JPH09258552A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform thin layer of developer on a developer carrier and to use the uniform thin layer for development by excellently regulating a one-component developer on the developer carrier without sticking the developer remaining after the development to the surface of the developer carrier by a developer regulating member being in press-contact with the developer carrier. SOLUTION: As a toner regulating member, a toner regulating roller 1 is used and constituted in such a manner that an elastic layer 1b is formed on the circumference of a metallic shaft 1a and a dielectric layer 1c is formed on the surface of the elastic layer 1b. Then, the elastic layer 1b is made conductive or semiconductive, to be constituted as an electric field generating means. The regulating roller 1 is rotated in press-contact with the surface of a developing sleeve 3 and an AC voltage is applied to the shaft 1a from AC power 9 to generate an alteruating electric field from the elastic layer 1b in the very small gap between the upstream and downstream sides of a press-contact part in the rotational direction of the developing sleeve 3, so that nonmagnetic toner T on the developing sleeve 3 is flown up and moved up and down. Thus toner is regulated.

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 visualizing an electrostatic latent image formed on an image bearing member such as an electrophotographic photosensitive member or an electrostatic recording dielectric member.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an image recording apparatus, a printer, a facsimile, etc., an electrostatic latent image is formed on an image bearing member composed of an electrophotographic photosensitive member or an electrostatic recording dielectric material. A latent image is developed by a developing device to be visualized as a toner image.

As one of such developing devices, various dry one-component developing devices have been proposed and put into practical use.
However, there is a problem that it is difficult to form a thin layer of the toner of the one-component developer on the developer carrier in any of the developing devices.

However, at the present time when improvements in image resolution and sharpness are required, development of a toner thin layer forming method and apparatus therefor is indispensable, and some measures have been proposed for this. ing.

For example, Japanese Patent Laid-Open No. 54-43038 discloses that
An elastic blade made of rubber or metal is brought into contact with the developing sleeve as the developer carrying member, and the toner layer is configured to pass between the abutting portion of the elastic blade and the developing sleeve. There is described a developing device which regulates the toner, thereby forming a thin layer of the toner on the developing sleeve, and imparting sufficient triboelectric charge (tribo) to the toner by friction at the contact portion.

In this case, when the non-magnetic toner is regulated by the elastic blade, a separate supplying member for supplying the toner onto the developing sleeve is required. This is because in the case of the magnetic toner, the toner can be supplied onto the developing sleeve by the magnetic force of the magnet in the developing sleeve, but in the case of the non-magnetic toner, the toner cannot be supplied by the magnetic force. .

The conventional developing device shown in FIG.
No. 116,559), a fur brush structure in which the developing container 102 in which the non-magnetic toner 106 is stored as a one-component developer is in contact with the developing sleeve 103 at a position upstream of the elastic blade 104 in the rotational direction of the developing sleeve 103. The supply roller 105 for the developing sleeve 103 is installed.
The toner 106, which is not consumed for the above development and remains, is peeled off by the supply roller 105, and the development sleeve 10
3 is supplied with new toner 106.

With this structure, a thin layer of non-magnetic toner can be satisfactorily formed on the developing sleeve 103, and the electrostatic latent image on the image carrier, that is, the photosensitive drum 101 can be satisfactorily developed. By developing, it became possible to faithfully reproduce a solid black image of high density and a wide area, and always obtain a stable image. Further, this developing device can provide a developing device which is simpler and smaller in size than the conventional two-component developing device and has a large toner capacity.

The toner used in the developing device will be described. As a method for producing a toner, a resin, a release agent composed of a low softening point substance, a colorant, a charge control agent, etc. are uniformly dispersed using a pressure kneader extruder or a media disperser, and then mechanically Alternatively, after colliding with a target under a jet stream and finely pulverizing to a desired toner particle size, a particle size distribution is further sharpened through a classification step,
A so-called crushing method for forming a toner; Japanese Patent Publication No. 56-1394
A method for obtaining a spherical toner by atomizing a molten mixture in the air using a disk or a multi-fluid nozzle described in JP-A-5-58; JP-B-36-10231 and JP-A-59-5.
A method of directly producing a toner by using the suspension polymerization method described in JP-A-3856 and JP-A-59-61842; an aqueous organic solvent in which a monomer is soluble but a polymer is insoluble. A dispersion polymerization method of directly producing a toner by using it; an emulsion polymerization method typified by a soap-free polymerization method in which a toner is produced by directly polymerizing in the presence of a water-soluble polar polymerization initiator, and the production of toner Is available for.

The polymerized toner is preferably one produced by a suspension polymerization method under normal pressure or under pressure. According to the suspension polymerization method, the particle size distribution is relatively easy and the particle size is 4 to 4
It is possible to obtain fine particle toner of 8 μm, and the toner has a spherical shape and a smooth surface.

Coefficients SF-1 and SF- indicating the shape of the toner
2 will be described. Toner shape factors SF-1 and SF
-2 uses a FE-SEM (S-800) manufactured by Hitachi, Ltd. to randomly sample 100 toner particle images, and the image information is transferred to an image analysis device (Luxex3) manufactured by Nicole Co. through an interface. It was introduced, analyzed, and defined as the value obtained by the following formula.

SF-1 = {(MXLNG) ² / ARE
A｝ × (π / 4) × 100 SF-2 = {(PERI) ² / AREA} × (π / 4)
× 100 where AREA: toner projected area MXLNG: absolute maximum toner length PERI: toner circumference

This SF-1 shows a spherical degree, and if it is larger than 140, it gradually becomes indefinite from a spherical shape. SF-2 indicates the degree of unevenness, and when it is larger than 120, the unevenness of the toner surface becomes remarkable. If the SF-1 exceeds 140 or the SF-2 exceeds 120, the fog of the toner may increase or the durability may be slightly deteriorated.

The effect of the spherical shape of the toner is to improve the fluidity of the toner, reduce the mechanical stress of the toner, and obtain the transfer efficiency up to 100%. For irregularly shaped toner such as pulverized toner, if the pressing force is high on the transfer roller, the toner is mechanically pressed against the photosensitive drum, and so-called "character missing" transfer failure easily occurs. With toner, that is unlikely to occur.

According to the suspension polymerization method, a low softening point substance can be included. Specifically, by setting the polarity of the material in the aqueous medium so that the low softening point substance is smaller than the main monomer, and by adding a small amount of a resin or monomer having a large polarity, It is possible to obtain a toner having a so-called core / shell structure in which the inner low softening point substance is coated with the outer shell resin.

To control the particle size of the toner and the particle size distribution,
A method of changing the type and amount of a soft water-soluble inorganic salt or a dispersant that acts as a protective colloid, mechanical device conditions, such as rotary speed, number of passes, stirring blade shape, stirring conditions, container shape, or in an aqueous solution. A predetermined toner can be obtained by controlling the solid content concentration and the like.

In the polymerized toner having the core / shell structure, by using the low softening point substance as the core substance,
Thermal fixing can be performed with a smaller amount of heat than before. Therefore, a low softening point substance is preferable as a main component of the core portion, and a compound having a main body maximum peak value measured in accordance with ASTM D3418-8 of 40 to 90 ° C. is preferable.
When the maximum peak value is less than 40 ° C., the self-aggregating force of the low softening point substance becomes weak, and as a result, the high temperature offset property becomes weak, which is not preferable. On the other hand, if the maximum peak exceeds 90 ° C., the fixing temperature becomes high, which is not preferable. Further, when the toner is obtained by the direct polymerization method, since the granulation / polymerization is carried out in an aqueous system, when the temperature of the maximum peak value is high, the low softening point substance mainly precipitates during granulation, and the suspension system is formed. It is not preferable because it inhibits.

For measuring the temperature of the maximum peak value, for example, DSC-7 manufactured by Perkin Elmer Co. is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium. An aluminum pan was used as a sample, an empty pan was set as a control, and measurement was performed at a temperature rising rate of 10 ° C./min.

[0019]

However, in the conventional developing device shown in FIG. 5, the supply roller 105 abuts against the developing sleeve 103 at a predetermined pressure and rubs it, so that new toner is transferred onto the developing sleeve 103. Before the supply, the toner remaining after development on the developing sleeve 103 is peeled off to cancel the development history such as ghost on the developing sleeve. However, since the toner cannot be completely peeled off, the following drawbacks occur. there were.

(1) When a plurality of images with a low printing rate such as solid white are continuously output while repeatedly supplying new toner without completely removing the toner on the developing sleeve 103, the developing sleeve 103 Since the same toner above passes through the supply roller 105 a plurality of times, the toner is pressed against the developing sleeve 103 densely.
Firmly adheres to the upper surface. In particular, under high temperature and high humidity environment, toner easily fuses to the surface of the developing sleeve,
Image defects such as white streaks occur.

(2) If the toner is clogged at the elastic blade 102 or the toner having a large amount of charge adheres,
Since the toner continues to rub against the developing sleeve 103, it is fused to the elastic blade 102 by frictional heat. If the toner is fused to the elastic blade 102, the toner coating on the developing sleeve 103 is hindered, and image defects such as streaks occur.

In order to solve the problem (1), it is possible to increase the contact pressure of the supply roller 105 with the developing sleeve 103 to strongly peel off the toner on the developing sleeve 103. The driving torque of the developing sleeve and the like must be increased, which not only increases the cost of the developing device, but also the toner is strongly rubbed against the developing sleeve, so that the surface of the toner is changed and the charging property is deteriorated. . When the chargeability of the toner is lowered, the toner is attached to the non-image portion of the electrostatic latent image on the photosensitive drum 101 to cause fog, the image density is lowered, and the image quality is similarly deteriorated.

In order to eliminate the problem (2), it is effective to lower the contact pressure of the elastic blade 102 with the developing sleeve 103 because the generation of frictional heat can be suppressed. Since the amount decreases, image quality deterioration such as fogging and density decrease occurs in the developed image.

The occurrence of the problems (1) and (2) largely depends on the toner properties such as the shape and hardness of the toner and the surface property. For example, with spherical toner, although the fluidity and transferability are improved, since the toner particles tend to be packed more closely together, the problem (1) becomes more serious than with ordinary irregular toner, while low toner A toner using a softening point substance can lower the fixing temperature,
The problems (2) and (1) were also likely to occur.

The object of the present invention is to fix the one-component developer on the developer carrier to the surface of the developer carrier by the developer regulating member pressed against the developer carrier and to the developer remaining after development. It is an object of the present invention to provide a developing device capable of forming a uniform thin layer of a developer on a developer carrying member and controlling the satisfactorily without being regulated without being subjected to development.

[0026]

The above object can be achieved by the developing device according to the present invention. In summary, the present invention provides:
By carrying and rotating the one-component developer, a developer carrying member that conveys the one-component developer toward the developing area facing the image carrying member,
A developing device provided with a developer regulating member that presses against the surface of the developer carrier and regulates the developer conveyed to the developing area, and forms a uniform thin layer of the developer on the developer carrier. The developer regulating member is composed of an elastic roller equipped with an electric field generating means, which rotates in pressure contact with the surface of the developer carrying body, and the electric field generating means is a developer carrying body with respect to a rotating direction of the developer carrying body. A developing device characterized in that an alternating electric field is generated that causes the developer on the developer carrier to fly and reciprocates in a minute gap at least on the downstream side of the minute gap generated upstream and downstream of the pressure contact portion with the body. is there.

According to one aspect of the present invention, the elastic roller has at least an elastic layer provided around a metal shaft, and the elastic layer is formed of a conductive or semi-conductive elastic member. It constitutes an electric field generating means, and the application of an AC voltage to the shaft causes the elastic layer to generate the electric field in the minute gaps upstream and downstream of the pressure contact portion with the developer carrying member. A dielectric surface layer may be provided on the elastic layer. The dielectric may have a charging polarity opposite to that of the toner.

According to another aspect of the present invention, in the elastic roller, a cylindrical electrode member is concentrically and non-rotatably arranged inside a rotating elastic cylinder made of a dielectric material. , A dielectric layer is provided around the shaft, and an electrode constituting an electric field generating means is provided on the surface of the dielectric layer, the electrode being downstream of a pressure contact portion with the developer carrier in a rotation direction of the developer carrier. And an alternating voltage is applied to the electrode to cause the electrode to generate the electric field in a minute gap downstream of a pressure contact portion with the developer carrying member. The dielectric of the elastic cylinder may have a charging polarity opposite to that of the toner.

According to the present invention, preferably, the frequency of the alternating voltage is 300 to 3000 Hz. The rotating direction of the elastic roller is such that the developer carrying member and the pressure contact portion thereof move in opposite directions. Shape factor SF-1 of the developer
Is 100 to 140, and SF-2 is 100 to 120.
A part or all of the developer is formed by a polymerization method. A part or all of the developer is a low softening point substance, and the melting point of the low softening point substance is 40 to 90 ° C.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention. The developing device of this embodiment is a non-magnetic one-component developing device.

As shown in FIG. 1, the developing device is provided with a developing container 4 containing a non-magnetic toner T as a one-component developer, and an opening of the container 4 facing a photosensitive drum (not shown) is opened in the direction of the arrow. It has a developing sleeve 3 that rotates. A toner supply roller 5 is installed inside the container 4 of the developing sleeve 3 as a toner stripping / supplying member, and a toner stirring member 6 is installed in the interior of the container 4.

In this embodiment, the non-magnetic toner T is a polymerized toner produced by the above-mentioned suspension polymerization method and having a sharp particle size distribution. Its weight average particle diameter is about 7.5 μm. The non-magnetic toner T produced by this suspension polymerization method is the toner 1
Specific surface area by BET method is 200 m ^{2 with} respect to 00 parts by weight
/ G of hydrophobic silica was externally added at a ratio of 2 parts by weight and used.

The developing sleeve 3 is a conductive cylinder made of aluminum and having a diameter of 16 mm, and is arranged with a gap of 300 μm from the photosensitive drum by a gap regulating member (not shown). The toner stirring member 6 rotates in the direction of the arrow in the figure,
The non-magnetic toner T in the container 4 is agitated and conveyed toward the developing sleeve 3 and the supply roller 5.

The toner supply roller 5 is an elastic roller having a urethane sponge around a core metal. In this embodiment, an open-cell urethane sponge is used, and the sponge is a low hardness product having an Asker C hardness of 20 °. And Supply roller 5
Has a diameter of 8 mm, and the supply roller 5 elastically abuts the developing sleeve 3 with an intrusion amount of 1 mm. A driving force was supplied to the supply roller 5 by a gear (not shown), and the supply roller 5 was rotationally driven at a peripheral speed of 50 mm / sec in the counter direction in which the supply roller 5 was moved in the opposite direction at the contact portion with the developing sleeve 3.

By the rotation of the supply roller 5 in the counter direction, the surface of the developing sleeve 3 is rubbed and the toner remaining after the development on the developing sleeve 3 is peeled off, and the toner history (ghost) on the surface is removed. , New toner T
Are supplied onto the developing sleeve 3.

A major feature of the present invention is that the solid regulating roller 1 is provided as the toner regulating member. The toner regulating roller 1 is provided with an elastic layer 1b around the metal mandrel 1a, and by making the elastic layer 1b conductive or semi-conductive, it is configured as an electric field generating means. Preferably, dielectric layer 1c is provided as a surface layer on elastic layer 1b.

In this embodiment, the metal shaft 1a has a diameter of 4 mm.
The elastic layer 1b was formed of urethane sponge, the dielectric layer 1c was formed of nylon resin having a thickness of 50 μm, and the entire diameter of the toner regulating roller 1 was set to 8 mm. The elastic layer 1b of urethane sponge was adjusted to have a medium resistance (semiconductive) of about 10 ⁶ Ω by dispersing carbon black. The Asker C hardness (total weight: 500 g) of the regulation roller 1 itself is 30 °.

The regulating roller 1 is pressed against the surface of the obliquely upper portion of the developing sleeve 3 on the container 4 side, and is rotated in the counter direction in which the contact portion with the developing sleeve 3 moves in the opposite direction to rotate the developing roller. The toner T on the toner 3 is regulated so that the toner T is charged with an electric charge suitable for development, and the toner is formed on the toner thin layer 7 having a predetermined thickness to reduce the amount of toner conveyed to the development area facing the photosensitive drum. The amount is appropriate. In this embodiment, the regulation roller 1 is provided on the surface of the developing sleeve 3 at 30 g / c.
It was pressed with a pressure of m and was rotationally driven in the counter direction at a peripheral speed of 5 mm / sec.

A developing power source in which a DC power source 8 and an AC power source 9 are connected in series is connected to the developing sleeve 3, and at the time of development, a DC voltage of -500 V is applied between the developing sleeve 3 and the photosensitive drum by the developing power source. 1.5kVpp, 2kHz
The developing bias with the AC voltage is applied. Due to this developing bias, the thin toner layer 7 conveyed to the developing area
The toner T constituting the toner flies and adheres to the latent image on the photosensitive drum 1, and the latent image is developed and visualized as a toner image.

The scraper 2 is in contact with the portion of the toner regulating roller 1 on the side of the developing container 4. The scraper 2 is made of urethane rubber having a thickness of 2 mm, and by abutting against the surface of the regulation roller 1, the toner adhered on the regulation roller 1 is scraped off to prevent the toner from scattering outside the developing container 4. .

According to the present invention, the metal shaft 1a of the toner regulating roller 1 is connected to the AC power source. In this embodiment,
Instead of newly providing an AC power source, the shaft 1a was connected between the DC power source 8 and the AC power source 9 as the developing power source, and this AC power source 9 was used. An alternating electric field is generated between the regulation roller 1 and the developing sleeve 3 by applying an AC voltage from the AC power supply 9. Therefore, as shown in FIG.
The toner T, which is carried on the upper surface of the regulating roller 1 and is charged with electric charge in the sliding portion Y of the regulation roller 1 and has a thin layer, is located in a downstream portion (flying region) of the sliding portion in the rotation direction of the developing sleeve 3.
At X, they are separated from the developing sleeve 3 by an alternating electric field and fly, and reciprocally move in a minute gap between the regulation roller 1 and the developing sleeve 3 in the flying region X to rearrange them on the developing sleeve 3.

Therefore, the toner remaining on the developing sleeve 3 after the development is peeled off by the supply roller 5, and the developing sleeve 3 is removed.
Even if the toner remaining after the development is left on the upper surface, excessive packing of the remaining toner is eliminated, and fusion of the toner to the developing sleeve 3 and sleeve ghost can be prevented.

Further, the frequency of the alternating electric field between the regulation roller 1 and the developing sleeve 3 is sufficiently higher than the peripheral speed of the developing sleeve 3, and the toner reciprocates at a high speed, so that the toner is thin on the developing sleeve 3. A layer toner coat layer is obtained with a uniform thickness. If the frequency of the alternating electric field is too high, the reciprocating motion of the toner cannot follow and the width of the flying region X is narrowed, so 3000 Hz or less is preferable.

The toner coating amount on the developing sleeve 3 does not change regardless of the application of the alternating electric field because there is no DC potential difference between the regulating roller 1 and the developing sleeve 3.
Therefore, neither excessive toner adhesion nor toner scattering to the regulation roller 1 occurred.

Also in the region Z upstream of the rubbing portion Y,
In the minute gap between the regulation roller 1 and the developing sleeve 3, an alternating electric field having an electric field strength equal to that of the flying area X downstream of the rubbing portion is generated, so that the toner on the developing sleeve 3 also reciprocates, but fly. Since the amount of toner is remarkably larger than that in the region X, the peeling effect from the developing sleeve 3 is weak, and the rearrangement of the toner on the developing sleeve 3 remains auxiliary.

In the rubbing portion Y, since the regulating roller 1 rotates, the toner does not stay, and for example, even if charged toner adheres to the regulating roller 1, it is carried out from the rubbing portion Y. Therefore, the frictional heat is not accumulated in the toner at the rubbing portion Y, and the toner fusion can be prevented for a long time.

The rotation direction of the regulation roller 1 may be the forward direction with respect to the developing sleeve 3, but the counter direction is more effective as in the present embodiment. This is because by rubbing the toner on the developing sleeve 3 in the counter direction, the toner is prevented from being pushed back toward the inside of the developing container 4 and flying out of the developing container 4. Therefore, with the conventional toner regulating member on the blade, even spherical toner such as polymerized toner which is difficult to regulate due to slipping can be regulated without slipping off by the regulating roller 1 and a toner coat layer can be stably obtained. it can.

As the material of the elastic layer 1b of the regulation roller 1, a material having a charging series and a polarity opposite to that of the toner is preferable, and in the present embodiment, the non-magnetic toner T is a negative charging material, so that it is as described above. In addition, a positively chargeable elastic material such as urethane rubber was used, and the elastic layer 1b was formed by this sponge. By using such an elastic layer having a charging property opposite to that of the toner, it is possible to impart a sufficient frictional charge of −10 to −20 mC / kg to the toner T and obtain an image with stable density. You can

As the positively chargeable elastic material used for the elastic layer 1b, in addition to urethane rubber, general rubber such as NBR, EPDM, and silicon rubber can be used, and the conductive material for resistance adjustment contained therein. As the agent, not only carbon black but also various fine metal powders can be used.

The outermost dielectric layer 1c of the regulation roller 1 is
It is provided in order to prevent the leakage of the AC voltage applied to the regulation roller 1, but since it also serves as a toner charge-imparting material, the dielectric layer 1c is made of a material such as urethane or acrylic whose charge series is opposite to that of the toner. It is possible to use a dielectric material of

Since the developing device of this embodiment is configured as described above, even if the undeveloped toner remains on the developing sleeve 3 when the undeveloped toner is peeled off by the supply roller 5, the developing sleeve remains. 3 and the toner regulating roller 1 do not cause toner sticking or fusion to the surface, and the toner carried on the developing sleeve 3 is well regulated for a long period of time without streaks or toner fluffing to a predetermined thickness. It is possible to stably coat a thin toner layer, which allows a high quality image to be obtained.

Another embodiment of the present invention will be described. FIG. 3 is a schematic configuration diagram showing another embodiment of the developing device of the invention. A major feature of this embodiment is that the toner regulating roller 12 is configured by disposing the electrode member 11 inside the hollow elastic roller 10. Other configurations of this embodiment are
Similar to the developing device shown in FIG. 1, the same reference numerals as those in FIG. 3 denote the same members in FIG.

As shown in FIG. 4, the elastic roller 10 is a hollow roller having an elastic layer 10a formed on a cylinder 10b. The material of the elastic layer 10a is preferably a material that has elasticity, can obtain a smooth surface property, and is charged to a polarity opposite to the charging polarity of the toner in the charging series. The cylinder 10b is made of, for example, a dielectric material such as resin, and if the toner can be pressed uniformly in the longitudinal direction of the developing sleeve 7, there is no limitation on the material selection. In this embodiment, the elastic layer 10a of urethane rubber is formed on the cylinder 10b of polycarbonate resin having a thickness of 300 μm to have a thickness of 2 mm to form the hollow elastic roller 10. The hardness of this elastic roller 10 was 50 ° in terms of Asker C hardness (total weight: 500 g).

The electrode member 11 has a cylinder 11b made of a dielectric material such as resin formed around the shaft 11c.
An electrode 11a is provided on the surface of b. The shaft 11c is cut with a D cut for setting the position of the electrode 11a. The outer diameter of the cylinder 11 b is the cylinder 1 of the elastic roller 10.
In order to arrange the electrode member 11 in 0b in a non-contact manner, the diameter is made slightly smaller than the inner diameter of the cylinder 10b. Electrode 1
1a is made of a conductive or medium resistance material, and has a cylindrical shape 11
The width of the flying region of the toner is formed in one place on the surface of b, and is formed over the entire region in the longitudinal direction. In this embodiment, the cylinder 11
b is made of polycarbonate resin with an outer diameter of 4 mm,
An electrode 11a is formed on the surface of the resin column 11a with conductive paint.
To have a width of 2 mm.

The elastic roller 10 is rotatably attached to the side plate of the developing container 4, whereby the elastic roller 10 is pressed against the surface of the obliquely upper portion of the developing sleeve 3 on the container 4 side. The scraper 2 is brought into edge contact with the surface of the elastic roller 10. The electrode member 11 inside the elastic roller 10 is non-rotatably attached to the side plate of the container 4, and at this time, the electrode 11a of the shaft 11c is arranged inside the elastic roller 10 so that the electrode 11a faces the minute gap downstream of the toner regulation nip portion. Position in advance by D cut.

In this embodiment, the elastic roller 10 is brought into contact with the developing sleeve 3 at a contact pressure of 10 g / cm, and the contact portion with the developing sleeve 3 moves in the opposite direction in the counter direction.
It was driven at a peripheral speed of 5 mm / sec.

The electrode 11a of the electrode member 11 is connected between the DC power source 8 and the AC power source 9 of the developing power source. Therefore, when an AC voltage is applied between the electrode 11a and the developing sleeve 3 by the AC power supply 9, an alternating electric field is generated from the electrode 11a. Since the elastic layer 10a and the resin cylinder 10b of the elastic roller 10 are dielectrics, this alternating electric field is applied to the electrode 1
With a width of 1a, it is possible to concentrate in the minute gap in the downstream region X (FIG. 2) of the toner regulation nip portion.

In this embodiment, since the alternating electric field generated from the toner regulating roller 12 is limited to the downstream region X of the toner regulating nip in this way, the entire electric field of the toner regulating roller 1 is alternated as in the previous embodiment. Power consumption can be reduced and vibration of the regulation roller 12 due to the alternating electric field can be suppressed as compared with the case of generating an electric field. Further, since no voltage is applied to the restriction nip portion, there is an effect that electrical leakage is unlikely to occur.

The voltage applied between the electrode 11a and the developing sleeve 3 depends on the distance between the electrode 11a and the developing sleeve 3, but 200 Vpp or more is required to cause the toner on the developing sleeve 3 to fly, and the leakage is prevented. Is 5 kVp
It is preferably p or less. In this embodiment, as in the previous embodiment, the AC power supply 9 of the developing power supply is used in order to omit the power supply.
Since it is shared, the electrode 11a has 1.5 kVpp and 2 kVpp.
Hz was applied.

According to the present embodiment, as described above, the vibration of the regulating roller 12 due to the alternating electric field can be reduced, so that the contact pressure of the elastic roller 10 against the developing sleeve 3 is reduced to 10.
Even with a low g / cm, the non-magnetic toner T on the developing sleeve 3 can be regulated with a stable coating amount. Therefore, as in the previous example, a polymerized toner produced by the suspension polymerization method is used as the non-magnetic toner T. In the present example, a polymerized toner having a core / shell structure, particularly a low core substance, is used. A polymerized toner containing a paraffin wax as a softening point substance was used.

The prescription of the polymerized toner is as follows.

Styrene monomer 165 g n-Butyl acrylate 15 g Metal salicylate compound (charge control agent) 3 g Saturated polyester (polar resin. Acid value 14, peak molecular weight 8000) 10 g Paraffin wax (releasing agent, melting point 60 ° C.) 50 g

In the conventional developing apparatus, the polymerized toner containing paraffin wax which melts at such a low temperature is likely to be fused to the developing sleeve and the toner regulating member to cause image defects such as streaks. In the example, the toner regulating roller 12 is pressed against the developing sleeve 3 with a low contact pressure to rotate, and the toner is ejected and reciprocates in the minute gap in the downstream region of the toner regulating nip portion, so that the toner is reciprocated for a long period of time. The toner carried on the developing sleeve 3 is satisfactorily regulated without streaks and toner fluffing, so that a thin toner layer having a predetermined thickness can be stably coated, and a high quality image can be obtained. Became. In addition, the fixing temperature of the toner is lowered, which reduces the power consumption of the entire image forming apparatus.

[0065]

As described above, according to the present invention,
The one-component developer on the developer carrier is satisfactorily regulated by the developer regulating member pressed against the developer carrier, without sticking to the surface of the developer carrier in the residual developer.
A uniform thin layer of the developer can be formed on the developer carrying member and can be used for development, whereby a high quality image 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 an explanatory diagram showing a vicinity of a pressure contact portion between a toner regulating roller and a developing sleeve installed in the developing device of FIG.

FIG. 3 is a sectional view showing another embodiment of the developing device of the invention.

FIG. 4 is a cross-sectional view showing components of a toner regulating roller of the developing device of FIG.

FIG. 5 is a sectional view showing a conventional developing device.

[Explanation of symbols]

 1 Toner Regulation Roller 1a Shaft 1b Elastic Layer 1c Dielectric Layer 2 Scraper 3 Developing Sleeve 5 Toner Supply Roller 9 AC Power Supply 10 Elastic Roller 10a Elastic Layer 10b Cylinder 11 Electrode Member 11a Electrode 11b Resin Cylinder 11c Shaft

Claims (11)

[Claims] 1. A developer carrying member that carries a one-component developer and rotates to carry it toward a developing region facing the image carrying member, and a developing region that is brought into pressure contact with the surface of the developer carrying member. In a developing device including a developer regulating member that regulates the developer conveyed to the developer carrier and forms a uniform thin layer of the developer on the developer carrier, the developer regulating member is a member of the developer carrier. An elastic roller provided with an electric field generating means that rotates in pressure contact with the surface, and the electric field generating means is a minute gap generated upstream and downstream of a pressing portion with the developer carrying body in the rotational direction of the developer carrying body. A developing device characterized in that an alternating electric field that causes the developer on the developer carrier to fly and reciprocates is generated in a minute gap at least on the downstream side of the developing device. 2. The elastic roller is provided with at least an elastic layer around a metal shaft, and the elastic layer is formed of a conductive or semi-conductive elastic member to constitute an electric field generating means. The developing device according to claim 1, wherein the elastic layer generates the electric field in the minute gaps upstream and downstream of the pressure contact portion with the developer carrier by the application of an AC voltage to the shaft. 3. The developing device according to claim 2, further comprising a surface layer made of a dielectric material on the elastic layer. 4. The developing device according to claim 2, wherein the dielectric has a charging polarity opposite to that of the toner. 5. The elastic roller comprises a cylindrical electrode member concentrically and non-rotatably arranged inside a rotating elastic cylinder made of a dielectric material, wherein the electrode member has a dielectric layer around a shaft. Is provided, an electrode constituting an electric field generating means is provided on the surface of the dielectric layer, and the electrode is positioned toward the downstream in the rotation direction of the developer carrier of the pressure contact portion with the developer carrier,
2. The developing device according to claim 1, wherein the electrode generates the electric field in a minute gap downstream of a pressure contact portion with the developer carrying member by applying an AC voltage to the electrode. 6. The developing device according to claim 5, wherein the dielectric of the elastic cylinder has a charging polarity opposite to that of the toner. 7. The frequency of the alternating voltage is 300 to 300.
The developing device according to claim 1, which is 0 Hz. 8. The developing device according to claim 1, wherein the elastic roller is rotated in the opposite direction between the developer bearing member and the pressure contact portion thereof. 9. The shape factor SF-1 of the developer is 100.
~ 140, SF-2 is 100-120,
2, 3, 4, 5, 6, 7 or 8 developing device. 10. A part or all of the developer is formed by a polymerization method.
8 or 9 developing device. 11. The developer according to claim 1, wherein a part or the whole of the developer is a low softening point substance, and the melting point of the low softening point substance is 40 to 90 ° C. , 8, 9 or 10 developing device.