JPH028860A - Carrier for developing electrostatic image - Google Patents

Abstract

PURPOSE:To obtain the carrier having excellent triboelectrostatic charge performance and durability by mixing a ore material and resin particles and applying repetitive impact power to this mixture, thereby subjecting the mixture to coating. CONSTITUTION:The carrier core material is coated with the resin particles dispersed with a carbon black by the dry process coating consisting in applying the mechanical impart to the mixture and depositing and fixing the resin particles on the core material. Namely, the impact force is applied to the mixture composed of the magnetic material particles and resin particles sealed from, for example, a raw material charge valve 11 by the collision against a rotary plate 15, blades 16 and a stator 17 or the collision of the particles against each other, by which the resin particles are spread and fixed onto the surfaces of the magnetic material particles. Further, the mixture receives such impact force repeatedly while circulating in a piping 18 for recycling, by which the dry process coating is attained. The carrier is produced by the simple method in this way and the carrier having the excellent triboelectrostatic chargeability and durability is obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to electrostatic image developing carriers used in electrophotography, electrostatic recording, electrostatic printing, etc. This invention relates to a carrier for electrostatic image development coated with a resin in which black is dispersed.

[Background of the Invention] Two-component developers generally consist of a non-magnetic toner and a magnetic carrier. As this carrier, fine particles of iron, ferrite, etc. are used. However, these fine particles are easily crushed and have insufficient triboelectrification performance, so there are 3 degrees of problems in that it is not appropriate to use them as they are.

Therefore, in the past, efforts were made to improve durability and triboelectric charging properties by using a coated coated carrier on the surface of magnetic particles with resin.9 However, this coatied carrier has an apparent resistivity of Since it has a high resistance of about X 1014 ΩC, it tends to cause the 1-periphery effect, and has the disadvantage of poor reproducibility in wide black areas and halftone areas. Therefore, it has been proposed to mix a conductive substance such as carbon black into the coating layer made of resin.

For example, JP-A-56-126,843 discloses a carrier coated with a material containing carbon black and resin as main components, and JP-A-62-182,759 discloses a carrier coated with a material containing carbon black and a resin as main components, and JP-A-62-182,759 discloses a carrier coated with a material containing carbon black and a resin as main components. A carrier coated with silicone resin is disclosed, and Japanese Patent Publication No. 45984/1984 discloses a carrier coated with porous carbon black in RIIM.

As mentioned above, when conductive fine particles such as carbon black are mixed in the resin coating of the carrier, it is necessary to consider a suitable coachide carrier.

By the way, the following are conventionally known as this type of coachoid carrier. The carriers disclosed in the above-mentioned publications can also be said to belong to these categories as coachid carriers.

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

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

(3) Sintered Cortide Carrier A cortichide 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.

[Problems to be Solved by the Invention] However, the carriers of the techniques (1) to (3) above each have the following drawbacks when manufacturing the carrier.

In the technique (1) above, since a solvent is used, the granulation rate increases, and as a result, the diameter of the carrier increases, and when obtaining a carrier with the desired particle size distribution, the yield decreases significantly.
Because a drying process is required.

There is a problem in that it takes a considerable amount of time to manufacture the carrier and the productivity is low.

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

In the technique (3) above, sintering requires a considerably long time, and since a solvent is used, the granulation rate becomes high, resulting in low productivity. Also.

Because the resin is thermally crosslinked by sintering, the carrier is coated with r!
There is a problem that Im tends to be non-uniform and the durability of the carrier is low.

Furthermore, in the above conventional technology, the subject r! Incorporating conductive particles such as carbon black in one layer involves dispersing the conductive particles in a solution, which causes non-uniformity in the dispersion state, resulting in variations in properties. .

Furthermore, in the coating method using a solution in which carbon black is dispersed, free carbon black that is not fixed in the coating layer is generated. These particles adhere to the carrier surface or exist between the carriers, and during development they act to reduce the triboelectric charging properties of the developer, which has the disadvantage of reducing the durability of the developer. .

On the other hand, Japanese Patent Application Laid-Open No. 63-37358.

A carrier is disclosed in which a layer of fine polymer particles containing magnetic powder is formed on the surface of a carrier core material, and the rII layer is fixed. That is, this carrier is made by mechanically mixing a carrier core material and polymer fine particles containing magnetic powder, and then coating the surface of the carrier core material with polymer fine particles.
A resin layer is coated on the surface of the carrier core material by attaching a sieve to form a coating layer, and then melting and fixing the polymer fine particles with heat, or melting and fixing them with a solvent. It is obtained by

According to this technique, the problem of uneven distribution of conductive features,
Moreover, it is thought that the problem of the release of conductive fine particles can be solved to some extent.

However, in the technique described in JP-A No. 63-37358, since the fine polymer particles are fixed by being melted by heat, the stickiness of the fine polymer particles increases, resulting in the following problems.

(2) Polymer fine particles and carrier core materials coagulate with each other via the polymer fine particles, forming agglomerates.

■ Adhesion occurs inside the fixing device.

(2) Air bubbles are generated due to the expansion of the gas trapped between the polymer particles, and pinholes are formed due to the escape of these air bubbles, making the coating ii non-uniform and deteriorating durability.

■ Long-term processing is required to crush pinholes in response to air bubbles. Moreover, in this case, the problems (1) and (2) described above will further progress.

As mentioned above, according to this technology, in order to obtain a uniform and durable carrier for the rite, a long treatment time is required, and the granulation rate is high, so it must be sorted using a sieve. However, there are problems in that it is time-consuming and the yield is low in obtaining carriers with a desired particle size distribution. In addition, since granules of polymer fine particles cannot be removed even with a sieve and remain, these granules migrate to the photoreceptor during development, causing image fogging and poor cleaning of the photoreceptor. There is.

On the other hand, in the technique described in the above publication, when polymer fine particles are fixed by dissolving them in a solvent, there are problems similar to those pointed out in the technique (1) above.

The present invention has been made to solve the above-mentioned problems, and its first purpose is to be able to produce the product by simple means and at a high yield, to have excellent triboelectric charging properties, and to be durable. An object of the present invention is to provide a carrier for electrostatic image development that has the following properties.

A second object of the present invention is to suppress the occurrence of granulation of resin particles, thereby preventing image fogging caused by transfer of the granules to the photoreceptor and the occurrence of poor cleaning of the photoreceptor. An object of the present invention is to provide a carrier for electrostatic image development.

Furthermore, a third object of the present invention is to provide a carrier for electrostatic image development that has appropriate conductivity, suppresses the occurrence of fringe effects, and has excellent reproducibility in wide black areas and halftone areas. It is in.

[Means for Solving the Problem] As a means for solving one problem, the present invention provides resin particles in which carbon black is dispersed in a carrier core Murakami.
It is characterized by being coated with a dry coating that adheres and fixes by applying mechanical impact.

In the dry coating, it is preferable that the *a force is repeatedly applied to the mixture of the carrier core material and the resin particles in which carbon black is dispersed at a temperature at which the resin particles do not melt.

In the present invention, the temperature at which melting does not occur means a temperature lower than the softening point Tsp determined by the following measurements.

The measurement uses 71J-Tester rcFT-500J (manufactured by Shimadzu Corporation).

Specifically, the measurement conditions were: load 20 kg/ffl, nozzle diameter 1 nxn + nozzle length 1 cycle, preheating 8
At 0°C for 5 minutes, increase at a rate of 6°C/min, and sample amount 1aJ (weight expressed as true specific gravity x 1-) is 1ll.
When the height of the S-shaped curve in the flow tester's plunger drop amount-temperature curve m (softening flow curve) obtained when recording l + constant is 11, the temperature at 11/2 is the softening point '1 6 In addition, the above-mentioned carrier for electrostatic image development has a property that the adhesion and fixation by dry coating of the resin particles is effective against impact force within the range of temperature up to 50°C higher than the glass transition point of the resin particles. It is preferable that it be obtained by repeatedly applying .

That is, the temperature of the resin particles to which the impact force is applied while attached to the core material is set to be 5eC higher than the glass transition point of the resin particles and lower than this temperature. Therefore, the temperature may be lower than the glass transition point.

It is preferable to apply the impact force at a temperature that does not cause aggregation of resin particles or deterioration of the charge control agent. For example, the impact force application time may be shortened.

The glass transition point Tg in the present invention is determined according to differential scanning calorimetry (DSC), for example, rDSC-20J.
(manufactured by Seiko Electronics Industries). Specifically, the sample 10+eg was heated at a constant heating rate (10°C/
1 lIin) and obtained from the intersection of the pace line and the slope of the endothermic peak.

In addition, the product temperature in the present invention refers to a temperature measuring probe inserted into a particle group in which particles made of resin particles attached to a core material are flowing under an impact force, and the particles are randomly contacted with the probe. This is the approximate average value of the surface temperature of particles obtained by The temperature measurement probe is composed of a thermocouple, a resistance temperature detector, etc., and can measure temperature by electrically measuring its electromotive force, resistance value, etc. Examples of thermocouples include chromel-alumel thermocouples.

In the present invention, the temperature of the product is measured using a material with a length of 10 cm and a diameter of 6.
Chromel-alumel thermocouple with 4mm stainless steel (ST+5304) cover (manufactured by Hayashi Denko Co., Ltd., T2O
ni-2-6,4-100-U-304-KX-G-30
00), insert its end into the recycling pipe of the apparatus shown in Fig. 1, which will be described later, from the upper part of the elbow of the R section of the pipe to a depth of 5 cm, with the tip approximately at the center of the pipe cross section. Insert it so that it is positioned at , and then take the measurement.

Magnetic particles are used as the carrier core material. The magnetic particles may have an amorphous shape, but are preferably spherical. The size of the magnetic particles is such that the weight average particle diameter is 20 to 200.
A range of μm is preferred, and a range of 30 to 120 μm is even more preferred.

It is not easy to reduce the particle diameter to 1/10 or less, and it is difficult to form an N layer.On the other hand, particles larger than 200 μm result in a coarse-grained image.

Further, it is preferable to use resin particles having a weight average particle diameter of 1/10 or less of the magnetic particles.The smaller the resin particles, the easier it is to form a uniform film. The resin particles may have any shape, and their surfaces may be smooth or uneven.

Carbon black is pre-dispersed in the resin particles.
The mixing weight ratio of the two varies depending on the specific gravity, etc., and cannot be generally specified, but for example, if the resin particles are 100%
% of carbon black, preferably about 5 to 40 parts. If the content of carbon black is too small, the carrier resistivity will not decrease and a suitable conductive product will not be obtained.
On the other hand, when the content is excessive, triboelectric charging properties deteriorate and the durability of the carrier decreases.

As the carbon black, all carbon blacks such as furnace black, acetylene black, and channel black can be used.The particle size may be any size that can be dispersed in the resin particles, for example, 1 to 50.
It may be about 0 nm.

Carbon black may be dispersed into resin particles by any appropriate method. For example, resin particles and carbon black may be mixed, the resulting mixture is crushed, and the crushed mixture is then classified. A method of obtaining resin particles of a desired particle size by
Alternatively, when forming resin particles, carbon black is dispersed in a polymerization solvent system, a polymerization initiator and a additive are added to the resin particle raw materials, and polymerization is carried out while incorporating carbon black to form resin particles. There is a way to get it.

Further, charge control agent fine particles may be dispersed together with carbon black.

Depending on the core, carbon black, and charge control agent used in the carrier, the preferable value of the specific resistance of the carrier cannot be determined unconditionally, but it is preferably 10 7 to 10 12 Ωl, and 10” to 10 Ωl.
A 10″ 1Ω opening is more preferable.

If it is larger than this value, the reproducibility of narrow black characters (text, line drawings) is good, but the reproducibility of wide black characters (solid black) is poor.
If it is smaller than this value, the reproducibility of narrow black characters (letters, line drawings) is poor, but the reproducibility of wide black characters (C peta black) is good.

In one aspect of the present invention, the average pile diameter is 20 as the core material.
Magnetic particles of ~200 μm and resin particles whose average particle diameter is 1710 or less of the magnetic particles and in which carbon black has been dispersed are mixed and stirred to form a uniform mixed state, and this mixture is repeatedly subjected to impact force. In some cases, resin particles in which carbon black is dispersed are spread and adhered onto magnetic particles to obtain a coated coat layer containing carbon black.

In the above embodiment, charge control agent fine particles are preferably dispersed in the resin particles together with carbon black.

The mixing weight ratio of magnetic particles and resin particles varies depending on the specific gravity of the magnetic material, etc., and cannot be generally specified.1 For example, the mixing weight ratio of magnetic particles and resin particles is:
The ratio is preferably about 100:1 to 100:10.

The impact force applied to the mixture of magnetic particles and resin particles may be of a magnitude that does not crush the magnetic particles and resin particles. For example, the impact force applied to the mixture of magnetic particles and resin particles may be large enough to not crush the magnetic particles and resin particles. ~ About 1/10 the size? #Impact power is fine.

As the magnetic particles, as described above, magnetic particles having a weight average particle diameter of 20 to 200 μm are used.

When the weight average particle diameter is too small, the obtained corchid carrier has a small diameter, which tends to cause the carrier to adhere to the latent image carrier, resulting in deterioration of image quality. On the other hand, when the 1 weight average coarse diameter is too large, the resulting cotchiid carrier has 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 amount of toner, the equipment cost is high, and it is difficult to carry the coachoid carrier uniformly and at a high density on the developer carrier. The amount of toner that adheres to the carrier and is transported to the developing space becomes unstable, resulting in poor developing performance and deterioration of image quality.

Materials for 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 containing these metals. or compounds, alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment 1. For example, alloys called Heusler alloys such as manganese-copper-aluminum or manganese-copper-tin, or dioxide Chromium or the like can be used.

Note that ferrite here is a general term for magnetic oxides containing iron, and is not limited to spinel-type ferrite represented by the chemical formula of Fe, O,.

In addition, in the above chemical formula, M represents a divalent metal, and specifically represents nickel, copper, zinc, manganese, magnesium, lithium, etc.

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 cortichoid carrier will have a high circularity. The fluidity of the toner increases, and as a result, it becomes possible to stably convey an appropriate amount of toner to the developing space, and more excellent developing performance is exhibited.

Here, the circularity is defined by the following formula.

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

As the resin particles, resin particles having a weight average particle diameter of 1710 or less than that of the magnetic particles are used as described above. 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, in order to obtain a coachoid carrier by dry coating,
It is now possible to use resins that are difficult to dissolve in solvents,
The selection range of resins is quite wide, specifically one example is styrene resin.

Acrylic resin, styrene-acrylic resin, vinyl resin, ethylene resin, rosin modified resin.

Various resins such as polyamide resin and polyester resin can be used. These resins may be used in combination. Particularly preferred are styrene-acrylic resins, acrylic resins, and styrene resins.

Specific examples of styrene monomers used in the production of styrene resins or styrene-acrylic resins include styrene, 0-methylstyrene, m-methylstyrene, and p-methylstyrene.

α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-t
ert-butylstyrene, p-n-hexylstyrene,
p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-
Examples include chlorstyrene, 3,4-dichlorostyrene, etc., and these monomers may be used alone,
A combination of a plurality of them may be used.

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,
Acrylic acid or its esters such as dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate: methacrylic acid, methyl methacrylate, Ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylamino methacrylate Examples include methacrylic acid or its esters such as ethyl and diethylaminoethyl methacrylate; and others, and 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 acrylic component makes the coating film tough. In addition, by appropriately changing the composition ratio, it is possible to control to a considerable extent the amount of toner band fl during frictional charging between the coachoid carrier and toner.

In addition, when forming a coachoid carrier using a styrene-acrylic resin with a weight average molecular weight Mw of 30,000 to 200,000, it is necessary to use a styrene-acrylic resin with a high adhesion strength of one resin particle to a magnetic particle. This improves the durability of the carrier. If such a resin is used, the adhesion of the coachoid carrier particles is low and blocking resistance is excellent, and the occurrence of so-called toner filming, in which toner substances adhere to the surface of the carrier particles, can be effectively prevented.

As mentioned above, charge control agent fine particles that can be used with carbon black have a weight average particle size of 2.
It is preferable that the thickness is less than μm.

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 in the resin particles.
As a result, variations may occur in the triboelectric charging properties of the toner.

As the material for the charge control agent fine particles, one of various dyes, pigments, etc. can be used. Specifically, examples of materials that make the carrier negatively chargeable include 1, for example, JP-A-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
Gold y4 complexes of aromatic oxycarboxylic acids and aromatic dicarboxylic acids disclosed in publications such as No. 26; for example, sulfonylamine derivatives of copper phthalocyanine dyes or copper as disclosed in JP-A-52-45931; Examples include phthalocyanine sulfonamide derivative dyes, phthalocyanine sulfonamide and sulfonic acid or sulfonate derivative dyes, and the like.

In addition, examples of carriers that make the carrier positively charged and conductive include, for example, JP-A-49-51951 and JP-A-52-10141.
Quaternary ammonium compounds disclosed in various publications such as JP-A-56-11461 and JP-A-54-1
58932, U.S. Patent No. 4,254,205
Alkylpyridinium compounds and alkylpicolinium compounds disclosed in the specification etc.; for example, nigrosine S
○, Nigrosine dyes such as Nigrosine EX; examples include addition condensates disclosed in JP-A-49-80320.

It is preferable that the weight average particle size of the carrier is within an appropriate range corresponding to the magnetic particles.In other words, if the weight average particle size of the carrier is too small, the carrier tends to adhere to the latent image carrier, resulting in poor image quality. to degrade. On the other hand, when the 5 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. As a result, developability deteriorates.

Furthermore, in order to obtain carriers with uniform properties, it is preferable that the carrier particle size distribution be narrow.

In addition, the weight average particle size is "Microtrack" (Leeds & Northrup (LEEDS & N0RTH)
-RUP), TYPE 7981-OX).

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

That is, magnetic particles having a weight average particle size of 20 to 200 μm and resin particles having a weight average particle size of 1/10 or less of the magnetic particles and having carbon black dispersed therein are mixed using, for example, a normal stirring device. Stir to mix evenly,
the resulting mixture.

For example, when a normal impact-type crushing device is transferred to an improved device or the like, and the bag V1 is subjected to normal crushing.

For example, by repeatedly applying an impact force to the mixture over a period of 1 to 20 minutes at a rotation speed of about 1/10, the resin particles are spread and adhered to the surface of the magnetic particles and coated. Get an id carrier.

FIG. 1 shows an example of an apparatus preferably used for dry coating of the present invention.

11 is a raw material input valve, and 12 is a raw material input chute.

13 is a product discharge valve, and 14 is a product discharge chute.

15 is a rotary disk (c+-tar), 1G is a blade (rotary vane) provided on the rotary disk 15, 17 is a stator, 1
8 is recycling piping, 19 is Jaquera 1- (cooling or heating possible), 20 is casing, 21 is chromel-
This is a product thermometer that uses an alumel thermocouple as the temperature measurement probe. In addition, recycling piping 18, input and output shoes 1-12. ．． In this device, which has a jacket structure in which 14 portions are cooled or heated, a mixture of magnetic particles and resin particles encapsulated through a raw material input valve 11 is fed to a rotary disk 15.
, while being rotationally dispersed by the blade 16.

Due to the rotation i15, collisions with the blades 16 and stator 17, and collisions between particles, an impact force is applied, and the resin particles are spread and fixed on the surface of the magnetic particles, and further, while circulating through the recycling pipe 18, By repeatedly receiving such impact force, it is fixed and dry coating is achieved.

In the figure, arrows indicate trajectories of raw material particles and the like.

In the apparatus shown in FIG. 1 above, it is preferable that the impact force be repeatedly applied at a temperature at which the resin particles do not melt, especially at a temperature that is 50°C higher than the glass transition point of the resin particles. It is preferable that the impact force be applied within the range of .

Note that the temperature of one item is measured by the one item temperature meter 21 when the resin particles pass through the recycling pipe 18.

When the temperature exceeds 50° C. higher than the glass transition point of the resin particles, the adhesiveness of the resin particles gradually increases, and as a result, the resin particles tend to aggregate and form lumps. The higher the temperature, the more the magnetic particles are bound together by the resin particles and become granulated, and when the temperature reaches which the resin particles begin to melt, it becomes difficult to uniformly adhere the resin particles to the surface of the magnetic particles. This device can also be used to fix carbon black to resin particles. Therefore, carbon black may be first fixed to the resin particles and then the resin particles may be fixed to the magnetic particles using the same device.

Coverage of the carrier of the present invention! The IN film thickness is determined by the mixed weight ratio of magnetic particles and resin particles. By the way, it is easier to form a film by applying an impact force while covering magnetic particles with a single layer of resin particles than by coating a large amount of resin particles at once. In the case of coating, the film thickness can be adjusted to y4 by appropriately selecting the diameter ratio of the resin particles. and,
By repeating such dry coating, a coating layer with a desired thickness can be formed.

The content of carbon black in the coating layer of the carrier can be appropriately set by dispersing a desired amount of carbon black into the resin particles.

Alternatively, resin particles in which carbon black is dispersed may be diluted with resin particles in which carbon black is not dispersed to obtain a desired carbon black content as a whole.

Further, the content of carbon black may be controlled by appropriately mixing resin particles having different amounts of carbon black dispersed therein.

In the present invention, for adjusting triboelectric charging properties.

Charge control agent fine particles can be added together with carbon black. In this case, the content of the charge control agent fine particles can be controlled by adjusting the two-dispersion amount and diluting, as in the case of carbon black described above. In addition, resin microparticles containing carbon black and resin particles containing a charge control agent may be mixed and used. In this case, the mixing ratio of both may be set appropriately, and if necessary, both may be added. The desired content can be achieved by diluting with uncontained resin particles.

In addition, when forming a film by repeating dry coating multiple times, a film forming process using resin particles in which carbon black is dispersed and a film forming process using resin particles in which carbon blank is not dispersed are appropriately combined, and as a whole, The content may be controlled to a desired content. Further, charge control agent fine particles may be mixed in one or both of the above film forming steps, and of course, a film forming step using only resin particles in which charge control agent fine particles are dispersed may also be included.

In order to effectively exhibit its charge control performance, it is preferable to control the content of the charge control agent fine grains so that they are distributed near the surface of the coating layer.

In the present invention, since the charge control agent is added in the presence of carbon black, electrostatic repulsion between charge control agent fine particles is suppressed and a high-density single particle layer can be formed. Therefore, film formation becomes easy.

[Operation and Effect] In the present invention, resin particles are added to the core material. Coat with lf impact force. That is, the core material and resin particles are mixed, and the mixture is coated by repeatedly applying impact force. When the core material and resin particles are mixed, the resin particles are electrostatically attached to the core material. When force is applied in this state, the mechanical energy fixes the resin particles to each other and the resin particles to the core material.
The resin particles form an integral layer on the surface of the core material to form a coating layer. As a result, a carrier with excellent durability can be formed.

In the present invention, when this impact force is applied, the resin particles are not melted or dissolved.Therefore, coating can be performed by simple means without the need for melting or dissolving means. Furthermore, various troubles associated with melting and dissolution of resin particles, especially granulation, hardly occur, so carriers can be obtained in high yield. As a result, the rate at which resin particle granules are mixed into the developer can be extremely reduced, and the occurrence of image fogging and photoreceptor cleaning defects caused by resin particle granules can be suppressed. I can do it.

In addition, in the present invention, carbon black is added to the resin particles in advance, so the resulting carrier has appropriate conductivity, suppresses the occurrence of fringe effects, and eliminates large black areas (so-called solid areas) and Shows excellent reproducibility in the midtone area.

Note that if a charge control agent is contained together with carbon black, excellent triboelectric charging performance can be expected.

[Example] An example of the present invention will be described below. Note that the present invention is not limited to these examples.

(Manufacture of resin particles) 100 parts by weight of methyl methacrylate-butyl methacrylate copolymer resin (Tg = 71°C, Ts p = 189°C), Nigrosine SO (manufactured by Orient Kagaku Kogyo Co., Ltd., average 5 parts by weight of carbon black (particle size 0.3 μm) and 20 parts by weight of Palcan Amorphous resin particles having an average particle size of 6.9 μm and containing a charge control agent dispersed therein were obtained. This is designated as No-1.

Resin particles were produced in the same manner as No-1 above.

These are designated as Nos. 2 to 11.

Regarding the resin particles of N0-1 to 12 above, the resin used,
The charge control agent and carbon black are summarized in Table 1.

In addition, Palkan XC-7 used as carbon black
2R, Palcan XC-72, Zi-Gal 660R, and Mogul L types are Furnace Bratz (dry coating) Spherical iron powder carrier DSP-135 (manufactured by Dowa Iron Powder Co., Ltd., average particle size 100 μm - circularity 0.80) 1000 parts by weight, N containing dispersed carbon blank and charge control agent
12 parts by weight of resin particles of o-1 were mixed with a YGG mixer (manufactured by Yayoi Co., Ltd.) at loorpm for 20 minutes, and N
A mixture was obtained in which o-1 resin particles were uniformly deposited on the surface of the iron powder carrier.

Subsequently, the resulting mixture was subjected to hybridizer-NH5-
Type 1 (manufactured by Nara Kikai Co., Ltd.) was placed in a modified device, and impact force was repeatedly applied to the mixture for 10 minutes at room temperature.
Obtained coachid carrier.

This carrier will be referred to as Example-1.

The product temperature rose to a maximum of 121°C.

An iron powder carrier and resin particles in which carbon black had been dispersed in advance were mixed as shown in Table 2, and dry coating was performed in the same manner as in Example 1 to obtain Examples 2 to 7 and Comparative Examples 1 and 2. 's coachoid career exploded.

Comparative Example-3 was obtained by the following manufacturing method.

Styrene-methyl methacrylate-butyl methacrylate copolymer resin (Tg=71°C, Tsp=173°C) 10
0 parts by weight, 5 parts by weight of Nigrosine S○, Palcan XC-
20 parts by weight of 72R were mixed using a Henschel mixer, mixed, crushed and classified to obtain pre-dispersed amorphous resin particles with an average particle size of 6.9 μm.

14 parts by weight of these resin particles are mixed and dissolved in 200 parts by weight of a mixed solvent of toluene/methanol = 90/10% by volume, mixed and dispersed using a suitable dispersion machine, and suspended and fluidized in hot air using a fluidized bed coater. A coated carrier was obtained by spray coating 1000 parts by weight of spherical iron powder carrier DSP-135 (manufactured by Dowa Iron Powder Co., Ltd.).

Adjustment of developer> 97 parts by weight of the carrier produced in the above Examples and Comparative Examples and the electrophotographic copying machine rU-BixL550MRJ
(manufactured by Konica Corporation) and 3 parts by weight of toner for Yaa
A developer was prepared by mixing for 20 minutes at LOORPM in a mixer.

<Evaluation of developer> Carrier Examples-1, 2, 5, 6, 7 and Comparative Example-1
, 3 is used in the electrophotographic machine "U-Bix 2
022J (manufactured by Konica Corporation) was used, and the developer using carrier Examples 3 and 4 and Comparative Example 2 was rU-Bix1550 MRJ (-Nika (
It is for use with stock>ta>modified machines.

Both images were evaluated under the environmental conditions of a temperature of 33° C. and a relative humidity of 80%.

Furthermore, the presence or absence of carrier granules, coating efficiency, apparent resistivity, and toner triboelectric charge were determined as follows.

Presence or absence of carrier granules; 80 mesh (177 μm)
Confirm the presence or absence of material recovered on the sieve.

Covering efficiency: Covering efficiency = I got more.

Apparent resistivity: 100 V was applied to a 1 cm carrier layer under the conditions of an electrode area of 1 d and a load of 1 kg, and the value was calculated from the current value flowing there. For measurements, the manufactured carrier was used at the start of running, and after the start of running, the carrier from which the toner had been removed by blow-off was used.

Amount of toner friction band M1: After photographing the evaluation image.

It was determined by the usual blow-off method from the developer sampled from the sleeve of the developing machine.

There were no granules in Examples 1 to 7 and Comparative Examples 1 and 2. In Comparative Example 3, granulation occurred, and the yield of carrier excluding granules was 90%.

The coating efficiency was approximately 100% for Examples-1 to 7 and Comparative Example-1°2, and 85% for Comparative Example-3.

Table 3 summarizes the triboelectric charging f (Q/M) of each developer and the apparent resistivity of the carrier at the start and after 20,000 yen.6 In the carrier of the present invention, carbon black deteriorates the triboelectric charging performance. It can be seen that there is an effect of adjusting only the apparent resistivity of the carrier.

Furthermore, it can be seen that almost no change in resistivity occurs even after 20,000 copies have been printed. In addition, the reproducibility of wide-area black characters (solid black) and narrow-area black characters (letters, line drawings) is good and uniform, and there are no practical problems, and even after 20,000 copies, the initial image is maintained and is sufficient. It was revealed that the material has excellent durability.

The carriers of Comparative Examples 1 and 2 maintained their initial images even after 20,000 copies were made, and although the reproduction of black areas in narrow areas was generally good, there was unevenness in black areas in wide areas. It was noticeable and at a level that would pose a practical problem.

The carrier of Comparative Example-3 had a triboelectric charge of -1 at the start.
0.1pc7g, and the apparent resistivity was 2.2 x 10<7>Ω·I, which had already exceeded the limit of the practical level of the image, so no further actual photographic evaluation was performed.

Table 3 Furthermore, in order to demonstrate the present invention, carriers of Comparative Examples 4 and 5 were produced.

Comparative Example 4 was prepared in the same way as Examples 1 to 7 using resin particles No. 1 in which carbon black was dispersed, to obtain a mixture in which the resin particles were uniformly adhered to the surface of the iron powder carrier.

The resulting mixture was charged into a hybridizer NH3-1 (manufactured by Nara Kikai Co., Ltd.) whose jacket portion was heated to 50 to 60° C., and impact force was repeatedly applied for 10 minutes to obtain a coachoid carrier.

The product temperature rose to a maximum of 170°C.

The surface of the obtained cochoid carrier was rough and non-uniform.

Developer l! Jll was performed as described above.

The evaluation of the developer is based on the electrophotographic copying machine “υ-Bix2022”.
Using a modified machine J (manufactured by Konica Corporation), the temperature was 33°C.

A live-action evaluation was conducted under an environmental condition of 80% relative humidity.

The presence or absence of carrier granules, coating efficiency, and apparent resistivity were also determined in the same manner as described above.

Granulation occurred, and when the granules were removed using an 8o mesh (177 μm) sieve, the granulation rate was 56% by weight.

Fusion occurred in the recycling piping and rotating blades.

The coating efficiency was 96%.

In addition, the toner triboelectric charge amount at the start and at the end of 20,000 copies is -23.5 and -25, Oμc/g, and the apparent resistivity is 2.1xlO' and 3.5XlO'Ω'Cf.
It was f1.

In the evaluation image, the reproducibility of wide and narrow areas equivalent to that of Example-1 was obtained, but there was a slight fog on the white background at the start, and the fog was 100%.
It disappeared after the first one.

Furthermore, the yield was as low as 40%, and the rate at which resin particle granules were mixed into the developer was high.

Comparative Example-5 is a hybridizer-NMS-1 (similar to Comparative Example-4) in which a mixture in which resin particles are uniformly adhered to the surface of an iron powder carrier is heated at a temperature of 80 to 90°C at the jacket part.
A coachoid carrier was obtained by charging the carrier into a Nara Kikai Co., Ltd. and repeatedly applying TJ'll force for 10 minutes.

The product temperature rose to a maximum of 194°C.

A large number of granules were generated, and the corchid carrier could not be recovered due to severe adhesion to the interior of the equipment, recycling piping, and rotating blades.

Furthermore, after obtaining a carrier that differs only in the mixing weight ratio of resin particles from Example-2 as shown in Table 1-4, the MA of the developer was determined in the same manner as in Example-2. A 1° developer was evaluated.

No granulation occurred and the coating efficiency was about 100%.

In addition, the toner triboelectric charge amount and carrier apparent resistivity at the start and at the end of 20,000 copies are summarized in Table 4.

Regarding the evaluation images, even after 20,000 copies of Example-A, the value of apparent resistivity did not change, and the performance of the initial image was almost maintained, and the reproduction of black characters in narrow areas was generally good.

However, the wide-area surplus is slightly uneven.

In Example-D, the black characters in a wide area were generally good, but the reproducibility in a narrow area was poor, and fogging in the white area of the background slightly occurred after 10,000 copies.

Both Examples A and D are at a level that is at the limit of practical use.

Examples-B and C had the same performance as Example-2, and were at a level that caused no practical problems.

In Example M-E, the uniformity of black characters in a wide area and the reproducibility of black characters in a narrow area are generally good. The toner triboelectric charge amount decreased from the start to the end of 20,000 copies. The level of dirt inside the copying machine after completing 20,000 copies was slightly inferior to that of Example-2 containing a charge control agent. This is considered to be caused by scattering of weakly charged toner.

As is clear from the above, the carrier according to the present invention, that is, the carrier core Murakami, is coated with resin particles in which carbon black is dispersed by dry coating, which is fixed by applying a mechanical impact force. The carrier for electrostatic image development, which has been repeatedly subjected to impact force at a temperature up to 50° C. higher than the glass transition point of the resin particles, has a high yield and produces granulated resin particles in the developer. The rate of contamination by resin particles can be extremely reduced, and the occurrence of image quality fogging and poor cleaning of the photoreceptor due to resin particle granules can be suppressed. In addition, it has appropriate conductivity, suppresses the occurrence of peripheral effects, and exhibits excellent reproducibility in wide black areas (so-called solid areas) and halftone areas.

Further, in the present invention, it is preferable to use about 40 parts of carbon black S-1 per 100 parts of resin particles, and it is also preferable to use a charge control agent.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a modified dry coating apparatus. 11... Raw material input valve 12... Raw material input chute 13... Product discharge valve 14... Product discharge chute 15... Turntable 16... Blade 17... Stator 18... For recycling Piping 19... Jacket 20... Casing 21... Temperature needle/Figure f18 Refresh/I, story arrangement

Claims (5)

[Claims] (1) A carrier for electrostatic image development, characterized in that a carrier core material is coated with resin particles in which carbon black is dispersed by dry coating, which is adhered and fixed by applying mechanical impact. (2) For electrostatic image development, characterized in that a carrier core material is coated with resin particles in which carbon black and a charge control agent are dispersed by a dry coating that is adhered and fixed by applying mechanical impact. carrier. (3) The electrostatic coating according to claim 1 or 2, wherein the dry coating repeatedly applies impact force to the mixture of the carrier core material and the resin particles in which carbon black is dispersed at a temperature at which the resin particles do not melt. Carrier for image development. (4) The carrier for electrostatic image development according to claim 1 or 2, wherein the dry coating is repeatedly applied with impact force at a high temperature range with an upper limit of 50° C. higher than the glass transition point of the resin particles. . (5) The carrier for electrostatic image development according to claim 1, 2, 3 or 4, wherein the resin particles are a mixture of those in which carbon black is dispersed and those in which carbon black is not dispersed.