JPH0568697B2 - - Google Patents

Description

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

[Prior art]

In order to develop a latent image using an insulating one-component developer, it is necessary to charge the developer in a direction opposite to the latent image charge polarity before the development process, and to uniformly supply the developer to the development area. There is.

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

In the frictional 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, but this method makes it difficult to control the amount of charge and requires no mechanical pressure. Because of this, the developer is susceptible to mechanical damage. Therefore, the phenomenon of developer aggregation is likely to occur, making it difficult to achieve another condition for achieving good developability: "supplying a uniform developer layer to the developing section."

In the corona charging method, a corona discharge wire is used to discharge a corona, and the developer is charged with the corona ions.However, charging efficiency is generally low, and dirt on the corona discharge wire may cause uneven charging. It has some disadvantages that may occur.

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

However, with this method, 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 occur in the developed image. It has its drawbacks.

Furthermore, since the layer thickness of the developer is regulated by mechanical pressure, the developer tends to aggregate, resulting in the formation of visualization units with large particle diameters, resulting in a decrease in the clarity of the developed image.

On the other hand, a developing method in which a developer with a controlled charge and layer thickness acts on an electrostatic latent image on a latent image carrier to make it visible is a development method in which the developer layer has a contact area with the latent image carrier. There are two main types: a contact method, in which the developer is selectively ejected by a force such as electrical attraction, and a non-contact method, in which a gap is provided even at the closest portion, and the developer is selectively ejected for development.

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 latent image agent 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 that acts in the direction that causes the developer to fly is weaker than the adhesion force that acts between the developer and the developing roll, and the developer cannot fly, resulting in a low-density image. . 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 fly not only to the image area but also to the non-image area, resulting in images with significant fog. I'm getting used to it. In this way, in non-contact development methods, it is very important to control the amount of charge charged on the group agent, but with the conventional charging methods described above, sufficient amount of charge and its uniformity cannot be obtained, and as a result, fogging occurs. It has been difficult to obtain clear images due to problems such as problems or a decrease in image density.

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

Furthermore, if a developer that has agglomerated is used, the agglomerated particles become flying units and image constituent units, which may cause edges, lines, etc. of the image to be visible, or cause a decrease in the graininess of solid areas. . 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 obtained. In order to solve these problems, a method has been proposed in which the developer is supplied to the latent image carrier using a developing device as shown in FIG.

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 conveyance 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.
On the other hand, the conveying roll 4 is arranged below the developing roll 3 with an appropriate gap therebetween. An insulating non-magnetic one-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 the deposited insulating non-magnetic one-component developer. This insulating non-magnetic one-component developer 5 adheres to the surface of the transport roll due to frictional charging, but the adhered developer is regulated to an appropriate layer thickness while being transported to the developing roll 3. As a means for regulating the layer thickness, a trimmer 6 is attached to the developer hopper 2 so that its tip is adjacent to the surface of the transport 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 with the developing roll 3 in between.
It acts to strip off the developer remaining on the surface of the developing roll without flying away.

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. A DC power source 10 and an AC power source 11 are connected in series to the conveyance roll 4, so that an AC bias voltage on which a DC voltage is superimposed is applied to the conveyance roll 4. As a result, an alternating electric field is formed between the conveying 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 latent image is developed by causing developer to fly toward the latent image carrier using a DC electric field formed between a DC bias 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, a bias is not applied to the developing roll side. However, it is difficult to selectively attach a developer of one polarity. Therefore, a developer layer with a wide charge distribution is formed on the developing roll.
As mentioned above, the disadvantages when the developer has a wide charge distribution cannot be improved.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a developing method using an insulating one-component developer that can form a clear developed image.

[Means for solving problems]

In order to solve the above-mentioned problem, the developing method according to the present invention supplies an insulating one-component developer to a developing roll via a conveyance roll, and then flies the developer to an electrostatic latent image on a latent image carrier. In a developing method in which the developing roll and the conveying roll are held opposite each other for a certain period of time, and a control electrode is provided between the developing roll and the transport roll in a plane substantially perpendicular to a plane formed by the central axes of both rolls. A member is provided, an alternating electric field is formed between the control electrode member and the conveyance roll, and a DC electric field is formed between the control electrode member and the developing roll. The alternating electric field charges the developer while vibrating it, and decomposes the aggregated developer. On the other hand, the DC electric field selectively supplies only one of the charged developers charged to one polarity to the developing roll, thereby forming a uniform layer of developer without agglomeration on the developing roll.

In other words, the developing method of the present invention separates the developer agglomeration/decomposition/charging step and the developer polarity selection step, so that the developing roll is sufficiently charged to one polarity and the charge amount distribution is maintained. The width of the developer is small, and it forms a uniform layer of developer without agglomeration.
This developer layer is used to develop an electrostatic latent image.

〔Example〕

FIG. 1 shows an example of a developing device 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 disposed in the gap between the developing roll 3 and the conveying roll 4, and a DC power source 13 is connected to the control electrode 12. . In this developing device, the thickness of the insulating non-magnetic one-component developer (hereinafter referred to as toner) adhered to the surface of the transport roll in the developer hopper 2 is controlled by the trimmer 6.
Continuing to convey it as the conveyance roll 4 rotates. In this case, the amount of toner deposited on the transport roll can be controlled by the conventional regulation methods shown in the figure, i.e., by transporting the developer through a gap between a metal trimmer and the surface of the transport roll, or by using a rubber blade. Uniformity achieved by, for example, a method of pressing the toner onto the surface of a transport roll is sufficient. This is because, in this developing device, the toner layer is made uniform again in the subsequent flying process between the conveying roll 4 and the developing roll 3, as will be described later.

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 close portion, the gap between the transport roll 4 and the developing roll 3 is
The control electrode member 12 arranged in the gap maintained at about 0.1 to 3.0 mm includes a plurality of conductive wires,
Alternatively, it consists of a conductive screen. In the developing device configured as shown in FIG. 1, one of the roles of the control electrode member 12 is to provide an alternating current between the transport roll 4 and the control electrode member 12 by the alternating current bias voltage applied to the transport roll 4. The purpose is to form an electric field and 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 the toner cloud generated between the transport roll and the control electrode member, and to place it on the development roll as necessary for development. The objective is to be able to supply the desired amount of toner.

The shape of the charge control member is determined based on the requirements of both parties as described above, but when using wire, a metal wire with a diameter of 20 to 100 μm is used with a diameter of 0.1 to 2.1 μm.
This is satisfied by a configuration in which a plurality of them are provided at intervals of mm. When a screen is used, a screen made of a conductive material with a number of lines of 5 or more and an area covered by holes of 50% or more is used. Regarding its installation position, it can be installed in almost the entire area except near the transport roll and 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. preferable. Furthermore, if the gap between the control electrode member and the developing roll becomes too narrow, a hollow film-like appearance of the control electrode member tends to occur in the developer layer on the developing roll, so it is preferable to provide a gap of 50 μm or more.

Figure 2 shows the conveyor roll and
This is a schematic representation of the movement of toner between the control electrode member and the developing roll. Conveyance roll 4
An alternating current bias voltage is applied by an alternating current power supply 11 to form an alternating electric field in the space between the control electrode member and the control electrode member. The frequency of the AC bias is set in the range of 50 to 2000 Hz because the ability to vibrate the toner decreases if it is too high or too low, and its amplitude is set in the range of 50 to 1000 V (100 to 2000 V peak-to-peak).
The range is set to .

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 in the control electrode member that acts in the direction of attracting toner charged to one polarity (○ polarity in Fig. 2) onto the developing roll,
A DC bias is applied in consideration of the bias voltage applied to the developing roll. 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, on the transport roll, the DC bias component between the transport roll and the control electrode member is almost zero, or an electric field with a DC component is formed in a direction that facilitates the movement of toner of the polarity to be selected toward the developing roll. First, 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. In FIG. 3, a DC bias voltage lower than the DC bias voltage applied to the control electrode member 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 between the control electrode member and the control electrode member. It is also possible to automatically change the potential difference between the transport rolls so as to continue to maintain it.

With this configuration, when toner is conveyed on the conveyance roll into the gap between the conveyance roll and the developing roll where an electric field is formed, as shown in the schematic diagram of FIG. The control electrode member begins to vibrate. FIG. 3 shows changes in the charge distribution of toner inside the hopper, after vibration between the transport roll and the control electrode, and on the developing roll.

Since toner is normally a fine powder in the untreated state of the hopper, it is somewhat electrically charged (Figure 3a). Because of this slight electrical charge, the toner receives Coulombs in an alternating electric field. Vibration is started, and the toner particles collide with each other due to the vibrations. Collision between the toner and the control electrode member or the toner and the transport roll increases the amount of charge (as shown in Figure 3b). This results in a wide charge distribution.

The 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 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, DC power sources 9 and 1 are installed.
The DC electric field formed by No. 3 is dominant.

Therefore, among the charged toner particles flying near the control electrode member due to the alternating electric field, one polarity of the toner (i.e., the polarity that attracts the Coulomb force in the direction of attraction by the DC electric field between the control electrode member and the developing roll), The charged toner (in FIG. 2) 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-Kurska, 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 the selectivity of polarity in the control electrode member/developing roll space, a layer containing only toner sufficiently charged to one polarity is formed on the developing roll. (Figure 2,
and Figure 3C).

This charged toner layer is then conveyed to a portion close to the latent image carrier 1 which is moving at approximately the same speed as the developing roll 3, and is affected by the latent image charge and the DC bias voltage applied to the developing roll 3. Due to the electrostatic attraction caused by the developing electric field thus formed, it flies towards the latent image and develops the latent image.

After development, the residual toner remaining on the developing roll and the residual toner remaining on the transporting roll after passing through the vicinity of the transporting roll and the developing roll are separated from each roll by scrapers 8 and 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 has the role of charging the toner by colliding with and contacting the toner, but 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 negative effects caused by charge accumulation, the transport roll 4
It is preferable that the surface is conductive, and specifically, it is preferably made of A1, 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 of 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 with the control electrode member in addition to the DC power source 13, so that an AC power source 15 having approximately the same amplitude at the same frequency and phase 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 current bias voltage is further superimposed. That is, the relationship between the bias applied to the developing roll (V _D ) and the bias applied to the control electrode (V _E ) is expressed by the following equation.

V _D = V _DAC SINω _D t+V _DDC V _E = V _EAC SINω _E tkV _EDC V _DAC −V _EAC , ω _D = ω _E where V _DAC : Amplitude of AC bias voltage applied to the developing roll V _DAC : AC bias applied to the control electrode Amplitude of voltage ω _D : Angular velocity of AC bias voltage applied to the developing roll ω _E : Angular velocity of AC bias voltage applied to the control electrode V _DDC : Value of DC bias voltage applied to the developing roll V _DDC : Value of DC bias voltage applied to the control electrode This allows for development. In the space between the roll and the control electrode member, a difference (V _D −V _E ) between the DC bias (V _D ) applied to the developing roll and the DC bias (V _E ) applied to the control electrode member is formed. A DC electric field is formed, and by setting V _E appropriately,
Similar to the space between the developing roll and the control electrode member in FIG. 1, a space is formed in which only toner charged to one polarity can selectively fly.

On the other hand, a DC bias voltage is applied to the transport roll, and an alternating electric field is formed between the control electrode member to which AC and DC biases are applied, and as in the configuration example shown in FIG. Vibration is caused, and the aggregated toner is decomposed and the toner is charged.

The AC bias applied as the developing bias has a frequency of 50 to 2000 Hz and an amplitude of 1000 V or less, which is also a value suitable for vibrating the toner between the transport roll and the control electrode member, and therefore By adopting the configuration shown in Figure 4, the first
As shown in the figure, a clear developer can be obtained.

Although the rotation direction of the transport roll 4 is shown in FIGS. 1 and 4 in the same direction as the developing roll 3, the same effect can be obtained even if the transport roll 4 is configured to rotate in the opposite direction to the developing roll 3. can get.

Although the above embodiments apply the present invention to a non-contact developing method using an insulating non-magnetic one-component developer, the present invention may also be applied to an insulating non-magnetic one-component developer. Similar effects can be obtained even when applied to a contact type developing method.

〔Effect of the invention〕

According to the present invention, since the agglomeration/decomposition/charging process of the insulating one-component developer and the selection process based on developer polarity are separated, one polarity is sufficiently charged and the width of the charge amount distribution is small. A small, uniform, non-agglomerated developer layer can be formed on the developer. Therefore, by performing development using this uniform developer layer, it is possible to form a clear image with smooth edges and uniform graininess in the solid parts.

[Brief explanation of the drawing]

FIG. 1 is a schematic 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 to explain,
Figure 3 is a graph showing the charge distribution of toner;
FIG. 5 is a schematic sectional view showing another example of a developing device that implements the developing method of the present invention, and 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
...Development roll, 4...Transport roll, 5...Insulating non-magnetic one-component developer, 6...Trimmer, 7,8
...Scraper, 9,10,13...DC power supply,
11, 14, 15... AC power supply, 12... Control electrode.

Claims (1)

[Claims] 1. A developing method in which an insulating one-component developer is supplied to a developing roll via a transport roll, and then the developer is caused to fly onto an electrostatic latent image on a latent image carrier for development, wherein the developing roll and the transport A control electrode member is provided in a plane substantially perpendicular to a plane formed by the central axes of both rolls, and a control electrode member is provided between the control electrode member and the transport roll. The developer is charged while being vibrated by forming an alternating electric field, and further, by forming a DC electric field between the control electrode member and the developing roll, the charged developer is charged to one polarity. A uniform developer layer is formed on the developing roll by selectively supplying only the developer to the developing roll, and the developer is caused to fly from the developer layer to the latent image bearing member. A method of developing an image.