JPH05107801A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To improve the dependence characteristics of a polymer toner having a small particle size on environmental humidity by depositing a silicone oil having specified viscosity on the surface of the polymer toner having a specified particle size produced by polymn. method. CONSTITUTION:A silicone oil having <=300cs viscosity is deposited by 0.01-5 pts.wt. on the surface of a polymer toner by 100 pts.wt. having 2mum-10mum average particle size produced by polymn. method. If the toner has <=2mum average particle size, surface fogging on copies and bad cleaning property is caused. If the toner has >=100mum average particle size, picture qualities, especially resolution, become bad. If the vicosity of the silicone oil exceeds 300cs, the silicone oil cannot be uniformly applied on the toner surface when the silicone oil is to be deposited on the polymer toner. If the add amt. of the oil is less than 0.01 pts.wt., the effect to improve dependence characteristics of the polymer toner on humidity is not obtd., while if the amt. exceeds 5 pts.wt., the viscosity of the polymer toner increases, which decreases the fluidity of the toner to cause blocking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner 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 the average particle diameter of the toner is uniformly controlled to a small particle diameter of 10 μm or less as one means for increasing the resolution of an image. However, in the conventional toner, additives such as a colorant such as carbon black and a charge control agent are kneaded in a thermoplastic resin, uniformly dispersed, and then pulverized by a pulverizer and classified by a classifier, so-called pulverization. Since it is manufactured by the classification method, if the particle size is as small as 10 μm or less, it will not be possible to obtain a uniform small particle size, and individual particles will be uniform in colorant, charge control agent, etc. Since it is difficult to disperse the particles in the toner, triboelectrification and uneven coloring of the copied image occur, and the production yield is low, resulting in high cost. Therefore, there is a limit in producing a toner having a small particle diameter by the pulverizing and classifying method.

On the other hand, although a toner by a polymerization method has been proposed as a means for obtaining a toner having a small particle diameter, since the toner has a smaller average particle diameter than ordinary toner particles, it has a large toner surface area, and at the polymerization stage Since a highly hydrophilic material such as a polymerization initiator is used, there is a problem that the humidity dependence of the environment is extremely poor.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic toner in which the environment-dependent humidity dependence of a small particle size polymerization toner is improved.

[0005]

The present invention relates to a polymerized toner 100 having an average particle diameter of 2 to 10 μm produced by a polymerization method.
The toner for electrophotography is characterized in that 0.01 to 5 parts by weight of silicone oil having a viscosity of 300 cs or less is attached to the surface of the toner. Hereinafter, the present invention will be described in detail.

The electrophotographic toner of the present invention comprises a suspension polymerization method,
A polymerized toner having an average particle diameter of 2 to 10 μm produced by a polymerization method such as a solution polymerization method or an emulsion polymerization method is used. Of these, in the solution polymerization method, several hundreds μ in the polymerization granulation step.
Although it is possible to obtain irregularly shaped particles of m or more, it is difficult to produce particles having an average particle diameter of 2 to 10 μm necessary as toner particles, and the emulsifier used in the emulsion polymerization method has a strong hydrophilicity. However, since the emulsifier remains on the surface of the toner particles obtained by emulsion polymerization, the toner particles themselves tend to have strong hydrophilicity, resulting in a marked deterioration of environmental characteristics. For the above reasons, the toner obtained by the suspension polymerization method is preferable.

To obtain a toner 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.
Granulate to the particle size of the toner using an appropriate stirrer, and polymerize the polymerizable monomer by radicals generated when the polymerization initiator added in advance or the newly added polymerization initiator is decomposed by heat. Then, a polymer is formed to produce a toner.

The polymerizable monomer used in the toner of the suspension polymerization method is, for example, styrene, o-methylstyrene, m.
-Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene,
2,4-dimethylstyrene, pn-butylstyrene,
Styrene and its derivatives such as p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene; ethylene, propylene, butylene, isobutylene, Ethylenically unsaturated monoolefins such as; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride; vinyl acetates such as vinyl acetate, vinyl propionate, vinyl benzoate, etc .;
Methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate,
Methacrylic acid and its derivatives such as n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n acrylate
-Acrylic acid and its derivatives such as octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc. Vinyl vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; vinyl naphthalenes; There are polymerizable monomers such as acrylonitrile, methacrylonitrile, and 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, from the viewpoint of improving the developing characteristics and durability of the toner.

Carbon black is suitable as the colorant used in the toner of the polymerization method, and the carbon black used in the present invention can be used without limitation in number average particle size, oil absorption, pH and the like. The following are commercially available products. For example, Regal 400, 660, 330, 30 manufactured by Cabot Corporation in the United States.
0, SRF-S, STERRING S
O, V, NS, R; Raven H20, MT-P, 410, 4 manufactured by Columbia Carbon Japan Co., Ltd.
20, 430, 450, 500, 760, 780, 10
00, 1035, 1060, 1080; Mitsubishi Kasei Kogyo Co., Ltd. # 10B, # 5B, # 30, # 40, # 240.
0B, MA-100; and the like.

These carbon blacks may be used alone or in combination of two or more in various compositions. As the colorant other than carbon, any colorant can be used without particular limitation. Examples include phthalocyanine pigments and rhodamine.
Examples include lake pigments, iron oxides, azo lake pigments, titanium oxide, alumina, barium sulfate and the like.

In the electrophotographic toner of the present invention, waxes such as paraffin wax, low molecular weight polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene, etc. are used in order to improve heat fixing property and anti-offset property. A low softening point compound having releasability may be added to the monomer composition.

Furthermore, in the electrophotographic toner of the present invention, a suspension polymerization may be carried out by adding a crosslinking agent in order to improve blocking resistance and durability. As such a cross-linking agent, a known cross-linking agent such as divinylbenzene can be added to the monomer composition. Furthermore, in the electrophotographic toner of the present invention, a known charge control agent may be added to the monomer composition, if necessary. Examples of such a charge control agent include a metal complex of an organic compound having a carboxyl group, a sulfonate ester or a nitrogen-containing group, a metal-containing dye, and the like. The polymerization initiator used in the electrophotographic toner of 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 peroxide Examples thereof include oxycarbonate and other peroxide type polymerization initiators.

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

The average particle size of the polymerized toner of the present invention is measured by a Coulter counter manufactured by Coulter Co., and the volume is 50%.
The particle diameter obtained by the diameter (aperture diameter 100 μm) is referred to. In the present invention, the average particle size is 2μ.
If it is smaller than m, the background fog on the copy and the cleaning property are poor, and if it is larger than 10 μm, the image quality, particularly the resolution is deteriorated. The silicone oil attached to the surface of the polymerized toner needs to have a viscosity of 300 cs or less at 25 ° C. The viscosity is measured by a Canon-Fenske viscometer. Viscosity 3
If it exceeds 00 cs, the viscosity of the silicone oil is too high when it is attached to the surface of the polymerized toner, and the toner surface cannot be uniformly coated with the silicone oil.
The amount of silicone oil added is 100
If the amount of addition is less than 0.01 parts by weight, the effect of improving the humidity-dependent properties of the polymerized toner is not obtained, and if the amount is more than 5 parts by weight, the polymerization is not performed. Since the viscosity of the toner is increased, the fluidity is significantly deteriorated and blocking occurs.

The silicone oil constituting the present invention is not particularly limited, but the following general formula (I) is used.
A silicone oil having a dimethylpolysiloxane structure represented by is preferred.

[0018]

[Chemical 1] (However, R ₁ and R ₂ represent a phenyl group or an alkyl group, and n represents a positive integer of 1 or more.)

As a method for adhering the silicone oil to the surface of the polymerized toner particles, the polymerized toner particles and the silicone oil may be simultaneously put in a powder mixer such as a Henschel mixer or a super mixer to be agitated and adhered.
Alternatively, the polymerized toner particles may be sprayed and adhered by a powder mixer with a spoo while stirring.

[0020]

EXAMPLES The present invention will be described below based on examples. In the examples, all parts are parts by weight. Example 1 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method. Silicone oil KF-69 manufactured by Shin-Etsu Chemical Co., Ltd. based on 100 parts by weight of the polymerized toner particles obtained above.
(Viscosity 20 cs) was added in an amount of 0.2 part by weight and surface-treated with a Henschel mixer to obtain the electrophotographic toner of the present invention.

Example 2 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method. Silicone oil KF-69 manufactured by Shin-Etsu Chemical Co., Ltd. based on 100 parts by weight of the polymerized toner particles obtained above.
(Viscosity 20 cs) was added in an amount of 0.2 part by weight and surface-treated with a Henschel mixer to obtain the electrophotographic toner of the present invention.

Example 3 The material having the above composition was put in a polymerization kettle together with a polymerization initiator to start suspension polymerization, and granulation was advanced. When the average particle size was granulated to 5 μm, granulation was stopped. Then, the granulated particles were washed with water and dried to obtain a positively chargeable toner by a polymerization method. Silicone oil KF-96 manufactured by Shin-Etsu Chemical Co., Ltd. based on 100 parts by weight of the polymerized toner particles obtained above.
0.2 part by weight of (viscosity 50 cs) was added and surface treatment was carried out with a Henschel mixer to obtain the electrophotographic toner of the present invention.

Example 4 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method. To 100 parts by weight of the polymerized toner particles obtained above, silicone oil SH-200 manufactured by Toray Silicone Co., Ltd.
(Viscosity 100 cs) was added in an amount of 0.2 part by weight and surface-treated with a Henschel mixer to obtain the electrophotographic toner of the present invention.

Comparative Example 1 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method.

Comparative Example 2 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method.

Comparative Example 3 The material having the above composition was put in a polymerization kettle together with a polymerization initiator to start suspension polymerization, and granulation was advanced. When the average particle size was granulated to 5 μm, granulation was stopped. Then, the granulated particles were washed with water and dried to obtain a positively chargeable toner by a polymerization method. To 100 parts by weight of the polymerized toner particles obtained in Comparative Examples 1 to 3, 0.2 parts by weight of silicone oil KF-96H (viscosity 6000 cs) manufactured by Shin-Etsu Chemical Co., Ltd. was added and surface-treated with a Henschel mixer for comparison. To obtain a toner for electrophotography.

Comparative Example 4 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method. Silicone oil KF-54 manufactured by Shin-Etsu Chemical Co., Ltd. based on 100 parts by weight of the polymerized toner particles obtained above.
(Viscosity 400 cs) was added in an amount of 0.2 part by weight and surface-treated with a Henschel mixer to obtain a comparative electrophotographic toner.

Comparative Example 5 The above-prepared materials were put into a polymerization kettle together with a polymerization initiator to start suspension polymerization to proceed with granulation, and the granulation was stopped when the average particle size was granulated to 6 μm. Then, the granulated particles were washed with water and dried to obtain a negatively chargeable toner by a polymerization method. Silicone oil KF-961 manufactured by Shin-Etsu Chemical Co., Ltd. based on 100 parts by weight of the polymerized toner particles obtained above.
(Viscosity 800 cs) was added in an amount of 0.2 part by weight and surface-treated with a Henschel mixer to obtain a comparative electrophotographic toner.

[Evaluation of each developer] 4 parts by weight of each toner obtained in Examples 1 to 4 and Comparative Examples 1 to 5 and a carrier F-95-100100 manufactured by Powdertec Co., which is a ferrite particle coated with a silicone resin. Parts were mixed to prepare a developer. These developers are set in a commercially available PPC copier, and are kept at room temperature and normal humidity (20 ° C / 50% RH), low temperature and low humidity (10%).
Table 1 shows the results of a copy test after leaving for 24 hours under each of the environmental conditions of ° C / 15% RH) and high temperature and high humidity (35 ° C / 85% RH). As the PPC copying machine used at that time, SF-8800 manufactured by Sharp was used for Example 3 and Comparative Example 3, and FT-4030 manufactured by Ricoh was used for other Examples and Comparative Examples. In Table 1, the image density was measured by a Macbeth densitometer, the background fog was measured by a Hunter whiteness meter, and the triboelectric charge amount was measured by a charge amount measuring device by a blow-off method. Fine line reproducibility is line width 0.1m
A line chart with m and line spacing of 0.1 mm was copied, and the reproducibility of the line chart was visually evaluated. The evaluation criteria are as follows.

[0030]

[Table 1]

As is clear from the results shown in Table 1, the developer using the electrophotographic toner of the present invention has a practically sufficient image density in any environment of normal temperature and normal humidity, low temperature and low humidity, and high temperature and high humidity. Fog was small and the fine line reproducibility was also good. On the other hand, the developer using the comparative toner had insufficient image density in a low temperature and low humidity environment, reproducibility of fine lines was remarkably poor, and ground fog occurred in a high temperature and high humidity environment.

[0032]

INDUSTRIAL APPLICABILITY The present invention can provide an electrophotographic toner capable of obtaining a high-resolution copy with sufficient image density and little background fog regardless of environmental conditions.

Claims (2)

[Claims] 1. The average particle size produced by the polymerization method is from 2 to 2.
The viscosity is 3 with respect to 100 parts by weight of the polymerized toner of 10 μm.
A toner for electrophotography, characterized in that 0.01 to 5 parts by weight of silicone oil of 0.01 cs or less is adhered to the surface. 2. The toner for electrophotography according to claim 1, wherein the polymerized toner is produced by a suspension polymerization method.