JPH0486873A - Method and device for development wherein carrier tailing is prevented - Google Patents

Abstract

PURPOSE:To reduce carrier tailing at the time of development by setting the magnetic force in a tangent direction when a developer layer finishes rubbing within a specific range and setting the position where the maximum value of the magnetic force in a normal direction is obtained to a specific position. CONSTITUTION:The whole developing sleeve 16 is constituted by putting a magnetic roll which has many magnetic poles N and S in a sleeve 51 and a magnetic brush is formed of a two-component developer layer 18 on the outer peripheral surface of the sleeve and moves as the sleeve 51 rotates. Only toner is transferred to an electrostatic latent image formed in a photosensitive material layer 24 at a rubbing part (part A) which rubs against the magnetic brush to develop the image. A point P on the sleeve surface 51 corresponds to the position where the rubbing of a developer ends and the magnetic force in the tangent direction X at the point P is so set that X >= 430 gauss; when the magnetic force does not reach 430 gauss, the value in the normal direction Y is so set that Y >= -X+800 gauss and the position Yp where the maximum magnetic force in the normal direction Y is set upstream within a range of 0.035R - 0.5 R (R: radius of sleeve) of a developer flow from the sleeve surface when the sleeve and a drum are at the shortest distance. An alternating bias potential is set between the sleeve and drum to prevent the carrier tailing.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a developing method and a developing device for copying machines, printers, etc., and more specifically to a two-component developer consisting of a toner and a carrier. The present invention relates to the developing method used and the developing device.

(Adjunct Technique #i) In the field of electrophotography, two-component magnetic developers are widely used as a means for developing electrostatic latent images. A two-component developer usually consists of toner particles containing a colorant and magnetic carrier particles, which are stirred during development. The toner and carrier are triboelectrically charged by Ml agitation, and the toner is adsorbed onto the surface of the carrier due to the electrostatic charge. The developer in this state is supplied onto a developing sleeve equipped with a magnet inside, and is formed into a magnetic brush by the attraction of the internal magnet. The developer is conveyed in this state by the sleeve and sent to the photoreceptor having the electrostatic latent image.

The developer is rubbed against the surface of the photoreceptor as a magnetic brush, and the charged toner is transferred to the electrostatic latent image surface by Coulomb force based on the potential difference with the electrostatic latent image surface to form a toner image. On the other hand, the magnetic carrier is attracted by the magnet in the sleeve and remains on the sleeve. The toner image on the electrostatic latent image surface is transferred and fixed onto a subsequent transfer paper or the like to form an image.

FIG. 5 is an explanatory diagram of a general developing device. As shown in FIG. 5, the developing device 2 is provided with a developer supply mechanism 4, and a developer 6 is supplied from above. The developer 6 is supplied into the lower developing device 10 through a supply port 8 with a feeder, and is stirred by an agitator 12, 12 in the developing device 10. In the case of a two-component developer, the carrier and toner are charged by friction and bond to each other.

Inside the developing device 10 is a developing sleeve 16 having a large number of magnetic poles.
The developing sleeve 16 is supplied with the developer 14 after being triboelectrically charged, and a magnetic brush is formed by the developer on the sleeve surface. The length of the magnetic brush is adjusted by a doctor blade 20, and the magnetic brush is conveyed to the nip position of the photosensitive layer 24 of the electrophotographic photosensitive drum 22.

The distance D of the photosensitive drum 22 from the developing sleeve 16 is
The developing sleeve 16 and the photosensitive drum 22 are rotatably supported by a machine frame (not shown), and the moving directions (arrows) at the nip position are the same (or opposite). It is driven as follows.

A corona charger 26 connected to a variable high voltage power supply 25 and an exposure optical system 28 are arranged around the photoreceptor drum 22.
is disposed upstream of the developing device 10 to form an electrostatic WI image with a predetermined surface potential. A bias power supply 33 equipped with a voltage adjustment mechanism 30 is connected between the photosensitive drum 22 and the developing sleeve 12, and a bias power source 33 having a voltage adjustment mechanism 30 is connected to the photosensitive drum 22 and the developing sleeve 12. A value (bias potential) can be applied. Further, a transfer mechanism 34 for transferring the toner image 27 onto copy paper is provided around the photosensitive layer 24 and downstream of the developing section.

In such a configuration, the developer 14 is transferred to the developing sleeve 1.
8 to form a magnetic brush 18 and a doctor blade 20
After being regulated by, the toner image 27 is formed on the photosensitive layer 24 by reacting with the electrostatic latent image on the photosensitive layer 24 at the nip position.

(Problem to be Solved by the Invention) Normally, in order to increase the image density during development, it is considered to increase the electric field strength between the developing sleeve and the photoreceptor, and the voltage applied between the developing sleeve and the photoreceptor is increased. It is possible to increase the size or to shorten the distance between the developing sleeve and the photoreceptor. However, such excessive voltage application may cause carrier particles to migrate to the surface of the photoreceptor, making it easy to cause so-called carrier pull. Further, when the magnetic binding force of the magnetic brush is strengthened by using carriers with low saturation magnetization in order to improve image quality, carrier attraction becomes more likely to occur.

Conventionally, in order to prevent such carrier pull, it was necessary to make the magnetic force on the developing sleeve surface stronger, or to change the positional relationship between the N and S poles arranged alternately in the developing sleeve and the developing area. For example, if the magnetic flux center position of the main magnet is tilted 2 degrees to 15 degrees upstream from the position facing the photoreceptor (proposed by Japanese Patent Application Laid-open No. 82-17775, the magnetic force entering the developing area and the magnetic force exiting the developing area are Things that have changed (JP-A-59-22868
1 public 11i proposal has been proposed.

However, although these methods prevent carrier attraction to some extent, the developer magnetic brush in the developing area becomes hard due to strong magnetism, and the carrier particles adversely affect the latent image area of the M light body, making it difficult to obtain good image quality. do not have.

In addition, digital copying machines, which have recently become mainstream, reproduce halftones using a laser dot array, but the quality of this image depends on how to prevent toner scattering around the dots (scattering and adhesion around the dot image). is a detailed topic.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing method and a high-density developing device that can produce high-density images without any traces while preventing carrier attraction.

Another object of the present invention is to transfer toner only to the latent image portion of the finely formed dot portion.

It is an object of the present invention to provide a developing method and a developing device capable of forming high-quality images in intermediate tones such as dot areas.

In addition, in recent years, with the development of full-color developing systems that require multiple developing devices, there has been a desire to downsize the developing devices, so the sleeve diameter has been reduced, especially carriers using 20 mm or less diameter. There is an urgent need to develop a developing device that does not cause drag.

Therefore, another object of the present invention is to provide a developing method and a developing device in which the sleeve is miniaturized.

(Means for Solving the Problems) According to the present invention, a magnetically formed developer layer on the surface of the developing sleeve is rubbed against the surface of the photoreceptor drum to develop an electrostatic latent image on the surface of the photoreceptor drum. In the developing method, the magnetic force X in the tangential direction of the sleeve surface is set to 430 Gauss or more at the position where the developer layer finishes rubbing against the photoreceptor drum surface, or the magnetic force X in the tangential direction is 430 Gauss. When the magnetic force Y in the normal direction is Y≧-X+800 (Gauss), the position Yp having the maximum magnetic force in the normal direction Y is set as the developer from the sleeve surface between the shortest distance D-5 between the sleeve and the photoreceptor drum. Flow of 0-03SR to 0. A developing method for preventing carrier pull, characterized in that an alternating bias potential is set between a developing sleeve and a photoreceptor drum, and an alternating bias potential is set to exist on the upstream side of the range of SR (R is the radius of the sleeve). provided.

The present invention also provides a developing device that performs development by rubbing a developer layer on the surface of a developing sleeve formed by magnetic force against the surface of a photoreceptor drum, in which the developer layer finishes rubbing against the surface of the photoreceptor drum. At the position, the magnetic force X in the tangential direction of the developing sleeve surface
and when the magnetic force Y in the normal direction has X≧430 (Gauss), Y≧O, and when X<430 (Gauss), Y≧
-X+800 (Gauss), and the position Yp of the sleeve surface with the maximum magnetic force in the normal direction is the shortest distance ml between the sleeve and the photoreceptor drum.The developer flow from the sleeve surface between D-3 is 0. 035R to 0. A developing device is provided in which a developing sleeve located on the upstream side of a range of SR (R is the radius of the sleeve) and the photosensitive drum are provided in close proximity and an alternating bias potential is applied thereto.

The present invention may be characterized in that the developing sleeve has a diameter of 20 mm or less.

Note that the normal direction is the radial direction of the sleeve, the magnetic force in the normal direction is the value in the normal direction when magnetic force is vectorized, and the tangential direction is where the developer finishes rubbing. It refers to the direction of the tangent when a tangent is drawn on the circumferential surface of the sleeve at the position, and the magnetic force in the tangential direction refers to the value in the tangential direction when the magnetic force is vectorized.

(Function) The present invention sufficiently prevents carrier pull during development by setting the magnetic force and the direction of the magnetic force within a specific range at the position on the developing sleeve surface where the developer finishes sliding against the photoreceptor. This is based on the knowledge that defects such as 1t and m defects after solid image areas due to carrier attraction are prevented.

The present invention also provides that the position (Yp) at which the magnetic force in the normal direction on the developing sleeve surface is at its maximum is within the range of 0.035R to 0.000.
It was discovered that if the developing brush is placed upstream within the range of 5R (R is the radius of the sleeve), the degree of freedom of the developing brush increases during development, and this results in extremely good image quality and greatly expands the effective rubbing area. , based on the knowledge that a dot-type electrostatic image can be developed with good image quality by forming the developing sleeve into a solid shape and applying an alternating bias voltage between the developing sleeve and the photoreceptor surface in the state of the developing area. It is something.

In the present invention, the magnetic state that appears on the surface of the developing sleeve when the developing layer is rubbed is important, and the magnetic force X in the tangential direction at the position where the developer finishes rubbing against the photoreceptor surface is 430 Gauss or more. This is very important.

As mentioned above, the tangential direction means that the direction of the magnetic lines of force is parallel or oblique to the sleeve surface. These are N, which are provided alternately within the developing sleeve.
It can be set based on the overall relationship between the magnetic pole strength and distance of the S pole, and the sleeve diameter. When the tangential magnetic force X satisfies the above range, the magnetic brush serving as the developer layer is sufficiently bent with respect to the photoreceptor surface at a position away from the photoreceptor. It is understood that such a brush condition has a large effect on the rubbing portion as well.

Even when the diameter of the sleeve is so small that sufficient strength of the main pole at the rubbing portion cannot be ensured, an image without carrier pull or chipping at the rear end of the image can be obtained.

Furthermore, when the tangential magnetic force
It is important to

The normal direction is a direction extending perpendicularly to the sleeve surface, and means a state in which the magnetic brush of the developer stands up.

As is clear from Table 1 of Examples to be described later, in a device that satisfies the above relationship, carrier pull does not occur and X≧
As in the case of 430 Gauss, the developer is stuck to the sleeve surface of the sliding portion, and the above effect is fully exerted.

In addition, in the present invention, the position Yp where the magnetic force in the normal direction on the developing sleeve surface is maximum is the shortest distance between 11tH (between D and 8), and the developer flows from the sleeve surface (position S in FIG. 2). 0.035R to 0. It is important that it be present on the upstream side of the range of SR (R is the radius of the sleeve). The fact that the magnetic force in the normal direction is at its maximum at such a position means that the magnetic brush is magnetically attracted in the tangential direction in the developing area and lies on the sleeve surface.

In this case, it is possible to satisfy the tangential magnetic force value at point P within the above range, and this is important as described above. The fact that the magnetic force in the normal direction is maximized at the above position means that the magnetic brush does not strongly hit the photoreceptor in the developing area during development, and the degree of freedom of the magnetic brush, that is, the degree of freedom of the carrier is increased. . In this state of the magnetic brush, the image quality can be improved and the effective rubbing area can be greatly expanded, so it is possible to reduce the diameter of the developing sleeve and make it compact. Furthermore, in the sliding area, the magnetic brush of the developer is bound so as to stick to the sleeve surface, which lowers the magnetic force strength in the normal direction, making it possible to use a carrier with low saturation magnetization. A brush can be formed to give a clear development. Further, it is desirable that the maximum magnetic force in the normal direction appearing on the alternately placed poles in the sleeve, that is, on the sleeve surface, be 1500 Gauss or less, particularly 1200 Gauss or less. If the magnetic force of the main pole is too large, a soft magnetic brush cannot be formed, depending on the diameter of the sleeve, and a clear image cannot be obtained.

In the present invention, it is also important to set an alternating bias potential between the developing sleeve and the photoreceptor drum. In normal development or reverse development, a constant DC bias electric field is formed between the developing sleeve and the photoreceptor drum to facilitate the transfer of toner to the latent image area on the photoreceptor surface. in this case,
The polarity of the charge on the toner is opposite to that of the electrostatic portion, and is set so that the polarity is the same as that of the photoreceptor surface other than the electrostatic portion, or the potential thereof is approximately the same as that of the photoreceptor surface. In the present invention, it is important to superimpose an alternating bias electric field in addition to the DC bias electric field.By superimposing the alternating bias electric field, the bias potential can be adjusted to be lower than the photoreceptor drum surface potential (absolute (+1)) or higher than the residual potential (absolute 411). It is desirable that the period of the alternating bias potential be varied between
Preferably, the frequency is in the range of 4 kHz to 4 kHz.

Normally, the above-mentioned toner scattering is caused by positive development (positive surface potential).
Regardless of whether it is reverse development (surface potential is negative), it appears around the dot area, which is an electrostatic image, and this toner is considered to be excessive migration and is not electrically attracted to the latent image area. This is thought to be caused by an excessive amount of toner having nowhere to go, and is thought to be physically or slightly electrically attached around the latent image area. However, when alternating bias potentials are superimposed as in the present invention, the toner physically attached around the dots is again adsorbed and collected by the carrier, which is the opposite polarity, when the bias potential is in a periodic low potential state. As a result, unnecessary adhesion due to toner scattering around the dots is prevented, and the image becomes clearer. In this case, as mentioned above, the carrier has a magnetic field set to a specific value, so it has a degree of freedom on the surface of the developing sleeve and is likely to move slightly due to electrical amplitude, and this state of the carrier prevents toner from scattering. This is thought to make collection more effective.

Therefore, by applying an alternating bias potential between the photoreceptor and the developing sleeve, the image of the dotted electrostatic portion is made clearer when the carrier is in good condition.

(Embodiments of the Invention) Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 111 and 312 are essential 51-yt clear drawings of the developing device according to the present invention, and the other parts have almost the same structure as the device shown in its entirety in FIG. 5, so detailed explanation thereof will be omitted. do.

As shown in FIG. 1, in the entire developing sleeve 16, a magnet roll 52 having a large number of magnetic poles N and S is housed in a sleeve 51 made of a non-magnetic material such as aluminum, and this magnet roll 52 is fixed and the sleeve 51 is provided to be driven and rotated in the direction of the arrow, that is, in the counterclockwise direction. A magnetic brush, which is a two-component developer layer 18 , is formed on the outer peripheral surface of this sleeve 51 .
moves in the same direction as the sleeve rotation direction as the sleeve 51 rotates.

Only toner is transferred to the electrostatic latent image formed on the photoreceptor layer 24 of the opposing photoreceptor 22 in the development area, that is, the rubbing area with the magnetic brush (portion A in FIG. 1). The image area is developed. Also, the point P shown in FIG. 1 on the sleeve surface 51
corresponds to the position where the sliding portion of the developer ends, and is the intersection of the sleeve surface and the straight line connecting the sliding portion end position on the photoreceptor layer 24 and the center of the sleeve.

In the present invention, as shown in FIG. 2, a predetermined magnetic force is applied from an internal magnet roll 52 at a point P, and the magnetic force is directed into a vector in a normal direction Y (perpendicular to the sleeve surface) and a tangential direction X. Decompose it and measure its scalar quantity,
The value is set within a certain range. j13rgJ
(^) shows a chart of the magnetic force acting in the normal direction on the sleeve surface. In addition, the jla diagram (B
) shows a chart of the magnetic force acting tangentially on the sleeve surface. The equidistant reference circles of the sleeve 51 indicate the scalar ik (Gauss) of the magnetic force, which indicates the strength of the magnetic field in the normal and tangential directions on the sleeve surface.

In the present invention, the sleeve surface point P where the sliding ends
The magnetic force in the tangential direction X is X≧430 Gauss,
Such magnetic force is created by adjusting the positional relationship and distance between the N and SW of the magnet rolls 52 in the sleeve 51 in accordance with the radius of the sleeve. Further, when the magnetic force in the tangential direction X is less than 430 Gauss, the value in the normal direction Y is limited and set so that Y≧−x+soo Gauss.

Furthermore, in the present invention, it is preferable that the maximum magnetic force of N and S41 is 1500 Gauss or less, especially 1200 Gauss or less, as the ears of the magnetic brush tend to be maintained softly on the sleeve set in such a range. .

Further, the diameter of the developing sleeve 16 in the present invention can be used in the range of 15 to 5 degrees, and the length of the magnetic brush to be cut is 0.5 to 5 degrees, which reduces the volume occupied by the developing sleeve 16 in the developing mechanism section. 2.0, especially 0.7 to 1
．． Also, the distance between the photoreceptor and the developing sleeve (D-3 problem WX> is 0.5 to 2.0 m, especially 0.5 to 1.0 m.
It is desirable that it be within the scope of the Cabinet.

Examples of the photoreceptor include photoreceptors conventionally used in electrophotography, such as selenium photoreceptors, amorphous silicon photoreceptors, zinc oxide photoreceptors, cadmium selenide photoreceptors, cadmium sulfide photoreceptors, and various organic photoreceptors. etc. are all used.

As a developing condition, the DC bias voltage applied between the developing sleeve and the photoreceptor conductive substrate has an average electric field strength of 10
0 to 1000 V/+a, especially i: Preferably in the range of 25 to 800 V/am,
The alternating bias voltage superimposed on it is 100 to 800
V, especially fi@ of 300 to 700 V, is used, and it is desirable that the superimposed potential is between the surface potential of the photoreceptor surface and the residual potential. Further, the period (frequency) of the alternating bias potential is 0.2 to 4 kHz, especially 0.5 to 3 kHz.
Other developing conditions, which are preferably in the kHz range, include the ratio of the circumferential speed of the photoreceptor vD to the circumferential speed of the developing sleeve vS (
vS/vD) is generally preferably in the range from 1 to 5, particularly from 1.5 to 3.

Conventionally, for example, iron zinc oxide (ZnFe2
0. ) - iron oxide indolium (Y, Fe, O, ),
Cadmium iron oxide (cdFe20j) - Gadolinium iron oxide (GdsFe, 0+t) + Iron steel oxide (CuF
e20. ), iron oxide complex (PbFe, 20.@)-iron nickel oxide (NiFe20a), iron oxide neodymium (N
dFeO, ), barium iron oxide (BaFe+20+J
, magnesium iron oxide (MzFe20.), iron manganese oxide (MnFe=O,)-lanthanum iron oxide (LaFeO
Sintered ferrite particles having a composition consisting of one or more of s) are used, and in particular Cu, Zn, Mz,
Soft ferrites containing at least one, preferably two or more metal components selected from the group consisting of Mn and Ni, such as copper-zinc-magnesium ferrite, are used. Use one that satisfies the conditions.

The saturation magnetization of the carrier is 40 to 65 emu/g.

In particular, it is desirable that it be in the range of 45 to 56 erau/. The magnetic carrier is preferably a ferrite carrier that satisfies the above conditions, particularly a spherical ferrite carrier, and has a particle size of 20 to 140 μm.

In particular, it is desirable that the thickness be in the range of 50 to 100 μm.

The electrical resistance of a ferrite carrier varies not only depending on its chemical composition, but also on its particle structure, manufacturing method, and coating type and thickness. Generally, its volume resistivity is between 5 x 10” and 5
X I O”Q ・cri, special lXl0・～lX
It is preferable that it be in the range of 10''Ω·cm.

The toner generally has a density ρL of 1.00 to 1.401, although it depends on the density of the magnetic carrier and the toner concentration.
/am, especially 1.10 to 1.20g#+m
are used.

The toner used in the present invention is one in which a colorant and a charge control agent, or further toner ingredients known per se, are blended in a fixing resin medium. The toner used in the present invention is also l
Xl0-” to 5X10-'S/cm, especially 5X10-
It preferably has a conductivity of 10 to I x 10-'S/c+a, and its dielectric constant is preferably in the range 2.5 to 4.5, particularly 2.5 to 4.2.

The fixing resin medium, colorant, charge control agent, and other toner compounding agents for the toner are preferably selected and combined so as to obtain the above characteristics. First, as the resin medium for fixing, styrene resin, acrylic Jugetsuji, styrene-acrylic Jugetsuji, polyester, epoxy resin, rosin-modified maleic acid resin, silicone resin, xylene resin, polyvinyl butyral resin, etc. are used. Ru. Further, the resin used preferably has an acid value of 0 to 25. Further, from the viewpoint of fixing properties, it is preferable that the toner has a glass transition temperature (Tg) of 50 to 65°C.

As the coloring agent to be contained in the resin, any inorganic or organic pigments or dyes known per se may be used alone or in combination of two or more.For example, carbon black such as furnace black and channel black; Iron black such as iron trioxide; titanium dioxide such as rutile type or anatase type; phthalocyanine blue; phthalocyanine green; cadmium yellow; molybrene orange; pyrazolone red; fast violet B and the like.

As the charge control agent, any charge control agent known per se may be used, such as oil-soluble dyes such as Nigrosine base (CI50415), oil black (CI20150), and Subiron blank, and 1:1 type or 2:1 type metals. Complex dyes, metals such as (alkyl) salicyl m and naphthoic acids 1)
Salt etc. are used.

The particle size of the toner particles is 8 to 14 μm on a volume basis, especially 10 μm as measured by a Coulter counter.
The particle size is preferably in the range of 12 μm to 12 μm, and the particle shape may be amorphous particles produced by a melt-kneading/pulverization method, or spherical particles produced by a dispersion or suspension polymerization method.

Furthermore, the electrical resistance of the developer as a whole ranges from 1XIO3 to 1X10''Ω'am, especially from 5XIO' to 5x 10
For the purpose of the present invention, it is preferable that the resistance is in the range of Ω·C11.

Examples and comparative examples according to the present invention will be shown below according to experimental examples.

(Experiment Example 1) Using a modified laser printer LPX-1 (trade name) manufactured by Natsume Sanda Kogyo ■, developing sleeve diameter: 20 mm, developing sleeve circumferential speed: 210 mm/sec, photoreceptor drum diameter:
60 mm, photoreceptor drum peripheral speed near 0 mm/see, photoreceptor drum: organic photoreceptor for negative charging, photoreceptor surface potential:
-700 yen, development bias potential knee 500V, the position of the maximum magnetic force in the two normal directions of the development magnetic pole is on the line connecting the centers of the magnet roller and the photosensitive drum, and the magnetic force in the normal direction at point P , with different magnetic forces in the tangential direction), toner: polyester with carbon black dispersed in it, true density with a volume-based median diameter of 11 μm 1. l1g/cm! Toner and carrier: Ferrite near resin coated with saturation magnetization of 55 e
A carrier with a true density of 5 g/Cm9 and an electrical resistance of 5X10''Ω'Cm.

Image formation was performed under the above development conditions. Table 1 shows the results.
Nishimesu.

When the magnetic force in Table 1 is X and the magnetic force in the normal direction is Y, the magnetic force in the tangential direction is 430 Gauss or more, or the magnetic force in the tangential direction is 4
In the case of less than 30 Gauss, j[direct &! Y=
It can be seen that in the region represented by Y≧−X+SOO with the boundary of the straight line −X+800 (magnetic force in the Y binormal direction, X: magnetic force in the tangential direction), generation of carrier attraction is effectively prevented.

(Experimental Example 2) In Experimental Example 1, it was confirmed that carrier attraction (adhesion) could be suppressed when the magnetic force strength in the normal and tangential directions at the end of the developing nip had a specific relationship. Images were produced by using a magnetic field sensor and variously changing the position of the maximum magnetic force in the normal direction. Figure 3 (A
) and (B) are diagrams showing magnetic force distribution charts of Nα2, and I! Figure 4 (^) and CB) are diagrams showing magnetic force distribution charts of Nα10.

The results of Table-1 are shown in Figure 4.0 From the tangential direction From the results of Table-2, the position of the magnetic pole showing the maximum magnetic force in the normal direction on the developing sleeve connects the center of the photoreceptor drum and the developing sleeve. A specific length (
0,035R to 0.5R) and move it to the printing end part (P
) satisfies the relationship in Experimental Example 1 for the magnetic forces in the normal and tangential directions, which prevents carrier pull (adhesion) and chipping of the rear edge of the image area, eliminates carrier sweep marks, and improves the reproducibility of line images. It was confirmed that the condition was good.

(Experimental Example 3) In addition to the conditions of Nα2.5.8.10 in Experimental Example 2,
AC voltage (frequency: 1kHz) [■
-150--650V, -150--800V,
(1) -50 to -650 V and (2) -50 to -750 V were applied to form a dot image, and toner scattering in the periphery of the dot image was reduced. In particular, the effect was remarkable under the condition (■), and a clear and sharp image could be formed. On the other hand, under the condition (2), the fogging tended to be slightly worse than that under which only DC voltage was applied. In addition, in case (2), carrier adhesion tended to be slightly worse than that in which only DC voltage was applied. (2) The latter showed a slightly worse tendency in terms of toner scattering than the one in which only DC voltage was applied.

As a result, it was confirmed that application of an AC voltage, especially an AC voltage with a vehicle peak between the surface potential and the residual potential, can prevent toner scattering and improve image quality.

(Experimental Example 4) In Experimental Example 3 above, the saturation magnetization of the carrier is 45 e
Images were produced by changing the carrier to a carrier with an average particle size of 65 μm (mu/g) and a volume resistivity of 3×IO”Ω-cm, which tends to cause carrier attraction (adhesion). No adhesion was observed, resulting in a soft image and further improved image quality.

(Effects of the Invention) As explained above, according to the present invention, the position of the maximum value of the magnetic force in the normal direction is set at a specific position in the development area during development, so that the development area passing through the development area Forms high-density images with no toner scattering when the agent has good fluidity.
By reducing the diameter of the developing sleeve, it is possible to downsize the entire developing device.

In addition, by setting the magnetism generated on the surface of the developing sleeve, especially the tangential magnetic force at the point where the developer layer finishes rubbing, to a specific range, or by setting the tangential and normal magnetic forces to a specific range. By doing so, it is possible to eliminate carrier pull during development. Furthermore, it is possible to form a soft developer layer by lowering the magnetic force within the developing sleeve and using a carrier with low saturation magnetization. Furthermore, since the carrier has a degree of freedom and an alternating bias potential is applied, it is possible to prevent toner scattering that occurs around the electrostatic image area formed by dots.

[Brief explanation of the drawing]

1 and 2 are explanatory views of the main parts of the developing method and apparatus according to the present invention, FIGS. 113(A) and 113(B) are distribution charts showing the magnetic force distribution at point P, and FIG. A) and (
B) is a distribution chart showing the magnetic force distribution at point P in another experimental example, Figure 5 is a diagram showing the relationship between the magnitude of magnetic force in the normal direction and the tangential direction, and Figure 6 is the one normally used. FIG. 2 is a diagram illustrating the principle of a developing device. Patent applicant Sanda Kogyo Co., Ltd. No. 1 Figure 2 Figure 5

Claims (4)

[Claims] (1) A developing method in which an electrostatic latent image on the photoreceptor drum surface is developed by rubbing a magnetically formed developer layer on the surface of the developing sleeve with the photoreceptor drum surface, the developer layer being photosensitive. At the position where the rubbing with the drum surface ends,
The magnetic force X in the tangential direction of the sleeve surface is 430 Gauss or more, or the magnetic force Y in the normal direction is Y≧-X+800 (Gauss) when the magnetic force The position Yp of the sleeve surface having magnetic force is set at 0.035R to 0.5R (R
A developing method for preventing carrier pull, characterized in that the bias potential is set to be present on the upstream side of the range (radius of the sleeve), and an alternating bias potential is set between the developing sleeve and the photoreceptor drum. (2) In a developing device that performs development by rubbing a developer layer on the surface of a developing sleeve formed by magnetic force against the surface of a photoreceptor drum, the developer layer finishes rubbing against the surface of the photoreceptor drum. At the position, when the magnetic force X in the tangential direction and the magnetic force Y in the normal direction of the developing sleeve surface have X≧430 (Gauss), Y≧0.
So, when X<430 (Gauss), Y≧-X+800 (
Gaussian), and the position Yp of the sleeve surface where the maximum magnetic force in the normal direction is located is 0.035R to 0.00% of the developer flow from the sleeve surface between the shortest distance D-S between the sleeve and the photoreceptor drum. A developing device in which a developing sleeve located on the upstream side within a range of 5R (R is the radius of the sleeve) and the photosensitive drum are provided in close proximity and an alternating bias potential is applied. (3) The developing device according to claim 2, wherein the maximum magnetic force on the sleeve surface is 1500 Gauss or less. (4) The developing device according to claim 2, wherein the diameter of the developing sleeve is 20 mm or less.