JP4169272B2 - Toner for electrophotography - Google Patents

Description

  The present invention relates to an electrophotographic toner (hereinafter sometimes simply referred to as “toner”), and more particularly to a toner in which a wax is dispersed and mixed in a binder resin.

  Toner used in an image forming apparatus such as a copying machine using electrophotography is required not to cause image contamination due to an offset phenomenon during heat fixing, that is, to have excellent offset resistance. In particular, in response to the recent demand for improvement in low-temperature fixability of toner in response to the energy saving of society, it is required to simultaneously prevent the occurrence of offset while improving the low-temperature fixability of toner. For this reason, it has been conventionally practiced to include a release agent such as wax in the toner. However, if the wax is simply contained in the toner, the desired dispersion of the wax in the binder resin cannot be obtained, and sufficient offset resistance cannot be achieved. On the other hand, if a large amount of wax is contained in the toner, offset can be prevented, but a so-called filming phenomenon occurs in which the wax is detached from the toner and is fixed to the surface of the photoreceptor.

  Therefore, for example, in Patent Document 1, a resin composition containing, as a binder resin, a low-melting crystalline compound and a vinyl copolymer containing a side chain capable of taking an aggregate structure with this compound is used as a binder resin. It is disclosed that this can prevent the low-melting crystalline compound from being detached, and can provide good storage stability, low-temperature fixability, and offset resistance.

Further, Patent Document 2 proposes that a specific hydrocarbon wax is contained in the toner so as to have specific viscoelastic characteristics and DSC curve characteristics, and thereby excellent fixing properties, offset resistance, and blocking resistance. Is disclosed.
JP-A-9-138521 (Claims, paragraph 0025, paragraph 0026) JP-A-5-249735 (Claims, FIGS. 1 and 2)

  However, with the proposed technology of Patent Document 1, the dispersibility of the wax in the binder resin cannot be controlled to a fine level, and the wax particle size becomes too small to obtain the desired offset resistance. Further, in the proposed technique of Patent Document 2, various thermal characteristic values are measured from the DSC curve, but the relationship between the shape of the DSC curve and the dispersibility of the wax is not conscious at all. The dispersibility of the wax in the resin is not finely controlled, and the desired offset resistance may not be obtained or a filming phenomenon may occur.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a toner that is excellent in anti-offset properties and does not cause filming.

As a result of intensive studies to achieve the above object, the present inventors have found that there is a close relationship between the shape of the differential curve of the DSC curve and the dispersion of the wax in the binder resin. It came to make. That is, the toner of the present invention is an electrophotographic toner having at least a binder resin, a wax, and a compatibilizer for dispersing the wax in the binder resin, and the content of the compatibilizer is The exothermic peak is in the range of 75 to 100 ° C. in the DSC curve when the temperature is lowered by a differential scanning calorimeter with a value in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin. And the differential curve of the DSC curve has at least one maximum value of zero or less on the higher temperature side than the exothermic peak.

  The DSC curve in the present invention was measured according to ASTM D3418-82. Measurement was started from room temperature, the temperature was increased to 180 ° C. at a temperature increase rate of 10 ° C./min, and the temperature decrease rate was 10 ° C. It is measured by lowering the temperature at / min.

  In order to obtain the shape of the differential curve of the DSC curve, various methods can be considered as will be described later, but it is preferable that a compatibilizing agent for dispersing the wax in the binder resin is contained in the toner. As such a compatibilizing agent, a graft copolymer of polyolefin and vinyl polymer is preferable.

  A change in state due to the heat of the toner appears in the shape of the DSC curve. Therefore, the present inventors conducted various studies on the anti-offset property, the occurrence of photoconductor filming, the DSC curve, and the shape of its differential curve through experiments and the like to be described later. As a result, a toner having an exothermic peak in the range of 75 to 100 ° C. in the DSC curve at the time of temperature reduction and at least one maximum value of zero or less on the high temperature side of the exothermic peak in the differential curve of the DSC curve. The present inventors have found that it has excellent anti-offset property and at the same time, no filming phenomenon due to wax desorption from the toner does not occur.

  In the case of the differential curve shape of the DSC curve, why the effect of improving the anti-offset property and preventing the filming is not yet clarified so far, but it has been pointed out so far. It is presumed that the interface state of the wax in the binder resin, not the dispersed particle diameter of the wax, has an effect on the above characteristics. In addition, the more preferable generation | occurrence | production range of the exothermic peak in the DSC curve at the time of temperature fall is a 80-95 degreeC range.

  In order to obtain the differential curve shape of the DSC curve at the time of temperature reduction as described above, for example, a compatibilizing agent for dispersing wax in the binder resin is added, or processing in the toner production process, particularly in the melt-kneading process. It was found that the conditions should be adjusted. This is considered that the effect of improving the offset resistance and preventing the filming can be obtained by setting the dispersion state of the wax in the binder resin within a predetermined range. Even if the dispersion state of the wax in the binder resin is too good or too bad, we have found that the offset resistance decreases and filming is likely to occur, but the detailed reason is unknown It is.

  Examples of the compatibilizer that can be used here include a graft copolymer of polyolefin and vinyl polymer, an alkylstyrene copolymer, and the like. Among these, a graft copolymer of polyolefin and vinyl polymer is preferable. Examples of the polyolefin include polyethylene, polypropylene, an ethylene-glycidyl methacrylate copolymer, an ethylene-vinyl acetate copolymer, and an ethylene-ethyl acrylate-maleic anhydride copolymer. Examples of the vinyl polymer include polystyrene, polymethyl methacrylate, acrylonitrile-styrene copolymer, and styrene-acrylic acid copolymer. Among these, a polystyrene-polyethylene graft copolymer is preferable.

  Further, the content of the compatibilizing agent when used may be appropriately determined from the type and amount of the wax and the binder resin, but is usually 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin. A range is particularly preferred. When the content of the compatibilizing agent is less than 0.5 parts by weight, mixing of the wax and the binder resin becomes insufficient, and the wax may be exposed on the toner surface and detached. On the other hand, when the content is more than 5 parts by weight, the wax is excessively dispersed in the binder resin, and in the differential curve of the DSC curve, at least one maximum value of zero or less appears on the higher temperature side than the exothermic peak of the DSC curve. This is because there is a risk of not.

  In order to obtain the differential curve shape of the DSC curve at the time of cooling as described above by adjusting the processing conditions in the melt-kneading process in the toner manufacturing process, for example, the following may be performed. The dispersibility of the wax is adjusted by heating the kneader to a temperature several degrees C. to several tens of degrees C. higher than the softening point of the binder resin, and applying an appropriate shearing / stirring force to the melted toner composition.

  When the kneading temperature is high or the rotation speed of the extrusion shaft is high, the dispersibility of the wax in the binder resin becomes too high, and in the differential curve of the DSC curve, at least 1 is higher than the exothermic peak of the DSC curve. Two maxima below zero do not appear. On the other hand, when the kneading temperature is low and the rotational speed of the extrusion shaft is low, the wax dispersibility in the binder resin is similarly lowered, and at least one maximum value of zero or less does not appear in the differential curve of the DSC curve. Therefore, it is necessary to melt and knead at an appropriate kneading temperature and the number of rotations of the extrusion shaft. Here, in order to further promote the dispersion of the wax in the binder resin, the compatibilizing agent may be further mixed into the binder resin.

  As the wax that can be used in the present invention, conventionally known waxes can be used, for example, polyhydric alcohol esters of fatty acids, higher alcohol esters of fatty acids, alkylene bis fatty acid amide compounds, natural waxes, and number average molecular weights of 1,000 to 10,000. 000, particularly 2,000 to 6,000, such as polypropylene, polyethylene, and propylene-ethylene copolymer. One or more kinds of waxes may be appropriately selected and used from these. The addition amount of the wax is preferably in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The binder resin used in the present invention is not particularly limited, and examples thereof include styrene-acrylic resins and polyester resins. Of course, if necessary, other resins may be used in combination with these resins.

  Examples of the monomer that serves as the base of the styrene-acrylic resin include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, p-chlorostyrene, and hydroxystyrene; methacrylic acid, methyl (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, methoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, Ethoxydiethylene glycol (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylonitrile, (meth) Kurylamide, N-methylol (meth) acrylamide, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, trimethylolethane tri (meth) acrylate And (meth) acrylic acid esters.

  The mixture of various monomers can be polymerized by any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, and the like, and can be used as a binder resin used in the present invention. In the polymerization, usable polymerization initiators include acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2 , 2′-azobis-4-methoxy-2,4-dimethylvaleronitrile and other known polymerization initiators can be used. These polymerization initiators are preferably used in the range of 0.1 to 15% by weight based on the total weight of the monomers.

  The polyester resin is obtained mainly by condensation polymerization of polyvalent carboxylic acids and polyhydric alcohols. Examples of the polyvalent carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, 1, 2 , 4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, pyromellitic acid and other aromatic polycarboxylic acids; maleic acid, fumaric acid, succinic acid, adipic acid , Sebacic acid, malonic acid, azelaic acid, mesaconic acid, citraconic acid, glutaconic acid and other aliphatic dicarboxylic acids; cyclohexanedicarboxylic acid, cyclohexene dicarboxylic acid and other alicyclic dicarboxylic acids; anhydrides and lower alkyl esters of these carboxylic acids 1 type or 2 types or more of these are used.

  Here, the content of the trivalent or higher component depends on the degree of cross-linking, and the addition amount may be adjusted in order to obtain a desired degree of cross-linking. In general, the content of trivalent or higher components is preferably 15 mol% or less.

  On the other hand, examples of the polyhydric alcohols used in the polyester resin include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, and neopentyl glycol. Alkylene glycols such as 1,5-pentane glycol and 1,6-hexane glycol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; 1,4 -Alicyclic polyhydric alcohols such as cyclohexanedimethanol and hydrogenated bisphenol A; bisphenols and bisphenols such as bisphenol A, bisphenol F, and bisphenol S Can be mentioned alkylene oxide, it can be used in combination of two or more thereof.

  For the purpose of adjusting the molecular weight and controlling the reaction, monocarboxylic acid and monoalcohol may be used as necessary. Examples of the monocarboxylic acid include benzoic acid, parahydroxybenzoic acid, toluene carboxylic acid, salicylic acid, acetic acid, propionic acid, and stearic acid. Examples of the monoalcohol include monoalcohols such as benzyl alcohol, toluene-4-methanol, and cyclohexanemethanol.

  The polyester resin used in the present invention is produced by a usual method using these raw materials. For example, an alcohol component and an acid component are charged into a reaction vessel at a predetermined ratio, and the reaction is started at a temperature of 150 to 190 ° C. in the presence of a catalyst while blowing an inert gas such as nitrogen. By-product low molecular weight compounds are continuously removed from the reaction system. Thereafter, the reaction temperature is further increased to 210 to 250 ° C. to accelerate the reaction, and the target polyester resin is obtained. The reaction can be carried out under any of normal pressure, reduced pressure, and increased pressure, but after the reaction rate reaches 50 to 90%, the reaction is preferably carried out under reduced pressure of 200 mmHg or less.

  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 binder resin used in the present invention preferably has a glass transition temperature in the range of 45 to 90 ° C. If the glass transition temperature is less than 45 ° C., the toner cartridge or the developing device may be hardened. On the other hand, if the glass transition temperature exceeds 90 ° C., the toner may not be sufficiently fixed on the transfer object such as paper.

  Examples of the colorant that can be used in the present invention include black pigments such as acetylene black, lamp black, and aniline black; black pigments such as yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, Nickel Titanium Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; orange pigment, reddish yellow lead, molybten orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK; red pigment, Bengala, cad Umred, lead red, mercury cadmium sulfide, permanent red 4R, risol 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 Lake; As Blue Pigment, Bitumen, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Induslen Blue BC; as a green pigment, chromium green, chromium oxide, pigment green B, malachite green lake, fanal yellow green G; As color pigments, zinc oxide, titanium oxide, antimony white, zinc sulfide, barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white can be used. One or more of these colorants may be used in combination.

  The total content of the colorant is preferably 0.1 to 20 parts by weight, particularly 1 to 15 parts by weight per 100 parts by weight of the binder resin.

  The toner of the present invention can be produced by a per se known method such as a pulverization classification method, a melt granulation method, a spray granulation method, a suspension / emulsion polymerization method or the like. The method can be suitably used. This pulverization classification method will be described below. First, a binder resin, a colorant, a wax and, if necessary, a toner composition such as a charge control agent and magnetic powder are premixed with a Henschel mixer or a V-type mixer, and then a melt kneader such as a twin screw extruder is used. Melt and knead. The melt-kneaded product is cooled, then coarsely pulverized and finely pulverized, and then classified as necessary to obtain toner particles having a predetermined particle size distribution. If necessary, the surface of the toner particles is treated with a surface treatment agent to obtain the toner of the present invention.

  Here, as the charge control agent, conventionally known charge control agents can be used. For example, as the positively chargeable charge control agent, a nigrosine dye, a fatty acid-modified nigrosine dye, a carboxyl group-containing fatty acid-modified nigrosine dye, a quaternary ammonium salt. An amine compound, an organometallic compound, and the like can be used. As the negatively chargeable charge control agent, a hydroxycarboxylic acid metal complex, an azo compound metal complex, a metal complex dye, a salicylic acid derivative, or the like can be used. The addition amount of the charge control agent is preferably in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

Further, magnetic powder may be added in order to suppress toner scattering due to insufficient charge amount. Examples of the magnetic powder include triiron tetroxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₃ O ₄ ), and iron yttrium oxide (Y ₃ Fe ₅ O _12). ), Iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron oxide copper (CuFe ₂ O ₄ ), iron oxide lead (PbFe ₁₂ O ₁₉ ), iron oxide nickel (NiFe ₂₎ O _4), iron oxide neodymium (NdFeO _3), barium iron oxide (BaFe ₁₂ O _19), iron oxide magnesium (MgFe ₂ O _4), manganese iron oxide (MnFe ₂ O _4), iron oxide, lanthanum (LaFeO _3), Examples thereof include iron powder (Fe), cobalt powder (Co), and nickel powder (Ni). A particularly suitable magnetic powder is particulate iron trioxide (magnetite). A suitable magnetite has a regular octahedral shape and a particle diameter of 0.05 to 1.0 μm. The magnetite particles may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like. The content of the magnetic powder may be a small amount of internal addition such as 0.1 to 5 parts by weight, particularly 0.5 to 3.0 parts by weight per 100 parts by weight of the binder resin.

  The toner of the present invention can be used as a one-component developer or a two-component developer. There are no limitations on the carrier used when used as a two-component developer, for example, magnetic metals such as iron, nickel, cobalt and their alloys, or alloys containing rare earths, hematite, magnetite, manganese-zinc Sintering and atomizing magnetic materials such as ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, lithium ferrite and other soft ferrites, copper-zinc ferrite and other iron-based oxides, and mixtures thereof The magnetic particles produced by this method, and those obtained by coating the surfaces of the magnetic particles with a resin can be used. In addition, a magnetic material dispersed resin can be used as the carrier. In this case, the magnetic material described above can be used as the magnetic material used, and examples of the binder resin include vinyl resins, polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, and polyresins. Mention may be made of ether resins or mixtures thereof.

The particle diameter of the carrier is generally 30 to 200 μm, particularly preferably 50 to 150 μm, expressed in terms of particle diameter by electron microscopy. Further, the apparent density of the carrier is preferably in the range of 2.4 to 3.0 g / cm ³ , although it varies depending on the composition of the magnetic material, the surface structure and the like when the magnetic material is mainly used.

  The toner concentration in the two-component developer comprising the toner and carrier is 1 to 10% by weight, preferably 1 to 7% by weight. When the toner density is less than 1% by weight, the image density becomes too thin, while when the toner density exceeds 10% by weight, the toner scatters in the developing device, and the toner adheres to the background portion such as dirt inside the machine or transfer paper. This is because there is a risk of malfunction.

  The photoreceptor used with the toner of the present invention is not particularly limited, and conventionally known ones such as a selenium photoreceptor, an organic photoreceptor, and an amorphous silicon photoreceptor can be used.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated, this invention is not limited only to a following example.
<Example 1>

  100 parts by weight of styrene-butyl acrylate copolymer (molar copolymerization ratio 8: 2, weight average molecular weight Mw: 202,000, number average molecular weight Mn: 6,000, Mw / Mn: 33.7) as binder resin, carbon black as colorant 7 parts by weight (MA-100 manufactured by Mitsubishi Chemical Corporation), 5 parts by weight polyethylene (PE130 manufactured by Hoechst) as a wax, and 2 parts polystyrene-polyethylene graft copolymer (molar copolymerization ratio 7: 3) as a compatibilizer. 5 parts by weight of styrene-dimethylaminoethyl methacrylate copolymer as a charge control agent and 5 parts by weight of each were put into a Henschel mixer and mixed for 10 minutes.

  Then, the mixing amount of the mixed material is set to 100 g / min, the temperature of the kneading part is 120 ° C., the rotational speed of the extrusion shaft is 180 rpm, and melt-kneaded with a twin-screw extruder (PCM-30 manufactured by Ikegai Seisakusho) Cooled with a flaker. Next, coarsely pulverized with a hammer mill, then finely pulverized with a jet mill, and classified using an air classifier to produce toner particles (volume center particle size: 9 μm).

  The DSC curve at the time of temperature reduction of the toner particles was measured at a temperature decrease rate of 10 ° C./min using a differential scanning calorimeter (“Q1000” manufactured by TA Instruments). Moreover, the differential curve of the said DSC curve was computed by calculating | requiring the difference of the data (measurement temperature interval: 0.1 degreeC) of the Heat Flow value in each measured temperature (refer following formula (1)). A DSC curve and its differential curve are shown in FIG.

  In the present invention, the relationship between the DSC curve function: f (t) and the differential curve function: f ′ (t) of the DSC curve function is defined as follows (t: temperature).

f ′ (t) = {f (t + Δt) −f (t)} / Δt (Δt = 0.1 ° C.)
= {F (t + 0.1) -f (t)} / 0.1 (1)
According to FIG. 1, the toner particles of Example 1 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum value at 90 ° C. in the differential curve of the DSC curve.

  Next, 0.5 parts by weight of hydrophobic silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) as a surface treatment agent was added to 100 parts by weight of the toner particles, and the resulting mixture was mixed with high stirring with a Henschel mixer to obtain a toner. This toner was blended in a ferrite carrier having an average particle size of 80 μm whose surface was coated with a silicone resin so that the toner concentration would be 5% by weight, and the mixture was uniformly stirred and mixed to obtain a two-component developer. Then, the developer prepared in an electrophotographic copying machine (trade name “KM-2030”) manufactured by Kyocera Mita Co., Ltd. was mounted, and the presence or absence of filming and offset generation was observed by the following method as a severe test. The results are shown in Table 1.

<Filming>
The copying machine was modified to reduce the wire thickness of the cleaning blade by 0.4 g / mm, and after 100,000 sheets were printed, the surface of the photosensitive drum and the image were visually observed, and no filming occurred. The case was “◯”, the case of slight occurrence was “Δ”, and the case of large occurrence was “X”.

<Offset>
The copying machine is controlled to change the fixing temperature to 200 ° C., and five sheets are continuously fed. The passed image was visually observed. The case where no offset occurred was indicated by “◯”, the case where slight offset occurred, “Δ”, and the case where a large amount occurred, “X”.

<Comprehensive evaluation>
Comprehensively judging from the filming and offset occurrence situation, “good” indicates “good”, “good” indicates “good”, and “good” indicates “poor”.
<Example 2>

  A toner was prepared in the same manner as in Example 1 except that the polystyrene-polyethylene graft copolymer as a compatibilizer was changed from 2 parts by weight to 1 part by weight. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data. The DSC curve and its differential curve are shown in FIG.

According to FIG. 2, the toner particles of Example 2 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum value at 91 ° C. in the differential curve of the DSC curve. Also, the presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.
<Example 3>

  A toner was prepared in the same manner as in Example 1 except that the polystyrene-polyethylene graft copolymer as a compatibilizer was changed from 2 parts by weight to 5 parts by weight. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data.

The toner particles of Example 3 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum value at 88 ° C. in the differential curve of the DSC curve. The presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.
<Example 4>

[ Reference Example 1 ]
A toner was produced in the same manner as in Example 1 except that the polystyrene-polyethylene graft copolymer as a compatibilizer was changed from 2 parts by weight to 6 parts by weight. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data.

The toner particles of Reference Example 1 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum value at 87 ° C. in the differential curve of the DSC curve. The presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.

  A toner was prepared in the same manner as in Example 1 except that the type of the compatibilizer was changed from the polystyrene-polyethylene graft copolymer to the polystyrene-polypropylene graft copolymer (molar copolymer ratio 7: 3). Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data.

The toner particles of Example 5 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum value at 92 ° C. in the differential curve of the DSC curve. The presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.
<Comparative Example 1>

  A toner was prepared in the same manner as in Example 1 except that the melt kneading temperature of the biaxial extruder was 20 ° C. higher than that in Example 1 to 140 ° C. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data. The DSC curve and its differential curve are shown in FIG.

According to FIG. 3, the toner particles of Comparative Example 1 only had an exothermic peak at 86 ° C. in the DSC curve and did not have a negative maximum value in the differential curve of the DSC curve. Also, the presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.
<Comparative example 2>

  A toner was prepared in the same manner as in Example 1 except that it did not contain a polystyrene-polyethylene graft copolymer as a compatibilizer. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data. The DSC curve and its differential curve are shown in FIG.

According to FIG. 4, the toner particles of Comparative Example 2 have positive maximum values near 83 ° C. and 86 ° C. in the differential curve of the DSC curve, but do not have a maximum value less than zero, and the DSC curve. And had an exothermic peak at 88 ° C. Also, the presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.
<Comparative Example 3>

  A toner was prepared in the same manner as in Example 1 except that the melt kneading temperature of the biaxial extruder was 20 ° C. lower than that in Example 1 to 100 ° C. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data.

The toner particles of Comparative Example 3 had an exothermic peak at 89 ° C. in the DSC curve, and did not have a negative maximum value in the differential curve of the DSC curve. The presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.
<Comparative example 4>

  A toner was prepared in the same manner as in Example 1 except that the rotation speed of the extrusion shaft of the biaxial extruder was lowered by 70 rpm to 110 rpm from that in Example 1. Further, the DSC curve when the toner particles were cooled was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured exothermic data.

  The toner particles of Comparative Example 4 had an exothermic peak at 90 ° C. in the DSC curve and did not have a negative maximum value in the differential curve of the DSC curve. The presence or absence of filming and offset was observed in the same manner as described above. The results are shown in Table 1.

However, for Reference Example 1 , a slight hot offset occurred in this evaluation method (this is a severe test with a fixing temperature of 200 ° C., and there is no problem in actual use). This is presumably because the amount of the compatibilizer added in Reference Example 1 was as large as 6 parts by weight, and the wax tended to be too well dispersed in the binder resin.

  As for Example 5, slight filming occurred in this evaluation method (a severe test in which the linear pressure of the cleaning blade is weakened and there is no problem in actual use). The detailed reason for this is unknown, but in Example 5, the dispersibility of the polyethylene wax in the binder resin was slightly deteriorated by changing the type of the compatibilizer to polystyrene-polypropylene graft copolymer. It is guessed. Therefore, it is inferred that the interaction between polypropylene and polyethylene wax, which is the graft part of the compatibilizer, was lower than when the graft part was polyethylene, and the dispersibility of the polyethylene wax tended to deteriorate. Is done.

  In Comparative Example 1, a large amount of hot offset occurred. This is presumably because the wax was clearly dispersed too much in the binder resin because the melt kneading temperature was increased.

  In Comparative Examples 2, 3, and 4, filming occurred. This is because the compatibilizing agent was not added in Comparative Example 2, and therefore the melt kneading temperature was lowered in Comparative Example 3, so that the biaxial rotation speed during melt kneading was lowered in Comparative Example 4, and thus the binder resin It is considered that the dispersion of the wax in the toner deteriorated so much that the wax detached from the toner adhered to the photosensitive drum and filming occurred.

  As described above, by setting the dispersibility of the wax in the binder resin within a predetermined range, the differential curve of the DSC curve has at least one maximum value of zero or less on the higher temperature side than the exothermic peak of the DSC curve. As a result, it has become clear that the occurrence of offset and filming can be prevented. The toner having the differential curve shape of the DSC curve is used at the time of toner production by melt kneading by adding a wax compatibilizer to the toner, for example, as shown in the above examples or comparative examples. It can be obtained by appropriately setting the melt kneading temperature of the twin screw extruder and the rotational speed of the extrusion shaft. Further, it was confirmed that the amount of the compatibilizing agent added is particularly preferably up to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  And in both cases, the dispersibility of the wax in the binder resin does not have a maximum value of zero or less in the differential curve of the DSC curve, and the dispersibility of the wax does not increase. It has been confirmed that hot offset occurs when it becomes too good, and filming occurs when the dispersibility of the wax becomes too bad.

  Furthermore, the present invention makes it very easy to evaluate the toner material design. That is, the differential curve shape of the DSC curve of the toner has at least one maximum value less than or equal to zero at a temperature higher than the exothermic peak of the DSC curve without actually performing a printing test using 100,000 sheets of paper. It is possible to estimate the offset resistance and filming resistance of the toner only by investigating whether or not.

FIG. 3 is a diagram showing a DSC curve and a differential curve of the DSC curve when the toner particles of Example 1 are cooled. FIG. 6 is a diagram illustrating a DSC curve and a differential curve of the DSC curve when the toner particles of Example 2 are cooled. 6 is a diagram showing a DSC curve and a differential curve of the DSC curve when the toner particles of Comparative Example 1 are cooled. FIG. 6 is a diagram showing a DSC curve and a differential curve of the DSC curve when the toner particles of Comparative Example 2 are cooled. FIG.

Claims (3)

An electrophotographic toner comprising at least a binder resin, a wax, and a compatibilizing agent for dispersing the wax in the binder resin ,
The content of the compatibilizing agent is a value within the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin,
In the DSC curve at the time of temperature drop measured by a differential scanning calorimeter,
An electrophotographic toner having an exothermic peak in a range of 75 to 100 ° C. and having at least one maximum value of zero or less on a higher temperature side than the exothermic peak in a differential curve of the DSC curve. 2. The electrophotographic toner according to claim 1, wherein the temperature on the high temperature side of the at least one exothermic peak having a maximum value of zero or less is a value in a range of 88 to 92 ° C. 3. 3. The electrophotographic toner according to claim 1, wherein the electrophotographic toner has a melting temperature in the range of more than 100 ° C. and less than 140 ° C. when the electrophotographic toner is produced using a twin-screw extruder. .

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