JP2632251B2 - Electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner applied to a two-component developer 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 fields to increase the resolution of copied images in electrophotography. It is known that one of the means for improving the resolution of an image is to uniformly control the average particle diameter of the toner to a small particle diameter of 10 μm or less. However, the conventional toner kneads additives such as a colorant and a charge control agent such as carbon black in a thermoplastic resin, and after uniformly dispersing, pulverizes with a pulverizer and classifies with a classifier, so-called pulverization. When the particle size is reduced to 10 μm or less,
Because a small particle diameter of uniform size cannot be obtained, and the colorant and charge control agent are difficult to uniformly disperse in individual particles, triboelectric charging and uneven coloring of the copied image occur, and the production yield is poor. The problem of high cost has arisen. Therefore, there is a limit in producing a toner having a small particle diameter by a pulverizing method.

On the other hand, although a toner having a small particle diameter by a polymerization method has been proposed in addition to the pulverization method, a technique for applying the toner as a two-component developer has not been established, so that a high-resolution image can be obtained. Could not. In addition, there is a disadvantage that the surface area of the toner is significantly increased due to the reduction in the particle diameter of the toner, and the environmental dependency of the toner is increased. Under low temperature and low humidity, the image density is significantly reduced due to an increase in the toner charge amount.

[0004]

SUMMARY OF THE INVENTION In the present invention, specific carbon particles are adhered to the surface of a polymerized toner having a small particle diameter in order to reduce the environmental dependence of the toner and obtain a large number of high-resolution copied images. An object of the present invention is to provide an electrophotographic toner.

[0005]

According to the present invention, toner particles having an average particle diameter of 30 m.mu. or more and an oil absorption of 100 m are formed on the surface of toner particles having an average particle diameter of 3 to 8 .mu.m produced by a polymerization method.
1/100 g or more of carbon black is added to the toner particles 1
This is an electrophotographic toner adhered to 0.05 to 1 part by weight per 00 parts by weight. Hereinafter, the present invention will be described in detail.

The toner particles constituting the electrophotographic toner of the present invention have an average particle diameter of 3 to 8 μm produced by a polymerization method such as a suspension polymerization method, a solution polymerization method, and an emulsion polymerization method. Among the polymerization methods, toner particles obtained by a suspension polymerization method, which can easily obtain toner particles as compared with other polymerization methods, are particularly preferable.

In the present invention, the average particle size of the toner particles and carbon black can be measured with a Coulter counter manufactured by Coulter Corporation. To obtain toner particles by the suspension polymerization method, a monomer composition containing at least carbon black as a colorant is dispersed in an aqueous medium containing a dispersion stabilizer using an appropriate stirrer. The polymerized monomer is polymerized by radicals that are granulated to a diameter and are generated when a previously added polymerization initiator or a newly added polymerization initiator is decomposed by heat, thereby forming a polymer. It produces particles.

The polymerizable monomer for producing the toner particles according to the present invention by a polymerization method includes, for example, styrene and o.
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene,
p-ethylstyrene, 2,4-dimethylstyrene, p-
n-butylstyrene, p-tert-butylstyrene,
Styrene such as pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene and derivatives thereof; ethylene-unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; organic acid vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid, methyl methacrylate, and methacrylic acid Ethyl acrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate,
Methacrylic acid and its derivatives, such as stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and acrylic acid Acrylic acid such as propyl, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate and the like; vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl Vinyl ethers such as ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl Indole, N- vinyl compounds such as N- vinyl pyrrolidone; vinyl naphthalenes; acrylonitrile, methacrylonitrile, is acrylamide.

These polymerizable monomers are used alone or, if necessary, in combination of two or more kinds in various compositions. Among the above polymerizable monomers, it is preferable to use styrene or a styrene derivative alone or in a mixture with another polymerizable monomer from the viewpoint of improving the developing characteristics and durability of the toner.

Next, carbon black is suitable as a colorant used when the toner particles of the present invention are obtained by a polymerization method. The carbon black used in the present invention can be used without any limitation on the number average particle diameter, oil absorption, pH and the like, and the following are commercially available products.
For example, Regal 4 manufactured by Cabot Corporation, USA
00, 660, 330, 300, SRF-S, STELLING SO, V, NS, R; Raven H2 manufactured by Columbia Carbon Japan Co., Ltd.
0, MT-P, 410, 420, 430, 450, 50
0, 760, 780, 1000, 1035, 1060,
1080; # 10B, # 5B, # manufactured by Mitsubishi Kasei Kogyo Co., Ltd.
30, # 40, # 2400B, MA-100;

Further, these carbon blacks are used alone or in combination of two or more kinds in various compositions. As the colorant other than carbon, any colorant can be used without particular limitation, and phthalocyanine pigments, rhodamine
Lake pigment, iron oxide, azo lake pigment, titanium oxide, alumina, barium sulfate and the like.

Further, the toner particles constituting the present invention include:
In order to improve heat fixing property and anti-offset property, a low softening point compound having releasability, such as waxes such as paraffin wax, low molecular weight polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene, is used as a monomer composition. May be added.

Further, in the toner particles constituting the present invention, a crosslinking agent may be added for suspension polymerization 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. Further, in the toner particles constituting the present invention, a known charge control agent may be added to the monomer composition as needed. Examples of such charge control agents include metal complexes of organic compounds having a carboxyl group, a sulfonic acid ester or a nitrogen-containing group, and metal-containing dyes. The polymerization initiator used for the toner particles constituting the present invention is preferably soluble in the polymerizable monomer.

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 par Oxycarbonates and other peroxide-based polymerization initiators are exemplified.

The dispersion stabilizer is a compound having the ability to prevent and stabilize the coalescence of the monomer composition particles formed in the granulation step, and includes a hydrophilic organic compound and solid fine powder. Can be However, in the case of a solid fine powder, a hydrophilic organic compound is preferably used since an extra step of dissolving and removing the solid fine powder with an acid, an alkali or the like is included in the post-treatment after polymerization. Such dispersion stabilizers, for example,
Examples include cellulose derivatives such as polyvinyl alcohol, casein, gelatin, methylcellulose, methylhydroxypropylcellulose and ethylcellulose, starch and its derivatives, polyacrylic acid and salts thereof.

The carbon black adhered to the surface of the toner particles in the present invention is produced by a method such as a furnace method or an impact method, and has an average particle diameter of 30.
mμ or more, preferably 35 mμ or more and an oil absorption of 10
It is characterized by being at least 0 ml / 100 g.

When the average particle diameter of the carbon black adhered to the surface of the toner particles is smaller than 30 mμ or the carbon black has an oil absorption of less than 100 ml / 100 g, the carbon black is easily detached from the surface of the toner particles, resulting in an image. Produces carbon stains.

Commercially available carbon blacks applicable to the present invention include, for example, the following. That is,
# 20, # 30, # 32, # 305 manufactured by Mitsubishi Kasei Kogyo
0: VALCANX C72R, BL manufactured by Cabot Corporation in the United States
ACK PEARLS 280, BLACK PEAR
LS 170, TINTA CARB 35: Raven 825 BEADS, RA manufactured by Columbia Carbon Co.
VEN 890 POWDER, RAVEN 22P
OWDER, etc., and the above-mentioned carbon blacks can be used alone or in combination of two or more.

The method for adhering carbon black to the surface of the toner particles is as follows: using a mixer such as a V-type mixer, a turbine-type stirrer, or a Henschel mixer, add 0.05 to 500 parts by weight of the specific carbon black to 100 parts by weight of the toner particles. It is performed by mixing and stirring 1 part by weight. In this case, if the amount of the carbon black is less than 0.05 parts by weight, the effect of adding the carbon black is small, and the toner adheres to the surface of the developing sleeve. , The image quality deteriorates.

In the present invention, in addition to carbon black, fine silica powder or the like may be adhered to the toner particles in order to improve fluidity.

[0021]

The present invention will be described below with reference to examples. In the examples, all parts are parts by weight. Example 1 [Production of toner] The material having the above composition was put into a polymerization vessel together with a polymerization initiator, polymerization was started, and granulation was progressed. When the average particle diameter was granulated to 6 μm, the granulation was stopped. Thereafter, the granulated particles were washed with water and dried to obtain negatively chargeable toner particles by a polymerization method.

Next, 100 parts by weight of the above toner particles were subjected to a carbon tintacarb 35 manufactured by Cabot Corporation (average particle diameter 41 mμ, oil absorption 121 ml / 100 g, PH
9) and 0.3 part by weight of silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) using a Henschel mixer to mix carbon black on the surface of the toner particles. A toner was obtained.

Example 2 [Production of Toner] The material having the above composition was put into a polymerization vessel together with a polymerization initiator, polymerization was started, and granulation was progressed. When the average particle diameter was granulated to 6 μm, the granulation was stopped. Thereafter, the granulated particles were washed with water and dried to obtain negatively chargeable toner particles by a polymerization method.

Next, Carbon Raven 22 manufactured by Columbia Carbon Co., Ltd. is used with respect to 100 parts by weight of the toner particles.
(Average particle diameter 62 mμ, oil absorption 113 ml / 100 g,
PH7) and 0.1 parts by weight of silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) using a Henschel mixer to mix carbon black on the surface of the toner particles. A toner was obtained.

Example 3 [Production of Toner] The material having the above composition was placed in a polymerization vessel together with a polymerization initiator, polymerization was started, and granulation was progressed. When the average particle diameter was reduced to 5 μm, the granulation was stopped. Thereafter, the granulated particles were washed with water and dried to obtain positively chargeable toner particles by a polymerization method.

Next, carbon # 30 (average particle diameter 30 m) manufactured by Mitsubishi Kasei Kogyo Co., Ltd. was used for 100 parts by weight of the toner particles.
μ, oil absorption 113 ml / 100 g, PH 9) 0.2
Parts by weight, silica (R-972 manufactured by Nippon Aerosil Co., Ltd.)
Mix 0.5 parts by weight using a Henschel mixer,
Carbon black was attached to the surface of the toner particles to obtain the toner for electrophotography of the present invention.

Example 4 [Production of Toner]

The material having the above composition is put into a polymerization vessel together with a polymerization initiator, polymerization is started, granulation is advanced, and the average particle diameter is 6 μm.
When the granulation was completed, the granulation was stopped. Thereafter, the granulated particles were washed with water and dried to obtain negatively chargeable toner particles by a polymerization method.

Next, carbon # 30 manufactured by Mitsubishi Kasei Kogyo Co., Ltd. (average particle diameter 30 m
μ, oil absorption 113 ml / 100 g, PH 9) 0.2
Parts by weight, silica (R-972 manufactured by Nippon Aerosil Co., Ltd.)
Mix 0.5 parts by weight using a Henschel mixer,
Carbon black was attached to the surface of the toner particles to obtain the toner for electrophotography of the present invention.

Comparative Example 1 [Production of Toner] The material having the above composition was put into a polymerization vessel together with a polymerization initiator, polymerization was started, and granulation was progressed. When the average particle diameter was granulated to 6 μm, the granulation was stopped. Thereafter, the granulated particles were washed with water and dried to obtain negatively chargeable toner particles by a polymerization method, and this was used as it is as a comparative electrophotographic toner.

Comparative Example 2 0.3 parts by weight of silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) was mixed with 100 parts by weight of the toner particles obtained in Comparative Example 1 using a Henschel mixer to form a mixture on the surface of the toner particles. A comparative electrophotographic toner was obtained.

Comparative Example 3 100 parts by weight of the toner particles obtained in Comparative Example 1 were subjected to carbon MOGUL manufactured by Cabot Corporation (average particle diameter of 24 m).
μ, oil absorption 60 ml / 100 g, PH 3) 0.2 parts by weight, and silica (R-972 manufactured by Nippon Aerosil Co., Ltd.)
Mix 0.5 parts by weight using a Henschel mixer,
Carbon black was attached to the surface of the toner particles to obtain a comparative electrophotographic toner.

Comparative Example 4 [Production of Toner] The material having the above composition was placed in a polymerization vessel together with a polymerization initiator, polymerization was started, and granulation was progressed. When the average particle diameter was reduced to 5 μm, the granulation was stopped. Thereafter, the granulated particles were washed with water and dried to obtain positively chargeable toner particles by a polymerization method, which was used as it is as a comparative electrophotographic toner.

Comparative Example 5 100 parts by weight of the toner particles obtained in Comparative Example 4 were mixed with 0.5 part by weight of silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) using a Henschel mixer and adhered to the surface of the toner particles. Thus, a comparative electrophotographic toner was obtained.

Comparative Example 6 A carbon CF-9 (average particle diameter of 40 m) manufactured by Mitsubishi Kasei Kogyo Co., Ltd. was used with respect to 100 parts by weight of the toner particles obtained in Comparative Example 4.
μ, oil absorption 65 ml / 100 g, PH 8) 0.2 parts by weight, and silica (R-972 manufactured by Nippon Aerosil Co., Ltd.)
0.5 parts by weight were mixed using a Henschel mixer and attached to the surface of the toner particles to obtain a comparative electrophotographic toner.

[Evaluation of each developer] Next, a ferrite carrier (trade name: F-95-100) 10 manufactured by Powder Tech Co., Ltd.
0 parts by weight and Example 1, Example 2, Example 4, Comparative Examples 1 to
The mixture of No. 3 with 4 parts by weight of each toner was stirred for 1 hour in a ball mill to obtain a two-component developer for evaluation. Each of the developers was used with a commercially available copier FT-403 manufactured by Ricoh Co., Ltd.
0, normal temperature and normal humidity (20 ° C., 50%), high temperature and high humidity (35
(85 ° C., 85%) and low-temperature, low-humidity (10 ° C., 15%) environment tests. In addition, Ferrite carrier (trade name: FL-96-100) manufactured by Powder Tech Co., Ltd.
00 parts by weight and each toner 4 of Example 3 and Comparative Examples 4 to 6
The mixture was stirred for 1 hour in a ball mill in combination with parts by weight to obtain a two-component developer for evaluation. Each developing agent is a commercial copying machine, SF-8800 manufactured by Sharp Corp., at room temperature and normal humidity (20 ° C., 50%) and at high temperature and high humidity (35 ° C., 85%).
%) And low-temperature and low-humidity (10 ° C., 15%) environmental tests were performed. Table 1 shows the results. In Table 1, the image density was measured by a Macbeth densitometer, the ground fog was measured by a Hunter whiteness meter, and the triboelectric charge was measured by a charge measuring device by a blow-off method. Fine line reproducibility is 0.1m
A line chart of m and 0.1 mm between lines was copied, and the reproducibility of the line chart was visually evaluated. In the evaluation of the reproducibility of fine lines, the mark ○ means that the line width and the portion between lines can be clearly distinguished visually. △ indicates that the line width and the portion between the lines are visually distinguishable or indistinguishable. The crosses indicate that the line width and the portion between the lines are visually indistinguishable at all.

[0037]

[Table 1]

As is clear from the results shown in Table 1, Examples 1 to 4 of the present invention were at room temperature and normal humidity (20 ° C., 50%), high temperature and high humidity (35 ° C., 85%), and low temperature and low humidity (10 ° C., 15%). %), An image having a small increase in the charge amount and a small decrease in the image density was obtained in each environment (%). Also, in the reproducibility of fine lines, a fine line of 0.1 mm could be clearly distinguished. On the other hand, in the toners of Comparative Examples 1, 2, 4, and 5, the charge amount of the toner significantly increased and the image density decreased at low temperature and low humidity. Fine line reproducibility was also poor, and it was difficult to distinguish thin lines. Further, the average particle diameter of the carbon blacks of Comparative Examples 3 and 6 was smaller than 30 mμ or the oil absorption was 100 m
In the case of 1/100 g or less, the ground fog was remarkably bad in each environment.

[0039]

According to the present invention, a polymerized toner having a small particle size, an average particle size of 30 μm or more, and an oil absorption of 100 ml / 100 g are provided.
Since it is composed of the above-mentioned carbon black, the toner for electrophotography has a small increase in toner charge amount, has a good image density, and can obtain a large number of high-resolution copy images even at normal temperature and normal humidity, high temperature and high humidity, and low temperature and low humidity. Can be provided.

Claims (1)

(57) [Claims] An average particle size produced by a polymerization method is from 3 to 3.
Carbon black having an average particle diameter of 30 mμ or more and an oil absorption of 100 ml / 100 g or more is applied to the surface of the 8 μm toner particles in an amount of 0.05 to 100 parts by weight based on 100 parts by weight of the toner particles.
1 part by weight of an electrophotographic toner.