JP3047073B2 - High density development method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method used for a developing device such as a copying machine or a printer, and more particularly, to a two-component developer comprising a toner and a carrier. And a developing method for obtaining high-density image quality by using the method.

(Prior Art) In the field of electrophotography, two-component magnetic developers are widely used as a means for developing an electrostatic latent image.
The two-component developer usually consists of toner particles containing a colorant and magnetic carrier particles, and is agitated during development. The toner and the carrier are frictionally charged by stirring, and the toner is attracted to the carrier surface by the charging. The developer in such a state is supplied onto a developing sleeve having a magnet therein, and is formed into a magnetic brush shape by suction of the internal magnet. The developer is transported by the sleeve in this state, and is sent to the photoconductor having the electrostatic latent image.

The developer rubs against the photoreceptor surface as a magnetic brush, and the charged toner moves to the electrostatic latent image surface by a Coulomb force based on a potential difference from 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 as it is on the sleeve. The toner image on the surface of the electrostatic latent image is transferred and fixed to a transfer paper or the like at a subsequent stage and development is performed.

In a two-component developer, the necessary conditions for obtaining a sufficient image density, no toner scattering, and maintaining these characteristics for a long period are determined by the compatibility between the toner and the carrier. As a general trend,
When the toner density is high, a high image density can be obtained, but the triboelectricity of the toner tends to be insufficient, the ability to bond with the carrier is reduced, and the toner enters and exits in the developing device becomes more intense. Some tendency is recognized. For this reason, in the conventional two-component developing method, although the toner density is suppressed to a lower level, the developing efficiency generally tends to be low and the density of a solid portion or the like is low.

To prevent this drawback, Japanese Patent Application Laid-Open No. 62-63970 discloses that an alternating electric field is formed between a drum and a sleeve, and the volume occupied by the magnetic carrier per volume between the drum and the sleeve is 1.5 to 30. It is proposed to be in the range of%.

(Problems to be Solved by the Invention) If the charging characteristics between the toner and the carrier in the two-component developer are sufficient, even when the toner concentration is high, the image density is high and the toner scattering is low. As expected, this is nearly impossible to achieve with commercial toners and development methods. That is, in toner production, defective toner particles that do not contain or contain a small amount of the charge control agent are necessarily generated at a certain probability, and the charge control agent is also used during development by mechanical force inside and outside the developing device. Is lost or toner particles having a reduced content occur at a certain frequency. Further, since uncharged toner particles for which the necessary charging was temporarily not obtained due to a change in the area ratio of the original or a change in the environment are included, toner scattering is inevitably generated. This leads to contamination inside the copying machine and contamination of the copy.

In another invention, the present inventors have found that in a developer using a two-component developer composed 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 in relation to this flow state, It has been found that by setting the development conditions within a certain range, toner scattering can be effectively prevented even when a toner having a relatively high toner concentration and containing defectively charged particles is used. However, although the above proposal is optimal as a countermeasure against such poorly charged particles, the degree of freedom of the developer in a development area, that is, a development nip portion is small, so that the developer hits the photoreceptor strongly and an image In some cases, after-sweep tends to occur and the image may be degraded. For this reason, lowering the carrier saturation magnetization,
Although there is a method of reducing the magnetic strength of the magnet roll in the developing sleeve, such a simple method cannot prevent carrier pulling.

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 sweeping an image while preventing carrier pulling.

In recent years, miniaturization has been desired in the development of full-color developing systems and the like, and development of a developing device using a sleeve having a diameter of 20 mm or less and having no carrier pulling is urgently required.

Thus, the object of the invention is also to reduce the size of the sleeve,
An object of the present invention is to provide a developing method capable of obtaining a high density image.

(Means for Solving the Problems) According to the present invention, a two-component developer composed of a magnetic carrier and black toner is supplied onto a developing sleeve having a magnet inside, and the developer is supplied to the developing sleeve. The developing device is formed by developing the electrostatic latent image formed on the photosensitive drum by transporting it in the form of a magnetic brush to a developing area between the photosensitive drum and rubbing the photosensitive drum surface. In the method, the photoconductor drum and the developing sleeve may have a DS distance between 0.06 and 0.14, which indicates an interval at a position where they are closest to each other.
cm, the toner concentration in the developer is set in a range of 3 to 10% by weight, and the developer is contained in a unit area of the developing sleeve.
An amount of 0.06 to 0.25 g / cm ² is supplied onto the developing sleeve, and the magnetic brush of the developer is supplied to the developing area after being cut to a height of 0.6 to 1.6 mm, and the developing conditions are adjusted. The following equation (1): 30 <M × (T / D × 1 / ρt + C / D × 1 / ρc) ÷ H <40
(1) In the formula, M is the supply amount of the developer per unit area of the sleeve (g / cm ² ), H is the DS distance (cm), and T / D is the developer Is the toner concentration weight fraction (% by weight), and C / D is the carrier concentration weight fraction (% by weight) in the developer.
Where ρt is the true density of the toner (g / cm ³ ), and ρc is the true density of the carrier (g / cm ³ ). The maximum magnetic force is 1000 gauss or less, and the magnetic force X in the tangential direction is on the developing sleeve surface located on a line connecting the position where the magnetic brush of the developer finishes rubbing the photosensitive drum surface and the center of the developing sleeve.
430 Gauss or more, or tangential magnetic force X is 430
A high-density developing method is provided, wherein the magnetic force distribution is set so that the magnetic force Y in the normal direction is less than Gauss and satisfies Y ≧ −X + 800 (Gauss).

The present invention can further be characterized in that the developing sleeve is used with a diameter of 20 mm or less.

The normal direction is the radial direction of the sleeve, and the magnetic force in the normal direction means a value in the normal direction when the magnetic force is vector-decomposed. The tangential direction refers to the direction of the tangent when a tangent is drawn on the circumferential surface of the sleeve at the position where the developer finishes rubbing, and the tangential magnetic force is the tangential direction when the magnetic force is vector-decomposed. Value.

(Function) The present invention is directed to developing conditions, that is, the amount of the developer applied per unit area of the sleeve (M; g / g) so that the above-mentioned formula (1) is satisfied.
cm ² ), a distance H (also referred to as a distance between DS and DS) on a line connecting the centers of both the photosensitive drum and the sleeve, a toner weight fraction (T / D) in the developer, and a true density of the toner (Ρt; g / c
m ³ ), the carrier weight fraction in the developer (C / D) and the carrier affinity (ρc; g / cm ³ ), the flow state of the two-component developer in the development zone is remarkably improved. hand,
Even under the developing condition where the image density becomes high, the toner scattering is effectively suppressed, and the magnetic force at the position of the developing sleeve surface at which the developer finishes rubbing with the photoreceptor and the direction of the magnetic force are within a specific range. Is based on the finding that carrier pulling during development is sufficiently prevented, and particularly, defects at the rear end of a solid image portion due to carrier pulling are prevented.

That is, the mixed state of the toner and the carrier in the developing area is represented by the following equation: R = M × (T / D × 1 / ρt + C / D × 1 / ρc) ÷ H (1a) R is a dimensionless number It indicates the volume ratio of the two-component developer in the development zone volume,
By maintaining the value of R at a value greater than 30% and less than 40%, toner scattering can be effectively prevented.

First, when the developer occupation ratio (R) becomes 30% or less,
The volume occupied by the developer in the DS-developing area is reduced, and the magnetic brush in this area entrains air from above the valley between DS and transports it to below the valley between DS,
An airflow is generated, and the toner tends to be scattered together with the airflow inside the apparatus outside the developing device. On the other hand, when the developer occupation ratio (R) is 40% or more, the developer is excessively clogged in the valley between DS and D, and the developer does not flow smoothly. In addition, the rotation of the sleeve is not performed smoothly, so that the developer is disturbed, and the toner is easily scattered on the upper side of the valley.
On the other hand, within the range specified in the present invention, D
While the flow of the developer is smoothly performed through the valley between -S, the above-described generation of the air flow is also prevented, and the toner scattering is effectively prevented even when the toner concentration is high.

In the present invention, the relationship between the developer occupancy (R) and various factors of the developing conditions is clear from the above-mentioned formula (1a). That is, R increases as the amount M of developer applied to the sleeve increases, and R decreases as the distance H between DS becomes larger. In general, ρt <ρc (3). Therefore, as the toner concentration (weight fraction) in the two-component developer increases, the developer occupancy increases.

In the present invention, the application amount (that is, the supply amount) of the developer on the developing sleeve surface is in the range of 0.06 to 0.25 g / cm ² , particularly 0.1 to 0.2 g / cm ² per unit area of the developing sleeve. The DS distance (H) is in the range of 0.06 to 0.14 cm, and the toner concentration of the developer used is 3 to 10% by weight, especially 3.5 to 10% by weight.
The range is set so that the above-mentioned developer volume ratio (R) satisfies the condition of the expression (1) within this range.

Further, in the present invention, as is clear from FIG. 5 obtained by an experimental example described later, the state of the magnetism that appears on the developing sleeve surface when the developing layer is rubbed is important,
It is important that the tangential magnetic force X on the developing sleeve surface (the position indicated by P in FIG. 2) corresponding to the position where the developer finishes rubbing the photoconductor surface is 430 gauss or more. As described above, the tangential direction means that the direction of the line of magnetic force is in a direction parallel to or inclined with respect to the sleeve surface. This is provided alternately in the developing sleeve
It can be set by the overall relationship between the strength and distance of the magnetic poles of the N and S poles and the sleeve diameter. Tangential magnetic force X
When the value satisfies the above range, the magnetic brush is in a state of being resilient to the surface of the photoconductor at a position away from the photoconductor. Such a brush state has a great effect on the rubbing portion, which is a developing area, and there is no carrier pulling even when the diameter of the sleeve is small and the strength of the main pole in the rubbing portion cannot be sufficiently secured, or An image with no missing image trailing edge is obtained.
Further, in such a state, it is possible to use a carrier having a low saturation magnetization by reducing the strength of the main pole, and to form a magnetic brush of a soft developer to perform sharp development. Further, in the rubbing part, the magnetic brush of the developer is bound so as to stick to the surface of the sleeve, so that the carrier is prevented from scattering at this part. Is prevented. When the magnetic force X in the tangential direction is less than 430 gauss, it is important to regulate the magnetic force Y in the normal direction at the rubbing portion end position, and the magnetic force Y in the normal direction is Y ≧ −X + 800 (Gauss). This is very important. The normal direction is a direction extending perpendicular to the sleeve surface, and means a state in which the magnetic brush of the developer is raised. As is clear from Table 1 of the embodiment described later, in the device satisfying the above-mentioned relationship, no carrier pulling occurs and the device is stuck on the sleeve surface at the sliding portion as in the case of X ≧ 430 Gauss. The above function is sufficiently exhibited.

It is also important for the present invention that the maximum magnetic force appearing on the main poles or alternating poles in the sleeve, ie the sleeve surface, is less than 1000 Gauss, especially less than 900 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.

(Embodiments of the Invention) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 to FIG. 3 are main part explanatory diagrams of the developing device according to the present invention.

In FIG. 1 for explaining a magnetic brush developing method used in the present invention, a magnet roll 11 having a large number of magnetic poles N and S is accommodated in a developing sleeve 12 made of a non-magnetic material such as aluminum. A photosensitive drum 15 composed of a base 13 and an electrophotographic photosensitive layer 14 provided thereon is provided with a small 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 direction (arrow) at the nip position is the same direction (the rotating directions are opposite to each other). You. The developing sleeve 12 is located at an opening of the developing device 16, and a mixing and stirring device 17 for a two-component developer (that is, a mixture of a toner and a magnetic carrier) 18 is provided inside the developing device 16. Above it, a toner supply mechanism 20 for supplying toner is provided. After the two-component developer 18 is mixed by the stirrer 17 and the toner obtains a triboelectric charge, the toner is supplied to the developing sleeve 12,
The magnetic brush 21 is formed on the surface. This magnetic brush 21
Of the electrophotographic photosensitive layer
The photosensitive drum 14 is conveyed to a nip position where the electrostatic latent image is formed on the photosensitive layer 14 with toner.

The developing sleeve 12 is located at the opening of the developing device generally indicated by 23, the above-described scissor mechanism 22 is disposed on the supply side to the developing sleeve, and on the circulation side from the sleeve to the developing device. A developer receiver 25 having an opening edge 24 is disposed.

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

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

The electrostatic latent image formed on the photoreceptor surface of the opposing photoreceptor layer 14 has a development area, that is, a rubbing portion with a magnetic brush (A in FIG. 2).
Portion), only the toner is transferred, whereby the latent image portion is developed. A point P shown in FIG. 2 on the surface of the sleeve 12 corresponds to a position at which the rubbing of the developer ends, and a straight line connecting the friction end position on the photosensitive layer 4 to the center of the magnet roll and the surface of the developing sleeve. Is the intersection with

In the present invention, as shown in FIG. 3, a predetermined magnetic force acts from the internal magnet roll 11 at a point P, and the magnetic force is vectorized in a normal direction Y (perpendicular to the sleeve surface) and a tangential direction X. Disassemble and measure the scalar amount,
The value is set in a certain range. FIG. 4A shows a chart of the magnetic force acting on the sleeve surface in the normal direction. FIG. 4 (B) shows a chart of the magnetic force acting on the sleeve surface in the tangential direction. The equidistant reference circle of the sleeve 12 indicates the scalar amount (Gauss) of the magnetic force, and indicates the strength of the magnetic field in the normal direction and the tangential direction on the sleeve surface.

In the present invention, the magnetic force in the tangential direction X at the sleeve surface point P at which the rubbing is completed is X ≧ 430 Gauss,
Such a magnetic force is formed by adjusting the positional relationship between the N and S poles of the magnet roll 4 in the sleeve 6 and the distance according to the radius of the sleeve. Also, the tangential direction X
Is less than 430 gauss, the value in the normal direction Y is limited, and is set so that Y ≧ −X + 800 gauss.

Further, in the present invention, it is desirable that the maximum magnetic force of the N and S poles is 1000 Gauss or less, particularly 900 Gauss or less. On the sleeve set in such a range, the ears of the magnetic brush tend to be kept soft.

The diameter of the developing sleeve 12 in the present invention is 15 to 50.
It can be used in the range of mm, and particularly when it is used in a thickness of 20 mm or less, the area occupied by the developing sleeve 12 in the developing mechanism section decreases.

Further, the developer, the amount of the applied developer, and the distance between DS are set so as to satisfy the expression (1).

Developer The magnetic carrier depends on the carrier concentration C / D, but generally has a density ρc of preferably 3.50 to 6.50 g / mm, particularly preferably 4.00 to 5.50 g / mm, and particularly a ferrite-based magnetic carrier is used. You.

Conventionally, as ferrite, for example, iron oxide zinc (ZnFe
₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide (CdFe ₂ O ₄ ), gadolinium iron oxide (Gd ₃ Fe
₅ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe
₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFeO ₃ ), iron barium oxide (BaFe ₁₂ O ₁₉ ), iron magnesium oxide (MgFe ₂ O ₄ ), iron manganese oxide (MnFe)
Sintered ferrite particles having a composition of one or more of ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), and the like are used. Soft ferrite containing at least one, and preferably two or more, of the metal components used, for example, copper-zinc-magnesium ferrite, among these ferrites,
Those that satisfy the above conditions are used.

Carrier saturation magnetization is 40 to 65 emu / g, especially 45 to 56 em
It is preferably in the range of u / g. As the magnetic carrier, a ferrite carrier that satisfies the above conditions, particularly a spherical ferrite carrier, is preferable, and the particle size is 20 to 14.
It is preferably in the range of 0 μm, especially 50-100 μm.

The electrical resistance of the ferrite carrier naturally varies depending on its chemical composition, but also varies depending on its particle structure, production method, coating type and thickness. Generally, its volume resistivity is 5 × 10 ^{8 to} 5 × 10
^It is preferably in the range of ¹¹ Ω · cm, particularly 1 × 10 ^{9 to} 1 × 10 ¹¹ Ω · cm.

As a toner, although it depends on the density of the magnetic carrier and the toner concentration, the density ρt is generally 1.00 to 1.40 g / mm ³ ,
In particular, those having a ratio of 1.10 to 1.20 g / mm ³ are used.

The toner used in the present invention is obtained by blending a colorant and a charge control agent or a toner compounding agent known per se in a fixing resin medium. The toner used in the present invention also includes
1 × 10 ^{7 to} 3 × 10 ¹⁰ Ω · cm, especially 2 × 10 ^{7 to} 8 × 10 ¹⁰
It preferably has a volume resistivity of Ω · cm and a dielectric constant in the range of 2.5 to 4.5, particularly 2.5 to 4.2.

The fixing resin medium for the toner, the colorant, the charge control agent and the other compounding agents for the toner are preferably selected and combined so as to obtain the above-mentioned properties. First, as a fixing resin medium,
Styrene resins, acrylic resins, styrene-acryl resins, polyesters, epoxy resins, rosin-modified maleic resins, silicone resins, polyvinyl butyral resins, and the like are used.

Further, the resin used generally preferably has an acid value of 0 to 25. Further, from the viewpoint of fixability, it is preferable that the glass transition temperature (Tg) is 50 to 65 ° C.

As the colorant to be contained in the resin, a known black color or organic pigment or dye is used alone or in combination of two or more. For example, carbon black such as furnace black and channel black, iron black such as triiron tetroxide and the like can be exemplified.

Examples of the charge control agent include any charge control agent known per se, for example, oil-soluble dyes such as nigrosine base (CI50415), oil black (CI20150), and spiron black, and 1: 1 or 2: 1 metal Complex salt dyes, metal (complex) salts of (alkyl) salicylic acid and naphthoic acid and the like are used.

The particle size of the toner particles, as measured by a Coulter counter, is preferably in the range of 8 to 14 μm, particularly 10 to 12 μm in terms of volume-based median, and the particle shape was determined by a melt kneading / pulverization method. It may be of a regular shape or a spherical shape produced by a dispersion or suspension polymerization method.

The toner weight fraction T / D in the developer is 3 to 10% by weight,
In particular, it is in the range of 3.5 to 7.5% by weight.

The electric resistance of the whole developer is preferably in the range of 5 × 10 ^{8 to} 5 × 10 ¹² Ω · cm, particularly 1 × 10 ^{9 to} 5 × 10 ¹¹ Ω · cm.

Other Development Conditions The amount M of the developer applied is preferably in the above-described range.
This depends on both the peripheral speed of the developing sleeve and the magnetic flux density and the spike length of the developing sleeve. For this reason, the peripheral speed of the developing sleeve is set to 60 to 800 cm / sec, particularly 90 to 450 cm / sec. The length depends on the magnetic flux density, but 0.6 to 1.6 mm,
Particularly, the range of 0.8 to 1.4 mm is appropriate.

The DS distance (H) is set in the range of 0.06 to 0.14 cm.

As the photoconductor, a photoconductor conventionally used in electrophotography, for example, a selenium photoconductor, an amorphous silicon photoconductor,
A zinc oxide photoreceptor, a cadmium selenide photoreceptor, a cadmium sulfide photoreceptor, and various organic photoreceptors are all used.

As another developing condition, the bias voltage applied between the developing sleeve and the photoconductor conductive substrate has an average electric field strength of 10
Those having a range of 0 to 1000 V / mm, particularly 125 to 800 V / mm are preferable.

(Experimental Example 1) LPX manufactured by Mita Kogyo Co., Ltd. based on the following developing conditions
-1 using a modified machine, developer application amount M, toner weight fraction
Images were obtained by variously changing the T / D, the carrier weight fraction C / D, the distance between the drum and the sleeve, and the ear-cut gap.

Developing condition Developing sleeve diameter: 20mm, developing sleeve peripheral speed: 210mm / SE
C, photoreceptor drum: organic photoreceptor for negative charging, photoreceptor surface potential: -700V, developing bias potential: -500V, developing magnetic pole: 330 gauss normal magnetic force at point P, tangential direction at point P Magnetism 440 gauss, toner: true density with a median diameter of 11 μm based on a volume of carbon black dispersed in polyester 1.
11g / cm ³ toner, carrier: Ferrite core resin-coated with saturation magnetization of 55 emu / g and electrical resistance of 5 × 10 ⁹ Ω ·
The true density of cm is 5 g / cm ³ .

From the results in Table 1, it was found that those having a developer occupation ratio in the range of 30 to 40% can prevent toner scattering and obtain a high density. Further, for No. 1 (Comparative Example), image formation was performed by widening the ear-cutting gap, applying a coating amount of 0.111 g / cm ² and developing occupancy of 37.3% (No. 1 'Example). Toner scattering was prevented, and the image density was improved. No. 3 (Example) drums
The distance between sleeves was reduced to 0.07cm, and the development occupancy was 40.2%.
As a result, density unevenness occurred in the image, and toner scattering occurred. As a result, the developer occupancy is reduced to 30 to 40%.
Was confirmed to be effective. On the other hand, these images were good in image density and toner scattering, but when the magnetic force in the tangential direction of the developing magnetic pole was lower than 430 gauss, the trailing edge of the solid image was chipped or the carrier was swept in the image area. Also, the carrier is developed in some places in the non-image area.

(Experimental Example 2) Under the above-mentioned favorable No. 2, No. 3 and No. 1 'developing conditions of Experimental Example 1, images were produced using developing magnet rolls having various magnetic intensities. As shown in FIG. 5, the magnetic force in the tangential direction on the surface of the developing sleeve corresponding to the development end portion of the development area is 430 gauss or more, or in the drawing, the line is above the straight line with the straight line of Y = −X + 800. setting the magnetic force relationship relationship (FIG. 4 (a) and (B), the point P of the experimental examples showing the P ₁ of FIG. 5 is a in force distributed chart.) Then, the image density is satisfactory It was confirmed that the traces of the magnetic carrier and the adhesion of the magnetic carrier were eliminated from the image. In the drawing, ● indicates that the carrier has been drawn or that a sweep mark due to the carrier has occurred on the image, and ○ indicates that the above-described problem does not occur.

(Effects of the Invention) As described above, according to the present invention, the composition and density of the developer, the amount of the applied developer, and the distance between the drum and the sleeve satisfy the above (1) in the development zone during development. With this selection, a high-density image without toner scattering can be formed with good fluidity of the developer passing through the development area. Carrier pull during development can be reduced by setting the tangential magnetic force at the point where ends to a specific range, or by setting the tangential and normal magnetic forces to a specific range. Moreover, it is possible to form a soft developer layer by using a carrier having a low saturation magnetization by reducing the magnetic force in the developing sleeve, and to reduce the diameter of the developing sleeve to reduce the size of the entire developing device. It is possible.

[Brief description of the drawings]

1, 2 and 3 are explanatory views of a main part of the developing method and the apparatus according to the present invention, and FIGS. 4 (A) and (B) are magnetic force distribution charts at point P. FIG. 5 is a diagram showing the magnitude relationship between the magnetic force in the normal direction and the tangential direction.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Watanabe 1-2-28 Tamazuki, Chuo-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (72) Inventor Yoshihisa Kuramae 1-2-2 Tamazuki, Chuo-ku, Osaka-shi, Osaka No. 28, Mita Kogyo Co., Ltd. (56) References JP-A-63-4281 (JP, A) JP-A-2-79878 (JP, A) JP-A-62-192757 (JP, A) JP-A-2- 284162 (JP, A) JP-A-4-86869 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/09 G03G 15/08

Claims (2)

(57) [Claims] 1. A two-component developer comprising a magnetic carrier and a black toner is supplied onto a developing sleeve having a magnet therein, and the developer is supplied to a developing zone between the developing sleeve and the photosensitive drum. And developing the electrostatic latent image formed on the photosensitive drum by transferring the photosensitive drum and the developing sleeve by rubbing against the surface of the photosensitive drum. Means that the distance between DS, which indicates the interval at the position where they are closest, is 0.06 to 0.14 cm
The toner concentration in the developer is set in a range of 3 to 10% by weight.
06 to 0.25 g / cm ² is supplied onto the developing sleeve, and the magnetic brush of the developer is supplied to the developing area after being cut off to a height of 0.6 to 1.6 mm, and the developing conditions are adjusted. The following formula: 30 <M × (T / D × 1 / ρt + C / D × 1 / ρc) ÷ H <40 In the formula, M is a supply amount (g / cm ² ) of the developer per unit area of the sleeve. , H is the DS distance (cm), T / D is the toner concentration weight fraction (% by weight) in the developer, and C / D is the carrier concentration weight percentage in the developer. Ρt is the true density of the toner (g / cm ³ ), and ρc is the true density of the carrier (g / cm ³ ). A developing sleeve whose maximum magnetic force on the developing sleeve surface is 1000 gauss or less, and which is located on a line connecting the position where the magnetic brush of the developer finishes rubbing with the photosensitive drum surface and the center of the developing sleeve; In Bed plane, the magnetic force X tangential
430 Gauss or more, or tangential magnetic force X is 430
A high-density developing method, wherein the magnetic force distribution is set so that the magnetic force Y in the normal direction below Gauss satisfies Y ≧ −X + 800 (Gauss). 2. The developing method according to claim 1, wherein a developing sleeve having a diameter of 20 mm or less is used.