JPS6269275A - Preparation of developing toner for electrostatic image - Google Patents

Abstract

PURPOSE:To obtain a toner having superior dispersibility for colorant by mixing and dispersing a specified dispersion stabilizer together with a colorant in a monomer, and forming granulated polymer particles by causing suspension polymn. CONSTITUTION:Carbon black is dispersed in a polymerizable monomer in the presence of polymer having amido groups in the side chain, ad the mixture is polymerized. Suitable polymers having amido groups in the side chain are copolymers obtd. from a monomer expressed by the formula (I), typically vinyl pyrrolidone, or those expressed by the formula (II), typically acrylamide, or copolymers containing N-methylol acrylamide, etc. as copolymer unit. A copolymer contg, vinyl pyrrolidone as the copolymer unit is most preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry toner for developing electrostatic images in electrophotography, electrostatic recording, and electrostatic printing, and a method for producing the same.

A developing method using a dry toner whose main components are a colorant and a resin is as follows: i) The dry toner is mixed with a carrier whose particle size is larger than that of the toner, and the toner is charged with a polarity opposite to that of the electrostatic latent image by frictional charging. A two-component developer that develops the electrostatic latent image by bringing a developer, which is a mixture of toner and carrier, into contact with the electrostatic latent image.ii) A toner containing a magnetic substance is brought into contact with or in close proximity to the electrostatic latent image. There is a one-component developer used for development.

[Conventional technology and problems]

Conventionally, in order to obtain these toners, thermoplastic resin was melted, coloring agents such as dyes and pigments, and if necessary magnetic materials, tribostatic charge control agents, anti-offset agents, lubricants, etc. were added and thoroughly mixed. The method used was to cool and solidify the powder, pulverize it, and then classify it to obtain the desired particle size.

However, the methods described above have various drawbacks. Firstly, polymerization equipment for resin production, equipment for mixing and purification,
Equipment associated with many processes, such as a crusher and a classifier, is required, and the number of processes and energy consumption is large, which causes high costs. The second reason is that it is difficult to obtain a uniform mixture in the kneading process, and the conditions for uniform dispersion are particularly delicate. Thirdly, in the grinding process, it is not possible to obtain only the appropriate fine powder particle size range to obtain clear, fog-free images; fine powder and coarse powder are by-produced and must be classified and removed. There are disadvantages that lead to increased costs, such as the complexity of the process, such as the failure to obtain a desired particle size range, and poor yield to obtain the desired particle size range. Fourthly, the resulting powder has an amorphous shape due to the pulverization, the poor fluidity of the fine powder, and the capri of the image caused by the fine powder generated by the pulverization due to stirring during frictional charging. It will be done.

In contrast, Special Publication No. 36-10231, Special Publication No. 10231, Special Publication No. 47-
Publications such as Japanese Patent Publication No. 518305 and Japanese Patent Publication No. 51-14895 describe methods for producing toner by suspension polymerization. This suspension polymerization method does not require pulverization, the manufacturing process is simplified, and the above-mentioned drawbacks can be overcome. However, there are problems with suspension polymerization.

In other words, dry toner consists of a thermoplastic resin, but it is mixed with materials to impart and improve various functions, such as coloring agents such as dyes and pigments, and charging materials to improve triboelectric charging properties. Examples include a control agent, a magnetic material that provides adhesion to the developing roller, an anti-offset agent that prevents toner from adhering to the fixing roller, and a toner fluidity improver.

If these materials dissolve uniformly in the polymerizable monomer and do not inhibit the polymerization reaction, there is no particular problem. It is difficult to make these materials exist in a uniform state in polymer particles because of their lack of affinity for polymeric monomers.

If the added material has a significantly poor affinity for the polymerizable monomer, it may migrate to the aqueous phase during polymerization and may not exist in the polymerized toner particles.

Since the added materials are non-uniformly present in the toner, the toner cannot fully perform its functions, such as not being sufficiently charged.

In particular, carbon black used as a colorant or charge control agent is lipophilic, but the particle diameter is 10 mμ.
In addition to being as fine as ~3011μ, it forms primary aggregates that deteriorate during production, and secondary aggregates that are further agglomerated, and are difficult to disperse in polymerizable monomers simply by dispersion means such as a ball mill. In this way, toner particles containing poorly dispersed carbon blanks not only reduce the blackness of the toner and make it impossible to obtain a black image, but also increase the variation in the electric resistance and triboelectric charge of the toner particles, making it difficult to use. It is not possible to obtain high image quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner and a method for producing the toner that overcome the above-mentioned drawbacks. That is, the first object of the present invention is to provide a toner that has a sufficient carbon black dispersion state and provides excellent image quality.
The purpose of the present invention is to provide a method for producing toner that overcomes the drawbacks of suspension polymerization.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned goal, the present inventors discovered that when dispersing a carbon blank in a monomer having a polymerizable unsaturated group, a polymer having an amide group in the side chain was used. The present inventors have discovered that the dispersibility of carbon black can be significantly improved by performing dispersion in the presence of carbon black, leading to the present invention.

That is, the present invention involves dispersing a carbon blank in a monomer having a polymerizable unsaturated group (hereinafter abbreviated as a polymerizable monomer), and then producing a toner for developing an electrostatic image by a suspension polymerization method. A method for producing a toner for developing an electrostatic image, characterized in that a carbon blank is dispersed in a polymerizable monomer in the presence of a polymer having an amide group in a side chain, and then polymerization is performed. It is something.

The polymer having an amide group in the side chain used in the present invention has the general formula (1) represented by vinylpyrrolidone.
) (In the formula, R1 is H or C113, and n-2 to 4.) or a monomer represented by the general formula (n ) (wherein, R7 is H or C113 and % R1% Rs
are H or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. Examples include copolymers having the monomers represented by the following as comonomers, and copolymers containing N-methylolacrylamide, N-butoxymethylacrylamide, dia-7ton acrylamide, etc. as copolymerized units. Particularly preferred are copolymers containing vinylpyrrolidone as a copolymerized unit.

Other comonomers copolymerized with the polymerizable monomer containing an amide group in the side chain include styrene and styrene derivatives, methyl methacrylate, methyl acrylate, n
- One or more acrylic esters such as butyl methacrylate and 2-ethylhexyl acrylate-1, methacrylic ester monomers, and vinyl ester monomers such as vinyl acetate and vinyl propionate. Things can be mentioned.

The composition ratio of the monomer having an amide group in the side chain in the polymer having an amide group used in the present invention is 1
00 to 0.1%, preferably 20 to 0.5%. In addition, the amount of the polymer having an amide group in the side chain is as follows:
The amount is preferably 20% by weight or less, more preferably 0.5 to 5% by weight based on the polymerizable monomer. In addition, the molecular weight of the polymer having an amide group in the side chain is 1000 to 1oooooo
and preferably 3,000 to 100,000.

Specific examples of polymers having an amide group in the side chain used in the present invention are listed below.

C(1゜nl:n-=95=5 Ctl+ GHz CI+3 n+ :n, :n,=85:10:5 In the present invention, in the presence of a polymer having an amide group in the side chain, a coloring agent is used. A certain carbon blank is mixed and dispersed in a polymerizable monomer, used as an oil phase, and polymerized by a suspension polymerization method to produce a polymer glue.

In the suspension polymerization method, a dispersion of the oil phase is added to an aqueous phase in which a suspension stabilizer such as a water-soluble polymer or a poorly water-soluble inorganic salt is uniformly dissolved or dispersed, and the dispersion is carried out using a homomixer, homogenizer, etc. Disperse into 5-30 droplets depending on the method. The weight ratio of the oil phase to the aqueous phase is set in the range of 1:2 to 1:1O, so that coalescence of particles does not occur during polymerization. Transfer the dispersion liquid in which the oil phase is uniformly dispersed in the water phase to a separable flask equipped with a stirring device, condenser, thermometer, and nitrogen inlet tube, and raise the temperature to the temperature at which the polymerization initiator decomposes (50 to 90 °C). Then polymerization is carried out under a nitrogen atmosphere.

After the polymerization is completed, the aqueous phase is removed by filtration, and if inorganic powder is attached to the toner surface, it is removed by treatment with dilute acid, and after washing with water, water is removed by spray drying, vacuum drying, etc. until the toner is finished. Manufactured.

As the polymerizable monomer used in the present invention, all polymerizable monomers can be used, such as styrene, p
-Chlorstyrene, p-methylstyrene, vinyl acetate,
Vinyl propionate, vinyl benzoate, methyl acrylate, ethyl acrylate, n-butyl acrylate,
1so-butyl acrylate, dodecyl acrylate,
n-octyl acrylate, methyl methacrylate-1.
Ethyl methacrylate, n-butyl methacrylate, 1
so-butyl methacrylate, diethylaminoethyl methacrylate, t-butylaminomethyl methacrylate,
Acrylonitrile, 2-vinylpyridine, 4-vinylpyridine and the like can be used alone or in combination.

Furthermore, in the present invention, by adding polyfunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, glycidyl methacrylate, and glycidyl acrylate to the above monomers as a crosslinking agent, a more durable toner can be produced. I can do it. The content of polyfunctional molecules is 0.05 to 20% by weight (preferably 0
5 to 5% by weight) is good.

As the polymerization initiator, commonly used oil-soluble peroxide-based or ab-based initiators can be used. For example, benzoyl peroxide, lauroyl peroxide, 2,2'-abbisisobutyronitrile, 2,2''-azobis-(2,4-
dimethylvaleronitrile), ortsk-1-cor benzoyl peroxide, and orthomethoxybenzoyl peroxide. These are used in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the polymerizable jn-mer.

Suspension stabilizers used in the present invention include water-soluble polymers such as gelatin, starch, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl alkyl ether, and polyvinyl alcohol;
Examples include poorly water-soluble inorganic salts such as barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, and calcium phosphate, and these are used in an amount of 0.1 to 5% by weight, preferably 0.5 to 2% by weight of water. .

Further, the toner of the present invention may contain a low molecular weight olefin polymer known as a so-called mold release agent for the purpose of preventing offset, improving fluidity, improving fixing properties, and the like.

It is preferable that this low molecular weight olefin polymer be present during monomer polymerization together with the colorant used in the present invention.

Examples of the low molecular weight olefin polymer used in the toner of the present invention include polyethylene, polypropylene, ethylene acetate picopolymer, chlorinated polyethylene wax, polyamide, polyester, polyurethane, polyvinyl butyral, butadiene rubber, phenolic resin, epoxy resin, and rosin. Examples include modified resins, silicone oils, and silicone waxes.

The amount of the low molecular weight olefin polymer used is 1 to 20 parts by weight, preferably 3 parts by weight, per 100 parts by weight of the resin component of the toner.
The amount is 15 parts by weight or less, and if it is less than 1 part by weight, it may not have a sufficient offset prevention effect, and if it is more than 20 parts by weight, gelation may occur during polymerization, which is not preferable.

To form an image using the toner of the present invention, for example, by electrophotography, a selenium photoreceptor or an inorganic photoconductive material such as zinc oxide, cadmium sulfide, cadmium selenide, cadmium selenide sulfide, lead oxide, mercury sulfide, etc. A photoreceptor in which a photosensitive layer containing a material dispersed in a binder resin is provided on a conductive support, or an organic photoconductive material such as anthracene or polyvinylcarbazole is contained in a binder resin as necessary. A photoreceptor is used in which a photosensitive layer is provided on a conductive support. For example, a roller 1 is placed on the surface of the photosensitive layer of such a photoreceptor.
- The entire surface is charged by corona discharge using a ron or scorotron charger, and then imagewise exposure is performed to form an electrostatic charge image. Next, this electrostatic charge image is developed, for example, by a cascade method or a magnetic brush method, with a developer consisting of a mixture of the toner of the present invention and a glass beads or iron powder carrier to form a toner image.

This toner image is transferred onto the transfer paper by being pressed against the transfer paper under, for example, corona discharge. The toner image transferred onto the transfer paper is heat-fixed by a hot roll fixing device coated with a fluorine-based resin or silicone rubber having mold-releasing properties.

〔Effect of the invention〕

As explained above in detail, the toner for developing electrostatic images of the present invention is produced by mixing and dispersing a specific dispersion stabilizer together with a colorant in a monomer, and then suspension polymerizing the mixture to form granulated polymer particles. As a result, we were able to obtain a toner with even better colorant dispersibility than toner produced using conventional manufacturing methods, which not only improved the degree of toner blackening and fogging during copying, but also improved development efficiency. It was also possible to provide a toner that was further improved in terms of properties, transferability, fixing properties, and storage stability, as well as a method for producing the same.

〔Example〕

Examples of the present invention are shown below, but the present invention is not limited thereto.

Note that "parts" in the examples are "parts by weight."

Example-1 85 parts of styrene, 15 parts of n-butyl acrylate, carbon black (manufactured by Mitsubishi Kasei ■, #44), 2 parts of the above compound (1), low molecular weight polyethylene (manufactured by Mikata Petrochemical Industry ■2. A mixture of 2 parts of HYWAX 210P) was dispersed in a ball mill for 10 hours.

Add 1 2'-azobisisobutyronitrile to this dispersion.
1% aqueous solution of polyvinyl alcohol (manufactured by Nippon Gohsei Kagaku Kogyo, GOHSENOL GL-05)
In addition to 50 parts, add a homomixer (manufactured by Tokushu Kika Kogyo ■) to T.
The mixture was stirred for 3 minutes at 6000 rpm. When the oil droplets after stirring were observed under an optical microscope, the dispersibility of carbon black in the oil droplets was extremely good. This suspension was subjected to a polymerization reaction in a separable flask at 75° C. for 8 hours under a nitrogen atmosphere at a stirring speed of 1100 rpm using a conventional stirrer. After polymerization, centrifugation and water washing were repeated,
After drying under reduced pressure, a spherical toner having an average particle size of 11 μm was obtained.

Carrier iron powder (D, M) is added to 5 parts of this toner.

95 parts of CB-100 (manufactured by Stuart Corporation) were mixed to prepare a developer. When this developer was used to create an image using Ricoh FT4060, a clear black image without fogging was obtained.

Comparative Example-1 Polymerization was carried out under exactly the same conditions as in Example-1 except that the compound (1) was not added.

In the polymerizable mixture taken out from the ball mill, agglomeration of carbon blanks was observed, and the dispersion state was poor. The produced polymer was spherical particles of 10 to 20μ, but the carbon black was unevenly distributed in the particles, and there were quite a lot of transparent parts and transparent particles, and the obtained powder was not black. Rather, it looked gray. It was also confirmed that there were carbon blanks that were not incorporated into the particles, and were either stuck to the particle surface or existing alone. When an image was produced using this toner in the same manner as in Example-1, the result was an image?
The flatness was not sufficient and fogging also occurred.

Example-2 A toner was produced in the same manner as in Example-1 except that the compound (2) was used in place of the compound +11. When an image was produced using this toner in the same manner as in Example-1, the image density was sufficient.
A clear image without fogging was obtained.

Example-3 80 parts of styrene, 1 to 10 parts of n-butyl methacrylate,
10 parts of 2-ethylhexyl acrylate, 5 parts of carbon black (manufactured by Mitsubishi Kasei QI, #30), the above compound (
3) 1 part, low molecular weight polyethylene (Mikata Petrochemical Industry ■
1.5 parts of the mixture was dispersed in a ball mill for 10 hours.

After dissolving 2 parts of 2,2'-7zobis-(2,4-dimethylvaleronitrile) in this dispersion, polyvinyl alcohol (manufactured by Nippon Gosei Kagaku Kogyo ■, Gohsenol GM-1) was added.
The mixture was added to 200 parts of the 1.5% aqueous solution of 4) and stirred for 3 minutes at 7000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo ■). After that, the average particle size was 10 in the same manner as in Example-1.
Example 1 A spherical toner of μm was manufactured and used
When an image was produced in the same manner as above, a clear image with sufficient image density and no fog was obtained.

Example 4 A toner was produced in the same manner as in Example 3, except that the compound (4) was used instead of the compound (3). When an image was produced using this toner in the same manner as in Example-1, the image density was sufficient.
A clear image without fogging was obtained.

Claims (1)

[Claims] 1. In a method for producing a toner for developing an electrostatic image by a suspension polymerization method after dispersing carbon black in a monomer having a polymerizable unsaturated group, an amide group is added to the side chain. 1. A method for producing a toner for developing an electrostatic image, comprising dispersing carbon black in the polymerizable monomer in the presence of a polymer containing the same, and then performing polymerization. 2. The manufacturing method according to claim 1, wherein the polymer having an amide group in a side chain contains vinylpyrrolidone as a copolymerized unit.