JP2009276532A - Carrier, developer, developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve carrier for two-component developer, stably maintaining charging quantity of toner, having a coating layer of carrier favorably coated, and outputting a high image quality image without image defect such as adhesion of carrier over a long period of time. <P>SOLUTION: In the coating layer 2b of a carrier core material 2a surface of the carrier 2, binder resin containing at least one of silicone resin and its denatured resin includes: an amino silane coupling agent; a hardening catalyst, which is an organic metal compound for controlling the hardening speed of the binder resin; a negative charge control agent, which is a negatively charged salt compound to the carrier core material 2a surface or the coating layer 2b; and conductive particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a carrier used in an electrophotographic system that develops and visualizes an electrostatic latent image formed on an image carrier, a developer including the carrier, a developing device using the developer, and image formation The present invention relates to an apparatus and an image forming method.

  2. Description of the Related Art Conventionally, with respect to image output devices using electrophotographic technology such as printers and copiers, toner and carrier are used as developers for developing an electrostatic latent image formed on an image carrier and forming a visible image. And a one-component developer composed of a single toner have been used. Of these, the magnetic brush development method using a two-component developer is superior in terms of image quality compared to other development methods, can be colored, and is relatively inexpensive. Has been used.

  2. Description of the Related Art A conventional image forming apparatus using a magnetic brush developing system includes a cylindrical metal sleeve and a magnet roller in which permanent magnets, which are magnetic field generating means, are arranged alternately in N and S poles. And a developer carrying member. A two-component developer is carried on the surface of the metal sleeve of the developer carrying member, and only the metal sleeve is rotated while the magnet roller is fixed, so that the developing region facing the image carrying member on which the electrostatic latent image is formed is moved. A two-component developer can be conveyed. Then, by a developing electric field applied between the developer carrier and the image carrier, only the charged toner is electrostatically attached to the image carrier to form a visible image.

  The toner in the two-component developer is contact frictionally charged by being mixed and stirred with a carrier in a developing unit including a developer carrier. In dry two-component development, an image is formed by electrical handling using the electrostatic force of the frictionally charged toner, but control of the toner charge amount is important. The toner charge amount is determined by various requirements on the system, but it is desirable for the stability of the system that the value is stable.

  Further, as a recent trend of copying machines and printers, increasing the image quality and speeding up of printing is regarded as important. In this case, the stability of the developer is particularly important. In order to achieve high image quality, it is necessary to dispose a predetermined amount of toner at a predetermined location. In electrophotography, toner is handled using electrostatic force, and in order to overcome the external force such as adhesion force and move the toner by an electric field, it is necessary to maintain a high charge of a certain level or more. Is done. Further, as the speed of the machine increases, the number of printed sheets or the number of times inevitably increases, so the demand for maintenance has increased, and there is a need for a developer that can operate stably over a long period of time. .

  In such a two-component developer, stabilizing the toner charge amount is an important factor for maintaining high-quality image output over a long period of time. Under this circumstance, the carrier used to charge the toner used in the two-component developer, unlike the toner, stays in the development unit for a long period of time, so that the charge due to toner spent, external additive transfer, stirring and mixing stress, etc. There are concerns about a decrease in granting ability. In addition, the toner scattering due to this may cause contamination in the image forming apparatus. Therefore, there is a need for a highly durable carrier that can withstand deterioration over time and can stably maintain the charge amount of the toner over a long period of time. Therefore, various efforts have been made regarding the formulation of charge control additives to be added to the resin material for coating the core material of the carrier.

For example, Patent Document 1 discloses a technique for increasing the charge amount by adding an aminosilane coupling agent to a silicone resin. Patent Document 2 discloses a technique for suppressing variation in charge amount by coating with a silicone resin. Patent Document 3 discloses a technique for suppressing a change in resistance due to deterioration over time by providing an additive used for coating with an inclination in the film direction. Patent Document 4 discloses a technique for increasing the hardness of a coating film by adding a Ti compound or an aluminum compound to a methylphenyl silicone resin to increase the developer life. Patent Document 5 discloses a technique for maintaining a high charge amount over a long period of time by containing an aminosilane coupling agent and a quaternary ammonium salt compound.
JP-A-1-284862 (published on November 16, 1989) JP 7-295303 A (published on November 10, 1995) JP 7-160059 A (released on June 23, 1995) Japanese Unexamined Patent Publication No. 2000-181146 (released on June 30, 2000) JP 2002-229325 A (released on August 14, 2002)

  As described above, in order to maintain high-quality image formation over a long period of time, it is an extremely important issue to improve the stability of the toner charge amount by contact frictional charging with a carrier. Therefore, there is an urgent need to search for and select a prescription that can withstand carrier performance deterioration due to toner spent on the carrier, transfer of external additives, coating resin peeling due to mechanical stress, and the like.

  However, it is difficult to say that the above-described conventional technique has a sufficient effect. In particular, the effect is limited in a toner having a small particle diameter that is frequently used in recent years and a toner having externally added large particles used for improving transfer efficiency, such as a color toner.

  In recent years, the demand for environmental safety has been increasing, and there is a tendency for regulations to be imposed on substances added in minute amounts in carriers.

  Specifically, in the technique of Patent Document 1, when the charge amount is improved by aminosilane, the charge amount at the start of printing of the developer greatly increases, but the charge amount rapidly decreases as the number of printed sheets increases. is there.

  Further, in the technique described in Patent Document 2, a specific silicone resin and a curing catalyst are used to advance crosslinking to reduce unreacted reactive groups, thereby preventing deterioration over time. However, charging due to an increase in the number of printed sheets is possible. Reduction has not been prevented.

  The technique described in Patent Document 3 aims to reduce resistance change by providing a concentration gradient of the additive in the direction of the coating film and to achieve stable printing. Less effective.

  In the technique described in Patent Document 4, the toner spent is prevented and the developer life is extended by increasing the hardness of the coating resin by using methylphenyl silicone and Ti compound or Al compound. It is not sufficient for the print deterioration due to the decrease in the charge amount due to the factor.

  In the technique described in Patent Document 5, the charge amount is increased and maintained for a long time by using aminosilane and a quaternary ammonium salt in combination. According to this method, the toner charge amount can be increased and maintained by the effect of the additive. However, if a strong positively charged aminosilane and a positively chargeable charge control agent CCA are used at the same time, high charge can be maintained over a long period of time, but the initial charge amount tends to be excessive. There remains a problem in that the amount of change until the charge amount settles is large and the charge amount cannot be maintained stably.

  In addition, in order to maintain the charge amount, it is necessary to reduce the spent of the developer by using a low surface energy resin for the coating material itself. For this purpose, a silicone or fluorine-based low surface energy resin is used. There is a tendency. In general, since a fluorine-based resin exhibits a strong negative chargeability, when used as a carrier coating, the toner is positively charged and cannot be used in a development system using a negatively charged toner. Therefore, it is desirable to use a carrier coated with a silicone resin as a developer used in a developing system for negatively charged toner.

  There are many types of silicone resins and modified resins thereof, and resins having various characteristics can be used depending on the combination and the cross-linked state, but it is necessary to control the cured state at the same time. A catalyst or a curing agent is used for that purpose. However, most of the quaternary ammonium salts described in Patent Document 5 are polar in view of their function, and when used for coating, there is a tendency to inhibit the curing of the silicone resin. Therefore, since the coat state of the carrier is deteriorated, there is a limitation on the amount of addition in use.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is to stably maintain the charge amount of toner, particularly toner having a small particle diameter, and the coating layer of the carrier is well coated. It is an object of the present invention to provide a carrier for a two-component developer, a developer including the carrier, a developing device, and an image forming apparatus that can output a high-quality image with few image defects such as carrier adhesion over a long period of time.

  In order to solve the above problems, the carrier according to the present invention has a coating layer on the surface of the core material in which an aminosilane coupling agent is added to a binder resin containing at least one of a silicone resin and a modified resin thereof. The coating layer includes a curing catalyst that is an organic metal compound that controls the curing rate of the binder resin, a negative charge control agent that is a negatively charged salt compound with respect to the core material surface or the coating layer, It is characterized by containing conductive particles.

  According to the above configuration, since the binder resin containing at least one of the silicone resin and the modified resin contains the aminosilane coupling agent and the negative charge control agent, the charge amount is high even when used for a long time. In addition, it is possible to provide a carrier with little charge reduction from the beginning. Moreover, since the curing catalyst which is an organic metal compound which controls the curing rate of the binder resin is contained, the coating state of the carrier coating layer can be improved.

  In addition, even if the carrier is subjected to mechanical stress during long-term use and the coating layer is scraped or peeled off, the negative charge control agent and conductive particles existing on the newly exposed coating layer surface function effectively. In addition, it is possible to prevent a decrease in toner charge amount due to carrier deterioration due to an increase in the number of printed sheets.

  Therefore, the carrier having the above structure can stably charge the toner even when the number of printed sheets increases, and can contribute to long-term stable image quality. Over a long period of time, it is possible to reproduce an image with high definition, to form a high-quality image with good color reproducibility, high image density, and few image defects.

  In the carrier according to the present invention, in addition to the above configuration, the curing catalyst is preferably a titanium compound or an aluminum compound. Titanium compounds or aluminum compounds have a high ability as a resin curing accelerator, and can balance the precipitation of silicone resin or its modified resin and additives added to this resin and the curing of the resin. it can.

  In the carrier according to the present invention, in addition to the above-described configuration, the negative charge control agent preferably includes at least one of a holobis potassium salt, a salicylic acid zinc salt, and a salicylic acid chromium salt. These salt compounds can be effectively used as a charge control agent.

  In the carrier according to the present invention, in addition to the above configuration, the aminosilane coupling agent is preferably added in an amount of 0.1 to 10 parts with respect to 100 parts by weight of the binder resin. When the aminosilane coupling agent is added within this range, the toner can be charged more efficiently.

  In addition, in the carrier according to the present invention, in addition to the above configuration, the charge control agent is preferably added in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. Thus, by optimizing the addition amount of the charge control agent, the charging characteristics can be stabilized, and stable image formation can be achieved over a long period of time.

  In the carrier according to the present invention, in addition to the above configuration, the curing catalyst is preferably added in an amount of 0.2 to 5 parts by weight with respect to 100 parts by weight of the binder resin. By adding 0.2 to 5 parts by weight of the curing catalyst with respect to 100 parts by weight of the binder resin, the effect is easily exhibited. When the curing catalyst is less than 0.2 parts by weight, it is difficult to exert the effect of curing the resin, and when it is more than 5 parts by weight, carrier adhesion tends to occur. Therefore, the above range is preferable.

  In the carrier according to the present invention, in addition to the above configuration, it is preferable that 0.2 parts by weight or more of the tin compound is not contained with respect to 100 parts by weight of the binder resin. In the carrier coating layer, since the tin compound is not contained in an amount of 0.2 parts by weight or more with respect to 100 parts by weight of the binder resin, the carrier in consideration of environmental pollution and human damage, and development using the carrier The production of the agent becomes possible. Further, when the charge control agent is contained in the binder resin of the coating layer, the mechanical strength of the resin is not lowered.

  In the carrier according to the present invention, in addition to the above configuration, the average particle diameter is preferably 55 μm or less. When the carrier has an average particle diameter of 55 μm or less, toner conveyance is stabilized and high-definition image formation is possible in the developer containing the carrier.

  In order to solve the above problems, a developer according to the present invention is characterized by including any one of the carriers described above and a toner. According to the above configuration, it is possible to provide a developer that exhibits the same effect as the carrier and has stable charging even when the number of printed sheets increases. Therefore, by using the developer having the above-described configuration, it is possible to stably form a high-quality image with high-definition, good color reproducibility, high image density, and few image defects such as fog.

  Further, the developer according to the present invention is in addition to the above configuration. The toner preferably has an average particle diameter of 6.7 μm or less. By using a toner having an average particle diameter of 6.7 μm or less and a carrier having the average particle diameter of 55 μm or less, it is possible to output an image while achieving both the graininess and fine line uniformity of the halftone portion. That is, in the developer according to the present invention, the charge amount can be stably maintained even with the toner having a small particle size as described above.

  In order to solve the above-described problems, the developing device according to the present invention performs development using any one of the above-described developers. Such a developing apparatus can perform development while stabilizing the charge amount of the toner, and has the same effect as the carrier and the developer.

  In order to solve the above-described problems, an image forming apparatus according to the present invention includes the above-described developing device.

  According to the above configuration, since the developer including the carrier according to the present invention having the above configuration is used, the charge amount of the toner can be stabilized. Therefore, the effects of the carrier and developer according to the present invention can be expressed more effectively.

  As described above, the carrier according to the present invention is a carrier having a coating layer in which an aminosilane coupling agent is added to a binder resin containing at least one of a silicone resin and a modified resin thereof, on the surface of the core material. Is a curing catalyst that is an organic metal compound that controls the curing rate of the binder resin, a negative charge control agent that is a salt compound that is negatively charged with respect to the core surface or the coating layer, and conductive particles. And containing.

  According to the above configuration, since the binder resin containing at least one of the silicone resin and the modified resin contains the aminosilane coupling agent and the negative charge control agent, the charge amount is high even when used for a long time. In addition, it is possible to provide a carrier with little charge reduction from the beginning. Moreover, since the curing catalyst which is an organic metal compound which controls the curing rate of the binder resin is contained, the coating state of the carrier coating layer can be improved.

  In addition, even if the carrier is subjected to mechanical stress during long-term use and the coating layer is scraped or peeled off, the negative charge control agent and conductive particles existing on the newly exposed coating layer surface function effectively. In addition, it is possible to prevent a decrease in toner charge amount due to carrier deterioration due to an increase in the number of printed sheets.

  Therefore, the carrier having the above structure can stably charge the toner even when the number of printed sheets increases, and can contribute to long-term stable image quality. Over a long period of time, it is possible to reproduce an image with high definition, to form a high-quality image with good color reproducibility, high image density, and few image defects.

  An embodiment of the present invention will be described with reference to FIGS. 1 and 2 as follows.

  The developer 1 according to the present embodiment is a two-component developer including a toner 3 and a carrier 2. The toner, the carrier, and the developer will be described in this order. Hereinafter, unless it is described as particles, it refers to the entire toner and the entire carrier.

(toner)
The toner 3 includes, as raw materials, a binder resin and a colorant as essential components, and may further include a charge control agent, a release agent, and the like. In addition, two or more types of external additives having different particle diameters are added to the toner 3.

  The binder resin is not particularly limited, and a known binder resin for black toner or color toner can be used. Examples thereof include polyester resins, polystyrene, styrene resins such as styrene-acrylic acid ester copolymer resins, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyurethane, and epoxy resins. Moreover, you may use resin obtained by mixing a raw material monomer mixture with a mold release agent and performing a polymerization reaction. Binder resin may be used individually by 1 type, and may use 2 or more types together.

  When a polyester resin is used as the binder resin, examples of the aromatic alcohol component for obtaining the polyester resin include bisphenol A, polyoxyethylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane. , Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene -(2.2) -Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (6) -2,2-bis (4-hydroxyphenyl) propane , Polyoxypropylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- 2.4) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene - (3.3) -2,2-bis (4-hydroxyphenyl) propane and derivatives thereof, and the like.

  The polybasic acid component of the polyester resin includes succinic acid, adipic acid, sebacic acid, azelaic acid, dodecenyl succinic acid, n-dodecyl succinic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid. , Dibasic acids such as cyclohexanedicarboxylic acid, orthophthalic acid, isophthalic acid, terephthalic acid, etc., acids having three or more bases such as trimellitic acid, trimetic acid, pyromellitic acid and their anhydrides, lower alkyl esters, From the viewpoint of heat-resistant aggregation, terephthalic acid or its lower alkyl ester is preferred.

  Here, the acid value of the polyester resin constituting the toner 3 is preferably 5 to 30 mgKOH / g. When the acid value is less than 5 mgKOH / g, the charging characteristics of the resin are lowered and the charge control agent is difficult to disperse in the polyester resin. This adversely affects the charge amount stability of repeated development due to rising of the charge amount or continuous use. Therefore, the above range is preferable.

  As the colorant, various colorants can be used depending on the desired color. Examples thereof include a yellow toner colorant, a magenta toner colorant, a cyan toner colorant, and a black toner colorant. .

  Examples of the colorant for yellow toner include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 15, C.I. I. Azo pigments such as CI Pigment Yellow 17; inorganic pigments such as yellow iron oxide and ocher; I. Nitro dyes such as Acid Yellow 1, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, C.I. I. Examples thereof include oil-soluble dyes such as Solvent Yellow 21.

  Examples of the colorant for magenta toner include C.I. I. Pigment red 49, C.I. I. Pigment red 57, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15 etc. are mentioned.

  Examples of the colorant for cyan toner include C.I. I. Pigment blue 15, C.I. I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 25, C.I. I. Direct Blue 86 and the like can be mentioned.

  Examples of the colorant for black toner include carbon black such as channel black, roller black, disk black, gas furnace black, oil furnace black, thermal black, and acetylene black. From these various types of carbon black, an appropriate carbon black may be appropriately selected according to the design characteristics of the toner to be obtained.

  As the colorant, in addition to these pigments, a red pigment, a green pigment, or the like may be used. A coloring agent may be used individually by 1 type, and may use 2 or more types together. Two or more of the same color can be used, and one or more of the different colors can also be used.

  The colorant may be used in the form of a masterbatch. The master batch of the colorant can be produced in the same manner as a general master batch. For example, it can be produced by kneading a melt of a synthetic resin and a colorant to uniformly disperse the colorant in the synthetic resin, and then granulating the resulting melt-kneaded product. As the synthetic resin, the same kind as that of the toner binder resin or one having good compatibility with the toner binder resin is used. At this time, the use ratio of the synthetic resin and the colorant is not particularly limited, but is preferably 30 to 100 parts by weight with respect to 100 parts by weight of the synthetic resin. The master batch is granulated to a particle size of about 2 to 3 mm.

  The amount of the colorant used is not particularly limited, but is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the binder resin. This is not the amount of the master batch but the amount of the colorant itself contained in the master batch. By using the colorant in this range, an image having a high image density and a very good image quality can be formed without impairing various physical properties of the toner.

  The charge control agent is added for the purpose of controlling the triboelectric charging property of the toner 3. As the charge control agent, a negative charge control agent commonly used in this field can be used. Examples of the charge control agent for controlling the negative charge include oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, naphthenic acid metal salts, metal complexes and metal salts of salicylic acid and its derivatives ( Examples of the metal include chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, and resin acid soaps. Among these, a boron compound is particularly preferable as it does not contain a heavy metal. What is necessary is just to use a charge control agent properly according to a use. One charge control agent may be used alone, or two or more charge control agents may be used in combination as required. The amount of the charge control agent used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the binder resin.

  As the release agent, those commonly used in this field can be used, for example, petroleum wax such as paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, Low molecular weight polypropylene wax and derivatives thereof, hydrocarbon-based synthetic waxes such as polyolefin polymer waxes (low molecular weight polyethylene wax and the like) and derivatives thereof, carnauba wax and derivatives thereof, rice wax and derivatives thereof, candelilla wax and derivatives thereof , Plant waxes such as wood wax, animal waxes such as beeswax and spermaceti, synthetic fat waxes such as fatty acid amides and phenol fatty acid esters, long chain carboxylic acids and their derivatives Long chain alcohols and derivatives thereof, silicone polymers, such as higher fatty acids. Derivatives include oxides, block copolymers of vinyl monomers and waxes, graft modified products of vinyl monomers and waxes, and the like. The amount of the release agent used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

  As the external additive 3a of the toner 3, those commonly used in this field can be used, and examples thereof include silicon oxide, titanium oxide, silicon carbide, aluminum oxide, and barium titanate. In the present embodiment, two or more kinds of external additives having different particle diameters are used in combination, and at least one kind of primary particle diameter is 0.1 μm or more. When an external additive having at least one kind of primary particle diameter of 0.1 μm or more is used, particularly in a color toner, transferability is improved, and charging due to adhesion of the external additive to the carrier surface is reduced. The toner 3 can be charged stably and for a long time without causing it. The amount of the external additive used is not particularly limited, but is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of toner 3.

  The raw materials of the toner 3 are mixed by a mixer such as a Henschel mixer, a super mixer, a mechano mill, or a Q-type mixer, excluding external additives, and the resulting raw material mixture is a biaxial kneader, a single screw kneader, a continuous type After being melt-kneaded at a temperature of about 70 to 180 ° C. by a kneader such as a two-roll kneader, the mixture is cooled and solidified. The melted and kneaded material of the toner 3 after cooling and solidification is coarsely pulverized by a cutter mill, a feather mill or the like. The resulting coarsely pulverized product is finely pulverized. For fine pulverization, a jet mill, a fluidized bed type jet pulverizer, or the like is used. These pulverizers pulverize the toner particles by causing the toner particles to collide with each other by colliding the air flow containing the toner particles from a plurality of directions. Thereby, the nonmagnetic toner 3 having a specific particle size distribution can be manufactured. The particle diameter of the toner 3 is not particularly limited, but the average particle diameter is preferably in the range of 5 to 7 μm. Furthermore, particle size adjustment such as classification may be performed as necessary. The external additive 3a is added to the toner 3 thus produced by a known method. The manufacturing method of the toner 3 is not limited to the above.

(Career)
The carrier 2 of the present embodiment takes into consideration that a sufficient charge is imparted to the toner 3 and the like, and as shown in FIG. 1, the surface of the carrier core material 2a is coated with a coating resin (binder resin) and an aminosilane coupling agent. And a coating layer 2b made of a coating resin composition containing a negative charge control agent, conductive particles, and a curing catalyst.

  As the carrier core material 2a, those commonly used in this field can be used, and examples thereof include magnetic metals such as iron, copper, nickel and cobalt, and magnetic metal oxides such as ferrite and magnetite. When the carrier core material 2a is a magnetic material as described above, a carrier suitable for a developer used in the magnetic brush development method can be obtained. The carrier core material 2a preferably has an average particle diameter of 25 to 100 μm.

  In the coating resin composition that forms the coating layer 2b on the surface of the carrier core material 2a, the aminosilane coupling agent, the charge control agent, the conductive particles, and the curing catalyst are contained in the coating resin (binder resin). Is.

  As the coating resin, use of a silicone resin leads to better results because it can achieve both the releasability with the toner 3 and the adhesion with the carrier core material 2a.

  The silicone resin is not particularly limited, and a silicone resin commonly used in this field can be used, but a cross-linked silicone resin is preferable. The cross-linked silicone resin is a known silicone resin that is cured by crosslinking between hydroxyl groups bonded to Si atoms or a hydroxyl group and a group -OX by a heat dehydration reaction, a room temperature curing reaction, or the like, as shown in the following chemical formula.

  As the crosslinkable silicone resin, either a heat curable silicone resin or a room temperature curable silicone resin can be used. In order to crosslink the thermosetting silicone resin, it is necessary to heat the resin to about 200 to 250 ° C. Heating is not necessary to cure the room temperature curable silicone resin, but it is preferable to heat at 150 to 280 ° C. in order to shorten the curing time.

  Among the cross-linked silicone resins, those in which the monovalent organic group represented by R is a methyl group are preferable. Since the crosslinked silicone resin in which R is a methyl group has a dense crosslinked structure, when the coating layer 2b is formed using the crosslinked silicone resin, a carrier 2 having good water repellency and moisture resistance can be obtained. . However, if the cross-linked structure becomes too dense, the coating layer 2b tends to become brittle, so selection of the molecular weight of the cross-linked silicone resin is important.

  Moreover, it is preferable that the weight ratio (Si / C) of silicon and carbon in the crosslinkable silicone resin is 0.3 to 2.2. If Si / C is less than 0.3, the hardness of the coating layer 2b may be reduced, and the life of the carrier 2 may be reduced. On the other hand, when Si / C exceeds 2.2, the charge imparting property of the carrier 2 with respect to the toner 3 is likely to be affected by the temperature change, and the coating layer 2b may become brittle.

  When a cross-linked silicone resin is used as the coating resin, a commercially available product can be used. KR272, KR274, KR216, KR280, KR282, KR261, KR260, KR255, KR266, KR251, KR155, KR152, KR214, KR220, X-4040-171, KR201, KR5202, KR3093 (all trade names, Shinetsu Chemical Industries ))). One type of cross-linked silicone resin may be used alone, or two or more types may be used in combination.

  Moreover, you may use modified silicone resins, such as an acryl and an epoxy, from the point that the adhesiveness with respect to the carrier core material 2a improves more.

  As the charge control agent contained in the coating layer 2b, those generally used for toner can be used. Accordingly, the charge control agent for the carrier 2 used for the negatively charged toner may be a negative charge control agent. As charge control agents for controlling negative charges, oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and its derivatives, metal complexes and metal salts (metal is Chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, resin acid soaps, and the like. Among these, a boron compound is particularly preferable as it does not contain a heavy metal.

  When the charge control agent is added to the coating resin, it can be dissolved or dispersed in accordance with the properties of the charge control agent and added to the resin solution. In that case, it is also possible to dilute the resin solution with an appropriate organic solvent for adjusting the viscosity and adjusting the polarity. In order for the charge control agent to exert its effect, it is desirable that it be present in the coating resin as uniformly as possible. When a charge control agent is added to adjust the charge, the electric resistance of the carrier tends to be lowered due to the property of having charge controllability. Some charge control agents may inhibit the curing of the silicone resin, so it is necessary to pay attention to the coating state when coating is performed.

  In addition, a charge control agent may be used individually by 1 type, and may use 2 or more types together as needed. The amount of the charge control agent used is not particularly limited and can be appropriately selected from a wide range, but is preferably 1 to 10 parts by weight, more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the coating resin.

  As the conductive particles, for example, conductive carbon black, oxides such as conductive titanium oxide and tin oxide are used. Carbon black or the like is suitable for developing the conductivity with a small addition amount, but there is a concern that the color toner may be desorbed from the coating layer 2b of the carrier 2. In this case, conductive titanium oxide doped with antimony is used.

  Further, the coating layer 2b of the carrier 2 contains a silane coupling agent having an electron donating functional group, here, an aminosilane coupling agent for the purpose of adjusting the charge amount to the toner 3. An aminosilane coupling agent is a silane coupling agent containing an amino group. A well-known thing can be used as an aminosilane coupling agent, For example, what is represented by the following General formula (1) can be used.

(Y) nSi (R) m (1)
(In the formula, m R represents the same or different alkyl group, alkoxy group or chlorine atom. N Y represents a hydrocarbon group containing the same or different amino group. M and n are 1 to 3 respectively. (Where m + n = 4).
In the general formula (1), examples of the alkyl group represented by R include a straight chain having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group. Examples thereof include a chain or branched alkyl group. Among these, a methyl group, an ethyl group, etc. are preferable. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, and a tert-butoxy group. . Among these, a methoxy group, an ethoxy group, etc. are preferable. Examples of the hydrocarbon group containing an amino group represented by Y, for _{example, - (CH 2) a-} X ( wherein, X is an amino group, an aminocarbonyl amino group, an aminoalkyl group, phenylamino group or dialkylamino A represents an integer of 1 to 4, and -Ph-X (wherein X is the same as above, -Ph- represents a phenylene group).

  Specific examples of the aminosilane coupling agent include the following.

H ₂ N (H ₂ C) ₃ Si (OCH ₃ ) ₃ ,
H ₂ N (H ₂ C) ₃ Si (OC ₂ H ₅ ) ₃ ,
H ₂ N (H ₂ C) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ ,
_{H 2 N (H 2 C)} 2 HN (H 2 C) 3 Si (CH 3) (OCH 3) 2,
H ₂ NOCHN (H ₂ C) ₃ Si (OC ₂ H ₅ ) ₃ ,
H ₂ N (H ₂ C) ₂ HN (H ₂ C) ₃ Si (OCH ₃ ) ₃ ,
_{H 2 N-Ph-Si (} OCH 3) 3 ( wherein -Ph- indicates a p- phenylene group),
Ph-HN (H ₂ C) ₃ Si (OCH ₃ ) ₃ (wherein Ph- represents a phenyl group),
(H ₉ C ₄ ) ₂ N (H ₂ C) ₃ Si (OCH ₃ ) ₃
An aminosilane coupling agent may be used individually by 1 type, or may use 2 or more types together. The amount of the aminosilane coupling agent used is appropriately selected from the range that gives sufficient charge to the toner 3 and does not significantly reduce the mechanical strength of the coating layer 2b. The amount is preferably 10 parts by weight or less, more preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the resin contained in the coating resin composition.

  The coating resin composition can contain other resins together with the silicone resin as long as the preferable characteristics of the coating layer 2b formed of the silicone resin (particularly the cross-linked silicone resin) are not impaired. Examples of other resins include epoxy resins, urethane resins, phenol resins, acrylic resins, styrene resins, polyamides, polyesters, acetal resins, polycarbonates, vinyl chloride resins, vinyl acetate resins, cellulose resins, polyolefins, and copolymers thereof. Examples thereof include resins and compounded resins.

  The coating resin composition may contain a bifunctional silicone oil in order to further improve the moisture resistance, releasability, and the like of the coating layer 2b formed of a silicone resin (particularly a cross-linked silicone resin).

  The coating resin composition can be produced by mixing predetermined amounts of a silicone resin and an aminosilane coupling agent and the like, and if necessary, an appropriate amount of a resin other than the silicone resin and an additive such as a bifunctional silicone oil. As one form of the resin composition for coating, a form of a solution in which the above components are dissolved in an organic solvent can be mentioned. The organic solvent is not particularly limited as long as it can dissolve the silicone resin. For example, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, and higher alcohols. And a mixed solvent of two or more of these.

  If this solution resin composition for coating (hereinafter referred to as “coat resin solution”) is used, the coating layer 2b can be easily formed on the surface of the carrier core material 2a. For example, a coating resin solution is applied to the surface of the carrier core material 2a to form a coating layer, and the organic solvent is volatilized and removed from the coating layer by heating or decompression and a combination thereof, and the coating layer is heated and cured during or after drying. By simply curing, the covering layer 2b is formed, and the carrier 2 is manufactured.

  Examples of the method of applying the coating resin liquid onto the surface of the carrier core material 2a include, for example, an immersion method in which the carrier core material 2a is impregnated with the coating resin liquid, a spray method in which the coating resin liquid is sprayed on the carrier core material 2a, Examples thereof include a fluidized bed method in which a coating resin liquid is sprayed onto the carrier core material 2a in a state. Among these, the dipping method is preferable because film formation can be easily performed.

  Here, in order to carry out the coating appropriately, it is necessary to balance both the precipitation of the resin caused by solvent evaporation and the curing of the silicone resin and the incorporation of the additive into the resin. These vary greatly depending on the heating temperature, the amount of reduced pressure, and the like, but a certain amount of time is required for that purpose.

  Therefore, a curing accelerator is used for drying the coating layer (coat resin solution). Organic compound catalysts such as Sn compounds, Al compounds, Ti compounds and the like having high ability as curing accelerators for silicone resins are preferred. These curing catalysts have a function of promoting the curing of the silicone resin. The curing catalyst is preferably contained in an amount of 0.2 to 5 parts by weight with respect to 100 parts by weight of the coating resin.

  When Sn (Sn compound) is used as the catalyst, the coating state deteriorates because the curing rate is too high. In order to balance the precipitation of the resin and additives and the curing of the resin, it is desirable to use an Al compound or Ti compound curing catalyst that does not react too quickly.

  The coating layer is cured while selecting a heating temperature according to the type of silicone resin. For example, it is preferable to carry out by heating to about 150 to 280 ° C. Of course, when the silicone resin is a room temperature curable silicone resin, heating is not necessary, but for the purpose of improving the mechanical strength of the coating layer to be formed, shortening the curing time, etc., 150 to 280 ° C. You may heat to the extent.

  The total solid content concentration of the coating resin liquid is not particularly limited, and the film thickness of the coating layer 2b after curing is usually 5 μm or less, preferably 0.1 while considering the workability of application to the carrier core material 2a. What is necessary is just to adjust so that it may be set to about ~ 3 micrometers.

  The average particle size of the carrier 2 thus obtained is preferably 55 μm or less. The carrier 2 preferably has a high electrical resistance and a spherical shape, but the effect of the present invention is not lost even if it is conductive or non-spherical.

(Developer)
The developer 1 is manufactured by mixing the toner 3 and the carrier 2. The mixing ratio of the toner 3 and the carrier 2 is not particularly limited, but considering use in a high-speed image forming apparatus (40 sheets / min or more for an A4 size image), the volume average particle diameter of the carrier / the volume of the toner. The ratio of the total projected area of toner (the total projected area of all toner particles) to the total surface area of the carrier (total surface area of all carrier particles) with the average particle diameter being 5 or more (total projected area of toner / carrier The total surface area × 100) is about 30 to 70%.

  As a result, the chargeability of the toner 3 can be stably maintained in a sufficiently good state, and can be used as a suitable developer that can form a high-quality image stably and for a long period of time even in a high-speed image forming apparatus.

  When the toner concentration in the developer 1 is low, the toner charge amount tends to increase, and when the toner concentration is high, the toner charge amount tends to decrease. Therefore, it is possible to adjust the charge amount to some extent using this phenomenon. However, when the developer 1 is used by being mounted on an actual machine, if the toner density is lowered, the rising of the carrier becomes a problem due to an increase in the contact area between the carrier 2 and the photosensitive member. As the toner concentration is increased, toner scattering becomes more serious as the charge amount decreases.

  For example, when the volume average particle diameter of the toner is 6.5 μm, the volume average particle diameter of the carrier is 90 μm, and the ratio of the total projected area of the toner to the total surface area of the carrier is 30 to 70%, 100 parts by weight of the carrier in the developer 1 The toner contains about 2.2 to 5.3 parts by weight of toner. When developing at such a high speed with the developer 1, the toner consumption amount and the toner supply amount supplied to the developing tank of the developing device in accordance with the toner consumption are maximized, and the supply-demand balance is not impaired. When the amount of the carrier 2 in the developer 1 is larger than about 2.2 to 5.3 parts by weight, not only the charge amount tends to be lowered and desired development characteristics cannot be obtained, but also the toner supply amount. However, the amount of toner consumption increases, and sufficient charge cannot be imparted to the toner 3, resulting in deterioration of image quality. On the other hand, when the amount of the carrier 2 is small, the charge amount tends to be high, and it becomes difficult for the toner 3 to be separated from the carrier 2 by the electric field, resulting in deterioration of image quality.

  In the present embodiment, the total projected area of toner is calculated as follows. The specific gravity of the toner is assumed to be 1.0, and calculation is performed based on the volume average particle diameter obtained with a Coulter counter (trade name: Coulter Counter Multisizer II, manufactured by Beckman Coulter, Inc.). That is, the number of toners with respect to the toner weight to be mixed is calculated, and the number of toners × the toner area (calculated assuming a circle) is set as the total toner projected area. Similarly, the surface area of the carrier is calculated from the carrier weight mixed based on the particle diameter obtained from Microtrac (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.). The carrier specific gravity at this time is 4.7. The mixing ratio is calculated by the total toner projected total area / carrier total surface area × 100 obtained above.

(Developing apparatus and image forming apparatus)
The developing device 20 of the present embodiment performs development using the developer 1 of the present embodiment described above. As shown in FIG. 2, the developing device 20 includes a developing unit 10 that stores the developer 1, and a developer carrier (developer carrying carrier) 13 that conveys the developer 1 to the image carrier 15.

  The developer (two-component developer) 1 of the present embodiment, which is composed of the carrier 2 and the toner 3 of the present embodiment that has been put in advance in the developing unit 10, is stirred and charged by the stirring screw 12. Then, the developer 1 is held on the surface of the developer carrier 13 by being conveyed to the developer carrier 13 having a magnetic field generating unit disposed therein. The developer 1 held on the surface of the developer carrier 13 is regulated to a constant layer thickness by the developer regulating member 14 and is conveyed to a development area formed in the proximity area between the developer carrier 13 and the image carrier 15. Then, the electrostatic charge image on the image carrier 15 is visualized by a reversal development method under an oscillating electric field formed by applying an AC bias voltage to the developer carrier 13. Further, toner consumption due to visible image formation is detected by the toner density sensor 16, and the consumed amount is replenished from the toner hopper 17 until the toner density sensor 16 detects that a predetermined specified toner density has been reached. Thus, the toner density in the developer 1 inside the developing unit 10 is kept substantially constant.

  The image forming apparatus of this embodiment includes the developing device 20. For other configurations, a known electrophotographic image forming apparatus can be used. For example, an image carrier having a photosensitive layer capable of forming an electrostatic image on the surface, and charging for charging the surface of the image carrier to a predetermined potential. Means, an exposure means for irradiating the surface of the image carrier with signal light corresponding to the image information to form an electrostatic charge image (electrostatic latent image) on the surface of the image carrier, and a developing device 20. A transfer means for transferring the toner image on the surface of the image carrier developed by supplying the toner 3 to the intermediate transfer body and then transferring it to the recording medium; a fixing means for fixing the toner image on the surface of the recording medium to the recording medium; A cleaning unit that removes toner, paper dust, and the like remaining on the surface of the image carrier after the transfer of the toner image to the recording medium, and a cleaning unit that removes excess toner adhered to the intermediate transfer member. .

  When developing an electrostatic charge image, a developing process for developing the electrostatic charge image on the image carrier 15 by reversal development is performed for each color of toner, and a plurality of toners having different colors are formed on the intermediate transfer member. A multicolor toner image is formed by superimposing the images. In this embodiment, an intermediate transfer method using an intermediate transfer member is employed, but a configuration in which a toner image is directly transferred from an image carrier to a recording medium may be used.

  By using the image forming apparatus of this embodiment, it is possible to stably maintain the charge amount of the toner and to output a high-quality image over a long period of time.

〔Example〕
Examples and comparative examples according to the present invention will be described below. The present invention is not limited to this example unless it exceeds the gist.

(Development of developer)
First, a developer (two-component developer) obtained by mixing the toner and the carrier used in this example and the comparative example will be described.

The toner was manufactured as follows. Using polyester as the binder resin (main resin), a pigment, a release agent, and a charge control agent (manufacturer: Nippon Carlit Co., Ltd., product name: LR-147) are melt-kneaded, pulverized and classified through a volume average particle. A negatively charged magenta toner (nonmagnetic magenta toner) having a volume average particle diameter of 6.7 μm was prepared by externally adding two types of hydrophobic treated silica having a diameter of 100 nm and 12 nm. LR-147 has the substance name “Boro bis (1.1-diphenyl-1-oxo-acetyl) potassium salt”, the chemical formula is represented by C ₂₈ H ₂₀ BKO ₆ and is a negative charge control agent.

On the other hand, the carrier was produced as follows. Mn-Mg based ferrite (maker: Dowa iron powder, saturation magnetization 65 emu / g, average particle size φ40 μm) is used as a carrier core material (core material), and conductive particles (conductive agent) (manufacturer: Fuji Dye Co., Ltd., product name) : 9-19-1), charge control agent, coupling agent (aminosilane coupling agent) (manufacturer: Toray Dow Corning Co., Ltd., product name: AY43-059), and aluminum compound catalyst (manufacturer: Shine Chemical Co., Ltd., product name: CAT-AC) is added and dispersed into the silicone resin (Manufacturer: Shin-Etsu Chemical Co., Ltd., product name: KR-350). Coated with 0.5 μm. The coating method is not limited to the dipping method, and other coating methods such as a spray method and a fluidized bed method may of course be used. Thereafter, after a curing process with a curing temperature of 200 ° C. and a curing time of 1 hour, the carrier (magnetic carrier) was produced by sieving with a sieve having an opening of 150 μm. Here, eight types of carriers were produced as shown below. Each density of each particle, the carrier 4.7 g / cm ^3, the toner was 1.0 g / cm ^3.

The following carriers (1) to (4) were prepared using the following charge control agents to be added to the carrier.
(1) P-51 (manufactured by Orient Chemical Co., Ltd.) having a positive charging property opposite to the charging polarity of the toner was used. The carrier to which P-51 is added in the above carrier manufacturing method is referred to as Type-P1.
(2) E-81 (manufactured by Orient Chemical Co., Ltd.) having a negative charging property of the same polarity as the charging polarity of the toner was used. In the carrier manufacturing method, a carrier to which E-81 is added is referred to as Type-N1.
(3) E-84 (manufactured by Orient Chemical Co., Ltd.) having negative chargeability of the same polarity as the toner charge polarity was used. In the carrier manufacturing method, a carrier to which E-84 is added is referred to as Type-N2.
(4) The same LR-147 as the charge control agent added to the toner was used. In the carrier manufacturing method, a carrier to which LR-147 is added is referred to as Type-N3.

Further, the following carriers (5) to (8) were prepared, respectively, to which no charge control agent or coupling agent was added.
(5) A carrier to which no charge control agent is added. The carrier produced by removing the charge control agent in the above carrier production method is referred to as Type-A.
(6) A carrier to which no charge control agent or coupling agent is added. A carrier prepared by removing the charge control agent and the coupling agent in the above-described carrier manufacturing method is referred to as Type-K.
(7) A carrier in which P-51 of (1) above is used as the charge control agent and no coupling agent is added. In the above carrier production method, P-51 is used, and a carrier produced by removing the coupling agent is referred to as Type-P.
(8) A carrier in which LR-147 of (4) above is used as the charge control agent and no coupling agent is added. In the above carrier production method, LR-147 is used, and the carrier produced by removing the coupling agent is Type-N.

Here, the charge control agent P-51 is a substance name “benzyltributylammonium 4-hydroxynaphthalene-1-sulfonate”, and a chemical formula is represented by C ₂₉ H ₄₁ NSO ₄ . Therefore, the constituent element of the charge control agent P-51 is a quaternary ammonium salt, which is a positive charge control agent. E-81 is a substance name “alkyl (c = 8 to 10) salicylate (Cr)”, a chemical formula is represented by C ₃₀ H ₄₀ CrO ₆ , and is a negative charge control agent. Further, E-84 is a substance name “zinc 3,5-di-tert-butylsalicylate”, a chemical formula is represented by C ₃₀ H ₄₀ ZnO ₆ , and is a negative charge control agent.

  The addition amount of the charge control agent in the eight types of carriers (Type-P1, N1, N2, N3, A, K, P, N) described in the above (1) to (8) is the coating layer (carrier coating). In the case of being included in the layer), the amount was 10 parts by weight with respect to 100 parts by weight of the silicone resin. Further, in any carrier, the amount of the silicone resin with respect to 100 parts by weight of the carrier core material (core material) was 1.5 parts by weight. Regarding the additives, the addition amounts of the conductive agent, the coupling agent, and the curing catalyst were 5 parts by weight, 3 parts by weight, and 1 part by weight with respect to 100 parts by weight of the silicone resin, respectively. In the descriptions of (1) to (8), when there is no addition, the additive is coated without being added to the coating solution.

  Table 1 summarizes the carriers produced as described above.

  The developer (two-component developer) obtained by mixing the toner and the carrier is set to 8 wt% in the toner weight mixing ratio (hereinafter referred to as toner concentration) in the total developer weight. The toner and the carrier were put into a cylindrical container, and then mixed and agitated under conditions of 200 rpm and 1 hour on a double-axis driven plastic bottle rotating base.

(Aging test)
A measuring machine and measurement conditions will be described with respect to an aging test performed using eight types (one type of toner × 8 types of carrier) of developer prepared under the above-described conditions.

  An aging test by continuous image printing with a printing rate of 5% using a digital multi-function peripheral was carried out using the eight types of developers produced under the conditions described above. As a measuring machine, a digital full-color composite machine MX-6200N (print speed: <color> 41 ppm, <monochrome> 62 ppm) manufactured by Sharp Corporation was used. In this apparatus, in the developing unit storing the developer (two-component developer) 1, the developer 1 is stirred and charged by the stirring screw 12 as shown in FIG. 2. The developer 1 is transported to the developer carrier 13 having a magnet roller as a magnetic field generating means disposed therein, so that the developer 1 is held on the surface of the developer carrier 13 by a magnetic restraining force. Next, the developer 1 held on the surface of the developer carrier 13 is regulated to a certain layer thickness by the developer regulating member 14, and a magnetic brush is formed at the opposed portion between the developer carrier 13 and the image carrier 15. Then, by applying a bias voltage obtained by superimposing the DC bias voltage on the AC bias voltage to the developer carrier 13, toner is applied to the electrostatic latent image formed on the surface of the image carrier 15 by a charging unit and an exposure unit (not shown). A visible image is formed by adhering only. In this apparatus, the surface of the image carrier 15 is charged to a negative potential by the charging unit, and exposure is performed only on the region where the toner is adhered by the exposure unit.

  Here, the DC bias value of the bias voltage applied to the developer carrier 13 in the aging test is appropriately changed according to the toner charge amount in each developer, so that the image density of the solid image becomes a specified value. It was adjusted. The potential difference between the non-image portion potential on the image carrier 15 and the developer carrier 13 was 200V.

  Further, toner consumption due to visible image formation is detected by the toner density sensor 16 as a change in toner density, which is a toner weight ratio with respect to the developer weight, and the consumed amount has reached a predetermined specified toner density. This is replenished from the toner hopper 17 until the toner density sensor 16 detects this, and the toner density in the developer 1 inside the developing unit 10 is kept substantially constant. In this apparatus, the gap between the developer carrier 13 and the developer regulating member 14 and the gap between the developer carrier 13 and the image carrier 15 in the development region are 0.4 [mm] in this experimental example. ] Was set. Of course, it is not limited to this value.

(Comparison of charge control agents)
FIGS. 3 and 4 show changes in the toner charge amount with respect to the number of printed sheets when an aging test with a printing rate of 5% was performed with the above measuring machine and measurement conditions. FIG. 3 is a transition in the case where a developer containing Type-P, K, A, and N is used among the carriers described above. As can be seen from FIG. 3, in any of Type-P, K, A, and N, it can be seen that the toner charge amount decreases as the number of prints increases, and the charge amount is 15 μC / g in absolute value. It will be reduced to the following (the toner is negatively charged, so it is displayed as minus in the figure, but it will be described in absolute value, the same applies hereinafter). Among these, when a developer containing Type-A carrier to which an aminosilane coupling agent (hereinafter referred to as amine) is used, the initial charge amount is as large as 35 μC / g or more in absolute value, but printing 5 k Within a significant decrease. In the case of using a developer containing each of the three types of types K, P, and N, the charge amount does not exceed 25 μC / g in absolute value. Further, the absolute value is 15 μC / g or less within 5 k of printing.

  Next, FIG. 4 shows a change in toner charge amount when a developer containing Type-P1, N1, N2, and N3 carriers is used. In any two-component developer containing any carrier, the charge amount changes at an absolute value of approximately 15 μC / g or more. In particular, it can be seen that the developer containing Type-N3 has a small decrease in the toner charge amount and is stable for a long time.

  FIG. 5 shows the change in the toner charge amount when using a developer containing Type-P1, N1, N2, and N3 carriers, and the maximum and minimum values of the toner charge amount up to 20,000 printed sheets. It is the figure which showed the difference (charge amount fluctuation amount [μC / g]). As can be seen from FIG. 5, the fluctuation in the charge amount when using a two-component developer containing Type-P1, which is a carrier to which a charge control agent having a positive charge property opposite to the charge polarity of the toner is added, is extremely high. It is remarkable. However, when using a developer containing Type-N1, N2, and N3, each of which is a carrier to which a charge control agent having a negative chargeability of the same polarity as that of the toner is added, the amount of charge variation is Type-P1. Compared to the case of using a developer containing it.

  That is, when the charge control agent having negative chargeability is added to the carrier, the fluctuation of the toner charge amount with respect to the increase in the number of printed sheets can be further reduced. It can be seen that when Type-N3 is used as the charge control agent for the carrier, fluctuations in the toner charge amount are further suppressed and the toner charge amount is stabilized.

  From the above, it can be considered that by adding the negative charge control agent to the carrier, the toner charging characteristics with respect to the increase in the number of printed sheets can be stabilized, and the fluctuation of the image due to the fluctuation of the charge amount can be further reduced.

  Furthermore, in the aging test using the developer containing the carriers of Type-P1, N1, N2, and N3, the image quality of the output images when the number of prints was 0 and 20,000 was visually compared. . As a result, in the developer containing Type-P1, it was confirmed that the image contrast was clearly increased and the image quality variation was remarkable in the image at 20,000 sheets compared to the image at 0 sheets. It was done. On the other hand, in the developer containing Type-N1, N2, and N3, the difference in image contrast between the time of 0 sheets and 20,000 sheets is smaller than that of Type-P1, and the image quality fluctuation is improved. It was.

(Toner charge)
Next, focusing on the toner charge amount, the image density and toner scattering at each charge amount were evaluated. The results are shown in Table 2.

  The charge amounts shown in Table 2 are values at 0 k, 5 k, 10 k, 15 k, and 20 k in the continuous printing process when developers containing Type-P1, N1, N2, and N3 carriers are used. Evaluation was performed as follows. Also here, an aging test with a printing rate of 5% was carried out using the above-described measuring machine and measurement conditions.

  Regarding the image density, the density of the solid image obtained when the DC bias value of the bias voltage applied to the developer bearing member is −400 V is measured by an X-Rite 939 spectrocolorimetric densitometer, and the measured value is 1. It was judged that it was good (◯) if it was .4 or more and was slightly bad (Δ) if it was 1.2 or more and less than 1.4, and it was judged as bad (x) if it was less than 1.2. It should be noted that even when the image density was significantly higher than 1.4, it was determined that the appropriate density was obtained by adjusting the development bias value, and therefore it was determined to be good.

  As for toner scattering, at each measurement point, the toner adhesion on the housing portion at the top of the developing unit is visually evaluated, and if it is comparable to Type-P1, it is good (◯), compared with Type-P1. If it was dirty, it was judged as slightly defective (Δ), and if it was dirty, it was judged as defective (x).

  Table 2 shows that the image density strongly correlates with the toner charge amount. When the toner charge amount exceeds 35 μC / g in absolute value, it is found that the target density is less than 1.4, and the absolute value is less than 35 μC / g. It can be seen that a sufficient image density can be obtained.

  As for toner scattering, it can be seen that when the charge amount of the toner is less than 15 μC / g in absolute value, the scattering becomes remarkable, and when the absolute value exceeds 15 μC / g, the scattering is reduced.

  As described above, in order to obtain the target image density, the toner charge amount needs to be 35 μC / g or less in absolute value, and in order to prevent toner scattering, the charge amount is 15 μC / g or more in absolute value. Need to be. Therefore, in order to achieve both the achievement of the target image density and the suppression of toner scattering, it is effective to set the absolute value of the charge amount of the toner used for development to 15 μC / g or more and 35 μC / g or less. By setting the absolute value of the charge amount of the toner to 15 μC / g or more and 35 μC / g or less, it is possible to prevent toner scattering and image fogging due to low charging, and to prevent insufficient solid image density due to high charging. . As a result, good image quality can be maintained.

(Amount of aminosilane coupling agent added)
Next, the amount of aminosilane coupling agent added to the carrier coating layer was examined. Carriers were produced in which the amount of aminosilane coupling agent added to the Type-N3 carrier of (4) above using LR-147 as the charge control agent was changed as follows. That is, the addition amount of the aminosilane coupling agent contained in the coating layer is 0.01 parts by weight, 0.1 parts by weight, 0.4 parts by weight, 1 part by weight, 5 parts by weight with respect to 100 parts by weight of the silicone resin, respectively. A carrier having a weight part, 7 parts by weight, 10 parts by weight, and 13 parts by weight was prepared in the same manner as the carrier of Type-N3 except for the addition amount of the aminosilane coupling agent. These carriers are referred to as Type-N31, N32, N33, N34, N35, N36, N37, and N38, respectively. Developers using these eight types of carriers, Type-N3 carrier, and Type-N carrier (8) as a comparative example were prepared, and the toner charge amount at 0 k was measured. The results are shown in Table 3.

  It was confirmed that the toner charge amount increased as the amount of aminosilane coupling agent added increased. At this time, the case where the charge amount increased compared with the case where no aminosilane coupling agent was added was determined to be effective (O). In the case where 0.01 part by weight of the aminosilane coupling agent was added, the increase in charge amount was equivalent to that in the case where no aminosilane coupling agent was added, so it was judged that there was no effect (Δ). When 0.1 part by weight was added, a sufficient effect could be confirmed. As the amount added increased, the amount of charge gradually increased. However, when 13 parts by weight was added, the amount of charge suddenly increased, and it was judged to be inappropriate (x). The reason why it was determined to be inappropriate is that if the initial charge amount is excessive, the amount of change until the charge amount settles is large, and the charge amount cannot be stably maintained. As described above, it has been found that the amount of charge can be adjusted by controlling the amount of aminosilane coupling agent added.

(image quality)
Next, the relationship between image quality and toner charge amount is shown. Here again, as described above, an aging test was conducted at a printing rate of 5% using the above measuring machine and measurement conditions. In particular, the graininess is evaluated here and used as an image quality evaluation score (image score). In FIG. 6, a test chart of an image is printed on the developer using the carrier Type-P1, N1, N2, and N3, using the charge amount at the time of printing at 0k and 20k, and the developer at that time, and the granularity thereof is printed. The relationship with the image score which evaluated sex is shown. Note that the smaller the score value, the better the graininess, and the halftone image can be printed without roughness. Graininess was evaluated using an automatic printer image evaluation system (APQS manufactured by Oji Scientific Instruments).

  The image is evaluated by adjusting the developing bias so that the image density is as close to 1.5 as possible. From FIG. 6 showing the relationship between the charge amount and the graininess, it can be seen that the graininess tends to be better when the absolute value of the charge amount is higher. From this, it can be said that it is necessary to improve the image quality that the charge amount of the developer is kept high.

  Table 4 shows the result of visually confirming the score difference and the degree of change in the test chart of 0k and 20k printing. In Table 4, with respect to visual confirmation, those that are known to have deteriorated are indicated as “Δ”, and those that are not known to be changed are indicated as “◯”.

  As can be seen from Table 4, if the charge amount is kept high, the score becomes low, and a tendency to improve the image quality can be confirmed. Further, the smaller the drop in charge amount, the smaller the difference in score change. Therefore, image deterioration due to an increase in the number of printed sheets is difficult to notice, and a stable image can be provided over a long period of time. Thus, in order to maintain high image quality over a long period of time, it is necessary to maintain a high charge amount over a long period of time, and it has been confirmed that this can be achieved by using a negative charge control agent and an aminosilane coupling agent. did it.

(Evaluation of the amount of charge control agent added)
Next, the amount of the charge control agent added to the carrier coating layer was examined. Carriers were prepared in which the amount of charge control agent added to the carrier of Type-N3 (4) above using LR-147 as the charge control agent was changed as follows. That is, the addition amount of the charge control agent (LR-147) contained in the coating layer is 0.3 parts by weight, 1 part by weight, 3 parts by weight, 7 parts by weight, and 12 parts by weight with respect to 100 parts by weight of the silicone resin, respectively. A carrier was prepared in the same manner as the Type-N3 carrier except for the addition amount of the charge control agent. These carriers are referred to as Type-N39, N40, N41, N42, N43, and N44, respectively. Developers were prepared using these six types of carriers, Type-N3 carrier, and Type-A carrier of (5) and Type-N carrier of (8) as comparative examples, respectively. .

  In order to produce a developer using these carriers and confirm the ability to maintain the toner charge amount in continuous printing, an aging test was performed at a printing rate of 5% using the above measuring machine and measurement conditions, as described above, The toner charge amount of was measured. The results are shown in Table 5.

  When the addition amount of the charge control agent is 0.3 parts by weight, the effect of increasing the charge by the amine is hardly confirmed.

  When the charge control agent was increased to 1 part by weight or more, the ability to maintain the charge amount for 20k printing was confirmed.

(Carrier adhesion)
Next, the carrier adhesion was evaluated for the carrier for which the addition amount of the charge control agent was evaluated. Carrier adhesion at the end of 20k was evaluated. Development was performed by applying a voltage of 200 V, and the number of carriers adhered in a fixed area (297 mm × 24 mm) in the non-image area on the image carrier was measured. The results are shown in Table 5 above. Here, the number of carriers attached is 0 to 20 and the adhesion is low and good, “O”, 21 to 40, and a little attached “△”, 41 or more, and the defective one. Evaluated as “x”.

  From the above results, it can be seen that the charge control agent has an effect of deteriorating the carrier adhesion state. This is considered to be caused by the influence on the resin coating due to the addition of the charge control agent, and it is presumed that the coating state is deteriorated because the conditions for resin curing do not match. By setting the addition amount of the charge control agent added to the resin contained in the coating layer of the carrier to 1 part by weight or more, the toner charge amount can be maintained during the continuous printing process, and more preferably 1 to 10 parts by weight is added. Therefore, it can be used as a developer with less carrier adhesion.

(Examination of catalyst)
Next, regarding the deterioration of the coating state by the charge control agent, the carrier adhesion was evaluated in order to examine the type of curing catalyst. The carrier adhesion was measured by the same evaluation method as described above and evaluated according to the same evaluation criteria as described above.

  The carriers examined were Type-Ti, Type-N1, Type-N1, Type-N2, Type-N3, Type-Ti, Type-N- Sn, Type-K. Type-Ti carrier is titanium compound catalyst D-20 (manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter referred to as D-20) instead of an aluminum compound catalyst that is a curing catalyst for Type-N3 carrier. Is a carrier produced in the same manner as Type-N3. The carrier of Type-Sn is prepared in the same manner as Type-N3 except that the tin compound catalyst SRX67 (manufactured by Dow Corning Toray, hereinafter SRX67) is used instead of the aluminum compound catalyst of the carrier of Type-N3. A career. The Type-K carrier is a carrier produced in the same manner as Type-N3, except that the curing catalyst for the Type-N3 carrier is not added.

  Evaluation of carrier adhesion was carried out for developers using these carriers (Type-P1, N1, N2, N3, Sn, Ti, K). The results are shown in Table 6.

  Here, T / D described in Table 6 indicates the concentration of toner in the developer. T / D is expressed by (toner weight) / (toner weight + carrier weight). Usually, it is used at a concentration of about 1 to 20%, and the suitable concentration varies depending on the carrier particle size and toner particle size. When the toner is consumed by the development, the toner is supplied to the developing tank so that the toner density sensor has a constant T / D.

  From Table 6, it can be seen that there is a large difference in carrier adhesion depending on the type of curing catalyst added to the coating layer of the carrier. The carrier adhesion tends to increase because the charge is more likely to flow into the core of the carrier as the coating state is not good. The difference in carrier adhesion due to the change of the curing catalyst is considered to be due to the change in the coating state. The improvement effect by this curing catalyst is presumed to be due to the difference in the curing rate of the coating resin (silicone resin). In order to carry out coating suitably, it is considered that a certain amount of time is required for curing because of the precipitation of the coating resin. Therefore, it can be said that it is effective to use an Al catalyst or a Ti catalyst as the curing catalyst.

(Examination of catalyst addition amount)
Next, the amount of the curing catalyst added to the carrier coating layer was examined. A carrier in which the curing catalyst for the carrier of Type-N3 in (4) and the addition amount thereof were changed as follows was prepared. That is, with respect to 100 parts by weight of the silicone resin as the charge control agent contained in the coating layer, 0.2 parts by weight of Al, 5 parts by weight of Al, 10 parts by weight of Al, and 0 parts by weight of Sn as a curing catalyst. 2 parts by weight, 2 parts by weight of Sn, 5 parts by weight of Sn, 0.2 parts by weight of Ti, 5 parts by weight of Ti and 10 parts by weight of Ti, except for the curing catalyst and its addition amount, Type-N3 A carrier similar to the above carrier was prepared. These carriers are sequentially referred to as Type-Al1, Al3, Al4, Sn1, Sn2, Sn5, Ti1, Ti3, and Ti4. The eight types of carriers, the Type-K carrier to which no curing catalyst is added, the Type-N3 carrier to which 1 part by weight of the curing catalyst Al is added, and the Type to which 1 part by weight of the curing catalyst Sn is added. Developers were prepared using the -Sn carrier and the Type-Ti carrier to which 1 part by weight of the curing catalyst Ti was added. Then, in the same manner as described above, an aging test was performed at a printing rate of 5% using the above measuring machine and measurement conditions, and carrier adhesion at the end of 20k was evaluated. The results are shown in Table 7. Again, the carrier adhesion evaluation method and evaluation criteria were the same as described above.

  It can be seen that in the carrier prepared by adding 5 parts by weight of the curing catalyst, the carrier adhesion for the Sn catalyst is increased compared to 1 part by weight. In addition, with respect to the Al catalyst and the Ti catalyst, the carrier adhesion state was good (not adhered or almost not adhered) compared to 1 part by weight even when the amount was 5 parts by weight. Measurement was also performed with a developer containing a carrier containing 2 parts by weight of Sn catalyst, but no improvement in adhesion was observed. It can be seen that when the addition amount of the curing catalyst is increased to 10 parts by weight, the carrier adhesion state is deteriorated in both the Al catalyst and the Ti catalyst.

  On the other hand, in the developer containing the carrier prepared by reducing the addition amount of the curing catalyst from 1 part by weight to 0.2 part by weight, the carrier adhesion is better for the Al catalyst and the Ti catalyst compared to 1 part by weight. However, in the case of the Sn catalyst, no improvement is seen compared to the one part by weight. As a result, it can be judged that the Sn catalyst is not very suitable, and it is preferable not to use it.

(Carrier and toner size)
The carrier of Type-N3 of (4) above and a carrier having a volume average particle diameter of 35, 55, 70, and 95 μm of the core material in this carrier were prepared, respectively, and the volume average particle diameter was 5.5 μm, 6 .7 μm and 7.2 μm toners were prepared as described above. Then, the image quality of the output image at the time of 20k printing was evaluated for each developer composed of each carrier and each toner. The results are shown in Table 8.

  It can be seen from Table 8 that both the graininess and the fine line uniformity are improved by setting the volume average particle diameter of the carrier core material to 55 μm or less. Further, if the toner has a small particle diameter, the image quality is further improved. It can be seen that the volume average particle diameter of the core material of the carrier is preferably 55 μm or less and the toner volume average particle diameter is preferably 6.7 μm or less in order to achieve both the granularity and the fine line uniformity of the halftone part.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made within the scope of the claims. That is, embodiments and examples obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

  The carrier, developer, developing device, and image forming apparatus of the present invention can be suitably used for electrophotographic copying machines, printers, fax machines, and the like.

FIG. 2 is a schematic diagram illustrating a toner and a carrier included in a developer according to an exemplary embodiment of the present invention. 1 is a schematic diagram illustrating a developing device according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a change in toner charge amount during an aging process of a developer using a carrier of a comparative example. FIG. 6 is a graph showing a change in toner charge amount during an aging process of a developer using carriers of Examples and Comparative Examples. FIG. 6 is a diagram illustrating the amount of change in the toner charge amount during the aging process of the developer using the carriers of Examples and Comparative Examples. FIG. 6 is a diagram illustrating a relationship between a charge amount of a developer using an example and a carrier of a comparative example and an image score.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developer 2 Carrier 2a Carrier core material 2b Coating layer 3 Toner 3a External additive 10 Developing unit 12 Stirring screw 13 Developer carrying member 14 Developer regulating member 15 Image carrier 16 Toner density sensor 17 Toner hopper

Claims (12)

In a carrier having a coating layer on the surface of a core material in which an aminosilane coupling agent is added to a binder resin containing at least one of a silicone resin and a modified resin thereof,
The coating layer is
A curing catalyst that is an organic metal compound that controls the curing rate of the binder resin;
A negative charge control agent which is a salt compound negatively charged with respect to the core material surface or the coating layer;
Conductive particles;
The carrier characterized by containing.   The carrier according to claim 1, wherein the curing catalyst is a titanium compound or an aluminum compound.   The carrier according to claim 1 or 2, wherein the negative charge control agent comprises at least one of a holobis potassium salt, a salicylic acid zinc salt, a salicylic acid chromium salt, and a salicylic acid chromium salt.   The carrier according to any one of claims 1 to 3, wherein 0.1 to 10 parts of the aminosilane coupling agent is added to 100 parts by weight of the binder resin.   The carrier according to any one of claims 1 to 4, wherein the negative charge control agent is added in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.   The carrier according to any one of claims 1 to 5, wherein 0.2 to 5 parts by weight of the curing catalyst is added to 100 parts by weight of the binder resin.   The carrier according to any one of claims 1 to 6, wherein 0.2 parts by weight or more of a tin compound is not contained with respect to 100 parts by weight of the binder resin.   The carrier according to any one of claims 1 to 7, wherein an average particle diameter is 55 µm or less.   A developer comprising: the carrier according to claim 1; and a toner.   The developer according to claim 9, wherein the toner has an average particle size of 6.7 μm or less.   A developing device that performs development using the developer according to claim 9.   An image forming apparatus comprising the developing device according to claim 11.

Images