JP2003177608A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of obtaining excellent developing property though small particle size toner is used and forming a high-quality visible image. <P>SOLUTION: In the developing device of the image forming apparatus, the image is developed with two-component developer satisfying conditions that the volume average particle size (dt) of the toner is 3 to 5 μm (condition 1), the volume average particle size (dc) of carrier is 5 dt to 10 dt (condition 2), and the weight ratio Rw of the toner and the carrier is 1.6(dt/dc)×(ρt/ρc) to 2.4(dt/dc)×(ρt/ρc) (condition 3, ρt and ρc are the density of the toner and that of the carrier, respectively), a main magnetic pole on a rotating sleeve is arranged at a position near the most proximate position to an image forming body, and the most proximate distance D between the rotating sleeve and the image forming body satisfies 0.5 H to 0.8 H with respect to the free napping height H of a magnetic brush by the main magnetic pole. It is desirable that the real supply amount of the toner is regulated to a specified range. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of forming a clear and high quality visible image.

[0002]

2. Description of the Related Art In recent years, in electrophotographic image formation, a technique using a small particle diameter toner has been proposed in order to form a visible image of high image quality equivalent to that of offset printing.

For example, (1) colored particles having a volume average particle size of 2.0 to 5.0 μm and a particle size of 1.0 μm or less are formed of colored particles containing at least a binder resin and a colorant. 20% by number or less, particle size is 5.0μ
By using a toner in which the number of colored particles exceeding m is 10% by number or less and (2) the colorant is pigment particles, fine line reproducibility and gradation are extremely high, and a visually uncomfortable feeling can be given. No image, high quality image of offset printing or higher, and good cleaning property, and at least cyan, magenta,
In a full-color image forming method in which four color toner images of yellow and black are laminated on a transfer material to form a full-color image, fine line reproduction is achieved by using a four-color toner that satisfies the above conditions. It has been proposed that the properties and the disturbance of the image on the transfer material are improved, the image thickness is reduced, and an extremely high quality image can be formed (for example, refer to Patent Document 1).

Further, the conditions (particle size, resistance) of the carrier combined with the above toner are disclosed (for example,
See Patent Document 2. ).

[0005]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-81722

[Patent Document 2] Japanese Patent Laid-Open No. 2000-98657

However, since the toner having a small particle size has a larger Van der Waals force as the particle size becomes smaller, the adhesive force to the carrier is larger than that of the conventional toner. Even if an attempt is made to develop by the conventionally known two-component magnetic brush developing method described in Japanese Patent Publication No. 81722 or 2000-305361, sufficient developability is not obtained, and as a result, in the visible image formed, For example, insufficient image density and thin horizontal lines occur. Then, for example, when the linear velocity of the developing roller is extremely increased in order to secure the developing property, a phenomenon in which a carrier adheres to an image forming member made of a photoconductor (carrier adhesion) or a phenomenon in which a carrier scatters (carrier scattering) Occur. For the above reasons, when using a toner having a small particle diameter, it is necessary to actually take some developing property improving means.

Based on the above circumstances, as a result of various investigations by the present inventors for the purpose of improving developability in the case of forming a visible image using a toner having a small particle diameter, a conventional method of developing with an electric field That is, in the method in which the development is performed by electrostatically peeling the toner from the carrier mainly by the force of the electric field formed between the rotating sleeve that conveys the developer and the photoconductor, a non-electrostatic method is used. When a small particle size toner having a large van der Waals force acting as an adhesive force is used, it is difficult to peel the toner from the carrier sufficiently effectively, but the two-component developer is strongly disturbed under specific conditions. At this time, it was found that the small particle size toner can be effectively peeled off from the carrier, and the developability is improved.

In order to strongly disturb the developer,
Usually, a means for increasing the linear velocity of the rotary sleeve is effective, but such means is not an advantageous method because the centrifugal force in the rotary sleeve also increases and carrier adhesion or carrier scattering occurs.

Further, in order to increase the disturbance of the developer,
It has been found practical to reduce the height of the magnetic brush ears by reducing the amount of developer on the rotating sleeve so that the developer is not packed in the development area. That is, according to this method, the magnetic brush with the two-component developer on the rotating sleeve and the photoconductor are brought into slight contact with each other to perform development on the magnetic poles, so that the disturbance of the developer in the developing region becomes strong, which causes a small disturbance. The toner having the particle diameter is easily peeled off from the carrier, and the developing efficiency is improved.

[0010]

The present invention has been completed based on the above findings, and its purpose is to:
It is an object of the present invention to provide an image forming apparatus capable of forming a high-quality visible image with excellent developability obtained by using a toner having a small particle size.

[0011]

An image forming apparatus of the present invention comprises an image forming body and a developing device for developing a latent image formed on the image forming body with a two-component developer including toner and carrier. The developing device includes a rotary sleeve which is arranged to face the image forming body and which conveys the two-component developer, and a two-component developer which is arranged inside the rotary sleeve and is on the surface of the rotary sleeve. And a magnet system for forming a plurality of magnetic poles for forming a magnetic brush, and a developer amount regulation for regulating the amount of the two-component developer conveyed by the rotary sleeve, which is arranged so as to face the surface of the rotary sleeve. An image forming apparatus having a member, the volume average particle diameter of the toner in the two-component developer is dt (μm),
The density is ρt (g / cm ³ ), and the volume average particle diameter of the carrier is d.
c (μm), density ρc (g / cm ³ ), and weight ratio of toner to carrier (ratio of toner weight to carrier weight) is Rw, Condition 1: Toner volume average particle diameter dt is 3 ≦ 5 μm, Condition 2: Carrier volume average particle diameter dc is 5 dt to 10 d
and the condition 3: the weight ratio Rw of the toner and the carrier is 1.6 (d
t / dc) × (ρt / ρc) to 2.4 (dt / dc) ×
The main magnetic pole forming the strongest magnetic field on the surface of the rotating sleeve among the plurality of magnetic poles in the magnet system is the closest position between the rotating sleeve and the image forming body. When the free brush height of the magnetic brush formed at the position of the main pole is H (mm) and the closest distance between the rotating sleeve and the image forming body is D (mm), the condition is 4: It is characterized that the closest distance D is satisfied in the range of 0.5H to 0.8H.

In the above, in the developing area where the rotating sleeve faces the image forming body, the moving directions of the rotating sleeve and the image forming body are the same, and in the two-component developer,
Regarding the weight ratio Rw of the toner and the carrier, it is preferable that the following condition 3A is satisfied. Condition 3A: Weight ratio Rw of toner to carrier is 1.8.
(Dt / dc) × (ρt / ρc) to 2.2 (dt / d)
c) Be within the range of (ρt / ρc).

Alternatively, in the developing area where the rotating sleeve faces the image forming body, the moving directions of the rotating sleeve and the image forming body are opposite to each other, and in the two-component developer, the weight ratio Rw of the toner and the carrier is as follows. It is preferable that the condition 3B is satisfied. Condition 3B: The weight ratio Rw of the toner and the carrier is 1.6.
(Dt / dc) × (ρt / ρc) to 2.0 (dt / d
c) Be within the range of (ρt / ρc).

The image forming apparatus of the present invention comprises an image forming body and a developing device for developing the latent image formed on the image forming body with a two-component developer composed of toner and carrier. , Disposed opposite the image-forming body,
A rotary sleeve for carrying the two-component developer; a magnet system disposed inside the rotary sleeve for forming a plurality of magnetic poles on the surface of the rotary sleeve for forming a magnetic brush of the two-component developer; An image forming apparatus having a developer amount regulating member which is arranged so as to face a surface of a rotating sleeve and regulates the amount of the two-component developer conveyed by the rotating sleeve. The particle size is dt (μm), and the transport amount per unit area of the two-component developer transported by the rotating sleeve is W.
(Mg / cm ² ), the toner concentration in the two-component developer is T
c (weight%), where Rv is the ratio of the moving speed of the rotating sleeve to the moving speed of the image forming body, Condition 1: The volume average particle diameter dt of the toner is in the range of 3 to 5 μm, Condition 5: 2 Transport amount W of the component developer is 10 to 50 mg / c
m ² and the condition 6: the actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of ² to 10 mg / cm ² , and the magnet system is satisfied. Among the plurality of magnetic poles in, the main magnetic pole that forms the strongest magnetic field on the surface of the rotating sleeve is arranged in the vicinity of the closest position between the rotating sleeve and the image forming body, and is formed at the position of the main magnetic pole. When the free brush height of the magnetic brush is H (mm) and the closest distance between the rotating sleeve and the image forming body is D (mm), Condition 4: The closest distance D is in the range of 0.5H to 0.8H. Characterized by being satisfied.

In the above, the volume average particle diameter of the toner in the two-component developer is dt (μm) and the density is ρt (g / c).
m ³ ), the volume average particle diameter of the carrier is dc (μm), the density is ρc (g / cm ³ ), and the weight ratio of the toner and the carrier (ratio of the weight of the toner to the weight of the carrier) is Rw. 2: Carrier volume average particle size dc is 5 dt to 10 d
and the condition 3: the weight ratio Rw of the toner and the carrier is 1.6 (d
t / dc) × (ρt / ρc) to 2.4 (dt / dc) ×
It is preferable that the condition of (ρt / ρc) is further satisfied.

Further, in the above, in the developing region where the rotary sleeve faces the image forming body, it is preferable that the moving directions of the rotary sleeve and the image forming body are the same, and the following condition 6A is satisfied. Condition 6A: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of 4 to 8 mg / cm ² .

Alternatively, in the developing area where the rotary sleeve faces the image forming body, it is preferable that the moving directions of the rotary sleeve and the image forming body are opposite to each other, and the following condition 6B is satisfied. Condition 6B: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of ² to 6 mg / cm ² .

In the image forming apparatus described above, it is preferable that a bias voltage in which a DC voltage and an AC voltage are superposed is applied to the rotating sleeve in the developing device. Further, in the developing device, it is preferable that the main magnetic pole is arranged on the upstream side in the moving direction of the image forming body with respect to the closest position between the rotating sleeve and the image forming body.

The image forming apparatus of the present invention includes a plurality of image forming bodies for forming respective toner images of yellow, magenta, cyan and black, and toner images formed on the plurality of image forming bodies. And an intermediate transfer member which is sequentially transferred and superposed, and a color image can be formed.

[0020]

According to the image forming apparatus as described above, the toner having the small particle diameter satisfying the condition 1 and the carrier having the small particle diameter satisfying the condition 2 are contained in the ratio satisfying the condition 3. By using a two-component developer, the main magnetic pole is provided in a specific arrangement state, the magnetic pole development is performed, and the free brush height of the magnetic brush is in a specific state satisfying the condition 4. Since the latent image on the photoconductor drum is developed in a state where only the tip of the photoconductor comes into contact with the photoconductor drum, it is basically clear and fine, and therefore a high-quality visible image equivalent to or better than offset printing, for example. Can be easily formed.

Further, by satisfying the conditions 5 and 6, the actual supply amount of the toner actually conveyed to the developing area is secured, and thus even in the developing performed in the above-mentioned state. As a result, it is possible to surely prevent the image density from being lowered, and thus it is possible to surely form a high-quality visible image.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory schematic diagram showing a configuration of an example of an image forming apparatus of the present invention, and FIG. 2 is an explanatory sectional view showing an enlarged example of the configuration of a developing device in the image forming apparatus. The image forming apparatus 10 is of a so-called in-body discharge type. Specifically, the front surface of the outer casing 11 (the surface on the front side relative to the paper surface) and one side surface (the left side surface in the drawing) of the outer casing 11. ), A sheet discharging portion 13 is provided in a recess 12 formed so as to open in a sheet receiving mechanism 13.
A is provided.

A manuscript image reading mechanism 15 for reading a manuscript image to acquire image data by optically scanning the manuscript is provided in the outer casing 11 at the upper position, and at the middle position, the manuscript image is read. An image forming unit 20 that forms a visible image based on image data from the reading mechanism 15 is provided, and a sheet supply unit 16 that stores a sheet of image recording material such as transfer paper at a lower position.
A and 16B are arranged. In the figure, 17 is a manual sheet feeding unit. Further, R is a reverse conveyance mechanism, and when a visible image is formed on both sides of a sheet,
It is for carrying again the sheet having the visible image formed on one surface thereof to the image forming unit 20.

In the image forming apparatus 10, selection and designation of conditions such as the number of copies, enlargement ratio or reduction ratio, recording material size performed in the operation unit, and a command signal by a series of command operations such as start of copying, The document image reading mechanism 15 optically scans the document to read the document image, and based on the image data from the document image reading mechanism 15, the image forming unit 20 causes the toner on the photosensitive drum 21 which is an image forming body. An image is formed, on the other hand, a sheet selected from the sheet feeding units 16A and 16B and the manual sheet feeding unit 17 is fed along the feeding path by the guide roller 181, and the inclination and the deviation of the sheet are corrected. Registration roller 1
By 82, the image is conveyed to the image forming unit 20 in synchronization with the toner image formed on the photosensitive drum 21 in the image forming unit 20.

Then, after the toner image formed by the image forming unit 20 is transferred to the conveyed sheet and a fixing process is performed in the fixing device 19, the surface on which the visible image is formed is faced down. Then, the discharge roller 18
The sheet 3 is discharged onto the sheet storage mechanism 13A. When a visible image is formed on both sides of the sheet, the sheet discharged from the fixing device 19 is conveyed along the reverse conveying path by the guide roller 181A, and the reverse roller 184 is used.
Thus, the other side of the sheet on which the visible image is formed faces the photoconductor drum 21 of the image forming unit 20 and is conveyed again toward the image forming unit 20 to form the visible image on the other side of the sheet. To be done.

As shown in FIG. 2, the image forming unit 20 includes a photosensitive drum 21 which is rotationally driven counterclockwise,
Along the outer circumference of the photosensitive drum 21, the photosensitive drum 2
It is composed of a charging device 22, an exposure device 23, a developing device 24, a transfer device 25, a separation device 26 and a cleaning device 30 which are arranged in the order of operation in the rotation direction of 1.

The photosensitive drum 21 is, for example, a drum-shaped metal substrate on which an appropriate photosensitive layer is formed, and the type of the photosensitive layer is not particularly limited. For example, selenium, An inorganic photosensitive layer made of arsenic selenium, amorphous selenium (a-Se), cadmium sulfide (CdS), zinc oxide (ZnO ₂ ), amorphous silicon (a-Si), an organic photosensitive layer made of an organic photoconductive compound, etc. Used and preferred is an organic photoreceptor having a photosensitive layer formed of a resin containing an organic photoconductor, and a function-separated type in which a charge transport layer and a charge generation layer are laminated. Particularly preferred.

The exposure device 23 is constituted by a laser irradiation device which constitutes a digital optical system for converting the digitized image data into an optical signal and exposes the photosensitive member, for example, a laser optical system. The laser light from a light source (not shown) is selectively applied to the surface of the photosensitive drum 21 via an optical system including a rotated polygon mirror, an fθ lens, and a cylindrical lens.

As shown in FIG. 2, the developing device 24
Is a rotary sleeve 40 for carrying and carrying the two-component developer on the surface (outer peripheral surface) in a housing 49 filled with the two-component developer consisting of toner and carrier.
And a developer amount regulating member 44 which is arranged so as to face the surface of the rotary sleeve 40 and regulates the thickness of the developer layer on the rotary sleeve 40. Reference numeral 45 is a paddle type developer carrying / supplying member for carrying and feeding the developer to the rotating sleeve 40 while stirring the developer, and 46 and 47 are spiral rotating screws for mixing the two-component developer in the housing 49. It is a developer stirring member that stirs and stirs.

The rotary sleeve 40 is made of, for example, aluminum, and its surface opposes the outer peripheral surface of the photosensitive drum 21 at a developing opening of the housing 49 with a slight gap, and in the developing area P due to this gap, the photosensitive sleeve is exposed. In order to move in the same direction as the body drum 21, it is configured to rotate in the clockwise direction shown by the arrow in the figure.

Inside the rotary sleeve 40, a plurality of fixed magnets for forming a magnetic brush of two-component developer are arranged on the surface of the rotary sleeve 40 to form a magnet system. In this magnet system, the first (first) one on the downstream side of the developer amount regulating member 44 in the rotation direction of the rotating sleeve 40 is the main developing magnetic pole M.
The main magnetic pole M is arranged in the vicinity of the closest position between the rotary sleeve 40 and the photosensitive drum 21, for example, at a position slightly upstream of the rotational direction of the photosensitive drum 21.

More specifically, as shown in FIG.
Position of the main magnetic pole M is a position displaced in the upstream side in the rotational direction of the photosensitive drum 21 than the straight line L ₀ connecting the center C ₀ of the center C ₁ and the photosensitive drum 21 of the rotary sleeve 40. That is, as shown in FIG. 3, when the rotary sleeve 40 and the photoconductor drum 21 move in the same direction in the developing area P, the position of the main magnetic pole M is displaced to the upstream side in the rotary direction of the rotary sleeve 40. When the rotary sleeve 40 and the photosensitive drum 21 move in opposite directions in the developing area P, the rotary sleeve 40 is positioned downstream of the rotary sleeve 40 in the rotational direction. Then, regardless of the rotating direction of the rotating sleeve 40, the rotating sleeve 40 and the photosensitive drum 2
1, the straight line L ₁ connecting the center of the rotary sleeve 40 and the main magnetic pole M to the straight line (the straight line connecting the center of the rotary sleeve 40 and the center of the photoconductor drum 21) L ₀ . The displacement angle θ formed by is preferably 5 ° or less.

According to such a configuration, the rotary sleeve 4
At 0, the maximum height position of the magnetic brush B formed by the main magnetic pole M is located slightly upstream in the rotational direction of the photoconductor drum 21 than the position of the rotary sleeve 40 closest to the photoconductor drum 21. In the developing area P in the gap between the rotary sleeve 40 and the photoconductor drum 21, the magnetic brush is used.
The electrostatic latent image on the photoconductor drum 21 is developed and a toner image is formed by being brought into contact with the surface of the photosensitive drum 21 under specific conditions.

At the position where the main magnetic pole M is arranged, the free brush height (the magnetic brush B formed on the surface of the rotary sleeve 40 without contacting the photosensitive drum 21) is freely formed. The maximum height of the bristles of the brush B is H (mm), and the separation distance (closest distance in the developing area P) between the rotary sleeve 40 and the photoconductor drum 21 is D (mm). At this time, the following condition 4 is satisfied.

Condition 4: Closest distance D in developing area P
The value of is in the range of 0.5H to 0.8H. This condition 4 includes the state of each part of the developing device, for example, the magnitude of the magnetic force of the main magnetic pole M, the rotation speed of the rotating sleeve 40, and the toner 2
It can be realized by appropriately setting the characteristics of the component developer and the other conditions. When the condition 4 is satisfied, the value of the free spike height H is 1.25 to 2 times the closest distance D in the developing area P.

In the image forming apparatus of the present invention, a two-component developer composed of a toner and a carrier which satisfy the following conditions 1 to 3 is used as the developer. Condition 1: The volume average particle diameter dt of the toner is in the range of 3 to 5 μm. With the small particle size toner satisfying the condition 1, a clear and highly reproducible visible image is basically obtained. That is, when such a toner having a small particle diameter is used, the image quality of halftone is improved, and the image quality of fine lines and dots can be improved.

Condition 2: Carrier volume average particle diameter dc (μ
m) is 5 dt to 10 dt. The carrier satisfying the condition 2 has a small particle size 5 to 10 times the volume average particle size of the toner, and the volume average particle size of the toner is 3 to 5 μm as described above. Diameter is 15-50
It is a carrier of μm.

By using such a carrier having a specific small particle diameter, the total surface area of the carrier becomes large.
In other words, the absolute amount of toner actually conveyed, that is, the actual supply amount is increased. In addition, since the degree of magnetization in the carrier is reduced, the formed magnetic brush B has a small free spike height H, and thus it is possible to easily realize the state that satisfies the condition 4 regarding the free spike height of the magnetic brush B. it can.

Condition 3: The ratio Rw of the weight of the toner to the weight of the carrier in the two-component developer is 1.6 (dt /
dc) × (ρt / ρc) to 2.4 (dt / dc) × (ρ
Be within the range of t / ρc). In the equation of Condition 3, ρt and ρc are the densities of toner and carrier (unit: g / cm ³ ), respectively. This Rw is 1.8 (dt / dc) × when the rotating sleeve 40 and the photosensitive drum 21 move in the same direction in the developing area P.
(Ρt / ρc) to 2.2 (dt / dc) × (ρt / ρ
c) is preferable (Condition 3A), and when moving in the opposite direction, 1.6 (dt / dc) × (ρt /
ρc) to 2.0 (dt / dc) × (ρt / ρc) is preferable (condition 3B).

The condition 3 defines the ratio of the total surface area of the toner to the total surface area of the carrier in the two-component developer, and is a factor relating to the coverage rate of the toner on the surface of the carrier.

Satisfaction of Condition 3 means that the surface coverage of the carrier with the toner (hereinafter simply referred to as "toner coverage") is substantially 45 to 65%, and , Condition 3A is satisfied,
It means that the toner coverage is substantially 50 to 60%, and that Condition 3B is satisfied means that the toner coverage is substantially 45 to 55%. Here, if Rw is too small and the toner coverage is too low, the actual supply amount of toner to the developing area P becomes insufficient, the image density in the formed visible image becomes insufficient, and the horizontal line thinning of the image occurs. On the other hand, when Rw is excessive and the toner coverage is too high, the toner is insufficiently charged, and fogging or the like may occur in a visible image formed.

In the above structure, the closest distance D between the rotary sleeve 40 and the photosensitive drum 21 is 0.
It is set to 2 to 0.6 mm, and preferably 0.24 to 0.5 mm. Further, the size of the free spike height H of the magnetic brush B formed on the rotary sleeve 40 by the main magnetic pole M is preferably 0.25 to 1.2 mm, and particularly 0.3 to 1.0 mm.

In the developing device, the following conditions are satisfied with respect to the actual developing conditions. Condition 5: The transport amount W of the two-component developer transported by the rotating sleeve 40 per unit area is 10 to 50 mg / cm.
Must be in the ² range. The condition 5 is satisfied
This value in the conventional image forming apparatus is 80 to 100 mg.
In consideration of the fact that the amount is about / cm ² , the amount of the transported developer is regulated to be small in the present invention.

By satisfying the condition 5, the free spike height H of the magnetic brush B by the main magnetic pole M on the surface of the rotary sleeve 40 is basically reduced, and therefore, the closest distance D is not increased. It becomes easy for the magnetic brush B to realize a “fine contact state” in which the magnetic brush B slightly contacts the photoconductor drum 21 at the tip of its ear. In an actual developing device, the distance between the developer amount regulating member 44 and the rotary sleeve 40 is usually preferably 0.2 to 0.6 mm.

In addition to the above, the development is carried out under the condition that the following condition 6 is satisfied. Condition 6: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of ² to 10 mg / cm ² . In particular, when the rotating sleeve 40 and the photosensitive drum 21 move in the same direction in the developing area P, it is preferable that the following condition 6A is satisfied, and when moving in the opposite direction, the following condition 6B is satisfied. Is preferably satisfied. Condition 6A: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of 4 to 8 mg / cm ² . Condition 6B: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of ² to 6 mg / cm ² . In the condition 6 or the condition 6A or the condition 6B, Tc represents the toner concentration (wt%) of the two-component developer, and Rv represents the ratio of the linear velocity Vs of the rotary sleeve 40 to the linear velocity Vp of the photosensitive drum 21 ( Vs / Vp) is shown.

When the condition 6 is satisfied, the maximum amount of toner adhering on the photosensitive drum 21 is, for example, 0.2 mg / cm ² , 0.3 mg / cm ² , 0.4 m within the range of the actual toner supply amount.
When g / cm ² and 0.5 mg / cm ² , the development efficiency is 2 to 10%, 3 to 15%, 4 to 20% and 5 to 25%, respectively.

As described above, the condition where the condition 6 is satisfied is
In the two-component developer conveyed to the developing area P, the actual supply amount of toner is regulated, and therefore,
The obtained visible image is prevented from being accompanied by such a bad effect that the image density becomes low.

The operation of the image forming apparatus having the above-described structure is as follows. An image of a document is read by the document image reading mechanism 15 to obtain image information, and an exposure device 23 performs exposure based on the image information to form an electrostatic latent image on the surface of the photoconductor drum 21. It
At the same time, the sheet feeding units 16A, 1
A transfer sheet, which is a recording material, is delivered from the 6B or the manual sheet feeding unit 17 and is conveyed toward the transfer unit 25 in a state of being synchronized with the photosensitive drum 21.

In the developing device 24, the housing 49
The toner and the carrier are stirred and mixed therein by the rotating screws 46 and 47, and the developer conveyed by the developer conveying and supplying member 45 adheres to the surface of the rotating sleeve 40 to form a developer layer. This developer layer is regulated to a predetermined amount by the developer amount regulating member 44 regulating the thickness thereof. This developer layer is conveyed to the developing area P by the rotation of the rotating sleeve 40.
In the developing area P, the developer layer is applied to the surface of the photoconductor drum 21 by the action of the main magnetic pole M and the magnetic brush B.
By forming and contacting the photosensitive drum 21.
In accordance with the electrostatic latent image formed on the surface of the toner, toner adheres and development is performed to form a toner image.

The toner image thus formed on the surface of the photosensitive drum 21 is transferred to the recording material such as paper conveyed by the transfer means 25 and is in close contact with the photosensitive drum 21. The recording material is separated from the photosensitive drum 21 by the separating means 26 immediately after the transfer of the toner image. The paper separated from the photoconductor drum 21 is conveyed toward the fixing device 19, the toner image is thermally fixed on the fixing device 19, and a visible image corresponding to the image of the original is formed on the paper. It is transported and discharged to the outside. In addition, the photoconductor drum 21 after the paper is separated
After passing through the cleaning device 30, the toner remaining on the surface is removed.

The two-component developer used in the image forming apparatus of the present invention comprises a non-magnetic toner and a magnetic carrier. As the non-magnetic toner, for example, a toner composed of colored particles containing a binder resin and a colorant is used, and a toner obtained by adding inorganic fine powder and the like to the toner powder is particularly preferable. The binder resin of the non-magnetic toner is not particularly limited, but a known resin such as a styrene resin, an acrylic resin, a styrene-acrylic copolymer resin, or a polyester resin can be used.

As the colorant used for the non-magnetic toner, for example, carbon black or nigrosine dye is used for the black toner, and the pigments necessary for the yellow, magenta and cyan toners are C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15, C.I.
I. Pigment Blue 15: 6, C.I. I. Pigment Blue 68, C.I. I. Pigment Red 48-3, C.I.
I. Pigment Red 122, C.I. I. Pigment Red 212, C.I. I. Pigment Red 57-1, C.I.
I. Pigment Yellow 17, C.I. I. Pigment Yellow 81, C.I. I. Pigment Yellow 154 and the like can be preferably used.

If necessary, the particles of the non-magnetic toner may contain a releasing agent, a charge control agent, a fluidizing agent, a lubricant, a cleaning aid, and other additives. Known ones can be used.

As a method for producing a non-magnetic toner, a polymerization method for obtaining a toner by utilizing emulsion polymerization or suspension polymerization can be used. According to this manufacturing method, it is possible to easily obtain a toner having a sharp physical property distribution such as a particle size distribution and a charge amount distribution, or a small-diameter spherical toner.
Further, in this method, inorganic fine powder can be added and mixed as an external additive.

As the carrier, conventionally known materials such as metals such as iron, ferrite and magnetite and alloys of these metals with metals such as aluminum and lead can be used. Ferrite particles are particularly preferable.

Examples of preferable carriers include resin-coated carriers in which the surface of magnetic particles is coated with a resin, and so-called resin dispersion type carriers in which magnetic particles are dispersed in a resin. The resin constituting the resin-coated carrier is not particularly limited, but examples thereof include olefin resin, styrene resin, styrene / acrylic resin, silicone resin, polyester resin, fluorine-containing polymer resin and the like. The resin constituting the resin-dispersed carrier is not particularly limited, and known ones can be used, for example, styrene-acrylic resin, polyester resin, fluorine resin, phenol resin and the like.

The two-component developer is prepared by mixing the above non-magnetic toner and magnetic carrier. When mixing the non-magnetic toner and the magnetic carrier, a conventionally known mixer can be used.
It is possible to use a mixer with less stress applied to the non-magnetic toner and the magnetic carrier, for example, a rotation mixer such as a V-shaped mixer, a W-cone mixer, a rocking mixer rather than a high-speed stirring mixer such as a Henschel mixer. preferable.

A bias voltage, for example, a DC voltage superimposed with an AC voltage is preferably applied to the rotary sleeve 40. As a result, the efficiency of peeling the toner from the carrier in the developing region P is improved, so that the so-called solid image density uniformity is ensured, and in this respect, a high-quality visible image can be formed.

According to the image forming apparatus of the present invention, the toner having the small particle diameter satisfying the condition 1 and the carrier having the small particle diameter satisfying the condition 2 are contained in the ratio satisfying the condition 3. By using the component developer, the main magnetic pole is provided in a specific arrangement state, development is performed on the magnetic pole, and the free brush height of the magnetic brush B is in a specific state that satisfies the condition 4. Since the latent image on the photoconductor drum 21 is developed in a slight contact state in which only the front end portion of B touches the photoconductor drum 21, it is basically clear and fine, and thus a high-quality visible image equivalent to, for example, offset printing. Can be easily formed.

Moreover, by satisfying the conditions 5 and 6, the actual supply amount of the toner actually conveyed to the developing area P is ensured, so that in the development performed in the above-described state. However, it is possible to reliably prevent the image density from being lowered, and thus it is possible to reliably form a high-quality visible image.

In the development on the magnetic pole by such a slight contact,
Compared to the conventional case where magnetic pole development is performed in a state where a magnetic brush is compressed, carrier adhesion is more likely to occur, but the present invention satisfies the following conditions. As a result, carrier adhesion is suppressed in practice, and the visible image is not adversely affected.

Condition: The main magnetic pole M is located closer to the photoconductor drum 21 than the closest position between the photoconductor drum 21 and the rotary sleeve 40.
It must be located near the upstream side of the rotation direction.
By satisfying this condition, an appropriate magnetic line of force is formed on the surface of the rotary sleeve 40, so that the magnetic brush B suddenly rises at the position where the photoconductor drum 21 is separated from the rotary sleeve 40, and the magnetic brush B rises to the photoconductor drum 21. The phenomenon that the carrier adheres is prevented, and the phenomenon such as so-called "character scattering" is prevented.

The image forming apparatus according to the present invention can be suitably implemented especially as a color image forming apparatus using an intermediate transfer body method. This color image forming apparatus is provided with, for example, four image forming units each having a photoconductor drum, and an intermediate transfer member made of, for example, an intermediate transfer belt, and the yellow and magenta formed by each image forming unit. The cyan, black, and black toner images are sequentially transferred to the intermediate transfer member and superimposed, whereby a full-color color image is formed. Then, by satisfying all of the above conditions, a color visible image of extremely high quality is formed.

[0064]

EXAMPLES Examples of the present invention will be described below.
The present invention is not limited to these.

<Example> An image forming apparatus equipped with the developing device having the structure shown in FIG. 2 was manufactured in accordance with the structure shown in FIG. In this image forming apparatus (10), the photoconductor drum (21) is made of an organic photoconductor having a diameter of 60 mm, and the developing device (24) is formed by subjecting an outer peripheral surface of an aluminum sleeve material having a diameter of 25 mm to a stainless steel spray treatment. It has a rotating sleeve (40) roughened to have a surface roughness Ra of 1.0 μm, and inside thereof, a magnet system made of ferrite forming a main magnetic pole (M) is provided. Further, a developer amount regulating member (44) made of aluminum is arranged so as to face the rotating sleeve (40).

The specific specifications of each part and the conditions of the two-component developer in this image forming apparatus are as follows. Two
The toner of the component developer has a volume average particle diameter dt of 4.0 μm produced by an emulsion polymerization method of styrene-acryl,
The density ρt was 1.1 g / cm ³ (condition 1). The carrier has a volume average particle size dc of 3 in which the surface of magnetic particles made of ferrite is coated with a silicone resin.
The density is 0 μm and the density ρc is 4.5 g / cm ³ , and this value corresponds to dc = 7.5 dt (condition 2).

The two-component developer is obtained by mixing the toner and the carrier in a proportion such that the toner concentration Tc is 6.0% by mass, and the weight ratio Rw of the toner and the carrier in the two-component developer is 0. 0.06 and 2.0 (dt / d
c) × (ρt / ρc) (condition 3).

In the developing device, the rotating sleeve (40)
Is in the same direction as the photosensitive drum (21), and the magnitude of the displacement angle θ of the main magnetic pole (M) provided inside the rotating sleeve (40) is upstream in the rotating direction of the photosensitive drum (21). 5 ° to the side (upstream in the direction of rotation of the rotating sleeve (40))
And the magnetic brush B formed by the main pole (M)
The free spike height H is 0.8 mm, and the closest distance between the rotary sleeve (40) and the photosensitive drum (21) is 0.5 m.
m, and this closest distance D corresponds to 0.63H (condition 4).

Further, the linear velocity Vp of the photosensitive drum (21)
Is 180 mm / sec, the linear velocity Vs of the rotating sleeve (40) is 540 mm / sec, and Rv (= Vs / V
Under the condition that the value of p) is 3.0, the separation distance between the surface of the rotary sleeve (40) and the developer amount regulating member (44) is 0.4 mm, which allows the two-component developer to be conveyed. The amount W was set to 35 mg / cm ² (condition 5). From the above, the actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 was 6.3 mg / cm ² .

Further, for the rotating sleeve (40),
A developing bias voltage in which a peak-to-peak voltage of 1.5 kV and an AC voltage having a frequency of 2 kHz were superimposed on a DC voltage of -600 V was applied.

A continuous 10,000 visible images were formed by operating the image forming apparatus having the above configuration, and the image density, fog, line width, character quality and carrier adhesion were evaluated by the following evaluation methods. All visible images obtained were of very high quality.

[Image Density] The transmission density of the solid portion is measured by an image evaluation device “imageXpert” (ImageXpe).
rt). [Fog] Image evaluation device "im
The relative reflection density of the paper is 0.00 by "ageXpert".
It was measured as 0.

[Line Width] The line width of a 2-dot horizontal line having a writing density of 400 dpi was measured by an image evaluation device “imageXpert”. (Evaluation method) A line width of 115 μm or more and 135 μm or less. X: Line width less than 115 μm or line width over 135 μm. [Character quality] Three-point alphabetic characters (“KONICA”) and six-point Japanese characters (“Gion Seisha no Bell Bell Voice”) are magnified and observed with a digital microscope (manufactured by KEYENCE CORPORATION), and the sharpness of the edges (sharp And the toner scattering (scattering of characters) around the edges. (Evaluation method) ⊚: Characters are not scattered, and the sharpness (sharpness) of the edge and the tip of the character is very excellent. ○: Characters are not scattered, and sharpness is also good. X: Character scatter is conspicuous and inferior in sharpness.

[Carrier Adhesion] The presence or absence of the carrier adhered to the background portion adjacent to the 2-dot vertical line was visually observed, and the white spots in the solid portion (the carrier came off when the carrier adhered to the photosensitive drum). After that, the presence or absence of white spots) was visually observed. (Evaluation method) O: No adhesion of carrier on the background and generation of white spots. × ... One or both of adhesion of carrier on the background and white spots occurred.

<Image Forming Test> In accordance with the conditions shown in Tables 1 and 2, various conditions of each part of the image forming apparatus were variously changed and the same visible image forming test was conducted and evaluated. Although Table 1 and Table 2 are divided for convenience of description, they should be understood as one piece. In Table 1, α in “Rw / α” among the items listed in the condition 3 column is (dt / dc) ×
(Ρt / ρc) (same in Table 3).

[0076]

[Table 1]

[0077]

[Table 2]

In the developing device having the structure shown in FIG. 2, the position of the developer amount regulating member (44) is set to the housing (4
9) Change to the lower part (bottom side) in the rotating sleeve (4
0) is the opposite direction to the photosensitive drum (21),
Main magnetic pole (M) provided inside the rotating sleeve (40)
Of the displacement angle θ of 5 to the upstream side in the rotation direction of the photosensitive drum (21) (downstream side in the rotation direction of the rotating sleeve (40)).
The same visible image forming test was carried out by using the developing device having the above constitution and various conditions of each part of the image forming apparatus were changed according to the conditions shown in Tables 3 and 4, and the evaluation was conducted.

[0079]

[Table 3]

[0080]

[Table 4]

As is clear from the results of Tables 1 to 4, according to the present invention, a large number of visible images of extremely high image quality can be stably formed.

As described above, according to the image forming apparatus of the present invention, the toner having the small particle size satisfying the condition 1 and the carrier having the small particle size satisfying the condition 2 have a ratio satisfying the condition 3. The main magnetic pole is provided in a specific arrangement using the contained two-component developer to perform the development on the magnetic pole, and the free brush height of the magnetic brush is in a specific state that satisfies Condition 4. As a result, the latent image on the photoconductor drum is developed in a slight contact state where only the tip of the magnetic brush comes into contact with the photoconductor drum. An image can be easily formed.

Further, according to the image forming apparatus of the present invention, since the conditions 1, 4, 5, and 6 are satisfied, the actual amount of toner actually fed to the developing area P is reduced. By ensuring the above, it is possible to reliably prevent the image density from being lowered even in the development performed in the above-described state, and thus it is possible to reliably form a high-quality visible image.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a configuration in an example of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing an outline of a configuration of an image forming unit in the image forming apparatus shown in FIG.

3 is an explanatory diagram of a developing device of the image forming apparatus of FIG.

[Explanation of symbols]

10 image forming apparatus 11 outer casing 12 recess 13 Sheet ejection section 13A seat accommodation mechanism 15 Original image reading mechanism 16A, 16B sheet supply unit 17 Manual sheet feeding unit R Reverse transport mechanism 181,181A Guide roller 182 Registration roller 183 discharge roller 184 Reversing roller 19 Fixing device 20 Image forming unit 21 photoconductor drum 22 charging means 23 Exposure equipment 24 Developing device 25 Transfer means 26 Separation means 30 cleaning device 40 rotating sleeve 44 Developer amount control member 45 Developer Transport Supply Member 46,47 rotating screw 49 housing P development area M main pole B magnetic brush

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/06 101 G03G 15/06 101 15/08 504 15/08 504A 506 506A (72) Inventor Takenobu Kimura Tokyo 2970 Ishikawa-cho, Hachioji-shi Konica stock company (72) Inventor Yotaro Sato 2970 Ishikawa-cho, Hachioji-shi Konica stock company F-term (reference) 2H005 EA05 EA07 EA10 2H031 AC08 AC14 AC18 AC19 AC20 AC30 AD03 AD15 BA05 BA09 CA11 CA13 FA01 2H073 AA01 BA04 BA13 BA43 CA03 CA22 2H077 AD02 AD06 AD13 AD17 AD36 BA03 BA07 EA01 EA03 FA19 GA13 2H300 EB04 EB07 EB12 EC02 EC05 EF03 EF09 EG03 EH16 EJ02 EJ09 EJ22 EJ26 EJ33 EJ35 EJ42 EJ47 EJ50 EJ52 FF05 GG02 GG11 HH14 HH16 MM11 PP06

Claims (13)

[Claims] 1. An image forming body, and a developing device for developing the latent image formed on the image forming body with a two-component developer consisting of toner and carrier, the developing device facing the image forming body. A rotary sleeve for carrying the two-component developer and a plurality of magnetic poles for forming a magnetic brush of the two-component developer on the surface of the rotary sleeve. An image forming apparatus having a magnet system to be formed and a developer amount regulating member which is arranged so as to face a surface of a rotating sleeve and regulates the amount of the two-component developer conveyed by the rotating sleeve. The volume average particle diameter of the toner in the agent is dt (μ
m), the density is ρt (g / cm ³ ), the volume average particle size of the carrier is dc (μm), the density is ρc (g / cm ³ ), and the weight ratio of the toner and the carrier (of the weight of the toner to the weight of the carrier is When the ratio is Rw, Condition 1: The volume average particle diameter dt of the toner is in the range of 3 to 5 μm, Condition 2: The volume average particle diameter dc of the carrier is 5dt to 10d.
and the condition 3: the weight ratio Rw of the toner and the carrier is 1.6 (d
t / dc) × (ρt / ρc) to 2.4 (dt / dc) ×
The main magnetic pole forming the strongest magnetic field on the surface of the rotating sleeve among the plurality of magnetic poles in the magnet system is the closest position between the rotating sleeve and the image forming body. When the free brush height of the magnetic brush formed at the position of the main magnetic pole is H (mm) and the closest distance between the rotating sleeve and the image forming body is D (mm), the condition is 4: An image forming apparatus characterized in that the closest distance D is satisfied in the range of 0.5H to 0.8H. 2. The image forming apparatus according to claim 1, wherein in the developing device, a bias voltage in which a DC voltage is superimposed on an AC voltage is applied to the rotary sleeve. 3. In the developing area where the rotary sleeve faces the image forming body, the moving directions of the rotary sleeve and the image forming body are the same, and in the two-component developer, the weight ratio R of the toner to the carrier is R.
The image forming apparatus according to claim 1 or 2, wherein the following condition 3A is satisfied for w. Condition 3A: Weight ratio Rw of toner to carrier is 1.8.
(Dt / dc) × (ρt / ρc) to 2.2 (dt / d)
c) Be within the range of (ρt / ρc). 4. In a developing area where the rotary sleeve faces the image forming body, the moving directions of the rotary sleeve and the image forming body are opposite to each other, and in the two-component developer, the weight ratio R of the toner to the carrier is R.
The image forming apparatus according to claim 1 or 2, wherein the following condition 3B is satisfied for w. Condition 3B: The weight ratio Rw of the toner and the carrier is 1.6.
(Dt / dc) × (ρt / ρc) to 2.0 (dt / d
c) Be within the range of (ρt / ρc). 5. The developing device, wherein the main magnetic pole is arranged upstream of the closest position between the rotating sleeve and the image forming body in the moving direction of the image forming body.
The image forming apparatus according to claim 4. 6. A plurality of image forming bodies each forming a toner image of each color of yellow, magenta, cyan and black,
A color image is formed by comprising an intermediate transfer member on which the toner images formed on the plurality of image forming members are sequentially transferred and superposed. Item 6. The image forming apparatus according to any one of items 5. 7. An image forming body, and a developing device for developing the latent image formed on the image forming body with a two-component developer consisting of toner and carrier, the developing device facing the image forming body. A rotary sleeve for carrying the two-component developer and a plurality of magnetic poles for forming a magnetic brush of the two-component developer on the surface of the rotary sleeve. An image forming apparatus having a magnet system to be formed and a developer amount regulating member which is arranged so as to face a surface of a rotating sleeve and regulates the amount of the two-component developer conveyed by the rotating sleeve. The volume average particle diameter of the toner in the agent is dt (μ
m), the transport amount per unit area of the two-component developer transported by the rotary sleeve is W (mg / cm ² ), the toner concentration in the two-component developer is Tc (wt%), and When the ratio of the moving speed of the rotating sleeve is Rv, Condition 1: The volume average particle diameter dt of the toner is in the range of 3 to 5 μm, Condition 5: The transport amount W of the two-component developer is 10 to 50 mg / c.
m ² and the condition 6: the actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is within the range of ² to 10 mg / cm ² , and the magnet system is satisfied. The main magnetic pole that forms the strongest magnetic field on the surface of the rotating sleeve among the plurality of magnetic poles is located near the closest position between the rotating sleeve and the image forming body, and is formed at the position of the main magnetic pole. When the free brush height of the magnetic brush is H (mm) and the closest distance between the rotating sleeve and the image forming body is D (mm), Condition 4: The closest distance D is in the range of 0.5H to 0.8H. An image forming apparatus characterized by satisfying certain things. 8. The volume average particle diameter of the toner in the two-component developer is dt (μm), the density is ρt (g / cm ³ ), the volume average particle diameter of the carrier is dc (μm), and the density is ρc (g / g / cm ³ ). c
m ³ ), where Rw is the weight ratio of the toner to the carrier (ratio of the weight of the toner to the weight of the carrier), Condition 2: The volume average particle diameter dc of the carrier is 5 dt to 10 d
and the condition 3: the weight ratio Rw of the toner and the carrier is 1.6 (d
t / dc) × (ρt / ρc) to 2.4 (dt / dc) ×
The image forming apparatus according to claim 7, wherein the condition (ρt / ρc) is further satisfied. 9. The image forming apparatus according to claim 7, wherein in the developing device, a bias voltage obtained by superimposing an AC voltage on a DC voltage is applied to the rotary sleeve. 10. A developing region in which the rotating sleeve faces the image forming body, the moving directions of the rotating sleeve and the image forming body are the same, and the following condition 6A is satisfied.
The image forming apparatus according to claim 9. Condition 6A: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of 4 to 8 mg / cm ² . 11. The developing region in which the rotating sleeve faces the image forming body, the moving directions of the rotating sleeve and the image forming body are opposite to each other, and the following condition 6B is satisfied.
The image forming apparatus according to claim 9. Condition 6B: The actual supply amount of the toner represented by the formula (W × Tc × Rv) / 100 is in the range of ² to 6 mg / cm ² . 12. The developing device, wherein the main magnetic pole is arranged upstream of the closest position between the rotating sleeve and the image forming body in the moving direction of the image forming body. Item 12. The image forming apparatus according to any one of items 11. 13. A plurality of image forming bodies forming toner images of respective colors of yellow, magenta, cyan and black, and toner images formed on the plurality of image forming bodies are sequentially transferred. The image forming apparatus according to claim 7, further comprising: an intermediate transfer member that is superposed on the intermediate transfer member to form a color image.