JP2004301990A - Toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner free of hot offset despite of low-temperature fixability, also having good storage stability, and ensuring no fogging even after continuous printing over a prolonged period of time. <P>SOLUTION: The toner has the highest maximum value P1 of electric current measured with a thermally stimulated current measuring device at 70-110°C, and has a softening temperature Ts of 55-75°C and a flowage beginning temperature Tfb of 90-130°C measured with a flow tester. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５４】
表１のトナーの評価結果から、以下のことがわかる。
熱刺激電量装置で測定される電流の最大極大値が本発明で規定する範囲よりも低い比較例１のトナーは、耐久性が悪く、最低定着温度も高くなる。
熱刺激電量装置で測定される電流の最大極大値が本発明で規定する範囲よりも高く、フローテスターで測定される流動開始温度が本発明で規定する範囲よりも高い比較例２のトナーは、最低定着温度が高くなる。
フローテスターで測定される軟化温度が本発明で規定する範囲よりも低い比較例３のトナーは、保存性や耐久性が悪く、最低定着温度も高くなる。
フローテスターで測定される軟化温度と流動開始温度が本発明で規定する範囲よりも高い比較例４のトナーは、耐久性が悪く、最低定着温度も高くなる。
フローテスターで測定される流動開始温度が本発明で規定する範囲よりも低い比較例５のトナーは、保存性や耐久性が悪く、ホットオフセットも発生し易くなる。
これに対して、本発明のトナーは、低温で定着できるにもかかわらず、保存性がよく、長期間に亘って耐久印刷を行っても、カブリの発生がないことが分かる。
【００５５】
【発明の効果】
本発明によれば、低温で定着できるにもかかわらず、ホットオフセットの発生がなく、保存性もよく、長期間に亘って耐久印刷を行っても、カブリの発生がないトナーが提供される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic image for developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method, or the like.
[0002]
[Prior art]
Many methods are known for electrophotography, but in general, an electrostatic latent image is formed on a photoconductor using a photoconductive substance, and the electrostatic latent image is developed with toner. A toner image is transferred to a transfer material such as paper, and then fixed by heating, pressing, or solvent vapor to form a final image. Then, the toner remaining without being transferred onto the photoconductor is cleaned by various methods, and the above-described steps are repeated.
There are a one-component developing method and a two-component developing method as a developing method in the image formation. The two-component developing system is used in high-speed mass printing apparatuses and the like because the image forming speed can be increased. However, there is a problem that the developing device becomes large. On the other hand, the one-component developing method has been applied to image forming apparatuses such as small printers and copiers for small offices and personal users.
The one-component developing system includes a magnetic one-component developing system and a non-magnetic one-component developing system. The non-magnetic one-component developing method has attracted attention because it can easily cope with full-color image formation.
[0003]
In this non-magnetic one-component developing system, toner is supplied from a supply roll to a development roll, and the toner supplied on the development roll is adjusted to a thin and constant layer thickness by a layer thickness regulating means such as a blade. Although the toner is charged by friction with the blade or the surface of the developing roll, if the toner layer is too thick, there will be toner that cannot be sufficiently charged, and fog and toner scattering will easily occur. In the non-magnetic one-component developing system, since the blade is pressed against the developing roll in order to regulate the layer thickness, a strong stress is also applied to the toner. Therefore, in the non-magnetic one-component developing method, the toner is liable to be deteriorated, and the fogging gradually increases when printing is performed for a long time. Further, compared to a toner for a two-component developing system charged by friction with a carrier, a toner for a non-magnetic one-component developing system needs to have a predetermined charge amount with a small friction.
[0004]
As a method for evaluating the charging characteristics of a toner, it has been proposed to measure a heat stimulation current. Non-Patent Document 1 discloses a toner in which the maximum value of the current measured by the thermal stimulation current measuring device is at 100 to 110 ° C. Patent Document 1 discloses a toner in which the maximum value of the current measured by the thermal stimulation current measuring device is around 100 ° C., the glass transition temperature is around 80 ° C., and the melting point is around 125 ° C. I have.
[0005]
[Non-patent document 1]
Kazuo Ikezaki and 1 other, "Basic electrical properties in fine powder state", Journal of the Electrostatics Society of Japan, 1998, Vol. 22, No. 2, p. 79-82
[Patent Document 1]
JP-A-8-62885
[Problems to be solved by the invention]
However, according to the study of the present inventor, the toner disclosed in Non-Patent Document 1 and Patent Document 1 merely having the maximum value of the heat stimulation current at around 100 ° C. for a long period of time. It was found that fog was generated by the durable printing, and the balance between the storability and the fixing property was not good.
Therefore, an object of the present invention is to provide a toner which does not generate hot offset, has good storability, and does not generate fog even when durable printing is performed for a long period of time, even though fixing can be performed at a low temperature. It is in.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve this object, and as a result, have found that the above object can be achieved with a toner having a specific heat stimulus current value and a specific melting property. The invention has been completed.
Thus, according to the present invention, it has a maximum value P1 of the current measured by the thermal stimulation current measuring device at 70 to 110 ° C, the softening temperature Ts measured by the flow tester is 55 to 75 ° C, and A toner having a starting temperature Tfb of 90 to 130 ° C. is provided.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The toner of the present invention has a maximum current maximum value P1 measured by a thermal stimulation current measuring device at 70 to 110 ° C. Preferably it has 75-95 degreeC, More preferably, it has 80-90 degreeC. If P1 is lower than 70 ° C., if various stresses are applied to the toner during printing over a long period of time, the chargeability of the toner becomes unstable and fogging occurs. On the other hand, when the temperature is higher than 110 ° C., the interaction between the binder resin and the charge control agent or between the colorant and the charge control agent is strong, and the fixing property (fusing property), which is an important quality as a toner, deteriorates. .
P1 preferably has a half width of 30 ° C. or less, more preferably 25 ° C. or less, and even more preferably 20 ° C. or less. If the half width is larger than 30 ° C., when various stresses are applied to the toner during printing over a long period of time, the chargeability of the toner becomes unstable and fogging may occur.
Further, the absolute value of the current of P1 is preferably at least 0.03 pA, more preferably at least 0.1 pA, even more preferably at least 0.3 pA. If the current value is smaller than 0.03 pA, the thermal stability of charging of the toner is deteriorated, and fog may occur in a high-temperature holding environment or during durable printing.
[0009]
The toner of the present invention preferably further has a maximum value of at least one current measured by a thermal stimulation current measuring device at 30 to 70 ° C, more preferably at 40 to 70 ° C, and more preferably at 50 to 70 ° C. More preferred. If the maximum value is lower than 30 ° C., the toner has poor storage stability, and the toner may be blocked during holding at a high temperature. It can be.
In addition, the temperature difference between the maximum value P2 and the maximum value P1 among the maximum values at 30 to 70 ° C. is preferably 10 to 70 ° C., and more preferably 20 to 40 ° C. If the temperature difference is less than 10 ° C., the fixability may decrease, and if it is more than 70 ° C., the storage stability may deteriorate.
[0010]
This heat stimulation current can be measured using, for example, TS-POLAR (manufactured by Rigaku Denki Co., Ltd.), TSC / RMA9000 (Syscom), or the like. This thermal stimulation current can be measured whether the toner is charged negatively or positively.
[0011]
The toner of the present invention has a softening temperature Ts measured by a flow tester of 55 to 75 ° C, preferably 60 to 75 ° C, and more preferably 65 to 70 ° C. If the softening temperature is lower than 55 ° C., the thermal stability of the toner is poor and the storage stability is reduced. Conversely, if the softening temperature is higher than 75 ° C., the toner does not have a sufficient melt viscosity and the fixability is poor.
The flow start temperature Tfb also measured by a flow tester is 90 to 130 ° C, preferably 90 to 120 ° C, and more preferably 100 to 120 ° C. If the flow start temperature is lower than 90 ° C., hot offset tends to occur. Conversely, if the flow start temperature is higher than 130 ° C., the melt viscosity increases and the fixability deteriorates.
[0012]
The toner of the present invention has a volume average particle size (dv) of usually 2 to 20 μm, preferably 3 to 12 μm, and more preferably 4 to 10 μm. If the particle size is small, the fluidity is reduced, transferability is reduced, blurring may occur, and the print density may be reduced. Conversely, if the particle size is large, fog or toner scattering occurs, and Resolution may be reduced.
The particle size distribution (dv / dp), which is the ratio between the volume average particle size (dv) and the number average particle size (dp), is 1.0 to 1.3, and more preferably 1.0 to 1.2. . If the particle size distribution is large, blurring may occur, or transferability, print density, and resolution may decrease.
The volume average particle size and the particle size distribution can be easily adjusted to the above ranges by, for example, classification.
The volume average particle size and the particle size distribution of the toner can be measured using, for example, a Multisizer (manufactured by Beckman Coulter, Inc.).
[0013]
The toner of the present invention has an average sphericity (Sc / Sr) of 1 to 1.3 obtained by dividing an area (Sc) of a circle whose diameter is the absolute maximum length of a particle by a substantial projected area (Sr) of the particle. Yes, it is more preferably from 1.0 to 1.2, and even more preferably from 1.0 to 1.15. When the average sphericity is larger than 1.3, the transferability may be reduced.
The average sphericity can be easily adjusted to the above range by using, for example, a phase inversion emulsification method, a dissolution suspension method, and a polymerization method.
Here, the average sphericity is determined by taking an electron micrograph of the toner, and photographing the photograph with an image processing / analysis apparatus Luzex IID (manufactured by NIRECO). It is a value obtained by measuring under 100 conditions and averaging the sphericity of the obtained 100 colored particles.
[0014]
The toner of the present invention contains a binder resin, a colorant and a charge control agent, and preferably further contains a release agent, and may contain a magnetic material and the like as necessary.
Specific examples of the binder resin include polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin, which are conventionally used widely in toner. The weight average molecular weight of the binder resin is not particularly limited, but is usually 5,000 to 50,000, preferably 7,000 to 30,000.
[0015]
As the colorant, any pigment and / or dye can be used in addition to carbon black, titanium black, magnetic powder, oil black, and titanium white. As the black carbon black, those having a primary particle diameter of 20 to 40 nm are suitably used. When the particle size is in this range, carbon black can be uniformly dispersed in the toner, and fog is reduced, which is preferable.
[0016]
When obtaining a full-color toner, a yellow colorant, a magenta colorant and a cyan colorant are usually used.
As the yellow colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 83, 90, 93, 97, 120, 138, 155, 180, 181, 185, 186, and 186.
As the magenta colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Red 31, 48, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251; I. Pigment Violet 19 and the like.
As the cyan coloring agent, a copper phthalocyanine compound and its derivative, an anthraquinone compound and the like can be used. Specifically, C.I. I. Pigment Blue 2, 3, 6, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17, 60 and the like.
The amount of such a coloring agent is usually 1 to 10 parts by weight based on 100 parts by weight of the binder resin.
[0017]
As the charge control agent, a charge control agent conventionally used for a toner can be used. Among the charge control agents, it is preferable to include a charge control resin because it has high compatibility with the binder resin, is colorless, and can provide a toner having stable chargeability even in high-speed color continuous printing. The charge control resin is a quaternary ammonium produced according to the description in JP-A-63-60458, JP-A-3-175456, JP-A-3-243954, JP-A-11-15192 and the like. A salt-containing group-containing copolymer or a sulfonic acid (salt) group-containing copolymer produced according to the description in JP-A-1-217464, JP-A-3-15858 or the like is used.
The monomer unit having a quaternary ammonium (salt) group or a sulfonic acid (salt) group contained in the copolymer is 0.5 to 15% by mass, preferably 1 to 10% by mass in the copolymer. It is. When the content is within this range, the charge amount of the toner can be easily controlled, and the occurrence of fog can be reduced.
[0018]
The weight average molecular weight of the charge control resin is usually 2,000 to 50,000, preferably 4,000 to 40,000, and more preferably 6,000 to 30,000. When the weight average molecular weight is within this range, the compatibility with the binder resin is high, and the chroma and transparency of the toner can be maintained.
The glass transition temperature of the charge control resin is usually from 40 to 80C, preferably from 45 to 75C, more preferably from 45 to 70C. When the glass transition temperature is in this range, the storability and fixability of the toner can be improved in a well-balanced manner.
The amount of the charge control resin is usually 0.01 to 20 parts by mass, preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the binder resin.
[0019]
Examples of the release agent include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; natural plant waxes such as candelilla, carnauba, rice, wood wax, jojoba; paraffin, microcrystalline, petrolactam, etc. And waxes modified therefrom; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, and dipentaerythritol hexamyristate;
These can be used alone or in combination of two or more.
[0020]
Among these release agents, synthetic waxes and polyfunctional ester compounds are preferred. Among these, in the DSC curve measured by the differential scanning calorimeter, a polyfunctional ester whose endothermic peak temperature at the time of temperature rise is in the range of 30 to 150 ° C, preferably 40 to 100 ° C, more preferably 50 to 80 ° C. Compounds are preferred because they have a good balance between fixation and releasability during fixing. In particular, those having a molecular weight of at least 1,000, dissolving at least 5 parts by weight with respect to 100 parts by weight of styrene at 25 ° C., and having an acid value of 1 mg / KOH or less are more preferable because they have a remarkable effect on lowering the fixing temperature. Endothermic peak temperature is a value measured by ASTM D3418-82.
The amount of the release agent is usually 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight based on 100 parts by weight of the binder resin.
[0021]
Examples of the magnetic material include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite; metals such as iron, cobalt, and nickel; or these metals and aluminum, cobalt, copper, lead, and magnesium. And alloys with metals such as tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof.
[0022]
The toner of the present invention is so-called core-shell type (or also referred to as “capsule type”) particles obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles. Can be. In the core-shell type toner, by coating the inside (core layer) low softening point substance with a substance having a higher softening point, it is possible to balance between lowering the fixing temperature and preventing aggregation during storage. preferable.
The weight ratio between the core layer and the shell layer of the core-shell toner is not particularly limited, but is usually 80/20 to 99.9 / 0.1, preferably 90/10 to 99.8 / 0.2, and more preferably. 95/5 to 99.7 / 0.3.
By setting the ratio of the shell layer in the above range, it is possible to have both the storage stability of the toner and the fixability at a low temperature.
[0023]
The average thickness of the shell layer of the core-shell toner is generally considered to be 0.001 to 1.0 μm, preferably 0.003 to 0.5 μm, and more preferably 0.005 to 0.2 μm. When the thickness is large, the fixing property is reduced, and when the thickness is small, the storability is sometimes reduced. It is not necessary that the entire surface of the core layer constituting the core-shell type toner is covered with the shell layer, and it is sufficient that a part of the surface of the core layer is covered with the shell layer.
[0024]
The toner of the present invention is not particularly limited by its manufacturing method, and can be obtained by, for example, a pulverization method, a phase inversion emulsification method, and a polymerization method. Among them, the toner obtained by the suspension polymerization method is preferable because it becomes substantially spherical, and the transferability and the fixability are improved, and high resolution image quality and high speed printing can be supported.
[0025]
Preferred methods for producing a core-shell toner include spray drying, interfacial reaction, in situ polymerization, and phase separation. Specifically, a toner obtained by a pulverization method, a polymerization method, an association method or a phase inversion emulsification method is used as a core particle, and a shell layer is coated thereon to obtain a core-shell type toner. Among these production methods, an in situ polymerization method and a phase separation method are preferable from the viewpoint of production efficiency.
[0026]
Hereinafter, a method of producing a core-shell toner by the most preferable in situ polymerization method will be described.
A polymerizable monomer, a colorant, a charge controlling agent, and a release agent are uniformly mixed using a media type disperser such as a ball mill to obtain a polymerizable monomer composition for a core, containing a dispersion stabilizer. After the composition is added to the aqueous dispersion medium to be stirred, the mixture is stirred to form droplets, and then the polymerization initiator is added. The stirring speed and time are adjusted to form smaller droplets. The temperature of the aqueous dispersion medium when forming droplets is usually from 10 to 40C, preferably from 20 to 30C.
Next, while maintaining stirring to such an extent that the dispersed droplets do not separate or settle, the temperature is raised to a predetermined temperature to start the polymerization, and the polymerization is continued for a certain period of time to obtain a predetermined polymerization conversion rate. After confirming that, a polymerizable monomer for shell and a polymerization initiator for shell are added, and the polymerization is further continued for a certain time to obtain an aqueous dispersion of core-shell type toner particles. Thereafter, in order to remove unreacted polymerizable monomers from the aqueous dispersion as necessary, and further to remove the dispersion stabilizer used during polymerization from the toner particles, washing and dehydration are repeated and dried. To produce toner.
The polymerization temperature is usually 40 to 100 ° C, preferably 50 to 95 ° C, and the polymerization time is 1 to 20 hours, preferably 2 to 10 hours. The drying temperature is usually 20 to 60C, preferably 30 to 50C.
[0027]
Examples of the polymerizable monomer for obtaining the binder resin include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized to become a binder resin component.
Monovinyl monomers include aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic acid. (Meth) such as propyl, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobonyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and (meth) acrylamide Acrylic monomers; monoolefin monomers such as ethylene, propylene, and butylene; and the like.
Monovinyl monomers may be used alone or in combination of a plurality of monomers. Among these monovinyl monomers, an aromatic vinyl monomer alone or a combination of an aromatic vinyl monomer and a (meth) acrylic monomer is preferred, and a combination of styrene and butyl methacrylate is most preferred.
[0028]
When a crosslinkable monomer is used together with the monovinyl monomer, hot offset is effectively improved. The crosslinkable monomer is a monomer having two or more vinyl groups. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof; diethylenically unsaturated carboxylic esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline, divinyl ether and the like And compounds having three or more vinyl groups such as pentaerythritol triallyl ether and trimethylolpropane triacrylate. These crosslinkable monomers may be used alone or in combination of two or more.
The amount of the crosslinkable monomer is usually 10 parts by weight or less, preferably 0.1 to 2 parts by weight, per 100 parts by weight of the monovinyl monomer.
[0029]
Further, it is preferable to use a macromonomer together with the monovinyl monomer, because the balance between the preservability and the fixing property at a low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the terminal of the molecular chain, and is usually an oligomer or polymer having a number average molecular weight of 1,000 to 30,000.
The macromonomer is preferably one that gives a polymer having a glass transition temperature higher than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer.
The amount of the macromonomer is usually 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, more preferably 2 to 4 parts by weight, based on 100 parts by weight of the monovinyl monomer.
[0030]
Examples of dispersion stabilizers include inorganic salts such as barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, and calcium phosphate, inorganic oxides such as aluminum oxide and titanium oxide, aluminum hydroxide, magnesium hydroxide, and ferric hydroxide. Water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like. These may be used alone. Two or more types may be combined.
Of these, dispersion stabilizers containing colloids of poorly water-soluble inorganic hydroxides in particular can narrow the particle size distribution of the polymer particles, and have less residual stability after washing of the dispersion stabilizer, This is preferable because an image can be clearly reproduced.
[0031]
The dispersion stabilizer is used usually in a ratio of 0.1 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer. When the ratio is in the above range, sufficient polymerization stability is obtained, the formation of polymerization aggregates is suppressed, and a toner having a desired particle size can be obtained, which is preferable.
[0032]
Examples of the polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid) and 2,2′-azobis (2-methyl-N- (2-hydroxyethyl ) Propionamide), azo such as 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile Compounds: di-t-butyl peroxide, dicumyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t -Butylperoxypivalate, di-isopropylperoxydicarbonate, di-t-butylperoxyisophthalate, 1,1 3,3-tetramethylbutyl peroxy-2-ethylhexanoate, and the like can be exemplified peroxides such as t- butyl peroxy isobutyrate. Redox initiators obtained by combining these polymerization initiators with a reducing agent can also be mentioned.
[0033]
Among these, an oil-soluble polymerization initiator soluble in a polymerizable monomer is preferable. If necessary, a water-soluble polymerization initiator can be used in combination with the oil-soluble polymerization initiator. The polymerization initiator is used in an amount of 0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the polymerizable monomer.
[0034]
It is preferable to use a molecular weight modifier at the time of polymerization. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, 2,2,4,6,6-pentamethylheptane-4-thiol; carbon tetrachloride, Halogenated hydrocarbons such as carbon bromide; and the like. These molecular weight regulators can be added before the start of the polymerization or during the polymerization. The molecular weight modifier is used in an amount of usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.
[0035]
As the polymerizable monomer for the shell, monomers that form a polymer having a glass transition temperature exceeding 80 ° C., such as styrene, acrylonitrile, and methyl methacrylate, may be used alone or in combination of two or more. it can. Among these, it is preferable to use methyl methacrylate.
The amount of the shell polymerizable monomer is usually 0.1 to 10 parts by weight, preferably 0 to 10 parts by weight, based on 100 parts by weight of the monovinyl monomer used to obtain the core polymerizable monomer composition. 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight.
[0036]
If a water-soluble polymerization initiator is added during the addition of the polymerizable monomer for the shell, by-products of fine particles can be prevented, and a polymer (shell) can be easily formed on the surface of the core particle.
Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) propionamide), 2,2′-azobis- Azo-based initiators such as (2-methyl-N- (1,1-bis (hydroxymethyl) ethyl) propionamide) and the like can be mentioned. The amount of the water-soluble polymerization initiator is usually 0.1 to 50 parts by weight, preferably 1 to 30 parts by weight, based on 100 parts by weight of the polymerizable monomer for shell.
[0037]
The toner of the present invention employs a suspension polymerization method, uses styrene and butyl methacrylate as monovinyl monomers, and uses 2 to 4 parts by weight of a macromonomer to prepare a polymerizable monomer composition for a core. It can be relatively easily obtained by forming a core-shell type using 1 to 3 parts by weight of methyl methacrylate as a shell monomer.
[0038]
The toner of the present invention preferably contains an external additive. Examples of the external additive include inorganic particles and organic resin particles. These particles added as external additives have a smaller average particle size than the toner particles. For example, inorganic particles include silica, aluminum oxide, titanium oxide, zinc oxide, tin oxide, barium titanate, strontium titanate, and the like, and organic resin particles include methacrylate polymer particles, acrylate Examples include coalesced particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, and core-shell type particles in which the core is a styrene polymer and the shell is a methacrylic acid ester polymer. Among these, silica particles and titanium oxide particles are preferable, particles whose surface is subjected to a hydrophobic treatment are preferable, and silica particles whose surface is subjected to a hydrophobic treatment are particularly preferable. The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight based on 100 parts by weight of the toner particles.
[0039]
The toner of the present invention can be manufactured by adhering or partially embedding the external additive on the surface of the toner particles by stirring the toner particles and the external additive in a mixer such as a Henschel mixer. .
[0040]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples. Parts and percentages are by weight unless otherwise specified.
In this example, evaluation was made by the following method.
[0041]
(1) Volume average particle size and particle size distribution The volume average particle size (dv) of the colored particles and the particle size distribution, that is, the ratio (dv / dp) of the volume average particle size to the number average particle size (dp), are determined by using Multisizer. (Manufactured by Beckman Coulter, Inc.). The measurement by this multisizer was performed under the conditions of an aperture diameter: 100 μm, a medium: Isoton II, a concentration of 10%, and the number of measured particles: 100,000.
[0042]
(2) Thermal stimulation current The thermal stimulation current (TSC) was measured using TS-POLAR (manufactured by Rigaku Corporation) in the following manner.
The toner is rubbed and filled in a dedicated aluminum pan, and the charge generated in the toner is removed by a soft X-ray generator. After confirming that the charge has disappeared with a surface electrometer, a negative charge is applied to the toner by a corona charger under a charging condition of 1 kV grid voltage, 20 kV corona generator voltage, and 1 minute. Next, the surface potential is measured, and after confirming that the toner is charged by corona discharge, the toner is set together with the aluminum pan in a thermal stimulation current measuring device, and is heated from 23 ° C. to 150 ° C. by a non-contact method in air. The temperature was raised to 10 ° C. at 10 ° C. per minute, and the current released during the temperature increase was measured.
[0043]
(3) Softening Temperature and Flow Start Temperature 1 to 1.3 g of toner is put into a flow tester (CFT-500D, manufactured by Shimadzu Corporation), and the softening temperature (Ts) and flow start temperature (TFb) are measured under the following measurement conditions. did.
Measurement start temperature: 35 ° C, heating rate: 3 ° C / min, preheating time: 5 minutes,
Cylinder pressure: 10 kgf / cm ² , die diameter: 0.5 mm,
Die length 1.0 mm, shear stress: 2.451 × 10 ⁵ Pa
[0044]
(4) Put the preservative toner sample in a sealable container, seal it, submerge the container in a thermostatic water bath at a temperature of 60 ° C., take it out after 6 hours, and put it on a 42-mesh sieve. Is transferred so as not to destroy the aggregate structure of the toner. The vibration intensity was set to 1 mm in amplitude with a powder measuring device (trade name “Powder Tester” manufactured by Hosokawa Micron Corp.), and after vibrating for 30 seconds, the weight of the toner remaining on the sieve was measured, and the weight of the aggregated toner was measured. And The storage stability (% by weight) of the toner was calculated from the weight of the aggregated toner and the weight of the sample. The smaller the value, the higher the preservability.
[0045]
(5) Minimum Fixing Temperature A fixing test was performed using a printer modified so that the temperature of the fixing roll portion of a commercially available non-magnetic one-component developing system printer (28-sheet machine) can be changed. In the fixing test, the temperature of the fixing roll of the remodeled printer was changed by 5 ° C., and black solid printing was performed on the printing paper at each temperature, and the fixing rate of the toner was measured.
The fixation rate was calculated from the ratio of the print density before and after the tape peeling operation for the black solid region on the printing paper printed by the modified printer. That is, assuming that the image density before tape removal was before ID and the image density after tape removal was after ID, the fixing rate was calculated from the following equation.
Fixing rate (%) = (after ID / before ID) × 100
Here, the tape peeling operation is to attach the above-described adhesive tape (manufactured by Sumitomo 3M, Scotch Mending Tape 810-3-18) to the measurement portion of the test paper, press and adhere with a 500 g steel roller, Means a series of operations for peeling the adhesive tape in a direction along the paper at a constant speed. Further, the image density was measured using a Macbeth reflection image densitometer.
In this fixing test, the lowest temperature among the fixing roll temperatures at which the fixing rate became 80% or more was defined as the minimum fixing temperature of the toner.
[0046]
(6) Hot offset temperature In the same manner as in the measurement of the minimum fixing temperature, the fixing roll temperature was changed by 5 ° C. in increments of 5 ° C., black solid printing was performed, and the occurrence of hot offset was examined. The minimum fixing roll temperature at which hot offset occurs was defined as the toner hot offset temperature. The occurrence of hot offset was examined in the range of the fixing roll temperature up to 220 ° C. In the table, “220 <” indicates that hot offset did not occur even at 220 ° C.
(7) Durability (fog)
Put the toner to be evaluated in the developing unit of a commercially available non-magnetic one-component developing system printer (28 sheets), leave it for 24 hours in an environment of a temperature of 23 ° C and a humidity of 50%, and print continuously on a printing paper at 5% printing density. Is performed, and the solid printing is performed every 500 sheets, printing is stopped halfway, and the toner on the photoreceptor after development is peeled off with an adhesive tape (Sumitomo 3M, Scotch Mending Tape 810-3-18). , And stuck it on new printing paper. Next, the whiteness (B) of the printing paper to which the adhesive tape was affixed was measured by a whiteness meter (manufactured by Nippon Denshoku Co., Ltd.). A) was measured. The difference between the whiteness (A) and the whiteness (B) was calculated, and the number of sheets capable of maintaining a fog value of 1 or less was recorded as a fog value. This test was completed after 15,000 sheets.
[0047]
(Example 1)
A polymerizable monomer for core comprising 80 parts of styrene, 20 parts of n-butyl methacrylate, 0.8 parts of divinylbenzene, and 2 parts of polymethyl methacrylate macromonomer (trade name “AA6” manufactured by Toa Gosei Chemical Industry Co., Ltd.) 8 parts of carbon black (trade name “# 25B” manufactured by Mitsubishi Chemical Corporation), charge control resin (trade name “FCA-207-P” manufactured by Fujikura Kasei Co., Ltd .; weight average molecular weight 20,000, glass transition temperature 60 ° C.) One part, 10 parts of dipentaerythritol hexamyristate and 1.75 parts of t-dodecylmercaptan were dispersed at room temperature in a bead mill to obtain a polymerizable monomer composition for a core.
[0048]
On the other hand, an aqueous solution obtained by dissolving 6.2 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added to an aqueous solution obtained by dissolving 10.2 parts of magnesium chloride in 250 parts of ion-exchanged water. A colloidal dispersion was prepared. When the particle size distribution of the formed colloid was measured by a SALD particle size distribution analyzer (manufactured by Shimadzu Corporation), the particle size Dp50 of 50% in the total number calculated from the small particle size side was 0.35 μm. Dp90 which is 90% was 0.62 μm.
On the other hand, 2 parts of methyl methacrylate and 65 parts of water were mixed to obtain an aqueous dispersion of a polymerizable monomer for shell.
[0049]
The polymerizable monomer composition for a core is charged into the magnesium hydroxide colloidal dispersion obtained as described above, and the mixture is stirred until the droplets are stabilized, and t-butyl peroxy-2-ethylhexanoate ( After adding 5 parts of Nippon Oil & Fats Co., Ltd., trade name "Perbutyl O"), the mixture was further subjected to high shear stirring at 15,000 rpm for 30 minutes using an Ebara Milder (manufactured by Ebara Corporation), and a smaller single unit was added. Droplets of the monomer mixture were formed to obtain a suspension.
[0050]
The above suspension was put into a reactor equipped with a stirring blade, and the temperature was raised to start the polymerization reaction. After the temperature reached 90 ° C., the temperature was controlled to be maintained at 90 ° C. Reached about 100%, and an aqueous dispersion of the polymerizable monomer for shell and a water-soluble initiator dissolved in 20 parts of ion-exchanged water (trade name "VA-086" manufactured by Wako Pure Chemical Industries, Ltd.) 0.3 parts of 2,2′-azobis (2-methyl-N (2-hydroxyethyl) -propionamide) were added to the reactor. After adding the polymerizable monomer for shell and continuing polymerization for 4 hours, the reaction was stopped to obtain an aqueous dispersion of core-shell type toner particles.
While stirring the aqueous dispersion of the colored particles obtained above, sulfuric acid was added to adjust the pH to 4 or less, acid washing was performed, and water was separated by filtration. Further, water washing and dehydration were repeated several times, the solid content was separated by filtration, and dried at 45 ° C. for 2 days and nights in a drier to obtain a volume average particle size (dv) of 7.1 μm and a particle size distribution (dv / d). As a result, core-shell toner particles having a dp) of 1.14 and an average sphericity of 1.12 were obtained.
[0051]
To 100 parts of the obtained core-shell type toner particles, 1 part of silica (trade name “HDK2150” manufactured by Clariant Japan Co., Ltd.) is added as an external additive, and mixed at a peripheral speed of 30 m / s for 5 minutes using a Henschel mixer. And a toner was obtained.
Table 1 shows the characteristics of the obtained toner and the results of the image quality evaluation.
[0052]
(Example 2, Comparative Examples 1 to 5)
Colored particles and a toner were obtained in the same manner as in Example 1 except that the raw materials used for the polymerization were changed as shown in Table 1. However, since Comparative Example 4 was not a core-shell type colored particle, a polymerization initiator for polymerizing the polymerizable monomer for shell was not used. Table 1 shows the properties of the obtained colored particles and the toner, and the results of the image quality evaluation.
[0053]
[Table 1]

[0054]
The following can be seen from the evaluation results of the toners in Table 1.
The toner of Comparative Example 1 in which the maximum value of the current measured by the thermal stimulation coulomb is lower than the range specified in the present invention has poor durability and a high minimum fixing temperature.
The toner of Comparative Example 2 in which the maximum value of the current measured by the thermal stimulation coulometer is higher than the range specified in the present invention and the flow start temperature measured by the flow tester is higher than the range specified in the present invention, The minimum fixing temperature increases.
The toner of Comparative Example 3 whose softening temperature measured by a flow tester is lower than the range specified in the present invention has poor storage stability and durability, and also has a high minimum fixing temperature.
The toner of Comparative Example 4 whose softening temperature and flow start temperature measured by a flow tester are higher than the ranges specified in the present invention has poor durability and a high minimum fixing temperature.
The toner of Comparative Example 5 whose flow start temperature measured by a flow tester is lower than the range specified in the present invention has poor storage stability and durability, and easily causes hot offset.
On the other hand, it can be seen that the toner of the present invention has good storability even though it can be fixed at a low temperature, and does not generate fog even when durable printing is performed for a long period of time.
[0055]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, although it can fix at low temperature, there is no generation | occurrence | production of hot offset, storage stability is good, and the toner which does not generate | occur | produce fog even if it performs durable printing for a long period of time is provided.

Claims (5)

It has a maximum current value P1 measured by a thermal stimulation current measuring device at 70 to 110 ° C, a softening temperature Ts measured by a flow tester is 55 to 75 ° C, and a flow start temperature Tfb is 90 to 130 ° C. Toner. 2. The toner according to claim 1, further comprising a local maximum value of at least one current measured by a thermal stimulation current measuring device at 30 to 70 [deg.] C. The toner according to claim 1, wherein a temperature difference between a maximum value P <b> 2 and the maximum value P <b> 1 among the maximum values at 30 to 70 ° C. is 10 to 70 ° C. 3. The toner according to claim 1, wherein a half width of P1 is 30 ° C. or less. 5. The toner according to claim 1, wherein the absolute value of the current P1 is 0.03 pA or more.