JP2841331B2 - Dry two-component developer for electrostatic latent image development - Google Patents

Description

Description of the Related Art Conventionally, a so-called dry two-component developer comprising a mixture of carrier particles and toner particles is well known. In this dry two-component developer, minute toner particles are held on the surface of a relatively large particle by the electric force generated by the friction between the two particles. When the toner comes close to the electrostatic latent image, an electrostatic latent image is formed. The attraction force in the latent image direction on the toner particles due to the electric field that overcomes overcomes the bonding force between the toner particles and the carrier particles, and the toner particles are attracted and adhered on the electrostatic latent image so that the electrostatic latent image is visualized. It is. The developer is used repeatedly while replenishing the toner consumed by the development.

Therefore, the carrier must always triboelectrically charge the toner particles with a desired polarity and a sufficient amount of charge during long-term use. However, the conventional developer, collision between particles,
Alternatively, a toner film is formed on the carrier surface due to mechanical collision such as collision between particles and a developing machine, or heat generated by these actions, so-called spent occurs, the charging characteristics of the carrier decrease with use time, and the developer The whole needs to be replaced.

In order to prevent such spent, a method of coating the carrier surface with various resins has been conventionally proposed, but no satisfactory method has yet been obtained. For example, a carrier coated with a resin such as a styrene-methacrylate copolymer or a styrene polymer has excellent charging characteristics, but has a relatively high critical surface tension of the surface, and also causes spent during repeated copying. The life as a developer was not so long.

On the other hand, a carrier coated with a silicone resin having a low surface tension has been proposed. However, for example, due to strong stirring such as in a high-speed copying machine or long-time stirring in the developing unit, the carrier particles are dispersed in the developing unit. If it collides against the wall or the surface of the photoreceptor, or particles collide with each other, the silicone resin coating layer wears and separates over time, and the triboelectric charge changes from the charge between the toner and the silicone resin to the charge between the toner and the carrier core particles. Therefore, there has been a problem that the charge amount of the developer cannot be kept constant and the image quality deteriorates. Further, when the carrier particles are coated with a silicone resin, the electrical resistance of the silicone resin itself is high, so that when used as a developer, there is a disadvantage that the image quality is inferior due to edge development or charge accumulation phenomenon.

On the other hand, a method has been proposed in which a conductive substance such as carbon black is added to the silicone resin coating layer to control the electric resistance of the carrier. However, in general, conductive materials are poorly dispersible in silicone resin and are easily exposed to the surface of the coating layer. As a result, the conductive material detaches from the coating layer and the surface properties of the carrier change after long use. However, there has been a problem that the charge amount of the developer increases.

Object of the present invention is to provide a dry two-component developer for solving the above-mentioned drawbacks. The purpose is as listed below.

(1) An object of the present invention is to provide a dry two-component developer having a coating layer that prevents toner fusion to a carrier surface and has stable charging characteristics and low critical surface tension.

(2) An object of the present invention is to provide a dry two-component developer in which the coating layer does not peel off even when the developer is used for a long time and the change in the developer charge is small.

(3) An object of the present invention is to provide a dry two-component developer free from an edge phenomenon.

Structure The present invention comprises (a) a toner comprising at least a binder resin, a colorant, and a polarity controlling agent, and (b) a carrier comprising core particles coated with a silicone resin containing conductive carbon and titanium oxide fine powder. A dry two-component developer for electrostatic latent image development, wherein the content of conductive carbon is 2 to 30 parts by weight per 100 parts by weight of silicone resin. .

According to the present invention, the advantage of the conventional silicone resin-coated carrier is similarly maintained by selecting a silicone resin as a coating layer forming product, and the charge accumulation phenomenon on the carrier is imparted by imparting conductivity to the carrier. Is effectively deterred. Further, by simultaneously containing conductive carbon and titanium oxide in the carrier coating layer, it is possible to suppress a change in the developer charge amount. It is not clear why the change in charge amount can be reduced, but the titanium oxide fine powder adheres to the suspended carbon detached from the carrier coating layer and blocks it, which not only prevents charge leakage due to carbon, but also prevents carrier leakage. Therefore, a change in the charge amount can be suppressed.

As the carrier core particles coated with the silicone resin in the present invention, conventionally known particles may be used, for example, iron,
Ferromagnetic metals such as cobalt and nickel; alloys and compounds such as magnetite, hematite and ferrite; glass beads; The average particle size of these core particles is usually 10
10001000 μm, preferably 30-500 μm. The amount of the silicone resin used is usually 1 to 10% by weight based on the carrier core particles.

The silicone resin used in the present invention may be any conventionally known silicone resin, for example, KR26 manufactured by Shin-Etsu Silicone Co., which is available as a commercial product.
1, KR271, KR272, KR275, KR280, KR282, KR285, KR251, KR155,
KR220, KR201, KR204, KR205, KR206, SA-4, ES1001, ES1001
N, ES1002T, KR3093 and SR2100, SR210 made by Toray Silicone
1, SR2107, SR2110, SR2108, SR2109, SR2115, SR2400, SR241
0, SR2411, SH805, SH806A, SH840, etc. are used. As a method for forming the silicone resin layer, the silicone resin may be applied to the surface of the carrier core particles by a spraying method, an immersion method, or the like, as in the related art.

The coating layer composition is prepared by adding conductive carbon and semiconductive fine powder to a silicone resin solution and dispersing with a suitable mixer.

As the conductive carbon dispersed in the coating layer, conventionally known carbon black may be used, and examples thereof include contact black, furnace black, and thermal black. The addition amount is 2 to 30 parts by weight based on 100 parts by weight of the solid content of the silicone resin. Various types of conventionally known titanium oxide may be used as the titanium oxide fine powder.

As the toner particles used together with the carrier particles of the present invention, those obtained by a conventionally known method are used. Specifically, a mixture comprising a binder resin, a colorant, and a polarity controlling agent is melt-kneaded by a hot roll mill, then cooled and solidified, and pulverized and classified.

Examples of the binder resin used in the toner of the present invention include a homopolymer of styrene such as polystyrene, poly p-styrene and polyvinyl toluene and a substituted product thereof, a styrene-p-chlorostyrene copolymer, and a styrene-propylene copolymer. Polymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene- Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer,
Styrene-based copolymers such as styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, and polymethyl methacrylate , Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or aliphatic hydrocarbon Resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be used alone or in combination.

As the colorant used in the present invention, any known colorants for toner can be used. As the black colorant, for example, carbon black, aniline black, furnace black, lamp black and the like can be used. As the cyan coloring agent, for example, phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, ultramarine blue and the like can be used. Examples of magenta colorants include Rhodamine 6G Lake, Watching Red, Rose Bengal,
Rhodamine B, alizarin lake and the like can be used. As a yellow colorant, for example, chrome yellow, benzidine yellow, high the yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used.

As the polarity control agent, any of known compounds such as an amino compound, a quaternary ammonium compound, and an organic dye can be used.

The amount of the carrier and the toner used is preferably such that the toner particles adhere to the surface of the silicone resin of the carrier particles and are mixed so that the particles occupy 30 to 90% of the surface area.

EXAMPLES Hereinafter, the present invention will be described by producing carriers according to Examples and Comparative Examples and comparing the properties thereof. Table 1 shows the formulations and evaluation results of Examples 1 to 4 and Comparative Examples 1 to 5.
1 and Table-2.

Example 1 Composition of coating layer forming liquid 100 parts by weight of silicone resin solution (KR206 manufactured by Shin-Etsu Silicone Co., Ltd.) 2 parts by weight of carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo) 2 parts by weight of titanium oxide fine particles (P-25 manufactured by Nippon Aerosil Co., Ltd.) 100 parts by weight of toluene The above formulation was dispersed with a homomixer for 30 minutes to prepare a coating layer forming liquid. This coating layer forming liquid was used to form a coating layer on the surface of 1,000 parts by weight of spherical ferrite having an average particle diameter of 100 μm using a fluidized bed type coating apparatus, thereby obtaining carrier particles I.

Composition of toner particles Styrene-n-butyl methacrylate copolymer 87 parts by weight Carbon black 10 parts by weight A mixture of 3 parts by weight of basic nigrosine dye was melt-kneaded with a hot roll at 120 ° C.
The mixture was cooled and solidified, pulverized with a jet mill, and classified to obtain toner particles I having an average of 10 μm.

100 parts by weight of the carrier particles I and 3 parts of the toner I
The following test was conducted by mixing the parts by weight to obtain a developer I.

Test Using the above-mentioned developer I, the latent image on the organic photoreceptor was discharged for 30 minutes per minute.
The process of developing and transferring at a speed of 100 times was repeated 100,000 times.

In order to evaluate the developer by this test, the developer was sampled at the start of the test, after 1,000 times, after 10,000 times, and after 100,000 times, and the blow-off charge amount was measured. Further, the toner and the carrier were separated from the developer by blow-off after 100,000 times, and the state of the coating layer was evaluated by observing the surface of the carrier with an SEM.

As a result, the toner charge at the start of the test was + 18.0μC / g
The charge after 1000 times is + 18.4μC / g, after 10,000 times + 19.1μC / g, and after 100,000 times + 19.5μC / g
And the image quality of the copied image hardly changed. Also, there was no peeling of the coating layer.

Example 2 Composition of coating layer forming liquid Silicon resin solution 100 parts by weight (SR2400 manufactured by Toray Silicone Co., Ltd.) Carbon black 2 parts by weight (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) Titanium oxide fine particles 2 parts by weight (P-25 manufactured by Nippon Aerosil Co., Ltd.) 100 parts by weight of toluene A coating layer was formed on the above formulation in the same manner as in Example 1 to obtain carrier particles II. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles II and 3 parts by weight of the toner particles I to obtain a developer II.

As a result, the toner charge at the start of the test was +19.8 μC / g
The charge amount after 1000 times is +19.0 μC / g, the charge amount after 10,000 times is +19.5 μC / g, and the charge amount after 100,000 times is +20.0 μC / g.
And the image quality of the copied image hardly changed. Also, there was no peeling of the coating layer.

Example 3 Composition of Coating Layer Forming Solution Silicone resin solution 100 parts by weight (KR206 Shin-Etsu Silicone Co., Ltd.) Carbon black 2 parts by weight (BPL Cabot Corporation) Titanium oxide fine particles 2 parts by weight (P-25 Nippon Aerosil Co., Ltd.) Toluene 100 Parts by weight The above formulation was used to form a coating layer in the same manner as in Example 1 to obtain carrier particles III. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles III and 3 parts by weight of the toner particles I to obtain a developer III.

As a result, the toner charge at the start of the test was + 20.0μC / g
The charge amount after 1000 times is +19.3 μC / g, the charge amount after 10,000 times is +19.7 μC / g, and the charge amount after 100,000 times is +20.0 μC / g.
And the image quality of the copied image hardly changed. Also, there was no peeling of the coating layer.

Example 4 Composition of Coating Layer Forming Solution Silicone resin solution 100 parts by weight (SR2400 manufactured by Toray Silicone Co., Ltd.) Carbon black 2 parts by weight Ketjen Black EC Lion Akzo Co., Ltd.) Titanium oxide fine particles 2 parts by weight (P-25 manufactured by Nippon Aerosil Co., Ltd.) 100 parts by weight of toluene A coating layer was formed using the above formulation in the same manner as in Example 1 to obtain carrier particles IV. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles IV and 3 parts by weight of the toner particles I to obtain a developer IV.

As a result, the toner charge at the start of the test was +17.8 μC / g
The charge after 1000 cycles is + 18.0μC / g, the charge after 10,000 cycles is + 18.5μC / g, and the charge after 100,000 cycles is + 18.0μC / g
And the image quality of the copied image hardly changed. Also, there was no peeling of the coating layer.

Comparative Example 1 Composition of coating layer forming liquid 100 parts by weight of Teflon resin solution (Polyflon Daikin Industries, Ltd.) 2 parts by weight of carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 2 parts by weight of titanium oxide fine particles (P-25 manufactured by Nippon Aerosil Co., Ltd.) 100 parts by weight of toluene A coating layer was formed using the above formulation in the same manner as in Example 1 to obtain carrier particles V. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles V and 3 parts by weight of the toner particles I to obtain a developer V.

As a result, the toner charge at the start of the test was + 21.3μC / g
The charge amount after 1,000 times is +18.8 μC / g, the charge amount after 10,000 times is +14.4 μC / g, and the charge amount after 100,000 times is 9.1 μC / g.
The image quality of the copied image was gradually reduced, and the image quality of the copied image was also much lower. On the other hand, the coating layer was peeled off, exposing the core particles.

Comparative Example 2 Composition of coating layer forming liquid Silicon resin solution 100 parts by weight (KR206 Shin-Etsu Silicone Co., Ltd.) Carbon black 2 parts by weight (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) Silicon oxide fine particles 2 parts by weight (R972 Nippon Aerosil Co., Ltd.) Toluene 100 parts by weight A coating layer was formed by the same method as in Example 1 to obtain carrier particles VI. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles VI and 3 parts by weight of the toner particles I to obtain a developer VI.

As a result, the toner charge at the start of the test was + 22.3μC / g
The charge after 1000 cycles is +29.7 μC / g, the charge after 10,000 cycles is +32.5 μC / g, and the charge after 100,000 cycles is +35.9 μC / g
The image quality of the copied image was poor with low image density. On the other hand, there was no peeling of the coating layer.

Comparative Example 3 Composition of coating layer forming liquid Silicon resin solution 100 parts by weight (SR2400 manufactured by Toray Silicone Co., Ltd.) Carbon black 2 parts by weight (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) Silicon carbide fine particles 2 parts by weight (GC # 8000 Fujimi abrasive) Toluene 100 parts by weight A coating layer was formed using the above formulation in the same manner as in Example 1 to obtain carrier particles VII. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles VII and 3 parts by weight of the toner particles I to form a developer VII.

As a result, the toner charge at the start of the test was + 14.8μC / g
The charge amount after 1000 times is + 18.4μC / g, the charge amount after 10,000 times is + 20.3μC / g, and the charge amount after 100,000 times is + 26.6μC / g
The image quality of the copied image was poor with low image density. On the other hand, there was no peeling of the coating layer.

Comparative Example 4 Composition of coating layer forming liquid Silicon resin solution 100 parts by weight (KR206 Shin-Etsu Silicone Co., Ltd.) Carbon black 2 parts by weight (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) Toluene 100 parts by weight The above formulation was prepared in the same manner as in Example 1. To form a coating layer to obtain carrier particles VIII. 100 particles of the above carrier particles VIII
3 parts by weight of the toner particles I and 3 parts by weight of the toner particles I were used as a developer VIII.

As a result, the toner charge at the start of the test was + 17.0μC / g
The charge amount after 1000 times is + 19.8μC / g, the charge amount after 10,000 times is + 25.3μC / g, and the charge amount after 100,000 times is + 36.7μC / g
The image quality of the copied image was poor with low image density. On the other hand, there was no peeling of the coating layer.

Comparative Example 5 Composition of coating layer forming liquid Styrene-methyl methacrylate copolymer resin 100 parts by weight Carbon black 2 parts by weight (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) Titanium oxide fine particles 2 parts by weight (P-25 manufactured by Nippon Aerosil Co., Ltd.) Toluene 100 Parts by weight The above formulation was used to form a coating layer in the same manner as in Example 1 to obtain carrier particles IX. The same test as in Example 1 was conducted by mixing 100 parts by weight of the carrier particles IX and 3 parts by weight of the toner particles I to obtain a developer IX.

As a result, the toner charge at the start of the test was + 10.3μC / g
The charge after 1000 times is + 8.8μC / g, the charge after 10,000 times is + 5.0μC / g, and the charge after 100,000 times is gradually reduced to + 0.2μC / g. The image quality of the image was also a lot of ground cover. On the other hand, the coating layer was peeled off, exposing the core particles.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasutaka Iwamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-60-12558 (JP, A) JP-A Heihei 1-1101560 (JP, A) JP-A-55-155363 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/113

Claims (1)

(57) [Claims] 1. A carrier comprising (a) a toner comprising at least a binder resin, a colorant, and a polarity controlling agent, and (b) a carrier having core particle particles coated with a silicone resin containing conductive carbon and titanium oxide fine powder. A dry two-component developer for developing electrostatic latent images, wherein the content of conductive carbon is 2 to 30 parts by weight per 100 parts by weight of silicone resin.