JP4974926B2 - Toner, toner manufacturing method, two-component developer, developing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a toner, a toner manufacturing method, a two-component developer, a developing device, and an image forming apparatus.

  Conventionally, a kneading pulverization method has been widely used as a toner production method. However, the pulverized toner has an irregular shape with many irregularities on the surface, and the pulverized surface after pulverization directly becomes the toner surface, resulting in an uneven surface composition. It is easy to control the surface condition uniformly. If the toner surface has an irregular shape with many irregularities, problems such as a decrease in toner fluidity or generation of fog or toner scattering due to non-uniform toner composition occur.

  In view of the problem of the irregular shape, many methods for producing toner by mixing and aggregating a dispersion of toner raw materials by a wet method instead of the kneading and pulverization method have been proposed. However, in the case of the wet method, since a dispersion stabilizer and a flocculant are frequently used, some of the components remain on the surface or inside of the toner, resulting in a decrease in moisture resistance and a deterioration in charging characteristics. It has the disadvantage of becoming unstable.

  Among the characteristics required for the toner, the charging characteristics that have a great influence on the behavior and quality in development and transfer (such as toning process and transfer process control) are particularly important required characteristics.

  On the other hand, with the trend toward higher image quality in recent years, the particle size of toner has progressed, and the content ratio of small particle size toner that is fine powder tends to increase. In a two-component developer containing a small particle size toner, cracking or shape change of the small particle size toner due to stress in the developing device causes toner spent on the carrier and the resulting charging deterioration of the developer, resulting in deterioration of image quality. It is a factor inviting.

  Further, with the trend of colorization in recent years, color toners have been fixed at low temperature, and toner components having a low temperature softening tend to be used.

  Therefore, as a result of the necessity of designing a toner having good fluidity and transferability, uniform charging performance, excellent offset resistance, and various other functions, the surface of the core particles is a resin layer. There has been proposed a capsule toner coated with the above.

  In Patent Document 1, a phase separation method is employed as a capsule toner encapsulation method. In the phase separation method, the shell material is dissolved in a good solvent that is low-soluble or insoluble in the core particles and good in solubility in the shell material, and the core particles are dispersed. Next, it is a method in which a shell material is deposited on the surface of the core particle by adding a poorly soluble poor solvent to the shell material, although well accustomed to the good solvent. In small-diameter toner, core particles containing at least a colorant and a soft solid substance are coated with an outer shell, and by defining the particle size distribution, the fine line reproducibility and gradation are excellent, and the performance changes over a long period of use. No capsule toner can be obtained.

  In Patent Document 2, a suspension polymerization method is employed as a capsule toner encapsulation method. Suspension polymerization is a method of encapsulating a polymerizable monomer for a shell by suspension polymerization in the presence of colored polymer core particles obtained by suspension polymerization in an aqueous dispersion medium at room temperature. It is. By defining the particle size distribution in a small particle size polymerized toner containing at least a binder resin and a colorant and having a core / shell structure, image quality deterioration due to long-term use can be prevented.

  However, even if the irregularly shaped pulverized toner is encapsulated by the encapsulation methods disclosed in Patent Documents 1 and 2, the pulverized toner whose core particle surface is a crushed surface cannot be completely covered. There is a concern that the components become non-uniform and the storage stability, charge uniformity, etc., which are easily affected by the toner surface characteristics, are reduced.

  Patent Document 3 discloses a step of mixing and kneading a low-melting-point binder component and a colorant and then finely pulverizing the toner core, and a high-melting-point resin particle having a particle size defined on the surface of the toner core. Disclosed is a technology for forming a thick and uniform outer shell of a toner by an external addition step and a step of forming a high melting point resin shell layer on the surface of the inner core of the toner by treating the inner core of the toner with low melting point resin particles with a solvent. Has been.

  However, in the encapsulation method disclosed in Patent Document 3, the outer shell of the toner is formed to be thick and uniform, so that the outer shell of the toner is too strong and difficult to deform, and the outer shell is not appropriately destroyed at the time of fixing. There is a risk of impairing the fixability of the inner core component.

JP-A-3-5763 International Publication No. WO00 / 13063 JP-A-4-182660

  An object of the present invention is to provide a toner, a toner production method, a two-component developer, a developing device, and an image forming apparatus that have both improved storage durability and fixing property.

The present invention has at least an amorphous core resin containing an amorphous polyester resin, a colorant and a release agent, and a shell layer covering the core particle,
The shell layer is forming a film formed on the core particle surface,
The thickness of the shell layer, 0.05 .mu.m or more, the portion to be 0.5μm or less account for at least 80% of the surface area, and a toner and satisfies the equation (1),
A × 2 <B (1)
A: Average value at a portion where the shell layer is thin B: Average value at a portion where the shell layer is thick
In the irregular core particles obtained by the pulverization step,
In a state where styrene-acrylic copolymer resin fine particles having a glass transition temperature Tg of 50 to 80 ° C. and an average particle diameter of 0.2 μm or less are adhered, the glass transition temperature is less than the glass transition temperature of the core particles, (Tg-20) ° C. The toner is produced by forming the shell layer by forming a film of the styrene-acrylic copolymer resin fine particles by stirring while controlling the heating as described above .

The present invention also provides a method for producing the above toner,
The above irregular core particles obtained by the grinding process;
In the presence of an adhesion aid that increases the adhesion of styrene-acrylic copolymer resin fine particles having a glass transition temperature Tg of 50 to 80 ° C. and an average particle diameter of 0.2 μm or less , constituting the shell layer, In a state where the core particles and the styrene-acrylic copolymer resin fine particles are brought into contact with each other and the styrene-acrylic copolymer resin fine particles are adhered to the core particles, the glass particles have a glass transition temperature Tg lower than (Tg- 20) A method for producing a toner, wherein the shell layer is formed by forming the shell layer by forming a film of the styrene-acrylic copolymer resin fine particles adhering to the core particles by stirring while controlling the temperature to be equal to or higher than ° C. .

  In the present invention, the adhesion aid contains at least one of water and lower alcohol.

  The present invention also provides a two-component developer comprising the toner described above and a carrier.

  According to another aspect of the present invention, there is provided a developing device that performs development using a developer containing the toner.

  According to another aspect of the present invention, there is provided an image forming apparatus that forms an image using the developing device.

  According to the present invention, there is provided a toner having at least an amorphous core resin containing an amorphous polyester resin, a colorant and a release agent, and a shell layer covering the core particle, the shell layer being the surface of the core particle A film is formed.

The shell layer is characterized in that a portion having a thickness of 0.05 μm or more and 0.5 μm or less occupies at least 80% of the surface area and satisfies the formula (1).
A × 2 <B (1)
A: Average value at a portion where the shell layer is thin B: Average value at a portion where the shell layer is thick

  By forming a shell layer having a thickness difference as shown by the formula (1) on the surface of the irregularly shaped core particles, a toner having excellent fixability while maintaining storage durability can be obtained.

  In the case of an irregular core particle, if the entire surface of the core particle is not coated, the probability that the internal wax or pigment will be exposed increases, but if this is coated with a shell layer with a uniform film thickness, the fixability may be impaired. There is. By covering the entire surface of the core particle with a shell layer having a moderate thickness difference, the toner of the present invention can easily deform the shell layer during fixing, and can easily adhere (fix) the core particle component to the paper surface.

  When the thickness of the shell layer is 0.05 μm or more and 0.5 μm or less, less than 80% of the surface area, the probability that the wax or pigment inside the core particle is exposed increases, and the low melting point component contained in the core particle May soften and the toner may aggregate.

  If the average value of the portion where the thickness of the shell layer is thick is not more than twice the average value of the portion where the thickness of the shell layer is thin, the shell layer becomes difficult to deform during fixing, and the core particle component is fixed on the paper surface. A lot of energy is required, and it becomes difficult to secure a fixable area.

Moreover, according to this invention, a shell layer consists of a material whose glass transition temperature is 50-80 degreeC.
Thereby, the film thickness adjustment of a shell layer becomes easy. When the glass transition temperature exceeds 80 ° C., it is difficult to reduce the thickness of the shell layer, and the fixability deteriorates. When the glass transition temperature is less than 50 ° C., the storage stability and durability of the toner deteriorate due to aggregation of the toner.

According to the invention, the shell layer is mainly composed of a styrene-acrylic copolymer resin.
By using a styrene-acrylic copolymer resin as a main component, it is possible to cover the shell layer on substantially the entire surface, and the film thickness can be easily controlled. Further, by performing the dyeing process, the thickness of the shell layer can be easily observed with a transmission electron microscope.

  Further, according to the present invention, the toner of the present invention is obtained by bringing the core particles and the resin fine particles into contact with each other in the presence of an adhesion auxiliary agent that increases the adhesion between the amorphous core particles and the resin fine particles constituting the shell layer. Can be obtained.

  The surface of the core particles and the surface of the fine particles are moistened by the adhesion aid to promote the fusion of the fine particles, the core particles, and the fine particles, and a film can be formed while suppressing the free fine particles. In addition, the film thickness can be controlled by combining the mechanical impact force and the heating effect by temperature adjustment.

  According to the invention, the shell layer is formed by forming fine particles containing a styrene-acrylic copolymer resin into a film. By forming the shell layer by forming resin fine particles into a film, the controllability of the film thickness is further improved.

  According to the invention, the average particle size of the fine particles containing the styrene-acrylic copolymer resin is 0.2 μm or less.

  When the shell layer is formed on the irregular core particles, it is necessary to attach the fine particles to the concavo-convex portions, and the coating becomes easier by making the average particle size of the fine particles 0.2 μm or less.

  When the average particle size exceeds 0.2 μm, the concave portions cannot be coated, or the number of fine particles necessary for covering the whole surface increases, the shell layer becomes difficult to deform, and the core particle component is fixed on the paper surface. However, a lot of energy is required, and it is difficult to secure a fixable area.

  According to the invention, the adhesion aid contains at least one of water and lower alcohol.

  Adhesion aids are used for the effect of wetting the core particles and fine particles, and if these are completely dissolved, agglomeration occurs, which is not preferable. Water or lower alcohol is suitable as an adhesion aid because it improves wettability and does not dissolve the core particles and fine particles.

  Further, according to the present invention, even the irregular core particles obtained by the pulverization step can be functionalized on the toner surface, which has been impossible in the past, and smoothness, storage durability and the like are improved.

  According to the present invention, the resin fine particles are formed into a shell layer by stirring while controlling the heating below the glass transition temperature of the core particles with the resin fine particles attached to the core particles.

  Resin fine particles adhere to the surface of the core particle by mechanical impact force due to stirring, and the resin fine particles can be fused to form a film by continuing stirring while controlling the temperature below the glass transition temperature of the core particle. .

  Moreover, according to this invention, it stirs, heating-controlling below the glass transition temperature Tg of a core particle, and (Tg-20) degreeC or more.

  If the temperature is equal to or higher than the glass transition temperature Tg of the core particles, the core particles may be excessively melted and aggregation of the core particles may occur. If the temperature is lower than the glass transition temperature Tg (° C.) by 20 ° C., the core particle surface is not sufficiently swollen and softened, and a shell layer cannot be formed over substantially the entire surface of the core particle.

  According to the invention, there is provided a two-component developer comprising the above toner and a carrier.

  By using the toner described above, the two-component developer of the present invention can maintain stable charging characteristics.

  According to the invention, there is provided a developing device characterized in that development is performed using the developer containing the toner.

  By using the developer containing the toner, the developing device of the present invention can stably form a toner image on the photoreceptor.

  According to the invention, an image forming apparatus is characterized in that an image is formed using the developing device.

  By performing development using the above developing device, the image forming apparatus of the present invention can form a high-quality image with good fixability over a long period of time.

  The toner of the present invention includes an amorphous core particle and a shell layer formed on the surface of the core particle.

  The core particles include at least an amorphous polyester resin, a colorant, and a release agent. The shell layer is formed into a film on the surface of the core particle.

  The thickness of the shell layer is 0.05 μm or more and 0.5 μm or less, and the average value of the portion where the shell layer is thick is the average value of the portion where the shell layer is thin, It is characterized by being formed thicker than twice the value.

  The average value of the portion where the thickness of the shell layer is thick and the average value of the thin portion are, for example, a cross-sectional image of the toner particles is taken with a transmission electron microscope, and image analysis is performed by image processing or the like. Measure the layer thickness. A predetermined number of measurement values are selected in order from the thickest portion, and these average values are taken as the average value of the thick portions. Similarly, for a thin portion, a predetermined number of measurement values are selected in order from the thinnest portion, and these average values are used as the average value of the thin portions. It should be noted that the thick and thin portions may be places outside the above thickness range of 0.05 μm or more and 0.5 μm or less. The predetermined number is two or more points, and the average of the measured values is the average value of the shell layer thickness.

  When the surface area of the core particle in the portion covered with the shell layer is less than 80% of the entire surface area of the core particle, the area where the surface of the core particle is exposed increases, and the wax, pigment, etc. contained in the core particle The low melting point component may soften and the toner may aggregate.

  Therefore, the area of the core particle in the portion covered with the shell layer is preferably 80% or more and 100% or less of the surface area of the core particle. The surface area of the core particle can be calculated by regarding the core particle as a sphere and measuring the volume average particle diameter of the core particle. Moreover, the area of the core particle of the part coat | covered with the shell layer is computable using an image analyzer etc. from the picked-up image with an electron microscope. When the shell layer is formed on most of the surface of the core particle (80% or more), the same effect as that obtained when the shell layer is formed on the entire surface of the core particle can be obtained. A case where the layer is formed on the entire surface of the core particle will be described as an example.

  Since the toner of the present invention has a shell layer formed on the surface of the core particles, the toner particles can be prevented from aggregating even when stress is applied by stirring in the developing container. This prevents changes in the properties of the toner due to long-term use.

  Further, since the core particles are indefinite, toner is easily caught on the cleaning blade, and appropriate cleaning properties can be maintained. In addition, since the shell layer has a film thickness difference, the shell layer easily deforms due to heat and pressure during fixing, and the core particle component melts on the paper surface, so that the fixing property of the core particle can be maintained. .

  Further, when the average value of the portion where the thickness of the shell layer is thick is not more than twice the average value of the portion where the thickness of the shell layer is thin, the shell layer is hardly deformed at the time of fixing, and the core particle component is fixed on the paper surface. Therefore, a lot of energy is required, and it becomes difficult to secure a fixable area.

  Examples of other toner additive components in the toner of the present invention include a charge control agent.

  Hereinafter, a method for producing the toner of the present invention will be described. The toner of the present invention is produced, for example, by attaching and fusing resin fine particles to the core particles using an adhesion aid that increases the adhesion between the core particles and the resin fine particles.

FIG. 1 is a process diagram showing a toner manufacturing method according to an embodiment of the present invention.
The toner manufacturing method in the present embodiment includes a core particle preparation process in step s1, a shell layer material preparation process in step s2, and a coating process in step s3. The order of the core particle preparation step of step s1 and the shell layer material preparation step of step s2 may be reversed in time or in parallel.

<Core particle production process>
In the core particle preparation step of step s1, core particles containing a binder resin, a colorant, and a release agent are prepared. The core particles used in the toner of the present invention contain a binder resin, a colorant, and a release agent, and may further contain a charge control agent and the like.

  An amorphous polyester resin is used as the binder resin. The amorphous polyester resin is usually one or more selected from a divalent alcohol monomer and a trihydric or higher polyhydric alcohol monomer, a divalent carboxylic acid monomer and a trivalent as a constituent monomer. What is obtained by polycondensation using 1 or more types chosen from the above polyhydric carboxylic acid monomer is used.

  Examples of the divalent alcohol monomer include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4- Hydroxyphenyl) propane, polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis Alkylene oxide adducts of bisphenol A such as (4-hydroxyphenyl) propane and polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane, ethylene glycol, diethylene glycol, triethylene glycol, 1,2- Propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopenty Glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, bisphenol A propylene adduct of A, ethylene adduct of bisphenol A, hydrogenated bisphenol A and the like.

  Examples of the trihydric or higher polyhydric alcohol monomer include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4. -Butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxy Examples include methylbenzene.

  In the present invention, these dihydric alcohol monomers and trihydric or higher polyhydric alcohol monomers can be used alone or in combination.

  As the acid component, divalent carboxylic acid monomers such as maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid , Azelaic acid, malonic acid, n-dodecenyl succinic acid, n-dodecyl succinic acid, n-octyl succinic acid, isooctenyl succinic acid, isooctyl succinic acid, and anhydrides or lower alkyl esters of these acids.

  Examples of the trivalent or higher polyvalent carboxylic acid monomer include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4. -Butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1 2,7,8-octanetetracarboxylic acid, pyromellitic acid, emporic trimer acid, their acid anhydrides, lower alkyl esters and the like.

  In the present invention, these divalent carboxylic acid monomers and trivalent or higher polyvalent carboxylic acid monomers can be used alone or in combination.

  The method for producing an amorphous polyester resin in the present invention is not particularly limited, and can be produced by esterification or transesterification using the above monomers. Here, the amorphous polyester resin is a resin having no clear melting point.

  In the present invention, an amorphous polyester resin is used as the binder resin, but other polyester resins may be contained. For example, a crystalline polyester resin is generally easy to soften because of its low resistance and low glass transition point. Therefore, when exposed on the toner surface, stability over time such as storage stability and chargeability deteriorates. Therefore, it is not preferable to use it as the main resin, but if it is used as an additive, it has the effect of lowering the melt viscosity of the toner, and the fixability to the paper surface can be improved. In such a case, the melting point of the crystalline polyester resin is preferably 60 to 120 ° C., and the amount used is not particularly limited, but is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the amorphous polyester resin.

  In the present invention, in addition to the amorphous polyester resin, one or more kinds of binder resins known for toner can be used in combination, and examples thereof include polyurethane, epoxy resin, acrylic resin, styrene-acrylic resin and the like. . Among these resins, acrylic resins and styrene-acrylic resins are preferable among these.

  Although it does not restrict | limit especially as an acrylic resin, An acidic group containing acrylic resin can be used preferably. The acidic group-containing acrylic resin is, for example, an acrylic resin monomer or an acrylic resin monomer containing an acidic group or a hydrophilic group and / or a vinyl having an acidic group or a hydrophilic group when an acrylic resin monomer or an acrylic resin monomer and a vinyl monomer are polymerized. It can manufacture by using together a system monomer. Known acrylic resin monomers can be used, for example, acrylic acid that may have a substituent, methacrylic acid that may have a substituent, acrylic ester that may have a substituent, and a substituent. Methacrylic acid ester and the like. Specific examples of the acrylic resin monomer include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, acrylic Acrylic acid ester monomers such as 2-ethylhexyl acid, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylate Methacrylate monomers such as amyl, methacrylate n-hexyl, methacrylate 2-ethylhexyl, methacrylate n-octyl, decyl methacrylate, dodecyl methacrylate, hydroxyethyl acrylate, hydroxy methacrylate Propyl and the like hydroxyl group (hydroxyl group) containing (meth) acrylic acid ester monomers such as. Acrylic resin monomers can be used alone or in combination of two or more. As the vinyl monomer, known monomers can be used, and examples thereof include styrene, α-methylstyrene, vinyl bromide, vinyl chloride, vinyl acetate, acrylonitrile and methacrylonitrile. A vinyl monomer can be used individually by 1 type, or can use 2 or more types together. The polymerization is carried out by solution polymerization, suspension polymerization, emulsion polymerization or the like using a general radical initiator.

  Examples of the styrene-acrylic resin include styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate. Examples thereof include a copolymer, a styrene-butyl methacrylate copolymer, and a styrene-acrylonitrile copolymer.

  The binder resin preferably has a glass transition temperature Tg of 30 ° C. or higher and 80 ° C. or lower. When the glass transition temperature of the binder resin is less than 30 ° C., blocking in which the toner thermally aggregates easily occurs in the image forming apparatus, and storage stability may be deteriorated. When the glass transition temperature of the binder resin exceeds 80 ° C., the fixability of the toner to the recording medium is lowered, and there is a possibility that fixing failure occurs.

  As the colorant, organic dyes, organic pigments, inorganic dyes, inorganic pigments and the like commonly used in the electrophotographic field can be used.

  Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Examples of yellow colorants include chrome lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, and benzidine. Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment orange 31, C.I. I. And CI Pigment Orange 43.

  Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, and brilliant carmine 6B. Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of purple colorants include manganese purple, fast violet B, and methyl violet lake.

  Examples of blue colorants include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated products, first sky blue, induslen blue BC, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. And CI Pigment Blue 60.

  Examples of the green colorant include chrome green, chromium oxide, pigment green B, micalite green lake, final yellow green G, C.I. I. And CI Pigment Green 7.

  Examples of the white colorant include compounds such as zinc white, titanium oxide, antimony white, and zinc sulfide.

  One colorant can be used alone, or two or more different colorants can be used in combination. Moreover, even if it is the same color, 2 or more types can be used together. The amount of the colorant to be used is not particularly limited, but is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the release agent, those commonly used in this field can be used, for example, petroleum wax such as paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax (polyethylene wax, polypropylene Wax etc.) and derivatives thereof, low molecular weight polypropylin wax and derivatives thereof, hydrocarbon polymer waxes such as polyolefin polymer wax (low molecular weight polyethylene wax etc.) and derivatives thereof, carnauba wax and derivatives thereof, rice wax and derivatives thereof , Candelilla wax and its derivatives, plant wax such as wood wax, animal wax such as beeswax and whale wax, fatty acid amide, phenol fatty acid ester, etc. Oil-based synthetic waxes, long-chain carboxylic acids and their derivatives, long-chain alcohols and derivatives thereof, silicone polymers, such as higher fatty acids. Derivatives include oxides, block copolymers of vinyl monomers and waxes, graft modified products of vinyl monomers and waxes, and the like. The amount of the wax used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.2 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, particularly preferably 100 parts by weight of the binder resin. 1.0 to 8.0 parts by weight.

  As the charge control agent, those for positive charge control and negative charge control commonly used in this field can be used. Examples of charge control agents for positive charge control include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, and triphenylmethane. Derivatives, guanidine salts, amidine salts and the like can be mentioned. As charge control agents for controlling negative charges, oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and its derivatives, metal complexes and metal salts (metal is Chromium, zinc, zirconium, etc.), fatty acid soaps, long-chain alkyl carboxylates, resin acid soaps, and the like. The charge control agent can be used alone or in combination of two or more as required. The amount of the charge control agent used is not particularly limited and can be appropriately selected from a wide range.

  The charge control agent may be contained in the core particles, or may be contained in a shell layer made of resin fine particles in the coating process described later. When the charge control agent is contained in the core particles, it is preferable to contain 0.5 to 3 parts by weight with respect to 100 parts by weight of the core particles.

  When the charge control agent is contained in the shell layer, it is preferable to contain 0.5 to 3 parts by weight with respect to 100 parts by weight of the shell layer material.

  The core particles can be manufactured according to a general toner manufacturing method. As a general toner production method, for example, a dry method such as a pulverization method, a suspension polymerization method, an emulsion aggregation method, a dispersion polymerization method, a dissolution suspension method, and a wet emulsion method such as a melt emulsification method are used.

  The present invention can be obtained by kneading and pulverization in that coating with a shell layer having suitable characteristics enables functionalization of the toner surface, which has been impossible in the past, and improves smoothness and durability. There is a remarkable effect when the irregularly shaped core particles are used.

  The term “indeterminate core particle” as used herein refers to a particle in which each particle has a different shape, not a uniform shape, and the surface thereof has an uneven surface. As the amorphous core particles, particles having a shape factor SF-1 representing the particle shape of 140 to 160 and SF-2 of about 130 to 150 can be used.

  By forming a shell layer on the surface of the core particle, the shape factor is changed. As toner particles coated with the shell layer, those having SF-1 of 130 to 150 and SF-2 of about 120 to 140 are obtained. It is done.

Below, the preparation method of the core particle by the grinding | pulverization method is demonstrated.
In the pulverization method, the toner composition containing the binder resin, the colorant, the release agent and other toner additive components described above is dry-mixed with a mixer and then melt-kneaded with a kneader. The kneaded material obtained by melt kneading is cooled and solidified, and the solidified material is pulverized by a pulverizer. Thereafter, particle size adjustment such as classification is performed as necessary to obtain core particles.

  Known mixers can be used, such as Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), etc. Henschel type mixing device, ong mill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), and the like.

  A well-known thing can be used also as a kneading machine, for example, common kneading machines, such as a twin-screw extruder, a 3 roll, a laboratory blast mill, can be used. More specifically, for example, TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), etc. Extruder, Needex (trade name, manufactured by Mitsui Mining Co., Ltd.) and other open roll type kneaders.

  Synthetic resin additives such as colorants may be used as a master batch to uniformly disperse the synthetic resin additive in the kneaded product. Two or more additives for synthetic resin may be used as composite particles. The composite particles can be produced, for example, by adding an appropriate amount of water, lower alcohol or the like to two or more additives for synthetic resin, granulating with a general granulator such as a high speed mill, and drying. Masterbatch and composite particles are mixed into the powder mixture during dry mixing.

  The core particles obtained by the pulverization method preferably have a volume average particle size of 3 μm or more and 10 μm or less, and more preferably 5 μm or more and 8 μm or less. When the volume average particle diameter of the core particles is 3 μm or more and 10 μm or less, a high-definition image can be stably formed over a long period of time. When the volume average particle size of the core particles is less than 3 μm, the particle size of the core particles becomes too small, and there is a possibility that high charge and low fluidity may occur. When this high charging and low fluidization occur, it becomes impossible to stably supply the toner to the photoreceptor, and there is a possibility that background fogging and a decrease in image density may occur. When the volume average particle size of the core particles exceeds 10 μm, the particle size of the core particles is large, so that a high-definition image cannot be obtained. Further, as the particle diameter of the core particle increases, the specific surface area decreases, and the charge amount of the toner decreases. When the charge amount of the toner is small, the toner is not stably supplied to the photoconductor, and there is a possibility that in-machine contamination due to toner scattering occurs.

<Shell layer material preparation process>
In the shell layer material preparation step of step s2, resin fine particles containing at least a resin are produced. Also, an adhesion aid that increases the adhesion between the core particles and the resin particles is prepared.

  The resin that can be used for the resin fine particles is not particularly limited, and for example, a polyester resin, an acrylic resin, a styrene-acrylic copolymer resin, a styrene resin, or the like can be used.

  The resin fine particles preferably include a styrene-acrylic copolymer resin among the resins exemplified above. Resin fine particles containing a styrene-acrylic copolymer resin are attached to the surface of the core particle and formed into a film to form a shell layer, thereby further improving the controllability of the film thickness. Further, by using a styrene-acrylic copolymer resin as a main component, it is possible to control the entire surface coverage and film thickness. Moreover, by performing the dyeing | staining process, it becomes possible to observe a shell layer with a transmission electron microscope, and can measure the thickness of a shell layer easily.

  In addition, the styrene-acrylic copolymer resin can easily adjust the glass transition temperature and the softening temperature, and depending on the synthesis method, the particle size can be easily adjusted, it is lightweight and has high strength, and also has transparency. It has many advantages as a resin material constituting the shell layer, such as being expensive and inexpensive.

  The resin contained in the resin fine particles may be the same type as the binder resin of the core particle, or may be a different type of resin. However, different types of resins may be used in terms of modifying the surface of the toner. It is preferable to be used. When different types of resins are used as the resin contained in the resin fine particles, it is preferable to use a resin whose softening temperature of the resin contained in the resin fine particles is higher than the softening temperature of the binder resin of the core particles. As a result, the toner is prevented from fusing with each other during storage, and storage stability can be improved.

  The preferred range of the softening temperature of the resin contained in the resin fine particles varies depending on the image forming apparatus in which the toner is used, but is preferably 80 ° C. or higher and 140 ° C. or lower.

  Furthermore, the glass transition temperature of the resin contained in the resin fine particles is preferably in the range of 50 to 80 ° C, and more preferably in the range of 60 to 80 ° C.

  By using the resin in such a range, the resin fine particles can be easily formed into a film, and the film thickness can be easily adjusted (giving a thickness difference) by softening. When the glass transition temperature exceeds 80 ° C., it is possible to form a film, but it is difficult to reduce the film thickness and the fixability deteriorates. Films having a glass transition temperature of less than 50 ° C. can be formed into a film, but problems such as aggregation of toners occur with respect to storage stability and durability of the toner.

Such resin fine particles can be obtained, for example, by polymerization of monomers.
The average particle size of the resin fine particles before coating needs to be sufficiently smaller than the average particle size of the core particles. Further, the average particle size of the resin fine particles before coating is preferably 0.2 μm or less. When the average particle diameter of the resin fine particles before coating is 0.2 μm or less, in the irregular core particles, the resin fine particles are easily embedded in the recesses on the surface, and the shell layer covers the entire surface of the core particles. It becomes easy.

  When the average particle diameter exceeds 0.2 μm, the concave portions of the core particles cannot be coated, or the number of fine particles necessary for covering the entire surface increases. In addition, the shell layer is not easily deformed, and a large amount of energy is required to fix the core particle component on the paper surface, making it difficult to secure a fixable region.

  Further, in the shell layer material preparation step of step s2, an adhesion aid that increases the adhesion between the core particles and the resin fine particles is also prepared. An adhesion aid is a liquid that can improve the wettability of resin fine particles to the core particles. The adhesion aid is preferably a liquid that does not dissolve the core particles. Further, since the adhesion aid needs to be removed after the coating of the resin fine particles, it is preferably a liquid that easily evaporates.

  As an adhesion assistant, for example, it is preferable to contain water or a lower alcohol, and a plurality may be used in combination. Examples of the lower alcohol include methanol, ethanol, propanol and the like.

<Coating process>
In the coating step of step s3, the resin fine particles are adhered and fused to the core particles using an adhesion aid that increases the adhesion between the core particles and the resin fine particles. As a result, the core particles are coated with resin fine particles to form a shell layer.

  The coating of the resin fine particles is performed using, for example, a surface modification device. The surface modification device is a device that includes a container that accommodates core particles and resin fine particles therein, and spraying means that sprays an adhesion aid inside the container. Further, in the present embodiment, the surface modification apparatus includes a stirring unit that stirs the core particles in the container.

  A closed container can be used as the container for containing the core particles and the resin fine particles inside. The spraying means is a core for storing an adhesion aid storage part for storing an adhesion aid, a carrier gas storage part for storing a carrier gas, an adhesion assistant and a carrier gas, and a resulting mixture contained in a container. A liquid spraying unit that sprays toward the particles and sprays droplets of the deposition aid onto the core particles. Compressed air or the like can be used as the carrier gas. Commercially available products can be used as the liquid spray unit. For example, a two-fluid nozzle (trade name: HM-6 type, a sticking auxiliary agent is passed through a tube pump (trade name: MP-1000A, manufactured by Tokyo Rika Kikai Co., Ltd.) A product connected so as to be quantitatively fed to Fuso Seiki Co., Ltd. can be used. As the stirring means, a stirring rotor or the like capable of imparting mechanical and thermal energy mainly composed of impact force to the core particles is used.

  Commercially available products can be used as the container equipped with the stirring means. For example, Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), Mechano Mill (trade name, Okada Seiko) Henschel type mixing equipment such as Co., Ltd., Ongmill (trade name, manufactured by Hosokawa Micron Corporation), Hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo System (trade name, manufactured by Kawasaki Heavy Industries, Ltd.) Etc. By installing the liquid spray unit in the container of such a mixer, this mixer can be used as the surface modification device of the present embodiment.

The coating of the resin fine particles on the core particles is performed as follows.
First, core particles and resin fine particles are put into a container, and an adhesion assistant is sprayed inside the container in a state where the core particles and resin fine particles are stirred by the stirring means. The surface of the core particles and resin fine particles is swelled and softened by spraying the adhesion aid and applying thermal energy by stirring. A mechanical impact force is applied to the surface by the stirring means to fix the resin fine particles to the surface of the core particles, and a part of the resin fine particles are melted while being flattened with at least one of the core particles and the adjacent resin fine particles. To wear.

  As a temperature condition, a shell layer formed into a film over almost the entire surface of the core particle is formed by coating with stirring while controlling the heating to a temperature lower than the glass transition temperature Tg of the core particle and above (Tg-20) ° C. can do.

  If the temperature in the container of the surface modification device is equal to or higher than the glass transition temperature Tg of the core particles, the core particles may be excessively melted in the container at the time of toner production, and the core particles may be aggregated. If the temperature is lower than the glass transition temperature Tg (° C.) by 20 ° C., the core particle surface is not sufficiently swollen and softened, and a shell layer cannot be formed over substantially the entire surface of the core particle.

  In order to prevent agglomeration of the core particles, the inside of the container of the surface modification device is preferably cooled as necessary.

  Further, the adhesion assistant is preferably sprayed in a state where the core particles and the resin fine particles, or the core particles to which the resin fine particles are adhered, float in the container. When the mixture of the resin fine particles and the adhesion aid is sprayed in a state where the core particles are suspended in the container, the time for the core particles sprayed with the adhesion aid to be contacted can be shortened. As a result, toner aggregation during toner production can be prevented and generation of coarse particles can be prevented, so that a toner having a uniform particle diameter can be obtained. The state in which the core particles float in the container can be realized, for example, by stirring with stirring means, supplying air, or the like.

  The usage rate of the resin fine particles is not particularly limited, but it is necessary that the usage rate is such that the entire surface of the core particles can be coated. The resin fine particles are preferably used at a usage ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the core particles. If the resin fine particles are less than 1 part by weight, the entire surface of the core particles may not be covered with the shell layer. When the resin fine particle exceeds 30 parts by weight, the thickness of the shell layer becomes too large, and depending on the constituent material of the resin fine particle, there is a possibility that the toner fixing property is lowered.

  The amount of the adhesion aid is not particularly limited, but it is preferably an amount that wets the entire surface of the core particles. The amount of adhesion aid used is determined by the amount of core particles used. Moreover, the amount of the adhesion assistant can be adjusted by the spraying time by the spraying means, the number of spraying, and the like. Therefore, the spraying amount per unit time by the spraying means is set according to the average particle diameter of the core particles, the use ratio of the core particles and the resin fine particles, the material of the core particles and the material of the resin fine particles, for example, the resin fine particles in the container When most of them adhere to the core particles, the spraying of the adhesion aid by the spraying means may be terminated.

  The coating of the resin fine particles on the core particles may be performed by a surface modification device including a container that accommodates the core particles therein, and a spraying unit that sprays a mixture of the resin fine particles and the adhesion auxiliary agent inside the container. . As such a surface modification device, the same device as that described above can be used except that the mixture of the adhesion assistant and the resin fine particles is stored in the adhesion assistant reservoir.

  The coating of the resin fine particles onto the core particles by such a surface modification apparatus is performed as follows. First, core particles are put into a container, and a mixture of an adhesion assistant and resin fine particles is sprayed inside the container in a state where the core particles are stirred by the stirring means. The surface of the core particle is swollen and softened by spraying the adhesion aid and applying thermal energy by stirring. The fine resin particles are mixed together with the adhesion aid, sprayed inside the container, and then stirred and applied with thermal energy, so that the surface thereof swells and softens like the core particles. A mechanical impact force is applied to the surface by the stirring means to fix the resin fine particles to the surface of the core particles, and a part of the resin fine particles are melted while being flattened with at least one of the core particles and the adjacent resin fine particles. To wear.

  As temperature conditions, as in the above-described apparatus conditions, coating is performed while stirring while controlling the heating to a temperature lower than the glass transition temperature Tg of the core particles and (Tg−20) ° C. or higher. A filmed shell layer can be coated.

  When spraying a mixture of an adhesion aid and resin fine particles, the adhesion aid is preferably used in a proportion of 1 part by weight or more and 99 parts by weight or less with respect to 1 part by weight of the resin fine particles. The coating liquid that is a mixture of the adhesion aid and the resin fine particles is prepared in advance in the shell layer material preparation step in step s2.

  When a mixture of resin fine particles and adhesion aid is sprayed from the same spraying means, a mixture in which the resin fine particles and adhesion aid are mixed at the above ratio is used to improve the wettability of the resin fine particles to the core particles. It can be sufficiently increased and the time for removing the adhesion aid can be shortened. Further, the viscosity of the mixture is suitable, and the spraying of the mixture by the spraying means is easy. If the adhesion aid is less than 1 part by weight, the viscosity of the mixture becomes too high and the nozzle holes of the spray unit may be clogged. If the adhesion aid exceeds 99 parts by weight, the content of the adhesion aid will be too high, and the time for removing the adhesion aid will be too long.

  The amount of the mixture of the resin fine particles and the adhesion aid is not particularly limited, but it is necessary to include an amount of the resin fine particles that can cover the entire surface of the core particles. The preferred amount of the resin fine particles that can cover the entire surface of the core particles is 1 to 30 parts by weight with respect to 100 parts by weight of the core particles as described above. It is determined according to the content of the resin fine particles.

  When the coating of the resin fine particles on the entire surface of the core particles is completed, the adhesion aid is removed. The removal of the adhesion aid is performed by vaporizing the adhesion aid with a dryer, for example. For removal of the adhesion aid, for example, a commonly used dryer such as a hot air receiving dryer, a conductive heat transfer dryer, or a freeze dryer is used.

  As described above, the toner of the present invention is obtained in which a smooth shell layer having a thickness difference is formed into a film in a portion occupying 80% or more of the surface area of the amorphous core particles. Since the surface of the shell layer itself is smoothed, as a result, the irregularities on the surface of the core particles are reflected in the thickness of the shell layer, and a shell layer having an appropriate thickness difference can be formed. That is, since the surface of the shell layer itself is smoothed, the thickness of the shell layer is such that the portion covering the concave portion of the core particle surface is relatively thick and the portion covering the convex portion of the core particle surface is relatively thin. Become.

  Since such a toner is coated with a shell layer having a thickness difference, the shell layer is easily deformed at the time of fixing, and the core component can be easily adhered (fixed) to the paper surface. In addition, the resin fine particles fused with the core particles strengthen the adhesion between the shell layer and the core particles, so that, for example, the shell layer can be prevented from being detached from the core particles by stirring in the developing container. The property of the toner can be prevented from changing due to long-term use. Further, since a smooth shell layer is formed on the surface of the irregular core particles, the toner is easily caught on the cleaning blade during cleaning, and the cleaning property is maintained.

  By forming such a shell layer, it is possible to realize a toner excellent in fixability while maintaining durability. Compared to a shell layer formed with a uniform film thickness, due to the difference in thickness, when an external force is applied during fixing, the force concentrates on the thin part, and the shell layer is easily deformed, and the core particle component is on the paper surface. It becomes easy to adhere (fix). In addition, by having a thick part, the shell layer as a whole has an appropriate strength and prevents the toner from agglomerating because the shell layer is held without being detached during storage or stirring in the developing tank, Changes in toner characteristics due to long-term use can be prevented. Furthermore, since a smooth shell layer is formed on the surface of the irregular core particles, the toner is easily caught by the cleaning blade during cleaning, and the cleaning performance is maintained.

  An external additive may be added to the toner of the present invention. Known external additives can be used, and examples thereof include silica and titanium oxide. These are preferably surface-treated with a silicone resin, a silane coupling agent or the like. The amount of the external additive used is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the toner.

  The toner of the present invention can be used as a one-component developer or a two-component developer. When used as a one-component developer, the toner is used alone without using a carrier. When used as a one-component developer, a blade and a fur brush are used, and the toner is conveyed by frictional charging with a developing sleeve to adhere the toner onto the sleeve, thereby forming an image. When used as a two-component developer, the toner of the present invention is used with a carrier.

  As the carrier, a known carrier can be used. For example, a resin-coated carrier or a resin in which iron or copper, zinc, nickel, cobalt, manganese, chromium or the like alone or a composite ferrite and carrier core particles are coated with a coating material. And a resin-dispersed carrier in which magnetic particles are dispersed. Known coating materials can be used, such as polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal compound of ditertiary butylsalicylic acid, styrene resin, acrylic resin , Polyamide, polyvinyl butyral, nigrosine, amino acrylate resin, basic dye, basic dye lake, silica fine powder, alumina fine powder, and the like. Moreover, although it does not restrict | limit especially as resin used for a resin dispersion type carrier, For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin, etc. are mentioned. Either of them is preferably selected according to the toner component, and one kind can be used alone or two or more kinds can be used in combination.

The shape of the carrier is preferably a spherical shape or a flat shape. The particle size of the carrier is not particularly limited, but is preferably 10 to 100 μm, more preferably 20 to 50 μm, considering high image quality. Furthermore, the resistivity of the carrier is preferably 10 ⁸ Ω · cm or more, more preferably 10 ¹² Ω · cm or more. The carrier resistivity is determined by placing a carrier in a container having a cross-sectional area of 0.50 cm ² and tapping it, then applying a load of 1 kg / cm ² to the particles packed in the container and placing the load between the load and the bottom electrode. This is a value obtained by reading a current value when a voltage generating an electric field of 1000 V / cm is applied. When the resistivity is low, when a bias voltage is applied to the developing sleeve, charges are injected into the carrier, and carrier particles easily adhere to the photoreceptor. Further, breakdown of the bias voltage is likely to occur.

  The magnetization strength (maximum magnetization) of the carrier is preferably 10 to 60 emu / g, more preferably 15 to 40 emu / g. The magnetization strength depends on the magnetic flux density of the developing roller, but under the general magnetic flux density conditions of the developing roller, if it is less than 10 emu / g, the magnetic binding force does not work and causes carrier scattering. There is a fear. On the other hand, if the magnetization strength exceeds 60 emu / g, the rising of the carrier becomes too high, so that it is difficult to maintain the non-contact state with the image carrier in the non-contact development. Further, in the contact development, there is a risk that a sweep is likely to appear in the toner image.

The use ratio of the toner and the carrier in the two-component developer is not particularly limited and can be appropriately selected according to the kind of the toner and the carrier. However, if a resin-coated carrier (density 5 to 8 g / cm ² ) is taken as an example, the development is performed. The toner may be used so that the toner is contained in 2 to 30% by weight, preferably 2 to 20% by weight of the total amount of the developer. In the two-component developer, the coverage of the carrier with toner is preferably 40 to 80%.

  FIG. 2 is a cross-sectional view schematically showing the configuration of the image forming apparatus 1 according to the embodiment of the present invention. The image forming apparatus 1 is a multifunction machine having both a copying function, a printer function, and a facsimile function, and forms a full-color or monochrome image on a recording medium in accordance with transmitted image information. That is, the image forming apparatus 1 has three types of printing modes, ie, a copier mode (copying mode), a printer mode, and a facsimile mode, and an operation input from an operation unit (not shown), a personal computer, a portable terminal device, information A print mode is selected by a control unit (not shown) in response to reception of a print job from an external device using a recording storage medium or a memory device. The image forming apparatus 1 includes a toner image forming unit 2, a transfer unit 3, a fixing unit 4, a recording medium supply unit 5, and a discharge unit 6. Each member constituting the toner image forming unit 2 and some members included in the intermediate transfer unit 3 are black (b), cyan (c), magenta (m), and yellow (y) included in the color image information. In order to correspond to the image information of each color, four each are provided. Here, each member provided by four according to each color is distinguished by attaching an alphabet representing each color to the end of the reference symbol, and when referring collectively, only the reference symbol is used.

  The toner image forming unit 2 includes a photosensitive drum 11, a charging unit 12, an exposure unit 13, a developing device 14, and a cleaning unit 15. The charging unit 12, the developing device 14, and the cleaning unit 15 are arranged around the photosensitive drum 11 in this order. The charging unit 12 is disposed below the developing device 14 and the cleaning unit 15 in the vertical direction.

  The photosensitive drum 11 is supported by a driving unit (not shown) so as to be rotatable around an axis, and includes a conductive substrate (not shown) and a photosensitive layer formed on the surface of the conductive substrate. The conductive substrate can take various shapes, and examples thereof include a cylindrical shape, a columnar shape, and a thin film sheet shape. Among these, a cylindrical shape is preferable. The conductive substrate is formed of a conductive material. As the conductive material, those commonly used in this field can be used. For example, metals such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum, etc. A conductive layer made of one or more of aluminum, aluminum alloy, tin oxide, gold, indium oxide and the like is formed on a film-like substrate such as two or more alloys, synthetic resin film, metal film, paper, etc. And a resin composition containing a conductive film, conductive particles and / or a conductive polymer. In addition, as a film-form base | substrate used for an electroconductive film, a synthetic resin film is preferable and a polyester film is especially preferable. Moreover, as a formation method of the electroconductive layer in an electroconductive film, vapor deposition, application | coating, etc. are preferable.

  The photosensitive layer is formed, for example, by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. In that case, it is preferable to provide an undercoat layer between the conductive substrate and the charge generation layer or the charge transport layer. By providing an undercoat layer, the scratches and irregularities present on the surface of the conductive substrate are coated to smooth the surface of the photosensitive layer, to prevent deterioration of the chargeability of the photosensitive layer during repeated use. Alternatively, an advantage of improving the charging characteristics of the photosensitive layer in a low humidity environment can be obtained. Further, a laminated photoreceptor having a three-layer structure having a high durability and having a photoreceptor surface protective layer as the uppermost layer may be used.

  The charge generation layer is mainly composed of a charge generation material that generates a charge when irradiated with light, and contains a known binder resin, plasticizer, sensitizer and the like as necessary. As the charge generation material, those commonly used in this field can be used, for example, perylene pigments such as perylene imide and perylene acid anhydride, polycyclic quinone pigments such as quinacridone and anthraquinone, metal and metal-free phthalocyanines, and halogenated compounds. Phthalocyanine pigments such as metal-free phthalocyanine, squalium dye, azulenium dye, thiapyrylium dye, carbazole skeleton, styryl stilbene skeleton, triphenylamine skeleton, dibenzothiophene skeleton, oxadiazole skeleton, fluorenone skeleton, bis stilbene skeleton, distyryl oxa And azo pigments having a diazole skeleton or a distyrylcarbazole skeleton. Among these, metal-free phthalocyanine pigments, oxotitanyl phthalocyanine pigments, bisazo pigments containing a fluorene ring and / or a fluorenone ring, bisazo pigments composed of aromatic amines, trisazo pigments, etc. have high charge generation ability and high sensitivity. Suitable for obtaining a photosensitive layer. One type of charge generating material can be used alone, or two or more types can be used in combination. The content of the charge generation material is not particularly limited, but is preferably 5 to 500 parts by weight, more preferably 10 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. As the binder resin for the charge generation layer, those commonly used in this field can be used. For example, melamine resin, epoxy resin, silicone resin, polyurethane, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, polycarbonate, phenoxy resin , Polyvinyl butyral, polyarylate, polyamide, polyester and the like. Binder resin can be used individually by 1 type, or can use 2 or more types together as needed.

  The charge generation layer generates charge by dissolving or dispersing appropriate amounts of charge generation materials, binder resins and, if necessary, plasticizers and sensitizers in an appropriate organic solvent capable of dissolving or dispersing these components. It can be formed by preparing a layer coating solution, applying this charge generation layer coating solution to the surface of the conductive substrate and drying. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 0.05 to 5 μm, more preferably 0.1 to 2.5 μm.

  The charge transport layer laminated on the charge generation layer has a charge transport material having the ability to accept and transport the charge generated from the charge generation material and a binder resin for the charge transport layer as essential components. Contains known antioxidants, plasticizers, sensitizers, lubricants and the like. As the charge transport material, those commonly used in this field can be used, for example, poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensation product and derivatives thereof, Polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline Derivatives, phenylhydrazones, hydrazone derivatives, triphenylamine compounds, tetraphenyldiamine compounds, triphenylmethane compounds, stilbene compounds, 3-methyl-2-benzothiazoline -Donating substances such as azine compounds, fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyano Examples include electron-accepting substances such as ethylene, tetracyanoquinodimethane, promanyl, chloranil, and benzoquinone. The charge transport materials can be used alone or in combination of two or more. The content of the charge transport material is not particularly limited, but is preferably 10 to 300 parts by weight, more preferably 30 to 150 parts by weight with respect to 100 parts by weight of the binder resin in the charge transport material. As the binder resin for the charge transport layer, those commonly used in this field and capable of uniformly dispersing the charge transport material can be used. For example, polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy resin, polyurethane , Polyvinyl ketone, polystyrene, polyacrylamide, phenol resin, phenoxy resin, polysulfone resin, and copolymer resins thereof. Among these, in consideration of film formability, wear resistance of the resulting charge transport layer, electrical characteristics, etc., polycarbonate containing bisphenol Z as a monomer component (hereinafter referred to as “bisphenol Z type polycarbonate”), bisphenol Z type polycarbonate And a mixture of polycarbonate with other polycarbonates are preferred. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The charge transport layer preferably contains an antioxidant together with the charge transport material and the binder resin for the charge transport layer. As the antioxidant, those commonly used in this field can be used, and examples thereof include vitamin E, hydroquinone, hindered amine, hindered phenol, paraphenylenediamine, arylalkane and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. It is done. One antioxidant can be used alone, or two or more antioxidants can be used in combination. The content of the antioxidant is not particularly limited, but is 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the total amount of components constituting the charge transport layer. The charge transport layer is dissolved or dispersed in a suitable organic solvent that can dissolve or disperse these components in an appropriate amount such as a charge transport material and a binder resin, and if necessary, an antioxidant, a plasticizer, and a sensitizer. The charge transport layer coating liquid is prepared, and the charge transport layer coating liquid is applied to the surface of the charge generation layer and dried. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 10 to 50 μm, more preferably 15 to 40 μm. Note that a photosensitive layer in which a charge generation material and a charge transport material are present can be formed in one layer. In that case, the type, content, binder resin, and other additives of the charge generation material and the charge transport material may be the same as in the case of separately forming the charge generation layer and the charge transport layer.

  In this embodiment, the photosensitive drum formed by forming the organic photosensitive layer using the charge generation material and the charge transport material as described above is used. Instead, an inorganic photosensitive layer using silicon or the like is formed. Can be used.

  The charging unit 12 faces the photosensitive drum 11 and is arranged so as to be separated from the surface of the photosensitive drum 11 along the longitudinal direction of the photosensitive drum 11 with a gap, and the surface of the photosensitive drum 11 has a predetermined polarity and Charge to potential. As the charging unit 12, a charging brush type charger, a charger type charger, a sawtooth type charger, an ion generator, or the like can be used. In the present embodiment, the charging unit 12 is provided so as to be separated from the surface of the photosensitive drum 11, but is not limited thereto. For example, a charging roller may be used as the charging unit 12 and the charging roller may be disposed so that the charging roller and the photosensitive drum are in pressure contact with each other, or a contact charging type charger such as a charging brush or a magnetic brush may be used. .

  The exposure unit 13 is arranged such that light of each color information emitted from the exposure unit 13 passes between the charging unit 12 and the developing device 14 and is irradiated on the surface of the photosensitive drum 11. The exposure unit 13 branches the image information into light of each color information of b, c, m, and y in the unit, and the surface of the photosensitive drum 11 charged to a uniform potential by the charging unit 12 is light of each color information. To form an electrostatic latent image on the surface. As the exposure unit 13, for example, a laser scanning unit including a laser irradiation unit and a plurality of reflecting mirrors can be used. In addition, a unit in which an LED array, a liquid crystal shutter, and a light source are appropriately combined may be used.

  FIG. 3 is a cross-sectional view schematically showing the configuration of the developing device 14 according to the embodiment of the present invention. The developing device 14 includes a developing tank 20 and a toner hopper 21. The developing tank 20 is disposed so as to face the surface of the photosensitive drum 11, and is a container that supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 11 and develops it to form a visible toner image. It is a shaped member. The developing tank 20 accommodates toner in its internal space and accommodates a roller member such as a developing roller 20a, a supply roller 20b, and a stirring roller 20c, or a screw member, and rotatably supports it. An opening is formed in a side surface of the developing tank 20 facing the photosensitive drum 11, and a developing roller 20 a is rotatably provided at a position facing the photosensitive drum 11 through the opening. The developing roller 20 a is a roller-like member that supplies toner to the electrostatic latent image on the surface of the photoconductor 11 at the pressure contact portion or the closest portion with the photoconductor drum 11. When supplying the toner, a potential having a polarity opposite to the charging potential of the toner is applied to the surface of the developing roller 20a as a developing bias voltage (hereinafter simply referred to as “developing bias”). As a result, the toner on the surface of the developing roller 20a is smoothly supplied to the electrostatic latent image. Further, by changing the developing bias value, the amount of toner (toner adhesion amount) supplied to the electrostatic latent image can be controlled. The supply roller 20b is a roller-like member provided so as to be rotatable and facing the developing roller 20a, and supplies toner around the developing roller 20a. The agitation roller 20c is a roller-like member provided so as to be able to rotate and face the supply roller 20b, and feeds toner newly supplied from the toner hopper 21 into the developing tank 20 to the periphery of the supply roller 20b. The toner hopper 21 is provided so that a toner replenishing port (not shown) provided at the lower part in the vertical direction communicates with a toner receiving port (not shown) provided at the upper part in the vertical direction of the developing tank 20. The toner is replenished according to the toner consumption status of 20. Further, the toner hopper 21 may not be used, and the toner may be directly supplied from each color toner cartridge.

  The cleaning unit 15 removes the toner remaining on the surface of the photosensitive drum 11 after transferring the toner image to the recording medium, and cleans the surface of the photosensitive drum 11. For the cleaning unit 15, for example, a plate-like member such as a cleaning blade is used. In the image forming apparatus 1 of the present invention, an organic photosensitive drum is mainly used as the photosensitive drum 11, and the surface of the organic photosensitive drum is mainly composed of a resin component. Surface degradation is likely to proceed due to the chemical action of ozone generated by the discharge. However, the deteriorated surface portion is worn by receiving a rubbing action by the cleaning unit 15 and is gradually but surely removed. Therefore, the problem of surface deterioration due to ozone or the like is practically solved, and the charging potential by the charging operation can be stably maintained over a long period of time. Although the cleaning unit 15 is provided in this embodiment, the present invention is not limited to this, and the cleaning unit 15 may not be provided.

  According to the toner image forming unit 2, the surface of the photosensitive drum 11 that is uniformly charged by the charging unit 12 is irradiated with signal light corresponding to the image information from the exposure unit 13 to form an electrostatic latent image. Toner is supplied from the developing device 14 to form a toner image. After the toner image is transferred to the intermediate transfer belt 25, the toner remaining on the surface of the photosensitive drum 11 is removed by the cleaning unit 15. This series of toner image forming operations is repeatedly executed.

  The transfer unit 3 is disposed above the photosensitive drum 11, and includes an intermediate transfer belt 25, a driving roller 26, a driven roller 27, an intermediate transfer roller 28 (b, c, m, y), and a transfer belt cleaning unit. 29 and the transfer roller 30. The intermediate transfer belt 25 is an endless belt-like member that is stretched by a driving roller 26 and a driven roller 27 to form a loop-shaped movement path, and is driven to rotate in the direction of an arrow B.

  When the intermediate transfer belt 25 passes through the photosensitive drum 11 while being in contact with the photosensitive drum 11, an intermediate transfer roller 28 disposed on the surface of the photosensitive drum 11 is opposed to the photosensitive drum 11 via the intermediate transfer belt 25. A transfer bias having a polarity opposite to the charging polarity of the toner is applied, and the toner image formed on the surface of the photosensitive drum 11 is transferred onto the intermediate transfer belt 25. In the case of a full-color image, each color toner image formed on each photoconductor drum 11 is sequentially transferred onto the intermediate transfer belt 25 to form a full-color toner image. The drive roller 26 is provided so as to be rotatable around its axis by a drive means (not shown), and the intermediate transfer belt 25 is driven to rotate in the arrow B direction by the rotation drive. The driven roller 27 is provided so as to be able to be driven and rotated by the rotational drive of the driving roller 26, and applies a certain tension to the intermediate transfer belt 25 so that the intermediate transfer belt 25 does not loosen. The intermediate transfer roller 28 is provided in pressure contact with the photosensitive drum 11 via the intermediate transfer belt 25 and capable of being driven to rotate about its axis by a driving unit (not shown). The intermediate transfer roller 28 is connected to a power source (not shown) for applying a transfer bias as described above, and has a function of transferring the toner image on the surface of the photosensitive drum 11 to the intermediate transfer belt 25. The transfer belt cleaning unit 29 is provided so as to face the driven roller 27 through the intermediate transfer belt 25 and to contact the outer peripheral surface of the intermediate transfer belt 25. Since the toner adhering to the intermediate transfer belt 25 due to contact with the photosensitive drum 11 causes the back surface of the recording medium to be contaminated, the transfer belt cleaning unit 29 removes and collects the toner on the surface of the intermediate transfer belt 25. The transfer roller 30 is provided in pressure contact with the drive roller 26 via the intermediate transfer belt 25, and can be driven to rotate about an axis by a drive unit (not shown). At the pressure contact portion (transfer nip portion) between the transfer roller 30 and the drive roller 26, the toner image carried and conveyed by the intermediate transfer belt 25 is transferred to the recording medium fed from the recording medium supply means 5 described later. Is done. The recording medium carrying the toner image is fed to the fixing unit 4. According to the transfer unit 3, the toner image transferred from the photosensitive drum 11 to the intermediate transfer belt 25 at the pressure contact portion between the photosensitive drum 11 and the intermediate transfer roller 28 rotates the intermediate transfer belt 25 in the arrow B direction. It is conveyed to a transfer nip portion by driving, and transferred to a recording medium there.

  The fixing unit 4 is provided downstream of the transfer unit 3 in the conveyance direction of the recording medium, and includes a fixing roller 31 and a pressure roller 32. The fixing roller 31 is rotatably provided by a driving unit (not shown), and heats and melts the toner constituting the unfixed toner image carried on the recording medium to fix it on the recording medium. A heating unit (not shown) is provided inside the fixing roller 31. The heating unit heats the fixing roller 31 so that the surface of the fixing roller 31 reaches a predetermined temperature (heating temperature). For example, a heater or a halogen lamp can be used as the heating means. The heating means is controlled by fixing condition control means described later. The control of the heating temperature by the fixing condition control means will be described in detail later. A temperature detection sensor is provided near the surface of the fixing roller 31 to detect the surface temperature of the fixing roller 31. The detection result by the temperature detection sensor is written in the storage unit of the control means described later. The pressure roller 32 is provided so as to be in pressure contact with the fixing roller 31 and is supported so as to be driven to rotate by the rotation drive of the pressure roller 32. The pressure roller 32 assists fixing of the toner image on the recording medium by pressing the toner and the recording medium when the toner is melted and fixed on the recording medium by the fixing roller 31. A pressure contact portion between the fixing roller 31 and the pressure roller 32 is a fixing nip portion. According to the fixing unit 4, the recording medium onto which the toner image is transferred by the transfer unit 3 is sandwiched between the fixing roller 31 and the pressure roller 32, and the toner image is recorded under heating when passing through the fixing nip portion. By being pressed against the medium, the toner image is fixed on the recording medium and an image is formed.

  The recording medium supply unit 5 includes an automatic paper feed tray 35, a pickup roller 36, a transport roller 37, a registration roller 38, and a manual paper feed tray 39. The automatic paper feed tray 35 is a container-like member that is provided in the lower part of the image forming apparatus 1 in the vertical direction and stores a recording medium. Recording media include plain paper, color copy paper, overhead projector sheets, postcards, and the like. The pick-up roller 36 takes out the recording medium stored in the automatic paper feed tray 35 one by one and feeds it to the paper transport path S1. The conveyance rollers 37 are a pair of roller members provided so as to be in pressure contact with each other, and convey the recording medium toward the registration rollers 38. The registration rollers 38 are a pair of roller members provided so as to be in pressure contact with each other, and the recording medium fed from the conveyance roller 37 is used to convey the toner image carried on the intermediate transfer belt 25 to the transfer nip portion. Synchronously, it is fed to the transfer nip. The manual paper feed tray 39 is a device for taking a recording medium into the image forming apparatus 1 by manual operation, and the recording medium taken from the manual paper feed tray 39 passes through the paper conveyance path S2 by the conveyance roller 37. Then, it is fed to the registration roller 38. According to the recording medium supply means 5, the toner image carried on the intermediate transfer belt 25 is conveyed to the transfer nip portion of the recording medium supplied one by one from the automatic paper feed tray 35 or the manual paper feed tray 39. In synchronism with this, it is fed to the transfer nip portion.

  The discharge unit 6 includes a conveyance roller 37, a discharge roller 40, and a discharge tray 41. The conveyance roller 37 is provided downstream of the fixing nip portion in the sheet conveyance direction, and conveys the recording medium on which the image is fixed by the fixing unit 4 toward the discharge roller 40. The discharge roller 40 discharges the recording medium on which the image is fixed to a discharge tray 41 provided on the upper surface in the vertical direction of the image forming apparatus 1. The discharge tray 41 stores a recording medium on which an image is fixed.

  The image forming apparatus 1 includes a control unit (not shown). The control means is provided, for example, in the upper part of the internal space of the image forming apparatus 1 and includes a storage unit, a calculation unit, and a control unit. The storage unit of the control unit includes various setting values via an operation panel (not shown) arranged on the upper surface of the image forming apparatus 1, detection results from sensors (not shown) arranged at various locations inside the image forming apparatus 1, external devices, and the like. The image information from is input. In addition, programs for executing various means are written. Examples of the various means include a recording medium determination unit, an adhesion amount control unit, and a fixing condition control unit. As the storage unit, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). As the external device, an electric / electronic device capable of forming or acquiring image information and electrically connected to the image forming apparatus 1 can be used. For example, a computer, a digital camera, a television receiver, a video recorder DVD (Digital Versatile Disc) recorder, HDDVD (High-Definition Digital Versatile Disc), Blu-ray disc recorder, facsimile apparatus, portable terminal apparatus, and the like. The arithmetic unit takes out various data (image formation command, detection result, image information, etc.) written in the storage unit and programs of various means, and performs various determinations. The control unit sends a control signal to the corresponding device according to the determination result of the calculation unit, and performs operation control. The control unit and the calculation unit include a processing circuit realized by a microcomputer, a microprocessor, or the like provided with a central processing unit (CPU). The control means includes a main power supply together with the processing circuit described above, and the power supply supplies power not only to the control means but also to each device in the image forming apparatus 1.

  By forming an image using the toner, the two-component developer, the developing device 14 and the image forming apparatus 1 of the present invention, a high-quality image with good fixability can be formed over a long period of time.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
Each physical property in Examples and Comparative Examples was measured as follows.

[Volume average particle diameter and coefficient of variation CV of toner]
To 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), 20 mg of a sample obtained in Examples and Comparative Examples and 1 ml of sodium alkyl ether sulfate are added, and an ultrasonic disperser (trade name: UH- 50, manufactured by STM) for 3 minutes at an ultrasonic frequency of 20 kz to prepare a measurement sample. This sample for measurement was measured using a particle size distribution measuring device (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 100 μm, number of measured particles: 50000 count, and volume particle size distribution of sample particles. From these, the standard deviation in volume average particle size and volume particle size distribution was determined. The coefficient of variation (CV value,%) was calculated based on the following formula.
CV value (%) = (standard deviation in volume particle size distribution / volume average particle diameter) × 100

[Average particle diameter of resin fine particles]
The average particle size of the resin fine particles of the shell layer material was obtained by calculating the average particle size by magnifying it 20000 times using a real surface view microscope (trade name: VE-9800, manufactured by Keyence).

[Glass transition temperature of binder resin (Tg)]
Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), according to Japanese Industrial Standard (JIS) K7121-1987, 1 g of a sample was heated at a heating rate of 10 ° C. per minute and a DSC curve was measured. did. Draw the endothermic peak corresponding to the glass transition of the obtained DSC curve at a point where the slope is maximum with respect to the straight line that extends the base line on the high temperature side to the low temperature side and the curve from the rising part of the peak to the vertex. The temperature at the intersection with the tangent was determined as the glass transition temperature (Tg).

[Binder resin softening temperature (Tm)]
In a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-100C, manufactured by Shimadzu Corporation), a load of 10 kgf / cm ² (9.8 × 10 ⁵ Pa) was applied and a sample 1 g was a die (nozzle diameter 1 mm, length). 1 mm) was set to be extruded, heated at a heating rate of 6 ° C. per minute, and the temperature at which half of the sample flowed out from the die was determined as the softening temperature.

[Melting point of release agent]
Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), 1 g of the sample is heated from a temperature of 20 ° C. to 200 ° C. at a heating rate of 10 ° C. per minute, and then rapidly cooled from 200 ° C. to 20 ° C. The operation was repeated twice and the DSC curve was measured. The temperature at the top of the endothermic peak corresponding to the melting of the DSC curve measured in the second operation was determined as the melting point of the release agent.

Example 1
[Core particle production process]
Amorphous polyester resin (trade name: Diacron, manufactured by Mitsubishi Rayon Co., Ltd., glass transition temperature 55 ° C., softening temperature 130 ° C.) 85 parts as binder resin, C.I. I. 5 parts of Pigment Red 57: 1, 8 parts of mold release agent (carnauba wax, melting point 82 ° C.), and 1 part of charge control agent (Bontron E84, Orient Chemical Co., Ltd.) are mixed and dispersed (trade name: Henschel mixer, Mitsui). (Mine Co., Ltd.) for 3 minutes to mix and disperse. The obtained raw material was melt-kneaded using a twin screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.).

  This melt-kneaded product is coarsely pulverized with a cutting mill (trade name: VM-16, manufactured by Orient Co., Ltd.), then finely pulverized with a jet mill (manufactured by Hosokawa Micron Co., Ltd.), and further an air classifier (manufactured by Hosokawa Micron Co., Ltd.). To obtain irregular core particles having an average particle diameter of 6.9 μm and a coefficient of variation CV of 22%.

[Shell layer material preparation process]
As resin fine particles, styrene-butyl acrylate copolymer fine particles A (glass transition temperature 72 ° C., softening temperature 126 ° C.) having a volume average particle size of 0.1 μm were prepared. The resin fine particles were obtained by freeze-drying a polymer of styrene and butyl acrylate. Moreover, ethanol was prepared as an adhesion aid.

[Coating process]
100 parts of core particles and 10 parts of resin particles are put into a surface modification device (trade name: Hybridization system NHS-1 type, manufactured by Nara Machinery Co., Ltd.) equipped with a two-fluid nozzle that can spray liquid in the container. Then, after retaining at a rotation speed of 8000 rpm for 10 minutes, compressed air is sent to the two-fluid nozzle, and ethanol is adjusted to be sprayed at 0.5 g / min as an adhesion aid, and sprayed for 40 minutes. The entire surface was coated with shell particles. The coating was carried out while controlling the temperature in the apparatus during coating to 40 to 65 ° C. (below the glass transition temperature of the core particles).

  The core particles on which the shell layer was formed by coating resin fine particles on the entire surface of the core particles were lyophilized to obtain the toner of Example 1. The toner of Example 1 had a volume average particle size of 7.0 μm and a coefficient of variation of 26%.

(Example 2)
A toner of Example 2 was obtained in the same manner as in Example 1 except that the resin fine particles were changed to styrene-butyl acrylate copolymer fine particles B (glass transition temperature 64 ° C., softening temperature 129 ° C.). The toner of Example 2 had a volume average particle size of 7.1 μm and a coefficient of variation of 27%.

(Example 3)
A toner of Example 3 was obtained in the same manner as in Example 1 except that the resin fine particles were changed to styrene-butyl acrylate copolymer fine particles C (glass transition temperature 65 ° C., softening temperature 127 ° C.). The toner of Example 3 had a volume average particle size of 7.1 μm and a coefficient of variation of 27%.

Example 4
A toner of Example 4 was obtained in the same manner as in Example 1 except that the resin fine particles were changed to styrene-butyl acrylate copolymer fine particles D (glass transition temperature 52 ° C., softening temperature 128 ° C.). The toner of Example 4 had a volume average particle size of 7.2 μm and a coefficient of variation of 33%.

(Comparative Example 1)
A toner of Comparative Example 1 was obtained in the same manner as in Example 1 except that the resin fine particles were changed to styrene-butyl acrylate copolymer fine particles E (glass transition temperature 64 ° C., softening temperature 130 ° C.). The toner of Comparative Example 1 had a volume average particle size of 7.4 μm and a coefficient of variation of 30%.

(Comparative Example 2)
A toner of Comparative Example 2 was obtained in the same manner as in Example 1 except that the resin fine particles were changed to styrene-butyl acrylate copolymer fine particles F (glass transition temperature 82 ° C., softening temperature 145 ° C.). The toner of Comparative Example 2 had a volume average particle size of 7.1 μm and a coefficient of variation of 30%.

(Comparative Example 3)
A toner of Comparative Example 3 was obtained in the same manner as in Example 1 except that the resin fine particles were changed to styrene-butyl acrylate copolymer fine particles G (glass transition temperature 81 ° C., softening temperature 126 ° C., average particle size 0.35 μm). It was. The toner of Comparative Example 3 had a volume average particle diameter of 7.1 μm and a coefficient of variation of 40%, but the thickness of the shell layer was 0.05 μm or more and 0.5 μm or less, and the portion where the thickness was less than 80% of the surface area Met.

(Comparative Example 4)
The core particle obtained in the core particle preparation step of Example 1 was used as the toner of Comparative Example 4 without being subjected to the coating treatment. The toner of Comparative Example 4 had a volume average particle size of 6.9 μm and a coefficient of variation of 22%.
The production conditions of the toners of Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in Table 1.

  Table 2 shows the toner physical properties of Examples 1 to 4 and Comparative Examples 1 to 4.

  The following evaluations were performed on the toners of Examples 1 to 4 and Comparative Examples 1 to 4 as described above.

<External toner addition>
To 100 parts of the toners of Examples 1 to 4 and Comparative Examples 1 to 4, 1.0 part of silica particles having an average primary particle diameter of 20 nm hydrophobized with a silane coupling agent was mixed and externally added.

<Preparation of two-component developer>
A toner to which silica particles were externally added and a ferrite core carrier having a volume average particle diameter of 60 μm were mixed so as to have a toner concentration of 6% to prepare a two-component developer having a toner concentration of 6%.

(Evaluation)
The following evaluation was performed using the toners of Examples 1 to 4 and Comparative Examples 1 to 4 or the two-component developers containing the toners of Examples 1 to 4 and Comparative Examples 1 to 4.

[Coating state]
The shell layer was covered with a hardened material obtained by embedding the toner in a room temperature curable epoxy resin, and cut into a plurality of ultrathin sections of about 100 nm using a microtome equipped with diamond teeth. The dyed one was magnified 20000 times with a transmission electron microscope (TEM, trade name: H-8100, manufactured by Hitachi, Ltd.), and a cross section of the toner was photographed.

  The shell layer is dyed and the film state is clearly known and can be distinguished from the core particles. Therefore, the photographed image is analyzed using image analysis software, and the circumference of the toner and the shell layer film covering the core particles are analyzed. The thickness and the length of the covered part were measured.

  First, it was calculated whether or not the portion having a thickness of the shell layer of 0.05 μm or more and 0.5 μm or less occupies at least 80% of the surface area.

  Next, 36 straight lines were drawn radially from the center of the toner particles every 10 degrees, and the film thickness was measured perpendicular to the shell layer from the portion intersecting the shell layer. The average value A was calculated by selecting five measurement values in order from the thinnest among the measurement values, and the average value B was calculated by selecting five measurement values in order from the thickest.

The evaluation criteria for the thickness range are as follows.
○: Good. A portion having a thickness of 0.05 μm or more and 0.5 μm or less is 80% or more of the surface area.
X: Defect. A portion having a thickness of 0.05 μm or more and 0.5 μm or less is less than 80% of the surface area.

The evaluation criteria for the thickness difference are as follows.
○: Good. A × 2 <B
X: Defect. A × 2 ≧ B

[Preservation]
100 g of the externally added toner was sealed in a plastic container and allowed to stand at 50 ° C. for 48 hours, and then the toner was taken out. By the method of JIS K5101-12-1 (apparent density), the toner was dropped into a container through a sieve having an aperture of 0.5 mm, and the weight of the toner before and after being left was measured to obtain the apparent density. The amount of change in apparent density before and after standing was calculated and evaluated according to the following evaluation criteria.

The smaller the amount of change before and after being left, the more the toner does not block and the better the storage stability.
○: Good. Density change is less than 10%.
X: Defect. Density change is 10% or more.

[Developer durability]
The two-component developer is set in a developing unit of a copying machine (trade name: MX-2300G, manufactured by Sharp Corporation) having a commercially available two-component developing device, and adjusted to prevent development on the photosensitive member at 35 ° C. Only the developing device was continuously driven at a constant temperature for 5 hours, and the presence or absence of aggregates was visually confirmed. The evaluation criteria are as follows.
○: Good. No occurrence of aggregates ×: Poor. Aggregates are generated

[Formation of evaluation image]
The two-component developer is introduced into a developing device of a test copying machine obtained by removing a fixing device from a commercially available copying machine (trade name: MX-2300G, manufactured by Sharp Corporation), and Japanese Industrial Standard (JIS) P0138. A rectangular solid image portion having a length of 20 mm and a width of 50 mm was formed in an unfixed state on an A4 size recording paper defined in the above item with an adjustment so that the toner adhesion amount was 0.5 mg / cm ² . . An unfixed toner image formed was fixed by using an external fixing machine at a recording paper passing speed of 120 mm / sec (120 mm / sec) to form an evaluation image. For the external fixing machine, an oil-less fixing device taken out from a commercially available full-color copying machine (trade name: LIBRE AR-C260, manufactured by Sharp Corporation) is set so that the surface temperature of the heating roller can be set to an arbitrary value. A modified version was used. The heating roller surface temperature at the time of evaluation was set to 170 ° C. The oilless fixing device is a fixing device that performs fixing without applying a release agent such as silicone oil to a heating roller.

[High temperature offset resistance evaluation]
In the formed evaluation image, whether or not the high temperature offset phenomenon has occurred is determined by visually observing whether or not the toner image has been retransferred from the heating roller to the white background portion of the recording paper. did.

  This operation is repeated by sequentially increasing the surface temperature of the heating roller from 130 ° C. to 220 ° C. by 5 ° C., and the maximum surface temperature of the heating roller that does not cause the high temperature offset phenomenon (hereinafter referred to as the maximum fixing temperature). Asked.

  As a method for evaluating the fixing strength, lightly bend the paper with the printing surface on the inside, apply a predetermined load to the bent portion, rub the fixed image with a waste cloth, lightly rub it, Evaluation was based on the size of the width (width in the vertical direction at the fold).

Evaluation criteria were implemented by sensory evaluation as follows. A temperature region was determined in which a crease was found but the image was not missing or was low. Evaluation of high temperature offset resistance was performed according to the following criteria.
○: Good. Maximum fixing temperature is 200 ° C or higher.
X: Defect. Maximum fixing temperature is less than 200 ° C.

[Non-offset area evaluation]
Similarly to the evaluation of the high temperature offset resistance, the surface temperature of the heating roller is sequentially increased from 130 ° C. to 220 ° C. by 5 ° C. to form an image, and the low temperature offset phenomenon in which the toner image is not fixed on the recording paper, A non-offset region where no high temperature offset phenomenon in which the toner image is retransferred from the heating roller to the white background portion to be white background was examined to evaluate the offset resistance.

  The non-offset range is the lowest fixing temperature (° C) that is the lowest temperature of the heating roller that does not cause the low temperature offset phenomenon, and the highest fixing temperature (° C) that is the highest temperature of the surface of the heating roller that does not cause the high temperature offset phenomenon. It is obtained from the temperature difference.

As a method for evaluating the fixing strength, lightly bend the paper with the printing surface on the inside, apply a predetermined load to the bent portion, rub the fixed image crease with a waste cloth, and remove the toner drop-off portion that occurs at the fold portion. Evaluation was based on the size of the width (width in the vertical direction at the fold). Evaluation criteria were implemented by sensory evaluation as follows. A temperature region was determined in which a crease was found but the image was not missing or was low. The non-offset area was evaluated according to the following criteria.
○: Good. Non-offset range is 25 ° C or higher.
X: Defect. Non-offset range is less than 25 ° C.

[Image density]
For the image formed when the surface temperature of the heating roller is 170 ° C., the reflection density meter (trade name: RD918, manufactured by Macbeth Co.) is used to measure the optical reflection density of the solid image portion. did. The image density evaluation criteria are as follows.
○: Good. Image density is 1.40 or higher.
X: Defect. Image density is less than 1.40.

[Thin line reproducibility (character missing)]
A character image with a printing rate of 5% was printed, and the missing and missing characters were visually observed. The evaluation criteria for fine line reproducibility are as follows.
○: Good. An image with good fine line reproducibility was obtained.
X: Defect. Fine line reproducibility was poor, and an image with voids was obtained.

[Cleanability]
After 1000 sheets of a chart having a printing rate of 5% were continuously printed, the cleaning property was visually checked to determine whether filming had occurred on the surface of the photoreceptor. The evaluation criteria for the cleaning property are as follows.
○: Good. Filming has not occurred.
X: Defect. Filming has occurred.

[Comprehensive evaluation]
A total evaluation was performed according to the following criteria, combining the results of the storage stability, fixability, durability, image density evaluation, fine line reproducibility, and cleaning performance.
○: Good. There is no cross in the evaluation result.
X: Defect. There is a cross in the evaluation result.
Table 3 shows the evaluation results of Examples 1 to 4 and Comparative Examples 1 to 4.

The toners of Examples 1 to 4 were good in all evaluation items.
In the toners of Comparative Examples 1 and 2, although resin shells were formed on the core particles to obtain a shell layer, the thickness difference was insufficient, so that the toner was poor in terms of evaluation items for fixability.

  In the toner of Comparative Example 3, the shell layer obtained by forming the resin fine particles into the core particles is incomplete, and there are portions where the film is not formed in some places, and the portion having a film thickness of 0.05 μm to 0.5 μm Did not reach 80% of the surface area. Therefore, it became defective in the evaluation items of storage stability, durability, and fine line reproducibility.

  Further, since the toner of Comparative Example 4 did not form a shell layer, the evaluation items of storage stability, durability, and fine line reproducibility were poor.

FIG. 6 is a process diagram illustrating a toner manufacturing method according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 1 that is an embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of a developing device 14 according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Toner image forming means 3 Transfer means 4 Fixing means 5 Recording medium supply means 6 Ejecting means 11 Photosensitive drum 12 Charging means 13 Exposure unit 14 Developing means 15 Cleaning unit 20 Developing tank 21 Toner hopper 25 Intermediate transfer belt 26 Drive Roller 27 Follower roller 28 Intermediate transfer roller 29 Transfer belt cleaning unit 30 Transfer roller 31 Fixing roller 32 Pressure roller 35 Automatic paper feed tray 36 Pickup roller 37 Transport roller 38 Registration roller 39 Manual paper feed tray 40 Discharge roller 41 Discharge tray

Claims (6)

At least an amorphous core resin containing an amorphous polyester resin, a colorant and a release agent, and a shell layer covering the core particle,
The shell layer is forming a film formed on the core particle surface,
The thickness of the shell layer, 0.05 .mu.m or more, the portion to be 0.5μm or less account for at least 80% of the surface area, and a toner and satisfies the equation (1),
A × 2 <B (1)
A: Average value at a portion where the shell layer is thin B: Average value at a portion where the shell layer is thick
In the irregular core particles obtained by the pulverization step,
In a state where styrene-acrylic copolymer resin fine particles having a glass transition temperature Tg of 50 to 80 ° C. and an average particle diameter of 0.2 μm or less are adhered, the glass transition temperature is less than the glass transition temperature of the core particles, (Tg-20) ° C. A toner produced by forming the shell layer by forming a film of the styrene-acrylic copolymer resin fine particles by stirring while controlling the heating as described above. A toner production method according to claim 1 , comprising:
The amorphous core particles according to claim 1 obtained by a pulverization step;
An adhesion aid for increasing adhesion to styrene-acrylic copolymer resin fine particles having a glass transition temperature Tg of 50 to 80 ° C. and an average particle diameter of 0.2 μm or less constituting the shell layer according to claim 1. in the presence of the core particles and the styrene - contacting the acrylic copolymer resin fine particles, the styrene to the core particles - in a state adhered with acrylic copolymer resin fine particles, a glass transition temperature below the Tg of the core particles , (Tg-20) A method for producing a toner, wherein the shell layer is formed by forming the shell layer by forming the styrene-acrylic copolymer resin fine particles into a film by stirring while controlling the temperature to be higher than or equal to. The toner production method according to claim 2 , wherein the adhesion aid contains at least one of water and a lower alcohol. A two-component developer comprising the toner according to claim 1 and a carrier. A developing device that performs development using a developer containing the toner according to claim 1 . An image forming apparatus that forms an image using the developing device according to claim 5 .

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