JPH05100483A - Production of polymer toner - Google Patents

Abstract

PURPOSE:To provide a production method of a toner of small particle size having good picture image characteristics and cleaning property by suspension polymn. CONSTITUTION:The toner for development of electrostatic latent images is produced by dispersing a polymerizable monomer mixture liquid containing at least monomers having an ethylene unsatd. double bond and a coloring agent in water with using a dispersion stabilizer to effect suspension polymn. The dispersion stabilizer is removed at temp. higher than the glass transition temp. of the polymer to flocculate polymer particles to form amorphous associated particles. These particles are then pulverized into <=7.0mum volume average particle size. Thus, the obtd. toner gives high-precision picture images and have good blade cleaning property.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to toners for developing electrostatic latent images. In particular, it relates to a method for producing a toner in which a high-definition image can be obtained in a polymerization method toner in which a toner is directly obtained by polymerizing a monomer composition in a dispersion medium.

[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 an image and recording the image. In this electrophotographic method, a photoconductive substance is generally used, an electric latent image is formed on a photoconductor by various means, and then this latent image is developed with a toner to form a toner image. The obtained toner image is fixed as it is, or is transferred onto paper or the like and then fixed by means of heating, pressing or the like to form a copy. Various methods such as a powder cloud method, a touch-down method, and a magnetic brush developing method have been proposed as a method of developing using toner, and a method suitable for each image forming process is adopted.

Conventionally, toners used for these purposes are generally obtained by melt-kneading a colorant composed of a magnetic material or a dye / pigment in a thermoplastic resin to uniformly disperse the colorant in the resin, followed by pulverization and classification. By doing so, a toner having a predetermined particle size distribution has been manufactured.

This method of producing a toner by kneading and pulverizing can produce a toner having excellent characteristics, but has certain limitations. That is, it was necessary to use a resin that was easily crushed, in other words, was highly brittle. When a toner using a resin having high brittleness is subjected to actual development, the toner is further pulverized due to the stress of development, and deterioration called selective development or toner spent is likely to occur.

Further, in this kneading-grinding method, it is difficult to disperse solid fine particles such as a colorant in the resin completely and uniformly, and depending on the degree of dispersion, the toner composition has a distribution, which causes toner development. In some cases, the characteristics may fluctuate. Further, generally, the resolution of an image formed by toner, the denseness of a solid portion, and the gradation reproducibility depend largely on the characteristics of the toner, particularly its particle size, and the smaller the particle size, the higher the quality image can be obtained. It is known. Therefore, recent high-quality copying machines and printers often use small particle size toner. However, the production of a small particle diameter toner by the kneading-pulverization method has a limit of about 7.0 μm in volume average particle diameter due to the ability of the pulverizer. Therefore, in order to solve the problems of these kneading-grinding methods,
A toner by a polymerization method has been proposed.

[0006]

The suspension polymerization method is known as one of the methods for producing a toner by polymerization. In the suspension polymerization method, a polymerizable monomer and a colorant, a polymerization initiator as necessary, a charge control agent, a monomer composition in which other additives are dissolved or dispersed, a suspension stabilizer. Toner particles are manufactured by adding the mixture to an aqueous phase containing it under agitation and granulating, polymerizing and then filtering and drying the particles. Since this suspension polymerization method does not include a pulverization step at all, it is a method that can relatively easily produce a small particle diameter toner.

However, the particles produced by suspension polymerization tended to be spherical due to the interfacial tension of the droplets generated in the dispersion process. Spherical toner has good fluidity even with a small particle size, and is advantageous for developing machine design such as hopper design and torque for rotating the developing roll, but it is difficult to clean with some cleaning methods. There was a problem. In the cleaning method,
Generally, a blade, a fur brush, or a magnetic brush is used, but in the blade cleaning method, spherical toner rotates between the blade and the photoconductor and enters the gap, which makes the cleaning difficult.

In order to adapt the toner obtained by the polymerization method to the blade cleaning method, several methods have been known so far. For example, Japanese Patent Laid-Open No. Sho 62
As described in JP-A-266550, there is a method in which high speed stirring is carried out before the completion of polymerization and a mechanical force is applied to the particles to make the polymer particles into an amorphous shape. In this method, since the stable dispersion state is broken, the particles are likely to coalesce with each other and eventually become a lumpy polymer, which makes it difficult to control stirring and is not practical. Further, in Japanese Patent Laid-Open No. 2-511164, polyvinyl alcohol having a specific saponification degree is used as a dispersant to agglomerate the particles to 5-2.
By using the aggregate particles of 5 μm, the cleaning property is improved. However, this method is not suitable for producing a small particle size toner, because the particle size of the associated particles tends to be large.

As a method for producing an irregular toner, in addition to the above, Japanese Patent Laid-Open No. 167564/1990 discloses that particles produced by suspension polymerization are heat-treated during drying to form blocks and then mechanically pulverized. Then, a method of forming an irregular toner is known. By this method, an amorphous toner having a small particle size can be produced, but crushing the block-shaped fused material into fine particles not only complicates the process but also causes a large energy loss. is there. Furthermore, JP-A-61-1
Japanese Patent No. 67956 describes a method of subjecting emulsion-polymerized particles to an aggregation treatment at a temperature equal to or higher than the glass transition temperature thereof. Since the emulsion-polymerized particles have a small primary particle size of 1 μm or less, it is possible to prepare a small-sized irregular toner having a particle size of about 5 to 7 μm by aggregating treatment, but due to the hygroscopicity of the remaining emulsifier,
There is a problem that the toner does not have sufficient chargeability.

An object of the present invention is to provide a method for producing a toner in which toner particles produced by suspension polymerization have an irregular shape, a small particle size, and excellent image characteristics.

[0011]

The present invention has been made to solve the above problems, and is a polymerizable monomer mixed liquid containing at least a monomer having an ethylenically unsaturated double bond and a colorant. Is dispersed in water using a dispersion stabilizer, and the suspension polymerization is carried out to produce toner particles. By removing the dispersion stabilizer at a temperature not lower than the glass transition temperature of the polymer, the polymer particles After agglomerating each other to form amorphous associated particles, the volume average particle diameter is 7.0 μm.
It is characterized by crushing as follows.

[0012]

In the present invention, a small particle size toner having an irregular shape is manufactured by adjusting the degree of aggregation in the step of removing the dispersion stabilizer of particles in suspension polymerization. Generally, when the dispersion stabilizer remains on the toner surface, it adversely affects the charging property and the fixing property, so that it is removed by acid or alkali. When the dispersion stabilizer was removed at a temperature equal to or higher than the glass transition temperature of the polymer, the particles fused to each other to become associated particles. It has been found that the particles obtained by crushing the associated particles have an indefinite shape, have a small particle size, and exhibit excellent blade cleaning properties. As the temperature condition for removing the dispersion stabilizer for forming the associated particles, it is desirable that the temperature is not less than the glass transition temperature of the produced polymer and not more than the softening temperature. Also,
The primary particle size of the produced polymer is preferably about 1 to 7 μm, and it is preferable to agglomerate the polymer to form associated particles of 5 to several hundred μm. Since the rate of filtration and dehydration is remarkably improved by using the associated particles, this method is also advantageous as a process for producing a small particle size polymerized toner. The particles after dehydration can be dried by ordinary vacuum drying or hot air drying.

Crushing of the particles dried as the aggregate particles can be carried out by using an ordinary fine pulverizer. However, the energy required for crushing is small, and the crushing can be efficiently performed under conditions slower than the conditions required for crushing ordinary resins, for example, by increasing the feed rate of the crushed object. In this case, the particle size after crushing is less likely to be smaller than the primary particle size, so that a particle size distribution in a relatively narrow range can be easily obtained. Further, if necessary, a desired particle size distribution can be obtained by using an air stream classifier or the like.

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

Monovinyl monomers include styrene and o.
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, pn
-Butyl styrene, p-tert-butyl styrene, p
-N-hexyl styrene, pn-octyl styrene,
pn-nonylstyrene, pn-decylstyrene, p
-N-dodecylstyrene, 2,4-dimethylstyrene,
Examples thereof include styrene such as 3,4-dichlorostyrene and its derivatives.

Acrylic monomers include 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, ethyl β-hydroxyacrylate, γ-aminoacrylate propyl, stearyl methacrylate, methacrylic Examples thereof include dimethylaminoethyl acidate and diethylaminoethyl methacrylate.

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

As the oil-soluble polymerization initiator used in the present invention, known polymerization initiators can be used alone or in combination of two or more. For example, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethyl) valeronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, benzoylper- Polymerization can be carried out using oxides, 2,4-dichloroperoxide, isopropylperoxycarbonate, cumene hydroperoxide, lauroylperoxide initiators and the like. The amount of these polymerization initiators used is preferably about 0.1 to 5% by weight of the monomer composition.

As the crosslinking agent, a crosslinking monomer having two or more unsaturated bonds in one molecule is preferably used and copolymerized. As the crosslinkable monomer, divinylbenzene,
Divinylnaphthalene, divinyl ether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,
Examples thereof include diallyl phthalate. The proportion of these crosslinkable monomers copolymerized with the polymerizable monomers is preferably 0.2 to 2% by weight based on the total amount of the monomers. The amount of the crosslinkable monomer used is 0.2% by weight of the total amount of the monomers.
When it is less than the range, the offset resistance of the toner is low, and the particles are likely to coalesce during the polymerization, resulting in a wide particle size distribution.
On the other hand, if the amount of the crosslinkable monomer exceeds 2% by weight of the total amount of the monomers, the softening temperature of the toner rises and the fixing property deteriorates.

Further, by dispersing solid fine particles such as a colorant in the polymerizable monomer and the crosslinkable monomer using a polyester dispersant, the dispersibility is remarkably improved. As a result, the amount of colorant or polar compound exposed on the toner surface is reduced, and it is possible to prevent the deterioration of the charging characteristics, especially in a high humidity environment, and the accompanying scattering and fogging of the toner.

As the colorant, known dyes and pigments can be used. For example, the dyes are nigrosine dye, CI direct red 1, CI direct red 4, CI acid red 1, CI basic red 1, CI solvent red, CI bat red, CI direct blue 1,
CI Direct Blue 2, CI Acid Bull-15, C.
I. Basic Blue 3, CI Solvent Blue, CI Direct Green 6, CI Solvent Red, etc. Examples of the pigment include furnace black, acetylene black, cadmium yellow, Hansa yellow G, naphthol yellow S, pyrazolone red, permanent red 4R, molybdenum orange, fast violet B, phthalocyanine blue, malachite green and phthalocyanine green. It is necessary that these colorants be contained in a ratio suitable for forming a visible image with a sufficient concentration, and usually in a ratio of 2 to 20% by weight based on the total amount of the monomer composition. ..

In order to use the toner as a magnetic toner,
It is also possible to add fine magnetic particles to the monomer composition. Such magnetic materials include powders of ferromagnetic metals such as iron, cobalt and nickel, or chromium in these powders,
A fine powder of an alloy containing manganese, copper, zinc, aluminum, a rare earth element, or the oxide thereof, magnetite, or ferrite is used. The addition amount of these magnetic materials is preferably 20 to 70% by weight based on the total weight of the toner.

When the above monomer composition is suspended in water by a mechanical or ultrasonic homogenizer and polymerized, in order to stabilize the suspended state in water, calcium carbonate, magnesium carbonate and phosphorus are added. It is common to use fine particles of poorly water-soluble inorganic salts such as magnesium acid salt, barium sulfate, silica and alumina as a dispersion stabilizer. 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 the target particle size can be obtained with a smaller amount. These dispersion stabilizers are preferably used in a proportion of 0.01 to 10% by weight with respect to the monomer. In addition to these dispersion stabilizers, a small amount of stabilizing aid may be added. As the dispersion stabilizing aid, water-soluble polymers such as gelatin, carboxymethyl cellulose, starch and polyvinyl alcohol, surfactants and the like can be used.

In the present invention, in addition to the components described above, additives such as a charge control agent, a fluidity modifier, a cleaning agent, and a filler may be added, if necessary. Examples of the charge control agent include nigrosine, quaternized ammonium salts, polyalkylamides, molybdic acid chelate pigments, metal complexes of monoazo dyes, naphthenic acid metal salts, and salicylic acid metal complexes. As the fluidity modifier, fine powder of hydrophobic silica, titanium oxide, polyvinylidene fluoride, metal soap and the like is used, and as a cleaning aid, zinc stearate, calcium stearate, magnesium stearate, polymethylmethacrylate is used. Fine powders of rate, nylon, polytetrafluoroethylene, silicon carbide, etc. can be used. These additives may be mixed and dispersed in the monomer composition for use, or may be added to the surface of the resulting toner particles.

[0025]

EXAMPLES The contents of the present invention will be described in more detail below with reference to examples. In addition, the part in an Example and a comparative example represents a weight part.

(Example 1) 70 parts of styrene, 30 parts of n-butyl methacrylate, 0.1 part of divinylbenzene, 5 parts of carbon black (# 3750 manufactured by Mitsubishi Kasei), polyester-based dispersant (Hypermer LP5 manufactured by ICI). 1 copy,
Charge control agent (Kayacharge T-2N manufactured by Nippon Kayaku) 0.5
Part, polypropylene (Viscole 660P manufactured by Sanyo Kasei)
One part was mixed and dispersed for 6 hours with an attritor.

Next, the container was aerated with nitrogen gas 50
1000 parts of ion-exchanged water and 5 parts of finely powdered silica (Aerosil # 300 manufactured by Nippon Aerosil Co., Ltd.) were added, and the mixture was stirred with a homogenizer (homomixer manufactured by Nippon Tokushu Kika Kogyo Co., Ltd.), and azobis 2,4-dimethyl was added to the dispersion medium. Add the above monomer composition mixture with the addition of 2 parts valeronitrile and add 6000r.
Dispersion granulation was performed at pm for 10 minutes. After replacing the reaction vessel with nitrogen, change to a stirrer equipped with a paddle stirring blade,
While continuing stirring at pm, the temperature was raised to 70 ° C. and the reaction was carried out for 8 hours. The temperature of the reaction system was lowered to 65 ° C., 20 parts of sodium hydroxide was added, and the mixture was stirred for 4 hours to remove silica fine particles used as a dispersant. The obtained polymer was filtered, washed with water, dehydrated, and dried under reduced pressure at 50 ° C. for 12 hours to obtain fine granular powder.

This powder was crushed using a jet mill (PJM-1) manufactured by Nippon Pneumatic Mfg. Co., Ltd., and 0.5 part of hydrophobic silica (R972 manufactured by Nippon Aerosil) was added to obtain Toner 1. When the particle size of Toner 1 was measured with a Coulter counter, the volume average particle size was 6.3 μm,
95% or more of particles having a size of 10 μm or less were contained, and classification operation was unnecessary. The glass transition temperature of Toner 1 was measured by differential scanning calorimetry (DSC) to be 62 ° C. When the shape of Toner 1 was observed with a scanning electron microscope (SEM), it had an irregular shape as shown in FIG.
This toner-4 parts and ferrite carrier (KB
N-120) 100 parts to prepare a developer, and a blade cleaning type commercial copying machine (manufactured by Toshiba BD55
50), the image density was 1.42.
(OD), a high-quality image free of brush marks and fogging, good in resolution, gradation, and denseness of solid portions was obtained. Further, when the cleaning property was examined by continuous copying of 10,000 sheets, no cleaning failure was observed.

(Example 2) 92 parts of styrene, 8 parts of 2-ethylhexyl acrylate, 0.2 parts of divinylbenzene.
Part, carbon black (Mitsubishi Chemical Industries MA-600)
5 parts, 1.0 part of a polyester-based dispersant (polyhexamethylene adipate), and 1 part of a charge control agent (Bontron S-34 manufactured by Orient Chemical Co., Ltd.) were put in a ball mill and mixed for 8 hours. The obtained monomer composition mixture was dispersed in water in the same manner as in Example 1, 3.5 parts of 2,2′-azobisisobutyronitrile as a polymerization initiator was added, and polymerization was carried out at 80 ° C. Then, the system temperature was set to 60 ° C., and the toner was treated in the same manner as in Example 1 to obtain Toner 2.

Toner 2 had a volume average particle size of 5.5 μm, and classification operation was unnecessary. The glass transition temperature of Toner 2 was 59 ° C. When this toner was used to perform image evaluation in the same manner as in Example 1, it was found that the image density was 1.38 (OD) and that the high-quality image similar to that in Example 1 with very little fog and dust of characters was obtained. An image was obtained. The cleaning characteristics were also good.

(Example 3) A silane coupling agent (Toray Dow Corning.
Magnetic toner 3 was obtained by producing polymer particles by the same method as in Example 1 except that 40 parts of magnetite (KBC-100 manufactured by Kanto Denka Co., Ltd.) surface-treated with silicone SZ6083) was added. The toner 3 thus obtained had a volume average particle diameter of 6.8 μm and did not require a classification operation. The glass transition temperature of Toner 3 was 60 ° C.

Using this toner, image evaluation was carried out with a commercially available magnetic toner type printer (PC-PR601 manufactured by NEC). As a result, the image density was 1.35, and a sharp image without fog or bleeding was obtained. Also A4, 5
When 000 sheets of test patterns were printed, the change in image quality was small and the cleaning property was also good.

Comparative Example 1 Toner 4 was prepared in the same manner as in Example 1 except that the alkali treatment was carried out at 50 ° C. in Example 1 and the crushing was not carried out by a jet mill. Got The toner 4 had a volume average particle diameter of 6.0 μm. When the shape of the toner was observed by SEM, it was spherical as shown in FIG. Further, when the image evaluation was performed in the same manner as in Example 1, the image density was 1.45, but a ghost image was generated from the initial stage due to poor cleaning.

Comparative Example 2 In Example 2, the polymer was dehydrated and then dried under reduced pressure at 100 ° C. for 6 hours, and the resulting lump was crushed with a rotoplex coarse crusher. A toner was obtained by using the same composition and method as in Example 2 except that the jet mill was pulverized at a feed rate of 2% or less. Since fine powder was generated in Toner 5 due to excessive pulverization, it was classified by a zigzag classifier (manufactured by Alpine) so that particles having a size of 3 μm or less were 10% or less.

The toner 5 had a volume average particle diameter of 6.8 μm and a glass transition temperature of 58 ° C. When an image was evaluated with a copying machine using Toner 5 in the same manner as in Example 1, the image density was 1.32 and the cleaning property was good, but bridging occurred in the toner hopper and the toner supply was stopped. It caused the inconvenience of doing. When the fluidity of Toner 5 was examined, the angle of repose was as high as 60 degrees, and the fluidity was insufficient.

[0036]

EFFECT OF THE INVENTION The method for producing a polymerized toner of the present invention has the constitution and operation as described above. In the method for producing a toner by suspension polymerization, the blade cleaning property is excellent, the image density is high, and the fogging is high-definition. A toner that gives an image can be provided.

[Brief description of drawings]

FIG. 1 is a photograph of a particle structure of an amorphous polymerized toner according to an embodiment of the present invention.

FIG. 2 is a photograph of a particle structure of a conventional spherical polymerized toner.

Claims (1)

[Claims] 1. A toner monomer is obtained by dispersing a polymerizable monomer mixture containing at least a monomer having an ethylenically unsaturated double bond and a colorant in water using a dispersion stabilizer, and carrying out suspension polymerization. In the method for producing, the dispersion stabilizer is removed at a temperature not lower than the glass transition temperature of the polymer to cause the polymer particles to aggregate to form irregularly associated particles, and then the volume average particle diameter is set to 7.0 μm or less. A method for producing a polymerized toner, which comprises crushing.