JPH0762779B2 - Development method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-component development type developing method and apparatus for performing development using magnetic carrier particles and toner particles in an alternating electric field.

The present invention is a developing method and apparatus applicable to various kinds of display devices for image recording formation, printers, and facsimile electrophotographic devices.

[Background technology]

The applicant of the present application, unlike the conventional two-component developing method,
There is provided a method and apparatus for developing in an alternating electric field by supplying only one-component toner to a developing section with two-component toner in the developing container (JP-A-58-143360 and 59-101680).

As described above, the developing method in which the magnetic particles and the toner particles are mixed only in the developing container is useful because the drawbacks due to the toner containing the magnetic material are eliminated. However, the edge effect of the image is strong, the density of the solid portion is low, and the negative property (the image density decreases with the increase of the latent image potential) may be exhibited, which has a drawback of the developing property.

Therefore, the applicant has been able to solve these inconveniences through many experiments, and has developed a developing device which produces a great effect in a two-component developing device which positively supplies the magnetic carrier particles to the developing portion, in Japanese Patent Application No. 60-204605 ( (September 17, 1985 application) etc. Further, in recent years, various methods of developing in various fields using a two-component developer in an alternating electric field have been proposed.

On the other hand, the technique of applying an alternating electric field to a two-component developing device is basically described in JP-A-55-32060. This is an excellent invention which discloses that carrier particles are used as a developing electrode to obtain an antifoggant effect.

Further, the carrier particles used in a general two-component developing device are conductive carriers or medium resistance carriers of ferrite alone, and are liable to be deteriorated due to adhesion of toner particles, resulting in problems such as deterioration of durability and ability to impart charge to toner. .

It has been known for a long time that resin-coated carrier particles are used to improve the durability and the charge imparting ability. Conventional resin-coated carrier particles exhibit a considerable insulating property, have an increased charge imparting ability, and have a good surface property, and are therefore practically preferable in terms of durability.

Since the two-component developing method in which an alternating electric field is applied naturally needs durability, it is a matter of course to use the conventional high-resistivity resin-coated carrier particles, but it causes a new problem. In addition to resin coating, there are magnetic fine particle resin-bonded type carrier particles as the high resistance carrier particles, but they exhibit extremely high electric resistance. This is because the higher the electrical resistance of the carrier particles and the closer they are to the insulating property, the more the electrical leakage is prevented in the developing section, the higher the latent image potential and the alternating electric field can be set, and the developing characteristics due to the alternating electric field can be expected. .
However, for example, a carrier with an insulation resistance of 10 ¹⁴ Ωcm or more is charged in the opposite polarity to the toner, and it is easy for the carrier to be drawn in the non-printed solid white area, and even though the carrier is used, the edge effect is strong. There is a drawback that

Therefore, in the two-component developing method, there is a further demand for improvement in image reproducibility when using durable carrier particles.

[Object of the Invention]

It is an object of the present invention to solve a new problem caused by resin-coated carrier particles when an alternating electric field is applied.

It is an object of the present invention to provide a developing method capable of forming a high-quality image by further improving the developing effect in the alternating electric field application development under the conditions of resin-coated carrier particles.

[Outline of Invention]

The present invention has been made as a result of focusing on the insulating property of resin-coated carrier particles and seeking properties different from those of conventional carrier particles. The durability is of course, and the charging property and electrode effect given to toner particles are maintained. To obtain good quality images.

That is, the present invention focuses on the electric resistance of the resin-coated carrier particles, and is based on the fact that the electric field-dependent change in the resistance value of the carrier particles, which has hitherto been unrecognized, greatly affects the reproducibility. It is a thing.

According to the present invention, a developer having magnetic particles and toner particles is used, and the magnetic particles are brought into contact with the photoconductor in the state where an alternating electric field is applied between the photoconductor and the developer carrying member, thereby toner In the developing method for forming an image, the photoreceptor is an OPC.
The magnetic particles have a resistance value of 10 ⁸ or more and 10 ¹¹ Ωcm or less in an electric field of 0.2 × 10 ³ V / cm, or a resistance value of 2 × 10 ⁷ or more and 3 × 10 ⁷ in an electric field of 2 × 10 ³ V / cm. It is characterized by being ⁹ Ωcm or less.

According to the present invention, the magnetic particles are not made to be insulative, but have a resistance value through which an electric current flows to some extent, so that the ears of the magnetic particles serve as a developing electrode, and a very high toner vibration effect is obtained in the developing section. Since it is obtained, the developing property becomes very excellent.

However, when the resistance of the magnetic particles is set to 10 ⁷ to 10 ¹¹ Ωcm in this way, there is no problem with a photoreceptor having excellent surface properties, but there are many pinholes such as a-Si and Se which easily scratches. The development bias leaks to scratches and scratches.

If the resistance value of the magnetic particles is increased in order to prevent the development, the developing electrode effect of the magnetic particles described above is impaired.

Therefore, the present invention uses OPC as the photoconductor. OPC is extremely unlikely to cause pinholes and scratches. Therefore, leakage of the developing bias can be prevented while obtaining the developing electrode effect of the spikes of magnetic particles.

〔Example〕

FIG. 2 is a sectional view of a developing device to which the present invention can be applied.
The latent image carrier 1 is a photosensitive drum or photosensitive belt having a photoconductive insulating material layer made of OPC (Organic Photoconductor). The latent image carrier 1 is rotated in the direction of arrow a by a driving device (not shown). Reference numeral 22 denotes a developing sleeve which is in proximity to or in contact with the latent image carrier 1, and is made of a non-magnetic material such as aluminum or SUS316. The developing sleeve 22 has a laterally long opening formed in the lower left wall of the developing container 36 in a longitudinal direction of the container so that a substantially right half peripheral surface projects into the container 36, and a substantially left half peripheral surface is exposed outside the container and rotatably supported. It is installed horizontally and is driven to rotate in the direction of arrow b.

Reference numeral 23 is a fixed permanent magnet (magnet) as fixed magnetic field generating means which is inserted into the developing sleeve 22 and positioned and held in the position and orientation shown in the drawing. Even if the developing sleeve 22 is driven to rotate, the magnet 23 is at the position shown in the drawing. It is fixedly held as it is. The magnet 23 has four magnetic poles, an N-pole magnetic pole 23a, an S-pole magnetic pole 23b, an N-pole magnetic pole 23c, and an S-pole magnetic pole 23d. The magnet 23 may be an electromagnet instead of the permanent magnet.

The reference numeral 24 is fixed to the side wall of the container on the upper edge side of the developer supply device in which the developing sleeve 2 is arranged, and the tip side is projected to the outside of the container 36 from the position of the upper edge of the opening to extend along the length of the upper edge of the opening. A non-magnetic blade serving as a developer regulating member that is arranged as described above, for example, is obtained by bending SuS316 into a letter shape in a cross-section path.

Reference numeral 26 is a magnetic particle limiting member whose upper surface is in contact with the lower surface side of the non-magnetic blade 24 and whose front end surface is the developer guide surface 261.

27 is a magnetic particle having a particle size of 20 to 100 μm, preferably 30
Resin coated to an apparent density of about 2.4 to 2.8 g / cc ferrite particles (up to 60 to 70 emu / g maximum) of -80 μm can be used.

If it is less than 20μ, the spikes on the developing sleeve will be poor,
The image tends to be uneven. On the other hand, if it is larger than 100 μm, the ability to impart tribo to the toner is lowered and the photosensitive plate is apt to be damaged.

37 is a non-magnetic developer toner.

Reference numeral 31 is a magnetic material disposed on the inner surface of the lower portion of the developing container so as to face the developing sleeve 22 in order to prevent leakage of the magnetic particles 27 or the non-magnetic toner particles 37 from the lower portion of the developing container 36 in which the developing sleeve 22 is disposed. There is, for example, an iron plate to which plating is applied. In the magnetic field between the magnetic body 31 and the S-polarized magnetic pole 23d, a sealing effect for achieving recovery of the magnetic particles 27 and leakage prevention can be obtained.

Reference numeral 39 denotes a toner supply member for supplying toner to the brush portion of magnetic particles formed by the fixed magnetic pole 23 in the developing sleeve 22, and a rubber sheet is attached to a sheet metal rotatably bearing to sweep the toner as if sweeping the lower surface of the developing container. Transport. Toner is supplied to the toner supply member 39 by a toner conveying member in a toner storage container 38 (not shown).

38 and 35 are a toner storage container and a magnetic particle storage container, respectively.

Reference numeral 40 denotes a seal member for sealing the toner accumulated in the lower portion of the developing container 36, which has elasticity and is bent in the rotation direction of the sleeve 22, and elastically presses the surface side of the sleeve 22. The seal member 40 has an end portion on the downstream side in the sleeve rotation direction in the contact area with the sleeve so as to allow the developer to enter the inside of the container.

Reference numeral 30 denotes a scattering prevention electrode plate for preventing the scattering by floating voltage generated in the developing process by applying a voltage having the same polarity as that of the developer to adhere to the photosensitive member side.

Further, the S magnetic pole 23d is a magnetic field for magnetic sealing for forming a magnetic field from one side to the other with the magnetic member 31, and one part faces the magnetic member 31.

The magnetic member 31 is located below the developing device at a substantial end of the developer storage portion of the developer container, and the magnetic carrier particles collected around the inside of the container cause the magnetic member 31 to move into the developer on the sleeve surface. Intake toner particles located in the lower part of the container. Therefore, the stable recovery of magnetic particles has the effect of stabilizing the developing ability.

By arranging the magnetic pole 23d as described above, the magnetic pole 23a
Another preferable effect is obtained in relation to. That is, due to the above-described relationship between the bottom of the container of the container 21 and the magnetic pole 23d, the magnetic brush is inside the 21 (compared to a stagnant state).
Since it is not formed in a rough state, the amount of toner particles taken into the magnetic particles does not become excessive. Excessive incorporation leads to insufficient charging of the toner and causes fogging.

This configuration is also effective when magnetic particles and non-magnetic or weakly magnetic toner are mixed in the developer container.

The distance d ₂ between the end 241 of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 50 to 800 μm, preferably 150 to 500 μm. If this distance is less than 50 μm, the magnetic particles to be described later become clogged between them and the developer layer is likely to have unevenness, and the developer necessary for good development cannot be applied, resulting in a thin developed image with a large unevenness. There is a drawback that can only be obtained. On the other hand, if it is larger than 800 μm, the amount of the developer applied onto the developing sleeve 22 increases and the predetermined developer thickness cannot be regulated, the magnetic particles adhere to the latent image carrier more, and the circulation of the developer described later, There is a drawback that the regulation of development by the developer limiting member 26 is weakened, toner and tribo are insufficient, and fogging is likely to occur.

Next, the magnetic particle layer in the vicinity of the non-magnetic blade 24, which is the developer application amount controlling member, and in the vicinity of the limiting member 26 will be described. The limiting member not only mechanically prevents unnecessary invasion of the replenishment toner into the developer regulating portion. As described above, the magnetic pole 23 in the restriction region surrounded by the member 26 is
The magnetic particles conveyed by the rotation of the sleeve by the N pole of a are packed along the guide surface 261 of the limiting member 26, and the density increases. In this area, the magnetic particles that are conveyed and enter and the magnetic particles that flow out from the blade are exchanged dynamically, so that the magnetic particles collide with each other and are in a blunt state. It is in a practical packing state. Therefore, tribo is imparted to the toner from the magnetic particles or the sleeve, and the toner having a small tribo imparted to the magnetic particles or the sleeve by a weak force and conveyed is separated from the magnetic particles or the sleeve. That is, toner selection and charging improvement are performed. Therefore, the toner to which tribo is sufficiently imparted can be used for development. Further, the non-uniform state during the transportation of the magnetic particles is leveled in the space, and the coating of the magnetic particle layer is made uniform and stable. Therefore, the guide surface 261 is essential for the limiting member 26, and the inclination of the slope and the volume of the space have a great influence on the packing state of the magnetic particles in the space.

On the other hand, the magnetic pole 23 fixedly arranged in this area
In a, the magnetic particles in the packing state are rearranged along the lines of magnetic force. The packing state in the space is unstable with respect to the tribo application, and a constant packing state is always required for stabilization. This forms a magnetic brush with the force of directing the magnetic particles conveyed almost tangentially on the sleeve to the direction, so that not only the stirring effect on the magnetic particles but also the loosening effect works, and Tribo and uniform coating of magnetic particle layer
Stabilization is further promoted. At this time, if the concentrated developer due to the peripheral configuration is still under a great pressure, there is a problem that the developer gets too clogged, but the portion of the magnetic pole 23a that generates the maximum magnetic force faces the guide surface 261. Prevents excessive pressure concentration in the regulated area,
It is considered that the concentration of the developer and the stable high-density magnetic particle existence ratio can be maintained.

Due to the above-mentioned restriction region, a stable amount of magnetic particles and sufficiently charged toner particles can be formed as a thin developer layer on the surface of the developing sleeve. Therefore, the developing effect in the developing area 102 becomes stable. An alternating electric field forming means is provided for forming in the developing section an alternating electric field for transferring at least the toner particles carried on the surface of the developing carrying member among the developers conveyed to the developing section to the electrostatic latent image carrier. In the developing section, the volume ratio of the magnetic particles of the developer transported to the developing section to the volume of the space defined by the electrostatic latent image carrier and the developer carrying member is
It has been confirmed that a great effect is exerted on the developing method and apparatus which are 1.5% to 30%.

FIG. 2 shows a magnetic material on the non-magnetic blade side of the developer limiting member 26.
The case where 50 is installed is shown. In this case, it is not preferable to provide the magnetic body 50 at a position facing the magnetic pole 23a. This is because when they face each other, a strong concentrated magnetic field is generated between the magnetic pole 23a and the magnetic particle agitation and loosening effect of the magnetic pole 23a is reduced. However, it is effective to provide a magnetic body in the restricting portion to magnetically restrict the magnetic particles between the restricting portion and the magnet 23 inside the sleeve, because the gap tolerance between the restricting member and the sleeve is increased. Also, when comparing the magnetic particles or the toner adhered on the sleeve, the amount of electrified charge of the toner adhered on the sleeve is smaller than that on the magnetic particles because the movement of the sleeve also carries the magnetic particles. This is because the toner on the sleeve is less likely to be rubbed by the magnetic particles. In order to raise the toner on the sleeve to a predetermined value, it is necessary to positively rub the toner on the sleeve. That is, it is necessary to have magnetic particles in the vicinity of the sleeve surface that cause a relative velocity shift against the movement of the sleeve.

However, simply lowering the transportability of the magnetic particles is impossible in view of the above-mentioned toner intake action. Further, as described above, it is also possible to arrange a magnetic body in the restricting portion so as to face the in-sleeve magnetic pole 23a and generate a concentrated magnetic field to improve the rubbing force of magnetic field particles on the sleeve, as described above. The effect of arranging the maximum magnetic force generating portion of the magnetic pole in the space formed by the regulating member 26 is reduced.

Therefore, in this embodiment, the magnetic body 50 is provided on the downstream side of the magnetic pole 23a in the sleeve rotation direction so that the magnetic lines of force on the blade side of the magnetic pole 23a are substantially concentrated in the tangential direction of the sleeve surface. As a result, the magnetic particles only near the surface of the sleeve formed a magnetic brush along the surface of the sleeve and rubbed the toner on the sleeve to enhance tribo-impartment of the toner on the sleeve.

In the above device configuration, the magnetic particles 27, the measurement condition is a measurement electrode area 4cm ² , using a gap between the electrodes 0.4cm, using a sun-touch type cell, under pressure of 1kg weight to one electrode, the applied voltage between both electrodes Applying E (V / cm) to obtain the resistance value of magnetic particles from the current flowing in the circuit (the following magnetic particles
The resistance of 27 is the value under this measurement condition), and E = 0.2 × 1
A resistance value of 3.1 × 10 ⁹ Ωcm at 0 ³ and 4.0 × 10 ⁸ Ωc at E = 2 × 10 ³
As medium resistance resin coated carrier particles showing a resistance value of m,
When the image was developed under an alternating electric field, a good quality image was obtained without carrier adhesion in the image area and without developing defects such as white spots in solid black in the image area.

In this way, the magnetic particles do not have an insulating property and the resistance of a slight amount of current is used so that the spikes of the magnetic particles serve as a developing electrode and a very high toner vibration effect is obtained in the developing section. High fog prevention effect, high density, and excellent halftone reproducibility.

The resistance value condition of this magnetic particle is the above E = 0.2 × 10 ³ , E = 2
Specified within the range of × 10 ³ is that the electric field-dependent electric resistance change greatly changes within this range, and there is a gradual decrease in resistance at higher electric fields. This is because it can be recognized that the change in resistance inside corresponds to the change in electric field during the alternating electric field.

The present inventors have found from a number of experiments that the resistance change within this range has a large effect on the developability, and the following conditions have been reached by making many improvements to the commercially available insulating carrier.

That is, if the resistance of the magnetic carrier particles is R (Ωcm),
Measurement voltage E (V / cm) is 0.2 × 10 ³ (V / cm) or more 2 × 10 ³ (V
/ cm) within the following range, If the resin-coated magnetic carrier particles exhibit resistance characteristics of passing at least one point in the area defined by, the image will not be disturbed in an alternating electric field, and the image will be durable and stable with little carrier loss. To achieve. Needless to say, because of the resin coating, the characteristics do not change in response to changes in humidity, the fluidity is high and the practical advantage is covered.

The magnetic particles used in this example are known sintered ferrites, and are made by sintering one or more compositions of Zn, Fe, Cd, Cu, Pb, Ni, Mg, Mn. A composition particularly suitable for the present invention is a metal oxide containing CuO, ZnO and Fe ₂ O ₃ as main components.

Figure 1 area (ABCD) shows how effective the above conditions are.
And explain with data.

The magnetic particles indicated by the symbols k, l, m, n, o, p, g, r, s, and t in FIG. 1 are the sintering conditions using the copper oxide and zinc, and / or the resin is used as the sintered ferrite particles. 6 is an electric resistance characteristic curve of magnetic particles in a graph showing the electric field for measurement E on the horizontal axis and the resistance value R of the magnetic particles on the vertical axis when the coating conditions are changed. For example, the amount of coating resin for n magnetic particles is twice that of p magnetic particles. The measurement was performed at normal temperature and normal humidity. The resin coating material has been used conventionally. A carrier coating material for a two-component developer, such as an acrylic fluorine resin or a silicone resin, may be used, but in the example of FIG. 1, a silicone resin is used. Maximum magnetic 64emu / g, viscosity distribution 70-50μ (250
/ 350 mesh) ferrite was used.

The table below shows the image evaluation of magnetic particles having characteristics of k to t. The amount of resin coating is small from the particles k to t, and the particles o and p are obtained by changing the sintering conditions.

×: Image is bad △: Image is slightly good ○: Image is good ◎: Image is best In addition, the commercially available insulating carrier particles showed a considerably high resistance and could not be described in the graph of FIG. 3, and the image image using this image shows satisfactory whiteness and adhesion of the carrier particles. It didn't go.

The magnetic particles t having an electric resistance lower than that of the line CD in FIG. 1 are likely to cause a brush mark of the developer on the image, and easily generate a white spot where an image is missing in a solid image portion. These are due to leakage of latent image charges generated through the magnetic particles. In addition, magnetic particles tend to adhere to the solid black image area. According to the present invention, the generation of these can be effectively prevented by making the resistance of the magnetic particles exceed the line segment AB.

The magnetic particles having an electric resistance higher than that of the line segment AB in FIG. 1 have a stronger charging property of the magnetic particles themselves and firmly adhere to the toner particles, so that they are less likely to fly to the latent image charge in the developing area. Therefore, the image density is reduced. In addition, the effect of the magnetic particles acting as a developing electrode also decreases, causing a decrease in density. Further, since the magnetic particles are likely to be charged with the polarity opposite to the charge polarity of the toner, the carrier is likely to be attached to the solid white portion in the non-image area. In particular, in the developing device of the embodiment to which the present invention is applied, when the replenishment toner required by the circulating action of the magnetic particle layer in the container is incorporated into the magnetic particle layer, the chargeability of the magnetic particles is too strong, This causes instability of the toner taken into the magnetic particle layer, which easily causes streaks and unevenness on the image. However, application of the present invention can solve this problem. This is an important technique as it solves the device problem.

The same result was obtained when an experiment was conducted by changing the resin of the above-mentioned example to an acrylic fluorine resin. Further, when the diameter of the magnetic particles was changed, no change was observed on the image, and it was confirmed that the above resistance characteristics are extremely effective for the developing method in which an alternating electric field is applied.

As can be understood from the above example, the measured electric field 0.2 × 10 ³ ~
A more preferable image can be formed when the resistance value of the magnetic particles is 2 × 10 ³ (V / cm) and is entirely within the above range. It is considered that this is because the alternating electric field changes in intensity, and therefore exhibits stable behavior by showing only the resistance change in this region. Of particular note is that magnetic particles have an electric field of 0.2 × 10 ³ (V / cm).
At 10 ⁸ Ωcm or more and at 10 ¹¹ Ωcm or less, 2 × 10 ³ (V / cm) at 2 × 10 ⁷
The above behavior can be obtained by exhibiting a resistance value of Ωcm or more and 3 × 10 ⁹ Ωcm or less.

More importantly, E (0.2 × 10 ³ , 2 × 10 ¹⁰ ), F (2 ×
10 ³ , 10 ⁹ ), H (2 × 10 ³ , 5 × 10 ⁷ ), G (0.2 × 10 ³ , 2 × 10 ⁸ )
Very preferable results were obtained for those in which the resistance change of the magnetic particles was entirely within the region Z (hatched portion) in which the four points were connected to each other. This is also an intermediate area of the above area.

This is because, assuming that the curve in the figure is extended and the applied voltage under the maximum strength of the actual alternating electric field is changed to the measured value, the magnetic particles are 5 × 10 ⁷ under the development of the maximum alternating electric field. In addition to showing a high resistance of Ωcm or more (at least 2 × 10 ⁷ Ωcm or more) of 10 ⁹ Ωcm or less within a stable range, a high resistance of a stable area Z even under a low electric field should be a high resistance of a stable area Z. It is thought to be because.

In any case, by using magnetic particles having electric resistance characteristics that do not exceed the line sentence AB and do not fall below the line segment CD, the drawbacks of the conventional resin-coated insulating carrier particles can be effectively prevented.

As described above, the area surrounded by the four line segments in FIG. 1 is extremely critical with respect to the quality of the image to be developed. I think it is obvious from the experimental fact that

The magnetic flux density of the magnetic pole 23a is 600 G or higher, preferably 700 G or higher. This is because the applied state of the developer tends to be more stable as the magnetic flux density of the cut magnetic pole is higher, against changes in the toner content of the magnetic particle layer. Particularly, in the developing device of the present invention which does not have an automatic toner replenishing device for maintaining the toner content, it is preferable that the magnetic flux density is 800 G or more.

In FIG. 2, the magnetic pole 23c is a developing magnetic pole. The developing magnetic pole is located almost at the developing portion and preferably has a magnetic flux density of 800 G or more in order to prevent magnetic particles from adhering to the latent image.

It goes without saying that the present invention includes any combination of the above-described configurations.

In any case, the present invention can provide a high image quality which has not been obtained by the conventional developing method and apparatus, and has an excellent effect that the developing apparatus can be a disposable type small-sized apparatus.

The toner supply member is in the developing container 36 and is close to or in contact with the magnetic particle layer to rotate and drive in the direction of arrow d to supply the toner 37 to the magnetic particle layer.

A toner storage container 38 for storing toner is arranged adjacent to the developing container 36 in a substantially horizontal direction, and a toner conveying member (not shown) for feeding the toner into the developing container 36 is provided in the toner storage container. Has been.

The S magnetic pole 23b is a carrier magnetic pole provided to prevent the developer layer applied uniformly on the nonmagnetic blade 24 from being disturbed because the cut magnetic pole 23a and the developing magnetic pole 23c are separated from each other. Since the S magnetic pole 23b does not disturb the developer layer, the strength of the magnetic pole is approximately equal to or slightly lower than that of the developing magnetic pole 23c.
When using a developing sleeve with a diameter of 20φ, if the distance between the cutting magnetic pole and the developing magnetic pole is within 100 ° at the sleeve center angle, the developer layer on the sleeve is less disturbed, but if it exceeds 100 °, the developer layer It is preferable that a carrier electrode be provided in the middle because the carrier is greatly disturbed.

The S magnetic pole 23d is a recovery magnetic pole for recovering the developer after development, and is arranged on the upstream side in the moving direction of the developing sleeve with respect to the tip of the magnetic seal. If the magnetic pole 23d is located downstream of the tip of the magnetic seal, the magnetic particles 23d will have a spiked portion near the toner intake port at the bottom of the developing container, and it will be extremely easy to take in toner, resulting in insufficient triboelectrification. It is easy to cause fog.

Here, the volume ratio of the magnetic particles in the developing section will be described. The “developing portion” is a portion where the toner is transferred or supplied from the sleeve 22 to the photosensitive drum 1. "Volume ratio" is the percentage of the volume occupied by the magnetic particles present therein to the volume of this developing zone. In the above-mentioned developing device, it is extremely preferable that this volume ratio has an important influence, and that it is 1.5 to 30%, particularly 2.6 to 26%.

If it is less than 1.5%, a reduction in developed image density is observed,
A sleeve ghost occurs, a remarkable density difference occurs between a portion where the spikes 51 are present and a portion where the spikes 51 are not present, and the thickness of the developer image formed on the surface of the sleeve 22 is generally uneven. It is not preferable in that it becomes.

When it exceeds 30%, the degree of closing the sleeve surface increases,
It is not preferable in terms of fogging.

In particular, for the present invention, the above-mentioned conditions listed as the preferred developing method do not cause the image quality to monotonically deteriorate or increase as the volume ratio increases or decreases, but 1.5 to 30%.
A sufficient image density can be obtained in the range of, and 30% even if it is less than 1.5%.
This is based on the fact that the image quality is deteriorated even if the value exceeds the above range, and neither the sleeve ghost nor the fog occurs in the range of the above numerical value where the image quality is sufficient. It is considered that the former image quality deterioration is due to the negative characteristic, and the latter is because the amount of magnetic particles present becomes large and the surface of the sleeve 22 cannot be opened, and the toner supply amount from the surface of the sleeve 22 is significantly reduced. To be

On the other hand, if it is less than 1.5%, the reproducibility of the line image is inferior, and the image quality density is significantly lowered. On the other hand, if it exceeds 30%, there are problems that the magnetic particles damage the surface of the photosensitive drum, and transfer and fixing problems that occur because they adhere as part of the image quality.

When the presence of magnetic particles is close to 1.5%, partial development unevenness called "arabi" occurs when reproducing a large area uniform high-density image (solid black) (e.g. under special environment). Therefore, it is preferable that the volume ratio is such that these are less likely to occur. This value is because the volume ratio of the magnetic particles to the developing portion is 2.6% or more, this range becomes a more preferable range, and when the presence of the magnetic particles is close to 30%, the spikes of the magnetic particles are There is a case where toner supply from the sleeve surface is delayed around the contacting portion (when the developing speed is high, etc.), and scaly density unevenness may occur during solid black reproduction. As a certain range for preventing this, the volume ratio of the magnetic particles is more preferably 26% or less.

If the volume ratio is in the range of 1.5% to 30% (4 in the embodiment)
%), And the ears 51 are formed on the surface of the sleeve 22 in a sparse state to a desired degree as shown in FIG. Both the toner on the sleeve 22 and the ears are sufficiently opened to the photosensitive drum 1, and the toner 100 on the sleeve also fly-transfers due to the alternating electric field, so that almost all of the toner is ready for consumption for development. High development efficiency (ratio of toner that can be consumed for development among the toner existing in the development area)
And high image density is obtained. Preferably, a slight but severe spike vibration is produced, which loosens the magnetic particles and the toner 100 adhering to the sleeve 22. In any case, it is possible to prevent the generation of uneven sweep and ghost image as in the case of a magnetic brush. Further, the friction of the magnetic particles 27 and the toner 28 is activated by the vibration of the ears, so that the triboelectric charge on the toner 28 can be improved and the occurrence of fogging can be prevented. High development efficiency is suitable for downsizing of the developing device. The developing magnetic pole in FIG. 3 is the S pole 23b, which is different from the developing pole 23c in FIG. 2, but either one may be used in this example.

The volume ratio of the magnetic particles 27 existing in the developing section is (M / h)
It can be calculated by × (1 / ρ) × [(C / (T + C)], where M is the coating amount (g / cm) of the developer (mixture ... in the non-peaking) per unit area of the sleeve. ² ), h is the height of the developing space (cm), ρ is the true density of magnetic particles g / cm ³ , C /
(T + C) is the weight ratio of magnetic particles in the developer on the sleeve.

The ratio of the toner to the magnetic particles in the developing section defined above is preferably 4 to 40% by weight. When the alternating electric field is strong (the rate of change is large or Vpp is large) as in the above-mentioned embodiment, the ears separate from the sleeve 22 or the base thereof, and the separated magnetic particles 27 are separated from the sleeve 22 and the photosensitive drum 1.
Reciprocates in the space between. Since the energy of this reciprocating motion is large, the effect of the above-mentioned vibration is further promoted.

The above behavior was confirmed by shooting 8000 frames / sec with a high-speed camera (manufactured by Hitachi, Ltd.). Even when the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is made small to increase the contact pressure between the photosensitive drum 1 and the ears and the vibration is made small, the gap is large on the inlet side and the outlet side of the developing section, so it is sufficient. However, when the magnetic field is not applied, the ears do not come into contact with the photosensitive drum 1 when the magnetic field is not applied. It is preferable that the distance is such that they come into contact with each other.

In FIG. 2, a sleeve 22 is made of an aluminum sleeve having a diameter of 20 mm, the surface of which is subjected to irregular sandblasting with alundum abrasive grains.
A pole and a south pole were used alternately as shown in FIG. The maximum value of the surface magnetic flux density by the magnet 23 was about 900 gauss.

As the blade 24, 1.2 mm thick non-magnetic stainless steel was used, and the angle θ was set to 15 °. Ferrite (maximum magnetization 64 emu / g) having a particle size of 70 to 50 μ (250/350 mesh) having a surface coated with a particle 0 exhibiting resistance characteristics within the above range was used as the magnetic particles. Good results were obtained by using the n, o, p, q curves of FIG. 1 for the electric resistance.

In the system in which the toner intake is controlled by circulating the magnetic particle layer on the sleeve as in the embodiment of FIG. 1, it is preferable that the resistance of the magnetic particles is not high. This is because the toner intake is stabilized when the magnetic particles themselves are less charged. If the magnetic particles have a strong charging property, the toner adheres strongly to the magnetic particles, so when newly incorporating the toner into the magnetic particle layer, the toner that was previously attached and the toner that is newly incorporated. It is difficult for the replacement of. For this reason, the toner that was previously attached remains on the sleeve for a long time, and the toner itself causes excessive charging. Preferably, it is necessary that the region surrounded by the line segment connecting each of the four points of E, F, G, and H in FIG. 1 intersects with the electric resistance characteristic curve. More preferably, it is necessary that EG and FH intersect with the line segment.

As the non-magnetic toner, a blue toner obtained by externally adding 0.6% of colloidal silica to a toner powder having an average particle size of 10 μm, which is composed of 100 parts of styrene / butadiene copolymer resin and 5 parts of copper phthalocyanine pigment, is used. A toner coating layer having a coating thickness of about 10 to 30 μm was obtained on the surface, and a magnetic particle layer having a thickness of 200 to 300 μ was obtained as an upper layer. The toner adheres to the surface of each magnetic particle.

At this time, the total weight of the magnetic particles on the sleeve 22 and all the toner was about 2.43 × 10 ^-2 g / cm ² .

At this time, the weight ratio of the toner attached to the magnetic particles and the toner attached to the sleeve was about 2: 1.

The magnetic particles are magnetic poles inside the sleeve 22 at and near the developing unit.
By 23b, the spikes were erected by a magnetic field to form a shaving brush with a maximum length of about 1.2 mm.

When the charge amount was measured by the blow-off method, the triboelectric charge amount of the toner on the sleeve and the magnetic particles was +12 μC / g.

When this developing device was installed in a PC-10 type copying machine manufactured by Canon Inc. and the distance between the photosensitive drum 3 (made of an organic photosensitive material) and the surface of the sleeve 22 was 350 μm, the volume ratio was calculated to be about 10 %Met. (H = 350 μm, M = 2.43 × 1
0 ^-2 g / cm ² , ρ = 5.5 g / cm ³ , T / (T + C) = 20.4%). Frequency 1600Hz, peak-to-peak value 130 as bias power supply 4
When development was carried out using an alternating voltage of 0 V and a DC voltage of −300 V superimposed, a good blue image was obtained.

Further, when the solid black image was developed and the sleeve surface after the development was observed, the toner adhering to the magnetic particles and the toner on the sleeve were almost consumed, and the development was performed at a developing efficiency close to 100%.

Regarding the developing characteristics, there was no fogging and no carrier adhesion, and good developing characteristics could be obtained.

In addition, because OPC is used as a photoconductor, which is extremely resistant to pinholes and scratches, a current of 10 ⁷ to 10 ¹¹ Ωcm flows, and even if magnetic particles that produce the developing electrode effect are used, a concentrated leak of the developing bias occurs. Does not occur.

Further, regarding the effect of the magnetic member 31, it was confirmed that good intrusion and leakage of magnetic particles and good circulation can be performed.

As described above, according to this embodiment, high image density,
It is possible to perform development without fog, ghost image, unevenness of sweep, and negative characteristics with high development efficiency.

As the material of the sleeve 22, a conductor such as brass or stainless steel, a paper cylinder or a cylinder of synthetic resin can be used in addition to aluminum. Further, the surface of these cylinders can be made to function as a developing electrode if they are subjected to a conductive treatment or are made of a conductor. Further, a core roll may be used to wind a conductive elastic body, for example, a conductive sponge, around the peripheral surface of the core roll.

Regarding the magnetic pole 23b of the developing unit, the magnetic pole is arranged at the center of the developing unit in the embodiment, but it may be displaced from the center, or the developing unit may be arranged between the magnetic poles.

To the toner, silica particles may be externally added to improve the fluidity, and abrasive particles or the like may be externally added for polishing the surface of the photosensitive drum 3, which is a latent image holding member in the transfer type image forming method. You may use what added a small amount of magnetic particles to the toner. That is, the magnetic toner is remarkably weaker than the magnetic particles, and a magnetic toner can be used as long as the toner can be tribocharged.

In order to prevent ghost image development, the developer layer remaining on the sleeve 22 that has not been used for development from the surface of the sleeve 22 that has returned to the inside of the container 21 and has been rotated is scraped off once by a scraper means (not shown). The scraped sleeve surface may be brought into contact with the magnetic particle layer to recoat the developer.

A mechanism may be provided for detecting the concentrations of the magnetic particles and the toner and automatically replenishing the toner according to the output.

The developing device of the present invention includes a container 21, a sleeve 22 and a blade.
Even as a used type developing device that integrates 24 etc.,
It can also be used as a normal developing device fixed to the image forming apparatus.

Further, by using the magnetic carrier of the present invention, it is possible to use a fine particle toner having a particle diameter of 10 μ or less.

Although the present invention has been described as a developing method by applying an alternating electric field, the magnetic particles can solve the problem of carrier adhesion when used with the two-component developing type magnetic particles in which only a DC component is added as a developing bias. , Should be certified as a new invention.

〔The invention's effect〕

According to the present invention, magnetic particles are not adhered on an image, white spots of solid black are prevented from occurring, and a good image can be obtained.

According to the present invention, the magnetic particles and the toner are agitated and mixed on a developer carrier such as a sleeve or a belt, and used simply.
It is possible to stably maintain the toner density of the component developing device. That is, since the specific developing conditions are not deteriorated, the action of the magnetic particles can be stabilized and a highly reliable developing device can be provided.

In addition, when the developing roller of the developing device having the above-mentioned configuration has a smaller diameter sleeve, the amount of magnetic particles on the sleeve may decrease.
The application of the present invention is effective because the toner is stably incorporated into the magnetic particle layer.

[Brief description of drawings]

FIG. 1 is a graph for explaining the resistance characteristics of magnetic carrier particles in the developing method, FIG. 2 is an explanatory view of a preferred developing constitution in which the present invention is carried out, and FIG. 3 is an explanatory view of developing in the developing section of FIG. 23a to 23d are magnetic poles, 31 is a magnetic member, and 27 is magnetic particles.

Front Page Continuation (72) Inventor Hoshika Reikyu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Taka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masahide Kinoshita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-58-184158 (JP, A) JP-A-59-121077 (JP, A) ) JP-A-60-123859 (JP, A)

Claims (3)

[Claims] 1. A toner comprising a magnetic particle and a toner particle, wherein the magnetic particles are brought into contact with the photoconductor while an alternating electric field is applied between the photoconductor and the developer carrier. In the developing method for forming an image, the photoreceptor is OPC, and the magnetic particles are 0.2 × 10 ³ V / cm.
Resistance value in the electric field of 10 ^{8 to} 10 ¹¹ Ωcm or less, or resistance value in the electric field of 2 × 10 ³ V / cm is 2 × 10 ^{7 to} 3 × 10
A developing method characterized by being ⁹ Ωcm or less. 2. The developing method according to claim 1, wherein the volume ratio of the magnetic particles in the developing portion is 1.5% or more and 30% or less. 3. The developing method according to claim 2, wherein the toner particles are non-magnetic toner particles and have a ratio of 4 to 40% by weight with respect to the magnetic particles in the developing section. .