JP2011137867A - Electrophotographic carrier and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic carrier showing stable charging property and free from fog or toner scattering for a long period of time in repeated image formation and providing stable picture quality, and to provide an image forming method. <P>SOLUTION: The electrophotographic carrier has a resin layer on a surface of a magnetic particle. The resin layer is formed by using a styrene-acrylic resin, an acrylic resin or a methacrylic resin having a weight average molecular weight (Mw) of 30,000 to 150,000 and substantially soluble with a predetermined solvent. When the specific resistance (Ω cm) of the electrophotographic carrier before dissolved in a predetermined solvent and the specific resistance (Ω cm) of the electrophotographic carrier after dissolved in the predetermined solvent are denoted by R1 and R2, respectively, R1 and R2 satisfy expression (1):-1.0≤logR1-logR2≤1.5. The shape factor (SF-1) of the electrophotographic carrier after dissolved in the specified solvent is from 110 to 130. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic carrier and an image forming method.

  In general, image formation using an electrophotographic system includes steps of charging, exposure, development, transfer, and fixing. According to the development method, it is roughly classified into a one-component development method and a two-component development method, but the two-component development method is superior in stability because it controls charging by mixing with a carrier having a charge imparting function. Widely adopted for reasons.

  In particular, a resin-coated carrier has excellent charge controllability, and has been widely developed and put into practical use from the viewpoint of imparting appropriate chargeability including ensuring environmental dependency and stability over time.

  However, if the developer is used for a long time, the charge imparting function deteriorates due to the progress of the adhesion of the toner fine powder to the carrier surface and the external additive adhering to the surface for the toner modification, and the toner scattering and fogging are deteriorated. The image quality deterioration problem occurs.

  The toner fine powder is fixed because the melt caused by the heat generated in the micro area at the time of frictional charging is fixed. For example, the surface tension can be reduced by coating with a low surface tension resin such as fluororesin or silicone resin. Many proposals have been made to suppress the adhesion of toner fine powder.

  However, the fluororesin has a strong property of charging the toner to the positive electrode side, and is not suitable for a negatively chargeable developer, and the silicone resin also has a low negative charge imparting property and requires a charge control agent to be used. The problem remains that it is inferior.

  Furthermore, in recent years, the toner particle size has been reduced in order to improve the image quality, but more external additives are required to improve the powder characteristics, and the external additive is more than the contamination by the toner fine powder. Contamination due to the surface is becoming dominant, and the resin having a low surface tension cannot prevent the contamination due to the external additive.

  On the other hand, styrene acrylic resins or acrylic resins have also been proposed as resins that have high charge imparting properties and are less likely to lose chargeability even when contaminated. As in Document 1, there has also been proposed a method of removing contaminants by adding self-polishing properties by adding inorganic fine particles. However, when an inorganic fine particle is added to the resin layer to provide a polishing function, the polishing becomes non-uniform, the portion where the inorganic fine particle exists acts as a non-uniform charging point, and the fog and toner scattering are not sufficiently improved.

  In order to solve such a problem, as in Patent Document 2 below, the weight average molecular weight (Mw) of the resin is increased to 300,000 to 600,000 to suppress wear, and flat inorganic fine particles are added to add a contamination source. A method for suppressing the embedding of the toner external additive in the resin coating layer has been proposed.

JP 7-261465 A JP 2009-9000 A

  However, even if the resin that coats the carrier is increased in molecular weight as in Patent Document 2, the wear is not sufficient, and although it is possible to suppress burying of the toner external additive that becomes a contamination source with inorganic fine particles, it still remains. However, since the inorganic fine particles function as non-uniform charging points, there has been a problem that sufficient improvement cannot be achieved.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to stabilize the chargeability in the case of repeated image formation, and to stably prevent fogging and toner scattering over a long period of time. An object of the present invention is to provide an electrophotographic carrier and an image forming method capable of obtaining image quality.

  In order to solve the above problems, according to an aspect of the present invention, there is provided an electrophotographic carrier in which a resin layer is formed on the surface of magnetic particles, and the resin layer has a weight average molecular weight (Mw) of 30,000 to 150,000, which is formed using a styrene acrylic resin, an acrylic resin or a methacrylic resin that is substantially soluble in a predetermined solvent, and has a specific resistance (Ω · cm), and the specific resistance (Ω · cm) of the electrophotographic carrier after being dissolved in the predetermined solvent is R1 and R2, respectively, the R1 and R2 satisfy the following formula 1. The electrophotographic carrier having the shape factor (SF-1) of 110 to 130 after being dissolved in the predetermined solvent is provided.

    −1.0 ≦ logR1−logR2 ≦ 1.5 (Formula 1)

  With such a configuration, the electrophotographic carrier according to the present invention is such that the resin layer excellent in the charge imparting ability is uniformly worn at an appropriate speed due to the collision between the particles, and prevents the occurrence of the charge nonuniformity point. Can do. As a result, the electrophotographic carrier according to the present invention can provide stable image quality with stable chargeability and no fogging or toner scattering over a long period of time when images are repeatedly formed.

  The resin used for the resin layer preferably further has a second molecular weight peak in the range of 200,000 to 400,000. According to this configuration, the resin layer according to the present invention can be more evenly worn.

  In order to solve the above problems, according to another aspect of the present invention, a developer layer thickness regulating member is provided, and the developer thickness regulating member is provided per unit time (1 sec) and unit width (1 cm). There is provided an image forming method using an image forming apparatus having a mass of 1.0 g to 4.0 g of the developer passing therethrough and a developer containing the above-described electrophotographic carrier.

  With this configuration, the developer including the electrophotographic carrier according to the present invention is subjected to an appropriate stress by the developer thickness regulating member, and the resin layer of the electrophotographic carrier is evenly worn at an appropriate speed. It becomes possible to do.

  As described above, according to the present invention, even when images are formed repeatedly, the charging property is stable, and it is possible to obtain stable image quality without fogging and toner scattering over a long period of time.

It is explanatory drawing which showed the carrier for electrophotography which concerns on the 1st Embodiment of this invention. FIG. 2 is an explanatory diagram illustrating an outline of an image forming apparatus according to the embodiment. FIG. 6 is an explanatory diagram illustrating an example of a configuration of a developing unit according to the embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
<About the carrier for electrophotography>
First, the electrophotographic carrier according to the first embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is an explanatory diagram showing an electrophotographic carrier according to the present embodiment.

  As a result of intensive studies by the present inventors to solve the above-mentioned problems, in order to maintain a uniform chargeability over a long period of time, it is covered with a resin coating layer excellent in charge imparting ability, and collision between particles As a result, it was thought that it is important that the resin coating layer is worn out at a uniform and appropriate speed, and that no non-uniform charging point is generated.

  In order to realize such matters, an electrophotographic carrier (hereinafter also simply referred to as a carrier) 1 according to the present embodiment is formed on a carrier core material 10 and the surface of the carrier core material 10 as illustrated in FIG. And a resin coating layer (hereinafter also simply referred to as a resin layer) 20 that covers the carrier core material 10.

[About carrier core]
Although any conventionally known carrier core material 10 according to the present embodiment can be used, for example, it is preferable to use ferrite or magnetite. As another carrier core material, for example, iron powder is known. However, in the case of iron powder, since the specific gravity is large and the toner is easily deteriorated, ferrite and magnetite are more stable.

  Ferrite is a compound represented by the following chemical formula 1. Here, in the following chemical formula 1, M is at least one element selected from Cu, Zn, Fe, Mg, Mn, Ca, Li, Ti, Ni, Sn, Sr, Al, Ba, Co, Mo, and the like. is there. X and Y indicate mass mol ratios and satisfy the condition X + Y = 100.

(MO) _X (Fe ₂ O ₃ ) _Y (Chemical Formula 1)

  M is one or a combination of several kinds of Li, Mg, Ca, Mn, Sr, and Sn, and the content of other components is preferably ferrite particles of 1% by mass or less. When Cu, Zn, and Ni elements are added, the resistance tends to be low, and charge leakage tends to occur. In addition, resin coating tends to be difficult, and environmental dependency tends to deteriorate. Furthermore, these elements are heavy metals, and the stress applied to the carrier becomes strong, which may adversely affect the storage stability. In addition, from the viewpoint of safety, in recent years, the addition of Mn element or Mg element has become widespread.

As the carrier core material 10 according to the present embodiment, a ferrite core material is more preferable. As a raw material of the carrier core material 10, Fe ₂ O ₃ is an essential component, and magnetic particles used further include magnetite and maghemite. Ferromagnetic iron oxide particles such as spinel ferrite particles containing one or more metals other than iron (Mn, Ni, Zn, Mg, Cu, etc.), magnet plumbite type ferrite particles such as barium ferrite Examples thereof include particles of iron or iron alloy particles having an oxide film on the surface.

  Further, the carrier core material 10 used in the present embodiment is produced through a process of granulating and drying raw material ferrite and the like, then performing a baking process by heat treatment, and crushing and classifying the formed fired product. can do. Here, in the firing treatment step, particles obtained by granulation and drying are put into a container, and the container is placed in a firing furnace to perform firing.

  Here, in order to prevent the occurrence of the above-mentioned charge nonuniformity point, it is necessary to control the shape of the carrier that is considered to have a large influence on the generation of the charge nonuniformity point. Here, the shape of the carrier is greatly influenced by the shape of the carrier before the resin layer 20 is coated (that is, the shape of the carrier core material 10). This is because if there is a convex portion when coating the resin, the coating of the resin partially becomes thin and becomes a non-uniform point. Even if the resin layer 20 can be formed in a shape corresponding to the convex portion, stress concentration occurs, resulting in non-uniform wear and non-uniform points. On the other hand, when the carrier shape approaches a perfect sphere, the mixing property with the toner deteriorates and sufficient charging cannot be performed.

  Therefore, in order to achieve both appropriate charge imparting properties and prevention of the occurrence of charge nonuniformity, in the carrier core material 10 according to the present embodiment, the value of the shape factor (SF-1) shown in the following equation 101 is 110 to 130. This shape factor (SF-1) is a factor representing the degree of roundness of the particles. Control of the shape of the carrier can be achieved by controlling the conditions of the carrier core firing process.

  Here, in the above formula 101, MAX_LENGTH represents the maximum particle diameter of the particles, and AREA represents the projected area of the particles.

  Since the carrier core material 10 according to the present embodiment has such a shape that the shape factor (SF-1) is within the above-described range, uniform wear can be realized and the mixing property with the toner is also good. When the shape factor (SF-1) is less than 110, the shape of the carrier becomes too close to a true sphere, and it becomes difficult to impart appropriate chargeability to the toner. The mixing property is deteriorated and toner scattering occurs. In addition, when the shape factor (SF-1) is more than 130, the wear becomes uneven and it becomes difficult to impart appropriate chargeability to the toner, and toner scattering occurs. .

  This shape factor (SF-1) can be measured and calculated using a flow particle image analyzer, an image analyzer, or the like. In the present embodiment, the shape factor (SF-1) is calculated after the developer including the carrier 1 in which the resin coating layer 20 is coated on the carrier core material 10 is manufactured. A method for calculating the shape factor will be described in detail later.

[Resin coating layer]
Next, the resin coating layer 20 will be described.
The resin coating layer 20 according to the present embodiment is formed using a styrene acrylic resin, an acrylic resin, or a methacrylic resin that is substantially soluble in a solvent such as methyl ethyl ketone (MEK) or tetrahydrofuran (THF). Here, styrene acrylic resin, acrylic resin or methacrylic resin refers to polymers and copolymers such as acrylic acid and esters thereof, methacrylic acid and esters thereof, (meth) acrylamide, and (meth) acrylonitrile. Can include polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate, polycyclohexyl methacrylate, and the like. Moreover, as resin which comprises the resin coating layer 20, it is also possible to mix other resin by making an acrylic resin into a main component.

  Further, the coating amount of the coating resin according to the present embodiment on the carrier core material 10 is such that the resin solid content is 0.5 mass% to 10 mass%, preferably 1.0 mass% to 3.0 mass%. When the coating amount is less than 0.5% by mass, the coating effect by the resin of the carrier core material 10 is not sufficient, and the coating amount exceeding 10% by mass is meaningless, and the resin is excessive from the viewpoint of production. May be present alone, which is not preferable.

  Here, it is necessary to optimize the molecular weight of the resin as described above in order to realize the resin coating layer 20 that has excellent charge imparting ability and wears at a uniform and appropriate speed. When the molecular weight is too large, the depletion effect is not sufficiently exhibited, and when the molecular weight is too small, the depletion rate becomes too fast and non-uniformity increases. In addition, when a coating layer insoluble in a polar solvent such as MEK or THF is present, proper wear does not occur.

  In order to achieve such uniform and appropriate depletion, the resin according to this embodiment has a molecular weight peak in the range of 30,000 to 150,000 in terms of weight average molecular weight (Mw). When the weight average molecular weight of the resin is less than 30,000, the carrier is depleted rapidly and non-uniformly, and the toner using the carrier is scattered, which is not preferable.

  Moreover, it is preferable that the resin which concerns on this embodiment has a 2nd molecular weight peak in the range of 200,000-400,000 by a weight average molecular weight (Mw). By having the second molecular weight peak in such a range, more uniform depletion can be realized. This is presumably because the low molecular weight component is depleted while the high molecular weight component relieves stress, thereby effectively promoting the depletion. When the weight average molecular weight of the resin exceeds 400,000, contaminants on the carrier surface (for example, external additives used in the toner and residual toner) are not removed, and the charging performance gradually increases. Since it deteriorates, it is not preferable.

  The weight average molecular weight of the resin can be measured, for example, by gel permeation chromatography (GPC). In addition, a weight average molecular weight (Mw) means a polystyrene (PS) conversion weight average molecular weight. The method for measuring the molecular weight of the resin in this embodiment will be described in detail below.

Regarding the conductive agent In the resin coating layer 20 provided on the carrier core material 10, the resistance value of the resin coating layer 20 is also important in determining the performance of the carrier, and thus the toner using the carrier. It becomes a factor. Therefore, in the resin coating layer 20 according to the present embodiment, the resistance value is adjusted by dispersing a conductive agent (conductive powder) in the resin.

  The conductive powder used for adjusting the resistance of the resin coating layer 20 preferably contains, for example, at least one of carbon black, zinc oxide, and tin oxide. In particular, in order to minimize the occurrence of non-uniform charging points, it is preferable to use a small diameter and low resistance, and it is more preferable to use fine particles made of carbon black.

[Method for forming resin coating layer]
As a method of forming the resin coating layer 20 according to the present embodiment on the surface of the carrier core material 10, a wet coating method or a dry coating method can be used. In addition, when forming the resin layer 20 so that two molecular weight peaks exist, it is preferable to utilize a dry coat method.

  As the wet coating method, a fluidized bed spray coating method, a dip coating method, a kneader coating method, a polymerization method, or the like can be used.

  The fluidized bed spray coating method is a method in which a coating solution in which a coating resin is dissolved in a solvent is spray-coated on the surface of a carrier core material in a fluidized bed, and then dried to produce a coating on the surface of the carrier core material. .

  The immersion coating method is a method in which a carrier core material is immersed in a coating solution in which a coating resin is dissolved in a solvent, followed by drying, and then dried to produce a coating.

  The kneader coating method is a method in which a coating solution in which a coating resin is dissolved in a solvent is put into a vacuum degassing type kneader together with a carrier core material, and heated and dried under reduced pressure while stirring to produce a coating film.

  In the polymerization method, the carrier core material is dipped in a coating solution in which a reactive compound (that is, a polymerizable monomer) is dissolved in a solvent, and then the polymerization reaction is started by heating and the like. In this method, a coating film is formed on the surface of the core material.

  In the dry coating method, resin particles are applied to the surface of the carrier core material, and then the resin particles applied are melted or softened by applying a mechanical impact force so that the resin is applied to the surface of the carrier core material. It is a method of fixing and producing a film. That is, in the dry coating method, the carrier core material, the resin, the charge control particles and the low resistance fine particles are subjected to high-speed stirring using a high-speed stirring mixer that can impart mechanical impact force without heating or under heating, and the mixture is impacted. The coating is applied by repeatedly applying force and dissolved or softened on the surface of the carrier core material. In the case of heating, the heating temperature is preferably 60 to 130 ° C. This is because if the heating temperature is excessive, aggregation of carrier particles tends to occur.

[About carrier resistivity]
Next, the specific resistance of the electrophotographic carrier 1 having the carrier core material 10 and the resin coating layer 20 as described above will be described in detail.

  As described above, the electrophotographic carrier 1 according to the present embodiment removes surface contaminants by a self-polishing function utilizing wear and maintains the function. On the other hand, since the electrophotographic carrier has a function of imparting chargeability to the toner, it is desired that the function does not change due to wear. More specifically, the film thickness of the resin coating layer 20 is reduced due to wear. However, as the film thickness decreases, the resistance as a developer changes, and the effective electric field in the developing unit in the image forming apparatus changes. Strength will increase. As a result, the mass of the developing toner increases, causing an image density change. Therefore, the electrophotographic carrier is required not to cause such an image density change.

  In order to suppress such a problem, it is important to suppress a resistance change due to film depletion. Therefore, in the present embodiment, attention is paid to the specific resistance before the carrier 1 is dissolved in a solvent (for example, THF or MEK) in which the resin used for the resin coating layer 20 is dissolved, and the specific resistance after the dissolution. .

  Here, in the carrier 1 according to the present embodiment, when the specific resistance of the carrier before dissolution is R1 (Ω · cm) and the specific resistance of the carrier after dissolution is R2 (Ω · cm), the following formula 102 Meet. Here, in the following formula 102, “log” is a common logarithm (base 10 logarithm).

    −1.0 ≦ logR1−logR2 ≦ 1.5 (Formula 102)

  Since the specific resistance R1 is the specific resistance of the carrier 1 before being dissolved in the solvent as described above, it means the specific resistance of the carrier composed of the carrier core material 10 and the resin coating layer 20. Moreover, since the specific resistance R2 is the specific resistance of the carrier 1 after being dissolved in the solvent, the resin coating layer 20 of the carrier 1 is eluted in the solvent and means the specific resistance of the carrier made of the carrier core material 10. . Therefore, the expression 102 means that, in the carrier 1 according to the present embodiment, even if the resin coating layer 20 is all worn down, the specific resistance does not change so much that the number of digits changes greatly. It is. In other words, the carrier 1 according to the present embodiment has a small change in specific resistance due to wear.

  The carrier 1 according to the present embodiment can suppress a change in image density over time (that is, image deterioration) by satisfying the relationship expressed by the above formula 102, and can maintain a stable image density. Is possible. Further, when (logR1-logR2) exceeds -1 or exceeds 1.5, the image density changes with time, which is not preferable.

  The specific resistance measurement method will be described in detail later.

<About the measurement method of physical properties>
Next, the measurement method for each physical property value characterizing the electrophotographic carrier 1 according to the present embodiment will be specifically described.

[Measurement method of shape factor]
First, the shape factor measurement method will be described in detail.
First, 1.0 g of developer containing carrier 1 according to the present embodiment, several drops of activator and 50 ml of pure water are put into a 50 cc beaker, and after being vibrated with an ultrasonic disperser, the bottom of the beaker is placed. Discard the supernatant while holding it against the magnet. Again, add 50 ml of pure water and repeat 5 times in the same manner. Thereafter, the carrier is dried at 60 ° C. to obtain a carrier alone.

  3.0 g of the obtained carrier is placed in a 20 cc glass container together with 15.0 ml of THF and sealed, dissolved by rotating stirring for 10 minutes, and the supernatant is discarded while holding the carrier with a magnet. The process of adding 15.0 ml of THF again, dissolving, and extracting the supernatant is repeated twice, and the remaining carrier is dried to obtain a carrier after dissolving the THF (that is, a carrier core material).

  It should be noted that “substantially soluble in THF” means a decrease when the weight loss of the carrier after dissolving the above-mentioned THF (carrier after THF dissolution) is measured by thermogravimetry (TG) (residual resin weight). Is a case where 0.10% by weight or less. Specifically, this weight loss was measured using EXSTER TG / DTA 6200 (manufactured by Seiko Instruments Inc.).

  The obtained carrier after dissolution in THF was photographed with a scanning electron microscope at a magnification of 150 and 100 particles were photographed, and the image taken from the scanner was image processing analyzer LUZEX AP (manufactured by Nireco Corporation). And the shape factor (SF-1) is calculated by the above equation 101.

[Method for measuring molecular weight]
Subsequently, a method for measuring the molecular weight will be described in detail.
First, the sample is dissolved in THF so that the sample concentration becomes 1 mg / ml. Dissolution is performed at room temperature for 5 minutes using an ultrasonic disperser. Subsequently, after processing with a membrane filter having a pore size of 0.2 μm, 10 μL of the solution is injected into the GPC.

The measurement conditions are as follows.
Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKguardcolumn, TSKgelSuperHZM-M3 series (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: THF
Flow rate: 0.2 ml / min
Detector: Refractive index detector (RI detector)

  In the measurement of the molecular weight of the sample, the molecular weight distribution of the sample was determined by using monodisperse polystyrene standard particles (manufactured by Showa Denko KK, trade name “shodex”, weight average molecular weight: 1030000, manufactured by Tosoh Corporation, weight average molecular weight: 5480000, 3840000. 355,000, 102000, 37900, 9100, 2630, 870).

The resin was removed from the carrier as follows.
First, a developer, an activator, and pure water are put into a beaker, and after vibrating with an ultrasonic disperser, a supernatant is discarded while a magnet is applied to the bottom of the beaker and held. Again, add pure water and repeat 5 times. Thereafter, the carrier is dried at 60 ° C. to obtain a carrier alone. 3.0 g of the resulting carrier was placed in a 20 cc glass container together with 15.0 ml of THF and sealed, dissolved by rotating and stirring for 10 minutes, only the supernatant was taken out while holding the carrier with a magnet, and 15.0 ml of THF was added again and dissolved. The supernatant is extracted. The extraction process was repeated three times, and the extracted solution was dried to obtain a coating resin.

[Specific resistance measurement method]
Resistance measurement can be performed as follows.
First, 0.200 g of a sample is filled between two electrodes arranged in parallel at an interval of 2 mm. At the time of filling, a magnet (surface magnetic flux density 1500 Gauss, area in contact with electrodes: 10 mm × 30 mm) is arranged outside the electrodes, and a magnetic field is formed between the electrodes to fill the magnetic field. Thereafter, a voltage of 500 V is applied between the electrodes, and the specific resistance is measured using an insulation resistance meter SM-8210 (manufactured by Toa Decay Corporation). The measurement is performed in an environment controlled at a temperature of 20 to 25 ° C., humidity, and 50 to 60 RH%. The sample is left in the above environment for 8 hours or more before measurement.

<About developer>
The electrophotographic carrier 1 according to this embodiment as described above is preferably mixed with toner and used as a two-component developer. The two-component developer can be produced by mixing about 5 to 15% by mass of toner with respect to the carrier.

  An apparatus for mixing the carrier and the toner is not particularly limited, and a Nauter mixer, a W cone, a V-type mixer, or the like can be used.

[About toner]
The toner is not particularly limited, and a known toner containing a binder resin and a colorant as main components and containing a release agent or the like as necessary can be used. The toner may be produced by a dry production method such as a kneading and pulverization method, or may be produced by a wet production method such as an emulsion polymerization aggregation method, a dissolution suspension method, or a suspension polymerization method. Good.

Regarding Binder Resin Examples of the polymerizable monomer used for the production of the binder resin for toner include styrenes, monoolefins, esters of α-methylene aliphatic monocarboxylic acid, vinyl ethers, vinyl ketones and the like.

  Specific examples of styrenes include styrene and chlorostyrene. Specific examples of the monoolefin include ethylene, propylene, butylene, isobutylene and the like.

  Specific examples of esters of α-methylene aliphatic monocarboxylic acid include vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, acrylic Examples include octyl acid, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and dodecyl methacrylate.

  Specific examples of vinyl ether include vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, and specific examples of vinyl ketone include vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, and the like.

  Homopolymers or copolymers of these polymerizable monomers can be used as the binder resin for the toner.

  Particularly representative binder resins include, for example, polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, and styrene / anhydrous maleate. Examples include acid copolymers, polyethylene, and polypropylene.

  Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin waxes and the like.

About colorant As the colorant used in the toner, for example, various pigments and dyes can be used, and these pigments and dyes can be used alone or in combination of two or more. it can.

  Specific examples of pigments include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brillianthamine 3B, brillianthamine 6B, DuPont oil red, pyrazolone red, risor red, rhodamine B rake, lake red C, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalate it can.

  Specific examples of dyes include acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico, thioindico, phthalocyanine, and aniline black. And various dyes such as polymethine, polymethine, triphenylmethane, diphenylmethane, thiazine, thiazole, and xanthene.

  The content of the colorant in the toner according to the exemplary embodiment is preferably in the range of 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the binder resin. It is also effective to use a surface-treated colorant or a pigment dispersant as necessary. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner, and the like can be obtained.

○ About release agents Examples of release agents that can be used in toners include low molecular weight polyolefins, silicones that have a softening point when heated, fatty acid amides, plant waxes, animal waxes, mineral waxes, petroleum waxes. , And these modified products can be used.

  Specific examples of low molecular weight polyolefins include polyethylene, polypropylene, polybutene and the like. Specific examples of fatty acid amides include oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid amide and the like.

  Specific examples of plant waxes include ester wax, carnauba wax, rice wax, candelilla wax, wood wax, jojoba oil, etc. Specific examples of animal waxes include beeswax, whale wax, shellac, lanolin and the like. There is. Specific examples of the mineral wax include montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax.

  These release agents can be added in a range of 50% by mass or less based on the toner.

<Regarding Image Forming Apparatus and Image Forming Method>
The image forming apparatus according to this embodiment includes (i) an image holding member, (ii) a latent image forming unit that forms an electrostatic latent image on the surface of the image holding member, and (iii) an electrostatic image using a developer. A developing unit that develops the latent image to form a toner image; and (iv) a transfer unit that transfers the developed toner image to the transfer target. Further, as the developer, an electrostatic charge image developing developer including the above-described electrophotographic carrier 1 and toner is used.

  In addition, the image forming apparatus according to the present embodiment fixes means other than those listed above, for example, (v) charging means for charging the image holding member, and (vi) toner image transferred to the surface of the transfer target. And (vii) cleaning means for removing residuals such as toner and carrier remaining on the surface of the image carrier.

  Next, an example of the image forming apparatus 100 according to the present embodiment will be briefly described with reference to FIG. FIG. 2 is an explanatory diagram showing an outline of the image forming apparatus 100 according to the present embodiment.

  As illustrated in FIG. 2, the image forming apparatus 100 includes a charging unit 101, an exposure unit 103, an electrophotographic photosensitive member 105 that is an image holding member, a developing unit 107, a transfer unit 109, and a cleaning unit 111. The fixing unit 113 is mainly provided.

  In the image forming apparatus 100, a charging unit 101 that is a charging unit that charges the surface of the electrophotographic photosensitive member 105 and the charged electrophotographic photosensitive member 105 are exposed around the electrophotographic photosensitive member 105 according to image information. The exposure unit 103 that is a latent image forming unit that forms an electrostatic latent image, the developing unit 107 that is a developing unit that develops the electrostatic latent image with toner to form a toner image, and the surface of the electrophotographic photosensitive member 105 A transfer unit 109 that is a transfer unit that transfers the toner image formed on the surface of the transfer object 115, and a cleaning unit 111 that is a cleaning unit that removes toner remaining on the surface of the electrophotographic photosensitive member 105 after the transfer. Are arranged in this order.

  In addition, a fixing unit 113 that is a fixing unit that fixes the toner image transferred to the transfer target 115 is disposed on the left side of the transfer unit 109 (on the traveling method side of the transfer target 115).

An operation of the image forming apparatus 100 according to the present embodiment will be described.
First, the surface of the electrophotographic photosensitive member 105 is uniformly charged by the charging unit 101 (charging process). Next, the exposure unit 103 irradiates the surface of the electrophotographic photosensitive member 105 with light, and the charged charges in the irradiated part are removed, and an electrostatic charge image (electrostatic latent image) is formed according to the image information. (Latent image forming step). Thereafter, the electrostatic image is developed by the developing unit 107, and a toner image is formed on the surface of the electrophotographic photosensitive member 105 (developing process).

  For example, consider a digital electrophotographic copying machine that uses an organic photoreceptor as the electrophotographic photoreceptor 105 and a laser beam as the exposure unit 103. In this case, the surface of the electrophotographic photosensitive member 105 is given a negative charge by the charging unit 101, a digital latent image is formed in a dot shape by the laser beam light, and the developing unit 107 applies toner to the portion irradiated with the laser beam light. Applied and visualized. At this time, a negative bias is applied to the developing unit 107.

  Subsequently, in the transfer unit 109, a transfer object 115 such as paper is superimposed on the toner image, and a charge having a polarity opposite to that of the toner is given to the transfer object 115 from the back side of the transfer object 115, and the toner is generated by electrostatic force. The image is transferred to the transfer object 115 (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 113 and is fused and fixed to the transfer target 115 (fixing step).

  On the other hand, toner remaining on the surface of the electrophotographic photosensitive member 105 without being transferred is removed by the cleaning unit 111 (cleaning step). One cycle is completed in a series of processes from charging to cleaning.

  In FIG. 2, the toner image is directly transferred to the transfer body 115 such as paper by the transfer unit 109, but may be transferred via a transfer body such as an intermediate transfer body.

  Hereinafter, a charging unit, an image holding member, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a fixing unit in the image forming apparatus 100 illustrated in FIG. 2 will be described.

[Charging means]
For example, a charging device such as a corotron as shown in FIG. 2 is used as the charging unit 101 as a charging unit, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 105 or may apply an alternating current superimposed thereon. The surface of the electrophotographic photosensitive member 105 is charged by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 105 by such a charging unit 101. Normally, the electrophotographic photosensitive member 105 is charged to −300V or more and −1000V or less by the charging unit 101. In addition, the conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be further provided.

[Image carrier]
The image carrier has a function of forming at least a latent image (electrostatic charge image). As the image carrier, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 105 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer, a charge generation layer containing a charge generation material, and a photosensitive layer containing a charge transport layer containing a charge transport material are formed in this order, if necessary. It is. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single layer type photoreceptor included in the above layer may be used, but a laminated type photoreceptor is preferred. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

[Exposure means]
There are no particular limitations on the exposure unit 103 that is an exposure unit, and examples thereof include optical equipment that can expose a light source such as semiconductor laser light, LED light, and liquid crystal shutter light on the surface of the image carrier in a desired image-like manner. Can be mentioned.

  The developing unit 107, which is a developing unit, will be described in detail later.

[Transfer means]
As the transfer unit 109 serving as a transfer unit, for example, a charge opposite in polarity to the toner is applied to the transfer target 115 from the back side of the transfer target 115 as shown in FIG. 2, and the toner image is transferred to the transfer target 115 by electrostatic force. A transfer roll and a transfer roll pressing device using a conductive roll or a semiconductive roll that transfers directly to the surface of the transfer target 115 via the transfer target 115. it can. A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll can be arbitrarily set depending on the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. The transfer method may be a method of transferring directly to the transfer target 115 such as paper or a method of transferring to the transfer target 115 via an intermediate transfer member.

  A known intermediate transfer member can be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend materials, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is preferable.

[Cleaning means]
The cleaning unit 111 that is a cleaning unit may be appropriately selected from those that employ a blade cleaning method, a brush cleaning method, and a roll cleaning method, as long as they can clean residual toner on the image carrier. Among these, it is preferable to use a cleaning blade having elasticity.

[Fixing means]
The fixing unit 113 that is a fixing unit (image fixing device) fixes the toner image transferred to the transfer body 115 by heating, pressing, or heating and pressing, and includes a fixing member.

[Development means]
In order to realize an image forming method capable of obtaining more appropriate film wear, the conditions of the developer regulating portion are also important. First, a configuration example of the developing unit 107 as a developing unit will be briefly described with reference to FIG. FIG. 3 is an explanatory diagram showing an example of the configuration of the developing unit 107.

  As illustrated in FIG. 3, the developing unit 107 mainly includes a developing roller 120 and stirring and conveying members 130 and 140.

  The developing roller 120 is a developer carrier that supplies toner to the electrostatic latent image formed on the peripheral surface of the electrophotographic photosensitive member 105. The developing roller 120 includes, for example, a developing sleeve 124 and a magnet 122 disposed inside the developing sleeve 124. The developing sleeve 124 is a cylindrical member made of a nonmagnetic metal. In the developing roller 120, only the developing sleeve 124 rotates, and the magnet 122 disposed in the developing sleeve 124 is fixed to the casing. Further, the developing roller 120 is provided with a developing bias applying unit (not shown) for applying a developing bias.

  The magnet 122 has a plurality of magnetic poles, for example, a region facing the electrophotographic photosensitive member 105, that is, a region for developing the electrostatic latent image formed on the electrophotographic photosensitive member 105, and stirring from the developing region. Different magnetic poles can be alternately arranged up to a position facing the conveying member 130. This is because the developer is conveyed on the developing sleeve 124 by a magnetic force. Further, in the developing area, the magnetic brush of the developer is raised, and the magnetic brush is brought into contact with or close to the electrostatic latent image of the electrophotographic photosensitive member 105, so that a pole position or a gap is arranged in the developing area. You can also. On the other hand, magnetic poles having the same polarity are arranged adjacent to each other in the circumferential direction at a position where the developing roller 120 corresponds to the stirring and conveying member 130. The magnetic poles of the same polarity reduce the magnetic force in the tangential and normal directions with respect to the rotation direction of the developing sleeve 124 between the poles. For this reason, the developer is peeled from the developing sleeve 124 at a position where the developing roller 120 and the agitating / conveying member 130 face each other as the developing sleeve 124 rotates.

  Further, a layer regulating member 150 is provided on the upstream side in the rotation direction of the developing sleeve 124 with respect to the position where the developing sleeve 124 of the developing roller 120 and the electrophotographic photosensitive member 105 face each other. The layer regulating member 150 is a member that equalizes the developer attached on the peripheral surface of the developing sleeve 124 into a layer having a uniform thickness, and may be formed of, for example, a metal blade.

  The agitating / conveying unit is an area in which the magnetic carrier and the non-magnetic or weak magnetic toner constituting the developer are agitated to charge the carrier and the toner. The agitation transport unit includes a first agitation transport member 130 and a second agitation transport member 140.

  The first stirring / conveying member 130 is disposed so as to face the developing roller 120 in a substantially vertical direction, and supplies the mixed and stirred developer to the developing roller 120. The first stirring / conveying member 130 includes a first support shaft 132 and a first stirring blade 134. The first support shaft 132 is rotatably provided on the inner wall of the housing via a bearing. The first stirring blade 134 is provided on the outer peripheral surface of the first support shaft 132, and includes a spiral inclined surface arranged in the longitudinal direction of the first support shaft 132.

  The second agitating and conveying member 140 plays a role of mixing and agitating the developer to sufficiently charge the developer, and conveys the charged developer to the first agitating and conveying member 130. Similar to the first stirring and conveying member 130, the second stirring and conveying member 140 includes a second support shaft 142 and a second stirring blade 144. The second support shaft 142 is rotatably provided on the inner wall of the housing via a bearing. The second stirring blade 144 is provided on the outer peripheral surface of the second support shaft 142, and includes a spiral inclined surface arranged in the longitudinal direction of the second support shaft 142.

  The first agitation transport member 130 and the second agitation transport member 140 are arranged in, for example, a substantially horizontal direction (the developing roller 120 and the first support shaft 132 so that the first support shaft 132 and the second support shaft 142 are substantially parallel to each other. Are arranged side by side in a direction substantially orthogonal to the adjacent direction. A partition wall is provided between the first stirring and conveying member 130 and the second stirring and conveying member 140, and the first stirring and conveying member 130 and the second stirring and conveying member 140 are separated from each other. It is provided so that it may communicate in the both ends of the stirring conveyance member.

  The developer conveyed while being agitated by the second agitating and conveying member 140 moves to the peripheral surface of the developing roller 120 while being agitated and conveyed by the first agitating and conveying member 130. The second stirring / conveying member 140 is provided with a toner concentration sensor (not shown) for detecting the toner concentration, and from the toner tank (not shown) when the toner concentration in the conveying path decreases. The developer is supplied into the transport path via the developer supply unit 160.

[Image forming method]
In order to realize an image forming method capable of obtaining appropriate film wear in such a developing unit 107, a layer regulating member 150 that is a developer thickness regulating member and a developing roller 110 that is a developer carrier. And the developer mass passing through the layer regulating member 150 per unit time (1 sec) and unit width (1 cm) is 1.0 g to 4.0 g.

  Here, the developer passage amount of the layer regulating member 150 is determined by collecting the developer in an area of 1.0 cm × 3.0 cm from the developing sleeve 114 after the rotation of the developing sleeve 114 is stopped, and the unit width. The hit mass was calculated and multiplied by the developing sleeve rotation speed.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

<Carrier core: Production of magnetic particles>
Manganese (Mn) -magnesium (Mg) ferrite particles were produced by the following procedure, and core material particles (carrier core materials) “core 1 to core 5” having a shape factor SF-1 of 110 to 135 were produced.

First, the manganese content is 21.0 mol% in terms of MnO, the magnesium content is 3.3 mol% in terms of MgO, the strontium content is 0.7 mol% in terms of SrO, and the iron content is in terms of Fe ₂ O ₃ Thus, ferrite particles of 75.0 mol% were prepared by the following procedure.

  Various commercially available raw materials were blended so that the contents of manganese, magnesium, strontium, and iron were the above-mentioned values, water was added to the blend, and the mixture was pulverized for 10 hours by a wet ball mill and mixed. Thereafter, the obtained mixture was dried and kept at 950 ° C. for 4 hours.

  The retentate obtained by the above-mentioned retention was made into a slurry again, and further, the slurry was granulated by performing a pulverization treatment for 24 hours with a wet ball mill, and dried. The obtained granulated product is put into a firing furnace and held at 1100 ° C. for 4 hours, and then pulverized to adjust the particle size so that the particle size becomes 35 μm. 1 was produced.

  Moreover, the core 2-the core 4 were produced by carrying out similarly except having changed the temperature in a baking furnace into 1200 degreeC, 1300 degreeC, and 1400 degreeC in the process which produced the core 1. FIG.

  Furthermore, the core 2 was subjected to an oxidation treatment by heating and holding at 550 ° C. for 2 hours in the air in an electric furnace to obtain the core 5.

<Coating resin>
The following dry resin powder was prepared by emulsion polymerization.

Resin 1: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 20000, glass transition point 100 ° C., particle size 120 nm
Resin 2: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 30000, glass transition point 98 ° C., particle size 115 nm
Resin 3: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 40000, glass transition point 101 ° C., particle size 105 nm
Resin 4: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 100000, glass transition point 100 ° C., particle size 110 nm
Resin 5: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 150,000, glass transition point 101 ° C., particle size 105 nm
Resin 6: Methyl methacrylate / styrene copolymer (copolymerization ratio: 90/10)
Mw = 200000, glass transition point 102 ° C., particle size 110 nm
Resin 7: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 200000, glass transition point 102 ° C., particle size 125 nm
Resin 8: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 400000, glass transition point 103 ° C., particle size 115 nm
Resin 9: Methyl methacrylate / styrene copolymer (copolymerization molar ratio 90/10)
Mw = 500,000, glass transition point 106 ° C., particle size 105 nm
Resin solution 1: Silicone resin solution “SR2406” (manufactured by Toray Silicone Co., Ltd .: solid content: 20%), 100 parts by mass, γ- (2-aminoethyl) aminopropyltrimethoxysilane, 5 parts by mass, carbon black (MOGUL L: CABOT) (Manufactured) coating resin solution obtained by dissolving 1.6 parts by mass in 300 parts of toluene

<Formation of resin coating layer>
○ Career 1
20 parts by mass of “Resin 3” was dissolved in 2000 parts by mass of toluene, and then 1.2 parts by mass of carbon black (MOGUL L: manufactured by CABOT) was dispersed to obtain a coating resin solution. 1000 parts by mass of “Core 2” was placed in a rotating cylindrical flow apparatus, and the coating resin solution was sprayed and coated under heating at 70 ° C. while flowing. Thereafter, drying treatment was performed at 100 ° C. for 1 hour, and pulverized and classified to prepare “Carrier 1”.

○ Career 2
In the production of the carrier 1, the resin 3 was changed to “resin 2”, the mass of carbon black was changed from 1.2 parts by mass to 1.6 parts by mass, and the resin coating was performed in the same manner as the carrier 1. "

○ Career 3
In the production of the carrier 1, the “resin 3” is changed to “resin 5”, the mass of carbon black is changed from 1.2 parts by mass to 2.4 parts by mass, and “core 2” is changed to “core 3”. Resin coating was carried out in the same manner to obtain “Carrier 3”.

○ Career 4
1000 parts by weight of “Core 3”, 19.0 parts by weight of “Resin 1”, 1.0 part by weight of “Resin 7”, 1.6 parts by weight of carbon black, and into a high-speed stirring mixer, 25 ° C. Was mixed for 10 minutes, heated to 110 ° C. and stirred for 40 minutes, and then cooled to obtain “Carrier 4”.

○ Career 5
In the manufacture of the carrier 4, “resin 1” is changed to “resin 4”, the mass is changed to 16.5 parts by mass, “resin 7” is changed to “resin 8”, and the mass is changed to 3.5 parts by weight. ”Was changed to“ core 2 ”and resin-coated in the same manner as carrier 4 to obtain“ carrier 5 ”.

○ Career 6
In the production of the carrier 4, the carbon black mass is changed from 1.6 parts by mass to 3.0 parts by mass, the “core 3” is changed to the “core 5”, and the resin coating is performed in the same manner as the carrier 4. Obtained.

○ Career 7
In the manufacture of the carrier 4, the carbon black mass is changed from 1.6 parts by mass to 2.0 parts by mass, the “core 3” is changed to “core 1”, and the resin coating is performed in the same manner as the carrier 4 to form “carrier 7”. Obtained.

○ Career 8
In the production of the carrier 4, “resin 1” is changed to “resin 4”, the mass is changed to 17.5 parts by mass, “resin 7” is changed to “resin 9”, and the mass is changed to 2.5 parts by mass. The mass was changed from 1.6 parts by mass to 2.0 parts by mass, and the resin coating was performed in the same manner as the carrier 4 to obtain “Carrier 8”.

○ Career 9
The resin solution 1 was sprayed and coated under heating at 70 ° C. while 1000 parts by mass of the “core 2” was placed in a rotating cylindrical fluidizer and allowed to flow. Thereafter, baking treatment was performed at 150 ° C. for 1 hour, pulverization and classification were performed, and “Carrier 9” coated with a cross-linked resin was produced.

○ Career 10
In the manufacture of the carrier 4, the “core 3” was changed to the “core 4”, and resin coating was performed in the same manner as the carrier 4 to obtain “carrier 10”.

○ Career 11
In the production of the carrier 1, the “resin 3” is changed to “resin 1”, the mass of carbon black is changed from 1.2 parts by mass to 0.8 part by mass, and the resin is coated in the same manner as the carrier 1. "

○ Career 12
In the manufacture of carrier 1, “resin 3” is changed to “resin 6”, and the mass of carbon black is changed from 1.2 parts by weight to 1.8 parts by weight. Obtained.

○ Career 13
In the manufacture of the carrier 1, the “resin 3” is changed to “resin 5”, the mass of carbon black is changed from 1.2 parts by mass to 0.6 parts by mass, and the resin coating is performed in the same manner as the carrier 1. Got.

○ Career 14
In the production of the carrier 1, the “resin 3” is changed to “resin 5”, the mass of carbon black is changed from 1.2 parts by mass to 3.0 parts by mass, and the resin coating is performed in the same manner as the carrier 1. Got.

  In addition, the specific resistance was measured for each of the above-described carrier 1 to carrier 14 using the method described above.

  The obtained results are summarized in Table 1 below.

<Adjustment of developer>
100 parts by mass of each carrier produced as described above and 7.0 parts by mass of toner for magiccolor 8650DN (manufactured by Konica Minolta) were mixed with a stirrer to prepare “Developer 1” to “Developer 14”.

<Live-action evaluation>
The image forming apparatus having the configuration shown in FIG. 2 was used as an evaluation machine, and the development unit (development unit) having the configuration shown in FIG. 3 was used. Here, live-action evaluation was performed under the following two conditions. For printing evaluation, “C ² ” paper manufactured by Fuji Xerox Co., Ltd. was used.

○ Condition 1
Developer regulation distance: 600 μm
Development sleeve rotation speed: 640 mm / s

○ Condition 2
Developer regulation distance 400μm
Development sleeve rotation speed: 240 mm / s

  Here, the developer passage amount under Condition 1 was 4.0 g / sec, and the developer passage amount under Condition 2 was 1.0 g / sec. In addition, 100,000 evaluation of Life was implemented.

<Fog measurement>
The fog density was measured by measuring the absolute image density at 20 locations using a Macbeth reflection densitometer “RD-918” and averaging the blank paper unprinted. Next, the absolute image density at 20 locations was similarly measured and averaged for the white background portion of the 500,000th evaluation formed image, and the value obtained by subtracting the white paper density from this average density was evaluated as the fog density. A fog density of 0.010 or less was determined to be practically acceptable.

◎: Less than 0.003 ○: 0.003 or more and less than 0.006 Δ: 0.006 or more and less than 0.010 ×: 0.010 or more

<Evaluation of toner scattering>
500,000 prints were produced using the evaluation machine described above, and the state of toner scattering in the machine was evaluated by visually judging the degree of dirt on the hand when the toner cartridge was replaced.

◎: There is no dirt. ○: When you look closely, you can see the dirt. △: You can see the dirt.

<Image density>
First, a print is created by the above-described evaluation machine, and a Macbeth transmission densitometer “TD-904” (20 white background portions on the A3 whole solid image of the first evaluation formed image is used with reference to a non-printed blank paper. The transmission image density was measured using Macbeth Co.), and the average density was taken as the initial density. In addition, for the evaluation image after 500,000 prints were produced using the above-described evaluation machine, the same measurement was performed for 20 A3 full-color image portions on the basis of unprinted blank paper in the same manner as the first sheet. The average concentration was taken as the concentration after Life. Further, the difference between the average concentration after Life and the initial average concentration was calculated, and the determination was made based on the following criteria.

◎: Less than 0.10 ○: 0.10 or more and less than 0.20 Δ: 0.20 or more and less than 0.30 ×: 0.30 or more

  These results are shown in Table 2 below.

  As is clear from Table 2, Examples 1 to 8, which are examples of the present invention, are all good in performance, but Comparative Examples 1 to 6 outside the present invention have problems in at least any of the performances. I understand that there is.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Electrophotographic carrier 10 Carrier core material 20 Resin coating layer

Claims (3)

An electrophotographic carrier having a resin layer formed on the surface of magnetic particles,
The resin layer has a weight average molecular weight (Mw) of 30,000 to 150,000, and is formed using a styrene acrylic resin, an acrylic resin, or a methacrylic resin that is substantially soluble in a predetermined solvent,
The specific resistance (Ω · cm) of the carrier for electrophotography before being dissolved in the predetermined solvent, and the specific resistance (Ω · cm) of the carrier for electrophotography after being dissolved in the predetermined solvent, respectively When R1 and R2 are set, the R1 and R2 satisfy the following formula 1,
The electrophotographic carrier according to claim 1, wherein a shape factor (SF-1) of the electrophotographic carrier after being dissolved in the predetermined solvent is 110 to 130.

−1.0 ≦ logR1−logR2 ≦ 1.5 (Formula 1)
  2. The electrophotographic carrier according to claim 1, wherein the resin used for the resin layer further has a second molecular weight peak in the range of 200,000 to 400,000. An image forming apparatus having a developer layer thickness regulating member, wherein the mass of the developer passing through the developer thickness regulating member per unit time (1 sec) and unit width (1 cm) is 1.0 g to 4.0 g When,
A developer comprising the electrophotographic carrier according to claim 1;
An image forming method using the method.

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