JP2005107381A - Toner for electrostatic image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for developing an electrostatic charge image that is excellent in storage stability and fluidity and has little deterioration in image quality due to environmental changes.
An electrostatic charge image developing toner containing colored resin particles comprising at least a binder resin and a colorant, wherein the colored resin particles have a volume average particle diameter (Dv) of 4 to 10 μm and an average circular shape. The zeta potential (E1) of the toner for developing an electrostatic charge image after being left to stand in an environment having a temperature of 0.930 to 0.995, a temperature of 23 ° C. and a humidity of 50% for a whole day and night is 5 to 35 mV. The electrostatic charge image development wherein the difference between the zeta potential (E2) of the electrostatic charge image developing toner and E1 is less than 5 mV after the charge development toner is left in an environment of 50 ° C. and 80% humidity for 2 weeks. Toner.
[Selection figure] None

Description

  The present invention relates to an electrostatic charge image developing toner, and more particularly, to an electrostatic charge image developing toner that is excellent in storage stability and fluidity and has little deterioration in image quality due to environmental fluctuations.

In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an electrostatic latent image formed on a photoreceptor is first developed with toner. Next, the formed toner image is transferred to a transfer material such as paper or an OHP sheet, and then fixed by a method such as heating, pressurization, or solvent vapor.
In recent years, functions of image forming apparatuses have been advanced, and there is a demand for high resolution and high speed by a method of forming an electrostatic latent image with a laser. For this reason, in addition to reducing the particle size and sharpening the particle size distribution so that the resolution can be increased, the toner is required to have a low-temperature fixing that can be applied to high-speed models. On the other hand, image forming apparatuses are increasingly used in high-temperature and high-humidity areas, and it has been required to improve image density stability, fluidity, storage stability, and the like.

  Conventionally, in an image forming apparatus, a pulverized toner produced by melt-mixing and uniformly dispersing a thermoplastic resin containing a colorant, a charge control agent, etc., and then performing pulverization and classification has been mainly used. . However, it is difficult to control the particle size of the toner produced by the pulverization method, and the classification process must be performed, and the manufacturing process is complicated. Further, since fine powder remains on the surface of the toner obtained by pulverization, due to the influence of the fine powder, a decrease in image quality due to a change in charge amount was observed, and a product having good fluidity and storage stability was not obtained. .

  In order to solve such a problem, a toner manufacturing method by a so-called polymerization method has been proposed. For example, the present applicant has disclosed in Japanese Patent Application Laid-Open No. Hei 6-273997, an electrostatic charge comprising a step of wet-grinding a polyolefin wax in a polymerizable monomer, adding a colorant, mixing, dispersing, and suspension polymerization. A method for producing a toner for image development is disclosed. The toner obtained by the production method is excellent in fixability and developability and excellent in durability without filming on the photosensitive member or developing blade, but further improved in durability under high temperature and high humidity environment. It is hoped that

  Further, as described above, the toner is required to be fixed at a low temperature corresponding to a high-speed model. In order to achieve low-temperature fixing, a large amount of softening agent is included, so that when stored for a long period of time, the external additive may be embedded in the resin. Therefore, there existed a problem that storage stability was impaired and image quality was lowered at the same time. In order to solve this problem, a toner in which capsules are formed outside the polymerization toner has been proposed. For example, the present applicant has disclosed in JP-A-11-72949 a developer composed of polymer particles and an external additive, wherein the pH of the aqueous extract of the developer obtained by a specific method is 4 to 4. 7 is disclosed. The developer disclosed in the publication can be fixed at a low temperature, and the fluidity, long-term storage, and charging stability are improved by encapsulation. However, in recent years, the number of cases where toner is used in high-temperature and high-humidity areas has increased, and it is necessary to further improve these performances. Therefore, when a conventional capsule toner containing a large amount of a release agent having a low softening point and a charge control resin having a hygroscopic property is stored under a long period of high temperature and high humidity, it is possible to further reduce image density reduction and fogging. It is desired.

  On the other hand, Japanese Patent Laid-Open No. 4-217267 discloses a toner for developing an electrostatic image in which a fluidity improver having a controlled zeta potential at a hydrogen ion concentration pH of 5 is adhered to the surface of toner particles. According to this publication, the electrostatic charge image developing toner disclosed in this publication has little change in triboelectric charge amount under conditions from low temperature and low humidity to high temperature and high humidity, and a clear image density and good gradation can be obtained. It is disclosed. However, the electrostatic image developing toner disclosed in the publication has a problem that the fixing temperature is high.

JP-A-6-273777 JP 11-72949 A JP-A-4-217267

  Accordingly, an object of the present invention is to provide a toner for developing an electrostatic charge image that is excellent in storage stability and fluidity and has little deterioration in image quality due to environmental fluctuations.

  As a result of intensive studies to achieve the above object, the present inventor made the volume average particle diameter (Dv) and average circularity of the colored resin particles, and the zeta potential of the toner for developing an electrostatic charge image within a specific range and specified The present inventors have found that the above object can be achieved by a toner for developing an electrostatic charge image in which the amount of change in zeta potential after standing for a certain period of time under these environmental conditions is within a specific range.

The present invention has been made based on the above findings, and is an electrostatic charge image developing toner containing colored resin particles comprising at least a binder resin and a colorant, and the volume average particle diameter (Dv) of the colored resin particles. ) Is 4 to 10 μm, the average circularity is 0.930 to 0.995, the zeta potential (E1) of the toner for developing an electrostatic charge image after being left overnight in an environment of a temperature of 23 ° C. and a humidity of 50%. ) Is 5 to 35 mV, and the difference between the zeta potential (E2) of the electrostatic charge image developing toner and E1 after the electrostatic charge image developing toner is left in an environment of 50 ° C. and 80% humidity for 2 weeks. Is a toner for developing an electrostatic charge image having a voltage of less than 5 mV.
The toner for developing an electrostatic image is excellent in storage stability and fluidity, and has low-temperature fixability.

In the toner for developing an electrostatic charge image, the charge control agent is added so that the product of the added weight part of the charge control agent with respect to 100 parts by weight of the binder resin and the base number (mgHCl / g) of the charge control agent is 7 or less. It is preferably contained.
The toner for developing an electrostatic charge image contains a polyfunctional ester compound having a hydroxyl value (a) of 4 mgKOH / g or less as a release agent, and an addition part (b) of the release agent with respect to 100 parts by weight of the binder resin. And the hydroxyl value (a) is preferably 40 or less.

  According to the present invention, a toner for developing an electrostatic charge image is provided that has excellent storage stability and fluidity and is less susceptible to image quality degradation due to environmental fluctuations.

The electrostatic charge image developing toner of the present invention will be described below.
The toner for developing an electrostatic charge image of the present invention contains colored resin particles comprising at least a binder resin and a colorant. The colored resin particles preferably further contain a charge control agent and a release agent.
Specific examples of the binder resin include conventionally widely used resins such as polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.

  As the colorant, any colorant and dye other than carbon black, titanium black, magnetic powder, oil black, and titanium white can be used. As the black carbon black, those having a primary particle diameter of 20 to 40 nm are suitably used. When the particle size is within this range, carbon black can be uniformly dispersed in the toner and fogging is reduced, which is preferable.

When obtaining a full-color toner, a yellow colorant, a magenta colorant and a cyan colorant are usually used.
Examples of the yellow colorant include compounds such as an azo colorant and a condensed polycyclic colorant. Specifically, C.I. I. Pigment yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 90, 93, 97, 120, 138, 155, 180, 181, 185, and 186.
Examples of the magenta colorant include compounds such as an azo colorant and a condensed polycyclic colorant. Specifically, C.I. I. Pigment Red 31, 48, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251 and C.I. I. Pigment violet 19 and the like.
As the cyan colorant, for example, a copper phthalocyanine compound and a derivative thereof, an anthraquinone compound, and the like can be used. Specifically, C.I. I. Pigment blue 2, 3, 6, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17, and 60.
The amount of the colorant is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the charge control agent, a charge control agent conventionally used for toner can be used without any limitation. Of the charge control agents, charge control resins are preferred. This is because the charge control resin has high compatibility with the binder resin, is colorless, and a toner having stable chargeability can be obtained even in continuous color printing at high speed. Examples of the charge control resin include quaternary ammonium produced according to the descriptions in JP-A-63-60458, JP-A-3-175456, JP-A-3-243594, JP-A-11-15192, and the like. (Salt) group-containing copolymers, sulfonic acid (salt) group-containing copolymers produced according to the descriptions in JP-A-1-217464, JP-A-3-15858, and the like can be used. .

In the present invention, a quaternary ammonium group-containing copolymer is preferably used, and the amount of monomer units having a quaternary ammonium group is preferably 0.1 to 5% by weight, more preferably 0.3 to 3% by weight. When the content is in this range, the charge amount of the electrostatic image developing toner can be easily controlled, and the occurrence of fog can be reduced. The charge control resin has a number average molecular weight of 3,000 to 30,000. Those of 3,000 to 20,000 are more preferred, and those of 5,000 to 15,000 are most preferred. If the number average molecular weight of the charge control resin is less than 3,000, offset tends to occur. Conversely, if the number average molecular weight exceeds 30,000, the fixability tends to deteriorate.
The glass transition temperature of the charge control resin is preferably 40 to 80 ° C, more preferably 45 to 75 ° C, and most preferably 45 to 70 ° C. When the glass transition temperature is less than 40 ° C., the storage stability of the toner tends to deteriorate, and when it exceeds 80 ° C., the fixability tends to decrease.

The base number of the charge control resin is preferably 1.5 mg HCl / g or less, and more preferably 1 mg HCl / g or less. If the base value of the charge control resin exceeds 1.5 mg HCl / g, fog may occur.
The amount of the charge control agent described above is usually 0.01 to 30 parts by weight, preferably 0.3 to 25 parts by weight with respect to 100 parts by weight of the binder resin.

Examples of the release agent include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; plant-based natural waxes such as candelilla, carnauba, rice, wood wax, jojoba; paraffin, microcrystalline, petrolatum, etc. Petroleum waxes and modified waxes thereof; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, dipentaerythritol hexapalmitate; and the like.
A mold release agent can be used 1 type or in combination of 2 or more types.

  Of the release agents, synthetic waxes and polyfunctional ester compounds are preferred. Among these, in the DSC curve measured by a differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is preferably 30 to 150 ° C, more preferably 40 to 100 ° C, and most preferably 50 to 80 ° C. A polyfunctional ester compound is preferable because a toner having an excellent fixing-peeling balance at the time of fixing can be obtained. In particular, those having a molecular weight of 1000 or more, dissolving at least 5 parts by weight with respect to 100 parts by weight of styrene at 25 ° C., and having an acid value of 10 mgKOH / g or less show a remarkable effect on lowering the fixing temperature, and thus are more preferable. As such a polyfunctional ester compound, dipentaerythritol-hexapalmitate and pentaerythritol tetramyristate are particularly preferable. Endothermic peak temperature refers to the value measured by ASTM D3418-82.

The hydroxyl value of the release agent is preferably 4 mgKOH / g or less, more preferably 3 mgKOH / g or less. When the hydroxyl value of the release agent exceeds 4 mgKOH / g, fog may occur.
The amount of the release agent is usually 3 to 20 parts by weight, preferably 5 to 15 parts by weight with respect to 100 parts by weight of the binder resin.
Further, when the addition part by weight of the release agent with respect to 100 parts by weight of the binder resin is b and the hydroxyl value (mgKOH / g) of the release agent is a, the product of a and b (a × b) is 40. Or less, more preferably 30 or less. If the product of a and b exceeds 40, fog may occur.

The colored resin particles constituting the toner for developing an electrostatic charge image of the present invention are so-called core-shell type (or “capsule” obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles. Also referred to as “type”). In the core-shell type particle, the low softening point material in the inside (core layer) is coated with a material having a higher softening point, so that it is possible to balance the lowering of the fixing temperature and the prevention of aggregation during storage. preferable.
Usually, the core layer of the core-shell type particle is composed of the binder resin, the colorant, the charge control agent and the release agent, and the shell layer is composed of the binder resin alone.

The weight ratio between the core layer and the shell layer of the core-shell type particle is not particularly limited, but is usually 80/20 to 99.9 / 0.1.
By setting the ratio of the shell layer in the above range, the storage stability of the electrostatic charge image developing toner and the fixing property at a low temperature can be combined.

The average thickness of the shell layer of the core-shell type particles is usually 0.001 to 1.0 μm, preferably 0.003 to 0.5 μm, and more preferably 0.005 to 0.2 μm. When the thickness is increased, the fixability is lowered, and when the thickness is reduced, the storage stability may be lowered. The core particles forming the core-shell type colored resin particles need not have the entire surface covered with the shell layer, and may be one in which a part of the surface of the core particle is covered with the shell layer. .
When the core particle diameter and the thickness of the shell layer of the core-shell type particle can be observed with an electron microscope, it can be obtained by directly measuring the particle size and the shell thickness randomly selected from the observation photograph. When it is difficult to observe the core and the shell, it can be calculated from the particle size of the core particle and the amount of the monomer that forms the shell used for producing the toner for developing an electrostatic charge image.

  The colored resin particles constituting the toner for developing an electrostatic charge image of the present invention have a volume average particle diameter Dv of 4 to 10 μm, preferably 5 to 8 μm. When Dv is less than 4 μm, the fluidity of the toner is reduced, fogging occurs, transfer residue is generated, cleaning properties are deteriorated, and when it exceeds 8 μm, fine line reproducibility is deteriorated.

The ratio (Dv / Dp) of the volume average particle diameter (Dv) to the number average particle diameter (Dp) of the colored resin particles constituting the toner for developing an electrostatic charge image of the present invention is preferably 1.0 to 1. 3, more preferably 1.0 to 1.2. If Dv / Dp exceeds 1.3, fog may occur.
The volume average particle diameter and the number average particle diameter of the colored resin particles can be measured using, for example, Multisizer (manufactured by Beckman Coulter).

The colored resin particles constituting the electrostatic image developing toner of the present invention have an average circularity of 0.930 to 0.995, preferably 0.950 to 0, as measured by a flow type particle image analyzer. .995. If the average circularity is less than 0.930, the fine line reproducibility is poor.
By producing a toner for developing an electrostatic charge image using a phase inversion emulsification method, a dissolution suspension method, a polymerization method (suspension polymerization method or emulsion polymerization method), etc., this average circularity can be easily adjusted to the above range. can do.

  In the present invention, the circularity is defined as the ratio between the circumference of a circle having the same projected area as the particle image and the circumference of the projected image of the particle. The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the particles, and is an index indicating the degree of unevenness of the colored resin particles. This average circularity is 1 when the colored resin particles are completely spherical, and the value becomes smaller as the surface shape of the colored resin particles becomes uneven. The average circularity (Ca) is a value obtained by the following equation.

In the above formula, n is the number of particles for which the circularity Ci is obtained.
In the above equation, Ci is the circularity of each particle calculated by the following equation based on the circumferential length measured for each particle in a particle group having an equivalent circle diameter of 0.6 to 400 μm.
Circularity (Ci) = peripheral length of circle equal to projected area of particle / peripheral length of projected particle image In the above formula, fi is the frequency of particles having a circularity Ci.
The circularity and the average circularity can be measured using a flow type particle image analyzer “FPIA-2100” or “FPIA-2000” manufactured by Sysmex Corporation.

The toner for developing an electrostatic charge image of the present invention has a zeta potential (E1) of 5 to 35 mV, preferably 5 to 20 mV after being left at a temperature of 23 ° C. and a humidity of 50% for one day. If the zeta potential is less than 5 mV, fog occurs, or the toner remains on the photoreceptor without being transferred, and if it exceeds 35 mV, the image density decreases.
The difference between the zeta potential (E2) and E1 after leaving the toner for developing an electrostatic charge image of the present invention in an environment of 50 ° C. and 80% humidity for 2 weeks is less than 5 mV, preferably less than 3 mV. is there. If the difference between E2 and E1 is 5 mV or more, fog occurs.

  The zeta potential can be measured, for example, by a laser Doppler method, also known as an electrophoretic light scattering measurement method. When particles dispersed in a liquid are charged, when an electric field is applied to the system, the particles move toward the electrode, but the moving speed is proportional to the charge of the particles. Therefore, the zeta potential can be obtained by measuring the moving speed of the particles. In the laser Doppler method, when light or sound waves are reflected or scattered by a moving object, the frequency of the light or sound waves changes in proportion to the speed of the object. Speed). When laser light is applied to the electrophoretic particles, the frequency of the scattered light from the particles shifts due to the Doppler effect, and the amount of shift is proportional to the migration speed of the particles. It is possible to determine the migration speed.

From the migration velocity (V) and electric field (E) obtained here, the electric mobility (U) is obtained by the following formula (1).
U = V / E (1)
The zeta potential (ζ) can be obtained from the electric mobility (U) using the following equation (2) (Smoluchowski equation).
ζ = 4πηU / ε (2)
In the formula (2), η and ε are as follows.
η: Viscosity of solvent ε: Dielectric constant of solvent In the present invention, a mixed solution of ethanol and ion-exchanged water (50/50: volume standard, 25 ° C.) is used to determine the zeta potential. η is 0.993 mPa and ε is 52.0.

  The value of zeta potential is a function of the viscosity and dielectric constant of the solvent as described above, and is easily affected by the ions present in the solvent and the pH of the solvent, so it is measured in the range of pH 6.5 to 7.5. To do. The ion-exchanged water used for measuring the zeta potential preferably has a conductivity of 10 μS / cm or less, more preferably 1 μS / cm or less. In order to accurately measure the zeta potential of the electrostatic image developing toner, bubbles do not adhere to the surface when the electrostatic image developing toner is mixed with the measurement solvent, and the surface of the electrostatic image developing toner is sufficiently Solvents that can be wetted are used. If air bubbles adhere to the surface of the electrostatic image developing toner, a small amount of a neutral surfactant may be added to the solvent in order to improve the wettability between the electrostatic image developing toner and the solvent. The toner for developing an electrostatic charge image may be mixed with a solvent and then subjected to ultrasonic treatment.

  The toner for developing an electrostatic charge image of the present invention has little influence on the stability of image density even if a small amount of ionic substance remains on the surface or inside thereof, so that the elution of the ionic substance in the medium is small. preferable. Therefore, the toner for developing an electrostatic charge image of the present invention is dispersed in ion-exchanged water having a conductivity σ1 of 0 to 10 μS / cm so that the toner concentration is 6% by weight, heated and boiled for 10 minutes. Preferably, the conductivity σ2 of the water extract obtained by adding ion-exchanged water boiled separately to make up the original volume by replenishing the evaporated water and cooling to room temperature (a temperature of about 25 ° C.) Is 20 μS / cm or less, more preferably 10 μS / cm or less. Further, σ2−σ1 is preferably 10 μS / cm or less, and more preferably 6 μS / cm or less. When the electrical conductivity σ2 exceeds 20 μS / cm, the dependency of the charge amount on the environment becomes high, and image quality may be deteriorated due to environmental fluctuations (changes in temperature and humidity). Even when σ2−σ1 exceeds 10 μS / cm, the dependency of the charge amount on the environment is increased, and the image quality may be deteriorated due to environmental fluctuations (changes in temperature and humidity).

The toner for developing an electrostatic charge image of the present invention can be used as it is for developing an electrophotographic image as it is, but usually, in order to adjust the chargeability, fluidity, storage stability and the like of the toner for developing an electrostatic charge image, It is preferable to use after adhering or embedding fine particles (hereinafter referred to as external additives) having a smaller particle diameter than the colored resin particles on the surface of the colored resin particles.
Examples of the external additive include inorganic particles and organic resin particles that are usually used for the purpose of improving fluidity and chargeability. These particles added as an external additive have an average particle size smaller than that of the colored resin particles. Examples of inorganic particles include silica, aluminum oxide, titanium oxide, zinc oxide, and tin oxide. Examples of organic resin particles include methacrylic acid ester polymer particles, acrylic acid ester polymer particles, and styrene-methacrylic acid esters. Examples thereof include copolymer particles, styrene-acrylate copolymer particles, and core-shell particles in which the core is a styrene polymer and the shell is a methacrylic ester polymer. Of these, silica particles and titanium oxide particles are suitable, particles whose surface is subjected to a hydrophobic treatment are preferable, and silica particles subjected to a hydrophobic treatment are particularly preferable. The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight with respect to 100 parts by weight of the colored resin particles.

  The toner for developing an electrostatic charge image of the present invention is produced by a method for producing a toner such as a polymerization method (suspension polymerization method, emulsion polymerization aggregation method), a dissolution suspension method, or a pulverization method. It can be produced by controlling the amount and type of monomer.

  Next, a method for producing colored resin particles constituting the electrostatic image developing toner by suspension polymerization will be described. The colored resin particles constituting the toner for developing an electrostatic charge image of the present invention are prepared by adding a colorant, a charge control resin, a release agent, a chain transfer agent, and other additives to the polymerizable monomer that is a raw material of the binder resin. Is dissolved or dispersed, polymerized by adding a polymerization initiator in an aqueous dispersion medium containing a dispersion stabilizer, and as necessary, particles are associated with each other and / or additional polymerizable monomer is added. Then, after the polymerization, it can be produced by filtration, washing, dehydration and drying.

Examples of the polymerizable monomer include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized to become a binder resin component.
Monovinyl monomers include aromatic vinyl monomers such as styrene, vinyl toluene, and α-methylstyrene; (meth) acrylic acid; (meth) acrylic acid methyl, (meth) acrylic acid ethyl, (meth) acrylic acid (Meth) acrylic copolymers such as propyl, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate; mono, such as ethylene, propylene, butylene Olefin monomer; and the like.
Monovinyl monomers may be used alone or in combination of a plurality of monomers. Of these monovinyl monomers, an aromatic vinyl monomer alone or a combination of an aromatic vinyl monomer and a (meth) acrylic monomer is preferably used.

  When a crosslinkable monomer is used together with a monovinyl monomer, hot offset is effectively improved. A crosslinkable monomer is a monomer having two or more vinyl groups. Specific examples include divinylbenzene, divinylnaphthalene, ethylene glycol dimethacrylate, pentaerythritol triallyl ether, and trimethylolpropane triacrylate. These crosslinkable monomers can be used alone or in combination of two or more. The amount of the crosslinkable monomer is usually 10 parts by weight or less, preferably 0.1 to 2 parts by weight per 100 parts by weight of the monovinyl monomer.

Further, it is preferable to use a macromonomer together with the monovinyl monomer because the balance between the storage stability and the fixing property at a low temperature becomes good. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is usually an oligomer or polymer having a number average molecular weight of 1,000 to 30,000.
The macromonomer is preferably one that gives a polymer having a glass transition temperature higher than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer.
The amount of the macromonomer is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, and more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the monovinyl monomer.

  Examples of the polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), dimethyl 2,2′-azobis (2-methylpropionate), 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) propionamide, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvalero) Nitrile), azo compounds such as 2,2′-azobisisobutyronitrile; di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy- 2-ethylhexanoate, t-butyl peroxypivalate, di-isopropyl peroxydicarbonate, di-t-butyl pero Examples thereof include peroxides such as cyisophthalate and t-butylperoxyisobutyrate, etc. A redox initiator in which the above polymerization initiator and a reducing agent are combined may be used. , 2'-azobis (2-methylpropionate) is preferred.

  The amount of the polymerization initiator is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 15 parts by weight, and most preferably 0.5 to 100 parts by weight of the polymerizable monomer. -10 parts by weight. The polymerization initiator may be added in advance to the polymerizable monomer composition, but depending on the case, it may be added to the aqueous dispersion medium after droplet formation.

  Examples of the dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide. Metal hydroxides such as aluminum hydroxide, magnesium hydroxide and ferric hydroxide; water-soluble polymers such as polyvinyl alcohol, methylcellulose and gelatin; anionic surfactants, nonionic surfactants, Examples include amphoteric surfactants. The said dispersion stabilizer can be used 1 type or in combination of 2 or more types.

Among the above dispersion stabilizers, a dispersion stabilizer containing a metal compound, particularly a colloid of a sparingly water-soluble inorganic hydroxide, can narrow the particle size distribution of the colored resin particles. This is preferable because the remaining amount after washing is small and the image can be reproduced clearly.
The colloid of the poorly water-soluble metal hydroxide has a particle size distribution (Dp50) of not more than 0.5 μm with a cumulative number from the small particle size side in the number particle size distribution. It is preferable that the particle diameter (Dp90) of which the cumulative number from the small particle diameter side is 90% is 1 μm or less. When the particle size of the colloid is increased, the stability of the polymerization may be lost and the stability of the electrostatic image developing toner may be lowered.

  The amount of the dispersion stabilizer is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the polymerizable monomer. If the amount of the dispersion stabilizer is less than 0.1 parts by weight, it may be difficult to obtain sufficient polymerization stability, and polymer agglomerates may be easily formed. As a result, the particle size of the colored resin particles after polymerization becomes too fine, which may not be practical.

  In the polymerization, a molecular weight modifier is preferably used. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, 2,2,4,6,6-pentamethylheptane-4-thiol and the like. Among these, 2,2,4,6,6-pentamethylheptane-4-thiol is preferable. The molecular weight modifier can be added before or during polymerization. The amount of the molecular weight modifier is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the polymerizable monomer.

  There is no restriction | limiting in particular as a method of manufacturing the preferable core-shell type colored resin particle mentioned above, It can manufacture by a conventionally well-known method. Examples thereof include a spray drying method, an interfacial reaction method, an in situ polymerization method, and a phase separation method. Specifically, colored resin particles obtained by a pulverization method, a polymerization method, an association method, or a phase inversion emulsification method are used as core particles, and core-shell colored resin particles are obtained by coating a shell layer thereon. Among these production methods, an in situ polymerization method and a phase separation method are preferable from the viewpoint of production efficiency.

A method for producing capsule-type colored resin particles having a core-shell structure by an in situ polymerization method will be described below.
A capsule having a core-shell structure by adding a polymerization monomer (polymerization monomer for shell) and a polymerization initiator for forming a shell into an aqueous dispersion medium in which core particles are dispersed, and polymerizing the mixture. Mold colored resin particles can be obtained.
As a specific method of forming the shell, a method of continuously polymerizing by adding a polymerizable monomer for the shell to the reaction system of the polymerization reaction performed to obtain the core particles, or by using another reaction system. Examples of the method include preparing a core particle and adding a shell polymerizable monomer thereto to perform polymerization.
The polymerizable monomer for the shell may be added all at once in the reaction system, or may be added continuously or intermittently using a pump such as a plunger pump.

As the polymerizable monomer for shell, the glass transition temperature of styrene, acrylonitrile, methyl methacrylate or the like is 80 ° C. so that the glass transition temperature of the obtained polymer is 60 to 110 ° C., preferably 80 to 105 ° C. Monovinyl monomer that forms a polymer exceeding 10%, and hydrophilic polyfunctional polymerization such as triethylene glycol diacrylate, 1,6-hexanediol acrylate, EO adduct diacrylate of bisphenol A, trimethylolpropane triacrylate, etc. It is preferable to combine with a monomer.
The amount of the polymerizable monomer for the shell is usually 0.1 to 10 parts by weight with respect to 100 parts by weight of the monovinyl monomer used for obtaining the polymerizable monomer composition for the core, preferably Is 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight.

  The monovinyl monomer and the hydrophilic polyfunctional polymerizable monomer can be used alone or in combination of two or more. Moreover, it is preferable that the usage-amount of a monovinyl monomer and a hydrophilic polyfunctional polymerizable monomer is 1: 5-5: 1. If the use ratio of the monovinyl monomer and the hydrophilic polyfunctional polymerizable monomer is within this range, the storability and fluidity of the toner for developing an electrostatic image having the obtained colored resin particles as constituents are sufficient. In addition to the improvement, it is possible to reduce image quality degradation due to environmental fluctuation.

  When adding the polymerizable monomer for shell, it is preferable to add a water-soluble polymerization initiator because colored resin particles having a core-shell structure can be easily obtained. When a water-soluble polymerization initiator is added during the addition of the shell polymerizable monomer, the water-soluble polymerization initiator moves to the vicinity of the outer surface of the core particle to which the shell polymerizable monomer has migrated, and the core particle surface It is thought that it becomes easy to form a polymer (shell).

  Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) propionamide), 2,2′-azobis- An azo initiator such as (2-methyl-N- (1,1-bis (hydroxymethyl) 2-hydroxyethyl) propionamide) can be used. The amount of the water-soluble polymerization initiator is usually 0.1 to 50 parts by weight, preferably 1 to 30 parts by weight with respect to 100 parts by weight of the polymerizable monomer for shell.

  The temperature during the polymerization is preferably 50 ° C. or higher, more preferably 60 to 95 ° C. Moreover, reaction time becomes like this. Preferably it is 1 to 20 hours, More preferably, it is 2 to 10 hours. After completion of the polymerization, it is preferable to carry out filtration according to a conventional method, and to repeat washing and dehydrating operations several times as necessary and then drying.

When an aqueous dispersion of colored resin particles obtained by polymerization uses an inorganic compound such as an inorganic hydroxide as a dispersion stabilizer, an acid or alkali is added and the dispersion stabilizer is dissolved in water. It is preferable to remove. When a colloid of a poorly water-soluble inorganic hydroxide is used as the dispersion stabilizer, it is preferable to adjust the pH of the aqueous dispersion to 6.5 or less by adding an acid. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids such as formic acid and acetic acid can be used, but sulfuric acid is particularly preferable because of its high removal efficiency and low burden on production equipment. It is.
The method for filtering and dewatering the colored resin particles from the aqueous dispersion medium is not particularly limited. Examples thereof include a centrifugal filtration method, a vacuum filtration method, and a pressure filtration method. Of these, the centrifugal filtration method is preferred.

  The toner for developing an electrostatic charge image of the present invention can be obtained by mixing colored resin particles and external additives and, if necessary, other fine particles using a high-speed stirrer such as a Henschel mixer.

  Hereinafter, the present invention will be described in more detail with reference to examples. Needless to say, the scope of the present invention is not limited to such examples. In the following examples, parts and% represent parts by weight or% by weight unless otherwise specified.

(1) Particle size, particle size distribution and average circularity Into a container, 10 ml of ion-exchanged water is put in advance, 0.02 g of a surfactant (alkylbenzenesulfonic acid) is added as a dispersant, and colored resin particles 0 are further added. 0.02 g was added, and dispersion treatment was performed with an ultrasonic disperser at 60 W for 3 minutes. The toner concentration at the time of measurement is adjusted to 3,000 to 10,000 particles / μL, and 1,000 to 10,000 colored resin particles having an equivalent circle diameter of 1 μm or more are flow type particle image analysis manufactured by Sysmex Corporation. It measured using apparatus "FPIA-2100". From the measured values, the volume average particle size, the particle size distribution, that is, the ratio (Dv / Dp) between the volume average particle size and the number average particle size (Dp), and the average circularity were determined.

(2) Zeta potential The ethanol / ion-exchanged water (conductivity: 0.8 μS / cm) = volume ratio 50 / to 30 g of the electrostatic charge image developing toner after being left overnight in an environment of temperature 23 ° C. and humidity 50%. After adding 50 solvents to 100 g, the mixture was dispersed with an ultrasonic disperser for 5 minutes. Subsequently, the measurement was performed at a temperature of 25 ° C. using a zeta potential measuring device (Malvern, Zetasizer 3000HS).
The measured value immediately after the electrostatic charge image developing toner was dispersed in the solvent was defined as E1. Further, after the electrostatic charge image developing toner was allowed to stand at a temperature of 50 ° C. and a humidity of 80% for 2 weeks, the zeta potential was measured in the same manner as in E1, and this value was taken as E2.

(3) Conductivity 6 g of electrostatic image developing toner is dispersed in ion exchange water (σ1 is 0.8 μS / cm; pH = 7) to make 100 g. This is heated and boiled, and the boiled state is maintained for about 10 minutes (boiled for 10 minutes), and then ion-exchanged water (σ1 is 0.8 μS / cm; pH = 7) previously boiled for about 10 minutes. It replenished, it returned to the capacity | capacitance before boiling, it cooled to room temperature (about 22 degreeC), the electrical conductivity (sigma) 2 of the extract was measured, and (sigma) 2- (sigma) 1 was computed. The conductivity was measured using a conductivity meter “ES-12” (manufactured by Horiba, Ltd.).

(4) Base number The base number of the charge control resin was measured as follows.
About 2 g of the weighed charge control resin is put into a 200 ml Erlenmeyer flask, 80 ml of tetrahydrofuran (THF) is added and dissolved by stirring for 1 hour. Next, ultrasonic treatment was performed for 10 minutes in an ultrasonic cleaner with an output of 20 W. The solution was subjected to suction filtration using filter paper (filter paper for Kiriyama funnel GFP retention particles: 0.8 μm). The liquid in which the inside of the Erlenmeyer flask was washed with 10 ml of THF was also filtered with a filter paper. The filtrate was titrated with 0.01N perchloric acid MIBK solution. In addition, thymol blue was added as an indicator, and the discoloration point was set as the end point. The base number (mgHCl / g) of the charge control resin was determined from the amount of perchloric acid MIBK solution required for neutralization. The measurement was performed in a nitrogen atmosphere so as not to be affected by moisture and carbon dioxide in the air.

(5) Printing density The copy sheet is set in a commercially available non-magnetic one-component developing type printer (18 sheets), the electrostatic charge image developing toner is put in the developing device, and the electrostatic charge image development supplied on the developing roll is developed. Fixed at a point where the amount of toner used is 0.40 to 0.45 mg / cm ² and left to stand overnight in a (N / N) environment at a temperature of 23 ° C. and a humidity of 50%, and printing is performed at a print density of 5%. Solid printing was performed on 10 sheets, and the printing density was measured using a Macbeth reflection type image density measuring machine. Similarly, the electrostatic charge image developing toner was allowed to stand in an environment of a temperature of 50 ° C. and a humidity of 80% for 2 weeks, and then the electrostatic charge image developing toner was placed in a developing device and the print density was measured.

(6) Fog To the developing device of the printer used in (5), the toner for developing an electrostatic charge image that is left for 2 weeks in an environment of a temperature of 50 ° C. and a humidity of 80% is continuously printed at an initial concentration of 5%. White solid printing is performed for each sheet, the white solid printing is stopped halfway, and the toner in the non-image area on the developed photoreceptor is adhesive tape (Sumitomo 3M, Scotch Mending Tape 810-3-18). Adhered to. It was affixed to a new printing paper, and the whiteness (B) was measured with a whiteness meter (manufactured by Nippon Denshoku). At the same time, only the adhesive tape was attached to the printing paper, and the whiteness (A) was measured. The difference in whiteness (A−B) was defined as a fog value (%), and the number of continuous prints capable of maintaining an image quality having a numerical value of 1% or less was examined. The final evaluation was 10,000 sheets. What is described as 10,000 sheets or more in the table means that the image quality can be maintained even with 10,000 sheets.

(7) Preservability The toner for developing an electrostatic charge image is taken out after being left for 2 weeks in an environment with a temperature of 50 ° C. and a humidity of 80% or more. The toner for developing an electrostatic image is taken out from the inside and carefully transferred onto a sieve. This sieve is vibrated for 30 seconds using a powder measuring machine (manufactured by Hosokawa Micron: trade name “Powder Tester”), vibrated for 30 seconds, and developed for the electrostatic image remaining on the sieve. The weight of the toner was measured, and this was used as the weight of the aggregated toner. The ratio (% by weight) of the weight of the aggregated toner to the weight of the electrostatic charge image developing toner initially placed in the container was calculated. Each sample was measured three times, and the average value was used as an index of storage stability. In addition, the smaller the numerical value, the better the storage stability (% by weight) of the toner.

(8) Fluidity The electrostatic image developing toner was left in an environment of a temperature of 50 ° C. and a humidity of 80% or more for 2 weeks. Next, the electrostatic increasing development toner is overlaid with three types of sieves having openings of 150 μm, 75 μm, and 45 μm in this order from the top, and 4 g of a sample (toner) is placed on the topmost sieve. Was precisely weighed and placed. Subsequently, the three types of sieves were vibrated for 15 seconds under the condition of a vibration intensity of 4 using a powder measuring machine (manufactured by Hosokawa Micron Corporation: trade name “Powder Tester”), and remained on each sieve. Measure the toner mass. Each measured value is inserted into the following calculation formula to obtain a fluidity value. One sample was measured three times, and the average value was obtained.
Formula:
a = (mass of toner remaining on a sieve having an opening of 150 μm (g)) / 4 (g) × 100
b = (mass of toner remaining on a sieve having an opening of 75 μm (g)) / 4 (g) × 100 × 0.6
c = (mass of toner remaining on a sieve having an opening of 45 μm (g)) / 4 (g) × 100 × 0.2
Fluidity (%) = 100− (a + b + c)

(9) Fixing temperature of electrostatic charge image developing toner A fixing test was performed using a printer modified so that the temperature of the fixing roll portion of the printer used in (5) could be changed. The fixing test was performed by changing the temperature of the fixing roll of the modified printer by 5 ° C., measuring the fixing rate of the developer at each temperature, and determining the relationship between the temperature and the fixing rate. The fixing ratio was calculated from the ratio of the image density before and after the tape peeling operation in the black solid area on the test paper printed with the modified printer. That is, when the image density before tape peeling is before ID and the image density after tape peeling is after ID, the fixing ratio can be calculated from the following equation.
Fixing rate (%) = (after ID / before ID) × 100
The tape peeling operation means that an adhesive tape (Scotch Mending Tape 810-3-18 manufactured by Sumitomo 3M Co.) is applied to the measurement part of the test paper and pressed and adhered with a 500 g steel roller, and then at a constant speed. It means a series of operations for peeling the adhesive tape in the direction along the paper. The image density was measured using a reflection type image density measuring machine manufactured by Macbeth. In the fixing test, the lowest temperature of the fixing roll at which the fixing rate becomes 80% or more was defined as the toner fixing temperature.

(10) Hot offset occurrence temperature As with the measurement of the fixing temperature in (9) above, printing is performed by changing the temperature of the fixing roll by 5 ° C., and the toner remains on the fixing roll and the minimum temperature at which stains occur. Was defined as the hot offset occurrence temperature.

Production Example 1
Production of positive charge control resin composition A Polymerizability consisting of 83% styrene, 15% butyl acrylate and N, N-diethyl-N-methyl-N- (2-methacryloylethyl) ammonium P-toluenesulfonic acid unit 2% 100 parts of the monomer was put into a mixed solvent of 500 parts of toluene and 400 parts of methanol and reacted at 80 ° C. for 8 hours in the presence of 4 parts of 2,2′-azobisdimethylvaleronitrile. After completion of the reaction, the solvent was distilled off to obtain a quaternary ammonium base-containing copolymer (hereinafter referred to as positive charge control resin 1). The obtained positive charge control resin 1 had a weight average molecular weight of 1.2 × 10 ⁴ , a glass transition temperature of 67 ° C., and a base number of 0.3 mg HCl / g.
100 parts of the obtained positive charge control resin 1 was dispersed in 24 parts of toluene and 6 parts of methanol and mixed with a roll while cooling. When the positive charge control resin 1 is wound around the roll, 100 parts of a cyan pigment (CI Pigment Blue 15-3; manufactured by Clariant) is gradually added and mixed for 1 hour to obtain a positive charge control resin composition. A was produced. At this time, the roll interval is 1 mm in the initial stage, thereafter, the interval is gradually increased, and finally, the interval is increased to 3 mm, and an organic solvent (toluene / methanol = 4/1 mixed solvent) is mixed with the positive charge control resin composition A. Added several times while looking at the state. The used organic solvent was removed under reduced pressure after completion of mixing.

Production Example 2
Same as Production Example 1 except that a polymerizable monomer composed of 82% styrene, 11% butyl acrylate, and 7% N-benzyl-N, N-dimethyl-N- (2-methacryloyl) ethylammonium chloride was used. The quaternary ammonium base-containing copolymer (hereinafter referred to as positive charge control resin 2) was obtained. The obtained positive charge control resin 2 had a weight average molecular weight of 1.2 × 10 ⁴ , a glass transition temperature of 67 ° C., and a base number of 1.2 mg HCl / g.
For the obtained positive charge control resin 2, the same operation as in Production Example 1 was carried out to produce a charge control resin composition B.

Production Example 3
Same as Production Example 1 except that a polymerizable monomer composed of 85% styrene, 9% butyl acrylate, and 6% N-benzyl-N, N-dimethyl-N- (2-methacryloylethyl) ammonium chloride was used. The quaternary ammonium base-containing copolymer (hereinafter referred to as positive charge control resin 3) was obtained. The obtained positive charge control resin 3 had a weight average molecular weight of 2.3 × 10 ⁴ , a glass transition temperature of 67 ° C., and a base number of 2.0 mg HCl / g.

Example 1
An aqueous solution obtained by dissolving 9.8 parts of magnesium chloride (water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water and an aqueous solution obtained by dissolving 6.9 parts of sodium hydroxide (alkali metal hydroxide) in 50 parts of ion-exchanged water. The mixture was gradually added under stirring to prepare a magnesium hydroxide colloid (slightly water-soluble metal hydroxide colloid) dispersion. The particle size distribution of the colloid thus produced is expressed as the number average particle size D50 (50% cumulative value of the number particle size distribution) and D90 (90% cumulative value of the number particle size distribution). Measured by a manufacturer, model name “SALD2000A”). The measurement using the particle size distribution measuring device was performed under the conditions of refractive index = 1.55-0.20i, ultrasonic irradiation time = 5 minutes, and using 10% saline as a dispersion medium during droplet measurement.

Polymeric monomer composition for core consisting of 80.5 parts of styrene and 19.5 parts of butyl acrylate, 12 parts of positive charge control resin composition A obtained in Production Example 1, 3 parts of t-dodecyl mercaptan, penta Erythritol tetramyristate (hydroxyl value: 2.0 mg KOH / g) and polymethyl methacrylate macromonomer (manufactured by Toa Gosei Chemical Co., Ltd., trade name “AA6”) 0.8 parts are stirred, mixed and uniformly dispersed. A monomer composition for the core was obtained.
On the other hand, 2 parts of methyl methacrylate, 1 part of EO adduct diacrylate of bisphenol A (trade name “Light Acrylate BP-4EA”, manufactured by Kyoei Chemical Co., Ltd.) and 100 parts of water are mixed to form a polymerizable monomer for shell. An aqueous dispersion was obtained.

  The polymerizable monomer composition for the core was put into the magnesium hydroxide colloidal dispersion obtained as described above, and stirred until the droplets were stabilized. After the droplet is stabilized, 6 parts of t-butyl peroxy-2-ethylhexanoate (Nippon Yushi Co., Ltd., trade name “Perbutyl O”) is added, and then Ebara Milder rotating at 15,000 rpm (Made by Ebara Manufacturing Co., Ltd., trade name “MDN303V”) was subjected to shear stirring to form droplets of the monomer composition. The aqueous dispersion of the monomer mixture for core is put into a reactor equipped with a stirring blade, and the temperature is raised and controlled so that the temperature becomes constant at 90 ° C., so that the polymerization conversion reaches almost 100%. Water-soluble initiator dissolved in 65 parts of distilled water and a water-soluble initiator (trade name “VA-086”, manufactured by Wako Pure Chemical Industries, Ltd.) (2, 2) 0.2 parts of '-azobis (2-methyl-N- (2-hydroxyethyl) -propionamide) was placed in the reactor, the polymerization reaction was continued for 4 hours, the reaction was stopped, and the pH was 9.5. An aqueous dispersion of resin particles was obtained.

While stirring the aqueous dispersion of colored resin particles obtained as described above, sulfuric acid is added, the pH of the system is adjusted to 5 or less, acid washing (25 ° C., 10 minutes) is performed, and water is separated by filtration. After that, 500 parts of ion-exchanged water was newly added to form a slurry again and washed with water. Next, dehydration and water washing were repeated several times again, and the solid content was filtered and separated, followed by drying at 45 ° C. for 2 days and nights to obtain colored resin particles.
The dried colored resin particles were taken out, the measured volume average particle diameter (DV) was 6.4 μm, the volume average particle diameter (Dv) / number average particle diameter (Dp) was 1.20, and the average circularity was 0.973.

  In 100 parts of the colored resin particles obtained as described above, the degree of hydrophobicity is 65%, the number average particle diameter of primary particles is 0.5 part of silica fine particles of 0.5 parts, and the degree of hydrophobicity is 64%. Two parts of silica fine particles having a number average particle diameter of 40 nm were mixed and mixed with a Henschel mixer for 10 minutes at a rotation speed of 1,400 rpm to prepare an electrostatic image developing toner. The properties of the obtained electrostatic charge image developing toner and the evaluation of the image and the like were evaluated as described above. The results are shown in Table 1.

Example 2
As a polymerizable monomer for shell, obtained by mixing 1.5 parts of methyl methacrylate, 0.5 part of trimethylolpropane triacrylate and 100 parts of water, and performing fine dispersion treatment with an ultrasonic emulsifier. Except that was used, the same operation as in Example 1 was carried out to obtain an electrostatic charge image developing toner. The characteristics and images of the obtained electrostatic charge image developing toner were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
As a core monomer composition, a core polymerizable monomer composition comprising 80.5 parts of styrene and 19.5 parts of butyl acrylate, and 12 parts of a positive charge control resin composition B obtained in Production Example 2 , 3 parts of t-dodecyl mercaptan and 10 parts of pentaerythritol tetrastearate (hydroxyl value: 8.1 mg KOH / g) were stirred and mixed to obtain a monomer composition for shell. Except for using 2 parts of methacrylic acid and 100 parts of water, the same operation as in Example 1 was performed to obtain an electrostatic image developing toner. The characteristics and images of the obtained electrostatic charge image developing toner were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2
80 parts of styrene, 20 parts of n-butyl acrylate, 6 parts of cyan pigment (CI Pigment Blue 15-3; manufactured by Clariant), 12 parts of the positive charge control resin composition obtained in Production Example 3, 0 of divinylbenzene .6 parts, 1 part of t-dodecyl mercaptan, and 2 parts of Sazol wax (trade name “Paraflint Spray 30”, manufactured by Sazol) were dispersed with a bead mill at room temperature to obtain a uniform mixed solution. While stirring the mixed solution, 5 parts of a polymerization initiator “Perbutyl O” (trade name; manufactured by NOF Corporation) was added, and stirring was continued until the droplets became uniform. Obtained.

  On the other hand, 6.8 parts of sodium hydroxide (alkali hydroxide) were dissolved in 50 parts of ion-exchanged water in an aqueous solution obtained by dissolving 9.5 parts of magnesium chloride (water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water. The aqueous solution was gradually added with stirring to prepare a magnesium hydroxide colloid (slightly water-soluble metal hydroxide colloid) dispersion. The polymerizable monomer composition was charged into the colloid and stirred with high shear at 12000 rpm using a TK homomixer to granulate droplets of the polymerizable monomer mixture. The aqueous dispersion of the granulated polymerizable monomer mixture was put into a reactor equipped with a stirring blade, heated to 90 ° C. and controlled to be constant at a temperature of 90 ° C., polymerized for 8 hours, and then cooled. Thus, an aqueous dispersion of colored resin particles was obtained.

  While stirring the aqueous dispersion of the colored resin particles obtained as described above, the pH of the system is lowered to 4 or less with sulfuric acid, water is separated by filtration, and 500 parts of ion-exchanged water is newly added and re-added. Slurried and washed with water. Thereafter, again, dehydration and water washing were repeated several times, and the solid content was separated by filtration, followed by drying at 45 ° C. for two days and nights to obtain colored resin particles.

  The colored resin particles obtained by the above-described method were operated in the same manner as in Example 1 to obtain an electrostatic charge image developing toner. The characteristics and images of the obtained electrostatic charge image developing toner were evaluated in the same manner as in Example 1. The results are shown in Table 1.

From the evaluation results of the electrostatic image developing toner shown in Table 1, the following can be understood.
The zeta potential (E1) of the electrostatic charge image developing toner after being left overnight in an environment of a temperature of 23 ° C. and a humidity of 50%, and the electrostatic charge image developing toner in an environment of a temperature of 50 ° C. and a humidity of 80%. The electrostatic charge image developing toners of Comparative Examples 1 and 2 in which the difference from the zeta potential (E2) of the electrostatic charge image developing toner after standing for a week is outside the range defined in the present invention has a low print density. , Environmental durability, storage stability and fluidity are not good.
On the other hand, the electrostatic charge image developing toners of Examples 1 and 2 of the present invention have high printing density even after being left for 2 weeks in an environment of a temperature of 50 ° C. and a humidity of 80%. It has excellent fluidity.

Claims (3)

An electrostatic charge image developing toner containing colored resin particles comprising at least a binder resin and a colorant,
The volume average particle diameter (Dv) of the colored resin particles is 4 to 10 μm, the average circularity is 0.930 to 0.995,
The electrostatic charge image developing toner has a zeta potential (E1) of 5 to 35 mV after being left for a whole day and night in an environment of a temperature of 23 ° C. and a humidity of 50%. The toner for developing an electrostatic charge image, wherein the difference between the zeta potential (E2) and E1 of the toner for developing an electrostatic charge image after being left to stand for 2 weeks in a% environment is less than 5 mV. The charge control agent is contained so that the product of the addition weight part of the charge control agent with respect to 100 parts by weight of the binder resin and the base number (mgHCl / g) of the charge control agent is 7 or less. The positively chargeable electrostatic image developing toner described. The release agent contains a polyfunctional ester compound having a hydroxyl value (a) of 4 mgKOH / g or less, and the product of the added weight part (b) of the release agent and the hydroxyl value (a) with respect to 100 parts by weight of the binder resin. The toner for developing an electrostatic charge image according to claim 1, wherein the toner is 40 or less.