JPH0279863A - Developing method - Google Patents

Abstract

PURPOSE:To obtain an image of high quality by using a developer obtained by mixing resin-coated magnetic particles and toner particles and forming an alternate electric field in a developing gap between a latent image carrier and a developer carrier. CONSTITUTION:Under the state that an alternate electric field is impressed between the latent image carrier 1 and the developer carrier 22, a toner image corresponding to an electrostatic latent image is formed by using the developer obtained by mixing magnetic particles 27 and toner particles 37. The electric resistance of the magnetic particles 27 is a field dependent high resistance compared with an impressed voltage, and when it is defined that the electric field to be applied to the magnetic particles 27 is E (V/cm) and the electric resistance of the magnetic particles 27 is R (OMEGAcm), development under the alternate electric field can be executed by using medium-resistance resin-coated carrier particles showing the resistance value of 3.1 X 10<9>OMEGAcm at E = 0.2 X10<3> e.g. and the resistance value of 4.0 X 10<8>OMEGAcm at E = 2 X 10<3>. Consequently, an image of high quality can be obtained without sticking carrier to an image part and generating developing defects such as white points in solid black of an image part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a two-component development method in which development is performed using magnetic carrier particles and toner particles in an alternating electric field.

The present invention is a developing method that can be applied to various types of display devices, printers, and facsimile electrophotographic devices for forming image records.

[Background technology]

Patent application No. 60-204605, No. 60-Z, 7556, No. 60-Z, 7559, No. 60-252317, No. 60-
252319, 60-252316, 60-252
No. 320, No. 61-207013 proposes a method that improves development efficiency and image quality. These inventions are
This invention relates to a developing method and apparatus using a thin two-component developer layer and an alternating electric field, and has advantages over the conventional two-component developing method using a developer layer of about 5 mm.

The invention can significantly improve the problem of unnecessary carrier adhesion remaining on the photoreceptor due to the action of alternating electric fields, and has the effect that the developed image is excellent in adapting to the potential of the latent image forming the image. be.

The carrier particles used in general two-component developing devices are conductive carriers and medium-resistance carriers made of ferrite.
Easily deteriorates due to adhesion of toner particles (problems include decreased durability and ability to impart charge to toner).

It has been known for quite some time that resin-coated carrier particles are used to improve durability and chargeability. Conventional resin-coated carrier particles exhibit considerable insulating properties, have increased charge-imparting ability, and have good surface properties, so they are practically preferable in terms of durability.

Since the two-component development method that applies an alternating electric field also requires durability, it is a natural design issue to use conventional high-resistance resin-coated carrier particles, but the inventors discovered that this would bring about a new problem. I found it. In addition to resin-coated carrier particles, these high-resistance carrier particles include magnetic microparticle resin-bonded carrier particles, which exhibit extremely high electrical resistance.

The higher the electrical resistance of carrier particles (the closer to insulating properties), the more electrical leakage can be prevented in the developing area, and the higher the latent image potential and alternating electric field can be set, and the better the developing characteristics due to alternating electric fields can be expected. Yes, but for example 1014Ωc
A carrier with an insulation resistance of m or more is charged to a fairly high potential with the opposite polarity to that of the toner, and carrier attraction tends to occur in non-image areas and solid white areas, and even though a carrier is used, there is a strong edge effect ( The present inventors have also discovered that this phenomenon is particularly noticeable when the charging characteristics of the toner or the characteristics of the carrier change significantly due to deterioration of the carrier particles or the environment. In any case, the loss of carrier particles is a major problem for cleaning and development of transfer ability.

[Purpose and outline of the invention]

The present invention focuses on the fact that sudden abnormal development, which has not been elucidated in the past, largely depends on the magnetic carrier particles themselves and/or the proportion of ears formed by the magnetic carrier particles.

An object of the present invention is to provide a developing method that can significantly prevent loss of high-resistance carrier particles in an apparatus that performs development while forming alternating electric fields.

The first representative example of the present invention was developed by focusing on the resistance value of resin-coated carrier particles and seeking characteristics different from those of conventional carrier particles. This is to maintain the electrode effect and obtain high quality images.

In other words, this representative example focuses on the electrical resistance of resin-coated carrier particles, and is based on the fact that electric field-dependent changes in the resistance value of carrier particles, which had not been recognized in the past, have a strong effect on reproduced image quality. It is based on

The present invention uses a developer having a mixture of magnetic particles and toner particles to form a toner image corresponding to an electrostatic latent image while an alternating electric field is applied between a latent image carrier and a developer carrier. The magnetic particles have a high electrical resistance that is dependent on the electric field with respect to the applied voltage, and the electric field applied to the magnetic particles is set to E (V/cm) and the electric field of the magnetic particles. The electrical resistance is R (Ωcm), the horizontal axis on the coordinate graph is the electric field E, the vertical axis is the electrical resistance R, and the four coordinate points A on the graph are (0, 2 × 103, 109)
, B (zXlo”, 3xlO’), C (0,2×10
3, 10').

Straight line AB determined by D (2×103, 2×107).

This developing method is characterized in that the area surrounded by BD, DC, and CA intersects the electrical characteristic curve of magnetic particles obtained by the measurement method described below.

According to the present invention, the present invention can be applied either when the developer is in contact with the photoreceptor without applying an alternating electric field in the development area, or when the developer is not in contact with the photoreceptor, and good images can be obtained.

The second representative example of the present invention is based on experimental facts (to be described later), and is centered on the number of ears that magnetic particles form in a magnetic field.This is also an invention that focuses on the number of ears that magnetic particles form in a magnetic field. This has the effect of preventing carrier loss due to

The present invention provides a developing device that develops a latent image using a developer having magnetic particles and toner particles in a developing section, and a developer container containing a developer having toner particles and magnetic particles; forming a developing section that faces the latent image carrier and supplies toner particles to the latent image carrier;
a developer carrier carrying and transporting developer from the container to the developing section; and a developer carrying member provided on the opposite side of the latent image carrier of the developer carrying member to the latent image carrier in the developing section. a developer application amount regulating member having a first magnetic field generating means brought into contact with the member, and a regulating portion distal end located upstream of the developing section with respect to the moving direction of the developer carrying member and spaced apart from the surface of the developer carrying member. a second magnetic field generating means provided on a side of the developer carrying member opposite to the regulating member and located upstream of the developer regulating member with respect to the moving direction of the developer carrier; and an alternating electric field forming means for forming in the developing section an alternating electric field that transfers the toner particles carried on the surface of the developer carrying member to the latent image carrier, where Z is the number of ears per 1 mi, and X is the height of the ears in the developing section, and Y is the closest distance between the latent image carrier and the developer carrier, and 2≦6.5. According to , the development characteristics have been improved, and even without using magnetic carrier particles with the above-mentioned resistance value, sufficient development efficiency can be achieved while preventing carrier loss, and the image quality can also be obtained as a high density within an appropriate range. It will be done.

〔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 an insulated drum for electrostatic recording or a-3e.
, CdS, ZnO2, OPC, A-3T, and the like. The latent image carrier l is moved by an arrow a by a drive device (not shown).
rotated in the direction A developing sleeve 22 is in close proximity to or in contact with the latent image carrier 1, and is made of a non-magnetic material such as aluminum or stainless steel (SUS) 316. The developing sleeve 22 has a right half circumferential surface extending into the container 36 through a horizontally elongated opening formed in the lower left wall of the developing container 36 in the longitudinal direction of the container, and a left substantially half circumferential surface exposed outside the container so as to be rotatably supported. It is installed horizontally and is driven to rotate in the direction of the arrow.

Reference numeral 23 designates a fixed permanent magnet (magnet) as a fixed magnetic field generating means that is inserted into the developing sleeve 22 and positioned and maintained at the position and orientation shown in the figure. It remains fixed in its position. This magnet 23 has magnetic poles 23a of N pole, S
The magnetic pole 23b of the pole, the magnetic pole 23c of the north pole, the magnetic pole 23 of the south pole
It has four magnetic poles of d. The magnet 23 may be an electromagnet instead of a permanent magnet.

Reference numeral 24 has a base fixed to the side wall of the container on the upper edge side of the opening of the developer supply device in which the developing sleeve 2 is disposed, and the tip side is made to protrude to the outside of the container 36 beyond the position of the upper edge of the opening, and extends along the longitudinal direction of the upper edge of the opening. The blade is a non-magnetic blade which serves as a developer regulating member and is made by bending, for example, 5uS316 into a cross-sectional shape.

Reference numeral 26 denotes 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 a developer guide surface 261.

27 is a magnetic particle with a particle size of 20 to 100 μm, preferably 30 to 80 μm, and an apparent density of 2.4 to 2.8 g/c.
C ferrite particles (maximum value 60 to 70 emu/g) coated with a resin may be used.

If it is smaller than 20 μm, there is a tendency that the spikes on the developing sleeve will be poor and the image will be uneven.

If it is larger than 100μ, the ability to impart triboelectricity to the toner is reduced and the photosensitive plate is likely to be damaged.

37 is a non-magnetic developer toner.

Reference numeral 31 denotes a developing sleeve 22 on the inner surface of the lower part of the developing container in order to prevent leakage of magnetic particles 27 or non-magnetic toner particles 37 from the lower part of the developing container 36 in which the developing sleeve 22 is disposed.
It is a magnetic material placed opposite to the magnetic material, for example, a plated iron plate. Magnetic body 31 and S polarity magnetic pole 23
A sealing effect that achieves collection of the magnetic particles 27 and prevention of leakage can be obtained by the magnetic field between the magnetic particles 27 and d.

Reference numeral 39 denotes a toner supplying member that supplies toner to a brush portion of magnetic particles formed by the fixed magnetic pole 23 in the developing sleeve 22. A rubber sheet is attached to a rotatably bearing plate, and the toner is swept over the lower surface of the developing container. transport. The toner supply member 39 is supplied with toner 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 sealing member for sealing the toner accumulated in the lower portion of the developer container 36, which is elastic and curved in the direction of rotation of the sleeve 22, and elastically presses the surface side of the sleeve 22. This sealing member 40 has an end on the downstream side in the rotational direction of the sleeve in a 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 that applies a voltage of the same polarity as the developer to cause the floating developer generated in the developing process to adhere to the photoreceptor side and prevent it from scattering.

Further, the S magnetic pole 23d is a magnetic field generating means for magnetic sealing to form a magnetic field from one side to the other between the S magnetic pole 23d and the magnetic member 31, and a portion thereof faces the magnetic member 31.

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

By arranging the magnetic pole 23d as described above, another favorable effect can be obtained in relation to the magnetic pole 23a.

That is, due to the above-mentioned relationship between the bottom of the storage part of the container Z and the magnetic pole 23d, the magnetic brush is not formed in a coarse state (compared to a state where it is simply stagnant) within the Z, so that the magnetic brush is not formed in the magnetic particles. The amount of toner particles taken in will not become excessive. Excessive uptake leads to insufficient charging of the toner and causes fogging.

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

The distance d2 between the end 241 of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 50 to 800 μm, preferably 15
It is 0 to 500 μm. If this distance is smaller than 50 μm, magnetic particles, which will be described later, will tend to clog between the gaps, causing unevenness in the developer layer, and it will not be possible to apply the developer necessary for good development, resulting in a developed image with a thin and uneven density. There are drawbacks that can only be obtained. If it is larger than 800 μm, the amount of developer applied onto the developing sleeve 22 increases, making it impossible to regulate the thickness of the developer to a predetermined value, increasing the amount of magnetic particles attached to the latent image carrier, and increasing the circulation of the developer as described below. This has the drawback that the development regulation by the developer limiting member 26 is weakened, resulting in a shortage of toner and tribo, resulting in easy fogging.

Even when the sleeve 22 is rotated in the direction indicated by the arrow, the movement of this magnetic particle layer slows down as it moves away from the sleeve surface due to the balance between the restraining force based on magnetic force and gravity and the conveying force in the moving direction of the sleeve 2. (The upper part of the magnetic particle layer forms a stationary layer that can move a little, but is mostly immobile.Of course, some particles fall due to the influence of gravity.

Therefore, the arrangement positions of the magnetic poles 23a and 23d and the magnetic particles 27
By appropriately selecting the fluidity and magnetic properties of the magnetic particle layer, the closer the magnetic particle layer is to the sleeve, the more it is transported toward the magnetic pole 23a, forming a moving layer. This movement of magnetic particles causes the magnetic particle layer (first
layer) takes in the toner from the toner layer (second layer), and the toner is triboelectrically charged by rubbing against the magnetic particles or the sleeve.The toner is transported to the development area as the sleeve 2 rotates and is subjected to development. .

The movement of the magnetic particle layer is determined by the fluidity and magnetic force of the developer. When the toner content in the magnetic particles is low, the stationary layer becomes smaller and most of the magnetic particle layer moves quickly, removing toner from the toner layer. take in. Also, when the toner content is high, the static layer becomes large and the moving layer of magnetic particles cannot contact the toner layer covered by the static layer and hardly takes up toner.

Therefore, some toner content is naturally maintained.

Next, the magnetic particle layer near the non-magnetic blade 24 and the limiting member 26, which are developer application amount regulating members, will be described. The limiting member not only mechanically prevents unnecessary entry of replenishment toner into the developer regulating section. As previously mentioned,
In the restriction area where the member 26 is surrounded by the sleeve, the magnetic particles transported by the magnetic N1 pole as the sleeve rotates are packed along the guide surface 261 of the restriction member 26 and become dense. In this region, the magnetic particles that are transported into the blade are dynamically replaced by the magnetic particles that flow out from the blade, causing the magnetic particles to collide with each other and create a hidden state. Therefore, triboelectricity is applied to the toner from the magnetic particles or the sleeve, and toner with small triboelectricity is attached to the magnetic particles or sleeve with a weak force and is transported. are separated from the magnetic particles or the sleeve. In other words, the toner is sorted and the charging is improved. Therefore, the toner with sufficient triboelectricity can be used for development. Also, the non-uniformity during conveyance of the magnetic particles The state is also equalized in the space,
Uniform and stable application of the magnetic particle layer is also achieved. Therefore, the guide surface 261 is essential for the limiting member 26, and the slope of the slope and the volume of the space have a great influence on the backing state of the magnetic particles in the space.

On the other hand, the magnetic pole 2 fixedly arranged with respect to this area
3a rearranges the magnetic particles in the backing state along the lines of magnetic force. The backing state in this space is unstable with respect to tribo-imposition, and a constant backing state is always required to stabilize it. This creates a magnetic brush by applying a force perpendicular to the direction of the magnetic particles conveyed on the sleeve in an almost tangential direction, which not only has a stirring effect on the magnetic particles but also has a stripping effect, and the toner particles are The uniformity and stabilization of the application of triboelectric particles and the application of the magnetic particle layer are further promoted. At this time, if the developer concentrated by the surrounding structure remains under great pressure, there is a problem that the developer will become clogged.
It is believed that by having the portion that generates the maximum magnetic force of a facing the guide surface 261, excessive pressure concentration in the regulated area can be prevented, and developer concentration and stable high-density magnetic particle existence ratio can be maintained. It will be done.

Due to the above-mentioned regulation area, a stable amount of magnetic particles and sufficiently charged toner particles can be formed as a thin layer of developer on the surface of the developing sleeve. Therefore, the development effect in the development area 102 becomes stable. And an alternating electric field forming means for forming an alternating electric field in the developing section that causes at least the toner particles carried on the surface of the developer carrying member to be transferred to the electrostatic latent image carrying member. in the developing section, the volume occupied by the magnetic particles of the developer conveyed to the developing section with respect to the volume of the space defined by the electrostatic latent image carrier and the developer carrying member; It was confirmed that the developing method and apparatus having a ratio of 1.5% to 30% have a great effect.

FIG. 2 shows a case where a magnetic body 50 is installed on the non-magnetic blade side of the developer limiting member 26. In this case, magnetic material 5
0 is not preferably provided at a position facing the magnetic pole 23a. This is because if they face each other, a strong concentrated magnetic field will be generated between them and the magnetic pole 23a, reducing the effect of stirring and loosening the magnetic particles by the magnetic pole 23a. However, it is effective to provide a magnetic material in the regulating portion and to magnetically regulate the magnetic particles between the regulating member and the sleeve internal magnet 23, since this increases the gap tolerance between the regulating member and the sleeve. Also, when comparing the toner attached to the magnetic particles or sleeve,
The amount of charge on the toner attached to the sleeve is smaller than that attached to the magnetic particles.The reason for this is that as the sleeve moves, the magnetic particles are also transported, so the toner on the sleeve is rubbed by the magnetic particles. This is because there are fewer opportunities to do so. In order to lift the toner on the sleeve to a predetermined value, it is necessary to actively rub the toner on the sleeve. That is, it is necessary to have magnetic particles near the sleeve surface that cause a shift in relative velocity against the movement of the sleeve.

However, it is impossible to simply reduce the transportability of magnetic particles, considering the above-mentioned toner uptake effect. Furthermore, as described above, a magnetic material may be disposed in the regulating portion facing the magnetic pole 23a in the sleeve to generate a concentrated magnetic field and improve the sliding force of the magnetic field particles on the sleeve. The effect of arranging the maximum magnetic force generating portion of the magnetic pole in the space created by the regulating member 26 is reduced.

Therefore, in this embodiment, the magnetic body 50 is provided downstream of the magnetic pole 23a in the sleeve rotation direction, and
The lines of magnetic force on the blade side of a are concentrated in the tangential direction of the sleeve surface.As a result, the magnetic particles only near the sleeve surface form a magnetic brush along the sleeve surface, and the toner on the sleeve is rubbed. However, it was possible to increase the triboelectricity of the toner on the sleeve.

In the above device configuration, the magnetic particles 27 are measured using a sandwich type cell with a measurement electrode area of 4 c rrr s and an inter-electrode gap of 0.4 cm, and 1 kg of magnetic particles 27 are placed on one electrode.
Under weight pressure, an applied voltage E (V/cm) is applied between both electrodes and the resistance value of the magnetic particles is obtained from the current flowing through the circuit (the resistance of the magnetic particles 27 below is measured under this measurement condition). ), E=0.2xlo3 and 3.1x10
Resistance value of 7Ωcm, E = 2 × 10” and 4.0×
When development was performed under an alternating electric field using medium-resistance resin-coated carrier particles exhibiting a resistance value of 107 Ωcm, there was no carrier adhesion in the image area, and there was no development defect such as white spots in the solid black and white of the image area. Good quality images were obtained.

The resistance value conditions of this magnetic particle are the above E=0, 108),
D (2 x 103, 2 x 107, E = 2 x 10'
The reason why the resistance within this range is specified is that the electric field-dependent change in electrical resistance changes greatly within this range, and there is a gradual decrease in resistance in larger electric fields. This is because the change can be recognized as corresponding to the electric field change in the alternating electric field.

The inventor of the present invention has found through numerous experiments that a change in resistance within this range greatly affects developability, and has arrived at the following conditions by making numerous improvements to commercially available insulating carriers.

That is, if the resistance of the magnetic carrier particles is R (Ωcm), the measurement voltage E (V/cm) is 0.2×103 (V/cm).
cm) or more and 2×103 (V/cm) or less,
Resin-coated magnetic carrier particles that exhibit resistance characteristics such as passing through at least one point within the area defined by Achieve an image.Because it is coated with resin, its properties do not change due to changes in humidity, and it has high fluidity, which has practical advantages.

The magnetic particles used in this example are known sintered ferrite, and include Zn, Fe, Cd, Cu, Pb, N
i, Mg.

Sintered material with one or more compositions such as Mn (
It will be done. Particularly suitable compositions for the present invention are Cub and ZnO.

It is a metal oxide whose main component is Fe203.

How effective the above conditions are is shown in the area of Figure 1 (ABC
D) will be explained using data.

In Figure 1, 1. m, n, o, p, g,
Magnetic particles denoted by symbols r, s, and t are measured using electric field E on the horizontal axis when the copper oxide and zinc are used to change the sintering conditions and/or the resin coating conditions on the sintered ferrite particles. It is an electrical resistance characteristic curve of magnetic particles in a graph showing the resistance value R of the magnetic particles on the vertical axis. For example, the amount of coating resin for n-magnetic particles is twice that of p-magnetic particles.

Measurements were carried out at room temperature and humidity. Note that resin coating materials have been used conventionally. The Jahlia coating material for the two-component developer may be, for example, an acrylic fluororesin or a silicone resin, but in the example shown in FIG. 1, a silicone resin is used.

Maximum magnetism 64emu/g, viscosity distribution 70-50μ (2
50/350 mesh) ferrite was used.

The table below shows image evaluation of magnetic particles with characteristics up to -t. The amount of resin coating decreases from particle k to particle t (particles 0 and p are obtained by changing the sintering conditions.

×: Image area Δ: Good image O: Image area ◎ Best of 2 images Furthermore, commercially available insulating carrier particles exhibit a considerably high resistance and cannot be described in the graph of Figure 3 (this is The image used was unsatisfactory, with white spots and adhesion of carrier particles observed.

Magnetic particles t having an electrical resistance lower than the line CD in FIG. 1 are likely to cause developer brush marks on the image, and white spots where the image is missing are likely to occur in the solid image area.

These are caused by leakage of latent image charges generated through the magnetic particles. Also, magnetic particles tend to adhere to solid black image areas. According to the present invention, these occurrences can be effectively prevented by making the resistance of the magnetic particles exceed the line segment AB.

Magnetic particles that exhibit a higher electrical resistance than the line AB in FIG. 1 have a strong chargeability (and are firmly attached to toner particles), making it difficult for them to fly to the latent image charge in the development area. The density decreases. Also, the effect of the magnetic particles acting as a developing electrode decreases, causing a decrease in density.Also, since the magnetic particles tend to be charged with the opposite polarity to the charge polarity of the toner, carriers may be deposited in solid white areas of non-image areas. In particular, in the developing device of the embodiment to which the present invention is applied, the necessary replenishment toner is taken into the magnetic particle layer by the circulating action of the magnetic particle layer in the container, so the charging property of the magnetic particles is reduced. If it is too strong, it causes instability in toner uptake into the magnetic particle layer, which tends to cause streaks and unevenness on the image (However, by applying the present invention, this disadvantage can also be solved. This is an important technology because it solves the problem of

Similar results were obtained when an experiment was conducted by changing the resin in the above experimental example to an acrylic fluorine resin.

Further, when the diameter of the magnetic particles was changed, no change in the image was observed, and it was confirmed that the above-mentioned resistance characteristics were extremely effective in the developing method of applying an alternating electric field.

As can be understood from the above experimental example, the measurement electric field is 0.2×1
03 to 2×10 3 (V/cm), and if the resistance value exhibited by the magnetic particles is all within the above range, a more preferable image can be formed. This is considered to be because since the alternating electric field changes in intensity, it always exhibits stable behavior by only showing resistance changes within this region. What is particularly noteworthy is that the magnetic particles have an electric field of 108 Ωcm or more and 10 Ωcm or less in an electric field of 0.2 × 103 (V/cm), 2
), the above behavior can be obtained by exhibiting a resistance value of 10'Ωcm or more and 10'Ωcm or less.

More importantly, E (0,2×103, 2X1
010).

F (2 x 103, 10'), H (2 x 103, 5 x 1
07), G(0,2×103.

Extremely favorable results were obtained in the case where all the resistance changes of the magnetic particles were within region 2 (shaded area) connecting four points of 2×10 3 ). This is the top.

This shows the middle area of the recording area.

This can be seen by extending the curve in the figure and changing the applied voltage under the maximum intensity of the actual alternating electric field to the measured value. (at least 2 x 10'Ωcm or more) 10'Ωc
It is thought that this is because it shows a high resistance of m or less within a stable range, and also shows a high resistance in the stable region Z, which is stable even under a low electric field.

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

As mentioned above, the area surrounded by the four line segments in Figure 1 is extremely critical in terms of the quality of the developed image. This is considered to be obvious from the experimental fact that .

The magnetic flux density of the magnetic pole 23a is preferably 600G or more, preferably 700G or more. This is because the state of application of the developer tends to be more stable with respect to changes in the toner content of the magnetic particle layer as the magnetic flux density of the cut magnetic pole is higher. In particular, in the developing device of the present invention that does not have an automatic toner replenishment device to maintain toner content,
Preferably, the magnetic flux density is 800G or more.

In FIG. 2, the magnetic pole 23c is a developing magnetic pole, and this developing magnetic pole is located in the developing area, 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-mentioned configurations.

In any case, the present invention can provide high image quality that could not be obtained with conventional developing methods and devices, and has the excellent effect of making the developing device small and disposable.

The toner supply member is located in the developer container 36 and rotates in the direction of arrow d while being close to or in contact with the magnetic particle layer to supply the toner 3.
7 is supplied to the magnetic particle layer.

Toner is stored approximately horizontally adjacent to the developer container 36 (a toner storage container 38 is disposed, and a toner transport member (a toner transport member) for transporting the toner into the developer container 36 is disposed in the toner storage container 38 .
(not shown) is provided.

The S magnetic pole 23b is a transport magnetic pole provided to prevent the developer layer uniformly applied by the non-magnetic blade 24 from being disturbed due to the large distance between the cut magnetic pole 23a and the developing magnetic pole 23c. The strength of the S magnetic pole 23b is preferably approximately equal to or slightly lower than that of the developing magnetic pole 23c so as not to disturb the developer layer. When using a 20φ developing sleeve, if the distance between the cut magnetic pole and the developing magnetic pole is within 1.00° at the center angle of the sleeve, the developer layer on the sleeve will not be disturbed, but if it exceeds 100°, the developing Since the agent layer is largely disturbed, it is preferable to provide a transport electrode in the middle.

The S magnetic pole 23d is a collection magnetic pole that collects the developer after development, and is arranged upstream of the magnetic seal tip in the direction of movement of the developing sleeve. When the magnetic pole 23d is placed downstream from the tip of the magnetic seal, a spike of magnetic particles is generated by the magnetic pole 23d near the toner intake port at the bottom of the developer container, making it extremely easy to take in toner (and toner charging is not sufficiently performed). This can easily cause fogging, etc.

Here, the volume ratio of magnetic particles in the developing section will be explained. The "developing section" refers to the area from the sleeve 22 to the photosensitive drum 1.
This is the part to which toner is transferred or supplied. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present in the developing area relative to the volume of the developing area. In the above-mentioned developing device, this volume ratio has an important influence, and it is highly preferred that it be between 1.5 and 30%, particularly between 2.6 and 26%.

If it is less than 1.5%, a decrease in the density of the developed image will be observed, a sleeve ghost will occur, a noticeable difference in density will occur between the area where the ears 51 are present and the area where the ears 51 are not present, and the concentration on the surface of the sleeve 22 will be reduced. This is undesirable in that the thickness of the developer image formed is non-uniform throughout.

If it exceeds 30%, the degree of closure of the sleeve surface increases, which is undesirable because fogging may occur.

In particular, for the present invention, the conditions listed above as a preferable developing method are such that the image quality does not monotonically deteriorate or increase as the volume ratio increases or decreases;
Sufficient image density can be obtained in the range of 0%, image quality will deteriorate if it is less than 1.5% or exceeds 30%, and neither sleeve ghost nor fogging will occur in the range of the above values where image quality is sufficient. This is based on the fact that The former image quality deterioration is thought to be due to negative characteristics, while the latter is caused by the presence of large magnetic particles (as a result, the surface of the sleeve 22 cannot be opened, and the amount of toner supplied from the surface of the sleeve 22 is significantly reduced). it is conceivable that.

On the other hand, if it is less than 1.5%, the reproducibility of line images is poor and the image quality and density are significantly lowered. On the other hand, if it exceeds 30%, there will be problems with the magnetic particles damaging the photosensitive drum surface and problems with transfer and fixing caused by the magnetic particles adhering as part of the image.

When the presence of magnetic particles is close to 1.5%, when reproducing a large-area uniform high-density image (solid ring),
In some cases (such as under special environments), partial development unevenness called ``developing unevenness'' may occur (under special environments, etc.), so it is preferable to set the volume ratio to prevent these from occurring.This value is based on the volume ratio of magnetic particles to the developing area If the amount is 2.6% or more, this range becomes a more preferable range. Also, if the presence of magnetic particles is close to 30%, toner replenishment from the sleeve surface will occur around the area where the ears of magnetic particles come into contact. There are cases where there is a delay (such as when the development speed is high), and scale-like density unevenness may occur when solid black is reproduced.As a reliable range to prevent this, the above volume ratio of magnetic particles is 26% or less. It becomes more preferable.

If the volume ratio is in the range of 1.5% to 30% (set to 4% in the practical example), the sleeve 22 as shown in FIG.
The spikes 51 are formed on the surface in a sparse manner to a preferable degree, and both the sleeve 22 and the toner on the spikes are sufficiently exposed to the photosensitive drum l, and the toner 100 on the sleeve is
Since the toner is also transferred flying by alternating electric fields, almost all of the toner is in a state that can be consumed for development, resulting in high development efficiency (ratio of toner that can be consumed for development out of the toner present in the development area) and high Image density can be obtained. Preferably, a minute but strong vibration of the spike is generated, thereby removing the magnetic particles and the toner 1 attached to the sleeve 22.
00 is loosened. In any case, it is possible to prevent uneven sweeping and ghost images that occur in the case of magnetic brushes. Furthermore, the vibration of the ears activates the frictional contact between the magnetic particles 27 and the toner 28, thereby improving the frictional charging of the toner 28 and preventing the occurrence of fogging. Note that high developing efficiency is suitable for downsizing of the developing device. The developing magnetic pole in FIG. 3 is an 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/
It can be determined by h) crt
r), h is the height of the developing section space (cm), and ρ is the true density of magnetic particles g/cn? , C/ (T+C) is the weight percentage of magnetic particles in the developer on the sleeve.

Note that in the developing section defined above, the ratio of toner to magnetic particles is preferably 4 to 40% by weight. As in the above embodiment, the alternating electric field is strong (the rate of change is large or Vl).
) is large), the ear detaches from the sleeve 22 or from its base, and the detached magnetic particles 27 are removed from the sleeve 22.
and the photosensitive drum 1. Since the energy of this reciprocating motion is large, the effect of the vibration described above is further promoted.

The above behavior was measured using a high-speed camera (manufactured by Hitachi) at 8.00.
This was confirmed by shooting at 0 frames per second. Even if the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is reduced (to increase the contact pressure between the photosensitive drum 1 and the ear) and the vibration is reduced (the gap is large at the entrance and exit sides of the developing section, , sufficient vibration occurs and the above-mentioned effects are produced.

Conversely, it is preferable to increase the gap between the photosensitive drum 1 and the sleeve 22 so that the ears do not come into contact with the photosensitive drum 1 when no magnetic field is applied, but do come into contact when a magnetic field is applied.

In Fig. 2, the sleeve 22 is an aluminum sleeve with a diameter of 20 mm whose surface has been subjected to irregular sandblasting with Alundum abrasive grains, and the magnet 23 is 4-pole magnetized so that the N and S poles alternate as shown in Fig. 2. I used something like the one shown in . The maximum value of the surface magnetic flux density due to the magnet 23 is approximately 9
00 Gauss.

The blade 24 was made of nonmagnetic stainless steel with a thickness of 1.2 mm, and the angle θ was set to 15°. The magnetic particles are particles 0 exhibiting resistance characteristics within the above range and have a particle size of 70 to 50μ (250/
ferrite (maximum magnetization 64emu/
g) was used. Electrical resistance is n + o * in Figure 1
Good results were obtained using the p*9 curve.

In a system in which toner uptake is controlled by circulating the magnetic particle layer on the sleeve, as in the embodiment shown in FIG. 1, it is preferable that the resistance of the magnetic particles is not high. This is because toner uptake becomes more stable when the magnetic particles themselves are less charged. If the magnetic particles are highly charged, the toner is firmly attached to the magnetic particles, so when new toner is introduced into the magnetic particle layer, the previously attached toner and the newly introduced toner may be replaced. Hard to occur.

Therefore, the previously attached toner remains on the sleeve for a long time, and this toner itself becomes overcharged.

Preferably, it is necessary that the electrical resistance characteristic curve intersects the region surrounded by line segments connecting each of the four points E, F, G, and H in FIG. More preferably EG.

It is necessary for FH to intersect with the line segment.

The non-magnetic toner is a toner powder with an average particle size of 10 μ which is composed of 100 parts of a styrene/butadiene copolymer resin and 5 parts of a copper phthalocyanine pigment, and 0.6 parts of colloidal silica.
When using blue toner with external addition of %, sleeve 2
A toner coating layer with a thickness of 10 to 30 .mu.m was obtained on the 2 surface, and a magnetic particle layer of 200 to 300 .mu.m was further formed as an upper layer thereon. The toner is attached to the surface of each magnetic particle.

At this time, the total weight of the magnetic particles and all the toner on the sleeve 22 was about 2.43 x 10-''g/crr?.

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 raised into spikes by the magnetic field generated by the magnetic pole 23b in the sleeve 22 in the developing area and its vicinity, and have a maximum length of approximately 1.5 mm.
It formed a standing brush about 2 mm in diameter.

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

This developing device is installed in a PC-10 copying machine manufactured by Canon Inc., and the volume ratio is determined under the conditions that the distance between the photosensitive drum 3 (made of organic photosensitive material) and the surface of the sleeve 22 is 350 μm. %Met.

(h=350μm, M=2.43X10-”g/crr
r, ρ=5.5g/crtr, T/ (T+C) =
20.4%). Frequency 1600H as bias power supply 4
z, -30 to an AC voltage of 1,300 V peak-to-peak.
When development was performed using a superimposed DC voltage of 0 V, a good blue image was obtained.

Further, when a solid black image was developed and the sleeve surface after development was observed, it was found that most of the toner attached to the magnetic particles and the toner on the sleeve were consumed, and development was performed with nearly 100% development efficiency.

As for the development characteristics, there was no fog and there was no carrier adhesion, and good development characteristics could be obtained.

Furthermore, regarding the effects of the magnetic member 31, it was confirmed that good penetration of magnetic particles, prevention of leakage, and good circulation were achieved.

As described above (according to this embodiment, high image density,
It is possible to perform development with high development efficiency without fogging, ghost images, uneven sweeping, or negative characteristics.

As the material of the sleeve 22, in addition to aluminum, conductive materials such as brass and stainless steel, paper tubes, and synthetic resin cylinders can be used. Furthermore, if the surfaces of these cylinders are subjected to conductive treatment or made of a conductive material, they can function as developing electrodes. Furthermore, a core roll may be used and a conductive elastic body, for example, a conductive sponge, may be wound around the circumferential surface of the core roll.

Regarding the magnetic pole 23b of the developing section, although the magnetic pole is arranged at the center of the developing section in the embodiment, it may be placed at a position shifted from the center, or the developing section may be arranged between the magnetic poles.

The toner may be externally supplemented with silica particles to improve its fluidity, or abrasive particles to polish the surface of the photosensitive drum 3, which is a latent image holding member in a transfer image forming method, for example. A toner containing a small amount of magnetic particles may also be used. That is, magnetic toner can also be used as long as it has significantly weaker magnetism than magnetic particles and can be tribocharged.

In order to prevent the ghost image phenomenon, the sleeve 2 is removed from the surface of the sleeve 22 which has returned inside the container Z and has been rotated, without being subjected to development.
The developer layer remaining on the sleeve may be first scraped off by a scraper means (not shown), and the scraped sleeve surface may be brought into contact with the magnetic particle layer to recoat the developer. .

A mechanism may be provided that detects the concentration of magnetic particles and toner and automatically replenishes toner according to this output.

The developing device of the present invention can be used either as a disposable type developing device in which the container Z, sleeve 22, blade 24, etc. are integrated, or as a normal developing device fixed to an image forming apparatus.

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

Although the present invention has been described as a developing method of applying an alternating electric field, the above magnetic particles can solve the problem of carrier adhesion when used with magnetic particles of a two-component developing method that applies only a DC component as a developing bias. , should be recognized as a new invention.

According to the present invention, there is no adhesion of magnetic particles on the image, the generation of solid black white spots can be prevented, and a good image can be obtained.

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

Also, when the developing roller of the developing device with the above configuration is made into a small diameter sleeve, the amount of magnetic particles on the sleeve decreases.
Application of the present invention is effective because it stabilizes the incorporation of toner into the magnetic particle layer.

Next, another embodiment of the present invention will be described using FIGS. 4 to 6.

The developing device shown in FIG. 5 is the same as that shown in FIG. 2 except that the magnetic blade 50 of the device shown in FIG. 2 is removed. Therefore, in this example,
The regulation area includes the non-magnetic blade 24 and the developer limiting member 26.
(guiding surface 261), and as described above, it is possible to supply a stable amount of magnetic particles into the developer layer containing the sufficiently charged toner, and it is possible to stably form a thin developer layer. do.

Conversely, FIG. 6 shows the structure of the device shown in FIG.
1 is brought into contact with the surface of the regulated developer in front of the regulated area.

When using a developing sleeve with a diameter of 10 to 30 mm,
The distance between the cut magnetic pole and the developing magnetic pole is 120 mm at the center angle of the sleeve.
° More preferably, if it is within 1oo0, there will be less disturbance of the developer layer on the sleeve, but if it exceeds 120°,
Since the developer layer is greatly disturbed, it is preferable to provide a transport pole in the middle.

Here, we will discuss the effects on images of factors such as the state of spikes in the developing section and the closest distance between the developing sleeve 22 and the latent image carrier l in the developing section (hereinafter abbreviated as SD gap). Table 1 above shows the basic configuration of the developing device as shown in FIG. Strength of pole 23c, cut pole 2t3
The height of the spikes in the developing section and the density of the spikes in the developing section were determined by changing the conditions for five components, including the strength of a and the presence or absence of a leveling member for leveling the developer applied on the surface of the developing sleeve. This is the result of the change. By changing the above five components for developing units No. and A to F, the height of the spikes and the density of the spikes in the developing section were obtained as shown on the right side of Table 1. The magnetic particles used at this time were ferrite particles with an average particle diameter of 52 μm (maximum magnetization 600 μm) coated with silicone resin on the surface.
/g). Now, regarding the relationship between the state of the spike applied to the developing area and the S-D gap, if the amount of magnetic particles in the developing area exceeds a certain value, the developer will accumulate between S-D and fog will occur. On the other hand, if the amount of magnetic particles is less than a certain value, there is a risk that problems such as low concentration may occur.

Therefore, using each of the developing devices A to F shown in Table 1,
By changing the distance between D to 0.15-0.80mm, carrier retention between S and D, Vo (solid black) and vL part (solid white)
Image printing was performed for five items: carrier adhesion fog, Dmax, and solid black roughness. In this case, V D=
An alternating electric field was applied between the photosensitive drum 1 and the developing sleeve 22 to form an image under latent image conditions of -600V and VL=-150V (solid white). The bias condition at this time is AC
The peak-to-peak is 1. The voltage was appropriately selected between OkV and 2.5 KV, and the frequency was approximately between I KHz and 3 KHz. The results are shown in Table 2. In Table 2, O marks indicate good results with no problems. A Δ mark indicates that there is a slight problem, and a Δ mark indicates that there is a problem and is not at a practical level.

In addition, since the height of the spikes in developing units A to F is different, in order to make the height of the spikes occupying the space of the developing section a constant scale, the height of the spikes in the developing section (X) is Between S-0 (
Y) was calculated by dividing X/Y, so that the same comparison could be made for each of the developing devices A to F. Next, based on Table 2, the horizontal axis is (X/Y) and the vertical axis is the density of spikes in the developing area on the sleeve surface (2), and five items such as carrier retention between S and D are taken. ○ if all of the items are O, Δ if there is a Δ at any time among the 5 items, × if there is an × in at least one of the 5 items.
, which is shown in the graph as , is shown in FIG.

From FIG. 4, the area in which there are no problems with the above five items is limited to the diagonally shaded area surrounded by the four curved lines in the figure. Anything outside this shaded area may cause carrier retention or a low concentration, for example.

Next, we will discuss the meaning of this area in more detail.

Z=18.3 (X/Y)-” line, but Z
> 18.3 (X/Y)-0j, the amount of carrier adhesion increases and fogging also worsens. This is because the amount of developer present in the developing area is large (the magnetic field is weakened in the actual development area, especially near the surface of the image carrier, making it easier for carrier adhesion to occur), and the amount of developer is large. It is thought that the regulation in the regulation part near the non-magnetic blade is weak (easily fogged).Therefore, 2≦18.3 (x/y)-0j is desirable.Next j: Z=4.9 (X/Y)""'
I will tell you about the 5th innite. Z<4.9 (X/Y)-”
In this case, a sufficient Dmax may not be obtained, or irregularities may occur in solid black. This solid black “Rabbi” is
This is a phenomenon in which differences in shading occur locally when reproducing solid black over a large area, and is particularly likely to occur in special environments. this is,
This occurs because there are very few magnetic particles or spikes in the development area. Not enough toner particles are supplied to the development area, resulting in a low density, and the development density is higher in the spikes than in areas without spikes. It is thought that this could lead to "mistakes". Therefore, 2≧4.9 (X/y)−”
is desirable. Also, regarding (X/Y), (X/Y)
>7, stagnation occurs between S and 0, making it impossible to produce an image. Further, when (X/Y)<1.7, density distortion occurs. This is considered to be because the gap between the developing sleeve 22 and the image carrier is wide and the toner particles coated on the developing sleeve 22 are not sufficiently contributed to the development, resulting in a low density.

Therefore, it is desirable that 1.7≦(X/Y)≦7.0. Finally, when Z > 6.5, most of the area on the developing sleeve is covered with spikes, making it impossible to supply toner from the sleeve surface. Then, carrier adhesion increases, and if an attempt is made to prevent carrier adhesion, the concentration becomes insufficient.Therefore, 2≦6.5 is desirable.

As explained above, within the shaded area in FIG. 4, the ears 51 are formed sparsely on the surface of the sleeve 22 as shown in FIG. Both of the toners on the sleeve are sufficiently exposed to the photosensitive drum 1, and the toner 100 on the sleeve is also transferred by flight due to the alternating electric field, so almost all of the toner is in a state where it can be consumed for development. Development efficiency (ratio of toner present in the development section that can be consumed for development) and high image density are obtained. Preferably, a minute but strong vibration of the spike is generated, thereby loosening the magnetic particles and the toner 100 adhering to the sleeve 22. In any case, it is possible to prevent uneven sweeping and ghost images that occur in the case of magnetic brushes. Furthermore, the vibration of the ears activates the frictional contact between the magnetic particles 27 and the toner 28, which improves the frictional electrification of the toner 28.
Fogging can be prevented. Note that a high developing efficiency is suitable for downsizing the developing device. The magnetic pole S pole 23b in FIG. 2 may be changed to the developing pole 23c, and either one may be used in this example.

The ratio of toner to magnetic particles in the developing section is preferably 4 to 40% by weight. When the alternating electric field is strong (the rate of change is large or the VpI is large) as in the above embodiment, the ears separate from the sleeve 22 or from its base, and the separated magnetic particles 27 are disposed between the sleeve 22 and the photosensitive drum l. It moves back and forth in the space between. Since the energy of this reciprocating motion is large, the effect of the vibration described above is further promoted.

The above behavior was observed using a high-speed camera (newly manufactured by Hitachi).
This was confirmed by taking pictures at o frames/second. Even if the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is reduced to increase the contact pressure between the photosensitive drum 1 and the ears and to reduce vibration, the gaps are large at the entrance and exit sides of the developing section, so vibration occurs, and the above-mentioned effects are produced.

In Figures 5 and 6, the sleeve 22 has a diameter of 20 m.
The surfaces of aluminum sleeves of 16 mm and 16 mm were subjected to amorphous sandblasting using alundum abrasive grains, and the magnets 23 were 4-pole magnetized with alternating north and south poles.

As the blade 24, non-magnetic stainless steel with a thickness of 1.2 mm was used.

The non-magnetic toner is a toner powder with an average particle size of 10μ, consisting of 100 parts of a styrene/butadiene copolymer resin and 5 parts of a copper phthalocyanine pigment, and 0.6 parts of colloidal silica.
When using blue toner with external addition of %, sleeve 2
A toner coating layer of coating summary 10-30 μm was obtained on 2 surfaces.

When the amount of charge was measured by the blow-off method, the amount of triboelectric charge of the toner on the sleeve and on the magnetic particles was +6 to 18 μC/
It was g.

Further, when a solid black image was developed and the sleeve surface after development was observed, it was found that most of the toner attached to the magnetic particles and the toner on the sleeve were consumed, and development was performed with nearly 100% development efficiency. Good development characteristics could be obtained.

As described above (according to this embodiment, high image density,
It is possible to perform development with high development efficiency without fogging, ghost images, uneven sweeping, or negative characteristics.

As the material of the sleeve 22, in addition to aluminum, conductive materials such as brass and stainless copper, paper tubes, and synthetic resin cylinders can be used. Furthermore, if the surfaces of these cylinders are subjected to conductive treatment or made of a conductive material, they can function as developing electrodes. Furthermore, a core roll may be used and a conductive elastic body, for example, a conductive sponge, may be wound around the core roll.

Regarding the magnetic pole 23c of the developing section, although the magnetic pole is arranged at the center of the developing section in the embodiment, it may be placed at a position shifted from the center.

Silica particles may be externally added to the toner to improve fluidity, and abrasive particles may be added to the toner to polish the surface of the photosensitive drum 1, which is a latent image holding member in a transfer image forming method. A toner containing a small amount of magnetic particles may also be used. That is, magnetic toner can also be used as long as it has significantly weaker magnetism than magnetic particles and can be tribocharged.

In order to prevent the ghost image phenomenon, the sleeve 2 is removed from the surface of the sleeve 22 which has returned inside the container Z and has been rotated, without being subjected to development.
The developer layer remaining on the sleeve may be first scraped off by a scraper means (not shown), and the scraped sleeve surface may be brought into contact with the magnetic particle layer to recoat the developer. .

A mechanism may be provided that detects the concentration of magnetic particles and toner and automatically replenishes toner according to this output.

The developing device of the present invention can be used either as a disposable type developing device in which the container 36, sleeve 22, blade 24, etc. are integrated, or as a normal developing device fixed to an image forming apparatus.

As explained above, 1 mrr in the developing section? When the number of ears per hit is Z, the height of the ears at the developing area is X, and the SD gap is Y, 1.7≦(X/Y)≦7.0゜4
．． 9 (X/Y)-”≦Z≦18.3 (X/Y)-”
By satisfying the condition of Z≦6.5, it is possible to perform development with high image density, high development efficiency, and no fogging, ghost images, uneven sweeping, or negative characteristics.

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

In particular, the electrical resistance of the magnetic particles is electric field dependent at room temperature and humidity, and the electric field applied to the magnetic particles is E(
V/am) and the electrical resistance of the magnetic particles are R (9 cm), the horizontal axis on the coordinate graph is the electric field E, the vertical axis is the electrical resistance R, and the four coordinate points A (0,2 x 103
, 10”), B (2×103.

3×109), C(o, 2×103, 10'),
D (2xlo”.

2 x 10') and straight line AB and straight line BD determined by
, straight line DC, and straight line CA intersect with the electrical characteristic curve of the magnetic particle obtained by the measurement method described below. When the number of ears per hit is Z, the height of the ears in the developing section is X (mm), and the closest distance between the latent image carrier and the developer carrier is Y (mm), and 2≦ Alternating electric field forming means that satisfies the conditions of 6.5 and forms an alternating electric field in the developing section that transfers toner particles carried to the developing section and carried on the surface of the developer carrying member to the latent image carrier. A developing device having the following is ideal for the present invention. This device is a unique case in which the number of ears formed by magnetic particles temporarily deviates from the shaded area above even if it becomes unstable due to changes in the T/C ratio or variations in the development scanning configuration. Since it also satisfies the above-mentioned resistance value change characteristics, carrier loss can be prevented even with mechanical fluctuations, and there is no additional practical disadvantage to image quality.On the contrary, the resistance value In special cases where the carrier temporarily deviates from the above range due to its own deterioration or unique environment, the effect of the ears can prevent carrier loss and stabilize the image quality.The alternating electric field action If one of the above conditions is satisfied, it is possible to form an excellent image even under some adverse conditions.
It will be clear from the above description that the layer has elements to overcome all problems. According to these, high-speed development can also be sufficiently achieved.

〔effect〕

According to the present invention, a developed image of good quality can be obtained while preventing carrier loss.

[Brief explanation of the drawing]

FIG. 1 is a graph illustrating the resistance characteristics of magnetic carrier particles in the developing method of the present invention, FIG. 2 is an explanatory diagram of a preferred development configuration implementing the present invention, and FIG. 3 is an explanatory diagram of the phenomenon in the developing section of FIG. 2. , FIG. 4 is a graph showing the relationship between the density of spikes in the developing section and (height of spikes/between S-D) and image quality, showing examples and reference examples in which the present invention was carried out, and FIG. 5 is a graph showing the image quality. FIG. 6 is a schematic cross-sectional view of a developing device showing one embodiment of the present invention, and FIG. 6 is a schematic cross-sectional view of a developing device showing another embodiment of the present invention. 1 is an electrophotographic photoreceptor, 22 is a nonmagnetic sleeve, 23 is a fixed magnet, 27 is a magnetic carrier, and 37 is a toner.

Claims (1)

[Scope of Claims] (1) A container containing a developer having a mixture of resin-coated magnetic particles and toner particles, a developer carrier provided opposite to the latent image carrier, and the developer carrier. means for forming a layer of the developer on the surface of the body; means for forming a magnetic field in the development gap for conveying the magnetic particles to the development gap where the latent image carrier and the developer carrier face each other; This is a method of developing with an apparatus equipped with means for forming an alternating electric field in which the direction of the electric field changes in a development gap, and the magnetic particles are electric field-dependent high-resistance particles, and the electric field applied to the magnetic particles is (V/cm) and the electrical resistance of the magnetic particles is R
(Ωcm), the horizontal axis on the coordinate graph is the electric field E, the vertical axis is the electric resistance R, and the four coordinate points A (
0.2×10^3, 10^1^1), B(2×10^3
, 3×10^9), C(0.2×10^3, 10^8)
, D (2 x 10^3, 2 x 10^7), and the area surrounded by straight line AB, straight line BD, straight line DC, and straight line CA determined by A developing method in which the characteristic curves intersect. (Measurement method) Electrode area: 4cm^2, inter-electrode gap: 0
．． A 4 cm sandwich type cell is used, one electrode is pressurized with a weight of 1 kg, and a voltage is applied between both electrodes. (2) The electrical resistance characteristic curve of the magnetic particles is the straight line A
2. The developing method according to claim 1, wherein the volume ratio occupied by the magnetic particles in the developing area, which intersects with the straight line C and the straight line BD, is 1.5% or more and 30% or less. (3) The electric resistance characteristic curve of the magnetic particles is the straight line AC
intersects with BD, and the electric field is 0.2×10^3 (V/cm)
2. The developing method according to claim 1, wherein the developing method is entirely contained in the above range within a range of 2×10^3 (V/cm) or less. (4) E (0.2 x 10^3, 2 x 10^1^0), F
(2×10^3, 10^9), H(2×10^3, 5×
10^7), G (0.2 x 10^3, 2 x 10^8), and all the resistance changes of the magnetic particles fall within the region Z (shaded area). Development method described. (5) Claim (1), wherein the volume ratio of the magnetic particles in the space in the developing section is 1.5% or more and 30% or less.
The development method described in . (6) 1 m above the surface of the developer carrying member in the developing section
When the number of ears per m^2 is Z, the height of the ears in the developing section is X (mm), and the closest distance between the latent image carrier and the developer carrier is Y (mm), 1.7≦(X/Y
)≦7.0 and 4.9 (X/Y)^-^1^. ^8≦z≦18.3(X
/Y) ^-^0^. The developing method according to claim (1), which satisfies the following conditions: ^9 and Z≦6.5. (7) Forming a developer container containing a developer having toner particles and magnetic particles, and a developing section that faces a latent image carrier carrying a latent image and supplies toner particles to the latent image carrier. At the same time, a developer carrier carries and transports developer from the container to the developing section, and the magnetic particles provided on the opposite side of the latent image carrier of the developer carrier member are transferred in the developing section. A developer having a first magnetic field generating means brought into contact with the latent image carrier, and a regulating portion distal end located upstream of the developing section with respect to the moving direction of the developer carrier and spaced apart from the surface of the developer carrier. a coating amount regulating member; a second magnetic field generating means provided on the side of the developer carrying member opposite to the regulating member and located upstream of the developer regulating member with respect to the moving direction of the developer carrier; A method for developing with an apparatus comprising an alternating electric field forming means for forming an alternating electric field in the developing section to transfer the toner particles carried to the developing section and carried on the surface of the developer carrying member to the latent image carrier, The number of ears per 1 mm^2 on the surface of the developer carrying member in the developing section is Z, the height of the ears in the developing section is X (mm), and the distance between the latent image carrier and the developer carrying member is Z. When the contact distance is Y (mm), 1.7≦(X/Y)≦7.0 and 4.9(X/Y)^-^1^. ^8≦z≦18.3(X
/Y) ^-^0^. A developing method characterized by satisfying the following conditions: ^9 and Z≦6.5. (8) The developing method according to item (7), wherein the magnetic particles are ferrite particles having an average particle size of 50 to 60 μm.