnetic force of the fixed magnet 4b causes the insulating magnetic component developer 5 to adhere to the surface of the conveying roll, and the adhered developer is regulated to an appropriate layer thickness while being conveyed to the developing roll 3. As a means for controlling the layer thickness, a trimmer 6 is attached to the developer hopper 2 so that its tip is adjacent to the surface of the first general feed roll. On the other hand, a scraper 7 is provided on the opposite side of the transport roll 4 from the trimmer 6, and has the function of scraping off the developer remaining on the transport roll surface after the process of supplying the developer to the development roll 3 is completed. do. Similarly, a scraper 8 is provided on the opposite side of the latent image carrier 1 across the developing roll 3, and scrapers 8 to scrape the developer remaining on the surface of the developing roll without flying to the latent image carrier 1 during the development process. It has a stripping effect.

A DC power source 9 is connected to the developing roll 3, and thereby a DC developing bias voltage is applied to the developing roll 3. The conveyance roll 4 is provided with a DC power supply 10 and an AC power supply 11.
are connected in series, whereby the transport roll 4
An AC bias voltage on which a DC voltage is superimposed is applied. As a result, an alternating electric field is formed between the transport roll 4 and the developing roll 3. In the conventional method, the alternating electric field is used to vibrate the developer, loosen the agglomerated parts, and charge the developer. After the developer charged to one polarity is caused to fly and adhere to the developing roll, the DC bias is applied. The latent image is developed by causing the developer to fly toward the latent image carrier by a direct current electric field formed between the voltage and the latent image.

[Problem that the invention seeks to solve]

However, in this method, the developer is sufficiently loosened and charged by the alternating electric field, but since the alternating electric field is working in the entire area between the developing roll and the transport roll, even if a bias is applied to the developing roll side, It is difficult to selectively attach a developer of one polarity. Therefore, develop! −
A developer layer having a wide charge distribution is formed in the developer layer, and the above-mentioned disadvantages when the developer has a wide charge distribution cannot be improved.

Therefore, the present invention uses an insulating magnetic component developer to produce clear, developed images.
(An object of the present invention is to provide a developing method that allows the formation of

[Means for solving problems]

In order to solve the above-mentioned problems, the developing method according to the present invention includes:
In a non-contact developing method, in which an insulating magnetic component developer is supplied to a developing roll via a conveying roll, and then the magnetic developer is caused to fly onto an electrostatic latent image on a latent image carrier for development. A roll and the conveyance roll are arranged opposite each other with a constant gap maintained, a control electrode member is provided in the gap, an alternating electric field is formed between the control electrode member and the conveyance roll, and the control electrode member and the developing It is characterized by forming a DC electric field between it and the roll. The alternating current electric field charges the magnetic developer while vibrating it and does not decompose the agglomerated developer.On the other hand, the direct current electric field selectively charges only one polarity of the charged magnetic developer. is supplied to the developing roll,
To form a uniform layer of developer without agglomeration on the developing roll.

In other words, the developing method of the present invention involves coagulation and decomposition of the developer.
By separating the charging process and the selection process based on developer polarity, a uniform layer of magnetic developer is formed on the developing roll that is sufficiently charged to one polarity, has a narrow charge amount distribution, and is free from agglomeration. Using this developer layer, an electrostatic latent image is developed by a non-contact development method.

〔Example〕

FIG. 1 shows a row of developing devices for carrying out the developing method of the present invention.

The developing device shown in FIG. 1 is the same as the developing device shown in FIG. 5, in which a control electrode 12 is arranged in the gap between the developing roll 3 and the conveyance roll 4, and a DC power source 13 is connected to the control electrode 12. . In this developing device, the layer thickness of the insulating magnetic component developer (hereinafter referred to as toner) adhered to the surface of the transport roll in the developer hopper 2 is regulated by a trimmer 6, and the developer is continuously transported as the transport roll 4 rotates.

In this case, the amount of toner deposited on the transport roll can be regulated by the conventional regulation method shown in the figure, that is, by transporting the developer through a gap between a metal trimmer and the surface of the transport roll, or by using a rubber blade to control the amount of toner deposited on the transport roll. Uniformity achieved by a method such as pressing the material against the surface of a conveyor roll is sufficient. This is because, in this developing device, as will be described later, the toner is further made uniform again in the subsequent flying process between the conveying roll 4 and the developing roll 3.

The developer layer whose thickness has been regulated by the trimmer 6 is then conveyed to a portion adjacent to the conveying roll and a developing roll provided close to it. In this vicinity, the gap between the conveying roll 4 and the developing roll 3 is maintained at about 0.1 to 3.0 mm, and the control electrode member 12 disposed in the gap is made of a plurality of conductive wires or a conductive wire. It consists of a screen. In the developing device configured as shown in FIG. 1, one of the roles of the control electrode member 12 is to create an alternating electric field between the transport roll 4 and the control electrode member 12 by the AC bias voltage applied to the transport roll 4. At the same time, the purpose is to prevent the influence of the AC bias voltage from propagating into the space between the control electrode member 12 and the developing roll 3.

The second role is to prevent the passage of toner sufficiently charged to one polarity from among the toner cloud generated between the transport roll and the control electrode member, and to transfer the toner onto the developing roll.
The purpose is to be able to supply the amount of toner required for development.

The shape of the charge control member is determined based on the requirements of both parties as described above, but when using a wire, the shape of the charge control member is
This is satisfied by a configuration in which a plurality of metal wires each having a diameter of 100 μm are provided at intervals of 0.1 to 2.1 mm.

When a screen is used, a screen IJ-n made of a conductive material with a number of lines of 5 or more and the area covered by the holes of 50% or more is used. Regarding its installation position, it can be installed in almost the entire area except for the vicinity of the first general feed roll and the developing roll, but in order to cause sufficient vibration between the transport roll and the control electrode, the distance between the two should be 50 μm or more. It is preferable. Furthermore, if the gap between the control electrode member and the developing roll becomes too narrow, a film-like appearance of the cavity of the control electrode member is likely to occur in the developer layer on the developing roll.
It is preferable to have a gap of μm or more.

FIG. 2 is a schematic representation of the movement of toner between the conveying roll, control electrode member, and developing roll based on the configuration shown in FIG. An alternating current bias voltage is applied to the conveying roll 4 by an alternating current power source 11 in order to form an alternating electric field in a space between the conveying roll 4 and the control electrode member. The frequency of the AC bias is set in the range of 50 to 20001 (z) because the ability to vibrate the toner decreases if it is too high or too low.
Further, the amplitude is set in the range of 100 to 100 (IV (100 to 2000 V peak-to-peak)).

On the other hand, a DC bias voltage is applied to the developing roll 3 by a DC power supply 9. This bias voltage acts as a development bias for non-contact development and controls the development density. In order to form a DC electric field that acts in the direction of attracting the toner charged with one polarity (O polarity in Figure 2) onto the development roll, the control electrode member is provided with a DC current that takes into account the bias voltage applied to the development roll. Bias is applied. In FIG. 2, a bias voltage lower than the bias voltage applied to the developing roll 3 is applied to the control electrode member 12. In FIG.

Furthermore, the transport roll has an electric field of a DC component that either has a DC bias component between the transport roll 1;'I control electrode member that is almost zero, or that the toner of the polarity to be selected moves easily toward the developing roll. A DC bias voltage that takes into account the DC bias voltage applied to the control electrode member is superimposed on the AC bias voltage so that the control electrode member is formed. In FIG. 3, a DC bias voltage lower than the DC bias voltage applied to the control electrode δ6 material is superimposed.

It goes without saying that the DC bias voltage applied to each of the developing roll/control electrode member and the transport roll can be adjusted separately as necessary. In addition, when changing the DC bias voltage value applied to the developing roll, which corresponds to the developing bias, the DC bias voltage value applied to the control electrode member and the transport roll is changed between the developing roll and the control electrode member and the control electrode member, respectively. It is also possible to automatically change the potential difference between the electrode member and the conveyance roll so as to continue to maintain it.

When toner is conveyed on the conveying roll into the gap between the conveying roll and the developing roll where an electric field is formed by such a configuration, as shown in the schematic diagram of FIG. The parts begin to vibrate. Third
The figure shows that after vibration inside the hopper, between the conveyor roll and the control electrode,
and shows changes in charge distribution of toner on the developing roll.

Toner normally has some electrical charge because it is a fine powder in its unprocessed state in the hopper. (Figure 3 (a)) Due to this slight electrical charge, the toner receives Coulomb force in the alternating electric field and starts to vibrate, and this vibration causes collision between the toner and the control electrode member.
Alternatively, the amount of charge increases due to the collision between the toner and the transport roll, resulting in a wide charge distribution as shown in Figure 3 (b)).

Toner with an increased amount of electrical charge is subjected to a stronger Coulomb force, and vibrates alternately in the direction of the control electrode member and the direction of the transport roll. On the other hand, in the space from the control electrode member to the developing roll, instead of the alternating electric field shielded by the control electrode member, a direct current electric field formed by the direct current power source 9.13 is dominant.

Therefore, among the charged toner particles flying near the control electrode member due to the alternating electric field, toner of one polarity (i.e., the toner of the second polarity, which is attracted by the Coulomb force in the direction of attraction by the DC electric field between the control electrode member and the developing roll), The 0-charged toner (in the figure) continues to receive Coulomb force in the direction of the developing roll, reaches the developing roll, and adheres thereto due to mirror image force, Wander-Keuls force, etc. On the other hand, toner charged opposite to the polarity toner is subjected to Coulomb force in the direction of the transport roll between the control electrode member and the developing roll, and cannot reach the developing roll. Due to this polarity selectivity in the control electrode member/developing roll space, a layer containing only toner sufficiently charged to one polarity is formed on the developing roll.

(Figures 2 and 3 (C)).

This layer of charged toner is then transported to a part close to the latent image carrier 1, which is moving at approximately the same speed as the developing roll 3, and the latent image charge and the DC bias applied to the developing roll 3 are transferred. It flies toward the latent image by electrostatic attraction due to the developing electric field formed by the voltage, and develops the latent image.

After development, the residual toner remaining on the developing roll and the residual toner remaining on the transport roll after passing through the vicinity of the first general transport roll and the developing roll are separated from each roll by a scraper 8.7 as necessary and collected in a hopper. After passing through the scraper, each roll moves on to the next development cycle.

Note that the transport roll 4 used in the present invention does not collide with the toner.
It has the role of charging the toner by contacting it, and at the same time as the toner is charged, the transport roll 4 is charged to the opposite polarity. Therefore, in order to eliminate the adverse effects caused by charge accumulation, the surface of the transport roll 4 is preferably electrically conductive, and specifically, it is preferably composed of a layer, alumite, stainless steel, or the like.

FIG. 4 shows another example of a developing device for carrying out the developing method according to the present invention.

In the configuration example shown in FIG. 4, an AC power source 14 is connected in series to the developing roll 3 in addition to the DC power source 9. As shown in FIG.

That is, in the configuration example shown in FIG. 1, the developing bias is a DC component, whereas in this configuration example, an AC component is applied in addition to the DC component to cause the developer to fly and develop. In this case, an AC power source 15 is connected in series to the control electrode member in addition to the DC power source 13, so that an AC power source 15 having the same frequency, the same phase, and approximately the same amplitude as the AC bias voltage applied to the developing roll is connected in series to the control electrode member. A bias voltage is applied, and a DC bias voltage is further superimposed. That is, the relationship between the bias applied to the developing roll (VD) and the bias applied to the control electrode (■E) is expressed by the following equation.

Vo -VDACSIN ωat 十VoocVi
= VEACSIN ωεt+VcocVIIACV
l:AC+ω. =ω.

Here, VDAC is the amplitude of the AC bias voltage applied to the developing roll. C: The amplitude ω of the AC bias voltage applied to the control electrode. : Angular velocity ω of the AC bias voltage applied to the developing roll, : Angular velocity V of the AC bias voltage applied to the control electrode: V nnc : DC bias voltage value applied to the developing roll V aoc : DC bias voltage value applied to the control electrode. In the space, a DC electric field is formed by the difference (vo - VE) between the DC bias (VD) applied to the developing roll and the DC bias (■, ) applied to the control electrode member.
By appropriately determining Va, the developing roll and
Similar to the space between the control electrode members, a space of 11 L is formed, which selectively contains only toner charged to one polarity.

On the other hand, a DC bias voltage is applied to the removal roll, and an alternating electric field is formed between it and the control electrode member to which AC and DC biases are applied. causes vibration, which decomposes the aggregated toner and charges the toner.

The AC bias applied as the developing bias has a frequency of 50 to 2000) and an amplitude of 1000 V or less, which is also a value suitable for vibrating the toner between the first general feed roll and the control electrode member. Therefore, by adopting the configuration as shown in FIG. 4, it is possible to obtain a clear developed image as in FIG. 1.

Note that although the rotation direction of the transport roll 4 is shown in the same direction as the developing roll 3 in FIGS. 1 and 4,
A similar effect can be obtained even if the rotation is made in the opposite direction.

〔Effect of the invention〕

According to the present invention, the agglomeration and decomposition of the insulating magnetic component developer
Since the charging process and the selection process based on the polarity of the developer are separated, a uniform layer of magnetic developer layer that is sufficiently charged to one polarity, has a narrow charge amount distribution, and is free from agglomeration can be used as a developer. 1 can be formed on top. therefore,
By performing non-contact development using this uniform developer layer, it is possible to form a clear image with clear edges and uniform graininess in the solid portion.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a developing device for carrying out the developing method of the present invention, and FIG. 2 shows how toner moves between the conveyance roll and the developing roll in the developing method of the present invention. Schematic diagram for explanation, FIG. 3 is a graph showing the charge distribution of toner, and FIG. 4 is a graph showing the charge distribution of toner.
FIG. 5 is a schematic cross-sectional view showing another example of a developing device that implements the developing method of the present invention. FIG. 5 is a schematic diagram showing an example of a developing device that implements the conventional developing method. 1...Latent image carrier, 2...Developer hopper, 3...
・Developing roll, 4... General feed roll, 5... Insulating magnetic component developer, 6... Trimmer, 7.8... Scraper, 9.10.13... DC power supply, 11 .14.
15...AC power supply, 12...control electrode. FIG. 1 1--, V image carrier 642. G1,7
-4... Conveyance roll 119.
AC power, Seri Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a non-contact developing method, in which an insulating magnetic one-component developer is supplied to a developing roll via a conveyance roll, and then the magnetic developer is caused to fly onto an electrostatic latent image on a latent image carrier for development. A roll and the conveyance roll are arranged opposite each other with a constant gap maintained, a control electrode member is provided in the gap, and an alternating electric field is formed between the control electrode member and the conveyance roll to vibrate the magnetic developer. The magnetic developer is electrically charged while causing the magnetic developer to move, and further, by forming a DC electric field between the control electrode member and the developing roll, only one of the charged magnetic developers charged to one polarity is selectively supplied to the developing roll. A non-contact developing method in which a uniform magnetic developer layer is formed on the developing roll, and the latent image on the latent image carrier is developed by flying the magnetic developer from the magnetic developer layer to the latent image carrier. .