JP3044390B2 - Electrophotographic carrier - Google Patents

Description

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

[Prior Art] Various methods have been described as electrophotography in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910, Japanese Patent Publication No. 43-24748, etc. Also, an electrostatic latent image is formed by irradiating the photoconductive layer with a light image corresponding to the original, and then, a colored fine powder called a toner having a polarity opposite to this is attached to the electrostatic latent image. The electrostatic latent image is developed, and if necessary, a toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, or solvent vapor 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 and adhered on the electrostatic latent image (in the case of reversal development, In general, a method of developing such an electrostatic latent image using toner is roughly divided into a so-called two-component method in which a small amount of toner is dispersed in a medium called a carrier. There is a method using a system 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 developer are roughly classified into conductive carriers and insulating carriers.

Oxidized or unoxidized iron powder is generally 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 and is formed by the developer. There is a problem that fogging occurs in the 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 example of the insulating carrier is a carrier obtained by uniformly covering the surface of a carrier core material made of a ferromagnetic material such as iron, nickel, or ferrite 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 must have sufficient abrasion resistance and strong adhesion to the core material (durability), and the carrier must be coated with a toner film. That the coating layer has good anti-sticking properties so that no toner is formed (toner spent properties), and that a desired value and a charged state of polarity can be obtained by friction with a specific toner used together with the carrier (chargeability) Is required. That is, the carrier is rubbed with other carrier particles and toner particles in the developing device, but when the toner adheres to the surface of the carrier coating layer to form a film, the charging characteristics become unstable.

In order to prevent such spent, a method of coating the carrier surface with various resins has been conventionally proposed, but no satisfactory method has been obtained.

For example, a carrier coated with a fluorine-based resin such as an ethylene tetrafluoride copolymer has a low critical surface tension, so that it is difficult for the toner to be spent. However, the film-forming property is poor and the carrier core material can be covered sufficiently uniformly. And stable charging characteristics cannot be obtained. Also, the adhesiveness to the core material is weak, and the wear resistance is unsatisfactory. Further, due to the relationship with the charging series, the fluorine-based resin-coated carrier cannot have a sufficient charging ability in a negatively chargeable toner.

On the other hand, a carrier coated with an acrylic resin such as a styrene-methacrylate copolymer has good film-forming properties, strong adhesion with a carrier core material, and excellent wear resistance.
It is used as a mixture with the above-mentioned fluororesin or used alone. However, since this acrylic resin has a relatively high critical surface tension, spent toner tends to occur when it is repeatedly used, and there is a problem in the life of the developer.

In addition, if the film forming property is improved, the resistance is inevitably increased, and the toner separation from the carrier due to the charge-up of the toner as described above is deteriorated.

Further, if the development is continued for a long time in such a state that the toner hardly separates from the carrier, it is not preferable because the above-mentioned spent of the carrier by the toner is further promoted.

Also, if the carrier has too high resistance, the image density is reduced, the solid-state halftone reproducibility is degraded, or the carrier is developed on the photoreceptor and the photoreceptor is damaged,
Carriers may adhere to the image.

Thus, it is very important but difficult to control the resistance of the carrier surface and not to impair the film forming property of the coating material.

In addition, the surface resistance of a carrier generally tends to change with changes in environmental conditions such as low temperature, low humidity, and high temperature and high humidity. as a result,
For example, under low temperature and low humidity, the resistance increases due to a decrease in the amount of water, and the image density decreases due to charge-up.
Under high temperature and high humidity, problems such as low resistance due to an increase in water absorption, fog and scattering due to a decrease in tribo would be caused.

Therefore, it is an important characteristic that the surface resistance of the carrier does not depend on environmental fluctuation.

[Problems to be Solved by the Invention] It is an object of the present invention to provide a carrier that has a small variation in triboelectric charging characteristics with respect to a variation in environment and provides an extremely stable image for a long period of time. Still another object is to provide a carrier which has an appropriate surface resistance, is less likely to be charged up, always provides a high developing efficiency stably, and can maintain a high image density. Still another object is to provide a carrier which has an appropriate surface resistance and does not adhere to a photoreceptor or paper.
Still another object is to provide a carrier coated with a coating material having excellent adhesiveness to a carrier core material. Still another object is to provide a carrier coated with a coating having sufficient mechanical strength against abrasion and impact. Still another object is to provide a highly durable coated carrier in which toner is less likely to be spent.

[Means and Actions for Solving the Problems] The present invention provides a carrier core material having an average particle diameter of 45 to 100 μm, which is coated with a crosslinked alkoxyalkylated polyamide resin. 30% by weight of a carrier, wherein the carrier is at 23 ° C./60% RH, at 15 ° C./20% RH, and
Under each environment of 2.5 ℃ / 80% RH, volume resistivity is 10
^The present invention relates to a carrier for electrophotography, which has a resistivity of ^{8 to} 10 ¹³ Ω · cm.

In general, polyamide resins represented by 6 nylon and the like have high abrasion resistance and elasticity, and have been considered as good carrier coating resins. As a coating resin for a carrier, which is generally coated with a resin solution by a spray method or the like, there is a problem.

In the present invention, in order to improve this, using nylon as a raw material, the hydrogen atom of the amide bond -NHCO- on the main chain of nylon is substituted with an alkoxyalkyl group to make it soluble in alcohol or the like, and then acid or the like. A resin characterized in that a crosslinked structure is provided inside the molecule by using the above catalyst and the mechanical strength is improved is used as the carrier coating resin.

As a further significant feature, the resistance of the resin can be controlled by this alkoxyalkylation. That is, ordinary nylon such as 6 nylon has a volume resistivity of 10 ¹⁴
Although the resistance is extremely high at Ω · cm or more, and as described above, the resistance is too high, the volume resistivity can be controlled to 10 ⁸ to 10 ¹³ Ω · cm by the alkoxyalkylation according to the present invention.

Further, by providing the resin with a crosslinked structure, it is possible to remarkably improve various properties such as abrasion resistance, mechanical strength, moisture absorption resistance, and chargeability.

The carrier of the present invention is obtained by coating a carrier core material with a crosslinked alkoxyalkylated polyamide resin. As a step of obtaining the present resin-coated carrier, first, in a polyamide resin to be a base, a functional group in a main chain thereof is alkoxyalkylated by a substitution reaction. Next, this resin is applied to a carrier, and after the coating film is formed, crosslinking is carried out using an arbitrarily selected acid as a catalyst.

The effect of the cross-linked structure in the present invention is as follows. Cross-linking results in a three-dimensional complex three-dimensional network structure. Therefore, it can be said that the carrier has a desirable form as a carrier coating material whose mechanical properties such as abrasion resistance and impact resistance are required as its important characteristics. Uncrosslinked polyamide resin has a slight tack, when coated with a carrier,
Although the fluidity of the carrier is slightly reduced, the surface is hardened by forming a crosslinked body, the friction between the carriers is reduced, and the fluidity is improved. In addition, water resistance is also improved by forming a crosslinked product.

The alkoxyalkylated polyamide resin used in the present invention is a resin in which the hydrogen atom of the amide bond -NHCO- in the resin is substituted with an alkoxyalkyl group, and has the following structure.

R ₁ is preferably an alkyl group having 10 or less carbon atoms,
R ₂ and R ₃ are preferably an alkyl group having 5 or less carbon atoms or hydrogen, and more preferably at least one of R ₂ and R ₃ is hydrogen.

In the crosslinked alkoxyalkylated polyamide resin used in the present invention, the degree of alkoxyalkylation is as follows:
10 to 50 mol%, preferably 20 to 40 mol%, is suitable. Ten
If the amount is less than mol%, the effect of the present invention is not sufficient, and it is difficult to dissolve in a solvent. Further, as the degree of alkoxyalkylation increases, the solubility in a solvent tends to increase, and the rubber elasticity tends to increase. If it is 50 mol% or more, it is too soft and unsuitable as a carrier coating material.

The volume resistivity of the carrier can be controlled by adjusting the above-mentioned degree of alkoxyalkylation, depending on the type of alkoxyalkyl group. The volume resistivity can be adjusted in the range of 10 ⁸ to 10 ¹³ Ω · cm, and a “proper value that is not too high”, which is one of the features of the present invention, can be obtained.

The alkoxyalkylation ratio is measured, for example, by the following Viebock-Schwappach method (Berichteder Deutschen Che
It is measured using mischen Gesellschaft, 63 , 2318 (1930).

RI + Br ₂ → RIBr ₂ → RBr + IBr IBr + 2Br ₂ + 3H ₂ O → HIO ₃ + 5HBr HIO ₃ + 5HI → 3I ₂ + 3H ₂ O 3I ₂ + 6Na ₂ S ₂ O ₃ → 6NaI + 3Na ₂ S ₄ O ₆ As shown in the above formula, the alkoxyl group is When heated with hydroiodic acid, it readily decomposes to form alkyl iodides. The generated alkyl iodide is absorbed by a mixed solution of sodium acetate and acetic acid containing a small amount of bromine to be converted into alkyl bromide and iodine bromide. The latter is further oxidized to iodic acid and hydrogen bromide, but excess bromine is decomposed with formic acid, hydrogen bromide is neutralized with sodium acetate, and potassium iodide is added.
The released iodine is titrated with a sodium thiosulfate solution.

As can be seen from the above chemical reaction formula, when 1 [mol] of an alkoxyl group is present, 3 [mol] of iodine is released, and this iodine is titrated with 6 [mol] of sodium thiosulfate. Assuming that the concentration of sodium thiosulfate used for titration is 0.1 [N] and the titer is x [ml], this corresponds to sodium thiosulfate 0.1 × x / 1000 [mol]. The molar amount of the group is It is. Therefore, if the total amount of a sample (molecular weight M) containing an alkoxyl group is S [g], Becomes

The alkoxyalkylation ratio is determined as described above.

As an example of the synthesis of an alkoxyalkylated polyamide resin, for example, 50 g of a nylon-6 resin is mixed with 250 g of formic acid and 2 g of acetic anhydride.
Stir and dissolve in 50 g of mixed solvent. 15 g of paraformaldehyde and 15 g of methanol are added thereto, and the mixture is heated to 60 ° C. and reacted for 5 hours. Next, the reaction solution is cooled to room temperature, poured into acetone 5, and reprecipitated and filtered to obtain a white reaction product. This product is stirred and washed in a large amount of water, and filtered at 40 ° C.
After drying under reduced pressure at 10 to 20 mmHg, 54.1 g of methoxymethylated nylon 6 (alkoxyalkylation rate: 30.6 m
ol%).

Here, the alkoxyalkylated polyamide resin which is the main chain of the crosslinked alkoxyalkylated polyamide resin used in the present invention will be exemplified.

The coating resin used in the present invention is obtained by further crosslinking the alkoxyalkylated polyamide resin as described above.

Further, as the carrier coating resin, the crosslinked alkoxyalkylated polyamide resin of the present invention can be used alone, but it can also be used as a mixture with other resins used for carrier coating. it can.

Next, the crosslinking of the alkoxyalkylated polyamide resin will be described.

The alkoxyalkylated polyamide resin synthesized by the above method and an organic acid such as citric acid, adipic acid, tartaric acid, maleic acid or hypophosphorous acid or the like are dissolved in the same solvent, and the carrier is subjected to a heat treatment at the time of forming a film. The self-crosslinking reaction using the catalyst as a catalyst proceeds to form a crosslinked body. Regarding where in the molecule the cross-linking reaction occurs, the alkoxyalkyl group is decomposed by the acid as a catalyst and self-cross-links to form a cross-linked body. Therefore, in order for the polyamide resin of the present invention to exhibit its original properties, it is essential that the polyamide resin retains a predetermined amount of an alkoxyalkyl group, and in order to do so, the reaction is controlled so as to partially crosslink. There is a need to.

As a method for this, it is possible to select a kind of an acid to be a catalyst of a crosslinking reaction, or to change a crosslinking rate by controlling a reaction temperature, or to increase a content of an alkoxyalkyl group in advance in anticipation of loss due to crosslinking. There are adjustment methods.

 Hereinafter, specific examples of the method will be described.

First, 0.45 parts by weight of citric acid is dissolved in 85 parts by weight of methanol. In this solution, 15 parts by weight of the alkoxyalkylated polyamide resin (1) is dissolved. This solution is applied as a carrier coating solution to a ferrite carrier having an average particle size of 70 μm using an applicator (Spira Coater, manufactured by Okada Seiko Co., Ltd.). After the application, it is pre-dried at 70 to 80 ° C to evaporate the solvent, and then heat-treated at 120 to 130 ° C for 5 to 10 minutes. The resin coating amount of the obtained resin-coated carrier was 0.70% by weight.
The degree of cross-linking of the coating resin of this carrier was calculated from the amount of disappeared alkoxyalkyl groups using the above-described method for measuring the alkoxyalkylation ratio, and was 8.2 mol%.

When the coating amount of the coating resin according to the present invention with respect to the carrier core material is 0.05 to 30% by weight, and less than 0.05% by weight, the effect of coating the carrier core material is not sufficient.

As the carrier core material used in the present invention, commonly used materials such as iron powder and ferrite can be used, and the particle size is 10 to 1000 μm, preferably 20 to 200 μm. Has an average particle size of 45 to 100 μm.

In the present invention, as a method of measuring the specific electric resistance (volume resistivity), a method of measuring by the method of FIG. 1 is exemplified. That is, generally, the specific electrical resistance (volume specific resistance) of the carrier is measured with a device shown in FIG. 1 by applying a voltage of 100 V and measuring the minute current flowing at that time. ) Ρ (ohm · cm) is obtained, but care must be taken because the carrier is a powder and may vary depending on the filling rate.

Here, the method for 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.

FIG. 2 is an explanatory diagram of the triboelectric charge amount measuring device. 50 at the bottom
Metallic measuring container with conductive screen 23 of 0 mesh (can be changed to a size that does not allow carrier particles to pass through)
A magnetic brush (mixture of toner and magnetic particles) on the developer carrier whose frictional charge is to be measured is placed in 22 and a metal lid 24 is closed. At this time, weigh the entire measuring container 22
W ₁ (g). Next, in the suction device 21 (at least a portion in contact with the measuring container 22 is at least an insulator), the pressure of the vacuum gauge 25 is adjusted to 250 mmHg by adjusting the air volume control valve 26 by suction from the suction port 27. In this state, suction is sufficiently performed (about 1 minute) to remove the toner by suction. The potential of the electrometer 29 at this time is set to V (volt). Where 28 is 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.

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

[Example] Example 1 15 parts by weight of the resin example (1) described above was dissolved in 85 parts by weight of methanol in which 0.3 part by weight of citric acid was previously dissolved to prepare a carrier coating solution. This solution was applied to an amorphous iron powder having an average particle size of 100 μm using a coating machine (Spira Coater, manufactured by Okada Seiko Co., Ltd.). The resin coating amount of the resin-coated carrier obtained through the drying process is 0.91% by weight, and the core material of the iron powder is the coating resin based on observation with an electron microscope, and the core material is uniformly coated without exposing the surface of the core material. It was recognized that it was.

After leaving the obtained carrier in each environment of normal temperature and normal humidity (23 ° C / 60% RH), low temperature and low humidity (15 ° C / 20% RH), and high temperature and high humidity (32.5 ° C / 80% RH) for 4 days, When the resistance (volume resistivity) was measured by the method of FIG. 1, the resistance was 5.7 × 10 ⁹ Ω · cm and 1.2, respectively.
× 10 ¹⁰ Ω · cm and 3.8 × 10 ⁹ Ω · cm.

This carrier was mixed with a toner for Canon NP-5000 (toner concentration: 2%) to prepare a developer, and an image forming test was performed in various environments using an NP-5000 copying machine.

As a result, the image reflection density was 1.35 at normal temperature and normal humidity, 1.32 at low temperature and low humidity, and 1.37 at high temperature and high humidity, and clear images were obtained. The triboelectric charge of the toner at this time was measured to be −7.7 μc / g under normal temperature and normal humidity, and −
It was 8.1 μc / g and −7.1 μc / g under high temperature and high humidity, and was stable without substantially depending on the difference in environment. Further, when a copying durability test of 200,000 sheets was carried out at room temperature and normal humidity using this developer, the image reflection density was sufficiently high at 1.32 even after 200,000 sheets, and a clear image was obtained. Observation of the carrier surface with an electron microscope revealed that there was no deterioration such as toner spent or peeling of the coating resin.

Example 2 A carrier coating solution was prepared by dissolving 15 parts by weight of the resin example (2) described above in 85 parts by weight of methanol in which 0.5 part by weight of citric acid was dissolved, and ferrite particles having an average particle diameter of 45 μm were prepared in the same manner as in Example 1. Coating and drying were performed by the methods described above to obtain a resin-coated carrier. The resin coating amount of the carrier was 0.93% by weight, and observation with an electron microscope confirmed that the carrier was uniformly coated with the resin. The first of this carrier
The specific electrical resistance (volume specific resistance) by the method shown in the figure is 5.8 × 10 ^{10 in} each environment of normal temperature and normal humidity, low temperature and low humidity, and high temperature and high humidity.
Ω · cm, 9.8 × 10 ¹⁰ Ω · cm, 8.1 × 10 ⁹ Ω · cm.

This carrier and Canon full color copier CLC-500
The toner was mixed with a cyan toner for use (toner concentration: 5%) to prepare a developer, and an image forming test was performed under various environments using CLC-500 in which the development contrast was set to 350V.

As a result, the image reflection density was 1.52 under normal temperature and normal humidity, 1.49 under low temperature and low humidity, and 1.55 under high temperature and high humidity, which were sufficiently high, respectively, and a clear and excellent gradation image was obtained.

When a solid image was copied immediately after 300 continuous white solid copies were made at a low temperature and a low humidity, the image reflection density was sufficiently high at 1.48, and no image deterioration such as density reduction and fog due to charge-up was observed.

Example 3 25 parts by weight of the resin example (3) described above was dissolved in 0.5 parts by weight of malonic acid and 75 parts by weight of ethanol to prepare a coating solution.
It was applied to ferrite particles having an average particle size of 100 μm in the same manner as in Example 1 to obtain a resin-coated carrier. The resin coating amount of this carrier was 0.88% by weight, and surface observation with an electron microscope confirmed that the carrier was uniformly coated. The carrier was allowed to stand in each environment for 4 days, and the specific electrical resistance (volume resistivity) was measured by the method shown in FIG. 1 to find that it was 8.1 × 10 ¹⁰ Ω · cm at room temperature and normal humidity and at low temperature and low humidity.
It was 8.8 × 10 ¹⁰ Ω · cm and 7.4 × 10 ¹⁰ Ω · cm under high temperature and high humidity.

This carrier was mixed with a toner for NP-5000 (toner concentration: 2%) to prepare a developer, and a three-environmental tribo was measured. The result was −7.7 μc / g at room temperature and normal humidity, and −8.1 μc / g at low temperature and low humidity.
g and -7.4 μc / g under high temperature and high humidity. Using this developer, a copy durability test of 200,000 sheets was continuously conducted at room temperature and normal humidity with a modified NP-5000 machine.

As a result, the image reflection density was 1.32 in the initial stage of durability,
Even after copying 200,000 sheets, the density was sufficiently high at 1.30, and no image deterioration due to fog, scattering and the like was observed. Also,
The developer after the endurance of 200,000 sheets was collected, only the carrier was separated, and the surface thereof was observed with an electron microscope. As a result, no deterioration of the carrier such as toner spent or peeling of the coating material was observed.

Example 4 15 parts by weight of Resin Example (4) described above was dissolved in 85 parts by weight of methanol in which 0.5 part by weight of citric acid was dissolved to prepare a carrier coating solution. This solution was applied to ferrite particles having an average particle size of 70 μm using a coating machine (Spira Coater, manufactured by Okada Seiko Co., Ltd.). The resin coating amount of the resin-coated carrier obtained through the drying process is 0.85% by weight. From observation by an electron microscope, the core material of the ferrite is the coating resin, and the core material is uniformly coated without exposing the surface of the core material. It was recognized that.

The resulting carrier normal temperature and humidity, after leaving the low temperature and low humidity, for each environment of high temperature and high humidity for 4 days, when the specific electric resistance (volume resistivity) was measured in the first diagram of the method, each 3.6 × 10 ¹¹ Ω · c
m, 3.5 × 10 ¹¹ Ω · cm and 3.7 × 10 ¹¹ Ω · cm.

This carrier is mixed with a red toner for the color copying machine of Canon NP-4835 (toner concentration 8%) to prepare a developer,
As a result of an image formation test, the image reflection density was 1.35 at room temperature and normal humidity, 1.34 at low temperature and low humidity, and 1.37 at high temperature and high humidity, respectively, and a clear image without fog was obtained. At this time, the toner has a triboelectric charge of +18.9 μc / at room temperature and normal humidity.
g, + 18.2μc / g under low temperature and low humidity, + 19.0μc / g under high temperature and high humidity
g, and was substantially independent of environmental differences and stable. After leaving the developer for one month in each of the above environments, the same image was formed, but no abnormality was observed in the initial image at this time.

Comparative Example 1 6,66,610 copolymerized nylon (weight average molecular weight 175,000,
Weight composition ratio 6/66/610 = 2/2/1) 2 parts by weight of methanol 98
Dissolve in parts by weight and apply this solution to a coating machine (spira coater,
(OKADA SEIKO Co., Ltd.), and applied to irregular-shaped iron powder having an average particle size of 100 μm. The resin coating amount of the resin-coated carrier obtained through the drying process is 0.83% by weight. When the surface is observed with an electron microscope, the coating on the protruding portion of the core material is thin, and is uniformly coated. Turned out not to be. After the obtained carrier was allowed to stand for 4 days in an environment of normal temperature and normal humidity, low temperature and low humidity, and high temperature and high humidity, the specific electrical resistance (volume specific resistance) was measured to be 7.3 × 10 ¹⁴ Ω · cm and 4.8 × 10
^{It was 15} Ω · cm and 8.4 × 10 ⁸ Ω · cm.

This carrier was mixed with a toner for Canon NP-5000 (toner concentration 2%) to prepare a developer, and the triboelectric charge of the toner was measured. At room temperature and normal humidity, it was -10.0 μc / g, and at low temperature and low humidity. Environmental fluctuations were observed at -11.5 µc / g and -6.4 µc / g under high temperature and high humidity. When the image formation test was performed in three environments, the image reflection density was 1.21 under normal temperature and normal humidity, 1.03 under low temperature and low humidity, and 1.40 under high temperature and high humidity. A copy durability test of 10,000 sheets was performed below.

As a result, the image reflection density gradually decreased under low temperature and low humidity, and was 0.80 at 2,000 sheets. Investigation of the cause revealed that the toner triboelectric charge was -16.0 μc / g, which was considerably charged up. The image density at 10,000 sheets was 0.72. After the endurance, the developer was collected, only the carrier was separated, and the surface was observed with an electron microscope. As a result, it was recognized that the toner was partially spent. Further, under high temperature and high humidity, image deterioration due to scattering became severe after about 100 sheets, and the durability test was stopped at 1500 sheets. When investigating the cause, the toner tribo charge amount was -3.4
It was found that it was remarkably reduced to μc / g.

[Effects of the Invention] In the present invention, the resistance of the resin can be controlled by alkoxyalkylation, and various properties such as abrasion resistance, mechanical strength, hygroscopicity, and chargeability are imparted to the coating resin by crosslinking. Gives a stable image with high density over a long period of time in any environment.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing an apparatus for measuring the specific electric resistance (volume resistivity) of a carrier, and FIG.
The figure is a schematic diagram schematically showing an apparatus for measuring the triboelectric charge of the toner of the two-component developer.

Claims (2)

(57) [Claims] 1. A carrier comprising a carrier core material having an average particle diameter of 45 to 100 μm and coated with a crosslinked alkoxyalkylated polyamide resin and having a resin coating solid content of 0.05 to 30% by weight, Carrier is under 23 ℃ / 60% RH, 15 ℃ / 20% RH and 32.5 ℃
An electrophotographic carrier, wherein the carrier has a volume resistivity of 10 ^{8 to} 10 ¹³ Ω · cm under each environment of ° C / 80% RH. 2. The carrier for electrophotography according to claim 1, wherein the crosslinked alkoxyalkylated polyamide resin is crosslinked by using an organic acid or hypophosphorous acid as a catalyst. .