JP5868830B2 - Toner for electrostatic image development - Google Patents

Description

  The present invention relates to a toner for developing an electrostatic image.

  In recent years, toner used in electrophotography is sometimes used in which resin fine particles are adhered to the toner surface in addition to inorganic fine particles. The resin fine particles are close in charge series to the binder resin of the toner, and have an effect of suppressing poor charging of the toner. For this reason, when the toner having resin fine particles attached to the surface is used, it is easy to suppress the occurrence of fog in the formed image and the scattering of the toner in the image forming apparatus.

  Further, with respect to such a toner, from the viewpoint of energy saving and downsizing of the apparatus, a toner excellent in low temperature fixability that can be fixed satisfactorily without heating the fixing roller as much as possible is desired. When preparing a toner excellent in low-temperature fixability, a polyester resin is widely used as a binder resin.

  From the viewpoint of environmental considerations, polyester resins for toners that have been synthesized using monomers that can be obtained from biomass in consideration of carbon neutral are attracting attention. Among the monomers for polyester that can be obtained from biomass, 1,2-propanediol (propylene glycol) is known as a suitable monomer.

  A toner containing a polyester resin containing a unit derived from 1,2-propanediol as a binder resin is obtained by condensation polymerization of an alcohol component containing 70 mol% or more of an aliphatic polyhydric alcohol and a carboxylic acid component. There has been proposed a toner containing a binder resin which is a polyester resin and a charge control agent, wherein the charge control agent is a metal complex of a specific azo compound (see Patent Document 1).

JP 2012-215857 A

  However, since the polyester resin containing a unit derived from 1,2-propanediol is soft among the resins used as the binder resin, the toner described in Patent Document 1 and the resin fine particles are combined. When used, if a stress such as stirring in the developing device is applied to the toner, there is a problem that the resin fine particles are easily detached from the surface of the toner particles. When the resin fine particles are detached, it becomes difficult to supply a desired amount of toner when forming a toner image due to the deterioration of the fluidity of the toner in the developing device, and the image density of the formed image is reduced. It may decrease. Further, when the resin fine particles are detached, filming is likely to occur on the surface of the member that is in contact with the toner for a long period of time, and an image defect such as a color point due to filming is likely to occur.

  Apart from the above-mentioned problem of detachment of resin fine particles, since the toner described in Patent Document 1 uses a soft binder resin, when externally adding hard resin separation particles, the toner is stressed over a long period of time. When received, the resin fine particles are easily embedded in the surface of the toner. If the external additive is embedded in the toner surface, the fluidity of the toner in the developing device deteriorates. Then, when forming a toner image, it is difficult to supply a desired amount of toner from the developing device, and the image density of the formed image may be reduced.

  The present invention has been made in view of such circumstances, and is excellent in low-temperature fixability, in the case of forming an image over a long period of time, the occurrence of image defects such as color points accompanying the occurrence of filming, An object of the present invention is to provide an electrostatic charge image developing toner capable of suppressing a decrease in image density of a formed image.

The present invention relates to a toner base particle containing a binder resin containing a polyester resin containing a unit derived from 1,2-propanediol,
Resin fine particles attached to the surface of the toner base particles,
The glass transition point of the resin constituting the resin fine particles is 125 ° C. or more and 140 ° C. or less,
The following steps 1) to 3) with respect to the BET specific surface area S1 of the unused electrostatic charge image developing toner:
1) A step of putting 2 g of unused electrostatic charge image developing toner and 500 ml of ion-exchanged water containing 0.2 g of sodium alkyl ether sulfonate into a glass container,
2) Place the glass container in an ultrasonic bath filled with water, and apply the unused electrostatic charge image developing toner in the ion-exchanged water for 10 minutes under conditions of an output of 100 W and a frequency of 50 kHz. Irradiating a sound wave; and
3) a step of recovering the electrostatic image developing toner by filtering the dispersion of the electrostatic image developing toner irradiated with ultrasonic waves using a filter having a pore diameter of 0.8 μm and then drying the dispersion;
The electrostatic charge image developing toner has a BET specific surface area S2 ratio S2 / S1 of 0.85 or more and 0.95 or less.

  According to the present invention, it has excellent low-temperature fixability, and suppresses the occurrence of image defects such as color points due to the occurrence of filming and the decrease in image density of formed images when an image is formed over a long period of time. An electrostatic charge image developing toner that can be provided can be provided.

It is a figure explaining the measuring method of the softening point using a Koka flow tester.

  Hereinafter, embodiments of the present invention will be described in detail. However, 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 electrostatic image developing toner according to the present invention (hereinafter also simply referred to as toner) includes toner base particles containing a binder resin containing a polyester resin containing units derived from 1,2-propanediol, and a toner base. Resin fine particles adhering to the surface of the particles. In the specification and claims of this application, particles to be processed using an external additive such as resin fine particles and inorganic fine particles are referred to as “toner mother particles”. The glass transition point of the resin constituting the resin fine particles adhering to the surface of the toner base particles is 125 ° C. or higher and 140 ° C. or lower. The electrostatic charge image developing toner of the present invention is a ratio of the BET specific surface area S2 of the electrostatic charge image developing toner treated with ultrasonic waves according to a specific method to the BET specific surface area S1 of the unused electrostatic charge image developing toner. S2 / S1 is 0.85 or more and 0.95 or less.

  The toner of the present invention may contain components such as a colorant, a charge control agent, a release agent, and magnetic powder in the binder resin, if necessary. In addition to the resin fine particles, the toner of the present invention may be one that has been externally added using inorganic fine particles as external additives. Furthermore, the toner of the present invention can be mixed with a desired carrier and used as a two-component developer.

  Hereinafter, a binder resin, a colorant, a charge control agent, a release agent, a magnetic powder, and an external additive, which are essential or optional components constituting the electrostatic image developing toner, and the electrostatic image developing toner And the carrier used when the toner of the present invention is used as a two-component developer will be described in order.

[Binder resin]
The toner of the present invention essentially contains a polyester resin as a binder resin. The polyester resin is a copolymer of a divalent or trivalent or higher alcohol component containing 1,2-propanediol 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 dihydric or trihydric or higher alcohol component used as a monomer of the polyester resin used as the binder resin contains at least 1,2-propanediol. The amount of 1,2-propanediol in the alcohol component is preferably 60% by mass or more, more preferably 75% by mass or more, and particularly preferably 100% by mass in the alcohol component.

  The production method of 1,2-propanediol is not particularly limited, and is produced using a method such as chemical synthesis, fermentation method, or a combination of these methods. As a specific method, vegetable oils and fats are hydrolyzed, glycerin is purified from the obtained reaction product, and the obtained glycerin and hydrogen are reacted in the presence of a hydrocracking catalyst to obtain 1,2- Examples thereof include a method for obtaining propanediol (see JP 2010-111618).

  The alcohol component may contain a divalent, trivalent or higher alcohol component other than 1,2-propanediol. Specific examples of other dihydric or trihydric or higher alcohol components other than 1,2-propanediol include 1,3-propanediol, 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, ethylene glycol, dipropylene glycol, Diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; Bitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, di Trihydric or higher alcohols such as glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, glycerin Is mentioned. It is particularly preferable to use 1,3-propanediol and glycerin as other divalent or trivalent or higher alcohol components other than these 1,2-propanediol.

(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, alkyl such as isododecenyl succinic acid or alkenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5- Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4- Phthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Examples thereof include trivalent or higher carboxylic acids such as acid, 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, the above-mentioned 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 ° C. or more and 250 ° C. or less while removing volatile components by-produced. 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.

  From the viewpoint of carbon neutral, the binder resin contained in the toner preferably contains a polyester resin synthesized using biomass-derived 1,2-propanediol. 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. Specific examples of methods for producing 1,2-propanediol from biomass include chemical hydrolysis using vegetable oils or animal fats acids or bases, or biological hydrolysis using enzymes or microorganisms. Is mentioned. Glycerin can also be produced using a fermentation method from a substrate containing a saccharide such as glucose. Moreover, when the alcohol component which is a monomer of the polyester resin contains 1,3-propanediol or glycerin in addition to 1,2-propanediol, these are also preferably derived from biomass.

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, when the concentration of ¹⁴ C contained in the toner is XpMC, the proportion of carbon derived from biomass in the carbon in the toner can be obtained according to 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. Accordingly, it is preferable to prepare the polyester so that the concentration of the carbon radioactive carbon isotope ¹⁴ C 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.

  Although the acid value of a polyester resin is not specifically limited, 5 mgKOH / g or more and 20 mgKOH / g or less are preferable. When the acid value of the polyester resin is too high, various performances of the toner are easily affected by humidity under high humidity conditions.

  Although the softening point of a polyester resin is not specifically limited, 90 degreeC or more and 140 degrees C or less are preferable. By using a polyester resin having a softening point in such a range as a binder resin for the toner, it is easy to obtain a toner that has excellent low-temperature fixability and is less likely to cause an offset during fixing at a high temperature. The softening point of the polyester resin can be measured according to the following method.

<Softening point measurement method>
The softening point of the polyester resin is measured using a Koka flow tester (CFT-500D (manufactured by Shimadzu Corporation)). Specifically, the softening point of the polyester resin is measured as follows. A polyester resin 1.5 g is used as a sample, and a die having a height of 1.0 mm and a diameter of 1.0 mm is used. Then, the measurement is performed under the conditions of a heating rate of 4 ° C./min, a preheating time of 300 seconds, a load of 5 kg, and a measurement temperature range of 60 ° C. to 200 ° C. The softening point is read using an S-curve relating to temperature (° C.) and stroke (mm) obtained from measurement of a polyester resin flow tester.

How to read the softening point will be described with reference to FIG. The maximum value of the stroke and S1, the stroke value of the low-temperature side of the base line and S _2. In the S-shaped curve, the temperature at which the stroke value becomes (S ₁ + S ₂ ) / 2 is defined as the softening point of the polyester resin.

  Although the glass transition point (Tg) of a polyester resin is not specifically limited, 55 to 65 degreeC is preferable. By using a polyester resin having a glass transition point in such a range as a binder resin for the toner, it is easy to obtain a toner that has excellent low-temperature fixability and is less likely to cause an offset during fixing at a high temperature.

  The glass transition point of the polyester resin can be determined from the change point of the specific heat of the polyester resin using a differential scanning calorimeter (DSC) according to JIS K7121. A more specific measuring method is as follows. It can obtain | require by measuring the endothermic curve of a polyester resin using the differential scanning calorimeter DSC-6200 by Seiko Instruments Inc. as a measuring apparatus. 10 mg of a measurement sample is put in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the polyester resin can be determined from the endothermic curve of the polyester resin obtained by measurement at a temperature range of 25 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min.

  The number average molecular weight (Mn) of the polyester resin is more preferably 3,000 or more and 5,000 or less. When the number average molecular weight (Mn) of the polyester resin is in such a range, a toner that can be satisfactorily fixed on a paper in a wide temperature range can be obtained. Moreover, the molecular weight distribution (Mw / Mn) represented by the ratio of the number average molecular weight (Mn) and the mass average molecular weight (Mw) is preferably 1 or more and 40 or less. When the molecular weight distribution of the polyester resin is within such a range, it is easy to obtain a toner having excellent low-temperature fixability. The number average molecular weight (Mn) and the mass average molecular weight (Mw) of the polyester resin can be measured using gel permeation chromatography.

  The binder resin may contain other thermoplastic resins of polyester resin as long as the object of the present invention is not impaired. When the binder resin includes a combination of a polyester resin and another thermoplastic resin of the polyester resin, the other thermoplastic resin of the polyester resin is appropriately selected from the thermoplastic resins conventionally used as the binder resin for toner. You can select and use.

  The content of the polyester resin in the binder resin is not particularly limited as long as the object of the present invention is not impaired. The content of the polyester resin in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 100%.

[Colorant]
The toner of the present invention may contain a colorant as necessary. 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, Naples Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, yellow pigments; Orange pigments such as Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Red, Mercury Cadmium Sulfide, Permanent Red Red pigments such as 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B; Manganese Purple, Fast Violet B, Methyl Violet Purple pigments such as lakes; blue pigments such as bitumen, cobalt blue, alkali blue lakes, Victoria blue partial chlorinated products, first sky blue, indanthrene blue BC; chrome green, chromium oxide, pigment green B, malachite green lake, Green pigments such as final yellow green G; white pigments such as zinc white, titanium oxide, antimony white, zinc sulfide; barite powder, barium carbonate, clay, silica, white carbon , Talc, extender pigments such as alumina white. These colorants can be used in combination of two or more for the purpose of adjusting the hue of the toner to a desired hue.

  The amount of the colorant used is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 3 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Charge control agent)
The toner of the present invention may contain a charge control agent as necessary. The charge control agent improves the stability of the charge level of the toner and the charge rise characteristic that is an indicator of whether the toner can be charged to a predetermined charge level in a short time. Used for gaining purposes. When developing with positively charged toner, a positively chargeable charge control agent is used. When developing with negatively charged toner, a negatively chargeable charge control agent is used.

  The type of charge control agent can be appropriately selected from 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 and quinoxaline; Azin Fast Red FC, Azin Fast Red 12BK, Azine Violet BO, Azine Direct dyes composed of azine compounds such as N-Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, and Azin Deep Black 3RL; Nigrosine such as Nigrosine, Nigrosine Salt, Nigrosine Derivative Compounds; Acid dyes consisting of nigrosine compounds such as nigrosine BK, nigrosine NB, nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; 4 such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride A class ammonium salt is mentioned. 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.

  A resin having a quaternary ammonium salt, carboxylate, or 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, and a carboxylate Styrene resin having carboxylate, acrylic resin having carboxylate, styrene acrylic resin having carboxylate, polyester resin having carboxylate, styrene resin having carboxyl group, acrylic resin having carboxyl group, carboxyl group Styrene acrylic resin having a carboxyl group and polyester resin having a carboxyl group. 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.

  Specific examples of the negatively chargeable charge control agent include organometallic complexes and chelate compounds. Examples of organometallic complexes and chelate compounds include acetylacetone metal complexes such as aluminum acetylacetonate and iron (II) acetylacetonate, and salicylic acid metal complexes such as chromium 3,5-di-tert-butylsalicylate. A salicylic acid metal salt is preferable, and a salicylic acid metal complex or a salicylic acid metal salt is more preferable. These negatively chargeable charge control agents can be used in combination of two or more.

  Typically, the amount of the positively or negatively chargeable charge control agent used is preferably 0.5 parts by mass or more and 15 parts by mass or less, and 1.0 part by mass when the total amount of toner is 100 parts by mass. The amount is more preferably 8.0 parts by mass or less, and particularly preferably 3.0 parts by mass or more and 7.0 parts by mass or less. When the amount of charge control agent used is too small, it is difficult to stably charge the toner to a predetermined polarity, so that the image density of the formed image falls below a desired value, or it is difficult to maintain the image density over a long period of time. There are things to do. In such a case, the charge control agent is difficult to uniformly disperse in the toner, so that the formed image is likely to be fogged or the latent image carrier is easily contaminated due to adhesion of the toner component. When the amount of the charge control agent used is excessive, the latent image carrier is caused by image defects in the formed image due to poor charging under high temperature and high humidity due to deterioration of environmental resistance, or due to adhesion of toner components. Contamination is likely to occur.

〔Release agent〕
The toner of the present invention may contain a release agent for the purpose of improving the toner fixability and offset resistance. The type of release agent is not particularly limited as long as it is conventionally used as a release agent for toner.

  Suitable mold release agents include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin waxes, microcrystalline waxes, paraffin waxes, and aliphatic hydrocarbon waxes such as Fischer-Tropsch wax; oxidized polyethylene waxes, and Oxides of aliphatic hydrocarbon waxes such as block copolymers of oxidized polyethylene waxes; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, and rice wax; beeswax, lanolin, and whale Animal waxes such as waxes; mineral waxes such as ozokerite, ceresin, and vetrolactam; waxes based on fatty acid esters such as montanate ester wax and castor wax; Some fatty acid esters such as acid carnauba wax, or wax deoxidizing the like all.

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. Specifically, the amount of the release agent used is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to the mass of the toner. When the amount of the release agent used is too small, a desired effect may not be obtained with respect to suppression of occurrence of offset and image smearing in the formed image. On the other hand, when the amount of the release agent used is excessive, the heat resistant storage stability of the toner may be reduced due to the fusion between the toners.

[Magnetic powder]
The toner of the present invention can be blended with magnetic powder as necessary. Examples of suitable magnetic powders include irons such as ferrite and magnetite; ferromagnetic metals such as cobalt and nickel; alloys containing iron and / or ferromagnetic metals; compounds containing iron and / or ferromagnetic metals A ferromagnetic alloy subjected to a ferromagnetization treatment such as heat treatment; chromium dioxide.

  The particle size of the magnetic powder is preferably from 0.1 μm to 1.0 μm, and more preferably from 0.1 μm to 0.5 μm. When magnetic powder having a particle diameter in such a range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

  For the purpose of improving the dispersibility of the magnetic powder in the toner, a magnetic powder surface-treated with a surface treatment agent such as a titanium coupling agent or a silane coupling agent can be used.

  The amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, more preferably 40 parts by weight or more and 60 parts by weight or less when the toner is used as a one-component developer and the total amount of toner is 100 parts by weight. preferable. If the amount of magnetic powder used is excessive, it may be difficult to maintain the image density at a desired value over a long period of time, or the toner fixability may be extremely reduced. If the amount of magnetic powder used is too small, fog may easily occur in the formed image, or it may be difficult to form an image having a desired image density over a long period of time. When the toner is used as a two-component developer, the amount of magnetic powder used is preferably 20% by mass or less and more preferably 15% by mass or less when the total amount of toner is 100 parts by mass.

(External additive)
In the toner of the present invention, resin fine particles are externally added to the surface of toner base particles. The glass transition point of the resin constituting the resin fine particles used as the external additive is 125 ° C. or higher and 140 ° C. or lower. The toner base particles may be externally added using inorganic fine particles in addition to the resin fine particles. Hereinafter, the resin fine particles and the inorganic fine particles will be described in order.

(Resin fine particles)
The resin fine particles are not particularly limited as long as the glass transition point of the constituent resin is 125 ° C. or higher and 140 ° C. or lower. By using resin fine particles made of a resin having a glass transition temperature in such a range as an external additive, it is excellent in low-temperature fixability, and the color associated with the occurrence of filming when an image is formed over a long period of time. It is easy to obtain toner that can suppress the occurrence of image defects such as dots and the decrease in image density of the formed image.

  The glass transition point of the resin constituting the resin fine particles can be adjusted by a method of adjusting the molecular weight of the resin or a method of introducing a crosslinked structure into the resin. In general, the higher the molecular weight of the resin, the higher the glass transition point of the resin. Moreover, there exists a tendency for the glass transition point of resin to become high, so that a crosslinking degree is high. Examples of a method for introducing a crosslinked structure into the resin include a method using a polyfunctional crosslinking monomer when preparing the resin.

  The resin constituting the resin fine particle may be any of a polymer obtained through polycondensation such as polyester, polyamide, polyesteramide, polyimide, polycarbonate, and a polymer obtained through addition polymerization of one or more monomers having an unsaturated bond. Can also be used. As the resin constituting the resin fine particles, it is more preferable to use a polymer obtained by addition polymerization of one or more monomers having an unsaturated bond, since it is easy to prepare resin fine particles having a uniform particle diameter.

  Hereinafter, a polymer obtained by addition polymerization of one or more monomers having an unsaturated bond will be described. A polymer obtained by addition polymerization of one or more monomers having an unsaturated bond is added by combining a monofunctional monomer having one unsaturated bond with a polyfunctional monomer having a plurality of unsaturated bonds as necessary. Manufactured by polymerization.

  Specific examples of the monofunctional monomer include vinyl aromatic compounds such as styrene, p-chlorostyrene, vinyl naphthalene; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-acrylate (Meth) acrylates such as octyl, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide, etc. Other (meth) acrylic acid derivatives; Ethylene unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; Vinyl halides such as vinyl chloride, vinyl bromide and vinyl fluoride; Vinyl acetate, vinyl propionate and benzoic acid vinyl, Vinyl esters such as vinyl acid; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl N-vinyl compounds such as indole and N-vinylpyrrolidene. These monofunctional monomers can be used in combination of two or more.

  Specific examples of the polyfunctional monomer include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinylaniline, divinyl ether, And divinyl compounds such as divinyl sulfide and divinyl sulfone. These polyfunctional monomers can be used in combination of two or more. When a monofunctional monomer and a polyfunctional monomer are copolymerized, it is easy to increase the outflow start temperature of the polymer.

  As a method for addition polymerization of a monomer having an unsaturated bond, any method such as solution polymerization, bulk polymerization, emulsion polymerization and suspension polymerization can be selected. Among these production methods, the emulsion polymerization method is preferred because it is easy to prepare resin fine particles having a uniform particle diameter.

  Polymerization initiators that can be used for addition polymerization of monomers having an unsaturated bond include potassium persulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, and 2,2′-azobis. Known polymerization initiators such as -2,4-dimethylvaleronitrile and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile can be used. The amount of these polymerization initiators used is preferably 0.1% by mass or more and 15% by mass or less based on the total amount of monomers.

  The method for producing resin fine particles by emulsion polymerization may be a method of emulsifying the reaction solution using a surfactant, or a soap-free method of emulsifying the reaction solution without using a surfactant. When using a surfactant for emulsion polymerization, any of a cationic surfactant, an anionic surfactant, and a nonionic surfactant can be used.

  Specific examples of the cationic surfactant include dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl ammonium bromide and the like. Specific examples of the anionic surfactant include fatty acid soaps such as sodium stearate and sodium dodecanoate, and sulfonates such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate. Specific examples of the nonionic surfactant include polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene sorbitan monooleate ether, monodecanoyl sucrose, and the like.

  Among the polymers produced by combining these monomers, it is easy to produce resin fine particles with a uniform particle size, and since it has sufficient hardness, it is difficult to deform or drop off from the surface of the toner base particles, A polymer produced by emulsion polymerization of a plurality of addition-polymerizable monomers including a polyfunctional monomer having a plurality of unsaturated bonds is preferable because it hardly adheres to the surface of the photoreceptor or the developing roller. Specifically, a copolymer obtained by emulsion polymerization of styrene, a (meth) acrylic monomer, and divinylbenzene is particularly preferable. Examples of the (meth) acrylic monomer include the above (meth) acrylic acid ester and the above (meth) acrylic acid derivative. For such a polymer, the ratio of the styrene / (meth) acrylic monomer is preferably 50/50 or more and 90/10 or less as the mass ratio of the monomers. Moreover, the usage-amount of divinylbenzene has preferable 5 mass% or more and 15 mass% or less with respect to the sum total of the mass of styrene, a (meth) acryl monomer, and divinylbenzene.

  Typically, the amount of the resin fine particles used is preferably 3.5 parts by mass or more and 6.5 parts by mass or less, more preferably 4.5 parts by mass or more and 5.5 parts by mass or less with respect to 100 parts by mass of the toner base particles. preferable.

  The average primary particle diameter of the resin fine particles used in the production of the toner of the present invention is typically preferably 80 nm to 120 nm, and more preferably 90 nm to 110 nm. The average primary particle diameter of the resin fine particles can be measured using a scanning electron microscope. When determining the average primary particle size, the particle size is measured for 50 or more particles. The particle diameter of the resin fine particle diameter can be obtained by image analysis from an electron microscope image. The particle diameter of the resin fine particles is the diameter of spherical particles (the diameter of a circle having the same projected area as the particle image). Further, the glass transition temperatures of the resin fine particles A to E were measured using a differential scanning calorimeter (DSC 6220 (manufactured by Seiko Instruments Inc.)). The average primary particle diameter of the resin fine particles can be adjusted by adjusting polymerization conditions, known pulverization methods, classification methods, and the like.

(Inorganic fine particles)
Specific examples of the inorganic fine particles that can be used as an external additive together with the resin fine particles include metal oxides such as silica, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These inorganic fine particles can be used in combination of two or more. These inorganic fine particles can also be used after being hydrophobized using a hydrophobizing agent such as an aminosilane coupling agent or silicone oil. In the case of using hydrophobic inorganic fine particles, it is easy to suppress a decrease in charge amount of the toner under high temperature and high humidity, and it is easy to obtain a toner excellent in fluidity.

  The particle diameter of the inorganic fine particles is preferably 0.01 μm or more and 1.0 μm or less.

  Typically, the amount of inorganic fine particles used is preferably 0.2 parts by mass or more and 5 parts by mass or less, and more preferably 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the toner base particles.

[Method for producing toner for developing electrostatic image]
In the toner of the present invention, an external additive containing resin fine particles made of a resin having a predetermined glass transition point is externally added to toner base particles containing a binder resin containing the specific polyester resin described above. The toner base particles are obtained by blending a binder resin with components such as a colorant, a charge control agent, and a release agent, if necessary.

  As a specific method for producing toner base particles, a binder resin and components such as a colorant, a charge control agent, and a release agent are mixed, and the resulting mixture is melt-kneaded, and the melt-kneaded product is pulverized and mixed. There is a “grinding method” for classification. The pulverization method is preferable in that a toner having a desired particle diameter can be easily prepared.

  In addition, fine particles of components such as a binder resin, a colorant, a charge control agent, and a release agent are aggregated in a liquid medium such as an aqueous medium to form aggregated particles, and the aggregated particles are heated, An “aggregation method” in which the components contained in the aggregated particles are united is also preferable as a method for producing toner mother particles. In the aggregation method, it is easy to prepare a toner having a uniform shape and a narrow particle size distribution width.

  The average particle diameter of the toner is generally preferably 5 μm or more and 10 μm or less.

  The toner thus obtained is treated using the external additive containing the resin fine particles described above. The toner processing method using the external additive can be appropriately selected from conventionally known processing methods using 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 using the external additive is performed using a mixer such as a Henschel mixer or a Nauter mixer. .

The toner of the present invention has the following steps 1) to 3) with respect to the BET specific surface area S1 of the unused toner:
1) A step of putting 2 g of unused toner and 500 ml of ion-exchanged water containing 0.2 g of sodium alkyl ether sulfonate into a glass container,
2) A step of placing the glass container in an ultrasonic bath filled with water and irradiating the unused toner in the ion-exchanged water for 10 minutes under conditions of an output of 100 W and a frequency of 50 kHz. ,as well as,
3) A step of collecting the toner dispersion liquid, which has been irradiated with ultrasonic waves, using a filter having a pore size of 0.8 μm and then drying to collect the toner;
The ratio S2 / S1 of the BET specific surface area S2 of the toner processed by the method is 0.85 or more and 0.95 or less.

In the toner of the present invention, when an external additive is added to the toner base particles so that S2 / S1 is a value within the above range, the toner is stressed in the developing unit. The excessive detachment of the resin fine particles from the toner base particles and the excessive embedding of the resin fine particles on the toner base particle surfaces are suppressed. For this reason, an electrostatic charge image developing toner that can suppress the occurrence of image defects such as color points due to the occurrence of filming and the decrease in image density of the formed image when an image is formed over a long period of time. The purpose is to provide.

  The value of S2 / S1 can be adjusted by adjusting the external addition conditions. By increasing the external addition processing time, the value of S2 / S1 tends to decrease. Further, when external addition processing is performed using a device such as a Henschel mixer or a Nauter mixer, the value of S2 / S1 can be reduced by increasing the number of revolutions of the device.

[Career]
The toner of the present invention can be mixed with a desired carrier and used as a two-component developer. When preparing a two-component developer, it is preferable to use a magnetic carrier.

  Suitable carriers when the toner of the present invention is used as a two-component developer include those in which a carrier core material is coated with a resin. Specific examples of the carrier core material include particles such as iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, and cobalt, and particles of alloys of these materials with manganese, zinc, and aluminum. , Particles like 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, titanate Ceramic particles such as lead, lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate and Rochelle salt, and the above magnetic particles dispersed in resin A resin carrier is mentioned.

  Specific examples of the resin covering the carrier core material include (meth) acrylic polymer, styrene polymer, styrene- (meth) acrylic copolymer, olefin polymer (polyethylene, chlorinated polyethylene, polypropylene). , Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyfluoride) Vinylidene), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, and amino resin. These resins can be used in combination of two or more.

  The particle diameter of the carrier is a particle diameter measured using an electron microscope, preferably 20 μm or more and 120 μm or less, and more preferably 25 μm or more and 80 μm or less.

  When the toner of the present invention is used as a two-component developer, the content of the toner in the two-component developer is preferably 3% by mass or more and 20% by mass or less, and preferably 5% by mass or more with respect to the mass of the two-component developer. 15 mass% or less is more preferable. By setting the toner content in the two-component developer within such a range, it is easy to maintain the image density of the formed image at an appropriate level, and image formation caused by suppression of toner scattering from the developing device Contamination inside the apparatus and toner adhesion to transfer paper can be suppressed.

  The toner for developing an electrostatic charge image of the present invention described above is excellent in low-temperature fixability, and when an image is formed over a long period of time, an image defect such as a color point accompanying the occurrence of filming, Reduction of image density can be suppressed. For this reason, the toner for developing an electrostatic charge image of the present invention is suitably used in various image forming apparatuses.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the scope of the examples.

[Synthesis Example 1]
[Production of 1,2-propanediol]
Vegetable oil was hydrolyzed to obtain glycerin. 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. An aqueous solution of glycerin was separated from the reaction solution after saponification, and the aqueous solution of glycerin was distilled and purified. Distilled glycerin was treated with activated carbon to obtain purified glycerin.

1,2-propanediol was produced from glycerin obtained according to 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. The resulting reaction solution was purified according to a conventional method to obtain 1,2-propanediol.

[Synthesis Example 2]
1142 g of 1,2-propanediol obtained in Synthesis Example 1, 1743 g of terephthalic acid, and 0.5 g of tin (II) dioctanoate that is an esterification catalyst were added to a nitrogen introduction tube, a dehydration tube, a rectifying device, and a stirrer. And a 5-L four-necked flask equipped with a thermocouple. The contents of the flask were heated to 230 ° C. under a nitrogen atmosphere. Next, the contents of the flask were stirred at the same temperature for 15 hours, and then the pressure in the flask was reduced to 8.0 kPa. After decompression, the contents of the flask were stirred at 230 ° C. for 1 hour. Thereafter, the temperature of the contents of the flask was lowered to 180 ° C., and 288 g of trimellitic anhydride was added to the flask at the same temperature. After heating the contents of the flask to 210 ° C. over 3 hours, the reaction was carried out at the same temperature and atmospheric pressure for 10 hours. After reducing the pressure in the flask to 20 kPa, the polymerization reaction was continued at 210 ° C. until the polyester resin in the flask reached the desired softening point. After stopping the polymerization reaction, the contents in the flask were recovered to obtain a polyester resin.

[Synthesis Example 3]
[Production of resin fine particles A to E]
A round bottom flask was charged with styrene, acrylonitrile, divinylbenzene, 4.5 parts by mass of potassium persulfate (water-soluble polymerization initiator), and 100 parts by mass of ion-exchanged water in the amounts shown in Table 1. The contents of the flask were heated to 70 ° C., and the contents of the flask were stirred for 8 hours at an agitation speed of 100 rpm using an anchor type stirring blade to perform soap-free emulsion polymerization. The reaction liquid after completion of the polymerization reaction was cooled to room temperature, and then the dispersion liquid containing resin fine particles in the flask was filtered, and the collected resin fine particle wet cake was dried to obtain resin fine particles A to E. The average primary particle diameter of the resin fine particles A to E measured with a scanning electron microscope was about 100 nm. The average primary particle size of the resin fine particles was obtained by measuring the particle size of 50 or more resin fine particles. The particle diameter of the resin fine particle diameter was obtained by image analysis from an electron microscope image. The particle diameter of the resin fine particles is the diameter of the spherical particles (the diameter when the area of the circular projection image having the same projection area as the particle image is regarded as a circle). Further, the glass transition temperatures of the resin fine particles A to E were measured using a differential scanning calorimeter (DSC 6220 (manufactured by Seiko Instruments Inc.)). Table 1 shows glass transition points of the resin fine particles A to E.

[Examples 1 to 5 and Comparative Examples 1 to 4]
100 parts by mass of polyester A (binder resin) obtained in Synthesis Example 2, 7 parts by mass of wax (release agent, WEP-3 (manufactured by NOF Corporation)), and quaternary ammonium salt (charge control agent, Bontron P-51 (manufactured by Orient Chemical Co., Ltd.)) 1.5 parts by mass and carbon black (colorant, MA-100 (manufactured by Mitsubishi Chemical Co., Ltd.)) 7 parts by mass were mixed with a stirrer (Henschel mixer 20B ( Nippon Coke Kogyo Co., Ltd.)). The obtained mixture was melt-kneaded using a melt-kneader (PCM-30 (manufactured by Ikegai Co., Ltd.)) to obtain a melt-kneaded product. The obtained melt-kneaded product was coarsely 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 7 μm.

  With respect to 100 parts by mass of the obtained toner base particles, 1.2 parts by mass of hydrophobic silica fine particles (RA-200H (manufactured by Nippon Aerosil Co., Ltd.)) and titanium oxide (EC-100 (titanium) are used as external additives. Industrial Co., Ltd.)) 0.8 parts by mass and 0.5 part by mass of resin fine particles of the type shown in Table 2, and using a stirrer (Henschel Mixer 10B (Nihon Coke Industries Co., Ltd.)), The toner was subjected to external addition treatment by mixing at a rotational speed of 1000 rpm and a jacket control temperature of 20 ° C. for the time shown in Table 2.

  Using the obtained toner, the ratio S2 / S1 of the BET specific surface area S2 of the ultrasonically treated toner to the BET specific surface area S1 of the unused toner was measured according to the following method. The values of S2 / S1 obtained are shown in Table 2.

  2 g of unused toner and 500 ml of ion-exchanged water containing 0.2 g of sodium alkyl ether sulfonate were placed in a glass beaker. The beaker was placed in an ultrasonic bath (Vs-F100 (manufactured by As One Co., Ltd.) filled with water, and ultrasonic waves were applied to unused toner in ion-exchanged water for 10 minutes under the conditions of an output of 100 W and a frequency of 50 kHz. After ultrasonic irradiation, the dispersion liquid of the toner irradiated with ultrasonic waves was filtered using a filter having a pore diameter of 0.8 μm, and then the toner was dried to obtain ultrasonically treated toner.

  The BET specific surface area of the unused toner and the ultrasonically treated toner were measured using a fully automatic specific surface area meter (Macsorb model-1201 (manufactured by Mountec Co., Ltd.)). After that, the toner sample was pretreated for 30 minutes at 45 ° C. Next, nitrogen gas as an adsorption gas was adsorbed to the toner sample at a temperature of 25 ° C., and the BET specific surface area was measured. The value of S2 / S1 was calculated from the values of S2 and S1.

≪Evaluation≫
For the toners obtained in Examples 1 to 5 and Comparative Examples 1 to 4, the image density of the image formed using the toner and the generation of color points during image formation after the image was formed over a long period of time Existence and low temperature fixability were evaluated according to the following methods. The evaluation was performed using a two-component developer prepared according to Preparation Example 1 below. Table 2 shows the evaluation results of the toners of Examples 1 to 5 and Comparative Examples 1 to 4.

[Preparation Example 1]
(Preparation of two-component developer)
A developer carrier (a carrier for a printer FS-5200DN (manufactured by Kyocera Document Solutions Co., Ltd.), a ferrite carrier) and a toner of 10% by mass with respect to the mass of the carrier using a ball mill under normal temperature and humidity conditions For 30 minutes to obtain a two-component developer.

<Image density>
The black developing device of the printer (FS-5200DN (manufactured by Kyocera Document Solutions Co., Ltd.)) is filled with the two-component developer prepared according to Preparation Example 1 above, and the black toner container of the printer of the example or comparative example Filled with toner, the image density of the solid print portion of the initial sample image formed in an atmosphere of 20 ° C. and 50% RH and the sample image formed after printing 50000 sheets at a print density of 4% is defined as the reflection density. RD914 (manufactured by Gretag Macbeth Co., Ltd.) The image density of the initial image and the image after printing 50000 sheets was determined according to the following criteria: ○ is acceptable, Δ and × are unacceptable. Pass.
○: Image density 1.2 or more.
Δ: Image density of 1.1 or more and less than 1.2.
X: Image density less than 1.1.

<Color point>
The image after printing 50000 sheets formed by image density evaluation was evaluated for the presence or absence of a color point. The case where a color point did not occur was determined as ◯, and the case where a color point occurred was determined as x.

<Low temperature fixability>

  A printer remodeling machine (FS-5200DN (manufactured by Kyocera Document Solutions Co., Ltd.) with the fixing device removed) was used as an evaluation machine. The black developing device of the evaluation machine was filled with the two-component developer prepared in accordance with Preparation Example 1 above, and the toner of the example or comparative example was filled into the black toner container of the evaluation machine. Then, an unfixed black solid image was formed on the recording medium using the evaluation machine. Thereafter, an unfixed image was used by using an evaluation fixing device (fixing device for a printer (FS-5200DN (manufactured by Kyocera Document Solutions Co., Ltd.) modified so that the fixing temperature can be adjusted and can be driven independently)). Was fixed on the recording medium.

The specific evaluation method is as follows. Using an evaluation machine, an unfixed solid image having a toner applied amount of 1.5 g / cm ² was formed on a recording medium (CC90 (manufactured by Mondi)). The obtained unfixed image was fixed under the condition of a linear speed of 130 mm / sec using an evaluation fixing device set at a predetermined temperature. The image after fixing was folded in half so that the image portion was on the inside, and was rubbed 5 times on the crease using a 1 kg brass weight covered with a cloth on the bottom. The toner peeling at the bent portion was determined to be acceptable within 1 mm, and over 1 mm was determined to be unacceptable. Evaluation was performed by increasing the fixing temperature from 140 ° C. in 1 ° C. increments, and the lowest fixing temperature determined to be acceptable was set as the minimum fixing temperature, and the low temperature fixing property was evaluated according to the following evaluation criteria. ○ is acceptable, and Δ and × are unacceptable.
○: The minimum fixing temperature is 150 ° C. or lower.
Δ: The minimum fixing temperature is more than 150 ° C. and 155 ° C. or less.
X: The minimum fixing temperature exceeds 155 ° C.

  According to Examples 1 to 5, resin fine particles are externally added to toner base particles containing a binder resin containing a polyester resin containing a unit derived from 1,2-propanediol, thereby forming resin fine particles. The electrostatic image developing toner having a resin glass transition point of 125 ° C. or higher and 140 ° C. or lower and an S2 / S1 value of more than 0.85 and less than 0.95 is excellent in low-temperature fixability and has a long-term image quality. It can be seen that the occurrence of image defects such as color points due to the occurrence of filming and the reduction in the image density of the formed image can be suppressed.

  According to Comparative Example 1, it can be seen that when the glass transition point of the resin constituting the resin fine particles as the external additive is too high, the low-temperature fixability of the toner is impaired. According to Comparative Example 2, when the glass transition point of the resin constituting the resin fine particles as the external additive is too low, or when an image is formed over a long period of time, an image defect such as a color point due to the occurrence of filming It can be seen that the occurrence of the image and the decrease in the image density of the formed image are likely to occur.

  According to Comparative Example 3, it can be seen that when the value of S2 / S1 is too low, the image density of the formed image is likely to decrease when an image is formed over a long period of time. According to Comparative Example 4, it can be seen that when the value of S2 / S1 is too high, an image defect such as a color point due to filming is likely to occur when an image is formed over a long period of time.

Claims (1)

Toner base particles containing a binder resin containing a polyester resin containing units derived from 1,2-propanediol;
Resin fine particles attached to the surface of the toner base particles,
The resin fine particles do not include a polymer containing an acrylate monomer unit having an isobornyl group,
The glass transition point of the resin constituting the resin fine particles is 125 ° C. or more and 140 ° C. or less,
The following steps 1) to 3) with respect to the BET specific surface area S1 of the unused electrostatic charge image developing toner:
1) A step of putting 2 g of unused electrostatic charge image developing toner and 500 ml of ion-exchanged water containing 0.2 g of sodium alkyl ether sulfonate into a glass container,
2) A step of placing the glass container in an ultrasonic bath filled with water and irradiating the unused toner in the ion-exchanged water for 10 minutes under conditions of an output of 100 W and a frequency of 50 kHz. ,as well as,
3) a step of recovering the electrostatic image developing toner by filtering the dispersion of the electrostatic image developing toner irradiated with ultrasonic waves using a filter having a pore diameter of 0.8 μm and then drying the dispersion;
A toner for developing an electrostatic charge image, wherein the ratio S2 / S1 of the BET specific surface area S2 of the toner for developing an electrostatic charge image processed by the method is from 0.85 to 0.95.

Images