JP3141298B2 - Electrophotographic carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier comprising an electrostatic image developer mixed with a toner.

[0002]

2. Description of the Related Art U.S. Pat.
7, 691, JP-B-42-23910, JP-B-43-24748, and the like, various methods are described. In any of these methods, a photoconductive layer is formed on a photoconductive layer according to an original. An electrostatic latent image is formed by irradiating the image, and then a fine colored powder called a toner having a polarity opposite to that of the electrostatic latent image is deposited on the electrostatic latent image to develop the electrostatic latent image. After the transfer of the toner image onto a transfer material such as paper, the image is fixed by heat, pressure, solvent vapor, or the like to obtain a copy.

In the process of developing the electrostatic latent image, toner particles charged to the opposite polarity to the latent image are attracted by electrostatic attraction and adhered on the electrostatic latent image (reversal development). In the case of (1), a toner having a triboelectric charge having the same polarity as the charge of the latent image is used). Generally, the method of developing such an electrostatic latent image using the toner is roughly divided into a small amount of toner dispersed in a medium called a carrier. There are a method using a so-called two-component developer and a method using a so-called one-component developer using a toner alone without using a carrier.

In general, carriers constituting such a two-component type developer are roughly classified into conductive carriers and insulating carriers.

[0005] Oxidized or unoxidized iron powder is usually used as the conductive carrier. However, in a developer containing the iron powder carrier as a component, the triboelectric charging property with respect to the toner is unstable. There is a problem that fogging occurs in the formed visible image. That is, with the use of the developer, the toner particles adhere to the surface of the iron powder carrier particles, so that the electric resistance of the carrier particles increases, the bias current decreases, and the triboelectrification becomes unstable. The image density of the visible image decreases and fog increases.

A typical carrier typically has a carrier core material made of a ferromagnetic material such as iron, nickel or ferrite and the surface of which is uniformly coated with an insulating resin. In a developer using this carrier, toner particles are less likely to fuse to the surface of the carrier than in the case of a conductive carrier, and have excellent durability and a long service life. It has the advantage of being suitable.

However, in this insulating carrier, the coating layer covering the surface of the carrier core material has sufficient abrasion resistance and strong adhesion to the core material, and the toner is fused to the carrier surface, so-called toner spent. Is not required, and it is required to impart a desired and sufficient amount of triboelectric charge to a specific toner used together with the carrier. That is, the carrier is rubbed with other carrier particles and toner particles in the developing device, but if the carrier coating layer does not have sufficient film strength and adhesiveness with the core material, the coating film is peeled off from the core material. The toner is missing, and the ability to impart charge to the toner is reduced. Also, when toner spent occurs on the carrier surface, the inherent triboelectric charging ability of the carrier coating layer cannot be exerted, and the charging characteristics become unstable.

Conventionally, as a technique for solving such a disadvantage,
In the case of a carrier not coated with an insulating resin, Japanese Unexamined Patent Publication No.
As disclosed in JP-A-180563, attempts have been made to form a thin film of a fatty acid metal salt on the surface of a carrier core material to increase the toner spent resistance and improve the charge imparting property.
However, if the developer using the carrier is left under high temperature and high humidity for a long time, the fatty acid metal salt on the surface of the carrier core moves to the toner resin layer having a high affinity, and as a result, the charging of the toner becomes unstable. There is a problem that image deterioration such as fogging and scattering occurs. Furthermore, if not covered with an insulating resin to some extent, ferrite particles as well as iron oxide powder are unsuitable for a developing system in which a bias voltage is applied due to current leakage or carrier adhesion to the photoreceptor. It is.

As the carrier coated with an insulating resin, U.S. Pat. S. P. 3,922,382,
In the above-mentioned prior art, the carrier coated with only the fluoropolymer has poor film-forming properties, and can only partially cover the carrier surface, and the charging characteristics become unstable. Further, in order to improve the film forming property of the fluorine-containing polymer, a method of coating by mixing with a polymer having a relatively good film forming property is disclosed in U.S.
S. P. 4,297,427, JP-A-54-11083.
No. 9 is proposed. However, it is considered that any of these can be advantageously used for a positive toner because a fluoropolymer having a strong negative property in terms of charging characteristics is used as a constituent, but a desired moderate size is considered for a negative toner. It is expected that it is difficult to obtain the charge amount, and even if a sufficient value is obtained as the magnitude of the charge amount,
It is considered that the rising speed of charging is slow and it is difficult to maintain stable charging properties.

[0010] Furthermore, Japanese Patent Application Laid-Open No. 58-216261 proposes a carrier in which a metal core is coated with a binder resin containing calcium stearate. Due to mixing and stirring of the agent in the developing device for a long time,
There is a problem that peeling occurs and stable charging characteristics cannot be maintained.

On the other hand, in order to speed up the rise of the frictional charge of the toner, as is conventionally known, there is a method of adding a charge control agent or a charge control resin to the toner, but this alone is not sufficient. The rise of the charge amount cannot be made faster, and conversely, in an environment such as high temperature and high humidity, or low temperature and low humidity, the frictional charge amount and the rise of the charge may be considerably different, which is caused by fog and density as an image. For example, it is not sufficient as a method for controlling the charge of the toner, for example, it is thin. A method of increasing the triboelectric charging property of a toner by adding fine particles positioned in the opposite direction to the toner on the triboelectric series to the toner is also disclosed in JP-A-62-755.
No. 51.

However, with this method alone, toner charge control is still insufficient. If fine particles charged to the opposite polarity to the toner are added to the toner until the frictional charge amount of the toner is sufficiently controlled, the reverse As a result, the toner particles aggregate and the fluidity of the toner deteriorates. As a result, the carrier and the toner cannot be sufficiently mixed, and it is necessary to provide a stronger and more uniform stirring device in the configuration of the developing device. Further, when the fluidity of the toner deteriorates, it may cause an adverse effect on a cleaning device of a copying machine.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and to provide a developer which is excellent in durability and toner-spent resistance, has a very fast rise of charging and provides a stable image. Is provided.

A further object of the present invention is to provide a carrier constituting a developer which has excellent fluidity and gives an extremely stable image over a long period of time.

Still another object of the present invention is to provide a carrier which has an appropriate resistance and is less likely to leak current or adhere to a photosensitive member even when a bias voltage is applied. .

[0016]

SUMMARY OF THE INVENTION The present invention provides an electrophotographic carrier coated with a resin composition having a domain-matrix structure and containing a fatty acid metal salt,
The domain particles have an average particle size of 5 μm or less, the resin constituting the domains has a carboxyl group, a glass transition point Tg ₁ of 20 to 70 ° C., and an acid value of 15 or more, and constitutes the matrix. The resin has substantially no carboxyl group and has a glass transition point Tg ₂ of 5
0 to 80 ° C., an acid value of 10 or less, and Tg ₂ ≧ Tg ₁ .

The present inventors believe that the reason why the resin-coated carrier used in the present invention is excellent in the above-mentioned properties is as follows. That is, the resin-coated carrier is excellent in durability because a so-called sea-island structure comprising a domain-matrix in which a resin having a high Tg is used as the sea and a resin having a carboxyl group and a low Tg is used as an island. As a result, it is possible to absorb or reduce the impact caused by the contact between the toner and the carrier and between the carrier and the carrier. Furthermore, the islands formed by the sites having polar groups are dispersed at a microscopic level and countlessly, so that they are strongly adhered to the carrier core material, and the covering property is improved.
It is in a state that is even stronger than ordinary resins.

Further, in the carrier of the present invention, a fatty acid metal salt is contained in the coating resin. However, since the resin is composed of a domain-matrix, the fatty acid metal salt is a matrix of a hydrophobic resin portion having a high affinity. It is in a state of being unevenly dispersed to the side. Therefore, the smoothness of the carrier surface is improved, the fluidity of the developer is increased, and a rapid rise of charge is realized. Furthermore, while the fatty acid metal salt with excellent charge-imparting property is present in the matrix mainly involved in the power generation of the charge,
It has a polar group involved in the leakage of electric charge, and in the domain that is water-absorbing, it is possible to separate the function of the charge, which is almost absent. -ing

It is possible to blend an incompatible resin completely as a carrier coating resin and add a graft or a block polymer as a dispersing agent to make the resin have an apparent Shanghai island structure. In addition, the polarity of the graft or block polymer, which acts as a dispersant for the formed domains, is not so strong, so that the domains become large with long-term storage, and therefore, the durability and the developer The liquidity of the material deteriorates.

As a method for producing a resin having a domain-matrix structure, a method of blending a vinyl resin with a condensation resin such as polyester or epoxy resin is known. In this method, the weight average molecular weight is 50%.
With a molecular weight of 10,000 or more, and a vinyl resin with a very low polarity is formed by melting and kneading with a condensation resin such as polyester or epoxy resin, and sometimes no graft or block polymer is added,
Even if domains are formed, it is very difficult to control the domain diameter itself, and the domain diameter becomes larger due to long-term storage. As described above, when used as a carrier coating resin, durability and chargeability are increased. In addition, in terms of the rise of charging, the state in which the fatty acid metal salt is dispersed only in the matrix due to the weak polarity of the resin is not sufficient, and thus does not reach a satisfactory level.

The inventors of the present invention have conducted intensive studies and, as a result, have invented a carrier coated with a resin which does not cause the above-mentioned various problems. The coating resin in the present invention is Tg ₁
The present invention comprises a domain resin having a carboxyl group having an acid value of 15 or more at 20 to 70 ° C. and a matrix resin having a Tg _{2 of} 50 to 80 ° C. and an acid value of 10 or less and having substantially no carboxyl group. The carrier in the above uses the coating resin composition. With such a configuration, a carrier having excellent durability and excellent charging characteristics can be obtained because the Tg is lower than the matrix resin by 5 ° C.
In addition, since the domain resin having a carboxyl group associates with the carboxyl group to form micelles, it is dispersed very finely and stably.

Here, if Tg ₁ is lower than 20 ° C., the fluidity of the developer is deteriorated even if Tg ₂ is increased, and if Tg ₁ exceeds 70 ° C., the rise of charging is delayed. When the acid value of the domain resin is less than 15, the dispersion stability of the domain resin is poor, and therefore, the adhesion to the core material and the chargeability are poor. In addition, Tg ₁ is 50 ° C.
If the temperature is lower than 80 ° C., the fluidity deteriorates. If the temperature exceeds 80 ° C., the adhesion to the core material and the charging characteristics deteriorate. Further, when the acid value of the matrix resin exceeds 10, the compatibility with the domain resin increases, and the dispersion stability of the domain resin deteriorates.
Therefore, the durability is inferior. Accordingly, the glass transition point Tg of the domain resin constituting the coating resin composition
₁ is more preferably 25 to 60 ° C., and the glass transition point Tg ₂ of the matrix resin is more preferably 55 to 7
Desirably, the temperature is 0 ° C. Further, in order to exert the effect more in the present invention, Tg ₂ is desirably higher than Tg ₁ by 10 ° C. or more.

The amount ratio of the matrix resin to the domain resin is preferably 5 to 100 parts by weight per 100 parts by weight of the matrix resin. This is because if the amount of the domain resin is less than 5 parts by weight, the durability is insufficient and the charging characteristics are deteriorated. If the amount exceeds 100 parts by weight, the sea-island structure may be reversed. is there.

In the coating resin composition used in the present invention, examples of the matrix resin include a vinyl resin, a polyester resin, a phenol resin, and an epoxy resin. Among them, the vinyl resin has a weak polarity,
Therefore, since the dispersion stability of the domain particles is improved,
It is more preferable as the resin used in the present invention. As the domain resin, any polymer may be used as long as it has a carboxyl group.
A composition similar to the matrix resin can make the domain particles smaller. This is thought to be because the domains are partially compatible with the matrix resin, but in the case described above (when the acid value of the matrix resin exceeds 10).
On the contrary, the domains are not broken (the dispersion stability of the domain particles is deteriorated) by the polarity of the matrix resin, so that the durability is not inferior.

In the coating resin used in the present invention, the following can be cited as examples of vinyl monomers constituting the matrix resin.

For example, styrene, o-methylstyrene,
m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p- n-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o -Nitrostyrene, p-
Styrene derivatives such as nitrostyrene, and ethylene and unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride Vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and n-methacrylate
-Octyl, dodecyl methacrylate, methacrylic acid-2
Α-methylene aliphatic monocarboxylic esters such as -ethylhexyl, stearyl methacrylate, phenyl methacrylate; methyl acrylate, ethyl acrylate,
Acrylic esters such as n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N- N-vinyl compounds such as vinyl pyrrolidone; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Use of two or more those polymerized, is used.

In the coating resin used in the present invention, the following can be mentioned as the vinyl monomer constituting the domain.

For example, styrene, o-methylstyrene,
m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p- n-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o -Nitrostyrene, p-
Styrene derivatives such as nitrostyrene, and ethylene and unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride Vinyl halides such as vinyl acetate, vinyl propionate, and vinyl benzoate; methacrylic acid and methyl methacrylate, ethyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid α-methylene aliphatic monocarboxylic esters such as n-octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate; acrylic acid and methyl acrylate; Acrylic acid such as ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate Esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N
N- such as vinylindole and N-vinylpyrrolidone
One or more vinyl compounds; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; and acroleins are used.

In the present invention, the carboxyl group-containing vinyl monomer constituting a domain includes acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic anhydride, fumaric acid, maleic acid, and methyl, ethyl, Monoesters such as butyl and 2-ethylhexyl are mentioned, and one kind or two or more kinds of these monomers are used together with the above-mentioned monomers.

In the present invention, the content of the carboxyl group-containing vinyl monomer constituting the domain is 0.1 to 5 in the domain resin in order to reduce the domain particle diameter to 5 μm or less.
It is desirably 0% by weight, preferably 1 to 30% by weight.

In the present invention, the number average molecular weight (Mn) of the domain resin is from 1500 to 40000, preferably from 3 to
500-30000, weight average molecular weight (Mw) 300
0 to 300,000, preferably 5000 to 10000
Desirably, it is 0. The number average molecular weight (Mn) of the matrix resin is 1500 to 20000, preferably 3000 to 10000, and the weight average molecular weight (Mw) is 3
000 to 50,000, preferably 6,000 to 30,000
It is desirable that In the case of synthesizing the resin used in the present invention, when the resin is synthesized from a vinyl monomer, a generally known method, such as a method obtained by solution or suspension polymerization using a peroxide as an initiator, is used. No.

As a method of obtaining a domain-matrix (sea-island) structure using the matrix and domain resin obtained by this method, a simple and fine sea-island structure can be obtained simply by dry blending and melt-kneading. It is very difficult to make

As a result of intensive studies, the present inventors have succeeded in forming a uniform and fine sea-island structure by the following method.

Each of the polymerized resins is dissolved in a non-polar solvent (even if a polar solvent is used, a sea-island structure can be formed, but the domain particle size increases), and the solution is heated and strongly stirred. Blend with. In the present invention, it is very important to control the domain particle size small. The domain particle size is determined by the dissociation state of the carboxyl group. Therefore, in the case of blending, an auxiliary agent that does not react with a small amount of water or alcohol such as methanol or a carboxyl group, and dissociates the carboxyl group more is added, while increasing the temperature and increasing the stirring power at the time of blending. By doing so, the size can be further reduced.

When the domain resin is polymerized using a non-polar solvent and then the matrix resin is polymerized in the presence of the domain resin, the domain resin is blended in a micro-dispersed state. Can be very small. Also in this case, as described above,
Addition of a carboxyl group dissociation aid that does not inhibit polymerization is also effective in reducing the domain particle size.

Also, contrary to this method, the domain resin can be polymerized after first polymerizing the matrix resin. As still another production method, there is a method in which a polymer dissolved in unreacted monomer taken out after stopping at a certain reaction rate by performing bulk polymerization is obtained by suspension or solution polymerization. In this case, the carboxyl group-containing monomer has a higher reaction rate than other vinyl monomers, so it may be used at the stage of bulk polymerization, but more preferably, after bulk polymerization of the matrix resin, the domain resin is subjected to solution polymerization. A synthesis method is desirable.

The present inventors have also found that the more uniform the distribution of the monomer containing a carboxyl group in the polymer, the smaller the domain particle size and the more uniform the distribution of the domain particle size. So this means that
The above-mentioned resin can be obtained by a method in which a monomer having a carboxyl group is added little by little during the polymerization of the domain resin.

The fatty acid metal salts used in the present invention include aluminum stearate, calcium stearate, potassium stearate, magnesium stearate, barium stearate, lithium stearate,
Zinc stearate, copper stearate, lead stearate,
Nickel stearate, strontium stearate,
Cobalt stearate, cadmium stearate, zinc oleate, manganese oleate, iron oleate, cobalt oleate, copper oleate, magnesium oleate, lead oleate, zinc palmitate, cobalt palmitate, copper palmitate, palmitate magnesium,
Aluminum palmitate, calcium palmitate,
Zinc linoleate, cobalt linoleate, calcium linoleate, zinc ricinoleate, cadmium ricinoleate,
And lead caproate. This amount is 0.05 to 80% by weight based on the coating resin, and more preferably 0.1% by weight.
5 to 40% by weight.

In the present invention, as the carrier core material, iron powder,
All general materials such as ferrite can be used. The coating amount of the coating resin according to the present invention with respect to the carrier core material,
Resin solid content is 0.1 to 30% by weight, preferably 0.5 to
10% by weight. If the amount is less than 0.1% by weight, the effect of coating the carrier core material with the resin is not sufficient, and the coating amount exceeding 30% by weight is meaningless. Absent.

In the present invention, as the carrier core material, all general materials such as iron powder and ferrite powder can be used.
This is also one of the major features of using resin. The particle size of the carrier core material used is 10 to 1000.
μm, preferably 20 to 200 μm.

In the present invention, the coating resin of the present invention is applied to a carrier core material by dissolving or suspending the coating resin in a general solvent, and further dissolving a fatty acid metal salt in an arbitrarily selected solvent. Or, mix the dispersed solution and mix well with a mixer to prepare a solution in which the coating resin and the fatty acid metal salt are dissolved or suspended to the maximum. Coating method using a typical coating apparatus.

Incidentally, the carrier of the present invention can be used for positive, negative and opposite toners.

Here, the method of measuring the triboelectric charge amount of the toner with respect to the carrier in the present invention will be described in detail with reference to FIG.

A magnetic brush on a developer carrier for measuring a triboelectric charge amount in a metal measuring container 2 having a conductive screen 3 of 400 mesh (which can be appropriately changed to a size not allowing the passage of carrier particles) at the bottom. (A mixture of toner and magnetic particles) and a metal lid 4 is formed. At this time, the weight of the entire measurement container 2 is weighed and defined as W ₁ (g). Next, the suction machine 1
In the part (at least the part in contact with the measurement container 2 which is an insulator), the pressure of the vacuum gauge 5 is adjusted to 70 mmHg by adjusting the air volume control valve 6 by suctioning from the suction port 7. This state is enough (about 1
(Minutes) to remove the toner by suction. The potential of the electrometer 9 at this time is set to V (volt). Here, reference numeral 8 denotes a capacitor, whose capacity is C (μF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). The triboelectric charge amount Q (μC / g) is calculated as in the following equation.

Q (μC / g) = C × V / (W ₁ −W ₂ ) where the measurement conditions are 23 ° C. and 65% RH.

Next, the glass transition temperature: Tg will be described. In the present invention, a differential thermal analyzer (DSC)
Measurement device), DSC-7 (manufactured by PerkinElmer).

The measurement sample is 5 to 20 mg, preferably 10
Weigh the mg precisely.

This was put in an aluminum pan, and an empty aluminum pan was used as a reference.
The measurement is performed at a temperature rising rate of 10 ° C./min under normal temperature and normal humidity between 00 ° C.

In this temperature rising process, an endothermic peak of a main peak in a temperature range of 40 to 100 ° C. is obtained.

The intersection point between the line of the midpoint of the baseline before and after the endothermic peak appears and the differential heat curve is defined as the glass transition temperature Tg in the present invention.

Next, a method for measuring the molecular weight will be described.

In the present invention, the molecular weight of a chromatogram by GPC (gel permeation chromatography) is measured under the following conditions.

That is, the column was stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) was passed through the column at this temperature as a solvent at a flow rate of 1 ml per minute, and the sample concentration was 0.05 to 0.6 wt. % Of the THF sample solution of the resin adjusted to 50% to 200 μl is measured. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number. As a standard polystyrene sample for preparing a calibration curve, for example, a molecular weight of 6 × 10 ² , 2.1 × 10 ³ , manufactured by Pressure Chemical Co. or Toyo Soda Kogyo Co., Ltd.
4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.
1 × 10 ⁵ , 3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 1
0 ⁶ , 4.48 × 10 ⁶ , and at least 10
It is appropriate to use about a few standard polystyrene samples. An RI (refractive index) detector is used as the detector.

The column used is 10 ³ to 2 × 10 ^6.
In order to accurately measure the molecular weight region of the polystyrene gel column, a plurality of commercially available polystyrene gel columns may be used in combination. For example, μ-styra gel 500, 10 ³ , 10
⁴ , 10 ⁵ combinations, Showdex KF-80M, KF-801, 803, 804, 80
5 combination, KA-802, 803, 804, 805 combination, or TSKgel G100 manufactured by Toyo Soda
0H, G2000H, G2500H, G3000H, G
4000H, G5000H, G6000H, G7000
A combination of H and GMH is preferred.

Next, the acid value and a method for measuring the acid value will be described.

The acid value is important as it accurately indicates the progress of esterification in a short time. Generally, the esterification check starts at an acid value of about 80 and ends as needed between about 20 and 50.

The acid value is defined as the number of milligrams of potassium hydroxide required to neutralize the carboxyl group contained in 1 g of the resin. Accordingly, the acid value indicates the number of terminal groups. The measuring method is as follows.

Samples 2 to 10 g are weighed 200 to 300 ml
Weighed in an Erlenmeyer flask, and methanol: toluene = 3
About 50 ml of a 0:70 mixed solvent is added to dissolve the resin.
If the solubility is poor, a small amount of acetone may be added. Using a mixed indicator of 0.1% bromthymol blue and phenol red, a standardized N / 10
Titrate with potassium hydroxide to alcohol solution, and determine the acid value from the consumption of alcoholic potassium solution by the following calculation.

Acid value = KOH (ml number) × N × 56.1 / sample weight (where N is a factor of N / 10 KOH) Next, the average particle size of the domain particles will be described.

In the present invention, the average particle size of the domain particles is measured, for example, under the following conditions. About 0.1 g of the coating resin is placed on a glass plate and dissolved with a hot plate.
After dissolving the resin, apply rhodamine dye dissolved in ethanol
Add ~ 3 drops. As soon as the dye has been applied, a thin sample of the coating resin / rhodamine is made while covering and holding down the cover glass. (The domain resin is a polymer having a carboxyl group as described above.
Therefore, the rhodamine dye dissolved in ethanol is attracted by the carboxyl group and selectively colors the domain resin. ) This is observed with an optical microscope, and a photograph of at least four fields of view is taken at random. Particles that can be visually identified in these photographed photographs are measured for particle diameter. The average value of the particle diameters measured by the above method is obtained (number average), and is defined as the average particle diameter of the domain particles.

In the case where it cannot be seen by this method, osmic acid or ruthenic acid is used as a dye, and the domain is dyed in the same manner as described above. Thereafter, there is a method in which a slice is formed, the dispersion state of the domain is observed with a transmission electron microscope, and the average particle diameter of the domain is measured in the same manner as described above.

[0062]

The present invention will be described in detail below with reference to examples.

Production Example 1 of Carrier Coated Resin (Resin Blend) Polymerization of Domain Resin 92 g of styrene 78 g of n-butyl acrylate 15 g of monobutyl maleate (half ester) 15 g + 15 g (after 4 hours) Benzoyl peroxide 15 g 85 g of toluene 500 g The polymerization reaction is carried out at a temperature of 10 ° C for 10 hours. Monobutyl maleate was added and reacted in two portions, at the start of the polymerization and 4 hours after the start, in order to make the composition distribution in the polymer uniform. As a result, Mn5400, Mw130
A copolymer having a Tg of 33.0 ° C. was obtained (resin).

Polymerization of Matrix Resin 243 g of styrene 57 g of n-butyl acrylate 22.5 g of benzoyl peroxide 2750 g of toluene A polymerization reaction is carried out at 85 ° C. for 16 hours. As a result, a copolymer having Mn of 6000, Mw of 17000 and Tg of 59.0 ° C. was obtained (resin).

Next, the polymer-toluene solution after the polymerization reaction is weighed so that the ratio of (resin) to (resin) is 3: 7, and the (resin) and (resin) are mixed. . The temperature of the mixed solution was raised to 80 ° C and 0.1%
Of water, and after vigorous stirring, is dried to obtain a coating resin I.

The acid value of the coating resin I was 18.0, and the domain average particle size was 2.2 μm.

Production Example 2 of Coating Resin for Carrier (Polymerization in the Presence of Resin) Polymerization of Matrix Resin 165 g of styrene 35 g of n-butyl acrylate 15 g of benzoyl peroxide 15 g of 500 g of toluene A polymerization reaction was carried out at 85 ° C. for 10 hours and Mn 58
A copolymer having a Mw of 15,500 and a Tg of 61 ° C. was obtained.
Next, the domain resin was polymerized in the resin solution as described below.

Polymerization of Domain Resin Styrene 104 g N-butyl acrylate 66 g Monobutyl maleate 30 g Benzoyl peroxide 15 g Toluene 500 g is added to the resin solution, and further a polymerization reaction is performed at 85 ° C. for 16 hours. As a result, Mn5500, Mw1600
0 was obtained. This was dried to obtain a coating resin II. The acid value of the coating resin II was 16.0, and the domain average particle size was 0.6 μm. The Mn of the resin obtained by polymerizing only the domain resin was 6000, Mw 170
00, Tg 40.0 ° C.

Hereinafter, by changing the amount of the initiator and the ratio of the amount of the monomers,
Resins III-V were synthesized. Also, comparative resins A to E
Was also synthesized.

[0070]

[Table 1]

[0071]

[Table 2] Example 1 Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight Phthalocyanine pigment 5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight The above materials were sufficiently premixed with a Henschel mixer. Thereafter, the mixture was melt-kneaded at least twice with a three-roll mill, cooled, and coarsely ground to a particle size of about 1 to 2 mm using a hammer mill. Next, it was pulverized by a pulverizer using an air jet method. Further, the obtained finely pulverized product was classified to obtain a negatively triboelectrically-chargeable cyan powder having a volume average particle size of 9.2 μm.

100 parts by weight of the above colored powder and 0.5 part by weight of silica fine powder subjected to hydrophobic treatment with hexamethyldisilazane were mixed to obtain a cyan toner.

Next, the carrier coating resin I was dissolved in methyl ethyl ketone to prepare a 10% by weight coating resin solution.
A toluene solution of 10% by weight of aluminum stearate was added, and when the concentration of aluminum stearate relative to the solid content of the coating resin was adjusted to 5.0% by weight, the solution was stirred with a stirrer until it was sufficiently mixed to obtain a carrier coating solution. .

Next, the coating solution was applied to spherical ferrite particles having an average particle size of 45 μm by a coating machine (Spira Coater, manufactured by Okada Seiko Co., Ltd.). The obtained coated carrier was dried at 45 ° C. for 2 hours to remove the solvent, and then heated at 70 ° C. for 2 hours to obtain a resin-coated carrier.

The resin coating amount of the obtained carrier was 0.64.
By observation with an electron microscope, it was confirmed that the core material of ferrite was uniformly coated with the resin.

Further, this carrier and the above-mentioned cyan toner were mixed at a toner concentration of 5% in an N / N (23 ° C./60%) environment to prepare a developer, and a full-color copying machine CLC-500 manufactured by Canon Inc. was used. An image output test was performed under the above environment. The above results show excellent durability as shown in Table 3,
It can be seen that an image of good quality can be obtained stably. After collecting the developer after the endurance from the developing device, the toner / carrier is separated, and the collected carrier and the new cyan toner are mixed at a concentration of 5% in an N / N environment to obtain an N / N. When the charge amount was measured at / N, as shown in Table 3, the charge amount was almost the same as that of the new carrier. Also,
Observation of the recovered carrier with an electron microscope revealed no significant spent or toner peeling of the coating resin.

Further, during a series of image forming tests, the amount of carrier adhered to the photosensitive drum or paper is extremely small.
A good image with clear and sufficiently high density without fog and density unevenness was obtained.

Comparative Example 1 The carrier coating resin A was dissolved in a methyl ethyl ketone solution to prepare a coating solution of 10% by weight.

Next, the coating solution was applied to spherical ferrite particles having an average particle diameter of 45 μm by a coating machine (Spira Coater, manufactured by Okada Seiko Co., Ltd.). The obtained coated carrier was dried at 45 ° C. for 2 hours to remove the solvent, and then heated at 65 ° C. for 3 hours to obtain a resin-coated carrier.

The resin coating amount of the obtained carrier was 0.70
By observation with an electron microscope, it was confirmed that the core material of ferrite was uniformly coated with the resin.

Further, this carrier and the above-described cyan toner were mixed at a toner concentration of 5% in an N / N (23 ° C./60%) environment to prepare a developer, and a full-color copying machine CLC-500 manufactured by Canon Inc. was used. An image output test was performed under the above environment. In the above results, as shown in Table 3, the fluctuation of the charge amount is large due to the durability, and as a result, the difference in image density is large. In addition, the deterioration of the fluidity of the developer was observed. To investigate the cause, the developer after recovery was collected from the inside of the developing device, and the surface was observed with an electron microscope. The toner was spent on the carrier surface. There was found.

Example 2 Example 1 except that the carrier coating resin I was changed to II
And the results in Table 3 were obtained.

Example 3 Example 1 except that the carrier coating resin I was changed to IV
And the results in Table 3 were obtained.

Comparative Examples 2 and 3 Comparative Example 1 except that the carrier coating resin was changed to BC.
And the results in Table 3 were obtained.

[0085]

[Table 3]

[0086]

As described above, according to the present invention, (1) it is possible to obtain an image which is excellent in durability and toner-spent resistance, and has a fast charging rise and is stable. (2) The developer has excellent fluidity and gives a stable image for a long period of time. (3) Even when a bias voltage is applied, current leakage or carrier adhesion to the photosensitive member is small. There are advantages such as.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing an apparatus for measuring a triboelectric charge of a toner of a two-component developer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suction machine 2 Measurement container 3 Conductive screen 4 Lid 5 Vacuum gauge 6 Air flow control valve 7 Suction port 8 Condenser 9 Electrometer

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-238363 (JP, A) JP-A-1-167852 (JP, A) JP-A-62-138859 (JP, A) JP-A-5-138 72813 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/113

Claims (1)

(57) [Claims] 1. An electrophotographic carrier coated with a resin composition having a domain-matrix structure and containing a fatty acid metal salt, wherein the domain particles have an average particle size of 5 μm.
m or less, the glass transition point Tg ₁ resin constituting the domain and a carboxyl group is 20 to 70 ° C., and an acid value of 15 or more, substantially resin constituting the matrix of the carboxyl group Not having, and a glass transition point Tg ₂ of 50 to 80 ° C., an acid value of 10 or less,
An electrophotographic carrier, wherein Tg ₂ ≧ Tg ₁ .