JPH06282113A - Electrophotographic carrier - Google Patents

Abstract

PURPOSE:To obtain a carrier coating material which satisfies the required electrification property and shows excellent property against toner spent and good stability which gives high picture quality by coating a structural unit with a specified copolymer. CONSTITUTION:The carrier is coated with copolymers having both of the structural units expressed by formulae I and II and containing the structural unit of formula II by 0.1-50wt.% of the total weight of the copolymers. In formula I, A is a straight chain, branched chain, or cyclic alkylidene group having 1-10 carbon number, aryl substd. alkylidene group, arylene dialkylidene group, or -O-, -S-, -CO-, -SO-, or-SO2-, and R1-R4 are independently hydrogen atoms, halogen atoms or alkyl groups or alkenyl groups of 1-4 carbon number. In formula II, R5 is an alkylene group or alkylidene group of 2-6 carbon number, R6, R7 are alkyl groups, phenyl groups, or substd. phenyl groups of 1-3 carbon number, and n is an integer 1-200.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier which constitutes an electrostatic charge developer together with a toner.

[0002]

2. Description of the Related Art US Pat. No. 2,29 as an electrophotographic method
Various methods are described in Japanese Patent No. 7,691, Japanese Patent Publication No. 42-24748, Japanese Patent Publication No. 43-24748, etc., and all of these methods are applied to the photoconductive layer according to the original. An electrostatic latent image is formed by irradiating an image, and then a colored fine powder called toner having a polarity opposite to this is deposited on the electrostatic latent image to develop the electrostatic latent image. The toner image is transferred to a transfer material such as paper in accordance with the requirements, and then fixed by heat, pressure, solvent vapor or the like to obtain a copy.

In the step of developing the electrostatic latent image, toner particles charged to a polarity opposite to that of the latent image are attracted by electrostatic attraction to adhere to the electrostatic latent image (reversal development). In the case of, a toner having a triboelectric charge of the same polarity as that of the latent image is used). Generally, a method of developing such an electrostatic latent image with toner is roughly classified into a so-called two-component method in which the toner is dispersed in a medium called a carrier in a small amount. A method using a system developer,
There is a method of using a so-called one-component developer in which a toner is used alone without using a carrier.

Generally, the carriers constituting such a two-component developer are roughly classified into conductive carriers and insulating carriers.

Oxidized or unoxidized iron powder is usually used as the conductive carrier, but the triboelectrification property to the toner is unstable in the developer containing the iron powder carrier as a component, and depending on the developer. There is a problem that fog occurs in the formed visible image. That is, as the developer is used, the toner particles adhere to the surface of the iron powder carrier particles, the electric resistance of the carrier particles increases, the bias current decreases, and the triboelectrification becomes unstable. The image density of the visible image is reduced and the fog is increased.

As the insulating carrier, a carrier obtained by uniformly coating the surface of a carrier core material made of a ferromagnetic material such as iron, nickel and ferrite with an insulating resin is typical. In the developer using this carrier,
Toner particles are not significantly fused to the surface of the carrier as compared with the case of a conductive carrier, and the durability is excellent, and the service life is long, which is an advantage that it is particularly suitable for high-speed electronic copying machines.

However, in this insulating carrier, the coating layer for coating the surface of the carrier core material has sufficient abrasion resistance and strong adhesiveness with the core material (durability), and the toner is provided on the carrier surface. The coating layer has good anti-sticking property (toner spent property) so that a film body due to is not formed, and a frictional state with a specific toner used together with the carrier can obtain a polar charged state to a desired value. (Charging property) is required. That is, the carrier is rubbed with other carrier particles and toner particles in the developing device, but if the toner adheres to the surface of the carrier coating layer to form a film, the charging property becomes unstable.

In order to prevent such spent formation, a method of coating the surface of a carrier with various resins has been proposed in the past, but a satisfactory method has not been obtained yet.

For example, a carrier coated with a fluororesin such as an ethylene tetrafluoride copolymer has a low critical surface tension, so that the toner is less likely to be spent, but the film-forming property is poor and the carrier core material is sufficiently uniform. It cannot be coated and stable charging characteristics cannot be obtained. In addition, the adhesiveness with the core material is weak, and the abrasion resistance is unsatisfactory. Furthermore, from the relationship with the charging series, the fluororesin coated carrier is
The negative charging property cannot have sufficient charging ability.

On the other hand, a carrier coated with an acrylic resin such as a styrene / methacrylate copolymer has a good film forming property and a good adhesive property with the carrier core material. However, the styrene-acrylic polymer has a relatively high critical surface tension, and the toner is liable to be spent during repeated use, and there is a slight problem in the life of the developer. From the viewpoint of wear resistance, it cannot be said that the surface hardness is sufficient although it is relatively high.

Silicone resin has a low surface energy and is known to reduce the spent, but the mechanical strength of the silicone resin itself is weak, and the coating layer is worn away while stirring in the developing device, It was difficult to stabilize the charging characteristics. It is also possible to use a polymer compound having a polydialkylsiloxane structural unit mixed with another, for example, a styrene-acrylic copolymer, and in this case, the polymer compound containing the mixed polydialkylsiloxane is also used. Since it is concentrated on the surface, the polydialkylsiloxane structural unit is lost by abrasion during stirring in the developing device, and it is difficult to stabilize the charging property for a long period of time.

[0012] Therefore, there is a demand for a carrier coating agent which is excellent in toner spent property, high in image quality and good in stability while satisfying the charging characteristics required for a carrier of a two-component developing system.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carrier which gives a very stable image for a long period of time. Still another object of the present invention is to provide a carrier coated with a highly durable coating agent having sufficient mechanical strength against abrasion and impact. Still another object of the present invention is to provide a coated carrier which is excellent in surface release of the carrier coating agent, is less likely to be spent on the toner, and is highly stable and has high image quality.

[0014]

The above-mentioned object of the present invention is achieved by the following general formula [1].

[0015]

[Chemical 7]

(In the formula, A is a linear, branched or cyclic alkylidene group having 1 to 10 carbon atoms, an aryl substituted alkylidene group, an arylenedialkylidene group, or -O.
-, - S -, - CO -, - SO-, and -SO ₂ - indicates, R ₁ to R ₄ represents hydrogen, halogen or alkyl group having 1 to 4 carbon atoms, an alkenyl group independently. ) And the following general formula [2]

[0017]

[Chemical 8]

(In the formula, R ₅ is an alkylene group or alkylidene group having 2 to 6 carbon atoms, and R ₆ and R ₇ are 1 to 3 carbon atoms.
Is an alkyl group, a phenyl group or a substituted phenyl group, and n represents an integer of 1 to 200. ), Wherein the structural unit represented by the general formula [2] is 0.1 to 0.1% by weight based on the total weight of the copolymer.
Achieved by an electrophotographic carrier characterized by being coated with 50% by weight of copolymer.

That is, the copolymer according to the present invention has the following general formula [3]:

[0020]

[Chemical 9]

(R _{1 to} R ₇ are the same as above. M + n = 10
0, n = 0.1-50)
It is a polydiorganosiloxane block copolymer.

Polycarbonate resins are generally known to have excellent impact resistance and good film-forming properties, but their surface releasability is poor, so that as the durability progresses, the toner on the carrier surface becomes However, it is difficult to continuously obtain a carrier coating having stable charging characteristics because the toner is spent and the charging characteristics are significantly deteriorated.

Various proposals have been made to improve the toner spent property of the above-mentioned polycarbonate resin,
For example, a polycarbonate copolymer prepared by copolymerizing polyorganosiloxane has been proposed. However, the conventional polyorganosiloxane copolymerized polycarbonate resin cannot form a homogeneous copolymer because it is difficult to synthesize the copolymer with good uniformity when synthesizing the copolymer. It has a drawback that the strength of the cast film is significantly reduced.

Therefore, the present invention improves the above-mentioned drawbacks,
In order to provide a highly durable and highly stable developer composition, a block copolymerized polycarbonate resin is used as a carrier coating resin, which is said to improve the surface releasability and does not reduce the film strength.

That is, in the present invention, a polydialkylsiloxane structural unit is sufficiently and uniformly copolymerized with a polycarbonate resin which is originally known to have good impact resistance, whereby the polydialkylsiloxane structural unit is introduced into the resin itself. The surface lubricity is imparted while maintaining the impact resistance.

By using the above-mentioned polycarbonate resin as a carrier coating agent, the releasability of the carrier coating is improved, so that it becomes possible to remarkably prevent the shortening of the carrier life due to toner spent. Further, it is possible to homogenize the resin coating solution and prevent the strength of the carrier coating layer from being lowered. As a result, it becomes possible to provide a developer composition having improved durability and high durability and stability.

That is, since the copolymer of the present invention becomes a transparent solution when dissolved in a solvent and forms a good resin coating film, a sufficiently strong resin coating film can be formed. This is because when the copolymerization reaction is carried out using the dialkylsiloxane block diphenol compound represented by the general formula [2] used in the present invention, the polymerization is sufficiently randomized, and therefore the long-chain polydialkylsiloxane block is used. It is presumed that white turbidity does not occur due to the growth of the soybeans and the decrease in solubility or the decrease in compatibility. Further, it has stable characteristics without forming a copolymer containing only polydialkylsiloxane at the same time.

The carrier of the present invention is obtained by coating the carrier core material with the above-mentioned polycarbonate resin. In the step of obtaining the resin-coated carrier of the present invention, first, a polycarbonate-polydialkylsiloxane copolymer represented by the general formula [3] is used as a base, and a suitable solvent such as benzene, toluene, xylene, or the like is used. Group solvents, halogen compounds such as dichloromethane, trichloroethane, chlorobenzene, etc., and tetrahydrofuran,
A resin coating is formed by dissolving it in a cyclic ether such as tetrahydropyran or dioxane, applying this to a core material, and drying after forming a coating film.

The copolymer of the present invention is synthesized by a polymerization method such as a phosgene method, a transesterification method, and a method involving chloroformate. In order to stably reproduce the randomness of the copolymer, the copolymer in a solution is used. The thing formed by the polymerization method by the phosgene method is suitable. Specific examples of the method for producing the block polycarbonate resin include the method described in JP-A-48-64199.

Specific examples of the diphenol compound that can be used to obtain the polycarbonate-polyorganosiloxane copolymer of the general formula [3] of the present invention include the following compounds.

[0031]

[Chemical 10]

[0032]

[Chemical 11]

[0033]

[Chemical 12]

[0034]

[Chemical 13]

Among the above compounds, the exemplified compound N is particularly preferable.
o. 3,8,16,19 and 21 are preferred.

Next, specific examples of the polyorganosiloxane used in the present invention will be shown, but the invention is not limited thereto. Exemplified compound No.

[0037]

[Chemical 14]

The copolymerization ratio in the general formula [3] is the weight ratio of monomers charged to give the structural unit represented by the general formula [2] from the viewpoint of physical properties such as mechanical strength and impact resistance of the copolymer ( (Substantially the same as the weight ratio in the composition) 0.1 to 5
It is preferably in the range of 0% by weight. This ratio is 0.1
When it is smaller, the mechanical strength is insufficient and the durability is lowered, and when it exceeds 50, the durability and the charging stability upon repeated use are lowered.

The molecular weight of the polycarbonate copolymer represented by the general formula [3] is preferably in the range of 10,000 to 100,000 in terms of weight average molecular weight. When the molecular weight is less than 10,000, the durability deteriorates, and when the molecular weight is more than 100,000, the viscosity becomes too high when coating the core material, and it is difficult to coat the resin with a predetermined coating amount. .

The carrier of the present invention is prepared by dissolving the above-mentioned block polycarbonate resin in a suitable solvent, for example, a solvent such as dichloromethane, and using this solution as a carrier coating solution, a coating machine (Spiracoater, Okada Seiko Co., Ltd.). It is formed by applying it to a ferrite carrier having an average particle size of 70 μm. 70-8 after application
After pre-drying at 0 ° C to volatilize the solvent, 120 ~ 16
Heat treatment is performed at 0 ° C. for 0.5 to 1 hour. The resin coating amount of the resin-coated carrier can be appropriately selected so as to satisfy desired durability and charging characteristics, and is usually preferably in the range of 0.01 to 30% by weight based on the carrier core. If it is less than 0.05% by weight, the effect of coating the carrier core material is not sufficient.

The resin coating amount referred to here depends on the true specific gravity of the core material. When Z is the true specific gravity of the carrier, the optimum value of the resin coating amount is in the range shown by the following formula.

1 / 2Z ≦ resin coating amount ≦ 50 / Z (wt%) More preferably, 1 / Z ≦ resin coating amount ≦ 25 / Z (wt%).

The carrier core material used in the present invention is iron,
Generally used materials such as ferrite can be used.
The average particle size of the carrier particles of the present invention is 5 to 100.
The range of μm is preferable. Carrier particle size is 5 μm
If it is less than 100 μm, carrier adhesion to the photoconductor tends to occur, and if it exceeds 100 μm, the share of the developer in the developing device becomes large, and the deterioration of the developer, especially peeling of the external additive of toner particles, It tends to cause shape changes. Furthermore, if the particle size is large, the specific surface area becomes small, so that the amount of toner that can be held when the toner is formed as a developer becomes small, resulting in an image lacking fineness. Regarding the particle size of the carrier used in the present invention, 300 or more carriers were randomly extracted with an optical microscope, and the horizontal Feret diameter was used as the carrier particle size by an image processing analysis device Luzex3 manufactured by Nireco.

The resistance value of the coated carrier used in the present invention is preferably in the range of 10 ⁸ to 10 ¹⁴ Ωcm. In the present invention, the method for measuring electric resistance can be exemplified by the method shown in FIG. That is, generally, the electric resistance of the carrier is the device shown in FIG. 1, the cell A is filled with the carrier, the electrodes 1 and 2 are arranged so as to be in contact with the filled carrier, and a voltage is applied between the electrodes. The minute electric current flowing at that time is measured, and the specific resistance ρ (Ωcm) is obtained from this, but the carrier is a powder, and therefore it may vary depending on the filling rate, so it is necessary to pay attention to the measurement. The resistance value of the carrier measured by the above method can be measured not only in the case of the carrier core alone, but also in the state in which the carrier is coated, and in any case, the carrier itself is measured by the above measuring method. It is required to have a predetermined resistance value when being pressed. The measurement conditions of the specific resistance in the present invention were: contact area S between the filled carrier and the electrode S = about 2.3 cm ² , thickness = about 1 mm, load 275 g on the upper electrode 2, and applied voltage 100V.

The triboelectric charge amount of the coated carrier in the present invention with respect to the toner is preferably in the range of 5 to 50 μC / g. The method of measuring the triboelectric charge amount of the carrier with respect to the toner in the present invention will be described in detail with reference to FIG.

FIG. 2 is an explanatory view of the triboelectric charge amount measuring device. A magnetic brush (on a toner carrier) on the developer carrier for which the triboelectric charge amount is to be measured is provided in a metallic measuring container 22 having a conductive screen 23 of 500 mesh (which can be appropriately changed to a size in which carrier particles do not pass) at the bottom. (Mixture of magnetic particles) is put in, and a metallic lid is weighed and designated as W ₁ (g). Next, in the suction device 21 (at least the portion in contact with the measurement container 22 is an insulator), suction is performed from the suction port 27 to prepare the air volume control valve 26, and the pressure of the vacuum gauge 25 is set to 250 mmHg. In this state, suction is sufficiently performed (for about 1 minute) to remove the toner by suction. The potential of the electrometer 29 at this time is V (volt). Here, 28 is a condenser, and the capacity is C
(ΜF). The weight of the entire measuring container after suction is weighed and is W ₂ (g). This triboelectric charge amount (μC / g) can be calculated by the following formula.

[0047]

[Equation 1]

However, the measurement conditions are 23 ° C. and 65% RH.
And

In the present invention, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, vinyltris- (methoxyethoxysilane), and vinyltrimethoxysilane are used for the purpose of improving the adhesion at the interface between the coating resin and the carrier core material. Acetoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ- (aminoethyl) aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, β- (3,4-epoxycyclohexyl)
Silane coupling agents such as ethyltrimethoxysilane and γ-chloropropyltrimethoxysilane, specifically, tetraisopropyl titanate, tetraisopropyl titanate polymer, tetrabutyl titanate, tetrabutyl titanate polymer, tetrastearyl titanate, 2-ethylhexyl titanate. It is also possible to use an organic titanium compound such as isopropoxytitanium stearate, titanium acetylacetonate and titanium lactate, or an organic phosphoric acid-based adhesion promoter. The above compounds may be used alone or in combination of two or more. Furthermore, the carrier coating agent of the present invention may be applied after treating the carrier core with the above compound in advance, or the above-mentioned adhesion improver may be mixed in the coating agent and applied at once. Good.

The coating resin used in the present invention may be a block copolymer polycarbonate resin having a structure represented by the general formula [3] alone, but
Specifically, for example, acrylic resin, styrene-acrylic copolymer, ethylene-vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, polyvinylcarbazole resin, phenoxy resin, polycarbonate resin, polyvinyl butyral resin, polystyrene resin, polyvinyl acetate. Resin, polyarylate resin,
It may be used as a mixture with a polysulfone resin or the like.

[0051]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to the examples. The percentages and parts in the following formulations are by weight.

Example 1 Block copolymerized polycarbonate resin having the following structural formula

[0053]

[Chemical 15]

15 parts of (weight average molecular weight 25,000) was dissolved in 85 parts of tetrahydrofuran to form a coating solution for forming a carrier coating. This solution was applied to a spherical ferrite core having an average particle diameter of 45 μm using a coating machine (Spira coater, Okada Seiko Co., Ltd.). This is first 20 at 80 ℃
After preliminarily drying for 15 minutes, the resin-coated carrier was obtained by drying at 150 ° C. for 40 minutes. The resin coating amount of the resin coated carrier obtained through the above drying step was 0.94%, and it was confirmed by observation with an electron microscope that the resin coated carrier was well coated.

On the other hand, polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Di-tert-butylsalicylic acid chromium complex salt 4 parts After thoroughly premixing with a Henschel mixer, 3 parts The mixture was melt-kneaded 3 times with a roll mill, cooled, and then coarsely pulverized with a hammer mill to a particle size of about 1 to 2 mm. Then, it was pulverized by an air jet pulverizer. Furthermore, the obtained finely pulverized product was classified to have a weight average particle diameter of 8.3.
A negatively chargeable cyan toner having a size of μm was obtained.

100 parts of the above-mentioned cyan toner and 0.4 part of silica fine powder hydrophobically treated with hexamethylene disilazane were mixed by a Henschel mixer to prepare a cyan toner having silica fine powder on the toner particle surface.

This cyan toner and the above carrier were mixed in an environment of temperature / humidity of N / N (23 ° C./60% RH) so that the toner concentration would be 15% to obtain a developer. 100 g of the obtained developer was placed in a 250 cc plastic bottle, and shaken with a Turbula mixer at room temperature and normal humidity for 1 hour. After that, the developer was taken out and observed with an electron microscope. As a result, peeling of the coating material from the carrier and filming by the toner were not observed.

Further, this developer was subjected to an image forming test using a modified full color laser copying machine CLC-500 manufactured by Canon.

As a result, a clear image having a sufficiently high density of a solid image and free from fogging in the non-image area and roughness in the halftone area was obtained. The developing unit is 200 rpm
Spinning was performed for 40 minutes at the speed of. After that, when the image forming test was carried out again, a good result was obtained without any roughness in the halftone portion.

The results obtained are listed in Table 1.

Example 2 Block copolymerized polycarbonate resin having the following structural formula

[0062]

[Chemical 16]

15 parts of (weight average molecular weight 15,000) was dissolved in 85 parts of dioxane to form a coating liquid for forming a carrier coating. This solution was applied to a ferrite core having an average particle size of 45 μm, which had been previously treated with methyltrimethoxysilane, using an applicator (Spira coater, Okada Seiko Co., Ltd.). This is first pre-dried at 80 ° C for 20 minutes and then 150
A resin-coated carrier was obtained by drying at 40 ° C. for 40 minutes. The resin coating amount of the resin coated carrier obtained through the above drying step was 0.95%, and it was confirmed by observation with an electron microscope that the resin coated carrier was well coated.

When this was evaluated in the same manner as in Example 1, good results were obtained. The results are shown in Table 1.

Example 3 Block copolymerized polycarbonate resin having the following structural formula

[0066]

[Chemical 17]

(Weight average molecular weight 45,000)
And tetraisopropyl titanate (1 part) were dissolved in tetrahydrofuran (85 parts) to form a carrier coating forming coating solution. This solution was applied to a ferrite core having an average particle size of 50 μm using a coating machine (Spira coater, Okada Seiko Co., Ltd.). This was first pre-dried at 80 ° C. for 20 minutes and then at 150 ° C. for 40 minutes to obtain a resin-coated carrier. The resin coating amount of the resin coated carrier obtained through the above drying step was 0.91%, and it was confirmed by observation with an electron microscope that the resin coated carrier was well coated.

When this was evaluated in the same manner as in Example 1, good results were obtained. The results are shown in Table 1.

Example 4 Block copolymerized polycarbonate resin having the following structural formula

[0070]

[Chemical 18]

15 parts of (weight average molecular weight 30,000) was dissolved in 85 parts of dioxane to form a coating liquid for forming a carrier coating. This solution was applied to a ferrite core having an average particle size of 50 μm using a coating machine (Spira coater, Okada Seiko Co., Ltd.). This was first pre-dried at 80 ° C. for 20 minutes and then at 150 ° C. for 40 minutes to obtain a resin-coated carrier. The resin coating amount of the resin coated carrier obtained through the above-mentioned drying step was 0.90%, and it was confirmed by observation with an electron microscope that the resin coated carrier was well coated.

When this was evaluated in the same manner as in Example 1, good results were obtained. The results are shown in Table 1.

Example 5 Block copolymerized polycarbonate resin having the following structural formula

[0074]

[Chemical 19]

(Weight average molecular weight 25,000)
Parts and 1 part of methyltriethoxysilane were dissolved in 85 parts of dioxane to form a coating liquid for forming a carrier coating. This solution was applied to a ferrite core having an average particle size of 50 μm using a coating machine (Spira coater, Okada Seiko Co., Ltd.). This is first pre-dried at 80 ° C for 20 minutes and then at 150 ° C for 4 minutes.
It was dried for 0 minutes to obtain a resin-coated carrier. The resin coating amount of the resin coated carrier obtained through the above-mentioned drying step is 0.
It was 90%, and it was confirmed by observation with an electron microscope that it was well covered.

When this was evaluated in the same manner as in Example 1, good results were obtained. The results are shown in Table 1.

Example 6 Block copolymerized polycarbonate resin having the following structural formula

[0078]

[Chemical 20]

15 parts of (weight average molecular weight 28,000) was dissolved in 85 parts of tetrahydrofuran to form a coating liquid for forming a carrier coating. This solution was applied to a ferrite core having an average particle size of 50 μm using a coating machine (Spira coater, Okada Seiko Co., Ltd.). This was first pre-dried at 80 ° C. for 20 minutes and then at 150 ° C. for 40 minutes to obtain a resin-coated carrier. The resin coating amount of the resin coated carrier obtained through the above-mentioned drying step was 0.90%, and it was confirmed by observation with an electron microscope that the resin coated carrier was well coated.

When this was evaluated in the same manner as in Example 1, good results were obtained. The results are shown in Table 1.

Example 7 Block copolymerized polycarbonate resin having the following structural formula

[0082]

[Chemical 21]

15 parts of (weight average molecular weight 95,000) was dissolved in 95 parts of chlorobenzene to form a coating liquid for forming a carrier coating. This solution was applied to a ferrite core having an average particle size of 50 μm using a coating machine (Spira coater, Okada Seiko Co., Ltd.). This was first pre-dried at 80 ° C. for 20 minutes and then at 150 ° C. for 40 minutes to obtain a resin-coated carrier. The resin coating amount of the resin coated carrier obtained through the above-mentioned drying step was 0.90%, and it was confirmed by observation with an electron microscope that the resin coated carrier was well coated.

When this was evaluated in the same manner as in Example 1, good results were obtained. The results are shown in Table 1.

Comparative Example 1 Acrylic copolymer having the following composition: Styrene-2-ethylhexyl methacrylate copolymer (copolymerization ratio 40/60) Weight average molecular weight 30,000
A resin-coated carrier was formed and evaluated in the same manner as in Example 1 except that (polystyrene-equivalent value using gel permeation chromatogram) was used, and it was confirmed by an electron microscope after the shaking test. Toner spent was confirmed. Further, after carrying out the durability test in the same manner as in Example 1, a fog in the non-image area was observed, and a half-tone, unsharp image having a sharpness was obtained.

Comparative Example 2 Polycarbonate-siloxane copolymer having the following composition

[0087]

[Chemical 21]

A resin-coated carrier was formed and evaluated in the same manner as in Example 1 except that (weight average molecular weight of 20,000) was used, and favorable results were obtained with respect to the toner spent and the like. However, the image quality was severely deteriorated after the durability test with the idle rotation of the developing device. This is because the coating film strength of the resin coating layer was not sufficient and the coating resin layer was missing as the durability progressed.

[0089]

[Table 1]

[0090]

According to the present invention, by using the siloxane block copolymerized polycarbonate resin of the present invention as a coating agent for a resin-coated carrier, the toner spent property is excellent, and high image quality can be provided from the initial stage to the durability and high It has become possible to provide a durable, highly stable and long-life resin-coated carrier.

[Brief description of drawings]

FIG. 1 is a schematic view schematically showing an apparatus for measuring the specific resistance of carriers.

FIG. 2 is a schematic view schematically showing an apparatus for measuring a triboelectric charge of toner of a two-component developer. 1 Lower Electrode 2 Upper Electrode 3 Insulator 4 Ammeter 5 Voltmeter 6 Constant Voltage Device 7 Sample (Carrier) 8 Guide Ring A Measuring Cell 21 Suction Machine 22 Measuring Container 23 Conductive Screen 24 Lid 25 Vacuum Gauge 26 Air Flow Control Valve 27 Suction port 28 Condenser 29 Electrometer

Claims (5)

[Claims] 1. The following general formula [1]: (In the formula, A is a linear, branched or cyclic alkylidene group having 1 to 10 carbon atoms, an aryl-substituted alkylidene group,
Arylenedialkylidene group, or -O-, -S-,
Represents --CO--, --SO--, and --SO _2- , and R _{1 to} R
₄ independently represents hydrogen, halogen, or an alkyl group or alkenyl group having 1 to 4 carbon atoms. ) And the following general formula [2] (In the formula, R ₅ is an alkylene group or alkylidene group having 2 to 6 carbon atoms, R ₆ and R ₇ are alkyl groups having 1 to 3 carbon atoms, a phenyl group or a substituted phenyl group, and n is 1 to 1
Indicates an integer of 200. And a structural unit represented by the general formula [2] in an amount of 0.1 to 50% by weight based on the total weight of the copolymer. An electrophotographic carrier characterized by being coated. 2. The structure represented by the above formula [1] is represented by the following formula: The carrier for electrophotography according to claim 1, which is represented by: 3. The structure represented by the above formula [1] is represented by the following formula: The carrier for electrophotography according to claim 1, which is represented by: 4. The structure represented by the above formula [1] is represented by the following formula: The carrier for electrophotography according to claim 1, which is represented by: 5. The structure represented by the above formula [1] is represented by the following formula: The carrier for electrophotography according to claim 1, which is represented by: