JP2000258958A - Polymer toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the nonmagnetic black toner having dispersibility assured even in the case of changing an amount of carbon black to be added and grain diameters in the toner. SOLUTION: The polymer toner is obtained by polymerizing a liquid mixture containing the carbon black having an absorption amount of DBP of 70-300 cm3/100 g and a dispersant and a polymerizable monomer, and the carbon black content in the toner is >=0.02d+2.1 and <=0.02d+7.8 (weight %), where d (nm) is the primary particle diameter of the carbon black particles in the range of 20-80 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymerized toner for developing a latent electrostatic image. In particular, the present invention relates to a polymerized toner which gives a high definition image in a small particle size toner obtained by polymerizing a monomer composition.

[0002]

2. Description of the Related Art Electrophotography is known as one of various processes for developing an electric or magnetic latent image to form and record an image. In the electrophotography, a photoconductive substance is generally used to form an electric latent image on a photoreceptor by various means, and then the latent image is developed with toner to form a toner image. The obtained toner image is fixed as it is, or is transferred to paper or the like and then fixed by means such as heating and pressurization to obtain a copy. As a method of developing using toner, various methods such as a powder cloud method, a touch-down method, and a magnetic brush developing method have been proposed, and a method suitable for each image forming process has been adopted.

[0003] Among these developing methods, the magnetic brush developing method is widely used because of its good image quality, easy downsizing of the apparatus and long life. Among the magnetic brush development methods, there are a two-component development method using a magnetic carrier and a non-magnetic toner, and a one-component development method using a non-magnetic toner or a magnetic toner, and the like, and each has its own characteristics. Among them, the developing method using a non-magnetic toner has the advantages that the apparatus is smaller and a high-resolution image is formed.

Conventionally, toners used for these purposes have generally been prepared by melt-kneading a colorant comprising a dye and a pigment into a binder resin comprising a thermoplastic resin, dispersing the colorant uniformly in the resin, and then pulverizing the mixture. By classifying the toner, a toner having a predetermined particle size distribution has been manufactured. However, in recent years, higher resolution images have been demanded, and it has been found that reducing the toner particle diameter is effective for this purpose. For this reason, attempts have been made to reduce the particle size of the toner, but the limit of the average particle size of the toner obtained by the pulverization method is about 7 μm. Therefore, as a method for producing a toner having a smaller particle size, a toner by a polymerization method has been proposed.

[0005] A suspension polymerization method is known as one of the toner production methods by polymerization. In the suspension polymerization method, a monomer composition obtained by dissolving or dispersing a polymerizable monomer and a colorant, and, if necessary, a polymerization initiator, a charge control agent, and other additives is used as a suspension stabilizer. Is added to the aqueous phase under stirring, and the mixture is granulated. After the polymerization reaction, the particles are filtered and dried to produce binder resin particles (toner particles). Since this suspension polymerization method does not include a pulverizing step at all, it is a method that can relatively easily produce a small particle size toner.

[0006]

When a black toner is produced by a suspension polymerization method, carbon black particles as a coloring agent are usually uniformly dispersed in a resin. If the dispersibility is poor, a sufficient image density cannot be obtained, and the chargeability of the toner becomes unstable. As a countermeasure against this, conventionally, a dispersant has been added to the monomer liquid to increase the affinity between the surface of the carbon black and the resin to improve the dispersibility. However, if this measure alone is used, a sufficient effect may not be obtained if the addition ratio or the particle size of the carbon black in the toner is changed.

Accordingly, the present invention provides a non-magnetic black toner which ensures a sufficient dispersibility even if the addition ratio or particle size of carbon black in the toner is changed, and provides sufficient image density and toner chargeability. The purpose is to do.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and have found that carbon black particles dispersed in toner particles and chain-like carbon black particles in which particles are in close proximity to each other. Have been found to preferably coexist. That is, if all of the carbon black particles are dispersed in the toner particles, the image density becomes high, but the electric resistance becomes too high, so that the toner is easily charged up, and if all of the carbon black particles are continuous in a chain. Not only is a sufficient image density not obtained, but also toner particles that cannot obtain a sufficient charge amount due to the formation of a conductive path are generated. When the dispersed carbon black particles and the chain-like carbon black particles coexist in one toner particle, a sufficient image density and an appropriate charge amount can be achieved.

[0009] The carbon black in the toner particles to the state is important DBP absorption of carbon black, the value is 70~300cm ³ / 100g, preferably 90~200cm ³ / 100g, further Preferably 100
~130cm is a ³ / 100g. DBP absorption is 70 cm ³ /
Is less than 100g in a state where all of the particles of carbon black particles are dispersed, all the particles of carbon black particles is chain exceeds 300 cm ^{3 /} 100g.

However, the present inventors have also found that a sufficient image density and an appropriate charge amount are not necessarily achieved only by setting the DBP absorption amount within the above range. As a result of further study, it has been found that it is important that the carbon black particles are not exposed on the surface of the toner particles. When the carbon black particles are exposed, current easily flows on the surface of the toner particles, and the triboelectric charging of the toner becomes unstable. Whether or not the carbon black particles are exposed depends on the content of the carbon black particles in the toner particles, and when a preferable content is C (% by weight),

[0011]

## EQU00001 ## It is represented by 0.02d + 2.1.ltoreq.C.ltoreq.0.02d + 7.8. Here, d is the primary particle diameter (nm) of the carbon black particles. If the content exceeds the range indicated by the expression 1, the carbon black particles are likely to be exposed. If the content is less than this range, the image density tends to decrease and the toner is charged up. Even if the content is the same, the larger the carbon black particles, the smaller the number of particles, so the probability of exposure is small, and the content can be increased accordingly.

The non-magnetic toner of the present invention can be prepared by a usual suspension polymerization method. For example, first, a colorant, a dispersant, a release agent, a charge control agent, a polymerization initiator, and a crosslinking agent are added to a polymerizable monomer, and these are uniformly mixed and dispersed by a wet mill such as a ball mill. Let me know. Next, after the suspension stabilizer and water (ion-exchanged water) were charged into the polymerization tank, the temperature was adjusted (5.
(About 0 ° C.) and pH adjustment (pH 5 to 6), followed by stirring with a homogenizer (1 to several minutes), and after adding a polymerization initiator, stirring with a homogenizer to perform suspension granulation.
Thereafter, the temperature inside the polymerization vessel was raised (around 70 ° C.), and after the polymerization initiator was charged, the mixture was stirred for several hours (about 8 hr) using a stirrer equipped with stirring blades instead of a homogenizer, thereby causing a polymerization reaction. I do. During this polymerization reaction (for example, 2-3 hours)
After the passage), a high Tg polymerizable monomer containing a cross-linking agent may be dropped to infiltrate the monomer into the surface of the polymer particles to increase the molecular weight of the surface. After the completion of the polymerization reaction, remove the suspension stabilizer by adding a dissolving agent,
Filtration, washing, dehydration and drying are performed, and if necessary, additives (fluidity modifier, cleaning aid, etc.) are externally added and classified to a predetermined particle size (for example, 5 to 8 μm) to obtain a polymerized toner.

The polymerizable monomer used in the present invention is a radical polymerizable monomer, and is used alone or in combination of two or more so that the resulting polymer has the required thermal and electrostatic properties of the toner. You. Examples of such monomers include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers. and so on.

As the monovinyl monomer, styrene, o
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, pn
-Butylstyrene, p-tert-butylstyrene, p
-N-hexylstyrene, pn-octylstyrene,
pn-nonylstyrene, pn-decylstyrene, p
-N-dodecylstyrene, 2,4-dimethylstyrene,
Styrene such as 3,4-dichlorostyrene and its derivatives are exemplified.

As the acrylic monomer, acrylic acid,
Methacrylic acid, methyl acrylate, ethyl acrylate,
Butyl acrylate, 2-ethylhexyl acrylate,
Cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, β-hydroxyethyl acrylate, γ-aminopropyl acrylate, stearyl methacrylate, methacryl Dimethylaminoethyl acrylate, diethylaminoethyl methacrylate and the like.

The vinyl ester monomers include vinyl acetate, vinyl propionate and vinyl benzoate, and the vinyl ether monomers include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether and vinyl phenyl ether. . Examples of the diolefin-based monomer include butadiene, isoprene, and chloroprene, and examples of the monoolefin-based monomer include ethylene, propylene, isobutylene, butene-1, pentene-1, and 4-methylpentene-1.

As the high Tg polymerizable monomer dropped during the polymerization reaction, the Tg on the surface of the toner particles is the Tg of the polymer constituting the inside of the toner particles (usually about 60 ° C.).
It is preferable to use a monomer which is higher by about 5 to 70 ° C. (65 to 130 ° C.), for example, polymethyl methacrylate (Tg is about 130 ° C.), vinyl biphenyl (Tg is about 150 ° C.), vinyl naphthalene (Tg is about 1
40 ° C.).

Examples of the dispersant include the following. As the silane coupling agent, γ-methacryloxypropyltrimethoxysilane, N-β- (N-
(Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride, vinyltriacetoxysilane, vinyltrimethoxysilane, and γ-anilinopropyltrimethoxysilane. Also, there are titanate coupling agents such as isopropyl triisostearic titanate, sodium p-styrenesulfonate, potassium p-styrenesulfonate, calcium styrenesulfonate, acrylic acid, methacrylic acid, p-chlorostyrene and the like.

The amount of the dispersant added is not particularly limited, but is preferably 0.1 to 10 parts by weight, preferably 0.3 to 7 parts by weight, per 100 parts by weight of carbon black.
Parts by weight. The use of the above dispersant in combination with an existing dispersant as a dispersing aid does not impose any problem. As a method of dispersing the colorant, monomer monomers,
The colorant, the peroxide-based polymerization initiator, the dispersant, and the charge control agent may be dispersed by a known mixing device such as a ball mill, a sand mill, and an attritor.

As the cross-linking agent, a cross-linkable monomer having two or more unsaturated bonds in one molecule can be used and copolymerized. Examples of the crosslinkable monomer include divinylbenzene, divinylnaphthalene, divinyl ether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and diallyl phthalate. The ratio of copolymerizing these crosslinkable monomers to polymerizable monomers is
The content is preferably 0.1 to 2% by weight based on the monomer composition.

Examples of the charge controlling agent include nigrosine, quaternary ammonium salts, polyalkylamides, molybdate chelate pigments, metal complexes of monoazo dyes, metal salts of naphthenic acid, and metal complexes of salicylic acid. These charge control agents are added in an amount of 0.1 to 5% by weight based on the total weight of the toner.
Is preferred.

The above-mentioned monomer composition is suspended in water by a mechanical or ultrasonic homogenizer, and during polymerization, calcium carbonate, magnesium carbonate, phosphorus It is common to use fine particles of poorly water-soluble inorganic salts such as magnesium acid, barium sulfate, silica, and alumina as dispersion stabilizers. In particular, colloidal silica is suitable as a suspension stabilizer for toner because its primary particle size is as small as 10 to 30 nm and a desired particle size can be obtained with a smaller amount. These dispersion stabilizers are preferably used at a ratio of 0.01 to 10% by weight based on the monomer. In addition to these dispersion stabilizers, a small amount of a stabilizing aid can be added. As the dispersion stabilizing aid, gelatin, carboxymethyl cellulose, starch, water-soluble polymers such as polyvinyl alcohol, surfactants and the like can be used.

In the present invention, as the peroxide-based polymerization initiator used for dispersing the colorant, for example, the following compounds can be used alone or in combination of two or more. For example, benzoyl peroxide, lauroyl peroxide,
Isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorylbenzoyl peroxide, methyl ethyl ketone peroxide and the like can be used. The amount of the polymerization initiator used is preferably about 0.1 to 2% by weight of the monomer composition. In the present invention, as the polymerization initiator to be used after the colorant is dispersed, one or a combination of two or more known polymerization initiators can be used. For example, 2,
2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethyl) valeronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, benzoyl peroxide, 2, 4-dichloropar-
The polymerization can be carried out using an oxide, isopropyl peroxycarbonate, cumene hydroperoxide, lauroyl peroxide-based initiator or the like.
The amount of these polymerization initiators used is about 0.1 to 5 of the monomer composition for polymerizing the polymer constituting the toner particles.
% By weight.

In the present invention, additives such as a fluidity modifier, a cleaning aid, and a filler may be added, if necessary, in addition to the components described above. As the minute polymer particles added to the polymer particle surface, polyethylene, polypropylene, polystyrene, polymethyl methacrylate,
There are polymers or copolymers such as polyvinylidene fluoride and polytetrafluoroethylene. In particular, particles obtained by dispersion polymerization or soap-free emulsion polymerization and having no water absorption on the surface are preferable.

As the fluidity modifier, fine powders such as hydrophobic silica, titanium oxide, polyvinylidene fluoride and metal soap are used. As the cleaning aid, zinc stearate, calcium stearate, magnesium stearate, Fine powders such as polymethyl methacrylate, nylon, polytetrafluoroethylene, and silicon carbide can be used. These additives may be used by mixing and dispersing them in the monomer composition, or may be added to the surface of the obtained toner particles.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in more detail with reference to examples.

(Example 1) 1895 g of styrene monomer (manufactured by Yoneyama Pharmaceutical Co., Ltd.) 330 g of 2-ethylhexyl acrylate (manufactured by Kanto Chemical Co., Ltd.) 6.5 g of divinylbenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) 6.5 g of carbon black (Mitsubishi Chemical Corporation) Company Ltd. # 20) 118 g [primary particle size 40 nm, DBP absorption 121cm ³ / 100g] · charge control agent (manufactured by Nippon Kayaku Co., Ltd. T-2N) 18g · benzoyl peroxide (75%, manufactured by Katayama chemical Co.) 33 g · A material consisting of 3 g of titanate coupling agent (Furanact TTS manufactured by Ajinomoto Co., 2.5 parts by weight with respect to 100 parts by weight of carbon black) was placed in a ball mill, and mixed and dispersed at room temperature for 12 hours to obtain a monomer liquid.

Next, 20 liters of ion-exchanged water and 150 g of hydrophilic silica (# 130, manufactured by Nippon Aerosil Co., Ltd.) were added as a suspension stabilizer to a 30 liter polymerization tank, and the temperature was raised to 50 ° C., and the mixture was homogenized (Nihon Special Co., Ltd.). 8 by Kikakosha
The suspension was stirred at 950 rpm for 1 minute, and a suspension obtained by mixing 85 g of azobis 2,4-dimethylvaleronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator in the monomer solution was placed in the suspension. At 8950 rp
The mixture was stirred for 9 minutes at m. Then, after the reaction vessel was replaced with nitrogen, the stirring vessel was changed to a stirring apparatus equipped with paddle stirring blades, and stirring was continued at 140 rpm for 7 minutes.
The polymerization reaction was performed at 0 ° C. for 8 hours. 500 g of sodium hydroxide was added to this suspension polymerization solution, and the mixture was stirred at 50 ° C. for 2 hours to dissolve the suspension stabilizer, filtered, washed with water and dehydrated, and dried under reduced pressure at 50 ° C. for 12 hours to obtain a suspension. 0.2 kg of polymer powder was obtained. When the particle size of the polymer powder was measured with a Coulter counter, the volume average particle size was 10 μm.

2,000 g of the above polymerized powder 20 g of hydrophobic silica fine powder (RX200 manufactured by Nippon Aerosil Co., Ltd.) 6 g of zinc stearate (manufactured by Yoneyama Pharmaceutical Co., Ltd.) 2 g of polymethyl methacrylate (MP5000 manufactured by Soken Chemical Co., Ltd.) The mixture was mixed with a mixer at 1670 rpm for 5 minutes, and cut with a zigzag classifier at a size of 20 μm or more and 5 μm or less to obtain a toner.

When an image was formed using a toner on a commercially available printer (LP1800, manufactured by Seiko Epson Corporation), dispersibility of carbon black in toner particles, triboelectric charge, image density (ID), Table 1 shows the evaluation results of fog and fog. The carbon black content is determined by dissolving a given amount of the obtained toner in a given amount of THF, measuring the light transmittance of the coloring solution, and preparing a polymer solution prepared by dispersing a known amount of carbon black. It was determined from the calibrated calibration curve. The dispersibility of the carbon black was determined by observing the cross section of the toner particles under a microscope and determining the degree of aggregation of the primary particles.も の indicates little aggregation (excluding chain-like ones), を indicates slight aggregation, 僅 か indicates half-aggregation, and x indicates almost aggregation. As for the image density, the reflection optical density of the solid black portion was measured by a Macbeth densitometer, and a good value of 1.35 or more was determined. Fog was measured using a color difference meter to determine the difference in whiteness of the paper before and after passing.
The following is defined as ①.

Example 2 Carbon black was added to 167
g, titanate coupling agent is carbon black 10
Example 1 except that the amount was changed to 0.5 part by weight with respect to 0 part by weight.
A polymerized toner was obtained in the same manner as described above. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

Example 3 148 carbon black
g, titanate coupling agent is carbon black 10
A polymerized toner was obtained in the same manner as in Example 1, except that the amount was changed to 0 parts by weight to 5 parts by weight. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

Example 4 A polymerized toner was obtained in the same manner as in Example 1 except that the carbon black was # 40 and the amount was changed to 174 g. Example 1 using the obtained toner
Table 1 shows the results when the image was formed under the same conditions as in the above.

Example 5 Carbon black was used as MA22
A polymerized toner was obtained in the same manner as in Example 1 except that 183 g was used instead of 0. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

(Example 6) 133 carbon blacks
g, a polymerized toner was obtained in the same manner as in Example 1 except that the titanate coupling agent was changed to 338X manufactured by Ajinomoto Co. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

(Example 7) 95 g of carbon black,
A polymerized toner was obtained in the same manner as in Example 1 except that the titanate coupling agent was changed to Span80 manufactured by Altas Water Company. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

Example 8 Carbon black # 305
A polymerized toner was obtained in the same manner as in Example 1 except that the amount was changed to 0 and 77 g. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

Example 9 Carbon black was used as MA10
A polymerized toner was obtained in the same manner as in Example 1 except that the amount was changed to 0 and 62 g. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

In each of the examples, the dispersed carbon black particles and the chain-like carbon black particles coexist in one toner particle, and almost no exposure of the carbon black particles to the toner particle surface was recognized. Was.

Comparative Example 1 A polymerized toner was obtained in the same manner as in Example 1 except that the surface treatment of carbon black was not performed. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1.

(Comparative Example 2) Carbon black was converted to MA60
A polymerized toner was obtained in the same manner as in Example 1 except that the amount was changed to 0 and 120 g. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1. Since the carbon black of this comparative example had a very small particle size of 18 nm, aggregation was observed.

Comparative Example 3 A polymerized toner was obtained in the same manner as in Example 1, except that the carbon black was # 10 and the amount was changed to 120 g. Example 1 using the obtained toner
Table 1 shows the results when the image was formed under the same conditions as in the above. Since the carbon black of this comparative example has a relatively large particle size of 84 nm, the image density is low. (Comparative Example 4) A polymerized toner was obtained in the same manner as in Example 1 except that the carbon black was changed to # 95 and 86 g. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1. Although the carbon black particles are dispersed, almost no chain-like carbon black particles are recognized. When the surface of the toner particles was observed with an electron microscope, the carbon black particles were exposed.

Comparative Example 5 210 g of carbon black
A polymerized toner was obtained in the same manner as in Example 1 except that the toner was changed. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1. The dispersed carbon black particles and the chain-like carbon black particles coexisted in one toner particle. When the surface of the toner particle was observed with an electron microscope, the carbon black particles were exposed.

Comparative Example 6 A polymerized toner was obtained in the same manner as in Example 5 except that the amount of carbon black was changed to 62 g. Table 1 shows the results when an image was formed using the obtained toner under the same conditions as in Example 1. Charge-up is observed and the image density is low. The dispersed carbon black particles and the chain-like carbon black particles coexisted in one toner particle. When the surface of the toner particle was observed with an electron microscope, the carbon black particles were not exposed.

FIG. 1 is a plot of the above Examples and Comparative Examples in relation to the content of carbon black and its particle size.

From Table 1 and FIG. 1, it can be seen that the polymerized toner of the present invention has excellent carbon black dispersibility, and a sufficient image density and toner chargeability can be obtained.

[0047]

[Table 1]

[0048]

The present invention has the constitution and operation as described above, and can provide a polymerized toner by a suspension polymerization method which is excellent in carbon black dispersibility, image density and toner chargeability.

[Brief description of the drawings]

FIG. 1 is a graph plotting the relationship between the content of carbon black and the particle size of an example and a comparative example.

Claims (1)

[Claims] 1. A polymerization toner DBP absorption amount is obtained by polymerizing a mixture containing carbon black and the dispersing agent and the polymerizable monomer is a 70~300cm ^{3 /} 100g, carbon black content in the toner Is the formula: 0.02d + 2.1 ≦ C ≦ 0.02d + 7.8 [where C (% by weight) is the carbon black content, d
(Nm) is a primary particle diameter of the carbon black particles of 20 to
A range of 80 nm].