JP2003255710A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device and an image forming apparatus which are used for a long term only by replenishing toner without replacing parts even when used as a high speed apparatus. <P>SOLUTION: The developing device includes: a developer t, a developer carrier 41, and a developer restricting member 45 arranged at a position separated from the developer carrier 41. Magnetic toner t of one component system is used as the developer, wherein a volume average particle size is 6.0-10.0 μm, the proportion of the 5 μm or less particle size is 6.0-10.0 vol.%, and saturation magnetization is 16-27 Am<SP>2</SP>/kg. The developer carrier 41 includes a freely rotatable development sleeve 41a; and a magnet roller 41b which is incorporated into and fixed to the development sleeve 41a. In the magnet roller 41b, a first magnetic pole S<SB>2</SB>with a magnetic force of 800×10<SP>-4</SP>to 1,000×10<SP>-4</SP>T is arranged at the opposite position of the developer restricting member 45, and a second magnetic pole N<SB>2</SB>with a polarity reverse to that of the first magnetic pole S<SB>2</SB>, and with the magnetic force of 300×10<SP>-4</SP>to 500×10<SP>-4</SP>T is arranged at the position of 70-90° from the opposite position in the reverse direction of a development sleeve rotating direction. A magnet 45a with the magnetic force of 350×10<SP>-4</SP>to 600×10<SP>-4</SP>T is adopted as the developer restricting member 45. <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 a developing device and an image forming apparatus using the same, and more specifically, a one-component magnetic toner (hereinafter may be simply referred to as "toner").
The present invention relates to a developing device using the image forming apparatus and an image forming apparatus using the developing device.

[0002]

2. Description of the Related Art In conventional image forming apparatuses, the photoconductor and the members arranged around the photoconductor are integrated as a developing unit, and after a predetermined number of images are formed, the development is performed by placing importance on the convenience of parts replacement. I was replacing the whole unit with a new one. However, as environmental awareness has increased in recent years, there has been a strong demand for reduction of disposable parts and extension of life of each part. In order to meet such demand, even in image forming apparatuses such as copiers and printers, a model that can be used for a long period of time without replacing the developing unit instead of replacing the entire developing unit but only replenishing toner consumption・ Various developments have been made. As a result, a so-called low / medium speed machine having an image forming speed of about 40 sheets / minute or less has already become commercially available, which can achieve the above-mentioned effects.

[0003]

However, in a so-called high-speed machine whose image forming speed exceeds 40 sheets / minute,
It is difficult to use the toner for a long time (for example, 50,000 sheets) only by replenishing the toner without replacing the parts.

The present invention has been made in view of such conventional problems, and it is an object of the present invention to develop a toner that can be used for a long period of time only by replenishing toner without replacing parts even when used in a high speed machine. An apparatus and an image forming apparatus are provided.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, set each physical property of each of the developer, the developer carrying member, and the developer regulating member to a specific range, and Only by combining them,
The present invention has been completed by finding that it is possible to form an image of more than 50,000 sheets only by replenishing toner without replacing parts.

That is, the developing device of the present invention comprises a developer,
The developer carrying member and the developer carrying member are arranged at a position apart from the developer carrying member.
A developing device including a provided developer regulating member,
The developer has a volume average particle diameter of 6.0 to 10.0 μm.
And the proportion of particles having a particle diameter of 5 μm or less is 6.0 to 10.0 vol%
And the saturation magnetization is 16-27 emu / g, a one-component magnetic system
The developer carrier is toner, and the developer carrier is rotatable.
Reeve and magnet fixed inside this developing sleeve
A roller, and the developer regulation of the magnet roller.
The magnetic force is 800 × 10 at the facing position of the control member.^-Four~ 1000x
10^-FourFrom the first magnetic pole of T and the facing position,
The magnetic force is 3 at the position of 70-90 ° in the opposite direction to the rotary direction.
00 x 10^-Four~ 500 × 10^-FourT has the opposite polarity to the first magnetic pole
The second magnetic poles are respectively magnetized, and the developer regulating member is
Magnetic force 350 × 10^-Four~ 600 x 10 ^-FourWith a T magnet,
Magnetic toner on the developing sleeve by the developer regulating member
It is characterized in that a thin layer is formed and development is performed.

Here, from the viewpoint of further suppressing problems such as reduction in image density, a third magnetic pole having a magnetic force of 800 × 10 ^{−4 to} 1000 × 10 ⁻⁴ T is magnetized at a position facing the image carrier of the magnet roller. Is preferred. Further, in order to maintain the image density while suppressing the increase in the fog density, it is preferable that the gap between the developer carrying member and the developer regulating member be in the range of 0.25 to 0.40 mm.

Further, the image forming apparatus of the present invention which achieves the above object, irradiates an image carrier, a charging means for charging the surface of the image carrier, and a light to the charged surface of the image carrier. Exposure means for forming an electrostatic latent image, developing means for supplying a developer to the electrostatic latent image for development, and transfer for transferring the developer of the image carrier developed by the developing means to a transfer target member. An image forming apparatus having means, wherein the developing device described above is used as the developing means.

From the viewpoint of suppressing the increase in fog density and improving the image quality, the gap between the image carrier and the developing sleeve is made larger than the thickness of the magnetic toner thin layer formed on the developing sleeve, and the image is formed. It is desirable to apply an AC bias voltage between the carrier and the developing sleeve to supply a developer to the electrostatic latent image for development.

To further suppress the increase in fog density,
It is preferable that a magnetic toner having the same polarity as that of the non-exposed portion of the image carrier is attached to the exposed portion to develop the electrostatic latent image.

For use without replacement for a long period of time, it is preferable to use an amorphous silicon photoconductor as the image bearing member.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, each constitution of the developing device of the present invention will be explained in order. First, the one-component magnetic toner used in the developing device of the present invention will be described. The volume average particle diameter of the magnetic toner is 6.0 to 10.0 μm. This is because if the volume average particle diameter of the toner deviates from the above range, the image density becomes insufficient from the initial stage, and if the volume average particle diameter is smaller than 6.0 μm, the fog density becomes high. A more preferable range of the volume average particle size is 7.0 to 9.0 μm.

The ratio of toner particles having a particle size of 5 μm or less is 6.0.
It is important to be ˜10.0 vol%. Particle size 5μ
When the ratio of m or less is less than 6.0 vol%, the image density becomes insufficient from the initial stage. On the other hand, if it is more than 10.0 vol%, the image density becomes insufficient and the fog density becomes high. A more preferable ratio of particle size of 5 μm or less is 7.0.
It is in the range of 9.0 vol%.

Further, the saturation magnetization of the toner is 16 to 27 em.
It must be in the u / g range. Toner saturation magnetization is 16
If it is smaller than emu / g, the fog density becomes high, while on the other hand, it becomes 2
This is because if it is larger than 7 emu / g, the image density will be insufficient from the initial stage. More preferable saturation magnetization is 20 to 24 emu.
/ G range. In addition, in the present specification, the saturation magnetization is measured by using a magnetic field of 7 by using "VSM-P7" manufactured by TOEI.
It is measured at 9.6 kA / m (1 kOe).

Such a toner can be manufactured by a method known per se such as a pulverizing and classifying method, a melt granulating method, a spray granulating method, and a suspension / emulsion polymerization method. Therefore, the pulverizing and classifying method can be preferably used. In such a pulverizing and classifying method, a binder resin, magnetic particles, and if necessary, a colorant,
A toner composition such as a charge control agent and a release agent is pre-mixed with a Henschel mixer, a V-type mixer, or the like, and then melt-kneaded using a melt-kneading device such as a twin-screw extruder. After this melt-kneaded product is cooled, it is roughly pulverized and finely pulverized, and if necessary, then classified to obtain toner particles having a predetermined particle size distribution. Then, if necessary, the surface of the toner particles is treated with a surface treating agent to obtain a toner. It should be noted that in order to bring the particle size distribution of the toner into the above-mentioned range, various conditions such as the air volume and the air speed of the classifier in the classifying step may be adjusted, or the toner fine powder prepared separately may be mixed. . Further, the saturation magnetization of the toner can be set within the specified range by adjusting the type and content of the magnetic substance contained in the toner.

The binder resin used for the toner is not particularly limited, and examples thereof include styrene-acrylic resin and polyester resin. Of course, if necessary, other resins may be used in combination with these resins.

Examples of the styrene-acrylic resin base monomer include styrene, α-methylstyrene, p
-Styrene derivatives such as methylstyrene, pt-butylstyrene, p-chlorostyrene and hydroxystyrene;
Methacrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, glycidyl (meth)
Acrylate, methoxyethyl (meth) acrylate,
Propoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate,
(Meth) acrylonitrile, (meth) acrylamide,
N-methylol (meth) acrylamide, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, trimethylolethane tri (meth) acrylate, etc. (Meth) acrylic acid ester can be mentioned.

The mixture of various monomers described above can be polymerized by any method such as solution polymerization, bulk polymerization, emulsion polymerization and suspension polymerization to obtain the binder resin used in the present invention. Polymerization initiators that can be used in such polymerization include acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, and 2 A known polymerization initiator such as 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile can be used. These polymerization initiators are preferably used in the range of 0.1 to 15% by weight based on the total weight of the monomers.

The polyester resin is mainly obtained by polycondensation of polyvalent carboxylic acids and polyhydric alcohols, and examples of the polyvalent carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, 1,
Aromatic polycarboxylic acids such as 2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid and pyromellitic acid; maleic acid, fumaric acid, succinic acid, adipine Acids, sebacic acid, malonic acid, azelaic acid, mesaconic acid, citraconic acid, glutaconic acid and other aliphatic dicarboxylic acids; cyclohexanedicarboxylic acid, methylmedic acid and other alicyclic dicarboxylic acids; anhydrides and lower alkyl esters of these carboxylic acids And one or more of these are used.

The content of the trivalent or higher valent component depends on the degree of crosslinking, and the addition amount may be adjusted to obtain the desired degree of crosslinking. Generally, the content of trivalent or higher components is 1
It is preferably 5 mol% or less.

On the other hand, the polyhydric alcohols used for the polyester resin include, for example, ethylene glycol,
Alkylene glycols such as 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, neopentyl glycol, 1,5-pentane glycol and 1,6-hexane glycol Alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol;
Alicyclic polyhydric alcohols such as 1,4-cyclohexanedimethanol and hydrogenated bisphenol A; bisphenols such as bisphenol A, bisphenol F and bisphenol S, and alkylene oxides of bisphenols, and one of these Alternatively, two or more kinds can be used in combination.

If desired, monocarboxylic acid or monoalcohol may be used for the purpose of adjusting the molecular weight or controlling the reaction. Examples of the monocarboxylic acid include benzoic acid, parahydroxybenzoic acid, toluenecarboxylic acid, salicylic acid, acetic acid, propionic acid and stearic acid. Examples of the monoalcohol include benzyl alcohol, toluene-4-methanol and cyclohexanemethanol.

The binder resin used has a glass transition temperature of 45.
Those in the range of to 90 ° C are preferable. Glass transition temperature is 4
If the temperature is lower than 5 ° C., the toner may be solidified in the toner cartridge or the developing device. On the other hand, if the temperature is higher than 90 ° C., the toner may not be sufficiently fixed on the transferred material such as paper.

Further, in the case of a magnetic toner, since the toner color is black due to the magnetic particles, it is generally unnecessary to use a colorant when used as a black toner, but acetylene black, run black, aniline black or the like is used as a color reinforcement. Carbon black may be dispersed and mixed in the toner particles. In this case, the content of the coloring agent is 10
It is about 0.1 to 10 parts by weight with respect to 0 parts by weight.

The magnetic particles added to the binder resin include, for example, iron trioxide (Fe ₃ O ₄ ) and iron sesquioxide (γ-Fe).
₂ O ₃ ), zinc iron oxide (ZnFe ₃ 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 ( N
dFeO ₃ ), iron oxide barium (BaFe ₁₂ O ₁₉ ), iron oxide magnesium (MgFe ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ),
Iron powder (Fe), cobalt powder (Co), nickel powder (N
i) etc. are mentioned. A particularly suitable magnetic particle is finely particulate iron trioxide (magnetite). The preferred magnetite has a regular octahedral shape and a particle size of 0.05 to 1.0 μm. The magnetite particles may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like. The content of the magnetic particles is preferably 50 to 30 parts by weight, and particularly preferably 70 to 150 parts by weight, per 100 parts by weight of the binder resin.

As the charge control agent, conventionally known charge control agents can be used. For example, as the positively chargeable charge control agent, nigrosine dye, fatty acid modified nigrosine dye, carboxyl group-containing fatty acid modified nigrosine dye, quaternary ammonium salt can be used. , Amine compounds, organometallic compounds and the like can be used, and as the negatively chargeable charge control agent, metal complexes of oxycarboxylic acid, metal complexes of azo compounds, metal complex salt dyes, salicylic acid derivatives and the like can be used.

Various waxes and low molecular weight olefin resins can be used as the release agent. Examples of waxes include polyhydric alcohol esters of fatty acids,
Higher alcohol esters of fatty acids, alkylene bis fatty acid amide compounds and natural waxes can be used. The low molecular weight olefin resin has a number average molecular weight of 1,000 to 10,000, particularly 2,000 to 6,0.
In the range of 00, polypropylene, polyethylene, propylene-ethylene copolymer and the like can be used, and polypropylene can be particularly preferably used.

As the surface treatment agent, an inorganic material such as (hydrophobic) silica, alumina, titanium oxide, zinc oxide, magnesium oxide, calcium carbonate, etc. is used in order to adjust the charge controllability and bulk density (fluidity) of the toner. Fine powders; organic fine powders such as polymethylmethacrylate; fatty acid metal salts such as zinc stearate; and the like, and one or more of these may be used in combination. The amount of surface treatment agent added is
The range of 0.1 to 2.0 wt% per toner is preferable.
The surface treatment agent and the toner particles can be mixed using, for example, a Henschel mixer, a V-type mixer, a Turbula mixer, a hybridizer, or the like.

The developer carrying member used in the present invention comprises a developing sleeve and a magnet roller fixedly incorporated in the developing sleeve. Then, a magnetic force of 800 × 10 ^{−4 to} 1000 × is applied to a position of the magnet roller facing the developer regulating member.
The first magnetic pole of 10 ⁻⁴ T (S ₂ in FIG. 1) is magnetized.
By the cooperative action of the first magnetic pole and the developer regulating member,
A uniform thin toner layer is formed on the developing sleeve, and the toner is charged. When the magnetic force of the first magnetic pole is lower than 800 × 10 ⁻⁴ T, the fog density is high from the initial stage because the toner is not uniformly charged. on the other hand,
When the magnetic force is higher than 1000 × 10 ⁻⁴ T, the toner charge amount becomes too high and the image density becomes insufficient from the initial stage. In this specification, the magnetic force refers to the direction of the normal line, and is measured as follows. First, regarding the magnetic force of the magnetic poles of the magnet roller, fix the developer carrier to the jig,
Apply the magnetic force measurement probe to the developing sleeve. A Gauss meter ("TGM-8900F" manufactured by Toyo Magnetic Industry Co., Ltd.) is connected to the magnetic force measurement probe. Then, the magnet roller in the developing sleeve is rotated to measure the magnetic force of each magnetic pole magnetized in the magnet roller. The magnetic force of the developer regulating member described later is also measured using this magnetic force measuring probe and a Gauss meter.

Further, a magnetic force of 300 × 10 ^{−4 to} 500 × 10 ⁻⁴ T with a magnetic force of 300 × 10 ^{−4 to} 500 × 10 ⁻⁴ T at a position of 70 to 90 ° in the direction opposite to the developing sleeve rotation direction from the position facing the developer regulating member is applied. Two magnetic poles (N ₂ in FIG. 1) are magnetized. This second
The magnetic pole has an effect of pumping the toner in the developing device onto the developing sleeve by a predetermined amount, and also has an effect of rotating and charging the toner on the developing sleeve in cooperation with the first magnetic pole. If the magnetic force of the second magnetic pole is smaller than 300 × 10 ⁻⁴ T,
Since the amount of toner scooped onto the developing sleeve is small, the image density is low from the initial stage. On the other hand, the magnetic force is 500 × 1
If it is larger than 0 ⁻⁴ T, the amount of toner on the developing sleeve becomes too large, so that sufficient charge cannot be imparted by the developer regulating member and the image density is lowered.

In addition, it is preferable to magnetize a third magnetic pole (N ₁ in FIG. ₁ ) having a magnetic force of 800 × 10 ^{−4 to} 1000 × 10 ⁻⁴ T at a position facing the image carrier of the magnet roller.
This third magnetic pole directly affects the development of the electrostatic latent image. If the magnetic force of the third magnetic pole is less than 800 × 10 ⁻⁴ T, the toner can be easily separated from the developing sleeve, so that the electrostatic latent image is formed. The toner may adhere to other portions, and the fog density may increase. On the other hand, if the magnetic force is larger than 1000 × 10 ⁻⁴ T, the toner cannot be separated from the developing sleeve, which may lower the image density. Note that it is of course possible to further form magnetic poles on the magnet roller.

The surface roughness of the developing sleeve is 3.0 μm in order to improve the toner transportability and obtain a uniform thin layer.
m or more, on the other hand, if the surface roughness is too large, the toner enters the concave portion of the surface of the current developing sleeve and is fused.
The upper limit is preferably 5.5 μm. A more preferable surface roughness is in the range of 3.5 to 4.5 μm. The surface roughness represents a ten-point average roughness defined by JIS B0601. To make the surface roughness of the developing sleeve within the above range, for example, the developing sleeve may be blasted, and the type of blasting material, compressed air pressure, blasting time,
A desired surface roughness may be obtained by appropriately adjusting the distance between the blast nozzle and the developer carrying member. Examples of the blast material used here include sand, glass beads, and steel balls. The material of the developing sleeve is preferably non-magnetic material such as stainless steel or aluminum alloy, and stainless steel is preferable in consideration of wear resistance.

Next, the developer regulating member used in the developing device of the present invention is provided with a magnet having a magnetic force of 350 × 10 ⁻⁴ to 600 × 10 ⁻⁴ T and is arranged at a position separated from the developing sleeve. By passing the toner between the developer regulating member and the developing sleeve, a thin toner layer is formed on the developing sleeve. If the magnetic force of the magnet is less than 350 × 10 ⁻⁴ T, the thin layer formation becomes uneven. On the other hand, if the magnetic force is greater than 600 × 10 ⁻⁴ T, the thin layer becomes too thin and the amount of toner is small. There is a problem that the image density is decreased and the image density is decreased.
More preferable magnetic force range is 400 × 10 ^{−4 to} 500 × 1.
It is 0 ^-4 T.

The gap between the developer regulating member and the developing sleeve may be appropriately determined in view of the thickness of the toner thin layer to be obtained, the toner charge amount, etc., but is generally 0.25 to 0.40.
The range of mm is preferred. If the gap is narrower than 0.25 mm, the toner necessary for developing the electrostatic latent image may not be conveyed to the developing section, while if it is wider than 0.40 mm, a uniform toner charge amount may not be obtained. Is.

FIG. 1 is a sectional view showing an example of the developing device of the present invention. The developing device 4 includes a magnet roller 41.
The developer carrying member 41 in which b is fixedly incorporated in the developing sleeve 41a, the spiral first stirring and conveying member 42, and the spiral second stirring and conveying member 43 are also provided. A blade (developer regulating member) 45 having a magnet 45a on the lower surface thereof is arranged at a right upper portion of the developing sleeve 41a at a predetermined distance from the developing sleeve 41a. Pole the blade facing the position of the magnet roller 41b built in the developing sleeve 41a S ₂ (first magnetic pole) is magnetized, the magnetic pole at a position of about 80 ° from the magnetic pole S ₂ counterclockwise N ₂ (second
The magnetic pole) is magnetized. Further, a magnetic pole N ₁ (third magnetic pole) is magnetized at a position facing the photosensitive drum (image bearing member) 1, and a magnetic pole S ₁ (fourth magnetic pole) is magnetized at a position about 80 ° clockwise from the magnetic pole N _1. ing. Further, the toner sensor 4 for detecting the toner amount is provided on the right side wall of the second stirring and conveying member 43.
4 are provided. When the toner sensor 44 detects that the toner amount in the developing device 4 is insufficient, the toner t is supplied from the toner hopper (not shown) to the developing device 4. The supplied toner t is first transferred to the second stirring / transporting member 43.
With this, it is conveyed while being stirred from the front to the back of the figure,
It is sent from the second stirring / transporting member 43 to the first stirring / transporting member 42 at the rear end. Then, the first agitating / conveying member 42 conveys the agitating member from the back of the drawing to the front side while agitating, and during that period, the toner is appropriately supplied to the developing sleeve 41a.

That is, the toner t agitated by the first agitating / conveying member 42 and the second agitating / conveying member 43 is drawn up onto the developing sleeve 41a by the magnetic force of the magnetic pole N ₂ magnetized by the magnet roller 41b. Then, by the rotation of the developing sleeve, the developing sleeve is conveyed to the gap between the blade 45 and the developing sleeve 41a. When the toner t passes through this gap, the amount of toner sent to the developing unit is regulated by the magnetic pole S ₂ and the blade 45, and at the same time a thin toner layer is formed. Further, the toner t is triboelectrically charged. Of course, the toner is charged mainly by friction with the developing sleeve while being conveyed on the developing sleeve 41a. Then, the electrostatic latent image on the photoconductor drum 1 is developed by the toner t conveyed to the developing unit, which is an area opposite to the photoconductor drum 1.

The method for developing the electrostatic latent image on the photosensitive drum 1 is a positive development method in which the electrostatic latent image is developed with toner having a charge of the opposite polarity to the non-exposed portion of the photosensitive drum 1. Any of the reversal development methods in which an electrostatic latent image is developed with toner having a charge of the same polarity as that of the unexposed area, and the development method is a contact development method in which a thin toner layer and a photoreceptor are in contact, or both are in contact. Any of the non-jumping development methods may be used, but from the viewpoint of obtaining a high quality image, the reversal development method and the jumping development method are preferable, and the combination thereof is more preferable. In this case, the photoconductor drum 1 is charged to the same polarity as the toner t, and the charge of the latent image portion is removed by exposure. Then, in the developing unit, the developing sleeve 41
An alternating voltage, in which a direct current and an alternating current are superimposed, is applied as a developing bias between the a and the photosensitive drum 1, so that the toner t on the developing sleeve 41a is removed from the electrostatic latent image on the photosensitive drum 1. And is attached to the electrostatic latent image as a toner image.

The material of the photoconductor that can be used here is not limited, and conventionally known materials can be used. For example, an amorphous silicon-based photoconductor, an organic-based photoconductor, a Se-based photoconductor, a ZnO photoconductor, a CdS-based photoconductor, and the like can be mentioned. Among them, the amorphous silicon photoconductor is preferably used from the viewpoint of durability. The shape of the photosensitive member is not limited, and a conventionally known shape can be used. For example, a drum shape, a sheet shape, a belt shape, a web shape and the like can be mentioned. Of these, the drum shape is preferable.

Next, the image forming apparatus of the present invention will be described. FIG. 2 is a sectional view showing an example of the image forming apparatus of the present invention. The charging unit 2 uniformly charges the surface of the photoconductor 1 in a positive polarity. Next, an electrostatic latent image (exposed portion) is formed on the surface of the photoconductor 1 by the exposure means 3. Then, by using the developing device 4 described above, a toner is attached to the electrostatic latent image by a thin toner layer formed on the developing sleeve having a magnet inside to visualize the electrostatic latent image. In the transfer means 5,
The toner image on the photoconductor 1 is transferred to the transfer target member 7. The toner image on the transferred member 7 is then fused and fixed on the transferred member 7 by applying heat and pressure in a fixing unit (not shown). On the other hand, the untransferred toner remaining on the photoconductor 1 is previously cleaned by the cleaning brush 61 in the cleaning unit 6, and then completely cleaned by the cleaning blade 62.

[0040]

Example (Preparation of Toner) Styrene as a binder resin
100 parts by weight of acrylic resin, 7 parts by weight of charge control agent (Nigsilon dye, N-01, manufactured by Orient Chemical Co., Ltd.),
Magnetic powder (EPT-1000, manufactured by Toda Kogyo) is 70 parts by weight for Example 1 and Comparative Examples 1 to 12, 80 parts by weight for Example 2, 48 parts by weight for Example 3, and for Comparative Example 13. 45 parts by weight, 8 for Comparative Example 14
5 parts by weight, wax (PP wax, Biscol 550
P, manufactured by Sanyo Kasei Kogyo Co., Ltd.) was put into a Henschel mixer and mixed, then melt-kneaded with a twin-screw extruder, cooled with a drum flaker, and coarsely crushed with a hammer mill. Next, it was finely pulverized with a mechanical mill and classified with an air classifier to prepare toner particles having a predetermined volume average particle size and particle size distribution. Then, 0.6 wt% of hydrophobic silica (particle diameter 0.012 μm) and 1.4 wt% of titanium oxide (particle diameter 0.25 μm) were added to the toner particles,
Highly stirred and mixed with a Henschel mixer to prepare positively chargeable one-component magnetic toners used in Examples 1 to 3 and Comparative Examples 1 to 14. The volume average particle diameter and the weight average particle diameter of the produced toner were measured with a Coulter Multisizer (manufactured by Coulter Co.) with an aperture tube of 100 μm.

(Evaluation of Image) Using the above-prepared one-component magnetic toner, a high-speed printer of 50 sheets / minute (Kyocera LS-9500 development remodeling machine) having the configuration of FIG. 2 was used at room temperature and normal humidity. Under (23 ± 3 ℃, 55 ± 10% RH)
Then, the image density (ID) and the fog density (FD) were measured at the initial stage and after printing 50,000 sheets. The specific measuring method is as follows. The results are shown in Table 1. The above printer is
An amorphous silicon photoconductor is used as a photoconductor, a bias power source has a frequency of 2.5 kHz, and a peak-to-peak voltage of 1.
The surface potential of the latent image on the photosensitive drum is set to 10 V for the light portion and 240 V for the dark portion by using the AC voltage of 9 kV superimposed with the direct current of 160 V, and the distance between the developing sleeve and the photosensitive drum is set to 3 V.
Jumping development was performed at a setting of 20 μm. In the printing durability test, the average toner consumption per sheet was set to 55 mg, A4 size paper (64 g paper) was used, and the short side direction of the paper was set as the paper conveyance direction. For the measurement of image density and fog density, the same A4 size paper (64
(g paper), the short side direction of the paper is used as the paper conveyance direction, and the measurement image has a solid image area of 3 × 3 cm on the paper.
1 piece, 1 at the center of the paper transport direction with respect to the paper transport direction
Using ones arranged vertically at 0 cm intervals, one solid image portion was measured at 5 points, and the average value of 5 sheets was obtained.
For fogging, the non-printed portion of the paper on which the above-mentioned image for measurement was printed was measured at 5 locations per sheet, and the average value of the 5 sheets was obtained. A reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.) was used for measuring the image density and the fog density. As the evaluation criteria, the image density is 1.300 or more and the fog density is 0.008 or less.

(Measurement of Image Density and Fog Density) Using a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.), the densities of a black solid portion and a non-image portion of a copied image were measured. The evaluation criteria are that the initial image density is 1.300 or more and the initial fog density is 0.008 or less. The image density is measured at 5 points for one solid image part of the measurement image,
The average value of 5 sheets was calculated. For fogging, the non-printed portion of the paper on which the above-mentioned image for measurement was printed was measured at 5 locations per sheet, and the average value of the 5 sheets was obtained. The measurement results are summarized in Table 1.

[0043]

[Table 1]

As is clear from Table 1, in the tests using the developing devices of Examples 1 to 3, both the initial image density, the image density after printing, and the fog density satisfied the evaluation criteria. On the other hand, in the test using the developing device of Comparative Example 1 using the toner having a small average particle diameter, neither the initial image density nor the fog density satisfied the evaluation criteria. On the other hand, in the test using the developing device of Comparative Example 2 in which the toner having a large average particle size was used, the fog density satisfied the evaluation standard, but the initial image density was low. In the test using the developing device of Comparative Example 3 using a toner having a small particle size of 5 μm or less, the initial image density was low, while the developing device of Comparative Example 4 using a toner having a large ratio of particle size of 5 μm or less was used. In the test, neither the initial image density nor the fog density satisfied the evaluation criteria. Toner whose saturation magnetization is less than 16 emu / g
In the test using the developing device of Comparative Example 13 using No. 3, the fog density did not satisfy the evaluation standard. Saturation magnetization is 27em
In the test using the developing device of Comparative Example 14 using the toner exceeding u / g, the initial image density did not satisfy the evaluation standard.

In a test using the developing device of Comparative Example 5 using a magnet roller having a large magnetic force of the first magnetic pole, the fog density satisfied the evaluation standard, but the initial image density was low. On the other hand, in the test using the developing device of Comparative Example 6 using the magnet roller in which the magnetic force of the first magnetic pole was small, the initial image density satisfied the evaluation standard, but the fog density was high. In the tests using the developing devices of Comparative Example 7 and Comparative Example 8 in which the magnetic roller of which the magnetic force of the second magnetic pole was out of the specified range was used, the initial image of the fog density satisfied the evaluation standard The concentration was low. In a test using the developing device of Comparative Example 9 using a developing device having a small blade magnetic force, the initial image density satisfied the evaluation criteria, but the initial fog density was high. On the other hand, in the test using the developing device of Comparative Example 10 using a developing device having a large blade magnetic force, the fog density satisfied the evaluation criteria, but the initial image density was low. Further, in the tests using the developing devices of Comparative Example 7 and Comparative Example 8 in which the magnet roller in which the angle between the magnetic pole S2 and the magnetic pole N2 is out of the specified range was used,
The fog density satisfied the evaluation criteria, but the initial image density was low.

[0046]

In the developing device and the image forming apparatus of the present invention, the volume average particle diameter of the developer used, the ratio of the particle diameter of 5 μm or less, and the saturation magnetization are set within a specific range, and the magnetic pole position of the magnet roller and the magnetic force thereof are set. Since the magnetic force of the magnet provided in the developer regulating member is set in the specific range, even when used in a high speed machine, it is possible to form more than 50,000 images by simply replenishing toner without replacing parts.

In addition, a magnetic force of 800 × 10 ^{-4 to} 1000 × 10 ^-4 T is applied to the third position of the magnet roller facing the image carrier.
By magnetizing the magnetic poles, problems such as a decrease in image density during printing can be further suppressed. Further, when the gap between the developer carrying member and the developer regulating member is set in the range of 0.25 to 0.40 mm, the image density can be increased while suppressing the increase in fog density.

The gap between the image carrier and the developing sleeve is made larger than the thickness of the magnetic toner thin layer formed on the developing sleeve, and an AC bias voltage is applied between the image carrier and the developing sleeve to electrostatically discharge. By supplying a developer to the latent image and developing the latent image, an increase in fog density can be suppressed and the image quality can be improved.

Further, when a magnetic toner having the same polarity as that of the non-exposed portion of the image bearing member is adhered to the exposed portion to develop the electrostatic latent image, an increase in fog density can be further suppressed. If an amorphous silicon photoconductor is used as the image carrier, it can be used without replacement for a long period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a developing device of the present invention.

FIG. 2 is a sectional view showing an example of an image forming apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor (image bearing member) 2 Charging means 3 Exposure means 4 Developing means 5 Transfer means 6 Cleaning means 7 Transferred member t Toner (one-component magnetic toner) S ₂ First magnetic pole N ₁ Third magnetic pole N ₂ Second Magnetic pole 41 Developer carrying member 41a Developing sleeve 41b Magnet roller 42 First agitating / conveying member 43 Second agitating / conveying member 44 Toner sensor 45 Blade (developer regulating member)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/08 504 G03G 15/08 506A 506 9/08 101 (72) Inventor Seiji Kikushima Osaka City, Osaka Prefecture Kyocera Mita Co., Ltd. 1-228 Chuo-ku, Kyocera Mita Co., Ltd. (72) Inventor Toru Takazuna Osaka City, Osaka Tamazo 1-2-28 Kyocera Mita Co., Ltd. (72) Inventor Hiroko Sugimoto Osaka, Osaka Chuo-ku Tamakozo 1-228 Kyocera Mita Corporation F-term (reference) 2H005 CB02 EA02 EA05 EA10 2H031 AA09 AC08 AC19 AC20 AC31 AC33 AD03 AD05 BA06 BA08 CA10 CA11 FA09 2H068 DA23 2H077 AD06 AD13 AD18 AD24 AD36 BA16 DA15 DA42 DA42 FA19

Claims (7)

[Claims] 1. A developing device comprising a developer, a developer carrying member, and a developer regulating member arranged at a position separated from the developer carrying member, wherein the developer has a volume average particle diameter. Is 6.0 to 10.0 μm
And the proportion of particles having a particle diameter of 5 μm or less is 6.0 to 10.0 vol%
And a saturation magnetization of 16 to 27 emu / g is a one-component magnetic toner, and the developer carrying member includes a rotatable developing sleeve and a magnet roller fixed to the developing sleeve. Of the first magnetic pole having a magnetic force of 800 × 10 ^{−4 to} 1000 × 10 ⁻⁴ T at the position opposite to the developer regulating member, and 70 to 90 ° from the facing position in the direction opposite to the developing sleeve rotation direction. Magnetic force 300 × 10 ^-4
The first magnetic pole and the second magnetic pole having the opposite polarity are magnetized at ˜500 × 10 ⁻⁴ T, and the developer regulating member has a magnetic force of 350 × 10 ⁻⁴ to 600 ×.
A developing device comprising a magnet of 10 ⁻⁴ T, wherein the developer regulating member forms a thin magnetic toner layer on the developing sleeve to perform development. 2. A third magnetic force of 800 × 10 ^{−4 to} 1000 × 10 ⁻⁴ T at a position facing the image bearing member of the magnet roller.
The developing device according to claim 1, wherein the magnetic poles are magnetized. 3. The developing device according to claim 1, wherein the gap between the developer carrying member and the developer regulating member is in the range of 0.25 to 0.40 mm. 4. An image carrier, charging means for charging the surface of the image carrier, exposure means for irradiating the charged surface of the image carrier with light to form an electrostatic latent image, An image forming apparatus comprising: a developing unit that supplies a developer to an electrostatic latent image to develop the latent image; and a transfer unit that transfers the developer of the image carrier developed by the developing unit to a transfer target member. An image forming apparatus using the developing device according to claim 1 as a developing means. 5. A gap between the image carrier and the developing sleeve is made larger than a thickness of a magnetic toner thin layer formed on the developing sleeve, and an AC bias voltage is applied between the image carrier and the developing sleeve. The image forming apparatus according to claim 4, wherein the electrostatic latent image is supplied with a developer to develop the electrostatic latent image. 6. The image forming apparatus according to claim 4, wherein in the developing means, a magnetic toner having the same polarity as the non-exposed portion of the image carrier is attached to the exposed portion to develop the electrostatic latent image. 7. The image forming apparatus according to claim 4, wherein the image carrier is an amorphous silicon photoconductor.