JP3458354B2 - Dry-type two-component developing resin-coated carrier and developer having the carrier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry two-component system resin-coated carrier for electrostatic image development and a developer containing the carrier.

[0002]

2. Description of the Related Art Conventionally, as a method of developing an electrostatic latent image for electrophotography, a carrier in a developer prepared by mixing toner and carrier particles frictionally charges the toner and conveys the toner to contact the electrostatic latent image. There is known a two-component developing method in which the development is performed. Then, various improvements have been continuously carried out in order to improve the quality of images obtained by the two-component developing system. For example, Japanese Unexamined Patent Publication (Kokai) No. 59-131944 discloses a carrier in which the surface of core particles for a carrier is coated with a room temperature curable silicone having a siloxane bond. However, although this silicone-coated carrier is excellent in the function of preventing the spent phenomenon in which the surface energy of the coating resin is low and the toner adheres to the carrier surface, the adhesiveness with the core material is poor and the desired image quality can be obtained for a long time. Difficult to maintain.

As a countermeasure, an acrylic resin, an epoxy resin, a polyester resin or the like having good adhesion is used as a binder, and a fluororesin having a small surface energy is dispersed in the resin for the purpose of imparting charge and preventing toner spent. A resin-coated carrier prepared by the above method has been proposed.
For example, a carrier coated with a composition containing 50% or more of a fluorine compound (Japanese Patent Publication No. 17110/1990), or a carrier coated with a composite of a fluoropolymer and a conductive material (Japanese Patent Laid-Open No. Sho 61-206).
No. 54-7343) has been proposed. However, although these carriers are excellent in adhesiveness and spent resistance, the flowability of the developer is poor and image defects such as stripes are likely to occur in the image. Although this image defect can be slightly improved by mechanical processing, it was difficult to obtain a high-quality image for a long period of time.

Research has also been conducted on a carrier in which particles are added to the coating, and a coating layer obtained by curing an epoxy resin containing 1 to 10% by weight of fine powder silica having a surface area of 90 to 410 m ² / g with a polyamide resin. Carrier (Japanese Patent Publication No. 3-628) or two coating layers on the surface of the core material, and silica, titania, alumina is used as the outermost coating layer.
A developer has been proposed in which an inorganic oxide fine powder such as zinc oxide or tin oxide is contained, and substantially the same inorganic oxide fine powder is also contained in a toner (JP-A-6-202381). . In the above-mentioned silica-added carrier, the coating film containing the cured epoxy resin is strong, and due to the contained silica, the spent on the carrier surface by the toner is prevented and the chargeability is stabilized. However, in recent years high image quality, colorization,
Due to energy saving, long life, and high speed, the toner has a smaller particle size and a lower melting point. With the silica-added carrier, a high-quality image can be stably obtained over a long period of time. There wasn't.

Further, in the above-mentioned carrier having silica or the like in the outermost shell coating layer, the oxide contained in the toner is made substantially the same to prevent the spent by the toner and stabilize the charging property. When the outermost shell coating layer is peeled off due to long-term printing, the oxide powder is also removed and the effect of addition is lost, so that satisfactory results have not been obtained at present. Further, for the purpose of improving the fluidity, a coated carrier in which aluminum oxide or zirconium oxide having a number average particle diameter of 5 to 1000 nm is added to the coating resin layer, and melamine-formaldehyde condensed fine particles having a number average particle diameter of 5 to 1000 nm are added to the coating layer. A coated carrier has been proposed (Japanese Patent Laid-Open No. 2000-194156). However, sufficient fluidity is not obtained by only adding these particles, and a high quality image cannot be maintained for a long period of time.

[0006]

As described above, research and development for improving the carrier performance of a two-component developer have been conventionally performed, but none of them has reached a satisfactory level.
That is, as a carrier of a two-component developer, in addition to high image quality, spent resistance, adhesiveness with a core material, fluidity and long-term image stability are required. However, none of them have all of the above performances, and there is no carrier which is particularly satisfactory in terms of fluidity, which adversely affects long-term image stability. The present invention is
It is an object of the present invention to provide a carrier for a two-component developer, which preferably has all the above-mentioned properties, at least the fluidity and the spent resistance.

[0007]

The present invention provides a resin coat carrier for a dry two-component developer, wherein a coating resin layer is formed on the surface of a core material, wherein the coating resin layer comprises a fluororesin and a fluororesin.
From acrylic resin, epoxy resin and styrene resin
A binder resin and a silicone resin selected from the group consisting of
And / or octylsilane surface-treated dispersed silica particles, the silica particles have a BET specific surface area of 80 to 230 m ² / g, and the average particle size of the primary particles is 10
The resin-coated carrier for a dry two-component developer and the developer containing the carrier.

The present invention will be described in detail below. As is clear from the above description of the prior art, in the two-component developer carrier having a resin coating layer containing a fluororesin and a binder resin, the spent resistance and the core resistance can be improved by appropriately selecting the type. Adhesion with the material can be provided. However, with regard to liquidity, none of the conventional proposals have deficiencies and a satisfactory carrier has not been realized. For example, attempts have been made to add silica particles to improve the fluidity, but sufficient results have not been obtained. The inventors have further promoted the idea of improving fluidity by adding silica particles, and have fluidity by using silica particles having a specific surface area and an average particle diameter of primary particles within a specific range. The carrier was realized and the present invention was achieved.

The core material usable in the present invention is copper-
There are known ferrite such as zinc, copper-zinc-magnesium, nickel-zinc, manganese or lithium, iron powder, alloy powder having magnetism or composite magnetic powder in which resin and magnetic powder are essential, and particularly ferrite is used. preferable. Magnetic core material 20~190Am ² / kg approximately, its particle size 20~200μ
About m is desirable, and may be appropriately selected according to the developing conditions. Next, a coating resin layer is formed on the surface of the core material by coating. The coating resin layer contains at least a fluororesin and a binder resin, and silica particles dispersed in both resins. As the fluororesin, vinylidene fluoride, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer and the like can be used.

As the binder resin, acrylic resin,
Epoxy resin and styrene resin are used, and it is particularly preferable to use epoxy resin. Silica particles have a BET specific surface area of 80
~ 230m ² / g and the average particle size of the primary particles is 10 ~ 20nm
The primary particles mean raw material particles. Also, the fluidity of the developer stably for a long time by the surface of the silica particles of this treatment with octyl silane or silicone oil, and durability is improved. It is desirable that the total amount of the fluororesin and the binder resin in the coating resin layer be 0.1 to 5.0% by weight with respect to the core material, and
If it is less than 1% by weight, a sufficient function as the coating resin layer may not be exhibited, and if it exceeds 5.0% by weight, the effect of increasing the amount of the coating resin layer is almost lost and it becomes uneconomical.

The ratio of fluororesin to binder resin is
Fluorine resin 20-80% by weight, binder resin 80-20% by weight
It is desirable that if the above range is not satisfied, the characteristics of each resin may not sufficiently appear. The amount of silica particles dispersed in the coating resin layer is preferably 5 to 30% by weight based on the total amount of fluororesin and binder resin. This is because the effect of adding silica particles, which will be described later, becomes most remarkable within this range. In order to form a coating resin layer with these components, a fluororesin or a binder resin is dissolved or suspended in an organic solvent, silica particles are added to this solution or suspension, and uniformly dispersed to obtain a solution. The core material surface is coated by other techniques such as dipping the core material in a solution or suspension or using a fluidized bed.

After the solvent is removed by drying, or immediately after the coating resin layer is formed, the core material is heated and calcined and further crushed to obtain the intended carrier. The particle size of the carrier is substantially equal to the value obtained by adding the thickness of the coating resin layer to the particle size of the core material. The carrier thus obtained comprises a fluororesin, a binder resin, and silica particles having a specific specific surface area and a specific average particle diameter dispersed in these resins, and achieves both improvement of fluidity and prevention of spent. A dry two-component developing resin-coated carrier is obtained. Although the mechanism by which such an effect is obtained has not been clarified, it can be inferred that it is due to the low surface energy of the material of the silica particles.

The binder resin in the coating resin layer improves the adhesion between the coating resin layer and the core material to prevent peeling, the fluororesin improves the charge imparting ability, and the synergistic action of silica particles and the fluororesin. The spent on the surface of the carrier due to the toner is prevented, the silica particles improve the fluidity of the carrier, and the fluidity does not change for a long period of time, whereby high-quality image can be maintained for a long period of time. The effect of these silica particles is that the specific surface area and the specific average particle diameter, that is, the BET specific surface area is 80 to 230 m ^2.
/ G and the average particle size of the primary particles is 10 to 20 nm. Durability of the developer is improved by the surface of this silica particles treated with octyl silane or silicone oil. The carrier having such high performance can be used in the developer which is the original application, and when this developer is used, an image that can maintain high quality for a long time can be obtained.

In the two-component developer of the present invention, as the toner, any toner in which a colorant is dispersed in a binder resin and which is generally used in electrophotography can be used, and the toner is not particularly limited. Not a thing. Examples of the binder used in the toner include styrenes such as styrene and parachlorostyrene; α-such as methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl (meth) acrylate.
Methylene aliphatic monocarboxylic acid esters; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone, Vinyl ketones such as vinyl ethyl ketone; unsaturated hydrocarbons such as ethylene and propylene and their halides, homopolymers of monomers such as halogenated unsaturated hydrocarbons such as chloroprene, and these monomers A copolymer obtained by combining two or more kinds, and a mixture thereof, a rosin-modified phenol formalin resin,
A non-vinyl condensation resin such as an epoxy resin, a polyester resin, a polyamide resin, or a polyether resin, or a mixture of these with the vinyl resin can be used.

As the colorant used in the toner, known dyes and pigments such as carbon black, phthalocyanine blue, induslen blue, permanent red, lake red, chrome yellow and Hansa yellow can be used. The blending amount is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin. Further, the toner usable in the present invention may use a charge control agent in order to stabilize the charging characteristics. Charge control agents that can be used include
There are amino compounds, quaternary ammonium compounds, and salicylic acid chelate compounds. The amount used is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. Further, as materials to be added to the toner, there are an offset preventing agent, a fluidity improving agent and the like, and these known materials can be combined. To prevent the production of these toners, a method of producing the toner by mechanically pulverizing and classifying the toner-constituting materials after sufficiently kneading the toner-constituting materials with a heat kneader such as a hot roll or a kneader, a monomer that constitutes the binder resin A known method for producing a toner and a method for producing the emulsion by polymerizing the emulsion suspension after mixing a predetermined material therewith can be used. The particle size of the toner is 4 to 14 μm, more preferably 5 to 10 μm.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the carrier of the present invention will be described, but the examples do not limit the present invention.

Example 1 5% by weight of fluororesin and epoxy resin 5 as a binder
% By weight was dissolved in 90% by weight of toluene to obtain a resin solution having a solid content of 10% by weight. Using a homomixer, 10% by weight of silica particles (BET: 150 m ² / g, average particle diameter of primary particles: 12 nm, silica surface treated with octylsilane) based on the solid content of the resin solution was used. It was uniformly dispersed in the resin solution to obtain a silica-dispersed resin solution. Cu- as core material particles
Zn ferrite (trade name: F-2535, Ms: 64 Am ² / k
g, average particle size 60 μm) was used. The core material is fluidized in a fluidized bed containing the silica-dispersed resin solution, and on the surface of the core material, about 0.5 parts by weight of the fluororesin and the epoxy resin and 100 parts by weight of the core material and silica particles contained in these resins are used. Was coated. After coating, the resultant was heated at 230 ° C. for 1 hour, baked, cooled and crushed to obtain a carrier 1.

Example 2 The same conditions as in Example 1 except that BET: 100 m ² / g, average particle size of primary particles of 15 nm, and silica particles having their surfaces treated with silicone oil were used as the silica particles. And the carrier 2 was obtained.

Example 3 Example 2 except that the BET of the silica particles was 200 m ² / g and the average particle size of the primary particles was 12 nm and no surface treatment was performed.
Carrier 3 was obtained by operating under the same conditions as above.

Comparative Example 1 Carrier 4 was obtained by the same operation as in Example 1 except that silica particles were not added to the resin.

Comparative Example 2 Carrier 5 was obtained by the same conditions as in Example 1 except that silica particles having a BET of 260 m ² / g and an average primary particle size of 7 nm were used. .

Comparative Example 3 Instead of silica particles, aluminum oxide (BET: 11
Carrier 6 was prepared under the same conditions as in Example 2 except that 0 m ² / g was used and the average particle size of primary particles was 13 nm.
Got

Comparative Example 4 Instead of silica particles, titanium oxide (BET: 70 m ² /
The carrier 7 was obtained under the same conditions as in Example 1, except that the average particle size of the primary particles was 100 nm.

Evaluation Method First, the charge amount, resistance and fluidity of the carriers 1 to 7 obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were measured. For the charge amount, a blow-off powder charge amount measuring device manufactured by Toshiba Chemical Co., Ltd. is used, for the resistance, SM-5E super mega ohm meter manufactured by Toa Denpa Kogyo Co., Ltd. is used, and the fluidity is JIS-Z2502 "metal powder". The flow rate test method "was used for each measurement. The results are shown in Table 1.
Next, each carrier was mixed with a polyester positively chargeable toner so that the toner concentration was 4% by weight, and printing was carried out by reversal development PPC equipped with a commercially available positively charge OPC photoreceptor. The initial image quality, the image quality after printing 5,000 sheets, the image quality after printing 10,000 sheets, and the image quality after printing 50,000 sheets were evaluated for each carrier.

The results are shown in Table 1. In the table, ⊚ indicates that the initial image quality is excellent or that there is almost no change in the image quality after printing. ○ indicates that the initial image quality is good or that there is some change in the image quality after printing, but it is acceptable. △
Indicates that the initial image quality is inferior or there is a change in the image quality after printing, and the allowable limit. X is unacceptable because the initial image quality is considerably poor or there is a change in image quality after printing,
Are shown respectively. Image quality was evaluated by combining image density and fog. The image density was measured by using a Macbeth densitometer for the density of solid areas, and the fog on a white background image was measured with a colorimetric difference meter Z-300A manufactured by Nippon Denshoku Industries Co., Ltd.

[0026]

[Table 1]

[0027]

INDUSTRIAL APPLICABILITY The present invention provides a resin coat carrier for a dry type two-component developer in which a coating resin layer is formed on the surface of a core material, wherein the coating resin layer is a fluororesin and an acrylic resin.
Selected from the group consisting of fats, epoxy resins and styrene resins
Binder resin and the silicone oil is and / or
Containing dispersed silica particles surface-treated with octylsilane, the silica particles having a BET specific surface area of 80 to 230 m ²
/ G and the average particle diameter of the primary particles is 10 to 20 nm, which is a resin coated carrier for a dry two-component type developer (claim 1), wherein the epoxy resin is used as the binder resin.
It is desirable to use a resin (Claim 2). This carrier has a BET specific surface area of 80 to
It contains silica particles having an average particle size of 10 to 20 nm and a primary particle size of 230 m ² / g. The silica particles improve the fluidity of the carrier and maintain good fluidity for a long period of time, and further prevent synergistic action of the silica particles and the fluororesin to prevent spent on the carrier surface by the toner. Can maintain high quality image for a long time. Change
The silica particles are mixed with silicone oil and / or
Durability of the carrier as it is surface-treated with chillsilane
Improves image quality and provides high-quality image for a longer period of time
it can.

[0028] The total amount of the fluorine resin and the binder resin of the covering resin layer is 0.1 to 5.0 wt% with respect to the core material, from 20 to 80 wt% ratio of the two resins is a fluorine resin, the binder resin 80
The amount of silica particles dispersed in the coating resin layer is preferably 5 to 30% by weight based on the total amount of the fluororesin and the binder resin (claim 3). Therefore, the carrier of the present invention can exhibit good performance. Further, such a carrier having high performance can be used by being contained in a developer which is the original purpose (claim 4), and an image obtained by using this developer has a high quality for a long time. Can be maintained. Especially binder resin
It is desirable that the resin is a resin (Claim 5).

Front page continuation (56) Reference JP 2000-194156 (JP, A) JP 10-142843 (JP, A) JP 9-319155 (JP, A) JP 9-6039 (JP, A) JP-A-6-317937 (JP, A) JP-A-2-210365 (JP, A) JP-A-4-274255 (JP, A) JP-A-1-120566 (JP, A) JP-A-7 −43953 (JP, A) Japanese Patent Publication 3-628 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 9/10

Claims (5)

(57) [Claims] 1. A resin coat carrier for a dry two-component developer, wherein a coating resin layer is formed on the surface of a core material, wherein the coating resin layer is a fluororesin , an acrylic resin, or an epoxy.
Resin and silicone oil and / or octyl sila selected from the group consisting of resins and styrene resins
Comprising dispersed silica particles surface-treated with
A resin coated carrier for a dry two-component developer, characterized in that the silica particles have a BET specific surface area of 80 to 230 m ² / g, and the primary particles have an average particle diameter of 10 to 20 nm. 2. A contract wherein the binder resin is an epoxy resin
The dry two-component developer resin-coated carrier according to claim 1
A. 3. The total amount of the fluororesin and the binder resin in the coating resin layer is 0.1 to 5.0% by weight with respect to the core material, and the ratio of both resins is 20 to 80% by weight of the fluororesin and the binder resin.
The dry two-component according to claim 1 or 2, wherein the content is 80 to 20% by weight, and the amount of silica particles dispersed in the coating resin layer is 5 to 30% by weight based on the total amount of the fluororesin and the binder resin. Resin coated carrier for system developers. 4. A fluororesin and acrylic resin are provided on the surface of the core material.
Resin, epoxy resin and styrene resin
Binder resin and the silicone oil is selected and /
Alternatively, it comprises dispersed silica particles whose surface is treated with octylsilane, and the silica particles have a BET specific surface area of 80 to 23.
A developer comprising a resin coated carrier for a dry two-component developer, which has a coating resin layer having an average particle diameter of 0 m ² / g and a primary particle of 10 to 20 nm. 5. The contract wherein the binder resin is an epoxy resin
The developer according to claim 4.