JP4760522B2 - Electrophotographic developer - Google Patents

Description

  The present invention relates to an electrophotographic developer used for developing an electrostatic latent image in electrophotography, electrostatic recording method and the like.

  In electrophotography, an electrostatic latent image formed on the surface of a latent image carrier (photoconductor) is developed with a toner containing a colorant, and the obtained toner image is transferred to the surface of a recording material, which is then heated. An image can be obtained by fixing with a roll or the like. On the other hand, the latent image carrier is cleaned again to form an electrostatic latent image.

  A dry developer (electrophotographic developer) used for such electrophotography is a one-component developer that uses a toner in which a colorant or the like is mixed with a binder resin, and a carrier mixed with the toner. The two-component developer is roughly classified. Furthermore, the one-component developer is conveyed by a developer carrier by magnetic force using magnetic powder, and is conveyed by the developer carrier by a developing roll or the like without using magnetic powder and the magnetic one-component developer to be developed, It can be classified as a non-magnetic one-component developer to be developed.

In recent years, color machines have also become widespread, and in particular, two-component developers are used for these medium-speed and high-speed machines. In particular, with regard to full color image quality, high image quality close to high-quality printing and silver salt photography is desired.
Digitization processing is indispensable as means for achieving high image quality, and the effect of digitization related to such image quality is that complex image processing can be performed at high speed. This makes it possible to control characters and photographic images separately, and the reproducibility of both qualities is greatly improved compared to analog technology.

On the other hand, it is necessary to faithfully create a latent image produced by an optical system as an image output, and as a toner, activities aiming at faithful reproduction have been accelerated as the particle diameter is increasingly reduced.
However, since the toner surface area per unit weight is increased by reducing the particle size of the toner, the charge amount is higher than that of the large particle size toner. This means that in the development / transfer, the development / transfer amount decreases with a smaller diameter in the same electric field. In particular, development / transfer is difficult to perform because of high charge at low temperature and low humidity.

Conversely, when the particle size is reduced, the surface area is increased and the hygroscopicity is increased as compared with the toner having a large particle size. In the frictional charging, the adsorbed water causes a deterioration of the charge, so that the charge is likely to decrease under high humidity. When the charging is reduced, problems such as fogging due to the reverse polarity toner and cloud of the low charging toner occur.
In other words, a charging design for a small particle size toner requires a toner design that does not have a high charge amount under low temperature and low humidity, does not have a low charge amount under high temperature and high humidity, and has a good environmental difference (small environmental fluctuation). .

  Conventionally, fine particles have been externally added to the toner surface for the purposes of charge control, powder characteristics improvement, and transferability impartment, which are basic characteristics of the toner. In particular, the addition of inorganic fine particles is an effective means that has been used to improve toner fluidity, increase the charge level, and improve transfer characteristics. In order to improve the environmental difference, the following are studied as external additive designs.

For example, a method has been proposed in which external additive particles are selected by paying attention to the polarity with respect to the toner or carrier, and the chargeability of the toner including environmental characteristics is improved (see, for example, Patent Documents 1 to 6). However, the combined use of an external additive that is charged with a polarity opposite to that of the carrier and positive polarity can improve the control of the charge level and the environmental difference of the toner as a whole by adjusting the amount and type. When the agent is charged with the carrier, it may generate a reverse polarity charge on the carrier surface, which widens the charge distribution of the toner and deteriorates the responsiveness when adding the toner, eventually causing problems such as fogging and clouding. There was a thing.

  Further, using an external additive having a polarity opposite to that of the toner lowers the chargeability of the toner, and simply acts as a toner having a low charge amount. Further, since the external additive adheres to the toner, frictional charging hardly occurs between the toner and the external additive. In other words, it can be used for the purpose of lowering the charge, but for the purpose of increasing the charge level at high temperature and high humidity or improving the environmental difference, if the charge with the carrier is not adjusted, Problems such as fog and cloud cannot be solved.

  In addition, attempts have been made to use silica and alumina having different charge levels as external additives (see, for example, Patent Document 7). Here, silica particles have a strong negative charging property of −50 to −150 μC / g, and alumina has a weak negative charging property of +10 to −30 μC / g. If you add it after adjusting. Certainly, adjusting the amount of charge by mixing a highly charged external additive with a low charged external additive is a technique that has been widely used in the past. This is not limited to the external additive core type, but is synonymous with the adjustment based on the type of the surface treatment agent, the amount of the treatment agent, and the like. However, this method simply lowers the charge, and the improvement effect is not sufficient. Furthermore, even when an external additive with a bad environmental difference and an external additive with a good environmental difference were used in combination, the external additive with the poor environmental difference was dominant and never showed a good environmental difference between the external additives. .

As described above, the addition of various external additive particles has been studied in order to improve the difference in the toner charging environment. However, it has been established that these can be compatible with each other including maintainability in the actual machine. There is no current situation.
JP-A-61-250658 Japanese Patent Publication No.7-131788 JP-A-4-142558 JP-A-8-227178 JP-A-9-160282 Japanese Patent Laid-Open No. 10-20540 JP 2003-107793 A

An object of the present invention is to solve the conventional problems and achieve the following objects.
That is, an object of the present invention is to provide an electrophotographic developer capable of improving the environmental stability of the toner charge amount and stably obtaining a high-quality image.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by optimizing the relationship between the particle size of external additive particles externally added to the toner surface and their characteristics, The present invention has been completed. That is, the present invention

<1> A two-component developer comprising a toner and a carrier,
The toner comprises toner base particles, external additive particles A and external additive particles B having different particle diameters surface-treated with different surface treatment agents,
The average primary particle diameter of the external additive particles A is 80 nm or more, the average primary particle diameter of the external additive particles B is 60 nm or less, and the charging polarity of each of the external additive particles A and B by the electrode plate method is Q1. Electrophotography satisfying the relationship of the following formulas (1) and (2) when the molecular weights of the surface treatment agents used for _A and Q1 _B and the external additive particles A and B are X _A and X _B , respectively. Developer.
(−) Q1 _A <0 <Q1 _B (+) Formula (1)
_{X A} <X B ··· formula (2)

<2> When the triboelectric charge amounts (μC / g) of the external additive particle A and external additive particle B by the blow-off method with the carrier are Q2 _A and Q2 _B , respectively, these are represented by the following formula (3): The electrophotographic developer according to <1>, which satisfies the relationship.
Q2 _B <Q2 _A <0 Formula (3)

<3> The electrophotographic developer according to <1> or <2>, wherein the core material of the external additive particle A is silica.

<4> The electrophotographic developer according to any one of <1> to <3>, wherein the core material of the external additive particle B is zinc oxide and / or alumina.

<5> The electrophotographic developer according to any one of <1> to <4>, wherein the toner is produced by a wet granulation method.

<6> The electrostatic image developing toner according to <5>, wherein the wet granulation method is an emulsion aggregation method.

<7> The electrophotographic developer according to any one of <1> to <6>, wherein the external additive particle A has a spherical shape and a true specific gravity of 2.5 or less.

  According to the present invention, it is possible to provide an electrophotographic developer capable of improving the environmental stability of the toner charge amount and stably obtaining a high-quality image.

Hereinafter, the present invention will be described in detail.
The electrophotographic developer of the present invention is a two-component developer composed of a toner and a carrier, and the toner is surface-treated with a different surface treatment agent from toner base particles and external additive particles A having different particle diameters. And external additive particles B, the average primary particle diameter of the external additive particles A is 80 nm or more, the average primary particle diameter of the external additive particles B is 60 nm or less, When the charge polarities of the additive particles A and B are Q1 _A and Q1 _B and the molecular weights of the surface treatment agents used for the external additive particles A and B are X _A and X _B , respectively, 1) and the relationship of Formula (2) are satisfied.
Q1 _A <0 <Q1 _B ... Formula (1)
_{X A} <X B ··· formula (2)

  The design of the external additive is very important in controlling the chargeability of the toner. In particular, in order to improve the environmental fluctuation of the charge amount, a plurality of types of external additives are used to combine the respective functions. Means are considered effective. However, as described above, in the examination so far, the environmental fluctuation has not been improved sufficiently, and there are other problems derived from it, so that a sufficient effect has not been obtained.

  In order to solve the above problems, the present inventors have examined a charging mechanism, a charge contributing factor, and the like with respect to a plurality of external additives that greatly affect the chargeability of the toner, particularly focusing on charging between the external additive particles. As a result, when external additive particles having different particle sizes are used, the large particle size external additive particles, unlike the small particle size external additive particles, have a weak adhesion to the toner, and the toner base when sliding with the carrier is small. It was found to be moving on the particle surface.

  As a result of intensive studies by the present inventors, it depends on the toner particle size, resin type, surface property, adhesion method, etc., but if the particle size is 80 nm or more, the adhesion property becomes weak and the toner surface moves. It was confirmed that it was easy. In the present invention, an external additive having a particle size of 80 nm or more, which is present on the toner surface but is capable of moving the toner surface during frictional stirring with a carrier, is sometimes referred to as a large particle size external additive.

  Further confirmation shows that when both the small particle size external additive particles and the large particle size external additive particles are used in combination, the small particle size / large particle size external additive particles are formed by the movement of the large particle size external additive particles. It turns out that they are mutually charged. This is a phenomenon that has not occurred between the small-sized external additive particles. In addition, as a result of the combination evaluation of various external additives, it has been found that the charge between the external additive particles tends to be derived from the charge train.

In the present invention, by utilizing the above phenomenon, the design guideline is different from the above-described external additive design utilizing the charge difference with the carrier, and without lowering the charge under high temperature and high humidity, in a low temperature and low humidity environment. It was possible to suppress the increase in charge.
That is, (1) At least two external additive particles having a small particle size and a large particle size are used, both are negatively charged with respect to the carrier, and the external additive particles are smaller than the large particle size external additive particles. (2) When the external additive particles are triboelectrically charged with each other, the large particle size external additive particles are smaller with the small particle size external additive. Make negative chargeability stronger than agent particles. In other words, the negative charge of external addition of large particle size is stronger than the small particle size for carriers, and the negative charge of external addition of small particle size is stronger than external particles between external additives. As a result, it was found that the increase in charge in a low temperature and low humidity environment can be suppressed and the charge amount in a high temperature and high humidity environment can be raised.

  In order to realize the opposite charging design, the present inventors have intensively studied and paid attention to the charging between the carrier and the external additive and the charging between the external additives. We found the factors that influence them. That is, the surface treatment agent of the external additive mainly contributes to the charging between the carrier and the external additive particles, and the core material (external additive core) contributes largely to the frictional charging between the external additive particles. I understood. Therefore, by selecting materials using these, the charge design between the carrier and the external additive particles and the charge design between the external additive particles shown in (1) and (2) can be performed. Thus, it is possible to provide an electrophotographic developer that suppresses environmental fluctuations in the charge amount and is excellent in the spread of charge distribution and the responsiveness when adding toner.

  More specifically, the triboelectric charging characteristics between the external additive particles can be estimated by the electrode plate method as described later, and the charge between the carrier and the external additive particles is directly mixed and measured by the blow-off method. Therefore, satisfying the conditions specified in the present invention satisfies the charging design conditions shown in the above (1) and (2).

The average primary particle size of the large particle size external additive particles (external additive particles A) in the present invention needs to be 80 nm or more. If the thickness is less than 80 nm, adhesion to the toner becomes strong, the toner surface cannot be moved, and mutual charging with the small particle size external additive (external additive particle B) does not occur. The average primary particle size of the external additive particles A is preferably 90 nm or more, and more preferably 100 nm or more.
On the other hand, the average primary particle size of the small particle size external additive particles (external additive particles B) in the present invention needs to be 60 nm or less. If it exceeds 60 nm, large particle size external additive (external additive particle A)
It becomes difficult to charge with each other. Further, the external additive particles B also easily move on the toner surface. Since the external additive that is easy to move moves from the convex portion of the toner to the concave portion, the external additive does not exist in the convex portion that is a charging site. Without the convex external additive, the charge is the same as that of the non-externally added toner, and the effect of charging by the external additive cannot be obtained. Moreover, if there is no external additive in the convex part, the fluidity is also deteriorated. The small particle size external additive is preferably of a size that does not move on the toner surface. This size is 60 nm or less. The average primary particle size of the external additive particles B is preferably 50 nm or less, and more preferably 40 nm or less.

  The average primary particle diameter (volume average particle diameter) can also be measured for each powder by a laser diffraction / scattering particle size distribution measuring device as will be described later. Further, the particle diameters dispersed on the surface of the toner base particles observed by an electron microscope or the like can be measured one by one and expressed as an average value thereof. In this method, it is desirable to measure 500 or more pieces.

The electrophotographic developer of the present invention (hereinafter sometimes simply referred to as “developer”) is a two-component developer composed of a toner and a carrier. Each will be described below.
<Toner>
The toner in the present invention includes toner base particles, external additive particles A and external additive particles B having different particle diameters that have been surface-treated with different surface treatment agents, and other components as necessary. It has. These will be described later.

(Toner mother particles)
First, toner base particles in the present invention will be described.
The toner base particles in the present invention contain a binder resin and a colorant, and contain other components as necessary.

  Binder resins include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Homopolymers and copolymers of vinyl ethers such as methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone;

  In particular, typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride. A copolymer, polyethylene, polypropylene, etc. are mentioned. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax, and the like can also be mentioned. Among these, styrene-alkyl acrylate copolymers and styrene-alkyl methacrylate copolymers are particularly preferable.

From the viewpoint of low-temperature fixability, a crystalline resin is also preferably used.
Specific examples of crystalline resins include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid and other long-chain alkyl dicarboxylic acids, butanediol, pentanediol, and hexanediol. , Polyester resins using long-chain alkyl and alkenyl diols such as heptanediol, octanediol, nonanediol, decanediol, batyl alcohol; amyl (meth) acrylate, hexyl (meth) acrylate, (meth) acrylic acid Heptyl, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, tridecyl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate , (Meth) acrylic acid steari , Vinyl resins using long-chain alkyls such as oleyl (meth) acrylate and behenyl (meth) acrylate, and (meth) acrylic esters of alkenyl; and the like. From the viewpoint of adjusting the melting point within a preferable range, a polyester resin-based crystalline resin is preferable.

  The colorant for the toner base particles is not particularly limited and may be either a dye or a pigment, but a pigment is preferred from the viewpoint of light resistance and water resistance.

  Preferred pigments include carbon black, aniline black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, Quinacridone, benzidine yellow, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 185, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. A known pigment such as CI Pigment Blue 15: 3 can be used.

Magnetic powder can also be used as a colorant. As the magnetic powder, known magnetic materials such as ferromagnetic metals such as cobalt, iron and nickel, alloys and oxides of metals such as cobalt, iron, nickel, aluminum, lead, magnesium, zinc and manganese can be used.
The above colorants can be used alone or in combination of two or more. The content of the colorant in the toner of the present invention is preferably 0.1 to 40 parts by mass, and more preferably 1 to 30 parts by mass with respect to 100 parts by mass of the total toner raw material. In addition, by appropriately selecting the type of the colorant, each color toner such as yellow toner, magenta toner, cyan toner, and black toner can be obtained.

  A release agent or a charge control agent may be added to the toner base particles as necessary. Generally as a mold release agent, it uses for the purpose of improving mold release property. Specific examples of the release agent include low molecular weight polyolefins such as polyethylene, polypropylene, and polybutene; silicones having a softening point by heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, and stearic acid amide Plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, etc. Mineral / petroleum waxes; ester waxes such as fatty acid esters, montanic acid esters, and carboxylic acid esters. In this invention, these mold release agents may be used individually by 1 type, and may use 2 or more types together.

  The content of the release agent is preferably 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass with respect to 100 parts by mass of all raw materials of the toner base particles. If the amount is less than 1 part by mass, the effect of adding a release agent may not be obtained. If the amount exceeds 20 parts by mass, adverse effects on the chargeability tend to appear, and the toner is easily destroyed inside the developing machine, so that the mold release is performed. In addition to the effect that the agent or toner resin becomes spent on the carrier and the charge is likely to decrease, for example, when color toner is used, the surface of the image at the time of fixing becomes insufficient. This is not preferable because the release agent may easily stay in the image and the transparency may deteriorate.

  The melting point of the release agent is preferably 50 to 120 ° C, more preferably 60 to 100 ° C. If the melting point of the release agent is less than 60 ° C., the change temperature of the release agent may be too low, and the blocking resistance may be inferior, or the developability may deteriorate when the temperature in the copying machine increases. When the melting point exceeds 120 ° C., although there is an effect on hot offset, the toner may not be heated to the melting point of the release agent practically and may not substantially exhibit the action of the release agent. .

  The charge control agent is generally used for the purpose of improving the chargeability. Examples of the charge control agent include metal-containing azo compounds such as chromium azo dyes, iron azo dyes, and aluminum azo dyes; salicylic acid metal complexes, nigrosine and quaternary ammonium salts.

The toner base particles in the present invention are not particularly limited by the production method, and can be obtained by a known method. Specifically, for example, particles obtained by a kneading and pulverizing method of kneading, pulverizing, and classifying a binder resin and a colorant and, if necessary, a release agent and a charge control agent are mechanically mixed. A method of changing the shape by impact force or thermal energy, emulsion polymerization of a polymerizable monomer of a binder resin, a formed dispersion, a colorant, and a release agent and a charge control agent as necessary Emulsion polymerization agglomeration method to obtain toner base particles by mixing and agglomerating and heat-fusing the dispersion, a polymerizable monomer to obtain a binder resin, a colorant, if necessary, a release agent, charging Suspension polymerization in which a solution such as a control agent is suspended in an aqueous solvent for polymerization, a binder resin and a colorant, and if necessary, a solution such as a release agent and a charge control agent is suspended in an aqueous solvent. Examples thereof include a dissolution suspension method for granulation.
Further, a manufacturing method may be performed in which the toner base particles obtained by the above method are used as a core, and further, aggregated particles are attached and heat-fused to have a core-shell structure. From the viewpoint of the shape controllability of the toner base particles, it is preferably a wet granulation method of any one of the emulsion polymerization aggregation method, suspension polymerization method, and dissolution suspension method. More preferably.

  The toner base particles produced as described above preferably have a small particle size for the purpose of improving the image quality. However, if the diameter is too small, development is difficult with the conventional system from the viewpoint of charging and fluidity. That is, the volume average particle size is preferably in the range of 2 to 8 μm, and more preferably in the range of 4 to 7 μm.

  If the volume average particle size exceeds 8 μm, the image quality such as reproducibility of fine lines and halftone graininess deteriorates, and it is difficult to obtain good image quality when outputting photographic image quality. On the other hand, if it is less than 2 μm, the powder characteristics and the charging characteristics are extremely deteriorated, and it may be difficult to output at high speed by a conventional machine.

  A known method may be used as the particle size measurement method. A Coulter counter TA-II type (manufactured by Beckman-Coulter) is used as the measuring apparatus, and ISOTON-II (manufactured by Beckman-Coulter) is used as the electrolyte. As a measuring method, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant. This is added to 100 to 150 ml of the electrolytic solution. The electrolytic solution in which the sample is suspended is dispersed for about 1 minute with an ultrasonic disperser, and the particle size distribution of the particles is measured using the Coulter counter TA-II with an aperture diameter of 50 μm to determine the volume average distribution. Find the number average distribution. The number of particles to be measured is preferably 50,000. The volume average particle diameter is obtained as 50% of the particle diameter from the small diameter side in the volume average distribution thus determined.

  When the crystalline resin described above is used, the melting point of the binder resin is preferably 50 to 180 ° C, and more preferably 60 to 150 ° C. When the melting point is lower than 50 ° C., toner storage stability and image storage stability after fixing may become a problem. On the other hand, when the temperature is higher than 180 ° C., the power consumption of the machine is increased, which may not be economical.

  In the case of a crystalline resin, a plurality of melting peaks may be shown. In the present invention, the maximum peak is regarded as the melting point. For measurement of the glass transition temperature (Tg) and melting point (Tm) of the toner base particles, DSC-7 (differential thermal analyzer) manufactured by Perkin Elmer can be used. The temperature correction of the detection part of the apparatus uses the melting points of indium and zinc, and the correction of heat quantity uses the heat of fusion of indium. As the sample, an aluminum pan was used, and an empty pan was set as a control, and measurement was performed at a heating rate of 10 ° C./min.

(External additive particles)
Next, the external additive particles used in the present invention will be described.
In the toner base particles of the present invention, external additive particles A and external additive particles B having different particle diameters, which are surface-treated with different surface treatment agents, are dispersed on the surface thereof. Here, as described above, the average primary particle size of the external additive particles A is 80 nm or more, and the average primary particle size of the external additive particles B is 60 nm or less.

In the present invention, first, when the charging polarities of the external additive particles A and B by the electrode plate method are Q1 _A and Q1 _B , they must satisfy the relationship of the formula (1).
(−) Q1 _A <0 <Q1 _B (+) Formula (1)

  The electrode plate method in the present invention is a measurement method capable of obtaining an index of triboelectric charging characteristics between external additive particles as will be described later, and the above formula (1) is an external additive particle A and an external additive. When the particles B are frictionally charged, the large additive particle A is negatively charged (the small additive particle B is positively charged by mutual friction). . As a result, for example, the charge amount (negative) of the toner in a low-temperature and low-humidity environment increases as a whole, but the negative chargeability of the large particle size particles is suppressed by the simultaneous charging of the external additive particles, thereby increasing the charge amount. Can be reduced.

In the present invention, the external additive particles A and B are further subjected to surface treatment. When the molecular weights of these surface treatment agents are X _A and X _B , they are represented by the following formula (2). It is necessary to satisfy the relationship.
_{X A} <X B ··· formula (2)

The larger the molecular weight of the surface treatment agent, the higher the hydrophobizing ability. Therefore, by treating each of the external additive particles A and B with the surface treatment agent having the relationship of the formula (2), the carrier and the external additive particles are treated. In addition, the negative charge amount of the external additive particles B having a small particle size can be further increased. Thereby, for example, even under high temperature and high humidity, the charge amount with the carrier of the external additive particles B occupying a large part of the surface of the toner base particles can be improved, whereby the total charge amount can be raised.
Therefore, by satisfying the above two relations, an increase in charge amount in a low temperature and low humidity environment can be suppressed and a charge amount in a high temperature and high humidity environment can be increased, so that fluctuations in the charge amount environment can be reduced.

Here, the molecular weight X of the surface treatment agent is defined as follows.
(1) When the surface treating agent is a coupling agent that reacts with the external additive core When the coupling agent is represented by x-M-R (x is an unbonded functional group, M is Si or Ti, R Is a reactive group bonded to the external additive core), and the molecular weight of x is X. For example, hexamethyldisilazane has a molecular weight of 161 as the treating agent. However, in the above definition, since the molecular weight of the functional group x not containing Si or Ti and not bonded is the molecular weight of the treating agent, (CH ₃ ) ₃ = 45 is the molecular weight X.
(2) When the surface treatment agent is silicone oil, the average molecular weight of the silicone oil is X.
(3) When a plurality of surface treatment agents are used as the surface treatment agent, each component ratio in the mixed surface treatment agent is indicated by a mole fraction, and (each mole fraction × molecular weight) for each surface treatment agent. The sum is defined as an average molecular weight X of the surface treatment agent.

The triboelectric chargeability between the external additive particles and the carrier can be evaluated by the charge amount Q2 measured by the blow-off method in the same manner as the usual toner charge amount measurement method.
In the present invention, the external additive particles A and the external additive particles B satisfying the relationship of the formula (2) have the triboelectric charge amounts (μC / g) by the blow-off method with the carrier as Q2 _A and Q2 _B , respectively. It is preferable that these satisfy the relationship of the following formula (3).
Q2 _B <Q2 _A <0 Formula (3)

  As described above, the blow-off method is a measurement method that can directly determine the triboelectric charging characteristics between the carrier and the external additive particles, and the above formula (3) indicates that the external additive particles A and B are each rubbed with the carrier. When charged, the external additive particles B having a smaller particle diameter have a higher negative chargeability (a toner having the external additive particles dispersed on the surface has a higher negative chargeability). As a result, even if there is a decrease in charge amount due to frictional charging between the external additive particles in a high temperature and high humidity environment as described above, the charge amount (negative) of the toner can be maintained high as a whole.

Regarding the charge amount Q2 of the two external additive particles A and B having different particle sizes in the present invention with the carrier by the blow-off method, Q2 _A of the large particle size external additive particles A is in the range of 5 to 200 μC / g, small The Q2 _B of the particle size external additive particle B is preferably in the range of 10 to 1000 μC / g.
The measurement method using the blow-off method will be described later.

  The core material of the external additive particles in the present invention is not particularly limited, but inorganic fine particles are preferably used. Examples of the inorganic fine particles include all inorganic fine particles usually used as an external additive on the toner surface, such as silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, and cerium oxide. Resin fine particles can also be preferably used, and examples thereof include polymethyl methacrylate resin, styrene resin, styrene-methyl methacrylate resin, phenol resin, melamine resin, and polyester resin.

As described above, frictional charging between the external additive particles is influenced by the core material (external additive core). Therefore, in the present invention, silica, titania, resin fine particles, and the like are used as the core material of the external additive particles A having a large particle size so that the external additive particles satisfy the relationship of the above formula (1). Preferably, zinc oxide, alumina, magnesium oxide or the like is used as the core material of the external additive particle B having a small particle size.
In particular, a combination using silica as the core material of the external additive particle A and zinc oxide and / or alumina as the core material of the external additive particle B is most preferable.

In the present invention, the external additive particles A and B are surface-treated with different surface treatment agents.
Although there is no restriction | limiting in particular as a hydrophobization processing agent, For example, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, silane coupling agents are preferred.

  As the silane coupling agent, for example, any one of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. Here, the following can be illustrated as a hydrophobic treatment agent used for surface treatment.

  That is, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxy Silane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N-bis (trimethylsilyl) Urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxy Lan, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercapto Representative examples include propyltrimethoxysilane and γ-chloropropyltrimethoxysilane.

In the present invention, the external additive particles A and B having different particle sizes need to satisfy the relationship of the above formula (2), but in the present invention, as the surface treatment agent selected from the above viewpoint, For the external additive particles A, hexamethyldisilazane, dimethyldichlorosilane, ethylmethoxysilane or the like is preferably used. For the external additive particle B, it is preferable to use butylsilane, hexylsilane, octylsilane, decylsilane, C18 silane, silicone oil, reactive silicone oil, or the like.
In particular, a combination using hexamethyldisilazane for the external additive particles A and decylsilane for the external additive particles B is most preferable.

The treatment amount of the surface treatment agent is preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the external additive core. The processing amount may not be the same as that of the external additive particles A and B, and it is preferable to increase the processing amount of the external additive particles B. In this case, it is more preferable that the processing amount for the external additive particles A is in the range of 0.1 to 5 parts by mass, and the processing amount for the external additive particles B is in the range of 5 to 20 parts by mass.
The amount of treatment refers to the amount of the hydrophobizing agent used for the external additive core during the hydrophobizing treatment, not the amount of the hydrophobizing agent actually treated on the external additive particles.

Examples of methods for treating various surface treatment agents on the external additive core include a method of treating in an aqueous medium, a method of treating in an organic solvent, and a method of treating in a gas phase.
In the method of treatment in the aqueous medium, the external additive core particles to be treated such as inorganic fine particles are dispersed so as to become primary particles, and for example, the treatment is performed while hydrolyzing the silane compound. Moreover, in the case of silicone oil, it processes using an emulsion. In this treatment method, since the external additive core particles to be treated can be produced, the aqueous paste can be dispersed in the aqueous medium without passing through the drying step, so that it is easily dispersed in the primary particles. When processing with several kinds of processing agents, they may be added simultaneously or sequentially.

  The gas phase method is a method of treating the external additive core particles to be treated by dropping or spraying the processing agent while sufficiently stirring mechanically or in an air stream (this is referred to as “gas phase method 1”). ) At this time, the reactor is preferably purged with nitrogen or heated to 50 to 350 ° C. When the viscosity of the treatment agent is high, it may be diluted with a solvent such as alcohol, ketone, or hydrocarbon. Further, ammonia, amine, alcohol, and water may be added to increase the reactivity during the treatment. This treatment method is a preferable method because the reaction is carried out firmly, so that high hydrophobicity and uniformity can be easily obtained.

  As another method of the gas phase method, hydrophobization is performed immediately after the core particles of the external additive to be processed are formed in the carrier gas by the gas phase method (chlorine method, low temperature oxidation method, etc.). There is a method (hereinafter referred to as “gas phase method 2”) in which the processing agent is diluted with a solvent in some cases, and vaporized and atomized to be processed into particles to be processed in the gas phase. In this method, in addition to the advantages of the vapor phase method 1, the treatment is performed before the particles to be treated are united. When processing with several kinds of processing agents, they may be added simultaneously or sequentially.

  The method of treating in the organic solvent is a method in which the external additive core particles to be treated are dispersed in an organic solvent, treated with a hydrophobizing agent, filtered or distilled off, and then dried. In order to reduce agglomerates, it is also preferable to perform a pulverization treatment thereafter with a pin mill or a jet mill. The drying process may be stationary or flowing, and is preferably heated to about 50 to 350 ° C., and may be decompressed. As the organic solvent, hydrocarbon organic solvents such as toluene, xylene, hexane and isopar are preferably used. As a dispersion treatment method, a stirrer, a shaker, a pulverizer, a mixer, and a disperser are used, and among them, a disperser using a medium such as a ball or a bead made of ceramics, agate, alumina, zirconia, or the like is preferable. Used. For example, there are a sand mill, a grain mill, a basket mill, a ball mill, a sand grinder, a visco mill, a paint shaker, an attritor, a dyno mill, and a pearl mill.

  Particularly preferred treatment methods include a method in which the external additive core particles to be treated are dispersed in an organic solvent to form a paste, and then the treatment agent is added to the disperser, and the paste in an organic solvent containing the treatment agent is dispersed. There are a method of applying a treating agent and particles to be treated to an organic solvent, a method of applying a paste to a disperser, and a method of adding a treating agent while applying the paste to the disperser. A method of treating in an organic solvent is a preferred method because the particles to be treated can be treated in a dispersed state, coalescence hardly occurs after the treatment, and aggregates hardly occur. When treating with several types of hydrophobizing agents, they may be added simultaneously with the preparation of the slurry, may be added sequentially, or may be added when applied to a disperser. Alternatively, when it is applied to the disperser several times, each time it is applied to the disperser, it may be added in advance when it is added and mixed in the slurry or applied to the disperser.

The above four methods can be used, and the processing agents may be processed simultaneously, or may be processed in several steps in random order. In the case of processing in a plurality of times, any combination of processing methods may be used.
In any process, after the treatment, it is preferable to perform a crushing treatment using a pulverizer such as a pin mill, a hammer mill or a jet mill in order to reduce aggregates.

  When the external additive core is titanium oxide fine particles or alumina fine particles, in order to prevent coalescence at the time of processing, to suppress the generation of aggregates, to achieve uniform high hydrophobicity and uniform releasability, Either treat the silane compound type treating agent and the silicone oil type treating agent simultaneously (add both at the same time as the treating agent), or treat with the silane compound type treating agent and then treat with the silicone oil type treating agent. Is also possible.

  Further, when the external additive core is silica, the gas phase method 1 and the gas phase method 2 are preferable. When titanium oxide is used, the aqueous method, the solvent method, and the gas phase method 2 are preferable. Solvent method, gas phase method 1 and gas phase method 2 are preferably used.

  Regarding the external additive particles obtained as described above, in the present invention, it is preferable that the external additive particles A having a large particle size have a spherical shape and a true specific gravity of 2.5 or less. In the present invention, it is assumed that the external additive particles having a large particle size move on the surface of the toner base particles, and that the external additive particles are frictionally charged with each other. The shape of the external additive particles A is not spherical or has a true specific gravity. If the value exceeds 2.5, it may be impossible to move the surface of the toner base particles.

The definition of the above “spherical shape” can be discussed in terms of Wadell's sphericity, which will be described later, and this sphericity is 0.6 or more, preferably 0.8 or more.
The true specific gravity is more preferably 2.3 or less, and further preferably 2.0 or less.

  In addition to the two external additive particles, the toner in the present invention includes inorganic fine particles, a charge control agent, a lubricant, an abrasive, and a cleaning agent for the purpose of improving charging characteristics, powder characteristics, transfer characteristics, and cleaning characteristics. A known additive such as an auxiliary agent may be externally added. Known inorganic fine particles can be used. Examples thereof include silica, alumina, titania, metatitanic acid, zinc oxide, zirconia, magnesia, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide, and strontium titanate. Examples of the resin fine particles include spherical particles such as PMMA, nylon, melamine, benzoguanamine, and fluorine, and amorphous powders such as vinylidene chloride and fatty acid metal orchards. In addition, the surface treatment of the small-diameter inorganic fine particles is effective because the dispersibility becomes high and the effect of increasing the powder fluidity increases.

  The toner for developing an electrostatic latent image of the present invention can be obtained by mixing toner base particles and external additive particles, but there is no particular limitation on the mixing (blending) method, and it is performed by a known method. Can do. For example, a dry method using a V-type blender, a Henschel mixer, a Redige mixer, a Q-type mixer, a hybridization system or the like may be used, or when toner base particles are prepared by a wet manufacturing method, they may be blended as they are by a wet method. Good. Moreover, in order to remove the coarse powder generated by blending, it is preferable to sieve after the blending step. The electrostatic latent image developing toner of the present invention may be mixed with a known cleaning auxiliary material, if necessary.

  The addition amount of the two external additive particles A and B is preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the toner base particles. If the amount is less than 0.1 parts by mass, the function of each particle may not be exhibited. If it exceeds 10 parts by mass, it may not adhere to the surface of the toner base particles, causing peeling and the like, which may cause image quality defects.

More specifically, the coverage (coverage) F represented by the following formula (4) on the surface of the toner base particles by each external additive particle is preferably in the range of 5 to 80%. If it is less than 5%, the function of each particle is not expressed, and if it exceeds 80%, the function of other external additives may be difficult to be expressed. If all three external additives exceed 80%, the total coverage will exceed 240%. In-machine contamination due to detachment of external additives and output of OHP may deteriorate image transparency. .
F = √3 · D · ρ t (2π · d · ρ a) ⁻¹ · C × 100 (4)
(In the above formula, F is the coverage (%), D is the volume average particle size (μm) of the toner base particles, ρ t is the true specific gravity of the colored particles, d is the average primary particle size (μm) of the external additive, ρ a represents the true specific gravity of the external additive, and C represents the ratio (x / y) of the mass x (g) of the external additive to the mass y (g) of the toner base particles.

The electrostatic latent image developing toner of the present invention can be suitably manufactured by the above manufacturing method, but is not limited to this manufacturing method.
The volume average particle diameter of the toner in the present invention is preferably in the range of 2 to 8 μm, and more preferably in the range of 3 to 6 μm. Moreover, as a number average particle diameter, the range of 2-8 micrometers is preferable. Further, the value of (volume average particle diameter ÷ number average particle diameter), which is an index of particle size distribution, is preferably 1.6 or less, and more preferably 1.5 or less. When this value is larger than 1.6, the spread of the particle size distribution becomes large, so that the distribution of the charge amount becomes wide and reverse polarity toner or low charge toner is likely to be generated.

Further, the toner shape factor SF1 in the present invention is preferably in the range of 110 to 140.
If the shape factor SF1 is less than 110, the blade cleaning property of the transfer residual toner on the photoconductor is impaired. If the shape factor SF1 exceeds 140, the fluidity of the toner is lowered, and the transferability may be adversely affected from the beginning.

Here, the shape factor SF1 is obtained by the following equation (5).
SF1 = (ML ² / A) × (π / 4) × 100 (5)
In the above formula (5), ML represents the absolute maximum length of the toner particles, and A represents the projected area of the toner particles.
The SF1 is quantified mainly by analyzing a microscope image or a scanning electron microscope (SEM) image using an image analyzer, and can be calculated as follows, for example. That is, an optical microscope image of the toner scattered on the surface of the slide glass is taken into a Luzex image analyzer through a video camera, the maximum length and the projected area of 100 or more toner particles are obtained, calculated by the above formula (5), and the average Obtained by determining the value.

<Career>
The electrophotographic developer of the present invention is a two-component developer obtained by mixing the toner and a carrier.
As the carrier, it is preferable to use a resin-coated carrier having a resin coating layer in which a conductive material is dispersed and contained in a matrix resin on a core material in terms of charge controllability and resistance controllability. As a volume average particle diameter of a carrier core material, generally 10-100 micrometers is preferable and 20-80 micrometers is more preferable. If it is smaller than 10 μm, the magnetic force per carrier particle is lowered, and carrier skipping may occur easily. If it is larger than 100 μm, there may be a problem that sufficient charge cannot be imparted to the toner or the image deteriorates.

  The core material of the carrier is not particularly limited, and examples thereof include magnetic metals such as iron, steel, nickel and cobalt, magnetic oxides such as ferrite and magnetite, glass beads, and the like, from the viewpoint of using the magnetic brush method. Is preferably a magnetic carrier.

  The coating resin includes polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer. Examples include polymers, straight silicone resins composed of organosiloxane bonds or modified products thereof, fluororesins, polyesters, polyurethanes, polycarbonates, phenol resins, amino resins, melamine resins, benzoguanamine resins, urea resins, amide resins, epoxy resins, etc. However, it is not limited to these.

  The average film thickness of the resin coating layer formed by the above method is usually in the range of 0.1 to 10 μm, and preferably in the range of 0.2 to 5 μm. When the thickness is less than 0.1 μm, the core is easily peeled off, and the core is easily exposed over time, and the charge imparting ability and resistance may be lowered, and stable image quality may not be obtained. When the film thickness exceeds 10 μm, the change with time does not easily occur, but the resistance becomes too high, so that the image quality may be deteriorated. In addition, fluidity may be deteriorated.

  In order to reduce the resistance while increasing the film thickness, the resin matrix may contain conductive powder. Examples of the conductive material include metals such as gold, silver and copper, and titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, carbon black, magnetite, and the like. Is not to be done.

  The content of the conductive material is preferably 1 to 50 parts by mass and more preferably 3 to 20 parts by mass with respect to 100 parts by mass of the matrix resin.

  If the carrier resistance is too low, the carrier adheres to the image area of the photoreceptor due to charge injection from the sleeve, or the latent image charge escapes through the carrier, resulting in a latent image distortion or image loss. Such problems arise. On the other hand, when the carrier resistance is high, the carrier charge is less likely to leak, resulting in an edged image. On the other hand, the edge effect is that the image density at the center is very thin on a large image area. Problems arise.

  Examples of the method for producing the carrier include an immersion method in which the powder of the carrier core material is immersed in a solution for forming the coating layer, a spray method in which the solution for forming the coating layer is sprayed on the surface of the carrier core material, and the carrier core material is fluidized air. The fluidized bed method in which the coating layer forming solution is sprayed in a suspended state, the kneader coater method in which the carrier core material and the coating layer forming solution are mixed in the kneader coater to remove the solvent, and the coating resin is made into fine particles. Examples of the powder coating method include a carrier core material and a kneader coater which are mixed at a melting point or higher and cooled to form a film, and the kneader coater method and the powder coat method are particularly preferably used.

  The mixing ratio (mass ratio) of the toner and the carrier in the electrophotographic developer (two-component developer) of the present invention is preferably in the range of toner: carrier = 1: 100 to 30: 100, The range of about 3: 100 to 20: 100 is more preferable.

The image forming method using the electrophotographic developer of the present invention will be described below.
As an image forming method, for example, a latent image forming step for forming an electrostatic latent image on the surface of the latent image carrier and a developer carried on the developer carrier are used. A developing process for developing the electrostatic latent image to form a toner image, a transfer process for transferring the toner image formed on the surface of the latent image carrier, and a cleaning process for cleaning the toner remaining on the surface of the latent image carrier; And a fixing step of thermally fixing the transferred image. The electrophotographic developer of the present invention is used as the developer.

  The latent image forming step is a step of forming an electrostatic latent image by uniformly charging the surface of the latent image carrier with a charging means and then exposing the latent image carrier with a laser optical system or an LED array. is there. As charging means, a contact-type charger such as corotron or scorotron, and a contact-type charger that charges the surface of the latent image carrier by applying a voltage to a conductive member in contact with the surface of the latent image carrier. Examples of the charger include any charger. However, a contact charging type charger is preferable from the viewpoint that the amount of ozone generated is small, environmentally friendly, and excellent printing durability. In the contact charging type charger, the shape of the conductive member may be any of a brush shape, a blade shape, a pin electrode shape, a roller shape, and the like, but a roller-like member is preferable. The image forming method is not subject to any particular limitation in the latent image forming process.

  The developing step refers to bringing a developer carrier having a developer layer containing at least toner on the surface thereof into contact with or in proximity to the electrostatic latent image on the surface of the latent image carrier. Is a step of forming a toner image on the surface of the latent image carrier. The development method can be performed using a known method, but examples of the development method using a two-component developer include a cascade method and a magnetic brush method. The image forming method is not particularly limited with respect to the development method.

  The cleaning step is a step of removing untransferred toner, paper dust, dust, etc. adhering to the surface of the latent image carrier by bringing a blade, brush, roll, etc. into direct contact with the surface of the latent image carrier. The most commonly employed method is a blade cleaning method in which a rubber blade such as polyurethane is pressed against the latent image carrier. When a toner having a small shape factor and a small particle diameter that is difficult to clean is used, it is effective to increase the resilience of the blade material. In addition, it is possible to select cleaning conditions suitable for each toner by adjusting the hardness of the blade material, the pressing accuracy, the nip amount with respect to the photoreceptor, and the like.

  The fixing step is a step of fixing the toner image transferred to the surface of the recording medium with a fixing device. As the fixing device, a heat fixing device using a heat roll is preferably used. The heat fixing device includes a heater roller for heating inside a cylindrical metal core, a fixing roller in which a so-called release layer is formed by a heat resistant resin coating layer or a heat resistant rubber coating layer on the outer peripheral surface thereof, and the fixing roller. The pressure roller or the pressure belt is disposed in pressure contact with the roller and has a heat-resistant elastic layer formed on the outer peripheral surface of the cylindrical metal core or the surface of the belt-like base material. The fixing process of the unfixed toner image is performed by inserting a recording medium on which an unfixed toner image is formed between a fixing roller and a pressure roller or a pressure belt, so that a binder resin, an additive, etc. Fix by heat melting. In the image forming method, the fixing method is not particularly limited.

  The image forming method using the electrophotographic developer of the present invention is not particularly limited and can be applied to conventionally known image forming apparatuses. As a specific image forming apparatus, for example, a normal monocolor image forming apparatus in which only a single color toner is accommodated in a developing device, or a toner image carried on an image carrier is sequentially subjected to primary transfer to an intermediate transfer member. Examples include a color image forming apparatus that repeats, and a tandem type color image forming apparatus in which a plurality of image carriers each having a developing device for each color are arranged in series on an intermediate transfer member.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following description, “parts” and “%” mean “parts by mass” and “% by mass”.
Production of the toner, carrier and developer used in each Example and Comparative Example, and each measurement were performed by the following methods.

(Measurement of average primary particle diameter of external additives, volume average particle diameter of resin particles, etc.)
The measurement was performed using a laser diffraction / scattering particle size distribution analyzer (Mastersizer 2000, manufactured by Malvern).
As a measurement method, a sample in a dispersion is adjusted to have a solid content of about 2 g, and ion exchange water is added thereto to make about 40 ml. This is put into the cell until an appropriate concentration is reached, waits for about 2 minutes, and is measured when the concentration in the cell becomes almost stable. Regarding the obtained volume particle size distribution for each channel, the volume average particle size is the place where the cumulative particle size is 50% from the smaller particle size, and this is the average primary particle size of the external additive particles in the present invention. .

  When measuring each particle such as external additive particles, 2 g of a measurement sample is added to 50 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate, and 2 minutes with an ultrasonic disperser (1000 Hz). A sample was prepared by dispersing, and the sample was measured in the same manner as the above dispersion. The volume average particle diameter of resin particles and the like is also determined according to the above.

(Sphericality of external additive particles)
As the sphericity, Wadell's true sphericity Ψ was adopted, and the sphericity was obtained from the following equation.
Sphericity = (surface area of a sphere having the same volume as an actual particle) / (surface area of an actual particle)
Here, in the above formula, (the surface area of a sphere having the same volume as the actual particles) is obtained by arithmetic calculation from the average particle diameter of the toner. (Surface area of actual particles) was substituted with the measured BET specific surface area using Shimadzu powder specific surface area measuring device SS-100 type.

(True specific gravity of external additive particles)
Using a Lechatelier specific gravity bottle, the true specific gravity of the external additive was measured in accordance with JIS-K-0061 5-2-1. The operation was performed as follows.
(1) About 250 ml of ethyl alcohol is put into a Lechatelier specific gravity bottle and adjusted so that the meniscus is at the position of the scale.
(2) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(3) About 100 g of a sample is weighed and its mass is set to W.
(4) Put the weighed sample in a specific gravity bottle to remove bubbles.
(5) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature becomes 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(6) The true specific gravity is calculated by the following formula.
D = W / (L2-L1)
S = D / 0.9982
In the above formula, D is the density of the sample (20 ° C.) (g / cm ³ ), S is the true specific gravity (20 ° C.) of the sample, W is the apparent mass (g) of the sample, and L1 is the sample in a specific gravity bottle. The previous meniscus reading (20 ° C.) (ml), L2 is the meniscus reading after placing the sample in the density bottle (20 ° C.) (ml), 0.9982 is the density of water at 20 ° C. (g / cm ³ ).

(Charging polarity Q1 by electrode plate method)
1.00 g of each external additive was placed in a mortar with a width of 9 cm, and stirred lightly 30 times so that the weight of the pestle was applied.
On the other hand, prepare two smooth steel plates 200mm long, 100mm wide, 2mm thick and two plastic plates 200mm long, 10mm wide, 5mm thick, and place two plastic plates on one iron plate. It was placed on both ends of the iron plate according to the vertical position of 200 mm. In addition, the other iron plate was put on this, fastened with a clip, and a 5 mm wide space, 200 mm long and 80 mm wide (because both ends of the iron plate are 10 mm plastic plates) were arranged in parallel. . This was installed so that the vertical direction was vertical, and a voltage of +300 V was applied to one iron plate and −300 V was applied to the other iron plate, and this was used as an electrode plate measuring instrument.

  The mixed powder thus obtained was slowly and evenly poured between the electrode plates from above. The electrode plate with the external additive attached was photographed with a scanning electron microscope (SEM), and it was confirmed from the particle size which of the external additive particles A and B was positively or negatively charged. In this case, the external additive particles attached to the + 300V side are negatively charged, and the external additive particles attached to the −300V side are positively charged. Those having poor flowability are attached to both electrode plates, and therefore, when 100 particles are observed, 70 or more particles are regarded as external additives drawn on the electrode plates.

(Charge amount Q2 by blow-off method)
The coverage with respect to the carrier was calculated from the particle diameter and specific gravity of the external additive particles to be measured, and the amount of the external additive charged so that the coverage of the external additive particles with respect to the carrier was 200% was obtained from the following formula.
200 (%) = (√3 / 2π) × (Dc · ρc) / (Da · ρa) × (external additive charge) / (carrier charge) × 100
(In the above formula, Dc represents the carrier particle size (μm), ρc represents the carrier specific gravity, Da represents the external additive particle size (μm), and ρa represents the external additive specific gravity.)

  Next, 10 g of the carrier used for the developer and the amount of the external additive obtained by the above calculation were mixed and mixed for 20 minutes with a tumbler mixer. Thereafter, the charge amount was measured by the blow-off method using a charge amount measuring device TB-200 (manufactured by Toshiba).

<Preparation of toner mother particle 1>
-Preparation of resin particle dispersion-
-Styrene 370 parts-N-butyl acrylate 30 parts-Acrylic acid 8 parts-Dodecanethiol 24 parts-Carbon tetrabromide 4 parts A nonionic surfactant (Nonipol 400: Sanyo Chemical Co., Ltd.) 6 parts and anionic surfactant (Neogen SC: Daiichi Kogyo Seiyaku Co., Ltd.) 10 parts were emulsion polymerized in a flask dissolved in ion-exchanged water 550 parts and mixed slowly for 10 minutes. Then, 50 parts of ion-exchanged water in which 4 parts of ammonium persulfate was dissolved was added thereto. After carrying out nitrogen substitution, the inside of the flask was stirred and heated in an oil bath until the contents reached 70 ° C., and emulsion polymerization was continued for 5 hours. As a result, a resin particle dispersion was obtained in which resin particles having a volume average particle size of 150 nm, Tg = 52 ° C., and weight average molecular weight Mw = 10500 were dispersed. The solid content concentration of this dispersion was 40%.

-Preparation of colorant dispersion (1)-
・ Carbon black (Mogal L: Cabot) 60 parts ・ Nonionic surfactant (Nonipol 400: Sanyo Chemical Co., Ltd.) 6 parts ・ Ion-exchanged water 240 parts

  The above components are mixed, dissolved, stirred for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA), then dispersed with an optimizer and a colorant having a volume average particle diameter of 250 nm ( A colorant dispersant (1) having carbon black particles dispersed therein was prepared.

-Preparation of colorant dispersion (2)-
・ Cyan pigment (CI Pigment Blue 15: 3) 60 parts ・ Nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) 5 parts ・ Ion-exchanged water 240 parts

  The above components are mixed, dissolved, stirred for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA), then dispersed with an optimizer and a colorant having a volume average particle diameter of 250 nm ( Cyan pigment) A colorant dispersant (2) in which particles were dispersed was prepared.

-Preparation of colorant dispersion (3)-
・ Magenta pigment (CI Pigment Red 122) 60 parts ・ Nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) 5 parts ・ Ion-exchanged water 240 parts

  The above components are mixed, dissolved, stirred for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA), then dispersed with an optimizer and a colorant having a volume average particle diameter of 250 nm ( Magenta pigment) A colorant dispersant (3) in which particles were dispersed was prepared.

-Preparation of colored dispersion (4)-
・ Yellow pigment (CI Pigment Yellow 180) 90 parts ・ Nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) 5 parts ・ Ion-exchanged water 240 parts

  The above components are mixed, dissolved, stirred for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA), then dispersed with an optimizer and a colorant having an average particle size of 250 nm (Yellow) A colorant dispersant (4) in which (pigment) particles were dispersed was prepared.

-Release agent dispersion-
Paraffin wax (HNP0190: manufactured by Nippon Seiwa Co., Ltd., melting point 85 ° C.) 100 parts Cationic surfactant (Sanisol B50: manufactured by Kao Corporation) 5 parts Ion-exchanged water 240 parts

  The above components were dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA) for 10 minutes, and then dispersed with a pressure discharge homogenizer, and the volume average particle diameter was 550 nm. A release agent dispersion liquid in which release agent particles are dispersed was prepared.

(Toner mother particle K1)
-Resin particle dispersion 234 parts-Colorant dispersion (1) 30 parts-Release agent dispersion 50 parts-Polyaluminum chloride (Paho2S, manufactured by Asada Chemical Co., Ltd.) 0.5 parts-Ion-exchanged water 600 parts

  The above components were mixed and dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA), and then heated to 40 ° C. while stirring the flask in a heating oil bath. . After maintaining at 40 ° C. for 30 minutes, it was confirmed that aggregated particles having a D50 of 4.5 μm were produced. Further, the temperature of the applied oil bath was raised and maintained at 56 ° C. for 1 hour, and D50 was 5.3 μm. Thereafter, 26 parts by mass of a resin particle dispersion was added to the dispersion containing the aggregate particles, and then the temperature of the heating oil bath was raised to 50 ° C. and held for 30 minutes. The dispersion containing the aggregated particles was added with 1N sodium hydroxide to adjust the pH of the system to 7.0, and then the stainless steel flask was sealed and heated to 80 ° C. while continuing stirring using a magnetic seal. And held for 4 hours. After cooling, the toner base particles were separated by filtration, washed four times with ion exchange water, and then lyophilized to obtain toner base particles K1. The toner base particle K1 had a particle size of 5.9 μm, a volume average particle size of 5.9 μm, and a shape factor SF1 of 132.

(Toner mother particle C1)
Toner base particles C1 were obtained in the same manner as the toner base particles K1, except that the colorant dispersion liquid (2) was used instead of the colorant dispersion liquid (1). The toner base particle C1 had a particle size of 5.8 μm, a volume average particle size of 5.8 μm, and a shape factor SF1 of 131.

(Toner mother particle M1)
Toner base particles M1 were obtained in the same manner as the toner base particles K1, except that the colorant dispersion (3) was used instead of the colorant dispersion (1). The toner mother particles M1 had a volume average particle size of 5.5 μm and a shape factor SF1 of 135.

(Toner mother particle Y1)
Toner base particles Y1 were obtained in the same manner as the toner base particles K1, except that the colorant dispersion liquid (4) was used instead of the colorant dispersion liquid (1). The toner base particle Y1 has a volume average particle size of 5.9 μm and a shape factor SF1 of 130.

<Preparation of toner mother particles 2>
-Synthesis of crystalline polyester resin (1)-
In a heat-dried three-necked flask, 17.4 parts of 1,10-decanediol, 2.2 parts of sodium dimethyl 5-sulfoisophthalate, 10 parts of dimethyl sulfoxide, 0.03 part of dibutyltin oxide as a catalyst, After that, the air in the container was replaced with nitrogen gas by a depressurization operation to create an inert atmosphere, and the mixture was stirred at 180 ° C. for 3 hours by mechanical stirring. Dimethyl sulfoxide was distilled off under reduced pressure, 26.5 parts of dimethyl dodecanedioic acid was added under a nitrogen stream, and the mixture was stirred at 180 ° C. for 1 hour.

Thereafter, the temperature was gradually raised to 220 ° C. under reduced pressure, and the mixture was stirred for 30 minutes. When it became viscous, it was air-cooled to stop the reaction, and 36 parts of crystalline polyester resin (1) was synthesized. The crystalline polyester resin (1) obtained had a weight average molecular weight (M _W ) of 9,200 and a number average molecular weight (M _n ) of 6,000 as determined by gel permeation chromatography.

  Further, when the melting point (Tm) of the crystalline polyester resin (1) was measured by a differential scanning calorimeter (DSC) by the above-described measuring method, it had a clear peak and the peak top temperature was 79 ° C. Met. The content ratio of the copolymerization component (5-sulfoisophthalic acid component) and the dodecanedioic acid component measured and calculated from the NMR spectrum of the resin was 7.5: 92.5.

(Toner mother particle C2)
-Preparation of resin particle dispersion (1)-
150 parts of the obtained crystalline polyester resin (1) was put into 850 parts of distilled water, and mixed and stirred with a homogenizer (manufactured by IKA Japan: Ultra Tarax) while heating to 85 ° C. to obtain a resin particle dispersion ( 1) was obtained.

-Preparation of colorant dispersion (5)-
Mixing 250 parts of phthalocyanine pigment (manufactured by Dainichi Seika Co., Ltd .: PV FAST BLUE), 20 parts of anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: Neogen RK), and 730 parts of ion-exchanged water Then, after being dissolved, it was dispersed using a homogenizer (manufactured by IKA: Ultra Tarax) to prepare a colorant dispersion (5) in which a colorant (phthalocyanine pigment) was dispersed.

-Preparation of aggregated particles-
2400 parts of resin particle dispersion (1), 100 parts of colorant dispersion (5), 63 parts of release agent dispersion, 10 parts of lauroyl peroxide, 5 parts of aluminum sulfate (manufactured by Wako Pure Chemical Industries, Ltd.) , 100 parts of ion-exchanged water are contained in a round stainless steel flask, adjusted to pH 2.0, dispersed using a homogenizer (IKA Corporation: Ultra Turrax T50), and then in a heating oil bath At 72 ° C. with stirring. After maintaining at 72 ° C. for 3 hours, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.0 μm were formed. After further heating and stirring at 72 ° C. for 1 hour, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.5 μm were formed.

-Fusion process-
The pH of the aggregated particles was 2.4. Therefore, an aqueous solution obtained by diluting sodium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) to 0.5% by weight was gently added to adjust the pH to 5.0, then heated to 83 ° C. while continuing stirring and held for 3 hours. did.

  Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum drier to obtain toner base particles C2. The obtained toner base particles C2 were measured for volume average particle size using a Coulter counter [TA-II] type (aperture diameter: 50 μm, manufactured by Coulter), and the D50 of the toner base particles C2 was 5.5 μm. The shape factor SF1 was 131.

<Creation of carrier>
14 parts of toluene, 2 parts of styrene-methyl methacrylate copolymer (component ratio: 80/20, weight average molecular weight: 70000), and 0.2 part of carbon black (Regal 330, manufactured by Cabot Corp.) are mixed and stirred for 10 minutes. A solution for forming a coating layer in which carbon black was dispersed was prepared by stirring. Next, this coating solution and 100 parts of ferrite particles (volume average particle size: 38 μm) are put in a vacuum degassing kneader and stirred at 60 ° C. for 30 minutes, and then degassed by further reducing pressure while heating. The carrier was prepared by drying. This carrier had a volume resistivity of 10 ¹¹ Ωcm when an electric field of 800 V / cm was applied.

<Surface treatment of external additive particles>
The hydrophobic treatment of the external additive particles was performed as follows. Silane and a silane coupling agent were used as the treating agent.
In a reaction vessel, 80 parts of an external additive core is added to a mixed solvent in which 1000 parts of pure water and 100 parts of 2-propanol are mixed to form a slurry. Next, with respect to 100 parts of the external additive core, the processing agent types shown in Table 1 below were charged in the amount of the processing agent shown in Table 1 into a slurry-like reaction vessel. After replacing the inside of the reaction vessel with dry nitrogen gas, the temperature was raised, 30 parts of 0.1N HCl was added dropwise, and the mixed solution was heated to about 80 ° C. while stirring under a nitrogen gas stream.

Thereafter, the reaction was stirred for 3 hours while heating and refluxing in an oil bath. After cooling, the mixed solution was taken out, fine particles were separated by a centrifuge, and the supernatant was removed. The operation of mixing and stirring the filtered fine particles in a 10% aqueous methanol solution and centrifuging was repeated three times. Furthermore, after mixing and stirring in pure water and repeating the centrifugation operation three times, the fine particle wet product was lyophilized to remove moisture. After vacuum drying at 160 ° C. for 2 hours, the mixture was crushed with an agate mortar and sieved with a 40 μm sieve mesh.
As described above, a combination of external additives I to V including two types of external additive particles was obtained.

In addition, the (sphericity, true specific gravity) of the large-diameter external additive particles A in the external additives I to V are I: (0.98, 1.8) and II: (0.98, 1.8), respectively. ), III: (0.98, 1.8), IV: (0.98, 1.7), V: (0.98, 1.8).
With respect to these external additives I to V, the charge polarity Q1 by the electrode plate method and the charge amount Q2 by the blow-off method were measured by the above methods. These results are also shown in Table 1.

<Example 1>
For each 100 parts of the toner base particles K1, C1, M1, and Y1, 1.0 part of a small-diameter external additive (external additive particle B) in Table 1 and a large-diameter external additive (external) 1.5 parts each of additive particles A) were added, blended for 15 minutes at a peripheral speed of 30 m / s using a 5 liter Henschel mixer, and then coarse particles were removed using a sieve with an opening of 45 μm, Toner 1 was produced.

  10 parts of the obtained toner 1 and 100 parts of the carrier are stirred with a V-blender at 40 rpm for 20 minutes, and sieved with a sieve having an opening of 212 μm to produce a developer 1 for color electrophotography. did.

<Example 2>
To 100 parts of each of the toner base particles K1, C1, M1, and Y1, 0.8 parts of a small-diameter external additive and 1.5 parts of a large-diameter external additive in Table 1 are added. After blending for 15 minutes at a peripheral speed of 30 m / s using a 5 liter Henschel mixer, coarse particles were removed using a sieve having an opening of 45 μm to prepare toner 2.
Using the toner 2 obtained, an electrophotographic developer 2 was produced in the same manner as in Example 1.

<Example 3>
To 100 parts of the toner base particles C2, 1.0 part of a small-diameter external additive I and 1.5 parts of a large-diameter external additive in Table 1 are added, respectively, and a 5 liter Henschel mixer is used. After blending for 15 minutes at a speed of 30 m / s, coarse particles were removed using a sieve having an opening of 45 μm to prepare toner 3.
Using the toner 3 thus obtained, an electrophotographic developer 3 was produced in the same manner as in Example 1.

<Comparative Example 1>
To 100 parts of each of the toner base particles K1, C1, M1, and Y1, 0.8 parts of the small-diameter external additive III and 1.5 parts of the large-diameter external additive in Table 1 are added. After blending for 15 minutes at a peripheral speed of 30 m / s using a liter Henschel mixer, coarse particles were removed using a sieve having an opening of 45 μm to prepare toner 4.
Using the obtained toner 4, an electrophotographic developer 4 was produced in the same manner as in Example 1.

<Comparative example 2>
To 100 parts of each of the toner base particles K1, C1, M1, and Y1, 0.8 parts of the small-diameter external additive IV and 1.5 parts of the large-diameter external additive in Table 1 are added. After blending for 15 minutes at a peripheral speed of 30 m / s using a liter Henschel mixer, coarse particles were removed using a sieve having an opening of 45 μm to prepare toner 5.
Using the toner 5 thus obtained, an electrophotographic developer 5 was produced in the same manner as in Example 1.

<Comparative Example 3>
To 100 parts of each of the toner base particles K1, C1, M1, and Y1, 0.8 parts of the small diameter external additive V and 1.5 parts of the large diameter external additive in Table 1 are added. After blending for 15 minutes at a peripheral speed of 30 m / s using a liter Henschel mixer, coarse particles were removed using a sieve having an opening of 45 μm to prepare toner 6.
Using the toner 6 thus obtained, an electrophotographic developer 6 was produced in the same manner as in Example 1.

<Evaluation>
The developers shown in Examples and Comparative Examples were evaluated as follows.
Each of the above developers was used, and DocuCenterColor400 (Fuji Xerox Co., Ltd.) was used as the apparatus.
(Output image)
As an actual machine image output method, a gradation chart of four colors was used. As the gradation chart, “A4 size chart (20%) for each color of image density (A)” and “A4 size chart (3% for each color of image density) (B)” were used. The image density is adjusted by the area ratio of the image portion. Each gradation chart has a solid portion, a halftone portion, and a background portion.

(Charging characteristics evaluation)
(1) The gradation chart A is output under high temperature and high humidity (30 ° C./80% RH), and the developer on the mag roll after 100 sheets (initial) and the mag roll after 5,000 sheets (after durability) The developer was collected and the charge amount was measured.
(2) Output a gradation chart B under low temperature and low humidity (10 ° C./10% RH), collect the developer on the mag roll after 100 sheets and the developer on the mag roll after 5,000 sheets, and charge amount Measurements were performed.
The charge amount was measured by a blow-off method using a charge amount measuring device TB-200 (manufactured by Toshiba). The measurement conditions at this time were blow-off gas with air at a pressure of 1.0 kg / cm ³ and a measurement sample amount of 0.2 g. The evaluation results are shown only for Cyan.

(Image quality evaluation)
-Fog evaluation-
After 100 sheets and 5,000 sheets of gradation chart A output under high temperature and high humidity (30 ° C./80%) and gradation chart B output under low temperature and low humidity (10 ° C./10%) The fog of the background portion was visually evaluated using the output chart.
The evaluation results are shown only for Cyan.

-Image density-
The image density of the solid portion of the output image was measured with an image densitometer X-Rite (manufactured by X-Rite). The evaluation criteria for image density were as follows.
The case where the concentration of X-Rite was 1.4 or more was rated as “◯”, and the case where it was less than 1.4 was evaluated as “×” (the concentration was insufficient).
The above evaluation results are summarized in Tables 2 and 3.

  As shown in Tables 2 and 3, when two kinds of external additives having different particle diameters are used for the toner base particles, the external additive core and the surface treatment agent are represented by the formulas (1) and ( When the selection is made so as to satisfy the relationship of 2), it can be seen that an electrophotographic developer capable of obtaining a high-quality image free from fogging or the like with little change in the environment of the charge amount can be obtained. On the other hand, when either one of the formulas (1) and (2) is not satisfied as in the comparative example, the charging characteristics and further, the problem of image quality deterioration due to the charging characteristics arises.

Claims (4)

A two-component developer comprising a toner and a carrier,
The toner comprises toner base particles, external additive particles A and external additive particles B having different particle diameters surface-treated with different surface treatment agents,
The average primary particle diameter of the external additive particles A is 80 nm or more, the average primary particle diameter of the external additive particles B is 60 nm or less, and the charging polarity of each of the external additive particles A and B by the electrode plate method is Q1. _A and Q1 _B and when the molecular weights of the surface treatment agents used for the external additive particles A and B are X _A and X _B , they satisfy the relationship of the following formulas (1) and (2): A developer for electrophotography.
(−) Q1 _A <0 <Q1 _B (+) Formula (1)
_{X A} <X B ··· formula (2) When the triboelectric charge amounts (μC / g) of the external additive particle A and external additive particle B by the blow-off method with the carrier are Q2 _A and Q2 _B , respectively, these satisfy the relationship of the following formula (3) The electrophotographic developer according to claim 1.
Q2 _B <Q2 _A <0 Formula (3)   The electrophotographic developer according to claim 1, wherein the toner is prepared by a wet granulation method.   The electrophotographic developer according to claim 1, wherein the external additive particle A has a spherical shape and a true specific gravity of 2.5 or less.