JPH0611972A - Development device - Google Patents

Abstract

PURPOSE:To provide a development device in which toner of fine particle can be used and development of high developing efficiency with no blur can be performed. CONSTITUTION:An electrode body 86 which is a plate member covered with insulating members 86b, 86c centering an electrode 86a is provided on the upper stream part of a development territory A, the extreme end of the insulating member 86c is brought in contact with the surface of a photosensitive body 1, the extreme end of the insulating member 86b is brought in contact with the layer of developer D on a developing sleeve 81, a first oscillating electric field B is formed between the electrode 86a and the developing sleeve 81, a second oscillating electric field C is formed between the photosensitive body 1 and the developing sleeve 81, the first oscillating electric field is set stronger than the second oscillating electric field, and an electric field to move the toner to the photosensitive body 1 is formed between the photosensitive body 1 and the electrode 86a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image using a one-component developer composed of non-magnetic toner in an electrophotographic copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, in electrophotographic copying machines and the like,
A developing device using a one-component developer made of non-magnetic toner is used. This developing device has a cylindrical developing sleeve rotatably supported, and toner particles are adhered and held on the surface of the developing sleeve and conveyed to a developing area for developing.

As a conventional developing device using such a developer, a developer made of a non-magnetic toner having an average particle diameter of about 10 μm is used, and since the toner particles are coarse,
There is a problem in that it is difficult to obtain a high-quality image that reproduces delicate lines, dots, or a difference in shade. Therefore, in order to obtain a high image quality in this developing method, many efforts have been made in the past, but the current situation is that still a stable and sufficiently satisfactory image cannot be obtained. Therefore, it is considered necessary to make the toner particles finer in order to obtain a high quality image. However, if the toner particles have an average particle size of 20 μm or less, especially 10 μm or less, the effect of van der Waals force appears relatively to the Coulomb force at the time of development, and the toner particles also appear in the background of the image background. So-called fogging that adheres occurs, and it becomes difficult to prevent fogging even by applying a DC bias voltage to the developer carrier. It becomes difficult to control the triboelectric charging of the toner particles, and aggregation easily occurs. Since the above-mentioned side effects are more prominent in the atomization and a clear image cannot be obtained, it is difficult to actually use the atomized toner for that reason.

As a method for solving the above problem, Japanese Patent Laid-Open No. 59-59
As described in JP-A-223467, a method of providing a control electrode for controlling the flight of toner in a developing area and performing development under an oscillating electric field generated by applying a bias voltage having an AC voltage component, -94368 publication,
A method of providing a leveling member between the central portion of the developing region and a regulating member for regulating the layer thickness of the developer layer, and applying a DC voltage having a polarity opposite to the charging polarity of the toner to the leveling member, Kohei
As described in 4-56977 publication, disposing the electrode body,
A method of applying an AC voltage as a bias voltage to the electrode body has been proposed.

[0005]

However, in the method using the control electrode proposed in the above, the control electrode is contaminated as it is used, or the control electrode vibrates during use. Further, it is difficult to hold the control electrode in a straight line, so that density unevenness occurs and the desired effect cannot be exhibited.

Further, in the method using the leveling member, a bias voltage having a polarity opposite to the charging polarity of the toner is applied to the leveling member, so that the toner adheres to the leveling member, and the toner adheres to the image carrier. There is a problem in that good development cannot be performed due to image stains and changes in the vibration conditions of the developer.

It is an object of the present invention to provide a developing device which solves the problem of atomization of the developer in the developing device in which the developing sleeve rotates, and which has a high developing efficiency and allows uniform development.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device for developing a latent image on an image bearing member, wherein an image bearing member and a developing sleeve for carrying a developer are opposed to each other. The first oscillating electric field is provided between the electrode of the electrode body and the developing sleeve so that the first oscillating electric field is provided between the electrode of the electrode body and the developing sleeve so as to be in contact with the carrier and the developer. A second oscillating electric field is set to the first oscillating electric field, and the first oscillating electric field is set stronger than the second oscillating electric field, and an electric field is formed between the image carrier and the electrode to move the toner to the image carrier. It is achieved by the developing device.

Further, the electrode body is constructed such that both surfaces of the electrode are covered with an insulator, and a voltage having the same polarity as that of the toner is applied to the electrode body so that the first oscillating electric field and the first oscillating electric field are applied. The developing device is characterized in that the oscillating electric field of No. 2 has the same phase.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a schematic sectional view showing an embodiment of a developing device of the present invention, and FIG. 1B is a developing area A in FIG. 1A.
It is an expanded sectional view showing the neighborhood.

In FIG. 1, reference numeral 1 is a drum-shaped photosensitive member which is an image bearing member having a photosensitive layer provided on a conductive substrate, and 81 is a non-magnetic material such as aluminum or stainless steel, the surface of which is sandblasted. According to JIS 10-point average roughness (JIS-B0610), the developing sleeve is a developer carrier that is rotatably supported by roughening 1-2 μm and 83 is agitating developer D to uniformly charge developer D. A stirrer for controlling, 84 is a fur brush for supplying the developer D to the developing sleeve 81, 85 is a regulating blade which is a developer layer regulating member for regulating the layer thickness of the developer D, and 86 is a developer layer on the developing sleeve 81. Is a plate-like member provided on the upstream side of the developing region A for forming an oscillating electric field, and the electrode body 86 is the developer D on the developing sleeve 81 or the photoreceptor 1. Insulation such as rubber provided so as to contact the surface Become more insulating member 86b, 86
A plate-like electrode 86a made of a conductive material such as metal is sandwiched between c and integrated. 87 is a cleaning blade for removing the developer D that has passed through the developing area A from the developing sleeve 81, 88 is a developer reservoir, and 89 is a casing.

The layer of the developer D, the layer thickness of which is regulated by the regulating blade 85 and the electrode body 86, is moved by the rotation of the developing sleeve 81 and is conveyed to the developing area A. The gap between the developing sleeve 81 and the electrode body 86 and the gap between the developing sleeve 81 and the photoconductor 1 are adjusted so that the developer layer formed on the developing sleeve 81 does not contact the surface of the photoconductor 1 and maintains the gap. It

The developing sleeve 81 has a DC bias power source E1
Then, a bias voltage in which direct current is superposed on alternating current is applied through the protective resistor R1 by the alternating current bias power source E2. A DC bias voltage is applied to the electrode 86a of the electrode body 86 from the DC bias power source E3 via the protection resistor R2.

In the present invention, the first oscillating electric field is generated between the developing sleeve 81 and the electrode 86a which is integrally provided on the insulating member 86b which is in contact with the developer D layer on the developing sleeve 81. The strength of the first oscillating electric field is stronger than that of the second oscillating electric field as compared with the oscillating electric field formed between the photosensitive member 1 and the developing sleeve 81 in the conventional device (this is referred to as a second oscillating electric field). It is characterized in that the electric field for moving the toner to the photoconductor 1 is formed between the photoconductor 1 and the electrode 86a.

FIG. 1B is an enlarged sectional view showing the vicinity of the developing area A. As shown in FIG. 1A, the developing sleeve 81 receives a bias voltage in which a direct current is superimposed on an alternating current, and
A DC bias voltage is applied to the electrode 86a of 86.
For example, when reversal development is performed using the photoreceptor 1 having an OPC photoreceptor layer that is negatively charged and the developer D of the toner that is negatively charged, if the photoreceptor is charged to −800 V, for example, To the electrode 86a of the electrode body 86,-(800 to 1,500) V whose absolute value is larger than the photoconductor potential is applied. The developing sleeve 81 has a DC voltage component of -700V and a frequency of 100H.
z to 10 KHz, preferably 1 to 5 KHz with a peak-to-peak voltage of 2
A bias voltage of an AC voltage component of 00 to 4,000 V is superimposed and applied. As a result, a voltage having an absolute value higher than that of the developing sleeve 81 and a polarity opposite to that of the toner charging is applied to the electrode 86a of the electrode body 86, so that the toner does not adhere to the electrode body 86 and the toner on the photoconductor 1 is prevented. From the toner image, the toner is the electrode body
It does not adhere to 86. Since the electrode 86a is provided closer to the developing sleeve 81 than the photoconductor 1, the strength of the first oscillating electric field becomes larger than the strength of the second oscillating electric field, and both oscillating electric fields are generated by the AC bias power source E2. Therefore, they are in phase.

The closest gap d ₂ between the electrode 86 a and the developing sleeve 81 is preferably d ₂ = (0.2 to 0.6) d ₁ with respect to the closest gap d ₁ between the photoreceptor 1 and the developing sleeve 81. . Note that d ₁ is 0.2 to 1.0 mm.

In order to install the electrode in a narrow developing area, it is desirable that the angle θ between the electrode 86a and the position where the developing sleeve 81 and the photosensitive belt 1 face each other is 5 to 45 ° on the upstream side. The developing sleeve 81 preferably has a diameter of 10 to 30 mm.

The first oscillating electric field causes the toner particles to vibrate in a direction perpendicular to the lines of electric force, so that the toner can fly and a cloud haze-shaped toner cloud can be sufficiently generated. This toner cloud is assisted by the flight toward the latent image on the photoconductor 1 by the second oscillating electric field having the same phase as the first oscillating electric field, and uniform development is performed.

Here, it is important that the first and second oscillating electric fields have the same phase. Since they are in the same phase, development is performed without causing undulations in toner vibration. Further, no dielectric breakdown due to a strong electric field when the phase changes occurs.

The waveform of the AC voltage component is not limited to a sine wave, and may be a rectangular wave or a triangular wave. Although the frequency is also related, the higher the voltage value, the more the toner vibrates, but on the other hand, dielectric breakdown such as fogging and lightning strike phenomenon easily occurs. The occurrence of fogging is prevented by the DC voltage component,
The dielectric breakdown can be prevented by coating the surface of the developing sleeve 81 with a resin, an oxide film, or the like so as to be insulating or semi-insulating.

FIG. 2 is a partial sectional view showing another embodiment of the present invention. In this embodiment, a notch 86d is provided at the tip of the insulating member 86b of the electrode body 86, and a V-shaped space for generating a toner cloud is formed between the electrode 86 and the developing sleeve 81. The tip of the electrode 86a is also covered with an insulating member.

As described above, the developing device of the present invention is
The developer layer of the component developer is kept in non-contact with the photoconductor 1 which is an image carrier, a toner cloud is generated by the first oscillating electric field, and separation and flight to the photoconductor 1 is improved.
The selective adsorption to the electrostatic image by the oscillating voltage is improved. Therefore, it is made possible to use fine particles as the toner so that a high quality image can be developed. For that purpose, it is preferable to use the following developer made of non-magnetic toner.

In general, when the average particle size of the toner becomes small, the amount of charge qualitatively decreases in proportion to the square of the particle size, and the adhesive force such as the Van der Waals force relatively increases, and the developing sleeve. It strongly adheres to 81 and is easily scattered on the non-image portion, and fogging is likely to occur. In the conventional developer layer developing method, when the average particle diameter is 10 μm or less, such a problem becomes remarkable.

In the developing apparatus of the present invention, this point is solved by developing under a double oscillating electric field.
That is, the toner particles are strongly vibrated in the first oscillating electric field, form a toner cloud away from the developing sleeve 81, and are carried to the nearby developing area A, and have the same phase as the first oscillating electric field. The weaker second oscillating electric field assists the flight, so that the toner particles are faithfully adsorbed to the electrostatic latent image on the photoconductor 1. Further, since the toner having a low charge amount hardly migrates to the image portion or the non-image portion, and the toner does not rub against the photoconductor 1, it does not adhere to the photoconductor 1 by frictional charging. Even toner particles having a particle size of about 1 μm can be used.

As the average particle size of the toner becomes large, as already mentioned, the roughness of the image becomes noticeable. Usually, for development with a resolution of fine lines arranged at a pitch of about 10 lines / mm, even a toner having an average particle size of about 20 μm does not pose any problem, but when a finely divided toner having an average particle size of 1 to 5 μm is used, The resolving power is remarkably improved, and a clear high-quality image that faithfully reproduces the grayscale difference can be obtained. For the above reasons, the average particle size of the toner is 10 μm or less, preferably 1 to 5 μm. Further, since the toner particles follow the electric field, the toner charge amount is 1 to 3 μm.
It is desirable that it is larger than C / g (preferably 3 to 30 μC / g).

In the developing device of the present invention, preferable toners are styrene resin, vinyl resin, ethyl resin,
A resin such as a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin, a polyester resin, a silicon resin, or a fluororesin is used, and a coloring component such as a color pigment or a charge control agent if necessary is added to the resin, which is conventionally known. The toner particles can be manufactured by the same method as the toner particle manufacturing method.
Particles having an average particle size of 20 μm or less, preferably 10 μm or less, and particularly preferably 1 to 7 μm are selected and obtained by selecting the particle size by a conventionally known average particle size selecting means.

In the developing device of the present invention, a developer comprising spherical non-magnetic toner particles as described above is preferably used, and in order to improve the flow slippage of the particles, the developer is preferably used. A fluidizing agent and a cleaning agent useful for cleaning the surface of the image bearing member are mixed. As a fluidizing agent,
Colloidal silica, silicon varnish, metal soap, nonionic surface active agents, etc. can be used, and fatty acid metal salts, organic group-substituted silicon, surface active agents such as fluorine, etc. can be used as cleaning agents.

In the developing device as described above, 100 parts by weight of styrene-acrylic resin (Haimer up110 manufactured by Sanyo Kasei Co., Ltd.) in toner and 10 parts by weight of color pigment have a weight average particle diameter of 5 μm.
Using non-magnetic particles obtained by the pulverization and granulation method of m, development was performed by the apparatus shown in FIG. The average charge amount of each toner was −10 μC / g.

In this case, the photoconductor 1 is an OPC photoconductor, the peripheral speed is 180 mm / sec, the maximum potential of the electrostatic latent image formed on the photoconductor 1 is -800 V, the outer diameter of the developing sleeve 81 is 30 mm, and the rotation speed thereof. 150 rpm, thickness of developer D layer is 0.4 mm, developing sleeve 81
0.7 mm gap between the photoconductor 1 and the photoconductor 1, the electrode body 86 and the developing sleeve 81
The bias voltage applied to the developing sleeve 81 is DC voltage component -700 V, AC voltage component 4 KHz, peak-to-peak voltage 1,000 V, and DC voltage -1,000 V is applied to the electrode 86a. As the electrode body 86, one having a structure in which an electrode 86a having a thickness of 100 μm was sandwiched between urethane rubbers was used.

FIG. 3 shows the results of changing the frequency and voltage of the AC voltage component applied to the developing sleeve 81 in the above embodiment. In FIG. 3, the range shaded with horizontal lines is the range where fogging is likely to occur, the range shaded with vertical lines is the range where dielectric breakdown is likely to occur, and the range shaded with diagonal lines is the range where image quality degradation is likely to occur. There is a preferable range in which a stable and clear image can be obtained. As is clear from the figure, the range in which fogging is likely to occur changes with changes in the AC voltage component. The waveform of the AC voltage component is not limited to a sine wave, and may be a rectangular wave or a triangular wave. Further, the low frequency region shaded with dots in the figure is a range where uneven development occurs due to the low frequency. Similar results were obtained in this preferable range under the above-mentioned preferable d ₁ and d ₂ .

In the above embodiment, at the time of non-development,
The rotation of the developing sleeve 81 was stopped, and the application of the AC bias applied to the developing sleeve 81 was stopped. That is, a bias voltage having a floating state or the same or different polarity as the toner is applied. A voltage having the same polarity as the toner is applied to the electrode 86a as in the image formation, or the electrode 86a is set in a floating state to prevent the toner from adhering.

After developing under the above-mentioned conditions, it was transferred onto plain transfer paper by corona discharge, and passed through a heat roller fixing device having a surface temperature of 140 ° C. to fix the transfer paper. The image had no edge effect and no fog, and had a high density and was extremely clear, and after continuously recording 50,000 sheets, it was possible to obtain a recorded image which was stable from the beginning to the end.

The developing device of the present invention is particularly suitable for reversal development, but is not limited to a recording device by electrophotography,
It can also be used as a developing device of a recording device by an electrostatic recording method using a multi-stylus electrode or the like.

[0034]

As described above, according to the present invention, the electrode body in which both surfaces of the electrode are covered with the insulating member is provided on the upstream side of the developing region also as a leveling plate, and the electrode has a bias of the same polarity as the toner. It was configured to apply a voltage. As a result, the average particle size
It is possible to provide a developing device in which even if a toner having a particle size of 10 μm or less is used, the electrode body is not contaminated by the toner, the developing efficiency is high, and a clear high-quality image without unevenness or fogging can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a developing device of the present invention.

FIG. 2 is a partial sectional view showing another embodiment of the developing device of the invention.

FIG. 3 is a graph showing a developing state when the AC component of the bias voltage is changed in this embodiment.

[Explanation of symbols]

 1 Photoreceptor (Image Carrier) 81 Development Sleeve 83 Stirrer 84 Fur Brush 85 Control Blade (Developer Layer Control Member) 86 Electrode Body (Plate Member) 86a Electrode 86b, 86c Insulation Member E1, E3 DC Bias Power Supply E2 AC Bias power supply R1, R2 Protection resistance A Development area D Developer

Claims (4)

[Claims] 1. A developing device for developing a latent image on an image bearing member, wherein an image bearing member and a developing sleeve carrying a developer face each other, and an electrode which is in contact with the image bearing member and the developer. A body is provided in an upstream portion of the developing region, and a first oscillating electric field is formed between the electrode of the electrode body and the developing sleeve, and a second oscillating electric field is formed between the image carrier and the developing sleeve; The developing device is characterized in that the first oscillating electric field is set to be stronger than the second oscillating electric field, and an electric field for moving toner to the image bearing member is formed between the image bearing member and the electrode. 2. The developing device according to claim 1, wherein the electrode body is configured such that both surfaces of the electrode are covered with an insulator. 3. The developing device according to claim 1, wherein a voltage having the same polarity as that of the toner is applied to the electrode. 4. The developing device according to claim 1, wherein the first oscillating electric field and the second oscillating electric field have the same phase.