JPS63235964A - Electrostatic image developing carrier - Google Patents

Abstract

PURPOSE:To secure superior durability and negative triboelectrifiability by attaching fine fluororesin particles to each magnetic carrier particle by the dry coating process. CONSTITUTION:The coated carrier particles are obtained by attaching the fine fluororesin particles to the surface of each magnetic carrier particle by the dry coating process, preferably, by mixing both particles with stirring, repeatedly applying impact to the obtained uniform mixture, and spreading the fluororesin particles on the surfaces of the magnetic particles, thus permitting the carrier to be produced in a short time at high yield, and enhanced in durability in durability, and to secure negative triboelectrifiability of a toner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carrier for electrostatic image development used in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Background of the invention]

In general, in electrophotography, a uniform electrostatic charge is applied to a latent image carrier, i.e., a photoreceptor, which has a photosensitive layer made of a photoconductive material, and then image exposure is performed to create an electrostatic potential on the surface of the photoreceptor. An image is formed, and this electrostatic latent image is developed with a developer to form a toner image. The obtained toner image is transferred to a transfer material such as paper and then fixed by heating or pressure to form a copy image.

Wet developing methods and dry developing methods are known as methods for developing electrostatic latent images. The former wet development method uses a liquid developer, which has the problem of emitting a bad odor, and also requires high energy to dry the transfer material, making high-speed copying difficult. The latter dry developing method does not have such problems and is a preferred method for developing electrostatic latent images.

The developers used in the dry development method are generally one-component developers consisting only of magnetic toner containing a magnetic substance, and so-called one-component developers consisting of a non-magnetic toner containing no magnetic substance and a magnetic carrier. Two-component developers are known.

The latter two-component developer uses mechanical stirring of the toner and carrier to triboelectrically charge the toner, so by selecting the characteristics of the carrier, stirring conditions, etc., the polarity of toner charge and charge It is possible to control the amount to a considerable degree, and there is a wide selection range of colors that can be imparted to the toner, and these points are superior to the former one-component developer.

Recently, as a latent image carrier, an organic latent image with a photosensitive layer made of a conductive semiconductor has been used as a latent image carrier because it is cheaper and is superior to a selenium-based latent image carrier in terms of safety. Supports are attracting attention. Therefore, the charging polarity of selenium-based latent image carriers is negative in most cases, whereas the charging polarity of organic latent image carriers is not only negative but also positive. Something exists.

Therefore, in order to perform development using an organic latent image carrier having positive charge polarity, it is necessary to charge the toner negatively.

As a carrier used in a two-component developer, a coated carrier formed by coating the surface of magnetic particles with a resin is preferably used because it can improve the durability, triboelectric charging properties, etc. of the carrier. . Fluorine-containing resins are known as coating resins, particularly for negatively charging toner.

As such coated carriers, the following ones are conventionally known.

(1) Fluidized bed spray coating carrier A coating carrier obtained by spraying a coating solution prepared by dissolving a coating resin in a solvent onto the surface of magnetic particles using a fluidized bed, and then drying.

(2) Dipping type coating carrier A coating carrier obtained by immersing magnetic particles in a coating solution prepared by dissolving a coating resin in a solvent, applying the coating, and then drying.

(3) Sintering type coating carrier A coating carrier obtained by applying a coating solution prepared by dissolving a coating resin in a solvent onto the surface of magnetic particles, and then sintering the resin.

[Problem that the invention seeks to solve]

However, in the technique (1) above, the granulation rate increases due to the use of a solvent, and as a result, the diameter of the carrier increases, resulting in a significant decrease in yield when obtaining a carrier with the desired particle size distribution. Because of the required steps, it takes a considerable amount of time to manufacture the carrier, resulting in a problem of low productivity. Furthermore, when a fluorine-containing resin is used as the coating resin, there is a problem in that the film is likely to peel off and the durability of the carrier is low. On the other hand, in order to shorten the time and increase productivity, it is conceivable to (1) increase the concentration of the coating resin in the coating solution, or (2) increase the number of spray nozzles. However, in the case of (■) above, the viscosity of the coating liquid increases, so the coating liquid does not spread smoothly on the magnetic particles, resulting in an uneven coating, and as a result, the durability of the carrier decreases. do. Additionally, once magnetic particles come into contact with each other, they easily granulate due to the high viscosity of the coating liquid.
The carrier yield is significantly reduced. In addition, in the case of ■ above, there is a limit to the increase in the number of spray nozzles, and
When the amount of coating liquid sprayed at one time increases, the granulation rate of magnetic particles increases, resulting in the same problem as above. On the other hand, some technologies include a mechanism called an agitator that applies shear force within the fluidized bed in order to prevent granulation.
When the granules are forcibly crushed by an agitator, the surface becomes rough and non-uniform, resulting in a decrease in the durability of the carrier.

In the technique (2) above, since the magnetic particles are directly immersed in the coating process, significant granulation occurs during drying after coating, resulting in a significant decrease in carrier yield.

The technique (3) above has the problem that sintering takes a considerably long time, and since a solvent is used, the granulation rate tends to be high, resulting in low productivity. In addition, since the resin is thermally crosslinked by sintering, the top layer of the carrier tends to be uneven.
There is a problem that the durability of the carrier is low.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and the object thereof is to be able to produce toner by simple means in a short time and at a high yield, and to have excellent durability and to reliably produce toner. An object of the present invention is to provide a carrier for electrostatic image development that can be triboelectrically charged negatively.

[Means for solving problems]

The electrostatic image developing carrier of the present invention is characterized in that fluorine-containing resin fine particles are adhered to magnetic particles by dry coating.

[Function and effect of the invention]

According to the carrier for electrostatic image development of the present invention, it can be manufactured by simple means in a short time and at a high yield, and it has excellent durability and can reliably triboelectrically charge the toner negatively. .

In other words, since the carrier is obtained by dry coating using magnetic particles and fluorine-containing resin fine particles, processing such as washing and drying is not necessary, the time required for coating is significantly shortened, and ■ the granulation rate is small and the As a result, it is possible to obtain carriers with a particle size distribution that corresponds to magnetic particles at a high yield, ■ Processing equipment such as solvent recovery equipment and solvent combustion equipment is not required, and production costs can be reduced. It is possible to reduce the amount of fluorine-containing resin fine particles relative to the particles, making it possible to use raw materials efficiently. ＜＜It has excellent durability and can reliably triboelectrically charge the toner negatively.

(Specific structure of the invention) The present invention will be explained in detail below.

The carrier for electrostatic image development of the present invention is formed by coating magnetic particles with fluorine-containing resin fine particles by dry coating.

In a preferred embodiment, magnetic particles and fine fluorine-containing resin particles are mixed and stirred to obtain a uniform mixed state, and impact force is repeatedly applied to this mixture, thereby forming fine fluorine-containing resin particles on the surface of the magnetic particles. to obtain a coating carrier.

The mixing weight ratio of magnetic particles and fluorine-containing resin fine particles is
The ratio varies depending on the specific gravity of the magnetic material, etc., and cannot be defined unconditionally, but is preferably about 100:1 to 100:10, for example.

The impact force applied to the mixture of magnetic particles and fluorine-containing resin fine particles should be of a magnitude that does not crush the fluorine-containing resin fine particles (e.g., 115 ~ It is sufficient if the impact force is about 1/10 of the size.Specifically, it depends on the characteristics of the fluorine-containing resin fine particles and cannot be specified unconditionally, but in the example, , 1.59X10-'~9.56X10-5er
g, preferably 1.20 x 10-' to 1.60
An impact force of X 10-'erg is sufficient.

As the magnetic particles, it is preferable to use magnetic particles having a weight average particle diameter of 20 to 200 μm. When the weight average particle diameter is too small, the resulting coating carrier has a small diameter, which tends to cause carrier adhesion to the latent image carrier, and as a result, image quality tends to deteriorate. On the other hand, when the weight average particle size is too large, the coating carrier obtained will have a large diameter, resulting in a small specific surface area.
As a result, in order to triboelectrically charge the toner appropriately, it is necessary to strictly control the toner concentration, which increases equipment costs, and it is necessary to carry the coating carrier uniformly and at a high density on the developer carrier. As a result, the amount of toner that adheres to the carrier and is transported to the development space becomes unstable, resulting in poor developability and easy to cause deterioration in image quality.

Materials for the magnetic particles include substances that are strongly magnetized in the direction of a magnetic field, such as iron, ferrite, magnetite, and other ferromagnetic metals such as iron, nickel, and cobalt, or alloys or compounds containing these metals.
Use alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment, such as alloys called Heusler alloys such as manganese-copper-aluminum or manganese-copper-tin, or chromium dioxide. be able to.

Note that ferrite herein is a general term for magnetic oxides containing iron, and is not limited to the spinel type ferrite represented by the chemical formula MO'Fe, 03. In addition, in the above chemical formula, M represents a divalent metal, and specifically represents nickel, copper, zinc, manganese, magnesium, lithium, etc.

Ferrite has low magnetization and is less likely to damage small particle size toner, thus improving the durability of the developer. Further, since ferrite can obtain various magnetic properties by changing the composition of the metal components contained therein, a carrier suitable for the purpose can be easily obtained. In addition, since ferrite powder is an oxide, its specific gravity is smaller and lighter than metal powders such as iron powder and nickel powder, making it easier to mix and stir with toner, resulting in a uniform toner concentration in the developer. transformation,
It is also suitable for optimizing the amount of charge on the toner.

Moreover, ferrite powder has a specific resistance of 10B to 10B.
At 12Ω・cm, it is larger than iron powder, nickel powder, cobalt powder, etc., so even when the thickness of the coating film made of fluorine-containing resin particles is reduced, it is sufficient for development methods that apply a high bias voltage to the development space. This has the advantage that a usable insulating carrier can be obtained.

The ferrite preferably has a saturation magnetization of 10 to 80 emu/g in an external magnetic field of 10,000 e, a coercive force of 0.1 to 1,000 e, and a specific resistance of lXl0' to 1 x 10 days Ωcm. , specific gravity is 4.0
~5.5, and the porosity is preferably 1.0 to 10%. By using magnetic particles having such preferable characteristics, even better developability can be obtained.

It is preferable that the magnetic particles have a circularity of 0.70 or more. When such highly circular magnetic particles are used, the resulting coating carrier has a high circularity, which increases the fluidity of the carrier, and as a result, it is possible to stably transport an appropriate amount of toner to the developing space. This makes it possible to achieve even better developability.

Here, the circularity is defined by the following formula.

Circularity=This circularity can be measured using, for example, an image analysis device (manufactured by Nippon Avionics).

The fluorine-containing resin fine particles preferably have a weight average particle size of 1/10 or less of the magnetic particles.

When the weight average particle size of the fluorine-containing resin fine particles is too large, it becomes difficult for the fluorine-containing resin fine particles to spread on the surface of the magnetic particles, making dry coating processing difficult.

As the material for the fluorine-containing resin fine particles, the following exemplified substances can be used. These may be used in combination.

[Example substance]

(1) Polymer of CF2=CF2 (TFE, tetrafluoroethylene) (2) CFZ=CF (hexafluoropropylene)
■ CF, polymer (3) CF2=CF2I (CTFE, chlorotrifluoroethylene) polymer (4) CH2= CF z (V d F, vinylidene fluoride) polymer (5) CFz=CF (hexa Fluoropropyl O
C, 3F? (6) 3FM Hs + CH2-C+7 Coo CH2CF3 (7) 4FM CH's + CH2C+.

00 CH2CFZ CF2H (8) Vinylidene fluoride-tetrafluoroethylene copolymer + CH2-CF2←-→CF2-CF2±1 (trade name;
rVT-1004 (manufactured by Daikin Industries, Ltd.), rVT-5
0J (manufactured by Daikin Industries), rKynar7
201j (manufactured by Benwald) (9) Polytetrafluoroethylene (PTFE) + C
F z CF 2 + − (Product name; rAIgofronJ (Montec
(manufactured by atint Edison), rFIuon
J (manufactured by IC1), rHaion TFEJ
(manufactured by Allied Chemica1), r
HostaflonJ (manufactured by Hoechst), rPo
lyflonJ (manufactured by Daikin Industries) + rso
reflonj (manufactured by Ugine Kuhlmann).

rTeflon T F El (manufactured by DuPont)
, “TeflonJJ (manufactured by Mitsui Fluorochemical Co., Ltd.)) (10) Polychlorotrifluoroethylene (PCT
FE) −(−CF, −CFC1+.

(Product name: rDaiflon J (manufactured by Daikin Industries, Ltd.).

rKel-F J (manufactured by 3M), rPlasko
n CT F El (81lied Chemica1
) + rVoltalefJ (UgineKuh
(manufactured by DuPont)) (11) Polyvinylidene fluoride (PVdF) q (-CH2-CF,
Dyflorj (manufactured by Dynamit Nobe1) +
rFraflon J (Ugine Kuh-Im
ann), rKF Polymer (manufactured by Kureha Chemical Industry Co., Ltd.) + rKynarJ (Pennwalt Chem)
icals), rSo-1efJ (Solva
(manufactured by y company)) (12) Tetrafluoroethylene-hexafluoropropylene copolymer (F E P) + CFZ CF2-) □c Fz CF + -
F n (product name; rNeoflonj (manufactured by Daikin Industries), rTe-flonFEPj (manufactured by DuPont)
) (13) Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) (-CF2-C
F, Mo → CF2-CF+.

■OC3F? (Product name: rTeflonP F AJ (manufactured by DuPont)) (14) Tetrafluoroethylene-ethylene copolymer (ETFE) 1+CH2-CH2←-→CF, -CF! 10 (Product name: [Aflon C0PJ (manufactured by Asahi Glass Co., Ltd.).

rTefzelJ (manufactured by DuPont) (15) Chlorotrifluoroethylene-ethylene copolymer (ECTF)
E) + CHz CHz←--(CF2-CFC1+.

(Product name; rHalarJ (Allied Che
(manufactured by mica1)) (16) Vinylidene fluoride-hexafluoropropylene copolymer + CH2CF z←-→CF, -CF+7■ [ν1tonJ (manufactured by DuPont), rFIuore
lJ (manufactured by 3M) + rTechnoflon N,
FORJ (manufactured by Montedison) (17) Hynylidene fluoride-chlorotrifluoroethylene copolymer + CHz CF z←-→CF, -CFaS□ (product name; rKel F Elastmarj (manufactured by 3M)) (18 ) Hinylidene fluoride-pentafluoropropylene copolymer (trade name: rTechnoflonT S J (M
ontedison)) (19) Tetrafluoroethylene-perfluoronitrotumecune copolymer (trade name; rNitroso RubberJ (T
(manufactured by hjokol Chemica 1)) (20) Tetrafluoroethylene-perfluoromethyl vinyl ether copolymer-(-cl"2-cFz←-→CF2-CF-).

OCF s (Product name: rKalrezJ (manufactured by DuPont)
) (21) Tetrafluoroethylene-propylene copolymer + CF z CF z←-→CH2-CH+7CH
3 (Product name: "Afras" (manufactured by Asahi Glass Co., Ltd.)) The weight average particle diameter of the carrier is preferably within an appropriate range corresponding to the magnetic particles. That is, when the weight average particle diameter of the carrier is too small, the carrier tends to adhere to the latent image carrier, resulting in deterioration of image quality. On the other hand, when the weight average particle size is too large, the specific surface area becomes small, making it difficult to triboelectrically charge the toner appropriately, and also making it difficult to support the carrier uniformly and at a high density on the developer carrier. , developability deteriorates.

Further, in order to obtain a carrier with uniform properties, it is preferable that the particle size distribution of the carrier is narrow.

In addition, the weight average particle size is "Microtrack" (LEEDS & N0RT-
It was measured by dry method using TYPE7981-OX) manufactured by HRUP).

The electrostatic image developing carrier of the present invention can be produced, for example, by the following method.

That is, magnetic particles and fluorine-containing resin fine particles are
For example, the mixture is uniformly mixed by stirring using a normal stirring device, and the resulting mixture is transferred to, for example, a device that is an improved version of a normal impact-type grinding device, and the device is used to carry out normal grinding, for example, about 10 minutes. With the rotation speed adjusted to about /10,
By repeatedly applying impact force to the mixture for, for example, 1 to 20 minutes, fine fluorine-containing resin particles are spread and adhered to the surface of the magnetic particles to obtain a coating carrier, which can be used for dry coating as shown in Fig. 1. It is an explanatory view showing an example of the device, and in the same figure, 11 is a raw material inlet, 12 is an inlet lid, 13 is an outlet, 14 is an outlet lid,
15 is a stirring motor, 16 is a rotating blade, 17A and 1
7B is a recycling pipe.

In this device, a mixture of magnetic particles and resin particles encapsulated from a raw material 11 is crushed by a rotating blade 16 to spread the resin particles on the surface of the magnetic particles, and these particles are recycled. Piping 17A or 17
After passing through B, it is again struck by the rotating blade 16. Such operations are repeated to achieve dry coating.

Dry coating may be performed at room temperature or may be performed while being heated to soften it slightly. However, if the heating temperature is too high, the viscosity of the fluorine-containing resin particles will increase, resulting in the resin particles agglomerating together and forming agglomerates, and also causing the magnetic particles to be bonded together by the resin particles, resulting in granulation. This makes it difficult to uniformly adhere the resin particles to the surface of the magnetic particles.

[Specific examples]

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

(Manufacture of carriers) (1) Carriers 01 to C6 Using a normal mixing and stirring device, mix and stir the combinations of magnetic particles and resin particles shown in Table 1 below, and then apply the resulting mixture to a normal impact Approximately 1/101 of the time when the improved type pulverizer is used for normal pulverization.
The mixture was driven at 0.00 rpm and impact force was repeatedly applied to the mixture for 15 minutes to obtain each coated carrier.

The granulation rate and final yield of each coated carrier are shown in Section 1 below.
It is also shown in the table.

(2) Carrier C7 fluorine-containing resin (VT-100, vinylidene fluoride-tetrafluoroethylene copolymer, manufactured by Daikin Industries, Ltd.) is dissolved in acetone/methyl ethyl ketone (515) solvent at a ratio such that the concentration is 3%. A coating solution was prepared, and this coating solution was used to wet-coat magnetic particles made of ferrite having a weight average particle size of 120 nm by a fluidized bed spray coating method to obtain a coated carrier. This is called “Carrier C7J.

The granulation rate of this carrier C7 was as high as about 12%.

(2) Carrier C8 Fluorine-containing resin (3FM,
A coated carrier was obtained by processing in the same manner as Carrier 7 except that the carrier was changed to poly(1,1-sibide loba-fluoroethyl methacrylate).

This is called [Carrier C8J].

The granulation rate of this carrier C8 was as high as about 8%.

Structural formula (1) %Formula% (Preparation of developer) Each of the above carriers 01 to C8 and a toner for an electrophotographic copying machine [U-Bix 1550M RJ (manufactured by Konishiroku Photo Industry Co., Ltd.)] Each of the developers D1 to D8 was prepared by mixing them in a proportion that gave an appropriate amount of charge.

(Evaluation of Durability of Carrier) Using each of the above developers D1 to D8, an electrophotographic copying machine rU-Bix 1550M RJ (manufactured by Konishiroku Photo Industries Co., Ltd.) was used at a temperature of 20°C and a relative humidity of 6.
A test was conducted in which copy images were repeatedly formed under 5% environmental conditions, and changes over time in the amount of triboelectric charge of the toner were measured. The amount of triboelectric charge of the toner was determined by a known blow-off method. The results are shown in Table 2 below.

Table 2 Unit: 〆/g (actual copying test) Using each of the above developers D1 to D8, an electrophotographic copying machine "U-Bix1550M" equipped with a contact type developer was used.
A photocopying test was conducted using a modified RJ (manufactured by Konishi Roku Photo Industry Co., Ltd.) to form a copy image, and the following items were evaluated. The results are shown in Table 3 below.

■Image quality The copied images were judged visually. The evaluation was ``○'' if it was good, ``Δ'' if it was slightly poor but at a practical level, and ``x'' if it was poor and had a practical problem.

(2) Adhesion of carrier to latent image carrier The surface of the latent image carrier was visually observed, and judgment was made based on the presence or absence of carrier adhesion to the latent image carrier. When the evaluation is good with almost no carrier deposits observed, it is evaluated as "
``○'', a case where some carrier deposits were observed but at a practical level was rated "Δ", and a case where a large amount of carrier deposits were observed and there was a practical problem was rated "x".

(2) Durability Copy image formation was repeated and judgment was made based on whether or not a good copy image was obtained. The evaluation is "○" if it is good, and "△" if it is slightly poor but at a practical level.
”, and cases where it is defective and has a practical problem are marked as “×”.

As can be understood from the results of the Examples shown in Table 3 and above, according to the carriers 01 to C6 of the present invention, the carriers can be obtained in a short time with a high yield by simple means, and they also have excellent durability. It exhibits excellent and stable triboelectric charging properties, and can form images of good quality without carrier adhesion.

On the other hand, according to comparative carriers C7 and C8, since they are fluidized bed spray coating carriers,
The adhesion strength of the coating film of the carrier to the magnetic particles is low, and therefore the triboelectricity changes significantly over time, resulting in low durability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus that can be suitably used for dry coating. 11...Raw material population 12...Entrance lid 13
...Exit 14...Exit lid 15...
・Stirring motor 16...Rotating blades 17A, 17
B...Recycling piping procedure amendment (voluntary) June 24, 1988 Director General of the Patent Office Yoshi 1) Takeshi Moon 1, Indication of the case Patent Application No. 1982-67997 2, Name of the invention Electrostatic image development Relationship with the amendment carrier case 3 Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name Name
(127) Konica Co., Ltd. 4, Agent 6, Contents of amendment (1) ■ Lines 7 to 9 of page 20 of the specification are corrected as follows. "The device in this example is a batch type device, with one rotating blade
When the rotary blade 6 is rotated at high speed, centrifugal force is applied to the surrounding air by the rotary blade 16, the outside of the rotary blade 16 becomes pressurized, and the center of the rotary blade 16 becomes under negative pressure. Since the outer side and the center of the rotating blade 16 are connected by the recycling pipes 17A and 17B, the pressurized air outside the rotating blade 16 is transferred to the rotating blade 16 via the recycling pipes 17B and 17A. Moving to the center, a circulating flow of air is formed. Therefore, in this device, a mixture of magnetic particles and fluorine-containing resin fine particles encapsulated from the raw material 11 is crushed by the rotating blade 16 so that the fluorine-containing resin fine particles are the surface of the magnetic particles.'' ■Specification No. 21 Insert the following between the second and third lines of the page. "Figure 2 is an explanatory diagram showing another example of an apparatus that can be used for dry coating, and in the same figure, 61
62 is a powder input valve, 62 is a powder input chute, 63 is a circulation circuit, 64 is a casing, 65 is a rotary disk, 66 is a blade, 67 is a stator, 68 is a jacket for cooling or heating, 69 is a powder discharge chute , 70 is a powder discharge valve. Note that the arrow represents the locus of the powder. When the rotary disk 65 having the blades 66 is rotated at high speed,
The centrifugal force acts on the internal air by the blades 66, so that the outside of the rotary disk 65 is pressurized, and the center of the rotary disk 65 is under negative pressure. Since the outside and center of the rotary disk 65 are connected by the circulation circuit 63, the pressurized air outside the rotary disk 65 moves to the center of the rotary disk 65 through the circulation circuit 63. A circulating flow of air is formed. In a state where such a circulating flow of air is formed, when a powder raw material consisting of a mixture of magnetic particles and fluorine-containing resin particles is introduced from the powder input chute 62 provided in the middle of the circulation circuit 63, the powder material is introduced. The powder raw material comes to circulate through the circulation circuit 63 along with this circulation flow, and during this circulation process, the powder raw material collides with the blade 66 and receives an impact force, which causes the fluorine-containing resin fine particles to It comes to be spread on the surface of the magnetic particles. After this circulation process has been carried out for a certain period of time, the powder discharge valve 7o is opened to discharge the processed powder raw material by centrifugal force, thereby obtaining a dry coated carrier. In such a circulation process, the circulation circuit 63 and the powder official chute 69 may be cooled or heated by a jacket 68 provided on the stator 67 side in order to control the temperature inside the apparatus. In addition, in the device of this example, since the inlet side passage of the circulation circuit 63 extends along the tangential direction of the rotary disk 65,
The circulation of powder raw materials becomes smooth and efficient. Further, since the outlet passage of the powder discharge chamber 69 also extends along the tangential direction at the bottom of the rotary disk 65, the powder raw material to be processed can be discharged smoothly and efficiently. . (2) ■ Lines 5 to 6 of page 28 of the specification are corrected as follows. "Figures 1 and 2 are explanatory diagrams each showing an example of an apparatus that can be suitably used for dry coating. The following is added next to line 10 on page 28 of the specification. "61. ...Powder inlet valve 62...Powder inlet chute 63...Circulation circuit 64...Casing 65...Rotary disk 66...Blade 67
...Stator 68...Jacket 69...
Powder discharge chute 70...powder discharge valve" (3) ■ Figure 1 of the drawing is corrected as shown in the attached correction diagram. ■Add Figure 2 of the drawings as shown in the attached sheet. =5- (corrected diagram)

Claims (1)

[Scope of Claims] 1) A carrier for electrostatic image development, characterized in that fluorine-containing resin fine particles are adhered to magnetic particles by dry coating. 2) The first claim characterized in that the dry coating is performed by mixing and stirring magnetic particles and fine fluorine-containing resin particles, and repeatedly applying impact force to the mixture.
Carrier for electrostatic image development as described in . 3) The carrier for electrostatic image development according to claim 1 or 2, wherein the magnetic particles have a circularity of 0.70 or more.