JP2008020795A - Two-component developer and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-component developer showing good developing properties. <P>SOLUTION: The two-component developer showing good developing properties is provided by mixing a toner and a carrier with a crank and rocker mechanism type mixing apparatus and confining the BET specific surface area S of the resultant developer to a range of 0.190 m<SP>2</SP>/g<S<0.210 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a two-component developer including a toner and a carrier.

  Conventionally, in image formation by a printer, a copier, etc., various techniques have been proposed for improving image quality, specifically for realizing an appropriate image density, reducing fog, and improving gradation. ing.

For example, Patent Document 1 describes a non-magnetic one-component toner. In order to eliminate problems such as fogging and toner scattering, the electrostatic latent image carrier has a diameter of 10 mm to 40 mm, and the developer carrier In an image forming apparatus having a diameter of 5 mm or more and 20 mm or less, the average circularity is 0.960 or more and 0.995 or less, the volume average particle diameter in the Coulter counter is 4.5 μm or more and 10 μm or less, and the number average particle diameter is 4 μm or less. It describes that a non-magnetic one-component toner having a ratio of 10% or less and a volume average particle diameter of 12.7 μm or more of 5% or less is used. The document further describes that the nonmagnetic one-component toner has a BET value of 2.0 m ² / g or more.

On the other hand, in order for the two-component developer to achieve good development characteristics, it is important that the charge amount of the developer is appropriately controlled. Therefore, in Patent Document 2, a carrier and toner particles are put into a Nauta mixer in this order, mixed, discharged once, and recharged, and further mixed until the charge amount of the developer reaches a target value. A method for producing a developer is described.
JP 2005-164875 A (released on December 2, 2003) Japanese Patent Laid-Open No. 9-6041 (published on January 10, 1997)

  However, with the conventional two-component developer, the quality of the obtained image is not sufficient, and there is room for improvement.

  In order for the two-component developer to realize good development characteristics, it is required that the adhesion force between the toner and the carrier is appropriately controlled. If this adhesion force is too small, the image density becomes too high or fogging occurs. On the other hand, if the adhesive force is too large, the image density becomes thin and an appropriate density cannot be obtained.

  However, since the invention of Patent Document 1 relates to a non-magnetic one-component developer, no consideration is given to the charge amount and the adhesion between the toner and the carrier in the two-component developer, and the fluctuations in image density resulting therefrom. Absent.

  Further, although the invention of Patent Document 2 is intended for a two-component developer, it cannot be said that sufficient image quality is obtained, and there is room for improvement.

  The present invention has been made in view of this problem, and an object thereof is to provide a two-component developer capable of realizing higher image quality and a method for manufacturing the same.

  In order to obtain high image quality, the present inventor paid attention not only to the charge amount but also to the adhesion between the toner and the carrier. As a result, the Nauter mixer used in Patent Document 2 is a device that stirs a substance in a container by rotating a screw in the container and has a strong stirring force, so that the adhesion between the toner and the carrier is strong. It has been found that the BET specific surface area of the developer has an influence on the adhesion between the toner and the carrier, and has led to the present invention.

The two-component developer according to claim 1 is a two-component developer in which a toner and a carrier are mixed by a rotating and shaking type mixing device, and the BET specific surface area S of the two-component developer is 0.19 m ² / It satisfies g <S <0.21 m ² / g.

  According to a second aspect of the present invention, there is provided a method for producing a two-component developer according to the first aspect, wherein when the toner and the carrier are mixed by a rotationally oscillating mixing device, mixing at different rotational speeds is performed. Do more than once.

  The method for producing a two-component developer according to claim 3 is the developer production method according to claim 2, wherein mixing at different rotational speeds is performed twice, and the rotational speed of the second mixing is determined from the rotational speed of the first mixing. Enlarge.

By setting the BET specific surface area S within the above range, the adhesion force between the toner and the carrier can be set to an appropriate magnitude. Therefore, the two-component developer of the present invention has an appropriate image density,
Good gradation can be realized.

  The developer of the present invention is a two-component developer obtained by mixing a toner and a carrier.

(toner)
As the toner, a conventional toner can be used. As the toner, specifically, a toner containing a binder resin, a colorant, a wax, and inorganic fine particles can be used as an internal additive.

  Examples of the binder resin include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl acetate, and methyl acrylate. , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl methyl ketone, Examples include homopolymers or copolymers of vinyl ketone such as vinyl hexyl ketone and vinyl isopropenyl ketone, especially polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer. Body, styrene - acrylonitrile copolymer, styrene - butadiene copolymer, styrene - maleic anhydride copolymer, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, paraffin, and waxes. These may be used alone or in combination of two or more.

  Examples of the colorant include carbon black, nigrosine, aniline blue, calcoyl blue, chrome yellow, ultramarine blue, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 12, C.I. I. Pigment blue 15: 1, C.I. I. And CI Pigment Blue 15: 3.

  Examples of the wax include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, and polyolefin wax and derivatives thereof. Derivatives include oxides, polymers with vinyl monomers, and graft modified products. In addition, alcohols, fatty acids, plant waxes, animal waxes, mineral waxes, ester waxes, acid amides, and the like can be used. These may be used alone or in combination of two or more.

  As inorganic fine particles, for example, known inorganic compounds such as silica, alumina, titania and the like can be used without particular limitation, and these may be used alone or in combination of two or more. Also good. Examples of the silica fine particles include those containing aluminum silicate, sodium silicate, potassium silicate and the like in addition to anhydrous silica.

  The toner can contain other components in addition to those described above as long as the color development property, developability, and the like of the developer are not impaired. Examples of other components include those for the purpose of improving the long-term storability, fluidity, or developability of the developer, or charging adjustment. These additives may be internal additives added to the inside of the toner particles or external additives added so as to cover the outside of the toner particles.

  In particular, the toner preferably contains a charge control agent for adjusting charging as an internal additive. Examples of the charge control agent include benzoic acid metal salts, salicylic acid metal salts, alkyl salicylic acid metal salts, catechol metal salts, metal-containing bisazo dyes, tetraphenylborate derivatives, quaternary ammonium salts, alkylpyridinium salts, and the like. May be used alone or in combination of two or more.

  In order to further improve the long-term storability, fluidity, developability and transferability of the toner, the toner may contain inorganic powder and resin powder alone or in combination of two or more. Examples of the inorganic powder include carbon black, silica, alumina, titania, and zinc oxide. Examples of the resin powder include PMMA, nylon, melamine, benzoguanamine, fluorine-based spherical particles, and vinylidene chloride. Examples include amorphous powders such as fatty acid metal salts.

  The method for producing the toner is not particularly limited, and a conventionally known method such as a melt kneading method can be used. When using the melt-kneading method, it is preferable to produce the toner by kneading the internal additive by melt-kneading, then pulverizing and classifying, adding the external additive, and stirring and mixing.

  The kneading can be performed using various conventionally known heat kneaders, that is, a three-roll type, a screw type and the like. The pulverization of the kneaded product can be performed using a micronizer, a turbo mill or the like. For classification, an elbow jet using a Counder effect, a wind power type, or the like can be used, and the stirring and mixing after adding the external additive may be performed using a stirrer such as a Henschel mixer.

(Career)
As the carrier, a known carrier can be used. Specifically, as a carrier, a coated carrier in which metal particles such as ferrite, magnetite, or iron powder, or core particles in which these metal particles or metal particles are dispersed in a resin, are coated with a coating material is used. Can do.

  As the coating material for the coat carrier, a charge imparting resin for imparting chargeability to the toner and a low surface energy material for preventing the toner component from being transferred to the carrier are used. Conductive powder for control can be used. Examples of the charge imparting resin for imparting negative chargeability to the toner include amino resins such as urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, and epoxy resin. Examples thereof include polyvinylidene resins, acrylic resins, polymethyl methacrylate resins, polyacrylonitrile resins, polyvinyl acetate resins, polyvinyl acetate resins, polyvinyl alcohol resins, polyvinyl butyral resins, and cellulose resins such as ethyl cellulose resins. Examples of charge imparting resins for imparting positive chargeability to the toner include polystyrene resins such as polystyrene resins and styrene acrylic copolymer resins, halogenated olefin resins such as polyvinyl chloride, polyethylene terephthalate resins, and polybutylene terephthalate resins. And polyester resins and polycarbonate resins.

  Low surface energy materials for preventing the transfer of toner components to the carrier include polystyrene resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, fluorocarbon resin. Fluoroterpolymers such as copolymers of vinylidene fluoride and acrylic monomers, copolymers of vinylidene fluoride and vinyl fluoride, terpolymers of tetrafluoroethylene, vinylidene fluoride and non-fluorinated monomers, In addition, silicone resin and the like can be used.

  Further, as the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide, or the like can be used.

  The method for producing the carrier is not particularly limited, and a conventionally known technique can be used. For example, in the case of a coat carrier, the core particles may be coated with a coating material by a spray coating apparatus, or a dry coating method in which the core particles and the coating material are stirred at high speed may be used.

(Two-component developer)
The two-component developer of the present invention has a BET specific surface area S satisfying 0.190 m ² /g<S<0.210 m ² / g. By setting the BET specific surface area S within this range, the developability and gradation are improved.

  The two-component developer preferably contains a combination of a toner having a particle size of 5 to 10 μm, particularly 7 to 10 μm, and a carrier having a particle size of 10 to 100 μm, particularly 30 to 50 μm.

  The weight ratio of the toner to the carrier is preferably 5 to 30 and more preferably 5 to 15 when the toner is 1.

(Production method)
The method for producing a two-component developer according to the present exemplary embodiment includes a step of mixing toner and a carrier with a rotation and swing type mixing device. If the BET specific surface area S of the obtained developer falls within the above range, other conditions, that is, various conditions such as toner and carrier manufacturing methods, materials other than toner and carrier, equipment, processing temperature, processing time, etc. It is not limited at all, and a known technique can be used.

  A rotary rocking mixer is a device that simultaneously performs diffusion mixing by rotating a capsule and moving mixing by rocking the capsule. The rotationally oscillating mixing device generally includes a device called a rocking mixer. The rotationally oscillating mixing device is difficult to deform the particles of the powder in the capsule and can be mixed uniformly in a short time, so that the toner and the carrier can be mixed uniformly, and the charge amount and It becomes easy to adjust the adhesive force between the toner and the carrier within an appropriate range.

  An example of a rotating and shaking type mixing apparatus is shown in FIG. In addition, this invention is not limited to description of this drawing, A conventionally well-known rotation rocking | swiveling apparatus can be used suitably.

  The mixing device 1 includes a capsule 2, a first gear 3, a support unit 4, a rotating unit 10, and a swinging unit 20. The capsule 2 has a substantially cylindrical shape, and the toner and the carrier (a mixture of the toner and the carrier, indicated by reference numeral 30 in the figure) can be stirred therein. The first gear 3 is a circular gear that is provided at both ends in the longitudinal direction of the capsule 2 and whose radial direction is perpendicular to the longitudinal direction of the capsule 2. The rotating unit 10 is rotatable in the direction of arrow A about the rotating shaft 11 and the rotating shaft 11, and is engaged with the first gear 3 to rotate the first gear 3 (that is, the capsule 2) in the direction of arrow B. A drive mechanism (not shown) for rotating the two gears 12 and the second gear 12 is provided. The support part 4 supports the rotating shaft 11 so as to be swingable. Further, the swinging unit 20 can swing the capsule 2 by swinging the rotating shaft 11 up and down (in the direction of arrow C).

  When the toner and the carrier are mixed by such a rotationally oscillating mixing device, it is preferable to perform mixing at different rotational speeds twice or more. “Rotational speed” means the number of rotations per unit time and is a parameter expressed in unit rpm.

“Mixing at different rotation speeds two or more times” means mixing at a rotation speed x ₁ when mixing at a constant rotation speed for a predetermined time is “single mixing”. 1st mixing), mixing at rotation speed x ₂ (2nd mixing), ... mixing at rotation speed x _N (N-th mixing, N is a natural number of 2 or more), each continuously for 5 minutes or more And the rotation speed in at least one of the N mixings is different from the rotation speed of any other mixing. That is, if N = 4, for example, x ₁ ≠ x ₂ ≠ x ₃ ≠ x ₄ , x ₁ ≠ x ₂ = x ₃ = x ₄ , x ₁ = x ₂ = x ₃ ≠ x _4, etc. The rotation speed can be set. In other words, “mixing at different rotational speeds two or more times” can be paraphrased as changing the rotational speed one or more times.

  It is not necessary to maintain the same rotational speed during each mixing, and it is sufficient that the rotational speed is substantially the same. The fact that the rotational speed is substantially the same includes the case where the speed difference is less than 5 rpm.

  “Different rotational speeds” include a case where the rotational speed of the predetermined mixing is 5 rpm or more higher than the rotational speed of the other mixing.

  Moreover, when changing a rotational speed between predetermined | prescribed mixing and other mixing, a rotational speed may be changed without stopping rotation, and rotation may be stopped once.

  The rotational speed can be arbitrarily set so that the BET specific surface area S is in the above range, but is preferably in the range of 10 to 90 rpm, and more preferably in the range of 20 to 60 rpm. Furthermore, when the internal volume of the capsule is 5 to 15 L, the rotation speed is preferably 20 to 60 rpm in all mixing.

  The swing speed is not limited as long as it is a value that can sufficiently mix the toner and the carrier. Moreover, it may be constant regardless of the rotational speed, or may be changed. In all the mixing, the rocking speed is preferably 5 to 30 spm or less, and more preferably 10 to 20 spm.

  The time required for each mixing may be appropriately set depending on the rotational speed, the rocking speed, the amount of toner and carrier, etc., but is preferably 5 to 20 minutes. The time required for each mixing may be the same or different.

  The number of times of mixing may be appropriately set according to the time required for one mixing, the rotation speed, the rocking speed, the amount of toner and carrier, etc., but is preferably 4 times or less, and 2 times. Is more preferable.

  In order to set the BET specific surface area S of the obtained two-component developer within the above range, as a particularly preferable method, mixing is performed at a rocking speed of 10 to 20 spm and a rotating speed of 20 to 50 rpm for 5 to 10 minutes. The method of mixing for 5 to 10 minutes by changing to 40-60 rpm is mentioned.

In order to obtain a developer superior in gradation, it is preferable that N = 2 and x ₁ <x _2, and in particular, the relationship between x ₁ and x ₂ is (x ₂ / x ₁ ) ≧ 2. It is preferable that

  By mixing under the above conditions, the BET specific surface area S can be set within the above-described range, and a developer excellent in development characteristics and gradation can be produced.

[Example 1]
The following materials were premixed and colored particles having a volume average particle size of 9.0 μm were obtained through melt-kneading, coarse pulverization, fine pulverization, and classification steps.

Polyester resin: 100 parts Refined carnauba wax: 5 parts Charge control agent P-51: 2 parts by weight Carbon black: 5 parts by weight Hydrophobic silica particles (90 m ² / g) are added to these colored particles at a final concentration of 1.8 wt%, Black toner is prepared by adding 0.1 parts of titanium oxide particles (250 nm) at a final concentration of 1.0 wt% and 0.1 parts of resin fine particles (115 m ² / g) and stirring and mixing with a Henschel mixer at a rotating peripheral speed of 40 m / s and a mixing time of 5 minutes. Got.

  This toner and a powder tech ferrite carrier were mixed at a weight ratio of 1:10, that is, T / C of 10%. The mixing was performed using a rocking mixer (Model: RM-10, manufactured by Aichi) first at a low speed (20 rpm) for 5 minutes and then at a high speed (60 rpm) for 5 minutes. The rocking speed was constant at 10 spm.

[Example 2]
A two-component developer was obtained by the same procedure as in Example 1, except that the mixture was mixed at a high speed (60 rpm) for 5 minutes and then at a low speed (40 rpm) for 5 minutes using a rocking mixer.

[Comparative Example 1]
A two-component developer was obtained by the same procedure as in Example 1 except that the mixing was performed at a high speed (60 rpm) for 5 minutes and then at a low speed (20 rpm) for 5 minutes using a rocking mixer.

[Comparative Example 2]
A two-component developer was obtained by the same procedure as in Example 1 except that the mixing was performed at a constant speed (60 rpm) for 10 minutes using a rocking mixer.

[Comparative Example 3]
A two-component developer was obtained by the same procedure as in Example 1 except that the mixture was stirred for 5 minutes at a constant speed (60 rpm) with a rocking mixer.

[Comparative Example 4]
A two-component developer was obtained by the same procedure as in Example 1 except that the mixture was stirred for 20 minutes at a constant speed (60 rpm) with a rocking mixer.

[Comparative Example 5]
A two-component developer was obtained by the same procedure as in Example 1 except that the mixture was stirred for 30 minutes at a constant speed (60 rpm) with a rocking mixer.

[Comparative Example 6]
Instead of mixing with a rocking mixer, the same procedure as in Example 1 was performed except that the mixture was stirred for 10 minutes with a Nauter mixer.

[Evaluation of gradation]
Using the two-component developers obtained in the above Examples and Comparative Examples, images were formed on paper with FS-C5016 manufactured by Kyocera Mita Co., Ltd., and the gradation was evaluated visually. The gradation is evaluated in five steps (the larger the numerical value, the better the gradation), and the result is shown in Table 1 together with the BET specific surface area of each developer.

表１に示すように、実施例１及び２で得られた現像剤はＢＥＴ比表面積Ｓが０．１９ｍ^２／ｇ＜Ｓ＜０．２１ｍ^２／ｇを満たし、階調性の評価が５又は４と、優れた現像特性を示した。これに対して比較例１〜６は、ＢＥＴ比表面積Ｓが上記範囲外であって、階調性の評価は３又は２であり、現像特性が実施例１・２より劣る結果となった。また、画像濃度についても同様の結果が得られ、階調性が良いものほど画像の濃度においても優れ、カブリ等の不具合の発生が少ない結果となった。

As shown in Table 1, the developers obtained in Examples 1 and 2 have a BET specific surface area S satisfying 0.19 m ² /g<S<0.21 m ² / g, and the evaluation of gradation is 5 or 4 and excellent development characteristics. On the other hand, in Comparative Examples 1 to 6, the BET specific surface area S was outside the above range, the evaluation of gradation was 3 or 2, and the development characteristics were inferior to those of Examples 1 and 2. Similar results were obtained with respect to the image density, and the better the gradation, the better the image density and the less occurrence of defects such as fogging.

It is a front view which shows an example of a rotation oscillation type mixing apparatus.

Explanation of symbols

1 Rocking mixer (rotary rocking mixing device)
2 Capsule 3 First gear 4 Supporting part 10 Rotating part 20 Oscillating part B Rotating direction C Oscillating direction

Claims (3)

A two-component developer in which a toner and a carrier are mixed by a rotary swing mixing device;
A two-component developer satisfying a BET specific surface area S of 0.190 m ² /g<S<0.210 m ² / g of the two-component developer. A method for producing a two-component developer according to claim 1,
A method for producing a two-component developer, wherein the toner and the carrier are mixed by a rotationally oscillating mixing device, and mixing at different rotational speeds is performed twice or more.   The method for producing a two-component developer according to claim 2, wherein mixing at different rotational speeds is performed twice, and the rotational speed of the second mixing is made larger than the rotational speed of the first mixing.

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