JPH04242265A - Two-component developer for electrophotography - Google Patents

Abstract

PURPOSE:To obtain an image having high resolution by using a developer consisting of a toner having 3-8mum average particle size produced by polymn. and a coated ferrite carrier having 10-50mum average particle size and >=10<10>OMEGA.cm volume resistivity. CONSTITUTION:This two-component developer for electrophotography consists of a toner having 3-8mum average particle size produced by polymn. and a coated ferrite carrier having 10-50mum average particle size and >=10<10>OMEGA.cm volume resistivity. The toner is produced by polymn. such as suspension polymn., soln. polymn. or emulsion polymn., preferably suspension polymn. ensuring simpler production of the toner than other polymn. Since this developer consists of the polymerized toner and the coated ferrite carrier each having small particle size as mentioned above, many copied images having high resolution are obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer for electrophotography used in electrophotography, electrostatic printing, and the like.

0002

2. Description of the Related Art In recent years, with the development of copying technology, there has been a strong demand from various quarters to improve the resolution of copied images in electrophotography. It is known that one of the means for increasing image resolution is to uniformly control the average particle size of toner to a small particle size of 10 μm or less. However, conventional toners are produced by kneading additives such as colorants such as carbon black and charge control agents into a thermoplastic resin, uniformly dispersing the resin, pulverizing it with a pulverizer, and classifying it with a classifier. Since it is manufactured by a method, if the particle size is reduced to 10 μm or less,
It is not possible to obtain small particles with a uniform size, and it is difficult to uniformly disperse colorants, charge control agents, etc. into individual particles, resulting in triboelectric charging properties and uneven coloring of copied images, as well as poor manufacturing yields. The problem was that the cost was high. Therefore, there is a limit to the ability to produce toner of small particle size using the pulverization method.

On the other hand, although small-particle toners produced by polymerization methods other than pulverization methods have been proposed, the technology for applying these toners as two-component developers has not been established, making it difficult to obtain high-resolution images. could not.

0004

[Problems to be Solved by the Invention] The present invention provides a two-component developer for electrophotography, which is composed of a polymerized toner having a small particle size in combination with a specific carrier in order to obtain a large number of high-resolution copied images. The purpose is to

[0005]

[Means for Solving the Problems] The present invention provides a toner having an average particle diameter of 3 to 8 μm produced by a polymerization method, and a toner having an average particle diameter of 10 to 50 μm and a volume resistivity of 1010Ω.
This is a two-component developer for electrophotography, characterized by comprising a coated ferrite carrier of cm or more. The present invention will be explained in detail below.

[0006] The toner constituting the two-component developer for electrophotography of the present invention is a toner having an average particle diameter of 3 to 8 μm and produced by a polymerization method such as a suspension polymerization method, a solution polymerization method, or an emulsion polymerization method. It is something. Among the polymerization methods, a toner obtained by a suspension polymerization method is particularly preferable because it is easier to obtain a toner than other polymerization methods.

[0007] In the present invention, the average particle diameter of the toner can be measured using a Coulter Counter manufactured by Coulter. To obtain a toner by the suspension polymerization method, a monomer composition containing at least carbon black as a colorant is mixed into an aqueous medium containing a dispersion stabilizer, and the particle size of the toner is adjusted using an appropriate stirrer. The radicals generated when the previously added polymerization initiator or newly added polymerization initiator is decomposed by heat,
A toner is produced by polymerizing a polymerizable monomer to form a polymer.

Examples of polymerizable monomers used in toners produced by the polymerization method include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3
, 4-dichlorostyrene, p-ethylstyrene, 2,4
-dimethylstyrene, p-n-butylstyrene, p-t
ert-butylstyrene, p-n-hexylstyrene,
p-n-octylstyrene, p-n-nonylstyrene,
Styrene and its derivatives such as p-n-decylstyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, etc. Organic acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, methacrylic acid dodecyl, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate,
Methacrylic acid and its derivatives such as diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, acrylic acid Acrylic acid and its derivatives such as 2-ethylhexyl, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl methyl ketone, vinyl hexyl ketone , vinyl ketones such as vinyl isopropenyl ketone; N-vinylpyrrole, N-vinylcarbazole, N-vinylindole,
N-vinyl compounds such as N-vinylpyrrolidone; vinylnaphthalenes; acrylonitrile, methacrylonitrile,
There are polymerizable monomers such as acrylamide.

These polymerizable monomers may be used alone or in combination of two or more in various compositions, if necessary. Among the above-mentioned polymerizable monomers, it is preferable to use styrene or a styrene derivative alone or in combination with other polymerizable monomers in order to improve the development characteristics and durability of the toner.

[0010] Carbon black is suitable as a coloring agent used in a polymerized toner, and the carbon black used in the present invention can be used without any restrictions on number average particle size, oil absorption, pH, etc. Commercially available products include the following. For example, REGAL 400, 660, 330, 300 manufactured by Cabot, USA
, SRF-S, STERLING SO,
V, NS, R; RAVEN H20, MT-P, 410, 420 manufactured by Columbia Carbon Japan Co., Ltd.
, 430, 450, 500, 760, 780, 1000
, 1035, 1060, 1080; Mitsubishi Chemical Industries, Ltd.
Manufactured by #10B, #5B, #30, #40, #2400B,
MA-100; etc. are mentioned.

[0011] These carbon blacks may be used alone or in combination of two or more in various compositions. Coloring agents other than carbon can be used without particular limitations, and include phthalocyanine pigments, rhodamine lake pigments, iron oxides, azo lake pigments, titanium oxide, alumina, barium sulfate, and the like.

[0012] In addition, in order to improve heat fixability and anti-offset properties in the toner constituting the present invention, release agents such as waxes such as paraffin wax, and low molecular weight polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene are used. A low softening point compound having moldability may be added to the monomer composition.

Furthermore, in the toner constituting the present invention, a crosslinking agent may be added and suspension polymerization may be carried out in order to improve blocking resistance and durability. As such a crosslinking agent, a known crosslinking agent such as divinylbenzene can be added to the monomer composition. Furthermore, in the toner constituting the present invention, a known charge control agent may be added to the monomer composition, if necessary. Such charge control agents include metal complexes of organic compounds having carboxyl groups, sulfonic acid esters, or nitrogen-containing groups, metal-containing dyes, and the like. The polymerization initiator used in the toner constituting the present invention is preferably soluble in the polymerizable monomer.

[0014] As such a polymerization initiator, 2,2'
-azobisisobutyronitrile, 2,2'-azobis-
(2,4-dimethylvaleronitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, other azo or diazo polymerization initiators; benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxide Examples include oxycarbonate and other peroxide polymerization initiators.

[0015] The dispersion stabilizer is a compound having the ability to prevent coalescence and stabilize the monomer composition particles formed in the granulation process, and includes hydrophilic organic compounds and solid fine powders. It will be done. However, in the case of solid fine powder, a hydrophilic organic compound is preferably used because post-treatment after polymerization involves an extra step of dissolving and removing the solid fine powder with acid, alkali, or the like. Such dispersion stabilizers include, for example,
Examples include polyvinyl alcohol, casein, gelatin, cellulose derivatives such as methyl cellulose, methyl hydroxypropyl cellulose, and ethyl cellulose, starch and its derivatives, polyacrylic acid and salts thereof, and the like.

On the other hand, the carrier constituting the present invention has an average particle diameter of 10 to 50 μm and a volume resistivity of 1010Ω.
・It is a coated ferrite carrier of cm or more. If the average particle diameter is less than 10 μm, the toner cannot be triboelectrically charged and attached to the carrier surface, and if it is larger than 50 μm or the volume resistivity is less than 1010 Ω·cm, a high-resolution copy image cannot be obtained. .

In the present invention, the average particle diameter of the coated ferrite carrier is measured with a Coulter counter manufactured by Coulter Co., Ltd., and the volume resistivity is measured with an area of 5 cm2.
Load the coated ferrite carrier into a cylindrical resistance measuring device having a circular upper electrode and a lower electrode while adjusting the distance between the upper electrode and the lower electrode to 0.5 cm,
A voltage of 500 V is applied to the upper electrode and the lower electrode, and the resistance value is determined from the measured resistance value at that time.

The carrier constituting the present invention is a resin-coated carrier in which the surface of a ferrite core material is coated with silicone resin, acrylic resin, fluororesin, styrene-acrylic copolymer resin, polyester resin, polybutadiene resin, etc. Particularly preferred is a carrier coated with a silicone resin that can enhance the durability of the developer. The silicone resin may be any conventionally known silicone resin, such as a room temperature curable silicone resin represented by the following structural formula, but other silicone resins may also be used.

[0019]

[Chemical formula 1]

[Case 2]

[Chemical formula 3]

[C4]

[C5]

[C6]

The volume resistivity of the coated ferrite carrier can be adjusted by changing the composition of the core material and the manufacturing method, and it is particularly effective to adjust the volume resistivity by increasing or decreasing the amount of coating resin. . In addition, as a method for coating the core material with the resin, the resin may be used as it is, or it may be dissolved in a solvent and applied to the surface of the core material by a known method such as a spray dryer method or a fluidized bed coating method.

[0021]

[Manufacture of toner]

[0022] The above blended materials were put into a polymerization pot together with a polymerization initiator to start polymerization and proceed with granulation until the average particle diameter was 6 μm.
The granulation was stopped when the granulation was completed. Thereafter, the granulated particles were washed with water and dried to obtain a negatively charged toner produced by the polymerization method. 100 parts of the silicone coated ferrite carrier obtained above and 8 parts of toner were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography of the present invention.

Example 2 A two-component developer for electrophotography of the present invention was obtained in the same manner as in Example 1, except that the toner was manufactured under the following conditions. [Manufacture of toner] The above-mentioned blended materials were put into a polymerization pot together with a polymerization initiator to start polymerization, proceed with granulation, and stop granulation when the average particle size reached 6 μm. Thereafter, the granulated particles were washed with water and dried to obtain a negatively charged toner produced by the polymerization method.

Example 3 [Production of carrier] A non-coated ferrite carrier (manufactured by Dowa Iron Powder Co., Ltd.) having an average particle diameter of 30 μm was coated with styrene acrylic resin (CPR-100, manufactured by Mitsui Toatsu Co., Ltd.) on the surface of the carrier using a spray dryer. A styrene-acrylic coated ferrite carrier having a volume resistivity of 2×10 13 Ω·cm was obtained. [Manufacture of toner]

[0025] The above-mentioned blended materials were put into a polymerization pot together with a polymerization initiator to start polymerization and proceed with granulation until the average particle diameter was 5 μm.
The granulation was stopped when the granulation was completed. Thereafter, the granulated particles were washed with water and dried to obtain a positively chargeable toner produced by the polymerization method. 100 parts of the styrene-acrylic coated ferrite carrier obtained above and 8 parts of toner were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography of the present invention.

Example 4 A two-component developer for electrophotography of the present invention was obtained in the same manner as in Example 3, except that the toner was manufactured under the following conditions. [Manufacture of toner]

[0027] The above-mentioned blended materials were put into a polymerization pot together with a polymerization initiator to start polymerization and proceed with granulation until the average particle diameter was 6 μm.
The granulation was stopped when the granulation was completed. Thereafter, the granulated particles were washed with water and dried to obtain a negatively charged toner produced by the polymerization method.

Comparative Example 1 [Manufacture of carrier] Silicone resin (SR2400, manufactured by Toray Silicone Co., Ltd.) was coated on the surface of a non-coated ferrite carrier (manufactured by Dowa Iron Powder Co., Ltd.) with an average particle diameter of 70 μm using a spray dryer, and the volume resistivity was determined. A silicone coated ferrite carrier of 1×10 12 Ω·cm was obtained. 100 parts of the above silicone coated ferrite carrier and 7 parts of the toner obtained in Example 1 were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

Comparative Example 2 [Production of carrier] A non-coated ferrite carrier (manufactured by Dowa Iron Powder Co., Ltd.) with an average particle diameter of 60 μm was coated with silicone resin (SR2400, manufactured by Toray Silicone Co., Ltd.) on the surface of the carrier using a spray dryer to determine the volume resistivity. A silicone coated ferrite carrier of 2×10 12 Ω·cm was obtained. 100 parts of the above silicone coated ferrite carrier and 8 parts of the toner obtained in Example 2 were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

Comparative example 3

The above blended materials were melt-kneaded using a two-roll kneader, pulverized using a jet mill, and classified to obtain a toner having an average particle size of 12 μm. Next, Example 3
Styrene acrylic coated ferrite carrier 10 obtained from
0 part and 8 parts of the above toner were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

Comparative Example 4 100 parts of silicone-coated ferrite carrier F-95-100 manufactured by Powdertech (average particle diameter 60 μm, volume resistivity 4×10 12 Ω·cm) and 4 parts of the toner obtained in Comparative Example 3 were milled in a ball mill. The mixture was stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

Comparative Example 5 Average particle diameter is 40 μm and volume resistivity is 5×1010Ω
100 parts of a non-coated ferrite carrier of cm (manufactured by Dowa Iron Powder Co., Ltd.) and 8 parts of the toner obtained in Example 1 were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

Comparative Example 6 Average particle diameter is 40 μm and volume resistivity is 7×10 7 Ω
100 parts of a non-coated ferrite carrier of cm (manufactured by Dowa Iron Powder Co., Ltd.) and 8 parts of the toner obtained in Example 1 were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

Comparative Example 7 Average particle diameter is 50 μm and volume resistivity is 3×10 12 Ω
・cm silicone coated iron oxide powder (manufactured by Dowa Iron Powder Co., Ltd.) 1
00 parts and 8 parts of the toner obtained in Example 1 were placed in a ball mill and stirred for 1 hour to obtain a two-component developer for electrophotography for comparison.

[Evaluation of each developer] Next, Example 1, Example 2, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Examples 5 to 7
Each developer is used in a commercially available copying machine Ricoh FT-403.
0 and conducted live-action tests of up to 100,000 sheets. Further, each of the developers of Example 3, Comparative Example 3, and Comparative Example 4 was subjected to a photocopying test of up to 100,000 sheets using a commercially available copier SF-8800 manufactured by Sharp Corporation. The results are shown in Table 1. In Table 1, the image density was measured using a Macbeth densitometer, the ground fog was measured using a Hunter whiteness meter, and the amount of triboelectric charge was measured using a charge amount measuring device using a blow-off method. In addition, the fine line reproducibility is 0.1 mm in line width,
A line chart with a line spacing of 0.1 mm was copied, and the reproducibility of the line chart was visually evaluated.

[0037]

[Table 1]

As is clear from the results in Table 1, the developer of the present invention has sufficient image density from the initial stage to after 100,000 copies.
The image had little background fog. Furthermore, in terms of fine line reproducibility, it was possible to clearly distinguish a fine line of 0.1 mm. On the other hand, all of the comparative developers had poor fine line reproducibility and it was difficult to distinguish fine lines. Also, Comparative Example 1
In Comparative Example 5, the image density decreased after 100,000 copies, and in Comparative Example 5, Comparative Example 6, and Comparative Example 7, poor cleaning occurred.

[0039]

Effects of the Invention The present invention provides a two-component developer for electrophotography that can produce a large number of high-resolution copies because it is composed of a polymerized toner with a small particle size and a coated ferrite carrier with a small particle size. can be provided.

Claims (1)

[Claims] [Claim 1] Particles produced by a polymerization method with an average particle diameter of 3
A two-component developer for electrophotography, characterized by comprising a toner having a particle size of ~8 μm and a coated ferrite carrier having an average particle diameter of 10 to 50 μm and a volume resistivity of 1010 Ω·cm or more.