JP2008233341A - Magnetic material dispersed resin carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier having high adhesion between a coating layer and a carrier core and high durability. <P>SOLUTION: The magnetic material dispersed resin carrier is obtained, by forming a coating layer on a surface of a core particle containing a binder resin and a magnetic material, wherein the carrier has a 50% average particle diameter of 15-45 μm and the coating layer contains a vinyl polymer, by using at least N-isopropylacrylamide and/or N-isopropylmethacrylamide as an essential component and having a peak molecular weight of 2,000-80,000. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic material-dispersed resin carrier used as a developer for developing an electrostatic charge image in electrophotography, electrostatic recording method or the like.

  In the electrophotographic method, the process of developing the electrostatic charge image is a process in which charged toner particles are deposited on the electrostatic charge image using electrostatic interaction of the electrostatic charge image to form a toner image. Of the developers for developing an electrostatic charge image using toner, two-component developers such as magnetic toner obtained by dispersing a magnetic material in resin, non-magnetic toner and magnetic carrier particles are mixed. There is a component developer. In particular, the latter is preferably used in a full-color image forming apparatus such as a full-color copying machine or a full-color printer that requires high image quality.

  Furthermore, in recent years, such an electrophotographic apparatus has been strictly pursued to be smaller, lighter, faster, and more reliable. For example, it is used not only for a general-purpose copying machine for copying an original document, but also for copying a high-definition image such as a digital printer or graphic design as a computer output. Furthermore, it has begun to be used for light printing (print-on-demand applications capable of high-mix low-volume printing from document editing to copying and bookbinding on a personal computer) that require more image stability. Therefore, higher definition and higher image quality are required as image quality, high reliability is required, and performance required for developers has become higher.

  As magnetic carrier particles used in a two-component developer, an iron powder carrier, a ferrite carrier, and a magnetic material dispersion type resin carrier are known. A magnetic material-dispersed carrier capable of adjusting the resistance, magnetization, particle size, and true density of a carrier that affects image quality is suitably used particularly when high image quality is required.

  That is, since the magnetic material dispersion type carrier has a higher resistance than the iron powder carrier and the ferrite carrier, it is possible to reduce the halftone non-uniformity caused by the leakage of the carrier charge to the photosensitive drum. In addition, since the carrier brush does not become stiff due to its relatively small magnetic force, it is excellent in fine line reproducibility, and it is easy to reduce the carrier particle size in order to make the carrier brush denser. Further, since the true density is low, the impact force applied to the toner is reduced, and the toner spent is suppressed and higher durability is obtained.

  However, while the magnetic material dispersion type resin carrier is a very effective technique for improving the image quality of electrophotography, it has a problem that it easily adsorbs moisture as compared with an iron powder or ferrite carrier. Yes.

  In particular, as a technique for easily obtaining a carrier having a relatively sharp particle size distribution, a polymerization type carrier obtained by polymerization in an aqueous medium can be mentioned. It is highly soluble and comes into contact with water during the production process. For this reason, even when compared with a pulverized magnetic carrier or a magnetic dispersion carrier that is polymerized in a hydrophobic solvent, the amount of moisture adsorption tends to increase. As a result, there are problems such as fogging due to a decrease in the charge amount under high temperature and high humidity.

  In order to solve such a problem, a method has been proposed in which a magnetic material used in a magnetic material-dispersed resin carrier is treated with a titanate or silicone coupling agent (see, for example, Patent Document 1). In addition, one or more kinds of resins capable of reacting with N-alkoxyalkylated polyamide and N-alkoxyalkylated polyamide resin containing silicone having at least a silanol group and / or a hydrolyzable group are used as the coating layer forming material. A method has been proposed (see, for example, Patent Document 2). Furthermore, a magnetic material-dispersed resin carrier (see, for example, Patent Document 3) characterized in that the coat resin is a polyimide resin has been proposed.

  However, these methods are methods in which the hydrophilicity of the coating resin forming the coating layer formed on the surface of the carrier core is reduced by any method, and only make up for insufficient charge amount under high temperature and high humidity. there were. That is, this method is not a method for fundamentally controlling the change in the amount of adsorbed moisture on the carrier surface, but the amount of adsorbed moisture changes relative to the ambient humidity. Therefore, if the coating layer is designed by paying attention only to the charging property under high temperature and high humidity, there may be a problem that the charge amount becomes high under low temperature and low humidity.

  In addition, as a method of fundamentally suppressing changes in the amount of moisture absorbed by the carrier, a random copolymer resin that hydrates or dehydrates depending on the ambient temperature, specifically, a carrier having a resin coating layer containing N-substituted acrylamide is proposed. (See Patent Document 4).

  According to the study by the present inventors, when a relatively small magnetic material-dispersed resin carrier having a 50% average particle diameter of 15 to 45 μm is used for the purpose of high image quality, at least N-isopropylacrylamide and / or N-isopropylmethacrylate is used. If the peak molecular weight of the amide-containing copolymer is used without optimization, the strength of the surface coating layer may be weakened, and the film may be easily peeled off, or coarse particles may be easily generated during production. .

  The reason for this is not clear, but it is considered that the curvature of the carrier surface is increased by decreasing the carrier particle size, and the coating is more easily peeled off. In addition, it seems that the affinity / adhesion between the surface of the magnetic material-dispersed resin carrier core and the vinyl polymer containing at least N-isopropylacrylamide and / or N-isopropylmethacrylamide is involved. This consideration will be described in detail later.

  On the other hand, as described above, in recent years, the electrophotographic apparatus has been used for light printing, and not only can a high-quality image be obtained, but the high-quality image can be stably used over a long period of time. The so-called “image quality stability” that can be supplied is also an important issue. In addition, the stability is required to be higher than the “image quality stability” that has been considered in conventional electrophotography.

  The present inventors consider that the above-mentioned “image quality stability” can be divided into the following two “stabilities”. First of all, the stability of image quality before and after printing for a long time, so-called durability stability ". The cause of the loss of durability and stability is related to deterioration of parts such as a developer and a photosensitive drum, as conventionally considered.

  This is the “unstable image quality” observed even in the relatively early stage of durability, with no deterioration of the parts as described above. This is, for example, the following phenomenon.

  Even when the deterioration of parts such as the developer and the photosensitive drum is not observed at the initial stage of relatively durability, for example, when 100 sheets are continuously printed, the 10th sheet, the 20th sheet, the 30th sheet, and the 40th sheet. In some cases, the image quality of the first image cannot be obtained at all.

  This phenomenon is particularly noticeable when the image density is low, such as halftone, at the so-called “rise” after an interval of a certain period, and when several tens to several hundreds of pages are continuously printed. Observed.

  Further, according to the study by the present inventors, it has been found that this phenomenon is a phenomenon observed more prominently when the particle size of the magnetic substance-dispersed carrier is reduced for the purpose of improving the image quality. This seems to be because, in the case of the carrier described above, the image formed is very high in the first place, so that the fluctuation is observed more remarkably.

  The cause of the instability of the image without the deterioration of the parts as described above is unknown in detail, but according to the observations of the present inventors, the development is caused by a subtle change in the temperature and humidity atmosphere during printing. It was also found that the charging characteristics of the agent cause subtle fluctuations.

  For example, a large amount of continuous printing such as tens or hundreds of sheets causes subtle changes in temperature and humidity in the machine, and the subtle changes in temperature and humidity cause subtle fluctuations in charging for the developer, resulting in fluctuations in image quality. I think to give it.

  Furthermore, this is more remarkable when a magnetic material-dispersed carrier that is relatively susceptible to the amount of water and a carrier having a small specific particle size and a large specific surface area is used.

  In the above sense, in order to obtain image quality stability with a view to high-speed, large-volume, high-definition printing such as light printing, in addition to conventional durability stability, the surrounding subtle temperature and humidity A carrier that is unaffected by change is another form of development.

Japanese Patent Laid-Open No. 09-127736 JP 2004-341063 A JP 2002-278166 A JP-A-10-213924

  The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to provide at least N-isopropylacrylamide and / or N-isopropylmethacrylate in a magnetic material-dispersed resin carrier having a relatively small particle diameter. An object of the present invention is to provide a carrier having a vinyl polymer coating layer containing amide as a constituent component, wherein the carrier has high adhesion between the coating layer and the carrier core and has high durability.

As a result of intensive studies to solve the above problems, the inventor of the present invention has a magnetic material-dispersed resin carrier in which a coating layer is formed on the surface of core particles containing at least a binder resin and a magnetic material.
50% average particle size of the carrier is 15 μm to 45 μm, and the coating layer contains at least N-isopropylacrylamide and / or N-isopropylmethacrylamide as an essential component and has a peak molecular weight of 2,000 to 80,000 The present inventors have found that this problem can be solved by a magnetic material-dispersed resin carrier containing a vinyl polymer, and have reached the present invention.

According to the present invention,
1. There is no decrease in charge amount under high temperature and high humidity, or extreme increase or decrease in charge amount under low temperature and low humidity.
2. Excellent halftone uniformity,
3. Excellent reproducibility of the latent image on the photosensitive drum by being able to form a non-rigid, dense magnetic brush,
4). Even if used for a long time, it is hard to cause toner spent,
5. There is no peeling of the coating agent.
6). A magnetic material-dispersed resin carrier capable of stably supplying high-quality images can be provided. Thereby, even when high-definition images are printed at high speed and in large quantities, stable high image quality can be provided.

  Hereinafter, N-isopropylacrylamide and N-isopropylmethacrylamide will be described.

  N-isopropylacrylamide and / or N-isopropylmethacrylamide groups are known as groups having temperature responsiveness. The temperature responsiveness of N-isopropylacrylamide and / or N-isopropylmethacrylamide is a property in which the property showing affinity with water molecules and the property showing non-affinity change abruptly at a certain temperature. For example, a homopolymer of N-isopropylacrylamide exhibits water solubility at temperatures below 32 ° C. and no solubility in water at higher temperatures. This can be confirmed by preparing an aqueous solution of a homopolymer of N-isopropylacrylamide at 32 ° C. or lower, and heating the aqueous solution to precipitate the polymer at around 32 ° C., and the aqueous solution becomes cloudy. This change in affinity / non-affinity for water occurs suddenly in a very narrow temperature range, and this temperature is called a lower critical solution temperature (LCST) (Non-patent Document 1). reference).

M.M. Heskins and J.M. E. Gullet, J. et al. Macromol. sci. Chem. A2 8, 1441 (1968)

  Further, it is known that this LCST varies depending on the kind and amount of the monomer copolymerized with N-isopropylacrylamide, and further the molecular weight. Further, it is known that the copolymerization with a hydrophobic monomer shifts to a lower temperature side and the copolymerization with a hydrophilic monomer shifts to a higher temperature side.

  From the facts described above, the resin comprising N-isopropylacrylamide and / or N-isopropylmethacrylamide as a constituent at a certain lower temperature becomes hydrophilic at a lower temperature and becomes hydrophobic at a higher temperature. It can be said that there is a property to show.

  The present inventors believe that the above-mentioned carrier problem can be solved by utilizing the properties of N-isopropylacrylamide and / or N-isopropylmethacrylamide that are hydrophilic at a low temperature and hydrophobic at a high temperature. It was. That is, by covering the surface of the carrier core with a vinyl polymer containing at least N-isopropylacrylamide and / or N-isopropylmethacrylamide as an essential component (hereinafter referred to as the vinyl polymer of the present invention), the humidity at low temperature is low. In a state, it is hydrophilic and relatively easy to adsorb water. On the contrary, it was considered that a carrier having hydrophobicity and water repelling properties can be prepared under high temperature and high humidity, so that a certain amount of water can be maintained even if the ambient humidity changes.

  Actually, when the vinyl polymer of the present invention is used as a coating layer on the surface of a magnetic material-dispersed carrier, the variation in charge amount between low temperature and low humidity and high temperature and high humidity can be suppressed compared to the case where it is not used. As a result, the present invention was achieved.

  The magnetic material-dispersed resin carrier, which is another feature of the present invention, will be described.

  As described above, the magnetic material dispersion type resin carrier has high resistance, low magnetic force, low density, and high image quality that makes it easy to reduce the particle size compared to conventional carriers using iron powder or ferrite as the core. It is a very effective career when thinking about conversion.

  Furthermore, the particle size of the magnetic material-dispersed resin carrier of the present invention is essentially 15 to 45 μm with a 50% average particle size.

  If it is smaller than 15 μm, carrier adhesion to the non-image area by particles on the fine particle side of the carrier particle size distribution may not be satisfactorily prevented. On the other hand, if it is larger than 45 μm, the surface area of the magnetic brush formed by the carrier becomes small and the image on the photoconductor cannot be faithfully reproduced, resulting in inferior fine line reproducibility. Cannot be achieved.

  Further, according to the study by the present inventors, such a carrier dispersion-type magnetic material-dispersed resin carrier as a carrier core and at least N-isopropylacrylamide and / or N-isopropylmethacrylamide as a coating layer are included. When used in combination with a vinyl polymer, the peak molecular weight of the vinyl polymer is 2000 or more and 80,000 or less (preferably 5000 or more and 40,000 or less) in order to obtain the durability of the carrier. I found out.

  If the peak molecular weight is less than 2000, the entanglement between the molecular chains becomes weak, and the magnetic material-dispersed resin carrier surface cannot be coated well.

  If the peak molecular weight is larger than 80,000, the adhesion between the surface of the magnetic material-dispersed resin carrier core particles and the vinyl polymer is remarkably deteriorated, and the coating layer is peeled off after a long period of durability, thereby causing deterioration of the image. I will wake you up. Further, when forming a coating layer on the surface of the carrier core, coarse particles or the like are likely to be generated and the yield may be lowered.

  The reason for this is not clear, but in addition to the fact that the carrier core has a small particle size and a high curvature, the coating layer is easily peeled off in the first place, and further, the unique property of the vinyl monomer used in the present invention I guess that.

  That is, it is considered that the vinyl polymer that changes hydrophilicity and hydrophobicity depending on the temperature as used in the present invention also changes the affinity with the magnetic material-dispersed resin carrier core, particularly the resin constituting the carrier core, depending on the temperature. It is done. Here, the affinity between the carrier core and the coating layer does not change with temperature when a vinyl monomer that changes hydrophilicity and hydrophobicity with temperature as in the present invention is not used. However, the monomer containing at least N-isopropylacrylamide and / or N-isopropylmethacrylamide used in the present invention changes hydrophilicity / hydrophobicity depending on temperature. For this reason, it seems that the change may also change the adhesiveness of a coating layer and a carrier core. Specifically, for example, even if the adhesiveness is high at the temperature in the coating layer forming step, the adhesiveness may deteriorate due to subsequent cooling treatment or the like.

  In addition, as described above, this is a more serious problem in consideration of the fact that the curvature increases as the carrier particle size decreases, and the coating layer tends to peel off in the first place.

  Furthermore, in order to consider the adhesion between the magnetic material-dispersed resin carrier core and the polymer that changes the hydrophilicity / hydrophobicity depending on the temperature, such as the vinyl polymer of the present invention, only the change in hydrophilicity / hydrophobicity of the vinyl monomer due to the ambient temperature. Instead, the moisture content of the carrier core itself may be affected. Therefore, the balance between the two must be finely adjusted, but this is also not preferable because the design latitude of the vinyl monomer and the carrier core is narrowed. That is, in order to coat the vinyl monomer as in the present invention on the surface of a magnetic material-dispersed resin carrier having a relatively small particle size, the ambient temperature and the moisture content of the carrier core particles are changed. Even if the hydrophilicity / hydrophobicity of is changed, a device that does not change the adhesion between the core and the coating layer is required.

  As described above, the peak molecular weight of the vinyl polymer containing at least N-isopropylacrylamide and / or N-isopropylmethacrylamide is adjusted to 2000 or more and 80,000 or less (preferably 5000 or more and 40,000 or less). It was found that the adhesion between the magnetic material dispersed carrier having a small particle size and the vinyl polymer was improved, and the durability could be improved. As a result, high image quality due to the small particle size magnetic material dispersed resin carrier, environmental stability due to monomers containing N-isopropylacrylamide and / or N-isopropylmethacrylamide, and subtle ambient temperature and humidity. The present invention has succeeded in realizing a carrier that has both stability that is not affected by this, and has reached the present invention.

  Hereinafter, the coating amount of the coating layer of the magnetic material-dispersed resin carrier of the present invention on the carrier core will be described.

  In the present invention, the above-described coating amount is one of means for adjusting the resistance. In order to obtain a desired resistance value, there is no particular limitation, but the amount of the coating resin used for the coating layer is 0.8 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the carrier core particles. It is preferable.

  If the amount exceeds 5.0 parts by mass, a uniform coat cannot be formed at the time of coating, which may affect production stability. The small particle size magnetic material dispersion type carrier tends to have a higher charge amount than the large particle size carrier. However, in the present invention, if the coating amount exceeds 5.0 parts by mass, the charge amount is too high. The toner becomes difficult to be developed. As a result, problems such as poor halftone reproducibility, or too high resistance and poor whiteout may occur.

  On the other hand, when the amount is less than 0.8 part by mass, there may be a problem that the carrier core is not sufficiently coated and the resistance value becomes too low. Further, since the coating amount is small, the effect of the vinyl polymer of the present invention is hardly exhibited, and the environmental stability may be slightly inferior, or the carrier resistance may be lowered and the halftone uniformity may be inferior.

  The vinyl polymer of the present invention is preferably a random copolymer of N-isopropylacrylamide and / or N-isopropylmethacrylamide and any vinyl monomer.

Examples of the vinyl monomer that can be used by copolymerization include one or more monomers selected from styrene, acrylic acid esters, and methacrylic acid esters. For example, an aromatic vinyl monomer [styrene, alkyl styrene (for example, vinyl toluene), α-alkyl styrene (for example, α-methyl styrene, etc.)];
α, β-unsaturated carboxylic acid [monocarboxylic acid such as (meth) acrylic acid, polyvalent carboxylic acid such as maleic acid, fumaric acid, itaconic acid or acid anhydride thereof (for example, maleic anhydride etc.)] ;
Esters of (meth) acrylic acid [(meth) acrylic such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate Acid C1 to C14 alkyl ester, hydroxyalkyl (meth) acrylate (hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc.), glycidyl (meth) acrylate];
(Meth) acrylonitrile;
Carboxylic acid vinyl ester [for example, vinyl acetate, etc.]; Conjugated diene monomer [for example, butadiene, isoprene, etc.];
Olefinic monomers [eg, ethylene, propylene, etc.];
Vinyl halide [eg, vinyl chloride, etc.];
And vinylidene halides [for example, vinylidene chloride and the like].

  As described above, the hydrophilicity / hydrophobicity change of N-isopropylacrylamide and / or N-isopropylmethacrylamide, which is a characteristic of the vinyl polymer of the present invention, changes drastically at a certain temperature.

  In view of keeping the carrier water amount constant with respect to the change in ambient temperature and humidity, which is the object of the present invention, the temperature showing the change in hydrophilicity / hydrophobicity is intermittently higher than a certain temperature. It is preferable to change.

  Here, the temperature at which the hydrophilicity / hydrophobicity of the vinyl polymer changes, that is, the lower critical solution temperature (LCST) is the hydrophilicity of the copolymerizable monomer copolymerized with N-isopropylacrylamide and / or N-isopropylmethacrylamide. It varies slightly depending on the properties, copolymerization ratio, and molecular weight.

  From the above, in the present invention, it is ideal that a plurality of resins having various LCSTs are mixed and used as the coating layer. That is, other vinyl monomer species copolymerized with N-isopropylacrylamide and / or N-isopropylmethacrylamide, a plurality of types of vinyl polymers are mixed from the viewpoint of copolymerization ratio, molecular weight, and the like to form a coating layer. This is a more preferable form in the present invention.

  Among these, since the copolymerization ratio of N-isopropylacrylamide and / or N-isopropylmethacrylamide is high in sensitivity to LCST, it is more preferable to use a mixture of vinyl polymers having different copolymerization ratios of the monomers.

  This is not only a drastic change from low temperature and low humidity to high temperature and high humidity, but also keeps the moisture content of the carrier as constant as possible against subtle fluctuations such as temperature rise in the machine. This is more effective from the viewpoint of stably supplying image quality.

  When the resin forming the coating layer of the magnetic material-dispersed resin carrier of the present invention is 100% by mass, the content ratio (preparation ratio) of N-isopropylacrylamide and / or N-isopropylmethacrylamide is 10% by mass to 60%. Mass% is preferred. More preferably, it is 10 mass% to 45 mass%. If it is less than this, the effect of N-isopropylacrylamide and / or N-isopropylmethacrylamide is difficult to be expressed, and if it is more than this, the charge amount is too high and carrier adhesion may be promoted.

  The ratio (preparation ratio) of N-isopropylacrylamide and / or N-isopropylmethacrylamide in one molecule of the vinyl polymer of the present invention is 3% by mass to 90% by mass, more preferably 5% by mass to 45% by mass. Preferably there is. If it is less than this, the effect of the change in hydrophilicity / hydrophobicity of N-isopropylacrylamide and / or N-isopropylmethacrylamide described above will not be exhibited. On the other hand, if more than this, depending on the monomer to be copolymerized, the hydrophilicity of the random copolymer becomes too high and becomes soluble in water in a certain temperature range, and the amount of water absorption in that temperature range increases abnormally. Become. For this reason, problems such as being easily peeled off from the carrier core and an excessive charge amount with respect to the toner are caused.

  In the present invention, a vinyl polymer not containing N-isopropylacrylamide and / or N-isopropylmethacrylamide for the purpose of adjusting the charge amount, adhesion to the core, durability, and the like, and additions other than vinyl polymers You may mix and use resin. However, in order not to impair the effects of N-isopropylacrylamide and / or N-isopropylmethacrylamide of the present invention, this added resin is preferably 20% by mass or less of the resin forming the coating layer.

  In the present invention, it is more preferable that the vinyl polymer of the present invention has a graft structure in order to improve adhesion to the carrier core. In the present invention, by using a macromonomer as a comonomer, the graft structure can be easily provided, and it is more preferably used. By providing a graft structure by copolymerizing the macromonomer, the adhesion to the core is increased. For example, a coating layer that does not peel from the carrier core even after long-time use can be provided, and stable high image quality can be maintained even during long-time printing.

  Examples of the macromonomer that can be used include a structure having an aromatic vinyl monomer represented by polystyrene as a repeating unit, and a (meth) acrylic ester vinyl monomer represented by polymethyl methacrylate as a repeating unit. Well-known macromonomer such as structure with polymethacrylic acid (meth) acrylic acid vinyl monomer as repeating unit, silicone structure, polyester structure, polyether structure, polyvinyl butyral structure, polyurethane structure Can be used. In our study, polystyrene macromonomer, polymethyl methacrylate macromonomer, silicone macromonomer, polyester in consideration of the adhesion to the core, the production stability of the macromonomer, and the polymerizability in the magnetic material dispersed carrier. More preferably, a macromonomer is used.

  The macromonomer described above is preferably polymerized at a ratio of 0.5 to 50% by mass, more preferably 1 to 30% by mass in the vinyl polymer used in the present invention. If it is used more than this, the reactivity at the time of polymerization of the vinyl polymer may be lowered and the productivity of the coating resin itself may be deteriorated, or the glass transition temperature of the vinyl polymer may be lowered too much and the strength of the coating layer may be decreased. There is.

In the present invention, if necessary, a bifunctional or higher functional vinyl monomer may be used. For example, glycol monomers [ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane Tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, divinylbenzene, methylenebisacrylamide, etc.];
Epoxy group-containing monomers [glycidyl (meth) acrylate, (meth) allyl glycidyl ether, 1-allyloxy-3,4-epoxybutane, 1- (3-butenyloxy) -2,3-epoxypropane, 4-vinyl- 1-cyclohexene-1,2-epoxide, etc.]

  By using these bifunctional or higher functional vinyl monomers, the strength of the coating layer on the surface of the carrier of the present invention can be increased, and for example, an effect that it does not peel off from the core even after prolonged use can be expected. However, when used in large quantities, the solubility in a solvent is remarkably reduced, and in the present invention, it is difficult to coat the surface layer of the magnetic material-dispersed resin carrier. It is preferable to use in the range of 1% or less.

  In the present invention, a chain transfer agent can also be used to adjust the peak molecular weight of the vinyl monomer. Examples of the chain transfer agent include α-methylstyrene dimer, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, n-octyl mercaptan, and the like, preferably α-methylstyrene dimer and n-dodecyl mercaptan.

  The glass transition temperature (Tg) of the vinyl polymer of the present invention is preferably 40 ° C. or higher and 120 ° C. or lower, more preferably 55 ° C. or higher and 100 ° C. or lower.

  If the glass transition temperature is lower than this, the strength of the coating layer becomes weak, and there may be a problem that, for example, the coating layer peels off when stirred with toner for a long time. On the other hand, if it is higher than this, the yield may be lowered during the production of the vinyl polymer of the present invention, or problems may occur when the coating layer is formed on the carrier core particles by the method described later.

  There is no restriction | limiting in particular about the manufacturing method of the vinyl polymer of this invention, Well-known methods, such as block polymerization, solution polymerization, block-suspension polymerization, suspension polymerization, emulsion polymerization, can be used.

As the polymerization initiator of the vinyl polymer of the present invention, an oil-soluble initiator and / or a water-soluble initiator is used. For example, as the oil-soluble initiator, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile) Azo compounds such as 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2-azobis-2-methoxypropionic acid dimethyl ester;
Acetylcyclohexylsulfonyl peroxide, diisopropyl peroxide, decanonyl peroxide, lauroyl peroxide, stearoyl peroxide, propionyl peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t -Peroxide-based initiators such as butyl peroxyisobutyrate, cyclohexanone peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, cumene hydroperoxide .

  Water-soluble initiators include ammonium persulfate, potassium persulfate, 2,2′-azobis (N, N′-dimethyleneisobutyroamidine) hydrochloride, 2,2′-azobis (2-aminodinopropane) hydrochloric acid Salts, sodium azobis (isobutylamidine) hydrochloride, sodium 2,2′-azobisisobutyronitrile sulfonate, ferrous sulfate or hydrogen peroxide.

  If necessary, the coating layer described above may contain 1 to 20 parts by mass of conductive particles with respect to 100 parts by mass of the coating resin to adjust the resistance of the magnetic carrier and to maintain the surface of the magnetic carrier. This is one of the preferred modes for removing charges.

The conductive particles preferably have a specific resistance of 1 × 10 ⁸ Ωcm or less, and more preferably have a specific resistance of 1 × 10 ⁶ Ωcm or less.

  Specifically, the conductive particles are preferably particles containing at least one kind of particles selected from carbon black, magnetite, graphite, titanium oxide, alumina, zinc oxide, and tin oxide. In particular, as the conductive particles, carbon black can be preferably used without impairing irregularities caused by fine particles on the surface of the magnetic carrier having a small particle size.

  The particle size of the conductive particles has a peak value of 10 nm to 60 nm (more preferably 15 to 50 nm) on the basis of the number, so that residual charges on the surface of the magnetic carrier can be removed well and desorption from the magnetic carrier can be achieved. It is preferable for preventing it well.

  In the present invention, the method of coating the surface of the core particles of the magnetic material-dispersed resin carrier containing at least the magnetic material and the resin with the resin is not particularly limited, and may be performed by a known method. For example, a method of mixing the core particles and the resin using a stirrer such as a Henschel mixer or a high speed mixer, a method of impregnating the core particles in a solvent containing the resin, and spraying the resin on the core particles using a spray dryer Methods and the like.

The specific resistance of the magnetic material-dispersed resin carrier of the present invention is preferably 1 × 10 ^{8 to} 1 × 10 ¹⁶ Ω · cm when 5000 V is applied. If it is less than 1 × 10 ⁸ Ω · cm, the developing bias leaks through the carrier, disturbing the electrostatic latent image drawn on the drum, and for example, the halftone uniformity is inferior. appear. Further, when the resistance is low, carrier adhesion is likely to occur, and there is a problem that image defects are caused by scratching the photoreceptor or being directly transferred onto paper.

On the other hand, if the resistance of the carrier exceeds 1 × 10 ¹⁶ Ω · cm, an edge-enhanced image is obtained, and problems such as white spots occur. In addition, it is difficult for the charge on the carrier surface to leak, causing problems such as low image density due to the charge-up phenomenon and fogging and scattering due to the inability to charge the newly supplied toner. To do.

In the present invention, the magnetic characteristics of the carrier are preferably low magnetic force carriers whose magnetization intensity (σ1000) at 79.58 kA / m (1000 Oe) is 29 to 54 Am ² / kg.

When the strength of magnetization exceeds 54 Am ² / kg, it is also related to the carrier particle size, but the magnetic brush formed on the developing sleeve at the developing pole becomes rigid and the density becomes low, so that, for example, the reproducibility of fine lines is inferior. Problems arise.

If it is less than 29 Am ² / kg, the binding force to the magnetic roll is weakened, the carrier adheres easily, and there is a problem that image defects are caused, for example, by scratching the photoreceptor or being directly transferred onto paper. . This phenomenon becomes a more serious problem when the particle size of the carrier is reduced.

In the present invention, the density is preferably 3.0 g / cm ³ or more and 4.0 g / cm ³ or less. If the true density of the carrier is too larger than 4.0 g / cm ³ , the load applied to the developer increases when the developer is made to have a predetermined layer thickness on the sleeve by the developer layer thickness regulating member. For this reason, carrier contamination and toner deterioration are likely to occur during long-term use of the developer, resulting in image quality deterioration of the developed image. In addition, the stirring torque increases. On the other hand, if the true density of the carrier is less than 3.0 g / cm ³ , the fluidity of the developer is lowered, the developer is not circulated, and poor mixing between the replenished toner and the carrier occurs. Easy to prevent high image quality.

  The method for obtaining the magnetic material-dispersed resin carrier core is not particularly limited, and is a method in which the resin is melted and kneaded with the magnetic material and pulverized to a desired particle size; the resin is dissolved in a solvent or melted In which the core is prepared by dispersing at least the magnetic material in a medium such as water and then dispersing in a desired particle size and then removing or cooling the solvent; Examples thereof include a method of preparing a core by polymerizing constituent monomers and a magnetic substance.

  In the present invention, a polymerization method can be suitably used as a method for easily preparing a carrier having a small particle diameter.

  In the present invention, as described above, it is more preferable to use a three-dimensionally crosslinked resin in order to increase the strength of the carrier core. In this sense, in the present invention, it is more preferable to use a thermosetting resin as a binder for the carrier core.

  Specific examples of thermosetting resins that can be used in the present invention include phenol resins, modified phenol resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, or maleic anhydride, terephthalic acid, and polyhydric alcohols. Unsaturated polyester obtained by polycondensation with urea, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guatemine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, Examples thereof include polyimide, polyamideimide resin, polyetherimide resin, polyurethane resin, and the like.

  In the present invention, it is preferable to use a phenol-based resin as a binder resin for the carrier core from the viewpoint of adhesion to the vinyl polymer of the present invention used as the coating layer, dispersibility of the magnetic material, and the like.

  The monomer of the above-mentioned thermosetting resin is illustrated below. Examples include bisphenols and epichlorohydrin as starting materials for epoxy resins; phenols and aldehydes of phenol resins; ureas and aldehydes of urea resins; melamine and aldehydes.

  As described above, the most preferred binder resin in the present invention is a phenolic resin. Examples of the starting material include phenol compounds such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcil, and p-tert-butylphenol, and aldehyde compounds such as formalin, paraformaldehyde, and furfural. A combination of phenol and formalin is particularly preferable.

  When these phenol resins or melamine resins are used, a basic catalyst can be used as a curing catalyst. As the basic catalyst, various catalysts used in the production of ordinary resole resins can be used. Specific examples include ammonia water, amines such as hexamethylenetetramine, diethyltriamine, and polyethyleneimine, and the use of ammonia water is particularly preferable.

  As a monomer for preparing a thermoplastic resin that can be used when a carrier core is prepared from a monomer by a polymerization method, for example, a radical polymerizable monomer can be used. For example, styrene; styrene derivatives such as o-methyl styrene, m-methyl styrene, p-methoxy styrene, p-ethyl styrene, p-tertiary butyl styrene; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate Acrylates such as n-propyl acrylate, isobutyl acrylate, octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; methacrylic acid, methyl methacrylate , Ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, meta Methacrylic acid esters such as phenyl laurate, dimethylaminomethyl methacrylate, diethylaminoethyl methacrylate, benzyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide; methyl vinyl ether, ethyl vinyl ether , Propyl vinyl ether, n-butyl ether, isobutyl ether, β-chloroethyl vinyl ether, phenyl vinyl ether, p-methylphenyl ether, p-chlorophenyl ether, p-bromophenyl ether, p-nitrophenyl vinyl ether, p-methoxyphenyl vinyl ether And vinyl ethers; and diene compounds such as butadiene.

  These monomers can be used alone or as a mixture, and a suitable polymer composition can be selected so that preferable characteristics can be obtained.

  In the present invention, considering the strength of the carrier core particles, when the binder resin of the carrier core particles is a thermosetting resin, it is more preferable that the resin is partially or entirely cross-linked three-dimensionally. preferable. As a result, the dispersed metal compound particles can be firmly bound, so that the strength of the carrier core can be increased and the metal compound is not detached even when a large number of copies are made.

  As the crosslinking agent, it is preferable to use a crosslinking agent having two or more polymerizable double bonds per molecule. Cross-linking agents include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylol Propane triacrylate, trimethylolpropane trimethacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, penta Erythritol tetramethacrylate, glycerol acoxydimethacrylate DOO, N, N-divinyl aniline, divinyl ether, divinyl sulfide, and divinyl sulfone. Two or more types may be appropriately mixed and used. The cross-linking agent can be mixed in advance with the polymerizable mixture, or can be appropriately added during the polymerization as necessary.

  The binder resin (binder resin) that can be used when the carrier core particles used in the present invention are prepared by mixing at least a binder resin and a magnetic material is not particularly limited, and any resin can be used. Can be used.

  Examples of thermoplastic resins include polystyrene; polymer compounds obtained from styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene- Vinyl naphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer Styrene copolymer such as polymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, maleic resin, acrylic resin, methacrylic resin , Vinyl acetate, silicone resin; polyester resin having a monomer selected from aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and diphenol as a structural unit; polyurethane resin; Examples thereof include polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, and petroleum resin.

Examples of the magnetic material that can be used in the present invention include magnetite or ferrite represented by the formula MO · Fe ₂ O ₃ or M · Fe ₂ O ₄ . In the formula, M represents a trivalent, two or monovalent metal ion. As M, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Ba, Pb, Li is mentioned. M can be used alone or in combination. For example, magnetite, Zn—Fe ferrite, Mn—Zn—Fe ferrite, Ni—Zn—Fe ferrite, Mn—Mg—Fe ferrite, Ca—Mn—Fe ferrite, Ca—Mg—Fe ferrite, Li And iron-based oxides such as -Fe-based ferrite and Cu-Zn-Fe-based ferrite.

In addition to the iron-based oxide, nonmagnetic metal oxide particles can be used in combination in order to adjust the magnetic characteristics and electrical resistance as a carrier. For example, A1 ₂ O ₃ , SiO ₂ , CaO, TiO ₂ , V ₂ O ₅ , CrO ₂ , MnO ₂ , α-Fe ₂ O ₃ , CoO, NiO, CuO, ZnO, SrO, Y ₂ O ₃ , ZrO ₂ Etc. When non-magnetic metal oxide particles are used in combination, it is more preferable to use particles having similar densities and shapes in order to increase adhesion with the binder and carrier strength. In the magnetic carrier used in the present invention, hematite is preferably used in combination as the nonmagnetic metal oxide particles.

  When the above metal oxide particles are dispersed in a resin to form a carrier, the number average particle size of the metal oxide particles exhibiting magnetism varies depending on the carrier particle size, but those having a particle size of 0.02 to 2 μm are preferably used. Can do. When two or more kinds of metal oxide particles are dispersed and used, the metal oxide particles exhibiting magnetism can have a number average particle size of 0.02 to 2 μm, and the other metal oxide particles can be used. A number average particle diameter of 0.05 to 5 μm can be used.

  In this case, the particle size ratio rb / ra of the other metal oxide particles (particle size: rb) to the magnetic metal oxide particles (particle size: ra) is more than 1.0 and 5.0 times or less. It is preferable. When it is 1.0 times or less, magnetic metal oxide particles having a low specific resistance are likely to appear on the surface, the carrier resistance cannot be sufficiently increased, and it is difficult to obtain the effect of preventing carrier adhesion in the present invention. Become. On the other hand, if it exceeds 5.0 times, the metal oxide particles cannot be taken into the resin well, the carrier strength is lowered, and the metal oxide particles are liable to be detached. A method for measuring the particle size of the metal oxide particles used in the present invention will be described later.

  In the carrier of the present invention, the total content of the magnetic substance and the metal compound contained in the core particle is preferably 50 to 99% by mass when the carrier core particle is 100% by mass. When the amount of the metal compound is less than 50% by mass, the above-described appropriate magnetic force and appropriate density cannot be obtained. Moreover, when it exceeds 90 mass%, carrier strength will fall and it will become easy to produce problems, such as a crack of the carrier by durability.

  In the present invention, when the magnetic body and other metal oxide are used in combination in the carrier core, the magnetic content is preferably 50 to 93% by mass. If it is less than 50% by mass, the magnetic force as a carrier is reduced, which may cause carrier adhesion. On the other hand, if it exceeds 95% by mass, the magnetic force cannot be kept within the above-mentioned range, and the problem arises that the ears formed by the carrier become stiff and the line reproducibility is poor.

  In the magnetic material-dispersed carrier of the present invention, the metal compound contained in the carrier core is preferably oleophilic in order to prevent the metal compound particles from being detached from the carrier. Regardless of melt kneading, dissolution / melt suspension, or direct polymerization, when forming carrier core particles in which a metal compound subjected to lipophilic treatment is dispersed, the higher the affinity between the binder resin and the magnetic material, the more magnetic The body is difficult to detach.

  Further, when a carrier core is produced by a polymerization method, such as the carrier core production method exemplified in detail above, the polymerization reaction proceeds from the solution in which the monomer system is uniform, and the solution is simultaneously added to the solution. Insolubilized particles are formed. At that time, it is considered that the metal oxide is taken in uniformly and at a high density inside the particles and has an effect of preventing aggregation of the particles and sharpening the particle size distribution.

  Examples of the lipophilic agent for a magnetic substance and other metal oxides that can be used in the present invention are given below.

  For example, it is preferably treated with a lipophilic agent which is an organic compound having one or more functional groups selected from an epoxy group, an amino group and a mercapto group, or a mixture thereof. In particular, an epoxy group is preferably used.

  The magnetic metal oxide particles are treated with 0.1 to 10 parts by mass (more preferably 0.2 to 6 parts by mass) of a lipophilic agent per 100 parts by mass of the magnetic metal oxide particles. It is preferable for enhancing lipophilicity and hydrophobicity.

  Examples of the lipophilic agent having an amino group include γ-aminopropyltrimethoxysilane, γ-aminopropylmethoxydiethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltri Methoxysilane, N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, ethylenediamine, ethylenetriamine, styrene- (meth) acrylic acid dimethylaminoethyl copolymer, Isopropyltri (N-aminoethyl) titanate or the like is used.

  Examples of the lipophilic agent having a mercapto group include mercaptoethanol, mercaptopropionic acid, γ-mercaptopropyltrimethoxysilane, and the like.

  Examples of the lipophilic agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, epichlorohydrin, and glycidol. And styrene- (meth) acrylic acid glycidyl copolymer.

  The carrier of the present invention is particularly effective when a toner containing at least a binder resin and a colorant is used as a developer using a toner having a weight average particle diameter of 3 to 10 μm. When a toner of less than 3 μm is used, problems such as charge-up occur particularly in a low humidity environment, and the effect of using the carrier of this configuration cannot be seen. Also, the toner itself has low handling properties as a powder. When the weight average particle diameter of the toner exceeds 10 μm, problems such as scattering and fogging occur particularly under high temperature and high humidity, and the effect of using the carrier of this configuration cannot be seen. Furthermore, since one toner particle becomes large, it is difficult to obtain a denser image with high resolution. Further, when electrostatic transfer is performed, toner scattering is likely to occur.

  As a method for producing toner particles, a method is known in which a binder resin, a colorant, and other internal additives are melt-kneaded, and the kneaded product is cooled and then pulverized and classified. Besides, the so-called suspension granulation method obtained by melting the constituent components of the toner or dissolving it in a solvent to liquefy it, for example, suspending in a medium such as water and then solidifying, and further suspension polymerization method A method for directly generating toner particles using a monomer, a dispersion polymerization method for directly generating toner particles using a water-based organic solvent that is soluble in monomers and insoluble in a polymer, or has a water-soluble polar polymerization initiator Examples thereof include a method of producing toner particles using an emulsion polymerization method represented by a soap-free polymerization method in which toner particles are directly polymerized under the above.

  The following are mentioned as a monomer of the polyester resin used for this invention.

  As alcohol components, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexane Examples include diol, neopentyl glycol, 2-ethyl 1,3-hexanediol, hydrogenated bisphenol A, bisphenol derivatives represented by the following (formula 1), and diols represented by the following (formula 2).

（式中、Ｒはエチレン又はプロピレン基を示し、ｘ及びｙはそれぞれ１以上の整数であり、かつｘ＋ｙの平均値は２乃至１０である。）

(In the formula, R represents an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10.)

  Acidic components include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid or anhydrides thereof; Succinic acid substituted with an alkyl group or an anhydride thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid and citraconic acid or anhydrides thereof;

  Examples of other toner binder resins include polystyrene; polymer compounds obtained from styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, Styrene-vinyl naphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone Styrene copolymer such as copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, male resin, acrylic resin, Methacrylic tree Polyvinyl acetate, silicone resins; Polyester resins having monomers selected from aliphatic polyhydric alcohols, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aromatic dialcohols and diphenols as structural units; polyurethane resins , Polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, and petroleum resin.

  In the toner of the present invention, the above resins may be mixed and used, or a so-called hybrid resin having two or more skeletons among the above resins may be used as a binder resin for the toner.

Examples of vinyl monomers that can be used when toner particles are produced by a direct polymerization method include:
-Aromatic vinyl monomers [styrene, alkyl styrene (for example, vinyl toluene), α-alkyl styrene (for example, α-methyl styrene, etc.)];
.Alpha.,. Beta.-unsaturated carboxylic acids [monocarboxylic acids such as (meth) acrylic acid, polyvalent carboxylic acids such as maleic acid, fumaric acid and itaconic acid, or acid anhydrides thereof (for example, maleic anhydride, etc.) ];
・ (Meth) acrylic acid esters [methyl (meth) acrylate, methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, etc. Acrylic acid C1 to C14 alkyl ester, hydroxyalkyl (meth) acrylate (hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc.), glycidyl (meth) acrylate];
(Meth) acrylamide or a derivative thereof (for example, N-methylol (meth) acrylamide); maleimide or a derivative thereof (for example, N-methylmaleimide, N-phenylmaleimide, etc.)];
(Meth) acrylonitrile; carboxylic acid vinyl ester [for example, vinyl acetate];
Conjugated diene monomers [for example, butadiene, isoprene, etc.];
-Olefin monomers [for example, ethylene, propylene, etc.];
-Vinyl halide [eg, vinyl chloride, etc.]; Vinylidene halide [eg, vinylidene chloride, etc.]
Etc.

  In the present invention, if necessary, a bifunctional or higher functional vinyl monomer may be used. For example, [ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (Meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate , Pentaerythritol tetra (meth) acrylate, divinylbenzene, methylenebisacrylamide, etc.], epoxy group-containing monomer [glycidyl (meth) acrylate (Meth) allyl glycidyl ether, 1-allyloxy-3,4-epoxybutane, 1- (3-butenyloxy) -2,3-epoxypropane, 4-vinyl-1-cyclohexene-1,2-epoxide, etc.], methylol Group-containing monomer or derivative thereof [N-C1 to C14 alkoxymethyl (meth) acrylamide, such as N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, or N-butyrol (meth) acrylamide) Can do.

  In the present invention, examples of the colorant used in the toner include the following.

  As the yellow colorant, compounds typified by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 150, 168, 180 can be suitably used.

  As the magenta colorant, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254 can be suitably used.

  Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 and the like can be used particularly preferably. These colorants can be used alone or in combination and further in the form of a solid solution.

  Examples of the black colorant include carbon black and those prepared by using the yellow / magenta / cyan colorant described above toned to black.

  In the case of a color toner, the colorant is selected from the viewpoints of hue angle, saturation, brightness, weather resistance, OHP transparency, and dispersibility in the toner. The colorant is added in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the resin.

  Known charge control agents can be used for the toner. In the case of a color toner, in particular, a charge control agent that is colorless or light in color, has a high toner charging speed, and can stably maintain a constant charge amount is preferable. Further, when the direct polymerization method is used in the present invention, a charge control agent having no polymerization inhibition and no solubilized product in an aqueous medium is particularly preferable.

  For example, as a negative charge control agent, salicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid or a metal compound of their derivatives; a polymer compound having a sulfonic acid or carboxylic acid in the side chain; a boron compound; a urea compound; silicon Compound; Carycus arene and the like. As the positive charge control agent, a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, or an imidazole compound is preferably used. The charge control agent is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the resin. However, the addition of a charge control agent to the toner particles is not essential.

  The toner may be classified to control the particle size distribution. As the method, a multi-division classifying device using inertial force is preferably used. By using this apparatus, a toner having a preferable particle size distribution in the present invention can be efficiently produced.

  These toners may use at least silica and / or titanium oxide fine particles as external additives. Providing fluidity to the developer and improving environmental characteristics. In particular, when silica is used, the developer has a longer life.

  Other external additives include metal oxide powder (such as aluminum oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, and zinc oxide), nitride powder (such as silicon nitride), and carbide powder. Body (silicon carbide, etc.), metal salt powder (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salt powder (zinc stearate, calcium stearate, etc.), carbon black, silica powder, polytetrafluoroethylene, Fine powders of materials such as polyvinylidene fluoride, polymethyl methacrylate, polystyrene, and silicone are preferred. The number average particle size of the fine powder is preferably 0.2 μm or less. When the number average particle diameter exceeds 0.2 μm, the fluidity is lowered, and the image quality is lowered during development and transfer. The measuring method is based on the method for measuring the particle size of the metal oxide.

  The amount of the external additive used is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the toner particles. The external additives may be used alone or in combination. The external additive is more preferably hydrophobized.

  The mixing treatment of the toner particles and the external additive can be performed using a mixer such as a Henschel mixer.

  In the present invention, the peak molecular weight of the resin in the coating layer on the carrier surface was measured by a chromatogram by GPC (gel verme chromatography) as follows.

The column was stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) as a solvent was passed through the column at this temperature at a flow rate of 1 ml / min, and the sample concentration was adjusted to 0.05 to 0.6% by mass. Measurement is made by injecting 50 to 200 μl of a THF sample solution of the resin. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of the calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Chemical Co. Manufactured by Toyo Soda Kogyo Co., Ltd. and having molecular weights of 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3 .9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ are used, and it is appropriate to use at least about 10 standard polystyrene samples. An RI (refractive index) detector is used as the detector.

As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns in order to accurately measure a molecular weight region of 10 ^{3 to} 2 × 10 ⁶ . For example, a combination of μ-styragels 500, 10 ³ , 10 ⁴ , and 10 ⁵ manufactured by Waters, a shodex KF-80M manufactured by Showa Denko KK, a combination of KF-801, 803, 804, and 805, KA-802 A combination of 803, 804, 805 or a combination of TSKgel, G1000H, G2000H, G25000H, G3000H, G4000H, G5000H, G6000H, G7000H, GMH manufactured by Tosoh Corporation is preferable.

  As a specific GPC measurement method, a solution obtained by melting 100 mg of the resin to be measured in 20 ml of tetrahydrofuran at room temperature for 24 hours is filtered through a solvent-resistant membrane filter having a pore diameter of 0.2 μm to obtain a sample solution.

  In addition, when calculating | requiring the peak molecular weight of resin contained in the surface coating layer from carrier particle | grains, the pore diameter of the solution which removed the magnetic body from the solution which melt | dissolved 10 g of carriers in 20 ml of THF at room temperature for 24 hours is 0.00. The sample solution can be measured by filtration through a 2 μm solvent-resistant membrane filter.

  The glass transition temperature (Tg) of the resin contained in the coating layer of the carrier of the present invention is measured by the following measuring method.

  It measures according to ASTM D3418-82 using a differential scanning calorimeter (DSC measuring device) and DSC-7 (manufactured by Perkin Elmer).

  The sample to be measured is precisely weighed from 5 to 20 mg, preferably 10 mg. This is put into an aluminum pan, and an empty aluminum pan is used as a reference, and measurement is performed at a temperature rise rate of 10 ° C./min at room temperature and humidity in a measurement temperature range of 30 ° C. to 200 ° C. An endothermic peak of the main peak in the temperature range of 40 ° C. to 100 ° C. is obtained during this temperature raising process.

  At this time, the point of intersection between the base line midpoint before and after the endothermic peak and the differential heat curve is defined as the glass transition temperature (Tg) in the present invention.

  In addition, when calculating | requiring the glass transition temperature of resin contained in the surface coating layer from a carrier, it prepares a sample solution similarly to the case where the peak molecular weight of resin in a coating layer is calculated | required from the carrier mentioned above, and then THF DSC measurement can be performed by the above-described method after removing and drying.

  For the average particle size and particle size distribution of the magnetic carrier, a laser diffraction particle size distribution measuring device HELOS (manufactured by JEOL) is used in combination with a dry dispersion unit RODOS (manufactured by JEOL). In the measurement conditions of a lens focal length of 200 mm, a dispersion pressure of 3.0 bar, and a measurement time of 1 to 2 seconds, a particle size range of 0.5 μm to 350.0 μm is divided into 31 channels as shown in Table 1 below. The 50% particle diameter (median diameter) of the volume distribution is obtained as the average particle diameter, and the volume percentage of particles in each particle diameter range is obtained from the volume-based frequency distribution.

In the present invention, the amount of the coating layer coated on the surface of the magnetic material-dispersed resin carrier was measured as follows. About 10 g of the carrier is weighed and put into a sample bottle, and an appropriate amount of acetone is put in and lightly soaked. Acetone is removed after attaching a strong magnet to the sample bottle and fixing the carrier. After repeating this operation five times, the carrier was dried under reduced pressure at 40 ° C. overnight, the mass was measured, and the amount of the coating layer was calculated from the following formula using the following formula.
Mass part of coating layer = (decreasing mass g) × 100 / {(initial mass g) − (decreasing mass g)}

The resistance of the carrier was measured using a powder insulation resistance measuring instrument manufactured by Vacuum Riko Co., Ltd. Conditions at that time, 23 ° C., put left carrier for 24 hours or more at 60% in the measuring cell of φ20mm (0.283cm ^2), sandwiched between the load electrode of 11.8kPa (120g / cm ^2), the thickness The applied voltage was measured at 2 V and the applied voltage was 500 V (FIG. 1).

The measurement of the magnetic properties was performed using an oscillating magnetic field type magnetic property automatic recording apparatus BHV-35 manufactured by Riken Denshi Co., Ltd. As a condition, an external magnetic field having a magnetic characteristic value of 79.58 kA / m (1 K oersted) was created, and the strength of magnetization at that time was obtained. Prepare the carrier packed in a cylindrical plastic container so that the carrier particles do not move sufficiently, measure the magnetization moment in this state, measure the actual mass when the sample is put in The magnetization strength (Am ² / kg) was determined.

  The true density of the carrier is determined by a dry automatic densimeter AccuPick 1330 (manufactured by Shimadzu Corporation).

  The number average particle size of the metal oxide is 300 particles randomly having a particle size of 0.01 μm or more using a photographic image magnified 5000 to 20000 times with a transmission electron microscope H-800 manufactured by Hitachi, Ltd. Extracted as described above, measured as a metal oxide particle diameter with a horizontal ferret diameter by an image processing analyzer Luzex3 manufactured by Nireco Corporation, and averaged to calculate the number average particle diameter.

  In the present invention, the average particle size and particle size distribution of the toner are measured using a Coulter Counter TA-II type (manufactured by Coulter), but a Coulter Multisizer (manufactured by Coulter) can also be used. As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is subjected to a dispersion process for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of toner particles of 2.00 μm or more are measured using the 100 μm aperture as the aperture by the measuring device. Distribution and number distribution were calculated. Then, a weight-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention (the median value of each channel is a representative value for each channel) was obtained.

<Preparation example of vinyl polymer>
◎ Production example 1 of vinyl polymer
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combine 1 was prepared.
N-isopropylacrylamide 10 parts by mass Styrene 90 parts by mass 2-ethylhexyl acrylate 10 parts by mass Styrene macromer (manufactured by Toa Gosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 mass parts The obtained vinyl polymer 1 had a peak molecular weight of 14,000 and a glass transition temperature of 60 ° C.

◎ Vinyl polymer production examples 2 to 10
Vinyl polymers 2 to 10 were prepared in the same manner as in Production Example 1 of vinyl polymer except that the ratio of each vinyl monomer was changed as shown in Table 2. Table 2 shows the peak molecular weight and glass transition temperature of the obtained vinyl polymer.

◎ Production example 11 of vinyl polymer
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combine 11 was prepared.
-N-isopropylacrylamide 10 parts by mass-Styrene 90 parts by mass-Butyl acrylate 15 parts by mass-Methyl methacrylate macromonomer 5 parts by mass (manufactured by Toa Gosei Co., Ltd .: AA-6: Number average molecular weight 6,000)
The peak molecular weight and glass transition temperature of the obtained vinyl polymer 11 are shown in Table 2.

◎ Vinyl Polymer Production Examples 12 to 14
Vinyl polymers 12 to 14 were prepared in the same manner as in Production Example 11 of vinyl polymer, except that the ratio of each vinyl monomer was changed as shown in Table 2. Table 2 shows the peak molecular weight and glass transition temperature of the obtained vinyl polymer.

◎ Vinyl polymer production example 15
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 15 was prepared.
N-isopropylacrylamide 10 parts by mass Styrene 90 parts by mass Dimethyl silicone macromer 20 parts by mass (manufactured by Toagosei Co., Ltd .: AK-5: number average molecular weight 5,000)
The peak molecular weight and glass transition temperature of the obtained vinyl polymer 15 are shown in Table 2.

◎ Vinyl polymer production examples 16 to 18
Vinyl polymers 16 to 18 were prepared in the same manner as in Production Example 15 of vinyl polymer, except that the ratio of each vinyl monomer was changed as shown in Table 2. Table 2 shows the peak molecular weight and glass transition temperature of the obtained vinyl polymer.

◎ Vinyl polymer production example 19
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 19 was prepared.
N-isopropylacrylamide 10 parts by mass Methyl methacrylate 90 parts by mass Styrene macromer (manufactured by Toa Gosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl polymer 19 are shown in Table 2.

◎ Vinyl polymer production example 20
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 20 was prepared. In addition, the quantity of the initiator used the quantity 1/3 times the manufacture example 1 of a vinyl polymer.
N-isopropylacrylamide 30 parts by mass Styrene 70 parts by mass Styrene macromer (manufactured by Toagosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl monomer 20 are shown in Table 2. The peak molecular weight of the vinyl monomer 20 was adjusted higher than that of the vinyl monomer 1.

◎ Vinyl polymer production example 21
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 21 was prepared. In addition, the amount of the initiator was ½ times that of Production Example 1 of vinyl polymer.
N-isopropylacrylamide 30 parts by mass Styrene 70 parts by mass Styrene macromer (manufactured by Toagosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl monomer 21 are shown in Table 2. The peak molecular weight of the vinyl monomer 21 was adjusted higher than that of the vinyl monomer 1.

◎ Vinyl polymer production example 22
Except for using toluene as a polymerization solvent, 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as an initiator, and further adding 1 part by mass of α-methylstyrene dimer as a chain transfer agent. In the same manner, solution polymerization was carried out at the following monomer charge ratio to prepare vinyl polymer 22. The amount of initiator used was twice that of vinyl polymer production example 1.
N-isopropylacrylamide 30 parts by mass Styrene 70 parts by mass Styrene macromer (manufactured by Toagosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl monomer 22 are shown in Table 2. The peak molecular weight of the vinyl monomer 22 was adjusted to be lower than that of the vinyl monomer 1.

◎ Vinyl Polymer Production Example 23
Using toluene as a polymerization solvent, dimethyl ester of 2,2-azobis-2-methoxypropionic acid (manufactured by Wako Pure Chemical Industries, Ltd .: V601) as an initiator, and further adding 2 parts by mass of α-methylstyrene dimer as a chain transfer agent. In the same manner as above, solution polymerization was carried out at the following monomer charge ratio to prepare vinyl polymer 23. The amount of the initiator was twice as much as that in Production Example 1 of the vinyl polymer, and the polymerization temperature was set 3 times higher.
N-isopropylacrylamide 30 parts by mass Styrene 70 parts by mass Styrene macromer (manufactured by Toagosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl monomer 23 are shown in Table 2. The peak molecular weight of the vinyl monomer 23 was adjusted to be lower than that of the vinyl monomer 1.

◎ Vinyl Polymer Production Examples 24 to 27
Vinyl polymers 24 to 27 were prepared in the same manner as in Production Example 1 of vinyl polymer, except that the ratio of each monomer was changed as shown in Table 2. Table 2 shows the peak molecular weight and glass transition temperature of the obtained vinyl polymer.

◎ Vinyl polymer production example 28
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 28 was prepared.
N-isopropylmethacrylamide 10 parts by mass Styrene 90 parts by mass 2-ethylhexyl acrylate 10 parts by mass Styrene macromer (manufactured by Toa Gosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl polymer 28 are shown in Table 2.

◎ Vinyl polymer production examples 29 to 32
Vinyl monomers 29 to 32 were obtained in the same manner as in Production Example 28 of vinyl polymer, except that the ratio of vinyl monomers was changed as shown in Table 2. Table 2 shows the peak molecular weight and glass transition temperature of the obtained vinyl polymer.

◎ Production example 33 of vinyl polymer
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 33 was prepared.
-Dimethylacrylamide 30 parts by mass-Styrene 70 parts by mass-Styrene macromer (manufactured by Toa Gosei Co., Ltd .: AS-6: Number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl polymer 33 are shown in Table 2.

◎ Vinyl Polymer Production Example 34
Using toluene as the polymerization solvent and 2,2-azobis-2-methoxypropionic acid dimethyl ester (Wako Pure Chemical Industries, Ltd .: V601) as the initiator, solution polymerization was performed at the following monomer charge ratio, and vinyl heavy Combined 34 was prepared.
Styrene 100 parts by mass Styrene macromer (manufactured by Toa Gosei Co., Ltd .: AS-6: number average molecular weight 6,000)
10 parts by mass The peak molecular weight and glass transition temperature of the obtained vinyl polymer 34 are shown in Table 2.

<Method for preparing carrier core particles>
◎ Production example 1 of carrier core particles
(I) Phenol 7.5 parts by mass (ii) Formalin solution 11.25 parts by mass (formaldehyde about 40%, methanol about 10%, the rest is water)
(Iii) Magnetite fine particles oleophilicized with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane 90 parts by mass (iv) Lipophilicizing with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane Hematite fine particles 10 parts by mass The above-mentioned lipophilic treatment of magnetite and hematite was carried out by using 1.0 part by mass of γ-glycidoxypropyltrimethoxysilane with respect to each of 99.0 parts by mass of magnetite and 99.0 parts by mass of hematite. And premixed and stirred at 100 ° C. for 30 minutes in a Henschel mixer.

  The materials (i) to (iv) and 13 parts by mass of water were mixed for 1 hour while maintaining at 40 ° C.

  To this slurry, 2.0 parts by mass of 28% by mass ammonia water as a basic catalyst and 11 parts by mass of water were added, and the temperature was raised to 85 ° C. for 40 minutes while stirring and mixing, followed by reaction for 3 hours. Resin was produced and cured to obtain carrier core particles 1. The 50% diameter of the carrier core particles was 40 μm. Table 3 below shows the carrier core formulation, manufacturing method, 50% diameter, specific gravity, resistance, and magnetic force.

◎ Production example 2 of carrier core particles
In Production Example 1 of carrier core particles, magnetite fine particles treated with lipophilic treatment with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane and lipophilication with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane Carrier core particles 2 were obtained in the same manner except that the ratio of the treated hematite fine particles was 90:10 and was changed to 60:40. The 50% diameter of the carrier core particles was 45 μm.

◎ Production example 3 of carrier core particles
In Production Example 1 of carrier core particles, magnetite fine particles treated with lipophilic treatment with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane and lipophilication with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane Carrier core particles 3 were obtained in the same manner except that the ratio of the treated hematite fine particles was 90:10 and was changed to 93: 7. The 50% diameter of the carrier core particles was 43 μm.

◎ Production example 4 of carrier core particles
-Vinyl polymer adjusted at a ratio of styrene / butyl acrylate / divinylbenzene = 90/10 / 0.5: 100 parts by mass-Magnetite fine particles treated with lipophilicity with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane 90 parts by mass of hematite fine particles lipophilically treated with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane 10 parts by mass The above materials are mixed with a Henschel mixer, and the pentro is connected to a suction pump and suctioned. Melt kneading was performed with a shaft extruder. This melt-kneaded product was roughly crushed with a hammer mill to obtain a 1 mm mesh pass crushed product. Further, after finely pulverizing with a jet mill, classification was performed with a multi-division classifier (elbow jet) to obtain carrier core particles 4. The 50% diameter of the obtained carrier core particles was 45 μm.

◎ Carrier core particle 5
Ferrite particles having a 50% average particle diameter of 50 μm were used as carrier core particles 5.

◎ Carrier core particle 6
Carrier core particles 6 were prepared in the same manner as in the production method of Carrier Core Particle Production Example 1, except that the stirring speed was halved. The obtained carrier core particles 6 had a 50% average particle diameter of 50 μm.

◎ Carrier core particle 7
Carrier core particles 7 were prepared in the same manner except that the stirring speed was doubled in the production method of Production Example 1 of Carrier Core Particles. The obtained carrier core particles 7 had a 50% average particle size of 10 μm.

<Method for preparing coat carrier>
◎ Coat carrier production example 1
19 parts by weight vinyl polymer 2 19 parts by weight vinyl polymer 3 19 parts by weight vinyl polymer 4 19 parts by weight vinyl polymer 5 19 parts by weight vinyl polymer 34 5 parts by weight Toluene 1000 parts by weight And a 10% vinyl polymer toluene solution was prepared. The proportion of N-isopropylacrylamide in this vinyl polymer as a whole was 44%.

Next, the carrier core particle 1 is put into a 100 part by weight coater, and 15 parts by weight of the above 10% vinyl polymer toluene solution is put into the coater while continuously applying a shearing stress. Was coated. In addition, the said process was performed, volatilizing a solvent under 40 degreeC and 500 torr (6.7 * 10 < ⁴ > Pa), dry nitrogen stream. Subsequently, baking was performed at 140 ° C. for 20 minutes.

The coated particles were passed through a 100-mesh sieve to cut coarse particles due to aggregation to obtain a coated carrier 1. The average 50% average particle diameter of the obtained coated carrier 1 was 40 μm, and the coating amount was 1.0 part by mass with respect to 100 parts by mass of the carrier core. The electric resistance when 5000 V was applied was 2 × 10 ¹² Ω · cm.

  Table 4-1 shows the type and ratio of the vinyl polymer used for the coating layer of each coated carrier, the coating amount, and the 50% average particle diameter of the obtained coated carrier and the electrical resistance when 5000 V is applied. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

◎ Coat carrier production example 2
Coated carrier 2 was prepared in the same manner except that the type and ratio of the vinyl monomer used in Production Example 1 of the coated carrier were changed to Table 4-1. The proportion of N-isopropylacrylamide in the entire vinyl polymer was 48% in the charged amount. Table 4-1 shows the coating amount of the obtained coat carrier, the 50% average particle diameter, and the electrical resistance when 5000 V is applied. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

◎ Production example 3 of coat carrier
The same except that the type and ratio of the vinyl monomer used in Production Example 1 of the coated carrier were changed to Table 4-1 and the vinyl polymer toluene solution to be added to 100 parts by mass of the carrier was changed to 10 parts by mass. In this manner, a coat carrier 3 was prepared. The ratio of N-isopropylacrylamide in the whole vinyl polymer was 35% in charging ratio, and the coating amount of the obtained coat carrier, 50% average particle diameter, and electrical resistance when 5000 V was applied are shown in Table 4-1. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

◎ Coating carrier production examples 4 to 6
Coated carriers 4 to 6 were prepared in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coated carrier were changed to Table 4-1. Table 4-1 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in the whole vinyl polymer, the coating amount, the 50% average particle diameter, and the electric resistance when 5000 V is applied. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

◎ Coating carrier production examples 7 to 10
Coated carriers 7 to 10 were prepared in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coated carrier were changed to Table 4-2. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in the whole vinyl polymer, the coating amount, the 50% average particle diameter, and the electric resistance when 5000 V is applied. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

◎ Production examples 11 and 12 of coat carrier
Coat carrier 11 was prepared in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coated carrier were changed to Table 4-2 and the temperature at the time of charging the carrier core particles was changed from 40 ° C to 50 ° C , 12 were prepared. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

  These coat carriers produced aggregates around the coater during production, and the yield was slightly worse than other coat carriers.

◎ Coat carrier production examples 13 and 14
Coat carrier 13 was prepared in the same manner except that the type and ratio of the vinyl monomer used in Production Example 1 of the coated carrier were changed to Table 4-2 and the temperature at the time of charging the carrier core particles was changed from 40 ° C to 30 ° C. 14 were prepared. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coated carrier and the magnetization strength of 1 k Oersted was the same value as the carrier core particles used.

◎ Coat carrier production example 15
Coat carrier 15 was prepared in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coat carrier were changed to Table 4-2. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Coating carrier production examples 16 to 18
Coated carriers 16 to 18 were prepared in the same manner as in Carrier Production Example 1 except that carrier core particles 1 were used, respectively, except that carrier core particles 2, 3, and 4 were used. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Example 19 of coated carrier production
A 10% vinyl polymer toluene solution was prepared in the same manner as in Production Example 1 of the coated carrier. Next, 1 part by mass of carbon black was added to this solution, placed in a pressure-resistant container, 50 parts by mass of 1 mm diameter glass beads were added, and the mixture was dispersed for 30 minutes with a paint shaker. Next, the carrier core particle 1 is put into a 100 part by weight coater, and 10 parts by weight of the above carbon black-dispersed 10% vinyl polymer toluene solution is put into the coater particle surface while applying shear stress continuously. The inventive vinyl monomer was coated. In addition, the said process was performed, volatilizing a solvent under 40 degreeC, 500 torr (6.7 * 104 Pa), and dry nitrogen stream. Subsequently, baking was performed at 140 ° C. for 20 minutes.

  The coated particles were passed through a 100-mesh sieve to cut coarse particles due to aggregation to obtain a coated carrier 19. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Coated carrier production examples 20, 21
In Production Example 1 of the coated carrier, 15 parts by mass of a 10% vinyl polymer toluene solution was added to 100 parts by mass of carrier core particles, whereas the toluene solution was added to 6 parts by mass and 55 parts by mass, respectively. Coat carriers 20 and 21 were prepared in the same manner. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Coat carrier production example 22
Coated carrier 22 was prepared in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coated carrier were changed to Table 4-2. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Coat carrier production example 23
Coated carrier 23 was prepared in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coated carrier were changed to Table 4-2. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Coated carrier production examples 24 and 25
A vinyl polymer containing no N-isopropylacrylamide or N-isopropylmethacrylamide was used in the same manner except that the types and ratios of the vinyl monomers used in Production Example 1 of the coated carrier were changed to Table 4-2. Coat carriers 24 and 25 were prepared. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

◎ Coating carrier production examples 26 to 28
Coated carriers 26 to 28 were prepared in the same manner except that the carrier core particles 1 in the coated carrier production example 1 were changed to carrier core particles 5, 6, and 7, respectively. Table 4-2 shows the ratio of N-isopropylacrylamide or N-isopropylmethacrylamide in these vinyl polymers as a whole, and the electric resistance when 50% average particle diameter and 5000 V are applied. The magnetic force σ1000 at the true density of the coat carrier and the magnetization intensity of 79.58 kA / m (1 k Oersted) was the same value as that of the carrier core particles used.

<Example of toner production>
◎ Toner production example 1
Polyester resin (condensed polymer of propoxylated bisphenol A and fumaric acid, acid value 10.8 mg KOH / g) 100 parts by mass I. Pigment Blue 15: 3 7 parts by mass · Aluminum compound of dialkyl salicylic acid 3 parts by mass · Low molecular weight polypropylene 5 parts by mass The above materials are mixed by a Henschel mixer, and the vent port is connected to a suction pump and sucked, and the biaxial extruder is used. Then, melt kneading was performed. This melt-kneaded product was roughly crushed with a hammer mill to obtain a 1 mm mesh pass crushed product. Furthermore, after finely pulverizing with a jet mill, classification was performed with a multi-division classifier (Elbow Jet) to obtain cyan toner particles.

  To 100 parts by mass of the cyan toner particles, 1.5 parts by mass of hydrophobized titanium oxide fine powder (number average particle diameter of primary particles: 0.02 μm) is mixed by a Henschel mixer to obtain a weight average particle diameter of 6.0 μm. Of cyan toner 1 was obtained.

◎ Toner production example 2
To 710 parts by mass of ion-exchanged water, 500 parts by mass of 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Special Machine Industries). did. To this, 70 parts by mass of a 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

-Styrene 143 mass parts-N-butyl acrylate 35 mass parts-C.I. I. Pigment Blue 15: 3 (coloring agent) 15 parts by mass / dialkyl salicylic acid metal compound (charge control agent) 5 parts by mass / saturated polyester (polar resin) 10 parts by mass / ester wax (melting point 70 ° C.) 50 parts by mass Was heated to 60 ° C. and uniformly dissolved and dispersed at 11000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). In this, 10 parts by mass of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition was put into the aqueous medium and stirred at 11000 rpm for 10 minutes in a TK homomixer at 60 ° C. under N ₂ atmosphere to granulate the polymerizable monomer composition. . Then, it heated up at 80 degreeC, stirring with a paddle stirring blade, and was made to react for 10 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure, and after cooling, hydrochloric acid was added to dissolve calcium phosphate, followed by filtration, washing with water and drying to obtain cyan toner particles.

  To 100 parts by mass of the obtained cyan toner particles, 1.5 parts by mass of hydrophobized silica fine powder (number average particle diameter of primary particles: 0.03 μm) was externally added to give a weight average particle diameter of 5.8 μm. Cyan toner 2 was obtained.

[Examples 1 to 4]
<Initial evaluation>
-Measurement of charge amount The charge amount of each developer was measured by the method described later so that the combination of carrier and toner shown in Table 5 would result in a toner concentration of 6% by mass. The measurement was carried out after being allowed to stand for 24 hours under the following five temperature / humidity conditions and adjusted to the respective temperature / humidity conditions. 1) 10 ° C / 5% RH, 2) 15 ° C / 10% RH, 3) 23.5 ° C / 60% RH, 4) 27.5 ° C / 70% RH, 5) 30.2 ° C / 80% RH . The measurement results are shown in Table 6.

  It was confirmed that the developer of each example had little variation in charge amount even when the temperature and humidity conditions varied. In addition, even when the conditions were finely tuned as described above, the fluctuation was very small because vinyl polymers having various N-isopropylacrylamide group contents were blended in a well-balanced manner. It seems that the change of hydrophobicity occurred intermittently and the water content was kept constant.

Image Evaluation Next, the combinations of carrier and toner shown in Table 5 were mixed with a V-type mixer so that the toner concentration was 6% by mass, and cyan developers were prepared respectively.

  Using these developers, image evaluation was performed using a modified machine of Canon full-color copier CLC-5000. The image evaluation was performed according to the following criteria. This evaluation was performed under three conditions: 1) 15 ° C./10% RH, 2) 23.5 ° C./60% RH, and 3) 30.2 ° C./80% RH. The results are shown in Table 7-1.

  Each developer had good halftone uniformity under normal temperature and humidity conditions, that is, 23.5 ° C./60% RH, in all images. Furthermore, it was confirmed that the image stability was high, there was no white spot and no carrier adhesion, and a high-quality image excellent in line reproducibility was formed. As described above, this is considered to be achieved by the high resistance / low magnetic force, which is a characteristic of the magnetic material-dispersed resin carrier. Further, this good result was maintained without fluctuation even under a low temperature / low humidity of 15 ° C./10% RH and under a high temperature / high humidity of 30.2 ° C./80% RH. This is considered to be because the water adsorption amount is kept constant by N-isopropylacrylamide which is a feature of the present invention.

  The results are shown in Table 7-1.

<Evaluation after printing for a long time>
・ Measurement of charge amount / image evaluation Next, 1) 15 ° C./10% RH, 2) 23.5 ° C./60% RH, 3) 30.2 ° C./80% RH under each environmental condition 60,000 A printing test for a long time up to the sheet was performed. Thereafter, the charge amount under each temperature and humidity condition, halftone uniformity evaluation, and stability evaluation by color difference were performed in the same manner as the initial evaluation described above.

  As a result, in any developer, the variation under each temperature and humidity condition is suppressed even after a long-time printing test, and the effect of the N-isopropyl group-containing monomer of the present invention is Was also kept. In addition, it was found that the uniformity and stability of the halftone can form a uniform image stably as in the initial stage. The results are shown in Table 8-1.

Method for Measuring Charge Amount The method for measuring the triboelectric charge amount of toner in the present invention will be described below. First, a predetermined carrier and toner particles are placed in a plastic bottle with a lid, and shaken with a shaker (YS-LD, manufactured by Yayoi Co., Ltd.) at a speed of 2 reciprocations per second for 1 minute. The developer consisting of is charged. Next, the charge amount is measured by the apparatus for measuring the triboelectric charge amount shown in FIG. The charge amount measuring method using the triboelectric charge measuring device shown in FIG. 2 will be described below. In FIG. 2, about 0.5 to 1.5 g of the developer is placed in a metal measuring container 2 having a 500 mesh screen 3 at the bottom, and a metal lid 4 is formed. The total mass of the measurement container 2 at this time is weighed and is defined as W1 (g). Next, in the suction machine 1 (at least the part in contact with the measurement container 2) is suctioned from the suction port 7 and the air volume control valve 6 is adjusted so that the pressure of the vacuum gauge 5 is 250 mmAq. In this state, the toner is removed by suction for 2 minutes. The potential of the electrometer 9 at this time is set to V (volt). Here, 8 is a capacitor, and the capacity is C (mF). Moreover, the mass of the whole measurement container after suction is weighed and is defined as W2 (g). The triboelectric charge amount (μC / g) of this sample is calculated as follows.
Sample triboelectric charge (μC / g) = C × V / (W1−W2)

◎ Measurement of halftone uniformity Using the modified machine, 100 halftone images of 30H density were continuously printed, and the 100th image was visually observed to evaluate halftone uniformity.
A: A uniform halftone image is printed B: When viewed over light, it can be confirmed that the image is a slightly uneven non-uniform halftone image C: A slightly uneven non-uniform halftone image D: Is a non-uniform halftone image

◎ Measurement of halftone stability Furthermore, images of 20, 40, 60, 80, and 100 images extracted as image samples adjusted in the above halftone uniformity evaluation For the above, it was determined whether or not a halftone image was stably formed by measuring a change in color tone. Specifically, for the 10th, 20th, 40th, 60th, and 100th images adjusted by the above method, the color tone is measured by the method described later, and the color tone of the sample printed on the 10th sheet and each The difference in color tone of the sample, that is, the absolute value of the color difference was calculated and evaluated according to the following criteria.
A: (Color difference 0.0 or more and less than 0.8) Highly stable B: (Color difference 0.8 or more and less than 1.5) High stability C: (Color difference 1.5 or more and less than 2.0) Stability Is slightly inferior D: (color difference of 2.0 or more) Stability is inferior Note that the 30H image is a value in which 256 gradations are displayed in hexadecimal, 00H is solid white (non-image), and FFH is solid black This is a halftone image when (full image) is set.

Measurement of white spots A chart in which halftone horizontal bands (30H width 10 mm) and solid black horizontal bands (FFH width 10 mm) are alternately arranged in the transfer paper conveyance direction is output. The image is read by a scanner and binarized. Taking the luminance distribution (256 gradations) of a certain line in the conveyance direction of the binarized image, drawing a tangent to the luminance of the halftone at that time, and deviating from the tangent at the rear end of the halftone part until it intersects with the solid part luminance The brightness area (area: sum of the brightness numbers) is used as the whiteness degree.
A: 50 or less Almost inconspicuous and very good.
B: 51 to 150 Good.
C: 151 to 300 There are white spots, but it is at a level where there is no practical problem.
D: 301 to 600 White spots are conspicuous, which is a problem.
E: 601 or more Very noticeable.

Measurement of carrier adhesion For carrier adhesion, a solid white image was formed on the photosensitive drum, and the portion on the photosensitive drum between the developing portion and the transfer portion was visually evaluated.
A: Very good B: Good C: Somewhat bad D: Bad

◎ Measurement of fine line reproducibility Canon original images were output by the modified machine, and the reproducibility of fine lines in printout images was evaluated.
A: good reproducibility of fine lines B: slight fluctuations in the width of fine lines are observed C: thin lines are scattered and scattered D: thin lines are broken in some places, and reproducibility is inferior

Method for measuring fog The fog was measured using REFECTOMETER MODELTC-6DS manufactured by Tokyo Denshoku Co., Ltd., and for cyan toner images, an amber filter was used, and the fog was calculated from the following formula. The smaller the value, the less fog.
Fog (reflectance) (%) = reflectance of standard paper (%) − reflectance of non-image part of sample (%)

Evaluation was according to the following criteria.
A: Less than 2% B: 2% or more and less than 4% C: 4% or more and less than 6% D: 6% or more

[Examples 5 and 6]
Developers 5 and 6 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. It was. The obtained results are shown in Tables 6, 7-1, and 8-1, respectively. Both developers had good image quality, and the amount of charge and the variation in image quality between ambient temperature and humidity conditions were small both in the initial stage and after printing for a long time due to the N-isopropyl group.

  In Example 5, the degree of carrier adhesion was slightly worse than in Examples 1 to 4. This is probably because the amount of N-isopropylacrylamide in the resin is as high as 64%, and the charge amount is high. In addition, the variation in ambient temperature and humidity conditions and the image stability were slightly greater in Example 6 than in Examples 1 to 4. This seems to be less effective because the N-isopropylacrylamide content in the resin is as low as 9%. However, both levels were satisfactory.

Example 7
Developer 7 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-1, and 8-1, respectively. This developer also had good image quality, and the amount of charge and the variation in image quality between ambient temperature and humidity conditions were small both in the initial stage and after printing for a long time due to the N-isopropyl group.

  In this developer, the image stability was slightly inferior. This seems to have occurred because the vinyl polymer used in the carrier coating layer used in this example could not cope with subtle temperature and humidity changes such as in-machine temperature rise. However, the degree was not a problem.

Example 8
Developer 8 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-1, and 8-1, respectively. This developer also had good image quality, and the amount of charge and the variation in image quality between ambient temperature and humidity conditions were small both in the initial stage and after printing for a long time due to the N-isopropyl group. However, this developer was slightly inferior to the carrier adhesion as compared with Example 1. This seems to be because the charge amount was high, but it was not problematic in practical use.

Example 9
Developer 10 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-1, and 8-1, respectively.

  In comparison with Example 1, this developer also showed some poor image stability. This is probably because, as described in Example 7, there was one type of vinyl polymer used for the carrier coating layer. These carriers were slightly inferior in line reproducibility as compared with Examples 1 and 7. This is presumably because the molecular weight of the vinyl polymer of the carrier is high, so the particle size becomes coarse during the production of the coated carrier, and the denseness of the carrier brush is slightly weakened.

  In addition, the developer of Example 9 was slightly deteriorated in image evaluation after printing for a long time as compared with Examples 1 and 7, and a decrease in charge amount was observed compared to the initial value. The variation in the charge amount at the time was large. This is presumably because Example 9 had a high peak molecular weight of the vinyl polymer used, so that the strength of the coating layer deteriorated and it was easy to peel off from the carrier core. However, these levels were satisfactory.

Example 10
Developer 10 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-1, and 8-1, respectively.

  Both developers showed some poor image stability as compared to Example 1. This is probably because, as described in Example 7, there was one type of vinyl polymer used for the carrier coating layer.

  Also, in these image evaluations after long-time printing, the degree of deterioration is slightly worse than in Examples 1 and 7, and a decrease in charge amount is observed compared to the initial value, and the charge amount under each environment is The fluctuation was large. This is presumably because Example 10 had a low peak molecular weight of the vinyl polymer used, so that the strength of the film deteriorated and it was easy to peel off from the carrier core. However, these levels were not problematic for practical use.

[Examples 11 and 12]
Developers 11 and 12 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. It was. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively.

  Both developers showed some poor image stability as compared to Example 1. This is probably because, as described in Example 7, there was one type of vinyl polymer used for the carrier coating layer. These carriers were slightly inferior in line reproducibility as compared with Examples 1 and 7. This is probably because the glass transition temperature of the vinyl polymer of the carrier is high, so that the particle size becomes coarse during the production of the coated carrier, and the denseness of the carrier brush is slightly weakened.

  Also, in the image evaluation after printing for a long time, the degree of deterioration is slightly worse than in Examples 1 and 7, and a decrease in the charge amount is recognized compared to the initial value, and the change in the charge amount in each environment. It was getting bigger. This seems to be because in Examples 11 and 12, since the vinyl polymer used had a high glass transition temperature, the film became brittle and easily peeled off from the carrier core. However, these levels were satisfactory.

[Examples 13 and 14]
Developers 13 and 14 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. It was. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively.

  Both developers showed some poor image stability as compared to Example 1. This is probably because, as described in Example 7, there was one type of vinyl polymer used for the carrier coating layer.

  Also, in these image evaluations after long-time printing, the degree of deterioration is slightly worse than in Examples 1 and 7, and a decrease in charge amount is observed compared to the initial value, and the charge amount under each environment is The fluctuation was large. This is because the glass transition temperature of the vinyl polymer used in Examples 13 and 14 is low, and the vinyl monomer becomes soft under high temperature conditions, so the strength of the film deteriorates and the film tends to peel off from the carrier core. It seems that it was because of However, these levels were not problematic for practical use.

Example 15
Developer 16 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively. This developer also had good image quality, and the amount of charge and the variation in image quality between ambient temperature and humidity conditions were small both in the initial stage and after printing for a long time due to the N-isopropyl group.

[Examples 16 and 17]
Using the carrier and toner shown in Table 5, developers 16 and 17 were prepared in the same manner as in Example 1, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. It was. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively. In both developers, there was no fluctuation in image stability, charge amount and image quality with respect to ambient temperature and humidity.

  However, it was confirmed that the carrier adhesion in Example 16 was slightly higher than that in Example 1. This was thought to be due to the low magnetic force of the developer carrier.

  In Example 17, compared with Example 1, the halftone uniformity and fine line reproducibility were slightly inferior. This was thought to be because the magnetic brush became stiff due to the strong magnetic force of the carrier used in this developer. However, neither carrier had any practical problems.

Example 18
Developer 18 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively. This developer also had good image quality, and the amount of charge and the variation in image quality between ambient temperature and humidity conditions were small both in the initial stage and after printing for a long time due to the N-isopropyl group. However, a tendency that the image quality fluctuated after printing for a long time was recognized. This seems to be because the core particles of the carrier are particles of the pulverization method, so that the adhesion with the vinyl polymer is poor.

Example 19
Using the carrier and toner shown in Table 5, a developer 19 was prepared in the same manner as in Example 1, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively. This developer also had good image quality, and there was little variation in charge amount and image quality between ambient temperature and humidity conditions both in the initial stage and after printing for a long time due to the N-isopropyl group.

[Examples 20 and 21]
Developers 20 and 21 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 5, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. It was. The obtained results are shown in Tables 6, 7-2 and 8-2, respectively. This developer also had good image quality, and the amount of charge and the variation in image quality between ambient temperature and humidity conditions were small both in the initial stage and after printing for a long time due to the N-isopropyl group.

  However, in Example 20, the halftone uniformity is slightly inferior to that in Example 1, and this is because the coating amount of the vinyl monomer is small, so that sufficient coating cannot be performed and the resistance of the carrier is low. So I thought. In addition, a decrease in the stability of the image was slightly deteriorated even after the initial and after durability. This may be because the coating layer of the present invention has little effect due to the small coating amount.

  Further, in Example 21, white spots were slightly inferior to Example 1. This seems to be due to the increased resistance of the carrier due to the large amount of vinyl monomer coating.

[Comparative Examples 1 and 2]
Comparative developers 1 and 2 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 9, and the same <Initial evaluation> and <Evaluation after long-time printing> as in Example 1 were performed. went. The obtained results are shown in Tables 10, 11, and 12, respectively.

  The developers of Comparative Examples 1 and 2 showed no problem in terms of image quality, and exhibited good initial characteristics with little variation in charge amount with respect to the surrounding temperature and humidity conditions. However, in the evaluation after printing for a long time, it was confirmed that the phenomenon was significantly deteriorated as compared with Example 1 and Example 7. As described above, since the peak molecular weight of the vinyl polymer containing at least N-isopropylacrylamide and / or N-isopropylmethacrylamide is high or low, the adhesion of the coating layer to the carrier core is low. This is probably because the coating layer was peeled off from the carrier and the resistance was lowered, or the effect of the coating layer of the present invention was reduced.

[Comparative Examples 3 and 4]
Comparative developers 3 and 4 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 9, and the same <Initial evaluation> and <Evaluation after long-time printing> as in Example 1 were performed. went. The obtained results are shown in Tables 10.11 and 12, respectively. Although there was no problem in image quality with the developer of Comparative Example 1, the variation in charge amount with respect to the surrounding temperature and humidity conditions was significantly inferior to that of Example 7 using a single resin. This seems to be because the coating layer of this carrier does not contain N-isopropylacrylamide and / or N-isopropylmethacrylamide. Further, although the carrier of Comparative Example 3 was coated in the developing device, it was not developed on the photosensitive drum. This seemed to be because the charge amount of this developer was too low.

[Comparative Example 5]
Comparative developer 5 was prepared in the same manner as in Example 1 using the carrier and toner shown in Table 9, and <Initial evaluation> and <Evaluation after long-time printing> were performed as in Example 1. . The obtained results are shown in Tables 10.11 and 12, respectively. Although this developer has little variation in charge amount and image quality with respect to ambient temperature and humidity, the results are inferior in line reproducibility and halftone uniformity as compared with Example 1. This seems to be because the carrier of this developer has ferrite as the core, so that the 50% diameter is relatively large, the magnetic force is relatively high, and the resistance is relatively low.

[Comparative Examples 6 and 7]
Comparative developers 6 and 7 were prepared in the same manner as in Example 1 using the carrier and toner shown in Table 9. <Initial evaluation> and <Evaluation after long-time printing> were the same as in Example 1. went. The obtained results are shown in Tables 10.11 and 12, respectively. Comparative Example 6 had significantly more carrier adhesion than Example 1 and exceeded the practical range. This seems to be because, in Comparative Example 6, the 50% average particle size of the carrier is too small.

  Comparative Example 7 was inferior in line reproducibility compared to Example 1. This seems to be because the carrier brush became sparse because the 50% average particle size was too large.

The schematic sectional drawing of the apparatus which measures the specific resistance of the magnetic carrier metal oxide of this invention. FIG. 3 is an explanatory diagram of an apparatus used for measuring the triboelectric charge amount of toner.

Explanation of symbols

21 Lower electrode 22 Upper electrode 23 Insulator 24 Ammeter 25 Voltmeter 26 Constant voltage device 27 Carrier 28 Guide ring d Sample thickness E Resistance measurement cell 1 Suction machine (at least the part in contact with the measurement container 2 is an insulator)
2 Metal measuring container 3 500 mesh screen 4 Metal lid 5 Vacuum gauge 6 Air flow control valve 7 Suction port 8 Condenser 9 Electrometer

Claims (8)

In a magnetic material-dispersed resin carrier in which a coating layer is formed on the surface of core particles containing at least a binder resin and a magnetic material,
The carrier has a 50% average particle diameter of 15 μm to 45 μm, and the coating layer contains at least N-isopropylacrylamide and / or N-isopropylmethacrylamide as an essential component, and has a peak molecular weight of 2,000 to 80,000 A magnetic material-dispersed resin carrier comprising: a vinyl polymer.   2. The magnetic substance-dispersed resin carrier according to claim 1, wherein the vinyl polymer has a peak molecular weight of 5,000 or more and 40,000 or less.   The magnetic material-dispersed resin carrier according to claim 1, wherein the binder resin forming the carrier core particles is thermosetting.   The magnetic material-dispersed resin carrier according to claim 3, wherein the thermosetting resin is a phenol resin.   The vinyl polymer is a random copolymer of at least one monomer selected from styrene, acrylic acid ester, and methacrylic acid ester, and N-isopropylacrylamide and / or N-isopropylmethacrylamide, The magnetic substance-dispersed resin carrier according to any one of claims 1 to 4, wherein the polymer has a glass transition temperature of 40 ° C to 120 ° C.   The magnetic material-dispersed resin carrier according to any one of claims 1 to 5, wherein the coating layer is 0.8 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the carrier core particles. .   The content ratio of N-isopropylacrylamide and / or N-isopropylmethacrylamide when the resin constituting the coating layer is 100% by mass is 10% by mass to 60% by mass. 7. The magnetic material-dispersed resin carrier according to any one of 6 above.   8. The vinyl polymer constituting the coating layer is a mixture of at least two kinds of resins having different content ratios of N-isopropylacrylamide and / or N-isopropylmethacrylamide. The magnetic material-dispersed resin carrier according to any one of the above.

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