JPH0486871A - High-density developing method - Google Patents

Abstract

PURPOSE:To form a high-density image by selecting the composition, concentration, etc., of a developer so that a specific inequality holds, and specifying the position where the maximum value of a magnetic force in a normal direction is obtained. CONSTITUTION:Development conditions, i.e. the coating amount (M; g/cm<2>) of the developer per sleeve unit area, the distance H (icm) between a photosensitive drum 15 and a sleeve 12 on the line connecting the centers of the both, the toner weight rate (T/D) of toner in the developer, the real concentration (rhot; g/cm<2>) of carriers, the weight rate (C/D) of carriers in the developer, and the real concentration (rhoc; g/cm<2>) of the carriers are so set that the inequality hold, thereby suppressing toner scattering. Then the magnetic force X in the tangent direction and the magnetic force Y in the normal direction at the position where a developer layer on the sleeve finish rubbing against the drum surface are so related that Y >= 20 when X >= 430 or Y >= -X+800(gauss) when X < 430; and the position Yp where the maximum magnetic force in the normal direction Y is obtained is set upstream within a range of 0.035R - 0.5 R (R: radius of sleeve) of a developer flow from the sleeve surface and an alternating bias potential is set between the sleeve and drum to prevent carriers from tailing.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a developing method used in a developing device such as a copying machine or a printer, and more specifically to a two-component developer consisting of a toner and a carrier. The present invention relates to a developing method that allows high-density, high-quality images to be obtained by using the above-described method, and also enables miniaturization of a developing device.

(Prior Art) In the field of electrophotography, two-component magnetic developers are widely used as a means for developing electrostatic latent images. Two-component developers usually consist of toner particles containing a colorant and magnetic carrier particles, and are stirred during development. The toner and carrier are triboelectrically charged by stirring, and the toner is attracted to 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.

In a two-component developer, the necessary conditions to obtain sufficient image density, to be free from toner scattering, and to maintain these characteristics over a long period of time are determined by the compatibility between the toner and the carrier. As a general tendency, when the toner concentration increases, a high image density can be obtained, but the triboelectric charging of the toner tends to be insufficient, the ability to combine with the carrier is lost, and moreover, the movement of toner in and out of the developing device increases. A tendency for toner scattering to increase is observed. For this reason, in conventional two-component developing methods, the toner concentration is kept low.

In general, there is a tendency for the development efficiency to be low and the density of solid areas to be low.

To prevent this drawback, Japanese Patent Application Laid-Open No. 62-6397
Publication No. 0 proposes forming an alternating electric field between the drum and the sleeve, and setting the volume occupied by the magnetic carrier per volume between the drum and the sleeve in the range of 1.5 to 30%. .

(yap to be solved by the invention> If the charging characteristics of the toner and carrier in the two-component developer are sufficient, the image density will be high and toner scattering will be low even when the toner concentration is high. Although this is expected, this is nearly impossible to achieve with commercial toners and development methods.In other words, in toner manufacturing, there is a certain probability that defective toner particles that do not contain or contain a small amount of charge control agent are produced. During development, the charge control agent is lost due to mechanical forces inside and outside the developing device, or toner particles with a reduced content are formed.Also, the area ratio of the original changes. In addition, toner particles also include uncharged toner particles that were temporarily unable to obtain the necessary charge due to environmental changes, etc., so toner scattering will inevitably occur, causing contamination inside the copying machine and causing damage to copies. This will lead to pollution.

In another invention, the present inventors have discovered that in a developer using a two-component developer consisting of a magnetic carrier and a toner, there is a key point in the flow state of the developer passing through the development area, and that there is a key point in relation to this flow state. It has been found that by setting development conditions within a certain range, toner scattering can be effectively prevented even when toner having a relatively high toner concentration and containing defective charged particles is used. However, although the above proposal is optimal as a countermeasure against such defective charged particles, the degree of freedom of the developer in the development area, that is, the development nip, is small, so it is difficult for the developer to hit the photoreceptor. If it is strong, sweeping marks may occur on the image, which may deteriorate the image quality. For this reason, there are methods of lowering the saturation magnetization of the carrier or lowering the magnetic strength of the magnet roll in the developing sleeve, but such simple methods tend to cause carrier bowing.

Furthermore, digital copying machines, which have recently become mainstream, reproduce halftones using laser dot arrays, but the quality of these images depends on how well they prevent toner scattering around the dots (dot scattering and adhesion around the dot image). This is an issue.

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

Another object of the present invention is to provide a high-density development method that allows toner to be transferred only to latent image areas of finely formed dot areas, thereby forming high-quality images in intermediate tones such as dot areas. There is a particular thing.

In addition, in recent years, with the development of full-color developing systems that require multiple developing devices, there has been a desire for a /h type developing device, and the use of smaller sleeves, especially those with a sleeve diameter of 2 mm or less, is required. There is an urgent need to develop a developing device that does not cause such carrier pull.

Therefore, another object of the present invention is to provide a developing method that can reduce the size of the sleeve and provide a high-density surface image.

(Means for Solving Problem 11) According to the present invention, a two-component developer consisting of a magnetic carrier and toner is conveyed from a developing device to a developing area by a sleeve, and in the developing area, a static image on a photoreceptor drum is removed. In a developing method in which a latent image is developed, the developing conditions are expressed by the formula %, where M is the amount of developer applied per unit area of the sleeve (
g/crtf), H is the distance i1 (am) on the line connecting the centers of the photoreceptor drum and the sleeve, and T/
D is the toner concentration weight fraction in the developer, C/D is the carrier concentration weight fraction in the developer, ρ7 is the true density of the toner (g/c+n), and ρC is the true density of the carrier. The relationship between the density (z/cm9), the magnetic force X in the tangential direction of the sleeve surface and the magnetic force Y in the normal direction at the position where the developer layer on the sleeve finishes rubbing against the photoreceptor drum surface is as follows. When X≧430 (Gauss), Y≧0, or X<430
When (Gauss), satisfy Y≧-X+800 (Gauss).

The position yp having the maximum magnetic force in the normal direction Y is located upstream in the range of 0.035R to 0.5R (R is the radius of the sleeve) of the developer flow from the sleeve surface between the shortest distance H between the sleeve and the photoreceptor drum. An object of the present invention is to provide a high-density developing method characterized in that an alternating bias potential is set between a developing sleeve and a photosensitive drum.

The present invention may also be characterized in that when the alternating bias potential is set, the amplitude of the bias potential is set to be less than or equal to the absolute value of the photoreceptor surface potential and greater than or equal to the absolute value of the residual potential6. The maximum magnetic force on the sleeve surface is 1000
It can be characterized by making it less than Gaussian.

The present invention may be characterized in that the developing sleeve is used with a diameter of 20 inches 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 provides development conditions such that the above formula (1) is satisfied;
That is, developer application per unit area of sleeve f (M;
g/cy2), the distance H (icm) on the line connecting the centers of both the photoreceptor drum and the sleeve (also referred to as D-3 problem), the toner weight fraction in the developer (T/D), and The true density of the toner (ρt: g/am'), the carrier weight fraction in the developer (C/D) and the true density of the carrier (
By setting ρcog/cm, the fluidity of the two-component developer in the developing area is significantly improved, toner scattering is effectively suppressed even under development conditions where image density is high, and furthermore, the developer is exposed to light. By setting the magnetic force and the direction of the magnetic force within a specific range at the position of the surface of the developing sleeve where the sliding contact with the developing sleeve ends, carrier pull is sufficiently prevented during development, especially at the rear end of the solid image area due to carrier pull. This is based on the knowledge that defects in parts can be prevented.

Furthermore, in the present invention, the position (Yp) where the magnetic force in the normal direction on the surface of the developing sleeve is maximum is the shortest distance between H (between D and 3).
The developer flow from the sleeve surface is 0.035R to 0. S
It was discovered that when the developing brush is placed upstream in the range of R (R is the radius of the sleeve), the degree of brightness of the developing brush increases during development, and this results in extremely good image quality and greatly expands the effective rubbing area. , the developing sleeve can be miniaturized, and furthermore, by applying an alternating bias voltage between the developing sleeve and the photoreceptor surface in the state of the developing area of the developer, it is possible to develop a dot-type electrostatic image with good image quality. It is based on knowledge.

First, the mixing state of the toner and carrier in the development ms is defined by the following formula (%) R is a dimensionless number and indicates the volume ratio occupied by the two-component developer in the volume of the developing area. ,
By maintaining the value of R at a value greater than 30% and less than 75%, toner scattering can be effectively prevented.

First, when this developer occupancy (R) becomes 30% or less,
The volume occupied by the developer in the development area between D-5 becomes small, and the magnetic brush in this fIli area draws in air from above the valley between D-5 and carries it to the bottom of the valley between D-8, increasing the airflow. There is a tendency for the toner to be scattered outside the developing unit and into the inside of the machine along with the airflow.

When the developer tends to get stuck between D-3, the condition of the developer brush has a large influence, and the condition of the developer brush is influenced by the maximum value of the magnetic force in the normal direction, which will be described later. In this case, this developer occupancy (R) is 75
% or more, the developer is too clogged in the valley between D-3,
The developer does not flow smoothly, which puts a considerable load on the developer sleeve, which prevents the sleeve from rotating smoothly and causes disturbance to the developer, making it more likely that toner will scatter above the valley. . 1 for this
In the range specified in the present invention, while the developer flows smoothly through the valley between D-8 in the developing area, the generation of the air current described above is also prevented, and toner scattering is prevented even when the toner concentration is high. , can be effectively prevented.

In the present invention, the relationship between the developer occupancy (R) and the double edge of the development conditions is clear from the above equation (1a). That is, the larger the developer application RM to the sleeve, the more R
increases, and the larger the distance H between D and 3, the more R
becomes smaller. In addition, since ρt is generally ρC (3), the higher the toner concentration (weight fraction) in the two-component developer, the higher the developer occupancy.

More specifically, M is generally between 0.606 and 0.25 g/
am', especially in the range of 0.1 to 0.21/can', 4H generally ranges from 0.04 to 0.16c+n, especially 0.
from the range of 0.06 to 0.14c+*, and the toner weight fraction in the developer is from 0.03 to 0.08, especially 0.035
From the range of 0.075 to 0.075, it is determined that R when these are combined satisfies formula (1).

Furthermore, in the present invention, the magnetic state that appears on the surface of the developing sleeve when the developing layer is rubbed is important, as is clear from FIG. 6 obtained from the experimental example described later. It is important that the magnetic force X in the tangential direction at the rubbing end position is 430 Gauss or more. As mentioned above, the tangential direction means that the direction of the magnetic lines of force is parallel or parallel to the sleeve surface. This can be set by the overall relationship between the strength and distance of the N and S poles and the g1 poles provided alternately in the developing sleeve, 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 sliding part, and even if the diameter of the sleeve is small and the strength of the main pole at the sliding part cannot be ensured, it is possible to prevent carrier pull or An image without chipping at the rear end of the image can be obtained. Furthermore, when the tangential magnetic force
(Gaussian) is important. 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 the Examples described below, in the device satisfying the above relationship, carrier pull does not occur, and the developer sticks to the sleeve surface of the sliding portion as in the case of X≧430 Gauss. The above effect is fully exhibited.

Further, 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 11iH (between D and 8), and the developer flows from the sleeve surface (position S in FIG. 2). 0.03SR 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 reason why the magnetic force in the normal direction is maximum at the above position is that the magnetic brush does not strongly hit the photoreceptor in the developing area during development, and in addition to the effect of the developer occupancy rate (R) mentioned above,
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 part, the magnetic brush of the developer is bound so as to stick to the sleeve surface, and by lowering the magnetic force strength in the normal direction, it is possible to use a carrier with low saturation magnetization, and the magnetic brush of the soft developer can be used. It can be formed and developed into a clear image. Also, if the maximum magnetic force in the normal direction that appears on the alternately placed poles in the sleeve, that is, on the sleeve surface, is less than Gauss,
In particular, it is desirable that it be less than Gauss. 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 further 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. The carrier tends to be attracted with opposite polarity to the drum surface, but is stopped by the magnetism of the sleeve. 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 lowered to below the photoreceptor drum surface potential (absolute value) and above the residual potential (absolute value). It is desirable to vary between Also, the cycle of the alternating bias potential at this time depends on the circumferential speed of the sleeve, but considering the effect of collecting scattered toner, it is 200H.
z to 4Kl (preferably in the range of z).

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 adsorbed and collected again 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 development occupancy rate and magnetic field set to specific values, so it has a degree of freedom on the surface of the development sleeve and is likely to move slightly due to electrical amplitude. This is considered to make the collection of scattered toner 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. 1 to 3 are explanatory diagrams of main parts of a developing device according to the present invention.

In FIG. 1 for explaining the magnetic brush developing method used in the present invention, a magnet roll 11 having a large number of magnetic poles N and S is housed in a developing sleeve 12 made of a non-magnetic material such as aluminum. A photosensitive drum 15 consisting of a base body 13 and an electrophotographic photosensitive IW 14 provided thereon is provided at a minute gap, that is, H, from the developing sleeve 12 . The developing sleeve 12 and the photosensitive drum 15 are rotatably supported by a machine frame (not shown), and are driven so that the moving directions (arrows) at the nip position are the same (the rotating directions are opposite to each other). Ru. The developing sleeve 12 is located at the opening of the developing device 16, and inside the developing device 16 is provided a mixing agitator 17 for a two-component developer (i.e., a mixture of toner and magnetic carrier) 18. A toner supply mechanism 20 for supplying toner is provided above it. The two-component developer 18 is mixed by the stirrer 17 to give the toner a triboelectric charge, and then supplied to the developing sleeve 12 to form a magnetic brush 21 on its surface. This magnetic brush 21 has its spike height adjusted by a spike cutting mechanism 22, and the electrophotographic photosensitive layer 14
The electrostatic latent image is conveyed to the nip position with the toner to form a visible image on the photosensitive layer 14.

The developing sleeve 12 as a whole is located at the opening of the developing device indicated by 23, and the above-mentioned panicle cutting mechanism 22 is arranged on the supply side to the developing sleeve, and the above-mentioned panicle cutting mechanism 22 is arranged on the circulation side from the sleeve to the developing device. , a developer bone 25 having an open edge 24 is disposed.

The developer application amount M can be set to a predetermined value by changing the circumferential speed of the sleeve 12 and by adjusting the distance between the sleeve 12 and the ear cutting mechanism 22.

As shown in FIG. 2, the sleeve 12 is provided so as to be actively rotated in the direction of the arrow, that is, in the counterclockwise direction. A magnetic brush, which is a two-component developer layer 21 , is formed on the outer peripheral surface of the sleeve 12 .
As the sleeve rotates, it moves in the same direction as the sleeve rotation direction.

The electrostatic latent image formed on the photoreceptor surface of the opposing photoreceptor layer 14 has a development area, that is, a rubbing area with the magnetic brush (A in FIG. 2).
Only the toner is transferred in the area), and the latent image area is thereby developed. Further, point S shown in FIG. 2 on the surface of the sleeve 12 is the position of the sleeve surface at the shortest distance between the photoreceptor surface 14 and the surface of the sleeve 12, and point P is the position where the sliding of the developer ends. There is.

In the present invention, as shown in FIG. 3, a predetermined magnetic force acts from the internal magnet roll 11 at the beam P, and the magnetic force is directed into a vector in the normal direction Y (perpendicular to the sleeve surface) and the tangential direction X. Decompose it and measure its scalar quantity,
The value is set within a certain range. FIG. 4(A) shows a chart of the magnetic force acting in the normal direction on the sleeve surface. Moreover, FIG. 4 CB) shows a chart of the magnetic force acting in the tangential direction on the sleeve surface. The equidistant reference circles of the sleeve 12 indicate a scalar amount (Gauss) of magnetic force, and indicate 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 S poles of the magnet roll 11 within the sleeve 12 in accordance with the radius of the sleeve. Also,
If the magnetic force in the tangential direction X is less than 430 Gauss,
The value of the normal direction Y is limited and set so that Y≧−X+800 Gauss.

In the present invention, the upstream side of the developer flow from the position of point S (
7) 0.03SR to 0. The maximum value YP in the normal direction is set in the range of SR (R1! It is desirable to set it to less than Gauss. On a sleeve set in such a range, the ears of the magnetic brush tend to be maintained in a soft, bent state in the developing area.

Development conditions: The peripheral speed of the development sleeve is 60 to 800 cm/sec.
In particular, the cutting time is 90 to 450 clllsec, and the length of the panicle is suitably in the range of 0.6 to 1.6 mm, particularly 0.8 to 1.4 mm, although it also depends on the magnetic flux density.

In addition, D-8 problem tJi (H) is 0.4 to 1.6
It is preferable to select from the range of mm, especially 0.6 to 1.4a+m. The diameter of the developing sleeve 12 in the present invention is 15
It can be used in a range of 50 mm to 50 mm, and the volume occupied by the developing sleeve 12 in the section a of the developing machine is reduced by tJ\.

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 is on average over 118 volts.
00 to 1000 V/IIm, special +: 125
It is preferable that the voltage is in the range of 700 to 700 V/mm, and the alternating bias voltage to be superimposed on it is 100 to 8
○■, especially one with an amplitude 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. In addition, the period (frequency) of the alternating bias potential is 0.2 to 4 KHz, especially 0.5 to 3 KHz.
Preferably, it is in the KHz range.

The developer magnetic carrier generally has a density ρC of 3.50 to 6.50 g/am, although it depends on the carrier concentration C/D.
In particular, those having a ratio of 4.00 to 5.501/IIa are preferred, and ferrite-based magnetic carriers are particularly used.

Conventional ferrites include (ZnFe20.), iron oxides such as iron zinc thorium oxide (Y3Fe50+2), iron cadmium oxide ((dl"e20.l), iron gadolinium oxide (GdsFe, 0+2), iron copper oxide (CuF), etc.
e20. l), iron oxide complex (PbFe120.o),
Nickel iron oxide (NjFe20.), neodymium iron oxide (NdFed, ), barium iron oxide (BaFe, 2 layers,
), magnesium iron oxide (MgFe20a), manganese iron oxide (MnFe20.), lanthanum iron oxide (La
Sintered ferrite particles with a composition consisting of one or more types such as FeOg) are used, and in particular Cu, Zn, M
Soft ferrites, such as copper-zinc-magnesium ferrites, containing at least one, preferably two or more, metal components selected from the group consisting of g, Mn and Ni are used, but among these ferrites, , use one that satisfies the above conditions.

The saturation magnetization of the carrier is preferably in the range of 40 to 65 emu/g + especially 45 to 56 ernu/g. The magnetic carrier is preferably a ferrite carrier that satisfies the above conditions, particularly a spherical ferrite carrier, and its particle size is 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 due to its chemical transformation, but also due to its particle structure, manufacturing method, and coating type and thickness. Generally, its volume resistivity is between 5×10e and 5×1
011Ω・clll, especially 1X10G to lXl0II
It is preferable that it be in the range of Ω·cm.

The toner generally has a density ρL of 1.00 to 1.40H, although it depends on the density of the magnetic carrier and the toner concentration.
/am, especially 1.10 to 1.20 (/mm
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 also includes I
XIQ-11 to 5X10S/am, especially 5XlO-I
It preferably has a conductivity of Q to 1 x 10-'S/cm, and its dielectric constant is from 2.5 to 4.5, especially 2.5.
Fixing resin medium 1 for toner, preferably in the range of from 4.2 to 4.2 Colorants, charge control agents, and other toner compounding agents are preferably selected and combined so as to obtain the above characteristics. First, as the fixing resin medium, styrene resin, acrylic resin, styrene-acrylic resin, polyester, epoxy resin, rosin-modified maleic acid resin, silicone resin, xylene resin, polyvinyl butyral resin, etc. are used. In addition, the resin used is
It is generally preferred to have an acid value of O to 25. In addition, from the viewpoint of fixing properties, the glass transition temperature (Tg) is 50 to 65°C.
).

As the colorant contained in the resin, any known inorganic or organic pigments, dyes, etc. may be used alone or in combination of two or more. For example, carbon black such as furnace blank and channel blank; iron black such as triiron tetroxide; titanium dioxide such as rutile type or anatase type; phthalocyanine blue; phthalocyanine green; cadmium yellow; molybrene orange; pyrazolone red; fast violet B etc.

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 Blank (CI20150), and Subiron Black, and 1:1 type or 2:1 type metals. complex dye,
Metal salts of (alkyl)salicylic acid and naphthoic acid 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 mixing/grinding method, or spherical particles produced by a dispersion or suspension polymerization method.

The toner weight fraction T/D in the developer is generally in the range of 0.03 to 0.08, particularly 0.035 to 0.075.

In addition, the electrical resistance of the developer as a whole is 1Xl0e to 1Xl0"Ω'cm, especially 5X10' to 5XIOII
A range of Ω·cm is preferred for the purposes of the present invention.

In the present invention, the toner weight fraction (T/D) in the developer
If you want to increase the amount of developer applied (M), problem D-3! Increasing (H) is effective in preventing toner scattering.

Experimental examples in which examples and comparative examples are shown are shown below.

(Experimental Example 1) Based on the following development conditions, the positions of developer application tM, toner weight fraction T/D, carrier weight fraction C/D, drum-sleeve distance, and ear cutting gap were variously changed. I then created an image.

Development conditions Development sleeve diameter = 20mm, Development sleeve peripheral speed: 210
mm/see, photoreceptor drum diameter: 60 mm, photoreceptor drum peripheral speed near 0 mm/sec, photoreceptor drum: organic photoreceptor for negative charging, photoreceptor surface potential knee 700■, development bias potential knee 500■, development magnetic pole two The position of the maximum magnetic force in the normal direction is on the line connecting the center of the magnet roller and the photosensitive drum, the magnetic force in the normal direction at point P is 630 Gauss, the magnetic force in the tangential direction at Point P is 150 Gauss, toner: polynissian diameter is l1μm true density 1. l1g/Cm' toner, carrier: resin coated ferrite core with saturation magnetization of 5
5 e m u / g, electrical resistance is 5X10'Ω'
A carrier with a true density of Qm of 5 g/Cm'.

Table-1 Volume-based method of dispersing carbon black in chill-1
The results show that when the developer occupancy is in the range of 30 to 40%, toner scattering can be prevented and high density images can be obtained. Furthermore, when we created an image with Na 1 by widening the cutting gap and applying a coating amount of 0°111 g/cm 2 with a developer occupancy of 37.3%, toner scattering was prevented and the image density was also improved. Improved. Also,
In the case of Nα4, when the drum-to-sleeve distance was narrowed to 0°07 cm and the developer occupancy was 40.2, density unevenness occurred in the image and toner scattering occurred.

(Experimental Example 2) Under the conditions of Experimental Example 1 where the developer occupancy was 40.2% and 43.2%, the position of the maximum magnetic force in the normal direction of the developing magnetic pole was moved 0.04R to the upstream side in the rotational direction of the developing sleeve. (R is the radius of the developing roller) and the magnetic force in the normal direction at point P was 590 Gauss and the magnetic force in the tangential direction at Point P was 220 Gauss, which suppressed toner scattering and fogging. A high-density, clear image was obtained with no traces of carrier sweeping or carrier adhesion on the image area.

(Experimental Example 3) By shifting the position of the maximum magnetic force in the normal direction of the developing m-pole to the rotating direction of the developing sleeve in Experimental Example 2, the effective developer occupancy rate is increased and the sweep marks on the image area by the carrier are reduced. Since it was confirmed that the developer and carrier adhesion could be suppressed, images were produced by variously changing the developer occupancy rate and changing the positions of the magnet roller and magnetic pole.

The results are shown in Table 2 below. In addition, Fig. 4 (A) and (B
) is a chart of the magnetic force distribution of Nα6, and Fig. 5 (A
) and (B) are charts showing the magnetic force distribution of Nα11.

From Table 2, by changing the magnet roller, the position of the maximum magnetic force in the normal direction of the developing magnetic pole is moved within a specific range upstream in the rotational direction of the developing sleeve, and the sliding '! ! If the magnetic force on the developing sleeve at the end of the X area has a specific relationship, the image density and fine line reproducibility are good, and high quality images can be formed without image fogging, carrier adhesion, or carrier sweep marks in the image area. I was able to confirm that it is possible.

In addition, Figure 6 shows the magnetic force in the normal and tangential directions on the developing sleeve and the carrier adhesion (
This is a plot of the occurrence of carrier sweep marks), and from the figure, the magnetic force in the normal direction (Y) and the magnetic force in the tangential direction (X) are Y≧-X+800 (X<430) (7)
It can be seen that carrier adhesion does not occur when the relationship is X≧430. In the figure, . represents the occurrence of carrier adhesion, and O
represents no carrier adhesion.

(Experimental Example 4) For the Nα6, Na 9, N (111) of Experimental Example 3 above, in addition to the DC voltage as a bias voltage, an AC voltage (frequency: 1 kHz) [■Vehicle Beak Knee 150~
-650■■-150~-5oov■-50~-650
When a dot image was reproduced by applying a voltage of -50 to -750 V, toner scattering at the periphery of the dot image was reduced compared to using only a DC voltage. Particularly, the effect was remarkable when the voltage was applied in the range of the vehicle peak (2), and the image quality was clear and sharp. On the other hand, under the condition (2), the degree of fogging tended to be worse than that when only DC voltage was applied. (2) After that, carrier adhesion tended to be worse than when only DC voltage was applied. (2) After that, toner scattering tended to be worse than when only DC voltage was applied. As a result, the scattering of toner around the dot image is suppressed by the application of an alternating current voltage, resulting in high-quality images with excellent various image characteristics, especially when the vehicle beak is between the surface potential and the residual potential of the photoreceptor. was confirmed.

(Effects of the Invention) As explained above, according to the present invention, the composition and density of the developer, the amount of developer applied, and the distance between the drum and sleeve satisfy the above (1) in the development area during development. Since the position of the maximum value of the magnetic force in the normal direction is set at a specific position, the developer passing through the development area has good fluidity, and a high-density image without toner scattering can be formed. ,
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, carrier attraction during development can be reduced. 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 in the electrostatic image area formed by dots.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are illustrations of the main parts of the developing method and apparatus according to the present invention, and FIGS. 4(A) and (B) are
Magnetic force distribution chart at points S and P, Figure 5 (A
) and (B) are magnetic force distribution charts at AS and point P, and Figure 116 is a diagram showing the relationship between the magnitudes of magnetic force in the normal direction and the tangential direction. Figure 1 Patent applicant: Sanda Kogyo Co., Ltd. Figure 2 Figure 3 Tangential direction X Figure 6

Claims (4)

[Claims] (1) In a developing method in which a two-component developer consisting of a magnetic carrier and toner is transported from a developing device to a developing area by a sleeve, and an electrostatic latent image on a photoreceptor drum is developed in the developing area, the developing conditions are as follows: Expression 30<M×[(T/D)×(1/ρt)+(C/D)×
(1/ρc)]÷H<75 In the formula, M is the amount of developer applied per unit area of the sleeve (g/cm^2), and H is on the line connecting the centers of the photoreceptor drum and sleeve. is the distance (cm), T/D is the toner concentration weight fraction in the developer, C/D is the carrier concentration weight fraction in the developer, and ρt is the toner true density (g/cm ^3), where ρc is the true density of the carrier (g/cm^3) and the magnetic force in the tangential direction of the sleeve surface at the position where the developer layer on the sleeve finishes rubbing against the photoreceptor drum surface. The relationship between X and the magnetic force Y in the normal direction is: When X≧430 (Gauss), Y≧0, or X<430
When (Gauss), Y≧-X+800 (Gauss) is satisfied, and the position Yp of the sleeve surface having the maximum magnetic force in the normal direction Y is determined from the developer flow from the sleeve surface between the shortest distance H between the sleeve and the photoreceptor drum. A high density device that is set to exist on the upstream side in the range of 0.035R to 0.5R (R is the radius of the sleeve) and that an alternating bias potential is set between the developing sleeve and the photoreceptor drum. Development method. (2) The developing method according to claim 1, wherein the amplitude of vibration of the bias potential when the alternating bias potential is set is within a range of less than the absolute value of the photosensitive drum surface potential and more than the absolute value of the residual potential. (3) The developing method according to claim 1, characterized in that the maximum magnetic force on the sleeve surface is 1000 Gauss or less. (4) The developing method according to claim 1, wherein the developing sleeve is used with a diameter of 20 mm or less.