JP2014059394A - Carrier for electrostatic charge image development, electrostatic charge image developer, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development that suppresses a variation in image concentration occurring when images are continuously formed irrespective of image density.SOLUTION: A carrier for electrostatic charge image development includes magnetic particles, and coating resin layers coating the magnetic particles and including additives having a structure represented by the following general formula (A), where any one of Rto Ris an OH group and others are each independently a hydrogen atom or an alkyl group, and any one of Rto Ris an OH group and others are each independently a hydrogen atom or an alkyl group.

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developer, a process cartridge, and an image forming apparatus.

In electrophotography, an electrostatic latent image formed on the surface of an image carrier (photoreceptor) is developed with toner containing a colorant, and the resulting toner image is transferred to a recording medium, which is heated on a roll or the like. An image can be obtained by fixing with. The residual toner is removed from the image carrier to form an electrostatic latent image again. Note that the cleaning process may be omitted when there is almost no residual toner as in the case of using spherical toner.
As described above, dry developers used for electrophotography and the like are divided into a one-component developer using a toner in which a binder is mixed with a colorant and the like, and a two-component developer in which the toner is mixed with a carrier. Broadly divided.

Patent Document 1 discloses a carrier for electrophotography characterized in that a carrier core material is coated with an alkoxyalkylated polyamide resin.
Patent Document 2 discloses an electrophotographic developer carrier characterized in that a resin-coated carrier whose surface is coated with a resin has a specific structure in which a component constituting the coating resin contains a fluorine atom. It is disclosed.
In Patent Document 3, in a developer carrier in which a magnetic material is used as a core and the surface of the core is cured with resin, the charge amount when the frictional charging with the toner is repeated is 1.0 ≦ C2 / C1 ≦ 1. 3 A carrier for developer characterized by satisfying (I) (in formula (I), C1 is the charge amount of the developer comprising toner and carrier, C2 is the carrier separated from the developer after measuring C1) And a triboelectric charge amount measured by stirring a mixture of the same toner and the same toner).

In Patent Document 4, in a carrier for developing an electrostatic charge image in which a multilayer resin coating layer having at least an inner layer and an outer layer is provided on the surface of a carrier core material, the inner layer is co-polymerized with vinylidene chloride and the vinylidene chloride. A carrier for developing an electrostatic charge image, comprising a copolymer resin with at least one monomer having a polymerizable unsaturated double bond, wherein the outer layer contains a silicone resin. Is disclosed.
In Patent Document 5, a charge having the same polarity as the charge controlled by the charge control agent contained in the toner is used for a two-component developer including at least a binder resin and a toner containing an organic colorant and a carrier. A carrier characterized by having a coating layer containing a charge control agent to be controlled and conductive particles on the surface of a core material is disclosed.

In Patent Document 6, in an electrophotographic carrier in which a coating resin layer is provided on a magnetic particle, the coating resin layer is formed of a resin containing a polycarbonate resin having a specific repeating unit containing a silicon atom. An electrophotographic carrier characterized by the above is disclosed.
Patent Document 7 discloses a magnetic material-dispersed carrier comprising at least a magnetic material, a polyester binder resin, and a charge control agent, wherein the polyester binder resin has a hydroxyl value of 20 to 50 mgKOH / g and the charge control agent. An electrostatic latent image developing carrier is disclosed in which is a compound containing Cr element.

In Patent Document 8, in a carrier for a two-component developer used for a developer composed of at least a toner and a carrier, (1) the carrier used for the developer has a specific resistance under the condition of 23 ° C./50% RH. Is coated with a coating resin layer of 10 ¹³ Ωcm or more, (2) the coating resin layer contains a charge control agent, (3) the average particle size of the carrier is 100 μm or less, and (4) the carrier The carrier for electrophotography is characterized in that the specific resistance of (10) is 10 ¹² Ωcm or more, and (5) the carrier core material surface has a resin coverage of 90% or more of carrier particles occupying 80% by number or more. It is disclosed.

Patent Document 9 discloses a two-component electrostatic image developer including a toner and a carrier used in an electrophotographic system using static electricity, wherein (a) the toner has a circularity of 85% or more. (B) an electrostatic image developer characterized by satisfying that the weight average particle diameter of the toner is in the range of 0.5 to 6 μm.
In Patent Document 10, in an electrophotographic carrier used as a developer composed of at least a toner and a carrier, (1) magnetic material-dispersed resin fine particles obtained by dispersing a magnetic powder in the carrier used in the developer. (2) The carrier is coated with a resin having a specific resistance of 23 ° C. and 50% RH and having a resistance of 10 ¹³ Ωcm or more. (3) The coating resin layer contains a charge control agent. (4) The average particle diameter of the carrier is 100 μm or less, (5) the specific resistance of the carrier is 10 ¹² Ωcm or more, and (6) the carrier particles having a resin coverage of 90 or more on the surface of the carrier core material as a whole. An electrophotographic carrier is disclosed, which occupies 80% by number or more.

Japanese Patent Laid-Open No. 3-152566 JP-A-6-138711 JP 2001-154415 A JP-A-5-107818 JP 2008-298891 A Japanese Patent Laid-Open No. 11-352731 Japanese Patent Laid-Open No. 10-10789 JP-A-7-301958 JP-A 63-208862 JP 2002-214842 A

  An object of the present invention is to provide a carrier for developing an electrostatic charge image in which fluctuations in image density that occur when images are continuously formed are suppressed regardless of the image density.

In order to achieve the above object, the following invention is provided.
The invention of claim 1 is an electrostatic charge image developing carrier comprising magnetic particles and a coating resin layer that covers the magnetic particles and includes an additive having a structure represented by the following general formula (A).

(In the formula (A), any one of R ^{1 to} R ⁵ is an OH group, the others are each independently a hydrogen atom or an alkyl group, and any one of R ^{6 to} R ^10. Are OH groups, and the others are each independently a hydrogen atom or an alkyl group.)
According to a second aspect of the present invention, in the general formula (A), at least one of R ^{1 to} R ¹⁰ is the alkyl group.
The invention according to claim 3 is the electrostatic image developing carrier according to claim 1 or 2, wherein the alkyl group has 1 to 5 carbon atoms.
According to a fourth aspect of the present invention, there is provided the electrostatic image developing carrier according to the first to third aspects, wherein the alkyl group is a t-butyl group.
The invention of claim 5 is an electrostatic image developer comprising a toner and the electrostatic image developing carrier according to any one of claims 1 to 4.
According to a sixth aspect of the present invention, there is provided developing means for accommodating the electrostatic charge image developer according to the fifth aspect and developing the electrostatic latent image formed on the image carrier as a toner image by the electrostatic charge image developer. A process cartridge provided and detachable from the image forming apparatus.
According to a seventh aspect of the present invention, there is provided an image holding member, a charging unit that charges the image holding member, an electrostatic latent image forming unit that forms an electrostatic latent image on the charged image holding member, and the fifth aspect. And developing means for developing the electrostatic latent image formed on the image carrier as a toner image with the electrostatic charge image developer, and transferring the toner image to the transfer target. An image forming apparatus comprising: a transfer unit;

According to the invention of claim 1, it occurs when images are continuously formed irrespective of the image density as compared with the case where the coating resin layer does not contain the additive having the structure represented by the general formula (A). Provided is a carrier for developing an electrostatic image in which fluctuations in image density are suppressed.
According to the second aspect of the present invention, compared to the case where R ^{1 to} R ¹⁰ in the formula (A) are all hydrogen atoms, the variation in image density that occurs when a high-density image is continuously formed is greater. A suppressed electrostatic charge image developing carrier is provided.
According to the invention of claim 3, an electrostatic charge image in which fluctuations in image density that occur when low-density images are continuously formed are more suppressed than when the alkyl group has 1 to 5 carbon atoms. A development carrier is provided.
According to the invention of claim 4, electrostatic charge image development in which fluctuations in image density caused when images are continuously formed regardless of image density is further suppressed as compared with the case where the alkyl group is not a t-butyl group. Carriers are provided.
According to the invention of claim 5, when the coating resin layer of the carrier does not contain an additive having the structure represented by the general formula (A), images are continuously formed regardless of the image density. An electrostatic charge image developer is provided in which fluctuations in image density occurring in the toner are suppressed.
According to the inventions of Claims 6 and 7, compared with the case where the coating resin layer of the carrier constituting the developer does not contain the additive having the structure represented by the general formula (A), the image is obtained regardless of the image density. The present invention provides a process cartridge and an image forming apparatus in which fluctuations in image density that occur when the film is continuously formed are suppressed.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows an example of the image forming apparatus of other this embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described in detail.

(Carrier for developing electrostatic image)
The electrostatic charge image developing carrier according to the exemplary embodiment (hereinafter, appropriately referred to as carrier) is coated with magnetic particles and magnetic particles, and has an additive (hereinafter referred to as the following general formula (A)). And a coating resin layer containing an additive A as appropriate).

In formula (A), any one of R ^{1 to} R ⁵ is an OH group, the other is each independently a hydrogen atom or an alkyl group, and any one of R ^{6 to} R ¹⁰ is OH group, the others are each independently a hydrogen atom or an alkyl group.

  By using the electrostatic charge image developing carrier of the present embodiment, fluctuations in image density that occur when images are continuously formed are suppressed regardless of image density, that is, both high-density images and low-density images. . The reason is not clear, but is presumed as follows.

  In recent years, label printing and package printing using an electrophotographic method have increased, and high-density image formation with a large solid surface (image area having an image density of 100%) has increased. In high-density image formation, toner consumption is high, and a lot of new toner continues to be supplied in the developing device. At this time, since uncharged toner continues to be supplied, charging due to the stirring of the developer in the developing machine may not be in time, and the charge amount of the toner may be reduced. When the charge amount of the toner is lowered, image development may occur more than necessary, resulting in an image defect such as an increase in image density and fogging.

  To cope with this, for example, it is conceivable to suppress the occurrence of fog and the like by setting the charge of the toner to be high. However, when printing with low image density, such as text, is continuously performed, undeveloped toner continues to be stirred in the developer because the amount of toner in the developer is small, and development is difficult due to excessive frictional charging. As a result, the concentration tends to be thin.

  On the other hand, in the carrier of the present embodiment, it is considered that the friction on the carrier surface is moderately increased when the coating resin layer contains the additive A. As a result, developer agitation is improved, and triboelectric charging during developer agitation is likely to occur stably. Particularly, even when a large amount of new toner is added to the developer in high-density image formation, the agitation is good. It is considered that the charging of the toner is stabilized early. Therefore, it is considered that a stable image can be obtained with little change in image density even in high-density image formation in which the amount of toner supply increases.

  In addition, the additive A has an S atom which is a weak electron-withdrawing group, and a phenyl group having π electrons exists. This is considered to stabilize the negative charge of the hydroxyl group. Even when the toner remains in the developer due to low-density image formation and the toner is easily charged, the negative charge of the hydroxyl group of the additive A contained in the coating resin layer of the carrier is stabilized. It is considered that the toner density is not increased so much and stable charging of the toner is obtained, and the image density is stable even in the formation of a low density image.

  Additive A has a hydroxyl group in the phenyl group, so that the negative polarity becomes moderately strong, the strong polarity of the hydroxyl group, and the affinity with water are alleviated, and the carrier is considered to achieve suitable charge control. . Additive A is considered to have high affinity with the coating resin and increase dispersibility in the coating resin layer due to the presence of -S- at the molecular center. Therefore, it is considered that there is little charge bias and stable charge control is realized as compared with the case where other general charge control agents are added. Similarly, additive A is considered to have a good dispersibility on the surface of the coating resin layer, so that the friction on the carrier surface is less biased and the stirring charge is likely to be uniform.

  Examples of the magnetic particles (magnetic powder) serving as the core material of the carrier according to this embodiment include magnetic metals such as iron oxide, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

  Examples of the resin (coating resin) for coating the magnetic particles include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene. -Acrylic acid copolymer, straight silicone resin comprising an organosiloxane bond or a modified product thereof, fluororesin, polyester, polycarbonate, phenol resin, epoxy resin and the like.

As for the additive A contained in the coating resin layer of a carrier, it is desirable that at least any one of R ^{1 to} R ^{10 in} the formula (A) is an alkyl group. Since the alkyl group is a weak electron donating group, it is considered that the negative charge of OH is moderately strengthened.
When an alkyl group is present in the formula (A), the alkyl group preferably has 1 to 8 carbon atoms, and more preferably 1 to 5 carbon atoms. Moreover, since it is thought that when there are too many alkyl groups and a steric hindrance will interfere with the effect of OH groups, the number of alkyl groups present in formula (A) is preferably 1 or more and 5 or less.
Further, the alkyl group present in the formula (A) is preferably branched rather than linear, and is particularly preferably a t-butyl group. The t-butyl group is an electron donating group, and it is considered that the effect is enhanced because the negative charge is further stabilized.

  Specific examples of the additive A include, for example, 2,2′-thiobis (4-methyl-6-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 4,4 '-Thiobis (3-methyl-6-t-butylphenol), 2,2'-thiobis (4-t-octylphenol), 4,4'-thiobis (2-methylphenol), 4,4'-thiobisphenol, Examples include 4,4 ′-(2,6′-di-t-butylphenol), but are not limited thereto. These additives A are synthesized by a normal organic synthesis reaction.

  The content of additive A contained in the coating resin layer of the carrier is preferably 0.5% by mass or more based on the entire coating resin layer from the viewpoint of effectively suppressing fluctuations in image density. % Or more and 3% by mass or less is more desirable.

In addition to the additive A, the carrier coating resin layer may contain other additives such as a conductive material.
Examples of the conductive particles that can be added to the coating resin layer include metal oxides such as carbon black, various metal powders, titanium oxide, tin oxide, magnetite, and ferrite. These may be used individually by 1 type and may use 2 or more types together. Among these, carbon black particles are desirable from the viewpoints of production stability, cost, conductivity, and the like. The type of carbon black is not particularly limited, but carbon black having a DBP oil absorption of about 50 ml / 100 g or more and 250 ml / 100 g or less is preferable because of excellent production stability.

In order to form the coating resin layer on the surface of the magnetic particles, for example, a coating resin layer forming solution (coating solution) in which the coating resin, additive A, and other various additives as required are dissolved in an appropriate solvent. And the like. The solvent is not particularly limited, and may be selected in consideration of the coating resin to be used, coating suitability, and the like.
Specific methods include an immersion method in which the core material is immersed in the coating resin layer forming solution, a spray method in which the coating layer forming solution is sprayed on the surface of the core material, and the magnetic particles are coated in a state of being suspended by fluid air. Examples thereof include a fluidized bed method in which the resin layer forming solution is sprayed, a kneader coater method in which the magnetic particles of the carrier and the coating resin layer forming solution are mixed in a kneader coater, and the solvent is removed.

  The coating amount of the coating resin on the core material (magnetic particles) is, for example, 0.5% by mass or more (preferably 0.7% by mass or more and 6% by mass or less, more preferably 1.0% by mass with respect to the mass of the entire carrier. % To 5.0% by mass).

The coating amount for coating the core material with the coating resin is obtained as follows.
In the case of a solvent-soluble coating resin, a precise amount of carrier is dissolved in a soluble solvent (for example, toluene), the magnetic powder is held by a magnet, and the solution in which the coating resin is dissolved is washed away. By repeating this several times, the magnetic powder from which the coating resin has been removed remains. The coating amount is calculated by drying, measuring the mass of the magnetic powder, and dividing the difference by the carrier amount.
Specifically, 20.0 g of the carrier is measured, put into a beaker, 100 g of toluene is added, and the mixture is stirred with a stirring blade for 10 minutes. A magnet is applied to the bottom of the beaker, and toluene is allowed to flow so that the core material (magnetic powder) does not flow out. This is repeated 4 times, and the beaker after washing is dried. After drying, the amount of magnetic powder is measured, and the coating amount is calculated by the formula [(carrier amount−magnetic powder amount after washing) / carrier amount].
On the other hand, in the case of a solvent-insoluble coating resin, Rigaku's Thermo plus EVOII differential type differential thermobalance TG8120 is heated in a nitrogen atmosphere in the range of room temperature (25 ° C.) to 1000 ° C., and its mass is reduced. From this, the coating amount is calculated.

  The volume average particle diameter of the carrier is, for example, 20 μm or more and 60 μm or less, desirably 25 μm or more and 40 μm or less, more desirably 25 μm or more and 38 μm or less.

Here, the volume average particle diameter of the carrier is measured as follows.
The carrier is measured for particle size distribution using a laser diffraction / scattering particle size distribution analyzer (LS Particle Size Analyzer (manufactured by Beckman-Coulter)), and the electrolyte is ISOTON-II (manufactured by Beckman-Coulter). The number of particles to be measured is 50,000.
Then, a cumulative distribution is drawn from the smaller diameter side of the measured particle size distribution with respect to the divided particle size range (channel), and the particle size at which 50% is accumulated is defined as “volume average particle size”.

(Electrostatic image developer)
The electrostatic image developer according to the exemplary embodiment (hereinafter, appropriately referred to as a developer) includes the above-described carrier and toner.
The toner constituting the developer according to the exemplary embodiment includes toner particles including, for example, a binder resin and, if necessary, a colorant, a release agent, and other additives.

  The binder resin constituting the toner is not particularly limited. For example, styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-acrylate -Esters having a vinyl group such as butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; acrylonitrile, methacrylonitrile Vinyl nitriles such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; polyolefins such as ethylene, propylene and butadiene Homopolymer consisting of a monomer, such as emissions acids, or copolymers obtained by combining two or more of these, more mixtures thereof. In addition, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, etc., non-vinyl condensation resins, or a mixture of these with the vinyl resin, or vinyl monomers in the presence of these resins Examples thereof include a graft polymer obtained by polymerization.

Styrene resin, (meth) acrylic resin, and styrene- (meth) acrylic copolymer resin are obtained by known methods, for example, by combining styrene monomers and (meth) acrylic acid monomers alone or in appropriate combination. It is done. “(Meth) acryl” is an expression including both “acryl” and “methacryl”.
The polyester resin can be obtained by selecting and combining suitable ones from a dicarboxylic acid component and a diol component and synthesizing them using a conventionally known method such as a transesterification method or a polycondensation method.

  When using a styrene resin, a (meth) acrylic resin or a copolymer resin thereof as a binder resin, the weight average molecular weight Mw is 20,000 or more and 100,000 or less, and the number average molecular weight Mn is 2,000 or more and 30,000 or less. It is preferable to use the thing of the range. On the other hand, when a polyester resin is used as the binder resin, a resin having a weight average molecular weight Mw of 5,000 or more and 40,000 or less and a number average molecular weight Mn of 2,000 or more and 10,000 or less may be used. preferable.

  The glass transition temperature of the binder resin is desirably in the range of 40 ° C. to 80 ° C., particularly in the range of 45 ° C. to 55 ° C. When the glass transition temperature is in the above range, the minimum fixing temperature is easily maintained.

The colorant is selected from known colorants according to the intended toner color.
Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like. I. Pigment Blue 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 13, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 17, 23, 60, 65, 73, 83, 180, C.I. I. Vat cyan 1, 3 and 20, etc., bitumen, cobalt blue, alkali blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated products of phthalocyanine blue, fast sky blue, indanthrene blue BC cyan pigment, C.I. I. And cyan dyes such as solvent cyan 79 and 162.

  Examples of the magenta colorant include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazole compounds, thioindigo compounds, perylene compounds, and the like. For example, C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90 112, 114, 122, 123, 163, 184, 202, 206, 207, and 209, pigment violet 19 magenta pigments, C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 30, 49, 81, 82, 83, 84, 100, 109, 121, C . I. Disper thread 9, C.I. I. Basic Red 1, 2, 9, 9, 13, 14, 15, 17, 17, 18, 22, 23, 24, 27, 29, 32, 34, the same 35, 36, 37, 38, 39, 40, etc. Magenta dyes, etc., Bengala, Cadmium Red, Lead Tan, Mercury Sulfide, Cadmium, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red, Calcium Salt, lake red D, brilliant carmine 6B, eosin lake, rotamin lake B, alizarin lake, brilliant carmine 3B and the like.

  Examples of the yellow colorant include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, allylamide compounds, and the like. I. And CI pigment yellow 2, 3, 15, 16, 17, 97, 180, 185, 139 and the like.

  Examples of the black colorant include carbon black (acetylene black, furnace black, thermal black, channel black, ketjen black), copper oxide, manganese dioxide, aniline black, titanium black, activated carbon, nonmagnetic ferrite, and magnetite. .

  As the colorant, a surface-treated colorant may be used as necessary, or it may be used in combination with a dispersant. A plurality of colorants may be used in combination.

  As content of a coloring agent, the range of 1 to 30 mass parts is desirable with respect to 100 mass parts of binder resin.

  Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester types such as fatty acid esters and montanic acid esters. Wax; and the like, but is not limited thereto.

  The melting temperature of the release agent is preferably 50 ° C. or higher and more preferably 60 ° C. or higher from the viewpoint of storage stability. Further, from the viewpoint of offset resistance, the temperature is desirably 110 ° C. or less, and more desirably 100 ° C. or less.

  The content of the release agent is preferably 1 part by mass or more and 15 parts by mass or less, more preferably 2 parts by mass or more and 12 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin. Even more desirable.

  Examples of other internal additives include magnetic materials, charge control agents, inorganic powders, and the like.

  The volume average particle diameter of the toner particles is, for example, 3 μm or more and 10 μm or less, preferably 3 μm or more and 8 μm or less, particularly 3 μm or more and 6 μm or less.

The volume average particle diameter of the toner particles is measured using a Coulter Multisizer-II type (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 50 μm. At this time, the measurement is performed after the toner particles are dispersed in an electrolyte aqueous solution (isoton aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more.
As a measuring method, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant, and this is added to 100 to 150 ml of the electrolytic solution. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the particle size distribution of the particles is measured. The number of particles to be measured is 50,000.
For the measured particle size distribution, a cumulative distribution is drawn from the smaller diameter side with respect to the divided particle size range (channel), and the particle size at which 50% is accumulated is defined as the volume average particle size.

  The toner particles may have a single layer structure or a structure (so-called core / shell structure) constituted by a core part and a coating layer covering the core part.

  The toner (toner particles) is preferably produced by a wet granulation method. Examples of the wet granulation method include known melt suspension methods, emulsion aggregation / unification methods, and dissolution suspension methods.

  In the developer according to the exemplary embodiment, the mixing ratio (mass ratio) of the toner and the carrier is preferably in the range of toner: carrier = 1: 100 to 30: 100, and is preferably about 3: 100 to 20: 100. Range is more desirable.

(Image forming device)
FIG. 1 schematically shows an example of the configuration of an image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 101 according to the present embodiment includes, for example, an electrophotographic photosensitive member 10 (an example of an image holding member) that rotates clockwise as indicated by an arrow A, and an electrophotographic photosensitive member. A charging device 20 (an example of a charging unit) that is provided above the body 10 and is opposed to the electrophotographic photoreceptor 10 and charges the surface of the electrophotographic photoreceptor 10, and the electrophotographic photoreceptor 10 charged by the charging device 20. An exposure device 30 (an example of an electrostatic latent image forming unit) that exposes the surface of the toner to form an electrostatic latent image, and a toner contained in the developer is attached to the electrostatic latent image formed by the exposure device 30. A developing device 40 (an example of a developing unit) that forms a toner image on the surface of the electrophotographic photosensitive member 10, and a transfer device that transfers the toner image on the electrophotographic photosensitive member 10 to a recording paper P (an example of a transfer target). 50 (an example of transfer means) and electrophotography And a cleaning device 70 (an example of a toner removing means) for cleaning the surface of the optical member 10.
The image forming apparatus 101 according to the present embodiment is provided with a fixing device 60 that fixes the toner image while conveying the recording paper P on which the toner image is formed.

  Details of main components in the image forming apparatus 101 according to the present embodiment will be described below.

-Electrophotographic photoreceptor-
Examples of the electrophotographic photoreceptor 10 include an inorganic photoreceptor in which a photosensitive layer provided on a conductive substrate is made of an inorganic material, and an organic photoreceptor in which a photosensitive layer is made of an organic material. Organic photoreceptors include a functionally separated photoreceptor in which a charge generation layer that generates charges by conductive exposure and a charge transport layer that transports charges are stacked on a conductive substrate, or a charge on a conductive substrate. And a photoconductor provided with a single-layer type photosensitive layer in which the same layer performs the function of generating a charge and the function of transporting charges. Examples of the inorganic photoreceptor include a photoreceptor in which a photosensitive layer made of amorphous silicon is provided on a conductive substrate.
The shape of the electrophotographic photoreceptor 10 is not limited to a cylindrical shape, and a known shape such as a sheet shape or a plate shape may be employed.

-Charging device-
Examples of the charging device 20 include a contact charger using a conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, and the like.
Examples of the charging device 20 include a non-contact type roller charger and a known charger such as a scorotron charger using a corona discharge or a corotron charger.

-Exposure device-
Examples of the exposure apparatus 30 include optical system devices that expose the surface of the electrophotographic photoreceptor 10 with light such as semiconductor laser light, LED light, and liquid crystal shutter light imagewise. The wavelength of the light source is preferably within the spectral sensitivity region of the electrophotographic photoreceptor 10. The wavelength of the semiconductor laser is preferably near infrared having an oscillation wavelength of around 780 nm, for example. However, the present invention is not limited to this wavelength, and an oscillation wavelength laser in the 600 nm range or a laser having an oscillation wavelength of 400 nm to 450 nm as a blue laser may be used.
As the exposure device 30, for example, a surface-emitting laser light source of a multi-beam output type is also effective for color image formation.

-Development device-
Examples of the developing device 40 include a general developing device that develops a two-component developer in contact or non-contact. The developing device 40 is not particularly limited as long as it has a developing function, and is selected from known developing devices according to the purpose. For example, the developing device 40 includes a known developing device having a function of attaching a two-component developer to the electrophotographic photoreceptor 10 using a brush, a roller, or the like. The developing device 40 preferably uses a developing roller holding a developer on the surface.

-Transfer device-
As the transfer device 50, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade or the like, or a known transfer charger such as a scorotron transfer charger using a corona discharge or a corotron transfer charger. Can be mentioned.

-Cleaning device-
The cleaning device 70 includes, for example, a casing 71, a cleaning blade 72, and a cleaning brush 73 disposed on the downstream side of the cleaning blade 72 in the rotation direction of the electrophotographic photosensitive member 10. Further, for example, a solid lubricant 74 is disposed in contact with the cleaning brush 73.

  Hereinafter, the operation of the image forming apparatus 101 according to the present embodiment will be described. First, the electrophotographic photoreceptor 10 rotates along the direction indicated by the arrow A, and at the same time, is negatively charged by the charging device 20.

  The electrophotographic photoreceptor 10 whose surface is negatively charged by the charging device 20 is exposed by the exposure device 30, and a latent image is formed on the surface.

  When the portion where the latent image is formed on the electrophotographic photosensitive member 10 approaches the developing device 40, toner is attached to the latent image by the developing device 40 (developing roll 41), and a toner image is formed.

  When the electrophotographic photosensitive member 10 on which the toner image is formed further rotates in the direction of arrow A, the toner image is transferred onto the recording paper P by the transfer device 50. As a result, a toner image is formed on the recording paper P.

  The toner image is fixed on the recording paper P on which the image is formed by the fixing device 60.

For example, as illustrated in FIG. 2, the image forming apparatus 101 according to the present embodiment includes an electrophotographic photosensitive member 10, a charging device 20, an exposure device 30, a developing device 40, and a cleaning device 70 in a housing 11. May be provided with a process cartridge 101 </ b> A in which are integrally stored. The process cartridge 101A integrally contains a plurality of members and is attached to and detached from the image forming apparatus 101.
The configuration of the process cartridge 101A according to the present embodiment is not limited to this. It is sufficient that the process cartridge 101A includes at least the developing device 40 containing the developer described above. For example, the electrophotographic photosensitive member 10, the charging device 20, It is good also as a structure provided with at least one selected from the exposure apparatus 30, the transfer apparatus 50, and the cleaning apparatus 70. FIG.

  In addition, the image forming apparatus 101 according to the present embodiment is not limited to the above configuration, and is, for example, a cleaning device around the electrophotographic photosensitive member 10 and downstream of the transfer device 50 in the rotation direction of the electrophotographic photosensitive member 10. A first neutralization device may be provided on the upstream side of the rotation direction of the electrophotographic photosensitive member from 70 so that the polarity of the remaining toner is aligned and easy to remove with a cleaning brush. Alternatively, a configuration may be adopted in which a second static elimination device for neutralizing the surface of the electrophotographic photosensitive member 10 is provided on the downstream side in the rotation direction of the electrophotographic photosensitive member and on the upstream side in the rotational direction of the electrophotographic photosensitive member relative to the charging device 20. .

  The image forming apparatus 101 according to the present embodiment is not limited to the above-described configuration, and a known configuration, for example, a toner image formed on the electrophotographic photosensitive member 10 is transferred to the intermediate transfer member and then transferred to the recording paper P. An intermediate transfer type image forming apparatus or a tandem type image forming apparatus may be used.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.
Unless otherwise specified, “part” means “part by mass” and {%} means “% by mass”.

(Coating solution 1)
Cyclohexyl acrylate resin (weight average molecular weight 50,000) 36 parts by mass Carbon black VXC72 (manufactured by Cabot) 4 parts by mass 4,4′-thiobisphenol (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.4 parts by mass Toluene 250 parts by mass Isopropyl alcohol 50 Parts by mass

  The above components and glass beads (particle size: 1 mm, the same amount as toluene) were put into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a coating solution 1 having a solid content of 11%.

(Coating solution 2)
A coating solution was prepared in the same manner except that the additive 4,4′-thiobisphenol was changed to 4,4′-thiobis (3-methyl-6-tert-butylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.) in the preparation of coating solution 1. 2 was prepared.

(Coating solution 3)
A coating solution 3 was prepared in the same manner except that the additive 4,4′-thiobisphenol was changed to 4,4′-thiobis (2-methylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.) in the preparation of the coating solution 1.

(Coating solution 4)
A coating solution 4 was prepared in the same manner except that the additive 4,4′-thiobisphenol was not added in the preparation of the coating solution 1.

(Coating solution 5)
A coating solution 5 was prepared in the same manner except that the additive 4,4′-thiobisphenol was changed to Bontron E304 (manufactured by Orient Chemical Co., Ltd.) in the preparation of the coating solution 1.

(Coating solution 6)
The coating solution 6 was prepared in the same manner except that the additive 4,4′-thiobisphenol was changed to 2,2′-thiobis (4-tert-octylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.) Prepared.

(Coating solution 7)
A coating solution 7 was prepared in the same manner except that the additive 4,4′-thiobisphenol was changed to 2,2-thiobis (4-chlorophenol) (self-made) in the preparation of the coating solution 1.

<Preparation of carrier 1>
In a vacuum degassing type 5 L kneader, 2000 g of DFC350 (average particle size: 35 μm) manufactured by Dowa Mining Co., Ltd. was added, and 560 g of coating liquid 1 was further added. The mixture was stirred at 60 ° C. to −200 mmHg and mixed for 15 minutes. Thereafter, the temperature was increased / decreased and the mixture was stirred and dried at 94 ° C./−720 mHg for 30 minutes to obtain coated particles. Next, sieving was performed with a 75 μm mesh sieving net to obtain Carrier 1.

<Production of carriers 2 to 7>
Carriers 2, 3, 4, 5, 6, and 7 were prepared in the same manner as carrier 1 except that coating liquid 1 was changed to coating liquids 2, 3, 4, 5, 6, and 7, respectively. Produced.

(Colorant dispersion 1)
Cyan pigment: Copper phthalocyanine B15: 3 (manufactured by Dainichi Seika Co., Ltd.) 50 parts by mass Anionic surfactant: Neogen SC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by mass Ion-exchanged water 200 parts by mass Dispersion was carried out for 5 minutes with an Ultra-Turrax manufactured by IKA and for 10 minutes with an ultrasonic bath to obtain a colorant dispersion 1 having a solid content of 21%.
It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Releasing agent dispersion 1)
Paraffin wax: HNP-9 (Nippon Seiki Co., Ltd.) 19 parts by weight Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.) 1 part by weight Ion-exchanged water 80 parts by weight The above components are mixed in a heat-resistant container. The mixture was heated to 90 ° C. and stirred for 30 minutes. Next, the melt was circulated from the bottom of the container to the gorin homogenizer, and a circulation operation corresponding to 3 passes was performed under a pressure condition of 5 MPa. Thereafter, the pressure was increased to 35 MPa, and a circulation operation corresponding to three passes was performed. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent dispersion 1.
It was 240 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Resin particle dispersion 1)
(Oil layer)
Styrene (manufactured by Wako Pure Chemical Industries, Ltd.) 30 parts by mass n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 10 parts by mass β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.) 1.3 parts by mass Dodecane Thiol (Wako Pure Chemical Industries, Ltd.) 0.4 parts by mass

(Water layer 1)
17 parts by weight of ion-exchanged water Anionic surfactant (Dowfax, manufactured by Dow Chemical Company) 0.4 parts by weight

(Water layer 2)
Ion-exchanged water 40 parts by weight Anionic surfactant (Dowfax, manufactured by Dow Chemical Co.) 0.05 parts by weight Ammonium peroxodisulfate (Wako Pure Chemical Industries, Ltd.) 0.4 parts by weight

The above oil layer component and water layer 1 component were placed in a flask and mixed with stirring to obtain a monomer emulsified dispersion.
The components of the aqueous layer 2 were charged into the reaction vessel, the inside of the vessel was sufficiently replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring.
Further, the above-mentioned monomer emulsified dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. After completion of the dropping, the polymerization was further continued at 75 ° C., and the polymerization was terminated after 3 hours.

The obtained resin particles were 250 nm when the volume average particle diameter D50v of the resin particles was measured with a laser diffraction particle size distribution analyzer LA-700 (manufactured by Horiba, Ltd.).
It was 53 degreeC when the glass transition point of resin was measured with the temperature increase rate of 10 degree-C / min using the differential scanning calorimeter (DSC-50 Shimadzu Corporation make).
When the number average molecular weight (polystyrene conversion) was measured using THF (tetrahydrofuran) as a solvent using a molecular weight measuring instrument (HLC-8020 manufactured by Tosoh Corporation), it was 13,000.
As a result, a resin particle dispersion 1 having a volume average particle size of 250 nm, a solid content of 42%, a glass transition point of 53 ° C., and a number average molecular weight Mn of 13,000 was obtained.

<Production of toner>
Resin particle dispersion 1 150 parts by weight Colorant particle dispersion 1 30 parts by weight Release agent particle dispersion 1 40 parts by weight Polyaluminum chloride 0.4 part by weight

  Each of the above components was sufficiently mixed and dispersed in a stainless steel flask using an IKE ultra turrax, and then heated to 48 ° C. while stirring the flask in a heating oil bath. After maintaining at 48 ° C. for 80 minutes, 70 parts by mass of the same resin particle dispersion 1 as above was gradually added thereto.

Then, after adjusting the pH in the system to 6.0 using an aqueous sodium hydroxide solution having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heat to 97 ° C. and hold for 3 hours. After completion of the reaction, the temperature lowering rate was cooled at 1 ° C./min, filtered and thoroughly washed with ion-exchanged water, and then solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed with 3 L of ion exchanged water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes.
This washing operation was further repeated 5 times. When the pH of the filtrate was 6.54 and the electric conductivity was 6.5 μS / cm, No. 2 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner mother particles.

The volume average particle diameter D50v of the toner base particles was measured with a Coulter counter. As a result, it was 6.2 μm and the volume average particle size distribution index GSDv was 1.20.
When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 135, and it was observed that the shape was distorted like a potato.
The glass transition point of the toner was 52 ° C.

Further, this toner was subjected to a surface hydrophobization treatment with hexamethyldisilazane (HMDS), silica (SiO ₂ ) particles having an average particle size of 40 nm, and an average particle size of a primary product which is a reaction product of metatitanic acid and isobutyltrimethoxysilane. A metatitanic acid compound particle having a particle diameter of 20 nm was added so that the coverage with respect to the surface of the toner particle was 40%, and mixed with a Henschel mixer to prepare a toner.

[Evaluation]
On a modified Docu Center Color 400 manufactured by Fuji Xerox Co., Ltd. (fixed toner density 8%, printing speed 70 sheets / min), cyan (Cyan) so that the toner density is 8% by mass with one of the above prepared carriers and toner. ) And 10000 solid patches were printed on A4 paper so that the area coverage was 2%. The image density of the first sheet and that of the 10,000th sheet were compared to determine the difference in L *.

  Next, 10,000 sheets were printed on A4 paper with an area coverage of 100%. The image density of the first sheet and that of the 10,000th sheet were compared to determine the difference in L *.

  L * means L * of CIE L * a * b * representing a color space standardized by the CIE (International Commission on Illumination), L * represents lightness, and 0 to 100 represents black to white. Here, L * was measured using a concentration measuring device X-right 938 (manufactured by X-rite).

The difference in L * was evaluated according to the following criteria.
◎: L * difference is 1.2 or less ◎: L * difference is more than 1.2 to 1.5 or less ○: L * difference is more than 1.5 to 1.8 or less △: L * difference is 1 .8 and 2.1 or less ×: L * difference is more than 2.1

<Example 1>
The above evaluation was performed using a developer containing carrier 1.
In the image comparison with an area coverage of 2%, the difference between the two L * s was 1.8.
In an image comparison with an area coverage of 100%, the difference between the two L * s was 1.6.

<Example 2>
The above evaluation was performed using a developer containing carrier 2.
In an image comparison with an area coverage of 2%, the difference in L * between the two was 1.4.
In an image comparison with an area coverage of 100%, the difference between the two L * s was 1.0.

<Example 3>
The above evaluation was performed using a developer containing carrier 3.
In an image comparison with an area coverage of 2%, the L * difference between the two was 1.6.
In an image comparison with an area coverage of 100%, the difference between the L * values was 1.5.

<Example 4>
The above evaluation was performed using a developer containing carrier 6.
In the image comparison with an area coverage of 2%, the difference in L * between them was 2.1.
In an image comparison with an area coverage of 100%, the difference between the L * values was 1.5.

<Comparative Example 1>
The above evaluation was performed using a developer containing carrier 4.
In an image comparison with an area coverage of 2%, the difference in L * between the two was 5.0.
In the image comparison with an area coverage of 100%, the difference between the two L * s was 4.8.

<Comparative example 2>
The above evaluation was performed using a developer containing carrier 5.
In the image comparison with an area coverage of 2%, the difference in L * between them was 2.8.
In the image comparison with an area coverage of 100%, the difference between the two L * s was 4.6.

<Comparative Example 3>
The above evaluation was performed using a developer containing carrier 7.
In the image comparison with an area coverage of 2%, the difference between the two L * s was 4.8.
In the image comparison with an area coverage of 100%, the difference between the two L * s was 3.2.

  Table 1 summarizes the differences between the carriers used in Examples and Comparative Examples and L * in image formation for each area coverage (AC).

From the above results, it can be seen that the image density difference L * is smaller in the present embodiment than in the comparative example in both low-density image formation and high-density image formation. In particular, it can be seen that this example has a good image density difference L * in both low-density image formation and high-density image formation, as compared with Comparative Example 3 containing chlorine atoms in addition to OH groups.
In Examples 2 to 4, in which at least one of R ^{1 to} R ¹⁰ in the formula (A) is the alkyl group, the area coverage is higher than that in Example 1 in which R ^{1 to} R ¹⁰ are all hydrogen atoms. From the 100% image comparison, it can be seen that the difference between the two L * is good.
Examples 2 and 3 in which the carbon number of the alkyl group is 1 or more and 5 or less are compared with Example 4 in which the carbon number of the alkyl group is not 1 or more and 5 or less. It can be seen that the difference is good.
In Example 2 in which the alkyl group is a t-butyl group, the difference in L * between the areas is 2% and 100% compared to Examples 3 and 4 in which the alkyl group is not a t-butyl group. I understand that there is.

10 Electrophotographic photoreceptor (an example of an image carrier)
11 Housing 20 Charging device (an example of charging means)
30 exposure apparatus (an example of electrostatic latent image forming means)
40 Developing device (an example of developing means)
41 Developing roll 50 Transfer device (an example of transfer means)
60 Fixing Device 70 Cleaning Device 71 Housing 72 Cleaning Blade 73 Cleaning Brush 74 Lubricant 101 Image Forming Device 101A Process Cartridge P Recording Paper

Claims (7)

Magnetic particles,
A coating resin layer that covers the magnetic particles and includes an additive having a structure represented by the following general formula (A);
A carrier for developing an electrostatic charge image.

(In the formula (A), any one of R ^{1 to} R ⁵ is an OH group, the others are each independently a hydrogen atom or an alkyl group, and any one of R ^{6 to} R ^10. Are OH groups, and the others are each independently a hydrogen atom or an alkyl group.) The electrostatic charge image developing carrier according to claim 1, wherein at least one of R ^{1 to} R ^{10 in} the general formula (A) is the alkyl group.   The carrier for developing an electrostatic charge image according to claim 1, wherein the alkyl group has 1 to 5 carbon atoms.   The carrier for developing an electrostatic image according to claim 1, wherein the alkyl group is a t-butyl group. Toner and
The electrostatic charge image developing carrier according to any one of claims 1 to 4,
An electrostatic charge image developer. A developing means for accommodating the electrostatic charge image developer according to claim 5 and developing the electrostatic latent image formed on the image carrier as a toner image with the electrostatic charge image developer,
A process cartridge that is detachable from the image forming apparatus. An image carrier,
Charging means for charging the image carrier;
Electrostatic latent image forming means for forming an electrostatic latent image on the charged image carrier;
Development means for containing the electrostatic charge image developer according to claim 5 and developing the electrostatic latent image formed on the image carrier as a toner image with the electrostatic charge image developer;
Transfer means for transferring the toner image to a transfer object;
An image forming apparatus comprising: