JP2009109971A - Toner for electrophotography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner for electrophotography, which is excellent in both low temperature fixing ability and storage property, also is excellent in durability and can maintain excellent transfer efficiency and image density even in a plate wear test of a low printing ratio, and to provide an image forming method using the toner for electrophotography. <P>SOLUTION: The toner for electrophotography includes: toner mother particles containing a binder resin and wax; and external additive, wherein the binder resin includes a crystalline polyester, a calorie of an area surrounded by an endothermic curve of the toner determined with a differential scanning calorimeter and a straight line connecting the top of an endothermic peak appearing at the lowest temperature among endothermic peaks originated from the binder resin to the top of an endothermic peak originated from the wax having the lowest melting point among the waxes is 0.1 to 10.0 J/g, the average circularity of the toner is 0.940 to 0.980 and the content of particles having particle size of <3 μm is ≤5% by number. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method, and the like, and an image forming method using the toner.

  In recent years, a toner capable of being fixed at a lower temperature has been demanded from the viewpoint of speeding up and downsizing of the apparatus, and various types of toners containing crystalline polyester as a binder resin have been studied.

In addition, a method of performing a heat treatment process on a production intermediate such as a melt-kneaded product or a classified product in a production process of a toner using crystalline polyester has been proposed (see Patent Documents 1 to 3).
JP 2005-308995 A JP 2006-65015 A JP 2006-65077 A

  However, although conventional toners including toners containing crystalline polyesters are effective for improving low-temperature fixability, they are compatible with amorphous polyesters when the toner raw material is melt-kneaded, and the crystal structure thereof is destroyed. , Causing a decrease in storage stability and durability.

  Moreover, even if it heat-processes like patent documents 1-3, it is difficult to obtain the stable image under the influence of the fine powder which generate | occur | produces by long-term durability, and it is sufficient durability when crystallization is inadequate. I can't get sex. In particular, a decrease in transfer rate in printing durability with a low printing rate is remarkable.

  Further, when a low-melting-point wax is used for the purpose of improving the fixability, durability becomes a problem.

  An object of the present invention is to provide an electrophotographic toner that is excellent in both low-temperature fixability and storage stability, is excellent in durability, and can maintain good transfer efficiency and image density even in printing durability with a low printing rate, and the toner An object of the present invention is to provide an image forming method using toner.

The present invention
[1] An electrophotographic toner comprising toner base particles containing a binder resin and a wax, and an external additive, wherein the binder resin comprises a crystalline polyester, The endothermic curve measured by the differential scanning calorimeter of the toner, the endothermic peak that appears at the lowest temperature among the endothermic peaks derived from the binder resin, and the endothermic peak that originates from the wax with the lowest melting point among the waxes. The amount of heat in a region surrounded by a straight line connecting the apexes is 0.1 to 10.0 J / g, the average circularity of the toner is 0.940 to 0.980, and the content of particles having a particle size of less than 3 μm is 5% by number or less. And [2] an image forming method using the electrophotographic toner described in [1] in a non-contact developing type image forming apparatus.

  The toner for electrophotography of the present invention is excellent in both low temperature fixability and storage stability, and further excellent in durability, and can maintain good transfer efficiency and image density even in printing durability with a low printing rate. It has an excellent effect.

  The present invention relates to a toner containing toner base particles containing a binder resin and a wax, and an external additive, derived from the endothermic curve measured by the differential scanning calorimeter of the toner and the binder resin. The amount of heat in the region surrounded by a straight line connecting the top of the endothermic peak that appears at the lowest temperature among the endothermic peaks and the top of the endothermic peak derived from the wax with the lowest melting point in the wax, and the average circularity of the toner And the content of particles having a particle size of less than 3 μm is in a specific range.

  The toner of the present invention appears at the lowest temperature among the endothermic curve measured by a differential scanning calorimeter (DSC Q20, manufactured by TA Instruments Japan) and the endothermic peak derived from the binder resin. The amount of heat in a region surrounded by a straight line connecting the top of the endothermic peak and the top of the endothermic peak derived from the wax having the lowest melting point among the waxes is 0.1 to 10.0 J / g, preferably 1.0 to 7.0 J / g. g, more preferably 1.0 to 5.0 J / g. The amount of heat is measured by the method described in the examples described later. The amount of heat increases according to the content of the crystalline polyester having a broken crystal structure, and increases as the content of the low melting point wax increases. Therefore, the amount of heat can be reduced by reducing the content of the crystalline polyester whose crystal structure is broken by the heat treatment step described later, and reducing the content of the low melting point wax. As a means for reducing the content of the crystalline polyester having a broken crystal structure, for example, there is a method of performing a heat treatment step described later in the toner production process.

  The average circularity of the toner of the present invention is from 0.940 to 0.980, preferably from 0.950 to 0.970, and more preferably from 0.955 to 0.960, from the viewpoint of suppressing the generation of fine powder that becomes a problem during durability. The average circularity of the toner is:

Is the average value of the circularity calculated by the equation, and the “peripheral length of a circle having the same area as the projected image of particles” and the “peripheral length of the projected particle image” are, for example, FPIA-2000 or FPIA-3000 (manufactured by Sysmex Corporation) is used for measurement in an aqueous dispersion. Moreover, since the value obtained by the above-described analyzer is a value obtained as an average value of several thousand and at least 3000, the reliability of the average circularity in the present invention is extremely high. In the present specification, the average circularity measuring device is not limited to the above-mentioned device, and any device can be used as long as the average circularity can be obtained based on the above equation based on the same principle. May be measured.

  In the toner of the present invention, the content of particles having a particle size of less than 3 μm is 5% by number or less, preferably 4% by number or less, more preferably 3% by number or less from the viewpoint of improving durability. The particle diameter and the content (number%) in terms of the number of particles having a particle diameter of less than 3 μm are measured by the method described in Examples below.

  The glass transition point of the toner of the present invention is preferably 48 to 65 ° C, more preferably 50 to 60 ° C, from the viewpoint of storage stability.

Further, the BET specific surface area of the toner becomes large when the toner has a large amount of fine powder, the particle size of the external additive is small, or the external additive is not sufficiently attached to the toner surface. Therefore, if the BET specific surface area is too large, it may cause a bad influence on the durability of the toner. From this point of view, BET specific surface area is preferably 2.5 m ² / g or less, more preferably 0.5 to 2.5 m ² / g, more preferably 0.7~2.0m ² / g. The BET specific surface area is determined by a nitrogen adsorption method.

  In the present invention, the binder resin preferably contains at least a crystalline polyester, and further contains an amorphous polyester from the viewpoint of storage stability. In the present invention, “crystalline polyester” refers to a polyester having a crystallinity index of 0.6 to 1.5, preferably 0.8 to 1.2, and “amorphous polyester” refers to a crystallinity index of greater than 1.5 or 0.6. Polyester less than, preferably greater than 1.5. Here, the crystallinity index is a physical property that is an index of the degree of crystallization of the resin, and is determined by the ratio between the softening point and the maximum endothermic peak temperature by the differential scanning calorimeter (softening point / maximum endothermic peak temperature). Is defined. In general, a resin having a crystallinity index exceeding 1.5 is amorphous, and a resin having a crystallinity index of less than 0.6 has low crystallinity and many amorphous portions. The degree of crystallization can be adjusted by the type and ratio of the raw material monomers, production conditions (for example, reaction temperature, reaction time, cooling rate) and the like. The highest endothermic peak temperature refers to the temperature of the peak on the highest temperature side among the observed endothermic peaks. If the maximum peak temperature is within 20 ° C. from the softening point, the melting point is set, and the peak having a difference from the softening point exceeding 20 ° C. is a peak due to glass transition.

  Both the crystalline polyester and the amorphous polyester are obtained by using an alcohol component and a carboxylic acid component as raw material monomers and subjecting them to condensation polymerization.

  The alcohol component in the crystalline polyester preferably contains a monomer that promotes the crystallinity of the resin, such as an aliphatic diol having 2 to 8 carbon atoms.

  Examples of the aliphatic diol having 2 to 8 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, Examples include 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,4-butenediol, and α, ω-linear alkanediol is particularly preferable. These may be contained alone or in admixture of two or more.

  From the viewpoint of high crystallinity, the content of the aliphatic diol having 2 to 8 carbon atoms is preferably 80 mol% or more, more preferably 85 mol% or more, and further preferably 90 mol% or more in the alcohol component. Further, when two or more kinds of aliphatic diols having 2 to 8 carbon atoms are used, one kind of the aliphatic diol in them contains 70 mol% or more, preferably 80 to 95 mol% in the alcohol component. It is desirable to occupy. Among these, 1,4-butanediol and 1,6-hexanediol are preferable, and 1,6-hexanediol is more preferable. These are contained in the alcohol component, preferably 70 mol% or more, more preferably 80 mol% or more. It is desirable that

  Examples of the alcohol component in the amorphous polyester include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane, etc. (I):

(In the formula, RO is an alkyleneoxy group, R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average number of added moles of alkylene oxide, and the sum of x and y is 1 to 16, preferably 1.5-5)
It is preferable that the monomer which accelerates | stimulates amorphization of resin, such as aromatic diols, such as alkylene oxide adduct of bisphenol A represented by these, is contained.

  The content of the alkylene oxide adduct of bisphenol A represented by the formula (I) is preferably 50 mol% or more, more preferably 70 mol% or more, more preferably 90 mol% or more in the alcohol component from the viewpoint of chargeability. Further preferred.

  The carboxylic acid compound contained in the carboxylic acid component includes adipic acid, oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, sebacic acid, azelaic acid, n-dodecyl succinic acid Aliphatic dicarboxylic acids having 2 to 30 carbon atoms, preferably 2 to 8 carbon atoms such as n-dodecenyl succinic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; Examples thereof include trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl (C1-3) esters of acids. Among these, aliphatic dicarboxylic acid compounds are preferable. In crystalline polyesters, from the viewpoint of crystallinity, aliphatic dicarboxylic acid compounds having 2 to 8 carbon atoms are crystalline polyesters. From the viewpoint of dispersibility, fumaric acid is more preferable.

  The content of the aliphatic dicarboxylic acid compound is preferably 70 mol% or more, more preferably 80 to 100 mol%, still more preferably 90 to 100 mol% in the carboxylic acid component.

  In the present invention, the amorphous polyester is preferably a linear amorphous polyester. While it is common knowledge of those skilled in the art that linear polyester lacks durability compared to cross-linked polyester, even if linear polyester is used, an unexpected effect that durability can be improved is achieved, Both durability and low-temperature fixability can be achieved. The linear polyester is presumed to have improved low-temperature fixability compared to the crosslinked polyester and to improve the durability because the toner is spheroidized efficiently. Here, the linear polyester means that the content of the dicarboxylic acid compound in the carboxylic acid component is 80 mol% or more and does not contain a trihydric or higher polyhydric alcohol, or even in the case where it is contained in the alcohol component. Obtained by polycondensation of an alcohol component and a carboxylic acid component that is less than 20 mol% in the carboxylic acid component even if it contains no or less than 0.05 mol% and a trivalent or higher polyvalent carboxylic acid compound. Polyester.

  Note that the molar ratio of the carboxylic acid component to the alcohol component in the crystalline polyester (carboxylic acid component / alcohol component) is preferably higher in the alcohol component than the carboxylic acid component when increasing the molecular weight of the crystalline polyester. Further, from the viewpoint of easily adjusting the molecular weight of the polyester by distilling off the alcohol component during the reduced pressure reaction, 0.9 to 1 is preferable, and 0.95 to 1 is more preferable.

  In addition, a monovalent alcohol may be appropriately contained in the alcohol component, and a monovalent carboxylic acid compound may be appropriately contained in the carboxylic acid component from the viewpoint of adjusting the molecular weight.

  The polyester is obtained by polycondensing an alcohol component and a carboxylic acid component, for example, in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst. The reaction temperature is preferably 120 to 230 ° C. in the production of crystalline polyester, and 180 to 250 ° C. in the production of amorphous polyester.

  In the production of crystalline polyester, all monomers are charged together to increase the strength of the resin, or divalent monomers are first reacted in order to reduce low molecular weight components. You may use methods, such as adding a monomer and making it react. Further, the reaction may be accelerated by reducing the pressure of the reaction system in the latter half of the polymerization.

  In order to obtain a higher molecular weight crystalline polyester, the molar ratio of the carboxylic acid component and the alcohol component is adjusted as described above, the reaction temperature is increased, the amount of catalyst is increased, and dehydration is performed for a long time under reduced pressure. What is necessary is just to select reaction conditions, such as performing reaction. In addition, under high power required for stirring, it is possible to produce a high-viscosity crystalline polyester having a high molecular weight. However, when producing without particularly selecting production equipment, the raw material monomer is a non-reactive low-viscosity resin. A method of reacting with a solvent is also an effective means.

  The softening point of the crystalline polyester is preferably from 70 to 140 ° C, more preferably from 80 to 130 ° C, and even more preferably from 105 to 130 ° C, from the viewpoint of low-temperature fixability.

  The melting point of the crystalline polyester is preferably 60 to 140 ° C., more preferably 70 to 130 ° C., and further preferably 80 to 120 ° C. from the viewpoint of fixability.

  The softening point of the amorphous polyester is preferably 80 to 150 ° C, more preferably 85 to 145 ° C, and still more preferably 90 to 145 ° C.

  The glass transition point of the amorphous polyester is preferably from 40 to 80 ° C, more preferably from 50 to 70 ° C, from the viewpoint of pulverization and storage.

  The acid value of the amorphous polyester is preferably 1 to 50 mgKOH / g, more preferably 10 to 30 mgKOH / g.

  From the viewpoint of dispersibility of the crystalline polyester, the crystalline polyester and the amorphous polyester are preferably those obtained using at least one common compound as a raw material monomer. Such a common compound is preferably a carboxylic acid component, fumaric acid and phthalic acid are more preferable, and fumaric acid is more preferable from the viewpoint of increasing the crystallinity of the crystalline polyester.

  The content of the crystalline polyester is preferably 2 to 35% by weight, more preferably 3 to 30% by weight in the binder resin, from the viewpoint of durability, transfer efficiency and image density improvement.

  When the binder resin contains amorphous polyester, the weight ratio of crystalline polyester to amorphous polyester (crystalline polyester / amorphous polyester) is from the viewpoint of durability, transfer efficiency and image density improvement. 3/97 to 35/65 are preferred, and 5/95 to 30/70 are more preferred.

  In the present invention, the polyester may be a polyester modified to such an extent that the characteristics are not substantially impaired. Examples of the modified polyester include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. And a composite resin having two or more kinds of resin units including a polyester unit.

  In the present invention, in addition to crystalline polyester and amorphous polyester, a range in which other binder resins do not impair the effects of the present invention may be used as appropriate. Examples of other binder resins include binder resins other than polyesters such as vinyl resins, epoxy resins, polycarbonates, and polyurethanes. The total content of the crystalline polyester and the amorphous polyester is not particularly limited, but is preferably 80% by weight or more and more preferably 90% by weight or more in the binder resin from the viewpoint of low-temperature fixability.

  Examples of the wax in the present invention include natural ester waxes such as carnauba wax and rice wax, synthetic waxes such as polypropylene wax, polyethylene wax, and Fischer Tropu, pentaerythritol and fatty acids such as behenic acid, stearic acid, and palmitic acid. Examples thereof include petroleum waxes such as synthetic ester wax and paraffin wax, coal-based waxes such as montan wax, and waxes such as alcohol-based waxes, and these may be contained alone or in admixture of two or more. Of these, carnauba wax, pentaerythritol behenate wax and pentaerythritol stearate wax are preferred, and carnauba wax and pentaerythritol stearate wax are more preferred from the viewpoint of offset resistance and durability.

  The melting point of the wax is preferably 50 to 120 ° C., more preferably 60 to 120 ° C., and further preferably 70 to 90 ° C. from the viewpoint of low-temperature fixability and offset resistance.

  The content of the wax is preferably 0.5 parts by weight or more with respect to 100 parts by weight of the binder resin from the viewpoint of offset resistance, and more preferably 0.5 to 5 parts by weight from the viewpoint of blocking prevention and durability during heat treatment. 1 to 3 parts by weight is more preferable.

  The toner base particles of the present invention further include a colorant, a release agent, a charge control agent, a magnetic powder, a fluidity improver, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, and an antioxidant. In addition, additives such as an antiaging agent and a cleaning property improving agent may be appropriately contained.

  As the colorant, all of dyes and pigments used as toner colorants can be used, such as carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Isoindoline, Disazo Yellow and the like can be used, and the toner of the present invention may be either black toner or color toner. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The electrophotographic toner of the present invention includes, for example, a melt-kneading step of melt-kneading a raw material of toner base particles containing a binder resin containing a crystalline polyester and an appropriately used colorant, and pulverizing the obtained melt-kneaded product The pulverizing step, the pulverized product obtained are classified to obtain toner base particles, and the obtained toner base particles and an external additive are mixed together. In, it is preferable to perform a heat treatment process after the crushing process. By performing the heat treatment step, it is possible to promote recrystallization of the crystalline structure of the crystalline polyester broken by melt kneading, and it is possible to control the amount of heat, which is a feature of the present invention, and to increase the circularity. You can also. The heat treatment step may be after the classification step or after the external addition step, but is preferably performed after the external addition step from the viewpoint of blocking prevention during heat treatment and toner shape control.

In the heat treatment step, the heating temperature t (° C.) is
Tg ₁ ≤ t ≤ Tm-10,
Preferably, Tg ₁ + 5 ≦ t ≦ Tm−10,
More preferably, Tg ₁ + 10 ≦ t ≦ Tm−20,
More preferably, Tg ₁ + 15≤t≤Tm-30
(In the formula, Tg ₁ is the glass transition point (° C.) of the workpiece to be subjected to the heat treatment step, and Tm is the softening point (° C.) of the workpiece to be subjected to the heat treatment step)
It is desirable to carry out under conditions that satisfy

  The time of the heat treatment step is preferably 2 to 36 hours, more preferably 5 to 30 hours, from the viewpoint of productivity and shape control.

  Further, the relative humidity during the heat treatment step is preferably 10 to 70%, more preferably 20 to 60%, from the viewpoint of solving electrostatic aggregation of the external additive and preventing aggregation of the toner particles.

  In addition, when performing the heat treatment step after the external addition step, from the viewpoint of caking during heating, generation of aggregates and fixing properties, the coverage by the external additive before the heat treatment step is preferably 50% or more, 70-120% is more preferable

  An oven or the like can be used for the heat treatment step. For example, when an oven is used, the heat treatment step can be performed by maintaining the melt-kneaded material at a constant temperature in the oven. Further, a thermo-hygrostat or a vibrating fluidized bed (VIA-16D type (manufactured by Chuo Kako Co., Ltd.)) can also be used.

  Hereinafter, each process other than the heat treatment process will be described.

  The melt-kneading step is a step of melt-kneading a binder resin containing at least a crystalline polyester and raw materials such as a colorant used as appropriate. The raw materials such as crystalline polyester and colorant used for the melt kneading step are preferably mixed using a Henschel mixer and then used for the melt kneading step.

  The raw material can be melt-kneaded using a known kneader such as a closed kneader, a single- or twin-screw extruder, or an open roll kneader, but a twin-screw extruder is preferably used. The temperature of the melt-kneading is not particularly limited as long as the raw materials are sufficiently mixed.

  The melt-kneaded product obtained by the melt-kneading process is rolled and cooled. The method of rolling and cooling is not particularly limited. Examples of the rolling means include a rolling roll and a rolling drum, and examples of the cooling means include an air cooling method, a water cooling method, and a steel cooling belt method. The thickness after rolling can be adjusted by adjusting the interval between the rolling rolls and the rolling drum.

  The thickness of the melt-kneaded material that is subjected to cooling after rolling is preferably 3 mm or more, more preferably 4 to 6 mm, from the viewpoints of improvement in wax dispersibility and productivity.

  The pulverization step is a step of pulverizing the obtained melt-kneaded product to preferably have a volume median particle size of 20 μm or less, more preferably 10 μm or less. It uses for a crushing process and a classification process.

  The pulverization process may be performed in multiple stages. For example, the melt-kneaded product may be coarsely pulverized to about 1 to 5 mm and further finely pulverized. Further, in order to improve the productivity during the pulverization / classification step, the melt-kneaded product may be mixed with inorganic fine particles such as hydrophobic silica and then pulverized.

  The pulverizer used in the pulverization step is not particularly limited. For example, as a pulverizer suitably used for coarse pulverization, an atomizer, a rotoplex, etc., as a pulverizer suitably used for fine pulverization, a jet mill, a collision Examples thereof include a plate mill and a rotary machine mill.

  Examples of the classifier used in the classification process include an air classifier, an inertia classifier, and a sieve classifier. In the classification step, the pulverized product that has been removed due to insufficient pulverization may be subjected to the pulverization step again. The classification step may be appropriately performed after an external addition step and a heat treatment step described later.

The volume median particle size (D ₅₀ ) of the toner base particles is preferably 4 to 12 μm, and more preferably _{5 to} 10 μm. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  Examples of the external additive include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide. Among these, silica having a small specific gravity is preferable from the viewpoint of preventing embedding.

From the viewpoint of environmental stability, the silica is preferably hydrophobic silica that has been subjected to a hydrophobic treatment. The hydrophobizing method is not particularly limited, and examples of the hydrophobizing agent include hexamethyldisilazane (HMDS), dimethyldichlorosilane, silicone oil, methyltriethoxysilane, and the like. Among these, hexamethyldisilazane is included. Is preferred. The treatment amount of the hydrophobizing agent is preferably 1 to 7 mg / m ² per surface area of the inorganic fine particles.

  The average particle diameter of the external additive is preferably from 3 to 300 nm, more preferably from 5 to 100 nm, from the viewpoint of chargeability and prevention of scratches on the photoreceptor. The external addition step may be further performed after the heat treatment step other than before or after the heat treatment step, but the average particle size of the external additive used in the external addition step before the heat treatment step is From the viewpoint of preventing the toner from being buried in the toner and heating it uniformly, it is preferably 20 to 120 nm, and more preferably 30 to 100 nm.

  The content of the external additive is preferably 0.1 to 5 parts by weight and more preferably 0.3 to 3 parts by weight with respect to 100 parts by weight of the toner base particles.

  The external addition step is preferably a dry mixing method in which the external additive and the toner base particles are mixed using a high-speed stirrer such as a Henschel mixer or a super mixer, a V-type blender or the like. The external additives may be mixed in advance and added to a high-speed stirrer or a V-type blender, or may be added separately.

  In the production of the toner of the present invention, when the heat treatment step is performed after the external addition step, the coverage of the object to be processed to be subjected to the heat treatment step is determined from the viewpoint of preventing toner aggregation during the heat treatment step. 20% or more is preferable, and 30 to 120% is more preferable.

  After the external addition step, it is preferable to perform a sieving step of removing coarse powder (aggregates) by sieving the toner. When the heat treatment step and the sieving step are performed after the external addition step, the heat treatment step is preferably performed between the external addition step and the sieving step.

  The electrophotographic toner of the present invention can be used without being limited to a developing method, and exhibits excellent low-temperature fixability, storage stability and durability even in high-speed continuous printing. In addition, it can be suitably used in a two-component development system that requires high durability. Therefore, the toner of the present invention can be mixed with a carrier and used as a two-component developer.

In the present invention, from the viewpoint of image characteristics, it is preferable to use a carrier with low saturation magnetization that weakens the area around the magnetic brush. Saturation magnetization of the carrier is preferably ^{40~100Am 2 / kg, 50~90Am 2 /} kg is more preferable. The saturation magnetization is preferably 100 Am ² / kg or less from the viewpoint of adjusting the hardness of the magnetic brush and maintaining gradation reproducibility, and preferably 40 Am ² / kg or more from the viewpoint of preventing carrier adhesion and toner scattering.

  As the core material of the carrier, those made of known materials can be used without particular limitation, for example, ferromagnetic metals such as iron, cobalt, nickel, magnetite, hematite, ferrite, copper-zinc-magnesium ferrite, Examples include alloys and compounds such as manganese ferrite and magnesium ferrite, and glass beads. Among these, iron powder, magnetite, ferrite, copper-zinc-magnesium ferrite, manganese ferrite, and magnesium ferrite are preferable from the viewpoint of chargeability. From the viewpoint of image quality, ferrite, copper-zinc-magnesium ferrite, manganese ferrite and magnesium ferrite are more preferable.

  The surface of the carrier is preferably coated with a resin from the viewpoint of preventing spent. The resin that coats the carrier surface varies depending on the toner material. For example, fluororesin such as polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin such as polydimethylsiloxane, polyester, styrenic resin, Acrylic resins, polyamides, polyvinyl butyral, amino acrylate resins, and the like can be used, and these can be used alone or in combination of two or more. However, when the toner is negatively charged, the chargeability and surface From the viewpoint of energy, a silicone resin is preferable. The method for coating the core material with the resin is not particularly limited, for example, a method in which a coating material such as a resin is dissolved or suspended in a solvent and applied to the core material, or a method of simply mixing with a powder.

  In the two-component developer obtained by mixing the toner and the carrier, the toner to carrier weight ratio (toner / carrier) is preferably 1/99 to 10/90, and more preferably 2/98 to 8/92.

  Further, the toner and the two-component developer of the present invention are excellent in low-temperature fixability, storage stability and durability, and can maintain a high quality image, so that the linear speed is 750 mm / sec or more, preferably 850 to 2000 mm. It can be suitably used in an image forming method using a high-speed developing device of / sec. In addition, the toner and the two-component developer of the present invention contain a crystalline polyester excellent in low-temperature fixability, can maintain storage stability and durability by heat treatment, and can also reduce adhesive force by shape control. It can improve transfer efficiency and can be suitably used for a non-contact development system such as a jumping system. Examples of the non-contact fixing method include flash fixing, oven fixing, and a belt nip fixing device.

[Softening point (Tm) of the object to be subjected to resin and heat treatment process]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample is heated at a heating rate of 6 ° C / min, and a 1.96 MPa load is applied by a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Maximum peak temperature of resin endotherm]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature is raised to 200 ° C, and the sample cooled to 0 ° C at a temperature drop rate of 10 ° C / min is measured at a temperature rise rate of 10 ° C / min. . Among the observed endothermic peaks, the temperature of the peak on the highest temperature side is defined as the highest endothermic peak temperature.

[Glass transition point of resin]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature is raised to 200 ° C, and the sample cooled to 0 ° C at a temperature drop rate of 10 ° C / min is measured at a temperature rise rate of 10 ° C / min. . When the difference between the maximum endothermic peak temperature and the softening point is within 20 ° C, the peak extension line below the peak temperature observed at a temperature lower than the maximum endothermic peak temperature and the peak from the rising edge of the peak The temperature at the point of intersection with the tangent indicating the maximum inclination to the top of is read as the glass transition point. When the difference between the maximum endothermic peak temperature and the softening point exceeds 20 ° C, an extension of the baseline below the maximum endothermic peak temperature and a tangent line indicating the maximum slope from the peak of the peak to the peak apex The temperature at the intersection is read as the glass transition point.

(The glass transition point (Tg) and endothermic curve of the object to be processed and the toner subjected to the heat treatment process, and the endothermic peak that appears at the lowest temperature among the endothermic peaks derived from the binder resin and the wax among the most. (The amount of heat in the area surrounded by a straight line connecting the top of the endothermic peak derived from the low melting point wax)
The endotherm obtained when the sample is heated from -20 ° C to 160 ° C at a rate of 10 ° C / min using a differential scanning calorimeter (DSC Q20, manufactured by TA Instruments Japan) In the curve, connect the top of the endothermic peak that appears at the lowest temperature among the endothermic peaks derived from the binder resin with the top of the endothermic peak that originates from the wax with the lowest melting point of the wax used. Then, the area surrounded by the measurement curve is obtained, and this is defined as the amount of heat.
In addition, the temperature at the intersection of the base line extension below the peak temperature observed at the lowest endothermic temperature of the endothermic peak and the tangent line indicating the maximum slope from the rising edge of the peak to the peak apex. Read as glass transition point (Tg).

[Resin acid value]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Melting point of wax]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The maximum peak temperature of heat of fusion is taken as the melting point.

[Volume-median particle size (D ₅₀ ) of toner and content of particles having a particle size of less than 3 μm]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 5% electrolyte dispersion condition: 10 mg of measurement sample is added to 5 ml of dispersion, and dispersed for 1 minute with an ultrasonic disperser. Then, 25 ml of the electrolytic solution is added, and further dispersed with an ultrasonic disperser for 1 minute.
Measurement conditions: Add 100 ml of electrolyte and dispersion in a beaker, measure 30,000 particles at a concentration that can measure the particle size of 30,000 particles in 20 seconds, and determine the volume-median particle size ( D ₅₀ ) and the content (number%) of particles having a particle size of less than 3 μm are determined.

[Average circularity of toner]
Measuring machine: FPIA-3000 (manufactured by Sysmex Corporation)
Standard unit (10x objective lens)
Measurement mode HPF mode Version 00-10
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB13.6) 5% by weight Electrolyte dispersion condition: 10 mg of measurement sample was added to 10 ml of dispersion, and dispersed for 1 minute with an ultrasonic disperser. Thereafter, 10 ml of distilled water is added, and further dispersed for 2 minutes with an ultrasonic disperser.
Measurement conditions: Toner dispersed in a dispersion is measured at 20 ° C. at a concentration of 1800 to 2200 particles.

[Average particle size of external additives]
The average particle size of the external additive refers to the number average particle size. The particle size (average value of major axis and minor axis) of 500 particles is measured from a scanning electron microscope (SEM) photograph, and the average value is averaged. The particle size.

[External additive coverage]
Coverage (%) = √3 / 2π × (D · ρt) / (d · ρs) × C × 100
(Where D is the volume median particle size (D ₅₀ ) (μm) of the toner base particles, d is the average particle size (μm) of the external additive, ρt is the specific gravity of the toner base particle, and ρs is the external additive. Specific gravity, C indicates the weight ratio of toner base particles to external additives (external additive / toner base particles))
Is calculated by
The total coverage of external additives is the sum of the coverages calculated for each external additive.

[Carrier saturation magnetization]
(1) Fill a plastic case with a lid of 7 mm outer diameter (6 mm inner diameter) and 5 mm height while tapping the carrier, and calculate the mass of the carrier from the difference between the weight of the plastic case and the weight of the plastic case filled with the carrier. .
(2) Set a plastic case filled with a carrier in the sample holder of the magnetic property measuring device “BHV-50H” (VSMAGNETOMETER) of RIKEN ELECTRONICS CO., LTD., While vibrating the plastic case using the vibration function, Saturation magnetization is measured by applying a magnetic field of 79.6 kA / m. The obtained value is converted into saturation magnetization per unit mass in consideration of the mass of the filled carrier.

Production Example of Amorphous Polyester The raw material monomers (alcohol component and carboxylic acid component) shown in Table 1 are placed in a 5-liter glass four-necked flask together with 8 g of tin (II) octylate as an esterification catalyst, and the temperature A total, a stainless steel stirrer, a flow-down condenser and a nitrogen introduction tube were attached, and the reaction was carried out at 220 ° C. for 8 hours while stirring in a nitrogen stream in an electric heating mantle, followed by reaction at 8.3 kPa for 1 hour. Furthermore, it was made to react until it reached a desired softening point at 210 degreeC, and resin AC was obtained.

Production Example 1 of Crystalline Polyester
Put raw material monomers (alcohol component and carboxylic acid component) and 2 g of hydroquinone shown in Table 2 into a 5-liter glass 4-necked flask, and attach a thermometer, stainless steel stirrer, flow-down condenser and nitrogen inlet tube, electric heating mantle The mixture was reacted for 5 hours at 160 ° C. with stirring in a nitrogen stream, and then heated to 200 ° C. for 1 hour. Furthermore, it was made to react at 8.0 kPa for 1 hour, and resin a was obtained.

Production Example 2 of Crystalline Polyester
Raw material monomers (alcohol component and carboxylic acid component) shown in Table 2, 2 g of hydroquinone and 307 g of polypropylene wax “NP-105” (Mitsui Chemicals, melting point: 145 ° C.) are placed in a 5-liter glass four-necked flask. Attach a thermometer, stainless steel stirrer, flow-down condenser, and nitrogen inlet tube, react with stirring in a nitrogen flow in an electric heating mantle at 160 ° C for 5 hours, then raise the temperature to 200 ° C. Reacted for hours. Furthermore, it was made to react at 8.0 kPa for 3 hours, and resin b was obtained.

Examples 1-6, Comparative Example 1
Binder resin shown in Table 3, carbon black “NIPEX60” (Degussa) 6 parts by weight, charge control agent “T-77” (Hodogaya Chemical Co., Ltd.) 1 part, and carnauba wax “Carnauba wax C-1” 2 parts by weight (Made by Kato Yoko Co., melting point: 83 ° C) are thoroughly mixed with a Henschel mixer. (Ikegai Iron Works Co., Ltd.) was used for melt kneading at a barrel heating temperature of 100 ° C., a screw rotation speed of 200 r / min, and a discharge rate of 10 kg / hr.

  The obtained melt-kneaded product is cooled and coarsely pulverized to about 1 to 3 mm, and then the coarsely pulverized product is finely pulverized by a jet mill `` AFG200 '' (manufactured by ALPINE) And toner mother particles were obtained.

  100 parts by weight (10 kg) of the obtained toner base particles, hydrophobic silica “NAX50” (manufactured by Nippon Aerosil Co., Ltd., average particle size 40 nm, specific gravity 2.3, hydrophobizing agent HMDS) 1.0 part by weight (100 g) and hydrophobic silica `` R972 '' (manufactured by Nippon Aerosil Co., Ltd., average particle size 16 nm, specific gravity 2.3, hydrophobizing agent DMDS) 0.9 parts by weight (90 g) was put into a 75 liter Henschel mixer and mixed for 90 seconds at a rotation speed of 1500 r / min. Then, hydrophobic silica was externally added to the surface of the toner base particles.

  The externally added toner (10 kg) was placed in a bucket and left open for 24 hours under the conditions shown in Table 3 using a thermo-hygrostat and heat-treated. Thereafter, the obtained toner was passed through a shaking sieve equipped with a mesh having an opening of 100 μm to remove coarse particles, thereby obtaining a toner.

  A chart obtained by differential scanning calorimetry of the toner obtained in Example 3 is shown in FIG.

Comparative Example 2
A toner was obtained in the same manner as in Example 4 except that the heat treatment step after the external addition step was not performed.

Comparative Example 3
A toner was obtained in the same manner as in Example 3 except that the heat treatment step after the external addition step was not performed.

Comparative Example 4
For the fine pulverization and classification of the coarsely pulverized product, "IDS-2 type" (Nippon Pneumatic Co., Ltd.) equipped with a fine pulverizer for colliding the crushed material with a jet stream and a classifier for centrifugal separation with a swirling flow was used Except for the above, a toner was obtained in the same manner as in Example 3, but aggregates were generated after the heat treatment.

Comparative Example 5
After melt-kneading in the same manner as in Example 2, a 1 to 3 mm coarsely pulverized product was obtained. The obtained coarsely pulverized product is left in the bucket and opened in a constant temperature and humidity chamber for 24 hours under the conditions shown in Table 3. After heat treatment, the coarsely pulverized product is allowed to collide with a jet stream. Toner mother particles were obtained using an “IDS-2 type” (Nippon Pneumatic Co., Ltd.) equipped with a pulverizer and a classifier that performs centrifugal separation with a swirling flow.

  100 parts by weight (10 kg) of the obtained toner base particles, hydrophobic silica “NAX50” (manufactured by Nippon Aerosil Co., Ltd., average particle size 40 nm, specific gravity 2.3, hydrophobizing agent HMDS) 1.0 part by weight (100 g) and hydrophobic silica `` R972 '' (manufactured by Nippon Aerosil Co., Ltd., average particle size 16 nm, specific gravity 2.3, hydrophobizing agent DMDS) 0.9 parts by weight (90 g) was put into a 75 liter Henschel mixer and mixed for 90 seconds at a rotation speed of 1500 r / min. Then, hydrophobic silica was externally added to the surface of the toner base particles to obtain a toner.

Test example 1 [minimum fixing temperature]
After mounting the toner on the non-contact development type copier “MICROLINE 3050” (Oki Data Co., Ltd.) and adjusting the bias applied to the development roll so that the toner amount is 0.6 mg / cm ² , before the fixing. The image was taken out and an unfixed image was obtained. Furthermore, using a non-contact fixing type image forming device "Vario stream 9000" (manufactured by Océ Printing Systems), an external fixing device is used, and the temperature on the paper is increased from 90 ° C to 150 ° C to 10 ° C. A fixed image was obtained by sequentially raising the image. "UNICEF Cellophane" (Mitsubishi Pencil Co., Ltd., width: 18mm, JISZ-1522) is pasted on the image fixed at each temperature, pressure is applied to the tape with a roller so that a load of 500g is applied, and then the tape is peeled off. The image density before and after peeling was measured. The temperature on the paper where the fixing rate (image density after tape peeling / image density before tape application × 100) first exceeded 90% was defined as the minimum fixing temperature. The paper used for the fixing test is a cardboard “CopyBond SF-70NA” (75 g / m ² ) manufactured by Sharp Corporation. The results are shown in Table 3.

Test Example 2 [transfer efficiency, image density and durability]
342 g of toner and 5000 g of ferrite carrier (volume average particle diameter: 60 μm, saturation magnetization: 68 Am ² / kg) were mixed to obtain a two-component developer. The obtained two-component developer was mounted on a non-contact developing type image forming apparatus “Vario stream 9000” (manufactured by Ose Printing Systems) and printed for 2 hours at a linear speed of 1000 mm / sec and a printing rate of 9%. After that, the printing time was 0.15% for 3 hours, the printer was urgently stopped, the toner amount (To) on the photoconductor and the toner amount (Tp) on the paper were measured, and the value obtained by Tp / To x 100 Was defined as transfer efficiency.

  Further, three image samples at that time were collected, and the optical reflection density (OD) of the black solid portion of the image was measured as an image density by a reflection densitometer “RD-915” (manufactured by Macbeth).

  Then, after further printing for 20 hours at a printing rate of 9%, the spent amount was measured according to the following method, and the durability was evaluated according to the evaluation criteria. The results are shown in Table 3.

(1) The two-component developer is passed through a 20 μm mesh with a vacuum cleaner, and the carbon content of the remaining carrier is measured with a carbon analyzer (carbon analyzer: manufactured by HORIBA).
(2) The carrier whose carbon content is measured in (1) is washed with chloroform, and the toner adhering to the carrier is removed. After cleaning, the amount of carbon in the carrier is measured.
(3) The amount of spent toner is obtained by subtracting the amount of carbon measured in (2) from the amount of carbon measured in (1). The spent amount is expressed as% by weight relative to the carrier.

[Durability Evaluation Criteria]
◎: Spent amount is less than 0.03% by weight ○: Spent amount is 0.03% by weight or more and less than 0.15% by weight △: Spent amount is 0.15% by weight or more and less than 0.30% by weight ×: Spent amount is 0.30% by weight or more

Test Example 3 [Preservability]
5 g of toner was placed in a 50 ml polybin and left for 48 hours in an environment of a temperature of 50 ° C. and a relative humidity of 60%. Thereafter, the toner was sieved with a mesh having an opening of 100 μm, the residual toner on the mesh was weighed, and storage stability was evaluated according to the following evaluation criteria. The results are shown in Table 3.

〔Evaluation criteria〕
○: Residual toner is less than 0.5 g △: Residual toner is 0.5 g or more, less than 1 g ×: Residual toner is 1 g or more

  From the above results, the toners of Examples 1 to 6 are excellent in both low-temperature fixability and storage stability as compared with the toners of Comparative Examples 1 to 5, and good transfer even in printing durability at a low printing rate. It can be seen that efficiency is maintained.

  The toner for electrophotography of the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

FIG. 1 is a chart based on differential scanning calorimetry of the toner obtained in Example 3.

Explanation of symbols

A Endothermic peak apex B derived from binder resin Endothermic peak apex C derived from wax C Region surrounded by endothermic curve and A and B

Claims (4)

  An electrophotographic toner comprising toner base particles comprising a binder resin and a wax and an external additive, wherein the binder resin comprises a crystalline polyester, The endothermic curve measured by a scanning calorimeter, the endothermic peak that appears at the lowest temperature among the endothermic peaks derived from the binder resin, and the endothermic peak that originates from the wax with the lowest melting point among the waxes. The amount of heat in the region surrounded by the connecting straight line is 0.1 to 10.0 J / g, the average circularity of the toner is 0.940 to 0.980, and the content of particles having a particle size of less than 3 μm is 5% by number or less. Toner for photography.   2. The electrophotographic toner according to claim 1, wherein the content of the crystalline polyester is 2 to 35% by weight in the binder resin.   The toner for electrophotography according to claim 1 or 2, wherein the wax has a melting point of 50 to 120 ° C.   An image forming method using the electrophotographic toner according to claim 1 in an image forming apparatus of a non-contact development type.

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