WO2014119482A1 - 重合トナーの製造方法 - Google Patents
重合トナーの製造方法 Download PDFInfo
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- WO2014119482A1 WO2014119482A1 PCT/JP2014/051491 JP2014051491W WO2014119482A1 WO 2014119482 A1 WO2014119482 A1 WO 2014119482A1 JP 2014051491 W JP2014051491 W JP 2014051491W WO 2014119482 A1 WO2014119482 A1 WO 2014119482A1
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- polymerizable monomer
- polymerization
- glass transition
- toner
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Classifications
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/0802—Preparation methods
- G03G9/0804—Preparation methods whereby the components are brought together in a liquid dispersing medium
- G03G9/0806—Preparation methods whereby the components are brought together in a liquid dispersing medium whereby chemical synthesis of at least one of the toner components takes place
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/0802—Preparation methods
- G03G9/0804—Preparation methods whereby the components are brought together in a liquid dispersing medium
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/087—Binders for toner particles
- G03G9/08784—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775
- G03G9/08797—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775 characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/09—Colouring agents for toner particles
- G03G9/0902—Inorganic compounds
- G03G9/0904—Carbon black
Definitions
- the present invention relates to an electrostatic image developing toner (polymerized toner) that can be used for developing an image forming apparatus using electrophotography such as a copying machine, a facsimile machine, and a printer.
- a method of forming a desired image by developing an electrostatic latent image with toner for developing an electrostatic image is widely used.
- an electrostatic latent image formed on a photoreceptor is developed with a toner in which other particles such as an external additive and a carrier are blended with colored resin particles as necessary, and then paper or OHP. After transferring to a recording material such as a sheet, the toner is fixed to obtain a printed matter.
- the toner is required to have the following various characteristics.
- a process that consumes a large amount of energy is a process of fixing the toner transferred onto a transfer material such as paper, that is, a so-called fixing process.
- a heat roll of 150 ° C. or higher is used for fixing, and the energy consumption of the fixing process can be reduced by lowering the heat roll temperature.
- it is necessary to increase the fixing temperature because the time for a transfer material such as paper to pass through the fixing roll is shortened. However, this has the problem of increasing energy consumption.
- the required toner characteristics include stable image characteristics (environmental stability) even in various environments (high temperature and high humidity environment and low temperature and low humidity environment), and repeated printing. Characteristics such as that the image does not deteriorate (print durability) can be given.
- toners are roughly classified into those produced by a pulverization method and a polymerization method.
- the pulverization method produces colored resin particles by a method of pulverizing and classifying solids of a colored resin obtained by a method of melt-kneading a binder resin and a colorant or a method of polymerizing a mixture containing a monomer and a colorant.
- the polymerization method is, for example, a suspension polymerization method in which droplets of a polymerizable monomer composition containing a polymerizable monomer and a colorant are formed, and the droplets are polymerized to produce colored resin particles.
- An emulsion polymerization aggregation method in which an emulsified polymerizable monomer is polymerized to obtain resin fine particles and aggregated with a colorant or the like to produce colored resin particles.
- the colored resin particles obtained by the pulverization method are indefinite, whereas the colored resin particles obtained by the polymerization method are almost spherical and have a small particle size and a sharp particle size distribution.
- a toner whose shape and particle size distribution are highly controlled is used, such as a toner obtained by a polymerization method (so-called polymerization method toner). It has become.
- a so-called core-shell structure in which a resin having a low glass transition point is coated with a resin having a high glass transition point has been proposed.
- Patent Document 1 in a method for producing toner particles by a suspension polymerization method, first, polymer particles having a glass transition temperature of 80 ° C. or less are formed as core components (nuclear particles), and then the core components are formed. By adding a monomer that forms a polymer having a glass transition temperature higher than that of the polymer, the polymerization reaction is continued, and a shell component coating layer having a high glass transition temperature is formed on the surface of the core component. It has been proposed to make a mold toner.
- Patent Document 2 discloses a method of producing a capsule toner for heat and pressure fixing, which includes a heat-meltable core material containing a thermoplastic resin and a colorant, and an outer shell provided so as to cover the surface of the core material.
- Encapsulated particles in which the core material and the hydrophilic outer shell material are dispersed in an aqueous dispersion medium and the hydrophilic outer shell material is coated on the core surface by an in situ polymerization method are used as precursor particles, and then the precursor At least a vinyl polymerizable monomer and a vinyl polymerizable initiator are added to an aqueous suspension of body particles and absorbed in the precursor particles, and then the monomer components in the precursor particles are polymerized.
- the toner of the above-mentioned patent document is insufficient to provide a toner for developing an electrostatic charge image having both heat-resistant storage stability and low-temperature fixability.
- An object of the present invention is to provide a method for producing a polymerized toner excellent in the balance between heat-resistant storage stability and low-temperature fixability.
- the present inventors have found that the above-mentioned problems can be solved by adding a part of the polymerizable monomer at a specific timing when producing a polymerized toner.
- the first-stage polymerizable monomer composition containing at least the first-stage polymerizable monomer and the colorant is suspended in the aqueous dispersion medium containing the dispersion stabilizer.
- a first method for producing a polymerized toner is provided.
- Tg 1 Tg 2 formula (1)
- Tg 1 represents the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer
- Tg 2 represents the second-stage polymerizable monomer polymerized. The glass transition temperature (° C.) of each polymer is shown.
- the first-stage polymerizable monomer composition containing at least the first-stage polymerizable monomer and the colorant is suspended in the aqueous dispersion medium containing the dispersion stabilizer.
- the polymerization conversion rate up to the second stage polymerization step is 95% or more, a polymerization initiator and a third stage polymerizable monomer satisfying the following formula (2) are further added to perform suspension polymerization.
- Tg 1 represents the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer
- Tg 2 represents the second-stage polymerizable monomer polymerized.
- Tg 1 + 2 ⁇ Tg 3 formula (2) (In the above formula (2), Tg 1 + 2 is the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer, and Tg 3 is the three (The glass transition temperature (° C.) of the polymer obtained by polymerizing the stage polymerizable monomer is shown respectively.)
- Tg 1 is preferably 5 ° C. to 250 ° C. higher than Tg 2 .
- Tg 3 is preferably 10 ° C. to 100 ° C. higher than Tg 1 + 2 .
- the glass transition of the polymer obtained by polymerizing the first-stage polymerizable monomer when the polymerization conversion rate in the first-stage polymerization process falls within a specific range.
- a second-stage polymerizable monomer constituting a polymer having a glass transition temperature Tg 2 lower than the temperature Tg 1 and further polymerizing a polymerized toner having an excellent balance between heat-resistant storage stability and low-temperature fixability can be obtained. Provided.
- a first-stage polymerizable monomer composition containing at least a first-stage polymerizable monomer and a colorant is placed in an aqueous dispersion medium containing a dispersion stabilizer.
- the polymerization conversion in the first polymerization step and the first-stage polymerization step is 20 to 80%
- a second-stage polymerizable monomer satisfying the following formula (1) is further added to perform suspension polymerization.
- Tg 1 Tg 2 formula (1)
- Tg 1 represents the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer
- Tg 2 represents the second-stage polymerizable monomer polymerized. The glass transition temperature (° C.) of each polymer is shown.
- the first-stage polymerizable monomer composition containing at least the first-stage polymerizable monomer and the colorant is placed in an aqueous dispersion medium containing a dispersion stabilizer.
- Tg 1 + 2 ⁇ Tg 3 formula (2) (In the above formula (2), Tg 1 + 2 is the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer, and Tg 3 is the three (The glass transition temperature (° C.) of the polymer obtained by polymerizing the stage polymerizable monomer is shown respectively.)
- the second production method is obtained by adding a third stage polymerization step to the first production method.
- the first manufacturing method will be described.
- paragraph polymerization process shall serve as description of a 2nd manufacturing method.
- the polymerized toner obtained by the present invention contains at least a binder resin obtained by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer, and colored resin particles containing a colorant.
- the colored resin particles used in the present invention are produced by a suspension polymerization method including the following process.
- Step of preparing the first-stage polymerizable monomer composition First, the first-stage polymerizable monomer, the colorant, and other additives such as a charge control agent added as necessary are mixed, and the first-stage polymerization is performed. Preparation of the functional monomer composition. For mixing at the time of preparing the first-stage polymerizable monomer composition, for example, a media type disperser is used.
- the polymerizable monomer means a monomer having a polymerizable functional group, and the polymerizable monomer is polymerized to become a binder resin. It is preferable to use a monovinyl monomer as the main component of the polymerizable monomer.
- Examples of the monovinyl monomer include styrene; styrene derivatives such as vinyl toluene and ⁇ -methylstyrene; acrylic acid and methacrylic acid; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, acrylic acid 2
- Acrylic esters such as ethylhexyl and dimethylaminoethyl acrylate
- methacrylic esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and dimethylaminoethyl methacrylate
- acrylonitrile And nitrile compounds such as methacrylonitrile
- amide compounds such as acrylamide and methacrylamide
- olefins such as ethylene, propylene, and butylene.
- the first-stage polymerizable monomer means a polymerizable monomer used for polymerization from the first-stage polymerization step (that is, the first polymerization step) among the polymerizable monomers used in the present invention. Refers to that.
- a crosslinkable polymerizable monomer means a monomer having two or more polymerizable functional groups.
- the crosslinkable polymerizable monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; alcohols having two or more hydroxyl groups such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; Ester compounds in which two or more carboxylic acids having carbon-carbon double bonds are ester-bonded; other divinyl compounds such as N, N-divinylaniline and divinyl ether; compounds having three or more vinyl groups; Can be mentioned.
- crosslinkable polymerizable monomers can be used alone or in combination of two or more.
- the crosslinkable polymerizable monomer is usually 0.1 to 3 parts by mass, preferably 0.3 to 2 parts per 100 parts by mass of the total amount of monovinyl monomers used in the present invention. It is desirable to use at a ratio of parts by mass.
- a macromonomer as a part of the polymerizable monomer because the balance between the storage stability (heat resistance) and the low-temperature fixability of the obtained toner is improved.
- the macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is a reactive oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000.
- the macromonomer is preferably one that gives a polymer having a higher Tg than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer (hereinafter sometimes referred to as “Tg”).
- Tg glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer
- the macromonomer is preferably used in an amount of 0.03 to 5 parts by weight, more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the total amount of monovinyl monomers used in the present invention.
- a colorant is used.
- black, cyan, yellow, and magenta colorants can be used.
- the black colorant for example, carbon black, titanium black, magnetic powder such as zinc zinc oxide and nickel iron oxide can be used.
- cyan colorant for example, a copper phthalocyanine compound, a derivative thereof, and an anthraquinone compound can be used. Specifically, C.I. I. Pigment blue 2, 3, 6, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17: 1, 60, and the like.
- yellow colorant examples include compounds such as monoazo pigments, azo pigments such as disazo pigments, and condensed polycyclic pigments.
- monoazo pigments examples include compounds such as monoazo pigments, azo pigments such as disazo pigments, and condensed polycyclic pigments.
- azo pigments such as disazo pigments
- condensed polycyclic pigments examples include compounds such as monoazo pigments, azo pigments such as disazo pigments, and condensed polycyclic pigments.
- magenta colorant examples include compounds such as monoazo pigments, azo pigments such as disazo pigments, and condensed polycyclic pigments.
- each colorant can be used alone or in combination of two or more.
- the amount of the colorant is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the total amount of monovinyl monomers used in the present invention.
- a release agent to the polymerizable monomer composition.
- Any releasing agent can be used without particular limitation as long as it is generally used as a releasing agent for toner.
- the release agent preferably contains at least one of ester wax and hydrocarbon wax.
- the melting point of the release agent measured by differential scanning calorimetry (DSC) is preferably 55 to 85 ° C, more preferably 60 to 75 ° C.
- the ester wax suitably used as a release agent in the present invention is more preferably a polyfunctional ester wax, for example, a pentaerythritol ester such as pentaerythritol tetrapalinate, pentaerythritol tetrabehenate, pentaerythritol tetrastearate, etc.
- hydrocarbon wax suitably used as a release agent in the present invention examples include polyethylene wax, polypropylene wax, Fischer-Tropsch wax, petroleum-based wax, etc. Among them, Fischer-Tropsch wax and petroleum-based wax are preferable, and petroleum-based wax. Is more preferable.
- the petroleum wax examples include paraffin wax, microstalline wax, and petrolatum, and paraffin wax is particularly preferable.
- the number average molecular weight of the hydrocarbon wax is preferably 300 to 800, more preferably 400 to 600. Further, the penetration of the hydrocarbon wax measured by JIS K2235 5.4 is preferably 1 to 10, and more preferably 2 to 7.
- the mold release agent for example, natural wax such as jojoba; mineral wax such as ozokerite;
- the mold release agent may be used in combination with one or more waxes as described above.
- the release agent is preferably used in an amount of 0.1 to 30 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the total amount of monovinyl monomers used in the present invention.
- a positively or negatively chargeable charge control agent can be used to improve the chargeability of the toner.
- the charge control agent is not particularly limited as long as it is generally used as a charge control agent for toner, but among charge control agents, the compatibility with the polymerizable monomer is high, and stable chargeability. (Charge stability) can be imparted to the toner particles, and therefore a positively or negatively chargeable charge control resin is preferred. Further, from the viewpoint of obtaining a positively chargeable toner, a positively chargeable charge control resin is preferred. More preferably used.
- positively chargeable charge control agents include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds and imidazole compounds, polyamine resins as charge control resins that are preferably used, and quaternary ammonium group-containing copolymers. , And quaternary ammonium base-containing copolymers.
- Negatively chargeable charge control agents include azo dyes containing metals such as Cr, Co, Al, and Fe, salicylic acid metal compounds and alkylsalicylic acid metal compounds, and sulfonic acid group containing charge control resins that are preferably used Examples thereof include a copolymer, a sulfonate group-containing copolymer, a carboxylic acid group-containing copolymer, and a carboxylic acid group-containing copolymer.
- the charge control agent is usually 0.01 to 10 parts by weight, preferably 0.03 to 8 parts by weight, based on 100 parts by weight of the total amount of monovinyl monomers used in the present invention. It is desirable to use it. If the addition amount of the charge control agent is less than 0.01 parts by mass, fog may occur. On the other hand, when the addition amount of the charge control agent exceeds 10 parts by mass, printing stains may occur.
- a molecular weight modifier when polymerizing a polymerizable monomer that is polymerized to become a binder resin.
- the molecular weight modifier is not particularly limited as long as it is generally used as a molecular weight modifier for toners.
- t-dodecyl mercaptan t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2, Mercaptans such as 4,6,6-pentamethylheptane-4-thiol; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N′-dimethyl-N, N′-diphenylthiuram disulfide, N, And thiuram disulfides such as N′-dioctadecyl-N, N′-diisopropylthiuram disulfide; These molecular weight modifiers may be used alone or in combination of two or more.
- the molecular weight modifier is usually used in a proportion of 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, with respect to 100 parts by mass of the total amount of monovinyl monomers used in the present invention. It is desirable.
- the first-stage polymerization is carried out by suspending the first-stage polymerizable monomer composition containing at least the first-stage polymerizable monomer and the colorant in an aqueous dispersion medium containing a dispersion stabilizer.
- a suspension in which droplets of the functional monomer composition are dispersed is obtained.
- the method of forming droplets is not particularly limited.
- an (inline type) emulsifying disperser (trade name: Milder, manufactured by Taiheiyo Kiko Co., Ltd.), an emulsifying disperser (trade name: Cavitron, manufactured by Taiheiyo Kiko Co., Ltd.), high-speed emulsifying dispersion
- an apparatus capable of strong stirring such as a machine (manufactured by PRIMIX Corporation, trade name: TK homomixer MARK II type).
- the polymerization initiator used in the first-stage polymerization step may be added after the first-stage polymerizable monomer composition is dispersed in the aqueous dispersion medium and before droplet formation. It may be added to the first-stage polymerizable monomer composition before being dispersed.
- 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), and 2,2′-azobisisobutyronitrile Azo compounds such as: di-t-butyl peroxide, benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-methylbutanoate, t-butyl peroxy-2 -Ethylbutanoate, t-hexylperoxy-2-ethylbutanoate, t-hexylperoxyisobutyrate, diisopropylperoxy Carbonate, di -t
- peroxyesters are preferable because non-aromatic peroxyesters, that is, peroxyesters having no aromatic ring, are preferable because initiator efficiency is good and the amount of remaining polymerizable monomers can be reduced. More preferred.
- the addition amount of the polymerization initiator used in the first stage polymerization step is preferably 0.1 to 20 parts by mass, more preferably 100 parts by mass of the total amount of monovinyl monomers used in the present invention.
- the amount is 0.3 to 15 parts by mass, and particularly preferably 1 to 10 parts by mass.
- the polymerization initiator used in the first stage polymerization step may also serve as the polymerization initiator in the second stage polymerization step. That is, in the second-stage polymerization step, a polymerization initiator is not particularly added, and the polymerization initiator added before the first-stage polymerization step may be involved in both the first-stage polymerization step and the second-stage polymerization step.
- the aqueous dispersion medium refers to a medium containing water as a main component.
- the aqueous dispersion medium preferably contains a dispersion stabilizer.
- 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; metals such as aluminum oxide and titanium oxide.
- the said dispersion stabilizer can be used 1 type or in combination of 2 or more types.
- inorganic compounds particularly colloids of poorly water-soluble metal hydroxides are preferred.
- a colloid of an inorganic compound, particularly a poorly water-soluble metal hydroxide the particle size distribution of the colored resin particles can be narrowed, and the residual amount of the dispersion stabilizer after washing can be reduced.
- the toner can reproduce the image clearly and has excellent environmental stability.
- Polymerization process In the manufacturing method of this invention, it has at least a 1st stage polymerization process and a 2nd stage polymerization process as a polymerization process.
- these two steps, and preferably the third-stage polymerization step that follows them will be described in order.
- the first-stage polymerization step in the present invention is a step of performing suspension polymerization in the presence of a polymerization initiator using a suspension containing at least a first-stage polymerizable monomer and a colorant. .
- Suspension polymerization begins primarily by heating the first stage polymerizable monomer composition.
- the heating temperature (polymerization temperature) of the first-stage polymerizable monomer composition is preferably 50 ° C. or higher, more preferably 60 to 95 ° C.
- the first-stage polymerizable monomer is defined by the glass transition temperature Tg 1 of a polymer obtained by polymerizing the first-stage polymerizable monomer.
- Tg glass transition temperature of the polymer
- the calculated Tg can be calculated by the following formulas (I) and (II).
- the glass transition temperature (K) of the homopolymer of the monomer is shown respectively.
- Tg 100 ° C.
- the glass transition temperature is calculated by calculating the glass transition temperature Tg 2 of the polymer obtained by polymerizing the second-stage polymerizable monomer, the first-stage polymerizable monomer and the second-stage polymerizable monomer being polymerized. for also the polymer glass transition temperature Tg 1 + 2 of comprising, a three-stage polymerizing the glass transition temperature Tg 3 of the polymer monomer is polymerized, can be carried out in the same manner.
- the second-stage polymerization step in the present invention comprises a second-stage polymerizable monomer that satisfies the following formula (1) when the polymerization conversion in the first-stage polymerization step is 20 to 80%. Further, it is a step of adding and performing suspension polymerization.
- Tg 1 is the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer
- Tg 2 is the weight obtained by polymerizing the second-stage polymerizable monomer.
- the glass transition temperature (° C.) of the coalescence is shown respectively.
- the second-stage polymerizable monomer refers to a polymerizable monomer used for suspension polymerization from the second-stage polymerization step among the polymerizable monomers used in the present invention. .
- the glass transition temperature on the outermost surface is higher than that at the center, and the low-temperature fixability is deteriorated.
- the polymerization conversion rate in the first-stage polymerization step is 20 to 80%, for example, when n-butyl acrylate is further added as the second-stage polymerizable monomer, acrylic acid is added at the end of the polymerization.
- the distribution of the styrene monomer units in the resulting polymer is expected to be more homogeneous than when the second-stage polymerization step is not performed. Since the distribution of the glass transition temperature in such a polymer becomes more uniform as compared with the case where the second-stage polymerization is not performed, it is considered that the low-temperature fixability is improved.
- the second-stage polymerizable monomer those similar to the first-stage polymerizable monomer can be used within the range of the glass transition temperature defined in the above formula (1).
- the second-stage polymerization constituting a polymer having a glass transition temperature lower than 60.5 ° C.
- a sex monomer may be used.
- the first-stage polymerizable monomer at least one of styrene and a styrene derivative having a relatively high glass transition temperature can be used.
- the second-stage polymerizable monomer at least one of acrylic acid ester and methacrylic acid ester having a relatively low glass transition temperature can be used.
- a polymerizable monomer having a homopolymer glass transition temperature of 100 ° C. or higher is used as the first-stage polymerizable monomer, and a homopolymer glass transition temperature of 10 ° C. is used as the second-stage polymerizable monomer.
- a polymerizable monomer having a temperature of 0 ° C. or lower can be used in combination.
- a part of the polymerizable monomer having a glass transition temperature of the homopolymer of 10 ° C. or lower may be used as the first-stage polymerizable monomer together with the polymerizable monomer having a glass transition temperature of the homopolymer of 100 ° C. or higher. Good.
- Examples of combinations of the first-stage polymerizable monomer and the second-stage polymerizable monomer include a combination using styrene as the first-stage polymerizable monomer and n-butyl acrylate as the second-stage polymerizable monomer.
- a combination using styrene as the first-stage polymerizable monomer, and n-butyl acrylate as the second-stage polymerizable monomer; and styrene and n-acrylate as the first-stage polymerizable monomer is preferred.
- Preferred is a combination of butyl and n-butyl acrylate as the second-stage polymerizable monomer.
- This step is started when the polymerization conversion rate in the first stage polymerization step becomes 20 to 80%.
- the first stage polymerization process is started when the polymerization conversion rate is less than 20%
- the second stage polymerization process is started without sufficiently proceeding with the first stage polymerization process.
- the obtained toner is inferior in low-temperature fixability.
- the first stage polymerization process is started after the polymerization conversion rate exceeds 80%, the glass transition temperature of the polymer existing on the toner surface is lowered because the start of the second stage polymerization process is too late. As a result, the obtained toner is inferior in heat resistant storage stability as shown in Comparative Example 3 described later.
- the second stage polymerization step is preferably started when the polymerization conversion rate in the first stage polymerization step is 30 to 75%, and is started when the polymerization conversion rate is 35 to 65%. Is more preferable, and it is even more preferable to start when the polymerization conversion reaches 45 to 60%.
- Tg 1 is preferably 5 ° C. to 250 ° C. higher than Tg 2 .
- Tg 2 is less than 5 ° C.
- Tg 1 and Tg 2 exceeds 250 ° C.
- the glass transition temperature on the surface of the toner particles becomes high and the low-temperature fixability may be lowered.
- Tg 1 it is more preferably higher 100 ⁇ 160 ° C. than Tg 2.
- the use ratio of the first-stage polymerizable monomer is too higher than the above, the resulting colored resin particles become too hard, and as a result, the low-temperature fixability may be poor.
- the usage-amount of a 2nd-stage polymerizable monomer is too higher than the above, as a result of the colored resin particle obtained becoming too soft, there exists a possibility that it may be inferior to heat-resistant storage stability.
- the charging ratio of the first-stage polymerizable monomer and the second-stage polymerizable monomer is substantially the same as the ratio of monomer units in the obtained polymer.
- the above-described polymerization initiator may be added as necessary. However, the polymerization may be continued using the polymerization initiator added in the first stage polymerization step as it is without adding a new polymerization initiator in the second stage polymerization step.
- the polymerization temperature in the second-stage polymerization step is preferably 50 ° C. or higher, more preferably 60 to 95 ° C., similarly to the polymerization temperature in the first-stage polymerization step.
- Third-stage polymerization step In the present invention, it is preferable to further perform a third-stage polymerization step after the second-stage polymerization step.
- the third-stage polymerization step is a third-stage polymerizable monomer that satisfies the polymerization initiator and the following formula (2) when the polymerization conversion rate up to the second-stage polymerization step is 95% or more. Is further added to the suspension polymerization.
- Tg 1 + 2 ⁇ Tg 3 formula (2) In the above formula (2), Tg 1 + 2 is the glass transition temperature (° C.) of the polymer obtained by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer, and Tg 3 is the third-stage polymerizable.
- the third-stage polymerizable monomer is a polymerizable monomer used for suspension polymerization from the third-stage polymerization step among the polymerizable monomers used in the present invention. Refers to the body.
- a polymer having a glass transition temperature Tg 3 higher than the glass transition temperature Tg 1 + 2 of the colored resin particles on the outside of the colored resin particles formed up to the second stage polymerization step. can be coated.
- the colored resin particles by coating the colored resin particles with a substance having a higher glass transition temperature, it is possible to balance low-temperature fixability and heat-resistant storage stability.
- the glass transition temperature Tg 1 + 2 of the polymer obtained by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer is an average glass of colored resin particles obtained by polymerization until the second-stage polymerization step. Represents the transition temperature.
- Tg 1 + 2 can be calculated by utilizing the additivity of the glass transition temperature of the polymer described above. For example, when 75 parts by mass of styrene and 15 parts by mass of n-butyl acrylate are used as the first-stage polymerizable monomer and 10 parts by mass of n-butyl acrylate are used as the second-stage polymerizable monomer, Tg 1 + 2 of a polymer obtained by polymerizing monomers is as follows.
- This step is started when the polymerization conversion rate up to the second stage polymerization step becomes 95% or more.
- the third stage polymerization process is started when the polymerization conversion rate is less than 95%, the second stage polymerization process is not sufficiently advanced, so the third stage polymerization process is started.
- the glass transition temperature of the polymer existing on the toner surface becomes too low, so that the obtained toner is inferior in heat resistant storage stability.
- the third stage polymerization step is preferably started when the polymerization conversion rate up to the second stage polymerization step is 96% or more, and is started when the polymerization conversion rate is 98% or more. Is more preferable.
- Tg 3 is preferably higher by 10 ° C. to 100 ° C. than Tg 1 + 2 .
- Tg 3 and Tg 1 + 2 are preferably higher by 10 ° C. to 100 ° C. than Tg 1 + 2 .
- Tg 3 is more preferably 30 to 90 ° C. higher than Tg 1 + 2 , and Tg 3 is more preferably 50 to 75 ° C. higher than Tg 1 + 2 .
- the third-stage polymerizable monomer is the same as the first-stage polymerizable monomer and the second-stage polymerizable monomer described above within the range of the glass transition temperature defined in the above formula (2).
- Examples of the polymerization initiator used for the polymerization of the third-stage polymerizable monomer include persulfate metal salts such as potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methyl-N- (2-hydroxy Water-soluble azo initiators such as ethyl) propionamide) and 2,2′-azobis- (2-methyl-N- (1,1-bis (hydroxymethyl) 2-hydroxyethyl) propionamide); Can be mentioned. These can be used alone or in combination of two or more.
- the amount of the polymerization initiator is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the third-stage polymerizable monomer.
- the polymerization temperature in the third stage polymerization step is preferably 50 ° C. or higher, more preferably 60 to 95 ° C.
- the polymerization reaction time is preferably 1 to 20 hours, and more preferably 2 to 15 hours.
- washing, filtration, dehydration, and drying steps For the aqueous dispersion of colored resin particles obtained by polymerization, filtration, removal of the dispersion stabilizer is removed according to a known method after the completion of the polymerization, washing, dehydration, and drying. The operation is preferably repeated several times as necessary.
- an inorganic compound when used as the dispersion stabilizer, it is preferable to dissolve and remove the dispersion stabilizer in water by adding an acid or alkali to the aqueous dispersion of the colored resin particles.
- an acid or alkali 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 colored resin particle aqueous dispersion to 6.5 or less by adding an acid.
- 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. Particularly, since the removal efficiency is large and the burden on the manufacturing equipment is small, Sulfuric acid is preferred.
- dehydration and filtration methods there are no particular limitations on the dehydration and filtration methods, and various known methods can be used. Examples thereof include a centrifugal filtration method, a vacuum filtration method, and a pressure filtration method. Also, the drying method is not particularly limited, and various methods can be used.
- Colored resin particles Colored resin particles are obtained by the suspension polymerization method described above. Hereinafter, the colored resin particles constituting the toner will be described.
- the volume average particle diameter (Dv) of the colored resin particles is preferably 4 to 12 ⁇ m, more preferably 5 to 10 ⁇ m.
- Dv volume average particle diameter
- the volume average particle diameter (Dv) of the colored resin particles is preferably 4 to 12 ⁇ m, more preferably 5 to 10 ⁇ m.
- Dv is less than 4 ⁇ m, the fluidity of the toner is lowered, the transferability may be deteriorated, and the image density may be lowered.
- Dv exceeds 12 ⁇ m the resolution of the image may decrease.
- the ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of the colored resin particles is preferably 1.0 to 1.3, and more preferably 1. 0 to 1.2. If Dv / Dn exceeds 1.3, transferability, image density, and resolution may decrease.
- the volume average particle diameter and the number average particle diameter of the colored resin particles can be measured using, for example, a particle size analyzer (trade name “Multisizer” manufactured by Beckman Coulter).
- the average circularity of the colored resin particles in the present invention is preferably 0.96 to 1.00, more preferably 0.97 to 1.00, and 0.98 to More preferably, it is 1.00.
- the average circularity of the colored resin particles is less than 0.96, the fine line reproducibility of printing may be deteriorated.
- the circularity is defined as a value obtained by dividing the circumference of a circle having the same projected area as the particle image by 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.
- the average circularity is determined by the colored resin particles. 1 is shown in the case of a perfect sphere, and the value becomes smaller as the surface shape of the colored resin particles becomes more complicated.
- the colored resin particles are mixed and stirred together with an external additive and subjected to an external addition treatment, whereby the external additive is attached to the surface of the colored resin particles, thereby producing a one-component toner ( Developer) is preferable.
- the one-component toner may be further mixed and stirred together with carrier particles to form a two-component developer.
- the stirrer that performs the external addition treatment is not particularly limited as long as the stirrer can attach the external additive to the surface of the colored resin particles.
- an FM mixer (trade name, manufactured by Nippon Coke Kogyo Co., Ltd.), Super Mixer (: trade name, manufactured by Kawada Seisakusho Co., Ltd.), Q mixer (: trade name, manufactured by Nihon Coke Kogyo Co., Ltd.), mechano-fusion system (: trade name, manufactured by Hosokawa Micron), and mechano mill (: trade name, manufactured by Okada Seiko Co., Ltd.)
- the external addition treatment can be performed using a stirrer capable of mixing and stirring. *
- External additives include inorganic fine particles made of silica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, calcium carbonate, calcium phosphate, cerium oxide, etc .; polymethyl methacrylate resin, silicone resin, melamine resin, etc. Organic fine particles; and the like.
- inorganic fine particles are preferable, and among inorganic fine particles, silica and titanium oxide are preferable, and fine particles made of silica are particularly preferable.
- These external additives can be used alone or in combination of two or more. Among these, it is preferable to use two or more types of silica having different particle diameters in combination.
- the external additive it is desirable to use the external additive at a ratio of usually 0.05 to 6 parts by mass, preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the colored resin particles.
- a ratio of usually 0.05 to 6 parts by mass preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the colored resin particles.
- the added amount of the external additive is less than 0.05 parts by mass, a transfer residue may occur. If the amount of the external additive exceeds 6 parts by mass, fog may occur.
- the toner of the present invention is a toner having an excellent balance between heat resistant storage stability and low temperature fixability.
- a heat resistant temperature determined by the following method can be mentioned. After a predetermined amount of toner is put in a container and sealed, the container is left under a predetermined temperature condition. After a predetermined time has passed, the toner is transferred from the container onto a sieve and set on a powder measuring machine (trade name: Powder Tester PT-X, manufactured by Hosokawa Micron). After vibrating for a predetermined time under the condition of a predetermined amplitude, the mass of the toner remaining on the sieve is measured, and this is defined as the mass of the aggregated toner. The maximum temperature at which the mass of the aggregated toner is equal to or less than a predetermined threshold is determined as the heat resistant temperature of the toner.
- the heat-resistant temperature is preferably 55 ° C or higher.
- the heat resistant temperature is less than 55 ° C., blocking is likely to occur when exposed to high heat, and the quality after transportation may not be guaranteed.
- the heat-resistant temperature is high and the heat-resistant storage stability is excellent, if the minimum fixing temperature is too high, a large amount of energy is required for fixing with the image forming apparatus, which is not environmentally preferable. .
- the first-stage polymerizable monomer composition is added to the magnesium hydroxide colloid dispersion obtained as described above, and further stirred, to which t-butylperoxy-2-ethylbutanoate ( 4.4 parts of Kayaku Akzo, trade name: Trigonox 27) were added.
- t-butylperoxy-2-ethylbutanoate 4.4 parts of Kayaku Akzo, trade name: Trigonox 27
- the glass transition temperature Tg 1 of the polymer obtained by polymerizing the first-stage polymerizable monomer is 60.5 ° C.
- the dispersion liquid formed into droplets was put into a reactor, and the temperature was raised to 90 ° C. to conduct a polymerization reaction (first stage polymerization step).
- first stage polymerization step 10 parts of n-butyl acrylate was added as a second-stage polymerizable monomer and reacted at 90 ° C. for 4 hours (second-stage polymerization step).
- the glass transition temperature Tg 2 of the polymer obtained by polymerizing the second-stage polymerizable monomer is ⁇ 55 ° C. Therefore, Tg 1 is 116 ° C. higher than Tg 2 .
- 2,2 ′ which is a polymerization initiator dissolved in 3.0 parts of methyl methacrylate as a third-stage polymerizable monomer and 30 parts of ion-exchanged water.
- -0.3 parts of azobis- (2-methyl-N- (1,1-bis (hydroxymethyl) 2-hydroxyethyl) propionamide) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086) was added.
- the reaction was continued at 90 ° C. for 3 hours (third stage polymerization step). Thereafter, the reaction was stopped, and an aqueous dispersion of colored resin particles having a core-shell structure was obtained.
- the glass transition temperature Tg1 + 2 of the polymer formed by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer is 43.7 ° C.
- the glass transition temperature Tg 3 of the polymer the third stage polymerizable monomer is polymerized is 105 ° C.. Therefore, Tg 3 is 61.3 ° C. higher than Tg 1 + 2 .
- the aqueous dispersion of colored resin particles obtained as described above was dropped with sulfuric acid while stirring at room temperature until the pH was 6.5 or lower. Subsequently, filtration separation was performed, 500 parts of ion-exchanged water was added to the obtained solid content to make a slurry again, and water washing treatment (washing, filtration, and dehydration) was repeated several times. Subsequently, filtration separation is performed, and the obtained solid content is put in a container of a dryer, and dried at 40 ° C. for 48 hours. Of 1.12 and an average circularity of 0.987 were obtained.
- Example 2 In Example 1, when preparing a magnesium hydroxide colloidal dispersion, 10.0 parts of magnesium chloride was changed to 9.6 parts, 7.0 parts of sodium hydroxide was changed to 6.7 parts, and the first stage Instead of using 75 parts of styrene and 15 parts of n-butyl acrylate as the polymerizable monomer, 75 parts of styrene and 5 parts of n-butyl acrylate are used, and n- Instead of using 10 parts of butyl acrylate, 20 parts of n-butyl acrylate was used, and the start of the second stage polymerization process was changed when the polymerization conversion in the first stage polymerization process reached 55%.
- Example 2 the polymerized toner of Example 2 was produced in the same manner as in Example 1.
- the glass transition temperature Tg 1 of the polymer obtained by polymerizing the first-stage polymerizable monomer is 80.0 ° C.
- the second-stage polymerizable monomer is polymerized.
- the glass transition temperature Tg 2 of the coalescence is ⁇ 55 ° C. Therefore, Tg 1 is 135 ° C. higher than Tg 2 .
- Table 1 The test results are shown in Table 1.
- Example 3 In Example 1, when preparing the magnesium hydroxide colloidal dispersion, 10.0 parts of magnesium chloride was changed to 9.4 parts, 7.0 parts of sodium hydroxide was changed to 6.6 parts, and the first stage Instead of using 75 parts of styrene and 15 parts of n-butyl acrylate as the polymerizable monomer, 75 parts of styrene are used, and 10 parts of n-butyl acrylate are used as the second-stage polymerizable monomer.
- Example 1 and A polymerized toner of Example 3 was produced by the same method.
- the glass transition temperature Tg 1 of the polymer obtained by polymerizing the first-stage polymerizable monomer is 100 ° C.
- the polymer obtained by polymerizing the second-stage polymerizable monomer is 100 ° C.
- the glass transition temperature Tg 2 is ⁇ 55 ° C. Therefore, Tg 1 is 155 ° C. higher than Tg 2 .
- the test results are shown in Table 1.
- Example 4 In Example 2, the start time of the second stage polymerization step was changed when the polymerization conversion rate in the first stage polymerization step reached 41%, in the same manner as in Example 2, A polymerized toner was produced. The test results are shown in Table 1.
- Example 5 In Example 2, the start time of the second stage polymerization step was changed when the polymerization conversion rate in the first stage polymerization step reached 71%, in the same manner as in Example 2, A polymerized toner was produced. The test results are shown in Table 1.
- Example 6 In Example 1, when preparing a magnesium hydroxide colloidal dispersion, 10.0 parts of magnesium chloride was changed to 9.6 parts, 7.0 parts of sodium hydroxide was changed to 6.7 parts, and the first stage As the polymerizable monomer, instead of using 75 parts of styrene and 15 parts of n-butyl acrylate, 79 parts of styrene and 1 part of 2-ethylhexyl acrylate were used, and n- Instead of using 10 parts of butyl acrylate, 20 parts of 2-ethylhexyl acrylate was used, and the start of the second stage polymerization process was changed when the polymerization conversion in the first stage polymerization process reached 52%, And, the start of the third stage polymerization step was changed when the polymerization conversion rate of the second stage polymerization step reached 99.5%, by the same method as in Example 1, Heavy To produce a toner.
- Example 6 the glass transition temperature Tg 1 of the polymer obtained by polymerizing the first-stage polymerizable monomer is 96.1 ° C., and the polymer obtained by polymerizing the second-stage polymerizable monomer.
- the glass transition temperature Tg 2 of the polymer is -70 ° C.. Therefore, Tg 1 is 166 ° C. higher than Tg 2 .
- the glass transition temperature Tg 1 + 2 of the polymer obtained by polymerizing the first-stage polymerizable monomer and the second-stage polymerizable monomer is 44.2 ° C., and the third-stage polymerizable monomer is polymerized.
- polymer glass transition temperature Tg 3 of comprising Te is 105 ° C.. Therefore, Tg 3 is 60.8 ° C. higher than Tg 1 + 2 .
- Table 1 The test results are shown in Table 1.
- Example 1 when preparing a magnesium hydroxide colloidal dispersion, 10.0 parts of magnesium chloride was changed to 10.4 parts, 7.0 parts of sodium hydroxide were changed to 7.3 parts, and the first stage The polymerization process is carried out by using 75 parts of styrene and 25 parts of n-butyl acrylate instead of using 75 parts of styrene and 15 parts of n-butyl acrylate as the first stage polymerizable monomer. Polymerization was carried out in the same manner as in Example 1 except that the above was not performed. Thereafter, the reaction was carried out at 90 ° C.
- Example 2 In Example 2, the start time of the second stage polymerization step was changed when the polymerization conversion rate in the first stage polymerization step reached 10%, and the same method as in Example 2 was followed. A polymerized toner was produced. The test results are shown in Table 1.
- Example 2 the start time of the second stage polymerization step was changed when the polymerization conversion rate in the first stage polymerization step reached 90%, by the same method as in Example 2, A polymerized toner was produced.
- the test results are shown in Table 1.
- Aperture diameter 100 ⁇ m
- medium Isoton II
- number of measured particles volume average particle diameter (Dv)
- the mass of the toner remaining on the sieve is measured, and this is regarded as the mass of the aggregated toner.
- the maximum temperature of 5% or less was defined as the heat resistant temperature, and the heat resistant storage stability was evaluated.
- the tape peeling operation means that an adhesive tape (manufactured by Sumitomo 3M Co., Ltd., trade name: Scotch Mending Tape 810-3-18) is applied to the measurement part (solid black area) of the test paper and pressed with a constant pressure. It is a series of operations for attaching and then peeling the adhesive tape in a direction along the paper at a constant speed. The image density was measured using a reflection densitometer (manufactured by Macbeth, trade name: RD918). In this fixing test, the minimum fixing roll temperature at which the fixing rate is 80% or more was defined as the minimum fixing temperature of the toner.
- Table 1 shows the measurement and evaluation results of the polymerized toners of Examples 1 to 6 and Comparative Examples 1 to 3.
- St is styrene
- BA is n-butyl acrylate
- 2-EHA is 2-ethylhexyl acrylate
- MMA is methyl methacrylate.
- the polymerized toner of Comparative Example 1 is a toner produced without performing the second-stage polymerization process in the present invention.
- the polymerized toner of Comparative Example 1 has a high heat resistance temperature of 56 ° C. Therefore, in the polymerized toner of Comparative Example 1, there is at least no problem with heat resistant storage stability.
- the toner of Comparative Example 1 has a minimum fixing temperature as high as 140 ° C. Therefore, it can be seen that the polymerized toner of Comparative Example 1 produced without performing the second-stage polymerization step in the present invention has a problem that the low-temperature fixability is inferior.
- the polymerized toner of Comparative Example 2 is a toner obtained by starting the second stage polymerization process when the polymerization conversion rate in the first stage polymerization process reaches 10%.
- the polymerized toner of Comparative Example 2 has a high heat resistant temperature of 56 ° C. Therefore, in the polymerized toner of Comparative Example 2, there is no problem with at least heat resistant storage stability.
- the polymerized toner of Comparative Example 2 has a minimum fixing temperature as high as 140 ° C. Therefore, it can be seen that the polymerized toner of Comparative Example 2 produced by starting the second-stage polymerization process when the polymerization conversion rate in the first-stage polymerization process is too low has a problem that the low-temperature fixability is poor.
- the polymerized toner of Comparative Example 3 is a toner obtained by starting the second stage polymerization process when the polymerization conversion rate of the first stage polymerization process reaches 90%.
- the polymerized toner of Comparative Example 3 has a minimum fixing temperature as low as 130 ° C. Therefore, in the polymerized toner of Comparative Example 3, there is no problem with at least low-temperature fixability.
- the polymerized toner of Comparative Example 3 has a heat resistant temperature as low as 51 ° C. Therefore, it can be seen that the polymerized toner of Comparative Example 3 produced by starting the second-stage polymerization process after the polymerization conversion rate in the first-stage polymerization process has become sufficiently high has a problem that the heat-resistant storage stability is poor.
- the first-stage polymerizable monomer was polymerized when the polymerization conversion rate in the first-stage polymerization process was 20 to 80%.
- the second-stage polymerizable monomer constituting the polymer having a glass transition temperature Tg 2 lower than the glass transition temperature Tg 1 of the polymer is further added.
- the polymerized toners of Examples 1 to 6 all have a heat resistant temperature of 55 ° C. or higher, and have excellent heat resistant storage stability.
- the polymerized toners of Examples 1 to 6 all have a minimum fixing temperature of 135 ° C. or less and have excellent low-temperature fixability.
- the polymerized toners of Examples 1 to 6 manufactured by the manufacturing method that satisfies the above-described conditions can achieve a well-balanced improvement in heat-resistant storage stability and low-temperature fixability, which were conventionally in a trade-off relationship. I understand.
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Abstract
Description
まず、電子写真方式の複写機、プリンター等においては、消費電力低減とともに高速印刷が要求されている。電子写真方式の中で、特に消費エネルギーの多い工程は、紙などの転写材上に転写されたトナーを定着する工程、いわゆる定着工程である。一般に、定着のために150℃以上の熱ロールが使用され、この熱ロール温度を下げることで定着工程のエネルギー消費を低減できる。また、高速印刷に対応するには、紙などの転写材が定着ロールを通過する時間が短くなるため、定着温度を上げる必要がある。しかしそのことはエネルギー消費を大きくさせてしまう問題がある。消費電力低減と高速印刷の要求の両立をはかるため、トナーの定着温度を下げることが不可欠になってきている。
その他に、要求されているトナーの特性としては、様々な環境下(高温高湿環境下及び低温低湿環境下)でも画像特性が安定していること(環境安定性)、印刷枚数を重ねても画像が劣化しないこと(印字耐久性)などの特性があげられる。
粉砕法は、結着樹脂と着色剤を溶融混練する方法、又はモノマーと着色剤を含有する混合物を重合させる方法により得た着色樹脂の固形物を粉砕し、分級する方法により着色樹脂粒子を製造する。
一方、重合法は、例えば重合性単量体と着色剤を含有する重合性単量体組成物の液滴を形成し、該液滴を重合させて着色樹脂粒子を製造する懸濁重合法や、乳化させた重合性単量体を重合し、樹脂微粒子を得て、着色剤等と凝集させ、着色樹脂粒子を製造する乳化重合凝集法などが挙げられる。粉砕法で得られる着色樹脂粒子が不定形であるのに対して、重合法で得られる着色樹脂粒子は形状が球形に近く、小粒径でシャープな粒径分布をもつ。特に、画像再現性や精細性等の画質を向上させる観点から、重合法により得られるトナー(いわゆる重合法トナー)のように、形状や粒径分布が高度に制御されたトナーが用いられるようになってきた。また、低温定着性と耐熱保存性を両立させるトナーの構造として、低ガラス転移点を有する樹脂を、高ガラス転移点を有する樹脂で被覆した、いわゆるコアシェル構造が提案されている。
Tg1>Tg2 式(1)
(上記式(1)中、Tg1は前記一段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg2は前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。)
Tg1>Tg2 式(1)
(上記式(1)中、Tg1は前記一段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg2は前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。)
Tg1+2<Tg3 式(2)
(上記式(2)中、Tg1+2は前記一段目重合性単量体及び前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg3は前記三段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。)
Tg1>Tg2 式(1)
(上記式(1)中、Tg1は前記一段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg2は前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。)
Tg1+2<Tg3 式(2)
(上記式(2)中、Tg1+2は前記一段目重合性単量体及び前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg3は前記三段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。)
本発明により得られる重合トナーは、少なくとも、一段目重合性単量体及び二段目重合性単量体が重合した結着樹脂、並びに着色剤を含む着色樹脂粒子を含有する。
以下、本発明に用いられる着色樹脂粒子の製造方法、当該製造方法により得られる着色樹脂粒子、当該着色樹脂粒子を用いた本発明の重合トナーの製造方法及び当該製造方法により得られる重合トナーについて、順に説明する。
本発明に用いられる着色樹脂粒子は、以下に示すプロセスを含む懸濁重合法により製造される。
まず、一段目重合性単量体、及び着色剤、さらに必要に応じて添加される帯電制御剤等のその他の添加物を混合し、一段目重合性単量体組成物の調製を行う。一段目重合性単量体組成物を調製する際の混合には、例えば、メディア型分散機を用いる。
本発明において一段目重合性単量体とは、本発明に使用される重合性単量体のうち、一段目重合工程(すなわち最初の重合工程)から重合に使用される重合性単量体のことを指す。
本発明では、架橋性の重合性単量体を、本発明に使用されるモノビニル単量体の総量100質量部に対して、通常、0.1~3質量部、好ましくは0.3~2質量部の割合で用いることが望ましい。
ブラック着色剤としては、例えば、カーボンブラック、チタンブラック、並びに酸化鉄亜鉛、及び酸化鉄ニッケル等の磁性粉等を用いることができる。
本発明において離型剤として好適に用いられるエステルワックスは、多官能エステルワックスがより好適であり、例えば、ペンタエリスリトールテトラパルミネート、ペンタエリスリトールテトラベヘネート、ペンタエリスリトールテトラステアレート等のペンタエリスリトールエステル化合物;ヘキサグリセリンテトラベヘネートテトラパルミネート、ヘキサグリセリンオクタベヘネート、ペンタグリセリンヘプタベヘネート、テトラグリセリンヘキサベヘネート、トリグリセリンペンタベヘネート、ジグリセリンテトラベヘネート、グリセリントリベヘネート等のグリセリンエステル化合物;ジペンタエリスリトールヘキサミリステート、ジペンタエリスリトールヘキサパルミネート等のジペンタエリスリトールエステル化合物;等が挙げられる。
炭化水素系ワックスの数平均分子量は、300~800であることが好ましく、400~600であることがより好ましい。また、JIS K2235 5.4で測定される炭化水素系ワックスの針入度は、1~10であることが好ましく、2~7であることがより好ましい。
離型剤は、上述した1種又は2種以上のワックスを組み合わせて用いてもよい。
上記離型剤は、本発明に使用されるモノビニル単量体の総量100質量部に対して、好ましくは0.1~30質量部用いられ、更に好ましくは1~20質量部用いられる。
帯電制御剤としては、一般にトナー用の帯電制御剤として用いられているものであれば、特に限定されないが、帯電制御剤の中でも、重合性単量体との相溶性が高く、安定した帯電性(帯電安定性)をトナー粒子に付与させることができることから、正帯電性又は負帯電性の帯電制御樹脂が好ましく、さらに、正帯電性トナーを得る観点からは、正帯電性の帯電制御樹脂がより好ましく用いられる。
正帯電性の帯電制御剤としては、ニグロシン染料、4級アンモニウム塩、トリアミノトリフェニルメタン化合物及びイミダゾール化合物、並びに、好ましく用いられる帯電制御樹脂としてのポリアミン樹脂、並びに4級アンモニウム基含有共重合体、及び4級アンモニウム塩基含有共重合体等が挙げられる。
負帯電性の帯電制御剤としては、Cr、Co、Al、及びFe等の金属を含有するアゾ染料、サリチル酸金属化合物及びアルキルサリチル酸金属化合物、並びに、好ましく用いられる帯電制御樹脂としてのスルホン酸基含有共重合体、スルホン酸塩基含有共重合体、カルボン酸基含有共重合体及びカルボン酸塩基含有共重合体等が挙げられる。
本発明では、帯電制御剤を、本発明に使用されるモノビニル単量体の総量100質量部に対して、通常、0.01~10質量部、好ましくは0.03~8質量部の割合で用いることが望ましい。帯電制御剤の添加量が、0.01質量部未満の場合にはカブリが発生することがある。一方、帯電制御剤の添加量が10質量部を超える場合には印字汚れが発生することがある。
分子量調整剤としては、一般にトナー用の分子量調整剤として用いられているものであれば、特に限定されず、例えば、t-ドデシルメルカプタン、n-ドデシルメルカプタン、n-オクチルメルカプタン、及び2,2,4,6,6-ペンタメチルヘプタン-4-チオール等のメルカプタン類;テトラメチルチウラムジスルフィド、テトラエチルチウラムジスルフィド、テトラブチルチウラムジスルフィド、N,N’-ジメチル-N,N’-ジフェニルチウラムジスルフィド、N,N’-ジオクタデシル-N,N’-ジイソプロピルチウラムジスルフィド等のチウラムジスルフィド類;等が挙げられる。これらの分子量調整剤は、それぞれ単独で、あるいは2種以上を組み合わせて用いてもよい。
本発明では、分子量調整剤を、本発明に使用されるモノビニル単量体の総量100質量部に対して、通常0.01~10質量部、好ましくは0.1~5質量部の割合で用いることが望ましい。
本工程では、少なくとも一段目重合性単量体及び着色剤を含有する一段目重合性単量体組成物を、分散安定化剤を含有する水系分散媒体中に懸濁させることにより、一段目重合性単量体組成物の液滴が分散した懸濁液を得る。液滴形成の方法は特に限定されないが、例えば、(インライン型)乳化分散機(太平洋機工社製、商品名:マイルダー)、乳化分散機(太平洋機工社製、商品名:キャビトロン)、高速乳化分散機(プライミクス株式会社製、商品名:T.K.ホモミクサー MARK II型)等の強攪拌が可能な装置を用いて行う。
重合開始剤としては、過硫酸カリウム、及び過硫酸アンモニウム等の過硫酸塩:4,4’-アゾビス(4-シアノバレリック酸)、2,2’-アゾビス(2-メチル-N-(2-ヒドロキシエチル)プロピオンアミド)、2,2’-アゾビス(2-アミジノプロパン)ジヒドロクロライド、2,2’-アゾビス(2,4-ジメチルバレロニトリル)、及び2,2’-アゾビスイソブチロニトリル等のアゾ化合物;ジ-t-ブチルパーオキシド、ベンゾイルパーオキシド、t-ブチルパーオキシ-2-エチルヘキサノエート、t-ブチルパーオキシ-2-メチルブタノエート、t-ブチルパーオキシ-2-エチルブタノエート、t-ヘキシルパーオキシ-2-エチルブタノエート、t-ヘキシルパーオキシイソブチレート、ジイソプロピルパーオキシジカーボネート、ジ-t-ブチルパーオキシオキシイソフタレート、及びt-ブチルパーオキシイソブチレート等の有機過酸化物等が挙げられる。これらは、それぞれ単独で、あるいは2種以上組み合わせて用いることができる。これらの中で、残留重合性単量体を少なくすることができ、印字耐久性も優れることから、有機過酸化物を用いるのが好ましい。
なお、一段目重合工程に使用される重合開始剤は、二段目重合工程における重合開始剤を兼ねてもよい。すなわち、二段目重合工程において特に重合開始剤を添加せず、一段目重合工程前に添加された重合開始剤を、一段目重合工程及び二段目重合工程の両方に関与させてもよい。
本発明の製造方法においては、重合工程として、少なくとも一段目重合工程及び二段目重合工程を有する。以下、これら2つの工程、及び好ましくはこれらに続く三段目の重合工程について、順に説明する。
本発明における一段目重合工程は、少なくとも一段目重合性単量体と着色剤とを含有する懸濁液を用いて、重合開始剤の存在下で懸濁重合を行う工程である。
懸濁重合は、主に、一段目重合性単量体組成物を加熱することにより始まる。一段目重合性単量体組成物の加熱温度(重合温度)は、好ましくは50℃以上であり、更に好ましくは60~95℃である。
ところで、重合体のガラス転移温度(以下、Tgと称する場合がある。)は、絶対温度での加成性が成り立つことが知られている。したがって、一段目重合性単量体として、2種類以上のモノマーを用いた場合には、以下の式(I)及び式(II)により計算Tgを算出することができる。
計算Tg(K)=(MA+MB+MC+・・・)/[(MA/TgA)+(MB/TgB)+(MC/TgC)+・・・] 式(I)
計算Tg(℃)=計算Tg(K)-273 式(II)
(なお、上記式(I)中、MA、MB、MC、・・・は、各モノマーの添加量(質量部)を、TgA、TgB、TgC、・・・は、各モノマーのホモポリマーのガラス転移温度(K)を、それぞれ示す。)
例えば、一段目重合性単量体としてスチレン(ホモポリマーのTg=100℃)75質量部とアクリル酸n-ブチル(ホモポリマーのTg=-55℃)15質量部を用いる場合には、これら単量体が重合してなる重合体のTg1は、以下の通りである。
Tg1=[75(質量部)+15(質量部)]/[{75(質量部)/(100+273(K))}+{15(質量部)/(-55+273(K))}]
=90/(0.201+0.0688)
=333.5(K)=60.5(℃)
このようなガラス転移温度の計算は、二段目重合性単量体が重合してなる重合体のガラス転移温度Tg2、一段目重合性単量体及び二段目重合性単量体が重合してなる重合体のガラス転移温度Tg1+2、三段目重合性単量体が重合してなる重合体のガラス転移温度Tg3についても、同様に行うことができる。
本発明における二段目重合工程は、一段目重合工程における重合転化率が20~80%となったときに、下記式(1)を満たす二段目重合性単量体をさらに添加して懸濁重合を行う工程である。
Tg1>Tg2 式(1)
上記式(1)中、Tg1は一段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg2は二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。
本発明において二段目重合性単量体とは、本発明に使用される重合性単量体のうち、二段目重合工程から懸濁重合に使用される重合性単量体のことを指す。
しかし、そのような従来の予測に反し、本発明者らは、一段目重合工程において重合させた重合体を、当該重合体よりも低いガラス転移温度を有する重合体により被覆することによって、従来よりも優れた低温定着性が得られることを見出し、多段重合による重合トナーの製造方法を完成させた。
しかし、例えば、一段目重合性単量体としてスチレン及びアクリル酸n-ブチルを混合したものを用いた場合、アクリル酸n-ブチルの方がその反応性の高さゆえに先に重合に費やされ、重合の終盤においてスチレンが多く残る結果、スチレン単量体単位の割合は、重合体粒子の中心部よりも重合体粒子の最表面の方が高くなると推測される。このような重合体においては、最表面のガラス転移温度が中心部よりも高くなり、低温定着性が悪くなると予測される。
一方、一段目重合工程の重合転化率が20~80%のときに、例えば、二段目重合性単量体としてアクリル酸n-ブチルをさらに添加した場合には、重合の終盤においてもアクリル酸n-ブチルが比較的多く残る結果、得られる重合体におけるスチレン単量体単位の分布は、二段目重合工程を行わない場合と比較して、より均質になると予想される。このような重合体におけるガラス転移温度の分布は、二段目重合を行わない場合と比較してより均一になるため、低温定着性が向上すると考えられる。
また、本発明においては、一段目重合性単量体としてホモポリマーのガラス転移温度が100℃以上の重合性単量体を、二段目重合性単量体としてホモポリマーのガラス転移温度が10℃以下となる重合性単量体を組み合わせて用いることができる。ホモポリマーのガラス転移温度が100℃以上の重合性単量体としては、スチレン(ホモポリマーのTg=100℃)、メタクリル酸メチル(ホモポリマーのTg=105℃)、アクリロニトリル(ホモポリマーのTg=125℃)、メタクリロニトリル(ホモポリマーのTg=120℃)等が挙げられる。また、ホモポリマーのガラス転移温度が10℃以下となる重合性単量体としては、アクリル酸2-エチルヘキシル(ホモポリマーのTg=-70℃)、アクリル酸n-ブチル(ホモポリマーのTg=-55℃)、アクリル酸エチル(ホモポリマーのTg=-24℃)、アクリル酸メチル(ホモポリマーのTg=10℃)等が挙げられる。ホモポリマーのガラス転移温度が10℃以下となる重合性単量体の一部は、ホモポリマーのガラス転移温度が100℃以上の重合性単量体と共に一段目重合性単量体として用いてもよい。
一段目重合性単量体と二段目重合性単量体の組み合わせの例としては、一段目重合性単量体としてスチレン、二段目重合性単量体としてアクリル酸n-ブチルを用いる組み合わせ;一段目重合性単量体としてスチレン、二段目重合性単量体としてアクリル酸2-エチルヘキシルを用いる組み合わせ;一段目重合性単量体としてスチレン及びアクリル酸n-ブチル、二段目重合性単量体としてアクリル酸n-ブチルを用いる組み合わせ;一段目重合性単量体としてスチレン及びアクリル酸2-エチルヘキシル、二段目重合性単量体としてアクリル酸2-エチルヘキシルを用いる組み合わせ;等が挙げられる。
これらのうち、特に、一段目重合性単量体としてスチレン、二段目重合性単量体としてアクリル酸n-ブチルを用いる組み合わせ;並びに、一段目重合性単量体としてスチレン及びアクリル酸n-ブチル、二段目重合性単量体としてアクリル酸n-ブチルを用いる組み合わせ;が好ましい。
二段目重合工程は、一段目重合工程における重合転化率が30~75%となったときに開始されるのが好ましく、当該重合転化率が35~65%となったときに開始されるのがより好ましく、当該重合転化率が45~60%となったときに開始されるのが更に好ましい。
前記式(1)において、Tg1がTg2より50~200℃高いことがより好ましく、Tg1がTg2より100~160℃高いことがさらに好ましい。
なお、一段目重合性単量体と二段目重合性単量体の仕込み比は、得られる重合体における単量体単位の比と実質的に同じである。
本発明においては、二段目重合工程後に、さらに三段目重合工程を行うことが好ましい。三段目重合工程とは、上述した二段目重合工程までの重合転化率が95%以上となったときに、重合開始剤、及び下記式(2)を満たす三段目重合性単量体をさらに添加して懸濁重合を行う工程である。
Tg1+2<Tg3 式(2)
上記式(2)中、Tg1+2は一段目重合性単量体及び二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg3は三段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。
本発明の好適な態様において、三段目重合性単量体とは、本発明に使用される重合性単量体のうち、三段目重合工程から懸濁重合に使用される重合性単量体のことを指す。
Tg1+2=[75(質量部)+25(質量部)]/[{75(質量部)/(100+273(K))}+{25(質量部)/(-55+273(K))}]
=100/(0.201+0.115)
=317(K)=44(℃)
したがって、一段目重合性単量体としてスチレン75質量部とアクリル酸n-ブチル15質量部を用い、二段目重合性単量体としてアクリル酸n-ブチル10質量部を用いた場合には、44℃より高いガラス転移温度を有する重合体を構成する三段目重合性単量体を使用することが好ましい。
三段目重合工程は、二段目重合工程までの重合転化率が96%以上となったときに開始されるのが好ましく、当該重合転化率が98%以上となったときに開始されるのがより好ましい。
上記式(2)において、Tg3がTg1+2より30~90℃高いことがより好ましく、Tg3がTg1+2より50~75℃高いことがさらに好ましい。
重合により得られた着色樹脂粒子の水分散液については、重合終了後に、公知の方法に従い、ろ過、分散安定化剤の除去を行う洗浄、脱水、及び乾燥の操作が、必要に応じて数回繰り返されることが好ましい。
上述した懸濁重合法により着色樹脂粒子が得られる。以下、トナーを構成する着色樹脂粒子について述べる。
上記着色樹脂粒子の平均円形度が0.96未満の場合、印字の細線再現性が悪くなるおそれがある。
本発明においては、上記着色樹脂粒子を、外添剤と共に混合攪拌して外添処理を行うことにより、着色樹脂粒子の表面に、外添剤を付着させて1成分トナー(現像剤)とすることが好ましい。なお、1成分トナーは、さらにキャリア粒子と共に混合攪拌して2成分現像剤としてもよい。
なお、これらの外添剤は、それぞれ単独で用いることもできるが、2種以上を併用して用いることができる。中でも粒径の異なる2種以上のシリカを併用することが好ましい。
本発明のトナーは、耐熱保存性と低温定着性のバランスに優れるトナーである。
耐熱保存性の指標としては、例えば、以下の方法により決定した耐熱温度が挙げられる。
所定量のトナーを容器に入れて密閉した後、当該容器を所定の温度条件下放置する。所定時間経過後、容器からトナーを篩の上に移し、粉体測定機(ホソカワミクロン社製、商品名:パウダテスタPT-X)等にセットする。所定の振幅の条件下で所定時間振動した後、篩上に残ったトナーの質量を測定し、これを凝集したトナーの質量とする。この凝集したトナーの質量が所定の閾値以下となる最大の温度を、そのトナーの耐熱温度に決定する。
所定のプリンターを用いて、所定の温度におけるトナーの定着率を測定する。定着率は、当該プリンターにより試験用紙に印刷した黒ベタ領域の、所定のテープ剥離操作前後の画像濃度の比率から計算する。即ち、テープ剥離前の画像濃度をID(前)、テープ剥離後の画像濃度をID(後)とすると、定着率は、次式から算出することができる。なお、画像濃度は、反射型濃度計(マクベス社製、商品名:RD918)等を用いて測定する。
定着率(%)=(ID(後)/ID(前))×100
この定着試験において、定着率が所定の閾値以上となる定着温度を、そのトナーの最低定着温度に決定する。
本実施例及び比較例において行った試験方法は以下のとおりである。
[実施例1]
一段目重合性単量体としてモノビニル単量体であるスチレン75部及びn-ブチルアクリレート15部、マクロモノマーとしてポリメタクリル酸エステルマクロモノマー(東亜合成化学工業社製、商品名:AA6、Tg=94℃)0.25部、及びブラックの着色剤としてカーボンブラック(三菱化学社製、商品名:#25B)7部を、メディア型湿式粉砕機を用いて湿式粉砕を行った。湿式粉砕により得られた混合物に、帯電制御剤として帯電制御樹脂(藤倉化成社製、商品名:アクリベース FCA-161P)0.5部と、離型剤としてヘキサグリセリンオクタベヘネート(酸価:0.5mgKOH/g、水酸基価:0.5mgKOH/g)2部、パラフィンワックス(日本精蝋社製、商品名:HNP-11)4部、及び分子量調整剤としてテトラエチルチウラムジスルフィド(大内新興化学工業株式会社製、商品名:ノクセラーTET-G)1.0部を混合、溶解して、一段目重合性単量体組成物を得た。
なお、一段目重合性単量体が重合してなる重合体のガラス転移温度Tg1は、60.5℃である。
その後、重合転化率が99.8%に達したところで、三段目重合性単量体としてメチルメタアクリレート3.0部と、イオン交換水30部に溶解した重合開始剤である2,2’-アゾビス-(2-メチル-N-(1,1-ビス(ヒドロキシメチル)2-ヒドロキシエチル)プロピオンアミド)(和光純薬工業社製、商品名:VA-086)0.3部を添加し、90℃で3時間反応を継続した(三段目重合工程)。その後、反応を停止し、コアシェル構造を有する着色樹脂粒子の水分散液を得た。
なお、一段目重合性単量体及び二段目重合性単量体が重合してなる重合体のガラス転移温度Tg1+2は、43.7℃である。また、三段目重合性単量体が重合してなる重合体のガラス転移温度Tg3は、105℃である。したがって、Tg3はTg1+2より61.3℃高い。
実施例1において、水酸化マグネシウムコロイド分散液を調製するときに、塩化マグネシウム10.0部を9.6部に、水酸化ナトリウム7.0部を6.7部に変更し、且つ、一段目重合性単量体として、スチレン75部及びn-ブチルアクリレート15部を使用する替わりにスチレン75部及びn-ブチルアクリレート5部を使用し、且つ、二段目重合性単量体として、n-ブチルアクリレート10部を使用する替わりにn-ブチルアクリレート20部を使用し、且つ、二段目重合工程の開始時を、一段目重合工程の重合転化率が55%に達したときに変更したこと以外は、実施例1と同様の方法により、実施例2の重合トナーを製造した。なお、実施例2においては、一段目重合性単量体が重合してなる重合体のガラス転移温度Tg1は80.0℃であり、二段目重合性単量体が重合してなる重合体のガラス転移温度Tg2は-55℃である。したがって、Tg1はTg2より135℃高い。試験結果を表1に示す。
実施例1において、水酸化マグネシウムコロイド分散液を調製するときに、塩化マグネシウム10.0部を9.4部に、水酸化ナトリウム7.0部を6.6部に変更し、且つ、一段目重合性単量体として、スチレン75部及びn-ブチルアクリレート15部を使用する替わりにスチレン75部を使用し、且つ、二段目重合性単量体として、n-ブチルアクリレート10部を使用する替わりにn-ブチルアクリレート25部を使用し、且つ、二段目重合工程の開始時を、一段目重合工程の重合転化率が58%に達したときに変更したこと以外は、実施例1と同様の方法により、実施例3の重合トナーを製造した。なお、実施例3においては、一段目重合性単量体が重合してなる重合体のガラス転移温度Tg1は100℃であり、二段目重合性単量体が重合してなる重合体のガラス転移温度Tg2は-55℃である。したがって、Tg1はTg2より155℃高い。試験結果を表1に示す。
実施例2において、二段目重合工程の開始時を、一段目重合工程の重合転化率が41%に達したときに変更したこと以外は、実施例2と同様の方法により、実施例4の重合トナーを製造した。試験結果を表1に示す。
実施例2において、二段目重合工程の開始時を、一段目重合工程の重合転化率が71%に達したときに変更したこと以外は、実施例2と同様の方法により、実施例5の重合トナーを製造した。試験結果を表1に示す。
実施例1において、水酸化マグネシウムコロイド分散液を調製するときに、塩化マグネシウム10.0部を9.6部に、水酸化ナトリウム7.0部を6.7部に変更し、且つ、一段目重合性単量体として、スチレン75部及びn-ブチルアクリレート15部を使用する替わりにスチレン79部及び2-エチルヘキシルアクリレート1部を使用し、且つ、二段目重合性単量体として、n-ブチルアクリレート10部を使用する替わりに2-エチルヘキシルアクリレート20部を使用し、且つ、二段目重合工程の開始時を、一段目重合工程の重合転化率が52%に達したときに変更し、且つ、三段目重合工程の開始時を、二段目重合工程の重合転化率が99.5%に達したときに変更したこと以外は、実施例1と同様の方法により、実施例6の重合トナーを製造した。なお、実施例6においては、一段目重合性単量体が重合してなる重合体のガラス転移温度Tg1は96.1℃であり、二段目重合性単量体が重合してなる重合体のガラス転移温度Tg2は-70℃である。したがって、Tg1はTg2より166℃高い。また、一段目重合性単量体及び二段目重合性単量体が重合してなる重合体のガラス転移温度Tg1+2は44.2℃であり、三段目重合性単量体が重合してなる重合体のガラス転移温度Tg3は105℃である。したがって、Tg3はTg1+2より60.8℃高い。試験結果を表1に示す。
実施例1において、水酸化マグネシウムコロイド分散液を調製するときに、塩化マグネシウム10.0部を10.4部に、水酸化ナトリウム7.0部を7.3部に変更し、且つ、一段目重合工程を、一段目重合性単量体として、スチレン75部及びn-ブチルアクリレート15部を使用する替わりにスチレン75部及びn-ブチルアクリレート25部を使用して重合し、二段目重合工程を行わなかったこと以外は、実施例1と同様の方法により重合を実施した。その後、90℃で4時間反応を行い、重合転化率が99.8%に達したところで、実施例1と同様の方法により、三段目重合工程以降の工程を実施し、比較例1の重合トナーを製造した。すなわち、比較例1においては、実施例1における二段目重合工程を行わなかった。試験結果を表1に示す。
実施例2において、二段目重合工程の開始時を、一段目重合工程の重合転化率が10%に達したときに変更したこと以外は、実施例2と同様の方法により、比較例2の重合トナーを製造した。試験結果を表1に示す。
実施例2において、二段目重合工程の開始時を、一段目重合工程の重合転化率が90%に達したときに変更したこと以外は、実施例2と同様の方法により、比較例3の重合トナーを製造した。試験結果を表1に示す。
上記実施例1~実施例6、及び比較例1~比較例3の重合トナーについて、着色樹脂粒子特性及びトナー特性、並びに印字特性を調べた。詳細は以下の通りである。
(a)着色樹脂粒子の体積平均粒径(Dv)、個数平均粒径(Dn)及び粒径分布(Dv/Dn)
測定試料(着色樹脂粒子)を約0.1g秤量し、ビーカーに取り、分散剤としてアルキルベンゼンスルホン酸水溶液(富士フイルム社製、商品名:ドライウエル)0.1mLを加えた。そのビーカーへ、更にアイソトンIIを10~30mL加え、20W(Watt)の超音波分散機で3分間分散させた後、粒径測定機(ベックマン・コールター社製、商品名:マルチサイザー)を用いて、アパーチャー径;100μm、媒体;アイソトンII、測定粒子個数;100,000個の条件下で、着色樹脂粒子の体積平均粒径(Dv)、及び個数平均粒径(Dn)を測定し、粒径分布(Dv/Dn)を算出した。
容器中に、予めイオン交換水10mLを入れ、その中に分散剤として界面活性剤(アルキルベンゼンスルホン酸)0.02gを加え、更に測定試料(着色樹脂粒子)0.02gを加え、超音波分散機で60W(Watt)、3分間分散処理を行った。測定時の着色樹脂粒子濃度が3,000~10,000個/μLとなるように調整し、0.4μm以上の円相当径の着色樹脂粒子1,000~10,000個についてフロー式粒子像分析装置(シメックス社製、商品名:FPIA-2100)を用いて測定した。測定値から平均円形度を求めた。
円形度は下記計算式1に示され、平均円形度は、その平均をとったものである。
計算式1:(円形度)=(粒子の投影面積に等しい円の周囲長)/(粒子投影像の周囲長)
容量100mLのポリエチレン製容器にトナーを20g充填し、水の浸入がないよう、蓋をシールして密閉し、所定の温度に設定した恒温水槽(ヤマト科学社製:BK300)内の水中に該容器を沈め、8時間経過した後に取り出した。取り出した容器からトナーを42メッシュの篩(目開き355μm)の上にできるだけ振動を与えないように移し、粉体測定機(ホソカワミクロン社製、商品名:パウダテスタPT-X)にセットした。篩の振幅を1.0mmに設定して、30秒間振動した後、篩上に残ったトナーの質量を測定し、これを凝集したトナーの質量とみなし、凝集したトナー質量が仕込んだトナー質量の5%以下となる最高の温度を耐熱温度とし、耐熱保存性を評価した。
(a)定着温度の測定
市販の非磁性一成分現像方式のプリンター(印刷速度:20枚/分)の定着ロールの温度を変化できるように改造したプリンターを用いて、定着試験を行った。定着試験は、改造プリンターの定着ロールの温度を5℃刻みで変化させ、それぞれの温度でのトナーの定着率を測定した。
定着率は、改造プリンターで試験用紙に印刷した黒ベタ領域の、テープ剥離操作前後の画像濃度の比率から計算した。即ち、テープ剥離前の画像濃度をID(前)、テープ剥離後の画像濃度をID(後)とすると、定着率は、次式から算出することができる。
定着率(%)=(ID(後)/ID(前))×100
ここで、テープ剥離操作とは、試験用紙の測定部分(黒ベタ領域)に粘着テープ(住友スリーエム社製、商品名:スコッチメンディングテープ810-3-18)を貼り、一定圧力で押圧して付着させ、その後、一定速度で紙に沿った方向に粘着テープを剥離する一連の操作である。また、画像濃度は、反射型濃度計(マクベス社製、商品名:RD918)を用いて測定した。
この定着試験において、定着率が80%以上になる最低定着ロール温度をトナーの最低定着温度とした。
なお、下記表1中、「St」とはスチレンを、「BA」とはn-ブチルアクリレートを、「2-EHA」とは2-エチルヘキシルアクリレートを、「MMA」とはメチルメタアクリレートを、それぞれ意味する。
以下、表1を参照しながら、トナーの評価結果について検討する。
表1より、比較例1の重合トナーは、本発明における二段目重合工程を行わずに製造したトナーである。比較例1の重合トナーは耐熱温度が56℃と高い。したがって、比較例1の重合トナーにおいては、少なくとも耐熱保存性に問題は見られない。
しかし、比較例1のトナーは、最低定着温度が140℃と高い。したがって、本発明における二段目重合工程を行わずに製造された比較例1の重合トナーは、低温定着性に劣るという問題があることが分かる。
しかし、比較例2の重合トナーは、最低定着温度が140℃と高い。したがって、一段目重合工程の重合転化率が低すぎるときに二段目重合工程を開始して製造された比較例2の重合トナーは、低温定着性に劣るという問題があることが分かる。
しかし、比較例3の重合トナーは、耐熱温度が51℃と低い。したがって、一段目重合工程の重合転化率が十分高くなった後に二段目重合工程を開始して製造された比較例3の重合トナーは、耐熱保存性に劣るという問題があることが分かる。
表1より、実施例1~実施例6の重合トナーは、いずれも耐熱温度が55℃以上であり、優れた耐熱保存性を有する。また、表1より、実施例1~実施例6の重合トナーは、いずれも最低定着温度が135℃以下であり、優れた低温定着性を有する。
したがって、上述した条件を満たす製造方法により製造された実施例1~実施例6の重合トナーは、従来は背反の関係にあった耐熱保存性の向上と低温定着性の向上をバランスよく達成できることが分かる。
Claims (5)
- 少なくとも一段目重合性単量体及び着色剤を含有する一段目重合性単量体組成物を、分散安定化剤を含有する水系分散媒体中に懸濁させることにより、一段目重合性単量体組成物の液滴が分散した懸濁液を得る懸濁工程、
前記懸濁液を用いて重合開始剤の存在下で懸濁重合を行う一段目重合工程、並びに
前記一段目重合工程における重合転化率が20~80%となったときに、下記式(1)を満たす二段目重合性単量体をさらに添加して懸濁重合を行う二段目重合工程、を有することを特徴とする重合トナーの製造方法。
Tg1>Tg2 式(1)
(上記式(1)中、Tg1は前記一段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg2は前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。) - 少なくとも一段目重合性単量体及び着色剤を含有する一段目重合性単量体組成物を、分散安定化剤を含有する水系分散媒体中に懸濁させることにより、一段目重合性単量体組成物の液滴が分散した懸濁液を得る懸濁工程、
前記懸濁液を用いて重合開始剤の存在下で懸濁重合を行う一段目重合工程、
前記一段目重合工程における重合転化率が20~80%となったときに、下記式(1)を満たす二段目重合性単量体をさらに添加して懸濁重合を行う二段目重合工程、並びに
前記二段目重合工程までの重合転化率が95%以上となったときに、重合開始剤、及び下記式(2)を満たす三段目重合性単量体をさらに添加して懸濁重合を行う三段目重合工程、を有することを特徴とする重合トナーの製造方法。
Tg1>Tg2 式(1)
(上記式(1)中、Tg1は前記一段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg2は前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。)
Tg1+2<Tg3 式(2)
(上記式(2)中、Tg1+2は前記一段目重合性単量体及び前記二段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、Tg3は前記三段目重合性単量体が重合してなる重合体のガラス転移温度(℃)を、それぞれ示す。) - 前記一段目重合性単量体と前記二段目重合性単量体の質量割合が、一段目重合性単量体:二段目重合性単量体=60:40~95:5であることを特徴とする請求項1又は2に記載の重合トナーの製造方法。
- 前記式(1)において、Tg1がTg2より5℃~250℃高いことを特徴とする請求項1乃至3のいずれか一項に記載の重合トナーの製造方法。
- 前記式(2)において、Tg3がTg1+2より10℃~100℃高いことを特徴とする請求項2乃至4のいずれか一項に記載の重合トナーの製造方法。
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JP7392307B2 (ja) | 2019-07-17 | 2023-12-06 | 富士フイルムビジネスイノベーション株式会社 | 静電荷像現像用トナー、静電荷像現像剤、トナーカートリッジ、プロセスカートリッジ、印刷物の製造装置及び印刷物の製造方法 |
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JP2019056919A (ja) | 2019-04-11 |
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