JP2013114228A - Two-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-component developer using a toner that uses glycerin or a glycerin derivative as an alcohol component, in which the toner can be charged into a desired charge amount.SOLUTION: The two-component developer includes a toner and a carrier. The toner comprises at least a binder resin, a colorant, a charge control agent, and a release agent; and the binder resin is a polyester resin that is a copolymer between an alcohol component having a valence of two or more and comprising at least glycerin and/or a glycerin derivative and ethylene glycol, and a carboxylic acid component having a valence of two or more. The carrier comprises a carrier core coated with a coating agent and has an average circularity of 0.98 or more; and the coating agent comprises a fluorocarbon resin and at least one polyamide/imide resin selected from the group consisting of a polyamide resin, a polyimide resin, and a polyamide imide resin.

Description

  The present invention relates to a two-component developer.

  In general, in an image forming method such as electrophotography, the surface of an electrostatic latent image carrier (photoconductor) is charged by corona discharge or the like, and then exposed by a laser or the like to form an electrostatic latent image. The electrostatic latent image is developed with toner to form a toner image, and the toner image is transferred to a recording medium to obtain a high quality image. Usually, the toner used for forming the toner image is mixed with a binder resin such as a thermoplastic resin, a colorant, a charge control agent, a release agent, etc., kneaded, pulverized, and classified to have an average particle diameter of 5 to 10 μm. Toner particles are used. For the purpose of imparting fluidity to the toner, controlling the charge amount of the toner, and improving the cleaning property of the toner remaining on the photoreceptor without being transferred, inorganic fine particles such as silica and titanium oxide are used. Powder or the like is externally added to the toner.

  With respect to such toner, from the viewpoints of energy saving, apparatus miniaturization, and the like, a toner having excellent low-temperature fixability that can be fixed satisfactorily without heating the fixing roller is desired. However, toners with excellent low-temperature fixability often use a binder resin with a low melting point or glass transition point or a release agent with a low melting point, and generally tend to aggregate when stored at high temperatures. There's a problem.

  Various studies have been made in order to solve such problems. For example, a toner using a polyester resin using glycerin, a trivalent polyhydric alcohol as a monomer, as a binder resin has been proposed (patent). Reference 1).

JP 2010-20170 A

  The toner is often used as a two-component developer containing a toner and a carrier because the toner can be easily charged to a desired charge amount in a short time and is suitable for high-speed printing. However, the polyester resin described in Patent Document 1 using glycerin as a monomer contains many negatively charged ester bonds in the molecular chain because glycerin is a low molecular weight and polyhydric alcohol. In the case of a toner, even if the toner is used as a two-component developer, it may be difficult to charge the toner to a desired charge amount. For this reason, there is a need for a toner that solves the above-mentioned problems related to chargeability without impairing low-temperature fixability and storage stability at high temperatures.

  The present invention has been made in view of such circumstances, and the toner can be charged to a desired charge amount while using a toner using a polyester resin obtained by synthesizing glycerin or a glycerin derivative as an alcohol component. An object is to provide a two-component developer.

  The inventors include a positively chargeable toner and a carrier, and the positively chargeable toner includes at least a binder resin, a colorant, a charge control agent, and a release agent, and the binder resin includes at least glycerin, And / or a polyester resin that is a copolymer of a divalent or trivalent or higher valent alcohol component containing ethylene glycol and a divalent or trivalent or higher carboxylic acid component, and the carrier is a carrier core. Is coated with a coating agent, and the average circularity is 0.98 or more, and the coating agent is one or more kinds of polyamides / polyamides selected from the group consisting of fluororesin, polyamide resin, polyimide resin, and polyamideimide resin. The present inventors have found that the above problems can be solved by a two-component developer containing an imide resin, and have completed the present invention. More specifically, the present invention provides the following.

(1) including a positively chargeable toner and a carrier;
The positively chargeable toner includes at least a binder resin, a colorant, a charge control agent, and a release agent.
The binder resin is at least one selected from the group consisting of at least glycerin and / or 1,2-propanediol, 1,3-propanediol, and monoacylglycerol in which the acyl group has 8 to 20 carbon atoms. It is a polyester resin that is a copolymer of a divalent or trivalent or higher alcohol component containing two or more kinds of glycerin derivatives and ethylene glycol, and a divalent or trivalent or higher carboxylic acid component,
The carrier has a carrier core covered with a coating agent and an average circularity of 0.98 or more,
The coating agent is a two-component developer containing a fluororesin and at least one polyamide / imide resin selected from the group consisting of a polyamide resin, a polyimide resin, and a polyamideimide resin.

  (2) In the alcohol component, the substance amount ratio A / B between the content (A) of the glycerin and / or glycerin derivative and the substance amount (B) of the ethylene glycol is 15% or less. 1) The two-component developer described above.

  According to the present invention, it is possible to provide a two-component developer capable of charging a toner to a desired charge amount while using glycerol and / or toner using glycerol derivative as an alcohol component. .

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

  The two-component developer according to the present invention includes a positively chargeable toner (hereinafter also simply referred to as toner) and a carrier, and the positively chargeable toner includes at least a binder resin, a colorant, a charge control agent, and a release agent. A copolymer of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher carboxylic acid component containing an agent, wherein the binder resin contains at least glycerol and / or a glycerol derivative and ethylene glycol. The carrier core is coated with a coating agent, and the average circularity is 0.98 or more. The coating agent is made of fluororesin, polyamide resin, polyimide resin, and polyamideimide resin. And one or more polyamide / imide resins selected from the group consisting of: Hereinafter, the positively chargeable toner and carrier constituting the two-component developer of the present invention and the method for producing the two-component developer will be described in order.

[Positively chargeable toner]
The positively chargeable toner contained in the two-component developer of the present invention contains a binder resin, a colorant, a charge control agent, and a release agent. Further, the positively chargeable toner contained in the two-component developer may be one having an external additive attached to the surface thereof. Hereinafter, the binder resin, the colorant, the charge control agent, the release agent, the external additive, and the method for producing the positively chargeable toner will be described in order.

[Binder resin]
A positively chargeable toner contained in the two-component developer uses a polyester resin as a binder resin. The polyester resin is a copolymer of a divalent or trivalent or higher alcohol component containing at least glycerin and / or a glycerin derivative and ethylene glycol, and a divalent or trivalent or higher carboxylic acid component. Hereinafter, regarding the binder resin, the alcohol component, the carboxylic acid component, and the method for producing the binder resin will be described in order.

(Alcohol component)
In the present invention, the divalent or trivalent or higher alcohol component used as a monomer of the polyester resin used as the binder resin contains at least glycerin and / or a glycerin derivative and ethylene glycol.

  Examples of the glycerin derivative include 1,2-propanediol, 1,3-propanediol, and monoacylglycerol. The acyl group in monoacylglycerol is not particularly limited as long as the object of the present invention is not impaired, and may be a saturated acyl group or an unsaturated acyl group. Further, the acyl group in monoacylglycerol may be a linear acyl group or a branched acyl group. The number of carbon atoms of the acyl group in monoacylglycerol is preferably 12-20. More preferred glycerin derivatives include propanediol, and those containing either 1,2-propanediol, 1,3-propanediol, or both are particularly preferred.

  The manufacturing method of glycerol and a glycerol derivative is not specifically limited, A glycerol and a glycerol derivative are manufactured by chemical synthesis, a fermentation method, the combination of these methods, etc. For example, the method of hydrolyzing vegetable fats and oils and purifying glycerol from the obtained reaction product is mentioned. Moreover, the method of obtaining the propanediol as a glycerol derivative by making the obtained glycerol and hydrogen react in presence of a hydrocracking catalyst is mentioned (refer Unexamined-Japanese-Patent No. 2010-111618).

  Further, since it is easy to obtain a toner having excellent low-temperature fixability, the alcohol component contains ethylene glycol in addition to glycerin and / or a glycerin derivative. The substance amount ratio of glycerin and / or glycerin derivative to ethylene glycol ((glycerin and / or glycerin derivative) / ethylene glycol) is preferably 15% or less. When glycerin and / or a glycerin derivative and ethylene glycol are used in such a ratio, it is particularly easy to obtain a toner with good low-temperature fixability.

  The total content of glycerin, glycerin derivative, and ethylene glycol in the alcohol component is not particularly limited as long as the object of the present invention is not impaired. Typically, 70% by mass or more is preferable, and 90% by mass or more is preferable. More preferred is 100% by mass.

  The alcohol component may contain other divalent or trivalent or higher alcohol components other than glycerin, glycerin derivatives, and ethylene glycol as long as the object of the present invention is not impaired. Specific examples of glycerin, glycerin derivatives, and ethylene glycol other divalent or trivalent or higher alcohol components include diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1, 4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetra Diols such as methylene glycol; bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1, 2, 3, 6 Hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, diglycerol, 2-methylpropanetriol, 2- Examples thereof include trivalent or higher alcohols such as methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

(Carboxylic acid component)
Examples of the divalent or trivalent or higher carboxylic acid component used as the monomer of the polyester resin used as the binder resin include the following. Specific examples of the divalent or trivalent or higher carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, Sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid Divalent carboxylic acids such as acids, isododecyl succinic acid, isododecenyl succinic acid and the like or alkyl or alkenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid Acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalene Tricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, And trivalent or higher carboxylic acids such as tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

(Binder resin production method)
The method for producing the polyester resin used as the binder resin is not particularly limited, and can be appropriately selected from known polyester resin production methods. As a method for producing a polyester resin, for example, the above-described alcohol component and carboxylic acid component are put in a reaction vessel, and in the presence of a catalyst, a polycondensation reaction is performed at 200 to 250 ° C. while removing by-product volatile components. The method of performing is mentioned. During the polycondensation reaction, the reaction vessel can be depressurized for the purpose of removing volatile components and promoting the polycondensation reaction. Examples of the catalyst include metals such as tin, titanium, antimony, manganese, nickel, zinc, lead, iron, magnesium, calcium, and germanium, and these metal-containing compounds.

  The amount of the alcohol component and the carboxylic acid component used in producing the polyester resin is not particularly limited as long as the object of the present invention is not impaired. The amount of the alcohol component and the carboxylic acid component used is preferably such that the number of moles of the hydroxyl group contained in the alcohol component is typically 4 times or more the number of moles of the carboxyl group contained in the carboxylic acid component, An amount of 4 to 5 times is more preferable. When the number of moles of hydroxyl groups contained in the alcohol component is increased relative to the number of moles of carboxyl groups contained in the carboxylic acid component, the acid value of the resulting toner tends to decrease and the amount of water absorption of the toner tends to increase. For this reason, by adjusting the magnification of the number of moles of hydroxyl groups contained in the alcohol component with respect to the number of moles of carboxyl groups contained in the carboxylic acid component, the acid value and water absorption of the toner obtained can be adjusted.

  When the carboxylic acid component is an acid halide or a lower alkyl ester, the number of moles of the carboxyl group contained in the carboxylic acid component is calculated using the number of moles of the halocarbonyl group or the lower alkoxycarbonyl group as the number of moles of the carboxyl group. . Further, when the carboxylic acid component is an acid anhydride, the number of moles of the carboxyl group contained in the carboxylic acid component is calculated using the number obtained by doubling the number of moles of the acid anhydride group as the number of moles of the carboxyl group.

  The positively chargeable toner used in the present invention preferably uses a biomass-derived material as a raw material of the polyester constituting the binder resin from the viewpoint of carbon neutral. The kind of biomass is not particularly limited, and may be plant biomass or animal biomass.

  Among the biomass-derived materials, plant biomass-derived materials are more preferred because they are readily available in large quantities and are inexpensive. Among polyester raw materials, it is preferable to use glycerin and / or glycerin derivatives as biomass-derived materials. Specific examples of methods for producing glycerin and / or glycerin derivatives from biomass include chemical hydrolysis of vegetable oils or animal fats with acids, bases, etc., or biological hydrolysis with enzymes, microorganisms, etc. Is mentioned. Glycerin can also be produced by fermentation from a substrate containing a saccharide such as glucose.

Among the CO ₂ present in the atmosphere, the concentration of CO ₂ containing radioactive carbon ( ¹⁴ C) is kept constant in the atmosphere. On the other hand, a plant takes in CO ₂ containing ¹⁴ C in the atmosphere in the process of photosynthesis, so that the concentration of ¹⁴ C in carbon in its organic component is the same as the concentration of CO ₂ containing ¹⁴ C in the atmosphere. The concentration is 107.5 pMC (percent Modern Carbon). Moreover, since carbon in animals is derived from carbon contained in plants, the concentration of ¹⁴ C in carbon in the organic components of animals is the same as that in plants.

Here, assuming that the concentration of ¹⁴ C contained in the toner is XpMC, the ratio of carbon derived from biomass out of carbon in the toner can be obtained by the following formula (1).
<Formula (1)>
Ratio of carbon derived from biomass (%) = (X / 107.5) × 100 (1)

In addition, as a particularly preferable plastic product from the viewpoint of carbon neutrality, a biomass product (Japan Bioplastics Association certification) is given to a plastic product in which the proportion of carbon derived from biomass in the carbon contained in the product is 25% or more. . Then, when the concentration X of ¹⁴ C in the toner in which the proportion of carbon derived from biomass in the carbon contained in the toner is 25% or more is obtained from the above formula (1), it is 26.9 pMC or more. Therefore, it is preferable to prepare the polyester resin so that the concentration of the radioactive carbon isotope ¹⁴ C of carbon contained in the toner is 26.9 pMC or more. The concentration of ¹⁴ C in the carbon element of the petrochemical product can be measured according to ASTM-D6866.

The softening point of the polyester resin is preferably 80 ° C. or higher and 150 ° C. or lower, and more preferably 90 ° C. or higher and 140 ° C. or lower.
[Colorant]
The positively chargeable toner contained in the two-component developer of the present invention contains a colorant in the binder resin. The toner can be appropriately selected from known pigments and dyes according to the desired color of the toner particles. Specific examples of suitable colorants to be added to the toner include black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow , Yellow pigments such as Navels Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; Red Yellow Yellow Lead, Molybdenum Orange, Permanent Orange Orange pigments such as GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Tan, Mercury Cadmium, Permanent Red 4R, Lithium Red pigments such as Lured, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B; Purple such as Manganese Purple, Fast Violet B, Methyl Violet Lake Pigment: Blue pigment such as bitumen, cobalt blue, alkali blue lake, Victoria blue partially chlorinated, First Sky Blue, Indanthrene Blue BC; Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Final Yellow Green G, etc. Green pigments; white pigments such as zinc white, titanium oxide, antimony white, zinc sulfide; barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white, etc. It includes the quality pigments. These colorants may be used in combination of two or more for the purpose of adjusting the toner to a desired hue.

  The amount of the colorant used is not particularly limited as long as the object of the present invention is not impaired. Specifically, 1-10 mass parts is preferable with respect to 100 mass parts of binder resin, and 3-7 mass parts is more preferable.

(Charge control agent)
The positively chargeable toner contained in the two-component developer of the present invention contains a positively chargeable charge control agent. The type of the positively chargeable charge control agent is not particularly limited as long as the object of the present invention is not impaired, and can be appropriately selected from positively chargeable charge control agents conventionally used in toners. Specific examples of the positively chargeable charge control agent include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1, 2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, Azine compounds such as phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, azine Direct dyes composed of azine compounds such as Laun 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Dep Black EW, and Azin Dee Black 3RL; Nigrosine Compounds such as Nigrosine, Nigrosine Salts, Nigrosine Derivatives; Nigrosine Acid dyes comprising nigrosine compounds such as BK, nigrosine NB, and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride It is done. Among these positively chargeable charge control agents, a nigrosine compound is particularly preferable in that a more rapid start-up property can be obtained. These positively chargeable charge control agents can be used in combination of two or more.

  Quaternary ammonium salts, carboxylates, or resins having a carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carboxylic acid Styrene resin with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with carboxyl group 1 type, or 2 or more types, such as resin, the styrene-acrylic resin which has a carboxyl group, and the polyester-type resin which has a carboxyl group, are mentioned. The molecular weight of these resins is not particularly limited as long as the object of the present invention is not impaired, and may be an oligomer or a polymer.

  Among resins that can be used as a positively chargeable charge control agent, a styrene-acrylic copolymer having a quaternary ammonium salt as a functional group from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. A resin is more preferable. Specific examples of preferable acrylic comonomers to be copolymerized with styrene units in a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group include methyl acrylate, ethyl acrylate, n-propyl acrylate, and acrylic acid. (Meth) such as iso-propyl, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate Examples include alkyl acrylates.

  As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate, dialkyl (meth) acrylamide, or dialkylaminoalkyl (meth) acrylamide through a quaternization step is used. Specific examples of the dialkylaminoalkyl (meth) acrylate include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like. Specific examples of dialkyl (meth) acrylamide include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl (meth) acrylamide include dimethylaminopropylmethacrylamide. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

  The amount of the positively chargeable charge control agent is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the positively chargeable charge control agent used is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the binder resin. When the amount of the charge control agent used is too small, it is difficult to stably charge the toner to a predetermined polarity, which may make it difficult to maintain the image density of the formed image over a long period of time. In such a case, the charge control agent is difficult to disperse uniformly, and the fog in the formed image and the contamination of the photoreceptor due to the toner are likely to occur. When the amount of the charge control agent used is excessive, image defects due to deterioration of the environmental resistance due to charging failure under high temperature and high humidity, contamination of the photoreceptor with toner, and the like are likely to occur.

〔Release agent〕
The toner for developing an electrostatic charge image of the present invention contains a release agent. The release agent is used for the purpose of improving the toner fixing property and offset resistance. The type of release agent added to the toner is not particularly limited as long as the object of the present invention is not impaired. The mold release agent is preferably a wax, and examples of the wax include polyethylene wax, polypropylene wax, fluororesin-based wax, Fischer-Tropsch wax, paraffin wax, ester wax, montan wax, rice wax and the like. These release agents can be used in combination of two or more. By adding such a release agent to the toner, it is possible to more efficiently suppress the occurrence of offset and image smearing (dirt around the image when the image is rubbed).

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. The amount of the specific release agent used is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the binder resin. If the amount of the release agent used is too small, the desired effect may not be obtained in terms of suppressing the occurrence of offset and image smearing in the formed image. If the amount of release agent used is excessive, In some cases, the storage stability of the toner may be reduced due to the fusing.

(External additive)
For the purpose of improving the fluidity, storage stability, cleaning properties, etc. of the toner, an external additive may be attached to the surface of the toner.

  The type of external additive is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from external additives conventionally used for toners. Specific examples of suitable external additives include silica and metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These external additives can be used in combination of two or more.

  The particle diameter of the external additive is not particularly limited as long as the object of the present invention is not impaired, and typically 0.01 to 1.0 μm is preferable.

  The volume specific resistance value of the external additive can be adjusted by forming a coating layer made of tin oxide and antimony oxide on the surface of the external additive and changing the thickness of the coating layer and the ratio of tin oxide to antimony oxide. .

  The amount of the external additive used for the toner is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the external additive used is preferably 0.1 to 10 parts by mass and more preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the toner. When the external additive is used in such an amount, it is easy to obtain a toner excellent in fluidity, storage stability, and cleaning properties.

[Method for producing positively chargeable toner]
The positively chargeable toner used in the present invention was obtained by mixing components such as a colorant, a charge control agent, and a release agent in the above-described polyester resin, which is a binder resin, as necessary, and then kneading and kneading. It can be produced by pulverizing and classifying the kneaded product. The melt-kneading apparatus used for producing the toner is not particularly limited, and can be appropriately selected from apparatuses used for melt-kneading thermoplastic resins. Specific examples of the kneading apparatus include a uniaxial or biaxial extruder. The average particle size of the pulverized and classified toner is not particularly limited as long as the object of the present invention is not impaired, but generally 5 to 10 μm is preferable.

The surface of the toner thus obtained may be treated with an external additive as necessary. The method for treating the toner with the external additive is not particularly limited, and can be appropriately selected from conventionally known methods for treating the external additive. Specifically, the processing conditions are adjusted so that the particles of the external additive are not embedded in the toner base particles, and the processing with the external additive is performed by a mixer such as a Henschel mixer or a Nauter mixer.
[Career]
The carrier contained in the two-component developer of the present invention is one in which a carrier core (carrier core material) is coated with a coating agent containing a specific resin. Hereinafter, the carrier core constituting the carrier and the coating agent will be described in order.

  The carrier contained in the two-component developer of the present invention is one in which a carrier core (carrier core material) is coated with a coating agent containing a specific resin. Hereinafter, the carrier core constituting the carrier, the coating agent, and the method for producing the carrier will be described in order.

[Carrier Core]
The type of carrier core is not particularly limited as long as it is a carrier core conventionally used for carriers for two-component developers. Specific examples of the carrier core include particles of iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, etc., and particles of alloys of these materials with manganese, zinc, aluminum, etc., Particles such as iron-nickel alloy, iron-cobalt alloy, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, Ceramic particles such as lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate and Rochelle salt, resin carriers in which the above magnetic particles are dispersed in a resin, etc. Can be mentioned.

  The carrier used in the present invention has an average circularity of 0.980 or more. The circularity of the carrier can be adjusted by a method of preparing a carrier using a carrier core having a high circularity, or a method of applying mechanical and mechanical or thermal stress to the carrier surface after coating the carrier core with a coating agent. The circularity of the carrier core can be adjusted by adjusting the production conditions such as the firing temperature and the firing time when the carrier core is prepared. As a general trend, the longer the firing time or the higher the firing temperature, the higher the circularity of the carrier core. However, if the firing time is too long or the firing temperature is too high, the circularity of the carrier core may be lowered due to melting of the carrier core or the like. Hereinafter, a method for measuring the average circularity of the carrier will be described.

<Average circularity measurement method>
The average circularity of the carrier was sampled randomly using 100 FE-SEM (S-800) manufactured by Hitachi, Ltd., and 100 times the carrier image enlarged to a magnification of 100 to 300 times, and the image information was obtained via the interface. Analyzed by an image analysis apparatus (Luxex III) manufactured by Nicole. Specifically, the average circularity of the carrier is calculated by the following formula.
Circularity = (circle circumference obtained from equivalent circle diameter) / (perimeter of particle projection image)

[Coating agent]
The coating agent for coating the carrier core includes, in particular, at least one polyamide / imide resin selected from the group consisting of polyamide resin, polyimide resin, and polyamideimide resin, and a fluororesin. In the specification and claims of this application, the generic term of polyamide resin, polyimide resin and polyamideimide resin is referred to as “polyamide / imide resin”.

  By using a polyamide / imide resin as a component of the coating agent, the coating agent containing a fluororesin can be easily fixed to the surface of the carrier core. Further, by using a fluororesin as a component of the coating agent, it is possible to suppress adhesion of the external additive or the like to the carrier. For this reason, in the case of using a coating agent containing a polyamide / imide resin and a fluororesin in a two-component developer, peeling of the coating agent from the carrier surface due to stress when the carrier and the toner are stirred, The adhesion of an external additive or the like to the carrier surface is suppressed, and the toner is easily charged to a desired charge amount even when printing is performed continuously for a long period of time.

  The total content of the fluororesin and the polyamide / imide resin in the coating agent is not particularly limited as long as the object of the present invention is not impaired, but is preferably 80% by mass or more, more preferably 90% by mass or more, and 95 Mass% or more is particularly preferable, and 100 mass% is most preferable. Examples of the resin other than the fluororesin, polyamide resin, polyimide resin, and polyamideimide resin that may be included in the coating agent include aromatic polyetherketone resin, (meth) acrylic polymer, styrene heavy polymer Polymer, styrene- (meth) acrylic copolymer, olefin polymer (polyethylene, chlorinated polyethylene, polypropylene, etc.), polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyurethane Examples thereof include resins, epoxy resins, silicon resins, phenol resins, xylene resins, diallyl phthalate resins, polyacetal resins, amino resins, and the like.

  Hereinafter, the fluororesin and the polyamide / imide resin will be described in order.

(Fluorine resin)
The fluororesin is not particularly limited as long as it is conventionally used as a carrier coating agent contained in a two-component developer, and can be appropriately selected and used. Specific examples of the fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), poly And chlorotrifluoroethylene (PCTFE). Among these fluororesins, polytetrafluoroethylene (PTFE), perfluoroalkoxy fluororesin (PFA), and tetrafluoroethylene-6-6 are easily adhered to the carrier core surface and easy to form a coat layer. One or more resins selected from the group consisting of a fluorinated propylene copolymer (FEP) are more preferable.

(Polyamide / imide resin)
The polyamide resin, polyimide resin, and polyamideimide resin are not particularly limited as long as they are conventionally used as a carrier coating agent contained in a two-component developer, and can be appropriately selected and used. Specific examples of the polyamide resin include aliphatic polyamides (nylon 6, nylon 11, nylon 12, nylon 46, nylon 66, nylon 610, nylon 612, etc.), and polyamides in which at least the diamine component is an aliphatic compound (nylon 6T, nylon 6T copolymer, nylon 9T, etc., or semi-aromatic (copolymerized) polyamide (nylon MXD6, nylon 6T / 6, nylon 6T / 66, nylon 6T / 12, nylon 6I / 6, nylon 6I / 66, nylon 6T / 6I, nylon 6T / 6I / 6, nylon 6T / 6I / 66, nylon 6T / MST, etc.). Specific examples of the polyimide resin include pyromellitic acid (PMDA) -based polyimide, biphenyltetracarboxylic acid-based polyimide, bismaleimide-based resin (bismaleimide / triazine-based, etc.), benzophenone tetracarboxylic acid-based polyimide, acetylene-terminated polyimide, A thermoplastic polyimide etc. are mentioned. Specific examples of the polyamideimide resin include polyamideimide using trimellitic acid.

[Method for producing carrier]
The carrier contained in the two-component developer of the present invention is produced by coating the carrier core with the coating agent, and then heat-treating the carrier core coated with the coating agent to fix the coating agent to the surface of the carrier core. . 0.1-15 mass% is preferable with respect to the mass of a carrier core, and, as for the usage-amount of the coating agent at the time of manufacturing a carrier, 1-7 mass% is more preferable.

  The method for coating the carrier core with the coating agent is not particularly limited, and is appropriately selected from methods conventionally used for producing carriers. The method of coating the carrier core with the coating agent may be a wet method in which the solvent is removed after the solution of the coating agent is sprayed onto the carrier core, or a dry method in which the powder of the coating agent is attached to the surface of the carrier core. Either may be sufficient. Since the operation is simple and it can be applied to a resin that is hardly soluble in an organic solvent, the carrier core is more preferably coated by a dry method. The method for coating the carrier core with the powder of the coating agent is not particularly limited, and examples thereof include a method using a dry coating apparatus such as Nobilta (registered trademark) (manufactured by Hosokawa Micron Corporation).

  Hereinafter, a method for coating the carrier core with a coating agent containing a polyamide / imide resin and a fluororesin, which is a preferable coating agent, will be described. As a method of coating the carrier core with a powder of a coating agent by a dry method, a method of coating a single layer with a coating agent containing a polyamide / imide resin and a fluororesin, or a carrier core with a polyamide / imide system A method of covering with two layers consisting of a resin layer and a fluororesin layer can be mentioned. When the carrier core is coated with two layers, either the polyamide / imide resin layer or the fluororesin layer may be the outer layer, but the strength of the coating agent binding to the carrier core, Considering the difficulty of adhesion of external additives to the agent, the layer made of polyamide / imide resin is preferably the inner layer, and the layer made of fluororesin is preferably the outer layer.

  When the carrier core is coated with a single layer with a coating agent comprising a mixture containing a polyamide / imide resin and a fluororesin, it is preferable in that the carrier can be prepared by a single coating operation and the carrier can be easily prepared.

  In addition, the coating layer in the case of coating with a single layer, the polyamide / imide resin layer, the fluororesin layer, and the aromatic polyether ketone resin in the case of coating the carrier core with multiple layers do not impair the object of the present invention. Within the range, a resin other than the polyamide / imide resin, the fluororesin, and the aromatic polyetherketone resin may be included. Specific examples of resins other than polyamide / imide resins and fluororesins include (meth) acrylic polymers, styrene polymers, styrene- (meth) acrylic copolymers, olefin polymers (polyethylene, chlorine). Polyethylene, polypropylene, etc.), polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyurethane resin, epoxy resin, silicone resin, phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, An amino resin etc. are mentioned. When the carrier core is coated with multiple layers, the polyamide / imide resin layer, the fluororesin layer, and the aromatic polyetherketone resin layer are each interposed between the polyamide / imide resin layer and the aromatic polyetherketone resin layer as long as the object of the present invention is not impaired. Resins other than imide resins, fluororesins, and aromatic polyether ketone resins may be present.

  0.1-2.5 mass parts is preferable with respect to 100 mass parts of carrier core particles, and, as for the usage-amount of a polyamide / imide type resin, 0.3-1.5 mass parts is more preferable. Moreover, the usage-amount of a fluororesin has preferable 0.5 to 5% with respect to the total mass of a carrier.

  By the above method, the carrier core is coated with the coating agent powder by the dry method, and then the carrier core coated with the coating agent powder is heat-treated to obtain a carrier. Although the temperature of heat processing changes with kinds of resin contained in a coating agent, it is typically performed at 250-320 degreeC. The time for heating the carrier core is not particularly limited, and is typically 30 minutes to 2 hours. By such heat treatment, the coating agent is softened and melted and fixed to the surface of the carrier core.

  The particle diameter of the carrier is not particularly limited as long as the object of the present invention is not impaired, but is preferably 20 to 200 μm, more preferably 30 to 150 μm, as measured by an electron microscope.

The apparent density of the carrier is not particularly limited as long as the object of the present invention is not impaired. The apparent density varies depending on the carrier composition and surface structure, but typically 2400 to 3000 kg / m ³ is preferable.

[Method for producing two-component developer]
The production method of the two-component developer is not particularly limited as long as the toner and the carrier can be uniformly mixed. For example, the toner and the carrier may be mixed by a mixing device such as a ball mill. The content of the toner in the two-component developer is preferably 2 to 20% by mass and more preferably 4 to 15% by mass with respect to the mass of the two-component developer. By setting the toner content in the two-component developer within such a range, an appropriate image density is maintained in the formed image, and the toner scattering from the developing device or the like is suppressed to prevent contamination inside the image forming device or transfer paper. Toner adhesion can be suppressed.

  The two-component developer of the present invention described above is excellent in low-temperature fixability while utilizing glycerin or glycerin induction, and can charge the toner to a desired charge amount when stored at a high temperature. For this reason, the two-component developer of the present invention and the two-component developer using the developer are preferably used in various image forming apparatuses.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Synthesis Example 1]
(Preparation of glycerin derivative)
The following propanediol was used as the glycerin derivative used as the polyester monomer.
1,3-propanediol: Sasterapropanediol (plant-derived, manufactured by DuPont).
1,2-propanediol: 1,2-propanediol obtained in the following synthesis example.

(Production of 1,2-propanediol)
Glycerol was obtained by hydrolyzing vegetable fats and oils. Specifically, the vegetable oil was completely saponified under heating by adding 10% aqueous sodium hydroxide solution twice the amount necessary to completely saponify the vegetable oil. After separating the aqueous solution of glycerin from the reaction solution after saponification, the aqueous solution of glycerin was purified by distillation. Distilled glycerin was treated with activated carbon to obtain purified glycerin.

Propanediol was produced as a glycerin derivative from glycerin obtained by the above method.
First, ethylene glycol (200 g) and cupric nitrate trihydrate (76 g) were added to a reactor having a reflux condenser, and after stirring with heating at 80 ° C. for 2 hours, tetraethoxysilane (52 g) was added dropwise. The mixture was stirred with heating at ° C for 2 hours. Thereafter, water (18 g) was added dropwise, and the mixture was heated and stirred at 80 ° C. for 3 hours to obtain a precipitate. The produced precipitate was dried at about 120 ° C. and calcined in air at 400 ° C. for 2 hours to obtain a copper / silica catalyst (copper content 50%). An aqueous solution of tetraammineplatinum (II) nitrate [Pt (NH3) 4 (NO3) 2] (29.8 mg) was added to the obtained copper / silica catalyst (3 g), and dried and dried on a rotary evaporator. The obtained solid was dried at 120 ° C., calcined in air at 400 ° C. for 2 hours, and copper-platinum / silica catalyst (Cu / Pt / Si = 50 / 0.5 / 17) (copper content 50% )
Next, 2 g of a copper-platinum / silica catalyst and 200 g of glycerin were added to a 500 mL iron autoclave equipped with a stirrer and replaced with hydrogen. Thereafter, hydrogen was introduced into an autoclave at 230 ° C. at 5 L / min (25 ° C., H ₂ ), and reacted at a pressure of 2 MPa for 7 hours to obtain a reaction solution. 1,2-propanediol was obtained from the resulting reaction solution by a conventional purification method.

[Synthesis Example 2]
(Synthesis of polyester resin A)
72.20 parts by weight of propanediol obtained in Synthesis Example 1, 3.10 parts by weight of ethylene glycol, 11.62 parts by weight of terephthalic acid, 104.40 parts by weight of fumaric acid, and 3.84 parts by weight of trimellitic anhydride, and As a condensation catalyst, 1 part by mass of dibutyltin oxide and 0.3 part by mass of hydroquinone were charged into a reaction vessel and reacted for 5 hours while removing water at 200 ° C. under normal pressure to obtain polyester resin A.

(Synthesis of polyester resin B)
A polyester resin B was synthesized in the same manner as the polyester resin A except that the types and amounts of the alcohol component and the carboxylic acid component were changed to the types and amounts shown in Table 1.

[Production Example 1]
(Manufacture of toner A)
100 parts by weight of polyester resin A as a binder resin, 5 parts by weight of magenta pigment (PR122 (Sanyo Dye)), 1 part by weight of charge control agent (P-51 (manufactured by Orient Chemical Co., Ltd.)), wax (release) 5 parts by mass of a mold, WEP-3 (manufactured by NOF Corporation) was mixed using a Henschel mixer (20B (manufactured by Nippon Coke Corporation)).
The obtained mixture was melt-kneaded using a twin screw extruder (PCM-30 (manufactured by Ikegai Co., Ltd.)) under the conditions of a material supply speed of 6 kg / hr, a shaft rotation speed of 160 rpm, and a cylinder temperature of 120 ° C., and then cooled. Thus, a kneaded product was obtained. The obtained kneaded material is roughly pulverized with a pulverizer (Rotoplex 16/8 type (manufactured by Toa Machinery Co., Ltd.)) and then finely pulverized with a pulverizer (Turbo Mill RS (manufactured by Turbo Industry Co., Ltd.)). The finely pulverized product was classified with an elbow jet (EJ-LABO model EJ-L-3 (manufactured by Nippon Steel Mining Co., Ltd.)) to obtain toner base particles having a volume average particle diameter of 8 μm.

(External processing)
To 100 parts by mass of the obtained toner base particles, 1.0 part by mass of hydrophobic silica fine particles (RA-200H (manufactured by Nippon Aerosil Co., Ltd.)) is added as an external additive, and a Henschel mixer (10C (Nippon Coke Co., Ltd.) is added. The toner A was externally added by mixing at a rotational speed of 3000 rpm and a jacket control temperature of 20 ° C. for 2 minutes.

(Manufacture of toner B)
A toner B was produced in the same manner as the toner A, except that the polyester resin used as the binder resin was changed to the polyester resin B.

[Production Example 2]
(Manufacture of carrier A)
A reactive group is added to the end of a polar solvent solution (polyamideimide resin solution) of polyamideimide resin obtained by adding and copolymerizing trimetic anhydride (TMA) and 4,4'-diphenylmethane diisocyanate (MDI). The tetraethoxysilane was contained at a ratio of 10 parts by mass with respect to 100 parts by mass of the polyamideimide resin. Furthermore, 100 parts by mass of tetrafluoroethylene / hexafluoropropylene copolymer (MP-102 (manufactured by DuPont)) as a fluororesin is dispersed with respect to 100 parts by weight of the total amount of polyamideimide resin and tetraethoxysilane. A coating agent was obtained in which the fluororesin and the polyamideimide resin containing tetraethoxysilane were in a weight ratio of 50:50.

Next, 40 parts by mass of MnO, 9 parts by mass of MgO, 50 parts by mass of Fe ₂ O ₃ , and 1 part by mass of SrO were prepared and pulverized by a ball mill for 2 hours and then fired at 1000 ° C. for 5 hours to obtain a carrier core.

  The core material was spray coated at a ratio of 5 parts by weight with respect to 100 parts by weight of the obtained carrier core using a fluid coating apparatus. Then, in addition to a mechanical coating apparatus (Nobilta (registered trademark) 130 (manufactured by Hosokawa Micron Corporation)), coating was performed at 5000 rpm for 5 minutes. The core carrier coated with the coating agent was heat-treated at 280 ° C. for 1 hour in a small high temperature chamber (STH-120 (manufactured by Espec Corp.)) to obtain carrier A. It was 0.985 when the average circularity of the obtained carrier A was measured according to the following method.

<Average circularity measurement method>
The average circularity of the carrier was sampled randomly using 100 FE-SEM (S-800) manufactured by Hitachi, Ltd., and 100 times the carrier image enlarged to a magnification of 100 to 300 times, and the image information was obtained via the interface. It was obtained by analysis with an image analysis apparatus (Luxex III) manufactured by Nicole. Specifically, the average circularity of the carrier was calculated by the following formula.
Circularity = (circle circumference obtained from equivalent circle diameter) / (perimeter of particle projection image)

(Manufacture of carrier B)
A carrier B having the circularity shown in Table 2 was produced in the same manner as the carrier A except that a carrier core obtained by finely adjusting the firing conditions was used.

(Manufacture of carrier C)
A carrier C having a circularity shown in Table 2 was produced in the same manner as the carrier B, except that a coating agent composed only of a fluororesin was used as the coating agent.

(Manufacture of carrier D)
A carrier D having the circularity shown in Table 2 was produced in the same manner as the carrier B except that the coating agent was prepared as follows.

  A reactive group is added to the end of a polar solvent solution (polyamideimide resin solution) of polyamideimide resin obtained by adding and copolymerizing trimetic anhydride (TMA) and 4,4'-diphenylmethane diisocyanate (MDI). The tetraethoxysilane was contained at a ratio of 10 parts by mass with respect to 100 parts by mass of the polyamideimide resin. Further, 100 parts by mass of an epoxy resin (Epicoat 1001 (manufactured by Mitsubishi Chemical Corporation)) is dispersed with respect to 100 parts by weight of the total amount of polyamideimide resin and tetraethoxysilane, and contains an epoxy resin and tetraethoxysilane. A coating agent having a weight ratio of 50:50 with the polyamideimide resin was obtained.

(Manufacture of carrier E)
A carrier E having the circularity shown in Table 2 was produced in the same manner as the carrier A except that a carrier core obtained by finely adjusting the firing conditions was used.

(Manufacture of carrier F)
A carrier F having a circularity shown in Table 2 was produced in the same manner as the carrier A except that a carrier core obtained by finely adjusting the firing conditions was used.

[Example 1]
(Preparation of two-component developer)
Carrier A and 10% by mass of toner A based on the mass of carrier A were mixed with a ball mill for 30 minutes to prepare a two-component developer.

  The obtained two-component developer is filled in a black developer of a multifunction machine (TASKalfa-550i (manufactured by Kyocera Mita Co., Ltd.)), and the obtained toner is filled in a black toner container. Image density, fog density, charge amount, toner scattering state, and low-temperature fixability were evaluated. Further, using the toner of Example 1, the heat resistant storage stability and the radioactive carbon concentration were evaluated according to the following methods. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

<Image density>
An initial image for evaluation was printed, and the image density of the initial image was measured with a reflection densitometer (RD914 (manufactured by Gretag Macbeth)). Next, after 100,000 sheets were continuously printed at a printing rate of 5%, an evaluation image was printed and the image density was measured in the same manner as the initial image. An image density of 1.4 or more was judged as ◯, 1.3 or more and less than 1.4 as Δ, and less than 1.3 as x.

<Fog density>
The reflection density of the non-printed portion of the evaluation image used for measuring the image density was measured with a reflection densitometer (RD914 (manufactured by Gretag Macbeth)). Further, the reflection density of the recording paper before printing was measured. The difference between the reflection density of the printed portion of the evaluation image and the reflection density of the recording paper before printing was defined as the fog density. A fog density of 0.003 or less was evaluated as ◎, a value of 0.003 or more and 0.007 or less was evaluated as ○, and a value exceeding 0.007 was determined as ×.

<Charge amount>
An initial image for evaluation was printed, and the charge amount of the toner at the time of initial image formation was measured by sucking the toner on the developing sleeve using a suction type small charge amount measuring device (manufactured by TReK). Next, 100,000 sheets were continuously printed at a printing rate of 5%. The toner charge amount after 100,000 sheets of continuous printing was measured in the same manner as the initial charge amount.

<Toner scattering>
The toner (scattered toner) accumulated in the tray installed at the bottom of the developing unit after continuous printing of 100,000 sheets was collected, and the amount (scattered amount) was measured. The scattering amount of 50 mg or less was evaluated as “◯”, the amount exceeding 50 mg was evaluated as “Δ”, and the amount exceeding 200 mg was evaluated as “x”.

<Low temperature fixability>
A solid image having an image density of 1.3 or more was rubbed with a 500 g weight covered with a cloth so that only the weight of the weight was applied to the image, and the image density after the friction was measured. The image density was measured using Gretag Macbeth Spectroeye (manufactured by Gretag Macbeth). According to the following formula, the fixing rate was calculated from the image density before and after friction.
Fixing rate (%) = (image density after friction / image density before friction) × 100

  In the above friction test, a fixing rate of 90% or more was obtained, and the lowest temperature at which no cold offset occurred was defined as the minimum fixing temperature. In the friction test, a fixing rate of 90% or more was obtained, and the highest temperature at which hot offset did not occur was defined as the upper limit fixing temperature.

<Heat resistant storage stability>
3 g of the toner of Example 1 was stored at 58 ° C. for 3 hours, and then cooled to room temperature. The cooled toner was sieved by a powder tester (manufactured by Hosokawa Micron Corporation) using a 330 mesh sieve on a vibration scale 5. In the evaluation of heat-resistant storage stability, a pass rate of 90% by mass or more was evaluated as ◎, 80% or more and less than 90% as 〇, 70% or more and less than 80% as Δ, and less than 70% as ×.

<Radiocarbon concentration measurement>
The concentration of ¹⁴ C contained in the toner of Example 1 was measured according to ASTM-D6866.

[Example 2]
A two-component developer was prepared in the same manner as in Example 1 except that the toner A was changed to the toner B. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and the heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

Example 3
A two-component developer was prepared in the same manner as in Example 1 except that carrier A was changed to carrier B. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and the heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

[Comparative Example 1]
A two-component developer was prepared in the same manner as in Example 1 except that carrier A was changed to carrier C. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and the heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

[Comparative Example 2]
A two-component developer was prepared in the same manner as in Example 1 except that carrier A was changed to carrier D. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and the heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

[Comparative Example 3]
A two-component developer was prepared in the same manner as in Example 1 except that carrier A was changed to carrier E. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and the heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

[Comparative Example 4]
A two-component developer was prepared in the same manner as in Example 1 except that carrier A was changed to carrier F. Table 3 shows the evaluation results of image density, fog density, charge amount, and toner scattering state. Table 4 shows the evaluation results of the low-temperature fixability and the heat-resistant storage stability. The radioactive carbon concentration is shown in Table 5.

  In a two-component developer, when a toner using a glycerin having a relatively low molecular weight or a polyester resin using a glycerin derivative as a monomer is used as a binder resin, the toner tends to be difficult to be charged to a desired charge amount. However, the two-component developers of Examples 1 to 3 use glycerin or a glycerin derivative by using a carrier in which the carrier core is coated with a coating agent containing a fluororesin and a polyamide / imide resin. However, since the toner can be charged to a desired charge amount, an image with a good image density can be formed, and fogging hardly occurs. Further, according to the toner contained in the two-component developer described in Examples 1 to 3, an image having a good image density can be formed even after continuous printing of 100,000 sheets, and fog and toner scattering can be suppressed. It was. Furthermore, since the toner contained in the two-component developer described in Examples 1 to 3 uses a glycerin derivative and ethylene glycol as the alcohol component, it has excellent low-temperature fixability and heat-resistant storage stability. .

  In Comparative Example 1, the carrier coating agent contains a fluororesin, but does not contain a polyamideimide resin. Therefore, in the two-component developer of Comparative Example 1, the toner can be charged to a desired charge amount at the time of printing the initial image, but the charge amount is remarkably reduced after continuous printing of 100,000 sheets. In addition, fogging and toner scattering occurred. Because the coating agent does not contain polyamideimide resin, it is difficult for the coating agent to adhere well to the surface of the carrier core, and the coating agent peels off from the carrier due to the stress applied to the carrier by stirring during continuous printing it is conceivable that. In Comparative Example 2, the carrier coating agent contains a polyamideimide resin, but does not contain a fluororesin. For this reason, with the two-component developer of Comparative Example 2, a sufficient charge amount was not obtained even when the initial image was printed and after 100,000 sheets were continuously printed, and an image with good image density was formed. Hateful. Since the polyamide-imide resin is a soft material, it is considered that the coating agent on the carrier was scraped or the external additive or the like adhered to the carrier surface.

  In Comparative Examples 3 and 4, carriers having an average circularity of carriers lower than 0.980 are used. With the two-component developers of Comparative Examples 3 and 4, a good image can be formed at the time of printing the initial image, but it is difficult to form an image with a good image density after the continuous printing of 100,000 sheets. Since the carrier contained in the developers of Comparative Examples 3 and 4 has a low average circularity, the carrier is easily subjected to stress due to the collision between the carrier and the carrier and the toner due to the stirring during the continuous printing. For this reason, in the developers of Comparative Examples 3 and 4, it is difficult to charge the toner to a desired charge amount due to peeling of the coating agent on the carrier and adhesion of an external additive to the carrier surface. It is considered that density reduction, fogging, and toner scattering occurred.

Claims (2)

A positively chargeable toner and a carrier,
The positively chargeable toner includes at least a binder resin, a colorant, and a charge control agent,
The binder resin is at least one selected from the group consisting of at least glycerin and / or 1,2-propanediol, 1,3-propanediol, and monoacylglycerol in which the acyl group has 8 to 20 carbon atoms. It is a polyester resin that is a copolymer of a divalent or trivalent or higher alcohol component containing two or more kinds of glycerin derivatives and ethylene glycol, and a divalent or trivalent or higher carboxylic acid component,
The carrier has a carrier core covered with a coating agent and an average circularity of 0.98 or more,
The coating agent is a two-component developer containing a fluororesin and at least one polyamide / imide resin selected from the group consisting of a polyamide resin, a polyimide resin, and a polyamideimide resin.   2. The substance amount ratio A / B between the content (A) of the glycerin and / or glycerin derivative and the substance amount (B) of the ethylene glycol in the alcohol component is 15% or less. Two-component developer.