JP4019765B2 - Toner and image forming method - Google Patents

Description

【００８０】
表１のトナーの評価結果から、以下のことがわかる。本発明で規定する範囲より着色粒子の球形度が大きく、トナーの安息角が大きく、ゆるみ見掛け比重が小さい比較例１のトナーは、Ｈ／Ｈ環境及びＬ／Ｌ環境のいずれにおいても、耐久印字の途中で大量のカブリが発生した。本発明で規定する範囲よりコアシェル型着色粒子の体積平均粒径が小さく、安息角が大きく、ゆるみ見掛け比重が小さい比較例２のトナーは、Ｈ／Ｈ環境及びＬ／Ｌ環境のいずれにおいても、耐久印字後の印字濃度が低く、カブリも発生し易い。本発明で規定する範囲よりコアシェル型着色粒子の体積平均粒径が大きく、トナーの安息角が小さい比較例３のトナーは、Ｈ／Ｈ環境及びＬ／Ｌ環境のいずれにおいても、耐久印字後にカブリが発生し易く、解像度も悪い。本発明で規定する範囲より着色粒子の粒径分布が大きく、トナーの安息角が大きくゆるみ見掛け比重が小さい比較例４のトナーは、Ｈ／Ｈ環境及びＬ／Ｌ環境のいずれにおいても、耐久印字後の印字濃度が低く、カブリも発生し易い。これに対して、本発明の実施例１〜２のトナーは、２０，０００枚の耐久印字を行なった後でも、Ｈ／Ｈ環境及びＬ／Ｌ環境のいずれにおいても、印字濃度が高く、カブリが発生し難く、得られる画質の解像度も高いことが分かる。
【００８１】
【発明の効果】
本発明によれば、長期間に亘って高速で耐久印刷を行っても、転写性が良く、印字濃度の低下やカブリの発生がなく、且つ解像度の高い優れた画像を得ることができるトナー及びこのトナーと用いる画像形成方法が提供される。
【図面の簡単な説明】
【図１】 図１は本発明の一実施形態に係る画像形成装置の概略図である。
【図２】 図２は本発明の一実施形態に係るタンデム方式のカラー画像形成装置の概略図である。
【符号の説明】
１・・感光ドラム
２・・クリーニング装置
３・・帯電ロール
４・・レーザー光照射装置
５・・転写ロール
７・・現像ロール
８・・層厚規制ブレード
９・・供給ロール
１０・・トナー
１１・・現像装置
１３・・加熱ロール
１４・・加圧ロール
１５・・搬送ベルト[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a toner for developing an electrostatic latent image formed by electrophotography, electrostatic recording, or the like, and an image forming method using the toner. In particular, the present invention relates to a toner having good transferability even when performing durable printing at a high speed over a long period of time and causing no reduction in print density or fogging, and an image forming method using this toner.
[0002]
[Prior art]
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 onto a transfer material such as paper as necessary, and then fixed by various methods such as heating, pressurization, or solvent vapor. Further, the toner remaining without being transferred onto the photoreceptor is cleaned by a method such as blade cleaning or fur brush cleaning, and then the above-described image forming process is repeated.
[0003]
In recent years, there has been an increasing demand for such an image forming apparatus to be reduced in size, weight, and speed. In order to meet these demands for reduction in size and weight, a so-called cleaner-less method has been proposed in which an apparatus used in the cleaning method is omitted. In the cleanerless system, after passing through the charging process, toner is attracted to the developing device and collected by electrostatic force due to the difference between the surface potential of the charged photoreceptor and the developing bias. Therefore, since the collected toner can be used in the next image forming process, waste toner can be eliminated. In order to employ this cleaner-less method, the toner needs to have high fluidity.
Further, in order to respond to the increase in the speed of the image forming apparatus, the fluidity of the toner is required so that the toner follows the developing roll and the photosensitive member that rotate at high speed.
[0004]
In order to improve fluidity, it is known that it is effective to add inorganic fine particles such as hydrophobic silica fine particles as a fluidizing agent (hereinafter also referred to as “external additive”). The angle of repose is used as an index representing this fluidity. The angle of repose is said to be such that the smaller the value, the better the fluidity. However, if the fluidity is too good, the transferability is improved, but other toner characteristics such as fogging may be deteriorated.
JP-A-8-15904 discloses a magnetic one-component toner having an average particle diameter of 8 to 14 μm, an angle of repose of 30 to 45 °, and a corrected bulk specific gravity of 0.25 to 0.40 g / cc. JP-A No. 107771 discloses an electrostatic latent image developing toner satisfying specific conditions including an angle of repose of 28 to 38 ° and a volume average particle size of 3 to 10 μm. And an electrophotographic toner having a volume average particle size of 6.0 μm or more and an angle of repose of 35 ° or less. In an image forming apparatus, these toners may break when stress is applied in various states such as contact between toner particles, between a supply roll and a development roll, and between a development roll and a photoreceptor. As a result, there is a problem that the fluidity is lowered or the printing density is lowered.
[0005]
Japanese Patent Laid-Open No. 9-197713 discloses a developing device that develops a latent image formed on an image carrier in a non-contact manner with a one-component developer carried on the developer carrier, and has a volume average particle size of 9 μm and an angle of repose. Describes a spheroidizing toner having an angle of repose of 42 ° and an angle of repose change of 8 degrees or less.
However, as a result of studies by the present inventors, it has been found that when the above toner is used, when an image is formed at a high speed, the print density decreases or fog occurs.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a toner that has good transferability and does not cause a decrease in print density or fog even when durable printing is performed at high speed for a long period of time, and an image forming method using this toner. .
[0007]
[Means for Solving the Problems]
  As a result of intensive studies to achieve this object, the present inventor has found that the above object can be achieved by controlling several toner characteristics within a specific range. It came to be completed.
  Thus, according to the present invention, the volume average particle size (dv) is 8.5 to 10.0 μm, the particle size distribution (dv / dp) is 1.0 to 1.3, and the absolute maximum of the particles The average sphericity (Sc / Sr) obtained by dividing the area (Sc) of a circle having a diameter as a length by the actual projected area (Sr) of the particle is 1.0 to 1.3.Core shell typeProvided are a toner comprising colored particles and an external additive and having an angle of repose of 15 to 30 ° and a loose apparent specific gravity of 0.40 to 0.45 g / cc, and an image forming method using the toner. .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The toner of the present invention contains colored particles and an external additive.
The colored particles contain a binder resin, a colorant, and a charge control agent as essential components, and may contain a release agent, a magnetic material, and the like as necessary.
[0009]
Specific examples of the binder resin include conventionally widely used resins such as polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.
[0010]
As the colorant, any pigment and / or 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.
[0011]
When obtaining a full-color toner, a yellow colorant, a magenta colorant and a cyan colorant are usually used.
As the yellow colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 83, 90, 93, 97, 120, 138, 155, 180, 181, 185 and 186.
As the magenta colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Red 48, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251 and C.I. I. Pigment violet 19 and the like.
As the cyan colorant, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, 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 such a colorant is usually 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.
[0012]
As the charge control agent, a charge control agent conventionally used in toners can be used. For example, Bontron N-01 (manufactured by Orient Chemical Co., Ltd.), Nigrosine Base EX (manufactured by Orient Chemical Co., Ltd.), Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), T-77 (manufactured by Hodogaya Chemical Co., Ltd.), Bontron S -34 (manufactured by Orient Chemical Industries), Bontron E-81 (manufactured by Orient Chemical Industries), Bontron E-84 (manufactured by Orient Chemical Industries), COPY CHARGE NX (manufactured by Clariant), COPY CHARGE NEG (manufactured by Clariant) ) And the like, and in accordance with the description in JP-A-63-60458, JP-A-3-175456, JP-A-3-243594, JP-A-11-15192, etc. Quaternary ammonium (salt) group-containing copolymers, JP-A-1-217464, JP-A-3 A sulfonic acid (salt) group-containing copolymer according to the description of JP-A-15858 can be synthesized and used as a charge control agent (hereinafter referred to as “charge control resin”).
[0013]
Among these, it is preferable to use a charge control resin. The charge control resin is preferable because it has high compatibility with the binder resin, is colorless, and can obtain a toner having stable chargeability even in color continuous printing at high speed.
The glass transition temperature of the charge control resin is usually 40 to 80 ° C., preferably 45 to 75 ° C., more preferably 45 to 70 ° C. When the glass transition temperature is within this range, the storability and fixability of the toner can be improved in a balanced manner.
The amount of the charge control agent is usually 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.
[0014]
Examples of mold release agents 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, petrolactam, etc. And other modified waxes; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, dipentaerythritol hexamyristate; and the like.
These can be used alone or in combination of two or more.
[0015]
Of these, synthetic waxes, terminal-modified polyolefin waxes, petroleum waxes, polyfunctional ester compounds and the like are preferable. Among polyfunctional ester compounds, in the DSC curve measured by a differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is in the range of 30 to 200 ° C, preferably 40 to 160 ° C, more preferably 50 to 120 ° C. A polyfunctional ester compound such as pentaerythritol ester or dipentaerythritol ester having the same endothermic peak temperature in the range of 50 to 80 ° C. is particularly preferable from the viewpoint of fixing-releasability balance as a toner. Among polyfunctional ester compounds such as pentaerythritol ester having an endothermic peak temperature in the range of 30 to 200 ° C. and dipentaerythritol ester having the endothermic peak temperature in the range of 50 to 80 ° C., the molecular weight is 1000 or more. It is more preferable that 5 parts by weight or more dissolve at 25 ° C. with respect to 100 parts by weight of styrene, and that the acid value is 10 mg / KOH or less, since it has a remarkable effect on lowering the fixing temperature. The endothermic peak temperature is a value measured by ASTM D3418-82.
The amount of the release agent is usually 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin.
[0016]
Examples of the magnetic material include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite; metals such as iron, cobalt, and nickel or these metals and aluminum, cobalt, copper, lead, and magnesium. And alloys with metals such as tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof.
[0017]
  Used in the present inventionThe colored particles are particles of a so-called core-shell type (also referred to as “capsule type”) obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particle.TheIn core-shell type particles, the low softening point material in the interior (core layer) is encapsulated with a material having a higher softening point, so that it is possible to balance the reduction in fixing temperature and the prevention of aggregation during storage. Therefore, it is preferable.
[0018]
In the case of the core-shell type particles, the volume average particle size of the core particles is 8.5 to 10.0 μm, preferably 9.0 to 10.0 μm. The particle size distribution (dv / dp), which is the ratio of the volume average particle size (dv) to the number average particle size (dp), is preferably 1.0 to 1.3, preferably 1.0 to 1.2. More preferably.
[0019]
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 to the above ratio, both the storage stability of the toner and the fixing property at a low temperature can be achieved.
[0020]
The average thickness of the shell layer of the core-shell type particles is considered to be 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. Note that the core particles forming the core-shell type toner particles do not have to be entirely covered with the shell layer, and only a part of the surface of the core particles may be 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 in the production of the toner.
[0021]
The colored particles used in the present invention have a volume average particle diameter (dv) of 8.5 to 10.0 μm, preferably 9.0 to 10.0 μm. If the particle size is small, the fluidity is lowered, the transferability is lowered, the blur is generated, and the printing density is lowered. On the contrary, if it is large, fogging and toner scattering occur, and the resolution of the image decreases.
The particle size distribution (dv / dp), which is the ratio of the volume average particle size (dv) to the number average particle size (dp), is 1.0 to 1.3, more preferably 1.0 to 1.2. . When the particle size distribution is large, blurring occurs, and transferability, print density, and resolution decrease.
Said volume average particle diameter and particle size distribution can be made into the said range by classifying, for example.
The volume average particle size and particle size distribution of the colored particles can be measured using, for example, Multisizer (manufactured by Beckman Coulter, Inc.).
[0022]
The colored particles used in the present invention have an average sphericity (Sc / Sr) obtained by dividing the area (Sc) of a circle whose diameter is the absolute maximum length of the particle by the actual projected area (Sr) of the particle. 3, 1.0 to 1.2 is more preferable, and 1.0 to 1.15 is more preferable. When the average sphericity is larger than 1.3, the transferability may be lowered.
This average sphericity can be brought to the above range by using, for example, a phase inversion emulsification method, a dissolution suspension method, a polymerization method and the like.
Here, the average sphericity is obtained by taking an electron micrograph of colored particles, and using the image processing analysis device Luzex IID (manufactured by Nireco), the average area ratio of the particles to the frame area is 2% at maximum and the total number of processed particles Is an average value of the sphericity of 100 colored particles obtained.
[0023]
  ArrivalThe color particles are not particularly limited by the production method. For example, (1) in a thermoplastic resin as a binder resin component, a colorant, a charge control agent, a release agent and the like are melt-mixed and uniformly dispersed to obtain a composition, and then the composition is pulverized. Colored particles obtained by classification, (2) dissolving or suspending a colorant, a charge control agent, a release agent, etc. in a polymerizable monomer that is a binder resin raw material, and after adding a polymerization initiator, Colored particles obtained by dispersing in an aqueous dispersion medium containing a dispersion stabilizer, heating to a predetermined temperature to start suspension polymerization, and filtering, washing, dehydrating and drying after completion of the polymerization, (3) emulsification The primary particles of a binder resin containing a polar group obtained by polymerization are aggregated by adding a colorant and a charge control agent to form secondary particles, and further stirred at a temperature higher than the glass transition temperature of the binder resin. Coloring obtained by filtering and drying the associated particles (4) A hydrophilic group-containing resin is used as a binder resin, a colorant or the like is added thereto and dissolved in an organic solvent, and then the resin is neutralized to perform phase inversion. Examples thereof include colored particles obtained by subsequent drying. Among these, substantially spherical colored particles obtained by the suspension polymerization method (2) are preferable from the viewpoint of obtaining a toner that can cope with high resolution image quality and printing speed.
[0024]
Hereinafter, a method for producing toner by suspension polymerization will be described.
Examples of the polymerizable monomer for obtaining the binder resin include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized to become a binder resin component.
Specific examples of the monovinyl monomer include aromatic vinyl monomers such as styrene, vinyl toluene, and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, ( Meth) propyl acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth) acrylamide, etc. (Meth) acrylic acid derivatives; monoolefin monomers such as ethylene, propylene, butylene; 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 acid derivative is preferably used.
[0025]
When a crosslinkable monomer and polymer are used together with a monovinyl monomer, hot offset is effectively improved. A crosslinkable monomer is a monomer having two or more vinyl groups. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline, divinyl ether, and the like And a compound having 3 or more vinyl groups such as pentaerythritol triallyl ether and trimethylolpropane triacrylate. The crosslinkable polymer is a polymer having two or more vinyl groups in the polymer, and specifically, polyethylene, polypropylene, polyester, polyethylene glycol, etc. having two or more hydroxyl groups in the molecule. Mention may be made of esters obtained by condensation reaction of a polymer and an unsaturated carboxylic acid monomer such as acrylic acid or methacrylic acid. These crosslinkable monomers and crosslinkable polymers can be used alone or in combination of two or more. The amount used 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.
[0026]
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. When the number average molecular weight is in the above range, it is preferable because fixability and storage stability can be maintained without impairing the meltability of the macromonomer.
Examples of the polymerizable carbon-carbon unsaturated double bond at the end of the macromonomer molecular chain include an acryloyl group and a methacryloyl group, and a methacryloyl group is preferred from the viewpoint of ease of copolymerization.
[0027]
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.
Specific examples of the macromonomer used in the present invention include polymers obtained by polymerizing styrene, styrene derivatives, methacrylic acid esters, acrylic acid esters, acrylonitrile, methacrylonitrile, etc., alone or in combination of two or more thereof, and polysiloxane skeletons. Among them, a hydrophilic monomer, particularly a polymer obtained by polymerizing a methacrylic ester or an acrylic ester alone or in combination thereof is preferable.
When using a macromonomer, the amount is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, and more preferably 0.05 to 100 parts by weight of the monovinyl monomer. -1 part by weight. It is preferable that the amount of the macromonomer used be in the above range since the fixability is not lowered while maintaining the storage stability.
[0028]
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, metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; water-soluble polymers such as polyvinyl alcohol, methyl cellulose, gelatin; anionic surfactants, nonionic surfactants, amphoteric Surfactant etc. can be mentioned, These may be used independently or may combine 2 or more types.
Among these, dispersion stabilizers containing colloids of metal compounds, particularly poorly water-soluble metal hydroxides, can narrow the particle size distribution of the polymer particles, and the residual properties after washing of the dispersion stabilizers. This is preferable because the image can be reproduced clearly.
[0029]
The colloid of a hardly water-soluble metal hydroxide has a particle size distribution in which the cumulative number of particles calculated from the small particle size side is 50%, the particle size Dp50 is 0.5 μm or less and the 90% particle size Dp90 is 1 μm. The following is preferable. When the particle size of the colloid is increased, the stability of polymerization is lost and the storage stability of the toner is lowered.
[0030]
The dispersion stabilizer is usually used at a ratio of 0.1 to 20 parts by weight with respect to 100 parts by weight of the polymerizable monomer. It is preferable for this ratio to be in the above-mentioned range since sufficient polymerization stability is obtained, the formation of polymerization aggregates is suppressed, and a toner having a desired particle diameter can be obtained.
[0031]
As a polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) ) Propionamide), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile and other azo Compound: di-t-butyl peroxide, dicumyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t -Butyl peroxypivalate, di-isopropyl peroxydicarbonate, di-t-butyl peroxyisophthalate, It can be exemplified 1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, and the like peroxides such as t- butyl peroxy isobutyrate. Moreover, the redox initiator which combined these polymerization initiators and reducing agents can be mentioned.
[0032]
Among these, it is particularly preferable to select an oil-soluble polymerization initiator that is soluble in the polymerizable monomer to be used, and a water-soluble polymerization initiator can be used in combination with it, if necessary. The polymerization initiator is used in an amount of 0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, and more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer.
The polymerization initiator can be added to the polymerizable monomer composition in advance, but in the case of suspension polymerization, the suspension after the droplet formation step of the polymerizable monomer composition, emulsion polymerization In some cases, it can be added directly to the emulsion after completion of the emulsification step.
[0033]
In the polymerization, it is preferable to use a molecular weight modifier. 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; carbon tetrachloride, four And halogenated hydrocarbons such as carbon bromide; These molecular weight modifiers can be added before the start of polymerization or during the polymerization. The molecular weight modifier is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the polymerizable monomer.
[0034]
  Mentioned above,Asher typeColored particlesExamples of the method for producing the compound include a spray dry method, an interfacial reaction method, an in situ polymerization method, and a phase separation method. Specifically, obtained by pulverization method, polymerization method, association method or phase inversion emulsification methodColored particlesCore-shell type by coating it with a shell layerColored particlesIs obtained. Among these production methods, an in situ polymerization method and a phase separation method are preferable from the viewpoint of production efficiency.
[0035]
A method for producing a core-shell type toner by an in situ polymerization method will be described below.
A core-shell type toner is obtained 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. be able to.
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. For example, a method in which core particles are charged and a polymerizable monomer for shell is added thereto to perform polymerization stepwise can be exemplified.
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.
[0036]
As the polymerizable monomer for the shell, monomers forming a polymer having a glass transition temperature exceeding 80 ° C., such as styrene, acrylonitrile, and methyl methacrylate, can be used alone or in combination of two or more. .
[0037]
When adding the polymerizable monomer for shell, it is preferable to add a water-soluble polymerization initiator because a core-shell type toner is easily obtained. If a water-soluble polymerization initiator is added during the addition of the shell polymerizable monomer, the water-soluble polymerization initiator enters 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).
[0038]
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) ethyl) 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 shell monomer.
[0039]
The external additive is composed of silica fine particles (A) whose primary particles have a volume average particle diameter of 5 to 18 nm, preferably 7 to 16 nm. Preferred external additives include organic fine particles (C-1) or inorganic fine particles (C-) as fine particles (C) whose primary particles have a volume average particle diameter of 0.1 to 1 μm, preferably 0.2 to 0.8 μm. 2) is further contained. Further, the external additive may contain silica fine particles (B) whose primary particles have a volume average particle diameter of 20 to 60 nm, preferably 25 to 50 nm.
[0040]
When the volume average particle size of the silica fine particles (A) is small, the photoconductor is liable to cause filming. When the volume average particle diameter of the silica fine particles (B) is small, the photoconductor is likely to cause filming. On the other hand, when the silica fine particles (B) is large, the fluidity may be decreased and the silica particles may be easily lost. When the volume average particle size is small, the fine particles (C) have poor polishing properties, and when they are large, the fluidity may decrease.
[0041]
These silica fine particles (A) or silica fine particles (B) are preferably hydrophobized. Hydrophobized silica fine particles are generally commercially available, but can also be obtained by hydrophobizing with other silane coupling agents, higher fatty acid metal salts, silicone oils, and the like.
The hydrophobization method includes a method of dripping or spraying silicone oil as a treatment agent while stirring the fine particles at a high speed, and after adding and mixing the fine particles in an organic solvent in which the treatment agent is dissolved and stirred. And a method of heat treatment. In the former case, the treatment agent may be diluted with an organic solvent or the like.
The degree of hydrophobicity is such that the degree of hydrophobicity measured by the methanol method is 20 to 90%, preferably 40 to 80%. When the degree of hydrophobicity is small, it is easy to absorb moisture under high humidity, and when the degree of hydrophobicity is too high, sufficient polishing properties may not be obtained.
[0042]
The organic fine particles (C-1) usually have a glass transition temperature or melting point of 80 to 250 ° C., preferably 90 to 200 ° C., from the viewpoint of suppressing blocking between particles.
Examples of the compound constituting the organic fine particles include methyl methacrylate polymer and styrene-methyl methacrylate copolymer.
The average sphericity (Sc / Sr) obtained by dividing the area (Sc) of the circle having the absolute maximum length of the organic fine particle as the diameter by the actual projected area (Sr) of the particle is not particularly limited, but is usually 1-1. 3, preferably 1 to 1.2. If the average sphericity is large, the transferability may be lowered.
[0043]
The inorganic fine particles (C-2) are made conductive by surface treatment with silica, calcium carbonate, titanium oxide, aluminum oxide, zinc oxide, tin oxide, barium titanate, strontium titanate, and tin or antimony. And those that have been granted.
[0044]
The addition amount of the silica fine particles (A) is not particularly limited, but is usually 0.1 to 3 parts by weight, preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of the colored particles. If this amount is small, fluidity may be reduced and blurring may occur. Conversely, if the amount is large, fluidity may be high and fogging may occur.
The addition amount of the silica fine particles (B) is not particularly limited, but is usually 0.1 to 3 parts by weight, preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of the colored particles. If this amount is small, the polishing property may be reduced and filming may occur. Conversely, if the amount is large, the fluidity may be reduced and the film may be easily lost.
The addition amount of the fine particles (C) is not particularly limited, but is usually 0.1 to 2 parts by weight, preferably 0.2 to 1 part by weight with respect to 100 parts by weight of the colored particles. If the amount is less than this amount, filming may occur. On the other hand, if the amount is more than this amount, the fluidity may be lowered, and the film may be easily distorted.
[0045]
The toner of the present invention is produced by putting the above-described colored particles and the external additive in a mixer such as a Henschel mixer and stirring, thereby attaching or partially embedding the external additive to the surface of the colored particles. As a result, the toner can be excellent in chargeability, fluidity, storage stability, and the like.
[0046]
  The toner of the present invention has an angle of repose of 15 to 30 °, preferably 15 to 25 °. If the angle of repose is small, fogging and toner scattering occur. Conversely, if the angle of repose is large, blurring occurs, and transferability and print density decrease. Loose apparent specific gravity is 0.40~ 0.45 g / cc. When the loose apparent specific gravity is small, blurring occurs and the transferability and print density decrease. Conversely, when the apparent specific gravity is large, fogging and toner scattering occur. The angle of repose and loose apparent specific gravity are measured using, for example, a powder measuring machine (trade name “Powder Tester” manufactured by Hosokawa Micron Corporation).
[0047]
In the toner of the present invention, in order to make the angle of repose and loose apparent specific gravity within the above ranges, the volume average particle size, particle size distribution and average sphericity of the colored particles are set within the above ranges, and the external additive to be added is appropriately selected. And what is necessary is just to control using the above powder measuring machines.
[0048]
  Hereinafter, the image forming method of the present invention will be described in detail with reference to the drawings. The image forming method of the present invention forms an electrostatic latent image on the surface of a uniformly charged photoconductor, develops the electrostatic latent image into a toner image with toner, and transfers the obtained toner image to a transfer roll. The toner has a volume average particle size (dv) of 8.5 to 10.0 μm and a particle size distribution (dv / dp) of 1.0 to 1.3. The average sphericity (Sc / Sr) obtained by dividing the area (Sc) of the circle having the diameter of the absolute maximum length of the particle by the actual projected area (Sr) of the particle is 1.0 to 1.3.Core shell typeIt consists of colored particles and an external additive, has an angle of repose of 15 to 30 °, and a loose apparent specific gravity of 0.4.0Use a toner of ~ 0.45 g / cc.
[0049]
FIG. 1 is a diagram showing an example of an image forming apparatus to which the image forming method of the present invention can be applied. As shown in FIG. 1, the image forming apparatus has a photosensitive drum 1 as a photosensitive member, which is rotatably mounted in the direction of arrow A.
The photosensitive drum 1 has a photoconductive layer provided on a conductive support drum. Examples of the photoconductive layer include an organic photoconductor, a selenium photoconductor, a zinc oxide photoconductor, and an amorphous silicon photoconductor. , Preferably composed of an organic photoreceptor. Examples of the resin that binds the photoconductive layer to the conductive support drum include polyester resin, acrylic resin, polycarbonate resin, phenol resin, epoxy resin, hydrogenated polystyrene resin, and the like. From the viewpoint of sex.
[0050]
Around the photosensitive drum 1, a charging roll 3, a laser beam irradiation device 4 as an exposure device, a developing device 11, a transfer roll 5, and a cleaning device 2 are arranged along the circumferential direction.
Charging is to charge the surface of the photosensitive drum 1 positively or negatively by a charging member. In addition to the charging roll 3 shown in FIG. 1, there are a charging method using a charging member, a contact charging method for charging with a fur brush, a magnetic brush, a blade, etc., and a scorotron non-contact charging method using corona discharge. It is possible to replace them.
[0051]
Exposure is to irradiate a charged photosensitive member with light by an exposure apparatus. For example, a laser light irradiation apparatus 4 as shown in FIG. 1 is used as the exposure apparatus to emit light corresponding to an image signal. Irradiating the surface of the photosensitive drum, an electrostatic latent image can be formed on the surface of the charged drum. The laser light irradiation device 4 is composed of, for example, a laser irradiation device and an optical system lens. In addition, as an exposure apparatus, there is an LED irradiation apparatus.
[0052]
A developing device 11 shown in FIG. 1 is a developing device used in a one-component contact developing system, and has a developing roll 7 and a supply roll 9 in a casing 12 in which toner 10 is accommodated. The developing roll 7 is disposed so as to partially contact the photosensitive drum 1 and rotates in the direction B opposite to the photosensitive drum 1. The supply roll 9 comes into contact with the developing roll 7 and rotates in the same direction C as the developing roll 7, and supplies the toner 10 to the outer periphery of the developing roll 7. As another development method, there is a one-component non-contact development method.
[0053]
In the development, toner is supplied to the developing roll 7 by the supply roll 9, the toner layer thickness is adjusted by the layer thickness regulating blade 8 described above, and the toner on the developing roll is formed by the toner on the developing roll. In other words, a corresponding toner is attached to the electrostatic latent image. At this time, a bias is applied between the developing roll 7 and the photosensitive drum 1 so that the toner can be attached only to the light irradiation portion in the reverse development and the toner can be attached only to the light non-irradiation portion in the normal development. A voltage is applied.
[0054]
In the casing of the developing device, a supply roll may be disposed so as to be rotatable in the vicinity of the developing roll in order to make toner adhere well to the outer peripheral surface of the developing roll. It is preferable that a bias voltage is applied to the conductive shaft of the developing roll.
In the case of reversal development, a voltage having the same polarity as that of the electrostatic latent image on the photoreceptor is applied to the conductive shaft of the developing roll.
[0055]
  The transfer is to transfer a toner image on the surface of the photosensitive drum formed by the developing device 11 to a transfer material 6 such as paper by applying a transfer voltage having a polarity opposite to that of the toner by the transfer roll 5. At this time, the pressing force of the transfer roll against the photosensitive drum is 200 to 1000 g / cm.², Preferably 300-800 g / cm²It is. If the pressing force is small, the nip width may be narrowed and the transfer rate may decrease. Conversely, if the pressing force is large, the developed toner may adhere and white spots may occur..
[0056]
Fixing is fixing the toner image transferred to the transfer material 6 such as paper so that the toner image is not peeled off from the transfer material. Normally, heat fixing is performed by two rolls (a heating roll 13 and a pressure roll 14) as shown in FIG. 1, but another pressure roll is used instead of the heating roll 13. There are pressure fixing performed in this manner, flash fixing performed using a xenon lamp without using any roll, or solvent fixing performed using an organic solvent.
[0057]
Although it is not necessary when cleaning is performed at the same time as development, it is preferable to have a cleaning step for removing toner remaining on the surface of the photosensitive drum by the cleaning device 2 between the transfer roll and the charging member. Normally, a cleaning blade is used for this cleaning device. In addition, cleaning using a fur brush, a magnetic brush, a cleaning roll, static electricity or the like has also been proposed.
[0058]
In the image forming apparatus shown in FIG. 1, the surface of the photosensitive drum 1 is uniformly charged negatively by the charging roll 3, and then an electrostatic latent image is formed by the laser beam irradiation device 4. 11 develops the toner image.
Subsequently, the toner image on the photosensitive drum 1 is transferred to a transfer material 6 such as paper by a transfer roll 5 and fixed to the transfer material by two fixing rolls (a heating roll 13 and a pressure roll 14). If necessary, the untransferred toner remaining on the surface of the photosensitive drum is cleaned by the cleaning device 2 and then enters the next image forming cycle.
[0059]
The image forming apparatus shown in FIG. 1 is for monochrome use, but the image forming method of the present invention can also be applied to a color image forming apparatus such as a copying machine or a printer that forms a color image.
As a color image forming apparatus, a multi-development system in which a multi-color toner image is developed on a photosensitive member and transferred to a transfer material at a time, a single-color toner image is developed on the photosensitive member, and then a transfer material There is a multiple transfer system in which the transfer is repeated by the number of colors of the color toner. In addition, the multiple transfer system is a transfer drum system in which a transfer material is wound around a transfer drum and transfer is performed for each color, and primary transfer is performed for each color on an intermediate transfer member, and a multicolor image is formed on the intermediate transfer member. An intermediate transfer system that performs secondary transfer all at once after formation, a developing device is arranged in tandem around the photoconductor, the transfer material is sucked and conveyed by a transfer conveyance belt, and each color is sequentially transferred to the transfer material There is a tandem system. Among these, a tandem image forming apparatus that can perform image formation at high speed is preferable.
[0060]
FIG. 2 is a schematic diagram showing an example of a tandem color image forming apparatus to which the image forming method of the present invention can be applied. In the tandem color image forming apparatus, there are provided as many image forming portions as a set of the laser light irradiation device 4, the photosensitive drum 1, the developing device 11, and the cleaning device 2 as many as the number of colors of toner to be used. Each image forming unit is normally arranged in the order of yellow, magenta, cyan, and black along the conveying belt 15, and the image formed by each image forming unit is sucked and conveyed by the conveying belt. The transfer material 5 is sequentially superimposed and transferred onto the transfer material 7 and fixed. As described above, the transfer material is generally transported by a transport belt, but can be transported by being attracted to a transfer drum. In this case, the image forming units are sequentially arranged along the transfer drum.
Note that the alphabets Y, M, C, and K shown in FIG. 2 correspond to yellow, magenta, cyan, and black, which are toner colors of each image forming unit, respectively.
[0061]
According to the image forming method of the present invention, an image in which a cleaning defect does not occur on the photoreceptor or the charging roll can be obtained. Therefore, when applied to a color image forming method, a clear image can be obtained without toner mixing. .
[0062]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited only to these examples. Parts and% are based on weight unless otherwise specified.
In this example, evaluation was performed by the following method.
[0063]
1. Colored particle characteristics
(1) Average particle size and particle size distribution of toner
The volume average particle size (dv) and the particle size distribution of the colored particles, that is, the ratio (dv / dp) between the volume average particle size and the number average particle size (dp) were measured by Multisizer (manufactured by Beckman Coulter). The measurement with this multisizer was performed under the conditions of an aperture diameter: 100 μm, a medium: Isoton II, a concentration of 10%, and a number of measured particles: 100,000.
(2) Average sphericity
The average sphericity (Sc / Sr), which is a value obtained by dividing the area (Sc) of a circle having the diameter of the absolute maximum length of the particle by the actual projected area (Sr) of the particle, is obtained by taking an electron micrograph of each particle. Then, the image was measured with an image processing analyzer Luzex IID (manufactured by Nireco) under the conditions of the area ratio of particles with respect to the frame area: 2% at the maximum and the total number of processed particles: 100. Value.
[0064]
2. Toner characteristics
(1) Angle of repose
Using a powder measuring machine (trade name “Powder Tester PT-E” manufactured by Hosokawa Micron Co., Ltd.), place a sample funnel on the stand of this device, and stack a standard sieve with an opening of 250 μm, fix it, vibrate, and sample Through the funnel, the toner was dropped onto a circular table having a diameter of 8 cm to form a toner pile. The angle between the ridgeline of the mountain and the horizon was measured with a laser beam as the angle of repose. The amplitude of the vibration was adjusted to such an extent that the toner peak did not collapse, and the falling speed of the toner was adjusted.
(2) Loose apparent specific gravity
Using the powder measuring machine described above, a sample chute is placed on the stand of this apparatus, and a standard sieve having an opening of 250 μm is stacked, fixed, vibrated, dropped, and received in a prescribed container (cup 100 ml). Adjust the drop speed so that the cup reaches a heap in 20-30 seconds, and after completion, level the pile with a cutter, measure the weight of the powder, measure the weight per volume, and measure the loose apparent specific gravity did.
[0065]
3. Image quality evaluation
(1) Fog and print density
Copy paper is set in a commercially available non-magnetic one-component development type printer (trade name “Microline 24DX” manufactured by Oki Data Corporation), and the temperature is 10 ° C. and the humidity is 20% (L / L) using the printer described above. ) In the environment and at a temperature of 35 ° C and humidity of 80% (H / H), leave it all day and night, print continuously at 5% density, perform solid printing every 1,000 sheets, and stop printing halfway Then, the toner in the non-image area on the developed photosensitive member was peeled off with an adhesive tape (manufactured by Sumitomo 3M, Scotch Mending Tape 810-3-18), and this was attached to a new copy sheet. The whiteness (B%) of the printing paper with the adhesive tape attached is measured with a whiteness meter (manufactured by Nippon Denshoku Co., Ltd.). Similarly, the whiteness (A %). A difference ΔY between the whiteness (A%) and the whiteness (B%) was calculated, and this value was counted when the number exceeded 15%, and simultaneously the print density was measured. With respect to those in which continuous printing was performed up to 20,000 sheets and no fogging occurred, printing was terminated at 20,000 sheets and the print density was measured.
The print density was measured using a McBeth transmission image density measuring machine.
[0066]
(2) Resolution
At the same time as the black solid printing performed to evaluate the above-mentioned fog and print density, 2 dots and 4 dots lines and 2 dots and 4 dots white lines are printed, and whether the image quality can be reproduced optically. It observed with the microscope and evaluated on the following references | standards.
○: A 2-dot line and a 2-dot white line are reproduced.
Δ: The 2-dot line and 2-dot white line are not reproduced, but the 4-dot line and 4-dot white line are reproduced.
X: Neither 4-dot line nor 4-dot white line is reproduced.
[0067]
Example 1
Core consisting of 80 parts of styrene, 20 parts of n-butyl acrylate, 0.6 part of divinylbenzene and 0.25 part of polymethacrylate macromonomer (manufactured by Toa Gosei Chemical Co., Ltd., trade name “AA6”, Tg = 94 ° C.) Polymerizable monomer, 7 parts of carbon black (trade name “# 25B” manufactured by Mitsubishi Chemical Corporation), charge control resin (trade name “FCA-626-NS” manufactured by Fujikura Kasei Co., Ltd.); weight average molecular weight 24,000 2 parts of glass transition temperature 60 ° C.), 1 part of t-dodecyl mercaptan and 10 parts of dipentaerythritol hexamyristate were dispersed with a bead mill at room temperature to obtain a polymerizable monomer composition for core.
[0068]
On the other hand, to an aqueous solution in which 9.9 parts of magnesium chloride was dissolved in 250 parts of ion-exchanged water, an aqueous solution in which 6.0 parts of sodium hydroxide was dissolved in 50 parts of ion-exchanged water was gradually added with stirring. A colloidal dispersion was prepared. When the particle size distribution of the generated colloid was measured with a SALD particle size distribution measuring instrument (manufactured by Shimadzu Corporation), the particle size Dp50 with a cumulative total number of 50% calculated from the small particle size side was 0.36 μm. 90% Dp90 was 0.68 μm.
On the other hand, 2 parts of methyl methacrylate and 65 parts of water were finely dispersed with an ultrasonic emulsifier to obtain an aqueous dispersion of a polymerizable monomer for shell. The droplet of the polymerizable monomer for shell had a Dp90 of 1.6 μm.
[0069]
Into the magnesium hydroxide colloidal dispersion obtained as described above, the core polymerizable monomer composition is charged and stirred until the droplets are stabilized. Then, t-butylperoxy-2-ethylhexanoate ( After adding 5 parts of Nippon Oil & Fats, trade name “Perbutyl O”, then pass through Ebara Milder (trade name “MDN303V”, manufactured by Ebara Manufacturing Co., Ltd.) rotating at 15,000 rpm in a total residence time of 3 seconds. The dispersion liquid passed through was passed through the inner nozzle and returned and circulated into the original stirring tank at an ejection speed of 0.5 m / s to form droplets of the monomer composition. In addition, it adjusted so that the front-end | tip of an inner nozzle might be located 50 mm below the dispersion liquid level in a stirring tank, and the droplet was formed by the frequency | count of circulation 10 times. A cooling jacket was attached around the Ebara milder, and cooling water of about 15 ° C. was circulated.
[0070]
One part of sodium tetraborate decahydrate was added to the magnesium hydroxide colloidal dispersion in which droplets were formed by dispersing the core monomer composition, and the mixture was placed in a reactor equipped with a stirring blade. After the polymerization reaction was started at 0 ° C. and the polymerization conversion rate reached approximately 100%, a water-soluble initiator (trade name “VA-086, manufactured by Wako Pure Chemical Industries, Ltd.” was added to the aqueous dispersion of the polymerizable monomer for shell. "= 2,2'-azobis (2-methyl-N (2-hydroxyethyl) -propionamide)) was dissolved and added to the reactor. After the polymerization was continued for 4 hours, the reaction was stopped to obtain an aqueous dispersion of core-shell type colored particles.
While stirring the aqueous dispersion of the colored particles obtained above, sulfuric acid was added to adjust the pH to 4 or less, acid washing was performed, water was separated by filtration, and 500 parts of ion-exchanged water was newly added to reslurry. And washed with water. Then, again, dehydration and water washing were repeated several times, and the solid content was separated by filtration, followed by drying at 45 ° C. for 2 days and nights with a volume average particle diameter (dv) of 9.7 μm and a particle diameter. Core-shell colored particles having a distribution (dv / dp) of 1.10 and an average sphericity of 1.12 were obtained.
[0071]
To 100 parts of the obtained core-shell colored particles, 0.7 parts of silica having a hydrophobicity of 45% and a volume average particle size of 12 nm (trade name “R104” manufactured by Nippon Aerosil Co., Ltd.) as an external additive and a volume average particle size of 0 0.3 parts of .mu.m styrene-methyl methacrylate copolymer particles were added and mixed using a Henschel mixer for 10 minutes at a rotational speed of 1400 rpm to obtain a toner.
The obtained toner had an angle of repose of 16 ° and a loose apparent specific gravity of 0.43 g / cc. Further, the image quality of the obtained toner was evaluated, and the result is shown in Table 1.
[0072]
(Example 2)
  In Example 1, when preparing the magnesium hydroxide colloid, the example was changed except that the amount of magnesium chloride was changed from 9.9 to 10.6 parts and the amount of sodium hydroxide was changed from 6.0 to 6.4 parts. Same as 1Core shell typeColored particles and toner were obtained. Table 1 shows the characteristics of the obtained colored particles and toner, and the results of image quality evaluation.
[0073]
(Comparative Example 1)
100 parts of a styrene acrylate copolymer (softening point 145 ° C., glass transition point 64 ° C.), 7 parts of carbon black (trade name “# 25” manufactured by Mitsubishi Chemical Corporation), low molecular weight polypropylene (Sanyo Chemical Co., Ltd.) as a release agent "Viscol 550P") 1 part and charge control agent (Hodogaya Chemical Co., Ltd., trade name "Spiron Black TRH") 2 parts are blended to prepare a colored particle material, kneaded in a melt extruder and cooled. It was extruded on a belt in a plate shape and cooled and solidified.
Next, the cooled and solidified colored particle raw material is pulverized with a hammer mill, coarsely pulverized to a weight average particle size of about 300 μm, then pulverized with an air jet pulverizer, and the pulverized toner raw material is classified with a classifier. As a result, colored particles having a volume average particle size of 9.3 μm, a particle size distribution (dv / dp) of 1.23, and an average sphericity of 1.38 were obtained.
[0074]
To 100 parts of the obtained colored particles, 0.7 part of silica having a hydrophobization degree of 45% and a volume average particle diameter of 12 nm (trade name “R104” manufactured by Nippon Aerosil Co., Ltd.) as an external additive and a volume average particle diameter of 0.4 μm. Then, 0.3 part of styrene-methyl methacrylate copolymer particles were added and mixed for 10 minutes at 1400 rpm using a Henschel mixer to obtain a toner.
The obtained toner had an angle of repose of 41 ° and a loose apparent specific gravity of 0.38 g / cc. Further, as a result of evaluating the image quality of the obtained toner, a large amount of fog was generated during continuous printing. Therefore, printing was stopped and printing density and resolution were not evaluated.
[0075]
(Comparative Example 2)
  In Example 1, when producing the magnesium hydroxide colloid, the amount of magnesium chloride was changed from 9.9 to 12.9 parts, and the amount of sodium hydroxide was changed from 6.0 to 7.8 parts. Same as 1Core shell typeColored particles and toner were obtained. Table 1 shows the characteristics of the obtained colored particles and toner, and the results of image quality evaluation.
[0076]
(Comparative Example 3)
  In Example 1, when producing the magnesium hydroxide colloid, the amount of magnesium chloride was changed from 9.9 to 7.9 parts, and the amount of sodium hydroxide was changed from 6.0 to 4.8 parts. Same as 1Core shell typeColored particles and toner were obtained. Table 1 shows the characteristics of the obtained colored particles and toner, and the results of image quality evaluation.
[0077]
(Comparative Example 4)
Polymerization consisting of 80 parts of styrene, 20 parts of n-butyl acrylate, 0.6 part of divinylbenzene and 0.25 part of polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Co., Ltd., trade name “AA6”, Tg = 94 ° C.) Polymerizable monomer comprising carbonaceous monomer, carbon black (trade name “# 25”, manufactured by Mitsubishi Chemical Corporation), 6 parts of the above-described charge control resin, 1 part of t-dodecyl mercaptan, and 10 parts of dipentaerythritol hexamyristate. The monomer composition was heated to 70 ° C. and dissolved and dispersed. Next, this was mixed for 5 minutes while heating to 60 ° C. in a container equipped with a high shear mixing device (trade name “TK Homomixer” manufactured by Tokushu Kika Kogyo Co., Ltd.), and then azobisisobutyro 3 parts of nitrile were dissolved.
Separately, 2 parts of silica fine particles (manufactured by Nippon Aerosil Co., Ltd., trade name “# 200”) as a dispersant are added to 500 parts of ion-exchanged water, heated to 60 ° C., and then stirred under the above TK homomixer. The polymerizable monomer composition was added and further stirred at 8000 rpm for 1 hour. Thereafter, this mixed liquid was put into a reactor equipped with a stirring blade, and polymerization was completed while stirring to obtain an aqueous dispersion of colored particles. A sodium hydroxide solution is added to the obtained aqueous dispersion to dissolve the dispersant, and filtration and washing are repeated, followed by drying to obtain a volume average particle size (dv) of 9.0 μm, / dp) was 1.48 and an average sphericity of 1.12 was obtained.
[0078]
To 100 parts of the obtained colored particles, 0.2 part of silica having a hydrophobicity of 45% and a volume average particle size of 12 nm (trade name “R104” manufactured by Nippon Aerosil Co., Ltd.) is added as an external additive, and a Henschel mixer is used. For 10 minutes at a rotational speed of 1400 rpm to obtain a toner.
The obtained toner had an angle of repose of 43 ° and a loose apparent specific gravity of 0.37 g / cc. Further, the image quality of the obtained toner was evaluated, and the result is shown in Table 1.
[0079]
[Table 1]

[0080]
  From the toner evaluation results in Table 1, the following can be understood. The toner of Comparative Example 1 in which the sphericity of the colored particles is larger than the range specified in the present invention, the repose angle of the toner is large, and the loose apparent specific gravity is small is the durable print in both the H / H environment and the L / L environment. A lot of fog occurred on the way. From the scope defined by the present inventionCore shell typeThe toner of Comparative Example 2 in which the volume average particle diameter of the colored particles is small, the angle of repose is large, and the loose apparent specific gravity is small has a low print density after durable printing in both the H / H environment and the L / L environment. Fog is also likely to occur. From the scope defined by the present inventionCore shell typeIn the toner of Comparative Example 3 in which the volume average particle diameter of the colored particles is large and the angle of repose of the toner is small, fogging is likely to occur after durable printing in both the H / H environment and the L / L environment, and the resolution is poor. The toner of Comparative Example 4 in which the particle size distribution of the colored particles is larger than the range defined in the present invention, the angle of repose of the toner is large, and the apparent specific gravity is small is the durability printing in both the H / H environment and the L / L environment. Later printing density is low and fog is likely to occur. On the other hand, the toners of Examples 1 and 2 of the present invention have high print density and fog in both H / H and L / L environments even after 20,000 sheets of durable printing have been performed. It can be seen that the resolution of the obtained image quality is high.
[0081]
【The invention's effect】
According to the present invention, a toner capable of obtaining an excellent image with high transferability, no reduction in print density, no occurrence of fogging, and high resolution even when durable printing is performed at high speed for a long period of time. An image forming method for use with the toner is provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a tandem color image forming apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1. Photosensitive drum
2. Cleaning device
3. Charging roll
4. ・ Laser beam irradiation device
5. Transfer roller
7. Development roll
8. Layer thickness regulating blade
9. Supply roll
10. Toner
11. Development device
13. Heating roll
14. Pressurizing roll
15. Conveyor belt

Claims (3)

The area of a circle having a volume average particle size (dv) of 8.5 to 10.0 μm, a particle size distribution (dv / dp) of 1.0 to 1.3, and the absolute maximum length of the particles as a diameter It consists of core-shell type colored particles having an average sphericity (Sc / Sr) of 1.0 to 1.3 obtained by dividing (Sc) by the substantial projected area (Sr) of the particles and an external additive, and an angle of repose. Is a toner having a slack apparent specific gravity of 0.40 to 0.45 g / cc. The external additive contains silica fine particles (A) having a volume average particle size of primary particles of 5 to 18 nm and fine particles (C) having a volume average particle size of primary particles of 0.1 to 1.0 μm. The toner according to claim 1 . An electrostatic latent image is formed on the surface of the uniformly charged photoreceptor, the electrostatic latent image is developed into a toner image with toner, and the obtained toner image is transferred to a transfer material by a transfer roll. An image forming method for fixing, wherein the toner has a volume average particle size (dv) of 8.5 to 10.0 μm and a particle size distribution (dv / dp) of 1.0 to 1.3. A core-shell type having an average sphericity (Sc / Sr) of 1.0 to 1.3 obtained by dividing the area (Sc) of a circle having the diameter of the absolute maximum length of the particle by the actual projected area (Sr) of the particle An image forming method comprising colored particles and an external additive, an angle of repose of 15 to 30 °, and a loose apparent specific gravity of 0.40 to 0.45 g / cc.

Images