JPH02158751A - Carrier for developing electrostatic image - Google Patents

Abstract

PURPOSE:To obtain the carrier for developing electrostatic images which can maintain stable image quality in spite of repetitive use by coating a core material with resin particles of <=0.45mum thereon by a dry process coating. CONSTITUTION:The core material is subjected to the dry process coating using the resin particles having <=0.45mum average grain size, by which the resin layer is provided on the core material. The resin particles sticking on the core material receive impact force and are rearranged under movement on the core material or deformation and further, the resin particles come into contact with the core material and the adjacent resin particles and are thereby immobilized. The deformed components are pushed into gaps and the denser coating layer is formed. This process is smoothly progressed by using the resin particles having <=0.45mum average grain size. The resin having the excellent film formability and high coating efficiency is obtd. in a short period of time. The resin layers are resistant to flawing and the stable images are obtd. in spite of the repetitive use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a carrier for electrostatic image development, in which a core material is coated with resin particles of 0.45 μm or less by dry coating.

[Background of the Invention] A two-component developer consisting of a toner and a carrier can control the charge polarity and charge amount of the toner to a considerable extent, and the range of colors that can be applied to the toner is wide. It has the advantage of being spacious.

In two-component developers, the carrier core material is often coated with resin. With such coated carriers, the characteristics of the core material are not exposed on the surface even after repeated use, so the carrier core material is coated with resin. Control of triboelectricity of toner,
Excellent in extending developer life and maintaining recorded image quality.

However, as high-speed copying machines have become popular in recent years, the developer is used under harsh conditions, and the surface of the carrier is easily damaged, resulting in an extremely short service life. Therefore, it is necessary to frequently replace the carrier.

[Problems to be Solved by the Invention] Dry coating, fluidized bed spray coating, immersion coating, sintering coating, and the like are known as methods for coating a core material with a resin in a coated carrier. Among these, dry coating has many manufacturing advantages, as it does not require the use of solvents or sintering equipment.

It is said to be preferable because it does not cause granulation and has high productivity.

On the other hand, in order to extend the life of the carrier, it is necessary to increase the amount of resin coated on the carrier core material, increase the coating efficiency, and cover the core material sufficiently with the resin. There is a limit to the amount of resin that can stick to the surface, and it becomes necessary to apply dry coating several times, which greatly reduces production efficiency.

On the other hand, it is also possible to increase the amount of resin fixed in one dry coating by increasing the particle size of the 4$I fat and increasing the applied impact force. However, increasing the resin particle size makes it difficult to make the thickness of the resin layer uniform during the process of adhering and fixing the resin onto the core material and forming a film.In addition, increasing the impact force may cause problems with the core material. Abrasion and fragmentation of the material occurs, resulting in carriers that differ from the target particle size. In addition, a one-class sieving step is required because fine powder of the core material is generated.

By the way, Japanese Patent Publication No. 63-26385 discloses a technique in which a core material is coated with a resin by dry coating and then heated to fuse the resin onto the core material.

Since the above technology adheres the resin to the core material by heat fusing, it is prone to agglomeration.In particular, in order to thicken the coating layer on the core material, the amount of resin is increased, or the resin particle size is increased. This causes granulation. This requires a single sieving step, which increases the number of production steps and reduces yield.

In addition, JP-A No. 63-37858 discloses that a titanium coupling agent is dry-coated on a core material, and then 0.5 μm resin particles are coated on the core material by dry coating, and then a resin layer is formed by heating. A technique for fusing the two is disclosed.

In the above technology, since the resin particles are bonded to the core material using a sealing agent, the temperature of heat fusing can be adjusted to
Although it can be lowered according to Japanese Patent No. 26385, since the resin particle size is large, the +! The film forming properties of the 1 resin layer are poor, and when used repeatedly, the resin layer peels off and the characteristics of the core material are exposed on the carrier surface, resulting in a decrease in image quality.

As described above, in order to obtain an electrostatic image developing carrier suitable for the harsh conditions of use of high-speed copying machines, there remain issues to be solved in terms of manufacturing and quality.

The present invention has been made to solve the above problems,
The purpose is to provide a carrier for electrostatic image development that has high production efficiency, is low cost, and can maintain stable image quality even after repeated use.

[Means for Solving the Problems] As a means for solving the above problems, the carrier for electrostatic image development of the present invention is provided by dry-processing resin particles having an average particle size of 0.45 μm or less on a core material. It is characterized by being covered with a coating.

The surface of the core material is preferably surface-treated with a coupling agent.

The above coupling agent is a titanium coupling agent, aluminum coupling 41. Alternatively, it is preferable that it consists of at least one kind of silane coupling agent.

It is preferable that the dry coating is performed by repeatedly applying a force of 1 frffl after mixing and stirring the core material whose surface has been treated with a coupling agent and the resin particles.

The resin particles used in the present invention have an average particle size of 0.45μ
m or less, preferably 0.25 μm or less. If resin particles having an average particle size of more than 0.45 μm are fixed onto the core material by dry coating, film forming properties are poor and the resin will peel off from the carrier when used repeatedly.

If you try to increase the impact force to improve film formation, the core material will wear out and break up, resulting in carriers with a particle size different from the desired size.In order to remove the core material fine particles, a classification sieve process is also required. It becomes necessary.

The average particle size of the resin particles was measured using a centrifugal automatic particle size distribution analyzer CAPA-500 (manufactured by Horiba, Ltd.).
An aqueous solution containing resin particles dispersed in a quartz cell was placed at 25°C.
The measurement was carried out at a rotational speed of 300 rpm. The average particle size obtained is the number average particle size.

In the present invention, the core material to which the resin particles are fixed preferably has a specific resistance of lXl0''Ω·1 or more, more preferably lXl0″Ω·1 or more.

Setting the specific resistance to the above value means that the core material is completely covered with the resin layer, and the properties of the core material are shielded and do not affect the properties of the carrier particles. The carrier always has a constant performance regardless of the electrical conductivity of the core material.

When the weight average particle diameter of the resin particles is too large, it becomes difficult for the resin particles to spread on the surface of the core material, making dry coating processing difficult.

Examples of resins used in the present invention include styrene resins (styrene homopolymer, copolymers of styrene and alkyl (meth)acrylate, etc.), epoxy resins (copolymers of bisphenol A and epichlorohydrin, etc.), and acrylic resins. resins (polymethyl methacrylate, etc.), polyolefin resins (polyethylene resins, LLDPE, polybutadiene resins, etc.), polyurethane resins (polyurethane resins, etc.).

Polyester-polyurethane resins, etc.), nitrogen-containing vinyl copolymers (polyvinylpyridine, etc.), polyester resins (polymers manufactured from diols such as ethylene glycol and divalent organic carboxylic acids such as maleic acid or phthalic acid, etc.) ), polyamide resin (6 nylon, 6
-6 nylon, etc.), polycarbonate (phthalic acid polyethylene, etc.).

Examples of cellulose derivatives include trocellulose, alkylcellulose, etc.) and silicone resins.

Among these, styrene and acrylic resins are particularly preferred.

Since styrene and acrylic resins have good adhesion to the core material, the mechanical strength of the obtained carrier is improved, and the chargeability is more stable than when other resins are used. Furthermore, under high temperature and high humidity conditions (e.g., temperature: 30°C)
Even if the carrier is stored or used for a long time at 280% humidity, there is almost no change in the chargeability of the carrier, and furthermore, there is little deterioration in powder properties.

Examples of the styrene resin include styrene, methylstyrene, dimethylstyrene, trimethylstyrene,
Alkylstyrenes such as ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene and octylstyrene, halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dipromostyrene and iodostyrene, nitro Homopolymers of styrene monomers such as styrene, acetylstyrene and methoxystyrene, and homopolymers of alkyl (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate and butyl (meth)acrylate. and copolymers thereof.

Among these styrene resins, copolymers of styrene and alkyl (meth)acrylates are preferred, and in this case, the alkyl (meth)acrylate is usually 1.
Methyl methacrylate (MMA) is used. in this case,
The molar ratio of styrene repeating units and methyl methacrylate repeating units in the copolymer is 5:95 to 9.
5:5 (smooth, preferably 10:90 to 90:10
), and by using a copolymer within the above range, the powder retention of the carrier under high temperature and high humidity conditions is further improved, and the chargeability is improved. Its properties are maintained for a long time.

The number average molecular weight of the styrene homopolymer or the above-mentioned copolymer used in the present invention is usually so or oo.

~200,000, Mw/Mn
The value of is.

Usually within the range of 1.0 to 5.0, preferably 1.5 to
It is within the 2.5 range.

Note that this copolymer or styrene homopolymer may contain other repeating units. However, if the layer is made of a styrenic copolymer, in order to effectively utilize the properties of the styrene copolymer, the content of the styrene copolymer in this layer is usually 50% by weight. Do more than that.

In order to effectively bring the specific resistance of the core material having a resin layer to the above value, the amount of resin is usually 0.1% by weight or more, preferably 0.5 to 1000% by weight based on the weight of the core material. The thickness of the resin layer formed by using a resin such as styrene resin in the above weight ratio to the weight of the core material is usually within the range of is 0.05μm
Above, preferably in the range of 0.1 to 5.0 μm.

The coupling agent used in the present invention is characterized by comprising at least one of a titanium coupling agent, an aluminum coupling agent, and a silane coupling agent. The above coupling agents may be used in combination.

By surface-treating the surface of the core material with a coupling agent, the affinity between the resin and the core material increases; that is, the coupling agent of the present invention is the central element.

Hydrophilic and lipophilic groups may be attached to titanium, aluminum, and silane.

It is preferable that the coupling agent covers the surface of the core material in a monomolecular layer. In order to uniformly form a resin layer, it is necessary to cover the entire surface of the core material with the coupling agent. but,
When it is thicker than a monomolecular layer, the stickiness of the core material increases and film formability deteriorates.

The amount of the coupling agent used in the present invention varies depending on the type of core material and coupling agent used, but is 0.
001 to 1.0% by weight is preferable, and more preferably 0.01 to 1.0% by weight.
0.5% by weight is more preferable. If it is less than 0.001% by weight, the adhesion between the resin layer and the core material is insufficient, and if it is more than 1.0% by weight, the adhesiveness of the resin layer to the core material increases. On the contrary, the film formability deteriorates.

The method of surface treating the core material with a coupling agent is as follows:
While stirring the core material in a mixer or blender,
There is a dry method in which a coupling agent is added, a spray method in which the coupling agent is dissolved in water or an organic solvent and sprayed onto the core material, and a slurry method in which the core material is immersed in the coupling agent solution. .

The coupling agent used in the present invention will be specifically described below, but the present invention is not limited thereto.

Examples of the silane coupling agent include vinyltrichlorosilane, vinyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane,
γ-chloropropylmethyljethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(
β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane,
Examples include γ-methacryloxypropylmethyldimethoxysilane.

Examples of the titanium coupling agent include a monoalkoxy type having an isopropoxy group, a chelate type having an oxyacetic acid residue or an ethylene glycol residue, and a coordinate type in which ethyl phosphite is added to a tetraalkyl titanate.

Monoalkoxy types include isopropyl dimethacrylic isostearoyl titanate and isopropyl tri(dioctyl phosphate) titanate.

Examples include isopropyl tricumylphenyl titanate, isopropyl tri(N-aminoethylaminoethyl) titanate, isopropyl trioctanoyl titanate, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctylpyrophosphate) titanate, and the like.

Chelate types include bis(dioctylpyrophosphate)oxyacetate titanate, dicumylphenyloxyacetate titanate, diisostearoylethylene titanate, and the like.

The coordinated type is tetraisopropylbis (
Examples include ditridecyl phosphite) titanate and tetraoctyl bis(ditridecyl phosphite) titanate.

Examples of the aluminum coupling agent include acetalkoxyaluminum diisopropylate.

As the core material of the carrier used in the present invention.

Inorganic powders such as glass peas, metal powders such as aluminum powder, iron powder and nickel powder, metal oxide powders such as iron oxide, ferrite and magnetite, and organic metal powders such as carbonium iron powder Part 1 of a suitable coat carrier. Materials used as core materials can be used.

Among these, carriers using ferrite as a core material are particularly preferred because they provide high image quality and high durability.However, ferrite is prone to wear and fragmentation when subjected to impact force due to dry coating. According to the present invention, since the impact force can be alleviated, dry coating can be performed without causing wear and fragmentation.

In the present invention, the specific resistance of the core material itself is 1×to”Ω・
1 or less, more preferably lXl0''Ω·1 or less.

Among these, the present invention is particularly effective when using magnetic particles such as iron powder and ferrite powder.

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

Note that in the above chemical formula, 1M represents a divalent metal, and specifically represents nickel, copper, zinc, manganese, magnesium, lithium, etc.

The ferrite preferably used as the core material may have an amorphous shape, but is preferably spherical. The size of the ferrite is preferably in the range of 20 to 200 μm, with a weight average particle diameter of 30 μm.
Particles in the range of ~120 μm are more preferable; particles smaller than 20 μm are difficult to form a resin layer;
Particles larger than μm result in a coarse-grained image.

The mixing weight ratio of ferrite and resin particles varies depending on the specific gravity of ferrite and cannot be generally defined, but is preferably about 100:1 to 100:10, for example.

The IT force applied to the mixture of ferrite and resin particles may be of a magnitude that does not abrade or crush the ferrite and does not crush the resin particles.

As the ferrite, ferrite having a weight average particle diameter of 20 to 200 μm is used as described above.

When the weight average particle diameter is too small, the resulting coated carrier has a small diameter, which tends to cause the carrier to adhere to the latent image bearing member, resulting in deterioration in image quality. On the other hand, when the weight average particle size is too large, the resulting coated 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 toner concentration.

Equipment costs are high, and it is difficult to support the coated carrier uniformly and with high density on the developer carrier, resulting in an insufficient amount of toner adhering to the carrier and being transported to the developing space. It becomes unstable, resulting in poor developability and deterioration of image quality.

The circularity of the ferrite is preferably 0.70 or more. When such magnetic particles with high circularity are used, the resulting coated carrier has high circularity, so the fluidity of the carrier increases, and as a result, an appropriate amount of toner can be stably delivered to the developing space. It becomes possible to transport the layer and exhibits excellent developability.

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.).

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.

Note that the weight average particle size is determined by "rMicrotrack" (LEEDS & NORTHR).
It was measured using a dry method using TYPE 7981-OX manufactured by UP).

Examples of manufacturing equipment for the carrier for electrostatic image development of the present invention include a hybridizer (manufactured by Nara Kikai Seisakusho) as an impact type surface modification device, a Mechano Mill (manufactured by Kaida Seiko Ill.), and a laboratory as a high-speed stirring type granulator. - Matrix (manufactured by Nara Kikai Seisakusho), Particle Granulator - (manufactured by Fuji Sangyo), Spiral Flow Coater (manufactured by Freund)
, New Marmerizer (manufactured by Fuji Sangyo);
A turbo sneaker mixer (manufactured by Shinmaru Enterprises) is an example.

FIG. 1 shows a high-speed stirring mixer preferably used in the dry coating of the present invention. In the figure, 10 is a main body container, 11 is an upper lid of the main body, 12 is a raw material inlet, 13 is a bag filter, and 114 is a Jacket, 15 is a thermometer, 1
6 is a main stirring blade consisting of three pieces (an auxiliary stirring blade may be attached from the side in FIG. 1), and 17 is a product discharge port.

In this device, a mixture of core material and resin particles inputted from a raw material input port 10 is rotated and dispersed by a main stirring blade 16, and generates an impact force due to collisions with the main stirring blade 16 and collisions between the particles. The resin particles are spread and fixed on the surface of the core material.

In addition, in the present invention, a core material surface-treated with a coupling agent can be obtained using the method described above.

In the apparatus shown in FIG. 1, the fr impact force is preferably applied repeatedly at a temperature at which the resin particles do not melt. In particular, 50°C above the glass transition point of the resin particles.
It is preferable that the impact force is applied within a product temperature range with the upper limit being a high temperature.

Note that the product temperature is measured using a product thermometer 15.

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 core materials are bound together by resin particles and become granulated, and when the temperature reaches where the resin particles begin to melt, it becomes difficult to uniformly adhere the resin particles to the surface of the core material. Become.

The temperature here refers to particles made by adhering resin particles to a core material. A temperature subchamber probe is inserted into a particle group in which particles are flowing due to an impact force, and the particles are randomly transferred to the probe. This refers to the approximate average value of the surface temperature of particles obtained by contacting them. 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 by measuring 10 mm in length and 6 mm in diameter.
4am stainless steel (SUS304) wild blackmer-alumel thermocouple with cover (manufactured by Hayashi Denko Co., Ltd., T2O-
ni-2-6,4-100-U-304-KX-G-30
00) is used.

Then, point the one-item thermometer from a point approximately 1/3 of the height of the main container in the apparatus shown in Figure 1, parallel to the bottom of the main container, toward the center of the main stirring blade. Measurements are taken by inserting it so that it is located approximately 1/3 of the length of the tube.

On the other hand, the glass transition point 'rg can be determined by differential scanning calorimetry (D
SC), and can be measured, for example, by rDSC-20J (manufactured by Seiko Electronics Industries, Ltd.).

Specifically, approximately 10 cm of the sample was heated at a constant heating rate (10°C/
IIkin) and obtain from the intersection of the baseline and the slope of the endothermic peak.

The layer thickness of the carrier produced in this way is less than 5 μm, preferably less than 2 μm.

When using the carrier of the present invention, the toner particles and the carrier of the present invention are mixed in a weight ratio of 1:99 to 10:90, preferably 2:98 to 8:92. The carrier and toner can be mixed according to one conventional method.

[Effect] The present invention provides a carrier for electrostatic image development.

By performing dry coating using resin particles with an average particle size of 0.45 g or less, a resin layer with good film formability and high coating efficiency is provided on the core material.

The film formation process of dry coating is thought to be linear, although it is not necessarily clear.

In the ordered mixture state, the resin particles adhering to the core material are rearranged while moving or deforming on the core material under impact force. Further, the resin particles are fixed by contacting with the core material and adjacent resin particles, and the deformed portion is pushed into the voids, thereby making the coating layer dense.

When resin particles having an average particle diameter of 0.45 μm or less are used, the above process can proceed smoothly. Therefore, a resin with excellent film-forming properties and high coating efficiency can be obtained in a short time.

Furthermore, since the above process proceeds regardless of the glass transition point of the resin particles or the temperature of the dry coating, the range of manufacturing conditions can be expanded.

Furthermore, when the surface of the core material is treated with a coupling agent, the resin particles strongly adhere to the core material. Therefore, in order to thicken the resin layer, even if the amount of resin is increased, unfixed resin will not be generated.
No reduction in coating efficiency.

The electrostatic image developing carrier obtained in this way does not easily scratch the resin layer even after repeated use, and the characteristics of the core material are not exposed on the surface, so stable images can be obtained. .

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

Example group - 5 kg of octspherical ferrite particles (average particle size 80 μm),
75 g of a methyl methacrylate-butyl acrylate-butyl methacrylate copolymer (glass transition point = 70°C) having an average particle size of 0.06 μm was mixed and stirred at room temperature to obtain an ordered mixture.

Impact force was repeatedly applied to the above mixture using a high-speed stirring type mixer at a product temperature of 70 to 80°C to obtain a carrier of Example-1.

The product temperature was measured by inserting a chromel-alumel thermocouple into the rotating particle bed. In addition, the absence of granulation was confirmed by particle size distribution using a sieve method.

In the same manner as in Example 1, carriers of Examples 2 to 4° and Comparative Examples 1 to 2 were obtained in which the average particle diameters of the resin particles used were different, as shown in Table 1.

The peripheral speed of stirring was set to the standard speed in Examples 1 to 4 and Comparative Example-1, and was set to 1.5 times the standard speed in Comparative Example-2.

The charge coverage was obtained according to the following formula.

Next, the effective coverage was obtained according to the following formula.

The coating efficiency can be obtained from the following formula.

The amount of coating resin is determined by removing unfixed resin particles.
Only the resin fixed in the film was dissolved using methyl ethyl ketone and determined by gravimetric method.

Furthermore, in parentheses, the apparent effective coverage was determined before unfixed resin particles were removed, and then the apparent coverage efficiency was determined and its value is shown.

FIG. 2 shows the change over time in the amount of triboelectrification with respect to the film formation fixation treatment time. The amount of triboelectric charge was determined by adding toner for U-Bix5070 (manufactured by Konica Corporation) at a toner concentration of 4% by weight, mixing with shaking, and then using a blow-off method.

The terms in FIG. 1, other than coating efficiency, have the following meanings.

Peripheral speed: Shown as the rotational peripheral speed of the tip of the main stirring blade.

Processing time: repeated impact force and applied time, i.e.
This is the stirring time.

Surface condition: Surface condition was observed using a scanning electron microscope.

Note that the numbers in [ ] indicate the processing time of the am sample.

Film-forming time: The processing time that converged to an appropriate amount of triboelectric charge was defined as the film-forming time.

FIG. 2 shows the relationship between the amount of triboelectric charge and the processing time.

Example Group-B Example 5 shown in Table 2 was carried out in the same manner as Examples-1 to 4, except that methyl methacrylate-styrene copolymer (glass transition point = 110°C) loog was used as the resin particles.
~8 carriers were obtained.

Furthermore, using the same recipe as in Examples 1 to 8, the peripheral speed was 0.3 times the reference speed, and one product was processed at a temperature of 35 to 50°C.
Carriers of Examples 9 to 16 shown in the table were obtained.

The coating efficiency and film-forming time of the carriers of Examples 5 to 16 were
The results are summarized in Table 3.

Although repeated washing was performed to determine the amount of unfixed resin particles, there was no change in the coating efficiency and there were no unfixed resin particles.

Table 2 Example Group - While stirring spherical ferrite particles (average particle size 100 μm) 5-, 25 g of isopropyl dimethacrylylisostearoyl titanate was added as a titanium coupling agent using a dry method, and the surface of the core material was Processed.

Furthermore, a methyl methacrylate-butyl acrylate-butyl methacrylate copolymer (glass transition point 70°C) and a methyl methacrylate-styrene copolymer (glass transition point 110°C) with resin particles having a particle size of 0.25 μm were charged for coverage. The required amount was added so as to have three levels of 1.5, 2.5 and 3.5%, and the mixture was mixed and stirred to adhere resin particles onto the core material to obtain a mixture.

A carrier was obtained by repeatedly applying impact force to the above mixture at a temperature of 70 to 80° C. using a high-speed stirring type mixer.

As a comparative example, the charging coverage was 0.5% and 1.0%.

It becomes 1.5%, 2.0%, 2.5%. A carrier without core material surface treatment with a coupling agent was also produced.

The effective wave* factor and coating efficiency were determined for these Examples and Comparative Examples and summarized in Table 4.

Furthermore, FIG. 3 shows a graph of the relationship between effective coverage and coverage efficiency.

Example group-D and 96 parts by weight of the carrier used in Example Group-8.

4 parts by weight of toner for an electrophotographic copying machine rU-B i x5070J (manufactured by Konica Corporation) was mixed with a YGG mixer ((
(manufactured by Yayoi Co., Ltd.) at ioorpm for 20 minutes to prepare a developer. Regarding Comparative Examples -1 and -2,
It was used after removing unfixed resin particles by washing.

(Evaluation of developer) The developer used was an electrophotographic copying machine rU-B i X5000J.
With a modified machine (manufactured by Konica Corporation), the temperature was 33℃,
A live-action evaluation was conducted under an environmental condition of 80% relative humidity.

For evaluation, initial charge amount, initial image, final image, number of continuous copies (durability), and apparent resistivity were investigated. 5th result
It is summarized in the table.

The meanings of the terms in Table 5 are as follows.

rIg r74 amount" is the value of the amount of triboelectric charge per 1 g of developer measured by the blow-off method.

rpmaXJ represents the highest image density, expressed as the relative density of the developed image when the image density of the original image is 1.3.

"Fog" is expressed by the relative density of the developed image when the density of the original image is O.

"Durability" is the number of copies when the fog value of the developed image becomes 0.03 or more or the value of D+sax becomes 0.7 or less. In addition, the number of copies is r 5ooo
``more than o copies'' also means 5oooo copies.

This means that neither the fog value nor the D*ax value reached the above limit value.

The "specific resistance" was calculated from the current value flowing through a 1 cm carrier layer when 100 V was applied under the conditions of an electrode area of 1 d and a load of 1 kg. For the 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.

As is clear from Table 1 and FIG. 2, the carriers of the Examples using resin particles with an average particle size of 0.45 μm or less required a shorter time to form a film.

Moreover, the film-forming property is good, and since the amount of unfixed resin is small, the coating efficiency is high, and the core material is sufficiently covered with the resin layer.

On the other hand, in the carrier of the comparative example, the amount of triboelectric charge did not converge even after being treated for 180 minutes, and a film was only partially formed on the surface of the core material. Even if attempts are made to improve film formability by increasing the circumferential speed, wear and fragmentation of the core material still occurs.

As is clear from Tables 2 and 3, regardless of whether the glass transition point of the resin particles used is higher or lower than the material temperature, the carrier of the present invention can maintain the core material by repeatedly applying VVa force. Good film forming properties and high coating efficiency without causing abrasion or fragmentation.

As is clear from Table 4 and Figure 2, when a carrier using a core material whose surface is not surface-treated with a coupling agent is used, when trying to increase the charging coverage to 1.5% or more, the resin particles are removed from the core material. The amount of unfixed resin increases, the coating efficiency decreases, and the resin layer cannot be thickened.

On the other hand, a carrier using a surface-treated core material does not reduce the coating efficiency even when the amount of resin is increased, and has good film forming properties because there is no free resin.

As is clear from Table 5, the developer using the carrier of the present invention exhibits stable and good running performance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of the dry coating device;
FIG. 2 is a view of the main stirring blade in direction A in FIG. 1, FIG. 3 is a graph showing the relationship between the amount of triboelectric charge and processing time, and FIG. 4 is a graph showing coating efficiency and measured coverage. 10... Main body container, 11... Main body upper lid, 12...
・Raw material input port, 13...Bag filter-114...
Jacket, 15... Temperature needle, 16... Main stirring blade, 17... Product discharge port.

Claims (4)

[Claims] (1) Resin particles with an average particle size of 0.45 μm or less,
A carrier for electrostatic image development, characterized in that a core material is coated with a dry coating. (2) The carrier for electrostatic image development according to claim 1, wherein the surface of the core material is surface-treated with a coupling agent. (3) The coupling agent is a titanium coupling agent,
3. The carrier for electrostatic image development according to claim 2, comprising at least one of an aluminum coupling agent and a silane coupling agent. (4) The carrier for electrostatic image development according to claim 1, 2 or 3, wherein the dry coating is performed by repeatedly applying impact force after mixing and stirring the core material and the resin particles.