JP2004272221A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner which has excellent anti-offset properties and is free of filming phenomenon. <P>SOLUTION: The electrophotographic toner comprises at least binder resin and wax. On a DSC curve measured with a differential scanning calorimeter in temperature reduction, the toner has an exothermic peak in a range of 75 to 100°C, and on the differential curve of the DSC curve, the toner has at least one maximum value below zero on the higher temperature side than the exothermic peak, which makes the toner free of offset and filming. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

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

  A toner used in an image forming apparatus such as a copying machine using an electrophotographic method is required to be free from image contamination due to an offset phenomenon at the time of heat fixing, that is, to have excellent offset resistance. In particular, in a situation where improvement of low-temperature fixing property of toner is strongly demanded recently in response to energy saving of society, it is required to prevent occurrence of offset at the same time while improving low-temperature fixing property of toner. For this reason, a release agent such as a wax is conventionally contained in the toner. However, simply adding wax to the toner does not provide the desired dispersion of the wax in the binder resin, and does not provide sufficient offset resistance. 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 detaches from the toner and adheres to the surface of the photoreceptor.

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

Patent Document 2 proposes that a specific hydrocarbon wax be contained in a toner to have specific viscoelastic characteristics and DSC curve characteristics, thereby providing excellent fixability, 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, according to the technique disclosed in Patent Document 1, the dispersibility of the wax in the binder resin cannot be controlled to a small extent, and the wax particle size becomes too small to obtain the desired offset resistance in some cases. Further, in the proposed technique of Patent Document 2, although various thermal characteristic values are measured from the DSC curve, there is no awareness of the relationship between the shape of the DSC curve and the dispersibility of the wax, and the results are similar to the above. It is not possible to control the dispersibility of the wax in the resin to a very small degree, 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 a conventional problem, and an object of the present invention is to provide a toner which has excellent offset resistance and does not cause a filming phenomenon.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, 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 do. That is, the toner of the present invention is an electrophotographic toner having at least a binder resin and wax, and has an exothermic peak in the range of 75 to 100 ° C. in a DSC curve at the time of temperature decrease measured by a differential scanning calorimeter. In the differential curve of the DSC curve, the DSC curve has at least one maximum value equal to or lower than zero on the higher temperature side than the exothermic peak.

  The DSC curve in the present invention was measured according to ASTM D3418-82. The measurement was started from room temperature, and after the temperature was raised to 180 ° C. at a rate of 10 ° C./min, the temperature was lowered at a rate of 10 ° C. The temperature was measured at a temperature of / min.

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

  The shape of the DSC curve shows a state change due to the heat of the toner. Accordingly, the present inventors have conducted various studies on the offset resistance, occurrence of photoreceptor filming, and the shape of the DSC curve and its differential curve through experiments described below. As a result, the toner having an exothermic peak in the range of 75 to 100 ° C. in the DSC curve at the time of temperature decrease and having at least one maximum value of zero or less on the higher temperature side than the exothermic peak in the differential curve of the DSC curve is It has been found that the film has excellent offset resistance and at the same time does not cause filming due to detachment of wax from the toner.

  The answer to this question has not yet been clarified why such a differential curve shape of the DSC curve can provide an effect of improving the anti-offset property or preventing filming, but has been pointed out so far. It is presumed that the interface state of the wax in the binder resin, not the dispersed particle size of the wax, is effective in the above-mentioned properties. In addition, a more preferable generation range of the exothermic peak in the DSC curve at the time of temperature fall is in the range of 80 to 95 ° C.

  In order to obtain the differential curve shape of the DSC curve at the time of temperature decrease as described above, for example, a compatibilizer for dispersing wax in a binder resin is added, or processing is performed during a toner manufacturing process, particularly in a melt kneading process. We have found that the conditions need to be adjusted. It is considered that the effect of improving the anti-offset property 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, it has been found that the offset resistance decreases and filming easily occurs, but the detailed reason is unknown. It is.

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

  The content of the compatibilizer when used may be appropriately determined based on the type and amount of the wax and the binder resin, but is usually 0.5 to 5 parts by weight based on 100 parts by weight of the binder resin. A range is particularly preferred. If the content of the compatibilizer is less than 0.5 part by weight, the 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, if the content is more than 5 parts by weight, the wax is excessively dispersed in the binder resin, and at least one local maximum value less than zero appears on the higher temperature side than the exothermic peak of the DSC curve in the differential curve of the DSC curve. This is because there is a possibility that there is not.

  In order to obtain the above-mentioned differential curve shape of the DSC curve at the time of cooling by adjusting the processing conditions in the melt-kneading step in the toner production step, for example, the following may be performed. The dispersibility of the wax is adjusted by heating the kneader to a temperature several to several tens of degrees higher than the softening point of the binder resin and applying an appropriate shearing / stirring force to the molten 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 No two maxima below zero. Conversely, when the kneading temperature is low and the rotation speed of the extrusion shaft is low, the wax dispersibility in the binder resin is also low, and at least one local maximum value of zero or less does not appear in the differential curve of the DSC curve. Therefore, it is necessary to perform melt-kneading at an appropriate kneading temperature and the rotation speed of the extrusion shaft. Here, in order to further promote the dispersion of the wax in the binder resin, the compatibilizer may be further mixed with 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, alkylenebisfatty acid amide compounds, natural waxes, and number average molecular weights of 1,000 to 10, 000, especially 2,000 to 6,000. One or more waxes may be appropriately selected and used from these. The amount of the wax is preferably in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin.

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

  Examples of the monomer serving 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) Acrylamide, 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 the like.

  The mixture of the above 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 the binder resin used in the present invention. In such a polymerization, usable polymerization initiators include acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, A known polymerization initiator such as 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile 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 polycondensation of a polycarboxylic acid and a polyhydric alcohol. Examples of the polycarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, 1,2 Polycarboxylic acids such as 2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and pyromellitic acid; maleic acid, fumaric acid, succinic acid, and adipic acid Aliphatic dicarboxylic acids such as sebacic acid, malonic acid, azelaic acid, mesaconic acid, citraconic acid, glutaconic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and cyclohexene dicarboxylic acid; anhydrides and lower alkyl esters of these carboxylic acids And one or more of these are used.

  Here, the content of the trivalent or higher-valent component depends on the degree of crosslinking, and the amount of addition may be adjusted to obtain a desired degree of crosslinking. Generally, the content of the trivalent or higher valent component is preferably 15 mol% or less.

  On the other hand, as polyhydric alcohols used for polyester resins, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, neopentyl glycol Alkylene glycols such as 1,1,5-pentane glycol and 1,6-hexane glycol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; Alicyclic polyhydric alcohols such as cyclohexane dimethanol 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, a monocarboxylic acid or a monoalcohol may be used if necessary. Examples of the monocarboxylic acid include benzoic acid, parahydroxybenzoic acid, toluenecarboxylic 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. The by-product low-molecular compound is continuously removed to the outside of the reaction system. Thereafter, the reaction temperature is further raised to 210 to 250 ° C. to accelerate the reaction, and the desired polyester resin is obtained. The reaction can be performed under any of normal pressure, reduced pressure, and increased pressure. However, after the reaction rate reaches 50 to 90%, the reaction is preferably performed 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 compounds containing these metals.

  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 lower than 45 ° C., the toner may harden in the toner cartridge or the developing device. If the glass transition temperature is higher than 90 ° C., the toner may not be sufficiently fixed on an object to be transferred such as paper.

  Examples of the colorant that can be used in the present invention include, as black pigments, acetylene black, lamp black, carbon black such as aniline black; and as yellow pigments, graphite, 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; Red pigment, molybdenum orange, permanent orange as orange pigment GTR, pyrazolone orange, Vulcan orange, induslen brilliant orange RK, benzidine orange G, induslen brilliant orange GK; red pigments such as bengara and cad Um red, lead red, mercury cadmium sulfide, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; as purple pigment , Manganese Purple, Fast Violet B, Methyl Violet Lake; Blue pigments include navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, indaslen blue BC; as green pigments, chrome 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 preferably 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 method known per se such as a pulverization classification method, a melt granulation method, a spray granulation method, a suspension / emulsion polymerization method, and the like. The method can be suitably used. The pulverization and classification method will be described below. First, a toner composition such as a binder resin, a colorant, a wax, and, if necessary, a charge control agent and a magnetic powder is premixed with a Henschel mixer or a V-type mixer, and then, using a melt-kneading device such as a twin-screw extruder. Melt and knead. After cooling the melt-kneaded product, it is roughly pulverized and finely pulverized, and if necessary, classified to obtain toner particles having a predetermined particle size distribution. If necessary, the surface of the toner particles is treated with a surface treating agent to obtain the toner of the present invention.

  Here, as the charge control agent, known charge control agents can be used. Examples of the positive charge control agent include a nigrosine dye, a fatty acid-modified nigrosine dye, a carboxyl group-containing fatty acid-modified nigrosine dye, and a quaternary ammonium salt. , An amine compound, an organometallic compound and the like, and as the negatively chargeable charge control agent, a metal complex of a hydroxycarboxylic acid, a metal complex of an azo compound, a metal complex salt dye, a salicylic acid derivative and 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 based on 100 parts by weight of the binder resin.

Magnetic powder may be added to suppress toner scattering due to insufficient charge. Examples of the magnetic powder include iron trioxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₃ O ₄ ), and yttrium iron oxide (Y ₃ Fe ₅ O _12). ), Cadmium iron oxide (CdFe ₂ O ₄ ), gadolinium iron oxide (Gd ₃ Fe ₅ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂₎ O ₄ ), iron neodymium oxide (NdFeO ₃ ), barium iron oxide (BaFe ₁₂ O ₁₉ ), iron oxide magnesium (MgFe ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), Iron powder (Fe), cobalt powder (Co), nickel powder (Ni) and the like are listed. A particularly preferred magnetic powder is particulate iron tetroxide (magnetite). The preferred magnetite is octahedral and has a particle size of 0.05 to 1.0 μm. The magnetite particles may be surface-treated with a silane coupling agent, a titanium-based coupling agent, or the like. The content of the magnetic powder may be as small 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. The carrier used when used as a two-component developer is not limited. For example, magnetic metals such as iron, nickel, and cobalt and alloys thereof, or alloys containing rare earth elements, hematite, magnetite, manganese-zinc based Sintering and atomizing magnetic materials such as soft ferrites such as ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, and lithium ferrite, and iron-based oxides such as copper-zinc ferrite and mixtures thereof. The magnetic particles produced as described above, and those obtained by coating the surfaces of the magnetic particles with a resin can be used. Further, a magnetic material-dispersed resin can be used as the carrier. In this case, the above magnetic material can be used as the magnetic material to be used, and as the binder resin, for example, vinyl resin, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, poly Ether resins or mixtures thereof can be mentioned.

The carrier preferably has a particle diameter of 30 to 200 μm, particularly preferably 50 to 150 μm, as represented by a particle diameter determined by electron microscopy. The apparent density of the carrier, when mainly composed of a magnetic material, varies depending on the composition and surface structure of the magnetic material, but is generally preferably in the range of 2.4 to 3.0 g / cm ³ .

  The toner concentration in the two-component developer comprising the toner and the carrier is 1 to 10% by weight, preferably 1 to 7% by weight. When the toner concentration is less than 1% by weight, the image density becomes too low. On the other hand, when the toner concentration exceeds 10% by weight, the toner scatters in the developing device, and the toner adheres to the inside of the apparatus and the background portion such as transfer paper. This is because there is a possibility that a malfunction may occur.

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

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to only the following Examples.
<Example 1>

  100 parts by weight of a 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 a binder resin, and carbon black as a colorant 7 parts by weight (MA-100 manufactured by Mitsubishi Chemical Corporation), 5 parts by weight of polyethylene (PE130 manufactured by Hoechst) as a wax, and 2 parts of a polystyrene-polyethylene graft copolymer (molar copolymerization ratio 7: 3) as a compatibilizer. 5 parts by weight of a styrene-dimethylaminoethyl methacrylate copolymer as a charge control agent and 5 parts by weight of each were charged into a Henschel mixer and mixed for 10 minutes.

  The input amount of the mixed material was set to 100 g / min, the temperature of the kneading section was 120 ° C., and the number of rotations of the extrusion shaft was 180 rpm. Cooled on a breaker. Next, after coarsely pulverized by a hammer mill, finely pulverized by a jet mill and classified using an air classifier, toner particles (volume center particle size: 9 μm) were produced.

  The DSC curve of the toner particles when the temperature was lowered was measured at a temperature lowering rate of 10 ° C./min using a differential scanning calorimeter (“Q1000” manufactured by TA Instruments). The differential curve of the DSC curve was calculated by calculating the difference between the measured Heat Flow value data (measurement temperature interval: 0.1 ° C.) at each temperature (see the following equation (1)). The DSC curve and its derivative 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 treating agent was added to 100 parts by weight of the toner particles, and the mixture was mixed with high stirring using a Henschel mixer to obtain a toner. This toner was blended with a ferrite carrier having an average particle size of 80 μm, the surface of which was coated with a silicone resin, so that the toner concentration was 5% by weight, and uniformly stirred and mixed to obtain a two-component developer. The prepared developer was mounted on an electrophotographic copying machine (trade name "KM-2030") manufactured by Kyocera Mita Co., Ltd., and the occurrence of filming and offset was observed by the following severe test. The results are shown in Table 1.

<Filming>
The cleaning machine was modified to reduce the line thickness of the cleaning blade to 0.4 g / mm, and after printing for 100,000 sheets, the surface of the photosensitive drum and the image were visually observed, and no filming occurred. The case was indicated by “○”, the case where slight occurrence occurred was indicated by “△”, and the case where a large amount occurred was indicated by “×”.

<Offset>
Control remodeling is performed so that the fixing temperature of the copying machine is 200 ° C., and five sheets are continuously passed. Then, the passed image was visually observed. The case where no offset occurred was indicated by “○”, the case where slight occurrence occurred was indicated by “△”, and the case where a large amount occurred was indicated by “×”.

<Comprehensive evaluation>
Judging comprehensively from the filming and the occurrence of the offset, "good" was given as "◎", "good" as "○", and "bad" as "x".
<Example 2>

  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 1 part by weight. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation data. The DSC curve and its derivative 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 at 91 ° 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 3>

  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 5 parts by weight. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation data.

The toner particles of Example 3 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum 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>

  A toner was produced in the same manner as in Example 1 except that the amount of the polystyrene-polyethylene graft copolymer as the compatibilizer was changed from 2 parts by weight to 6 parts by weight. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation data.

The toner particles of Example 4 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum 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.
<Example 5>

  A toner was produced in the same manner as in Example 1, except that the type of the compatibilizer was changed from a polystyrene-polyethylene graft copolymer to a polystyrene-polypropylene graft copolymer (molar copolymerization ratio: 7: 3). The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation data.

The toner particles of Example 5 had an exothermic peak at 86 ° C. in the DSC curve and a negative maximum 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 produced in the same manner as in Example 1 except that the melt-kneading temperature of the twin-screw extruder was set to 140 ° C., which was 20 ° C. higher than that in Example 1. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation data. The DSC curve and its derivative 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. 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 the composition did not contain a polystyrene-polyethylene graft copolymer as a compatibilizer. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation data. The DSC curve and its derivative curve are shown in FIG.

According to FIG. 4, although the toner particles of Comparative Example 2 have positive maximum values at around 83 ° C. and around 86 ° C. in the differential curve of the DSC curve, they do not have local maximum values below zero, and the DSC curve Had an exothermic peak at 88 ° C. 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 produced in the same manner as in Example 1 except that the melt-kneading temperature of the twin-screw extruder was lowered by 20 ° C. from that in Example 1 to 100 ° C. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation 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 produced in the same manner as in Example 1 except that the number of revolutions of the extrusion shaft of the twin-screw extruder was reduced by 70 rpm from that in Example 1 to 110 rpm. The DSC curve of the toner particles at the time of temperature decrease was measured using a differential scanning calorimeter. Then, a differential curve of the DSC curve was calculated from the measured heat generation 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.

表１によれば、本発明の要件を具備する実施例１〜３のトナーでは、１０万枚の耐刷後もフィルミング及びオフセットは全く発生しなかった。

According to Table 1, the toners of Examples 1 to 3 satisfying the requirements of the present invention did not cause any filming and no offset even after printing of 100,000 sheets.

  However, in Example 4, a slight hot offset occurred in this evaluation method (a severe test in which the fixing temperature was 200 ° C., and there was no problem in actual use). This is considered to be because the amount of the compatibilizer added in Example 4 was as large as 6 parts by weight, and the wax tended to be too well dispersed in the binder resin.

  In Example 5, slight filming occurred in this evaluation method (a severe test in which the linear pressure of the cleaning blade was reduced, and there was no problem in actual use). Although the detailed reason for this is unknown, in Example 5, the dispersibility of polyethylene wax in the binder resin was slightly deteriorated by changing the type of the compatibilizer to a polystyrene-polypropylene graft copolymer. It is presumed. Therefore, it is speculated that the interaction between polypropylene and polyethylene wax, which are graft portions of the compatibilizer, was reduced as compared with the case where the graft portion 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 considered to be because the wax was clearly excessively dispersed in the binder resin due to an increase in the melt-kneading temperature.

  In Comparative Examples 2, 3, and 4, filming occurred. This is because the compatibilizer was not added in Comparative Example 2, the melt-kneading temperature was lowered in Comparative Example 3, and the biaxial rotation speed during melt-kneading was reduced in Comparative Example 4. It is considered that the dispersion of the wax inside deteriorated extremely, and the wax detached from the toner adhered to the photosensitive drum to cause filming.

  As described above, by setting the dispersibility of the wax in the binder resin to 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. It became clear that the occurrence of offset and the occurrence of filming were prevented. The toner having such a differential curve shape of the DSC curve is used, for example, by adding a wax compatibilizer to the toner and producing the toner by melt-kneading, as shown in the above Examples and Comparative Examples. It can be obtained by appropriately setting the melt-kneading temperature of the twin-screw extruder and the rotation speed of the extrusion shaft. It was also confirmed that the amount of the compatibilizer added was particularly preferably up to 5 parts by weight based on 100 parts by weight of the binder resin.

  Then, even if the dispersibility of the wax in the binder resin is too good or too bad, in any case, the differential curve of the DSC curve does not have a maximum value of zero or less in the differential curve, and the dispersibility of the wax is low. It was confirmed that when the temperature was too good, hot offset occurred, and when the dispersibility of the wax was too bad, filming occurred.

  Further, the present invention makes it very easy to evaluate the material design of the toner. That is, even if a printing test is not actually performed using as many as 100,000 sheets of paper, the differential curve shape of the DSC curve of the toner has at least one maximum value of zero or less at a temperature higher than the heat generation peak of the DSC curve. It is possible to estimate the offset resistance and the filming resistance of the toner only by examining whether or not the toner is offset.

FIG. 3 is a diagram illustrating a DSC curve and a differential curve of the DSC curve when the temperature of the toner particles of Example 1 is lowered. FIG. 13 is a diagram illustrating a DSC curve and a differential curve of the DSC curve when the temperature of the toner particles of Example 2 is lowered. FIG. 9 is a diagram illustrating a DSC curve and a differential curve of the DSC curve when the temperature of the toner particles of Comparative Example 1 is lowered. FIG. 9 is a diagram illustrating a DSC curve and a differential curve of the DSC curve when the temperature of the toner particles of Comparative Example 2 is lowered.

Claims (3)

An electrophotographic toner having at least a binder resin and a wax, which has an exothermic peak in a range of 75 to 100 ° C. in a DSC curve at the time of temperature decrease measured by a differential scanning calorimeter, and An electrophotographic toner having at least one local maximum value of zero or less on a higher temperature side than the exothermic peak in a differential curve. The electrophotographic toner according to claim 1, further comprising a compatibilizer for dispersing the wax in the binder resin. The electrophotographic toner according to claim 2, wherein the content of the compatibilizer is in the range of 0.5 to 5 parts by weight based on 100 parts by weight of the binder resin.

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