JP2011248253A - Manufacturing method of toner, toner, two-component developer and image formation device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner having an excellent hot offset property without impairing dispersibility of a carbon black.SOLUTION: In a manufacturing method of a toner containing at least a binder resin and a colorant, a kneading step of the binder resin is a step for kneading the colorant with a resin mixture of a vinyl resin (A) and a vinyl resin (B). The kneading step is the manufacturing method of the toner comprising a dispersion step and a crosslinking step following the dispersion step.

Description

  The present invention relates to a method for producing toner for electrophotography, a toner, a two-component developer, and an image forming apparatus using them.

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method has been widely used for a copying machine, a printer, a facsimile machine, and the like. For example, an electrophotographic image forming apparatus forms an image through the following steps.

  First, an electrostatic latent image based on image information is formed by various image forming processes on a photosensitive drum having a photosensitive layer containing a photoconductive substance formed on the surface as an image carrier. This electrostatic latent image is developed with a developer containing toner supplied from a developing device to form a visible image (toner image). Next, the toner image is transferred to a recording medium such as paper. Thereafter, the toner image is fixed (fused) on the recording medium by heating and melting the toner with a fixing roller.

  In recent years, in order to prevent global warming, the power consumption of image forming apparatuses has been reduced. In connection with this, toner that is easily soluble even at a low fixing temperature is required. In order to improve the low-temperature fixability of the toner, a method of lowering the molecular weight of the binder resin can be mentioned. However, when the molecular weight is lowered, hot offset tends to occur.

  As a technique for preventing hot offset, for example, there is JP-A-6-11890 (Patent Document 1). In this publication, by using a styrene-acrylic resin containing a carboxyl group and a styrene-acrylic resin containing a glycidyl group, a crosslinking reaction is caused by kneading at a temperature of 160 ° C. or higher, thereby increasing the molecular weight. A method for producing a toner containing a binder resin with improved hot offset property is disclosed. Japanese Patent Laid-Open No. 3-63661 (Patent Document 2) obtains a styrene acrylic resin containing acrylic acid and then reacts with a polyvalent metal compound and then crosslinks with a styrene acrylic resin having a glycidyl group in a kneading step. Disclosed toners are disclosed.

JP-A-6-11890 Japanese Patent Laid-Open No. 3-63661

  In any of the above methods, since there is no step of dispersing the colorant in the kneading step and only the step of cross-linking the binder resin, depending on the temperature of the kneading step, the degree of cross-linking of the binder resin cannot be controlled and the toner is manufactured. In some cases, kneading was performed. That is, when kneading in the production of toner is performed in a state where the degree of cross-linking of the binder resin is low, the cross-linking does not proceed sufficiently and it may be difficult to control the viscosity. As a result, there are cases where the toner does not exhibit desired characteristics with respect to hot offset properties. In addition, when kneading in the production of toner is performed in a state where the binder strength of the binder resin is high, the viscosity of the binder resin is increased and the dispersion of the colorant may be deteriorated. As a result, the toner may not be excellent in charging characteristics.

  The present application has been made in view of the above problems, and the kneading step includes a dispersion step performed at a low temperature of 120 to 140 ° C. and a crosslinking step performed subsequent to the dispersion step at a high temperature of 160 to 190 ° C. Thus, since the kneading in the production of the toner is performed in a state in which the degree of crosslinking of the binder resin is controlled, it is an object to provide a toner excellent in hot offset property without impairing the dispersibility of the colorant.

  The present invention relates to a method for producing a toner containing at least a binder resin and a colorant. In the binder resin kneading step, the resin mixture of a vinyl resin having a carboxyl group (A) and a vinyl resin having a glycidyl group (B) is colored. And a crosslinking step of crosslinking the carboxyl group-containing vinyl resin (A) and the glycidyl group-containing vinyl resin (B). .

  In the invention, it is preferable that the dispersing step is a toner manufacturing method in which the temperature is lower than that of the crosslinking step.

  In the invention, it is preferable that the dispersion step is performed at a temperature of 120 to 140 ° C., and the crosslinking step is a method for producing a toner performed at a temperature of 160 to 190 ° C.

  In the invention, it is preferable that the colorant is a method for producing a toner having an acidic pH of 2 to 6.

  In addition, the present invention is preferably a toner manufacturing method in which the colorant is contained in an amount of 1 to 15% by weight with respect to 100% by weight of the resin mixture.

  In the present invention, the vinyl resin (A) having a carboxyl group is selected from acrylic acid, methacrylic acid, fumaric acid, methyl fumarate, ethyl fumarate, propyl fumarate, butyl fumarate and octyl fumarate. A method for producing a toner that is a resin derived from a monomer is preferable.

  In the present invention, the vinyl resin (B) having a glycidyl group is derived from a monomer selected from glycidyl acrylate, β-methylglycidyl acrylate, glycidyl methacrylate, and β-methylglycidyl methacrylate. It is preferable that the toner is a method for producing the toner.

  The vinyl resin (A) having a carboxyl group has a weight average molecular weight Mw of 5000 ≦ Mw ≦ 100,000, and the vinyl resin (B) having a glycidyl group has a weight average molecular weight Mw of 10,000 ≦ Mw ≦ 1000000. It is preferable that the toner is a method for producing the toner.

  The present invention is preferably a two-component developer containing the toner and a carrier.

  In addition, the present invention is a toner including the crosslinked product obtained in the crosslinking step.

  In the present invention, the component amount of the crosslinked body is preferably 5 to 50% by weight.

  The present invention also provides a photosensitive drum, a charging device that charges the surface of the photosensitive drum, an exposure device that forms an electrostatic latent image on the surface of the photosensitive drum, a developing device, and the toner image. An image forming apparatus including a transfer device for transferring to a recording medium and a fixing device for fixing the transferred toner image to the recording medium is provided.

  According to the present invention, a toner having a large molecular weight of the binder resin in the toner and a highly dispersed colorant can be obtained, so that a toner having excellent hot offset property and excellent charging stability can be obtained. In a two-component developer and an image forming apparatus using the toner, a stable image can be obtained over a long period of time.

  Moreover, according to this invention, since the dispersion | distribution process which disperse | distributes a coloring agent is performed at the low temperature of 120-140 degreeC, there are few molecular cutting | disconnections which reduce the molecular weight of binder resin, and a coloring agent can also be disperse | distributed minutely. Therefore, a toner excellent in hot offset property and colorant dispersibility can be obtained.

  According to the present invention, the crosslinking step for crosslinking the binder resin is performed at a high temperature of 160 to 190 ° C., but is performed subsequent to the dispersion step performed at a low temperature of 120 to 140 ° C. And a toner having excellent charge stability can be obtained.

  Further, according to the two-component developer of the present invention, since the colorant does not adhere to the carrier surface, a two-component developer that exhibits stable charging properties over a long period of time can be obtained.

1 is a schematic explanatory diagram illustrating an overall configuration of an image forming apparatus. FIG. 2 is a schematic front sectional view showing a configuration around a toner cartridge and a developing device in FIG. 1.

  In the toner kneading step of the present invention, a colorant is kneaded into a resin mixture of a vinyl resin (A) having a carboxyl group and a vinyl resin (B) having a glycidyl group.

The kneading step includes a dispersion step for dispersing the colorant in the resin mixture and a crosslinking step for crosslinking the vinyl resin (A) having a carboxyl group and the vinyl resin (B) having a glycidyl group. Moreover, the component amount of the crosslinked body obtained in the crosslinking step is not more than a specific ratio.
[Toner material]
First, toner materials that can be used in the toner of the present invention will be described.
(1) Binder resin The binder resin used as the raw material of the toner includes a vinyl resin (A) having a carboxyl group and a vinyl resin (B) having a glycidyl group.
(1-1) Vinyl resin having a carboxyl group (A)
The vinyl resin (A) is a resin obtained by polymerizing a carboxyl group-containing vinyl monomer. The vinyl resin (A) may be a resin obtained by copolymerizing a carboxyl group-containing vinyl monomer and a carboxyl group-free vinyl monomer.

  Examples of carboxyl group-containing vinyl monomers include unsaturated monobasic acids such as acrylic acid and methacrylic acid, unsaturated dibasic acids such as maleic anhydride, maleic acid, fumaric acid, and cinnamic acid, and methyl fumarate and fumarate. And monoesters of unsaturated dibasic acids such as propyl acid, butyl fumarate, octyl fumarate, methyl maleate, ethyl maleate, propyl maleate, butyl maleate and octyl maleate. These vinyl monomers may be used alone or in combination. Particularly preferred carboxyl group-containing vinyl monomers are acrylic acid, methacrylic acid, fumaric acid, methyl fumarate, ethyl fumarate, propyl fumarate, butyl fumarate and octyl fumarate.

  Examples of the vinyl monomer not containing a carboxyl group include styrenes (styrene, p-methylstyrene, α-methylstyrene, vinyltoluene, etc.), acrylic esters (methyl acrylate, ethyl acrylate, propyl acrylate, Butyl acrylate, octyl acrylate, cyclohexyl acrylate, stearyl acrylate, benzyl acrylate, furfuryl acrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, dimethylaminomethyl acrylate, dimethylaminoethyl acrylate, etc.), methacrylic acid Esters (methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, benzyl methacrylate, Furfuryl acrylate, hydroxyethyl methacrylate, hydroxybutyl methacrylate, dimethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, etc., diesters of unsaturated dibasic acid (dimethyl fumarate, dibutyl fumarate, dioctyl fumarate, malein) Dimethyl acid, dibutyl maleate, dioctyl maleate, etc.), acrylonitrile, methacrylonitrile, amides (acrylamide, methacrylamide, N-substituted acrylamide, N-substituted methacrylamide, etc.). These vinyl monomers may be used alone or in combination. Particularly preferred carboxyl group-free vinyl monomers are styrenes, acrylic esters, methacrylic esters, diesters of unsaturated dibasic acids, acrylonitrile, acrylamide and methacrylamide.

  The weight ratio of the carboxyl group-containing vinyl monomer and the carboxyl group-free vinyl monomer is preferably in the range of 1: 0 to 1: 100, and preferably in the range of 1: 1 to 1: 100. More preferred. By being in this range, in the kneading step, a cross-linked product of an appropriate proportion of the vinyl resin (A) and the vinyl resin (B) is generated. A more preferred weight ratio is 1: 2 to 1:50.

  The vinyl resin (A) preferably has a weight average molecular weight (Mw) in a range represented by 5000 ≦ Mw ≦ 100,000. By having Mw within this range, the high molecular weight and gelation due to the reaction with the vinyl resin (B) occur so that the mechanical strength and the viscosity are balanced, and the toner having good durability and fixing properties. Can provide. A more preferable range of Mw is 10,000 ≦ Mw ≦ 80000, and a particularly preferable range of Mw is 10,000 ≦ Mw ≦ 50000. In addition, Mw was calculated | required by GPC method and is the conversion molecular weight which created the analytical curve with the monodisperse standard polystyrene.

  The vinyl resin (A) preferably has a glass transition temperature (Tg (A)) of 40 to 75 ° C. A more preferable glass transition temperature is 50 to 60 ° C.

  The glass transition temperature is a value measured according to JIS K-7121. By setting the glass transition temperature within this range, a toner having both hot offset property and low temperature fixability can be provided.

Moreover, it is preferable that the vinyl resin (A) has an acid value of 1 to 30 KOHmg / g. A more preferable acid value is 5 to 30 KOHmg / g. The acid value is the number of mg of potassium hydroxide necessary to neutralize 1 g of the resin, and is a value measured according to JIS K-5601-2-1. By setting the acid value within this range, a toner having both hot offset property and low temperature fixability can be provided.
(1-2) Vinyl resin (B) having a glycidyl group
The vinyl resin (B) is a resin obtained by polymerizing a glycidyl group-containing vinyl monomer. The vinyl resin (B) may be a resin obtained by copolymerizing a glycidyl group-containing vinyl monomer and a glycidyl group-free vinyl monomer.

  Examples of the glycidyl group-containing vinyl monomer include glycidyl acrylate, β-methylglycidyl acrylate, glycidyl methacrylate, and β-methylglycidyl methacrylate.

  Examples of the glycidyl group-free vinyl monomer include the same monomers as the carboxyl group-free vinyl monomer.

  The weight ratio of the glycidyl group-containing vinyl monomer and the non-glycidyl group-containing vinyl monomer is preferably in the range of 1: 0 to 1: 100, and preferably in the range of 1:10 to 1: 100. More preferred. A more preferred weight ratio is 1:20 to 1:50. By being in this range, in the kneading step, a cross-linked product of an appropriate proportion of the vinyl resin (A) and the vinyl resin (B) is generated.

  The vinyl resin (B) preferably has a weight average molecular weight (Mw) in a range represented by 10,000 ≦ Mw ≦ 1000000. By having Mw within this range, the high molecular weight and gelation by reaction with the vinyl resin (A) occur so that the mechanical strength and the viscosity are balanced, and the toner having good durability and fixability. Can provide. A more preferable range of Mw is 15000 ≦ Mw ≦ 85000, and a particularly preferable range of Mw is 25000 ≦ Mw ≦ 75000.

  The vinyl resin (B) preferably has a glass transition temperature (Tg (B)) of 40 to 75 ° C. A more preferable glass transition temperature is 50 to 60 ° C. By setting the glass transition temperature within this range, a toner having both hot offset property and low temperature fixability can be provided.

The vinyl resin (B) preferably has an epoxy equivalent (CEP) of 1000 g / Eq ≦ CEP ≦ 20000 g / Eq. A more preferable epoxy equivalent is 1000 g / Eq ≦ CEP ≦ 15000 g / Eq, and a particularly preferable epoxy equivalent is 1000 g / Eq ≦ CEP ≦ 10000 g / Eq. In addition, an epoxy equivalent means the mass (g number) of the epoxy resin per 1g equivalent of epoxy groups. By having an epoxy equivalent in this range, high molecular weight and gelation occur due to reaction with the vinyl resin (A). As a result, it is possible to provide a toner in which the mechanical strength and the viscosity are balanced and the durability and the fixing property are well balanced.
(1-3) Weight ratio of vinyl resin (A) and vinyl resin (B) The weight ratio of carboxyl group-containing vinyl resin (A) and glycidyl group-containing vinyl resin (B) is 1: 0.01 to 1: 1.0 is preferable. A more preferred weight ratio is 1: 0.1 to 1: 1.0, and a particularly preferred weight ratio is 1: 0.1 to 1: 0.5. By setting it within this range, a binder resin capable of producing a toner excellent in low-temperature fixability and storage stability can be obtained.

By being in this range, high dispersion of the colorant can be achieved, and a binder resin that can produce a toner having excellent charging characteristics can be obtained.
(2) Colorant As the colorant, carbon black having a carboxyl group on the surface can be used. Specifically, it can be appropriately selected from various conventionally known carbon blacks such as channel black, loin black, disc black, oil furnace black, and acetylene black. In particular, carbon black having a pH of 2 to 6 is preferable because it can easily achieve high dispersion in the binder resin in the kneading step.

  When the pH exceeds 6, the carboxyl group that is an acidic functional group of carbon black, which plays a role in inhibiting the crosslinking reaction of the binder resin, is almost absent. Kneading is carried out. As a result, the viscosity of the binder resin is increased, the dispersion of carbon black is deteriorated, and a toner having excellent charging characteristics cannot be obtained. On the other hand, when the pH is less than 2, high dispersion in the binder resin is achieved, but the carboxyl group, hydroxyl group, quinone group, lactone group, etc., which are the acidic functional groups of carbon black, are crosslinked in the binder resin. Since the reaction is inhibited so much, the crosslinking does not proceed and it becomes difficult to control the viscosity. As a result, the toner does not exhibit desired characteristics with respect to hot offset properties.

The addition amount of carbon black is preferably 1 to 15% by weight with respect to 100% by weight of the resin mixture of the vinyl resin (A) having a carboxyl group and the vinyl resin (B) having a glycidyl group. When the addition amount is within this range, it is possible to provide a toner that exhibits stable chargeability over a long period of time. The addition amount is more preferably in the range of 3 to 12% by weight.
(3) Other components The toner contains other components other than the binder resin and the colorant. Examples of other components include a release agent, a charge control agent, and an external additive.
(3-1) Release agent By including a release agent in the toner, the release property of the toner with respect to the fixing roller can be improved, and the low-temperature fixability at the time of fixing is improved and the effect of preventing hot offset is achieved. can get.

  A well-known thing can be used as a mold release agent. For example, petroleum waxes such as paraffin wax and microcrystalline wax, carnauba wax, rice wax, candelilla wax, plant waxes such as wood wax, animal waxes such as beeswax and whale wax, minerals such as montan wax and ozokerite Oils and fats synthetic waxes such as wax, fatty acid amides, phenol fatty acid esters, low molecular weight polypropylene waxes, low molecular weight polyethylene waxes, hydrocarbon synthetic waxes such as Fischer-Tropsch wax, alcoholic synthetic waxes and ester synthetic waxes, etc. It is done. These release agents may be used alone or in combination of two or more.

The amount of the release agent added is not particularly limited, but generally it is preferably 5% by weight or less, more preferably 1 to 5% by weight with respect to 100% by weight of the binder resin.
(3-2) Charge Control Agent As the charge control agent, any charge control agent known in the art that can impart positive and negative chargeability to the toner can be used.

  Specifically, as a charge control agent imparting negative chargeability, chromium azo complex dye, iron azo complex dye, cobalt azo complex dye, salicylic acid or its derivative chromium / zinc / aluminum / boron complex or salt compound, naphtholic acid ( Chromium / zinc / aluminum / boron complex or salt compound of hydroxy naphthoic acid) or its derivative, chromium / zinc / aluminum / boron complex or salt compound of benzylic acid or its derivative, long chain alkyl / carboxylate, long chain alkyl / Examples thereof include sulfonates.

  Examples of the charge control agent that imparts positive chargeability include nigrosine dyes and derivatives thereof, triphenylmethane derivatives, quaternary ammonium salts, quaternary phosphonium salts, quaternary pyridinium salts, guanidine salts, amidine salts, and the like. be able to.

The addition amount of the charge control agent is preferably 20% by weight or less with respect to 100% by weight of the binder resin, more preferably in the range of 0.1 to 20% by weight, and 0.5 to 5% by weight. More preferably, it is in the range.
(3-3) External additive As an external additive, a surface obtained by subjecting inorganic fine particles such as silica fine particles to a hydrophobic treatment with a surface treatment agent such as a silane coupling agent, a titanium coupling agent, or silicone oil. Examples thereof include treated silica fine particles. As the primary particle diameter of the surface-treated silica fine particles (number average value measured using a scanning electron microscope), those having a particle diameter of 5 to 50 nm can be suitably used.

  The volume resistivity of the external additive can be adjusted by changing the type of surface treatment agent used and the amount of treatment. An external additive obtained by treating silica fine particles using hexamethyldisilazane as a silane coupling agent has high resistance and excellent hydrophobicity. Therefore, a toner having a stable charge amount can be provided even in a high humidity environment, which is preferable.

The addition amount of the external additive is preferably 5% by weight or less, and more preferably 0.5 to 5% by weight with respect to 100% by weight of the binder resin. If the amount added is too large, the fixability may be lowered. In order to obtain the effect of the external additive, it is preferable to add 0.5% by weight or more. Moreover, it is preferable to adjust the addition amount of an external additive so that it may become the coverage (20-80%) of the grade which the binder resin surface is covered moderately.
[Toner Production Method]
The toner is kneaded by adding a component other than the binder resin and carbon black to a resin mixture of a vinyl resin (A) having a carboxyl group and a vinyl resin (B) having a glycidyl group. In the kneading step, following the dispersion step of dispersing the colorant at a low temperature, the vinyl resin (A) having a carboxyl group and the vinyl resin (B) having a glycidyl group are crosslinked at a high temperature by the same heating kneader. Then, it undergoes a crosslinking step for producing a crosslinked body. Hereinafter, a method for producing the toner will be specifically described.
(4) Kneading step (4-1) Dispersing step In the dispersing step performed at a low temperature, the vinyl resin (A) having a carboxyl group, the vinyl resin (B) having a glycidyl group, and other components and carbon other than these binder resins Along with black, carbon black is finely dispersed by heating and kneading in a heating kneader at a low temperature. The components other than the binder resin and carbon black are preliminarily pulverized to about 1 mm together with a resin mixture of a vinyl resin having a carboxyl group (A) and a vinyl resin having a glycidyl group (B), a Henschel mixer, It is preferable to mix using an air flow mixer such as a super mixer, mechano mill, or Q-type mixer in terms of improving dispersibility.

  When the dispersion step is performed at a temperature lower than 120 ° C., the binder resin may not be sufficiently melted, so that the dispersibility of the carbon black may not be sufficiently obtained. On the other hand, when the temperature exceeds 140 ° C., the crosslinking reaction of the binder resin proceeds first, and the dispersibility of the carbon black may not be sufficiently obtained.

  As the heat kneader, a known heat kneader used for kneading the binder resin can be used. Of these, a biaxial kneader is preferred in that fine temperature control is possible. The heat-kneading is preferably performed so that the maximum kneading temperature of the kneaded product obtained by kneading is in the range of 120 to 140 ° C.

Thus, if a dispersion | distribution process is made into the range of 120-140 degreeC, there will be few molecular cutting | disconnections which reduce the molecular weight of binder resin, and a colorant can also be disperse | distributed minutely. Therefore, a toner excellent in hot offset property and colorant dispersibility can be obtained.
(4-2) Crosslinking step In the crosslinking step, the kneaded product obtained in the dispersing step is continuously heated with the heating kneader used in the dispersing step, and heated and kneaded at a high temperature. Thereby, the vinyl resin (A) which has a carboxyl group, and the vinyl resin (B) which has a glycidyl group raise | generate a crosslinking reaction, and a crosslinked body is produced | generated.

  The crosslinking step is preferably performed so that the maximum kneading temperature of the kneaded product is in the range of 160 to 190 ° C. If it is less than 160 ° C., the crosslinking reaction of the binder resin does not proceed easily, so that the hot offset property may not be sufficiently obtained. On the other hand, when the temperature exceeds 190 ° C., the molecular chain of the crosslinked product is cut to reduce the molecular weight, and the hot offset property may not be sufficiently obtained.

  The resulting crosslinked product in the toner can be expressed as a tetrahydrofuran-insoluble component, and the amount of the component preferably contains 5 to 50% by weight of the tetrahydrofuran-insoluble component. The component amount of a preferable crosslinked body is 15 to 30% by weight. If the amount of the cross-linked component is less than 5% by weight, a sufficient toner storage period may not be ensured. On the other hand, if it exceeds 50% by weight, the low-temperature fixability of the toner may be lowered. It is considered that the crosslinked body mainly includes a crosslinked body having a high degree of crosslinking.

The component amount of the crosslinked product in the toner means a value measured by the following method. That is, 2.0 g of toner is placed in 200 ml of tetrahydrofuran and stirred at 25 ± 3 ° C. for 12 hours to completely dissolve soluble components to prepare a solution. The concentration of this solution is expressed as (RC). Next, insoluble components are separated from the obtained solution using a centrifuge. After separation, the supernatant concentration (SC) is analyzed. The concentration (SC) of the supernatant is calculated from the weight of the remaining solvent-insoluble component after 5 g of the supernatant is collected and dried at 120 ° C. for 1 hour to remove tetrahydrofuran. From the obtained RC ′ value and SC ′ value, the ratio of the content of the crosslinked product in the toner is obtained by the following formula.
Crosslinked component content in toner = [(RC-SC) / RC] × 100 (% by weight)
(5) Grinding step The obtained crosslinked product may be subjected to a grinding step. In the pulverization step, particulate toner is generated by pulverizing the crosslinked product obtained in the kneading step. The crosslinked body is cooled and solidified before pulverization, and can be pulverized by an air pulverizer such as a jet mill. Furthermore, the particle size may be adjusted by classifying the pulverized product as necessary.
(6) External Addition Step The toner may be subjected to an external addition step for attaching an external additive. In the external addition step, the toner and the external additive are mixed using an airflow mixer such as a Henschel mixer, a super mixer, a mechano mill, or a Q-type mixer.
[Developer]
The toner of the present invention can be used for both a one-component developer and a two-component developer. When used as a two-component developer, a carrier is used in addition to the toner.
[Career]
As the carrier, fine particles having a volume resistivity in the range of 1 × 10 ⁹ to 2 × 10 ¹¹ Ω · cm when measured by a bridge method can be suitably used. Such a carrier can be obtained by coating the surface of magnetic core particles with a coating material (resin) containing a conductive material. When the volume resistivity is less than 1 × 10 ⁹ Ω · cm, when the carrier comes into contact with the surface of the photosensitive drum during development, the charge on the surface of the photosensitive drum is likely to leak to the carrier, and brush streaks are likely to occur. . Conversely, when the volume resistivity exceeds 2 × 10 ¹¹ Ω · cm, the charge amount of the toner increases and the image density tends to decrease. A more preferable volume resistivity is in the range of 4 × 10 ⁹ to 1 × 10 ¹¹ Ω · cm.

  The volume resistivity of the carrier in the bridge method is a value measured by the following procedure. That is, under an environmental condition of an air temperature of 20 ° C. and a humidity of 65%, a carrier of 0.2 g is filled between two copper plate electrodes having a width of 30 mm and a height of 10 mm that are installed with a gap of 6.5 mm. A bridge formed by carriers is formed by the magnetic lines of force of two magnets (100 mT) arranged outside each copper plate electrode so that the N pole and the S pole face each other. In this state, the value after 15 seconds of voltage application of 500 V is the volume resistivity.

  Examples of such a carrier include a coated carrier having a volume average particle diameter of 30 to 100 μm in which a coating material is provided on the surface of magnetic particles such as ferrite. If the particle size of the carrier is too small, the carrier may move from the developing roller to the photosensitive drum during development, and white spots may occur in the obtained image. On the other hand, if it is too large, the charge amount of the toner decreases, dot reproducibility deteriorates, and the image may become rough. In addition, the volume average particle diameter of the carrier is obtained when a dry dispersion apparatus RODOS (manufactured by SYMPATEC) is used in a laser diffraction particle size distribution measuring apparatus HELOS (manufactured by SYMPATEC) under a dispersion pressure of 3.0 bar. Value.

  The lower the saturation magnetization of the carrier, the softer the magnetic brush in contact with the photosensitive drum, so that an image faithful to the electrostatic latent image can be obtained. However, if the saturation magnetization is too low, carriers adhere to the surface of the photosensitive drum and white spots are likely to occur. If the saturation magnetization is too high, it becomes difficult to obtain an image faithful to the electrostatic latent image due to the stiffening of the magnetic brush. Therefore, the saturation magnetization of the carrier is preferably in the range of 30 to 100 emu / g.

  As the core particles, known magnetic particles can be used, but ferrite particles are preferable from the viewpoint of chargeability and durability. Known ferrite particles can be used, such as zinc ferrite, nickel ferrite, copper ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, copper-magnesium ferrite, manganese-zinc ferrite, Manganese-copper-zinc ferrite and the like can be mentioned.

These ferrite particles can be produced by a known method. For example, ferrite raw materials such as Fe ₂ O ₃ and Mg (OH) ₂ are mixed, and this mixed powder is heated in a heating furnace and calcined. The obtained calcined product is cooled and then pulverized to a particle size of about 1 μm with a vibration mill, and a dispersant and water are added to the pulverized powder to prepare a slurry. The slurry is wet pulverized with a wet ball mill, and the resulting suspension is granulated and dried with a spray dryer to obtain ferrite particles.

  Further, when the volume average particle diameter of the ferrite-based particles is in the range of 30 to 100 μm, an image with good dot reproducibility can be obtained without causing white spots in the image due to carrier adhesion to the photoreceptor. This is preferable.

Further, the volume resistivity of the ferrite-based particles is preferably in the range of 1 × 10 ^{8 to} 5 × 10 ¹⁰ Ω · cm from the viewpoint of electrical insulation and the ability to remove counter charges remaining on the carrier surface. . Such ferrite particles can prevent fogging and edge effects in a solid image and a decrease in image density.

  A known resin material can be used as the covering material, and examples thereof include an acrylic resin and a silicone resin. In particular, a coated carrier coated with a silicone resin is preferred because the boron compound is less likely to be spent (fused) on its surface and can maintain the charge imparting ability of the toner over a long period of time.

  The covering material may be added with a conductive material in order to control the volume resistivity of the carrier. Examples of the conductive material include silicon oxide, alumina, carbon black, graphite, zinc oxide, titanium black, iron oxide, titanium oxide, tin oxide, potassium titanate, calcium titanate, aluminum borate, magnesium oxide, barium sulfate, Examples thereof include calcium carbonate. A conductive material can be used individually by 1 type, or can use 2 or more types together. As a usage-amount of a electrically conductive material, 0.1-20 weight% is used with respect to 100 weight% of coating | covering materials.

  Among these conductive materials, carbon black is preferable from the viewpoint of production stability, cost, and low electrical resistance. The type of carbon black is not particularly limited, but a carbon black having a DBP (dibutyl phthalate) oil absorption in the range of 90 to 170 ml / 100 g is preferable in terms of excellent production stability. A primary particle size of 50 nm or less is particularly preferable because of excellent dispersibility.

In order to coat the core material with the coating material, a known method can be employed. For example, an immersion method in which the core particles are immersed in an organic solvent solution of the coating material, a spray method in which the organic solvent solution of the coating material is sprayed onto the core particles, and an organic solvent solution of the coating material in a state where the core particles are suspended by flowing air And a kneader coater method in which a core particle and an organic solvent solution of a coating material are mixed in a kneader coater to remove the solvent. At this time, a conductive material for resistance value control is added to the organic solvent solution of the coating material together with the coating material.
[Method for producing two-component developer]
The two-component developer can be produced by mixing the toner and the carrier with a mixer such as a Nauter mixer. The mixing ratio of the carrier and the toner is usually 3 to 15% by weight of the toner with respect to 100% by weight of the carrier. More preferably, it is in the range of 4 to 12% by weight. When the mixing ratio is within this range, a toner having excellent storage stability and fluidity can be provided.
[Image forming apparatus]
FIG. 1 is a schematic explanatory view showing the entire configuration of the image forming apparatus, and FIG. 2 is a schematic front sectional view showing the periphery of the toner cartridge and the developing device constituting the image forming apparatus of FIG.

  The image forming apparatus 30 includes a toner cartridge 10, a developing device 20, a photosensitive drum 17, a charging device 25, an exposure device 22, a cleaning device 26, a transfer device 24, a fixing device 23, a paper feed cassette 21, a paper discharge tray 29, and the like. A scanner unit 31 is provided.

  The photosensitive drum 17 is supported by a driving unit (not shown) so as to be rotatable around an axis, and is constituted by a roller-like member on which an electrostatic latent image and thus a toner image is formed. For the photosensitive drum 17, for example, a conductive substrate and a roller-shaped member formed on the surface of the conductive substrate can be used. As the conductive substrate, a conductive substrate such as a cylindrical shape, a columnar shape, or a sheet shape can be used, and among them, a cylindrical conductive substrate is preferable. Examples of the photosensitive drum 17 include an organic photosensitive drum and an inorganic photosensitive drum.

  As an organic photoreceptor drum, a layered photoreceptor drum of a charge generation layer which is a resin layer containing a charge generation material and a charge transport layer which is a resin layer containing a charge transport material, or a charge generation material in one resin layer And a single-layer photosensitive drum containing a charge transport material.

  Examples of the inorganic photosensitive drum include a film containing one or more selected from zinc oxide, selenium, amorphous silicon and the like. A base film may be interposed between the conductive substrate and the photosensitive drum, and a surface film (protective film) for mainly protecting the photosensitive drum may be provided on the surface of the photosensitive drum. .

  The charging device 25 performs corona discharge on the photosensitive drum 17 and employs a sawtooth charger. As the charging device 25, a charger such as a charger-type charger, a charging brush-type charger, a roller-type charger, or a magnetic brush can be used in addition to the saw-tooth type charger.

  The charging device 25 receives a voltage from a power source (not shown) and charges the surface of the photosensitive drum 17 to a predetermined polarity and potential.

  The exposure device 22 receives image information of a document read by the scanner unit 31 or image information from an external device, and irradiates the charged surface of the photosensitive drum 17 with signal light corresponding to the image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 17. As the exposure device 22, a laser scanning device including a light source is used.

  The developing device 20 includes a toner cartridge 10, a developing tank 11, a stirring roller 13, a developing roller 12, a regulating member 14, and a toner concentration detection sensor 15.

  The developing tank 11 is a container member having an internal space, rotatably supports the stirring roller 13 and the developing roller 12, and contains a two-component developer composed of toner and a carrier.

  The stirring roller 13 is rotationally driven by a driving unit (not shown) and stirs the two-component developer accommodated in the developing tank 11.

  The developing roller 12 is composed of a roller-like member, and conveys the two-component developer to the photosensitive drum 17, and is rotationally driven around an axis by driving means (not shown). The developing roller 12 is provided so as to face the photosensitive drum 17 through the opening 16 of the developing tank 11 and be separated from the photosensitive drum 17 with a gap.

  The two-component developer conveyed by the developing roller 12 comes into contact with the photosensitive drum 17. This contact area is a development nip portion. In this development nip portion, a developing bias voltage is applied to the developing roller 12 from a power source (not shown), and the developer on the surface of the developing roller 12 electrostatically charges the surface of the photosensitive drum 17. Toner is supplied to the latent image.

  The regulating member 14 is composed of a plate-like member extending in parallel along the axial direction of the developing roller 12. One end of the short side direction is supported by the developing tank 11 and the other end is vertically above the developing roller 12. Is provided so as to be separated from the surface of the developing roller 12 with a gap. As the material of the regulating member 14, stainless steel can be used, but aluminum, synthetic resin, or the like can also be used.

  The toner concentration detection sensor 15 is mounted on the bottom surface of the developing tank 11 below the stirring roller 13 in the vertical direction, and is provided so that the sensor surface (upper surface) 15 a is exposed inside the developing tank 11. The toner concentration detection sensor 15 is electrically connected to control means (not shown). This control means controls to rotate the toner discharge member 3 according to the detection result by the toner concentration detection sensor 15 and supply the toner into the developing tank 11 through the toner discharge port 2.

  For example, when it is determined that the detection result by the toner density detection sensor 15 is lower than the toner density setting value, the control means sends a control signal to the driving means for driving the toner discharge member 3 to rotate.

  A general detection sensor can be used as the toner concentration detection sensor 15. Examples thereof include a transmitted light detection sensor, a reflected light detection sensor, and a magnetic permeability detection sensor. Among these, a magnetic permeability detection sensor is preferable.

  The permeability detection sensor is a type of sensor that receives the control voltage and outputs the toner density detection result as an output voltage value. Basically, the sensitivity near the median value of the output voltage is good. It is used by applying a control voltage to obtain a voltage. Examples of this type of magnetic permeability detection sensor include TS-L, TS-A, and TS-K (all are trade names, manufactured by TDK).

  A power source (not shown) is connected to the toner concentration detection sensor 15 using the magnetic permeability detection sensor. The power supply applies to the toner concentration detection sensor 15 a drive voltage for driving the toner concentration detection sensor 15 and a control voltage for outputting the detection result of the toner concentration to the control means. The application of voltage to the toner concentration detection sensor 15 by the power source is controlled by the control means.

  The transfer device 24 is composed of a roller-like member, is rotatably supported by a support member (not shown), is rotatably provided by a driving means (not shown), and is provided so as to be in pressure contact with the photosensitive drum 17.

  For the transfer device 24, for example, a roller-shaped member including a metal cored bar having a diameter of 8 to 10 mm and a conductive elastic layer formed on the surface of the metal cored bar is used. As the metal forming the metal core, stainless steel, aluminum, or the like can be used. As the conductive elastic layer, a rubber material in which a conductive material such as carbon black is blended with a rubber material such as conductive ethylene-propylene rubber (EPDM), foamed EPDM, or foamed urethane can be used.

  The toner image is conveyed to the pressure contact portion (transfer nip portion) between the photosensitive drum 17 and the transfer device 24 by the rotation of the photosensitive drum 17 and from the paper feeding cassette 21 via the paper feeding roller 27. Recording media are supplied one by one. A means the conveyance direction of the recording medium. As the recording medium passes through the transfer nip portion between the photosensitive drum 17 and the transfer device 24, the toner image on the surface of the photosensitive drum 17 is transferred to the recording medium.

  A power supply (not shown) is connected to the transfer device 24, and a voltage having a polarity opposite to the charging polarity of the toner constituting the toner image is applied to the transfer device 24 when the toner image is transferred to a recording medium. As a result, the toner image is smoothly transferred to the recording medium.

  The cleaning device 26 includes a cleaning blade (not shown) and a toner storage tank (not shown). The cleaning blade is composed of a plate-like member extending in parallel along the axial direction of the photoconductive drum 17, and is provided so that one end of the plate-like member in the short direction contacts the surface of the photoconductive drum 17. ing. The cleaning blade comes into contact with the surface of the rotating photosensitive drum 17 so as to remove toner, paper dust, and the like remaining on the surface of the photosensitive drum 17 from the surface of the photosensitive drum 17 after the toner image is transferred to the recording medium. It has become. The toner storage tank is composed of a container-like member having an internal space, and temporarily stores the toner removed by the cleaning blade. The surface of the photosensitive drum 17 after the toner image is transferred is cleaned by the cleaning device 26 configured as described above.

  The fixing device 23 includes a fixing roller 32 and a pressure roller 33. The fixing roller 32 is composed of a roller-like member, is rotatably supported by a support member (not shown), and is provided so as to be rotatable around an axis line by a drive means (not shown). This fixing roller 32 has a heating member (not shown) inside, and heats and melts the toner constituting the unfixed toner image carried on the recording medium conveyed from the transfer nip portion to fix it on the recording medium. It is like that.

  The fixing roller 32 is composed of a cylindrical cored bar and a roller-shaped member provided with an elastic layer on the surface thereof. The core metal is formed of a metal such as iron, stainless steel, or aluminum. The elastic layer is formed of an elastic material such as silicone rubber or fluorine rubber having a thickness of 3 to 10 mm, for example. The heating member receives heat from a power source (not shown) and generates heat. A halogen lamp, an infrared lamp, or the like can be used as the heating member.

  The pressure roller 33 is composed of a cylindrical cored bar and a roller-shaped member provided with a release layer on the surface thereof. The core metal is formed of a metal such as iron, stainless steel, or aluminum. The release layer is formed of a low surface energy film such as PTFE (polytetrafluoroethylene). It is composed of a roller-like member, is rotatably supported, and is provided so as to be pressed against the fixing roller 32 by a pressure member (not shown). The pressure roller 33 is rotated by the rotation of the fixing roller 32. A pressure contact portion between the fixing roller 32 and the pressure roller 33 is a fixing nip portion.

  The pressure roller 33 promotes fixing of the toner image to the recording medium by pressing the toner in a molten state against the recording medium when the fixing roller 32 heat-fixes the toner image to the recording medium. As the pressure roller 33, a roller-like member having the same configuration as that of the fixing roller 32 can be used. A heating member may also be provided inside the pressure roller 33. As this heating member, the same heating member as that in the fixing roller 32 can be used.

  In the fixing device 23, when the recording medium on which the toner image is transferred passes through the fixing nip portion, the toner constituting the toner image is melted and pressed against the recording medium, and the toner image is fixed on the recording medium. The recording medium on which the image is printed is discharged to a paper discharge tray 29 via a paper discharge roller 28.

  The paper feed cassette 21 is a tray that stores recording media such as plain paper, coated paper, color copy paper, and OHP film. A recording medium is fed one by one in synchronization with the toner image on the surface of the photosensitive drum 17 being conveyed to the transfer nip portion by a pickup roller (not shown) and a conveying roller.

  The scanner unit 31 is provided with a document setting tray (not shown), an automatic reversing document feeder (RADF), and the like, and a document reading device (not shown).

  The toner cartridge 10 includes a toner container 1, a toner stirring member 8, a toner scooping blade 9, a toner discharge member 3, and a toner discharge port 2. The toner discharging member 3 and the toner stirring member 8 are configured to rotate by a driving force from a gear transmission mechanism and a driving motor (not shown).

  The toner container 1 is a substantially semi-cylindrical container member having an internal space. The toner container 1 accommodates toner therein and rotatably supports the toner stirring member 8 and the toner discharge member 3.

  Further, the toner container 1 is formed such that one end portion in the axial direction of the toner discharge member 3 protrudes, and a toner discharge port 2 that is opened in a rectangular shape is provided at the lower portion of the toner discharge member 3 in the vertical direction. .

  The toner discharge port 2 is arranged at a position facing the developing device 20 provided in the image forming apparatus 30 when the toner cartridge 10 is mounted on the image forming apparatus 30.

  The toner agitating member 8 is integrally provided with a rotating shaft 8a, a toner pumping blade 9 and an agitating gear (not shown), and a driving force is transmitted through the agitating gear to rotate around the rotating shaft 8a. The toner contained in 1 is agitated.

  The toner pumping blade 9 is made of a polyethylene terephthalate (PET) sheet having a thickness of about 0.5 to 2 mm and has a flexibility. The toner pumping blade 9 pumps the toner in the toner container 1 and transports it to the toner discharge member 3. It is attached to both ends of the stirring member 8.

  The toner cartridge 10 according to the present embodiment rotates to discharge the toner in the toner container (toner container) 1 to the outside of the toner container 1 and the toner agitation for agitating the toner in the toner container 1. The image forming apparatus 30 includes a member 8 and is detachable from the developing device 20 mounted on the image forming apparatus 30.

  The toner discharge member 3 supplies the toner conveyed by the toner scooping blade 9 to the developing tank 11 from the toner discharge port 2, and includes a toner discharge member rotating shaft 3a, a toner transfer unit 6, and a discharge gear (not shown).

  The toner conveying unit 6 is formed of a so-called screw auger or spiral coil formed of a spiral and continuous blade body, and is rotated by a driving force of a driving motor (not shown) via a discharge gear.

  The direction of the spiral of the toner transport unit 6 is set so that the toner is transported from one axial end of the toner discharge member 3 toward the toner discharge port 2.

  Between the toner discharge member 3 and the toner stirring member 8, a toner discharge member partition wall that divides the inside of the toner container 1 into the toner discharge member 3 side and the toner stirring member 8 side along the axial direction of the toner discharge member 3. (Partition wall) 4 is provided. The toner discharge member partition 4 holds an appropriate amount of toner pumped up by the toner stirring member 8 around the toner discharge member 3.

  Next, an operation for supplying toner from the toner cartridge 10 to the developing device 20 in the image forming apparatus 30 will be described.

  When toner is supplied to the developing device 20 by the toner cartridge 10, the toner is drawn up by the toner pumping blade 9 while rotating the toner stirring member 8 in the direction of arrow E in the toner cartridge 10 and stirring the toner in the toner container 1. Pump to the toner discharge member 3 side.

  At this time, the toner scooping blade 9 rotates while deforming while sliding on the inner wall 1a of the toner container 1 due to the flexibility of the material constituting the blade, so that the toner on the downstream side in the rotation direction, that is, in the toner container 1 The toner positioned on the right side (near the developing device 20) and above the toner pumping blade 9 is supplied to the toner discharge member 3 side.

  A predetermined amount of toner supplied to the toner discharging member 3 side is stored on the toner discharging member 3 by the toner discharging member partition wall 4, and excess toner falls to the toner stirring member 8 side. Thereby, the amount of toner conveyed by the toner discharge member 3 can be made constant.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
<Toner T1-1>
In order for the vinyl resin (A) having a carboxyl group to obtain a weight average molecular weight as described above, a mixture of a low molecular weight one and a high molecular weight one is preferable.
Low molecular weight polymerization liquid (AL)
A solution consisting of 80% by weight of styrene, 19% by weight of n-butyl acrylate, 1.0% by weight of methacrylic acid which is a carboxyl group-containing vinyl monomer, and 80% by weight of a xylene solvent is mixed with 3% by weight of 100% by weight of styrene. A solution in which -t-butyl peroxide is uniformly dissolved is polymerized by continuously supplying 750 ml / hour to a 5 L reactor maintained at an internal temperature of 190 ° C. and an internal pressure of 6 kg / cm ^2. AL).
High molecular weight polymerization liquid (AH)
Separately, as a vinyl monomer, 73% by weight of styrene, 24.7% by weight of n-butyl acrylate, and 2.3% by weight of methacrylic acid which is a carboxyl group-containing vinyl monomer were charged into a nitrogen-substituted flask, and the internal temperature was 120. After raising the temperature to 0 ° C., the same temperature was maintained and bulk solution polymerization was carried out for 10 hours. Next, 50% by weight of a xylene solvent was added, and 50% by weight of a 0.1% by weight xylene solvent of dibutyl peroxide previously mixed and dissolved was continuously added over 8 hours while maintaining the internal temperature at 130 ° C. Further, 0.2% by weight of di-t-butyl peroxide was added and the reaction was continued for 2 hours. Thereafter, 0.5% by weight of di-t-butyl peroxide was further added and held for 2 hours to complete the reaction, whereby a high molecular weight polymerization liquid (AH) was obtained.
Vinyl resin A1
Next, 150% by weight of the high molecular weight polymerization solution (AH) and 120% by weight of the low molecular weight polymerization solution (AL) were mixed, and then flashed in a vessel at 90 ° C. and 10 mmHg to distill off the solvent and the like, and the glass transition Point: 62 ° C., weight average molecular weight: 32000, oxidation: 10 KOH mg / g vinyl resin A1 was obtained.
Vinyl resin B1
A flask purged with 80% by weight of a xylene solvent with nitrogen was charged and heated to the reflux temperature of xylene. Under reflux of xylene, 71.5% by weight of styrene previously mixed and dissolved, 28% by weight of n-butyl acrylate, 0.5% by weight of glycidyl methacrylate as a vinyl monomer containing glycidyl group, di-t- 0.5% by weight of butyl peroxide was continuously added over 5 hours, and the reflux was further continued for 1 hour. Thereafter, the internal temperature was maintained at 130 ° C., 0.5% by weight of di-t-butyl peroxide was added and the reaction was continued for 2 hours to complete the reaction, thereby obtaining a polymerization solution. This was flashed in a vessel at 160 ° C. and 10 mmHg to distill off the solvent and the like to obtain a glycidyl group-containing vinyl resin B1 having a glass transition point: 58 ° C., a weight average molecular weight: 55000, and an epoxy equivalent: 10000 g / Eq.

In order to mix the materials uniformly,
-85% by weight of the above vinyl resin A1 having a carboxyl group
-15% by weight of the above-mentioned vinyl resin B1 having a glycidyl group
Carbon black (pH = 3.5, Mitsubishi Chemical Corporation MA100) 5% by weight
・ Polypropylene wax (Sanyo Kasei Co., Ltd .: 550P) 3% by weight
・ Charging control agent (TRH manufactured by Hodogaya Chemical Co., Ltd.) 2% by weight
Was mixed in a Henschel mixer for 10 minutes.
The obtained mixture was melt kneaded at 120 ° C. in the dispersion step and 180 ° C. in the cross-linking step using a biaxial kneader (Ikegai Co., Ltd .: PCM30 type) to obtain a kneaded product.

  The obtained kneaded material was coarsely pulverized with a cutting mill, and then finely pulverized with a jet pulverizer (manufactured by Nippon Pneumatic Kogyo Co., Ltd .: IDS-2 type). The finely pulverized product was classified using an air classifier (manufactured by Nippon Pneumatic Industry Co., Ltd .: MP-250 type) to obtain a toner having a volume average particle size of 6.0 μm. The ratio of the crosslinked body in the toner was 20% by weight.

1% by weight of silica particles (Degussa) whose surface was treated with hexamethyldisilazane having a number average particle diameter of 7 nm was added to 100% by weight of the obtained toner, and the tip speed of the stirring blade was set to 15 m / sec. The negatively chargeable toner T1-1 was prepared by stirring for 2 minutes with the airflow mixer (Mitsui Mining Co., Ltd .: Henschel mixer).
<Toners T1-2 to T2-14>
Except that the maximum kneading temperature of the kneaded product in the dispersion step and the crosslinking step, the weight average molecular weight of the vinyl resin (A) and the vinyl resin (B), the pH and the addition amount of the carbon black are different, the same method as the toner T1-1. The toners T1-2 to T1-20 and T2-1 to T2-14 shown in Tables 1 and 2 were produced under different conditions. This is shown in Tables 1 and 2 below. T1-1 to T1-20 shown in Table 1 are examples, and T2-1 to T2-14 shown in Table 2 are comparative examples.

In the above table, the weight average molecular weight is appropriately adjusted depending on the amount of methacrylic acid which is a carboxyl group-containing vinyl monomer and glycidyl methacrylate which is a glycidyl group-containing vinyl monomer, the internal temperature, the reaction time, and the like. . In adjusting the pH of the carbon black, it can be obtained by performing an oxidation treatment. Oxidation treatment may be wet oxidation using oxidizing agents such as hydrogen peroxide, permanganic acid, chlorous acid, sodium hypochlorite, bromine, nitric acid, air, gas containing specially adjusted oxygen, ozone Vapor phase oxidation treatment is performed using a gas containing gas. In addition, acidic carbon black having pH = 2 and pH = 6 can be obtained by performing this oxidation treatment, and acidic carbon black having pH = 1.5 is manufactured by Mitsubishi Chemical Corporation # 980, pH = 6.5. As the acidic carbon black, # 2600 manufactured by Mitsubishi Chemical Corporation was used.

  Toners T1-2 to T1-9 are examples in which the maximum kneading temperatures of the kneaded product in the dispersion step and the crosslinking step are in the range of 120 to 140 ° C. and 160 to 190 ° C., respectively.

  The toner T1-10 is an example in which the weight average molecular weight of the vinyl resin (A) is slightly over 5000, and the toner T1-11 is an example in which the weight average molecular weight of the vinyl resin (A) is slightly smaller than 100,000.

  The toner T1-12 is an example in which the weight average molecular weight of the vinyl resin (B) is slightly over 10,000, and the toner T1-13 is an example in which the weight average molecular weight of the vinyl resin (B) is slightly smaller than 1,000,000.

  The toner T1-14 is an example in which the pH of carbon black is 2, and the toner T1-15 is an example in which the pH of carbon black is 6.

  Toners T1-16 to T1-18 are examples in which the amount of carbon black added is in the range of 1 to 15% by weight.

  Toner T1-19 is an example in which the component amount of the crosslinked body in the toner is 5% by weight, and Toner T1-20 is an example in which the component amount of the crosslinked body in the toner is 50% by weight.

  Toners T2-1 to T2-4 are comparative examples in which the maximum kneading temperature of the kneaded product in either the dispersion step or the crosslinking step is outside the range of 120 to 140 ° C. and 160 to 190 ° C., respectively.

  Toner T2-5 is a comparative example in which the maximum kneading temperature of the kneaded product in the dispersion step and the crosslinking step is higher than the ranges of 120 to 140 ° C and 160 to 190 ° C, respectively.

  Toner T2-6 is a comparative example in which the kneading maximum temperatures of the kneaded product in the dispersion step and the crosslinking step are lower than the ranges of 120 to 140 ° C and 160 to 190 ° C, respectively.

  The toner T2-7 is a comparative example in which the weight average molecular weight of the vinyl resin (A) is slightly smaller than 5000, and the toner T2-8 is a comparative example in which the weight average molecular weight of the vinyl resin (A) is slightly more than 100,000.

  The toner T2-9 is a comparative example in which the weight average molecular weight of the vinyl resin (B) is slightly smaller than 10,000, and the toner T2-10 is a comparative example in which the weight average molecular weight of the vinyl resin (B) is slightly more than 1,000,000.

  Toner T2-11 is a comparative example in which the pH of carbon black is less than 2, and toner T2-12 is a comparative example in which the pH of carbon black exceeds 6.

Toners T2-13 and T2-14 are comparative examples in which the addition amount of carbon black is outside the range of 1 to 15% by weight.
<Career>
A ferrite raw material (manufactured by Kanto Denka Co., Ltd.) was mixed with a ball mill and then calcined at 900 ° C. with a rotary kiln. The obtained calcined powder was finely pulverized to a mean particle diameter of 2 μm or less by a wet pulverizer (using steel balls as a pulverizing medium). The obtained ferrite powder was granulated by a spray drying method, and the granulated product was fired at 1300 ° C. After firing, core particles made of a ferrite component having a volume average particle diameter of about 45 μm and a volume resistivity of 1 × 10 ⁹ Ω · cm were obtained by crushing using a crusher.

  Next, a coating solution S1 for forming a thermosetting silicone resin layer for coating the core particles was prepared by adding 100% by weight of dimethyl silicone resin (manufactured by Toshiba Silicone) and 5% by weight of octylic acid as a curing agent in a toluene solvent. It was obtained by dissolving in The core particles were coated with the resin layer by a dip coating apparatus for immersing the core particles in the coating liquid S1. Then, after completely removing toluene by evaporation, carrier C1 was produced by performing curing (thermosetting) at 190 ° C. for 30 minutes.

Carrier C1 had a volume average particle diameter of 46 μm, a coverage of 100%, a volume resistivity of 1 × 10 ¹² Ω · cm, and a saturation magnetization of 65 emu / g.
<Two-component developer>
By mixing carrier C1 with toners T1-1 to T2-14, two-component developers of Examples and Comparative Examples were produced. The two-component developer was prepared by charging 6% by weight of toner and 94% by weight of carrier into a Nauter mixer (trade name: VL-0, manufactured by Hosokawa Micron Corporation) and stirring and mixing for 25 minutes.

Various evaluation items and measurement methods are described below.
<Evaluation>
[Continuous print test]
The produced toners T1-1 to T2-14 were subjected to a continuous print test using the image forming apparatus shown in FIG. 1, and the fluidity change of the toner and the two-component developer and the stability of the image density were investigated.

As the development conditions of the image forming apparatus, the peripheral speed of the photosensitive drum is 200 mm / second, the peripheral speed of the developing roller is 280 mm / second, the gap between the photosensitive drum and the developing roller is 0.4 mm, the developing roller 12 and the regulating blade 14 The gap was set to 0.5 mm. Further, the surface potential of the photosensitive drum and the developing bias were adjusted so that the toner adhesion amount on the paper in the solid image was 0.5 mg / cm ² and the toner adhesion amount in the non-image area was minimized.

  As fixing conditions of the image forming apparatus, the peripheral speed of the heating roller and the pressure roller is set to 200 mm / second, the set temperature is set to 180 ° C., the fixing nip width is set to 8 mm, and A4 size electrophotographic paper (plain paper) is used as a recording medium. )It was used.

  The continuous print test is a continuous print test of 10000 sheets of 100 character images intermittently with a print image area ratio of 6% printed on electrophotographic paper at a temperature of 35 ° C. and a humidity of 60%. Went.

  Regarding the change in the fluidity of the toner and the two-component developer, the developer state in the developing device is visually observed at the timing when the defect occurs in the image, the developer fluidity is lowered, and the developer on the developing roller The state where the toner was not supplied normally was judged as a decrease in the fluidity of the developer.

  Image evaluation such as image density was performed by measuring toner charge amount, image density, and fog density on the initial 5000th sheet and 10,000th sheet by the following measurement method.

  The toner charge amount was evaluated using a suction-type small charge amount measuring device (Trek Japan Co., Ltd .: 210HS-2A) for all of the initial 5000th sheet and 10,000th sheet developer. If it was within the range of 20 ± 3 μC / g, it was judged good, and if it was outside the range of 20 ± 3 μC / g, it was judged as bad.

  As the evaluation of the image density, the optical density of the evaluation image was measured using a spectrocolorimetric densitometer (manufactured by Nihon Denshi Printing Co., Ltd .: X-Rite 938) in all of the initial images of the 5000th and 10000th images, An image density of 1.2 or higher was judged good and a density of less than 1.2 was judged poor.

  As for the fog density, the density of the non-image area is calculated by the following procedure. Using a whiteness meter (Nippon Denshoku Industries Co., Ltd .: Z-Σ90 COLOR MEASURING SYSTEM), the whiteness of the electrophotographic paper before printing was measured in advance. Next, the whiteness in the non-image portion of the electrophotographic paper after printing is measured using a whiteness meter, and the difference from the whiteness before printing is obtained. This difference was defined as fog density.

In the evaluation of fog density, in all initial images of the 5000th sheet and the 10,000th sheet, less than 1.0 was good and 1.0 or more (a state where fog was clearly visible with the naked eye) was regarded as poor.
[Fixability test]
Regarding the fixing strength, lightly fold the solid image portion of the fixed electrophotographic paper, and further roll a cylindrical roller having a weight of 100 g, a diameter of 10 cm, and a width of 2 cm to form a crease, and then fold the electrophotographic paper. The toner that had fallen off the crease was wiped off with a clean and spread cloth, and the case where no toner separation was confirmed was good, and the case where toner separation was confirmed was regarded as poor.

Regarding the hot offset property, the toner attached to the fixing roller is visually checked to see if it has been retransferred to the electrophotographic paper. .
<Result>
In Table 1, it can be seen that in the fixability test of toners T1-1 to T1-20 as examples, good results were obtained for both the fixing strength and the hot offset property.

  As shown in Table 2, in the fixing test using the toners T2-1 to T2-6 shown in the comparative example, in the toner T2-1, the toner T2 caused by the temperature of the dispersion step being lower than 120 ° C. -2 is caused by the temperature of the dispersion step being higher than 140 ° C. In the toner T2-3, the temperature of the crosslinking step is lower than 160 ° C. In the toner T2-4, the temperature of the crosslinking step is 190. In the toner T2-5, which is caused by the temperature higher than ° C., the temperature of the dispersion process is higher than 140 ° C., and in the toner T2-6, the temperature of the dispersion process is higher than 190 ° C., the temperature of the dispersion process is 120 ° C. The hot offset caused by the temperature lower than ℃ and the temperature of the cross-linking process also lower than 160 ℃ occurred, respectively, and good results were not obtained. Among them, in toners T2-4 and T2-5, the proportion of tetrahydrofuran insolubles exceeded 50% by weight, resulting in poor low-temperature fixability, and good results were not obtained.

  As shown in Table 3, in the continuous print test using the toners T1-1 to T1-20 shown in the examples, the toner charge amount, image density, and fog density are stable, and the developer flow It was in a good state with no change in sex.

  Table 3 below shows the results of the continuous print test of T1-1 to T1-20 of the example.

  Table 4 below shows the results of the continuous print test of T2-1 to T2-14 of the comparative example.

  As shown in Table 4, in the continuous print test using toners T2-1, T2-2, T2-5, and T2-6, the temperature of the dispersion process is outside the range of 120 to 140 ° C. As a result, the fog density was poor from the beginning, and good results could not be obtained.

  In the fixing test using toners T2-7 and T2-9, the toner T2-7 has a vinyl resin (A) having a weight average molecular weight smaller than 5000, and the toner T2-9 has a vinyl resin (B). As a result, a hot offset defect occurred due to the weight average molecular weight of less than 10,000, and good results were not obtained.

  In a fixing test using toners T2-8 and T2-10, the toner T2-8 has a vinyl resin (A) having a weight average molecular weight greater than 100,000, and the toner T2-10 has a vinyl resin (B). The low-temperature fixability caused by the weight average molecular weight of greater than 1,000,000 occurred, and good results were not obtained. Among them, in the toner T2-10, the ratio of tetrahydrofuran insolubles exceeded 50% by weight, resulting in poor low-temperature fixability, and good results could not be obtained.

  In the fixing test using the toners T2-11 and T2-12, the toner T2-11 has a hot offset defect due to the pH of the carbon black being less than 2, and a good result was not obtained. . Further, in the toner T2-12, since the pH of the carbon black exceeds 6, the carboxyl group that is an acidic functional group of the carbon black that plays a role in inhibiting the crosslinking reaction of the binder resin is almost absent, and as a result, The proportion of tetrahydrofuran insolubles exceeded 50% by weight, resulting in poor low-temperature fixability, and good results could not be obtained.

  Further, in the continuous print test using the toner T2-12, sufficient dispersibility of carbon black was not obtained, and the fog density was poor from the beginning, and good results were not obtained.

  In the fixing test using toners T2-13 and T2-14, good results were obtained in both fixing strength and hot offset property. However, in the continuous print test, the amount of carbon black added was 1 in toner T2-13. Due to the fact that it is less than% by weight, an increase in the charge amount outside the range of 20 ± 3 μC / g from the initial stage and a decrease in image density as much as less than 1.2 occur, and good results are obtained. There wasn't. In addition, in the toner T2-14, due to the addition amount of carbon black being more than 15% by weight, the charge amount is lowered from the range of 20 ± 3 μC / g from the beginning, and becomes 1.0 or more. The fog density was poor and good results were not obtained.

  In addition, in the toners T2-3, T2-6, and T2-11, a hot offset defect was caused due to the amount of the crosslinked component being less than 5% by weight, and good results were not obtained.

DESCRIPTION OF SYMBOLS 1 Toner container 1a Inner wall 2 Toner discharge port 3 Toner discharge member 3a Toner discharge member rotating shaft 4 Toner discharge member partition wall 6 Toner conveying part 8 Toner stirring member 8a Rotating shaft 9 Toner pumping blade 10 Toner cartridge 11 Developing tank 12 Developing roller 13 Stirring Roller 14 Restricting member 15 Toner concentration detection sensor 15a Sensor surface (upper surface)
16 Opening 17 Photoconductor drum 20 Developing device 21 Paper cassette 22 Exposure device 23 Fixing device 24 Transfer device 25 Charging device 26 Cleaning device 27 Paper feed roller 28 Paper discharge roller 29 Paper output tray 30 Image forming device 31 Scanner unit 32 Fixing Roller 33 Pressure roller

Claims (13)

In a method for producing a toner containing at least a binder resin and a colorant,
The binder resin kneading step includes a dispersion step of dispersing a colorant in a resin mixture of a vinyl resin having a carboxyl group (A) and a vinyl resin having a glycidyl group (B), and the vinyl resin having a carboxyl group (A). And a crosslinking step of crosslinking the vinyl resin (B) having the glycidyl group.   The method for producing a toner according to claim 1, wherein the dispersing step is performed at a temperature lower than that of the crosslinking step.   3. The toner manufacturing method according to claim 1, wherein the dispersing step is performed at a temperature of 120 to 140 ° C., and the crosslinking step is performed at a temperature of 160 to 190 ° C. 4.   The method for producing a toner according to claim 1, wherein the colorant is acidic at a pH of 2 to 6.   The method for producing a toner according to claim 1, wherein the colorant is contained in an amount of 1 to 15% by weight with respect to 100% by weight of the resin mixture.   The vinyl resin (A) having a carboxyl group is derived from a monomer selected from acrylic acid, methacrylic acid, fumaric acid, methyl fumarate, ethyl fumarate, propyl fumarate, butyl fumarate and octyl fumarate. 6. The method for producing a toner according to claim 1, wherein the toner is a resin.   The vinyl resin (B) having a glycidyl group is a resin derived from a monomer selected from glycidyl acrylate, β-methylglycidyl acrylate, glycidyl methacrylate, and β-methylglycidyl methacrylate. The method for producing a toner according to any one of claims 1 to 5.   The vinyl resin (A) having a carboxyl group has a weight average molecular weight Mw of 5000 ≦ Mw ≦ 100,000, and the vinyl resin (B) having a glycidyl group has a weight average molecular weight Mw of 10,000 ≦ Mw ≦ 1000000. 8. The method for producing a toner according to any one of 7 above.   A toner manufactured by the toner manufacturing method according to claim 1.   The toner according to claim 9, comprising a crosslinked product obtained in the crosslinking step.   11. The toner according to claim 9, wherein the amount of the component of the crosslinked product is 5 to 50% by weight.   A two-component developer comprising the toner according to claim 9 and a carrier.   Photosensitive drum, charging device for charging the surface of the photosensitive drum, exposure device for forming an electrostatic latent image on the surface of the photosensitive drum, a developing device, and transfer for transferring the toner image to a recording medium And a fixing device for fixing the transferred toner image to a recording medium. The developing device contains the toner according to claim 9 and is formed on a surface of the photosensitive drum. An image forming apparatus, comprising: a developing device that forms a toner image by developing the electrostatic latent image.