JPS63235960A - Electrostatic image developing carrier - Google Patents

Abstract

PURPOSE:To secure superior durability and stable triboelectrifiability by coating fine magnetic particles having a specified average particle diameter range with fine resin particles and fine electric charge controller through the dry coating method. CONSTITUTION:The magnetic particles having a weight average particle diameter of 20-200mum are coated with the fine resin particles having a weight average particle diameter of <=1/10 that of the magnetic particles by the dry coating method, preferably, by mixing both particles with stirring, repeating application of impact to the uniform mixture of them, spreading and attaching the fine resin particles and the fine charge controller particles on the surface of the magnetic particles to form the coated carrier particles, thus permitting the carrier to be produced in a short time at high yield, and to obtain superior durability and superior triboelectrifiability.

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 triboelectrically charges the toner by mechanically stirring the toner and carrier.
By selecting carrier characteristics, stirring conditions, etc.
It is possible to control the charge polarity and charge amount of the toner to a considerable extent, and there is a wide selection range of colors that can be imparted to the toner, and these are superior to the former one-component developer.

However, when the amount of triboelectric charge of the toner is low, the toner tends to adhere to the non-image area of the latent image carrier, resulting in the problem of fogging, while on the other hand, when the amount of triboelectricity of the toner is high, A problem arises in that the image density decreases. Therefore, in order to achieve good development,
Proper triboelectric charging of the toner is required.

As means for improving the triboelectric charging properties of toner, there are known means for incorporating a charge control agent into the toner, means for incorporating a charge control agent into the film of a coating carrier, and the like. In the former method, since toner is consumed each time an image is formed, the amount of charge control agent required increases, which is disadvantageous in terms of cost. On the other hand, the latter method is advantageous in that the required amount of the charge control agent can be considerably reduced since the carrier is used repeatedly.

Conventionally, the following coating carriers are 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 Coating Carrier A coating carrier obtained by dipping magnetic particles in a coating liquid 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, since a solvent is used, the granulation rate becomes high, and as a result, the diameter of the carrier increases, resulting in a significant decrease in yield when obtaining a carrier with a desired particle size distribution. Since a drying process is required, it takes a considerable amount of time to manufacture the carrier, resulting in low productivity. 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. Furthermore, once the magnetic particles come into contact with each other, they easily granulate due to the high viscosity of the coating liquid, resulting in a significant decrease in carrier yield.

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, causing the same problem as above. There is. On the other hand, in order to prevent granulation, some technologies include a mechanism called an agitator that applies shear force within the fluidized bed, but if the granules are forcibly broken up by the agitator, the surface condition becomes rough. This results in non-uniformity, which reduces the durability of the carrier. When a charge control agent is included in the film of a coating carrier, it is necessary to dissolve or uniformly disperse the charge control agent in the coating solution, but some charge control agents cannot be dissolved in a solvent. Some charge control agents are difficult to coat or disperse, which narrows the selection range of charge control agents.Also, the dispersion state of the charge control agent tends to be uneven in the coating solution, so the charge control agent is not uniformly contained in the coating. As a result, the triboelectric charging properties of the coating carrier become non-uniform, resulting in a problem that the triboelectric charging amount of the toner used in combination with the coating carrier becomes broad and the developability deteriorates.

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. When the charge control agent is contained in the coating of the coating carrier, there are problems similar to those described above.

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 carrier coating layer tends to be uneven.
There is a problem that the durability of the carrier is low. When the charge control agent is contained in the film of the coating carrier, there is a problem that the charge control agent is exposed to high temperatures, leading to its deterioration.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its objects are to be able to be produced by simple means in a short time and at a high yield, and to have excellent triboelectric charging properties. An object of the present invention is to provide a carrier for electrostatic image development that has excellent durability.

[Means for solving problems]

The carrier for electrostatic image development of the present invention has a weight average particle size of 20
It is characterized in that resin particles and charge control agent fine particles having a weight average particle size of 1/10 or less of the magnetic particles are coated on magnetic particles of ~200μ by dry coating.

[Function and effect of the invention]

According to the carrier for electrostatic image development of the present invention, it can be produced by simple means in a short time and at a high yield, and exhibits excellent triboelectric charging properties and excellent durability.

In other words, since the carrier is obtained by dry coating using magnetic particles, resin particles, and charge control agent fine particles of a specific particle size, processing such as washing and drying is not necessary, and the time required for coating is significantly shortened. ■The granulation rate is small, and as a result, carriers with a particle size distribution compatible with magnetic particles can be obtained at a high yield. ■Processing equipment such as solvent recovery equipment and solvent combustion equipment is not required, reducing production costs. ■It is possible to reduce the amount of resin particles and charge control agent fine particles relative to the magnetic particles, allowing efficient use of raw materials, and ■It is possible to reduce the amount of resin particles and charge control agent particles on the surface of the magnetic particles. Because the agent fine particles are attached and spread, they are not peeled off.As a result, excellent triboelectric charging properties and excellent durability are exhibited.■Can also be used with resins and charge control agents that are difficult to dissolve in solvents. As a result, the selection range of resins and charge control agents becomes much wider, and coated carriers with various properties can be obtained.

In addition, since magnetic particles having an average particle size within a specific range are used, the resulting coating carrier is
The specific surface area falls within an appropriate range, and therefore the mixing ratio with the toner required to appropriately triboelectrically charge the toner can be adjusted with a considerable degree of freedom, making it easy to control the toner concentration. ■Since magnetic particles with an average particle size within a specific range are used, the resulting coating carrier has a suitable particle size distribution, making it possible to support the carrier uniformly and at a high density on the developer carrier. As a result, the toner adhered to the carrier by electrostatic force can be stably transported to the development space in an appropriate amount, making it possible to achieve excellent development.

[Specific structure of the invention]

The present invention will be explained in detail below.

The carrier for electrostatic image development of the present invention has a weight average particle size of 20
Resin particles and charge control agent fine particles having a weight average particle size of 1/1O or less of the magnetic particles are coated on magnetic particles of ~200p by dry coating.

In a preferred embodiment, the weight average particle size is between 20 and 2
00n magnetic particles, resin particles whose weight average particle diameter is 1/10 or less of the magnetic particles, and charge control agent fine particles are mixed and stirred to obtain a uniform mixed state, and impact force is repeatedly applied to this mixture. By applying the resin particles and the charge control agent fine particles to the surface of the magnetic particles, the resin particles and the charge control agent fine particles are spread and adhered to the surface of the magnetic particles, thereby obtaining a coated carrier.

The mixing weight ratio of magnetic particles, resin particles, and charge control agent fine particles varies depending on the specific gravity of the magnetic material, etc., and cannot be unconditionally defined, but for example, the mixing weight ratio of magnetic particles and resin particles is It is preferably about 100:1 to 100:1e, and the mixing weight ratio of the total of magnetic particles and resin particles to charge control agent fine particles is preferably about 100:0.1 to 100:5.

The impact force applied to the mixture of magnetic particles, resin particles, and charge control agent fine particles may be of a size that does not crush the resin particles and charge control agent fine particles. target energy 1
An impact force of about 15 to 1/10 is sufficient. Specifically, it varies depending on the characteristics of the resin particles and the charge control agent fine particles, and cannot be defined unconditionally, but in the example, 1.59X10- per magnetic particle.
3-9.56 x 110-5er, preferably 1.
An impact force of 20×10 −3 to 1.60×10 −’erg is sufficient.

As the magnetic particles, magnetic particles having a weight average particle size of 20 to 200 μm are used. When the weight average particle size is too small, the coating carrier obtained will have a small diameter, and the carrier will easily adhere to the latent image carrier.
As a result, image quality deteriorates.

On the other hand, if the weight average particle size is too large, the resulting coating carrier will have a large diameter, resulting in a small specific surface area.As a result, in order to properly triboelectrically charge the toner, it is necessary to strictly control the toner concentration. This requires high equipment costs, and it is difficult to support the coating carrier uniformly and at a high density on the developer carrier, resulting in a decrease in the amount of toner that adheres to the carrier and is transported to the development space. It becomes unstable, resulting in poor developability and deterioration of 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 spinel-type ferrite represented by the chemical formula MO-FezOi. 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, so it is easier to mix and stir with toner, and the toner concentration in the developer is even. magnetization,
It is also suitable for optimizing the amount of charge on the toner.

Moreover, ferrite powder has a specific resistance of 108 to 10
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 resin particles is reduced, it can be used in development methods that apply a high bias voltage to the development space. It has the advantage that a highly insulating carrier can be obtained.

In addition, the ferrite preferably has a saturation magnetization of 10 to 80 emu/g in an external magnetic field of 10000e, a coercive force of 0.1 to 1000e, and a specific resistance of 1 x 106 to 1 x 10 Ω. cm, 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 weight average particle size of the resin particles is 1/1 that of the magnetic particles.
Resin particles having a particle size of 0 or less are used. When the weight average particle size of the resin particles is too large, it becomes difficult for the resin particles to spread on the surface of the magnetic particles, making dry coating processing difficult.

The material for the resin particles is not particularly limited, and various resins can be used. That is, in the present invention, since the coating carrier is obtained by dry coating, it is possible to use resins that are difficult to dissolve in solvents, and the range of resin selection is considerably wide. Specifically, various resins such as styrene resin, acrylic resin, styrene-acrylic resin, vinyl resin, ethylene resin, rosin modified resin, polyamide resin, and polyester resin can be used. These resins may be used in combination.

Specific examples of styrenic monomers used in the production of styrene resins or styrene-acrylic resins include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methylstyrene, Ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n
-hexylstyrene, p-n-octylstyrene, p
n-nonylstyrene, p-n-decylstyrene, p-
Examples include n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, etc., and these monomers may be used alone or in combination You may use a combination of things.

Specific examples of acrylic monomers used in the production of acrylic resins or styrene-acrylic resins include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate,
Propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-acrylate
Acrylic acid or its esters such as chloroethyl, phenyl acrylate, methyl α-chloroacrylate; methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n- methacrylate Methacrylic acid or its esters such as octyl, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; and others; These monomers may be used alone or in combination.

When obtaining the styrene-acrylic resin, the composition ratio of the styrene monomer and the acrylic monomer is preferably 9:1 to 1:9 by weight. The styrene component makes the coating film hard, and the acrylic component makes the coating tough. Furthermore, by appropriately changing these composition ratios, the amount of charge of the toner during frictional charging between the coating carrier and the toner can be controlled to a considerable extent.

In addition, when forming a coating carrier using a styrene-acrylic resin with a weight average molecular weight axis of 30,000 to 200,000, the adhesion strength of the resin particles to the magnetic particles is high, The durability of the carrier is improved. According to such a resin, the coating carrier particles have low adhesion and excellent blocking resistance, and can effectively prevent so-called toner filming, in which toner substances adhere to the surface of the carrier particles.

The charge control agent fine particles preferably have a weight average particle size of 2p or less. When the weight average particle size of the charge control agent fine particles is too large, it becomes difficult to uniformly disperse the charge control agent fine particles on the surface of the magnetic particles, resulting in variations in the triboelectric charging properties of the toner.

Various dyes, pigments, etc. can be used as the material for the charge control agent fine particles. Specifically, as a carrier that makes the carrier negatively chargeable, for example, Japanese Patent Laid-Open No. 57-14
No. 1452, JP-A-58-7645, JP-A-58-1
No. 11049, JP-A-58-185653, JP-A-5
2:1 type metal-containing azo dyes disclosed in JP-A No. 7-167033, JP-A-44-6397, etc.; for example, JP-A-57-104940, JP-A-57-111541, JP-A-57 No.-124357, JP-A-53-1277
Metal complexes of aromatic oxycarboxylic acids and aromatic guicarboxylic acids disclosed in various publications such as No. 26; for example, sulfonylamine derivatives of copper phthalocyanine dyes or copper phthalocyanine dyes disclosed in JP-A-52-45931; Sulfonamide derivative dyes, sulfonamide and sulfonic acid or sulfonate derivative dyes of copper phthalocyanine; etc. can be mentioned.

In addition, examples of materials that make the carrier positively chargeable include quaternary ammonium compounds disclosed in JP-A-49-51951 and JP-A-52-10141; No. 11461, JP-A-54-15
Alkylpyridinium compounds and alkylpicolinium compounds disclosed in each publication of No. 8932, U.S. Patent No. 4,254,205, etc.; for example, nigrosine SO
, Nigrosine dyes such as Nigrosine EX; examples include addition condensates disclosed in Japanese Patent Publication No. 49-80320 G.

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 having a weight average particle size of 20 to 200 μm, resin particles having a weight average particle size of 1/10 or less of the magnetic particles, and charge control agent fine particles are mixed using, for example, a normal stirring device. The resulting mixture is mixed uniformly by stirring, and the resulting mixture is transferred to, for example, a device that is an improved version of a normal impact-type grinder, and the device is operated at a rate of, for example, about 1/1 of the normal grinding speed.
By repeatedly applying impact force to the mixture over a period of, for example, 1 to 20 minutes while adjusting the rotation speed to about 10, the resin particles and charge control agent fine particles are spread and adhered to the surface of the magnetic particles to form a coating carrier. get.

FIG. 1 is an explanatory diagram showing an example of an apparatus that can be used for dry coating. In the 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, resin particles, and charge control agent fine particles encapsulated from a raw material 11 is beaten by a rotating blade 16, and the resin particles and charge control agent fine particles adhere to the surface of the magnetic particles. After being spread, these particles pass through the recycling pipe 17A or 17B and are again struck by the rotary vane 16, and this operation is 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 adhesiveness of the resin particles or charge control agent fine particles will increase, resulting in a phenomenon in which the resin particles or charge control agent fine particles aggregate and form a lump, and the magnetic particles may The resin particles or charge control agent fine particles combine to form granules, making it difficult to uniformly adhere the resin particles and charge control agent fine 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 C9 Using an ordinary mixing and stirring device, the combinations of magnetic particles, coating resin particles, and charge control agent fine particles shown in Table 1 below are mixed and stirred, and then the obtained The resulting mixture was charged into an improved conventional impact-type crushing device, and the device was driven at approximately 1/10 the rotational speed of normal crushing to repeatedly apply impact force to the mixture for 15 minutes. Each coated carrier was obtained.

The granulation rate and yield of each coated carrier are also shown in Table 1 below.

(2) Carrier CIO polymethyl methacrylate (softening point T sp'; 1
90°C) with a weight average particle diameter of 0.41 and charge control agent fine particles (Spiron Black TRH, manufactured by Hodogaya Chemical Co., Ltd.) in an acetone/methanol mixed solvent at a concentration of 6%. A coating solution is prepared by dissolving the coating solution in a proportion as follows, and this coating solution is used to wet-coat nearly spherical copper-zinc ferrite magnetic particles with a weight average particle size of 100μ by a fluidized bed spray coating method. A coated carrier was obtained. This will be referred to as "carrier C10."

The granulation rate of this carrier C100 was as large as about 4%.

(3) Carrier C11 A coated carrier was obtained in the same manner as in the production of carrier C1 except that the charge control agent fine particles were not used. This will be referred to as "carrier C11."

(4) Carrier CI2 A coated carrier was obtained in the same manner as in the production of carrier C4, except that the charge control agent fine particles were not used. This is referred to as [carrier Cl2J.

(Preparation of developer) Each of the carriers 01 to C3 and C7 to C1l,
Toner for an electrophotographic copying machine rU-Bix1550MRJ (manufactured by Konishi Roku Photo Industry Co., Ltd.) is mixed with the toner at a ratio that provides an appropriate initial charge amount of the toner to form developers D1 to D3. D7～
Dll was prepared, and the above carriers 04 to C6, C12
and an electrophotographic copying machine rU-Bix2500M
Developer D4 is prepared by mixing toner for RJ (manufactured by Konishiroku Photo Industry Co., Ltd.) at a ratio that gives the toner an appropriate initial charge amount.
~D6. DI2 was prepared.

(Evaluation of triboelectricity of carrier) The above-mentioned developers D1 to D3. D7 to Dll were made using a modified electrophotographic copying machine r U -Bix 1550M RJ (manufactured by Konishi Roku Photo Industry Co., Ltd.), and the developers D4 to D6゜DI2 were used using an electrophotographic copying machine r U -Bix 2500M.
Using a modified RJ machine (manufactured by Konishiroku Photo Industry Co., Ltd.), a test was conducted in which copied images were repeatedly formed under environmental conditions of a temperature of 33° C. and a relative humidity of 80%, 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.

Further, when the distribution of the amount of triboelectric charge of the toner was measured, all of the developers D1 to D6 formed by combining the carriers of the present invention showed a sharp distribution and were able to triboelectrically charge the toner well. On the other hand, developer DI which is made by combining carrier C10 obtained by wet coating
O showed a broad distribution, and considerable variation in the amount of triboelectric charge of the toner was observed.

Table 2 (Part 1) Numerical value; Absolute value, Unit: JJC, /g Table 2 (Part 2) Numerical value; Absolute value, Unit: 〆/g (Actual photo test) The above developers D1 to D3. D7 to Dll are electrophotographic copying machines equipped with a contact type developing device, r U-Bix 15
With the modified 50MRJ (manufactured by Konishiroku Photo Industry Co., Ltd.),
Moreover, the above-mentioned developers D4 to D6. DI2 is an electrophotographic copying machine r U-Bix 2500M equipped with a contact type developing device.
A photocopy test was conducted to form a copy image using a modified RJ (manufactured by Konishiroku Photo Industry Co., Ltd.), and the following items were evaluated. The results are shown in Table 3 below.

A 0-quality copy image was visually determined. The evaluation was ``○'' if it was good, ``△'' 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 "△", 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 above examples, according to the carriers 01 to C6 of the present invention, the carriers can be obtained in a short time and in high yield by simple means, and in the live-action test, It exhibits excellent triboelectric charging properties and durability, and can stably form images of good quality many times without carrier adhesion.

On the other hand, according to comparative carrier C7, since the weight average particle size of the magnetic particles is too small, carrier adhesion is likely to occur, resulting in poor image quality and poor durability.

According to the comparative carrier C8, the weight average particle size of the magnetic particles is too large, resulting in a defective image from the beginning of the actual photographic test.

According to comparative carrier C9, since the weight average particle size of the resin particles is too large, durability is poor and stable triboelectric charging properties cannot be obtained. This is because the particle size of the resin particles is large.
This is thought to be due to poor adhesion between the resin particles adhering to the surface of the magnetic particles.

According to Comparative Carrier C10, since it is a fluidized bed spray coating carrier, there is less charge control agent present on the surface of the coating in the carrier, resulting in a decrease in chargeability and, as a result, fogging.

According to the comparative carriers C1l and C12, the triboelectric charging properties were not appropriate, resulting in poor images.

[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 Japan Patent Office Yoshi 1) Takeshi Moon 1, Indication of the case Patent Application No. 1982-67993 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 5, Subject of amendment (1) Column for detailed explanation of the invention in the specification (2) Column 6 for brief explanation of drawings in the specification, Contents of amendment (1) ■ Line 6 of page 22 of the specification is corrected as follows. [The device in this example is a batch type device, and the rotating blade 16
When rotated at high speed, centrifugal force is applied to the surrounding air by the rotating blades 16, the outside of the rotating blades 16 becomes pressurized, and the center of the rotating blades 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, the raw material is sealed from the raw material number 11.'' ■The following is inserted between the third and fourth lines of page 23 of the specification. [FIG. 2 is an explanatory diagram showing another example of an apparatus that can be used for dry coating. In the figure, 61 is a powder input valve, 62 is a powder input chute, 63 is a circulation circuit, and 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, and 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, a powder raw material consisting of a mixture of magnetic particles, resin particles, and charge control agent fine particles is fed from the powder input cabinet 62 provided in the middle of the circulation circuit 63. When the powder raw material is introduced, the powder raw material is circulated through the circulation circuit 63 together with the circulation flow, and during this circulation process, the powder raw material collides with the blade 66 and receives an impact force, thereby causing The resin particles and charge control agent fine particles come to be spread on the surface of the magnetic particles. After performing this circulation process for a certain period of time, the powder discharge valve 70 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 input 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. Furthermore, in the device of this example, the circulation circuit 630 artificial side passage 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 chute 69 also extends along the tangential direction at the lower part of the rotary disk 65, the powder raw material to be processed can be discharged smoothly and efficiently. (2) ■ Lines 4 to 5 of page 32 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 9 on page 32 of the specification. 61...Powder official valve 62...Powder input chute 63...Circulation circuit 64...Casing 65...Rotary plate 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. (Corrected diagram) 1st m

Claims (1)

[Claims] 1) Magnetic particles having a weight average particle diameter of 20 to 200 μm,
1. A carrier for electrostatic image development, characterized in that resin particles and charge control agent fine particles having a weight average particle size of 1/10 or less of the magnetic particles are coated by dry coating. 2) The dry coating includes magnetic particles, resin particles,
The carrier for electrostatic image development according to claim 1, wherein the carrier is mixed with fine particles of a charge control agent and stirred, and an impact force is repeatedly applied thereto. 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.